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A study of interfacial heat transfer and process parameters in squeeze casting and low pressure permanent mold casting.

机译：对挤压铸造和低压永久铸模中界面传热和工艺参数的研究。

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摘要

With the emerging demand for energy efficient and environment-friendly automobiles, cast aluminum alloys are increasingly being used in their manufacture. In this context, two permanent mold casting processes, namely, Squeeze Cast Permanent Mold and Low Pressure Permanent Mold (LPPM) have become very popular in the production of high integrity shape-cast aluminum components. However, many industries are yet to benefit from the full potential of these processes due to limited understanding of the effect of process parameters on casting quality and the necessary boundary conditions for computer modeling and simulation so as to minimize costly field trials. This dissertation attempts to address some of these concerns facing today's foundry industry.; An experimental investigation of the Indirect Squeeze Casting Process was conducted by pouring molten Al-7Si-0.3Mg (A356) alloy into a specially designed and instrumented mold, mounted on a horizontal clamped-vertical shot squeeze caster (HVSC). Temperature measurements close to the metal/mold interface were made and compared with the results of the numerical simulation of heat flow during solidification and cooling of castings. The Heat Transfer Coefficient (HTC), a critical parameter essential for any solidification simulation, was estimated based on the simulation that gave the best fit to the experimental temperature data. During the solidification process, the HTC is relatively uniform over the entire casting and on reaching a critical solidification pressure, the HTC is close to 4500 W/m2 K. The work has also provided a correlation of Secondary Dendrite Arm Spacing (SDAS) with cooling rate for a modified A356 alloy.; Low Pressure Permanent Mold Casting experiments were conducted by pouring a nearly identical aluminum alloy into an instrumented, coated mold mounted on a low pressure casting machine. The pressure levels, along with the time required to achieve complete filling, were microprocessor controlled in the casting machine. The HTC evaluation and SDAS-Cooling Rate Correlation were made in a similar manner to the Squeeze Casting study. A novel approach to estimating the HTC, accounting for the temporal and spatial temperature and thermal property variations, is presented. The maximum and minimum values of the HTC in this case were close to 2000 W/m2 K with no air gap and 400 W/m2 K with an air gap formation. The influences of air gap formation and mold coatings in controlling interfacial heat transfer were also modeled.; It is expected that the HTCs and SDAS-Cooling Rate Correlations for the two casting processes will assist foundry engineers in deriving maximum benefits from each process.
机译：随着对节能和环保汽车的新兴需求，铸造铝合金越来越多地用于其制造中。在这种情况下，两种永久铸模工艺，即挤压铸造永久铸模和低压永久铸模（LPPM）在生产高完整性铸型铝组件时非常流行。但是，由于对工艺参数对铸件质量的影响以及计算机建模和仿真所需的边界条件的了解有限，从而使昂贵的现场试验最少，许多行业尚未从这些工艺的全部潜力中受益。本文试图解决当今铸造业面临的一些问题。通过将熔融的Al-7Si-0.3Mg（A356）合金倒入专门设计和仪表化的模具中进行的间接挤压铸造工艺的实验研究，该模具安装在卧式垂直夹紧式挤压铸造机（HVSC）上。进行了接近金属/模具界面的温度测量，并将其与铸件凝固和冷却过程中热流的数值模拟结果进行了比较。传热系数（HTC）是任何凝固模拟必不可少的关键参数，它是根据最适合实验温度数据的模拟进行估算的。在凝固过程中，HTC在整个铸件上相对均匀，并且在达到临界凝固压力时，HTC接近4500 W / m 2 K。具有改进的A356合金的冷却速度的枝晶臂间距（SDAS）。通过将几乎相同的铝合金倒入安装在低压铸造机上的仪器化涂层模具中，进行低压永久铸模铸造实验。压力水平以及完成完全填充所需的时间在铸造机中由微处理器控制。 HTC评估和SDAS冷却速率相关性与挤压铸造研究相似。提出了一种新的估算HTC的方法，该方法考虑了时间和空间温度以及热特性的变化。在这种情况下，HTC的最大值和最小值接近2000 W / m 2 K（无气隙）和400 W / m 2 K（形成气隙） 。还模拟了气隙形成和模具涂层对控制界面传热的影响。预计两个铸造过程的HTC和SDAS冷却速率相关性将帮助铸造工程师从每个过程中获得最大的收益。

著录项

  • 作者

    Krishna, Prasad.;

  • 作者单位

    University of Michigan College of Engineering Graduate Professional Programs.;

  • 授予单位 University of Michigan College of Engineering Graduate Professional Programs.;
  • 学科 Engineering Mechanical.; Engineering Materials Science.; Engineering Metallurgy.
  • 学位 D.Eng.
  • 年度 2001
  • 页码 207 p.
  • 总页数 207
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;工程材料学;冶金工业;
  • 关键词

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