本文關(guān)鍵詞： 形變誘導(dǎo)相變 晶粒細(xì)化 工藝參數(shù) 熱力學(xué) 動(dòng)力學(xué)　出處：《河北工程大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：隨著科技的進(jìn)步,各行各業(yè)蓬勃發(fā)展,對(duì)鋼鐵的需要與日俱增。不同行業(yè)對(duì)鋼鐵材料的使用性能提出了不同的要求。鋼鐵材料在以“潔凈化、均質(zhì)化、細(xì)晶化”的思路朝著巨型化和微型化的方向發(fā)展。采用物理或化學(xué)的方法可以提高材料某方面的性能,而細(xì)晶強(qiáng)化是目前唯一一種可以在提高材料強(qiáng)度的同時(shí),塑韌性不降低或者略微降低的最佳強(qiáng)化機(jī)制。利用該技術(shù),可以降低結(jié)構(gòu)鋼的成本,甚至可以替代一些合金鋼。本文通過理論分析和實(shí)驗(yàn),對(duì)20Cr鋼在熱塑性變形過程中晶粒細(xì)化行為進(jìn)行了深入的研究。分析了一些工藝參數(shù)在變形過程中對(duì)晶粒細(xì)化的影響,探討了晶粒細(xì)化的機(jī)理,并對(duì)變形過程中的熱力學(xué)及動(dòng)力學(xué)進(jìn)行了分析。為超細(xì)晶低碳鋼和低合金鋼在軋制生產(chǎn)或零件鍛造生產(chǎn)提供參考。主要結(jié)論如下:(1)在研究變形溫度對(duì)形變誘導(dǎo)鐵素體相變的影響時(shí)發(fā)現(xiàn),溫度超過相變的溫度范圍后,在壓縮過程中相變不會(huì)發(fā)生;在溫度范圍內(nèi),晶粒在溫度降低的過程中逐漸細(xì)化,當(dāng)達(dá)到一定程度后,再降低溫度,細(xì)化效果不顯著;鐵素體的體積分?jǐn)?shù)逐漸增加,當(dāng)?shù)竭_(dá)750℃后,帶狀組織的出現(xiàn)使鐵素體的體積分?jǐn)?shù)有所降低。(2)形變誘導(dǎo)相變的發(fā)生需要一定的應(yīng)變量。相變后鐵素體體積分?jǐn)?shù)在應(yīng)變量增大的過程中而增多,而晶粒尺寸會(huì)稍微的增大。(3)在低溫,小的變形速率會(huì)使組織出現(xiàn)帶狀組織。在變形速率增加的過程中,帶狀組織逐漸消失,鐵素體的轉(zhuǎn)變量增加,晶粒逐漸被細(xì)化。晶粒細(xì)化到一定數(shù)量級(jí)后,繼續(xù)增加變形速率,晶粒尺寸幾乎不變。(4)不同溫度奧氏體化后的20Cr鋼在經(jīng)過壓縮變形后所得的組織存在著一定的差異,但差異不大。相變后的晶粒尺寸幾乎不受奧氏體化溫度的影響,而在較低奧氏體化溫度后變形獲得的鐵素體的體積分?jǐn)?shù)較大。(5)20Cr鋼的應(yīng)變誘導(dǎo)相變機(jī)制為動(dòng)態(tài)再結(jié)晶和擴(kuò)散相變共同作用。
[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，

本文編號(hào)：1472186