Friction Welding of Titanium and Plain Carbon Steel

Titanium-steel is a combination of dissimilar materials, which are difficult to weld in general, owing to inevitable formation of the brittle intermetallic compounds. A prominent feature of friction welding process is being able to weld dissimilar materials in many kinds of combinations. This report deals with friction weldability of pure titanium and S25C steel with a diameter of 12 mm. Main results are summarized as follows; (1) A suitable welding condition to obtain sound weld, which has over 100% joint efficiency, is Rotational speed N: 2440 rpm, Friction pressure P1 : 20 kgf/mm2, Upsetting pressure P2: 24 kgf/mm2, Friction time T1: 2.5-5.0s. (2) Bond condition at central part of weld interface has a great influence on tensile strength of joint. (3) The welded joints fracture at titanium base metal in rotary bending fatigue test. It shows that fatigue limit of the weld must be over that of base metal, 24 kgf/mm2. (4) The joint, made under even the suitable welding condition, has poor bending ductility.and impact value. (5) The decarbulized layer is formed in S25C steel along the weld interface and thin intermetallic compounds arc formed at the weld interface excepting central part. (6) Tensile fracture takes place in the heat affected zone of S25C steel at central part of weld. However, the intermetallic compounds at peripheral and middle parts cause brittle fracture of weld.