The welding of ferritic steel 501 B and austenitic steel 316 LN was carried out by using tungsten inert gas arc welding, and the microstructure and mechanical properties of welded joint were tested and analyzed.The results show that coarse grains appear in the heat affected zone(HAZ) of ferritic steel and slight grain growth is detected in the HAZ of austenite steel. Fine equiaxed grains are formed in fusion zone, and columnar grains perpendicular to the welding orientation are formed in the center of weld ...