Please wait a minute...
Acta Metall Sin  2016, Vol. 52 Issue (4): 410-418    DOI: 10.11900/0412.1961.2015.00482
Orginal Article Current Issue | Archive | Adv Search |
Zhengyan ZHANG1,2,Xinjun SUN1(),Qilong YONG1,2,Zhaodong LI1,Zhenqiang WANG3,Guodong WANG2
1 Department of Structural Steels, Central Iron and Steel Research Institute, Beijing 100081, China
2 State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China
3 College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, China
Download:  HTML  PDF(1235KB) 
Export:  BibTeX | EndNote (RIS)      

Recently, increasing attention has been focused on the high strength low alloy (HSLA) steels mircoalloyed with multiple miroalloying elements, such as Nb-Ti, Nb-V and Ti-Mo, which can form synthetic carbide in steel, such as (Nb, Ti)C, (Nb, V)C and (Ti, Mo)C. Compared with the simplex carbide, such as NbC, TiC, those synthetic carbides with nanometer size exhibiting a superior thermal stability to exert their powerful influence mainly through their precipitation hardening in ferrite. It is reported that the precipitation hardening of approximate 300 MPa which can be obtained in Ti-Mo-bearing steel was developed by JFE steel, attributing to the synthetic (Ti, Mo)C particle precipitated in ferrite. However, as common microalloying elements, Nb and Mo are added synchronously in steel. The strengthening mechanism of Nb-Mo mircoalloyed as-rolled steel and the role of the carbide precipitated in Nb-Mo mircoalloyed as-rolled steel are rarely reported. Therefore, in the present study, the strengthening mechanism, microstructure and the precipitate characteristics of Nb and Nb-Mo microalloyed steels produced by thermo mechanical control process (TMCP) were comparatively investigated by means of SEM, EBSD, HRTEM and physical and chemical phase analysis, in order to systematically study the synergistic effect of Nb-Mo addition on the strength of as-rolled steel. The results shows that the microstructure is finer and the density of low-angle grain boundaries is higher in Nb-Mo microalloyed steel compared with that of in the Nb microalloyed steel. What's more, the Mo addition could increase the precipitation ratio of Nb, and the amount of the MC-type carbide with nanometer size in Nb-Mo microalloyed steel is evidently larger than that of in Nb microalloyed steel. Those MC-type carbide were identified as synthetic carbide (Nb, Mo)C, exhibiting low coarsening rate than that of NbC precipitated in Nb microalloyed steel, which thus contributed to a higher precipitation hardening. This is main reason of the difference in strength between Nb and Nb-Mo microalloyed steel.

Key words:  Nb-Mo microalloyed      strength mechanism      nanometer-sized carbide      precipitation     
Received:  15 September 2015     
Fund: Supported by Supported by National Basic Research Program of China (No.2015CB654803) and High Technology Research and Development Program of China (No.2015AA034302)

Cite this article: 


URL:     OR

Steel C Mn P S Si Al Mo Ti Nb B Fe
Nb 0.036 1.35 0.0034 0.0057 0.024 0.012 - 0.010 0.1 0.0012 Bal.
Nb-Mo 0.042 1.38 0.0040 0.0060 0.016 0.014 0.19 0.015 0.1 0.0010 Bal.
Table 1  Chemical compositions of Nb and Nb-Mo microalloyed steels (mass fraction / %)
Fig.1  Tensile engineering stress-strain curves of Nb and Nb-Mo microalloyed steels at room temperature
Steel σb / MPa σ0.2 / MPa δ / % Yield ratio
Nb 679 630 23 0.92
Nb-Mo 739 699 21 0.94
Table 2  Mechanical properties of Nb and Nb-Mo microalloyed steels at room temperature
Fig.2  SEM images of Nb (a) and Nb-Mo (b) microalloyed steels (RD—rolling direction, ND—normal direction)
Fig.3  EBSD grain boundary distribution maps of Nb (a) and Nb-Mo (b) microalloyed steels (Where black and red lines represent the high misorientation angle boundaries (≥15°) and low misorientation angle boundaries (2°~15°), respectively) and the total grain boundary density of Nb and Nb-Mo microalloyed steels vs the misoritentation of ferrite grain ranged 0°~60° (c)
Fig.4  HRTEM image of a MC-type particle precipitated in austenite of Nb-Mo mircoalloyed steel (a) and its fast Fourier transformed (FFT) result along the [111]MC and [001]α-Fe zone axis (b)
Fig.5  TEM images of nanometer sized precipitates (a, b) and corresponding EDS (c, d) of Nb (a, c) and Nb-Mo (b, d) microalloyed steels
Fig.6  XRD spectra of precipitates in Nb and Nb-Mo microalloyed steels
Steel N3C (N=Fe, Mn, Mo) MC (M=Nb, Ti, Mo)
Fe Mn Mo C* Nb Ti Mo C*
Nb 0.177 0.032 - 0.015 0.076 0.0095 - 0.0098
Nb-Mo 0.168 0.022 0.014 0.014 0.078 0.0150 0.028 0.0133
Table 3  Element contents in precipitates of Nb and Nb-Mo microalloyed steels (mass fraction / %)
Fig.7  Size distribution of MC-type precipitate in Nb and Nb-Mo microalloyed steels
d / nm fm / % fV / % σp / MPa
Nb Nb-Mo Nb Nb-Mo Nb Nb-Mo
1~5 0.005246 0.04236 0.005234 0.04230 43.0 122.1
5~10 0.006192 0.00996 0.006178 0.00994 27.3 34.6
10~18 0.007826 0.01560 0.007808 0.01560 20.0 28.2
18~36 0.014448 0.00492 0.014415 0.00491 16.7 9.8
36~60 0.011008 0.00948 0.010983 0.00946 9.3 8.7
Table 4  Volume fractions of precipitates with different sizes and the corresponding precipitation strengthening increments in Nb and Nb-Mo microalloyed steels
Fig.8  Analysis and comparison of the strengthening mechanism for Nb and Nb-Mo microalloyed steels
Fig.9  Ripening rate of precipitates vs temperature in ferrite of Nb and Nb-Mo microalloyed steels
[1] Weng Y Q.Ultra-Fine Grained Steels. Beijing: Metallurgical Industry Press, 2008: 20
[1] (翁宇庆. 超细晶钢. 北京:冶金工业出版社, 2008: 20)
[2] Miao C L, Shang C J, Zhang G D, Subramanian S V.Mater Sci Eng, 2010; A527: 4985
[3] Wang C Y, Shi J, Cao W Q, Hui W J, Wang M Q, Dong H.Acta Metall Sin, 2011; 47: 720
[3] (王存宇, 时捷, 曹文全, 惠卫军, 王毛球, 董瀚. 金属学报, 2011; 47: 720)
[4] Wan R C, Sun F, Zhang L T, Shan A D.Mater Des, 2012; 35: 335
[5] Yong Q L, Ma M T, Wu B R.Microalloyed Steel-Physical and Mechanical Metallurgy. Beijing: China Machine Press, 1989: 22
[5] (雍岐龙, 马鸣图, 吴宝榕. 微合金钢-物理和力学冶金. 北京: 机械工业出版社, 1989: 22)
[6] De Ardo A J. In: Fu J Y, Wang W Z eds., Niobium Science & Technology. Beijing: Metallurgical Industry Press, 2003: 271
[6] (De Ardo A J. 见: 付俊岩, 王伟哲主编, 铌科学与技术. 北京: 冶金工业出版社, 2003: 271)
[7] Liu Q D, Liu W Q, Wang Z M, Zhou B X.Acta Metall Sin, 2008; 44: 786
[7] (刘庆冬, 刘文庆, 王泽民, 周邦新. 金属学报, 2008; 44: 786)
[8] Liu Q D, Liu W Q, Peng J C.Trans Mater Heat Treat, 2008; 29(4): 118
[8] (刘庆冬, 刘文庆, 彭剑超. 材料热处理学报, 2008; 29(4): 118)
[9] Cao S M, Li C, Liu W Q.Trans Mater Heat Treat, 2013; 34(2): 47
[9] (曹双梅, 李聪, 刘文庆. 材料热处理学报, 2013; 34(2): 47)
[10] Chen J, Lü M Y, Tang S, Liu Z Y, Wang G D.Acta Metall Sin, 2014; 50: 524
[10] (陈俊, 吕梦阳, 唐帅, 刘振宇, 王国栋. 金属学报, 2014; 50: 524)
[11] Li X L, Wang Z D.Acta Metall Sin, 2015; 51: 417
[11] (李小琳, 王昭东. 金属学报, 2015; 51: 417)
[12] Funakawa Y, Shiozaki T, Tomita K, Yamamoto T, Maeda E.ISIJ Int, 2004; 44: 1945
[13] Wang Z Q.PhD Dissertation, Tsinghua University, Beijing, 2013
[13] (王振强. 清华大学博士学位论文, 北京, 2013)
[14] Duan X G, Cai Q W, Wu H B.Acta Metall Sin, 2011; 47: 251
[14] (段修刚, 蔡庆伍, 武会宾. 金属学报, 2011; 47: 251)
[15] Jang J H, Lee C H, Heo Y U, Suh D W.Acta Mater, 2012; 60: 208
[16] Kim Y W, Kim J H, Hong S G, Lee C S.Mater Sci Eng, 2014; A605: 244
[17] Kim Y W, Song S W, Seo S J, Hong S G, Lee C S.Mater Sci Eng, 2013; A565: 430
[18] Jang J H, Lee C H, Han H N, Bhadeshia H K D H, Suh D W.Mater Sci Technol, 2013; 29: 1074
[19] Park D B, Huh M Y, Shim J H, Suh J Y, Lee K H, Jung W S.Mater Sci Eng, 2013; A560: 528
[20] Cao J C, Yong Q L, Liu Q Y, Sun X J.J Mater Sci, 2007; 42: 10080
[21] Pan J S, Tong J M, Tian M B.Fundamentals of Material Science. Beijing: Tsinghua University Press, 2011: 660
[21] (潘金生, 仝健民, 田民波. 材料科学基础. 北京: 清华大学出版社, 2011: 660)
[22] Zhang Z Y, Sun X J, Li Z D, Wang X J, Yong Q L, Wang G D.Chin J Mater Res, 2015; 29: 269
[22] (张正延, 孙新军, 李昭东, 王小江, 雍岐龙, 王国栋. 材料研究学报, 2015; 29: 269)
[23] Yong Q L.Secondary Phase in Steels. Beijing: Metallurgical Industry Press, 2006: 361
[23] (雍岐龙. 钢铁材料中的第二相. 北京: 冶金工业出版社, 2006: 361)
[24] Zhang Z Y, Li Z D, Yong Q L, Sun X J, Wang Z Q, Wang G D.Acta Metall Sin, 2015; 51: 315
[24] (张正延, 李昭东, 雍岐龙, 孙新军, 王振强, 王国栋. 金属学报, 2015; 51: 315)
[25] Wan R C.PhD Dissertation, Shanghai Jiao Tong University, 2012
[25] (万荣春. 上海交通大学博士学位论文, 2012)
[26] Wan R C, Sun F, Zhang L T, Shan A D.Mater Des, 2012; 36: 227
[27] Zhang Z Y, Sun X J, Wang Z Q, Li Z D, Yong Q L, Wang G D.Mater Lett, 2015; 159: 249
[28] Cao Y B, Xiao F R, Qiao G Y, Huang C J, Zhang X B, Wu Z X, Liao B.Mater Sci Eng, 2012; A552: 502
[1] SUN Xinjun,LIU Luojin,LIANG Xiaokai,XU Shuai,YONG Qilong. TiC Precipitation Behavior and Its Effect on Abrasion Resistance of High Titanium Wear-Resistant Steel[J]. 金属学报, 2020, 56(4): 661-672.
[2] LUO Haiwen,SHEN Guohui. Progress and Perspective of Ultra-High Strength Steels Having High Toughness[J]. 金属学报, 2020, 56(4): 494-512.
[3] Chao CAI,Yang LI,Jinfeng LI,Zhao ZHANG,Jianqing ZHANG. Correlation Between Ageing Precipitation, Potential and Intergranular Corrosion of 2A97 Al-Li Alloy Sheet[J]. 金属学报, 2019, 55(8): 958-966.
[4] Zhengyan ZHANG,Feng CHAI,Xiaobing LUO,Gang CHEN,Caifu YANG,Hang SU. The Strengthening Mechanism of Cu Bearing High Strength Steel As-Quenched and Tempered and Cu Precipitation Behavior in Steel[J]. 金属学报, 2019, 55(6): 783-791.
[5] Xiaodong LIN,Qunjia PENG,En-Hou HAN,Wei KE. Effect of Annealing on Microstructure of Thermally Aged 308L Stainless Steel Weld Metal[J]. 金属学报, 2019, 55(5): 555-565.
[6] HUANG Yu, CHENG Guoguang, LI Shijian, DAI Weixing. Precipitation Mechanism and Thermal Stability of Primary Carbide in Ce Microalloyed H13 Steel[J]. 金属学报, 2019, 55(12): 1487-1494.
[7] Xuemei XIANG, Yuxiang LAI, Chunhui LIU, Jianghua CHEN. Sn-Induced Modification of the Precipitation Pathways upon High-Temperature Ageing in an Al-Mg-Si Alloy[J]. 金属学报, 2018, 54(9): 1273-1280.
[8] Mingliang HUANG, Hongyu SUN. Interaction Between β-Sn Grain Orientation and Electromigration Behavior in Flip-Chip Lead-Free Solder Bumps[J]. 金属学报, 2018, 54(7): 1077-1086.
[9] Zhiming GAO, Wanqi JIE, Yongqin LIU, Haijun LUO. Formation Mechanism and Coupling Prediction of Microporosity and Inverse Segregation: A Review[J]. 金属学报, 2018, 54(5): 717-726.
[10] Fengming QIN, Yajie LI, Xiaodong ZHAO, Wenwu HE, Huiqin CHEN. Effect of Nitrogen Content on Precipitation Behavior and Mechanical Properties of Mn18Cr18NAustenitic Stainless Steel[J]. 金属学报, 2018, 54(1): 55-64.
[11] Junzhou CHEN, Liangxing LV, Liang ZHEN, Shenglong DAI. Quantitative Characterization on the Precipitation of AA 7055 Aluminum Alloy by SAXS[J]. 金属学报, 2017, 53(8): 897-906.
[12] Yi CHEN, Mingxing GUO, Long YI, Bo YUAN, Gaojie LI, Linzhong ZHUANG, Jishan ZHANG. Optimization and Controlling on the Microstructure, Texture and Properties of an Advanced Al-Mg-Si-Cu-Zn Alloy Sheet[J]. 金属学报, 2017, 53(8): 907-917.
[13] 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[J]. 金属学报, 2017, 53(6): 648-656.
[14] Yutian DING,Yubi GAO,Zhengyi DOU,Xin GAO,Dexue LIU,Zhi JIA. Precipitation Behavior of δ Phase of Deformation Induced GH3625 Superalloy Hot-Extruded Tube[J]. 金属学报, 2017, 53(6): 695-702.
[15] Sihan CHEN,Tian LIANG,Long ZHANG,Yingche MA,Zhengjun LIU,Kui LIU. Study on Evolution Mechanism of bcc Phase During Solution Treatment in 6%Si High Silicon Austenitic Stainless Steel[J]. 金属学报, 2017, 53(4): 397-405.
No Suggested Reading articles found!