Study on the Physicochemical Properties of Burnt Lime for the Iron and Steel Refining.

Research Project

Project/Area Number	60550476
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	金属精錬・金属化学
Research Institution	Kumamoto University
Principal Investigator	MITSUO Toshiharu Faculty of Engineering, Kumamoto University. Professor, 工学部, 教授 (80166058)
Co-Investigator(Kenkyū-buntansha)	SUNAYAMA Hiroyuki Faculty of Engineering, Kumamoto University. Assistant, 工学部, 助手 (30040413) KAWAHARA Masayasu Faculty of Engineering, Kumamoto University. Associate Professor (60145282)
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥1,800,000 (Direct Cost: ¥1,800,000) Fiscal Year 1986: ¥700,000 (Direct Cost: ¥700,000) Fiscal Year 1985: ¥1,100,000 (Direct Cost: ¥1,100,000)
Keywords	Pretreatment of hot metal / Ladle refining / Desulfurization of molten iron / Dephosphorization of molten iron / Flux for refining / Burnt lime for refining / Limestone for iron and steel making / 生石灰の滓化
Research Abstract	Several properties of limestones and their burnt limes were investigated on six commercially available limestones for the iron and steel refining. Additional experiments were carried out to study the relationships between hydration reactivity of burnt limes and reactivity to molten iron and fluxing property to molten slags. 1. For the hydration reactivity test, the early value after 1 minute indicates closer relationship to the reactivity with molten iron than the value after 10 minutes which has been widely used in steelmaking practice. In other words, large scatter in early value of hydration reactivity was observed even for soft burnt lime, but the reactivity to molten iron increased with increasing of the early value. 2. High early value of hydration reactivity was obtained for the limestone having large grain size in spite of relatively low temperature calcination almost independent of calcination conditions. On the other hand, low early value was obtained for the limestone having small grain size by relatively low temperature calcination, and it was improved by high temperature calcination or holding for a long time. 3. It was found out that the factor controlling the early value of hydration reactivity and reactivity to molten iron was not the microstructure of burnt lime surface but macro crack of 1 <mu> m order in width. 4. The formation of crack of 1 <mu> m order in width depends on the grain size of limestone and the calcination conditions (calcination temperature and holding time), and it may be attributed to micro grain growth of burnt lime by sintering. 5. The relationship between the early value of hydration reactivity and fluxing property to molten slag may consist with the reactivity to molten iron. However, more examinations may be required to make it clear.