Influences of Welding Techniques on Fatigue Behaviors of Thick-Walled Cylinders of 30CrMnSiNi2A Steel

30CrMnSiNi2A steel has been widely used to manufacture airplane structural parts. The fatigue behaviors of weld metals (WMs) of electron beam welding (EBW) joints and shielded metal arc welding (SMAW) joints (hereinafter shorted as EBW-WM and SMAW-WM, respectively) of 26-mm-thick 30CrMnSiNi2A ultrahigh-strength steel were compared. The fatigue behavior of the EBW-WM is obviously superior to that of the SMAW-WM. Microstructures and microdefects are important causes for the great difference between WMs of the two types of joints in term of the fatigue behaviors. Microstructures in the EBW-WM are similar to those in the BM, both containing a large amount of lath martensite. However, martensite is not found in the SMAW-WM; instead, blocky ferrite and nonmetallic inclusions are present in the SMAW-WM. The research findings provide data support for the updating and upgrading of welding techniques of 30CrMnSiNi2A thick-walled cylinders.