SE453968B - CASTED METAL BODY AND SET TO MAKE IT SAME - Google Patents

Description

453 968 The invention is explained in more detail below with reference to the accompanying drawings, which schematically illustrate the inventive concept.

Fig. 1 shows a sand core to be thermally sprayed with a metal alloy; Fig. 2 shows the sand core with a sprayed, thin first layer; Fig. 3 shows the pipe intended for grouting after removal of the sand core and spraying of a relatively thick second layer on the first layer; Fig. 4 schematically shows a cast metal body with cast-in pipe, which forms a channel in the metal body.

Thus, in a manner known per se, a core body 1 is made of casting sand with phenolic resin as binder. As shown in Fig. 1, this core body 1 has an external configuration corresponding to the internal configuration of the desired tubular object, and in addition holding portions 1a, 1b at each end for clamping the core body. In the exemplary embodiment, the desired object consists of an exhaust duct in a cylinder head for an internal combustion engine.

In accordance with Fig. 2, a relatively thin and substantially pore-free layer 2 of a metal alloy containing about 5% Al, 22% Cr and the remainder mainly Fe is sprayed on this core body 1. '(Levels refer to weight%). When the layer thickness amounts to at least 0.5 mm, preferably about 1 millimeter, the spraying is stopped, after which the sand core 1 is removed by heating the sprayed sand core in an oven at about 600 ° C for 2-3 hours and the sand is then discharged from the thin , tubular metal alloy layer 2.

Then a second layer 3 is sprayed on the outside of the first, self-supporting thin layer 2. By the absence of core body d 10 ä 0 25 30 453 968 3 the first layer 2 is allowed to expand and shrink freely under the influence of temperature variations, without risk of stresses and accompanying cracking. The thickness of this second layer can be at least 1.5 mm. The spraying can be carried out without interruption for cooling or cooling.

Different methods of spraying are conceivable. Preferably, the first, relatively thin layer 2 is sprayed with a wire-fed flame sprayer, which gives a dense layer. If a surface layer of high purity is sought (small amounts of oxides and pores), the layer can be applied by plasma spraying. The second layer 3 can be conveniently applied with a powder-fed flame sprayer to obtain a suitable amount of pores and oxides. In this case, a total amount of 5 - 25%, preferably about 15%, pores and oxides are sought.

However, the second layer 3 does not have to have the same material composition as the first layer 2, but may consist of some other metal alloy with high heat resistance or a ceramic material. However, there are no requirements for corrosion resistance.

The prefabricated pipe 2,3 is then mounted in a tool for producing a sand mold for the desired metal body. The pipe 2,3 is then refilled with sand, so that it will enclose the corresponding part of the sand mold. The metal body is then cast in a conventional manner, the tube 2,3 forming a channel, as shown schematically in Fig. 4. (The outer contours of the metal body have in reality complicated geometry but are shown for simplicity as a parallelepipedic body).

The channel formed by the molded pipe 2,3 thus has an inner surface, which consists of the first sprayed layer 2, which is substantially pore-free and resistant to high temperatures and corrosive gases. It can thus serve as an exhaust duct in an internal combustion engine. The second layer 3, which lies inside the surface layer 2, on the other hand, has more pores and oxides and is thicker, so that it serves as an effective heat barrier against the rest of the goods in the metal body. Of course, with the method according to the invention it is possible to produce metal bodies with practically arbitrary shape of internal cavities and channels by pre-manufacturing shell or pipe bodies with corresponding geometry. The cavities or cavities can also form part of the outside of the metal body, e.g. together with another body to form a space exposed to excessive heat and corrosive gases, such as a combustion chamber, valve chamber, exhaust duct, etc.

Compared with the prior art, the following advantages are obtained: -: complicated cavities or channels can be prefabricated quickly and easily and then cast into the metal body; - the handling becomes easier and the disposal less; The precision of the casting becomes high; - compared with the application of ceramic materials as a liquid layer, the method is cheaper and better due to good metal-to-metal adhesion and there are no problems with different temperature expansion.

GJ

Claims (5)

5 453 968 P A T E N T K R A V Cast metal body with one or more corrosion- and high-temperature-resistant channels and / or cavities with a complicated shape, in particular intended to be included in an internal combustion engine, wherein the wall surface of resp. channel or cavity consists of a prefabricated tube (2,3) or shell, characterized in that said prefabricated tube (2,3) or shell comprises a first, relatively thin and substantially pore-free layer (2), which forms a inner wall surface in said channel resp. cavity and which consists of a high-temperature and corrosion-resistant metal alloy, and a second, relatively thick layer (3), which serves as a heat barrier and which consists of a material with high heat-strength, and that the other goods of the metal body are made by casting in a sand mold, wherein said prefabricated pipes (2,3) or shells are filled with mold sand, so that it encloses the corresponding part of the sand mold during casting. A cast metal body according to claim 1, characterized in that said first and second layers (2,3) have the same material composition. Cast metal body according to claim 1 or 2, characterized in that said first layer (2) is produced by thermal spraying on the outer surface of the first layer (2) after removal of the sand core (1). Cast metal body according to any one of claims 1-3, characterized in that at least said first layer (2) consists of 1-12% Al, 10-30% Cr, possibly small amounts of one or more elements in the group Si, Mn, Co, Y, Hf, possibly small amounts of oxides and nitrides and the residue Fe. 5. A method of producing a cast metal body according to any one of claims 1-4, characterized in that the said pipe or shell is prefabricated and installed resp. tube or shell in a tool for producing a sand mold, that the sand mold is produced, whereby also resp. pipes or shells are filled with molding sand, so that the pipe or shell encloses the corresponding part of the sand mold, after which the casting is carried out and the molding sand is removed.