CS · carbon steel
Carbon Steel 1045 (C45)
Medium carbon: the first grade on this list that actually hardens. Published index around 57% against B1112 = 100% - noticeably tougher to cut than 1018, and it will not take a deep cut as readily.
Quoting this material
- Typical lead time
- 7–12 working days
- Condition
- As-rolled, normalised, or quenched and tempered (commonly 28–32 HRC)
- Achievable finish
- Ra 1.6 µm 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.
Medium carbon: the first grade on this list that actually hardens. Published index around 57% against B1112 = 100% - noticeably tougher to cut than 1018, and it will not take a deep cut as readily.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength | 565 | MPa |
| Yield strength | 310 | MPa |
| Elongation | 16 | % |
| Hardness (as-rolled) | 179 | HB |
| Thermal conductivity | 49.8 | 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
As-rolled, normalised, or quenched and tempered (commonly 28–32 HRC)
Heat treatment
Through-hardens properly: austenitise around 820–860 °C, quench in water or oil, temper to suit. A water quench gives more hardness but a higher cracking risk on a complex part - 4140 is the safer choice when the geometry is complicated.
Achievable surface finish
Ra 1.6 µm
Ra 0.4 µm
Machines to a good finish in the annealed state. Where it is supplied pre-hardened, plan on grinding or hard turning the critical features.
Tooling and cutting parameters
Cutting speed
- 120–250 m/min (carbide, annealed)
Feed
- 0.15–0.30 mm/rev turning · 0.08–0.20 mm/tooth milling
Tooling
- Coated carbide; a tough substrate is worth it on interrupted cuts
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
- Drive shafts and axles
- Gears and sprockets (heat treated)
- Studs, pins and keys
- Machine tool components
- Hydraulic rod stock
DFM notes for this grade
- Harden before finishing, not after: a 1045 part quenched to 50 HRC distorts and needs the final grind allowed for on the drawing
- Not the alloy for a complex thin section - a water-quenched 1045 part cracks where the section changes; 4140 with an oil quench is the more forgiving choice
- Free-machining additives are not present, so chip control on a deep bore is a real planning item rather than an assumption
Questions buyers ask
- 1045 or 4140 for a shaft?
- 4140 for almost anything that carries a bending load or has a stress concentration. It hardens deeper at the same carbon level because of the chromium and molybdenum, so a 4140 shaft is through-hardened at the core where a 1045 shaft may only be hard at the surface.
- Can 1045 be welded?
- It can be welded, but it is not a weldable steel in the ordinary sense - the heat-affected zone hardens and can crack without preheat and post-weld heat treatment. If the design has a weld, either specify a low-carbon steel or design the weld as a separate low-carbon component.