冷硝酸法による鋼中析出物の分離定量

抄録

An investigation has been made on extraction and determination of various precipitates in steel by cold nitric acid method, comparing with other available methods.
The results obtained are as follows:
(1) TiC, TiN, Ti₂O₃ and sulfide of titanium in steel are quantitatively extracted by nitric acid (1+8) at -5°C. TiN is especially stable to cold nitric acid.
(2) ZrC, ZrN and ZrO₂ in steel are quantitatively extracted in a wide range of conditions of cold nitric acid method.
(3) VC and VN in steel are quantitatively extracted by nitric acid (1+8) at -5°C. The vanadium compounds are, however, rather less stable to cold nitric acid, and completely decomposed by nitric acid (1+1) at -5°C.
(4) NbC, NbN, (Fe, Nb) O₂, FeO·Nb₂O₅ and Fe₂Nb in steel are quantitatively extracted by nitric acid (1+1) at -20°C. The niobium compounds are in general stable to cold nitric acid.
(5) Molybdenum carbides in steel-(Fe, Mo) ₃C, Mo₂C, (Fe, Mo) ₂₃C₆ and (Fe, Mo) ₆C-are unstable to cold nitric acid.
(6) The cold nitric acid method is thus found to be applicable with good reproducibility to extraction. and determination of various precipitates in steel. The time required for extraction is 1-2 hrs under stirring for lg of drillings of the sample.