关键词: 重轨钢, 连铸坯, 中心偏析, 超声波探伤, 工艺改进

Abstract: The metallurgical flow sheet o£ studied heavy rail steel (/% : 0. 68 ~ 0. 73C, 0. 20 ~ 0. 30Si, 1. 05 ~ 1. 15Mn, ≤0.015P, ≤0.012S, ≤O.OO3 5A1, ≤0.000 15[H]，≤0.006 0[N],≤0.002 0 [0]) is metal desulphurization pretreated- 120 t converter-LF-RH-280 mm x 380 mm bloom easting. It is identified by analysis that the casting bloom segregation is main cause for unqualified rolled rail by macrostructure examination and supersonic testing. The effect of liquid overheating extend, casting speed, mould magnetic stirring, secondary water cooling rate and dynamic soft reduction at end of solidification on center carbon segregation of casting bloom is tested and studied. With using the optimized process measures including controlling liquid overheating extent 15 ~ 30 T , casting speed 0. 60 ~0. 75 m/min and constant speed casting, mould magnetic stirring intensity 400 A, secondary water cooling rate 0. 25 L/kg and soft reduction 6 〜7 mm, the rating of general porosity ≤1. 0, of center porosity ≤0. 5, of spot segregation ≤0. 5, the ratio of equiaxed zone is more than 37% , the center carbon segregation index is 0. 94 ~ 1. 06 and the qualified ratio of steel rail tested by supersonic method increases up to more than 99. 3%.