CS · carbon steel
Structural Steel A36 (S235JR equivalent)
Structural plate and section steel. Machines fine at moderate feeds, but it is bought for welding and load capacity per unit cost, not for a machined finish or a tight tolerance.
Quoting this material
- Typical lead time
- 5–10 working days
- Condition
- As-rolled
- Achievable finish
- Ra 3.2 µm typical · Ra 1.6 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.
Structural plate and section steel. Machines fine at moderate feeds, but it is bought for welding and load capacity per unit cost, not for a machined finish or a tight tolerance.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength | 400–550 | MPa |
| Yield strength | 250 | MPa |
| Elongation | 20 | % |
| Hardness | 140 | HB |
| Thermal conductivity | 51.9 | W/m·K |
| Modulus of elasticity | 200 | 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
As-rolled
Heat treatment
Not heat treatable in any useful sense; it is a structural grade.
Achievable surface finish
Ra 3.2 µm
Ra 1.6 µm
Usually left as-machined on functional faces and painted or galvanised elsewhere.
Tooling and cutting parameters
Cutting speed
- 150–300 m/min (carbide)
Feed
- 0.15–0.35 mm/rev turning · 0.10–0.25 mm/tooth milling
Tooling
- Coated carbide
Coolant
- Mist or 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
- Machine base plates and weldments
- Frames and structural brackets
- Guard and safety structures
- Pallets and transport frames
- Foundation and mounting hardware
DFM notes for this grade
- Mill scale is abrasive and hard - take it off with a roughing pass rather than trying to finish through it
- Finished faces are for location, not for appearance: A36 is not a cosmetic steel
- Where the part also needs a machined wear surface, consider welding a 4140 or a plate of better material into the assembly rather than machining A36 to a tolerance it will not hold
Questions buyers ask
- Can A36 be machined to a tight tolerance?
- On a machined face, yes - the material machines acceptably. The issue is stability: A36 plates are rolled, not stress relieved, and a large plate with a lot of metal removed will move. If the tolerance matters, specify a stress-relieved or pre-machined plate.
- When should a base plate be A36 rather than a cast iron?
- When it is welded into a larger structure or the quantity does not justify a pattern. Cast iron gives better damping and a more stable machined surface; A36 is the choice for one-offs, weldments and anything that has to meet a structural code.