Induction heating is the output of high-frequency current from the induction heating device. An alternating magnetic field is generated by the induction coil. The eddy current is formed through the metal workpiece placed in the induction coil to rapidly heat it. The induction coil itself does not generate heat. It has been for decades. History. In the mid-1990s, solid-state induction heating equipment began to appear with IGBT modules as its core. Compared with electronic tube high-frequency equipment and SCR induction heating equipment, energy savings were 10%-40%. Once on the market, many advantages such as its energy conservation and environmental protection, high processing quality, easy operation, safe and reliable operation, and low maintenance cost have become the ideal heating methods in the field of small metal heating.
Different frequency induction heating devices produce different heating effects, determine the quality of the heating; power size, determines the workpiece heating speed and processing efficiency, so, according to the heating requirements of the workpiece, select the correct frequency and power is very important.
First, how to choose frequency induction heating equipment. According to different output frequencies, it can be roughly divided into: UHF, high frequency, super audio, mid-frequency and so on. Different heating process requirements require different frequencies. If the frequency is not selected correctly, the heating requirements cannot be met. For example, the heating time is slow, the working efficiency is low, the heating is not uniform, and the temperature does not meet the requirements. This can easily damage the workpiece. The correct choice of frequency, first, to understand the heating process requirements of the product, probably the following situations: 1, the workpiece through the heat, such as: fasteners, standard parts, auto parts, hardware tools, rigging, twist drill heat Hot rolling, etc., the larger the workpiece diameter, the lower the frequency should be. Such as: Φ4 mm or less, for high frequency, ultra-high frequency (100-500KHz) Φ4-16, mm for high frequency (50-100 KHz) Φ16-40 mm for ultra-audio (10-50 KHz) Φ40 mm or more suitable for intermediate frequency (0.5-10 KHz) 2. Heat treatment, shafting, gears, quenching and annealing of stainless steel products, etc. For quenching, for example, the shallower the quenched layer, the higher the frequency, and the deeper the quenched layer, the lower the frequency. Such as: quenching layer is 02.-0.8mm for 100-250 KHz UHF, high frequency 1.0-1.5mm for 40-50 KHz high frequency, super audio 1.5-2.0mm for 20-25 KHz super audio 2.0-3.0mm Suitable for 8-20 KHz super audio, medium frequency 3.0-5.0mm for 4-8 KHz intermediate frequency 5.0-8.0mm for 2.5-4 KHz intermediate frequency 3, brazing, bits, turning tools, reamers, cutters, drills, etc. and stainless steel Composite welding of different materials at the bottom of the pot. The larger the welding volume, the lower the frequency should be. Take the lathe welding as an example. For example: 20 mm or less tool, suitable for 50-100 KHz high frequency 20 --30 mm or more for 10-50 KHz High-frequency, super-audio 30 mm or more tool for 1-8 KHz IF. 4. Melting of precious metals such as gold, silver, copper, lead, etc. It depends on the furnace and production efficiency. , Small-capacity optional high frequency, most of the selected super audio, mid-frequency super audio can meet the general application of the die casting industry, the general application of 200KG aluminum ingot can be melted per hour.
Second, how to select the power, when you determine the frequency of the machine according to the requirements of your workpiece, the next step is to select the appropriate machine power according to the production conditions. The greater the power of the machine, the faster its heating, but its price will increase accordingly. Low-power equipment, low cost, and its slow heating rate. 1. There are usually two types of induction heating power: output power and oscillation power. The induction heating equipment must rectify the alternating current to obtain the oscillating current and voltage. The oscillating power is the product of the two. Generally speaking, the power is the load power of the machine, also called output power, and the oscillation power is only about 60% of the actual output power. If the oscillating power 50KW equipment and the output power 30KW induction heating equipment have the same heating effect under the same conditions. The following is a comparison of output power/oscillation power of commonly used devices. 25KW/42 KW, 30 KW/50 KW, 50KW/80 KW, 80 KW/125 KW At present, there is no national model calibration method for induction heating equipment. Most manufacturers like to label the product with the identification number + power. Forms such as: XX-20, YY-60, ZZ-100, etc., so some manufacturers usually have the power referred to as the oscillation power, and some manufacturers have to calibrate the oscillation power as the output power or just to say the general landmark. For power, mislead customers. What's more, simply do not write the power, the input current number calibration model, so that customers mistakenly believe that the literacy is the machine's power. The two are far from each other. Induction heating equipment, usually bought for a long time will not be updated, so that customers understand the differences between the district often repent. Therefore, when companies introduce products to you, don't just care about the model, and don't forget to ask what the output power is and get it done. 2, the same workpiece processing, different working speeds, power options are also very different, such as; a fastener company to hot-forging processing Φ30 mm length 50mm screw, heating temperature 1000 degrees, production speed 20 pieces / minute, it should be selected A machine with a frequency of ultra-audio (10-40KHZ) output power of 80 KW is used. If the production speed is reduced to 10 pcs/min, a machine with a frequency of 50 megawatts of super audio (10-40) output power can meet the application. 80 KW The price is higher than 50KW, so manufacturers can choose the appropriate model according to their actual situation, so as to avoid waste. In addition, the power selection must also take into account the fluctuation of the power supply voltage. For users of three-phase AC power supply, if the voltage is reduced by 10V, the output power will be reduced by about 7%. In general, enterprises use the equipment. , A batch of workpiece heating time is fixed, when the voltage is reduced, in order to ensure that the heating effect, you should increase the power of the machine to achieve the same heating effect. However, if your heating time is set on the premise of a large power state of the equipment, when the voltage is reduced, the same heating effect can be achieved only by prolonging the heating time. In this case, it is necessary to re-experiment, obtain the time setting parameter, and delay production. Work does not guarantee the quality of the work piece. Therefore, it is recommended that the power output of the device be adjusted to about 85-90% power state when in use, leaving a margin, which in turn can extend the service life, and can easily deal with the adverse effects of voltage fluctuations.
Third, how to avoid the price trap When you determine the frequency and power of the machine according to your workpiece requirements, you must select the appropriate supplier according to the production situation. The price is of course more concerned to you, and how to avoid the price trap will be another problem you face. At present, with the widespread use of IGBT induction heating equipment, manufacturers also have many manufacturers, but in the small (400KW) field can have independent intellectual property rights, have independent high-level R & D team, a full range of products, only a few companies nationwide At home, most companies are counterfeiting and assembly. Therefore, even among different manufacturers, the quality of products with the same power (calibration) varies greatly. Buying a practical, inexpensive product is what every user expects. Because the price of the equipment is closely related to the power of the equipment, the higher the power, the higher the price. Therefore, the power vacancy becomes a misleading customer. means. Usually manifested as: 1. The power nominally oscillating power. 2. The enterprise calibrates the oscillating power as the output power or simply refers to the power in general terms. 3. If the power is not written, the input current is calibrated and the customer is mistaken for the following Literacy is the power of the aircraft. 4, casually marked low power written high power. Compared to the above situation, the following situation is even worse. Some domestic manufacturers in order to seek profits, through the adjustment of certain parameters of IGBT module, to achieve the purpose of increasing the power of low-power equipment, such as the 30KW equipment is adjusted to 40-50KW, sell it as a 45KW equipment, the result of the pony Pulling carts, heavy equipment loads, and shortening the service life of equipment, products that could have been used normally for five years were scrapped in one or two years. This kind of situation can't be noticed by customers for a short time, but it's just a matter of time. Moreover, due to the change of the parameters, the compatibility of the equipment is deteriorated, the mutual interference is serious, and the failures are many and affect the production. A better way to avoid this is to look for domestic large-scale manufacturers, or listen to peer reviews. In fact, but in any case, you just need to pay a little attention, it is not difficult to distinguish. Here's a brief introduction. 1, the same use of power comparison For example, when you determine that the factory will buy a high-frequency heating equipment for welding, you determine the three companies A, B, C products, respectively, A-25 (output power 25KW) 14800 Yuanjia-40 (output power 40KW) 26800 yuan B-25 (oscillating power 25KW) 12500 yuan B-40 (oscillating power 40KW) 18800 yuan C-25 (oscillating power 25KW) 11000 yuan C-40 ( Oscillating power 40KW) 16800 yuan As the A-25 is the output power, it is converted into oscillation power, A's oscillation power is 42 KW So, to complete the same work, B, C comparison models for B-40 (oscillating power 40KW ) 18800 yuan C-40 (oscillating power 40KW) 16800 yuan So, A-25, 14,800 yuan is a lower price. In this way, you can fall into the price trap of ethylene propylene. 2. Comparison of the same artifacts As the saying goes, I am afraid that I do not know the goods, I am afraid that the goods will be delivered to the above suppliers. I will get different heating time, shorter heating time, and the power is higher. Compare them. Similar models, screening.
Fourth, how to choose a good product. A good product should have the following points: good stability, good cost performance, good adaptability, quick and thoughtful after-sales service. When you choose a product, it is necessary to consider not only his comprehensive utilization costs in the later period, including factors such as loss of work stoppages, parts replacement, maintenance after the warranty period, and upgrading ability. Practice is the standard for testing products. You can ask for The other party will install the equipment into your factory and conduct on-site testing. If possible, it can be used for a few days. Good equipment, neat appearance, clear identification, easy to use. Most small power devices (oscillating power below 30KW) most companies use light emitting diodes to display the size of the current, but it can not really show the size of the power, can only be used as a reference to adjust the power. When the oscillation power is more than 30KW, the standard metering voltage (oscillation) and current (oscillation) table should be used. When the equipment is working, the operating voltage (oscillation) and current (oscillation) can be visually displayed, and the enterprise can not be falsified, and it is also convenient for the operator to be objective and accurate. Master the machine running state. If such high-power devices still use light-emitting diodes to display, be careful. High-power equipment is generally separate main power supply and induction coil transformer, transformer performance directly affects the efficiency of the induction coil, and some transformers use oil immersion, this transformer is relatively backward, easy to pollute, once damaged, almost The value that cannot be repaired or repaired is the eliminated product. Most companies now choose dry-type transformers. The same host, because of the different parts, the transformer is not exactly the same. For example, when an output power 30KW induction heating equipment is used for welding, the induction coil is in 1-2 circles, and the induction coil is in 4-8 revolutions when the induction heating equipment is annealed. The induction coil is on the premise of ensuring the normal output of power. The more the number is, the more uniform the workpiece is heated, and the stronger the ability of the equipment to handle irregular workpieces. However, in some enterprise equipment, transformers can only load 1-2 induction coils, encounter large workpieces, and induction coils can only be manufactured and managed. The process is complicated and the heating efficiency is low. Once encountered such a situation, heating a diameter of 16 cm, height 20 cm stainless steel enamel products, using a 30KW equipment for stainless steel annealing process, induction coil 7 åŒ, output power reached 32KW, annealing in just 13 seconds, the same induction circle , The same workpiece, put on another brand test machine called 40KW, heating speed even more than 90 seconds, almost can not be used, the number of turns of the coil is 3-4 turns, can barely heat, had to install the rotating device on the bottom of the workpiece . If conditions permit, it can also require equipment manufacturers to open the chassis, a good device, a reasonable layout of electronic components, neat lines, you can see the key components such as IGBT power modules, power capacitors and other raw materials, from the overall appearance of the device , Weight has a better understanding of the equipment. Most manufacturers do not have independent high-level R&D teams and do not have their own core technologies, and their homogeneity is serious. Most enterprise product control circuit boards and drive circuit boards are integrated. When one of the drive circuits fails, the entire circuit board has to be replaced. This situation generally occurs when the warranty period expires, thereby increasing the burden on the user. Therefore, it is preferable to be able to select an independent product of the main control circuit board and the drive circuit board, and the maintenance cost is low. This may be to ask the other technical personnel. Strong enterprises, full spare parts, fast and efficient, after-sales service, and thoughtful, but also to provide customers with spare equipment, a greater degree of assurance that the company's production work will not be affected. So far, you may have a simple understanding of IGBT induction heating equipment, but it does not meet all areas of metal heating. The physical characteristics of the IGBT power module determine its power can not be made very large, at present, some foreign companies have developed input power 4000KW equipment, only a few companies in the country have the ability to produce about 1000KW equipment, high power heating equipment still use the traditional The transistor and electron tube technology, in addition, the use technology of IGBT in the UHF field still needs further breakthrough. (Guangzhou Wei Shida Electronic Technology Co., Ltd. to provide information).
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