Nb-Ti微合金化X100管线钢中的纳米析出规律

Nano-precipitates in Nb-Ti microalloy X100 pipeline steel

通过微合金化与控轧控冷技术的有机结合,在Nb-Ti微合金化X100管线钢中形成了大量纳米尺寸的析出粒子,对其形貌进行了观测分析,对组织中的析出粒子尺寸分布及其析出强化作用进行了定量分析,通过动力学计算分析了Nb（C,N）在奥氏体中的析出规律。结果表明：高级别管线钢中的析出相主要有两种类型,Nb（C,N）析出（1~30 nm）和（Ti,Nb）（C,N）复合析出（50~300 nm）,均为面心立方结构;X100管线钢析出强化贡献值约为70 MPa;对Nb-Ti微合金化管线钢中Nb（C,N）析出的动力学计算表明,在热连轧生产线生产高级别管线钢时,热轧过程中碳氮化物析出不到10%,90%均在随后的冷却过程中析出,在中厚板生产线生产级高级别管线钢时,热轧过程中碳氮化物析出近70%,其余30%主要在随后的冷却过程中析出。

Large quantities of nano-precipitation particles were obtained in Nb-Ti microalloy X100 pipeline steel after treated by microalloying and TMCP process. The morphology of these particles was observed and analyzed by TEM. The size distribution and precipitation strengthening of the precipitated particles were analyzed by quantitative analysis. Austenite precipitation regularity of the Nb（ C,N） steel was analyzed by dynamic calculation. The results show that there are mainly two types of precipitated phase in high grade pipeline steels,which are Nb（ C,N） precipitates（ 1-30 nm） and（ Ti,Nb）（ C,N） composite precipitates（ 50-300 nm）,both of the two types are face-centered cubic structure; the contribution value of precipitation of X100 steel on strength is about 70 MPa; the dynamic calculation of Nb（ C,N） precipitated phases shows that when the high grade pipeline steels are made on hot strip mill line,the microalloy carbonitride precipitation is less than 10% in hot rolling process and the rest 90% precipitates in the subsequent cooling process; in middle plate mill production of high grade pipeline steel,the precipitation is nearly70% in hot rolling process,the remaining 30% mainly precipitates in the subsequent cooling process.