JPH0140910B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention provides a contact chip for arc welding,
This invention relates to a method of applying ceramic coatings to improve wear resistance, spatter resistance and reaction resistance. [Prior art] Contact tips for arc welding are usually made of copper-based alloys or aluminum alloys, but since the surface of the contact tip is metal, the nozzle part may wear out due to spatter adhesion or thermochemical reactions during welding. Otherwise, clogging occurred, which significantly shortened the life of the contact tip. As a method to solve the above-mentioned problems, as described in Japanese Utility Model Application Publication No. 52-26630, Japanese Utility Model Application Publication No. 59-49478, or Japanese Utility Model Application Publication No. 57-82484,
A method of protecting the nozzle part of a contact tip with a ceramic guide. Or Utility Model Application Publication No. 76021/1983, Utility Model Application Publication No. 57-
A method of coating contact chips with ceramic has been proposed as described in Japanese Patent No. 160887. However, the above-mentioned method of protecting the nozzle part with a ceramic guide not only complicates the structure of the contact chip and causes problems in terms of manufacturing costs, but also has the problem that the entire contact chip cannot be protected from spatter that is scattered over a wide area. It was hot. On the other hand, the method of coating the contact chip with ceramic has the potential to solve the problem of complicating the structure and protecting the entire chip, but the coating method has not yet been established, and depending on the coating method, it may not be possible to use it. Occasionally, there were problems such as cracking or peeling of the ceramic layer. As a result of intensive research into a method of coating a contact chip with ceramic, the inventors of the present invention developed a method of coating ceramic with a PVD method or a CVD method, and previously filed an application as Utility Model Application No. 163202/1983. As a result of further research into this method, the present inventors succeeded in improving the spatter resistance and reaction resistance of contact chips and significantly extending their lifespan using the technology disclosed in Utility Application No. 163202/1983. However, even with this technology, the thickness of the ceramic coating layer remains
If it is less than 10μ, the heat insulation effect is not sufficient, and when applying CVD and PVD methods, it is necessary to heat the contact chip to about 500 to 1000℃, respectively.
This heating causes the contact tip to become annealed, resulting in a decrease in hardness, which increases wire wear and reduces strength, making accurate welding difficult.To prevent this, further hardening treatment is required after ceramic coating. We found that there are several issues that need further improvement, such as the need to perform [Problems to be Solved by the Invention] The present invention solves the problems of cracking, peeling, film thickness, and annealing softening of the ceramic coating layer, which were problems when applying a ceramic coating to a contact chip for arc welding. The aim is to provide a way to solve both problems at the same time. [Means for Solving the Problems] As a result of intensive research and development of means for achieving the above-mentioned object, the present invention has revealed that when a contact chip is coated with ceramic by plasma spraying,
The thickness of the ceramic coating can be set as desired.
It was also developed after discovering that its adhesion is strong, and that the temperature of the contact chip base during the ceramic coating process can be suppressed to about 100°C, preventing the contact chip base from becoming annealed and softened.Specifically, arc welding After cleaning the surface of the contact chip substrate, such as degreasing by ultrasonic cleaning and removing oxide film by sandblasting, an oxidation-resistant metal is sprayed as necessary, then a ceramic is plasma sprayed, and finally, By employing a structure in which the surface is smoothed, the above-mentioned problems are simultaneously solved. [Operation] Since the contact tip base body 1 for arc welding is usually manufactured by forging or grinding, oils and fats such as lubricating oil are attached to the surface of the base body. When ceramic plasma is sprayed with oil and fat adhered to it, the flame distance is generally short in plasma spraying, and the thermal energy transmitted to the substrate surface is small, making it difficult to completely remove the oil and fat from the substrate surface by scattering. As shown in Figure 4 A, carbon 5
In this state, it gets rolled up in the ceramic coating layer 3. The carbon 5 entrapped in the ceramic coating layer causes cracking or peeling of the ceramic coating layer during use of arc welding. Therefore, when coating ceramic by plasma spraying, it is important to remove oil and fat from the substrate surface in advance by ultrasonic cleaning or the like in order to improve the strength of the ceramic coating layer. In addition, the contact tip base for arc welding is
It is mainly made of copper alloy or aluminum alloy, and has a strong oxide film formed on its surface. If a plasma ceramic coating is applied in the presence of an oxide film, an oxide layer 7 will remain between the substrate and the ceramic coating layer as shown in Figure 4B, and this will cause the ceramic coating layer to peel off. Therefore, it is important to remove the oxide film on the surface of the substrate in advance by sandblasting or the like in order to further improve the adhesion of the ceramic coating layer. Incidentally, when we compare the peel strength of ceramic coating layers with and without an oxide layer remaining in the middle, we find that the former has a significantly lower peel strength of about 50% of the latter. was confirmed.
If the contact chip base is made of copper alloy or aluminum alloy, even if the oxide film is removed, a strong oxide film will form again if left exposed to the atmosphere, so remove the oxide film by sandblasting, etc. It is not only advantageous in terms of workability to coat the ceramic with an oxidation-resistant metal 4 such as a nickel-chromium alloy, but also to improve adhesion by selecting a metal that easily bonds with ceramics, such as a Ni-Cr alloy. It is effective in further improving the In the present invention, after the above-described pretreatment, the ceramic is subjected to plasma spraying. In plasma spraying, the temperature of the plasma flame itself is 6,000 to 10,000°C, but especially under oxidizing conditions (in air), the flame distance is short and the ceramic particles are small, so the temperature of the plasma flame itself is 6,000 to 10,000°C. The thermal energy transferred is relatively small, and the temperature rise can be limited to 100-150°C for a normal-sized arc welding contact tip. This is a great advantage compared to the case where the ceramic coating is applied using the CVD method or the PVD method, in which the temperature of the substrate is heated to 500° C. or higher. In other words, contact tips for arc welding are usually made of copper alloy or aluminum alloy. Copper alloys undergo an annealing softening phenomenon at around 250°C, so when conventional CVD or PVD methods are applied, they are work hardened. This results in a decrease in hardness and bending strength of the contact tip. On the other hand, when the ceramic coating is applied by plasma spraying as in the present invention, the temperature of the substrate is 250°C.
Since the temperature does not rise above .degree. C., no annealing softening phenomenon occurs and there is no need for another hardening treatment. Another major advantage of ceramic coating by plasma spraying is that when CVD or PVD methods are applied, there is a limit to the thickness of the ceramic coating layer, and it is usually difficult to increase the thickness to 10μ or more. , in the case of plasma spraying, it is possible to form a ceramic coating layer of any thickness, from 100μ to
It is also possible to form ceramic layers with a thickness of 200μ. The effect of applying a ceramic coating to a contact tip for arc welding is not only to prevent spatter adhesion but also to block radiant heat during welding and prevent annealing and softening of the contact tip due to radiant heat during welding. However, when using the CVD or PVD method, the thickness of the ceramic coating layer can be adjusted as described above.
It is difficult to achieve a thickness of 10μ or more, and a ceramic coating layer of this thickness cannot sufficiently prevent the annealing softening phenomenon caused by radiant heat during welding, resulting in a decrease in hardness during welding and, ultimately, a decrease in wear resistance. Wear increases as the wire passes through it. On the other hand, when a ceramic coating layer is formed by plasma spraying as in the present invention, the thickness of the ceramic coating layer can be arbitrarily determined as described above, and a ceramic coating layer with a thickness of about 100 to 200 μm can be easily formed. Since the radiant heat during welding can be effectively blocked and annealing softening can be prevented, the hardness does not decrease even during welding and wear resistance can be maintained. Contact chip materials include Cu-Ni and Cu-Cr as long as they have conductivity and heat resistance.
It goes without saying that various known copper alloys or aluminum alloys such as Cu-Cr-Zr alloys, Cu-Cr-Zr alloys, Cu-Be alloys, and Al-Mg alloys can be used. Further, as the ceramic material used in the present invention, any ceramic material commercially available for plasma spraying can be used to obtain the desired effect, but from the experimental results of the present inventors, Al ₂ O ₃
system, Al ₂ O ₃ −TiO ₂ system, Tio ₂ system, CrO ₃ system, Cr ₂ O ₃ −
It has been found that particularly remarkable effects can be obtained when SiO ₂ -based, SiC-based, Si ₃ N ₄ -based and BN-based ceramics are used. In the present invention, polishing treatment is performed at the end, and this is based on the following technical reasons. That is, as described above, during arc welding, spatter from high-temperature spheres is scattered, and a portion of it is attached to the surface of the contact chip as shown in FIGS. 5A and 5B. When investigating the manner in which this spatter adheres, it was found that not only does it depend on the material of the surface of the contact chip, but the roughness of the surface is also an extremely important factor. . When considering spatter adhesion, the chemical reaction with the material should be mainly considered, but the surface condition must also be considered not only from a chemical perspective but also from a physical perspective. That is,
As shown in FIG. 4B, adhesion occurs in the concave portions of the surface due to physical entrapment, and in the convex portions, a thermochemical reaction occurs, and the synergistic effect promotes spatter adhesion, making removal difficult. CVD method or PVD
When applying this method, the surface of the substrate is smoothed before being coated with ceramic, so subsequent polishing treatment is not so necessary. However, in the present invention, as mentioned above, the substrate The surface roughness is rough, and since the molten ceramic spheres are hit on the substrate surface at high speed by plasma spraying, the surface roughness after coating is relatively rough and uneven, so as mentioned above, spatter adhesion is likely to occur if left as is. . Therefore, when coating ceramics by plasma spraying as in the present invention, it is necessary to polish the surface after coating with sandpaper or abrasive grains to smooth the surface. If the surface is smooth, it is possible to prevent adhesion due to spatter particles being caught in the recesses, and even if
Even if the spatter particles once adhere to the surface of the substrate, they can be easily removed because they are attached by point contact as shown in FIG. 4A. According to the experimental results of the present inventors, the above effects can be obtained by reducing the temperature to 20S or less, but from an industrial perspective, especially if the temperature is 5S or less, spatter resistance and reaction resistance can be improved even more effectively. It turned out that it can be done. [Example] <Example 1> A contact chip base 1 for arc welding was prepared by grinding a copper-nickel alloy consisting of Ni: 0.85 to 1.0%, Si: 0.4 to 0.6% and the balance copper, and this was subjected to the following process. Ceramic coating was applied. First, (1) submerge the contact chip base in water,
A normal ultrasonic alkaline cleaning treatment is applied for 3 to 5 minutes to completely remove the oil and fat adhering to the surface, and then a sandblasting treatment is applied for 1 minute to destroy and remove the oxide film on the substrate surface. Immediately after that, Al ₂ O ₃ by plasma spraying under the following conditions to 125 μm on the substrate surface.
An Al ₂ O ₃ coating layer 3 having a thickness of 100 mL was formed, and finally polished with SiC #180 sandpaper to produce an Al ₂ O ₃ coated contact tip for arc welding with a smooth surface.

[Table] Actual welding conditions for three types: the arc welding contact chip made in the above process, the arc welding contact chip coated with Al ₂ O ₃ by CVD method, and the arc welding contact chip without coating. The results of measuring the amount of spatter deposited and the amount of wear due to the wire after using it for 24 hours are as follows: The contact tip for arc welding made according to the present invention has the least amount of spatter deposit and the amount of wear due to the wire. I understand that.

[Table] <Example 2> As in Example 1, the base of an arc welding contact chip made of a copper-nickel alloy was subjected to ultrasonic cleaning and/or (ultrasonic + Freon) cleaning, and the oxide film was further destroyed and removed. After treatment, Ni:
After thermal spray coating with 80% Cr:20% nickel-chromium alloy powder (particle size -105 to +45μ) under the following conditions, Al ₂ O ₃ was plasma sprayed in the same manner as in Example 1, and finally a polishing treatment was performed. A contact tip for arc welding was created.

[Table] Regarding the arc welding contact tip made by this process and the arc welding contact tip made according to Example 1, the spatter adhesion amount and wear amount were under the same conditions as Example 1, and the adhesion strength was measured under the same conditions as Example 1. The results of testing the time taken for this to occur are as follows: The arc welding contact tip made in Example 2 was much better than the one made in Example 1, especially in terms of adhesion strength to ceramic. I can see that it is being done.

[Table] <Example 3> A contact tip for arc welding made of a copper-beryllium alloy (Be: 1.8-2.0%) was subjected to the same surface cleaning treatment as in Example 1, and then treated with nickel under the following conditions. Thermal spray coated with chromium alloy.

[Table] Next, the spray-coated contact chip is fixed to the rotating shaft in a vacuum chamber, the vacuum chamber is evacuated, and the gas vent valve of the chamber immediately before the spraying is replaced with Ar. Si ₃ N ₄ under the following conditions: open for discharge)
The Si 3 N 4 based ceramic was subjected to plasma spraying and finally subjected to the same polishing treatment as in Example 1 to produce an Si ₃ N ₄ based ceramic coated contact tip for arc welding.

[Table] The arc welding contact tip produced in the above process was subjected to the same test as in Example 2, and the results were as follows.

[Table] <Example 4> Below, Al ₂ O ₃ −TiO ₂ ,
Select TiO ₂ , Cr ₂ O ₃ , Cr ₂ O ₃ −SiO ₂ and BN,
The results of measuring the spatter adhesion amount and adhesion strength of ceramic coatings applied in the same steps as in Examples 1 and 2 are as follows.

【table】

〔Effect of the invention〕

As explained in detail above, the present invention not only reduces the amount of spatter adhesion by changing the surface material of ceramic coating and smoothing the surface, but also reduces the amount of spatter adhesion, which has been a problem with conventional ceramic coating treatments using CVD or PVD methods. This solution simultaneously solves the problem of accelerated wear due to annealing softening during coating treatment and annealing softening due to radiant heat during arc welding due to the limit of the thickness of the ceramic coating layer. Considering that the lifespan of arc welding contact tips is determined by clogging due to adhesion of spatter and wear due to wire passage, the present invention, which simultaneously solves these problems, has an extremely large impact on the arc welding industry. It can be said that it has an effect.

[Brief explanation of drawings]

Figure 1 shows an arc welding contact chip before plasma spraying, Figure 2 shows an arc welding contact chip coated with ceramic plasma spray immediately after cleaning treatment, and Figure 3 shows cleaning treatment. Fig. 4 shows an arc welding contact chip in which an oxidation-resistant metal is thermally sprayed and then a ceramic plasma spray coating is applied. FIGS. 5A and 5B are diagrams showing the surface treatment of a contact tip for welding; FIGS. 5A and 5B are views showing spatter adhesion when the surface of the contact tip for arc welding is smooth and uneven, respectively; FIGS. 1...Contact chip base for arc welding, 2
...Wire passing hole, 3...Ceramic coating layer, 4
... Oxidation-resistant metal layer, 5 ... Carbon, 6 ... Spatter adhesion particles, 7 ... Oxide layer.

Claims (1)

[Scope of Claims] 1. A contact tip for arc welding, characterized in that the surface of the base body is subjected to a cleaning treatment, then a ceramic plasma spray coating is applied, and then the sprayed surface is subjected to a polishing treatment. Ceramic coating method for contact tips. 2. The arc welding contact chip according to claim 1, wherein the cleaning treatment comprises degreasing by ultrasonic cleaning and/or (ultrasonic + Freon) cleaning and removing oxide film by sandblasting. Ceramic coating method. 3. The method of coating a contact tip for arc welding with ceramic according to claim 1 or 2, wherein the contact tip for arc welding is made of a copper-based alloy or an aluminum-based alloy. 4 On the surface of the contact chip base for arc welding,
A contact chip for arc welding characterized in that a cleaning treatment is performed, a pretreatment process is then performed in which an oxidation-resistant metal is thermally sprayed, a ceramic plasma-sprayed coating is applied, and the thermally sprayed surface is then polished. Ceramic coating method. 5. The contact tip for arc thermal spraying according to claim 4, wherein the cleaning treatment comprises degreasing by ultrasonic cleaning and/or (ultrasonic + Freon) cleaning, and removing oxide film by sandblasting. Ceramic coating method. 6. The method of coating a contact tip for arc welding with ceramic according to claim 4 or 5, wherein the contact tip for arc welding is made of a steel alloy or an aluminum alloy. 7. A ceramic coating method for an arc welding contact tip according to any one of claims 4 to 6, wherein the oxidation-resistant metal is a nickel-chromium alloy.