RU2159219C1 - Magnesium mass for lining of metallurgical units - Google Patents

Abstract

FIELD: refractory industry; applicable in repairs and lining of metallurgical units including intermediate ladles. SUBSTANCE: magnesian mass including periclase-containing filler and binder contains binder in form of sodium polyphosphate and sodium metasilicate, and/or magnesium sulfate, bentonite, silicon dioxide and inorganic fiber with the following amounts of components, wt.%: periclase-containing filler of 1-0.063 mm fraction 57-75; and fraction below 0.063 mm 17-31; sodium polyphosphate 0.2-0.8; sodium metasilicate and/or magnesium sulfate 1.7-3.5; bentonite of 0.50-0 mm fraction 1.7-3.5; silicon dioxide of fraction below 0.01 mm 1.5-3.4; inorganic fiber 0.5-1.3. EFFECT: stabilized linear sizes and strength characteristics of offered mass in process of its heating, increased adhesion of mass to lining surface. 2 tbl, 1 ex

Description

 The invention relates to the refractory industry, and in particular to compositions of refractory masses for the repair and lining of metallurgical units, including intermediate ladles.

Known refractory mass based on periclase, used as a coating of metallurgical units, containing, wt.%: Periclase fraction less than 0.075 mm (with Fe ₂ O ₃ - 1-3%, water absorption less than 4%) - 77.5, bentonite powder 3 ,5; powder of sodium metasilicate Na ₂ SiO ₃ 5H ₂ O - 19 (UK Patent N 1272845, C 04 B 19/04, B 22 C 3/00, 1972). The main disadvantage of these masses is a rather high change in linear dimensions during the heat treatment and low strength characteristics.

Known refractory mass of the composition, wt.%:
Magnesia aggregate fraction <0.008 mm - 25 - 40
Magnesia aggregate fraction 1.5-0.5 mm - Base
Binder (alumina cement, phosphate binder, sodium metasilicate) - 5 - 20
Wood flour fractions <0.2 mm - 1 - 5
(A.S. USSR N 1616881, C 04 B 35/68, 35, 1989).

 However, this mass also has a large shrinkage during the heat treatment and low strength characteristics.

 The prototype is a refractory mass, mainly for intermediate ladles, including a filler from the group of magnesia, magnesia-chromite or forsterite refractory materials in the amount of 75-95 wt.%, 3-12% perlite, 0.5-5% binder and 0.1- 5% plasticizer (application EP N 0047728 A1, C 04 B 35/66, 03/17/82). As a binder, sodium polyphosphate, sodium silicate, magnesium sulfate and other inorganic binders can be used. Concrete can be used as a plasticizer. From 0.5 to 10% by weight of the refractory aggregate can be replaced with an inorganic fiber, in particular glass or mineral fiber.

However, the strength characteristics of this mass at a temperature of 110 ^o C and above do not satisfy the operating conditions of metallurgical units, contribute to the premature failure of the said units.

 The problem to which the invention is directed, is to stabilize the linear dimensions and strength characteristics of the mass during heating.

The problem is solved due to the fact that the magnesia mass for lining metallurgical units, including periclase-containing aggregate, sodium polyphosphate binder and sodium metasilicate and / or magnesium sulfate, bentonite and inorganic fiber, additionally contains silicon dioxide fraction <0.01 in the following ratio of components , wt.%:
Periclase-containing aggregate fraction 1-0.063 mm - 57 - 75
fractions <0,063 mm - 17 - 31
Sodium Polyphosphate - 0.2 - 0.8
Sodium metasilicate and / or magnesium sulfate - 1.7 - 4.8
Bentonite fraction 0.5-0 mm - 1.7 - 3.5
Silicon dioxide fractions <0.01 mm - 1.5 - 3.4
Inorganic fiber - 0.5 - 1.3
Introduction to the shotcrete mass of the proposed amount of refractory periclase-containing aggregate provides the required refractoriness.

 A binder introduced into the shotcrete mass ensures adhesion of the mass to the surface to be coated. As a binder, sodium polyphosphate and sodium metasilicate and / or magnesium sulfate are used.

 Magnesium sulfate is introduced in order to reduce the alkali content in the mass, since an increased alkali content leads to undesirable consequences in the process of mass service. At the same time, the content of magnesium sulfate in the mass should not exceed 5%, since a larger amount does not affect the properties of the mass, and in some cases even worsens them.

If in the mass only magnesium sulfate is used as a binder, then it is possible to stabilize the change in linear dimensions in the temperature range from 110 to 1400 ^o C, but the strength characteristics are reduced.

The combined introduction of sodium polyphosphate, sodium metasilicate and magnesium sulfate allows you to stabilize characteristics such as a change in linear dimensions in the temperature range from 110 to 1400 ^o C and strength in the temperature range from 20 to 1400 ^o C.

 Concrete is a plasticizer and retarder.

 The introduction of silicon dioxide into the mass makes it possible to compensate for the shrinkage during the heat treatment, and in some cases even a slight increase in the linear dimensions of the mass is observed, which has a good effect on the operational characteristics of the mass.

 Inorganic fiber - basalt or kaolin, introduced into the mass, creates a reinforcing frame and allows to reduce shrinkage or growth of samples, thereby creating a stabilizing effect.

Example
Sintered periclase containing MgO of at least 91% was used as initial components; periclase-chromite containing MgO not less than 55%, Cr ₂ O ₃ 15-25%; calcined dunite, with an MgO content of at least 46% of a fraction of 1-0 mm, sodium metasilicate with a fraction of less than 0.1 mm, ground bentonite of a fraction of 0.5-0 mm, magnesium sulfate MgSO ₄ • 7H ₂ O fractions of less than 1 mm, silicon dioxide finely dispersed company "Elkem", sodium polyphosphate fractions of 0.1-0 mm, inorganic fiber (basalt and kaolin) 10-12 mm long. All components are mass industrial manufactured.

 For the manufacture of samples, all the starting components were mixed in a high-speed mixer for 2-3 minutes. Water was added to the finished mass (15-20% in excess of 100% of the mass components), mixed for a minute. The moisture content of the mass was up to 20%.

The apparent density and open porosity were determined according to GOST 2409-80, kerosene with a density of 0.8 g / cm ^{3 was} used as a saturating liquid.

 The compressive strength was determined according to GOST 4071.2-94 on cubes measuring 50 x 50 x 50 mm.

The change in linear dimensions was determined by measuring the parameters of the cube before and after heat treatment according to the formula:
Δl = (l ₀ -l ₁ ) / l ₀ ,
where l ₀ is the sample size before heat treatment;
l is the sample size after heat treatment.

 To determine the apparent density and open porosity, compressive strength, and determine changes in linear dimensions, the samples were prepared as follows: the masses were placed in steel molds by packing and kept in air for 24 hours.

A day later, the formwork was removed and linear dimensions were measured, and set to dry at 110 ^° C for 24 hours. After this, one third of the samples were fired at 1100 ^° C with a holding time of 3 hours and a third at 1380 ^° C with a holding of 2 hours.

 The compositions of the tested masses and the mass of the prototype are given in table. 1, the results of their tests are in table. 2.

As can be seen from the tables, the research results show that the developed mass in comparison with the prototype has a smaller change in linear dimensions in the temperature range from 110 to 1400 ^o C and in the same temperature range it was possible to stabilize the strength characteristics.

Claims (1)

Magnesia mass for lining metallurgical units, including periclase-containing aggregate, a binder - sodium polyphosphate and sodium metasilicate and / or magnesium sulfate, bentonite and inorganic fiber, characterized in that it additionally contains silicon dioxide fraction less than 0.01 mm in the following ratio of components, wt .%:
Periclase-containing aggregate
fractions 1 - 0.063 mm - 57 - 75
fractions less than 0,063 mm - 17 - 31
Sodium Polyphosphate - 0.2 - 0.8
Sodium metasilicate and / or magnesium sulfate - 1.7 - 4.8
Bentonite fraction 0.5 - 0 mm - 1.7 - 3.5
Silicon dioxide fractions less than 0.01 mm - 1.5 - 3.4
Inorganic fiber - 0.5 - 1.3

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