About an Induction Forge
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Induction forging is a process in which an induction heating system preheats metals and presses them into shape using a hammer or press. The applications for induction forging vary greatly, but before you get started assessing your applications, it's helpful to have a good understanding of the process. So, let's get started.
Read our guide: Induction Heating for Forging
More Induction Forging Application Notes
Principal Process
First, it's important to understand that induction heating is a non-contact process that uses the main principles of electromagnetic induction in order to effectively produce heat. Electric current can flow through a material when it is placed in a strong alternative magnetic field; this causes Joule heating. With magnetic materials, the excess heat is generated below the Curie Point -- the Curie point is the temperature at which certain magnetic materials undergo a sharp change in their magnetic properties. The Curie point of iron, for example, is 1,418 degrees Fahrenheit (770 degrees Celsius).
The depth of the generated current is determined by both the frequency of the alternating field as well as the material's permeability. Materials with high permeability (100'500) are easier to heat via induction heating. Iron and its alloys respond well to induction heating due to their ferromagnetic nature.
Consumption of Power
Before getting started with your own applications for induction forging, you need to understand the power that it requires. The power supplies needed for induction forging can vary greatly, from just a few kilowatts to multiple megawatts. The component geometry can also dictate power supply frequency, which can vary from about 50 Hz to 200 kHz. Keep in mind that most applications for induction forging use a range of between 1 kHz and 100 kHz.
Selecting the correct power for your induction forge application requires you to calculate the thermal energy needed to raise the chosen material to the necessary temperature within the allotted time frame. After this measurement is determined, you'll have to factor in other components such as radiated losses, coil losses, and other system losses. (And, THE LAB at Ambrell can help you do this with complimentary applications testing.)
Output Frequency and Power Source
After determining the power consumption necessary for an induction forging application, you'll have to consider the next main parameter -- the output frequency of the power source. While the heat is primarily generated in the surface of the component, it's critical to choose a frequency that offers the deepest and most practical penetration depth into the work piece. You should also keep in mind that it does take time for the heat to penetrate toward the center of the work piece. Furthermore, if too much heat or power is applied too quickly, it is possible to melt the work piece's surface while the core is still cool.
Benefits
The top three benefits of induction forging are fast heating cycles, accurate heating patterns, and cores that remain relatively cold and stable. Induction forging, however, also boasts many benefits. First and foremost, the process is highly calculated, and therefore, controllable. Traditional heating systems, such as gas furnaces, require a preheat and shutdown, whereas induction forging applications do not. Furthermore, the heat is available on demand with rapid availability. If a downstream interruption to production ever occurs, the power can easily be turned off, preventing unnecessary energy loss.
Induction forging is also an energy-efficient process. This is a result of the heat being generated within the component as opposed to around it. The transfer of heat and energy is made much more efficient because the induction heating system only heats the work piece, not the atmosphere surrounding it.
Ultimately, understanding the processes and benefits of induction heating and forging applications is essential to determining what is induction forging and whether or not it's right for your process.
Additional Benefits
We've already discussed some benefits of the induction forging process; specifically, its controllable processes and energy efficiency. However, there are many more benefits that most people aren't quite aware of. For example, unlike other types of heating, induction forging does not create any harmful or toxic byproducts when the process is complete. It's a completely clean process that does not contribute to environmental waste. No smoke or toxins are created as a result of induction forging.
Furthermore, part of the answer to the question, "How does forging work?" includes the element of consistency with results. When all is said and done, the process is highly controllable, which means it can be easily and quickly repeated time-after-time with little-to-no change in the result. There's nothing unexpected or surprising about induction forging because there's no guesswork involved. Such uniform results help to prevent the need for post-forging machining.
Additionally, induction forging causes high temperature rises, ensuring that each component reaches its necessary temperature quickly and efficiently. This reduces the scale as well as the possibility for surface defects of the material upon completion.
Bar End Heating
Bar end heating is a type of forging in which only a portion of the bar is forged. These applications typically include hot heating of bolts and some mining tools. For example, the end of a bar might be heated and then hot heated to create a large fastener. Bar end heating is very similar to induction forging.
Ultimately, the efficiency of an induction heating system for a specific application depends on four factors: the characteristics of the part itself, the design of the coil, the capacity of the power supply, and the amount of temperature change required for the application. Understanding the detailed processes of induction forging is the best way to determine whether or not your business can benefit from forging with induction heating equipment.
Induction forging refers to the use of an induction heater to pre-heat metals prior to deformation using a press or hammer. Typically metals are heated to between 1,100 and 1,200 °C (2,010 and 2,190 °F) to increase their malleability and aid flow in the forging die.[1]
Process
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Induction heating is a non-contact process which uses the principle of electromagnetic induction to produce heat in a workpiece. By placing a conductive material into a strong alternating magnetic field, electric current is made to flow in the material, thereby causing Joule heating. In magnetic materials, further heat is generated below the Curie point due to hysteresis losses. The generated current is predominantly in the surface layer, the depth of this layer being dictated by the frequency of the alternating field and the permeability of the material.[2]
Power consumption
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Power supplies for induction forging vary in power from a few kilowatts to many megawatts and, depending on the component geometry, can vary in frequency from 50 Hz to 200 kHz. The majority of applications use the range between 1 kHz and 100 kHz.[3]
In order to select the correct power it is necessary to first calculate the thermal energy required to raise the material to the required temperature in the time allotted. This can be done using the heat content of the material, which is normally expressed in KW hours per tonne, the weight of metal to be processed and the time cycle. Once this has been established other factors such as radiated losses from the component, coil losses and other system losses need to be factored in. Traditionally this process involved lengthy and complex calculations in conjunction with a mixture of practical experience and empirical formula. Modern techniques utilise finite element analysis[4] and other computer aided modeling techniques, however as with all such methods a thorough working knowledge of the induction heating process is still required.
Output frequency
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The second major parameter to be considered is the output frequency of the power source. As the heat is predominantly generated in the surface of the component it is important to select a frequency which offers the deepest practical penetration depth into the material without running the risk of current cancellation.[5] It will be appreciated that as only the skin is being heated time will be required for the heat to penetrate to the centre of the component and that if too much power is applied too quickly it is possible to melt the surface of the component whilst leaving the core cool. Utilising thermal conductivity data for the material[6] and the customer's specified homogeneity (physics) requirements regarding the cross sectional 'T it is possible to calculate or create a model to establish the heat time required. In many cases the time to achieve an acceptable 'T will exceed what can be achieved by heating the components one at a time. A range of handling solutions including conveyors, in line feeders, pusher systems and walking beam feeders are utilised to facilitate the heating of multiple components whilst delivering single components to the operator at the required time cycle.
Advantages
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For more induction forging machineinformation, please contact us. We will provide professional answers.
- Process controllability ' Unlike a traditional gas furnace the induction system requires no pre-heat cycle or controlled shutdown. The heat is available on demand. In addition to the benefits of rapid availability in the event of a downstream interruption to production the power can be switched off thus saving energy and reducing scaling on the components.
- Energy efficiency ' Due to the heat being generated within the component energy transfer is extremely efficient. The induction heater heats only the part, not the atmosphere around it.
- Rapid temperature rise ' High power densities ensure that the component reaches temperature extremely rapidly. Scale is reduced as are surface defects and undesirable effects on the surface metallurgy.
- Process consistency ' The induction heating process produces extremely uniform consistent heat. This improves accuracy of the forging and can in extreme cases reduce post forging machining allowances and have a positive effect on die life.
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- No harmful byproducts ' Induction heating does not generate any environmental waste products and is a clean process as opposed to more traditional heating methods that generate smoke and toxic emissions.
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Types
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Bar end heating
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Bar end heating is typically used where only a portion of the bar is to be forged. Typical applications of bar end heating are:
- Hot heading of bolts
- Anti roll bars
- Mining tools
Subject to the required throughput, handling systems can vary from simple two- or three-station pneumatic pusher systems to walking beams and conveyors.
Billet heating
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In the induction billet heater the whole of the billet or slug is heated. Normally for short billets or slugs a hopper or bowl is used to automatically present the billets in line to pinch rollers, chain driven tractor units or in some cases pneumatic pushers. The billets are then driven through the coil one behind the other on water cooled rails or ceramic liners are used through the coil bore which reduce friction and prevent wear. The length of the coil is a function of the required soak time, the cycle time per component and the length of the billet. In high volume large cross section work it is not unusual to have 4 or 5 coils in series to give 5 m (16 ft) of coil or more.[10]
Typical parts processed by in line billet heating:[11]
- Small crankshafts
- Camshafts
- Pneumatic and hydraulic fittings
- Hammer heads
- Engine valves
Single shot
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For long billets, single shot heating can be used. This process utilises similar systems to bar end heating except that the whole of the billet is driven into individual coils. As with bar end heating the number of coils is governed by 'T required and the thermal properties of the material being heated.
Typical parts processed by single shot billet heating:[12]
- Lorry axles
- Marine camshafts
See also
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References
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Notes
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