WO2019205362A1

WO2019205362A1 - Aluminum alloy electrical pulse quenching forming process and device

Info

Publication number: WO2019205362A1
Application number: PCT/CN2018/101503
Authority: WO
Inventors: 陈明和; 张鹏; 谢兰生
Original assignee: 南京航空航天大学
Priority date: 2018-04-25
Filing date: 2018-08-21
Publication date: 2019-10-31
Also published as: CN108704967A

Abstract

A novel aluminum alloy electrical pulse quenching forming process and device, the device comprising an AC power source (7), positive and negative electrodes of the AC power source (7) respectively contacting an aluminum alloy plate (3) by means of two electrical brushes (5) and (6), such that in a stamping process an electrical current continuously passes through the aluminum alloy plate (3). The process comprises applying an electrical pulse to achieve heating; heating the aluminum alloy plate (3) to a solid solution temperature and maintaining the temperature; sizing; constant-temperature cooling and storage; aging; placing the aluminum alloy plate (3) into an electrical pulse auxiliary forming device and performing stamping and maintaining a pressing force.

Description

Aluminum alloy electric pulse new quenching forming process and device

Technical field

The invention belongs to the process of stamping and heat treatment of aluminum alloy sheet material, in particular to a new quenching forming process and device for electric pulse of aluminum alloy.

Background technique

Compared with other metal materials, aluminum alloy has the advantages of low density, close to 2.7g/cm ³ , high specific strength, specific stiffness, high specific modulus, good thermal conductivity, corrosion resistance, plastic processing properties and impact resistance. It is widely used in aviation, aerospace, shipbuilding, transportation and other fields.

Aluminum alloys are the most important structural materials on aircraft, such as fuselage skins, beams, ribs, purlins, bulkheads and landing gear. In the latest civil aircraft, the amount of aluminum alloy accounts for 70% to 80%, and the amount of military use is 40% to 60%. In the aerospace field, aluminum alloy is still the main structural material of spacecraft such as launch vehicles, spacecrafts, space stations, etc. It is also one of the important structural materials for missile systems such as missiles. Aluminum alloy can replace steel in ships and reduce the weight of components by more than 50%. It plays an important role in high-end metal materials in marine engineering equipment industry. Aluminum alloy is the most ideal material for the modern transportation industry. It is used in rail vehicles, automobiles, armored vehicles and tanks. The application of aluminum alloy can achieve the most effective weight reduction, which can greatly reduce the weight of the body, thereby achieving energy saving and emission reduction, and the aluminum alloy material can be recycled and reused, thereby reducing environmental damage and waste of resources.

Although aluminum alloy has so many advantages, it is poorly formed at room temperature with respect to steel, and its elongation is low. The modulus of elasticity is only about one-half of that of steel sheet, so the rebound phenomenon of aluminum alloy formed parts is more serious. Only by improving the forming properties of aluminum alloys can we produce more accurate products. The existing aluminum alloy warm and hot forming method can improve the forming property of the material during the forming process, but there are still some problems that are difficult to solve, such as: grain growth and abnormality after heat treatment will affect the mechanical properties of the product, energy consumption Too high, low productivity and many other issues. Aluminum alloys are divided into two categories: deformable aluminum alloys and cast aluminum alloys. In practical applications, they are mainly made of deformable aluminum alloys. For the heat-treated reinforced aluminum alloy stamped and formed parts, after heat treatment, aging treatment, and processing, can meet the functional requirements of the product. During the heat treatment of the test piece, the thinned part will be warped and deformed due to thermal expansion and contraction, which will seriously affect the final size and shape accuracy of the formed part, and some of the more complicated parts will crack. Therefore, the formation process of an aluminum alloy product which not only improves the forming performance but also reduces the cost, and can accurately form and maintain high strength is explored, and plays an important role in the production and application of the aluminum alloy in the production manufacturing industry.

Summary of the invention

In view of the above-mentioned deficiencies of the prior art, the present invention provides an aluminum alloy electric pulse new quenching forming process and apparatus, which can improve the use performance of the heat treatable aluminum alloy stamping product, and can ensure the accurate forming of the stamping product, and greatly reduce the shape after forming. The warpage deformation reduces the amount of manual knocking work, shortens the production cycle, and saves costs.

To achieve the above object, the present invention adopts the following technical solutions:

An electric pulse new quenching forming process for aluminum alloy, wherein an aluminum alloy sheet material is placed into an electric pulse auxiliary forming device for stamping forming in a newly quenched state; the electric pulse auxiliary forming device comprises a punch, a die, and an AC power source. The anode and the cathode of the alternating current power source are respectively connected to the anode brush and the cathode brush, and the brush contacts of the anode brush and the cathode brush respectively contact the aluminum alloy sheet.

Preferably, the method comprises the following steps:

Step 1: heating the aluminum alloy sheet to a solution temperature and maintaining the temperature;

Step 2: Aligning the aluminum alloy sheet;

Step 3: Perform constant temperature cooling storage on the aluminum alloy sheet after the calibration;

Step 4: aging treatment of the aluminum alloy sheet after constant temperature cooling storage;

Step 5: The aluminum alloy sheet is placed in an electric pulse assisted forming device for press forming and holding.

Preferably, in the step 1, the aluminum alloy sheet is a 2XXX series, a 6XXX series or a 7XXX series.

Preferably, in step 4, the temperature of the constant temperature cooling storage is -15 ° C, and the longest storage time is 7 days and nights.

Preferably, in step 5, the time for moving the aluminum alloy sheet into the electric pulse auxiliary forming device and connecting the power source is 5-20 seconds.

Preferably, in step 5, the threshold value of the current density of the electric pulse auxiliary forming device is 7.4-11.4 A/mm ² .

Preferably, in step 5, the pressure holding time is 5-10 min.

Preferably, the aluminum alloy sheet is heated by electric pulse heating.

An electric pulse auxiliary forming device comprises a machine tool, a punch, a die, an aluminum alloy sheet, a crimping ring disposed above the aluminum alloy sheet, a machine tool connecting the punch, and an AC power source, wherein the AC power source is positive The anode is connected to the anode brush and the cathode brush respectively; the pressure ring is provided with two through holes, the two through holes are respectively located on the left and right sides of the aluminum alloy sheet, and the two through holes are respectively An anode brush and a cathode brush are installed, and the brush contacts of the anode brush and the cathode brush respectively contact the aluminum alloy sheet; the sidewalls of the through holes on the left and right sides and the outer walls on the left and right sides of the binder ring Wire passages are respectively provided for passing the wires between the anode brush and the AC power source, the cathode brush and the AC power source; the punch is insulated from the machine tool, and the bead ring is insulated from the aluminum alloy sheet, and the die is Aluminum alloy sheet insulation.

Beneficial effects: (1) Under the new quenching condition, the forming property of the aluminum alloy sheet is obviously improved compared with the annealing state, the bending force required is small, the deformation amount is large, and the forming precision is high.

(2) Electrical pulse assisted forming From the macroscopic point, the plastic deformation ability has been greatly improved, the yield strength and tensile strength are significantly reduced, the area shrinkage and elongation are significantly increased, the degree of work hardening is reduced, and the surface quality is improved; From the microstructural analysis, the heat treatable aluminum alloy undergoes dynamic recrystallization, improves the microstructure and effectively inhibits the cracking. Therefore, the processing method combining the new quenching heat treatment process and the electric pulse assisted forming can improve the aluminum alloy product. The forming performance ensures the processing precision of the product forming, reduces the workload of manual finishing, shortens the production cycle, reduces the cost, and has important practical value.

(3) Advantages of electric pulse assisted forming device:

1) Compared with the power supply wire directly connected to the two ends of the forming member (or the wire is welded to both ends of the forming member), the sheet material is pressed during the forming process, although the pressing ring is fixed to the sheet material, but the pressed portion of the sheet material is pressed. It will still move with the formation, and it is not guaranteed that the wire and the sheet are always in contact with each other and the power is good. However, the device can effectively solve the problem;

2) Open the hole at the corresponding position of the crimping ring, and apply an insulating layer (such as bakelite powder) to the through hole to fix the brush. A wire passage is formed between the side wall of the through hole and the outer side wall of the binder ring, and the power source is connected to the brush through the wire passage. While ensuring the insulation and safe production of the non-energized part, it can ensure that the electric pulse assisted forming is not affected when the blank holder force is applied.

(4) The aluminum alloy sheet is heated to the solution temperature by electric pulse self-heating, without using conventional heating equipment, such as electric furnace.

DRAWINGS

1 is a flow chart of a new quenching process for an electric pulse of an aluminum alloy;

Figure 2 is a schematic view of an electric pulse assisted forming device;

In the figure, the label: 1, punch; 2, die; 3, aluminum alloy sheet; 4, crimping ring; 5, anode brush; 6, cathode brush; 7, AC power; 8, wire channel.

detailed description

The invention will be further explained below in conjunction with the drawings.

As shown in FIG. 1 , the aluminum alloy electric pulse new quenching forming process provided by the present invention comprises the following steps:

(1) preparing a heat treatable aluminum alloy sheet: processing a heat treatable aluminum alloy into a blank test piece of a designed shape by punching, wire cutting, water cutting or laser cutting, and performing trimming treatment; said aluminum The alloy sheet is 2XXX series, 6XXX series or 7XXX series;

(2) The aluminum alloy sheet is heated to the solution temperature and kept warm: the aluminum alloy sheet is heated to a solution temperature of 420-540 ° C, and kept for 20-60 minutes. In the initial heating and heat preservation, the aluminum alloy forms a supersaturated solid solution, thereby obtaining a single metal structure; during the post-heating, the alloying elements are diffused and uniformly diffused into the aluminum matrix to form a uniform high-temperature supersaturated solid solution;

(3) Calibration: calibration of all samples;

(4) Constant temperature cooling storage: The test piece after the calibration is placed in the refrigerator at a low temperature of -15 ° C and stored at a constant temperature. The actual time allowed for refrigeration in the production is about 7 days and nights;

(5) Aging: natural aging or artificial aging can be used to precipitate the alloy atoms in the supersaturated solid solution at room temperature after solution treatment to form a fine strengthening phase uniformly distributed on the substrate, and the sample is taken from the refrigerator. The aging time is calculated by taking out to room temperature; the specific aging time can be determined according to the performance requirements of the process;

The above steps allow the aluminum alloy sheet to be newly quenched.

(6) Perform electric pulse assisted forming in the new quenching state: at the corresponding aging time point, move the test piece into the forming device and connect the power supply, adjust the current density, start stamping and holding the test piece; move into the forming device and connect The good power supply time is 5-20 seconds; the current density threshold is between 7.4-11.4 A/mm ² ; the holding time is 5-10 min.

Electric pulse assisted forming is mainly the result of the combined action of pure electroplastic effect and Joule heating effect, which can improve the plasticity of the heat treatable reinforced aluminum alloy. Taking stretching as an example, electric pulse-assisted drawing can be deepened at a lower temperature. Through microstructure observation, the heat-treated reinforced aluminum alloy can dynamically recrystallize at a lower temperature, effectively solving the cracking problem. For bending forming, electric pulse assisted forming can reduce the bending force and reduce the amount of rebound. Compared with the room temperature stretching, the yield strength and tensile strength of the aluminum alloy specimens after electric pulse assisted forming are greatly reduced, while the section shrinkage and elongation are significantly increased, and the deformation resistance of the heat treatable aluminum alloy is lowered, and the plasticity is improved. Significant improvement.

In order to obtain and maintain the optimum new quenching state of the sheet, it is necessary to strictly control the entire process from the quenching process to the electric pulse assisted forming. In the process of aging, the test is marked on the test piece, and the time for the transfer of the test piece to the test equipment is shortened. The processes are coordinated with each other and time records are made.

As shown in FIG. 2, the electric pulse auxiliary forming device comprises a machine tool, a punch 1, a die 2, an aluminum alloy sheet 3, a bead ring 4 disposed above the aluminum alloy sheet 3, and the bead ring 4 is provided. There are two through holes, which are respectively located on the left and right sides of the aluminum alloy sheet 3, and the anode brush 5 and the cathode brush 6 are respectively installed in the two through holes, the anode brush 5 and the cathode electric The brush contacts of the brush 6 are respectively in contact with the surface of the aluminum alloy sheet 3, and the other ends are respectively connected to the positive and negative electrodes of the alternating current power source 7. Electric pulse assisted forming not only ensures that the aluminum alloy sheet material 3 is energized, but also makes the whole set of equipment in a safe state for production, so that only the aluminum alloy sheet material 3 is connected to the alternating current, so for the punch 1 and the machine tool, the crimping The ring 4 and the aluminum alloy sheet 3, the concave mold 2 and the aluminum alloy sheet 3 are insulated.

The punch 1 is insulated from the machine tool: a layer of bakelite is applied to the punch 1 and the machine tool to fix the punch 1 , the connected bolts are insulated (can be coated with a layer of bakelite powder) or insulated bolts are applied.

The bead ring 4 is insulated from the aluminum alloy sheet 3: a film is placed over the edge of the aluminum alloy sheet 3 for insulation.

The die 2 is insulated from the aluminum alloy sheet 3: a film is placed over the edge of the aluminum alloy sheet 3 for insulation.

Special treatment of the bead ring 4: two symmetrical holes are formed in the appropriate part of the bead ring 4, the surrounding material is coated with an insulating material, and a brush is installed at the through hole; the side wall of the through hole to the bead ring 4 The outer side wall opens the wire passage 8 and is coated with an insulating material on the side wall of the wire passage 8. The AC power supply 7 can be connected to the brush wire through the wire passage 8, and the electric pulse device can be prevented from being affected during the application of the blanking force, the forming and the pressure holding process while ensuring the insulation and safe production of the non-energized portion. So that the synchronous cooling electric pulse can be carried out safely and normally.

The function of the brush: the two brush contacts are always in contact with the aluminum alloy sheet 3, and the other ends of the two brushes are respectively connected to the positive and negative poles of the alternating current power source 7. During the heating and forming process of the aluminum alloy sheet 3, the aluminum alloy sheet 3 is always kept passing current.

The above description is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. It should be considered as the scope of protection of the present invention.

Claims

An electric pulse new quenching forming process for aluminum alloy, characterized in that in an newly quenched state, an aluminum alloy sheet is placed in an electric pulse auxiliary forming device for press forming; the electric pulse auxiliary forming device comprises a punch, a die, The alternating current source, the positive and negative electrodes of the alternating current power source are respectively connected to the anode brush and the cathode brush, and the brush contacts of the anode brush and the cathode brush respectively contact the aluminum alloy sheet.
The aluminum alloy electric pulse new quenching forming process according to claim 1, comprising the steps of:

Step 1: heating the aluminum alloy sheet to a solution temperature and maintaining the temperature;

Step 2: Aligning the aluminum alloy sheet;

Step 3: Perform constant temperature cooling storage on the aluminum alloy sheet after the calibration;

Step 4: aging treatment of the aluminum alloy sheet after constant temperature cooling storage;

Step 5: The aluminum alloy sheet is placed in an electric pulse assisted forming device for press forming and holding.
The aluminum alloy electric pulse new quenching forming process according to claim 1, wherein in the step 1, the aluminum alloy sheet material is a 2XXX series, a 6XXX series or a 7XXX series.
The aluminum alloy electric pulse new quenching forming process according to claim 2, wherein in the step 4, the temperature of the constant temperature cooling storage is -15 ° C, and the longest storage time is 7 days and nights.
The aluminum alloy electric pulse new quenching forming process according to claim 2, wherein in step 5, the time for moving the aluminum alloy sheet into the electric pulse auxiliary forming device and connecting the power source is 5-20 seconds.
The aluminum alloy electric pulse new quenching forming process according to claim 2, wherein in step 5, the current density of the electric pulse auxiliary forming device has a threshold value of 7.4-11.4 A/mm 2 .
The aluminum alloy electric pulse new quenching forming process according to claim 2, wherein in the step 1, the aluminum alloy sheet is heated by electric pulse heating.
An aluminum alloy electric pulse auxiliary forming device comprises a machine tool, a punch mold, a concave mold, an aluminum alloy sheet material, a bead ring disposed above the aluminum alloy sheet material, and a machine tool connecting the punch mold, wherein the utility model further comprises an AC power source. The anode and the cathode of the alternating current power source are respectively connected to the anode brush and the cathode brush; the pressure ring is provided with two through holes, and the two through holes are respectively located on the left and right sides of the aluminum alloy sheet, An anode brush and a cathode brush are respectively installed in the two through holes, and the brush contacts of the anode brush and the cathode brush respectively contact the aluminum alloy sheet; the side walls of the through holes on the left and right sides and the bead ring Wire passages are respectively formed between the outer walls of the left and right sides for respectively passing the wires between the anode brush and the alternating current power source, the cathode brush and the alternating current power source; the punch is insulated from the machine tool, and the bead ring and the aluminum alloy plate are respectively Material insulation, the die is insulated from the aluminum alloy sheet.