RU2167123C2 - Spinel-periclasocarbon refractory - Google Patents

Abstract

FIELD: refractories industry, more particularly manufacture of highly resistant refractories for lining of most heavily wearable areas of thermal units in ferrous and non- ferrous metallurgy. SUBSTANCE: spinel periclasocarbon refractory is prepared from body comprising, %: granular periclase of less than 3 mm fraction which is substrate; finely grained alumomagnesium spinel having fraction of less 0.5 mm, 15-30; dispersed mixture of periclase with alumomagensium spinel having fraction of less than 0.063 mm, 20-30; carbon-containing material, 4-18; organic binder, 4-8; and combined antioxidant based on aluminium powder and alumomagnesium alloy and silicon carbide powder at 2:1 to 1:2 ratios, 1-5. Refractory samples have higher slag resistance to low basic slags, dissolution rate of 0.2-0.3 mg/sq.cm, lower oxidizability and higher heat resistance. EFFECT: improved properties of the refractory. 2 tbl

Description

 The invention relates to the refractory industry, in particular to the production of highly resistant carbon-containing refractories for lining the most worn sections of thermal units of ferrous and non-ferrous metallurgy, in particular for oxygen converters, steel after-treatment plants, electric steel furnaces and argon-oxygen refining units.

Known carbon-containing refractory obtained from the mass of the following composition, wt.%:
magnesium aluminum spinel - 65 - 75
periclase - 15 - 25
graphite - 10 - 15
organic binder - 4 - 7
In this case, aluminum-magnesium spinel in the form of fused material fr. <3 mm has a mass ratio of MgO and Al ₂ O ₃ from 33:67 to 58:42 and periclase as a mixture of sintered and fused material in the ratio (10:90) - (90:10) fr. less than 0,063 mm (patent of the Russian Federation N 2040507, CL 6 C 04 B 35/04, publ. 07/27/96. Bull. N 21).

 A disadvantage of the known technical solution is the low slag resistance of the refractory due to the low compaction and sintering of ceramic phases at service temperatures, which is explained by the low activity of spinel to sintering obtained by melting on a "block".

 The oxidation stability of such a refractory is insufficient, because the resulting decarburized working zone has a porous structure. As a result of capillary impregnation, it is saturated from the melting space with slag, which intensively interacts with periclase of the ceramic bond with the formation of low-melting compounds. The fire resistance of the working zone of the products is reduced, and it is easily washed off together with ceramic grains of aluminum-magnesium spinel under the erosive influence of slag-metal melt.

Also known in the prior art is a carbon-containing refractory made from a mass of the following composition, wt.%:
fused aluminum-magnesium spinel fr. <3 mm, crystallized at eutectic temperature with non-stoichiometry for oxygen - 42 - 75
periclase-containing component - 15 - 40
carbon-containing material - 10 - 18
organic binder - 4 - 8
In this case, the periclase-containing component in the form of fr. 1-0 and less than 0.063 mm has a mass ratio of (0: 100) - (50:50) (Patent of the Russian Federation N 2068823 class 6 C 04 B 35/04, publ. 10.11.96, Bull. N 31).

The specified aluminum-magnesium spinel is characterized by an extremely defective structure, which determines its active sintering at temperatures above 1400 ^o C. The greater activity to sintering spinel obtained by melting on the "drain", in comparison with the spinel obtained by melting on the "block", predetermines higher thermal strength properties carbon-containing refractories.

 The closest in composition to the proposed carbon-containing refractory is a carbon-containing refractory mass according to the application DE 3344852 A1, C 04 B 35/68, publ. 06/14/1984, 13 p. the following composition, wt.%: 30-50 graphite, 50-97 refractory aggregate and 1-10 at least one metal alloy in powder form, selected from the group of alloys Al-Mg and Al-Mg-Cr, per 100 wt. hours total amount of graphite and refractory aggregate.

 A disadvantage of the known technical solution is the insufficiently high slag resistance of the refractory to low basic slags. With the indicated ratio of components in the carbon-containing refractory, the ceramic bond is formed mainly by fine periclase after carbon burnout. Such a ligament is not sufficiently developed and is characterized by high porosity. Upon contact with slag, the porous periclase ceramic binder of the refractory is intensively saturated with iron-silicate melts. When periclase ceramic binder is dissolved in slag, granular spinel is easily washed out under the erosive influence of slag-metal melt, without fully realizing all the valuable characteristics caused by the history of its preparation.

 The technical result of the invention is to increase the wear resistance of refractories to slags of a low basic nature, increase the heat resistance properties and reduce the oxidation rate. The indicated properties of the refractory are achieved by forming in the structure of the refractory a highly resistant ceramic bond based on aluminum-magnesium spinel and a combined antioxidant.

To solve this problem, spinel-periclase-carbon refractory is made from a mass including a granular periclase fraction of less than 3 mm, a fine-grained aluminum-magnesium spinel fraction of less than 0.5 mm, a dispersed mixture of periclase with aluminum-magnesium spinel in the ratio (90:10) - (10:90), carbon-containing material , organic binder and combined antioxidant - passivated metal powder of aluminum or its alloy with magnesium and silicon carbide powder, taken in the ratio (2: 1) - (1: 2),
in the following ratio of components, wt.%:
granular periclase fr. less than 3 mm - base
fine-grained aluminum-magnesium spinel fr. less than 0.5 mm - 15 - 30
dispersed mixture of periclase with aluminum-magnesium spinel fr. less than 0,063 mm - 20 - 30
carbon-containing material - 4-18
organic binder - 4-8
the specified combined antioxidant is 1-5
In the refractory composition of the proposed composition, carbon burnout slows down due to the action of the combined antioxidant and the formation of a dense gas-tight ceramic film formed during sintering of spinel and periclase in a finely ground component.

At relatively low temperatures 400-700 ^o C, a decrease in the thermal oxidation of the carbon binder is achieved due to the oxidation of oxygen-free components.

As the temperature rises above 1000 ^o C, silicon carbide and passivated aluminum begin to oxidize and a dense gas-tight ceramic film is formed, which prevents the penetration of gases and slag metal melt deep into the refractory.

 The combined antioxidant, which includes silicon carbide, performing its main function, shows a new quality, namely, due to the formation of silicon dioxide, it initiates mullite formation and forsterite formation, accompanied by the filling of pores and densification of the carbon-ceramic bond.

 An active sintering dispersed mixture of periclase with aluminum-magnesium spinel compensates at high temperatures for the volumetric changes characteristic of spinel. This determines the compaction of the formed shard without significant changes. Refractories do not chip or peel during service.

 The selection and combination of antioxidants was made depending on the purpose of the refractory and specific service conditions. The criteria used were the affinity of antioxidants for oxygen, oxidizability and slag resistance of spinel-periclase-carbon samples.

 Examples.

 Cooking masses, including the mass of the prototype, was carried out by mixing the components in the ratios indicated in the table. 1, in a laboratory slider mixer according to the commonly accepted technology, which involves feeding part of the binder to pre-mixed granular powders, followed by introducing the remaining amount of binder at the end of the batch after loading fine fractions of materials (fine-ground mixture of periclase with aluminum-magnesium spinel, graphite, a mixture of combined antioxidant and TFP) .

Samples were formed from the prepared masses on a hydraulic press at a pressing pressure of 100 n / mm ² and heat-treated at 200 ^o C. The heat-treated samples were used to determine the compressive strength at 1400 ^o C in an oxidizing medium and the degree of oxidation, which was evaluated by the depth of decarburization of the samples after they holding in a muffle furnace for 2 hours at a temperature of 1400 ^o C.

Slag resistance was determined by the method of rotation of a cylinder sample in a low-basic slag of the following chemical composition molten at 1600 ^° C, wt.% MgO - 2.4, CaO - 43.2, SiO ₂ - 33.4, Al ₂ O ₃ - 1.8, Fe ₂ O ₃ - 1.3, MnO - 15.2, FeO - 2.2 basicity - 1.29.

 As can be seen from the table. 2, samples obtained from the masses of the proposed compositions, in comparison with the prototype are characterized by increased slag resistance in relation to slags of a low basic nature (<2.5), reduced oxidizability and an increased thermal strength index.

Claims (1)

Spinel-periclase-carbon refractory obtained from a mass comprising a periclase-containing component, fused aluminum-magnesium spinel, carbon-containing material, a combined antioxidant and an organic binder, characterized in that the mass contains a granular periclase fraction of less than 3 mm, a fine-grained aluminum-magnesium spinel fraction of less than 0.5 mm of a spinel fraction of less than 0.5 mm of spinel fraction with aluminum-magnesium spinel in the ratio (90:10) - (10:90), and as a combined antioxidant - passivated metal powder of aluminum or its alloy lava with magnesium and silicon carbide powder, taken in a ratio of 2: 1-1: 2, in the following ratio of components, wt.%:
Granular periclase fraction less than 3 mm - Basis
Fine-grained aluminum-magnesium spinel fractions less than 0.5 mm - 15-30
Dispersed mixture of periclase with aluminum-magnesium spinel fractions less than 0.063 mm - 20-30
Carbon-containing material - 4-18
Organic Binder - 4-8
Specified Combined Antioxidant - 1-5

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