20Cr钢热塑性变形过程晶粒细化研究

发布时间：2018-01-29 01:59

  本文关键词： 形变诱导相变 晶粒细化 工艺参数 热力学 动力学　出处：《河北工程大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着科技的进步,各行各业蓬勃发展,对钢铁的需要与日俱增。不同行业对钢铁材料的使用性能提出了不同的要求。钢铁材料在以“洁净化、均质化、细晶化”的思路朝着巨型化和微型化的方向发展。采用物理或化学的方法可以提高材料某方面的性能,而细晶强化是目前唯一一种可以在提高材料强度的同时,塑韧性不降低或者略微降低的最佳强化机制。利用该技术,可以降低结构钢的成本,甚至可以替代一些合金钢。本文通过理论分析和实验,对20Cr钢在热塑性变形过程中晶粒细化行为进行了深入的研究。分析了一些工艺参数在变形过程中对晶粒细化的影响,探讨了晶粒细化的机理,并对变形过程中的热力学及动力学进行了分析。为超细晶低碳钢和低合金钢在轧制生产或零件锻造生产提供参考。主要结论如下:(1)在研究变形温度对形变诱导铁素体相变的影响时发现,温度超过相变的温度范围后,在压缩过程中相变不会发生;在温度范围内,晶粒在温度降低的过程中逐渐细化,当达到一定程度后,再降低温度,细化效果不显著;铁素体的体积分数逐渐增加,当到达750℃后,带状组织的出现使铁素体的体积分数有所降低。(2)形变诱导相变的发生需要一定的应变量。相变后铁素体体积分数在应变量增大的过程中而增多,而晶粒尺寸会稍微的增大。(3)在低温,小的变形速率会使组织出现带状组织。在变形速率增加的过程中,带状组织逐渐消失,铁素体的转变量增加,晶粒逐渐被细化。晶粒细化到一定数量级后,继续增加变形速率,晶粒尺寸几乎不变。(4)不同温度奥氏体化后的20Cr钢在经过压缩变形后所得的组织存在着一定的差异,但差异不大。相变后的晶粒尺寸几乎不受奥氏体化温度的影响,而在较低奥氏体化温度后变形获得的铁素体的体积分数较大。(5)20Cr钢的应变诱导相变机制为动态再结晶和扩散相变共同作用。
[Abstract]:With the progress of science and technology, all kinds of industries are booming, the need for steel is increasing. Different industries put forward different requirements for the performance of steel materials. Iron and steel materials are "clean, purification, homogenization". The idea of fine crystallization is developing towards the direction of mega and miniaturization. Physical or chemical methods can improve the properties of materials in some aspects, and fine crystal strengthening is the only way to improve the strength of materials at the same time. The best strengthening mechanism that the ductility does not decrease or decrease slightly. With this technology, the cost of structural steel can be reduced and even some alloy steels can be replaced. In this paper, theoretical analysis and experiments are carried out. The grain refinement behavior of 20Cr steel during thermoplastic deformation was studied. The effect of some process parameters on grain refinement was analyzed and the mechanism of grain refinement was discussed. The thermodynamics and kinetics in the process of deformation are analyzed, which provides a reference for the production of ultra-fine grain low carbon steel and low alloy steel in rolling or forging of parts. The main conclusions are as follows: 1). The effect of deformation temperature on deformation-induced ferrite transformation is studied. When the temperature exceeds the temperature range of phase transition, the phase transition will not occur in the compression process. In the temperature range, the grain is gradually refined in the process of decreasing the temperature, and when the temperature reaches a certain degree, the effect of refining is not obvious. The volume fraction of ferrite increases gradually, when it reaches 750 鈩，

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