發(fā)布時間：2018-04-26 12:04

  本文選題：38MnVTi非調(diào)質(zhì)鋼 + 織構(gòu)　； 參考：《重慶理工大學(xué)》2017年碩士論文

【摘要】：非調(diào)質(zhì)鋼由于其后續(xù)不需要調(diào)質(zhì)處理,即減少了高能耗的熱處理環(huán)節(jié),因而能夠降低能耗,節(jié)約能源。隨著非調(diào)質(zhì)鋼的發(fā)展,當(dāng)前生產(chǎn)汽車所使用的大多數(shù)關(guān)鍵設(shè)備如動力部件、連接功能件、車輪轉(zhuǎn)向部件等都使用非調(diào)質(zhì)鋼來進行加工。這些汽車零部件在使用過程中會不斷的承受拉伸、沖擊、彎曲等比較復(fù)雜的載荷,因此要求材料在鍛造成形后具有較高的強度、較好的韌性、高的抗疲勞性。良好的綜合力學(xué)性能取決于熱鍛和鍛后冷卻組織的演變,因此對非調(diào)質(zhì)鋼成形和冷卻過程當(dāng)中顯微結(jié)構(gòu)演化規(guī)律的研究是比較重要的。通過模型和實際生產(chǎn)情況的結(jié)合,可以有效的減少材料的浪費和提高產(chǎn)品的質(zhì)量,對我國非調(diào)質(zhì)鋼的研發(fā)和應(yīng)用具有重大的意義。本文以38MnVTi鋼為實驗對象,對熱壓縮過程中的顯微組織演化進行了重點探討。根據(jù)單道次熱壓縮實驗的結(jié)果建立了高溫流動應(yīng)力模型,然后通過線性回歸的方法確定了高溫流動應(yīng)力模型的參數(shù),并根據(jù)38MnVTi鋼的金相數(shù)據(jù),建立了其對應(yīng)的動態(tài)再結(jié)晶金相規(guī)律和相應(yīng)的晶粒尺寸模型。在雙道次熱壓縮實驗的基礎(chǔ)上建立了靜態(tài)再結(jié)晶動力學(xué)模型和對應(yīng)的尺寸模型,并詳細討論了靜態(tài)再結(jié)晶體積分數(shù)的影響因素如形變的溫度、第一道次的應(yīng)變量、形變的速率等,得出影響體積分數(shù)的主要原因是形變的溫度和第一道次的應(yīng)變量,而形變的速率對其影響不大。通過奧氏體晶粒長大實驗重點探討了奧氏體區(qū)保溫時間和加熱溫度對晶粒尺寸的影響,結(jié)果顯示溫度的停留時間變化與晶粒尺寸間近似呈拋物線函數(shù)關(guān)系;加熱溫度的高低與晶粒尺寸間近似呈指數(shù)函數(shù)的關(guān)系,最后通過大量晶粒尺寸的平均化處理得到了相應(yīng)的晶粒尺寸模型。通過物理實驗的方法,探討了冷卻終鍛溫度和冷卻速度與非調(diào)質(zhì)鋼顯微金相組織之間的關(guān)系。由于本文采用的鋼為典型的鐵素體-珠光體型鋼,珠光體的層片間距對非調(diào)質(zhì)鋼的綜合性能有很大的影響,因而借助掃描電鏡得出了冷卻溫度和冷卻速度對珠光體層片間距的影響規(guī)律。最后借助于EBSD技術(shù)研究了冷卻速率對38MnVTi非調(diào)質(zhì)鋼的晶粒取向差和織構(gòu)的影響,得出冷卻速率對38MnVTi非調(diào)質(zhì)鋼的織構(gòu)是有一定影響,但并沒有固定的規(guī)律。本文通過大量的實驗建立了38MnVTi非調(diào)質(zhì)鋼在鍛造過程中的微觀組織演變模型,并把得到的模型與實驗值進行了對比,實驗值與模型的吻合程度較高。并用金相技術(shù)和EBSD技術(shù)研究了冷卻工藝參數(shù)對熱鍛完成后冷卻過程微觀組織的影響,為實際生產(chǎn)過程中的工藝參數(shù)優(yōu)化提供了有效的理論指導(dǎo)。
[Abstract]:Non-quenched and tempered steel can reduce energy consumption and save energy because it does not need to be tempered and tempered in the subsequent process, that is to say, it can reduce the heat treatment link with high energy consumption. With the development of non-quenched and tempered steels, most of the key equipments used in the production of automobiles, such as power components, connection functions, wheel steering parts, etc., are processed by non-quenched and tempered steel. In the process of using these automobile parts will bear more complex loads such as tensile impact bending and so on. Therefore the material must have higher strength better toughness and higher fatigue resistance after forging. The good comprehensive mechanical properties depend on the evolution of hot forging and cooling microstructure after forging, so it is important to study the evolution of microstructure in the forming and cooling process of non-quenched and tempered steel. Through the combination of the model and the actual production conditions, the waste of materials and the quality of products can be effectively reduced, which is of great significance to the research and development and application of non-quenched and tempered steels in China. In this paper, the microstructure evolution of 38MnVTi steel during hot compression is discussed. A high temperature flow stress model is established based on the results of a single pass thermal compression experiment. Then the parameters of the high temperature flow stress model are determined by linear regression, and the metallographic data of 38MnVTi steel are obtained. The corresponding dynamic recrystallization metallography and the corresponding grain size model were established. Based on the two-pass thermal compression experiment, the static recrystallization kinetic model and the corresponding dimension model are established, and the influence factors of the static recrystallization volume integral number such as the deformation temperature, the first order dependent variable are discussed in detail. It is concluded that the temperature and the first strain of the deformation are the main factors influencing the volume fraction, but the rate of deformation has little effect on the deformation. The effect of holding time and heating temperature in austenitic region on grain size is discussed through austenite grain growth experiment. The results show that the relationship between temperature residence time and grain size is approximately parabola function. The relationship between the heating temperature and the grain size is approximately exponential function. Finally, the corresponding grain size model is obtained through the average treatment of a large number of grain sizes. The relationship between the final forging temperature, cooling rate and microstructure of non-quenched and tempered steel was investigated by physical experiments. Because the steel used in this paper is a typical ferrite-pearlite section steel, the interlaminar spacing of pearlite has a great influence on the comprehensive properties of non-quenched and tempered steel. The influence of cooling temperature and cooling rate on the lamellar spacing of pearlite was obtained by SEM. Finally, the effect of cooling rate on the grain orientation and texture of 38MnVTi non-quenched and tempered steel is studied by means of EBSD technology. It is concluded that the cooling rate has a certain effect on the texture of 38MnVTi non-quenched and tempered steel, but there is no fixed rule. In this paper, the microstructure evolution model of 38MnVTi non-quenched and tempered steel in forging process is established by a large number of experiments, and the obtained model is compared with the experimental value, and the experimental value is in good agreement with the model. The effect of cooling process parameters on the microstructure of cooling process after hot forging was studied by metallography and EBSD technology, which provided an effective theoretical guidance for the optimization of process parameters in actual production process.
【學(xué)位授予單位】：重慶理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG142.1

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本文編號：1805948