Avoiding hydrogen cracking by preheating

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Avoiding hydrogen cracking by preheating

As mentioned above , the cracking risk is depending on the combination of the material, high tensile stresses and the presence of hydrogen. By adjusting the welding process and joint configuration the risk of cracking can often be minimized. However, sometimes there is a need for further action. Preheat is the most utilized and effective way of avoiding hydrogen cracking when other means are insufficient. There are three primary reasons to utilize preheat:

It lowers the cooling rate in the weld metal and base metal, producing a more ductile metallurgical structure with greater resistant to cracking
The slower cooling rate provides an opportunity for hydrogen that may be present to diffuse out harmlessly without causing cracking
It reduces the shrinkage stresses in the weld and adjacent base metal, which is especially important in highly restrained joints

More about pre-heating and SSAB recommendation can be found here and in the SSAB Welding handbook.

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How to weld How to avoid hydrogen cracking

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