SIMA法中预变形工艺对100Cr6钢晶粒细化的影响

发布时间：2018-05-27 05:33

本文选题：100Cr6钢 + SIMA法的预变形工艺　；参考：《湘潭大学》2017年硕士论文

【摘要】：应变诱导熔化激活法(Strain Induced Melt Activation,SIMA)是一种优良的半固态坯料制备方法,它既适用于低熔点合金也可用于高熔点合金的半固态坯料制备;SIMA法主要分为预变形和半固态等温处理(重熔)两个阶段,而预变形晶粒细化是SIMA法制备半固态坯料的首要环节。但在国内,SIMA法多用于制备铝、镁等低熔点合金的半固态坯料,很少用于制备钢铁等高熔点合金的半固态坯料。因此,SIMA法制备钢半固态坯料时,研究预变形工艺对晶粒细化的影响,以获得晶粒细小的非枝晶坯料具有重要意义。本文以100Cr6钢为研究对象,采用镦粗或轴向多道次镦拔作为SIMA法预变形方式,以试样晶粒大小作为评判标准,研究了预变形方式及其工艺参数对100Cr6钢晶粒细化的影响。主要研究内容及研究结果如下:1.合理选取预变形工艺参数并设计了实验方案,进而在400公斤空气锤和光学显微镜等设备上完成了100Cr6钢镦粗实验,研究了镦粗锻造比对100Cr6钢晶粒细化的影响。实验结果表明:晶粒的平均直径随锻造比的增大而减小。2.通过轴向多道次镦拔实验研究了锻造比和镦拔道次对100Cr6钢晶粒细化的影响。研究发现:随锻造比和镦拔道次的增加,晶粒的平均直径先快速减小;当锻造比超过1.67、镦拔道次超过2时,晶粒的平均直径随锻造比和镦拔道次的继续增加而进一步减小的趋势变缓,晶粒进一步细化的效果并不明显。3.对比分析两种预变形方式对100Cr6钢晶粒的细化效果发现:与镦粗相比,轴向多道次镦拔对晶粒的细化效果和均匀化效果更佳;故轴向多道次镦拔为更合适的预变形方式,其细化晶粒的合理工艺参数为锻造比2.0,镦拔道次3。在此预变形工艺参数下,所得试样心部晶粒的平均直径从274.1μm减小到25.0μm,减小了90.9%;试样边部晶粒的平均直径从293.4μm减小到23.1μm,减小了92.1%;表明轴向多道次镦拔是优良的SIMA法预变形晶粒细化工艺。4.利用扫描电镜、能谱分析仪、硬度计等设备,对镦拔变形水淬试样的微观组织与硬度进行了观测分析发现:镦拔变形水淬后,100Cr6钢试样的微观组织为淬火针状马氏体+少量团块状淬火屈氏体;试样的硬度在59.3HRC~62.5HRC之间,且随锻造比和镦拔道次的变化而改变,但硬度变化不大。
[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.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG316.11;TG142.1

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