RU2085539C1 - Mass for the basic refractory article making - Google Patents

Abstract

FIELD: ferrous metallurgy. SUBSTANCE: mass has, wt.-%: periclase powder 40-90; aluminomagnesium spinel of fraction 0.3 mm containing fraction less 0.1 mm 25% (not above) obtained by pouring melting at the rate of pouring providing caking rate 0.05-0.55 that is determined by formula: K =

where: П_o - total porosity of sample before roasting, %; П - total porosity of sample after roasting, % 5-30; chrome-containing component 5-30. Properties: compression strength limit is 62.1-66.1 H/мм², porosity is 15.5-16.2%, slag-corrosion coefficient is 4.8-5.1%. Mass is used for lining the melting equipments in ferrous and nonferrous metallurgy. EFFECT: enhanced quality of mass. 3 tbl

Description

 The invention relates to masses for the manufacture of basic refractories and masses, and can be used for linings of melting units of ferrous and non-ferrous metallurgy, as well as rotary kilns.

Known refractory composition (Germany patent N 3532228 C 04 B 35/04, 04.17.86), including 10-30 wt.h. spinels based on Al ₂ O ₃ • MgO, containing 40-70% Al ₂ O ₃ , 25-60% MgO and <10% impurities and 90-70 parts by weight magnesium oxide based material containing> 90% MgO. The composition contains 10-25% Al ₂ O ₃ and 90-75% MgO.

 Products from this refractory composition have high strength after firing. However, they withstand an average of 5 cyclic thermal loads. In addition, refractories have a reduced slag resistance to metallurgical slag.

Closest to the invention is a mixture for the manufacture of refractories (ed. St. N 554251 C 04 B 35/04, 16.12.75), including the following components, mass fraction,
Magnesite 47 77
Fused aluminum-magnesia spinel 15 30
Temporary ligament 3 5
Needle crystals of zirconium dioxide 5 20
Refractory products from this mixture withstand 5 cyclic thermal loads, with a loss of strength of ≈ 86%. This is due to the inversion of zirconia crystals from the cubic modification to monoclinic and vice versa, accompanied by a change in volume during temperature drops from 0 to 1600 ^o C.

 In addition, these refractories have low slag resistance to metallurgical slag.

 The technical result of the invention is to increase the compressive strength, slow down the high temperature aging of refractories during thermal cycling and increase their slag resistance.

 The technical result is achieved in that the mass for the manufacture of basic refractory products, including periclase powder and fused aluminum-magnesium spinel, contains aluminum-magnesium spinel of a fraction of 0-3 mm with a fraction of less than 0.1 mm in it containing not more than 25% obtained by melting to the drain at a casting speed providing a degree of sintering of 0.05-0.55, and further comprises a chromium-containing component, with the following components in wt.

где П_о общая пористость образца до обжига,
П общая пористость после обжига,
Общая пористость рассчитывается по формуле:
П = (1 - ρ_к/ρ)•100,
где ρ_к кажущаяся плотность образца, г/см³;
ρ истинная плотность образца, г/см³.Periclase Powder 40 90
Specified aluminum-magnesium spinel 5 30
Chromium-containing component 5 30
The sintering degree of aluminum-magnesium spinel is expressed by the relative reduction in pore volume in firing and is calculated by the formula:

where P _{about the} total porosity of the sample before firing,
P total porosity after firing,
The total porosity is calculated by the formula:
P = (1 - ρ _c / ρ) • 100,
where ρ _{to the} apparent density of the sample, g / cm ³ ;
ρ is the true density of the sample, g / cm ³ .

 (Strelov K.K. Mamykin P.S. Textbook. Technology of refractories. M. Metallurgy, 1978, p.16 and 66).

 The following refractory materials are used as the chromium-containing component: chrome ore, its concentrate, fused periclase-chromite and its fused crust.

 The technical solution carries out the task of increasing the wear resistance of thermally stressed sections of the lining of thermal units.

 The essence of the technical solution is as follows.

In the inventive composition, fused aluminum-magnesium spinel fr. 3-0 mm with a sintering degree of 0.05-0.55 and a fraction content of <0.1 mm in it no more than 25% and also a chromium-containing component can be formed during firing at temperatures of 1560-1750 ^o C thermodynamically stable structure of the refractory due to:
firstly, filling the vacancies of the spinel crystal lattice with oxygen;
secondly, due to the occurrence of solid-phase reactions with the formation of refractory phases such as magnesioferrite, forsterite, complex chrome spinelide, etc. which form a high-strength bond with closed pores between the grains of periclase, aluminum-magnesium spinel and complex chrome spinel, which allows to increase the compressive strength and slow down the compressive strength, slow down during thermal cycling of refractories and increase their slag resistance.

 When using fused aluminum-magnesium spinel with a sintering degree <0.05, the refractory is characterized by high compressive strength and a low rate of high-temperature aging during thermal cycling, but the temperature of the onset of softening under load decreases.

 When using fused aluminum-magnesium spinel with a sintering degree> 0.55, the refractory structure loosens with an increase in volume. Products are characterized by low mechanical strength and, as a consequence, a higher rate of high-temperature aging during thermal cycling.

The use of fused aluminum-magnesium spinel in the form of a fraction of 3-0 mm with a fraction content of <0.1 mm in it no more than 25% contributes to the formation of a structure with annular pores that impede the formation and transportation of silicates in the temperature range 1500-1750 ^o C. transitions, probably not clearly expressed, and under cyclic temperature loads it experiences less stress, which does not lead to noticeable changes in the structure of the refractory with the formation of cracks. This makes it possible to repeatedly regenerate products to obtain highly resistant refractory linings.

 When using fused aluminum-magnesium spinel in the form of a 3-0 mm fraction with a fraction content of <0.1 mm in it over 25% in the indicated temperature range, the formation of a structure with annular pores around the spinel grains does not occur. In this connection, during cyclic thermal loading, no obstacles are created for the propagation of the zone of transformational transitions with the formation of cracks. With a sufficiently high compressive strength, the products are characterized by a high rate of high temperature aging during thermal cycling.

 It is mandatory to comply with the specified ratio of the components of the charge, since even with a slight deviation from it, the physical-ceramic properties of the refractory change: with the introduction of fused aluminum-magnesium spinel <5% of the product with a sufficiently high mechanical strength are characterized by a high aging rate during thermal cycling, with the introduction of fused spinel> 30 % along with high rates of high-temperature aging during thermal cycling and heat resistance of the product have low compressive strength.

 When the content of the chromium-containing component is more than 30%, the density and strength of the refractory sharply decrease due to the inhibitory effect of a large amount of complex chrome spinel on the formation of the ceramic structure.

 When the content of the chromium-containing component is less than 5%, the corrosion resistance of the refractory to aggressive reagents of thermal units sharply decreases.

 The manufacture of mass compositions are given in table 1.

 Table 2 presents the chemical compositions of the starting materials.

To determine the degree of sintering, fused aluminum-magnesium spinel was crushed, dispersed into classes, a LST solution was added, samples were mixed and pressed at a specific pressure of 200 N / mm ² . The apparent density of the samples was determined before and after firing at a temperature of 1600 ^o C.

 Magnesium-magnesium spinel with a sintering degree of 0.05-0.55 was obtained in an electric arc furnace by fusion "at the sink" at certain speeds of casting the melt into the molds and its crystallization.

The mass preparation was carried out in mixing runners with the addition of a solution of LST. The products were pressed at a pressure of 130 N / mm ² and fired at a temperature of ≥ 1650 ^o C. The rate of high-temperature aging during thermal cycling was determined for calcined samples. Why samples with a static compression load <0.035 N / mm ² were heated to 1600 ^o C, kept at this temperature for 6 hours and cooled to room temperature. After each cycle, the compressive strength (GOST 4071-87), open porosity (GOST 2409-87) and the coefficient of slag erosion were determined for the samples.

 The coefficient of slag erosion was determined by the following method.

The products were placed in metallurgical (manganese) slag having a melting point of 1250 ^° C and rotated at a speed of 200 rpm for 30 minutes. Then, the product corrosion coefficient was calculated when determining slag resistance by the ratio of the initial volume to the sample volume after the test.

 The properties of the products are presented in table 3, whence it can be seen that products made from the proposed mass (compositions 1-5) have several advantages compared to the prototype, namely: they are characterized by high compressive strength, lower high-temperature aging rate during thermal cycling and increased slag resistance.

Claims (1)

The mass for the manufacture of basic refractory products, including periclase powder and fused aluminum-magnesium spinel, characterized in that it contains aluminum-magnesium spinel fraction 0 3 mm when the fraction contains less than 0.1 mm of not more than 25% obtained by melting to drain at a casting speed that provides the degree of sintering 0.05-0.55, which is determined by the formula K P _about P / P _about , where P _{about the} total porosity of the sample before firing, P the total porosity of the sample after firing, and additionally contains a chromium-containing component in the following ratio entov, wt. Periclase Powder 40 90
Specified aluminum-magnesium spinel 5 30
Chromium component 5 302

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