抄録
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.
