Abstract
The carbides of the ball bearing steels are isolated electrolytically and their nature is investigated. The results are as follows.
(1) Electrolytic isolation of the carbide of the annealed ball-bearing steels is more effectively performed (its efficiency is about 92%). But in case of the hardened steels its efficiency falls to about 70-80%. In some material the matrix undissolves partly and contaminates the residue of the carbides.
(2) The annealed ball-bearing steels contain the carbide about 15%. Cr, Mn, and V are contained more in the carbide and Ni in the matrix, and particularly Cr is conspicuous. In SKF steels Cr content of cementite is 9.23%, and in home-made steels 8.79%. The carbide contains 98% (SKF) and 93% (H.M) of the total Cr.
(3) When the bearing steels are heated above A1, the chemical composition of the non-dissolved cementite changes as follows. Cr increases with the temperature, V also a little, Mn decreases first and increases somewhat afterwards.
(4) The ball-bearing steels are usually hardened at 820-840°C, at this state the non-dissolved cementite content is 8-9% in SKF steels and 7-8% in home-made steels. The chemical compositions of the matrix are 0.5% C, 0.5-0.6% Cr and 0.2% Mn in SKF steels and 0.5% C, 0.6-0.7% Cr and 0.3% Mn in home-made steels.
