SU1736671A1 - Double layer antiburning-strengthening coating for cast rods - Google Patents

Abstract

The invention relates to a foundry, in particular to compositions of anti-burner-strengthening coatings used mainly in the manufacture of complex cast iron castings. The purpose of the invention is to eliminate burns and burns on castings by increasing the penetration depth of the coating and the surface strength of the rods, as well as reducing the level of internal stresses of the coatings. As a reinforcing coating pre-applied on the surface of the rod, a composition containing the following ingredients, in wt%, is used: technical lignosulfonates 69.5-71.5; graphitized filter dust 0.5-1.5; 3-4 urea, water the rest. Then, a non-stick layer is applied to the reinforcing composition, containing the following ingredients, wt%: talc 32.9-34.4; graded filter dust 1-2, syrup 10.1-10.2; urea 1.5-2.0; clay 2.8-3.1; water the rest. For the reinforcement layer, graphitized filter dust with a particle size of 0.071 mm is used. Urea in combination with organic binders leads to a decrease in internal stresses in coatings by increasing the plastic properties of the resinous product forming. This releases a large amount of coke, which serves as a high-temperature binder. The use of the invention reduces the scrap of cores and castings, and also reduces the laboriousness of cleaning and cutting operations. 2 tab. (L with CN O vl

Description

The invention relates to a foundry, namely, anti-burn-up coating compositions for rods, used mainly in the manufacture of complex cast iron castings.

The purpose of the invention is to eliminate burns and burns on castings by increasing the penetration depth of the coating and the surface strength of the rods, as well as reducing the level of internal stress of the coatings.

The following materials are used to prepare the coatings.

Talc (TMK-28, TMK-27, TMK-24) is a magnesian silicate, which is similar in chemical composition to the formula 4SI02-ZMdO NaO. It is obtained by mechanical grinding of rock by means of talcite or by mechanical enrichment of rock of talcomagnesite, the main component of which is talc. Talc refractoriness

1200-1300 ° C, density 2700 kg / m3 In the foundry industry, talc is used that meets the following requirements: calcined residue insoluble in hydrochloric acid, not less than 85%, humidity not more than 1.0%. The degree of grinding: the residue on the sieve 0090 is not more than 2%, on the sieve 014 is not normalized. It is used as a paint filler for iron casting. Molasses (OST 18-395-82) is a waste of sugar beet production. Contents - aqueous solutions of sucrose and non-sugar substances. The density of the syrup is at least 1300 kg / m, and the dry matter content is at least 50%. Used as a binder.

Technical lignosulfonates (LST) is a by-product of wood processing for cellulose by the sulfite method (OST 13-183-83) of grade A. The main indicators of LST: density of 1230 kg / m. mass fraction of solids not less than 47.0%, mass fraction of solids by weight of solids, not less than 18.0, pH of a 20% solution not less than 4.4, viscosity conditional not more than 320 °. also used as a binder.

Urea (carbamide) is a colorless crystalline substance, odorless, highly soluble in water. Mass fraction of urea is not less than 99.8%. M.p. 132-133 ° C.

Urea is introduced as a reinforcing component, which increases the penetration depth of the reinforcing and nonstick layers. This causes an increase in the strength of the surface layer and the strength of the nonstick paint in general. Along with this, urea, interacting with LST, forms a urea-lignic resinous product, which additionally serves in the anti-adhesive coating as a bonding and non-stick material.

Clay ogneupornna Nizhneuvelskogo field brand NU-1.TU 14-8-336-80 Density 1500 kg / m3. Used as an additional inorganic binder that enhances the refractoriness of the coating.

Graphitized filter dust is a black soot powder, oily to the touch, quite mobile. For its physicochemical properties it meets the requirements of TU 4814-24-84,%:

Mass dale ashNot more than 10

Mass fraction of carbide

flint Not more than 5

Mass fraction

with a particle size of 0.071 mm 100

Mass fraction of sulfurNot more than 0

Graphitized filter dust is formed by trapping particles with special filters after machining electrodes that have undergone high-temperature graphitization at 2500 ° C.

The addition of graphite filter dust increases the antiburning properties of the coating. Graphite filter dust with a particle size of not more than 0.071 mm is used in the reinforcement layer.

Its introduction into the reinforcement layer provides high penetration of dust into the pores of the rod, which improves the nonstick properties of the coating. In addition, the use of fine carbonaceous material improves the covering power of the subsequent layer to form a uniform coating without smudges on the surface of the rod.

The coating on the rods is obtained after applying to the surface a composition prepared as follows.

To obtain a strengthening (penetrating) composition, LST, urea, graphitized filter dust and water are loaded into the container, which are constantly mixed with air due to sparging. The prepared composition has a density of 1160-1180 kg / m. Water, urea, molasses, clay, graphitized filter dust and talc are introduced into the container to prepare the nonstick composition. The components are constantly mixed with a mechanical stirrer, the density of the composition is 1380-1420 kg / m. The hardening compound is applied to the surface of the rod with a spray gun. The drying of the rods with the applied composition is carried out in a vertical dryer at 240-280 ° C for 1.5-2.0 hours. After drying, the rods are subjected to finishing treatment followed by a second spray coating composition with a spray gun, after which the rods are collected in a conductor and sprayed with an additional paint anti-burn compound) assembled block of rods. After that, the finished block of rods is subjected to heat treatment in a continuous dryer at 240-280 ° C for 40-60 minutes.

The compositions of the anti-stick coating are listed in Table. 1 (compositions 1-3 are hardening, and compositions 4-6 are nonstick), and the properties of the compositions obtained from these coatings, as well as the quality of castings, are given in Table. 2

The use of urea in combination with a water-soluble organic binder in the coating leads to a decrease in its internal stresses due to an increase in the plastic properties of the resulting resinous product, contributing to the relaxation of the stresses.

Urea also increases the depth of penetration of the coating into the mixture, which increases the strength of the surface layer and the strength of the nonstick coating as a whole. Along with this, urea, interacting with LST or molasses, forms a resinous product that acts as a binder and additionally contributes to the release of large amounts of coke. At high temperatures, the resinous product degrades with the release of pyrocarbon and coke, which additionally protect the casting from being burned.

In addition, the presence of urea in the coating composition contributes to a deeper penetration of the paint into the rod and thus provides an increase in surface strength. The presence of finely dispersed carbon-containing material in both layers of the coating creates the conditions for the protection of thermal units of large and complex castings from burning.

The use of the proposed anti-stick-hardening coating reduces the scrap of cores and castings, as well as reduces the labor intensity of chopping and cleaning operations.

Claims (1)

Invention Formula A two-layer anti-stick and reinforcement coating for casting cores used mainly for the manufacture of complex cast iron castings, comprising a reinforcing layer containing an organic binder and a liquid phase, and an anti-stick layer containing a filler, an organic binder and a liquid phase characterized by that, in order to eliminate burns and burns in castings by increasing the penetration depth of the coating and the surface strength of the rods, as well as reducing the level of internal stresses of the coatings, n emitting layer as the organic binder contains technical lignosulfonates and urea as water and liquid phase further comprises graphitized The filter dust with the following contents of ingredients, wt.%: Technical lignosulphonates 69, 5-71.5 Graphite filter dust 0.5-1.5 Urea 3.0-4.0 Water The rest and the nonstick layer contains talc as a filler, binder contains pathoka and urea, liquid phase and additional contains graphitized graphite dust and clay with the following content of ingredients, wt.%: Talc32.9-34.4 Graphite filtered dust1.0-2.0 Molasses 10.1-10.2 Urea1.5-2.0 Clay2.8-3.1 Water Else Table 1 table 2