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CN116913438B - Method and device for calculating freezing temperature of frozen sand mold - Google Patents

Method and device for calculating freezing temperature of frozen sand mold Download PDF

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CN116913438B
CN116913438B CN202311160923.9A CN202311160923A CN116913438B CN 116913438 B CN116913438 B CN 116913438B CN 202311160923 A CN202311160923 A CN 202311160923A CN 116913438 B CN116913438 B CN 116913438B
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temperature
sand mold
sand
casting
freezing
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CN116913438A (en
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孙玉成
李继超
陈秀明
孙浩梅
朱海杰
姜爱龙
李娜娜
李娜
冯月雪
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Weichai Power Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/02—Sand moulds or like moulds for shaped castings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D46/00—Controlling, supervising, not restricted to casting covered by a single main group, e.g. for safety reasons
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G06F17/11—Complex mathematical operations for solving equations, e.g. nonlinear equations, general mathematical optimization problems
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
    • G—PHYSICS
    • G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
    • G16C—COMPUTATIONAL CHEMISTRY; CHEMOINFORMATICS; COMPUTATIONAL MATERIALS SCIENCE
    • G16C60/00—Computational materials science, i.e. ICT specially adapted for investigating the physical or chemical properties of materials or phenomena associated with their design, synthesis, processing, characterisation or utilisation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2111/00—Details relating to CAD techniques
    • G06F2111/10—Numerical modelling
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2113/00—Details relating to the application field
    • G06F2113/22—Moulding
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/08—Thermal analysis or thermal optimisation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
    • Y02P90/30—Computing systems specially adapted for manufacturing

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  • Management, Administration, Business Operations System, And Electronic Commerce (AREA)
  • Investigating Or Analyzing Materials Using Thermal Means (AREA)

Abstract

The invention discloses a method and a device for calculating freezing temperature of a frozen sand mold, wherein a first pouring temperature is set through a known pouring temperature range, and then the freezing temperature of the sand mold is obtained through combination with production environment temperature and reverse calculation, so that the obtained freezing temperature of the sand mold is more in accordance with an actual process flow, and whether the obtained freezing temperature of the sand mold meets process requirements is further verified through forward heating calculation, the problem that after the frozen sand mold is taken out of a freezing bin, the temperature is raised to a certain value, the shape and basic performance of the sand mold change, and if the freezing temperature of the sand mold is improperly set, the quality of a casting is influenced is solved, the rapid prediction of the freezing temperature of the sand mold under any temperature condition is realized, the guiding effect is provided for the setting of the freezing temperature of the sand mold when a process is carried out by process personnel, and the stability of the frozen sand mold is ensured through related prediction and optimization results.

Description

Method and device for calculating freezing temperature of frozen sand mold
Technical Field
The invention relates to the technical field of frozen sand molds, in particular to a method and a device for calculating freezing temperature of a frozen sand mold.
Background
The frozen sand casting technology is a casting technology in which water is used as a binder for sand casting, molding sand is frozen in a low-temperature environment to form a sand mold, and a casting is obtained after a melt is poured. The supercooling degree of the melt in the frozen sand mould is high, the temperature gradient of the melt in the solidification process is large, and the metal casting is strengthened by fine crystals, so that the structure is compact and the mechanical property is good. The sand mould naturally collapses under the impact of high-temperature melt, and no strong irritating gas is generated in the casting process.
The strength construction of the sand mold in the frozen sand mold casting process is realized by freezing water, and the frozen sand mold is in a temperature rising process after leaving the freezing equipment in the casting process under the non-frozen environment condition. For the casting process, the effective connection of the whole process needs to be considered, if the freezing temperature of the frozen sand mold is higher, the temperature is increased to a higher temperature under the influence of the ambient temperature in the transportation and whole process preparation process, the sand mold shape retention is poorer, the molding sand at the part contacting with the high-temperature melt is often broken at one touch, the impact resistance is poor, the molding sand at the outer surface layer is also often influenced by the sublimation and melting phenomena of the frozen binder, and the characteristics of the basic performance, the shape and the size of the casting are further influenced, so that the freezing temperature of the frozen sand mold is set, and the setting of the freezing temperature becomes one of important influencing factors for guaranteeing the product quality of the frozen sand mold casting process.
Disclosure of Invention
The invention provides a method and a device for calculating freezing temperature of a frozen sand mold, which are used for solving the problem that in the casting process of the frozen sand mold, as the temperature is raised to a certain value after the frozen sand mold is taken out from a freezing bin, the shape and basic performance of the sand mold change, and if the freezing temperature of the sand mold of the frozen sand mold is too high, the casting quality is affected.
According to an aspect of the present invention, there is provided a method for calculating a freezing temperature of a frozen sand mold, comprising:
determining technological parameters according to a sand mold process, and obtaining sand mold transfer time and production environment temperature; the technological parameters comprise a temperature range during sand casting;
according to the sand mold process, a three-dimensional model of a sand mold is established;
setting a time step according to the sand mold transferring time; setting a first casting temperature according to the temperature range during casting of the sand mould;
according to the technological parameters, the first pouring temperature and the production environment temperature, discretizing and solving a temperature field equation of the three-dimensional model in the sand mold transferring time, and reversely calculating to obtain a sand mold freezing temperature;
according to the technological parameters, the sand mold freezing temperature and the production environment temperature, discretizing and solving a temperature field equation of the three-dimensional model in the sand mold transferring time, and carrying out forward calculation to obtain a second pouring temperature;
Judging whether the second casting temperature falls within a temperature range of the sand casting;
if yes, the freezing temperature of the sand mold meets the requirement.
Optionally, according to the process parameter, the first pouring temperature and the production environment temperature, in the sand mold transfer time, discretizing the temperature field equation of the three-dimensional model, and reversely calculating to obtain a sand mold freezing temperature, including:
dispersing the three-dimensional model into a plurality of cells in three dimensions;
setting the thermophysical performance parameters of the unit cells;
setting the first casting temperature as an initial condition of a plurality of the cells, setting the production environment temperature as a boundary condition of the cell which is in contact with the production environment among the plurality of the cells, and setting the first casting temperature as a boundary condition of the rest of the cells;
according to the technological parameters, the initial conditions and the boundary conditions, carrying out iterative solution on the temperature field equation of the discretized cells at the next moment to obtain temperature change values of the cells, and further reversely calculating to obtain temperature values of the cells at the last moment;
Obtaining the sand mold freezing temperatures of a plurality of unit cells at the initial moment of sand mold transfer according to continuous iteration on the time step;
and selecting the minimum value of the sand mold freezing temperatures as the sand mold freezing temperature of the three-dimensional model.
Optionally, according to the process parameter, the freezing temperature of the sand mold and the production environment temperature, discretizing the temperature field equation of the three-dimensional model in the sand mold transfer time, and calculating forward to obtain a second casting temperature, where the method includes:
dispersing the three-dimensional model into a plurality of cells in three dimensions;
setting the thermophysical performance parameters of the unit cells;
setting the sand mold freezing temperature as an initial condition of a plurality of the cells, setting the production environment temperature as a boundary condition of the cell contacting with the production environment among the plurality of the cells, and setting the sand mold freezing temperature as a boundary condition of the rest of the cells;
according to the technological parameters, the initial conditions and the boundary conditions, carrying out iterative solution on the temperature field equation of the discretized cells at the next moment to obtain temperature change values of the cells, and further carrying out forward calculation to obtain temperature values of the cells at the next moment of the cells;
Obtaining the second pouring temperatures of a plurality of the unit cells at the final moment of sand mold transfer according to continuous iteration on the time step;
and selecting the maximum value of the plurality of second pouring temperatures as the second pouring temperature of the three-dimensional model.
Optionally, after judging whether the second casting temperature falls within a temperature range of the sand casting, the method further comprises the steps of;
if not, judging whether the second casting temperature is smaller than the minimum value of the temperature range during sand casting;
if yes, sequentially acquiring the minimum values of the temperatures of a plurality of cells after a plurality of time steps at the initial time of sand mold transfer as the sand mold freezing temperature of the three-dimensional model; and repeatedly calculating the second pouring temperature until the second pouring temperature falls into the temperature range when the sand mould is poured.
Optionally, after the determining whether the second casting temperature is less than the minimum value of the temperature range during the sand casting, the method further includes:
if not, calculating the absolute value of the difference between the second pouring temperature and the maximum value of the temperature range during sand casting, calculating the increasing iteration number of the time step based on the temperature change value and the absolute value of the last moment of the sand mould transferring initial moment in the reverse calculation process of the sand mould freezing temperature, carrying out reverse iteration solution on the current sand mould freezing temperature based on the increasing iteration number and the time step to obtain a plurality of sand mould freezing temperatures, and selecting the minimum values of the sand mould freezing temperatures as the sand mould freezing temperatures of the three-dimensional model; and repeatedly calculating the second pouring temperature until the second pouring temperature falls into the temperature range when the sand mould is poured.
Optionally, the dispersing the three-dimensional model into a plurality of cells in three dimensions includes:
and discretizing the three-dimensional model by using a finite difference method, a finite element analysis method or a finite volume analysis method to form three-dimensional unit cells.
Optionally, the iteratively solving the temperature field equation of the discretized multiple cells according to the process parameters, the initial conditions and the boundary conditions, to obtain multiple sand mold freezing temperatures of the multiple cells includes: and iteratively solving a discretized temperature field equation of a plurality of cells according to the process parameters, the initial conditions and the boundary conditions by using one of Python, matlab, comsol, C, C ++ and Procast.
Optionally, the obtaining the production environment temperature includes:
and fitting according to the workshop environment historical temperature measurement data of the sand mould to obtain a production environment temperature curve.
Optionally, the obtaining the sand mold transferring time includes:
determining transfer parameters of the sand mold, and selecting a common sand mold according to the transfer parameters;
and simulating the drilling transportation process through the common sand mould to obtain the sand mould transportation time.
According to another aspect of the present invention, there is provided a frozen sand mold freezing temperature calculating apparatus, comprising:
The sand mold parameter acquisition module is used for acquiring the technological parameters of the sand mold, the sand mold transfer time and the production environment temperature; the technological parameters comprise a temperature range during sand casting;
the sand mould three-dimensional model calculation module is used for establishing a three-dimensional model of the sand mould;
the sand mold freezing temperature calculation module is used for setting a time step of cooling calculation according to the sand mold transfer time; setting a first casting temperature according to the temperature range during casting of the sand mould; the temperature field equation of the three-dimensional model is discretized and solved in the sand mold transfer time according to the technological parameters, the first pouring temperature and the production environment temperature, and the temperature of the sand mold is obtained by reverse calculation;
and the sand casting temperature calculation module is used for discretizing and solving a temperature field equation of the three-dimensional model in the sand transportation time according to the technological parameters, the sand freezing temperature and the production environment temperature, and calculating forward to obtain a second casting temperature.
According to the technical scheme, through simulating a reverse process that a frozen sand mold is delivered from a freezing warehouse to a pouring area through transferring, a first pouring temperature is set according to a temperature range when the sand mold is poured, a time step is set, a three-dimensional model of the sand mold is built, according to technological parameters, the first pouring temperature and production environment temperature, in a sand mold transferring time, the temperature of the frozen sand mold is reduced to a sand mold freezing temperature from the first pouring temperature in a set time step, calculation of the sand mold freezing temperature is completed, further after the sand mold freezing temperature is obtained, a forward process that the frozen sand mold is delivered from the freezing warehouse to the pouring area through transferring is simulated again, after the frozen sand mold is delivered from the freezing warehouse to the pouring area, the temperature of the frozen sand mold is obtained, namely, a second pouring temperature is obtained, and whether the frozen temperature of the sand mold meets requirements is judged by judging whether the second pouring temperature range when the sand mold is poured. According to the technical scheme, the first pouring temperature is set through the temperature range in the pouring process, the sand mold freezing temperature is obtained through the reverse calculation by combining the production environment temperature, the obtained sand mold freezing temperature is more in accordance with the actual process flow, and whether the obtained sand mold freezing temperature meets the process requirement is verified through the forward heating calculation, so that the problem that the shape and the basic performance of the sand mold change when the frozen sand mold is taken out of a freezing bin and the quality of a casting is affected due to the fact that the sand mold freezing temperature of the frozen sand mold is set improperly is solved, the rapid prediction of the sand mold freezing temperature under any temperature condition is realized, the guiding effect is provided for the setting of the sand mold freezing temperature when the process is carried out by process personnel, the stability of the freezing process is guaranteed through the related prediction and optimization results, and the freezing temperature calculation method of the frozen sand mold can be suitable for the frozen sand mold with specific size, shape and material components, and the applicability of the temperature calculation method is improved.
It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the invention or to delineate the scope of the invention. Other features of the present invention will become apparent from the description that follows.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for calculating freezing temperature of a frozen sand mold according to an embodiment of the invention;
FIG. 2 is a flow chart of a cooling solving method for a frozen sand mold temperature field provided by the embodiment of the invention;
FIG. 3 is a flow chart of a temperature field heating solving method of a frozen sand mold provided by the embodiment of the invention;
FIG. 4 is a flowchart of another method for calculating the freezing temperature of a frozen sand mold according to an embodiment of the invention;
fig. 5 is a schematic structural diagram of a freezing temperature calculating device for a frozen sand mold according to an embodiment of the invention;
Fig. 6 is a schematic diagram of another apparatus for calculating a freezing temperature of a frozen sand mold according to an embodiment of the present invention.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The frozen sand casting technology is a casting technology in which water is used as a binder for sand casting, molding sand is frozen in a low-temperature environment to form a sand mold, and a casting is obtained after a melt is poured. The supercooling degree of the melt in the frozen sand mould is high, the temperature gradient of the melt in the solidification process is large, and the metal casting is strengthened by fine crystals, so that the structure is compact and the mechanical property is good. The sand mould naturally collapses under the impact of high-temperature melt, and no strong irritating gas is generated in the casting process. However, the shape retention of a purely frozen sand mold at a higher temperature is poor, molding sand tends to collapse at one touch at a part contacted with a high-temperature melt, the impact resistance is poor, and the molding sand on the outer surface layer is also often influenced by sublimation and melting phenomena of a frozen binder, so that the basic performance, the shape and the size characteristics are influenced.
For the casting process, the effective engagement of the entire process needs to be considered. Wherein, the casting of molten metal needs to be kept at a specific temperature, and the temperature is controlled by a process from the tapping to the casting. Therefore, the pouring process of the molten metal requires fine control over the time course. The strength of the sand mould in the traditional casting process is constructed by bonding the foundry sand by using binders such as resin, clay and the like, and the strength control is related to the denaturation of moisture and binders, namely the traditional casting sand mould can be kept for a long time, usually several weeks under normal ambient temperature and humidity. Thus, the manufacturing and transfer process of sand molds in conventional casting processes often do not require excessive time management.
However, the strength construction of the sand mold in the frozen sand mold casting process is realized by freezing water, and the frozen sand mold is in a temperature rising process after leaving the freezing equipment in the casting process under the non-frozen environment condition except for a few extremely cold regions or seasons in which the regions are located. The frozen state of the frozen sand mold and the strength of the sand mold are related to a plurality of factors, such as the production environment temperature, the freezing temperature of the sand mold, the sand mold transfer time, the waiting time before casting, and the like. The ambient temperature has a great influence on the retention of the frozen sand mold under different environmental conditions. In particular, setting a proper sand mold freezing temperature of a frozen sand mold is a continuing problem in manual single-piece production and small-batch production line production.
In order to solve the above problems, the technical solution of the present invention provides a method for calculating a freezing temperature of a frozen sand mold, and fig. 1 is a flowchart of the method for calculating a freezing temperature of a frozen sand mold according to the present invention, where the method is applicable to a frozen sand mold casting process, and is performed in a frozen sand mold molding, transferring and melt casting production line. As shown in fig. 1, the method includes:
s100, determining technological parameters according to a sand mold process, and acquiring sand mold transfer time and production environment temperature; the process parameters include the temperature range during sand casting.
The process parameters may also include, among other things, melt casting temperature, melt casting time, and melt transfer time. Temperature range (T) s-min ，T s-max ），T s-min Is the minimum value of the range boundary, T s-max For the range boundary maximum, the actual values and the temperature differences can be set according to the actual requirements, for example, according to the melt casting temperature or the casting environment temperature. The melt casting temperature can be set according to the melt material composition, the melt material phase diagram, the freeze casting process and the like, and the melt transfer time and the melt casting time can be set by drilling or acquiring historical transfer data. In the actual execution, the temperature range (T s-min ，T s-max ) The melt pouring temperature, the melt pouring time and the melt transferring time are that in the actual process, all links have intersection and areThe temperature difference may generate heat transfer effects such as heat conduction, heat convection and heat radiation, so that various process parameters may be comprehensively considered according to sand mold process.
The sand mold transferring time can be obtained through historical data or through sand mold transferring simulation exercise, and when the sand mold transferring method is specifically implemented, the common sand mold used for replacing the frozen sand mold to perform simulation exercise can be selected through determining transferring parameters of the frozen sand mold to be transferred, and then the transferring time is measured and recorded in the simulation transferring process through the common sand mold simulation transferring process. It should be noted that the transferring parameters may be the weight and structure of the frozen sand mold to be transferred, the handling difficulty, the speed of the transferring tool, the posture adjustment time after transferring, and the like. Through using ordinary sand mould simulation transportation process, avoided using the sand mould waste that the simulation drill caused of freezing sand mould, and the transportation time reliability that uses ordinary sand mould to obtain is higher.
The production environment temperature can be a production environment temperature curve, which can be a historical temperature change curve obtained according to workshop-mounted temperature measurement equipment, or can be a production environment temperature curve which is obtained by fitting workshop environment temperature measurement with a smelting furnace starting condition, a melt discharging condition and a melt transferring condition and takes the influence of a melt process on the environment temperature into consideration.
Specifically, according to the sand mold process, a temperature range (T s-min ，T s-max ) The method comprises the steps of setting a reasonable sand casting temperature, namely a first casting temperature according to a temperature range during sand casting, wherein the first casting temperature is the temperature of a frozen sand mold as an initial condition, and further performing reverse cooling calculation of sand mold transfer. The method can comprehensively consider the actual factors such as melt temperature, melt transportation, casting and the like, so that the reliability of the prediction result is higher.
S200, establishing a three-dimensional model of the sand mold according to a sand mold process.
The sand mold process may include sand mold size and shape, and the three-dimensional model establishment includes but is not limited to CAD software establishment, and when in specific implementation, the software type may be selected according to actual conditions.
Specifically, according to a sand mold process, for example, the size and shape of a casting, a frozen sand mold for casting needs to have a specific size and shape, and it is understood that the size and shape of the sand mold are different, and the temperature changes are different, so that a three-dimensional model of the sand mold can be established according to the sand mold process, and further, temperature field solutions can be respectively carried out on different regions of the sand mold in space according to the established three-dimensional model.
S300, setting a time step according to sand mold transfer time; and setting a first casting temperature according to the temperature range during sand casting.
The value of the time step can be solved in a convergence mode according to the size of the cell, the specific setting is carried out according to the requirement in the solved value range, and when the method is implemented in a specific mode, the smaller the actual value of the time step is, the more accurate the calculation result is. The first casting temperature is the initial temperature of the freezing temperature calculation method of the frozen sand mould, and the actual numerical value can be any numerical value falling in the temperature range of sand mould casting according to requirements.
In the concrete calculation process, the time step can be accumulated to the total sand mold transfer time, so that the direction process of transferring the sand mold from the freezing bin to the pouring area is simulated, namely, the process that the temperature of the sand mold is reduced from the first pouring temperature to the temperature when the sand mold is discharged from the freezing bin is simulated.
S400, discretizing and solving a temperature field equation of the three-dimensional model in the sand mold transfer time according to the technological parameters, the first pouring temperature and the production environment temperature, and reversely calculating to obtain the sand mold freezing temperature.
The discretization solving comprises, but is not limited to, dispersing a three-dimensional model of the sand mold into three-dimensional cells based on a finite difference method, and carrying out iterative solving through a temperature field equation of multiple cells, wherein the time step requirement meets the convergence of the equation solving, so that the freezing temperature of the sand mold is predicted.
Specifically, the temperature field equation of the three-dimensional model is performedDiscretization is required according to the temperature range (T s-min ，T s-max ) And accumulating time steps based on conditions such as melt casting temperature, melt casting time, process parameters of melt transfer time, production environment temperature and the like, comprehensively considering melt casting process and production environment temperature, carrying out iterative cooling solution on a temperature field equation of the three-dimensional model, and further calculating to obtain the sand mold freezing temperature.
In the specific implementation process, as the temperature changes of all parts of the sand mold are different, the temperature required by the frozen sand mold casting process when the sand mold is transported to a casting area is considered to be lower than the temperature of the sand mold during casting as much as possible, and the lowest temperature in the calculation result can be selected as the freezing temperature of the sand mold in order to ensure the reliability of the calculation result and enable the calculation result to guide technicians to better complete the casting process flow.
S500, discretizing and solving a temperature field equation of the three-dimensional model in the sand mold transfer time according to the technological parameters, the sand mold freezing temperature and the production environment temperature, and calculating forward to obtain a second pouring temperature.
Specifically, discretizing the temperature field equation of the three-dimensional model requires that the temperature range (T s-min ，T s-max ) And (3) accumulating time steps based on conditions such as melt casting temperature, melt casting time, process parameters of melt transfer time, production environment temperature and the like, comprehensively considering the melt casting process and the production environment temperature, and carrying out iterative heating solving on a temperature field equation of the three-dimensional model, so as to calculate and obtain a second casting temperature, wherein the second casting temperature is the temperature of the frozen sand mold.
In the specific implementation process, as the temperature changes of all parts of the sand mold are different, the temperature required by the frozen sand mold casting process when the sand mold is transported to the casting area is considered to be lower than the temperature of the sand mold during casting as much as possible, and the highest temperature in the calculation result can be selected as the second casting temperature in order to ensure the reliability of the calculation result and enable the calculation result to guide technicians to better complete the casting process flow.
S600, judging whether the second casting temperature falls into a temperature range during sand casting.
Specifically, the second casting temperature is within (T s-min ，T s-max ) In the range, the preferable basic performance and shape and size characteristics can be maintained by judging whether the predicted second casting temperature falls within the temperature range (T s-min ，T s-max ) And then judging whether the casting temperature of the sand mould obtained by the reverse cooling calculation of the first casting temperature meets the requirement of the sand casting process, performing freezing molding of the sand mould by using the freezing temperature of the sand mould, wherein the obtained frozen sand mould is used for casting melt, and judging whether the finished product of the finally obtained casting meets the requirement.
And S610, if yes, the sand mold freezing temperature meets the requirement.
Specifically, if the second casting temperature falls within the temperature range (T s-min ，T s-max ) And the sand mold freezing temperature obtained by reverse calculation is the practicable sand mold freezing temperature, the complete frozen sand mold casting process flow can be completed by using the sand mold freezing temperature, and the casting quality is ensured.
According to the technical scheme, the first pouring temperature is set through the temperature range in the pouring process, the sand mold freezing temperature is obtained through the reverse calculation by combining the production environment temperature, the obtained sand mold freezing temperature is more in accordance with the actual process flow, and whether the obtained sand mold freezing temperature meets the process requirement is verified through the forward heating calculation, so that the problem that the shape and the basic performance of the sand mold change when the frozen sand mold is taken out of a freezing bin and the quality of a casting is affected due to the fact that the sand mold freezing temperature of the frozen sand mold is set improperly is solved, the rapid prediction of the sand mold freezing temperature under any temperature condition is realized, the guiding effect is provided for the setting of the sand mold freezing temperature when the process is carried out by process personnel, the stability of the freezing process is guaranteed through the related prediction and optimization results, and the freezing temperature calculation method of the frozen sand mold can be suitable for the frozen sand mold with specific size, shape and material components, and the applicability of the temperature calculation method is improved.
Optionally, fig. 2 is a flowchart of a method for solving a cooling problem of a temperature field of a frozen sand mold according to an embodiment of the present invention, where the method shown in fig. 2 is one of embodiments in which step S400 shown in fig. 1 may be implemented, and as shown in fig. 2, the method includes:
s410, dispersing the three-dimensional model into a plurality of cells in three dimensions.
The discrete method comprises, but is not limited to, a finite difference method, a finite element analysis method or a finite volume analysis method, and special casting simulation software ProCast with secondary development function and settable boundary parameters can be adopted for calculation, so that the programming workload is reduced. In specific implementation, a mode of dispersing the three-dimensional model can be selected according to actual requirements, for example, programming is carried out on a sand mold temperature field equation through programming software such as C, C ++, matlab, python and the like, so that discretization iteration solution is realized; or using common simulation software such as multi-physical field simulation software Comsol and the like to carry out discrete solution. In the concrete implementation, the three-dimensional model of the sand mold can be imported through setting the physical field type and setting parameters, so that calculation is completed, a result can be observed, or special casting simulation software Procast can be used, the special casting simulation software Procast has a secondary development function, a user can independently develop the functions of boundary conditions, initial condition setting and the like, and the discrete solution of finite elements on the three-dimensional model is completed.
Specifically, in the process of transferring the sand mold to the pouring area after the sand mold is taken out of the warehouse from the freezing warehouse, as the sand mold has a certain size and shape, the temperature change of each position of the sand mold is different, so that the three-dimensional model is divided into a plurality of cells in three dimensions, when the freezing temperature of the sand mold is reversely calculated, the temperature field equation of the plurality of cells can be iteratively solved, the process of inconsistent temperature change of each position of the sand mold is simulated, and the reliability of the calculation result is higher.
S420, setting the thermophysical performance parameters of the unit cells.
The thermophysical performance parameters include, but are not limited to, density, specific heat capacity and thermal conductivity, and in specific implementation, the thermophysical performance parameters can be obtained through experimental measurement.
Specifically, because the sand mold has a certain shape and size, in the actual production process, the environments contacted by the cells are different, for example, the outer surfaces of the cells on the surface layer of the sand mold are directly contacted with the environment, the inner surfaces of the cells are contacted with the adjacent sand mold cells, the temperature reduction amplitude of the cells is different within the same time, and the temperature field equation of the cells can be accurately solved by setting the thermophysical performance parameters of the cells, so that the reliability of a prediction result is ensured.
S430, setting the first casting temperature as an initial condition of a plurality of cells, setting the production environment temperature as a boundary condition of a cell which is in contact with the production environment among the plurality of cells, and setting the first casting temperature as a boundary condition of the rest cells.
Wherein, the initial condition and the boundary condition are both variable parameters which can be input, and the boundary condition is a dynamic curve.
Specifically, in the actual production process, when the frozen sand mold is taken out of the warehouse from the freezing warehouse, the temperature values of a plurality of cells of the sand mold are approximately the same, after the frozen sand mold is transported to the casting area, as the frozen sand mold has a certain size and shape, the environmental temperatures at various positions of the sand mold are different, the temperature change at various positions of the frozen sand mold has a difference, and the initial conditions of the cells are all set to be the first casting temperature in consideration of the simplicity of the reverse calculation, it is understood that the initial conditions of the cells are all the first casting temperature, and the difference exists in the obtained results of the cells after the reverse calculation, namely the discrete iterative cooling solution, but the lower temperature value in the cells can be selected as the calculation result because the required temperature of the frozen casting is as lower than the standard temperature of the casting process as possible.
In the sand mold transferring process, because the environmental temperature contacted by the sand mold is different, for example, the cell contacted with the production environment has a heat transfer effect with the production environment, and the cell not contacted with the production environment is adjacent to the cell in which heat transfer occurs, the three-dimensional model of the sand mold is scattered into a plurality of cells, and related thermophysical performance parameters are set, the production environment temperature can be set as the boundary condition of the cell contacted with the production environment, the first casting temperature is set as the boundary condition of the other cells, and the reverse production process of transferring the sand mold from the freezing warehouse to the casting area is simulated.
S440, carrying out iterative solution on the temperature field equation of the discretized multiple cells at the next moment according to the process parameters, the initial conditions and the boundary conditions to obtain temperature change values of the multiple cells, and then reversely calculating to obtain temperature values of the multiple cells at the last moment.
Specifically, in the actual process, the temperature rising process of the sand mold during actual transfer can be simulated based on the temperature value of the cell at the current moment according to the process parameters, the initial conditions and the boundary conditions, the temperature change value of a time step is calculated, the reverse calculation is performed based on the temperature change value and the current temperature, namely, the temperature change value is taken as a cooling change value, the reverse cooling process of the sand mold is simulated, and the temperature value before the time step of the sand mold is obtained, so that the temperature change value can be obtained through the iterative calculation of the time step in the transfer time, the freezing temperature of the sand mold of a plurality of cells is further obtained through the forward temperature rising, and then the reverse temperature change of the sand mold in the production process is simulated, and the problem of large calculation result error caused by the cooling iteration based on the current temperature value is solved.
S450, obtaining the sand mold freezing temperatures of the multiple cells at the initial time of sand mold transfer according to continuous iteration on the time step.
Specifically, based on the multiple forward calculation temperature change values in step S440, the obtained temperature change values are further reversely cooled on the basis of the current temperature values, so as to obtain the sand mold freezing temperatures of the multiple cells, and further reversely simulate the sand mold transferring process.
S460, selecting the minimum value of the sand mold freezing temperatures as the sand mold freezing temperature of the three-dimensional model.
Specifically, since the temperature variation amplitude of the plurality of cells in the actual transportation process is different, in order to ensure the reliability of the determination result, the discretization solving result, that is, the lowest temperature in the sand mold freezing temperatures of the plurality of cells, can be selected as the sand mold freezing temperature of the whole sand mold.
In one embodiment, since there is a difference in the temperature value of the initial condition during iterative calculation of each time step, there is a difference in the temperature variation amplitude of each time step, so the cumulative iteration number n, n=t/dt can be calculated first according to the sand mold transfer time t and the time step dt, and the temperature variation value can be calculated step by step based on the time step dt and the iteration number. Next, the temperature value T [ i ] of the current time of the plurality of cells is obtained ] t0 In [ i ]]Represents any one of the cells and the temperature value is calculated as TI] t0 As an initial condition for calculating the sand mold freezing temperatures of the plurality of cells. Further, based on the time step dT, calculating the temperature change value of a plurality of cells of the three-dimensional model of the sand mold after one time step dT, namely, transferring one time step dT when simulating the actual transfer of the sand mold, wherein the temperature change values dT [ i ] of the plurality of cells] t0 dT [ i ] is a simulated temperature rise process] t0 Positive values. Further, according to the obtained temperature value T [ i ] of the plurality of cells at the current time T0] t0 Temperature change value dT [ i ]] t0 The temperature value T [ i ] before one time step dt of the cells, i.e., (T0-1 dt), is calculated in reverse] t0-1dt =T[i] t0 -dT[i] t0 . Further based on the current time (t 0-1 dT), a temperature change value dT [ i ] after a time step dT is calculated] t0-1dt And then reversely calculating to obtain the temperature value T [ i ] of the unit cell at the moment (T0-2 dt) after a time step dt] t0-2dt =T[i] t0-1dt -dT[i] t0-1dt . The iteration is continued in time steps, and the initial moment (T0-ndt) of sand mould transferring and the temperature value (Ti) of the unit cell are obtained] t0-ndt =T[i] t0-(n-1)dt -dT[i] t0-(n-1)dt . Thus, all temperature results of the multiple cells from t0 to (t 0-ndt) can be obtained, further iteration data can be obtained, and if the obtained sand mold freezing temperature does not meet the actual process The appropriate temperature can be selected as the sand mold freezing temperature based on the data of multiple iterations, such as the second pouring temperature T obtained during reverse verification based on the sand mold freezing temperature obtained by the current n-time iterative calculation pour2 The temperature value is too low, which is lower than the temperature range (T s-min ，T s-max ) Is the minimum value T of (2) s-min It can be known that in the reverse calculation process of sand mold freezing, if the iteration number is reduced, the sand mold freezing temperature with higher temperature value can be obtained, so that the temperature value obtained in the n-1 th time and the n-2 th time can be selected as the sand mold freezing temperature to carry out forward verification based on the iteration data recorded last time, and the higher second pouring temperature T can be obtained pour2 . For example, in another embodiment, if the second casting temperature T is obtained pour2 The temperature value is too high, which is higher than the temperature range (T s-min ，T s-max ) Maximum value T of (2) s-max The iteration can be continued on the basis of the current sand mold freezing temperature value, the temperature value results of n+1 times and n+2 times of iteration are obtained, and the forward verification is performed again, so that the lower second pouring temperature T can be obtained pour2 。
Optionally, fig. 3 is a flowchart of a temperature field heating solving method for a frozen sand mold provided by the embodiment of the present invention, where the method shown in fig. 3 is one of the embodiments that, in step S500 shown in fig. 1, according to a process parameter, a freezing temperature of the sand mold, and a production environment temperature, in a sand mold transfer time, discretizing a temperature field equation of a three-dimensional model is solved, and a second pouring temperature is obtained by forward calculation, and as shown in fig. 3, the method includes:
S510, dispersing the three-dimensional model into a plurality of cells in three dimensions.
Specifically, the specific implementation of step S510 in the embodiment of the present invention may refer to step S410 in the above embodiment.
S520, setting the thermophysical performance parameters of the unit cells.
Specifically, the specific implementation of step S520 in the embodiment of the present invention may refer to step S420 in the above embodiment.
S530, setting the sand mold freezing temperature as an initial condition of a plurality of cells, setting the production environment temperature as a boundary condition of a cell which is in contact with the production environment among the plurality of cells, and setting the sand mold freezing temperature as a boundary condition of the rest of cells.
Wherein, the initial condition and the boundary condition are both variable parameters which can be input, and the boundary condition is a dynamic curve.
Specifically, in the actual production process, when the frozen sand mold is taken out of the freezing warehouse, the temperature values of the plurality of cells of the sand mold are approximately the same, and therefore, the freezing temperature of the sand mold is set to be the initial condition of the plurality of cells, and the actual process of transferring the frozen sand mold to the pouring area after taking out of the freezing warehouse is simulated.
In the sand mold transferring process, because the environmental temperature contacted by the sand mold is different, for example, the cells contacted with the production environment have heat transfer effect with the production environment, and the cells not contacted with the production environment are adjacent sand mold cells for transferring heat with the production environment, the three-dimensional model of the sand mold is scattered into a plurality of cells, and related thermophysical performance parameters are set, the production environment temperature can be set as the boundary condition of the cells contacted with the production environment, the freezing temperature of the sand mold is set as the boundary condition of the other cells, and the actual production process of transferring the sand mold from the freezing warehouse to the pouring area is simulated.
S540, carrying out iterative solution on the temperature field equation of the discretized multiple cells at the next moment according to the process parameters, the initial conditions and the boundary conditions to obtain temperature change values of the multiple cells, and further carrying out forward calculation to obtain the temperature values of the multiple cells at the next moment.
Specifically, in the actual process, the temperature field equation of the multiple cells of the discretized sand mold can be solved iteratively according to the process parameters, the initial conditions and the boundary conditions, and specifically, the temperature values of the multiple cells can be obtained based on time step successive iterative calculation, so that the iterative time step is continued in the transfer time, and the temperature change of the sand mold in the production process is simulated.
S550, obtaining the sand mold freezing temperatures of the multiple cells at the initial moment of sand mold transfer according to continuous iteration on the time step.
Specifically, based on the multiple iterations of step S440, a second casting temperature of the multiple cells is obtained, thereby simulating the sand mold transfer process.
S550, selecting the maximum value of the plurality of second pouring temperatures as the second pouring temperature of the three-dimensional model.
Specifically, as the temperature variation amplitude of the multiple cells in the actual transferring process is different, in order to ensure the reliability of the judging result, the discretization solving result can be selected, namely, the highest temperature in the second pouring temperatures of the multiple cells is used as the temperature before pouring of the whole sand mold, and as the lower the pouring temperature of the sand mold is, the higher the stability of the sand mold is, the maximum value in the second pouring temperatures is used as the second pouring temperature of the three-dimensional model, namely, the temperature value of the cell with the highest temperature in the multiple cells of the three-dimensional model is used as the temperature value of the whole three-dimensional model, and if the cell with the highest temperature can meet the sand mold process requirement, the cells with lower rest temperatures can meet the process requirement.
Optionally, fig. 4 is a flowchart of another method for calculating a freezing temperature of a frozen sand mold according to an embodiment of the present invention, as shown in fig. 4, after determining whether the second casting temperature falls within a temperature range during sand casting in step S600, the method further includes:
and S620, if not, judging whether the second casting temperature is less than the minimum value of the temperature range during sand casting.
Specifically, if the second casting temperature does not fall within the temperature range (T s-min ，T s-max ) In the method, according to the change rule that the temperature of the frozen sand mold starts to rise when the frozen sand mold is taken out of the warehouse, whether the second pouring temperature is smaller than the temperature range (T) s-min ，T s-max ) Is the minimum value T of (2) s-min Further, it is determined whether the sand mold freezing temperature calculated by the freezing sand mold freezing temperature calculating method provided in the above-described embodiment satisfies the requirement.
S621, if yes, sequentially acquiring the minimum values of the temperatures of a plurality of cells after a plurality of time steps at the initial time of sand mold transfer as the sand mold freezing temperature of the three-dimensional model; and repeatedly calculating the second pouring temperature until the second pouring temperature falls into the temperature range of sand casting.
Specifically, if the second casting temperature calculated at present is smaller than the minimum value T of the temperature range during sand casting s-min If the value is adopted as the sand mold freezing temperature value in the actual process, the sand mold needs to be kept for a period of time after being transported to a pouring area, and the time value needs to be accurately calculated. It can be understood that in the cooling solving method of the frozen sand mold temperature field shown in fig. 2, the temperature values of the cells corresponding to a plurality of time steps after the initial time of transferring the sand mold are solved, and as the method shown in fig. 3 is based on the first pouring temperature for cooling treatment, a plurality of intermediate temperature values obtained in the solving process of the method shown in fig. 2 can be obtained, and are used as the freezing temperature of the sand mold, further used as the freezing temperature of the sand mold of the three-dimensional model, the process of transferring the sand mold from the freezing warehouse to the pouring area is repeatedly simulated, the temperature before pouring the sand mold, namely the second pouring temperature, is obtained, whether the temperature value meets the process requirement or not is judged, until the temperature value falls into the temperature range when the second pouring temperature falls into the sand mold pouring, and the freezing process guiding parameters of the frozen sand mold can be set according to the freezing temperature of the sand mold adopted in the operation process.
In one embodiment, the TI is finally obtained by the method shown in FIG. 2] t0-1dt 、T[i] t0-2dt 、T[i] t0-3dt 、……、T[i] t0-ndt The n temperature values are represented by Ti] t0-ndt When the forward simulated sand mold transfer calculation is carried out as the sand mold freezing temperature, the obtained second pouring temperature T pour2 The temperature value is too low, which is lower than the temperature range (T s-min ，T s-max ) Is the minimum value T of (2) s-min It can be seen that in the reverse calculation of sand mold freezing, if the iteration number is reduced, a sand mold cold with a higher temperature value can be obtainedThe freezing temperature, so that the temperature value Ti obtained in the n-1 th time can be selected based on the iteration data recorded last time] t0-(n-1)dt Temperature value Ti obtained n-2 times] t0-(n-2)dt Or selecting other values according to the actual values to be used as the sand mold freezing temperature for forward verification, thereby obtaining a higher second pouring temperature T pour2 。
Optionally, with continued reference to fig. 4, after determining in step S620 whether the second casting temperature is less than the minimum value of the temperature range during sand casting, the method further includes:
s622, if not, calculating the absolute value of the difference between the second pouring temperature and the maximum value of the temperature range during sand casting, calculating the increasing iteration number of the time step based on the temperature change value and the absolute value of the last moment of the sand mold transfer initial moment in the sand mold freezing temperature reverse calculation process, and carrying out reverse iteration solving on the current sand mold freezing temperature based on the increasing iteration number and the time step to obtain a plurality of sand mold freezing temperatures.
Specifically, if the second casting temperature is greater than the maximum value T of the temperature range during sand casting s-max It can be known that in the calculation process, the set initial condition, i.e., the freezing temperature of the sand mold is too high, which results in the process of simulating the transfer of the sand mold to the casting area, the obtained temperature before casting, i.e., the second casting temperature, is too high to ensure the performance of the sand mold, so that the initial condition of the calculation step, i.e., the freezing temperature of the sand mold, can be cooled, and when the calculation is implemented, the maximum value T of the current second casting temperature and the temperature range during casting of the sand mold can be calculated s-max And obtaining the absolute value of the difference value of the temperature change value of the sand mold at the moment immediately before the initial moment of sand mold transfer in the process of reversely calculating the sand mold freezing temperature in the previous step, further calculating the number of times of iteration on the basis of the current sand mold freezing temperature according to the temperature change value and the absolute value obtained by calculation, and obtaining the sand mold transfer temperature by dividing the absolute value by the temperature change value in the specific implementation.
S623, selecting the minimum value of the plurality of sand mold freezing temperatures as the sand mold freezing temperature of the three-dimensional model; and repeatedly calculating the second pouring temperature until the second pouring temperature falls into the temperature range of sand casting.
Specifically, the process of transferring the sand mold to the pouring area after the sand mold is taken out of the freezing warehouse is simulated again, the temperature before sand mold pouring, namely the second pouring temperature, is obtained, whether the temperature value meets the process requirement is judged, until the temperature value falls into the temperature range when the second pouring temperature falls into the sand mold pouring, and the freezing sand mold casting process guiding parameters can be set according to the sand mold freezing temperature adopted in the operation process.
In one embodiment, the temperature range (T s-min ，T s-max ) Setting the first casting temperature as Ti] t0 ，T s-min ＜T[i] t0 ＜T s-max Setting a first casting temperature Ti] t0 Setting the obtained production environment temperature as the boundary condition of the cells contacting with the production environment in the multiple cells for the initial condition of the multiple cells of the sand mold three-dimensional model, and setting the first casting temperature Ti] t0 Set as boundary conditions for the remaining cells. According to the technological parameters, initial conditions and boundary conditions, carrying out iterative solution on temperature field equations of a plurality of discretized cells, and based on a set first pouring temperature Ti] t0 Calculating a temperature increase change value dT [ i ] of a set specific time step dT at time t0] t0 And then based on the current temperature Ti] t0 Calculating the temperature value of the unit cell at the time t0-1dt according to the temperature rise change value, repeating the calculation steps, and calculating the temperature value of the unit cell at the time t of transferring s-move The internal time step length is accumulated with dt, and sand mold freezing temperature Ti of a plurality of cells is calculated] t0-ndt =T[i] t0-(n-1)dt -dT[i] t0-(n-1)dt Total time t s-move Let dt×n, n be the number of temperature iterations, and the total transit time t s-move The number of divisions over a time step dt. Based on the temperature reduction treatment in the total transfer time, the temperature distribution T of the sand mold is obtained s-fenbu The lowest temperature according to the temperature of each cell of the sand mold at the moment is set as the freezing temperature T of the sand mold s-initial （T s-initial =min(T s-fenbu ))。
For the sand mold freezing temperature T s-initial Forward simulation verification is carried out based on total transfer time, and the freezing temperature T of the frozen sand mold based on the sand mold obtained by the steps is calculated s-initial Whether the condition is satisfied. The specific implementation method is as follows: calculating to obtain a second pouring temperature T pour2 And T is equal to s-min、 T s-max A comparison is made.
If T s-min <=T pour2 <=T s-max Sand mold freezing temperature T s-initial Meets the requirements, otherwise does not.
Under the condition of unsatisfied, if T pour2 >T s-max The sand mold freezing temperature needs to be reduced, so that the current sand mold freezing temperature value T can be obtained s-initial The iteration is continued on the basis of the above steps, which can be specifically: first, the current second pouring temperature T is calculated pour2 Maximum T of temperature range during sand casting s-max Absolute value of difference of (T) pour2 -T s-max I, and obtaining a temperature change value dT [ i ] at the moment immediately before the initial moment of sand mold transfer ] t0-(n-1)dt Based on the temperature change value and the absolute value, calculating the increasing iteration number m= |T of the current sand mold freezing temperature pour2 -T s-max |÷dT[i] t0-(n-1)dt Further at the current sand mold freezing temperature T s-initial Based on the above, according to the reverse calculation method for solving the freezing temperature of the sand mold based on the first casting temperature, the freezing temperature of the sand mold with lower temperature is obtained, and the forward verification is performed again to obtain the second casting temperature, thereby obtaining the second casting temperature T with lower temperature pour2 . Acquisition of T s-min <=T pour2 <=T s-max Sand mold freezing temperature T at the time s-initial。
Based on the same conception, the technical solution of the embodiment of the present invention further provides a device for calculating a freezing temperature of a frozen sand mold, and fig. 5 is a schematic structural diagram of the device for calculating a freezing temperature of a frozen sand mold according to the embodiment of the present invention, as shown in fig. 5, where the device includes:
the sand mold parameter acquisition module 10 is used for acquiring the technological parameters of the sand mold, the sand mold transfer time and the production environment temperature; the process parameters include the temperature range during sand casting.
The sand mold three-dimensional model calculation module 20 is used for establishing a three-dimensional model of a sand mold.
The sand mold freezing temperature calculation module 30 is used for setting a time step of cooling calculation according to the sand mold transfer time; setting a first casting temperature according to the temperature range during sand casting; and the method is also used for discretizing and solving a temperature field equation of the three-dimensional model in the sand mold transferring time according to the technological parameters, the first pouring temperature and the production environment temperature, and reversely calculating to obtain the sand mold freezing temperature.
The sand casting temperature calculation module 40 is configured to perform discretization solution on a temperature field equation of the three-dimensional model in a sand transportation time according to the process parameter, the freezing temperature of the sand and the production environment temperature, and calculate forward to obtain a second casting temperature.
Optionally, the sand mold parameter obtaining module 10 is further configured to obtain a production environment temperature curve by fitting according to historical temperature measurement data of a workshop environment of the sand mold.
Optionally, the sand mold parameter obtaining module 10 is further configured to determine a transfer parameter of the sand mold, and select a common sand mold according to the transfer parameter; and obtaining sand mold transfer time through the ordinary sand mold simulation drilling transfer process.
Optionally, the sand mold freezing temperature calculation module 30 is further configured to discrete the three-dimensional model into a plurality of cells in three dimensions; setting the thermophysical performance parameters of the cells; setting a first casting temperature as an initial condition of a plurality of cells, setting a production environment temperature as a boundary condition of cells in the plurality of cells, which are in contact with the production environment, and setting the first casting temperature as a boundary condition of the remaining cells; and carrying out iterative solution on the temperature field equation of the discretized multiple cells at the next moment according to the process parameters, the initial conditions and the boundary conditions to obtain temperature change values of the multiple cells, and further carrying out reverse calculation to obtain temperature values of the multiple cells at the last moment. And according to continuous iteration on the time step, obtaining sand mold freezing temperatures of a plurality of cells at the initial moment of sand mold transfer, and selecting the minimum value of the sand mold freezing temperatures as the sand mold freezing temperature of the three-dimensional model.
Optionally, the sand mold freezing temperature calculation module 30 is further configured to discretize the three-dimensional model to form three-dimensional cells by using a finite difference method, a finite element analysis method or a finite volume analysis method.
Optionally, the sand mold freezing temperature calculation module 30 is further configured to perform iterative cooling solution on the temperature field equations of the discretized multiple cells according to the process parameters, the initial conditions and the boundary conditions by using one of Python, matlab, comsol, C, C ++ and Procast.
Optionally, the sand casting temperature calculating module 40 is further configured to disperse the three-dimensional model into a plurality of cells in three dimensions; setting the thermophysical performance parameters of the cells; setting the sand mold freezing temperature as an initial condition of a plurality of cells, setting the production environment temperature as a boundary condition of a cell which is in contact with the production environment among the plurality of cells, and setting the sand mold freezing temperature as a boundary condition of the rest cells; according to the technological parameters, the initial conditions and the boundary conditions, carrying out iterative solution on the temperature field equation of the discretized multiple cells at the next moment to obtain temperature change values of the multiple cells, and further carrying out forward calculation to obtain the temperature values of the multiple cells at the next moment of the multiple cells; obtaining second pouring temperatures of a plurality of cells at the final moment of sand mold transfer according to continuous iteration on the time step; and selecting the maximum value of the plurality of second pouring temperatures as the second pouring temperature of the three-dimensional model.
Optionally, fig. 6 is a schematic diagram of another apparatus for calculating a freezing temperature of a frozen sand mold according to an embodiment of the present invention, as shown in fig. 6, where the apparatus further includes a sand mold casting temperature determining module 50, where the sand mold casting temperature determining module 50 is configured to determine whether the second casting temperature falls within a temperature range during sand mold casting; if yes, judging that the freezing temperature of the sand mold meets the requirement.
Optionally, the sand casting temperature judging module 50 is further configured to further judge whether the second casting temperature is less than a minimum value of a temperature range during sand casting if the second casting temperature does not fall within the temperature range during sand casting; if so, the sand mold freezing temperature calculation module 30 sequentially obtains the minimum values of the temperatures of a plurality of cells after a plurality of time steps at the initial time of sand mold transfer as the sand mold freezing temperature of the three-dimensional model. The sand casting temperature calculation module 40 repeatedly calculates the second casting temperature until the second casting temperature falls within the temperature range at the time of sand casting.
Optionally, the sand casting temperature judging module 50 is further configured to, if it is determined that the second casting temperature is not less than the minimum value of the temperature range during sand casting and does not fall within the temperature range during sand casting, calculate an absolute value of a difference between the second casting temperature and the maximum value of the temperature range during sand casting, calculate an increase iteration number of a time step based on a temperature change value and the absolute value of a last time of an initial time of sand transportation in a sand freezing temperature reverse calculation process by the sand freezing temperature calculating module 30, and perform a reverse iteration solution on a current sand freezing temperature based on the increase iteration number and the time step, obtain a plurality of sand freezing temperatures, and select the minimum value of the plurality of sand freezing temperatures as the sand freezing temperature of the three-dimensional model; the sand casting temperature calculation module 50 repeatedly calculates the second casting temperature until the second casting temperature falls within the temperature range at the time of sand casting.
The frozen temperature calculating device for the frozen sand mold provided by the embodiment of the invention can execute the frozen temperature calculating method for the frozen sand mold provided by any embodiment of the invention, and has the corresponding functional modules and beneficial effects of the executing method.
It should be appreciated that various forms of the flows shown above may be used to reorder, add, or delete steps. For example, the steps described in the present invention may be performed in parallel, sequentially, or in a different order, so long as the desired results of the technical solution of the present invention are achieved, and the present invention is not limited herein.
The above embodiments do not limit the scope of the present invention. It will be apparent to those skilled in the art that various modifications, combinations, sub-combinations and alternatives are possible, depending on design requirements and other factors. Any modifications, equivalent freezing and improvements made within the spirit and principles of the present invention should be included within the scope of the present invention.

Claims (10)

1. The method for calculating the freezing temperature of the frozen sand mold is characterized by comprising the following steps of:
determining technological parameters according to a sand mold process, and obtaining sand mold transfer time and production environment temperature; the technological parameters comprise a temperature range during sand casting;
According to the sand mold process, a three-dimensional model of a sand mold is established;
setting a time step according to the sand mold transferring time; setting a first casting temperature according to the temperature range during casting of the sand mould;
according to the technological parameters, the first pouring temperature and the production environment temperature, discretizing and solving a temperature field equation of the three-dimensional model in the sand mold transferring time, and reversely calculating to obtain a sand mold freezing temperature;
according to the technological parameters, the sand mold freezing temperature and the production environment temperature, discretizing and solving a temperature field equation of the three-dimensional model in the sand mold transferring time, and carrying out forward calculation to obtain a second pouring temperature;
judging whether the second casting temperature falls within a temperature range of the sand casting;
if yes, the freezing temperature of the sand mold meets the requirement.
2. The method according to claim 1, wherein the discretizing the temperature field equation of the three-dimensional model in the sand mold transfer time according to the process parameter, the first casting temperature and the production environment temperature, and performing inverse calculation to obtain a sand mold freezing temperature comprises:
Dispersing the three-dimensional model into a plurality of cells in three dimensions;
setting the thermophysical performance parameters of the unit cells;
setting the first casting temperature as an initial condition of a plurality of the cells, setting the production environment temperature as a boundary condition of the cell which is in contact with the production environment among the plurality of the cells, and setting the first casting temperature as a boundary condition of the rest of the cells;
according to the technological parameters, the initial conditions and the boundary conditions, carrying out iterative solution on the temperature field equation of the discretized cells at the next moment to obtain temperature change values of the cells, and further reversely calculating to obtain temperature values of the cells at the last moment;
obtaining the sand mold freezing temperatures of a plurality of unit cells at the initial moment of sand mold transfer according to continuous iteration on the time step;
and selecting the minimum value of the sand mold freezing temperatures as the sand mold freezing temperature of the three-dimensional model.
3. The method according to claim 1, wherein the discretizing the temperature field equation of the three-dimensional model in the sand mold transfer time according to the process parameter, the sand mold freezing temperature and the production environment temperature, and the forward calculating to obtain the second casting temperature comprises:
Dispersing the three-dimensional model into a plurality of cells in three dimensions;
setting the thermophysical performance parameters of the unit cells;
setting the sand mold freezing temperature as an initial condition of a plurality of the cells, setting the production environment temperature as a boundary condition of the cell contacting with the production environment among the plurality of the cells, and setting the sand mold freezing temperature as a boundary condition of the rest of the cells;
according to the technological parameters, the initial conditions and the boundary conditions, carrying out iterative solution on the temperature field equation of the discretized cells at the next moment to obtain temperature change values of the cells, and further carrying out forward calculation to obtain temperature values of the cells at the next moment of the cells;
obtaining the second pouring temperatures of a plurality of the unit cells at the final moment of sand mold transfer according to continuous iteration on the time step;
and selecting the maximum value of the plurality of second pouring temperatures as the second pouring temperature of the three-dimensional model.
4. The method according to claim 2, characterized by further comprising, after determining whether the second casting temperature falls within a temperature range at the time of casting of the sand mold;
If not, judging whether the second casting temperature is smaller than the minimum value of the temperature range during sand casting;
if yes, sequentially acquiring the minimum values of the temperatures of a plurality of cells after a plurality of time steps at the initial time of sand mold transfer as the sand mold freezing temperature of the three-dimensional model; and repeatedly calculating the second pouring temperature until the second pouring temperature falls into the temperature range when the sand mould is poured.
5. The method according to claim 4, further comprising, after said determining whether said second casting temperature is less than a minimum value of a temperature range at the time of casting said sand mold:
if not, calculating the absolute value of the difference between the second pouring temperature and the maximum value of the temperature range during sand casting, calculating the increasing iteration number of the time step based on the temperature change value and the absolute value of the last moment of the sand mould transferring initial moment in the reverse calculation process of the sand mould freezing temperature, carrying out reverse iteration solution on the current sand mould freezing temperature based on the increasing iteration number and the time step to obtain a plurality of sand mould freezing temperatures, and selecting the minimum values of the sand mould freezing temperatures as the sand mould freezing temperatures of the three-dimensional model; and repeatedly calculating the second pouring temperature until the second pouring temperature falls into the temperature range when the sand mould is poured.
6. A method of calculating a freezing temperature of a frozen sand mold according to any one of claims 2 or 3, wherein the dispersing the three-dimensional model into a plurality of cells in three dimensions comprises:
and discretizing the three-dimensional model by using a finite difference method, a finite element analysis method or a finite volume analysis method to form three-dimensional unit cells.
7. A method of calculating a freezing temperature of a frozen sand mold according to any one of claims 2 or 3, wherein iteratively solving the discretized temperature field equations of the plurality of cells according to the process parameters, the initial conditions, and the boundary conditions, to obtain a plurality of freezing temperatures of the sand mold of the plurality of cells comprises: and iteratively solving a discretized temperature field equation of a plurality of cells according to the process parameters, the initial conditions and the boundary conditions by using one of Python, matlab, comsol, C, C ++ and Procast.
8. The method of claim 1, wherein the obtaining the production environment temperature comprises:
and fitting according to the workshop environment historical temperature measurement data of the sand mould to obtain a production environment temperature curve.
9. The method of claim 1, wherein the obtaining the sand mold transfer time comprises:
determining transfer parameters of the sand mold, and selecting a common sand mold according to the transfer parameters;
and simulating the drilling transportation process through the common sand mould to obtain the sand mould transportation time.
10. A frozen sand mold freezing temperature calculating device, characterized by comprising:
the sand mold parameter acquisition module is used for acquiring the technological parameters of the sand mold, the sand mold transfer time and the production environment temperature; the technological parameters comprise a temperature range during sand casting;
the sand mould three-dimensional model calculation module is used for establishing a three-dimensional model of the sand mould;
the sand mold freezing temperature calculation module is used for setting a time step of cooling calculation according to the sand mold transfer time; setting a first casting temperature according to the temperature range during casting of the sand mould; the temperature field equation of the three-dimensional model is discretized and solved in the sand mold transfer time according to the technological parameters, the first pouring temperature and the production environment temperature, and the temperature of the sand mold is obtained by reverse calculation;
and the sand casting temperature calculation module is used for discretizing and solving a temperature field equation of the three-dimensional model in the sand transportation time according to the technological parameters, the sand freezing temperature and the production environment temperature, and calculating forward to obtain a second casting temperature.
CN202311160923.9A 2023-09-11 2023-09-11 Method and device for calculating freezing temperature of frozen sand mold Active CN116913438B (en)

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