Nb、Ti微合金钢中碳氮化物固溶与再析出的研究

利用光学显微镜(OM)、透射电子显微镜(TEM)研究了再加热温度、奥氏体区变形温度和组织转变温度的变化对Nb、Ti微合金钢组织性能及其碳氮化物固溶与再析出行为的影响.结果表明:钢中加入铌,主要利用铌的碳氮化物在奥氏体形变过程中的再析出,抑制形变奥氏体的再结晶,在随后的组织演变过程中细化了组织;而钢中加入较高含量的钛,主要利用钛的碳化物在铁素体中的析出,产生明显的沉淀强化作用.这主要是铌、钛的碳氮化物固溶后,在奥氏体和铁素体中再析出的不同所造成的.钢中复合加入Nb-Ti后既起到细化晶粒的作用,又起到析出强化的作用.细晶强化既提高钢的强度又提高钢的韧性,但沉淀强化在大幅提高钢的强度的同时恶化了钢的韧性.

Solid Solution and Re-precipitation of Carbonitride in Nb,Ti-microalloyed Steel

The effect of reheating temperature,austenite deformation temperature and transformation temperature on mechanical property,solid solution and re-precipitation of Nb,Ti carbonitrides in Nb/Ti microalloyed steels were investigated by optical microscope (OM) and transmission electronmicroscope (TEM).Results showed that there had been a noticeable refinement in the microstructure in Nb microalloyed steel,as carbonitrides of niobium re-pricipitated during austenite deformation,inhibited austenite recrystalization,and acted as a grain refiner during subsequent microstructure revolution.The addition of Ti enhanced the strength of steel obviously,but had little effect on the microstructure refinement.Obvious grain refinement strengthening and precipitation strengthening can be confirmed in Nb-Ti microalloyed steel,both of which brought benefit to steel's strength.Grain refinement strengthening improved the toughness of experimental steel,while on the contrary precipitation strengthening deteriorated the toughness.