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通过对不同钒、氮质量分数的试验钢进行热模拟压缩试验和实验室轧制试验,用OM、SEM和TEM分析试验钢的显微组织,研究增氮对钒微合金钢组织和性能的影响。结果表明,普通钒微合金钢为板条贝氏体+粒状贝氏体组织,增加氮质量分数,可促进晶内铁素体相变,得到针状铁素体组织,使M/A组织细化且弥散分布,改善韧性;而增加钒质量分数,可以增加析出强化作用,提高强度,但组织形态无明显变化,不能提高韧性。增氮钢中的钒在奥氏体内以VN析出,低氮钢内的钒在铁素体内以VC的形式析出,奥氏体-铁素体、VC-铁素体和VN-铁素体的平面点阵错配度分别为6.72%、3.89%和1.55%,在奥氏体内析出的VN可以作为铁素体的优先形核位置,促进晶内铁素体相变。
The effects of nitrogen addition on microstructure and mechanical properties of vanadium microalloyed steel were investigated by thermal simulation and compression tests and laboratory rolling tests on the test steels with different vanadium and nitrogen contents. The microstructures of the test steels were analyzed by OM, SEM and TEM . The results show that ordinary vanadium microalloyed steels are lath bainite and granular bainite. Increasing the mass fraction of nitrogen can promote the intragranular ferrite transformation and obtain acicular ferrite microstructure. And dispersion, improve the toughness; and increase the mass fraction of vanadium can increase the precipitation strengthening effect, improve the strength, but no significant changes in the morphology, can not improve the toughness. Vanadium in nitrogen-enriched steel is precipitated as VN in austenite, vanadium in low-nitrogen steel is precipitated as VC in ferrite, austenite-ferrite, VC-ferrite and VN-ferrite The planar lattice mismatch degrees are 6.72%, 3.89% and 1.55%, respectively. The VN precipitated in austenite can promote the intragranular ferrite transformation as a preferential nucleation site of ferrite.