C70S
1.1232High-carbon unalloyed steel for springs and cutting tools with 0.65–0.75% carbon. Good combination of hardness and toughness compared to higher-carbon grades. Used for coil springs, leaf springs, saw blades, chisels, and shear blades. Can achieve 50–56 HRC after proper heat treatment. The S suffix indicates suitability for spring applications per EN 10132-4.
Mechanical properties
Related materials
C45E
1.1191Unalloyed special steel with controlled chemistry (E grade) and 0.42–0.50% carbon. Tighter P and S limits than standard C45 for improved consistency. The most widely used medium-carbon steel for quenching and tempering. Good balance of strength (620–850 MPa QT) and toughness. Through-hardening up to ø60mm. Surface hardening by induction to HRC 58. Used for shafts, gears, bolts, connecting rods, crankshafts, and general machine parts.
C25E
1.1158Unalloyed special steel with controlled chemistry (E grade) and ~0.25% carbon. Tighter P and S limits (max 0.025%) than standard C25 for improved consistency. Suitable for quenching and tempering to moderate strength levels. Good machinability and weldability. Used for shafts, bolts, transmission parts, crankshafts, and machine components of moderate stress.
C30
1.0528Medium-carbon unalloyed steel with approximately 0.30% carbon. Intermediate strength between C25 and C35. Good machinability and moderate weldability (preheating recommended for thicker sections). Used for moderately stressed structural parts, shafts, bolts, levers, and connecting rods in general mechanical engineering.
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