SU1741962A1 - Method for producing combination pattern compound - Google Patents

Abstract

Use: foundry, in particular, the production of complex thin-walled castings in molds on melted models. Invention: wax and crystalline components of the model composition are melted, these melts are mixed, the mixture of melts is heated to a temperature not exceeding 10 & amp ° C The melting point of the crystalline composition of the composition. This melt is then fed to the intensively cooled surface of the rotating drum, while providing a cooling rate for the composition of 2-5 ° C. C / s. The resulting cooled layer of the composition with a thickness of less than 2 mm is mechanically removed from the surface of the drum and used to make models that are being melted. 5 tab., 1 Il. SO with

Description

The invention relates to foundry, in particular, to methods for making model compositions used in casting on melted models.

A known composition for the manufacture of complex models, which is a mechanical mixture, comprising a low-melting plasticizer based on paraffin, brown coal and peat wax, and a dextrin powder filler.

The disadvantages of this composition are that it does not guarantee the complete removal of the dextrin powder filler with all known methods of removing any individual mass from the mold cavity. Dextrin residues can cause clogging defects, especially for castings of complex geometry.

A known composition for making water-soluble rods and models, including urea, polyvinyl alcohol and polyethylene glycol.

This composition also cannot be used for castings of complex geometry.

Also known is the combined model composition, the preparation of which is carried out as follows. A wax-like substance (or a finished wax-like mass) and a crystalline substance (urea), pre-ground to grains no more than 0.2 mm, are loaded into a thermostat in a given ratio; after heating the mixture to 85-95 ° C, the model composition is mixed mechanically, poured into molds in the form of bars or in a thermostat with

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temperature 80-95 ° C. Such a model composition provides blade models with satisfactory surface cleanliness. However, it is almost impossible to reduce the amount of shrinkage of models less than 0.5%. With an increase in the amount of solid filler in the composition of more than 50%, it loses its technological properties: the surface roughness of models and blades increases; conditions of formation of models of complex geometry deteriorate; It is impossible to obtain models of sectional (block) blades.

The closest to the proposed method is a method for preparing a composition for producing complex thin-walled models, including melting the wax component and introducing technical urea into this melt, also in the molten state, mixing the ingredients to form a uniform consistency, followed by pouring it onto the cooled surface of the mold with a layer 1-4 mm for preparing the finished composition in the form of flakes or plates.

However, the known method does not guarantee a stable thickness of the layer of the hardened composition and, therefore, a strictly homogeneous distribution of dispersed particles of solid filler (urea) throughout the thickness of the layer.

And the absence of conditions for regulating the heat sink leads to the formation in the layer of a hardened composition of urea particles with different sizes of dispersion and shape, and therefore the shrinkage of the models is unstable.

The aim of the invention is to improve the quality of the model composition due to the uniform distribution of the crystalline substance after mixing melts of waxy and crystalline substances.

This goal is achieved in that according to the method of obtaining a combined model composition for complex-shaped thin-walled castings using melted models such as blocks of nozzle apparatuses, including melting wax-like and crystalline substances, mixing them and intensively cooling the composition, the composition overheats to a temperature not higher than 10 °. From the melting point of the crystalline substance, and the composition is cooled by freezing it onto the rotating surface of the drum, which is They put the model composition into the melt, while the cooling rate of the composition is 2-5 ° C / s.

The proposed method for preparing a combined model composition is implemented as follows.

The finished wax-like model mass, for example, VIAM-102B, consisting of peat wax, brown coal wax, paraffin, triethanolamine is melted

0 at 100 ° C in one of the converters. In another converter, a crystalline model mass (for example, MPVS-2 with a melting point of 125 ° C) or a crystalline substance (for example, urea) is melted.

5 The melts are drained through a heated funnel into the crystallization bath. Technological additives are introduced into the mass melt, the composition is heated to 135 ° C (in the case of crystalline matter, mass

0 MPVS-2), mix with the impeller for 5 minutes. Then, a water-cooled drum is immersed in the bath with the melt of the model composition and rotated from the inside, while the cooling rate

5 frozen compositions provide 2-5 ° C / s. The model composition, which has got onto the drum surface, is removed with the help of a knife mounted on the machine. The thickness of the cut plates and scales

0 is predominantly 0.5-1.5 mm. The preparation of a model composition for pressing the models is carried out in tanks with a water bath with constant stirring until a uniform pasty

5 states with a maximum heating temperature of not more than 78 ° C.

Results on the state of fracture of the model composition depending on the superheat temperature and cooling rate

0 are shown in table 1 and figure 1.

The crystalline substance at the expense of optimal cooling rates crystallizes throughout the thickness of the layer of the composition in the form of crystals with dendrites of the first and

5 second time dkov. The gaps between the dendrites are filled with a wax component.

Such a method of preparing a model composition makes it possible to obtain models of GTE patch packs with low and stable shrinkage.

The return of the model composition can be used many times after it is melted and re-crystallized by freezing.

Table 2 shows the properties of perepla5 BOB model composition by the proposed method. In table 3 and 4 - the properties of the model composition in comparison with the prototype. In table 4 - indicators on the quality of the models on the geometry in comparison with the prototype.

Table 5 shows the indicators of the quality of models in geometry from model compositions by the proposed method in comparison with the known.

Parameters setting for the preparation of a combined model composition:

Diameter of the drum, mm 800

Drum circumference, mm 2200

Drum cooling water temperature, ° С 10-14

Compared with the known, the proposed manual provides improved quality of the model composition.

Claims (1)

Invention Formula The method of obtaining a combined model composition for complex-shaped thin-walled castings based on melted models such as nozzle blocks 0 five apparatus, including melting of waxy and crystalline substances, their mixing and intensive cooling of the composition on a cooling surface, characterized in that, in order to improve the quality of the model composition due to uniform distribution of the crystalline substance after mixing melts of waxy and crystalline substances, the composition overheats to temperature not higher than the melting point of the crystalline substance, and the composition is cooled by freezing it on a spin yuschuyus surface of the drum which is immersed in a melt of the composition model, the rate of cooling compositions provide 2-5 ° C / s. Table 1 no data in prototype Table 2 Table3 Table4 Dandy you P-th dca -.fc & Cool surface. / Table5 1st order dendrites The main axis of the dendrite