JPH0442066Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a contact tip for arc welding which is welded using a welding wire, and particularly to a contact tip for arc welding coated with a high melting point metal.

[Conventional technology]

In gas-shielded arc welding or non-gas arc welding methods in which welding wire, which is a consumable electrode, is continuously melted, the welding wire is energized by a contact tip attached to the tip of the welding torch, and the welding wire is energized by a contact tip attached to the tip of the welding torch. An arc is generated between the wire and the workpiece, and the welding wire is melted by the heat of the arc, turning into molten metal, which transfers to the workpiece and welds it. At this time, the area around the arc and molten metal is isolated from the air by a shielding gas, thereby preventing the generation of porosity and oxidation of the molten metal.

Among the above-mentioned arc welding methods, gas shielded arc welding is more efficient than shielded arc welding, and is therefore often used in automatic or semi-automatic welding equipment and welding robots.

Among the gas-shielded arc welding methods mentioned above, carbon dioxide welding is a commonly used welding method, but spatter often occurs during welding, and this can occur at the tip of the copper or copper alloy contact tip at the tip of the welding torch, or at the tip of the copper or copper alloy contact tip. It tends to adhere to the tip of the gas nozzle that supplies shielding gas.

If spatter adheres to the contact tip or gas nozzle, the smooth flow of shielding gas will be obstructed, making it easier for air to be drawn in, causing porosity.

Furthermore, if a large amount of spatter adheres to the contact tip and the gas nozzle is connected, sparks may be generated when the gas nozzle welds the workpiece, which may burn out the torch.

Furthermore, if the spatter travels from the tip of the contact tip into the hole or through the gas flow path in the gas nozzle, enters the contact tip, and adheres to the hole in the contact tip, it will clog the wire and cause welding to be interrupted. It may happen.

Spatter is hot particles that fly during welding and consists of molten slag and molten metal. The temperature of this molten metal is high, 1800-2300°C, and it tends to adhere to the contact tip and gas nozzle.

On the other hand, there are two factors that cause spatter to adhere: metallurgical and physical factors.The former is when the sputter collides with the contact chip, melts its surface, forms an alloy layer, and welds. The higher the temperature of the sputter and the higher the temperature of the contact tip, the stronger the adhesion and the more difficult it is to remove. The latter is mechanical adhesion caused by the surface roughness of the contact tip, and may cause scratches on the contact tip, etc.
The rougher the surface, the easier it will be to adhere.

In order to prevent spatter adhesion, various improvement measures have been proposed in the past.

As described in Japanese Utility Model Application Laid-Open No. 52-26630, a contact chip in which a ceramic tip guide is fixed to the tip of the contact chip base was proposed, and as described in Japanese Utility Model Application Publication No. 57-82484, A contact chip in which a ceramic tip is bonded to the tip of a tip base has also been proposed.

Since these ceramic chips have a much smaller coefficient of thermal expansion than the copper alloy contact chip base, the problem of cracking was unavoidable.

Next, as described in Japanese Utility Model Application No. 61-77175,
Contact chips have also been proposed in which a thin layer of hard ceramic is coated on the entire surface, both inside and outside the contact chip. This had the problem that the ceramic coating was easily peeled off.

[Problem that the invention attempts to solve]

Conventional contact chips coated with ceramics have a problem in that the coating tends to peel off, resulting in a shortened lifespan.

It is an object of the present invention to provide a contact chip which eliminates this problem, has a coating that is difficult to peel off, and has a long life.

[Means for solving the problem] The object of the present invention is to provide a welding wire having a hole through which a welding wire is passed;
In arc welding contact chips made of copper or copper alloy that supply welding current to the welding wire within the hole, the surface of the contact chip base has a melting point of 2500
This is achieved by providing a contact tip for arc welding coated with a high melting point metal, which is characterized by having a coating of a metal with a high melting point of 0.degree. C. or higher.

[Effect]

The entire surface of the copper or copper alloy contact chip base is coated with a high melting point metal with a melting point of 2500℃ or higher.
When deposited by CVD method, that is, chemical vapor deposition method,
The vapor-deposited high melting point metal diffuses into the surface layer of the contact chip substrate to form an alloy layer with copper, and as a result, the adhesion of the high melting point metal coating is greatly improved. Even if sputters collide and local thermal shock is repeatedly applied,
Peeling of the high melting point metal coating is less likely to occur.

〔Example〕

Examples will be explained with reference to FIGS. 1 and 2.

The surface of the contact chip base 1a made of copper alloy containing 1% chromium for arc welding is coated by CVD method.
Refractory metal coating 3, i.e. tungsten coating
Coat to a thickness of 14 μm.

In this CVD method, a contact chip substrate 1a is placed in a reaction chamber, the temperature of the chamber is raised to 430°C, a raw material gas WF ₆ and a carrier gas H ₂ are fed, and a tungsten metal layer is formed on the entire surface of the contact chip substrate 1a. Let it precipitate. The reaction formula is shown by the following formula: WF ₆ +3H ₂ →W+6HF.

Contact chip 1 manufactured in this way
Let this be sample A.

Next, to prepare a comparative test piece, a nickel layer with a thickness of 1 μm was applied in advance to the entire surface of a separate piece of the same contact chip base as above by electroplating method, and then a tungsten metal layer was applied in the same way as sample A above. Sample B is a sample coated with 14 μm thick.
Further, the same contact chip substrate as above without any coating was designated as sample C.

The results of a comparative test conducted on the above samples A, B, and C will be explained below.

First, regarding peeling of the coating, almost no peeling of the coating occurred in both samples A and B.

The reason for this is that in the case of sample A, when tungsten metal is deposited on the surface of the contact chip by CVD, the tungsten metal diffuses to the surface of the contact chip substrate, forming an alloy layer with copper, and the adhesion is greatly improved. This is because it has increased.

In the case of sample B, this is because the intermediate layer of nickel applied by electroplating has good adhesion to both copper and tungsten.

Next, regarding the adhesion of sputters, the adhesion of spatters was greatly reduced in samples A and B compared to sample C.

The reason for this is that even if a high temperature sputter of 1800°C to 2300°C collides with contact chip 1, the melting point is 3370°C.
This is because the tungsten coating 3 at 0.degree. C. does not melt, so almost no spatters adhere to it, and since peeling hardly occurs, no spatters adhere to the peeled portions.

Furthermore, since the inside of the hole 2 of the contact chip base 1a is also coated with tungsten by the CVD method, even if small particles of spatter fly in from the tip of the contact chip 1, they do not stick to it, so that wire clogging is reduced by half.

Next, the results of a life test performed on each of the above samples A, B, and C will be explained below.

The test method for the life test is carbon dioxide gas welding, a welding current of 150A, an arc for 10 minutes, and 5
The cycle of stopping for a minute was repeated, and the spatter was not removed during the process.

In addition, the life span in this example refers to the total welding time during which the welding current begins to drop rapidly due to spatter adhesion or friction, which causes the position where power is supplied to the welding wire to fluctuate and become unstable within the contact tip. ing.

As for the test results, as shown in Figure 2, the lifespan of sample C was approximately 100 minutes, while that of sample A was approximately 500 minutes, and that of sample B was approximately 800 minutes, significantly extending the lifespan. In addition, the lifespan of samples A and B is
Ceramics described in Publication No. 77175
This is a significant improvement in life compared to the TiN-coated contact chip, which was tested under the same conditions and had a lifespan of approximately 230 minutes.

The main reason why the lives of Samples A and B were greatly improved compared to Sample C is that the aforementioned tungsten coating 3 was less likely to peel off.

In addition, the tungsten coatings of samples A and B are better than the ceramic TiN coatings.
The main reason for the significant improvement in service life is that ceramics deposited by CVD do not diffuse into the surface layer of the contact chip substrate, whereas in the case of tungsten coating, when tungsten metal is deposited, it diffuses into the contact chip substrate or This is because it diffuses within the nickel intermediate layer to form an alloy layer and has good adhesion.

Note that as one method of expressing adhesion, tensile strength in the direction perpendicular to the adhesive surface is used. Since CVD coatings are very thin, there is no suitable way to perform a tensile test, and the tensile strength is not clear. However, comparative test results using plasma spraying, which can apply thick coatings, show that the tensile strength is higher than that of the alloy layer. While it is 100-200Kg/ ^cm2 for a ceramic coating that does not form an alloy layer, it is 400-200Kg/cm2 for a metal coating that forms an alloy layer.
CVD is known to be as high as 500Kg/ ^cm2 .
Even in the case of a ceramic coating without an alloy layer, it is thought that the tensile strength of a high melting point metal coating with an alloy layer is significantly superior to that of a ceramic coating without an alloy layer.

Based on the above results, a comparison of the operating rates of welding machines shows that for a robot automatic machine process with 20 automatic welding machines, the robot work efficiency is 50%, that is, welding is performed for 4 hours out of 8 hours per shift. As a result, the lifespan of each contact tip was approximately doubled, from 100 objects to be welded using the conventional method, to 200 objects using the present invention, and the occurrence of wire jamming was reduced to 200 objects per contact tip. The conventional method required four welders per shift for the entire machine, but this was halved to two with the present invention, greatly improving the operating rate of the welding machine.

In this example, the case of tungsten as the high melting point metal was explained, but the same applies to tantalum with a melting point of 3000°C, molybdenum with a melting point of 2620°C, and alloys between the above high melting point metals. Effects can be obtained.

[Effect of idea]

By providing a coating of a high-melting point metal with a melting point of 2,500°C or higher on the surface of the copper or copper alloy contact chip substrate, the coating will not peel off even if a high-temperature sputter collides with it and repeatedly applies localized thermal shock. Therefore, since the high-melting point metal coating is not melted, spatters are less likely to adhere to the peeled area, and the life of the contact tip is greatly improved as a whole.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a contact chip coated with a high melting point metal according to the present invention, and FIG. 2 is a comparison diagram of the results of a life test of the contact chip. DESCRIPTION OF SYMBOLS 1... Contact chip, 1a... Contact chip base, 2... Hole, 3... Refractory metal coating.

Claims (1)

[Claims for Utility Model Registration] 1. A contact tip for arc welding made of copper or copper alloy that has a hole through which a welding wire passes and supplies welding current to the welding wire within the hole, the surface of the contact tip base having a melting point. A contact chip for arc welding coated with a high melting point metal, characterized by having a coating of a high melting point metal of 2500°C or higher. 2. The high melting point contact chip according to claim 1 of the utility model registration claim, which has another metal layer between the contact chip base and the high melting point metal coating that has good adhesion to the base and coating metals respectively. Metal coated contact tip for arc welding.