Ultrasonic-assisted hot and cold spinning forming method and device for magnesium alloy rotary parts

Abstract

The present invention belongs to the technical field related to the forming of magnesium alloys, and discloses an ultrasonic-assisted hot and cold spinning forming method and device for magnesium alloy rotary parts. The method includes: S1: Processing a magnesium alloy sheet into a circular blank, and immersing it in liquid nitrogen until it reaches the liquid nitrogen temperature; S2: Rapidly transferring the circular blank to a spinning machine tool, fixing it at the end of a mandrel through a tailstock, so as to rotate synchronously with the mandrel and the main shaft; S3: Performing ultrasonic-assisted thickening spinning on the circular blank along the radial direction of the circular blank to obtain a pre-deformed blank; S4: Heating the pre-deformed blank to the forming temperature, and performing ultrasonic-assisted thinning spinning on the pre-deformed blank along the generatrix of the mandrel to obtain the required rotary part. This application can greatly promote the weakening of the basal texture of magnesium alloy materials, improve the anisotropy of mechanical properties and forming properties, and can reduce the overall forming force and improve the flow condition of the material, and improve the surface quality of the formed parts.

Description

Technical Field

[0001] The present invention belongs to the technical field related to the forming of magnesium alloys, and more specifically, relates to an ultrasonic-assisted hot and cold spinning forming method and device for magnesium alloy rotary parts. Background Art

[0002] Magnesium alloys have a low density, high specific strength and specific stiffness, and currently there is an increasing tendency to use magnesium alloys to manufacture various lightweight thin-walled parts. Magnesium alloy conical or curved generatrix thin-walled rotary parts are one of the typical high-performance lightweight components and are widely used in high-end equipment in fields such as aerospace and weaponry.

[0003] Magnesium alloys have a close-packed hexagonal crystal structure and a low room-temperature elongation. The increase in temperature can promote the initiation of non-basal slip, greatly improving the processing performance of magnesium alloys. Therefore, their plastic deformation mainly occurs in the heated state. Tube spinning is an effective method to achieve precision near-net forming of rotary parts, including flow spinning, shear spinning, etc. Chinese Patent CN107855394B discloses a cross-spinning strengthening method for magnesium alloy thin-walled cylindrical parts, and Chinese Patent CN10998595 discloses a hot-strength spinning forming method for preparing magnesium alloy cylindrical parts with internal ribs. Both achieve the deformation of magnesium alloys through hot spinning. However, the basal slip that dominates the hot spinning process is extremely likely to lead to strong basal texture and exhibit obvious anisotropy, severely restricting the improvement of the mechanical properties and forming performance of magnesium alloys. At the same time, due to the existence of frictional resistance between the material and the mandrel, the material flow differences between the inner and outer surfaces are relatively large, and problems such as uneven wall thickness distribution and roundness distribution are likely to occur, affecting the dimensional accuracy of the parts. Chinese Patents CN112029973, CN111069393 and CN104438536B disclose the use of ultrasonic-assisted deformation to achieve grain refinement and improve the surface quality of parts. However, for magnesium alloys, the mechanical property anisotropy and poor forming performance caused by basal texture are difficult to improve only through ultrasonic-assisted deformation, which greatly limits the popularization and application of magnesium alloy materials. Summary of the Invention

[0004] Aiming at the above defects or improvement requirements of the prior art, the present invention provides an ultrasonic-assisted hot and cold spinning forming method and device for magnesium alloy rotary parts. The present application can introduce a large number of twin structures into magnesium alloys, effectively reduce the anisotropy of the material and improve the forming performance, and can promote grain refinement of magnesium alloys and improve the material flow condition, significantly enhancing the mechanical properties and surface quality of the formed parts.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided an ultrasonic-assisted hot and cold spinning forming method for magnesium alloy rotary parts, and the method includes: S1: Processing a magnesium alloy sheet into a circular blank and immersing it in liquid nitrogen until it reaches the liquid nitrogen temperature; S2: Rapidly transferring the circular blank to a spinning machine tool and fixing it to the end of a mandrel through a tailstock to rotate synchronously with the mandrel and the main shaft; S3: Performing ultrasonic-assisted thickening spinning on the circular blank along the radial direction of the circular blank to obtain a pre-deformed blank; S4: Heating the pre-deformed blank to the forming temperature and performing ultrasonic-assisted thinning spinning on the pre-deformed blank along the generatrix of the mandrel to obtain the required rotary part.

[0006] Preferably, in step S3, a liquid nitrogen device is used to spray liquid nitrogen on the circular blank and cool it down.

[0007] Preferably, in step S3, the deformation amount of the pre-deformed blank is 1% to 10%.

[0008] Preferably, in step S4, a laser or a flame is used to locally heat the deformation zone of the circular blank.

[0009] Preferably, in step S3, a thickening roller is used to perform thickening spinning on the circular blank; in step S4, a butterfly roller is used to perform thinning spinning.

[0010] Preferably, step S3 specifically includes: starting the spinning machine tool, enabling the circular blank to rotate synchronously with the mandrel and the main shaft, and using a thickening roller to gradually feed along the radial direction of the circular blank for thickening.

[0011] Preferably, in step S4, local heating of the spinning deformation area is further included during the ultrasonic-assisted thinning spinning process.

[0012] Preferably, step S1 further includes drilling a center hole in the circular blank, and the tailstock fixes the circular blank on the mandrel through the center hole.

[0013] Preferably, the mandrel has the same shape as the rotary part to be formed.

[0014] According to another aspect of the present invention, there is provided a device for the ultrasonic-assisted hot and cold spinning forming method for the above-mentioned magnesium alloy rotary parts, and the device includes: a liquid nitrogen device for fully cooling the blank; a tailstock for fixing the sheet to be deformed; a mandrel, which is conical or has a curved generatrix and is connected to the main shaft of the spinning machine tool to rotate under the drive of the main shaft; an ultrasonic power supply, a transducer, and a horn are connected in sequence, and the end of the horn is a detachable end; a thickening roller and a butterfly roller for connecting with the detachable end.

[0015] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the ultrasonic-assisted hot and cold spinning forming method and device for magnesium alloy rotary parts provided by the present invention have the following beneficial effects:

[0016] 1. Before the thermoplastic deformation of the magnesium alloy, by cryogenically treating the magnesium alloy material to be processed and applying a small-strain compressive pre-deformation along the thickness direction, a large number of twin structures can be introduced into the matrix while restricting the movement of dislocations inside the material, effectively changing the grain orientation and weakening the basal texture. In addition, by utilizing the acoustic softening effect and friction reduction effect of ultrasonic vibration, the grain refinement and material flow condition can be promoted, and the mechanical properties and surface quality of the workpiece can be improved. Therefore, the hot and cold spinning forming method combining cryogenic pre-deformation and ultrasonic vibration assistance provides a new way for the preparation of high-quality magnesium alloy rotary parts.

[0017] 2. Since the object of this application is magnesium alloy, which mainly undergoes basal slip during the thermoplastic deformation process, this easily leads to a strong basal texture, causing obvious mechanical property anisotropy of the material and reducing its formability, greatly restricting the application range of magnesium alloy. And simple ultrasonic-assisted deformation is difficult to weaken the basal texture. Therefore, ultrasonic-assisted thickening spinning is carried out before ultrasonic-assisted thinning spinning in this application. A large number of twin structures are introduced through small-strain compressive pre-deformation under ultra-low temperature conditions, promoting the change of grain orientation and the weakening of the basal texture, and then overcoming the problems of significant anisotropy and poor formability of magnesium alloy materials during the ultrasonic-assisted thinning spinning process, which is crucial for the preparation of high-quality magnesium alloy rotary parts.

[0018] 3. The thickening pre-deformation amount in this application is 1-10%. A reasonable pre-deformation amount is the key to controlling the volume fraction of the introduced twin structure. If the pre-deformation amount is too low (<1%), it is difficult to introduce enough twin structures to weaken the basal texture of the magnesium alloy, while if the pre-deformation amount is too large (>10%), it is easy to cause defects such as cracks in the magnesium alloy due to poor low-temperature formability.

[0019] 4. During the ultrasonic-assisted thickening spinning process, the spinning part is cooled by spraying liquid nitrogen, which can ensure that the material is in an ultra-low temperature state to the greatest extent and greatly promote the generation of twin structures.

[0020] 5. During the ultrasonic-assisted thinning spinning process, local heating of the spinning part is included, which can further improve the formability of the magnesium alloy, induce dynamic recrystallization and promote grain refinement.

[0021] 6. The device used in the method of this application is simple. The preparation of rotary parts can be realized by simply replacing the tool head on a set of devices. The process is simple and convenient for commercial application. Description of the Drawings

[0022] Figure 1 It is a step diagram of the ultrasonic-assisted hot and cold spinning forming method for magnesium alloy rotary parts in the embodiment of the present application;

[0023] Figure 2 It is a schematic diagram of the device in the ultrasonic-assisted spinning thickening process of the ultrasonic-assisted hot and cold spinning forming method for magnesium alloy rotary parts in the embodiment of the present application;

[0024] Figure 3 It is a schematic diagram of the device in the ultrasonic-assisted spinning thinning process of the ultrasonic-assisted hot and cold spinning forming method for magnesium alloy rotary parts in the embodiment of the present application.

[0025] In all the drawings, the same reference numerals are used to represent the same elements or structures, where:

[0026] 1 - Liquid nitrogen tank; 2 - Liquid nitrogen nozzle; 3 - Tailstock; 4 - Circular blank; 5 - Mandrel; 6 - Thickening spinning wheel; 7 - Horn; 8 - Transducer; 9 - Ultrasonic power supply; 10 - Laser; 11 - Butterfly spinning wheel. Detailed implementation manners

[0027] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] Please refer to Figure 1 , the present invention provides an ultrasonic-assisted hot and cold spinning forming method for magnesium alloy rotary parts, and this method includes the following steps S1 to S4.

[0029] S1: Process the magnesium alloy sheet into a circular blank, and place it in the liquid nitrogen tank 1 to soak until it reaches the liquid nitrogen temperature;

[0030] According to the geometric dimensions of the magnesium alloy rotary part to be formed, the magnesium alloy sheet is pretreated according to the principle of constant volume of the material during the deformation process to obtain a circular blank.

[0031] In a preferred solution, it also includes drilling a center hole in the circular blank.

[0032] S2: Quickly transfer the circular blank to the spinning machine, and fix it at the end of the mandrel through the tailstock to rotate synchronously with the mandrel and the main shaft;

[0033] The tailstock fixes the circular slab on the core mold through the central hole. The shape of the core mold is the same as that of the magnesium alloy revolving body part to be formed. The core mold is fixed to the main shaft of the spinning machine tool through a flange plate to rotate axially driven by the main shaft motor.

[0034] S3: Carry out ultrasonic-assisted incremental spinning on the circular slab along the radial direction of the circular slab to obtain a pre-deformed slab.

[0035] Start the spinning machine tool to make the circular slab rotate driven by the main shaft and the core mold. Open the liquid nitrogen nozzle to cool the spinning part by spraying liquid nitrogen. Turn on the ultrasonic power supply. The ultrasonic signal is converted into ultrasonic vibration by the transducer and the horn and acts on the tool head. Start the main shaft of the spinning equipment to drive the core mold and the slab to rotate synchronously. The tool head feeds along the radial direction at a certain speed to make the slab undergo local thickening deformation. The tool head is an incremental spinning wheel. The deformation amount of the pre-deformed slab is 1% - 10%.

[0036] S4: Heat the pre-deformed slab to the forming temperature and carry out ultrasonic-assisted incremental spinning on the pre-deformed slab along the generatrix of the core mold to obtain the required revolving body part.

[0037] Locally heat the circular slab by laser or flame. Turn on the ultrasonic power supply. The ultrasonic signal is converted into ultrasonic vibration by the transducer and the horn and directly acts on the tool head. Start the main shaft of the spinning equipment to drive the slab and the core mold to rotate synchronously. The tool head feeds along the generatrix direction of the core mold at a certain speed to make the slab undergo local thinning deformation. During the spinning process, use a laser or a flame gun to carry out follow-up heating on the deformation zone. The tool head is a butterfly spinning wheel during this process.

[0038] On the other hand, the present application provides a device for the ultrasonic-assisted spinning forming method of the above-mentioned magnesium alloy revolving body part, as Figure 2 and Figure 3 shown. The device includes:

[0039] A liquid nitrogen tank 1 for soaking the circular slab; a liquid nitrogen nozzle 2 for spraying liquid nitrogen on the circular slab; a tailstock 3 for fixing the sheet to be deformed; a core mold 5, which is conical or has a curved generatrix shape and is connected to the main shaft to rotate driven by the main shaft motor; an ultrasonic power supply 9, a transducer 8 and a horn 7 are connected in sequence, and the end of the horn 7 is a detachable end; an incremental spinning wheel 6 and a butterfly spinning wheel 11 for connecting to the detachable end.

[0040] Embodiment

[0041] Step 1: Use AQ80 magnesium alloy rolled plates to form the required conical parts. According to the geometric dimensions of the parts and the principle of constant material volume during the deformation process, process the AQ80 magnesium alloy rolled plates into circular blanks 4 with a central hole, and place the circular blanks 4 in a liquid nitrogen tank 1 for soaking until the liquid nitrogen temperature of 77 K is reached;

[0042] Step 2: Quickly transfer the circular blank 4 to a spinning machine tool, fix it to the end of the mandrel 5 through the tailstock 3, and start the main shaft of the spinning equipment to drive the blank 4 and the mandrel 5 to rotate synchronously.

[0043] Step 3: Open the liquid nitrogen nozzle 2 to cool the blank 4 by spraying liquid nitrogen; turn on the ultrasonic power supply 9, and the ultrasonic signal is converted into ultrasonic vibration through the transducer 8 and the horn 7 and directly acts on the thickening spinning wheel 6; as Figure 2 shown, the thickening spinning wheel 6 feeds along the radial direction at a certain speed, causing local thickening deformation of the blank, and the pre-deformation amount is between 1% and 10%;

[0044] Step 4: Laser heat the pre-deformed blank to 300 °C through the laser 10; as Figure 3 shown, replace the thickening spinning wheel 6 in the ultrasonic device in Step 3 with a butterfly spinning wheel 11; turn on the ultrasonic power supply 9, and the ultrasonic signal is converted into ultrasonic vibration through the transducer 8 and the horn 7 and directly acts on the butterfly spinning wheel 11; start the main shaft of the spinning equipment to drive the circular blank 4 and the mandrel 5 to rotate synchronously, and the butterfly spinning wheel 11 feeds along the generatrix direction of the mandrel at a certain speed, causing local thinning deformation of the blank, and finally obtaining a magnesium alloy conical part with both high dimensional accuracy and excellent tissue properties. During the spinning process, the laser 10 is used to conduct follow-up heating on the deformation zone.

[0045] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. An ultrasonic-assisted hot and cold spinning forming method for a magnesium alloy rotary part, characterized in that The method includes: S1: Processing a magnesium alloy sheet into a circular blank and immersing it in liquid nitrogen until it reaches the liquid nitrogen temperature; S2: Rapidly transferring the circular blank to a spinning machine tool, fixing it to the end of a mandrel through a tailstock, and rotating synchronously with the mandrel and the main shaft; S3: Performing ultrasonic-assisted thickening spinning on the circular blank along the radial direction of the circular blank to obtain a pre-deformed blank; S4: Heating the pre-deformed blank to the forming temperature, and performing ultrasonic-assisted thinning spinning on the pre-deformed blank along the generatrix of the mandrel to obtain the required rotational part.

2. The method according to claim 1, wherein In step S3 during thickening spinning, it also includes using a liquid nitrogen device to spray liquid nitrogen on the circular blank and cool it down.

3. The method according to claim 1, characterized in that, In step S3, the deformation amount of the pre-deformed blank is 1% - 10%.

4. The method according to claim 1, characterized in that In step S4, a laser or flame is used to locally heat the deformation area of the circular blank.

5. The method according to claim 1, characterized in that, In step S3, a thickening spinning wheel is used to perform thickening spinning on the circular blank; in step S4, a butterfly spinning wheel is used to perform thinning spinning.

6. The method according to claim 4, characterized in that, Step S3 specifically is: Starting the spinning machine tool, making the circular blank rotate synchronously with the mandrel and the main shaft, and using a thickening spinning wheel to gradually feed along the radial direction of the circular blank for thickening.

7. The method according to claim 1, characterized in that, In step S4 during ultrasonic-assisted thinning spinning, it also includes locally heating the spinning deformation area.

8. The method according to claim 1, wherein Step S1 also includes drilling a center hole in the circular blank so that the tailstock in step S2 can fix the circular blank on the mandrel through the center hole.

9. The method according to claim 1, wherein The mandrel has the same shape as the rotational part to be formed.

10. An apparatus for an ultrasonic-assisted hot and cold spinning forming method of a magnesium alloy rotary part according to any one of claims 1 to 8, characterized in that, The device includes: A liquid nitrogen tank (1) and a liquid nitrogen nozzle (2) for sufficiently cooling the blank; A tailstock (3) for fixing the sheet to be deformed; A mandrel (5), which is conical or has a curved generatrix, is connected to the main shaft of the spinning machine tool, and rotates synchronously under the drive of the machine tool main shaft; An ultrasonic power supply (9), a transducer (8), and a horn (7) connected in sequence, and the end of the horn (7) is a detachable end; A thickening spinning wheel (6) and a butterfly spinning wheel (11) for connecting with the detachable end.

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