CS208916B1 - Oven for melting or remelting of glass - Google Patents

Description

The invention relates to a furnace for melting or remelting glass, in particular a furnace for drawing glass fibers.

Melting and remelting furnaces, in particular intended for drawing glass fibers, have so far been predominantly made of platinum, since this is considered to be a completely neutral metal with respect to glass. Glass fiber drawing glass, in particular boron-added glass having a melting temperature above 1400 ° C, must be maintained at a temperature of about 1500 ° C for drawing glass fibers and extremely stressing the platinum furnace both thermally and mechanically. Considering that the platinum melting temperature is about 1770 ° C, the difference between this temperature and the glass holding temperature of 1500 ° C is not great and the failure of platinum in this case is more than understandable. Taking into account that roughly, at half the absolute melting temperature, the strength of all metals is approximately the same and decreases with increasing temperature, until at the absolute melting temperature it drops to zero, the failure of platinum is even clearer. Other platinum group metals of higher melting temperatures, such as iridium or osmium, are even more deficient and more expensive than platinum.

Metals whose melting temperature is considerably higher than the holding temperature of the glass, and which at these temperatures would be neutral to the glass and would not degrade the glass, are not many. These include, but are not limited to, refractory metals such as molybdenum with a melting temperature of 2620 ° C or tungsten with a melting temperature of 3370 ° C, and possibly other refractory metals with higher melting temperatures and which do not adversely affect the molten glass. However, they have a number of other disadvantages, in particular the high oxidisability, which is so disastrous for some of these metals that they practically disintegrate at higher temperatures in contact with the air.

The invention overcomes all of these disadvantages, the essence of which is that these refractory metals are clad with a thin sheet, in the order of tenths of a millimeter, with a platinum group metal, platinum or an alloy thereof, and preferably explosively. Thus, when a refractory furnace is used for a metal of the refractory metal group, it is provided with a continuous and continuous layer of metal of the platinum group and, on the other hand, with a protective layer which would also prevent oxidation of the refractory metal. Such protective coatings include fused corundum, fused zirconium silicate and some similar ceramics which, in order to be completely and continuously applied and to protect the refractory metal perfectly, are best applied by a plasma torch.

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With respect to the calibrated nozzles in the bottom of such a furnace necessary for drawing the fiber itself, nozzles made in the usual manner from a metal or metals of the platinum group are used and inserted into the newly produced bottom.

The advantage of this new solution is that platinum is not used to produce such a melting or remelting furnace, which at the desired temperatures is almost at its breaking strength, but some of the refractory metals which still exhibit considerable strength at these temperatures. Since these refractory metals are more than 100 times or 200 times cheaper, the purchase and maintenance costs of these furnaces are also significantly reduced.

Claims (1)

SUBJECT Glass melting or remelting furnace, in particular for drawing glass fibers, consisting of a bottom, walls and lid, characterized in that the walls and lid consist of a refractory metal of the group consisting of molybdenum and tungsten, being explosively clad on the inside with a layer of metal groups of platinum metals or their alloys having a thickness of 0,1 to 1 mm and, on the outside, coated on their surface with a continuous and continuous coating of a thickness Exemplary embodiment Important parts of the remelting furnace were made, namely wall, lid and bottom parts, made of 1 mm thick molybdenum, on which an 0.1 mm thin platinum sheet was explosively applied. Platinum-rhodium alloy nozzles were embedded in a portion of the bottom, equally made. These parts were subjected to the same stresses and conditions as they would with a real remelting furnace (molten glass with boron, interface of this glass and air). These parts were thus stressed for over 9 months without any damage, at least as much as today's remelting furnaces. Molybdenum, however, is not as deficient as platinum and moreover is 100 to 200 times cheaper than platinum. OF THE INVENTION at least 0.2 mm of at least one high-melting mass of the group consisting of fused corundum, fused silicide and aluminum silicide, and the furnace bottom consists of molybdenum and tungsten refractory metal clad on both sides with a platinum group metal holes for inserting calibrated metal nozzles from the platinum group.