The classic oil-hardening cold-work grade. Easy to machine, easy to heat-treat, stable in service — a go-to for short-run dies, jigs, gauges, and master tooling where extreme wear life isn't the priority.
AISI O1 · UNS T31501 · Lindquist code TBO197
| C | Mn | Cr | W | V |
|---|---|---|---|---|
| 0.90 | 1.20 | 0.50 | 0.50 | 0.20 |
| Machinability | 90 (vs 1% C steel = 100) — approaches W-grade |
|---|---|
| Dimensional stability | +0.0015 in/in plus, partially offset by scaling |
| Critical points (heating) | Ac 1390–1450°F |
| Critical points (cooling) | Ar 1280–1260°F |
| Forging | 1850–1950°F, stop at 1500°F, cool slowly |
|---|---|
| Normalizing | Do not normalize |
| Annealing | 1450°F, furnace-cool · BHN 202 max |
| Preheat | 1200°F (large parts) |
| Hardening | 1475°F, oil-quench to 150°F |
| Tempering | 300–450°F → HRC 61/63 |
| Temper °F | Rockwell C |
|---|---|
| None | 65 |
| 300 | 63 |
| 350 | 62.5 |
| 400 | 62 |
| 450 | 61 |
| 500 | 60 |
| 700 | 53 |
| 800 | 50 |
| 900 | 47 |
| 1000 | 44 |
| 1100 | 39 |
| 1200 | 31 |
→ Based on 1″ rounds, oil-quenched from 1475°F, 2-hr temper. Hold tempering temp ≥1 hr (small) to ≥2 hr/in (large). Second temper 25°F lower than first.
For best machinability anneal: heat slowly to 1450°F, furnace-cool at 20°F/hr to 900°F, then air. Yields BHN 202 max.
A general-purpose, air-hardening, medium-alloy cold-work tool steel with excellent dimensional stability, good wear resistance, and the ease of heat treatment that has made it the workhorse of the cold-work category.
The industry-standard high-carbon, high-chromium, air-hardening cold-work die steel.
The shock-resisting tool steel.
We stock O1 in plate, block, round, groundstock, drill rod. Tell us the size and quantity — we'll come back with a price and a date.
Datasheet content reproduced from Lindquist technical bulletin Lindquist code TBO197. Heat-treatment recommendations are typical — confirm specifics with your metallurgist for production work.