Preparation method of high-performance heat-treatment-free aluminum alloy material

Abstract

The invention belongs to the field of aluminum alloy manufacturing, and particularly relates to a preparation method of a high-performance heat-treatment-free aluminum alloy material, which comprises the following steps of: transferring a refined solution of aluminum alloy into a jacketed heating furnace, controlling the temperature of the inner wall of the jacketed heating furnace to be 575-650 DEG C, and sequentially arranging at least three layers of copper nets and at least three layers of aluminum alloy in the jacketed heating furnace from top to bottom, each layer of copper net is connected with an intermittent power supply to treat the refined melt in the jacketed heating furnace, so as to obtain a repeatedly crystallized melt; and feeding the repeatedly crystallized melt into a die-casting machine for die-casting treatment to obtain a cast ingot / rod. According to the method, through continuous remelting, crystallization, re-remelting and other processes after refining, even if the Fe content reaches 0.37% and other rare earth elements are not added, all components of the aluminum alloy and Fe can form a stable phase, and the tolerance to the impurity Fe can be greatly improved. And under the test condition of 3 million cycles, the fatigue strength of the aluminum alloy material reaches 120 MPa or above.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy manufacturing, and specifically relates to a method for preparing a high-performance heat-treatment-free aluminum alloy material. Background Art

[0002] The performance of aluminum alloy is controlled by the microstructure, and heat treatment is an effective way to improve its performance. At a specific temperature, the heating speed of the aluminum alloy is controlled, and it is quickly cooled after reaching a certain temperature within a specified time, which will change the internal structure of the aluminum alloy. A reasonable heat treatment system is very important to improve the microstructure of aluminum alloy materials.

[0003] Traditional die-cast aluminum alloys usually use heat treatment technology (high temperature solid solution + artificial aging) to improve the alloy's mechanical properties such as yield strength and elongation.

[0004] At present, the research on heat-treatment-free die-casting aluminum alloys is mostly focused on the Al-Si series and Al-Mg series. The mainstream heat-treatment-free materials are based on the traditional Al-Si series alloys, adding appropriate chemical modification elements, and then combining the actual solidification conditions during die-casting to produce fine grains and fully dispersed refined structures, so that the mechanical properties that could only be obtained by traditional solid solution aging strengthening can be obtained.

[0005] The current heat-treatment-free die-cast aluminum alloy materials still have significant problems in application. They are not tolerant to the impurity element iron (Fe), and the mass percentage of iron must be controlled below 0.16%. This strict requirement requires that the raw materials used for production must be high-purity electrolytic aluminum, which increases production energy consumption and costs. Alternatively, rare earth elements are added to aluminum alloys. The atomic radius of rare earth elements is larger than that of aluminum. The crystal structure of aluminum is a face-centered cubic lattice, while rare earth elements are a close-packed hexagonal lattice. Therefore, rare earth elements dissolve less in aluminum alloys and are not easy to form solid solutions. After adding rare earth elements to aluminum alloys, the rare earth elements will gather in front of the solid-liquid interface, so there will be a situation of supercooling of the components, and the mechanical properties of the aluminum alloy will be improved. For impurities such as Fe in the alloy, rare earth elements can react with them to purify the aluminum liquid.

[0006] Therefore, whether using high-purity electrolytic aluminum as raw material or adding rare earth elements, these limit the application of heat-treatment-free aluminum alloys.

[0007] Based on this, the present invention is proposed. Summary of the invention

[0008] The object of the present invention is to provide a method for preparing a high-performance heat-treatment-free aluminum alloy material to solve the above-mentioned problems.

[0009] A method for preparing a high-performance heat-treatment-free aluminum alloy material comprises the following steps:

[0010] Step 1: Add aluminum alloy raw materials into a furnace, heat and smelt to obtain a metal solution;

[0011] Step 2, adjusting the temperature in the furnace to 760-770° C., adding a refining agent for refining, and degassing during the refining process to obtain a refined melt;

[0012] Step 3, transferring the refined melt into a jacketed heating furnace, controlling the inner wall temperature of the jacketed heating furnace to be 575-650°C, and having at least three layers of copper mesh from top to bottom in the jacketed heating furnace, all of which are submerged in the refined melt; each layer of copper mesh is connected to an intermittent power supply to treat the refined melt in the jacketed heating furnace, and after the treatment, a multi-crystallized melt is obtained;

[0013] Step 4, feeding the multi-crystallized melt into a die-casting machine for die-casting to obtain a die-cast ingot / rod; cooling to room temperature to obtain the high-performance heat-treatment-free aluminum alloy material;

[0014] The mass percentage of iron in the high-performance heat-treatment-free aluminum alloy material is less than or equal to 0.37%, and the high-performance heat-treatment-free aluminum alloy material does not contain rare earth elements.

[0015] As a further improvement, the mesh of the copper mesh is a regular hexagonal structure.

[0016] As a further improvement, the mesh side length of the copper mesh is 3 to 4 cm.

[0017] As a further improvement, the copper mesh in the jacketed heating furnace is laid out in a flat area that increases from top to bottom, and the copper mesh in the jacketed heating furnace is coaxially arranged.

[0018] Further improvement, the output current of the intermittent power supply is 11000-12000A, the output voltage of the intermittent power supply is 50-55V, the working cycle of the intermittent power supply is T=12s, and the braking time is t b =9s, no-load time t k =3s, T = t b +t k .

[0019] As a further improvement, each layer of copper mesh is connected to an intermittent power supply to treat the refined melt in the jacketed heating furnace for 30 to 40 minutes.

[0020] As a further improvement, the high-performance heat-treatment-free aluminum alloy material comprises the following components in percentage by mass:

[0021] Si: 0.4% ~ 0.8%; Mg: 0.8% ~ 1.2%; Cu: 0.15% ~ 0.4%; Zn: ≤ 0.25%;

[0022] Mn: ≤0.15%; Ti: ≤0.15%; Cr: 0.04%~0.35%; Fe: ≤0.37%; the balance is Al and unavoidable impurity elements.

[0023] As a further improvement, the refining agent is one or more of NaCl, KCl, CaF2, Na3AlF6, and Na2SiF6.

[0024] As a further improvement, the jacket of the jacketed heating furnace is filled with heat transfer oil, and the temperature of the heat transfer oil is not lower than 150°C.

[0025] As a further improvement, in step 4, the temperature of the multi-crystallized melt when entering the die-casting machine is 620-635°C, the die-casting pressure is 85 MPa, and the die-casting speed is 3 m / s.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention uses continuous remelting, crystallization, and remelting processes after refining, so that even if the Fe content reaches 0.37% and no other rare earth elements are added, the various components of the aluminum alloy can form a stable phase with Fe, which can greatly improve the tolerance to impurity Fe.

[0028] 2. The high-performance heat-treatment-free aluminum alloy material of the present invention has a yield strength of 270 MPa, a tensile strength of 300 MPa, and an elongation of 11-15% without heat treatment.

[0029] 3. Under the test condition of 30 million cycles, the fatigue strength of aluminum alloy material reaches more than 120MPa. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below through specific examples.

[0031] Example 1

[0032] Aluminum alloy material formula:

[0033] The following components are included in mass percentage:

[0034] Si: 0.4% ~ 0.8%; Mg: 0.8% ~ 1.2%; Cu: 0.15% ~ 0.4%; Zn: ≤ 0.25%;

[0035] Mn: ≤0.15%; Ti: ≤0.15%; Cr: 0.04%~0.35%; Fe: 0.37%; the balance is Al and unavoidable impurity elements.

[0036] Step 1: Add aluminum alloy raw materials into a furnace and heat and smelt to obtain a molten metal.

[0037] Step 2: Adjust the temperature in the furnace to 760-765° C., add the refining agent Na2SiF6 for refining, degas during the refining process, and obtain a refined melt.

[0038] Step 3, transfer the refined melt to a jacketed heating furnace, control the inner wall temperature of the jacketed heating furnace to 555-650°C, and place three layers of copper mesh in the jacketed heating furnace from top to bottom, all of which are submerged in the refined melt; each layer of copper mesh is connected to an intermittent power supply to treat the refined melt in the jacketed heating furnace, and after the treatment, a multi-crystallized melt is obtained. The mesh of the copper mesh is a regular hexagonal structure. The side length of the mesh of the copper mesh is 3 cm.

[0039] The copper mesh in the jacketed heating furnace is laid out in increasing areas from top to bottom, and is arranged in order from top to bottom as follows: the first layer of copper mesh, the second layer of copper mesh and the third layer of copper mesh. The laying area of ​​the first layer of copper mesh is 0.7 m 2 The second layer of copper mesh has a flat area of ​​1.1m 2 , the paving area of ​​the third layer of copper mesh is 1.5m 2 .

[0040] The copper mesh in the jacketed heating furnace is coaxially arranged.

[0041] The output current of the intermittent power supply is 11000A, the output voltage of the intermittent power supply is 55V, the working cycle of the intermittent power supply is T=12s, and the braking time is t b =9s, no-load time t k =3s, T = t b +t k .

[0042] Each layer of copper mesh is connected to an intermittent power supply to treat the refined melt in the jacketed heating furnace for 30 minutes.

[0043] The jacket of the jacketed heating furnace is filled with heat transfer oil, and the temperature of the heat transfer oil is not lower than 150°C.

[0044] Step 4: feeding the multi-crystallized melt into a die-casting machine for die-casting to obtain a die-casting rod; cooling to room temperature to obtain an aluminum alloy material 1. The temperature of the multi-crystallized melt when entering the die-casting machine is 620-625° C., the die-casting pressure is 85 MPa, and the die-casting speed is 3 m / s.

[0045] The mass percentage of iron in the aluminum alloy material 1 is less than or equal to 0.37%, and the high-performance heat-treatment-free aluminum alloy material does not contain rare earth elements.

[0046] Example 2

[0047] Aluminum alloy material formula:

[0048] The following components are included in mass percentage:

[0049] Si: 0.4% ~ 0.8%; Mg: 0.8% ~ 1.2%; Cu: 0.15% ~ 0.4%; Zn: ≤ 0.25%;

[0050] Mn: ≤0.15%; Ti: ≤0.15%; Cr: 0.04%~0.35%; Fe: ≤0.33%; the balance is Al and unavoidable impurity elements.

[0051] Step 1: Add aluminum alloy raw materials into a furnace and heat and smelt to obtain a molten metal.

[0052] Step 2: Adjust the temperature in the furnace to 765-770°C, add the refining agent Na2SiF6 for refining, degas during the refining process, and obtain a refined melt.

[0053] Step 3, transfer the refined melt to a jacketed heating furnace, control the inner wall temperature of the jacketed heating furnace to 555-650°C, and have at least three layers of copper mesh from top to bottom in the jacketed heating furnace, all of which are submerged in the refined melt; each layer of copper mesh is connected to an intermittent power supply to treat the refined melt in the jacketed heating furnace, and after the treatment, a multi-crystallized melt is obtained. The mesh of the copper mesh is a regular hexagonal structure. The side length of the mesh of the copper mesh is 4 cm.

[0054] The copper mesh in the jacketed heating furnace is arranged with the flattened area increasing from top to bottom, and the copper mesh in the jacketed heating furnace is arranged coaxially.

[0055] The output current of the intermittent power supply is 12000A, the output voltage of the intermittent power supply is 50V, the working cycle of the intermittent power supply is T=12s, and the braking time is t b =9s, no-load time t k =3s, T = t b +t k .

[0056] Each layer of copper mesh is connected to an intermittent power supply to treat the refined molten metal in the jacketed heating furnace for 40 minutes.

[0057] The jacket of the jacketed heating furnace is filled with heat transfer oil, and the temperature of the heat transfer oil is not lower than 150°C.

[0058] Step 4: feeding the multi-crystallized melt into a die-casting machine for die-casting to obtain a die-casting rod; cooling to room temperature to obtain an aluminum alloy material 1. The temperature of the multi-crystallized melt when entering the die-casting machine is 625-630° C., the die-casting pressure is 85 MPa, and the die-casting speed is 3 m / s.

[0059] The mass percentage of iron in the aluminum alloy material 1 is less than or equal to 0.37%, and the high-performance heat-treatment-free aluminum alloy material does not contain rare earth elements.

[0060] Example 3

[0061] Aluminum alloy material formula:

[0062] The following components are included in mass percentage:

[0063] Si: 0.4% ~ 0.8%; Mg: 0.8% ~ 1.2%; Cu: 0.15% ~ 0.4%; Zn: ≤ 0.25%;

[0064] Mn: ≤0.15%; Ti: ≤0.15%; Cr: 0.04%~0.35%; Fe: ≤0.31%; the balance is Al and unavoidable impurity elements.

[0065] Step 1: Add aluminum alloy raw materials into a furnace and heat and smelt to obtain a molten metal.

[0066] Step 2: Adjust the temperature in the furnace to 763-768°C, add the refining agent Na2SiF6 for refining, degas during the refining process, and obtain a refined melt.

[0067] Step 3, transfer the refined melt to a jacketed heating furnace, control the inner wall temperature of the jacketed heating furnace to 555-650°C, and have at least three layers of copper mesh from top to bottom in the jacketed heating furnace, all of which are submerged in the refined melt; each layer of copper mesh is connected to an intermittent power supply to treat the refined melt in the jacketed heating furnace, and after the treatment, a multi-crystallized melt is obtained. The mesh of the copper mesh is a regular hexagonal structure. The side length of the mesh of the copper mesh is 4 cm.

[0068] The copper mesh in the jacketed heating furnace is arranged with the flattened area increasing from top to bottom, and the copper mesh in the jacketed heating furnace is arranged coaxially.

[0069] The output current of the intermittent power supply is 11500A, the output voltage of the intermittent power supply is 50V, the working cycle of the intermittent power supply is T=12s, and the braking time is t b =9s, no-load time t k =3s, T = t b +t k .

[0070] Each layer of copper mesh is connected to an intermittent power supply to treat the refined molten metal in the jacketed heating furnace for 35 minutes.

[0071] The jacket of the jacketed heating furnace is filled with heat transfer oil, and the temperature of the heat transfer oil is not lower than 150°C.

[0072] Step 4: feeding the multi-crystallized melt into a die-casting machine for die-casting to obtain a die-casting rod; cooling to room temperature to obtain an aluminum alloy material 1. The temperature of the multi-crystallized melt when entering the die-casting machine is 630-635° C., the die-casting pressure is 85 MPa, and the die-casting speed is 3 m / s.

[0073] The mass percentage of iron in the aluminum alloy material 1 is less than or equal to 0.37%, and the high-performance heat-treatment-free aluminum alloy material does not contain rare earth elements.

[0074] Comparative Example 1

[0075] The only difference between this example and Example 1 is that step 3 is omitted, and the refined molten metal is directly fed into the die-casting machine for die-casting. The rest is the same as Example 1, and finally the aluminum alloy material a1 is obtained.

[0076] Comparative Example 2

[0077] The only difference between this example and Example 1 is that in step 3, the temperature of the inner wall of the jacketed heating furnace is controlled to be not less than 750° C., and the rest is the same as Example 1, and finally aluminum alloy material a2 is obtained.

[0078] Comparative Example 3

[0079] The only difference between this example and Example 1 is that in step 3, the mesh of the copper mesh is a circular structure, and the rest is the same as Example 1, and finally aluminum alloy material a3 is obtained.

[0080] The properties of the aluminum alloy materials corresponding to Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1:

[0081] Table 1

[0082] Tensile strength / MPa Yield strength / MPa Elongation / % Fatigue strength / MPa Example 1 301 272 13 123 Example 2 298 270 11 120 Example 3 300 272 15 118 Comparative Example 1 115 63 27 69 Comparative Example 2 124 71 25 88 Comparative Example 3 288 259 17 91

[0083] In Table 1, the fatigue strength test was conducted at a frequency of 35 Hz, a stress of 69 MPa, and 30 million cycles.

[0084] It can be seen from Table 1 that when the iron content exceeds 0.16%, if the aluminum alloy melt is not subjected to multiple remelting, cooling, crystallization, remelting, cooling, crystallization and arc shock caused by auxiliary intermittent power supply, the tolerance of each component in the aluminum alloy to the impurity element iron can be maximized, thereby significantly improving the fatigue strength.

[0085] During the smelting process of aluminum alloy, the aluminum alloy is completely melted when the temperature rises to 660℃. However, in order to ensure the quality of aluminum alloy and reduce problems such as oxidation and hydrogen absorption, the smelting temperature is generally controlled between 700℃ and 750℃. Therefore, low-temperature heat transfer oil is introduced into the jacketed heating furnace to adjust the temperature of the inner wall of the jacketed heating furnace. At this time, the inner wall of the jacketed heating furnace will be used as the starting point to facilitate crystallization; after the copper mesh is powered on, the huge contact resistance between copper and aluminum is conducive to further remelting.

[0086] In the above process, if the copper mesh flattening area in the jacketed heating furnace is the same, both are 0.7m 2 The direct consequence is that the disturbance in the aluminum alloy melt is aggravated, resulting in an increase of more than 53% in the amount of aluminum slag removed; if the paving area is 1.5m 2 , the amount of aluminum slag removed increased by more than 115%.

[0087] In addition, if the mesh of the copper mesh is a diamond structure, the diamond structure will be constantly pulled and deformed during the disturbance process in the aluminum alloy melt, which will eventually lead to uneven uniformity of crystallization. The most intuitive impact is that the maximum difference between the compressive strength test values ​​of different areas is 33MPa.

[0088] In addition, it should be noted that if the no-load time is too short, the final fatigue strength will be lower than 106MPa because the impact is not severe enough; if the no-load time is too long, such as t k When =9s, the remelting effect will be significantly reduced, resulting in reduced mechanical properties of the aluminum alloy material (such as yield strength will be lower than 203MPa).

[0089] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a high-performance heat-treatment-free aluminum alloy material, characterized in that: The following steps are involved: Step 1: Add aluminum alloy raw materials into a furnace, heat and smelt to obtain a metal solution; Step 2, adjusting the temperature in the furnace to 760-770° C., adding a refining agent for refining, and degassing during the refining process to obtain a refined melt; Step 3, transferring the refined melt into a jacketed heating furnace, controlling the inner wall temperature of the jacketed heating furnace to be 555-650°C, and having at least three layers of copper mesh from top to bottom in the jacketed heating furnace, all of which are submerged in the refined melt; each layer of copper mesh is connected to an intermittent power supply to treat the refined melt in the jacketed heating furnace, and after the treatment, a multi-crystallized melt is obtained; Step 4, feeding the multi-crystallized melt into a die-casting machine for die-casting to obtain a die-cast ingot / rod; cooling to room temperature to obtain the high-performance heat-treatment-free aluminum alloy material; The mass percentage of iron in the high-performance heat-treatment-free aluminum alloy material is less than or equal to 0.37%, and the high-performance heat-treatment-free aluminum alloy material does not contain rare earth elements.

2. The method for preparing a high-performance heat-treatment-free aluminum alloy material according to claim 1, characterized in that: The mesh of the copper mesh is a regular hexagonal structure.

3. The method for preparing a high-performance heat-treatment-free aluminum alloy material according to claim 1, characterized in that: The side length of the mesh of the copper mesh is 3 to 4 cm.

4. The method for preparing a high-performance heat-treatment-free aluminum alloy material according to claim 1, characterized in that: The copper mesh in the jacketed heating furnace is arranged with the flattened area increasing from top to bottom, and the copper mesh in the jacketed heating furnace is arranged coaxially.

5. The method for preparing a high-performance heat-treatment-free aluminum alloy material according to claim 1, characterized in that: The output current of the intermittent power supply is 11000-12000A, the output voltage of the intermittent power supply is 50-55V, the working cycle of the intermittent power supply is T=12s, and the braking time is t b =9s, no-load time t k =3s, T = t b +t k .

6. The method for preparing a high-performance heat-treatment-free aluminum alloy material according to claim 1, characterized in that: Each layer of copper mesh is connected to an intermittent power supply to treat the refined molten metal in the jacketed heating furnace for 30 to 40 minutes.

7. The method for preparing a high-performance heat-treatment-free aluminum alloy material according to claim 1, characterized in that: The high-performance heat-treatment-free aluminum alloy material comprises the following components in percentage by mass: Si: 0.4% to 0.8%; Mg: 0.8% ~ 1.2%; Cu: 0.15% ~ 0.4%; Zn: ≤0.25%; Mn: ≤0.15%; Ti: ≤0.15%; Cr: 0.04%~0.35%; Fe: ≤0.37%; the balance is Al and unavoidable impurity elements.

8. The method for preparing a high-performance heat-treatment-free aluminum alloy material according to claim 1, characterized in that: The refining agent is one or more of NaCl, KCl, CaF2, Na3AlF6, and Na2SiF6.

9. The method for preparing a high-performance heat-treatment-free aluminum alloy material according to claim 1, characterized in that: The jacket of the jacketed heating furnace is filled with heat transfer oil, and the temperature of the heat transfer oil is not lower than 150°C.

10. The method for preparing a high-performance heat-treatment-free aluminum alloy material according to claim 1, characterized in that: In step 4, the temperature of the multi-crystallized melt when entering the die-casting machine is 620-635° C., the die-casting pressure is 85 MPa, and the die-casting speed is 3 m / s.