Nonequilibrium Reversion of Low Alloy Steels by Rapid Heating

低合金钢快速加热的非平衡回复

• 批准号: 63550540
• 负责人: TOMIMURA Kouki
• 金额: $ 1.34万
• 依托单位: Kyushu 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: 1988
• 资助国家: 日本
• 起止时间: 1988 至 1989
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63550540/
• 关键词: Rapid heating; Nonequilibrium state; Reversion; Low alloy steel; Martensite; Austenite; Recrystallization; Carbide; オーステナイト

Under heating method by electric resistance of sample itself such as high-frequency induction, a steel is heated efficiently.It is,therefore,reasonable to expect that the transformation occurs under noneqilibrium state by considerable rapid heating. The present work was carried out,aiming to obtain fundamental information relevant to process of nonequilibrium reversion with rapid heating. The effect of alloying elements and prior structure have been investigated. One alloy (A) contains 0.2% carbon and the other alloy (B) contains low alloy such as molybdenum and nickel. The prior structure was selected as a thermal, cold rolled, and recrystallized martensite. The results are as follows:(1) On heating no carbide precipitation was detected in non-deformed structure,whereas the formation of fine carbide was detected in deformed structure. (2) Martensite is directly reversed to austenite without occurrence of martensite recrystallization,i.e. formation of ferrite, in non-deformed structure. But formation of recrystallized martensite was detected in deformed structure. (3) The critical deformation to detect carbide precipitation and recrystallized martensite on heating is about 10%. (4) Precipitated carbide is finer in alloy (B steel) as comparison with that in free alloy(A steel). (5) There is excellent relative relation between the grain size of recrystallized martensite and that of reversed austenite.Decreasing the grain size of recrystallized martensite,does that of reversed austenite decreases. It suggests that grain boundary of recrystallized martensite is one of important nucleation site of austenite.

在高频感应等利用样品本身电阻的加热方法下，钢被有效加热。因此，可以合理地预期，通过相当快的快速加热，在非平衡状态下会发生转变。本工作旨在获得快速加热非平衡回复过程的基础信息。研究了合金元素和先前结构的影响。一种合金(A)含有0.2%的碳，另一种合金(B)含有低合金，例如钼和镍。先前的结构被选择为热轧、冷轧和再结晶马氏体。结果如下：(1)加热时，未变形组织中未观察到碳化物析出，而变形组织中则有细小的碳化物形成。 (2)马氏体直接反转为奥氏体，不发生马氏体再结晶，即马氏体再结晶。在非变形结构中形成铁素体。但在变形组织中检测到再结晶马氏体的形成。 (3)加热时检测碳化物析出和再结晶马氏体的临界变形量约为10%。 (4)与游离合金(A钢)相比，合金(B钢)中的析出碳化物更细小。 (5)再结晶马氏体晶粒尺寸与反转奥氏体晶粒尺寸之间存在良好的相对关系。再结晶马氏体晶粒尺寸减小，反转奥氏体晶粒尺寸也随之减小。这表明再结晶马氏体晶界是奥氏体的重要形核位点之一。