1. What Is This Product?
High-Strength Carbon Steel Strip is a narrow, precision-rolled carbon steel product with carbon content typically ranging from 0.42% to 1.05%. It is produced by cold rolling, slitting, annealing, and—when required—quenching and tempering to achieve high tensile strength, elastic limit, and fatigue resistance.
Compared with hot-rolled steel strip, precision cold-rolled carbon steel strip offers:
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Tight thickness tolerances
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Excellent flatness and straightness
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Smooth surface finish
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Consistent hardness and microstructure
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Suitability for high-speed stamping, forming, and spring winding
Typical process routes include:
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Cold-rolled / cold-worked (+CR) — higher strength, limited formability
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Annealed (+A) — softer, easier to form and stamp
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Hardened & tempered (+QT) — final high-strength spring or cutting condition
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Spheroidized annealed — optimized for precision blanking and cold forming
2. Grade Range and Typical Equivalents
| Carbon Content | Grade | Typical Material No. | Typical EN / AISI Equivalent | Typical Applications |
|---|---|---|---|---|
| 0.42–0.50% | CK45 | 1.1191 | C45E, AISI 1045 | Shafts, clutch parts, washers |
| 0.47–0.55% | CK50 | 1.1206 | C50E, AISI 1050 | Spring washers, stamped parts |
| 0.52–0.60% | CK55 | 1.1203 | C55E, AISI 1055 | Spring strips, mechanical parts |
| 0.57–0.65% | CK60 | 1.1221 | C60E, AISI 1060 | Springs, tools, gauges |
| 0.62–0.70% | CK67 | 1.1231 | C67S, AISI 1070 | Springs, tape measures, clutch springs |
| 0.62–0.70% | CK70 | 1.1231 | C70E, AISI 1070 | Springs, blades |
| 0.68–0.76% | CK75 | 1.1248 | C75S, AISI 1075 | Springs, saw blades, diaphragm springs |
| 0.72–0.80% | CK80 | 1.1525 | C80S, AISI 1080 | Heavy-duty springs, blades |
| 0.82–0.90% | CK95 | 1.1252 | C95S, AISI 1095 | Saw blades, cutting tools, needles |
| 0.95–1.05% | CK100 | 1.1274 | C100S, AISI 1095 | Precision knives, cutting edges, fine blanking |
Note: Material numbers and equivalents are indicative. Final grade and chemical composition must be confirmed against the current EN standard and the mill test certificate.
CK67 and CK75 are commonly associated with EN 10132-4 for springs and similar applications. CK45 and CK50 are commonly associated with EN 10132-3 for cold-rolled non-alloy steel strip for heat treatment.
3. Supply Form and Specifications
| Parameter | Range / Option | Notes |
|---|---|---|
| Thickness | 0.10–5.5 mm | Precision tolerances available by agreement |
| Width | 3–550 mm | Slit from wider coil |
| Delivery Condition | Annealed (+A), Cold-Rolled (+CR), Hardened & Tempered (+QT), Spheroidized Annealed | Selected by application |
| Surface | Oiled, blued, phosphated, passivated | For corrosion protection or downstream processing |
| Edge | Slit round edge, slit straight edge, deburred | Burr-controlled options available |
| Coil Weight | 100–1500 kg | Custom coil weights on request |
| Coil ID | 300 / 400 / 508 mm | Standard coil cores |
| Standards | EN 10132-3, EN 10132-4 | Other standards by agreement |
| Packaging | Eye-to-sky, eye-to-wall, wooden pallet, steel strapping, VCI paper | Export-ready packaging |
Typical Mechanical Properties
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CK75 annealed: Tensile strength ≥ 695 MPa, yield strength ≥ 410 MPa
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CK75 hardened & tempered: Tensile strength ≥ 1225 MPa; hardness approximately 57–63 HRC depending on tempering temperature
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CK67 / C67S hardened & tempered: Tensile strength can reach ≥ 1510 MPa depending on section and heat treatment
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Spheroidized annealed CK67 / CK75: Hardness ≤ 190 HV, suitable for precision blanking
Actual properties are confirmed by the mill test certificate.
4. Typical Applications by Industry
Automotive
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Clutch diaphragm springs
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Transmission washers
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Seat belt springs
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Brake pad backing plates
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Spring clips and retaining rings
High-carbon strip in the hardened and tempered condition provides stable elastic modulus and fatigue resistance under repeated dynamic loads.
Tools and Blades
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Band saw blades
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Hand saw blades
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Utility knife blades
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Surgical blades
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Cutting edges
Grades CK75–CK100 can reach approximately HRC 55–63 after hardening and tempering, combining high hardness with sufficient toughness.
Measuring and Instrumentation
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Tape measure strips
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Caliper springs
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Clock springs
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Precision springs
CK67 and CK75 are classic choices for tape measure strip because they require high elastic limit, low residual deformation, and good straightness.
General Machinery
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Valve springs
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Pump diaphragms
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Precision stamped parts
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Textile machinery components
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Wear-resistant strips
Spheroidized annealed CK67 / CK75 is often selected for precision blanking because the carbide morphology is uniform and the blanked edge quality is stable.
5. Purchasing Decision Points
| Item | Details |
|---|---|
| MOQ | 1 tonne; mixed specifications may be combined |
| Sample Policy | 2–5 kg free sample for standard specifications; freight collect. Custom samples quoted separately |
| Lead Time | 7–15 days for standard specifications; 15–30 days for custom thickness, width, condition, or surface |
| Certifications | EN 10204 3.1 / 3.2 mill certificate, SGS / BV third-party inspection, RoHS / REACH declarations |
| Quality System | ISO 9001; IATF 16949 where applicable |
| Price | Price on request. Quotation within 24 hours based on grade, thickness, width, condition, surface, and quantity |
| Customization | Non-standard thickness, special width slitting, custom surface treatment, tighter tolerances |
| Technical Support | CCT curves, Jominy hardenability curves, recommended heat treatment parameters |
| Heat Treatment Reference | Quenching 780–830°C; tempering 400–600°C depending on required hardness and toughness |
6. FAQ
Q1: What is the difference between CK75 and C75S?
A: They refer to essentially the same steel type under different standard systems. CK75 is an older DIN designation; C75S is the current EN 10132-4 designation, with material number 1.1248. C75S is explicitly intended for springs and similar applications. Chemical composition ranges are broadly similar.
Q2: What is the narrowest width available for 0.10 mm thickness?
A: For thickness ≤ 0.30 mm, the narrowest slit width can be as low as 3 mm. For thickness > 0.30 mm, a minimum width of 5 mm is generally recommended to maintain slit quality and flatness. Final feasibility should be confirmed by sample trial.
Q3: What hardness can be achieved in the hardened and tempered condition?
A: For CK75, hardness after quenching and tempering is typically 57–63 HRC, depending on tempering temperature. Tensile strength can range from approximately 1225 MPa to 1900 MPa. CK67 in the hardened and tempered condition can reach tensile strength ≥ 1510 MPa.
Q4: Do you supply spheroidized annealed strip for precision blanking?
A: Yes. CK67 and CK75 can be supplied in spheroidized annealed condition with a spheroidization rate ≥ 95% and hardness ≤ 190 HV. This condition is suitable for precision blanking and cold forming, producing small rollover and minimal burr.
Q5: What is the minimum order quantity and sample policy?
A: MOQ is 1 tonne; mixed specifications can be combined. Standard specifications can be sampled at 2–5 kg free of charge, with freight collect. Custom samples are quoted separately and may be credited against a bulk order.
