薄板ステンレス鋼の曲げ性と表面地疵に及ぼす非金属介在物の影響

抄録

The effects of oxide and sulphide inclusions on the bending property and the surface defects of cold rolledsheet of 18-8 and 18 Cr stainless steels were investigated. The results are summarized as follows:
(1) The bending property of the sheet containing chromium-oxide as a main constituent of oxide inclusionsis far superior to that of the sheet containing silicate.
(2) An increase in the sulphide quantity in the range of this experiment causes a decline in the bendingproperty, but hardly affects other mechanical properties, with the exception of a slight deterioration of theErichsen value on 18-8 stainless steel sheet.
(3) When the sulphide quantity is equal, chromium-oxide coexisting with sulphide inclusion improves thebending property far more than the other-oxide. This is due to the fact that the particles of chromium-oxideincluded in sulphides prevent the sulphides from the string-like elongation.Consequently, in order to improve the bending property both in 18-8 and 18 Cr stainless steels, it isessential to reduce the amount of sulphide inclusion by lowering the sulphur content in metal and toprovide oxide Inclusions which are reluctant to take a stringer shape such as chromium-oxide formedby lowering the silicon content and increasing the manganese content in metal within the limit of specifications.
(4) Independent of the main constituent of oxide inclusions, chromium-oxide or silicate, surfacedefects and sand marks are formed whenever the oxide inclusions crowd locally, however, the defectsoccurring due to chromium-oxide can be removed not more easily than those due to silicate by mechanicalsurface conditionings.
Thus, while chromium-oxide formed by lowering the silicon content in metal considerably improvesthe bending property, it affects deterioratively on the removal of the surface defects.