Technical Overview
Hardening and tempering (often referred to as quench-and-temper) is a two-stage thermal process designed to optimize the mechanical properties of medium-carbon and alloy steels, providing high yield strength along with structural ductility.
Metallurgical Principles
Hardening involves heating above critical limits to create austenite, followed by rapid oil quenching to produce hard martensite. Martensite is extremely hard but brittle. Tempering reheats the martensitic structure below transformation limits, allowing carbon precipitates to redistribute. This reduces brittleness while retaining high tensile strength.
Typical Thermal Cycle Parameters
Hardening at 820-860?C, oil quenched. Tempered immediately at 200-650?C depending on target tensile strength and hardness specifications.
Key Component Applications
Commonly specified for: High tensile fasteners, connecting rods, driveshafts, structural brackets, springs, and gears.
Process Specifications Table
| Parameter / Metric | Operational Specification Value |
|---|---|
| Hardening Temp | 800?C to 880?C |
| Quench Medium | Accelerated quenching oil (temperature regulated at 60-80?C) |
| Tempering Range | 180?C to 650?C based on tensile requirements |
| Materials | Medium carbon & alloy steels (EN19, EN24, EN9, 4140, 4340) |