Two carbon-spring grades from EN 10132-4 — C67S at 0.65–0.73% C for formability, C75S at 0.72–0.80% C for maximum spring force. Supplied spheroidized for blanking or quenched and tempered to 45–55 HRC for finished springs, circlips and washers.
C67S and C75S are the workhorse grades of the carbon spring range — lean on alloy, consistent in heat treat, and cost-effective at volume. The 0.07% carbon gap between them is the difference between a part that forms easily and one that holds maximum spring force.
C67S (0.65–0.73% C) blanks and bends more readily before hardening — the default for complex-geometry springs and circlips. C75S (0.72–0.80% C) trades formability for higher peak hardness and spring force — the call for simple-shape high-load springs and washers.
C67S for complex geometry; C75S for maximum load.50CrV4 adds Cr and V for deeper hardening and higher fatigue life in heavier sections — the grade for automotive valve and suspension springs. C67S / C75S are the leaner choice for thin-strip flat springs, circlips and washers where alloy additions are unnecessary.
C67S/C75S for thin-gauge strip; 50CrV4 for heavy fatigue parts.SK5 (0.80–0.90% C) is optimized for edge retention in knives and blades. C67S / C75S are spring steels — they prioritize toughness and elastic limit over maximum hardness. For springs and washers, use the spring grade; for cutting edges, use the tool steel.
Spring steel for elastic parts; tool steel for cutting edges.Both grades share Si, Mn and residual limits. The only specification difference is the carbon range. Actual heat chemistry confirmed on MTC.
| Element | C67S (%) | C75S (%) | Notes |
|---|---|---|---|
| Carbon (C) | 0.65 – 0.73 | 0.72 – 0.80 | Primary hardening and spring-force element |
| Silicon (Si) | 0.15 – 0.35 | 0.15 – 0.35 | Deoxidizer; contributes to elastic limit |
| Manganese (Mn) | 0.60 – 0.90 | 0.60 – 0.90 | Hardenability |
| Phosphorus (P) | ≤ 0.025 | ≤ 0.025 | Residual; controlled for toughness |
| Sulfur (S) | ≤ 0.025 | ≤ 0.025 | Residual; controlled for shear-face quality |
Reference: EN 10132-4. Values typical per standard, actual confirmed on MTC. Compare with other spring grades in our spring steel standards comparison.
Supplied in two conditions: spheroidized for blanking and forming, or hardened-and-tempered for finished spring properties.
| Condition | Hardness (typ.) | Tensile (typ.) | Typical use |
|---|---|---|---|
| Spheroidized (soft annealed) | ≤ 220 HB | ~540 – 620 MPa | Fine blanking, cold forming — part quenched afterwards |
| H&T (C67S) | 42 – 50 HRC | ~1,150 – 1,400 MPa | Flat springs, circlips, wave washers |
| H&T (C75S) | 45 – 55 HRC | ~1,250 – 1,550 MPa | High-load springs, Belleville washers, clutch discs |
Indicative only. Hardness depends on section size, quench medium and tempering temperature. Thin strip (≤1.5 mm) achieves the upper end more readily. Typical per standard, actual confirmed on MTC.
Chemistry ranges overlap but are not identical. Confirm against your governing standard before substitution.
| Standard | C67S approx. | C75S approx. | Notes |
|---|---|---|---|
| EN 10132-4 | C67S (1.1231) | C75S (1.1248) | Base reference |
| ASTM / AISI | 1065 | 1075 | Plain carbon spring steel |
| JIS | S65C | S75C | Carbon machine structural steel |
| GB (China) | 65# / 65Mn | 75# | 65Mn adds Mn for thicker sections |
Equivalents are approximate. For safety-critical parts, confirm full chemistry against your governing spec and the MTC.
0.3–2.0 mm strip, blanked and formed in the spheroidized state, then Q&T to 45–52 HRC. Used in automotive seat mechanisms, appliance latches and electrical contact springs. Consistent carbon across the coil keeps the spring rate within a tight band.
0.5–1.5 mm C67S strip, fine-blanked to circlip geometry, then hardened and tempered. The spheroidized condition ensures clean shear faces and consistent blanking tool life — critical for the tight radial tolerances of retaining ring grooves.
0.2–1.0 mm C75S strip, stamped into wave or conical shapes, then Q&T to 48–55 HRC for maximum set resistance. C75S is preferred here because the higher carbon gives the elastic limit needed for washers that must not take a permanent set under repeated compression.
0.8–2.5 mm strip, blanked into clutch disc spring shapes, then Q&T. The combination of toughness and spring force makes these grades suitable for automotive and motorcycle clutch components under repeated cyclic loading. See our clutch disc spring guide.
Full cycle conditioning the carbide structure for clean fine blanking and cold forming — the difference between a clean shear face and a torn one. Read more in our spheroidizing guide.
Multi-pass rolling to your gauge tolerance, with controlled surface finish for blanking and forming. Thickness tolerances agreed per order and documented on the MTC.
Width tolerance and burr managed on our line — coils for progressive dies, sheets for blanking feeders. Narrow widths from 6 mm; burr direction confirmed at quoting.
For customers who want finished spring properties off the shelf, we supply H&T strip to a specified hardness band. Flatness managed through tension leveling after heat treat.
For C67S / C75S and EN 10132 spring steel: chemistry ranges, hardness bands for spheroidized vs hardened-and-tempered delivery, thickness and width tolerances, surface finish and decarburization limits — the specification framework for consistent spring and blanking performance.
Include thickness × width, quantity, condition (spheroidized or H&T) and destination port. Reply within one working day.