Study of composition and structure of NLMK BF No. 6 hearth scull (Report 1)

Analysis of blast furnaces running experience in Japan, Europe and North America shows, that duration of their operating period determines to a great extent by hearth and bottom lining endurance. Study of structure change of scull and hearth walls and bottom lining at different burden compositions and BF heat conditions will enable to elaborate organization and technical solutions for BF efficiency increasing. Study of hearth scull composition at the level of iron notch and lower at PAO NLMK BF No. 6 after 2nd category overhaul stoppage from 26.08.2016 through 29.09.2016. Lump samples of mass from 10 up to 70 kg were taken with careful visual inspection to exclude oxidized and hydrated pieces. Based on visual inspection of samples as well as petrographic, chemical, X-ray structural and microprobe analysis it was determined, that the scull base comprises products formed during crystallization of heat products. They included a metal, in which a magnetic part (α-iron) is prevailed with iron carbide and graphite inclusions, graphite as a separate phase, slag components with a base of melilite at the level of iron notch and silicates (X-ray amorphous) of variable content of СaO–K2O–Na2O–SiO2–Al2O3system. The quantity of metal and graphite in the hearth walls scull increases from iron notch to the bottom and reaches a value >85 % at the level 300 mm lower than iron notch. Content of titanium compounds in oxide form in all the samples as well as nitrides, carbo-nitrides totally does not exceeds 1–2%.