初始组织对一种Nb-Mo微合金化中锰TRIP钢组织演变与力学性能的影响

研究了热轧后冷却方式和冷轧压下量对一种Nb-Mo微合金化中锰TRIP钢临界退火过程中组织演变与力学性能的综合影响规律.结果表明:当热轧后冷却方式由油淬变为炉冷时,在冷轧压下量一定的条件下,退火组织中长条状铁素体的体积分数增加,且长轴/短轴比增大,而等轴铁素体的晶粒尺寸变化不明显;对于热轧后油淬试样,当冷轧压下量由50%增至75%时,退火组织中长条状铁素体的体积分数减少,铁素体的平均晶粒尺寸由400~500 nm减至300~400 nm.综合分析,增加热轧后的冷却速率,可在较小的冷轧压下量条件下获得一种综合性能良好的超细晶中锰TRIP钢,其性能指标为:屈服强度为976 MPa,抗拉强度为1 165 MPa,延伸率可达34.1%,强塑积接近40 GP·%.

Influence of initial microstructure on microstructural evolution and mechanical properties of a cold - rolled Nb - Mo microalloyed medium Mn steel

In this work, the combined effects of cooling pattern after hot rolling and cold rolling reduction on microstructural evolution and mechanical properties of a Nb-Mo microalloyed 6. 5Mn-TRIP steel was investigated. The results show that as the cooling pattern after hot rolling changed from oil quenching to furnace cooling, the volume fraction of elongated ferrite increased after intercritical annealing at 650 ℃ for 1 h, and the ratio of long and short axis of ferrite increased as well; however, the grain size of equiaxed ferrite did not change significantly. In the case of oil quenching, as the cold rolling reduction increased from 50% to 75%, the volume fraction of elongated ferrite decreased and its grain size was further refined to 300-400 nm. It can be concluded that the ultrafine-grainedduplex phase TRIP steel exhibited an excellent combination between tensile strength and ductility by increasing the cooling rate after hot rolling with relatively small cold rolling reduction of 50%, i. e. YS ( yield strength) =976 MPa, UTS ( ultimate tensile strength) =1165 MPa, El ( total elongation) =34. 1% and UTS?El was close to 40 GP·%.