Electron Beam Weld Metal Toughness for Heavy Section Low Alloy Steel.

Electron beam welding is featured in (1) capability of welding thick plates by a single pass, (2) less weld distortions, and it has been applied to welding of heavy section large structures.But, when a heavy section low alloy steel plate is welded, the weld metal toughness deteriorates. Therefore, it is very important to increase the weld metal toughness.Weld metal toughness is affected by weld metal structure and carbide precipitation.Then we have investigated the effects of the electron beam welding cooling rate and PWHT conditions on weld metal toughness and we have also studied the mechanism of toughness changes metallographically. Consequently, it has been clarified that in order to increase the toughness of electron beam weld metal for low alloy steel, the structure should be lower bainite by increasing welding cooling rate and a temper parameter of about 19 should be selected as the key for PWHT.