JPH0361547B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to surface treatment of a torch nozzle for arc welding. [Background of the Invention] The welding methods in which the torch nozzle for arc welding of the present invention is used are MIG welding, TIG welding, and MAG welding. This is a method of welding by melting a supply wire such as a welding wire using the heat generated by the spark between the welding wire and the welded material. During welding, not all of the molten metal lands on the material to be welded; it becomes spherical due to surface tension and scatters as spatter. This spatter flies to the inner and outer peripheries of the torch nozzle 1 (see FIG. 2) without being sufficiently cooled in the air. Since the spatter is not cooled and is in a high temperature state, the sputter and the conventional metal torch nozzle 1
Adhesion occurs at the contact interface. If the adhesion occurs on the inner circumferential surface of the torch nozzle 1, the space between the contact tip 2 and the torch nozzle 1 becomes gradually narrower, the amount of supplied gas 3 decreases, and as a result, welding defects occur. To explain this point in more detail, there is a contact tip 2 inside the torch nozzle 1, and the contact tip 2 is usually made of copper and has a hole inside. 4. Supply welding current to 4. This contact chip 2 is attached to a head adapter 5. And torch nozzle 1
There is a space between the contact tip 2 and the contact tip 2, and a gas 3 is flowed into this space to spray the gas onto the welding part to prevent oxidation. When this supplied gas decreases, oxidation cannot be prevented, and furthermore, the arc during welding becomes unstable, resulting in the aforementioned welding defects. For this reason, conventionally, the welding work is performed while periodically removing spatter adhering to the inner and outer circumferential surfaces of the torch nozzle. However, this removal work cannot be performed permanently; in other words, by forcibly removing the spatter, the adhesion interface between the spatter and the torch nozzle is removed, and the surface layer of the torch nozzle is removed. will be gradually removed. Therefore, the more spatter is removed, the more the surface of the torch nozzle becomes rough and the spatter becomes more likely to adhere to it, ultimately making the torch nozzle unusable. In order to prevent this spatter, various techniques have been proposed in the past in which the surface of a metal torch nozzle is coated with ceramics. As this technology, for example, Japanese Patent Application Laid-open No. 51-37053, Utility Model Application No. 59
−49477, Utility Model 59-47476, Utility Model 49-64528,
1986-1526, 6576-6576, 56-
34677, Sho 51-23525, Sho 50-76021, Sho 53-26630, Sho 57-82484, Sho 57-
There are 160887 and 49478 in the 1980s. [Problem] However, in the above techniques, the torch nozzle is simply coated with ceramics, and nothing is mentioned about the optimum physical properties of ceramics for coating the torch nozzle. In other words, there are many different types of ceramics, and the ceramics coated on the torch nozzle can crack due to the heat generated during welding and the heat from adhesion of spatter, making it impractical for practical use. It was something that couldn't be helped. [Object of the Invention] The present invention has been made in view of the above problems, and an object thereof is to provide a torch nozzle coated with ceramics that does not cause cracks during welding work. [Means for achieving the object] The present invention provides a metal torch nozzle for arc welding whose entire inner and outer periphery has a thermal conductivity of 0.03 [cal/cm・
sec・℃] or more, the thermal expansion coefficient is 7.3×10 ^-6 [1/℃]
The coated ceramic is coated with at least one non-oxide ceramic selected from SiC, Si ₃ N ₄ , BN, B ₄ C by chemical vapor deposition or physical vapor deposition method. It is further characterized in that at least one titanium compound selected from TiC, TiN, and TiC+TiN is coated in one layer or in multiple layers by chemical vapor deposition or physical vapor deposition. The inventor considered that the cause of cracks in the ceramic coated on the torch nozzle is that the coating ceramic is locally heated and expanded by the heat during welding and the heat when spatter is attached. did. Therefore, in order to prevent the above-mentioned cracking, we thought it would be best to find out which range of thermal conductivity and coefficient of thermal expansion should be used among a wide variety of ceramics. Therefore, in manufacturing the torch nozzle 1 shown in FIG. 1, first, the torch nozzle itself was manufactured from the ceramic materials shown in Table 1 in order to be coated on the metal torch nozzle, and the welding work was performed using those torch nozzles. An experiment was conducted to see if cracking occurred. The results of this experiment are shown in Table 1. (In other words, Table 1 shows the thermal conductivity, thermal expansion coefficient, and cracking properties of the ceramic itself.)

【table】

[Table] From this experimental result, the thermal conductivity is 0.03 [cal/cm・
sec・℃] or more, and the coefficient of thermal expansion is 7.3×10 ^-6
It was determined that ceramics satisfying the condition of less than [1/°C] would not cause cracks during welding work. The reason why a high thermal conductivity gives good results is that it can promote the dissipation of heat applied to the coating ceramic and prevent thermal reactions with spatter (molten metal). Furthermore, the reason why a small coefficient of thermal expansion produces good results is that cracking due to thermal expansion can be directly prevented. Next, Table 2 shows the physical properties of typical conventional ceramics.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the shape of a torch nozzle according to the same embodiment, and the entire inner and outer surfaces of the torch nozzle 1 are coated with SiC as a non-oxide ceramic.
Therefore, the physical properties of the torch nozzle surface are as shown in Tables 1 and 2, with a thermal conductivity of 0.25 [cal/cm・
sec・℃], thermal expansion coefficient 4.0×10 ^-6 [1/℃], bending strength 5500 [Kg/cm ² ], Bitkers hardness 1900 [Kg/mm ² ]
It is. As is clear from the above explanation and experimental results,
The thermal conductivity value of SiC promotes heat dissipation of ceramics,
Therefore, thermal reaction with spatter is prevented, and with the thermal expansion value of SiC, cracking due to thermal expansion does not occur, and a ceramic coating with good durability under working conditions can be obtained. As a vapor deposition method for SiC ceramics, a physical vapor deposition method or a chemical vapor deposition method that is compatible with characteristics such as covalent bond properties of SiC is suitable. In other words, ceramic coatings made by physical vapor deposition generally exhibit characteristics such as strong adhesion to the substrate, high hardness, and stability at high temperatures, making them suitable for welding torch nozzles like the one in this example. Become. When using a chemical vapor deposition method, it is desirable that the thickness of the ceramic coating be several μm or less in order to increase the adhesion strength. When carrying out the present invention, not only the thermal conductivity and thermal expansion coefficient of the coating ceramics but also the
It is better to consider bending strength, Vickers hardness, and even surface roughness. That is, the bending strength is 2500
[Kg/mm ² ] or more, Bitkers hardness is 1200 [Kg/mm ² ]
As mentioned above, it is desirable that the surface roughness is 1.0 to 0.5S. The reason why bending strength is considered is that cracks occur in coating ceramics because thermal stress caused by heat during welding behaves in the same way as bending stress. Therefore, if it is strong against bending stress, it will be strong against thermal stress and will not crack. The reason for considering the Vickers hardness is to prevent the surface of the torch nozzle from being worn and uneven when removing adhering spatter with a metal brush or the like. The reason for considering surface roughness is that it is directly related to spatter biting into the surface of the torch nozzle. That is, when the above-mentioned welding experiment was carried out with the surface roughness of the coating ceramics changed to 5S, 3S, and 1S, the adhesion of spatter became more pronounced in the order of increasing surface roughness. This is because a thermal reaction occurs with the spatter at the apex of the convex portion on the surface, and the spatter easily adheres thereto. Therefore, reducing the unevenness on the surface of the torch nozzle and making it as close to a flat surface as possible will prevent thermal reactions and the adhesion of spatter. Therefore, the smaller the surface roughness, the better, but from an industrial perspective, 1 to 0.5 S is considered to be good. To this end, in this embodiment, a single layer of TiC (not shown) is further coated on the SiC coating. TiC is even harder than SiC and has a flatness of 9 or more, so the surface hardness of the torch nozzle is further strengthened to, for example, 3300 to 4600 (VHN), and its wear resistance and heat resistance are improved. Furthermore, TiC creates dents in the rough surface of SiC ceramics, and as a result, the surface roughness decreases by a factor of 1/2 to 1/5. As for the method of depositing TiC, a physical vapor deposition method or a chemical vapor deposition method that is suitable for its characteristics is also suitable. As described above, according to this example, a good torch nozzle surface with excellent wear resistance and heat resistance and reduced surface roughness can be obtained. In the above embodiment, the TiC coating was made into a single layer, but the present invention is not limited thereto, and the TiC coating may be made into a plurality of layers. Further, in the above embodiment, the ceramic material of the torch nozzle was SiC, but the present invention is not limited thereto. Like SiC, it is hexagonal, has covalent properties, and has a thermal conductivity of 0.03. [cal/
cm・sec・℃] or more, the thermal expansion coefficient is 7.3×10 ^-6
Si ₃ N ₄ , BN, which satisfies the condition of less than [1/℃]
At least one type of non-oxide ceramic selected from B ₄ C can be used. Furthermore, in the above example, the coating on the ceramic layer was TiC, but the present invention is not limited thereto; it is an equiaxed crystal system like TiC, and has similar properties such as hardness and heat resistance. Similarly good effects can be obtained using a titanium compound selected from TiN or a mixture of both TiC+TiN. [Effects of the Invention] As described above, according to the arc welding torch nozzle of the present invention, the ceramic coated on the surface of the torch nozzle can be prevented from cracking during welding work, and a practical ceramic coating torch nozzle can be obtained. can be provided.

[Brief explanation of drawings]

FIG. 1 is a partial side sectional view of a torch nozzle for arc welding according to an embodiment of the present invention, and FIG. 2 is a partial side sectional view of a conventional metal torch nozzle for arc welding. 1...Torch nozzle, 2...Contact chip, 3...Gas, 4...Welding wire, 5...Head adapter, 6...Ceramics.

Claims (1)

[Claims] 1. The entire inner and outer periphery of a metal torch nozzle for arc welding has a thermal conductivity of 0.03 [cal/cm・sec・℃] or more and a thermal expansion coefficient of 7.3×10 ^-6 [1/℃]. less than
Coating with at least one non-oxide ceramic selected from SiC, Si ₃ N ₄ , BN, and B ₄ C by chemical vapor deposition or physical vapor deposition, and further depositing on the coated ceramic A torch nozzle for arc welding, characterized in that at least one titanium compound selected from TiC, TiN, and TiC+TiN is coated in one layer or in multiple layers by chemical vapor deposition or physical vapor deposition.