Dải thép cường lực xanh được sử dụng rộng rãi trong các dụng cụ, Lưỡi dao, vòng đệm mùa xuân, ban nhạc cưa, dụng cụ đo lường, and industrial components requiring a combination of high hardness, strong elasticity, and excellent fatigue resistance. Its signature blue surface is not simply for aesthetics — it is the result of a precise heat treatment process designed to enhance performance.
Trong bài viết này, we explore the full manufacturing process of blue-tempered steel strips and explain why this material has become a top choice for high-strength applications.
What Is Blue-Tempered Steel Strip?
Blue-tempered steel strip (also known as blued steel strip) is a hardened and tempered high-carbon or alloy steel strip with a controlled oxide film on the surface, giving it a deep blue color.
Its key characteristics include:
- High hardness (typically 48–52 HRC depending on grade)
- Excellent elastic limit
- Superior fatigue resistance
- Smooth, oxide-protected surface
- Good dimensional stability
Common grades include 65Mn, SK5, C75s, 50CRV4, and other heat-treated carbon or alloy steel strips.
The Manufacturing Process of Blue-Tempered Steel Strip
1. Cold Rolling the Steel Strip
The process begins with cold-rolled steel strip, typically between 0.1 mm and 2.0 mm thick.
Cold rolling improves:
- Dimensional accuracy
- Surface finish
- Strength through cold deformation
At this stage, the steel is still soft and requires heat treatment to reach high hardness.
2. Hardening (Làm dịu đi)
The steel strip is heated to its austenitizing temperature, usually between 780°C and 850°C depending on the grade.
During this phase:
- The microstructure transforms into austenite
- Carbon is dissolved into the matrix
- The material is prepared for martensitic transformation
The strip is then rapidly quenched, commonly in oil or water-based polymer fluids.
Result:
A fully hardened martensitic structure with very high hardness — but also high brittleness.
3. Tempering — The Key to Blue Steel
Tempering is the decisive step that creates both the mechanical properties and the famous blue color.
Sau khi dập tắt, the hardened strip is reheated to a controlled temperature, typically between:
- 280°C – 320°C for blue tempering
During tempering:
- Hardness decreases slightly
- Toughness improves significantly
- Internal stresses are relieved
- Elasticity and fatigue resistance increase
At this temperature range, a thin oxide layer forms on the surface, resulting in the blue, blue-purple, or blue-black appearance.
This oxide film also provides:
- Enhanced corrosion resistance
- A smoother, more uniform appearance
- A protective barrier for downstream processing
4. Controlled Atmosphere & Continuous Furnaces
Modern manufacturers use:
- Continuous mesh belt tempering furnaces
- Electrically heated or gas-fired systems
- Controlled oxygen levels
These conditions ensure:
- Uniform color across the entire coil
- Stabilized hardness
- Consistent mechanical properties
- No surface contamination
This is one of the reasons high-quality blue-tempered strips from professional suppliers look clean, deep blue, and evenly tempered.
5. Straightening, Tension Levelling, and Coil Finishing
After tempering, the strip undergoes:
- Tension levelling to reduce wave or camber
- Precision straightening
- Shearing, rạch, or cutting to customer dimensions
The final product is:
- Flat
- Stable
- Stress-balanced
- Ready for stamping, bending, punching, or forming
Why Blue-Tempered Steel Strip Is Popular
The combination of độ cứng + elasticity + visual indication of quality makes blue-tempered strip ideal for demanding applications.
Key Advantages:
- Strong fatigue resistance for springs
- Sharpenability for blade applications
- Excellent dimensional stability
- Protective oxide layer
- Attractive industrial appearance
Industries that rely on blue-tempered steel strip include:
- Hand tools
- Knives and precision blades
- Lò xo và clip
- Saws and cutting tools
- Measuring instruments
- Building hardware
Phần kết luận
Blue-tempered steel strip is not just a colored material — it is a carefully engineered product created through cold rolling, hardening, and precise tempering. The blue surface comes from controlled oxidation during tempering, while the mechanical properties result from exact heat treatment parameters.
Manufacturers such as Jiaxiao MTC use advanced continuous hardening and tempering lines to ensure consistent hardness, elasticity, and surface finish, delivering high-quality blue-tempered steel strips for global industrial applications.
