Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Patent
1992-09-23
1994-05-31
Bell, Mark L.
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
501120, C04B 2806, C04B 3544
Patent
active
053165713
DESCRIPTION:
BRIEF SUMMARY
INDUSTRIAL FIELD OF USE
This invention relates to alumina-spinel type monolithic refractories having excellent spalling resistance, corrosion resistance and slag penetration resistance.
PRIOR ART
In recent years, the conditions for using lining refractories for ladles have become severe because of diversification of the steel making process, i.e. 1 a rise in continuous casting ratio and an increase in degasification ratio; 2 the introduction of ladle refining; and 3 a rise of tapping temperatures accompanying transportation of molten steel, extension of holding time of molten steel, agitation of molten steel and like.
In the past, lining refractories for ladles were based on Roseki and/or zircon refractories, but high-alumina refractories are now being used as refractories having a low silica content not only because of said diversification in the steel making process, but also because of strong demand for high quality steel. Also, even though basic materials such as magnesia refractories and the like were partially investigated, said materials never became practical, because of a great deal of cracking and peeling owing to thermal and structural spalling.
Compared with Roseki and zircon refractories, high-alumina refractories have the following disadvantages: (a) slag penetration is great, (b) spalling resistance is inferior.
As processes inhibiting slag penetration of high-alumina refractories, alumina-spinel type, alumina-spinel-magnesia type or alumina-magnesia type castable refractories that are combined with MgO-Al.sub.2 O.sub.3 type spinel and/or magnesia were proposed in Japanese Patent Laid-Open Nos. 55-23004, 59-128271, 60-60985 and 64-87577.
In more detail, Japanese Patent Laid-Open No. 55-23004 described a material comprising from 10 to 85 percent by weight of a spinel clinker having a theoretical composition with a MgO:Al.sub.2 O.sub.3 molar ratio of 1:1, from 5 to 30 percent by weight of an alumina and from 10 to 25 percent by weight of a high-alumina cement; Japanese Patent Laid-Open No. 59-128271 described a material comprising from 50 to 95 percent by weight of a spinel having an approximate theoretical composition with a MgO:Al.sub.2 O.sub.3 molar ratio of from 0.8:1.2 to 1.1:0.9 and the balance being substantially Al.sub.2 O.sub.3 ; Japanese Patent Laid-Open No. 60-60985 described a material comprising at least 60 parts by weight of a spinel clinker having a theoretical composition, from 10 to 35 parts by weight of an alumina clinker and from 3 to 10 parts by weight of an alumina cement. Also, Japanese Patent Laid-Open No. 64-87577 described a material having good slag penetration resistance comprised of from 5 to 40 percent by weight of a spinel having an approximate theoretical composition with a MgO:Al.sub.2 O.sub.3 molar ratio of from 0.7:1.3 to 1.3:0.7, from 50 to 90 percent by weight of an alumina clinker and from 3 to 25 percent by weight of an alumina cement.
PROBLEMS THE INVENTION AIMS TO SOLVE
However, although it was found that if spinel or magnesia is added to said materials, the structural spalling and corrosion resistance in said materials are improved by inhibiting slag penetration in comparison with conventional high-alumina refractories, their effect in regards to slag penetration is less than that of Roseki and zircon refractories.
For example when a conventional spinel clinker with a MgO:Al.sub.2 O.sub.3 molar ratio close to the theoretical composition is used alone in an alumina-spinel type monolithic refractory as can be seen from the results shown in FIG. 2 of the corrosion test of an alumina-spinel type monolithic refractory using sintered spinel A having an almost theoretical composition with a MgO:Al.sub.2 O.sub.3 molar ratio of 1.02:0.98, there is a problem when the spinel clinker passes 40 percent in that it becomes easier for structural spalling to occur, because the slag penetration become large, even though corrosion resistance is increased.
Also, there have been various reports concerning the mechanism of inhibiting slag penetration and they describe
REFERENCES:
patent: 4780434 (1988-10-01), Watanabe et al.
patent: 4990475 (1991-02-01), Matsumoto et al.
patent: 5135896 (1992-08-01), Vezza
Database WPIL, AN 84-217067, JP-A-59 128 271, Jul. 24, 1984.
Patent Abstracts of Japan, vol. 15, No. 474 (C-890), Dec. 3, 1991, JP-A-32 05 368, Sep. 6, 1991.
Hamazaki Yoshihisa
Kaneshige Toshihiko
Kubota Yukitoshi
Nanba Makoto
Yamamura Takashi
Bell Mark L.
Sample David R.
Shinagawa Refractories Co. Ltd.
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