Founding corundum brick (RA-A) corundum namely α Al2O3, rhombohedron or board shape crystallization, true density 3000~4000kg/m3, melting point 2050 ℃ , mohs hardness 9, the systole when it is crystal 25% , apparent pore leads 10%-12% , bulk density 3000-3300KG/m3, especially the A-Al2O3 after crystallization, form a kind of faint microstructure tubal account, without vitreous photograph.
Because do not have vitreous photograph, the heatproof shake sex of its goods is very so poor, improvement way is to increase 5% β - A2O3, can make its bulk density is added to 3300~3500kg/m, or join density of 5% metals aluminous bulk to be able to be added to 3800kg/m3, its defect is thermal stability difference not only, and easy cause defect of glass of stripe whorl shape, apply to boracic silicon only so qualitative glass and kiln of high temperature channel are firing belt, the build by laying bricks or stones of the liner of furnace of black lead roast and nonferrous metal smelting furnace is built etc.
Recipe design and raw material choose
Founding corundum brick (RA-A): ? If introduce oxidation boron, press and smooth fears Huan? by an old name for Japan (B2O2)0.25%-1% , industrial alumina Al2O3 is less than 98.5% .
The workmanship of founding corundum goods and craft of brick of founding zirconium corundum are very much the same, its difference is:
Pouring temperature is high, 1960~2400 ℃ , the rising head bulk with pouring PT fills for the 20% beards of cast irrigate.
Mould should use black lead board model (sectional temperature difference is more than 1000 ℃ ) or corundum sand mold, metallic water-cooling (inside Tu Bao protects an aluminous oxygen or lime to wait) mark systole puts feet to make an appointment with 2%;
Drawing of patterns enters heat preservation case, annealing temperature is high, the heat preservation function of box of requirement heat preservation relatively AZS is better. It is to prevent craze not only, more important is to prevent product interior to crystallize not compact;
Give box product treatment, precision of treatment of requirement plane curved surface is tall, bright and clean degree tall.
Anneal of fused mould, heat preservation
(The electric arc of 1) oxidation melt cannot grow in that way like fusion AZS, because of voltage on the high side when, cast density can be reduced, next due flue gas removes dust ventilated, create atmosphere of the oxidation inside furnace.
(The temperature control of anneal of 2) heat preservation is very important, matter to the crackle of the product, after normally ARA2O irrigates infuse model, composition of modular wall incrustation is ABA2O3, and more to the center, criterion Na2O to shrinkage cavity center migratory, those who form AAl2O3 and Na2O(9-11)A2Q is inhomogenous distributing, bring about goods pole easy craze.
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