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球墨铸铁QT500与合金钢20MnCr5同轴双激光焊接工艺及组织性能研究 被引量:1

Study on Coaxial Dual-Beam Laser Welding Process and Microstructure and Properties of Nodular Cast Iron QT500 and Alloy Steel 20MnCr5
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摘要 针对球墨铸铁与合金钢异种材料焊接界面容易形成碳偏聚进而产生裂纹的问题,通过采用连续-脉冲同轴双激光焊接工艺及填充镍基合金焊丝,实现了QT500与20MnCr5的优质焊接。研究了同轴双激光中不同脉冲激光功率(360、400、440、480 W)对焊缝成形质量的影响规律,讨论了激光作用位置向钢侧偏移(偏移量)对焊接接头界面碳元素偏聚现象的影响机制,对焊接接头力学性能、金相组织及硬度分布进行了综合分析。结果表明:同轴双激光焊接工艺可用于球墨铸铁与合金钢的焊接,球墨铸铁侧的热输入对焊缝的成形质量及力学性能的影响较为显著;由于球墨铸铁侧莱氏体及马氏体的析出,断裂主要发生在该侧的熔合区;在保证熔深稳定的前提下,分别研究了不同偏移量(0.1、0.2、0.3 mm)对接头的影响,激光作用位置向钢侧偏移能够有效减小球墨铸铁侧的热输入,避免碳元素过度偏聚,力学性能得到相应的提升,断裂位置向热影响区移动,焊缝接头的强度得到优化。 Objective Ductile iron has been extensively used in various automotive components such as crankshafts and differential housing owing to its relatively low density and capacity for significant tensile strength.20MnCr5 is a robust and tough alloy steel commonly employed in the production of gears and shafts.Establishing effective welding between the shaft body and the gear material is a significant research challenge.However,the notable disparity in the thermal properties between ductile iron and alloy steel hinders the performance of the welding joint.The high carbon content of ductile iron promotes carbon segregation at the welding interface and exacerbates the formation of microcracks,thereby considerably increasing the complexity of the welding process.Owing to its high energy density,laser welding offers the advantage of generating welds with more precise heat-affected zones.In this study,a novel continuous-pulse coaxial dual-beam laser is employed as a welding heat source to enhance the surface quality of the weld seam.The high-quality welding of ductile iron and alloy steel is achieved by decreasing the laser input power and diminishing pore formation.We hope that our novel welding strategy and findings will be helpful in understanding the bonding mechanism of ductile iron and alloy steel and provide more application space for their connectors.Methods In this study,QT500-7 and 20MnCr5 are employed as the base materials,with ERNiCr-3 as the filling wire.A novel continuous-pulse dual-beam laser is used as the heat source.First,the pulsed laser power is varied with a constant continuous laser power to determine the optimal combination of heat sources.The laser action position is then adjusted to further enhance the weld strength.Microstructures are observed using a metallographic microscope,and mechanical performance testing and analysis are conducted using a tensile testing machine.The microhardness of the weld is measured using a microhardness tester.Additionally,the fracture behaviors of different specimens are analyzed using a field-emission scanning electron microscope.Results and Discussions The use of a continuous-pulse coaxial dual-beam laser as a welding heat source(Fig.2)produces highquality welding joints.When the pulsed laser power is varied,the weld formation varies considerably(Fig.4).The weld seam is found to have no defects,such as cracks or pores.When the laser action position shifts toward the steel side,the heat input on the ductile iron side gradually decreases.This reduction in the heat input suppresses the diffusion of carbon,leading to a significant decrease in the hardness values of the heat-affected and bond zones on the QT500 side(Fig.13).The cross-sectional morphology of the weld reveals significant changes in the melting amount of the QT500-7 side base material,with the centerline shifting toward the ductile iron side when the laser action position is changed(Fig.6).The segregation line of carbon caused by the high carbon content of the nodular cast iron is solved by changing the laser position to reduce the heat input on the side of the nodular cast iron(Fig.7).The best mechanical properties of the joint are obtained under a pulsed laser power of 440 W and offset of 0.2 mm.In summary,a continuouspulse coaxial dual-beam laser can yield high-quality welding joints.Better dual-beam laser welding parameters can be achieved by adjusting the laser power and action position.Furthermore,carbon segregation issues can be effectively resolved by reducing the heat input on the side of the nodular cast iron by changing the laser action position,and pulsed laser stirring proves useful.Conclusions In this study,a coaxial dual-beam laser welding technology is proposed to address the challenges of welding ductile iron QT500 and alloy steel 20MnCr5.The main problems are the precipitation of martensite and ledeburite in the heat-affected and bond zones on the QT500 side,which results in carbon segregation.The pulsed laser power and position are adjusted in this study.When the laser action position is shifted toward the steel side,the decreased heat input suppresses the diffusion of carbon,leading to a significant decrease in the hardness of the heat-affected and bond zones on the QT500 side.The best mechanical properties are achieved under a pulsed laser power of 440 W and laser offset of 0.2 mm.The continuous-pulse coaxial dual-beam laser welding technology not only improves the carbon segregation phenomenon on the ductile iron side but also reduces the formation of welding cracks.Overall,the proposed novel coaxial dual-beam laser welding technology is effective in improving welding quality,specifically for ductile iron and alloy steel dissimilar metals.The joint exhibits high-quality and high-performance characteristics by reducing carbon segregation and minimizing hardness values.This study advances the field of welding and provides a potential solution for the welding of dissimilar metals with different material properties.
作者 陈帅帅 张文东 刘祥环 陈启云 李博洋 崔双好 刘黎明 王红阳 Chen Shuaishuai;Zhang Wendong;Liu Xianghuan;Chen Qiyun;Li Boyang;Cui Shuanghao;Liu Liming;Wang Hongyang(Liaoning Provincial Key Laboratory of Advanced Connection Technology,School of Materials Science and Engineering,Dalian University of Technology,Dalian 116024,Liaoning,China;Zhuzhou Gear Co.,Ltd.,Zhuzhou 412000,Hunan,China)
出处 《中国激光》 EI CAS CSCD 北大核心 2024年第16期12-20,共9页 Chinese Journal of Lasers
基金 国家自然科学基金(52375308,51975090)。
关键词 激光技术 连续-脉冲双激光 球墨铸铁 合金钢 镍基合金 laser technique continuous-pulsed dual-beam laser ductile iron alloy steel nickel-based alloy
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