Research on Hardenability in High-purity Steels

高纯钢淬透性研究

• 批准号: 60550511
• 负责人: MAKI Tadashi
• 金额: $ 1.15万
• 依托单位: Kyoto University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1985
• 资助国家: 日本
• 起止时间: 1985 至 1986
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60550511/
• 关键词: High-purity steel; Hardenabilty; Impurity element; Jominy test; Transformation kinetics; Growth rate; 核生成速度

The present study has been undertaken to make clear the effect of impurity elements such as P and S on hardenabilty and isothermal transformation behavior in high-purity carbon steels without other alloying elements excepted for carbon. Four 0.35% carbon steels with different level of P and S contents (i,e., 10 ppmP + 10 ppmS, 70 ppmP + 10 ppmS, 410 ppmP + 10 ppmS, and 10 ppmP + 100 ppmS) were vacuum-melted and used for the Jominy tests, the continuous transformation tests, and the isothermal transformation tests. The main results obtained are as follows.(1) The Jominy distance increased with increase in the P content of specimen. The tendency of increase in the Jominy distance against the P content was parabolic, namely, the slope of the Jominy distance-the P content curve decreased with increase in the P content.(2) The diffusional transformation which competes with martensite transformation and controlls the hardenabilty in the present steels was the pearlite transformation at around 820 K.(3) The isothermal transformation kinetics from austenite to pearlite was markedly retarded by adding the impurity element of P as well as S.(4) The addition of the impurity elements of P and S strongly reduced the growth rate of the pearlite colony at 823 K but scarcely affected the nucleation rate.It can be concluded from these results that the hardenabilty increases by adding the impurity elements of P and S to high-purity 0.35% carbon steel and this increase in the hardenability is contributed to the decrease in the growth rate of the pearlite transformation which competes with the martensite transformation.

本文研究了除碳外不含其它合金元素的高纯碳钢中P、S等杂质元素对钢的淬透性和等温转变行为的影响。四种具有不同P和S含量水平的0.35%碳钢（即，10 ppmP + 10 ppmS、70 ppmP + 10 ppmS、410 ppmP + 10 ppmS和10 ppmP + 100 ppmS）真空熔融，并用于端淬试验、连续转变试验和等温转变试验。得到的主要结果如下。(1)Jominy距离随样品中P含量的增加而增大。Jominy距离随P含量的增加呈抛物线趋势，即Jominy距离-P含量曲线的斜率随P含量的增加而减小。(2)在820 K左右，与马氏体相变竞争并控制淬硬性的扩散相变是珠光体相变。(3)杂质元素P和S的加入显著地延缓了奥氏体向珠光体的等温转变动力学。(4)P、S杂质元素的加入，在823 K时，强烈地降低珠光体团的生长速率，但对形核速率影响不大，由此可知，当P、S杂质元素的加入量达到高纯0.35%时，可提高珠光体的淬透性碳钢，并且这种淬硬性的增加是由于与马氏体转变竞争的珠光体转变的生长速率的降低。