RU1780517C - Compound for producing antiburn strengthening coating of casting molds - Google Patents

Abstract

Usage: as a non-stick hardening coating of foundry molds, mainly sand, in the manufacture of rolls of rubber industry weighing 2-3 tons. Essence: coating is obtained from a composition containing the following ingredients, wt.%: Amorphous graphite 6.0 - /. 0 ; sodium chloride 3.5-4.5; boric acid 2.5-3.0; asbosurite 5.0-6.0; foundry coke 7.0-9.0; technical lignosulfonates 10.0-12.0; water is the rest. The asbosurite used in the composition consists of 12-15% asbestos and 85-88% diatomite and is a finely dispersed material that easily penetrates into the pores of the mixture. Diatomite included in its composition reduces warpage of the coating, as well as peeling and cracking, increases the resistance of the coating to abrasion and increases the sedimentation stability of the composition. The use of the composition according to the invention improves the quality of the molds and eliminates the marriage of rolls on burnout and blockages. 5 tab. sl c

Description

x | 00 AB

The invention relates to foundry, in particular to compositions of non-stick and hardening coatings for producing neck rolls in sand forms in the production of cast iron rolls of rubber and rubber industry weighing 2-3 tons.

Known non-stick coating for foundry Molds, consisting of the following components, wt.% 1

Asbestos Powder. 12-14 Gypsum 6-7

Amorphous graphite 2-2 5

Aluminum powder 3-3.5 Table salt 3.4-3.8

Refractory clay 1.5-2.0

Pulverbakelite-1.7-2.0

Sulphite-alcohol stillage 3.0-3.5

5% iodine solution of carboxymethyl cellulose 3.5-4.0

Water Else

After painting the roll forms (rubber-technical industry-RP) with a mass of 2-3 tons, drying and pouring them with metal, CO was detected

a rather large number of rolls are loaded with a burn on the necks and blockages on the barrels,

In order to obtain a clean neck surface, the heap needs to form a hard sand crust with a thickness of at least 6 mm. The formation of a crust depends on the degree of penetration of the coating into the form of the covering power.

It is not possible to use the known coating for molds in which neck rolls of 2-3 tons are obtained, since the penetration depth of the coating inside the mold is insignificant and the metal mass is much smaller than when casting rolls weighing 10-15 tons (for which it is intended), and the amount of heat given away by the metal to the mold is not enough to form a thick sandy crust,

A heat-insulating coating for metal forms is known, consisting of the following ingredients, wt.%:

Gypsum27.5-29.0

Asbestos powder 16.0-17.0 Sulphite-alcohol stillage 2.0-2.5

Sodium perborate 0.2-0.3

Water Else

This coating is intended for painting metal molds (chill molds) in order to increase the adhesion strength of the coating to the surface of the chill molds at a heating temperature of 80-120 ° C and increase their durability by reducing heat stroke on the chill mold.

When painting sand forms with this coating, the penetration depth of the coating was 1.5-2.0 mm, which is not enough, because fillers - asbestos powder and gypsum remain on the surface of the mold and do not penetrate into the pores of the mixture due to its fibrous structure (asbestos powder) and the large fraction of gypsum (02). Therefore, this coating cannot be used for coloring sand forms due to the small depth of penetration of the sand into the mold and the formation of a thin sticky crust, and hence the formation of a burnout on the surface of the necks of the rolls.

The closest in technical essence and the achieved effect to the invention is a non-stick coating for foundry molds, consisting of the following components, wt.%:

Asbestos Powder 12.0-14.0

Gypsum 6.0-7.0

Amorphous Graphite 2.0-2.5

Powdery

aluminum 2.2-2.5

Salt 2.4-3.0

Boric acid 0.8-1.0

Sulphite-alcohol

barda 3.0-3.5

Water Else

The coating has low gas permeability (88 units), high viscosity (35 s) and density (1.27 g / cm O. When this coating is coated with molds (lower necks) weighing 2-3 tons for RP rolls with a thickness of 0.6 -0.8 mm

(instead of 1.0-1.2 mm) the penetration depth of the coating was 2.5-3.0 mm, sedimentation stability 89%.

After pouring the molds with metal, a crust formed only 3-4

mm, which could not prevent the formation of burns on the surface of the neck of the roll. From cast 24 pcs. rolls weighing 2-3 tons were found to contain 29% partial burn and 37.5% continuous burn and earth shells.

The formation of burning, most likely,

depends on the depth of penetration

cover inside the mold (neck roll) was

insufficient due to the larger fractions of the filler. When determining the sieve analysis of the specified coating (prototype) it was found that the bulk of the materials were distributed on sieves 04-02 (54.1%), and only 25.6% on the basin. In addition, the content of the residue on the basin with a particle size of 20-50 microns was 82.6%, and particles of 20 microns or less - 17.4%. This analysis shows that there is a small amount of penetrating particles of 20 microns or less in the coating of the prototype, t .to. in a separate sieve analysis of asbestos powder and gypsum, the content of their particles by fractions in the basin was 20 and 10%, respectively, and mainly fractions of 20-50 microns.

The tanning ability of the coating, which was determined by the drip method and amounted to 1.49%, i.e. the coating is unevenly distributed over the surface.

The aim of the invention to obtain rolls of the rubber industry weighing 2-3 tons is to improve the quality of the molds and eliminate the marriage of rolls on burnout and blockages by increasing

penetrating ability of the composition, its sedimentation stability and hiding power.

This goal is achieved in that the coating containing amorphous graphite, sodium chloride, boric acid, technical lignosulfonates and water, additionally contains asbosurite and foundry coke in the following ratio of ingredients, wt.%:

Amorphous Graphite 6.0-7.0

Salt 3.5-4.5

Boric acid 2.5-3.0

Asbosurite 5.0-6.0

Foundry Coke 7.0-9.0

Technical lignosulfonates. 10.0-12.0

Water Else

Asbosurite (TU 36-130-77) - an insulating powdery material consisting of a mixture of asbestos (12-15%) and finely ground diatomite (85-88%), which has high oil absorption, good adhesion, reduces paint warping, peeling , crack formation, increases the resistance of the paint to abrasion and does not settle.

Asbosurite is used as mastic insulation of the surface of industrial equipment and pipelines at a temperature of up to 900 ° C. After heating it to 1300 ° C, it loses its properties. The chemical composition after calcination, investigated in 1979,% SI02-77.2; A 20s-5.38; Re2Oz-1.32; FeO-0.22; CaO - 0.39; KaO-0.93; MgO-6.23; Na20-0.39; PaOs - 0.32; TI02-0.11; , 34; p.p.p. 6.48. Investigated in 1985 ..%: 5102-76.2; A120s 3.35; CaO-1.22; MdO-7.2; Rv20z 1.1: 50z-0.35; p.p.p. 10.58,

Technical Requirements. For the production of asbosurite, soft asbestos of the K-6-30 or K-6-20 grades of grade GOST 12871-67 are used.

Depending on the volumetric mass, asbosurite is made of grades 600, 700, 800 (Table 1).

The content of diatomite particles larger than 10 mm is not allowed, and more than 5 mm is not more than 50% by mass. The content of non-wetting particles of asbosurite should not be more than 15% by mass.

Asbosurite increases the elasticity, the penetration depth of the coating inside the mold, reduces the viscosity and increases the adhesion strength to the mold surface. It is a stabilizer and enhances the sedimentation stability of the coating and improves the hiding power. When penetrated into the mold, it serves as a binder.

Foundry coke (GOST 3340-71) with a grinding fraction of 0.2-0.3 mm is introduced into the composition to increase the gas permeability of the paint layer and thereby accelerates the removal of moisture from the molds and eliminates cracking in the coating layer during drying, as well as creates a protective and reducing atmosphere between the surface of the mold and the liquid metal, which ensures a reduction of burn on castings.

According to the available data, in the known solutions there are no features similar to 5 all the features that differ from the prototype of the claimed technical solution, which allows us to conclude that it meets the criterion of significant differences.

0 The boundary values of amorphous graphite, sodium chloride, boric acid, asbosurite, foundry coke, and technical lignosulfonate in the coated coating were determined experimentally.

5 2/3 of the required amount of water is poured into the paint mixer, asbosurite and sodium chloride are charged, after 25-30 minutes of mixing amorphous graphite, boric acid and foundry coke are added.

0 After 12-15 minutes of stirring, water is added to a density of 1.36-1.38 g / cm3, and then technical lignosulfonates are added and mixed for 10-15 minutes. The coating density should be 1.16-1.18 g / cm3 .

5 To determine the effectiveness of the composition for obtaining a non-stick-hardening coating, depending on the amount of amorphous graphite, sodium chloride, boric acid, asbosurite, foundry coke and technical lignosulfonates added, compositions were prepared with boundary and optimal component ratios, as well as going beyond the boundary of new components.

5To select the optimal values was

7 mixtures were prepared and one known non-stick coating for the molds (prototype) indicated in the table. 2. When determining the sieve analysis of the coatings of the prototype and the claimed, it was found that the average value (%) of the residue on the basin was 25.6% for the prototype and 47.4% for the claimed (see table, 3, p, 1.2). This, most likely, depends on the fact that asbestos zurite has a greater amount of fine particles than asbestos and gypsum, because the residue on the basin was sized as follows; size 20-50 microns for the prototype 82.6%, claimed 65.2%,

0 i.e. 1.27 times smaller, the size of 10-20 microns is 7.8% and 11.1%, respectively, i.e. 1.42 times more and less than 10 microns in size, 9.6% and 23.7%, i.e. 2.47 times more. Therefore, in the enclosed coating of particles with a size of less than 20 μm, it is 2 times larger than that of the prototype; therefore, it penetrates into the pores more efficiently by impregnating a thicker layer of the mixture.

To compare some materials on a grain basis, a sieve analysis of asbestos powder, gypsum and asbosurite was carried out (Tables 3, 4, 5).

As can be seen from the table. 3, the residue on the asbestos powder basin is 20%, and the asbosurite is 55%, which is 2.5 times higher and is distributed by particle sizes of 10-20 microns and less than 10 microns in the sum of 9 and 52%, respectively. Thus, there are six times more fine particles in asbosurite than in asbestos powder, because asbestos is a fibrous material (mountain flax). It is well softened by water, but its fibrous structure does not change and, when used in coatings to paint the surface of molds and rods, it penetrates poorly and mainly remains on the surface.

I compared the content of asbestos powder in the known coating (prototype 12-14%) with the content of asbosurite in the claimed (5-6%) amount of fine particles with a size of 10-20 μm and less than 10 μm would be 2 times larger, i.e. versus 52% in asbosurite which is three times less

The amount of residue on the gypsum basin was 10% (table, 3.4) and was distributed in sizes of 10-20 microns and less than 10 microns. Therefore, gypsum does not have a significant role in the penetration of the coating into the pores; it remains on the surface.

As can be seen from the table. 3, 6 7, neither coke nor aluminum powder affects the depth of penetration of the coating into the pores of the mold, since no particles less than 10-20 microns,

The hiding power of the composition is evaluated by flow rate. Samples are made in the form of plates (130 x 25 x 25) from the test material. The plates are stained once by dipping into the test coating with a two-second exposure. Then 10 minutes are carried out, drying at 200 ° C in an upright position. After cooling, the thickness of the stained samples was measured in the upper and lower parts of the plate at a distance of 100 mm from each other. From the measurements obtained, the average results of the thickness of the coated sample in the upper and lower parts of the plate are derived (Table 4).

Flow rate is determined by the formula

PV - A

100%,

where P is the coating flow rate,%;

A - the average thickness of the plate with a coating in its upper part, mm

In - the average thickness of the plate with a coating in its lower part, mm:

I is the distance between the symmetrical upper and lower points on the plate equal to 100 mm,

For example, leakage for a prototype is

P28, 71 -27.22

100

 . S0 1.49%;

for the inventive composition 3 27.15-26.41

P

100

 100-0.74%.

As can be seen from the obtained values of leakage, it is two times less for the claimed coating. Therefore, the use of asbosurite with a large number of fine particles in the coating composition, most likely, helps to reduce leakage, i.e. improving the coating opacity.

Table 5 shows the properties of the compositions to obtain a non-stick hardening coating of the molds and the known (prototype).

The forms were painted using a brush with a layer thickness of 0.6-0.8 mm and in two consecutive doses. With every

the coating composition was cast in 24 pieces. rolls weighing 2-3 tons. Drying of the molds was carried out at a temperature of 420-440 ° C.

According to research and testing in industrial

The conditions of the claimed invention with a basic object (prototype) has the following advantages:

increased sedimentation stability of the coating, was 89%, became (average)

96% or higher by 8%;

the covering power of the coating, which was determined by the drip method, increased, was 1.49%, became (average) 0.74% or half as much;

the depth of the penetrated coating layer in the mold (penetration ability) was increased, instead of 2.8 mm it became on average 7.3 mm or 2.6 times higher;

increased thickness easily separable

crust from 3.5 mm to 7.7 mm, i.e. twice as high;

there was no marriage of rolls on a solid and partial burnout, as well as blockages.

Claims (1)

The claims Composition for producing non-stick hardening coating of foundry molds, mainly sand, for producing rolls of rubber industry weighing 2-3 tons, including amorphous graphite, sodium chloride, boric acid, technical lignosulfonates and water, characterized in that, in order to improve the quality of the foundry molds and eliminating the marriage of rolls on burnout and blockages by increasing the penetrating ability of the composition, its sedimentation stability and hiding power, it additionally contains asbosurite and foundry coke and the following ratio May%: Amorphous graphite 6.0 7.0 Table salt 3.5 -4 5 Boric acid 2 5-3.0 Asbosurite 50-60 Foundry coke 7.0-9.0 Technical lignosulfonates 10 .0-120 Water T Pi l 1 a table 2 Continuation of Table 2 in the numerator, the average value of the thicknesses obtained on the four samples of the upper points of the sample, and in the denominator, the lower points. Table 3 Continuation of Table 3. Table 4 Continuation of Table 4. Table 5