1 Overview:
This heating device is specially designed for the on-line annealing of copper tubes. For the characteristics of continuous heating in the movement and the workpiece being heated is copper, special design should be made for the parameters of the power supply and the inductor in the system design. The whole system is heated by a set of 800KW/6KHZ power supply. The outside of the inductor is made of aluminum closed casing and filled with protective gas (nitrogen) to prevent oxidation and oxidation of the copper pipe. This system has the following characteristics:
1.1 The intermediate frequency power supply is 800KW/6KHz. Due to the high power and high frequency, the power supply design has some special requirements. These will be detailed in the description of the power supply.
1.2 The intermediate frequency power supply and the sensor are all water-cooled, making the equipment small and easy to install.
1.3 Automatic continuous production, the production speed can be automatically adjusted according to different workpiece parameters.
1.4 Production line transmission raceway adopts frequency conversion speed regulation, plus PLC can realize closed-loop control of temperature, speed and power.
2. Process parameters:
Copper tube size: Φ9.52×0.37mm; Φ12.7×0.43 mm
Copper tube lifting temperature: 700 ° C
Roller speed: >200 m/min
3. System equipment operation plan:
3.1 System power selection:
The choice of total heating power is 800KW depending on your requirements.
3.2 Choice of program:
According to the heating condition, the characteristics of the equipment used for heating in fast operation, because the heating speed of induction heating is too fast, there is no heat preservation process, thus affecting the refinement process of the copper tube grain structure, so the system adopts pulse type segmentation continuous The heating method is suitable for continuous heating. It is the most advanced heating method in foreign countries. This heating method can make the copper pipe have a short-term heat preservation process in the non-furnace part. The annealing process of the copper tube ensures the refinement process of the grain structure, so that the internal crystal grains are fine and balanced, so that the copper tube can be annealed to meet the processing requirements of your company. At the same time, the heated copper tube in the heating furnace body does not cause an excessive temperature difference in the axial direction, so that the micro crack caused by the thermal stress can be overcome in some procedures.
3.3 Equipment configuration and realization of the heating process:
The required power supply 800KW/6KHZ is used to supply two heating furnace bodies, and two heating furnace bodies heat the copper pipes. After each furnace body performs a rapid temperature increase on the copper pipes, after a short time of heat preservation process, the process is There is no heating process. In order to prevent the steel pipe from falling into the next induction furnace, it is impossible to align. The mechanical roller device is positioned in the middle. In order to prevent the oxidation of the copper tube heating process, the two furnace bodies and the guiding part are loaded into one. Among the sealed outer casings, inert gas is introduced therein; the length of each furnace body is 400 mm, the distance between the mechanical roller device and the furnace body is 20 mm on one side, and the total length of the furnace body portion is 800 mm, considering the space occupied by the outer casing, The total length of the heating portion needs to be 1200 MM.
The two furnace bodies and a set of mechanical roller device bases are fixed on the same furnace body base. The outer shell of the furnace body is made of hard aluminum alloy, which can simultaneously protect the gas sealing and magnetic shielding, so that the frame, the roller, etc. It is not heated by magnetic flux leakage; the shell of the furnace body is designed to be detachable, which provides convenience for the inspection of the furnace body and the replacement of the mechanical roller device.
3.4 Control system and control principle:
The control system should realize the control of two processes, one is the speed-temperature automatic control at the beginning and the end of heating; the other is the automatic temperature control during the heating process; the hardware part of the two processes can be borrowed from your company equipment. The PLC and man-machine interface are programmed by the mathematical model provided by our company. The speed collection is provided by your company's equipment. The temperature collection is provided by the far-infrared thermometer configured by our company. The power adjustment interface is provided by the IF power supply provided by our company. Yes, the interface is a standard analog signal interface (4-20MA or 0-10V).
3.4.1 Power-speed-temperature control principle:
Since the system impedance (R) does not change after the device is designed and manufactured, the power can only be given by the output voltage (U) or current (I), and the relationship between current, voltage and power is square root. That is, P=U2/R=I2R; the relationship between speed (S), temperature (T) and power (P) is linear, ie: P=GT/Sη(G) is the coefficient related to the material specification, heating When the copper tube is fixed, the coefficient does not change. η is an efficiency factor and the initial value is an empirical parameter. This parameter depends on the overall operating state of the system and requires self-learning tuning. The control system is an automatic control system for setting open-loop data and closed-loop self-learning to set the efficiency factor η.
3.4.2 Speed-temperature control at the beginning of heating
According to the speed rise curve at the beginning, the required power curve is calculated by the mathematical model to set the power supply, and the system performs heating in the rising process according to the set power curve. The efficiency factor is corrected by comparing the actual temperature measured by the thermometer with the heating temperature required by the process during the heating process. After several automatic corrections, the subsequent heating is consistent with the heating temperature required for the process.
3.4.3 Temperature control in the middle section at constant speed
During the constant speed operation in the middle section, the required power is calculated by the mathematical model to set the power supply, and the system is heated according to the set power. The efficiency factor is corrected by comparing the actual temperature measured by the thermometer with the heating temperature required by the process during the heating process. After several automatic corrections .
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