形变热处理对新型无Ti马氏体时效钢焊缝组织与力学性能的影响

Effect of thermo-mechanical treatment on microstructure and mechanical properties of novel Ti-free maraging steel welding seam

对新型18Ni基无Ti、Al马氏体时效钢进行了电阻焊和后续的形变热处理,表征了焊接-高温退火-轧制-再结晶热处理-时效过程中焊缝的组织演变与性能变化,分析了形变热处理对焊缝组织、物相与力学性能的影响。结果表明,初始焊缝包括熔化区、过渡区、热影响区,其组织与基体差异明显,但物相基本为马氏体,依次经过1050℃高温退火、72.7%冷轧、900℃再结晶退火后,焊缝区与基体组织差异逐渐消失,再结晶后焊缝组织、物相、硬度、拉伸强度和延伸率等性能和基体趋于一致,拉伸载荷下焊缝处未出现应变集中和断裂;450℃时效后焊缝强度接近2 GPa,表明适当的形变热处理消除了新型马氏体时效钢焊缝组织与基体的差异。

A newly developed 18Ni based maraging steel without Ti and Al was welded and then subjected to a thermo-mechanical treatment.Microstructure evolution and property change during the welding,high temperature annealing,rolling,recrystallization heat treatment and aging processes were characterized,and the effects of thermo-mechanical treatment on the microstructure,phase and mechanical properties of the welding seam were analyzed.The results show that the initial welding seam includes melting zone,transition zone and heat affected zone,which is significantly different from the matrix,but the phase is basically martensite.After high temperature annealing at 1050 ℃,72.7%cold rolling and recrystallization annealing at 900 ℃,the difference in microstructure between the welding seam and the matrix gradually disappears.After recrystallization,the microstructure,phase,microhardness,tensile strength,elongation and other properties of the welding seam tend to be consistent with the matrix.There is no strain concentration or fracture at the welding seam under tensile loading.The strength of the welding seam after aging at 450 ℃ is close to 2 GPa,which indicates that the difference in microstructure between the welding seam and the matrix of the novel maraging steel can be eliminated by proper thermo-mechanical treatment.