| 摘要 |
#CMT# #/CMT# Ceramic surface for a casting mold comprises a layer (I) of (a) polymerized product infiltrated and/or diffused into a base material, (b) a structural part of alumina, silica, titania and/or zirconia in a 80-200 nm fraction and (c) a polymer comprising polymerized monoaluminum, monozinc, monomagnesium, sodium and/or boron phosphate, enclosing at least some of the primary, structural and sliding parts. #CMT# : #/CMT# Independent claims are included for: (a) a separating composition (A) for the production of a ceramic surface layer (I) as above, formed from completely demineralized water and containing (i) an acid former in the form of sodium hydroxide, potassium hydroxide and/or aluminum chloride, (ii) a phosphate-containing binder in the form of monoaluminum, monozinc, magnesium, manganese and/or boron phosphate, (iii) a structural part in the form of alumina and/or silica as 80-200 nm fraction and (iv) an organic dispersant; and (b) a method for forming a layer on a ceramic surface, involving applying (A) to the surface and heating the surface to 200[deg]C or more to cause chemical bonding of the phosphate with the ceramic and polymerization of the binder. #CMT#USE : #/CMT# Ceramic surface is specifically a surface outside the contour producing region of a casting mold (preferably a low pressure casting or gravity casting mold) to be contacted with liquid or flowable aluminum material, especially where the ceramic surface is of alumina, aluminum-titanium, silicon nitride or silicon carbide (all claimed). More generally the layers (I) are useful for protecting ceramic surfaces of molds for casting non-ferrous metals (especially aluminum) by minimizing the surface activity and increasing the thermal shock resistance. (I) is typically applied to the rising tube, channel or casting vessel regions. #CMT#ADVANTAGE : #/CMT# The layers (I) show good long term stability and high elasticity, have good sliding properties, do not adversely affect the quality of the casting and show good adhesion to the surface. The (I)-producing composition (A) is inexpensive to produce from non-toxic starting materials, and easy to apply without special apparatus (e.g. by spraying). Damage to (I) can be repaired by further application of (A) (claimed). #CMT#CERAMICS AND GLASS : #/CMT# Preferred Materials: (I) additionally contains sliding parts of boron nitride, magnesium aluminum silicate and/or molybdenum disulfide, as a 2-15 mu m fraction; and primary parts of alumina, zinc oxide, titania, zirconia and/or ceria in a 80-200 nm fraction, mounted in the cavities between the structural parts. (I) has a thickness of 1-80 (preferably 25-80) mu m. (A) also contains sliding parts and primary parts as above. (A) is adjusted to pH 4-5 with the acid former, and preferably contains the binder at 5 wt. % or less, the structural parts at 10 wt. % or less, the primary parts at not more than 3 (especially 1-3) wt. % and fines at 5 wt. % or less. |
