Preheating is the process of heating the groove and groove ends 100mm area to a predetermined temperature before welding, which is mainly used to reduce the cooling rate and welding stress of the weld, and is generally used for thick plates or materials with high hardening tendency.

Post-heating refers to the process measures of heating or insulating all butt-welded parts immediately after welding, so as to make them cool slowly.

The purpose of post-heating is to reduce the content of diffused hydrogen in welded joints, especially in the heat affected zone, so it is also called dehydrogenation treatment, which is an important technological measure to prevent delayed cracks when welding some low-alloy structural steels. The post-heating temperature is generally 200~350℃, and the time is not less than 30 minutes.

Extended data:

When welding, physical quantities (such as welding current, arc voltage, welding speed, linear energy, etc. ) The parameters selected to ensure the welding quality are collectively referred to as welding process parameters. The influence of process parameters on weld shape is as follows:

Welding current When other conditions are unchanged, increasing welding current will increase the thickness and residual height of the weld, while the width of the weld is almost unchanged (or slightly increased).

When other conditions remain unchanged, the arc voltage increases, the weld width increases significantly, while the weld thickness and residual height slightly reduce the welding speed. When other conditions remain unchanged, the welding speed increases and the weld width, weld thickness and residual height decrease.