A9
OtherA9
Air-hardening cold-work tool steel. (ASTM A681; equiv ASTM A681 / DIN 1.2363 / JIS SKD12). Nominal values—confirm mill certificate.
Chemical Composition (%)
| C | 0.45 |
|---|---|
| CR | 4.75 |
| MO | 1.3 |
| NI | 1.25 |
| V | 0.8 |
| MN | 0.3 |
| P | 0.03 |
| S | 0.03 |
Mechanical Properties
Hardness(annealed):≤248 HB;Hardness(hardened):55-60 HRC
Chinese Standard
ASTM A681 A9
Equivalent Standards
ASTM A681
Equivalent Grades
DIN 1.2363 / JIS SKD12
Applications
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Available Forms
Block"
Uses
Low-alloy engineering steel with enhanced hardenability and strength from alloying elements. Chromium (≈5.125%) improves hardenability, wear and corrosion resistance. Molybdenum (≈1.55%) raises high-temperature strength and prevents temper embrittlement. Nickel (≈1.5%) increases toughness and impact strength at low temperature. Vanadium (≈0.95%) refines grain and strengthens the tempered structure. Applied to gears, shafts, bolts, connecting rods, pressure parts and heavy forgings in automotive, energy and machinery sectors.
Heat Treatment
Austenitize at 820–870 °C (oil or water quench depending on section) and temper at 400–650 °C to the required strength/toughness balance.
Precautions
Preheat and control interpass temperature when welding; post-weld heat treatment or stress relief is recommended to avoid hard-zone cracking. Use low-hydrogen electrodes. Protect from decarburization during heating (controlled atmosphere or protective coating).
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