TS · tool steel
Tool Steel P20 (mould steel, pre-hardened)
Supplied pre-hardened at 28–32 HRC, so it machines like a tough alloy steel rather than a tool steel. This is the plastic mould steel, and the machining is the whole job - no post-hardening.
Quoting this material
- Typical lead time
- 10–18 working days
- Condition
- Pre-hardened and tempered
- Achievable finish
- Ra 0.4 µm typical · Ra 0.05 µm (mirror polished) 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.
Supplied pre-hardened at 28–32 HRC, so it machines like a tough alloy steel rather than a tool steel. This is the plastic mould steel, and the machining is the whole job - no post-hardening.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Hardness (as supplied) | 28–32 | HRC |
| Tensile strength | 1,000 | MPa |
| Wear resistance | Moderate (nitridable) | - |
| Polishability | Excellent | - |
| Thermal conductivity | 34 | 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
Pre-hardened and tempered
Heat treatment
Usually none after machining, which is the point of it - the mould is machined in the delivered condition and put into service. Nitriding is the common surface treatment when more wear resistance is needed on a specific face.
Achievable surface finish
Ra 0.4 µm
Ra 0.05 µm (mirror polished)
Polishes very well, which is the other reason it dominates injection moulds: the cavity finish becomes the part finish.
Tooling and cutting parameters
Cutting speed
- 120–200 m/min (carbide, coated)
Feed
- 0.10–0.30 mm/rev turning · 0.08–0.20 mm/tooth milling
Tooling
- Coated carbide with a strong edge; ball-nose for cavity finishing
Coolant
- Flood, and air blast on the finishing passes to clear the chip from the cavity
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
- Injection moulds and cavities
- Blow moulds
- Die holders and mould bases
- Machined fixture plates
- Vacuum forming tooling
DFM notes for this grade
- No hardening after machining means the geometry has to be right the first time - there is no grind allowance to hide in
- Nitriding adds a hard 0.1–0.3 mm case on a specific face where wear occurs, without the distortion of a full harden
- Machining a deep cavity with a long reach cutter is the constraint: tool deflection in a 250 mm deep pocket is what decides whether the gauge dimension is achievable
Questions buyers ask
- Why not harden P20 after machining like other tool steels?
- Because you do not need to. The point of P20 is that 30 HRC is enough for a plastic mould and the whole cavity can be machined to final form without the distortion and the grinding that a 52 HRC hardening would bring. For an abrasive filled plastic, the answer is nitriding, not full hardness.
- How much does the cavity finish cost in machining time?
- More than people expect: the finishing passes are at small stepovers with a ball-nose cutter, and going from Ra 0.4 to a mirror polish can double the cavity machining time. Decide the required finish from the part requirement, not by default.