双相区退火工艺对中锰钢组织与性能的影响
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摘要
采用扫描电镜(SEM)和X射线衍射(XRD)和单轴拉伸实验等研究了自主设计的"预淬火+双相区退火"热处理工艺对成分为0.15C-5Mn的中锰钢显微组织和力学性能的影响。结果表明:随着退火温度的升高,实验钢抗拉强度逐渐升高,屈服强度逐渐降低,伸长率和强塑积先升后降,此结果与相变诱导塑性(TRIP)效应有关;随着退火时间的延长,实验钢抗拉强度先增后降,屈服强度逐渐降低,伸长率和强塑积先增后降;当热处理工艺为"800℃保温30 min水淬+655℃退火4 h空冷"时,实验钢可以获得最佳组织和力学性能,此时其残留奥氏体的体积分数为25%,抗拉强度为1250 MPa,伸长率为37%,强塑积达到46 GPa·%。实验钢的高强度和高塑性是由超细晶组织和TRIP效应共同决定的。
The effects of self-designed "pre-quenching + intercritical annealing" heat treatment process on microstructure and properties of 0.15 C-5 Mn medium manganese steel were studied by means of scanning electron microscopy(SEM), X-ray diffraction(XRD) and uniaxial tensile test. The results show that with the increase of annealing temperature, the tensile strength of the tested steel increases gradually, the yield strength decreases gradually, and the elongation and the product of strength and plastic increase firstly and then decrease, this result is closely related to the phase transformation induced plasticity(TRIP) effect. With the increase of annealing time, the tensile strength of the tested steel increases firstly and then decreases, while the yield strength decrease gradually, and the elongation and the product of strength and plastic increase firstly and then decrease gradually. The optimum microstructure and mechanical properties of the tested steel can be obtained when the heat treatment process is holding at 800 ℃ for 30 min by water quenching and then annealing at 655 ℃ for 4 h by air cooling, and the volume fraction of retained austenite is 25.2%, the tensile strength is 1250 MPa, the elongation is 37%, and the product of strength and plastic is up to 46 GPa·%. According to the analysis, the high strength and high plasticity of the tested steel are determined by the combination of ultrafine grain structure and TRIP effect.
The effects of self-designed "pre-quenching + intercritical annealing" heat treatment process on microstructure and properties of 0.15 C-5 Mn medium manganese steel were studied by means of scanning electron microscopy(SEM), X-ray diffraction(XRD) and uniaxial tensile test. The results show that with the increase of annealing temperature, the tensile strength of the tested steel increases gradually, the yield strength decreases gradually, and the elongation and the product of strength and plastic increase firstly and then decrease, this result is closely related to the phase transformation induced plasticity(TRIP) effect. With the increase of annealing time, the tensile strength of the tested steel increases firstly and then decreases, while the yield strength decrease gradually, and the elongation and the product of strength and plastic increase firstly and then decrease gradually. The optimum microstructure and mechanical properties of the tested steel can be obtained when the heat treatment process is holding at 800 ℃ for 30 min by water quenching and then annealing at 655 ℃ for 4 h by air cooling, and the volume fraction of retained austenite is 25.2%, the tensile strength is 1250 MPa, the elongation is 37%, and the product of strength and plastic is up to 46 GPa·%. According to the analysis, the high strength and high plasticity of the tested steel are determined by the combination of ultrafine grain structure and TRIP effect.
引文
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[3] Chang Y,Wang M H,Wang N,et al.Investigation of forming process of the third-generation automotive medium-Mn steel part with large-fractioned metastable austenite for high formability[J].Materials Science and Engineering A,2018,4(721):179-188.
[4] 马鸣图,易红亮,路洪州,等.汽车轻量化[J].中国工程科学,2009,11(9):20-27.MA Ming-tu,YI Hong-liang,LU Hong-zhou,et al.Automotive lightweight[J].China Engineering Science,2009,11(9):20-27.
[5] 阳锋,罗海文,董瀚.退火温度对冷轧7Mn钢拉伸行为的影响及模拟研究[J].金属学报,2018,54(6):859-867.YANG Feng,LUO Hai-wen,DONG Han.Effects of intercritical annealing temperature on the tensile behavior of cold rolled 7Mn steel and the constitutive modeling[J].Acta Metallurgica Sinica,2018,54(6):859-867.
[6] 魏元生.第三代高强度汽车钢的性能与应用[J].金属热处理,2015,40(12):34-39.WEI Yuan-sheng.Performance and application of the 3rd generation high strength automobile steel[J].Heat Treatment of Metals,2015,40(12):34-39.
[7] Hu B,Luo H W,Yang F,et al.Recent progress in medium-Mn steels made with new designing strategies,a review[J].Journal of Materials Science and Technology,2017,12(33):1457-1464.
[8] 周天鹏,陈泽军,曹文全.中锰钢(0.15C-5Mn-Al)冷轧ART退火组织转变与力学性能[J].机械工程学报,2017,53(12):133-139.ZHOU Tian-peng,CHEN Ze-jun,CAO Wen-quan.Microstructure evolution and mechanical properties of ART-annealed medium manganese steel (0.15C-5Mn-Al) processed by cold rolling[J].Chinese Journal of Mechanical Engineering,2017,53(12):133-139.
[9] Wang C,Shi J,Wang C Y,et al.Development of ultrafine lamellar ferrite and austenite duplex structure in 0.2C5Mn steel during ART-annealing[J].ISIJ International,2011,51(4):651-656.
[10] Shi J,Hu J,Wang C,et al.Ultrafine grained duplex structure developed by ART-annealing in cold rolled medium-Mn steels[J].Journal of Iron and Steel Research International,2014,21(2):208-214.
[11] Gibbs P J,De Cooman B C,Brown D W,et al.Strain partitioning in ultra-fine grained medium-Mn transformation induced plasticity steel[J].Materials Science and Engineering A,2014,15(609):323-333.
[12] 肖斌,赵晖,时捷,等.Si对中锰钢淬火配分组织和性能的影响[J].材料研究学报,2011,25(1):45-50.XIAO Bin,ZHAO Hui,SHI Jie,et al.Effect of Si on microstructure and mechanical properties of quenching and partitioning steel[J].Chinese Journal of Material Research,2011,25(1):45-50.
[13] Arlazarov A,Hazotte A,Bouaziz O,et al.Evolution of microstructure and mechanical properties of medium Mn steels during double annealing[J].Materials Science and Engineering A,2012,30(542):31-39.
[14] 田亚强,张宏军,陈连生,等.低碳硅锰钢I&Q&P处理中C,Mn元素配分综合作用[J].材料工程,2016,44(4):32-38.TIAN Ya-qiang,ZHANG Hong-jun,CHEN Lian-sheng,et al.Comprehensive effect of C,Mn partitioning behavior on retained austenite of low cabon Si-Mn steel in I&Q&P process[J].Journal of Materials Engineering,2016,44(4):32-38.
[15] Chen C Y,Chen C C,Yang J R.Microstructure characterization of nanometer carbides heterogeneous precipitation in Ti-Nb and Ti-Nb-Mo steel[J].Materials Characterization,2014,88(2):69-79.
[16] Hong S,Lee J,Lee B J,et al.Effects of intergranular carbide precipitation on delayed fracture behavior in three twinning induced plasticity (TWIP) steels[J].Materials Science and Engineering A,2013,587(10):85-99.