EN 10132-4 Grade C125S: Premium Cold-Rolled Steel for Springs & Precision Applications

The steel C125S is used as cold rolled strip for springs and special applications in thicknesses of up to 6 mm and as tempered cold strip in thicknesses from 0.30 to 3.00 mm. The springs made of steel C125S are suitable for highly stressed tension springs, especially in the watch industry, as well as for pen nibs.

Properties

General

Property	Temperature	Value	Comment
Density	23.0 °C	7.8 - 7.9 g/cm³	Typical for Low Carbon Steel

Mechanical

Property	Temperature	Value	Comment
Elastic modulus	23.0 °C	200 - 215 GPa	Typical for Low Carbon Steel
Hardness, Vickers	20.0 °C	325 [-]
Poisson's ratio	23.0 °C	0.29 [-]	Typical for Low Carbon Steel
Shear modulus	23.0 °C	82 GPa	Typical for Low Carbon Steel
Tensile strength	20.0 °C	1200 MPa

Thermal

Property	Temperature	Value	Comment
Coefficient of thermal expansion	23.0 °C	1.32E-5 - 1.38E-5 1/K	Typical for Low Carbon Steel
Max service temperature		500 °C	Typical for Carbon Steel
Melting point		1480 - 1526 °C	Typical for Low Carbon Steel
Specific heat capacity	23.0 °C	465 J/(kg·K)	Typical for Low Carbon Steel
Thermal conductivity	23.0 °C	25 - 93 W/(m·K)	Typical for Low Carbon Steel

Electrical

Property	Temperature	Value	Comment
Electrical resistivity	23.0 °C	1.43E-7 - 1.74E-7 Ω·m	Typical for Carbon Steel

Magnetic

Property	Value	Comment
Curie temperature	770 °C	Typical for Low Carbon Steel

Chemical properties

Property	Value
Carbon	1.2 - 1.3 %
Chromium	0.4 %
Manganese	0.3 - 0.6 %
Molybdenum	0.1 %
Nickel	0.4 %
Phosphorus	0.03 %
Silicon	0.15 - 0.35 %
Sulfur	0.025 %

DIN 2391-2 St 30 Si Soft‑Annealed Tube – Grade A for Precision Construction EN 10132-4 Grade C125S Quenched Steel – Precision Spring & Strip Material

Metal