Please wait a minute...
Acta Metall Sin  2017, Vol. 53 Issue (6): 648-656    DOI: 10.11900/0412.1961.2016.00437
Orginal Article Current Issue | Archive | Adv Search |
Effect of Nb on the Continuous Cooling Transformation Rule and Microstructure, Mechanical Properties of Ti-Mo Bearing Microalloyed Steel
Xianling HE1,Gengwei YANG1(),Xinping MAO1,2,Chibin YU1,Chuanli DA1,Xiaolong GAN1,2
1 State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China
2 Research and Development Institute, Wuhan Iron and Steel (Group) Co., Ltd., Wuhan 430083, China
Download:  HTML  PDF(10892KB) 
Export:  BibTeX | EndNote (RIS)      

In recent years, with the fast development of automotive industry, more and more attention has been focused on developing high strength automobile steels with excellent formability. The microalloying elements, such as Nb, Ti, Mo, which can facilitate grain refinement and precipitation hardening, were added into steels to achieve high strength and good formability. The Ti-Mo and Ti-Mo-Nb microalloyed high strength ferritic steel were developed. In this work, the continuous cooling transformation curves (CCT) of Ti-Mo and Ti-Mo-Nb steels were obtained. And the effect of Nb on the microstructure and mechanical properties of Ti-Mo low carbon microalloyed steel was investigated by means of SEM, HRTEM and EDS. The results showed that Nb could raise the Ac1 and Ac3 temperatures, and restrain the ferrite-pearlite and bainite transformation. Moreover, Nb could also refine the microstructure and harden the matrix of steel which attributed to the strain-induced precipitation of nano-sized (Ti, Nb, Mo)C particles identified by HRTEM and EDS. It was also found that the strain-induced precipitation of (Ti, Mo)C was existed in the Ti-Mo steel. And both of (Ti, Mo)C and (Ti, Nb, Mo)C particles were NaCl type structure. The lattice constants/the average particle sizes of (Ti, Mo)C and (Ti, Nb, Mo)C were 0.432 nm and 0.436 nm / 12.11 nm and 8.69 nm, respectively.

Key words:  Ti microalloyed steel      CCT curve      Nb      nano-sized precipitation      hardness     
Received:  05 October 2016     
Fund: Supported by China Postdoctoral Science Foundation (No.2014M562072)

Cite this article: 

Xianling HE,Gengwei YANG,Xinping MAO,Chibin YU,Chuanli DA,Xiaolong GAN. Effect of Nb on the Continuous Cooling Transformation Rule and Microstructure, Mechanical Properties of Ti-Mo Bearing Microalloyed Steel. Acta Metall Sin, 2017, 53(6): 648-656.

URL:     OR

Steel C Si Mn Ti Mo Nb Cr N Fe
Ti-Mo 0.06 0.070 1.44 0.097 0.28 - 0.21 0.0035 Bal.
Ti-Nb-Mo 0.06 0.088 1.46 0.100 0.29 0.074 0.20 0.0083 Bal.
Table 1  Chemical compositions of the microalloyed steels (mass fraction / %)
Fig.1  Schematic of dynamic continuous cooling transformation (CCT) curve
Fig.2  Temperature-expansion curves of Ti-Mo and Ti-Mo-Nb steels
Fig.3  SEM images of Ti-Mo steel cooled by different cooling rates (P—pearlite, PF—polygonal ferrite, GB—granular bainite, LB—lath bainite) (a) 0.5 ℃/s (b) 1 ℃/s (c) 5 ℃/s (d) 10 ℃/s (e) 20 ℃/s (f) 30 ℃/s (g) 50 ℃/s
Fig.4  SEM images of Ti-Mo-Nb steel cooled by different cooling rates(a) 0.5 ℃/s (b) 1 ℃/s (c) 5 ℃/s (d) 10 ℃/s (e) 20 ℃/s (f) 30 ℃/s (g) 50 ℃/s
Fig.5  Dynamic CCT curves of Ti-Mo (a) and Ti-Mo-Nb (b) steels (F—ferrite, B—bainite, CR—cooling rate, Ac1—start temperature of austenite formation during heating, Ac3—finish temperature of austenite formation during heating)
Fig.6  Hardness of Ti-Mo and Ti-Mo-Nb steels after cooling at different cooling rates
Fig.7  Changes of precipitate volume fraction with temperature in Ti-Mo and Ti-Mo-Nb steels
Fig.8  Morphologies (a, c) and EDS analyses (circles) (b, d) of the precipitates in Ti-Mo (a, b) and Ti-Mo-Nb (c, d) steels cooling at 50 ℃/s
Fig.9  Low (a, d) and high (b, e) magnified HRTEM images and corresponding fast Fourier transformation (FFT) diffractograms (c, f) of the interphase precipitation carbides in Ti-Mo (a~c) and Ti-Mo-Nb (d~e) steels (d—interplanar spacing)
Fig.10  Size percentage of the second particles of Ti-Mo and Ti-Mo-Nb steels at cooling rate of 50 ℃/s
Fig.11  Austenite grain boundary diagrams of Ti-Mo (a) and Ti-Mo-Nb (b) steels after deformation
[1] Shimizu T, Funakawa Y, Kaneko S.High strength steel sheets for automobile suspension and chassis use-high strength hot-rolled steel sheets with excellent press formability and durability for critical safety parts[J]. JFE Tech. Rep., 2004, 4: 25
[2] Jha G, Das S, Sinha S, et al.Design and development of precipitate strengthened advanced high strength steel for automotive application[J]. Mater. Sci. Eng., 2013, A561: 394
[3] Funakawa Y. Mechanical properties of ultra fine particle dispersion strengthened ferritic steel [J]. Mater. Sci. Forum. Trans. Tech. Publications, 2012, 706-709: 2096
[4] Wang W, Shan Y Y, Yang K.Effect of acicular ferrite microstructure composition on strength of X65 pipeline steel[J]. Acta Metall. Sin., 2007, 43: 578
[4] (王伟, 单以银, 杨柯. 超低碳微合金管线钢中针状铁素体的组成对强度的影响[J]. 金属学报, 2007, 43: 578)
[5] Mao X P, Chen Q L, Sun X J.Metallurgical interpretation on grain refinement and synergistic effect of Mn and Ti in Ti-microalloyed strip produced by TSCR[J]. J. Iron Steel Res. Int., 2014, 21: 30
[6] Zhang K, Sun X J, Yong Q L, et al.Effect of tempering time on microstructure and mechanical properties of high Ti microalloyed quenched martensitic steel[J]. Acta Metall. Sin., 2015, 51: 553
[6] (张可, 孙新军, 雍岐龙等. 回火时间对高Ti微合金化淬火马氏体钢组织及力学性能的影响[J]. 金属学报, 2015, 51: 553)
[7] Chen J, Lü M Y, Tang S, et al.Microstructure, mechanical properties and interphase precipitation behaviors in V-Ti microalloyed steel[J]. Acta Metall. Sin., 2014, 50: 524
[7] (陈俊, 吕梦阳, 唐帅等. V-Ti微合金钢的组织性能及相间析出行为[J]. 金属学报, 2014, 50: 524)
[8] Kestenbach H J, Campos S S, Morales E V.Role of interphase precipitation in microalloyed hot strip steels[J]. Mater. Sci. Technol., 2006, 22: 615
[9] Yang G W, Sun X J, Yong Q L, et al.Austenite grain refinement and isothermal growth behavior in a low carbon vanadium microalloyed steel[J]. J. Iron Steel Res. Int., 2014, 21: 757
[10] Li X L, Wang Z D.Interphase precipitation behaviors of nanometer-sized carbides in a Nb-Ti-bearing low-carbon microalloyed steel[J]. Acta Metall. Sin., 2015, 51: 417
[10] (李小琳, 王昭东. 含Nb-Ti低碳微合金钢中纳米碳化物的相间析出行为[J]. 金属学报, 2015, 51: 417)
[11] Funakawa Y, Shiozaki T, Tomita K, et al.Development of high strength hot-rolled sheet steel consisting of ferrite and nanometer-sized carbides[J]. ISIJ Int., 2004, 44: 1945
[12] Zhang Z Y, Sun X J, Li Z D, et al.Effect of nanometer-sized carbides and grain boundary density on performance of Fe-C-Mo-M(M=Nb, V or Ti) fire resistant steels[J]. Chin. J. Mater. Res., 2015, 29: 269
[12] (张正延, 孙新军, 李昭东等. 纳米级碳化物及小角界面密度对Fe-C-Mo-M (M=Nb、V或Ti)系钢耐火性的影响[J]. 材料研究学报, 2015, 29: 269)
[13] Jang J H, Heo Y U, Lee C H, et al.Interphase precipitation in Ti-Nb and Ti-Nb-Mo bearing steel[J]. Mater. Sci. Technol., 2013, 29: 309
[14] Bu F Z, Wang X M, Chen L, et al.Performance of nanosized carbides precipitation and microstructure evolution in tempering process of Ti-Nb-Mo microalloyed steel[J]. Trans. Mater. Heat Treat., 2015, 36(8): 96
[14] (卜凡征, 王学敏, 陈琳等. Ti-Nb-Mo微合金钢回火过程中纳米碳化物的析出行为及组织演变[J]. 材料热处理学报, 2015, 36(8): 96)
[15] Zhang N.Effect of Nb on microstructure of CFB/M multiphase steel [D]. Beijing: North China Electric Power University (Beijing), 2009
[15] (张楠. Nb对CFB/M复相钢组织的影响[D]. 北京: 华北电力大学(北京), 2009)
[16] Weng Y Q.Microstructure Refinement Theory and Control Technology of Ultrafine Grained Steel [M]. Beijing: Metallurgical Industry Press, 2003: 57
[16] (翁宇庆. 超细晶钢——钢的组织细化理论与控制技术 [M]. 北京: 冶金工业出版社, 2003: 57)
[17] Mecozzi M G, Sietsma J, van der Zwaag S. Analysis of γ→α transformation in a Nb micro-alloyed C-Mn steel by phase field modelling[J]. Acta Mater., 2006, 54: 1431
[18] Liu X F, Jia T, Zhu B Q.Modeling the effect of Nb on austenite→ferrite phase transformation kinetics[J]. J. Northeastern Univ.(Nat. Sci.), 2016, 37: 642
[18] (刘雪峰, 贾涛, 朱本强. Nb对奥氏体→铁素体相变动力学影响的模型[J]. 东北大学学报(自然科学版), 2016, 37: 642)
[19] Bradley J R, Aaronson H I.Growth kinetics of grain boundary ferrite allotriomorphs in Fe-C-X alloys[J]. Metall. Trans., 1981, 12A: 1729
[20] Fossaert C, Rees G, Maurickx T, et al.The effect of niobium on the hardenability of microalloyed austenite[J]. Metall. Mater. Trans., 1995, 26A: 21
[21] Yuan X Q, Liu Z Y, Jiao S H, et al.The onset temperatures of γ to α-phase transformation in hot deformed and non-deformed Nb micro-alloyed steels[J]. ISIJ Int., 2006, 46: 579
[22] Chen C Y, Yen H W, Kao F H, et al.Precipitation hardening of high-strength low-alloy steels by nanometer-sized carbides[J]. Mater. Sci. Eng., 2009, A499: 162
[23] Duan X G, Cai Q W, Wu H B.Ti-Mo ferrite matrix micro-alloy steel with nanometer-sized precipitates[J]. Acta Metall. Sin., 2011, 47: 251
[23] (段修刚, 蔡庆伍, 武会宾. Ti-Mo全铁素体基微合金高强钢纳米尺度析出相[J]. 金属学报, 2011, 47: 251)
[24] Yong Q L.Secondary Phases in Steels [M]. Beijing: Metallurgical Industry Press, 2006: 27
[24] (雍岐龙. 钢铁材料中的第二相 [M]. 北京: 冶金工业出版社, 2006: 27)
[25] Irvine K J, Pickering F B, Gladman T R.Grain-refined C-Mn steels[J]. J. Iron Steel Inst., 1967, 205: 161
[26] Nordberg H, Aromsson B.Solubility of niobium carbide in austenite[J]. J. Iron Steel Inst., 1968, 206: 1263
[27] Pavlina E J, Speer J G, van Tyne C J. Equilibrium solubility products of molybdenum carbide and tungsten carbide in iron[J]. Scr. Mater., 2012, 66: 243
[28] Xu Y, Sun M X, Zhou Y L, et al.Precipitation behavior of (Nb, Ti)C in coiling process and its effect on micro-mechanical characteristics of ferrite[J]. Acta Metall. Sin., 2015, 51: 31
[28] (徐洋, 孙明雪, 周砚磊等. (Nb, Ti)C在轧后卷取中的析出及对铁素体相微观力学特征的影响[J]. 金属学报, 2015, 51: 31)
[29] Wu J B, Liu G Q, Wang H.Effect of Nb, Ti and V on the hot deformation behavior of low carbon Nb microalloyed steels[J]. Acta Metall. Sin., 2010, 46: 838
[29] (吴晋彬, 刘国权, 王浩. Nb, Ti和V对含Nb微合金钢热变形行为的影响[J]. 金属学报, 2010, 46: 838)
[1] QIAN Yue,SUN Rongrong,ZHANG Wenhuai,YAO Meiyi,ZHANG Jinlong,ZHOU Bangxin,QIU Yunlong,YANG Jian,CHENG Guoguang,DONG Jianxin. Effect of Nb on Microstructure and Corrosion Resistance of Fe22Cr5Al3Mo Alloy[J]. 金属学报, 2020, 56(3): 321-332.
[2] DENG Congkun,JIANG Hongxiang,ZHAO Jiuzhou,HE Jie,ZHAO Lei. Study on the Solidification of Ag-Ni Monotectic Alloy[J]. 金属学报, 2020, 56(2): 212-220.
[3] MA Xiaoqiang,YANG Kunjie,XU Yuqiong,DU Xiaochao,ZHOU Jianjun,XIAO Renzheng. Molecular Dynamics Simulation of DisplacementCascades in Nb[J]. 金属学报, 2020, 56(2): 249-256.
[4] Ling LI,Shenglian YAO,Xiaoli ZHAO,Jiajia YANG,Yexi WANG,Luning WANG. Fabrication and Properties of Anodic Oxide Nanotubular Arrays on Zr-17Nb Alloy[J]. 金属学报, 2019, 55(8): 1008-1018.
[5] Bo LI,Zhonghua ZHANG,Huasong LIU,Ming LUO,Peng LAN,Haiyan TANG,Jiaquan ZHANG. Characteristics and Evolution of the Spot Segregations and Banded Defects in High Strength Corrosion Resistant Tube Steel[J]. 金属学报, 2019, 55(6): 762-772.
[6] Zhengguan LU,Jie WU,Lei XU,Xiaoxiao CUI,Rui YANG. Ring Rolling Forming and Properties of Ti2AlNb Special Shaped Ring Prepared by Powder Metallurgy[J]. 金属学报, 2019, 55(6): 729-740.
[7] Chunbo LAN,Jianeng LIANG,Yuanxia LAO,Dengfeng TAN,Chunyan HUANG,Xianzhong MO,Jinying PANG. Anomalous Thermal Expansion Behavior of Cold-RolledTi-35Nb-2Zr-0.3O Alloy[J]. 金属学报, 2019, 55(6): 701-708.
[8] SHAO Yi , LI Yanmo , LIU Chenxi , YAN Zesheng , LIU Yongchang . Annealing Process Optimization of High Frequency Longitudinal Resistance Welded Low-CarbonFerritic Stainless Steel Pipe[J]. 金属学报, 2019, 55(11): 1367-1378.
[9] LI Dongmei, JIANG Beibei, LI Xiaona, WANG Qing, DONG Chuang. Composition Rule of High Hardness and Electrical Conductivity Cu-Ni-Si Alloys[J]. 金属学报, 2019, 55(10): 1291-1301.
[10] Bin ZHAI, Kai ZHOU, Peng Lü, Haipeng WANG. Rapid Solidification of Ti-6Al-4V Alloy Micro-Droplets Under Free Fall Condition[J]. 金属学报, 2018, 54(5): 824-830.
[11] Ke ZHANG, Zhaodong LI, Fengli SUI, Zhenghai ZHU, Xiaofeng ZHANG, Xinjun SUN, Zhenyi HUANG, Qilong YONG. Effect of Cooling Rate on Microstructure Evolution and Mechanical Properties of Ti-V-Mo Complex Microalloyed Steel[J]. 金属学报, 2018, 54(1): 31-38.
[12] Yajun HUI, Hui PAN, Kun LIU, Wenyuan LI, Yang YU, Bin CHEN, Yang CUI. Strengthening Mechanism of 600 MPa Grade Nb-Ti Microalloyed High Formability Crossbeam Steel[J]. 金属学报, 2017, 53(8): 937-946.
[13] Qianqian GU, Ying RUAN, Haizhe ZHU, Na YAN. Influence of Cooling Rate on Microstructural Formation of Melt-Spun Fe-Al-Nb Ternary Alloy[J]. 金属学报, 2017, 53(6): 641-647.
[14] Zhanxing CHEN,Hongsheng DING,Shiqiu LIU,Ruirun CHEN,Jingjie GUO,Hengzhi FU. Effects of Direct Current on Microstructure and Properties of Ti-48Al-2Cr-2Nb Alloy[J]. 金属学报, 2017, 53(5): 583-591.
[15] Wenhui TONG,Zilong ZHAO,Xinyuan ZHANG,Jie WANG,Xuming GUO,Xinhua DUAN,Yu LIU. Microstructure and Properties of TiC/Co-Based Alloyby Laser Cladding on the Surface of NodularGraphite Cast Iron[J]. 金属学报, 2017, 53(4): 472-478.
No Suggested Reading articles found!