Steelmaking aids, methods for their production and use, and methods for steelmaking

Abstract

The application discloses a steelmaking additive, a preparation method and application thereof, and a steelmaking method. The steelmaking additive is composed of elements with the following contents: Si 31-60 wt%, Fe 10-20 wt%, Al 5-15 wt%, Ca 5-25 wt% and O 5-15 wt%. The steelmaking additive is beneficial to reducing the end oxygen content of molten steel in a ladle, improving the silicon yield of molten steel in the ladle, improving the globularity of inclusions, and easily removing slag.

Description

Technical Field

[0001] This invention relates to a steelmaking additive, its preparation method and uses, and a steelmaking method. Background Technology

[0002] Deoxidation and alloying are crucial steps in the steelmaking process. Ferrosilicon (containing approximately 75% silicon) is one of the most widely used deoxidizers and alloying materials. Its function is to react silicon with dissolved oxygen in molten steel to generate silicon dioxide, thereby reducing the oxygen content and adjusting the silicon content in the steel to the level required for the target steel grade. However, using ferrosilicon for deoxidation still presents several problems: 1. Low deoxidation efficiency: The final oxygen content of ferrosilicon deoxidation is typically between 45 and 65 ppm, making deep deoxidation difficult. 2. Low silicon yield: Because ferrosilicon has a lower density than molten steel, it easily floats and oxidizes after addition, resulting in alloy waste. The silicon yield is typically only around 87%. 3. Poor inclusion morphology: The silicon dioxide deoxidation product has a high melting point and forms irregular shapes, easily agglomerating and difficult to remove, severely affecting the service life and toughness of the steel. 4. High cost: The production of ferrosilicon is an energy-intensive industry that cannot utilize monomeric silicon resources, resulting in high costs and failing to meet the requirements of green and low-carbon development.

[0003] CN114875197A discloses a process for controlling the type of inclusions in steel to improve the purity of molten steel. This method employs a self-designed refining slag system, controls the reaction intensity of the steel slag to promote the formation of magnesium-aluminum spinel inclusions in the steel, uses vacuum treatment to ensure efficient inclusion removal, and avoids calcium-induced deformation of inclusions in subsequent production processes, thus achieving stable and controllable oxygen content and inclusion size in the molten steel. However, this method is complex and costly. Furthermore, during the converter blowing process, ferrosilicon and aluminum blocks are still added for precipitation deoxidation, and calcium-aluminum-silicon-magnesium pre-melted refining slag is added, failing to fundamentally solve the problems of high oxygen content and unstable inclusion morphology in the molten steel.

[0004] CN117363837A discloses a method for deoxidation and alloying using silicon carbide. This method employs silicon carbide deoxidation and alloying, which is inexpensive. However, the silicon yield is only 75%, and it does not improve the deoxidation effect or inclusion stability of the molten steel. Furthermore, this method increases carbon dioxide emissions, failing to meet the environmental protection requirements of green and low-carbon practices.

[0005] CN120290822A discloses a deoxidizer for metal smelting and its preparation process. The deoxidizer is prepared by blending aluminum powder, silicon powder, titanium powder, zirconium powder, and carbon-coated lanthanum nanoparticles. Rapid deoxidation of aluminum and deep deoxidation of titanium and zirconium create a low-oxygen environment for selective inclusion modification of lanthanum, thereby reducing the oxygen content of the molten steel and achieving spheroidization modification of inclusions. However, the preparation process of this deoxidizer is complex and uses hazardous chemicals, resulting in high costs and environmental pollution. Furthermore, this deoxidizer does not improve silicon yield.

[0006] CN101857937A discloses a silicon-iron-aluminum high-pressure alloy ball and its processing technology. A mechanical high-pressure synthesis method is used to physically bond silicon-iron, aluminum particles, and iron powder together under the action of a binder. However, the silicon-iron-aluminum alloy bonded by physical methods has weak bonding strength, is easily dispersed, and seriously affects the stability of the steel.

[0007] CN109536727A discloses a method for preparing ferrosilicon-aluminum alloy by carbothermic reduction of fly ash. The method involves mixing fly ash with a reducing agent and additives to form pellets, followed by high-temperature reduction. This reduces the metal oxides in the fly ash to elemental forms, which then dissolve at high temperatures to generate the ferrosilicon-aluminum alloy. Summary of the Invention

[0008] One object of this invention is to provide a steelmaking aid. This aid can effectively remove dissolved oxygen from molten steel, reduce the final oxygen content, increase silicon yield, and improve the spheroidization rate of inclusions, making deoxidation products and impurities in the molten steel easier to float to the surface and form slag. Another object of this invention is to provide a method for preparing the steelmaking aid described above. This method is low in cost, low in energy consumption, and short in time, meeting the requirements of green and low-carbon development. A further object of this invention is to provide the use of the alloy described above in converter steelmaking. Using the alloy described above in converter steelmaking can reduce the final oxygen content of molten steel in the ladle, increase the silicon yield of molten steel in the ladle, and improve the spheroidization rate of inclusions. Yet another object of this invention is to provide a method for steelmaking.

[0009] The present invention achieves the above objectives through the following technical solutions.

[0010] On one hand, the present invention provides a steelmaking additive, which is composed of elements comprising the following contents:

[0011] Si 31~60wt%,

[0012] Fe 10~20wt%,

[0013] Al 5-15wt%,

[0014] Ca 5-25wt%, and

[0015] O 5~15wt%.

[0016] This invention also provides a steelmaking additive, which is composed of the following elements:

[0017] Si 40-55wt%,

[0018] Fe 12~19wt%,

[0019] Al 6-12 wt%,

[0020] Ca 8-15wt%,

[0021] The remainder consists of O and unavoidable impurities, with the O content being greater than or equal to 5 wt%.

[0022] The steelmaking additive according to the present invention preferably comprises elements with the following content:

[0023] Si 45-55wt%,

[0024] Fe 14~19wt%,

[0025] Al 7-9 wt%,

[0026] Ca 9-13 wt%,

[0027] The remainder consists of O and unavoidable impurities, with the O content being greater than or equal to 5 wt%.

[0028] On the other hand, the present invention provides a method for preparing the steelmaking additive as described above, comprising the following steps:

[0029] 1) Prepare raw materials: aluminum, calcium oxide, iron filings, and silicon powder;

[0030] 2) Heat the raw aluminum to melt it, and obtain molten aluminum liquid; add calcium oxide to the molten aluminum liquid to obtain the first molten liquid;

[0031] 3) Add iron filings and a portion of silicon powder to the first molten liquid in sequence to obtain the second molten liquid; then add another portion of silicon powder to the second molten liquid to obtain the third molten liquid; then add the remaining silicon powder to the third molten liquid to obtain the final molten liquid.

[0032] According to the preparation method of the present invention, preferably, in step 1), the average particle size of the raw material aluminum is 1-10 mm; the iron filings are turning shavings; the average particle size of the iron filings is 1-10 mm; and the average particle size of the silicon powder is less than 200 μm.

[0033] According to the preparation method of the present invention, preferably, in step 3), the mass of the portion of silicon powder accounts for 10-14 wt% of the total silicon powder mass, and the mass of the other portion of silicon powder accounts for 11-18 wt% of the total silicon powder mass.

[0034] According to the preparation method of the present invention, preferably, the temperature of the molten aluminum liquid is 560-800°C; the temperature of the first molten liquid is 800-890°C; the temperature of the second molten liquid is 850-930°C; and the temperature of the third molten liquid is 900-950°C.

[0035] According to the preparation method of the present invention, preferably, it further includes the following steps:

[0036] Under a protective atmosphere, the final melt is cooled in a mold to obtain a cooled product;

[0037] The cooled material is crushed to obtain a steelmaking additive with an average particle size of 10–80 mm.

[0038] In another aspect, the present invention provides the use of the steelmaking aid described above or the steelmaking aid obtained by the preparation method described above in reducing the final oxygen content of molten steel in a ladle, increasing the silicon yield of molten steel in a ladle, and increasing the inclusion spheroidization rate of molten steel in a ladle in converter steelmaking.

[0039] In another aspect, the present invention provides a steelmaking method, comprising the following steps: during the converter steelmaking process, molten steel is allowed to flow into a ladle, and when the amount of steel tapped from the converter reaches 1 / 4 to 1 / 2, the steelmaking additives described above are added to the molten steel in batches; wherein the tapping temperature of the converter is not lower than 1630°C.

[0040] The steelmaking aid of this invention can remove dissolved oxygen from molten steel, reduce oxide inclusions, lower the final oxygen content of molten steel in the ladle, improve deoxidation effect, and improve the quality of the obtained steel, reducing the final oxygen content to 20±3.0 ppm. Simultaneously, the steelmaking aid of this invention increases the silicon yield of molten steel. The silicon yield of molten steel in the ladle of this invention reaches 96.3±1.2% or higher. Furthermore, the steelmaking aid of this invention increases the spheroidization rate of inclusions in molten steel, making the slag formed during steelmaking easier to float and remove, thereby improving the service life of the obtained steel. The spheroidization rate of inclusions in molten steel in the ladle of this invention reaches 91.5±1.5% or higher. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0042] In converter steelmaking, replacing ferrosilicon with the steelmaking additives of the specific composition of this invention in existing technologies can significantly reduce the final oxygen content of molten steel in the ladle, increase silicon yield and inclusion spheroidization rate, and also reduce the amount of calcium oxide added in converter steelmaking, thus reducing slag volume. This invention not only improves the deoxidation efficiency of molten steel but also reduces costs, aligning better with the green and low-carbon development trend. Therefore, this invention is not a conventional choice.

[0043] Steelmaking additives

[0044] The steelmaking additive of the present invention can be used in the converter steelmaking process and can be added in the form of blocks, granules or powder.

[0045] The steelmaking additive of the present invention comprises elements in the following proportions: Si 31-60 wt%, Fe 10-20 wt%, Al 5-15 wt%, Ca 5-25 wt%, and O 5-15 wt%. Preferably, the steelmaking additive of the present invention comprises elements in the following proportions: Si 40-55 wt%, Fe 12-19 wt%, Al 6-12 wt%, Ca 8-15 wt%, with O and unavoidable impurities as the balance, wherein the O content is greater than or equal to 5 wt%. More preferably, the steelmaking additive of the present invention comprises elements in the following proportions: Si 45-55 wt%, Fe 14-19 wt%, Al 7-9 wt%, Ca 9-13 wt%, with O and unavoidable impurities as the balance, wherein the O content is greater than or equal to 5 wt%.

[0046] According to a specific embodiment of the present invention, the steelmaking additive of the present invention is composed of the following elements: Si 55wt%, Fe 18wt%, Al 9wt%, Ca 12wt%, O and unavoidable impurities 6wt% (wherein, the O content is greater than or equal to 5wt%). The unavoidable impurities may be one or more of K, Na, Mg, Mn, P, S, and Cl.

[0047] Si is the element silicon. Si is mainly used for deoxidation and silicon enrichment in steelmaking, and its deoxidation product is SiO2. In the steelmaking additive of this invention, the Si content can be 31-60 wt%, preferably 40-55 wt%, and more preferably 45-55 wt%. Such a Si content is more conducive to reducing the final oxygen content of the molten steel in the ladle, improving silicon yield and inclusion spheroidization rate. The Si in the steelmaking additive can come from one or more of high-purity silicon powder with a silicon content of ≥95% or high-purity photovoltaic waste such as monocrystalline silicon and polycrystalline silicon, preferably high-purity silicon powder. Individual silicon powder has a low density and high melting point; when directly added to molten steel, it easily floats, oxidizes, and has a low dissolution rate.

[0048] Fe is the element iron. Fe is mainly used to increase the density of steelmaking additives, allowing them to sink in molten steel and avoid floating at the steel-slag interface, while also reducing oxidation. Furthermore, the melting point of iron filings is close to that of molten steel, which is beneficial for heat conduction within the steelmaking additives and promotes the dissolution and diffusion of silicon, aluminum, etc., in the molten steel. In the steelmaking additive of this invention, the Fe content can be 10–20 wt%, preferably 12–19 wt%, and more preferably 14–19 wt%. Such a Fe content is more conducive to reducing the final oxygen content of the molten steel in the ladle, increasing silicon recovery and inclusion spheroidization rate. Fe can come from one or more of the following: iron filings generated during machining such as turning, milling, and planing; iron filings generated during mechanical casting, forging, and stamping; or iron filings generated during steel reinforcement processing in construction. These filings are then pickled and used in the production of the steelmaking additive of this invention.

[0049] Al is the element aluminum. Al is mainly used for deep deoxidation. In the steelmaking additive of this invention, the Al content can be 5-15 wt%, preferably 6-12 wt%, and more preferably 7-9 wt%. Such a content is more conducive to reducing the final oxygen content of molten steel in the ladle, improving silicon recovery and inclusion spheroidization rate. Al can be derived from elemental pure aluminum metal; it can also be derived from one or more of the following: scrap car wheel hubs, aluminum / aluminum alloy cables, or aluminum / aluminum alloy door and window scraps.

[0050] In this invention, Ca represents calcium and O represents oxygen. Ca and O are primarily derived from CaO (calcium oxide), which can be obtained from quicklime, ore, or directly purchased calcium oxide products. CaO is mainly used to adjust the basicity of slag, while calcium oxide can neutralize the acidic oxides produced by Si and Al deoxidation, preventing furnace lining erosion. Slag with high basicity has a strong ability to dissolve and capture silica and alumina, reducing inclusion content and the concentration of deoxidation products in the slag. In the steelmaking additive, the Ca content can be 5–25 wt%, preferably 8–15 wt%, more preferably 9–13 wt%; the O content can be 5–15 wt%, preferably 5–10 wt%, more preferably 5–8 wt%. Such Ca and O contents are more conducive to reducing the final oxygen content of molten steel in the ladle, increasing silicon recovery and inclusion spheroidization rate.

[0051] The raw materials for the steelmaking additive of the present invention can be mainly industrial waste. Such raw materials can not only meet the processing standards of molten steel in the converter steelmaking process, but also reduce waste and save energy.

[0052] <Preparation Methods of Steelmaking Additives>

[0053] The present invention provides a method for preparing a steelmaking additive, comprising the following steps: (1) preparing raw materials; (2) melting. Preferably, it further comprises (3) cooling and crushing.

[0054] The preparation method of this invention utilizes the exothermic reaction between the elements and controls the temperature of the molten liquid, allowing the elements to fuse together at a relatively low temperature. The steelmaking additive prepared in this way has a high binding energy. At the same time, it reduces costs and saves energy. A detailed description follows.

[0055] Steps for preparing raw materials

[0056] The raw materials prepared are aluminum, calcium oxide, iron filings, and silicon powder. The main raw materials of this invention are aluminum, calcium oxide, iron filings, and silicon powder. The aluminum has an average particle size of 1–10 mm, preferably 1–5 mm, and more preferably 3–5 mm. The purity of the aluminum is greater than or equal to 98%. The iron filings can be turning chips, with an average particle size of 1–10 mm, preferably 1–5 mm, and more preferably 3–5 mm. The purity of the iron filings is greater than or equal to 97%. The silicon powder has an average particle size of less than 200 μm, preferably less than or equal to 150 μm, and more preferably less than or equal to 100 μm. The purity of the silicon powder is greater than or equal to 95%. The purity of the calcium oxide is greater than or equal to 90%.

[0057] Melting step

[0058] The raw material aluminum is heated and melted to obtain molten aluminum liquid; calcium oxide is added to the molten aluminum liquid to obtain the first molten liquid; iron filings and a portion of silicon powder (denoted as the first silicon powder) are added to the first molten liquid in sequence to obtain the second molten liquid; then another portion of silicon powder (denoted as the second silicon powder) is added to the second molten liquid to obtain the third molten liquid; then the remaining silicon powder is added to the third molten liquid to obtain the final molten liquid.

[0059] In this invention, the temperature of the molten aluminum liquid can be 560–800°C, preferably 580–750°C, and more preferably 590–650°C. The temperature of the first molten liquid is 800–890°C, preferably 820–870°C, and more preferably 830–850°C. The temperature of the second molten liquid is 850–930°C, preferably 880–915°C, and more preferably 890–905°C. The temperature of the third molten liquid is 900–950°C, preferably 905–940°C, and more preferably 910–930°C.

[0060] Based on the total mass of silicon powder, the amount of the first silicon powder is 10-14 wt%, preferably 11-13 wt%, and more preferably 12-13 wt%. Based on the total mass of silicon powder, the amount of the second silicon powder is 11-18 wt%, preferably 13-17 wt%, and more preferably 14-16 wt%.

[0061] In the melting step of the present invention, the reaction is carried out under uniform stirring, and the stirring speed can be 100-300 rpm, preferably 150-250 rpm, and more preferably 170-210 rpm.

[0062] The stirring time for the first melt can be 1–8 min, preferably 2–6 min, and more preferably 3–5 min. The stirring time for the second melt can be 1–10 min, preferably 3–8 min, and more preferably 5–8 min. The stirring time for the third melt can be 5–15 min, preferably 8–15 min, and more preferably 12–15 min. The stirring time for the final melt can be 8–20 min, preferably 10–17 min, and more preferably 13–16 min.

[0063] In this invention, calcium oxide is added to molten aluminum, followed by iron filings, to ensure uniform temperature conduction in the first molten liquid. Simultaneously, silicon powder is added in stages, and through the aluminothermic reaction between the silicon powder and the molten aluminum, the silicon powder dissolves with minimal energy consumption.

[0064] The inventors of this application discovered that solid silicon powder particles disperse into the gaps of molten aluminum, forming a silicon-rich Al-Si eutectic wetting layer at the contact surface between the silicon powder and the molten aluminum. Through the aluminum-silicon eutectic reaction, the undissolved silicon particles encapsulated in the silicon-rich Al-Si eutectic wetting layer accelerate silicon dissolution. Simultaneously, the molten aluminum can penetrate the natural silica oxide film on the surface of the silicon powder, generating a competitive aluminothermic reaction at the microscopic level. An amorphous Al-Si-O transition layer with a thickness of 0.5–2 μm is formed at the solid-liquid interface. Aluminum atoms diffuse to the silica surface through lattice defects, forming the mesophase Al₂SiO₅. Controlled by solid-phase mass transfer, the diffusion activation energy of the system increases, further accelerating silicon dissolution.

[0065] This feeding sequence ensures that the high-melting-point silicon powder dissolves fully using relatively low energy. Furthermore, the steelmaking additive obtained under these temperature, dosage, stirring speed, and stirring time conditions is more conducive to reducing the final oxygen content in the molten steel in the ladle, increasing silicon yield, and improving the spheroidization rate of inclusions. This was achieved by the inventors through extensive experimental research and was not something easily conceived.

[0066] Cooling and crushing steps

[0067] Under a protective atmosphere, the final molten liquid is cooled in a mold to obtain a cooled material. The cooled material is then crushed to obtain a steelmaking additive with an average particle size of 10–80 mm.

[0068] In this invention, steelmaking additives are cooled and stored under a protective atmosphere. The protective atmosphere of this invention includes, but is not limited to, nitrogen or rare gases, including but not limited to helium, neon, argon, krypton, and xenon. Nitrogen is preferred. Such a protective atmosphere prevents the molten liquid from contacting oxygen in the air, thus avoiding oxidation. This is more conducive to reducing the final oxygen content of the molten steel in the ladle, increasing silicon yield, and improving the spheroidization rate of inclusions.

[0069] According to one specific embodiment of the present invention, the final molten liquid is poured into a mold under a nitrogen atmosphere and naturally cooled under a nitrogen atmosphere to obtain a cooled product.

[0070] In this invention, the steelmaking additive can be square blocks, cylindrical blocks, or spherical blocks, preferably square blocks. The average particle size of the steelmaking additive can be 10–80 mm, preferably 25–80 mm, and more preferably 28–60 mm. Such a particle size is more conducive to reducing the final oxygen content of molten steel in the ladle, increasing silicon yield, and improving the spheroidization rate of inclusions.

[0071] <Uses of Steelmaking Additives>

[0072] The present invention also provides the use of a steelmaking aid or a steelmaking aid obtained by the above preparation method in reducing the final oxygen content of molten steel in a ladle, increasing the silicon yield of molten steel in a ladle, and improving the inclusion morphology of molten steel in a ladle in converter steelmaking.

[0073] Using the steelmaking additives of this invention in converter steelmaking can reduce the final oxygen content of molten steel in the ladle to 20±3.0 ppm. During the deoxidation and alloying process, the silicon yield of the molten steel is significantly improved, with the silicon yield in the ladle increasing by more than 10% (i.e., the silicon oxidation loss rate decreasing by more than 10%). The silicon yield in the ladle of this invention is 96.3±1.2%.

[0074] Furthermore, in the calcium treatment process of this invention, calcium in the molten steel can react with manganese sulfide (MnS), transforming chain-like MnS inclusions into fine, spherical CaS-MnS composite inclusions. The diameter of these inclusions is reduced to 0.3–0.8 μm, and their aspect ratio is reduced to 1.2–2.0 (e.g., from 8:1 to 1.5:1). This increases the spheroidization rate of inclusions in the molten steel in the ladle, making slag removal easier. The spheroidization rate of inclusions in the molten steel in this invention reaches 91.5 ± 1.5%.

[0075] Compared with the traditional process (using ferrosilicon for converter steelmaking), the steelmaking additive of the present invention reduces the amount of CaO added during converter steelmaking, thereby reducing the amount of slag by more than 10% and maintaining the slag basicity in the range of 3.0 to 3.3, with its fluctuation range narrowed by more than 40%, which is more conducive to the stable control of the steelmaking process.

[0076] Methods of Steelmaking

[0077] The present invention also provides a steelmaking method, comprising the following steps:

[0078] During the converter steelmaking process, the molten steel flows into the ladle. When the amount of steel tapped from the converter reaches 1 / 4 to 1 / 2, steelmaking additives are added to the molten steel in batches. The tapping temperature of the converter is not lower than 1630℃.

[0079] In addition to the converter steelmaking step described above, the steelmaking method of the present invention may employ other processes known in the prior art, which will not be elaborated here.

[0080] The steelmaking additive in this invention can be added in two stages. The mass ratio of the two additions can be 7:3, 6:4, or 5:5.

[0081] This application reveals that the charging window when the steel volume reaches 1 / 4 (steel depth 1.2m, cooling rate 8-10℃ / second) is the key point for maximizing alloy efficiency. Missing this charging window will reduce silicon yield by more than 11%. Adding steelmaking additives when the steel volume is 1 / 4 increased the silicon yield by more than 4.2% compared to adding them when the steel volume is 1 / 3.

[0082] According to one specific embodiment of the present invention, 800 kg of steelmaking additives are added to a 100t converter for smelting. When the converter's tapping rate is 1 / 4 (i.e., the depth of molten steel in the ladle is 1.2 m) and the tapping temperature is not lower than 1630°C, 480 kg of steelmaking additives are added to the converter, and the temperature is controlled to decrease by no more than 5°C to ensure deoxidation. When the converter's tapping rate is 1 / 2 (i.e., the tapping temperature is not lower than 1630°C), the remaining 320 kg of steelmaking additives are added to the converter, and the temperature is controlled to decrease by no more than 5°C.

[0083] Such processing temperature and feeding window are more conducive to reducing the final oxygen content of molten steel in the ladle, increasing silicon yield and inclusion spheroidization rate.

[0084] <Testing Methods>

[0085] A rapid oxygen sensor was used to detect the final oxygen content of molten steel.

[0086] Silicon recovery rate in molten steel indicates the proportion of silicon element added during the steelmaking process that is effectively absorbed into the molten steel.

[0087] The following formula is used for calculation: Y 硅 = (C1−C0)×W s / W i ×δ i ,

[0088] Wherein, C1 is the silicon content (%) in the molten steel in the ladle; C0 is the silicon content (%) in the initial molten steel; W s W represents the net weight of molten steel (t). i The weight (kg) of steelmaking additives added; δ i The mass fraction (%) of silicon in steelmaking additives.

[0089] The silicon content in molten steel was determined using spectrophotometry.

[0090] The morphology of inclusions was observed using a scanning electron microscope, and the spheroidization rate of inclusions in molten steel was calculated by statistically analyzing the ratio of the number of spherical inclusions to the total number of inclusions.

[0091] The following explains the source of raw materials for the preparation example:

[0092] The raw aluminum comes from industrial waste aluminum, and the purity of the aluminum is 98%.

[0093] The iron filings are turning shavings, and the purity of the iron filings is 99%.

[0094] The raw material silicon powder is high-purity silicon powder, specifically with a purity of 95%.

[0095] Explanation of Q355B steel grade: Carbon structural steel is composed of Q + number + quality grade symbol, etc. Its steel grade is prefixed with "Q," representing the yield point of the steel, followed by a number indicating the yield point value in MPa. If necessary, a symbol indicating the quality grade and deoxidation method can be added after the steel grade. The quality grade symbols are A, B, C, and D.

[0096] Preparation Example - Preparation of Steelmaking Additives

[0097] Prepare the raw materials for steelmaking additives. The amount of raw material aluminum is 100 kg, the amount of calcium oxide is 120 kg, the amount of iron filings is 180 kg (the average particle size of the iron filings is 3 mm), and the amount of raw material silicon powder is 600 kg (the average particle size of the silicon powder is 75 μm).

[0098] Raw aluminum is heated to 600°C in a submerged arc furnace and stirred at 200 rpm for 30 minutes to obtain molten aluminum. The temperature is then increased to 850°C, and calcium oxide is added to the molten aluminum. The mixture is stirred at 200 rpm for 5 minutes to obtain the first molten liquid.

[0099] The first melt is heated to 900°C. Then, iron filings and a portion of silicon powder (referred to as the first silicon powder, accounting for 12.2 wt% of the total silicon powder mass, i.e., 600 × 12.2 wt% = 73.2 kg) are added to the first melt and stirred at 200 rpm for 7 minutes to obtain the second melt.

[0100] The temperature of the second melt was controlled at 920±10℃. Another portion of silicon powder (denoted as the second silicon powder, accounting for 15wt% of the total silicon powder mass, i.e., 600×15wt%=90kg) was added to the second melt, and the mixture was stirred at 200rpm for 8 minutes to obtain the third melt. The temperature of the third melt was then controlled at 920±10℃, and the remaining silicon powder was added to the third melt. The mixture was stirred at 200rpm for 15 minutes to obtain the final melt. Then, under a nitrogen atmosphere, the final melt was poured into a mold and allowed to cool naturally under a nitrogen atmosphere to obtain the cooled product.

[0101] The cooled material is crushed into steelmaking additives with an average particle size of 30 mm using a crusher.

[0102] The steelmaking additive was crushed using a press, and its compressive strength was tested to be 485 MPa. The steelmaking additive contained 9 wt% Al, 55 wt% Si, 18 wt% Fe, 12 wt% Ca, and 6 wt% O and unavoidable impurities (of which O content was 5 wt%).

[0103] Example - Steelmaking

[0104] The steelmaking additives prepared in the above preparation example are applied to the converter steelmaking process.

[0105] Q355B steel is smelted in a 100-ton converter. The total amount of steelmaking additives used is 8 kg / t. In this example, 800 kg of steelmaking additives are needed for 100 t of molten steel.

[0106] During tapping, the converter is tilted so that the molten steel flows into the ladle. When the converter has tapped 1 / 4 of its capacity (i.e., the depth of the molten steel in the ladle is 1.2m; if all the molten steel in the converter is transferred to the ladle, the depth of the molten steel in the ladle is 4.8m), and the tapping temperature of the converter is not lower than 1630℃, 480kg of the steelmaking additive prepared in the preparation example is added to the converter, and the temperature is controlled to drop by no more than 30℃ to ensure deoxidation. When the converter has tapped 1 / 2 of its capacity, and the tapping temperature of the converter is not lower than 1630℃, the remaining 320kg of steelmaking additive is added to the converter, and the temperature is controlled to drop by no more than 30℃. Then, all the molten steel in the converter flows into the ladle.

[0107] The final oxygen content, silicon yield, and inclusion spheroidization rate of the converter molten steel (i.e., the molten steel in the ladle) were tested, and the results are detailed in Table 1.

[0108] Comparative example

[0109] The only difference between this comparative example and the above embodiments is that the steelmaking additive added to the converter is a ferrosilicon alloy commonly used in the prior art (the silicon content in the ferrosilicon alloy is 75wt%).

[0110] The results of the endpoint oxygen content, silicon yield, and inclusion spheroidization rate tests on the converter molten steel (i.e., the molten steel in the ladle) are detailed in Table 1.

[0111] Table 1

[0112]

[0113] As shown in Table 1, the steelmaking additive of the present invention can significantly reduce the final oxygen content of molten steel in the ladle and improve the silicon yield and inclusion spheroidization rate of molten steel in the ladle.

[0114] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A steelmaking additive, characterized in that, It consists of the following elements in the following amounts composition: Si 45-55wt%, Fe 12~19wt%, Al 6-12 wt%, Ca 8-15wt%, O and unavoidable impurities are the balance, of which the O content is greater than or equal to 5 wt%; The steelmaking additive is prepared by the following steps: 1) Prepare raw materials: aluminum, calcium oxide, iron filings, and silicon powder; 2) Heat the raw aluminum to melt it, and obtain molten aluminum liquid; add calcium oxide to the molten aluminum liquid to obtain the first molten liquid; 3) Add iron filings and a portion of silicon powder sequentially to the first molten liquid to obtain the second molten liquid; then add another portion of silicon powder to the second molten liquid to obtain the third molten liquid; finally add the remaining silicon powder to the third molten liquid to obtain the final molten liquid; Under a protective atmosphere, the final melt is cooled in a mold to obtain a cooled product; The cooled material is crushed to obtain a steelmaking additive with an average particle size of 10–80 mm.

2. The steelmaking additive according to claim 1, characterized in that, It is composed of elements in the following amounts: Si 45-55wt%, Fe 14~19wt%, Al 7-9 wt%, Ca 9-13 wt%, The balance is O and unavoidable impurities, of which the O content is greater than or equal to 5 wt%.

3. A method for preparing a steelmaking additive according to any one of claims 1 to 2, characterized in that, Includes the following steps: 1) Prepare raw materials: aluminum, calcium oxide, iron filings, and silicon powder; 2) Heat the raw aluminum to melt it, and obtain molten aluminum liquid; add calcium oxide to the molten aluminum liquid to obtain the first molten liquid; 3) Add iron filings and a portion of silicon powder to the first molten liquid in sequence to obtain the second molten liquid; then add another portion of silicon powder to the second molten liquid to obtain the third molten liquid; The remaining silicon powder is then added to the third molten liquid to obtain the final molten liquid; Under a protective atmosphere, the final melt is cooled in a mold to obtain a cooled product; The cooled material is crushed to obtain a steelmaking additive with an average particle size of 10–80 mm.

4. The preparation method according to claim 3, characterized in that, In step 1), the average particle size of the raw aluminum is 1-10 mm; the iron filings are turning shavings; the average particle size of the iron filings is 1-10 mm; and the average particle size of the silicon powder is less than 200 μm.

5. The preparation method according to claim 3, characterized in that, In step 3), the mass of one portion of silicon powder accounts for 10 to 14 wt% of the total silicon powder mass, and the mass of the other portion of silicon powder accounts for 11 to 18 wt% of the total silicon powder mass.

6. The preparation method according to claim 3, characterized in that: The temperature of the molten aluminum liquid is 560–800°C; the temperature of the first molten liquid is 800–890°C; the temperature of the second molten liquid is 850–930°C; and the temperature of the third molten liquid is 900–950°C.

7. The use of a steelmaking additive according to any one of claims 1 to 2 or a steelmaking additive obtained by the preparation method according to any one of claims 3 to 6 in reducing the final oxygen content of molten steel in a ladle, increasing the silicon yield of molten steel in a ladle, and increasing the spheroidization rate of inclusions in molten steel in a ladle in converter steelmaking.

8. A method for steelmaking, characterized in that, Includes the following steps: During the converter steelmaking process, the molten steel flows into the ladle. When the amount of steel tapped from the converter reaches 1 / 4 to 1 / 2, the steelmaking additives described in any one of claims 1 to 2 are added to the molten steel in batches; wherein the tapping temperature of the converter is not lower than 1630°C.

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