Method and control system for smelting heavy rail steel with an electric furnace as a primary refining furnace

Abstract

The present application belongs to the technical field of steel smelting, and relates to a method for smelting heavy rail steel with an electric furnace as a preliminary smelting furnace and a control system. The control system comprises a raw material proportioning module and a process control module. The raw material proportioning module calculates a raw material structure based on a proportioning model of target components of a steel grade to compensate for element changes in the smelting process. The process control module controls the electric furnace smelting, LF refining and VD / RH degassing process to optimize the purity of molten steel. The raw material proportioning module outputs the raw material structure to the process control module for automatic electric furnace proportioning. The method comprises the following specific steps: calculating the raw material structure based on the proportioning model and electric furnace proportioning; electric furnace smelting control of nitrogen ≤0.005%, carbon ≥0.15%, phosphorus ≤0.012%, and oxygen 0.02% to 0.03%; SiFe / SiCaBa deoxidization tapping is used in the electric furnace tapping process; carbon powder / silicon carbide ball pre-deoxidization is used in the LF refining, the slag basicity is controlled to be 2.0 to 3.0, and soft blowing is ≥15 min; VD / RH degassing is ≥15 min, and qualified molten steel is obtained.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel smelting technology, and relates to a method and control system for smelting heavy rail steel using an electric furnace as the primary smelting furnace. Background Technology

[0002] Heavy rail steel is a high-strength pearlitic steel and a major component of railway tracks. With the development of modern high-speed and heavy-haul railway transportation, higher requirements have been placed on the quality and performance of heavy rail steel. Currently, the main development trends for heavy rail steel are high strength, high toughness, and high purity. Good fatigue and weldability are fundamental characteristics of rails used in high-speed railways. To ensure that all rail performance requirements are met, strict control over the steel's composition and microstructure is necessary, and high purity is also required, meaning that the content of harmful elements and gases in the steel must be minimized.

[0003] To meet the aforementioned quality requirements for heavy rail steel, domestic steel mills such as Panzhihua Iron and Steel Group, Wuhan Iron and Steel Group, Anshan Iron and Steel Group, Baotou Steel Group, and Handan Iron and Steel Group all use blast furnace hot metal as raw material and adopt a long process flow of hot metal pretreatment + converter + LF + VD / RH. Patent CN114231827A discloses a method for controlling Class B inclusions in high-speed rails. In this method, the smelting of heavy rail steel adopts a process of hot metal desulfurization treatment, converter blowing, LF refining, and RH vacuum treatment. In the LF refining process, white slag is made using quicklime, fluorite, and wollastonite, and deoxidizers are added to the slag surface to enhance deoxidation. The Al2O3 content in the refined slag is controlled at 20%–25%, the binary basicity is 3.0–3.5, and the white slag retention time is 10–15 minutes. Patent CN114058931A discloses a method for controlling manganese sulfide inclusions in heavy rail steel during its production. The heavy rail steel smelting process includes converter, LF furnace refining, RH vacuum treatment, and continuous casting. The carbon content at the end of the converter smelting is controlled to be 0.03-0.1%. No deoxidizer is added during the converter tapping process, but an alloy with low dissolved aluminum content is added. A silicon-containing deoxidizer is added during the LF furnace refining process to control the mass content of S in the molten steel to within 0.004-0.015%.

[0004] In summary, using a converter as a primary smelting furnace to produce heavy rail steel is a mature technology. With the future development of low-carbon technologies, using an electric arc furnace (EAF) as a primary smelting furnace to produce high-grade steel is a current hot research direction. However, because EAFs use scrap steel as raw material, their raw material structure, smelting process, and process control methods differ from those of converters. Currently, there are no methods on the market for smelting heavy rail steel using an EAF as a primary smelting furnace, which presents both new challenges and opportunities for the further development of heavy rail steel production technology. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method and control system for smelting heavy rail steel using an electric furnace as the primary smelting furnace, so as to solve the problem that there is no method for smelting heavy rail steel using an electric furnace as the primary smelting furnace in the prior art, and thus fill this technical gap.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A control system for smelting heavy rail steel using an electric furnace as the primary smelting furnace includes a raw material proportioning module and a process control module.

[0008] The raw material proportioning module calculates the raw material structure based on the batching model of the target composition of the steel grade to compensate for elemental changes during the smelting process; the process control module controls the electric furnace smelting, LF refining and VD / RH degassing processes to optimize the purity of molten steel; the raw material proportioning module outputs the raw material structure to the process control module for automatic batching in the electric furnace.

[0009] Furthermore, the batching model includes the following steps: collecting steel composition data to determine characteristics, matching the electric furnace short process, and applying the constraint equation Σ(element content in raw materials × process change rate) ≤ target content to calculate the raw material structure.

[0010] Furthermore, it also includes a storage device and an operating program for storing the ingredient model and process parameters, enabling real-time linkage and data feedback between modules.

[0011] Furthermore, the process control module controls the nitrogen content of the molten steel to be ≤0.005%, the carbon content to be ≥0.15%, the phosphorus content to be ≤0.012%, and the oxygen content to be 0.02% to 0.03% at the end of the electric furnace smelting process, and uses SiFe or SiCaBa alloy for deoxidation during the tapping process.

[0012] Furthermore, the process control module uses carbon powder or silicon carbide balls for pre-deoxidation during the LF refining stage, controls the basicity of the refining slag to 2-3, and the soft blowing time to ≥15min.

[0013] Furthermore, the process control module controls the vacuum treatment time to be ≥15min during the VD or RH degassing stage, further reducing the hydrogen, oxygen, and nitrogen content to ≤0.003%, ≤0.002%, and ≤0.004%, respectively, to obtain high-purity molten steel.

[0014] Furthermore, the steel properties include the content of elements C, Si, Mn, S, P, N, O, H, Als, Alt, Nb, V, Ti, Cr, Ni, and Cu, as well as trace elements As, Sn, and Sb.

[0015] Furthermore, the raw material structure includes one or more combinations of scrap steel, molten iron, DRI, and HBI, and their proportions are optimized according to constraint equations.

[0016] On the other hand, the present invention also provides a method for smelting heavy rail steel using an electric furnace as the primary smelting furnace, comprising operating the aforementioned control system, the specific steps of which are as follows:

[0017] Calculate the raw material structure and perform electric furnace batching based on the batching model;

[0018] Electric arc furnace smelting controls nitrogen ≤0.005%, carbon ≥0.15%, phosphorus ≤0.012%, and oxygen 0.02%~0.03%. The electric arc furnace tapping process adopts SiFe / SiCaBa deoxidation tapping.

[0019] LF refining employs carbon powder / silicon carbide sphere pre-deoxidation, controls slag basicity at 2.0–3.0, and uses soft blowing for ≥15 minutes;

[0020] VD / RH degassing ≥15min yields qualified molten steel.

[0021] Furthermore, the batching model includes the following steps: collecting steel composition data to determine characteristics, matching the electric furnace short process, and applying the constraint equation Σ(element content in raw materials × process change rate) ≤ target content to calculate the raw material structure, wherein the change rate takes into account oxidation and volatilization losses;

[0022] The constraint equations are calculated independently for each element.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. This invention integrates a raw material proportioning module and a process control module to achieve raw material optimization and precise parameter control in the short-process electric arc furnace smelting of heavy rail steel. Compared with the traditional blast furnace-converter long process, this scheme significantly reduces carbon emissions by approximately 60% (<0.6 tons of CO2 per ton of steel). This is achieved through a constraint equation model based on the target composition of the steel grade (Σ(raw material element content × process change rate) ≤ target content), which effectively compensates for elemental fluctuations in recycled materials such as scrap steel, ensuring efficient and low-carbon production.

[0025] 2. Regarding purity control, this scheme reduces the total amount of harmful elements and improves the cleanliness of molten steel by implementing phased control of N ≤ 0.005% and O 0.02%–0.03% at the electric furnace endpoint, combined with multi-process synergy including SiFe / SiCaBa deoxidation, LF refining soft blowing ≥ 15 min, and VD / RH degassing ≥ 15 min. This enhances the strength and toughness of heavy rail steel to better meet the requirements of high-speed railways.

[0026] 3. In addition, the control system is suitable for large-scale industrial production of various steel grades. Through the integration of storage devices and operating programs, the solution is easy to expand, reduces labor costs, and provides a reliable technical path for low-carbon transformation.

[0027] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0029] Figure 1 This is a flowchart of a method for smelting heavy rail steel using an electric furnace as the primary smelting furnace according to the present invention. Detailed Implementation

[0030] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0031] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0032] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0033] Example 1: Smelting U75V heavy rail steel using scrap steel and DRI as raw materials

[0034] This embodiment employs a control system and method for smelting heavy rail steel using an electric arc furnace as the primary smelting furnace. Targeting heavy rail steel U75V (target composition: C = 0.71–0.80%, Si = 0.50–0.80%, Mn = 0.70–1.05%, P ≤ 0.025%, S ≤ 0.025%, Alt ≤ 0.004%, V = 0.04–0.12%, H ≤ 0.00025%, O ≤ 0.0030%, Cr ≤ 0.15%, Ni ≤ 0.10%, Cu ≤ 0.15%), using scrap steel and direct reduced iron (DRI) as raw materials, it demonstrates raw material optimization and purity control under a short-process electric arc furnace method.

[0035] First, start the raw material proportioning module and input the target composition data of steel grade U75V into the batching model. Model execution steps: S1: Collect and analyze steel composition data to determine key characteristics, including major elements (C, Si, Mn, etc.) and trace elements (As, Sn, Sb), and identify potential impurity risks (such as high P and N content in scrap steel). Step S2: Match the electric arc furnace short process (electric arc furnace + LF + VD) to confirm the process change rate (based on historical data and thermodynamic simulation, determine the process change rate of each element). Step S3: Use constraint equations to independently calculate the raw material structure for each element, i.e., for element X, Σ(X content in raw material i × process change rate j) ≤ target X content, where the process change rate considers oxidation, volatilization, and alloying losses, and the calculation error is controlled within 5%.

[0036] The constraint equation, taking residual element copper as an example, is expressed as follows: 0 ≤ Σ Cu in raw materials + × Cu change rate in smelting process ≤ 0.15%, Cu change rate in smelting process is 100%, Σ Cu in raw materials = Cu content in scrap steel × scrap steel ratio + Cu content in DRI × DRI ratio; the Cu content in scrap steel is taken as 0.25%, the Cu content in DRI is taken as 0, and the scrap steel ratio + DRI ratio = 100%; other elements are similar, and the raw material structure is calculated as scrap steel + DRI, where the scrap steel ratio is 60% and the DRI ratio is 40%;

[0037] In this embodiment, the raw material structure is designed with a scrap steel ratio of 60% (e.g., total weight 60 tons) and a DRI ratio of 40% (e.g., total weight 40 tons) to compensate for the low carbon content and high impurities in the scrap steel, ensuring that the content of impurity elements and residual elements in the final molten steel is within the target requirements. This raw material structure is output to the storage device of the process control module to achieve real-time linkage between modules.

[0038] Secondly, the process control module automatically guides the electric furnace charging based on the raw material structure: scrap steel and DRI are charged into a 100-ton capacity electric furnace in a specific ratio, and smelting is started. The electric furnace is an AC electric arc furnace. The smelting process is divided into reduction, oxidation, and reduction refining phases. Endpoint control: real-time monitoring via a spectrometer ensures that the molten steel has the following specifications: nitrogen content ≤0.005% (actual 48ppm), carbon content ≥0.15% (actual 0.20%), phosphorus content ≤0.012% (actual 0.008%), and oxygen content 0.02%~0.03% (actual 0.025%). The tapping process uses SiCaBa alloy deoxidation to reserve space for subsequent refining and avoid premature Al deoxidation that introduces inclusions.

[0039] Molten steel is transferred to the LF ladle refining furnace: pre-deoxidation uses carbon powder combined with silicon carbide balls, adjusted in real time based on the O content. Slag formation uses quicklime and fluorite, controlling the refining slag basicity to 2.0–3.0 (actually 2.5). Soft blowing uses argon gas for ≥15 min (actually 18 min) to evenly distribute inclusions and reduce oxygen to 0.010%.

[0040] Subsequently, the steel is transferred to a VD vacuum degassing furnace: using the VD process, with a vacuum degree <2Pa and a processing time ≥15min (actually 20min), H is further reduced to ≤0.0002%, O to ≤0.002%, and N to ≤0.004%. After degassing, V is alloyed to 0.08% and Ti to 0.015%, yielding qualified molten steel.

[0041] In this embodiment, compared with the long process of blast furnace-converter smelting heavy rail steel, the carbon emission intensity is reduced to 0.60tCO2 / t steel, which proves the effectiveness of raw material optimization and multi-process control under the short process in this application.

[0042] In another embodiment, the raw material structure may also include one or more combinations of scrap steel, molten iron, DRI, and HBI, with the specific proportions calculated according to the constraint equation.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for smelting heavy rail steel using an electric furnace as the primary smelting furnace, characterized in that, This includes a control system for smelting heavy rail steel using an electric arc furnace as the primary smelting furnace. The control system includes a raw material proportioning module and a process control module. The raw material proportioning module calculates the raw material structure based on the batching model of the target steel composition to compensate for elemental changes during the smelting process; the process control module controls the electric furnace smelting, LF refining, and VD / RH degassing processes to optimize the purity of molten steel; the raw material proportioning module outputs the raw material structure to the process control module for automatic batching in the electric furnace. The specific steps are as follows: Calculate the raw material structure and perform electric furnace batching based on the batching model; Electric arc furnace smelting controls nitrogen ≤0.005%, carbon ≥0.15%, phosphorus ≤0.012%, and oxygen 0.02%~0.03%. The electric arc furnace tapping process uses SiFe or SiCaBa deoxidation tapping. LF refining employs carbon powder / silicon carbide sphere pre-deoxidation, controls slag basicity at 2.0~3.0, and uses soft blowing for ≥15 minutes; VD / RH degassing ≥15min yields qualified molten steel; Among them, the batching model execution step S1: collect and analyze steel composition data, determine key characteristics, including major elements and trace elements, and identify potential impurity risks; Step S2: Match the electric furnace short process, i.e., electric furnace + LF + VD, confirm the process change rate, and determine the process change rate of each element based on historical data and thermodynamic simulation; Step S3: Calculate the raw material structure independently for each element using constraint equations. The constraint equation is Σ(element content in raw material × process change rate) ≤ target content, where the process change rate includes oxidation, volatilization and alloying losses.

2. The method according to claim 1, characterized in that, It also includes a storage device and an operating program for storing the ingredient model and process parameters, enabling real-time linkage and data feedback between modules.

3. The method according to claim 1, characterized in that, The key characteristics include the content of elements C, Si, Mn, S, P, N, O, H, Als, Alt, Nb, V, Ti, Cr, Ni, and Cu, as well as the content of trace elements As, Sn, and Sb.

4. The method according to claim 1, characterized in that, The raw material structure includes one or more combinations of scrap steel, molten iron, DRI, and HBI, and their proportions are optimized according to constraint equations.

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