| CPC C22C 38/54 (2013.01) [C21D 1/28 (2013.01); C21D 1/84 (2013.01); C21D 6/005 (2013.01); C21D 9/0081 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01)] | 10 Claims |
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1. A controlled rolling and controlled cooling method suitable for an on-line normalizing treatment of a medium-carbon boron-containing steel, which is characterized in that, according to mass percentage, the chemical components of the medium carbon boron-containing steel comprise:
C 0.37-0.45%, Si 0.17-0.37%; Mn 0.60-0.90%; Al 0.020-0.060%; B 0.0008-0.0035%; Ti 0.030-0.060%; P≤0.025%; S≤0.025%; Cr≤0.25%; Ni≤0.20%; Mo≤0.10%; Cus 0.20%; the remainder is Fe and inevitable impurities;
the controlled rolling and controlled cooling method characterized in that,
the controlled rolling and controlled cooling method sequentially includes the following steps: heating, rough rolling, finish rolling, water cooling, and slow cooling in a cooling bed;
in the heating step, a billet steel is heated in a heating furnace at a heating temperature of 1100-1200° C. for a total heating time of 90-180 min;
in the rough rolling step, the billet steel enters into a rough rolling mill group at an inlet temperature of 1000-1050° C.;
in the finish rolling step, the billet steel enters a finish rolling mill group at an inlet temperature of 780-830° C.;
the water cooling refers to water spray cooling through a water tank, and after the water cooling, a finished steel leaves at a water-leaving temperature of 700-750° C.;
the water is supplied by the water tank at a volume flow rate of 40-60 L/min, the finished steel travels at a traveling speed of 3-8 m/s;
in the step of the slow cooling in a cooling bed, of the finished steel is cooled at a cooling velocity of 0.10-0.15° C./s;
in the step of the slow cooling in a cooling bed, the finished steel enters into a heat preservation cover so as to be cooled on the cooling bed, and is cooled to below 500° C. and leaves the heat preservation cover to have air cooling.
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