Contact tip for welding

Abstract

In this contact tip for welding, a molybdenum alloy housing 20 having a second central hole 21 that has a diameter smaller than that of a first central hole 11 is joined, through screwing, to the leading end of a copper alloy adaptor 10 having the first central hole 11. The adaptor 10 and the housing 20 are crimped and fixed together by being screwed together with a great torque so that threads are plastically deformed. The adaptor 10 and the housing 20 are screwed together with a great torque to have threads being plastically deformed, and are crimped and fixed together. The length of the second central hole 21 is set to at most 1 / 3 of the length of the first central hole 11 to obtain a structure in which a welding current passes, in a concentrated manner, through a welding wire on the inner surface of the second central hole 21. As a result, jamming causing by the welding wire is less likely to occur, variability in the welding current is less likely to occur, and the service life can be significantly extended.

Description

Contact tip for welding

[0001] The present invention relates to a contact tip for welding used in arc welding.

[0002] The contact tip for welding used in arc welding is attached to the tip of the torch of the welding machine and serves to supply a welding current to the welding wire while guiding the welding wire fed through the torch toward the welding position.

[0003] Conventional contact tips for welding usually have a central hole 2 of a certain diameter formed inside a copper alloy body 1 as shown in FIG. 5. Since the welding wire is clamped by a roller and fed from the base end side of the contact tip, if the clearance between the inner diameter of the central hole 2 and the outer diameter of the welding wire is small, the contact resistance with the inner surface of the central hole 2 increases, and there is a risk of an accident where the welding wire gets clogged inside and cannot be smoothly extruded. Therefore, for example, when the outer diameter of the welding wire is 1.2 mm, the inner diameter of the central hole 2 is generally made about 1.5 mm to have a sufficient clearance. However, when the clearance is increased in this way, the contact between the inner surface of the central hole 2 and the welding wire becomes unstable, and there is a problem that the welding current is likely to vary.

[0004] Also, the overall length of the contact tip for welding is 40 mm or 45 mm according to the specifications of the welding machine, but it is not easy to accurately drill a thin central hole 2 with an inner diameter of around 1.5 mm over the entire length. If the central hole 2 is bent or eccentric even slightly, the welding wire is likely to get clogged, and the welding current is likely to vary.

[0005] As described above, conventional welding contact tips have a problem in that increasing the clearance to prevent welding wire clogging easily leads to variations in welding current, and there is also a significant problem in that the diameter of the central hole 2 gradually increases due to contact wear with the welding wire. In particular, the tip of the central hole 2 close to the welding position is subjected to high heat from the arc, making it easy for the hole diameter to expand, which in turn can cause the direction of feeding the welding wire to be incorrect and result in incorrect welding positioning. For this reason, conventionally, welding work had to be interrupted at predetermined intervals to replace the welding contact tip with a new one, which led to a decrease in welding work efficiency and an increase in welding costs.

[0006] To solve this problem, Patent Document 1 describes a welding contact tip in which a tip 3 made of hard metal or ceramic is fitted to the tip of the central hole 2, as shown in Figure 6. While this welding contact tip is expected to prevent the hole diameter at the tip from expanding, if the central hole 2 of the main body 1 expands while the diameter of the central hole 4 of the tip 3 remains constant, a step will be created at the connection point with the tip 3, causing clogging. Furthermore, even with the contact tip structure shown in Figure 6, the problem that variations in welding current are likely to occur when the clearance of the central hole 2 is increased to prevent clogging remains unresolved. In addition, there is the problem of increased manufacturing costs for welding contact tips.

[0007] Japanese Utility Model Publication No. 64-15674

[0008] Therefore, the objective of the present invention is to solve the above-mentioned conventional problems and provide a welding contact tip that is less prone to welding wire clogging, less prone to welding current variation, and has a significantly extended continuous operating time (service life).

[0009] The present invention, made to solve the above problems, is a welding contact tip comprising a copper alloy adapter having a first central hole and a molybdenum alloy housing having a second central hole smaller in diameter than the first central hole, screw-connected to the tip of the copper alloy adapter, wherein the tip of the first central hole and the base end of the second central hole are in contact via a tapered hole portion, the adapter and the housing are fixed by crimping by plastically deforming the screw threads by screwing them together with a large torque, the length of the second central hole is set to 1 / 3 or less of the length of the first central hole, and the welding current is concentrated on the inner surface of the second central hole to pass through the welding wire.

[0010] The housing is preferably made of a molybdenum alloy containing titanium, zirconium, and carbon, with the remainder being molybdenum, and the adapter is preferably made of a copper alloy containing chromium.

[0011] It is preferable to set the inner diameter of the second central hole to be 0.08 to 0.12 mm larger than the outer diameter of the welding wire used.

[0012] Preferably, the total length of the adapter and the housing combined is 40 to 45 mm, and the length of the second central hole is 5 to 15 mm.

[0013] The welding contact tip of the present invention has a structure in which a housing having a second central hole smaller in diameter than the first central hole is attached to the tip of an adapter having a first central hole, and the length of this second central hole is set to 1 / 3 or less of the length of the first central hole. By making the shorter second central hole at the tip smaller in diameter in this way, the welding current can be concentrated on the welding wire through its inner surface. Furthermore, if sufficient clearance is provided in the longer first central hole, as in conventional products, the contact resistance with the welding wire is reduced, and clogging is less likely to occur.

[0014] Furthermore, the welding contact tip of the present invention has a structure in which the adapter and housing are crimped and fixed by plastically deforming the threads by screwing them together with a large torque. Conventional welding contact tips have existed in which the housing is detachably screwed onto the tip of the adapter, and have the advantage that the housing can be removed and replaced when the diameter of the hole at the tip enlarges. However, in order to make the housing replaceable, it is necessary to maintain the shape of the threads, and at a microscopic level, the flank surfaces of the male and female threads are in point contact. As a result, the path through which the welding current supplied from the adapter flows to the housing at the tip becomes unstable, leading to variations in the welding current. In contrast, by plastically deforming the threads and crimping and fixing them as in the present invention, the male and female threads are in a state of reliable surface contact, the current path from the adapter to the housing is stabilized, and variations in the welding current are suppressed.

[0015] Furthermore, since the welding contact tip of the present invention allows the adapter and housing to be manufactured separately, the length of the central hole in each can be shortened, simplifying the manufacturing process. Also, since the combination of the adapter and housing can be freely selected before crimping and fixing, both 40mm and 45mm lengths can be easily manufactured, reducing manufacturing costs.

[0016] Furthermore, if the housing of the welding contact tip of the present invention is made of a molybdenum alloy containing titanium, zirconium, and carbon, with the remainder being molybdenum, and the adapter is made of a copper alloy containing chromium, wear resistance will be improved, and the service life for continuous use can be increased to more than 40 times that of conventional products. This will reduce the frequency of replacing welding contact tips and improve the work efficiency of welding operations.

[0017] This is a central longitudinal cross-sectional view of a welding contact tip according to an embodiment. This is a partial cross-sectional view of the adapter. This is a partial cross-sectional view of the housing. This is a dimensional diagram. This is a cross-sectional view of a conventional contact tip. This is a cross-sectional view of the contact tip shown in Patent Document 1.

[0018] A preferred embodiment of the present invention is described below. Figure 1 is a central longitudinal cross-sectional view of a welding contact tip according to an embodiment, where 10 is an adapter and 20 is the housing on its tip side. The adapter 10 is provided with a first central hole 11, and the housing 20 is provided with a second central hole 21.

[0019] As shown in Figure 2, the adapter 10 has a cylindrical body 12 with a small diameter cylindrical portion 13 at the tip end, and a male thread 14 is formed on the outer circumference of the tip end. A male thread 15 is also formed at the base end of the cylindrical body 12 for attaching a welding contact tip to the welding machine torch. A first central hole 11 is formed along the entire length of the adapter 10, but the rear end has a tapered enlarged diameter portion 16, making it easier to insert the welding wire into the first central hole 11.

[0020] As shown in Figure 3, the housing 20 has a tapered main body 26 with a hollow cylindrical portion 22 at the rear. A female thread 23 is formed on the inner surface of the central part of this cylindrical portion 22, which engages with the male thread 14 of the adapter 10. A hole 24 with the same diameter as the inner diameter of this female thread 23 is formed between the cylindrical portion 22 and the main body 26. The main body 26 of the housing 20 has a second central hole 21 which is smaller in diameter than the first central hole 11, and a tapered hole portion 25 is formed at its rear end. In this embodiment, the taper angle of the tapered hole portion 25 is 30°.

[0021] The adapter 10 can be made of a copper alloy containing chromium, i.e., chromium copper or zircochromium copper. The housing 20 can be made of a molybdenum alloy. In this embodiment, a molybdenum alloy called TZM is used, which contains titanium, zirconium, and carbon, with the remainder being molybdenum. The conductivity of this molybdenum alloy is 22-25% IACS, which is inferior to that of copper alloys, but it is a hard material with an HRB of about 100 and has excellent heat resistance because its recrystallization temperature is raised to over 1300°C. For this reason, the hole diameter at the tip near the welding point is less likely to enlarge, and it can achieve a service life several tens of times longer compared to conventional contact tips made of chromium copper.

[0022] The total length of welding contact tips used domestically is 40 mm or 45 mm according to the specifications of the welding machine, but as shown in Figure 4, in either case, the length of the second central hole 21 of the housing 20 is shortened to less than 1 / 3 of the length of the first central hole 11. Specifically, the length of the second central hole is in the range of 5 to 15 mm. By shortening the length of the second central hole 21 of the housing 20 in this way, the work of drilling a small diameter second central hole 21 into a hard material such as molybdenum alloy becomes easier. For this reason, the length of the first central hole 11 drilled in the adapter 10 can reach a maximum of 40 mm, but since the adapter 10 is made of a soft copper alloy, accurate drilling is possible. If the length of the second central hole 21 is less than 5 mm, the contact distance with the welding wire will be insufficient, and the welding current will become unstable. Conversely, if the length exceeds 15 mm, drilling becomes difficult, and the current supply position from the second central hole 21 to the welding wire becomes unstable, reducing the effect of concentrating the welding current on the inner surface of the second central hole 21, which is a characteristic of the present invention. Thus, one of the features of the present invention is that the length of the second central hole 21 of the molybdenum alloy housing 20 is shortened.

[0023] As shown in Figure 1, the adapter 10 and the housing 20 are integrated by screwing together an external thread 14 and an internal thread 23, and the tip of the first central hole 11 and the base of the second central hole 21 are in contact via a tapered hole portion 25. The diameter of the first central hole 11 of the adapter 10 is set to have sufficient clearance to prevent clogging, as in conventional designs. In contrast, the clearance of the inner diameter of the second central hole 21 is very small.

[0024] Specifically, when the wire diameter of the welding wire is 1.2 mm, the diameter of the first central hole 11 of the adapter 10 is 1.5 mm, and the clearance of the first central hole 11 is 0.3 mm in diameter and 0.15 mm on each side. In contrast, the diameter of the second central hole 21 is 1.3 mm, and its clearance is 0.1 mm in diameter and 0.05 mm on each side, which is one-third the clearance of the first central hole 11. The absolute values ​​of these clearances change depending on the diameter of the welding wire used, and the clearance increases as the wire diameter increases. However, in any case, it is preferable that the inner diameter of the second central hole 21 be 0.08 to 0.12 mm larger than the outer diameter of the welding wire used, and the clearance be 0.04 to 0.06 mm on each side. If the clearance of the second central hole 21 is smaller than this range, there is a risk of clogging, and if it is larger than this range, there is a possibility of inconsistent conductivity.

[0025] Because the second central hole 21, which has a smaller clearance, is positioned at the tip of the first central hole 11, which has a larger clearance, the welding wire fed from the base end of the adapter 10 is less likely to come into contact with the inner surface of the first central hole 11 while passing through its interior. However, when passing through the second central hole 21, which has a smaller clearance, it comes into contact with its inner surface, and the welding current is concentrated thereafter. In this way, the current supply position from the contact tip to the welding wire is specified to the second central hole 21 of the housing 20 at the tip, and the welding current can be concentrated on the inner surface of the second central hole 21. As a result, variations in the welding current are suppressed.

[0026] As described above, the welding contact tip of the present invention is integrated by screwing the male thread 14 of the adapter 10 into the female thread 23 of the housing 20. Conventional screw-type welding contact tips were screwed in while maintaining the shape of the threads so that the housing 20 could be easily replaced. However, the welding contact tip of the present invention is fixed by setting a large torque on the torque wrench and screwing it in with excessive torque, thereby plastically deforming the threads. As a result, after coupling, the adapter 10 and the housing 20 are integrated and cannot be separated without using a special tool.

[0027] By plastically deforming the screw threads and crimping them in this way, it becomes impossible to replace only the housing 20 with an enlarged hole diameter as in the conventional method. However, at a microscopic level, the flank surfaces of the male thread 14 and female thread 23 are in surface contact, which has the advantage of stabilizing the current flow path from the adapter 10 to the housing 20 and suppressing variations in welding current. Furthermore, because the housing 20 at the tip of the welding contact tip of the present invention is made of a molybdenum alloy that combines heat resistance and hardness, the service life is more than 40 times that of conventional products, reducing the need to replace the housing 20. Therefore, when the service life is reached, the entire contact tip will be replaced, but the frequency of replacement is significantly reduced, so the total cost is greatly reduced and the work efficiency of welding operations can be improved.

[0028] The advantages of the welding contact tip of the present invention described above can be summarized as follows: (1) By making the diameter of the second central hole 23 on the tip side smaller and the diameter of the first central hole 11 on the base side larger, welding wire clogging can be prevented, and the welding current can be concentrated on the inner surface of the second central hole. (2) Because the housing 20 on the tip side is made of a molybdenum alloy that combines heat resistance and hardness, the service life is more than 40 times that of conventional products. (3) Because the length of the second central hole 23 of the hard molybdenum alloy housing 20 is made shorter to less than 1 / 3 of the length of the first central hole, drilling work can be performed accurately. (4) Because the adapter 10 and the housing 20 are manufactured separately, various combinations are possible to match the outer diameter of the welding wire and the total length of the contact tip, which can reduce manufacturing costs. (5) Because the adapter 10 and the housing 20 are crimped and fixed together, the current path from the adapter 10 to the housing 20 is stabilized, and variations in welding current are suppressed. As a result, welding quality can be significantly improved.

[0029] 1 Conventional contact tip body 2 Conventional contact tip center hole 3 Tip 10 Adapter 11 First center hole 12 Cylindrical body 13 Thin cylindrical section 14 Male thread 15 Male thread 16 Tapered enlarged section 20 Housing 21 Second center hole 22 Cylindrical section 23 Female thread 24 Hole section 25 Tapered hole section 26 Body

Claims

1. A welding contact tip comprising a copper alloy adapter having a first central hole, and a molybdenum alloy housing having a second central hole smaller in diameter than the first central hole, screw-connected to the tip of the copper alloy adapter, wherein the tip of the first central hole and the base of the second central hole are in contact via a tapered hole portion, the adapter and the housing are crimped and fixed by plastically deforming the screw threads by screwing them together with a large torque, the length of the second central hole is set to 1 / 3 or less of the length of the first central hole, and the welding current is concentrated on the inner surface of the second central hole to pass through the welding wire.

2. The welding contact tip according to claim 1, characterized in that the housing is made of a molybdenum alloy containing titanium, zirconium, and carbon, with the remainder being molybdenum, and the adapter is made of a copper alloy containing chromium.

3. The welding contact tip according to claim 1, characterized in that the inner diameter of the second central hole is set to be 0.08 to 0.12 mm larger than the outer diameter of the welding wire used.

4. The welding contact tip according to claim 1, wherein the total length of the adapter and the housing combined is 40 to 45 mm, and the length of the second central hole is 5 to 15 mm.

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