沸腾冷却区的宽度及其传达的信息

用摄像记录了液态介质中冷却时试样表面的冷却情况.试验发现,在液态介质中淬火时,试样表面的沸腾冷却是在呈带状的沸腾冷却区扫过的过程中完成的.这类沸腾冷却区通常多很窄,因此工件表面上任何部分经历沸腾冷却的时间都很短,靠沸腾冷却方式降低的温度都不多.淬火冷却中,从工件表面出现第一个超前扩展点开始,到蒸汽膜区完全消失为止的很长一段时间内,三种散热方式共同存在;其中,蒸汽膜冷却方式和与对流冷却方式对工件淬火冷却的贡献都比沸腾冷却的要大.

The Width of the Boiling Cooling Zone of the Liquid Medium and the Information it Carried

The cooling status on the surface of the work piece in a liquid medium was recorded by a video camera. It was found that when quenching in a liquid medium, the boiling cooling on the surface of the work piece was accomplished by the sweeping of the boiling cooling zone over the surface. Generally this kind of boiling cooling zone is quite narrow, therefore the duration undergoing cooling at any part on the surface of the work piece is very short, by which the temperature drop could not be much. During the cooling process in quenching, in the rather long time period from the appearance of the first advancing point, until the complete disappearance of the vapor membranes, there is the co - existence of all of the three heat dissipation mechanisms, in which the vapor membrane cooling and the convection cooling contribute more to the quench cooling of the work piece than the boiling cooling.