Microstructure and properties of Q345B and 430 stainless steel dissimilar welded joints by plasma arc welding

Plasma arc welding was used to butt welding of 3 mm thick Q345 low alloy steel and 430 stainless steel. Then microstructure, mechanical properties and corrosion resistance of welded joints were investigated. The results showed that when arc current was 100 A, microstructure in weld zone of plasma arc welding Q345B/430 dissimilar steel joints consisted of uniform martensite and acicular ferrite. The overall performance of welded joints was relatively superior. With the current increasing, microstructure of weld transformed into coarse lath martensite and ferrite. Microstructure of heat affected zone (HAZ) on both sides was coarsened in a certain degree, and Widmanstatten appeared in HAZ on the Q345B side. Weld had the maximum microhardness at the entire dissimilar steel joints, and the overall change trend of microhardness distribution of dissimilar steel joints were consistent under different arc currents. Tensile strength of welded joints under different arc currents and 430 stainless steel were equivalent, and all welded joints fractured at the 430 side near weld. When arc current was 100 A, tensile strength of welded joints reached the maximum value of 427 MPa. Corrosion resistance of welded joints was negatively correlated with welding current.Highlights: The experimental results provided process data and supports for the application of ferritic low alloy steel and ferritic stainless-steel dissimilar steel joints.