Practical application of welding preheating

Practical skills should also be paid attention to to avoid material softening problems caused by preheating. Choose those welding processes and electrodes that rarely introduce hydrogen. Certain techniques can reduce or reduce residual stress. Monitor carefully to ensure that the preheating method is used correctly. The following descriptions are very important to the successful use of these techniques.

Welding groove size and skills

The skill in the welding process has a great influence on the welding shrinkage of the workpiece, the result of residual stress, the control of heat input and the avoidance of cracks.

Compared with long welds, short welds have smaller longitudinal shrinkage. You can also use backhand welding or special welding sequence to reduce residual stress.

Control or reduce heat input. A linear weld with small oscillations can be used instead of a large oscillating weld.

Reduce cracks

Arc craters and weld cracks can be reduced or eliminated by using appropriate manufacturing processes.

1) Compared with welds with thin and wide cross-sections, welds with round cross-sections have the least cracks during welding.

2) Avoid sudden welding or stopping. Welding operation and weld formation are controlled by using up/down inclination welding techniques or electrical methods through the welding power source.

3) There must be enough deposited materials to avoid cracks caused by welding shrinkage or normal welding. The empirical approach to avoid cracks due to insufficient weld deposit material (also required in many production specifications) is: the amount of deposited metal is at least 3⁄8-in. (10 mm) or the thickness of the weld groove 25% of it.

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