Microstructure and mechanical properties of thick CLF-1 reduced activation steel weld joint made by electron beam welding joint

Abstract

The effect of post-welded heat treatment (PWHT) on microstructure and mechanical properties of electron beam welded joint of 35 mm thick China low-activation ferrite steel CLF-1 was studied. The results showed that the hardness and microstructure of the joint for both the as-welded and the PWHT were uniform along the thickness direction, and the hardness behaved a W-shaped distribution. The joint microstructure was composed of tempered martensite and precipitated phases which were mainly chromium and tungsten carbides. A small amount of δ-ferrite existed near the fusion line in the fusion zone. With the increase of tempering temperature, the microstructure of joint and base metal didn’t change significantly. With the extension of tempering time, the precipitated phases of base metal grew and the joint microstructure didn’t change significantly. The suitable PWHT was suggested as tempering at 1013 K for 2∼4 h, which not only ensured the strength of base metal, but also greatly improved low-temperature impact energy of the joint at 253 K.