宝钢890MPa高强钢焊接接头微观组织及疲劳性能研究
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摘要
890 MPa高强钢管主要应用于工程机械领域悬臂起重机,焊接接头在服役过程中遭受应力水平较高的低循环疲劳。本文对890MPa高强钢焊接接头的低周疲劳性能进行了研究,结果表明,焊接接头疲劳性能较好,当应变幅值为0.3%时,承受的最大应力为568MPa,其疲劳断裂周次在9 000次以上,断裂位置沿熔合线偏向焊缝区域,裂纹源为夹杂物及气孔等缺陷。多层多道焊焊接接头,母材中一定量的W促使贝氏体转变时间后移,抑制了大块状铁素体和粒状碳化物的形核、长大趋势,使焊接接头回火软化区的块状铁素体和粒状贝氏体均比较细小,且热影响区软化不明显,整个接头熔合线附近的焊接缺陷处成为疲劳损伤源。
890 MPa high strength steel pipe is mainly used for cantilever crane in the field of engineering machinery, and the welded joint always suffers low cycle fatigue with high stress state during the course of service. The low cycle fatigue properties of welded joint for 890 MPa high strength steel was investigated in this study. The results showed that the fatigue properties of welded joint was accepted when the strain amplitude was 0.3% and the maximum stress was 568 MPa. The fatigue fracture cycle was more than 9 000 times. The fracture position initiated at fusion line near the weld area because of the weld defects such as inclusions and pores in this position. For the multi-pass welded joint, a certain amount of tungsten element in the base material delayed the bainite transformation from the perspective of the materials thermodynamics and depressed the nucleation and growth trend of granular ferrite and carbides. The softening of heat affected zone was not obvious since the tiny granular ferrite and carbides appeared at tempering zone of welded joint. Finally, the weld defects near the fusion line of the welded joint became the fatigue damage sources and induced the fatigue fracture.
890 MPa high strength steel pipe is mainly used for cantilever crane in the field of engineering machinery, and the welded joint always suffers low cycle fatigue with high stress state during the course of service. The low cycle fatigue properties of welded joint for 890 MPa high strength steel was investigated in this study. The results showed that the fatigue properties of welded joint was accepted when the strain amplitude was 0.3% and the maximum stress was 568 MPa. The fatigue fracture cycle was more than 9 000 times. The fracture position initiated at fusion line near the weld area because of the weld defects such as inclusions and pores in this position. For the multi-pass welded joint, a certain amount of tungsten element in the base material delayed the bainite transformation from the perspective of the materials thermodynamics and depressed the nucleation and growth trend of granular ferrite and carbides. The softening of heat affected zone was not obvious since the tiny granular ferrite and carbides appeared at tempering zone of welded joint. Finally, the weld defects near the fusion line of the welded joint became the fatigue damage sources and induced the fatigue fracture.
引文
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[5]董现春,张熹,张立英,等.Q690CFD低碳贝氏体高强钢的焊接性能[J].机械工程材料,2010(8):68-71.
[6]秦浩,雷正龙,陈彦宾,等.低合金高强钢激光-MAG复合多层焊接头力学性能[J].2011,38(10):1-6.
[7]孟贺超,赵旭,段青辰.液压支架用高强钢焊接保护气体的工艺研究[J].焊接与切割,2016(18):28-30.
[8]李凤伦.WDB620钢的焊接热影响区最高硬度试验及试验结果分析[J].水电站机电技术,2016,39(9):10-13.
[2]赵琳,张旭东,陈武柱.800 MPa级低合金钢焊接热影响区韧性的研究[J].金属学报,2005(4):392-396.
[3]王勇.低合金调质高强钢焊接工艺研究进展[J].应用能源技术,2009(8):11-13.
[4]娄宇航,肖红军,彭云,等.690 MPa级低合金高强钢焊接接头组织性能[J].材料科学与工艺,2012,20(2):101-107.
[5]董现春,张熹,张立英,等.Q690CFD低碳贝氏体高强钢的焊接性能[J].机械工程材料,2010(8):68-71.
[6]秦浩,雷正龙,陈彦宾,等.低合金高强钢激光-MAG复合多层焊接头力学性能[J].2011,38(10):1-6.
[7]孟贺超,赵旭,段青辰.液压支架用高强钢焊接保护气体的工艺研究[J].焊接与切割,2016(18):28-30.
[8]李凤伦.WDB620钢的焊接热影响区最高硬度试验及试验结果分析[J].水电站机电技术,2016,39(9):10-13.