1. The high-strength aluminum alloy bolt material is characterized in that: the alloy material comprises the following chemical components: si: 0.8 to 1.5%, Fe: 0.1 to 0.5 percent; cu: cu: 0.3 to 0.8 percent; mn: 0.2 to 0.6 percent; mg: 0.8 to 1.4 percent; zn: 0.2 percent; ti: 0.10 to 0.2 percent; cr: 0.6 to 1.0 percent; v: 0.05 to 0.2 percent; ni: 0.08-0.5%; mo: 0.03-0.2%; al: and (4) the balance.

2. A preparation method of a high-strength aluminum alloy bolt material is characterized by comprising the following steps: it comprises the following steps:

(1) the high-strength aluminum alloy bolt material according to claim 1, which is subjected to component ratio and smelting to form a melt;

(2) after the melt is transferred into a standing furnace, refining the melt by using nitrogen and a refining agent at the refining temperature of 720 and 750 ℃ for 15 to 25 minutes, standing the melt for 20 to 30 minutes after refining, and degassing, deslagging and purifying the melt through the process; during casting, two filter plates are arranged between a casting mould and a furnace mouth for filtering, and glass fiber cloth with 14-30 meshes is used for filtering before casting, so that oxides and slag in a melt are fully filtered;

(3) carrying out homogenization annealing on the semicontinuous ingot casting along with a furnace, and homogenizing the temperature: keeping the temperature at 580 ℃ for 3-7 hours at 520-; the dispersion precipitation distribution of phase particles can be realized, and the size, the quantity and the morphological distribution of the dispersed phase particles are controlled;

(4) then heating the homogenized aluminum ingot to 450-480 ℃ for extruding a bar, and then drawing the bar to the required diameter at 320-380 ℃;

(5) cold upsetting the flange, performing a heat treatment process after the flange is passed, and finally performing thread rolling treatment

The heat treatment process comprises quenching at 420-.

Background

As the automotive industry has developed, there has been a trend toward lighter weight automobiles, and fasteners for engines and transmissions also need to be lighter, preferably from steel to aluminum alloys. The traditional 6XXX series material of the aluminum alloy material can be used for manufacturing the bolt through the working procedures of forging and the like, but the tensile strength of the bolt is 380Mpa, so that the requirements of the high-strength bolt on strength and plasticity cannot be met.

The heat-resistant strength of the existing 6XXX series aluminum alloy is poorer than that of steel, the room-temperature strength and the high-temperature strength of the alloy can be improved through the improvement of a heat treatment process, and the thread strength of a bolt can be increased through increasing the contact area of the bolt and a product.

Although the 7XXXX series material has high strength of 520MPa at room temperature, it has inferior heat resistance and severe stress corrosion compared with the 6XXX series material, and although the corrosion resistance can be improved by the heat treatment process, it is inferior, and it needs to be anodized, which increases the cost, and the oxide film is peeled off to cause stress corrosion and intergranular corrosion.

The bolt for connecting the automobile engine and the gearbox works in a complex alternating stress and high-temperature environment, and all the requirements of the bolt on high strength, high temperature resistance, corrosion resistance and the like are met, so that the high-strength and high-temperature-resistant aluminum alloy bolt is found.

Disclosure of Invention

The invention aims to provide a high-strength aluminum alloy bolt material and a preparation method thereof, mainly solves the defects of room temperature strength, high temperature strength, stress corrosion resistance, high temperature resistance and the like of the existing aluminum alloy material, and provides an alloy material for a high-strength aluminum alloy bolt with stress corrosion resistance and high temperature resistance for an automobile and a preparation method thereof. In particular provides a new heat treatment process, solves the problem of insufficient alloy strength, and leads the tensile strength of the alloy to reach 520Mpa and exceed the top level in foreign countries.

In order to achieve the above object, the present invention is realized by:

the high-strength aluminum alloy bolt material is characterized in that: the alloy material comprises the following chemical components: si: 0.8 to 1.5%, Fe: 0.1 to 0.5 percent; cu: cu: 0.3 to 0.8 percent; mn: 0.2 to 0.6 percent; mg: 0.8 to 1.4 percent; zn: 0.2 percent; ti: 0.10 to 0.2 percent; cr: 0.6 to 1.0 percent; v: 0.05 to 0.2 percent; ni: 0.08-0.5%; mo: 0.03-0.2%; al: and (4) the balance.

A preparation method of a high-strength aluminum alloy bolt material is characterized by comprising the following steps: it comprises the following steps:

(1) carrying out component proportion and smelting according to the high-strength aluminum alloy bolt material to form a melt;

(2) after the melt is transferred into a standing furnace, refining the melt by using nitrogen and a refining agent at the refining temperature of 720 and 750 ℃ for 15 to 25 minutes, standing the melt for 20 to 30 minutes after refining, and degassing, deslagging and purifying the melt through the process; during casting, two filter plates are arranged between a casting mould and a furnace mouth for filtering, and glass fiber cloth with 14-30 meshes is used for filtering before casting, so that oxides and slag in a melt are fully filtered;

(3) carrying out homogenization annealing on the semicontinuous ingot casting along with a furnace, and homogenizing the temperature: keeping the temperature at 580 ℃ for 3-7 hours at 520-; the dispersion precipitation distribution of phase particles can be realized, and the size, the quantity and the morphological distribution of the dispersed phase particles are controlled;

(4) then heating the homogenized aluminum ingot to 450-480 ℃ for extruding a bar, and then drawing the bar to the required diameter at 320-380 ℃;

(5) cold upsetting the flange, performing a heat treatment process after the flange is passed, and finally performing thread rolling treatment

The heat treatment process comprises quenching at 420-. The tensile strength of the alloy is more than or equal to 480MPa, the yield strength is more than or equal to 430MPa, and the elongation is more than or equal to 10%. The use requirement of the bolt is met.

Drawings

FIG. 1 is a metallographic structure diagram (400X) showing the structure of a sample in the application of the present invention.

Detailed Description

The invention discloses a high-strength aluminum alloy bolt material which comprises the following chemical components in percentage by mass: 0.8 to 1.5%, Fe: 0.1 to 0.5 percent; cu: 0.3 to 0.8 percent; mn: 0.2 to 0.6 percent; mg: 0.8 to 1.4 percent; zn: 0.2 percent; ti: 0.10 to 0.2 percent; cr: 0.5 to 1.0 percent; v: 0.05 to 0.2 percent; ni: 0.08-0.5%; mo: 0.05 to 0.2 percent; al: and (4) the balance. Through special homogenizing process, extrusion drawing, cold heading and thread rolling, and heat treatment, the material has tensile strength not lower than 480MPa, yield strength not lower than 430MPa and elongation not lower than 10%.

1. The invention mainly researches various alloy elements:

the change of Mg and Si content has no obvious effect on the tensile strength and plasticity of the alloy in an annealing state, but after quenching and aging treatment, the strength of the alloy is greatly improved, the maximum value is in a three-phase region, and when residual Si and Mg2Si exist in the alloy, the corrosion resistance is reduced along with the increase of the quantity. Only alloys which have the alloy in the two-phase region and the Mg2Si phase all solid-soluble in the single-phase region of the matrix have the best corrosion resistance and no tendency to stress corrosion cracking. Through research: the Si content is more than 1.5 percent, the stress corrosion resistance is poor and is less than 0.8 percent, the formed strengthening phase is less, and the strengthening is not obvious. Similarly, in order to form a Mg2Si strengthening phase by matching with the Si content, the ratio of Mg to Si is 1.73:1, and the Mg content is optimally controlled to be 0.8-1.4%.

The Cu content is controlled to be 0.3-0.8%, the alloy strengthening effect is not obvious when the Cu content is lower than 0.3%, and a CuAl2 strengthening phase is not formed in the whole solid solution matrix of Cu. Along with the increase of the Cu content in the hot working plasticity of the alloy, the heat treatment strengthening effect is obvious, the Cu content is higher than 0.8 percent, and the corrosion resistance of the alloy is poor.

The content of Cr and Mn, and the content of Mn is controlled to be 0.2-0.6%, so that the alloy strength can be improved, and the corrosion resistance and the impact toughness can be improved. Influences the recrystallization process, refines crystal grains, and reduces the plasticity and strength of the alloy because needle-shaped MnAl6 phase appears when the Mn content is too high. The Cr is controlled to be 0.5-1.0 percent, the Cr can refine grains, the corrosion resistance of the alloy is improved, the heat resistance of the alloy is improved more importantly, and the high-temperature strength is improved by 15 percent.

Ni, V and Mo have great influence on the heat resistance of the alloy, and the addition of Ni in the alloy for more than 0.5 percent can cause coarse inclusions, thereby influencing the stress corrosion resistance of the alloy. Mo and V mainly improve the heat resistance of the alloy, the high temperature resistance is obviously improved by adding a small amount of Mo, and the high and low temperature creep resistance is obviously obvious, so that the content of Mo is controlled to be 0.05-0.2 percent.

Ti content is 0.1-0.2%, which has obvious influence on improving columnar crystal structure, improving alloy forging performance, refining crystal grains, and if the addition amount is more than 0.2%, more impurities are needed, thus reducing the corrosion resistance of the alloy.

2. The invention adopts the following steps: keeping the temperature at 580 ℃ for 3-7 hours at 520-; can disperse, separate out and distribute phase particles and control the size, quantity and shape distribution of the dispersed phase particles. Then extrusion processing is carried out at 460-510 ℃ to obtainAnd (5) bars with equal specifications.

3. The heat treatment process adopted by the invention is that quenching is carried out firstly at 420-.

The bolt can meet the requirements of sufficient heat resistance, high-temperature performance, corrosion resistance and high strength, and can realize the light weight of the engine gearbox.

Practical case

Ingredient table

	Si	Fe	Cu	Mn	Mg	Zn	Ti	Cr	Ni	Mo	V
												Example 1	1.21	0.25	0.65	0.55	1.15	0.2	0.15	0.95	0.10	0.10	0.11
Example 2	1.23	0.21	0.31	0.21	0.92	0.1	0.10	0.67	0.35	0.11	0.10
												Example 3	0.89	0.34	0.56	0.38	0.98	0.1	0.12	0.89	0.24	0.10	0.14
Example 4	0.98	0.21	0.61	0.37	0.94	0.16	0.14	0.86	0.24	0.15	0.12
												Example 5	1.35	0.21	0.54	0.46	1.21	0.15	0.15	0.56	0.31	0.08	0.11
Example 6	1.10	0.18	0.67	0.26	1.12	0.15	0.11	0.84	0.35	0.11	0.12

Melting alloy according to the components in the table, preparing an aluminum bar by adopting a semi-continuous casting mode, and then carrying out homogenization treatment on the semi-continuous cast bar along with a furnace, wherein the homogenization temperature is as follows: 560 ℃, keeping the temperature for 6 hours, cooling the mixture to the temperature of 420-;

then heating the homogenized aluminum bar to 460 ℃ for extrusionThen drawing to diameter at 360 DEG CThese examples show no fracture during drawing.

Then cold heading is carried out, then heat treatment quenching is carried out at the temperature of 430 ℃/1H, heat preservation at the temperature of 550 ℃ is carried out, water quenching is carried out at the temperature of 550 ℃, aging is carried out at the temperature of 180 ℃/15H, and thread rolling is carried out to obtain the M10 bolt.

The above examples were tested for performance and resistance to high temperature and corrosion, as shown in the following table:

according to the test results of the alloy mixture ratio examples 1 to 6, the tensile strength is more than or equal to 485Mpa, the yield strength is more than or equal to 430Mpa, and the elongation is more than or equal to 10 percent at room temperature. The mechanical property is tested at the temperature of 200 ℃, and the result is that the tensile strength is more than or equal to 400Mpa, the elongation is more than or equal to 12 percent, and the alloy has good stress corrosion resistance.

In case 1, after the homogenized bar is subjected to cold heading and heat treatment, a sample is taken and metallographic structure analysis is carried out, and eutectic remelted spheres, coarse grain boundaries, spindle-shaped local grain boundary hairs and grain boundary hairs are not generated, the phenomenon of quenching cracks along the triangular grain boundaries or the grain boundaries is avoided, the eutectic is fine, particles of a strengthening phase are fine, and the strengthening phase is dispersed and uniformly distributed, so that a hypoeutectic structure is generated. See in particular fig. 1.

The invention has the advantages and positive significance that:

1. the heat resistance and the stress corrosion resistance of the alloy are improved by adding Cr and Mn into the alloy, the strength of the alloy can be improved, particularly, the Mn content is reduced by 0.2-0.6%, the Cr content is improved by 0.6-1.0%, the recrystallization temperature of the alloy is favorably improved, and the strength of the alloy is improved.

2. The alloy is added with Ni, Mo and V elements, so that the heat resistance and the stress corrosion resistance of the alloy are improved. In particular, the stress loss can be greatly reduced.

3. The alloy of the invention has mechanical properties tested at room temperature, tensile strength more than or equal to 485Mpa, yield strength more than or equal to 430Mpa and elongation more than or equal to 10%. The mechanical property is tested at the high temperature of 200 ℃, the tensile strength is more than or equal to 400Mpa, the yield strength is more than or equal to 330Mpa, and the elongation is more than or equal to 12%. And the stress corrosion resistance is good.

4. Cold upsetting the flange, then performing heat treatment quenching, firstly performing heat treatment quenching at 420-. And finally, thread rolling is carried out. This corresponds to a further cold working process after the heat treatment, which contributes to the improvement of the thread strength.

In summary, the present invention is only a preferred embodiment, and is not intended to limit the scope of the invention, i.e. all equivalent changes and modifications made according to the content of the claims of the present invention should be considered as the technical scope of the present invention.