SU1235608A1 - Composition for making foundry moulds and cores - Google Patents

Description

The invention relates to a foundry and can be used to make molds and cores from metal phosphate cold-hardening mixtures.

The purpose of the invention is to increase the strength, vitality and gas permeability of the mixture.

The proposed mixture contains refractory material, orthophosphoric acid, bauxite and water,

as a refractory material containing silica, quartz sand is used, which is a mixture filler, thermal acid and bauxite.

Bauxite used in the indicated mixtures can interact with orthophosphoric acid and induce hardening of the mixtures with the formation of high strength, vitality, gas permeability and improve other technological properties.

The formation of these properties is predetermined by the composition of bauxite, which contains 28% by weight of iron oxides, bound in vitamins; adheminine and silicate compounds. By virtue of this, the activity of iron oxides in compounds with respect to orthophosphoric acid is significantly less than in free form, as is the case in the material given in the known composition - cupola burner. In this connection, the incubation period of hardening and, consequently, the survivability of the mixture as a whole, increases, which provides greater flexibility in the organization of production, reduction of the mixture waste, the possibility of making medium and large in weight rods and shapes with uniform properties throughout the volume of products.

The hardening of known mixtures is facilitated by aluminophosphates formed from the interaction of orthophosphoric acid with aluminum powder. In the proposed mixture, similar aluminophosphates are formed by the interaction of orthophosphoric acid with 6OKCliTOM

where the process of hardening of mixtures proceeds due to the chemical reaction of replacing aluminates and iron silicates with the formation of complex, aluminoelisophosphate and silica furiouszofosfatni colloid compounds, which determine their hardening with the formation of deep coagulation bonds,

five

0

five

0

which provides high strength properties of mixtures. When a chemical reaction takes place between the ingredients, mass exchange occurs in the boxitic-orthophosphoric acid system, which results in the structuring of the binder with the formation of gas-permeable pores, due to which the gas permeability of the mixture increases 5-6 times, for example, from 40 to 200 units after I h extracts of freshly prepared mixture.

Offered for use in mixtures, bauxite is a widespread, cheap material.

Any type of bauxite can be used in blends, but B-4 and B-6 are preferred since they are light. To be crushed in any Katkov mixers used in foundries, there is no preliminary preparation,. Bauxite can also be pre-milled and applied as a powder in continuous slag mixers or paddle mixers.

When testing mixtures, the following parameters are controlled: vitality, strength and gas permeability.

Vitality is determined as follows. A portion of the mixture weighing 6 kg is prepared and portions of the mixture are taken out every 5–10 min from the calculation of the manufacture of three standard 5 samples for strength testing.

The survivability of the mixture is determined by the time it retains a given initial strength with deviations within 110%.

Strength is determined according to the standard method i n e under compression of cylindrical K1GH specimens 50x50 mm in size, compacted threefold. blow standard copra. Gas permeability is determined by the standard method. The residual strength of the mixtures is also monitored after preheating to 1000 ° C and then cooling to 25 ° C.

When tested in mixtures, the content of dry ingredients of quartz sand and bauxite is changed on the basis of their total content equal to 89% by weight. The content of orthophosphoric acid in the composition of the mixtures is increased by 1.0 wt.% For every 3 wt.% Of bauxite. Moreover, the total content of liquid components orthophosphorus0

0

five

five

hydrochloric acid and water in the mixture are saturated with nocTOHHHisiM and in the sum equal to II wt,%. The mixtures were prepared in a roller laboratory mixer in batches of 6 kg each.

The test results, the mixture compositions and their technological properties are presented in the table.

Of the optimal mixtures of molds, molds and cores for steel castings of rollers with a mass of 80 kg were made. The mixture was prepared on a roller-type mixer. The order of input of materials is as follows: sand and bauxite are loaded into the mixer, phosphoric acid and water are poured. The mixing time of the dry ingredients is 2.5 minutes, after loading the liquid components 3.5-4 minutes. The finished mixture is poured into a cube (box) and transported to

The place of manufacture of molds or cores. The manufacture of lined fory is carried out on a shaking machine. The filling mixture is used sandy clay, wet, with the characteristic: compressive strength rtpH 0.48 kgf / cm

gas permeability of 100 units. After making the mold, the portable gas burner is dried briefly (12-15 minutes).

The rods are prepared in wooden boxes when compacted by pneumatic rammer. Finished rods extracted from schie-

stand (wired on

40

air for 50-60 minutes and sent to form assembly. Forms are poured with carbon steel with leiO C at the pyrometer. The obtained castings are recognized as suitable, have good surface cleanliness inside and outside: The rods are easily knocked out on the knock out grid.

As can be seen from the table, when the content in mixtures is 15 wt%, the property of bauxite% 15 on the initial strength is relatively small and does not satisfy production.

Sand Bauxite

74 15

ten

fS

20

 . 25

40

15

2356084

When the content of bauxite in blends is more than 30% by weight, a marked decrease within 1 hour and an unacceptable reduction in gas permeability are observed. A decrease in the survivability of the mixture with an increase in the content of bauxite has been observed, which is explained by the influence on the chemical processes of interaction of the concentrations of the reacting ingredients. When the content of bauxite in the mixture is more than 30 wt.%, The survivability becomes unacceptable 5 O is small for the conditions of manufacture of medium and large forms and rods. Therefore, the following limits of bauxite content are accepted in mixtures: the lower limit is 20 and the upper limit is 30 wt.%.

The amount of orthophosphoric acid, corresponding to the optimal composition of the mixture, is in the range of 8.5 - 10.5 wt.%. The acid content is less than 8.5 wt.% Leads to a drop in the initial strength of the mixture, and with an increase in the acid content of more than 10.5 wt.%, Its gas permeability decreases.

The amount of water in the mixture should be 0.5-2.5 wt.%. An increase in Btmie water of 2.5 wt.% Leads to a decrease in the strength of the mixture, and a decrease in the content of less than 0.5 wt.% Leads to a decrease in survivability.

The amount of refractory filling material should be 57.0-71 wt.%.

The implementation of the invention allows to increase the strength of the mixtures, their vitality and gas permeability, as well as to simplify the organization of production using self-hardening mixtures based on orthophosphoric acid, to improve the quality of the molds and cores, and hence the cast products, to reduce the waste of the mixtures, and to reduce the cost of through the use of cheap material, bauxite, to improve the sanitary conditions of labor, as in the preparation and use of mixtures with bauxite any harmful excreta are eliminated into the environment.

thirty

35

69 20

64 25

59 30

54 35

Phosphoric acid

Water

Zhivychect min

Source strength, kgf / cm

Durability after I h-exposure, kgf / cm

Residual strength

kgf / cm

Gas permeability of the original mixture, u

Gas permeability through

 h, units

Compiled by V. Shuvalov. Editor N. Tupitsa Tehred V. Kadar Proofreader M. Maksimishinets

Order 3041/8 Circulation 757 Subscription

VNIIPI USSR State Committee

on inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab ,, 4/5

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Production and printing company, Uzhgorod, st. Project, 4

Table continuation

9.5 1.5

35, 2

27 7.8 41 200

10.5 0.5 30, 6

32 8.5 38 180

II

15

2.8

25

32

120

Claims (1)

COMPOSITION OF THE MIXTURE FOR PRODUCTION CASTING FORMS AND RODS, including silica-based refractory material, phosphoric acid, water and a material containing iron oxides, characterized in that, in order to increase the strength, fatigue and gas permeability of the mixture, it is used as a material containing iron oxides contains bauxite in the following ratio of ingredients, May Silica-based Refractory Material Phosphoric Acid Bauxite Water 57.0-71.0 8.5-10.5 20.0-30.0 0.5-2.5 K) 00 SP about >