RU2532765C1 - Dusting material for manufacture of shell-type moulds as per molten out models - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to foundry engineering. Dusting material contains the following, wt %: electrocorundum 30-40, iron scale 25-35, and iron is the rest.

EFFECT: improving quality of shell-type moulds and the obtained casts.

1 tbl, 1 ex

Description

The invention relates to foundry, and in particular to the production of investment castings.

A known suspension for the manufacture of shell forms based on ethyl silicate binder, including ethyl silicate, water, surfactant, hydrochloric acid, phosphoric acid, sodium aluminomethyl silicate in the form of a 15% aqueous neutralized solution with a pH of 2-6, a refractory filler, characterized in that it additionally contains electrostatic dust from the waste of ferroalloy furnaces in the smelting of silicon-containing compounds: technical silicon, ferrosilicon, silicochrome in the following ratios of the ingredient a, wt .: ethylsilicate 4,0-11,7; water 18.0-22.7; surfactant 0.09-0.1; hydrochloric acid 0.5-0.1; phosphoric acid 0.3-1.25; sodium aluminomethylsiliconate in the form of a 15% aqueous neutralized solution, pH 2-6, 1.9-2.5; electrostatic dust of ferroalloy furnaces 0.5-12.5; refractory filler - the rest [1].

Suspension has several disadvantages. Additional costs are required for the purchase of substances introduced into the suspension. In addition, the preparation of an aqueous neutralized solution of sodium aluminomethylsiliconate of the required concentration and pH is complicated.

A known method of manufacturing molds in investment casting using quartz sand to sprinkle the first layer applied to the slurry block, characterized in that in order to improve the quality of castings for sprinkling the second and subsequent layers, ground slag is used - waste of cupola, blast furnace or open-hearth production [ 2].

This method is not without drawbacks. An additional slag grinding operation is introduced, which is characterized by high labor intensity. The use of silicon dioxide as a coating material determines the possible negative consequences of polymorphic transformations in quartz, leading to a weakening of the strength of the molds and a decrease in their crack resistance.

A known method of manufacturing molds for investment casting, including the layered deposition on a lost wax model of a suspension based on a refractory material with an ethyl silicate binder and subsequent sprinkling with quartz sand of each layer, characterized in that starting from the third layer, the sprinkling is carried out with quartz sand with the addition of fused alumina in the amount of up to 30% by weight of quartz sand [3].

However, this method is not without drawbacks. Introduction to the composition of the material of shell forms of expensive electrocorundum leads to an increase in the cost of castings obtained by a known method.

Closest to the invention is a sprinkling material for the production of investment casting molds, including refractory granular material based on silicon oxide, characterized in that in order to improve the quality of the molds by increasing their strength, it additionally contains waste from the abrasive processing of castings from ferrous alloys, in the following the ratio of ingredients, wt.%: refractory granular material based on silicon oxide 60-90; waste abrasive castings from ferrous alloys 10-40 [4].

However, sprinkling material has several disadvantages. The high content of silicon oxide in the bulk material (both in the refractory granular material and in the composition of abrasive waste) in the prevailing amount determines the possible negative consequences of polymorphic transformations in quartz during calcination and casting operations with metal melt, which can provoke weakening of crack resistance and decrease in strength shell forms.

These shortcomings are eliminated by the proposed solution.

The problem of improving the technological process is solved in terms of using as a material a shell mold of a substance that provides stable strength and crack resistance of shell molds.

EFFECT: increased efficiency of the investment casting process due to the use of production waste in all layers of the shell mold with high quality shell molds and castings, achieved by completely eliminating silicon dioxide (quartz) from the composition of the bulk material and replacing it with aluminum oxide (electrocorundum) .

The technical result is achieved by the fact that as a sprinkling material for the manufacture of shell molds according to investment casting, a material is used that contains waste from abrasive processing of parts from ferrous alloys, including electrocorundum, iron oxide and iron, having the following composition,% mass .: electrocorundum 30-40, iron oxide 25-35, iron - the rest.

This technogenic waste is generated at machine-building enterprises, which include machining workshops, and in most cases are sent directly to industrial waste landfills for disposal.

Using abrasive processing of ferrous alloy parts as abrasive material (abrasive dust of grinding wheels for machining of ferrous alloy parts), which is a mechanical mixture of electrocorundum, iron oxide and iron, allows to increase the strength of shell forms by creating a kind of reinforcing framework with high iron thermal conductivity, as well as to increase the crack resistance of forms due to the presence of corundum in the shell material with a linear thermal coefficient Skog extension substantially smaller than that of quartz. In addition, the simultaneous presence of iron and aluminum oxides in the composition of the material creates the prerequisites for the formation of a ferrallite type spinel in the working layer of the shell at high temperatures, which can hold a large amount of moisture, which in turn provides accelerated sintering of ceramics.

At the same time, the costs of foundries for the purchase of expensive substances, as well as measures for the disposal of industrial waste from mechanical processing workshops at special landfills, are reduced.

Technogenic wastes used as sprinkling material provide the creation of a shell form of high strength, capable of withstanding significant mechanical and thermal loads. In addition, the high content of electrocorundum in the material contributes to an increase in the chemical and corrosion resistance of the molds, which guarantees high-quality castings.

Example

Shell forms were made as follows. For the manufacture of a refractory slurry, a ready-made binder GS-20E TU 6-02-1-046-95 and marshalite (pulverized silica) of grade A and B according to GOST 9077-82 were used. If necessary, nitric acid was used to adjust the binder to the working viscosity.

Abrasive dust of electrocorundum grinding wheels for machining parts from ferrous alloys on a bakelite bunch burning out at a temperature of 150-180 ° C was used as a backing material. Tests were carried out for the average component composition of the material that was sieved for distribution over fractions. For the first layer, material with a fraction size of 0.2-0.3 mm was used, for subsequent layers over 0.5 mm.

The total number of shell-shaped layers is five.

The results of industrial tests are presented in table 1. When using wastes of abrasive processing of parts from ferrous alloys with deviations from the specified parameters, the number of molds rejected by cracks after calcination and due to fracture during pouring increased and the yield of suitable castings decreased.

Tests have shown the effectiveness of using the proposed material with high quality shell molds and castings.

Information sources

1. Patent for the invention of the Russian Federation No. 2098217, class. B22C 1/16, B22C 1/02, B22C 1/10, 1997.

2. Copyright certificate of the USSR No. 231069, cl. B22C 9/04, 1969.

3. Patent for the invention of the Russian Federation No. 2297302, class. B22C 9/04, 2007.

4. Copyright certificate of the USSR No. 1364386, cl. B22C 1/00, 1988 - prototype.

Table 1 Prototype Proposed solution Number of forms 10 10 Number of molds rejected for cracks after calcination, pcs. 3 0 Number of molds rejected due to destruction during pouring, pcs. 2 one The yield of castings made in non-rejected forms,% 70.0 90.0

Claims (1)

Spraying material for the production of shell molds according to investment casting, containing waste from the abrasive processing of parts from ferrous alloys in the form of electrocorundum, iron oxide and iron, characterized in that it contains the specified waste in the following ratio, wt.%:
electrocorundum 30-40 iron oxide 25-35 iron rest