RU2295418C1 - Suspension prepared for ceramic mold making with use of investment patterns - Google Patents

Abstract

FIELD: foundry, namely with use of investment patterns, possibly manufacture of ceramic shell molds.

SUBSTANCE: suspension includes, mass %: aluminum boron phosphate, 16.0 - 18.0; water, 16.0 -18.0; surface active matter, 0.1 - 0.5; magnesium silicate powder, 3.5 - 5.0; pulverized refractory filler, the balance.

EFFECT: improved quality of cast products, increased rate of making ceramic mold.

3 cl, 2 tbl, 1 ex

Description

The invention relates to foundry, in particular to investment casting, and can be used for the manufacture of ceramic shell molds.

A known suspension for the manufacture of investment casting molds, including silica, ethyl silicate, sulfanol, butanol, pulverized silica and water. [Patent RU No. 2185260. Suspension for the manufacture of investment casting molds, IPC B 22 C 1/16, publ. July 20, 2002].

The disadvantages of the suspension include the duration of hardening and the need for additional chemical curing of the applied coatings.

The closest in composition is the composition of the suspension for the manufacture of ceramic molds by investment casting, containing in the following ratio of ingredients, wt.%: Alumochromophosphate binder 12.0-17.0, phosphoric acid 1.2-2.0, blacksmith carbon steel 10 , 0-14.0, surfactant 0.08-0.15, water 13.5-20.0 and dust-like refractory filler - stop. [Patent RU No. 2167022. Suspension for the manufacture of ceramic molds according to investment casting, MPK V 22 C 1/18, C 04 V 35/14, publ. May 20, 2001].

The disadvantages of the suspension include the low quality of the casting surface due to the high content (10-14%) of blacksmith scale, which is well wetted by metals and can form a chemical burnout, insufficient ceramic hardening rate, as well as negative sanitary and hygienic working conditions associated with the use of pure phosphoric acid and a chromium binder in large quantities (12-17%).

The objective of the invention is to obtain a suspension for the manufacture of ceramic molds by investment casting with an accelerated hardening period, as well as improving the quality of the casting surface.

To achieve the task, the proposed suspension for the manufacture of ceramic molds by investment casting, including a phosphate binder, water, a surfactant, a hardener and a dust-like refractory filler, according to the invention contains alumina borophosphate as a phosphate binder, and magnesium silicate powder as a hardener in the following ratio of ingredients, wt.%:

Aluminum phosphate 16.0-18.0 Water 16.0-18.0 Surface-active substance 0.1-0.5 Magnesium Silicate Powder 3,5-5,0 Dusty refractory filler Ost.

Magnesium silicate powder contains magnesium oxide, silicon oxide and oxides of calcium, chromium, aluminum in the following ratio, wt.%:

MgO≥75

SiO ₂ ≤20

CaO, Cr ₂ O ₃ , Al ₂ O ₃ ≤5

The suspension as a dust-like refractory filler contains electrocorundum.

The difference between the proposed solution and the known one is the introduction of aluminoborophosphate into the suspension instead of aluminochromophosphate and the replacement of blacksmith scale with magnesium silicate powder, which together with known components improve the technical result.

An example of a suspension. To obtain a suspension, three mixtures were prepared [Table 1].

Table 1. Ingredients The compositions according to the invention, wt.% No. 1 Number 2 Number 3 Prototype Aluminum phosphate concentrate 16 17 eighteen - Water 16 17 eighteen 16,0 Surfactant 0.1 0.3 0.5 0.1 Magnesium Silicate Powder 3,5 four 5 - Dusty refractory filler Ost. Ost. Ost. 55.2 AHFS - 15.0 H ₃ PO ₄ - 1.7 Blacksmith carbon steel - 12.0

To make a suspension, aluminoborophosphate (TU 113-08-606-83) is dissolved in the calculated amount of water (GOST 51232-98) to a density of about 1250 kg / m ³ , then a surfactant is added, which is used as a technical liquid lignosulfonate (LST) TU 13-0281036-029-94) in an amount of 0.1-0.5%, a pulverized refractory is introduced - electrocorundum (GOST 28818-90) and the suspension is mixed. In this form, the suspension has a long shelf life (at least 14 days), which distinguishes it from the prototype, in which the survivability is 6 hours.

The last ingredient in the suspension, immediately before the manufacture of the ceramic shell mold, is a hardener - magnesium silicate powder obtained by grinding forsterite refractory products (GOST 14832-96) containing magnesium oxide ≥75%, silicon oxide ≥20% and oxides of calcium, chromium, aluminum ≥5% in the amount of 3.5-5%.

The hardening process occurs as a result of a chemical reaction of an aluminum-borophosphate binder with magnesium oxide and silicon to form an aqueous solution of aluminum, magnesium, silicon and boron phosphates, which, like the aluminum-chromium iron phosphate binder, in the known solution hardens at room temperature. The difference is that the speed of the chemical reaction is higher and therefore, phosphoric acid is not required to be added to the suspension to increase it, in addition, the use of phosphoric acid in its pure form is undesirable under sanitary conditions.

The properties of the prepared suspensions and ceramic forms obtained from them are given in Table 2.

Table 2. Indicators of suspensions and ceramic forms Composition Examples No. 1 Number 2 Number 3 Prototype The curing time of the coating, min 0.5 mm layer twenty 12 fifteen 42 1.5 mm layer 45 22.5 25 Survival suspension, min. Without hardener Not less than 14 days 6 hours With hardener twenty 7 6 25 Contact angles in the suspension-smelting system (PS 50-50), θ, deg. 45 42.5 32 - Spreadability of the suspension according to the lost wax model (PS 50-50) d, mm 7.5 7.8 8.15 - Al-based alloy system — ceramic form, T = 1100 ° C, (σ _g = 710 MJ / m ² Contact angles θ, degrees 122 135 137 - The work of the adhesion of the phases W, MJ / m ² 334 208 191 -

From the data of table 2 it follows that the hardening time of the proposed ceramic suspension is 22.5 minutes versus 42 minutes for the known solution and depends on the thickness of the layer. The hardening time and survivability of the suspension also depends on the amount of hardener. The optimum content of magnesium silicate powder was experimentally established in the range of 3.5-5.0%.

The viscosity of the suspension is controlled by the content of aluminoborphosphate. When the content exceeds 18%, the wettability and spreadability become excessive (spreadability> 8.15, angle <32 °), and when the content is less than 16%, they become insufficient for technological coating (spreadability <7.5, angle> 45 °) .

Also from the data of Table 2 it follows that the ceramic form based on the proposed suspension has a high lyophobicity to liquid metal, which is expressed through a large contact angle of wetting (135 degrees) and a small work of phase adhesion (208 MJ / m ² ). Non-wetting of the metal surface of the ceramic mold improves the quality of casting, as well as the ease of knocking the casting out of the mold.

Thus, the use of the invention will improve the quality of the cast surface and increase the speed of manufacture of the shell mold.

Claims (3)

1. Suspension for the manufacture of ceramic molds according to investment castings, including a phosphate binder, water, a surfactant, a hardener and a dust-like refractory filler, characterized in that it contains aluminoborophosphate as a phosphate binder, and magnesium silicate powder as a hardener in the following ratio ingredients, wt.%: Aluminum phosphate 16.0-18.0 Water 16.0-18.0 Surface-active substance 0.1-0.5 Magnesium Silicate Powder 3,5-5,0 Dusty refractory filler Rest 2. The suspension according to claim 1, characterized in that the magnesium silicate powder contains magnesium oxide, silicon oxide and oxides of calcium, chromium, aluminum in the following ratio, wt.%: MgO ≥75 SiO ₂ ≤20 CaO, Cr ₂ O ₃ , Al ₂ O ₃ ≤5 3. The suspension according to claim 1, characterized in that it contains electrocorundum as a dusty refractory filler.