Fatigue Strength of Electron-Beam Welded Joint of Injection-Moulded and Sintered Stainless Steel.

Mechanical properties of the electron-beam welded joints of the sintered SUS304L which are produced by the injection moulding method are investigated to clear the influence of welding on the tensile and the fatigue strength.The results obtained are summarized as follows;(1)Formation of welding defects is strongly affected by beam active parameter and welding speed.When they have appropriate values, welding defects aren't created, except that large voids are formed at or near the bond.(2)When the sintered stainless steel is welded under the optimum welding condition, the tensile strength of the as-welded joint decreases about 10% and the fatigue limits of the as-welded joint and the joint whose undercut is removed decrease about 20% and 5% respectively as compared with that of the un-welded one.(3)In as-welded specimen, the fatigue crack of the electron-beam welded joint initiates at the root of the undercut in welds, on the other hand, in the specimen whose surface irregularity is removed, it initiates at the intereface of delta phase and austenite phase near the bond.(4)The fatigue crack of the electron-beam welded joint of the sintered stainless steel propagates along the bond because large voids exist there.(5)It is confirmed that the electron-beam welded joints of the sintered stainless steels under the optimum welding condition can be put into practical use.