DE2406856A1 - PROCESS FOR THE MANUFACTURING OF FIRE-RESISTANT COVERS FOR CONTAINERS - Google Patents

Description

Process for the production of refractory coatings for

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container

The invention relates to a method for producing refractory coatings for containers such as ladles, crucibles, Ovens, etc.

It is already known that inner coatings are based on of silicon dioxide are often used in containers designed to hold cast iron or molten steel and therefore withstand large thermal shock effects have to. Such coatings allow the containers to cool down quickly without significant cracks occurring.

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A procedure for producing refractory coatings based on silicon dioxide or quartz is already known. This working process is only used in electric induction furnaces and uses naturally pure silicon dioxide (99% silicon dioxide) or quartzite as the starting material. Such a broken or crushed one

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Quartzite is introduced into the / vessel / and m the circular space between the inner wall of the container to be coated and an inner region and to

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attached to the container coaxial metal mold / and the inner cavity limited by this. Such a shape is then shaken or tamped down to ensure the dry compaction of the Ensure quartzites. The quartzite mass is then solidified by sintering from the heat release generated by in This metal form induced Foucalt * see currents, developed will. Such a shape disappears the first time it is exposed to the oven, as it cannot be withdrawn beforehand, because the coating is then not yet sufficiently solidified. In the case of a coating obtained in this way, the silicon dioxide changes into its allotropic forms, tridymite and crystallite um, which allows the coating to reach a melting point of the order of 1770 ° C, which is sufficient for the Melting of iron and steel becomes possible.

This procedure shows considerable disadvantages. Initially, it can only be carried out in induction ovens, as it is necessary is to warm up the internal mold by means of electrical induction. In addition, the form disappears with the first one Application so that the cost price of the coating is increased by the price of the mold. In most cases this will result in the Cost price doubled.

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In order to avoid these disadvantages, a procedure has already been developed proposed in which a moist material based on quartzite and various additives in the Bottom of the container. And in the annular space introduces the between the inner wall of the container and a removable, concentrically arranged in the container and its inner space limiting inner shape was formed, wherein the material was then vibrated, dried and fired will.

Carrying out such a procedure gives excellent results Results, especially for coatings for pouring ladles, crucibles, etc. However, it has a disadvantage concerning their application to electric ovens. The coating contains water that is released when the Oven moves to the cold parts of the oven and could cause condensation on the electrical coils, which creates the risk of electrical flashovers could be. In French patent application 72.04835 a procedure is described by the applicants, whereby it is possible that contained in such a material To greatly reduce the amount of water. Even with such a procedure there is the hazard described above however continued.

The invention overcomes the disadvantages of these two modes of operation described above. It enables the production of silicon-containing products Coatings of comparable quality to those obtained by the aforementioned methods, with the security is completely given for any container and especially electric ovens.

The method according to the invention for the production of refractory, inner coatings for containers such as ladles, electric melting furnaces or analog devices, one being a material on

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Quartzite based on the. The bottom of this container and introduces into the annular gap which is formed between its inner wall and a removable inner shape which is concentric to this container and delimits its inner cavity, and wherein the material is then compacted or compressed and fired, is characterized by: that this material except quartzite from 0.5 "to 1.5 wt .- ^ contains at least one thermosetting substance, such as a formaldehyde-phenolic resin, and that this material, after compacting, is preheated to a temperature between 10O ⁰ C. and 280 ° C., after which the mold is removed and the material is fired The duration of a safe preheating can of course be varied depending on the thickness of the coating, but without exceeding two hours by the mechanical Maintain properties of the thermosetting substance.

The compaction of the material becomes dry carried out, wherein the density of a coating finished according to the invention is greater than 2.2, this means one Porosity of only 9 to 10 #. Thanks to preheating made possible the thermosetting material the .Sicherungs a sufficient mechanical strength in the compacted Material that prevents it from disintegrating during or after demolding or dismantling of this mold.

To make it easier to remove the inner mold from the mold, it can be made removable in the form of a single piece or dismantled in several parts. Their outer surface, which is in contact with the material described above, is said to have adhesion preventive protective means, e.g. with a silicone resin. It can be advantageous to have such a shape in front of it

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Introduce into the container to heat between 150 ° C and 25O ⁰ O in order to cover it with the anti-adhesive agent by spraying.

In order to further increase the mechanical strength of the coating, it is advantageous to add flux for the silicon dioxide, for example boron oxide, to the materials. In order not to lower the melting point of the mixture too much, while maintaining a high strength, the proportion by weight of such oxides must be between 0.1 and 2 fo .

When the material is heated, once the temperature has reached 236 0, the boron oxide melts and acts with the aforesaid thermosetting material from this temperature together to ensure the strength of the coating. This strength is therefore at low temperatures ^ up to about 500 G) through the thermosetting material and from there through this Flux for silica ensured, the thermosetting substance then disappears.

The coating obtained in this manner can have a density above 2.2 and a melting point of at least equal to ⁰ C.

Based on the drawing, the implementation of the erfindungsge is according to the procedure explained in more detail.

Figures 1 and 2 of the drawing show in axial partial section an induction melting furnace in two different ways Stages in the implementation of the method according to the invention.

Such a furnace has a concentric metal envelope 1 and a concentric safety coating 3, which are separated by an empty space 13, which is used for ventilation and

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for the electrical connection of the coils 14 is required. A pouring chute 4 is poured into this furnace dry material 5 (with less than 0.5 wt .- # moisture), the 96.5 to 99.4 weight percent quartzite, 0.5 to 1.5 weight percent of a formaldehyde-phenolic resin and 0.1 to 2 wt .-; 3 boron oxide · contains. In this way, a soil layer 6 is formed, which is compacted until it is completely degassed, either with the aid of a vibrating device 7 or manually. A mold 8 which can be dismantled in several parts 8a, 8b and 8c, these are held together by screw bolts 9, and the outer surface of which is covered with, for example, a silicone resin, is then placed coaxially with the coating 3 to delimit the internal cavity of the furnace. This form rests on the compacted layer 6, and forms between itself and the coating 3 an annular gap 10.

In this annular gap 10, the material 5 is then poured from the chute 4, which also served to form the bottom layer 6. Depending on the extent to which it is poured, the material 5 becomes in the circular ring-shaped Gap 10 is compacted with the aid of a removable vibrating device 11, which is located on the inner walls the form 8 is supported with the interposition of wooden blocks. The compacting or compressing is up to a complete Degassing carried out. '

Subsequently, the furnace for one hour, which Vorerhitzungsdauer is of course dependent on the strength of the coating is preheated to a temperature between 1OO ° C and 280 ⁰ G temperature by hot air burner or dryer. The formaldehyde-phenolic resin therefore serves as a binder for the quartzite and gives the material in the annular gap 10 sufficient mechanical strength.

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speed to enable the dismantling of the form 8. away the "boron oxide takes over the task of the formaldehyde-phenolic resin, to ensure this strength.

After removal of the mold 8! The coating of the furnace is progressively heated up to 110o ⁰ G to perform ui burning of the coating.

heated progressively up to 1100 ⁰ G in a known manner

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Claims (8)

- 8 claims 1. A process for the production of refractory, internal coatings for containers such as ladles, melting furnaces or similar devices, in which a quartzite-based material is introduced to the bottom of the container and into the annular space between its inner wall and a removable one Container concentric and its inner cavity limiting inner shape is present, and wherein the material is then compacted and fired, characterized in that a material is used which, in addition to the quartzite, 0.5 "to 1.5 wt. Fo at least one thermosetting substance contains, and that this material is subjected to preheating at a temperature between 100 ⁰ C and 280 ⁰ G after compaction, iron after one takes out the mold and carries out the firing of the material. 2. The method according to claim 1, characterized in that that a formaldehyde phenolic resin is used as the thermosetting substance. 3. The method according to claim 1, characterized in that that a material is used which contains at least one flux for the silicon dioxide. . Method according to claim 5 »characterized in that that silicon dioxide boron oxide is used as a flux. 5 · Method according to one of claims 3 or 4-, characterized in that the proportion of flux for the silica is between 0.1 and 2% by weight. 4 0 9 8 3 7/0715 6, method according to claim 1, characterized marked e t that the surface of the mold, which is in contact with the coating material, is treated with an anti-adhesive agent covered. 7- method according to claim 6, characterized in that that a silicone resin is used as an adhesive. 8. Containers for ladles, crucibles, furnaces or similar devices, thereby eichnet marked that they wear a fireproof, internal coating that obtained by the method according to any one of claims 1 to 7 became. 409837/0715 Empty see page