ЗАКОНОМЕРНОСТИ МАССОПЕРЕНОСА УГЛЕРОДА ПРИ ЦЕМЕНТАЦИИ В АТМОСФЕРАХ НИЗКОГО ДАВЛЕНИЯ И ГРАНИЧНЫЕ УСЛОВИЯ МАТЕМАТИЧЕСКОЙ МОДЕЛИ

Abstract

By significant advantages over other methods of case-hardening possess processes carried out in oxygenfree environment, in particular, vacuum and ionic atmospheres which are used for surface strengthening the most critical parts of machinery and tools. These processes are characterized with a great amount of possible options of technological modes, an optimum choice of which is difficult through an experimental way. That is why a wide practical use found simulators of vacuum and ionic case-hardening in which the boundary conditions describe carbon mass transfer from working medium into metal. It is determined in an experimental way that at vacuum and ionic case-hardening in working medium having hydrocarbons, in particular, acetylene upon a saturated metal surface is formed either graphite or cementite which are a source for carbon diffuse into a metal depth. Thereupon at the formation of simulators boundary conditions it is necessary to take into account that carbon activity in these stages is equal to 1. That is why in boundary conditions should be introduced carbon concentrations in austenite corresponding to these activities. An obtained earlier through methods of spectral analysis direct proportionality between a carbonizing capacity of working medium and an acetylene content in it is explained by hydrocarbon thermal decomposition offered by a basis reaction at which Pauly quantummechanical principle is carried out. The results obtained are true both for vacuum, and for ionic working medium used at case-hardening as the ionization of latter does not exceed 10% of vol.