title = "Induction Hardening: Process and Equipment"

content = """
Induction hardening uses electromagnetic induction to heat only the surface layer of a steel component rapidly to the austenitizing temperature, followed by a quench, hardening the surface while leaving the core unaffected. At Ridgecrest Metalworks, induction hardening is used for shafts, journals, gear teeth, splines, and flat surfaces where a selective hard surface with minimum distortion is required.

The induction hardening machine consists of an AC power supply (operating at frequencies from 1 kHz to 400 kHz), a work coil (inductor) shaped to deliver concentrated electromagnetic energy to the specific area to be hardened, and a quench system. The alternating magnetic field from the coil induces eddy currents in the conductive workpiece; these currents generate heat by resistance (the Joule effect). The depth to which heating penetrates (reference depth) is inversely proportional to the square root of the frequency: high frequency (100–500 kHz) heats a very thin surface layer (0.010–0.040 inch)—suitable for gears and fine-pitch features; medium frequency (3–30 kHz) heats deeper (0.050–0.150 inch) for large shafts, crankshafts, and cam lobes; low frequency (1–3 kHz) for deep hardening of large sections.

Induction hardening methods include: scan hardening (the part passes axially through a coil while the coil heats a narrow band; the band is quenched by a spray ring behind the coil—used for shafts and long surfaces); single-shot hardening (the entire surface to be hardened is surrounded by a custom-shaped coil and heated in one shot—used for gear teeth, ends of parts); and progressive hardening (similar to scan but for complex profiles).

Coil design is the most critical engineering element. The coil shape must concentrate flux precisely over the target area, maintaining a consistent small gap between the coil and the part surface (typically 0.060–0.120 inch). Coils are custom-machined from copper tubing and water-cooled. They have a limited life due to scale buildup, electrical erosion, and mechanical damage.

Power, time, and quench delay are the key process parameters. They are set by qualified process engineers through initial coupon testing, then held constant in production. After hardening, the part is tempered at 300–400°F to relieve quench stresses. Hardness and case depth are checked by Rockwell hardness at the surface and on metallographic cross-sections.
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version = "0.0.1"
