530 mm超厚20MnMoNb锻件的窄间隙埋弧焊

Narrow-gap submerged arc welding for 530mm thickness 20MnMoNb forging

对深海试验装置930压力筒的主体材料20MnMoNb锻件进行焊接性分析,针对530 mm超厚锻件试板的焊接结构,制定合适的焊接工艺方案,预防焊接缺陷的产生。采用窄间隙埋弧焊焊接试板,试板经焊后热处理后进行无损检测和力学性能检测,检测结果均符合设计要求,焊缝一次合格,完成了焊接工艺评定,为930压力筒的制造奠定了坚实的基础。对焊缝进行微观组织分析,发现其中有细小的针状铁素体析出,细化了粗大的晶粒,这对焊接接头的力学性能有一定的改善作用。本次焊接工艺评定的完成,对超壁厚焊接结构的问题解决提出了新的思路。

In this paper, the weldability of 20MnMoNb forging is analyzed. It is the main material of the undersea test equipment 930 pressure tank. An appropriate welding technology plan is formulated to avoid welding defects for the welding structure of 530 mm super thickness forging test plate. And the narrow-gap submerged arc welding is adopted to complete the test. After PWHT,the welds of test plate pass the NDT test and mechanical properties test without any repair,the results meet the design requirement,which means the test plate passes the welding procedure qualification. This lays a solid foundation for the manufacture of 930 pressure tank. Besides,the microstructure of weld is analyzed and many tiny acieular ferrite precipitates are found. These precipitates refine grain and improve the mechanical property of welded joint. The achievement of this welding procedure qualification puts forward a new idea fur the welding structure with super wall thickness.