Abstract
Most part of sulfur in steel precipitates as sulfide inclusions and it has remarkable effects; on the various properties of steel.
In order to reveal the effects of Mn, Al, Ti, Zr, V, Nb and Cr addition upon steel which contains up to 0.30%S, authors studied the crystal structures, the optical properties, the distribution, the etching behavior and the hot deformation characteristics of sulfide inclusions in steels containing one of those alloying elements.
The results are as follows:
(1) The formation of FeS, α-MnS, TiS, Zr3S4 or ZrS2, VS, CbS and “CrS” was respectively observed, and aluminum sulfide considered to be Al2S3, was observed.
(2) The crystal structure of sulfide inclusions was closely connected with their optical anisotropy. TiS, CbS and “CrS” were strongly anisotropic.
(3) The etching behaviors of sulfide inclusions were different from one another. TiS, VS, NbS and “CrS” were not chemically attacked by 20% HF×10min etching.
(4) a-MnS, “CrS” and sulfide in Al-added steel were deformed during hot-working. TiS, Zr3S4, ZrS2 and VS, however, showed no deformation. Fe-S steel and Nb-added steel were not forgeable.
