RU2155731C2 - Method manufacture of periclase-carbonaceous refractories - Google Patents

Abstract

FIELD: manufacture of carbon-containing refractories for lining of high-temperature units. SUBSTANCE: method includes mixing of coarse-grained periclase-containing material of up to 10 mm fraction with periclase-containing material of 1-0 mm fraction, carbonaceous component and finely dispersed component including periclase-containing material and phenolic powdery binder. Mixture is moistened with liquid binder and formed by pressing in 3-6 stages with specific pressure at the first stage of not in excess of 15% of final one, with its subsequent increase at each stage by a factor of up to 3.5, and formation rate of 2-16 mm/s. Formed articles are subjected to heat treatment. EFFECT: higher strength and density, reduced porosity of periclase-carbonaceous refractories due to air-removing forming conditions. 2 tbl

Description

 The invention relates to the refractory industry, and in particular: to methods for the production of carbon-containing refractories used for lining high-temperature aggregates, mainly converters, working on gas-oxygen and combined purge technology, as well as electric smelting furnaces and steel after-treatment units.

 A known method of manufacturing carbon-containing refractories of periclase composition, according to which the products are made from the mass obtained in the mixer by mixing with a bunch of fractionated periclase powders with a maximum grain size of 3 mm, graphite and a finely divided mixture of co-grinding of periclase powder with an antioxidant additive. Products are formed on hydraulic presses in 1-2 stages. (Amendment to the section "Production of periclase-carbon refractories" TI 200-0-45-95 of the Magnesite plant and molding process sheet).

 The disadvantage of this method is that it does not provide fire and explosion safety of the production process due to the likelihood of formation of air suspension with an explosive concentration of particles of the latter during joint grinding of periclase powder and antioxidant.

 In addition, with the adopted technology of molding products from a mine with a high content of fine fractions and a maximum grain size of 3 mm, it is difficult to remove air during compression of the mass. This reduces the strength and density of the refractory, and under certain conditions (for example, when molding products of large thickness) leads to an increased yield of rejects.

 Closest to the proposed invention is a method of manufacturing periclase-carbon refractories, according to which the coarse-grained component of the charge consists of a periclase-containing material of a fraction of 3-1 mm, which is initially mixed with a liquid binder, then with a periclase-containing material of a fraction of 1-0 mm and a carbon component, they are introduced into the resulting mixture pre-prepared fine component, including periclase-containing powder, antioxidant and phenolic powder binder, form ie products and produce their heat treatment (Patent RF N 2114799, 1998, C 04 B 35/035).

 A disadvantage of the known technical solution is the relatively weak compaction and hardening of the mass during molding. This is due to the fact that at a maximum grain size of 3 mm, due to the large extent, the grain surface boundary has a very large number of intergranular voids. When compressing such a press powder, it is difficult to remove air from the press through the gaps between the die and the mold, and when a certain degree of compaction of the mass is achieved, this process generally stops. As a result, a large amount of air is pressed into the product, which leads to significant internal stresses, and also reduces the density and strength and increases the open porosity of refractories due to the formation of air shells around the material grains that prevent particles from contacting (cohesion). This has a particularly negative effect on non-fired refractories (in particular, periclase-carbon refractories), because, unlike fired refractories, they undergo only low-temperature heat treatment, in which sintering processes do not occur. In addition, when a large amount of air is pressed in after releasing the pressing pressure and pushing the raw material out of the mold, its elastic expansion takes place, which often leads to the formation of structural defects.

 The objective of the invention is to increase the strength, density and decrease the porosity of periclase-carbon refractories.

 The problem is solved due to the air-separating mode of mass molding in 3-6 steps with a specific pressure in the first stage of no more than 15% of the final, its sequential increase from each subsequent stage no more than 3.5 times and the molding speed of 2-10 mm / with the simultaneous use for the manufacture of articles of periclase-containing material with a grain size of up to 10 mm

 A three-six-step increase in pressure with its value in the first stage no more than 15% of the final and the molding speed from 2 to 10 mm / s, in combination with a limitation of the intensity of pressure increase at each stage (no more than 3.5 times) provides the most complete removal of air from the mass of periclase-carbon composition with any standard sizes of the pressed product.

 Going beyond the boundaries of the above values of the claimed parameters either does not provide a sufficient technical effect, or is impractical due to a decrease in the productivity of the press.

 The proposed molding mode allows you to use for the manufacture of periclase-carbon refractories, the compositions are more coarse-grained in comparison with the prototype. The use of such compositions reduces the proportion of pressed air relative to its initial amount (compaction coefficient) by reducing the volume of intergranular voids, as well as the need for a technological bond, the removal of which during heat treatment is accompanied by the formation of voids (pores). Increasing the maximum grain size over 10 mm slightly reduces the compaction coefficient, while the appearance of the product is deteriorated (integrity of the corners, sharp edges, etc.).

 The combination of the claimed features: the mode of molding products and the maximum grain size of periclase-containing material - allows to increase the density and strength of the refractory and reduce its porosity.

 For the manufacture of periclase-carbon refractories according to the proposed method, fused or sintered periclase powder, fused or sintered aluminum-magnesia spinel, and the like can be used as the periclase-containing component; as the carbon component, graphite, pitch, soot, coke, etc .; as a solid resin, a phenolic powder binder; as a liquid binder, synthetic novolac and rezol phenol-formaldehyde resins, coal tar, ethylene glycol, etc.

 When using an antioxidant for the manufacture of refractory material, metal aluminum, silicon metal, Al-Si, Al-Mo alloys, boron-containing compounds, etc. can be used as the latter.

 In the table. 1 shows examples of the implementation of the proposed method for the manufacture of periclase-carbon refractories using fused periclase powder, graphite, a phenolic powder binder and ethylene glycol and product properties. The compositions of the blends adopted in the examples are calculated using the Fuller formula for mixtures with a maximum grain size of 5, 7, and 10 mm and are adjusted based on the results of experimental studies and the need to ensure the technological process.

 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 (fr. Finer than 0.063 mm) mixture of fused periclase powder with a phenolic powder binder, 10 wt. % 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. 89 wt. % of the obtained powder with 11 wt.% phenolic powder binder and stirred for 10 minutes in a paddle stirrer of periodic action. Mixing of all the components of the refractory material was carried out in the runners SM-568, where in quantities corresponding to the composition of the charge, periclase was loaded. 5-3 and 3-1 mm, 60% of the required amount of ethylene glycol was poured, stirred for 4 min, periclase powder was introduced. 1-0 mm and graphite at the same time, was stirred for 6 minutes, the remaining amount of ethylene glycol was poured, stirred for 5 minutes, after which a finely divided mixture of periclase powder with phenolic binder powder was fed and all components were finally mixed for 11 minutes.

From the prepared mass on the industrial hydraulic press "Lays" equipped with systems of multi-stage pressure increase and automatic maintenance of a given mode, the products were molded in 4 steps at a specific pressure of 5, 10, 30 and 100 N / mm ² , respectively, the molding speed was 5 mm /with. The molded products were heat-treated in an electric furnace at a temperature of 200 ^o C. Samples were cut from heat-treated products, on which the compressive strength, apparent density and open porosity were determined by standard methods.

 Example 2

 For the manufacture of periclase-carbon refractory adopted mixture 2 (table. 1). The sequence of manufacture of the mass, the mode of molding products and their heat treatment as in example 1.

 Example 3

 For the manufacture of periclase-carbon refractory adopted mixture 3 (table. 1). The sequence of manufacture of the mass, the mode of molding products and their heat treatment as in example 1.

 Example 4

For the manufacture of periclase-carbon refractory adopted mixture 4 (table. 1). The mass was prepared as in example 1. The products were molded on a Lays press in 4 steps at a specific pressure of 15, 30, 60, 100 N / mm ² , respectively, at a speed of 5 mm / s. Heat treatment was carried out as in example 1.

 Example 6

For the manufacture of periclase-carbon refractory adopted mixture 6 (table. 1). The mass was prepared as in example 1. The products were molded on the Lays press in 3 steps at a specific pressure of 15, 30, 100 N / mm ² , respectively, at a speed of 5 mm / s. Heat treatment was carried out as in example 1.

 Example 7

For the manufacture of periclase-carbon refractory adopted mixture 7 (table. 1). The mass was prepared as in example 1. The products were molded on the Lays press in 6 steps at a specific pressure of 5, 10, 20, 40, 60, 100 N / mm ² at a speed of 5 mm / s. Heat treatment was carried out as in example 1.

 Example 8

For the manufacture of periclase-carbon refractory adopted mixture 8 (table. 1). The mass was prepared as in example 1. The products were molded on the Lays press in 3 steps at a specific pressure of 15, 30, 100 N / mm ² , respectively, at a speed of 2 mm / s. Heat treatment was carried out as in example 1.

 Example 9

For the manufacture of periclase-carbon refractory adopted mixture 9 (table. 1). The mass was prepared as in example 1. The products were molded on the Lays press in 6 steps at a specific pressure of 5, 10, 20, 40, 60, 100 N / mm ² , respectively, at a speed of 10 mm / s. Heat treatment was carried out as in example 1.

 Example 10 (prototype).

For the manufacture of periclase-carbon refractory according to the known method, a mixture of 10 (table. 1). The mass was prepared as in example 1. The products were molded on the Lays press in 1 step at a speed of 12 mm / s. The products were heat treated at a temperature of 200 ^o C.

 Table 2 shows the properties of periclase-carbon refractories made from various types of periclase-containing materials, carbon-containing components and a liquid binder, as well as using antioxidants. In examples 11-15, mass preparation and heat treatment of the product was carried out according to example 1, and molding according to the mode of example 2.

 The data in tables 1 and 2 show that periclase-carbon refractories made by the proposed method are superior to periclase-carbon refractories made in a known manner in terms of compressive strength, apparent density and open porosity. At the same time, there are no differences in the values of the indicated properties of refractories made from various types of raw materials.

Claims (1)

 A method of manufacturing periclase-carbon refractories by mixing periclase-containing material fr. 3 - 1 mm with periclase-containing material fr. 1 - 0 mm, a carbon component and a finely dispersed component, including periclase-containing material and a phenolic powder binder, moistening the charge components with a liquid binder, molding the refractory and its heat treatment, characterized in that the molding of the refractory is carried out with a pressure increase of 3 to 6 steps at a specific pressure on the first stage is not more than 15% of the final one, its successive increase at each stage no more than 3.5 times and molding speed 2 - 10 mm / s, and coarse-grained periclase-containing material additionally contains a fraction of 3 to 10 mm.

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