O-1 Tool Blade Steel - Heat Treatment Recipe
Normalization:
Normalization is a process intended to refine grain and stress relieve blades prior to hardening when needed.
Turco, ATP-641, foil, or similar may be used to reduce surface decarburization and scaling.
Time at temperature suggested for varying thicknesses. Once knife has cooled to black and magnetic, it can be cycled again--be careful handling hot blades.
(1st cycle) 1,650°F / 898°C (10-15 min) |
(2nd cycle) 1,500°F / 815°C (10-15 min) |
(3rd cycle) 1,350°F / 732°C (10-15min) |
Hardening:
ATP-641, Turco, or similar high temperature anti-scale/decarburization coatings can be used to reduce scale or surface decarburization.
Data is representative of controlled heat treating equipment (e.g. oven, salts, etc.) temperatures and industrial standard quenchant.
Suggested quench oil: Parks AAA, Mcmaster 11-second, Houghton G--expected as quenched hardness may be lower if a slower quench oil or non-industrial quench medium is used.
-Parks 50 is not recommended.
*Austenizing soak time for O1 is a crucial factor and not recommended for forge heat treating without PID or similar calibrated equipment for holding austenizing temperature accurately.
**Do not put blades in oven when cold, insert at or just below austenizing temperature--temperature variances is for difference in stock thicknesses and a window of margin for error.
Austenizing temperature |
Hold/Soak Time |
Expected Rc (as quenched) |
1,465 to 1480°F / 801°C |
20-30 minutes |
64-65 |
Tempering:
Once blade is quenched and near ambient temperature, blades should be tempered accordingly, the times suggested are to ensure even, consistent temperature.
Figures supplied are as representative of industrial standards.
*If using a small toaster oven or household kitchen oven for tempering, using a blade holding rack made from kiln furniture, a roasting tray lined with fine sand, or similar large object will help retain thermal mass to reduce wide swinging temperatures as the device fluctuates trying to maintain temperature.
Note: Final hardness values vary based on initial as-quenched hardness and percentage of conversion to Martensite. Only reliable testing methods, e.g. calibrated Rockwell hardness tester, can provide actual hardness values--hardness calibrated files and chisels are relative testing methods and inaccurate for true hardness value reading.
Temper twice for 2hrs.
Temperature: |
Hardness (2 hour x2 guideline): |
300°F / 149°C |
65 |
350°F / 177°C |
63-64 |
400°F / 204°C |
60-61 |
450°F / 232°C |
57-58 |
500°F / 260°C |
55-56 |
550°F / 288°C |
53-54 |
600°F / 316°C |
52-53 |
650°F / 343°C |
50 |
***The included Heat Treat Schedule on this page is formulated based upon Industry standards and data from ASM International, Crucible and other foundry spec sheets, and Kevin Cashen (independent researcher, ferroalloy metallurgist, and bladesmith of Matherton Forge).
Suggested heat treatment is based on the recommended specifications for use in ovens, high temp salts, and similarly, properly calibrated equipment; and in line with proper industrial standards for quenching. Deviation from industry standards for schedules, equipment, quenching mediums; and hardness testing equipment may result in varied results. The supplied information on this page is on a generalized scale with the above mentioned standards and methods, which is why soak times and similar aspects may vary in time length to include a margin for the available heat treating equipment and steel cross section.
If you are unsure if you have the necessary means to heat treat on-site, we recommend professional heat treating services provided by Rob Ridley at HeatTreat.ca or 403 556 1113.
CKMS Ltd. is not liable or responsible if proper industry heat treating protocols are not applied; particularly and especially if sending to an independent heat treat provider if they do not follow the intended heat treat schedule or standards for that particular steel; or damage they cause while in their possession.