Service life of rammed ladle linings obtained from a quartzite-argillaceous body

Abstract

aceous body (TU 14-87252-77) obtained from the Krasnogorovsk Refractories Plant. The following parameters were used for lining the ladles: thickness at the lower portion of the ladle 190-220 mm, thickness in the central and the upper portions 160-220 mm, and the ramming duration 20-25 min; the surface hardness measured using a 071-model hardness tester amounted to (85  5) conditional units. The rammed lining was subjected to drying using a single-pipe natural-gas burner measuring i00 mm in diameter and 2000 n~n in length according to the following flow regime: 140-150 m3/h for 3 h, 260-270 m3/h for 8 h, and 350-390 m3/h for 8-10 h. The steel-teeming ladles are operated under the following conditions: the teeming temperature 1600-1655~ the residence duration of steel in the ladles 1 h 5 min-2 h 50 min, the basicity of the slags 1.8-3.4, the weight content of FeO in the slags 7.7-22.7%, and the weight of steel in the ladles 200-240 ton; molten steels handled in the ladles - rimming and killed (semikilled) steels in a I:i ratio. The life of the ladle lining is determined by the service conditons of the ladles and the quality of the lining. An analysis of the service life of the rammed ladle linings was carried out by processing the melt-charts of the open-hearth furnaces. We analyzed the data concerning the melting and teeming technology (in particular, the teeming temperature and the grade of the steel, the weight and the residence period of the steel in the ladle, the basicity of the slag and the FeO content in it, and the turnover factor of the ladle, i.e., the periodicity of filling it during teeming). Our analysis showed that the poor service life of the rammed ladle lining (less than I0 teemings) can be attributable mainly to the following factors: filling up the ladles for the first time after making the linings or filling them up in succession (2-3 times or more) with rimming steels (in particular, with the molten steels superheated up to 1635-1655~ low weight of molten steel in the ladles (220-240 ton with an average weight of 236 ton) and an increased weight of slag; and using insufficiently cooled ladles for successive teemings (after 1-3 h intervals). As a rule, under the simultaneous action of all the aforementioned factors, the life of the rammed linings does not exceed 5-7 teemings. High basicity and FeO content of the slags and a prolonged residence period of molten steel in the ladles (exceeding 2 h 30 min) reduce the service life of the ladle lining to a lesser extent. In the absence of proper technological measures (using one flinging port instead of two ports, imbalancing of the rotor of the sand-slinger equipment, using old ladles with different sizes of the abandoned portions, using ladles having a high ellipicity, deviations from the optimum drying regimes for the newly made linings etc.), the life of the rammed linings decreases and, as a rule, does not exceed 12 teemings. Our experience shows that deterioration of the quality of the ramming body (deviations from the desired chemical composition, granulometry, and moisture content) can reduce the life of the linings by 20-30%. When the rammed linings of the steel-teeming ladles of the open-hearth shop are made deviating from the norms of the ramming technology and are used properly, they exhibit a stable service life of not less than 15-17 teemings (in contrast to 8-9 teemings in the case of brick linings).