DE2429925A1 - THERMAL INSULATING MATERIAL AND METHOD FOR MANUFACTURING IT - Google Patents

Description

METALAIDS. PROCESSES LIMITED

Spring Lane Trading Estate

Malvern Link «Worcestershire WR 14 1AH / England

Thermally insulating material and process for its manufacture

The invention relates to an improved heat insulating one Material, particularly for use in the metal casting industry.

The use of heat-insulating, heat-resistant linings in the basins of block or casting molds and in casting mold risers has been known for many years. They serve in the form of bricks and corner stones, one-piece hot ceilings, hollow cylinders and so on

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the delay in solidification of the molten metal in the upper part of the casting mold or in the riser space and reduce hence the loss of metal due to shrinkage and segregation during cooling and solidification.

In particular, linings with significantly improved compositions have been based in the past decade on the incorporation of a proportion of organic and / or inorganic fibers in the refractory mixture became known. The incorporation of such fiber materials serves both to improve the thermal insulation properties the linings as well as improving their mechanical strength. As most of the inorganic fiber materials either expensive or unacceptable under current environmental laws is their use limited in such mixtures and is the main type of fiber material which has been used in practice up to now in the form of paper or cardboard pulp, both of which are both effective and inexpensive.

Although linings made from such compositions are effective in retarding solidification of the metal in the Mold head or in the riser space and thus reduce the shrinkage and decomposition of the metal their advantages, however, are at least partially negated by the fact that the metal in the surface of such Lining can penetrate. This penetration occurs because practical compositions have properties which is a compromise between sufficient density and fire resistance for resistance to penetration Sides of the molten material, sufficient thermal insulation to delay solidification of the metal and

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represent a sufficiently low cost to apply such linings in a usable ratio can. ·

Penetration of the metal into the surface of the linings normally occurs between the particles of the refractory material by softening, burning or displacement of the organic fibers and / or the binder and has the disadvantage that particles of the refractory or refractory material become trapped by the solidifying metal. These trapped particles of refractory or refractory material can in turn lead to rejection a part of a rolled-out casting or a casting, of which the sprue is a one-piece Part forms because of surface imperfections, although the metal below the surface is otherwise healthy.

There has been some success in formulating anti-penetration compositions made of metal in thermo-insulating, refractory or heat-resistant linings. So you have, for example Composite compositions are used in which one opposes the molten metal Layer of lining made of a highly refractory or heat-resistant, resistant to penetration Material consists, with only expensive inorganic fibers are used instead of organic fibers and one Backing layer made of a better thermally insulating, less expensive composition is used. These Linings have the disadvantage of increased material costs due to the installation of a relatively high proportion on expensive, refractory or heat-resistant fibers and

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increased production costs as a result of the extra work involved in making the composite Lining of two layers is required. Of course, a liner, "when only expensive, heat-resistant or refractory fibers and no organic fibers are used in a single composition be established by a simple operation and be successful in preventing intrusion, however, the cost of the large amount of inorganic fibers required is practically prohibitive.

The object of the invention is to create a thermally insulating lining that does not have the disadvantages indicated.

In view of this, includes a thermally insulating liner for use in the metal casting industry and in particular for lining the ceilings of casting molds and casting risers, a substrate or a carrier made of refractory material or heat-resistant material and organic and / or inorganic fiber material, the substrate or the carrier is covered on at least one of its surfaces with a layer of fiber material.

Normally only the surface or surfaces of the liner that will be used when it is in use should be used come into contact with the molten metal, be covered with a layer of fiber material. The covering The layer or the covering layers of fiber material can be attached to the dried substrate or carrier with the aid an adhesive, for example a refractory or heat-resistant cement. It has, however proved to be advantageous, the fibrous layer

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material as a one-piece part of the lining in the manufacture of the substrate or carrier by a molding process to be built in. This is done, for example, by preparing a substrate mixture in the form of a paste or slurry of the materials to be embedded in the substrate, pre-cutting a layer of fibrous Material for the shape of the substrate surface or surfaces to be clad, inserting the substrate mixture into the Mold cavity of a suitably shaped mold with the pre-cut Layer material between the substrate mixture and a permeable part of the mold surface of the mold and expressing the liquid from the substrate mixture, so that at least part of the squeezed out liquid passes through the fibrous sheet material before it Mold cavity exits through the permeable mold surface, so that the fibrous sheet material into the pressed Substrate or carrier mixture as a surface coating is installed on at least one surface.

In the method just described, the perforated or permeable mold surface of the mold can thereby be provided be that one or more walls of the mold are provided with holes of small diameter. The number and the size of these holes is chosen to suit the plasticity of the substrate or carrier mixture used and are adapted to the pressure of the mold. In this context, a relatively stiff one is advantageous Substrate or carrier mixture is used, for example one as described in DT-OS 2 405 712.3 is.

In the process just described, the fibrous

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Layer material prevents liquid and trapped air from escaping from the mixture through it however, the heat-resistant or fire-resistant and thermally insulating components together with a high proportion of the existing binder, whereby the coated Layer becomes a one-piece component of the lining produced and a one-piece component of the same after left to dry. On the other hand, a cover layer that does not stick to the carrier or substrate runs through Adhesive attached, more risk of being damaged or partially removed from the carrier or substrate during transport or be peeled off during handling and as a result may chip and allow the metal to penetrate, when it comes into contact with the molten metal.

The cover layer made of fiber material can be a paper or cloth made of non-heat-resistant or non-fire-proof Be fiber material. Preferred embodiments of such non-heat-resistant or non-refractory fibrous covering material for incorporation into the liner at the time the substrate or support is formed Layers of blotting paper or other types of absorbent paper, especially those with a thickness of about 1/4 mm up to 1mm. When used in conjunction with substrate or carrier mixtures that contain clay or a high proportion of very contain fine refractory or heat-resistant substances, these papers can be used in their usual form will. However, if you use them with substrate or carrier mixtures that contain an insufficient amount of clay or contain fine refractory or heat-resistant components, then it has proven to be useful to use the

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Impregnate paper with clay, for example kaolin, fireclay or ball clay, before molding it into the lining.

It is not possible at the moment to give an exact reason for the unexpected ability of a thin coating of non-refractory or non-refractory paper, or Cloth for improving the resistance to the penetration of molten metal on the finished thermally to give insulating linings. However, it can be assumed that there is a possible explanation therein too What is sought is that during the shaping of the wet substrate or carrier mixture, the layer of fibrous coating material allows the trapped air and liquid to pass through they leak through, but the layer forms a filter that the finest particles of refractory material from the Retains mixture along with a greater proportion of any binder and clay from the mixture than it otherwise would would be the case in the exposed zone of the liner. The result is a smoother, better bonded one hit ζ ehas permanent or refractory layer without large Gaps behind the cover layer, this layer resisting the penetration of molten metal, itself when the cover layer has already been destroyed. Another possible explanation for the case that the layer is made of inorganic Fiber paper or cloth is used as a coating material, consists in that this by the melted Metal turned into a thin layer of highly refractory or highly heat-resistant carbon which is pressed against the underlying carrier by the molten metal and thus an effective one Forms heat-resistant or fire-resistant screen for the wearer. Another possible explanation for the case of a liner, in which the covering material is impregnated with clay

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namely either during the molding process or as a preparatory stage for the molding process can be seen therein be that the clay is burned by the molten metal with which it comes in contact and one forms similar effective fire-resistant or heat-resistant screen for the carrier or the substrate.

In another embodiment of the thermally insulating lining according to the present invention, the cover layer can contain fire-resistant or heat-resistant fiber material, a particularly suitable material of this type is a paper or cloth made of aluminum silicate fiber. Such a fibrous sheet or web material with a thickness of 1/2 mm and 1 mm is sold under the trade name "Triton Kaowool ^11. However, other fire-resistant or heat-resistant papers or cloths with a thickness between 1/4 mm and 1 mm can also be used The use of such a thin layer of refractory or heat-resistant fiber material as a coating layer in a lining according to the present invention does not lead to a prohibitive increase in the cost of the lining, since far cheaper refractory or heat-resistant fibers can be used than in the case of a composite lining with a much thicker covering layer of refractory or heat-resistant fibers and because the additional production costs of coating with the layer of refractory or heat-resistant fiber material in the form before the penetration of the substrate or carrier mixture is negligible compared to the costs of the manufacturer development of composite linings using two different mixtures.

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The composition of the mixture used for preparing the support or substrate may be a conventional one as they are used in the manufacture of thermally insulating, Refractory or heat-resistant linings are used. The mixtures according to the examples are particularly suitable 1 and 2 of DT-OS 2 405 712.3.

A lining according to the present invention may be in the form of the heretofore known thermally insulating heat resistant or refractory linings are available. For example, it can be in the shape of a brick or a plate have, as they are used for lining metal casting molds, they can be in the form of a tile, a corner wedge or a one-piece hollow hot blanket, such as for the thermal insulation of Find covers of casting molds use. It can also be a Be a hollow cylinder, such as is used, for example, for the thermal insulation of a pouring riser.

The invention is to be described in more detail below with the aid of the examples are explained in which the specified parts are parts by weight.

The drawing shows in

Fig. 1 is a section through a device for performing the method according to the invention and in

Fig. 2 is a perspective view of a lining panel according to the invention.

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example 1

A pulp is made through. Addition of 10 T _e ilen dry newsprint to 100 parts water in a hydropulper. This mixture is whipped at high speed for 10 minutes, after which a fiber pulp has formed. This pulp is then fed to a Z-blade mixer, where 85 parts of ground chamotte with a particle size not exceeding 10 mesh (BSS sieve) and 5 parts of phenol-formaldehyde novolak resin have been added as a binder. The mixture was then mixed for a further 20 minutes, after which the mixture had a plastic consistency. This mixture was used to make a carrier or substrate of a thermally insulating brick in an open-topped brick making mold as shown in FIG. The shape of Fig. 1 has a cuboid shape with a flat bottom

1 and four plan side walls 2. The bottom and the side walls have a large number of fine holes 3. A mold pressure plate is located vertically in the mold cavity 5 »as defined by the bottom 1 and the side walls 2 4 movable, with narrow gaps 6 between the edges of the plate 4 and the adjacent side walls

2 remain.

A layer 8 of blotting paper with a thickness of 1/2 mm is cut into the shape of the mold bottom 1, in a slurry dipped from spherical clay and then laid out on the bottom of the mold. Then a measured amount of the Substrate or carrier mixture 9 filled into the mold using a shovel and raw in the Mold cavity 5 spread out on top of layer 8, now the mold pressure plate 4 is inserted into the mold over the

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Mix 9 is used and a pressure of about 3.6 kg / cm is applied to squeeze out the greater part of the water and compress the mixture into the desired shape. The water is pressed out through the fine holes 3 in the side walls of the mold and in the bottom of the mold and also through the narrow gaps 6. The compressed composition is then removed from the mold cavity and placed in a drying oven, where it is dried for a period of 3 1/2 hours at a temperature of 150 ^° C. in order to remove the remaining water and to harden the heart and the finished brick to manufacture. FIG. 2 of the drawings shows a perspective view of such a finished brick which has a carrier or a substrate 10 which is provided with a cover layer 8 which is integrally formed.

The finished brick exhibits satisfactory thermal Insulating properties, fire-resistant or heat-resistant and mechanical properties when it is part of the Insulating lining of the ceiling of a casting mold is used. Its dimensional accuracy and surface finish are excellent. When brick according to this embodiment as part of the insulating lining of a casting mold For the casting of 4 t steel castings use, no designated inclusions were made of heat-resistant or refractory material found in the rolled out molding, which is an indication that no molten Metal could penetrate the surface of the liner. This makes a very favorable comparison with respect to similar castings with the same mold using common ceiling liners that are unchangeable showed the presence of inclusions from the refractory or refractory material.

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Example 2

The procedure of Example 1 is repeated with the Exception that instead of using blotting paper as the cover layer, the latter consists of a layer of "Triton Kaowool "paper was 1/2 mm thick. This cover sheet was not made into a slurry of ball clay submerged, but laid out dry on the bottom of the mold.

The finished brick had the same excellent properties as the brick of Example 1 when used as part of an insulating lining in a mold. In addition, in an experiment in which molten steel poured over bricks according to the exemplary embodiment and over conventional bare bricks it was found that the molten steel flowed over the clad bricks and did not penetrate them, while the molten steel had penetrated the bare bricks.

Example 3

A mixture of 5 parts of dry shredded paper, 65 parts of crushed chamotte (-10 mesh), 23 parts of fumed alumina, 2 parts of spherical clay, 3 parts of dextrin and 60 parts of water were placed in a high-speed tumble mixer and mixed for 21/2 hours . After this period the mixture assumed the plastic consistency of a stiff paste in which the paper fibers were adequately distributed. Then a piece of dry blotting paper 1/2 mm thick was made into the shape of the

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The bottom F has been cut rm ₀ of FIG. 1 and laid on the bottom of the mold, after which introduced a metered amount of the mixture in the mold cavity 5 to the top of the blotting paper sheet. The mixture was then roughly distributed within the mold cavity. Two suitably shaped, pre-formed metal components were then lightly pressed into the mixture by hand before the pressure plate was inserted into the mold. The mixture was then pressed and dried in the oven under the same conditions as indicated in Example 1.

The finished brick had the same excellent properties as that of Example-1. The preformed Metal parts formed a one-piece part of the brick and served as a base on which metal hanging devices Could be connected to a simple but effective means of hanging the bricks from the Creating a ceiling of a shape.

Claims: - 14 -

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Claims (14)

Claims 1. Thermally insulating lining for use in the metal casting industry consisting of a substrate or supports made of heat-resistant or refractory material and organic and / or inorganic fiber material and optionally a binder, characterized in that at least one surface of the carrier or substrate is coated with a layer of fiber material. 2. Lining according to claim 1, characterized in that g e ke η η that the coating layer is in the form of a paper or cloth with a thickness of 0.25 to 1.0 mm having. 3. Lining according to claim 1 or 2, characterized in that the coating layer is made of absorbent Paper is made. 4. Lining according to claim 3, characterized in that the coating layer consists of blotting paper consists. 5. Lining according to claim 1 or 2, characterized in that the coating layer is heat-resistant or contains refractory fiber material. 6. Lining according to claim 5, characterized in that the coating layer is aluminum silicate fibers contains. 409884/1015 " ¹⁵ " 7. Lining according to one or more of claims 1 to 6, characterized in that the coating layer is attached to the carrier or substrate with an adhesive. 8. Lining according to claim 7, characterized in that the adhesive is a refractory or heat-resistant Cement is. 9. Lining according to one or more of the claims 1 to 6, characterized in that the coating layer is molded in one piece with the support. 10. A method of making a thermally insulating liner for use in the metal casting industry by producing a carrier, the heat-resistant or fireproof material and organic and / or inorganic Containing fibrous material and optionally a binder, characterized by attaching a preformed Layer of fibrous material on at least one surface of the carrier or substrate. 11. The method according to claim 10, characterized in that g e k e η η - ζ e i c h η et that the preformed layer of fiber material is attached to the carrier or substrate by an adhesive. 12. The method according to claim 10, characterized in that the preformed layer of fibrous Material incorporated as an integral part of the liner at the time of manufacture of the carrier by a molding process is. - 16 409884/1 01 5 Ai, 13. The method according to claim 12, characterized by preparing a substrate or carrier mixture in the form of a paste or slurry from the materials to be built into the carrier or into the substrate, production of a layer from the fiber material accordingly the shape of the carrier surface or surfaces to be clad, inserting the carrier or substrate mixture into the Mold cavity of a suitably shaped mold, with the layer material between the substrate or carrier mixture under a permeable part of the mold surface of the mold is used, and squeezing the liquid on the substrate or carrier mixture such that at least one Part of the squeezed out liquid passes through the fibrous sheet material before it passes through the mold cavity the permeable mold surface leaves, wherein the fibrous layer material in the pressed carrier substrate mixture as Surface cladding is installed at least one surface of the same. 14. The method according to claim 12 or 13, characterized in that prior to installation in the lining the layer of fibrous material is impregnated with clay. * ♦♦ 409884/101 5