High-Frequency vs Medium-Frequency Induction Hardening Systems
Compare frequency systems and their influence on case depth, heating rate, and metallurgical structure.
Introduction: Frequency — The Backbone of Induction Hardening
Every induction hardening process relies on one crucial factor: frequency. Whether you are hardening a gear tooth, a shaft, or a large industrial roller, the frequency of the induction system determines how deep and how fast the heat penetrates the metal surface.
At Thakur Induction, we use both high-frequency (HF) and medium-frequency (MF) induction systems to meet a wide range of industrial hardening requirements — from fine gear teeth to heavy shafts and axles.
Understanding Induction Frequency in Simple Terms
Frequency refers to how fast the current alternates in the induction coil. This alternating current produces a magnetic field that induces eddy currents in the metal surface, generating heat. The depth to which these currents penetrate — known as penetration depth or skin effect — depends on the frequency.
| Type of Frequency | Range (kHz) | Typical Penetration Depth | Application |
|---|---|---|---|
| High Frequency (HF) | 100–500 kHz | 0.5 – 1.5 mm | Gears, small parts, thin components |
| Medium Frequency (MF) | 3–30 kHz | 2 – 6 mm | Shafts, axles, spindles, heavy parts |
Higher frequency = shallower heat penetration; lower frequency = deeper heat penetration.
High-Frequency Induction Systems: Precision for Surface Hardening
High-frequency induction systems are best suited for components requiring thin, hard surface layers and minimal distortion.
Applications:
- Gear teeth
- Cam lobes
- Small shafts or pins
- Bearing races
- Tool edges
Advantages:
- Precise, localized heating
- Excellent surface finish
- Short heating cycles (milliseconds)
- Ideal for small components with complex geometry
Medium-Frequency Induction Systems: Power for Deeper Hardening
Medium-frequency systems are the industry standard for shaft, axle, and gear hardening where deeper case depth and uniform hardness are required.
Applications:
- Transmission shafts
- Automotive axles
- Spindles and rollers
- Forged components
Advantages:
- Deeper heat penetration (up to 6 mm)
- Uniform hardness distribution
- Suitable for large and heavy parts
- Lower distortion risk
Key Differences Between High and Medium Frequency Induction Systems
| Parameter | High-Frequency System | Medium-Frequency System |
|---|---|---|
| Frequency Range | 100–500 kHz | 3–30 kHz |
| Heat Penetration Depth | 0.5–1.5 mm | 2–6 mm |
| Best For | Small gears, pins, tools | Shafts, axles, forged parts |
| Heating Speed | Very fast | Moderate |
| Surface Finish | Excellent | Good |
| Energy Efficiency | High for thin parts | High for thick parts |
| Distortion Risk | Very low | Low |
High frequency gives control and accuracy; medium frequency offers depth and strength.
Choosing the Right System for Your Component
| Component Type | Recommended Frequency | Reason |
|---|---|---|
| Small gears, sprockets | High Frequency | Shallow hardening, no distortion |
| Automotive shafts, axles | Medium Frequency | Deeper hardening for wear zones |
| Camshafts, crankshafts | Medium Frequency | Strong case with ductile core |
| Tool edges, punches | High Frequency | Quick surface hardening |
| Forged spindles | Medium Frequency | Controlled case depth and strength |
Conclusion: The Right Frequency for the Right Part
Both high-frequency and medium-frequency induction systems have distinct advantages — the key is selecting the right one for your component geometry and load conditions. At Thakur Induction, Punjab, we bring decades of expertise in frequency selection, case depth control, and metallurgical optimization, ensuring consistent hardness, minimum distortion, and maximum component life.
Looking for Custom Frequency Hardening Solutions?
Contact Thakur Induction — specialists in high-frequency and medium-frequency heat treatment for industrial and automotive components.