RU2606351C2 - Method of protective scull forming on oxygen converter lining surface and magnesian briquetted flux (mbf) for its implementation - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to ferrous metallurgy, in particular, to methods of protective scull forming on converter lining surface. Method consists in final slag leaving in converter, preliminary blowing of final slag with oxygen and magnesia briquetted flux addition into converter with subsequent flux modified final slag blowing with neutral gas. Between lining spraying additionally performing is magnesia briquetted flux addition in supplied into converter charging on scrap metal, wherein at each stage flux is added in amount of 2.7–8.0 kg/t of steel, spraying and melting are carried out at temperature of 1,580–1,680 °C, and used magnesia briquetted flux is composition containing magnesian component, containing periclase-carbon, in form of melting and casting units waste lining scrap and dolomite.

EFFECT: enabling increased duration of vessel campaign period from 3,000 to 5,000–8,000 melts with considerable cost-cutting of used magnesian flux.

2 cl, 2 tbl, 3 ex

Description

The invention relates to ferrous metallurgy, in particular to methods for maintaining a converter lining by forming a stable protective skull on the lining surface.

During the life cycle of the converter until the wear of its main lining (campaign) is irreparable, regular scheduled work is carried out with a certain periodicity to repair the main zones of the converter and its structural elements: bottom, drain and purge holes, slag zone. Therefore, the main task of various schemes and methods for maintaining the lining of the converter during the campaign is to ensure that the maximum number of melts is possible and, therefore, reduce the unit cost of smelting 1 ton of steel.

A known method of restoring the lining of the Converter [description of the patent of the Russian Federation No. 2094475, IPC-6: C21C 5/44, F27D 1/16, publ. 10.27.1997], including leaving liquid slag in the converter after the metal is released through the tap hole, turning the converter relative to its vertical axis, supplying gas to the slag through a purge device and applying a slag skull on the lining, while the converter is turned relative to its vertical axis toward the tap hole by the angle is 90-125 °, and gas is supplied with an intensity of 0.08-0.25 m ³ / t⋅min through a purge device introduced into the notch.

A known method of applying a skull on the lining of the converter [description of RF patent No. 2109072, IPC-6: C21C 5/44, F27D 1/16, publ. 04/20/1998], including the release of the molten steel from the converter with the previous melting liquid slag left in it, introducing into the working space of the converter through its lance neck and supplying neutral gas through it to apply a layer of liquid slag to the converter walls when moving the lance in the vertical direction, characterized in that the neutral gas is supplied at a flow rate of 1-4 m ³ / min –1 of the steel of the previous heat for 1–8 min, while the lance is moved in the vertical direction back and forth from the maximum distance from the level with the late bath in the previous heat, equal to 80-150 calibers of the tuyere nozzles, to its minimum value equal to 1-40 calibers of the tuyere nozzles.

A known method of repairing the lining of the Converter [description of the patent of the Russian Federation No. 21194919, IPC-6: C21C 5/44, F27D 1/16, publ. 07/10/1998], which includes feeding lime into the converter during the melt blowing process, pouring the melt from the converter into the steel pouring ladle, leaving slag in the converter, adding dolomite to it, periodically tilting the converter in opposite directions and applying a skull on its lining, and after that the melt drain, the converter is installed in a vertical position, the lance is lowered into it and the slag remaining in it is blown with oxygen at a flow rate of 1.5-4.0 m ³ / min-melt in the previous melt for 5-30 s, while the lance in the oxygen purge process is installed along the height of the working cavity of the converter at a distance from the level of a calm melt bath in the previous heat equal to 5-50 calibers of the tuyere nozzles, then the oxygen supply is stopped, the tuyere is lifted and the unfired dolomite with a fraction of 5-50 mm is fed into the converter

There is a method of applying a slag skull on the lining of the converter [description of the patent of the Russian Federation No. 2128714, IPC-6: C21C 5/44, F27D 1/16, C21C 5/28, publ. 04/10/1999], including knocking down the converter and releasing from it a metal subjected to oxidative purging to a certain carbon content in it, leaving the slag of the previous smelting in the converter and applying it to the inside walls of the converter by applying neutral gas jets through the lance through the lance at its variable height, and depending on the carbon content in the metal before it is released on a converter chopper, carbonate and / or carbon-containing materials are introduced into the slag in an amount of 15-25% and 5-10% by weight of the slag, respectively, p and at a carbon content of more than 0.12% carbonate materials are introduced, with a carbon content of 0.06-0.12%, carbonate and carbon-containing materials are introduced, and with a carbon content of less than 0.06%, carbonaceous materials are introduced, and then the resulting mixture is mixed slag melt with a mixture of oxygen and neutral gas in a ratio of 1: (0.35-0.85) for 1-7% of the duration of the main oxidative purge, followed by its application to the converter lining with neutral gas jets with a flow rate of 100-200% of the nominal intensity of the main oxidizer blowing.

A known method of restoring the lining of the converter [description of the patent of the Russian Federation No. 2131467, IPC-6: C21C 5/44, publ. 10.06.1999], including leaving the final slag in the converter and foaming it with an additive of carbon-containing material and limestone, blowing up the slag with gas, while the carbon-containing material and limestone are added in the ratio (0.2-5.0) :( 0.5-7, 0) at a total flow rate of the mixture of 2.0-35.0 kg / t, and the start time of the slag blowing gas is determined from the moment the mixture is added, based on

τ = s / 1.399,

where τ is the time from the moment the mixture was added to the start of the slag blowing operation with gas, min;

C is the amount of carbon-containing material to be seated, kg / t;

1,369 is a constant empirical coefficient.

A known method of repairing the lining of the converter [description of the patent of the Russian Federation No. 2132392, IPC-6: C21C 5/44, publ. 06/27/1999], including feeding the melt in the converter with oxygen from above through the dolomite form and lime as slag-forming materials, pointing the magnesia slag melting through the dolomite prior to repairing the lining before repair, draining the melt from the converter into the steel pouring ladle and leaving it in the converter slag and the subsequent application of a skull on the lining of the converter, while the magnesian slag during the previous melting prior to repair is induced until it reaches a content of 5-12% MgO ohm of feeding 20-50 kg / t of dolomite melt, after the melt is released, 90-98% of the formed slag is left in the converter, and the skull is applied to the lining by blowing the slag from above through a tuyere with neutral gas for 0.5-30 minutes, while the consumption of neutral gas support equal to 0.4-1.2 oxygen consumption in the previous heat.

A known method of applying a slag skull [description of the patent of the Russian Federation No. 2170269, IPC-7: C21C 5/44, F27D 1/16, publ. 07/10/2001], including knocking down the converter and discharging metal from it, leaving the slag of the previous melting in the converter, introducing slag-forming materials containing Ca and Mg, mixing the resulting slag melt with a mixture of oxygen and neutral gas, and then applying it to the inside walls of the converter, with slag-forming the materials are introduced sequentially in two stages: at the first stage, Ca-containing materials are added and the resulting slag melt is mixed with a mixture of neutral gas with oxygen in a ratio of 1: (0.05-0.15), Mg-containing materials are planted in the second stage in an amount of 20-50% by weight of Ca-containing materials deposited in the first stage and Mg-containing materials with a slag melt are mixed with neutral gas, while the ratio of the mixing time of the slag melt in the first stage to the time of its mixing by the second stage is maintained equal to 1: (1.3-1.5), after which the slag melt is applied to the lining with jets of neutral gas.

A known method of repairing the lining of the converter [description of the patent of the Russian Federation No. 2277590, IPC: C21C 5/44, publ. 06/10/2006], which includes draining the metal from the converter into the steel pouring ladle, leaving slag in the converter, introducing flux containing calcium and magnesium oxides to the slag, applying the slag coating to the lining by applying nitrogen from the tuyere from above to the slag, and at the end of the metal draining and leaving the slag in the converter, oxygen is fed into the lining converter with horizontally directed jets with an intensity of 0.6-2.0 m ³ / min per ton of molten steel together with the magnesia exothermic mixture for 0.2-15 minutes, the slag coating is applied they are at a ratio of nitrogen to oxygen consumption equal to 1.1-7.0, and flux containing calcium and magnesium oxides is introduced into the slag before / or during nitrogen supply in an amount of 0.3-95.0% of the amount of blown oxygen exothermic mixture.

A known method of applying a slag skull on the lining of the converter [description of the patent of the Russian Federation No. 2342444, IPC: C21C 5/44, publ. 12/27/2008], including leaving the final slag in the converter and fanning it with nitrogen through a lance, supplying powdered magnesian materials, while simultaneously feeding the final slag with nitrogen, the powder materials are fed through a separate path in a stream of nitrogen in the ratio (10-25): 1 by weight, respectively, and apply them to the lining together with the final slag.

A known method of applying a skull on the lining of the Converter [description of the patent of the Russian Federation No. 2373291, IPC: C21C 5/44, publ. November 20, 2009], which includes leaving slag in the converter after the metal is drained, blowing the slag with nitrogen, adding a flux containing magnesium, calcium, iron and carbon oxides to provide ferrous periclase, while flux additionally containing metal is added to the slag left in the converter aluminum, oxides of aluminum and silicon in the following ratio of components, wt. %:

magnesium oxide 45.0-85.0 silica 0.5-7.0 iron oxide 2.0-20.0 aluminum oxides 1.0-15.0 metal aluminum 1.0-10.0 carbon 0.1-7.0 calcium oxide rest,

the basicity of the slag left in the converter is 1.5-4.5 with a ratio of iron oxides to magnesium oxides in the slag equal to 1.2-7.5, and the mass fraction of iron periclase in the flux is 2.0-75.0%.

A known method of applying a slag skull on the lining of the converter [description of the patent of the Russian Federation No. 2397253, IPC: C21C 5/44, publ. 08/20/2010], including knocking down the converter and releasing the metal subjected to oxidative purging from it, leaving the slag of the previous melting in the converter, introducing carbonate materials and carbon-containing fuel into the slag, applying it to the inside walls of the converter by applying neutral gas jets through the lance to the slag from above with a variable height above the level of a calm bath, while the quality of carbonate materials and carbon-containing fuel before and / or during the flow of neutral gas jets onto the left slag onto the left slag administered dolomite, lime and carbon-containing fuel in a ratio of 1: (0.2-0.6) :( 0.4-0.6), respectively, and feed the neutral gas in the first period of 10-30 seconds produce a rate of 20-25 m ³ / min⋅ of slag left from the previous smelting through a lance located at a height corresponding to 15-30 reduced calibres of the diameter of the tuyere nozzle above the metal level of a calm bath, followed by a decrease in the height of the tuyere to 7-12 reduced calibers of the diameter of its nozzle with a subsequent change in the height of the tuyere the range of 7-30 reduced calibres of the diameter of its nozzle for 5-25 s while the flow rate of neutral gas is maintained equal to 1.1-1.5 flow rate of the gas of the first period.

A known method of applying a skull on the lining of the Converter [description of the patent of the Russian Federation No. 2294379, IPC: C21C / 44, F27D / 16, publ. 12/27/2008], including leaving the final slag in the converter, blowing the final slag with nitrogen, adding a flux to the converter before blowing and / or in the process of blowing the final slag, moreover, self-dissolving magnesian granules in the amount of 0.2-30 are added as flux to the converter, 0 kg / t of steel obtained by pelletizing caustic and crude magnesite and coke and / or siderite, while the ratio of magnesium oxides to calcium oxides in self-decaying magnesia granules is 10-65, and the loss content during calcination is 20-50%; self-disintegrating magnesia granules contain, by weight. %: magnesium oxide 40-65, calcium oxide 1.0-2.5, carbon 4.0-20 and / or iron oxide 7.0-15.

There is also known a method of preparing slag for applying a skull coating on the lining of the converter [description of Ukrainian patent No. 99248 (application of Ukraine No. a201204761 from 04.17.2012, IPC-8: C21C 5/44], including leaving the final slag of the previous smelting, its modification with additives of magnesium-containing materials having in its composition sparingly soluble and readily soluble components, and blowing slag with nitrogen, while sparingly soluble and readily soluble components in magnesium-containing materials were taken in an amount providing the following ratio (0.65-0.35) :( 0.35-0.65), respectively, while at least 80% of the total number of sparingly soluble components were taken in a fraction of 2-6 mm, and with a FeO content of 17-20 % in the final slag, simultaneously with the additives of magnesium-containing materials, coal is added in the amount of 0.25-0.75 kg / t suitable steel, after which the converter is shaken.

Also known is a slag-forming briquette for metallurgical production [description of Ukrainian patent No. 99698 (application of Ukraine No. a201206727 dated 01.06.2012, IPC-8: C21C 5/36], containing a mixture of magnesium carbonate, carbon, an organic and / or mineral binder and additionally containing waste firing dolomite, taken in the ratio with magnesium carbonate equal to (0.15-0.75) :( 0.38-1.0), in the following ratio of components, wt.%:

Magnesium carbonate 30.0-66.0 Dolomite roasting waste 10.0-60.0 Carbon 4,5-10,0 Organic and / or mineral ligament 5.5-14.0

while the waste firing dolomite contains components in the following ratio, wt. %: magnesium oxide 18.0-40.0; calcium oxide 40.0-65.0; silica 1.5-4.5; iron oxide 1.5-5.5; alumina 0.5-4.5; the mixture of alkali metal oxides is 1.0-5.0, and dolomite firing wastes were taken with a fraction of 0.01-5.0 mm.

The disadvantages of the known methods of forming a protective skull on the surface of the converter lining and the compositions used in this case are the relatively low life of the refractory lining (campaign period) of up to 3,000 heats on average when carrying out scheduled repairs of the main structural elements of the converter described above, and the limited performance of the converter due to the need for frequent, after 1-3 melting, shotcrete, as well as the need to maintain a high, at the level of 8-12%, the content of magnesium oxide MgO in the slag for creating chemical equilibrium by introducing highly magnesian fluxes, which leads to a rise in the cost of a unit of final production.

The technical problem solved by the invention is the development of a method for forming on the surface of the lining of the converter a stable protective skull using the proposed magnesian briquetted flux (MBF) by increasing the thickness of the lining of the walls of the converter from the side of the bait, from 600-800 mm to 800-1100 mm, reducing the area of increased lining wear in the trunnion area (felling pockets) and, as a result, an increase in the campaign period from 3000 to 5000-8000 heats with an increase in the number of heats between two successive gas amicheskimi shotcrete from 1-3 to 3-5, as well as providing the possibility of maintaining the low MgO concentration in the slag at a level of 5-8%.

To solve the technical problem in the method of forming a protective skull on the surface of the lining of the converter, which includes leaving the final slag in the converter, preliminarily blowing the final slag with oxygen and adding briquetted magnesia flux to the converter, followed by blowing, modified with the final slag flux, neutral gas, while between shotcrete additionally, an additive of magnesia briquetted flux is added to the scrap metal fed to the converter, In this case, at each stage, flux is injected in the amount of 800-2400 kg / operation or 2.7-8.0 kg / t of steel, shotcrete and smelting are performed at temperatures of 1580-1680 ° C, and a composition including magnesian component containing periclase carbon in the form of scrap spent lining of melting and casting units and dolomite at a ratio, wt. %: 55-85 magnesian component containing periclase carbon, 15-45 dolomite, and the fractional composition of the composition is formed, wt. %: 70-85 francs 0 <2 mm, fr. 2 <5 mm - the rest.

Magnesia flux for forming a protective skull on the surface of the lining of the converter is molded in the form of a briquette of compressed particles, including magnesian components and dolomite, as well as an organic and / or inorganic binder. As a magnesian component containing periclase carbon, scrap scrap is used in the lining of melting and casting units in the ratio, wt. %: 55-85 magnesian component containing periclase carbon, 15-45 dolomite, while the fractional composition of the composition is formed, wt. %: 70-85 francs 0 <2 mm, fr. 2 <5 mm - the rest.

The chemical composition of the components of magnesia briquetted flux are shown in Table 1.

The proof of the achievement of the technical result from the use of magnesia briquetted flux (MBF) in the converter for the care of the lining is given below.

The formation of a skull layer on the surface of the refractory lining of the converter occurs due to the hardening of the slag suspension resulting from the MBF material modification of the final converter slag left after the melting was released, while it was inflated by high-pressure nitrogen jets. The skull coating is “compacted” from the cylindrical part to the lower cone, thereby protecting the most worn out areas of the masonry - “drain”, “filling”, “trunnion”. The presence in the magnesian briquetted flux of sparingly soluble components, in the amount of 55-85% (wt.%), At least 70% of which have a fraction of 0-2 mm, 2-5 mm the rest are delivered and evenly distributed throughout the volume of slag melt already in first seconds of nitrogen blowing.

This effect is achieved due to the presence in the material of highly soluble, finely dispersed components that contribute to the dispersion of the seated components. Upon contact with the slag, these components quickly assimilate (dissolve), increasing the MgO content in the slag. The regulated ratio of sparingly soluble and readily soluble components leads to the formation of a significant amount of refractory ferritic phases in the prepared slag and the formation of a strong "skeleton" in the cooled skull coating due to the "under-dissolved" fractions - "grains".

Method implementation examples

Example 1

Between shotcreting, a magnesian briquetted flux (MBF) of the following composition (wt.%) Was added to the scrap metal fed to the converter;

Magnesian component (including periclase carbon) 58 Dolomite 29th Bunch 13,

the amount of MBF introduced into the final slag was 8.0 kg / t of steel.

The material was added to the filling in one portion in an amount of 2.7 kg / t of steel after briefly blowing the final slag with oxygen for 10-15 seconds. Shotcrete and melting were performed at a temperature of 1580 ° C. As MBF, a composition was used that included a magnesian component containing periclase carbon in the form of scrap spent lining of melting and casting units and dolomite at a ratio of wt. %: 55 magnesia component containing periclase carbon, 45 dolomite, moreover, the fractional composition of the composition included, wt. %: 85 francs 0 <2 mm, fr. 2 <5 mm - the rest.

Example 2

Between shotcreting, a magnesian briquetted flux (MBF) of the following composition (wt.%) Was added to the scrap metal fed to the converter;

Magnesian component (including periclase carbon) 73 Dolomite 23 Bunch four,

the amount of MBF introduced into the final slag was 5.4 kg / t of steel.

The material was added to the filling in one portion in the amount of 5.4 kg / t of steel after briefly blowing the final slag with oxygen for 10-15 seconds. Shotcrete and melting were performed at a temperature of 1630 ° C. As MBF, a composition was used that included a magnesian component containing periclase carbon in the form of scrap spent lining of melting and casting units and dolomite at a ratio of wt. %: 70 magnesia component containing periclase carbon, 30 dolomite, moreover, the fractional composition of the composition included, wt. %: 80 francs 0 <2 mm, fr. 2 <5 mm - the rest.

Example 3

Between shotcreting, a magnesian briquetted flux (MBF) of the following composition (wt.%) Was added to the scrap metal fed to the converter;

Magnesian component (including periclase carbon) 80 Dolomite fourteen Bunch 6,

the amount of MBF introduced into the final slag was 2.7 kg / t of steel.

The material was added to the filling in one portion in the amount of 8.0 kg / t of steel after briefly blowing the final slag with oxygen for 10-15 seconds. Shotcrete and melting were performed at a temperature of 1680 ° C. As MBF, a composition was used that included a magnesian component containing periclase carbon in the form of scrap spent lining of melting and casting units and dolomite at a ratio of wt. %: 85 magnesia component containing periclase carbon, 15 dolomite, moreover, the fractional composition of the composition included, wt. %: 70 francs 0 <2 mm, fr. 2 <5 mm - the rest.

In all three cases, when MBF was added to the converter on the final slag, a good solubility of the material was noted, within 2 minutes, in the slag melt, which contributes to the rapid thickening of the converter slag.

Gas-dynamic shotcreting of the converter lining by the final slag modified by the experimental flux is carried out in accordance with the requirements of the technological instruction of the plant.

To assess the change in the MgO content in the final slag using MBF, samples of the final slag were taken before and after the addition of flux. The results are presented in table 1.

The results of using MBF on the MgO content (%) in the slag are given in table 2.

After processing the final slag under MBF flux blowing, a uniform, strong and stable slag skull with a thickness of 60-80 mm was formed on the lining surface. The resistance of the experimental protective coating (visual assessment) was 3-5 heats.

The MBF was added to scrap metal in an amount of 2.7 kg / t of steel, which made it possible to obtain converter slag with a mass fraction of MgO of 4-5% and ensured the formation of a stable skull on the surface of the converter lining.

In general, the use of the proposed technical solutions during the operation of the converter made it possible to increase the duration of the campaign from 3000 to 5000-8000 heats with a significant reduction in the cost of the magnesia flux used.

Claims (2)

1. The method of forming a protective skull on the surface of the lining of the converter, including leaving the final slag in the converter, pre-blowing the final slag with oxygen and adding a magnesia briquetted flux to the converter, followed by neutral gas blowing of the modified flux of the final slag, characterized in that the lining is additionally made between shotcrete magnesia briquetted flux into scrap metal fed to the converter, at each stage flux is planted in an amount of 2.7-8.0 kg / t of steel, shotcreting and smelting are performed at a temperature of 1580-1680 ° C, and a composition comprising a magnesian component containing periclase-carbon in the form of a scrap of the spent melting lining is used as a magnesian briquetted flux and casting aggregates and dolomite at a ratio, wt.%: 55-85 magnesian component containing periclase carbon and 15-45 dolomite, and the fractional composition of the composition is formed, wt.%: fr. 0 <2 mm - 70-85, fr. 2 <5 mm - the rest. 2. Magnesian briquetted flux for forming a protective skull on the surface of the lining of the converter, containing the magnesian component and dolomite, characterized in that the scrap lining of the melting and casting units is used as the magnesian component in a ratio, wt.%: 55-85 magnesian component containing periclase carbon, and 15-45 dolomite, and the fractional composition of the composition is formed, wt.%: fr. 0 <2 mm - 70-85, fr. 2 <5 mm - the rest.