A method for improving the yield of martensitic stainless steel powder
By subjecting martensitic stainless steel bars to primary and secondary aging treatments to introduce inverted austenite, the problems of bar shattering and low fine powder yield during plasma rotating electrode powder production were solved, resulting in higher powder yield and finer powder particle size.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAN SAILONG AM TECH CO LTD
- Filing Date
- 2026-03-17
- Publication Date
- 2026-06-02
AI Technical Summary
During the plasma rotating electrode powder production process, martensitic stainless steel bars with a nickel content of less than 8 wt% are prone to cracking, resulting in low fine powder yield and a large amount of powder being in granular form, which cannot be spherical, leading to equipment damage and poor powder quality.
Martensitic stainless steel bars undergo primary and secondary aging treatments to introduce inverted austenite, forming a network or diffuse distribution, which softens the material and buffers volume shrinkage. Subsequently, the material is atomized and powdered using a plasma rotating electrode powder-making device.
It improves powder yield, reduces non-spherical blocky powder, increases fine powder yield, and ensures the integrity of the electrode rod material structure under high temperature and high speed conditions, resulting in finer powder particle size.
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Figure CN121847792B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of martensitic stainless steel powder preparation technology, and in particular to a method for improving the yield of martensitic stainless steel powder. Background Technology
[0002] Martensitic stainless steel bars with a nickel content of less than 8 wt% are prone to cracking, low fine powder yield, large amounts of powder in granular form, and inability to form spheres during plasma rotating electrode powder production. This is because during plasma rotating electrode atomization powder production, the electrode bars are subjected to the combined effects of high heating rate from high-temperature plasma and high centrifugal force at high rotation speed. Depending on the degree, such alloys may exhibit the following: (1) Figure 1 As shown, the electrode rod end face was not fully melted and directly cracked; (2) as Figure 2 As shown, most of the structure on the end face of the electrode rod is not fully melted and is centrifuged into non-spherical large particles of powder; (3) the structure on the end face of the electrode rod is melted as a whole, but the overall superheat is low, resulting in coarser particle size of the powder ejected by centrifugation. This is mainly related to the uniformity of the structure of the electrode rod material used for powder making, the thermal shock resistance of the electrode rod, and the magnitude of the centrifugal force resistance at high temperature.
[0003] Taking 05Cr17Ni4Cu4Nb as an example, the standard delivery condition of commercially available 05Cr17Ni4Cu4Nb bars is usually in a solution-treated state or a high-strength aged state. In this state, the material microstructure is entirely martensitic, the hardness is usually greater than 40 HRC, and the toughness is poor. During the plasma rotating electrode powder production process, the end face of the electrode bar is subjected to the instantaneous high-temperature heating of the plasma gun (room temperature rises sharply to above 1500°C) and the centrifugal tensile stress caused by high-speed rotation (speed > 20000 rpm). Due to the lack of toughness of the martensitic matrix, and the accompanying volume shrinkage during the phase transformation (martensite → austenite) during rapid heating, the end face is extremely prone to thermal shock cracking. This results in the metal failing to fully melt and form a stable liquid film, instead being ejected in the form of solid or semi-solid fragments, causing an increase in irregular particles (lumpy powder) in the powder, a significant reduction in the yield of fine powder, and even damage to the equipment.
[0004] Therefore, it is necessary to provide a new technical solution to improve one or more of the problems existing in the above solutions.
[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention
[0006] The purpose of this application is to provide a method for improving the yield of martensitic stainless steel powder, thereby overcoming, at least to some extent, one or more problems caused by the limitations and defects of related technologies.
[0007] A method for improving the yield of martensitic stainless steel powder according to an embodiment of this application includes:
[0008] Prepare martensitic stainless steel bars; wherein the nickel content of the martensitic stainless steel bars is less than 8 wt%.
[0009] The martensitic stainless steel bar is subjected to a first-stage aging treatment, which includes: heating the martensitic stainless steel bar to a first preset temperature and holding it at that temperature for a first preset holding time, and then cooling it to room temperature.
[0010] The cooled martensitic stainless steel bar undergoes a two-stage aging treatment, comprising: reheating the cooled martensitic stainless steel bar to a second preset temperature and holding it at that temperature for a second preset holding time, and then cooling it to room temperature to obtain the target bar; wherein the second preset temperature is lower than the first preset temperature, the second preset holding time is longer than the first preset holding time, the hardness of the target bar is less than 33 HRC, and the microstructure of the target bar contains 8% to 20% by volume of inverted austenite, wherein the inverted austenite is distributed in a network or dispersed manner along the martensite grain boundaries;
[0011] The target rod is processed to obtain electrode rod material;
[0012] The electrode rod material is atomized and powdered using a plasma rotating electrode powder-making device to obtain martensitic stainless steel powder.
[0013] In the embodiments of this application, the first preset temperature is 750°C to 830°C, and the first preset heat preservation time is 2h to 4h.
[0014] In the embodiments of this application, the second preset temperature is 610°C to 690°C, and the second preset heat preservation time is 4h to 6h.
[0015] In the embodiments of this application, the step of processing the target rod to obtain the electrode rod material includes:
[0016] The oxide layer on the surface of the target rod is removed by turning to obtain the electrode rod material.
[0017] In the embodiments of this application, the diameter of the electrode rod is 25mm to 80mm, and the length of the electrode rod is 100mm to 600mm.
[0018] In the embodiments of this application, the step of atomizing the electrode rod material to obtain martensitic stainless steel powder using a plasma rotating electrode powder-making device includes:
[0019] After evacuating the atomization chamber, inert gas is introduced to bring the pressure in the atomization chamber to a preset pressure.
[0020] Set the powder-making process parameters and start the plasma rotating electrode powder-making equipment to make powder; wherein, the powder-making process parameters include: the rotation speed of the electrode rod, the current of the electrode rod, and the feed rate of the electrode rod, wherein the rotation speed of the electrode rod is greater than 0 and less than or equal to 50,000 rpm, the current of the electrode rod is 300A to 4000A, and the feed rate of the electrode rod is 0.5mm / s to 2.5mm / s.
[0021] In the embodiments of this application, the preset pressure is 0.05 MPa to 0.2 MPa.
[0022] In the embodiments of this application, the inert gas is argon.
[0023] The technical solutions provided by the embodiments of this application may include the following beneficial effects:
[0024] In one embodiment of this application, by performing primary and secondary aging treatments on martensitic stainless steel bars with a nickel content of less than 8 wt%, a target bar with a hardness of less than 33 HRC is obtained. The microstructure of this target bar contains 8%–20% by volume of inverted austenite, which is distributed in a network or dispersed manner along the martensite grain boundaries, encapsulating the martensite. This inverted austenite does not undergo phase transformation during heating and exhibits no volume shrinkage, thus microscopically segmenting and buffering the volume shrinkage during the transformation of martensite into inverted austenite. Simultaneously, the high-toughness inverted austenite can passivate crack tips through plastic deformation, preventing crack propagation. During plasma rotating electrode powder production, this inverted austenite can minimize the stress on the electrode bar material, maintain the integrity of the electrode bar material's microstructure, and ensure that the electrode bar material is fully melted before atomization and crushing, which is beneficial for crushing into finer powder particles and improving powder yield.
[0025] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description
[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.
[0027] Figure 1The image schematically illustrates an electrode rod whose end face was not fully melted and directly cracked in the prior art;
[0028] Figure 2 This schematically shows a scanning electron microscope image of a non-spherical large-particle powder that was not fully melted and was ejected by centrifugation from the end face of an electrode rod in the prior art.
[0029] Figure 3 The metallographic structure of 05Cr17Ni4Cu4Nb bar material in the prior art is schematically shown;
[0030] Figure 4 A schematic diagram of the microstructure of 05Cr17Ni4Cu4Nb rods in the prior art is shown.
[0031] Figure 5 This schematically illustrates a flowchart of the steps of a method for improving the yield of martensitic stainless steel powder in an exemplary embodiment of this application.
[0032] Figure 6 The diagram schematically illustrates the metallographic structure of the target bar after primary aging treatment and secondary aging treatment in an exemplary embodiment of this application;
[0033] Figure 7 The microstructure diagrams of the target bar after primary aging treatment and secondary aging treatment in the exemplary embodiments of this application are schematically shown.
[0034] Figure 8 This illustration shows a photograph of the head of a 05Cr17Ni4Cu4Nb rod material after the first and second stage aging treatments in Exemplary Embodiment 1 of this application.
[0035] Figure 9 This illustration shows a photograph of martensitic stainless steel powder obtained by pulverizing 05Cr17Ni4Cu4Nb rods using conventional methods in Exemplary Example 1 of this application.
[0036] Figure 10 This illustration shows a photograph of the 05Cr17Ni4Cu4Nb rod material head after primary aging treatment and secondary aging treatment in Exemplary Example 2 of this application;
[0037] Figure 11 This illustration schematically shows a scanning electron microscope image of martensitic stainless steel powder obtained by pulverizing 05Cr17Ni4Cu4Nb rods using the method of this application in Exemplary Example 2 of this application.
[0038] Figure 12 This illustration shows a photograph of the head of a 05Cr15Ni5Cu4Nb rod material after it has not undergone primary and secondary aging treatments in Exemplary Embodiment 3 of this application.
[0039] Figure 13 The image schematically illustrates the martensitic stainless steel powder obtained by pulverizing 05Cr15Ni5Cu4Nb rods using conventional methods in Exemplary Example 3 of this application.
[0040] Figure 14 This illustration shows a photograph of the 05Cr15Ni5Cu4Nb rod material head after primary aging treatment and secondary aging treatment in Exemplary Embodiment 4 of this application;
[0041] Figure 15 This illustration schematically shows a scanning electron microscope image of martensitic stainless steel powder obtained by pulverizing 05Cr15Ni5Cu4Nb rods using the method of this application in Exemplary Example 4 of this application.
[0042] Figure 16 This illustration shows a photograph of the head of a 1Cr11Ni2W2MoV rod material after primary and secondary aging treatments in Exemplary Embodiment 5 of this application.
[0043] Figure 17 The image schematically illustrates the martensitic stainless steel powder obtained by pulverizing 1Cr11Ni2W2MoV rods using conventional methods in Exemplary Example 5 of this application.
[0044] Figure 18 This illustration shows a photograph of the head of a 1Cr11Ni2W2MoV rod after primary and secondary aging treatments in Exemplary Example 6 of this application.
[0045] Figure 19 The illustration shows a scanning electron microscope (SEM) image of martensitic stainless steel powder obtained by grinding 1Cr11Ni2W2MoV rods using the method of this application in Exemplary Example 6 of this application. Detailed Implementation
[0046] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0047] Furthermore, the accompanying drawings are merely illustrative diagrams of this application and are not necessarily drawn to scale.
[0048] In related technologies, taking martensitic stainless steel bars (05Cr17Ni4Cu4Nb bars) with a nickel content of less than 8wt% as an example, the state is solution-treated. The hardness is 48HRC; under a microscope, its matrix structure exhibits a single, elongated, acicular lath martensite. Figure 3 As shown, the grain boundaries are clear and sharp, and the lath bundles are oriented differently but tightly packed. The matrix structure is extremely "clean," with only a very small amount of second-phase precipitation (such as carbides or austenite) in the martensitic matrix or at the grain boundaries. This single, supersaturated solid solution structure exhibits extremely high lattice distortion energy and internal stress. Due to the lack of a soft phase buffer, this structure displays high hardness (>40 HRC) and low impact toughness. Figure 4 As shown, electron backscatter diffraction analysis revealed a fully martensitic structure. Figure 4 In the diagram, red represents austenite, and green represents martensite, with an austenite content of <3% (only a small amount of residual austenite). When this type of microstructure is subjected to rapid thermal shock during plasma rotating electrode powder production, the volumetric shrinkage stress generated by the martensite-to-austenite inversion cannot be released through plastic deformation, leading to brittle cracking along grain boundaries or transgranularly. Frequent slag shedding is observed on the end face of the electrode rod during plasma rotating electrode powder production; for example... Figure 2 As shown, the collected powder contained a large number of non-spherical lumpy particles. Among them, the content of non-spherical powder larger than 100 mesh was as high as 40%, and the yield of fine powder below 270 mesh was less than 5%.
[0049] Based on this, this example embodiment provides a method for improving the yield of martensitic stainless steel powder. (Reference) Figure 5 As shown, the method may include steps S101 to S105.
[0050] Step S101: Prepare martensitic stainless steel bars; wherein the nickel content of the martensitic stainless steel bars is less than 8 wt%.
[0051] Step S102: Perform a first-level aging treatment on the martensitic stainless steel bar, including: heating the martensitic stainless steel bar to a first preset temperature, holding it at that temperature for a first preset holding time, and then cooling it to room temperature.
[0052] Step S103: Perform a secondary aging treatment on the cooled martensitic stainless steel bar, including: reheating the cooled martensitic stainless steel bar to a second preset temperature and holding it at that temperature for a second preset holding time, and then cooling it to room temperature to obtain the target bar; wherein, the second preset temperature is lower than the first preset temperature, the second preset holding time is longer than the first preset holding time, the hardness of the target bar is less than 33 HRC, and the microstructure of the target bar contains 8% to 20% of inverted austenite by volume, and the inverted austenite is distributed in a network or dispersed manner along the martensite grain boundaries.
[0053] Step S104: Process the target rod to obtain electrode rod material.
[0054] Step S105: The electrode rod material is atomized and powdered using a plasma rotating electrode powder making equipment to obtain martensitic stainless steel powder.
[0055] In one embodiment of this application, by performing primary and secondary aging treatments on martensitic stainless steel bars with a nickel content of less than 8 wt%, a target bar with a hardness of less than 33 HRC is obtained. The microstructure of this target bar contains 8%–20% by volume of inverted austenite, which is distributed in a network or dispersed manner along the martensite grain boundaries, encapsulating the martensite. This inverted austenite does not undergo phase transformation during heating and exhibits no volume shrinkage, thus microscopically segmenting and buffering the volume shrinkage during the transformation of martensite into inverted austenite. Simultaneously, the high-toughness inverted austenite can passivate crack tips through plastic deformation, preventing crack propagation. During plasma rotating electrode powder production, this inverted austenite can minimize the stress on the electrode bar material, maintain the integrity of the electrode bar material's microstructure, and ensure that the electrode bar material is fully melted before atomization and crushing, which is beneficial for crushing into finer powder particles and improving powder yield.
[0056] Below, we will refer to Figures 6 to 7 The steps of the method described above in this example embodiment will be explained in more detail.
[0057] In step S101, martensitic stainless steel bars are prepared; wherein the nickel content of the martensitic stainless steel bars is less than 8 wt%.
[0058] It is understandable that martensitic stainless steel bars are a type of low-nickel martensitic stainless steel bar, with a nickel content of less than 8 wt%. Due to the low nickel content, martensitic stainless steel bars with a nickel content of less than 8 wt% have weak austenite-forming ability, primarily relying on a fully martensitic structure to bear high strength, but exhibiting poor toughness. Because of their extremely low toughness, the conventional delivery condition of this type of steel is not well-suited to the powder-making conditions of plasma rotating electrode powder preparation, resulting in low powder yield. This application addresses the powder yield problem of martensitic stainless steel bars with a nickel content of less than 8 wt%. It should be noted that martensitic stainless steel bars with a nickel content of less than 8 wt% can be 05Cr17Ni4Cu4Nb bars, 05Cr15Ni5Cu4Nb bars, or 1Cr11Ni2W2MoV bars, etc., and this application does not impose any restrictions on this.
[0059] In step S102, the martensitic stainless steel bar undergoes a first-level aging treatment, which includes heating the martensitic stainless steel bar to a first preset temperature and holding it at that temperature for a first preset holding time, and then cooling it to room temperature.
[0060] Understandably, the purpose of first-stage aging treatment on martensitic stainless steel bars is to eliminate processing stress and provide thermodynamic conditions for austenite nucleation. The microstructure of martensitic stainless steel bars is entirely martensite. To soften and toughen them, a softer microstructure called "inverted austenite" needs to grow around them. At a first preset temperature of 750°C to 830°C, tiny austenite "seedlings" begin to emerge at the martensite grain boundaries; this process is austenite nucleation. In other words, at high-energy interfaces such as martensite lath interfaces, due to thermal activation, the nuclei of the inverted austenite phase begin to form and reach a critical size.
[0061] In one embodiment, the first preset temperature is 750°C to 830°C, and the first preset heat preservation time is 2h to 4h.
[0062] Specifically, the first preset temperature is the over-aging temperature of the martensitic stainless steel bar. Standard heat treatment aims to make the martensitic stainless steel bar harder, while this heat treatment aims to make it more tough. Therefore, a higher temperature is used to soften the martensitic stainless steel bar; this higher temperature is called the over-aging temperature. A first preset temperature of 750°C to 830°C allows for better heat treatment of the martensitic stainless steel bar. The first preset temperature can be 750°C, 760°C, 770°C, 790°C, 800°C, 810°C, 820°C, 825°C, 830°C, etc. The specific value of the first preset temperature can be set according to actual conditions, which will not be elaborated upon in this application. A first preset holding time of 2h to 4h allows for better heat treatment of the martensitic stainless steel bar after the first heating. The first preset heat preservation time can be 2h, 2.6h, 3h, 3.5h, 3.8h, 4h, etc. The specific value of the first preset heat preservation time can be set according to the actual situation, which will not be elaborated in this application.
[0063] This application achieves better elimination of processing stress and provides thermodynamic conditions for austenite nucleation by heating martensitic stainless steel bars to a first preset temperature of 750°C to 830°C, holding them at that temperature for a first preset holding time of 2h to 4h, and then cooling them to room temperature.
[0064] In step S103, the cooled martensitic stainless steel bar undergoes a secondary aging treatment, including: reheating the cooled martensitic stainless steel bar to a second preset temperature and holding it at that temperature for a second preset holding time, then cooling it to room temperature to obtain the target bar; wherein, the second preset temperature is lower than the first preset temperature, the second preset holding time is longer than the first preset holding time, the hardness of the target bar is less than 33 HRC, and the microstructure of the target bar contains 8% to 20% by volume of inverted austenite, and the inverted austenite is distributed in a network or dispersed manner along the martensite grain boundaries.
[0065] Understandably, the purpose of performing a secondary aging treatment on cooled martensitic stainless steel bars is to promote the dispersion and stabilization of inverted austenite along grain boundaries and lath boundaries.
[0066] Specifically, martensitic stainless steel bars undergo primary and secondary aging treatments to obtain the target bar. The target bar has a hardness less than 33 HRC, where HRC is a unit of hardness. Figure 7 As shown, red represents inverted austenite, and green represents martensite. The microstructure of the target bar includes martensite and inverted austenite. The microstructure of the target bar contains 8%–20% inverted austenite by volume, such as… Figure 6 As shown, the reverse austenite is distributed in a network or diffuse manner along the martensite grain boundaries. The reverse austenite is an austenitic structure formed by the reverse phase transformation of martensite. The reverse austenite is a relatively soft phase, while the martensite is a relatively hard phase. The reverse austenite in the microstructure of the target bar material encapsulates the martensite, forming a two-phase structure with alternating soft and hard phases. Under the extreme conditions of subsequent plasma rotating electrode powdering (the end face is instantly heated to the melting point), the reverse austenite in this two-phase structure can play two key roles: (1) Volume compensation effect: The reverse austenite itself is an austenitic structure and does not undergo phase transformation during heating, so there is no volume shrinkage. This microscopically divides and buffers the volume shrinkage when the martensite transforms into austenite; (2) Crack arrest effect: When thermal stress microcracks initiate, the highly tough reverse austenite can blunt the crack tip through plastic deformation and prevent crack propagation. Hardness was tested using a Rockwell hardness tester, and the microstructure of the target bar was detected using electron backscatter diffraction technology.
[0067] The target rod material of this application, due to its dual-phase microstructure, maintains its structural integrity even under the high-speed rotation and rapid heating conditions of plasma rotating electrode powder production. This transforms the powder production mode from brittle fragmentation to stable melting and atomization. Brittle fragmentation refers to the process where the fully martensitic microstructure breaks off or detaches from the rod material before complete melting due to the high brittleness of the electrode material under high centrifugal force and high temperature, forming non-spherical blocky particles. Stable melting and atomization refers to the process where the electrode material microstructure, after being fully melted (rather than prematurely fragmented), forms a stable liquid film and is then atomized into fine-particle-size spherical powder.
[0068] This application introduces inverted austenite and uses the precipitated inverted austenite as a micro-damper. During the rapid heating process of plasma rotating electrode powder making, the soft and tough inverted austenite film effectively absorbs the volume shrinkage stress and thermal expansion mismatch stress generated by the transformation of the martensitic matrix through plastic deformation, thus maintaining the stability of the martensite and liquid film formation.
[0069] Because the volume shrinkage of standard solution-treated stainless steel bars due to phase transformation under rapid heating conditions leads to end-face breakage and low fine powder yield during plasma rotating electrode powder production, the standard solution-treated stainless steel bars undergo primary and secondary aging treatments to introduce highly stable, dispersed inverted austenite into the martensitic matrix. This inverted austenite microscopically segments and buffers the volume shrinkage during the transformation of martensite to inverted austenite in plasma rotating electrode powder production. Simultaneously, the high-toughness inverted austenite can blunt crack tips through plastic deformation, preventing crack propagation. This inverted austenite minimizes the stress level of the electrode bars during plasma rotating electrode powder production, maintains the integrity of the microstructure, prevents end-face breakage, and ensures complete melting of the electrode bars before atomization and crushing, facilitating the production of finer powder particles and thus improving powder yield.
[0070] In one embodiment, the second preset temperature is 610°C to 690°C, and the second preset heat preservation time is 4h to 6h.
[0071] Specifically, the second preset temperature is the over-aging temperature of the martensitic stainless steel bar. A second preset temperature of 610°C to 690°C allows for better heat treatment of the martensitic stainless steel bar. The second preset temperature can be 610°C, 620°C, 625°C, 630°C, 640°C, 650°C, 670°C, 680°C, 690°C, etc. The specific value of the second preset temperature can be set according to actual conditions, which will not be elaborated in this application. A second preset holding time of 4h to 6h allows for better heat treatment of the martensitic stainless steel bar after secondary heating. The second preset holding time can be 4h, 4.6h, 5h, 5.5h, 5.8h, 6h, etc. The specific value of the second preset holding time can be set according to actual conditions, which will not be elaborated in this application.
[0072] This application improves the dispersion and stabilization of inverted austenite along grain boundaries and lath boundaries by heating the cooled martensitic stainless steel bar to a second preset temperature of 610°C to 690°C and holding it at that temperature for a second preset holding time of 4h to 6h, and then cooling it to room temperature.
[0073] In step S104, the target rod is processed to obtain electrode rod material.
[0074] Further, the step of processing the target rod to obtain the electrode rod material includes:
[0075] The oxide layer on the surface of the target rod is removed by turning to obtain the electrode rod material, which is then used to pulverize the rod material using a plasma rotating electrode powder making equipment.
[0076] In one embodiment, the diameter of the electrode rod is 25mm to 80mm, and the length is 100mm to 600mm. Specifically, the electrode rod with a diameter of 25mm to 80mm and a length of 100mm to 600mm is suitable for plasma rotating electrode powder production. The diameter of the electrode rod can be 25mm, 27mm, 28mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 64mm, 68mm, 70mm, 75mm, 80mm, etc. The specific value of the electrode rod diameter can be set according to actual conditions, and this application does not limit it. The length of the electrode rod can be 100mm, 130mm, 150mm, 180mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, or 600mm. The specific value of the electrode rod length can be set according to the actual situation, and this application does not impose any restrictions on it.
[0077] In step S105, the electrode rod material is atomized and powdered using a plasma rotating electrode powder-making device to obtain martensitic stainless steel powder.
[0078] Furthermore, the step of atomizing and pulverizing electrode rods using a plasma rotating electrode powder-making device to obtain martensitic stainless steel powder includes:
[0079] After evacuating the atomization chamber, inert gas is introduced to bring the pressure in the atomization chamber to the preset pressure.
[0080] Set the powder-making process parameters and start the plasma rotating electrode powder-making equipment to make powder; the powder-making process parameters include: the rotation speed of the electrode rod, the current of the electrode rod, and the feed rate of the electrode rod. The rotation speed of the electrode rod is greater than 0 and less than or equal to 50,000 rpm, the current of the electrode rod is 300A to 4000A, and the feed rate of the electrode rod is 0.5mm / s to 2.5mm / s.
[0081] Understandably, when using a plasma rotating electrode powder-making device to atomize and powder electrode rods, the atomization chamber first needs to be evacuated, and then an inert gas is introduced to ensure the pressure in the atomization chamber reaches a preset pressure. Secondly, under the preset pressure conditions, three powder-making process parameters are set: the rotational speed of the electrode rod, the current of the electrode rod, and the feed rate of the electrode rod. Then, the plasma rotating electrode powder-making device is started to produce martensitic stainless steel powder. It should be noted that the powder-making process using a plasma rotating electrode powder-making device can be understood by referring to existing technologies, and this application will not elaborate on it further.
[0082] Furthermore, the rotational speed of the electrode rod is greater than 0 and less than or equal to 50,000 rpm, the current of the electrode rod is 300A to 4000A, and the feed rate of the electrode rod is 0.5mm / s to 2.5mm / s. Specifically, the rotational speed of the electrode rod can be 100rpm, 5000rpm, 10000rpm, 20000rpm, 30000rpm, 40000rpm, 50000rpm, etc., and the specific value of the rotational speed can be set according to the actual situation, which is not limited in this application. The current of the electrode rod can be 300A, 400A, 500A, 600A, 700A, 1000A, 2000A, 3000A, 3500A, 4000A, etc., and the specific value of the current of the electrode rod can be set according to the actual situation, which is not limited in this application. The feed rate of the electrode bar can be 0.5 mm / s, 0.7 mm / s, 1.0 mm / s, 1.5 mm / s, 1.7 mm / s, 1.9 mm / s, 2.0 mm / s, 2.2 mm / s, 2.5 mm / s, etc. The specific value of the feed rate of the electrode bar can be set according to the actual situation, and this application does not limit it.
[0083] In one embodiment, the preset pressure is 0.05 MPa to 0.2 MPa. Within this preset pressure range, the electrode rod material can be better powdered. Specifically, the preset pressure can be 0.05 MPa, 0.1 MPa, 0.15 MPa, 0.18 MPa, 0.19 MPa, 0.2 MPa, etc. The specific value of the preset pressure can be set according to the actual situation, and this application does not limit it.
[0084] In one embodiment, the inert gas is argon. Specifically, introducing argon ensures that the pressure in the atomization chamber reaches a preset pressure, facilitating better powdering of the electrode rod material.
[0085] It should also be noted that after obtaining the martensitic stainless steel powder, it is sieved, packaged, and stored after being fully cooled.
[0086] The present application will be further illustrated below through examples.
[0087] Example 1 (Powdering using conventional methods)
[0088] Step 1: Prepare martensitic stainless steel bars with a nickel content of less than 8 wt%. These bars are 05Cr17Ni4Cu4Nb bars with a hardness of 48 HRC. Under a microscope, their matrix structure appears as a single, elongated, acicular lath martensite. The 05Cr17Ni4Cu4Nb bars in Example 1 have not undergone primary or secondary aging treatment, and their corresponding blanks are as follows... Figure 8As shown.
[0089] Step 2: Process the target rod to obtain the electrode rod. The diameter of the electrode rod is 75mm and the length of the electrode rod is 350mm.
[0090] Step 3: The electrode rod material is atomized and powdered using a plasma rotating electrode powder making equipment to obtain martensitic stainless steel powder.
[0091] Step 3 includes the following:
[0092] Sub-step 3-1: After evacuating the atomization chamber, argon gas is introduced to bring the pressure in the atomization chamber to the preset pressure of 0.1 MPa;
[0093] Sub-step 3-2: Set the powder-making process parameters: electrode rod rotation speed, electrode rod current, and electrode rod feed rate. The electrode rod rotation speed is 20000 rpm, the electrode rod current is 2300 A, and the electrode rod feed rate is 1.2 mm / s. Start the plasma rotating electrode powder-making equipment to obtain martensitic stainless steel powder. The martensitic stainless steel powder is then sieved, packaged, and stored. Figure 9 As shown, the proportion of non-spherical blocky powder in the martensitic stainless steel powder obtained by conventional powder preparation is 40%, and the yield of spherical powder in the martensitic stainless steel powder with a diameter of less than 53 μm is 3%.
[0094] Example 2 (Powdering using the method of this application)
[0095] Step 1: Prepare martensitic stainless steel bars with a nickel content of less than 8 wt%. The martensitic stainless steel bar is 05Cr17Ni4Cu4Nb bar.
[0096] Step 2: Perform a first-stage aging treatment on the martensitic stainless steel bar, including heating the martensitic stainless steel bar to a first preset temperature of 760°C±10°C and holding it at that temperature for a first preset holding time of 4 hours, and then cooling it to room temperature.
[0097] Step 3: Perform a two-stage aging treatment on the cooled martensitic stainless steel bar, including: reheating the cooled martensitic stainless steel bar to a second preset temperature of 620°C ± 10°C and holding it at that temperature for a second preset holding time of 6 hours, then cooling it to room temperature to obtain the target bar. The target bar's hardness is tested to be less than 33 HRC, and its microstructure contains 12% by volume of inverted austenite, which is distributed in a network or dispersed manner along the martensite grain boundaries. In Example 2, the 05Cr17Ni4Cu4Nb bar underwent both a first-stage and a second-stage aging treatment, and its corresponding feedstock... Figure 10 As shown.
[0098] Step 4: Process the target rod to obtain the electrode rod. The diameter of the electrode rod is 75mm and the length of the electrode rod is 350mm.
[0099] Step 5: The electrode rod material is atomized and powdered using a plasma rotating electrode powder making equipment to obtain martensitic stainless steel powder.
[0100] Step 5 includes the following:
[0101] Sub-step 5-1: After evacuating the atomization chamber, argon gas is introduced to bring the pressure in the atomization chamber to the preset pressure of 0.1 MPa;
[0102] Sub-step 5-2: Set the powder-making process parameters: electrode rod rotation speed, electrode rod current, and electrode rod feed rate. The electrode rod rotation speed is 20000 rpm, the electrode rod current is 2300 A, and the electrode rod feed rate is 1.2 mm / s. Start the plasma rotating electrode powder-making equipment to obtain martensitic stainless steel powder. The martensitic stainless steel powder is then sieved, packaged, and stored. Figure 11 As shown, the proportion of non-spherical blocky powder in the martensitic stainless steel powder obtained by the method of this application is less than 1%, and the yield of spherical powder in the martensitic stainless steel powder with a diameter of less than 53 μm is 45%.
[0103] Example 3 (Powdering using conventional methods)
[0104] Step 1: Prepare martensitic stainless steel bars with a nickel content of less than 8 wt%. These bars are 05Cr15Ni5Cu4Nb bars with a hardness of 46 HRC. Under a microscope, their matrix structure appears as a single, elongated, acicular lath martensite. The 05Cr15Ni5Cu4Nb bars in Example 3 did not undergo primary or secondary aging treatment, and their corresponding blanks are as follows... Figure 12 As shown.
[0105] Step 2: Process the target rod to obtain electrode rod material. The diameter of the electrode rod material is 50mm, and the length of the electrode rod material is 260mm.
[0106] Step 3: The electrode rod material is atomized and powdered using a plasma rotating electrode powder making equipment to obtain martensitic stainless steel powder.
[0107] Step 3 includes the following:
[0108] Sub-step 3-1: After evacuating the atomization chamber, argon gas is introduced to bring the pressure in the atomization chamber to the preset pressure of 0.1 MPa;
[0109] Sub-step 3-2: Set the powder-making process parameters: electrode rod rotation speed, electrode rod current, and electrode rod feed rate. The electrode rod rotation speed is 26000 rpm, the electrode rod current is 1100 A, and the electrode rod feed rate is 1.2 mm / s. Start the plasma rotating electrode powder-making equipment to obtain martensitic stainless steel powder. The martensitic stainless steel powder is then sieved, packaged, and stored. Figure 13 As shown, the proportion of non-spherical blocky powder in the martensitic stainless steel powder obtained by conventional powder preparation is 40%, and the yield of spherical powder in the martensitic stainless steel powder with a diameter of less than 53 μm is 3%.
[0110] Example 4 (Powdering using the method of this application)
[0111] Step 1: Prepare martensitic stainless steel bars with a nickel content of less than 8 wt%. The martensitic stainless steel bar is 05Cr15Ni5Cu4Nb bar.
[0112] Step 2: Perform a first-stage aging treatment on the martensitic stainless steel bar, including heating the martensitic stainless steel bar to a first preset temperature of 780°C±10°C and holding it at that temperature for a first preset holding time of 3 hours, and then cooling it to room temperature.
[0113] Step 3: Perform a two-stage aging treatment on the cooled martensitic stainless steel bar, including: reheating the cooled martensitic stainless steel bar to a second preset temperature of 630°C ± 10°C and holding it at that temperature for a second preset holding time of 5 hours, then cooling it to room temperature to obtain the target bar. The target bar's hardness is tested to be less than 33 HRC, and its microstructure contains 15% by volume of inverted austenite, which is distributed in a network or dispersed manner along the martensite grain boundaries. In Example 4, the 05Cr15Ni5Cu4Nb bar underwent both a first-stage and a second-stage aging treatment, and its corresponding feedstock... Figure 14 As shown.
[0114] Step 4: Process the target rod to obtain the electrode rod. The diameter of the electrode rod is 50mm and the length of the electrode rod is 260mm.
[0115] Step 5: The electrode rod material is atomized and powdered using a plasma rotating electrode powder making equipment to obtain martensitic stainless steel powder.
[0116] Step 5 includes the following:
[0117] Sub-step 5-1: After evacuating the atomization chamber, argon gas is introduced to bring the pressure in the atomization chamber to the preset pressure of 0.1 MPa;
[0118] Sub-step 5-2: Set the powder-making process parameters: electrode rod rotation speed, electrode rod current, and electrode rod feed rate. The electrode rod rotation speed is 26000 rpm, the electrode rod current is 1100 A, and the electrode rod feed rate is 1.2 mm / s. Start the plasma rotating electrode powder-making equipment to obtain martensitic stainless steel powder. Figure 15 As shown, the proportion of non-spherical blocky powder in the martensitic stainless steel powder obtained by the method of this application is less than 0.5%, and the yield of spherical powder in the martensitic stainless steel powder with a diameter of less than 53 μm is 65%.
[0119] Example 5 (Powdering using conventional methods)
[0120] Step 1: Prepare martensitic stainless steel bars with a nickel content of less than 8 wt%. These bars are 1Cr11Ni2W2MoV bars with a hardness of 44 HRC. Under a microscope, their matrix structure appears as a single, elongated, acicular lath martensite. In Example 5, the 1Cr11Ni2W2MoV bars did not undergo primary or secondary aging treatment, and their corresponding stock heads are as follows... Figure 16 As shown.
[0121] Step 2: Process the target rod to obtain electrode rod material. The diameter of the electrode rod material is 50mm, and the length of the electrode rod material is 260mm.
[0122] Step 3: The electrode rod material is atomized and powdered using a plasma rotating electrode powder making equipment to obtain martensitic stainless steel powder.
[0123] Step 3 includes the following:
[0124] Sub-step 3-1: After evacuating the atomization chamber, argon gas is introduced to bring the pressure in the atomization chamber to the preset pressure of 0.1 MPa;
[0125] Sub-step 3-2: Set the powder-making process parameters: electrode rod rotation speed, electrode rod current, and electrode rod feed rate. The electrode rod rotation speed is 26000 rpm, the electrode rod current is 1100 A, and the electrode rod feed rate is 1.2 mm / s. Start the plasma rotating electrode powder-making equipment to obtain martensitic stainless steel powder. The martensitic stainless steel powder is then sieved, packaged, and stored. Figure 17 As shown, the proportion of non-spherical blocky powder in the martensitic stainless steel powder obtained by conventional powder preparation is 40%, and the yield of spherical powder in the martensitic stainless steel powder with a diameter of less than 53 μm is 3%.
[0126] Example 6 (Powdering using the method of this application)
[0127] Step 1: Prepare martensitic stainless steel bars with a nickel content of less than 8 wt%. These martensitic bars are 1Cr11Ni2W2MoV bars.
[0128] Step 2: Perform a first-stage aging treatment on the martensitic stainless steel bar, including: heating the martensitic stainless steel bar to a first preset temperature of 700°C and holding it at that temperature for a first preset holding time of 4 hours, and then cooling it to room temperature.
[0129] Step 3: Perform a second-stage aging treatment on the cooled martensitic stainless steel bar, including: reheating the cooled martensitic stainless steel bar to a second preset temperature of 650°C and holding it at that temperature for a second preset holding time of 6 hours, then cooling it to room temperature to obtain the target bar. The target bar's hardness is tested to be less than 31 HRC, and its microstructure contains 13% by volume of inverted austenite, which is distributed in a network or dispersed manner along the martensite grain boundaries. In Example 6, the 1Cr11Ni2W2MoV bar underwent both a first-stage and a second-stage aging treatment, and its corresponding feedstock... Figure 18 As shown.
[0130] Step 4: Process the target rod to obtain the electrode rod. The diameter of the electrode rod is 50mm and the length of the electrode rod is 260mm.
[0131] Step 5: The electrode rod material is atomized and powdered using a plasma rotating electrode powder making equipment to obtain martensitic stainless steel powder.
[0132] Step 5 includes the following:
[0133] Sub-step 5-1: After evacuating the atomization chamber, argon gas is introduced to bring the pressure in the atomization chamber to the preset pressure of 0.1 MPa;
[0134] Sub-step 5-2: Set the powder-making process parameters: electrode rod rotation speed, electrode rod current, and electrode rod feed rate. The electrode rod rotation speed is 26000 rpm, the electrode rod current is 1100 A, and the electrode rod feed rate is 1.2 mm / s. Start the plasma rotating electrode powder-making equipment to obtain martensitic stainless steel powder. The martensitic stainless steel powder is then sieved, packaged, and stored. Figure 19 As shown, the proportion of non-spherical blocky powder in the martensitic stainless steel powder obtained by the method of this application is less than 0.5%, and the yield of spherical powder in the martensitic stainless steel powder with a diameter of less than 53 μm is 55%.
[0135] It should be noted that the 05Cr17Ni4Cu4Nb rods, 05Cr15Ni5Cu4Nb rods, and 1Cr11Ni2W2MoV rods that have undergone first-level and second-level aging treatments all have smooth tips, improved electrode rod end faces, and reduced non-spherical blocky particles on the sides.
[0136] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.
Claims
1. A method for improving the yield of martensitic stainless steel powder, characterized in that, include: Prepare martensitic stainless steel bars; wherein the nickel content of the martensitic stainless steel bars is less than 8 wt%. The martensitic stainless steel bar undergoes a first-stage aging treatment, comprising: heating the martensitic stainless steel bar to a first preset temperature and holding it at that temperature for a first preset holding time, and then cooling it to room temperature; wherein the first preset temperature is 750°C to 830°C, and the first preset holding time is 2h to 4h. The cooled martensitic stainless steel bar undergoes a two-stage aging treatment, comprising: reheating the cooled martensitic stainless steel bar to a second preset temperature and holding it at that temperature for a second preset holding time, then cooling it to room temperature to obtain the target bar; wherein the second preset temperature is lower than the first preset temperature, the second preset holding time is longer than the first preset holding time, the hardness of the target bar is less than 33 HRC, and the microstructure of the target bar contains 8% to 20% by volume of inverted austenite, the inverted austenite being distributed in a network or dispersed manner along the martensite grain boundaries; the second preset temperature is 610°C to 690°C, and the second preset holding time is 4h to 6h; The target rod is processed to obtain electrode rod material; The electrode rod material is atomized and powdered using a plasma rotating electrode powder-making device to obtain martensitic stainless steel powder.
2. The method for improving the yield of martensitic stainless steel powder according to claim 1, characterized in that, The step of processing the target rod to obtain the electrode rod material includes: The oxide layer on the surface of the target rod is removed by turning to obtain the electrode rod material.
3. The method for improving the yield of martensitic stainless steel powder according to claim 1, characterized in that, The diameter of the electrode rod is 25mm to 80mm, and the length of the electrode rod is 100mm to 600mm.
4. The method for improving the yield of martensitic stainless steel powder according to claim 1, characterized in that, The step of atomizing the electrode rod material into martensitic stainless steel powder using a plasma rotating electrode powder-making device includes: After evacuating the atomization chamber, inert gas is introduced to bring the pressure in the atomization chamber to a preset pressure. The powder-making process parameters are set, and the plasma rotating electrode powder-making equipment is started to produce martensitic stainless steel powder. The powder-making process parameters include: the rotation speed of the electrode rod, the current of the electrode rod, and the feed rate of the electrode rod. The rotation speed of the electrode rod is greater than 0 and less than or equal to 50,000 rpm, the current of the electrode rod is 300A to 4000A, and the feed rate of the electrode rod is 0.5mm / s to 2.5mm / s.
5. The method for improving the yield of martensitic stainless steel powder according to claim 4, characterized in that, The preset pressure is 0.05 MPa to 0.2 MPa.
6. The method for improving the yield of martensitic stainless steel powder according to claim 4, characterized in that, The inert gas is argon.