You Jingtian, Li Zhiying, Wang Jie, Li Changrong, Zeng Zeyun, Li Shiwang, Huang Sheng
College of Materials and Metallurgy, Guizhou University, Guiyang 550025, China.
Guizhou Provincial Key Laboratory of Metallurgical Engineering and Process Energy Saving, Guiyang 550025, China.
Materials (Basel). 2022 Dec 14;15(24):8940. doi: 10.3390/ma15248940.
The effects of niobium and composite strengthening on the phase transformation characteristics and precipitation behavior of continuous cooling transformation of high-strength rebar during thermal deformation and subsequent cooling were investigated. The results show that when the cooling rate was within 0.3-5 °C/s, ferrite transformation and pearlite transformation occurred in the experimental steels. The Nb content increased to 0.062 wt.%, and the starting temperature of the ferrite transformation decreased. Meanwhile, the ferrite phase transformation zone gradually expanded, and the pearlite phase transformation zone gradually narrowed with the increase in the cooling rate. When the cooling rate was 1 °C/s, bainite transformation began to occur, and the amount of transformation increased with the increase in the cooling rate. It was found that the main precipitates in the experimental steels were (Nb, Ti, V)C, with an average particle size of about 10-50 nm. When the Nb content was increased to 0.062 wt.% and the cooling rate was increased to 5 °C/s, the ferrite grain size was reduced from 19.5 to 7.5 μm, and the particle size of the precipitate (Nb, Ti, V)C could be effectively reduced. The strength of the steel was significantly improved, but the elongation of the steel was reduced. However, the comprehensive mechanical properties of 0.062 wt.% Nb experimental steel was significantly improved at a cooling rate of 5 °C/s.
研究了铌及复合强化对高强度钢筋在热变形及随后冷却过程中连续冷却转变的相变特性和析出行为的影响。结果表明，当冷却速率在0.3-5℃/s范围内时，试验钢中发生铁素体转变和珠光体转变。铌含量增加到0.062 wt.%时，铁素体转变的起始温度降低。同时，随着冷却速率的增加，铁素体相变区逐渐扩大，珠光体相变区逐渐变窄。当冷却速率为1℃/s时，贝氏体转变开始发生，且转变量随冷却速率的增加而增加。发现试验钢中的主要析出物为(Nb,Ti,V)C，平均粒径约为10-50 nm。当铌含量增加到0.062 wt.%且冷却速率增加到5℃/s时，铁素体晶粒尺寸从19.5μm减小到7.5μm，析出物(Nb,Ti,V)C的粒径可有效减小。钢的强度显著提高，但钢的伸长率降低。然而，0.062 wt.%铌试验钢在冷却速率为5℃/s时综合力学性能显著提高。
