【作者】 徐慧；

【导师】 赵建华；

【作者基本信息】 重庆大学 ， 材料加工工程， 2009， 硕士

【摘要】 发动机缸盖作为车辆系统的一个重要组成部分,其质量的好坏直接影响到汽车的性能和生产成本。发动机缸体缸盖的制造水平是衡量一个国家制造业水平的重要标志之一,它们在很大程度上代表了一个国家汽车工业的发展水平。面临着市场要求的提高对缸盖铸造所带来的巨大压力,国内外的企业纷纷采用不同的铸造方法及铸造工艺来改善缸盖件的质量,并利用计算机辅助技术来修改及优化铸造工艺,以求得到高质量低投入的铸件。本文应用计算机数值模拟对3S4G发动机缸盖的低压铸造工艺进行了研究。根据低压铸造凝固原理,利用Anycasting数值模拟研究,针对3S4G缸盖的低压铸造的充型和凝固过程进行数值模拟研究,并对缺陷进行预测和分析,完成最终工艺优化的目的。通过模拟试验,找出了利用现行铸造工艺方案生产3S4G发动机缸盖铸件存在的问题,然后针对这些问题采取具体的工艺优化方案进行模拟对比。通过模拟研究,得出获得高质量的缸盖件的最优工艺,具体如下:①充型阶段,将升液时间延长至12s,使升液平缓,保证了金属液体进入浇口时不再出现喷射现象;将保压压力增至1.5×105Pa,使补缩效果增强,保证所得铸件的内部组织更加致密。②在上模设置10根水冷管,侧模设置3根水冷管,下模设置2根风冷管,保证了铸件内部实现从上而下金属液冷却速度由大变小,温度梯度表现为上部温度低下部温度高,有效的实现了金属液的顺序凝固,保证最后凝固区域逐渐像浇口处推移。③将上模预热至250℃,下模预热至390℃,使下模预热温度高于上模预热温度,建立合理的温度梯度,从而实现顺序凝固。④在浇口处加保温套,使浇口成为最后凝固区域,保证铸件内部无缩孔缩松缺陷。同时,本文还重点探讨模具热平衡对铸件质量的影响。文章以AC4B铝合金在不同壁厚下产生的热节为研究对象,利用Anycasting铸造分析软件进行多循环凝固模拟,寻求实现凝固平衡的具体措施。研究结果表明:①单循环时,在铸件壁厚一定的条件下,随着模具壁厚(3mm～18mm)的增加,温度差值逐渐减小,模具局部冷却能力上升,可以通过增大模具壁厚的办法来实现凝固平衡。②多循环时,在铸件壁厚一定的条件下,随着循环次数及模具壁厚(3mm～18mm)的增加,温度差值逐渐增大,模具的局部冷却能力下降,可以通过减小模具壁厚的办法来实现凝固平衡。③循环浇注时,当循环浇注7次后,模具内部建立了相对稳定的温度梯度,说明模具已达到了热平衡,此时参考样模具的热平衡温度为182℃。更多还原

【Abstract】 As the important component of the vehicle system, the quality of the engine cylinder head influences directly the performance and production cost of the car. The manufacture level of the engine cylinder head is the important sign of the national manufacturing industry. They have represented the development level of a national auto industry. Facing the enormous pressures of the improvement of the market requirement for the cylinder head casting, the domestic and international enterprises adopt different casting methods and casting technology to improve the quality of the engine cylinder head, and used the computer-aided technology to modify and optimize casting technology.The paper studied the low pressure die casting process of 3S4G engine cylinder head via numerical simulation. According to the solidification principle of low pressure die casting process, the paper studied the solidification process of 3S4G engine cylinder head via numerical simulation with Anycasting software. The problem has been found in the existing method, and the research was carried on the element which influenced the quality of the castings assisted by numerical simulation. The following is the optimization methods:①Changing the pressure parameters to ensure the steady filling and effective solidification feeding. The changed key parameters include the lift time of 12s, the holding pressure of 1.53 kgf/cm2.②Setting up the cooling pipes to ensure the sequence solidification. The added pipes include ten water cooling pipes in the upper mould, three water cooling pipes in the side-mould, and two wind cooling pipes in the lower mould.③Changing the preheating temperature of the mould to ensure the sequence solidification. The parameters include 250℃of the upper mould, 390℃of the lower mould.④Add the heat insulation sleeve on the runner to ensure the runner becomes the last solidification area.The paper also studied the hot spot forming tendency during solidification of AC4B Aluminum alloy in permanent mould casting with the dies of different wall thickness via numerical simulation with Anycasting software. The results show that:①In a single cycle casting, the increase in the thicknes(s3mm～18mm) enhances the cooling ability of the mould and promotes balanced solidification in a certain degree.②In multi-cycle Casting, the thickened die-wall gradually loses its localized chilling effect. In contrast, the die with a decreased wall thickness in a certain range is easier to achieve the desired solidification balance.③During the cycle casting, the mould has already achieved the heat balance after the 7th cycle casting. The heat balance temperature of the reference sample is 182℃.更多还原