The principle of induction heating equipment is similar to the working principle of intermediate frequency induction furnace, both belong to the principle of electromagnetic induction. Therefore, the heating effect produced by induction heating equipment with different frequencies is different, which determines the heating quality, and the power determines the heating speed and efficiency.
First, frequency selection method of induction heating equipment
Induction heating equipment can be roughly divided into: ultra high frequency, high frequency, super audio, intermediate frequency and so on according to different output frequencies. Different heating processes require different frequencies. If the frequency is selected incorrectly, the heating requirements cannot be met, such as slow heating time, low working efficiency, uneven heating, and temperature failure to meet the requirements, which may easily cause workpiece damage. To correctly select the frequency, first of all, we must understand the heating process requirements of the product. Generally speaking, there are the following situations:
1. Work piece is heat permeable
For example: hot-rolling and hot-rolling of fasteners, standard parts, auto parts, hardware tools, rigging, twist drills, etc. The larger the workpiece diameter, the lower the frequency. Such as: Φ4mm or less, suitable for high frequency and ultra high frequency (100-500KHz), Φ4-16mm suitable for high frequency (50-100KHz), Φ16-40mm suitable for super audio (10-50KHz), Φ40mm or more suitable for intermediate frequency (0.5-10KHz) ).
2, heat treatment
Stern shafts, gears, quenching, and annealing of stainless steel products. Take quenching as an example. The shallower the quenching layer of the workpiece, the higher the frequency, and the deeper the quenching layer, the lower the frequency. For example: the quenching layer is 02.-0.8mm for 100-250KHz UHF and high frequency, 1.0-1.5mm for 40-50KHz HF and super audio, 1.5-2.0mm for 20-25KHz super audio, 2.0-3.0mm Suitable for 8-20KHz super audio, intermediate frequency, 3.0-5.0mm suitable for 4-8KHz intermediate frequency, 5.0-8.0mm suitable for 2.5-4KHz intermediate frequency.
The combined welding of different materials such as drills, turning tools, reamers, milling cutters, drills and the bottom of stainless steel pots, the larger the welding volume, the lower the frequency. Taking turning tool welding as an example, such as: tools below 20mm, suitable for 50- 100KHz high frequency, tools above 20-30mm are suitable for 10-50KHz high frequency and super audio, and tools above 30mm are suitable for 1-8KHz intermediate frequency.
4. Smelting precious metals
Precious metals such as gold, silver, copper, and lead depend on the specific melting furnace and production efficiency. High frequency can be selected for small capacity. Most of them are super audio and intermediate frequency. Ultra audio can meet the general application of the die casting industry. It can melt 200KG aluminum ingots per hour. General applications.
Two, power selection method of induction heating equipment
After you have determined the frequency of the machine according to the requirements of your workpiece, the next step is to choose the appropriate machine power according to the production situation. The larger the machine's power, the faster its heating speed, but its price will increase accordingly. Low-power equipment, low cost, and slow heating speed.
1, oscillating power
Induction heating equipment must rectify the alternating current to obtain the oscillating current and voltage, and the oscillating power is the product of the two. At present, there is no national model calibration method for induction heating equipment. Most manufacturers like to mark their products in the form of factory name identification number + power, such as: XX-20, YY-60, ZZ-100, etc. Manufacturers usually label power as oscillating power, and some manufacturers use oscillating power as output power or simply mark it as power in general, misleading customers. What's more, simply do not write the power, the input current number is calibrated to the model, so that customers mistakenly think that the following literacy is the power of the machine. The two are actually quite different. Induction heating equipment is usually not updated for a long time after it is bought, and customers often regret it when they understand the difference between central areas.
2, output power
The power usually refers to the load power of the machine, also called output power, and the oscillating power is only about 60% of the actual output power. For example, the calibration oscillation equipment with 50KW and output power of 30KW induction heating equipment are the same under the same conditions. The output power / oscillation power comparison of common equipment is 25KW / 42KW, 30KW / 50KW, 50KW / 80KW, 80KW / 125KW. When the company introduces the product to you, don't just care about the model, don't forget to ask him what the output power is, know what he knows.
For the same workpiece, the working speed is different, and the power selection is also very different. For example; a fastener company wants to hot-forge a screw with a length of Φ30mm and a length of 50mm, a heating temperature of 1000 degrees, and a production speed of 20 pieces / minute, then it should choose one A machine with a frequency of 10-40KHZ and an output power of 80KW is used. If the production speed is reduced to 10 pieces / minute, a machine with a frequency of 50KW and an output frequency of ultra-audio (10-40) can meet the application. The price of 80KW must be It is higher than 50KW, so manufacturers can choose the appropriate model according to their actual situation, so as not to cause waste.
The choice of power must also take into account the fluctuation of the power voltage. For users using three-phase AC power, if the voltage is reduced by 10V, the output power will be reduced by about 7%. Generally speaking, when enterprises use this equipment, The batch heating time is fixed. When the voltage decreases, in order to ensure the heating effect, the power of the machine should be increased to achieve the same heating effect. But if your heating time is set on the premise of the equipment power status, when the voltage is reduced, the same heating effect can only be achieved by extending the heating time, so you must re-experiment to obtain the time setting parameters and delay production work. Nor can the quality of the workpiece be guaranteed. Therefore, it is recommended to adjust the power output of the device to about 85-90% power state while using it, leaving a little margin, so as to prolong the service life and deal with the adverse effects of voltage fluctuations.
The above is an introduction to the power and frequency selection method of induction heating equipment. According to the heating requirements of the workpiece, it is very important to choose the correct frequency and power. After determining the frequency and power of the machine, it is necessary to select the appropriate supplier according to the production situation.