SU1639870A1 - Casting mould sand - Google Patents

Abstract

The invention relates to a foundry, namely, to mixtures for the manufacture of foundry molds, mainly in the production of cast iron. The purpose of the invention is to improve the quality of castings by reducing the burn and burning, as well as improving the erosion resistance of the molds at the ratio of the plant volume, to the MELTING-RELEASES reimuz chuzhuchstva and scorching the pouring metal to the volume of the mold mixture from 1 to 3-7. The composition contains the following ingredients May. %: ground coal 2.00-5.00; bentonite 4.00-10.00; soda ash 0.12-0.30; VAT residue of the production of hydrogenated fuel (KO) 0.10-1.00; refractory filler - the rest. The use of CO in a mixture containing hydrocarbons of various molecular weights contributes to the creation of a reducing atmosphere and counterpressure in it during the entire period of casting. In addition, KO improves the plastic properties of the mixture. The use of the mixture according to the invention makes it possible to obtain castings with good surface quality with a ratio of the volume of the cast metal to the volume of the mixture of the mold from 1 to 3-7. This reduces the cost of casting production, saves molding materials, and improves performance. 3 tab. (Ls

Description

The invention relates to the field of foundry, in particular, to compositions of mixtures for the manufacture of casting molds in the manufacture of castings, mainly of cast iron.

The purpose of the invention is to improve the quality of castings by reducing the burning and burning, as well as increasing the erosion resistance of the molds when the ratio of the volume of the cast metal to the volume of the form mixture is from 1 to 3-7.

As an additive, contributing to the achievement of the goal, the mixture contains the product of oil refining in the form of the bottoms of the production of hydrogenated fuel produced according to TU 381.018-83-83 under the brand name RJ-8.

RJ-8 is a mixture of hydrocarbons of different molecular weights and has the following characteristics;

Kinematic viscosity at 20 ° С, mm2 / s6.0-8.5

Flash point, determined in the closed

crucible, C

120 (not lower)

about

SA) O 00 VJ

ABOUT

Mass fraction of aromatic hydrocarbons,% 5.5 (no more) Content of mechanical impurities and waterNo

Pour point, ° С-6 (not below)

sulfur,% 0.01 (not more)

Coking ability,% 0.05 (not more than)

The self-ignition temperature, ° C 223 RJ-8, introduced into the mixture for making the forms, on contact with the molten metal releases pyrolytic carbon for 15–20 s, since its composition contains various hydrocarbons sublimated at different temperatures, then ensures the creation of a reducing atmosphere and back pressure over the entire period of casting the mold with metal. At the same time, its introduction does not affect the strength characteristics of the mixture in the zone of moisture condensation, i.e. does not create the danger of formation of coarse defects on castings. In addition, RJ-8 serves as a plasticizer for the mixture.

The mixture according to the invention is prepared as follows.

Refractory filler, bentonite, coal, soda ash and vat residue of hydrogenated fuel production are mixed into the mixer and mixed for 10 minutes.

The compositions of the mixtures are given in table. 1, their main properties in the table. 2, and the quality of the castings with a different ratio of metal to the form - in the table. 3

An increase in the coal content in the mixture above the upper limit leads to an increase in gas generation during the casting process, which causes an increased risk of gas defects in the castings. Reducing the carbon content below the lower limit does not provide sufficient antiburning properties of the mixture.

Increasing the bentonite content above the upper limit is economically and practically impractical. Reducing its content below the lower limit does not provide the required strength characteristics of the mixture both in the process of making the mold and in the process of pouring it and forming the casting (at high temperatures).

The content of the calcined salt is determined by the percentage of bentonite in the mixture. While maintaining the optimum ratio of bentonite and soda, the maximum strength value is reached in the zone of moisture condensation; with a decrease in soda content below the lower limit as well as with an increase in its

-

content above the upper limit, there is a significant decrease in the above strength.

The content of the bottom residue of the production of hydrogenated fuel below the lower limit does not significantly affect the improvement of the technological properties of the mixture, and an increase in its content above the upper limit increases the gas creativity of the mixture and increases the risk of such casting defects such as folding and geometry.

Thus, the introduction of the bottoms of the hydrogenated fuel production into the molding sand mixture increases the strength properties of the mixture in the wet state and the tensile strength in the moisture condensation zone, which affects the technological properties of the mixture. Wherein

reduction of the above-mentioned bottom residue allows reducing the mixture's tendency to change the geometry of the forms under the action of the melt in the process of pouring it and at the stage of forming the casting itself.

The fact that the proposed composition of the mixture allows to obtain high-quality castings in a wide state of the volume of the poured metal to the volume of the mixture of the mold reduces the cost of the production of castings (especially

at low ratios, saves molding materials, improves the performance of production.

35

Claims (1)

Invention Formula The mixture for the manufacture of casting molds in the manufacture of castings, mainly of cast iron, containing ground coal, bentonite, soda ash, a product of oil refining and a refractory filler, in order increasing the erosion resistance of the forms when the ratio of the volume of the poured metal to the volume of the mixture of the form from 1 to 3-7, it contains the bottom residue of the production of hydrogenated fuel as a product of oil refining at the following ratio enii ingredients May. %: Ground coal2.00-5.00 Bentonite 4.00-10.00 Soda Ash 0.12-0.30 Distillation of hydrogenated fuel 0.10-1.00 Refractory filler Rest Table 1 table 2 Table 3