DE2948162A1 - Thermally insulating refractory mouldings - contg. inexpensive bagasse; used esp. as hot top lining panels for ingot moulds - Google Patents

Abstract

Mouldings contain refractory particles; a binder; and defibred bagasse or the crushed stalks of other plants contg. pith. The pref. moulding contains by wt. 50-90% refractory powder, 3-10% binder, and 5-30% defibred bagasse powder or similar crushed trash, pressed as a mixt. in a mould or die while the binder hardens and sets. The moulding is pref. used as a lining in the top of an ingot mould, e.g. as panels forming a hot-top in which final solidification of the ingot occurs; it may also form an insulating- or exothermic- lining in tundishes etc. Defibred bagasse, i.e. sugar cane trash, is a scrap material with very low cost. The bagasse can easily be crushed in a hammer mill so the sepn. of the fibres is simple. The mouldings may also contain organic fillers such as paper pulp or sawdust.

Description

Molded, refractory, heat insulating articles

The invention relates to heat insulating articles, in particular for use in the metallurgical industry.

To limit the heat loss from molten metal, heat insulating and / or exothermic materials widely used in the metallurgical industry used.

For example, the head metal can be in a shape such as a block shape or in a separate pouring attachment or heating hood for such a mold from a so-called "hot-top" lining in the form of a socket or plates the end heat insulating and / or exothermic material are surrounded. The surface too of molten metal in a metallurgical vessel can be through a plate or Sheets of heat-insulating and / or exothermic material are covered, wherein such panels are known as anti-void panels in the case of block molds. Such plates can also be used to hold the upper metal surface in intermediate vessels or tundishes to cover, and the sides or bases of intermediate vessels clad with heat-insulating and / or exothermic panels.

According to the invention is a molded, refractory, heat insulating Article intended for use in a metallurgical vessel containing particulate, defibered bagasse or the like, a particulate refractory material and a Binder.

Certain plants have stems or stems that have an outer covering made of fiber material, which has a high proportion of juice-containing tissue, i.e. Marx, in the form of cells with thin, soft walls. Sugar cane is one example of such a plant, corn is another, and there are more Examples exist in the subfamilies of the Graminae (Gramineen), Saccharum and Achillea (YarrowB.

To obtain sugar from sugar cane, the sugar cane is crushed, the juice containing sugar in the pulp is extracted or pressed, and the residue is known as bagasse. In the present context, "Bagasse or the like." understood that it was bagasse or crushed or otherwise broken stems or stems of other pith-containing plants from which the sap is made has been extracted or which have been dried. In addition to the plants of the types mentioned above are also certain Woods, in particular Timbers from certain deciduous trees, suitable that have a significant proportion of marrow cells to have.

These special woods are also in the crushed state of the Expression "bagasse or the like." includes.

The term defibrated "means that a substantial proportion of the Fiber material e.g. from the outer shell of the stalks or stalks from the bagasse or the like. Has been removed. Bundles of fibers are scattered in the pulp of sugar cane or embedded that are generally aligned with and form the pipe a relatively small proportion of the volume of the inner part of the tube and can in their original proportion or preferably in a reduced proportion in the defibered bagasse suitable for the purposes of the invention be. The defibered bagasse or the like. can be made in the way they are ir! U.S. Patent No. 2,729,856. This means that the product is in the desired fine particle shape and sieved to any desired particle shape can be.

In the defibered bagasse or the like. the fiber content is preferred by 40 to 70, in particular by about 50%. The defibered bagasse od. The like. May preferably have a particle size that passes through a sieve with a Uchten Mesh size of about 1 to 8 mm (16 to 2 1 / 2'mesh) passes through it. In the practical Implementation of the invention was in particular a defibered bagasse or the like. used, which passed through a sieve with a mesh size of about 4.5 mm.

The defibered material can be obtained very cheaply because bagasse itself is basically a waste product, and it is their fiber content that usually is e.g. in paper production has been appreciated. In general dry hammer mill machining provides a convenient way to to the bagasse or the like. break down so that it can be easily defibrated.

The defibered material is highly porous and has a very low Bulk density, preferably in the range from 0.05 to 0.1 g / cm3, in particular from about 0.085 g / cm3.

In contrast, the bulk density of sawdust is around 0.2 g / cm3. The material has been found to be a very effective thermal insulator and the production of objects or moldings of low density, e.g. less than o, 7 g / cm3, permitted, whereby these objects auge = calibrated heat-insulating or have thermal insulation properties.

It can be assumed that the good insulating properties are not only with the high porosity of the fibers or the like, but also with the general small size of the pores.

The particulate refractory material can be one that commonly used in products of the general type under consideration, and mixtures of two or more such materials can be used. Preferably the refractory material is sand, silicon dioxide, quartz, chamotte (crushed, refractory stones), olivine, sillimanite, magnesium oxide, lime, calcined Dolomite, clay, zirconium, chromite, aluminum oxide or an aluminosilicate. The fireproof Material is preferably powder or granular, preferably with an average Grain size up to about 0.3 or 0.4 mm, however some or all of it can be fibrous and consist, for example, of aluminosilicate fibers. Inorganic fibers of limited refractory properties, e.g. glass wool and slag wool, can also be included. Some or all of the refractory material can be a Lightweight and made from expanded perlite or calcined rice husks, for example exist.

In addition to the particulate, defibered bagasse or the like. the product may contain other organic fillers, which may be fibrous, such as paper fibers or cellulose, or granular material such as sawdust.

The binder can be organic and, for example, made of starch, a resin such as urea formaldehyde or phenol formaldehyde resin, or it may be inorganic and consist, for example, of bentonite or a silicate such as sodium silicate. A mixture of binders can be used. The binder used should be compatible with the other components of the article, for example a resin that is hardened by the application of an acid should not be used as a binder to be used when the particulate refractory material is a base such as magnesium oxide.

Objects of the general kind under consideration are common produced by filtering aqueous slurries into permeable forms because, while there are drawbacks to this, other techniques are not practical was. Mud techniques are used in the manufacture of the articles according to the invention not used, and the articles can easily be made by that the constituents including a binder that can be used at low temperatures, e.g. room temperature, solidifies or hardens, mixes, the mixture into the desired Shape transferred and a solidification or hardening brings about. If a resin binder is used, this can be achieved by the at room temperature Use of a catalyst, usually an acidic one, for solidification or for Hardening can be brought about while if sodium silicate is used this is brought about by the action of carbon dioxide can be hardened. Optionally, binders can be used which are solidified by heating at a low temperature can be used can. Until the binder has solidified, the mixture is preferably below Pressure held.

To facilitate the formation of the mixture into the felted shape and / or to reduce the Dz. Density aes final object can be liquid in the mixture to be converted into foam, creating the correct filling of the used Shape is supported, and if the foam does not collapse before the binder solidified or hardened becomes a product with a certain foam structure and therefore results in a reduced density.

The proportions of the components can be varied widely, wherein the defibered bagasse or the like. e.g.

up to 50% by weight, e.g. 1 to 30%, preferably at least 596, while the refractory material forms e.g.

50 to 90% of the weight and the binder 1 to 20, 'of the weight, for example 3 to 10, ". Given the materials, allows selection of special proportions the regulation or control of the strength, the heat insulation or insulation properties and other properties of the objects. A suitable one Composition for the article contains e.g. lot binders, 20, 'bagasse and 7096 particulate refractory material.

Exothermic reacting materials can be in the constituent parts of the objects be included. Such exothermic reacting materials preferably comprise an easily oxidizable metal, e.g. aluminum, magnesium or their alloys in particle form and a solid oxidizing agent, e.g. iron oxide and / or manganese oxide, or a metal nitrate in particulate form. If aluminum is used, is preferred an inorganic fluoride such as cryolite is also used.

The items can take the form of sockets or inserts for lining the block mold heads or the casting attachments or the riser of casting molds, rings for arrangement on the lower part of Gic-ßform attachments or preferably plates or panels, in particular for lining mold heads or pouring attachments for steel blocks to have.

Metallurgischa vessels, which with objects or shaped bodies according to of the invention, form part of the invention as well as the Use of the vessels equipped in this way.

The invention is illustrated by the following example.

Example The following ingredients were used: 1) 68 wt., S0 Silica flour 1/2) 68% by weight of defibered bagasse '15.2% by weight of phenol-formaldehyde resole resin 8.4 wt.

65% strength aqueous p-toluenesulfonic acid 4.2% by weight of methanol 4.2% by weight.

1) (passes through a sieve with a mesh size of 0.355 mm) 2) (passes through Sieve with a mesh size of 4.5 mm).

The solid ingredients were mixed together thoroughly, the liquid ones Ingredients were mixed together and the liquid mixture then became the added solid mixture and mixed thoroughly with this.

The mixture was placed in a die or die, and a pressure of 13.5 kg / cm2 was applied. When the resin hardened, the Mixture taken out of the die in the form of a plate.

The plate had a smooth, uniform appearance and had a Density of 0.68 g / cm3 and a modulus of rupture of 24 kg / cm2, the plate was in contact tested with molten steel and it was found that they had little smoke or Emits haze, is resistant to penetration through the steel and is light stripped from the steel can after the steel solidifies would have.

By changing the ratio of silica flour to defibered Bagasse and / or applied pressure were generally similar plates, however made with different densities.

All parts and percentages in the present context are based on weight, unless otherwise stated.

Claims (4)

Claims 1. Shaped, refractory, heat-insulating article for use in a metallurgical vessel which is a particulate refractory Material and a binder, characterized in that it comprises particulate, defibered bagasse or crushed stems from other plants containing pulp contains. 2. The object of claim 1, characterized in that it gckennzeichnst 50 up to 90% by weight * 5 particulate. refractory material, 5 to 30 total% defibred Bagasse or the like. and contains 3 to 10 total% binder. 3. A method for producing a molded article according to claim 1 or 2, characterized in that a mixture of the refractory material the defibered bagasse or the like. and the binder is formed, the mixture placed in a mold and subjected to pressure, and that the binder solidified or allowed to solidify. 4. Use of a shaped article according to one of the claims 1 or 2 for lining the head or a pouring attachment of a block mold, wherein multiple molded articles can optionally be used.