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表面缺陷的存在及其严重性,例如直接水冷连继铸造产品中出现的冷隔,在很大程度上取决于模子热传导条件。在水平连续铸造直径20毫米的铅、锡、锌合金棒时,研究了热顶连续铸造模的热传导条件对冷隔形成机理的影响。冷隔的形成有两个阶段:界面控制凝固与随后的扩散控制凝固。用热顶模铸造时,有效热传导常数非常大,相当于直接水冷铸造。采用了一种稳态数值凝固法进行试验,结果发展了冷隔形成的临界铸造速度概念。如果实际铸造速度大于这个临界速度,就不能产生冷隔。换句话说,如果提高模子温度,降低模子的有效热传导常数,或实际上显著提高液体金属温度,就能使临界铸造速度降低,冷隔也可以消除。
The presence of surface defects and their severity, such as the occurrence of cold septa in direct water cooled continuous casting products, are largely dependent on the mold heat transfer conditions. The influence of the thermal conductivity of the continuous casting die with hot top on the formation mechanism of the cold separation was studied when the lead, tin and zinc alloy rods with a diameter of 20 mm were continuously cast horizontally. There are two phases in the formation of cold septa: interface control of coagulation followed by diffusion control of coagulation. When casting with a hot top mold, the effective heat transfer constant is very large, equivalent to direct water-cooled casting. A steady-state numerical solidification method was used to carry out the test, and as a result, the concept of the critical casting speed developed by cold separation was developed. If the actual casting speed is greater than this critical speed, you can not produce cold insulation. In other words, if the mold temperature is increased, the effective heat transfer constant of the mold is lowered, or the liquid metal temperature is substantially increased, the critical casting speed can be reduced and the cold interval can be eliminated.