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| Microstructure and properties of a new 440 MPa grade high strength bake hardening steel |
| HUI Ya-jun1,2，PAN Hui1，XIAO Bao-liang1，WU Ke-min3，LI Xiao-lin1，ZHANG Da-wei1 |
（1. Sheet Metal Research Institute， Technology Institute of Shougang Group Co.， Ltd.， Beijing 100043， China
2. Beijing Key Laboratory of Green Recyclable Process for Iron and Steel Production， Beijing 100043， China
3. Manufacturing Department， Qian’an Iron and Steel Company of Shougang Group Co.， Ltd.，Tangshan 064404， Hebei， China） |
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Abstract In order to develop a new 440 MPa grade high strength bake hardening steel，the microstructure，properties，strengthening mechanism and bake hardening mechanism were investigated by utilizing optical microscope （OM） and transmission electron microscopy （TEM）. The results showed that the microstructure was composed of ferrite and a small amount of pearlite. With the increase of mass percent of N and the decrease of coiling temperature，the ferrite would be refined. The ferrite grain sizes of the low N steel were 8.34 and 7.89 μm when coiling at 630 and 600 ℃，respectively. The contribution of fine grain strengthening to yield strength was 190 and 196 MPa，respectively. The ferrite grain sizes of the high N steel were 6.93 and 6.71 μm when coiling at 630 and 600 ℃，respectively. The contribution of fine grain strengthening to yield strength was 209 and 212 MPa，respectively. Both the yield strength and tensile strength exhibited an ascending tendency after bake hardening treatment. The smaller of the grain size and the higher of the mass percent of N was，the larger value of the tensile strength was. The BHT values of the high mass percent of N steel at 10% prestrain were all above 70 MPa and the tensile strength reached over 500 MPa，which mainly because the dislocations introduced by prestrain become firm during the baking treatment and promote dislocation enlargement and reborn during plastic deformation.
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Received: 09 March 2018
Published: 26 October 2018
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| [1] |
HUI Ya-jun, WU Ke-min, XU Ke-hao, XIAO Bao-liang, LINGHU Ke-zhi, LIU Kun. Development of 500 MPa grade high ductility square tube steel and its work hardening behavior[J]. Iron and Steel, 2020, 55(2): 131-138. |
| [2] |
SUN Chaofan，FANG Yuan，WANG Yaqing，LIU Wei，PAN Hongwei. Effect of coiling temperature on precipitation of second #br# phase in ultralow carbon T3 CA steel[J]. Iron and Steel, 2019, 54(7): 83-87. |
| [3] |
HOU Xiao-ying， BI Yong-jie， HAO Liang. Analysis on microstructure and strengthening mechanisms of hot-rolled TRIP980 steel[J]. Iron and Steel, 2019, 54(4): 63-67,83. |
| [4] |
DENG Jie1,SONG Xin-li1,ZHENG Ai-qin1,SUN Xin-jun2,JIA Juan1,LIANG Xiao-kai2. Effect of tempering temperature on microstructure and mechanical properties of CuCrTi martensite wear-resistant steel[J]. JOURNAL OF IRON AND STEEL RESEARCH , 2019, 31(12): 1031-1038. |
| [5] |
YANG Yuebiao1，2，DENG Shen2，FAN Lei2，ZHAO Zhengzhi1，. Microstructure，mechanical properties and strengthening #br#
mechanism of Ti microalloyed high strength steel[J]. Iron and Steel, 2019, 54(10): 72-79. |
| [6] |
CHEN Run-nong，，LI Zhao-dong，ZHANG Ming-ya，WANG Hui-min，YANG Zhong-min，YONG Qi-long. Microstructure and properties of Nb microalloyed ultra low yield point steel[J]. Iron and Steel, 2019, 54(1): 63-70. |
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2018, Vol. 53 
