硼在渗层中的行为与渗层淬透性

含硼钢化学热处理时,由于C、N、B之间的相互作用,B在整个渗层范围内发生明显的再分布在渗碳层中主要表现为表层B的富集和次表层B的贫化;在碳氮共渗层中则主要表现为表层和次表层内有大量BN形成以及在很宽的范围内固溶硼量很低
B的这种再分布对渗层材料的淬透性带来显著影响。在渗碳层中,除了要考虑C本身的作用和C对B效应的影响外,还要考虑次表层B贫化的影响。在碳氮共渗层中,大量BN的形成对渗透性有显著的不利影响,固溶硼贫化的作用也表现得更为突出。

An Investigation of Carbointriding Black Structure in Boron Steel

The black structure, non-martensite structure in carb o-nitriding case, is easy to occure in boron steel, when the heat treatment process is out of control, which reflects the decline of hardenability of case material.There are two kinds of black structure, surface black structure and transition region black structure, ed respectively by the inner-oxidati on of alloying eleasucments and the formation of carbide and nitride at the surfact, and by the redistribution and variation of occurence state of boron thought-out the case.
In order to prevent the both black structures high carbonitriding temperature, later supply of ammonia, large amount of kerosene and smmall amount of ammonia supplied in carbontriding stage, and rapid quenching after the treatment are recommended.