JP5200402B2 - Laser welding apparatus and laser welding method - Google Patents

Description

  The present invention relates to a laser welding apparatus and a laser welding method.

There is known a vehicle body frame structure that can easily set a compression load at the time of a collision in a wide area, increase a collision energy absorption amount per weight, and generate a stable compression load (for example, Patent Document 1). Specifically, two plate members bent into a V-shaped cross-sectional shape are joined by connecting the bent portions to each other to form a plate-shaped middle rib portion that becomes a square diagonal line, and by four outer peripheral plate members A square outer shape is formed, and the vicinity of the corners of the outer peripheral plate member and the plate-shaped middle rib portion are connected via a connecting plate member, and are joined by laser welding to form a frame of a hollow member. The distance between the connection point between the connecting plate and the outer peripheral plate and the corner (vertex) can be shortened, and the rigidity of the corner can be increased. The buckling wavelength representing the height in the waveform becomes small, and stable collision energy absorption with little load fluctuation at the time of buckling becomes possible.
JP 2003-220975 A

  By the way, in the technique disclosed in Patent Document 1, in order to increase the rigidity of the corner portion, between the vicinity of the corner portion of the outer peripheral plate material and the plate-shaped middle rib portion so as to be strong against buckling at the time of compressive deformation in the corner portion. Are connected via a connecting plate, and are joined by laser welding to form a frame of a hollow member. However, there is still room for improvement in terms of manufacturing a welded structural member with improved compressive strength that has improved the joint strength of the joint by laser welding. The present invention has been made in view of the above-described circumstances, and an object of the present invention is to manufacture a welded structural member having a strong compressive strength based on support of experimental data.

In order to solve the above-mentioned problems, in the laser welding apparatus according to the present invention, as a first means, in the laser welding apparatus constituting the welding robot, it was supported by experiments on at least material, heat input, target position, and beam profile. A database that stores shape sample data obtained by patterning sample images of the cross-sectional shape that is the penetration target, and compression strength characteristics for values obtained by dividing the sum of the weld metal cross-sectional area and heat-affected zone cross-sectional area by the square of the plate thickness database and, by controlling the reference to penetration properties the read shape-sample data and / or compressive yield strength properties from the database, control to the minimum necessary area and / or the penetration depth penetration relative to the plate thickness of the workpiece to be welded The department was adopted. In this way, since the residual stress is minimized by minimizing the cross-sectional area of the heat affected zone by supporting the experimental data, it is possible to improve the compressive yield strength of the welded member.

According to the laser welding apparatus according to the first means, the control unit controls the penetration properties with reference to the shape sample data and the compression strength characteristics read from the database. Therefore, the control data on the material, heat input, target position, beam profile read from the database, and the compressive strength characteristics data for the value obtained by dividing the sum of the weld metal cross-sectional area and the heat-affected zone cross-sectional area by the square of the plate thickness, Using automatic welding, automatic welding is performed to approach the target penetration shape.

As a second means, in the laser welding apparatus according to the first means, the control unit measures the three-dimensional photograph measuring means for measuring the dimension of the member to be welded before welding, and the three-dimensional photograph measuring means. Search means for searching the shape sample data close to the welded member of the specified size from the database for reference, management items for managing the penetration area of the welded member to the minimum necessary, and penetration depth are required Management items that are managed to a minimum are adopted.

According to the laser welding apparatus according to the second means, first, the search means searches the database for shape sample data close to the dimension of the member to be welded measured by the three-dimensional photograph measurement means, and controls the control unit. Provide items. The control unit refers to the shape sample data close to the dimension of the member to be welded, and management items for managing the penetration area of the welded member to the minimum necessary and management items for managing the penetration depth to the minimum necessary. And the welding robot is controlled using the control data of the database.
By doing so, it becomes possible to manufacture a welded structural member that is faithful to the experimental data and has a stronger compressive strength.

As a third means, in the laser welding apparatus according to the first or second means, the control unit includes at least a laser output, a welding speed, a defocus distance, and a shielding gas as laser welding conditions. Controllable control items including the type and the flow rate of the shielding gas were adopted. By doing so, it becomes possible to manufacture a welded structural member having a compression strength more reliably.

As a fourth means, in a laser welding method using a welding robot , a welded member having a penetration property that minimizes a value obtained by dividing the sum of the weld metal cross-sectional area and the heat-affected zone cross-sectional area by the square of the plate thickness is provided. A method of manufacturing a welded structural member in which the penetration area and / or the penetration depth with respect to the plate thickness of the steel sheet is minimized is adopted. According to this method, since the welding deformation and / or the residual stress is minimized, it is possible to improve the compression strength of the member to be welded. Moreover, according to this method, it becomes possible to improve the compression yield strength of a to-be-welded member reliably based on experiment support.

  According to the laser welding apparatus according to the present invention, it is possible to manufacture a welded structural member having a strong compressive strength while minimizing the residual stress on the basis of experimental data.

  Embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described below with reference to the drawings. First, FIG. 1 is a flowchart showing a procedure of a compressive strength improvement construction by a laser welding apparatus (hereinafter also referred to as “this apparatus”) E according to the present embodiment.

  Since the laser welding apparatus shown in FIG. 1 constitutes a welding robot, this apparatus E is also referred to as a welding robot as appropriate. Production of a welded structural member (hereinafter, also referred to as “welded member”, “welded member”, or “member”) is started by the welding robot. The production here means mass production of welded structural members having the same shape as standard products in lot units.

  First, referring to the data read from the databases DB1 and DB2, the heat input range is controlled by the control unit 10 of the welding robot so as to minimize welding deformation and / or residual stress (S1). This control unit 10 has controllable control items including at least laser output, welding speed, defocusing distance, shield gas type, and shield gas flow rate as laser welding conditions. . The database DB1 stores shape sample data used as a sample for controlling the melt properties. This shape sample data is supported by experiments on at least the material, heat input, target position, and beam profile of the member.

  In other words, based on the experimental design method, the cross-sectional photographs of the sample in the welding experiment in which each parameter is changed are easily standardized and compiled. As will be described later with reference to FIG. 2, a large number of cross-sectional photographs relating to the cross-sectional shape that is a fusion target are used as basic data, these cross-sectional photographs are converted into standard line drawings, the dimensions of each part are entered, and search codes are entered. Shape sample data is stored in a pattern that can be searched for by attaching it.

In addition, the database DB2, as described below along Fig. 3, the weld metal cross sectional area A _{W. It} stores a compression strength (Ultimate strength) characteristic “also called (ultimate strength characteristic)” for a value obtained by dividing the sum of _M and the heat-affected zone sectional area A _HAZ by the square of the plate thickness t. The controller 10 of the welding robot controls the penetration properties with reference to the shape sample data and the compression strength characteristics read from the databases DB1 and DB2. As a result, a welded structure member having a penetration property that minimizes the sum (hereinafter also referred to as “penetration area”) A of the weld metal cross-sectional area _AWM and the heat-affected _zone cross-sectional area _AHAZ with respect to the plate thickness t of the welded member. Can be manufactured by the apparatus E. In FIG. 1, there is a place where “heat-affected zone” is abbreviated as “HAZ”.

  And construction management is performed so as to confirm the heat input area (S2). Specifically, the corresponding part after welding is cut, and a three-dimensional photograph is measured and collated with a standard specification. This standard specification may be used by extracting a numerical value relating to the heat input area from the shape sample data.

  The control unit 10 includes a three-dimensional photo measurement unit 11 (not shown), a search unit 12 that searches for shape sample data, and a collation unit that compares a three-dimensional photo measurement result with respect to the shape sample data. The control unit 10 retrieves shape sample data and the like from the databases DB1 and DB2 for reference (S3). That is, whether the dimensions of each part of the member to be welded before and after welding are searched from the databases DB1 and DB2 for the shape sample data close to the member to be welded having the dimensions measured by the three-dimensional photograph measuring means 11, and is within the specified range. Judgment on quality control of lots is supported depending on whether or not (S3).

  Then, the construction management is performed so that the sample accuracy (initial shape) is confirmed by performing a destructive inspection on the sample extracted from one mass-produced lot based on a statistical method (S4). That is, as a result of the destructive inspection by sampling, if it is within a predetermined error range with respect to the dimensional accuracy indicated by the shape sample data, the total number of one lot is accepted (OK) and is sorted for use as a high strength member (S5). . On the other hand, if the result of the sampling inspection is outside the predetermined error range, the entire number of one lot is rejected (NG), and sorting is performed so that the members are used within the normal design proof stress range (S6).

  Since it is impossible to commercialize the sample subjected to the destructive inspection here, for the commercial purpose, the total number of one lot is estimated by performing a sampling inspection instead of performing the destructive inspection. That is, since one lot that is mass-produced under predetermined management can be regarded as being manufactured with almost uniform quality within a certain range of variation, a destructive inspection is performed by sampling from one lot based on a statistical method. According to the result of the sampling inspection, products are rated and determined for each lot, so that rational product sorting without waste is possible. The data such as the standard deviation σ, which means the degree of variation, is retrieved from the databases DB1 and DB2 by referring to data compiled based on samples obtained by destructively inspecting the total number of lots for research purposes.

In this way, in the laser welding apparatus in which the production line is constituted by a welding robot, the control of the penetration property that minimizes the sum A of the weld metal cross-sectional area _AWM and the heat-affected _zone cross-sectional area _AHAZ with respect to the plate thickness t of the welded member. Part 10 was adopted. That is, since the welding deformation and / or residual stress is minimized by minimizing the penetration area A by such control, the compressive strength of the member to be welded (hereinafter abbreviated as “member strength” in the drawings). It is possible to improve. This is based on experimental data support.

That is, the control unit 10 employs the management item 13 for managing the penetration area A = A _WM + A _HAZ of the member to be welded to the minimum necessary and the management item 13 for managing the penetration depth δ to the minimum necessary. ing. As is apparent from FIG. 2A, the relationship between the penetration area A and the penetration depth δ, which are these two management items 13, is that only one management item 13 is managed or the other or both are managed. As a result that is comparable to the above, it is possible to manage only those who are easy to manage.

  As described above, the control unit 10 controls the penetration properties with reference to the shape sample data and the compression strength characteristics read from the databases DB1 and DB2. As a result, the present apparatus E can manufacture a welded structure member having a penetration property that minimizes the penetration area A with respect to the plate thickness t of the member to be welded. By doing so, it becomes possible to manufacture a welded structural member that is faithful to the experimental data and has a stronger compressive strength.

  FIG. 2 is information stored in the database DB1 of the laser welding apparatus according to the present embodiment, and is (a) a penetration property definition diagram of a welding member and (b) a compression strength characteristic diagram. As shown in Fig. 2 (a), as a penetration property specification diagram for welded members, in addition to the depth of penetration (δ), the dimensions of the heat affected zone (Upper Fillet size, Lower Fillet size) are normalized. Or, by standardizing, the search is easily defined and the information search is facilitated.

  Specifically, the image information, which is a cross-sectional photograph of a number of samples subjected to welding experiments based on the experimental design method, is converted into a numerical pattern consisting of a line drawing pattern and a specified dimension, and is compiled and retrievable as shape sample data in the database DB1. Is remembered. When searching for information, for example, in addition to the penetration depth δ, it is possible to search for the most suitable shape sample data using, as a search key, the dimensions of each part of the heat affected zone HAZ or the numerical value of the plate thickness t.

In addition, as shown in the compression strength characteristic diagram of FIG. 2B, the vertical axis of the compression strength characteristic diagram is the compression strength (F _max / F _Y ), and the horizontal axis is the heat input range rate = (A _W.M + A _HAZ ) / t ² , for example, if the plate thickness is the same, the database DB2 is constructed from experimental data and / or theoretical calculation values, etc., that the compression yield strength increases as the width-thickness ratio parameter R decreases. . When the width-thickness ratio parameter R = 0, it means that welding has not been performed. Therefore, the necessary minimum is controlled to the target value without setting the heat input range rate = 0.

Although FIG. 2B shows a graph of a compression strength characteristic diagram, there is a display method for convenience of explanation, and the control data in this apparatus E is a graph that is not necessarily visually and easy to obtain intuitive understanding. It is not necessary that the data corresponding to the numerical value, that is, the numerical value table is configured in the databases DB1 and DB2.
_{AW. M} : weld metal cross section A _HAZ : heat affected zone cross section t: plate thickness

The plots α and β plotted on the compression strength characteristic graph of FIG. 2B are as follows.
Plot α: LBW laser welded structural member.
Plot β: GMAW Conventional welded structural member.
That is, if the plate thickness is the same, the plot α by the laser welded structural member LBW has a smaller heat input range rate, so that the compressive yield strength is larger than the plot β by the conventional welded structural member GMAW. Yes.

FIG. 3 is a compression proof stress characteristic diagram by the laser welding apparatus according to the present embodiment. As shown in FIG. 3, the vertical axis of the compressive strength characteristic diagram is the compressive strength (F _max / F _Y ), the horizontal axis is the representative value (R) of the width-thickness ratio parameter, and the theoretical value of Euler buckling strength and , The classification society strength curve and the Japan Road Association strength curve are superimposed.

In this compression strength characteristic diagram, the following experimental data are shown in plots 1 to 4. These are experimental results in which the same member manufactured a welded structure member by changing only the differences of the plots 1 to 4 shown below. Plots 1 and 2 are data obtained by a plate member having a thickness 1.5 times that of plots 3 and 4.
Plot 1: ○ Improved laser welding structural member Plot 2: ● Arc welding structural member Plot 3: △ Conventional welding structural member Plot 4: ▲ Arc welding structural member

  Thus, according to the laser welding apparatus according to the present invention, as shown in plot 1, it was confirmed that the compressive yield strength was improved to near the limit indicated by the theoretical Euler buckling strength. As described above, according to the laser welding apparatus according to the present invention based on the support of the experimental data, it is possible to manufacture a welded structural member having a strong compressive strength while minimizing the residual stress.

In other words, the control unit 10 of the welding robot adopting the management item 13 for managing the penetration area of the member to be welded to the minimum necessary and the management item 13 for managing the penetration depth δ to the minimum is the database. The penetration properties are controlled with reference to the shape sample data and compression strength characteristics read from DB1 and DB2. As a result, the present apparatus E has a weld metal cross-sectional area _AW. It becomes possible to manufacture a welded structural member having a penetration property that minimizes _M and the heat-affected zone cross-sectional area A _HAZ . By doing so, it becomes possible to manufacture a welded structural member that is faithful to the experimental data and has a stronger compressive strength.

FIG. 4 is a characteristic diagram of the residual stress (σ _R / σ _Y ) with respect to the heat input parameter (Q / t ² ) [J / mm ² ] by the laser welding apparatus E according to the present embodiment. The residual stress is a stress that remains in the base metal and the metal that is the welded portion because the metal melted by welding solidifies while shrinking. That is, the stress that is pulled by the base metal remains in the welded portion, while the stress that tries to shrink against the stress that is pulled by the welded portion remains in the base material.

FIG. 5 is a characteristic diagram of the maximum proof stress (F _max / F _Y ) against the residual stress (σ _R / σ _Y ) by the laser welding apparatus E according to the present embodiment. In FIG. 3, the maximum proof stress (F _max / F _Y ) is not referred to but the compressive proof stress (F _max / F _Y ).

  FIG. 6 is a conceptual diagram of a laser welding apparatus E according to this embodiment. As shown in FIG. 6, the laser welding apparatus E according to the present embodiment mainly constitutes a welding robot F for mass production. The control unit 10 of the welding robot F manages the penetration properties so as to minimize the penetration area A and / or the penetration depth δ with respect to the plate thickness t of the member to be welded. The control unit 10 includes three-dimensional photograph measuring means 11 for measuring the dimension of the member to be welded before welding, and shape sample data close to the member to be welded having the dimension measured by the three-dimensional photograph measuring means 11 in the databases DB1 and DB2. And a search item 12 for searching and providing for reference, a management item 13 for managing the penetration area A of the welded member to the minimum necessary, and a management item 13 for managing the penetration depth to the minimum necessary. Configured.

As described above, the present apparatus E is a laser welding apparatus E that constitutes a production line or the like with the welding robot R, and has a weld metal cross-sectional area A _{W. For M} and the heat-affected zone cross-sectional area A _HAZ , the control unit 10 that minimizes the “penetration property” defined by the following equation is employed.
Heat input ratio = (A _W.M + A _HAZ ) / t ²
This control unit 10 has a weld metal cross-sectional area _AW. By managing the sum A of _M and the heat-affected zone cross-sectional area A _{HAZ to} the minimum necessary, it becomes possible to minimize the welding stress and / or the residual stress and improve the compressive strength of the welded structural member. This is based on experimental data support.
This point is the essence of the present invention, and any laser welding apparatus and / or welding method including various robots, automation equipment, and control devices for realizing this technical idea can be regarded as being included in the present invention.

It is a flowchart which shows the procedure of the compressive strength improvement construction by the laser welding apparatus which concerns on embodiment (this embodiment) of this invention. It is the information memorize | stored in the database of the laser welding apparatus which concerns on this embodiment, Comprising: (a) The penetration characteristic definition figure of a welding member, (b) Compression strength characteristic figure. It is a compressive proof stress characteristic view by the laser welding apparatus concerning this embodiment. It is a characteristic view of the residual stress with respect to the heat input parameter by the laser welding apparatus which concerns on this embodiment. It is a characteristic figure of the maximum proof stress with respect to the residual stress by the laser welding apparatus concerning this embodiment. It is a conceptual diagram of the laser welding apparatus which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Control part 11 ... Three-dimensional photograph measurement means 12 ... Search means 14 ... Control item A ... Penetration area DB1, DB2 ... Database E ... Laser welding apparatus (this apparatus)
F ... Welding robot t ... Plate thickness δ ... Penetration depth

Claims (4)

In the laser welding apparatus constituting the welding robot,
A database storing shape sample data obtained by patterning a sample image of a cross-sectional shape to be a penetration target supported by experiments on at least material, heat input, target position, and beam profile;
A database storing compression strength characteristics for a value obtained by dividing the sum of the weld metal cross-sectional area and heat-affected zone cross-sectional area by the square of the plate thickness;
A control unit that minimizes the penetration area and / or the penetration depth with respect to the plate thickness of the member to be welded by controlling the penetration properties with reference to the shape sample data and / or compression strength characteristics read from the database ;
Laser welding apparatus comprising the. In the control unit,
  3D photo measurement means for measuring the dimensions of the welded member before welding;
  Search means for searching the shape sample data close to the member to be welded of the dimensions measured by the three-dimensional photo measuring means from the database for reference,
  Management items for managing the penetration area of the welded member to the minimum necessary,
  The laser welding apparatus according to claim 1, further comprising: a management item for managing the penetration depth to a minimum necessary. The control unit was provided with controllable control items including at least laser output, welding speed, defocus distance, shield gas type, and shield gas flow rate as laser welding conditions. The laser welding apparatus according to claim 1 or 2, wherein In the laser welding method by the welding robot,
  The penetration area and / or penetration depth for the plate thickness of the member to be welded is required by using the penetration property that minimizes the sum of the weld metal cross-sectional area and heat-affected zone cross-sectional area divided by the square of the plate thickness. A laser welding method for manufacturing a welded structural member that is minimized.

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