Method for manufacturing high-strength corrosion-resistant aluminum alloy profiles

Abstract

The application discloses a manufacturing method of high-strength corrosion-resistant aluminum alloy profiles, and the method steps are as follows: smelting, electromagnetic continuous casting, multi-stage aging treatment, soaking and micro-arc oxidation. The manufacturing method of the high-strength corrosion-resistant aluminum alloy profiles initiates a composite protection system of 'component gradient + ceramic layer + self-repairing', breaks through the limitation of single strengthening mechanism, cooperatively controls the distribution of precipitated phases through electromagnetic continuous casting and multi-stage aging, and realizes the synergistic optimization of strength, toughness and corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of metal materials technology, and specifically to a method for manufacturing high-strength corrosion-resistant aluminum alloy profiles with composite gradient structures. Background Technology

[0002] The existing high-strength aluminum alloy profiles have the following pain points: (1) There is a contradiction between strength and corrosion resistance. Traditional 2-series and 7-series aluminum alloys (such as 7075 and 2024) have high stress corrosion sensitivity due to grain boundary precipitates. When the tensile strength is >500MPa, the corrosion resistance will decrease significantly; (2) Complex process: Existing technology relies on multiple heat treatments (such as T6 and T8 states), which consumes a lot of energy and easily causes grain coarsening; (3) Strong coating dependence: The surface anti-corrosion coating (such as epoxy resin) is easy to peel off and cannot meet the requirements of harsh environments such as deep sea and chemical industry. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a manufacturing method for a high-strength corrosion-resistant aluminum alloy profile that synergistically improves high strength and corrosion resistance, has a simple process and low energy consumption, has a surface anti-corrosion layer that is not easy to peel off and has a self-healing function.

[0004] To solve the above problems, the technical solution adopted by the present invention is: a manufacturing method for high-strength corrosion-resistant aluminum alloy profiles, characterized in that: the method steps are as follows: melting → electromagnetic continuous casting → multi-stage aging treatment → immersion → micro-arc oxidation;

[0005] (1) During smelting: Aluminum alloy profiles are smelted according to the following composition (wt%): Cu: 1.8~2.5%, Mg: 2.5~3.2%, Zn: 5.0~6.5%, Mn: 0.3~0.6%, Zr: 0.1~0.25%, Sc: 0.05~0.15%, Ce+La: 0.1~0.3%, with the balance being Al;

[0006] (2) In electromagnetic continuous casting: a low-frequency alternating magnetic field is used to control the flow of the melt, so that the aluminum alloy profiles obtained have a gradient composition distribution with Cu and Mg rich in the surface and Zn rich in the core; the frequency of the low-frequency alternating magnetic field is 5 to 15 Hz and the magnetic induction intensity is 0.3 to 0.8 T.

[0007] (3) Immersion: Immerse the aluminum alloy profile in Na2MoO4 corrosion inhibitor. This allows the Na2MoO4 in the corrosion inhibitor to cover the surface of the aluminum alloy profile, causing oxidation of the aluminum alloy profile surface, thereby forming a passivation film on the surface of the aluminum alloy profile, generating aluminum oxide Al2O3, aluminum hydroxide Al(OH)3 and aluminum molybdate compounds.

[0008] (4) In micro-arc oxidation: the aluminum alloy profile is placed in Na2SiO3-KOH electrolyte, and a pulse voltage of 450±5V is applied in the Na2SiO3-KOH electrolyte to generate an Al2O3-SiO2 composite ceramic layer with a thickness of 50-80μm and a porosity of <5% on the surface of the aluminum alloy profile.

[0009] Furthermore, in the aforementioned manufacturing method of high-strength corrosion-resistant aluminum alloy profiles, the multi-stage aging treatment involves aging the aluminum alloy profiles in an aging furnace. The first stage is 120±5℃×8±1h, which causes the η' phase to precipitate; the second stage is 160±5℃×12±1h, which causes the S' phase to precipitate; and the third stage is 196±5℃×2±0.5h, which aims to stabilize the structure and improve toughness.

[0010] Furthermore, in the aforementioned method for manufacturing high-strength corrosion-resistant aluminum alloy profiles, the aluminum alloy profiles are smelted according to the following composition (wt%): Cu: 2.2%, Mg: 2.8%, Zn: 5.8%, Mn: 0.4%, Zr: 0.18%, Sc: 0.12%, Ce+La: 0.25%, with the balance being Al.

[0011] Furthermore, in the aforementioned method for manufacturing high-strength corrosion-resistant aluminum alloy profiles, the frequency of the low-frequency alternating magnetic field is 10Hz.

[0012] Furthermore, in the aforementioned manufacturing method of high-strength corrosion-resistant aluminum alloy profiles, during micro-arc oxidation, a 60μm thick Al2O3-SiO2 composite ceramic layer with a porosity of <4.2% is generated on the surface of the aluminum alloy profile.

[0013] The advantages of this invention are as follows: The manufacturing method of the high-strength corrosion-resistant aluminum alloy profiles pioneers a composite protection system of "composition gradient + ceramic layer + self-healing", breaking through the limitations of a single strengthening mechanism. Electromagnetic continuous casting and multi-stage aging synergistically regulate the distribution of precipitated phases, achieving synergistic optimization of strength, toughness, and corrosion resistance. By immersing the aluminum alloy profile in Na2MoO4 corrosion inhibitor, a passivation film is formed on the surface of the aluminum alloy profile, thereby releasing MoO4^2- ions at the damaged parts of the ceramic layer. These ions react with Al^3+ to generate an Al2(MoO4)3 repair film, thereby improving corrosion resistance. The produced aluminum alloy profiles have the following advantages: Mechanical properties: tensile strength ≥720MPa, fracture toughness KIC ≥35MPa·m^1 / 2, which is 40% higher than that of traditional 7075 alloy; Corrosion resistance: salt spray test (ASTM) B117) No pitting corrosion after 5000h, corrosion rate ≤0.002mm / a; self-corrosion potential in 3.5% NaCl solution -0.68V (vs. SCE), a positive shift of 450mV compared to the reference material; energy consumption reduced by 30%, yield increased to over 95%. Detailed Implementation

[0014] The present invention will now be described in further detail with reference to specific embodiments.

[0015] The manufacturing method of high-strength corrosion-resistant aluminum alloy profiles includes the following steps: smelting → electromagnetic continuous casting → multi-stage aging treatment → immersion → micro-arc oxidation;

[0016] (1) During smelting: Aluminum alloy profiles are smelted according to the following composition (wt%): Cu: 1.8~2.5%, Mg: 2.5~3.2%, Zn: 5.0~6.5%, Mn: 0.3~0.6%, Zr: 0.1~0.25%, Sc: 0.05~0.15%, Ce+La: 0.1~0.3%, with the balance being Al; Zr / Sc composite addition forms Al3(Sc,Zr) nanoparticles, which pin grain boundaries and inhibit corrosion propagation; Ce / La rare earth elements are preferentially oxidized to form CeO2 / La2O3 protective film, blocking the Cl- erosion path;

[0017] (2) In electromagnetic continuous casting: a low-frequency alternating magnetic field is used to control the flow of the melt, so that the aluminum alloy profiles obtained have a gradient composition distribution with Cu and Mg rich in the surface and Zn rich in the core; the frequency of the low-frequency alternating magnetic field is 5 to 15 Hz and the magnetic induction intensity is 0.3 to 0.8 T.

[0018] (3) In the multi-stage aging treatment: the aluminum alloy profile is aged in the aging furnace. The first stage is 120±5℃×8±1h, which causes the η' phase (MgZn2) to precipitate; the second stage is 160±5℃×12±1h, which causes the S' phase (Al2CuMg) to precipitate; the third stage is 196±5℃×2±0.5h, which is to stabilize the structure and improve toughness.

[0019] (4) Immersion: Immerse the aluminum alloy profile in Na2MoO4 corrosion inhibitor. This allows the Na2MoO4 in the corrosion inhibitor to cover the surface of the aluminum alloy profile, causing oxidation on the surface of the aluminum alloy profile, thereby forming a passivation film on the surface of the aluminum alloy profile, generating aluminum oxide Al2O3, aluminum hydroxide Al(OH)3 and aluminum molybdate compounds; Na2MoO4 is sodium molybdate;

[0020] (5) In micro-arc oxidation: the aluminum alloy profile is placed in Na2SiO3-KOH electrolyte, and a pulse voltage of 450±5V is applied in the Na2SiO3-KOH electrolyte to generate an Al2O3-SiO2 composite ceramic layer with a thickness of 50-80μm and a porosity of <5% on the surface of the aluminum alloy profile. Example 1

[0021] The aluminum alloy profiles were smelted according to the following composition (wt%): Cu: 2.2%, Mg: 2.8%, Zn: 5.8%, Mn: 0.4%, Zr: 0.18%, Sc: 0.12%, Ce+La: 0.25%, with the balance being Al. A low-frequency alternating magnetic field with a frequency of 10Hz and a magnetic induction intensity of 0.5T was used. The ingot diameter was Φ300mm, and after multi-stage aging treatment, the hardness reached 210HV. During micro-arc oxidation, a 60μm thick Al2O3-SiO2 composite ceramic layer with a porosity of <4.2% was formed on the surface of the aluminum alloy profiles. Performance verification: The tensile strength of the aluminum alloy profiles reached 735MPa, and no corrosion perforation was observed after 6000h of salt spray testing. Example 2

[0022] The aluminum alloy profiles were smelted according to the following composition (wt%): Cu: 1.8%, Mg: 3.2%, Zn: 5.0%, Mn: 0.6%, Zr: 0.25%, Sc: 0.15%, Ce+La: 0.3%, with the balance being Al. A low-frequency alternating magnetic field with a frequency of 15Hz and a magnetic induction intensity of 0.8T was used. The ingot diameter was Φ300mm, and after multi-stage aging treatment, the hardness reached 195HV. During micro-arc oxidation, a 50μm thick Al2O3-SiO2 composite ceramic layer with a porosity of <3.8% was formed on the surface of the aluminum alloy profiles. Performance verification: The tensile strength of the aluminum alloy profiles reached 722MPa, and no corrosion perforation was observed after 5000h of salt spray testing. Example 3

[0023] The aluminum alloy profiles are smelted according to the following composition (wt%): Cu: 2.5%, Mg: 2.5%, Zn: 6.5%, Mn: 0.3%, Zr: 0.1%, Sc: 0.05%, Ce+La: 0.1%, with the balance being Al. A low-frequency alternating magnetic field with a frequency of 5Hz and a magnetic induction intensity of 0.3T is used. The ingot diameter is Φ300mm, and after multi-stage aging treatment, the hardness reaches 190HV. During micro-arc oxidation, an 80μm thick Al2O3-SiO2 composite ceramic layer with a porosity of <4% is formed on the surface of the aluminum alloy profile. Performance verification: The tensile strength of the aluminum alloy profiles reaches 723MPa, and no corrosion perforation is observed after 5000h of salt spray testing.

Claims

1. A method for manufacturing high-strength, corrosion-resistant aluminum alloy profiles, characterized in that: The steps are as follows: smelting → electromagnetic continuous casting → multi-stage aging treatment → soaking → micro-arc oxidation; (1) During smelting: Aluminum alloy profiles are smelted according to the following composition wt%: Cu: 1.8~2.5%, Mg: 2.5~3.2%, Zn: 5.0~6.5%, Mn: 0.3~0.6%, Zr: 0.1~0.25%, Sc: 0.05~0.15%, Ce+La: 0.1~0.3%, with the balance being Al; (2) In electromagnetic continuous casting: a low-frequency alternating magnetic field is used to control the flow of the melt, so that the aluminum alloy profiles obtained have a gradient composition distribution with Cu and Mg rich in the surface and Zn rich in the core; the frequency of the low-frequency alternating magnetic field is 5 to 15 Hz and the magnetic induction intensity is 0.3 to 0.8 T. (3) Immersion: Immerse the aluminum alloy profile in Na2MoO4 corrosion inhibitor. This allows the Na2MoO4 in the corrosion inhibitor to cover the surface of the aluminum alloy profile, causing oxidation of the aluminum alloy profile surface, thereby forming a passivation film on the surface of the aluminum alloy profile, generating aluminum oxide Al2O3, aluminum hydroxide Al(OH)3 and aluminum molybdate compounds. (4) In micro-arc oxidation: aluminum alloy profiles are placed in Na2SiO 3￣ In KOH electrolyte, in Na2SiO 3￣ A pulsed voltage of 450±5V is applied to the KOH electrolyte to generate Al2O3 with a thickness of 50-80μm on the surface of the aluminum alloy profile. 3￣ SiO2 composite ceramic layer with a porosity of <5%.

2. The method for manufacturing high-strength corrosion-resistant aluminum alloy profiles according to claim 1, characterized in that: In the multi-stage aging treatment: the aluminum alloy profile is aged in an aging furnace. The first stage is 120±5℃×8±1h, which causes the η' phase to precipitate; the second stage is 160±5℃×12±1h, which causes the S' phase to precipitate; and the third stage is 196±5℃×2±0.5h, which is to stabilize the structure and improve toughness.

3. The method for manufacturing high-strength corrosion-resistant aluminum alloy profiles according to claim 1 or 2, characterized in that: Aluminum alloy profiles are smelted according to the following composition (wt%): Cu: 2.2%, Mg: 2.8%, Zn: 5.8%, Mn: 0.4%, Zr: 0.18%, Sc: 0.12%, Ce+La: 0.25%, with the balance being Al.

4. The method for manufacturing high-strength corrosion-resistant aluminum alloy profiles according to claim 1 or 2, characterized in that: The frequency of the low-frequency alternating magnetic field is 10Hz.

5. The method for manufacturing high-strength corrosion-resistant aluminum alloy profiles according to claim 1 or 2, characterized in that: In micro-arc oxidation: a 60μm thick layer of Al2O3 is formed on the surface of aluminum alloy profiles. 3￣ SiO2 composite ceramic layer with a porosity of <4.2%.