RU2155732C1 - Method of refractories production - Google Patents

Abstract

FIELD: manufacture of refractories, particularly, methods of manufacture of refractories used for lining of high-temperature units. SUBSTANCE: used for forming is mixture with bulk density of 45-52% of preset density of formed refractory. Forming at stage of preliminary compression up to specific pressure of not in excess of 10 N/sq.mm is effected at speed of not more than 10 mm/s, and forming force at all stages is directed to article faces located in unit brickwork across direction of heat flux. EFFECT: reduced heat conductance of refractory containing solid carbonaceous component in direction of propagation of heat flux in lining. 1 tbl

Description

 The invention relates to the refractory industry, and in particular to methods for the production of refractories used for lining high-temperature units, mainly converters operating on gas-oxygen and combined purge technologies, as well as electric smelting furnaces and out-of-furnace steel processing units, including steel-pouring ladles.

 In these thermal units, periclase-based refractories are widely used, containing a solid carbon component, mainly in the form of flake graphite. These refractories combine high refractoriness, heat resistance and resistance to metal-slag corrosion. Significant thermal conductivity of graphite provides high heat resistance of such refractories, however, at the same time it leads to large heat losses to the environment and can cause overheating of the metal casing of the unit.

 The negative effect of high thermal conductivity of periclase-carbon refractories is eliminated in practice by thickening the protective (reinforcing) layer of the lining and the use of additional thermal insulation. However, this method of reducing heat loss increases the consumption of materials and at the same time reduces the useful volume of the metallurgical unit and is therefore uneconomical.

Known accepted for the production of refractory semi-dry method of preparing the mass in the mixing runners, in which it is pressed for 4 minutes 100 times under pressure up to 0.6 N / mm ² (Kashcheev ND Production of refractories. "Metallurgy", M., 1993, p. 65-66).

 Periodic compression of the mass in the mixer at the specified pressure provides its preliminary compaction due to partial displacement of air and achieve closer contact of the material particles. However, due to the very slight anisotropy, the thermal conductivity of the refractory formed from it is almost equally high in all directions.

 A known method of manufacturing refractories, in which the movement speed of the pressing stamp in the first stage, when the free approach of the grains occurs, reaches 100 mm / s, in the second stage, with significant friction and rapprochement of the grains is 8-9 mm / s, and in the third stage, during which compaction is accompanied by partial destruction of the grain, does not exceed 1-2 mm / s (Kashcheev I.D. Production of refractories. "Metallurgy", M., 1993, p. 78-79).

 The disadvantage of this method is that at the accepted molding speeds it is impossible to reduce the thermal conductivity of the refractory in one of the directions.

Closest to the proposed invention is a method of manufacturing refractories containing a solid carbon component, according to which the mass is produced in runners with rollers for 20-22 minutes, and molding on hydraulic presses under unilateral or bilateral vertical compression at a specific pressure in the first stage (pre-compaction stage) 20-30 N / mm ² and a final pressure that ensures the achievement of a given apparent density of raw material (section "Production of periclase-carbon og neuporov "TI 200-0-45-95 of the Plant" Magnesite ", 1995 and the technological map of molding). In this case, the apparent criterion for the quality of the preparation of the mass is its apparent (bulk) density, which is more than 57% of the given density of the molded refractory.

 This mass provides, with the accepted molding parameters, the production of products with high density and compressive strength, however, they do not form a structure with significant anisotropy of thermal conductivity.

 The problem to which the present invention is directed is to reduce the thermal conductivity of a refractory containing a solid carbon component in the direction of propagation of the heat flux in the lining.

The problem is solved by preparing the mass with a bulk density before filling in the mold 45-52% of the specified density of the molded refractory, molding products to a specific pressure of not more than 10 N / mm ² with a speed of not more than 10 mm / s and the direction of the molding force perpendicular the product faces, which are located in the unit masonry across the direction of the heat flux.

 The decrease in the thermal conductivity of the refractory in one of the directions is obviously due to the fact that in bulk with the stated parameters of bulk density during free filling of the mold, spontaneous directed reorientation of particles of the solid carbon component occurs in one of the directions.

When molding from such a mass of products to a specific pressure of not more than 10 N / mm ² with a speed of not higher than 10 mm / s, this process continues under the condition of one-sided or two-sided compression of the mass, respectively, with one upper or lower and upper dies. In this case, obviously, there is already a forced reorientation of the carbon particles as a result of the fact that the lateral pressure arising in the mold due to the friction of the mass on the walls of the vertical plates is less than that applied by the pressing dies. The directed reorientation of the particles of the carbon component is accompanied by the formation of an anisotropic structure in the refractory, in which the thermal conductivity in the molding direction is much lower than in the transverse one. Anisotropy of thermal conductivity does not lead to a decrease in the density and strength of the refractory and is completely preserved at high temperatures.

 The combination of the claimed features: the manufacture of a mass with a bulk density before filling into the mold within 45-52% of the specified density of the molded refractory and limiting the molding speed (not higher than 10 mm / s) to a specific pressure of not more than 10 N / mm provides the optimal combination the degree of compaction of the mass and the decrease in the thermal conductivity of the refractory in the direction of application of the molding force. In this case, to reduce heat loss through the lining of the high-temperature unit, the molding force should be directed perpendicular to the faces of the product located in the masonry of the unit across the heat flux. The conditions for the formation of thermal conductivity anisotropy extend to the entire range of apparent practical values of the apparent density of the refractory after molding.

Since the deviation between the set and actual values of the apparent density of the molded refractories does not exceed 0.03-0.0 g / cm ³ (i.e., ~ 1%), the thermal conductivity anisotropy is maintained in the entire density range of products manufactured by the claimed method.

 Going beyond the boundaries of the above values of the claimed parameters either does not provide a sufficient technical effect, obviously, due to the limited possibility of reorienting the particles of the solid carbon component, or leads to a decrease in the density and strength of the molded refractory due to insufficient compression of the mass in the mixer.

 For the manufacture of refractory according to the proposed method, traditionally used refractory components are used (fused or sintered periclase powder, fused or sintered aluminum-magnesia spinel, etc.), carbonaceous substances (graphite, pitch, soot, coke, etc.), binders (binder phenolic powder, synthetic phenol-formaldehyde resins, coal tar, ethylene glycol, etc.) and antioxidant additives (metal aluminum, silicon metal, Al-Si, Al-Mg alloys, boron-containing compounds, etc.).

The table shows examples of the implementation of the proposed method for the manufacture of refractory. The bulk density of the mass was regulated by the pressure on it of the rollers of the mixing runners, which was changed by moving them vertically above the bowl using an articulated suspension system. Products with one-sided compression were molded on a K25001 press with an effort of 2000 tons, bilaterally - on a Lays press with an effort of 1600 tons. The specific pressure to which the products were molded at a speed of not more than 10 mm / s, and compression conditions (one-sided or two-sided) were taken with taking into account the technical characteristics and capabilities of the press, regardless of the type of raw material and bulk density. In all the examples shown in the table, the final specific pressure of the molding products was 120 N / mm ² .

 The values of the specific molding pressure and the rate of their growth were provided by control systems and maintaining a given operating mode of the presses.

 Example 1. A mass containing 10 wt.% Fused periclase powder fr. 5-3 mm, 37 wt.% Fused periclase powder, fr. 3-1 mm, 11 wt.% Fused periclase powder, fr. 1-0 mm, 32 wt.% Finely dispersed (f. Finer than 0.063 mi) mixture of fused periclase powder with aluminum metal and phenolic powder binder, 10 wt.% flake graphite and 1.7 wt.% (in excess of 100%) ethylene glycol were prepared as follows. Initially, fused periclase FR was ground in a two-chamber ball mill. 1-0 mm to a grain size smaller than 0,063 mm. 80 wt.% Of the obtained powder was weighed, 11 wt. % binder phenolic powder and 9 wt.% metal aluminum and was stirred for 10 min in a paddle mixer of periodic action. Mixing of all components of the mixture of refractory material was carried out in mixing runners, in which the rollers were raised above the level of the bowl to a height of 95 mm.

In runners in amounts corresponding to the composition of the charge, periclase fractions of 5-3 and 3-1 mm were loaded, 60% of the required amount of ethylene glycol was poured, mixed for 4 minutes, periclase powder of fractions of 1-0 mm and simultaneously graphite were added, mixed for 5 minutes, after which a fine mixture of periclase powder with a phenolic binder powder and aluminum powder was fed and all components were finally mixed for 11 minutes. From the prepared mass with a bulk density before filling in the mold 1.33 g / cm ³ on the press "Lays" with bilateral compression molded products in the form of a trapezoidal wedge (product No. 18 according to GOST 5341-69). The speed of molding products to a specific pressure of 10 N / mm ² was 10 mm / s. The thermal conductivity was determined by the method of plates on samples from an article with an apparent density of 2.96 g / cm ³ .

Example 2. For the manufacture of refractories, the materials and mixture of Example 1 were adopted. Mixing of the components of the mass was carried out in mixing runners when the rollers were raised above the bowl level of 80 mm, molding of products from the mass with a bulk density of 1.42 g / cm ^{3 was} carried out on the Lays press at two-sided compression according to the mode of example 1. Thermal conductivity was determined on samples from the product with an apparent density of 2.97 g / cm ³ .

Example 3. For the manufacture of refractories, the materials and mixture of Example 1 were adopted. Mixing of the components of the mass was carried out in mixing runners when the rollers were raised above the bowl level of 50 mm, molding of the products from the mass with a bulk density of 1.54 g / cm ^{3 was} carried out on the Lays press with bilateral compression according to the mode of example 1. Thermal conductivity was determined on samples of products with an apparent density of 2.98 g / cm ³ .

Example 4. For the manufacture of refractories, the materials and mixture of Example 1 were adopted. The components were mixed in the mixing runners according to the regime of Example 1 when the rollers were raised above the bowl level of 80 mm. The products were molded on a Lays press with double-sided compression from a mass with a bulk density of 1.45 g / cm ³ , the speed of movement of the upper pressing stamp to a specific pressure of 10 N / mm ² was 5 mm / s. The thermal conductivity was determined on samples from the product with an apparent density of 3.00 g / cm ³ .

Example 5. For the manufacture of refractories, the materials and mixture of Example 1 were adopted. The components were mixed in the mixing runners according to the mode of Example 1 when the rollers were raised above the bowl level of 50 mm. The products were molded on a K25001 press with one-sided compression from a mass with a bulk density of 1.55 g / cm ³ , the speed of movement of the stamp to a specific pressure of 5 N / mm ² was 10 mm / s. Thermal conductivity was determined on samples from the product with an apparent density of 3.00 g / cm ³ .

Example 6. For the manufacture of refractories, the materials and mixture of Example 1 were adopted. The components were mixed in the mixing runners according to the regime of Example 1 when the rollers were raised above the level of the bowl 95 mm. The products were molded on a K25001 press under unilateral compression from a mass with a bulk density of 1.35 g / cm ³ , the speed of movement of the stamp to a specific pressure of 5 N / mm ² was 5 mm / s. Thermal conductivity was determined on samples from the product with an apparent density of 3.01 g / cm ³ .

Example 7. For the manufacture of refractories used sintered periclase powder fr. 5-3, 3-1, 1-0 and finer 0,063 mm, carbon black, AI-Mg alloy, phenolic binder powder and bakelite varnish. The composition of the charge and the mixing mode of the components in the mixing runners when the rollers were raised above the bowl level of 80 mm corresponded to Example 1. The products were molded on a K25001 press with unilateral compression from the mass with a bulk density of 1.38 g / cm ³ , the speed of movement of the stamp to a specific pressure of 5 N / mm ² was 10 mm / s. Thermal conductivity was determined on samples with an apparent density of 2.38 g / cm ³ .

Example 8. For the manufacture of refractories, the materials of Example 7 were adopted. The composition of the mixture and the mixing mode of the components in the mixing runners when the rollers were raised above the bowl level of 80 mm corresponded to Example 1. The products were molded on the Lays press with double-sided compression from a bulk with a bulk density of 1.37 g / cm ^{3 the} speed of movement of the upper pressing stamp to a specific pressure of 10 N / mm ² was 10 mm / s Thermal conductivity was determined on samples from the product with an apparent density of 2.88 g / cm ³ .

Example 9 (prototype). For the manufacture of refractories, the materials and mixture of Example 1 were adopted. The components were mixed in the mixing runners according to the mode of Example 1 when the rollers were raised above the level of the bowl 35 mm. The products were molded on the Lays press under double-sided compression from a mass with a bulk density of 1/69 g / cm ³ , the speed of movement of the upper pressing stamp to a specific pressure of 10 N / mm ² was 15 mm / s. Thermal conductivity was determined on samples with an apparent density of 2.87 g / cm ³ .

 From the table it follows that the refractories made by the proposed method are not inferior to those made by the prototype in terms of apparent density and compressive strength, however, they have significantly lower thermal conductivity in the direction of application of the molding force.

Claims (1)

A method of manufacturing refractories containing a solid carbon component, comprising preparing the mass in a mixer and multi-stage molding under one-sided or two-sided compression, characterized in that the bulk density of the mass before filling in the mold is 45 - 52% of the specified density of the molded refractory, molding the stage of pre-compression to a specific pressure of not more than 10 n / mm ^{2 is} performed at a speed of not more than 10 mm / s, and the molding force is directed perpendicular to the faces of the product, having msya in the masonry of the unit across the direction of the heat flux.

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