Steel structure needs preheating before welding

Today, steel structure workshop is widely used, as one of the main building structures, often used in large factories, venues and other places, the quality of the structure is more important is the construction process, today we mainly introduce the preheating before welding, which is what is important, see below:

1. Preheating can reduce the constraint degree of welded steel structure, especially for reducing the constraint degree of corner joints. With the increase of preheating temperature, the incidence of crack decreases.

2. Preheating can reduce the welding stress of steel structure. The temperature difference (also known as temperature gradient) between welders in the welding area can be reduced by uniformly local or whole preheating. In this way, on the one hand, the welding stress is reduced, on the other hand, the welding strain rate is reduced, which is beneficial to avoid welding cracks.

3. Preheating can slow down the cooling speed after welding, which is conducive to the escape of diffused hydrogen in the weld metal and avoid hydrogen-induced cracks. At the same time, the hardening degree of weld and heat affected zone is reduced, and the crack resistance of welded joint is improved.

4. The uniformity of preheating temperature in the direction of steel plate thickness and in the weld area has an important influence on reducing welding stress. If the preheating of steel structure is not uniform, the welding stress will not be reduced, but will be increased.

Therefore, in general, preheating can directly affect the quality of steel structure, so it is an essential step, I hope the above content can help you.