Case depth in induction hardening is not decided by a single parameter. Material, frequency, power, heating time, coil structure, part geometry, scanning method, cooling conditions and the inspection standard all shape the final depth.
This article provides no fixed depth, frequency, power or time values, and no promises on hardness, structure or quality.
Material Sets the Hardenable Foundation
Different steels differ in carbon content, alloying, hardenability and initial structure, so they respond differently to the same heating and cooling. Identical process settings can yield different case depths on different materials.
Before discussing depth, confirm material grade, material state and heat-treatment objectives.
Frequency Shapes the Heat Source Distribution
Frequency influences how induced current distributes in the workpiece. For hardening, this determines whether heat concentrates at the surface or extends deeper.
Frequency cannot be judged apart from part size, material and target depth. Selection usually proceeds together with coil, power and scanning decisions.
Power and Time Govern Energy Input
Power sets heating intensity; heating time governs how deeply heat diffuses. Insufficient power or time means the target depth never reaches the required state; blindly raising either risks overheating, distortion or an oversized heat-affected zone.
Depth adjustment is therefore not "turn it up", but "match the temperature gradient to the target".
Coil and Part Geometry Change the Temperature Field
Coil shape, effective heating width, coupling gap, flux concentrators, scan direction and part geometry all affect the heated zone and temperature distribution.
Shoulders, holes, sharp corners, gear teeth and shaft steps can make local heating and cooling conditions complex. Depth problems often cannot be solved at the power supply alone.
Cooling Determines the Final Result
After suitable heating, cooling must support the intended transformation. Spray coverage, flow rate, quenchant condition and quench timing all affect the effective case.
With insufficient or uneven cooling, even near-target heating can end in a case depth that misses the requirement.
The Inspection Standard Defines How Depth Is Judged
"Case depth" must be measured by the method specified for the project - typically a hardness-gradient method, metallographic examination, or the customer-drawing convention.
Without a measurement standard, a claim that "the machine can reach X depth" has limited engineering meaning.
Summary
Case depth is determined jointly by material, frequency, power, time, coil, part geometry, cooling and the inspection standard. The right approach is not tweaking one parameter but building a verifiable process window around the target depth.