Stainless steel bar for soft magnetic valve seat and preparation method of stainless steel bar

Abstract

The invention discloses a stainless steel bar for a soft magnetic valve seat and a preparation method thereof, and relates to the technical field of stainless steel. The preparation method specifically comprises the following steps that S1, raw materials of the stainless steel bar for the soft magnetic valve seat are weighed and smelted to obtain a base material, and the base material is sequentially subjected to coating treatment and drying treatment; s2, primary rough extraction treatment is firstly carried out, and then primary solid solution heat treatment is carried out; s3, carrying out secondary rough extraction treatment and tertiary rough extraction treatment in sequence; s4, cleaning is conducted after straightening and cutting-off treatment is conducted; s5, straightening treatment is conducted after secondary solid solution heat treatment is conducted; and S6, the stainless steel bar for the soft magnetic valve seat is obtained after grinding treatment. According to the stainless steel bar for the soft magnetic valve seat, the base material is prepared through the smelting technology, through reasonable matching of cold drawing and solid solution, the magnetic performance and corrosion resistance are guaranteed, meanwhile, good machining formability and large-scale production feasibility are achieved, and the problems that a traditional soft magnetic valve seat material is low in magnetic conductivity, high in coercive force, complex in technology and the like are comprehensively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of stainless steel, and in particular to a stainless steel bar for a soft magnetic valve seat and a preparation method thereof. Background Art

[0002] With the rapid development of modern electronic information technology and high-end equipment manufacturing, precision electromagnetic devices are evolving towards high frequency, miniaturization and multifunctional integration. In cutting-edge fields such as medical imaging equipment, semiconductor manufacturing equipment, and aerospace precision instruments, soft magnetic materials are core functional components, and their comprehensive performance directly determines the operating accuracy and reliability of the equipment. The current industry faces two technical bottlenecks: on the one hand, although traditional austenitic stainless steel has excellent corrosion resistance and formability, its low magnetic permeability characteristics lead to insufficient magnetic field response sensitivity, making it difficult to achieve efficient energy transfer in precision electromagnetic conversion scenarios; on the other hand, although conventional ferritic or martensitic stainless steel has a certain magnetic conductivity, its corrosion resistance defects limit its long-term stability under complex working conditions, especially in harsh conditions such as marine environments and chemical corrosive media, where intergranular corrosion is prone to occur, seriously affecting the service life of the device.

[0003] In existing technologies, improving material properties through multi-element alloying faces multiple challenges: while adding high-melting-point metal elements can refine grains and enhance magnetic properties, it leads to increased work hardening and a narrower hot working window; while introducing rare earth elements can optimize the magnetic domain structure, the process is highly sensitive and the risk of compositional segregation is significantly increased; and relying solely on microstructural control (such as nanocrystallization) faces the problem of abnormal grain growth during large-scale production, resulting in fluctuations in magnetic properties. At the same time, traditional preparation processes generally suffer from high energy consumption and low yield rates, and in the context of the dual-carbon strategy, breakthroughs in green manufacturing technologies are urgently needed. Existing material systems struggle to strike an effective balance between magnetic properties, corrosion resistance, and processing adaptability, hindering the localization of high-end electromagnetic equipment. Therefore, developing new stainless steel materials for soft magnetic valve seats with independent intellectual property rights is of great strategic significance. Summary of the Invention

[0004] The object of the present invention is to provide a stainless steel bar for a soft magnetic valve seat having high magnetic permeability, high coercive force, good corrosion resistance and easy processing, and a preparation method thereof.

[0005] The present invention provides a method for preparing a stainless steel bar for a soft magnetic valve seat, the method specifically comprising the following steps: S1. Weigh the raw materials of stainless steel bars for soft magnetic valve seats and smelt them to obtain base materials, which are then subjected to coating and drying treatments in sequence. S2, first perform a roughing treatment and then perform a solution heat treatment; S3, performing secondary roughing treatment and tertiary roughing treatment in sequence; S4, cleaning after straightening and cutting; S5. Perform straightening treatment after secondary solution heat treatment; S6. After grinding, the stainless steel rod for the soft magnetic valve seat is obtained.

[0006] Compared with the existing technology, the stainless steel bar for the soft magnetic valve seat provided by the present invention adopts a smelting process to make the base material. Through the reasonable matching of cold drawing and solid solution, while ensuring the magnetic properties and corrosion resistance, it has good processing formability and large-scale production feasibility, and comprehensively improves the problems of traditional soft magnetic valve seat materials such as low magnetic permeability, high coercive force, and complex process.

[0007] In a possible embodiment, in step S1, the stainless steel bar for the soft magnetic valve seat is composed of the following components in mass percentage: C≤0.03%, 1.0%≤Si≤1.50%, 0.60%≤Mn≤1.00%, 0.20%≤Mo≤0.60%, P≤0.02%, 0.15%≤S≤0.25%, 16.50%≤Cr≤18.50%, Ni≤0.30%, N≤0.030%, and the remainder is Fe and unavoidable impurities.

[0008] Compared to existing technologies, this invention achieves breakthrough performance through a synergistic combination of compositional design and process technology: Mo optimizes the structure of the passive film on the stainless steel surface, improving its density and stability, and effectively inhibiting pitting and crevice corrosion caused by chloride ions. S combines with Mn in the steel to form manganese sulfide inclusions, which act as a lubricant during cutting, reducing cutting resistance and tool wear, thereby improving machining efficiency. The low-C design inhibits carbide precipitation, while the solid solution strengthening of Si and Mn in the ferrite matrix ensures that the material maintains the high magnetic permeability of a single ferrite structure while maintaining excellent turning formability and pitting resistance. This, combined with clean steelmaking technology to eliminate impurity segregation, ultimately achieves synergistic optimization of corrosion resistance, machinability, and soft magnetic properties.

[0009] In a possible implementation, in step S1, the diameter of the substrate is 7.5 mm.

[0010] Compared to existing technologies, this invention utilizes a 7.5mm diameter substrate design, precisely controlling the initial billet size to achieve synergistic optimization of the cold drawing process's deformation rate and microstructure uniformity. The standardized diameter design optimizes the die matching accuracy of continuous rolling equipment, reducing the uneven magnetic permeability caused by wall thickness fluctuations. It also reduces energy consumption by shortening the subsequent solution heat treatment cycle. Ultimately, while ensuring the stability of the material's magnetic properties, it significantly improves bar forming efficiency and yield.

[0011] In a possible implementation, in step S2, the surface reduction rate of a rough extraction process is 22-27%.

[0012] Compared with existing technologies, this invention balances material deformation strengthening with microstructural uniformity through precise control of the area reduction ratio (22-27%) during a single rough drawing. A moderate area reduction ratio avoids insufficient grain refinement or surface microcracks caused by excessive work hardening, while improving the uniformity of dislocation density distribution in the ferrite matrix and enhancing the efficiency of directional migration of magnetic domain walls. A gradient deformation design adapted to the multi-pass cold drawing process reduces single-pass stress concentration, promotes the directional alignment of sulfide inclusions along the drawing direction, and forms lubrication channels to reduce the risk of wire breakage during subsequent processing. This parameter, combined with solution heat treatment, synergistically optimizes grain orientation, ultimately achieving a synergistic improvement in the material's high magnetic permeability, low coercivity, and cold working stability, meeting the efficient forming requirements of precision valve seats.

[0013] In a possible embodiment, in step S2, the parameters of the single solution heat treatment are as follows: temperature of 800-900° C., and time of 2-4 hours.

[0014] Compared with the existing technology, the present invention achieves uniform solid solution of alloy elements while avoiding grain coarsening through the coordinated optimization of the single solution heat treatment temperature (800-900℃) and time (2-4h), promotes the formation of dense passivation film of elements such as Cr and Mo, and significantly improves the corrosion resistance of the material; moderate solid solution eliminates the hardening effect of the early cold drawing work, restores the plasticity of the ferrite matrix, reduces the subsequent deformation resistance, and adapts to the continuous forming requirements of the multi-pass cold drawing process; precise timing is controlled to avoid impurity segregation caused by overburning, maintain the high magnetic permeability characteristics of the single ferrite phase structure, and at the same time suppress dislocation recovery through dynamic precipitation, laying the foundation for the final material to have low coercivity, high magnetic response and processing stability.

[0015] In a possible implementation, in step S3, the surface reduction rate of the secondary roughing process is 20-25%.

[0016] Compared with the existing technology, the present invention achieves the coordinated optimization of material microstructure and processing performance through precise control of the secondary rough drawing reduction rate (20-25%). While avoiding excessive work hardening, the moderate reduction rate maintains the gradient distribution of dislocation density in the ferrite matrix and enhances the efficiency of directional migration of magnetic domain walls. The gradient deformation design adapted to the multi-stage cold drawing process reduces cross-sectional stress concentration, promotes the orderly arrangement of sulfide inclusions along the drawing direction, and forms self-lubricating channels to reduce the risk of wire breakage. This parameter, in conjunction with the solution heat treatment, coordinates the regulation of grain orientation, maintaining the high magnetic permeability characteristics of a single ferrite phase while suppressing residual stress accumulation through dynamic recovery. Ultimately, the material achieves a balance between high magnetic response, low coercivity, and cold working stability to meet the requirements of precision valve seat forming.

[0017] In a possible implementation, in step S3, the surface reduction rate of the three roughing treatments is 10-15%.

[0018] Compared with the existing technology, the present invention achieves the coordinated optimization of material microstructure and processing accuracy through precise control of the area reduction rate (10-15%) during three rough drawing steps. The low area reduction rate avoids the magnetic domain wall pinning effect caused by excessive work hardening, maintains the gradient distribution of dislocation density in the ferrite matrix, and enhances the stability of magnetic permeability. The gradient deformation design adapted to the multi-stage cold drawing reduces cross-sectional stress concentration, promotes the orderly arrangement of sulfide inclusions along the drawing direction, and forms self-lubricating channels to reduce the risk of wire breakage. This parameter cooperates with the solution heat treatment to regulate the degree of grain orientation, suppressing the accumulation of residual stress through dynamic recovery, and ultimately achieving a balanced adaptation of the material's high magnetic response, low coercivity, and dimensional accuracy to the requirements of precision valve seat molding.

[0019] In a possible embodiment, in step S5, the parameters of the secondary solution heat treatment are as follows: temperature of 800-900° C., and time of 2-4 hours.

[0020] Compared with existing technologies, this invention achieves a step-by-step optimization of material properties through precise replication of secondary solution heat treatment (800-900°C / 2-4h). High-temperature solution treatment completely eliminates the cumulative work hardening effects of multiple cold drawing stages, restoring the plasticity of the ferrite matrix to accommodate subsequent straightening processes. Dynamic precipitation inhibits abnormal grain growth, maintaining the low coercivity characteristics of the single-phase structure while promoting uniform diffusion of Cr and Mo elements and enhancing the density of the passivation film. Short-term temperature control prevents impurity segregation caused by overheating, ensuring the coordinated stability of magnetic domain wall migration efficiency and corrosion resistance, laying the foundation for the final material to combine high magnetic permeability, low-energy processing, and long-term service performance.

[0021] A second object of the present invention is to provide a stainless steel bar for a soft magnetic valve seat, wherein the stainless steel bar for a soft magnetic valve seat is produced by the above-mentioned production method. DETAILED DESCRIPTION

[0022] To make the above-mentioned objects, features and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only intended to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter ranges described in the present invention. Reasonable variations derived therefrom are still within the scope of protection of the claims of the present invention.

[0023] It should be noted that the endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0024] Unless otherwise defined, all terms, symbols and other scientific terms used herein are intended to have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. In some cases, terms with conventional meanings are defined herein for the purpose of clarification or ease of reference, and such definitions herein should not be construed as indicating significant differences from conventional understandings in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are adopted by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents and instruments was carried out in accordance with the protocols and parameters given by the manufacturers.

[0025] Example 1 This embodiment provides a stainless steel bar for a soft magnetic valve seat, which is produced by the following method: S1: Weigh raw materials of stainless steel bars for soft magnetic valve seats and smelt them to obtain substrates, which are then subjected to coating and drying treatments in sequence; wherein the diameter of the substrate is 7.50 mm, and the stainless steel bars for soft magnetic valve seats are composed of the following components by mass percentage: C: 0.017%, Si: 1.40%, P: 0.018%, S: 0.20%, Mn: 0.75%, Cr: 18.06%, Ni: 0.19%, N: 0.011%, Mo: 0.55%, and the balance is Fe and unavoidable impurities; S2: one rough drawing process, wherein the area reduction rate of the rough drawing process is 24.8%, and the diameter of the stainless steel rod after rough drawing is 6.50 mm; S3: a solid solution heat treatment, wherein the solid solution heat treatment temperature is 850 ° C and the temperature is kept for 3 hours; S4: secondary rough drawing process, wherein the area reduction rate of the secondary rough drawing process is 23.1%, and the diameter of the stainless steel rod after rough drawing is 5.70 mm; S5: three roughing treatments, wherein the area reduction rate of the three roughing treatments is 11.9%, and the diameter of the stainless steel rod after roughing is 5.35 mm; S6: straightening and cutting process; S7: cleaning process; S8: Secondary solution heat treatment, wherein the secondary solution heat treatment temperature is 850°C and the temperature is kept for 3 hours; S9: straightening treatment; S10: After grinding, a stainless steel rod is obtained. After grinding three times, a stainless steel rod with a diameter of 5.15 mm is obtained, which is the finished product.

[0026] Example 2 This embodiment provides a stainless steel bar for a soft magnetic valve seat, which is produced by the following method: S1: Weigh raw materials of stainless steel bars for soft magnetic valve seats and smelt them to obtain substrates, which are then subjected to coating and drying treatments in sequence; wherein the diameter of the substrate is 7.50 mm, and the stainless steel bars for soft magnetic valve seats are composed of the following components by mass percentage: C: 0.025%, Si: 1.35%, P: 0.011%, S: 0.18%, Mn: 0.88%, Cr: 17.55%, Ni: 0.21%, N: 0.02%, Mo: 0.35%, and the balance is Fe and unavoidable impurities; S2: one rough drawing process, wherein the area reduction rate of the rough drawing process is 22.5%, and the diameter of the stainless steel rod after rough drawing is 6.60 mm; S3: a solid solution heat treatment, wherein the solid solution heat treatment temperature is 800 ° C and the temperature is kept for 4 hours; S4: secondary rough drawing process, wherein the area reduction rate of the secondary rough drawing process is 20.5%, and the diameter of the stainless steel rod after rough drawing is 5.89 mm; S5: three roughing treatments, wherein the area reduction rate of the three roughing treatments is 14.8%, and the diameter of the stainless steel rod after roughing is 5.43 mm; S6: straightening and cutting process; S7: cleaning process; S8: Secondary solution heat treatment, wherein the secondary solution heat treatment temperature is 800°C and the temperature is kept for 4 hours; S9: straightening treatment; S10: After grinding, a stainless steel rod is obtained. After grinding three times, a stainless steel rod with a diameter of 5.15 mm is obtained, which is the finished product.

[0027] Example 3 This embodiment provides a stainless steel bar for a soft magnetic valve seat, which is produced by the following method: S1: Weigh raw materials of stainless steel bars for soft magnetic valve seats and smelt them to obtain substrates, which are then subjected to coating and drying treatments in sequence; wherein the diameter of the substrate is 7.50 mm, and the stainless steel bars for soft magnetic valve seats are composed of the following components in mass percentage: C: 0.012%, Si: 1.49%, P: 0.011%, S: 0.22%, Mn: 0.95%, Cr: 18.5%, Ni: 0.22%, N: 0.011%, Mo: 0.2%, and the balance being Fe and unavoidable impurities; S2: one rough drawing process, wherein the area reduction rate of the rough drawing process is 22%, and the diameter of the stainless steel rod after rough drawing is 6.62 mm; S3: a solid solution heat treatment, wherein the solid solution heat treatment temperature is 850 ° C and the temperature is kept for 3 hours; S4: secondary rough drawing process, wherein the area reduction rate of the secondary rough drawing process is 20%, and the diameter of the stainless steel rod after rough drawing is 5.92mm; S5: three roughing treatments, wherein the area reduction rate of the three roughing treatments is 15%, and the diameter of the stainless steel rod after roughing is 5.46 mm; S6: straightening and cutting process; S7: cleaning process; S8: Secondary solution heat treatment, wherein the secondary solution heat treatment temperature is 850°C and the temperature is kept for 3 hours; S9: straightening treatment; S10: After grinding, a stainless steel rod is obtained. After grinding three times, a stainless steel rod with a diameter of 5.15 mm is obtained, which is the finished product.

[0028] Example 4 This embodiment provides a stainless steel bar for a soft magnetic valve seat, which is produced by the following method: S1: Weigh raw materials of stainless steel bars for soft magnetic valve seats and smelt them to obtain substrates, which are then subjected to coating and drying treatments in sequence; wherein the diameter of the substrate is 7.50 mm, and the stainless steel bars for soft magnetic valve seats are composed of the following components in mass percentage: C: 0.01%, Si: 1.48%, P: 0.011%, S: 0.18%, Mn: 0.99%, Cr: 17.58%, Ni: 0.22%, N: 0.022%, Mo: 0.55%, and the balance is Fe and unavoidable impurities; S2: one rough drawing process, wherein the area reduction rate of the rough drawing process is 26%, and the diameter of the stainless steel rod after rough drawing is 6.45 mm; S3: a solid solution heat treatment, wherein the solid solution heat treatment temperature is 880 ° C and the temperature is kept for 2.5 hours; S4: secondary rough drawing process, wherein the area reduction rate of the secondary rough drawing process is 24%, and the diameter of the stainless steel rod after rough drawing is 5.63mm; S5: three roughing treatments, wherein the area reduction rate of the three roughing treatments is 12%, and the diameter of the stainless steel rod after roughing is 5.28 mm; S6: straightening and cutting process; S7: cleaning process; S8: Secondary solution heat treatment, wherein the secondary solution heat treatment temperature is 880°C and the temperature is kept for 2.5 hours; S9: straightening treatment; S10: After grinding, a stainless steel rod is obtained. After grinding three times, a stainless steel rod with a diameter of 5.15 mm is obtained, which is the finished product.

[0029] Example 5 This embodiment provides a stainless steel bar for a soft magnetic valve seat, which is produced by the following method: S1: Weigh raw materials of stainless steel bars for soft magnetic valve seats and smelt them to obtain substrates, which are then subjected to coating and drying treatments in sequence; wherein the diameter of the substrate is 7.50 mm, and the stainless steel bars for soft magnetic valve seats are composed of the following components in mass percentage: C: 0.03%, Si: 1.1%, P: 0.013%, S: 0.18%, Mn: 0.65%, Cr: 16.8%, Ni: 0.22%, N: 0.022%, Mo: 0.25%, and the balance is Fe and unavoidable impurities; S2: one rough drawing process, wherein the area reduction rate of the rough drawing process is 27%, and the diameter of the stainless steel rod after rough drawing is 6.41 mm; S3: a solid solution heat treatment, wherein the solid solution heat treatment temperature is 900 ° C and the temperature is kept for 2 hours; S4: secondary rough drawing process, wherein the area reduction rate of the secondary rough drawing process is 25%, and the diameter of the stainless steel rod after rough drawing is 5.55 mm; S5: three roughing treatments, wherein the area reduction rate of the three roughing treatments is 10%, and the diameter of the stainless steel rod after roughing is 5.26 mm; S6: straightening and cutting process; S7: cleaning process; S8: Secondary solution heat treatment, wherein the secondary solution heat treatment temperature is 900°C and the temperature is kept for 2 hours; S9: straightening treatment; S10: After grinding, a stainless steel rod is obtained. After grinding three times, a stainless steel rod with a diameter of 5.15 mm is obtained, which is the finished product.

[0030] The applicant randomly tested the tensile strength, hardness, and magnetic properties of the products obtained in Example 1, as follows: 1. Using a universal testing machine, the tensile strength of the stainless steel bar for the soft magnetic valve seat prepared in Example 1 was measured, and the final tensile strength was 515 MPa; 2. Using a Vickers hardness tester, the Vickers hardness of the stainless steel bar for the soft magnetic valve seat prepared in Example 1 was measured, and the final Vickers hardness was 186 HV; 3. The magnetic properties of the stainless steel bar for the soft magnetic valve seat prepared in Example 1 were measured using a magnetic property tester. The saturation magnetic induction intensity was 1.49 T, the remanence was 0.48 T, and the coercive force was 226.2 A / m.

[0031] It can be seen from the above records that the stainless steel rod for the soft magnetic valve seat provided by the present invention is made of a base material using a smelting process. Through the reasonable matching of cold drawing and solid solution, while ensuring the magnetic properties and corrosion resistance, it has good processing formability and feasibility of large-scale production, and comprehensively improves the problems of traditional soft magnetic valve seat materials such as low magnetic permeability, high coercive force, and complex process.

[0032] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for preparing stainless steel bars for soft magnetic valve seats, characterized in that: The preparation method specifically comprises the following steps: S1. Weigh the raw materials of stainless steel bars for soft magnetic valve seats and smelt them to obtain base materials, which are then subjected to coating and drying treatments in sequence. S2, first perform a roughing treatment and then perform a solution heat treatment; S3, performing secondary roughing treatment and tertiary roughing treatment in sequence; S4, cleaning after straightening and cutting; S5. Perform straightening treatment after secondary solution heat treatment; S6. After grinding, the stainless steel rod for the soft magnetic valve seat is obtained.

2. The preparation method according to claim 1, wherein In the step S1, the stainless steel bar for the soft magnetic valve seat is composed of the following components in mass percentage: C≤0.03%, 1.0%≤Si≤1.50%, 0.60%≤Mn≤1.00%, 0.20%≤Mo≤0.60%, 0.15%≤S≤0.25%, P≤0.02%, 16.50%≤Cr≤18.50%, Ni≤0.30%, N≤0.030%, and the balance is Fe and unavoidable impurities.

3. The preparation method according to claim 1, wherein In step S1, the diameter of the substrate is 7.5 mm.

4. The preparation method according to claim 1, wherein In step S2, the surface reduction rate of a rough extraction process is 22-27%.

5. The preparation method according to claim 1, wherein In step S2, the parameters of the single solution heat treatment are as follows: temperature is 800-900° C., and time is 2-4 hours.

6. The preparation method according to claim 1, wherein In step S3, the surface reduction rate of the secondary roughing process is 20-25%.

7. The preparation method according to claim 1, wherein In step S3, the surface reduction rate of the three roughing treatments is 10-15%.

8. The preparation method according to claim 1, wherein In step S5, the parameters of the secondary solution heat treatment are as follows: temperature is 800-900° C., and time is 2-4 hours.

9. A stainless steel bar for a soft magnetic valve seat, characterized in that: The soft magnetic valve seat stainless steel bar is made by the preparation method according to any one of claims 1 to 8.