FI91060B - A tool for making glass - Google Patents

Description

91060

Glass lighting tool - Ett Verktyg vid 5 framställning av glas

The invention relates to a tool for use in glass production, such as a glass mold, press or the like, in which at least some of the surfaces of the tool have a surface layer obtained by thermal spraying, such as plasma, detonation spraying or hypersonic flame spraying, or by sputtering or other suitable coating method part or all of the tool is made by any suitable method from the same material as the surface layer, and the surface layer of the tool consists essentially of at least one intermetallic compound.

20 In series production, for example, glass packages, such as bottles, the molten glass mass is formed into a product using a suitable mold in which the mass is formed by the combined action of either a mandrel or gas pressure and vacuum and solidifies into the resulting shape. The pulp shaping process 25 may include several work steps. During the first stages of work, the molten glass mass must move on the surface of the mold, whereby the frictional forces between the glass mass and the mold determine the quality of the product. High frictional forces indicate solidification events at different times in different parts of the mold, resulting in corrugation and microcracks in the glass.

In principle, the problem can be reduced by raising the temperature of the molten glass mass, thereby reducing its viscosity and improving its flowability. However, there is a problem with raising the mold temperature that at high temperatures the molten glass mass begins to adhere to the mold surface. Today, the temperature of the mold during glassmaking is about 500 ° C, which 2 allows the use of cast iron molds. To reduce friction and improve product quality, mold painting with graphite-based paint and mold lubrication with graphite grease are currently used. The painting lasts 5 to about 2-8 hours and lubrication must be performed about every 15 minutes. The use of lubrication is associated with a lot of smoke and noise nuisance. In the pursuit of high production rates, the transfer of heat from the molten glass mass to the mold and further to the cooling medium is also important. The high production rates required require that the "transfer resistance" associated with heat transfer at the interface between the molten mass and the mold be minimized.

15 Heat transfer in glass to cooling air The "narrowest gate" is the transfer of heat from the mold to the air. The resistance to heat inside the glass is relatively higher, but in the molding process the glass must remain in the molding viscosity until the final blowing. From the point of view of glass cooling 20, changing the mold material is not a very efficient operation. The thermal resistance at the interface between the glass and the mold is higher than in the mold itself. It is due to the surface roughness and the air trapped between the glass and the mold. Over time, heat transfer from glass to mold varies very strongly. 25 At the beginning of the contact, the heat transfer is very efficient, but slows down rapidly as the temperature difference decreases and when the heat conduction inside the glass limits the heat flow. The temperature of the outer surface of the mold, on the other hand, does not normally vary as a function of time. With ordinary packaging glass products, the thickness of the wall 30 is about 2-3 mm, regardless of the size of the package, and the ratio of the weight of the package to the outer surface area is also of the same order.

On the outer surface of the mold, the heat transfer takes place mainly through convection 35, i.e. the possibilities to increase the cooling associated with increasing the air flow rate or the heat transfer.

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91060 3 for increasing the top area by ribbing. Even more efficient cooling is obtained if water cooling or water mist cooling is used instead of air. However, this causes problems related to the rusting of molds and machines. These problems can also be overcome by selecting suitable materials for molds or by coating existing surfaces with suitable coatings, but such solutions require considerable investment.

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As the cooling capacity increases on the outer surface of the mold, it causes a greater temperature difference between the inner and outer surface of the mold.

If air cooling is used, the temperature of the outer surface of the mold does not decrease much and it means that the temperature of the inner surface 15 rises correspondingly. This can be avoided if the mold material is changed to be more thermally conductive. In this case, however, cost factors are again encountered.

Air pores remain between the mold and the glass, as has already been stated. How much air pores are left between the mold and the glass depends on the surface roughness, the contact temperature, the mold material and the properties of the glass. At the points of contact, heat is transferred by conduction and in the pores by radiation and conduction along the air. All forms of heat transfer are directly proportional to the heat transfer surface area, so a change in heat transfer surface area affects heat transfer.

If the most effective surface roughness in terms of heat transfer, about 20 μm, were introduced in the final mold, i.e. a surface roughly rough, it would cause a large number of microcracks in the surface of the product. It is therefore advisable to strive for the smoothest possible surface in the final mold, in which case a good heat transfer density is achieved and microcracks are minimized. Raising the contact temperature also improves heat transfer (the softer the glass fills the surface irregularities better) and at the same time the microcracks in the surface are reduced. At higher temperatures, the glass tends to adhere to the surface of the mold. The adhesion temperature is affected by the mold material, the viscosity of the glass, the roughness of the mold surface and the pressure that presses the glass against the mold.

5 The tendency of different mold materials to adhere depends on the surface tension of the material. The surface tensions of the metals are of the order of about 1.7 to 1.0 X 10- ^ N / cm. The surface roughness affects the adhesion through heat transfer, i.e. against a suitably rough surface the glass cools unevenly on its surface 10 and these cold spots prevent the glass from adhering to the mold. At the same time, however, they cause micro-cracks on the glass surface, as already mentioned earlier.

The object of the invention is to reduce and in part even eliminate the effects of the above-mentioned disadvantages and to be able to affect the cooling event of the part to be manufactured more effectively than at present.

The object of the invention is achieved by a tool characterized in that this intermetallic compound is characterized by an increase in strength values as a function of temperature from room temperature to at least 450 ° C.

As one started to map out the above-mentioned problems and at the same time find solutions to them, it was decided as a natural alternative that the tool materials be coated with a suitable coating or, in certain special applications, made either partially or completely from the coating material. When, at certain critical points 30, part or all of the tool is made of the same material as the coating used in, for example, other lighter parts, e.g., peeling and adhesion problems of the coating material can be avoided in these awkward places.

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91060 5

When evaluating different coatings, various ceramic coatings as well as superalloy coatings, which were widely used commercially, came to mind. Weaknesses of ceramic coatings are, for example, porosity and poor thermal conductivity. Poor thermal shock resistance also commonly plagues these coatings. The lack of easy or good machinability required of tools, and in particular the polishability of the mold surface, is also a downside to these coatings.

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Coatings made with various nickel or cobalt-based superalloys have given good or perhaps more accurately expected results. Thus, the properties of the final products did not give results that would have raised expectations for some clearly better tool in the manufacture of glass. Thus, coating alone did not offer an opportunity to solve the present problems.

20 Coating experiments also tested materials known per se, but relatively new as construction materials, namely various intermetallic compounds, which offered unexpected advantages. The use of intermetallic compounds as construction materials has not previously made sense due to the fragility that has plagued it. Only when the advantageous effect of certain alloying elements, such as boron, as a hardener was invented could intermetallic compounds be used as construction materials, i.e. both coatings and so-called bulk-pieces.

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In the experiments, it was surprisingly found that for certain intermetallic compounds, the adhesion temperature of the glass was quite high. Some intermetallic compounds are characterized by an increase in their strength values up to a certain limit when moving from room temperature to higher temperatures. For example, the hardness can increase up to 6-fold when moving from room temperature to 500 ° C. For certain intermetallic compounds, when suitably doped, strength values can increase up to temperatures of about 800 ° C.

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At room temperature, these modified compounds are relatively soft and thus easy to machine and polish, which are essential in selecting the mold material to be used in the manufacture of glass. As these are intermetallic compounds, it is clear that these materials are also characterized by good thermal conductivity. When the base material, most commonly cast iron, is coated with an intermetallic compound and the resulting surface is carefully polished, the formation of microcracks in the glass product can be significantly reduced. However, at certain critical points, it is necessary to be prepared that part of the tool, such as part of the mold or the entire mold, is made of the same material as the coating itself, but in bulk. In this case, the already mentioned risk of peeling or adhesion problems in the awkward parts of the tool 20 can be avoided. Due to the suitable surface material, i.e. whether this surface layer is obtained by coating or as part of the surface of the bulk article, the wall thicknesses of the glass products can be thickened and thus lighter products can be obtained which have the same strength as previous thicker wall strength products. When good machinability is also associated with an increase in the above-mentioned strength values and thus also hardness values, i.e. wear resistance, when moving from room temperature 30 to the operating temperature of the tool, e.g. 500-650 ° C, it is clear that such a material is excellently suitable as a glass material.

Suitable intermetallic compounds are those whose strength increases from room temperature to at least 450 ° C to 7,91060. The properties of these compounds can be improved by suitable doping, giving their toughness values. at room temperature are significantly improved and / or the increase in strength values can be continued up to a temperature of about 800 ° C. Such alloys include, for example, boron (improves room temperature toughness properties) and hafnium (continues to improve strength values at higher temperatures). Iron, titanium, manganese, zirconium, cerium and niobium are also used as alloys to improve the properties of these intermetallic compounds.

Good results have been obtained, for example, with various aluminides, such as titanium, zirconium, iron, cobalt or nickel aluminides. In particular, LI2 lattice ΝΪ3Α1, N13AI + B, Ni3 (Al + Mn) + B and CO3T1 as well as their modified forms and B2 type metal-to-metal compounds such as NiAl and its modified forms have proven to be good coating and surface materials. With these surface materials, the adhesion temperature of the glass could be increased from the typical value of 500-540 ° C for optimal cast iron to 600-630 ° C.

Coatings can be prepared by a variety of methods, such as plasma, detonation spraying, or hypersonic flame spraying, or by sputtering or other suitable coating methods. Various known methods can also be used in the manufacture of bulk goods.

The solution according to the invention can be applied within the scope of the inventive idea defined by the appended claims.

Claims (6)

A tool for use in the manufacture of glass, such as a glass mold, press or the like, wherein at least some of the surfaces of the tool have a surface layer obtained by thermal spraying, such as plasma, detonation spraying or hypersonic flame spraying, or by sputtering or other suitable coating method. or wherein part or all of the tool 10 is made by a suitable method from the same material as the surface layer, and the tool surface layer consists essentially of at least one intermetallic compound, characterized in that this intermetallic compound is characterized by an increase in strength values as a function of temperature from at least 450 ° Up to C temperature. Tool according to Claim 1, characterized in that the surface layer consists essentially of an intermetallic compound 20, characterized by an increase in hardness values as a function of temperature from room temperature to a temperature of at least 450 ° C. Tool according to Claim 1 or 2, characterized in that the surface layer consists essentially of an aluminum-based intermetallic compound, such as, for example, titanium, zirconium, iron, cobalt or nickel aluminide. Tool according to Claim 1 or 2, characterized in that the surface layer consists essentially of an intermetallic compound of the type N13 (Al + Mn) + B. II 35 91060 t Tool according to Claim 1 or 2, characterized in that the surface layer consists essentially of an intermetallic compound of the type N13AI + B. 5 Tool according to Claim 1 or 2, characterized in that the surface layer consists essentially of an intermetallic compound of the Co3Ti type.