Iron-chromium-aluminum series electrothermal alloy continuous casting square billet and preparation method thereof

Abstract

The invention relates to an iron-chromium-aluminum series electrothermal alloy continuous casting square billet and a preparation method thereof. The preparation method comprises the steps that molten steel is obtained through smelting, the obtained molten steel is loaded into a tundish, and the molten steel in the tundish is injected into a crystallizer for continuous casting to obtain the continuous casting square billet. Wherein the superheat degree range of the molten steel is controlled to be 30 DEG C plus liquidus temperature to 80 DEG C plus liquidus temperature, and the liquid level fluctuation range of the molten steel in the crystallizer is controlled to be-5 mm to + 5 mm; after the molten steel in the tundish is injected into the crystallizer, the method further comprises the steps that electromagnetic stirring is conducted on the molten steel in the crystallizer, the current range in the electromagnetic stirring process is controlled to range from 500 A to 600 A, and the frequency range in the electromagnetic stirring process is controlled to range from 5 Hz to 15 Hz. The preparation method has the advantages of low production cost, low energy consumption, high yield and the like; the continuous casting square billet prepared by the preparation method provided by the embodiment of the invention can be directly used for hot rolling to obtain the wire rod, and the hot working performance of the obtained wire rod is good.

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 electrothermal alloy is a high-temperature resistant ferritic stainless steel. The alloy contains relatively high Cr and Al elements by weight, and the C and N elements are required to be low. This type of alloy is easy to form a developed columnar crystal solidification structure in the billet, which not only reduces the plasticity of the billet but also causes a large number of cracks inside the billet. Therefore, this type of alloy often has quality problems such as cracking of rolled parts and cracking of wire rods during hot rolling to prepare wire rods.

[0003] The prior art only discloses that the continuous casting billet of the Fe-Cr-Al series electrothermal alloy is continuously cast by an arc-shaped square billet continuous casting machine, and is produced by a combination of a crystallizer and an end electromagnetic stirring during casting, but does not disclose the specific preparation method of the continuous casting billet; and the continuous casting billet of the prior art needs to be remelted by electroslag to become an electroslag ingot before it can be used for the 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 for 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 a 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 range of superheat of the molten steel is controlled to be: 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: 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 15 Hz.

[0010] Furthermore, the pulling 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 also includes: calculating a calculated value of the pulling speed during the solidification process of the continuous casting square billet according to the percentage of chromium and the 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.

[0012] Furthermore, the calculated value of the pulling speed during the solidification process of the continuous casting billet calculated based on the percentage of chromium and the percentage of aluminum in the alloy is specifically: the calculated value of the pulling speed is equal to the sum of the percentage of chromium and 1.95 times the percentage of aluminum in the alloy divided by 30, and the unit of the pulling speed calculated by the calculation formula is meter 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 water cooling treatment on the continuously cast billet twice, and the temperature range of the continuously cast billet at the outlet of the second water cooling is controlled to be 900°C to 980°C.

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

[0017] It can be seen from the above technical scheme that the Fe-Cr-Al series electrothermal alloy continuous casting billet and the preparation method thereof 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, high yield rate, etc. The continuous casting square billet prepared by the preparation method of the embodiment of the present invention can be directly used to obtain wire rods through hot rolling. 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 the 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 method 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 above range is considered to be 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 should be understood to include any and all subranges included 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 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 propose a preparation method of continuous casting square billets of iron-chromium-aluminum electrothermal alloys in view of the problems existing in the above-mentioned production method. The continuous casting square billets obtained in the embodiment of the present invention can be directly used for 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 square billets prepared by this embodiment are used for 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 continuous casting 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, the molten steel is loaded into the tundish for casting the continuous casting billet. The molten steel in the tundish enters the crystallizer to start the continuous casting of the billet. During the continuous casting process, the crystallizer keeps the liquid level stable and the crystallizer electromagnetic stirring (M-EMS) is used to treat the molten steel in the crystallizer.

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

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

[0029] Among them, the range of superheat of molten steel is controlled as: 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: -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 front 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 columnar crystals. Therefore, expanding the equiaxed crystal area is beneficial to improving the internal strength of the 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 molten steel stable in the crystallizer can allow the liquid slag to seep between the billet shell and the copper plate, playing a good lubricating role, thereby obtaining a cast 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 comprises: 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 15 Hz.

[0034] Specifically, the control of the liquid level fluctuation range of the molten steel in the crystallizer and the electromagnetic stirring (M-EMS) of the molten steel can improve the quality of the continuous casting billet. Among them, the use of electromagnetic stirring technology in the crystallizer can improve the surface and subcutaneous quality of the continuous casting billet, promote the uniform growth of the solidified billet shell in the crystallizer, and is conducive to reducing the cracks at the corners of the continuous casting billet and expanding the central equiaxed crystal area. In the electromagnetic stirring (M-EMS) of the embodiment of the present invention, the current range is controlled to be 500A to 600A, and the frequency range is controlled to be 5 to 15Hz.

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

[0036] The drawing speed is also called the billet drawing speed, which can affect the length and shape of the solid-liquid two-phase region during the solidification process of the continuous casting billet, and ultimately affect the quality of the continuous casting billet. When the drawing speed is low, the primary billet shell is thick and uneven, which is prone to cracks; when the drawing speed is high, the billet shell is thin, which is prone to problems such as billet surface cracks and steel leakage. The drawing speed range of this embodiment is controlled to be 0.65m / min to 1.10m / min, which can obtain a continuous casting billet with moderate billet shell thickness and high billet surface quality.

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

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

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

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

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

[0042] Among them, after the molten steel in the tundish is injected into the crystallizer to continuously cast the square billet to obtain the continuously cast square billet, the preparation method also includes: using electromagnetic stirring at the end of solidification to stir the unsolidified molten steel inside the continuously cast square 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 rate. The electromagnetic stirring at the end of solidification forces convection to cut off the front section of the columnar crystal, inhibit the growth of the columnar crystal, and promote the formation and growth of the equiaxed crystal, which is conducive to the formation of a large number of equiaxed crystal solidification structures, expand the proportion of equiaxed crystals inside the continuous casting billet, improve the center segregation and inhibit the expansion of internal cracks. In the embodiment of the present invention, the current range of the electromagnetic stirring at the end of solidification of the continuous casting billet is controlled to be 500A to 600A, and the frequency range is controlled to be 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] Among them, in the Fe-Cr-Al series electric heating alloy, the percentage of Cr is 11% to 21%, and the percentage of Al is 2% to 6%. Among them, the effects of Cr and Al elements and their influence on the quality of continuous casting billets are as follows: Cr is a strong ferrite-forming element. As the amount of Cr in the steel increases, the ferrite structure becomes more developed, and the developed ferrite structure will increase the brittleness of the continuous casting billet; Al is a ferrite-forming element. Adding Al to ferritic stainless steel can promote the formation of a single ferrite structure and increase the brittleness of the continuous casting billet.

[0046] The present invention is further described below by way of examples, 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) → vacuum oxygen decarburization furnace (VOD furnace) → ladle refining furnace (LF furnace), molten steel with a grade of 1Cr13Al4 is obtained, and its element content by 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 rest includes Fe and incidental impurities.

[0049] The obtained 1Cr13Al4 molten steel is loaded into a tundish for producing continuous casting square billets with cross-sectional dimensions of 220 mm in length and 220 mm in width.

[0050] The 1Cr13Al4 molten steel in the tundish enters the crystallizer to start the continuous casting of the billet. During the continuous casting 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~+4mm, and the molten steel is stirred by crystallizer electromagnetic stirring (M-EMS). The current range of 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 the end-solidification electromagnetic stirring (F-EMS), and the current range of the end-solidification electromagnetic stirring (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 electric arc furnace (EAF) → argon oxygen refining furnace (AOD) → ladle refining furnace (LF furnace), molten steel with a grade of 0Cr20Al3 is obtained, and its element content by 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 loaded into a tundish for producing continuous casting square billets with cross-sectional dimensions 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 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~+4mm, and the molten steel is stirred by crystallizer electromagnetic stirring (M-EMS). The current range of 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 in the range of 910℃~970℃.

[0062] The continuous casting billet adopts the end-solidification electromagnetic stirring (F-EMS), and the current range of the end-solidification electromagnetic stirring (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, high yield rate, etc. The continuous casting square billet prepared by the preparation method of the embodiment of the present invention can be directly used to obtain wire rods through hot rolling. 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 preparation methods described above. The macrostructure of the obtained continuous casting billet is as follows: Figure 1 As shown in Figure 2, the microstructure of the wire rod obtained by hot rolling of continuous casting billet is as follows: Figure 2 shown.

[0065] The continuously cast square billet 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 during the hot rolling process.

[0066] The present invention has been disclosed above with preferred embodiments, but those skilled in the art should understand that these embodiments are only used to describe the present invention and should not be understood as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to these embodiments should be deemed to be included in the scope of the claims of the present invention. Therefore, the scope of protection of the present invention should be based on 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 square billet to obtain a continuously cast square billet; 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.

2. The preparation method according to claim 1, characterized in that: The range of superheat of the molten steel is controlled to be: liquidus temperature plus 30°C to liquidus temperature plus 60°C.

3. The preparation method according to claim 1, characterized in that: After the molten steel in the tundish is injected 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 15 Hz.

4. The preparation method according to claim 1, characterized in that: 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.

5. The preparation method according to claim 1, characterized in that: 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 square billet according to the percentage of chromium and the 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.

6. The preparation method according to claim 5, characterized in that: The calculated value of the pulling speed during the solidification process of the continuous casting billet calculated based on the percentage of chromium and the percentage of aluminum in the alloy is specifically: the calculated value of the pulling speed is equal to the sum of the percentage of chromium and 1.95 times the percentage of aluminum in the alloy divided by 30, and the unit of the pulling speed calculated by the calculation formula is meter per minute.

7. 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: 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 to 600A, and the frequency range is controlled to be 5Hz to 15Hz.

8. 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 water cooling treatment on the continuously cast billet twice, and the temperature range of the continuously cast billet at the outlet of the second water cooling is controlled to be 900°C to 980°C.

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

10. An Fe-Cr-Al series electrothermal alloy continuous casting billet, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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