为了认识钢结构裂纹产生的原因，通过对钢结构常用的焊接方法，埋弧焊(SAW)，气体保护焊(FCAW)，手工焊(SMAW)及各种接头形式焊缝在结构中的位置进行磁粉干法检测和分析，发现缺陷的产生与焊接方法、焊缝在结构中的位置、工艺条件、焊接应力、装配情况相互联系。因此在焊接工艺制订，检测工艺制订时应该关注这些产生缺陷的原因、位置。

In order to recognize the reason of steel structure cracking, by analyzing steel structure's welding method (SAW,FCAW,SMAW) and some weld seam of different position's testing by MT, it was concluded that the defects hade some relations with welding method, welding position, welding procedure conditions, welding stress, assembly and so on. So the reason to cause defect and its position should be known before establishing WPS.