Strengthening mechanism of batch annealed Nb microalloyed steel for automobile
TIAN Fei1,WANG Zi-rong1,LI Zhao-dong1,2
1. Technique Center, Hunan Valin Lianyuan Iron and Steel Co., Ltd., Loudi 417009, Hunan, China 2. Department of Engineering Steels, Central Iron and Steel Research Institute, Beijing 100081, China
Abstract:Two series of cold rolled low-alloy and high-strength automotive steel, i.e. Mn-Si series and Nb microalloyed series, have been investigated to study the microstructure and mechanical properties through industrial trial with the same process, including batch annealing. The strengthening mechanism of the Nb microalloyed steel has been investigated by comparing with Mn-Si series cold rolled batch annealed low-alloy and high-strength steel. The microstructures of the hot-rolled and cold-rolled annealed sheets of those two kinds of steels were characterized by means of OM, SEM and TEM. The mechanical properties were also measured by tensile testing machine. The results were compared and showed that the sizes of the ferrite grains and nano precipitates of the two kinds of cold rolled annealed sheets were larger than those of the hot rolled sheets,which led to the reduction of the strength. Comparing with the Mn-Si steel, the sizes of ferrite grains and nano precipitates of hot-rolled and cold-rolled annealed sheets of Nb microalloyed steel were smaller, and the amount of the nano precipitates was larger. Thus the strength of the Nb microalloyed steel was higher with similar elongation. The strengthening mechanism analysis of cold rolled batch annealed sheet indicates that, the main strengthening method for Nb microalloyed low-alloy and high-strength steel is grain refinement strengthening and NbC precipitation strengthening. In the present study, grain refinement strengthening is stronger under 0.025% Nb microalloying.
收稿日期: 2015-01-08
出版日期: 2015-09-08
引用本文:
田 飞,王自荣,李昭东,. 罩式退火铌微合金化汽车钢的强化机理[J]. 钢铁, 2015, 50(9): 76-80.
TIAN Fei,WANG Zi-rong,LI Zhao-dong,. Strengthening mechanism of batch annealed Nb microalloyed steel for automobile. Iron and Steel, 2015, 50(9): 76-80.
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Kwon O J, Lee K Y, Kim G S, et al.New Trends in Advanced High Strength Steel Developments for Automotive Application[J].Materials Science Forum, 2010, 136(1):638-642