Quantitative Analysis of Ca-rich Oxide Inclusions in Steel by Galvanostatic Electrolysis

Abstract

It is well known that oxide inclusions, such as aluminum oxide or Ca-rich oxide, sometimes cause serious problems for steel products. Usually, oxide inclusions have been measured by the extraction method or by optical microscope observation prescribed by JIS and ASTM, but the quantity of inclusions in steel products are now below the detection limits of these conventional methods. Recently several new methods were developed to evaluate inclusions both in size and in amount; for example, electron beam melting method coupled with optical microscopic analysis and photo scattering method coupled with acid extraction. However, it is difficult to evaluate Ca-rich oxide inclusions in amount even though by using above mentioned new methods. The reason is as follows:
(1) It is difficult to extract Ca-rich oxide inclusion quantitatively from steel.
(2) The quantity of Ca-rich oxide inclusions in steel is quite low.
The authors developed a new method to extract ca-rich oxide inclusions in steel quantitatively, which method is based on galvanostatic electrolysis with non- aqueous electrolyte.
The composition of new type of electrolyte is 40% maleic anhydride-3% tetrametylammonium chloride-methanol.
100 gram of steel matrix can be electrolyzed with 1 liter of the new electrolyte.
This technique makes it possible to determine Ca-rich oxide inclusions quantitatively.