焊前为什么要预热众所周知,预热是防止工件在焊接时产生冷裂缝的有效手段。而在低合金高强度钢焊接时产生冷裂缝是一种普遍而又十分严重的缺陷。因此,对于这类材料的焊接大多提出预热的要求。产生冷裂缝(延迟裂缝)的原因,目前一致的看法是:焊后金属被淬硬(即形成了马氏体组织),接头的刚性过大,焊缝中存在大量的扩散氢等这些因素综合所致。工件焊前的预 Why preheat before welding As we all know, preheating is to prevent the workpiece in the welding cold cracks produced an effective means. Cold cracking of low alloy high strength steel during welding is a common and very serious defect. Therefore, most of the welding of such materials puts forward the requirement of preheating. The reason for the cold cracks (delayed cracks) is that the current consensus is that the metal is hardened after welding (ie, the formation of martensite), the joint stiffness is too large, there is a lot of diffusion in the weld hydrogen and other factors Due. Pre-welding the workpiece