根据热轧H型钢翼缘厚度方向变形集中在万能轧制阶段的特点，将万能阶段开轧温度设定在800~1 000℃，其余主要工艺参数不变。通过对热轧H型钢进行力学性能检验及显微组织对比分析，发现铁素体晶粒尺寸及外形对产品力学性能有至关重要的影响，而万能阶段开轧温度对铁素体晶粒尺寸及外形存在显著影响。当开轧温度在1 000~950℃时，虽然能够实现奥氏体动态再结晶，但在轧后分别从900和850℃空冷时，再结晶晶粒长大迅速，也易出现反常长大。当开轧温度为1 000℃时，铁素晶粒尺寸不一，存在明显的混晶，当温度降低至950℃时，虽然混晶情况有所改善，但依然无法消除。在温度降低至900℃时，不仅能够完成奥氏体动态再结晶，而且轧后空冷起始温度降低至800℃，再结晶晶粒长大被抑制，形成了细小且均匀的初始奥氏体组织，此时的铁素体晶粒为10~30 μm的等轴状。当温度进一步降低至850~800℃时，因无法达到促进奥氏体动态再结晶的热激活能需求，仅在未再结晶区进行了变形，最终形成扁平状铁素体晶粒，长轴与短轴尺寸比例接近2 ∶1，长轴尺寸减小不明显，短轴尺寸进一步减小。正因为如此，随着开轧温度从1 000℃降低至900℃，铁素体晶粒尺寸减小，从而增加了晶界面积，降低了应力集中程度，增大了瞬时变形的均匀分配能力，使得产品屈服强度从369 MPa升高至415 MPa，抗拉强度从508 MPa升高至546 MPa，断后伸长率从30.0%升高至31.5%，低温冲击功均值从36 J提升至99 J；当温度降低至850~800℃时，扁平状铁素体晶粒进一步增大了晶界面积，使得产品屈服强度和抗拉强度分布进一步升高至468 MPa和567 MPa，但由于长、短轴差距增大，导致塑性变形时需要协调转动而产生畸变能，断后伸长率降低至27.5%，低温冲击功均值提升至109 J，此时屈强比已达到0.83。鉴于降低开轧温度影响生产节奏，同时考虑万能轧机负荷、能耗及辊耗等经济因素，900~850℃是较为理想的开轧温度区间，此时产品不仅强度及塑性指标均保持在较高的水平，而且韧性指标大幅提升，耐候热轧H型钢的综合力学性能得到明显改善。
According to the deformation characteristics of hot-rolled H-section steel that flange thickness deformation concentrated in the universal rolling stage, the opening rolling temperature of universal stage was set at 800-1 000 ℃, and the other main technological parameters remained unchanged. Through the mechanical property test and microstructure comparison analysis of hot-ralled H-section steel, The result indicated the grain size and shape of ferrite have a significant effect on the mechanical properties of hot-rolled Hsection steel, and the opening rolling temperature of universal stage has a significant effect on the grain size and shape of ferrite. For 1 000-950 ℃ opening rolling temperature, dynamic recrystallization of austenite could be completed, but the initial air cooling after rolling was 900-850 ℃ and recrystallization grain growth was rapid and also easy to grow abnormally. For 1 000 ℃ opening rolling temperature, ferrite grain size was differ and there was an obvious mixed crystal. When the temperature decreased to 950 ℃, mixed crystal situation has improved, but it still cannot eliminate. When the temperature decreased to 900 ℃, austenite dynamic recrystallization could be completed and the initial air cooling temperature decreased to 800 ℃. The growth of recrystallized grains was inhibited, and the small and uniform initial austenite structure was formed. At this time, the ferrite grains were 10-30 μm at equiaxial shape. When the temperature further reduced to 850-800 ℃, the thermal activation energy required to promote dynamic recrystallization of austenite cannot be met, so the deformation only appeared in the unrecrystallized zone, and flat ferrite grain was formed with the ratio of the long axis to the short axis being nearly 2 ∶1. The size of the long axis was not significantly reduced, but the size of the short axis was further reduced. Because of this, as the open rolling temperature decreased from 1 000 ℃ to 900 ℃, the ferrite grain boundary area was increased with the decrease of grain size, reduced the stress concentration degree, and increased the ability of distribution with the instantaneous deformation. The product yield strength increased from 369 MPa to 415 MPa. The tensile strength increased from 508 MPa to 546 MPa, the percentage elongation after fracture increased from 30. 0% to 31. 5%, the impact energy at low temperature increased from 36 J to 99 J. When the temperature decreased to 850-800 ℃, flat ferrite grain further increased the grain boundary area, made the product yield strength and tensile strength further to 468 MPa and 567 MPa respectively. When the distortion increased due to coordinate rotation between different size grains in plastic deformation, the percentage elongation after fracture decreased to 27. 0%, the impact energy at low temperature increased to 109 J, and the yield to tensile ratio reached 0. 83. In view of the fact that the lower rolling temperature affects the production output, and considering the universal mill load, energy consumption and economic factors, 900-850 ℃ is an ideal open rolling temperature range. At this time, not only the strength and plasticity indicators of the product are maintained at a relatively high level, but also the toughness index has been greatly improved. The comprehensive mechanical properties of weathering resistant hot-rolled H-section steel have been significantly improved.