Martensite quenching and the deformation and the size of the stability. Martensite quenching and process, because parts of each place uneven cooling, it is inevitable to turn up the heat stress and organization of parts distortion and cause stress. After quenching and parts of the deformation (including size change and shape change) are influenced by many factors, is a very complex problem. Such as parts size and shape of the original organization, the uniformity of the rough machining, before quenching state (turning feed amount of size, machining the residual stress, etc), the heat of quenching speed and temperature, the way, put into the oil, and the characteristics of the medium way quenching and cycle way, the temperature of the media are affecting parts deformation. In a large number of both at home and abroad, and puts forward some measures to control deformation, if use rotation quenching, pressure die quenching, control parts of the way into the oil, etc. Beck, etc research shows that: the steam film phase to the boiling issue of the transition temperature is high, the big cold and produce large speed thermal stress to make low yield point of austenite distortion and cause parts distortion. Lubben and people think deformation is a single parts or components immersed between uneven cause, especially using the new oil is more likely to appear this kind of situation. Tensi, people think: in Ms point the cooling speed of deformation of decisive role in Ms point and under the low temperature of cold speed can reduce the deformation. Volkmuth who studied system quenching medium (including oil and salt bath) to taper roller bearings inside and outside the circle quenching deformation. The result indicates that the cooling in different ways, the diameter of the contractor will have different levels of "increases", and with the improvement of the temperature of the medium, the diameter size collar increase degree to the agreement, namely "horn" shape deformation reduced, at the same time, the collar of elliptic deformation (single radial plane within the diameter of the amount Vdp changes, Vdp) decreased; Inner circle for stiffness is bigger, its deformation less than outside. Martensite after quenching and part size stability is mainly affected by the influence of three different change: carbon from martensite formation in the grid work migration ε-carbide, austenite decomposition and form Fe3C, three change stack with each other. 50 ~ 120 ℃ between, because ε-their carbon precipitation exhalation, cause the parts reduced in size, general parts in 150 ℃ after tempering finish this transition, the future of parts in the process of using size can be ignored the effect on the stability of 100 ~ 250 ℃, and between the austenite decomposition, into martensite or bainite, will be accompanied by a large volume rose; More than 200 ℃, ε-carbide to cementite transformation, leading to reduced in size. Research also shows that: austenite outside under load or low temperatures (even in room temperature) can also occur decomposition, cause parts size change. Therefore, in be used actually, all of the bearing parts of tempering temperature higher than 50 ℃ temperature should be used, the size stability to demand higher parts to try to reduce the austenite content, and by using the higher temperature of tempering.
 



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