440c Precision Ground
Precision Ground 440C, high hardness and wear resistance, good resistance to corrosion. C: 1.05, SI: 0.40, Mn: 0.40, Cr: 17.00, Mo: 0.50
440C Precision Ground steel, machined steel, perhaps of all stainless steels, is more extended and used for both industrial and artisanal manufacture of knives.
Its main features:
- High wear resistance.
- Good edge retention.
- High resistance to corrosion.
- Up to 61 HRC.
Chemical composition (%): C: 1.05, Si: 0.40, Mn: 0.40, Cr: 17.00, Mo: 0.50
This steel is not recommended for beginners, its degree of difficulty of work is average.
Annealed (soft), is provided to facilitate the work, since tempered once is very difficult work.
- Forging: 900 to 1140ºC. Warm up to 950ºC for 15 to 25 minutes. Very slow cooling in furnace or insulation materials (sand, salt, mica).
- Normalizing: 750 to 850ºC. To eliminate the structural tensions caused by forging or grinding. Preferred time, 1 hour.
- Hardening (oil): 1010 to 1050ºC. Warmup at 900ºC, stabilized temperature, thermal jump to the hardening temperature, reached keep at least 2 minutes per millimeter. Cooling in oil to 180 - 200ºC to reduce thermal shock, keep cool for 15 to 30 minutes. Hardness 58 to 61 HRC.
- Tempering: slow heating up to the tempering temperature (see the temperature chart). Reached the temperature, keep 11 minutes per mm, the minimum recommended time is 1 hour.
Quenching and tempering is recommended in atmosphere conservative, see tempering foil. This is the recommended heat treatment, there are others. Temperatures, times or form of realization of it, you can vary depending on your needs or experience in such process.