KR20240037447A - Manufacturing methods of tool for friction stir welding by forging and rolling processing, and tool manufactured by the same - Google Patents

Abstract

The method of manufacturing tools for friction stir welding according to the present invention replaces the existing method of manufacturing tools through CNC machining, by making a tool shape through forging processing, and then forming a thread by rolling the tool pin portion of the tool shape. This manufacturing method can significantly reduce tool manufacturing time and unit cost compared to existing manufacturing methods, and thus improve product quality because tools can be replaced sufficiently frequently during welding.

Description

A method of manufacturing a tool for friction stir welding by forging and rolling processing, and a tool made by this manufacturing method {Manufacturing methods of tool for friction stir welding by forging and rolling processing, and tool manufactured by the same}

The present invention relates to a method of manufacturing a tool for friction stir welding, and more specifically, instead of manufacturing tools by existing CNC machining, a tool shape is made by forging and then the tool pin portion of the tool shape is rolled. This is about a tool manufacturing method that manufactures tools by processing them to form threads.

In addition, the present invention also relates to a tool made by this manufacturing method.

Friction stir welding involves rotating a tool consisting of a tool pin and a shoulder at high speed and inserting it into the material (base metal) to be welded, thereby producing frictional heat generated on the surface and inside of the material. It is a solid-state joining method that realizes joining by softening the material and simultaneously causing high-temperature plastic flow to stir and mix some of the material placed on the left and right sides of the tool into the opposite area.

Figure 1 shows welding two metal plates (base materials) using a tool, Figure 2(a) shows the tool before use (left view), and Figure 2(b) shows the tool worn out by use. Shows enlarged. During friction stir welding, the tool wears out and the base metal gets caught in the thread of the tool pin, necessitating tool replacement or work to remove the base metal stuck in the thread of the tool pin. Accordingly, each company has a tool replacement cycle that takes into account the material of the tool and the material of the base material.

However, because the price of the tool is high, it is expensive to replace the tool according to the replacement cycle, and as a result, there are cases where the tool replacement cycle is missed during work. In this case, the problem of poor product quality occurs. Therefore, there is a need to lower the manufacturing cost of tools so that tools can be replaced according to a set replacement cycle.

Meanwhile, Figure 3 is a flow chart sequentially showing each process of the tool manufacturing method. Tools are manufactured sequentially through design, machining using CNC, etc., heat treatment of the machined tool, and finishing and coating of the heat-treated tool.

However, this manufacturing method has the problem that it takes a lot of manufacturing time and the manufacturing cost is high. For example, when a tool for joining 5 mm thick specimens is manufactured using this manufacturing method, approximately 20 to 25 pieces can be produced in 3 days, and the unit price is approximately 100,000 won. As such, this manufacturing method has the problem that tools cannot be mass-produced and the manufacturing cost is also high.

The present invention was proposed to solve the above-mentioned problems, and its purpose is to provide a method of manufacturing tools through forging and rolling processing instead of the existing tool manufacturing through CNC machining.

Another object of the present invention is to provide a tool manufacturing method that can significantly increase tool production and reduce manufacturing costs compared to existing manufacturing methods.

Another object of the present invention is to provide a tool made by the above manufacturing method.

Another object of the present invention is to provide an inexpensive tool that can be replaced after use like a disposable product.

A method of manufacturing a tool for friction stir welding according to a preferred embodiment of the present invention includes the step of (a) manufacturing a tool shape (30a) by forging the workpiece (3). The forging process in step (a) may be performed by placing the workpiece 3 in the forging mold 100 and then hitting or pressing it. The tool-shaped body 30a may be formed by integrally forming the tool pin portion 10a and the shoulder portion 20a.

The tool manufacturing method may further include, after step (a), (b) forming the screw thread 12 by rolling processing the tool pin portion 10a of the tool shape body 30a.

In step (a), a groove 22 or a protrusion may be formed on the upper surface of the shoulder portion 20a to engage the lower end of the collar 1. The shoulder 20 and the collar 1 may be coupled by inserting the protrusion formed at the bottom of the collar 1 into the groove 22 or inserting the protrusion into the groove formed at the bottom of the collar 1.

It is desirable that the thickness (T) of the product to be welded and the height (H) of the tool pin satisfy Equation 1 below, and the width (W) of the shoulder 20 satisfies Equation 2 below.

[Equation 1]

[Equation 2]

2T ≤ W

Once the height (H) of the tool pin 10 and the width (W) of the shoulder are determined, a test tool with the height (H) and width (W) is manufactured and tested, and then the tool pin is manufactured by reflecting the results of the test. The final height of (10) and the final width of the shoulder (20) can be determined, and a forging mold (10) for manufacturing the tool (30) having the final height and the final width can be manufactured. The test tool may be manufactured through CNC machining.

The forging mold 100 used in the manufacturing method according to the present invention may include an upper mold 110 and a lower mold 120. The upper mold 110 may reciprocate up and down with respect to the lower mold 120 to hit or press the material to be processed (3).

The lower mold 120 includes a first part 121 having a space 122 in contact with the shoulder portion 20a; And, it may include a second part 123 having a space 124 that matches the tool pin part 10a. The first and second parts 121 and 123 are formed as one body, and the spaces 122 and 124 are connected to each other.

The upper mold 110 includes a first protrusion 111 that is inserted into the space 122 and hits or presses the material to be processed (3); And, it may include a second protrusion 112 formed to protrude downward from the first protrusion 111.

The tool 30, which is another aspect of the present invention, includes a tool pin 10 and a shoulder 20. The tool pin 10 and the shoulder 20 are made as one piece by forging, and the outer peripheral surface of the tool pin 10 is The screw thread 12 is formed by rolling processing.

The present invention has the following effects.

First, it provides a tool manufacturing method that can significantly increase tool production and lower manufacturing costs compared to existing manufacturing methods. For example, in the past, tools were manufactured by purchasing round bar alloy and performing CNC processing. Approximately 20 to 25 5T tools (tools for joining 5 mm thick specimens) could be produced in a total of 3 days, and the unit price of these tools was was about 100,000 won, but the manufacturing method according to the present invention can produce about 75,000 pieces of the same tool in 3 days, and the unit price is 1/100 of the existing tool.

Second, tools made using the above manufacturing method are provided. In particular, product quality can be improved because it can be replaced after use like a disposable product.

Figure 1 is a diagram showing a friction stir welding tool welding two metal plates (base materials).
Figure 2(a) is a view showing a tool before use, and Figure 2(b) is an enlarged view showing a tool worn out by use.
Figure 3 is a flow chart showing a tool manufacturing method according to the prior art.
Figure 4 is a flow chart showing a tool manufacturing method according to a preferred embodiment of the present invention.
Figure 5 is a front view and a bottom view showing a tool manufactured by the tool manufacturing method of Figure 4.
Figure 6 is a view showing making a tool shape using a forging mold.

Hereinafter, the present invention will be described in detail with reference to the attached drawings. Prior to this, the terms or words used in this specification and claims should not be construed as limited to their usual or dictionary meanings, and the inventor should appropriately use the concept of terms to explain his or her invention in the best way. It must be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle of definability. Accordingly, the embodiments described in this specification and the configurations shown in the drawings are only embodiments of the present invention and do not represent the entire technical idea of the present invention, so various equivalents can be substituted for them at the time of filing the present application. It should be understood that there may be variations.

Figure 4 is a flow chart showing a tool manufacturing method according to a preferred embodiment of the present invention, Figure 5 is a front view and a bottom view showing a tool manufactured by the tool manufacturing method, and Figure 6 is a tool mold using a forging mold. This is a drawing showing how to build the upper body.

As shown in the drawing, the tool manufacturing method includes a step of designing the forging mold 100 and the tool 30 (S10), a step of manufacturing the designed forging mold 100 (S20), and a forging mold 100. A step of manufacturing the tool shape 30a (S30), a step of roll processing the tool pin portion 10a of the tool shape 30a (S40), a heat treatment step (S50), and a coating step ( S60) may be included.

The design step (S10) may include designing a tool 30 to be manufactured and designing a forging mold 100 to manufacture the tool 300.

For example, when the thickness of the material to be joined (the product to be welded) is T, it is desirable that the height (H) of the tool pin 10 and the width (W) of the shoulder 20 satisfy the equations 1 and 2 below. .

[Equation 1]

[Equation 2]

2T ≤ W

If the height (H) of the tool pin (10) is less than T-0.5mm, there is a possibility that the joint at the bottom in the thickness direction of the material to be joined is insufficient, and if the height (H) of the tool pin (10) is greater than T+0.5mm, the joint is likely to be insufficient. There is a problem that the tool may be damaged due to the backing plate (anvil) placed under the joint material, and the backing plate and the material to be joined may become stuck.

In addition, if the width (W) of the shoulder 20 is less than 2T, it is not desirable because the frictional heat generated by friction between the shoulder 20 and the material to be joined may not be sufficient, and proper bonding may not be achieved.

On the other hand, when the thickness (T) of the material to be joined is 20 mm or less, the width (W) of the shoulder 20 is preferably 3 times or less than the height (H) of the tool pin 10, and the thickness (T) of the material to be joined is When exceeds 20 mm (i.e., when the material to be joined is thick), the width (W) of the shoulder 20 may be smaller than the height (H) of the tool pin 10.

The forging mold 100 is designed to manufacture the tool 30 that satisfies Equations 1 and 2 and the above. Preferably, the tool 30 that satisfies Equations 1 and 2 and the above is manufactured by CNC machining and used for the material to be joined to obtain the width (W) of the shoulder 20, the height (H) of the tool pin 10, and After evaluating the joining (welding) performance according to the material to be joined, etc., the final width of the shoulder 20 and the final height of the tool pin 10, which have the best joining (welding) performance, are determined. Then, a forging mold 100 capable of creating this final width and final height is designed and manufactured (S20).

As shown in Figure 6(a)(b), the forging mold 100 may include an upper mold 110 and a lower mold 120. The upper mold 110 reciprocates up and down with respect to the lower mold 120 and strikes or presses the workpiece to manufacture the tool shape 30a.

For reference, in this specification, 'tool shape' refers to a product made by forging a material to be processed and before rolling processing (S40). The tool shape 30a has a tool pin portion 10a and a shoulder portion 20a. The tool pin portion 10a later becomes the tool pin 10 and the shoulder portion 20a later becomes the shoulder 20.

The lower mold 120 includes a first part 121 having a space 122 that mates with the shoulder portion 20a, and a second part 123 with a space 124 that mates with the tool pin portion 10a. do. The first and second parts 121 and 123 are formed as one body, and the spaces 122 and 124 are connected to each other.

The space 122 is a space in which the shoulder portion 20a can be formed by forging. The space 122 has a shape that matches the shoulder portion 20a. For example, when the shoulder portion 20a has a circular cross-section, the space 122 also has a circular cross-section, and when the shoulder portion 20a has a square or elliptical cross-section, the space 122 also has a square cross-section. or may have an elliptical cross-section.

The second part 123 is formed integrally with the first part 121 below the first part 121 . A space 124 is formed inside the second part 123, and the space 124 is connected to the space 123.

The space 124 is a space where the tool pin portion 10a can be formed by forging. The space 124 has a shape that matches the tool pin portion 10a. For example, when the tool pin portion 10a has a cylindrical shape, the space 124 also has a cylindrical shape, and when the tool pin portion 10a has a tapered cylindrical shape, the space 124 also has a tapered cylindrical shape. And, when the tool pin portion 10a has a square shape, the space 124 may also have a square shape.

The lower surface of the first part 121 and the vertical surface of the second part 123 may be connected by a curved surface 125. The connection portion between the tool pin portion 10a and the shoulder portion 20a is formed as a curved surface that conforms to the curved surface 125. The curved surface 125 facilitates forging, and the connection portion formed by the curved surface 125 can serve to support the tool pin 10 during welding.

The upper mold 110 may include a first protrusion 111 inserted into the space 122. The first protrusion 111 has a cross section that matches the cross section of the space 122. The tool-shaped body 30a is created by striking or pressing the workpiece 3 while the first protrusion 111 is inserted into the space 122.

Preferably, the upper mold 110 may further include a second protrusion 112. The second protrusion 122 is a portion formed to protrude downward from the lower end (lower surface) of the first protrusion 111 and is used to form the groove 22. The groove 22 is a concave portion formed on the upper surface of the shoulder 20, and is a portion for engaging the lower end of the collar 1. A protrusion is formed at the bottom of the collar 1, and the collar 1 and the tool 30 can be coupled by inserting and combining the protrusion into the groove 22. Meanwhile, for combining the collar 1 and the tool 30, the insert metal disclosed in Korean Patent Registration No. 10-1816050 may be used together with the groove 22 and the protrusion or instead of the groove 22 and the protrusion.

On the other hand, when a protrusion (not shown in the drawing) is formed to protrude from the upper surface of the shoulder 20 in place of the groove 22, an insertion groove (not shown in the drawing) may be formed in place of the second protrusion 112. there is. Additionally, two or more grooves 22 or protrusions may be formed on the upper surface of the shoulder 20.

When the manufacturing of the forging mold 100 is completed, the material to be processed 3 is placed in the space 122 and struck or pressed with the upper mold 110 to manufacture the tool shape 30a (S30). The material to be processed 3 may be struck or pressed while heated to a high temperature, or may be struck or pressed at room temperature, depending on the material. Known materials used to make tool pins can be used as the material to be processed (3). For example, tungsten carbide (WC), tungsten carbide-cobalt sintered body, Al ₂ O ₃ , SiC, Si ₃ N ₄ , B ₄ C, etc. may be used.

The material to be processed (3) preferably matches the shape of the space (122) but has a size that can be inserted into the space (122). For example, if the space 122 has a cylindrical shape, it is preferable that the workpiece 122 also has a cylindrical shape.

Meanwhile, the material to be processed 3 may have a shape that matches the shapes of the space 122 and the space 124. In this case, a cylindrical protrusion that conforms to the shape of the space 124 and can be inserted into the space 124 may be formed at the bottom of the workpiece 3, and this cylindrical protrusion is formed in the space 124. A blow or pressure may be performed by the upper mold 110 while inserted into the . The material to be processed (3) can be made by sintering and molding a mixed powder consisting of tungsten carbide powder and cobalt powder integrally in a mold. Additionally, the content of tungsten carbide powder may decrease and the content of cobalt powder may increase as it moves upward from the cylindrical protrusion. For example, the cylindrical protrusion may be made of 95 to 97 wt% of tungsten carbide powder and 3 to 5 wt% of cobalt powder.

When manufacturing of the tool-shaped body 30a is completed, roll processing is performed on the tool pin portion 10a to form a screw thread 12 (S40). This step (S40) is not an essential step in the present invention, and if the tool pin 10 does not have threads, this step (S40) can be omitted.

The tool pin portion 10a becomes the tool pin 10 through this rolling processing step (S40). The screw thread 12 diffuses heat generated by friction with the material to be joined and facilitates the flow of the material so that the material to be joined can be well joined.

As is known, rolling processing is a special rolling method that engraves the surface shape of the tool on the outer or inner surface of the material by rotating the material and the tool together. In the present invention, a circular die rolling machine, a differential rolling machine, etc. may be used to form the thread 12 in the tool pin portion 10a. The circular die rolling machine uses a rolling die with threads formed on the outer circumferential surface of the roll, and includes a two-circle die type using two rolls and a three-circle die type using three rolls.

In the two-circle die type, one of the two rolls is fixed in position and can only rotate, and the other can move and rotate. Accordingly, the tool pin portion 10a is inserted between the two rolls, and the rolls are moved and pressed while rotating the two rolls in the same direction to form threads 12 on the outer peripheral surface of the tool pin portion 10a.

The three-circle die uses three rolls and can stably position the tool pin portion (10a), but its precision is lower than that of the two-circle die. After inserting the tool pin portion (10a) between the three rolls and pressing the three rolls while rotating them in the same direction, a thread is formed on the outer peripheral surface of the tool pin portion (10a).

The differential rolling machine rotates two circular dies (rolls) in the same direction and feeds the tool pin portion (10a) in the tangential direction at a speed of 1/2 of the circumferential speed difference of the dies (rolls) to pass the minimum gap between the rolls. When doing so, ensure that the thread processing is complete.

When the rolling processing step (S40) is completed, the tool 30 is heat treated (S50). Heat treatment can be performed in the same manner as the heat treatment (heat treatment step in FIG. 3) of the existing manufacturing method.

Subsequently, when the heat treatment is completed, the tool 30 is coated. This coating can also be done in the same way as the coating in the existing manufacturing method (coating step in FIG. 3).

1: Collar 3: Material to be processed
10: tool pin 10a: tool pin part
12: thread 20: shoulder
20a: shoulder portion 22: groove
30: Tool 30a: Tool shape body
100: Forging mold
110: upper mold 111: first protrusion
112: second protrusion 120: lower mold
121: first part 122: space
123: second part 124: space
125: connection part
H: Height of tool pin W: Width of shoulder

Claims (8)

In the method of manufacturing tools used for friction stir welding,
(a) manufacturing the tool shape (30a) by forging the workpiece (3),
The forging process in step (a) is performed by placing the material to be processed (3) into the forging mold (100) and then striking or pressing it,
A method of manufacturing a tool for friction stir welding, wherein the tool shape body (30a) is formed of a tool pin portion (10a) and a shoulder portion (20a) integrally. According to paragraph 1,
After step (a) above,
(b) forming a screw thread 12 by rolling processing the tool pin portion 10a of the tool shape 30a manufactured in step (a); manufacturing a tool for friction stir welding, characterized in that it further comprises a. method. According to paragraph 2,
A method of manufacturing a tool for friction stir welding, characterized in that in step (a), a groove 22 or a protrusion is formed on the upper end of the shoulder portion 20a for engaging the lower end of the collar 1. According to paragraph 2,
The thickness (T) of the product to be welded and the height (H) of the tool pin satisfy the equations below,
A method of manufacturing a tool for friction stir welding, characterized in that the width (W) of the shoulder (20) is more than twice the thickness (T).
[ceremony]

According to paragraph 4,
It further includes preparing or manufacturing a forging mold 100 before step (a),
The forging mold 100 includes an upper mold 110 and a lower mold 120, and the upper mold 110 reciprocates up and down with respect to the lower mold 120 while hitting or pressing the workpiece 3. do,
The lower mold 120 is,
a first portion (121) having a space (122) conforming to the shoulder portion (20a); and,
It includes a second part (123) having a space (124) in conformity with the tool pin part (10a),
The first and second parts 121 and 123 are formed as one body, and the spaces 122 and 124 are connected to each other,
The upper mold 110 is,
A method of manufacturing a tool for friction stir welding, comprising a first protrusion 111 that is inserted into the space 122 and hits or presses the material to be processed (3). According to clause 5,
Once the height (H) of the tool pin 10 and the width (W) of the shoulder are determined, a test tool with the height (H) and width (W) is manufactured and tested, and then the tool pin is manufactured by reflecting the results of the test. Determine the final height of (10) and the final width of the shoulder (20), and manufacture a forging mold (10) for manufacturing a tool (30) having the final height and the final width,
A method of manufacturing a tool for friction stir welding, characterized in that the test tool is manufactured by CNC machining. It is a tool 30 used for welding in friction stir welding,
The tool 30 includes a tool pin 10 and a shoulder 20,
A tool for friction stir welding, wherein the tool pin (10) and the shoulder (20) are made as one piece by forging, and a screw thread (12) is formed on the outer peripheral surface of the tool pin (10) by rolling processing. In clause 7,
The thickness (T) of the product to be welded and the height (H) of the tool pin satisfy the equations below,
A tool for friction stir welding, characterized in that the width (W) of the shoulder (20) is more than twice the thickness (T).
[ceremony]