RU2405046C1 - Method of steel smelting, deoxidation, alloying and treatment - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed method comprises loading the burden made up of metal scrap and fluxes, forcing natural gas and air or oxygen from below to smelt the burden by gas-air or gas-oxygen flame, equalising temperature and chemical composition of melt volume, adding slag-forming constituents, shutting off feed of natural gas and air or oxygen, and blowing the melt by inert gases from below. In melting, ladle-furnace is inclined to drain primary slag. Natural has and air or oxygen are forced via cooled gas-air or gas-oxygen nozzle made up of tubes inserted one into another and arranged in furnace gate valve pouring cup hole and dusted by dry refractory sand. Natural gas is fed via furnace outer tube, while air or oxygen is fed via inner tube. Ladle-furnace is closed by cover with electrodes jointed to bubbling washer to smelt additionally the burden by electric arcs. After smelting, primary slag is drained from ladle-furnace, move the latter into initial position to feed therein fluxing additives to form secondary slag. Now, blowing by inert gases is performed from below along with boiling, deoxidising, alloying, deep sulphur removal, dephosphorisation, homogenisation of chemical composition and temperature of finished steel.

EFFECT: higher efficiency and quality, lower production costs.

2 dwg

Description

The invention relates to the field of metallurgy and is intended, in particular, for the smelting, deoxidation, alloying and processing of steel.

A known method of producing steel [1] by melting the charge (due to the heat of the electric arc between the electrodes and the metal) in an arc steelmaking furnace (DSP) and further refinement of the obtained liquid intermediate in the ladle furnace [1] with a capacity of about 15-40 MW [2 ]. Processing at the ladle-furnace installation begins with feeding the ladle on a steel truck under the cover with electrodes and connecting the ladle to the bottom inert gas purging system, which uses argon. Preliminary purging and homogenization of the melt are carried out, as a result of which the temperature is finally averaged over the working layer of the lining of the bucket and liquid metal, then a sample is taken and the temperature is measured, after which the metal heating is turned on. During heating, slag-forming materials are added, slag is induced, the chemical composition and temperature of the metal are averaged. After that, sampling is carried out. According to the results of the analysis, ferroalloys are added to adjust the chemical composition of the metal and slag-forming substances to adjust the slag composition. The temperature rises to the set level [1].

There is also known a method of processing metal by inert gas purging through the gate of a steel pouring ladle [3] and a method of steel smelting by blowing natural gas and air into the open-hearth furnace bath through a steel outlet [4].

As the closest analogue, the method of steel smelting was selected, which includes the complete melting of the charge in a separate steelmaking unit (for example, in chipboard), the release of molten metal from it into the casting ladle, its transportation to the processing section in the ladle furnace, covering the lid with electrodes, heating the melt electric arc and deoxidation-alloying, some equalization of temperature and chemical composition of steel, purging of metal with argon in order to complete chemical and temperature homogenization of the finished steel [1].

The disadvantages of the closest analogue are as follows:

1) When discharged from the furnace, a relatively cold bucket removes heat from the steel until the temperature evens out between the lining of the bucket and liquid metal. With this in mind, steel is overheated by liquidus at 90-100 ° C. But the more overheating, the higher the content of gases, non-metallic inclusions in steel and its quality is worse.

2) The release of metal is mainly carried out manually, which requires heavy physical labor.

3) When released on the gutter, secondary oxidation (deterioration) of the metal occurs and, as a consequence, additional consumption of expensive deoxidants is required.

4) A lot of time is spent on the above operations, which comparatively reduces productivity, and the temperature of the metal also drops significantly and its quality deteriorates. The release of metal from the chipboard requires 15-20 minutes, transportation of the bucket to the processing section in the ladle furnace takes 15 minutes, heating of the metal from above and its deoxidation-alloying takes 15-20 minutes and 15-20 minutes are required for purging with argon.

In the end, from the time the melt is released to its casting, all of the above operations lose time from 1 hour to 1 hour 15 minutes. In order for the metal to maintain the temperature for casting on the continuous casting machine (continuous casting machine), it is heated to 100-120 ° C above the liquidus from the most heated section — from the chipboard sub-water through the slag insulation material, 250-300 mm thick, through the shared slag surface - metal to the entire depth of the liquid metal bath, to the coldest part of the liquid bath - to the bottom and the hole for the release of steel. To do this, a lot of energy and time is spent.

All of the above technological operations, except for reducing the productivity of the main units (chipboard and ladle furnace), significantly (in proportion to overheating of the metal) increase the number of gas and non-metallic inclusions in steel, which reduces its quality.

Given the magnitude of the necessary overheating for casting at a continuous casting machine, steelmakers are forced to heat the metal to 1640-1660 ° C, depending on the grade of the steel being smelted, the casting method, etc. Additional heating of the liquid bath is carried out only in order to compensate for the temperature loss of steel during metal flow at the chute, during refining, while holding in the casting and tundish ladles, which, together with casting of steel, takes about 2 hours 20 minutes - 2 hours 30 minutes.

The task is to improve the closest analogue while achieving a technical result in relation to simplifying technology, increasing productivity, as well as significantly improving the quality of steel and reducing its cost.

The specified technical result is achieved by the fact that the entire process of steel smelting, starting from loading the charge, is carried out in a ladle furnace, into which through a special non-water-cooled gas-air (gas-oxygen) nozzle in the form of concentrically inserted tubes into one another, placed in the opening of the pouring glass of the bucket slide gate (the gap between the purge uncooled nozzle and the nozzle opening is filled with dry quartz sand), natural gas is supplied through the outer pipe and air or oxygen through the inner and one TERM charged with this charge special tub. Then the bucket is covered with a lid with electrodes connected to the gas purification, by applying voltage to the electrodes between them and the charge, electric arcs are ignited, the charge is heated and melted by them from above and a gas-air or gas-oxygen torch from below. During the melting process, primary slag is downloaded by tilting the ladle-furnace, and this steelmaking unit is returned to its original position. A new, secondary slag is introduced by adding fluxing materials (for example, lime, bauxite, etc.) to the ladle furnace from special metering hoppers [18] through a filling device [19]. After melting and refinement, instead of gas and air or oxygen, inert gas (for example, argon) or nitrogen and slag-forming reagents are automatically blown from the bottom with the same pipes, combining this process with boiling, deoxidation, alloying, deep desulfurization, dephosphorization of steel, its homogenization chemical composition and temperature. Upon reaching the desired composition and temperature of the finished steel, the electric voltage is turned off and the casting ladder gate is closed.

In the drawings (Fig.1, 2) shows a schematic illustration of devices for implementing the proposed method, which are indicated:

1. High alumina bucket bricks of different sections 200 mm, 150 mm and 100 mm.

2. Rectangular high-alumina bricks for the bottom of a steel-pouring ladle.

3. Magnesite glass.

4. A pipe in a pipe for supplying a gas-air or gas-oxygen mixture.

5. The vault assembly ladle steel.

6. Three electrodes for maintaining the electric arc of the bucket.

7. Fixed refractory plate of bucket gate.

8. The movable refractory plate of the bucket gate.

9. Trunnions of a steel pouring ladle.

10. Support legs of a steel pouring ladle.

11. Housing with a slide gate actuator.

12. Dosing hoppers.

13. The control panel of the metering hoppers.

14. The pipeline for supplying argon.

15. The melt above the gas-air (gas-oxygen) nozzle.

16. The melt under the electrodes.

17. The mixture is unmelted.

18. Special bunker dispensers.

19. Filling device.

Steel smelting and its refining are carried out as follows. In the ladle furnace 1 with a hearth 2 shown in the diagram, a pre-weighed and loaded charge 17 together with fluxes (lime, bauxite or others) begins to melt above the gas-air (gas-oxygen) nozzle 15 (a torch formed by blowing natural gas and air or oxygen through the passed in the pouring nozzle 3 of the bucket there is a special non-water-cooled nozzle 4) and under the electrodes 16 (an electric arc passed through a set of 5 electrodes 6). Through the central pipe of the nozzle 4, air or oxygen is supplied, and through the annular gap between the outer and inner pipes - natural gas - CH ₄ . Under the influence of the thermal effect of an electric arc and a powerful gas-air (gas-oxygen) torch, a 100-120-ton melt in about 40-45 minutes will be ready for deoxidation.

Temperature control is carried out continuously throughout the entire melting period from the occurrence of the liquid phase to the time of deoxidation. Deoxidizing agents and alloying agents (for example, silicomanganese — SiMn, ferromanganese — FeMn and ferrosilicon — FeSi) are fed from special metering hoppers 18 through the filling device 19. After deoxidation, the valves automatically switch off with the supply of air (or oxygen) and natural gas switched off, instead of which inert gas and slag-forming reagents are blown through the pipes into the ladle furnace 1, which in time is combined with the deoxidation-doping process.

Due to the injection of inert gas in the volume of the ladle furnace, flows from the bottom upward flow in the melt 15, accelerating the interaction of slag-forming reagents, deoxidizing and alloying chemical elements with it, equalization of the temperature and chemical composition of the metal, and transition of the products of deoxidation (oxides into the slag from the metal phase) all components), removal of endogenous, exogenous and other non-metallic inclusions. The more intense the purge, the larger the interface between the metal and slag phases and the greater the number of non-metallic inclusions assimilates, accumulates in the slag.

The injection of calcium, magnesium, aluminum, silicocalcium, calcium fluoride and other reagents cause a process of deep desulfurization and dephosphorization. After the purge is completed, the shutters 7 and 8 are closed, after which the full bucket is transported to the continuous casting machine.

As follows from the above, the achievement of a technical result can be achieved only inextricably interconnected set of all the essential features of the claimed method, reflected in the claims. Its distinctive features give reason to draw a conclusion about the novelty of this technical solution, and the totality of the claimed claims in connection with their non-obviousness is about its inventive step, which is also proved by their detailed description given above. Compliance with the criterion of "industrial applicability" of the proposed method is proved both by its specific implementation and by the absence in the claimed claims of any features that are practically not practicable on an industrial scale.

The advantages of the presented method, which is proved by the achievement of the technical result, are as follows:

1) There is no need for a separate steelmaking unit (for example, in chipboard with its own powerful transformers), which, in addition to reducing capital costs, saves electricity and expensive heat-insulating magnesite refractory materials.

2) Secondary oxidation of the metal at the outlet is eliminated and the amount of endogenous and exogenous inclusions in steel is reduced.

3) The charge is melted faster than in a chipboard, despite the less (3-4 times) power consumed by the ladle-furnace.

4) A powerful torch formed by natural gas and air or oxygen blown from below will melt the charge in about 40-45 minutes and heat the metal to the optimum temperature, since the ladle heats up during the melting process and there is no need to overheat the metal 90-100 ° C higher liquidus.

5) Since the solubility of gases in a metal is directly proportional to the temperature increase, steel will contain less gases (hydrogen, nitrogen, carbon dioxide, etc.) and non-metallic inclusions.

6) Significantly reduced the time of the in-line technological cycle of steelmaking, deoxidation and out-of-furnace treatment of steel: 15-20 minutes at the outlet, 15 minutes - for transportation of the bucket to the processing section in the ladle furnace, 15 minutes - for deoxidation, 15 minutes - for purification and refining . As a result, almost 1 hour is saved.

There is a saving from reducing large investments in the main unit of the processing line - chipboard and its heavy-duty transformers, reducing the consumption of electricity and refractory materials.

For the production of one million tons of steel, 4-5 working casting ladles will be required, into which, like in an electric furnace, scrap metal will be loaded with special tubs.

The positive effect of the presented method of smelting, deoxidation, alloying and processing of steel is that capital costs are reduced - the main unit for steelmaking - chipboard with a powerful transformer is removed from the technological cycle, and the melting of the charge, refinement-refining, deoxidation-alloying and heating of metal together with its chemical and temperature homogenization is carried out in a ladle furnace, i.e. the consumption of electricity and refractory materials, the temperature of smelting of this iron-carbon alloy and the time of its production are reduced.

Information sources

1. Technology and installation of a ladle-furnace of the Vorskla Steel metallurgical plant under construction http: //www.vorsklasteel. corn / technology / Technology. http: //www.vorsklasteel.corn/technology/ladle_furnace/installing a ladle furnace.

2. Units ladle furnace URALMASH http: //www.uralmash.m/ms/products/catalogue/aboutprodnct.htm? Prod = 65

3. The method of processing metal. USSR copyright certificate No. 1410541, priority 04/10/1987

4. The method of steelmaking. USSR copyright certificate No. 701151, priority 06/08/1978

Claims (1)

A method of steel smelting in a ladle furnace, including loading the charge in the form of scrap metal and fluxes, supplying natural gas and air or oxygen under pressure from the bottom with melting the charge with a gas-air or gas-oxygen torch, equalizing the temperature and chemical composition of the melt in volume, adding slag-forming reagents, terminating the supply of natural gas and air or oxygen and the subsequent blowing of the melt from below with inert gases, while in the process of melting by tilting the ladle-furnace, primary and, moreover, natural gas and air or oxygen are supplied through a non-water-cooled gas or air or gas nozzle made in the form of concentrically inserted pipes into one another, placed in the opening of the filling cup of the slide gate of the ladle-furnace with dusting around it with dry refractory sand, and natural gas is supplied through it the outer pipe, and air or oxygen - on the inside, while the ladle furnace is covered with a lid with electrodes attached to the gas treatment and the charge is further melted by electric arcs from above and After melting, primary slag is downloaded from the ladle furnace, the ladle furnace is returned to its original position, fluxing reagents are fed to it for secondary slag induction and inert gases are purged from below with slag-forming reagents, combining this process with boiling, deoxidation, alloying, deep desulfurization, dephosphorization, homogenization of the chemical composition and temperature of the finished steel.

Images