交界线借用挑战有效厚度观念

运用液态淬火介质中冷却的四阶段理论分析得出:在工件淬火冷却过程中,交界线借用应当是非常普遍的现象.工件上较厚大部分可以借用相邻部分已有的交界线,直接由蒸汽膜阶段进入中间阶段的交界线扩展期.由于省略了超前扩展点的形成期,交界线借用可以明显增大工件获得的冷却速度.这与建立在三阶段理论基础上的有效厚度观念是相矛盾的.通过两组实验,分别演示了交界线借用能提早结束厚度更大试样的蒸汽膜阶段,以及能使更厚大试样获得更高的淬火硬度的现象.由此可以认为,交界线借用动摇了传统的有效厚度观念.

Borrowing the Demarcation Line has a Challenge to the Concept of Effective Thickness

using the theory of four-stage differentiation of heat removal,the following analyses can be made:during the course of quenching in liquid quenchants,borrowing a demarcation line is a common phenomenon.In a quenched workpiece,an existing demarcation line can be passed onto a relatively thi-cker area,thus the area enters directly into the timeframe of the spreading of the demarcation line.By omitting the formation period of the hyper-spreading spot,borrowing the demarcation line can greatly increase the attainable quenching speed.This runs contrary to the concepts of effective thickness based on the traditional three-stage differentiation.Comparative experiments have shown that sample of comparatively greater thickness entered and completed the middle stage,earlier and quicker by borrowing the demarcation line,and were also able to attain greater quenching hardness.It is our view that the borrowing of the demarcation line has shaken the concept of effective thickness.