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Induction Heating Since 2000

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What new induction heating heat treatment technologies are available?

With the development of new knowledge and equipment, it is possible to expand the application range of induction heating and apply it in the fields of furnace carburizing and other chemical heat treatment.

(1) Induction surfacing and hardening is one of the effective technologies to solve this problem. For the parts that are under severe wear, such as excavator plowshares, mining buckets, and railway parts, the surface of which needs to have a thick layer of wear resistance and corrosion resistance. The technology has been used for a long time in Russia, for example, to handle the blade of a plough. With the introduction of solid-state power, modern control systems, and new materials, this technology will become more attractive. A powder or paste mixture of flux and hard material powder is applied to the surface of the workpiece and heated by a stationary or moving sensor. The most commonly used are hairpin and vertical ring sensors. Hairpin sensors are fitted with Ferrotron 559 magnets that improve the coil parameters and help to optimize the distribution of energy in the parts. The original surface of the part is heated by a sensor and the surfacing material is melted. The hardening layer and the matrix are well bonded, and the diffusion zone between them is narrow.

The melting point of commonly used hardening materials is 50 ~ 100F lower than that of the matrix, that is, the matrix remains solid, but a eutectic pool can also be formed. As long as the correct choice of surfacing materials and operating conditions, surface surfacing hardening can increase the service life of parts several times or even more than 10 times.

(2) Induction “brush” induction heating is also widely used in coating treatment, such as preheating of parts before coating, remelting of galvanized layer, spraying or plasma spraying layer. Induction technology plays a very important role in the production of galvanized or galvanized steel products by diffusion treatment. It is used in preheating strip steel, remelting, crucible heating, and so on. The latest application of induction technology in hot-dip galvanizing is the removal of excess zinc or other alloys from the steel surface by electromagnetic method at the exit of the crucible. The traditional process USES an “air knife”, or high-speed jet, but the disadvantage is that the material to be removed cannot be completed, and the coating surface is not smooth enough. In the case of an induction brush, the electromotive force generated by alternating magnetic field interactions and eddy currents in the coating causes the molten metal to be transferred and “lifted”, and then the metal “waves” are removed by an air knife.

(3) Induction hardening is used in large parts instead of carburizing treatment. For example, a large part requires that the surface of the inner hole has a carburizing hardening layer of more than 4mm to ensure that it has sufficient strength and wear resistance. The operation steps of the traditional process are as follows:

(1) do not carburize parts for seepage treatment.

(2) for a long time to get more than a 4mm carburizing layer.

(3) In order to make the complete transformation of the structure, a special quenching process is used for the furnace heating quenching.

Deep grinding to correct the heat treatment distortion of parts.

The new technology does not require any auxiliary process, and the multi-turn sensor is used for scanning treatment. The required hardness and the depth of the hardening layer can be obtained after quenching with the spray ring. The induction coil is equipped with a copy magnet made with FluxtrolA [3]. The process and coil system adopt the virtual prototype design technology, and the computer simulation has successfully met the technical requirements of the parts. Advantages of the new technology: reduce the distortion of parts, reduce the amount of machining technology, shorten the time of heat treatment, save energy, can be used to replace the low price of carburized steel. This technology is still in the test and has not been applied in China.

(4) The surface chemical treatment of liquid medium has made many attempts to the induction heating gas carburizing but did not achieve the furnace carburizing effect.Dr. Saveliy Gugel proposed a process of high temperature treatment in a liquid active medium (LAM). Based on this vision, he patented a technology called the Linter Process. Sanova LLC has researched and developed the technology in theory and practice. Although this technique can be performed by contact heating or resistance heating, induction heating is the best method.

When using induction heating, the part is placed in a treatment chamber with a cold-active medium, and the surface is heated by an induction coil. When the surface of the part reaches a high temperature, a vapor film will be formed, thus reducing the heat lost to the medium. This boiling medium contains a high concentration of elements that can seep into the parts. The process is fast and stable, and the parts can be hardened immediately in the same liquid active medium or separately after treatment. If tempering is required, the parts can be taken out of the treatment chamber and tempered or heated separately. Interesting results have been obtained in the treatment of titanium alloys. For example, titanium alloys have been obtained with this experimental apparatus with a high surface hardness (up to 70HRC), high wear resistance, and low friction factor. As technology continues to advance, it will not be a problem to apply it to the production of actual artifacts.

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