Microstructure, Mechanical Properties, and Strengthening Mechanism of Cr-Mo Microalloy Cold Heading Steel

doi:10.11900/0412.1961.2021.00084

Acta Metall Sin

2022, Vol. 58

Issue (9): 1189-1198 DOI: 10.11900/0412.1961.2021.00084

Research paper

Current Issue | Archive | Adv Search

Microstructure, Mechanical Properties, and Strengthening Mechanism of Cr-Mo Microalloy Cold Heading Steel

CHEN Jilin¹^,²^,³(

), FENG Guanghong¹, MA Honglei², YANG Dong², LIU Wei²

^1.Metallurgical Technology Institute, Central Iron and Steel Research Institute, Beijing 100081, China
^2.Xingtai Iron and Steel Co., Ltd., Xingtai 054027, China
^3.Hebei Engineering Research Center for Wire Rod, Xingtai 054027, China

Cite this article:

CHEN Jilin, FENG Guanghong, MA Honglei, YANG Dong, LIU Wei. Microstructure, Mechanical Properties, and Strengthening Mechanism of Cr-Mo Microalloy Cold Heading Steel. Acta Metall Sin, 2022, 58(9): 1189-1198.

Download:

HTML

PDF(3959KB)
Export: BibTeX | EndNote (RIS)

Abstract

Lightweight and safety of automobiles is the development trend of high-strength automobile fasteners, which is conducive to saving resources and protecting the environment. High-strength fasteners connect parts of engine, and their strength affects the overall life of the engine, thereby affecting the safety performance of the vehicle. Presently, high-strength fastener steels for cars are mainly 35CrMo, and the fastener strength reaches 10.9/12.9 level, which must fulfill sufficient delayed fracture and fatigue properties. Therefore, it is important to develop cold heading steel with high fatigue and strong plasticity matching. In this study, the microstructure, mechanical properties, and strengthening mechanism of Cr-Mo microalloyed cold heading steel, under different thermomechanical control processes (TMCPs), were investigated using OM, SEM, and TEM. The results show that the TMCP parameters affect the structure and mechanical properties of the experimental steel. With an increase in the finish rolling temperature and acceleration of the cooling rate, the ferrite-pearlite composite structure in the steel gradually changes to bainitic, dislocation density gradually increases, tensile strength monotonously increases, and elongation fluctuates. When the finish rolling temperature is 935^oC, the microstructure is mainly uniformly distributed bainite phase, which is in the form of short rod and granular, and there is dislocation entanglement. The experimental results show that this process has the best strength and toughness matching. Its tensile strength and elongation reach 925 MPa and 20%, respectively, and the hardness at 7 mm from the quenched end (J7) is 53.1 HRC. When the finish rolling temperature is 900^oC, grain refinement strengthening is the main strengthening mechanism, accounting for 31%-36% of the yield strength; when the finish rolling temperature is more than 935^oC, dislocation strengthening is the main strengthening mechanism, accounting for the total strength of 35%-38%. The hardenability results show that the hardenability of the experimental steel is unaffected by the microstructure and mechanical properties, and it maintains high-quality hardenability. In addition, a model of the end quenching curve of the Cr-Mo microalloyed steel is established to predict hardenability.

Key words: Cr-Mo microalloying cold heading steel finish rolling temperature strengthening mechanism

Received: 26 February 2021

ZTFLH:

TG142.1

About author: CHEN Jilin, senior engineer, Tel: (0319)2042068, E-mail: chenjl@xtsteel.com

	Service

	E-mail this article
	Add to citation manager
	E-mail Alert
	RSS
	（）
	Articles by authors
	Jilin CHEN
	Guanghong FENG
	Honglei MA
	Dong YANG
	Wei LIU

URL:

https://www.ams.org.cn/EN/10.11900/0412.1961.2021.00084 OR https://www.ams.org.cn/EN/Y2022/V58/I9/1189

Table 1 Rolling technology of Cr-Mo microalloyed steels

Fig.1 OM (a, c, e, g) and SEM (b, d, f, h) images of Cr-Mo microalloyed steels under processes 1 (a, b), 2 (c, d), 3 (e, f), and 4 (g, h)

Fig.2 TEM images of Cr-Mo microalloyed steels under processes 1 (a), 2 (b), 3 (c), and 4 (d)

Fig.3 TEM images of dislocation (a) and twin (b) in Cr-Mo microalloyed steels

Fig.4 Tensile engineering stress-strain curves of Cr-Mo microalloyed steels at room temperature

Table 2 Mechanical properties of Cr-Mo microalloyed steels at room temperature

Fig.5 Tensile fracture SEM images of Cr-Mo microalloyed steel at room temperature (process 2)
(a) macroscopic feature (b) shear lip zone (c) edge of fiber zone (d) center of fiber zone (e) fiber zone

Fig.6 Hardenability curves of the Cr-Mo microalloyed steel by Jominy method

Fig.7 OM image of Cr-Mo microalloyed steel 7 mm from quenching end

Table 3 Calculated values of yield strength (σ_y) and its component of Cr-Mo microalloyed steels

1	Hui W J, Zhang Y J, Zhao X L, et al. Influence of cold deformation and annealing on hydrogen embrittlement of cold hardening bainitic steel for high strength bolts [J]. Mater. Sci. Eng., 2016, A662: 528
2	Zheng D S, Liu D, Luo D, et al. Effect of tempering temperature on microstructure and mechanical properties of ultra-high strength steel [J]. Trans. Mater. Heat Treat., 2020, 41(12): 90
	郑东升, 刘丹, 罗登等. 回火温度对超高强钢微观组织及力学性能的影响 [J]. 材料热处理学报, 2020, 41(12): 90
3	Ji C, Wang L, Zhu M Y. Effect of subcritical annealing temperature on microstructure and mechanical properties of SCM435 steel [J]. J. Iron Steel Res. Int., 2015, 22: 1031 doi: 10.1016/S1006-706X(15)30108-4
4	Dong H, Lian X T, Hu C D, et al. High performance steels: The scenario of theory and technology [J]. Acta Metall. Sin., 2020, 56: 558
	董瀚, 廉心桐, 胡春东等. 钢的高性能化理论与技术进展 [J]. 金属学报, 2020, 56: 558
5	Hu C D, Meng L, Dong H. Research and development of ultra-high strength steels [J]. Trans. Mater. Heat Treat., 2016, 37(11): 178
	胡春东, 孟利, 董瀚. 超高强度钢的研究进展 [J]. 材料热处理学报, 2016, 37(11): 178
6	Hui W J, Dong H, Weng Y Q. Research and development trends of high strength steel for bolts [J]. Mater. Mech. Eng., 2002, 26(11): 1
	惠卫军, 董瀚, 翁宇庆. 高强度螺栓钢的发展动向 [J]. 机械工程材料, 2002, 26(11): 1
7	Li Y B, Ma Y W, Lou M, et al. Advances in welding and joining processes of multi-material lightweight car body [J]. J. Mech. Eng., 2016, 52(24): 1
	李永兵, 马运五, 楼铭等. 轻量化多材料汽车车身连接技术进展 [J]. 机械工程学报, 2016, 52(24): 1 doi: 10.3901/JME.2016.24.001
8	Sun H R. Review on the fastener steels for automobiles [J]. China Metall., 2011, 21(7): 7
	孙浩然. 汽车紧固件用钢的发展动向 [J]. 中国冶金, 2011, 21(7): 7
9	Zhang H Y, Hui W J, Dong H, et al. Simplified spheroidizing annealing process of 42CrMo steel [J]. J. Iron Steel Res., 2007, 19(3): 62
	张怀宇, 惠卫军, 董瀚等. 简化42CrMo钢球化退火工艺的研究 [J]. 钢铁研究学报, 2007, 19(3): 62
10	Wang Q, Zhu J L. Certain new techniques of wire production development in recent years [J]. China Metall., 2014, 24(12): 1
	王强, 朱君龙. 线材生产发展的一些新技术 [J]. 中国冶金, 2014, 24(12): 1
11	Ruan S P, Wang L J, Chen J L, et al. Effect of control-rolling-cooling process on structure and properties of steel SCM435 rod coil [J]. Spec. Steel, 2016, 37(5): 45
	阮士朋, 王利军, 陈继林等. 控轧控冷工艺对SCM435钢盘条组织和性能的影响 [J]. 特殊钢, 2016, 37(5): 45
12	Parthiban R, Chowdhury S G, Harikumar K C, et al. Evolution of microstructure and its influence on tensile properties in thermo-mechanically controlled processed (TMCP) quench and partition (Q & P) steel [J]. Mater. Sci. Eng., 2017, A705: 376
13	Kitade A, Kawabata T, Kimura S, et al. Clarification of micromechanism on brittle fracture initiation condition of TMCP Steel with MA as the trigger point [J]. Procedia Struct. Integr., 2018, 13: 1845 doi: 10.1016/j.prostr.2018.12.330
14	Elhigazi F, Artemev A. The influence of carbide formation in ferrite on the bainitic type transformation [J]. Comput. Mater. Sci., 2021, 186: 109961 doi: 10.1016/j.commatsci.2020.109961
15	Elhigazi F, Artemev A. The interaction between the displacive transformation and the diffusion process in the bainitic type transformation [J]. Comput. Mater. Sci., 2019, 169: 109079 doi: 10.1016/j.commatsci.2019.109079
16	Ranjan R, Singh S B. Isothermal bainite transformation in low-alloy steels: Mechanism of transformation [J]. Acta Mater., 2021, 202: 302 doi: 10.1016/j.actamat.2020.10.048
17	Chen G H, Xu Y W, Liu M, et al. Effect of high-temperature deformation and undercooling on bainite transformation of a medium-carbon bainitic steel [J]. J. Iron Steel Res., 2020, 32: 984
	陈光辉, 徐耀文, 刘曼等. 高温变形和过冷度对中碳钢贝氏体相变的影响 [J]. 钢铁研究学报, 2020, 32: 984
18	Ravi A M, Kumar B, Herbig M, et al. Impact of austenite grain boundaries and ferrite nucleation on bainite formation in steels [J]. Acta Mater., 2020, 188: 424 doi: 10.1016/j.actamat.2020.01.065
19	Ji Y P, Liu Z C, Ren H P. Twin crystal substructure of martensite in steel [J]. Trans. Mater. Heat Treat., 2013, 34(4): 162
	计云萍, 刘宗昌, 任慧平. 钢中马氏体的孪晶亚结构 [J]. 材料热处理学报, 2013, 34(4): 162
20	Yong Q L, Ma M T, Wu B R. Microalloyed Steel—Physical and Mechanical Metallurgy [M]. Beijing: China Machine Press, 1989: 57
	雍岐龙, 马鸣图, 吴宝榕. 微合金钢——物理和力学冶金 [M]. 北京: 机械工业出版社, 1989: 57
21	Pickering F B. Physical Metallurgy and the Design of Steels [M]. London: Applied Science Publishing Ltd., 1978: 63
22	Kelly A. Strengthening Methods in Crystals [M]. London: Applied Science Publishers Ltd., 1971: 137
23	Li Z D, Yang Z G, Liu Z Y, et al. Effect of hot deformation on proeutectoid ferrite ledge growth from boundary of undercooled austenite [J]. J. Iron Steel Res. Int., 2007, 14: 306 doi: 10.1016/S1006-706X(08)60100-4
24	Zheng C S, Li L F, Yang W Y, et al. Microstructure evolution and mechanical properties of eutectoid steel with ultrafine or fine (ferrite+cementite) structure [J]. Mater. Sci. Eng., 2014, A599: 16
25	Yu D G. Theory and Design of Steel Strengthening and Toughening [M]. Shanghai: Shanghai Jiaotong University Press, 1990: 114
	俞德刚. 钢的强韧化理论与设计 [M]. 上海: 上海交通大学出版社, 1990: 114
26	Park S H, Hong S G, Chun Y S, et al. High-cycle fatigue characteristics of non-heat-treated steels developed for bolt applications [J]. Mater. Sci. Eng., 2012, A550: 118
27	Jin M, Lian J S, Jiang Z H. A new mathematical model describing hardenability of steels [J]. Acta Metall. Sin., 2006, 42: 265
	金满, 连建设, 江中浩. 描述钢淬透性的一个新数学模型 [J]. 金属学报, 2006, 42: 265
28	Huang R, Zhao S X, Huang Z Z. Effects of boron on hardenability for Cr-Mn-Mo quenched-tempered steel containing boron [J]. J. Iron Steel Res., 2021, 33: 437
	黄瑞, 赵四新, 黄宗泽. 硼对铬锰钼系含硼调质钢淬透性的影响 [J]. 钢铁研究学报, 2021, 33: 437
29	Wang D C, Wang L J, Guo J C, et al. Effect of alloy elements Mn and Cr on microstructure and properties of SWRCH45K steel [J]. Heat Treat. Met., 2020, 45(8): 82
	王冬晨, 王利军, 郭俊成等. 合金元素Mn、Cr对SWRCH45K钢组织和性能的影响 [J]. 金属热处理, 2020, 45(8): 82
30	Ruan S P. Microstructure and properties control of high quality cold heading steel containing boron [D]. Beijing: University of Science and Technology Beijing, 2020
	阮士朋. 高品质含硼冷镦钢的组织和性能调控 [D]. 北京: 北京科技大学, 2020

[1]	ZHU Yunpeng, QIN Jiayu, WANG Jinhui, MA Hongbin, JIN Peipeng, LI Peijie. Microstructure and Properties of AZ61 Ultra-Fine Grained Magnesium Alloy Prepared by Mechanical Milling and Powder Metallurgy Processing[J]. 金属学报, 2023, 59(2): 257-266.
[2]	WANG Hongwei, HE Zhufeng, JIA Nan. Microstructure and Mechanical Properties of a FeMnCoCr High-Entropy Alloy with Heterogeneous Structure[J]. 金属学报, 2021, 57(5): 632-640.
[3]	LIU Chenxi, MAO Chunliang, CUI Lei, ZHOU Xiaosheng, YU Liming, LIU Yongchang. Recent Progress in Microstructural Control and Solid-State Welding of Reduced Activation Ferritic/Martensitic Steels[J]. 金属学报, 2021, 57(11): 1521-1538.
[4]	WEN Bin, TIAN Yongjun. Mechanical Behaviors of Nanotwinned Metals and Nanotwinned Covalent Materials[J]. 金属学报, 2021, 57(11): 1380-1395.
[5]	LUAN Xiaosheng, LIANG Zhiqiang, ZHAO Wenxiang, SHI Guihong, LI Hongwei, LIU Xinli, ZHU Guorong, WANG Xibin. Strengthening Mechanism of 45CrNiMoVA Steel by Pulse Magnetic Treatment[J]. 金属学报, 2021, 57(10): 1272-1280.
[6]	ZHOU Xia,LIU Xiaoxia. Mechanical Properties and Strengthening Mechanism of Graphene Nanoplatelets Reinforced Magnesium Matrix Composites[J]. 金属学报, 2020, 56(2): 240-248.
[7]	XU Shuai, SUN Xinjun, LIANG Xiaokai, LIU Jun, YONG Qilong. Effect of Hot Rolling Deformation on Microstructure and Mechanical Properties of a High-Ti Wear-Resistant Steel[J]. 金属学报, 2020, 56(12): 1581-1591.
[8]	QIN Jiayu, LI Xiaoqiang, JIN Peipeng, WANG Jinhui, ZHU Yunpeng. Microstructure and Mechanical Properties of Carbon Nanotubes (CNTs) Reinforced AZ91 Matrix Composite[J]. 金属学报, 2019, 55(12): 1537-1543.
[9]	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.
[10]	Kechang HAN,Yiqi LIU,Guoqiang LIN,Chuang DONG,Kaiping TAI,Xin JIANG. STUDY ON ATOMIC-SCALE STRENGTHENING MECHANISM OF TRANSITION-METAL NITRIDE MN_x (M=Ti, Zr, Hf) FILMS WITHIN WIDE COMPOSITION RANGES[J]. 金属学报, 2016, 52(12): 1601-1609.
[11]	Yajun HUI,Hui PAN,Na ZHOU,Ruiheng LI,Wenyuan LI,Kun LIU. STUDY ON STRENGTHENING MECHANISM OF 650 MPa GRADE V-N MICROALLOYED AUTOMOBILE BEAM STEEL[J]. 金属学报, 2015, 51(12): 1481-1488.
[12]	HUANG Xiaoxu. SIZE EFFECTS ON THE STRENGTH OF METALS[J]. 金属学报, 2014, 50(2): 137-140.
[13]	LI Hai, MAO Qingzhong, WANG Zhixiu, MIAO Fenfen, FANG Bijun, SONG Renguo, ZHENG Ziqiao. EFFECT OF THE THERMO-MECHANICAL TREATMENT OF PRE-AGEING, COLD-ROLLING AND RE-AGEING ON MICROSTRUCTURES AND MECHANICAL PROPERTIES OF 6061 Al ALLOY[J]. 金属学报, 2014, 50(10): 1244-1252.
[14]	ZHUO Haiou TANG Jiancheng YE Nan. Cu–Y₂O₃ COMPOSITES PREPARED BY LIQUID PHASE IN SITU REACTION[J]. 金属学报, 2012, 48(12): 1474-1478.
[15]	. CHARACTERIZATIONS OF DLC/MAO COMPOSITE COATINGS ON AZ80 MAGNESIUM ALLOY[J]. 金属学报, 2011, 47(12): 1535-1540.

No Suggested Reading articles found!

Viewed

Full text

Abstract

Cited

Shared

Discussed