1996 年 82 巻 12 号 p. 1017-1022
The determination and phase control of Ca-containing inclusions are important for the successful production of Ca-treated steels such as hydrogen induced cracking resisted steels. In this work, the quantitative isolation of calcium aluminate (mCaO·nAl2O3), CaS and CaO in Ca-treated steels has been investigated. All operations of isolation procedure from matrix dissolution to filtration were carried out in a glovebox with an Ar atmosphere. The atmosphere was controlled to a relative humidity of 25% to prevent H2O from attacking the inclusions. Using this protection, 10% bromine-methanol method was capable of the quantitative isolation of mCaO·nAl2O3, whose reactivity with H2O was found to be increased with increasing the ratio of m/n. Constant current electrolysis in 10% acetylacetone-1% tetramethylammonium chloride-methanol electrolyte (AA electrolysis method) was capable of the quantitative isolation of mCaO·nAl2O3 and CaS. However, CaO was not isolated. On the basis of these results, the method for evaluating the amounts of the Ca-containing inclusions has been developed. The amount of mCaO·nAl2O3 was evaluated by converting the analytical values of metal elements in the residue isolated by 10% bromine-methanol method into oxide forms. The amount of CaS was calculated from the difference between the amounts of Ca isolated by AA electrolysis method and 10% bromine-methanol method. The amount of CaO was calculated from the difference between the amounts of total oxygen and oxygen as mCaO·nAl2O3.