RU2181738C1 - Heat-resistant paint for painting of metal surfaces - Google Patents

Abstract

FIELD: paint and varnish industry. SUBSTANCE: heat-resistant paint for painting of metal surface contains, wt.%: lime 25-40; salt of alkali metals 25-35; alum 1.2-1.8; silica gel 1.0-1.7; the balance, water. Heat-resistant paint based on lime withstands temperature of high metal in steel casting and rolling metallurgical processes. EFFECT: provided luminous heat-resistant coating with good adhesion properties. 6 cl, 7 ex

Description

 The invention relates to the field of paint and varnish industry, in particular to heat-resistant paint based on lime, capable of withstanding the temperature of hot metal in steel and rolling industries.

 Known paint for painting building structures on a lime basis, containing 10 l of the composition: 1.5 kg of lime-boiling water, 50-100 g of drying oil and about 400 g of pigment, or 10 l of the composition: 3 kg of lime dough, 100 g of table salt 200 g of alum and about 400 g of pigment (Shepelev A.M. Handbook of a home master. - M., Stroyizdat, 1995, p. 141).

 Known paint does not provide good adhesion to hot metal and cannot be used for painting hot metal surfaces.

Known heat-resistant paint for coatings on metal surfaces, exposed to high temperatures: 581-981 ^o With containing 14-19.5 parts by weight finely ground clay, 1.5-2.5 parts by weight finely ground asbestos, 14-19.5 parts by weight finely divided siliceous sand or siliceous stone flour, 18-30 parts by weight instant glass, 5-9 parts by weight red or black iron oxide or white titanium oxide, 0.5-1.7 parts by weight rosin and ≥ 3.6 parts by weight an aqueous solution containing 50 wt.% sodium hydroxide (US 3585052 A, 1971).

Also known is a heat-resistant composition for coating on metal surfaces that can withstand temperatures of 500 ^o C and higher, containing a refractory powder of inorganic oxide with particles with a diameter of ≤ 44 μm, a powder of an inorganic compound of a layered structure capable of cation exchange and swelling in water and not containing hydroxyl groups, synthetic mica or flugocyte with particles with a diameter of ≤ 30 μm at a mass ratio of 10: 90 to 90: 10, and a binder based on sodium silicate in an amount of 15-50% based on the total weight oxide and inorganic compounds of a layered structure (US 4608087A, 1986).

 A disadvantage of the known paints is the complexity of their technology, due to the need to use dry starting components in the form of finely divided particles and the inaccessibility of synthetic mica or flugocyte, and therefore the high cost of the resulting paint.

 The heat-resistant paint for hot metal surfaces described in DE 3410844 A1, 1984, contains water glass, quartz, alumina, lavalite, magnesium desiccant, pumice, cement, water and a small amount of phosphoric acid and is applied to the metal in the form of a melt.

 The disadvantage of this paint is the complexity of the technology of its application, due to the need for melting in a flame.

 The closest to the essence of the proposed paint is a heat-resistant paint for painting metal surfaces, in particular for marking hot metal products, containing 16-52 wt.h. metal oxide, preferably titanium dioxide, 40 to 70 parts by weight sodium silicate, 8-35 parts by weight kaolin and 60 - 263 parts by weight water.

This paint is applied to the metal by thermal transfer at 427 - 871 ^o C, paint particles that do not hit the metal surface, transferred with a special pencil (DE 1644733 B2, 1979).

 A disadvantage of the known paint is the complexity of the technology of its application.

The present invention is the development of heat-resistant paints for painting a metal surface, in particular for its marking, devoid of the above disadvantages. The essence of the invention lies in the fact that heat-resistant paint for painting a metal surface contains, wt.%:
Lime - 25 - 40
Alkali metal salt - 25 - 35
Alum - 1.2 - 1.8
Kremnegel - 1.0 - 1.7
Water - Else
The lime contained in the paint is an astringent obtained by calcining limestone or chalk. The paint preferably contains quicklime, containing mainly calcium and magnesium oxides with a small admixture of calcium carbonate, silicate, aluminates and calcium ferrates. More preferably, the paint contains quicklime, ground lime, a fine grinding product of lump lime.

 As the alkali metal salt, table salt may be used.

 As the alum, any known alum can be used, preferably aluminum potassium, aluminum sodium, aluminum ammonium, chromium potassium, iron ammonium.

 Silica gel is a polycondensation product of silicic acid formed in a supersaturated aqueous solution of amorphous silica (amorphous silica) at pH 5-6.

 The paint is prepared by introducing into water, taken in half the total consumption of water, salt, alum and silica gel, mixing the mixture until the components are completely dissolved, followed by lime. The resulting mixture is infused with stirring for 72-75 hours, the remainder of the water is added with constant stirring, and filtered through a mesh membrane with cells of the order of 2.5 mm. The filtered product is infused with stirring for 72 - 75 hours and again filtered through a mesh with cells of 0.8 - 1.0 mm. The re-filtration product is ready to use.

 The composition of the resulting paint is presented in the table.

The paint may further comprise a pigment, preferably an iron oxide red pigment with a heat resistance of about 1200 ^{° C.} in an amount of 0.1-2.0 wt.%.

 Marking on a metal surface having a high temperature - slabs, rolls, sheets - is carried out by spraying through the nozzles of the marking device.

The test results of the obtained paint layer showed that the use of paint according to examples 1-4 provides high-quality marking with the necessary brightness of 100 units, resistance to temperatures from 600 to 1000 ^o C and more, good adhesive properties.

 When the lime content in the paint is less than 25 wt.%, The required density of the solution is not provided, and more than 40 wt.% The viscosity increases and the flow to the nozzles and its spraying are difficult.

 When the salt content in the paint is less than 25 wt.%, High-quality application (adhesion) to hot metal (adhesion properties) is not ensured. A salt content of more than 35 wt.% Causes crystallization on the walls of the paint storage tanks (supersaturation).

 The use of alum with a content of 1.2 - 1.8 wt.% Increases the brightness of the coating.

 The introduction of silica gel into the paint provides the ability of the paint components to be in suspension (not to precipitate) for a long time (more than a day). The content of silica gel in the paint of less than 1.0 wt.% Does not provide the necessary particle weight in the solution, and more than 1.7 wt.% Ceases to affect the quality of the paint and leads to an increase in its cost.

 Thus, the proposed paint in comparison with the known technical level has easy accessibility, simplifies the method of its preparation and use, meets the necessary requirements for its use for marking metal surfaces having a high temperature.

Pilot industrial tests of the paint were carried out at continuous steel casting plants of the converter production of Severstal OJSC for technological marking of hot slabs at a temperature of 600-1000 ^o С. Clear, high-quality marking marks were obtained.

Claims (5)

1. Heat-resistant paint for painting metal surfaces containing a compound based on metal oxides, a silicon-containing substance and water, characterized in that as a compound based on metal oxides it contains lime, as a silicon-containing substance - silica gel and, in addition, an alkali metal salt and alum in the following ratio of components, wt. %:
Lime - 25 - 40
Alkali metal salt - 25 - 35
Alum - 1.2 - 1.8
Kremnegel - 1.0 - 1.7
Water - Else
2. Heat-resistant paint according to claim 1, characterized in that it contains quicklime.  3. Heat-resistant paint according to claim 2, characterized in that it contains quicklime ground lime.  4. Heat-resistant paint according to claim 1, characterized in that it contains sodium chloride.  5. Heat-resistant paint according to paragraphs. 1-3, characterized in that it contains chrome-potassium, or iron-ammonium, or alum-potassium alum.  6. Heat-resistant paint according to paragraphs. 1-4, characterized in that it further comprises an iron oxide red pigment in an amount of 0.1-2.0 wt. %

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