A preparation method for increasing the proportion of solid solution rare earth in a rare earth weathering steel

Abstract

The application relates to a preparation method for improving the proportion of solid-solution rare earth in rare earth weathering-resistant steel, and belongs to the technical field of steel metallurgy, so as to achieve the technical target of improving the proportion of solid-solution rare earth in rare earth weathering-resistant steel. The preparation method for improving the proportion of solid-solution rare earth in rare earth weathering-resistant steel comprises the following steps: S1, putting pure iron into an MgO crucible, and placing the pure iron into a tubular resistance furnace, opening a cooling water switch, and sending electric power to heat the pure iron to 1600-1650 DEG C under the protection of argon gas; S2, after the pure iron is melted, sequentially adding carbonizing agents and alloy metals, ferrosilicon and metallic manganese, aluminum particles, barium blocks and rare earth according to the composition of the rare earth weathering-resistant steel; S3, after the alloy is completely melted, starting a cooling program, and cooling the alloy in the furnace to room temperature; the proportion of the solid-solution rare earth in the rare earth weathering-resistant steel accounts for 3-64% of the total amount of the rare earth in the steel in terms of mass percentage [RE] solid-solution %. The proportion of the solid-solution rare earth in the rare earth weathering-resistant steel accounts for 3-64% of the total amount of the rare earth in the steel in terms of mass percentage [RE] solid-solution %.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, and specifically relates to a method for increasing the proportion of solid-solution rare earth in rare earth weathering steel. Background Technology

[0002] Due to the strong affinity of rare earth elements for oxygen, under current rare earth steel smelting processes, the vast majority of rare earth elements in rare earth steel (usually exceeding 90%) exist as inclusions, with only a very small amount existing in solid solution form. These rare earth inclusions improve the toughness and fatigue resistance of the steel by purifying the molten steel and altering its morphology. The very small amount of rare earth elements dissolved in the matrix or enriched at grain boundaries enhances the steel's strength and / or improves its oxidation resistance, and / or enhances special properties such as corrosion resistance.

[0003] Rare earth weathering steel is a type of steel whose corrosion resistance is enhanced by adding rare earth elements (such as La). It is widely used in construction, bridges, and other fields. Rare earth elements in weathering steel enhance its atmospheric corrosion resistance by promoting the formation of a more stable, dense, and strongly adhering protective rust layer. Specifically, rare earth elements accumulate at the rust layer / matrix interface, promoting the formation of α-FeOOH in the rust layer, inhibiting the loose and harmful γ-FeOOH phase, and promoting the formation of alloying elements (such as Cu) in the rust layer. The uniform distribution of rare earth elements (Cr) forms a denser, continuous amorphous or nanocrystalline protective rust layer, effectively blocking the intrusion of water, oxygen, and corrosive media. Solid-solution rare earth elements refine grains, making the matrix structure more uniform, thus facilitating the formation of a thinner, more uniform initial rust layer. Solid-solution rare earth elements can alter the internal stress of the rust layer, significantly improving the adhesion between the rust layer and the steel substrate, preventing the rust layer from peeling off due to stress or thermal expansion and contraction, exposing a new substrate surface. At localized damage sites in the rust layer, enriched rare earth ions can preferentially migrate and form stable compounds, assisting in the rapid repair of the protective rust layer and enhancing its durability in harsh and alternating wet and dry environments. Solid-solution rare earth elements segregate at grain boundaries, inhibiting grain growth and refining hot-rolled and normalized grains. While increasing strength, they can significantly improve low-temperature toughness, which is particularly important for weathering steels used in cold regions (such as bridges and towers). Therefore, increasing the proportion of solid-solution rare earth elements in rare earth weathering steel is extremely beneficial for improving the corrosion resistance of the steel. Summary of the Invention

[0004] To address the above technical requirements, this invention provides a method for increasing the proportion of dissolved rare earth elements in rare earth weathering steel, thereby achieving the technical objective of increasing the proportion of dissolved rare earth elements in rare earth weathering steel.

[0005] The objective of this invention is mainly achieved through the following technical solutions: This invention provides a method for increasing the proportion of solid-solution rare earth elements in rare earth weathering steel, comprising the following steps: Step S1: Place pure iron into an MgO crucible and then into a tube furnace. Turn on the cooling water switch and pass in the protective gas argon. Heat the furnace to 1600~1650℃. Step S2: After the pure iron is melted and cleared, add the carbon raiser and alloy metal, ferrosilicon and manganese metal, aluminum granules, barium blocks, and rare earth elements in the following order according to the composition setting of rare earth weathering steel; 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 and been refined, start the cooling program and cool the furnace to room temperature. The percentage by mass of dissolved rare earth elements in rare earth weathering steel [RE] 固溶 The percentage ranges from 3% to 64%.

[0006] Furthermore, the S content in rare earth weathering steel is ≤0.0035%, and the TO content is ≤0.002%.

[0007] Furthermore, the rare earth weathering 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≤0.0035%, TO≤0.002%, N≤0.005%, Cu: 0.25~0.55%, Cr: 0.40~0.80%, Ni≤0.65%, RE: 0.0020~0.05%, where RE is one or more of Ce, La, and Y, and the balance is Fe and unavoidable impurities.

[0008] Furthermore, the rare earth weathering 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≤0.0035%, TO≤0.002%, N≤0.005%, Cu: 0.25~0.45%, Cr: 0.40~0.70%, Ni≤0.60%, La: 0.0020~0.05%.

[0009] Furthermore, in step S2, the amount of barium added is 0.0020~0.1% of the mass of rare earth steel.

[0010] Furthermore, in step S2, the time interval between the subsequent batch of material and the previous batch of material added sequentially is 4 to 6 minutes.

[0011] Furthermore, the mass percentage of dissolved rare earth elements in rare earth weathering steel [RE] 固溶 The percentage and the content of added Ba and La follow [RE]. 固溶%=[0.2479+6.9749×10 4 ×(Ba)+3.3851×10 4 ×(La)-1.74×10 7 ×(Ba) 2 -1.916×10 7 ×(Ba)(La)-3.01×10 6 The mathematical relationship is [×(La)²]%, where (Ba) represents the mass percentage of Ba added relative to rare earth steel, and (La) represents the mass percentage of La added relative to rare earth steel.

[0012] Furthermore, in step S1, the pressure of the argon gas is 0.02~0.05MPa.

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

[0014] Furthermore, in step S3, refining involves letting it stand for 4-6 minutes.

[0015] Compared with the prior art, the present invention can achieve at least one of the following technical effects: (1) 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, the number of rare earth inclusions is relatively reduced, and the relative content of solid solution rare earth is increased. Moreover, the S in the steel is ≤0.0035% and TO is ≤0.002%, which is at a low level.

[0016] (2) In the smelting of rare earth weathering 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 and removed. Following Stokes' law, the efficiency is extremely high, which leads to a significant reduction in Al2O3 inclusions before the addition of rare earth. This reduces the probability of rare earth further reacting with Al2O3 to form rare earth inclusions after the addition of rare earth, thereby increasing the proportion of solid-solid rare earth in the steel.

[0017] (3) The detection of the dissolved rare earth content in the rare earth weathering steel obtained by the present invention shows that the percentage of dissolved rare earth in the steel accounts for the total rare earth content in the steel [RE]. 固溶 The percentage ranges from 3% to 64%, and [RE] increases with the amount of Ba and La added to the steel. 固溶 The percentage shows an increasing trend. [RE] 固溶 The percentage and the content of added Ba and La generally follow [RE]. 固溶%=[0.2479+6.9749×10 4 ×(Ba)+3.3851×10 4 ×(La)-1.74×10 7 ×(Ba) 2 -1.916×10 7 ×(Ba)(La)-3.01×10 6 The mathematical relationship of [×(La)²]. Detailed Implementation

[0018] The following detailed description of a method for increasing the proportion of dissolved rare earth elements in rare earth weathering steel, with reference to specific embodiments, is provided. These embodiments are for comparative and illustrative purposes only, and the present invention is not limited to these embodiments.

[0019] Current rare earth weathering steel smelting processes involve Al deoxidation before adding rare earth elements, or Al deoxidation followed by calcium treatment. However, after rare earth elements are added, they easily mix with oxygen, sulfur, and Al₂O₃ generated during deoxidation, forming rare earth oxides, rare earth sulfides, rare earth sulfur oxides, and rare earth aluminate composite inclusions that float to the surface. This results in a low retention rate of dissolved rare earth elements in the steel, failing to fully utilize their potential. Therefore, modifying the deoxidation process before rare earth addition to reduce the consumption of rare earth elements by these inclusions and ultimately increase the proportion of dissolved rare earth elements in rare earth weathering steel is a viable research direction.

[0020] 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.

[0021] In view of this, the present invention applies barium as a major deoxidizer in the rare earth weathering steel smelting process, and proposes a preparation method to increase the proportion of solid-solution rare earth in rare earth weathering steel, comprising the following steps: Step S1: Place pure iron into an MgO crucible and then into a tube furnace. Turn on the cooling water switch and purge with protective argon gas to 0.02~0.05MPa. Then, heat the furnace to 1600~1650℃. Step S2: After the pure iron is melted and cleared, add the carbon raiser, alloy metal, ferrosilicon and manganese metal, aluminum granules, barium blocks and rare earth in the following order according to the composition setting of rare earth weathering steel. Step S3: After all the added alloy has melted, let it stand and refine for 4-6 minutes, then start the cooling program and cool it to room temperature with the furnace.

[0022] This invention employs a specific alloy addition sequence and interval. After initial deoxidation with Si and Mn, deep deoxidation with Al, and supplementary deoxidation with Ba, the oxygen content in the molten steel is reduced to an extremely low level, the number of rare earth inclusions is relatively reduced, thereby increasing the relative content of dissolved rare earths. Ultimately, this results in S ≤ 0.0035% and TO ≤ 0.002% in the steel, which are at a low level.

[0023] Specifically, in step S1, the pure iron is industrial pure iron with an iron mass percentage of over 99.5%.

[0024] In step S2, the rare earth weathering steel is composed of the following components 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≤0.0035%, TO≤0.002%, N≤0.005%, Cu: 0.25~0.55%, Cr: 0.40~0.80%, Ni≤0.65%, RE: 0.0020~0.05%, where rare earth RE is one or more of Ce, La, Y, etc., and the balance is Fe and unavoidable impurities.

[0025] Further optimization reveals that the rare earth weathering 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≤0.0035%, TO≤0.002%, N≤0.005%, Cu: 0.25~0.45%, Cr: 0.40~0.70%, Ni≤0.60%, La: 0.0020~0.05%, with the balance being Fe and unavoidable impurities.

[0026] The raw materials are added sequentially, with a time interval of 4-6 minutes between each batch. That is, after the previous batch is added, the next batch is added 4-6 minutes later. First, the carbon raiser and alloy metals, including electrolytic copper, ferrochrome, and electrolytic nickel, are added simultaneously. After 4-6 minutes, ferrosilicon and metallic manganese are added simultaneously. Then, aluminum granules are added after 4-6 minutes; followed by barium blocks after 4-6 minutes; and finally, rare earth lanthanum is added after 4-6 minutes. The carbon raiser contains a fixed carbon (dry basis) mass fraction of over 95% and a sulfur (dry basis) mass fraction of less than 0.2%, with composition conforming to the relevant provisions of industry standard YB / T 192-2015 "Carbon Raisers for Steelmaking"; the electrolytic copper contains S≤0.0025%, with the remaining components conforming to the relevant provisions of the three grades listed in national standard GB / T 467-2010 "Cathode Copper"; the ferrochrome is low-carbon ferrochrome, with composition conforming to the relevant provisions of national standard GB / T 5683-2024 "Ferrochrome" regarding low-carbon ferrochrome; the electrolytic nickel contains S≤0.001%, with the remaining components conforming to the relevant provisions of national standard GB / T 6516-2025 "Electrolytic Nickel"; and the ferrosilicon is high-purity ferrosilicon, with S≤0.01%, and the remaining components conforming to national standard GB / T The relevant provisions for high-purity ferrosilicon in 2272-2020 "Ferrosilicon"; metallic manganese is electrolytic metallic manganese, of which S≤0.03%, and the remaining components refer to the relevant provisions of industry standard YB / T051-2023 "Electrolytic Metallic Manganese"; 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, such as 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, rare earth lanthanum is added according to a 50% yield.

[0027] It should be noted that in the tubular resistance 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 rare earth elements, such as lanthanum. Specifically, the carburizing agent and electrolytic copper, ferrochrome, and electrolytic nickel are added simultaneously first. Then, ferrosilicon and metallic manganese are added simultaneously after 4-6 minutes. Finally, aluminum granules, barium blocks, and rare earth elements, such as lanthanum, are added in sequence after 4-6 minutes.

[0028] After the steel ingot has cooled down, take a 20×20×5mm composition sample from the steel ingot. A 5×7mm oxygen-nitrogen sample was used. Composition analysis included ICP testing of the total rare earth content in the steel and an ONH-5500 oxygen-nitrogen analyzer for oxygen-nitrogen analysis. The composition and oxygen-nitrogen test 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.

[0029] Furthermore, the steel ingot is rolled into a rolled product, and a 20×6.0×80mm phase analysis sample is taken from the rolled product. Using phase analysis, the sample is electrolyzed with an electrolyte to obtain precipitated phases. The rare earth content of rare earth inclusions in the precipitated phases is determined using ICP. Finally, the total rare earth content in the steel is subtracted from the rare earth content of the rare earth inclusions in the precipitated phases to obtain the solid solution amount of rare earths in the steel.

[0030] Phase analysis involves electrolyzing the sample using a 10 g / L lithium chloride + 10% (v / v, volume ratio) acetylacetone-methanol solution. After electrolysis, any remaining precipitated phase powder is directly brushed into a beaker using a 10 g / L citric acid-ethanol solution. The precipitated phase powder in the beaker, along with the powder from the anolyte, is then filtered through an imported microporous membrane (0.2 μm), washed, and dried. The filter membrane is also transferred into the beaker. HCl, HNO3, and HF are added to dissolve the sample, and the solution is diluted to 100 mL in a volumetric flask. The rare earth element content is then determined using ICP-AES. Specifically, the phase analysis method refers to the "Method for Accurate Determination of Rare Earth Sulfide and Rare Earth Sulfide Oxide Inclusions in Rare Earth Weathering Steel" disclosed in invention patent CN115711790B.

[0031] The content of dissolved rare earth elements in rare earth weathering steel obtained by smelting was tested. The test results showed that the percentage of dissolved rare earth elements in the steel accounted for a certain percentage of the total rare earth content. [RE] 固溶 The percentage ranges from 3% to 64%, and [RE] increases with the amount of Ba and La added to the steel. 固溶 The percentage shows an increasing trend. [RE] 固溶 The percentage and the content of added Ba and La generally follow [RE]. 固溶 %=[0.2479+6.9749×10 4 ×(Ba)+3.3851×10 4 ×(La)-1.74×10 7 ×(Ba) 2 -1.916×10 7 ×(Ba)(La)-3.01×10 6The mathematical relationship is [×(La)²]. 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; 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.

[0032] 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.

[0033] Table 1 Standard Gibbs free energy (J / mol) of each chemical reaction at 1873 K

[0034] Based on the standard Gibbs free energy data and analysis of the chemical reaction in Table 1, under the conditions of this invention, by adopting a specific alloy addition sequence and addition interval, as the amount of Ba and La added to the steel increases, the number of rare earth inclusions decreases relatively, thereby increasing the relative content of solid-solution rare earth. Its core mechanism lies in a stepwise and controllable inclusion modification and purification process.

[0035] First, ferromanganese and ferrosilicon complete the initial deoxidation. Then, the addition of aluminum particles achieves deep deoxidation, generating a large amount of solid, high-melting-point Al2O3 initial inclusions. Barium has a stronger deoxidizing ability than aluminum, and its reaction is stable and less prone to splashing after being added to steel. However, Ba does not merely perform simple supplementary deoxidation; it can also "modify and remove" the already generated Al2O3. Specifically, BaO, generated by Ba deoxidation, easily combines with Al2O3 to form large-sized, high-temperature liquid composite inclusions, BaO·Al2O3. These inclusions readily aggregate and spheroidize in molten steel, forming larger spherical particles that then float to the surface for removal, following Stokes' law with extremely high efficiency. This results in a significant reduction in Al2O3 inclusions before the addition of rare earth elements. Compared to the previously added deoxidizing elements, the last rare earth element added, La, possesses extremely strong deoxidizing and desulfurizing capabilities. Typically, after being added to steel, it reacts with residual dissolved oxygen, sulfur, oxides, sulfides, and oxysulfides, such as BaO, Al2O3, BaS, SiO2, and MnO. However, due to the initial deoxidation by Si and Mn, the deep deoxidation by Al, and the supplementary deoxidation by Ba, not only is the oxygen content in the molten steel reduced to an extremely low level, but the Ba treatment also significantly reduces BaO and Al2O3 inclusions. Therefore, the probability of La forming inclusions decreases, thus relatively increasing the content of dissolved rare earth elements in the steel.

[0036] This invention employs a specific alloy addition sequence and interval. After initial deoxidation with Si and Mn, deep deoxidation with Al, and supplementary deoxidation with Ba, the oxygen content in the molten steel is reduced to an extremely low level. Furthermore, the BaO generated by Ba deoxidation readily combines with Al2O3 to form large spherical particles, which are easier to float and remove. This reduces the probability of lanthanide inclusions being formed after the addition of La, increases the proportion of solid-dissolved rare earth elements in the steel, and ultimately results in S ≤ 0.0035% and TO ≤ 0.002% in the steel, which are at a low level.

[0037] Example 1 A method for increasing the proportion of dissolved rare earth elements in rare earth weathering steel, the method comprising the following steps: Step S1: Place 975 grams of pure iron into an MgO crucible, then place it into a tube furnace. Turn on the cooling water and purge with argon gas at 0.02 MPa. Heat the furnace to 1600°C. The pure iron is industrial pure iron with an iron content of 99.5% by mass. Step S2: After the pure iron is melted and cleared, add the carbon raiser, alloy metal, ferrosilicon and manganese metal, aluminum granules, barium blocks and rare earth lanthanum in the following order according to the composition setting of rare earth steel. Rare earth weathering 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≤0.0035%, TO≤0.002%, N≤0.005%, Cu: 0.25~0.45%, Cr: 0.40~0.70%, Ni≤0.60%, La: 0.0020~0.05%, with the balance being Fe and unavoidable impurities. It is prepared by mass percentage of C: 0.15%, Si: 0.2%, Mn: 0.7%, Alt: 0.04%, Cu: 0.35%, Cr: 0.60%, Ni: 0.30%, La: 0.0050%, with a total weight of 1 kg. First, 1.55g of carbon raiser and alloy metals were added simultaneously, including 3.5g of electrolytic copper, 10.9g of ferrochrome and 3g of electrolytic nickel; 4 minutes after addition, 2.65g of ferrosilicon and 7g of metallic manganese were added simultaneously; then 0.6g of aluminum granules were added 4 minutes later; then 0.10g of barium blocks were added 4 minutes later; and then rare earth lanthanum was added 4 minutes later. The recarburizer used is the FC95 grade recarburizer in the industry standard YB / T192-2015 "Recarburizer for Steelmaking", with a sulfur (dry basis) mass fraction below 0.2%, and its composition meets 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 meets the relevant provisions of the national standard; the ferrochrome is low-carbon ferrochrome, using the FeCr55C0.25Ⅱ type low-carbon ferrochrome in the national standard GB / T 5683-2024 "Ferrochrome", and its composition meets the relevant provisions of the national standard, with S≤0.0025%; the electrolytic nickel uses the national standard GB / T The nickel grade Ni9990 in standard 6516-2025 "Electrolytic Nickel" conforms to the relevant national standard, with S≤0.001%; ​​the ferrosilicon is high-purity ferrosilicon, using grade GCFeSi75Ti0.02-B high-purity ferrosilicon as specified in national standard GB / T2272-2020 "Ferrosilicon", with composition conforming to the relevant national standard, S≤0.01%; the metallic manganese is electrolytic metallic manganese, using grade DJMnA electrolytic manganese as specified in industry standard YB / T 051-2023 "Electrolytic Metallic Manganese", with composition conforming to the relevant industry standard, S≤0.03%; 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%, with the amount of barium added being 0.01% of the mass of rare earth steel; the rare earth lanthanum is a lanthanum-iron alloy with a lanthanum mass percentage of 30%, with 0.33 grams of lanthanum-iron alloy added based on a 50% yield of rare earth lanthanum.

[0038] Step S3: After all the added alloy has melted, let it stand and refine for 4 minutes, then start the cooling program and cool it to room temperature with the furnace.

[0039] After the steel ingot has cooled, take a 20×20×5mm composition sample from the steel ingot. A 5×7 mm oxygen-nitrogen sample was prepared. Composition was determined using ICP method, and oxygen-nitrogen analysis was performed using an ONH-5500 oxygen-nitrogen analyzer. The composition and oxygen-nitrogen analysis results showed that the rare earth weathering steel composition was within the range defined in step S2, specifically La: 0.0049%, P: 0.0029%, S: 0.0033%, TO: 0.0018%, and N: 0.0027%.

[0040] The steel ingot was rolled into a rolled product, and a 20×6.0×80mm phase analysis sample was taken from the rolled product. The phase analysis method was used, and the sample was electrolyzed with an electrolyte to obtain the precipitated phase. The rare earth inclusions in the precipitated phase were determined by ICP method, and the rare earth content was 44.1 ppm.

[0041] Phase analysis involves electrolyzing the sample using a 10 g / L lithium chloride + 10% (v / v, volume ratio) acetylacetone-methanol solution. After electrolysis, any remaining precipitated phase powder is directly brushed into a beaker using a 10 g / L citric acid-ethanol solution. The precipitated phase powder in the beaker, along with the powder from the anolyte, is then filtered through an imported microporous membrane (0.2 μm), washed, and dried. The filter membrane is also transferred into the beaker. HCl, HNO3, and HF are added to dissolve the sample, and the solution is diluted to 100 mL in a volumetric flask. The rare earth element content is then determined using ICP-AES. Specifically, the phase analysis method refers to the "Method for Accurate Determination of Rare Earth Sulfide and Rare Earth Sulfide Oxide Inclusions in Rare Earth Weathering Steel" disclosed in invention patent CN115711790B.

[0042] Finally, subtracting the rare earth content of the rare earth inclusions in the precipitated phase from the total rare earth content of 49 ppm in the steel, we obtain the solid solution content of rare earth in the steel as 4.9 ppm.

[0043] Percentage of solid-solution rare earth elements in the total rare earth content of steel [RE] 固溶 % is 10%; [RE] 固溶 The percentage and the content of added Ba and La follow the following: [RE] 固溶 %=[0.2479+6.9749×10 4 ×(Ba)+3.3851×10 4 ×(La)-1.74×10 7 ×(Ba) 2 -1.916×10 7 ×(Ba)(La)-3.01×10 6 The mathematical relationship is ×(La)²]%, where (Ba) is 0.0001 and (La) is 0.0001.

[0044] Example 2 A method for increasing the proportion of dissolved rare earth elements in rare earth weathering steel, the method comprising the following steps: Step S1: Place 975 grams of pure iron into an MgO crucible, then place it into a tube furnace. Turn on the cooling water and purge with argon gas at 0.05 MPa. Heat the furnace to 1650°C. The pure iron is industrial pure iron with an iron content of 99.5% by mass. Step S2: After the pure iron is melted and cleared, add the carbon raiser, alloy metal, ferrosilicon and manganese metal, aluminum granules, barium blocks and rare earth lanthanum in the following order according to the composition setting of rare earth steel. Rare earth weathering 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≤0.0035%, TO≤0.002%, N≤0.005%, Cu: 0.25~0.45%, Cr: 0.40~0.70%, Ni≤0.60%, La: 0.0020~0.05%, with the balance being Fe and unavoidable impurities. It is prepared by mass percentage of C: 0.15%, Si: 0.2%, Mn: 0.7%, Alt: 0.04%, Cu: 0.35%, Cr: 0.60%, Ni: 0.30%, La: 0.010%, with a total weight of 1 kg. First, 1.55g of carbon raiser and alloy metals were added simultaneously, including 3.5g of electrolytic copper, 10.9g of ferrochrome and 3g of electrolytic nickel; 6 minutes after addition, 2.65g of ferrosilicon and 7g of metallic manganese were added simultaneously; then 0.6g of aluminum granules were added after 6 minutes; then 0.2g of barium blocks were added after 6 minutes; and then rare earth lanthanum was added after 6 minutes. The recarburizer used is the FC95 grade recarburizer in the industry standard YB / T192-2015 "Recarburizer for Steelmaking", with a sulfur (dry basis) mass fraction below 0.2%, and its composition meets 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 meets the relevant provisions of the national standard; the ferrochrome is low-carbon ferrochrome, using the FeCr55C0.25Ⅱ type low-carbon ferrochrome in the national standard GB / T 5683-2024 "Ferrochrome", and its composition meets the relevant provisions of the national standard, with S≤0.0025%; the electrolytic nickel uses the national standard GB / T The nickel grade Ni9990 in standard 6516-2025 "Electrolytic Nickel" conforms to the relevant national standard, with S≤0.001%; ​​the ferrosilicon is high-purity ferrosilicon, using grade GCFeSi75Ti0.02-B high-purity ferrosilicon as specified in national standard GB / T2272-2020 "Ferrosilicon", with composition conforming to the relevant national standard, S≤0.01%; the metallic manganese is electrolytic metallic manganese, using grade DJMnA electrolytic manganese as specified in industry standard YB / T 051-2023 "Electrolytic Metallic Manganese", with composition conforming to the relevant industry standard, S≤0.03%; 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%, with the amount of barium added being 0.02% of the mass of rare earth steel; the rare earth lanthanum is a lanthanum-iron alloy with a lanthanum mass percentage of 30%, with 0.67 grams of lanthanum-iron alloy added based on a 50% yield of rare earth lanthanum.

[0045] Step S3: After all the added alloy has melted, let it stand and refine for 6 minutes, then start the cooling program and cool it to room temperature with the furnace.

[0046] After the steel ingot has cooled, take a 20×20×5mm composition sample from the steel ingot. A 5×7 mm oxygen-nitrogen sample was prepared. Composition was determined using ICP method, and oxygen-nitrogen analysis was performed using an ONH-5500 oxygen-nitrogen analyzer. The composition and oxygen-nitrogen analysis results showed that the rare earth weathering steel composition was within the range defined in step S2, specifically La: 0.010%, P: 0.0035%, S: 0.0032%, TO: 0.0015%, and N: 0.0031%.

[0047] The steel ingot was rolled into a rolled product, and a 20×6.0×80mm phase analysis sample was taken from the rolled product. The phase analysis method was used, and the sample was electrolyzed with an electrolyte to obtain the precipitated phase. The rare earth inclusions in the precipitated phase were determined to have a rare earth content of 81 ppm using the ICP method.

[0048] The phase analysis method is exactly the same as in Implementation 1. Finally, the total rare earth content in the steel is calculated by subtracting the rare earth content of the precipitated phase (81 ppm) from the total rare earth content in the steel (100 ppm), resulting in a solid solution content of 19 ppm for rare earths in the steel.

[0049] Percentage of solid-solution rare earth elements in the total rare earth content of steel [RE] 固溶 % is 19%; [RE] 固溶 The percentage and the content of added Ba and La follow the following: [RE] 固溶 %=[0.2479+6.9749×10 4 ×(Ba)+3.3851×10 4 ×(La)-1.74×10 7 ×(Ba) 2 -1.916×10 7 ×(Ba)(La)-3.01×10 6 The mathematical relationship is ×(La)²]%, where (Ba) is 0.0002 and (La) is 0.0002 in the above formula.

[0050] Example 3 A method for increasing the proportion of dissolved rare earth elements in rare earth weathering steel, the method comprising the following steps: Step S1: Place 975 grams of pure iron into an MgO crucible, then place it into a tube furnace. Turn on the cooling water and purge with 0.035 MPa of protective argon gas. Heat the furnace to 1625°C. The pure iron is industrial pure iron with an iron content of 99.5% by mass. Step S2: After the pure iron is melted and cleared, add the carbon raiser, alloy metal, ferrosilicon and manganese metal, aluminum granules, barium blocks and rare earth lanthanum in the following order according to the composition setting of rare earth steel. Rare earth weathering 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≤0.0035%, TO≤0.002%, N≤0.005%, Cu: 0.25~0.45%, Cr: 0.40~0.70%, Ni≤0.60%, La: 0.0020~0.05%, with the balance being Fe and unavoidable impurities. It is prepared by mass percentage of C: 0.15%, Si: 0.2%, Mn: 0.7%, Alt: 0.04%, Cu: 0.35%, Cr: 0.60%, Ni: 0.30%, La: 0.010%, with a total weight of 1 kg. First, 1.55g of carbon raiser and alloy metals are added simultaneously, including 3.5g of electrolytic copper, 10.9g of ferrochrome and 3g of electrolytic nickel; 5 minutes after addition, 2.65g of ferrosilicon and 7g of metallic manganese are added simultaneously; then 0.6g of aluminum granules are added after 5 minutes; then 0.3g of barium blocks are added after 5 minutes; and then rare earth lanthanum is added after 5 minutes. The recarburizer used is the FC95 grade recarburizer in the industry standard YB / T192-2015 "Recarburizer for Steelmaking", with a sulfur (dry basis) mass fraction below 0.2%, and its composition meets 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 meets the relevant provisions of the national standard; the ferrochrome is low-carbon ferrochrome, using the FeCr55C0.25Ⅱ type low-carbon ferrochrome in the national standard GB / T 5683-2024 "Ferrochrome", and its composition meets the relevant provisions of the national standard, with S≤0.0025%; the electrolytic nickel uses the national standard GB / T The nickel grade Ni9990 in standard 6516-2025 "Electrolytic Nickel" conforms to the relevant national standard, with S≤0.001%; ​​the ferrosilicon is high-purity ferrosilicon, using grade GCFeSi75Ti0.02-B high-purity ferrosilicon as specified in national standard GB / T2272-2020 "Ferrosilicon", with composition conforming to the relevant national standard, S≤0.01%; the metallic manganese is electrolytic metallic manganese, using grade DJMnA electrolytic manganese as specified in industry standard YB / T 051-2023 "Electrolytic Metallic Manganese", with composition conforming to the relevant industry standard, S≤0.03%; 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%, with the amount of barium added being 0.03% of the mass of rare earth steel; the rare earth lanthanum is a lanthanum-iron alloy with a lanthanum mass percentage of 30%, with 0.67 grams of lanthanum-iron alloy added based on a 50% yield of rare earth lanthanum.

[0051] Step S3: After all the added alloy has melted, let it stand and refine for 6 minutes, then start the cooling program and cool it to room temperature with the furnace.

[0052] After the steel ingot has cooled, take a 20×20×5mm composition sample from the steel ingot. A 5×7 mm oxygen-nitrogen sample was prepared. Composition was determined using ICP method, and oxygen-nitrogen analysis was performed using an ONH-5500 oxygen-nitrogen analyzer. The composition and oxygen-nitrogen analysis results showed that the rare earth weathering steel composition was within the range defined in step S2, specifically La: 0.009%, P: 0.0035%, S: 0.0029%, TO: 0.0014%, and N: 0.0030%.

[0053] The steel ingot was rolled into a rolled product, and a 20×6.0×80mm phase analysis sample was taken from the rolled product. The phase analysis method was used, and the sample was electrolyzed with an electrolyte to obtain the precipitated phase. The rare earth inclusions in the precipitated phase were determined to have a rare earth content of 67.4 ppm using the ICP method.

[0054] The phase analysis method is exactly the same as in Implementation 1. Finally, the total rare earth content in the steel is 22.6 ppm, which is obtained by subtracting the rare earth content of the rare earth inclusions in the precipitated phase from the total rare earth content in the steel (67.4 ppm).

[0055] Percentage of solid-solution rare earth elements in the total rare earth content of steel [RE] 固溶 % is 25%; [RE] 固溶 The percentage and the content of added Ba and La follow the following: [RE] 固溶 %=[0.2479+6.9749×10 4 ×(Ba)+3.3851×10 4 ×(La)-1.74×10 7 ×(Ba) 2 -1.916×10 7 ×(Ba)(La)-3.01×10 6 The mathematical relationship is ×(La)²]%, where (Ba) is 0.0003 and (La) is 0.0002.

[0056] Comparative Example Compared with Example 1, the conventional deoxidation preparation method for rare earth weathering 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 0.1g, which is 0.010% of the mass of rare earth weathering steel. Lanthanum-iron alloy is then added after Ca.

[0057] The sampling and testing after smelting were exactly the same as in Example 1. The composition and oxygen / nitrogen test results showed that La: 0.0050%, P: 0.0031%, S: 0.0035%, TO: 0.0028%, and N: 0.0028%. Except for the TO content exceeding the standard, the remaining components were all within the required range.

[0058] The phase analysis method is exactly the same as in Implementation 1. The sample is electrolyzed using an electrolyte to obtain the precipitated phase. The rare earth inclusions in the precipitated phase are determined to have a rare earth content of 49 ppm using ICP. Finally, the total rare earth content in the steel (50 ppm) is subtracted by the rare earth content of the inclusions in the precipitated phase (49 ppm) to obtain the solid solution amount of rare earth in the steel (1 ppm). The percentage of solid solution rare earth in the steel relative to the total rare earth content in the steel is then calculated. [RE] 固溶 % is 2%.

[0059] As shown in Examples 1-3 and the comparative example, with the increase of Ba addition from 100 ppm to 300 ppm and La addition from 100 ppm to 200 ppm, the total oxygen (TO) content in the steel decreased from 18 ppm to 14 ppm, and the sulfur content decreased from 33 ppm to 29 ppm, while the proportion of dissolved rare earth elements increased from 10% to 25%. In the comparative example without Ba addition, the total oxygen (TO) content was 28 ppm and the sulfur content was 35 ppm, both higher than in Examples 1-3, while the proportion of dissolved rare earth elements was only 2%, lower than in Examples 1-3. This indicates that the addition of Ba is beneficial for the removal of oxygen and sulfur from the steel, reduces the consumption of rare earth element La, and lays the foundation for increasing the proportion of dissolved rare earth elements. Moreover, this effect becomes more pronounced with the increase of Ba addition.

[0060] 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 increasing the proportion of dissolved rare earth elements in rare earth weathering steel, characterized in that, The method includes the following steps: Step S1: Place pure iron into an MgO crucible and then into a tube furnace. Turn on the cooling water switch and pass in the protective gas argon. Heat the furnace to 1600~1650℃. Step S2: After the pure iron is melted and cleared, add the carbon raiser and alloy metal, ferrosilicon and manganese metal, aluminum granules, barium blocks, and rare earth elements in the following order according to the composition setting of rare earth weathering steel; 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 and been refined, start the cooling program and cool the furnace to room temperature. The mass percentage of dissolved rare earth elements in the rare earth weathering steel [RE] 固溶 The percentage is in the range of 3% to 64%.

2. The method according to claim 1, characterized in that, The rare earth weathering steel contains S≤0.0035% and TO≤0.002%.

3. The method according to claim 2, characterized in that, The rare earth weathering 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≤0.0035%, TO≤0.002%, N≤0.005%, Cu: 0.25~0.55%, Cr: 0.40~0.80%, Ni≤0.65%, RE: 0.0020~0.05%, where RE is one or more of Ce, La, and Y, and the balance is Fe and unavoidable impurities.

4. The method according to claim 3, characterized in that, The rare earth weathering 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≤0.0035%, TO≤0.002%, N≤0.005%, Cu: 0.25~0.45%, Cr: 0.40~0.70%, Ni≤0.60%, La: 0.0020~0.05%.

5. The method according to claim 1, characterized in that, In step S2, the amount of barium added is 0.0020~0.1% of the mass of rare earth steel.

6. The method according to claim 1, characterized in that, In step S2, the time interval between the sequentially added subsequent batches and the preceding batches is 4 to 6 minutes.

7. The method according to claim 4, characterized in that, The mass percentage of dissolved rare earth elements in the rare earth weathering steel [RE] 固溶 The percentage and the content of added Ba and La follow [RE]. 固溶 %=[0.2479+6.9749×10 4 ×(Ba)+3.3851×10 4 ×(La)-1.74×10 7 ×(Ba) 2 -1.916×10 7 ×(Ba)(La)-3.01×10 6 The mathematical relationship is [×(La)²]%, where (Ba) represents the mass percentage of Ba added relative to rare earth steel, and (La) represents the mass percentage of La added relative to rare earth steel.

8. The method according to claim 1, characterized in that, In step S1, the pressure of the argon gas is 0.02~0.05MPa.

9. The method according to claim 1, characterized in that, In step S2, the alloy metal includes electrolytic copper, ferrochrome, and electrolytic nickel.

10. The method according to claim 1, characterized in that, In step S3, the refining process involves letting the mixture stand for 4-6 minutes.

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