SA516Gr70钢焊接接头的力学性能及组织

Mechanical Properties and Microstructure of SA516Gr70 Steel Welded Joint

采用钨极氩弧焊（GTAW）工艺,以ER70S-6焊丝作填充金属,对12 mm厚的SA516Gr70低合金钢板进行焊接,测试了焊接接头的拉伸性能、弯曲性能、低温冲击韧性、硬度等力学性能,分析了拉伸断口、冲击断口形貌和接头的微观组织。结果表明,在选定的焊接工艺参数下,焊接接头力学性能良好,拉伸断口为韧性断裂,韧窝中存在的夹杂物或第二相质点主要为MC型碳化物和Si O2。

The gas metal arc welding（GTAW） of 12 mm thick SA516 Gr70 low alloy steel plates was conducted by using ER70 S-6 welding wire as filler metal. The tensile properties, bending properties, low temperature impact toughness and hardness of the welded joint were tested, and the morphologies of the tensile fracture, impact fracture and the microstructure of the welded joint were analyzed. The results show that the welded joint has good mechanical properties under proposed welding parameters, and the tensile fracture is ductile fracture, and the inclusions or second phase particles in dimples are mainly MC type carbides and Si O2. The impact toughness at-46 ℃ is good, and the impact fractures of weld zone（WM）, heat affected zone（HAZ） and base metal（BM） are ductile fracture. The impact absorption energy value from small to large is WM,HAZ, BM. The microstructure of weld zone is epitaxial crystallization, which consists of ferrite, pearlite, granular bainite and a small amount of precipitates, and the grain coarsening in the heat affected zone is not obvious. The hardness of the welded joint is symmetrical with the weld as the center, and the hardness of the weld zone is the largest, followed by the heat affected zone, and the hardness of the base metal is the lowest.