What are the causes of blowholes in welding?

1, the gas produced by arc welding contains excessive hydrogen and carbon monoxide;

2. The sulfur content in basic steel is too high;

3. The performance of flux and baking temperature are not high enough;

4. The cooling speed of welding parts is too fast;

5. The welding area is caused by oil pollution, paint, rust, water or galvanized layer;

6. There is too much moisture in the air.

Extended data

Classification of electric welding methods:

1. fusion welding is a method of heating the metal at the weld of the weldment to a molten state during welding, and generally completing the welding without pressure. When welding, the heat source makes the metal at the weld of the weldment and the filler metal added when necessary melt rapidly to form a molten pool, which extends with the movement of the heat source and forms a weld after cooling.

2. Pressure welding is a welding method to connect the seams of weldments under pressure. In the process of pressure welding, generally no metal is added. According to the different welding mechanism, pressure welding can be divided into resistance welding, high frequency welding, diffusion welding, friction welding and ultrasonic welding.

3. Brazing is a welding method in which materials (solder) with lower melting point than weldments are melted, then the weldments are bonded, and then the seams of weldments are connected together after cooling.

reference data

Baidu encyclopedia-welding blowhole