Stainless steel bar for pilot head of electromagnetic valve and preparation method of stainless steel bar

Abstract

The invention discloses a stainless steel bar for a pilot head of an electromagnetic valve and a preparation method of the stainless steel bar, and relates to the technical field of stainless steel. The preparation method specifically comprises the following steps that raw materials of the stainless steel bar for the electromagnetic valve pilot head are weighed and smelted to obtain a base material, and the base material is sequentially subjected to coating treatment and drying treatment; drawing treatment is firstly carried out, and then bright annealing treatment is carried out; cutting treatment is firstly carried out, and then straightening treatment is carried out; grinding treatment is carried out after chamfering treatment is carried out; and through eddy current flaw detection, qualified stainless steel bars are finished products for the pilot head of the electromagnetic valve. Through precise control of material chemical elements and process optimization, comprehensive improvement of wear resistance, corrosion resistance, magnetic performance and machining efficiency is achieved, the service life of parts is remarkably prolonged, the maintenance cost is reduced, the method is suitable for the field of high-precision electromagnetic control, and specifically, the tensile strength is larger than or equal to 450 MPa, the coercive force is smaller than or equal to 200 A / m, and the saturation induction density is larger than or equal to 1.4 T.

Description

Technical Field

[0001] The present invention relates to the technical field of stainless steel, and more specifically, to a stainless steel bar for an electromagnetic valve pilot head and a preparation method thereof. Background Art

[0002] As a core actuating element in industrial automation control systems, the performance of the pilot head of an electromagnetic valve directly determines the response speed, reliability, and service life of the valve. The current mainstream stainless steel materials face multiple technical bottlenecks in the application of pilot heads: on the one hand, the need to balance high magnetic permeability and low coercivity makes it difficult to control the microstructure of the material. Traditional alloying methods often focus on one aspect at the expense of the other - the addition of elements to improve magnetic properties weakens the corrosion resistance of the matrix, while the chromium-nickel components that enhance corrosion resistance reduce the efficiency of magnetic domain migration; on the other hand, the requirements for mechanical properties (such as strength and toughness) under complex working conditions further exacerbate the complexity of multi-objective optimization of the material, and conventional heat treatment processes are difficult to achieve an effective balance between refining grains and suppressing brittleness.

[0003] At the same time, existing surface treatment technologies (such as electroplating and nitriding) have problems such as long process chains and high energy consumption, and the insufficient bonding force of the coating is prone to peeling failure. Traditional cutting processing is severely restricted by tool wear caused by material hardness fluctuations, which seriously affects production efficiency. More importantly, the existing material system has poor adaptability to working conditions (such as high temperature, high humidity, and corrosive media), and is prone to magnetic degradation or stress corrosion cracking after long-term service, making it difficult to meet the stringent requirements of the intelligent manufacturing field for long-life and maintenance-free electromagnetic valves. Therefore, it is urgent to develop a new stainless steel matrix with synergistically improved magnetic, mechanical, and corrosion-resistant properties through composition innovation and gradient heat treatment processes guided by materials genomics, combined with one-step forming and surface modification integration technology, to break through the efficiency and cost constraints of traditional processes and provide core material support for the intelligent upgrading of high-end equipment. Summary of the Invention

[0004] In view of the deficiencies of the existing stainless steel materials and preparation processes for electromagnetic valve pilot heads, the present invention provides a stainless steel bar for an electromagnetic valve pilot head with high magnetic permeability, excellent mechanical properties, and corrosion resistance, and a preparation method thereof.

[0005] The present invention provides a preparation method for a stainless steel bar for an electromagnetic valve pilot head, and the preparation method specifically includes the following steps: S1. Weigh the raw materials for the stainless steel bar for the electromagnetic valve pilot head and obtain a base material through melting, and then sequentially perform film and drying treatments on the base material; S2. First perform drawing treatment and then bright annealing treatment; S3. First perform cutting treatment and then straightening treatment; S4. First perform chamfering treatment and then grinding treatment; S5. The finished stainless steel bars for solenoid valve pilot heads are those that pass eddy current flaw detection and are qualified.

[0006] Compared with the prior art, through smelting to optimize the composition design, the present invention synergistically improves the magnetic permeability, corrosion resistance and mechanical strength of the material from the source, avoiding the problem of one-sidedness in traditional alloying methods; the lubrication uniformity of the film treatment helps the stress distribution in the material to be more uniform during the deformation process, reducing local stress concentration and preventing crack generation; the thermo-mechanical treatment combining continuous drawing and bright annealing not only refines the grains and enhances the toughness, but also reduces the damage of the surface oxide layer, simplifying the traditional multi-process surface treatment process; the integrated processing mode of online straightening, chamfering and grinding significantly shortens the production line length and reduces material loss. At the same time, eddy current flaw detection replaces traditional destructive testing to achieve full-process automation and high-precision screening. The overall solution breaks through the bottleneck of multi-performance synergy through the synergy innovation of material-process-detection, takes into account high-efficiency production and low-cost adaptability, and meets the core requirements of industrial automation for long life and high reliability of solenoid valves.

[0007] In a possible implementation manner, in the step S1, by mass percentage, the stainless steel bars for solenoid valve pilot heads are composed of the following components with the following mass percentages: C≤0.03%, 1.30%≤Si≤2.20%, Mn≤0.50%, P≤0.035%, 0.015%≤S≤0.030%, 16.50%≤Cr≤18.00%, Ni≤0.40%, 0.20%≤Mo≤0.60%, Cu≤0.030%, N≤0.030%, and the balance is Fe and inevitable impurities.

[0008] Compared with the prior art, through precise control of the extremely low content of elements such as carbon, silicon and manganese and the synergistic ratio of chromium, molybdenum and nitrogen, while avoiding the risk of carbide precipitation and intergranular corrosion, the compactness of the oxide film and the passivation film repair ability are strengthened, realizing the balance of magnetic permeability and corrosion resistance; the low-nickel and high-nitrogen design replaces the traditional high-cost alloying path, combined with bright annealing and integrated processing technology, which not only inhibits work hardening and heat treatment deformation, but also simplifies the multi-process surface treatment process, and finally achieves the synergistic optimization of magnetic properties, mechanical strength and corrosion resistance, meeting the core requirements of industrial automation for high-reliability, low-energy-consumption and long-life solenoid valve materials.

[0009] In a possible implementation manner, in the step S1, the diameter of the substrate is 9.0 mm.

[0010] Compared with the prior art, the substrate of the present invention adopts a larger diameter design, which reduces the number of subsequent drawing and heat treatment processes, reduces the risk of work hardening, and improves the uniformity of the internal structure of the material, thereby optimizing the synergistic performance of magnetic domain migration efficiency and corrosion resistance; at the same time, by reducing material loss and energy consumption in the intermediate links, taking into account production efficiency and cost control, providing more stable heat conduction conditions for processes such as bright annealing, and finally achieving synchronous improvement of mechanical strength, magnetic properties and corrosion resistance, meeting the integrated manufacturing requirements of high-precision and low-defect valve body materials for industrial automation.

[0011] In a possible implementation manner, in the step S2, the reduction ratio of the drawing process is 12-17%.

[0012] Compared with the prior art, the drawing process with a medium reduction ratio adopted by the present invention refines grains and enhances the density of the material while avoiding excessive work hardening, maintaining the balance between matrix ductility and magnetic domain migration efficiency; by precisely controlling the amount of deformation, it reduces surface oxide layer damage and residual stress concentration, provides uniform heat conduction conditions for subsequent bright annealing, thereby synergistically improving mechanical strength and corrosion resistance, and simplifies the stress relief process between multiple processes, achieving the unity of high-efficiency production and high performance.

[0013] In a possible implementation manner, in the step S2, the parameters of the bright annealing process are as follows: the annealing temperature is 800-860 °C, and the holding time per millimeter of effective diameter is 240 s.

[0014] Compared with the prior art, the bright annealing with a specific temperature range adopted by the present invention precisely regulates the nucleation and growth rates of grains through gradient energy input, avoiding both the decrease in magnetic permeability and the increase in brittleness caused by coarse grains, and suppressing work hardening caused by excessive dislocation density; the matching holding time synergistically promotes the release of residual stress and the uniform diffusion of elements, reduces surface oxide layer damage, provides a low-defect matrix for subsequent straightening and grinding, thereby achieving the synergistic optimization of magnetic domain ordering, corrosion resistance and toughness while simplifying the process steps, meeting the requirements of high-precision and low-energy consumption automated production.

[0015] In a possible implementation manner, in the step S2, the bright annealing process is carried out in a protective atmosphere, and the protective atmosphere is a nitrogen-hydrogen mixture with a volume ratio of 1:3.

[0016] Compared with the prior art, the nitrogen-hydrogen mixed protective atmosphere effectively inhibits the oxidation reaction during annealing through a high proportion of reducing hydrogen, avoiding the deterioration of corrosion resistance caused by surface decarburization or the destruction of the passivation film. At the same time, nitrogen acts as a diluent to precisely control the reduction intensity and prevent the brittleness risk caused by excessive hydrogen permeation. On the basis of ensuring the material purity, this atmosphere design reduces subsequent surface treatment processes such as pickling, reduces energy consumption and pollution, and promotes uniform diffusion at grain boundaries and maintains the balance between magnetic domain migration efficiency and mechanical strength and toughness by synergistically optimizing the thermodynamic environment, meeting the preparation requirements of solenoid valve materials with high efficiency, low consumption, and high reliability.

[0017] In a possible implementation manner, in the step S2, the flow rate of the protective atmosphere is 1.5 ± 0.3 m / h.

[0018] Compared with the prior art, the design of the stable flow rate of the protective atmosphere dynamically balances the reducing environment and the thermal field distribution, avoiding oxidation segregation or decarburization defects caused by local atmosphere disorder, optimizing the grain boundary diffusion efficiency, and reducing the generation of surface brittle phases. The precise gas coverage efficiency reduces energy consumption and inhibits impurity adsorption, synergistically realizing the double improvement of material purity and magnetic domain ordering with the bright annealing process, while simplifying the subsequent surface treatment process, providing an efficient and low-consumption process guarantee for valve body materials with high corrosion resistance and high magnetic permeability.

[0019] The second object of the present invention is to provide a stainless steel bar for a solenoid valve pilot head, and the stainless steel bar for the solenoid valve pilot head is prepared by any of the above-mentioned preparation methods. Specific embodiments

[0020] To make the above objects, features, and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not used to limit the parameter range described in the present invention. Reasonable changes derived therefrom are still within the protection scope of the claims of the present invention.

[0021] It should be noted that the endpoints and any values within the ranges disclosed in this article are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0022] 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 this invention pertains. In some cases, terms with commonly understood meanings are defined herein for purposes of clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from the conventional understanding in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments is carried out according to the protocols and parameters provided by the manufacturers.

[0023] Example 1 This example provides a stainless steel rod for a solenoid valve pilot head, which is prepared by the following method: S1: Weigh the raw materials for the stainless steel rod for the solenoid valve pilot head and obtain the base material through melting. Then, the base material is subjected to film formation and drying treatments in sequence. Among them, the diameter of the base material is 9.00 mm. By mass percentage, the stainless steel rod for the solenoid valve pilot head is composed of the following components with the following mass percentages: C: 0.018%, Si: 1.39%, P: 0.023%, S: 0.19%, Mn: 0.32%, Cr: 16.79%, Ni: 0.12%, Mo: 0.26%, Cu: 0.05%, N: 0.016%, and the balance is Fe and inevitable impurities. S2: Drawing treatment, where the reduction rate of the drawing treatment is 14.95%, and the diameter of the drawn stainless steel rod is 8.30 mm. S3: Bright annealing and cutting treatment, where the annealing temperature is 800 °C, and the holding time per millimeter of effective diameter is 240 seconds. S4: Straightening treatment. S5: Chamfering treatment. S6: Grinding treatment, where the stainless steel rod with a diameter of 8.05 mm is obtained after grinding three times. S7: Eddy current flaw detection. The qualified stainless steel rod is the finished product.

[0024] Example 2 This example provides a stainless steel rod for a solenoid valve pilot head, which is prepared by the following method: S1: Weigh the raw materials of the stainless steel bar for the solenoid valve pilot head and obtain the base material through smelting. Then, perform film and drying treatments on the base material. Among them, the diameter of the base material is 9.00 mm. By mass percentage, the stainless steel bar for the solenoid valve pilot head is composed of the following components with the following mass percentages: C: 0.015%, Si: 1.85%, P: 0.022%, S: 0.018%, Mn: 0.32%, Cr: 17.88%, Ni: 0.23%, Mo: 0.35%, Cu: 0.019%, N: 0.012%, and the balance is Fe and inevitable impurities. S2: Drawing treatment, where the reduction rate of the drawing treatment is 12%, and the diameter of the drawn stainless steel bar is 8.44 mm. S3: Bright annealing and cutting treatment, where the annealing temperature is 800 °C, and the holding time per millimeter of effective diameter is 240 seconds. S4: Straightening treatment. S5: Chamfering treatment. S6: Grinding treatment, where the stainless steel bar with a diameter of 8.25 mm is obtained after grinding three times. S7: Eddy current flaw detection. The qualified stainless steel bar is the finished product.

[0025] Example 3 This example provides a stainless steel bar for a solenoid valve pilot head, which is prepared by the following method: S1: Weigh the raw materials of the stainless steel bar for the solenoid valve pilot head and obtain the base material through smelting. Then, perform film and drying treatments on the base material. Among them, the diameter of the base material is 9.00 mm. By mass percentage, the stainless steel bar for the solenoid valve pilot head is composed of the following components with the following mass percentages: C: 0.03%, Si: 1.85%, P: 0.032%, S: 0.017%, Mn: 0.44%, Cr: 17.90%, Ni: 0.36%, Mo: 0.22%, Cu: 0.03%, N: 0.03%, and the balance is Fe and inevitable impurities. S2: Drawing treatment, where the reduction rate of the drawing treatment is 17%, and the diameter of the drawn stainless steel bar is 8.20 mm. S3: Bright annealing and cutting treatment, where the annealing temperature is 860 °C, and the holding time per millimeter of effective diameter is 240 seconds. S4: Straightening treatment. S5: Chamfering treatment. S6: Grinding treatment, where the stainless steel bar with a diameter of 8.00 mm is obtained after grinding three times. S7: Eddy current flaw detection. The qualified stainless steel bar is the finished product.

[0026] Example 4 This embodiment provides a stainless steel bar for a solenoid valve pilot head, which is prepared by the following method: S1: Weigh the raw materials for the stainless steel bar of the solenoid valve pilot head and obtain the base material through melting. Then, perform film and drying treatments on the base material. Among them, the diameter of the base material is 9.00 mm. By mass percentage, the stainless steel bar for the solenoid valve pilot head is composed of the following components with the following mass percentages: C: 0.022%, Si: 2.10%, P: 0.034%, S: 0.015%, Mn: 0.35%, Cr: 16.5%, Ni: 0.26%, Mo: 0.58%, Cu: 0.029%, N: 0.015%, and the balance is Fe and unavoidable impurities; S2: Drawing treatment, where the reduction ratio of the drawing treatment is 13.85%, and the diameter of the drawn stainless steel bar is 8.36 mm; S3: Bright annealing and cutting treatment, where the annealing temperature is 820 °C and the holding time per millimeter of effective diameter is 240 seconds; S4: Straightening treatment; S5: Chamfering treatment; S6: Grinding treatment, where the stainless steel bar with a diameter of 8.00 mm is obtained after three grindings; S7: Eddy current flaw detection. The qualified stainless steel bar is the finished product.

[0027] Example 5 This embodiment provides a stainless steel bar for a solenoid valve pilot head, which is prepared by the following method: S1: Weigh the raw materials for the stainless steel bar of the solenoid valve pilot head and obtain the base material through melting. Then, perform film and drying treatments on the base material. Among them, the diameter of the base material is 9.00 mm. By mass percentage, the stainless steel bar for the solenoid valve pilot head is composed of the following components with the following mass percentages: C: 0.026%, Si: 2.15%, P: 0.031%, S: 0.018%, Mn: 0.5%, Cr: 17.23%, Ni: 0.32%, Mo: 0.52%, Cu: 0.01%, N: 0.016%, and the balance is Fe and unavoidable impurities; S2: Drawing treatment, where the reduction ratio of the drawing treatment is 15%, and the diameter of the drawn stainless steel bar is 8.30 mm; S3: Bright annealing and cutting treatment, where the annealing temperature is 840 °C and the holding time per millimeter of effective diameter is 240 seconds; S4: Straightening treatment; S5: Chamfering treatment; S6: Grinding treatment, where the stainless steel bar with a diameter of 8.05 mm is obtained after three grindings; S7: Eddy current flaw detection. The qualified stainless steel bars are the finished products.

[0028] Comparative Example 1 This comparative example provides a stainless steel bar for a solenoid valve pilot head. The difference from Example 1 is only that, during the preparation process of this comparative example, the annealing temperature in step S3 is 750 °C, and the others are the same as those in Example 1, which will not be elaborated here.

[0029] Comparative Example 2 This comparative example provides a stainless steel bar for a solenoid valve pilot head. The difference from Example 1 is only that, during the preparation process of this comparative example, the annealing temperature in step S3 is 780 °C, and the others are the same as those in Example 1, which will not be elaborated here.

[0030] Comparative Example 3 This comparative example provides a stainless steel bar for a solenoid valve pilot head. The difference from Example 1 is only that, during the preparation process of this comparative example, the annealing temperature in step S3 is 830 °C, and the others are the same as those in Example 1, which will not be elaborated here.

[0031] Comparative Example 4 This comparative example provides a stainless steel bar for a solenoid valve pilot head. The difference from Example 1 is only that, during the preparation process of this comparative example, the annealing temperature in step S3 is 860 °C, and the others are the same as those in Example 1, which will not be elaborated here.

[0032] Comparative Example 5 This comparative example provides a stainless steel bar for a solenoid valve pilot head. The difference from Example 1 is only that, during the preparation process of this comparative example, the annealing temperature in step S3 is 880 °C, and the others are the same as those in Example 1, which will not be elaborated here.

[0033] Comparative Example 6 This comparative example provides a stainless steel bar for a solenoid valve pilot head. The difference from Example 1 is only that, during the preparation process of this comparative example, the annealing temperature in step S3 is 920 °C, and the others are the same as those in Example 1, which will not be elaborated here.

[0034] The applicant uses a universal testing machine and a magnetic property tester to measure the stainless steel bars for solenoid valve pilot heads prepared under different annealing temperatures in Example 1 and Comparative Examples 1 - 6. The results are shown in Table 1: Table 1: Performance test results of stainless steel bars for solenoid valve pilot heads prepared under different annealing temperatures in Example 1 and Comparative Examples 1 - 6 Temperature (°C) Detection Items Comparative Example 1 (750 °C) Comparative Example 2 (780 °C) Example 1 (800 °C) Comparative Example 3 (830 °C) Comparative Example 4 (860 °C) Comparative Example 5 (880 °C) Comparative Example 6 (920 °C) Tensile Strength (MPa) 530 519 493 489 480 443 426 Saturation Magnetic Induction Strength (T) 1.22 1.26 1.64 1.58 1.55 1.83 1.89 Residual Magnetism (T) 0.50 0.49 0.52 0.56 0.53 0.56 0.59 Coercive Force (A / m) 150.1 159.5 175.9 163.8 166.3 189.3 192.6 Experimental data show that in the range of 750 °C to 780 °C, the tensile strength of the material decreases from 530 MPa to 519 MPa, and the saturation magnetic induction intensity increases from 1.22 T to 1.26 T; while above 860 °C, the tensile strength drops sharply to 426 MPa, and the saturation magnetic induction intensity increases from 1.55 T to 1.89 T; in the range of 800 °C to 860 °C, the tensile strength decreases from 493 MPa to 480 MPa, and the saturation magnetic induction intensity and coercivity tend to be stable, indicating that the magnetic properties of the material are sensitive to temperature.

[0035] Although the present disclosure is disclosed as above, the scope of protection 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 all fall within the protection scope of the present invention.

Claims

1. A preparation method of a stainless steel bar for a solenoid valve pilot head, characterized in that, The preparation method specifically includes the following steps: S1. Weigh the raw materials of the stainless steel bar for the solenoid valve pilot head and obtain the base material through melting, and then perform film and drying treatments on the base material in sequence; S2. First perform drawing treatment and then perform bright annealing treatment; S3. First perform cutting treatment and then perform straightening treatment; S4. First perform chamfering treatment and then perform grinding treatment; S5. Through eddy current flaw detection, those qualified are the finished products of the stainless steel bar for the solenoid valve pilot head.

2. The preparation method according to claim 1, wherein In the step S1, by mass percentage, the stainless steel bar for the solenoid valve pilot head is composed of components with the following mass percentages: C≤0.03%, 1.30%≤Si≤2.20%, Mn≤0.50%, P≤0.035%, 0.015%≤S≤0.030%, 16.50%≤Cr≤18.00%, Ni≤0.40%, 0.20%≤Mo≤0.60%, Cu≤0.030%, N≤0.030%, and the balance is Fe and inevitable impurities.

3. The preparation method according to claim 1, characterized in that, In the step S1, the diameter of the base material is 9.0 mm.

4. The preparation method according to claim 1, characterized in that, In the step S2, the reduction ratio of the drawing treatment is 12-17%.

5. The preparation method according to claim 1, characterized in that, In the step S2, the parameters of the bright annealing treatment are as follows: the annealing temperature is 800-860 °C, and the holding time per millimeter of effective diameter is 240 s.

6. The preparation method according to claim 1, characterized in that, In the step S2, the bright annealing treatment is carried out in a protective atmosphere, and the protective atmosphere is a nitrogen-hydrogen mixed gas with a volume ratio of 1:

3.

7. The preparation method according to claim 6, characterized in that, In the step S2, the flow rate of the protective atmosphere is 1.5±0.3 m / h.

8. A stainless steel bar for a solenoid valve pilot head, characterized in that, The stainless steel bar for the solenoid valve pilot head is obtained by the preparation method according to any one of claims 1-7.