A method for improving the preparation of inclusions in rare earth steel

Abstract

This invention relates to a method for preparing inclusions in rare earth steel, belonging to the field of iron and steel metallurgy technology. In the process of smelting rare earth steel, it can at least achieve one of the following technical objectives: easier and more stable deoxidation process, reduced risk of nozzle blockage, and reduced negative impact of inclusions on steel properties. The method involves aluminum deoxidation followed by barium treatment, and then the addition of rare earth elements during the rare earth steel smelting process. Detection of inclusions larger than the micrometer level in the rare earth steel prepared by this method shows that the percentage of brittle inclusion Al2O3 in the inclusions is in the range of 0.59% to 75%; the average size of the inclusions is in the range of 1.50 to 4.2 μm; and the number of inclusions is 13 to 43 per mm. 2 Within the range.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, and specifically relates to a method for improving inclusions in rare earth steel. Background Technology

[0002] Rare earth elements play a role in steel by modifying sulfides, refining grains, improving high-temperature performance, enhancing corrosion resistance, and improving processing performance. However, rare earth elements have a strong affinity for oxygen, and when added during smelting, they are easily consumed in large quantities during deoxidation, resulting in low yields and hindering their full potential in steel. Therefore, current rare earth steel smelting processes involve Al deoxidation before adding rare earth elements, or Al deoxidation followed by calcium treatment to reduce the oxygen content in the molten steel to extremely low levels, thus clearing the way for the addition of rare earth elements. However, when Al is used alone for deoxidation, a large amount of high-melting-point, solid Al2O3 clusters remain in the steel. These clusters affect the purity and casting performance of the steel (easily clogging the nozzle). More importantly, a significant portion of the subsequently added rare earth elements will modify the Al2O3 in the steel (because rare earth elements have a stronger affinity for oxygen), which will further deplete the rare earth elements. Since calcium reacts with solid Al2O3 to transform it into low-melting-point liquid calcium aluminate, using aluminum for deoxidation first, followed by calcium treatment, is a superior process compared to using aluminum alone for deoxidation.

[0003] Under current rare earth steel smelting processes, the main types of inclusions in steel are Al2O3, CaO, calcium aluminate, MnS, and rare earth oxides and sulfides, such as La-based La2O2S, La2O3, and La2S3. Among these, the presence of brittle inclusions like Al2O3 increases the risk of nozzle blockage during smelting and can become a crack initiation point during steel rolling, affecting steel performance. When using Ca treatment, the amount of Ca added must be precisely controlled; too little will result in incomplete Al2O3 modification, while too much will generate high-melting-point CaS or calcium aluminates, easily causing nozzle blockage. Furthermore, Ca has a low density (1.55 g / cm³) and a low boiling point (1491℃), reacting violently and uncontrollably in steel, easily causing secondary oxidation and the formation of large inclusions; the generation of large amounts of calcium vapor also has a significant adverse impact on the environment and the health of operators. It should be noted that inclusions in steel promote crack initiation and accelerate crack propagation, severely impairing the toughness and fatigue properties of the steel. Specifically, the fewer, smaller, more uniformly distributed, and more rounded the inclusions in steel, the less harmful they are to the performance, and vice versa; brittle inclusions usually have a greater negative impact on the performance of steel than ductile inclusions.

[0004] Therefore, given the current state of the technology, finding a rare earth steel smelting method with an easy-to-control and more stable preparation process, and with less harm to the steel properties caused by inclusions in the steel, has become a technological requirement. Summary of the Invention

[0005] To address the above technical requirements, this invention provides a method for improving the preparation of inclusions in rare earth steel. In the process of smelting rare earth steel, at least one of the following technical objectives can be achieved: the deoxidation process is easier to control and more stable, the risk of nozzle blockage is reduced, and the negative impact of inclusions on the performance of steel is minimized.

[0006] The objective of this invention is mainly achieved through the following technical solutions: This invention provides a method for improving inclusions in rare earth steel. In the process of smelting rare earth steel, aluminum is deoxidized and then treated with barium before rare earth is added.

[0007] Furthermore, in the barium treatment, the amount of barium added is 0.0020~0.1% of the mass of the rare earth steel.

[0008] Furthermore, after aluminum deoxidation, the residual total aluminum (Al) in the steel is in the range of 0.01% to 0.08%.

[0009] Furthermore, rare earth steel is steel containing 0.0020 to 0.05% rare earth by mass, wherein the rare earth is one or more of Ce, La, and Y.

[0010] Furthermore, the rare earth steel, by mass percentage, has the following composition: C: 0.10~0.16%, Si: 0.1~0.3%, Mn: 0.5~0.9%, Alt: 0.01~0.08%, P≤0.02%, S≤0.02%, TO≤0.005%, N≤0.005%, Cu: 0.25~0.55%, Cr: 0.40~0.80%, Ni≤0.65%, La: 0.0020~0.05%, with the balance being Fe and unavoidable impurities.

[0011] Furthermore, the preparation method for improving inclusions in rare earth steel includes the following steps: Step S1: Place pure iron into a crucible in a vacuum induction furnace, evacuate to 1~5 Pa, and heat to 1600~1650℃. Step S2: After the pure iron is melted and cleared, high-purity argon gas is introduced into the furnace until the pressure inside the furnace is 0.07~0.11 MPa. Then, according to the composition setting of rare earth steel, the carbon raiser and alloy metal, ferrosilicon and manganese metal, aluminum granules, barium blocks, and rare earth lanthanum are added in sequence. The entire feeding process is carried out with electromagnetic stirring, and the furnace is shaken immediately after each batch of materials is added. The carbon raiser and alloy metal are added at the same time, and the ferrosilicon and manganese metal are added at the same time. Step S3: After all the added alloy has melted, refine it and tap out the steel, then cast it into ingots.

[0012] Furthermore, in step S2, the time interval between the subsequent batch of material and the previous batch of material added sequentially is 2 to 4 minutes.

[0013] Furthermore, in step S2, the alloy metals include electrolytic copper, ferrochrome, and electrolytic nickel.

[0014] Furthermore, in step S2, the shaking amplitude of the furnace operation does not cause molten steel to overflow, and the duration is half a minute.

[0015] Furthermore, in step S3, refining involves letting it stand for 2-4 minutes.

[0016] Compared with the prior art, the present invention can achieve at least one of the following technical effects: (1) In the smelting of rare earth steel, after Al deoxidation, Ba treatment is used. The BaO generated by Ba deoxidation is easy to combine with Al2O3 to form large-sized, liquid composite inclusions BaO·Al2O3 at high temperature. These inclusions are very easy to aggregate and spheroidize in the molten steel to form larger spherical particles, which are then floated to the surface and removed. Following Stokes' law, the efficiency is extremely high, resulting in a reduction in the number and average size of inclusions larger than micrometers in the steel. The proportion of Al2O3 inclusions is greatly reduced, which reduces the risk of nozzle blockage during casting.

[0017] (2) In the preparation method of the present invention, after Al deoxidation, Ba treatment is used. After the barium is added to the steel, the reaction is stable and it is not easy to splash. Most of the Ba-containing inclusions float to the surface and are removed. Finally, the residual amount of Ba in the inclusions is extremely low, which reduces the risk of increasing the elemental composition of inclusions in the steel, further reduces the probability of the formation of composite inclusions, thereby reducing the uncertainty of the influence of inclusions on the steel properties and improving the process stability.

[0018] (3) The present invention adopts a specific alloy addition sequence and addition interval time. After Si and Mn are initially deoxidized, Al is deeply deoxidized, and Ba is supplemented for deoxidation, the oxygen content in the molten steel is reduced to an extremely low level, which provides a better condition for La to "appear" and play its role in modifying and altering inclusions.

[0019] (4) The detection of inclusions larger than micrometers in the rare earth steel prepared by the method of the present invention showed that the percentage of brittle inclusion Al2O3 in the inclusions was in the range of 0.59% to 75%, and the percentage of Al2O3 decreased with the increase of Ba and La added to the steel; the average size of the inclusions was in the range of 1.50 to 4.2 μm, and the average size of the inclusions decreased with the increase of Ba and La added to the steel; the number of inclusions was 13 to 43 per mm. 2 Within a certain range, and with the increase of Ba and La added to the steel, the number of inclusions shows a decreasing trend.

[0020] (5) The Ba treatment method of the present invention can spheroidize inclusions. The lanthanide inclusions in rare earth steel are spherical and smaller in size than those treated with Ca. Furthermore, the size of the inclusions tends to decrease further with the increase of the amount of treatment agent.

[0021] (6) The present invention performs electromagnetic stirring throughout the vacuum induction furnace smelting process, performs furnace shaking operation after the alloy is added, and performs static refining before tapping the steel, which provides favorable conditions for the removal of inclusions by floating. Attached Figure Description

[0022] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0023] Figure 1 is a SEM-EDS image of the lanthanide inclusions in Example 1; Figure 2 is a SEM-EDS image of the lanthanide inclusions in Example 2; Figure 3 is a SEM-EDS image of the lanthanide inclusions in Example 3; Figure 4 shows the SEM-EDS images of comparative Ca-Al system inclusions; Figure 5 shows the SEM-EDS images of comparative lanthanide inclusions. Detailed Implementation

[0024] The following detailed description of a method for improving inclusions in rare earth steel is provided in conjunction with specific embodiments. These embodiments are for comparative and illustrative purposes only, and the present invention is not limited to these embodiments.

[0025] Studies have shown that barium (Ba) has a slightly lower deoxidizing capacity than calcium (Ca) but a stronger capacity than aluminum (Al), and its desulfurization capacity is comparable to that of calcium (Ca). It also possesses comprehensive advantages such as high density (3.59 g / cm³), high boiling point (1640℃), and low vapor pressure (0.034 MPa). However, compared to existing mature and efficient steelmaking processes such as silicon-manganese deoxidation, aluminum deoxidation, and calcium treatment, barium-containing deoxidizers are not mainstream. Even when barium-containing deoxidizers are occasionally used, barium is usually not used as the primary deoxidizer alone, but rather as a component in composite deoxidizers, often combined with elements such as silicon, aluminum, and calcium, such as silicon-barium alloys, silicon-barium-aluminum alloys, silicon-calcium-barium alloys, and silicon-barium-calcium-aluminum alloys. Moreover, the mass percentage of barium in these alloys is usually below 20%, not a major component.

[0026] In view of this, the present invention applies barium as a major deoxidizer in the rare earth steel smelting process and proposes a method for improving the preparation of inclusions in rare earth steel. In the process of smelting rare earth steel, aluminum is used for deoxidation, followed by treatment with barium, and then rare earth is added.

[0027] Rare earth steel is steel containing 0.0020~0.05% rare earth elements by mass, where rare earth elements are one or more of Ce, La, Y, etc. Specifically, rare earth steel is rare earth weathering steel, with the following composition by mass percentage: C: 0.10~0.16%, Si: 0.1~0.3%, Mn: 0.5~0.9%, Alt: 0.01~0.08%, P≤0.02%, S≤0.02%, TO≤0.005%, N≤0.005%, Cu: 0.25~0.55%, Cr: 0.40~0.80%, Ni≤0.65%, La: 0.0020~0.05%, with the balance being Fe and unavoidable impurities.

[0028] After aluminum deoxidation, the residual aluminum (Al) in the steel is in the range of 0.01 to 0.08% by mass; the barium is metallic barium with a purity of 99.0% or higher, and the amount of barium added is 0.0020 to 0.1% of the mass of rare earth steel.

[0029] Micron-level inclusions were detected in the rare earth steel obtained by smelting. The results showed that the percentage of brittle inclusion Al2O3 in the inclusions ranged from 0.59% to 75%, and the Al2O3% decreased with the increase of Ba and La added to the steel. The Al2O3% and the content of added Ba and La roughly followed the relationship Al2O3% = {9004.81 ×

[10] 6 ×(Ba)] -0.5188 ×[10 6 ×(La)] -0.8761 The mathematical relationship between inclusion size and the percentage is as follows: The average size of inclusions ranges from 1.50 to 4.2 μm, and the average size of inclusions decreases with the increase of Ba and La added to the steel. The average size of inclusions and the content of added Ba and La roughly follow the relationship between inclusion size and percentage. 6 ×(Ba)+1]-0.0731×ln[10 6 The mathematical relationship is ×(La)+1]}μm. The number of inclusions is between 13 and 43 per mm. 2 Within a certain range, and with the increase of Ba and La added to the steel, the number of inclusions shows a decreasing trend. The number of inclusions and the content of added Ba and La roughly follow the relationship between the number of inclusions and the content of added Ba and La. 6 × (Ba)+10 6 × (La))]+8.72)} pieces / mm 2The mathematical relationship is as follows: In the above formula, (Ba) represents the mass percentage of Ba added relative to the rare earth steel, and (La) represents the mass percentage of La added relative to the rare earth steel; for example, if the amount of Ba added is 0.01%, then (Ba) is 0.0001, and if the amount of La added is 0.02%, then (La) is 0.0002. Furthermore, the lanthanide inclusions in the steel are spherical.

[0030] For vacuum induction furnace smelting, this method includes the following steps: Step S1: Place pure iron into a crucible in a vacuum induction furnace, evacuate to 1~5 Pa, and heat to 1600~1650℃. Step S2: After the pure iron is melted and cleared, high-purity argon gas is introduced into the furnace until the pressure inside the furnace is 0.07~0.11 MPa. Then, according to the composition setting of rare earth steel, the carbon raiser and alloy metal, ferrosilicon and metallic manganese, aluminum granules, barium blocks and rare earth lanthanum are added in sequence. The entire feeding process is carried out with electromagnetic stirring. After each batch of materials is added, the furnace is shaken immediately. The shaking amplitude should not cause the molten steel to overflow, and the duration is about half a minute. Step S3: After all the added alloy has melted, let it stand for 2-4 minutes to refine before tapping the steel and casting it into ingots.

[0031] Specifically, in step S1, the pure iron is industrial pure iron with an iron mass percentage of over 99.5%.

[0032] In step S2, the rare earth steel is rare earth weathering steel, and its composition by mass percentage is C: 0.10~0.16%, Si: 0.1~0.3%, Mn: 0.5~0.9%, Alt: 0.01~0.08%, P≤0.02%, S≤0.02%, TO≤0.005%, N≤0.005%, Cu: 0.25~0.55%, Cr: 0.40~0.80%, Ni≤0.65%, La: 0.0020~0.05%, with the balance being Fe and unavoidable impurities.

[0033] The raw materials are added sequentially, with a time interval of 2-4 minutes between each batch. That is, after the previous batch is added, wait 2-4 minutes before adding the next batch. First, the carbon raiser and alloy metals, including electrolytic copper, ferrochrome, and electrolytic nickel, are added simultaneously. 2-4 minutes later, ferrosilicon and metallic manganese are added simultaneously. Then, aluminum granules are added after 2-4 minutes; followed by barium blocks after 2-4 minutes; and finally, rare earth lanthanum is added after 2-4 minutes. Among them, the fixed carbon (dry basis) mass fraction in the carbon raiser is above 95%, and the composition refers to the relevant provisions of the industry standard YB / T 192-2015 "Carbon Raisers for Steelmaking"; the composition of electrolytic copper refers to the relevant provisions of the three grades listed in the national standard GB / T 467-2010 "Cathode Copper"; the ferrochrome is low-carbon ferrochrome, and the composition refers to the relevant provisions of the national standard GB / T 5683-2024 "Ferrochrome" regarding low-carbon ferrochrome; the composition of electrolytic nickel refers to the relevant provisions of the national standard GB / T6516-2025 "Electrolytic Nickel"; the ferrosilicon is high-purity ferrosilicon, and the composition refers to the relevant provisions of the national standard GB / T 2272-2020 "Ferrosilicon" regarding high-purity ferrosilicon; and the metallic manganese is electrolytic metallic manganese, and the composition refers to the industry standard YB / T According to the relevant provisions of 051-2023 "Electrolytic Manganese Metal"; aluminum granules are industrial pure aluminum with a purity of 98.8% or higher. The amount of aluminum added is related to the oxygen content and yield in the steel. After Al deoxidation, the residual total aluminum (Alt) in the steel is controlled within the range of 0.01~0.08%; barium blocks are metallic barium with a purity of 99.0% or higher. The amount of barium added is 0.0020~0.1% of the mass of rare earth steel; rare earth lanthanum is pure lanthanum or lanthanum-iron alloy. For example, pure lanthanum with a purity of 99.5% or higher or lanthanum-iron alloy with a mass percentage of 30% lanthanum is added according to a 50% yield.

[0034] It should be noted that in the vacuum furnace smelting of this invention, alloys are added roughly according to the oxygen affinity of the metal elements in the molten iron, from weakest to strongest. The order of oxygen affinity of the metal elements in the molten iron from weakest to strongest is copper, nickel, chromium, manganese, silicon, aluminum, barium, and lanthanum. Specifically, the carbon raiser and electrolytic copper, ferrochrome, and electrolytic nickel are added simultaneously first, then ferrosilicon and metallic manganese are added simultaneously after 2-4 minutes, and then aluminum granules, barium blocks, and rare earth lanthanum are added in sequence after 2-4 minutes.

[0035] Furthermore, a 20×20×5mm composition sample was taken from the bottom 1 / 4 and the edge 1 / 4 of the distance from the bottom of the smelted ingot. Oxygen and nitrogen samples of 5×7 mm and inclusion samples of 10×10×5 mm were used, and the inclusion samples were tested using Aspex and SEM-EDS.

[0036] The composition was analyzed using the ICP method, and oxygen and nitrogen were detected using an ONH-5500 oxygen and nitrogen analyzer. The composition and oxygen / nitrogen analysis results showed that the composition of the rare earth weathering steel was within the range defined in step S2. It should be noted that this invention achieves the control of harmful elements P, S, T, N, and other components in rare earth steel within the required range through raw material composition control, vacuum smelting atmosphere control, and deoxidizer addition control.

[0037] Inclusions of different particle sizes in steel have significantly different effects on steel properties. Generally, micrometers are used as the dividing line. Micrometer-sized inclusions larger than 1 μm, large inclusions, and ultra-large inclusions have a significant detrimental effect on steel properties, and the larger the size, the greater the detrimental effect. However, micrometer-sized inclusions smaller than 1 μm undergo a fundamental transformation, primarily having beneficial effects. Therefore, this invention only detects inclusions at the micrometer level and above.

[0038] Detection of inclusions at the micrometer level and above showed that the percentage of brittle inclusion Al2O3 in the inclusions ranged from 0.59% to 75%, and the Al2O3% decreased with the increase of Ba and La content added to the steel. The Al2O3% and the amount of added Ba and La roughly followed the relationship Al2O3% = {9004.81 ×

[10] } 6 ×(Ba)] -0.5188 ×[10 6 ×(La)] -0.8761 The mathematical relationship between inclusion size and the percentage is as follows: The average size of inclusions ranges from 1.50 to 4.2 μm, and the average size of inclusions decreases with the increase of Ba and La added to the steel. The average size of inclusions and the content of added Ba and La roughly follow the relationship between inclusion size and percentage. 6 ×(Ba)+1]-0.0731×ln[10 6 The mathematical relationship is ×(La)+1]}μm. The number of inclusions is between 13 and 43 per mm. 2 Within a certain range, and with the increase of Ba and La added to the steel, the number of inclusions shows a decreasing trend. The number of inclusions and the content of added Ba and La roughly follow the relationship between the number of inclusions and the content of added Ba and La. 6 × (Ba)+10 6 × (La))]+8.72)} pieces / mm 2The mathematical relationship is as follows: In the above formula, (Ba) represents the mass percentage of Ba added relative to the rare earth steel, and (La) represents the mass percentage of La added relative to the rare earth steel; for example, if the amount of Ba added is 0.01%, then (Ba) is 0.0001, and if the amount of La added is 0.02%, then (La) is 0.0002. Furthermore, the lanthanide inclusions in the steel are spherical.

[0039] Table 1 shows the standard Gibbs free energy data for possible reactions of Mn, Si, Al, Ba, La and O, S at 1600℃. As can be seen from Table 1, the stability of the deoxidation products, from strongest to weakest, is La₂O₂S, LaAlO₃, La₂O₃, BaO, Al₂O₃, SiO₂, MnO, indicating that their deoxidation capacity is La > Ba > Al > Si > Mn. The stability of the desulfurization products, from strongest to weakest, is La₂O₂S, La₂S₃, BaS, indicating that their desulfurization capacity is La > Ba > Mn. Combining the stability of the deoxidation and desulfurization products from strongest to weakest, the order is La₂O₂S, LaAlO₃, La₂O₃, La₂S₃, BaO, Al₂O₃, BaS, SiO₂, MnO.

[0040] Table 1 Standard Gibbs free energy (J / mol) of each chemical reaction at 1873 K

[0041] Based on the standard Gibbs free energy data and analysis of the chemical reactions in Table 1, under the conditions of this invention, by adopting a specific alloy addition sequence and interval, as the amount of Ba and La added to the steel increases, the average size and number of inclusions larger than micrometers decrease, and the proportion of Al2O3 inclusions significantly decreases. The core mechanism lies in a stepwise, controllable inclusion modification and purification process. First, ferromanganese and ferrosilicon complete preliminary deoxidation. Subsequently, the addition of aluminum particles achieves deep deoxidation, generating a large number of solid, high-melting-point Al2O3 initial inclusions. These nascent Al2O3 inclusions are small clusters or chains with a wide size distribution, and they are the main harmful inclusions that degrade the performance of steel. Compared with aluminum, barium has a stronger deoxidation ability, and its reaction is stable and less prone to splashing after being added to steel. However, Ba does not only perform simple supplementary deoxidation, but it can also "modify and remove" the already generated Al2O3. Specifically, BaO, generated from Ba deoxidation, readily combines with Al2O3 to form large-sized, liquid-at-high-temperature composite inclusions, BaO·Al2O3. These inclusions readily aggregate and spheroidize in molten steel, forming larger spherical particles that then float to the surface and are removed efficiently, following Stokes' law. This results in a reduction in the number and average size of micron-sized and larger inclusions in the steel, and a significant decrease in the proportion of Al2O3 inclusions. Furthermore, since the vast majority of Ba-containing inclusions float to the surface and are removed, the residual amount of Ba in the inclusions is extremely low, reducing the risk of increasing the elemental composition of inclusions in the steel. This further reduces the probability of composite inclusion formation, thereby reducing the uncertainty of the impact of inclusions on steel properties and improving process stability.

[0042] After initial deoxidation by Si and Mn, deep deoxidation by Al, and supplementary deoxidation by Ba, the oxygen content in the molten steel is reduced to an extremely low level, providing better conditions for La to better play its role in modifying and altering inclusions. Compared with the previously added deoxidizing elements, the last added rare earth element La has extremely strong deoxidation and desulfurization capabilities. After being added to the steel, it reacts with residual dissolved oxygen, sulfur, oxides, sulfides, and oxysulfides, such as BaO, Al2O3, BaS, SiO2, and MnO, to further purify the molten steel at an ultra-deep level. This generates inclusions such as La2O2S, La2O3, LaAlO3, and La2S3, which are less harmful to the steel and extremely stable, fine, and spherical. This further reduces the number and average size of inclusions larger than micrometers, as well as the proportion of brittle Al2O3 inclusions.

[0043] Furthermore, the present invention employs electromagnetic stirring throughout the vacuum induction furnace smelting process, performs furnace shaking operation after the alloy is added, and conducts static refining before tapping, providing favorable conditions for the removal of inclusions by flotation.

[0044] Example 1 A method for improving inclusions in rare earth steel involves deoxidizing aluminum, treating it with barium, and then adding rare earth elements during the rare earth steel smelting process.

[0045] The method includes the following steps: Step S1: Place 19.52 kg of pure iron into a crucible in a vacuum induction furnace, evacuate to 1 Pa, and heat to 1600 °C. The pure iron is industrial pure iron with an iron content of 99.5% by mass.

[0046] Step S2: After the pure iron is melted and cleared, high-purity argon gas is introduced into the furnace until the pressure inside the furnace is 0.07MPa. Then, according to the composition setting of rare earth steel, the carbon raiser and alloy metal, ferrosilicon and metallic manganese, aluminum granules, barium blocks and rare earth lanthanum are added in sequence. Electromagnetic stirring is carried out throughout the process. After each batch of materials is added, the furnace is shaken immediately. The shaking amplitude should not cause the molten steel to overflow, and the duration is half a minute. Rare earth steel is a rare earth weathering steel. Its composition by mass percentage is: C: 0.10~0.16%, Si: 0.1~0.3%, Mn: 0.5~0.9%, Alt: 0.01~0.08%, P≤0.02%, S≤0.02%, TO≤0.005%, N≤0.005%, Cu: 0.25~0.55%, Cr: 0.40~0.80%, Ni≤0.65%, La: 0.0020~0.05%, with the balance being Fe and unavoidable impurities. When preparing the mixture, the mass percentage is: C: 0.15%, Si: 0.2%, Mn: 0.7%, Alt: 0.04%, Cu: 0.40%, Cr: 0.60%, Ni: 0.30%, La: 0.0030%, with a total weight of 20 kg. First, 31g of carbon raiser and alloy metals are added simultaneously, including 80g of electrolytic copper, 218g of ferrochrome and 60g of electrolytic nickel; 3 minutes after addition, 53g of ferrosilicon and 140g of metallic manganese are added simultaneously; then 12g of aluminum granules are added after 3 minutes; then 1g of barium block is added after 3 minutes; then rare earth lanthanum is added after 3 minutes. The carbon raiser used is the FC95 grade carbon raiser specified in the industry standard YB / T 192-2015 "Carbon Raisers for Steelmaking," and its composition complies with the relevant provisions of the industry standard. The electrolytic copper uses standard copper No. 1 in the national standard GB / T 467-2010 "Cathode Copper," and its composition complies with the relevant provisions of the national standard. The ferrochrome is low-carbon ferrochrome, using the FeCr55C0.25Ⅱ type low-carbon ferrochrome specified in the national standard GB / T 5683-2024 "Ferrochrome," and its composition complies with the relevant provisions of the national standard. The electrolytic nickel uses the Ni9990 grade specified in the national standard GB / T 6516-2025 "Electrolytic Nickel," and its composition complies with the relevant provisions of the national standard. The ferrosilicon is high-purity ferrosilicon, using the GCFeSi75Ti0.02-B high-purity ferrosilicon specified in the national standard GB / T 2272-2020 "Ferrosilicon," and its composition complies with the relevant provisions of the national standard. The metallic manganese is electrolytic metallic manganese, using the industry standard YB / T... Electrolytic manganese of grade DJMnB in standard 051-2023 "Electrolytic Manganese Metal" has a composition that conforms to the relevant provisions of the industry standard; the aluminum granules are industrial pure aluminum with a purity of 99.0%; the barium blocks are metallic barium with a purity of 99.0%, and the amount of barium added is 0.0050% of the mass of rare earth steel; the rare earth lanthanum is a lanthanum-iron alloy with a lanthanum mass percentage of 30%, and 4 grams of lanthanum-iron alloy are added based on a 50% yield of rare earth lanthanum.

[0047] Step S3: After all the added alloy has melted, let it stand for 3 minutes to refine before tapping the steel and casting it into ingots.

[0048] A 20×20×5mm composition sample was taken from one-quarter of the way from the bottom and one-quarter of the way from the edge of the smelted ingot. Oxygen and nitrogen samples of 5×7 mm and inclusion samples of 10×10×5 mm were used, and the inclusion samples were tested using Aspex and SEM-EDS.

[0049] The composition was determined using the ICP method, and the oxygen and nitrogen were determined using an ONH-5500 oxygen and nitrogen analyzer. The composition and oxygen and nitrogen results showed that the composition of the rare earth weathering steel was within the range defined in step S2: P: 0.0029%, S: 0.0045%, TO: 0.0031%, N: 0.0027%.

[0050] Aspex analysis of inclusions at the micrometer level and above showed that the percentage of brittle inclusion Al2O3 in the inclusions was 33%. The Al2O3% and the content of added Ba and La followed the formula: Al2O3% = {9004.81 ×

[10] 6 ×(Ba)] -0.5188 ×[10 6 ×(La)] -0.8761 The mathematical relationship is as follows: The average size of the inclusions is 3.6 μm. The average size of the inclusions and the content of added Ba and La follow the formula: Inclusion average size = {6.4081 - 0.6357 × ln

[10] }. 6 ×(Ba)+1]-0.0731×ln[10 6 The mathematical relationship is ×(La)+1]}μm. The number of inclusions is 38 / mm. 2 The number of inclusions and the content of added Ba and La follow the formula: Inclusion number = {[9919.14 / (225.91+10)} 6 × (Ba)+10 6 × (La))]+8.72)} pieces / mm 2 The mathematical relationship is as follows. In the above formula, (Ba) is 0.00005 and (La) is 0.00006.

[0051] Figure 1 shows the SEM-EDS images of the lanthanide inclusions in this embodiment. The B and C sub-images in Figure 1 correspond to the energy dispersive spectroscopy (EDS) images of the locations shown in Figure A, respectively. The microstructure and chemical composition of the inclusions are shown in Table 2.

[0052] Example 2 A method for improving inclusions in rare earth steel involves deoxidizing aluminum, treating it with barium, and then adding rare earth elements during the rare earth steel smelting process.

[0053] The method includes the following steps: Step S1: Place 19.52 kg of pure iron into a crucible in a vacuum induction furnace, evacuate to 5 Pa, and heat to 1650 °C. The pure iron is industrial pure iron with an iron content of 99.5% by mass.

[0054] Step S2: After the pure iron is melted and cleared, high-purity argon gas is introduced into the furnace until the pressure inside the furnace is 0.11 MPa. Then, according to the composition setting of rare earth steel, the carbon raiser and alloy metal, ferrosilicon and metallic manganese, aluminum granules, barium blocks, and rare earth lanthanum are added in sequence. Electromagnetic stirring is carried out throughout the process, and the furnace is shaken immediately after each batch of materials is added. The shaking amplitude should not cause the molten steel to overflow, and the duration is half a minute. Rare earth steel is a rare earth weathering steel. Its composition by mass percentage is: C: 0.10~0.16%, Si: 0.1~0.3%, Mn: 0.5~0.9%, Alt: 0.01~0.08%, P≤0.02%, S≤0.02%, TO≤0.005%, N≤0.005%, Cu: 0.25~0.55%, Cr: 0.40~0.80%, Ni≤0.65%, La: 0.0020~0.05%, with the balance being Fe and unavoidable impurities. When preparing the mixture, the mass percentage is: C: 0.15%, Si: 0.2%, Mn: 0.7%, Alt: 0.04%, Cu: 0.40%, Cr: 0.60%, Ni: 0.30%, La: 0.0060%, with a total weight of 20 kg. First, 31g of carbon raiser and alloy metals are added simultaneously, including 80g of electrolytic copper, 218g of ferrochrome and 60g of electrolytic nickel; 2 minutes after addition, 53g of ferrosilicon and 140g of metallic manganese are added simultaneously; then 12g of aluminum granules are added after 2 minutes; then 2g of barium blocks are added after 2 minutes; and then rare earth lanthanum is added after 2 minutes. The carbon raiser used is the FC95 grade carbon raiser specified in the industry standard YB / T 192-2015 "Carbon Raisers for Steelmaking," and its composition complies with the relevant provisions of the industry standard. The electrolytic copper uses standard copper No. 1 in the national standard GB / T 467-2010 "Cathode Copper," and its composition complies with the relevant provisions of the national standard. The ferrochrome is low-carbon ferrochrome, using the FeCr55C0.25Ⅱ type low-carbon ferrochrome specified in the national standard GB / T 5683-2024 "Ferrochrome," and its composition complies with the relevant provisions of the national standard. The electrolytic nickel uses the Ni9990 grade specified in the national standard GB / T 6516-2025 "Electrolytic Nickel," and its composition complies with the relevant provisions of the national standard. The ferrosilicon is high-purity ferrosilicon, using the GCFeSi75Ti0.02-B high-purity ferrosilicon specified in the national standard GB / T 2272-2020 "Ferrosilicon," and its composition complies with the relevant provisions of the national standard. The metallic manganese is electrolytic metallic manganese, using the industry standard YB / T... Electrolytic manganese of grade DJMnB in standard 051-2023 "Electrolytic Manganese Metal" conforms to the relevant provisions of industry standards in terms of composition; aluminum granules are industrial pure aluminum with a purity of 99.0%; barium blocks are metallic barium with a purity of 99.0%, and the amount of barium added is 0.010% of the mass of rare earth steel; rare earth lanthanum is a lanthanum-iron alloy with a lanthanum mass percentage of 30%, and 8 grams of lanthanum-iron alloy are added based on a 50% yield of rare earth lanthanum.

[0055] Step S3: After all the added alloy has melted, let it stand for 2 minutes to refine before tapping the steel and casting it into ingots.

[0056] A 20×20×5mm composition sample was taken from one-quarter of the way from the bottom and one-quarter of the way from the edge of the smelted ingot. Oxygen and nitrogen samples of 5×7 mm and inclusion samples of 10×10×5 mm were used, and the inclusion samples were tested using Aspex and SEM-EDS.

[0057] The composition was determined using the ICP method, and the oxygen and nitrogen were determined using an ONH-5500 oxygen and nitrogen analyzer. The composition and oxygen and nitrogen results showed that the composition of the rare earth weathering steel was within the range defined in step S2: P: 0.0028%, S: 0.0039%, TO: 0.0023%, N: 0.0026%.

[0058] Aspex analysis of inclusions at the micrometer level and above showed that the percentage of brittle inclusion Al2O3 in the inclusions was 12%, and the Al2O3% and the content of added Ba and La followed the formula: Al2O3% = {9004.81 ×

[10] 6 ×(Ba)] -0.5188 ×[10 6 ×(La)] -0.8761 The mathematical relationship is as follows: The average size of the inclusions is 3.0 μm. The average size of the inclusions and the content of added Ba and La follow the formula: Inclusion average size = {6.4081 - 0.6357 × ln

[10] } 6 ×(Ba)+1]-0.0731×ln[10 6 The mathematical relationship is ×(La)+1]}μm. The number of inclusions is 31 / mm. 2 The number of inclusions and the content of added Ba and La follow the formula: Inclusion number = {[9919.14 / (225.91+10)} 6 × (Ba)+10 6 × (La))]+8.72)} pieces / mm 2 The mathematical relationship is as follows. In the above formula, (Ba) is 0.0001 and (La) is 0.00012.

[0059] Figure 2 shows the SEM-EDS images of the lanthanide inclusions in this embodiment. The B and C sub-images in Figure 2 correspond to the energy dispersive spectroscopy (EDS) images of the locations shown in Figure A, respectively. The microstructure and chemical composition of the inclusions are shown in Table 2.

[0060] Example 3 A method for improving inclusions in rare earth steel involves deoxidizing aluminum, treating it with barium, and then adding rare earth elements during the rare earth steel smelting process.

[0061] The method includes the following steps: Step S1: Place 19.52 kg of pure iron into a crucible in a vacuum induction furnace, evacuate to 3 Pa, and heat to 1625 °C. The pure iron is industrial pure iron with an iron content of 99.5% by mass.

[0062] Step S2: After the pure iron is melted and cleared, high-purity argon gas is introduced into the furnace until the pressure inside the furnace is 0.09 MPa. Then, according to the composition setting of rare earth steel, the carbon raiser and alloy metal, ferrosilicon and metallic manganese, aluminum granules, barium blocks, and rare earth lanthanum are added in sequence. Electromagnetic stirring is carried out throughout the process, and the furnace is shaken immediately after each batch of materials is added. The shaking amplitude should not cause the molten steel to overflow, and the duration is half a minute. Rare earth steel is a rare earth weathering steel. Its composition by mass percentage is: C: 0.10~0.16%, Si: 0.1~0.3%, Mn: 0.5~0.9%, Alt: 0.01~0.08%, P≤0.02%, S≤0.02%, TO≤0.005%, N≤0.005%, Cu: 0.25~0.55%, Cr: 0.40~0.80%, Ni≤0.65%, La: 0.0020~0.05%, with the balance being Fe and unavoidable impurities. When preparing the mixture, the mass percentage is: C: 0.15%, Si: 0.2%, Mn: 0.7%, Alt: 0.04%, Cu: 0.40%, Cr: 0.60%, Ni: 0.30%, La: 0.0060%, with a total weight of 20 kg. First, 31g of carbon raiser and alloy metals are added simultaneously, including 80g of electrolytic copper, 218g of ferrochrome and 60g of electrolytic nickel; 4 minutes after addition, 53g of ferrosilicon and 140g of metallic manganese are added simultaneously; then 12g of aluminum granules are added after 4 minutes; then 3g of barium blocks are added after 4 minutes; then rare earth lanthanum is added after 4 minutes. The carbon raiser used is the FC95 grade carbon raiser specified in the industry standard YB / T 192-2015 "Carbon Raisers for Steelmaking," and its composition complies with the relevant provisions of the industry standard. The electrolytic copper uses standard copper No. 1 in the national standard GB / T 467-2010 "Cathode Copper," and its composition complies with the relevant provisions of the national standard. The ferrochrome is low-carbon ferrochrome, using the FeCr55C0.25Ⅱ type low-carbon ferrochrome specified in the national standard GB / T 5683-2024 "Ferrochrome," and its composition complies with the relevant provisions of the national standard. The electrolytic nickel uses the Ni9990 grade specified in the national standard GB / T 6516-2025 "Electrolytic Nickel," and its composition complies with the relevant provisions of the national standard. The ferrosilicon is high-purity ferrosilicon, using the GCFeSi75Ti0.02-B high-purity ferrosilicon specified in the national standard GB / T 2272-2020 "Ferrosilicon," and its composition complies with the relevant provisions of the national standard. The metallic manganese is electrolytic metallic manganese, using the industry standard YB / T... Electrolytic manganese of grade DJMnB in standard 051-2023 "Electrolytic Manganese Metal" conforms to the relevant provisions of industry standards; the aluminum granules are industrial pure aluminum with a purity of 99.0%; the barium blocks are metallic barium with a purity of 99.0%, and the amount of barium added is 0.015% of the mass of rare earth steel; the rare earth lanthanum is a lanthanum-iron alloy with a lanthanum mass percentage of 30%, and 8 grams of lanthanum-iron alloy are added based on a 50% yield of rare earth lanthanum.

[0063] Step S3: After all the added alloy has melted, let it stand for 4 minutes to refine before tapping the steel and casting it into ingots.

[0064] A 20×20×5mm composition sample was taken from one-quarter of the way from the bottom and one-quarter of the way from the edge of the smelted ingot. Oxygen and nitrogen samples of 5×7 mm and inclusion samples of 10×10×5 mm were used, and the inclusion samples were tested using Aspex and SEM-EDS.

[0065] The composition was determined using the ICP method, and the oxygen and nitrogen were determined using an ONH-5500 oxygen and nitrogen analyzer. The composition and oxygen and nitrogen results showed that the composition of the rare earth weathering steel was within the range defined in step S2: P: 0.0026%, S: 0.0030%, TO: 0.0015%, N: 0.0025%.

[0066] Aspex analysis of inclusions at the micrometer level and above showed that the percentage of brittle inclusion Al2O3 in the inclusions was 10%. The Al2O3 percentage and the content of added Ba and La followed the formula: Al2O3% = {9004.81 ×

[10] 6 ×(Ba)] -0.5188 ×[10 6 ×(La)] -0.8761 The mathematical relationship is as follows: The average size of the inclusions is 2.87 μm. The average size of the inclusions and the content of added Ba and La follow the formula: Inclusion average size = {6.4081 - 0.6357 × ln

[10] } 6 ×(Ba)+1]-0.0731×ln[10 6 The mathematical relationship is ×(La)+1]}μm. The number of inclusions is 29 / mm. 2 The number of inclusions and the content of added Ba and La follow the formula: Inclusion number = {[9919.14 / (225.91+10)} 6 × (Ba)+10 6 × (La))]+8.72)} pieces / mm 2 The mathematical relationship is as follows. In the above formula, (Ba) is 0.00015 and (La) is 0.00012.

[0067] Figure 3 shows the SEM-EDS image of the lanthanide inclusions in this embodiment. The B sub-image in Figure 3 corresponds to the energy spectrum of the location shown in Figure A. The microstructure and chemical composition of the inclusions are shown in Table 2.

[0068] Comparative Example Compared with Example 1, the conventional deoxidation preparation method for rare earth steel uses the same raw materials, component ratios, P, S, T0, N control, and preparation process steps and parameters. The difference is that in this comparative example, after the addition of Al, Ba treatment is not used, but conventional Ca treatment is used. The amount of Ca added is 2g, which is 0.010% of the mass of rare earth steel. Lanthanum-iron alloy is then added after Ca.

[0069] The sampling and testing after smelting were exactly the same as in Example 1. The composition and oxygen-nitrogen test results showed that the composition of the rare earth weathering steel was within the defined range: P: 0.0031%, S: 0.0049%, TO: 0.0042%, N: 0.0028%.

[0070] Aspex analysis of inclusions at the micrometer scale and above showed that brittle inclusions, specifically Al2O3, accounted for 82.1% of the total inclusions, with an average inclusion size of 5.3 μm and a number of inclusions per mm. 2 .

[0071] Figure 4 shows the SEM-EDS images of the Ca-Al inclusions in this comparative example. Image B and image C in Figure 4 correspond to the energy dispersive spectroscopy (EDS) spectra of the sites shown in Image A, respectively. The microstructure and chemical composition of the inclusions are shown in Table 2. Figure 5 shows the SEM-EDS images of the lanthanide inclusions in this comparative example. Image B and image C in Figure 5 correspond to the EDS spectra of the sites shown in Image A, respectively. The microstructure and chemical composition of the inclusions are shown in Table 2.

[0072] For inclusions larger than the micrometer level in Examples 1-3 and the Comparative Example, the detection results using Aspex were compared. It can be seen that in the Ca-treated steel of the Comparative Example, the percentage of brittle inclusions Al2O3 in the inclusions was 82.1%, the average size of the inclusions was 5.3 μm, and the number of inclusions was 50 / mm. 2 In Examples 1-3, after treatment with Ba, as the Ba addition increased from 50 ppm to 150 ppm, the percentage of brittle Al2O3 inclusions in the steel decreased from 33% to 10%, the average inclusion size decreased from 3.6 μm to 2.87 μm, and the number of inclusions decreased from 38 per mm. 2 Reduced to 29 / mm 2 In Examples 1-3, the size and quantity of inclusions and the proportion of Al2O3 in the steel were all lower than those in the comparative example, and they showed a decreasing trend with the increase of Ba addition.

[0073] Table 2. Microstructure and chemical composition of inclusions in the examples and comparative examples.

[0074] Regarding the microstructure of the inclusions, as shown in Figure 2 and Table 2, the lanthanide inclusions in Examples 1-3 and the comparative example, as well as the Ca-Al inclusions in the comparative example, are all spherical. The inclusion diameters in Examples 1-3 are 3.3 μm, 1.6 μm, and 1.0 μm, respectively, all below 4.0 μm, and the inclusion diameter decreases with increasing dosage of the treatment agents (Ba, La). In contrast, the inclusion diameters in the comparative examples are 4.1 μm and 4.8 μm, both above 4.0 μm. This indicates that the Ba treatment method of the present invention can also spheroidize inclusions, and the inclusion size is smaller than that of the Ca treatment method. Furthermore, the inclusion size tends to decrease further with increasing dosage of the treatment agent, which is consistent with the Aspex detection results.

[0075] Since the chemical composition of rare earth steel is expressed as a mass percentage, to ensure consistency and ease of comparison, the chemical composition of inclusions obtained from energy dispersive spectroscopy (EDS) in Table 2, expressed as an atomic percentage, has been converted to a mass percentage. Regarding the chemical composition of the lanthanide inclusions in Examples 1-3, referring to Figures 1-3 and Table 2, it can be seen that no Ba element was detected in the lanthanide inclusions of Examples 1-3. The lanthanide inclusions in Figure A of Examples 1 and 2 consist of two parts: a smaller dark area and a larger bright area. EDS analysis shows that the dark area is an aluminum-containing lanthanide inclusion, and the bright area is an aluminum-free lanthanide inclusion. In the aluminum-containing lanthanide inclusions of Examples 1 and 2, the oxygen content is 20.7% and 7.7%, respectively, and the sulfur content is 2.4% and 2.1%, respectively, with the oxygen content higher than the sulfur content. The lanthanum content is 47.5% and 10.7%, respectively. In the aluminum-free lanthanide inclusions of Examples 1 and 2... The oxygen contents were 6.6% and 1.4%, respectively, and the sulfur contents were 9.5% and 11.1%, respectively, with the sulfur content being higher than the oxygen content. The lanthanum contents were 73.3% and 39.9%, respectively. Further comparison of these two parts of the lanthanide inclusions showed that the oxygen content in the aluminum-containing lanthanide inclusions was higher than that in the aluminum-free lanthanide inclusions, the sulfur content in the aluminum-free lanthanide inclusions was higher than that in the aluminum-containing lanthanide inclusions, and the lanthanum content in the aluminum-containing lanthanide inclusions was lower than that in the aluminum-free lanthanide inclusions.

[0076] The above indicates that after Al deoxidation followed by Ba treatment, the barium-containing inclusions generated floated fully into the slag, so no Ba element was detected in the inclusions remaining in the steel. This demonstrates that Ba treatment purifies the molten steel. It also shows that after Al deoxidation and Ba treatment, the oxygen content in the steel is extremely low. The addition of La does not primarily react with oxygen in the molten steel to form oxides, but rather reacts with existing oxides and S, such as Al2O3 and free S, to undergo modification reactions. Due to limitations in the dosage of the treatment agents (Ba, La) and metallurgical reactions, these reactions are incomplete. Therefore, aluminum-containing and non-aluminum-containing lanthanide inclusions coexist in the lanthanide inclusions, with the lanthanum content in the aluminum-containing inclusions being lower than that in the non-aluminum-containing inclusions. However, due to the extremely strong reducing properties of lanthanum, the non-aluminum-containing lanthanide inclusions already dominate in number, thus appearing as smaller dark areas and larger bright areas in the SEM image. Compared to the low concentration of solid inclusions Al2O3 and extremely low content of free O after Ba treatment, free S has the advantage of high concentration and free state in chemical reaction kinetics. The reaction between La and S can also proceed fully. Therefore, the oxygen content is higher than the sulfur content in aluminum-containing lanthanide inclusions, while the sulfur content is higher than the oxygen content in aluminum-free lanthanide inclusions. Correspondingly, the oxygen content is higher in aluminum-containing lanthanide inclusions than in aluminum-free lanthanide inclusions, and the sulfur content is higher in aluminum-free lanthanide inclusions than in aluminum-containing lanthanide inclusions.

[0077] Furthermore, comparing the lanthanide inclusions of Examples 1, 2, and 3, it was found that there was no dark portion in the lanthanide inclusions in Figure A of Example 3, and the area of ​​the dark portion in the lanthanide inclusions in Figure A of Example 2 was significantly smaller than that of Example 1. Energy dispersive spectroscopy (EDS) analysis showed that the aluminum and oxygen contents of the aluminum-containing lanthanide inclusions in the dark portion of the lanthanide inclusions in Example 1 were 19.2% and 20.7%, respectively; the aluminum and oxygen contents of the aluminum-containing lanthanide inclusions in the dark portion of the lanthanide inclusions in Example 2 were 7.2% and 7.7%, respectively; and the lanthanide inclusions in Example 3 did not contain any dark portion, that is, the aluminum and oxygen contents were both 0. It is evident that with the increase of Ba content or Ba+La content, the total amount of aluminum-containing lanthanide inclusions and the Al and O content in them both decrease. This indicates that since Ba and La have higher reducing properties than Al, they can effectively remove and reduce previously generated alumina inclusions, reducing Al2O3 brittle inclusions. This is consistent with the Aspex detection results.

[0078] The compositions of aluminum-free lanthanide inclusions in Examples 1, 2, and 3 were compared. In Example 1, the oxygen and sulfur contents in the aluminum-free lanthanide inclusions were 6.6% and 9.5%, respectively; in Example 2, they were 1.4% and 11.1%, respectively; and in Example 3, they were 2.6% and 11.6%, respectively. It is evident that with increasing Ba content or Ba+La content, the oxygen content in the aluminum-free lanthanide inclusions tends to decrease, while the sulfur content tends to increase. This indicates that with increasing Ba content or Ba+La content, the oxygen content in the steel decreases, and La gradually shifts from forming oxides to forming sulfides, thus better utilizing the role of modified sulfides. Meanwhile, the above data comparison also shows that when the Ba content increases from a low value and the Ba and La contents increase simultaneously, the effect of La metamorphic sulfides is more obvious, as seen in the comparison of the Ba and La addition amounts in Examples 1 and 2, and the corresponding oxygen and sulfur contents in the aluminum-free lanthanide inclusions. When the Ba content reaches a certain value and is further increased, and only Ba is increased while La is not, the marginal effect of this La metamorphic sulfide effect becomes lower and lower, as seen in the comparison of the Ba and La addition amounts in Examples 2 and 3, and the corresponding oxygen and sulfur contents in the aluminum-free lanthanide inclusions.

[0079] The composition of the Ca-Al and lanthanide inclusions in the comparative examples shows that after Al deoxidation and Ca treatment, all inclusions contain calcium. For example, Ca-Al inclusions contain approximately 30% Ca, and lanthanide inclusions contain approximately 10% Ca. This is completely different from the Ba treatment of the present invention, which does not contain Ba in the steel inclusions. This implicitly increases the elemental composition of inclusions in the steel, further increasing the probability of composite inclusion formation and the uncertainty of the inclusions' impact on steel properties. Therefore, improper control of the calcium treatment process can have a detrimental effect on the steel. Secondly, in the comparative example, 100 ppm of Ca was added, resulting in oxygen contents of 39.5% and 35.6% and sulfur contents of 1.0% and 1.7% in the Ca-Al inclusions; and oxygen contents of 9.1% and 7.2% and sulfur contents of 5.6% and 2.0% in the lanthanide inclusions. In Example 1 of the present invention, 50 ppm of Ba was added, resulting in oxygen and sulfur contents of 20.7% and 2.4% in the aluminum-containing lanthanide inclusions, and 6.6% and 9.5% in the aluminum-free lanthanide inclusions. The comparison shows that… In Example 1, the oxygen content of the aluminum-containing lanthanide inclusions was lower than that of the comparative Ca-Al inclusions, while the sulfur content was higher. Similarly, the oxygen content of the aluminum-containing lanthanide inclusions in Example 1 was lower than that of the comparative Ca-Al inclusions, and the sulfur content was higher. This demonstrates that even with only half the amount of Ba added for Ca treatment, the present invention still exhibits superior technical effects compared to the comparative example. It should be noted that the oxygen and sulfur content in the inclusions reflects the degree of deoxidation in the molten steel. Lower oxygen content in the molten steel results in lower oxygen content in the inclusions and correspondingly higher sulfur content, further reflecting the effect of rare earth modification and inclusion alteration.

[0080] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing improved rare earth steel containing inclusions, characterized in that, In the process of smelting rare earth steel, aluminum is deoxidized, then treated with barium, and then rare earth elements are added.

2. The method according to claim 1, characterized in that, In the barium treatment, the amount of barium added is 0.0020~0.1% of the mass of the rare earth steel.

3. The method according to claim 2, characterized in that, After the aluminum is deoxidized, the residual total aluminum (Alt) in the steel is in the range of 0.01% to 0.08%.

4. The method according to claim 3, characterized in that, The rare earth steel is steel containing 0.0020 to 0.05% rare earth by mass, wherein the rare earth is one or more of Ce, La, and Y.

5. The method according to claim 4, characterized in that, The rare earth steel, by mass percentage, comprises: C: 0.10~0.16%, Si: 0.1~0.3%, Mn: 0.5~0.9%, Alt: 0.01~0.08%, P≤0.02%, S≤0.02%, TO≤0.005%, N≤0.005%, Cu: 0.25~0.55%, Cr: 0.40~0.80%, Ni≤0.65%, La: 0.0020~0.05%, with the balance being Fe and unavoidable impurities.

6. The method according to claim 5, characterized in that, The method includes the following steps: Step S1: Place pure iron into a crucible in a vacuum induction furnace, evacuate to 1~5 Pa, and heat to 1600~1650℃. Step S2: After the pure iron is melted and cleared, high-purity argon gas is introduced into the furnace until the pressure inside the furnace is 0.07~0.11 MPa. Then, according to the composition setting of rare earth steel, the carbon raiser and alloy metal, ferrosilicon and manganese metal, aluminum granules, barium blocks, and rare earth lanthanum are added in sequence. The entire feeding process is carried out with electromagnetic stirring, and the furnace is shaken immediately after each batch of materials is added. The carbon raiser and alloy metal are added at the same time, and the ferrosilicon and manganese metal are added at the same time. Step S3: After all the added alloy has melted, refine it and tap out the steel, then cast it into ingots.

7. The method according to claim 6, characterized in that, In step S2, the time interval between the sequentially added subsequent batches and the preceding batches is 2 to 4 minutes.

8. The method according to claim 6, characterized in that, In step S2, the alloy metal includes electrolytic copper, ferrochrome, and electrolytic nickel.

9. The method according to claim 6, characterized in that, In step S2, the shaking amplitude of the furnace operation does not cause molten steel to overflow, and the duration is half a minute.

10. The method according to claim 6, characterized in that, In step S3, the refining process involves letting the mixture stand for 2-4 minutes.

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