瞬态法接触热阻实验研究及其在快速铸轧工艺参数仿真中的应用

【作者】 张云湘；

【导师】 黄明辉；

【作者基本信息】 中南大学 ， 机械设计及理论， 2004， 硕士

【摘要】 快凝铸轧过程中，熔融金属在铸轧区发生凝固、结晶，最后经轧制成形，金属在高温下发生大塑性变形。铸轧过程中的热量通过铸轧界面及辊套由冷却水带走。接触界面热阻是铸轧过程热分析的一个重要参数，国内外学者通常采用分段常值法处理，由于铸轧工作界面状态随铸轧过程不断发生变化，其界面热阻在不断发生变化。分段常值法的处理对热分析结果造成较大的误差，因此有必要对界面热阻的变化进行进一步研究。 在综合研究了国内外关于各类接触界面传热的基础上，就大塑性变形接触界面传热问题进行了较为深入的研究。目前国内外多用一维稳态热传导进行分析和实验，为了尽可能保证轴向一维热流，必须减小周向热量损失；保证试件长度与半径之比足够大及热量和温度的准确测量，导致这种测试方法只适应于低温小压力的工况。本文利用一维瞬态热传导方程计算了被激光照射的金属试样接触界面的温度分布，获得接触界面的理论温度差，并与实际测得的温升曲线进行对比以得到界面接触热阻。在此基础上以激光器为加热源设计了一套大塑性的瞬态接触热阻实验系统，该系统克服了传统稳态法测试接触热阻的温度测试不准、接触压力小、测试效率低的缺点；并在此基础上进行了大量的实验研究工作，对所得实验数据进行多元线性回归处理，建立了接触热阻的计算模型；实验发现，接触压力是影响接触热阻的一个主要因素，二者之间的关系满足h^* ∝（p^*）^0.93；同时，接触表面均方根粗糙度、中间介质、氧化膜厚度、热流密度的改变都将不同程度地影响接触热阻的大小，由实验数据得出了它们的关系曲线;用实验所得接触热阻计算模型综合分析了连续铸轧中带坯在铸轧区的传热和铸轧力的数学模型，在此基础上对连续铸轧工艺参数的变化进行了仿真研究。通过将仿真结果与实验结果比较，证明本文建立的接触热阻模型比较准确。更多还原

【Abstract】 In fast roll casting process, melting metals shape up after concreting and riming. They have big plastic deformation under high temperature. Heat is taken away through roll casting interstitial and roll sheath by water. Thermal contact resistance (TCR) is an important parameter, researchers home and abroad generally utilize subsection constant method to analyze this parameter, but this parameter changes continuously because of persistent change of the state of roll casting interstitial. Subsection method will bring big errors in thermal analyzing of roll casting, so in-depth research should be done for the metabolic rule of thermal contact resistance.On the basis of synthetically researching of different heat transfer of all sorts of thermal interstitial, the heat transfer of metallic interfacial under condition of high temperature and big plastic deformation was lubricated. One dimension stable thermal conductance method is used in analyzing and experiment. To assure axial one dimension thermal flow , circumambient thermal loss should be decreased as little as possible; To assure the ratio of radii and length of the two testing samples as big as possible ,stable method can only be applied to the condition of low temperature and low pressure .In this paper , a transient TCR experiment system was developed , the thermal resource of which is a laser, thetemperature distributing on the contact interface is calculated from one dimension transient thermal equation and it is contrasted with testing temperature curve to get the real TCR value .This system overcome the shortcoming that the traditional stable TCR experiment system can test TCR under the condition of low temperature and low pressure. According to experimental rule, much research work was done. After analyzing experimental data, a calculating model of TCR was founded and modified allowing for the real condition of fast: roll casting; We found that contact pressure is the main factor that affects TCR. The relationship between them is h (p0.93; At the same time, the change of RMS(Root mean Square)roughness, the medium of the interface, thickness of oxygenated film, direction of thermal flow, density of thermal flow will change TCR to different degree. Their interrelation curves were provided according to experimental data; The TCR calculating model was used to analyze the thermal and mechanical model of the strip in fast roll casting process. Finally, the emulator of these two models was founded to analyze the change rule of technological parameters in fast roll casting, the analyzing results basically fit for real testing data. It demonstrates that the experimental way and TCR is correct and reasonable.更多还原