1955 Volume 41 Issue 11 Pages 1188-1192
[Correction] Tetsu-to-Hagane Vol.41 No.12 (1955) pp.1271-1271
[Correction] Tetsu-to-Hagane Vol.42 No.12 (1956) pp.1122-1122
Studies on carbides in steel, generally, have been carried out as they were in steel matrix. While, recently, some direct investigations of them isolated from steels were reported.
The present paper deals with a direct investigation of carbide. extracted electrolytically from a ball bearing steel by chemical analysis, X-ray diffraction method and electron-micro-scopic examination.
The electrolysis for extraction of carbide in the present study was carried out under the following conditions: 0·5N hydrochloric acid solution, current density 10mA/cm2, hydrogen atmosphere. The results obtained were as follows:
1) Carbide in the ball bearing steel (1.13% C, 1.42% Cr) annealed at 750°C for 5 hrs contained 7.21% Cr.
2) Cr content of ferrite in the annealed steel was about 0.24%, and that of austenite at 840°C (usual quenching temperature of this steel) was about 0.9%.
3) Cr content of undissolved carbide contained in austenite at quenching temperature increased with the heating time at the temperature.
4) In tempering process of the hardened steel, the carbide precipitated from the matrix (martensite and retained austenite) at low temperature, such as 300°C or 400°C, had nearly the same content of Cr as that of the matrix (1.42% Cr). But the carbide precipitated by tempering at above 450°C had large amount of Cr which increased with the rise of tempera-ture and holding time.
5) Electron micrographs of carbide isolated from the steel variously heat treated such as that from lamellar pearlite, troostite, sorbite, and spheroidized structures, were shown.
