1. Overview
CK67 et CK75 are high carbon spring steel grades commonly used in bandes d'acier trempé et revenu.
These steels offer an outstanding combination of dureté, dureté, et propriétés du ressort, making them the preferred materials for ressorts de volet roulant, ressorts plats, saw blades, and hand tools.
Jiaxiao MTC fabrique le CK67 / CK75 strips under strict thermal and dimensional control, ensuring excellent flexibility, surface finish, and consistent mechanical behavior during coiling and bending.
2. Chemical Composition and Equivalent Grades
| Grade | C (%) | Mn (%) | Si (%) | P max | S max |
|---|---|---|---|---|---|
| CK67 | 0.64–0,68 | 0.60–1.10 | 0.17–0,37 | ≤0,035 | ≤0,035 |
| CK75 | 0.72–0,80 | 0.50–0,80 | 0.17–0,37 | ≤0,035 | ≤0,035 |
Equivalent international grades:
- AISI 1065 / 1075
- EN C67S / C75S
- BS CS70 / CS75
These steels belong to the high-carbon class (0.65–0,80%C), providing superior hardness after quenching and excellent elasticity after tempering.
3. Heat Treatment and Production Process
CK67 / CK75 strips are produced through a precisely controlled durcissement et revenu processus chez Jiaxiao MTC:
- Cold Rolling:
Reduces hot rolled coils to the desired thickness while ensuring excellent flatness. - Durcissement:
Heated above the critical temperature (approx. 800–850°C) and quenched rapidly to achieve high hardness. - Tempering:
Réchauffé à 300-450°C pour équilibrer la dureté avec la ténacité et la flexibilité. - Edge and Surface Treatment:
- Edge types: slit, arrondi, or square
- Surface finishes: natural, blue, jaune, blanc, or polished
All treatments are performed in controlled atmosphere furnaces to prevent oxidation or decarburization.
4. Mechanical Properties
| Condition | Hardness | Résistance à la traction | Surface Finish | Edge Type |
|---|---|---|---|---|
| Hardened & Tempered | 30–55 HRC | 1500–1800 N/mm² | Blue / Jaune / Brillant | Rounded / Square |
Thickness Range: 0.1–5.0 mm
Width Range: 2–500mm
The resulting strips show high fatigue life, uniform spring tension, et excellent repeatability during coiling, ensuring reliable operation for mechanical springs and shutter doors.
5. Rolling Shutter Spring Application
L'une des applications les plus reconnues du CK67 par Jiaxiao MTC / CK75 is in rolling shutter door springs.
In this field, flexibility and consistent performance sont des facteurs clés : l'acier doit résister à des cycles d'enroulement et de déroulement répétés sans se fissurer ni perdre son élasticité..
Each strip undergoes:
- Ébavurage des bords to prevent failure under tension,
- Hardness and width testing for dimensional stability, et
- Flexibility testing to ensure it meets required bending cycles.
Typical shutter spring specifications:
| Spring Size (mm) | Load (kg) | Material Example |
|---|---|---|
| 60 × 1.20 | 29 kg | CK75 |
| 55 × 1.20 | 26 kg | CK67 |
| 50 × 1.40 | 28 kg | CK75 |
| 45 × 1.00 | 15 kg | CK67 |
Ces valeurs démontrent comment l'épaisseur et la largeur de la bande déterminent le couple du ressort et la capacité de charge — un facteur critique dans les mécanismes d'équilibrage des volets et des portes..
6. Advantages of CK67 / CK75 Steel Strips
- High tensile strength and elasticity after controlled tempering
- Excellent fatigue resistance for repeated stress cycles
- Smooth surface finish with optional polished or blue-tempered coating
- Uniform flatness and edge accuracy for automatic coiling machines
- Stable mechanical properties due to high-quality quenching and tempering lines
7. Other Industrial Applications
Beyond shutter springs, CK67 and CK75 are widely used for:
- Flat and spiral springs in machinery and tools
- Saw blades and scraper knives requiring sharpness and resilience
- Putty knives, truelles, and flexible blades in construction tools
- Shoe shank and toe cap materials for durability and flexibility
Ces applications reposent sur la combinaison de l’acier dureté (HRC 30-55) et controlled toughness, making it ideal for bending, forming, and punching operations.
8. Dimensional Tolerances and Inspection
Jiaxiao MTC suit strictement les contrôles de tolérance standard:
- Thickness tolerance: ±0,015 à 0,070 mm
- Width tolerance: ±0,20–0,80 mm
- Straightness tolerance: Classe R1 à R4
- Flatness deviation: ≤0,3 % de la largeur
Each batch undergoes:
- Chemical composition testing (spectrometer)
- Hardness verification (Vickers, Rockwell)
- Surface inspection under magnification
- Elasticity and flexibility testing on coiling simulators
9. Packaging and Delivery
Every coil is:
- Lightly oiled et wrapped in plastic film and anti-rust paper,
- Packed in seaworthy wooden crates or steel pallets,
- Labelled with grade, dureté, size, and batch information for traceability.
This ensures safe international delivery and protection against corrosion or deformation.
10. À propos de Jiaxiao MTC
Guangzhou Jiaxiao Material Technology Co., Ltée.
is a professional manufacturer of bandes d'acier à haute teneur en carbone, alloy steel strips, et bandes d'acier inoxydable in both endurci & tempered et cold-rolled annealed formulaires.
With advanced facilities for acid washing, laminage à froid, recuit, refendage, trempe, tempering, et polissage, Jiaxiao MTC garantit une qualité constante dans l'ensemble de ses 15,000 tons annual capacity.
Its products are trusted worldwide in industries such as spring manufacturing, cutting tools, automotive components, and construction hardware.
