【摘要】 开展了不同焊接热输入、焊前免预热、焊后省略热处理的高强钢气保焊接实验。利用光学显微镜、扫描电镜及透射电子显微镜等分析手段研究焊接接头、焊缝和热影响区的显微组织特征及力学性能。结果表明,即使线能量增加到40 kJ/cm,焊接接头的性能仍能够满足设计要求,接头强度超过700 MPa,熔合线、焊接热影响区的-20℃低温冲击韧性大于47 J。焊缝组织是高韧性的细化针状铁素体,微米尺度细化的球形氧化物夹杂对钢的性能起重要影响作用;粗晶区贝氏体型板条粗大造成该区韧性下降;细晶区碳化物与高密度位错相互作用,显微组织尺度约2μm,细化的组织保证该区塑韧性最好。更多还原

【Abstract】 Without preheating and post-weld heat treatment(PWHT),the high strength steel samples were welded by gas shielded arc welding process under different welding heat inputs.Microstructural characteristics and mechanical properties of welded joint,weld seam and heat affect zone were investigated by means of optical microscopy,scanning electron microscope(SEM) and transmission electron microscope(TEM).Results indicate that the mechanical properties of the welded joint can come up to the design requirements even if the welding heat input attaining 40 kJ/cm.The tensile strength of welded joint is higher than 700 MPa.Both in the fusion zone(FZ) and HAZ,the-20 ℃ impact absorbed energy is much higher than 47 J,which indicates that welded joints have good low temperature impact ductility.The microstructure of the weld seam is fine ferrite acicular,which perfomance s good impact toughness.Ultradine oxide inclusions,whose feature size is micronscale structure,are of great importance to the quality of steel.The microstructure becomes coarsening and the toughness becomes worsening at the coarse grain heat affect zone.The carbides and high density dislocation in fine grain zone result in fine microstructure of 2 μm in feature size,which improves the material properties.更多还原