... ,work for 48hrs continuously 5,delivery fast high frequency small welding machine Product Features: 1, transistor (IGBT) high frequency ... hardening heat treatment, such as: crankshaft, connecting rod, piston pin, camshaft, valves,various gears within the gearbox, a variety of ... kinds of spline shaft, drive axle, various small shaft crank pin, a variety of rocker, rocker shaft, high-frequency hardening ...