RU2619548C2 - Manufacturing method of casts by gasified models - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes manufacture of the model in the mould by filling the mould with preliminary foamed expandable polystyrene raw beads with diameter 3-5 mm and layer thickness of 8-10 mm; the subsequent addition of modifying or alloying additives layer on the top in the form of the grains, dust, powder or pieces with thickness 1-2 mm and final foaming of expanded polystyrene raw beads to produce the model; model assembling in the model unit, painting of the unit with the antistick coating, drying, placing of the model unit in the moulding box, its filling with the support material, sealing, vacuuming and pouring of the metal.

EFFECT: method allows to manufacture the models from expanded polystyrene raw beads in moulds with uniform or gradient content and distribution of the modifying and alloying additives.

4 cl, 3 ex

Description

The invention relates to the field of foundry and can be used for the manufacture of castings of steel, cast iron, non-ferrous metals and their alloys using casting technology for gasified models in order to expand their scope.

The prior art method of modifying steel by introducing into the melt when draining into the ladle modifiers based on boron and its compounds (A.S. No. 1470777). The disadvantage of this method is the modification of the entire volume of the casting, which leads to an uneven distribution of modifiers in the volume of the casting, as well as a significant consumption of modifiers.

The prior art method for producing castings by gasified models, including obtaining models in molds by applying modifiers or alloying additives to pre-foamed granules of expanded polystyrene in the form of paint, subsequent drying, filling them into a mold and final foaming, assembling models in model block, painting the model block with gas-permeable non-stick paint, placing the model block in the flask, filling it with an unbound molding material, sealing it with vibration her, sealing and evacuation of the flask, pouring metal (RU 2048953 C1, B22C 7/02, 11.27.1995). The disadvantage of this method is the difficulty of obtaining high-quality models, since pre-foamed polystyrene granules after dyeing with an alloy coating and subsequent drying lose (partially or completely) the ability to subsequently increase their volume during final foaming in molds. Also, a significant amount of alloying and modifying elements in the volume of models can cause defects in castings (friability, shrinkage shells, spills, etc.).

The closest in technical essence is the method of introducing modifiers and alloying additives when casting on gasified models, including the manufacture of models of expanded polystyrene in molds that are filled with pre-foamed polystyrene granules, painted with alloying elements, with the addition of unpainted pre-foamed granules in an amount of 2 to 94% by volume (RU 2427442 C1, B22C 7/02, B22C 9/04, 08.27.2011). The disadvantage of this method is the difficulty of obtaining castings with uniformly distributed modifiers and alloying additives, since it is technically difficult to fill the mold volume so that the colored granules are evenly distributed. All this reduces the versatility of the method.

The proposed method is more versatile in relation to the prototype. Improving the versatility of the proposed method is expressed in the possibility of obtaining models of expanded polystyrene in molds with the required (uniform or gradient) content and distribution of modifiers and alloying additives.

The method is as follows.

In the manufacture of models in molds, their volume is filled in layers by pre-foamed polystyrene granules, with a layer of at least the size of granules, on top of which modifiers or alloying additives are added in the form of granules, powder, powders or pieces, with a layer of at least particle size of modifiers and alloying additives. Depending on the geometry of the model, its overall dimensions and the required casting properties, the quantity and thickness of the layers of modifiers and alloying additives are selected. To obtain a denser model, the method involves the addition of pre-foamed polystyrene granules with a layer of at least the size of the granules on the top layer of modifiers and alloying additives when filling the mold. For local modification and alloying of castings, the method provides for the addition of modifiers and alloying additives not over the entire surface of the layer of pre-foamed polystyrene granules, but locally, in one or more sections, while the area of additives should be at least 0.1% of the area of the pre-foamed granule layer . If the area of additives is at least 0.1%, then the modification and alloying of castings may be ineffective. In order to create a gradient of alloyed layers in castings, the method involves adding modifiers and alloying additives in various combinations with a different fraction on top of the layer of pre-foamed granules.

After filling the mold volume with pre-foamed polystyrene granules with the addition of modifiers and alloying additives, it is placed in an autoclave or other available equipment for the final foaming of polystyrene granules by heat. The resulting models are removed from the mold and, if necessary, they are dried. Modifiers and alloying agents introduced into the volume turn out to be firmly fixed in the model. Then the models are assembled into model blocks, stained with a non-stick coating and dried. Dry model blocks are placed in a flask, filled with support material, sealed, vauumized and filled with metal melt.

Examples of specific performance

Example 1. A cylindrical mold with a diameter of 30 mm and a height of 50 mm was filled in layers by pre-foamed polystyrene granules with a diameter of 3-5 mm, a layer of 8-10 mm. On top of each layer of pre-foamed granules, FX 60 ferrochrome was added in the form of powder with a 1-2 mm layer. The obtained models were poured with a melt of gray cast iron MF 15. The obtained castings contained chromium, their hardness was 58-62 HRC due to the formation of chromium carbides.

Example 2. The same as in example 1, only as an alloying element was added graphite, a fraction of 0.1-0.3 mm. Models were poured with bronze OCS 5-5-5. The resulting castings were contained in the inclusion volume of graphite.

Example 3. The same as in example 1, only as a modifier was added powdered corundum with a fraction of 0.1 mm. Models were poured with molten steel 40. The obtained castings had a crystalline structure on the surface, dendrites were in bulk. This indicates that the powdered corundum, introduced into the model volume, acts as a modifier, inhibiting the growth of dendrites on the surface, and creates new crystallization centers in the casting.

Claims (4)

1. A method of manufacturing castings by gasification models, including obtaining a model in a mold by filling the mold with pre-foamed polystyrene granules 3-5 mm in diameter with a layer of 8-10 mm thick, with the addition of additives modifying or alloying in the form of granules from the top, powder, powder or pieces 1-2 mm thick and the final foaming of polystyrene foam granules to obtain a model, assembling the model into a model block, painting the block with a non-stick coating, drying, placing the model block in the flask, apolnenie its support material, sealing, degassing and casting metal. 2. The method according to p. 1, characterized in that on the layer of additives modifying or alloying in the upper part of the mold add a layer of pre-foamed polystyrene granules with a layer thickness of 8-10 mm 3. The method according to p. 2, characterized in that the modifying or alloying additives are added locally to one or more surface areas of the pre-foamed polystyrene granules with an additive area of at least 0.1% of the pre-foamed granule layer area. 4. The method according to p. 3, characterized in that to create a gradient of the alloyed layers in the casting, modifying or alloying additives are added in various combinations with a different fraction.