新型Cr3MoNb管线钢焊接接头的力学性能与组织

利用TGS-2CML焊丝,采用钨极氩弧焊(gas tungsten arc weld,GTAW)对经济型低合金Cr3MoNb无缝管进行整管焊接,测试了焊接接头的硬度,研究了拉伸性能、冲击韧性,观察了微观组织.结果表明,在拟定焊接工艺下,Cr3MoNb钢焊接接头力学性能优良,无需预热和焊后热处理;调质处理下断后伸长率提高约1倍,达到挪威船级社制管工艺DNV-OS-F101标准;对于类似Cr3MoNb等低碳或超低碳管线钢,采用A(c)修正日本百合冈公式计算其焊接热影响区最高硬度是合适的;焊缝区组织主要为细小的粒状贝氏体,M-A相弥散分布于铁素体基体相中;焊缝区晶粒尺寸总体很小,区域晶粒大小存在细微差异,有少数较大尺寸柱状晶分布;焊缝区与热影响区以多边形铁素体和粒状贝氏体较自然过渡,无明显熔合分界线.

Microstructure and mechanical properties of welded joints of a novel Cr3MoNb pipeline steel

Gas tungsten arc welding (GTAW) of novel Cr3MoNb pipeline was conducted with TGS-2CML wire. The hardness,impact toughness and tensile properties of welded joints were measured,and the microstructure characteristics were examined. The results show that the welded joints can achieve good mechanical properties without preheating and PWHT. Elongation after thermal refining increased by one hundred percent, which fulfilled the DNV-OS-F101 standard. For low carbon or super low carbon pipeline steels,the calculation formula modified with A(c) was reasonable for predicting the maximum hardness on heat affected zone. The microstructure of weld metal mainly consisted of fine granular bainite with some dispersive MA islands in the ferrite matrix. The grain size in weld zone was quite small while subtle regional differences existed and a few large columnar crystals formed. Polygonal ferrite and granular bainite were distributed within the fusion zone,and no sharp boundary was observed between WM and HAZ.