CN101845606A - Method fur forming aluminum base composite material thin wall part by current self-resistance heating - Google Patents

Abstract

The invention relates to a method for forming thin-walled parts of aluminum-based composite materials by electric current self-resistance heating, which belongs to the field of thermal processing. The invention aims to solve the problem of poor forming quality of thin-walled parts when only heating blanks when stretching and forming particle-reinforced aluminum-based composite materials; If it is heated together with the mold, the heat utilization rate is low and a lot of energy is wasted. The method of the present invention includes: 1. placing the forming device on a press; 2. applying pressure to the upper electrode splint, clamping the blank to be formed, and turning on the power to heat the blank to be formed; 3. real-time measurement by an infrared thermometer temperature, and adjust the output current parameters of the power supply in real time, so that the heating rate of the billet to be formed reaches 5-20°C/s; 4. When the temperature of the billet to be formed reaches 350°C-450°C, the press removes the upper electrode The pressure of the splint is applied to the blank holder, so that the blank holder will press the blank to be formed on the lower mold; 5. The upper mold is pressed downward, and the blank to be formed is pressed and formed.

Description

Current Self-resistance Heating Forming Method for Thin-walled Aluminum Matrix Composite Parts

technical field

The invention relates to a method for electric current self-resistance heating and forming thin-walled parts of aluminum-based composite materials, which belongs to the field of thermal processing.

Background technique

Particle reinforced aluminum matrix composites have the advantages of high strength, high hardness, and low density, and are widely used in high-tech fields. However, the material has poor plasticity and is difficult to form by conventional stretch forming processes, so thermoforming must be used. If the traditional billet heating is used, the bad material of the thin-walled parts will dissipate heat quickly, the temperature will be uneven, and the forming quality will be unstable; if the overall heating of the mold is used, that is, the mold and the billet will be put into the furnace together for heating, which can improve the forming quality. However, generally Under normal circumstances, the volume of the mold is much larger than the volume of the billet to be formed, that is to say, in the process of common heating, most of the heat is applied to the mold. According to estimates, under normal circumstances, less than 5% of the heat consumed by superplastic forming is used for superplastic deformation of the billet, and the rest is consumed on other components such as molds, pressure heads, and air ducts. Therefore, in the traditional superplastic inflation forming process, the effective utilization rate of heat is very low, which will inevitably cause great energy waste. Moreover, in the heating process of the traditional process, the way the mold and the billet receive heat is mainly heat radiation and heat conduction, and the heat transfer speed is relatively slow. In order to make the billet reach a uniform and high superplastic forming temperature, the heating time is often very long. According to the process The difference is generally up to 1 to several hours, so the heating efficiency of this heating method is also very low, the production efficiency is very low, and it is difficult to adapt to the requirements of mass production.

Contents of the invention

The purpose of the present invention is to solve the problem that when the particle reinforced aluminum matrix composite is stretched and formed, if only the blank is heated, the forming quality of the thin-walled part will be poor; if it is heated together with the mold, the heat utilization rate will be low and a large amount of energy will be wasted. To solve the problem, a method for current self-resistance heating to form aluminum matrix composite thin-walled parts is provided.

The forming device used in the method of the present invention includes a power supply, a mould, an upper electrode splint, a lower electrode splint and an infrared thermometer,

The mold includes an upper mold and a lower mold. A blank holder is set on the mold. A pair of upper electrode splints and lower electrode splints corresponding to the upper and lower positions are arranged on the outside of the blank holder. The two electrodes clamped by the upper electrode splint and the lower electrode splint They are respectively connected to both ends of the power supply, and the upper electrode splint and the lower electrode splint are kept insulated from the mold.

The current self-resistance heating method for forming thin-walled aluminum matrix composite parts comprises the following steps:

Step 1, placing the forming device on a press, and placing the outer edge of the billet to be formed between the upper electrode splint and the lower electrode splint;

Step 2. The press pressurizes the upper electrode splint through the hydraulic system, so that the upper electrode splint and the lower electrode splint clamp the outer edge of the billet to be formed, and the power is turned on. The upper electrode splint and the lower electrode splint clamp two electrodes, The power supply and the blank to be formed form a power circuit to heat the blank to be formed;

Step 3. Measure the temperature of the billet to be formed in real time by an infrared thermometer, and adjust the output current parameters of the power supply in real time according to the measured temperature, so that the heating rate of the billet to be formed reaches 5-20°C/s, and the output current of the power supply The parameters are: voltage is 4V ~ 10V, current is 1000A ~ 20000A;

Step 4. When the temperature of the blank to be formed reaches 350°C to 450°C, the press removes the pressure on the upper electrode splint, and the press pressurizes the blank holder through the hydraulic system, so that the blankholder will press the blank to be formed The edge of the die is tightly pressed on the lower die;

Step 5. Apply pressure through the press to make the upper mold go down under pressure, and the pressure head of the upper mold presses the blank to be formed into the cavity of the lower mold, so that the blank to be formed is plastically deformed, and after bending, stretching, and molding In the deformation stage, the blank to be formed is bonded to the inner surface of the lower mold, and the plastic forming process of the blank to be formed is completed.

The advantage of the present invention is that because the Joule resistance heat generated by the current flowing through the blank is used to directly heat the blank itself, the blank itself is heated and its temperature is kept within the range of thermoforming temperature, and then a certain amount of pressure is applied to the blank by a pressing device The pressure makes it plastically deform in the mold cavity. Therefore, it not only avoids the loss of heat consumed by integral heating on other parts such as molds in the traditional superplastic forming process, but also makes the heating process very fast and the internal temperature distribution of the billet is very uniform, which greatly improves the energy utilization rate and heating efficiency. . In addition, since the billet can be formed immediately after reaching the temperature, the temperature is uniform, which is beneficial to the plastic deformation of the billet and improves the product quality.

Description of drawings

Fig. 1 is a flow chart of the method of the present invention, Fig. 2 is a schematic structural view of the forming device used in the method of the present invention, Fig. 3 is a schematic view of the structural principle of the forming process after heating, and Fig. 4 is an electrothermal performance curve of silicon carbide particle reinforced aluminum matrix composite .

Detailed ways

Specific Embodiment 1: The present embodiment will be described below in conjunction with FIGS. 1 to 4. The forming device used in the method of this embodiment includes a power source 1, a mold, an upper electrode splint 5, a lower electrode splint 6, and an infrared thermometer 8.

The mold includes an upper mold 2 and a lower mold 3, a blank holder 4 is arranged on the mold, and a pair of upper electrode splints 5 and lower electrode splints 6 corresponding to the upper and lower positions are arranged outside the blank holder 4, and the upper electrode splint 5 and the lower electrode splint The two electrodes clamped by 6 are respectively connected to both ends of the power supply 1, and the upper electrode splint 5 and the lower electrode splint 6 are kept insulated from the mold.

The current self-resistance heating method for forming thin-walled aluminum matrix composite parts comprises the following steps:

Step 1, placing the forming device on a press, and placing the outer edge of the blank 7 to be formed between the upper electrode splint 5 and the lower electrode splint 6;

Step 2: The press pressurizes the upper electrode splint 5 through the hydraulic system, so that the upper electrode splint 5 and the lower electrode splint 6 clamp the outer edge of the billet 7 to be formed, and connect the power supply 1, the upper electrode splint 5 and the lower electrode splint 6. The two electrodes clamped, the power supply 1 and the blank 7 to be formed form a power circuit to heat the blank 7 to be formed;

Step 3: Measure the temperature of the blank 7 to be formed in real time by the infrared thermometer 8, and adjust the output current parameters of the power supply 1 in real time according to the measured temperature, so that the heating rate of the blank 7 to be formed reaches 5-20°C/s, The current parameters output by power supply 1 are: voltage is 4V~10V, current is 1000A~20000A;

Step 4. When the temperature of the blank 7 to be formed reaches 350°C to 450°C, the press removes the pressure on the upper electrode splint 5, and the press pressurizes the blank holder 4 through the hydraulic system, so that the blank holder 4 Press the edge of the blank 7 to be formed tightly on the lower die;

Step 5. Apply pressure through the press to make the upper mold 2 go down under pressure. The pressure head of the upper mold 2 presses the blank 7 to be formed into the cavity of the lower mold 3, so that the blank 7 to be formed is plastically deformed. After bending, In the stage of stretching and molding deformation, the blank 7 to be formed is attached to the inner surface of the lower mold 3 , and the plastic forming process of the blank 7 to be formed is completed.

Open the mold to pick up the parts, correct the shape, trim the edges, and get the final parts.

The upper mold 2 and the lower mold 3 are respectively placed on the upper and lower sides of the blank 7 to be formed, the part to be formed of the blank 7 to be formed is placed above the cavity of the lower mold 3, and the outer edge of the blank 7 to be formed extends outside the edge of the mold. and placed between the upper electrode splint 5 and the lower electrode splint 6, so that the upper electrode splint 5 and the lower electrode splint 6 clamp the outer edge of the blank 7 to be formed,

In the present invention method, when the power supply 1 is turned on for heating, insulation is maintained between the upper electrode splint 5 and the lower electrode splint 6 and the mould, so the mold that occupies a large resistance does not participate in the energization circuit, and the upper electrode splint 5 and the lower electrode splint 6 are formed. Clamp two electrodes, power supply 1 and blank 7 to be formed to form a power circuit, and the insulation design prevents the mold from shunting the current flowing through the blank 7 to be formed, reducing energy loss. In the circuit, the resistance of the blank 7 to be formed is far greater than the resistance of other parts of the circuit, so the current will generate a large amount of Joule heat on the blank 7 to be formed, so that it can be heated in a short period of time (several seconds to tens of seconds) seconds) are heated to thermoforming temperature.

The current parameters described in step 3 are selected according to the cross-sectional size and resistance data of the billet 7 to be formed, and the temperature of the billet 7 to be formed is monitored by the infrared thermometer 8, and the output current parameters of the power supply 1 are adjusted to finally achieve the goal It is to make the heating rate of the blank 7 to be formed reach between 5°C/s and 20°C/s, so as to ensure that the blank 7 to be formed reaches the forming temperature quickly and efficiently.

Traditional current-assisted forming technology is generally used in wire drawing forming. Since the diameter of the wire is generally small and the process is simple, the power of the power supply is generally small and the implementation method is relatively simple. It is still a blank in China when it is applied to sheet metal forming. The size of the parts and sheets of this project is large, and the requirements for equipment and process methods are greatly increased. There are few reports at home and abroad, and there are certain difficulties in the implementation of the plan. In this project, the rapid heating of aluminum matrix composite materials can be realized by using the power supply, and a specific experimental result is given. 1 The output current parameters are: the voltage is 1.14V, and the current is 2500A. The experimental results are shown in Figure 4. It takes less than 100 seconds for the thin-walled part to reach 450 degrees from room temperature. The method of the invention can form particles with high efficiency and high quality to reinforce thin-walled parts of aluminum-based composite materials.

Embodiment 2: The difference between this embodiment and Embodiment 1 is that a high-temperature-resistant mica sheet, ceramic or asbestos rubber plate is fixed between the upper electrode splint 5 and the lower electrode splint 6 and the mold to achieve insulation. Others are the same as in the embodiment. One is the same.

Embodiment 3: The difference between this embodiment and Embodiment 1 is that the current parameters output by the power supply 1 described in step 3 are: the voltage is 6V-8V, the current is 5000A-10000A, and the others are the same as Embodiment 1.

Embodiment 4: The difference between this embodiment and Embodiment 1 is that the current parameters output by the power supply 1 described in step 3 are: the voltage is 7V-8V, the current is 8000A-10000A, and others are the same as Embodiment 1.

Embodiment 5: The difference between this embodiment and Embodiment 1 is that the temperature of the blank 7 to be formed in Step 4 reaches 380° C. to 420° C. Others are the same as Embodiment 1.

Embodiment 6: This embodiment differs from Embodiment 1 in that the temperature of the blank 7 to be formed in Step 4 reaches 390° C. to 400° C. Others are the same as Embodiment 1.

Embodiment 7: The difference between this embodiment and Embodiment 1 is that the temperature of the blank 7 to be formed in Step 4 reaches 400° C., and the others are the same as Embodiment 1.

Claims (7)

1. The method of current self-resistance heating and forming thin-walled aluminum matrix composite parts, characterized in that the forming device used in this method includes a power supply (1), a mold, an upper electrode splint (5), a lower electrode splint (6) and an infrared measurement thermometer (8), The mold includes an upper mold (2) and a lower mold (3). A blank holder (4) is set on the mold, and a pair of upper electrode splints (5) and lower electrode splints corresponding to the upper and lower positions are arranged on the outside of the blank holder (4). (6), the two electrodes clamped by the upper electrode splint (5) and the lower electrode splint (6) are respectively connected to the two ends of the power supply (1), the upper electrode splint (5) and the lower electrode splint (6) are connected to the Insulation between molds is maintained, The current self-resistance heating method for forming thin-walled aluminum matrix composite parts comprises the following steps: Step 1. Place the forming device on a press, and place the outer edge of the blank to be formed (7) between the upper electrode splint (5) and the lower electrode splint (6); Step 2. The press pressurizes the upper electrode splint (5) through the hydraulic system, so that the upper electrode splint (5) and the lower electrode splint (6) clamp the outer edge of the blank to be formed (7), and turn on the power (1 ), the two electrodes clamped by the upper electrode splint (5) and the lower electrode splint (6), the power supply (1) and the blank to be formed (7) form a power circuit to heat the blank to be formed (7); Step 3. Measure the temperature of the billet (7) to be formed in real time by the infrared thermometer (8), and adjust the output current parameters of the power supply (1) in real time according to the measured temperature, so that the heating speed of the billet (7) to be formed When it reaches 5-20°C/s, the output current parameters of the power supply (1) are: the voltage is 4V-10V, and the current is 1000A-20000A; Step 4. When the temperature of the billet (7) to be formed reaches 350°C-450°C, the press removes the pressure on the upper electrode splint (5), and the press pressurizes the blank holder (4) through the hydraulic system , so that the blank holder (4) tightly presses the edge of the blank (7) to be formed on the lower die; Step 5. Apply pressure through the press to make the upper mold (2) move downward under pressure, and the pressure head of the upper mold (2) presses the blank (7) to be formed into the cavity of the lower mold (3), so that the blank to be formed (7) Plastic deformation occurs, and the blank to be formed (7) is bonded to the inner surface of the lower mold (3) through the stages of bending, stretching, and molding deformation, and the plastic forming process of the blank to be formed (7) is completed. 2. The method of current self-resistance heating and forming thin-walled parts of aluminum matrix composite materials according to claim 1, characterized in that a high temperature resistant mica sheet is fixed between the upper electrode splint (5) and the lower electrode splint (6) and the mould. , ceramic or asbestos rubber sheet for insulation. 3. The method of current self-resistance heating and forming aluminum matrix composite thin-walled parts according to claim 1, characterized in that the current parameters output by the power supply (1) in step 3 are: the voltage is 6V-8V, and the current is 5000A～10000A. 4. The method of current self-resistance heating and forming aluminum matrix composite thin-walled parts according to claim 1, characterized in that the current parameters output by the power supply (1) in step 3 are: the voltage is 7V ~ 8V, and the current is 8000A～10000A. 5 . The method for forming thin-walled aluminum matrix composite parts by current self-resistance heating according to claim 1 , characterized in that the temperature of the blank ( 7 ) to be formed in step 4 reaches 380° C.-420° C. 6 . 6 . The method for forming thin-walled aluminum matrix composite parts by current self-resistance heating according to claim 1 , characterized in that the temperature of the blank ( 7 ) to be formed in step 4 reaches 390° C. to 400° C. 7 . 7 . The method for forming thin-walled aluminum matrix composite parts by current self-resistance heating according to claim 1 , characterized in that the temperature of the blank ( 7 ) to be formed in step 4 reaches 400° C. 7 . the

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