低压铸造476汽缸盖铸造缺陷及控制的研究
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摘要
本文首先利用宏观观察、MU200型X-射线透射扫描实时成像、金相显微分析、扫描电镜等实验方法对低压铸造铝合金476发动机汽缸盖铸造缺陷的类型、特点、形成原因进行了研究，结果表明：按照现行工艺生产的476发动机汽缸盖在热节处存在缩松、缩孔、裂纹、气孔、夹杂等缺陷。476发动机汽缸盖的主要缺陷是在D截面上形成30×15×2mm范围的缩松区，缩松区深约0.5～1.0mm；在D截面处发现穿透性裂纹(热裂纹)，长：7mm，宽：0.35mm，深：1.5mm；T截面上存在气孔，多在距件表面2～3mm处，大小尺寸为0.35mm左右；在皮下X截面处，约为Φ0.35mm针孔，但量极少；在缩松区局部发现有小的球团状氧化物夹杂颗粒，数量也很少。以现有低压铸造工艺生产的476发动机汽缸盖，产生的大量缩松及缩松区域内形成的穿透性热裂纹是铸件产生渗漏的主要原因。
其次，探索了锶变质处理对476发动机汽缸盖组织和铸造缺陷的影响规律，指出：加锶变质处理后，476发动机气缸盖铸件的显微组织得到明显改善，共晶硅由加锶前的短棒状转变为加锶后的细小、弥散的针状形态，缩松、裂纹缺陷得以减少，但针孔缺陷明显增多，这是由变质处理时的吸氢引起的。锶的变质存在衰退现象，锶的有效变质时间为1小时，此时锶的含量为0.0187％，超过1小时锶的变质作用明显减退。加锶变质和Al-Ti-B细化共同作用时，AC4B合金的晶粒得到明显细化。
为消除铸造缺陷、铸造优质健全的476发动机气缸盖成品件，应从铸造工艺和熔炼工艺入手，并严格控制锶变质和Al-Ti-B细化工艺，通过加锶变质处理来控制缺陷和提高铝合金476汽缸盖力学性能的方法是可行的。
In this paper the microstructure and freezing defects of 476 Al alloy engine cylinder head are studied, using type Olympus GX 71 optical microscope, MU200X-ray diffraction, type FEI SIRION SEM analysis. The results show that 476 engine cylinder head produced by recent process have defects of shrinkage porosity zone, shrinkage, crack defects, gas pole and inclusion in the hot spot. The major defect of 476 engine cylinder head a 30×15×2mm shrinkage porosity zone in the D section, shrinkage porosity zone is about 0.5-1.0mm high, through wall defects (thermal crack) can been observed at the D section,length 7mm,width 035mm,highth 1.5mm, and the T section has gas pole, mostly exist 2~3mm under the surface of the casting ,about 0.35mm length ;under the surface the T section is aboutΦ0.35mm pinpole, but quantity is small; small spheral oxides particulate inclusion can been observed shrinkage porosity zone, but quantity is small too. The 476 engine cylinder head is produced by present low pressure casting, and the large amount of shrinkage porosity and the through thermo crack existing in the shrinkage porosity zone is the main reason of leakage existing in the casting.Then, the effect of Sr modification treatment on the microstructure and freezing defects of 476 engine cylinder are also researched. The results reveal that after the Sr modification treatment, the microstructure of 476 engine cylinder castings has been improved obviously, and the form of eutectic Sr changes from short stick to fine and disperse specula. Shrinkage and crack defects decrease, but pinholes defects increase obviously as a result of hydrogen absorption during the modification treatment. There are degradation phenomena during Sr modification treatment, the effective modification time of Sr is one hour and the content of Sr at this moment is 0.0187%. After one hour the effect of Sr modification treatment degrades dramatically. With Sr modification treatment and Al-Ti-B refinement, the grains of AC4B alloy are refined greatly.
In order to eliminate casting defects and produce good quality of 476 engine cylinder head, casting technology and melting technology should be paid much attention and modification technology of Sr and refinement technology of Al-Ti- B should be controlled austerely. So it is fesiable to control defects and improve mechanical property of Al alloy 476 engine cylinder head by Sr modification.
其次，探索了锶变质处理对476发动机汽缸盖组织和铸造缺陷的影响规律，指出：加锶变质处理后，476发动机气缸盖铸件的显微组织得到明显改善，共晶硅由加锶前的短棒状转变为加锶后的细小、弥散的针状形态，缩松、裂纹缺陷得以减少，但针孔缺陷明显增多，这是由变质处理时的吸氢引起的。锶的变质存在衰退现象，锶的有效变质时间为1小时，此时锶的含量为0.0187％，超过1小时锶的变质作用明显减退。加锶变质和Al-Ti-B细化共同作用时，AC4B合金的晶粒得到明显细化。
为消除铸造缺陷、铸造优质健全的476发动机气缸盖成品件，应从铸造工艺和熔炼工艺入手，并严格控制锶变质和Al-Ti-B细化工艺，通过加锶变质处理来控制缺陷和提高铝合金476汽缸盖力学性能的方法是可行的。
In this paper the microstructure and freezing defects of 476 Al alloy engine cylinder head are studied, using type Olympus GX 71 optical microscope, MU200X-ray diffraction, type FEI SIRION SEM analysis. The results show that 476 engine cylinder head produced by recent process have defects of shrinkage porosity zone, shrinkage, crack defects, gas pole and inclusion in the hot spot. The major defect of 476 engine cylinder head a 30×15×2mm shrinkage porosity zone in the D section, shrinkage porosity zone is about 0.5-1.0mm high, through wall defects (thermal crack) can been observed at the D section,length 7mm,width 035mm,highth 1.5mm, and the T section has gas pole, mostly exist 2~3mm under the surface of the casting ,about 0.35mm length ;under the surface the T section is aboutΦ0.35mm pinpole, but quantity is small; small spheral oxides particulate inclusion can been observed shrinkage porosity zone, but quantity is small too. The 476 engine cylinder head is produced by present low pressure casting, and the large amount of shrinkage porosity and the through thermo crack existing in the shrinkage porosity zone is the main reason of leakage existing in the casting.Then, the effect of Sr modification treatment on the microstructure and freezing defects of 476 engine cylinder are also researched. The results reveal that after the Sr modification treatment, the microstructure of 476 engine cylinder castings has been improved obviously, and the form of eutectic Sr changes from short stick to fine and disperse specula. Shrinkage and crack defects decrease, but pinholes defects increase obviously as a result of hydrogen absorption during the modification treatment. There are degradation phenomena during Sr modification treatment, the effective modification time of Sr is one hour and the content of Sr at this moment is 0.0187%. After one hour the effect of Sr modification treatment degrades dramatically. With Sr modification treatment and Al-Ti-B refinement, the grains of AC4B alloy are refined greatly.
In order to eliminate casting defects and produce good quality of 476 engine cylinder head, casting technology and melting technology should be paid much attention and modification technology of Sr and refinement technology of Al-Ti- B should be controlled austerely. So it is fesiable to control defects and improve mechanical property of Al alloy 476 engine cylinder head by Sr modification.
引文
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5 S.Morimoto. Development of a Low-pressure Die Casting Process for Improved Soundness of Aluminum Casting. AFS Transaction, 2002, 28:22～87
6 H.nieswaag. Low-pressure Sand Casting of Aluminum Alloys (Metal Flow and Mechanical Properties). 55th International Foundry Congress Mockba CCCP. Cemtropb, 1988:11～16
7 茅春浦．流体力学．上海：上海交大出版社，1992：23～25
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9 D.G.Schmidt．铜合金的浇注系统．国外铸造，1982，(5)：1～7
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13 邱庆荣，孙宝德，周尧．铝合金铸件在汽车上的应用．铸造，1998，(1)：46～47
14 Nussbaum AI. Semi-solid Forming of Al-Mg. Light Metal Age, 1996, 54:5～6
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24 Liu Baicheng, Qiu Wei, Shen Houfa. Study and Application of Mold Filling Simulation of Shaped Castings. Journal of Science and Technology. 1993, 13: 313～322
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26 骆灼旋．压铸技术的现状及展望．特种铸造及有色合金，21世纪铸造技术论坛，1998，(4)：23～28
27 罗庚生，张志忠，吕有纲等．低压铸造．北京：国防工业出版社，1989：16～23
28 铸造工程师手册编写组．铸造工程师手册．北京：机械工业出版社，1997：12～14
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34 宋才飞．中国铸造行业现状及发展趋势．特种铸造及有色合金，1997，(1)：3～33
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36 张春平，白敏丽．排气道隔热方式对气缸盖整体温度场影响的研究．小型内燃机，2001，30(1)：1～4
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2 Ganesan S, Poirier D R. Conservation of Mass and Momentum Forth Flow of Interdendritic Liquid during Solidification. Met Trans, 18A, 1987:721～723
3 董秀琦．低压及差压铸造理论与实践．北京：机械工业出版社，2003：4～8
4 任天庆．《CLP》型差压铸造液面加压控制系统的研制．特种铸造及有色合金，1987，(2)：67～81
5 S.Morimoto. Development of a Low-pressure Die Casting Process for Improved Soundness of Aluminum Casting. AFS Transaction, 2002, 28:22～87
6 H.nieswaag. Low-pressure Sand Casting of Aluminum Alloys (Metal Flow and Mechanical Properties). 55th International Foundry Congress Mockba CCCP. Cemtropb, 1988:11～16
7 茅春浦．流体力学．上海：上海交大出版社，1992：23～25
8 刘志超，兰俊昌，常崇礼等．铸造薄壁耐压壳体用ZL-S305铸造铝合金及压力差铸造工艺的研究．全国铸造学会“特种铸造及有色合金”学组第一届学术会议铸造有色合金(论文集)，1981：112～113
9 D.G.Schmidt．铜合金的浇注系统．国外铸造，1982，(5)：1～7
10 董秀琦，王冬，叶荣茂．垂直缝隙式浇注系统的理论分析及模拟验证．铸造，1993，(9)：9～13
11 王乐仪．特种铸造工艺．北京：机械工业出版社，1984：13～18
12 王燕轲．250发动机汽缸体的低压铸模设计．特种铸造及有色和金．1985，(6)：19～25
13 邱庆荣，孙宝德，周尧．铝合金铸件在汽车上的应用．铸造，1998，(1)：46～47
14 Nussbaum AI. Semi-solid Forming of Al-Mg. Light Metal Age, 1996, 54:5～6
15 董秀琦，王冬，王承志．低压及差压铸造理论与实践．北京：兵器工业出版社，1995：261～263
16 唐多光．21世纪低压铸造技术的展望．特种铸造及有色合余，2002，2002年压铸专刊：170～181
17 陈会武，赵冬初．反压铸造设备设计．铸造设备通讯，1980，(2)：1～21
18 王乐仪，郑来苏，曲卫涛．特种铸造工艺．北京：国防工业出版社，1984： 12～16
19 徐洲，姚寿山．材料加工原理．北京：科学出版社，2003：3～4
20 董若景．冶金原理．北京：机械工业出版社，1980：156～162
21 Flemings MC. Solidification Processing. New York. NY: Mc-Graw-Hill Book Co, 1974:112～130
22 L.A.Tarshis. Experiments on the Solidification Structure of Alloys Casting. Met.Trass, 1971, 2:131～153
23 Launder B E, Spalding D B. The Numerical Computation of Turbulent Fows. Computer Methods in Applied Mechanics and Engineering, 1974, 3: 269～289.
24 Liu Baicheng, Qiu Wei, Shen Houfa. Study and Application of Mold Filling Simulation of Shaped Castings. Journal of Science and Technology. 1993, 13: 313～322
25 Nichols B D, Hirt C W, Hotchkiss R S. SOLA-VOF: A Solution Algorithm for Transient Fluid Flow with Multiple Free Boundaries. Los Alamos Scientific Laboratory Report, LA-8355, 1980:264～269
26 骆灼旋．压铸技术的现状及展望．特种铸造及有色合金，21世纪铸造技术论坛，1998，(4)：23～28
27 罗庚生，张志忠，吕有纲等．低压铸造．北京：国防工业出版社，1989：16～23
28 铸造工程师手册编写组．铸造工程师手册．北京：机械工业出版社，1997：12～14
29 铸造手册编写组．铸造有色金属手册．北京：机械工业出版社，1978：4～11
30 王乐仪，郑来苏，曲卫涛等．特种铸造工艺．北京：国防工业出版社，1984：12～15
31 吴战越，王赏．浅析低压铸造的工艺特点．煤矿机械，2002，(3)：40～41
32 Miller W.s., Zhuang l., Bottema J. Recent Development in Aluminum Alloys for the Automotive Industry. Materials Science and Engineering: A, 2000, 280(1): 37～49
33 吴浚郊．轿车发动机铝合金缸体和缸盖的铸造技术．铸造技术，2002，23(5)：273～275
34 宋才飞．中国铸造行业现状及发展趋势．特种铸造及有色合金，1997，(1)：3～33
35 董秀琦．
36 张春平，白敏丽．排气道隔热方式对气缸盖整体温度场影响的研究．小型内燃机，2001，30(1)：1～4
37 李隆盛．铸造工艺及原理．北京：机械工业出版社，1990：215～227
38 Hetu J F, Gao D M, Kαbanemi K Ketal. Numerical Modeling of Castincesses. Advanced Performance Materials, 1998, (5): 65～82
39 张玉海．硅橡胶模．发泡石膏型-低压铸造铝合金工艺．特种铸造及有色合金，2000，(3)：57～61
40 Morishima H, Kato Z, Vematsu Ketal. Development of Aluminum Titanate-Mullite Composite Having High Thermal Shock Resistance. J.Am.Cer.Soc, 1986, 69C(10): 226～227
41 Parker F J. Al_2TiO_5-ZrTiO_4-ZrO_2 Composites: A New Family of Low-Thermal-Expansion Ceramics. J.Am.Cer.Soc, 1990, 73(4): 929～932
42 徐刚，韩高荣．铝合金低压铸造用钛酸铝陶瓷升液管的制作．特种铸造及有色合金，2002，(5)：38～41
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