Assessment of Mechanical and Metallurgical Properties of Thermally Aged Electron Beam Welded AISI 321 Stainless Steel

Electron beam welding produces very narrow and deep penetration therefore it finds application where welding of thick materials is required. AISI 321 is susceptible to intergranular corrosion when it is used in high temperature and harsh conditions, owing to the Titanium depletion in the weld zone. However, the heat affected zone formed in electron beam welding extends to a narrow region across the weld pool. In the present study electron beam welding of austenitic 321 stainless steel is done to examine the mechanical and metallurgical properties of the joints. Microhardness tests along and across the weld bead were carried out. Tensile and impact tests were performed to analyze mechanical properties. The microstructures of the weld zone, fusion zone and base metals were also captured. Skeletal ferrites were seen in the weld metal. The aging treatment of 700°C for 24 hours which resulted in a change in morphology of the grains from skeletal to vermicular and promoted the formation of Ti-rich carbides on the grain boundaries. The maximum impact toughness at sub-zero temperature i.e. -40°C was recorded as 129.3 J in as-welded samples and it got reduced to 119.5 J after aging treatment. The average ultimate tensile strength was 582 N/mm2 and it got decreased to 481 N/mm2 after aging treatment.

Manual Self-Propagating High-Temperature Synthesis Welding of 45 Steel

A new style of emergency welding, named manual SHS welding ,was introduced. By this technique, metal materials could be welded on the condition of no electricity, no gas and no equipments. In this paper, the mechanism of manual SHS welding has been illustrated, the effect of thermit on welding and the microstructure of the welded joint have been studied, and the mechanical properties have been tested. Results showed that the combustion velocity of the combustion welding rod became higher when the content of (CuO+Al) thermit increased. The suitable (CuO+Al) content is 60%wt ~80%wt. The tested 45 steel plates were one-side welded with back formation. Microstructure analysis indicated that there are three zones in the welded joint, which are heat affected zone, fusion zone and weld metal. The weld metal and the 45 steel plates were combined metallurgically. The weld metal was copper based alloy. EDS patterns showed that there was diffusion of Cu, Fe and Ni in the three zones. The fracture of the weld joint is a typical ductile fracture. The tensile strength of the joints reached 400MPa and the impact absorbed energy was about 35J, which meet the requirement of mechanical properties for emergency welding. Manual SHS welding is an effective welding method for emergency maintenance in battlefield and outside field.