65Mn弹簧钢激光焊接研究

【作者】 李宾；

【导师】 刘其斌；

【作者基本信息】 贵州大学 ， 材料加工工程， 2008， 硕士

【摘要】 65Mn钢作为常用机器零件钢,广泛应用于机械、交通等部门。传统焊接65Mn钢时,由于该钢的含碳量过高,存在热影响区大,热脆性严重等问题,而难以达到工况要求。与传统焊接方法相比,激光焊接具有深宽比大、焊缝窄、焊缝结合强度高、热影响区小、焊接变形小及对周围组织无影响等特点而得到广泛应用。本文采用TJ5000W CO₂激光器对65Mn钢薄片进行激光焊接,利用OM、XRD、显微硬度仪、WDW3100型拉伸电子万能实验机、SEM和350A型X射线应力测定仪等测试手段对焊接接头的结晶状态、组织、显微硬度、相结构、抗拉强度、断口以及残余应力进行了研究,得出了激光焊接65Mn的最佳工艺参数、为将来65Mn钢激光焊接的应用提供理论指导。研究结果表明:（1）当P=2.0kW,V=7mm/s时,激光焊接65Mn钢质量最佳;（2）激光焊接65Mn钢后,从焊缝中心区到焊缝边缘依次形成等轴晶、树枝晶和胞状晶;热影响区组织主要是针状马氏体、贝氏体以及少量铁素体;（3）焊接接头主要由细小的基体相α—Fe及Fe₃C、FeSi等相组成。（4）在最佳工艺下,焊缝区最高硬度为720Hv,热影响区硬度最高值约为770Hv,从热影响区到基材硬度明显下降;激光焊接后材料的抗拉强度的平均值为375 MPa,最佳工艺参数下抗拉强度可达到498MPa;激光焊接65Mn钢的残余应力较低,热影响区残余应力平均值为-76MPa,而焊缝区的残余应力平均值为104MPa,残余应力随焊接功率和速度的增加而变大。更多还原

【Abstract】 As a kind of machine parts steel, 65Mn spring steel is widely used in machinery, transportation and other fields. As to the traditional welding technology for 65Mn steel, there exists problems such as big heat affected zone and serious thermal brittleness , therefore its application for some fields is limited. The comparision of laser welding with the traditional welding, it has many advantages such as high ratio of depth to widenth, the narrow welding zone , the small heat affected zone and small deformation etc, so laser welding is widely used in many industries.In this paper, 65Mn steel is welded by laser （5kw）, and crystallization, microstructure, microhardness, phase structure, tensile strength, fracture, residual stress are investigated with OM, microhardness tester, XRD, SEM. through the experiments we do above, the optimum laser welding parameter on 65Mn Steel is obtained. The above results we achieved provide theoretical guidance for the application of 65Mn Steel by laser welding.The experimental results show that: （1） When P=2.0kW, V=7mm/s, the perfect qualify of laser welding is obtained; （2） The fine equiaxed crystal, dendrite crystal and cell grain are formed from welding central zone to the edge zone, and martensite, bainite and a small amount of ferrite appeared mainly in the heat affected zone; （3） The welding joint mainly consists of fine a-Fe、Fe₃C and FeSi; （4）The average highest hardness in weldind zone is Hv720, and the highest hardness in heat affected zone is Hv770, the hardness obviously decreases from the heat affected zone to substrate.; the average tensile strength is 375 MPa, and the tensile strength can be up to 498MPa under the best welding parameters; and the residual stress is very low, the average residual stress in welding zone is 104MPa ,and the average residual stress in heat affected zone is -76MPa.更多还原