POST-WELD HEAT TREATMENT METHOD FOR 1,300 MPa-LEVEL LOW-ALLOY HEAT TREATED STEEL RAIL

A post-weld heat treatment method for 1,300 MPa-level low-alloy heat treated steel rail, wherein the method comprises the following steps:

• (1) subjecting a steel rail welded joint formed by welding and having a residual temperature of 900-1,100° C. to a first stage cooling so as to lower the welded joint surface temperature to 650-720° C., wherein the first stage cooling mode is natural cooling in the air, and the cooling rate is within a range of 4-6° C./s;
• (2) subjecting the steel rail welded joint to a second stage cooling so as to lower the welded joint surface temperature to 480-550° C., wherein the second stage cooling adopts a steel rail railhead profiling cooling device for cooling, the cooling medium is compressed air or water mist mixed gas, and the cooling rate is within a range of 2-3.5° C./s;
• (3) further subjecting the steel rail welded joint to a third stage cooling so as to lower the welded joint surface temperature to 10-30° C., wherein the third stage cooling adopts a steel rail railhead profiling cooling device for cooling, the cooling medium is compressed air or water mist mixed gas, and the cooling rate is within a range of 0.2-0.8° C./s;
• wherein a tensile strength of a steel rail base metal of the steel rail welded joint is 1,300 MPa, and the steel rail base metal comprises the following chemical components:
• 0.75-0.84 wt % of C, 0.6-0.85 wt % of Si, 0.8-1 wt % of Mn, 0.5-0.8 wt % of Cr, ≤0.02 wt % of P, ≤0.02 wt % of S, ≤0.01 wt % of V, the balance of Fe and inevitable impurities.