SU1806033A3 - Method for making molds for investment casting - Google Patents

Description

The invention relates to metallurgy and can be used in the manufacture of molds for investment casting of parts made of steel, aluminum and copper alloys without a supporting filler.

The purpose of the invention is to increase the productivity of the process and increase the durability of the reinforcing layers of the casting molds.

This goal is achieved by the fact that in the method of making molds for investment casting, including the sequential application of facing and strengthening layers to the model blocks, drying each layer, a slip on an aqueous solution of a metal phosphate binder with a granular aluminum-containing refractory filler is used to form the strengthening layers. In this case, the content of aluminum oxide in it is no less than 65%. For the hardening of the reinforcing layers, magnesite with a specific surface area of at least 2000 cm ² / g is used. ·

An alumochromophosphate compound is used as a metal phosphate binder in a slip, and mullite corundum is used as an aluminum-containing filler. In this case, a slip with a density of 2300 ... 2500 kg / cm ^{3 is used} .

Mullite is used as an aluminum-containing filler in the slip.

Distinctive features of the prototype are the use of a slip for the formation of reinforcing layers, the use of a metal phosphate binder slip, the use of a granular aluminum-containing refractory slurry filler, the use of aluminum oxide as a granular filler, the content

1806033 AZ of aluminum oxide in slip not less than 65%, use of each strengthening layer of magnesite as a chemical hardener, use of magnesite with a specific surface area of at least 2000 cm ² / g, use of an alumina-chromium phosphate compound as a metal-phosphate binder in slip, use in slip as an aluminum-containing granular refractory filler mullite rundum, density of the slip 2300 ... 2500 kg / m3, use in the slip as an aluminum-containing granular refractory filler mullite.

Examples of a specific implementation of the method that constitutes the subject of the invention are carried out on an automated line model 64001 of the Tiraspol foundry plant for the production of five-layer molds.

The molding of three facing layers is carried out in baths and sand dumps, respectively filled with a ceramic suspension on an ethyl silicate ready-made binder GSK 20 E TU 6-02-12-58388 with pulverized quartz of KPA or KP B GOST 9077-82 and quartz sand of IK 016 GOST 2189 -78.

The formation of two reinforcing layers is carried out in baths and sand dumps, respectively filled with a slip on an aqueous solution of an alumochromium phosphate binder grade AHFS TU 6-18-166-83 with a filler of mullite mass MMK 65 TU 14-8-387-80 (aluminum oxide content 65%) or mullite-corundum mass MMK 88 TU 14-8-391-82 (aluminum oxide content 88%) and magnesite grade PPGP 1-0 TU 14-200-328-84 (periclase magnesite powder with MDO content> 95%, hydrated for the production of plates, manufacturer PO Magnezit; when sprinkling reinforcing layers in sand dumps with a fluidized bed, fine fractions of magnesite are used from 0.05 mm to dust-like, corresponding to specific surfaces from

G\

2000 to 6000 cm / g). The layer-by-layer drying time in a single chamber of the line is 3 hours.

The table shows the comparative parameters of the prototype and the proposed method.

Of these parameters, a change in the density of the slip leads to an increase in mold losses during pouring with metal: less than 2300 kg / m ³ - an increase in breakdowns due to a decrease in the thickness of the slip layer, more than 2500 kg / m ³ - an increase in breakdowns due to breakdown of the feeders.

Thus, the use of the proposed method makes it possible to reduce the loss of 15 mold resistance when pouring metal from 28% to 3%, synchronization of the drying time of the facing and reinforcing layers and a decrease in the number of layers to 5 increased labor productivity in the manufacture of 20 molds for investment casting.

Claims (2)

Claim 1. A method of making molds for investment casting, - including sequential application on model 25 blocks of facing and reinforcing layers, drying of each layer, characterized in that, in order to increase the productivity of the process and increase the resistance of the reinforcing layers, to form 30 reinforcing layers, a slip is used on an aqueous solution of a metal phosphate binder with a granular aluminum-containing refractory filler, in which the content of aluminum oxide is 35 not less than 65%, and for its curing magnesite with a specific surface area of not less than 2000 cm ² / g is used. 2. The method according to claim 1, with the fact that as a metal phosphate bond 40, an alumochromophosphate compound is used in the slurry, and mullite corundum is used as the aluminum-containing filler, while the slip is used with a density of 2300-2500 kg / cm3. 45 3. The method according to claim 1, characterized in that mullite is used as the aluminum-containing filler in the slip. Comparative parameters Method of making molds Prototype | The proposed Equipment '' Conveyor speed, m / min Mode of air drying of molds in the chamber: - temperature, ° C - relative humidity,%. Automation line mod. 64001 1.67 22 ... 26 60 ... 70 D 6 Table continuation Comparative parameters Method of making molds Prototype I The proposed Number of forming layers, incl .: ! 5 - facing 3 - strengthening 2 Facing layers: - binder GSK2OE - suspension filler KPA or KP B - pH, pH 1.5. ... 2.5 - viscosity according to VZ-4, s 40. ... 50 - layer filler IKOI6 - drying time, h 3 Reinforcing layers - the physical state of the liquid phase suspension slip - binder liquid glass AChFS - liquid phase filler KPA or KPB with fireclay MMK65 or MMK88 - the content of aluminum oxide. % noah dust twenty% 65% 88% - pH, pH 10 ... 12 12 . - viscosity according to VZ-4, s 90 ... 120 - - density, kg / m ³ - 2300. ... ... 2500 - layer filler when sprinkling IKOI6 PPGP1-0 - drying time, h not less than 4 3 Loss of durability of forms (from pouring),% / up to 28 until 3