Method for smelting with waste steel added in liquid steel ladle

Abstract

The application provides a smelting method of molten steel with scrap steel in a separate ladle, which breaks through the limitation of the scrap steel adding amount in the traditional process through the operation of adding scrap steel in multiple batches in a main refining furnace and adding scrap steel in the main refining furnace and an auxiliary refining furnace after the separate ladle operation. The multiple batch operation of the main refining furnace and the arrangement of at least two furnace bodies provide more opportunities and space for the scrap steel adding; the separate ladle operation further increases the number of molten steel ladles, greatly increases the total amount of scrap steel, effectively improves the scrap steel utilization rate, and reduces the molten iron consumption.

Description

Technical Field

[0001] This application belongs to the field of steel preparation technology, and in particular relates to a smelting method of adding scrap steel to a steel slurry tank. Background Technology

[0002] As a recyclable resource, scrap steel has high economic, environmental and social benefits. Increasing the scrap steel ratio and reducing the consumption of molten iron not only saves energy and reduces emissions, but also effectively solves the problems of insufficient molten iron resources and surplus scrap steel resources.

[0003] Traditionally, adding scrap steel to the converter can increase the scrap ratio. However, once the scrap ratio in the converter is increased to a certain extent, it will disrupt the converter's heat balance, causing problems such as difficulty in melting scrap steel, increased end-point overblowing and make-up blowing rates, enhanced slag oxidation, severe erosion of furnace lining bricks, and increased steel material consumption. Therefore, it is necessary to find additional ways to add scrap steel to reduce the unit consumption of molten iron. Summary of the Invention

[0004] In view of this, this application provides a smelting method for adding scrap steel to molten steel in a smelting tank, which can increase the amount of scrap steel added to the molten steel in the refining process.

[0005] In a first aspect, this application provides a smelting method for adding scrap steel to molten steel in a molten steel ladle, comprising the following steps: adding a target alloy to molten steel in a converter to perform a steel alloying operation, obtaining a first molten steel, wherein the amount of the target alloy added is less than or equal to 50% of the total alloy added; transferring the first molten steel from the converter to a main refining furnace, adding a first slagging agent to form slag, and then heating it to T1 by power supply; under bottom argon blowing conditions, adding scrap steel at a preset temperature to the main refining furnace in multiple batches to obtain a second molten steel; wherein, in each batch, scrap steel is added to... After entering the main refining furnace, a second slagging agent is added, and the furnace is powered on to heat the scrap steel. The mixed melt in the refining furnace is then heated to T3, and the next batch of scrap steel is added. The main refining furnace includes at least two furnace bodies, with T1 ≥ 1620℃ and T2 ≥ 1600℃. A portion of the second molten steel from the at least two main refining furnaces is transferred to the auxiliary refining furnace. Scrap steel and a third slagging agent at a preset temperature are added to both the main and auxiliary refining furnaces to obtain the third molten steel. The third molten steel is then subjected to slagging alloying to obtain refined molten steel.

[0006] According to an embodiment of this application, the first molten steel is transferred from a converter to a main refining furnace, a first slagging agent is added to form slag, and then the temperature is raised to T1 by power supply. Under bottom argon blowing conditions, scrap steel at a preset temperature is added to the main refining furnace in multiple batches to obtain the second molten steel, which satisfies at least one of the following conditions:

[0007] (1) The scrap steel shall be added to the main refining furnace in at least two batches;

[0008] (2) The flow rate of bottom-blown argon is 600-1500 NL / min;

[0009] (3) The first slag-forming agent is 1-2t of hot continuous casting residue slag or 1-2kg / t of foaming agent;

[0010] (4) The preset temperature is 500-1000℃;

[0011] (5) The length of the scrap steel is ≤600mm and the thickness is ≤30mm;

[0012] (6) The scrap steel shall not be mixed with closed containers, ash and steel slag, or ferroalloys and non-ferrous metals;

[0013] (7) The slag in the main refining furnace is light yellow or light white, and the total iron content of the slag is ≤5%;

[0014] (8) The heating rate of the main refining furnace is 4-10℃ / min;

[0015] (9) The net clearance of the ladle for steel tapping from the converter is 600-1200mm.

[0016] According to an embodiment of this application, the specific steps for adding scrap steel to the refining furnace in two batches include: under bottom-blown argon conditions, adding 50-100 kg / t of scrap steel at a preset temperature to the refining furnace, then adding 1.0-4.0 kg / t of lime, and heating the molten steel to T3 by electric heating; wherein T3 ≥ 1620℃; under bottom-blown argon conditions, adding 50-100 kg / t of scrap steel at a preset temperature to the refining furnace a second time, then adding 0.25-0.5 kg / t of aluminum blocks or 0.5-1.5 kg / t of silicon-aluminum-calcium for slag formation, and heating the molten steel to T4 by electric heating; wherein T4 ≥ 1600℃.

[0017] According to an embodiment of this application, each refining furnace is associated with a set of scrap steel baking and preheating devices. The scrap steel is preheated by the scrap steel baking and preheating devices and then fed into the refining furnace. The feeding speed of the scrap steel baking and preheating devices is 500-2000 kg / min.

[0018] According to an embodiment of this application, the step of transferring a portion of the second molten steel from at least two refining furnaces to an auxiliary refining furnace, and adding auxiliary scrap steel and a third slagging agent at a preset temperature to the auxiliary refining furnace to obtain the third molten steel includes: transferring a portion of the second molten steel from two refining furnaces to an auxiliary refining furnace, or transferring a portion of the second molten steel from three refining furnaces to an auxiliary refining furnace.

[0019] According to embodiments of this application, the third slag-forming agent includes a foaming agent and at least one of aluminum blocks and silica-alumina-calcium.

[0020] According to an embodiment of this application, the step of transferring a portion of the second molten steel from at least two main refining furnaces to auxiliary refining furnaces, and adding scrap steel at a preset temperature and a third slagging agent to the main refining furnace and auxiliary refining furnace to obtain the third molten steel includes: after separation, adding 0-100 kg / t of scrap steel at a preset temperature to the main refining furnace and auxiliary refining furnace, and adding 1-2 kg / t of foaming agent and 0.25-0.5 kg / t of aluminum blocks or 0.5-1.5 kg / t of silicon-aluminum-calcium to form a reducing slag.

[0021] According to an embodiment of this application, 0-100 kg of preheated refined scrap steel is added to the auxiliary refining furnace before the second molten steel is introduced.

[0022] According to the embodiments of this application, the steps of slag alloying the third molten steel to obtain refined molten steel include: feeding pure calcium wire at 2-4.0 m / t using a calcium treatment mode, controlling the soft blowing flow rate at 50-200 NL / min during the soft blowing process, ensuring that the argon soft blowing time of the molten steel is ≥8 min, and the molten steel calming time is ≥15 min.

[0023] Secondly, this application provides an application of the smelting method of adding scrap steel to a smelting tank in the first aspect in the field of iron and steel smelting.

[0024] This application improves the physical heat of molten iron by adding scrap steel in stages and multiple times, and by increasing the temperature through power supply. This ensures that the scrap steel added to the molten iron can melt and mix quickly and evenly. It improves the physicochemical conditions for desulfurization and converter low iron consumption under conditions of strong slag layer oxidation and excessively low temperature after adding scrap steel to the ladle. It solves the problems of large slag removal losses and inadequate desulfurization caused by excessively low temperature. It also solves the problems of converter smelting difficulties, steel quality fluctuations, and environmental protection and high costs caused by converter reheating due to insufficient heat in converter smelting. It increases the amount of scrap steel added, reduces the unit iron consumption, reduces carbon emissions from scrap steel, improves desulfurization efficiency, and has little impact on steel quality, thereby achieving the goal of increasing steel production and economic benefits. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0026] Figure 1 This is a flowchart of the smelting method of adding scrap steel to a steel melting tank provided in this application.

[0027] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0028] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0029] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0030] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0031] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0032] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0033] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0034] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0035] Unless otherwise specified, this application uses conventional testing methods or testing methods recommended by the instrument.

[0036] Currently, scrap steel is generally added through external furnace baking and external furnace refining processes. Considering the large investment in external furnace baking equipment and plant requirements, external furnace refining and scrap steel addition is a relatively mature and suitable option with the characteristics of low investment, small demand space, high scrap steel recovery rate, energy saving and environmental protection. It will inevitably become a new trend in long-process steelmaking to reduce the unit consumption of molten iron.

[0037] Currently, the addition of scrap steel in ladle refining is often affected by factors such as uncontrolled molten steel composition, difficulty in slag formation, limited ladle space, insufficient electrode travel, and difficulty in melting scrap steel. The amount of scrap steel added is generally 50-150 kg per ton of steel, which is a problem of insufficient scrap steel addition in refining.

[0038] In view of the above problems, this application provides a smelting method for adding scrap steel to molten steel in a smelting tank, which can increase the amount of scrap steel added to the molten steel in the refining process.

[0039] Please see Figure 1 In a first aspect, this application provides a smelting method for adding scrap steel to a molten steel ladle, comprising the following steps:

[0040] S100: Add the target alloy to the molten steel in the converter to carry out the molten steel alloying operation to obtain the first molten steel. The amount of the target alloy added is less than or equal to 50% of the total alloy added.

[0041] S200: The first batch of molten steel is transferred from the converter to the main refining furnace. A first slagging agent is added to form slag, and then the furnace is heated to T1 by electricity. Under bottom argon blowing conditions, scrap steel at a preset temperature is added to the main refining furnace in multiple batches to obtain the second batch of molten steel. After each batch of scrap steel is added to the main refining furnace, a second slagging agent is added, and the furnace is heated by electricity to melt the scrap steel. Then, the mixed melt in the refining furnace is heated to T3, and the next batch of scrap steel is added. The main refining furnace includes at least two furnace bodies, with T1 ≥ 1620℃ and T2 ≥ 1600℃.

[0042] S300: Transfer a portion of the second molten steel from at least two main refining furnaces to the auxiliary refining furnaces, and add scrap steel and a third slagging agent at a preset temperature to the main refining furnaces and the auxiliary refining furnaces to obtain the third molten steel;

[0043] S400: The third type of molten steel is slag-forming alloyed to obtain refined molten steel.

[0044] This application's embodiment overcomes the limitations of traditional processes by adding scrap steel in multiple batches to the main refining furnace and then continuing to add scrap steel in both the main and auxiliary refining furnaces after separate ladle operations. The multiple-batch operation in the main refining furnace and the setup of at least two furnaces provide more opportunities and space for scrap steel addition; the separate ladle operation further increases the number of molten steel ladles, significantly increasing the total amount of scrap steel added, reaching over 300 kg / t, effectively improving scrap steel utilization and reducing iron consumption per unit.

[0045] The main refining furnace employs multiple batches of scrap steel addition and separate ladle operations, making the scrap steel addition and molten steel refining process more rational and orderly. Simultaneous operation of multiple furnaces and concurrent processing after ladle separation allows for parallel smelting operations, shortening overall smelting time and improving production efficiency. Furthermore, the rational operating procedures reduce production delays caused by difficulties in composition adjustment and scrap steel melting, ensuring continuous production.

[0046] In step S100, the amount of target alloy added to the molten steel in the converter is controlled during alloying, providing ample room for adjusting the steel composition in the main refining furnace and auxiliary refining furnace stages. During the refining process, the steel composition can be precisely adjusted by adding different slagging agents and alloys according to the changes in steel composition at each stage, ensuring that the steel composition meets the target requirements and improving the stability of steel quality.

[0047] For example, the amount of the target alloy added is equal to 25%, 30%, 35%, 40%, 45%, or 50% of the total alloy added.

[0048] In the S200 process, different slag-forming agents are added at different stages of the main refining furnace and auxiliary refining furnace to slag the steel according to the characteristics of each stage. Adding slag-forming agents after adding scrap steel can effectively promote the melting of scrap steel, while better adsorbing impurities in the molten steel, improving the slag's ability to remove impurities, purifying the molten steel, and enhancing its purity.

[0049] The sources of scrap steel include rebar pellets, hot-rolled trimmed scrap, cold-rolled trimmed wire, purchased recycled profiles, and scattered waste.

[0050] In some embodiments, scrap steel is added to the main refining furnace in at least two batches.

[0051] Adding scrap steel in at least two batches allows each batch more sufficient reaction space and time in the molten steel. Combined with bottom-blowing argon stirring, this ensures thorough contact between the scrap steel and the molten steel, guaranteeing complete melting. Furthermore, adding scrap steel batch by batch, adjusting the temperature and composition after each batch, helps to more evenly disperse the alloying elements in the scrap steel. This avoids localized enrichment or uneven dispersion of alloying elements caused by adding too much scrap steel at once, resulting in a more uniform and stable steel composition and improved steel quality. Adding scrap steel in batches also allows for timely and flexible adjustments to subsequent refining process parameters based on the actual condition of the molten steel after each batch.

[0052] For example, scrap steel can be added to the main refining furnace in two batches or in three batches.

[0053] In some embodiments, the specific steps of adding scrap steel to the refining furnace in two batches include: adding 50-100 kg / t of scrap steel at a preset temperature to the refining furnace under bottom-blown argon conditions, followed by adding 1.0-4.0 kg / t of lime, and heating the molten steel to T3 by electric heating; wherein T3 ≥ 1620°C; and adding 50-100 kg / t of scrap steel at a preset temperature to the refining furnace a second time under bottom-blown argon conditions, followed by adding 0.25-0.5 kg / t of aluminum blocks or 0.5-1.5 kg / t of silicon-aluminum-calcium alloy for slag formation, and heating the molten steel to T4 by electric heating; wherein T4 ≥ 1600°C.

[0054] When adding the first batch of scrap steel, under bottom-blown argon conditions, the scrap steel baking and preheating device of the refining furnace is turned on, and 50-100 kg / t of scrap steel at the preset temperature is added into the refining furnace in an orderly manner. Through the stirring effect of argon gas, the newly added scrap steel can be quickly dispersed in the molten steel, avoiding local accumulation of scrap steel, ensuring full contact between scrap steel and molten steel, and accelerating the melting process of scrap steel.

[0055] For example, the weight of scrap steel added to the refining furnace at a preset temperature is 50 kg / t, 55 kg / t, 60 kg / t, 65 kg / t, 70 kg / t, 75 kg / t, 80 kg / t, 85 kg / t, 90 kg / t, 95 kg / t, 100 kg / t, or any combination of two of the above values.

[0056] After the scrap steel is added, 1.0-4.0 kg / t of lime is immediately added to the furnace. Lime, acting as a slag-forming agent, has its main component, CaO, which reacts chemically with acidic oxides (such as SiO2 and P2O5) in the molten steel to form slag with suitable alkalinity. This appropriate slag alkalinity not only helps remove harmful impurities such as sulfur and phosphorus from the molten steel but also protects the steel and reduces gas absorption and secondary oxidation during subsequent heating.

[0057] For example, the amount of lime added is 1.0 kg / t, 1.5 kg / t, 2.0 kg / t, 2.5 kg / t, 3.0 kg / t, 3.5 kg / t, 4.0 kg / t, or any range of two of the above values.

[0058] After adding scrap steel and lime, the refining furnace is powered on and heated to T3 (≥1620℃). Heating to T3 promotes rapid melting of the scrap steel under the influence of the high-temperature molten steel. Furthermore, the higher temperature facilitates the rapid formation and melting of the slag, giving it good fluidity and allowing it to better adsorb inclusions and purify the molten steel. During the heating process, continuous bottom-blowing argon gas stirring ensures more uniform temperature and composition of the molten steel, preventing localized overheating or undercooling.

[0059] For example, the temperature of T3 is 1620°C, 1630°C, 1640°C, 1650°C, 1660°C, 1670°C or any range of two of the above values.

[0060] Once the molten steel reaches temperature T3 and the first batch of scrap steel has essentially melted and slag has begun to form, the second batch of scrap steel is added. Again, under bottom-blown argon conditions, 50-100 kg / t of scrap steel at the preset temperature is added to the refining furnace. At this point, the molten steel has a certain temperature base and good stirring conditions, which facilitates the faster integration of the second batch of scrap steel into the molten steel.

[0061] For example, scrap steel at a preset temperature is added to the refining furnace again at a weight of 50 kg / t, 55 kg / t, 60 kg / t, 65 kg / t, 70 kg / t, 75 kg / t, 80 kg / t, 85 kg / t, 90 kg / t, 95 kg / t, 100 kg / t, or any combination of two of the above values. Then, depending on the actual condition of the molten steel, 0.25-0.5 kg / t of aluminum blocks or 0.5-1.5 kg / t of silica-alumina-calcium alloy is added for slag formation. The addition of aluminum blocks or silica-alumina-calcium alloy further adjusts the composition and properties of the slag, making it more reducing. Under the action of the reducing slag, the oxygen content in the molten steel is effectively reduced, and it also helps to remove residual harmful impurities in the molten steel, further improving the purity of the molten steel.

[0062] For example, the amount of aluminum block added is 0.25 kg / t, 0.3 kg / t, 0.35 kg / t, 0.4 kg / t, 0.45 kg / t, 0.5 kg / t, or any range of two of the above values.

[0063] For example, the amount of silica-alumina-calcium added is 0.5 kg / t, 0.6 kg / t, 0.7 kg / t, 0.8 kg / t, 0.9 kg / t, 1.0 kg / t, 1.1 kg / t, 1.2 kg / t, 1.3 kg / t, 1.4 kg / t, 1.0 kg / t, or any range of two of the above values.

[0064] After adding the second batch of scrap steel and slag-forming materials, the power-on heating process is restarted to heat the molten steel to T4 (T4 ≥ 1600℃). This heating stage serves two purposes: firstly, to ensure the complete melting of the second batch of scrap steel, and secondly, to allow the molten steel to fully react with the newly added slag-forming materials, optimizing the slag's performance and ensuring the uniformity and stability of the steel's composition. During the heating process, continuous bottom-blowing argon gas stirring promotes mass exchange between the molten steel and slag, resulting in a more uniform steel composition and allowing inclusions to float and be removed.

[0065] For example, the temperature of T4 is 1600℃, 1610℃, 1620℃, 1630℃, 1640℃, 1650℃ or any range of two of the above values.

[0066] By adding two batches of scrap steel and performing corresponding treatments, efficient melting of scrap steel and control of molten steel composition can be achieved in the refining furnace.

[0067] In some embodiments, the flow rate of bottom-blown argon is 600-1500 NL / min.

[0068] When adding scrap steel to the refining furnace, bottom-blown argon gas is continuously introduced into the bottom of the molten steel at a flow rate of 600-1500 NL / min. The bubble flow formed by the argon gas overflowing upwards from the bottom of the ladle generates a strong stirring effect, driving the molten steel to circulate within the furnace. This ensures that the newly added 50-100 kg / t of scrap steel is no longer confined to the surface or a localized area of ​​the molten steel, but is rapidly dispersed throughout the entire molten steel pool. The contact area between the scrap steel and the high-temperature molten steel is significantly increased, accelerating the heat transfer and melting rate of the scrap steel.

[0069] When the argon flow rate is within the above range, it can enable the molten steel to form a reasonable circulation within the furnace, ensuring that the newly added material is fully mixed with the molten steel.

[0070] The flow rate of bottom-blown argon gas has a significant impact on the formation and function of slag. At a flow rate of 600-1500 NL / min, the agitation of molten steel increases the contact area between the slag and molten steel, promoting mass exchange between them. After slag with suitable basicity is formed, stable argon agitation allows the slag to better adsorb harmful impurities such as sulfur and phosphorus, as well as inclusions, from the molten steel. When aluminum blocks or silica-alumina-calcium alloys are added to adjust the slag to a reducing slag, an appropriate argon flow rate helps the slag and molten steel react fully, reducing the oxygen content in the molten steel.

[0071] For example, the flow rate of bottom-blown argon is 600 NL / min, 700 NL / min, 800 NL / min, 900 NL / min, 1000 NL / min, 1100 NL / min, 1200 NL / min, 1300 NL / min, 1400 NL / min, 1500 NL / min or any combination of two of the above values.

[0072] In some embodiments, the first slag-forming agent is 1-2t of hot continuous casting residue slag or 1-2kg / t of foaming agent.

[0073] Hot-casting residue carries a large amount of high-temperature heat, typically exceeding 1000℃. Adding it to molten steel rapidly releases this heat, replenishing the steel's temperature and mitigating temperature drops during transfer. Simultaneously, the residue is rich in slag-forming components such as CaO, SiO2, and Al2O3, which can directly participate in the slag-forming reaction, significantly reducing the amount of conventional slag-forming agents like lime. For example, when molten steel first enters the main refining furnace, the CaO in the residue reacts rapidly with acidic oxides in the steel, forming slag with suitable alkalinity in a very short time, shortening slag-forming time and improving the heating efficiency in the early stages of refining.

[0074] The CaO-SiO2-Al2O3 system in the continuous casting residue slag effectively captures inclusions such as Al2O3 and SiO2 during the settling or bottom-blowing argon stirring of the molten steel, promoting their flotation to the slag layer. Especially in the smelting of high-alloy steels, the trace alloying elements (such as Fe, Mn, Cr, etc.) in the residue slag can, to some extent, fine-tune the composition of the molten steel, reducing alloy consumption costs while improving the purity and uniformity of the steel.

[0075] The foaming agent can be composed of carbon powder, SiC, or metallic aluminum, or it can be a CaO-Na2CO3 based foaming agent. When it reacts with molten steel or slag, it produces gases such as CO and H2, which promotes the foaming and expansion of the slag to form a foamed slag layer of moderate thickness. This foamed slag layer has excellent thermal insulation properties, effectively isolating air and reducing the absorption of gases (such as hydrogen and nitrogen) by the molten steel and secondary oxidation. During the refining furnace's power-on heating stage, the foamed slag can also absorb the radiant heat from the electric arc, reducing the thermal load on the ladle refractory materials, extending the service life of the furnace lining, and simultaneously reducing heat loss from the molten steel surface, ensuring the uniformity of the molten steel temperature.

[0076] The porous structure of foamy slag greatly increases the contact area between slag and molten steel, significantly improving the mass exchange rate at the slag-steel interface.

[0077] In some embodiments, the preset temperature is 500-1000℃.

[0078] When scrap steel is added to molten steel, it absorbs a large amount of heat. If the temperature of the scrap steel is too low, it will cause a significant drop in the temperature of the molten steel, increasing the heating burden on the refining furnace. When the scrap steel is preheated to 500-1000℃, the heat it carries can significantly reduce its negative impact on the temperature of the molten steel.

[0079] Furthermore, scrap steel within the aforementioned temperature range reaches its melting point more quickly upon addition to molten steel, accelerating the melting process. The higher heat transfer efficiency of high-temperature scrap steel in contact with molten steel reduces its melting time. In multi-batch scrap steel addition operations in the main refining furnace, the preheated scrap steel rapidly integrates into the molten steel, ensuring rapid processing of each batch and making the entire refining process more compact and efficient, thus improving production efficiency.

[0080] For example, the preset temperature is 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃ or a range of any two of the above values.

[0081] In some embodiments, the scrap steel has a length ≤ 600 mm and a thickness ≤ 30 mm.

[0082] The smaller size of the scrap steel allows it to quickly and fully contact the high-temperature molten steel after being added. Scrap steel with a length ≤600mm and a thickness ≤30mm has a larger surface area per unit mass compared to larger scrap pieces, resulting in higher heat transfer efficiency. During the multiple batches of scrap steel added to the main refining furnace, this size of scrap steel can rapidly absorb the heat from the molten steel, shortening the melting time and ensuring that each batch of scrap steel melts promptly after addition, reducing the overall time consumed in the refining process and improving production speed.

[0083] If the scrap steel is too large, it may sink to the bottom of the ladle due to gravity after being added to the molten steel, causing the temperature of the molten steel at the bottom to drop and affecting the melting of the scrap steel. At the same time, large pieces of scrap steel are also prone to piling up, hindering the flow and agitation of the molten steel, making it difficult for the scrap steel to be heated evenly. Scrap steel that meets the size requirements, under the agitation of bottom-blown argon gas, can be evenly dispersed in the molten steel pool, avoiding sinking or piling up, and ensuring the stability and efficiency of the scrap steel melting process.

[0084] In some embodiments, the scrap steel does not contain sealed containers, does not contain ash or steel slag, and does not contain ferroalloys or non-ferrous metals.

[0085] Sealed containers may contain residual gas or liquid. When such containers are added to molten steel at high temperatures along with scrap, the internal substances expand rapidly due to heat, causing a sudden increase in pressure and posing a significant risk of a violent explosion. Such explosions not only cause molten steel to splash and threaten the lives of operators, but can also damage critical equipment such as refining furnaces and ladles, resulting in major production accidents and economic losses. Therefore, it is strictly prohibited to include sealed containers with scrap to ensure the safe and orderly conduct of the smelting process.

[0086] Ash slag often contains volatile or flammable substances such as moisture and organic matter. When it enters molten steel, these substances rapidly decompose or burn upon heating, generating large amounts of gas and causing the molten steel to violently churn and even splash. Furthermore, the complex composition of the mixed steel slag, with its basicity and oxidizing properties, does not match the slag composition required in the refining process, potentially interfering with normal slag-forming reactions and affecting the effectiveness of critical processes such as dephosphorization and desulfurization. In addition, the density and melting point of steel slag differ from those of scrap steel, leading to uneven steel composition, increasing the difficulty of subsequent composition adjustments, and even affecting the casting performance of the molten steel.

[0087] The composition of ferroalloys and non-ferrous metals often differs from the alloy ratio of the target steel grade. If these are mixed into molten steel from scrap, it will cause deviations in the steel's composition. For example, the addition of non-ferrous metals such as copper and zinc to molten steel will reduce its hot working properties, leading to hot brittleness. Furthermore, the accidental mixing of different types of ferroalloys may cause the alloy element content in the molten steel to exceed standard ranges, affecting key performance indicators such as strength and toughness. Strictly prohibiting the mixing of these substances into scrap steel allows for precise control of the molten steel composition, ensuring that finished steel products meet quality requirements and reducing product scrapping and rework costs due to substandard composition.

[0088] Ash and steel slag contain a large number of non-metallic inclusions (such as silicates and oxides). These inclusions, once incorporated into molten steel, are difficult to remove completely during refining and remain inside the steel, forming defects such as porosity and looseness, severely reducing the steel's density and mechanical properties. Eliminating the inclusion of ash and steel slag in scrap steel can significantly reduce the sources of inclusions in molten steel, improve its purity, and thus produce high-quality steel products that meet the stringent quality requirements of high-end manufacturing industries.

[0089] In some embodiments, the slag in the main refining furnace is pale yellow or pale white, and the total iron content of the slag is ≤5%.

[0090] The color of slag is closely related to its composition. Pale yellow or pale white slag indicates that its main components are basic oxides such as CaO and Al2O3, with a low content of iron oxide (FeO). CaO is a key component for dephosphorization and desulfurization of slag, and slag with high basicity (higher CaO / SiO2 ratio) helps improve dephosphorization and desulfurization efficiency. Low iron oxide content means that the slag has weak oxidizing properties, which can reduce the oxidation loss of alloying elements such as Mn and Si in the molten steel and reduce alloy consumption costs. If the slag is dark black or dark red, it usually means that the iron oxide content is too high and the slag has too strong an oxidizing property. This will not only aggravate alloy loss but may also lead to oxygenation in the molten steel, affecting the purity of the steel.

[0091] The total iron content in slag affects its reducibility. When the total iron content is controlled below 5%, the slag is in a weak oxidation-reduction state, which can effectively reduce the oxygen content in molten steel and promote the flotation and removal of inclusions. Ensuring a low total iron content in the slag before calcium treatment can prevent calcium from being oxidized by iron oxide, ensuring the effectiveness of calcium treatment and improving the fluidity and casting performance of molten steel. If the total iron content is too high, the oxidizing property of the slag will increase, making deoxidation of molten steel difficult, increasing the number of inclusions in the steel, and even causing secondary oxidation of the molten steel. Total iron includes forms such as FeO and Fe2O3.

[0092] In some embodiments, the heating rate of the main refining furnace is 4-10 °C / min.

[0093] During the refining process of molten steel, key reactions such as dephosphorization, desulfurization, and deoxidation require suitable temperature conditions and reaction time. If the heating rate is too fast, the temperature of the molten steel rises rapidly, and the chemical reaction between the slag and the molten steel may be insufficient due to insufficient reaction time, resulting in a decrease in dephosphorization and desulfurization efficiency and an inability to effectively remove harmful impurities from the molten steel. On the other hand, if the heating rate is too slow, it will prolong the refining cycle, increase the risk of gas absorption and secondary oxidation in the molten steel, and affect the purity of the molten steel.

[0094] Furthermore, the heating rate directly affects the melting and compositional uniformity of the slag. A heating rate of 4-10℃ / min allows slag-forming agents (such as lime, aluminum blocks, and silica-alumina-calcium) to gradually melt and fully react with the molten steel, forming a stable slag. Excessive heating may lead to localized overheating of the slag, causing some components to melt prematurely, resulting in uneven slag composition and affecting its ability to adsorb inclusions and purify molten steel. Conversely, excessively slow heating may leave the slag in an incompletely melted state for an extended period, preventing it from effectively protecting the molten steel and promoting the reaction.

[0095] For example, the heating rate of the main refining furnace is 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min or any combination of two of the above values.

[0096] In some embodiments, the clear space of the ladle at the converter tapping point is 600-1200 mm.

[0097] Ladle clearance refers to the distance from the surface of molten steel to the top edge of the ladle. It directly affects the physical and chemical reaction space of molten steel during the refining process and operational safety.

[0098] During the main refining furnace stage, scrap steel, slagging agents, and other materials need to be added multiple times, and power should be supplied to raise the temperature. Appropriate ladle clearance provides space for material addition, preventing insufficient clearance from hindering material addition and affecting the refining process. For example, if the ladle clearance is too small when adding scrap steel at a preset temperature, the added scrap steel may cause the molten steel to approach the top edge of the ladle, making it difficult to add the slagging agent subsequently, or even causing the molten steel to overflow.

[0099] The aforementioned ladle clearance provides ample buffer space for subsequent refining and ladle separation operations. During the main refining furnace heating, multiple batches of scrap steel are added, and ladle separation operations, the molten steel will fluctuate due to temperature changes, volume expansion, or agitation. If the clearance is too small, the molten steel may overflow the ladle, causing a safety accident. A clearance of 600-1200mm effectively avoids such situations, ensuring stable production.

[0100] For example, the net clearance of the ladle for tapping steel from the converter is 600mm, 650mm, 700mm, 750mm, 800mm, 850mm, 900mm, 950mm, 1000mm, 1050mm, 1100mm, 1150mm, 1200mm or any two of the above values.

[0101] The specific steps for S200 are as follows:

[0102] The first batch of molten steel is transferred from the converter to the main refining furnace. A first slagging agent is added to form slag, and then the furnace is heated to T1 (≥1620℃) under argon blowing conditions. Scrap steel at a preset temperature is added to the main refining furnace in multiple batches to obtain the second batch of molten steel. After each batch of scrap steel is added to the main refining furnace, a second slagging agent is added, and the furnace is heated to melt the scrap steel. The mixed melt in the main refining furnace is then heated to T2 (≥1600℃), and the next batch of scrap steel is added. In the main refining furnace refining process, at least two furnace bodies are used. Through multiple heating cycles, multiple batches of scrap steel addition, and slagging operations, the amount of scrap steel added is gradually increased while ensuring complete melting of the scrap steel and uniform composition of the molten steel.

[0103] For example, T1 is 1620℃, 1630℃, 1640℃, 1650℃, 1660℃, 1670℃ or a range consisting of any two of the above values.

[0104] For example, T2 is 1600℃, 1610℃, 1620℃, 1630℃, 1640℃, 1650℃ or a range consisting of any two of the above values.

[0105] In some embodiments, each refining furnace is associated with a scrap steel baking and preheating device, which preheats the scrap steel before feeding it into the refining furnace; wherein the feeding speed of the scrap steel baking and preheating device is 500-2000 kg / min.

[0106] For example, the feeding speed of the scrap steel baking preheating device is 500 kg / min, 600 kg / min, 800 kg / min, 1000 kg / min, 1200 kg / min, 1400 kg / min, 1500 kg / min, 1600 kg / min, 1800 kg / min, 2000 kg / min or any range of two of the above values.

[0107] Each refining furnace corresponds to a set of scrap steel baking and preheating devices, which can independently adjust the preheating temperature and time according to the smelting requirements of different heats. Independent temperature control also reduces the interference of switching scrap steel preheating parameters when smelting different steel grades, ensuring that each batch of scrap steel can reach the preset preheating temperature of 500-1000℃, laying the foundation for efficient melting and stable steel quality in the subsequent process. The main refining furnace adopts a multi-batch scrap steel feeding process, and the corresponding scrap steel baking and preheating device can dynamically adjust the feeding speed according to the scrap steel feeding rhythm.

[0108] The feeding speed is closely coordinated with the preheating process. A feeding speed in the range of 500-2000 kg / min can ensure that the scrap steel has sufficient residence time in the baking device to complete the preheating, while avoiding the accumulation of scrap steel in the device and overheating deformation due to slow feeding, or insufficient preheating of scrap steel due to fast feeding.

[0109] After the molten steel is ladled into a container, the refining furnace and auxiliary refining furnace can simultaneously perform scrap steel addition and refining operations. Each furnace has an independent preheating device that can independently control the feeding speed according to the state of the molten steel and processing requirements.

[0110] In step S300, a portion of the second molten steel from at least two main refining furnaces is transferred to an auxiliary refining furnace. Scrap steel and a third slagging agent at a preset temperature are added to both the main refining furnace and the auxiliary refining furnace to obtain the third molten steel.

[0111] In this embodiment, a ladle-splitting operation is performed. By redistributing the molten steel, the capacity and operational limitations of a traditional single refining furnace are broken, creating more favorable conditions for the addition of scrap steel and the refining of molten steel. After transferring part of the second molten steel from the main refining furnace to the auxiliary refining furnace, it is equivalent to adding a molten steel processing unit. The volume of molten steel in each refining furnace is reduced, and the net space of the ladle is increased, providing space for the subsequent addition of more scrap steel. At the same time, it also reduces the operational difficulty and safety risks caused by excessive molten steel during the refining process.

[0112] In some embodiments, portions of the second molten steel from the two refining furnaces are transferred to the auxiliary refining furnace, or portions of the second molten steel from the three refining furnaces are transferred to the auxiliary refining furnace.

[0113] When production is of medium scale and there are requirements for balancing steel quality and production efficiency, a portion of the second batch of molten steel from the two main refining furnaces can be transferred to the auxiliary refining furnace. This allows for rapid secondary distribution of the molten steel, resulting in three smaller ladles for subsequent processing. After the two main refining furnaces are used to separate the molten steel, subsequent process parameters can be adjusted based on the actual composition and temperature of each ladle. Because each ladle of molten steel is relatively small, the added scrap steel and alloys can mix and react with the molten steel more quickly and evenly, making the adjustment of the steel composition more timely and accurate.

[0114] When faced with large-scale production tasks or the need for rapid capacity increases, a portion of the second batch of molten steel from the three main refining furnaces can be transferred to auxiliary refining furnaces, forming four ladlefuls of molten steel for processing. This fully utilizes the equipment's production potential. Simultaneous operation of the four refining furnaces significantly increases the total amount of scrap steel added, further improving scrap steel utilization. Taking the production of high-strength low-alloy steel as an example, the separate operation of the three main refining furnaces allows for scrap steel input exceeding conventional limits, reaching higher levels. Simultaneously, parallel processing significantly increases the steel output per unit time, meeting the market's substantial demand for steel.

[0115] In some embodiments, the third slag-forming agent includes a foaming agent and at least one of aluminum blocks and calcium silicate.

[0116] In some embodiments, after separation into tanks, scrap steel at a preset temperature of 0-100 kg / t is fed into the main refining furnace and the auxiliary refining furnace, and 1-2 kg / t of foaming agent and 0.25-0.5 kg / t of aluminum blocks or 0.5-1.5 kg / t of silicon-aluminum-calcium are added to form reducing slag.

[0117] After the steel is separated into individual ladles, 0-100 kg / t of scrap steel at a preset temperature is added to each ladle. The amount added can be flexibly controlled based on the actual conditions such as the ladle clearance, steel temperature, and target composition of each ladle after separation. Adding scrap steel at a preset temperature can make full use of its own heat and reduce the temperature drop of the molten steel caused by the addition of scrap steel.

[0118] For example, the weight of scrap steel added to each furnace after separation into tanks is 0-100 kg / t, which is 5 kg / t, 10 kg / t, 20 kg / t, 40 kg / t, 50 kg / t, 60 kg / t, 80 kg / t, 100 kg / t, or any combination of two of the above values.

[0119] Adding 1-2 kg / t of foaming agent causes it to react with molten steel or slag to produce gases such as CO and H2, promoting the foaming and expansion of the slag to form a foamed slag layer. This foamed slag layer has excellent thermal insulation properties, effectively isolating air and reducing gas absorption and secondary oxidation in the molten steel, making it particularly suitable for steel smelting with strict requirements on gas content. During the refining furnace's power-on heating stage, the foamed slag can also absorb the radiant heat from the electric arc, reducing the thermal load on the ladle refractory materials and extending the furnace lining's service life. For example, the main components of the foaming agent are carbon powder, SiC, or metallic aluminum.

[0120] For example, the amount of foaming agent added is 1.0 kg / t, 1.2 kg / t, 1.4 kg / t, 1.5 kg / t, 1.6 kg / t, 1.8 kg / t, 2 kg / t, or any range of two of the above values.

[0121] Depending on the steel grade requirements, 0.25-0.5 kg / t of aluminum blocks or 0.5-1.5 kg / t of silica-alumina-calcium can be added, both of which are strong reducing agents. Aluminum blocks react with molten steel to form Al₂O₃, simultaneously consuming oxygen and reducing the oxidizing properties of the steel. Silica-alumina-calcium not only deoxidizes but also reacts with sulfur in the molten steel to form CaS, further desulfurizing it. By adjusting the amount of aluminum blocks or silica-alumina-calcium added, the reducing properties of the slag can be precisely controlled to meet the stringent oxygen and sulfur content requirements of different steel grades. For example, in the smelting of ultra-low oxygen steel and ultra-low sulfur steel, this operation can effectively reduce the content of harmful elements in the steel and improve its performance.

[0122] For example, the amount of aluminum block added is 0.25 kg / t, 0.3 kg / t, 0.35 kg / t, 0.4 kg / t, 0.45 kg / t, 0.5 kg / t, or any range of two of the above values.

[0123] For example, the amount of silica-alumina-calcium added is 0.5 kg / t, 0.6 kg / t, 0.7 kg / t, 0.8 kg / t, 0.9 kg / t, 1.0 kg / t, 1.1 kg / t, 1.2 kg / t, 1.3 kg / t, 1.4 kg / t, 1.0 kg / t, or any range of two of the above values.

[0124] This series of operations performed after the separation of the furnaces organically combines the addition of scrap steel, slag foaming, and the formation of reducing slag, significantly improving the overall efficiency of the smelting process. By flexibly controlling the amount of scrap steel added, the utilization rate of scrap steel is improved, and production costs are reduced. The synergistic effect of foaming agents and slag-forming materials optimizes slag performance, accelerates the steel refining reaction, and shortens smelting time. At the same time, precise control of composition and impurities ensures that the final steel produced is of stable quality and meets high standards, enhancing the company's competitiveness in the market.

[0125] In some embodiments, 0-100 kg of preheated refined scrap steel is added to the auxiliary refining furnace before the second molten steel is introduced.

[0126] When the second batch of molten steel from the main refining furnace is transferred to the auxiliary refining furnace, its temperature drops due to factors such as steel transfer and environmental heat dissipation. Preheating 0-100 kg of refined scrap steel to 500-1000℃ can compensate for the temperature loss of the molten steel by utilizing the heat inherent in the scrap steel.

[0127] Preheated scrap steel added beforehand can react with residual furnace gas or trace amounts of steel slag in the auxiliary refining furnace, consuming oxidizing gases and reducing the oxygen partial pressure, thus creating a relatively reducing reaction environment for subsequent molten steel input. When the second batch of molten steel is introduced, the reaction between the molten steel and scrap steel, slagging agents, and other materials can start more quickly, reducing the waiting time for the molten steel to react and accelerating the entire refining process. For example, the carbon in the scrap steel reacts with oxygen in the furnace, reducing the oxygen content and allowing subsequently added reducing slagging materials such as aluminum blocks and silica-alumina-calcium alloys to more efficiently perform deoxidation and desulfurization functions.

[0128] Depending on the smelting requirements of different steel grades and the actual condition of the molten steel after separation, the amount of scrap steel added to the auxiliary refining furnace in advance (0-100kg) can be flexibly controlled. For steel grades with high requirements for the amount of scrap steel added and those that need to further reduce iron consumption, the amount of scrap steel added in advance can be appropriately increased; while for special steel grades that are sensitive to temperature and have strict requirements for composition, the amount of scrap steel added in advance can be reduced or not added at all, prioritizing the stability of the molten steel temperature and composition, and then adding scrap steel precisely according to the test results, thereby enhancing the flexibility and adaptability of the process operation.

[0129] For example, before the second molten steel is introduced into the auxiliary refining furnace, scrap steel is pre-added in a weight range of 10 kg / t, 20 kg / t, 30 kg / t, 40 kg / t, 50 kg / t, 55 kg / t, 60 kg / t, 65 kg / t, 70 kg / t, 75 kg / t, 80 kg / t, 85 kg / t, 90 kg / t, 95 kg / t, 100 kg / t, or any two of the above values.

[0130] For example, the preheating temperature of scrap steel in the auxiliary refining furnace is 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C or a range of any two of the above values.

[0131] In step S400, the third molten steel undergoes slag-forming alloying to obtain refined molten steel. In the final refining step, the molten steel undergoes final composition adjustments and impurity removal to ensure its quality meets production requirements.

[0132] In some embodiments, the step of slag alloying the third molten steel to obtain refined molten steel includes: feeding pure calcium wire at 2-4.0 m / t using a calcium treatment mode, controlling the soft blowing flow rate at 50-200 NL / min during the soft blowing process, ensuring that the argon soft blowing time of the molten steel is ≥8 min, and the molten steel calming time is ≥15 min.

[0133] A calcium-treated feed line of 2-4.0 m / t is used to introduce calcium into the molten steel, altering the morphology and properties of inclusions. Calcium reacts with oxygen and sulfur in the molten steel, transforming previously harmful brittle inclusions such as Al2O3 and CaS into low-melting-point, spherical composite inclusions, such as CaO-Al2O3-CaS. These spherical inclusions have better fluidity in the molten steel, are less likely to clog the sprue of the continuous casting mold, and reduce the risk of nozzle clogging and blockage caused by inclusion aggregation during casting, ensuring the continuity and stability of the continuous casting process. This also reduces the cutting effect of inclusions on the steel matrix, significantly improving the steel's toughness, ductility, and fatigue resistance.

[0134] Based on the characteristics of the steel grade and the requirements for inclusion control, the calcium content in the molten steel can be precisely controlled by adjusting the feed rate of the pure calcium wire within the range of 2-4.0 m / t.

[0135] For example, the feed rate of pure calcium line is 2 m / t, 2.5 m / t, 3 m / t, 3.5 m / t, 4.0 m / t, or any range of two of the above values.

[0136] During soft blowing, the flow rate is controlled at 50-200 NL / min, and the soft blowing time is ensured to be ≥8 min. The gentle stirring effect of argon gas is utilized to achieve refined treatment of the molten steel. The lower argon flow rate produces a mild stirring effect, preventing violent turbulence in the molten steel from causing inclusions to be re-entered. During the ≥8 min soft blowing time, inclusions, driven by argon bubbles, have sufficient time to float to the slag-steel interface and be adsorbed and removed by the slag, effectively reducing the inclusion content in the steel and improving its purity.

[0137] The soft-blowing process allows the molten steel to flow slowly, promoting a uniform distribution of alloying elements and temperature. Especially after alloying, this ensures a consistent alloy composition in the molten steel, preventing performance differences caused by localized compositional deviations and guaranteeing the stability of the steel's quality. Simultaneously, a uniform temperature distribution contributes to the solidification quality of the molten steel during subsequent continuous casting, reducing the risk of defects such as shrinkage cavities and segregation in the cast billet.

[0138] Furthermore, a stable soft-blowing flow rate prevents the molten steel from violently scouring the slag layer, maintaining the integrity and coverage of the slag. The slag continues to adsorb inclusions and isolate air, preventing secondary oxidation and air absorption of the molten steel, thus further ensuring the quality of the molten steel.

[0139] For example, during the soft blow process, the flow rate is controlled to be 50NL / min, 60NL / min, 80NL / min, 100NL / min, 120NL / min, 140NL / min, 150NL / min, 160NL / min, 180NL / min, 200NL / min, or a range of any two of the above values.

[0140] For example, the soft blowing time is 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, or any range of two of the above values.

[0141] Ensuring a quenching time of ≥15 minutes for molten steel creates favorable conditions for the casting process. Extending the quenching time allows smaller inclusions that haven't yet floated more time to complete their flotation, further reducing the amount of residual inclusions in the steel and improving its internal quality. This is particularly important for producing high-end steels with extremely high purity requirements. During the quenching process, gases such as CO generated inside the molten steel can fully escape, preventing defects such as boiling and porosity caused by gas escape during casting. Simultaneously, the steel temperature tends to stabilize, reducing the impact of temperature fluctuations on casting speed and billet quality, thus improving the surface quality and yield of continuously cast billets.

[0142] For example, the molten steel calming time is 15 min, 16 min, 18 min, 20 min, 22 min, 24 min, 25 min, 26 min, 28 min, 30 min, or any range of two of the above values.

[0143] The embodiments of this application utilize the coordinated processes of calcium treatment, soft blowing, and sintering to ensure that each batch of refined steel meets the production standards for high-quality steel.

[0144] In some embodiments, the amount of slag dumped from the molten steel in the sub-tank should not exceed 2t to prevent the slag volume from affecting the addition of carbon (C) and scrap steel. The molten steel in the sub-tank should be controlled in terms of its rhythm, primarily by controlling the amount of scrap steel added. Sufficient time must be ensured for the addition of carbon (C) and desilication (S) to prevent high S levels at the station or rushing to the platform from affecting quality and rhythm. During controlled silicon smelting of the molten steel in the sub-tank, after adding scrap steel and powering on, stir for 1-2 minutes to desilicate (before adding aluminum). Add lime simultaneously with aluminum addition to prevent the slag from becoming too thin and causing a return to silicon. Add aluminum and lime promptly according to the slag condition. It is important to note that after adding aluminum blocks, stir for 1-2 minutes to check the slag deoxidation status, and continuously monitor the slag consistency. The soft blowing time for the molten steel should be at least 8 minutes.

[0145] In some embodiments, depending on the ladle clearance, the molten steel after each ladle can be heated by electricity.

[0146] When electricity is supplied for heating, molten steel will expand in volume and boil due to the increased temperature. If the ladle has insufficient clearance, the molten steel can easily overflow, causing a safety accident and interfering with normal smelting operations. Therefore, determining whether to supply electricity for heating, as well as the magnitude and rate of heating, based on the ladle clearance ensures that the molten steel has enough space to accommodate volume changes during the heating process, maintaining the stability of the smelting process.

[0147] When the ladle clearance is high, such as greater than 800mm, it indicates that there is ample space inside the ladle to accommodate the volume changes of the molten steel after heating. In this case, the power supply can be appropriately increased to accelerate the heating rate and meet the needs of the production schedule.

[0148] If the ladle clearance is low, such as less than 600mm, the power supply and heating operation must be carefully controlled to prevent molten steel from overflowing. On the one hand, reduce the power supply and use a smaller heating rate to allow the molten steel temperature to rise slowly; on the other hand, monitor the molten steel level and temperature changes in real time, and immediately suspend or adjust the power supply operation if any risk of molten steel overflow is detected.

[0149] Secondly, this application provides an application of the smelting method of adding scrap steel to a smelting tank in the first aspect in the field of iron and steel smelting.

[0150] In some embodiments, the smelting method is used to smelt rebar grades, Q235B-Q355B ordinary plate grades, or grades with appropriately loose steel composition ([C]≥0.08%, [N]≥0.0060%, [P]≥0.0180%, [S]≥0.0100%).

[0151] Example

[0152] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0153] Example 1

[0154] A smelting method for adding scrap steel to a ladle in steel smelting, applied to a 210t nominal tonnage ladle refining furnace, wherein the ladle clearance after tapping Q355B steel from the converter is 900mm, includes the following steps:

[0155] S1. Each ladle refining furnace in the refining process is equipped with a scrap steel baking and preheating device for preheating scrap steel.

[0156] S1.1 Refined scrap steel shall not contain closed containers, shall not be mixed with ash and steel slag, and shall not contain impurities such as ferroalloys and non-ferrous metals. The dimensions of refined scrap steel shall be ≤600mm in length and ≤30mm in thickness.

[0157] The S1.2 baking device can bake scrap steel to 800℃;

[0158] The S1.3 baking device can achieve a feeding speed of 1000 kg / min according to the vibration frequency.

[0159] S2, 185t of molten steel in the converter process, 100kg of aluminum added to the molten steel alloying, and 60kg of carbon raiser;

[0160] S3. 1.5t of hot continuous casting residue slag is poured into the molten steel from the converter process. The first refining process involves heating the molten steel to 1620℃ by power supply. While bottom blowing argon gas, 80kg / t of baked scrap steel is added through a baking device, followed by 1.0kg / t of lime. The second refining process involves heating the molten steel to 1620℃ by power supply. The second process involves bottom blowing argon gas while adding 80kg / t of baked scrap steel through a baking device, and appropriate amounts of 0.5kg / t aluminum blocks and 1.0kg / t silicon-aluminum-calcium alloy are added for slag formation. The third refining process involves power supply to raise the temperature to ≥1600℃.

[0161] The temperature of the scrap steel after baking is 620℃;

[0162] S3.2 When adding scrap steel, the bottom-blown argon flow rate is 1000 NL / min;

[0163] The color of S3.3 slag changes to pale yellow or pale white, and the total iron content of the slag is 3.8%.

[0164] S4. Pour 350 kg / t of the two molten steels into another empty ladle (50 kg / t of refined scrap steel is added to the ladle beforehand) to form a new ladle of molten steel. The three molten steels after splitting are 150 t, 150 t and 151 t respectively. After step S3 (without pouring in casting residue), after powering on, add 80 kg / t and 80 kg / t of baked scrap steel in two batches through the baking device. Add 1 kg / t of foaming agent, 0.5 kg / t of aluminum blocks and 1 kg / t of silica-alumina-calcium to form reducing slag.

[0165] The three molten steel tanks after the S4.1 split tank have net clearances of 1000mm, 1000mm, and 990mm respectively, and all can be powered.

[0166] S4.2 The new molten steel generated by the subcontracting produces a new furnace number code corresponding to the corresponding smelting information, but there is no converter smelting information;

[0167] S5. Normal smelting slag formation and alloying, adopting calcium treatment mode to feed pure calcium wire 2.0m / t, ensuring argon soft blowing time of molten steel for 8min and molten steel calming time for 20min.

[0168] The three refining processes combined the addition of 315 kg / t of scrap steel (172 t), fed 360 m of pure calcium wire, used a soft blowing flow rate of 160 NL / min, a soft blowing time of 8 min, and a molten steel calming time of 20 min. The molten steel quality was good, which significantly reduced the iron consumption per unit and increased the scrap steel ratio, thereby reducing the cost of converter smelting and increasing steel production.

[0169] Example 2

[0170] A smelting method for adding scrap steel to a ladle in steel smelting, applied to a 100t nominal tonnage ladle refining furnace, wherein the ladle clearance after tapping from the HRB400 converter is 1200mm, includes the following steps:

[0171] S1. Each ladle refining furnace in the refining process is equipped with a scrap steel baking and preheating device for preheating scrap steel.

[0172] S1.1 Refined scrap steel shall not contain closed containers, shall not be mixed with ash and steel slag, and shall not contain impurities such as ferroalloys and non-ferrous metals. The dimensions of refined scrap steel shall be ≤600mm in length and ≤30mm in thickness.

[0173] The S1.2 baking device can bake scrap steel to 900℃;

[0174] The S1.3 baking device can achieve a feeding speed of 800 kg / min according to the vibration frequency.

[0175] S2, 78t of molten steel in the converter process, with 60kg of carbon raiser and 500kg of silicon manganese added during steel alloying;

[0176] S3. 1.0t of hot continuous casting residue slag is poured into the molten steel from the converter process. The first refining process involves heating the molten steel to 1630℃ by power supply. Argon gas is blown from the bottom while 110kg / t of baked scrap steel is added through a baking device. Then, 1.0kg / t of lime is added. The second refining process involves heating the molten steel to 1620℃ by power supply. Argon gas is blown from the bottom while 110kg / t of baked scrap steel is added through a baking device. 2kg / t of silica-alumina-calcium is added to form slag. The third refining process involves power supply to raise the temperature to ≥1600℃.

[0177] The temperature of the scrap steel after baking is 650℃;

[0178] When adding scrap steel, the bottom-blown argon flow rate is 1200 NL / min.

[0179] S4. Pour 300 kg / t of the two molten steels into another empty ladle (100 kg / t of refined scrap steel is added to the ladle beforehand) to form a new ladle of molten steel. The three molten steels after splitting are approximately 70t, 70t and 70t respectively. Perform step S3 (no more casting residue is poured in) and after powering on, add 100 kg / t and 100 kg / t of baked scrap steel in two batches through the baking device. Add 1 kg / t of foaming agent and 2 kg / t of silica-alumina-calcium to form reducing slag.

[0180] The three molten steel tanks after the S4.1 split tank have net clearances of 950mm, 960mm, and 950mm respectively, and all can be powered.

[0181] S4.2 The new molten steel generated by the subcontracting produces a new furnace number code corresponding to the corresponding smelting information, but there is no converter smelting information;

[0182] S5. Normal smelting slag formation and alloying, ensuring argon soft blowing time of molten steel is 8 minutes and molten steel calming time is 15 minutes.

[0183] The three refining processes combined add 380 kg / t of scrap steel, or 104 t, with a soft blowing flow rate of 50 NL / min, a soft blowing time of 8 min, and a molten steel calming time of 15 min. The molten steel quality was good, which significantly reduced the iron consumption per unit and increased the scrap steel ratio, thereby reducing the converter smelting cost and increasing steel production.

[0184] The above are merely specific embodiments of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A smelting method for adding scrap steel to a molten steel ladle, characterized in that, Includes the following steps: A target alloy is added to the molten steel in a converter to perform a steel alloying operation, resulting in the first molten steel. The amount of the target alloy added is less than or equal to 50% of the total alloy added. The first molten steel is transferred from the converter to the main refining furnace, a first slagging agent is added to form slag, and then the temperature is raised to T1 by power supply. Under bottom argon blowing conditions, scrap steel at a preset temperature is added to the main refining furnace in multiple batches to obtain the second molten steel. Each batch of scrap steel is added to the main refining furnace, a second slagging agent is added, and the temperature is raised by power supply to melt the scrap steel. Then, the mixed melt in the main refining furnace is heated to T2, and the next batch of scrap steel is added. The main refining furnace includes at least two furnace bodies, with T1 ≥ 1620℃ and T2 ≥ 1600℃. A portion of the second molten steel from at least two of the main refining furnaces is transferred to an auxiliary refining furnace. Scrap steel and a third slagging agent at a preset temperature are added to the main refining furnace and the auxiliary refining furnace to obtain the third molten steel. The third molten steel is then subjected to slag-forming alloying to obtain refined molten steel.

2. The smelting method for adding scrap steel to a steel-water mixing tank according to claim 1, characterized in that, The step of transferring the first molten steel from the converter to the main refining furnace, adding the first slagging agent to form slag, then heating it to T1 by power supply, and adding scrap steel at a preset temperature to the main refining furnace in multiple batches under bottom argon blowing conditions to obtain the second molten steel satisfies at least one of the following conditions: (1) The scrap steel is added to the main refining furnace in two batches; (2) The flow rate of the bottom-blown argon gas is 600-1500 NL / min; (3) The first slag-forming agent is 1-2t of hot continuous casting residue slag or 1-2kg / t of foaming agent; (4) The preset temperature is 500-1000℃; (5) The length of the scrap steel is ≤600mm and the thickness is ≤30mm; (6) The scrap steel is not enclosed in sealed containers, is not mixed with ash and steel slag, and is not mixed with ferroalloys or non-ferrous metals; (7) The slag in the main refining furnace is light yellow or light white in color, and the total iron content of the slag is ≤5%; (8) The heating rate of the main refining furnace is 4-10℃ / min; (9) The net clearance of the ladle for steel tapping from the converter is 600-1200mm.

3. The smelting method for adding scrap steel to a steel-water mixing tank according to claim 2, characterized in that, The specific steps for adding the scrap steel to the main refining furnace in two batches include: Under bottom-blown argon conditions, 50-100 kg / t of scrap steel at the preset temperature is added to the main refining furnace, followed by 1.0-4.0 kg / t of lime. The molten steel is then heated to T3 by electricity; wherein T3 ≥ 1620℃. Under bottom-blown argon conditions, 50-100 kg / t of scrap steel at the preset temperature is added to the main refining furnace for the second time, followed by the addition of 0.25-0.5 kg / t of aluminum blocks or 0.5-1.5 kg / t of silicon-aluminum-calcium alloy for slag formation. The molten steel is then heated to T4 by power supply, where T4 ≥ 1600℃.

4. The smelting method for adding scrap steel to a steel-water mixing tank according to any one of claims 1-3, characterized in that, Each main refining furnace and auxiliary refining furnace is paired with a scrap steel baking and preheating device. The scrap steel is preheated by the scrap steel baking and preheating device and then fed into the main refining furnace or the auxiliary refining furnace. The feeding speed of the scrap steel baking and preheating device is 500-2000 kg / min.

5. The smelting method for adding scrap steel to a steel-water mixing tank according to claim 1, characterized in that, The step of transferring a portion of the second molten steel from at least two of the main refining furnaces to auxiliary refining furnaces, and adding scrap steel and a third slagging agent at a preset temperature to the main refining furnaces and the auxiliary refining furnaces to obtain the third molten steel includes: A portion of the second molten steel from the two main refining furnaces is transferred to the auxiliary refining furnace, or a portion of the second molten steel from the three main refining furnaces is transferred to the auxiliary refining furnace.

6. The smelting method for adding scrap steel to a molten steel tank according to claim 5, characterized in that, The third slag-forming agent includes a foaming agent and at least one of aluminum blocks and calcium silicate.

7. The smelting method for adding scrap steel to a molten steel tank according to claim 6, characterized in that, The step of transferring a portion of the second molten steel from at least two of the main refining furnaces to auxiliary refining furnaces, and adding scrap steel and a third slagging agent at a preset temperature to the main refining furnaces and the auxiliary refining furnaces to obtain the third molten steel includes: After separation into tanks, scrap steel at a preset temperature of 0-100 kg / t is added to the main refining furnace and the auxiliary refining furnace, along with 1-2 kg / t of foaming agent and 0.25-0.5 kg / t of aluminum blocks or 0.5-1.5 kg / t of silicon-aluminum-calcium to form reducing slag.

8. The smelting method for adding scrap steel to a molten steel tank according to claim 6, characterized in that, The auxiliary refining furnace is preheated with 0-100 kg of refined scrap steel before the second molten steel is introduced.

9. The smelting method for adding scrap steel to a steel-water mixing tank according to claim 1, characterized in that, The step of slag-forming and alloying the third type of molten steel to obtain refined molten steel includes: Using a calcium treatment mode, feed pure calcium wire at a rate of 2-4.0 m / t. During the soft blowing process, control the soft blowing flow rate at 50-200 NL / min, and ensure that the argon soft blowing time of molten steel is ≥8 min and the molten steel calming time is ≥15 min.

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