Toughness of Electron Beam Welds in Thick Section C-Mn and Microalloyed Steels

TWI Industrial Member Report Summary 259/1985

By C S Punshon and S Elliott

Background

The welding parameters of speed and weld width can substantially alter the weld metal microstructures of electron beam welds and therefore their mechanical properties. As electron beam welding is commonly carried out in the absence of filler additions, the resulting weld metal composition is similar to that of the parent plate, so variations in plate composition will affect weld metal properties. A range of 70mm thick structural steel plates, some containing microalloying additions, was selected for this preliminary investigation. Charpy impact tests made on the EB weld metals in the four steels chosen, using a range of
welding parameters, demonstrated the importance of controlling steel chemistry and welding procedure in order to obtain adequate toughness. The results suggest that steels with a low level of Nb or free from Nb are preferred in order to obtain good impact properties after PWHT. Steels of low carbon equivalent producing soft microstructures combined with welding conditions producing narrow welds are preferred to obtain good toughness in the as-welded condition.