Iron-chromium-aluminum series electric heating alloy continuous casting billet and preparation method thereof

Abstract

The present invention relates to an iron-chromium-aluminum electrothermal alloy continuous casting billet and a preparation method thereof, wherein the preparation method comprises smelting to obtain molten steel, charging the obtained molten steel into a tundish, and injecting the molten steel in the tundish into a crystallizer for continuous casting to obtain a continuous casting billet; wherein the superheat of the molten steel is controlled within a range of: liquidus temperature plus 30°C to liquidus temperature plus 80°C, and the range of liquid level fluctuation of the molten steel in the crystallizer is controlled within a range of: -5mm to +5mm; after injecting the molten steel in the tundish into the crystallizer, the method further comprises: electromagnetically stirring the molten steel in the crystallizer, wherein the current in the electromagnetic stirring is controlled within a range of 500A to 600A, and the frequency is controlled within a range of 5 to 15Hz. The preparation method of the present invention has the advantages of low production cost, low energy consumption, and high yield rate; the continuously cast billet prepared by the preparation method of the embodiment of the present invention can be directly used for hot rolling to obtain wire rod, and the obtained wire rod has good thermal processing performance.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material preparation, and in particular relates to an Fe-Cr-Al series electrothermal alloy continuous casting billet and a preparation method thereof. Background Art

[0002] Iron-chromium-aluminum (FeCrAl) electric heating alloys are high-temperature ferritic stainless steels. These alloys contain relatively high weight percentages of Cr and Al, while maintaining low C and N content. These alloys tend to form a well-developed columnar solidification structure in the billet. This columnar solidification structure not only reduces the billet's plasticity but also leads to numerous cracks within the billet. Consequently, these alloys often exhibit quality issues such as cracking in the rolled product and wire rod during hot rolling to produce wire rod.

[0003] The prior art only discloses that the continuous casting billets of the Fe-Cr-Aluminum electrothermal alloy are continuously cast using an arc-shaped square billet continuous casting machine, and are produced by a combination of a crystallizer and end electromagnetic stirring during casting, but does not disclose the specific preparation method of the continuous casting billets; and the continuous casting billets of the prior art need to be remelted by electroslag to become electroslag steel ingots before they can be used for hot rolling production of wire rods, so there are problems such as complex production process, high cost, and high energy consumption.

[0004] Therefore, there is an urgent need for a high-quality, low-cost preparation method for the continuous casting of Fe-Cr-Al alloy billets that can be directly used in wire rod hot rolling production. Summary of the Invention

[0005] In order to solve all or part of the above problems, the present invention aims to provide an Fe-Cr-Al series electrothermal alloy continuous casting billet and a preparation method thereof.

[0006] According to one aspect of the present invention, a method for preparing an Fe-Cr-Al series electrothermal alloy continuous casting billet is provided, comprising smelting to obtain molten steel, charging the obtained molten steel into a tundish, and injecting the molten steel in the tundish into a crystallizer to continuously cast the billet to obtain the continuously cast billet;

[0007] The range of superheat of the molten steel is controlled to be: liquidus temperature plus 30°C to liquidus temperature plus 80°C, and the range of liquid level fluctuation of the molten steel in the crystallizer is controlled to be: -5mm to +5mm.

[0008] Furthermore, the superheat of the molten steel is controlled within a range of liquidus temperature plus 30°C to liquidus temperature plus 60°C.

[0009] Furthermore, after the molten steel in the tundish is injected into the crystallizer, the method further comprises: performing electromagnetic stirring on the molten steel in the crystallizer, wherein the current in the electromagnetic stirring is controlled within a range of 500A to 600A, and the frequency is controlled within a range of 5 to 15 Hz.

[0010] Furthermore, the drawing speed during the solidification process of the continuous casting billet is controlled in the range of 0.65 m / min to 1.10 m / min.

[0011] Furthermore, after the molten steel in the tundish is injected into the crystallizer, the method further includes: calculating a calculated value of the pulling speed during the solidification process of the continuous casting billet based on the weight percentage of chromium and the weight percentage of aluminum in the alloy; and if the calculated value of the pulling speed is less than 0.65 m / min, controlling the pulling speed during the solidification process of the continuous casting billet to be 0.65 m / min; if the calculated value of the pulling speed is greater than or equal to 0.65 m / min, controlling the pulling speed during the solidification process of the continuous casting billet to be equal to the calculated value of the pulling speed.

[0012] Furthermore, the calculated value of the drawing speed during the solidification process of the continuous casting billet calculated based on the weight percentage of chromium and the weight percentage of aluminum in the alloy is specifically: the calculated value of the drawing speed is equal to the sum of the weight percentage of chromium and 1.95 times the weight percentage of aluminum in the alloy divided by 30, and the unit of the drawing speed calculated by the calculation formula is meters per minute.

[0013] Furthermore, after injecting the molten steel in the tundish into the crystallizer to continuously cast the billet to obtain the continuously cast billet, the method also includes: using electromagnetic stirring at the end of solidification to stir the unsolidified molten steel inside the continuously cast billet, and the current range of the electromagnetic stirring is controlled to be 500A~600A, and the frequency range is controlled to be 5Hz~15Hz.

[0014] Furthermore, after injecting the molten steel in the tundish into the crystallizer to continuously cast the billet to obtain the continuously cast billet, the method further includes: performing two water cooling treatments on the continuously cast billet, and the temperature range of the continuously cast billet at the second water cooling outlet is controlled to be 900℃~980℃.

[0015] Furthermore, in the iron-chromium-aluminum electrothermal alloy, the weight percentage of Cr is 11% to 21%, and the weight percentage of Al is 2% to 6%; the cross-sectional dimensions of the continuous casting billet are: 215 mm to 225 mm in length and 215 mm to 225 mm in width.

[0016] The present invention also provides an Fe-Cr-Al series electrothermal alloy continuous casting billet, which is prepared by any one of the above preparation methods.

[0017] As can be seen from the above technical solution, the Fe-Cr-Al series electrothermal alloy continuous casting billet and its preparation method provided by the present invention have the following beneficial effects:

[0018] The preparation method of the present invention has the advantages of low production cost, low energy consumption, and high yield rate; the continuous casting square billet prepared by the preparation method of the embodiment of the present invention can be directly used for hot rolling to obtain wire rods, and the obtained wire rods have good thermal processing performance and no cracking problem during the hot rolling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the macrostructure of the Fe-Cr-Al series electrothermal alloy continuous casting billet prepared in an embodiment of the present invention.

[0020] Figure 2 The microscopic grain structure of the wire rod obtained by hot rolling the Fe-Cr-Al series electrothermal alloy continuous casting billet according to the embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific embodiments. Except for the following contents, the process of the present invention adopts conventional methods or devices in the art. Unless otherwise specified, the following terms have the meanings commonly understood by those skilled in the art.

[0022] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0023] The production process of conventional iron-chromium-aluminum electrothermal alloys, such as 1Cr13Al4, 0Cr20Al3 and other alloys, is as follows: smelting into continuous casting billets in an electric furnace / medium frequency furnace, remelting the continuous casting billets through electroslag to obtain electroslag ingots, and the electroslag ingots are used for the hot rolling production of wire rods. This production method has the disadvantages of complex preparation process, high cost, and high energy consumption. The purpose of the embodiment of the present invention is to address the problems existing in the above-mentioned production method and propose a preparation method for continuous casting billets of iron-chromium-aluminum electrothermal alloys. The continuous casting billets obtained in the embodiment of the present invention can be directly used for the hot rolling of wire rods, and the preparation method of this embodiment has the advantages of low production cost, low energy consumption, and high yield rate. The continuous casting billets prepared by this embodiment are used for the hot rolling of wire rods without the problem of hot rolling cracking and have the advantage of good hot working performance.

[0024] The method for preparing a continuous casting billet according to an embodiment of the present invention comprises the following steps: smelting to obtain molten steel, charging the obtained molten steel into a tundish, and injecting the molten steel in the tundish into a crystallizer to continuously cast the billet to obtain the continuously cast billet.

[0025] Among them, smelting to obtain molten steel specifically includes: smelting through a converter (K-OBM-S) / electric arc furnace (EAF) / medium frequency induction furnace → vacuum oxygen decarburization furnace (VOD furnace) / argon oxygen refining furnace (AOD) → ladle refining furnace (LF furnace) to obtain molten steel.

[0026] After obtaining the molten steel, it is loaded into a tundish for continuous casting of billets. The molten steel in the tundish enters the crystallizer to start continuous casting of the billets. During the continuous casting process, the crystallizer maintains a stable liquid level and uses mold electromagnetic stirring (M-EMS) to treat the molten steel in the crystallizer.

[0027] Then, continuous casting billets are produced at a certain pulling speed. After being cooled in the first and second water-cooling sections of the arc-shaped continuous casting machine, the billets gradually solidify from the shell inward. Then, electromagnetic stirring at the end of solidification (F-EMS) is used to treat the unsolidified molten steel inside the continuous casting billet, thereby increasing the proportion of equiaxed grains in the core of the billet.

[0028] Finally, the fully solidified continuous casting billet can be cut into lengths as required.

[0029] Among them, the range of superheat of molten steel is controlled as follows: liquidus temperature plus 30°C to liquidus temperature plus 80°C, and the range of liquid level fluctuation of molten steel in the crystallizer is controlled as follows: -5mm to +5mm.

[0030] Specifically, in the process of injecting the molten steel in the tundish into the crystallizer, appropriately reducing the superheat of the molten steel will form a compositional supercooling zone at the leading edge of the columnar crystals of the billet, generating a large number of new crystal nuclei and growing into equiaxed crystals. The equiaxed crystals can block the growth of the columnar crystals. Therefore, expanding the equiaxed crystal area is beneficial to improving the internal strength of the square billet and inhibiting the generation and expansion of cracks. The range of the superheat of the molten steel in this embodiment is controlled to be: liquidus temperature plus 30°C to liquidus temperature plus 80°C. This range can expand the equiaxed crystal area and block the growth of columnar crystals.

[0031] Preferably, the superheat of the molten steel is controlled within a range of liquidus temperature plus 30°C to liquidus temperature plus 60°C.

[0032] Keeping the liquid level of the molten steel stable in the crystallizer allows the liquid slag to seep between the billet shell and the copper plate, playing a good lubricating role, thereby obtaining a billet with good surface quality. In this embodiment, the range of the liquid level fluctuation of the molten steel in the crystallizer is controlled to be: -5mm~+5mm.

[0033] After the molten steel in the tundish is injected into the crystallizer, the preparation method of this embodiment further includes: electromagnetically stirring the molten steel in the crystallizer, wherein the current range of the electromagnetic stirring is controlled to be 500A to 600A, and the frequency range is controlled to be 5 to 15Hz.

[0034] Specifically, controlling the range of molten steel level fluctuations within the mold and performing electromagnetic stirring (M-EMS) on the molten steel can both improve the quality of continuously cast billets. Using electromagnetic stirring within the mold can improve the surface and subsurface quality of the billet, promote uniform growth of the solidified shell within the mold, reduce corner cracks, and expand the central equiaxed grain area. In this embodiment of the present invention, the current of the electromagnetic stirring (M-EMS) is controlled within a range of 500A to 600A, and the frequency is controlled within a range of 5 to 15Hz.

[0035] The pulling speed during the solidification process of the continuous casting billet is controlled in the range of 0.65m / min to 1.10m / min.

[0036] The drawing speed, or the speed at which the billet is drawn, affects the length and shape of the solid-liquid phase region during the solidification process of the continuously cast billet, ultimately impacting its quality. Low drawing speeds result in a thick and uneven initial shell, making it prone to cracking. High drawing speeds result in a thin shell, which can lead to surface cracks and breakouts. In this embodiment, the drawing speed is controlled within a range of 0.65 m / min to 1.10 m / min, resulting in continuously cast billets with moderate shell thickness and high surface quality.

[0037] Among them, after the molten steel in the tundish is injected into the crystallizer, the preparation method further includes: calculating a calculated value of the pulling speed during the solidification process of the continuous casting square billet based on the weight percentage of chromium and the weight percentage of aluminum in the alloy; and if the calculated value of the pulling speed is less than 0.65 m / min, controlling the pulling speed during the solidification process of the continuous casting square billet to be 0.65 m / min; if the calculated value of the pulling speed is greater than or equal to 0.65 m / min, controlling the pulling speed during the solidification process of the continuous casting square billet to be equal to the calculated value of the pulling speed.

[0038] Among them, the calculated value of the drawing speed during the solidification process of the continuous casting billet is calculated based on the weight percentage of chromium and the weight percentage of aluminum in the alloy: the calculated value of the drawing speed is equal to the sum of the weight percentage of chromium and 1.95 times the weight percentage of aluminum in the alloy divided by 30, and the unit of the drawing speed calculated by the calculation formula is meters per minute.

[0039] By controlling the casting speed according to the comparison result between the calculated casting speed value and the minimum casting speed of 0.65m / min, a continuous casting billet with moderate shell thickness and high surface quality can be obtained.

[0040] Among them, after the molten steel in the tundish is injected into the crystallizer to continuously cast the billet to obtain the continuously cast billet, the preparation method also includes: performing two water cooling treatments on the continuously cast billet, and the temperature range of the continuously cast billet at the second water cooling outlet is controlled to be 900℃~980℃.

[0041] Formulating a reasonable first and second water cooling system for the continuous casting machine can meet the requirements of reducing cracks and center segregation inside the billet, suppressing quality defects such as bulging, etc. In the embodiment of the present invention, the temperature range of the continuous casting billet at the second water cooling outlet is controlled to be 900℃~980℃.

[0042] Among them, after the molten steel in the ladle is injected into the crystallizer to continuously cast the billet to obtain the continuously cast billet, the preparation method also includes: using electromagnetic stirring at the end of solidification to stir the unsolidified molten steel inside the continuously cast billet, and the current range in the electromagnetic stirring is controlled to be 500A~600A, and the frequency range is controlled to be 5Hz~15Hz.

[0043] Electromagnetic stirring (F-EMS) at the end of solidification can expand the equiaxed crystal zone and increase the equiaxed crystal ratio. Forced convection during F-EMS cuts off the front end of columnar crystals, inhibiting their growth and promoting the formation and growth of equiaxed crystals. This facilitates the formation of a large number of equiaxed crystals in the solidification structure, increases the proportion of equiaxed crystals within the continuous casting billet, improves center segregation, and inhibits internal crack propagation. In this embodiment of the present invention, the current during F-EMS at the end of solidification of the continuous casting billet is controlled within a range of 500A to 600A, and the frequency is controlled within a range of 5Hz to 15Hz.

[0044] The cross-sectional dimensions of the continuous casting billet prepared in the embodiment of the present invention are: 215 mm to 225 mm in length and 215 mm to 225 mm in width.

[0045] In Fe-Cr-Al electric heating alloys, the weight percentage of Cr is 11% to 21%, and the weight percentage of Al is 2% to 6%. The effects of Cr and Al on the quality of continuous casting billets are as follows: Cr is a strong ferrite-forming element. As the Cr content in the steel increases, the ferrite structure becomes more developed, which increases the brittleness of the continuous casting billet. Al is also a ferrite-forming element. Adding Al to ferritic stainless steel can promote the formation of a single ferrite structure, increasing the brittleness of the continuous casting billet.

[0046] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. The conditions and methods not specified in the following examples are conventional methods and conditions.

[0047] Example 1

[0048] Preparation of molten steel: After smelting in a converter (K-OBM-S) → a vacuum oxygen decarburization furnace (VOD furnace) → a ladle refining furnace (LF furnace), molten steel with a grade of 1Cr13Al4 is obtained. The element content of the molten steel, in terms of weight percentage, is C: 0.035%, Si: 0.38%, Mn: 0.25%, P: 0.018%, S: 0.001%, Cr: 12.25%, Ni: 0.02%, Al: 4.22%, and the remainder includes Fe and incidental impurities.

[0049] The obtained 1Cr13Al4 molten steel was charged into a tundish to produce continuous casting square billets with a cross-sectional size of 220 mm in length and 220 mm in width.

[0050] The 1Cr13Al4 molten steel in the tundish enters the crystallizer to start continuous casting of the billet. During the continuous casting process of the billet, the superheat range of the molten steel is controlled to be: [1486+ (30~60)] ℃.

[0051] The range of liquid level fluctuation of molten steel in the crystallizer is controlled to be -4mm to +4mm, and the molten steel is stirred using a crystallizer electromagnetic stirring (M-EMS). The current range of the crystallizer electromagnetic stirring (M-EMS) is controlled to be 500A, and the frequency range is controlled to be 5Hz.

[0052] The casting speed of the continuous casting billet is controlled at 0.68m / min.

[0053] After the continuous casting billet is cooled by the first water cooling and the second water cooling, the temperature of the continuous casting billet at the outlet of the second water cooling is controlled in the range of 930℃~980℃.

[0054] The continuous casting billet adopts electromagnetic stirring at the end of solidification (F-EMS), and the current range of the electromagnetic stirring at the end of solidification (F-EMS) is controlled to be 500A, and the frequency range is controlled to be 5Hz.

[0055] Example 2

[0056] Preparation of molten steel: After smelting in an electric arc furnace (EAF) → an argon oxygen refining furnace (AOD) → a ladle refining furnace (LF furnace), molten steel with a grade of 0Cr20Al3 is obtained. The element content of the molten steel in terms of weight percentage is C: 0.032%, Si: 0.41%, Mn: 0.29%, P: 0.023%, S: 0.002%, Cr: 18.14%, Ni: 0.04%, Al: 3.17%, and the rest includes Fe and incidental impurities.

[0057] The prepared 0Cr20Al3 molten steel is charged into a tundish for producing continuous casting square billets with a cross-sectional size of 220 mm in length and 220 mm in width.

[0058] The 0Cr20Al3 molten steel in the tundish enters the crystallizer to start continuous casting of the billet. During the continuous casting process of the billet, the superheat range of the molten steel is controlled to be: [1481+ (30~60)] ℃.

[0059] The range of liquid level fluctuation of molten steel in the crystallizer is controlled to be -4mm to +4mm, and the molten steel is stirred using a crystallizer electromagnetic stirring (M-EMS). The current range of the crystallizer electromagnetic stirring (M-EMS) is controlled to be 550A, and the frequency range is controlled to be 10Hz.

[0060] The casting speed of the continuous casting billet is controlled at 0.81m / min.

[0061] After the continuous casting billet is cooled by the first water cooling and the second water cooling, the temperature of the continuous casting billet at the outlet of the second water cooling is controlled to be in the range of 910℃~970℃.

[0062] The continuous casting billet adopts electromagnetic stirring at the end of solidification (F-EMS), and the current range of the electromagnetic stirring at the end of solidification (F-EMS) is controlled to be 550A and the frequency range is controlled to be 10Hz.

[0063] The preparation method of the present invention has the advantages of low production cost, low energy consumption, and high yield rate; the continuous casting square billet prepared by the preparation method of the embodiment of the present invention can be directly used for hot rolling to obtain wire rods, and the obtained wire rods have good thermal processing performance and no cracking problem during the hot rolling process.

[0064] The embodiment of the present invention also provides an Fe-Cr-Al series electrothermal alloy continuous casting billet, which is prepared by any one of the above preparation methods. The macrostructure of the obtained continuous casting billet is as follows: Figure 1 As shown in the figure, the micro grain structure of the wire rod obtained by hot rolling the continuous casting billet is as follows: Figure 2 shown.

[0065] The continuously cast billets according to the embodiment of the present invention can be directly used to obtain wire rods through hot rolling. The obtained wire rods have good hot working properties and no cracking problem occurs during the hot rolling process.

[0066] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art will appreciate that these embodiments are intended only to illustrate the present invention and are not to be construed as limiting the scope of the present invention. It should be noted that any equivalent variations and substitutions to these embodiments are to be considered encompassed within the scope of the claims of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope defined in the claims.

Claims

1. A method for preparing an Fe-Cr-Al series electrothermal alloy continuous casting billet, characterized in that: The method comprises smelting to obtain molten steel, charging the obtained molten steel into a tundish, and injecting the molten steel in the tundish into a crystallizer to continuously cast a billet to obtain a continuously cast billet; The superheat range of the molten steel is controlled to be: liquidus temperature plus 30°C to liquidus temperature plus 60°C, and the range of the liquid level fluctuation of the molten steel in the crystallizer is controlled to be: -4mm to +4mm; After the molten steel in the tundish is injected into the crystallizer, the method further comprises: performing electromagnetic stirring on the molten steel in the crystallizer, wherein the current of the electromagnetic stirring is controlled within a range of 500A to 550A and the frequency is controlled within a range of 5 to 10 Hz; After the molten steel in the tundish is poured into the crystallizer, the method further includes: calculating a calculated value of a drawing speed during the solidification process of the continuous casting billet based on the weight percentage of chromium and the weight percentage of aluminum in the alloy; and if the calculated value of the drawing speed is less than 0.65 m / min, controlling the drawing speed during the solidification process of the continuous casting billet to be 0.65 m / min; if the calculated value of the drawing speed is greater than or equal to 0.65 m / min, controlling the drawing speed during the solidification process of the continuous casting billet to be equal to the calculated value of the drawing speed; The calculated value of the drawing speed during the solidification process of the continuous casting billet is calculated based on the weight percentage of chromium and the weight percentage of aluminum in the alloy: the calculated drawing speed is equal to the sum of the weight percentage of chromium and 1.95 times the weight percentage of aluminum in the alloy divided by 30, and the unit of the drawing speed calculated by the calculation formula is meters per minute; After injecting the molten steel in the tundish into the crystallizer to continuously cast the billet to obtain the continuously cast billet, the method further includes: using electromagnetic stirring at the end of solidification to stir the unsolidified molten steel inside the continuously cast billet, and the current range of the electromagnetic stirring is controlled to be 500A~550A, and the frequency range is controlled to be 5Hz~10Hz.

2. The preparation method according to claim 1, characterized in that After injecting the molten steel in the tundish into the crystallizer to continuously cast the billet to obtain the continuously cast billet, the method further includes: performing two water cooling treatments on the continuously cast billet, and controlling the temperature range of the continuously cast billet at the outlet of the second water cooling to be 900°C to 980°C.

3. The preparation method according to claim 1, characterized in that In the iron-chromium-aluminum electrothermal alloy, the weight percentage of Cr is 11% to 21%, and the weight percentage of Al is 2% to 6%. The cross-sectional dimensions of the continuous casting billet are: 215mm to 225mm in length and 215mm to 225mm in width.

4. An Fe-Cr-Al series electrothermal alloy continuous casting billet, characterized in that: The method is prepared by the method according to any one of claims 1 to 3.

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