Induction Hardening for EN24 & 4340 Alloy Steels
In Punjab’s industrial manufacturing hubs — especially Ludhiana — high-strength steels like EN24 and 4340 are widely used for shafts, gears, axles, spindles, and transmission components.
These steels are known for their excellent toughness, fatigue resistance, and strength, but to perform optimally under load, they need surface hardening that enhances wear resistance while keeping the core ductile. That’s where induction hardening comes in — a fast, localized, and controllable process that strengthens the outer layer of EN24 and 4340 components without affecting their internal structure.
At Thakur Induction, Ludhiana, we specialize in precision-controlled induction hardening services for these alloy steels, using medium-frequency induction systems to achieve deep, uniform case hardening for heavy-duty parts.
Understanding EN24 and 4340 Alloy Steels
EN24 (AISI 4340 Equivalent)
EN24 is a nickel-chromium-molybdenum alloy steel offering a perfect combination of tensile strength, toughness, and wear resistance. It’s typically used in:
- Transmission shafts
- Gears and spindles
- Connecting rods and crankshafts
- Heavy-duty axles
4340 Steel (AISI 4340 / SAE 4340)
4340 is chemically similar to EN24 but has slightly higher nickel and molybdenum content, giving it better hardenability and impact resistance. It’s ideal for:
- Aerospace components
- Tractor and automotive drive shafts
- Powertrain and industrial machinery parts
Both materials respond exceptionally well to induction heat treatment, producing a hard, wear-resistant surface (up to 58–62 HRC) with a tough inner core.
How Induction Hardening Works for EN24 & 4340 Steels
Induction hardening uses electromagnetic heating to raise the steel’s surface temperature to around 850–900°C, followed by rapid polymer or water quenching to form martensite, the hardest phase of steel. Here’s a step-by-step process used at Thakur Induction:
- Surface Cleaning: Components are cleaned to remove oil, dirt, or oxide layers to ensure uniform heating.
- Induction Heating: An induction coil generates an alternating magnetic field that heats the surface rapidly and uniformly.
- Austenitizing: The heated layer reaches the austenitizing range (850–900°C) — transforming ferrite and pearlite to austenite.
- Quenching: The part is then quenched immediately using a polymer or water-based quenching system, converting austenite to martensite.
- Tempering (Optional): Tempering may follow to relieve internal stresses while maintaining required hardness and toughness.
Typical Hardness and Case Depth Achieved
| Material | Surface Hardness (HRC) | Case Depth (mm) | Quenching Medium |
|---|---|---|---|
| EN24 | 56–60 | 2.5–4.0 | Polymer (10–12%) |
| 4340 | 57–62 | 3.0–5.0 | Polymer or water |
| EN19 (Reference) | 54–58 | 2.0–3.5 | Polymer |
Thakur Induction ensures precise temperature and time control for each material batch, guaranteeing uniform hardness and case depth.
Benefits of Induction Hardening for EN24 & 4340 Steels
Superior Surface Hardness
Achieves a high-hardness martensitic layer (up to 62 HRC), making parts resistant to abrasion, impact, and fatigue.
Maintains Core Strength
Only the surface is hardened — the core retains its ductility and toughness, essential for absorbing shock loads.
High Fatigue and Wear Resistance
Ideal for rotating and load-bearing components, induction hardening improves component lifespan by 2–3 times.
Dimensional Accuracy and Low Distortion
Localized heating ensures minimal warping compared to furnace hardening or flame hardening.
Energy and Cost Efficiency
Induction hardening is faster, cleaner, and more efficient, with up to 40% lower energy use than traditional methods.
Conclusion: Hardness Meets Reliability
EN24 and 4340 induction hardening provide the perfect combination of surface strength and core toughness, making them indispensable for automotive, aerospace, and industrial applications. With Thakur Induction’s advanced medium-frequency systems, manufacturers across Punjab can ensure deep, uniform hardening, controlled case depth, and superior fatigue and wear resistance.
Contact Thakur Induction for EN24 & 4340 Hardening Services
Contact Thakur Induction, Ludhiana for EN24 and 4340 alloy steel heat treatment job work. Specializing in precision induction hardening, polymer quenching, and metallurgical quality testing for all industrial components.