Oct. 28, 2024
-01-05 From: Local Views
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Many people want to know what is advantage and disadvantage of induction heating, induction hardening, induction brazing, induction forging, induction melting or induction quenching.
High frequency induction machines and induction heating technology is currently regarded as one of the most efficient heating methods for metallic materials, characterized by rapid operation and environmental friendliness. It has found its way into numerous industries for thermal processing of metals, heat treatment, hot assembly, welding, and melting operations. The technology is capable of heating an entire workpiece, or selectively heating specific areas, allowing for in-depth and exact temperature control. It has also been shown to effectively heat non-metallic materials. As such, the applications of induction heating technology are extensive and varied.
Local heating of the workpiece is achieved through induced current heat treatment. This process is commonly utilized in surface hardening but can also be applied in partial annealing or tempering, and even for overall quenching and tempering. By the 1960s, nations like the United States and the Soviet Union had already integrated induction heating methods for surface hardening of various components. As industrial practices evolved, induction heating and heat treatment technology have continuously advanced, leading to broader utilization.
Understanding the basic principles: When a workpiece is placed within a coil inductor, and alternating current passes through the coil at a specific frequency, an alternating magnetic field is produced. This effect generates induced currents within the workpiece that creates thermal energy, particularly at the surface layer, which experiences a higher current density. This is known as the skin effect. Higher current frequencies correlate with greater temperature differentiation within the workpiece, ensuring effective surface heating and the attainment of critical points for hardening.
Classification: The process of induction heating and heat treatment corresponds to the alternating current frequency. These are divided into UHF, HF, RF, and MF categories based on frequency ranges:
(1) Ultra-high frequency induction heating employs frequencies up to 27 MHz for very minimal heating thickness, optimal for intricate surfaces like circular saws.
(2) High-frequency induction heating typically operates at 200 to 300 kHz, achieving a heating layer depth between 0.5 to 2 mm, suitable for gears and shafts.
(3) Radio induction heating runs at frequencies of 20 to 30 kHz, delivering surface hardening across the tooth profiles of small modulus gears.
(4) Medium frequency induction heating spans 2.5 to 10 kHz with depths ranging from 2 to 8 mm, mainly for larger gears and larger diameter shafts.
(5) Power frequency induction heating utilizes 50 to 60 Hz current for deeper heating layers of 10 to 15 mm, good for larger workpieces.
Characteristics and applications: The significant advantages of induction heating include minimal deformation of the workpiece, low power consumption, reduced environmental impact, rapid heating times, and lesser oxidation and decarbonization risks. Additional benefits include customizable surface hardening layers, easy integration into production lines, improved component fatigue strength, and a greater overall internal stress capacity.
The induction heating heat treatment does come with certain drawbacks. The complexity of the equipment compared to flame hardening, coupled with its limited adaptability, presents challenges in achieving consistent quality for parts with complex geometries.
Although induction heaters might involve higher initial investments, their operational efficiency often offsets these concerns over time.
Undoubtedly, the advantages of induction heating surpass the disadvantages.
Thus, it stands as a preferable method for metalworking applications, replacing traditional heating techniques, such as those that use coal, oil, gas, or electric ovens.
Applications: Induction heating is extensively employed for the surface hardening of critical components like gears, shafts, crankshafts, and rollers, ultimately enhancing their abrasion resistance and fatigue failure tolerance. For example, the surface hardening on automobile rear axles through induction techniques can lead to a fatigue design load cycle increase by nearly ten times compared to conventional processes. Typically, carbon steel is used for workpieces, while specialized low hardenability steels have been developed for specific needs. Both high-carbon steels and cast iron can benefit from induction heating treatments, commonly utilizing water or polymer solutions as quenching mediums.
Equipment: Induction heat treatment systems comprise power sources, quenching machines, and sensors. The power supply's primary role is to deliver the suitable frequency of AC. This includes components like high-frequency generators or SCR inverters, or systems able to vary frequency while using standard power sources.
Selection: Selecting the appropriate induction heating device depends on the required heating layer depth of the workpiece. Low-frequency power supplies are advised for deeper heating applications while high-frequency units are better suited for shallower layers. Care must be taken to ensure the power supply is adequate to meet the demands of the heating surface area, preventing inadequate heating due to insufficient current. It is particularly effective to leverage waste heat from the workpiece core during the heating process to improve efficiency and save energy.
For further details on induction heater controllers information, please contact us for professional assistance.
The core function of the induction heating machine involves positioning the workpiece and managing its movements. It requires additional quenching media devices, which can be categorized into standard and specialized machining tools based on their suitability for generic or complex workpieces, respectively.
To guarantee superior quality during the induction heating treatment and to enhance thermal efficiency, one must design and create appropriate sensors tailored to the workpiece shapes and their heat treatment requirements. Common sensor types include external surface sensors, internal cavity heating sensors, plane heating sensors, and various specialized sensor types optimized for unique heating tasks, including composite heating sensors and smelting furnaces.
There are several standards governing the inspection of carbon steel assets, structures, and
Much has been written, discussed and debated about the values of the process of induction heat treatment. Induction heat treatment is a now a mature process technique that offers clean work, high-speed production, easily automated process and repeatable metallurgical results.
The process works on the simple principle that when an electrical current is passed through a conductor, an electro-magnetic field is created around the conductor. The conductor is generally (not in all cases) a coiled copper conductor through which a high-frequency magnetic field is induced to flow through the coil. This sets up a magnetic field around the coil and within the coil. If a steel bar is inserted into the coil, the magnetic flux that is generated will create eddy currents within the surface of the steel bar, which creates heat within the immediate surface of the inserted bar within the conductance coil.
The depth of the heated and hardened surface will be dependent on the carbon content of the steel bar, induction frequency, induction power, residence time within the coil and quench medium.
The steels that can be used for an induction heat-treatment procedure will generally contain approximately 0.3-0.5% carbon. Care needs to be taken with the higher carbon grades for the potential risk of cracking. Chromium can be added to the steel (generally 0.25-0.35%) to interact with the carbon content of the steel and produce surface chromium carbides.
It is at this point that the decision should be made if the system will quench with water or a poly-alkaline glycol mixture to reduce the risk of cracking. The induction coil can be designed to accommodate any geometric shape that will allow access to the contour to be heat treated and quenched accordingly.
The following will show some of the advantages and disadvantages of induction heat treatment.
Advantages
Disadvantages
Do not be under any illusion that the process is distortion-free. The degree of distortion that will occur will be dependent on the amount of prior working that has occurred to the product when machining. Distortion will occur.
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