The dissimilar steel friction weldings on the exhaust valve of a certain type of diesel engine were studied. The hardness ,microstrueture and tensile strength of the welded joints were studied. The straightening technology of exhaust valve were improved. The results show that the microhardness of the welded joint, heat affected zone and matrix is inconsistent. The microstructure of the welded joint is martensite after friction welding. The microhardness becomes same and the microstmcture of the welded joint turns into tempered sorbite after ageing .The mechanical property of the welded joint c...