船用10Ni5CrMoV高强钢的疲劳性能

Fatigue Performance of Marine High Strength Steel 10Ni5CrMoV

通过对三轴疲劳加载试验后带有裂纹的10Ni5CrMoV钢T型焊接节点试样进行金相、硬度、断口试验,利用光学显微镜、扫描电镜对低合金高强钢10Ni5CrMoV的焊接接头的组织、结构和性能进行分析,并结合有限元方法研究其对疲劳特性的影响。分析结果表明:10Ni5CrMoV钢的组织主要为回火索氏体,焊接接头有明显的分区界限,各区的硬度不同,断口呈现韧性断裂的形貌。进一步研究表明,热影响区硬度高于母材区和焊缝区,断口含有孔洞、夹杂等缺陷,裂纹扩展路径受组织和外力影响较大,疲劳寿命对应力集中比较敏感。利用有限元模拟方法计算得到焊趾根部弯曲疲劳寿命,分析结果与试验有较好的吻合程度。因此,改善热处理工艺,改进结构设计,可以提高低合金高强钢10Ni5CrMoV的疲劳特性。

The fatigue properties of the T-shape welding joint of low alloy steel 10Ni5CrMoV has been studied using triaxial fatigue testing,hardness measurement,metallographic analysis and fracture surface morphology.The effect of stress concentration was evaluated by the finite element method.The results show that the metallographic structure consists of mainly tempered sorbite with three distinguishable regions,i.e. the base metal,heat-affected zone and the weld metal.The hardness test shows that the heat-affected zone has the highest hardness,while the weld metal has approximately the same value as the base metal.Ductile facture was confirmed by the typical dimple structures presented on the surface.Voids and inclusions were also found in the welding joint,serving as the crack nucleation sites.Crack propagation path was determined by both the local microstructure and the macroscopic stress states.Further numerical simulations revealed that the stress concentration greatly decreased the fatigue life.Therefore,improving the heat treatment process and optimizing the geometry of the welding joint will be the key to increasing the fatigue life of low alloy high strength steel 10Ni5CrMoV.