Method for manufacturing a component having a magnetic and a non-magnetic bi-phase

Abstract

Methods of forming a dual-phase magnetic component from an initial component comprising a non-magnetic austenitic composition are provided. The methods can include forming a coating on a portion of a surface of the initial component to form a masked region while leaving an unmasked region thereon. Thereafter, the initial component can be heated to a processing temperature such that nitrogen diffuses out of the unmasked region of the initial component to transform the non-magnetic austenitic composition to a magnetic phase in the unmasked region. Thereafter, the initial component can be cooled from the processing temperature to form a dual-phase magnetic component having a magnetic region corresponding to the unmasked region and a non-magnetic region corresponding to the masked region.

Description

[0001] Federal government-funded research

[0002] This invention was completed with government support under patent number DE-EE0007755 granted by the Department of Energy. The government holds certain rights to this invention. Technical Field

[0003] This invention generally relates to a component having multiple magnetic and non-magnetic regions, and a method for forming the component. More specifically, this invention relates to forming a component having multiple magnetic and non-magnetic regions by controlled nitrogen evacuation. Background Technology

[0004] The need for high power density and high efficiency motors (i.e., electric motors and generators) has long been prevalent across various applications, particularly in hybrid and / or electric vehicle traction applications. The current trend in hybrid / electric vehicle traction motor applications is to increase speeds to enhance machine power density, thereby reducing its mass and cost. However, it has been recognized that when motors are used in traction applications in hybrid / electric vehicles, there are significant trade-offs between power density, efficiency, and the machine's constant power speed range limited by rotor mechanical strength—trade-offs that present numerous design challenges.

[0005] The power density of a motor can be increased by increasing machine size, improving thermal management, increasing rotor speed, or increasing magnetic utilization. Magnetic utilization can be increased by using a combination of rotor lamination processing and alloying to create two-phase magnetic materials with localized regions of high and low permeability. These localized regions of high and low permeability typically reduce flux losses during rotor operation.

[0006] A series of iron-based soft magnetic components in rotor laminations can be austenitized through a combination of processes to form regions with low magnetic permeability. In the presence of carbides in the alloy, this phase transformation in selected regions during the process can be thermally driven. Upon localized heating, carbides present at selected sites dissolve in the matrix and lower the martensite initiation temperature, thus contributing to the stabilization of the austenitic region at room temperature. However, the presence of carbides in known magnetic microstructures increases coercivity and reduces magnetic saturation compared to conventional iron-based magnets. A different approach is needed to stabilize the austenitic phase in the intermediate regions of soft magnets at room temperature, while starting from a essentially single-phase microstructure to reduce coercivity. Summary of the Invention

[0007] The aspects and advantages will be set forth in part in the description which follows, or may be apparent from the description, or may be learned by practice of the invention.

[0008] A method is generally provided for forming a two-phase magnetic component from an initial component comprising a non-magnetic austenitic component. In one embodiment, the method may include: forming a coating on a portion of the surface of the initial component to form a masked region while leaving an unmasked region thereon. The initial component may then be heated to a processing temperature, causing nitrogen to diffuse out of the unmasked region of the initial component to transform the non-magnetic austenitic component into a magnetic phase in the unmasked region. The initial component may then be cooled from the processing temperature to form a two-phase magnetic component having a magnetic region corresponding to the unmasked region and a non-magnetic region corresponding to the masked region.

[0009] These and other features, aspects, and advantages will be better understood with reference to the following description and the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain certain principles of the invention. Attached Figure Description

[0010] The complete and practical disclosure of the invention, including its preferred mode, is set forth in the description with reference to the accompanying drawings, for those skilled in the art, wherein:

[0011] Figure 1 A masking component form for forming a two-phase magnetic component according to one embodiment is shown;

[0012] Figure 2 A masking component form for forming a two-phase magnetic component according to another embodiment is shown;

[0013] Figure 3 A masking component form for forming a two-phase magnetic component according to another embodiment is shown;

[0014] Figure 4 It shows the removal of, such as Figure 3 The two-phase magnetic component formed after the coating shown; and

[0015] Figure 5 An exemplary topology of a two-phase magnetic component, according to one embodiment, is shown that can be obtained by using the methods described herein.

[0016] Reference numerals used repeatedly in this specification and drawings are intended to indicate the same or similar features or elements of the invention. Detailed Implementation

[0017] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided to explain the invention, not to limit it. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from its scope. For example, features shown or described as part of one embodiment may be used with another embodiment to produce yet another embodiment. Therefore, the invention is intended to cover these modifications and variations that fall within the scope of the appended claims and their equivalents.

[0018] Various embodiments of the present invention relate to a two-phase magnetic component having a non-magnetic phase and a magnetic phase, and a method of forming the two-phase magnetic component. As used herein, the term "two-phase magnetic component" can refer to a magnetic part of any product, such as rotor laminations or stator laminations of an electric motor. The two-phase magnetic component described herein has a mixed first region and a second region, wherein the first region comprises a magnetic phase and the second region comprises a non-magnetic phase. "Mixed first region and second region" herein means that there are a plurality of first regions and second regions adjacent to each other.

[0019] Therefore, dual-phase magnetic components have dual magnetic regions, one set of which has a magnetic phase and the other set has a non-magnetic phase. As used herein, a "magnetic phase" is a region in which more than 99% by volume is magnetic and is typically used as the magnetic region. Furthermore, a "non-magnetic phase" can be a region in which more than 90% by volume is non-magnetic. Dual-phase magnetic components, as used herein, are typically fabricated from a single material. As an example, this material can be a composite dual-phase magnetic component formed by providing a non-magnetic portion (e.g., an austenitic portion) and a magnetic portion formed by controlled nitrogen evacuation to form a ferromagnetic portion. When manufacturing dual-phase magnetic components using a single material, the negative impact of bonding or other joining methods on the ferromagnetic and non-magnetic portions is reduced by ensuring the reliability, hermeticity, and bonding strength of the magnetic component, as many bonding methods for joining magnetic / non-magnetic materials suffer from a decrease in mechanical properties at the joint. Furthermore, the bonding methods for thin laminations are time-consuming, costly, and require additional surface finish, making them less suitable for mass production. Therefore, a monolithic material with magnetic and non-magnetic properties in a specified region is superior to any bonding method.

[0020] As used herein, a “magnetic phase” is a material in a magnetic state having a relative permeability greater than 1. In one embodiment, the magnetic phase of a first region of a magnetic component has a relative permeability greater than 100 and a saturation magnetization greater than 1.5 Tesla. As used herein, a “non-magnetic phase” has a volume percentage greater than 90% of the material, wherein the permeability is approximately 1 and the saturation magnetization is approximately zero.

[0021] Austenite, also known as gamma-Fe, is a metallic nonmagnetic allotrope of iron or a solid solution of iron. Heating iron, iron-based metals, or steel to the temperature at which the crystal structure transforms from ferrite to austenite is called austenitization. Adding certain alloying elements, such as manganese, nickel, nitrogen, and carbon, can stabilize the austenitic structure even at room temperature. Two-phase magnetic components can be formed by stabilizing austenite in some regions of the magnetic component at room temperature while retaining a strongly ferromagnetic martensite or ferrite phase in others.

[0022] The presence of carbon is known to stabilize non-magnetic austenitic structures. Early efforts have focused on dissolving carbides in selected regions of magnetic components to stabilize the non-magnetic phase in those regions. In one embodiment of the invention, the magnetic regions of the magnetic component are formed by removing nitrogen from those regions to create a ferrite structure (e.g., ferromagnetic martensite or a ferrite phase) while retaining the austenitic regions.

[0023] It is known that carbides as a second phase are undesirable for two-phase magnetic components. Therefore, in some embodiments of the invention, the material forming the two-phase magnetic component is substantially carbon-free. However, in other embodiments of the invention, the composition may contain a relatively small amount of carbon, which can sometimes increase the tensile strength of the magnetic region. In these embodiments, the total amount of carbon in both the magnetic and non-magnetic regions must be less than about 0.05% by weight.

[0024] Similar to carbon, the austenitic phase is stabilized as nitrogen dissolves into the iron alloy. Typically, the presence of carbides is established by alloying the initial material with carbon in the melt, and these carbides serve to stabilize the austenitic phase during localized heat treatment and dissolution.

[0025] In one embodiment, the initial component is formed of a non-magnetic austenitic iron-based alloy, which also includes chromium, manganese, nitrogen, and / or other alloying elements. In a particular embodiment, the initial component has a composition formed by melting high-nitrogen steel via high-pressure electroslag remelting or reverse pressure casting to produce a high-nitrogen austenitic ingot, because nitrogen has very low solubility in molten steel in conventional smelting methods without high-pressure nitrogen gas. Therefore, the non-magnetic region includes an amount of nitrogen that stabilizes the austenitic phase. In one embodiment, the austenitic composition of the initial component has a nitrogen concentration greater than 0.4 wt% (e.g., greater than 0.5 wt%). Therefore, the initial component 10 is non-magnetic.

[0026] A method for forming a two-phase magnetic component is generally disclosed. Thermodynamics and empirical calculations are used to predict the composition of an austenitic alloy, which removes nitrogen at high temperatures to form a ferromagnetic phase. The two-phase magnetic component using the designed austenitic alloy composition can be formed using conventional methods. In one embodiment, the formed nonmagnetic component undergoes selective nitrogen removal in specific regions near the final component without significantly altering the shape and size of the formed two-phase magnetic component after the selective nitrogen removal. As used herein, the term "selective nitrogen removal" refers to the removal of nitrogen from certain regions of the two-phase magnetic component without significantly altering the austenitic properties of the surrounding region. The austenitic properties of these regions can be considered "significantly altered" if the average saturation magnetization of the surrounding region increases by more than about 5%.

[0027] Selective nitrogen removal can be achieved to form two-phase magnetic components by using different nitrogen removal methods. Chemical, physical, or mechanical barriers (blocks) can be provided to areas of the initial component where nitrogen removal is undesirable to prevent magnetization in these areas. For example, a chemical component that prevents nitrogen from diffusing from the initial component can be used as a "nitrogen barrier" material for certain areas. Physical methods can be used to selectively remove nitrogen in selected areas while retaining nitrogen in other areas. Mechanical barriers can mechanically prevent nitrogen from diffusing in certain areas.

[0028] In one embodiment of the invention, high-temperature gas evacuation of nitrogen is a preferred method for removing nitrogen from a part. The high temperature in this technique allows nitrogen to diffuse rapidly out of unmasked areas, thus providing a rapid processing route. To avoid removing nitrogen in areas intended to retain austenite (and therefore nonmagnetic), in one embodiment, a mechanical mask or barrier material is applied to locations where nitrogen diffusion from the part is undesirable or where significant nitrogen loss is undesirable. Thus, in this embodiment, preselected areas corresponding to areas where nonmagnetic (austenitic) properties should be retained are masked using mechanical methods (e.g., nitrogen barrier materials). As used herein, a "nitrogen barrier material" is a material capable of significantly preventing nitrogen from leaving the area. The barrier material itself does not need to contain nitrogen.

[0029] Non-magnetic components that undergo selective nitrogen removal to form dual-phase magnetic components can be... Figure 1 The example below illustrates this. The initial component 10 is formed of an austenitic material, and its size and shape are required for the final application of the resulting component. In one embodiment, the initial component 10 is formed of a component with a very low carbon concentration (e.g., less than 0.05% by weight, or essentially carbon-free), and can be of any shape and size.

[0030] For ease of understanding, Figure 1 and Figure 2In this design, the initial component 10 is depicted as having a rectangular shape with a top surface 12 and a bottom surface 14, but it should be understood that the shape of the initial component 10 can be adapted to the needs of the component application. The initial component 10 has a specific length (l), width (w), and thickness (t). Figure 3 As shown, a coating 16 is applied to a portion of surfaces 12, 14 to define a first region 20 corresponding to the masked region 21 and a second region 30 corresponding to the unmasked exposed region 31.

[0031] Coating 16 can be formed of any material (e.g., a nitrogen-blocking material) suitable for suppressing and / or hindering nitrogen diffusion from the masking region 21 without significantly affecting other properties of component 10. For example, when formed of an iron alloy containing chromium, coating 16 can be formed of chromium oxide, aluminum silicate material, aluminum silicide material, or mixtures thereof. Coating 16 can be formed to a thickness generally sufficient to suppress and / or hinder nitrogen diffusion from the masking region 21 without being too thick and wasting excessive material. For example, coating 16 can have a thickness of 125 μm or less on surfaces 12, 14 of component 10 (e.g., 10 μm to 125 μm, such as 10 μm to 100 μm).

[0032] The first region 20 (corresponding to the masked region 21) is designed as a non-magnetic region, and the second region 30 (corresponding to the unmasked exposed region 31) is designed as a magnetic region. Reference Figure 3 The absence of coating 16 on the second region 30 within the unmasked region 31 allows nitrogen to diffuse out of the component 10, thereby making these regions magnetic. Those skilled in the art will understand that, depending on the shape and size of the magnetic and non-magnetic regions, the mask can be designed in different shapes and on different surfaces.

[0033] A nitrogen-barrier material mask formed by coating 16 can be applied to component 10, depending on the desired pattern of nitrogen evacuation (and non-evacuation) from component 10. For example, in Figure 1 In this process, coating 16 covers the thickness of component 10 at surface regions 12 corresponding to different first regions 20, and also at surface 14. Therefore, in Figure 1 In this process, nitrogen will be expelled from the component only through the second region 30 (unmasked region 31) on the top surface 12 and bottom surface 14, without passing through the component's thickness t. Figure 2 In the process, the surface through the thickness of component 10 also includes a shielded area and an unshielded area, so nitrogen is discharged from the top surface, bottom surface and side surface of the component in a controlled manner.

[0034] During the heat treatment process, nitrogen can diffuse out of component 10 via selective nitrogen evacuation. Typically, the diffusion of nitrogen from the unmasked region 31 is expected to increase with higher heat treatment temperatures and / or lower treatment pressures. For example, the heat treatment process can be carried out at treatment temperatures greater than 1000°C (e.g., 1100°C to 1300°C). Generally, the diffusion kinetics of nitrogen from the unmasked region 31 are expected to increase with higher heat treatment temperatures. However, if the treatment temperature is too low, interstitial nitrogen may form nitrides in the masked regions, which increases the magnetism therein. If the treatment temperature is too high (e.g., greater than 1300°C), coating integrity may be challenged.

[0035] Furthermore, as the processing pressure in the processing environment decreases, the diffusion of nitrogen from unmasked areas 31 is expected to increase. In one embodiment, the heat treatment process is carried out at a processing pressure less than atmospheric pressure (i.e., a negative pressure atmosphere with a pressure less than 1 atmosphere). For example, the processing pressure may be less than 0.75 atmospheres (e.g., less than 0.5 atmospheres). The processing pressure can be generated by evacuating the furnace chamber and can be maintained by continuously evacuating nitrogen during the processing. In some embodiments, the heat treatment can be carried out in an oxygen-deficient atmosphere, particularly when the component composition includes chromium, to suppress the formation of oxides (e.g., chromium oxide) on the surface of unmasked areas. Such oxides may interfere with the evacuation of nitrogen from those unmasked areas. In a particular embodiment, temperatures less than 1 atmosphere (e.g., less than 0.75 atmospheres) and greater than 1000°C (e.g., 1100°C to 1300°C) are used for selective nitrogen evacuation.

[0036] When the initial component 10 undergoes selective nitrogen removal, nitrogen diffuses out of component 10 through all exposed surfaces of component 10, including the top surface 12, the bottom surface 14, and all unmasked side surfaces of the component. This nitrogen removal, along with changes in the composition of component 10, alters the local phase stability in those unmasked regions 31 and transforms those regions from nonmagnetic austenite to magnetic ferromagnetic martensite or ferrite phases.

[0037] Nitrogen can diffuse out of the interior of component 10 through the unmasked surface regions, but depending on pressure, temperature, and certain other parameters, nitrogen can also slightly escape from the surface-masked regions 20, thus diffusing out from some of the masked regions 21. Therefore, the strict boundary between magnetic and non-magnetic regions in the surface portion can be more complete in the interior portion.

[0038] Through empirical and thermodynamic calculations, the parameters for selective nitrogen removal can be adjusted, and selective nitrogen removal in different directions can be predicted for certain regions of the magnetic component 10. This allows for changes in mask size and shape so that the final product obtained is approximately the desired result of selective nitrogen removal.

[0039] In one embodiment, the thickness of component 10 is in the range of 0.1 mm to 5 mm. The desired pattern of the magnetic and non-magnetic regions of the component can be obtained by selectively removing nitrogen from the selectively masked top surface 12 and bottom surface 14, while maintaining the thickness of the side surfaces completely masked. The width 24 of the masked region 21... Figure 2 The distance 34 between the obtained two-phase magnetic component 100 and the shielding area 21 can be determined according to the obtained two-phase magnetic component 100. Figure 4 Designed according to the requirements of ).

[0040] Selective removal of nitrogen from the initial component 10 under design conditions allows for the removal of a customized amount of interstitial nitrogen from the magnetic component. In one embodiment, the unmasked region 31 contains less than 0.4% by weight of nitrogen after heat treatment, for example, less than 0.1% by weight (e.g., less than 0.05% by weight). Nitrogen removal is not limited to the unmasked regions of the surface but can also occur in both surface and internal portions of the magnetic component 10. However, the nitrogen concentration in the surface and internal portions does not need to be uniform.

[0041] After the heat treatment process, the initial component 10 can be cooled from the processing temperature to form a two-phase magnetic component having magnetic regions corresponding to the unmasked regions and non-magnetic regions corresponding to the masked regions. For example, the component 10 can be quenched by rapid cooling to lock the phase transformation in the unmasked regions, so that the magnetic ferromagnetic martensite or ferrite phase is retained in the resulting two-phase magnetic component 100. Figure 4 In one embodiment, quenching may involve rapidly cooling from the processing temperature to less than 100°C (as measured at the temperature of surface 12) in a manner of 1 minute or less.

[0042] The coating 16 can then be removed from surfaces 12 and 14 by any method, including physical methods (e.g., sandblasting), chemical methods (e.g., chemical etching), laser removal methods, etc.

[0043] Figure 4 The biphasic magnetic component 100 is shown after the coating and mask have been removed to expose the entire surfaces 12 and 14. The biphasic magnetic component 100 includes a non-magnetic region 102 (corresponding to...). Figure 3 The masking region 21) and the magnetic region 104 (corresponding to Figure 3 The unmasked region 31). In a particular embodiment, the non-magnetic region 102 comprises an austenitic composition with a nitrogen concentration greater than 0.4 wt% (e.g., greater than 0.5 wt%), which may be substantially the same as the composition of the initial component. The magnetic region 104 of the dual-phase magnetic component 100 may have a nitrogen concentration of less than 0.4 wt%, for example less than 0.1 wt% (e.g., 0.05 wt%).

[0044] Depending on the application, the desired shape and proportions of the magnetic and non-magnetic regions can vary, and the selective evacuation of nitrogen can be designed to meet these requirements. Therefore, in one embodiment, the volume percentage of the first region in the surface and interior portions is equal to or greater than the volume percentage of the second region in the surface and interior portions. In one embodiment, at least one of the first and second regions has an interconnect geometry. As used herein, "interconnect geometry" means that a region is connected throughout the component and is therefore not completely isolated from similar regions and is completely surrounded by other regions.

[0045] By using this technology, different topological structures of dual-phase magnetic materials can be presented. This application... Figure 5 An example of a topology that can benefit from a two-phase material is shown. Component 40 may represent a portion of a reluctance machine, including magnetic region 42 and non-magnetic region 44, hereinafter collectively referred to as “stacked segments”. The selectively shaped rotor 43 of component 40 is configured as a four-pole machine. Each pole may include multiple axially extending, radially positioned (“stacked”) stacked segments 45, 47, 49, etc., extending from each pole and terminating at a central rotor shaft 51. As described in U.S. Patent 7,489,062 (Shah et al.), the number of poles and the number of stacked segments can vary considerably depending on the specific design of the reluctance machine.

[0046] Continue to refer to Figure 5 The laminations effectively guide magnetic flux in and out of rotor 43. Magnetic regions 42 restrict the path of magnetic flux, while non-magnetic regions 44 ensure that relatively high-density magnetic flux lines emerge from the rotor surface and enter the air gap between the rotor and stator. In manufacturing these types of reluctance machines according to conventional techniques, magnetic and non-magnetic laminations typically must be assembled through various mechanical / metalworking steps, such as cutting and welding. The inventors have discovered that many of the desired techniques can be obtained more efficiently through the masking and selective nitrogen removal process described herein.

[0047] Further aspects of the invention are provided by the subject matter of the following clauses:

[0048] 1. A method for forming a two-phase magnetic component from an initial component, the initial component comprising a non-magnetic austenitic composition and having a surface, the method comprising: forming a coating on a portion of the surface of the initial component to form a masked region while leaving an unmasked region thereon; thereafter heating the initial component to a processing temperature such that nitrogen diffuses from the unmasked region of the initial component to transform the non-magnetic austenitic composition into a magnetic phase in the unmasked region; and thereafter cooling the initial component from the processing temperature to form a two-phase magnetic component having a magnetic region corresponding to the unmasked region and a non-magnetic region corresponding to the masked region.

[0049] 2. The method according to any of the preceding clauses, wherein during heating the initial component to the processing temperature, nitrogen is retained in the unmasked region of the initial component such that the masked region retains the nonmagnetic austenitic composition.

[0050] 3. The method according to any of the preceding clauses, wherein the processing temperature is higher than 1000°C.

[0051] 4. The method according to any of the preceding clauses, wherein the processing temperature is 1100°C to 1300°C.

[0052] 5. The method according to any of the preceding clauses, wherein the initial component is cooled from the processing temperature at a sufficiently fast cooling rate to retain the magnetic and non-magnetic phases formed during heating.

[0053] 6. The method according to any of the preceding clauses, wherein the heating of the initial component is performed at a processing pressure of less than 1 atmosphere.

[0054] 7. The method according to any of the preceding clauses, wherein the heating of the initial component is performed at a processing pressure of less than 0.5 atmospheres.

[0055] 8. The method according to any of the preceding clauses, wherein the coating comprises chromium oxide.

[0056] 9. The method according to any of the preceding clauses, wherein the nonmagnetic austenitic component comprises an iron alloy containing chromium, manganese and nitrogen.

[0057] 10. The method according to any of the preceding clauses, wherein heating of the initial component is performed in an oxygen-deficient atmosphere to suppress the formation of chromium oxide on the unmasked area.

[0058] 11. The method according to any of the foregoing clauses further comprises: removing the coating from the biphasic magnetic component after cooling the initial component from the processing temperature.

[0059] 12. The method according to any of the preceding clauses, wherein removing the coating comprises mechanically or chemically removing the coating from the dual-phase magnetic component.

[0060] 13. The method according to any of the preceding clauses, wherein the nonmagnetic austenitic component has a nitrogen concentration of greater than 0.4% by weight.

[0061] 14. The method according to any of the preceding clauses, wherein the nonmagnetic austenitic component has a nitrogen concentration of greater than 0.5% by weight.

[0062] 15. The method according to any of the preceding clauses, wherein the magnetic region of the dual-phase magnetic component has a nitrogen concentration of less than 0.4% by weight.

[0063] 16. The method according to any of the preceding clauses, wherein the magnetic region of the dual-phase magnetic component has a nitrogen concentration of less than 0.1% by weight.

[0064] 17. A method for forming a two-phase magnetic component from an initial component, the initial component comprising a non-magnetic austenitic composition, the method comprising: removing nitrogen from a portion of the non-magnetic austenitic composition to form a magnetic region therein.

[0065] 18. The method according to any of the preceding clauses, wherein the nonmagnetic austenitic component has a nitrogen concentration of greater than 0.4% by weight.

[0066] 19. The method according to any of the preceding clauses, wherein the magnetic region of the two-phase magnetic component has a nitrogen concentration of less than 0.4% by weight.

[0067] 20. The method according to any of the preceding clauses, wherein removing nitrogen from a portion of the nonmagnetic austenitic component to form the magnetic region therein comprises: forming a coating on a portion of the surface of the initial component to form a masked region while leaving an unmasked region thereon; removing nitrogen from the unmasked region at a processing temperature and a processing pressure to transform the nonmagnetic austenitic component into a magnetic phase in the unmasked region, wherein the processing temperature is greater than 1000°C and the processing pressure is less than 1 atmosphere; and subsequently cooling the initial component from the processing temperature to form a biphasic magnetic component having a magnetic region corresponding to the unmasked region and a nonmagnetic region corresponding to the masked region.

[0068] This written description discloses the invention using exemplary embodiments, including the best mode, and also enables any person skilled in the art to practice the invention, including making and using any device or system and performing any combination of methods. The scope of the invention is defined by the claims, but may include other examples that would occur to a person skilled in the art. These other examples are intended to fall within the scope of the claims if they include structural elements that are not indistinguishable from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims.

Claims

1. A method for forming a two-phase magnetic component from an initial component, the initial component comprising a non-magnetic austenitic composition, wherein the non-magnetic austenitic composition comprises an iron alloy, the iron alloy comprising nitrogen, characterized in that, The method includes: Nitrogen is removed from a portion of the nonmagnetic austenitic composition to form magnetic regions therein; Removing nitrogen from a portion of the nonmagnetic austenitic component to form the magnetic region therein includes: forming a coating on a portion of the surface of the initial component to form a masked region while leaving an unmasked region thereon; Subsequently, the initial component is heated to a processing temperature, causing nitrogen to diffuse from the unmasked regions of the initial component, thereby transforming the non-magnetic austenitic component into a magnetic phase in the unmasked regions; and Subsequently, the initial component is cooled from the processing temperature to form a two-phase magnetic component having a magnetic region corresponding to the unmasked region and a non-magnetic region corresponding to the masked region.

2. The method according to claim 1, characterized in that, During the heating of the initial component to the processing temperature, nitrogen is retained in the unmasked region of the initial component, such that the masked region retains the nonmagnetic austenitic composition.

3. The method according to claim 1, characterized in that, The processing temperature is above 1000°C.

4. The method according to claim 1, characterized in that, The processing temperature is 1100°C to 1300°C.

5. The method according to claim 1, characterized in that, The initial component is cooled from the processing temperature at a sufficiently fast cooling rate to maintain the magnetic and non-magnetic phases formed during heating.

6. The method according to claim 1, characterized in that, The initial component is heated under a processing pressure of less than one atmosphere.

7. The method according to claim 1, characterized in that, The initial component is heated at a processing pressure of less than 0.5 atmospheres.

8. The method according to claim 1, characterized in that, The coating mentioned above includes chromium oxide.

9. The method according to claim 1, characterized in that, The non-magnetic austenitic component mentioned above includes an iron alloy containing chromium, manganese, and nitrogen.

10. The method according to claim 9, characterized in that, The initial component is heated in an oxygen-deficient atmosphere to suppress the formation of chromium oxide in the unmasked area.

11. The method according to claim 1, characterized in that, Further includes: After the initial component is cooled from the processing temperature, the coating is removed from the biphasic magnetic component.

12. The method according to claim 11, characterized in that, Removing the coating includes mechanically or chemically removing the coating from the biphasic magnetic component.

13. The method according to claim 1, characterized in that, The non-magnetic austenitic component has a nitrogen concentration of greater than 0.4% by weight.

14. The method according to claim 13, characterized in that, The non-magnetic austenitic component has a nitrogen concentration of greater than 0.5% by weight.

15. The method according to claim 13, characterized in that, The magnetic region of the dual-phase magnetic component has a nitrogen concentration of less than 0.4% by weight.

16. The method according to claim 13, characterized in that, The magnetic region of the dual-phase magnetic component has a nitrogen concentration of less than 0.1% by weight.

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