Nb-Ti低合金高强钢第二相析出及其对力学性能的影响
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摘要
采用光学显微镜、扫描电镜、透射电镜和拉伸试验机研究了Nb含量和热轧加热温度对Nb-Ti复合添加的低合金高强钢(HSLA)第二相析出行为,以及第二相析出对热轧及冷轧退火后钢板的显微组织和力学性能的影响。结果表明,在高的热轧加热温度下,含Nb碳氮化物可以充分溶解并优先在富Ti的(Ti,Nb)(C,N)粗大粒子上异质析出,阻止晶粒的长大;热轧后的第二相粒子特征可遗传到冷轧退火过程,对晶粒尺寸和第二相分布有重要影响。此外,0. 053%Nb钢在1 250℃的加热温度下,热轧和冷轧退火钢板中有较多的粗大及细小析出相;每添加0. 01%Nb产生的热轧析出强化增量约为40 MPa,冷轧退火后的强度增量约为30 MPa。
Effect of niobium contents and reheating temperatures on the second phase precipitation behavior of Nb-Ti microalloyed high strength low alloy( HSLA) steels was studied by optical,scanning electron and transmission electron microscope,and tensile tester,and the effect of second phase precipitates on the microstructure and mechanical properties of HSLA steels during hot rolling and annealing process was also studied. The results showed that under high reheating temperature,the Nb-containing carbonitrides could be fully dissolved and preferentially heterogeneous precipitated on large particles Ti( Ti,Nb)( C,N),thus preventing the growth of grains during hot rolling. The characteristics of the second phase precipitates formed in hot rolling could be inherited to the cold rolling and annealing process,which had an important effect on the grain size and the distribution of second phase precipitates. In addition,the 0. 053% Nb steel could obtain more coarse and fine precipitates in both hot-rolled and annealed steel plates at the reheating temperature of 1 250℃. An addition of 0. 01% Nb increased the tensile strength by about 40 MPa after hot rolling and by about 30 MPa after annealing through precipitation hardening.
Effect of niobium contents and reheating temperatures on the second phase precipitation behavior of Nb-Ti microalloyed high strength low alloy( HSLA) steels was studied by optical,scanning electron and transmission electron microscope,and tensile tester,and the effect of second phase precipitates on the microstructure and mechanical properties of HSLA steels during hot rolling and annealing process was also studied. The results showed that under high reheating temperature,the Nb-containing carbonitrides could be fully dissolved and preferentially heterogeneous precipitated on large particles Ti( Ti,Nb)( C,N),thus preventing the growth of grains during hot rolling. The characteristics of the second phase precipitates formed in hot rolling could be inherited to the cold rolling and annealing process,which had an important effect on the grain size and the distribution of second phase precipitates. In addition,the 0. 053% Nb steel could obtain more coarse and fine precipitates in both hot-rolled and annealed steel plates at the reheating temperature of 1 250℃. An addition of 0. 01% Nb increased the tensile strength by about 40 MPa after hot rolling and by about 30 MPa after annealing through precipitation hardening.
引文
[1]GONG P,PALMIERE E J,RAINFORTH W M. Dissolution and precipitation behaviour in steels microalloyed with niobium during thermomechanical processing[J]. Acta Materialia,2015,97:392-403.
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[6]刘志桥,张志建,陈刚,等. Nb含量及退火温度对冷轧低合金高强钢力学性能的影响[J].热加工工艺,2017,46(22):225-227.
[7] PALMIERE E J,GARCIA C I,DEARDO A J. Compositional and microstructural changes which attend reheating and grain coarsening in steels containing niobium[J]. Metallurgical&Materials Transactions A,1994,25(2):277-286.
[2]CITIC-CBMM中信微合金化技术中心.汽车用铌微合金化钢板[M].北京:冶金工业出版,2006.
[3] HONG S G, KANG K B, PARK C G. Strain-induced precipitation of NbC in Nb and Nb-timicroalloyed HSLA steels[J]. Scripta Materialia,2002,46(2):163-168.
[4]曹建春,刘清友,雍岐龙,等.铌对高强度低合金钢的组织和强化机制的影响[J].钢铁,2006,41(8):60-63.
[5]CHEN J,SHEN X J,JI F Q,et al. Effect of annealing time on microstructure and mechanical properties of cold-rolled niobium and titanium bearing micro-alloyed steel strips[J]. Journal of Iron and Steel Research,2013,20(9):86-92.
[6]刘志桥,张志建,陈刚,等. Nb含量及退火温度对冷轧低合金高强钢力学性能的影响[J].热加工工艺,2017,46(22):225-227.
[7] PALMIERE E J,GARCIA C I,DEARDO A J. Compositional and microstructural changes which attend reheating and grain coarsening in steels containing niobium[J]. Metallurgical&Materials Transactions A,1994,25(2):277-286.