1. Preheating in steel structure engineering can alleviate the cooling speed after welding, which is conducive to the escape of hydrogen dispersed in the welding metal materials and prevent hydrogen from cracking. In addition, it also reduces the hard backing level of welding and thermal hazard area, and improves the adhesion of welding.
2. Preheating can reduce the welding stress. Partial preheating or overall preheating can reduce the temperature difference between welded parts in the welding area (also known as temperature gradient direction). In this way, on the one hand, the welding stress field is reduced, on the other hand, the welding strain rate is reduced, which is beneficial to avoid welding cracks.
3. The necessity of preheating before welding of high-rise residential steel structure. In steel structure engineering, preheating will reduce the level of reasonable arrangement of tube bundle, especially the discussion of small angle connector. With the increase of preheating temperature, the crack rate decreases.
The selection of preheating temperature and solid layer temperature is not only related to the composition of steel and welding wire, but also related to the bending stiffness of reasonable welding layout, welding method and field temperature.
