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  本文選題：淬火配分 + 馬氏體��； 參考：《西安建筑科技大學(xué)》2015年碩士論文

【摘要】：淬火配分(Quenching and Partition,QP)工藝先通過不完全淬火獲得馬氏體,再控制碳從馬氏體向未轉(zhuǎn)變奧氏體的配分,最后淬火至室溫獲得馬奧組織,可以有效地提高強度鋼的塑性和韌性。Speer等提出了根據(jù)一次淬火馬氏體計算各項比例的方法,王存宇據(jù)馬氏體相變組織不均勻性初步探討了理論計算和實測值得差異,本文在此基礎(chǔ)上,用含碳量為0.2-0.5wt.%的5種高硅CrNiMo系合金結(jié)構(gòu)鋼為對象,利用掃描電鏡(SEM)、透射電鏡(TEM)、X射線衍射(XRD)和單軸拉伸試驗等多種方法,系統(tǒng)研究了一次淬火馬氏體比例對試驗鋼微觀組織、殘留奧氏體量和單軸拉伸性能的影響。試驗鋼經(jīng)QP工藝熱處理后獲得一次淬火馬氏體、二次淬火馬氏體、殘留奧氏體構(gòu)成的多相組織,隨著一次淬火馬氏體比例的增加二次淬火馬氏體的尺寸和數(shù)量都逐漸減少,殘留奧氏體的量先增大后減小,當一次淬火馬氏體比例為30%-50%時,未轉(zhuǎn)變奧氏體的尺寸相對均勻細小,容易吸收更多的碳而使殘留奧氏體的量增大,不同含碳量的試驗鋼的微觀組織和力學(xué)性能隨著一次淬火馬氏體比例的變化規(guī)律相同。隨著一次淬火馬氏體比例的增加,試驗鋼抗拉強度逐漸降低,屈服強度和斷面收縮率逐漸升高,斷后伸長率和強塑積先升高后降低,殘留奧氏體的量和穩(wěn)定性決定了鋼的塑性,殘留奧氏體的TRIP效應(yīng)使鋼獲得了高塑性和高強塑積,隨著一次淬火馬氏體比例的增加,一次淬火馬氏體和二次淬火馬氏體的納米硬度逐漸增加,含碳量高以及板條細小決定了二次淬火馬氏體的納米硬度高于一次淬火馬氏體,單軸拉伸條件下微孔洞主要形成于大尺寸夾雜物,未發(fā)現(xiàn)二次淬火馬氏體形成微孔洞的現(xiàn)象。
[Abstract]:Quenching and Partition (QP) process is used to obtain martensite by incomplete quenching, then to control the partition of carbon from martensite to untransformed austenite, and finally to obtain Mao microstructure by quenching to room temperature. The plasticity and toughness of strength steel can be improved effectively. Speer and others have put forward a method to calculate the proportion of martensite based on primary quenching. According to the inhomogeneity of martensite transformation microstructure, Wang Cunyu has preliminarily discussed the difference between the theoretical calculation and the measured value. On this basis, five kinds of high silicon CrNiMo alloy structural steels with a carbon content of 0.2-0.5 wt.% were used as objects, and various methods such as scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and uniaxial tensile test were used. The effect of martensite ratio of primary quenching on microstructure, residual austenite content and uniaxial tensile properties of test steel was studied systematically. After heat treatment with QP process, the multiphase structure of primary quenched martensite, secondary quenched martensite and residual austenite is gradually reduced with the increase of the ratio of primary quenching martensite to secondary quenched martensite. The amount of retained austenite first increases and then decreases. When the ratio of primary quenching martensite is 30% to 50%, the size of untransformed austenite is relatively uniform and fine, and it is easy to absorb more carbon, thus increasing the amount of retained austenite. The microstructure and mechanical properties of the tested steels with different carbon content are the same as those of the primary quenching martensite ratio. With the increase of martensite ratio of primary quenching, the tensile strength of test steel decreases gradually, the yield strength and section shrinkage increase gradually, and the elongation and strong plastic product increase first and then decrease. The plasticity of the steel is determined by the quantity and stability of retained austenite. The TRIP effect of residual austenite makes the steel gain high plasticity and high strength plastic product. With the increase of martensite ratio, the nano-hardness of primary quenching martensite and secondary quenched martensite increases gradually. The high carbon content and fine lath determined that the nano-hardness of secondary quenching martensite was higher than that of primary quenching martensite. Under uniaxial tensile condition, the micropores were mainly formed in large size inclusions, and no micropores formed in secondary quenching martensite.
【學(xué)位授予單位】：西安建筑科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG142.1

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本文編號：1918164