A8
Download A8 Spec sheetWM A-8 is an air-hardening tool steel that is characterized by a combination of very good toughness, intermediate wear resistance, & excellent dimensional stability in heat treatment. WM A-8 is an excellent steel for punches and dies that operate in the 55-60 Rockwell C hardness range. The combination of toughness and wear resistance make WM A-8 an excellent choice for applications that require higher toughness than that of the high-carbon, high-chromium steels such as D2 & better wear resistance than that of shock-resisting steels such as S7.
For hot work tooling applications, WM A-8 provides better resistance to erosion, wear and wash-out than the typical chromium-molybdenum hot work steels such as H11 and H13. However, it is not recommended for hot applications where thermal fatigue (heat checking) is the primary failure mode.
CHEMICAL COMPOSITION
| Carbon | 0.55 |
| Manganese | 0.30 |
| Silicon | 0.95 |
| Chromium | 5.00 |
| Molybdenum | 1.25 |
| Tungsten | 1.25 |
TYPICAL APPLICATIONS
PHYSICAL PROPERTIES
Density – 0.281 lb/in3
Specific gravity – 7.78
Coefficient of Thermal Expansion
| 70 – 800°F | 6.65 x 10-6 in/in/°F |
| 70 – 1000°F | 6.88 |
| 70 – 1200°F | 7.06 |
PREHEATING
AUSTENITIZING (high heat)
Furnace or Salt: 1825-1850°F
Soak for 30 minutes for the first inch of thickness, plus 15 minutes for each additional inch.
QUENCHING
Note: Sizes over 5 inches in cross section may not achieve full hardness by cooling in still air. It is usually necessary to increase the quench cooling rate between 1400 to 900°F by using an air blast, pressurized gas, or an interrupted oil quench. For the oil quench, quench until black, about 900°F, then cool in still air to 150-125°F.
TEMPERING
Hold temperature for 1 hour per inch of thickness, 2 hours minimum, then air cool to ambient temperature. The typical tempering range is 300 to 600°F. Double tempering is recommended for tempering temperatures of 900°F and higher.
To minimize internal stresses in cross sections greater than 6 inches and to improve stability in tools that will be EDM’d after heat treatment, a soaking time of 4 to 6 hours at the tempering temperature is strongly recommended.
Cryogenic Treatment: Some prefer to do cryogenic treatment as an extension of the quench from the austenitizing treatment. Others prefer to cryogenically treat after tempering.
ANNEALING
Heat at a rate not exceeding 400°F per hour to 1550°F, and hold at temperature for 1 hour per inch of maximum thickness; 2 hours minimum. Then cool slowly with the furnace at a rate not exceeding 50°F per hour to 1000°F. Continue cooling to ambient temperature in the furnace or in air. The resultant hardness should be a maximum of 241 HBW.