TS · tool steel
Tool Steel A2 (air hardening)
The safe general-purpose tool steel. In the annealed state it machines like a tough alloy steel; after hardening to 60 HRC it is a grind or an EDM job.
Quoting this material
- Typical lead time
- 10–18 working days
- Condition
- Annealed for machining; hardened and tempered for service
- Achievable finish
- Ra 0.8 µm after grinding typical · Ra 0.2 µm (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.
The safe general-purpose tool steel. In the annealed state it machines like a tough alloy steel; after hardening to 60 HRC it is a grind or an EDM job.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Hardness (working) | 58–60 | HRC |
| Wear resistance | High | - |
| Toughness | Good | - |
| Distortion in hardening | Low | - |
| Thermal conductivity | 26 | W/m·K |
| Modulus of elasticity | 210 | 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 for machining; hardened and tempered for service
Heat treatment
Air hardening: austenitise around 940–980 °C, cool in still air or a vacuum furnace, temper twice at 150–400 °C depending on the hardness/toughness balance. Air hardening is why A2 is chosen for complex shapes - it moves far less than an oil- or water-quenched steel, so a thin section keeps its dimension.
Achievable surface finish
Ra 0.8 µm after grinding
Ra 0.2 µm (polished)
Ground after hardening. For a mould or die surface, a fine polish follows the grind and the sequence has to be allowed for in the geometry.
Tooling and cutting parameters
Cutting speed
- 100–180 m/min annealed (carbide) · 40–60 m/min at 60 HRC (CBN)
Feed
- 0.10–0.25 mm/rev turning · 0.05–0.15 mm/tooth milling
Tooling
- Coated carbide annealed; CBN or ceramic for the hardened state; EDM for fine detail
Coolant
- Flood; a hardened cut without coolant will draw the temper at the edge
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
- Blanking and forming dies
- Punches and pierce tooling
- Fixture and gauge wear parts
- Plastic mould inserts
- Cutting blades and shear knives
DFM notes for this grade
- Leave 0.3–0.5 mm of stock on any ground face - heat treatment moves the part slightly even in an air-hardening grade, and the grind is what brings it back to size
- Sharp internal corners are a quench-cracking risk: radius them in the pre-hardened geometry, not in the finished part
- EDM the fine detail rather than milling it after hardening - a recast layer is a known problem, and the finishing passes after EDM matter as much as the EDM itself
Questions buyers ask
- A2 or D2 for a forming tool?
- A2 unless the wear mechanism is abrasive. A2 distorts less in the quench, so a complex pocketed die keeps its dimension; D2 holds an edge longer against abrasive material but moves more and is harder to grind. For most forming and blanking work A2 is the better default.
- Can hardened A2 be machined at all?
- Yes, with the right process: CBN or ceramic turning for round features, and EDM for pockets and sharp detail. What you cannot do is mill it with ordinary carbide and expect a good result - that is where hardened parts get scrapped.
Grades we would quote instead
D2
4/10Annealed it machines reasonably but it is abrasive on the tool because of the chromium carbides.
O1
5/10A classic oil-hardening tool steel: machines well in the annealed state, hardens to 60–64 HRC, and needs a careful quench because it moves more than an air-hardening grade.
S7
5/10The toughness grade.