CS207786B2 - Filtration method of making the castings from the fibrous materials containing metal components - Google Patents

Description

CZECHOSLOVAK SOCIALIST REPUBLIC (18) DESCRIPTION OF THE COVERED DEPARTMENT 207786 (11) (») (22) Registered 17 04 79 (21) (PV 2615-79) (32) (31) (33) Priority from 17 04 78 (78 11971 ) France (40) Published 15 09 80 (51) Int. Cl.3 B 28 B 1/52 ORAO FOR INVENTIONS AND DISCOVERIES (45) Published 15 03 84 (72)

Author of the invention BAUJON JEAN, DURTON (FRANCE) (73)

Patent holder SOCIÉTÉ EUROPÉENNE DES PRODUITS RÉFRACTAIRES, NEUILLYS / SEINE (France) (54) Filtering method for the production of fibrous material casting elements 1

The invention relates to a method for producing high-precision castings comprising fibrous materials comprising metal inserts, the suspension of fibrous materials embedded in the inserts being filtered through the mold walls. A method (French Patent No. 2,720,536) for obtaining castings of particularly complex forms is known , with a variable thickness and high precision, in which the fiber-containing suspension is dispersed in the liquid phase, and that the liquid phase is mainly removed in the exact zones of said panels. In a further development of this process, it has been found that this process can be used to produce cast parts provided with metal inserts in their housing, for example, to provide castings with improved mechanical resistance or to provide the inserts with mechanical or electrical inserts. isolation to the environment.

It is known to those skilled in the art that the insertion of metal parts, such as wires, rings, sheets, plates, into refractory material can be accomplished in, for example, heating elements in two ways:

According to a first method, a resistive wire is placed inside the metal tube, which is filled with a fine insulating refractory powder, for example magnesium oxide, or magnesia, rushing with vibration, and then treating the whole with a thrust so that the magnesium is very strongly compressed .

According to a second method, a non-flexible tube of refractory material is inserted between the outer tube and the steel wire. Unlike the first process, the panel thus obtained cannot be bent or folded; moreover, the refractory tubes can only have simple shapes.

Other processes use coating, in that a refractory paste is injected between the metal tube and the resistive wire by injecting a refractory paste formed by a sealant between the metal tube and the resistive wire, to which an exact amount of water has been added to provide a hardening by hydraulic action or was added water and additives to induce chemical solidification. This technique usually requires preliminary drying, followed by annealing to 500 ° C, which is a process in which cracks and even cracking of the refractory material can occur, so that there is a risk of direct contact or at least poor insulation of the abrasive wire. outer tube.

In all these cases, a metal surface is in contact with the surrounding environment, which may be unpleasant if the surface is corrodible as more or 207786 207786 less rapid destruction of the surface and environmental pollution can occur, especially if -free, dissolving this surface.

There are other methods in which the metal tube is not provided, for example, known refractory blocks pierced by cavities in which the heating elements are housed. However, these cells can move freely relative to the du-tin contour. If it is to be avoided that the refractory wall forms a strong squeegee against heat transfer, it needs to be thin-layered, which goes to the mechanical resistance of the whole. Some systems contain resistances simply immersed in a refractory material obtained by coating and firing. I lack brittle products that are most porous due to cracks due to their production or thermal shocks; they cannot be used in liquid environments, since the metal insert may be mechanically dropped or insufficiently insulated when a short circuit occurs when immersed in conductive media such as metal baths. Most of the solutions proposed so far for inserting metal members into refractory panels are mainly related to either the presence of a metal shell incompatible with the environment, or the presence of a brittle and brittle refractory or limiting the products obtained to simple shapes.

The invention is based, first, on the knowledge of the properties of the refractory mineral fibers of alumina and silicon dioxide, that they are compliant, resistant to high impact, impermeable, inert to most of the surrounding environment and even to a high temperature and knowledge. that it is possible to make such fibers by casting, by filtration, a suspension of these fibers in an aqueous medium and to provide these products with complex shapes of varying thickness and with very precise dimensions, by using filter-wall molds having a particular permeability as described in French Pat. spisuč. 2,356,488; The present invention is based on these features for providing a process for obtaining castings comprising metal inserts and not having the above-mentioned disadvantages. The products of the invention have very different shapes; the metal inserts are precisely positioned relative to the wall of the refractory and in any position; the outer metal sheath is eliminated; the refractory may be comprised of a material of a different nature that locally induces thermal insulation properties or, conversely, thermal transfer.

The process according to the invention depends on the fact that the liner is first placed on a frame, which is then inserted into a mold in which the permeability of the filter surface is greater in the zones requiring high shaping accuracy, the plunger being immersed in the fiber suspension, the liquid medium the suspension is filtered off, the frame is separated from the metal inserts and the mold is then re-immersed in the fiber suspension and subjected to further filtration.

The first feature of the invention is that the metal insert is placed on the frame.

This metal insert is a solid body that can be of any shape: wire, ring, plate, sheet metal, can be of a certain outline, can be compliant or non-rigid and can have any composition.

This insert is attached to the frame in a position to be retained within the casting. In the case of flexible inserts, the frame allows for a certain tension to be applied to the inserts and prevents any displacement in later operations, with any known system.

A second aspect of the invention is that the frame thus adapted is placed in a mold. Tose is performed by carefully adjusting the positioning of one portion relative to the other so that between the insert and the mold there is a sufficient distance to allow the fibers to settle in thickness but not too large to avoid too high a thermal resistance.

The mold itself has a filter wall such that its permeability is greatest in the zones requiring high molding accuracy. It has been found that molds used to produce complex shapes must be provided with a plurality of filter channels in zones requiring high shaping accuracy than in bands having simple geometric shapes: this density of filter channels is, for example, greater in bands with larger bulges or arches or in bands with sharp edges. The third feature of the invention is that the entire frame, liner and mold immerse the fiber suspensions. This suspension is kept in motion as long as there is no filtration to avoid segregation and local sedimentation. The slurry is comprised of fibers of known type or mixtures thereof, and their composition is chosen as a function of the use conditions of the casting at a certain temperature and as a chemical inertness to the liner. They may be mineral fibers based on alumina or silicate or mineral wool, kaolin, etc.

These fibers are dispersed in a liquid phase which may consist of water or organic or mineral solvents to give a favorable concentration of the suspension and a favorable viscosity to allow homogenous and rapid filtration of the liquid phase. Some binders such as sodium silicate, aluminum phosphate, etc. may be added to the fibers. A fourth aspect of the invention relates to filtering the liquid medium from the suspension. This is achieved by using a differential pressure between the inlet and the outlet of the mold, either by filling the mold under pressure higher than the pressure, or by applying a vacuum to the mold, or by combining both.

The fibers are thus deposited on the mold walls and on the metal insert. The fifth feature is that the frame is separated

Claims (3)

207786 from inserts and molds: the settling of the fibers made it possible to stabilize the metal inserts in the fibrous material and prevent any displacement thereof. It is thus possible to carry out a separation, whose task of keeping the inserts in place unnecessary. The sixth aspect depends on the new immersion of the mold and the insert in the new filtration, which is intended to give the casting precise and definitive dimensions. The process according to the invention is applicable to the production of numerous cast parts, such as a heating plate or tile, in which the metal insert consists of an electrical support which can be placed on the exact location of the casting in order to reach the local heating zones. These plates may have modular shapes and may form a heating jacket or chambers for vault, bottom or wall. They may be equipped with inserts of the desired function, namely either isolation or heating, and may have protrusions or hollows which allow their easy assembly or easy replacement in case of damage; in the process of the invention, it is also possible to produce heating modules which can be introduced into slabs or other refractory materials, which are provided with cavities for this purpose, blocks into which various apparatuses with a wide variety of shapes are inserted to be protected by ambient conditions, such as thermostats or other control devices, or heating tubes to maintain the temperature of the molten metal in the ladles. These applications are shown in Figures 1 and 2, of which Fig. 1 illustrates a heating plate and Fig. 2 a tube equipped with inserts according to the invention. FIG. 1 shows a heating plate 1 composed of refractory fibers 2. Its dimensions can be, for example: length 1100 mm, width 500 mm, thickness 80 mm. These plates, on one side, representing the thickness, the concave part 3 and on the opposite side the convex part 4. Such formation allows the plates to be assembled together to form either floors or walls or vaults. In the manufacturing process, an S-shaped electrical resistor in the form of fibers is placed inside the mold. This liner was made unfit by the frame and its location as close as possible to the heating side of the plate, so that sufficient fiber thickness was deposited during the slurry filtration so that the resistance would be noticeable on the plate surface, but not too strong. layer to prevent too high a calorie transfer resistance to the bodies to be heated. FIG. 2 shows a cylindrical tube 6 of silicon-aluminum fibers 7 having a height of approximately 600 mm with an outer diameter of 140 mm and having a circular opening of 70 mm in diameter along its axis. This tube passes through four 16 mm diameter cylindrical holes 8, which are distributed regularly around the tube axis, extending outwardly at a distance of 460 mm from the base of the tube and passing through the tube wall at a 45 ° angle so that they face downwards. At the bottom of the tube there are cutouts 9. Into the mass of the tube wall at a height of 220 mm to 30 mm from the base, electrical resistors 10 in six, wound in a spiral and arranged regularly round the tube, were placed parallel to the tube. These debris are supplied with electrical energy by means of wires, for example wires 11. It is known that in particular in the field of aluminum and its alloys it is very important that the draining temperatures are as stable as possible. These tubes immersed in the respective furnaces allow this to be achieved; due to their tubular construction and the location of the electrical debris in their interior, the metal to which they are immersed is heated, in particular, to the lower part of the tube base; as its density is less hot, it rises up, divides into the mass of the bath, while the cooler metal is sucked by the thermosyphon of the bottom of the tube cutouts 9. This circulation ensures a uniform temperature throughout the entire metal bath. OBJECT CLAIMS 1. A filtering method for the production of fiber-reinforced castings comprising metal components precisely positioned therein, characterized in that the metal insert is placed on the frame, the frame is then placed in a mold in which the permeability of the filter coating is greater in the bands requiring high casting accuracy, the whole is immersed in the fiber suspension, the liquid medium is filtered off from the suspension to form a first layer of fibers on the liner, the frame is separated from the liners and the mold, the whole of the metal liner covered with the first layer of fibers and mold re-immerse the fiber suspensions and filter the liquid medium off the suspension again. 2. The method of claim 1, wherein the metal insert comprises an electrical resistance. 3. The method of claim 1, wherein the insert comprises a meter. 1 sheet of drawings Severografia, n. P., Plant 7, Most