Contact tip for welding

Abstract

This contact tip for welding is constituted by a copper alloy composed of, by mass%, 1.0 to 5.0% of Ni, 0.4 to 2.0% of Si, and the balance of Cu with inevitable impurities. The service life can be improved to 6 to 8 times as long as conventional ones while suppressing manufacturing cost. The total amount of inevitable impurities is preferably 0.3% or less. Further, 2.0-4.0% of Ni and 0.8-1.5% of Si are particularly preferable.

Description

Welding Contact Tip

[0001] The present invention relates to a welding contact tip that serves to guide a welding wire and to supply a welding current to the welding wire.

[0002] A welding contact tip has a rod-shaped tip body made of a copper alloy with excellent conductivity and a wire insertion hole formed in the center thereof. The welding wire is guided through the wire insertion hole and is supplied with a welding current by contact with the inner wall surface of the wire insertion hole. The tip of the welding contact tip is exposed to high temperatures caused by the arc and is prone to wear due to contact with the welding wire, causing the hole diameter to expand, which can lead to a deterioration in weld quality. For this reason, the welding contact tip must be replaced at regular intervals, during which welding operations must be stopped.

[0003] Therefore, welding contact tips are strongly required to have excellent wear resistance and a long service life, and various innovations have been made to date. For example, Patent Document 1 describes a welding contact tip in which a ceramic cylindrical body is fitted into the tip of the wire insertion hole to improve wear resistance. Also, Patent Document 2 describes a welding contact tip in which a nickel-boron plating film and a lubricant coating layer are formed on the surface, including the inner surface of the wire insertion hole, to improve wear resistance. However, both of these require special processing, which results in high manufacturing costs.

[0004] For this reason, efforts have been made to improve the material of the copper alloy that constitutes the welding contact tip, as shown in Patent Document 3. In Patent Document 3, the copper alloy contains 0.03 to 0.7% silver, and the welding contact tip is subjected to drawing or cold working to increase the hardness and conductivity. However, the use of expensive silver poses the problem of high manufacturing costs. Because welding contact tips are consumables, users cannot ignore the cost issue.

[0005] In recent years, welding methods that periodically switch the welding current between positive and negative phases have become mainstream, and in this case, the diameter of the tip of the wire insertion hole is more likely to increase. Prior patent literature

[0006] Japanese Patent Laid-Open No. 10-193122 Japanese Patent Laid-Open No. 2017-189816 Japanese Patent Laid-Open No. 2009-90355

[0007] SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a welding contact tip having a service life that is dramatically improved over the prior art while suppressing manufacturing costs.

[0008] The welding contact tip of the present invention, which has been made to solve the above problems, is characterized in that the entire tip body is made of a copper alloy having a composition, in mass %, of 1.0 to 5.0% Ni, 0.4 to 2.0% Si, and the balance: Cu and unavoidable impurities.

[0009] The total amount of unavoidable impurities is preferably 0.3% or less, and it is particularly preferable that Ni be in the range of 2.0 to 4.0% and Si be in the range of 0.8 to 1.5%.

[0010] By setting the Ni and Si contents within the above ranges, the welding contact tip of the present invention is able to achieve a good balance between electrical conductivity and wear resistance, thereby successfully reducing manufacturing costs and dramatically improving the service life compared to conventional contact tips.

[0011] FIG. 2 is a cross-sectional view of a welding contact tip according to an embodiment.

[0012] An embodiment of the present invention will be described in detail below. Fig. 1 is a cross-sectional view showing an example of a welding contact tip, in which a welding wire insertion hole 11 is formed in the center of a cylindrical tip body 10, and a male thread portion 12 is formed at the rear end. The rear end of the insertion hole 11 forms a tapered wire introduction portion 13. The entire tip body 10 is made of a copper alloy having a composition of 1.0 to 5.0% Ni, 0.4 to 2.0% Si, and the balance: Cu and unavoidable impurities.

[0013] Ni is easily alloyed with copper and has a higher hardness than copper, so it is a component that contributes to improving wear resistance. Si also acts as a surfactant to promote bonding between metals and has a higher hardness than copper, so it is also a component that contributes to improving wear resistance. Therefore, the welding contact tip of the present invention, which is made of a copper alloy containing Ni and Si, can suppress breakage due to wear and extend its service life in welding with a fast wire feed speed or welding with high wear.

[0014] However, because Ni and Si have lower electrical conductivity than copper, increasing their content reduces the electrical conductivity of the welding contact tip, leading to increased heat generation, which can cause the contact tip to seize and deteriorate welding quality.Furthermore, because Si has lower heat resistance than copper, increasing its content can cause the welding contact tip to soften or melt at high temperatures.

[0015] Thus, Ni and Si are components that contribute to improving wear resistance, but they also inhibit electrical conductivity and heat resistance. As a result of repeated experiments, the inventors determined that a composition of 1.0 to 5.0% Ni, 0.4 to 2.0% Si, and the remainder Cu and unavoidable impurities is the most balanced composition for a welding contact tip.

[0016] That is, if Ni is less than 1.0%, hardness decreases, and if it exceeds 5.0%, hardness increases but electrical conductivity and heat resistance decrease. Similarly, if Si is less than 0.4%, hardness decreases, and if it exceeds 2.0%, electrical conductivity and heat resistance decrease. In particular, the range of Ni: 2.0 to 4.0%, Si: 0.8 to 1.5%, which is in the middle of the above range, is the most preferable range.

[0017] Copper alloys contain trace amounts of unavoidable impurities, which inhibit electrical conductivity, so their total content should preferably be 0.3% or less. There are also copper alloys with increased hardness due to the addition of hard metals such as chromium and cobalt, but these all reduce electrical conductivity and increase costs, making them undesirable materials for welding contact tips.

[0018] The results of experiments conducted to confirm the performance of the present invention are shown below. Welding contact tips were manufactured from copper alloy wires with varying Ni and Si compositions, as shown in Table 1. For comparison, a conventionally used chromium-copper contact tip and a silver-containing copper contact tip, as described in Patent Document 3, were also prepared. These were then set in an actual welding machine, and arc welding was performed in which the welding current was periodically switched between positive and negative phases, and data on service life was collected. The contents in Table 1 are in mass percent, with the remainder consisting of copper and unavoidable impurities.

[0019] To measure the service life, stainless steel wire was used as the welding wire, and the service life of the chromium copper contact tip was used as the standard, with equivalent items marked as ◯, less than that marked as ×, and better than that marked as ◎. The service life of contact tips Nos. 2, 3, and 6, which are products of the present invention, was 6 to 8 times that of the standard product, demonstrating a significantly longer life than conventional products. It was also confirmed that the service life of welding contact tips Nos. 2, 3, and 6 was 6 to 8 times that of the standard product when both non-plated wire and plated wire were used as the welding wire. The evaluation results are shown in Table 1.

[0020]

[0021] As shown in Table 1, welding contact tips Nos. 2, 3, and 6, which are products of the present invention, have excellent conductivity, are low cost, and have a significantly longer service life than conventional welding contact tips made of chromium copper.

[0022] The welding contact tip No. 1 had low Ni and Si contents and received an X rating in all evaluation items except for electrical conductivity. No. 4 had a low Si content, so its service life was equivalent to that of the standard product No. 8. No. 5 had an excessively high Si content, which reduced its heat resistance and electrical conductivity. No. 7 had an excessively high Ni content, which reduced its electrical conductivity. The silver-containing copper contact tip No. 9 had performance equal to or better than the standard product, but was more expensive. Furthermore, Nos. 5 and 7 had high Ni and Si contents, which made them prone to spatter adhesion.

[0023] As explained above, the welding contact tip of the present invention is able to achieve a good balance between electrical conductivity and wear resistance, and as a result, it is highly practical, with a service life that is dramatically improved to 6 to 8 times that of conventional products while keeping manufacturing costs down.

[0024] 10 Tip body 11 Welding wire insertion hole 12 Male thread portion 13 Wire introduction portion

Claims

1. A welding contact tip characterized in that the entire tip body is made of a copper alloy having the following composition, in mass percent: Ni: 1.0 to 5.0%, Si: 0.4 to 2.0%, the remainder: Cu and unavoidable impurities.

2. A welding contact tip according to claim 1, in which the total amount of unavoidable impurities is 0.3% or less.

3. A welding contact tip according to claim 1, containing Ni: 2.0 to 4.0% and Si: 0.8 to 1.5%.

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