SU1021677A1 - Refractory coating - Google Patents

Description

The invention relates to compositions of refractory coatings used to protect the refractory linings of smelting furnaces, for example, for aluminum-based alloys. The known refractory mass used to repair the chamotte lining of furnaces, including, weight D: aluminosilicate fireclay 83-97; refractory on clay 0-10; orthophosphoric acid 12-13; Aluminum hydroxide 3-7U When using a known mass for coating linings, for example, induction furnaces that smelt aluminum-containing alloys, it is characterized by increased metal permeability as a result of cracking, a low hardening rate at a normal temperature, which increases the repair time. The closest technical solution to the invention is the composition of a refractory coating, including weight: silicon carbide 7,, 0; og is refractory clay i, 0-8,0; alumochromophosphate binder 11% 5-15.0 and. magnesium oxide 0,. The disadvantages of this composition are also high metal permeability as a result of cracking (heat resistance of air shifts is 800 ° C) and expansion, low compressive strength (200225 kg / cm after calcination at 800 s) and flaking of the coating from the lining during heating. The purpose of the invention is to increase the mechanical strength and reduce metal permeability. The goal is achieved by the fact that the refractory coating containing silicon carbide, aluminum-chromophosphate binder and magnesium oxide additionally contains chamotte, cryo IT and aluminum hydroxide at the following ratio of components, ae.%: Silicon carbide Alumochrom-binder binding 25- 0 Magnesium Oxide 2-5 Shamot8-15 Cryolite 10-20 Aluminum hydroxide 5-10 Ka | ebid Silicon it is advisable to apply a grain size of less than 0.3 mm. Cryolite and aluminum hydroxide are sieved through a sieve with a 0.5 mm mesh before use. Magnesium oxide and chamotte are introduced into the mass in the form of a finely ground mixture obtained by joint grinding of sintered or fused magnesite containing not less than 90% of magnesium oxide and high-aluminous chamotte containing not less than 62% of alumina. Joint grinding is performed in a ball mill or a vibrating mill. The mixture contains 20–25% magnesium oxide, and, by grain composition, predominantly (70–80) is represented by a fraction of less than 0 mm. 1 mm. The alumochromophosphate binder is advisable to use a density of 1.55-1.60 g / cm. The coating compound is prepared as follows. The ready-to-use powders are thoroughly mixed in a dry state, then the required amount of the aluminum-chromophosphate binder is introduced and mixed to obtain a homogeneous mass. The application of the mass to the lining is done in any suitable manner. Examples of the preparation of the mass and the results of the test samples are placed in Table. 1 and 2. Table 1

table 2

Compressive strength, kg / cm,

after 12 hours of drying

after roasting at 800 ° C

Thermal stability, heat change air The advantages of the proposed coating are low metal permeability, high mechanical strength, increased corrosion and erosion resistance when melting aluminum-based alloys. Improved coating properties are achieved during the drying period at normal temperature. The use of a mixture of chamotte and agni oxide, obtained as a result of joint grinding, contributes to a more uniform distribution of the magnesium oxide activating additive, improving the uniformity of the structure and properties of the coating. Increasing the content of fireclay more than 15 weight. leads to an increase in the mass of silicon oxide, which, by actively interacting with aluminum melt, contributes to a decrease in the corrosion resistance of the coating. Reducing the content of fireclay less than 8weight. leads to deterioration of the homogeneity of the structure of the coating and its properties. The introduction of cryolite and aluminum hydroxide into the coating contributes to an increase in the viscosity of the bonding strength of the particles of silicon carbide and chamotte with the furnace lining, reducing crack formation and coating coating, and its wettability.

250

235

200

ZA5

370

315

103

125

112 with a melt, increasing the degree of mass caking, corrosion and erosion resistance, the formation of a dense, glazed, metal-tight working surface. Increasing the content of cryolite more than 20 wt.%, Aluminum hydroxide more than 10 weight does not improve the performance of the coating.; The use of a coating with a content of cryolite less than 10 weight. and hydroxide as much as mini less than 5 wt.% leads to a significant decrease in strength and increase in metal permeability: and coating. The use of a coating of this composition allows, by reducing the metal permeability of the lining, improving the structure of the coating, increasing its strength, corrosion and erosion resistance, to increase the resistance of induction crucible and other melting furnaces for melting aluminum-based alloys by 1.5 times. High performance coatings help reduce labor costs for cleaning and maintenance, specific consumption of refractories and other auxiliary materials, to increase the productivity of smelters.

Claims (2)

FIRE-RESISTANT COATING containing silicon carbide, aluminochromophosphate binder, magnesium oxide, τη, and moreover, in order to increase the mechanical strength and reduce the metal permeability, it additionally contains chamotte, with a design and engineering design. Institute of Metallurgical Heat Engineering, Non-Ferrous Metallurgy and Refractories (53) 666.76 (088.8) (56) 1. USSR Copyright Certificate No. 196594, cl. C 04 V 35/56; I960. ; 2. USSR copyright certificate 419498, cl. C 04 B 35/56, 1971 '(prototype). cryolite and aluminum hydroxide in the following ratio of components, wt.%: Silicon Carbide Alumochromophosphate - 25-35 new binder .. 25-40 Magnesium oxide 2-5 Fireclay 8-15 Cryolite 10-20 Aluminum hydroxide 5th SU do, 102167.7.