CS199559B2 - Cardboard lining coated,inpregnated or filled by heat-resistent mass - Google Patents

Abstract

1454635 Moulds; mould linings; casting processes REGIE NATIONALE DES USINES RENAULT 7 Feb 1974 [13 Feb 1973] 05759/74 Heading B3F A shape 4 of cellulose fibre or other cardboard, matching the cavity shape and including usual mould lining material, is fitted into each part 1 and 2 of a mould before closure of the parts, when lips 5 of the cardboard shapes 4 are nipped to hold the shapes, ready for pouring a metal such as C.I., steel, Al, bronze or Cu alloy. The carboard is burnt by the metal and is retained by the refractory lining material which sinters. The refractory material may be a filler in the carboard or be applied to it by spraying or dipping. A camshaft mould 1, 2 is shown and the thickness of cardboard is reduced or it is removed, to reduce insulation, where parts of the cams 6 are to be hardened, e.g. where there are cooling arrangements 7. Where pinion teeth are to be cut, softer areas are produced, the cardboard thickness being increased to at least 1 mm. by an additional layer 10. Filters 11 and air ducts 12 allow extraction of resultant gases. Increased insulation facilitates production of thin webs, by preserving a grey-iron structure, e.g. in casting pulleys or suspension arms or steering housings for cars.

Description

FIELD OF THE INVENTION The present invention relates to non-flammable cardboard linings for the inner walls of two-part casting molds for casting high melting metals. It is particularly applicable to the casting of cast iron or steel, but is also suitable for casting other metals such as aluminum, bronze and other copper-containing alloys.

When casting metals with a high melting point, they wear relatively quickly during the operation of the casting molds, and difficulties arise, in particular in the form of casting. In order to protect the functional surface of the casting molds, it is known that protective coatings are applied to parts of the casting molds in the form of a layer of carbon black or graphite slurries, for example applied by a plasma torch. However, the formation of such coatings is relatively laborious and delays the production process. .

The invention is based on the idea of forming a protective coating from a paper layer. It is based on a cardboard lining, coated, impregnated or filled with a refractory material for the inner walls of two-part molds intended for casting high-melting metals, which according to the invention consists of two preformed cardboard parts corresponding to the inner wall shape of two casting mold parts. the edges extending into the dividing plane of the two-part casting mold and the clamped mold parts.

Thus, the classical fibrite slurry is replaced by a cellulose fiber or other fiber carton that is heat resistant by being coated or saturated with a refractory material. In the most preferred embodiment, the refractory is already incorporated. into the base paper material, which is used for the production of carton, because it ensures non-flammability in the material itself and thus the highest durability. This solution is particularly advantageous for large series. It is also possible to saturate the carton additionally, for example with ceramic powder. It is also possible to apply the refractory mass by spraying or dipping onto. cardboard surface.

The use of the cardboard cladding in the form of a preform according to the invention makes it possible to reduce the molding costs by substantially saving working time. The time required to form a graphite slurry in the prior art is only replaced by the time required to insert the preformed carton parts. In addition, the insulating ability of the carton makes it possible to improve the quality of the castings while at the same time saving the casting molds by reducing the effects of thermal shock on the surface and by eliminating diffusion-related effects due to the contact of the ingot mold with the cast metal.

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If necessary, local changes in the casting structure can be achieved to a precisely determined degree by using the preformed cardboard linings according to the invention by varying the thickness of the cardboard linings. According to the invention, the preformed cardboard parts are provided with holes at the point where reinforced cast metal cooling is to be achieved by a casting mold. These openings are punched in cardboard lining corresponding to the area. Likewise, the preformed carton parts at the point where the cast metal cooling is to be reduced in the casting mold are provided with an additional carton part which locally increases the thickness of the carton lining. In contrast to the prior art coatings, where local thickening or thinning of the coating cannot be precisely controlled, the preformed carton parts of the invention allow local changes in the casting structure to be accurately controlled.

The carton according to the invention is explained in more detail in the following description by way of example with reference to the accompanying drawing, in which FIG. 1 shows a longitudinal section of a two-part casting mold for camshaft casting and FIG. 1.

As can be seen from the drawing, the casting mold for the production of a camshaft consists of steel or cast iron, consisting of an upper part 1 and a lower part 2. These two mold parts 1, 2 have a common separating plane 3 and each form a cavity of corresponding shape. corresponding to the camshaft half.

According to the invention, the graphite slurry coating on the inner surfaces of the casting mold parts 1, 2 is replaced by the mere insertion of preformed cardboard parts 4, manufactured in advance exactly according to the shape of the cavity of the corresponding mold part 1, 2. A completely conventional carton may be used, for example a gray carton having a thickness of 0.2 to 0.5 mm. The carton may be saturated with the refractory or simply coated, for example by spraying or dipping. The refractory mass can be, for example, a mass which serves to heat the coating slurries applied directly to the surface of the prior art casting mold.

The cardboard parts 4 are shaped according to conventional procedures of the cardboard industry to achieve the desired shape. As can be seen from the figures, both preformed cardboard parts 4 are provided with an edge 5 extending into the dividing plane 3 of the casting mold.

The insertion of the preformed carton parts 4 or into the casting mold parts 1 and 2 can be carried out very quickly, thus allowing the casting mold to be brought into operation quickly. As a result, the number of casting molds required to achieve a certain output is also reduced. Once the casting mold is closed again, the two carton parts 4 are clamped by their rim 5 in the casting mold dividing plane 3, thereby ensuring the tightness of the casting mold and the fastening of the preformed carton panels.

If molten high melting kqv, such as steel or cast iron, is poured under normal conditions, the liquid metal coming into contact with the carton will cause the carton material to burn, but the presence of a refractory covering or filling the carton, results in sintering of the refractory particles by the heat of the metal. The sintered refractory mass then serves as a carrier for the remainder of the burned cardboard which cannot then be removed by the flowing metal.

The insulating ability of the cardboard cladding substantially slows the heat exchange between the cast metal and the casting mold so that the casting is not cooled too fast and its quality is improved. Casting molds are also saved, since the casting is more favorable due to the reduction of the surface thermal impact. By providing an insulating intermediate layer with a cardboard lining, the diffusion on contact of the casting mold surface with the cast metal is further eliminated. Finally, after solidification, the casting can be removed more easily from the casting mold than with known coatings. /

If necessary, it is possible to reduce or even eliminate the effect of this thermal insulation by cardboard lining at some points of the casting mold to achieve a local hardening effect. For example, in the illustrated case, it is possible to obtain turbidity on the camshaft projections at locations 6 by simply cutting a hole in the carton piece 4 so that the metal can come into direct contact with the casting mold. In order to further enhance this quenching effect and to improve the operating conditions of the casting mold, an additional cooling means 7 located opposite this opening is used. Thus, after cooling, the casting has a much higher surface hardness at the locations 6 of the reinforced projection cooling, while the other casting remains in the normal annealed condition, i.e. especially in the axis region and at the bearings 8.

In some places of the casting, which are to be particularly soft, such as at the point 9, which serves to form a camshaft pinion, it is desirable to reduce the casting cooling of the cast metal. In such places, the insulating layer of the preformed carton piece 4 is strengthened by 1 mm or more by means of an additional carton piece 10, which results in the casting being protected against the cooling effect of nearby additional cooling means 7. However, this reinforced insulation has the disadvantage consisting of increased gas evolution which leads to the formation of bubbles in the casting. To prevent this, in the upper mold part 1 and the lower mold part 2, there are located gas filters 11 and gas outlets 12, solved by methods known in the field of ingot molding.

This. the local increase in thickness of the preformed carton piece is very important since it allows casting of thin cast iron castings while maintaining the gray cast iron structure. It is also possible, for example, to cast castors having a solid core. and a massive wreath joined together by a thin wall.

Experiments carried out with different types of cast iron have shown that with cardboard lining whose thickness is. of the order of 1 mm, thin-walled castings having a wall thickness of approximately 5 mm can be cast while maintaining the structure of gray cast iron throughout the wall. It is possible to further reduce the thickness of these weak casting walls by increasing the thickness of the cardboard lining and vice versa.

The cardboard lining according to the invention is suitable for the production of all. · kinds . · Castings, with particularly good results in the production of castings of different hardness, as is the case with the camshafts where it is. cooling of hardened points can be more effectively controlled, which is very difficult in conventional casting methods. Likewise, the cardboard lining according to the invention is very well suited for the production of all castings having thin walls, for example, crank suspension arms or automobile control boxes.

Claims (3)

Cardboard lining, coated, impregnated or filled with a refractory mass, for the inner walls of a two-part casting torque intended for casting of high-melting metals, characterized in that it consists of two preformed cardboard parts (4) corresponding to the inner wall shape of two parts ( Casting molds, with edges (5J extending into the separation plane) (3) of a two - piece casting mold and clamped mold parts (1, 2J). VYNALEZU Cardboard lining according to claim 1, characterized in that the preformed cardboard parts (4) are provided with holes in the mold (6) for enhanced cooling of the cast metal. Cardboard lining according to Claims 1 and 2, characterized in that - the preformed carton parts (4) are provided with an additional carton part (10) at the place (9) of reduced cast metal cooling.