Method for manufacturing high strength rail of excellent weldability

A method for manufacturing high strength rail of excellent weldability comprising the steps of:

• a. hot rolling a steel into a rail, said steel containing 0.65 to 0.85% of C, 0.50 to 1.20% of Si, 0.50 to 1.50% of Mn, 0.005 to 0.050% of Al, 0.004 to 0.050% of one or both of Nb and Ti, and the balance being iron and unavoidable impurities,
• b. cooling the hot rolled rail to a temperature less than the point Ar.sub.1 to cause the cooled rail complete cooling transformation,
• c. reheating the surface layer portion of the head of the transformed rail to a temperature not less than 850.degree. C. to obtain an austenite structure,
• d. quenching said reheated portion of the rail with a gas from 800.degree. C. to 600.degree. C. in from 15 o 250 seconds,
• e. gradually cooling down said rail thus quenched from 600.degree. C. to 450.degree. C. in a period of from 30 to b 1000 seconds with a gas, during which period pearlite transformation is substantially started and completed,
• f. subjecting said rail thus gradually cooled down to a subsequent quenching treatment or a subsequent air-cooling treatment with gas, liquid or combination thereof to below 450.degree. C.,
• whereby the surface layer of the head of the thus treated rail to a depth of 10 mm or more is transformed to a fine pearlite structure having a tensile strength of more than 120 kg/mm.sup.2, a reduction of area more than 40% and the surface hardness of said treated rail at said surface layer being H.sub.V 350 or more, and
• said excellent weldability being such that when said rail head is welded, the welded portion having properties which are almost the same as those of the non-welded portion.