Principle of high frequency induction heating

The principle of high-frequency induction heating: When a current flows through a conductor, a magnetic field is generated at the same time around it, and the high-frequency current flows to an induction coil (usually made of a copper tube) that is wound into a ring shape or other shape. High-frequency heating equipment manufacturers will provide you with more knowledge. The high-frequency heating device will generate a strong magnetic flux with a momentary change in polarity in the coil. The heated metal material will be placed in the induction coil, and the magnetic flux will pass through the entire The heating substance generates a large eddy current in a direction opposite to the heating current inside the material to be heated, and Joule heat is generated by the electric resistance of the heated metal substance, so that the temperature of the metal substance itself rises rapidly, thereby completing the heating of the metal workpiece.

Applications: Metallic eyewear manufacturing, connector soldering in the electrical and electronics industry, non-contact soldering inside small relays, high pressure soldering in the refrigeration industry, soldering between components in the jewelry industry, soldering in metal jewelry and metalworking manufacturing, and Various small metals, heat treatment such as quenching and annealing. Carbide saw blade size tooth welding, eyeglass frame, spare parts welding annealing, jewelry, watch welding; electronics industry: (very fine wire various electronic components fine parts soldering silver welding; electromechanical industry: (fine metal joint silver copper Welding micro motor shaft and other quenching and tempering); wire industry: wire strip annealing; tool welding: paper cutter, shoe knife edge quenching; toy industry: spring thin metal sheet tempering; small smelting, precious metal smelting (gold, Silver); brazing (with wire: silver, brazing, soldering) welding of diamond heads, welding of hard alloy saw blades, welding of diamond tools, grinding tools, drilling tools, machining of hard alloys Welding of knife saws, such as: welding of cutting tools such as turning tools, planing tools, milling cutters, reamers, etc., welding of mining tools, such as "one" word bit, column tooth bit, dovetail coal bit, riveting bit, various Shearer picks, welding of various roadhead picks, welding of various woodworking tools, such as welding of various woodworking planers, milling cutters and various woodworking drill bits; forging and rolling: heat of various twist drills Rolling. Standard parts, fasteners, such as high-strength bolts Nuts; heat treatment of various hardware tools and hand tools, such as pliers, wrenches, screwdrivers, hammers, axes, etc.; high-frequency quenching treatment of various auto parts and motorcycle parts, if solid-state high-frequency, super-audio power supply Not only the energy saving effect is remarkable, the efficiency is high, and the environment is protected.

The manufacturer of high-frequency heating equipment also believes that the service life of the medium-frequency induction furnace is inseparable from the choice of the charge. The stability of the physical and chemical properties of the selected refractory material is directly related to the length of the service life. How to extend the service life of the medium frequency induction furnace, we conducted a number of repetitive experiments and work research, and summed up a relatively complete program. Below we give you some knowledge to make your heating equipment more durable.

1, the choice of charge

The performance of furnace refractories is directly related to the service life of medium frequency induction furnaces. To choose furnace refractories with good performance, it must be carefully selected and scientifically managed. Master several basic principles: First, the charge has strong refractoriness and high capacity stability. Ensure that it will not be softened and melted under ultra-high temperature working conditions. Its strong thermal load performance is used to ensure that the volume of refractory material is not reduced. Inflation can only be within the allowable range of the specified value. Secondly, it is resistant to thermal shock. Good performance. It is used to ensure that the probability of cracks in the furnace can be greatly reduced when the temperature changes sharply, and the crack can be completely avoided. Finally, there must be high atmospheric temperature strength, high temperature thermal strength and supercharged gravity.
This requires us to scientifically select and manage the charge, that is, to select the charge, and to put the “fine material” into the furnace, not only to clear the charge entering the furnace, but also to strictly control the main components in the molten steel. There are two specific reference standards. One is to keep the types and quantities of harmful impurity elements as low as possible. The second is to ensure that the active ingredients are in the relevant standards.

2. Furnace process

The furnace laying process is a key link in the life and safety of the furnace. This requires the practitioners to strictly control the quality of the technology. In the process of paving the furnace, it is necessary to do a good job in all aspects of inspection to ensure the integrity of the coil. Once damage is found, the following parts must be added: First, apply Brushing the insulating varnish for repair; secondly, repairing the furnace wall with water glass refractory mud, laying down in order according to the premise of ensuring the cleanliness of the furnace wall and the bottom of the furnace, including mica board and alarm stainless steel meeting the specified size requirements Net and asbestos cloth; third, the alarm stainless steel mesh that has been connected with the copper core wire is passed out of the furnace coil, and then the lower, middle and top of the furnace wall that has been paved with asbestos cloth are used with three rising rings. The parts are tightened; the furnace is finally covered to prevent debris from falling into the furnace.

3, building a furnace

The knotting quality of the lining is also inextricably linked to the service life of the electric furnace. It is directly related to the quality of the sintering, which in turn affects its performance. Only when the sanding granules are evenly leveled and the high tightness of the feeding is ensured, the density of the lining after the knotting and the strength of the sintered layer after sintering can be ensured, so that the crack of the furnace wall can be effectively reduced. In addition, the vibrating compaction of the lining can also effectively reduce the leakage of molten metal. It is important to note that in the case of hand knotting, the surface must be loosened and refilled after the finish, which can effectively avoid the occurrence of delamination and unmatchable cracks.
In addition to the strict control of the furnace construction process, the selection of the furnace tools (including the construction of furnaces, tamping forks, flat hammers, and dies) and the requirements for preliminary preparation should also be taken seriously.

4, the grasp of the oven temperature

The sintered layer has a direct relationship with the service life of the furnace, and the oven is actually to obtain the sintered layer. It can be seen that the oven plays an important role in extending the service life of the medium frequency induction furnace. The oven link should not be underestimated. The most meticulous process of this process is the oven process. The specific steps are as follows: First, the heating speed should be strictly controlled. The faster the early speed of the oven, the more likely the crack will occur, and the service life of the furnace is also Secondly, when the lining temperature reaches 573 ° C and continues to heat up, the volume will expand by about 16%. In this process, if the heating is too slow, it is difficult to obtain the desired sintered layer, and if it is too fast, cracks are more likely to occur. And peeling, in the actual work research, we found that: when heating to 600 ° C at 400 ° C, the heating speed should be reduced, when it reaches 870 ° C, it will be perfectly disguised during the heat preservation for 1-2 hours. Third, sintering and heat preservation is the final stage of the oven. There is no hard regulation on the sintering temperature. Generally, the thickness of the sintered layer is required to be 30% of the thickness of the lining. This requires the sintering temperature to be 50~ higher than the temperature of the iron. 100 ° C.

5, smelting operation

Whether the metal charge in the melting period can be melted smoothly is the most important factor in the service life of the electric furnace and the production efficiency of the enterprise. The tightness of the charge directly affects the melting speed of the melt. Only when the material is packed as tightly as possible, the melting time can be shortened to avoid high temperature and violent eddy current, thereby protecting the furnace wall from the frame. Damage to the bridge and the bridge.

In addition, during the feeding process, attention should be paid to the feeding process. Once the electric furnace is placed at the high power input when the bulk material is added, the temperature, scouring and static pressure of the lining are at the maximum state, and the erosion is caused to the bottom. Also reached the maximum. This requires the operator to pay attention to the temperature and quality of the molten metal in the electric furnace. Once the standard is reached, it needs to be powered off immediately. This method of shortening the smelting time not only reduces the power consumption during the molten steel smelting process, but also effectively reduces the damage of the lower part of the lining, thereby prolonging the service life of the electric furnace.

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