低合金钢半固态挤压铸造工艺及组织性能研究

Study on Semi-solid Squeeze Casting Technique and Microstructure Property of Low Alloy Steel

作者: 专业:材料加工工程 导师:张励忠 年度:2007 学位:硕士  院校: 北京交通大学

关键词
半固态 挤压铸造 C级钢 近液相线保温法 成形质量 组织 低温冲击性能

Keywords
semi-solid, squeeze casting, C grade steel, near liquid line insulation, forming quality, microstructure, low-temperature impacting property
        随着现代铁路交通运输向着高速、重载方向发展,机车车辆铸钢件的服役条件越来越恶劣,普通碳钢铸钢已明显不能满足使用要求,正在逐步被低合金钢取代。铸钢材质升级为低合金钢后,传统的砂型铸造工艺在生产中暴露出了一系列问题。为了解决这些问题,本文首次提出采用半固态流变挤压铸造工艺进行机车车辆关键铸钢件的生产,并以机车钩舌通用材质C级钢(ZG25MnCrNiMo)为研究材料,以挤压成形轴箱体、性能样为例,从半固态浆料制备、成形质量的控制、铸件组织与力学性能等方面对该工艺进行了系统的实验与理论研究。采用近液相线保温法制备出了适宜于半固态流变挤压铸造成形的非枝晶组织浆料,并用平均等积圆直径定量分析了非枝晶组织特征,得出了最佳的工艺参数值:保温温度为1508℃,保温时间为15min。在此工艺参数条件下,ZG25MnCrNiMo非枝晶组织的平均等积圆直径为85.4μm。利用最佳工艺参数制备出的半固态浆料,以挤压铸造成形机车车辆铸钢件-轴箱体为例,对ZG25MnCrNiMo低合金钢半固态流变挤压铸造成形质量进行了研究。结果表明:半固态流变挤压成形工艺优势的获得,需要正确的工艺参数来保证。当工艺参数选择不合理时,铸件易出现表面皱皮、冷隔、缩孔、气孔、热裂纹等缺陷。在模具预热温度为400~425℃,冲头拔模斜度为1°,成形比压为100~115MPa,保压时间为5~10s时,挤压出了内、外质量良好的轴箱体铸件。利用自行设计的性能样模具,采用正交实验研究了半固态流变挤压铸造过程中成形比压、保压时间、模具温度对ZG25MnCrNiMo低合金钢组织与抗低温冲击性能的影响规律,优选出了最佳的工艺参数值:成形比压为200MPa、模具温度为400℃、保压时间为15s。在此工艺参数条件下,铸件组织致密、晶粒细小,-50℃时的冲击吸收功达到21.8J,是普通铸造ZG25MnCrNiMo低合金钢的5倍多,且低温冲击断口由一些大小不等的韧窝所组成,表现为韧性断裂。
    With the development of railway transportation towards high speed and over loading, the service conditions of engine vehicle are becoming much worse. Common carbon steel castings have been unable to satisfy the higher requirements at present, which are replaced by low alloy steel parts gradually. When low alloy steel replaced carbon steel castings, a series of questions were uncovered in traditional sand casting process. In order to solve the questions uncovered, semisolid rheological squeeze casting technique used as the process for critical steel castings of engine vehicle was put forward firstly in this paper. In this study, C grade steel (ZG25MnCrNiMo) which is the common material for coupler knuckle of engine vehicle is used as the research material, axle box body steel cast and property sample obtained through semisolid rheological squeeze casting were used as examples. The technique was studied systemically through experiments and theories in the following aspects: preparation of the semisolid slurry, control of the quality, structure of the formed parts and their mechanical properties etc.Nondendritic-structure slurry that suitable for semisolid rheological squeeze casting was made by near liquid line insulation, and characteristic of the nondendritic-structure slurry was analyzed quantitatively by the average equal-area-circle diameter, then the suitable process parameters are obtained: holding temperature of 1508℃, holding time of 15min. Under these processing parameters, the average equal-area-circle diameter of the ZG25MnCrNiMo nondendritic-structure is 85.4μm. Qualities of the ZG25MnCrNiMo low alloy steel formed by semisolid rheological squeeze casting process were studied through the example of axle box body cast, and the study was done under the most suitable processing parameters mentioned above. The results revealed was as: the suitable processing parameters are the critical factor to obtain the advantages of semisolid rheological squeeze casting process. If improper processing parameters are chosen in semisolid rheological squeeze casting process, flow marks and cold laps are engendered easily on the surface of the formed parts, shrinkage void and gas hole are formed easily. When preheating temperature of the die is 400~425℃, stripping angle of the punch is 1°, the forming pressure is among 100~115MPa, and the holding time is 5~10s, favorable axle box body casts are formed with excellent inner and outer quality. The effect of processing parameters on structure of C grade steel and low-temperature impact property were studied by orthogonal
        

低合金钢半固态挤压铸造工艺及组织性能研究

中文摘要5-6
ABSTRACT6-7
1 绪论12-26
    1.1 选题依据与研究意义12-13
    1.2 半固态流变挤压铸造原理与工艺特点13-15
        1.2.1 半固态流变挤压铸造原理13-14
        1.2.2 半固态流变挤压铸造工艺特点14-15
    1.3 半固态流变挤压铸造工艺的分类15-16
    1.4 半固态流变挤压铸造技术的关键16-24
        1.4.1 加压设备16-17
        1.4.2 半固态浆料的制备17-22
        1.4.3 半固态浆料定量浇注22-23
        1.4.4 模具23-24
        1.4.5 工艺过程的自动控制24
    1.5 论文研究目标、内容及技术路线24-26
        1.5.1 研究目标24
        1.5.2 研究内容24-25
        1.5.3 技术路线25-26
2 低合金钢半固态浆料近液相线保温法制备工艺研究26-37
    2.1 实验方法26-30
        2.1.1 实验材料26-27
        2.1.2 实验装置27-28
        2.1.3 实验方案28-29
        2.1.4 实验过程29-30
    2.2 实验结果30-33
        2.2.1 实验数据的正交处理30-31
        2.2.2 不同保温温度下ZG25MnCrNiMo 的激冷组织特征31-32
        2.2.3 不同保温时间下ZG25MnCrNiMo 的激冷组织特征32-33
    2.3 实验结果分析与讨论33-35
        2.3.1 近液相法制浆形核机理33-34
        2.3.2 保温温度对ZG25MnCrNiMo 组织的影响34-35
        2.3.3 保温时间对ZG25MnCrNiMo 激冷组织的影响35
    2.4 小结35-37
3 低合金钢半固态挤压成形质量的控制研究37-50
    3.1 实验材料、装置及过程37-41
        3.1.1 实验材料37
        3.1.2 实验装置37-40
        3.1.3 实验过程40-41
    3.2 实验结果41-42
    3.3 铸件缺陷形成机理与分析42-48
        3.3.1 表面皱皮42-43
        3.3.2 冷隔43-44
        3.3.3 缩孔44-45
        3.3.4 皮下气孔45-46
        3.3.5 热裂纹46-48
    3.4 控制缺陷的工艺措施48-49
    3.5 小结49-50
4 低合金钢半固态挤压铸造组织与低温冲击性能研究50-64
    4.1 实验50-55
        4.1.1 实验材料50
        4.1.2 实验装置50-52
        4.1.3 实验方案的确定52-53
        4.1.4 实验过程53-55
    4.2 实验结果55-59
        4.2.1 合金组织55
        4.2.2 低温冲击断口形貌55-57
        4.2.3 性能测试结果的正交处理57-59
    4.3 结果分析与讨论59-62
        4.3.1 成形比压对合金组织与性能的影响60-61
        4.3.2 模具温度对合金组织与性能的影响61-62
        4.3.3 保压时间对合金组织与性能的影响62
    4.4 小结62-64
5 结论64-65
参考文献65-69
作者简历69-70


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