What are the back protection methods for stainless steel welding?

What are the back protection methods for stainless steel welding?

With the rapid development of the petrochemical industry, stainless steel materials have been widely used in welding, which also puts forward higher requirements for pipe plate welding. The former stainless steel arc welding priming method has been phased out, using argon arc welding priming welding. Argon arc welding priming is faster and cleaner than electric arc welding priming. At the same time, there are some problems. In the welding process, the back side of the stainless steel argon-arc welding priming is prone to defects caused by oxidation, so back protection measures should be taken to ensure the mechanical properties and corrosion resistance of the weld. Therefore, effective protection measures should be taken when welding stainless steel.

A. Commonly used stainless steel welding back protection methods.

1. Stainless steel welding shield with argon protection

This method is usually used for stainless steel welding of steel plates and large diameter pipes. The protective cap connects the metal pipe to the argon hose. Open the argon valve and fill the protective cap with argon gas. Another person needs to hold the metal tube as a handle so that the protective cover slides over the back melt pool and synchronizes with the weld on the outside of the plate or pipe. In this way, the back is effectively protected. It is characterized by a centralized protection. Argon does not need to be opened too much and there is minimal argon waste.

2. Stainless steel welding part of the argon protection

For pipes with small local space and short size, it is easy to use local protection. Method: Seal the pipe welding joint with tape (to prevent gas leakage), seal both ends of the pipe with sponge, rubber, paper shell, etc., insert argon hose from one end to fill it with argon, and punch as many holes as possible in the sealed part of the other end of the pipe (without sponge), which is conducive to back welding head, when welding stainless steel, in order to prevent a large amount of argon gas from the weld, the sealing tape of the weld should be torn off and welded a section at a time to reduce the loss of more argon and effectively protect the weld. It is characterized by waste, slow argon filling speed and high cost.

3. Stainless steel welding mouth direct argon protection method

For the pipeline is too long, slightly larger pipe diameter, part of the argon filling is too wasteful, the quality can not be guaranteed, the project cost is too high. In order to save costs, the method of direct argon filling at the welded joint can be used.

B. Several stainless steel welding methods.

1.Stainless steel welding

Stainless steel welding is a process in which the welded joint melts at high temperatures throughout the welding process. Since the workpieces to be welded are inseparable, the molten liquids of the two product workpieces mix under the effect of temperature gradients, forces, etc., without pressure. After the temperature decreases, part of the melt solidifies and the two product workpieces are firmly welded together for welding.

2.Stainless steel welding arc welding

Stainless steel welding arc welding is a welding method in which a certain working pressure is released on the parts of the weldment with or without heating, causing plastic deformation or melting and causing the two molecules separated from the surface layer to produce metal bonding according to the effects of process hardening and external diffusion. There are many kinds of stainless steel welding arc welding, the common ones are resistance welding, forging welding, contact welding, friction welding, standard gas pressure welding, cold arc welding and explosion welding.

3.Stainless steel welding fiber welding

Stainless steel welding fiber welding refers to the filling metal less than the melting point of the weld and the welded parts are heated to the melting temperature of the filler metal, and fill the gap of the solid product workpiece with liquid filler metal to connect the metal material welding method. Stainless steel and fiber welding, should first clean the butt weld surface of the air oxide film and oil, in order to facilitate the full play of the blood vessels after the melting of the solder, improve the lubricity of the solder and hole-like fluidity. According to the different melting point of the solder, fiber welding can be divided into hard fiber welding and soft fiber welding.