SU835596A1 - Mixture for producing water soluble inserts and patterns - Google Patents

Description

one

The invention relates to foundry, in particular to the production of casting on melted models of caval blades, namely for the manufacture of ceramic rods and castings.

A known composition based on urea contains, in addition to urea, polyvinyl alcohol and sodium compounds 1.

Along with sufficient ductility, high strength and accuracy, this composition has significant drawbacks.

Upon dissolving the models, the sodium compounds remain in the pores of the ceramic of the mold and the rods, and after calcining the mold before pouring the metal, the compounds turn into sodium oxide, which is smooth for ceramics containing silica and alumina. This reduces the refractoriness of the mold and the rods.

It is difficult to extract models from molds, especially thin and complex in shape models are cracking.

The mixture has significant hygroscopicity with low dissolving ability in water at room temperature.

Closest to the invention is a urea based mixture containing ammonium halide 2.

This compound has high strength and

Accuracy, short time of dissolution of models, somewhat less hygroscopicity. But this composition also has drawbacks: the lack of plasticity of the composition, leading to the impossibility of making thin and complex in shape inserts and models by the method of pressing under pressure; the difficulty of removing models from molds and cracking thin and complex in shape models; still significant hygroscopicity.

The aim of the invention is to increase the strength and resistance to cracking, as well as to reduce the hygroscopicity.

For this, the known mixture, which includes urea and ammonium halide, contains polyvinyl alcohol, thermosetting resin and silicone hydrophobic liquid in the following ratio of ingredients, weight. %: Ammonium halide 0.3-23.0

Polyvinyl alcohol13.5- 5.0

Silicone hydrophobic liquid4.0-0.5 Thermosetting resin 22.5-6.5 Urea Rest As a thermosetting resin, a resol or novolac resin is used, the resin consisting of 60-70%

3

fractions of 100-160 microns and 30-40% of fraction 4U-50 microns.

As the organosilicon hydrophobic liquid, compounds of a siloxane series, liquid PMS-30, PMS-100 or NGL-94 are used.

The carbamide entering the mixture is a white crystalline substance with m. Pl. 127 ° C, which imparts solubility of the mixture in water at a comed temperature, strength, surface cleanliness, low shrinkage.

Polyvinyl alcohol is a chain-chain polymer, white powder, solid at room temperature, melting point 213 ° C, gives thermoplastic properties, resistance to cracking; increases the viscosity of the mixture in the molten state.

Ammonium halide - ammonium salts and halogen-hydrogen cations of the general formula H4X, where X - halogen atoms. Colorless crystals are well soluble in water. The decomposition temperature is 300 ° C. It promotes the solubility of the mixture in water at room temperature, increases the range of operating temperatures, reduces the melting point, reduces toxicity, the total ash content of the mixture.

As a thermosetting resin, pulver-bakelite (a finely ground mixture of Novolac resin HOSbN4CH2SbN4ON of the brand SFO12 with hexamine) with m. Pl. 126-Shb C, as well as bakelite lacquer - solution of IFF rezol resin in ethanol.

Polymerization at a temperature of 160 ° C.

Instead of resin, it may contain dextrin (SbH1OO5) x - a mixture of starch hydrolysis products.

After transferring these resins to a non-melting solidified state by teil processing and grinding, they are a dark brown powder.

Silicone hydrophobic liquid (PM.S-30 or PMS-100 - polymethylsiloxane; GKZH-94 - polyethylhydrosiloxane - clear, oily liquids, degradation temperature of 170 ° C) reduces the hygroscopicity of the mixture, increases compliance and longevity of models, eliminates the need for lubrication molds in the manufacture of models.

Example 1. The pre-transfer to the non-melting solidified state by heat treatment of novolac resin (binding PB - pulverbakelite) at a temperature of 180-200 ° C for 2 hours, then grinding the resin to a fraction of 100 µm 60-70% and 40-50 microns 30-40% and carry out sieving.

The carbamide is preheated to a PO-120 ° C temperature, ammonium bromine-fluoride is added with stirring, polyvinyl alcohol until dissolved, then

polyethylsiloxane fluid

NGL-94 and a pre-treated thermosetting resin. After the final mixing, the inserts are pressed at a temperature of 125130 ° C under a pressure of 3-10 n / m from the mixture with the following ratio of ingredients, weight. %: carbamide 64.5; polyvinyl alcohol 11.75; ammonium bromofluoride 0.35;

polyethylsiloxane liquid 3.4, thermosetting resin 20.0.

Inserts are obtained with a length of 40, a width of 8, a thickness of 1 mm, and with seventeen holes with a diameter of 0.79+ on them.

± 0.02 mm, which were used in the manufacture of ceramic rods, by pressing in a temperature of 125-135 ° C. After making the inserts in the cavity cavity, the inserts are dissolved in water at

room temperature for 20 min.

The rods are then fired and the blades are cast by the known technology with the above rods. The blades are then opened and a comparative measurement is made of the diameters of the holes in the inserts and elements of the blades, decorated with cavities and pins of rods made using the above inserts. The following results were obtained: the diameters in the inserts were 0.79 ± 0.02 mm, the diameters of the holes in the elements of the blades were 0.8loo2 mm. The shape of the cast element in the blades corresponds to the shape of the inserts from the mixture.

Example 2. The pre-transfer to the non-melting solidified state (transfer of the bakelite lacquer from the rezol to the resitic stage) by heat treatment at a temperature of 180

200 ° C for 2 hours, then grinding to a fraction of 160 µm-60-70% and 40 µm-30-40% and sieving. The carbamide is preheated to 95 ° C, and ammonium chloride is introduced during transfer.

and polyvinyl alcohol until complete dissolution, then with stirring and at a PO-120 ° C temperature, the PMS-30 or PMS-100 polymethylsiloxane liquid is sequentially introduced and

treated thermosetting resin.

After the final mixing of the entire composition of the mixture, models are made at 80-90 ° C by pressing from the mixture with the following ratio of ingredients, weight. %:

Urea 64,5

Polyvinyl alcohol9,69

Ammonium chloride11,19

Polymethylsiloxane

liquid0.97

Thermosetting resin13,55

Next, ceramic molds are made by painting, the models are dissolved in water at 95-100 ° C for 1.0-1.5 hours. After drying and calcining the forms, the forms are cast with metal and further control of the geometry and surface of the castings. Geometry and the surface of castings meet the technological requirements for castings. Along with this, the mixture additionally has the properties of ductility. 8358 5 96 lack of interaction with ceramics of the form and the rod, low shrinkage, a significant range of operating temperatures. The compositions of the mixtures are given in table. 1, physico-mechanical and technological properties - in table. 2 (in Table 1, Compositions 1 and 2 - a mixture of 2 is known, and Compositions 3-6 are proposed). Table 1

As follows from the table. 1 and 2, the use of the proposed mixture as compared to the known 2 provides improved technological properties, increased use and increased productivity by reducing hygroscopicity when using an organosilicone silicon hydrophobic liquid, acquiring thermoplastic properties, and significantly increasing strength by using polyvinyl alcohol and a thermosetting resin, mixture stability to cracking, in particular, in the manufacture of very thin and complex models.

Installing such blades on aircraft engines will increase the working temperature on the blades by 100 ° C, due to which an increase in engine thrust by about 1000 kg can be achieved, which will lead to a decrease in transportation costs.

table 2

Physico-mechanical and technological properties of mixtures of examples

Claims (3)

1. A mixture for the manufacture of water-soluble inserts and models, including carbamide, ammonium halide, characterized in that it contains polyvinyl alcohol, thermosetting resin and silicone hydrophobic liquid in the following ratio of ingredients in order to increase strength and resistance to cracking, as well as reduce hygroscopicity , weight. %: Ammonium halide 0.3-23.0 Polyvinyl alcohol13.5- 5.0 Silicone hydrophobic liquid 4,0- 0,5 Thermosetting resin 22,5- 6,5 Urea Rest 2. A mixture according to claim. 1, characterized in that the thermosetting resin contains 60- 78 70% fraction 100-160 microns and 30-40% Sources of information, fractions of 40-50 microns. taken into account in the examination 3. Mixture by n. 1, except that, 1. Japanese patent number 52-20405, cl. PA that as a silicone fluid, 21, 1977. This mixture contains a siloxane-5 compound. 2. USSR certificate of authorship of a wide range. No. 555966, cl. B 22C 7/02, 1974. 835Y96