CN113403449B - Production method for wide steel strip iron-chromium-aluminum continuous casting slab rare earth alloying - Google Patents
Production method for wide steel strip iron-chromium-aluminum continuous casting slab rare earth alloying Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
- B22D1/002—Treatment with gases
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/111—Treating the molten metal by using protecting powders
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/116—Refining the metal
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
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Abstract
The invention discloses a method for producing wide steel strip iron-chromium-aluminum continuous casting slab by rare earth alloying, which comprises the following steps: (1) preparing rare earth filaments; (2) the iron-chromium-aluminum molten steel is sequentially treated by a K-OBM-S furnace, a VOD furnace and an LF furnace; (3) conveying the molten steel treated in the step (2) to a continuous casting machine by virtue of a sealed and protected tundish, and pouring the molten steel into a crystallizer; (4) and feeding rare earth wires by a single-machine double-flow method to prepare a continuous casting plate blank. The invention realizes the rare earth alloying of the iron-chromium-aluminum continuous casting slab by reducing the oxygen-sulfur content of the molten steel, adopting measures of protective pouring, selecting proper wire feeding position and speed, optimizing the components of the protective slag and the like.
Description
Technical Field
The invention relates to the technical field of alloy smelting, in particular to a production method for rare earth alloying of a wide steel strip iron-chromium-aluminum continuous casting plate blank.
Background
The iron-chromium-aluminum alloy belongs to an electric heating engineering material, and the contents of Cr and Al elements respectively reach about 13-27 Wt.% and 3-7 Wt.%. The iron-chromium-aluminum strip has excellent high-temperature resistance and higher resistivity, and is widely applied to the fields of household appliances, industrial furnaces, motor vehicle tail gas purification carriers and the like. At present, a three-way catalyst carrier for purifying tail gas of a motor vehicle is mainly made of two materials, and firstly, the three-way catalyst carrier is made of a ceramic material, and the ceramic material has the main defects that the ceramic material is difficult to assemble, is easy to vibrate and is fragile in operation, and cannot be used for manufacturing a carrier with the size larger than 500 mm; secondly, the high-temperature resistant electric heating alloy, namely the iron-chromium-aluminum fine belt with the thickness of 0.04-0.08mm, is adopted, so that the long service life can be realized, and the assembly is easy. With the improvement of global environmental protection requirements in future, the substitution of metal for ceramic carriers has become a necessary trend, and the development prospect is wide.
A large number of experimental observations show that the addition of a small amount of rare earth elements such as Y, La, Ce, Hf and the like can significantly improve the high-temperature oxidation resistance of the metal and greatly improve the adhesion of an oxide layer and a substrate. By adding rare earth elements, the service life of the iron-chromium-aluminum metal carrier is prolonged. The addition of 0.02-0.10 Wt.% of rare earth elements to the iron-chromium-aluminum strip can significantly improve the oxidation resistance of the material at a high-temperature stage.
At present, smelting, forging and cogging are basically carried out at home and abroad by adopting a small-scale smelting mode of induction furnace and electroslag remelting. The process flow is simple in equipment and convenient to operate, has certain advantages in rare earth alloying, but is low in production efficiency, low in yield and large in component property fluctuation, and large-scale production cannot be carried out.
The iron-chromium-aluminum product produced in large scale by the process flow of VOD smelting and slab continuous casting has high yield, but has larger process difficulty in rare earth alloying. The main difficulties are as follows: the rare earth elements have low ignition point, are easy to burn at high temperature, are seriously burnt and cause unstable yield; the chemical activity of the rare earth elements is strong, the dissolved oxygen and the impurities in the molten steel must be reduced to a lower level, and the whole-process protective pouring is adopted to avoid influencing the microalloying effect; the rare earth elements are easy to interact with refractory materials such as ladle slag, water gaps, casting powder and the like, so that the problems of nodulation, water gap blockage, caking, casting break, inclusion on the surface of a casting blank and the like occur in the production process of a continuous casting slab, and the iron-chromium-aluminum alloy slab cannot be normally continuously cast. The addition of Al and rare earth elements deteriorates the surface quality of the cast slab, but the product is mainly used as a fine strip at the end, and inclusions must be strictly controlled.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for producing the wide steel strip iron-chromium-aluminum continuous casting slab by rare earth alloying, which solves the problems of low rare earth yield, continuous casting water blocking, transverse cracking of the casting blank and the like, so that the stable addition of 0.02-0.10 Wt.% of rare earth elements on the iron-chromium-aluminum continuous casting slab with the width of 1000-1300mm and the weight of more than 10 tons becomes possible, and the heat-resisting service life of the product is obviously prolonged.
The technical scheme of the invention is as follows:
a production method for rare earth alloying of a wide steel strip iron-chromium-aluminum continuous casting slab comprises the following steps:
(1) preparing rare earth filaments;
(2) the iron-chromium-aluminum molten steel is sequentially treated by a K-OBM-S furnace, a VOD furnace and an LF furnace;
(3) conveying the molten steel treated in the step (2) to a continuous casting machine by virtue of a sealed and protected tundish, and pouring the molten steel into a crystallizer;
(4) and feeding rare earth wires by a single-machine double-flow method to prepare a continuous casting plate blank.
Optionally, in the step (1), the diameter of the rare earth wire is 2.5-3.5 mm.
Optionally, in the step (1), the rare earth element adopted by the rare earth wire is any one or more of lanthanum, cerium and yttrium; the rare earth wire comprises more than or equal to 97 Wt.% of rare earth elements and the balance of iron and inevitable impurities.
Optionally, in the step (2), more than 85% of slag is removed after the converter is turned on, and the oxygen content and the sulfur content in the processed molten steel reach below 0.0012 Wt.% and 0.0020 Wt.%.
Optionally, in the step (3), the tundish is started to be poured after argon blowing is carried out for 6-8min at the temperature of 1525-1560 ℃.
Optionally, in the step (3), the mold flux of the crystallizer comprises the following components in percentage by weight: c: 6.0-8.0%, MgO: 0.5 to 2.0% of Al 2 O 3 ：1.2～3.0％、B 2 O 3 ：2.0～4.0％、Li 2 O：3.5～6.5％、F-：4.0～5.5％、Na 2 O: 5.5-8.0%, BaO: 5.0-7.0%; the balance being CaO and SiO 2 ；
Preferably, the basicity is combined (CaO + BaO)/SiO 2 Is 0.85-1.00.
Optionally, in the step (4), the drawing speed of the continuous casting slab is 0.40-0.80 m/min.
Optionally, in the step (4), the feeding lines of the rare earth wires are located at symmetrical positions on two sides of the water gap, the wire feeding point is located at the middle position of the thickness of the continuous casting slab, and the distance between the wire feeding point and the water immersion gap is 0.20-0.26 times of the width of the slab.
Alternatively, in the step (4), the wire feeding speed of the rare earth wire is determined according to the following formula:
wherein, V s : wire feeding speed, D: diameter of rare earth wire, rho s : density of rare earth filaments, V 1 : withdrawal speed, W: casting blank width, T: thickness of casting blank, rho g : density of casting blank, omega RE : target rare earth content, omega, in steel 0 : rare earth content in the rare earth filament, Y: and (4) obtaining the rare earth.
Optionally, in the step (4), the prepared continuous casting slab has a thickness of 180-230mm, a width of 1000-1300mm and a weight of more than 10 tons.
Compared with the prior art, the production method for the rare earth alloying of the wide steel strip iron-chromium-aluminum continuous casting slab realizes the rare earth alloying of the iron-chromium-aluminum continuous casting slab by reducing the oxygen and sulfur content of molten steel, adopting measures of protective pouring, selecting proper wire feeding position and speed, optimizing the components of protective slag and the like. The following beneficial effects are obtained:
(1) the yield of rare earth is greatly improved to over 85 percent; the rare earth content in the iron-chromium-aluminum plate blank is stabilized in the range of 0.02-0.10 Wt.%, and the rare earth content is uniformly distributed.
(2) Avoids the problem of nodulation of pouring water gaps of a large ladle and a middle ladle, has less slag strips, and is smooth in continuous casting without obstruction.
(3) The rare earth alloying of the iron-chromium-aluminum continuous casting slab with the thickness of 180-230mm, the width of 1000-1300mm and the weight of more than 10 tons is realized.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. In the drawings:
FIG. 1 is a cross-sectional view, W for width and T for thickness, showing a schematic illustration of a double strand feeding of rare earth wires in an iron chromium aluminum slab continuous casting crystallizer. The yarn feeding points are symmetrically fed at two sides of the soaking port, are located in the middle of the thickness of the plate blank and are 0.20-0.26 time as long as the soaking port.
Detailed Description
The present invention will be described in detail with reference to the following embodiments in order to fully understand the objects, features and effects of the invention. The process of the present invention employs conventional methods or apparatus in the art, except as described below. The following noun terms have meanings commonly understood by those skilled in the art unless otherwise specified.
Aiming at the problems of low rare earth yield, nozzle nodulation, covering slag denaturation and the like in the rare earth alloying process of the iron-chromium-aluminum alloy continuous casting plate blank at present, the inventor of the invention improves the production method through research, and realizes the rare earth alloying of the iron-chromium-aluminum alloy continuous casting plate blank by reducing the oxygen and sulfur content of molten steel, adopting measures of protective pouring, selecting proper crystallizer wire feeding position and speed, optimizing the components of the covering slag and the like.
Because rare earth elements have extremely strong activity and are easy to oxidize, the content of oxygen and sulfur elements in molten steel needs to be reduced, furnace slag is removed, and protective pouring is adopted in the process. Rare earth elements are added in the early stage of smelting, rare earth is easy to react, denature and consume in the treatment process, the yield of rare earth is low, the risk of water gap nodulation exists in the pouring process, and the problems can be avoided by feeding rare earth wires in a crystallizer. But considering the uniformity of the rare earth components of the slab, the requirement of the crystallizer wire feeding process on the matching accuracy of the wire feeding position, the wire feeding speed, the casting blank drawing speed and the like is high. Finally, the rare earth wires can cause the performance of the casting powder to change when passing through the casting powder of the crystallizer, so that the lubrication of the casting blank by the casting powder is poor, the defects of longitudinal cracks and the like on the surface of the casting blank are caused, and steel leakage accidents occur in serious cases. This problem can be avoided by the improvement of the mold flux.
Based on the above thought, the invention provides a production method for the rare earth alloying of a wide steel strip iron-chromium-aluminum continuous casting plate blank. The method of the invention is applicable to any type of wide steel strip iron-chromium-aluminium steel grade, and is particularly suitable for producing steel grades having the designations 1Cr13Al4, 0Cr15Al5, 0Cr18Al4 or 0Cr21Al 6. The method is mainly suitable for the wide steel strip iron-chromium-aluminum continuous casting plate blank, for example, the thickness of the continuous casting plate blank is 180-230mm, the width is 1000-1300mm, and the weight is more than 10 tons.
In a preferred embodiment, the method for producing the wide steel strip iron-chromium-aluminum continuous casting slab through rare earth alloying comprises the following steps:
(1) preparing rare earth filaments
Because the temperature of molten steel in the crystallizer is lower and is about to solidify, in order to improve the rare earth adding efficiency and reduce the pollution of other elements, the non-coated rare earth wire with higher purity is prepared, so that the rare earth wire can be rapidly melted, and the rare earth in the plate blank is more uniformly distributed. Based on the above objectives, the rare earth element is required to be any one or more of lanthanum, cerium and yttrium, and the content of the rare earth element is more than or equal to 97% by mass percent.
The rare earth wire diameter is specified to be 2.5-3.5mm for the following reasons: if the rare earth wires are too thin, bending stranded wires are easy to occur, and molten steel is difficult to feed; if the rare earth wires are too thick, the rare earth wires are too high in strength and are not easy to bend.
In addition, in the field actual operation, the quality of the rare earth wire is also important, otherwise, the smooth running of the wire feeding is influenced, so that the rare earth wire is required to have uniform diameter, be straight and not bent, be firmly welded with a joint and be not broken in use.
There is no particular requirement for the source of the rare earth filaments, so long as the above requirements are met.
(2) The iron-chromium-aluminum molten steel is treated by a K-OBM-S furnace, a VOD furnace and an LF furnace in sequence.
The rare earth is an active element with low melting point, and is easy to react with oxygen and sulfur in the molten steel rapidly, even to reduce steel slag, so the iron-chromium-aluminum molten steel must be processed through the process of K-OBM-S → VOD → LF, more than 85% of slag is guaranteed to be completely removed after the converter is fired, and the oxygen content is less than 0.0012% and the sulfur content is less than 0.0020% in percentage by mass.
The specific conditions of the K-OBM-S furnace, the VOD furnace and the LF furnace can be reasonably selected by a person skilled in the art according to actual production needs.
(3) Molten steel is conveyed to a continuous casting machine by a tundish protected by sealing and is poured into a crystallizer.
Before pouring, the pouring basket is sealed, and pouring is carried out after the pouring basket is blown with argon for 6-8 min.
Because the rare earth elements are more active, protective casting is adopted in the early treatment to control the oxygen content of the molten steel. In order to avoid crack defects, the temperature of the tundish is strictly controlled at 1525-.
After casting, adding special protective slag in the crystallizer, and blowing argon for protection.
Rare earth wires are easy to react with components of the casting powder to precipitate rare earth oxides, and the performance of the casting powder can be changed, so that slag strips appear in a crystallizer, and the smooth running of continuous casting is influenced. Aiming at the phenomenon, the special protective slag has the following characteristics: 1) has strong capacity of absorbing rare earth oxides, reduces residual rare earth inclusions in steel, and does not have obvious change in the performance of the casting powder. 2) In selecting the raw material for the mold flux, the use of components that are easily reactive with other components of the mold flux should be minimized. 3) The lower solidification temperature and crystallization rate can improve the lubricating and heat transfer performance of the casting powder, and the slag has glass properties.
Based on the above thought, the inventor develops the special covering slag aiming at the rare earth-containing iron, chromium and aluminum through research, obviously reduces slag strips and ensures the smooth casting. The special covering slag for the continuous casting crystallizer comprises the following components in percentage by weight: c: 6.0-8.0%, MgO: 0.5-2.0% of Al 2 O 3 ：1.2-3.0％、B 2 O 3 ：2.0-4.0％、Li 2 O：3.5-6.5％、F-：4.0-5.5％、Na 2 O: 5.5-8.0%, BaO: 5.0 to 7.0 percent; the balance being CaO and SiO 2 Comprehensive alkalinity (CaO + BaO)/SiO 2 Is 0.85-1.00.
(4) Feeding rare earth filaments at a certain filament feeding speed by adopting a single machine double-flow method.
When the wire is fed by the crystallizer, in order to fully melt the rare earth wire and stabilize the performance of the crystallizer covering slag, the pulling speed of the casting blank plate is not too fast and is stabilized between 0.40 and 0.80m/min, and the fluctuation value of the pulling speed is controlled to be +/-0.02 m/min.
Considering the homogenization of rare earth elements in the casting blank, the casting blank is required to be fed at equal speed at both sides of a water gap. And moreover, through flow field calculation, the wire feeding point is located in the middle position of the thickness of the casting blank and is 0.20-0.26 time as wide as the immersion water inlet, and the dynamic conditions for homogenizing and rapidly transferring the rare earth elements are achieved.
For example, FIG. 1 shows a schematic illustration of a double strand feeding of rare earth wires in an iron chromium aluminum slab continuous casting crystallizer. The wire feeding points are symmetrically fed at two sides of the water immersion port, are positioned in the middle of the thickness of the casting blank and are 0.20-0.26 time as long as the water immersion port.
The wire feeding speed should be calculated according to the target rare earth content of the steel grade for on-site control. The feed rate is given by the following formula:
wherein, V s : wire feeding speed, D: diameter of rare earth wire, rho s : density of rare earth filaments, V 1 : withdrawal speed, W: casting blank width, T: thickness of casting blank, rho g : density of casting blank, omega RE : target rare earth content, omega, in steel 0 : rare earth content in the rare earth filament, Y: and (4) obtaining the rare earth.
Examples
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
Example 1
Taking the mark 1Cr13Al4 as an example, the chemical components by mass percent are as follows: c: 0.015%, Si: 0.22%, Mn: 0.10%, P: 0.015%, S: 0.0015%, Cr: 13.9%, Al: 4.6%, Ti: 0.23%, N: 0.003% and the balance of Fe and other inevitable impurities. The specification of the iron-chromium-aluminum alloy continuous casting slab is as follows: the thickness is 200mm, the width is 1220mm, the weight is 16.5 tons, and the density of the casting blank is 7.4g/cm 3 。
The production method of the iron-chromium-aluminum continuous casting slab crystallizer wire feeding rare earth alloying in the embodiment 1 comprises the following steps:
(1) preparing rare earth wires with the diameter of 2.5mm, wherein the total percentage of lanthanum and cerium is 97.5 Wt.%, and the density of the rare earth wires is 6.3g/cm 3 The rare earth wires have uniform diameter.
(2) The iron-chromium-aluminum molten steel is subjected to K-OBM-S → VOD → LF treatment, more than 86% of slag is removed after the converter is heated, and the oxygen content and the sulfur content are respectively 0.0010 Wt.% and 0.0015 Wt.%.
(3) Before pouring, sealing protection of the tundish is well performed, pouring is performed after the tundish is blown with argon for 6min, and the temperature of the tundish is controlled to be 1525-.
After casting, adding special protective slag in the crystallizer, and blowing argon for protection. The continuous casting crystallizer casting powder comprises the following components in percentage by weight: c: 7.6%, MgO: 1.73% of Al 2 O 3 ：2.74％、B 2 O 3 ：3.64％、Li 2 O：5.7％、F-：4.8％、Na 2 O: 6.7%, BaO: 6.6 percent and the comprehensive alkalinity is 0.88.
(4) Feeding rare earth filaments at a certain filament feeding speed by adopting a single machine double-flow method. The drawing speed of the continuously cast slab is V l 0.70m/min, and the pulling speed fluctuation value is controlled to be +/-0.015 m/min. The wire feeding points are positioned at the symmetrical positions of the two sides of the water gap, and the wire feeding points are 100mm away from the wide surface and 260mm away from the water gap. The target rare earth content is 0.03 Wt.%, the yield is 85%, and the wire feeding speed is calculated to be 7.4m/min according to a formula.
By using the production method for rare earth alloying of the feeding wire of the iron-chromium-aluminum continuous casting slab crystallizer in the embodiment 1, almost no slag bar exists in the process of producing the 1Cr13Al4 continuous casting slab with the thickness of 200mm and the width of 1220mm, and the continuous casting is normally carried out; the actual rare earth content in the casting blank is 0.029-0.033 Wt.%, the rare earth distribution is uniform, and the yield is 88%.
Example 2
Taking the mark 0Cr18Al4 as an example, the chemical components by mass percent are as follows: c: 0.018%, Si: 0.21%, Mn: 0.48%, P: 0.014%, S: 0.0015%, Cr: 17.2%, Al: 4.0%, Ti: 0.12%, N: 0.004%, and the balance of Fe and other inevitable impurities. The specification of the iron-chromium-aluminum alloy continuous casting slab is as follows: the thickness is 200mm, the width is 1160mm, the weight is 15.7 tons, and the density of a casting blank is 7.3g/cm 3 。
The production method of the iron-chromium-aluminum continuous casting slab crystallizer wire feeding rare earth alloying in the embodiment 2 comprises the following steps:
(1) preparing rare earth wires with the diameter of 2.8mm, wherein the total percentage of lanthanum and cerium is 98.0 Wt.%, and the density of the rare earth wires is 6.3g/cm 3 The rare earth wire is straight and not bent.
(2) The iron-chromium-aluminum molten steel is subjected to K-OBM-S → VOD → LF treatment, more than 88% of slag is removed after the converter, and the oxygen content and the sulfur content are respectively 0.0009 Wt.% and 0.0012 Wt.%.
(3) Before pouring, sealing protection of the tundish is well done, pouring is started after argon blowing is carried out on the tundish for 7min, and the temperature of the tundish is controlled at 1535-1550 ℃.
After casting, adding special protective slag in the crystallizer, and blowing argon for protection. The continuous casting crystallizer casting powder comprises the following components in percentage by weight: c: 7.7%, MgO: 1.53% of Al 2 O 3 ：2.65％、B 2 O 3 ：3.54％、Li 2 O：5.8％、F-：4.9％、Na 2 O: 6.8%, BaO: 6.7 percent and the comprehensive alkalinity is 0.89.
(4) Feeding rare earth filaments at a certain filament feeding speed by adopting a single machine double-flow method. The drawing speed of the continuously cast slab is V l 0.60m/min, and the pulling speed fluctuation value is controlled to be +/-0.01 m/min. The wire feeding points are positioned at the symmetrical positions of the two sides of the water gap, and the wire feeding points are 100mm away from the wide surface and 280mm away from the water gap. The target rare earth content is 0.04 Wt.%, the yield is 85%, and the wire feeding speed is calculated to be 6.3m according to a formula/min。
By using the production method of the wire feeding rare earth alloying of the iron-chromium-aluminum continuous casting slab crystallizer in the embodiment 2, the slag bars are fewer in the process of producing the 0Cr18Al4 continuous casting slab with the thickness of 200mm and the width of 1160mm, and the continuous casting is smooth and unimpeded; the actual rare earth content in the casting blank is 0.038-0.042 Wt.%, the rare earth distribution is uniform, and the yield is 85%.
Example 3
Taking the mark 0Cr21Al6 as an example, the chemical components by mass percent are as follows: c: 0.017%, Si: 0.22%, Mn: 0.09%, P: 0.013%, S: 0.001%, Cr: 20.2%, Al: 5.5%, Nb: 0.08%, Ti: 0.13%, N: 0.003% and the balance of Fe and other inevitable impurities. The specification of the iron-chromium-aluminum alloy continuous casting slab is as follows: 200mm in thickness, 1080mm in width, 13.1 tons in weight and 7.2g/cm in casting blank density 3 。
The production method of the iron-chromium-aluminum continuous casting slab crystallizer wire feeding rare earth alloying of the embodiment 3 comprises the following steps:
(1) preparing rare earth wires with the diameter of 3.0mm, the lanthanum content of 97.0 Wt.%, and the rare earth wire density of 6.2g/cm 3 And the rare earth wire joint is firmly welded.
(2) The iron-chromium-aluminum molten steel is subjected to K-OBM-S → VOD → LF treatment, more than 90% of slag is removed after the converter is heated, and the oxygen content and the sulfur content are respectively 0.0008 Wt.% and 0.0010 Wt.%.
(3) Before pouring, sealing protection of the tundish is well performed, pouring is performed after the tundish is blown with argon for 8min, and the temperature of the tundish is controlled to be 1545-.
After casting, adding special protective slag in the crystallizer, and blowing argon for protection. The continuous casting crystallizer casting powder comprises the following components in percentage by weight: c: 7.8%, MgO: 1.72% of Al 2 O 3 ：2.83％、B 2 O 3 ：3.67％、Li 2 O：5.9％、F-：5.0％、Na 2 O: 6.9%, BaO: 6.5 percent and the comprehensive alkalinity is 0.93.
(4) Feeding rare earth filaments at a certain filament feeding speed by adopting a single machine double-flow method. The drawing speed of the continuously cast slab is V l Is 0.50m/min, and the pulling speed fluctuation value is controlled to be +/-0.005 m/min. The wire feeding part is positioned at the symmetrical positions of the two sides of the water gapThe distance between the wire feeding point and the wide surface is 100mm, and the distance between the wire feeding point and the water gap is 270 mm. The target rare earth content is 0.07 Wt.%, the yield is 85%, and the wire feeding speed is calculated to be 7.5m/min according to a formula.
By using the production method of the wire feeding rare earth alloying of the iron-chromium-aluminum continuous casting slab crystallizer in the embodiment 3, a small amount of slag strips are generated in the process of producing a 0Cr21Al6 continuous casting slab with the thickness of 200mm and the width of 1080mm, but the casting is not influenced; the actual rare earth content in the casting blank is 0.070-0.074 Wt.%, the rare earth distribution is uniform, and the yield is 87%.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other substitutions, modifications, combinations, changes, simplifications, etc., which are made without departing from the spirit and principle of the present invention, should be construed as equivalents and included in the protection scope of the present invention.
Claims (6)
1. A production method for rare earth alloying of a wide steel strip iron-chromium-aluminum continuous casting slab is characterized by comprising the following steps:
(1) preparing rare earth filaments;
(2) the iron-chromium-aluminum molten steel is sequentially treated by a K-OBM-S furnace, a VOD furnace and an LF furnace;
(3) conveying the molten steel treated in the step (2) to a continuous casting machine by virtue of a sealed and protected tundish, and pouring the molten steel into a crystallizer;
(4) feeding rare earth wires by a single-machine double-flow method to prepare a continuous casting slab;
wherein, in the step (1), the diameter of the rare earth wire is 2.5-3.5 mm;
wherein, in the step (2), more than 85% of slag is completely removed after the converter is turned on, the oxygen content in the processed molten steel is less than 0.0012 wt.%, and the sulfur content is less than 0.0020 wt.%;
wherein in the step (3), the casting powder of the crystallizer comprises the following components in percentage by weight: c: 7.6% -7.8%, MgO: 1.53% -1.73% of Al 2 O 3 ：2.65％～2.83％、B 2 O 3 ：3.54％～3.67％、Li 2 O：5.7％～5.9％、F-：4.8％～5.0％、Na 2 O: 6.7% -6.9%, BaO: 6.5 to 6.7 percent; the balance being CaO and SiO 2 (ii) a Comprehensive alkalinity (CaO + BaO)/SiO 2 0.88 to 0.93;
in the step (4), the wire feeding speed of the rare earth wire is determined according to the following formula:
wherein, V s : wire feeding speed, D: diameter of rare earth wire, rho s : density of rare earth filaments, V 1 : drawing speed, W: casting blank width, T: thickness of casting blank, rho g : density of casting blank, omega RE : target rare earth content, omega, in steel 0 : rare earth content in rare earth filament, Y: and (4) obtaining the rare earth.
2. The production method according to claim 1, wherein in the step (1), the rare earth element used for the rare earth wire is any one or more of lanthanum, cerium and yttrium; the rare earth wire comprises more than or equal to 97 wt.% of rare earth elements and the balance of iron and inevitable impurities.
3. The production method according to claim 1, wherein in the step (3), the tundish is started to be poured after being blown with argon at 1525-1560 ℃ for 6-8 min.
4. The production method according to claim 1, wherein in the step (4), the drawing speed of the continuous casting slab is 0.40 to 0.80 m/min.
5. The production method according to claim 1, wherein in the step (4), the feeding lines of the rare earth wires are located at symmetrical positions on both sides of the nozzle, and the feeding point is located at the middle position of the thickness of the continuous casting slab and is located between the range of 0.20 and 0.26 times of the width of the slab from the immersion nozzle.
6. The production method according to claim 1, wherein in the step (4), the prepared continuous cast slab has a thickness of 180 to 230mm, a width of 1000 to 1300mm, and a weight of more than 10 tons.
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