1.0503 - C45 - 12 050
Round bars:
+N – normalized
+U – untreated / not heat-treated
Flat bars:
+U – untreated / not heat-treated
Square bars:
+U – untreated / not heat-treated
Sheets and plates:
+N – normalized
+S – treated for cold shearing
+U – untreated / not heat-treated
⚙️ Basic steel designation
Material number (EN): 1.0503
EN designation: C45E / C45
DIN designation: Ck45
Standard: EN 10083-2
🔩 Properties
Good machinability in annealed condition.
More difficult weldability due to the higher carbon content; preheating and post-heating are required.
Suitable for heat treatment, hardening, tempering and surface case hardening.
Higher strength and wear resistance than soft structural steels, such as S235 and S355.
Mechanical properties, normalized condition:
Tensile strength Rm: approx. 600–800 MPa
Yield strength Re: approx. 355–500 MPa, depending on diameter and heat treatment
Hardness: approx. 170–210 HB, normalized condition
Hardness after hardening and tempering: up to 50 HRC, depending on treatment process
🧰 Applications
Shafts, pins, gears, spindles, connecting parts and machine components.
Piston rods, studs, bolts and tie rods.
Tools and parts exposed to dynamic stress.
⚗️ Chemical composition
C, carbon: 0.42–0.50 %
Si, silicon: max. 0.40 %
Mn, manganese: 0.50–0.80 %
P, phosphorus: max. 0.045 %
S, sulphur: max. 0.045 %
Cr, Ni, Mo: trace amounts only
🔥 Typical heat treatment
| Process | Temperature (°C) | Medium / Procedure | Purpose and result |
|---|---|---|---|
| Soft annealing | 650–700 | Slow cooling in furnace | Removal of internal stresses, hardness approx. 160–200 HB |
| Normalizing | 840–880 | Air cooling | Grain refinement, uniform mechanical properties |
| Hardening | 820–860 | Oil or water | Hardness after hardening approx. 50–55 HRC |
| Tempering | 540–680 | Air, 2–3 hours depending on thickness | Reduction of internal stresses, hardness approx. 160–220 HB |
| Nitriding, optional | 500–530 | – | Increased surface hardness, 900–1000 HV |
| Case hardening, optional | 880–930 | Followed by hardening and tempering | Hard surface, tough core |
⚙️ Additional notes
Steel C45 / 1.0503 is a medium-carbon structural steel, suitable for hardening and tempering.
After hardening and tempering, it achieves a good combination of hardness, strength and toughness.
Also suitable for induction surface hardening, with hardness up to approx. 54–56 HRC.
