DE2026071C3 - Two-stage process for the production of a crystalline glass object with parts of different crystalline dimensions and thus different transparency - Google Patents

Description

This is achieved by

1. a transparent, nicbt-Jcristallinen, however crystallizable glass object at temperatures of 800 to 960 ° C so heat-treated that under Maintaining the transparency devitrification takes place, and that

2. Parts of the glass object are cooled, while the object is ^{subjected to a further heat treatment at temperatures of 970 to 1150 °} C. in order to continue devitrification in the uncooled parts.

The cooling treatment, which is an essential feature of the invention and possibly also repeated application can be carried out by placing a cooling tube in the vicinity of the molded body or is brought into contact with the shaped body, or by blowing cold air onto the shaped body will.

When the transparent, non-crystallized, but crystallizable glass is heat-treated at 800 to 960 ° C., a crystallized, transparent glass plate is first obtained. The temperature range used must be precisely adhered to in order to result in a low coefficient of linear thermal expansion of about + 6 · 10 ⁷ cm / cm ⁰ C. The crystallized transparent glass thus obtained is then cooled in one part and then converted in this part into a white crystalline glass with a low coefficient of thermal expansion by means of the second heat treatment at a temperature of 970 to 1150 ° C. The overall glass article thus obtained has a low coefficient of linear thermal expansion and high heat resistance as a whole.

It was found that, depending on the heat treatment temperature, changes in the specific Weight occur, but the coefficient of thermal expansion is calculated from the coefficient of linear thermal expansion, hardly changes.

The change in specific gravity is due to the change in volume. When a Glass object subjected to a heat treatment at different temperatures in one part is, while no such heat treatment is carried out in the remaining part, takes place Change in volume takes place, which leads to tension. In the case of the glass objects according to the invention however, the change in specific gravity is 1.2% or less, resulting in no harmful Leads to tension.

If according to the invention a lid for incinerators is made, a transparent part in the form of a pattern is expediently on the lid made of the white crystalline glass formed or other different effects may be provided on the white crystalline glass will.

The invention can also be applied to the manufacture of electrical heating devices. If z. B. an electric heater is used, which consists of a tube of a transparent crystalline glass and a ribbon-like electrical wire inserted therein and the temperature of the electric wire is increased above 800 ° C, crystallization proceeds at the contact points between the electrical heating wire and the transparent crystalline Glass tube, causing the parts to become cloudy and eventually break. On the other hand, if the see-through crystalline glass tube according to the invention is produced so that only these parts are white Form crystalline glass, the difficulties listed above can be eliminated.

In the examples below, a non-crystallized Transparent crystallizable flat glass with the composition given below used.

Weight per:.-Nt

SiO ₂ 70.0

AhO ₃ 19.0

Li ₂ O 2.6

MgO 2.0

ZnO 1.7

ZrO ₂ 2.0

TiO ₂ 1.7

^ao SbO ₃ 0.5

AS ₂ Q ₃ 0.5

example 1

A non-crystallized transparent crystallizable one Flat glass was heat treated for about 2 hours at 800 to 960 ° C, with the entire Vitreous became transparent. A disc-shaped

Entire water cooling member was brought near or in contact with a desired part, while the remaining parts of the glass were kept ^{at temperatures of 970 to 115O 0 C for about 2 to 3 hours.}

Through these treatments, a white crystalline glass plate with a round transparent one became Part formed. If the glass plate obtained in this way is used as a cover for a gas heater was used, could the state of the flame

or the combustion in the gas heating device can be observed directly, creating complicated control devices became unnecessary. When a large number of small disk-like cooling members at Using the procedure described above, a dotted transparent pattern was obtained Preserved on the white crystalline glass plate.

Example 2

A non-crystallized, transparently crystallizable Glass plate was heat-treated for about 2 hours at 800 to 960 ° C, with the entire Glass plate became transparent. An annular one

The cooling element was placed near or in contact with the crystalline glass at the desired location, while the entire glass plate at a temperature of 970 to 1150 ° C for about 2 to Was held for 3 hours, causing a white

stable glass plate with a local transparent ring-like part was obtained.

When the crystalline glass plate was used as a lid for a gas heater, the state could the flame can be observed directly here, so that the use of complicated control devices became superfluous. In this case, if some annular cooling links have been used, a decorative pattern was obtained.

Eg game 3

A non-crystallized, transparently crystallizable Glass plate was heat-treated at 800 to 960 ° C for about 2 hours, with the entire Transparent glass plate wurtb. A number of band-shaped cooling links were brought near or in contact with the crystalline glass plate, while the remaining parts were held for about 2 to 3 hours at 970 to 1150 ° C, wherein a white crystalline glass plate with a transparent stripe pattern was obtained. In this In this case it is beneficial to make the ends of the transparent ribbons white.

When the crystalline glass plate thus prepared was used as a lid for a gas heater, it became possible to directly observe the state of the flame therein, and the use of complicated control devices became unnecessary. In addition, it is also sufficient to provide only one transparent band.

Example 4

A non-crystallized, transparently crystallized as cash. Glass tube was heat-treated at 800 to 960 ° C for about 2 hours, with the whole Glass tube became transparent. Two ribbon-shaped water cooling members were in proximity or in contact with the outer surface of the glass tube along the lengthwise direction on the opposite sides thereof while the other parts are kept at 970 to 1150 ° C for about 2 to 3 hours were, taking a crystalline clear glass tube with white parts in the longitudinal direction on the opposite Pages of the same was obtained. In this case it is favorable that the ends of the transparent parts are made white.

A ribbon-shaped electric wire was formed into a wave shape and inserted into the glass tube so as to that the upper and lower end parts of the corrugated tape are in contact with the white parts of the glass tube were brought. When the temperature of the electric wire has been raised above 800 ° C, the crystalline glass did not change, nor did it break

According to the above examples, the cooling treatment was carried out using water cooling devices, but air can also be used as a coolant. Furthermore, the transparent crystallization treatment was carried out at 800 to 960 ° C. for about 2 hours, but the glass can also be heat-treated at temperatures above 1000 ° C. according to the composition of the transparent crystallizable glass.

Claims (2)

zone shows a complete combustion or claim: not. In the following, a two-step process for the process for the production of a crystalline production of a crystalline glass object is proposed with parts of different 5, with the aid of which the difficulties of over-crystalline dimensions and associated with it are not overcome. . Numerous processes are already known for the production of a two-stage heat treatment of crystalline glasses, and these can be subjected to, thereby generally summarized as follows 1. A transparent, non-crystalline, each-contained, be thoroughly mixed and then put in but crystallizable glass object at temperature - a melting furnace with heating for vitrification Temperatures of 800 to 960 ° C so heat-treated components are melted. The melt is delt, that while maintaining the transparency forms, for example by compression molding, blow molding Devitrification takes place, and that 15 mung, tube forming or rolling, and the molding 2. Parts of the glass object are cooled, then by renewed heat treatment and while the object is crystallized to continue the subsequent cooling.
Devitrification in the uncooled parts of a white In French Patent 15 21393 are direct heat treatment at temperatures of partially devitrified glass objects and a process 970 to 1150 ⁰ C is subjected. »O _r s are described for their production. These glass objects have transparent parts that are not are crystallized, as well as crystallized parts. The physical However, the properties of these glass objects are insufficient with regard to the requirements The invention relates to a method for ^a 5 gene, which must be met when used as a viewing window in the incineration of a crystalline glass object with voltage devices.
Parts of different crystalline dimensions U.S. Patent 23 39 975 describes a and associated with it different transparency, process for the production of glass objects with being the glass object of a two-stage heat - an integral opaque pattern, being a glass that treatment is subjected. 30 can be clouded by the action of heat, with When attempting to remove exhaust gases of such a composition is melted, eus combustion systems are generally used to separate the germs of the turbidity inclusions Exhaust gas discharge passage or a wall to prevent temperature areas arise and grow, with cation of exhaust gas diffusion applied; for observing the germ formation area under the inclusion observation the combustion flame serves a growth area in the vicinity of 35. The melt becomes the viewing window located near the combustion zone and forming the glass article, and the molded case, however has the disadvantage that the object to be observed, which is still at temperatures above the direction of the combustion flame to a very narrow nucleation area is partially in Area is limited. According to the desired pattern Furthermore, a combustion indicator or 40 is a temperature within the nucleation flame indicator known, in which the combina- tion is cooled, whereupon the cooled area again tion of a transparent ceramic rod, with a template in the crystal growth area a glass rod, a quartz glass rod or temperature is heated to the growth of the germs a crystalline glass rod, and an oxidation-causing. permanent metal is applied. That of the oxy- 45 Here, glass objects are obtained, the parts dation-resistant metal when red-heated with relatively large crystals and crystal-free Teidie Combustion flame emitted light is obtained by len, the former being obtained by cooling observed the clear ceramic rod. Ob- became transparent while the uncooled parts but are probably such a combustion indicator. or flame inducer can be effective in cases, 50 The glass objects obtained in this way only meet the observation of the occurrence of deterioration. a temperature expansion to be carried out when used as a viewing window, whereby in this case it must not be placed in combustion zones,
It is possible to detect the state of combustion in the gas. The object of the invention is therefore to create a method for producing a crystalline combustion indicator by means of the above-mentioned type of a method for producing a crystalline combustion indicator which only indicates the occurrence of combustion in a glass object with parts of different types. crystalline dimensions and the associated under- In addition, a process of different transparency, with the cloudy parts suggested, in which the combination of a 60 an equally good mechanical strength and comparative combustion indicator and a photoelectric EIe- bar low thermal expansion like the transparenments is applied, where the light from the th parts and where the opaque parts have the Combustion indicator due to the photoelectric dazzling effect from the flames in the seated element is caught, which then prevent in an activity lender way. In particular, the steps to control the gas burner valve. A 65 invention to provide an improved crystalline type However, the method has a more complicated glass, which can be used, for example, as a mechanism and, in addition, it is difficult to use lidding material in incinerators recognize whether the internal state is the combustion net.