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.