本文選題：100Cr6鋼 + SIMA法的預變形工藝�。� 參考：《湘潭大學》2017年碩士論文

【摘要】：應變誘導熔化激活法(Strain Induced Melt Activation,SIMA)是一種優(yōu)良的半固態(tài)坯料制備方法,它既適用于低熔點合金也可用于高熔點合金的半固態(tài)坯料制備;SIMA法主要分為預變形和半固態(tài)等溫處理(重熔)兩個階段,而預變形晶粒細化是SIMA法制備半固態(tài)坯料的首要環(huán)節(jié)。但在國內,SIMA法多用于制備鋁、鎂等低熔點合金的半固態(tài)坯料,很少用于制備鋼鐵等高熔點合金的半固態(tài)坯料。因此,SIMA法制備鋼半固態(tài)坯料時,研究預變形工藝對晶粒細化的影響,以獲得晶粒細小的非枝晶坯料具有重要意義。本文以100Cr6鋼為研究對象,采用鐓粗或軸向多道次鐓拔作為SIMA法預變形方式,以試樣晶粒大小作為評判標準,研究了預變形方式及其工藝參數對100Cr6鋼晶粒細化的影響。主要研究內容及研究結果如下:1.合理選取預變形工藝參數并設計了實驗方案,進而在400公斤空氣錘和光學顯微鏡等設備上完成了100Cr6鋼鐓粗實驗,研究了鐓粗鍛造比對100Cr6鋼晶粒細化的影響。實驗結果表明:晶粒的平均直徑隨鍛造比的增大而減小。2.通過軸向多道次鐓拔實驗研究了鍛造比和鐓拔道次對100Cr6鋼晶粒細化的影響。研究發(fā)現:隨鍛造比和鐓拔道次的增加,晶粒的平均直徑先快速減小;當鍛造比超過1.67、鐓拔道次超過2時,晶粒的平均直徑隨鍛造比和鐓拔道次的繼續(xù)增加而進一步減小的趨勢變緩,晶粒進一步細化的效果并不明顯。3.對比分析兩種預變形方式對100Cr6鋼晶粒的細化效果發(fā)現:與鐓粗相比,軸向多道次鐓拔對晶粒的細化效果和均勻化效果更佳;故軸向多道次鐓拔為更合適的預變形方式,其細化晶粒的合理工藝參數為鍛造比2.0,鐓拔道次3。在此預變形工藝參數下,所得試樣心部晶粒的平均直徑從274.1μm減小到25.0μm,減小了90.9%;試樣邊部晶粒的平均直徑從293.4μm減小到23.1μm,減小了92.1%;表明軸向多道次鐓拔是優(yōu)良的SIMA法預變形晶粒細化工藝。4.利用掃描電鏡、能譜分析儀、硬度計等設備,對鐓拔變形水淬試樣的微觀組織與硬度進行了觀測分析發(fā)現:鐓拔變形水淬后,100Cr6鋼試樣的微觀組織為淬火針狀馬氏體+少量團塊狀淬火屈氏體;試樣的硬度在59.3HRC~62.5HRC之間,且隨鍛造比和鐓拔道次的變化而改變,但硬度變化不大。
[Abstract]:Strain Induced Melt activation method (SIMA) is an excellent method for the preparation of semi-solid billets. It can be used not only in low melting point alloy but also in semi-solid billet preparation of high melting point alloy. SIMA method is mainly divided into two stages: pre-deformation and semi-solid isothermal treatment (remelting), and pre-deformed grain refinement is the primary step in the preparation of semi-solid billet by SIMA method. But in China, Sima method is used to prepare semisolid billets of low melting point alloys such as aluminum and magnesium, and is seldom used to prepare semisolid billets of high melting point alloys such as iron and steel. Therefore, it is of great significance to study the effect of pre-deformation on grain refinement in the preparation of semi-solid steel billets by Sima method in order to obtain fine non-dendritic billets with fine grains. In this paper, 100Cr6 steel is used as the research object, the upsetting or axial multi-pass upsetting and drawing are used as the SIMA pre-deformation mode, and the grain size of the sample is taken as the criterion to study the effect of the pre-deformation mode and its technological parameters on the grain refinement of 100Cr6 steel. The main contents and results are as follows: 1. Reasonable pre-deformation parameters were selected and experimental scheme was designed. The upsetting experiment of 100Cr6 steel was carried out on 400kg air hammer and optical microscope. The effect of upsetting forging ratio on grain refinement of 100Cr6 steel was studied. The experimental results show that the average diameter of grain decreases with the increase of forging ratio. The effects of forging ratio and upsetting pass on grain refinement of 100Cr6 steel were studied by axial multi-pass upsetting and drawing experiments. It is found that the average diameter of grain decreases rapidly with the increase of forging ratio and upsetting pass times, and when the forging ratio is more than 1.67, the number of upsetting and drawing passes is more than 2. The average diameter of grain decreases with the increase of forging ratio and upsetting and drawing times, and the effect of grain refinement is not obvious. Comparing and analyzing the grain refinement effect of two kinds of predeformation modes on 100Cr6 steel, it is found that axial multi-pass upsetting and drawing have better grain refinement and homogenization effect than upsetting, so axial multi-pass upsetting is more suitable for pre-deformation. The reasonable technological parameters for grain refinement are forging ratio 2.0, upsetting and drawing times 3. In this pre-deformation process parameter, The average diameter of grain at the center of the sample was reduced from 274.1 渭 m to 25.0 渭 m, and that of the grain at the edge of the sample was reduced from 293.4 渭 m to 23.1 渭 m, which decreased 92.1%, indicating that axial multi-pass upsetting is an excellent pre-deformed grain refinement process of SIMA method .4. Using scanning electron microscope, energy spectrum analyzer, hardness meter and other equipment, The microstructure and hardness of the water quenched specimen during upsetting and drawing were observed and analyzed. It was found that the microstructure of the water quenched specimen was a small amount of quenched needle martensite, and the hardness of the specimen was between 59.3HRC~62.5HRC. It changes with the forging ratio and the number of upsetting and drawing, but the hardness does not change much.
【學位授予單位】：湘潭大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG316.11;TG142.1

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