Effect of Reheating Process on Austenite Grain Size and Decarburization Depth of Heavy Rail

The pearlite-colony size and lamellar-spacing as well as the decarburization depth of hot-rolled high-strength heavy rail steel exert important influence on the rail performance under the condition of wear and rolling contact fatigue.In order to make reasonable reheating schedule for U71Mn billet on the 100 meter rail rolling line with SMS-Meer Universal-Mill in Handan Steel Company,the laboratory experiments have been carried out to investigate the effects of reheating parameters on austenite grain size and decarburization depth for pearlite refining and decarburization control.The results show that when reheating temperature was reached 1050～1150°C and soaking time was 35 min,the austenite grain size and the decarburization depth were dramatically increased.The austenite grain size reached 120～160μm but approximately uniform,the functional decarburization depth increased to 0.42～0.61 mm.When the reheating temperature was increased to 1200～1250℃ the austenite grain size exceeded 180μm and got an significantly uneven-growth with the prolongation of holding time.The functional decarburization depth increased to 0.81～0.90 mm.According to above experimental data,the modified reheating schedule was proposed and applied to the production of U71Mn rail steel.As a result,the microstructure of pearlite and the decarburization depth in hot-rolled rail of U71Mn steel were controlled and qualified for the National Technical Standard and Railway Ministry Standards.