SU619272A1 - Mixture for making ceramic cores - Google Patents

Description

The invention relates to mixtures for the preparation of ceramic rods used in the manufacture of precision casting, for example turbine blades.

The closest to the described invention in terms of technical substance and effect achieved is a mixture for the manufacture of ceramic cores, including electroscorundum, powdered quartz, plasticizer, and an alcoholic solution of chloride;

When heating rods from a known mixture above 11OO C, the quartz in its composition (of which more than 2O% is in mass) changes to temperature changes with an abrupt change in volume, which leads to cracking and warping of the rods, therefore increasing their mechanical properties by increasing firing temperature is not possible.

Such a lack of ceramic masses is especially pronounced in the manufacture of rods of complex configuration with sharply varying thick sections.

The purpose of the invention is to increase the strength of the rods.

To achieve this goal, the mixture as a calcium salt of mineral acid contains calcium carbonate powder (CASOD. GOST 5972-51) with the following ratio of ingredients, wt.%: Elektrete orundBasic

Quartz pulverized 1О-2О Calcium carbonate О, О5-О, 4 Plasticizer12-18

Calcium carbonate decomposes during calcination with the formation of calcium compression, which, being a sintering mineralizer, forms complex aluminosilicates with silicon and aluminum oxides. The presence of the latter significantly reduces the sintering temperature, and also contributes to the transition of quartz to its high-temperature modifications, which, in turn, increases the temperature at which softening of the ceramic rods begins.

The proposed ceramic mixture for making rods is prepared as follows. In the drum mixer with balls, the pre-dried powders of the refractory filler and calcium carbonate are sewed for 30–30 min. In a heated mixer (converter with utapawH or paddle mixer), the plasticizer is loaded and melted and heated to 12 ° C. The resulting mixture is then exhausted (even in 2-3 steps). After the introduction of the mixture, the mixture is stirred at 1.5 -2.0 hours until smooth. The mass is poured into metal molds. or trays and used to make rods as needed. Ceramic rods of the proposed mixture are made according to the well-known tech- nology by the method of hot pressing at 65-12 ° C. The rods are fired at -13OO ° C in the backfill of the supporting floor of alumina. , Quartz pulverized Calcium carbonate. A mixture is known: quartz dust alcohol solution varnish KO-O86-5%: that calcium. The test results are shown in the table. To compare the sintering properties of core masses, burnt specimens (beams of 65 x 15 x 2 mm in size) are subjected to deflection under the action of their own weight with a distance of 58 mm between the supports. The beams are installed on two supports and placed in an oven, where the temperature is raised to 13OO, followed by aging for 24 hours (according to this mode, the samples underwent preliminary calcination). In addition to measuring the magnitude of the deflection, (when determining the strength of the samples at room temperature. 4 groups of samples manufactured within the proposed composition are tested; 2 groups of control samples (with a reduced and increased amount of quartz) and one group of known mixture samples. Below are c remaining mixtures, weight,%: (electrocorundum - base, plasticizer .5 weight%). JVV 2020ZO 0.20,40.4 O%; silicon carbide - 2%; orc

note For known and VI compositions strength

unacceptable for making thin rods for casting turbine blades; for composition 1, low mechanical heat resistance; Samples of compositions 11-V have high strength and satisfactory mechanical heat resistance.

As can be seen from the table, the most optimal is the composition of 1I, including 10% by weight of powdered quartz and 0.1% by weight % calcium carbonate.

The rods obtained from the proposed mixture have increased strength with satisfactory heat resistance and can be used to decorate thin and complex internal cavities in castings.

The proposed blend is simpler to manufacture than known and has a greater vitality in the molten state.

The mixture does not include scarce and expensive components.

To obtain rods from this mixture, it is not necessary to significantly increase the firing temperature, and, therefore, the rods can be sintered in widely used electric furnaces with silicon heaters.

The resulting rods are well extruded from the internal cavities of the castings.

Claims (1)

The formula isobregenic mixture for the manufacture of ceramic casting cores, which includes ectrocor, dust quartz, plasticizer, and calcium salt of mineral acid, characterized in that, in order to increase the strength of the rods, it contains norgaceas carbs "calcium calcium" to increase the strength of the rods ) in the following ratio of ingredient, weight. %: Electrocorundum Basis Quartz dust 1O-2O Calcium carbonate Oh ,, Plasticizer 12-18 Sources of information to take into account when experimenting: 1, USSR Author's Certificate No. 474386, MKL.2V 22 C 1/22, 31.O5.73.