焊接速度对30CrMnSiNi2A钢电子束焊接头组织和力学性能的影响

30CrMnSiNi2A钢由于其出色的质强比成为制造飞机起落架、襟翼的重要材料。电子束焊的焊接速度对工程应用中30CrMnSiNi2A钢的微观结构和机械性能产生极大影响。接头微观组织从热影响区细小等轴的回火索氏体与马氏体混合组织，转变为焊缝区域的树枝状板条马氏体晶粒。显微硬度由母材向焊缝中心逐渐增高，焊缝区域显微硬度最高可达690HV0.2，约为母材的两倍；拉伸强度最高为842MPa，达到母材强度的96.9%。此外随着焊接速度的提高，晶粒尺寸减小，显微硬度随之提高；但HAGB和渗碳体数量的下降对接头强度不利，使得接头抗拉强度随焊接速度提高而下降，不同焊接速度下接头断裂模式均为脆性断裂。

Effect of Welding Speed on Microstructure and Mechanical Properties of 30CrMnSiNi2A Steel Electron Beam Welded Joint

30CrMnSiNi2A steel has become an important material for manufacturing aircraft landing gear and flaps due to its excellent mass-strength ratio. The welding speed of electron beam welding has a great influence on the microstructure and mechanical properties of 30CrMnSiNi2A steel in engineering applications. The microstructure of the joint transforms from the small equiaxed tempered sorbite and martensite mixed structure in the heat-affected zone to dendritic lath martensite grains in the weld area. The microhardness gradually increases from the base metal to the center of the weld. The microhardness of the weld area can reach up to 690HV0.2, which is about twice that of the base metal; the tensile strength is up to 842MPa, reaching 96.9% of the base metal strength. In addition, as the welding speed increases, the grain size decreases and the microhardness increases. However, the decrease in the number of HAGB and cementite is not good for the strength of the joint, so that the tensile strength of the joint decreases with the increase of the welding speed. The fracture mode of the lower joint is brittle fracture.