模拟轧制过程的镁合金带材动态接触传热机理

Dynamic Contact Heat Transfer Mechanism of Magnesium Alloy Strip by Rolling Process Simulation

改进接触传热测量装置,利用有限元模拟镁合金轧制过程辊缝界面的瞬态换热特性,以准确分析温度、压力和粗糙度对接触传热系数的耦合影响。结果表明,接触传热存在2个明显的临界阈值。当温度在150℃以下且界面压力低于22.1 MPa时,存在良好的线性规律。当超过第一阈值后,接触传热明显增强,呈现显著的非线性特征。另外,当界面压力超过50 MPa(第二阈值)且温度超过300℃时,接触传热很快趋于稳定。显然,此时的第二阈值与镁合金带材表面摩擦峰的弹塑性变形直接相关,通过增加微接触面积和摩擦峰的交互扩散,从而形成高压接触传热。基于这一现象的规律特征,有助于精确控制辊缝的接触界面温度,便于设计合适的轧制参数或优化轧制工艺。

By ameliorating the contact heat transfer measurement device and simulating the transient heat exchange characteristics of roll gap by finite element model,the coupling influence of temperature,pressure,and roughness on the contact heat transfer coefficient was analyzed.Results show that there are two obvious critical thresholds for the contact heat transfer.When the interface pressure is less than 22.1 MPa at temperature<150℃,there is a good linear relationship.When the interface pressure exceeds the first threshold,the contact heat transfer is significantly enhanced,presenting the obvious nonlinear characteristic.In addition,once the interface pressure exceeds 50 MPa and the temperature is higher than 300℃,the contact heat transfer quickly tends to be stable.Obviously,the second threshold is directly related to the elastic-plastic deformation of friction peaks on the surface of magnesium alloy strip.The contact heat transfer at high pressure is caused by the increased micro-contact area and the interactive diffusion of friction peak.Based on these characteristics of the phenomena,it is beneficial to accurately control the contact temperature of roll gap,and therefore to design suitable rolling parameters and optimize the rolling technique.