RU2242688C2 - Method of production of a lining of a small roof of an electric furnace - Google Patents

Abstract

FIELD: iron and steel industry.

SUBSTANCE: the invention is dealt with field of iron and steel industry, in particular, with the methods of laying of a brick refractory lining of small roofs of arc steel-smelting furnaces. The technical result is an increase of mechanical strength of the refractory brickwork and a gas tightness of a lining, decrease of consumption of refractory products used for a lining repair, increased productivity of an electric furnace at the expense of an increase a furnace roof service life. The method of production of a lining of small roofs of electric furnaces includes fulfillment of refractory laying of a furnace roof with bricks with formation in a joints between the bricks of seams, filled in with a refractory bonding mud composed of a sealing agent - orthophosphoric acid and a dry refractory mixture, in the capacity of which aluminum and chromium oxides are used. Thickness of the seams in the joints between bricks makes 2-5 mm. For meeting the heat stresses originating in the refractory brickwork of a roof, a fiber-like heat insulating material of 10-15 mm thick is placed along the periphery between a water-cooled roof ring and the refractory brickwork. In the capacity of a fiber-like heat insulating material they use asbestos sheets.

EFFECT: the invention allows to raise productivity and service life of an electric furnace roof, mechanical strength of a refractory brickwork, a gas tightness of a lining; to decrease consumption of refractory products used for a lining repair.

2 cl

Description

The invention relates to the field of ferrous metallurgy, and more particularly to methods for laying brick refractory lining, and can be used in the lining of small arches of heavy-duty arc steelmaking furnaces.

A known method of laying a brick lining of a thermal unit, including filling horizontal joints between bricks with an oxide binder, the horizontal joints being pre-coated with a hydrophobic substance, and materials whose melting point is 10-50 ° C lower than the temperature occurring during the thermal service are used as an oxide binder unit on the line connecting the bricks, and as a hydrophobizing substance, an emulsion of colloidal graphite in trimethylchlorosilane or ethylsily is used kate in a ratio of 1: 3 (1).

However, this method of masonry is unacceptable for lining the arches of electric furnaces, since at temperatures arising during operation, the loss of mechanical strength and gas tightness of the brickwork due to leakage from the joints under the action of gravity of the oxide binder is possible.

Also known is a method of laying brick lining of metallurgical units, including filling the joints between bricks with a binder material, which is used as a chromomagnesite powder, impregnated with a 10-15% aqueous solution of phosphoric acid, which form one with brickwork (monolith) (2). This method is the closest in technical essence to the invention and adopted as a prototype.

One of the disadvantages of this method is that the joints filled with chromomagnesite powder are unevenly impregnated with a solution of phosphoric acid, which results in insufficient gas density of the refractory lining. At the same time, the resulting monolithic refractory lining of the arch experiences sharp periodic temperature drops and uncompensated thermal stresses that arise during the operation of the electric furnace, which leads to the formation of cracks in the brickwork and its further destruction.

The problem to which the invention is directed is to increase the mechanical strength of the refractory masonry and the gas tightness of the lining, reduce the consumption of refractories for repairing the lining, and also increase the productivity of the electric furnace by increasing the service life of the arch.

This object is achieved by the fact that a method of manufacturing a lining of small arches of electric furnaces is proposed, including the implementation of refractory masonry of the arch with a brick with the formation in the joint between the bricks of the joints filled with a refractory mortar consisting of a dry refractory mixture and a grout - phosphoric acid, while the base is dry refractory the mixtures use oxides of aluminum and chromium, moreover, the thickness of the joints in the joint between the bricks is 2-5 mm, and to compensate for arches arising in the refractory masonry thermally x stresses, on the periphery between the water-cooled arch ring and the refractory masonry, a fibrous heat-insulating material with a thickness of 10-15 mm is placed. As a fibrous thermal insulation material, sheet asbestos is used.

The use of a refractory mortar for bonding bricks, consisting of a dry refractory mixture based on aluminum and chromium oxides and a phosphoric acid grinder, allows the furnace to be sufficiently durable during use, having high refractoriness, heat resistance and gas tightness, a monolithic lining of the arch.

Refractory mortar consists of two components: a dry refractory mixture and a grout. The basis of the dry refractory mixture is composed of oxides of aluminum (70-75%) and chromium (10-15%).

The use of a dry refractory mixture as the basis, consisting mainly of aluminum oxides with a small amount of chromium oxides (up to 5%), does not allow a refractory solution to have sufficient thermal stability. The introduction of a high content of chromium oxides (up to 10-15%) into the composition of the refractory solution can significantly increase its heat resistance, slag resistance, and also contributes, from the point of view of the uniform distribution of thermal stresses arising in the refractory masonry, to reducing the difference between the linear expansion coefficients of the materials used ( refractory mortar and refractory products) used for masonry.

The use of orthophosphoric acid as a filler allows one to obtain a refractory mass with high adhesive ability during masonry of the arch, while maintaining a sufficiently high mechanical strength of the masonry of the arch as a whole during the operation of the electric furnace.

The thickness of the joints of 2-5 mm, formed by the refractory mortar between the bricks, provides a sufficiently high structural strength of the masonry of the small vault due to the wedging of it with locking bricks, on the other hand, this thickness of the joints partially compensates for the thermal stresses arising between the bricks in the masonry due to the expansion of the arch products during heating .

Reducing the thickness of the joint below the lower limit is not permissible, since a thinner joint is insufficient to compensate for the thermal stresses that arise between the bricks in the masonry, and the required volume of the joint, filled with refractory mortar, does not form, providing sufficient bond strength of the refractory products.

Exceeding the specified upper limit of the thickness of the seam is impractical due to the reduction of wedging forces in the masonry after clogging of the castle bricks, which, accordingly, reduces its structural strength.

To compensate for thermal stresses arising in the working layer of the lining during its unilateral high-temperature heating during operation of the furnace, laying of 10-15 mm of fibrous heat-insulating material (sheet asbestos) on the periphery between the water-cooled arch ring and the refractory masonry is provided. Laying a layer of sheet asbestos of less than 10 mm does not provide the required gap between the masonry and the water-cooled arch ring, sufficient to compensate for thermal stresses, laying a layer of more than 15 mm reduces the building strength of the refractory masonry of the small roof of the furnace.

The small arch of the steel furnace is selected as follows.

A refractory mortar for the set of the vault is prepared at the place of masonry in a mortar or concrete mixer of any type. In this case, a dry refractory mixture based on aluminum and chromium oxides should have a particle size of not more than 2 mm.

The dry mixture loaded into the mortar mixer is moistened with stirring agent, orthophosphoric acid, with a density of at least 1.45 g / cm ³ , to a consistency that ensures uniform distribution of the refractory mortar over the bonded surface and sticks to it.

Before filling the arch, the water-cooled arch ring is pressed with compressed air under pressure, then it is installed on the stand and centered. Initially, 2-3 layers of asbestos sheet are superimposed on the ring and then the arch is laid.

A set of arch is performed using conventional methods of masonry using a solution. At the same time, the layer of refractory mortar applied on the glued surfaces of the brick (refractory products ПХС, ПХСЭ, ПХК) should provide a thickness of the joints in the masonry of 2-5 mm, and the bricks (except the castle ones) should be carefully pressed together. In the central part of the masonry, 4-7 castle bricks are left, which should protrude above the arch surface by 50-70 mm, after the end of the set of the arch they are hammered with a pneumatic hammer with a thickened tip or a hammer, after laying a rubber gasket.

The tight fit of the bricks to each other with respect to the thickness of the joints within 2-5 mm is provided by wedging forces in the masonry after clogging of the castle bricks.

After stuffing, the small vault is installed on the furnace, where it is dried and heated during further operation.

The resistance of a small arch in the manufacture of it by this method compared with the base increases from 75 to 110 heats. Using the proposed method of lining the arch allows to increase the technical and economic indicators of the electric furnace by increasing its campaign in the arch by 1.5 times.

Sources of information

1. A.S. No. 996831, Ml. 3 F 27 D 1/00, pr. 05.31.79.

2. A.S. No. 51492, Ml. 3 F 27 D 1/00, pr. 02.27.75, the prototype.

Claims (2)

1. A method of manufacturing a lining of small arches of electric furnaces, including the implementation of refractory masonry of the arch with a brick with the formation in the junction between the bricks of the joints, filled with a refractory mortar consisting of a dry refractory mixture and a grout - phosphoric acid, characterized in that oxides are used as the basis of the dry refractory mixture aluminum and chromium, while the thickness of the joints in the junction between the bricks is 2-5 mm, and to compensate for thermal stresses arising in the refractory masonry of the arch along the periphery between the water a fibrous heat-insulating material with a thickness of 10-15 mm is placed by the cradle vault ring and the refractory masonry. 2. The method according to claim 1, characterized in that as a fibrous thermal insulation material is used, for example, sheet asbestos.