装配式建筑用500 MPa级热轧H型钢的开发

Development of Grade 500 MPa Hot Rolled H-beam For Prefabricated Building

通过采用微合金化元素Nb和轧后超快速冷却技术开发生产了屈服强度≥500 MPa、翼缘厚度≤20 mm热轧H型钢Q500。试验结果表明:随着轧件冷却速率的提高,成品厚度方向的显微组织变化显著:空冷组织为F+P,铁素体晶粒度为9.0~10.0级;温降速率为11.9℃/s时,超快冷侧出现B组织;温降速率为55.1℃/s时,轧件心部及内侧为F+P组织,铁素体晶粒度较空冷工艺提高1.0~1.5级。随着轧件超快冷后温度的降低,轧件屈服及抗拉强度提高、韧性下降;当超快冷后温度为520℃时,力学性能为屈服强度527 MPa,抗拉强度667 MPa,伸长率为22.5%,达到500 MPa级别且韧性最优。

Hot rolled H-beam Q500 with yield strength more than 500 MPa and flange thickness less than 20 mm was developed and produced by using microalloying element Nb and ultra-fast cooling technology after rolling.The experimental results show that the microstructure changes significantly in the thickness direction with the increase of cooling rate:the air cooling microstructure is F+P,and the ferrite grain size is grade 9.0-10.0.When the cooling rate is 11.9℃/s,B structure appears in the ultrafast cold side.When the cooling rate is 55.1℃/s,the center and inner side of the rolled piece are f+P structure,and the ferrite grain size is grade 1.0~1.5 higher than that of air cooling process.With the decrease of the temperature after ultra-fast cooling,the yield and tensile strength of the rolled piece increase and the toughness decreases.When the temperature after ultrafast cooling is 520℃,the yield strength is 527 MPa,tensile strength is 667 MPa,elongation is 22.5%,that reached the level of 500 MPa,and the toughness is the best.