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X70管线钢在用常规方法焊接时,焊接热影响区的晶粒容易粗化,造成焊接接头强度和韧性下降。采用间隙宽度为4 mm的焊剂带约束电弧超窄间隙焊接方法,对14 mm厚的管线钢进行单道多层焊接工艺试验,获得了根焊、填充焊、盖面焊的工艺参数。试验了加填充条、背面衬陶瓷衬垫的方法,可以得到良好的单面焊双面成型的根焊焊道。这种方法焊接线能量约为0.6 k J/mm;焊缝组织主要为细小的针状铁素体;热影响区未出现严重粗化;焊缝硬度比较高,高出母材30%左右;低温冲击韧性良好,韧脆转变温度约为-40℃。
X70 pipeline steel in the conventional method of welding, the heat affected zone of the grain easily coarsening, resulting in decreased strength and toughness of welded joints. The method of single-layer multi-layer welding was used to test the 14 mm thick pipeline steel with the flux-constrained arc narrow gap welding method with the gap width of 4 mm. The technological parameters of root welding, filler welding and capping welding were obtained. The method of adding filler strip and backing ceramic liner was tested, and a good single-sided welded double-sided rooted bead weld was obtained. In this method, the welding line energy is about 0.6 kJ / mm; the weld microstructure is mainly fine acicular ferrite; the HAZ does not show any serious coarsening; the weld hardness is relatively high, which is about 30% higher than the base metal; Low temperature impact toughness, ductile-brittle transition temperature of about -40 ℃.