20mn23alv non-magnetic steel and a preparation method thereof

Abstract

The application discloses 20Mn23AlV non-magnetic steel and a preparation method thereof. The method comprises the following steps: providing RH refining molten steel including C: 0.16-0.20%, Si: 0.05-0.25%, Mn: 23.0-25.0%, P: ≤0.030%, S: ≤0.0050%, Al: 1.50-2.0%, V: 0.06-0.10% and the balance of iron and inevitable impurities in percentage by mass; and continuously casting the RH refining molten steel, using high-alkalinity protection slag to protect the molten steel in a crystallizer when the RH refining molten steel starts to be cast, and using low-alkalinity protection slag to protect the molten steel when the casting length reaches 7-9 meters. By providing the molten steel and sequentially adjusting the protection slag during the continuous casting process, the heat transfer is controlled before the degeneration of the starting protection slag, and the lubrication is controlled after the serious degeneration of the protection slag, so that the transverse fold of the starting billet is reduced, the surface quality of the starting billet of the continuous casting is effectively improved, the sticking and leakage are prevented, the starting billet does not need to be ground or reduced, and the continuous casting billet is hot-charged, so that the production cost is reduced.

Description

Technical Field

[0001] This application belongs to the field of steel smelting technology, and in particular relates to a 20Mn23AlV non-magnetic steel and its preparation method. Background Technology

[0002] 20Mn23AlV non-magnetic steel is increasingly in demand as a key structural component in the manufacture of extra-large transformers. Because the composition of 20Mn23AlV non-magnetic steel requires an Al content as high as 1.5wt.% to 2.0wt.%, a slag-metal reaction occurs within the continuous casting crystallizer during the continuous casting process. Al + SiO2 → Si + Al2O3.

[0003] This reaction causes changes in the composition and properties of the protective slag, hindering its normal lubrication and heat transfer control functions. This leads to surface quality problems in continuously cast slabs, such as depressions and cracks, as well as frequent leaks in steel production. It has become a major limiting factor affecting the continuous casting of high-alumina steel, especially for the initial casting slab due to process instability. Figure 1 As shown, the surface of the first 10 meters or so of continuously cast slabs exhibits severe transverse folds, with cracks, slag inclusions, and air bubbles present at these folds. These slabs require grinding and anti-oxidation coating, significantly increasing the cost per ton of steel. Currently, there is no solution to the severe transverse folds in the first cast slab; all first cast slabs require grinding or downgrading. Summary of the Invention

[0004] This application provides a 20Mn23AlV non-magnetic steel and its preparation method, which enables the initial casting billet to be used without grinding or downgrading, thereby reducing production costs by hot charging of continuously cast slabs.

[0005] In a first aspect, this application provides a method for preparing 20Mn23AlV non-magnetic steel, comprising: We provide RH refined steel, which, by mass percentage, comprises the following components: C: 0.16%–0.20%, Si: 0.05%–0.25%, Mn: 23.0%–25.0%, P: ≤0.030%, S: ≤0.0050%, Al: 1.50%–2.0%, V: 0.06%–0.10%, with the balance being iron and unavoidable impurities. RH refined steel is continuously cast. When the casting of RH refined steel begins, a high-basicity protective slag is used in the crystallizer for steel protection. When the casting length of RH refined steel reaches 7 to 9 meters, a low-basicity protective slag is added for steel protection.

[0006] According to an embodiment of the first aspect of this application, RH-refined molten steel is provided, comprising the following preparation steps: Provide molten iron; The molten iron is subjected to KR desulfurization treatment to obtain desulfurized molten iron; The desulfurized molten iron is then smelted in a converter to obtain converter steel. LF refining treatment is performed on the molten steel from the converter to obtain LF refined molten steel; LF refined steel is subjected to RH refining treatment to obtain RH refined steel.

[0007] According to the embodiment of the first aspect of this application, in the step of KR desulfurization treatment of molten iron, the molten iron after desulfurization is required to have S≤0.01% and steel slag removal cleanliness≥90%.

[0008] According to an embodiment of the first aspect of this application, in the step of treating desulfurized molten iron by converter smelting, the temperature of the desulfurized molten steel is 1600℃~1700℃. The desulfurized molten steel is poured into a ladle with an internal temperature ≥800℃, and 300±50kg of active lime is added during the tapping process for slag washing to obtain converter molten steel. The converter molten steel includes the following components by mass percentage: C: 0.03%~0.10%, P: ≤0.0150%, S: ≤0.0150%, with the balance being iron and unavoidable impurities.

[0009] According to an embodiment of the first aspect of this application, in the step of LF refining of converter steel, the temperature of the steel at the end of LF refining is 1520℃~1550℃, and the LF refined steel comprises the following components by mass percentage: C: 0.16%~0.20%, Si: 0.05%~0.25%, Mn: 23.0%~25.0%, P: ≤0.030%, S: ≤0.0050%, Al: 1.60%~2.0%, V: 0.06%~0.10%, with the balance being iron and unavoidable impurities; and the soft blowing time is ≥6min, thus obtaining LF refined steel.

[0010] According to an embodiment of the first aspect of this application, LF refined steel is subjected to RH refining treatment, including: an RH circulation time of 15 min to 30 min and a circulation flow rate of 150 Nm³. 3 / h~200Nm 3 The RH refining process involves refining molten steel at a temperature of 1480℃~1510℃ per hour to obtain RH refined molten steel. By mass percentage, the RH refined molten steel comprises the following components: C: 0.16%~0.20%, Si: 0.05%~0.25%, Mn: 23.0%~25.0%, P: ≤0.030%, S: ≤0.0050%, Al: 1.50%~2.0%, V: 0.06%~0.10%, with the balance being iron and unavoidable impurities.

[0011] According to an embodiment of the first aspect of this application, when RH refined steel begins to be cast, a high-basicity protective slag of 0.30 kg / ton steel to 0.61 kg / ton steel is used for steel casting.

[0012] According to the embodiments of the first aspect of this application, the high alkalinity protective slag meets the following composition and content requirements: by mass percentage, it includes the following components: SiO2 25%–30%, CaO 35%–40%, Al2O3 6.0%–8.0%, C 3.0%–5.0%, Na2O 4.0%–7.0%, Li2O 4.0%–6.0%, with the balance being unavoidable impurities.

[0013] According to the embodiments of the first aspect of this application, the basicity of the high-alkalinity protective slag is 1.40 to 1.60, the melting point is 1040°C to 1080°C, and the viscosity is 0.10 Pa·s to 0.15 Pa·s.

[0014] According to the embodiments of the first aspect of this application, the low-alkalinity protective slag meets the following composition and content requirements: SiO2 36.8%~42.8%, CaO 16.1%~22.1%, Al2O3 1.7%~4.7%, C 5.0%~7.0%, Na2O 9.0%~11.0%, Li2O 5.0%~7.0%, with the remainder being other unavoidable impurities.

[0015] According to the embodiments of the first aspect of this application, the basicity of the low-alkalinity protective slag is 0.38 to 0.58, the melting point is 820°C to 900°C, and the viscosity is 0.10 Pa·s to 0.20 Pa·s.

[0016] According to an embodiment of the first aspect of this application, the method for preparing 20Mn23AlV nonmagnetic steel further includes: simultaneously reducing the cooling intensity of the crystallizer when the RH refined steel begins to be cast; the cooling water flow rate of the wide side of the crystallizer is 3400L / min to 3800L / min and the cooling water flow rate of the narrow side is 500L / min to 5400L / min for the first 10 meters of the RH refined steel begins to be cast; and the cooling water flow rate of the wide side of the crystallizer is 4100L / min to 4500L / min and the cooling water flow rate of the narrow side is 580L / min to 620L / min after the RH refined steel begins to be cast.

[0017] According to an embodiment of the first aspect of this application, the method for preparing 20Mn23AlV non-magnetic steel further includes: vibrating the crystallizer using a vibration curve #14 for the first 10 meters of RH refined steel casting, wherein the vibration frequency of the crystallizer is 168Hz~172Hz, the stroke is 3.6mm~4.0mm, and the skewness is 0.18~0.25; and vibrating the crystallizer using a vibration curve #15 after the first 10 meters of RH refined steel casting, wherein the vibration frequency of the crystallizer is 126Hz~130Hz, the stroke is 6.6mm~7.0mm, and the skewness is 0.20~0.30.

[0018] According to an embodiment of the first aspect of this application, the method for preparing 20Mn23AlV nonmagnetic steel further includes: when the RH refined molten steel begins to be cast, the initial casting speed is 0.2 m / min to 0.3 m / min, and after 2 minutes, the speed is increased to 0.2 m / min. 2 The acceleration increases the pulling speed to 0.6m / min to 0.8m / min.

[0019] Secondly, this application provides a 20Mn23AlV non-magnetic steel, which, by mass percentage, comprises the following components: C: 0.16%–0.20%, Si: 0.05%–0.25%, Mn: 23.0%–25.0%, P: ≤0.030%, S: ≤0.0050%, Al: 1.50%–2.0%, V: 0.06%–0.10%, with the balance being iron and unavoidable impurities.

[0020] The 20Mn23AlV non-magnetic steel and its preparation method in this application embodiment are continuously cast using molten steel with the corresponding steel composition. During the continuous casting process, the order of adding the protective slag is adjusted. Before the protective slag undergoes severe deformation, the process parameters are mainly selected to control heat transfer. After the protective slag undergoes severe deformation, the focus is on controlling lubrication, reducing transverse creases in the first casting billet, effectively improving the surface quality of the first casting billet, preventing sticking and leakage, and enabling the first casting billet to be used without grinding or downgrading, thus achieving hot charging of the continuous casting slab and reducing production costs. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a picture of the actual product of the continuous casting starter billet of the existing non-magnetic steel 20MnAlV, which is shown in Comparative Example 1.

[0023] Figure 2This is a picture of the actual product of the continuous casting starter billet of the existing non-magnetic steel 20MnAlV, which is shown in Comparative Example 2.

[0024] Figure 3 The image shown is an actual product drawing of the continuous casting starter billet of the existing non-magnetic steel 20MnAlV, which is shown in Comparative Example 3.

[0025] Figure 4 This is a picture of the actual product of the continuous casting starter billet of the existing non-magnetic steel 20MnAlV, which is shown in Comparative Example 4.

[0026] Figure 5 This is a schematic flowchart of the preparation method of non-magnetic steel 20MnAlV provided in the embodiments of this application.

[0027] Figure 6 This is an actual product image of the non-magnetic steel 20MnAlV provided in Embodiment 1 of this application.

[0028] Figure 7 This is an actual product image of the non-magnetic steel 20MnAlV provided in Embodiment 2 of this application.

[0029] Figure 8 This is an actual product image of the non-magnetic steel 20MnAlV provided in Embodiment 3 of this application.

[0030] Figure 9 This is an actual product image of the non-magnetic steel 20MnAlV provided in Embodiment 4 of this application. Detailed Implementation

[0031] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0032] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0033] To address the problems of the prior art, this application provides a 20Mn23AlV non-magnetic steel and its preparation method. The preparation method of the 20Mn23AlV non-magnetic steel provided in this application will be described below.

[0034] Figure 2 A schematic flowchart of the preparation method of 20Mn23AlV nonmagnetic steel provided in the embodiments of this application is shown.

[0035] like Figure 2 As shown, the method for preparing 20Mn23AlV non-magnetic steel provided in the first aspect of this application includes: providing RH refined molten steel, which, by mass percentage, comprises the following components: C: 0.16%–0.20%, Si: 0.05%–0.25%, Mn: 23.0%–25.0%, P: ≤0.030%, S: ≤0.0050%, Al: 1.50%–2.0%, V: 0.06%–0.10%, with the balance being iron and unavoidable impurities; continuously casting the RH refined molten steel, using a high-basicity protective slag for steel protection at the beginning of casting, and adding a low-basicity protective slag for steel protection when the casting length of the RH refined molten steel reaches 7 to 9 meters.

[0036] In the process of researching existing methods for preparing 20Mn23AlV nonmagnetic steel, the inventors of this application discovered through sampling and analysis of the protective slag that the slag-gold reaction in the crystallizer involves a gradual process. Therefore, based on this process, the existing preparation method was improved.

[0037] This application describes a method for preparing 20Mn23AlV non-magnetic steel. The method involves continuous casting of molten steel with the appropriate composition. During continuous casting, the order of adding the protective slag is carefully controlled. Before severe deformation of the protective slag during the initial casting, the process parameters primarily control heat transfer. After severe deformation, the focus shifts to lubrication, reducing transverse creases in the initial casting billet and effectively improving its surface quality. This prevents steel leakage and eliminates the need for grinding or downgrading of the initial casting billet, achieving cost reduction through hot charging of the continuous casting slab. Hot charging refers to charging the hot continuous casting billet into the furnace at a temperature ≥400℃. The cost reduction from hot charging of the continuous casting slab includes at least the reduction in costs associated with repairing and handling the initial casting billet and the continuous casting slab during intermediate production processes.

[0038] In some embodiments, providing RH refined molten steel includes the following preparation steps: providing molten iron; subjecting the molten iron to KR desulfurization treatment to obtain desulfurized molten iron; subjecting the desulfurized molten iron to converter smelting treatment to obtain converter molten steel; subjecting the converter molten steel to LF refining treatment to obtain LF refined molten steel; and subjecting the LF refined molten steel to RH refining treatment to obtain RH refined molten steel.

[0039] The 20Mn23AlV non-magnetic steel and its preparation method of this application involve desulfurization, decarburization, dephosphorization, deoxidation, denitrification and alloying treatments in a converter through the above steps, so that the composition of the molten steel meets the requirements of 20Mn23AlV non-magnetic steel.

[0040] In some embodiments, during the KR desulfurization treatment of molten iron, the molten iron after desulfurization is required to have an S ≤ 0.01% and a slag removal cleanliness ≥ 90%.

[0041] The 20Mn23AlV non-magnetic steel and its preparation method in this application embodiment control the S content of molten iron to ≤0.01% through KR desulfurization treatment, and control the slag removal cleanliness of the molten iron surface after desulfurization to ≥90%, thereby reducing the return of S content in the slag to the molten iron and preventing the S content in the molten iron from increasing again, so as to reduce the impact on the subsequent smelting process and the quality of steel.

[0042] In some embodiments, in the step of smelting desulfurized molten iron in a converter, the temperature of the desulfurized molten steel is 1600℃~1700℃. The desulfurized molten steel is poured into a ladle with an internal temperature ≥800℃, and 300±50kg of active lime is added during the tapping process for slag washing to obtain converter molten steel. The converter molten steel includes the following components by mass percentage: C: 0.03%~0.10%, P: ≤0.0150%, S: ≤0.0150%, with the balance being iron and unavoidable impurities.

[0043] This application describes a method for preparing 20Mn23AlV non-magnetic steel. The method involves decarburizing and dephosphorizing desulfurized molten steel before pouring it into a ladle with an internal temperature ≥800℃. During the converter smelting process, active lime is added for slag washing to rapidly form slag, improve desulfurization efficiency, protect the molten steel, prevent secondary oxidation, and adsorb inclusions and purify the steel. The active lime, also known as lightly calcined lime, is a high-purity, highly reactive calcium oxide product. The active lime contains ≥90 wt.% CaO by mass percentage.

[0044] In some embodiments, during the LF refining process of converter steel, the temperature of the steel at the end of the LF refining is 1520°C to 1550°C. The LF-refined steel comprises the following components by mass percentage: C: 0.16% to 0.20%, Si: 0.05% to 0.25%, Mn: 23.0% to 25.0%, P: ≤0.030%, S: ≤0.0050%, Al: 1.60% to 2.0%, V: 0.06% to 0.10%, with the balance being iron and unavoidable impurities. The soft blowing time is ≥6 minutes to obtain the LF-refined steel.

[0045] The 20Mn23AlV nonmagnetic steel and its preparation method in this application embodiment involve soft blowing after LF refining to promote the floating and removal of inclusions, and to make the steel liquid composition and temperature uniform.

[0046] In some embodiments, the LF-refined molten steel is subjected to RH refining treatment, including: an RH circulation time of 15 min to 30 min and a circulation flow rate of 150 Nm³. 3 / h~200Nm 3 The RH refining process involves refining molten steel at a temperature of 1480℃~1510℃ to obtain RH refined molten steel. By mass percentage, the RH refined molten steel comprises the following components: C: 0.16%~0.20%, Si: 0.05%~0.25%, Mn: 23.0%~25.0%, P: ≤0.030%, S: ≤0.0050%, Al: 1.50%~2.0%, V: 0.06%~0.10%, with the balance being iron and unavoidable impurities.

[0047] The 20Mn23AlV non-magnetic steel and its preparation method in this application embodiment use RH cycling to remove hydrogen and nitrogen from the molten steel, making the molten steel pure and with uniform composition and temperature.

[0048] In some embodiments, a high-basicity protective slag of 0.30 kg / ton to 0.61 kg / ton is used for casting RH refined steel at the beginning of the casting process.

[0049] In some embodiments, the high-alkalinity protective slag meets the following composition and content requirements: by mass percentage, it includes the following components: SiO2 25%–30%, CaO 35%–40%, Al2O3 6.0%–8.0%, C 3.0%–5.0%, Na2O 4.0%–7.0%, Li2O 4.0%–6.0%, with the balance being unavoidable impurities.

[0050] In some embodiments, the basicity of the high-basicity protective slag is 1.40 to 1.60, the melting point is 1040°C to 1080°C, and the viscosity is 0.10 Pa·s to 0.15 Pa·s.

[0051] The 20Mn23AlV non-magnetic steel and its preparation method in this application embodiment, when RH refined steel is first cast in the crystallizer, uses a high-basicity protective slag that meets the above-mentioned high basicity, high melting point and low viscosity to gradually modify the steel. With the control of the crystallizer cooling water flow rate and crystallizer vibration parameters, the influence of the crystallizer on the high-temperature molten steel during the solidification process can be effectively isolated. It can also effectively reduce the temperature of the billet shell, and at the same time play a role in lubricating the billet shell and the crystallizer of the continuous casting slab, so that the RH refined steel can start to solidify and continuously form a continuous casting slab.

[0052] In some embodiments, the low-alkalinity protective slag meets the following composition and content requirements: SiO2 36.8%–42.8%, CaO 16.1%–22.1%, Al2O3 1.7%–4.7%, C 5.0%–7.0%, Na2O 9.0%–11.0%, Li2O 5.0%–7.0%, with the remainder being other unavoidable impurities.

[0053] The 20Mn23AlV non-magnetic steel and its preparation method in this application embodiment, when the length of RH refined molten steel casting in the crystallizer reaches 7 to 9 meters, can replace the high-basicity protective slag that has been modified and has increased melting point, viscosity and adhesion after a period of continuous casting by using a low-basicity protective slag. It can also coordinate with the control of the crystallizer cooling water flow rate and the crystallizer vibration parameters to lubricate the crystallizer and the formed continuous casting slab, and continuously reduce the temperature of the continuous casting slab to further solidify it, thereby preventing sticking and leakage accidents caused by high-basicity protective slag.

[0054] In some embodiments, the basicity of the low-alkalinity protective slag is 0.38 to 0.58, the melting point is 820°C to 900°C, and the viscosity is 0.10 Pa·s to 0.20 Pa·s.

[0055] The 20Mn23AlV non-magnetic steel and its preparation method in this application embodiment, when the length of RH refined steel casting in the crystallizer reaches 7 to 9 meters, promotes the rapid renewal of slag by using the above-mentioned low-basicity and low-melting-point protective slag, so that the protective slag can still play a good lubricating function after the steel slag reacts and absorbs inclusions, effectively lubricating the gap between the crystallizer and the continuous casting slab shell, so as to ensure stable production of continuous casting slab.

[0056] The preparation method of 20Mn23AlV non-magnetic steel provided in this application uses a high-basicity protective slag in the crystallizer at the beginning of continuous casting of RH refined molten steel for 20Mn23AlV non-magnetic steel. This results in less slag-metal reaction accumulation in the crystallizer, and the lubrication and heat transfer performance of the protective slag meets requirements, leading to normal surface quality of the initial billet cast from the RH refined molten steel. However, when the casting length reaches 7-9 meters, slag-metal reaction accumulation increases, and overall modification becomes severe. Therefore, it is necessary to replace the protective slag with one that can effectively reduce slag-metal reaction, namely the low-basicity protective slag used in this application. This slag not only dilutes the previously modified protective slag but also balances the modification, lubrication, and heat transfer performance of the protective slag. Furthermore, it works in conjunction with adjustments to the crystallizer cooling intensity and vibration parameters to reduce the impact of slag-metal reaction on the surface quality of the initial billet cast, reducing transverse folds on the surface of the initial billet, i.e., reducing cracks, slag inclusions, and bubble defects at the transverse folds.

[0057] The preparation method of 20Mn23AlV non-magnetic steel provided in this application embodiment uses a high-basicity protective slag in the crystallizer at the beginning of continuous casting of RH refined molten steel for 20Mn23AlV non-magnetic steel. That is, when the continuous casting is carried out until the RH refined molten steel in the crystallizer submerges the chute of the tundish, a high-basicity protective slag is pushed into the crystallizer and spread on the surface of the molten steel in the crystallizer. The high-basicity protective slag is continuously replenished before the length of the continuously cast slab reaches 7 meters. After 7 to 9 meters, a low-basicity protective slag is pushed into the crystallizer to cover the original high-basicity protective slag. Then, the low-basicity protective slag is continuously replenished according to the thickness of the slag layer until the casting of the continuously cast slab is completed.

[0058] In some embodiments, the method for preparing 20Mn23AlV non-magnetic steel further includes: simultaneously reducing the cooling intensity of the crystallizer when the RH refined steel begins to be cast; the cooling water flow rate of the wide side of the crystallizer is 3400L / min to 3800L / min and the cooling water flow rate of the narrow side is 500L / min to 5400L / min for the first 10 meters of the RH refined steel begins to be cast; and the cooling water flow rate of the wide side of the crystallizer is 4100L / min to 4500L / min and the cooling water flow rate of the narrow side is 580L / min to 620L / min after the RH refined steel begins to be cast.

[0059] The preparation method of 20Mn23AlV non-magnetic steel provided in this application reduces the cooling intensity so that the high-alkalinity protective slag in the early stage of continuous casting does not undergo severe modification and has strong heat transfer capacity, thus preventing uneven growth of the billet shell in the crystallizer and aggravating the depression of the billet at the start of casting due to high cooling intensity.

[0060] In some embodiments, the crystallizer is vibrated using vibration curve #14 for the first 10 meters of RH refined steel casting, wherein the vibration frequency of the crystallizer is 168Hz~172Hz, the stroke is 3.6mm~4.0mm, and the skewness is 0.18~0.25; after the first 10 meters of RH refined steel casting, the crystallizer is vibrated using vibration curve #15, wherein the vibration frequency of the crystallizer is 126Hz~130Hz, the stroke is 6.6mm~7.0mm, and the skewness is 0.20~0.30.

[0061] The method for preparing 20Mn23AlV non-magnetic steel provided in this application adjusts the vibration frequency of the crystallizer. This is because the high-basicity protective slag has relatively good lubrication properties in the early stages of continuous casting, allowing for the use of high-frequency, low-amplitude vibration parameters to reduce the transverse depth of the continuously cast slab and prevent cracking defects. However, in the later stages of continuous casting, the high-basicity protective slag undergoes significant denaturation, increasing its viscosity. Consequently, the crystallizer requires lower frequency and higher amplitude vibration parameters to reduce friction between the slab shell and the crystallizer copper plate, and to increase the slag consumption of the low-basicity protective slag. The aforementioned crystallizer vibration parameters complement the chemical characteristics of the high-basicity and low-basicity protective slags during the continuous casting process.

[0062] In some embodiments, the preparation method of 20Mn23AlV non-magnetic steel involves starting the casting of RH refined molten steel at a speed of 0.2 m / min to 0.3 m / min, followed by a speed of 0.2 m / min after 2 minutes. 2 The acceleration increases the pulling speed to 0.6m / min to 0.8m / min.

[0063] Secondly, embodiments of this application provide a 20Mn23AlV non-magnetic steel, prepared according to the preparation method of the 20Mn23AlV non-magnetic steel provided in the first aspect embodiment; the components include the following contents by mass percentage: C: 0.16%~0.20%, Si: 0.05%~0.25%, Mn: 23.0%~25.0%, P: ≤0.030%, S: ≤0.0050%, Al: 1.50%~2.0%, V: 0.06%~0.10%, with the balance being iron and unavoidable impurities.

[0064] The technical solutions and effects of this application will be described in detail below through specific embodiments and comparative examples. The specifications, composition requirements, and available sources of the raw materials used in some embodiments and comparative examples are as follows.

[0065] It should be noted that the molten steel in the converter in Examples 1-4 and Comparative Examples 1-4 below is 200 tons.

[0066] Example 1 A method for preparing 20Mn23AlV nonmagnetic steel includes: The preparation process for providing RH refined molten steel includes the following steps: providing molten iron; subjecting the molten iron to KR desulfurization treatment to obtain desulfurized molten iron; subjecting the desulfurized molten iron to converter smelting treatment to obtain converter molten steel; subjecting the converter molten steel to LF refining treatment to obtain LF refined molten steel; and subjecting the LF refined molten steel to RH refining treatment to obtain RH refined molten steel. The RH refined molten steel contains the following components: C: 0.18%, Si: 0.16%, Mn: 23.2%, P: 0.018%, S: 0.0020%, Al: 1.82%, V: 0.065%, with the balance being iron and unavoidable impurities. The RH refined molten steel temperature is 1495℃. RH refined steel is continuously cast. When the RH refined steel is first cast in the crystallizer, a high-basicity protective slag of 0.35 kg / ton of steel is used to protect the molten steel. When the casting length of the RH refined steel reaches 8 meters, a low-basicity protective slag is added to protect the molten steel. At the same time, the cooling intensity of the crystallizer is reduced when the RH refined steel begins to be cast. The cooling water flow rate of the wide side of the crystallizer is 3800 L / min and the cooling water flow rate of the narrow side is 540 L / min for the first 10 meters of the RH refined steel casting process. After the RH refined steel casting process has started for 10 meters, the cooling water flow rate of the wide side of the crystallizer is 4100 L / min and the cooling water flow rate of the narrow side is 580 L / min. For the first 10 meters of RH refined steel casting, the crystallizer was vibrated using vibration curve #14, with a vibration frequency of 168Hz, a stroke of 4.0mm, and a skewness of 0.20. After 10 meters of RH refined steel casting, the crystallizer was vibrated using vibration curve #15, with a vibration frequency of 126Hz, a stroke of 6.6mm, and a skewness of 0.25. When the RH refined steel begins to be poured, the initial casting speed is 0.3 m / min, and after 2 minutes, it is increased to 0.2 m / min. 2 The acceleration increased the pulling speed to 0.8 m / min.

[0067] Example 2 A method for preparing 20Mn23AlV nonmagnetic steel includes: The preparation process for providing RH-refined molten steel includes the following steps: providing molten iron; subjecting the molten iron to KR desulfurization treatment to obtain desulfurized molten iron; subjecting the desulfurized molten iron to converter smelting treatment to obtain converter molten steel; subjecting the converter molten steel to LF refining treatment to obtain LF-refined molten steel; and subjecting the LF-refined molten steel to RH refining treatment to obtain RH-refined molten steel. The RH-refined molten steel contains the following components: C: 0.17%, Si: 0.19%, Mn: 23.7%, P: 0.0120%, S: 0.0015%, Al: 1.78%, V: 0.063%, with the balance being iron and unavoidable impurities. The RH-refined molten steel temperature is 1499℃. RH refined steel is continuously cast. When the RH refined steel is first cast in the crystallizer, a high-basicity protective slag of 0.45 kg / ton of steel is used to protect the molten steel. When the casting length of the RH refined steel reaches 8 meters, a low-basicity protective slag is added to protect the molten steel. At the same time, the cooling intensity of the crystallizer is reduced when the RH refined steel begins to be cast. The cooling water flow rate of the wide side of the crystallizer is 3400 L / min and the cooling water flow rate of the narrow side is 500 L / min for the first 10 meters of the RH refined steel casting process. After the RH refined steel casting process has started for 10 meters, the cooling water flow rate of the wide side of the crystallizer is 4100 L / min and the cooling water flow rate of the narrow side is 580 L / min. For the first 10 meters of RH refined steel casting, the crystallizer was vibrated using vibration curve #14, with a vibration frequency of 168Hz, a stroke of 4.0mm, and a skewness of 0.20. After 10 meters of RH refined steel casting, the crystallizer was vibrated using vibration curve #15, with a vibration frequency of 126Hz, a stroke of 6.6mm, and a skewness of 0.25. When the RH refined steel begins to be poured, the initial casting speed is 0.3 m / min, and after 2 minutes, it is increased to 0.2 m / min. 2 The acceleration increased the pulling speed by 0.8 m / min.

[0068] Example 3 A method for preparing 20Mn23AlV nonmagnetic steel includes: The preparation process for providing RH-refined molten steel includes the following steps: providing molten iron; subjecting the molten iron to KR desulfurization treatment to obtain desulfurized molten iron; subjecting the desulfurized molten iron to converter smelting treatment to obtain converter molten steel; subjecting the converter molten steel to LF refining treatment to obtain LF-refined molten steel; and subjecting the LF-refined molten steel to RH refining treatment to obtain RH-refined molten steel. The RH-refined molten steel comprises the following components: C: 0.19%, Si: 0.12%, Mn: 23.5%, P: 0.0016%, S: 0.0012%, Al: 1.98%, V: 0.061%, with the balance being iron and unavoidable impurities. The RH-refined molten steel is prepared at a temperature of 1496℃. RH refined steel is continuously cast. When the RH refined steel is first cast in the crystallizer, a high-basicity protective slag of 0.35 kg / ton of steel is used to protect the molten steel. When the casting length of the RH refined steel reaches 8 meters, a low-basicity protective slag is added to protect the molten steel. At the same time, the cooling intensity of the crystallizer is reduced when the RH refined steel begins to be cast. The cooling water flow rate of the wide side of the crystallizer is 3800 L / min and the cooling water flow rate of the narrow side is 540 L / min for the first 10 meters of the RH refined steel casting process. After the RH refined steel casting process has started for 10 meters, the cooling water flow rate of the wide side of the crystallizer is 4100 L / min and the cooling water flow rate of the narrow side is 580 L / min. For the first 10 meters of RH refined steel casting, the crystallizer was vibrated using vibration curve #14, with a vibration frequency of 172Hz, a stroke of 3.6mm, and a skewness of 0.20. After 10 meters of RH refined steel casting, the crystallizer was vibrated using vibration curve #15, with a vibration frequency of 126Hz, a stroke of 6.6mm, and a skewness of 0.25. When the RH refined steel begins to be poured, the initial casting speed is 0.3 m / min, and after 2 minutes, it is increased to 0.2 m / min. 2 The acceleration increased the pulling speed to 0.8 m / min.

[0069] Example 4 A method for preparing 20Mn23AlV nonmagnetic steel includes: The preparation process for providing RH refined molten steel includes the following steps: providing molten iron; subjecting the molten iron to KR desulfurization treatment to obtain desulfurized molten iron; subjecting the desulfurized molten iron to converter smelting treatment to obtain converter molten steel; subjecting the converter molten steel to LF refining treatment to obtain LF refined molten steel; and subjecting the LF refined molten steel to RH refining treatment to obtain RH refined molten steel. The RH refined molten steel contains the following components: C: 0.18%, Si: 0.16%, Mn: 23.2%, P: 0.018%, S: 0.0020%, Al: 1.82%, V: 0.065%, with the balance being iron and unavoidable impurities. The RH refined molten steel temperature is 1495℃. RH refined steel is continuously cast. When the RH refined steel is first cast in the crystallizer, a high-basicity protective slag of 0.35 kg / ton of steel is used to protect the molten steel. When the casting length of the RH refined steel reaches 8 meters, a low-basicity protective slag is added to protect the molten steel. At the same time, the cooling intensity of the crystallizer is reduced when the RH refined steel begins to be cast. The cooling water flow rate of the wide side of the crystallizer is 3400 L / min and the cooling water flow rate of the narrow side is 500 L / min for the first 10 meters of the RH refined steel casting process. After the RH refined steel casting process has started for 10 meters, the cooling water flow rate of the wide side of the crystallizer is 4100 L / min and the cooling water flow rate of the narrow side is 580 L / min. For the first 10 meters of RH refined steel casting, the crystallizer was vibrated using vibration curve #14, with a vibration frequency of 172Hz, a stroke of 3.6mm, and a skewness of 0.20. After 10 meters of RH refined steel casting, the crystallizer was vibrated using vibration curve #15, with a vibration frequency of 126Hz, a stroke of 6.6mm, and a skewness of 0.25. When the RH refined steel begins to be poured, the initial casting speed is 0.30 m / min, and after 2 minutes, it is increased to 0.2 m / min. 2 The acceleration increased the pulling speed to 0.8 m / min.

[0070] Comparative Example 1 provides a method for preparing existing 20Mn23AlV nonmagnetic steel, which includes: The preparation process for providing RH-refined molten steel includes the following steps: providing molten iron; subjecting the molten iron to KR desulfurization treatment to obtain desulfurized molten iron; subjecting the desulfurized molten iron to converter smelting treatment to obtain converter molten steel; subjecting the converter molten steel to LF refining treatment to obtain LF-refined molten steel; and subjecting the LF-refined molten steel to RH refining treatment to obtain RH-refined molten steel. The RH-refined molten steel contains the following components: C: 0.19%, Si: 0.17%, Mn: 23.1%, P: 0.0180%, S: 0.0021%, Al: 1.85%, V: 0.066%, with the balance being iron and unavoidable impurities. The RH-refined molten steel temperature is 1497℃. The RH refined steel is continuously cast. When the RH refined steel begins to be cast in the crystallizer, a low-basicity protective slag of 0.35 kg / ton of steel is added for casting, and the low-basicity protective slag is used throughout the casting process.

[0071] The cooling water flow rate of the wide side of the crystallizer is 4100 L / min, and the cooling water flow rate of the narrow side is 580 L / min; the vibration frequency of the crystallizer is 126 Hz, the stroke is 6.6 mm, and the skewness is 0.25. When the RH refined steel begins to be poured, the initial casting speed is 0.3 m / min, and after 2 minutes, it is increased to 0.2 m / min. 2 The acceleration increases the casting speed to 0.8 m / min. The first billet of the continuously cast slab is not ground and is directly loaded into the furnace for rolling.

[0072] Comparative Example 2 provides an existing method for preparing 20Mn23AlV nonmagnetic steel. The difference between Comparative Example 1 and Comparative Example 2 is that the first billet of the continuously cast slab is ground with a grinding wheel after cooling and coated with an anti-oxidation coating.

[0073] Comparative Example 3 provides a method for preparing 20Mn23AlV non-magnetic steel. The difference from Example 1 is that RH refined steel is continuously cast. High-basicity protective slag is added when the RH refined steel is first cast, and high-basicity protective slag is used throughout the casting process.

[0074] Comparative Example 4 provides a method for preparing 20Mn23AlV nonmagnetic steel. The difference from Example 1 is that: RH refined molten steel is continuously cast, the flow rate of cooling water on the wide side of the crystallizer is 4100L / min, and the flow rate of cooling water on the narrow side is 580L / min; the 15# vibration curve is used throughout, the vibration frequency of the crystallizer is 126Hz, the stroke is 6.6mm, and the skewness is 0.25.

[0075] The surface quality of the 20Mn23AlV nonmagnetic steel prepared in Examples 1-4 and Comparative Examples 1-4 was compared. The comparison included the first continuously cast slab produced by the production process of each of Examples 1-4 and Comparative Examples 1-4, and the 16 continuously cast slabs produced subsequently. The specifications of the continuously cast slabs were length × width × thickness = 10000mm × 2070mm × 230mm. The comparison results are recorded in Table 1 below.

[0076] Table 1 It should be noted that in Table 1, the process slab scrap rate refers to the 16 continuously cast slabs remaining after the first one. " / " indicates that no other events occurred.

[0077] The preparation methods of 20Mn23AlV nonmagnetic steel in Comparative Examples 1-4 and Comparative Examples 1-4, the production data of continuously cast steel billets in Table 1, and the appendices of Examples 1-4 and Comparative Examples 1-4 of this application are also compared. Figure 1-4 and appendix Figure 5-9 It can be concluded that: Figure 1 As shown, in Comparative Example 1, the surface of the continuously cast slab of 20Mn23AlV non-magnetic steel, within the first 10 meters of casting length, exhibits severe transverse folds. For example... Figure 2 As shown, the 20Mn23AlV nonmagnetic steel blank of Comparative Example 2 was coated with an anti-oxidation coating after grinding. Figure 3 As shown, in Comparative Example 3, the surface of the continuously cast slab of the 20Mn23AlV non-magnetic steel also exhibited severe transverse folds during the continuous casting process, with cracks, slag inclusions, and air bubbles present at the folds. Figure 4As shown, in Comparative Example 4, the 20Mn23AlV non-magnetic steel exhibited severe transverse folds in the center of the surface of the continuously cast slab during the continuous casting process.

[0078] like Figure 6 , Figure 7 , Figure 8 and Figure 9 As shown, the surface of the continuously cast slab is free of transverse folds, cracks, inclusions, and bubbles at the transverse folds, and the surface is regular. This indicates that the preparation method of the 20Mn23AlV non-magnetic steel in this application embodiment involves continuous casting of molten steel with the corresponding steel composition. During the continuous casting process, the order of adding the protective slag is adjusted. Before the protective slag undergoes severe deformation, the process parameters are mainly selected to control heat transfer. After the protective slag undergoes severe deformation, the focus is on controlling lubrication. This reduces transverse folds in the first casting slab, effectively improves the surface quality of the continuous casting first casting slab, prevents sticking and leakage, and eliminates the need for grinding or downgrading of the first casting slab. Furthermore, by coordinating the control of the cooling water flow rate and the crystallizer vibration parameters, the surface quality of the 20Mn23AlV non-magnetic steel prepared in this application can be further improved. Compared to the scrap reduction and modification rates of 3.42%–42.8% for the first-cast billets in Comparative Examples 1-4 and 0.92%–82.7% for the process slabs, the scrap reduction and modification rates of 1.35%–3.86% for the first-cast billets and 0.62%–1.02% for the process slabs in Examples 1-4 of this application are significantly lower. Furthermore, compared to the cost of 600 yuan / ton for grinding and oxide coating of the first-cast billets in Comparative Example 2, the preparation method of 20Mn23AlV non-magnetic steel provided in this application can reduce production costs by 6.78% through hot charging of continuously cast slabs.

[0079] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process described above can be referred to the corresponding process 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 method for preparing 20Mn23AlV nonmagnetic steel, characterized in that, include: We provide RH refined steel, which, by mass percentage, comprises the following components: C: 0.16%–0.20%, Si: 0.05%–0.25%, Mn: 23.0%–25.0%, P: ≤0.030%, S: ≤0.0050%, Al: 1.50%–2.0%, V: 0.06%–0.10%, with the balance being iron and unavoidable impurities. RH refined steel is continuously cast. When the casting of RH refined steel begins, a high-basicity protective slag is used in the crystallizer for steel protection. When the casting length of RH refined steel reaches 7 to 9 meters, a low-basicity protective slag is added for steel protection.

2. The method for preparing 20Mn23AlV nonmagnetic steel according to claim 1, characterized in that, Providing RH-refined molten steel includes the following preparation steps: Provide molten iron; The molten iron is subjected to KR desulfurization treatment to obtain desulfurized molten iron; The desulfurized molten iron is then smelted in a converter to obtain converter steel. LF refining treatment is performed on the molten steel from the converter to obtain LF refined molten steel; LF refined steel is subjected to RH refining treatment to obtain RH refined steel.

3. The method for preparing 20Mn23AlV nonmagnetic steel according to claim 2, characterized in that, In the step of KR desulfurization treatment of molten iron, the molten iron after desulfurization is required to have S≤0.01% and steel slag removal cleanliness≥90%.

4. The method for preparing 20Mn23AlV nonmagnetic steel according to claim 2, characterized in that, In the step of converting desulfurized molten iron into steel, the temperature of the desulfurized molten steel is 1600℃~1700℃. The desulfurized molten steel is poured into a ladle with an internal temperature ≥800℃. During the tapping process, 300±50kg of active lime is added for slag washing to obtain converter molten steel. By mass percentage, molten steel from a converter comprises the following components: C: 0.03%–0.10%, P: ≤0.0150%, S: ≤0.0150%, with the balance being iron and unavoidable impurities; and / or, In the step of LF refining the converter steel, the temperature of the steel at the end of LF refining is 1520℃~1550℃. The LF-refined steel, by mass percentage, comprises the following components: C: 0.16%~0.20%, Si: 0.05%~0.25%, Mn: 23.0%~25.0%, P: ≤0.030%, S: ≤0.0050%, Al: 1.60%~2.0%, V: 0.06%~0.10%, with the balance being iron and unavoidable impurities. The soft blowing time is ≥6 minutes to obtain the LF-refined steel. And / or, The RH refining treatment of LF refined steel includes: an RH circulation time of 15 min to 30 min and a circulation flow rate of 150 Nm³. 3 / h~200Nm 3 The RH refining process involves refining molten steel at a temperature of 1480℃~1510℃ to obtain RH refined molten steel. By mass percentage, the RH refined molten steel comprises the following components: C: 0.16%~0.20%, Si: 0.05%~0.25%, Mn: 23.0%~25.0%, P: ≤0.030%, S: ≤0.0050%, Al: 1.50%~2.0%, V: 0.06%~0.10%, with the balance being iron and unavoidable impurities.

5. The method for preparing 20Mn23AlV nonmagnetic steel according to claim 1, characterized in that, When the RH refined steel begins to be cast, a high-alkalinity protective slag of 0.30 kg / ton steel to 0.61 kg / ton steel is used for steel casting.

6. The method for preparing 20Mn23AlV nonmagnetic steel according to claim 1, characterized in that, The high-alkalinity protective slag meets the following composition and content requirements: by mass percentage, it includes the following components: SiO2 25%~30%, CaO 35%~40%, Al2O3 6.0%~8.0%, C 3.0%~5.0%, Na2O 4.0%~7.0%, Li2O 4.0%~6.0%, with the balance being unavoidable impurities; Optionally, the high-alkalinity protective slag has an alkalinity of 1.40–1.60, a melting point of 1040℃–1080℃, and a viscosity of 0.10 Pa·s–0.15 Pa·s; and / or, Optionally, the low-alkalinity protective slag, by mass percentage, meets the following composition and content requirements: SiO2 36.8%–42.8%, CaO 16.1%–22.1%, Al2O3 1.7%–4.7%, C 5.0%–7.0%, Na2O 9.0%–11.0%, Li2O 5.0%–7.0%, with the remainder being other unavoidable impurities; Optionally, the low-alkalinity protective slag has an alkalinity of 0.38 to 0.58, a melting point of 820°C to 900°C, and a viscosity of 0.10 Pa·s to 0.20 Pa·s.

7. The method for preparing 20Mn23AlV nonmagnetic steel according to claim 1, characterized in that, Also includes: At the same time, the cooling intensity of the crystallizer is reduced when the RH refined steel begins to be cast. The cooling water flow rate of the wide side of the crystallizer is 3400L / min to 3800L / min and the cooling water flow rate of the narrow side is 500L / min to 5400L / min for the first 10 meters of the RH refined steel casting process. After the RH refined steel casting process has started for 10 meters, the cooling water flow rate of the wide side of the crystallizer is 4100L / min to 4500L / min and the cooling water flow rate of the narrow side is 580L / min to 620L / min.

8. The method for preparing 20Mn23AlV nonmagnetic steel according to claim 1, characterized in that, Also includes: For the first 10 meters of RH refined steel casting, the crystallizer was vibrated using vibration curve #14, with a vibration frequency of 168Hz–172Hz, a stroke of 3.6mm–4.0mm, and a skewness of 0.18–0.

25. After 10 meters of RH refined steel casting, the crystallizer was vibrated using vibration curve #15, with a vibration frequency of 126Hz–130Hz, a stroke of 6.6mm–7.0mm, and a skewness of 0.20–0.

30.

9. The method for preparing 20Mn23AlV nonmagnetic steel according to claim 1, characterized in that, Also includes: When the RH refined steel begins to be poured, the initial casting speed is 0.2 m / min to 0.3 m / min, and after 2 minutes, it is reduced to 0.2 m / min. 2 The acceleration increases the pulling speed to 0.6m / min to 0.8m / min.

10. A type of 20Mn23AlV non-magnetic steel, characterized in that, The 20Mn23AlV non-magnetic steel is prepared according to any one of claims 1-9.

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