Variation of transition temperatures from upper to lower bainites in plain carbon steels
Variation of transition temperatures from upper to lower bainites in plain carbon steels
复制标题
普碳钢上贝氏体到下贝氏体转变温度的变化
DOI：
10.1051/jp4:1995877
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
H. Okamoto
中科院分区：
文献类型：
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作者：
M. Oka;H. Okamoto
从金相和运动学角度给出了含 0.20 至 1.80 wt%C 的碳钢中从上贝氏体到下贝氏体转变温度的实验结果和解释。实验结果总结如下： 1) 碳含量低于0.35 wt%的钢中不形成下贝氏体，并且不发生从上贝氏体到下贝氏体的转变。 2) 含有 0.54 至 1.10 %C 的钢的转变温度表示恒定温度 350°C，与碳含量无关。值得注意的是，350°C 的转变温度对应于 0.55%C 钢的 Ms 温度，即板条和板材之间马氏体形态的边界。 3) 超过1.10%C的钢的转变温度从T 0 成分线沿着低于约65℃的线下降。贝氏体相变本质上是马氏体相变的一种，其形核位置被认为是在等温保持温度下碳原子的热波动而导致的奥氏体中的贫碳区。在大于1.10wt%C的碳范围下，低于T 0 成分线约65℃的过冷归因于下贝氏体的位移生长的非化学自由能。
Experimental results and explanations for the transition temperature from upper to lower bainites in carbon steels containing from 0.20 to 1.80 wt%C were presented metallographically and kinematically. The experimental results are summarized as follows : 1) Lower bainite is not formed in steels with less than 0.35 wt%C and no transition from upper to lower bainite occurs. 2) The transition temperature of steels containing from 0.54 to 1.10 %C indicates a constant temperature of 350°C and does not depend on the carbon content. It is important to note that a transition temperature of 350°C corresponds to the Ms temperature of a 0.55%C steel being the boundary of the martensite morphology between a lath and a plate. 3) Transition temperatures of steels with more than 1.10%C decrease along the a line below about 65°C from T 0 -composition line. The bainitic transformation is essentially a kind of the martensitic one and its nucleation site is considered to be a carbon depleted zone in austenite by the thermal fluctuation of carbon atom at an isothermal holding temperature. The supercooling of about 65°C below the T 0 -composition line at the carbon range more than 1.10 wt%C is attributed to the non-chemical free energy for the displacive growth of lower bainite.