Linear Friction Welding (LFW) was applied to medium-high carbon steel S55C, which had difficulty in arc welding process, and fatigue strength of welded joints were evaluated. In LFW process, peak temperature can be easily controlled and fatigue strength of welded joints for two level of peak temperature are compared. As a result, the harmful welding defects are not detected in the joints. A remarkable difference was recognized for the hardness distribution between two kinds of joints, and low peak temp. joint came to have almost equivalent fatigue strength with a base material. The fatigue crack initiated at the interface of welded area.
