TWI834515B - Method for casting metal casting - Google Patents

Abstract

The present invention relates to a method for casting a metal casting. A cooling procedure in a bottom-up approach is performed on a low-temperature expansive metal material with a specific composition and a high purity by using a module containing cooling rings in the method for casting the metal casting, such that the low-temperature expansive metal material is directionally solidified, thereby obtaining a defect-free metal casting.

Description

Casting methods of metal castings

The present invention relates to a method for casting metal castings, and in particular to a method for casting metal castings using a low-temperature expanded metal material having a specific composition and high purity.

The conventional casting method of low-temperature expansion metal castings is to add seed crystals to the molten low-temperature expansion metal material, so as to use the seeds to promote the crystal growth of the molten low-temperature expansion metal material to form metal castings, thereby reducing defects of the metal castings.

However, the aforementioned seed crystal contains other metals besides low-temperature expansion metal, which reduces the purity of the cast metal casting. Therefore, the conventional method is not suitable for manufacturing metal castings with high purity requirements (such as purity greater than 99 weight percent). In view of this, there is an urgent need to develop a new casting method for metal castings to improve the above shortcomings.

In view of the above problems, one aspect of the present invention provides a method for casting metal castings. This casting method performs a bottom-up cooling step on a low-temperature expanded metal material with a specific composition and high purity to achieve directional solidification, thereby obtaining defect-free metal castings.

According to an aspect of the present invention, a method for casting metal castings is provided. In the casting method of metal castings, a low-temperature expansion metal material is first provided. The low-temperature expansion metal material is selected from the group consisting of antimony, bismuth, gallium, bronze and their alloys, and the purity of the low-temperature expansion metal material is Greater than 99 weight percent. Next, the low-temperature-expanded metal material is melted to a molten state, wherein the temperature of the low-temperature-expanded metal material is raised to above the melting temperature of the low-temperature expanded metal material. Then, the molten low-temperature expanded metal material is poured into the mold. This mold includes a cylinder, multiple cooling rings and temperature control components. The cylinder has a peripheral wall, a mold cavity, a bottom surface and an opening, and the melting point of the cylinder is higher than the current temperature of the low-temperature expanded metal material in the molten state. These cooling rings are embedded in the peripheral wall and surround the mold cavity, wherein the ring surface of each of these cooling rings is perpendicular to the center line of the cylinder, and adjacent two of these ring surfaces are separated by a distance along the center line. The temperature control element is connected to at least half of the cooling rings. In the direction from the bottom surface to the opening, the initial temperature of at least half of the cooling rings connected to the temperature control element increases gradually along the direction from the bottom surface to the opening, and the initial temperature is greater than the melting temperature.

Next, a cooling step is performed on the molten low-temperature expanded metal material to obtain a metal casting, wherein the temperature control element reduces at least half of the cooling rings at a cooling rate until each of at least half of the cooling rings The final temperature is less than the solidification temperature of the low-temperature expansion metal material.

According to an embodiment of the present invention, the operation of melting the low-temperature-expanded metal material includes melting the low-temperature-expanded metal material at a temperature more than 10° C. higher than the melting temperature.

According to another embodiment of the present invention, the inner diameter of the mold cavity is 5 cm to 10 cm.

According to another embodiment of the present invention, the cooling rings are embedded in the surface of the peripheral wall to a depth of 9 mm to 11 mm.

According to another embodiment of the present invention, the distance is 48mm to 52mm.

According to another embodiment of the present invention, along the direction of the center line and along the plane passing through the center line, the cross section of each of the cooling rings is circular, and the diameter of the circle is 15 mm to 18 mm.

According to another embodiment of the present invention, when the temperature control element is connected to all of the cooling rings, the initial temperatures of adjacent two cooling rings differ by 0.5°C to 5.5°C.

According to another embodiment of the present invention, when the temperature control element is connected to one half of the cooling rings, each of the half of the cooling rings connected to the temperature control element and the half of the cooling rings not connected to the temperature control element Each of the other half of the cooling ring is adjacent.

According to another embodiment of the present invention, the initial temperatures of two adjacent halves of the cooling rings differ by 0.5°C to 5.5°C.

According to another embodiment of the present invention, the cooling rate is -0.3°C/min to -0.7°C/min.

The casting method of metal castings of the present invention is applied, in which a mold containing a cooling ring is used to perform a cooling step from bottom to top on a metal material that has a specific composition and high purity and is expanded at low temperature, so that it can be directionally solidified, thereby obtaining a defect-free casting. Metal castings.

The making and using of embodiments of the invention are discussed in detail below. It is to be appreciated, however, that the embodiments provide many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are illustrative only and are not intended to limit the scope of the invention.

Referring to FIG. 1 , in the metal material casting method 100 , a low-temperature expanded metal material is first provided, as shown in operation 110 . The aforementioned low-temperature expansion metal material is selected from one of the group consisting of antimony, bismuth, gallium, bronze and alloys thereof. If metal materials other than the aforementioned metal materials are added to the low-temperature expanded metal material, the resulting metal casting will have defects. Defects may include structural damage to the casting, and specific examples thereof may include, but are not limited to, gaps and/or holes.

Furthermore, the purity of the low-temperature expanded metal material is greater than 99 weight percent. Here, the “purity” referred to in the present invention refers to the content (weight percent) of the metal with the highest content in the low-temperature expanded metal material based on 100 weight percent. Furthermore, the casting method 100 of metal castings excludes the use of seed crystals and uses low-temperature expanded metal materials with a purity greater than 99 weight percent to obtain metal castings with a purity greater than 99 weight percent.

After operation 110 , the low-temperature expanded metallic material is melted to a molten state, as shown in operation 120 . In operation 120, the temperature of the low-temperature expanded metal material is raised to above the melting temperature (also referred to as the melting point) of the low-temperature expanded metal material. In some embodiments, the melting temperature in operation 120 is more than 10° C. higher than the melting point of the low-temperature-expanded metal material to facilitate subsequent cooling steps, thereby facilitating subsequent directional solidification of the molten low-temperature-expanded metal material.

After operation 120 , the molten low-temperature expanded metal material is poured into the mold, as shown in operation 130 . Please refer to FIG. 2 and FIG. 3A to FIG. 3B. FIG. 2 is a schematic diagram of the mold 200 according to an embodiment of the present invention. FIG. 3A is a perspective view of the cylinder 210 of the mold 200 according to FIG. 2, and FIG. 3B is a schematic diagram of a single cooling ring according to FIG. 3A. The mold 200 includes a cylinder 210 , a plurality of cooling rings 220 and a temperature control element 230 . The cylinder 210 has a peripheral wall 211, a mold cavity 212, a bottom surface 213 and an opening 214. The mold cavity 212 of the cylinder 210 is used to receive the poured molten metal material that expands at low temperature.

In some embodiments, the inner diameter ID of the mold cavity 212 is 5 cm to 10 cm to facilitate subsequent directional solidification of the molten low-temperature expanded metal material. In addition, the melting point of the cylinder 210 is higher than the current temperature of the molten low-temperature-expanded metal material to ensure that the cylinder 210 will not be melted by the molten low-temperature-expanded metal material. Preferably, the melting point of the cylinder 210 is more than 10° C. higher than the melting temperature of the operation 120 .

For example, the material of the cylinder 210 may include but is not limited to casting sand, metal or ceramics. In some embodiments, the heat transfer coefficient of the cylinder 210 may be 10 W/mk to 38 W/mk to facilitate the cooling of the molten low-temperature expanded metal material, thereby facilitating its subsequent directional solidification.

These cooling rings 220 are embedded in the peripheral wall 211 and surround the mold cavity 212 . The temperature control element 230 is connected to at least half of the cooling rings 220, so that the cooling ring 220 connected to the temperature control element 230 is controlled by the temperature control element 230 to cool down, so as to cool the molten metal material that expands at low temperature. For example, the temperature control element 230 can be a device installed with program-controlled software to control the cooling of the cooling ring 220 through the program-controlled software.

In some embodiments, the depth SD of each of these cooling rings 220 and the surface SF of the peripheral wall 211 is 9 mm to 11 mm to facilitate subsequent cooling steps, thereby facilitating subsequent orientation of the molten low-temperature expanded metal material. solidification.

Furthermore, as shown in FIGS. 3A and 3B , the ring surface CP of each of the cooling rings 220 refers to the plane extending toward the center line AL of the cooling ring 220 (as shown in FIG. 3B ). The torus CP of each of the cooling rings 220 is perpendicular to the center line AL of the cylinder 210, and two adjacent torus CPs are separated by a distance DD along the center line AL (as shown in FIG. 3A) . In some embodiments, the distance DD is 48 mm to 52 mm to facilitate subsequent cooling steps, thereby facilitating subsequent directional solidification of the molten low-temperature expanded metal material. Furthermore, it can be understood that the number of cooling rings 220 is determined by the length of the distance DD between adjacent cooling rings 220 and the height of the column 210 . The height of the cylinder 210 and the inner diameter ID of the mold cavity 212 can be adjusted according to the volume of the low-temperature expanded metal material.

In some embodiments, the cooling rings 220 have the same size to correspond to the cylindrical column 210 used. In other embodiments, the cooling rings 220 have different sizes. For example, in the direction from the bottom surface 213 to the opening 214, the diameter of the ring surface CP of each of the cooling rings 220 increases or decreases to correspond to the application in a tapered cylinder (not shown) .

In some embodiments, along the plane passing through the centerline AL, the cross section of each of these cooling rings 220 is a circular CR, and the diameter CD of the circular CR is 15 mm to 18 mm to facilitate heat conduction within the peripheral wall 211 , thus facilitating the subsequent directional solidification of the metal material that expands at low temperature in the molten state.

In the direction from the bottom surface 213 to the opening 214, the initial temperature of at least half of the cooling rings 220 connected to the temperature control element 230 increases gradually along the direction from the bottom surface 213 to the opening 214, and the initial temperature is greater than the melting temperature. If the initial temperature does not increase as mentioned above, the cooling step from bottom to top cannot be carried out, so the molten metal material that expands at low temperature cannot undergo subsequent directional solidification. Incidentally, as can be understood by those with ordinary knowledge in the technical field to which the present invention belongs, when the molten low-temperature expanded metal material has just been poured into the mold 200, the temperature of the cooling rings 220 can also be raised through the temperature control element 230, so as to The initial temperature of these cooling rings 220 is made greater than the melting temperature of the low-temperature expanded metal material, or greater than the current temperature of the low-temperature expanded metal material. At this time, the cooling ring 220 is heated.

After operation 130 , the low-temperature expanded metal material in the molten state is subjected to a cooling step to obtain a metal casting, as shown in operation 140 . The temperature control element 230 reduces at least half of the cooling rings 220 at a cooling rate until the final temperature of each of at least half of the cooling rings 220 is less than the solidification temperature of the low-temperature expanded metal material. If the temperature control element 230 does not reduce at least half of the cooling rings 220 at the same cooling rate at the same time, the cooling step from bottom to top cannot be performed, so that the molten metal material expanded at low temperature cannot be directionally solidified. Specifically, the cooling rate may be 0.3°C/min to 0.7°C/min to facilitate directional solidification of the low-temperature expanded metal material in the molten state.

To elaborate, the closer the cooling ring 220 is to the bottom surface 213, the lower the initial temperature is. When the temperature control element 230 controls the cooling ring 220 to cool down, the cooling ring 220 closer to the bottom surface 213 reaches the melting point of the metal material faster. Then, after the cooling ring 220 cools down to lower than the solidification temperature of the metal material, the cooling ring 220 next to the cooling ring 220 The metal material begins to solidify. As a result, the metal material solidifies from the bottom surface 213 to the direction of the opening 214. That is, the solidification direction of the molten low-temperature expanded metal material is from the bottom surface 213 of the cylinder 210 (corresponding to the bottom of the cylinder 210) to the opening 214 (corresponding to the cylinder). the top of the body 210), so it can be called a cooling step from bottom to top. This top-down cooling step can achieve directional solidification.

On the contrary, if the initial temperatures of the cooling rings 220 connected to the temperature control element 230 decrease in the direction from the bottom surface 213 to the opening 214, the cooling rings 220 closer to the opening 214 will reach the solidification temperature of the metal material faster. Therefore, the solidification direction of the metal material is from the opening 214 of the cylinder 210 (corresponding to the top of the cylinder 210) to the bottom surface 213 (corresponding to the bottom of the cylinder 210), so it can be called a top-down cooling step. In this cooling step, the upper molten metal material with low-temperature expansion solidifies first, while the lower molten metal material with low-temperature expansion has not yet solidified, so directional solidification cannot be achieved, so the castings cast therefrom have defects, and even crack.

In the casting method 100 of the metal casting of the present invention, the operation 140 excludes the use of crystal seeds to promote the solidification or growth of metal materials with low-temperature expansion in the molten state. Therefore, compared with the casting method of metal castings using crystal seeds, the metal casting of the present invention The casting method 100 can produce metal castings with a purity higher than 99 weight percent.

In some embodiments, as shown in FIG. 2 , when the temperature control element 230 is connected to one half of the cooling rings 220 , each of the half of the cooling rings 220 connected to the temperature control element 230 is not connected to the temperature control element 230 . Each of the other halves of the cooling rings 220 connected to the temperature control element 230 is adjacent, and the initial temperatures of the adjacent halves of the cooling rings 220 differ by 0.5°C to 5.5°C to facilitate melting. A state of directional solidification of metal materials that expand at low temperatures. In other embodiments, as shown in FIG. 4 , when the temperature control element 430 connects all of the cooling rings 420 , the initial temperatures of two adjacent cooling rings 420 differ by 0.5°C to 5.5°C, so as to change It is beneficial to the directional solidification of metal materials that expand at low temperatures in the molten state.

In the casting method 100 of the low-temperature expanded metal material, the casting method 100 of the low-temperature expanded metal material may optionally include a demoulding step and a riser cutting step. The demoulding step may continue after operation 140 , and the riser cutting step may be performed between operations 130 and 140 .

The following examples are used to illustrate the application of the present invention, but they are not intended to limit the present invention. Anyone familiar with this art can make various changes and modifications without departing from the spirit and scope of the present invention.

Casting method for low-temperature expanded metal materials

Example 1

Antimony with a purity of 99.5 weight percent was cast according to Table 1 below. The antimony is first melted at a temperature of 640°C, and then the liquid antimony is poured into the mold. The mold contains 4 cooling rings. The inner diameter of the cylinder is 8cm. The melting point of the cylinder is 10°C higher than that of liquid antimony. The depth of each of these cooling rings to the surface of the peripheral wall is 10 mm. The distance between adjacent cooling rings is 50mm. These cooling rings have the same size and the cylinder is cylindrical. The longitudinal section of each of these cooling rings is circular, with a diameter of 16 mm.

Examples 2 to 12 and Comparative Examples 1 to 14

In Examples 2 to 12 and Comparative Examples 1 to 14, antimony rods were cast using the same method as Example 1. The difference is that Examples 2 to 6 and Comparative Examples 1 to 7 use different cooling conditions. In Examples 7 to 12 and Comparative Examples 8 to 14, bismuth with a purity of 100% by weight was used for casting, and the bismuth was melted at a temperature of 282° C., and then liquid bismuth was poured into a mold, where the mold contained 8 cooling rings. The specific conditions and evaluation results of the aforementioned Examples 1 to 6 and Comparative Examples 1 to 6 are shown in Table 1 below. The specific conditions and evaluation results of the aforementioned Examples 7 to 12 and Comparative Examples 8 to 14 are shown in Table 2 below.

Evaluation method

1. Evaluation of casting structure

The integrity of the appearance of the casting is observed with the naked eye, and the casting structure is divided into top, middle and bottom parts to evaluate. The specific evaluation criteria are as follows: ○: The casting structure is complete and defect-free, △: The casting structure is slightly defective, ╳: The casting structure is damaged and incomplete.

2. Evaluation of casting time

The casting time of the casting method is evaluated, and the specific evaluation criteria are as follows: Minimum: casting time is less than 1 hour, Short: casting time is not less than 1 hour and less than 3 hours, Moderate: casting time is not less than 3 hours and less than 5 hours, Long: The casting time is not less than 5 hours.

Table 1 Casting method Evaluation results Cooling step cooling ring Cooling rate (℃/min) Casting structure casting time Connected cooling ring Temperature difference(℃) top middle part bottom Example 1 from bottom to top all 1 0.5 ○ ○ ○ short 2 3 ○ ○ ○ Moderate 3 5 ○ ○ ○ long 4 Interval 1 1 △ △ ○ short 5 3 △ △ ○ Moderate 6 5 △ △ ○ long Comparative example 1 from top to bottom all 1 △ ╳ ╳ short 2 3 △ ╳ ╳ Moderate 3 5 △ ╳ ╳ long 4 Interval 1 1 △ ╳ ╳ short 5 3 △ ╳ ╳ Moderate 6 5 △ ╳ ╳ long 7 natural cooling No temperature control ╳ ╳ △ shortest Note: In Table 1 above and Table 2 below, the field "Connected cooling loops" represents the number of cooling loops connected to the temperature control components, where "all" represents all cooling loops connected to the temperature control components, "Interval 1""" represents that the cooling ring is connected to the temperature control element at intervals of 1, and the cooling ring at the bottom is connected to the temperature control element. The field "temperature difference" represents the difference in initial temperatures between adjacent cooling loops in the cooling loop connected to the temperature control element, and the cooling loop connected to the temperature control element moves along the bottom surface toward the opening. direction, the initial temperature increases gradually.

Table 2 Casting method Evaluation results Cooling step cooling ring Cooling rate (℃/min) Casting structure casting time Connected cooling ring Temperature difference(℃) top middle part bottom Example 7 from bottom to top all 1 0.5 ○ ○ ○ short 8 3 ○ ○ ○ Moderate 9 5 ○ ○ ○ long 10 Interval 1 1 △ △ ○ short 11 3 △ △ ○ Moderate 12 5 △ △ ○ long Comparative example 8 from top to bottom all 1 △ ╳ ╳ short 9 3 △ ╳ ╳ Moderate 10 5 △ ╳ ╳ long 11 Interval 1 1 △ ╳ ╳ short 12 3 △ ╳ ╳ Moderate 13 5 △ ╳ ╳ long 14 natural cooling No temperature control ╳ ╳ △ shortest

Please refer to Tables 1 and 2. Compared with the comparative examples, each embodiment uses a cooling step from bottom to top, which can indeed directional solidify the molten antimony, thereby obtaining a metal casting with a better structure. Secondly, using all cooling rings for cooling can further improve the structural integrity of metal castings.

To sum up, the casting method of metal castings of the present invention performs a bottom-up cooling step on a metal material that has a specific composition and high purity and undergoes low-temperature expansion to directional solidify it, thereby obtaining a defect-free metal casting.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field to which the present invention belongs can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended patent application scope.

100:Method 110,120,130,140: Operation 200,400:Mold 210,410: cylinder 213,413: Bottom surface 214,414: Opening 211,411:surrounding wall 220,420: Cooling ring 230,430:Temperature control element AL: center line CD: diameter CP: torus CR: round DD: distance ID:inner diameter SD: depth SF: surface

In order to have a more complete understanding of the embodiments of the present invention and its advantages, please refer to the following description together with the corresponding drawings. It must be emphasized that various features are not drawn to scale and are for illustration purposes only. The relevant diagram content is explained as follows: FIG. 1 is a flow chart illustrating a method for casting metal castings according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a mold according to an embodiment of the present invention, in which the cylinder of the mold is presented in a cross-section along a plane passing through the centerline. FIG. 3A is a perspective view of the column according to FIG. 2 . FIG. 3B is a schematic diagram of a single cooling ring according to FIG. 3A. FIG. 4 is a schematic diagram of a mold according to another embodiment of the present invention.

100:Method

110,120,130,140: Operation

Claims (10)

A casting method for metal castings, including: providing a low-temperature expansion metal material, wherein the low-temperature expansion metal material is selected from a group consisting of antimony, bismuth, gallium, bronze and alloys thereof, and the low-temperature expansion metal material One of the metal materials has a purity greater than 99% by weight; Melting the low-temperature expanded metallic material to a molten state, wherein the low-temperature expanded metallic material is heated to above a melting temperature of the low-temperature expanded metallic material; Pouring the molten low-temperature expanded metal material into a mold, wherein the mold includes: A cylinder having a peripheral wall, a mold cavity, a bottom surface and an opening, wherein a melting point of the cylinder is higher than a current temperature of the low-temperature expanded metal material in the molten state; A plurality of cooling rings are embedded in the peripheral wall and surround the mold cavity, wherein an annular surface of each of the cooling rings is perpendicular to a center line of the cylinder, and adjacent two of the annular surfaces are along the The center lines are a distance apart; and a temperature control element connected to at least half of the cooling rings, Wherein, in a direction from the bottom surface to the opening, the initial temperature of at least half of the cooling rings connected to the temperature control element increases along the direction from the bottom surface to the opening, and the initial temperature is greater than the melting temperature; and A cooling step is performed on the molten low-temperature expanded metal material to obtain the metal casting, wherein the temperature control element reduces at least half of the cooling rings at a cooling rate until at least half of the cooling rings A final temperature of each is less than a solidification temperature of the low-temperature expanded metallic material. The method of casting a metal casting as claimed in claim 1, wherein the operation of melting the low-temperature-expanded metal material includes melting the low-temperature-expanded metal material at a temperature higher than 10° C. above the melting temperature. The method for casting metal castings as described in claim 1, wherein the inner diameter of the mold cavity is 5 cm to 10 cm. The method of casting a metal casting as claimed in claim 1, wherein the cooling rings are embedded in a surface of the peripheral wall to a depth of 9 mm to 11 mm. The casting method of metal castings as described in claim 1, wherein the distance is 48mm to 52mm. The casting method of metal castings as described in claim 1, wherein along a plane passing through the center line, a cross section of each of the cooling rings is a circle, and a diameter of the circle is 15 mm to 18mm. The casting method of metal castings as described in claim 1, wherein when the temperature control element is connected to all of the cooling rings, the initial temperatures of adjacent two cooling rings differ by 0.5°C to 5.5°C. The casting method of metal castings as described in claim 1, wherein when the temperature control element is connected to one half of the cooling rings, each of the half of the cooling rings connected to the temperature control element is not Each of the other halves of the cooling rings connected to the temperature control element is adjacent to each other. The casting method of metal castings as described in claim 8, wherein the initial temperatures of two adjacent halves of the cooling rings differ by 0.5°C to 5.5°C. The casting method of metal castings as described in claim 1, wherein the cooling rate is -0.3°C/min to -0.7°C/min.

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