Abstract
When low manganese steel bars (C0.20%, Mn1.56%) are flash-butt-welded, the decrease of carbon and manganese in the weld metal are remarkable. And the heat affecled zone shows coarse widmanstätten structure containing troostite. This part must be postheated at just below A1 transformation point in order to change the troostite to sorbite, and postheated at about 800°C in order to change the widmanstätten structure to fine grain structure. Accordingly, if the both change are desired, it will be suitable that these parts are postheated at about 750°C.
In the case of postheating with a flash-butt-welder, the postheating at about 850°C is suitable. Holding time at postheating temperature is sufficient with one second.
