A method for producing a rare earth alloy steel

Abstract

The application provides a preparation method of a rare earth alloy steel, and focuses on improving a rare earth alloying adding mode, that is, rare earth alloying is performed on molten steel obtained through smelting by using a rare earth iron alloy, so that self loss and physical and chemical damage of the rare earth alloy in the production and alloying process can be avoided, and especially, the castability problem caused by accumulation and blockage of rare earth inclusions in the smelting process of the rare earth alloy steel can be effectively solved, and the control and application in the actual production process are facilitated.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, and specifically to a method for preparing rare earth alloy steel. Background Technology

[0002] Rare earth elements, due to their position in the periodic table and their electronic structure, are characterized by large atomic sizes and active chemical properties. In steel metallurgy, they primarily function to strengthen microalloying and modify inclusions, improving the overall properties of steel, especially yield strength and low-temperature impact resistance. Rare earth elements have larger atomic radii than γ-Fe, preventing them from forming substitutional or interstitial solid solutions. They mostly exist at grain boundaries, causing lattice distortion and thus producing solid solution strengthening. Rare earth elements can modify oxide and sulfide inclusions in molten steel, generating fine, nearly spherical rare earth compounds. Furthermore, the thermal expansion coefficient of rare earth inclusions is very close to that of the iron matrix, reducing stress crack initiation during hot working and thus affecting the steel's mechanical properties. They also prevent corrosion caused by the lack of bonding between inclusions and the surrounding matrix. Therefore, fine rare earth inclusions mitigate the adverse effects of conventional inclusions on steel.

[0003] However, due to the relatively reactive chemical properties of rare earth elements, they readily react with oxygen and sulfur in molten steel to form high-melting-point rare earth oxides (REO2, RE2O3), rare earth sulfides (RES, RE2S3), and rare earth sulfur oxides (RE2O2S). Their melting points are generally above 1900℃, and their densities are close to those of molten steel (molten steel density is 7.0 g / cm³). 3 Rare earth elements are difficult to remove by floating, leading to steel contamination. If the timing of rare earth addition is inaccurate or the amount added is excessive, large particles of composite compounds will aggregate, forming unevenly distributed, brittle rare earth intermetallic compounds. This deteriorates the steel's properties and causes nozzle clogging during continuous casting, affecting castability.

[0004] Due to their unique chemical properties, rare earth elements can play a role in purification, modification, and alloying in steel. The purification effect is mainly due to their deoxidation and desulfurization capabilities. However, on the one hand, current smelting processes can already achieve deoxidation and desulfurization in molten steel; using rare earth elements for deoxidation and desulfurization would be uneconomical and negatively impact steel properties. On the other hand, rare earth elements combine with oxygen and sulfur to form high-melting-point inclusions, which not only affect steel properties but also tend to adhere to the inner wall of continuous casting nozzles, affecting the castability of the molten steel. Therefore, the addition of rare earth elements to steel is primarily used to modify and alloy the molten steel, thereby improving its overall mechanical properties. However, the timing, method, and amount of rare earth element addition during the smelting process determine the overall mechanical properties and castability of rare earth alloy steel.

[0005] In summary, there is a need to develop a novel method for preparing rare earth alloy steel. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a method for preparing rare earth alloy steel. The preparation method focuses on improving the addition method of rare earth alloying, that is, using rare earth ferroalloys to alloy the molten steel obtained by smelting. This can avoid the self-loss and physicochemical damage caused by rare earth alloys during production and alloying processes. In particular, it can effectively solve the problem of castability caused by the accumulation of rare earth inclusions blocking the nozzle during the smelting process of rare earth alloy steel, which is convenient for control and application in actual production.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] The purpose of this invention is to provide a method for preparing rare earth alloy steel, the method comprising: smelting molten iron sequentially, alloying it with rare earth elements, and continuously casting it to obtain rare earth alloy steel;

[0009] The S content in the molten steel obtained by smelting is controlled to be ≤0.008wt.% and the O content is controlled to be ≤0.0015wt.%. The rare earth alloying includes: using rare earth ferroalloys to alloy the molten steel obtained by smelting with rare earth alloys.

[0010] The method for preparing rare earth alloy steel described in this invention focuses on improving the method of rare earth alloying, that is, using rare earth ferroalloys to alloy the molten steel obtained by smelting. This can avoid the self-loss and physicochemical damage caused by rare earth alloys during production and alloying processes. In particular, it can effectively solve the problem of castability caused by the accumulation of rare earth inclusions blocking the nozzle during the smelting process of rare earth alloy steel, which is convenient for control and application in actual production.

[0011] As a preferred technical solution of the present invention, the smelting includes sequential converter steelmaking and refining.

[0012] As a preferred technical solution of the present invention, a deep deoxidizer is added during the tapping process of the converter steelmaking.

[0013] Preferably, the deep deoxidizer comprises aluminum ingots.

[0014] Preferably, the amount of aluminum ingot added is 40-100 kg / furnace, such as 40 kg / furnace, 45 kg / furnace, 50 kg / furnace, 55 kg / furnace, 60 kg / furnace, 65 kg / furnace, 70 kg / furnace, 75 kg / furnace, 80 kg / furnace, 85 kg / furnace, 90 kg / furnace, 95 kg / furnace, or 100 kg / furnace, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0015] Preferably, during the steelmaking process in the converter, lime and refining slag are added for slag washing to achieve slag formation in advance.

[0016] Preferably, the amount of lime added is 500 kg / furnace.

[0017] Preferably, the amount of refining slag added is 300 kg / furnace.

[0018] Preferably, the composition control of the refining slag includes: CaO content ≥ 49 wt.%, MgO content ≤ 1.5 wt.%, SiO2 content ≤ 1.5 wt.%, and Al2O3 content ≥ 40 wt.%.

[0019] Preferably, the final sulfur content of the converter steelmaking process is 0.050-0.080 wt.%.

[0020] It is worth noting that the converter steelmaking process in the rare earth alloy steel preparation method of the present invention includes deoxidation and desulfurization, which helps to control the S content in the molten steel obtained by smelting to ≤0.008wt.% and the O content to ≤0.0015wt.%, thereby facilitating the subsequent rare earth alloying and solving the technical problem of the castability of rare earth alloy steel.

[0021] As a preferred embodiment of the present invention, the refining process includes the addition of diffusion deoxidizing materials.

[0022] Preferably, the diffusion deoxidizing material comprises aluminum particles and silicon carbide.

[0023] Preferably, the amount of aluminum granules added is 20-50 kg / furnace, such as 20 kg / furnace, 25 kg / furnace, 30 kg / furnace, 35 kg / furnace, 40 kg / furnace, 45 kg / furnace, or 50 kg / furnace, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0024] Preferably, the amount of silicon carbide added is 50-70 kg / furnace, such as 50 kg / furnace, 52 kg / furnace, 55 kg / furnace, 58 kg / furnace, 60 kg / furnace, 63 kg / furnace, 65 kg / furnace, 67 kg / furnace, or 70 kg / furnace, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0025] Preferably, the goal of adding the diffusion deoxidizing material is to ensure that the total content of FeO and MnO in the top slag is ≤1.0 wt.%.

[0026] Preferably, the refining process further includes adding lime powder for desulfurization.

[0027] Preferably, the CaO content of the lime powder is ≥90 wt.%.

[0028] Preferably, the activity of the lime powder is ≥350mL / 50g.

[0029] Preferably, the proportion of lime powder with a particle size of 10-40mm is ≥90%.

[0030] Preferably, the amount of lime powder added is 100-300 kg / furnace, such as 100 kg / furnace, 130 kg / furnace, 150 kg / furnace, 180 kg / furnace, 200 kg / furnace, 230 kg / furnace, 250 kg / furnace, 280 kg / furnace, or 300 kg / furnace, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0031] It is worth noting that the refining process described in this invention involves adding aluminum granules and silicon carbide during smelting to perform slag surface diffusion deoxidation, ensuring that the FeO+MnO content in the slag is ≤1.0%. It also includes adding lime powder for desulfurization. The refining process in the rare earth alloy steel preparation method of this invention also includes deoxidation and desulfurization, which helps control the S content in the molten steel to ≤0.008 wt.% and the O content to ≤0.0015 wt.%, thereby facilitating subsequent rare earth alloying and solving the technical problem of the castability of rare earth alloy steel.

[0032] It is worth noting that the S content ≤ 0.008 wt.% and O content ≤ 0.0015 wt.% of the molten steel obtained from smelting refers to the S content ≤ 0.008 wt.% and O content ≤ 0.0015 wt.% after refining. As a preferred technical solution of the present invention, the molten iron is subjected to inclusion modification treatment after smelting and before rare earth alloying.

[0033] Preferably, the inclusion modification treatment includes adding silicon-calcium wire to the molten iron for calcium treatment, so that the deoxidation product Al2O3 of aluminum during the smelting process is modified.

[0034] As a preferred technical solution of the present invention, the timing of rare earth alloying is controlled after the smelting is completed and before the ladle is hoisted, for example, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min or 10 min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0035] It is worth noting that the method for preparing rare earth alloy steel described in this invention further controls the timing of rare earth alloying using rare earth iron alloys, which can greatly improve the absorption rate of rare earth alloys while avoiding the formation of large particles of rare earth compounds.

[0036] Preferably, in the rare earth alloying process, the rare earth ferroalloy is added to the argon blowing point of the ladle.

[0037] Preferably, after rare earth alloying, the argon flow rate is adjusted to 20-180 NL / min, for example, 20 NL / min, 30 NL / min, 40 NL / min, 50 NL / min, 60 NL / min, 70 NL / min, 80 NL / min, 90 NL / min, 100 NL / min, 110 NL / min, 120 NL / min, 130 NL / min, 140 NL / min, 150 NL / min, 160 NL / min, 170 NL / min, or 180 NL / min. Adjust the argon pressure to 0.185-0.3 MPa, such as 0.185 MPa, 0.195 MPa, 0.205 MPa, 0.215 MPa, 0.225 MPa, 0.235 MPa, 0.245 MPa, 0.255 MPa, 0.265 MPa, 0.275 MPa, 0.285 MPa, 0.295 MPa, or 0.3 MPa, to ensure that the slag surface fluctuates slightly and does not churn. Exposed molten steel is strictly prohibited. However, this is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0038] As a preferred technical solution of the present invention, in the rare earth alloying, the amount of rare earth ferroalloy added is 0.06-0.15 kg / ton of steel, such as 0.06 kg / ton of steel, 0.07 kg / ton of steel, 0.08 kg / ton of steel, 0.09 kg / ton of steel, 0.1 kg / ton of steel, 0.11 kg / ton of steel, 0.12 kg / ton of steel, 0.13 kg / ton of steel, 0.14 kg / ton of steel, or 0.15 kg / ton of steel, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0039] It is worth noting that the method for preparing rare earth alloy steel described in this invention further controls the amount of rare earth ferroalloy added to avoid the generation of high-melting-point rare earth inclusions, thus avoiding any impact on the performance and castability of the steel product, and facilitating control and application in actual production. In addition, rare earth ferroalloys are not allowed to be stored at high temperatures, and each furnace needs to be accurately weighed before addition. The amount of rare earth ferroalloy added is 0.06-0.15 kg / ton of steel, depending on the amount of molten steel in each furnace.

[0040] As a preferred technical solution of the present invention, in the rare earth alloying process, the sulfur content in the molten steel is controlled, and the overall RE / S ratio is controlled at 2-4%.

[0041] As a preferred technical solution of the present invention, the continuous casting is a continuous casting with full protection, and the ladle nozzle is closed before slag is discharged from the ladle.

[0042] As a preferred technical solution of the present invention, the preparation method includes: smelting molten iron, alloying it with rare earth elements, and continuously casting it to obtain rare earth alloy steel.

[0043] The molten steel obtained from the smelting process is controlled to have an S content ≤0.008 wt.% and an O content ≤0.0015 wt.%. The smelting process includes sequential converter steelmaking and refining. A deep deoxidizer is added during the tapping process in the converter steelmaking; the deep deoxidizer includes aluminum ingots, and the amount of aluminum ingots added is 40-100 kg / heat. Lime and refining slag are also added during the tapping process in the converter steelmaking process for slag washing to accelerate slag formation; the amount of lime added is 500 kg / heat, and the amount of refining slag added is 300 kg / heat. The composition of the refining slag is controlled as follows: CaO content ≥49 wt.%, MgO content ≤1.5 wt.%, SiO2 content ≤1.5 wt.%, and Al2O3 content ≥40%. The final sulfur content in the converter steelmaking process is 0.050-0.080 wt.%. The refining process includes the addition of diffusion deoxidizing materials; the diffusion deoxidizing materials include aluminum granules and silicon carbide; the amount of aluminum granules added is 20-50 kg / heat, and the amount of silicon carbide added is 50-70 kg / heat; the goal of adding diffusion deoxidizing materials is to make the total content of FeO and MnO in the top slag ≤1.0 wt.%. The refining process also includes the addition of lime powder for desulfurization; the CaO content of the lime powder is ≥90 wt.%; the activity of the lime powder is ≥350 mL / 50 g; the proportion of lime powder particles with a size of 10-40 mm is ≥90%; the amount of lime powder added is 100-300 kg / heat.

[0044] After the smelting and before the rare earth alloying, the molten iron is subjected to an inclusion modification treatment; the inclusion modification treatment includes adding silicon-calcium wire to the molten iron for calcium treatment, so that the deoxidation product Al2O3 of aluminum during the smelting process is modified.

[0045] The rare earth alloying includes: using a rare earth ferroalloy to alloy the molten steel obtained from the smelting; the timing of the rare earth alloying is controlled after the smelting is completed and 3-10 minutes before the ladle is hoisted; in the rare earth alloying, the rare earth ferroalloy is added to the argon blowing point of the ladle, the argon flow rate is adjusted to 20-180 NL / min, the argon pressure is adjusted to 0.185-0.3 MPa, ensuring that the slag surface fluctuates slightly, slag surface turbulence is not allowed, and exposed molten steel is strictly prohibited; in the rare earth alloying, the amount of rare earth ferroalloy added is 0.06-0.15 kg / ton of steel; in the rare earth alloying, the sulfur content in the molten steel is controlled, and the overall RE / S ratio is controlled at 2-4%;

[0046] The continuous casting process is a fully protected continuous casting process, with the ladle nozzle closed before slag is discharged from the ladle.

[0047] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0048] (1) The method for preparing rare earth alloy steel described in this invention improves the addition method of rare earth alloying, that is, rare earth ferroalloys are used to alloy the molten steel obtained by smelting. This can avoid the self-loss and physical and chemical damage caused by rare earth alloys in the production and alloying process. In particular, it can effectively solve the problem of pourability caused by the accumulation of rare earth inclusions blocking the nozzle during the smelting process of rare earth alloy steel, which is convenient for control and application in actual production.

[0049] (2) The method for preparing rare earth alloy steel described in this invention further controls the timing of rare earth alloying using rare earth iron alloys, which can greatly improve the absorption rate of rare earth alloys and avoid the formation of large particles of rare earth compounds.

[0050] (3) The method for preparing rare earth alloy steel described in this invention further controls the amount of rare earth ferroalloy added, avoids the generation of high melting point rare earth inclusions, avoids affecting the performance and castability of steel products, and facilitates control and application in actual production processes. Attached Figure Description

[0051] Figure 1 The diagram shows the change curve of the stopper opening degree corresponding to a single casting stream monitored in the preparation method described in Example 1;

[0052] Figure 2 The figure shows the crystallizer liquid level fluctuation curve corresponding to a single casting stream monitored in the preparation method described in Example 1;

[0053] Figure 3 The curve showing the change in stopper opening degree corresponding to a single casting stream monitored in the preparation method described in Comparative Example 1 is shown.

[0054] Figure 4The crystallizer liquid level fluctuation curve corresponding to a single casting stream monitored in the preparation method described in Comparative Example 1 is shown. Detailed Implementation

[0055] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0056] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0057] Example 1

[0058] This embodiment provides a method for preparing rare earth alloy steel, the method comprising: smelting molten iron sequentially, alloying it with rare earth elements, and continuously casting it to obtain rare earth alloy steel;

[0059] The molten steel obtained from the smelting process is controlled to have an S content ≤0.008 wt.% and an O content ≤0.0015 wt.%. The smelting process includes sequential converter steelmaking and refining. A deep deoxidizer is added during the tapping process in the converter steelmaking; the deep deoxidizer includes aluminum ingots, and the amount of aluminum ingots added is 60 kg / heat. Lime and refining slag are also added during the tapping process in the converter steelmaking for slag washing to accelerate slag formation; the amount of lime added is 500 kg / heat, and the amount of refining slag added is 300 kg / heat. The composition of the refining slag is controlled as follows: CaO content ≥49 wt.%, MgO content ≤1.5 wt.%, SiO2 content ≤1.5 wt.%, and Al2O3 content ≤1.5 wt.%. The final sulfur content of the converter steelmaking process is ≥40 wt.%; the refining process includes the addition of diffusion deoxidizing materials; the diffusion deoxidizing materials include aluminum granules and silicon carbide; the amount of aluminum granules added is 30 kg / heat, and the amount of silicon carbide added is 60 kg / heat; the goal of adding diffusion deoxidizing materials is to make the total content of FeO and MnO in the top slag ≤1.0 wt.%; the refining process also includes the addition of lime powder for desulfurization; the CaO content of the lime powder is ≥90 wt.%; the activity of the lime powder is ≥350 mL / 50 g; the proportion of lime powder particles with a size of 10-40 mm is ≥90%; the amount of lime powder added is 200 kg / heat;

[0060] After the smelting and before the rare earth alloying, the molten iron is subjected to an inclusion modification treatment; the inclusion modification treatment includes adding silicon-calcium wire to the molten iron for calcium treatment, so that the deoxidation product Al2O3 of aluminum during the smelting process is modified.

[0061] The rare earth alloying includes: using a rare earth ferroalloy to alloy the molten steel obtained from the smelting; the timing of the rare earth alloying is controlled after the smelting is completed and 5 minutes before the ladle is hoisted; in the rare earth alloying, the rare earth ferroalloy is added to the argon blowing point of the ladle, the argon flow rate is adjusted to 100 NL / min, the argon pressure is adjusted to 0.185 MPa, ensuring that the slag surface fluctuates slightly, slag surface turbulence is not allowed, and exposed molten steel is strictly prohibited; in the rare earth alloying, the amount of rare earth ferroalloy added is 0.1 kg / ton of steel; in the rare earth alloying, the sulfur content in the molten steel is controlled, and the overall RE / S ratio is controlled at 3%.

[0062] The continuous casting process is a fully protected continuous casting process, with the ladle nozzle closed before slag is discharged from the ladle.

[0063] Example 2

[0064] This embodiment provides a method for preparing rare earth alloy steel, the method comprising: smelting molten iron sequentially, alloying it with rare earth elements, and continuously casting it to obtain rare earth alloy steel;

[0065] The molten steel obtained from the smelting process is controlled to have an S content ≤0.008 wt.% and an O content ≤0.0015 wt.%. The smelting process includes sequential converter steelmaking and refining. A deep deoxidizer is added during the tapping process in the converter steelmaking; the deep deoxidizer includes aluminum ingots, and the amount of aluminum ingots added is 40 kg / heat. Lime and refining slag are also added during the tapping process in the converter steelmaking for slag washing to accelerate slag formation; the amount of lime added is 500 kg / heat, and the amount of refining slag added is 300 kg / heat. The composition of the refining slag is controlled as follows: CaO content ≥49 wt.%, MgO content ≤1.5 wt.%, SiO2 content ≤1.5 wt.%, and Al2O3 content ≤1.5 wt.%. The final sulfur content of the converter steelmaking process is ≥40 wt.%; the refining process includes the addition of diffusion deoxidizing materials; the diffusion deoxidizing materials include aluminum granules and silicon carbide; the amount of aluminum granules added is 20 kg / heat, and the amount of silicon carbide added is 50 kg / heat; the goal of adding diffusion deoxidizing materials is to make the total content of FeO and MnO in the top slag ≤1.0 wt.%; the refining process also includes the addition of lime powder for desulfurization; the CaO content of the lime powder is ≥90 wt.%; the activity of the lime powder is ≥350 mL / 50 g; the proportion of lime powder particles with a size of 10-40 mm is ≥90%; the amount of lime powder added is 100 kg / heat;

[0066] After the smelting and before the rare earth alloying, the molten iron is subjected to an inclusion modification treatment; the inclusion modification treatment includes adding silicon-calcium wire to the molten iron for calcium treatment, so that the deoxidation product Al2O3 of aluminum during the smelting process is modified.

[0067] The rare earth alloying includes: using a rare earth ferroalloy to alloy the molten steel obtained from the smelting; the timing of the rare earth alloying is controlled after the smelting is completed and 3 minutes before the ladle is hoisted; in the rare earth alloying, the rare earth ferroalloy is added to the argon blowing point of the ladle, the argon flow rate is adjusted to 20 NL / min, the argon pressure is adjusted to 0.185 MPa, ensuring that the slag surface fluctuates slightly, slag surface turbulence is not allowed, and exposed molten steel is strictly prohibited; in the rare earth alloying, the amount of rare earth ferroalloy added is 0.06 kg / ton of steel; in the rare earth alloying, the sulfur content in the molten steel is controlled, and the overall RE / S ratio is controlled at 2%.

[0068] The continuous casting process is a fully protected continuous casting process, with the ladle nozzle closed before slag is discharged from the ladle.

[0069] Example 3

[0070] This embodiment provides a method for preparing rare earth alloy steel, the method comprising: smelting molten iron sequentially, alloying it with rare earth elements, and continuously casting it to obtain rare earth alloy steel;

[0071] The molten steel obtained from the smelting process is controlled to have an S content ≤0.008 wt.% and an O content ≤0.0015 wt.%. The smelting process includes sequential converter steelmaking and refining. A deep deoxidizer is added during the tapping process in the converter steelmaking; the deep deoxidizer includes aluminum ingots, and the amount of aluminum ingots added is 100 kg / heat. Lime and refining slag are also added during the tapping process in the converter steelmaking for slag washing to accelerate slag formation; the amount of lime added is 500 kg / heat, and the amount of refining slag added is 300 kg / heat. The composition of the refining slag is controlled as follows: CaO content ≥49 wt.%, MgO content ≤1.5 wt.%, SiO2 content ≤1.5 wt.%, and Al2O3 content ≤0.0015 wt.%. The amount of FeO is ≥40 wt.%; the final S content of the converter steelmaking is 0.050-0.080 wt.%; the refining includes the addition of diffusion deoxidizing materials; the diffusion deoxidizing materials include aluminum granules and silicon carbide; the amount of aluminum granules added is 50 kg / heat, and the amount of silicon carbide added is 70 kg / heat; the goal of adding diffusion deoxidizing materials is to make the total content of FeO and MnO in the top slag ≤1.0 wt.%; the refining also includes the addition of lime powder for desulfurization; the CaO content of the lime powder is ≥90 wt.%; the activity of the lime powder is ≥350 mL / 50 g; the proportion of the lime powder with a particle size of 10-40 mm is ≥90%; the amount of lime powder added is 300 kg / heat;

[0072] After the smelting and before the rare earth alloying, the molten iron is subjected to an inclusion modification treatment; the inclusion modification treatment includes adding silicon-calcium wire to the molten iron for calcium treatment, so that the deoxidation product Al2O3 of aluminum during the smelting process is modified.

[0073] The rare earth alloying includes: using a rare earth ferroalloy to alloy the molten steel obtained from the smelting; the timing of the rare earth alloying is controlled after the smelting is completed and 10 minutes before the ladle is hoisted; in the rare earth alloying, the rare earth ferroalloy is added to the argon blowing point of the ladle, the argon flow rate is adjusted to 180 NL / min, the argon pressure is adjusted to 0.3 MPa, ensuring that the slag surface fluctuates slightly, slag surface turbulence is not allowed, and exposed molten steel is strictly prohibited; in the rare earth alloying, the amount of rare earth ferroalloy added is 0.15 kg / ton of steel; in the rare earth alloying, the sulfur content in the molten steel is controlled, and the overall RE / S ratio is controlled at 4%.

[0074] The continuous casting process is a fully protected continuous casting process, with the ladle nozzle closed before slag is discharged from the ladle.

[0075] Comparative Example 1

[0076] This comparative example provides a method for preparing rare earth alloy steel. The only difference from the method for preparing rare earth alloy steel described in Example 1 is that rare earth alloying is carried out by feeding rare earth wires into a continuous casting crystallizer.

[0077] Comparative Example 2

[0078] This comparative example provides a method for preparing rare earth alloy steel. Compared with the method for preparing rare earth alloy steel described in Example 1, the only difference is that the rare earth alloying is controlled at 2 minutes after the smelting is completed and before the ladle is hoisted.

[0079] Comparative Example 3

[0080] This comparative example provides a method for preparing rare earth alloy steel. Compared with the method for preparing rare earth alloy steel described in Example 1, the only difference is that the rare earth alloying is controlled at 12 minutes after the smelting is completed and before the ladle is hoisted.

[0081] Comparative Example 4

[0082] This comparative example provides a method for preparing rare earth alloy steel. Compared with the method for preparing rare earth alloy steel described in Example 1, the only difference is that the amount of rare earth ferroalloy added is 0.19 kg / ton of steel, and the overall RE / S ratio is 5%.

[0083] Comparative Example 5

[0084] This comparative example provides a method for preparing rare earth alloy steel. Compared with the method for preparing rare earth alloy steel described in Example 1, the only difference is that the amount of rare earth ferroalloy added is 0.03 kg / ton of steel, and the overall RE / S ratio is 1%.

[0085] The pourability problem caused by the accumulation and blockage of the injection nozzle in the preparation methods described in the above embodiments and comparative examples was characterized by the change curve of the stopper opening degree and the fluctuation curve of the liquid level in the crystallizer during the casting process. The specific results are summarized in Table 1.

[0086] Figure 1 The figure shows the change curve of the stopper opening degree corresponding to a single casting stream monitored in the preparation method described in Example 1. Figure 2 The diagram shows the crystallizer liquid level fluctuation curve corresponding to a single casting stream monitored in the preparation method described in Example 1. It can be seen that in the preparation method described in Example 1, the change trend of the stopper opening degree is stable, and the crystallizer liquid level fluctuation is normal (≤±3mm). This indicates that there is no problem of rare earth inclusions accumulating and blocking the nozzle in Example 1, and normal casting is possible.

[0087] Figure 3 The curve showing the change in stopper opening degree corresponding to a single casting stream monitored in the preparation method described in Comparative Example 1 is shown. Figure 4 The diagram shows the crystallizer liquid level fluctuation curve corresponding to a single casting stream monitored in the preparation method described in Comparative Example 1. It can be seen that in the preparation method of Comparative Example 1, the stopper opening degree changes drastically, and the crystallizer liquid level fluctuates severely, indicating that Comparative Example 1 has a problem of rare earth inclusions accumulating and blocking the nozzle, preventing normal casting. The reason for this is that rare earth alloying is performed in the continuous casting crystallizer by wire feeding. After the wire is fed in, the composition is not sufficiently homogenized, resulting in uneven content of rare earth elements at different locations on the billet. Simultaneously, the small aperture of the continuous casting crystallizer is not conducive to wire feeding, and the feeding process causes the liquid level in the crystallizer to churn, easily forming slag and causing secondary pollution to the molten steel.

[0088] Table 1

[0089] Example 1 The trend of change is gradual. Fluctuations are normal (≤±3mm) Normal pouring is possible Example 2 The trend of change is gradual. Fluctuations are normal (≤±3mm) Normal pouring is possible Example 3 The trend of change is gradual. Fluctuations are normal (≤±3mm) Normal pouring is possible Comparative Example 1 Dramatic changes Severe fluctuations Unable to pour normally Comparative Example 2 Dramatic changes Severe fluctuations Unable to pour normally Comparative Example 3 Dramatic changes Severe fluctuations Unable to pour normally Comparative Example 4 Dramatic changes Severe fluctuations Unable to pour normally Comparative Example 5 Dramatic changes Severe fluctuations Unable to pour normally

[0090] In summary, the method for preparing rare earth alloy steel described in this invention significantly improves the method of rare earth alloying by using rare earth ferroalloys to alloy the molten steel. This avoids the self-loss and physicochemical damage caused by rare earth alloys during production and alloying. In particular, it effectively solves the problem of rare earth inclusions accumulating and blocking the nozzle during the smelting process, thus improving castability and facilitating control and application in actual production. Furthermore, the method further controls the timing of rare earth alloying with rare earth ferroalloys, greatly improving the absorption rate of rare earth alloys while avoiding the formation of large rare earth compounds. Finally, the method further controls the amount of rare earth ferroalloy added, preventing the formation of high-melting-point rare earth inclusions and avoiding any impact on the steel product's performance and castability, further facilitating control and application in actual production.

[0091] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0092] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0093] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0094] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing rare earth alloy steel, characterized in that, The preparation method includes: smelting molten iron sequentially, alloying it with rare earth elements, and continuously casting it to obtain rare earth alloy steel. Wherein, the S content in the molten steel obtained by smelting is controlled to be ≤0.008wt.% and the O content is controlled to be ≤0.0015wt.%; the rare earth alloying includes: using rare earth ferroalloys to alloy the molten steel obtained by smelting with rare earth alloys; The rare earth alloying is controlled at the time after the smelting is completed and 3-10 minutes before the ladle is hoisted; during the rare earth alloying, the rare earth ferroalloy is added to the ladle argon blowing point; after the rare earth alloying, the argon flow rate is adjusted to 20-180 NL / min and the argon pressure is adjusted to 0.185-0.3 MPa. In the rare earth alloying process, the amount of rare earth ferroalloy added is 0.06-0.15 kg / ton of steel; in the rare earth alloying process, the sulfur content in the molten steel is controlled, and the overall RE / S ratio is controlled at 2-4%.

2. The preparation method according to claim 1, characterized in that, The smelting process includes sequential converter steelmaking and refining.

3. The preparation method according to claim 2, characterized in that, The converter steelmaking process involves adding a deep deoxidizer during the tapping process.

4. The preparation method according to claim 3, characterized in that, The deep deoxidizer includes aluminum ingots.

5. The preparation method according to claim 4, characterized in that, The amount of aluminum ingots added is 40-100 kg / furnace.

6. The preparation method according to claim 3, characterized in that, The converter steelmaking process also involves adding lime and refining slag for slag washing during the tapping process, thus forming slag in advance.

7. The preparation method according to claim 6, characterized in that, The amount of lime added is 500 kg / furnace.

8. The preparation method according to claim 6, characterized in that, The amount of refining slag added is 300 kg / furnace.

9. The preparation method according to claim 8, characterized in that, The composition control of the refining slag includes: CaO content ≥ 49 wt.%, MgO content ≤ 1.5 wt.%, SiO2 content ≤ 1.5 wt.%, and Al2O3 content ≥ 40 wt.%.

10. The preparation method according to claim 2, characterized in that, The final sulfur content of the converter steelmaking process is 0.050-0.080 wt.%.

11. The preparation method according to claim 2, characterized in that, The refining process includes the addition of diffusion deoxidizing materials.

12. The preparation method according to claim 11, characterized in that, The diffusion deoxidizing material includes aluminum particles and silicon carbide.

13. The preparation method according to claim 12, characterized in that, The amount of aluminum granules added is 20-50 kg / furnace.

14. The preparation method according to claim 12, characterized in that, The amount of silicon carbide added is 50-70 kg / furnace.

15. The preparation method according to claim 11, characterized in that, The goal of adding diffusion deoxidizing material is to ensure that the total content of FeO and MnO in the top slag is ≤1.0 wt.%.

16. The preparation method according to claim 11, characterized in that, The refining process also includes adding lime powder for desulfurization.

17. The preparation method according to claim 16, characterized in that, The lime powder contains ≥90 wt.% CaO.

18. The preparation method according to claim 16, characterized in that, The activity of the lime powder is ≥350mL / 50g.

19. The preparation method according to claim 16, characterized in that, The proportion of lime powder with a particle size of 10-40mm is ≥90%.

20. The preparation method according to claim 16, characterized in that, The amount of lime powder added is 100-300 kg / furnace.

21. The preparation method according to claim 1, characterized in that, After the smelting and before the rare earth alloying, the molten iron is subjected to inclusion modification treatment.

22. The preparation method according to claim 21, characterized in that, The inclusion modification treatment includes adding silicon-calcium wire to the molten iron for calcium treatment, so that the deoxidation product Al2O3 of aluminum during the smelting process is modified.

23. The preparation method according to claim 1, characterized in that, The continuous casting process is a fully protected continuous casting process, with the ladle nozzle closed before slag is discharged from the ladle.

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