Technical Overview
Annealing encompasses heating metal to a specific high temperature, soaking, and slow cooling. It is designed to soften the material structure, reduce internal residual stress, refine crystal grains, and enhance cold-forming machinability.
Metallurgical Principles
Spheroidizing is a specialized sub-type of annealing for high-carbon steels. It aggregates carbide particles into tiny spherical shapes (spheroids) dispersed in a ferritic matrix, achieving the lowest possible hardness and highest ductility. Ferritizing converts cast iron structures into a soft ferritic configuration.
Typical Thermal Cycle Parameters
Heated above the upper critical temperature (760-860?C depending on alloy composition), soaked to uniformize phase, then slow-cooled inside the closed furnace at a rate of 10-20?C per hour.
Key Component Applications
Commonly specified for: Forged blanks, steel wire coils, structural castings, die tool blocks prior to machining.
Process Specifications Table
| Parameter / Metric | Operational Specification Value |
|---|---|
| Process Temperature | 720?C to 880?C depending on steel carbon weight |
| Cooling Mode | Closed furnace slow cooling (controlled descent rate) |
| Target Hardness | Reduced to 160-220 BHN (excellent machinability state) |
| Compatible Materials | Medium carbon, high carbon steels, tool steels (D2, H13, EN24, cast irons) |