Soft magnetic stainless steel and preparation method thereof

Abstract

The invention provides soft magnetic stainless steel and a preparation method thereof. The soft magnetic stainless steel provided by the invention comprises the following elements in percentage by weight: 0.01%-0.12% of C, 0.18%-0.80% of Si, 0.3%-1.2% of Mn, 10.8%-22.3% of Cr, 0.04%-0.25% of Cu, 0.04%-0.38% of Mo, 0.15%-1.2% of Ni, less than or equal to 0.004% of S, less than or equal to 0.03% of N, less than or equal to 0.0025% of O, 0.25%-1.5% of Al, 0.003%-0.015% of Re and the balance of Fe. The soft magnetic stainless steel provided by the invention has a uniform microstructure, excellent magnetic performance, corrosion resistance and workability.

Description

Technical Field

[0001] This disclosure relates to the field of metallic materials, and in particular to a soft magnetic stainless steel and its preparation method. Background Technology

[0002] Soft magnetic stainless steel, as a functional material possessing both excellent magnetic properties and corrosion resistance, has seen continuous growth in demand in recent years in fields such as electrical and electronic engineering, new energy vehicles, and renewable energy. Especially with the increasing driving range of new energy vehicles, the requirements for low iron loss and high permeability of soft magnetic stainless steel in new energy vehicle motors are gradually increasing. The number and size of inclusions in soft magnetic stainless steel are key factors affecting iron loss and permeability. Related technologies aim to improve magnetic properties by adding high levels of Si and reducing C and N content. However, high Si levels make it prone to grain boundary embrittlement and cracking during hot working, and its high hardness makes forming difficult during cold working. This is unfavorable for stamping complex-shaped components such as automotive parts. Single Al deoxidation results in high hardness and large size of Al2O3 inclusions, deteriorating high-frequency permeability; the high melting point of SiO2, a product of single Si deoxidation, easily forms composite inclusions with MnS, worsening magnetic properties and material mechanical properties. Existing materials technology cannot meet the demand for high-quality soft magnetic stainless steel in applications such as new energy vehicles. Therefore, it is urgent to develop an inclusion control method to achieve high magnetic properties, corrosion resistance and easy processing of high-quality soft magnetic stainless steel. Summary of the Invention

[0003] To address the problems existing in related technologies, this disclosure provides a soft magnetic stainless steel and a method for preparing the same.

[0004] According to one aspect of this application, a soft magnetic stainless steel is provided, the soft magnetic stainless steel comprising the following elements, expressed as a weight percentage:

[0005] C: 0.01%–0.12%, Si: 0.18%–0.80%, Mn: 0.3%–1.2%, Cr: 10.8%–22.3%, Cu: 0.04%–0.25%, Mo: 0.04%–0.38%, Ni: 0.15%–1.2%, S: ≤0.004%, N: ≤0.03%, O: ≤0.0025%, Al: 0.25%–1.5%, Re: 0.003%–0.015%, balance Fe.

[0006] In some embodiments of this disclosure, the weight percentage ratio, C1 = Al / Si, is 0.65 to 1.3.

[0007] In some embodiments of this disclosure, the weight percentage ratio, C2 = Re / (S + O), is 1.05 to 2.1.

[0008] In some embodiments of this disclosure, the soft magnetic stainless steel includes spherical inclusions, the average diameter of the spherical inclusions being less than or equal to 3 μm, and the particle size distribution D90 of the spherical inclusions being less than 8 μm.

[0009] The spherical inclusions are a mixture of Re, Al, Si, O and S.

[0010] According to one aspect of this application, a method for preparing soft magnetic stainless steel is provided, the method being used to prepare the soft magnetic stainless steel as described above, the method comprising:

[0011] The initial alloy liquid is subjected to a first refining treatment to decarburize and deoxidize, resulting in a first refined alloy liquid;

[0012] The first refined alloy liquid is subjected to a second refining process, and Re raw material is added to obtain a second refined alloy liquid;

[0013] The second refined alloy liquid is subjected to continuous casting to obtain a continuously cast billet;

[0014] The continuously cast billet is rolled to obtain a machined billet;

[0015] The processed blank is subjected to solution treatment to obtain the soft magnetic stainless steel.

[0016] In some embodiments of this disclosure, the first refining treatment of the initial alloy liquid to decarburize and deoxidize includes:

[0017] The initial alloy liquid is subjected to a first refining treatment in an AOD furnace, where oxygen is blown to decarburize it so that the weight percentage content of C in the initial alloy liquid is ≤0.01%; then argon gas is blown and stirred, and silicon and aluminum raw materials are added for deoxidation, controlling the weight percentage ratio of Cl = Al / Si in the initial alloy liquid to be 0.65~1.3, and controlling the weight percentage content of O in the initial alloy liquid to be ≤0.0025%.

[0018] In some embodiments of this disclosure, the second refining treatment of the first refined alloy liquid and the addition of Re raw material includes:

[0019] The first refined alloy liquid is subjected to a second refining treatment in an LF furnace. Re raw material is added to the LF furnace at a temperature of 1550-1610°C, and the weight percentage content W of Re in the first refined alloy liquid is controlled. (Re) The content is 0.003% to 0.015%, and the weight percentage ratio C2 = Re / (S+O) in the first refined alloy liquid is 1.05 to 2.1;

[0020] The duration of the second refining process is t = (0.045 ~ 0.85)W. (Re)min.

[0021] In some embodiments of this disclosure, the step of continuously casting the second refined alloy liquid to obtain a continuously cast billet includes:

[0022] The second refined alloy liquid is continuously cast under an axial magnetic field of 0.2 to 0.7 T, and the superheat is controlled at 15 to 55°C and the cooling gradient is 15 to 35°C / mm to obtain the continuously cast billet; wherein the compositional segregation of the continuously cast billet is ≤0.5%.

[0023] In some embodiments of this disclosure, the step of rolling the continuously cast billet to obtain a processed billet includes:

[0024] The continuously cast billet is hot-rolled to obtain the processed billet, wherein the heating temperature is 1150–1200℃ and the initial rolling temperature is T. 开 and final rolling temperature T 终 The relationship is T 开 -T 终 ≥200℃, and T 终 ≥900℃.

[0025] In some embodiments of this disclosure, the step of solution treatment of the processed billet to obtain the soft magnetic stainless steel includes:

[0026] The processed blank is subjected to a staged heating process under argon protection. In the first stage, the temperature is increased from 20-25°C to 750-850°C at a heating rate of 2-8°C / min. In the second stage, the temperature is increased from 750-850°C to 1050-1200°C at a heating rate of 10-20°C / min. In the third stage, the temperature is held at 1050-1200°C for 30-150 minutes. Then, the blank is cooled by water to obtain the soft magnetic stainless steel.

[0027] The beneficial effects of this disclosure include, but are not limited to: the soft magnetic stainless steel provided by this disclosure has a uniform microstructure, excellent magnetic properties, corrosion resistance and easy processing.

[0028] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of these embodiments. In these drawings, similar reference numerals are used to denote similar elements. The drawings described below are some embodiments of the present disclosure, but not all embodiments. Other drawings will be readily available to those skilled in the art based on these drawings without inventive effort.

[0030] Figure 1 This is a schematic flowchart of a method for preparing soft magnetic stainless steel, which is an exemplary embodiment of this disclosure. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions of this disclosure will be clearly and completely described below in conjunction with the embodiments of this disclosure. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this disclosure can be arbitrarily combined with each other.

[0032] This disclosure provides a soft magnetic stainless steel, characterized in that the soft magnetic stainless steel comprises the following elements, expressed as a weight percentage:

[0033] C: 0.01%–0.12%, Si: 0.18%–0.80%, Mn: 0.3%–1.2%, Cr: 10.8%–22.3%, Cu: 0.04%–0.25%, Mo: 0.04%–0.38%, Ni: 0.15%–1.2%, S: ≤0.004%, N: ≤0.03%, O: ≤0.0025%, Al: 0.25%–1.5%, Re: 0.003%–0.015%, balance Fe.

[0034] The roles and contents of each element in this soft magnetic stainless steel are explained below:

[0035] C is a strong austenite-forming element, and austenite is typically non-magnetic or weakly magnetic. Therefore, in the soft magnetic stainless steel of this disclosure, the weight percentage of C is controlled to not exceed 0.12% to ensure the magnetic properties and corrosion resistance of the soft magnetic stainless steel. Secondly, to ensure the strength of the soft magnetic stainless steel, the weight percentage of C in the exemplary embodiments of this disclosure is not less than 0.01%. That is, in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure, the weight percentage of C can be 0.01% to 0.12%; preferably, the weight percentage of C in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure can be 0.03% to 0.10%.

[0036] Si (silicon) is a deoxidizer used in the preparation of soft magnetic stainless steel. Adding Si reduces the oxygen (O) content and improves the magnetic properties of the stainless steel. However, excessive Si can cause the stainless steel to crack due to grain boundary embrittlement during hot working, and its high hardness during cold working makes forming difficult, hindering the stamping of complex shapes. Furthermore, the deoxidation product SiO2 has a high melting point and easily forms complex inclusions with MnS, deteriorating the magnetic and mechanical properties of the soft magnetic stainless steel. In the soft magnetic stainless steel provided in the exemplary embodiments of this disclosure, the weight percentage of Si is controlled to be 0.18% to 0.80%; preferably, the weight percentage of Si in the soft magnetic stainless steel provided in the exemplary embodiments of this disclosure can be 0.22% to 0.70%.

[0037] Mn is mainly used as a deoxidizer and can improve the hot workability of soft magnetic stainless steel. However, Mn combines with sulfur to form MnS inclusions, which are non-magnetic inclusions and degrade the magnetic properties of soft magnetic stainless steel. Therefore, in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure, the weight percentage of Mn is controlled to be 0.3% to 1.2%; preferably, the weight percentage of Mn in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure can be 0.4% to 1.0%.

[0038] Cr is a key element in the corrosion resistance of soft magnetic stainless steel, and as a ferrite-forming element, it is beneficial to the magnetic properties of soft magnetic stainless steel. However, excessive Cr content can increase the hardness and decrease the toughness of soft magnetic stainless steel. Therefore, in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure, the weight percentage of Cr is controlled to be 10.8% to 22.3%; preferably, the weight percentage of Cr in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure can be 12.0% to 19.0%.

[0039] Cu can improve the corrosion resistance of soft magnetic stainless steel, but excessive Cu content is detrimental to its magnetic properties. Therefore, in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure, the weight percentage of Cu is controlled to be 0.04% to 0.25%; preferably, the weight percentage of Cu in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure can be 0.05% to 0.20%.

[0040] Mo (Mo) can improve the corrosion resistance of soft magnetic stainless steel, and as a ferrite-forming element, it can stabilize the ferrite structure in soft magnetic stainless steel, thereby improving its strength and hardness. However, excessive Mo addition can deteriorate the toughness and magnetic properties of soft magnetic stainless steel. Therefore, in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure, the weight percentage of Mo is controlled to be 0.04% to 0.38%; preferably, the weight percentage of Mo in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure can be 0.05% to 0.30%.

[0041] Ni is an austenite-forming element. Adding Ni can improve the corrosion resistance of soft magnetic stainless steel; however, excessive Ni addition can damage the magnetic properties of the soft magnetic stainless steel and reduce its saturation magnetic induction. Therefore, in the soft magnetic stainless steel provided in the exemplary embodiments of this disclosure, the weight percentage of Ni is controlled to be 0.15% to 1.2%; preferably, the weight percentage of Ni in the soft magnetic stainless steel provided in the exemplary embodiments of this disclosure can be 0.20% to 1.0%.

[0042] Al is mainly used as a deoxidizer, which can effectively reduce the oxygen content in soft magnetic stainless steel, thereby reducing oxide inclusions. Furthermore, Al is a ferrite-forming element, which is beneficial to the magnetic properties of soft magnetic stainless steel. However, the deoxidation product Al₂O₃ inclusions have high hardness and large size, which can degrade the high-frequency permeability of soft magnetic stainless steel. Therefore, in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure, the weight percentage of Al is controlled to be 0.25% to 1.5%; preferably, the weight percentage of Al in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure can be 0.30% to 1.30%.

[0043] The addition of Re to soft magnetic stainless steel can preemptively occupy the nucleation sites of inclusions. Specifically, Re reacts strongly with S and O, consuming a large amount of S and O in the soft magnetic stainless steel. This significantly reduces the "raw material" for forming large, deformable plastic inclusions such as MnS inclusions during hot working. Instead, it forms numerous small, stable, high-melting-point spherical rare earth compounds, thus achieving "spheroidization" of the inclusion morphology and "refinement" of its size. Furthermore, the extremely high melting point and stability of these spherical rare earth inclusions result in a very low tendency for them to grow at high temperatures, thereby maintaining their small size. In the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure, the weight percentage of Re is controlled to be 0.003% to 0.015%; preferably, the weight percentage of Re in the soft magnetic stainless steel provided by the exemplary embodiments of this disclosure can be 0.004% to 0.012%.

[0044] S, N, and O are harmful elements in soft magnetic stainless steel. They can form hard and brittle inclusions with other elements such as Cr, Ti, Al, and Mn, thus deteriorating the magnetic properties of the soft magnetic stainless steel. Therefore, in the soft magnetic stainless steel provided in the exemplary embodiments of this disclosure, the weight percentage of S is controlled to be ≤0.004%, the weight percentage of N is controlled to be ≤0.03%, and the weight percentage of O is controlled to be ≤0.0025%; preferably, in the soft magnetic stainless steel provided in the exemplary embodiments of this disclosure, the weight percentage of S is controlled to be ≤0.002%, the weight percentage of N is controlled to be ≤0.02%, and the weight percentage of O is controlled to be ≤0.002%.

[0045] In addition to the elements mentioned above, the soft magnetic stainless steel provided in the exemplary embodiments of this disclosure also includes a balance of Fe element. Fe element is the basic metallic element of soft magnetic stainless steel, ensuring that the matrix of soft magnetic stainless steel is mainly ferrite, providing a basis for its magnetic properties.

[0046] It should be noted that, in addition to the elements mentioned above, the soft magnetic stainless steel provided in the exemplary embodiments of this disclosure may also include other unavoidable trace impurity elements.

[0047] In one embodiment, the weight percentage ratio, C1 = Al / Si, is 0.65 to 1.3.

[0048] In this embodiment, the weight percentage ratio C1 = Al / Si of the soft magnetic stainless steel is controlled within the range of 0.65 to 1.3. This ensures that during the preparation of the soft magnetic stainless steel, when dissolved aluminum and dissolved silicon are present in the molten steel, the deoxidation products of Al and Si elements are no longer pure SiO2 or pure Al2O3, but rather liquid aluminosilicates exist in the molten steel in a liquid form. These liquid aluminosilicate products are in the form of small droplets, with low floating resistance, resulting in a fast floating speed. Furthermore, when these liquid droplets meet, they are more likely to fuse into a larger droplet, with a growth efficiency far exceeding that of solid particles, thus facilitating aggregation. During the floating process, the liquid droplets can act like "magnets," adsorbing and assimilating other solid deoxidation products (such as SiO2 and Al2O3) encountered along the way, continuing to grow and accelerate floating, thus demonstrating strong adsorption capacity. Therefore, these small droplet-shaped liquid aluminosilicate products have extremely strong deoxidation capabilities. Furthermore, after these liquid aluminosilicate droplets float to the slag, their composition continues to change, forming liquid aluminosilicate slag that is easily separated from the molten steel. Therefore, in this embodiment, the weight percentage ratio C1 = Al / Si of the soft magnetic stainless steel is controlled within the range of 0.65 to 1.3, which can optimize the deoxidation process and inclusion morphology during the preparation of the soft magnetic stainless steel, thereby directly improving its soft magnetic properties.

[0049] In one embodiment, the weight percentage ratio, C2 = Re / (S+O), is 1.05 to 2.1. For example, in the soft magnetic stainless steel of this embodiment, the weight percentage ratio C1 = Al / Si can be 0.65, 0.84, 0.96, 1.2, or 1.3. The weight percentage ratio C1 = Al / Si can also be any value between the exemplary ratios, for example, the weight percentage ratio C1 = Al / Si can be any value between 0.8 and 1.2.

[0050] In the soft magnetic stainless steel provided in this embodiment, the addition of an appropriate amount of Re element and the control of the weight percentage ratio C2 = Re / (S+O) within the range of 1.05 to 2.1 allow the Re element to preemptively occupy the nucleation core of inclusions during the preparation of soft magnetic stainless steel, and react strongly with S and O elements, consuming a large amount of S and O elements in the soft magnetic stainless steel. This greatly reduces the "raw material" for forming large-sized plastic inclusions such as MnS that deform during hot working, and instead forms a large number of small, stable, high-melting-point spherical rare earth compounds, thereby achieving "spheroidization" of inclusion morphology and "refinement" of size. Furthermore, the extremely high melting point and stability of these spherical rare earth inclusions make them very low-prone to growth at high temperatures, thus maintaining a small size and comprehensively improving the toughness, corrosion resistance, and fatigue resistance of the soft magnetic stainless steel.

[0051] When the weight percentage ratio C2 = Re / (S+O) in soft magnetic stainless steel is too low, the Re element content is too low. During the preparation of soft magnetic stainless steel, it is easy to form strip-shaped MnS inclusions or "tadpole-shaped" composite inclusions, resulting in uneven performance improvement or even worse performance. When the weight percentage ratio C2 = Re / (S+O) in soft magnetic stainless steel is too high, the Re element content is too high. During the preparation of soft magnetic stainless steel, it is easy to form coarse rare earth oxide or nitride clusters, which may cause nozzle blockage and become crack sources in soft magnetic stainless steel, seriously damaging its toughness and fatigue life. Therefore, in this embodiment, the weight percentage ratio C2 = Re / (S+O) is controlled within the range of 1.05 to 2.1. This allows for the adjustment of the shape and size of inclusions during the preparation of soft magnetic stainless steel, achieving control over the size, quantity, and distribution of inclusions, ultimately resulting in soft magnetic stainless steel with excellent magnetic properties, corrosion resistance, and ease of processing. For example, in this embodiment, the weight percentage ratio C2 = Re / (S+O) of the soft magnetic stainless steel can be 1.05, 1.23, 1.5, 1.87 or 2.1. The weight percentage ratio C2 = Re / (S+O) can also be any value between the exemplary ratios, such as any value between 1.2 and 1.8.

[0052] In one embodiment, the soft magnetic stainless steel includes spherical inclusions with an average diameter of less than or equal to 3 μm and a particle size distribution D90 of less than 8 μm; the spherical inclusions are a mixture of Re, Al, Si, O and S.

[0053] With the aforementioned elemental composition, especially the addition of Re and the formulas C1 = Al / Si and C2 = Re / (S+O), the inclusions formed during the preparation of the soft magnetic stainless steel in this embodiment are Re-Al-Si-OS spherical inclusions. These spherical inclusions are small droplets with an average diameter of less than or equal to 3 μm, and their particle size distribution D90 < 8 μm (i.e., 90% of the spherical inclusions have a diameter less than 8 μm). The total number of inclusions is ≤ 3.5. These fine and stable spherical inclusions are less likely to cause stress concentration during rolling, reducing the risk of cracking and improving the ductility and fatigue strength of the soft magnetic stainless steel. This fine spherical inclusion morphology also helps stabilize grain boundaries, inhibit abnormal grain growth, and ensure the uniformity of magnetism in the soft magnetic stainless steel.

[0054] Below are examples of preferred value ranges for each element included in the soft magnetic stainless steel material according to this application, expressed as a weight percentage:

[0055] Preferred Example 1

[0056] C: 0.01%–0.12%, Si: 0.18%–0.80%, Mn: 0.3%–1.2%, Cr: 10.8%–22.3%, Cu: 0.04%–0.25%, Mo: 0.04%–0.38%, Ni: 0.15%–1.2%, S: ≤0.004%, N: ≤0.03%, O: ≤0.0025%, Al: 0.25%–1.5%, Re: 0.003%–0.015%, balance Fe.

[0057] The weight percentage ratio, C1=Al / Si, is 0.65~1.3.

[0058] Preferred Example 2

[0059] C: 0.01%–0.12%, Si: 0.18%–0.80%, Mn: 0.3%–1.2%, Cr: 10.8%–22.3%, Cu: 0.04%–0.25%, Mo: 0.04%–0.38%, Ni: 0.15%–1.2%, S: ≤0.004%, N: ≤0.03%, O: ≤0.0025%, Al: 0.25%–1.5%, Re: 0.003%–0.015%, balance Fe.

[0060] Among them, the weight percentage ratio C1 = Al / Si is 0.65 to 1.3, and the weight percentage ratio C2 = Re / (S+O) is 1.05 to 2.1.

[0061] Preferred Example 3

[0062] C: 0.03%–0.10%, Si: 0.22%–0.70%, Mn: 0.4%–1.0%, Cr: 12.0%–19.0%, Cu: 0.05%–0.20%, Mo: 0.05%–0.30%, Ni: 0.20%–1.0%, S: ≤0.004%, N: ≤0.03%, O: ≤0.0025%, Al: 0.30%–1.30%, Re: 0.004%–0.012%, balance Fe.

[0063] Preferred Example 4

[0064] C: 0.03%–0.10%, Si: 0.22%–0.70%, Mn: 0.4%–1.0%, Cr: 12.0%–19.0%, Cu: 0.05%–0.20%, Mo: 0.05%–0.30%, Ni: 0.20%–1.0%, S: ≤0.004%, N: ≤0.03%, O: ≤0.0025%, Al: 0.30%–1.30%, Re: 0.004%–0.012%, balance Fe.

[0065] The weight percentage ratio C1 = Al / Si is 0.8 to 1.2.

[0066] Preferred Example 5

[0067] C: 0.03%–0.10%, Si: 0.22%–0.70%, Mn: 0.4%–1.0%, Cr: 12.0%–19.0%, Cu: 0.05%–0.20%, Mo: 0.05%–0.30%, Ni: 0.20%–1.0%, S: ≤0.004%, N: ≤0.03%, O: ≤0.0025%, Al: 0.30%–1.30%, Re: 0.004%–0.012%, balance Fe.

[0068] Among them, the weight percentage ratio C1 = Al / Si is 0.8 to 1.2, and the weight percentage ratio C2 = Re / (S+O) is 1.2 to 1.8.

[0069] Preferred Example Six

[0070] C: 0.04%–0.08%, Si: 0.25%–0.60%, Mn: 0.5%–0.9%, Cr: 13.0%–17.5%, Cu: 0.08%–0.18%, Mo: 0.08%–0.25%, Ni: 0.28%–0.90%, S: ≤0.002%, N: ≤0.02%, O: ≤0.0020%, Al: 0.40%–1.10%, Re: 0.006%–0.010%, balance Fe.

[0071] Preferred Example 7

[0072] C: 0.04%–0.08%, Si: 0.25%–0.60%, Mn: 0.5%–0.9%, Cr: 13.0%–17.5%, Cu: 0.08%–0.18%, Mo: 0.08%–0.25%, Ni: 0.28%–0.90%, S: ≤0.002%, N: ≤0.02%, O: ≤0.0020%, Al: 0.40%–1.10%, Re: 0.006%–0.010%, balance Fe.

[0073] The weight percentage ratio C1 = Al / Si is 0.85 to 1.1.

[0074] Preferred Example 8

[0075] C: 0.04%–0.08%, Si: 0.25%–0.60%, Mn: 0.5%–0.9%, Cr: 13.0%–17.5%, Cu: 0.08%–0.18%, Mo: 0.08%–0.25%, Ni: 0.28%–0.90%, S: ≤0.002%, N: ≤0.02%, O: ≤0.0020%, Al: 0.40%–1.10%, Re: 0.006%–0.010%, balance Fe.

[0076] Among them, the weight percentage ratio C1 = Al / Si is 0.85 to 1.1, and the weight percentage ratio C2 = Re / (S+O) is 1.3 to 1.6.

[0077] This disclosure provides a method for preparing soft magnetic stainless steel, which is used to prepare soft magnetic stainless steel as described above. Figure 1 As shown, the preparation method includes:

[0078] S100. The initial alloy liquid is subjected to a first refining treatment to decarburize and deoxidize, resulting in a first refined alloy liquid.

[0079] S200. The first refined alloy liquid is subjected to a second refining process, and Re raw material is added to obtain the second refined alloy liquid.

[0080] S300. The second refined alloy liquid is continuously cast to obtain a continuously cast billet.

[0081] S400. The continuously cast billet is rolled to obtain a processed billet.

[0082] S500: The processed billet is subjected to solution treatment to obtain soft magnetic stainless steel.

[0083] The method for preparing soft magnetic stainless steel provided in this embodiment involves deep decarburization and deoxidation in the first refining process, laying a pure foundation for subsequent processing of the alloy melt; introducing Re element in the second refining process to optimize the morphology of inclusions in the alloy melt and further deoxidize; controlling the solidification process in the continuous casting process to reduce segregation; adjusting the grain structure and texture in the rolling process; and finally optimizing the microstructure in the solution treatment. The final product is a soft magnetic stainless steel with a uniform microstructure, high purity, good corrosion resistance, and excellent soft magnetic properties.

[0084] In one embodiment, the initial alloy liquid undergoes a first refining treatment to decarburize and deoxidize, including: performing a first refining treatment on the initial alloy liquid in an AOD furnace, blowing oxygen to decarburize so that the weight percentage content of C in the initial alloy liquid is ≤0.01%; then blowing argon gas to stir, and adding silicon raw materials and aluminum raw materials for deoxidation, controlling the weight percentage ratio of Cl=Al / Si in the initial alloy liquid to be 0.65~1.3, and controlling the weight percentage content of O in the initial alloy liquid to be ≤0.0025%.

[0085] An AOD furnace (argon oxygen decarburization furnace) is a refining device for the argon-oxygen refining process. The initial alloy liquid undergoes a first refining treatment in the AOD furnace, where oxygen blowing decarburizes the initial alloy liquid to ensure that the weight percentage of carbon is ≤0.01%, thus removing as much carbon as possible and preventing carbide precipitation from interfering with the magnetic properties of soft magnetic stainless steel. Argon gas is then blown into the initial alloy liquid for stirring to promote uniform reaction and accelerate the flotation of gases and inclusions, improving the purity of the initial alloy liquid. Simultaneously, Si and Al are introduced for deoxidation, and the weight percentage ratio Cl = Al / Si is controlled at 0.65–1.3, which forms liquid droplet-like inclusions with rapid flotation and strong adsorption capacity, beneficial for subsequent processing and the magnetic properties of soft magnetic stainless steel. The weight percentage of oxygen in the initial alloy liquid is controlled to ≤0.0025% to reduce oxide inclusions, providing a high-purity alloy liquid for subsequent second refining and continuous casting processes, reducing defects in soft magnetic stainless steel, and improving the yield.

[0086] In one embodiment, the first refined alloy liquid undergoes a second refining treatment, and Re raw material is added. This includes: performing the second refining treatment on the first refined alloy liquid in an LF furnace, adding Re raw material into the LF furnace at a temperature of 1550–1610°C, and controlling the weight percentage content W of Re in the first refined alloy liquid. (Re) The content is 0.003% to 0.015%, and the weight percentage ratio C2 = Re / (S + O) in the first refined alloy liquid is 1.05 to 2.1; wherein, the duration of the second refining treatment is t = (0.045 to 0.85)W. (Re) min.

[0087] The LF furnace (Ladle Furnace) is a ladle refining furnace. W is added to the LF furnace at a temperature of 1550–1610°C, representing a weight percentage of the total content. (Re) The Re feedstock is 0.003% to 0.015% to ensure that Re is fully dissolved and diffused in the first refined alloy liquid. The temperature at which the Re feedstock is added to the LF furnace can be, for example, 1550°C, 1580°C, 1600°C, or 1610°C. The temperature at which the Re feedstock is added to the LF furnace can also be any value between the exemplary temperatures, for example, any value between 1570°C and 1590°C.

[0088] Furthermore, controlling the weight percentage ratio C2 = Re / (S+O) in the first refining alloy liquid to 1.05–2.1 ensures that Re and S and O impurities react effectively to form fine and stable spherical inclusions. This guarantees the "spheroidization" of the inclusion morphology and the "refinement" of its size by Re. The extremely high melting point and stability of these spherical rare earth inclusions result in a very low tendency for them to grow at high temperatures, thus maintaining their small size and comprehensively improving the toughness, corrosion resistance, and fatigue resistance of the soft magnetic stainless steel. The duration of the second refining treatment is t = (0.045–0.85)W. (Re) The duration t of the second refining process is proportional to the weight percentage of Re, ensuring a complete reaction and preventing excessive Re burn-out or inclusion overgrowth due to excessive processing time. For example, the duration t of the second refining process can be 0.045 W. (Re) min, 0.09W (Re) min, 0.28W (Re) min, 0.56W (Re) min or 0.85W (Re) The duration t of the second refining process can also be any value within the exemplary time range, for example, the duration t of the second refining process can be (0.087~0.55)W. (Re) Any value between min and min.

[0089] In one embodiment, the second refined alloy liquid is subjected to continuous casting to obtain a continuously cast billet, including: continuously casting the second refined alloy liquid under an axial magnetic field of 0.2 to 0.7T, and controlling the superheat to be 15 to 55°C and the cooling gradient to be 15 to 35°C / mm to obtain a continuously cast billet; wherein the compositional segregation of the continuously cast billet is ≤0.5%.

[0090] The second refined alloy liquid is electromagnetically cast under an axial magnetic field of 0.2–0.7T. The Lorentz force is used to suppress turbulence in the second refined alloy liquid, making it laminar, reducing segregation, and improving uniformity. This results in a compositional segregation of ≤0.5% in the continuously cast billet, and significantly reduces the collision probability of inclusion particles in the second refined alloy liquid, inhibiting their aggregation and growth. The magnetic field strength range of 0.2–0.7T effectively achieves the flow control target. Excessively strong magnetic fields can lead to flow stagnation, temperature inhomogeneity, surface defects, and excessively high costs, while values ​​below this range are ineffective. For example, the axial magnetic field strength can be 0.2T, 0.4T, 0.6T, or 0.7T, or any value within the exemplary range, such as any value between 0.3 and 0.5T.

[0091] A superheat of 15–55°C and a cooling gradient of 15–35°C / mm can control the solidification rate during continuous casting, avoiding internal stress caused by excessively rapid cooling or grain coarsening caused by excessively slow cooling. This ensures that the continuously cast billet has a fine and uniform grain structure, reduces product defects, and improves the quality of the finished product. The superheat can be, for example, 15°C, 30°C, 45°C, or 55°C, or any value within the exemplary temperature range, such as any value between 20 and 45°C. Similarly, the cooling gradient can be, for example, 15°C / mm, 20°C / mm, 30°C / mm, or 35°C / mm, or any value within the exemplary gradient range, such as any value between 20 and 30°C / mm.

[0092] In one embodiment, the continuous casting billet is rolled to obtain a processed billet, including: hot rolling the continuous casting billet to obtain a processed billet, wherein the heating temperature is 1150-1200°C; the initial rolling temperature Tinitial and the final rolling temperature Tfinal are specified. 终 The relationship is T 开 -T 终 ≥200℃, and T 终 ≥900℃.

[0093] During the rolling process, the heating temperature is controlled at 1150–1200℃ and the initial rolling temperature T. 开 and final rolling temperature T 终 The relationship is T 开 -T终 ≥200℃, and T 终 At temperatures ≥900℃, the grain structure and texture in the continuously cast billet can be adjusted, optimizing texture and magnetism. The heating temperature can be, for example, 1150℃, 1180℃, or 1200℃, or any value between these exemplary temperatures, such as any value between 1160℃ and 1190℃. 开 -T 终 ≥200℃ and T 终 A temperature of ≥900℃ ensures that rolling is completed above the recrystallization temperature, promoting dynamic recrystallization, refining grains, and the large temperature difference contributes to uniform deformation, improves grain orientation, reduces anisotropy, and thus enhances the magnetic permeability of soft magnetic stainless steel. Among these, T... 终 The maximum temperature can not exceed 1050℃.

[0094] In one embodiment, the processing billet is subjected to solution treatment to obtain soft magnetic stainless steel, including: the processing billet is subjected to staged heating treatment under argon protection, wherein the first stage is heated from 20-25°C to 750-850°C at a heating rate of 2-8°C / min, the second stage is heated from 750-850°C to 1050-1200°C at a heating rate of 10-20°C / min, and the third stage is held at 1050-1200°C for 30-150 min; then the billet is cooled by water to obtain soft magnetic stainless steel.

[0095] In this embodiment, staged heating and water cooling under argon protection maximize the solid solution effect and optimize the microstructure and magnetism of the soft magnetic stainless steel. The first stage involves heating from 20–25°C to 750–850°C at a rate of 2–8°C / min. The second stage involves heating from 750–850°C to 1050–1200°C at a rate of 10–20°C / min, which reduces thermal stress, prevents cracking and deformation, and ensures uniform heating. The third stage involves holding at 1050–1200°C for 30–150 minutes to ensure the magnetic uniformity of the soft magnetic stainless steel.

[0096] The heating rate in the first stage can be, for example, 2℃ / min, 4℃ / min, 6℃ / min, or 8℃ / min. Alternatively, the heating rate can be any value between these exemplary heating rates, such as any value between 3 and 6℃ / min. The starting temperature of the first stage can be, for example, room temperature. The ending temperature of the first stage can be, for example, 750℃, 800℃, or 850℃. The ending temperature can also be any value between these exemplary temperatures, such as any value between 780 and 820℃.

[0097] The heating rate of the second stage can be, for example, 10℃ / min, 13℃ / min, 18℃ / min, or 20℃ / min. The heating rate of the second stage can also be any value between these exemplary heating rates, such as any value between 10 and 15℃ / min. The starting temperature of the second stage can be, for example, 750℃, 800℃, or 850℃. The starting temperature of the second stage can also be any value between these exemplary temperatures, such as any value between 780 and 820℃. The ending temperature of the second stage can be, for example, 1050℃, 1150℃, or 1200℃. The ending temperature of the second stage can also be any value between these exemplary temperatures, such as any value between 1100 and 1180℃.

[0098] The insulation temperature for the third stage can be 1050℃, 1150℃, or 1200℃, or any value between the exemplary temperatures, such as any value between 1100℃ and 1180℃. The insulation duration for the third stage can be 30 minutes, 90 minutes, 120 minutes, or 150 minutes, or any value between the exemplary durations, such as any value between 30 minutes and 120 minutes.

[0099] The following table further compares the composition (Table 1) and performance parameters (Table 2) of the soft magnetic stainless steel materials of this disclosure with those of the comparative examples. The content of the stainless steel material is expressed as a weight percentage. It should be noted that the total content of the components in the examples is slightly less than 100%, which can be understood as residual amounts being trace impurities or small amounts of components that cannot be analyzed.

[0100] Table 1

[0101]

[0102]

[0103] Table 1 (continued)

[0104]

[0105]

[0106] Table 2

[0107]

[0108] As can be seen from the specific values ​​in Tables 1 and 2 above, compared with the comparative stainless steel material, the soft magnetic stainless steel provided in this embodiment of the disclosure has a uniform microstructure, excellent magnetic properties, corrosion resistance, and ease of processing. Therefore, compared with the comparative stainless steel material, the soft magnetic stainless steel provided in this embodiment of the disclosure has achieved breakthrough progress in the control of inclusion shape and size, magnetic properties, corrosion resistance, and processability, achieving unexpected technical effects.

[0109] The above-described contents can be implemented individually or in various combinations, and all such variations are within the scope of this disclosure.

[0110] Finally, it should be noted that in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0111] The above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit it. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this disclosure.

Claims

1. A soft magnetic stainless steel, characterized by, The soft magnetic stainless steel comprises the following elements in percentage by weight: C: 0.01% to 0.12%, Si: 0.18% to 0.80%, Mn: 0.3% to 1.2%, Cr: 10.8% to 22.3%, Cu: 0.04% to 0.25%, Mo: 0.04% to 0.38%, Ni: 0.15% to 1.2%, S: ≤0.004%, N: ≤0.03%, O: ≤0.0025%, Al: 0.25% to 1.5%, Re: 0.003% to 0.015%, and the balance of Fe.

2. The soft magnetic stainless steel according to claim 1, characterized in that, The ratio C1 = Al / Si is 0.65 to 1.

3.

3. The soft magnetic stainless steel according to claim 1, characterized in that, The ratio C2 = Re / (S+O) is 1.05 to 2.

1.

4. The soft magnetic stainless steel according to claim 1, characterized in that, The soft magnetic stainless steel comprises spherical inclusions, the average diameter of the spherical inclusions is less than or equal to 3 μm, and the particle size distribution D90 of the spherical inclusions is less than 8 μm. The spherical inclusions are a mixture of Re, Al, Si, O and S.

5. A method for producing a soft magnetic stainless steel, characterized by, The preparation method is used for preparing the soft magnetic stainless steel according to any one of claims 1 to 4, and the preparation method comprises: performing first refining treatment on the initial alloy liquid to decarburize and deoxidize, so as to obtain a first refined alloy liquid; performing second refining treatment on the first refined alloy liquid and adding Re raw material, so as to obtain a second refined alloy liquid; performing continuous casting treatment on the second refined alloy liquid, so as to obtain a continuous casting blank; performing rolling treatment on the continuous casting blank, so as to obtain a processing blank; performing solid solution treatment on the processing blank, so as to obtain the soft magnetic stainless steel.

6. The method of producing a soft magnetic stainless steel according to claim 5, characterized by, The first refining treatment on the initial alloy liquid to decarburize and deoxidize comprises: performing first refining treatment on the initial alloy liquid in an AOD furnace, blowing oxygen to decarburize the initial alloy liquid so that the content of C in the initial alloy liquid is less than or equal to 0.01% by weight; then blowing argon to stir and adding silicon raw material and aluminum raw material to deoxidize, so as to control the ratio C1 = Al / Si in the initial alloy liquid to be 0.65 to 1.3 by weight and control the content of O in the initial alloy liquid to be less than or equal to 0.0025% by weight.

7. The method of producing a soft magnetic stainless steel according to claim 6, characterized in that, The second refining treatment on the first refined alloy liquid and the addition of Re raw material comprise: The first refined alloy liquid is subjected to a second refining treatment in an LF furnace, Re raw material is added into the LF furnace at a temperature of 1550-1610 °C, and the weight percentage content W of Re in the first refined alloy liquid is controlled to be 0.003%-0.015%, and the weight percentage ratio C2 = Re / (S+O) in the first refined alloy liquid is 1.05-2.

1. (Re) The first refined alloy liquid is subjected to a second refining treatment in an LF furnace, Re raw material is added into the LF furnace at a temperature of 1550-1610 °C, and the weight percentage content W of Re in the first refined alloy liquid is controlled to be 0.003%-0.015%, and the weight percentage ratio C2 = Re / (S+O) in the first refined alloy liquid is 1.05-2.

1. (Re) The first refined alloy liquid is subjected to a second refining treatment in an LF furnace, Re raw material is added into the The second refining treatment has a time length of t = (0.045-0.85)W (Re) min.

8. The method of producing a soft magnetic stainless steel according to claim 6, characterized by, The continuous casting treatment on the second refined alloy liquid to obtain a continuous casting blank comprises: performing continuous casting treatment on the second refined alloy liquid under an axial magnetic field of 0.2 to 0.7 T, controlling the superheat to be 15 to 55 ℃ and the cooling gradient to be 15 to 35 ℃ / mm, so as to obtain the continuous casting blank; wherein the composition segregation of the continuous casting blank is less than or equal to 0.5%.

9. The method of producing a soft magnetic stainless steel according to claim 6, characterized by, The rolling treatment on the continuous casting blank to obtain a processing blank comprises: The continuous casting billet is subjected to a hot rolling process to obtain the processed billet, wherein the heating temperature is 1150-1200°C; the open rolling temperature T 开 and the finish rolling temperature T 终 satisfy the relationship T 开 -T 终 ≥200°C, and T 终 ≥900°C.

10. The method of producing a soft magnetic stainless steel according to claim 6, characterized by, The solid solution treatment on the processing blank to obtain the soft magnetic stainless steel comprises: The processing blank is subjected to staged heating treatment under argon protection, wherein the first stage is heating from 20-25 ℃ to 750-850 ℃ at a heating rate of 2-8 ℃ / min, the second stage is heating from 750-850 ℃ to 1050-1200 ℃ at a heating rate of 10-20 ℃ / min, and the third stage is keeping the temperature of 1050-1200 ℃ for 30-150 min; and then water cooling is performed to obtain the soft magnetic stainless steel.

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