High-strength 6-series aluminum alloy for fasteners and method of manufacturing and use thereof

Abstract

The application belongs to the technical field of non-ferrous metals, and particularly relates to a high-strength 6-series aluminum alloy for fasteners as well as a preparation method and application thereof. The high-strength 6-series aluminum alloy comprises the following components: Mg 0.6-0.8 wt.%, Si 0.95-1.3 wt.%, Cu 0.5-0.8 wt.%, Mn 0.5-0.6 wt.%, Fe≤0.15 wt.%, Cr 0.1-0.2 wt.%, Ti≤0.1 wt.%, and unavoidable impurities with a total amount of≤0.5 wt.%, and the balance being Al. The application adjusts the contents of Mg and Si elements, improves the rolling temperature, reduces the volume fraction of coarse intermetallic compounds, and improves the corrosion resistance and deformation capacity of the material by adjusting the rolling process. The application optimizes the annealing process by adjusting the contents of trace elements Mn, Cr and Fe, effectively controls the material grains, and is conducive to the exertion of the deformation capacity, so that the application finally has high strength and plasticity, and is not prone to cracking in the roughening process.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metals technology, specifically relating to a high-strength 6-series aluminum alloy for fasteners, its preparation method, and its application. Background Technology

[0002] Fasteners are mechanical parts used to connect and secure components or parts. They are widely used in machinery, automobiles, ships, aerospace, communications, and other fields. They are used in large quantities and come in a wide variety of specifications, mainly including bolts, screws, studs, nuts, rivets, etc. Automotive fasteners account for approximately 23% of the total sales volume of the entire fastener industry, the largest share. In the automotive industry market, automotive-specific fasteners can be applied to almost every subsystem. Aluminum alloys, with their superior properties such as low density, high strength, ease of processing, good electrical and thermal conductivity, and corrosion resistance (after anodizing), are widely used in the manufacture of high-strength rivets and bolt rods. 2-series and 7-series aluminum alloys were among the earliest used fastener aluminum alloys, but they are prone to stress corrosion. Therefore, the T73 heat treatment process is usually used to improve stress corrosion resistance, but this process also reduces strength. 6-series aluminum alloys, due to their moderate strength and good corrosion resistance, are also beginning to be used in the automotive fastener field. For example, CN106834822A discloses a high-strength 6-series aluminum alloy for automotive fasteners and its preparation method, which has a tensile strength of up to 530 MPa and an intergranular corrosion resistance of Grade 1. However, the addition of a large amount of Ag and Er elements significantly increases the cost. CN114892050A provides a high-Cu 6-series aluminum alloy with a yield strength of 370-410 MPa and an elongation of 10-15%, but no reports have been found regarding its important indicator of intergranular corrosion resistance. CN112853169A provides a high-strength 6-series aluminum alloy bolt and its manufacturing method, which also uses a high-Cu alloy, and the aging process is mostly a single-stage process. Therefore, although the material has high strength, it does not improve the intergranular corrosion resistance. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a high-strength 6-series aluminum alloy for fasteners, its preparation method, and its applications, specifically including the following:

[0004] A high-strength 6-series aluminum alloy for fasteners, wherein the composition of the high-strength 6-series aluminum alloy includes:

[0005] Mg 0.6–0.8 wt.%;

[0006] Si 0.95~1.3wt.%;

[0007] Cu 0.5-0.8 wt.%;

[0008] Mn 0.5~0.6wt.%;

[0009] Fe ≤ 0.15 wt.%;

[0010] Cr 0.1–0.2 wt.%;

[0011] Ti ≤ 0.1 wt.%;

[0012] The total amount of unavoidable impurities is ≤0.5wt.%, with the balance being Al.

[0013] Preferably, the composition of the high-strength 6-series aluminum alloy includes:

[0014] Mg 0.7–0.78 wt.%;

[0015] Si 1.0~1.2wt.%;

[0016] Cu 0.6-0.7 wt.%;

[0017] Mn 0.52~0.58wt.%;

[0018] Fe ≤ 0.12 wt.%;

[0019] Cr 0.12~0.18wt.%;

[0020] Ti≤0.08wt.%;

[0021] The total amount of unavoidable impurities is ≤0.35wt.%, with the balance being Al.

[0022] Preferably, the high-strength 6-series aluminum alloy (W) Mg +0.42×W Si The value of W is 1.1-1.2. Mg The W represents the mass percentage of magnesium. Mg This represents the mass percentage of silicon.

[0023] Preferably, the diameter of Mg2Si in the high-strength 6-series aluminum alloy is ≤5μm; the surface fraction of Mg2Si is ≤0.5%.

[0024] A method for preparing a high-strength 6-series aluminum alloy for fasteners includes the following steps:

[0025] (1) Aluminum alloy wire rods were prepared by continuous casting and rolling.

[0026] (2) The aluminum alloy wire rod is annealed at 280-350℃ and then drawn;

[0027] (3) The drawn aluminum alloy is solution treated at 540-560℃;

[0028] (4) The solution-treated aluminum alloy is subjected to aging treatment to obtain a high-strength 6-series aluminum alloy.

[0029] Preferably, the continuous casting and rolling method described in step (1) is specifically operated as follows: aluminum ingots and intermediate alloys are melted, and then poured after degassing and purification to obtain aluminum alloy billets; the aluminum alloy billets are preheated to 540-570°C in an electromagnetic induction heating furnace, and then sent into the rolling mill, with the exit temperature set to be greater than 400°C to obtain aluminum alloy wire rods.

[0030] Preferably, the heat preservation time for the solution treatment in step (3) is 20-30 min.

[0031] Preferably, the specific method of the aging treatment in step (4) is as follows: first, keep it at 170-185℃ for 6-16 hours, and then keep it at 150-210℃ for 2-16 hours.

[0032] An aluminum alloy fastener, wherein the fastener is made of high-strength 6-series aluminum alloy.

[0033] The beneficial effects of this invention are:

[0034] (1) The present invention adjusts the content of Mg and Si elements in aluminum alloy. Through precise composition design, the volume fraction of coarse intermetallic compounds is reduced, which improves the corrosion resistance and deformation capacity of the material. By adjusting the content of trace elements Mn, Cr and Fe, the grain size of the material is controlled, which is conducive to the development of deformation capacity. In the end, the invented alloy has high strength and plasticity and is not prone to cracking during the upsetting process.

[0035] (2) While adjusting the content of Mg and Si elements, the present invention also adjusted the rolling process, increased the rolling temperature, reduced the volume fraction of coarse intermetallic compounds, and improved the corrosion resistance and deformation capacity of the material. While adjusting the content of trace elements Mn, Cr and Fe, the annealing process was also optimized, which effectively controlled the grain size of the material and facilitated the deformation capacity. Ultimately, the invented alloy has high strength and plasticity and is not prone to cracking during the upsetting process. Detailed Implementation

[0036] The present invention will now be described in detail with reference to specific embodiments. The embodiments shown below do not limit the scope of the invention as described in the claims. Furthermore, the complete contents of the configurations shown in the embodiments below are not limited to those necessary for the solution of the invention described in the claims.

[0037] Alloy composition is one of the key factors controlling the strength and deformability of materials. In the 6-series alloys, Mg and Si are the main strengthening elements, forming the strengthening phase Mg2Si. The strength level of this alloy is controlled by the total amount of Mg and Si. On the other hand, the content of Mg and Si also affects the strengthening effect and formability. When the Si content is greater than the Mg content, it is easier to promote the precipitation of the strengthening phase and also helps to improve the work hardening ability and uniform deformation ability of the material. Therefore, the alloy of this invention takes into account Mg 0.6-0.8 wt.% and Si 0.95-1.3 wt.%. At the same time, the content or ratio of Mg to Si also affects the formation of excess Mg2Si phase (i.e., Mg2Si exceeding the solid solution limit of the material, which cannot be dissolved in subsequent processing), thereby affecting the deformability of the material (the presence of coarse excess Mg2Si phase will cause defects such as deformation cracking). When Wmg + 0.42*Wsi is 1.1-1.2, the volume fraction of excess Mg2Si can be minimized.

[0038] Cu is a solid solution strengthening element and can increase the work hardening ability (deformation ability) of materials. Its content also affects the material's resistance to intergranular corrosion. In this invention, its content is controlled at 0.5-0.8 wt.%.

[0039] Mn and Cr are trace transition elements. Their addition helps control the grain size of the material, ensuring fine grains during deformation and thus improving the material's deformability. However, excessive amounts of these elements do not significantly improve grain size. Therefore, the optimal content is 0.5–0.6 wt.% for Mn and 0.1–0.2 wt.% for Cr.

[0040] Fe is an impurity element, and its content must be controlled to ≤0.15 wt.%. Ti mainly plays a role in grain refinement, and its content must be controlled to ≤0.1 wt.%.

[0041] This invention employs a continuous casting and rolling process to prepare alloy wire rods. After melting aluminum ingots and intermediate alloys, the ingots are degassed and purified before being cast into an aluminum alloy billet. The billet is then preheated to 540-570°C in an electromagnetic induction furnace and fed into a rolling mill, with an exit temperature exceeding 400°C, yielding the aluminum alloy wire rod. The hot-rolled rod is annealed at 280-350°C and then drawn into a wire rod. Controlling the preheating temperature to 540-570°C ensures a high-temperature process during deformation (approaching the solution temperature), promoting the dissolution of soluble phases such as Mg2Si during deformation. Controlling the exit temperature of the hot rolling process minimizes the precipitation of fine Mg2Si phases during rolling, ensuring the supersaturation of the matrix. Annealing the hot-rolled rod at 280-350°C before drawing softens the material, facilitating cold drawing, and temperatures exceeding 350°C can easily cause grain coarsening, reducing subsequent deformation capacity.

[0042] The solution treatment process for the aforementioned aluminum alloy wire rods involves holding at 540-560℃ for 20-30 minutes; the aging process involves holding at 170-185℃ for 6-16 hours, followed by holding at 150-210℃ for 2-16 hours. Controlling the solution temperature and holding time promotes the dissolution of Mg2Si, while the two-stage aging process ensures sufficient precipitation of the aging-strengthening phase and adjusts its precipitation state, thereby improving the material's resistance to intergranular corrosion.

[0043] A high-strength 6-series aluminum alloy for fasteners, wherein the composition of the high-strength 6-series aluminum alloy includes:

[0044] Mg 0.6–0.8 wt.%, for example 0.62 wt.%, 0.65 wt.%, 0.68 wt.%, 0.70 wt.%, 0.72 wt.%, 0.74 wt.%, 0.76 wt.%, 0.78 wt.%, etc.;

[0045] Si 0.95–1.3 wt.%, for example 0.96 wt.%, 1.0 wt.%, 1.05 wt.%, 1.1 wt.%, 1.15 wt.%, 1.2 wt.%, 1.25 wt.%, etc.;

[0046] Cu 0.5-0.8 wt.%, for example 0.55 wt.%, 0.58 wt.%, 0.60 wt.%, 0.62 wt.%, 0.65 wt.%, 0.68 wt.%, 0.70 wt.%, 0.75 wt.%, 0.78 wt.%, etc.;

[0047] Mn 0.5-0.6 wt.%, for example 0.52 wt.%, 0.54 wt.%, 0.55 wt.%, 0.56 wt.%, 0.58 wt.%, etc.;

[0048] Fe ≤ 0.15 wt.%, for example, less than or equal to 0.02 wt.%, 0.05 wt.%, 0.08 wt.%, 0.10 wt.%, 0.12 wt.%, 0.14 wt.%, etc.;

[0049] Cr 0.1–0.2 wt.%, for example 0.12 wt.%, 0.14 wt.%, 0.16 wt.%, 0.18 wt.%, 0.19 wt.%, etc.;

[0050] Ti ≤ 0.1 wt.%, for example, less than or equal to 0.01 wt.%, 0.02 wt.%, 0.05 wt.%, 0.08 wt.%, 0.09 wt.%, etc.;

[0051] The total amount of unavoidable impurities is ≤0.5wt.%, with the balance being Al.

[0052] The high-strength 6-series aluminum alloy (W) Mg +0.42×W Si The value is 1.1-1.2, for example, 1.12, 1.14, 1.16, 1.18, etc., where W is... Mg The W represents the mass percentage of magnesium. Mg The value represents the mass percentage of silicon. In the high-strength 6-series aluminum alloy, the diameter of Mg2Si is ≤5μm, for example, 1μm, 2μm, 2.5μm, 3μm, 4μm, 4.5μm, etc.; the surface fraction of Mg2Si is ≤0.5%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.45%, etc.

[0053] A method for preparing a high-strength 6-series aluminum alloy for fasteners includes the following steps:

[0054] (1) Aluminum alloy wire rods are prepared by continuous casting and rolling: aluminum ingots and intermediate alloys are melted, and then poured after degassing and purification to obtain aluminum alloy billets; the aluminum alloy billets are preheated to 540-570℃ (e.g. 542℃, 545℃, 548℃, 550℃, 555℃, 560℃, 562℃, 565℃, 568℃, etc.) in an electromagnetic induction heating furnace, and then fed into a rolling mill with an exit temperature greater than 400℃ (e.g. 420℃, 450℃, 480℃, 500℃, etc.) to obtain aluminum alloy wire rods;

[0055] (2) The aluminum alloy wire rod is annealed at 280-350℃ (e.g., 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 345℃, etc.) and then drawn.

[0056] (3) The drawn aluminum alloy is solution treated at 540-560℃ (e.g., 545℃, 548℃, 550℃, 552℃, 555℃, 558℃, etc.); the holding time is 20-30min (e.g., 22min, 24min, 25min, 26min, 28min, etc.);

[0057] (4) Aging treatment of the solution-treated aluminum alloy: First, hold at 170-185℃ (e.g., 172℃, 174℃, 176℃, 178℃, 180℃, 182℃, 184℃, etc.) for 6-16 hours (e.g., 8 hours, 10 hours, 12 hours, 14 hours, 15 hours, etc.), and then hold at 150-210℃ (e.g., 160℃, 170℃, 180℃, 190℃, 200℃, etc.) for 2-16 hours (e.g., 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, etc.) to obtain high-strength 6-series aluminum alloy.

[0058] An aluminum alloy fastener, wherein the fastener is made of high-strength 6-series aluminum alloy.

[0059] The technical solution of the present invention will be further described below through specific embodiments.

[0060] Example 1

[0061] The aluminum alloy composition, by mass percentage, is: Mg 0.6 wt.%, Si 1.3 wt.%, Mn 0.6 wt%, Cr 0.10 wt%, Cu 0.8 wt.%, Ti 0.1 wt%, Fe 0.15 wt%.

[0062] Alloy wire rods are prepared by continuous casting and rolling. After melting aluminum ingots and intermediate alloys, the ingots are degassed and purified before being cast into aluminum alloy billets. The billets are preheated to 540°C in an electromagnetic induction furnace and then fed into a rolling mill to form wire rods. The exit temperature is 480°C, resulting in aluminum alloy wire rods. The hot-rolled rods are then annealed at 350°C and drawn.

[0063] After the pole is thickened, the solution treatment process is carried out at 560℃ for 20 minutes; the aging process is carried out at 185℃ for 6 hours, and then at 150℃ for 16 hours.

[0064] Example 2

[0065] The aluminum alloy composition, by mass percentage, is: Mg 0.8 wt.%, Si 0.95 wt.%, Mn 0.5 wt%, Cr 0.20 wt%, Cu 0.5 wt.%, Ti 0.05 wt%, Fe 0.08 wt%.

[0066] Alloy wire rods are prepared by continuous casting and rolling. After melting aluminum ingots and intermediate alloys, they are degassed and purified before being cast into aluminum alloy billets. The billets are preheated to 570°C in an electromagnetic induction heating furnace and then fed into a rolling mill to form wire rods. The exit temperature is 530°C, resulting in aluminum alloy wire rods. The hot-rolled rods are then annealed at 280°C and drawn.

[0067] After the pole is thickened, the solution treatment process is carried out at 540℃ for 30 minutes; the aging process is carried out at 170℃ for 16 hours, and then at 210℃ for 2 hours.

[0068] Example 3

[0069] The aluminum alloy composition, by mass percentage, is: Mg 0.7wt.%, Si 1.25wt.%, Mn 0.55wt%, Cr 0.14wt%, Cu 0.65wt.%, Ti 0.07wt%, Fe 0.10wt%.

[0070] Alloy wire rods are prepared by continuous casting and rolling. After melting aluminum ingots and intermediate alloys, the ingots are degassed and purified before being cast into aluminum alloy billets. The billets are preheated to 556°C in an electromagnetic induction heating furnace and then fed into a rolling mill to form wire rods. The exit temperature is 521°C, resulting in aluminum alloy wire rods. The hot-rolled rods are then annealed at 340°C and drawn.

[0071] After the pole is thickened, the solution treatment process is carried out at 553℃ for 25 minutes; the aging process is carried out at 180℃ for 11 hours, and then at 195℃ for 3 hours.

[0072] Example 4

[0073] The aluminum alloy composition, by mass percentage, is: Mg 0.7wt.%, Si 1.2wt.%, Mn 0.57wt%, Cr 0.15wt%, Cu 0.69wt.%, Ti 0.08wt%, Fe 0.11wt%.

[0074] Alloy wire rods are prepared by continuous casting and rolling. After melting aluminum ingots and intermediate alloys, the ingots are degassed and purified before being cast into aluminum alloy billets. The billets are preheated to 556°C in an electromagnetic induction heating furnace and then fed into a rolling mill to form wire rods. The exit temperature is 521°C, resulting in aluminum alloy wire rods. The hot-rolled rods are then annealed at 340°C and drawn.

[0075] After the pole is thickened, the solution treatment process is carried out at 553℃ for 25 minutes; the aging process is carried out at 180℃ for 11 hours, and then at 195℃ for 3 hours.

[0076] Example 5

[0077] The aluminum alloy composition, by mass percentage, is: Mg 0.7wt.%, Si 1.07wt.%, Mn 0.54wt%, Cr 0.12wt%, Cu 0.71wt.%, Ti 0.09wt%, Fe 0.12wt%.

[0078] Alloy wire rods are prepared by continuous casting and rolling. After melting aluminum ingots and intermediate alloys, the ingots are degassed and purified before being cast into aluminum alloy billets. The billets are preheated to 556°C in an electromagnetic induction heating furnace and then fed into a rolling mill to form wire rods. The exit temperature is 521°C, resulting in aluminum alloy wire rods. The hot-rolled rods are then annealed at 340°C and drawn.

[0079] After the pole is thickened, the solution treatment process is carried out at 553℃ for 25 minutes; the aging process is carried out at 180℃ for 11 hours, and then at 195℃ for 3 hours.

[0080] Example 6

[0081] The aluminum alloy composition, by mass percentage, is: Mg 0.7wt.%, Si 0.95wt.%, Mn 0.55wt%, Cr 0.15wt%, Cu 0.73wt.%, Ti 0.10wt%, Fe 0.13wt%.

[0082] Alloy wire rods are prepared by continuous casting and rolling. After melting aluminum ingots and intermediate alloys, the ingots are degassed and purified before being cast into aluminum alloy billets. The billets are preheated to 553°C in an electromagnetic induction furnace and then fed into a rolling mill to form wire rods. The exit temperature is 531°C, resulting in aluminum alloy wire rods. The hot-rolled rods are then annealed at 350°C and drawn.

[0083] After the pole is thickened, the solution treatment process is carried out at 553℃ for 25 minutes; the aging process is carried out at 180℃ for 11 hours, and then at 195℃ for 3 hours.

[0084] Comparative Example 1

[0085] The aluminum alloy composition, by mass percentage, is: Mg 1.2wt.%, Si 1.5wt.%, Mn 0.9wt%, Cr 0.30wt%, Cu 0.25wt.%, Ti 0.25wt%, Fe 0.19wt%.

[0086] The process is the same as in Example 1.

[0087] Comparative Example 2

[0088] The composition is the same as in Example 1.

[0089] Alloy wire rods are prepared by continuous casting and rolling. After melting aluminum ingots and intermediate alloys, the ingots are degassed and purified before being cast into aluminum alloy billets. The billets are preheated to 416°C in an electromagnetic induction furnace and then fed into a rolling mill to form wire rods. The exit temperature is 321°C, and the aluminum alloy wire rods are obtained. The hot-rolled rods are then annealed at 210°C and drawn.

[0090] After the pole is thickened, the solution treatment process is carried out at 553℃ for 25 minutes; the aging process is carried out at 180℃ for 11 hours.

[0091] Table 1 shows the properties and microstructure characteristics of the alloys in the examples and comparative examples. The mechanical properties were tested according to the national standard GB / T 228.1-2010. As shown in Table 1, the present invention, by reasonably adjusting the content of each element in the aluminum alloy and the processing technology, enables the material to have high strength, high plasticity (deformation performance), and high corrosion resistance.

[0092] Table 1. Properties and microstructure characteristics of the alloys in Examples 1-6 and Comparative Examples 1-2

[0093]

[0094] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-strength 6-series aluminum alloy for fasteners, characterized in that, The composition of the high-strength 6-series aluminum alloy includes: Mg 0.6–0.8 wt.%; Si 0.95–1.3 wt.%; Cu 0.5–0.8 wt.%; Mn 0.5–0.6 wt.%; Fe ≤0.15 wt.%; Cr 0.1–0.2 wt.%; Ti ≤0.1 wt.%; and unavoidable impurities ≤0.5 wt.%, with the balance being Al; the high-strength 6-series aluminum alloy (W Mg +0.42×W Si The value of W is 1.1 to 1.

2. Mg The W represents the mass percentage of magnesium. Si The mass percentage of silicon; the diameter of Mg2Si in the high-strength 6-series aluminum alloy is ≤5μm, and the surface fraction of Mg2Si is ≤0.5%.

2. A high-strength 6-series aluminum alloy for fasteners according to claim 1, characterized in that, The composition of the high-strength 6-series aluminum alloy includes: Mg 0.7~0.78wt.%; Si 1.0~1.2wt.%; Cu 0.6~0.7wt.%; Mn 0.52~0.58wt.%; Fe≤0.12wt.%; Cr 0.12~0.18wt.%; Ti≤0.08wt.%; and unavoidable impurities ≤0.35wt.%, with the balance being Al.

3. A method for preparing a high-strength 6-series aluminum alloy for fasteners according to any one of claims 1-2, characterized in that, Includes the following steps: (1) Aluminum alloy wire rods are prepared by continuous casting and rolling; (2) The aluminum alloy wire rods are annealed at 280-350℃ and then drawn; (3) The drawn aluminum alloy is solution treated at 540-560℃; (4) The solution treated aluminum alloy is aged to obtain high-strength 6-series aluminum alloy.

4. The method for preparing a high-strength 6-series aluminum alloy for fasteners according to claim 3, characterized in that, The specific operation of the continuous casting and rolling method in step (1) is as follows: the aluminum ingot and intermediate alloy are melted, and then poured after degassing and purification to obtain an aluminum alloy billet; the aluminum alloy billet is preheated to 540-570°C in an electromagnetic induction heating furnace, and then sent into the rolling mill, with the exit temperature set to be greater than 400°C to obtain an aluminum alloy wire rod.

5. The method for preparing a high-strength 6-series aluminum alloy for fasteners according to claim 3, characterized in that, The heat preservation time for the solution treatment in step (3) is 20 to 30 minutes.

6. The method for preparing a high-strength 6-series aluminum alloy for fasteners according to claim 3, characterized in that, The specific method of the aging treatment in step (4) is as follows: first, keep it at 170-185℃ for 6-16 hours, and then keep it at 150-210℃ for 2-16 hours.

7. An aluminum alloy fastener, characterized in that, The fasteners described in any one of claims 1-2 are made of high-strength 6-series aluminum alloy.

Images