回火对Q960高强钢析出物和应变硬化行为的影响
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摘要
研究了回火温度对一种Q960工程机械用钢析出物和应变硬化行为的影响机理。经分析得出,低于650℃回火时,Q960钢呈现连续屈服,在650℃回火时拉伸曲线开始出现上屈服点,这与回火过程中位错结构、析出物和板条结构的演化有关。在拉伸速度恒定条件下,低碳贝氏体型Q960钢的真应力与真应变不遵循Hollomon关系;随着回火温度升高,初始应变硬化指数均降低;在均匀塑性变形阶段,随着真应变的增加,应变硬化指数逐渐下降,但应变硬化指数曲线的变化幅度减小,在高于550℃回火时应变硬化指数先降低然后增加,这种类型特征曲线的曲率变化的连续性和均匀塑性更好。
Effect mechanism of tempering temperature on tensile behavior of a low carbon bainitic steel Q960 for construction machinery was studied. The results show that continuous yield is observed in steel tempered below 650 ℃,but upper yield point appeared in the tensile curve of steel tempered at 650 ℃,which is related with the evolution of dislocation structure,precipitates and lath structure. Besides,Hollomon relationship is inapplicable for low carbon bainitic Q960 steel. With the increase of tempering temperature,the strain hardening exponent-strain curve has a lower change range and a smaller initial strain hardening exponent. In addition,when tempering temperature is below 550 ℃,the increase of true strain leads to the drop of strain hardening exponent in homogeneous plastic deformation zone. However,when tempering temperature reaches 550 ℃,the strain hardening exponent decreases at the beginning and increases thereafter,which represents a better continuity and uniform plasticity.
Effect mechanism of tempering temperature on tensile behavior of a low carbon bainitic steel Q960 for construction machinery was studied. The results show that continuous yield is observed in steel tempered below 650 ℃,but upper yield point appeared in the tensile curve of steel tempered at 650 ℃,which is related with the evolution of dislocation structure,precipitates and lath structure. Besides,Hollomon relationship is inapplicable for low carbon bainitic Q960 steel. With the increase of tempering temperature,the strain hardening exponent-strain curve has a lower change range and a smaller initial strain hardening exponent. In addition,when tempering temperature is below 550 ℃,the increase of true strain leads to the drop of strain hardening exponent in homogeneous plastic deformation zone. However,when tempering temperature reaches 550 ℃,the strain hardening exponent decreases at the beginning and increases thereafter,which represents a better continuity and uniform plasticity.
引文
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[3]Nie Y,Shang C,You Y,et al. 960 MPa grade high performance weldable structural steel plate processed by using TMCP[J]. Journal of Iron and Steel Research,International,2010,17(2):63-66.
[4]于浩,张道达,肖荣亭,等.回火温度对Q960钢析出物组织特征的影响[J].北京科技大学学报,2011,33(6):715-720.Yu Hao,Zhang Daoda,Xiao Rongting,et al. Effect of tempering temperature on the structural properties of precipitates in Q960 steel[J]. Journal of University of Science and Technology Beijing,2011,33(6):715-720.
[5]李晓林,蔡庆伍,余伟,等. N含量对Cr-Mo-V系超低碳贝氏体钢组织性能和析出行为的影响[J].材料工程,2013(3):16-21.Li Xiaolin,Cai Qingwu,Yu Wei,et al. Effect of nitrogen content on precipitation behavior,microstructure and properties of Cr-Mo-V ultralow carbon bainitic steel[J]. Journal of Materials Engineering,2013(3):16-21.
[6]Xie Baosheng,Cai Qingwu,Yu Wei. Effect of tempering temperature on resistance to deformation behavior for low carbon bainitic YP960 steels[J].Materials Science and Engineering A,2014,618:586-595.
[7]Wei Yan,Lin Zhu,Wei Sha,et al. Change of tensile behavior of a high-strength low-alloy steel with tempering temperature[J]. Materials Science and Engineering:A,2009(517):369-374.
[8]宋玉泉,管志平,马品奎,等.拉伸变形应变硬化指数的理论和实验规范[J].金属学报,2006,42(7):673-680.Song Yuquan, Guan Zhiping, Ma Pinkui, et al. Theoretical and experimental standardization of strain hardening index in tensile deformation[J]. Acta Metallurgica Sinica,2006,42(7):673-680.
[9]冯端.金属物理学[M].北京:科学技术出版社,1999.
[10]马鸣图.双相钢-物理和力学冶金[M].北京:冶金工业出版社,1988.