热处理对建筑用20MnV钢组织与性能的影响
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摘要
采用光学显微镜(OM)、扫描电镜(SEM)、万能拉伸试验机等研究了完全正火、亚温正火/亚温淬火对冷轧+回火态20MnV钢组织与性能的影响。结果表明:冷轧+回火态20MnV钢的组织由针状铁素体+块状铁素体+珠光体组成,完全正火+冷轧+回火态20MnV钢中的珠光体中片状渗碳体演变成断续分布的球状或者短棒状;800℃正火+冷轧+回火态20MnV钢的组织为铁素体+M/A岛+细小碳化物;800℃淬火+冷轧+回火态20MnV钢的组织为铁素体+回火索氏体,晶内和晶界上弥散分布着细小碳化物颗粒。冷轧+回火态20MnV钢具有较高的强塑性和较低的低温冲击韧性,完全正火/亚温正火+冷轧+回火态20MnV钢的强度和塑性相对冷轧+回火态试样有不同程度降低,但是低温冲击吸收能量明显提高,在正火温度为800℃时强度降低最为显著;亚温淬火+冷轧+回火态20MnV钢的强度与冷轧+回火态试样相当,断后伸长率略有减小,而-25℃和-45℃冲击吸收能量明显提升。与冷轧+回火态20MnV钢冲击断口截面上的剪切裂纹相比,800℃正火/800℃淬火+冷轧+回火态20MnV钢中的微裂纹数量更少、长度和宽度更小,裂纹扩展呈现弯曲和曲折状;800℃淬火+冷轧+回火态20MnV钢具有较高的强塑性和最佳的低温冲击韧性。
The effects of full normalizing, subcritical normalizing/subcritical quenching on microstructure and properties of cold rolled and tempered 20 MnV steel were studied by means of optical microscope(OM), scanning electron microscopy(SEM) and universal tensile testing machine. The results show that the microstructure of the cold-rolled and tempered 20 MnV steel is composed of acicular ferrite, massive ferrite and pearlite, and the lamellar cementite in pearlite of the cold-rolled and tempered 20 MnV steel after full normalizing is changed into a discontinuous distributed spherical or short rod; the microstructure of the cold-rolled and tempered 20 MnV steel after normalizing at 800 ℃ is ferrite, M/A island and fine carbides; the structure of the cold rolled and tempered 20 MnV steel after quenching at 800 ℃ is ferrite and tempered sorbite, in which fine carbide particles are dispersed in grain and grain boundaries. The cold-rolled and tempered 20 MnV steel has higher strength and plasticity and lower impact toughness at low temperature, the strength and plasticity of the cold-rolled and tempered 20 MnV steel after full normalizing or subcritical normalizing are lower than that of the cold-rolled and tempered steel, but the impact absorbed energy at low temperature is obviously increased, and the strength decreases most significantly when the normalizing temperature is 800 ℃. The strength of the cold-rolled and tempered 20 MnV steel after subcritical quenching is similar to that of the cold-rolled and tempered steel, and the elongation decreases slightly, while the impact absorbed energy at-25 ℃ and-45 ℃ increases obviously. Compared with the shear cracks on impact fracture section of the cold-rolled and tempered 20 MnV steel, the number, length and width of micro-cracks in the cold-rolled and tempered 20 MnV steel after normalizing or quenching at 800 ℃ are smaller, and the crack propagation presents bending and zigzag shape. The cold-rolled and tempered 20 MnV steel after quenching at 800 ℃ has higher strength and plasticity and optimum impact toughness at low temperature.
The effects of full normalizing, subcritical normalizing/subcritical quenching on microstructure and properties of cold rolled and tempered 20 MnV steel were studied by means of optical microscope(OM), scanning electron microscopy(SEM) and universal tensile testing machine. The results show that the microstructure of the cold-rolled and tempered 20 MnV steel is composed of acicular ferrite, massive ferrite and pearlite, and the lamellar cementite in pearlite of the cold-rolled and tempered 20 MnV steel after full normalizing is changed into a discontinuous distributed spherical or short rod; the microstructure of the cold-rolled and tempered 20 MnV steel after normalizing at 800 ℃ is ferrite, M/A island and fine carbides; the structure of the cold rolled and tempered 20 MnV steel after quenching at 800 ℃ is ferrite and tempered sorbite, in which fine carbide particles are dispersed in grain and grain boundaries. The cold-rolled and tempered 20 MnV steel has higher strength and plasticity and lower impact toughness at low temperature, the strength and plasticity of the cold-rolled and tempered 20 MnV steel after full normalizing or subcritical normalizing are lower than that of the cold-rolled and tempered steel, but the impact absorbed energy at low temperature is obviously increased, and the strength decreases most significantly when the normalizing temperature is 800 ℃. The strength of the cold-rolled and tempered 20 MnV steel after subcritical quenching is similar to that of the cold-rolled and tempered steel, and the elongation decreases slightly, while the impact absorbed energy at-25 ℃ and-45 ℃ increases obviously. Compared with the shear cracks on impact fracture section of the cold-rolled and tempered 20 MnV steel, the number, length and width of micro-cracks in the cold-rolled and tempered 20 MnV steel after normalizing or quenching at 800 ℃ are smaller, and the crack propagation presents bending and zigzag shape. The cold-rolled and tempered 20 MnV steel after quenching at 800 ℃ has higher strength and plasticity and optimum impact toughness at low temperature.
引文
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[12] Park D B,Huh M Y,Shim J H,et al.Strengthening mechanism of hot rolled Ti and Nb microalloyed HSLA steels containing Mo and W with various coiling temperature[J].Materials Science and Engineering A,2013,560(2):528-534.
[13] Rosenberg G,Sinaiová I,Hvizdo? P,et al.Development of cold-rolled dual-phase steels with tensile strength above 1000 MPa and good bendability[J].Metallurgical and Materials Transactions A,2015,46(10):4755-4771.
[14] Kuang C F,Zheng Z W,Zhang G T,et al.Effects of overaging temperature on the microstructure and properties of 600 MPa cold-rolled dual-phase steel[J].International Journal of Minerals,Metallurgy,and Materials,2016,23(8):943-948.
[15] Deng Y G,Di H S,Zhang J C.Effect of heat-treatment schedule on the microstructure and mechanical properties of cold-rolled dual-phase steels[J].Acta Metallurgica Sinica (English Letters),2015,28(9):1141-1148.
[2] 李科兴,赵彦华,毕建福.热处理对高层建筑用钢组织与力学性能的影响[J].热加工工艺,2018,47(12):217-221+227.LI Ke-xing,ZHAO Yan-hua,BI Jian-fu.Effect of heat treatment on microstructure and mechanical properties of high-rise building steel[J].Hot Working Technology,2018,47(12):217-221+227.
[3] 孙海宁,李英龙,石晓凯.两相区淬火+回火对建筑用钢组织与性能的影响[J].金属热处理,2018,43(4):167-172.SUN Hai-ning,LI Ying-long,SHI Xiao-kai.Effects of quenching and tempering in two-phase zone on the structure and properties of building steel[J].Heat Treatment of Metals,2018,43(4):167-172.
[4] 覃展鹏,王红鸿,童志,等.亚温淬火工艺对低碳低合金高强钢组织及性能的影响[J].材料热处理学报,2017,38(9):142-147.TAN Zhen-peng,WANG Hong-hong,TONG Zhi,et al.Effect of intermediate temperature quenching on microstructure and properties of low carbon low alloy high strength steel[J].Transactions of Materials and Heat Treatment,2017,38(9):142-147.
[5] 谢辉,杜林秀,胡军.冷却工艺对低碳Ti微合金化热轧超高强钢组织性能的影响[J].东北大学学报,2014,35(4):10-18.XIE Hui,DU Lin-xiu,HU Jun.Effect of cooling process on microstructure and properties of low carbon Ti microalloyed hot rolled ultra high strength steel[J].Journal of Northeast University,2014,35(4):10-18.
[6] Moon H K,Lee K B,Kwon H.Influences of Co addition and austenitizing temperature on secondary hardening and impact fracture behavior in P/M high speed steels of W-Mo-Cr-V(-Co) system[J].Materials Science and Engineering A,2008,474(1):328-334.
[7] 郑娟,葛文杰,束必清.热处理工艺对微合金建筑用钢力学性能的影响[J].热加工工艺,2016,45(16):186-189.ZHENG Juan,GE Wen-jie,SHU Bi-qing.Effect of heat treatment process on mechanical properties of microalloyed building steel[J].Hot Working Technology,2016,45 (16):186-189.
[8] 钟磊,吴开明,董航宇,等.热处理对微纳结构低温贝氏体钢组织与力学性能的影响[J].材料热处理学报,2018,39(10):52-58.ZHONG Lei,WU Kai-ming,DONG Hang-yu,et al.Effects of heat treatment on microstructure and mechanical properties of low temperature bainitic steel with micro-nanostructure[J].Transactions of Materials and Heat Treatment,2018,39(10):52-58.
[9] Suarez M A,Alvarez-Pérez M A,Alvarez-Fregoso O,et al.Effect of nanoprecipitates and grain size on the mechanical properties of advanced structural steels[J].Materials Science and Engineering A,2011,528(15):4924-4926.
[10] 崔军,刘希琴,周双双,等.正火与变形处理对高强度低温用结构钢组织和力学性能的影响[J].材料热处理学报,2017,38(12):35-40.CUI Jun,LIU Xi-qin,ZHOU Shuang-shuang,et al.Effects of normalizing and deformation treatment on the structure and mechanical properties of high strength low temperature structural steels[J].Transactions of Materials and Heat Treatment,2017,38(12):35-40.
[11] Chen C Y,Yen H W,Kao F H,et al.Precipitation hardening of high-strength low-alloy steels by nanometer-sized carbides[J].Materials Science and Engineering A,2009,499(1):162-166.
[12] Park D B,Huh M Y,Shim J H,et al.Strengthening mechanism of hot rolled Ti and Nb microalloyed HSLA steels containing Mo and W with various coiling temperature[J].Materials Science and Engineering A,2013,560(2):528-534.
[13] Rosenberg G,Sinaiová I,Hvizdo? P,et al.Development of cold-rolled dual-phase steels with tensile strength above 1000 MPa and good bendability[J].Metallurgical and Materials Transactions A,2015,46(10):4755-4771.
[14] Kuang C F,Zheng Z W,Zhang G T,et al.Effects of overaging temperature on the microstructure and properties of 600 MPa cold-rolled dual-phase steel[J].International Journal of Minerals,Metallurgy,and Materials,2016,23(8):943-948.
[15] Deng Y G,Di H S,Zhang J C.Effect of heat-treatment schedule on the microstructure and mechanical properties of cold-rolled dual-phase steels[J].Acta Metallurgica Sinica (English Letters),2015,28(9):1141-1148.
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