高温弛豫对无Nb和Ti等元素超低碳贝氏体钢的影响  

Effect of High Temperature Relaxation Process on Ultra Low Carbon Bainite Steel Without Nb, Ti and Other Elements

作　　者：刘庆锁[1] 杨巍巍[1] 袁连杰[1] 高斌[1] 孟亮[1] 

机构地区：[1]天津理工大学材料科学与工程学院,天津300384

出　　处：《钢铁》2014年第8期88-93,共6页Iron and Steel

摘　　要：针对试验用钢重点研究经历高温弛豫试样的中温相变点特征、450℃等温下的物相组成、显微组织结构及硬度随等温时间变化特征,以获得高温弛豫过程对不含Nb和Ti等合金化合物析出元素的超低碳钢贝氏体相变影响的新认识。试验结果表明,高温弛豫过程明显影响试验用钢的中温相变点,使试样的CCT曲线虽然仍具有两区特征,但相对未经历高温弛豫处理试样,在(t,θ)坐标系中的位置偏左上方;高温弛豫后450℃短时等温下形成尺寸较小的板条束状贝氏体,试样对应有较高的硬度水平,随等温时间延长,贝氏体长大,硬度随之下降;而未经历高温弛豫试样在450℃等温时发生变形回复与贝氏体相变2个过程,在等温时间小于30 min的较短范围内,变形回复与贝氏体相变过程对硬度影响的综合结果致使试样的硬度变化平缓。For the experimental steel the middle temperature phase transition point features of the high temperature relaxation process of the experimental steel, the isothermal phase composition under the 450 ℃, the state of microstructure, and the hardness when the isothermal time changes were studied. In order to get the new knowledge of the effect of high temperature relaxation process to the ultra low carbon steel without Nb, Ti alloy compounds precipitate elements＇ bainite transition. The results show that high temperature relaxation process significantly affected the experimental steel＇ s medium temperature transformation point. Although the CCT curve had two section characteristic, it moved to the left above compared with the samples which did not go through high temperature relaxation process. The dislocation cell structure forming in the high temperature relaxation process led to the forming of lath bunchy bainite with smaller size under 450 ℃ short-term isothermal, and the steel have a higher level of hardness. With the extension of isothermal time, the bainite grew up, and the hardness declined. While the samples without high temperature relaxation process went through deforma- tion-recovery process and bainite transformation process under the same 450 ℃. These two processes both had an effect on the steel＇ s hardness by working together to make the hardness change slowly when the isothermal time was less than 30 min.

关 键 词：超低碳钢 高温弛豫 显微组织 回复 硬度 

分 类 号：TG142.1[一般工业技术—材料科学与工程]