Abstract: Effect of rolling end-cooling temperature 880 ~320 °C of experiment of Q355B hot-rolled H-beam steel on the strength, toughness and structure of the H-beam steel flange is studied. The results show that as the temperature after controlled cooling is 570 °C , the yield strength of the steel increases by 73 MPa compared to that of the air cooling process, and the elongation after fracture is 23. 5% ； as the temperature after controlled cooling is 320 °C , the yield strength of the steel increases by 228 MPa compared to that of the air cooling process, and the elongation after fracture is 16. 0% , which shows that the elongation rate is not qualified. The microstructure and ferrite grain size of Q355B hot rolled H beam steel obtained by normalizing after rolling are F + P and 11. 0. When the temperature drop rate of controlled cooling process is 73. 9 °C/s and the end-cooling temperature is 570 °C , B appears on the surface of die jet flange, the structure of the inner and core of the flange is F + P, and the grain size is 12. 0 ~ 12. 5 ； as the cooling temperature drop rate is 91. 4 °C/s, and the end-cooling temperature is 320 °C , M appears on the surface at the spraying side, and B appears at the core and inner side, at this time, the strength of steel is too high and the plasticity is seriously insufficient.

摘要： 研究了Q355B热轧H型钢轧后冷却温度880～320℃对H型钢翼缘强度、韧性及组织的影响。结果表明,当控冷后温度为570℃时,钢的屈服强度较空冷工艺提高73 MPa,断后伸长率为23.5%;当控冷后温度为320℃时,钢的屈服强度较空冷工艺提高228 MPa,断后伸长率为16.0%,出现伸长率不合格的情况。Q355B热轧H型钢在轧后正火工艺所得金相组织为铁素体（F）+珠光体（P）,铁素体晶粒度为11.0级。当控冷工艺温降速度为73.9℃/s、冷后温度为570℃时,喷水侧翼缘表层出现贝氏体（B）,翼缘内侧及心部组织为F+P,晶粒度12.0～12.5级;当控冷温降速度为91.4℃/s,冷后温度为320℃时,喷水侧表层出现马氏体（M）,心部及内侧出现贝氏体（B）,此时钢的强度过高,塑性严重不足。

关键词: 控制冷却, 热轧H型钢, Q355B钢, 组织和性能, 晶粒细化