SU1183283A1 - Method of lost-pattern making of shell moulds - Google Patents

Description

The invention relates to foundry, in particular, to the technology of manufacturing casings for investment casting with gas-port channels. five

The purpose of the invention is to improve the quality of castings.

FIG. 1-4 is a schematic representation of the production of shell molds of U by investment casting.

On model 1 (Fig. 1), the rods 2 are fixed with a model composition 3 applied to them, having a stopper 5th protrusion 4, for example, in the form of a head. After forming the refractory shell 5 (figure 2) on the model unit 1 and melting the model, the upper part 6 of the shell 5 formed by the 20th exhaust gas duct 7 in place, the retaining tab 4 of the rod is opened and the rod 2 is removed.

The gap formed around the rod after the removal of the model composition, ensures it is free. extraction The core must be removed before calcining in order to avoid the formation of dross on it in the mold. The failure of the rod into the cavity of the shell mold prevents, due to the locking protrusion, the role of which can be performed or the cap at the end of the rod 2 (Fig. 1), the absence of a layer of iodine composition at the end of the rod, etc. the channel must be at least six diameters C. In this case, the outflow of metal through the channel is excluded. When ⁴⁰ random GOVERNMENTAL breakages channel walls 7 (fig.Z), reducing its length of less than six diameters of the channel wall to the level of contamination break outer mold surface A-A (fig.Z) and above the opening ⁴⁵ prikley- vayut (fig.Z) open loop

8 refractory pad 9 (figure 4).

This ensures the release of gases (shown by arrows in fig.Z), but eliminates the leakage of metal.

The diameter of the metal nails used is 2-3 mm, the thickness of the model composition layer applied on them is 0.20.5 mm. The required thickness is provided by dipping the nails into the molten model composition prepared for casting for 1-3 s.

The place of nails in the model is chosen from considerations of the best removal of gases from the mold during the process of pouring it. Mostly it can be thickening in the models, technological gains, etc. The maximum wall thickness of the models does not matter. This method is used on models with a minimum wall thickness of 4-5 mm, i.e. close to the minimum cast thickness of titanium alloys.

Example. In vacuum, centrifugal method produces shaped titanium castings of simple and complex configuration. Metal nails 60-70 mm long are used as rods. They are covered with a model composition, then soldered to the casting model to a depth of 30-35 mm. In case of accidental breakdowns, the number of which does not exceed 5%, the walls of the channels are broken down to the level of the surface of the mold, and the working capacity of the channels and the form is restored by gluing the shell molds to the surface of the mold above the resulting hole. Gluing is carried out on an open loop (fig. 3) on the mass with liquid glass, which is used to repair the molds. Due to the roughness of the lining surfaces and the shape between them, a gas-permeable gap is created. Of the poured the proposed method 349 shell forms in 14 cases, the wall of the exhaust

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1 183283

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the channels broke during the manufacturing process, and in 25 cases they were specially broken off to control the reliability of gluing the linings. In all 39 cases, the lining stuck on the open loop over the formed holes. As the overlays were used the wreckage of battle mold casting.

As a result of the testing, not a single case of displacement or removal of the pads and breakthrough of the liquid metal from the mold was observed. Testing. confirms that the reliability of this method is 100% guaranteed.

If we compare the proposed and known methods, then according to a known method, the gas outlet from the shell forms is carried out through the vents installed in the sockets made with the help of the corresponding protrusions on the models, and the vents are made by powder metallurgy from metal powders or from ceramics. The manufacture of the same venting channel according to the proposed method includes three simplest operations: applying a model composition to the rod, soldering the rod into the casting model and, after forming the shell and melting the model, opening the exhaust channel to extract the rod. With

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25

thirty

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This does not require any special materials.

According to a known method, special projections are made on the model to form nests, which are then opened in the shell and inserted into them. Venta manufactured by pressing metal or refractory powders, followed by high-temperature (at 1300-1500 ° C) roasting, mandatory in methods using ceramics. Special materials, accessories and equipment are needed for the manufacture of ventilation, which increases the cost of castings.

The proposed method greatly facilitates the manufacture of exhaust ducts in shell molds using investment casting, allows not only to simplify the manufacture of exhaust ducts or linings on the base of randomly broken channels, but also to reduce the cost of castings by eliminating the complicated manufacturing technology for vents, as well as to increase the reliability of gas removal and air from the shell mold when they are cast. The economic effect of the application of the invention will be 1000 rubles. per ton of suitable titanium castings.

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1183283

Claims (2)

1. METHOD OF MANUFACTURING SHELLS FORMES BY MELTED MODELS, used to obtain precision castings, which include applying a suspension on models of low-melting composition with the elements established in the models to form c. the form of the vapor channels, o * t -. distinguished by the fact that . to improve the quality of castings, • as elements for education gas channels use a model-coated rod with a protrusion at one end, set them in models with the opposite end before applying the suspension, and after melting the model composition from the shell, the location of the rod protrusion is opened and the rod is removed. 5Ts „„ 1183283 Fig.} 1183283 2. The method according to claim 1, characterized in that, in order to restore the operability of a randomly destroyed gas outlet duct, the latter is punctured to the level of the surface of the shell and the formed opening is closed with a refractory pad that is glued to the walls of the shell. . ί