Bar extrusion production method for forging 6063 aluminum alloy gas cylinder

Abstract

The invention provides a 6063 aluminum alloy gas cylinder forging bar extrusion production method which comprises the steps of burdening, casting, cast bar homogenization, extrusion, quenching, online drawing, fixed-length cutting and finished product annealing, in the extrusion process, an extrusion die comprises a flow guide plate and a die which are connected with each other, a flow guide pit is formed in the center of the flow guide plate and is a cylindrical through hole, and the flow guide hole is communicated with the die. The working chamber comprises a first conical area, a second conical area and a cylindrical area which are sequentially connected. By optimizing the alloy component proportion, extrusion stripes and oxidation flaws are reduced, the overall strength and subsequent machinable plasticity and turning performance of the bar for gas cylinder forging are improved, the supersaturated solid solution degree after quenching is inhibited by reducing the ingot casting homogenizing temperature and the extrusion cooling rate, and the yield of the bar for gas cylinder forging is improved. The ductility and the uniformity of the bar for forging the gas cylinder are greatly improved, and mechanical lines cannot be generated on the surface of the gas cylinder obtained after forging.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy processing technology, and specifically discloses a method for extruding bars for forging 6063 aluminum alloy gas cylinders. Background Art

[0002] With the continuous development of automotive lightweight technology, aluminum alloys are widely used in the field of automotive parts due to their lightweight, corrosion resistance, good plasticity, etc. 6063 aluminum alloy gas cylinders are mainly used for pressure-bearing parts in the automotive fuel system and are obtained by extruding bars for forging aluminum alloy gas cylinders. However, for the aluminum alloy gas cylinders produced by the existing conventional extrusion process and molds, during the subsequent cold forging process, defects such as surface cracks along the extrusion direction and excessive roughness after forging deformation occur, resulting in a sharp increase in the scrap rate of forging aluminum alloy gas cylinders. At the same time, the dimensional accuracy requirements for the bar diameter of the bars for forging gas cylinders are relatively strict, with the bar diameter accuracy requirement being ±0.15 mm. However, during the extrusion and stretching process of the bars for forging gas cylinders, due to the limitations of the stretching process, the diameter dimensional accuracy of the stretched bars cannot meet the forging requirements. The accuracy that can be achieved in the existing process is ±0.3 mm. Due to the poor dimensions, the scrap ratio of the bars for forging gas cylinders is very high. At the same time, in the subsequent forging process, the bars for forging gas cylinders cannot match the forging molds, often causing production interruptions and other situations. In addition, in the existing technology, in order to ensure the theoretical yield of the bars for forging gas cylinders, an extruder with a larger tonnage is usually selected for production, resulting in high extrusion costs. Moreover, a larger tonnage of the extruder will cause an increase in the deformation degree of the ingot during the extrusion process. Therefore, it is necessary to select a large-tonnage ingot at the same time. However, during the melting process of the large-tonnage ingot, due to the difference in the cooling process, the grain size of the ingot cross-section is small at the edge and large at the center. Therefore, during the extrusion process, the larger grains at the center are inherited into the extruded profiles. At the same time, in order to achieve stable and continuous production, water tank cooling is usually used during the quenching process. If the cooling speed is too fast, it will cause an increase in the internal stress of the extruded bars. The large internal energy storage has nowhere to release. Subsequently, during the subsequent heat treatment process, the internal structure of the metal will develop towards a stable state under the influence of the pre-existing internal stress, resulting in an increase in the static recrystallization temperature of the metal. Therefore, when the bars are heat-treated at a low temperature to improve their properties, the heat treatment temperature cannot be selected as high-temperature annealing, but only low-temperature annealing. Low-temperature annealing is not only time-consuming and laborious, but also the annealing effect is far lower than that of high-temperature long-time annealing. When the bars for forging gas cylinders obtained by the existing technology are forged subsequently, the ductility of the bars is poor, and the mechanical lines on the surface of the forged gas cylinders are relatively serious, unable to meet the requirements of subsequent surface treatment. In view of the above existing problems, it is very necessary to research and design a new method for extruding bars for forging 6063 aluminum alloy gas cylinders to overcome the problems existing in the existing extrusion production of bars for forging aluminum alloy gas cylinders. Summary of the Invention

[0003] In order to solve the problems existing in the extrusion production of bars for forging aluminum alloy gas cylinders, such as poor bar accuracy, poor bar ductility, and severe mechanical lines on the surface of the gas cylinders obtained after forging, a bar extrusion production method for forging 6063 aluminum alloy gas cylinders is proposed.

[0004] The present invention provides a bar extrusion production method for forging 6063 aluminum alloy gas cylinders, including the following steps: S1. Batching: Prepare aluminum alloy raw materials according to the following weight ratio: Si: 0.40% - 0.45%, Fe: 0.15% - 0.25%, Cu: 0.05% - 0.1%, Mn: ≤0.10%, Mg: 0.60% - 0.65%, Cr: 0.05% - 0.10%, Zn: ≤0.10%, single impurity: ≤0.05%, total impurity: ≤0.15%, and the balance is Al;

[0005] S2. Melting and casting: Put the prepared aluminum alloy raw materials in step S1 into a melting furnace for melting and casting to obtain a cast bar;

[0006] S3. Homogenization of the cast bar: Perform homogenization treatment on the cast bar obtained in step S2 to obtain a round ingot. The homogenization temperature is 460°C - 500°C, and the homogenization time is 6h - 8h;

[0007] S4. Extrusion: Put the round ingot obtained in step S3 into an extrusion device for extrusion molding to obtain a bar. The extrusion die includes a deflector plate and a die connected to each other. A diversion pit is provided at the center of the deflector plate. The diversion pit is a cylindrical through-hole. The diameter of the diversion pit is 55mm - 65mm, and the thickness of the diversion pit is 35mm - 45mm. A working chamber is provided at the corresponding position of the center of the die and the cylindrical opening. The working chamber includes a first conical zone, a working belt, a second conical zone, and a cylindrical zone connected in sequence. The diameter of the entrance of the first conical zone is equal to the diameter of the opening of the diversion pit. The diameter of the exit of the first conical zone is smaller than the diameter of the entrance of the first conical zone. The diameter of the working belt is equal to the diameter of the exit of the first conical zone. The diameter of the entrance of the second conical zone is equal to the diameter of the working belt. The diameter of the exit of the second conical zone is larger than the diameter of the entrance of the second conical zone. The diameter of the cylindrical zone is equal to the diameter of the exit of the second conical zone. The temperature of the extrusion die is set at 495°C - 515°C, the temperature of the round ingot is set at 440°C - 460°C, the extrusion speed is set at 5.5m / min - 7.5m / min, and the drawing speed is set at 5.5m / min - 7.5m / min;

[0008] S5. Quenching, online drawing, and sizing cutting: Quench the bar obtained in step S5. The quenching method is spray cooling. The temperature of the bar after quenching is ≥300°C. Straighten the quenched bar by stretching and then cut it into a specified length;

[0009] S6. Finish annealing: Anneal the cut bars obtained in step S5 under an annealing regime of 330 ± 5°C × 3 ± 0.5 h, and slowly cool them in the furnace to room temperature to obtain bars for forging gas cylinders.

[0010] For an extrusion production method of bars for forging 6063 aluminum alloy gas cylinders according to some embodiments of the present application, in step S1, the batching is as follows: Si: 0.41% - 0.45%, Fe: 0.15% - 0.20%, Cu: 0.06% - 0.09%, Mn: ≤0.05%, Mg: 0.62% - 0.65%, Cr: 0.06% - 0.09%, Zn: ≤0.10%, single impurity: ≤0.05%, total impurities: ≤0.15%, and the balance is Al.

[0011] For an extrusion production method of bars for forging 6063 aluminum alloy gas cylinders according to some embodiments of the present application, in step S1, the batching is as follows: Si: 0.41% - 0.42%, Fe: 0.15% - 0.18%, Cu: 0.08% - 0.09%, Mn: ≤0.05%, Mg: 0.63% - 0.65%, Cr: 0.08% - 0.09%, Zn: ≤0.10%, single impurity: ≤0.05%, total impurities: ≤0.15%, and the balance is Al.

[0012] For an extrusion production method of bars for forging 6063 aluminum alloy gas cylinders according to some embodiments of the present application, in step S2, semi - continuous casting is used for melting and casting. During the melting and casting process, bipolar foam ceramic filtration is adopted to filter non - metals and metal inclusions, and Al - Ti - B wire is used to refine the grains. The addition amount of scrap aluminum is controlled to be ≤10%. The melting temperature during melting and casting is 760°C - 800°C, and the refining temperature is 730°C - 760°C.

[0013] For an extrusion production method of bars for forging 6063 aluminum alloy gas cylinders according to some embodiments of the present application, in step S3, the diameter of the round ingot is 254 mm.

[0014] For an extrusion production method of bars for forging 6063 aluminum alloy gas cylinders according to some embodiments of the present application, in step S3, the cooling method for homogenization of the cast bar is water mist cooling.

[0015] For an extrusion production method of bars for forging 6063 aluminum alloy gas cylinders according to some embodiments of the present application, in step S4, extrusion is carried out by a 2750T horizontal extrusion press.

[0016] A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder according to some embodiments of the present application. In step S4, the distance from the inlet of the first conical zone to the outlet of the first conical zone is 25 mm, the diameter of the outlet of the first conical zone is 30 mm, and the length of the working belt is 5 mm to 10 mm.

[0017] A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder according to some embodiments of the present application. In step S4, the diameter of the inlet of the second conical zone is 30 mm, the diameter of the outlet of the second conical zone is 40 mm to 50 mm, and the distance from the inlet of the second conical zone to the outlet of the second conical zone is 20 mm.

[0018] A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder according to some embodiments of the present application. In step S6, the diameter of the bar for forging the gas cylinder is 30 mm.

[0019] A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder proposed by the present invention. By optimizing the alloy composition ratio, reducing the Fe and Si contents, controlling the addition amount of Mn / Cr, reducing extrusion stripes and oxidation defects, improving the overall strength of the bar for forging the gas cylinder and the subsequent workable plasticity and turning performance. By reducing the ingot homogenization temperature and the extrusion cooling rate, the supersaturated solid solution degree after quenching is inhibited. At the same time, a drawing and sizing operation is added after online cooling, so that the surface roughness of the bar for forging the gas cylinder produced is reduced, and the product size accuracy can reach ±0.1 mm, improving the accuracy of the bar for forging the gas cylinder. The bar for forging the gas cylinder can meet the requirements that after annealing or quenching treatment at a heat treatment temperature ≤ 500 °C, the grain grades of the matrix edge, middle and center of the bar for forging the gas cylinder are ≥ 2.5 levels, and the difference in grain grades is ≤ 1 level, and the ductility and uniformity are greatly improved, and no mechanical lines will be generated on the surface of the gas cylinder obtained after forging. Brief Description of the Drawings

[0020] Figure 1 It is a schematic flow chart of a method for extruding a bar for forging a 6063 aluminum alloy gas cylinder in the present invention;

[0021] Figure 2 It is a schematic diagram of the extrusion die structure in Embodiment 1 of the present invention;

[0022] Figure 3 It is a macrostructure diagram of a bar for forging a 6063 aluminum alloy gas cylinder produced by the prior art;

[0023] Figure 4 It is a macrostructure diagram of a bar for forging a 6063 aluminum alloy gas cylinder produced in Embodiment 2 of the present invention;

[0024] Figure 5The surface condition diagram of the gas cylinder forged from the bar for forging 6063 aluminum alloy gas cylinders produced by the prior art;

[0025] Figure 6 The surface condition diagram of the gas cylinder forged from the bar for forging 6063 aluminum alloy gas cylinders produced in Example 2 of the present invention;

[0026] Figure 7 The macrostructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Example 3 of the present invention;

[0027] Figure 8 The microstructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Example 3 of the present invention;

[0028] Figure 9 The macrostructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Example 4 of the present invention;

[0029] Figure 10 The microstructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Example 4 of the present invention;

[0030] Figure 11 The macrostructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Example 5 of the present invention;

[0031] Figure 12 The microstructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Example 5 of the present invention;

[0032] Figure 13 The macrostructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Example 6 of the present invention;

[0033] Figure 14 The microstructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Example 6 of the present invention;

[0034] Figure 15 The macrostructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Example 7 of the present invention;

[0035] Figure 16 The microstructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Example 7 of the present invention;

[0036] Figure 17 The macrostructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Comparative Example 1 of the present invention;

[0037] Figure 18 The microstructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Comparative Example 1 of the present invention;

[0038] Figure 19 The macrostructure diagram of the bar for forging 6063 aluminum alloy gas cylinders produced in Comparative Example 2 of the present invention;

[0039] Figure 20 This is the high-magnification micrograph of the bar for forging 6063 aluminum alloy gas cylinders produced in Comparative Example 2 of the present invention.

[0040] In the figure, 1 is the flow guide plate, 1-1 is the flow guide pit, 2 is the die, 2-1 is the first conical zone, 2-2 is the working belt, 2-3 is the second conical zone, and 2-4 is the cylindrical zone. Specific Embodiments

[0041] The following further describes in detail the embodiments of the present invention in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0042] Example 1. This example provides an extrusion production method for bars for forging 6063 aluminum alloy gas cylinders, as Figure 1 shown, including the following steps:

[0043] S1. Batching: Prepare aluminum alloy raw materials according to the following weight ratio: Si: 0.40% - 0.45%, Fe: 0.15% - 0.25%, Cu: 0.05% - 0.1%, Mn: ≤0.10%, Mg: 0.60% - 0.65%, Cr: 0.05% - 0.10%, Zn: ≤0.10%, single impurity: ≤0.05%, total impurity: ≤0.15%, and the balance is Al;

[0044] The core of the composition design of 6063 aluminum alloy is to precisely control the Mg-Si balance, supplemented by Fe impurity management and trace element optimization, and combined with the coordinated regulation of homogenization, extrusion and aging processes. The control of Fe element includes impurity control and optimization. In this invention, Fe is controlled to be ≤0.25%. Excessive Fe will form hard and brittle β-AlFeSi phase, reducing the ductility and anodic oxidation effect of the alloy. In this invention, Mn is controlled to be ≤0.1% or Cr is controlled to be ≤0.1% to promote the formation of spherical α-Al(FeMn)Si phase and reduce the harm of β-AlFeSi phase. When high surface requirements are needed for the product, Fe needs to be controlled lower, such as Fe ≤0.2%. It is also necessary to appropriately increase the Mg content and optimize the aging process, such as T6 treatment. Reducing the Fe and Si contents and controlling the addition amount of Mn / Cr can reduce the subsequent extrusion streaks and oxidation defects of the bars for gas cylinder forging. Controlling the Mg content can avoid the sensitivity to welding cracks. In the melting process, in order to increase the recrystallization temperature during the extrusion of the alloy, a trace amount of Cr element needs to be added. First, it can refine the grains, and second, it can improve the corrosion resistance of the alloy after subsequent forging. It has higher strength and better corrosion resistance than conventional 6063 aluminum alloy. The addition of Cu element, the first purpose is to improve the overall strength of the alloy and the subsequent processability and turning performance, and at the same time, the Cu element can effectively inhibit the precipitation of strengthening phases and other second-phase particles at the grain boundaries, affecting the corrosion performance. The second point is that the addition of Cu is also more beneficial to subsequent forging treatment and improves the overall forgeability of the alloy.

[0045] S2. Melting and casting: Put the prepared aluminum alloy raw materials in step S1 into a melting furnace for melting and casting to obtain cast bars;

[0046] As a preference of this embodiment, specifically, melting and casting is carried out by the semi-continuous casting method. During the melting and casting process, bipolar foam ceramic filtration is used to filter non-metallic and metallic slag. The grains are refined by Al-Ti-B wire. The addition amount of scrap aluminum is controlled to be ≤10% to ensure the quality of the melt and avoid the situation that the surface roughness of the bar is too large due to excessive impurities during the subsequent extrusion process. The melting temperature during melting and casting is 760°C to 800°C, and the refining temperature is 730°C to 760°C;

[0047] S3. Homogenization of cast bars: The cast bars obtained in step S2 are subjected to homogenization treatment to obtain round ingots. The homogenization temperature is 460°C to 500°C, and the homogenization time is 6h to 8h;

[0048] Preferably in this embodiment, specifically, the diameter of the round ingot is 254 mm. For the casting rod, low-temperature and short-time homogenization is adopted. The homogenization system is a homogenization temperature of 480 °C and a homogenization time of 6 h. The cooling method is water mist cooling, which promotes the dissolution of non-equilibrium solidification phases in the ingot and the uniform distribution of chemical components. At the same time, it ensures that the sizes of intermetallic compounds and MgSi2 strengthening phases do not grow abnormally, thus affecting the grain size of the product during subsequent annealing. After the composition design, the low-temperature and short-time homogenization annealing of aluminum alloy is an energy-efficient heat treatment process, especially suitable for Al-Mg-Si series alloys, such as 6063 aluminum alloy. Its core advantage lies in optimizing the temperature and time parameters, reducing costs and improving comprehensive performance while ensuring the homogenization effect. Low-temperature and short-time homogenization can inhibit the formation of coarse phases and refine the microstructure. Traditional high-temperature homogenization annealing, such as 540 - 580 °C / 8 - 24 h, is prone to grain coarsening and excessive aggregation of Mg2Si phases, affecting subsequent extrusion formability. The low-temperature and short-time process, such as 470 - 510 °C / 4 - 6 h, can inhibit the coarsening of brittle phases such as β-AlFeSi by reducing the temperature, reduce the formation of coarse primary Si, promote the uniform precipitation of fine and dispersed phases such as α-Al(FeMn)Si, refine the grains, and improve the mechanical properties and surface finish of the extruded rod. In addition, compared with traditional high-temperature homogenization annealing, the temperature of this method is reduced by about 60 - 100 °C, and the time is shortened to 1 / 3 - 1 / 2 of the traditional process, which can reduce power consumption by 30% - 50%, meeting the trend of green manufacturing. The low-temperature environment can also reduce the surface oxidation of aluminum alloy, especially reduce the volatilization of Mg element, and reduce the raw material loss of subsequent surface treatment, such as anodic oxidation. Low-temperature homogenization avoids the excessive dissolution or coarsening of Mg2Si at high temperatures, ensures its existence as fine particles during extrusion, enhances the dynamic recrystallization ability of the alloy, and the fine and uniform precipitation phases serve as dislocation pinning points, improving the age hardening effect. For example, the tensile strength after T6 treatment is increased by 5% - 10%, reducing the content of harmful phases such as β-AlFeSi, reducing the tendency of electrochemical corrosion, and extending the service life of building profiles in humid environments. In addition, the combination of low-temperature and short-time homogenization and alloy composition design can also inhibit the formation of coarse phases, make the anodic oxidation film denser and more uniform, and enhance the decorative and weather resistance. The composition design in the method of the present invention mainly adopts the design direction of high Mg and low Si. The alloy composition has a high second phase, and at the same time, low-temperature and short-time homogenization is adopted in the homogenization system, with a homogenization temperature of 480 °C × 6 h, different from the high-temperature homogenization or non-homogenization of 6063 aluminum alloy in the past. The purpose is to improve the extrusion performance, avoid poor product surface quality caused by excessive friction between the metal flow and the working belt 2-2 of the die during extrusion, and greatly increase the daily output per shift;

[0049] S4. Extrusion: The round ingot obtained in step S3 is placed into an extrusion device for extrusion forming to obtain a bar. The extrusion die includes a flow guide plate 1 and a die 2 which are connected to each other. A flow guide pit 1-1 is provided at the center of the flow guide plate 1. The flow guide pit 1-1 is a cylindrical through hole. The diameter of the flow guide pit 1-1 is 55 mm to 65 mm, and the thickness of the flow guide pit 1-1 is 35 mm to 45 mm. More specifically, the diameter of the flow guide pit 1-1 is 60 mm, and the thickness of the flow guide pit 1-1 is 40 mm. A working chamber is provided at the center of the die 2 corresponding to the cylindrical opening. The working chamber includes a first conical zone 2-1, a working zone 2-2, a second conical zone 2-3, and a cylindrical zone 2-4 which are connected in sequence. The diameter of the inlet of the first conical zone 2-1 is equal to the diameter of the opening of the flow guide pit 1-1. The diameter of the outlet of the first conical zone 2-1 is smaller than the diameter of the inlet of the first conical zone 2-1. The diameter of the working zone 2-2 is equal to the diameter of the outlet of the first conical zone 2-1. The diameter of the inlet of the second conical zone 2-3 is equal to the diameter of the working zone 2-2. The diameter of the outlet of the second conical zone 2-3 is larger than the diameter of the inlet of the second conical zone 2-3. The diameter of the cylindrical zone 2-4 is equal to the diameter of the outlet of the second conical zone 2-3. The temperature of the extrusion die is set to 495 °C to 515 °C, the temperature of the round ingot is set to 440 °C to 460 °C, the extrusion speed is set to 5.5 m / min to 7.5 m / min, and the drawing speed is set to 5.5 m / min to 7.5 m / min;

[0050] As a preferred embodiment of the present invention, specifically, extrusion is performed by a 2750T horizontal extruder, the distance from the inlet of the first tapered zone 2-1 to the outlet of the first tapered zone 2-1 is 25mm, the diameter of the outlet of the first tapered zone 2-1 is 30mm, the length of the working belt 2-2 is 5mm-10mm, the diameter of the inlet of the second tapered zone 2-3 is 30mm, the diameter of the outlet of the second tapered zone 2-3 is 40mm-50mm, and the distance from the inlet of the second tapered zone 2-3 to the outlet of the second tapered zone 2-3 is 20mm; the conventional extrusion rod die is designed for an ordinary guide pit cone feed inlet, the purpose of which is to achieve continuous extrusion, but the present invention adds a 120mm×φ60mm guide plate 1 before the die 2, and a guide pit 1-1 is provided in the center of the guide plate 1, and the guide pit 1-1 is cylindrical, which is different from the conventional oblique cone guide pit, the conventional The disadvantage of the oblique cone guide pit is that the amount of aluminum stored at the inlet of the die cavity after the extrusion die is completed is small, so the residual material is easily cut out when shearing and pressing. After the residual material is taken out, a gap will appear between the die 2 and the shearing residual. The shearing gap will directly affect the next extruded product. The upper half of the head end of the next extruded product will have defects such as bubbles, peeling, and delamination. Especially for products that require hot forging, the delamination defects on the surface of the bar will seriously affect the surface condition of the product after forging. The delamination defects will cause bubbles on the surface of the bar under high-temperature heating. After forging, the bar will directly become a sticky peeling residue, resulting in an increase in the scrap rate. Secondly, when the residual material is too low, continuous extrusion production cannot be achieved, and the operator needs to repeatedly adjust the traction machine, resulting in extrusion interruption. The extrusion interruption will not only cause downtime marks on the surface of the bar, seriously affecting the quality of the bar, but also increase the workshop grinding process. The extrusion die of the embodiment of the present invention adds a cylindrical structure guide plate 1 on the basis of the original die structure, which not only increases the amount of aluminum stored, making the connection between round ingots tighter, but also increases the gap caused by the shearing and pressing of the scissors, greatly reducing the bubbles on the surface of the bar, and reducing the probability of bubbles on the surface of subsequent forged products. In addition, a larger aluminum supply is conducive to improving the surface quality of the bar, reducing the pressure of the aluminum alloy in the straight cylinder of the guide plate 1, and the reduced pressure leads to a reduction in the friction between the bar and the die, so that the surface quality of the bar is further improved;

[0051] S5. Quenching, online drawing and cutting to length: quenching the bar obtained in step S5, the quenching method is spray cooling, and the solid solubility of the second phase in the aluminum matrix is ​​reduced by slow cooling, so as to ensure the subsequent annealing treatment. The temperature of the bar after quenching is ≥300°C, and the quenched bar is stretched and straightened and then cut into a specified length, specifically, the length can be 6m;

[0052] S6. Finish annealing: Anneal the cut bars obtained in step S5. The annealing regime is 330 ± 5 °C × 3 ± 0.5 h, and slowly cool it in the furnace to room temperature to obtain bars for gas cylinder forging. Specifically, as an optimization of this embodiment, the diameter of the bars for gas cylinder forging is 30 mm.

[0053] Example 2. This example provides a method for extruding bars for 6063 aluminum alloy gas cylinder forging, including the following steps: S1. Batching: Prepare aluminum alloy raw materials according to the following weight ratio: Si: 0.415%, Fe: 0.16%, Cu: 0.085%, Mn: 0.05%, Mg: 0.64%, Cr: 0.085%, Zn: 0.10%, single impurity: ≤0.05%, total impurities: ≤0.15%, and the balance is Al.

[0054] S2. Melting and casting: Put the prepared aluminum alloy raw materials in step S1 into a melting furnace and carry out melting and casting by semi - continuous casting method. During the melting and casting process, use bipolar foam ceramic filtration to filter non - metallic and metallic slag, refine the grains with Al - Ti - B wire, and control the waste aluminum addition amount ≤10% to obtain a cast bar. The melting temperature during melting and casting is 760 °C - 800 °C, and the refining temperature is 730 °C - 760 °C.

[0055] S3. Homogenization of the cast bar: Carry out homogenization treatment on the cast bar obtained in step S2 to obtain a round ingot. Use low - temperature and short - time homogenization for the cast bar. The homogenization temperature is 480 °C, the homogenization time is 6 h, and the cooling method is water mist cooling to promote the dissolution of non - equilibrium solidification phases in the ingot and the uniform distribution of chemical components.

[0056] S4. Extrusion: The round ingot obtained in step S3 is placed into an extrusion device for extrusion forming to obtain a bar. The extrusion die includes a flow guide plate 1 and a die 2 connected to each other. There is a flow guide pit 1-1 at the center of the flow guide plate 1. The flow guide pit 1-1 is a cylindrical through hole with a diameter of 60 mm and a thickness of 40 mm. At the center of the die 2 corresponding to the cylindrical opening, there is a working chamber, which includes a first conical zone 2-1, a working belt 2-2, a second conical zone 2-3, and a cylindrical zone 2-4 connected in sequence. The diameter of the inlet of the first conical zone 2-1 is equal to the diameter of the opening of the flow guide pit 1-1. The diameter of the outlet of the first conical zone 2-1 is smaller than the diameter of the inlet of the first conical zone 2-1. The distance from the inlet of the first conical zone 2-1 to the outlet of the first conical zone 2-1 is 25 mm. The diameter of the outlet of the first conical zone 2-1 is 30 mm. The diameter of the working belt 2-2 is equal to the diameter of the outlet of the first conical zone 2-1. The length of the working belt 2-2 is 5 mm to 10 mm, and more specifically, it can be 8 mm. The diameter of the inlet of the second conical zone 2-3 is equal to the diameter of the working belt 2-2. The diameter of the outlet of the second conical zone 2-3 is larger than the diameter of the inlet of the second conical zone 2-3. The diameter of the outlet of the second conical zone 2-3 is 40 mm to 50 mm. The distance from the inlet of the second conical zone 2-3 to the outlet of the second conical zone 2-3 is 20 mm. The diameter of the cylindrical zone 2-4 is equal to the diameter of the outlet of the second conical zone 2-3. The temperature of the extrusion die is set to 495°C to 515°C, the temperature of the round ingot is set to 440°C to 460°C, the extrusion speed is set to 5.5 m / min to 7.5 m / min, and the drawing speed is set to 5.5 m / min to 7.5 m / min;

[0057] S5. Quenching, in-line drawing, and cut-to-length: The bar obtained in step S5 is quenched. The quenching method is spray cooling. The temperature of the bar after quenching is ≥300°C. The quenched bar is subjected to stretch straightening treatment and then cut into a specified length. Specifically, the length can be 6 m;

[0058] S6. Finish annealing: The cut bar obtained in step S5 is annealed. The annealing regime is 330 ± 5°C × 3 ± 0.5 h, and it is slowly cooled to room temperature in the furnace to obtain a bar for gas cylinder forging. The diameter of the bar for gas cylinder forging is 30 mm.

[0059] In the prior art, in order to ensure the theoretical yield of the bar for gas cylinder forging, an extruder with a relatively large tonnage is usually selected for production. However, an overly large tonnage of the extruder will cause an increase in the deformation degree of the ingot during the extrusion process. Therefore, it is necessary to select a large-tonnage ingot at the same time. During the melting process of the large-tonnage ingot, due to the difference in the cooling process, the grain size of the ingot cross-section is small at the edge and large at the core. Therefore, during the extrusion process, the relatively large grains at the core are inherited into the extruded profile. The macrostructure results of the bar for gas cylinder forging obtained by the existing process are as Figure 3As shown, the grain size is small at the edge and large at the center. However, the macrostructure results of the bars for gas cylinder forging obtained by the method of the present invention are as follows Figure 4 As shown, the grain size is uniform. In addition, the dimensional accuracy requirements for 6063 aluminum alloy gas cylinders are relatively high. For the 6063 aluminum alloy gas cylinders forged from the bars for gas cylinder forging obtained by the prior art, severe orange peel is likely to appear on the surface, as shown in Figure 5 As shown, and there are even more defects such as cracks. Moreover, due to the fact that the accuracy of the bars for gas cylinder forging obtained by the prior art often exceeds the tolerance and cannot be controlled, it not only leads to relatively high extrusion production costs, but also in the subsequent forging process, the billets cannot match the forging dies, often resulting in production interruptions and other situations. By optimizing the alloy composition ratio, reducing the homogenization temperature of the ingot, and reducing the extrusion cooling rate, the present invention suppresses the supersaturated solid solution degree after quenching, and adds a drawing and sizing device after online cooling, thereby producing 6063 aluminum alloy bars with low surface roughness and a product dimensional accuracy of up to ±0.1 mm and high plasticity. The bars can meet the requirements that after annealing or quenching treatment at a heat treatment temperature ≤ 500 °C, the grain grades of the edge, middle, and center of the bar matrix are ≥ 2.5 levels, and the difference in grain grades is ≤ 1 level. As shown in Figure 6 As shown, there will be no defects such as orange peel and cracks on the surface of the 6063 aluminum alloy gas cylinders forged from the bars for gas cylinder forging obtained by this method.

[0060] Example 3. This example provides an extrusion production method for bars for 6063 aluminum alloy gas cylinder forging. The method proposed in Example 2 is used to produce aluminum alloy structural parts. However, different from Example 2, the batching in this example is carried out according to: Si: 0.40%, Fe: 0.15%, Cu: 0.05%, Mn: 0.06%, Mg: 0.60%, Cr: 0.05%, Zn: ≤0.10%, single impurity: ≤0.05%, total impurity: ≤0.15%, and the balance is Al. The results of the bars for gas cylinder forging obtained are as follows Figure 7 As shown, the microstructure results are as follows Figure 8 As shown, there will be no defects such as orange peel and cracks on the surface of the 6063 aluminum alloy gas cylinders forged from the bars for gas cylinder forging obtained by this method.

[0061] Example 4. This example provides an extrusion production method for bars for 6063 aluminum alloy gas cylinder forging. The method proposed in Example 2 is used to produce aluminum alloy structural parts. However, different from Example 2, the batching in this example is carried out according to: Si: 0.45%, Fe: 0.25%, Cu: 0.1%, Mn: 0.1%, Mg: 0.65%, Cr: 0.10%, Zn: ≤0.10%, single impurity: ≤0.05%, total impurity: ≤0.15%, and the balance is Al. The macrostructure results of the bars for gas cylinder forging obtained are as follows Figure 9 As shown, the microstructure results are as followsFigure 10 As shown, the surface of the 6063 aluminum alloy gas cylinder forged from the bar for gas cylinder forging obtained by using this method will not have defects such as orange peel and cracks.

[0062] Example 5: This example provides an extrusion production method for bars for 6063 aluminum alloy gas cylinder forging. The method proposed in Example 2 is used for the production of aluminum alloy structural parts. However, different from Example 2, the batching in this example is carried out according to: Si: 0.41%, Fe: 0.15%, Cu: 0.06%, Mn: 0.03%, Mg: 0.62%, Cr: 0.06%, Zn: ≤0.10%, single impurity: ≤0.05%, total impurity: ≤0.15%, and the balance is Al. The macrostructure result of the bar for gas cylinder forging obtained is as Figure 11 shown, and the microstructure result is as Figure 12 shown. The surface of the 6063 aluminum alloy gas cylinder forged from the bar for gas cylinder forging obtained by using this method will not have defects such as orange peel and cracks.

[0063] Example 6: This example provides an extrusion production method for bars for 6063 aluminum alloy gas cylinder forging. The method proposed in Example 2 is used for the production of aluminum alloy structural parts. However, different from Example 2, the batching in this example is carried out according to: Si: 0.45%, Fe: 0.20%, Cu: 0.09%, Mn: 0.05%, Mg: 0.65%, Cr: 0.09%, Zn: ≤0.10%, single impurity: ≤0.05%, total impurity: ≤0.15%, and the balance is Al. The macrostructure result of the bar for gas cylinder forging obtained is as Figure 13 shown, and the microstructure result is as Figure 14 shown. The surface of the 6063 aluminum alloy gas cylinder forged from the bar for gas cylinder forging obtained by using this method will not have defects such as orange peel and cracks.

[0064] Example 7: This example provides an extrusion production method for bars for 6063 aluminum alloy gas cylinder forging. The method proposed in Example 2 is used for the production of aluminum alloy structural parts. However, different from Example 2, the batching in this example is carried out according to: Si: 0.42%, Fe: 0.17%, Cu: 0.75%, Mn: 0.05%, Mg: 0.64%, Cr: 0.87%, Zn: ≤0.10%, single impurity: ≤0.05%, total impurity: ≤0.15%, and the balance is Al. The macrostructure result of the bar for gas cylinder forging obtained is as Figure 15 shown, and the microstructure result is as Figure 16 shown. The surface of the 6063 aluminum alloy gas cylinder forged from the bar for gas cylinder forging obtained by using this method will not have defects such as orange peel and cracks.

[0065] Comparative Example 1. This comparative example provides a method for extruding bars for forging 6063 aluminum alloy gas cylinders. The method proposed in Example 2 is used for the production of aluminum alloy structural parts. However, different from Example 2, in this comparative example, the high-temperature homogenization of the prior art is used in the homogenization process of the cast bar, and the homogenization system is 540-580 °C / 8-24 h. The macrostructure results of the bars for forging gas cylinders obtained are as Figure 17 shown, and the microstructure results are as Figure 18 shown. It can be seen that the grains are coarsened and there is excessive aggregation of the Mg2Si phase. Severe orange peel and cracks and other defects will appear on the surface of the 6063 aluminum alloy gas cylinders forged from the bars for forging gas cylinders obtained by this method.

[0066] Comparative Example 2. This comparative example provides a method for extruding bars for forging 6063 aluminum alloy gas cylinders. The method proposed in Example 2 is used for the production of aluminum alloy structural parts. However, different from Example 2, in this comparative example, the homogenization process of the cast bar is not carried out. The macrostructure results of the bars for forging gas cylinders obtained are as Figure 19 shown, and the microstructure results are as Figure 20 shown. It can be seen that the grains are severely coarsened. Severe orange peel and cracks and other defects will appear on the surface of the 6063 aluminum alloy gas cylinders forged from the bars for forging gas cylinders obtained by this method.

[0067] The embodiments of the present invention are given for purposes of illustration and description, and are not exhaustive or limit the invention to the disclosed form. Many modifications and variations are obvious to those of ordinary skill in the art. The embodiments are selected and described to better illustrate the principles and practical applications of the present invention, and to enable those of ordinary skill in the art to understand the present invention and thus design various embodiments with various modifications suitable for specific purposes.

Claims

1. A method for extruding bars used for forging 6063 aluminum alloy gas cylinders, characterized in that, It includes the following steps: S1. Batching: Prepare aluminum alloy raw materials according to the following weight ratio: Si: 0.40% - 0.45%, Fe: 0.15% - 0.25%, Cu: 0.05% - 0.1%, Mn: ≤0.10%, Mg: 0.60% - 0.65%, Cr: 0.05% - 0.10%, Zn: ≤0.10%, single impurity: ≤0.05%, total impurity: ≤0.15%, and the balance is Al; S2. Melting and casting: Put the prepared aluminum alloy raw materials in step S1 into a melting furnace for melting and casting to obtain a casting rod; S3. Homogenization of the casting rod: Perform homogenization treatment on the casting rod obtained in step S2 to obtain a round ingot. The homogenization temperature is 460°C - 500°C, and the homogenization time is 6h - 8h; S4. Extrusion: Put the round ingot obtained in step S3 into an extrusion device for extrusion molding to obtain a bar. The extrusion die includes a flow guide plate (1) and a die (2) connected to each other. There is a flow guide pit (1-1) at the center of the flow guide plate (1). The flow guide pit (1-1) is a cylindrical through hole. The diameter of the flow guide pit (1-1) is 55mm - 65mm, and the thickness of the flow guide pit (1-1) is 35mm - 45mm. A working chamber is provided at the center of the die (2) corresponding to the cylindrical opening. The working chamber includes a first conical zone (2-1), a working belt (2-2), a second conical zone (2-3), and a cylindrical zone (2-4) connected in sequence. The diameter of the inlet of the first conical zone (2-1) is equal to the diameter of the opening of the flow guide pit (1-1). The diameter of the outlet of the first conical zone (2-1) is smaller than the diameter of the inlet of the first conical zone (2-1). The diameter of the working belt (2-2) is equal to the diameter of the outlet of the first conical zone (2-1). The diameter of the inlet of the second conical zone (2-3) is equal to the diameter of the working belt (2-2). The diameter of the outlet of the second conical zone (2-3) is larger than the diameter of the inlet of the second conical zone (2-3). The diameter of the cylindrical zone (2-4) is equal to the diameter of the outlet of the second conical zone (2-3). The temperature of the extrusion die is set to 495°C - 515°C, the temperature of the round ingot is set to 440°C - 460°C, the extrusion speed is set to 5.5m / min - 7.5m / min, and the drawing speed is set to 5.5m / min - 7.5m / min; S5. Quenching, in-line drawing and cut-to-length: Quench the bar obtained in step S5. The quenching method is spray cooling. The temperature of the bar after quenching is ≥300°C. Straighten the quenched bar by stretching and then cut it into a specified length; S6. Finish annealing: Anneal the cut bar obtained in step S5. The annealing regime is 330 ± 5°C × 3 ± 0.5h, and slowly cool it to room temperature with the furnace to obtain a bar for gas cylinder forging.

2. A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder according to claim 1, characterized in that, In the step S1, the ingredients are: Si: 0.41% - 0.45%, Fe: 0.15% - 0.20%, Cu: 0.06% - 0.09%, Mn: ≤0.05%, Mg: 0.62% - 0.65%, Cr: 0.06% - 0.09%, Zn: ≤0.10%, single impurity: ≤0.05%, total impurities: ≤0.15%, and the balance is Al.

3. A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder according to claim 1, characterized in that, In the step S1, the ingredients are: Si: 0.41% - 0.42%, Fe: 0.15% - 0.18%, Cu: 0.08% - 0.09%, Mn: ≤0.05%, Mg: 0.63% - 0.65%, Cr: 0.08% - 0.09%, Zn: ≤0.10%, single impurity: ≤0.05%, total impurities: ≤0.15%, and the balance is Al.

4. A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder according to claim 1, characterized in that, In the step S2, semi - continuous casting method is used for melting and casting. During the melting and casting process, bipolar foam ceramic filtration is adopted to filter non - metals and metal slag inclusions. The grain refinement is carried out by Al - Ti - B wire, and the addition amount of scrap aluminum is controlled ≤10%. The melting temperature during melting and casting is 760°C - 800°C, and the refining temperature is 730°C - 760°C.

5. A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder according to claim 1, characterized in that, In the step S3, the diameter of the round ingot is 254 mm.

6. A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder according to claim 1, characterized in that, In the step S3, the cooling method for homogenization of the cast rod is water spray cooling.

7. A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder according to claim 1, characterized in that, In the step S4, extrusion is carried out by a 2750T horizontal extrusion press.

8. A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder according to claim 1, characterized in that, In the step S4, the distance from the inlet to the outlet of the first conical zone (2 - 1) is 25 mm, the diameter of the outlet of the first conical zone (2 - 1) is 30 mm, and the length of the working belt (2 - 2) is 5 mm - 10 mm.

9. A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder according to claim 1, characterized in that, In the step S4, the diameter of the inlet of the second conical zone (2 - 3) is 30 mm, the diameter of the outlet of the second conical zone (2 - 3) is 40 mm - 50 mm, and the distance from the inlet to the outlet of the second conical zone (2 - 3) is 20 mm.

10. A method for extruding a bar for forging a 6063 aluminum alloy gas cylinder according to claim 1, characterized in that, In the step S6, the diameter of the bar for gas cylinder forging is 30 mm.

Images