Induction hardening technology doesn’t use physical contact. Instead, a series of magnetic fields are projected from a large coil. Workpieces enter the coil, experience this induction effect, and respond by generating surface heat. That workflow suggests a production line of some kind. If so, is its ever-cycling configuration preferred over, say, flame or case hardening technology?
High-Volume Processing
In order to answer that query, consider the alternative. A focused flame functions as a targeted hardening method. The technique heat treats gear teeth and other finely wrought geometrical profiles. Even large surface areas can be scanned and hardened via a traveling flame nozzle. Still, it’s not considered a large volume solution, not one that can compete with induction hardening. Down on a fast-moving factory floor, the inductance effect slots neatly into a fast production environment because it’s able to accommodate a fast processing run while delivering a cheap and repeatable final result.
One-Shot VS. Traverse Hardening
The frequency-modulated coils act as an efficient one-shot hardening mechanism, a configuration that perfectly matches the dimensional profiles of axles and shafts. The longitudinal metal segments submit readily to the lines of magnetic energy, with the induced currents forming strong thermal tides that flow naturally along the long metal segments. Alternatively, a traverse mechanism can replace the one-shot methodology. In this case, the part is moved progressively into the coils. This layout suits a standard production line, with the parts moving from one stage to the next. In keeping with this mechanical configuration, a spray quench ring is typically activated at the end of the part’s treatment.
Fine-Grain Parts Treatment
The option to longitudinally vary the frequency or applied power in different sections of the induction coil makes this method a highly tunable technique. Even the velocity of the traverse mechanism subscribes to this work model, with the component slowing to experience additional depth hardening on specified sections. Indeed, processed pins, axles, and shafts are imbued with specified heat treatment profiles after they depart the induction treatment mechanism. That’s because the station is designed to accommodate longitudinal workpieces and to process each one with repeatable mechanical features, all while maintaining a high-volume work throughput.
A contactless hardening profile can reach down as far as 15-mm when induction technology is added to the production line. The long, cylindrical coils are perfectly configured for pin processing, axle hardening, and cost-effective shaft processing. Finally, all of this one-shot and traversing momentum assumes a cycling manner, a flow that’s guaranteed to repeatably process these long parts through ring-type coils while imprinting them with localized attributes that are as hard as any flame or case hardened solution.
The flame hardening process functions as an exceptional surface hardening solution. Its gas-generated flame hardens selected areas on command, then switches tact to heat treat large surface areas, no matter how eccentric the part’s geometry becomes. Let’s indulge in a little discrete analyzing, a look into flame hardening and the method’s gift for processing large and uniquely profiled parts.
Large-Scale Processing Suitability
An accelerated workflow is a prominent feature here, an upshot of the flame hardening method that assures wholesale depth-hardening, even when the workpiece surface is massive. In order to achieve the faster process times, a sweeping (scanning) flame head is used. It moves across sizable surface areas to assure full surface transformation. The shape of the flame head, the gas used, and the ability to focus the heat all contribute to this large-scale heat treatment faculty, with some uniquely innovative mechanical assets supplementing the mobility of the tooling assembly.
Utilitarian Workflow Benefits
Due to the streamlined tooling set-up, the equipment sports an optimized frame, a configuration that’s more cost-effective than some of the comparable hardening techniques we’ve mentioned so far. The versatile flame head adapts to complement the project, which means it opens up and scans to process massive parts, but that workflow is adaptable. Focusing adaptability sharpens the gaseous output and targets that fiery edge so that it can process gear teeth and other fatigue susceptible components until they’re fully surface-crystallized and rated as a toughened martensitic grain.
Transforms Eccentric Profiles
We’ve compared flame hardening methodologies to induction techniques with good reason. Essentially, they both use currents of energy to transform (harden) the surface of an alloy. But induction technology, as beneficial as the method undoubtedly is, relies on magnetic effects. Flame hardening, on the other hand, uses currents of pure thermal energy, burning gasses that precisely target gear teeth and other finely detailed work parts. As a result, the focused fire penetrates bore holes and all kinds of complex geometrical outlines predictably, without ever causing an engineer to worry about some hard-to-predict electromagnetic parameter.
If the reassuring presence of a controllable flame isn’t enough to determine this heat treatment method as an upper-echelon hardening solution, take note of the other benefits that accompany the process. Tooling requirements are straightforward, so costs are lower than a comparable induction set-up. Partner this shorter system tooling period with faster parts processing times and an ability to adapt to large-scale or focused processing and, well, the flame hardening method can be considered the equal of any induction hardening solution.
Induction hardening technology employs a refined control setup, with magnetically induced energy patterns acting as a contact-free heat treatment mechanism. A hardening profile is established by the induction station’s electrically manipulated magnetic fields. Science-based principles now gain traction, but what criteria are we hinting at here? A detailed analysis is required to understand the effects of these process parameters.
Process Parameters: A Brief Primer
Electromagnetic fields hold sway during the hardening cycle. The outer section of the processing station is surrounded by a series of coils, windings that selectively generate induction currents. The workpiece responds to the eddy currents on a molecular level by inducing great quantities of thermal energy. Logically, the process is finitely controllable. All that’s require is mastery of the electrically regulated coils.
Frequency-Regulated
The cycles-per-second generated by the power supply inversely affect hardening depth. That is, lower frequencies produce thick case hardened surface layers. Conversely, thinner hardened layers are spawned when higher frequencies are applied. An analysis of this process parameter indicates a need for a supremely uniform power supply. Otherwise, frequency inconsistencies could undermine the phase transformation process.
Inside The Process
The Joule heating mechanism (the coil) is a physical construct, but its operation is ruled by frequency responses, hysteresis losses, and power density considerations. When power is applied, the austenitizing temperature is reached and the surface of the workpiece transforms. The generated fields selectively target gear teeth and other complex geometrical outlines while larger magnetic currents envelop whole pieces. The contact-less process only concludes when the flux density enveloping the workpiece has transformed the material all the way down to a predetermined depth.
Analyzing Process Parameters
Uniform surface coverage is maintained by the power supply and the induced field. Frequency and voltage settings strengthen or weaken the field and dictate hardening depth. Naturally, the thickness of the component and its geometry will also impact the process, but these factors are typically accounted for by the heat treatment engineering team. There are undermining influences at work, though. For example, electromagnetic end effects will hamper part’s treatment. The end effect distorts the induction field pattern at the coil end regions. These and other field distorting effects require careful monitoring.
Fortunately, the electromagnetic fields are monitored in real-time, which is why the selected conditioning of gear teeth and the uniform treatment of large-scale workpieces both benefit from this potent heat treatment method. The only absolute necessity, a requirement that will assure predictable process parameters, is a non-fluctuating power supply, an induction source that’s designed to be implemented in induction hardening applications.
Workpiece hardening is a central part of any heat treatment facilities’ work output, so it’s only logical that several alternative techniques should develop in response to this need for mechanical toughness. Let’s compare two of these popular hardening techniques. Essentially, we’ll be noting the differences that exist between induction hardening and case hardening technology.
Processing Differences
Case hardening technology marries heat with chemistry to create a thermochemical process. Conversely, an induction hardened metal part uses pure electromagnetic energy to “induce” an alternating current within the part. The metal uses this contact-free energy gain to electromagnetically generate heat on the surface of the worked component.
Initial Production Comparisons
Logistically, a case hardened production run can process more parts simultaneously. Batch hardened work pieces pass quickly through the heat treatment facility due to this parallelism benefit. Conversely, the eddy currents generated within an induction processed setting mandate a piece-by-piece approach.
Realistic Production Differences
The gas diffusion batch processing method requires a number of sealed parts, including a closed furnace and a carburizing source. Gas parameters and thermal conditions need to be exactingly monitored if repeatable results are to be maintained. Conversely, the adjustment of the electromagnetic frequency ensures precise control of hardening depth, so repeatable results are much easier to achieve.
Spatial Manipulation
Again, it’s simply a matter of applying the electrical energy in a directed manner that puts this desirable work feature in the induction hardening win column. Localized alloy hardening is accomplished by optimizing a series of scalable magnetic fields. Unfortunately, a case hardened workpiece can only reproduce this methodology by using special pastes to influence the diffusion process. Not surprisingly, this less than scientific approach cannot be counted upon to create reproducible results.
Extolling Hardening Virtues
Geometrically complex parts do benefit from the finite control of an electrically controlled induction mechanism, its magnetic fields and frequency-controlled circuits, but case hardened parts leave the inner core of the workpiece entirely untouched. This means the alloy is still relatively flexible and soft, so it’s arguably more workable than the induction processed component.
On weighing the pros and cons of both heat hardening methods, the induction technique is the in-line but scalable winner. It works best on crankshafts and on gear teeth as a localized solution. Case hardening solutions, meanwhile, work best on larger, less geometrically detailed components, especially when they require the speed that comes with a batch processing production run.