Die and process for hot extrusion forming of high-magnesium-content aluminum alloy thin-wall part

Abstract

The invention discloses a die and process for hot extrusion forming of a high-magnesium-content aluminum alloy thin-wall part. A body of the die is provided with a flow guide cavity and a working belt. The flow guide cavity and the working belt have the same section shape and are I-shaped; the flow guide groove connected between the flow guide cavity and the working belt is a conical groove; the working tape is a variable-length working tape with three typical positions. The process comprises the following steps: (1) processing an aluminum alloy ingot; (2) preheating the extrusion die, heating the cast ingot in an induction heating mode, and controlling the temperature of the tail section of the cast ingot to be higher than that of the head section; (3) the tail section of the cast ingot is in front, the head section is in back, an extruder pushing rod pushes the cast ingot to pass through a mold, and finally forming is conducted; (4) the extruded thin-wall part profile is subjected to on-line strong wind cooling; and (5) standing the cooled thin-wall part profile at room temperature for at least 7 days, and carrying out two-stage aging treatment. The thin-wall profile obtained according to the method is low in density and has high surface quality, high dimensional precision and excellent comprehensive performance.

Description

Technical Field

[0001] This invention relates to the field of thin-walled part extrusion technology, specifically to a mold and process for hot extrusion forming of thin-walled aluminum alloy parts with high magnesium content. Background Technology

[0002] With the rapid development of aerospace, rail transportation and other fields, the demand for special aluminum alloy extruded profiles, such as thin-walled parts and irregularly shaped parts, is gradually increasing. As key components, these aluminum alloy profiles require high surface quality, high dimensional accuracy and excellent comprehensive performance.

[0003] Currently, the use of traditional alloys to prepare thin-walled profiles is limited by their density and overall performance, making it difficult to effectively reduce weight and save energy, and the material cost is relatively high. Patent document CN116065066B discloses a lightweight, high-strength, corrosion-resistant aluminum alloy material and its preparation method, which proposes a novel high-magnesium-content Al-Mg-Zn-Si alloy that combines low cost, low density, and corrosion resistance. Using this new series of alloys to prepare thin-walled profiles can further save energy and reduce costs. However, due to the thin wall thickness and asymmetrical shape of the extruded blanks, the high deformation resistance and sensitivity of the novel high-magnesium-content Al-Mg-Zn-Si alloy to the extrusion temperature window, thin-walled profiles are prone to twisting, bending, wavy, fracture, stalling, surface roughness, and substandard mechanical properties during the extrusion process. Summary of the Invention

[0004] The purpose of this invention is to provide a mold and process for hot extrusion forming of thin-walled aluminum alloy parts with high magnesium content, so that the density of the alloy thin-walled profile is ≤2.65g / cm³. 3 It has high surface quality, high dimensional accuracy and excellent overall performance.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A die for hot extrusion forming of thin-walled aluminum alloy parts with high magnesium content, the die body having a guide cavity and a working belt; the guide cavity and the working belt have the same cross-sectional shape and are both I-shaped, the guide groove connecting the guide cavity and the working belt is a conical groove with a taper angle of 2~4°; the working belt is a variable length working belt with three typical positions, wherein the contact surface length of the first typical position of the working belt is 5.9~6.5mm, the contact surface length of the second typical position is 4.7~5.2mm, and the contact surface length of the third typical position is 2.9~3.2mm.

[0006] Preferably, the thinnest wall thickness of the thin-walled component is 1.6 mm.

[0007] Preferably, the contact surface length at the first typical position of the working belt is 6.0 mm, the contact surface length at the second typical position is 5.0 mm, and the contact surface length at the third typical position is 3.0 mm.

[0008] Preferably, the mold is prepared by additive manufacturing, and the mold steel powder comprises the following elements by weight percentage: C 0.35-0.55%, Si 0.01-0.15%, Mn 1.50-2.90%, Cr 4.50-5.70%, Mo 0.6-0.90%, P≤0.025%, S≤0.015%, Nb 0.03-0.04%, N 0.03-0.05%, Al 0.05-0.09%, with the balance being Fe and unavoidable impurities.

[0009] A process for hot extrusion forming of novel high-magnesium-content aluminum alloy thin-walled parts using the aforementioned mold, characterized in that the aluminum alloy comprises the following components: Mg 6.0~9.9wt%, Zn 1.1~3.01wt%, Si 0.1~1.15wt%, and at least one of Mn, Cu, Zr, Sc, and Ti elements with a total content not exceeding 0.8wt%, the remainder being Al and unavoidable impurities; the process includes the following steps: (1) The aluminum alloy is processed into an aluminum alloy ingot according to the composition of the aluminum alloy; (2) Preheat the extrusion die and use induction heating to heat the ingot, controlling the temperature of the tail section of the ingot to be higher than that of the head section; (3) The ingot heated by induction is placed into the extrusion cylinder with the tail section in front and the head section behind. The extrusion press push rod pushes the ingot through the mold to finally form it. The extrusion temperature is 380~520℃, the extrusion press push rod speed is 0.2~1.4mm / s, the temperature of the extrusion cylinder and the mold is 440~500℃, and the outlet temperature is 350~390℃. (4) The extruded thin-walled profiles are subjected to online forced air cooling, with a final cooling temperature of 30~50℃ and a cooling rate of 2~8℃ / s; (5) After cooling, the thin-walled profiles are left at room temperature for at least 7 days and subjected to two-stage aging treatment. The first stage of aging is carried out at 50~110℃ for 2~96 hours, and the second stage of aging is carried out at 120~230℃ for 2~12 hours.

[0010] Preferably, the aluminum alloy is composed of the following components: Mg 6.5~7.8wt%, Zn 1.5~2.8wt%, Si 0.15~0.5wt%, and at least one of Mn, Cu, Zr, Sc and Ti elements with a total content not exceeding 0.6wt%, with the remainder being Al and unavoidable impurities.

[0011] Preferably, in step (2), boron nitride powder is added as a lubricant when the extrusion die is preheated to 150~200°C.

[0012] Preferably, in step (2), the temperature difference between the head section and the tail section of the extruded ingot is 60~90℃.

[0013] Preferably, in step (3), the extrusion temperature is 450~515℃, the extruder push rod speed is 0.5~1.2mm / s, the extrusion cylinder and die temperature is 440~500℃, and the outlet temperature is 420~495℃.

[0014] Preferably, in step (4), the final cooling temperature is 30~40℃, the wind speed is 40~60m / s, the nozzle height is 50~80mm, the angle between the nozzle and the horizontal plane of the profile is 30~45°, and the cooling rate is 2~8℃ / s.

[0015] Preferably, in step (5), the first aging regime is maintained at 50~80℃ for 4~18h, and the second aging regime is maintained at 175~215℃ for 6~12h.

[0016] A novel high-magnesium-content aluminum alloy thin-walled part, produced by the aforementioned process, exhibits no cracking, has a surface roughness of 0.4~1.2μm, and a bending curvature of less than 3 degrees per meter of thin-walled part profile.

[0017] Preferably, the density of the aluminum alloy thin-walled profile is ≤2.68 g / cm³. 3 The tensile strength in the L direction is ≥435MPa, the elongation after fracture is ≥12%, and the peeling corrosion grade is not lower than EA.

[0018] The beneficial effects of this invention are: This invention provides a thin-walled part extrusion die. Through optimized design of the working belt, differential speed control at different positions of the thin-walled part is achieved, significantly reducing twisting, bending, wavy, and breakage of the thin-walled profile during extrusion. Targeting the characteristics of a novel high-magnesium-content AlMgZnSi alloy, the invention optimizes the thin-walled profile extrusion process to solve problems such as stalling, surface roughness, and substandard mechanical properties. Ultimately, it achieves the preparation of a novel high-magnesium-content aluminum alloy thin-walled part with a surface roughness of 0.4~1.2μm, a bending radius of no more than 3 degrees per meter of thin-walled profile, and a density ≤2.68g / cm³. 3 The tensile strength in the L-direction is ≥435MPa, the elongation after fracture is ≥12%, and the exfoliation corrosion rating is not lower than EA. The mold process provided by this invention is very suitable for the industrial preparation and production of thin-walled aluminum alloy profiles with high magnesium content. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the mold used in this invention.

[0020] Figure 2 This is a schematic diagram of the longitudinal section of the thin mold used in this invention.

[0021] Figure 3 This is a schematic diagram of the cross-section of the mold used in this invention.

[0022] Figure 4 This is a schematic diagram of the differential speed control working belt in the mold used in this invention. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] like Figures 1-4 As shown, this invention discloses a mold for hot extrusion forming of thin-walled aluminum alloy parts with high magnesium content. The mold body 1 includes a guide cavity 2 and a working belt 3, with the guide cavity 2 and the working belt 3 having the same cross-sectional shape. The cross-sectional shape is that of an I-shaped thin-walled part, with a minimum wall thickness of 1.6 mm. The guide groove located between the guide cavity 2 and the working belt 3 is a conical groove with a taper angle of 2~4°. The working belt is a variable length working belt (differential speed control working belt), with the contact surface length at the first typical position 31 being 5.9~6.5 mm, the contact surface length at the second typical position 32 being 4.7~5.2 mm, and the contact surface length at the third typical position 33 being 2.9~3.2 mm. The mold is prepared by additive manufacturing. The mold steel powder contains the following elements by weight percentage: C 0.35-0.55%, Si 0.01-0.15%, Mn 1.50-2.90%, Cr 4.50-5.70%, Mo 0.6-0.90%, P≤0.025%, S≤0.015%, Nb 0.03-0.04%, N 0.03-0.05%, Al 0.05-0.09%, with the balance being Fe and unavoidable impurities.

[0025] The extrusion process steps for manufacturing novel high-magnesium content aluminum alloy thin-walled parts based on the mold provided by this invention are as follows: (1) The aluminum alloy is processed into an aluminum alloy ingot according to the composition of the aluminum alloy; the aluminum alloy is composed of the following components: Mg 6.0~9.9wt%, Zn 1.1~3.01wt%, Si 0.1~1.15wt%, and at least one of Mn, Cu, Zr, Sc and Ti elements with a total content not exceeding 0.8wt%, the remainder being Al and unavoidable impurities; a more preferred ratio range is: Mg 6.5~7.8wt%, Zn 1.5~2.8wt%, Si 0.15~0.5wt%, and at least one of Mn, Cu, Zr, Sc and Ti elements with a total content not exceeding 0.6wt%, the remainder being Al and unavoidable impurities; (2) Preheat the extrusion die and heat the ingot by induction heating, and control the temperature of the tail section of the ingot to be higher than that of the head section; when the extrusion die is preheated to 150~200℃, add boron nitride powder as a lubricant; control the temperature difference between the head section and the tail section of the ingot to be 20~90℃. (3) The ingot heated by induction is placed into the extrusion cylinder with the tail section in front and the head section behind. The extrusion press push rod pushes the ingot through the mold to finally form the shape.

[0026] In this step, the extrusion temperature is 450~515℃, the extruder push rod speed is 0.5~1.2mm / s, the extrusion barrel and die temperature is 440~500℃, and the outlet temperature is 420~495℃; more preferably, the extrusion temperature is 470~490℃, the extruder push rod speed is 0.7~1.0mm / s, the extrusion barrel and die temperature is 470~495℃, and the outlet temperature is 430~450℃.

[0027] (4) The extruded thin-walled profiles are subjected to online strong air cooling, with a final cooling temperature of 30~50℃ and a cooling rate of 2~8℃ / s.

[0028] More preferably, the final cooling temperature is 30~40℃, the wind speed is 40~60m / s, the nozzle height is 50~80mm, the angle between the nozzle and the horizontal plane of the profile is 30~45°, and the cooling rate is 2~8℃ / s.

[0029] (5) After cooling, the thin-walled profiles are left at room temperature for at least 7 days and subjected to two-stage aging treatment. The first stage of aging is carried out at 50~80℃ for 4~18h, and the second stage of aging is carried out at 175~215℃ for 6~12h.

[0030] More preferably, the first-stage aging regime is maintained at 60-75°C for 4-10 hours, and the second-stage aging regime is maintained at 185-210°C for 6-10 hours.

[0031] The following examples illustrate the implementation of the present invention in detail, thereby enabling a full understanding and implementation of how the present invention uses technical means to solve technical problems and achieve technical effects.

[0032] Example 1 The extrusion die used in this embodiment is as follows: Figures 1-4 As shown, the thinnest wall thickness of the thin-walled part is 1.6 mm, and the guide groove is a conical groove with a taper angle of 3°. The working belt is a variable length working belt, with a contact surface length of 6.0 mm at the first typical position 31, 5.0 mm at the second typical position 32, and 3.0 mm at the third typical position 33. The mold is prepared using an additive manufacturing method, and the mold steel powder contains the following elements by weight percentage: C: 0.40%, Si: 0.03%, Mn: 2.50%, Cr: 4.95%, Mo: 0.75%, P≤0.025%, S≤0.015%, Nb: 0.03%, N: 0.04%, Al: 0.07%, with the balance being Fe and unavoidable impurities. The extrusion process for preparing the thin-walled part using this mold is implemented according to the following steps: (1) A new type of high-magnesium aluminum alloy is used as the extrusion billet. The composition of the new alloy is as follows by mass ratio: 7.7wt% Mg, 2.7wt% Zn, 0.15wt% Si, and at least one of Mn, Cu, Zr, Sc, and Ti elements with a total content not exceeding 0.3wt%, with the remainder being Al and unavoidable impurities. The billet is processed into a cylindrical ingot with a diameter of 118mm and a height of 160mm.

[0033] (2) Preheat the extrusion die. When the temperature reaches 200~220℃, spray boron nitride powder as a lubricant. Continue heating the extrusion die to 475~485℃, then place the die on the extruder and heat the extrusion cylinder at the same time to bring the temperature of the extrusion cylinder to 475~490℃.

[0034] (3) The aluminum ingot is heated by induction heating. When the cylindrical ingot billet reaches the temperature range of 475~480℃ in the first section and 415~420℃ in the last section, it is ready for extrusion.

[0035] (4) The ingot billet heated by induction is placed into the extrusion cylinder. The extrusion press push rod pushes the ingot billet through the mold at a pushing speed of 0.9 mm / s. The outlet temperature is guaranteed to be within the range of 430~450℃.

[0036] (5) The extruded thin-walled profile is subjected to online strong air cooling with a final cooling temperature of 35℃, a wind speed of 60m / s, a nozzle height of 70mm, an angle of 45° between the nozzle and the horizontal plane of the profile, and a cooling rate of 5.5~7.5℃ / s.

[0037] (6) After online air cooling, the thin-walled profiles are left at room temperature for 30 days and then subjected to a two-stage aging treatment of 60℃ / 10h + 195℃ / 8h.

[0038] Analysis and testing were conducted on the aged thin-walled profiles. The profiles showed good forming properties, a surface roughness of 0.5 μm, and a bending radius of approximately 2 degrees per meter. The density of the thin-walled profiles was 2.65 g / cm³. 3 The tensile strength in the L direction is 442 MPa, the elongation after fracture is 12.7%, and the exfoliation corrosion rating is EA.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that the working strip of the extrusion die used is of equal length, and the contact surface lengths of the first typical position 31, the second typical position 32, and the third typical position 33 of the working strip are all 5.0 mm. The other steps are the same as in Example 1. During the extrusion process, the profile failed to form and twisted.

[0040] Comparative Example 2 The difference between this comparative example and Example 1 is that in step (1), the alloy composition by mass is: 7.5 wt% Mg, 3.5 wt% Zn, 0.15 wt% Si, 0.12 wt% Zr, 0.03 wt% Ti, with the remainder being Al and unavoidable impurities. The other steps are the same as in Example 1. During the extrusion process, the profile failed to form and broke.

[0041] Comparative Example 3 The difference between this comparative example and Example 1 is that in step (1), the alloy mass ratios are: 5.1 wt% Mg, 2.7 wt% Zn, 0.15 wt% Si, 0.12 wt% Zr, 0.03 wt% Ti, with the remainder being Al and unavoidable impurities. The other steps are the same as in Example 1. Analysis and testing were performed on the aged I-beam profiles. The profiles showed good forming, a surface roughness of 0.5 μm, and a bending radius of approximately 2 degrees per meter of thin-walled section; the density was 2.69 g / cm³. 3 The tensile strength in the L direction is 403 MPa, the elongation after fracture is 13.1%, and the exfoliation corrosion rating is EA.

[0042] Comparative Example 4 The difference between this comparative example and Example 1 is that in step (3), the aluminum ingot is heated by hot air. When the temperature of both the head and tail sections of the cylindrical ingot billet reaches 485°C, it is ready for extrusion. The other steps are the same as in Example 1. During the extrusion process, the profile failed to form, and its tail section broke.

[0043] Comparative Example 5 The difference between this comparative example and Example 1 is that in step (3), induction heating is used to heat the aluminum ingot. When the cylindrical ingot billet reaches a head temperature of 415~420℃ and a tail temperature of 475~480℃, it is ready for extrusion. The other steps are the same as in Example 1. During the extrusion process, the profile failed to be extruded, resulting in a stall.

[0044] Comparative Example 6 The difference between this comparative example and Example 1 is that, in step (4), the extruder push rod pushes the ingot billet through the die at a push rate of 1.7 mm / s. The other steps are the same as in Example 1. During the extrusion process, the profile failed to form and broke.

[0045] Comparative Example 7 The difference between this comparative example and Example 1 is that, in step (5), the extruded thin-walled profile is cooled by water cooling. During the extrusion process, the profile forming effect is poor, resulting in bending and wavy patterns.

[0046] Comparative Example 8 The difference between this comparative example and Example 1 is that in step (6), the thin-walled profile after online air cooling is not left to stand at room temperature, but immediately undergoes a two-stage aging treatment. Analysis and testing of the aged thin-walled profile showed good forming, a surface roughness of 0.5 μm, and a bending curvature of approximately 2 degrees per meter; the density of the thin-walled profile was 2.65 g / cm³. 3 The tensile strength in the L direction is 419 MPa, the elongation after fracture is 18.4%, and the exfoliation corrosion rating is EA.

Claims

1. A die for hot extrusion forming of thin-walled aluminum alloy parts with high magnesium content, characterized in that, The mold body has a flow guide cavity and a working belt; the flow guide cavity and the working belt have the same cross-sectional shape and are both I-shaped; the flow guide groove connecting the flow guide cavity and the working belt is a conical groove with a taper angle of 2~4°; the working belt is a variable length working belt with three typical positions, wherein the contact surface length of the first typical position of the working belt is 5.9~6.5mm, the contact surface length of the second typical position is 4.7~5.2mm, and the contact surface length of the third typical position is 2.9~3.2mm.

2. The differential speed control working belt mold for thin-walled parts according to claim 1, characterized in that, The thinnest wall thickness of the thin-walled component is 1.6 mm.

3. The differential speed adjustable working belt mold for thin-walled parts according to claim 1 or 2, characterized in that, The contact surface length at the first typical position of the working belt is 6.0 mm, the contact surface length at the second typical position is 5.0 mm, and the contact surface length at the third typical position is 3.0 mm.

4. The differential speed adjustable working belt mold for thin-walled parts according to claim 1 or 2, characterized in that, The mold is prepared by additive manufacturing. The mold steel powder contains the following elements by weight percentage: C 0.35-0.55%, Si 0.01-0.15%, Mn 1.50-2.90%, Cr 4.50-5.70%, Mo 0.6-0.90%, P≤0.025%, S≤0.015%, Nb 0.03-0.04%, N 0.03-0.05%, Al 0.05-0.09%, with the balance being Fe and unavoidable impurities.

5. A process for hot extrusion forming of novel high-magnesium-content aluminum alloy thin-walled parts using the mold described in any one of claims 1 to 4, characterized in that, The aluminum alloy is composed of the following components: Mg 6.0~9.9wt%, Zn 1.1~3.01wt%, Si 0.1~1.15wt%, and at least one of Mn, Cu, Zr, Sc, and Ti with a total content not exceeding 0.8wt%, the remainder being Al and unavoidable impurities; the process includes the following steps: (1) The aluminum alloy is processed into an aluminum alloy ingot according to the composition of the aluminum alloy; (2) Preheat the extrusion die and use induction heating to heat the ingot, controlling the temperature of the tail section of the ingot to be higher than that of the head section; (3) The ingot heated by induction is placed into the extrusion cylinder with the tail section in front and the head section behind. The extrusion press push rod pushes the ingot through the mold to finally form it. The extrusion temperature is 380~520℃, the extrusion press push rod speed is 0.2~1.4mm / s, the temperature of the extrusion cylinder and the mold is 440~500℃, and the outlet temperature is 350~390℃. (4) The extruded thin-walled profiles are subjected to online forced air cooling, with a final cooling temperature of 30~50℃ and a cooling rate of 2~8℃ / s; (5) After cooling, the thin-walled profiles are left at room temperature for at least 7 days and subjected to two-stage aging treatment. The first stage of aging is carried out at 50~110℃ for 2~96 hours, and the second stage of aging is carried out at 120~230℃ for 2~12 hours.

6. The process according to claim 5, characterized in that, The aluminum alloy is composed of the following components: Mg 6.5~7.8wt%, Zn 1.5~2.8wt%, Si 0.15~0.5wt%, and at least one of Mn, Cu, Zr, Sc and Ti elements with a total content not exceeding 0.6wt%, with the remainder being Al and unavoidable impurities.

7. The process according to claim 5, characterized in that, In step (2), when the extrusion die is preheated to 150~200°C, boron nitride powder is added as a lubricant.

8. The process according to claim 5, characterized in that, In step (2), the temperature difference between the head section and the tail section of the extrusion casting ingot is 20~90℃.

9. The process according to claim 5, characterized in that, In step (3), the extrusion temperature is 450~515℃, the extruder push rod speed is 0.5~1.2mm / s, the extrusion cylinder and die temperature is 440~500℃, and the outlet temperature is 420~495℃.

10. The process according to claim 5, characterized in that, In step (4), the final cooling temperature is 30~40℃, the wind speed is 40~60m / s, the nozzle height is 50~80mm, the angle between the nozzle and the horizontal plane of the profile is 30~45°, and the cooling rate is 2~8℃ / s.

11. The process according to claim 5, characterized in that, In step (5), the first aging regime is maintained at 50-80℃ for 4-18 hours, and the second aging regime is maintained at 175-215℃ for 6-12 hours.

12. A novel thin-walled aluminum alloy component with high magnesium content, characterized in that, The material is produced by any one of claims 5 to 11, and no cracking occurs. The surface roughness is 0.4 to 1.2 μm, and the bending curvature of the thin-walled profile per meter is less than 3 degrees.

13. The novel high-magnesium-content aluminum alloy thin-walled part according to claim 12, characterized in that, The density of the aluminum alloy thin-walled profile is ≤2.68 g / cm³. 3 The tensile strength in the L direction is ≥435MPa, the elongation after fracture is ≥12%, and the peeling corrosion grade is not lower than EA.

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