Abstract The instant invention is concerned with a unique method for crystallizing glass bodies into glass-ceramic articles. More particularly, this invention is drawn to a method whereby glass-ceramic articles can be formed without cooling the precursor glass below the transformation range thereof. Thus, the glass melt is cooled and formed into a vitreous body. This vitreous body is cooled to a temperature no lower than about 25°-250° C. above the transformation range where nucleation is developed therewithin. Essentially immediately thereafter, the nucleated body is exposed to a temperature between about 100°-500° C. higher than that of the nucleation step to cause the growth of crystals on the nuclei. The process significantly expedites the production of glass-ceramic articles and substantially reduces energy consumption from the forming stage to the finished product.
A method for making a fine-grained glass-ceramic article comprising the steps of: a. melting a batch for a thermally crystallizable glass; b. cooling the melt to a temperature between about 25°-250° C. above the transformation range to form a glass body and holding said glass body within that range of temperatures for about 1-30 minutes to develop nuclei therein; c. heating the nucleated glass body at a rate of at least 10° C./minute to a temperature about 100°-500° C. above the nucleation temperature and holding said nucleated glass body within that range of temperatures for about 1-30 minutes to cause the growth of crystals on the nuclei; d. cooling the crystallized body to room temperature.
Claim 2
Independent Claim
115 words
A method for making a fine-grained glass-ceramic article comprising the steps of: a. melting a batch for a thermally crystallizable glass; b. cooling the melt to a temperature between about 25°-250° C. above the transformation range to form a glass body and holding said glass body within that range of temperatures for about 1-30 minutes to develop nuclei therein; c. heating the nucleated glass body at a rate of at least 10° C./minute to a temperature about 100°-500° C. above the nucleation temperature and holding said nucleated glass body within that range of temperatures for about 1-30 minutes to cause the growth of crystals on the nuclei; d. cooling the crystallized body to room temperature.
Claim 3
Dependent Claim
16 words
A method according to claim 1 wherein said nucleation is carried out for about 1-5 minutes.
Claim 4
Dependent Claim
16 words
A method according to claim 1 wherein said crystallization is carried out for about 1-5 minutes.
Claim 5
Dependent Claim
18 words
A method according to claim 1 wherein said crystallization is carried out at temperatures between about 900°-1250° C.
Claim 6
Dependent Claim
22 words
A method according to claim 1 wherein said crystallization is carried out in an atmosphere containing SO 2 and/or SO 3 .
Claim 7
Dependent Claim
21 words
A method according to claim 1 wherein said crystallized body is quickly chilled to room temperature to thermally temper said body.