RU2845844C1 - Refractory mixture for making intermediate ladle lining - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to refractory industry and can be used for making steel teeming ladle lining. Refractory mixture contains periclase and/or forsterite-containing aggregate and binder in form of a mixture of low-temperature and medium-temperature components, taken in weight ratio of (2-3):1. Low-temperature binders are selected from a group which includes monosaccharides, and the medium-temperature binder is selected from a group which includes anhydrous sodium glass, anhydrous potassium glass, sodium hydrosilicate, potassium hydrosilicate, or combination thereof. Ratio of components of refractory mass, wt. %: periclase and/or forsterite-containing mineral fraction 0-5 mm – base, binder – 6-9. Additionally, organic or mineral fibre is added to the mixture in amount of not more than 1 % (over 100 %).

EFFECT: good workability, good sintering of the working layer and resistance during operation.

3 cl, 3 tbl, 1 ex

Description

The invention relates to the refractory industry and can be used for the manufacture of tundish linings.

A dry refractory mass for an intermediate ladle is known, containing in mass %: 25-38 magnesia with a particle size of 1-3 mm, 10-23 fused magnesia with a particle size of 0.074-1 mm, 15-30 fused magnesia with a particle size of less than 0.074 mm, 20-32 limestone, 4-13 - hydrated sodium metasilicate. Hydrated sodium metasilicate is sodium metasilicate pentahydrate, sodium metasilicate heptahydrate, metasilicate nonahydrate. (CN 106631056 A dated 24.11.2016 C04B 35/66).

The use of only hydrated sodium metasilicate as a binder (melting point 1086°C), with the declared permissibly high content in the batch (up to 13%) will lead to a decrease in the durability of the lining. Glasses are strong fluxes that reduce refractoriness. When a certain temperature is reached, a flux is formed on the surface and inside the lining, which itself is capable of carrying away grain from the lining, washing it away, facilitating active chemical interaction with slags, thereby also washing away the lining. The more glass in the batch, the more mobile phase will be formed. The introduction of 20-32% limestone contributes to accelerated corrosion wear when working with low-basic acid slags.

A dry refractory mass for an intermediate ladle is known, containing in parts by weight: waste magnesia-chromium brick 24-72; magnesia 41-92; bentonite 0.5~5; binder 1-5; high-alumina bauxite - 0.5-2 as an anti-penetration agent. At the same time, it contains the following fractional composition: 8-30 waste magnesia-chromite refractory (brick) 0-1 mm, 8-30 waste magnesia-chromite brick 1-3 mm, 12 waste magnesia-chromite brick 3-5 mm, 8-12 magnesia 200 mesh, 10-30 magnesia 0-1 mm, 5-22 magnesia 1-3 mm, 8-12 magnesia 3-5 mm. The binding agent is one or more components selected from: sodium silicate, glucose, borate, sulfate, maltose and sucrose. (CN 106915953 A dated 01.04.2017, C04B 35/047).

There are strict requirements for the chemical composition of steel and in some grades the presence of chromium is not welcomed. Therefore, the mass of this composition can be used for certain grades of steel. Another disadvantage is the presence of bauxite with a high content of alumina in the mass, which during operation (at a temperature of 1300-1500 ° C) will interact with the magnesia component (TCLE 13.5 10 ^-6 K ^-1 ) with the formation of aluminum magnesium spinel MgO-Al ₂ O ₃ (TCLE 8 10 ^-6 K ^-1 ), accompanied by a locally significant increase in volume (by 6.8%), which will lead to loosening of the structure and, as a consequence, an increase in the number of pores of various types.

The use of a disaccharide (maltose) as a binder ensures poor lining sintering. During high-temperature heating of the ladle, the strength of the masses based on low-melting disaccharides decreases sharply, conditions arise for the formation of non-uniform lining layers with local softening.

In addition, a binder in the amount of 1-5% is not enough for the lining behind the template to be well strengthened when it is heated at 300-350°C, and after removing the template, not to crumble or fall off, and also to have good mechanical strength when heating the intermediate ladle before pouring.

A dry refractory mass for an intermediate ladle is known, containing, by weight: sintered magnesia 42-49, fused magnesia 46-50, binder 2-5, additive 1-5, sintering accelerator 1-6. Sintered magnesia contains MgO≥95 wt. % and _SiO2 ≤2.2 wt. %; fused magnesia contains MgO≥96 wt. % and SiO2 _≤1.4 wt. %.The total mass percentage of sintered and fused magnesia is ≥92%.Sintered magnesia consists of particles of 3-5 mm, 3-1 mm in size, in the ratio of (15-22): (22-27).Fused magnesia consists of particles of 1 mm-200 mesh and less than 200 mesh in size, in the ratio of (20-26): (20-26).The additive is represented by two types in the ratio of 1: (3-5). Organic fiber is used as the first additive, and one or a mixture of several powders is used as the second: metallic aluminum, boron carbide and metallic silicon. The additive, consisting of organic fibers, metallic aluminum powder and metallic silicon, can be mixed in a mass ratio of 1: 3: 1.The sintering accelerator is represented by three types in the ratio of 4: (1-3): (0.5-2): magnesium sulfate; one or more selected from: borax, boric acid and quartz; one or more powders of boric glass, red clay and white clay. The binding agent is one or a combination of phenolic resin and glucose. (CN 14380577 A dated 24.03.2022, C04B 35/043).

One of the components of the binder is phenolic resin. Toxic materials are used in its production. Both phenol and formaldehyde are poisonous and flammable. Formaldehyde has a carcinogenic and depressant effect on the nervous system. Phenol-formaldehyde resins can have a harmful effect on the skin, they can cause dermatitis and eczema. Phenol has a pronounced pungent odor and is also highly toxic. In addition, the binder is introduced at 2-5%, this amount is insufficient and leads to a decrease in mechanical strength when heating the tundish before pouring, the lining behind the template will sinter poorly when heated at 300-350 ° C, and after removing the template, it will crumble and crumble.

A dry refractory mass for an intermediate ladle is known, containing in parts by weight: 62-95 sintered magnesia, 15-25 low-grade magnesia (beneficiation tailings), 4-7 composite binder, 0.2-1.5 sintering additive and 0.2-2.0 antioxidant. One or more components selected from powdered resin, glucose, sodium metasilicate pentahydrate, sodium tripolyphosphate are used as a binder. The mixture ratio is: resin powder: glucose: sodium metasilicate pentahydrate: sodium tripolyphosphate (0~3):(0~3):(0~1):(0~1). The sintering additive is a mixture of two or more components selected from boric acid, shavings (wood) and boron-containing glass powder. From 20 to 30 parts of sintered magnesia have large particles of less than 3 mm and greater than or equal to 1 mm in size, 30 to 40 parts have particles of less than 1 mm in size, and 12 to 25 parts have particles greater than or equal to 0.088 mm in size. (CN 115626830 A of 21.10.2022, C04B 35/66).

If resin is used, the mass will contain phenol and formaldehyde. Formaldehyde has a carcinogenic and depressant effect on the nervous system. Phenol-formaldehyde resins can have a harmful effect on the skin, they can cause dermatitis and eczema. Sodium tripolyphosphate provides poor sintering in anhydrous masses. 3% glucose and 1% sodium metasilicate pentahydrate are insufficient for uniform distribution in a microdispersed matrix, which in turn will not create conditions for high-quality binding of the mass components at high temperatures, and, accordingly, for good sintering of the lining.

The use of sintering additives and antioxidants complicates the mass manufacturing technology and makes the mass multicomponent. The formed structure of the consumable lining will have reduced refractory properties due to the fact that low-grade magnesia is used.

A dry refractory mass for an intermediate ladle is known, containing, by weight: 66-74 magnesia or forsterite of fraction 3-0.074 mm, 20-30 magnesia of fraction <0.074 mm, 3-5.5 composite binder with particle size <0.18 mm, 0.3-1% additives. Magnesia can be sintered magnesia or fused magnesia, or a mixture thereof. The content of magnesia or forsterite particles of fraction 3-0.074 mm is: 62-71%) of particles of size 3-1 mm and 29-38%) of particles of size 1-0.074 mm. The composite binder is a mixture of monosaccharides, phenolic resin and aqueous sodium metasilicate. The monosaccharide can be one or a mixture of glucose, galactose, mannose or sorbose. Sodium metasilicate hydrous may be one or a mixture of sodium metasilicate nonahydrate, sodium metasilicate pentahydrate and sodium metasilicate heptahydrate. One or a mixture of metallic aluminum powder, metallic silicon powder or silicon carbide powder is used as an additive. (CN 102674852 A dated 10.05.2012) The use of phenolic resin provokes the formation of a pungent odor during the execution and heat treatment of the lining, the release of free phenol and formaldehyde in the air of the working area creates a risk of exceeding the MAC, which leads to occupational diseases. When heating the tundish before pouring, metallic aluminum will first react with MgO to form spinel, ensuring the growth of the lining (however, there is a risk of cracking). In this case, the working lining, for which the template mass is intended, can be baked to the reinforcement lining, and this creates a risk of having a problem removing the working lining after casting. A significant content of dispersed (fine) filler fraction requires a larger amount of binder to bind a larger area of the contact surface between the particles. The introduced amount of binder (3-5.5%) is insufficient and will lead to a decrease in mechanical strength when heating the tundish before casting, the lining behind the template when heated at 300-350 °C will sinter poorly, and after removing the template - will crumble and crumble.

The technical result achieved in the present invention consists in obtaining a mass that ensures good workability, good sintering of the working layer, eliminating sintering to the reinforcement layer, the absence of harmful odors, both when performing lining and when drying intermediate ladles, good durability and removal of the spent working layer.

The specified technical result is achieved in that the refractory mass for producing the lining of an intermediate ladle, containing a periclase and/or forsterite-containing filler and a binder in the form of a mixture of low-temperature and medium-temperature components selected from the group including: monosaccharides, anhydrous sodium glass, anhydrous potassium glass, sodium hydrosilicate, potassium hydrosilicate, or a combination thereof, according to the invention, the ratio of low-temperature and medium-temperature components is (2-3): 1, with the following ratio of components, mass%:

periclase and/or forsterite-containing filler fraction 0-5 mm - base, binder - 6-9.

The ratio of granular and dispersed components of the mass is (2-3): 1. Additionally, organic fiber is introduced into the mass in an amount of no more than 1% (over 100%).

Periclase filler (periclase) can be obtained by firing or melting magnesite raw materials, grinding and subsequent sieving of the required fractions, with the MgO content in periclase being 90-94%. Olivinite or fired dunite with a particle size of no more than 5 mm is used as a forsterite-containing filler. Dunite firing is allowed at a temperature of 1000°C or higher. The MgO content in forsterite-containing materials, for example in olivinite, is 47-51%, SiO ₂ 38-41%, Fe ₂ O ₃ 7-9%, CaO <0.1%, Al ₂ O ₃ 0.1-0.2%. Periclase and/or forsterite-containing filler can be represented by the following fractions: 5-3 mm, 3-1 mm, 1-0.5 mm, less than 0.063 mm.

The ratio of the sum of granular and dispersed fractions of the components of the refractory mass is (2-3): 1. The specified ratio ensures good workability and obtaining optimal physical and mechanical properties of the refractory mass.

The binder is presented as a mixture of organic low-temperature components (monosaccharides: glucose, dextrose, fructose, ribose, galactose, mannose, xylose, etc.) and medium-temperature components (anhydrous sodium glass, anhydrous potassium glass, sodium hydrosilicate, potassium hydrosilicate) in the ratio (2-3) /1. The binder plays a responsible role in the formation of the lining. At 300 °C - the heating temperature of the metal template - it is important that there is enough organic low-temperature component and that it, heating up, melts and binds the entire refractory filler. The melting temperature of monosaccharides is about 100-150 °C. Heating occurs layer by layer - from the template into the layer made of the mass. It is important that both the temperature and time are sufficient to heat up the entire thickness of the layer and sinter it, so that after removing the template the layer remains sintered and does not crumble. A medium-temperature component in the form of anhydrous sodium glass and/or anhydrous potassium glass and/or sodium hydrosilicate and/or potassium hydrosilicate is sufficient in an amount 2-3 times smaller to maintain the strength of the already sintered lining further, when heating the intermediate ladles, before pouring to a temperature of 900-1100 ° C. Heating the lining before pouring is necessary to prevent an explosion during the feeding of hot molten steel into a cold ladle. In the absence of a medium-temperature binder, at 900-1100 ° C the organic low-temperature binder burns out completely and there is a risk of lining crumbling.

The introduction of less than 6% of the binder into the mass composition is insufficient for its uniform distribution in the microdispersed matrix of the mass; a low proportion of bound particles of refractory phases leads to a decrease in mechanical strength and, as a consequence, poor sintering at temperatures of 300°C, 900-1100°C.

Adding more than 9% binder results in a decrease in fire resistance due to the formation of an increased proportion of low-melting substances.

Two different-temperature binders, selected in the required quantities, provide the necessary properties of the lining throughout its entire operating cycle. The low-temperature organic binder, melting from the heating temperature of the template (300-400°C), glues the dispersed part and the grain immersed in it. The amount of this binder is sufficient to remove the template after heat treatment and obtain the so-called working lining, which is subjected to heat treatment again before pouring the intermediate ladle, but at a higher temperature of 900-1100°C. But at this temperature, the second binder, the medium-temperature one, melts, providing mechanical strength to the obtained working lining at this temperature. Subsequently, when feeding steel into the intermediate ladle, the lining, sintering, provides good mechanical strength.

If necessary, a small amount (no more than 1%, over 100%) of organic or mineral fiber can be added to the mass, this will contribute to the formation of a more porous structure and a decrease in thermal conductivity. When mixed, the fiber reduces the bulk density of the mass and contributes to the formation of additional porosity without reducing the stability of the mass.

With the addition of more than 1% fiber, a greater number of pores are formed and there is a risk of premature wear of the lining and a decrease in durability.

Below is an example of manufacturing a refractory mass and a method for using it. The mass is made from pre-prepared periclase and/or forsterite-containing powders and a binder. The quantitative content of the constituent components of the refractory mass is selected experimentally to obtain the properties necessary to achieve the declared technical result (Tables 1 and 2). The fractional composition of the refractory filler, as well as the combinations of components, are given as examples and do not exclude other fractions and other combinations of components in combinations and within the limits specified in the formula and description of the claimed invention. The refractory filler is dosed, then the pre-prepared binder is introduced. The mass in a dry state is unloaded into soft polypropylene containers with a polyethylene liner, excluding moisture ingress.

To assess the compressive strength of the masses, samples were made by pouring the dry masses into metal molds measuring (70x70x70 mm), leveling them with a metal ruler, covering them with a metal sheet and heat treating them at 300°C for 20 minutes. After cooling, the molds were disassembled and the samples were removed. Some of the samples were heat treated at 900°C and 1570°C.

An example of manufacturing a working lining of an intermediate ladle using the declared refractory mass. The lining of the bottom is produced by forming a uniform layer of the mass on the reinforcement lining of the intermediate ladle. After that, a metal template repeating the ladle profile is installed in the intermediate ladle. The template is centered so that the gap between the reinforcement lining of the ladle and the template corresponds to the thickness of the working layer of the intermediate ladle, 40-100 mm. The space between the template and the lining of the intermediate ladle is filled with dry mass. Sintering and strength gain of the filled layer occurs under the influence of heat from the gaseous coolant. Heating of the refractory material is carried out automatically through the wall of the template, to a temperature of ~ 300 ° C, followed by holding for a time selected individually at each enterprise and depending on the thickness of the lining and subsequent removal of the template. Heating the inner chamber of the template to a certain temperature ensures uniform sintering of the dry refractory mass along the height of the lining, while ensuring sufficient strengthening of the working area of the lining and reliable operation of the tundish lining during the steel pouring period.

Table 1 Binder compositions, mass fraction of components, %

Claims (5)

1. A refractory mass for producing a tundish lining, containing a periclase and/or forsterite-containing filler and a binder in the form of a mixture of low-temperature and medium-temperature components, where the low-temperature components are selected from a group including monosaccharides, and the medium-temperature components are selected from a group including anhydrous sodium glass, anhydrous potassium glass, sodium hydrosilicate, potassium hydrosilicate or a combination thereof, characterized in that the ratio of the mass fractions of the low-temperature and medium-temperature components of the binder is (2-3):1, with the following ratio of components, mass%: periclase and/or forsterite-containing mineral fr. 0-5 mm - base, binder - 6-9. 2. A refractory mass according to paragraph 1, characterized in that the ratio of the mass fractions of granular and dispersed components in the refractory mass is (2-3):1, wherein the dispersed components are a filler fraction of 0-0.063 mm and a binder. 3. A refractory mass according to paragraph 1, characterized in that organic or mineral fiber is additionally introduced in an amount of no more than 1% over 100%.