Analysis of softening zone on the surface of 20Mn2SiCrMo bainitic railway switch

• The fabrication processing causes softening zone existence on switch surface.
• Long duration in 500–700 °C in the fabrication is a direct reason for this zone.
• Heating temperature affects the zone width and higher temperature means wider zone.
• Heating temperature decrease and cooling rate rise could reduce the zone width.

The surface softening phenomenon of 20Mn2SiCrMo railway switch was studied using lab scale thermal simulation experiments followed by hardness measurement and macroscopic characterization. The thermal simulation experiments successfully reproduced the softening behavior observed in real manufacture processes. The softening zone formation mechanism is revealed by the comparison between thermal simulation experiments and real rail analysis under a series of inducting heating temperatures at different measurement locations. It is also found that the width of softening zone is related to induction heating temperature and cooling rate.