SU538808A1 - Ceramic mixture for casting molds and cores - Google Patents

Description

one

The invention relates to foundry, in particular, to the manufacture of ceramic molds according to permanent models.

The known technology of casting with depth KIIMI narrow cavities, which in paraffin-stearine models are made by urea rods, soluble in water, is characterized by complexity and duration of the process. Replacing carbamide rods with ceramic reduces labor intensity and shortens the production cycle.

The SHOW method is widely used in domestic enterprises in the manufacture of cores for hollow castings. However, the use of a 15% sodium hydroxide solution as a gel stimulator requires adherence not only to precise dosages, but also to a number of additional operations and conditions for the preparation of binding materials and mixtures. Thus, alkali solutions cannot be introduced into the prepared mixture due to the impossibility of their quick and uniform distribution in the viscous mixture. In this case, instantaneous gelation of the binder material occurs in its individual sections, accompanied by the formation of lumps and a sharp increase in the duration of solidification of the entire mass of the mixture. The need to introduce alkali into hydrolyzed ethyl silicate determines their low vitality and also leads to a number of process drawbacks: low strength and the tendency of ceramics to develop large cracks, causing breakages and an increased defect of rods. The above disadvantages can be eliminated only by finding new gelation stimulants, the activity of which would allow them to be introduced into the prepared mixture. A 30-100% solution of triethanolamine was used as such a gelation promoter for mixtures on hydrolyzed ethyl silicate.

The famous ceramic mixture for casting molds and cores made by permanent models, including dry filler, binder and gelation agent in the following ratio of ingredients, wt. %:

Hydralized ethyl silicate9-18

Gelation stimulator -

30-100% solution of triethanolamine 0.3-5

Dry fillerEverything

The disadvantages of the known mixture are the difficulty of controlling the curing process and increasing the dosage of the gelation promoter. In addition, there are deep cracks and warping of the rods.

In order to stabilize the mixture curing process as a gelation mover from the group of amino alcohols, the proposed mixture contains ethanolamines with the following ratio of components, wt. % Hydrated Ethyl Silicate12, 5-14.3 Gelation stimulator - ethanolamine 0.06-0.1 Dry Filler The remaining Mixture is prepared as follows.

Per 100 cm of hydrolyzed ethyl silicate (ethyl silicate 78%; acetone 12.6%; water 9.49%; HC1 0.1%) take 600 g of dry filler (electrocorundum No. 50 50 g, No. 10 300 g, M 7 150 g and Marshalite 100 g). The components are thoroughly mixed and 0.3-1 € of ethanolamine is added (depending on whether ethyl silicate is hydrolyzed with alcohol or acetone). After mixing, the mixture is poured into the mold.

After the mixture becomes rubbery, the mold is disassembled and the half in which the soft and fragile core remains is placed in hot water heated to a temperature not lower than 85 ° C to prevent the formation of large cracks and accelerate the hardening process. At the end of the curing process, the pre-form Loloin with the rod is removed from the water and the rod is extruded. With ethanolamine, the curing process is stabilized. The reject rate for warping is noticeably reduced. The advantage of ethanolamine over triethanolamine is also that its dosage is sharply reduced.

According to MRI 6-02-495-68, ethanolamine is the primary amino alcohol. In appearance, it is colorless or slightly yellowish viscous liquid. Density at 20 ° С 1,017 - 1,025 refractive index at

20 ° C 1.4535-1.4565; molecular weight 61.086; structural formula: H2N-CH2-CH2-OP.

The compositions of suspensions and physico-mechanical and technological parameters are given in the table.

Claims (1)

If you take a dry filler more than 87.5% of the composition of the ceramic mixture, it is impossible to ensure its homogeneity due to the large amount of dry filler, all other conditions being equal, which leads to an uneven distribution of the gelation stimulator between the particles of the dry filler. This forms a thick, loose mass that cannot be poured into the mold. In that case, if the dry filler is less than 85.7% of the composition of the ceramic mixture, the rods have reduced strength. If the content of hydrolyzed ethyl silicate is more than 14.3% of the composition of the ceramic mixture, the percentage of dry filler in it is reduced, which results in rods with reduced strength under other equal conditions. If the hydrolyzed ethyl silicate is less than 12.5% of the composition of the ceramic mixture, ceteris paribus, it is impossible to ensure its homogeneity, which leads to marriage. When the ethanolamine content is more than 0.1% of the composition of the ceramic mixture, its setting time is reduced. The time limit leads to the fact that they do not have time to stir and pour the mixture into the mold, i.e., a marriage appears. When the content of ethanolamine is less than 0.06% of the composition of the ceramic emulsion, the setting time of the mixture significantly increases, which leads to the distortion of the rod and the appearance of a network of deep fracture cracks. The invention The ceramic mixture for the manufacture of casting molds and cores can be divisible by constant, including a dry filler, hydrolyzed ethyl silicate, a gelation booster from the group of amino alcohols, so as to stabilize the process of hardening the mixture, as a result of 5 waketel gel it contains this 6 nolamine three the following ratio of ingredients, weight. %: Hydrated Ethyl Silicate 12.5-14.3 Ethanolamine 0.06-0.1 Dry Filler Else