Aluminum profile extrusion die and extrusion method for eliminating coarse grain ring

Abstract

The invention provides an aluminum profile extrusion die and extrusion method for eliminating a coarse grain ring, the extrusion die is provided with a flow guide pit, a sizing hole and a discharge port, the inlet end of the sizing hole is communicated with the flow guide pit, the outlet end of the sizing hole is communicated with the discharge port, a flow choking angle is arranged on a working belt of the inlet end of the sizing hole, and the outlet end of the sizing hole is communicated with the discharge port. And an empty cutter position is arranged at the outlet end of the sizing hole. The extrusion method sequentially comprises the steps of mold heating, aluminum bar ladder temperature heating, isothermal extrusion, quenching, stretch straightening, saw cutting, framing and aging heat treatment. The choke angle is arranged on the working belt at the inlet end of the sizing hole, so that the accumulation of deformation energy of aluminum alloy on the surface layer is reduced, the growth of recrystallized grains is inhibited, a coarse grain ring on the surface layer of the aluminum profile is eliminated, the aluminum profile obtains a fine and uniform recrystallized grain structure through isothermal extrusion, and the uniformity of the structure property on the cross section of the aluminum profile is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum profile extrusion, and particularly relates to an aluminum profile extrusion die and an extrusion method for eliminating coarse grain rings. Background Art

[0002] A coarse grain ring, a ring-shaped region of coarse grains formed around the perimeter of an extruded aluminum profile, is a common structural defect in extruded aluminum profiles. First, it causes uneven structural properties across the profile's cross-section, reducing its strength, plasticity, corrosion resistance, and fatigue resistance. Second, profiles with coarse grain rings are prone to cracking and surface roughness during deep processing such as forging and bending. Finally, it can cause defects such as color shift, mottling, and streaking in anodized aluminum profiles, seriously impacting the aesthetics and decorative effects of the oxidized and colored aluminum profiles.

[0003] Chinese patent publication CN118703812A discloses a method for preparing a high-hardness, high-conductivity aluminum alloy. The method includes smelting, refining, degassing and slag removal, online filtration and refinement, followed by reheat-top semi-continuous casting, extrusion, and aging treatments. By optimizing the extrusion and aging processes and parameters, the method improves the uniformity of the aluminum alloy's internal structure and reduces the presence of coarse grain rings.

[0004] Chinese patent publication CN118308673A discloses a method for manufacturing 6063 aluminum alloy bars, comprising the following steps: (1) homogenizing the cast bars; (2) extruding the homogenized cast bars, wherein the extrusion barrel temperature is 340-360°C, the cast bar loading temperature is 310-360°C, and the main cylinder forward speed of the extruder is 10-14 mm / s; and (3) in-line quenching to obtain the bars. By optimizing the extrusion process, this method can produce 6063 aluminum alloy bars with a coarse grain ring width of less than 1 mm.

[0005] Chinese patent publication CN115612897A discloses a method for reducing the coarse-grained layer in 6082 aluminum alloy profiles. The method involves preheating the raw materials, smelting the alloy, homogenizing, extruding, and aging. During the preheating process, pure aluminum, pure magnesium, and Al-Si and Al-Mn master alloys are preheated at 250°C. The resulting 6082 aluminum alloy profiles have a coarse-grained ring depth of less than 3 mm.

[0006] Chinese patent publication CN204220659U discloses a hot extrusion die for aluminum alloy bars. The die comprises a feed port and a working zone. The feed port is in the shape of a circular arc with a chamfer. The chamfer of the feed port has a size of 15-60 mm. This utility model reduces the intense friction between the aluminum alloy and the die end face during extrusion, making its flow rate more uniform and reducing lattice distortion during extrusion. The extruded product can essentially eliminate coarse grain rings.

[0007] Chinese patent publication CN108504914A discloses a method for producing aluminum alloy bars, including ingot casting, ingot heating, extrusion, quenching of the product in the desired quenched state, and stretching and straightening. This method utilizes a dual-hole die for reverse extrusion, which reduces the extrusion ratio, minimizes ingot deformation during extrusion, and inhibits the formation of coarse grains.

[0008] Chinese patent publication CN109722574A discloses a wrought aluminum alloy for improving the coarse-grained structure of extruded profiles. The alloy consists of the following components by mass: Si 0.75-0.8%, Fe 0.15-0.2%, Cu 0.05-0.1%, Mn 0.28-0.3%, Mg 0.53-0.58%, Zn ≤ 0.03%, Ti 0.01%-0.03%, Cr 0.06-0.1%, Zr 0.05-0.1%, with the balance being Al. By optimizing the alloy composition, the invention achieves a coarse-grained layer thickness of no greater than 0.15 mm in the aluminum alloy extruded profile.

[0009] Chinese patent publication CN107841663A discloses a method for preparing a composition-optimized 5A06 aluminum alloy bar. The method comprises subjecting an aluminum alloy ingot to homogenization annealing, heating, extrusion, annealing, and stretching to produce the aluminum alloy bar. The ingot composition comprises: 0-0.4% Si, 0-0.4% Fe, 0-0.1% Cu, 0.5-0.8% Mn, 5.8-6.8% Mg, 0.0001-0.005% Be, 0-0.2% Zn, 0.02-0.1% Ti, and 0.01-0.05% A, where A is one or both of Zr and Sc, and the balance is Al. The aluminum alloy bar produced by this method has a coarse grain ring depth of ≤3 mm.

[0010] Literature research indicates that the formation of coarse-grained rings and the factors influencing them are complex, affecting the die structure, extrusion method, extrusion process, and alloy composition. Based on practical experience, existing technologies can only reduce the thickness of the coarse-grained rings but cannot completely eliminate them. Therefore, current aluminum extrusion technologies still require improvement and development. Summary of the Invention

[0011] In response to the problems and shortcomings mentioned in the background technology, the present invention provides an aluminum profile extrusion die and extrusion method for eliminating coarse grain rings. By scientifically designing the structure of the extrusion die, optimizing the extrusion process of the aluminum profile, inhibiting the growth of surface grains of the aluminum profile, eliminating the coarse grain ring, and enabling the aluminum profile to obtain a fine and uniform recrystallized grain structure, thereby improving the uniformity of the organizational performance of the aluminum profile cross section.

[0012] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are as follows:

[0013] The first aspect of the present invention provides an aluminum profile extrusion die for eliminating coarse crystal rings, which is characterized in that: the extrusion die is provided with a guide pit, a sizing hole and a discharge port, the inlet end of the sizing hole is connected to the guide pit, the outlet end of the sizing hole is connected to the discharge port, a flow resistance angle is provided on the working belt of the inlet end of the sizing hole, and an empty tool position is provided at the outlet end of the sizing hole.

[0014] The formation of coarse-grained rings is closely related to the deformation behavior of aluminum alloy in the extrusion die. During the extrusion forming process of aluminum profiles, there is strong friction between the aluminum rod and the inner wall of the extrusion cylinder and the inner wall of the extrusion die, which leads to a fast flow rate of aluminum alloy in the central area of ​​the sizing hole of the extrusion die and a slow flow rate of aluminum alloy in the outer layer. Due to the uneven flow rate of the aluminum alloy, the deformation of the aluminum alloy is uneven. The outer layer of aluminum alloy is subjected to greater shear deformation, the internal energy of the outer layer of aluminum alloy increases, and the recrystallization temperature decreases, which induces the growth of recrystallized grains of the outer layer of aluminum alloy, and finally forms a coarse-grained ring with coarse grains on the surface of the aluminum profile.

[0015] In order to eliminate the coarse grain ring, the present invention first sets a diversion pit on the working surface of the extrusion die. Through the diversion effect of the diversion pit, the flow velocity difference between the central area and the outer layer of aluminum alloy in the extrusion die can be greatly reduced, and the uniformity of the aluminum alloy deformation in the extrusion die can be improved. Secondly, a flow blocking angle is creatively set on the working belt at the inlet end of the sizing hole of the extrusion die. The effect of the flow blocking angle is used to reduce the accumulation of deformation energy of the outer layer of aluminum alloy, prevent the reduction of the recrystallization temperature of the outer layer of aluminum alloy and the growth of recrystallized grains. Through a large number of experimental explorations and studies, the inventor found that, as a preferred embodiment, the angle of the flow blocking angle is 6°-7°, and the height of the flow blocking angle is 3-4mm. If the angle of the flow blocking angle is less than 6° or the height is less than 3mm, it will not effectively reduce the accumulation of deformation energy of the outer layer of aluminum alloy, and cannot prevent the reduction of the recrystallization temperature of the outer layer of aluminum alloy and the growth of recrystallized grains. If the angle of the flow blocking angle is greater than 7° or the height is higher than 4mm, the deformation resistance will be aggravated, making extrusion forming difficult.

[0016] A second aspect of the present invention provides an aluminum profile extrusion method for eliminating a coarse grain ring. The method uses the aluminum profile extrusion die for eliminating a coarse grain ring, and is characterized by sequentially comprising the following steps:

[0017] Step 1: heating the extrusion die;

[0018] Step 2: Preheat the aluminum rod using a gas furnace, and then use an electromagnetic induction furnace to heat the aluminum rod at a gradient temperature;

[0019] Step 3: Place the heated extrusion die and aluminum rod into the extruder, and isothermally extrude the aluminum rod into aluminum profiles through the extrusion die;

[0020] Step 4: sequentially subjecting the aluminum profile to quenching, stretching and straightening, sawing, framing, and aging heat treatment to obtain the aluminum profile with the coarse grain ring eliminated.

[0021] Preferably, the extrusion die in step 1 is heated to 330-340°C.

[0022] The heating temperature of the extrusion die is related to the characteristics of the extruded aluminum alloy and has a significant impact on the smooth extrusion process and whether coarse grain rings will form in the extruded aluminum profile. For extruded aluminum alloys with high strength, the heating temperature of the extrusion die should be appropriately higher; for extruded aluminum alloys with low strength, the heating temperature of the extrusion die can be appropriately lower. However, the heating temperature of the extrusion die cannot be lower than 330°C, otherwise it will easily lead to extrusion failure and a blocking phenomenon. However, the heating temperature of the extrusion die cannot be higher than 340°C, otherwise the temperature of the aluminum alloy surface inside the extrusion die will be too high, inducing grain growth and causing coarse grain rings in the aluminum profile.

[0023] Preferably, the aluminum rod in step 2 is composed of the following components in mass percentage: Mg 0.96%, Li 0.69%, Fe 0.34%, Co 0.13%, Be 0.08%, and the balance is Al and unavoidable impurities, with each unavoidable impurity being ≤0.05% and the total impurities being ≤0.15%.

[0024] The appearance of coarse grain rings is related to the composition of the aluminum rod. In order to eliminate the coarse grain rings, the present invention also optimizes the design of a lightweight, high-strength aluminum alloy with anti-coarse grain effect. Among them, Mg and Li are the main strengthening elements, which can significantly improve the strength and hardness of the aluminum profile. At the same time, the density of Mg and Li is lower than that of Al, which can also significantly reduce the density of the aluminum profile, achieving a significant lightweight effect. The main function of the Fe element is to enhance the high-temperature strength of the aluminum profile and improve the heat resistance of the aluminum profile. The main function of the Co element is to pin the grain boundaries and inhibit the growth of recrystallized grains. The main function of the Be element is to prevent the oxidation of the aluminum rod heated at high temperature. Be is a surfactant with a greater affinity for oxygen than Al, Mg, and Li, while its ionic radius is smaller than Al, Mg, and Li. Therefore, the Be element preferentially diffuses to the surface of the aluminum rod for oxidation, forming an oxide film with the characteristics of high resistance, low decomposition pressure, and good thermal stability, thereby improving the antioxidant ability of the aluminum rod and playing an effective protective role.

[0025] Preferably, in step 2, the aluminum rod is preheated to 370-380°C using a gas furnace, and the gradient temperature heating is performed by using an electromagnetic induction furnace to divide the aluminum rod into 6 sections, with a gradient temperature difference of 10°C in each section. The heating temperature of the first section is 440-450°C, and the heating temperature of the tail section is 390-400°C, so that a temperature gradient of 50°C is formed from the head section to the tail section of the aluminum rod.

[0026] Conventional aluminum rods for aluminum extrusion are heated evenly to 440-450°C in a gas furnace. During the extrusion process, the temperature of the aluminum alloy in the extrusion die gradually increases due to the friction between the aluminum rod and the inner wall of the extrusion barrel and the deformation of the aluminum rod. When the temperature exceeds the recrystallization temperature of the aluminum alloy, the aluminum alloy will recrystallize. If the temperature continues to rise, the recrystallized grains will grow and coarsen. In particular, the surface aluminum alloy is very likely to induce the growth and coarsening of recrystallized grains due to the large degree of deformation and uneven deformation, eventually forming a coarse grain ring with coarse grains around the aluminum profile.

[0027] To address the problems and shortcomings of existing gas furnace heating, the current method typically uses an electromagnetic induction furnace to heat the aluminum rod at a gradient temperature, keeping the tail end of the rod cooler than the head end, thereby offsetting the frictional heat and deformation heat generated during extrusion. However, direct electromagnetic induction heating with a gradient temperature causes the surface temperature of the aluminum rod to be higher than the core temperature due to the skin effect of electromagnetic induction heating. Ultimately, the surface temperature inside the die is higher than the core temperature during extrusion. The high surface temperature easily induces recrystallization and grain growth in the aluminum alloy, resulting in the appearance of coarse grain rings in the aluminum profile. Meanwhile, the low core temperature easily causes deformation difficulties, leading to extrusion difficulties and even machine stalling.

[0028] In order to solve the problems and shortcomings of existing gas furnace heating and electromagnetic induction heating and eliminate the coarse grain ring of aluminum profiles, the present invention creatively combines traditional gas furnace heating and electromagnetic induction furnace heating. The gas furnace is first used to preheat the aluminum rod to 370-380℃, and then the electromagnetic induction furnace is used to divide the aluminum rod into 6 sections, with a temperature difference of 10℃ between each section, for gradient heating. The heating temperature of the first section is 440-450℃, and the heating temperature of the tail section is 390-400℃, so that a temperature gradient of 50℃ is formed from the head section to the tail section of the aluminum rod. This heating method can not only reduce the temperature difference between the core and surface of the aluminum rod, but also quickly form a temperature gradient in the extension direction of the aluminum rod. By taking advantage of the fact that the temperature of the tail end of the aluminum rod is lower than that of the head end, the friction heat and deformation heat generated during the extrusion process are offset, so that the temperature of the aluminum alloy in the extrusion deformation zone and the temperature of the outlet aluminum profile are always constant, that is, isothermal pressurization is achieved to prevent the growth of recrystallized grains in the aluminum alloy caused by excessively high temperature. It can avoid the appearance of coarse grain rings in the aluminum profile and obtain fine and uniform completely recrystallized grains inside the aluminum profile, thereby improving the uniformity of the internal organizational properties of the aluminum profile, and ultimately improving the mechanical properties, deep processing properties and oxidation coloring properties of the aluminum profile.

[0029] Preferably, the extrusion ratio of the extrusion in step 3 is 45-55, and the pushing speed of the extrusion rod is 5-6 mm / s.

[0030] The extrusion process also plays a significant role in influencing the formation of a coarse-grained ring. Excessive extrusion ratios lead to more severe deformation of the aluminum alloy and generate more heat. Excessive extrusion speeds increase friction, preventing the dissipation of frictional and deformation heat generated by extrusion. This in turn causes the aluminum alloy to heat up within the die, inducing the growth and coarsening of recrystallized grains, resulting in the formation of a coarse-grained ring in the aluminum profile. Excessive extrusion ratios or slow extrusion speeds prevent complete recrystallization of the aluminum alloy, and the aluminum profile will not achieve fine, uniform recrystallized grains. Therefore, the extrusion ratio and extrusion rod advancement speed must be properly controlled.

[0031] Preferably, the quenching of the aluminum profile in step 4 is performed by passing the extruded aluminum profile through cooling water or water mist to cool it to room temperature.

[0032] The extruded aluminum profile is still in a high temperature state. Through quenching, the aluminum profile is quickly cooled down. On the one hand, it can prevent the growth and coarsening of grains, and on the other hand, it can make the aluminum profile obtain a supersaturated solid solution, so as to enhance the strength of the aluminum profile through aging later. In order to quickly cool the aluminum profile in a high temperature state, for aluminum profiles with larger wall thickness, it is preferred to pass the aluminum profile through cooling water for cooling. For aluminum profiles with smaller wall thickness, the aluminum profile can be cooled by passing it through water mist for cooling.

[0033] Preferably, the aging temperature of the aging heat treatment of the aluminum profile in step 4 is 120-130° C., and the aging time is 13-14 hours.

[0034] For aluminum profiles that can be strengthened by heat treatment, aging heat treatment is an effective means of further improving their strength and hardness. Aging heat treatment allows the strengthening phases in the aluminum profile to separate out, further enhancing their strength and hardness. The aging temperature should be moderate, and the aging time should be moderate. Otherwise, the aluminum profile will be under-aged and will not achieve high strength and hardness. The aging temperature should be moderate, and the aging time should be moderate. Otherwise, the aluminum profile will be over-aged and will not achieve high strength and hardness. Therefore, the aging temperature and aging time must be strictly controlled and appropriately matched to achieve optimal mechanical properties.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention optimizes the structure of the extrusion die. By setting a diversion pit and making full use of the diversion effect of the diversion pit, the flow velocity difference between the central area and the outer layer of aluminum alloy in the extrusion die is greatly reduced, thereby improving the uniformity of the deformation of the aluminum alloy in the extrusion die. At the same time, by setting a flow blocking angle on the working belt at the inlet end of the sizing hole of the extrusion die, the flow blocking angle is used to reduce the accumulation of deformation energy of the outer layer of aluminum alloy, prevent the reduction of the recrystallization temperature of the outer layer of aluminum alloy and the growth of recrystallized grains, which is conducive to preventing the appearance of coarse grain rings in the aluminum profile. The present invention also optimizes the composition and extrusion process of the aluminum profile. By scientifically designing the composition of the aluminum profile and optimizing the extrusion process, the isothermal extrusion of the aluminum profile is achieved, effectively preventing the temperature rise of the aluminum alloy in the extrusion die, inducing complete recrystallization of the aluminum alloy, so that the aluminum profile obtains a fine and uniform grain structure, and effectively preventing the growth and coarsening of recrystallized grains, thereby avoiding the appearance of coarse grain rings, thereby improving the uniformity of the organizational properties on the cross section of the aluminum profile and improving the mechanical properties of the aluminum profile. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the top structure of the aluminum profile extrusion die of the present invention.

[0038] Figure 2 This is a schematic diagram of the AA-plane cross-sectional structure of the aluminum profile extrusion die of the present invention.

[0039] Figure 3 This is a schematic diagram of the BB-plane cross-sectional structure of the aluminum profile extrusion die of the present invention.

[0040] Figure 4 It is a partially enlarged structural schematic diagram of the AA-plane cross-sectional view of the aluminum profile extrusion die of the present invention.

[0041] Figure 5 This is a macroscopic structural photograph of the cross section of the aluminum profile in Example 1.

[0042] Figure 6 This is a macroscopic photograph of the cross section of the aluminum profile of Comparative Example 1.

[0043] Figure 7 This is a macroscopic photograph of the cross section of the aluminum profile of Comparative Example 2.

[0044] Figure 8 This is a macroscopic photograph of the cross section of the aluminum profile of Comparative Example 3.

[0045] Figure 9 This is a macroscopic photograph of the cross section of the aluminum profile of Comparative Example 4. DETAILED DESCRIPTION

[0046] An aluminum profile extrusion die for eliminating coarse grain rings, such as Figures 1-4As shown, the extrusion die is provided with a diversion pit 11, a sizing hole 12, and a discharge port 13. The inlet end of the sizing hole 12 is connected to the diversion pit 11, and the outlet end of the sizing hole 12 is connected to the discharge port 13. A choke angle 14 is provided on the working zone at the inlet end of the sizing hole 12, and an empty tool position 15 is provided at the outlet end of the sizing hole 12. Preferably, the angle θ of the choke angle 14 is 6°-7°, and the height H of the choke angle 14 is 3-4 mm.

[0047] Example 1:

[0048] An aluminum profile extrusion die that eliminates the coarse grain ring is used, the flow blocking angle θ is 6.5°, and the height H of the flow blocking angle is 3.5 mm. The aluminum profile extrusion method includes the following steps in sequence:

[0049] Step 1: Heat the extrusion die to 335°C;

[0050] Step 2: Preheat the aluminum rod to 375°C in a gas furnace, then divide the aluminum rod into 6 sections with a 10°C temperature difference in each section using an electromagnetic induction furnace, heating the aluminum rod to a temperature of 445°C for the first section and 395°C for the last section, so that a temperature gradient of 50°C is formed from the first section to the last section of the aluminum rod. The aluminum rod is composed of the following components by mass percentage: Mg 0.96%, Li 0.69%, Fe 0.34%, Co 0.13%, Be 0.08%, and the balance being Al and unavoidable impurities, with each unavoidable impurity ≤ 0.05% and the total impurity ≤ 0.15%;

[0051] Step 3: Place the heated extrusion die and aluminum rod into the extruder. Under the conditions of an extrusion ratio of 50 and an extrusion rod advancing speed of 5.5 mm / s, the aluminum rod is isothermally extruded into an aluminum profile through the extrusion die.

[0052] Step 4: sequentially subjecting the aluminum profile to water quenching, stretching and straightening, sawing, framing and aging heat treatment, with an aging temperature of 125° C. and an aging time of 13.5 hours, to obtain the aluminum profile with the coarse grain ring eliminated.

[0053] Example 2:

[0054] An aluminum profile extrusion die that eliminates the coarse grain ring is used, the flow blocking angle θ is 6.5°, and the height H of the flow blocking angle is 3.5 mm. The aluminum profile extrusion method includes the following steps in sequence:

[0055] Step 1: Heat the extrusion die to 330°C;

[0056] Step 2: Preheat the aluminum rod to 380°C in a gas furnace, then divide the aluminum rod into 6 sections using an electromagnetic induction furnace, heating each section at a temperature gradient of 10°C. The heating temperature of the first section is 450°C, and the heating temperature of the last section is 400°C, so that a temperature gradient of 50°C is formed from the first section to the last section of the aluminum rod. The aluminum rod is composed of the following components by mass percentage: Mg 0.96%, Li 0.69%, Fe 0.34%, Co 0.13%, Be 0.08%, and the balance is Al and unavoidable impurities, with each unavoidable impurity ≤ 0.05% and the total impurities ≤ 0.15%;

[0057] Step 3: Place the heated extrusion die and aluminum rod into the extruder. Under the conditions of an extrusion ratio of 55 and an extrusion rod advancing speed of 5 mm / s, the aluminum rod is isothermally extruded into an aluminum profile through the extrusion die.

[0058] Step 4: sequentially subjecting the aluminum profile to water quenching, stretching and straightening, sawing, framing and aging heat treatment, with an aging temperature of 130° C. and an aging time of 13 hours, to obtain the aluminum profile with the coarse grain ring eliminated.

[0059] Example 3:

[0060] An aluminum profile extrusion die that eliminates the coarse crystal ring is used, the obstruction angle θ is 7°, and the height H of the obstruction angle is 3 mm. The aluminum profile extrusion method includes the following steps in sequence:

[0061] Step 1: Heat the extrusion die to 340°C;

[0062] Step 2: Preheat the aluminum rod to 370°C in a gas furnace, then divide the aluminum rod into 6 sections with a 10°C temperature difference in each section for gradient heating in an electromagnetic induction furnace. The heating temperature of the first section is 440°C and the heating temperature of the last section is 390°C, so that a temperature gradient of 50°C is formed from the first section to the last section of the aluminum rod. The aluminum rod is composed of the following components by mass percentage: Mg 0.96%, Li 0.69%, Fe 0.34%, Co 0.13%, Be 0.08%, and the balance is Al and unavoidable impurities, with each unavoidable impurity ≤ 0.05% and the total impurities ≤ 0.15%;

[0063] Step 3: Place the heated extrusion die and aluminum rod into the extruder. Under the conditions of an extrusion ratio of 45 and an extrusion rod advancing speed of 6 mm / s, the aluminum rod is isothermally extruded into an aluminum profile through the extrusion die.

[0064] Step 4: sequentially subjecting the aluminum profile to water quenching, stretching and straightening, sawing, framing and aging heat treatment, with an aging temperature of 120° C. and an aging time of 14 hours, to obtain the aluminum profile with the coarse grain ring eliminated.

[0065] Example 4:

[0066] An aluminum profile extrusion die that eliminates the coarse crystal ring is used, the obstruction angle θ is 6°, and the height H of the obstruction angle is 4 mm. The aluminum profile extrusion method includes the following steps in sequence:

[0067] Step 1: Heat the extrusion die to 335°C;

[0068] Step 2: Preheat the aluminum rod to 375°C in a gas furnace, then divide the aluminum rod into 6 sections with a 10°C temperature difference in each section using an electromagnetic induction furnace, heating the aluminum rod to a temperature of 445°C for the first section and 395°C for the last section, so that a temperature gradient of 50°C is formed from the first section to the last section of the aluminum rod. The aluminum rod is composed of the following components by mass percentage: Mg 0.96%, Li 0.69%, Fe 0.34%, Co 0.13%, Be 0.08%, and the balance being Al and unavoidable impurities, with each unavoidable impurity ≤ 0.05% and the total impurity ≤ 0.15%;

[0069] Step 3: Place the heated extrusion die and aluminum rod into the extruder. Under the conditions of an extrusion ratio of 50 and an extrusion rod advancing speed of 5.5 mm / s, the aluminum rod is isothermally extruded into an aluminum profile through the extrusion die.

[0070] Step 4: sequentially subjecting the aluminum profile to water quenching, stretching and straightening, sawing, framing and aging heat treatment, with an aging temperature of 125° C. and an aging time of 13.5 hours, to obtain the aluminum profile with the coarse grain ring eliminated.

[0071] Example 5:

[0072] An aluminum profile extrusion die that eliminates the coarse crystal ring is used, the obstruction angle θ is 7°, and the height H of the obstruction angle is 3 mm. The aluminum profile extrusion method includes the following steps in sequence:

[0073] Step 1: Heat the extrusion die to 340°C;

[0074] Step 2: Preheat the aluminum rod to 370°C in a gas furnace, then divide the aluminum rod into 6 sections with a 10°C temperature difference in each section for gradient heating in an electromagnetic induction furnace. The heating temperature of the first section is 440°C and the heating temperature of the last section is 390°C, so that a temperature gradient of 50°C is formed from the first section to the last section of the aluminum rod. The aluminum rod is composed of the following components by mass percentage: Mg 0.96%, Li 0.69%, Fe 0.34%, Co 0.13%, Be 0.08%, and the balance is Al and unavoidable impurities, with each unavoidable impurity ≤ 0.05% and the total impurities ≤ 0.15%;

[0075] Step 3: Place the heated extrusion die and aluminum rod into the extruder. Under the conditions of an extrusion ratio of 45 and an extrusion rod advancing speed of 6 mm / s, the aluminum rod is isothermally extruded into an aluminum profile through the extrusion die.

[0076] Step 4: sequentially subjecting the aluminum profile to water quenching, stretching and straightening, sawing, framing and aging heat treatment, with an aging temperature of 130° C. and an aging time of 13 hours, to obtain the aluminum profile with the coarse grain ring eliminated.

[0077] Comparative Example 1:

[0078] The aluminum profile extrusion method of this comparative example is the same as that of Example 1, except that the aluminum profile extrusion die is not provided with a flow resistance angle.

[0079] Comparative Example 2:

[0080] The aluminum profile extrusion die of this comparative example is the same as that of Example 1, except that step 1 is to heat the extrusion die to 350°C.

[0081] Comparative Example 3:

[0082] The aluminum profile extrusion die of this comparative example is the same as that of Example 1, except that in step 2, the aluminum rod is not heated by a stepwise heating induction furnace, but is directly heated to 445° C. by a gas furnace.

[0083] Comparative Example 4:

[0084] The aluminum profile extrusion die and extrusion method of this comparative example are the same as those of Example 1, except that the aluminum rod is composed of the following components in mass percentage: Mg 0.96%, Li 0.69%, Fe 0.34%, Be 0.08%, and the balance is Al and inevitable impurities, with each inevitable impurity being ≤0.05% and the total impurities being ≤0.15%.

[0085] Verification example:

[0086] Samples were taken from the aluminum profiles obtained in Example 1 and Comparative Examples 1-4, and the cross sections of the samples were treated with natron water. After cleaning, the macroscopic structure of the cross sections of the aluminum profiles was directly observed. Figure 5 This is a macroscopic photograph of the cross section of the aluminum profile of Example 1. Figure 6 This is a macroscopic photograph of the cross section of the aluminum profile of Comparative Example 1. Figure 7 This is a macroscopic photograph of the cross section of the aluminum profile of Comparative Example 2. Figure 8 This is a macroscopic photograph of the cross section of the aluminum profile of Comparative Example 3. Figure 9 This is a macroscopic photograph of the cross section of the aluminum profile of Comparative Example 4. Figure 5 It can be seen that there is no coarse grain ring in the cross section of the aluminum profile of Example 1, and the grain structure on the cross section is uniform. Figure 6-9As can be seen, in Comparative Example 1, due to the lack of a flow resistance angle in the extrusion die, in Comparative Example 2, due to the excessively high extrusion die heating temperature, in Comparative Example 3, due to the lack of a temperature gradient heating method for the aluminum rod in an electromagnetic induction furnace, and in Comparative Example 4, due to the absence of Co in the aluminum rod, the aluminum profile cross-sections all exhibited distinct coarse-grained rings, resulting in uneven grain structure. This comparison demonstrates that the technical solution of the present invention effectively avoids the formation of coarse-grained rings in aluminum profiles, thereby improving the uniformity of grain structure across the cross-sections of the aluminum profiles.

[0087] The present invention is described through embodiments, but does not constitute a limitation of the present invention. With reference to the description of the present invention, other changes to the disclosed embodiments are easy for professionals in this field to think of, and such changes should fall within the scope defined by the claims of the present invention.

Claims

1. An aluminum profile extrusion die for eliminating coarse grain rings, characterized in that: The extrusion die is provided with a diversion pit, a sizing hole and a discharge port. The inlet end of the sizing hole is connected to the diversion pit, the outlet end of the sizing hole is connected to the discharge port, a flow resistance angle is provided on the working belt of the inlet end of the sizing hole, and an empty tool position is provided at the outlet end of the sizing hole.

2. The aluminum profile extrusion die for eliminating coarse grain rings according to claim 1, characterized in that: The angle of the blocking angle is 6°-7°, and the height of the blocking angle is 3-4 mm.

3. A method for extruding an aluminum profile for eliminating a coarse grain ring, the method using the aluminum profile extrusion die for eliminating a coarse grain ring as claimed in claim 1 or 2, characterized in that: The following steps are included in sequence: Step 1: heating the extrusion die; Step 2: Preheat the aluminum rod using a gas furnace, and then use an electromagnetic induction furnace to heat the aluminum rod at a gradient temperature; Step 3: Place the heated extrusion die and aluminum rod into the extruder, and isothermally extrude the aluminum rod into aluminum profiles through the extrusion die; Step 4: sequentially subjecting the aluminum profile to quenching, stretching and straightening, sawing, framing, and aging heat treatment to obtain the aluminum profile with the coarse grain ring eliminated.

4. The aluminum profile extrusion method for eliminating coarse grain rings according to claim 3, characterized in that: The extrusion die in step 1 is heated to 330-340°C.

5. The aluminum profile extrusion method for eliminating coarse grain rings according to claim 3, characterized in that: In step 2, the aluminum rod is composed of the following components in mass percentage: Mg 0.96%, Li 0.69%, Fe 0.34%, Co 0.13%, Be 0.08%, and the balance is Al and inevitable impurities, wherein the individual inevitable impurities are ≤0.05%, and the total impurities are ≤0.15%.

6. The aluminum profile extrusion method for eliminating coarse crystal rings according to claim 3, characterized in that: In step 2, the aluminum rod is preheated to 370-380°C using a gas furnace. The gradient heating is to divide the aluminum rod into 6 sections evenly using an electromagnetic induction furnace, and each section is heated with a temperature difference of 10°C. The heating temperature of the first section is 440-450°C, and the heating temperature of the tail section is 390-400°C, so that a temperature gradient of 50°C is formed from the head section to the tail section of the aluminum rod.

7. The aluminum profile extrusion method for eliminating coarse crystal rings according to claim 3, characterized in that: The extrusion ratio of the extrusion in step 3 is 45-55, and the extrusion rod advancing speed is 5-6 mm / s.

8. The aluminum profile extrusion method for eliminating coarse crystal rings according to claim 3, characterized in that: The quenching of the aluminum profile in step 4 is to cool the extruded aluminum profile to room temperature by passing it through cooling water or water mist.

9. The aluminum profile extrusion method for eliminating coarse crystal rings according to claim 3, characterized in that: In step 4, the aging temperature of the aluminum profile is 120-130° C., and the aging time is 13-14 hours.

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