A manufacturing process of a magnesium alloy gas cylinder with one end sealed

Abstract

The application relates to the technical field of high-pressure containers, in particular to a manufacturing process of a magnesium alloy gas cylinder with a sealed bottom. First, suitable rod materials are selected, homogenization treatment is carried out on the rod materials, internal segregation of the cast rod is eliminated, the treated cast rod is extruded to obtain a once-extruded solid rod, the once-extruded solid rod is forged to obtain a forged cylinder with a sealed bottom; the straight cylinder part of the forged cylinder is heated and subjected to multi-pass strong spinning; the material stacking area at the front end of the straight cylinder is sawed, then the material stacking area is closed and the mouth is thickened, the blank extends 130mm out of the die; finally, the mouth is sawed, 32mm of the mouth is reserved, PZ19.2 taper threads are processed at the mouth, and the magnesium alloy gas cylinder with a sealed bottom is obtained. The magnesium alloy gas cylinder prepared in the way solves the anisotropy and deformation temperature sensitivity of the magnesium alloy material, greatly improves the spinnability of the magnesium alloy gas cylinder body and the uniformity of the magnesium alloy gas cylinder body organization, and the magnesium alloy gas cylinder with excellent performance can be obtained.

Description

Technical Field

[0001] This invention relates to the field of high-pressure vessel technology, and in particular to a manufacturing process for a magnesium alloy gas cylinder that can be sealed at one end. Background Technology

[0002] Gas cylinders, as the most common pressure vessels, are widely used in chemical, energy, metallurgical, medical, and aerospace fields. Currently, the global development trend of high-pressure gas cylinders is from Type I to Type IV. Although steel pressure gas cylinders represent the most mature and lowest-cost technology, their heavy weight makes them unsuitable for applications such as automotive and portable medical cylinders.

[0003] Currently, Type III / IV gas cylinders with aluminum alloy / plastic inner liner and carbon fiber outer layer are gradually replacing steel gas cylinders. However, the high cost of carbon fiber winding material is the main factor restricting its widespread adoption. Compared with the 6061 aluminum alloy used in Type III cylinders, some magnesium alloys have comparable mechanical properties and can further reduce weight by 1 / 3. Therefore, in application scenarios where lightweighting is more urgent, magnesium alloy gas cylinders have more advantages than aluminum alloy gas cylinders.

[0004] Magnesium has a close-packed hexagonal structure with strong anisotropy, making it difficult to deform. Moreover, magnesium has a much higher heat dissipation performance than aluminum, requiring timely heat replenishment during hot deformation. Therefore, magnesium alloy gas cylinders prepared by existing methods have low spinnability and low uniformity of cylinder structure, resulting in lower performance of magnesium alloy gas cylinders. Summary of the Invention

[0005] The purpose of this invention is to provide a manufacturing process for a magnesium alloy gas cylinder with one end sealed. This invention aims to solve the technical problems of magnesium having a close-packed hexagonal structure, strong anisotropy, and difficulty in deformation, as well as the fact that magnesium has a much higher heat dissipation performance than aluminum and requires timely heat replenishment during hot deformation. Therefore, the existing methods produce magnesium alloy gas cylinders with low rotatability and low uniformity of the cylinder structure, resulting in lower performance of the magnesium alloy gas cylinder.

[0006] To achieve the above objectives, the present invention employs a manufacturing process for a magnesium alloy gas cylinder with one end sealed, comprising the following steps:

[0007] Step 1: Homogenization of cast rods: First, select a semi-continuous cast rod of conventional AZ31 magnesium alloy, turn off the surface oxide scale and coarse grain layer to obtain a Φ505mm rod, and perform homogenization treatment at 320℃ for 2h + 380℃ for 6h to eliminate segregation inside the cast rod.

[0008] Step 2, primary extrusion deformation: The cast rod after homogenization in Step 1 is extruded and deformed to obtain a solid rod with a diameter of Φ300mm.

[0009] Step 3, Secondary forging deformation: The bar obtained in Step 2 is placed into a mold for forging deformation to obtain a forging cylinder with one end sealed; after forging, the inner and outer surfaces are bored and turned, and the surface roughness of the inner and outer surfaces is less than Ra1.6μm;

[0010] Step 4, Strong spinning and thinning: After heating the straight cylindrical part of the forging cylinder in Step 3 at 320℃ for 2 hours in an electric resistance furnace, use a three-wheel horizontal strong spinning machine to perform multiple strong spinning passes; the core die speed is S60~S200, the feed rate is F50~F200, the three spinning wheels are staggered by 2mm, and the spinning wheel angle is 22°.

[0011] Step 5, Hot Spinning and Closing: The material stacking area at the front end of the straight cylinder in Step 4 is sawn off, and then a closing spinning machine is used to close and thicken the mouth. The billet extends 130mm out of the mold. Elliptical forward spinning is used for thickening, with the core mold speed S300 and the feed rate F800. The 9th pass in the middle is reverse spinning to obtain the bottle mouth shape. The last pass is reverse spinning and shaping, and the feed rate is changed to F500.

[0012] Step 6, Thread Machining: Sawing the bottle mouth to retain a 32mm length, and machining a PZ19.2 tapered thread at the bottle mouth.

[0013] In step two, when the casting rod is extruded and deformed, the temperature of the extruded billet is 300-320℃, the temperature of the die is 300℃, and the extrusion speed is 1-10mm / s.

[0014] In step three, when the bar is forged and deformed, the temperature of the forging billet is 300-320℃, the temperature of the die is 300℃, and the end face of the forging cylinder is chamfered.

[0015] In step four, during the strong spinning and thinning process, an infrared thermometer is used for online temperature measurement. When the bottle temperature is <250℃, a flame torch is used for online heat replenishment. The process ends when the wall thickness of the straight cylinder is reduced to an outer diameter of 159+0.5+0.2mm.

[0016] In step five, during the hot-spinning process, an infrared thermometer is used to measure the temperature online, and a flame torch is used continuously to supplement the heat, ensuring that the temperature of the blank at the closing point is within the range of 380 to 420°C.

[0017] In step six, the PZ19.2 tapered thread at the bottle mouth is machined using a special industrial gas cylinder thread machining machine.

[0018] The present invention discloses a manufacturing process for a magnesium alloy gas cylinder with one end sealed. First, a semi-continuous casting ingot of conventional AZ31 magnesium alloy is selected. The surface oxide scale and coarse grain layer are removed by turning to obtain a Φ505mm ingot. The ingot is then subjected to homogenization treatment at 320℃ for 2 hours followed by 380℃ for 6 hours to eliminate internal segregation. The homogenized ingot is then extruded to obtain a Φ300mm solid extruded ingot. This solid ingot is then placed in a die for forging to obtain a forged cylinder with one end sealed. After forging, the inner and outer surfaces are bored and turned, with the surface roughness less than Ra1.6μm. The straight section of the forged cylinder is heated in a resistance furnace at 320℃ for 2 hours, followed by multiple passes of strong spinning using a three-wheeled horizontal high-speed spinning machine. The mandrel speed is S60~S200, and the feed rate is F50~F20. 0. The three spinning wheels are staggered by 2mm and the spinning wheel angle is 22°. The material accumulation area at the front end of the straight cylinder is sawn off, and then a necking spinning machine is used to neck and thicken the mouth. The billet extends 130mm out of the mold. Elliptical forward spinning is used for thickening. The core mold speed is S300 and the feed rate is F800. The 9th pass in the middle is reverse spinning to obtain the bottle mouth shape. The last pass is reverse spinning and shaping, and the feed rate is changed to F500. Finally, the bottle mouth is sawn off, leaving a 32mm length of bottle mouth. PZ19.2 tapered thread is machined at the bottle mouth to obtain a magnesium alloy gas cylinder with one end sealed. The magnesium alloy gas cylinder made in this way solves the anisotropy and deformation temperature sensitivity problems of magnesium alloy materials, greatly improves the spinnability of the magnesium alloy gas cylinder body and the uniformity of the cylinder body structure, and can obtain magnesium alloy gas cylinders with excellent performance. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of the steps in Embodiment 1 of the present invention.

[0021] Figure 2 This is a flowchart of the steps in Embodiment 2 of the present invention.

[0022] Figure 3 This is a flowchart of the steps in Embodiment 3 of the present invention.

[0023] Figure 4 This refers to the forging cylinder blank drawing in step S2 of the present invention.

[0024] Figure 5 This is a three-coordinate measurement diagram of the hot-spinning and closing process in step S5 of the present invention.

[0025] Figure 6 These are metallographic images of the inner and outer surfaces of the gas cylinders in Examples 1-3. Detailed Implementation

[0026] Example 1: Please refer to Figure 1 , Figure 1 This is a flowchart of the steps in Embodiment 1 of the present invention. The present invention provides a manufacturing process for a magnesium alloy gas cylinder with one end sealed, comprising the following steps:

[0027] Step 1: Homogenization of cast rods: First, select a semi-continuous cast rod of conventional AZ31 magnesium alloy, turn off the surface oxide scale and coarse grain layer to obtain a Φ505mm rod, and perform homogenization treatment at 320℃ for 2h + 380℃ for 6h to eliminate segregation inside the cast rod.

[0028] Step 2, primary extrusion deformation: The cast rod after homogenization in Step 1 is extruded and deformed to obtain a solid rod with a diameter of 300mm. The extrusion billet temperature is 305℃, the die temperature is 300℃, and the extrusion speed is 5mm / s.

[0029] Step 3, Secondary forging deformation: The bar obtained in Step 2 is placed into the mold for forging deformation to obtain a forging cylinder with one end sealed; the forging billet temperature is 311℃, and the mold temperature is 300℃; after forging, the inner and outer surfaces are bored and turned, and the surface roughness of the inner and outer surfaces is less than Ra1.6μm;

[0030] Step 4, Strong Swirling Thinning: After heating the straight cylindrical part of the forging cylinder in Step 3 at 320℃ for 2 hours in an electric resistance furnace, it is then subjected to multiple strong swirls using a three-wheel horizontal strong swirl machine; the mandrel speed is S60, the feed rate is F100, the three swirl wheels are staggered by 2mm, and the swirl wheel angle is 22°. During the strong swirl thinning process, an infrared thermometer is used for online temperature measurement. When the bottle temperature is <250℃, a flame torch is used for online reheating. The process ends when the wall thickness of the straight cylindrical part is reduced to an outer diameter of 159.4mm.

[0031] Step 5, Hot Spinning and Closing: The material stacking area at the front end of the straight cylinder in Step 4 is sawn off, and then a closing spinning machine is used to close and thicken the mouth. The billet extends 130mm out of the mold. Elliptical forward spinning is used for thickening, with the core mold speed S300 and the feed rate F800. The 9th pass in the middle is reverse spinning to obtain the bottle mouth shape. The last pass is reverse spinning and shaping, and the feed rate is changed to F500.

[0032] Step 6, Thread Machining: Sawing is performed on the bottle mouth, leaving a 32mm length of bottle mouth. PZ19.2 tapered thread is then machined on the bottle mouth using an industrial gas cylinder thread machining machine.

[0033] In step one, the magnesium alloy bottle material is not limited to AZ31. Any material with an elongation rate >12% after extrusion deformation can be used as the bottle material, and materials with higher yield strength have better pressure resistance than AZ31.

[0034] Metallographic experiments were conducted on samples taken from the inner and outer surfaces of the extruded, forged, and spun cylinders, with grain sizes of 11.5, 11, 9.5, and 11, respectively. Tensile tests were performed on samples taken from the straight section of the spun cylinder along the spun direction, yielding the following results: yield strength (178 MPa), tensile strength (274 MPa), and elongation (24.7%). The residual deformation rate under a peak pressure of 22.5 MPa was 2.3% when pressure was applied using a hydraulic pressure testing device. The burst pressure was 28.4 MPa when pressure was applied using a hydraulic pressure burst testing device.

[0035] Example 2: Please refer to Figure 2 , Figure 2 This is a flowchart of the steps in Embodiment 2 of the present invention. The present invention provides a manufacturing process for a magnesium alloy gas cylinder with one end sealed, comprising the following steps:

[0036] Step 1: Homogenization of cast rods: First, select a semi-continuous cast rod of conventional AZ31 magnesium alloy, turn off the surface oxide scale and coarse grain layer to obtain a Φ505mm rod, and perform homogenization treatment at 320℃ for 2h + 380℃ for 6h to eliminate segregation inside the cast rod.

[0037] Step 2, primary extrusion deformation: The cast rod after homogenization in Step 1 is extruded and deformed to obtain a solid rod with a diameter of Φ300mm. The extrusion billet temperature is 316℃, the die temperature is 300℃, and the extrusion speed is 7mm / s.

[0038] Step 3, Secondary forging deformation: The bar obtained in Step 2 is placed into the mold for forging deformation to obtain a forging cylinder with one end sealed; the forging billet temperature is 304℃, and the mold temperature is 300℃; after forging, the inner and outer surfaces are bored and turned, and the surface roughness of the inner and outer surfaces is less than Ra1.6μm;

[0039] Step 4, Strong Swirling Thinning: After heating the straight cylindrical part of the forging cylinder in Step 3 at 320℃ for 2 hours in an electric resistance furnace, it is then subjected to multiple strong swirls using a three-wheel horizontal strong swirl machine; the mandrel speed is S100, the feed rate is F200, the three swirls are offset by 2mm, and the swirl angle is 22°. During the strong swirl thinning process, an infrared thermometer is used for online temperature measurement. When the bottle temperature is <250℃, a flame torch is used for online reheating. The process ends when the wall thickness of the straight cylindrical part is reduced to an outer diameter of 159.1mm.

[0040] Step 5, Hot Spinning and Closing: The material stacking area at the front end of the straight cylinder in Step 4 is sawn off, and then a closing spinning machine is used to close and thicken the mouth. The billet extends 130mm out of the mold. Elliptical forward spinning is used for thickening, with the core mold speed S300 and the feed rate F800. The 9th pass in the middle is reverse spinning to obtain the bottle mouth shape. The last pass is reverse spinning and shaping, and the feed rate is changed to F500.

[0041] Step 6, Thread Machining: Sawing is performed on the bottle mouth, leaving a 32mm length of bottle mouth. PZ19.2 tapered thread is then machined on the bottle mouth using an industrial gas cylinder thread machining machine.

[0042] In step one, the magnesium alloy bottle material is not limited to AZ31. Any material with an elongation rate >12% after extrusion deformation can be used as the bottle material, and materials with higher yield strength have better pressure resistance than AZ31.

[0043] Metallographic experiments were conducted on samples taken from the inner and outer surfaces of the extruded, forged, and spun cylinders, with grain sizes of 10.5, 11, 10.5, and 11, respectively. Tensile tests were performed on samples taken from the straight section of the spun cylinder along the spun direction, with the following results: yield strength (202 MPa), tensile strength (279 MPa), and elongation (22.5%). The residual deformation rate under a peak pressure of 22.5 MPa was 1.4% when pressure was applied using a hydraulic pressure testing device. The burst pressure was 29.2 MPa when pressure was applied using a hydraulic pressure burst testing device.

[0044] Example 3: Please refer to Figure 3 , Figure 3 This is a flowchart of the steps in Embodiment 3 of the present invention. The present invention provides a manufacturing process for a magnesium alloy gas cylinder with one end sealed, comprising the following steps:

[0045] Step 1: Homogenization of cast rods: First, select a semi-continuous cast rod of conventional AZ31 magnesium alloy, turn off the surface oxide scale and coarse grain layer to obtain a Φ505mm rod, and perform homogenization treatment at 320℃ for 2h + 380℃ for 6h to eliminate segregation inside the cast rod.

[0046] Step 2, primary extrusion deformation: The cast rod after homogenization in Step 1 is extruded and deformed to obtain a solid rod with a diameter of Φ300mm. The extrusion billet temperature is 309℃, the die temperature is 300℃, and the extrusion speed is 2mm / s.

[0047] Step 3, Secondary forging deformation: The bar obtained in Step 2 is placed into the mold for forging deformation to obtain a forging cylinder with one end sealed; the forging billet temperature is 306℃, and the mold temperature is 300℃; after forging, the inner and outer surfaces are bored and turned, and the surface roughness of the inner and outer surfaces is less than Ra1.6μm;

[0048] Step 4, Strong Swirling Thinning: After heating the straight cylindrical part of the forging cylinder in Step 3 at 320℃ for 2 hours in an electric resistance furnace, it is then subjected to multiple strong swirls using a three-wheel horizontal strong swirl machine; the mandrel speed is S150, the feed rate is F100, the three swirl wheels are staggered by 2mm, and the swirl wheel angle is 22°. During the strong swirl thinning process, an infrared thermometer is used for online temperature measurement. When the bottle temperature is <250℃, a flame torch is used for online supplementary heating. The process ends when the wall thickness of the straight cylindrical part is reduced to an outer diameter of 159.2mm.

[0049] Step 5, Hot Spinning and Closing: The material stacking area at the front end of the straight cylinder in Step 4 is sawn off, and then a closing spinning machine is used to close and thicken the mouth. The billet extends 130mm out of the mold. Elliptical forward spinning is used for thickening, with the core mold speed S300 and the feed rate F800. The 9th pass in the middle is reverse spinning to obtain the bottle mouth shape. The last pass is reverse spinning and shaping, and the feed rate is changed to F500.

[0050] Step 6, Thread Machining: Sawing is performed on the bottle mouth, leaving a 32mm length of bottle mouth. PZ19.2 tapered thread is then machined on the bottle mouth using an industrial gas cylinder thread machining machine.

[0051] In step one, the magnesium alloy bottle material is not limited to AZ31. Any material with an elongation rate >12% after extrusion deformation can be used as the bottle material, and materials with higher yield strength have better pressure resistance than AZ31.

[0052] Metallographic experiments were conducted on samples taken from the inner and outer surfaces of the extruded, forged, and spun cylinders, with grain sizes of 11, 11, 10, and 11, respectively. Tensile tests were performed on samples taken from the straight section of the spun cylinder along the spun direction, with the following results: yield strength (198 MPa), tensile strength (278 MPa), and elongation (23.4%). The residual deformation rate under a peak pressure of 22.5 MPa was 1.6% when pressure was applied using a hydraulic pressure testing device. The burst pressure was 28.7 MPa when pressure was applied using a hydraulic pressure burst testing device.

[0053] As can be seen from the results of the above embodiments, the 15MPa-grade AZ31 magnesium alloy gas cylinder manufactured by the method for manufacturing a magnesium alloy gas cylinder with one end sealed by the present invention exhibits fine grains after two deformation processes: extrusion and forging, effectively ensuring the plasticity of deformation flow. The strong spinning process has a significant impact on the final product's dimensions and performance. Appropriately increasing the spindle speed and reducing the spinning wheel feed rate can alleviate material accumulation, resulting in an increased length of the straight cylinder section, sufficient stress on the inner and outer surfaces, small grain size differences, and improved tensile yield properties. The prepared gas cylinders underwent hydrostatic testing, with residual deformation rates all <5%; and hydrostatic burst testing showed burst pressures all >28MPa, meeting the design standard value for a gas cylinder with a nominal pressure of 15MPa.

[0054] Table 1 Summary of test results for the embodiments

[0055]

[0056] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A manufacturing process for a magnesium alloy gas cylinder with one end sealed, characterized in that, Includes the following steps: Step 1: Homogenization of cast rods: First, select a semi-continuous cast rod of conventional AZ31 magnesium alloy, turn off the surface oxide scale and coarse grain layer to obtain a Φ505mm rod, and perform homogenization treatment at 320℃ for 2h + 380℃ for 6h to eliminate segregation inside the cast rod. Step 2, primary extrusion deformation: The cast rod after homogenization in Step 1 is extruded and deformed to obtain a solid rod with a diameter of Φ300mm. Step 3, Secondary forging deformation: The bar obtained in Step 2 is placed into a mold for forging deformation to obtain a forging cylinder with one end sealed; after forging, the inner and outer surfaces are bored and turned, and the surface roughness of the inner and outer surfaces is less than Ra1.6μm; Step 4, Strong spinning and thinning: After heating the straight cylindrical part of the forging cylinder in Step 3 at 320℃ for 2 hours in an electric resistance furnace, use a three-wheel horizontal strong spinning machine to perform multiple strong spinning passes; the core die speed is S60~S200, the feed rate is F50~F200, the three spinning wheels are staggered by 2mm, and the spinning wheel angle is 22°. Step 5, Hot Spinning and Closing: The material stacking area at the front end of the straight cylinder in Step 4 is sawn off, and then a closing spinning machine is used to close and thicken the mouth. The billet extends 130mm out of the mold. Elliptical forward spinning is used for thickening, with the core mold speed S300 and the feed rate F800. The 9th pass in the middle is reverse spinning to obtain the bottle mouth shape. The last pass is reverse spinning and shaping, and the feed rate is changed to F500. Step 6, Thread Machining: Sawing the bottle mouth to retain a 32mm length, and machining a PZ19.2 tapered thread at the bottle mouth.

2. The manufacturing process of the magnesium alloy gas cylinder with one end sealed as described in claim 1, characterized in that, In step two, when the cast rod is extruded and deformed, the extrusion billet temperature is 300-320℃, the die temperature is 300℃, and the extrusion speed is 1-10mm / s.

3. The manufacturing process of the magnesium alloy gas cylinder with one end sealed as described in claim 2, characterized in that, In step three, when the bar is forged and deformed, the temperature of the forging billet is 300-320℃, the temperature of the die is 300℃, and the end face of the forging cylinder is chamfered.

4. The manufacturing process of the magnesium alloy gas cylinder with one end sealed as described in claim 3, characterized in that, In step four, an infrared thermometer is used to measure the temperature online during the strong spinning and thinning process. When the bottle temperature is <250℃, a flame torch is used for online heat supplementation. The process ends when the wall thickness of the straight cylinder is reduced to an outer diameter of 159+0.5+0.2mm.

5. The manufacturing process of the magnesium alloy gas cylinder with one end sealed as described in claim 4, characterized in that, In step five, an infrared thermometer is used to measure the temperature online during the hot spinning process, and a flame torch is used continuously to supplement the heat, ensuring that the temperature of the blank at the closing point is within the range of 380 to 420°C.

6. The manufacturing process of the magnesium alloy gas cylinder with one end sealed as described in claim 5, characterized in that, In step six, the PZ19.2 tapered thread at the bottle mouth is machined using a special industrial gas cylinder thread machining machine.

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