A method of smelting a high carbon steel

Abstract

The application provides a smelting method of high-carbon steel, which comprises the following steps: carrying out converter smelting on a mixture of scrap steel and molten iron to obtain converter tapping molten steel, wherein the mass fraction of carbon in the converter tapping molten steel is 0.3-0.5% based on the total mass of the converter tapping molten steel; adding a deoxidizer and a carbon additive to the converter tapping molten steel to obtain deoxidized and carbonized molten steel, wherein the mass fraction of carbon in the deoxidized and carbonized molten steel is 0.65-1.30%; and carrying out RH refining treatment on the deoxidized and carbonized molten steel to obtain high-carbon molten steel, wherein no aluminum source is added and no calcium treatment is carried out in the RH refining treatment. The application can shorten the smelting process, reduce the smelting cost and greatly improve the purity of the molten steel, and meet the application requirements of high-end carbon steel.

Description

Technical Field

[0001] This application relates to the field of steel manufacturing technology, and in particular to a method for smelting high-carbon steel. Background Technology

[0002] High-carbon steel is a type of steel with a carbon content of ≥0.6%. Its applications are very wide-ranging, with particularly high-tech applications including tools, knives, thin blades, springs, and wire ropes. Parts and equipment made from high-carbon steel generally possess ultra-high strength, high hardness, high wear resistance, excellent fatigue life, and good surface quality. Excellent fatigue performance and surface quality mean that the steel must have a high degree of internal purity; otherwise, the material is prone to cracking, surface pitting, and insufficient service life during processing or use. In terms of technical requirements: for example, spring steel typically requires a total oxygen content of less than 20 ppm, with high-quality spring steel requiring 10 ppm. Large brittle particles and point-like non-deformable inclusions must be controlled, ensuring that inclusions are small and dispersed to improve fatigue life. For knife and tool steel, the total oxygen content must be less than 10 ppm, and the levels of various inclusions (A, B, C, D, and Ds) must be strictly controlled, ideally all within grade 0.5, with inclusion size controlled within 2 μm.

[0003] Currently, the methods for smelting high-purity molten steel mainly employ electroslag remelting or dual refining using an LF ladle and RH (or VD vacuum furnace). Electroslag remelting is more commonly used in special steel production lines, while dual refining using an LF ladle and RH (or VD vacuum furnace) is the production process for most ordinary steel mills. For deoxidation of high-carbon molten steel, an alloy deoxidation system is generally used, with aluminum as the primary deoxidizer and silicon and manganese as auxiliary deoxidizers. Traditional processes employ "low-carbon tapping," resulting in low carbon content and high oxidizing properties. This necessitates the addition of large amounts of aluminum for forced deoxidation, leading to the formation of numerous Al2O3 inclusions. Subsequent processes rely on prolonged heating in an LF furnace for slag formation, reduction, and composition adjustment. Calcium treatment is then used to transform the high-melting-point Al2O3 into low-melting-point calcium aluminate to prevent nozzle blockage. In summary, traditional processes have the following problems: 1) Lower steel purity. On the one hand, high-aluminum deoxidation produces a large amount of native Al2O3 inclusions; on the other hand, arc heating in the LF furnace may exacerbate refractory material erosion and introduce foreign inclusions. 2) The production process is lengthy and costly. The LF furnace has a long processing cycle, high energy consumption (e.g., electricity, refractory materials), and large consumption of aluminum and calcium alloys. 3) Quality control stability is relatively complex. Due to the numerous process steps, fluctuations in the amount of aluminum and calcium added can easily affect the inclusion modification effect, potentially resulting in large, non-deforming inclusions of the Ds type. 4) The application fields of the finished product are limited. Although it can meet most conventional needs, the large number and wide size distribution of residual inclusions limit its application in high-performance applications. Summary of the Invention

[0004] This application provides a method for smelting high-carbon steel, which can shorten the smelting process, reduce smelting costs, and greatly improve the purity of molten steel, thus meeting the requirements for high-end carbon steel applications.

[0005] This application provides a method for smelting high-carbon steel, the method comprising: A mixture of scrap steel and molten iron is smelted in a converter to obtain molten steel tapped from the converter. The mass fraction of carbon in the molten steel tapped from the converter is 0.3% to 0.5% based on the total mass of the molten steel. Adding deoxidizer and carburizer to the molten steel tapped from the converter yields deoxidized and carburized molten steel, with a carbon content of 0.65~1.30% by mass. Deoxidized and carbonized molten steel is subjected to RH refining treatment to obtain high-carbon molten steel. In the RH refining treatment, no aluminum source is added and no calcium treatment is performed.

[0006] This application provides a method for smelting high-carbon steel. First, a mixture of scrap steel and molten iron is smelted in a converter to obtain converter tapped steel. The carbon content in the converter tapped steel is 0.3-0.5% by mass, resulting in a higher carbon content at the final tapping point, i.e., high-carbon tapping, which significantly reduces the oxygen content at tapping. Next, a deoxidizer and a carbonizer are added to the converter tapped steel for further deoxidation. Simultaneously, a carbonizer is added to control the oxygen content to an extremely low level, allowing for deep deoxidation through the carbon-oxygen reaction that occurs during subsequent RH refining. At this point, because the converter tapped steel already has a high carbon content, the amount of carbonizer used is reduced, and the compositional fluctuation of the steel is also reduced. Finally, the deoxidized and carbonized steel is subjected to RH refining. In this step, no additional aluminum source is actively added; instead, deep deoxidation is achieved using vacuum carbon deoxidation. This reduces the generation of endogenous oxide inclusions (such as alumina inclusions) from the source, thus eliminating the need for calcium treatment. In summary, the smelting method of this application embodiment includes only three steps: converter smelting, deoxidation and carbonization, and RH refining. It can be seen that this application eliminates the long-cycle and energy-intensive LF refining process, and significantly reduces the consumption of aluminum alloys and calcium alloys, thereby greatly saving smelting costs. Attached Figure Description

[0007] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 This is a schematic flowchart of a high-carbon steel smelting method provided in one embodiment of this application; Figure 2 This is a schematic diagram of the specific process of deoxidizing and carbonizing molten steel and then refining it with RH to obtain high-carbon molten steel. Detailed Implementation

[0009] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0010] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0011] In the production of carbon tool steel, the traditional process of "low-pulling carbon, LF+RH double refining and high-alumina-calcium treatment" is not only complex and time-consuming, but also produces molten steel with low cleanliness.

[0012] To address the aforementioned issues of high steelmaking costs and low cleanliness, such as... Figure 1 As shown in the embodiment of this application, a method for smelting high-carbon steel is provided, which may include steps S100 to S300: Step S100: The mixture of scrap steel and molten iron is subjected to converter smelting treatment to obtain converter tapped molten steel.

[0013] The mass fraction of carbon in the molten steel tapped from the converter is 0.3-0.5% based on the total mass of the molten steel.

[0014] This application requires precise control over the endpoint of the converter smelting process, demanding a high level of expertise in converter smelting operations. Due to the use of a high-carbon tapping process, the carbon content of the molten steel in the converter is high at tapping, resulting in a significant reduction in the oxygen content and, to some extent, lowering the difficulty of deoxidation in subsequent processing steps.

[0015] Step S200: Add deoxidizer and recarburizer to the molten steel tapped from the converter to obtain deoxidized and recarburized molten steel.

[0016] The mass fraction of carbon in deoxidized and carbonized molten steel is 0.65~1.30%.

[0017] Deoxidation of molten steel is achieved by adding deoxidizers. However, in order to further control the oxygen content to an extremely low level, a carburizing agent is added in this embodiment of the application. This allows for deep deoxidation by utilizing the carbon-oxygen reaction that occurs during subsequent RH refining. At this time, because the carbon content of the molten steel from the converter is already high, the amount of carburizing agent used can be reduced, and the fluctuation of the composition of the molten steel is thus reduced.

[0018] Step S300: The deoxidized and carbonized molten steel is subjected to RH refining treatment to obtain high-carbon molten steel.

[0019] In RH refining, no aluminum source is added, and no calcium treatment is performed. It's important to note that "no aluminum source added" here means that no aluminum source is actively added for deoxidation; instead, carbon deoxidation under vacuum is used to further reduce oxygen levels, and RH refining powerfully removes gases and inclusions. However, issues such as refractory corrosion, carryover from refining slag, impurities in alloys or auxiliary materials, and residues from previous heats can inevitably lead to aluminum entering the molten steel unintentionally. For example, ferrosilicon and ferromanganese alloys may contain trace amounts of aluminum; when these materials are added during RH refining, their aluminum impurities will also enter the molten steel.

[0020] Since the embodiments of this application avoid adding large amounts of aluminum sources throughout the RH refining process, reducing the generation of endogenous alumina inclusions from the source, calcium treatment is also unnecessary.

[0021] In summary, the smelting method of this application embodiment includes only three steps: converter smelting, deoxidation and carbonization, and RH refining. It can be seen that the embodiments of this application have the following advantages: 1) Higher steel purity: High-pulling carbonization process is used for steelmaking, utilizing vacuum carbon deoxidation reaction to deeply reduce oxygen, reducing the total content of oxide inclusions from the source, and utilizing the powerful circulation of the RH refining treatment device to remove gases and inclusions. 2) Simpler production process: The LF furnace refining process is eliminated, saving energy, refractory material consumption, and equipment occupancy time. 3) Lower cost: Reduces or even eliminates the use of expensive aluminum sources and calcium wire. 4) Higher quality control stability. On the one hand, due to the simplified process, interference factors are reduced, and the control of the final composition, especially the carbon element composition, is more precise. On the other hand, due to the use of high-pulling carbonization process for steelmaking, the use of subsequent carbonizing agents is reduced, resulting in smaller fluctuations in the steel composition. 4) Wider applicability of finished products: The extremely high-purity high-carbon steel obtained using the embodiments of this application can meet the stringent requirements of high-end carbon tool steel for uniformity, wear resistance, and fatigue performance. Moreover, no additional aluminum source is added during the refining process, nor is calcium treatment performed. Therefore, there are virtually no calcium aluminate inclusions in the steel, resulting in better isotropy of the finished materials obtained from this steel. Carbon tool steel is a type of high-carbon tool steel with a relatively simple chemical composition. Typical steel grades include T8, T9, T10, and T12, which are used in industries such as utility knife blades, rulers, and tape measures. The characteristic of this type of steel is that its chemical composition contains only major elements such as C, Si, and Mn, and it belongs to typical carbon steel.

[0022] In one embodiment, in step S100, where a mixture of scrap steel and molten iron is smelted in a converter to obtain molten steel, the converter smelting process is a top-and-bottom blowing converter smelting process. Specifically, oxygen is blown in from the top of the converter, and argon is blown in from the bottom throughout the entire process. It is worth noting that during the converter smelting process, argon is blown in from the bottom throughout the entire process. The bubbles generated by the bottom-blown argon rise from the bottom of the converter, causing the molten steel to circulate, allowing oxygen to meet and react with elements such as carbon, silicon, and phosphorus in the molten steel more quickly.

[0023] In one embodiment, in step S100, where a mixture of scrap steel and molten iron is smelted in a converter to obtain molten steel from the converter, the mass fraction of scrap steel is 10-30% and the mass fraction of molten iron is 70-90% based on the total mass of the mixture.

[0024] In one embodiment, step S100, which involves smelting a mixture of scrap steel and molten iron in a converter to obtain molten steel from the converter, may include: smelting the mixture of scrap steel and molten iron in a converter using a top-blown oxygen method and a supplementary oxygen method to obtain molten steel from the converter.

[0025] In one embodiment, in step S100, where a mixture of scrap steel and molten iron is smelted in a converter to obtain molten steel, the mass fraction of phosphorus in the molten steel is <0.015% based on the total mass of the molten steel. Before converter smelting, the [P] content in the molten iron should be controlled to ≤0.150%. In the early stages of converter smelting, sufficient lime and lightly calcined dolomite are added to the furnace in small, frequent, and batch-wise operations using a high-lance position to quickly form a slag with high basicity (R≥2.5), high FeO content (approximately 20-27%), and good fluidity, ensuring that most of the phosphorus is removed at this stage. After dephosphorization, the lance position and oxygen supply are adjusted to control the rate of steel heating and prevent slag "drying out" or splashing. High-pulling supplementary blowing is used in the later stages, ending the blowing process while the carbon content of the molten steel is still high to avoid excessive oxidation and subsequent phosphorus reversion.

[0026] In one embodiment, in step S100, the temperature of the molten steel tapped from the converter is ≥1600℃, where the mixture of scrap steel and molten iron is subjected to converter smelting.

[0027] In one embodiment, the step of using top-blown oxygen and supplemental oxygen to smelt a mixture of scrap steel and molten iron in a converter to obtain molten steel from the converter may include: Step S101: Scrap steel and molten iron are added to the converter in sequence, oxygen is blown from the top for converter smelting treatment, and slagging agent is added.

[0028] During the smelting process, materials such as lime, ore, and dolomite can be added to form slag and adjust the composition of converter slag.

[0029] In step S102, when the composition and temperature of the molten steel meet the preset conditions, the top blowing of oxygen is stopped, and oxygen is replenished for converter smelting to obtain the molten steel from the converter.

[0030] To maximize the temperature of the steel entering the RH furnace, the preset conditions can be set as follows: carbon content in the molten steel is 0.4-0.6%, phosphorus content is <0.015%, and the temperature of the molten steel is 1600-1640℃.

[0031] If the content of elements such as carbon and phosphorus in the molten steel still does not meet the target requirements after supplemental oxygen blowing, oxygen can be blown in short bursts for a short time. Note that the number of bursts should be ≤2.

[0032] In one embodiment, in step S200, deoxidizer and carbonizer are added to the molten steel tapped from the converter to obtain deoxidized and carbonized molten steel. The deoxidizer includes pre-deoxidizer and post-deoxidizer, and the deoxidizer is added all at once.

[0033] It's worth noting that the pre-deoxidizer is added first, followed by the post-deoxidizer. Generally, the pre-deoxidizer is added during the early stages of converter tapping, such as when about 1 / 3 of the steel has been tapped. At this time, the dissolved oxygen content in the molten steel can be rapidly reduced by vigorous stirring. The post-deoxidizer is generally added later in the converter tapping process, such as when about 3 / 4 of the steel has been tapped, or after the molten steel has been allowed to settle in the ladle for a short period. In other words, the post-deoxidizer is neither added simultaneously with nor immediately after the pre-deoxidizer.

[0034] In one embodiment, the pre-deoxidizer is one or more of silicon-manganese alloy, silicon-iron alloy, and manganese-iron alloy.

[0035] In one embodiment, the post-deoxidizer is an aluminum-iron alloy, the mass of which is determined based on the target mass fraction of aluminum in the high-carbon steel. The amount of aluminum-iron alloy deoxidizer added is determined according to the target mass fraction of aluminum in the steel to ensure a certain amount of residual aluminum remains after deoxidation. During the steel deoxidation process, the added aluminum plays two roles: 1) Deoxidation consumption, thereby reducing the oxygen content of the steel, allowing the Al2O3 formed by the aluminum-iron alloy to float into the steel slag for removal. 2) Residual alloying: After the deoxidation reaction is complete, a certain amount of acid-soluble aluminum remains in the steel, used for grain refinement, nitrogen fixation, or to meet steel performance requirements.

[0036] For example, when adding ferrosilicon, ferromanganese, and ferroaluminum alloys sequentially to the molten steel tapped from the converter, the added alloy content is based on the target values ​​of each chemical component for the steel grade, added in one go without subsequent large or small batch additions. In other words, in this embodiment, the deoxidizer is added in one go, without further large or small batch additions during the subsequent process. If the composition is not optimal, minor adjustments are made only in the RH furnace.

[0037] In one embodiment, in step S200, where a deoxidizer and a recarburizer are added to the molten steel tapped from the converter to obtain deoxidized and recarburized molten steel, the recarburizer is carbon powder.

[0038] Regarding the method of adding the carbon recarburizer, sufficient carbon powder can be placed at the bottom of the ladle before tapping from the converter, such as adding carbon powder at 1.2 times the target carbon content. Utilizing the impact and stirring effect of the high-temperature steel flow, the carbon recarburizer is quickly incorporated into the molten steel, avoiding burn-off from contact with air and significantly improving carbon yield and stability. Furthermore, the pre-deoxidation effect of carbon reduces the oxygen activity of the molten steel to a certain extent, effectively reducing the amount of alumina inclusions formed during subsequent deoxidation, thus contributing to improved steel purity.

[0039] In one embodiment, before step S300, which involves RH refining of the deoxidized and carburized molten steel to obtain high-carbon molten steel, the high-carbon steel smelting method may further include: placing the deoxidized and carburized molten steel in an argon station for argon blowing treatment. Samples of the molten steel can be taken before and after the argon blowing treatment to test its chemical composition.

[0040] Optionally, the argon blowing pressure is 0.4~0.9MPa and the argon blowing time is 8~12min.

[0041] Argon blowing treatment has the following effects: 1) Uniform steel temperature to ensure that the temperature of the molten steel in the entire ladle is within the target range during RH refining.

[0042] 2) Uniform steel composition: Since deoxidizers and carburizers are added during the tapping process, argon blowing can make them fully dissolve and evenly distribute in the molten steel, avoiding local component segregation.

[0043] 3) Promotes inclusion flotation and improves steel purity. The numerous tiny argon bubbles generated by argon blowing collide with small inclusions in the molten steel (such as deoxidation products and refractory material spallings) as they rise, causing the inclusions to adhere to the bubble surface or be captured by the bubbles and float upwards. Furthermore, the stirring effect of argon blowing significantly increases the probability of collisions between inclusions, causing them to aggregate into larger particles and accelerate their flotation. Removing some inclusions before RH treatment reduces the pressure on RH vacuum circulation for inclusion removal, thus improving the overall cleanliness of the molten steel.

[0044] 4) Reducing the oxygen activity of molten steel. Argon blowing and stirring promotes the contact between carbon and residual oxygen in the molten steel, resulting in a weak carbon-oxygen reaction that generates and releases bubbles. This process consumes some dissolved oxygen, which helps reduce the oxygen activity of the molten steel, meaning that the oxygen content of the molten steel will be lower during RH refining.

[0045] 5) Preventing secondary oxidation of molten steel. Argon blowing creates a slightly positive pressure argon atmosphere above the molten steel surface, effectively isolating it from air and preventing the molten steel from absorbing oxygen and nitrogen from the atmosphere while awaiting further treatment. This is especially important for high-carbon steel, as it is highly sensitive to nitrogen content.

[0046] 6) Avoid violent splashing during the initial stage of RH refining. If the dissolved gas content in the molten steel is high, direct entry into the RH vacuum chamber may cause violent boiling and splashing. Argon blowing before RH refining can remove some of the gases in advance, making the reaction of the molten steel more stable during RH refining and reducing the risk of splashing.

[0047] Figure 2 A schematic diagram illustrating the specific process of RH refining of deoxidized and carburized molten steel to obtain high-carbon molten steel is shown below. Figure 2As shown, this step may include: steps S301 to S305: Step S301: Insert the RH immersion tube into the deoxidized and carbonized molten steel, turn on the vacuum pump, and begin the RH refining process.

[0048] In step S302, ferrosilicon alloy is added according to the added mass of ferrosilicon alloy, and ferromanganese alloy is added according to the added mass of ferromanganese alloy to obtain the first molten steel.

[0049] The replenishment mass of ferrosilicon alloy is determined based on the difference between the actual mass fraction of silicon in the deoxidized and carbonized molten steel and the target mass fraction of silicon in the high-carbon molten steel. Similarly, the replenishment mass of ferromanganese alloy is determined based on the difference between the actual mass fraction of manganese in the deoxidized and carbonized molten steel and the target mass fraction of manganese in the high-carbon molten steel.

[0050] Step S303: The first molten steel is subjected to oxygen blowing treatment to adjust the mass fraction of each element in the first molten steel to the corresponding target mass fraction, thereby obtaining the second molten steel.

[0051] The oxygen blowing time for the oxygen blowing process is determined based on the difference between the actual mass fraction of carbon in the first molten steel and the target mass fraction of carbon in the high-carbon steel, as well as the difference between the actual mass fraction of aluminum in the first molten steel and the target mass fraction of aluminum in the high-carbon steel.

[0052] No aluminum is added during the RH refining process. The oxygen blowing time is determined based on the actual C and Al content and the excess of the target content, and the C and Al content is adjusted to the target value. The above-mentioned actual mass fraction / content is determined by taking steel samples after entering the refining station to test the chemical composition.

[0053] Step S304: Vacuum smelting is performed on the second molten steel to obtain vacuum smelted molten steel.

[0054] Optionally, the vacuum degree of the vacuum smelting process is 67~133 Pa, and the time is 15~25 min.

[0055] Step S305: After stopping the vacuuming, argon gas is blown in from the bottom of the ladle to perform low-soft argon blowing treatment on the vacuum smelting molten steel, thereby obtaining high-carbon molten steel.

[0056] The argon blowing time for low-temperature soft argon blowing treatment is determined based on the actual temperature of molten steel smelted in vacuum.

[0057] Low-pressure soft argon blowing refers to a process with low argon flow rate and low pressure, resulting in very small argon bubbles and a gentle stirring effect.

[0058] Optionally, the argon flow rate for low-soft-blown argon treatment is 80~110 L / min.

[0059] Optionally, the target temperature of the high-carbon steel molten steel is 40-50°C higher than its liquidus temperature. Once the high-carbon steel molten steel reaches the target temperature, it can be shipped out of the station for continuous casting.

[0060] In summary, this application implements comprehensive control from three aspects: converter endpoint control, smelting process design, and steel deoxidation system. By controlling each key step, the cleanliness of the molten steel is improved, and the content of gas and non-metallic inclusions in the steel is effectively reduced.

[0061] In one embodiment, a method for smelting high-carbon steel may further include: step S400, continuously casting high-carbon steel to obtain a high-carbon steel slab.

[0062] Optionally, the superheat of the continuous casting process is 15~30℃.

[0063] Optionally, the casting speed for continuous casting is 0.6~1.5 m / min.

[0064] It can incorporate functions such as electromagnetic stirring and dynamic light pressing to improve problems such as internal porosity and segregation in continuously cast slabs.

[0065] Example 1 The steel grade SK85 smelted in Example 1 has the following target chemical composition values: C: 0.85%, Si: 0.30%, Mn: 0.45%, Al: 0.008%, with the remainder being Fe and unavoidable impurity elements.

[0066] Example 1 provides a method for smelting high-carbon steel, comprising the following steps: 1) Converter smelting: A top-and-bottom blown converter is used for smelting, with argon gas blown into the bottom throughout the process. Scrap steel and molten iron are added sequentially to the converter, with scrap steel accounting for 19% and molten iron accounting for 81% of the total addition. Top-blown oxygen smelting is used, with lime, ore, and dolomite added during the smelting process to form slag and adjust the converter slag composition. High-pressure carbon blowing is used for smelting. When the carbon content reaches 0.51%, the phosphorus content is 0.032%, and the steel temperature is 1624℃, high-pressure carbon blowing is performed once. The final converter content is 0.37% carbon, the phosphorus content is 0.012%, and the tapping temperature is 1638℃.

[0067] 2) Deoxidation, alloying, and carbon enrichment: Pre-deoxidation is performed using a silicon-manganese alloy, followed by deoxidation using an aluminum-iron alloy. The silicon-iron alloy, ferromanganese alloy, and aluminum-iron alloy are added sequentially, with the alloy content determined based on the target values ​​of the steel grade's chemical composition. The alloys are added all at once, with the mass of the aluminum-iron alloy determined based on an Al content of 0.04%. Before tapping from the 200-ton converter, 147 bags of 10kg / bag carbon powder with a 95% pure carbon content are placed at the bottom of the ladle.

[0068] 3) Argon station soft blowing: Argon blowing pressure 0.6MPa, argon blowing time 12min. Take molten steel samples before and after argon blowing to test chemical composition.

[0069] 4) RH Refining: After entering the refining station, the temperature of the molten steel is measured, and a sample is taken to test the chemical composition, determining the difference between the contents of C, Si, Mn, and Al and the target composition. After the RH immersion tube is inserted into the molten steel, RH refining begins. The vacuum pump is turned on, and appropriate amounts of ferrosilicon alloy and ferromanganese alloy are added based on the difference between the Si and Mn contents and the target contents. Then, the vacuum degree is raised to 67 Pa. No aluminum is added during RH refining. The oxygen blowing time is determined based on the excess of C and Al contents compared to the target contents, and the C and Al contents are adjusted to the target values. No calcium treatment is performed throughout the RH refining process. The vacuum smelting time at 67 Pa is 19 minutes. After breaking the vacuum, the temperature of the molten steel is measured, and the ladle is subjected to low-level soft argon blowing at a flow rate of 90 L / min. The soft blowing time is determined based on the molten steel temperature. When the molten steel temperature reaches the target temperature of 1497℃, it is sent to continuous casting.

[0070] 5) Continuous casting: The superheat is controlled at 15~30℃, the casting speed is 1.4m / min, and electromagnetic stirring and dynamic light pressing functions are put into use to improve the problems of porosity and segregation inside the billet.

[0071] Example 2 The steel grade SK95 smelted in Example 2 has the following target chemical composition values: C: 0.95%, Si: 0.30%, Mn: 0.45%, Al: 0.008%, with the remainder being Fe and unavoidable impurity elements.

[0072] Example 1 provides a method for smelting high-carbon steel, comprising the following steps: 1) Converter smelting: A top-and-bottom blown converter is used for smelting, with argon gas blown into the bottom throughout the process. Scrap steel and molten iron are added sequentially to the converter, with scrap steel accounting for 28% and molten iron for 72% of the total addition. Top-blown oxygen smelting is employed, with lime, ore, and dolomite added during the smelting process to form slag and adjust the converter slag composition. High-pressure carbon blowing is used for smelting. When the carbon content reaches 0.48%, the phosphorus content is 0.036%, and the steel temperature is 1632℃, high-pressure carbon blowing is performed once. The final converter smelting results in a carbon content of 0.39%, a phosphorus content of 0.014%, and a tapping temperature of 1643℃.

[0073] 2) Deoxidation, alloying, and carbon enrichment: Pre-deoxidation is performed using a silicon-manganese alloy, followed by deoxidation using an aluminum-iron alloy. The silicon-iron alloy, ferromanganese alloy, and aluminum-iron alloy are added sequentially, with the alloy content determined based on the target values ​​of the steel grade's chemical composition. The alloys are added all at once, with the mass of the aluminum-iron alloy determined based on an Al content of 0.04%. Before tapping from the 200-ton converter, 148 bags of 10kg / bag carbon powder with a 95% pure carbon content are placed at the bottom of the ladle.

[0074] 3) Argon station soft blowing: Argon blowing pressure 0.6MPa, argon blowing time 10min. Take molten steel samples before and after argon blowing to test chemical composition.

[0075] 4) RH Refining: After entering the refining station, the temperature of the molten steel is measured, and a sample is taken to test the chemical composition, determining the difference between the contents of C, Si, Mn, and Al and the target composition. After the RH immersion tube is inserted into the molten steel, RH refining begins. The vacuum pump is turned on, and appropriate amounts of ferrosilicon alloy and ferromanganese alloy are added based on the difference between the Si and Mn contents and the target contents. Then, the vacuum is raised to 67 Pa. No aluminum is added during RH refining. The oxygen blowing time is determined based on the excess C and Al contents compared to the target contents, and the C and Al contents are adjusted to the target values. No calcium treatment is performed throughout the RH refining process. The vacuum smelting time at 67 Pa is 16 minutes. After breaking the vacuum, the temperature of the molten steel is measured, and the ladle is subjected to low-temperature soft argon blowing at a flow rate of 90 L / min. The soft blowing time is determined based on the molten steel temperature. When the molten steel temperature reaches the target temperature of 1497℃, it is sent to continuous casting.

[0076] 5) Continuous casting: The superheat is controlled at 15~30℃, the casting speed is 1.3m / min, and electromagnetic stirring and dynamic light pressure functions are put into use to improve the problems of porosity and segregation inside the billet.

[0077] Example 3 The steel grade smelted in Example 3 is SK105, with a target chemical composition of C: 1.05%, Si: 0.30%, Mn: 0.45%, Al: 0.008%, and the remainder being Fe and unavoidable impurity elements.

[0078] Example 1 provides a method for smelting high-carbon steel, comprising the following steps: 1) Converter smelting: A top-and-bottom blown converter is used for smelting, with argon gas blown into the bottom throughout the process. Scrap steel and molten iron are added sequentially to the converter, with scrap steel accounting for 23% and molten iron for 77% of the total addition. Top-blown oxygen smelting is employed, with lime, ore, and dolomite added during the smelting process to form slag and adjust the converter slag composition. High-pressure carbon blowing is used for smelting. When the carbon content reaches 0.54%, the phosphorus content is 0.029%, and the steel temperature is 1628℃, high-pressure carbon blowing is performed once. The final converter smelting results in a carbon content of 0.47%, a phosphorus content of 0.009%, and a tapping temperature of 1609℃.

[0079] 2) Deoxidation, alloying, and carbon enrichment: Pre-deoxidation is performed using a silicon-manganese alloy, followed by deoxidation using an aluminum-iron alloy. The silicon-iron alloy, ferromanganese alloy, and aluminum-iron alloy are added sequentially, with the alloy content determined based on the target values ​​of the steel grade's chemical composition. The alloys are added all at once, with the mass of the aluminum-iron alloy determined based on an Al content of 0.04%. Before tapping from the 200-ton converter, 153 bags of 10kg / bag carbon powder with a 95% pure carbon content are placed at the bottom of the ladle.

[0080] 3) Argon station soft blowing: Argon blowing pressure 0.6MPa, argon blowing time 11min. Take molten steel samples before and after argon blowing to test chemical composition.

[0081] 4) RH Refining: After entering the refining station, the temperature of the molten steel is measured, and a sample is taken to test the chemical composition, determining the difference between the contents of C, Si, Mn, and Al and the target composition. After the RH immersion tube is inserted into the molten steel, RH refining begins. The vacuum pump is turned on, and appropriate amounts of ferrosilicon alloy and ferromanganese alloy are added based on the difference between the Si and Mn contents and the target contents. Then, the vacuum is raised to 67 Pa. No aluminum is added during RH refining. The oxygen blowing time is determined based on the excess C and Al contents compared to the target contents, and the C and Al contents are adjusted to the target values. No calcium treatment is performed throughout the RH refining process. The vacuum smelting time at 67 Pa is 16 minutes. After breaking the vacuum, the temperature of the molten steel is measured, and the ladle is subjected to low-temperature soft argon blowing at a flow rate of 90 L / min. The soft blowing time is determined based on the molten steel temperature. When the molten steel temperature reaches the target temperature of 1497℃, it is sent to continuous casting.

[0082] 5) Continuous casting: The superheat is controlled at 15~30℃, the casting speed is 1.2m / min, and electromagnetic stirring and dynamic light pressing functions are put into use to improve the problems of porosity and segregation inside the billet.

[0083] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that, in step 2) deoxidation alloying and carburization, aluminum-iron alloy is not added, but rather in step 4) RH refining. Due to the unfavorable timing of the addition of the aluminum-iron alloy, the cleanliness of the resulting molten steel decreased.

[0084] Table 1 shows the cleanliness of the high-carbon steel molten material obtained in Examples 1-3 and Comparative Example 1.

[0085] Table 1. Cleanliness data of high-carbon steel molten material obtained in Examples 1-3 and Comparative Example 1

[0086] To illustrate the present invention, the present invention has been appropriately and sufficiently described above through embodiments. The above embodiments are only for illustrating the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent substitutions, improvements, etc., should be included within the protection scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. A method for smelting high-carbon steel, characterized in that, The method includes: A mixture of scrap steel and molten iron is subjected to converter smelting to obtain converter tapped molten steel. The carbon content in the converter tapped molten steel is 0.3-0.5% by mass, based on the total mass of the molten steel. A deoxidizer and a carburizer are added to the molten steel tapped from the converter to obtain deoxidized and carburized molten steel, wherein the carbon content in the deoxidized and carburized molten steel is 0.65~1.30% by mass. The deoxidized and carbonized molten steel is subjected to RH refining treatment to obtain high-carbon molten steel. In the RH refining treatment, no aluminum source is added and no calcium treatment is performed.

2. The smelting method according to claim 1, characterized in that, In the step of smelting a mixture of scrap steel and molten iron in a converter to obtain molten steel from the converter, the converter smelting process is a top-and-bottom combined blowing converter smelting process. Optionally, during the converter smelting process, oxygen is blown in from the top of the converter and argon is blown in from the bottom of the converter; Optionally, based on the total mass of the mixture, the mass fraction of the scrap steel is 10-30%, and the mass fraction of the molten iron is 70-90%.

3. The smelting method according to claim 1, characterized in that, The steps of smelting a mixture of scrap steel and molten iron in a converter to obtain molten steel from the converter include: The mixture of scrap steel and molten iron is smelted in a converter using top-blown oxygen and supplementary oxygen blowing methods to obtain molten steel from the converter. Optionally, based on the total mass of the molten steel tapped from the converter, the mass fraction of phosphorus in the molten steel tapped from the converter is <0.015%; Optionally, the temperature of the molten steel tapped from the converter is ≥1600℃.

4. The smelting method according to claim 3, characterized in that, The steps for smelting a mixture of scrap steel and molten iron in a converter using top-blown oxygen and supplemental oxygen methods to obtain molten steel for the converter tapping process include: Scrap steel and molten iron are added to the converter in sequence, oxygen is blown from the top for converter smelting, and slagging agent is added. When the composition and temperature of the molten steel meet the preset conditions, the top blowing of oxygen is stopped, and oxygen is added to carry out converter smelting treatment to obtain converter molten steel. The preset conditions are that the mass fraction of carbon in the molten steel is 0.4~0.6%, the mass fraction of phosphorus is <0.05%, and the temperature of the molten steel is 1600~1640℃.

5. The smelting method according to claim 3, characterized in that, In the step of adding deoxidizer and recarburizer to the molten steel tapped from the converter to obtain deoxidized and recarburized molten steel, the deoxidizer includes a pre-deoxidizer and a post-deoxidizer, and the deoxidizer is added all at once.

6. The smelting method according to claim 5, characterized in that, The pre-deoxidizer is one or more of silicon-manganese alloy, silicon-iron alloy, and manganese-iron alloy; Optionally, the post-deoxidizer is an aluminum-iron alloy, and the mass of the aluminum-iron alloy is determined based on the target mass fraction of aluminum in the high-carbon steel molten metal.

7. The smelting method according to claim 1, characterized in that, Before the step of performing RH refining treatment on the deoxidized and carbonized molten steel to obtain high-carbon molten steel, the method further includes: The deoxidized and carburized molten steel was placed in an argon station for argon blowing treatment. Optionally, the argon blowing pressure is 0.4~0.9MPa and the argon blowing time is 8~12min.

8. The smelting method according to claim 6, characterized in that, The step of performing RH refining treatment on the deoxidized and carburized molten steel to obtain high-carbon molten steel includes: Insert the RH impregnation tube into the deoxidized and carburized steel, turn on the vacuum pump, and begin the RH refining process. Ferrosilicon alloy is added according to the added mass of the ferrosilicon alloy, and ferromanganese alloy is added according to the added mass of the ferromanganese alloy to obtain the first molten steel. The added mass of the ferrosilicon alloy is determined based on the difference between the actual mass fraction of silicon in the deoxidized and carbonized molten steel and the target mass fraction of silicon in the high-carbon molten steel. The added mass of the ferromanganese alloy is determined based on the difference between the actual mass fraction of manganese in the deoxidized and carbonized molten steel and the target mass fraction of manganese in the high-carbon molten steel. The first molten steel is subjected to oxygen blowing treatment to adjust the mass fraction of each element in the first molten steel to the corresponding target mass fraction, thereby obtaining the second molten steel. The oxygen blowing time of the oxygen blowing treatment is determined based on the difference between the actual mass fraction of carbon in the first molten steel and the target mass fraction of carbon in the high-carbon steel, as well as the difference between the actual mass fraction of aluminum in the first molten steel and the target mass fraction of aluminum in the high-carbon steel. The second molten steel is subjected to vacuum smelting treatment to obtain vacuum smelted steel; optionally, the vacuum degree of the vacuum smelting treatment is 67~133 Pa and the time is 15~25 min. After the vacuuming is stopped, argon gas is blown in from the bottom of the ladle to perform a low-soft argon blowing treatment on the vacuum-smelted molten steel to obtain high-carbon molten steel. The blowing time of the low-soft argon blowing treatment is determined according to the actual temperature of the vacuum-smelted molten steel.

9. The smelting method according to claim 8, characterized in that, In the step of performing low-soft argon blowing treatment on the vacuum smelting molten steel based on the argon blowing time to obtain high carbon molten steel, the argon flow rate of the low-soft argon blowing treatment is 80~110L / min. Optionally, the target temperature of the high-carbon steel molten steel is 40-50°C higher than its liquidus temperature.

10. The smelting method according to any one of claims 1 to 8, characterized in that, The method further includes: The high-carbon steel molten steel is subjected to continuous casting to obtain a high-carbon steel slab; Optionally, the superheat of the continuous casting process is 15~30°C; Optionally, the casting speed of the continuous casting process is 0.6~1.5m / min.

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