JPH046659B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to crystallized glass mainly used as an industrial material and a method for producing the same. Crystallized glass, which is generally used as an industrial material for precision parts and insulating materials, is produced by melting the glass uniformly and then forming it into a desired shape using glass forming methods such as pressing, blowing, casting, or roll plate making. Heat treatment is performed at a temperature range where crystallization progresses to create a structure in which crystals are dispersed in the glass matrix. Conventional crystallized glass shrinks during the crystallization process, resulting in poor dimensional accuracy, and chipping and cracking occur when cutting, polishing, etc. are performed after crystallization, resulting in significantly lower strength. This makes it difficult to apply to precision parts or parts requiring post-processing. The present invention solves the above-mentioned drawbacks and at the same time provides a crystallized glass having various excellent properties as an industrial material and a method for easily producing the same. The crystallized glass of the present invention contains at least 90% by weight of SiO ₂ 41-56%, CaO 26-50%,
It has a composition consisting of 1 to 8% P ₂ O ₅ and 1 to 18.5% MgO, and is characterized by having a structure in which many dense crystals are dispersed in the glass. In addition, in the method for producing crystallized glass of the present invention, after molding the glass powder having the above composition and a particle size of 200 mesh or less, a dense preform is prepared by press molding into a desired shape, and then the glass powder is heated in the glass powder crystallization temperature range. It is characterized by heating and then heat treatment in a crystal precipitation temperature range. The crystallized glass products manufactured in this way have a dense structure with no voids, and the crystals are complex because the crystals form and grow inside the square powder particles and also grow inward from the surface of the powder particles. It becomes an intertwined crystal structure. As a result, it is possible to obtain crystallized glass which has high strength, does not chip or crack even when subjected to processing such as cutting, polishing, cutting, etc., and has good mechanical workability without causing a decrease in strength. In the present invention, the dense crystals in the crystallized glass are needle-like crystals of wollastonite and diopsite, and both have a complex intertwined structure and have the effect of increasing the mechanical strength of the crystallized glass. In addition, a small amount of very fine apatite crystals are precipitated in a form that fills the surfaces and gaps of the needle-like crystals. Due to the interaction of these three crystals, a crystallized glass with higher mechanical strength and good machinability without chipping or chipping during cutting or polishing steps can be obtained. The reason why the composition range of the crystallized glass of the present invention is limited as described above is as follows. When SiO ₂ is less than 41%, the chemical durability and mechanical strength of the glass decrease. If it is more than 56%, it becomes difficult to melt the glass, and at the same time, the precipitated crystal particles become large and the mechanical strength becomes low.
Machinability also deteriorates. When P ₂ O ₅ is less than 1%, the precipitated crystal particles are large and only needle-shaped crystals are formed, resulting in poor machinability. When the amount is more than 8%, the chemical durability of the glass becomes low. If CaO is less than 26%, the crystallinity will be low, the mechanical strength will be low, and the machinability will be poor. When the amount is more than 50%, devitrification becomes high and vitrification becomes difficult. If MgO is less than 1%, the viscosity of the molten glass will be high and uniform melting will be difficult. If it is more than 18.5%, the crystallization rate will be slow and the crystallinity,
Mechanical strength is low and machinability is poor. Furthermore, in addition to the above composition, an amount of less than 10%
BaO _, SrO, _ZnO , _B2O3 , _Al2O3 , _TiO2 , _ZrO2 ,
It is possible to contain one or more of Nb ₂ O ₃ , Ta ₂ O ₅ , and CaF ₂ . However, if the total amount of these additional components is more than 10%, it is not preferable because the amount and type of precipitated crystals may change or the mechanical strength and machinability may decrease. Note that alkaline components such as Li ₂ O, Na ₂ O, and K ₂ O are not preferred in terms of chemical stability, so no alkali components are included. In the method for producing crystallized glass of the present invention,
Uniformly molten glass is turned into a powder of 200 mesh or less using a grinder such as a ball mill, which is then press-formed into a predetermined shape, heated in a glass powder sintering temperature range, and then heat-treated in a crystal precipitation temperature range. It is characterized by The former heat treatment is important for obtaining crystallized glass with low porosity and high mechanical strength, and the latter heat treatment is important for precipitating a large number of dense wollastonite and diopsite crystals from the glass. . Converting glass into powder with a particle size of 200 mesh or less is an important condition in order to obtain, through heat treatment, crystallized glass with few pores and in which wollastonite and diopsite crystals are uniformly precipitated in fine particles. When molten glass is directly molded into a predetermined shape and then heat-treated, wollastonite crystals precipitate only from the glass surface, resulting in crystals with low mechanical strength and cracks inside. Only chemical glass can be obtained. The glass powder sintering temperature range is a temperature range from a thermal contraction start temperature to a thermal contraction termination temperature, and is determined by heating a glass powder compact at a constant rate and measuring the thermal contraction during that period. The crystal precipitation temperature range is the humidity range from the start temperature of heat generation due to crystal precipitation to the end temperature, and is determined by heating the glass powder at a constant rate and performing differential thermal analysis during that time. Examples of the glasses of the present invention are shown in Table 1 below.

【table】

[Table] The glass samples of the examples shown in Table 1 above were prepared as follows. A batch of raw materials prepared to have the glass composition of the example was placed in a platinum crucible and heated in an electric furnace.
Melt at 1400-1500°C for 4 hours. Next, the molten glass is poured between water-cooled rollers to form a ribbon-like glass, which is then crushed into a powder with a flow rate of 200 mesh or less. After these powders are isostatically pressed into a predetermined shape, they are heated in an electric furnace from room temperature to 1050℃ for 30 to 1000℃.
Heat at a rate of 60℃/hr, hold at 1050℃ for 2-10 hours to sinter and crystallize, and heat to room temperature at 30-120℃/hr.
Cool at hr.

【table】

[Table] Table 2 above compares the physical properties of the crystallized glass No. 2 in Table 1 with conventional glass ceramics that have good machinability. No. 2 crystallized glass is
The strength is more than double that of glass ceramic, the volume resistance is 3 to 5 orders of magnitude higher, and it exhibits excellent electrical insulation properties. As described above, the crystallized glass of the present invention exhibits good mechanical strength, machinability, excellent electrical insulation, and excellent dielectric properties as an industrial material, and therefore is useful in fields where these properties are required. be. Furthermore, the crystallized glass of the present invention can be used as an artificial bone and dental material because it causes a chemical bond between the crystallized glass and bone and also precipitates apatite crystals that improve biocompatibility, although in small amounts. It is also possible to use

Claims (1)

[Claims] 1. At least 90% by weight is SiO ₂ 41
~56%, CaO26~50%, _{P2O5 1} ~8%, MgO1~
A crystallized glass characterized by having a composition of 18.5% and 10% or less of impurities, and having a structure in which many dense crystals are dispersed in the glass. 2 BaO, SrO, ZnO, B ₂ O ₃ , Al ₂ O ₃ , TiO ₂ ,
The crystallized glass according to claim 1, which contains 10% by weight or less of any one or more of ZrO ₂ , Nb ₂ O ₃ , Ta ₂ O ₅ , and CaF ₂ . 3 At least 90% by weight is SiO ₂ 41
~56%, CaO26~50%, _{P2O5 1} ~8%, MgO1~
A method for producing crystallized glass, which comprises forming glass powder having a composition of 18.5% and having a particle size of 200 mesh or less, heating it in a glass powder sintering temperature range, and then heat-treating it in a crystal precipitation temperature range.