Device for production of magnesium alloy seamless tube

Abstract

A production device for a magnesium alloy seamless tube, including: an integrated piercing and rolling roll having a roll surface that defines both a piercing deformation zone and a pipe rolling zone, where the piercing deformation zone is configured to pierce a magnesium alloy billet to form a tube blank, and the pipe rolling zone is configured to receive the tube blank from the piercing deformation zone and to roll the tube blank; at least a pair of driven support guide rolls disposed in a circumferential vacant region of the integrated piercing and rolling roll, where a roll surface of each of the driven support guide rolls includes sections corresponding respectively to the piercing deformation zone and the pipe rolling zone; a piercing plug disposed within the piercing deformation zone; and a mandrel threadedly connected to the piercing plug and extending into the pipe rolling zone.

Description

CROSS‌-REFERENCE TO RELATED APPLICATIONS

[0001] Pursuant to 35 U.S.C.§ 119 and the Paris Convention Treaty, this application claims foreign priority to Chinese Patent Application No. 202510210016.3 filed Feb. 25, 2025, and to Chinese Patent Application No. 202511557595.5 filed Oct. 29, 2025. The contents of all of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document or the related applications should be directed to: Matthias Scholl P.C., Attn.: Dr. Matthias Scholl Esq., 245 First Street, 18th Floor, Cambridge, MA 02142.BACKGROUND

[0002] The disclosure relates to a device for the streamlined production of a magnesium alloy seamless tube with a combined piercing and rolling process using shared rollers.

[0003] Magnesium alloy, as a new-generation structural metallic material following steel and aluminum alloy, offers advantages such as low density, high specific strength and stiffness, good damping capacity, excellent thermal conductivity, favorable machinability, and stable part dimensions. It has found wide application in automotive, aerospace, and communication electronics industries, offering significant advantages in product lightweighting. For magnesium alloy to serve as a structural material, it is often used in the form of basic products such as sheet, tube, profile, and wire. Currently, magnesium alloy tubing has been adopted in certain fields, primarily manufactured by casting and extrusion.

[0004] In conventional tube-forming processes, piercing and subsequent elongating / sizing are carried out in separate steps. During piercing, rolls drive the billet to rotate helically while an axial feeding motion advances the billet along its own axis. The billet overcomes the constraint resistance of the piercing plug to achieve constrained piercing. This forming process requires secondary engagement. Due to magnesium alloy’s tendency for rapid heat dissipation, the billet is highly prone to rolling jamming during secondary engagement, which can further lead to cracking of the pierced shell, making it difficult to complete the piercing operation. Moreover, between different process steps, the billet and the hollow shell generally require reheating, resulting in high thermal energy costs. After recrystallization and thermal recovery, the grain structure of the shell coarsens and texture intensity increases, severely degrading the mechanical properties of the final tube.SUMMARY

[0005] One object of the disclosure is to provide a device for the streamlined production of a magnesium alloy seamless tube employing strong traction on an integrated piercing and rolling roll. The integrated system and process are configured to ensure the successful completion of the piercing-rolling sequence while enhancing piercing efficiency and enabling highly efficient online rolling to shorten the process flow. Upon completion of the first bite during piercing, the formed conical tube blank is immediately directed into the rolling stage of the integrated piercing and rolling roll. During the online rolling stage, an axial splitting traction force is applied to the tube blank, thereby sharing the secondary biting pressure and facilitating the high-efficiency production process.

[0006] In one embodiment, the disclosure provides a production device for a magnesium alloy seamless tube, the device comprising:

[0007] a) an integrated piercing and rolling roll having a roll surface that defines both a piercing deformation zone and a pipe rolling zone, where the piercing deformation zone is configured to pierce a magnesium alloy billet to form a tube blank, and the pipe rolling zone is configured to receive the tube blank from the piercing deformation zone and to roll the tube blank such that the tube blank directly enters a rolling deformation after piercing is completed, whereby a piercing load and a rolling traction force are shared on a single roll;

[0008] b) at least a pair of driven support guide rolls disposed in a circumferential vacant region of the integrated piercing and rolling roll, where a roll surface of each of the driven support guide rolls comprises sections corresponding respectively to the piercing deformation zone and the pipe rolling zone, for constraining radial flow of the tube blank during formation;

[0009] c) a piercing plug disposed within the piercing deformation zone; and

[0010] d) a mandrel threadedly connected to the piercing plug and extending into the pipe rolling zone, where the piercing plug comprises a liner boss positioned corresponding to the pipe rolling zone.

[0011] The integrated piercing and rolling roll comprises two functional zones integrated on a single roll body: a piercing deformation zone and a pipe rolling zone. The roll surface in the piercing deformation zone is substantially cylindrical, and the roll surface in the rolling zone is also substantially cylindrical. The rolling zone is disposed directly adjacent to and contiguous with the piercing deformation zone on the common roll body.

[0012] This integrated configuration effectively overcomes the conflict between the derived dragging force from reduction and the constraining load imposed by the plug during hole formation. It ensures that immediately after the first bite forms the conical tube blank, the blank is directly transitioned into the rolling zone of the integrated roll. During the rolling operation, an axial splitting component of the helical rolling force provides traction, thereby sharing the secondary biting pressure online.

[0013] In a class of this embedment, the integrated piercing and rolling roll is configured such that: a maximum roll diameter in the piercing deformation zone of the roll is from 4 to 6 times a diameter of the tube blank; an entry cone angle ranges from 1.8 degrees to 3.2 degrees; an exit cone angle ranges from 3 degrees to 4.2 degrees; and a thickness reduction ratio ranges from 11% to 17.5%.

[0014] In a class of this embedment, in the pipe rolling zone of the integrated piercing and rolling roll, a radial reduction ratio of the tube blank ranges from 8.5% to 12%; an entry cone angle ranges from 1 degree to 1.3 degrees; and an exit cone angle ranges from 1.7 degrees to 2.5 degrees.

[0015] In a class of this embedment, the integrated piercing and rolling roll comprises a metal non-contact region disposed between and connecting the piercing deformation zone and the pipe rolling zone; after being pierced and rounded, the tube blank does not directly contact the roll or the piercing plug within the metal non-contact region prior to entering the pipe rolling zone; a length of the metal non-contact region is from 0.25 to 0.32 times the diameter of the tube blank, and a maximum gorge diameter within the metal non-contact region is from 1.03 to 1.07 times the diameter of the tube blank.

[0016] In a class of this embodiment, each of the driven support guide rolls comprises a rolling surface and a piercing surface which operate at different rotational speeds, and the rolling surface is mounted to a corresponding driven support guide roll via a shaft-hole fit.

[0017] The disclosure also provides a method for producing a magnesium alloy seamless tube, the method comprising the steps of:

[0018] S1: pretreating a magnesium alloy bar stock by drilling a centering hole having a diameter from 10 mm to 15 mm at an end thereof, cleaning a surface of the bar stock with high-pressure water, drying the bar stock with a cold air blower, and subsequently charging the bar stock into an electric resistance heating furnace and heating the bar stock to a temperature from 300°C to 500°C for a soaking time from 0.6 to 2 hours;

[0019] S2: transporting the heated magnesium alloy bar stock from step S1 to a front end of the abovementioned production device for a magnesium alloy seamless tube using a V-shaped roller table;

[0020] S3: simultaneously inserting the mandrel with the piercing plug attached thereto into the pipe rolling zone of the production device, where the mandrel and a curved surface of the roll together define a piercing-rolling pass cavity, and maintaining a predetermined plug advance position;

[0021] S4: feeding the bar stock into a front section of the piercing deformation zone of the integrated piercing and rolling roll, where the roll rotates at a speed from 40 to 75 revolutions per minute (rpm), and a minor diameter of a roll gorge is from 78% to 90% of a diameter of the bar stock, whereby the bar stock, driven by a helical traction force of the roll and overcoming a hole-forming resistance of the piercing plug, achieves a first bite into the roll and is formed into a conical tube blank;

[0022] S5: immediately passing the conical tube blank from step S4 into the pipe rolling zone of the integrated piercing and rolling roll, where the conical tube blank, driven by a combined helical axial splitting force from opposing ends of the roll, undergoes a piercing-rolling operation of the conical tube blank to form a magnesium alloy tube blank; and

[0023] S6: after the piercing-rolling operation, retracting the mandrel, allowing the formed magnesium alloy tube blank to slide off to a cooling bed, and transferring the tube blank for air cooling.

[0024] The disclosure provides a method for producing a magnesium alloy seamless tube via a streamlined process employing strong traction on an integrated piercing and rolling roll. The method leverages the combined deformation advantages of skin-shear deformation from helical piercing and cavity formation within a multi-roll-surface system. This synergy induces a randomized evolution of wall thickness and axial microstructure, stimulates discrete mutations in crystal orientation, promotes uniformity of axial / radial structure, and weakens basal texture.

[0025] This approach is coupled with the localized deformation characteristics inherent to skew rolling using a shared, multi-surface roll. It enables the online sharing of the skin-shear traction load during the billet biting and hole-forming stage. Furthermore, the method optimally allocates the metal flow patterns between the piercing stage and the finish-rolling stage within the dual-stage deformation process of the integrated piercing and rolling operation. This coordinated control promotes the progression of microstructural evolution mechanisms within the initial tube blank, including dislocation slip, twinning, and dynamic recrystallization.

[0026] Consequently, while ensuring the successful completion of the piercing-rolling sequence, the method enhances piercing efficiency and enables highly efficient online rolling, thereby shortening the overall process flow. Upon completion of the first bite during piercing, the conical tube blank immediately enters the rolling stage of the integrated piercing and rolling roll. During rolling, an axial splitting traction force is concurrently applied to the tube blank, sharing the secondary biting pressure online. This integrated methodology achieves the high-precision and high-efficiency, streamlined production of high-performance magnesium alloy seamless tubes.

[0027] In addition, by employing a streamlined, integrated piercing and rolling process for the tube blank within a compact sequence, the method resolves the inherent conflict during the piercing of difficult-to-deform brittle metals between the derived dragging force from reduction and the constraining load imposed by the plug during hole formation. This ensures that immediately after the first bite forms the conical tube blank, the tube blank enters the rolling stage of the integrated piercing and rolling roll. During this rolling stage, an axial splitting traction force is provided to the tube blank, sharing the secondary biting pressure online. Consequently, the method achieves the high-precision and high-efficiency, streamlined production of high-performance magnesium alloy seamless tubes.

[0028] Furthermore, the method eliminates the intermediate reheating process required in conventional multi-step processes (e.g., billet piercing → cooling → reheating → offline rolling). This leads to increased production efficiency while simultaneously reducing the per-unit energy consumption.BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is a schematic diagram of a production device for a magnesium alloy seamless tube of the disclosure;

[0030] FIG. 2 is a sectional view of a production device for a magnesium alloy seamless tube of the disclosure; and

[0031] FIG. 3 is a schematic diagram of a driven support guide roll of the disclosure.DETAILED DESCRIPTION

[0032] To further illustrate the disclosure, embodiments detailing a device and method for the streamlined production of a magnesium alloy seamless tube are described below. It should be noted that the following embodiments are intended to describe and not to limit the disclosure.

[0033] As shown in FIGS. 1-3, the production device for a magnesium alloy seamless tube of the disclosure comprises:

[0034] a) an integrated piercing and rolling roll having a roll surface that defines both a piercing deformation zone and a pipe rolling zone, where the piercing deformation zone is configured to pierce a magnesium alloy billet to form a tube blank, and the pipe rolling zone is configured to receive the tube blank from the piercing deformation zone and to roll the tube blank such that the tube blank directly enters a rolling deformation after piercing is completed, whereby a piercing load and a rolling traction force are shared on a single roll;

[0035] b) at least a pair of driven support guide rolls disposed in a circumferential vacant region of the integrated piercing and rolling roll, where a roll surface of each of the driven support guide rolls comprises sections corresponding respectively to the piercing deformation zone and the pipe rolling zone, for constraining radial flow of the tube blank during formation;

[0036] c) a piercing plug disposed within the piercing deformation zone; and

[0037] d) a mandrel threadedly connected to the piercing plug and extending into the pipe rolling zone, where the piercing plug comprises a liner boss positioned corresponding to the pipe rolling zone.

[0038] In this disclosure, the piercing deformation zone refers to that portion of the roll surface configured to form a longitudinal cavity in a solid magnesium alloy billet through rotary piercing. The pipe rolling zone refers to that portion of the roll surface configured to subsequently reduce the wall thickness and diameter of the hollow shell received from the piercing deformation zone.

[0039] In certain embodiments, a maximum roll diameter in the piercing deformation zone of the integrated piercing and rolling roll is from 4 to 6 times a diameter of the tube blank; an entry cone angle ranges from 1.8 degrees to 3.2 degrees; an exit cone angle ranges from 3 degrees to 4.2 degrees; and a thickness reduction ratio ranges from 11% to 17.5%.

[0040] In certain embodiments, in the pipe rolling zone of the integrated piercing and rolling roll, a radial reduction ratio of the tube blank ranges from 8.5% to 12%; an entry cone angle ranges from 1 degree to 1.3 degrees; and an exit cone angle ranges from 1.7 degrees to 2.5 degrees.

[0041] In certain embodiments, the integrated piercing and rolling roll comprises a metal non-contact region disposed between and connecting the piercing deformation zone and the pipe rolling zone; after being pierced and rounded, the tube blank does not directly contact the roll or the piercing plug within the metal non-contact region prior to entering the pipe rolling zone; a length of the metal non-contact region is from 0.25 to 0.32 times the diameter of the tube blank, and a maximum gorge diameter within the metal non-contact region is from 1.03 to 1.07 times the diameter of the tube blank.

[0042] In certain embodiments, each of the driven support guide rolls comprises a rolling surface and a piercing surface which operate at different rotational speeds, and the rolling surface is mounted to a corresponding driven support guide roll via a shaft-hole fit.Example 1

[0043] The billet selected in this example is: an AZ31 magnesium alloy bar stock having original dimensions of 92 mm in outer diameter and 950 mm in length.

[0044] First, a centering hole having a diameter of about 15 mm and a depth of about 20 mm is formed at an end of the bar stock. The surface of the bar is cleaned with high-pressure water and dried with a high-speed blower. Subsequently, an electric resistance heating furnace is heated to 400°C. A quantity of five bar stock pieces are placed into the furnace. The temperature is then raised to 460°C along with the furnace, and maintained at this temperature for approximately half an hour. Thereafter, the bar stock is removed from the furnace.

[0045] The rolling mill is activated, with the roller speed set at about 60 rpm, the roll gorge diameter set at about 78 mm, and the mandrel advance set at about 55 mm. The heated bar stock is fed into the rolls. All five bar stock pieces are successfully pierced and elongated. The resulting pierced tube has an inner diameter of about 94.8 mm and a wall thickness of about 12 mm.

[0046] The pierced tube blank exhibits the following mechanical properties: a tensile strength of at least about 290 MPa, a yield strength of at least about 250 MPa, and an elongation after fracture of at least about 18%. The wall thickness tolerance between the head and tail ends of the tube is about 0.2 mm or less.Example 2

[0047] The billet selected in this example is an AZ61 magnesium alloy bar stock having original dimensions of about 40 mm in outer diameter and about 750 mm in length.

[0048] First, a centering hole having a diameter of about 10 mm and a depth of about 15 mm is formed at an end of the bar stock. The surface of the bar is cleaned with high-pressure water and subsequently dried with a high-speed blower. The bar stock is then heated to a temperature of about 420°C by means of induction-based online heating and held at this temperature in a soaking section for about 5 minutes.

[0049] The rolling mill is activated with a roller speed set at about 72 rpm, a roll gorge diameter set at about 34.5 mm, and a mandrel advance amount set at about 19 mm. The heated bar stock is then fed into the rolls. In a single batch, a total of eight bar stock pieces are successively pierced and elongated, all successfully. The resulting pierced tube has an inner diameter of about 32.5 mm and a wall thickness of about 4 mm.

[0050] The pierced tube blank exhibits the following mechanical properties: a tensile strength of at least about 320 MPa, a yield strength of at least about 273 MPa, and an elongation after fracture of at least about 14%. The wall thickness tolerance between the head and tail ends of the tube is about 0.15 mm or less.

[0051] It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications.

Claims

1. A production device for a magnesium alloy seamless tube, the device comprising:a) an integrated piercing and rolling roll having a roll surface that defines both a piercing deformation zone and a pipe rolling zone, wherein the piercing deformation zone is configured to pierce a magnesium alloy billet to form a tube blank, and the pipe rolling zone is configured to receive the tube blank from the piercing deformation zone and to roll the tube blank such that the tube blank directly enters a rolling deformation after piercing is completed, whereby a piercing load and a rolling traction force are shared on a single roll;b) at least a pair of driven support guide rolls disposed in a circumferential vacant region of the integrated piercing and rolling roll, wherein a roll surface of each of the driven support guide rolls comprises sections corresponding respectively to the piercing deformation zone and the pipe rolling zone, for constraining radial flow of the tube blank during formation;c) a piercing plug disposed within the piercing deformation zone; andd) a mandrel threadedly connected to the piercing plug and extending into the pipe rolling zone, wherein the piercing plug comprises a liner boss positioned corresponding to the pipe rolling zone.

2. The device of claim 1, wherein a maximum roll diameter in the piercing deformation zone of the integrated piercing and rolling roll is from 4 to 6 times a diameter of the tube blank; an entry cone angle ranges from 1.8 degrees to 3.2 degrees; an exit cone angle ranges from 3 degrees to 4.2 degrees; and a thickness reduction ratio ranges from 11% to 17.5%.

3. The device of claim 1, wherein in the pipe rolling zone of the integrated piercing and rolling roll, a radial reduction ratio of the tube blank ranges from 8.5% to 12%; an entry cone angle ranges from 1 degree to 1.3 degrees; and an exit cone angle ranges from 1.7 degrees to 2.5 degrees.

4. The device of claim 1, wherein the integrated piercing and rolling roll comprises a metal non-contact region disposed between and connecting the piercing deformation zone and the pipe rolling zone; after being pierced and rounded, the tube blank does not directly contact the roll or the piercing plug within the metal non-contact region prior to entering the pipe rolling zone; a length of the metal non-contact region is from 0.25 to 0.32 times the diameter of the tube blank, and a maximum gorge diameter within the metal non-contact region is from 1.03 to 1.07 times the diameter of the tube blank.

5. The device of claim 1, wherein each of the driven support guide rolls comprises a rolling surface and a piercing surface which operate at different rotational speeds, and the rolling surface is mounted to a corresponding driven support guide roll via a shaft-hole fit.

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