SU865489A1 - Method of making undetachable ceramic moulds by the investment pattern technique - Google Patents

Description

(54) METHOD OF MANUFACTURING NON-CONVERTIBLE CASTING CERAMIC FORMS BY REMOVABLE MODELS The invention relates to foundry and can be used in the manufacture of all-in-one molds for small and medium shaped castings. A known method of making shell molds includes obtaining a cast model from a low-melting material (for example, model mass), applying layers of the shell to the model, drying or chemically hardening the shell, removing the melted model from the ceramic shell, calcining the shell l. However, with this method of making molds produced by a molten model, it is difficult to apply a high-quality refractory coating on the internal cavities of the model, a long cycle of operations is associated with drawing a model of a refractory coating consisting of several (3-10) consecutively on the surface. layers applied to the model and their dryness are low productivity. It is known to manufacture casting molds according to the Show process, according to which the gelling suspension is applied to a permanent model, after forming the model is removed, then volatile substances released from the mold are ignited and calcined. 2. The disadvantages of the Show process are the need to simultaneously use the prepared mixture in a short period of time (2-4 minutes from the start of preparation: the mixture). The high sensitivity of the process even to minor deviations, which makes it unstable and difficult to control due to the need for good filling, as well as the duration of the process of making the forms. The closest in technical essence and the achieved result is a method of making ceramic molds and rods from a mixture based on refractory filler, ethyls of a regular binder, solvent and hardener by applying the prepared mixture to the model, removing the latter from the mold after curing, followed by ignition. The forms and rods are heated to 5O-2OUC before ignition for 5-6 O min L3j. However, this method has a high production time of the molds due to the impossibility of producing the one-piece molds, while not using the chucks used to burn solvent vapors out of the mold material. The purpose of the invention is to reduce the time of manufacture of casting molds. The goal is achieved by the fact that the known method of making permanent ceramic molds is removable; the business involves the application of a self-hardening ceramic suspension with a gelling agent to the model, the removal of the model after shaping the form, the burning of volatile substances from the mold and its subsequent calcination a low-melting non-gas-making model is made in a mold inside which the pressing tip is placed, which, after opening the mold, removes the model, and the self- A ceramic slurry with the heater is poured into the pressing chamber, into which the tip of the pressing piston is immersed together with the model, and in a fixed position of the model in the volume of the suspension, the self-hardening ceramic suspension is pressed, and after the ceramic suspension is completely cured, the tip of the pressing press is removed from the pressing chamber , extract the ceramic form and ignite volatile B (substances with simultaneous melting of the model from the ceramic form. FIG. Figure 1 shows the production of a cast model from a low-melting non-gas-forming material (Wood alloy, salt composition in Fig. 2 — extraction of the cast model from the mold; Fig. 3 — pouring a suspension from a hydrolyzed solution (} ethyl silicate and a mixture of refractory materials with the introduction of a gelling agent in the pressing chamber; in Fig. 4 — the injection of the cast melted model into the suspension for pressing the suspension with the model; in Fig. 5 — the extrusion of the obtained ceramic form from the pressing chamber; in Fig. 6 — the burning of solvent vapors from the foil material we also simultaneously melt the model out of the mold cavity. A device for implementing the proposed method comprises a split press86 94 form consisting of two halves 1 and 2, a device 3 for pressing low-melting material 4, a pressing piston 5, tip 6 on which the melted model 7 is fixed , the pressing chamber 8 and the ejector 9. After the halves 1 and 2 are closed, the tip 6 of the pressing piston 5 is inserted inside, while the piston 5 is pressed against the mold. Then, the mold cavity is pressed into a low-melting non-gas-forming material (for example, Wood alloy). After the mold has been opened, the model 7 remains with the tip 6, which acts as an extractor from the mold. After this, the prepared suspension 10 from a hydrolyzed solution and a mixture of refractory materials with the addition of gelation is poured into the extrusion chamber (Fig. 3): and with the help of the pressing piston 5, the melted model 7, fixed to the tip 6, is removed into the suspension (Fig. 4) and is pressed suspension together with a model 7 enclosed in it in a closed cavity. After the suspension has cured, the pressing mold 5 with the tip 6 is retracted to the upper position, and the model 7 remains in the mold cavity. Then, the mold 11 together with the model 7 is pushed out of the pressing chamber 8 by means of a rotator 9. The melting of the model from the cavity 12 of the mold 11 is performed simultaneously with the burning of solvent vapors (Fig. 6), while the melted material 13 flows into the pan 14. When With this, the model is introduced into the slurry and the simultaneous comprehensive pressing of the slurry model is carried out with a pressurized press acting on the open surface of the slurry. Despite the fact that the mobility of the suspension is mo-. It fluctuates in some limits, however, since the pressure in the liquid is equally distributed in all directions,. This results in high-quality filling of all slots and profile channels. The speed of formation due to the introduction of the melted model into the suspension, which is fixed on the tip of the pressing piston, at the same speed of the pressing die depends on the gap between the model and the inner surface of the pressing chamber, i.e. on the wall thickness of the future ceramic shape. If the cross section of the annular gap is smaller than the projected area of the model's joint on the horizontal plane, then the forming speed will be higher than the pressing speed, i.e. lowering the pressing piston. By shaping speed is meant: the linear velocity of movement of the suspension in the gap between the model and the stack of the compression chamber as a result of suspension of the suspension by the model. With the same gap between the model and the wall of the extrusion chamber, the forming speed depends on the speed of the pressing pistons. Although from the point of view of productivity increase, it is advisable to work at high speeds of pressing, however, this results in air trapping, slurry suspension and so on, etc. In this connection, the model should be brought to the surface of the suspension from idle speed, and then the pressing speed should be reduced. The speed of pressing (the rate of introduction of the model into the suspension) should not exceed 0.15 m / s and be adjusted depending on the gap between the model and the lateral inner surface of the pressing chamber. The proposed method was obtained one-piece from a suspension of the following composition. Example. A suspension of the following composition is taken: 12O cm of hydrolyzed ethyl silicate binder 24O g of filler - white electrocorundum (24 A grade according to OCT2-115-71, grit number according to GOST 3647-71 M 4Q) and 5 cm of gelling agent - 15% solution of NaOH . The suspension, after thorough mixing, is poured into the pressing chamber, where a degreased model (lid detail) of a low-melting alloy of the following composition was introduced,%: & 5O, Pb 25 5 and 12.5, - Cd 12.5 with a temperature of events of 68 ° C, weighing 69.7 g. The suspension together with the –concluded in 1 model is compressed under a pressure of 2 kgf / cm. After being held under pressure for 3 months, the resulting form, together with the model, is removed from the press chamber. By burning off the solvent vapor, the model material is smelted. The quality of the surface is good, the roughness is not lower than Py, 2,, O. Experiments have shown that the temperature of the flame during the burning of solvent vapors is not lower than VOSgS, while the outer surface of the ceramic heats up to 40 ° C and higher during the burning out of alcohol. According to the method, one-piece casting is obtained, mainly for small and medium shaped castings that can be poured with molten metal both in single form and in the bush (the model bush is decorated with one pressing of the model material} by analogy with the known casting in molds made by E to be melted models, i.e., applying H | a to the surface of the refractory model (the first coating consisting of several 3-1O layers consistently applied to the model and their drying. It was established experimentally that with group technology The unevenness of the thickness of the mold wall does not affect the quality of the mold, since during the Show process the entire surface of the mold is covered with a grid of microcracks, which increase the technological properties of the mold (compliance, gas permeability), which practically does not reflect on the state of the surface of the castings. The models, for example, can be broken up by group technology into the defined diameter of the pressing chamber (Fig. 3-5). In addition, it is allowed to use ceramic waste in the form of particles with a size of 1-10 mm in an amount up to 25% of the content of the refractory component, which makes it possible to compensate for the possible increase in the flow rate of the gel-forming suspension. The melting of a model from a light-melting composition during the burning of solvent vapors, as shown by experiments, is not accompanied by the release of a large amount of gas-forming components and allows the bulk of the low-melting composition to be retained for rotary use. The bulging action of the light-laminate composition during its melting is prevented by the central hole in the model after it is removed from the tip of the pressing piston. The remnants of the composition in small quantities in the most distant corners of the form are completely eliminated during subsequent piercing (burning) of the drinking form. Calcination (burning) with a casting mold ensures the cleaning of the mold cavity from the remnants of the model material and ensures reliable pouring of the melt metal. The casting of the molds prepared according to the proposed method is carried out by analogy with the well-known pouring form (4, prepared for the melted models with a multilayer ceramic coating. The cooking 76 can be in two versions: a) calcining the mold during EOO-EZO and cooling it with a stove, setting up molds in a flask with dry filler in the form of quartz sand, heating the molds together with the flask to 40 ° -7OO ° pouring the mold; b) installation of the manufactured mold (without calcination) in a flask with dry Filler in the form of quartz sand, heating the mold together with the flask to a temperature not lower than in the oven, holding and removing the flask from the oven, pouring the hot mold (exact temperature and time conditions are not indicated as they depend on the alloy, the size of the casting, etc.). Flexural strength (TC of ceramic samples made according to the proposed method according to ;; with a mold material on an ethyl silicate binder (example in description), kgf / cm. In the raw state 4.3-4.5 After calcination 7, 3-7.5 The gas production of the forms made according to the proposed method after burning} alcohol was determined in a tubular 98 furnace at 11 dp C) is given in Table 1. Table 1 Time from the beginning of gas production of forms, cm - / g count, s When burning solvent vapors in the form, micro-cracks appear and micropores that are formed Nsiruyut shrinkage of ceramics and do not appear on the quality of the cast. In this case, formulations widely used for the Szu process are used. The density of ceramics forms obtained by free-pouring and pressing are given in table. 2 and 3. Table 2

35

80

175,927

1.88

pressure 2 kgf / cm

260

Free pouring slurry

Table 3

with pressure kgf / cm

Claims (3)

1.48 L. b. Follows H; .I table. .1 and 2. Density: e | 1; r1iki susshe pyzhngann oapOF; a solution of | 1T (l for pressing anip suspensions under an air pressure P - 20 kgf: / cm increases by 10% compared to 1 {free with free flow. Illegal method of making casting molds allows: a) to improve the shaping by pressing the suspension together with the molten mode enclosed in it while its position in the suspension suspension is fixed; b) use a single suspension, regardless of the complexity of the models, for example, deep grooves, etc., by pressing the suspension together with the model enclosed therein; c) use the heat emitted by burning solvent vapors out of the material of the casting mold; the model is melted simultaneously with the burning of solvent vapors; d) to improve working conditions, since small particles of powdered refractory material pollute the atmosphere at workplaces; e) exclude rods and rods, which require independent tooling for their manufacture; e) to mechanize the telescopic manufacturing process of casting without cores, which must be labeled for exact fixation 1 | X) of the B casting mold, and therefore the increase in the thickness of the wall of the casting mold is fully compensated for:,. g) reduce the labor intensity of casting molds; h) reduce the required production area; i) reduce the consumption of low-melting melted material of the model due to the volume of the tip of the pressing pores on which the model is fixed when it is manufactured in a mold; k) eliminate the effect of the expansion of the model on the walls of the mold when melted by the hole in the model obtained after being removed from the tip; l) arrange the gating channel in the process of pressing the suspension together with the key behind its 80LO model using the tip of the pressing part; m) to provide the model position in the process of forming the mold, i.e. in the process of compressing the slurry, and thus reducing the difference in the thickness of the mold due to the displacement of the model by fixing it on the tip. For example, the model via Wu-p alloy is the more desirable model from the model composition based on paraffin, etc. and the introduction of the model into the suspension without fixing it on the tip does not ensure its position within the ceramic mass. Formula of the invention The method of manufacturing a casting ceramic molds by removable models, comprising applying to the model a self-hardening ceramic slurry with a gelling agent, removing the model after shaping the form, burning the volatile substances from the form and then calcining it, characterized in that ) For the time of manufacture of the molds, a low-melting non-gas-forming model is prefabricated in a mold, inside of which is placed the tip of the press molding, which, after opening The mold is removed by the model, and the ceramic suspension self-heating with the gelling agent is poured into the pressing chamber, into which the tip of the pressing piston is immersed together with the model and in a fixed position of the model in the suspension volume, the self-hardening ceramic suspension is pressed, and after the ceramic suspension is completely cured from the pressing chamber, tip, pressing the piston, remove the ceramic form and ignite volatile substances while melting the model amicheskoy form. Sources of information taken into account in the examination 1. Doshkar J. and others. Production of full-time castings. M., Mechanical Engineering, 979, p. 78 2. In the same place with 143-151. 3. Author's certificate of the USSR 287241, cl. B 22 C 9 / O4, 1969. fug. /