TS · tool steel
Tool Steel L6 (oil hardening, tough)
A tough oil-hardening tool steel sitting between O1 and S7: decent wear resistance with more shock tolerance than either D2 or O1.
Quoting this material
- Typical lead time
- 12–20 working days
- Condition
- Annealed; hardened in oil and tempered
- Achievable finish
- Ra 0.8 µm after grinding typical · Ra 0.4 µm best
Machined in-house to your drawing: see the precision CNC machining service and the machine and inspection capability it runs on.
Machinability
Our own 1–10 shop ranking, not a published index: 10 is free-cutting brass C360, 1 is Inconel 718. It ranks how a material behaves on the floor - cycle time, chip control and tool life together. Where a published index exists it is quoted in the note.
A tough oil-hardening tool steel sitting between O1 and S7: decent wear resistance with more shock tolerance than either D2 or O1.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Hardness (working) | 55–58 | HRC |
| Toughness | High | - |
| Wear resistance | Moderate | - |
| Distortion in hardening | Moderate (oil quench) | - |
| Thermal conductivity | 38 | W/m·K |
| Modulus of elasticity | 205 | GPa |
Hardness, tensile and thermal figures are typical published values for the condition stated. Actual mill certificates govern; send the specification with the drawing and we confirm against the certificate before the material is cut.
Condition
Annealed; hardened in oil and tempered
Heat treatment
Austenitise around 830–870 °C, oil quench, temper at 200–540 °C depending on the toughness required. The nickel addition gives it more shock resistance than O1 at similar hardness.
Achievable surface finish
Ra 0.8 µm after grinding
Ra 0.4 µm
Grinds like the other low-alloy tool steels; not normally polished for appearance.
Tooling and cutting parameters
Cutting speed
- 100–180 m/min annealed (carbide) · 45–70 m/min at 57 HRC
Feed
- 0.10–0.25 mm/rev turning · 0.06–0.15 mm/tooth milling
Tooling
- Coated carbide annealed; CBN hardened
Coolant
- Flood
Starting points for carbide on a rigid setup, not a guarantee. The right numbers depend on the machine, the toolholder and the fixturing - ask and we will say what we would actually run.
Typical applications
- Punches and impact tooling
- Machine-tool wear parts
- Shear blades for mixed stock
- Tough forming dies
- Gear and coupling tooling
DFM notes for this grade
- It is the compromise grade: where a part needs both decent wear resistance and impact tolerance and neither extreme matters
- Oil-quench distortion is real, so a complex part should either move to A2 or allow for the grind
- Not usually worth specifying where a standard A2 or S7 will do - the cost advantage is small and the availability is worse
Questions buyers ask
- When would a design specify L6?
- When a punch or a shear blade has to tolerate both abrasive stock and impact, and neither D2 (too brittle) nor S7 (too soft for the wear) works. It is a niche grade and the honest answer is often that the design has not decided which failure mode matters.
- Is L6 available as bar stock?
- Less readily than A2, D2 or O1, and often only in a restricted size range. Availability affects lead time more than machining does, so it is worth confirming before a design settles on it.