A magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloy

Abstract

This invention discloses a magnetic field-assisted thinning spinning process for molybdenum-rhenium alloys. The method utilizes a ring-shaped permanent magnet array to create a unidirectional DC magnetic field in the plastic deformation zone of the molybdenum-rhenium alloy billet. By applying preset spinning parameters, the molybdenum-rhenium alloy billet is thinned to a preset thickness through several passes of hot spinning. The magnetic field-assisted thinning spinning process provided by this invention effectively guides dislocation movement, prevents localized accumulation, and significantly improves the success rate and efficiency of high-thinning spinning of molybdenum-rhenium alloys.

Description

Technical Field

[0001] This invention belongs to the field of molybdenum-rhenium alloy processing technology, specifically relating to a magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloys. Background Technology

[0002] As an important refractory metal material, molybdenum-rhenium alloy is in high demand in high-end industrial fields for its thin-walled rotating components, and high-intensity spinning is an ideal process for manufacturing such components. However, molybdenum-rhenium alloy has poor intrinsic plasticity, and during spinning, internal dislocations tend to accumulate at defects such as grain boundaries, leading to stress concentration and cracking. Furthermore, the unidirectional feed of the spinning wheel causes directional dislocation accumulation, limiting the forming limit and efficiency, affecting the reliability of the components, and exacerbating work hardening.

[0003] To address issues such as cracking, dislocation accumulation, and work hardening during the spinning process of molybdenum-rhenium alloys, existing technologies primarily employ passive solutions. These include optimizing the spinning wheel geometry, reducing deformation per pass, and adding intermediate annealing processes between spinning passes to mitigate adverse effects. However, these passive solutions only alleviate the problems through process parameters or auxiliary treatments, lacking effective means to actively guide and control the physical nature of dislocation movement. They fail to address the root cause of directional dislocation accumulation due to unidirectional feeding of the spinning wheel, and thus cannot fundamentally improve the spinning forming limits, efficiency, and the uniformity and reliability of the component microstructure in molybdenum-rhenium alloy spinning processes. Summary of the Invention

[0004] To address the problem of directional dislocation accumulation caused by unidirectional feed of the spinning wheel in existing spinning processes, this invention provides a magnetic field-assisted thinning spinning process for molybdenum-rhenium alloys. This process can effectively guide dislocation movement, avoid local dislocation accumulation, and significantly improve the success rate and processing efficiency of high-thinning spinning of molybdenum-rhenium alloys.

[0005] To achieve the above objectives, the first aspect of the present invention provides a magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloys, comprising: A unidirectional DC magnetic field is formed in the plastic deformation zone of the molybdenum-rhenium alloy billet by an array of ring permanent magnets; By using preset spinning parameters, the molybdenum-rhenium alloy billet is hot-spun several times to reduce the thickness of the molybdenum-rhenium alloy to the preset thickness.

[0006] Furthermore, the molybdenum-rhenium alloy is placed on the mandrel of the spinning machine, and the preheating temperature of the mandrel is 200~500℃.

[0007] Furthermore, the magnetic field strength of the unidirectional DC magnetic field is 0.5-1.0T.

[0008] Furthermore, during the hot spinning process, the feed rate of the spinning wheel is 0.1 ~ 0.2 mm / r.

[0009] Furthermore, the spindle speed during the hot spinning process is 360 ~ 400 r / min.

[0010] Furthermore, the temperature of the molybdenum-rhenium alloy billet is maintained at 500℃~600℃ during the hot spinning process.

[0011] Furthermore, the thinning rate per pass during hot spinning is 20% to 35%.

[0012] Furthermore, after the spinning process is completed, the total thinning rate of the molybdenum-rhenium alloy is 75%~90%.

[0013] Furthermore, the distance between the permanent magnet and the blank is 5-10cm.

[0014] Furthermore, the billet must undergo pretreatment such as cleaning, degreasing, deburring, and chamfering before spinning.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The magnetic field-assisted high-thinning spinning process for molybdenum-rhenium alloys proposed in this invention can effectively guide dislocation movement, prevent local accumulation, and significantly improve the success rate and efficiency of high-thinning spinning of molybdenum-rhenium alloys. A unidirectional DC magnetic field is formed in the plastic deformation zone of the molybdenum-rhenium alloy billet by a ring-shaped permanent magnet array. This magnetic field alters the electron spin state of the free radical pairs between dislocations and obstacles, promoting their transition from the ground state to the excited state. This guides the dislocations to move along the spinning feed direction, preventing dislocation accumulation in localized areas, reducing the resistance to dislocations overcoming obstacles, and thus promoting depinning. The magnetic field facilitates atomic movement, increases the slip plane spacing, and reduces the critical shear stress, which is beneficial for dislocation slip, thereby improving the spinning efficiency of molybdenum-rhenium alloys. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the spinning die used in this invention; Figure 2 This is a diagram illustrating the mechanism of the effect of the applied magnetic field on dislocation motion in the spinning process of this invention. Among them, 1. Annular permanent magnet array; 2. Rotating wheel; 3. Blank; 4. Core mold. Detailed Implementation

[0018] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0019] In this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0020] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0021] It should be understood that in various embodiments of the present invention, the order of the above-mentioned processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0022] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0023] The weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope disclosed in the embodiments of this invention. Specifically, the mass described in the embodiments of this invention can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0024] Unless otherwise stated, all percentages in this document are by mass; temperature is in °C; dimensions are in mm and thickness is in μm; and rotation speed is in rpm.

[0025] Molybdenum-rhenium alloys, as important refractory metal materials, are in high demand in high-end industrial applications for thin-walled rotating components. High-intensity spinning is an ideal process for manufacturing such components. However, during spinning, due to the poor intrinsic plasticity of molybdenum-rhenium alloys, dislocations easily accumulate at grain boundaries and other defects during deformation, leading to stress concentration and subsequently microcracks and macroscopic cracking, severely limiting forming limits and efficiency. In current spinning processes, because the spinning wheel feeds unidirectionally along a fixed path, a large number of dislocations generated in the deformation zone are driven and mainly move towards the undeformed area in front of the spinning wheel. These dislocations strongly accumulate at grain boundaries, phase boundaries, and other crystal defects, causing the dislocation density to increase prematurely in areas where no macroscopic deformation has occurred. This directional dislocation accumulation limits the material's ultimate deformation capacity, resulting in an inhomogeneous microstructure, affecting its reliability, and exacerbating work hardening, leading to spinning instability. To address these problems, existing technologies mostly employ passive methods such as optimizing the spinning wheel geometry, reducing the deformation per pass, or adding intermediate annealing processes between passes. However, the lack of effective means to actively guide and control dislocation motion at its physical essence makes it impossible to solve the problem of directional dislocation accumulation caused by unidirectional feed of the spinning wheel. Therefore, there is an urgent need in this field for a new method that can actively intervene in dislocation motion, promote uniform dislocation distribution, and thus improve the uniformity of the microstructure and forming performance of spun parts.

[0026] like Figure 1 As shown, the existing spinning machine is improved by adopting a three-wheel high-power spinning machine; a specially designed annular permanent magnet array 1 is installed around the front end of each spinning wheel. The annular permanent magnet array 1 is composed of high-performance neodymium iron boron (N52 grade) permanent magnets, which can generate a stable and uniform unidirectional DC magnetic field in the tangential direction at the contact point between the spinning wheel 2 and the blank 3. This magnetic field device is rigidly connected to the spinning wheel 2, ensuring that the magnetic field region can move synchronously with the spinning wheel during the spinning process, continuously acting on the instantaneous deformation zone.

[0027] Based on this, the magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloy provided by the present invention includes the following steps: A unidirectional DC magnetic field is formed in the plastic deformation zone of the molybdenum-rhenium alloy billet by an array of ring permanent magnets; By using preset spinning parameters, the molybdenum-rhenium alloy billet is hot-spun several times to reduce the thickness of the molybdenum-rhenium alloy to the preset thickness.

[0028] The thinning spinning process provided by this invention involves installing a ring-shaped permanent magnet array at the spinning mill's rotating wheel. During spinning, the magnets move with the rotating wheel, applying a unidirectional DC magnetic field tangentially to the workpiece. With the assistance of this magnetic field, a stable unidirectional DC magnetic field can simultaneously act on the material's plastic deformation zone during the wheel's feed. This magnetic field alters the electron spin state of free radical pairs between dislocations and barriers such as grain boundaries and second phases, promoting their transition from a lower-energy ground state to a higher-energy excited state, thereby reducing the activation energy required for depinning. It guides dislocations along the spinning feed direction, preventing dislocation accumulation and entanglement in localized areas. Simultaneously, the magnetic field alters interatomic interactions, increasing the slip plane spacing and facilitating dislocation slip.

[0029] like Figure 2 The diagram illustrates the effect of a magnetic field (MF) on free radical pairs and dislocations, demonstrating the role of MF in a dislocation-barrier system. The system contains two local barriers (large black spheres), with a dislocation (black line) in the middle. Free radical pairs (electron pairs within red boxes) exist between the dislocation and the barriers. Without a magnetic field, the two electrons in the S state have opposite spins, and their spin magnetic moments cancel each other out. At this point, the binding energy of the free radical pair is high, pinning the dislocation and hindering its movement. When a magnetic field (SN poles in the diagram) is applied, the free radical pair is excited to the T state. In this state, the two electrons have the same or partially the same spin direction, reducing the binding energy and facilitating dislocation depinning.

[0030] In some specific embodiments of the present invention, the molybdenum-rhenium alloy is placed on the mandrel 4 of the spinning machine, and the preheating temperature of the mandrel 4 is 200~500℃. Preheating the mandrel 4 can reduce the instantaneous temperature difference between the molybdenum-rhenium alloy billet and the mandrel, and avoid the molybdenum-rhenium alloy from generating internal stress and microcracks due to severe thermal shock.

[0031] In some specific embodiments of the present invention, the magnetic field strength of the unidirectional DC magnetic field is 0.5-1.0T. Applying a suitable magnetic field strength can regulate dislocation movement and grain orientation during hot spinning plastic deformation, suppress the formation of coarse grains and inhomogeneous structures, and promote grain refinement and texture homogenization.

[0032] In some specific embodiments of the present invention, the feed rate of the spinning wheel during hot spinning is 0.1 ~ 0.2 mm / r; applying an appropriate feed rate can achieve uniform plastic deformation while ensuring forming efficiency, avoiding excessive feed leading to a sudden increase in local load, wrinkling or cracking of the billet, and adapting to the high strength and high brittleness characteristics of molybdenum-rhenium alloy.

[0033] In some specific embodiments of the present invention, the spindle speed during hot spinning is 360 ~ 400 r / min. Applying a suitable spinning speed can make the contact area between the spinning wheel and the blank form a suitable deformation frequency, ensuring the full plastic flow of the molybdenum-rhenium alloy at high temperature.

[0034] In some specific embodiments of the present invention, the temperature of the molybdenum-rhenium alloy billet is maintained at 500°C to 600°C during hot spinning; this allows the material to be in a better thermoplastic range, significantly reducing deformation resistance, improving the difficult-to-deform properties, and avoiding the problems of easy cracking and high-stress brittle fracture during low-temperature spinning.

[0035] In some specific embodiments of the present invention, the thinning rate per pass during hot spinning is 20% to 35%; the thinning rate per pass can achieve effective deformation and microstructure refinement, avoiding the increase of cumulative stress caused by too low a thinning rate; at the same time, it prevents problems such as local tearing and uneven wall thickness caused by too high a thinning rate.

[0036] In some specific embodiments of the present invention, after the spinning process is completed, the total thinning rate of the molybdenum-rhenium alloy is 75% to 90%.

[0037] In some specific embodiments of the present invention, the distance between the permanent magnet and the blank is 5-10 cm. In some specific embodiments of the present invention, the billet must undergo cleaning, degreasing, deburring, and chamfering pretreatment before spinning. Deburring can prevent stress concentration and the induction of cracks, while chamfering can reduce sudden changes in stress at the edges of the billet.

[0038] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0039] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under standard conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications in the art, unless otherwise stated.

[0040] Example 1 Billet preparation: Select Mo-50Re alloy bars (molybdenum and rhenium mass ratio of 1:1) as billets, and machine them into tubular molybdenum-rhenium alloy billets with an outer diameter of φ100mm and a wall thickness of 5mm. Perform pretreatment on the billets, and successively complete solvent ultrasonic cleaning to remove oil, mechanical deburring, polishing of inner and outer surfaces to remove oxide layer and microcracks, and rounding the edges with R1mm radius.

[0041] By adjusting the distance between the permanent magnet and the molybdenum-rhenium alloy billet to 7cm, the intensity of the unidirectional DC magnetic field acting on the plastic deformation zone of the billet is precisely controlled at 0.8T.

[0042] Preheat the mandrel of the spinning machine to 400°C, then fit the pretreated tubular blank onto the preheated mandrel. Use a ring heater to preheat the blank as a whole, so that its temperature rises uniformly to 550°C and is maintained at that temperature for 10 minutes.

[0043] The spinning forming process parameters are as follows: spindle speed 380 r / min, spinning wheel feed 0.1 mm / r. The spinning machine and annular permanent magnet array are started to form a stable unidirectional DC magnetic field in the tangential direction at the contact point between the spinning wheel and the billet. The molybdenum-rhenium alloy billet is hot-spun five times, with the single-pass thinning rate controlled within the range of 25%~30%. Under the above magnetic field-assisted thinning spinning process conditions, a 5 mm thick molybdenum-rhenium alloy tube billet was successfully spun to a thickness of 1 mm, achieving a total thinning rate of 80%. The wall thickness uniformity error of the formed part is ≤ ±0.04 mm, and the surface is free of defects such as cracks and wrinkles, with no obvious dislocation accumulation in the microstructure.

[0044] Example 2 Billet preparation: Select Mo-40Re alloy bars (molybdenum and rhenium mass ratio of 6:4) as billets, and machine them into tubular molybdenum-rhenium alloy billets with an outer diameter of φ80mm and a wall thickness of 6mm. Perform pretreatment on the billets, including alkaline washing to remove oil, acid pickling and passivation to remove the surface oxide layer, mechanical polishing to finish the surface, and rounding the edges with a radius of R0.8mm.

[0045] By adjusting the distance between the permanent magnet and the blank to 6cm, the unidirectional DC magnetic field strength in the plastic deformation zone is controlled at 0.5T.

[0046] Preheat the spinning die to 200°C, then fit the pretreated tubular blank onto the die. Preheat the entire blank using a ring heater until the temperature rises uniformly to 500°C and is maintained at that temperature for 15 minutes.

[0047] The spinning forming process parameters are as follows: spindle speed 360 r / min, spinning wheel feed 0.1 mm / r. The spinning machine and the ring-shaped permanent magnet array are started to form a stable unidirectional DC magnetic field. The molybdenum-rhenium alloy billet is hot-spun six times, with the single-pass thinning rate controlled within the range of 30%~35%. Under magnetic field assistance, a 6 mm thick tube blank was successfully spun to reduce its thickness to 0.6 mm, achieving a total thinning rate of 90%. The coaxiality error of the formed part is ≤0.05 mm, the surface finish Ra is ≤0.8 μm, and there are no macroscopic cracks or localized uneven wall thickness.

[0048] Example 3 Raw material preparation: Select Mo-25Re alloy bars (molybdenum and rhenium mass ratio of 75:25) as raw materials, and machine them into tubular molybdenum-rhenium alloy blanks with an outer diameter of φ120mm and a wall thickness of 4mm. Perform pretreatment on the blanks, including ultrasonic cleaning to remove oil, sandblasting to remove surface oxide scale, fine polishing, and rounding the edges with a radius of R1.5mm to ensure no machining defects.

[0049] By adjusting the distance between the permanent magnet and the blank to 5cm, the unidirectional DC magnetic field strength in the plastic deformation zone is controlled at 1.0T.

[0050] Preheat the spinning die to 500°C, place the blank onto the die, and preheat it to 600°C using a ring heater. Maintain this temperature for 10 minutes.

[0051] The spinning forming process parameters are as follows: spindle speed 400 r / min, spinning wheel feed 0.2 mm / r. The spinning machine and the ring-shaped permanent magnet array are started to form a stable unidirectional DC magnetic field; the billet is hot-spun four times, with the single-pass thinning rate controlled within the range of 20%~25%. Under magnetic field assistance, a 4 mm thick tube blank was successfully spun to reduce its thickness to 1 mm, achieving a total thinning rate of 75%. The formed part has no scratches or wrinkles on its surface, and the micro-grain structure is refined and uniform, meeting the requirements for thin-walled rotating components.

[0052] Example 4 Raw material preparation: Select Mo-35Re alloy bars (molybdenum and rhenium mass ratio of 65:35) as raw materials, and machine them into tubular molybdenum-rhenium alloy raw materials with an outer diameter of φ90mm and a wall thickness of 5.5mm. Perform pretreatment on the raw materials, including solvent cleaning to remove oil, mechanical polishing to remove oxide layer and machining marks, and rounding the edges with R1.2mm corners to ensure that the surface is free of pits and scratches.

[0053] By adjusting the distance between the permanent magnet and the blank to 8cm, the unidirectional DC magnetic field strength in the plastic deformation zone is controlled at 0.7T.

[0054] Preheat the spinning die to 350°C, place the blank onto the die, and preheat it to 580°C using a ring heater. Maintain this temperature for 12 minutes.

[0055] The spinning forming process parameters are as follows: spindle speed 390 r / min, spinning wheel feed 0.15 mm / r. The spinning machine and the ring-shaped permanent magnet array are started to form a stable unidirectional DC magnetic field; the billet is hot-spun 5 times, with the single-pass thinning rate controlled within the range of 28%~32%. Under magnetic field assistance, a tube blank with a wall thickness of 5.5 mm was successfully spun to a thickness of 0.825 mm, achieving a total thinning rate of 85%. The wall thickness deviation of the formed part is ≤±0.03 mm, and there is no local hardening problem caused by dislocation accumulation.

[0056] Example 5 Blank preparation: Select Mo-30Re alloy bar (molybdenum and rhenium mass ratio of 7:3) as blank, and machine it into a tubular molybdenum-rhenium alloy blank with an outer diameter of φ110mm and a wall thickness of 4.8mm. Perform pretreatment on the blank, including ultrasonic degreasing, mechanical deburring, polishing the inner and outer surfaces to Ra≤0.6μm, rounding the edges with R1mm, and removing all sharp corners.

[0057] By adjusting the distance between the permanent magnet and the blank to 10cm, the unidirectional DC magnetic field strength in the plastic deformation zone is controlled at 0.6T.

[0058] Preheat the spinning die to 300°C, place the blank onto the die, and preheat it to 520°C using a ring heater. Maintain this temperature for 18 minutes.

[0059] The spinning forming process parameters are as follows: spindle speed 370 r / min, spinning wheel feed 0.12 mm / r. The spinning machine and toroidal permanent magnet array are started to form a stable unidirectional DC magnetic field; the billet is hot-spun six times, with the single-pass thinning rate controlled within the range of 22%~28%. Under magnetic field assistance, a tube blank with a wall thickness of 4.8 mm was successfully spun to a thickness of 0.72 mm, achieving a total thinning rate of 85%. The formed part has no macroscopic cracks, a uniform microstructure, and wall thickness accuracy meeting high-end industrial application standards.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloys, characterized in that, include: A unidirectional DC magnetic field is formed in the plastic deformation zone of the molybdenum-rhenium alloy billet by an array of ring permanent magnets; By using preset spinning parameters, the molybdenum-rhenium alloy billet is hot-spun several times to reduce the thickness of the molybdenum-rhenium alloy to the preset thickness.

2. The magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloy according to claim 1, characterized in that, The molybdenum-rhenium alloy is placed on the mandrel of the spinning machine, and the preheating temperature of the mandrel is 200~500℃.

3. The magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloy according to claim 1, characterized in that, The magnetic field strength of the unidirectional DC magnetic field is 0.5-1.0T.

4. The magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloy according to claim 1, characterized in that, During hot spinning, the feed rate of the spinning wheel is 0.1 ~ 0.2 mm / r.

5. The magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloy according to claim 1, characterized in that, The spindle speed during hot spinning is 360 ~ 400 r / min.

6. The magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloy according to claim 1, characterized in that, During the hot spinning process, the temperature of the molybdenum-rhenium alloy billet is maintained at 500℃~600℃.

7. The magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloy according to claim 1, characterized in that, The thinning rate per pass during hot spinning is 20% to 35%.

8. The magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloy according to claim 1, characterized in that, After the spinning process is completed, the total thinning rate of the molybdenum-rhenium alloy is 75%~90%.

9. The magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloy according to claim 1, characterized in that, The distance between the annular permanent magnet array and the blank is 5-10cm.

10. The magnetic field-assisted thinning and spinning process for molybdenum-rhenium alloy according to claim 1, characterized in that, Before spinning, the blank is cleaned, degreased, deburred, and chamfered.

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