稀土耐候桥梁钢Q370qENH的研制

Development of Rare Earth Weathering Resistant Bridge Steel Q370qENH

通过稀土微合金化成分体系、TMCP+回火工艺设计,研制Q370qENH稀土耐候桥梁钢。采用两阶段轧制模式,粗轧阶段开轧温度1150~1190℃,精轧阶段开轧温度≥1100℃,终轧温度控制在780~820℃之间,轧后进行550~620℃高温回火。轧态和回火态显微组织均为细晶粒铁素体+珠光体,但回火态基体上有弥散的第二相NbC颗粒存在;试验钢板具有良好的强韧性、冷成型性能及耐腐蚀性能,尤其是-40℃低温冲击性能优异;试验钢板中的夹杂物仅为细小Ds类夹杂物,表明稀土通过净化钢液、改性夹杂,可以改善试验钢的低温冲击韧性及耐腐蚀性能。

By the design of rare earth microalloying composition,TMCP+tempering process,the rare earth weathering bridge steel Q370 qENH is developed.Two-phase rolling mode is applied with the start rolling temperature of roughing phase between 1150℃ and 1190℃,the start rolling temperature of finishing phase greater than or equal to 1100℃,high temperature tempering is performed at temperatures ranging between 550℃ and 620℃.The microstructure of as-rolled and tempered steel plate is refined ferrite and pearlite,but the second phase NbC particles exist on the tempered matrix.The test steel plate possesses good strength and toughness,cold forming performance and corrosion resistance,esp.excellent low temperature impact properties at -40℃.The inclusions in the test steel plate are of fine Ds type,denoting that the low temperature impact toughness and corrosion resistance can be improved by purifying molten steel and modifying inclusions.