Microstructure control of medium carbon steel joints by low-temperature linear friction welding

Medium carbon steel sheets of 2.6 mm thick were successfully welded by linear friction welding at various frequencies and applied pressures. The welding temperature decreased with the decreasing frequency, but unexpectedly with the increasing applied pressure. A medium carbon steel joint with no martensitic transformation could be obtained at a welding temperature below the A(1) point under the conditions of low frequency and high applied pressure. Moreover, the welding temperature evolution was found to be correlated with the behaviour of the flash expelling at the welding interface. It was revealed that the welding temperature can be determined as the temperature at which the ultimate tensile strength of the interface material decreased below the applied pressure.