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首页> 外文期刊>ISIJ international >The Onset Temperatures of γ to α-Phase Transformation in Hot Deformed and Non-deformed Nb Micro-alloyed Steels
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The Onset Temperatures of γ to α-Phase Transformation in Hot Deformed and Non-deformed Nb Micro-alloyed Steels

机译：热变形和非变形Nb微合金钢从γ转变为α相的起始温度

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In the present paper, continuous cooling transformation behaviors in Nb micro-alloyed steels were systematically investigated by the thermal dilatation method, during which the effects of Nb contents and hot deformation of austenite on phase transformation behaviors, especially the transformation start temperatures, were studied in detail. The tests were carried out with the samples having been reheated + hot deformed or reheated + non-deformed prior to the dilation measurements. It was found that the A_(r3) temperatures measured from the dilatometric curves changed with increasing Nb content in parabolic ways under both hot deformed and non-deformed conditions. It is believed that dissolved Nb in austenite may have had the Nb solute drag effect that could delay austenite to ferrite transformation. On the other hand, Nb precipitates in austenite could retard the growth of austenite grains and act as potential nucleation sites, both of which could enhance the transformation kinetics. Also, the interaction of strain, precipitation and temperature was estimated by using the Sellars model, which predicted that the strain induced precipitation had occurred in hot deformed Nb steels before phase transformation started, and in non-deformed steels with Nb content greater than 0.023 mass%, precipitation was also likely to have occurred under slow cooling rate before phase transformation started, which could have played an important role in determining A_(r3). These factors worked together to make A_(r3) changing with Nb content in the parabolic way. Based on the experimental results, a mathematical model for the A_(r3) calculation for Nb and C-Mn steels were developed, which exhibited a good accuracy in predicting the A_(r3) of the steels with and without hot deformation.
机译：本文通过热膨胀法系统研究了铌微合金钢的连续冷却转变行为，在此期间研究了铌含量和奥氏体的热变形对相变行为，特别是相变开始温度的影响。详情。在膨胀测量之前，对样品进行了重新加热+热变形或重新加热+不变形的测试。结果发现，在热变形和非变形条件下，由膨胀曲线测得的A_（r3）温度均以抛物线形式随Nb含量的增加而变化。据信，奥氏体中溶解的Nb可能具有Nb溶质拖曳效应，可能会延迟奥氏体向铁素体的转变。另一方面，奥氏体中的Nb沉淀物可能会阻碍奥氏体晶粒的生长并充当潜在的成核位点，这两者都可以增强相变动力学。另外，通过Sellars模型估算了应变，析出和温度的相互作用，该模型预测在相变开始之前热变形的Nb钢和Nb含量大于0.023质量的非变形钢中已经发生了应变诱发的析出。 ％，在相变开始之前，在缓慢的冷却速率下也可能发生沉淀，这可能在确定A_（r3）中起了重要作用。这些因素共同作用使A_（r3）随Nb含量以抛物线方式变化。基于实验结果，建立了Nb和C-Mn钢A_（r3）计算的数学模型，该模型在预测有无热变形的钢的A_（r3）时表现出良好的准确性。

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