METHOD FOR HEAT TREATMENT OF RAILS Russian patent published in 1994 - IPC

FIELD: metallurgy, heat treatment of rails of carbon, alloy, pre- and post-eutectoid steels. SUBSTANCE: the first stage of spheroidizing annealing consists of heating up to 200 - 300 C and of 1 to 3 h holding, the second stage does of 1 to 3 heating cycles of 50 to 100 C/h rate up to 740 - 780 C with 1 to 3 h holding followed by 1 to 6 C/s rate cooling down to 520 - 420 C the third stage consists of 650 - 700 C heating followed by 2 to 4 h holding at given temperature, 25 to 50 C/h rate cooling down to 620 to 540 C and final air cooling. Surface hardening is carried out by heating up to within 870 to 990 C followed by 7 to 26 C rate cooling within 720 to 460 C. When rail steel contains 0.82 to 0.85 wt. per cent of carbon the second stage of the spheroidizing annealing is carried out as one cycle, when it does 0.86 to 0.92 wt. per cent of carbon the annealing comprises two cycles, when it does 0.93 to 0.98 wt. per cent it involves three cycles. EFFECT: improved quality. 2 cl, 11 dwg, 1 tbl