Generally, the welding part needs to undergo heating-melting-metallurgical reaction-solidification crystallization-solid phase transformation-formation of joints and other processes.

Characteristics of welding thermal process

1. locality of heat effect

The locality of the heat action means that the welding heat is concentrated on the connection part of the weldment instead of uniformly heating the entire weldment. unlike metal heat treatment, uneven heating is the basic feature of the welding process.

2. transientness of heat action

in the welding process, the heat source moves at a certain speed, and the effect of heating at any point on the weldment is instantaneous, that is, with time, under the action of the concentrated heat source, the heating speed is very fast (arc welding is at 1500℃·s- 1 above), the heat is transferred from the heat source to the weldment in a short time.

Note: ERW steel pipe is manufactured by cold forming a flat steel strip into a rounded tube and passing it through a series of forming rollers to obtain a longitudinal seam.