Continuous Annealing Process and Microstructure Property of 1200mpa High Strength Steel by Ultrafast Cooling

Abstract:

The different dilatometric curves of continuous cooling transformation have been determined by DIL805 thermal mechanical simulate, through metallographic and hardness method to study the effect of different cooling rate on the microstructure of transition. The critical point Ac1 and Ac3 of the tested steel are 709°C and 865°C. With the increase of cooling rate, the hardness of the steel and the content of martensite increase. In the laboratory conditions, the steel in this experiment was heated to 780°C, 800°C, 820°C, 840°C and 860°C, for 80s, then slowly cooled to 680°C, and water quenched to room temperature finally. The aging temperature was 240°C for 300s, and the last the sample was air cooled to room temperature. The results show that the microstructure of the annealed experimental steel belongs to martensite and ferrite. With the increase of annealing temperature, the content of martensite, the tensile strength and yield strength of the experimental steel increase, and the elongation decreases continuously. The sample was annealed at 800°C for 80s, then slowly cooled to 680°C and finally water quenched to room temperature. After overaging at 240°C, the samples were obtained with high mechanical properties. The tensile strength, yield strength and elongation are 1223MPa, 605MPa and 9.2%, respectively.

• Periodical: Materials Science Forum (Volume 788)
• Pages: 351-356
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.788.351
• Online since: April 2014
• Authors: San Chuan Yu, Ren Bo Song*, Qi Feng Dai, Zhe Gao
• Keywords: Continuous Annealing, Mechanical Property, Microstructure Evolution, Ultra-Fast Cooling, Ultra-High Strength Steel

References

[1] R.O. Rocha, T.M.F. Melo, E.V. Pereloma, D.B. Santos. Microstructural evolution at the initial stages of continuous annealing of cold rolled dual-phase steel [J]. Materials Science and Engineering A. 391 (2005) 296–304.

DOI: 10.1016/j.msea.2004.08.081

[2] Sandip Ghosh Chowdhury, Elena V. Pereloma, D.B. Santos. Evolution of texture at the initial stages of continuous annealing of cold rolled dual-phase steel: Effect of heating rate [J]. Materials Science and Engineering A. 480 (2008) 540–548.

DOI: 10.1016/j.msea.2007.07.060

[3] Futao Don g, Lin xiu Du, Xianghua Liu, Fei Xue. Optimization of chemical compositions in low-carbon Al-killed enamel steel produced by ultra-fast continuous annealing [J]. Material Characterization. 84 (2013) 81– 87.

DOI: 10.1016/j.matchar.2013.07.006

[4] Shuang Kuang, Yong-lin Kang, Hao Yu, Ren-dong Liu. Effect of continuous annealing parameters on the mechanical properties and microstructures of a cold rolled dual phase steel [J]. International Journal of Minerals. 16(2009) 159-164.

DOI: 10.1016/s1674-4799(09)60027-3

[5] DAI Qi-feng, SONG Ren-bo, GUO Zhi-fei, HE Zi-long, YANG Fu-qiang. Effect of continuous annealing process on mechanical properties of ultra-high strength dual phase steels [J]. Material Science and Technology. 21 (2013) 6-13.

[6] ZHANG Zeng-lian，SONG Ren-bo，CHENG Zhi-song, ZHAO Ai-min，ZHAO Zheng-zhi，LIU Guang-ming，XIONG Ai-ming. Effect of Continuous Annealing Process and Ahoy Element on Microstructure and Mechanical Properties of 800MPa Cold Rolling Dual Phase Steel [J]. Material and Heat Treatment. 37 (2008) 27-29.

[7] Kang Yong Lin, Kuang Shuang, Liu Ren dong, Yan Ling. Production Technology and Structure Property of Cold Rolled Dual Phase Steel for Automobiles [J]. An Gang Technology. 2008(4):1-8.

[8] Chao Liu, Lei Wang, Yang Liu, Development of Advanced High-Strength Steel Used for Automobile and Its Application in Body Design [J]. Special Steel Technology. 2012(2):1-4.

[9] Jia-fu Wang, Qing-hua Lin,Shi-ze Qi, Lin-xiu Du, Xiang-hua Liu, Guo-dong Wang. Effect of Cooling Rate on Microstructure and Mechanical Properties of HSLA Steel [J]. Journal of Iron and Steel Research. 2004(5):51-55.

[10] Xuan Liang, Jun Li, Ying Hong Peng. Effect of water quench process on mechanical properties of cold rolled dual phase steel microalloyed with niobium [J]. Materials Letters. 62 (2008) 327 – 329.

DOI: 10.1016/j.matlet.2007.05.034

[11] H. Niakan, A. Najafizadeh. Effect of niobium and rolling parameters on the mechanical properties and microstructure of dual phase steels [J]. Materials Science and Engineering A. 527 (2010) 5410–5414.

DOI: 10.1016/j.msea.2010.05.078

[12] Qi ying Zeng. Study of Quantitative Relationship of Alloying Elements in Steel on the Influence of Phase Transformation Point AC1, AC3 [J]. Journal of Iron and Steel Research Institute. 1983,3(2):47-49.

[13] LI Hong-ying, GENG Jin-feng, ZHENG Zi-qiao, WANG Chang-jian, SU Yao, HU Bin. Continuous cooling transformation curve of a novel Al-Cu-Li alloy [J]. Transactions of Nonferrous Metals Society of China. 2006: 1110-1115.

DOI: 10.1016/s1003-6326(06)60386-5

[14] ZHAO Zheng-zhi, JIN Guang-can, NIU Feng, TANG Di, ZHAO Ai-min. Microstructure evolution and mechanical properties of 1000 MPa cold rolled dual-phase steel [J]. Transactions of Nonferrous Metals Society of China. 19(2009) s563-s568.

DOI: 10.1016/s1003-6326(10)60109-4

[15] A.J. DeArdo. Niobium in modern steels [J]. Int. Mater. Rev. 48 (No.6) (2003) 371 – 402.