Designation
DIN: | 40 CrMnMo 7 |
AFNOR: | 40 CMD 8
|
UNI: | 35 CrMo 8 KU |
AISI: | P20
|
Chemical composition:
C | 0.40
|
Si | 0.40 |
Mn | 1.50 |
Cr | 1.90 |
Mo | 0.20 |
Strength:
280 - 325 HB
(≈ 950 - 1100 N/mm²)
Thermal conductivity at 100 °C:
35 W/m K
Character:
alloyed and pre-toughened tool steel, especially suitable for polishing and nitriding; high dimensional stability
Application:
cavity plates, inserts and high-tensile machine parts
Treatment by
possible:
Etching, EDM
Polishing:
excellent polishing; for higher surface requirements we recommend steel for through hardening
Nitriding:
increases the steel's wear resistance
Hard chroming:
particularly increases the steel's wear resistance and corrosion resistance
Heat treatment:
already pre-toughened; usually no heat treatment required
Nitriding:
Before nitriding, stress-relief annealing is recommended at 580 °C. (Meusburger standard)
Hard chroming:
After the hard chroming the mold must be annealed about 3 to 4 hours at 180 °C to avoid brittle fractures from hydrogen.
Hardening:
840 to 860 °C
Cooling:
to 180 °C/220 °C in oil/hot bath, then in air to about 100 °C obtainable hardness: 52 HRC
Tempering:
Slow heating to tempering temperature immediately after hardening. Minimum time in furnace: 1 hour per 25 mm part thickness
Annealing graph:
Technical tip:
- Core strength decreases with increasing plate thickness ⇒ for thickness >300, 1.2738 is recommended.
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