CN109047685B - Method for preparing steel ingot - Google Patents
Method for preparing steel ingot Download PDFInfo
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- CN109047685B CN109047685B CN201811041752.7A CN201811041752A CN109047685B CN 109047685 B CN109047685 B CN 109047685B CN 201811041752 A CN201811041752 A CN 201811041752A CN 109047685 B CN109047685 B CN 109047685B
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- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D7/00—Casting ingots, e.g. from ferrous metals
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Abstract
The invention discloses a method for preparing a steel ingot. Pouring metal into an ingot mould with a riser, adding slag to the surface of liquid metal, heating the metal by an electroslag heating process, passing granular loose furnace charge or the liquid metal melted by metal blank through a slag pool to perform casting-on a steel ingot in order to inhibit segregation and compensate looseness generated during the crystallization of the metal, and balancing the temperature and chemical components of a liquid core in the crystallization process of the steel ingot by stirring; the granular loose burden comprises cuttings, chips, dust or other small metal blocks; the chemical composition of the liquid metal melted by the granular loose burden or the metal blank is consistent or inconsistent with that of the steel ingot. The invention can avoid the loosening defect formed at the center part of the head of the finally solidified steel ingot; the segregation can be effectively inhibited, and the chemical components of the steel ingot can be balanced; the weight of the steel ingot feeder head required to be cut off is reduced, and the yield of the steel ingot is improved.
Description
Technical Field
The invention relates to a method for preparing a steel ingot, which comprises a method for improving the quality of the steel ingot and belongs to the technical field of metallurgy.
Background
In the production of ingots using ingot moulds, the liquid metal is poured into the ingot mould and solidified in the ingot mould, it being necessary to ensure that the liquid metal above flows unimpededly into the loose layers below. By doing so, the formation of loose defects and segregation in the steel ingot can be prevented, the physical and chemical uniformity of the steel ingot can be improved, the weight of a steel ingot riser needing to be cut off can be reduced, and the yield of the steel ingot can be improved. For this purpose, the metal in the ingot cap must be kept liquid. In order to keep the metal in the riser in a liquid state for a long time, supplementary heating is required.
A common method of heating the metals in the riser is to use a mixture that gives off heat. However, the use of mixtures for exothermic or other modern heating of metals has the disadvantage that they burn for a short time and heat poorly. In addition, the metal may be contaminated with components of the mixture or products of the oxidation reaction.
The more effective method is to convert the electric energy into heat energy in the riser to supplement and heat the metal. Arc heating is a widely used method of melting metals in the metallurgical industry. However, this method cannot be used for the production of steel ingots, because of the excessive energy consumption caused by radiation, local overheating of metal can also occur in the arc action zone, and the loss of steel ingot alloy elements is increased.
Electroslag heating, in which heating of the metal is achieved by heat release from the slag bath, avoids the above-mentioned disadvantages. In addition, the slag is melted and heated by an electric current that is introduced through a non-consumable electrode located in the slag. When the method is adopted for heating, the heat is uniformly distributed along the surface of the metal, and the oxidation and heat loss of individual elements cannot be generated. In addition, the active slag charge can supplement refined metal and remove undesirable impurities and nonmetallic inclusions.
The known methods for heating the riser of a steel ingot by electroslag include: 1. authors g.s.tyagun-Belous, d.a.dudko, article "electroslag heating of ingot and casting head of special-shaped casting using non-consumable electrodes", publication "automatic welding", 1958, No. 10. P36-43; 2. authors s.p.bakumenko, b.b.gulyaev, e.v.verkhovtsev, article "reduction of scrap rate of steel ingots", publication "metallurgy", 1967, P220; 3. authors h.f. bastrakov, n. a. Tulin, b.p. nemchenko et al, article "electroslag casting of steel", publication "metallurgy", 1978 "-P56. The electroslag heating method can reduce the volume of the riser and improve the quality of the head part and the axle center part of the steel ingot. This method, however, does not fully compensate for the metal shrinkage that occurs in the central portion of the ingot when the metal solidifies. The volume shrinkage of the steel ingot can reach 4-7% according to different steel ingot components. As a result, various shrinkage defects are still formed in the head and core portions of the ingot which solidify last: shrinkage, porosity and hairline.
Known methods for heating a riser by using slag and a consumable electrode during the preparation of a steel ingot and melting the consumable electrode in the slag and exerting a conductive effect include: 1. authors Tyagun-Belous g.s., Dudko d.a., article "electroslag casting of flat ingots", publication "automated welding", 1958, No. 11, P66-70; 2. patent "a method for producing a steel ingot", U.S. Pat. No. 4265295 a. According to this patent, the metal melted by the electrodes is used to cast the ingot, compensating for the loose parts produced during the crystallization of the metal. However, when this method is used, there is a hard constraint relationship between the slag bath temperature and the electrode melting rate and amount. The slag pool can not be kept at high temperature for a long time, so that the liquid state of metal in the riser can be kept for a long time, and the lower or adjustable post-pouring speed adaptive to the compensation porosity can not be guaranteed.
Disclosure of Invention
The object of the present invention is to provide a method for producing a steel ingot in order to prevent the above-mentioned drawbacks and overcome the above-mentioned difficulties, to suppress segregation and to effectively compensate for the loosening defect occurring in the production of steel ingots.
The method for realizing the purpose comprises the following steps: pouring metal into an ingot mould with a riser, adding slag to the surface of liquid metal, heating the metal by an electroslag heating process, in order to inhibit segregation and compensate looseness generated during metal crystallization, passing granular loose furnace charge or liquid metal melted by metal blank through a slag pool to perform casting-on a steel ingot, and balancing the temperature and chemical components of a liquid core in the steel ingot crystallization process by stirring;
the granular loose burden comprises cuttings, chips, dust or other small metal blocks;
the chemical components of the granular loose burden or the metal blank are consistent or inconsistent with the steel ingot.
By adopting the method, any post-casting speed can be ensured by changing the amount of the metal added into the slag pool, so that the post-casting speed is consistent with the contraction speed of the liquid metal in the ingot mould. If necessary, the alloy element content of the solidifying ingot is adjusted by using metal with chemical composition different from that of the original cast metal, and the chemical composition of the metal is balanced along the longitudinal direction and the transverse direction of the ingot, so that the segregation process generated when the metal is converted from liquid state to solid state is inhibited.
In order for the metals that are fed through the slag bath during heating of the electroslag to be most effective in recasting the ingot and to suppress segregation, it is necessary to ensure that these metals reach all the crystallographic planes and balance the chemical composition of the liquid metal there. However, since the temperature and chemical composition in the ingot are not uniform, a layer of slowing down the flow of molten metal or even semi-solidifying occurs in the gradually solidified liquid core, particularly in the part close to the riser, and this hinders the replenishment of the molten metal to the lower layer and the balance of chemical composition. Therefore, the invention also takes measures to stir the original casting metal in the ingot mould and the metal which passes through the slag bath for casting again at the same time of casting again so as to promote the homogenization of the temperature and the chemical composition in the solidifying liquid core.
In the method of the invention, the liquid core of the steel ingot is stirred by various methods: immersing the tuyere into a metal molten pool, stirring by a mechanical arm, and electrifying the liquid metal or applying external magnetic field influence to the liquid metal.
In the method according to the invention, the heating of the metal surface is carried out in a riser with a refractory lining, a metal water-cooled riser or a combined riser with a refractory lining on the underside and a metal water-cooled riser on the upper side.
In the method, a non-consumable metal electrode, a graphite electrode or a consumable metal electrode is used for heating metal in a steel ingot feeder head; the choice of the type of electrode depends on the conditions required for the production of the ingot, the ingot weight and the chemical composition, and the electrodes are interchangeable during the slag heating process.
In the method of the invention, when the slag is used for heating the metal, one or more of the following electric systems are used for heating the metal:
-no change in heating power throughout the heating cycle;
-the heating power is periodically varied;
heating is staggered with pauses.
In the method, when inert gas is used for blowing and stirring the liquid core of the steel ingot, the depth of the air nozzle which is immersed into the metal melt is between 0.1 and 0.9 of the non-solidified part of the steel ingot. Too deep of immersion can adversely affect the crystalline surface because too shallow of an immersion does not stir the entire liquid core.
In the method, the tuyere is stably lifted in the process of continuously blowing the metal melt along with the growth of crystals at the lower part of the liquid core.
In the method of the invention, the metal melt is periodically subjected to blowing at different depths of immersion of the tuyere into the metal melt.
The invention has the following advantages:
1. the loosening defect is avoided from being formed at the center of the head of the finally solidified steel ingot;
2. effectively inhibiting segregation and balancing chemical components of steel ingots;
3. the weight of the steel ingot feeder head required to be cut off is reduced, and the yield of the steel ingot is improved.
Drawings
FIG. 1 is a schematic view showing the structure of electroslag heating and post-casting in the present invention, (a) post-casting with liquid metal, (b) post-casting with metal billet, and (c) post-casting with granular loose burden.
The respective symbols in fig. 1 mean:
1, a base; 2, ingot molding; 3, feeding a riser; 4, slag melting; 5 a non-consumable electrode; 6 pouring liquid metal; 7 molten metal bath; 8 a solid metal; 9 a metal blank; 10 granular loose charge.
FIG. 2 is a view showing a molten metal bath stirred by blowing an inert gas through a tuyere in the present invention.
Detailed Description
The experimental procedures used in the following examples are conventional unless otherwise specified.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
Example 1
22t of liquid metal, under the designation of 90X phi, are poured into a hexahedral ingot mould with an average diameter of 1300mm and a height of 2200mm and a water-cooled riser with a height of 400 mm. The cast metal reached the height of the riser 100 mm.
Immediately after the metal is poured, a slag pool is built by using a non-consumable graphite electrode and fluoride-oxide slag materials which are electrified, and the height of the slag pool is 200 mm. After the slag is completely melted and the temperature reaches 1600-1650 ℃, a metal blank with the diameter of 200mm is put into a slag pool, and the chemical components of the metal blank and the prepared steel ingot are the same. Two hours first, the billet was dosed at 33mm/min, then the feed rate was gradually decreased, seven hours after casting to 1mm/min, at which point the metal was almost completely crystallized. The metal consumed by the recasting is about 2.5 t. During this period the heating power remained stable, followed by a gradual decrease in power for one hour until the metal heating was completely stopped. And periodically stirring the liquid core of the steel ingot by blowing inert gas in the metal heating process. The tuyere is immersed in half of the depth of the molten metal bath and gradually lifted. The time of each air blowing is 3 to 5min, and the gas flow is 50 to 500dm 3/min. The total weight of the prepared steel ingot is 24.5 t. The weight of the cut-off risers is about 1.5t, or about 6% of the total weight of the ingot. When the traditional process is adopted to produce similar steel ingots, the weight of the cut-off feeder is generally not less than 15 percent of the total weight of the steel ingots. The ultrasonic flaw detection method is used for detecting the cold rolling roller prepared from the steel ingot, and the defect that the equivalent diameter is more than 1mm is not found, so that the physical and chemical uniformity of the steel ingot is proved to be very high.
Example 2
When 25 KHz 2M phi steel is used for producing steel ingot, the average diameter of ingot mould is 2200mm, its height is 3600mm, and the height of riser with refractory lining on the ingot mould is 1200mm, and 116t of liquid metal is poured into the ingot mould and riser. The poured metal reaches a height of 800mm of the riser, the weight of which is about 23t or about 20% of the total weight of the ingot.
A graphite electrode with the diameter of 400mm is used for manufacturing a slag pool with the height of 250mm, then the graphite electrode is replaced by a metal consumable electrode with the diameter of 300mm, the metal electrode is melted in the slag pool, and the steel ingot is subjected to casting again. The chemical composition of the metal electrode roughly corresponds to that of the steel ingot to be produced, except for the carbon content. The carbon content of the consumable electrode is 0.22-0.23% when the re-pouring is started, and the carbon content is 0.17-0.18% when the re-pouring is finished. In order to adjust the recasting rate, the metal consumable electrode was changed to a graphite electrode every 0.5 to 1.5 hours. The mass velocity of the fluid for the recast is close to that of the fluid for the metal shrinkage. The metal consumed by the recasting is 5.5 t. Electroslag heating lasted approximately 16 hours. In order to ensure that the slag temperature is 1600 ℃, the average power of electroslag heating is 2500 kW. The electroslag heating power is changed in the steel ingot forming process, the power is larger when the heating force is large, and the power is smaller when the heating force is small or the heating is suspended.
And an air nozzle immersed in metal is periodically used for blowing inert gas into the metal molten pool to stir the molten pool, so that the temperature and chemical components of the liquid core of the steel ingot are ensured to be uniform. When the depth of the metal molten pool is 3000mm, the immersion depth of the air nozzle is 2700mm or 90% of the liquid core depth of the steel ingot. When the depth of the molten metal pool is reduced, the immersion depth of the tuyere is reduced, but is not less than 10% of the depth of the unsolidified part of the steel ingot.
The weight of the prepared steel ingot is 121.5 t. The weight of the cut-off feeder is 11.5t or less than 10% of the total weight of the ingot. The carbon content of the head of the steel ingot is not more than 0.27 percent, and the carbon element is hardly segregated. The generator rotor shaft prepared from the steel ingot is detected, and all data including mechanical properties meet the requirements of technical conditions of the product.
Example 3
A flat ingot of 40-42t steel with weight, 1800 х 1000mm cross-section and 2800mm height is cast with 10 Г 2M phi steel, a combined riser is used, a 200mm height riser with lining is arranged below the combined riser, a 500mm height water-cooled riser is arranged above the combined riser, the cast metal reaches 150mm height of the riser with lining, about 37t, then a non-consumable metal electrode is placed to melt slag, the height of a slag pool is 220mm, after the slag reaches a specified temperature, a graphite electrode is replaced by a metal non-consumable electrode, chips of 10 Г 2M phi steel are added into the slag pool to carry out casting on the ingot, the weight is about 4t and is twice of the weight necessary for feeding, an air nozzle which is immersed in the metal is used for blowing inert gas to stir the liquid core of the ingot, air blowing is continuously carried out, the air nozzle which is used for blowing is gradually lifted along with the solidification of the metal, the qualified rate of products can be close to 100%, the defect of the rolled ingot is detected by using the non-consumable electrode and the ultrasonic wave before rolling the ingot.
Claims (3)
1. A method for preparing steel ingot, including pouring the metal into the ingot mould with feeder head, add the slag to the surface of liquid metal, use the electroslag heating process to heat the metal, characterized by that: in order to inhibit segregation and compensate loosening generated during metal crystallization, granular loose furnace burden or liquid metal melted by metal blank passes through a slag pool to perform casting-on a steel ingot, and the temperature and chemical components of a liquid core in the steel ingot crystallization process are balanced through stirring;
the granular loose charge comprises cuttings or other small pieces of metal;
the chemical components of the granular loose furnace charge or the metal blank are consistent or inconsistent with those of the prepared steel ingot;
the method for stirring the liquid core of the steel ingot is to blow air by using an air nozzle immersed in the molten metal;
when the liquid core of the steel ingot is stirred by the blowing method, the depth of the air nozzle immersed into the metal melt is 0.1-0.9 of the depth of the unset part of the steel ingot;
the tuyere is stably lifted in the process of continuously blowing the metal melt along with the growth of crystals at the lower part of the liquid core;
periodically blowing the metal melt at different depths of the metal melt immersed in the air nozzle;
the gas for blowing is inert gas;
using a non-consumable metal electrode, a graphite electrode or a consumable metal electrode in the process of heating metal by using slag; the choice of the type of electrode depends on the conditions required for the production of the ingot, the ingot weight and the chemical composition, and the electrodes are interchangeable during the slag heating process.
2. A method for producing a steel ingot according to claim 1, characterized in that: the heating process of the metal surface is carried out in a riser with a refractory material furnace lining, a metal water-cooled riser or a combined riser with the refractory material furnace lining below and the metal water-cooled riser above.
3. A method for producing a steel ingot according to claim 1, characterized in that: when the slag charge is used for heating metal, one or more of the following electricity consumption systems are adopted:
-no change in heating power throughout the heating cycle;
-the heating power is periodically varied;
heating is staggered with pauses.
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| CN111774550B (en) * | 2020-07-30 | 2021-11-23 | 安徽工业大学 | Electroslag feeding device for improving crystallization quality of large steel ingot |
| CN116117083B (en) * | 2023-01-06 | 2024-08-23 | 东北大学 | Solidification control device and method for large-scale die-cast steel ingot |
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| AT342796B (en) * | 1975-11-17 | 1978-04-25 | Ver Edelstahlwerke Ag | METHOD FOR PRODUCING BLOCKS |
| CN101480715A (en) * | 2009-01-21 | 2009-07-15 | 东北大学 | Electroslag smelting casting device with additional electromagnetic stirring and method |
| CN103014366B (en) * | 2011-09-20 | 2014-05-14 | 东北大学 | Large-scale electroslag remelting steel ingot enhancement cooling apparatus and method thereof |
| CN102806322B (en) * | 2012-08-20 | 2014-04-30 | 东北大学 | Device and method for preparing large-size homogeneous steel ingot by stirring with self-consuming stirrer |
| CN103406520B (en) * | 2013-08-27 | 2015-06-03 | 东北大学 | Device and method for producing large homogeneous electro-slag re-melting steel ingots added with consumable stirrer |
| CN104525919B (en) * | 2014-12-09 | 2016-05-18 | 抚顺特殊钢股份有限公司 | A kind of manufacture method of supercritical turbine Blade Steel electroslag remelting steel ingot |
| CN104439201B (en) * | 2015-01-05 | 2016-05-25 | 东北大学 | A kind of large-scale steel ingot electroslag heat-sealing ejection device and method that is uniformly distributed thermal source |
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Inventor after: Shabovalov Victor Inventor after: Bektakilov Falit Inventor after: Gnakushenko Alexander Inventor after: Xu Xiaohai Inventor after: Wang Yuan Inventor before: Shabovalov Victor Inventor before: Bektakilov Falit Inventor before: Gnakushenko Alexander |
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