Effects of electron beam local post-weld heat-treatment on the microstructure and properties of 30CrMnSiNi2A steel welded joints

摘要

To improve the microstructure and properties of electron beam welded joints, vacuum or furnace whole post-weld heat-treatment (FWPWHT) should usually be carried out. Electron beam local post-weld heat-treatment (EBLPWHT) is a quite new heat-treatment procedure that provides the advantages of high precision, flexibility and efficiency, energy saving, and higher productivity. In this paper, the microstructure, mechanical properties, fracture toughness and fatigue properties of electron beam welded joints of 30CrMnSiNi2A steel in the as-welded (AW) and EBLPWHT conditions have been investigated. The results show that the microstructures of different zones of joints in the AW condition are changed by the EBLPWHT procedure, in which the welds from coarse needle martensite are transformed into lath-shaped martensite; and the main structures of the heat-affected zones (HAZ) from lath-shaped martensite into lower bainite. The properties of the welded joints can be improved by EBLPWHT in some extent, especially the fracture toughness of the welds, and the fatigue crack resistance of welded joints can be improved significantly. However, more appropriate heat-treatment parameters of EBLPWHT have to be studied in order to improve the mechanical properties of the base metal near to the HAZ.