Preheating is Important

Why Preheating is Important?

Preheating minimizes the temperature difference between the arc and the material being welded. This benefits the weldment in the following ways.

1. it helps to reduce shrinkage stresses that can lead to cracking and distortion. 

2. proper preheating helps to slow the cooling rate of a weld and reduces hardness in the heat-affected zone. Slowing the cooling rate also allows hydrogen to escape weld metal.

When Preheating is required?

Preheating is especially important when welding the following parts:

Thick base materials, base materials that tend to be brittle, cast iron & dissimilar materials.
Preheating is also good for materials with a high-carbon equivalency.

How Are Parts Preheated?

Preheating with a flame from a torch is a common method, it is easy to use and it is also simple to use and has portability, the initial cost is low, and this process is known to welders. However, preheating with an open flame is inefficient compared to other options. It is also difficult to ensure consistent temperature throughout the part.

Induction heating is a good preheat option, this provides more consistent heat throughout the weldment.

Low hydrogen welding rod reduce cracking risks

Many filler metal manufacturers offer low-hydrogen tubular wires (FCAW wires) and shielded metal 
arc welding ( SMAW ) electrodes.