Cold-finished (CF) aluminum alloy bar refer to aluminum and aluminum alloy round or square bars formed by plastic deformation at room temperature (below their recrystallization temperature) through processes such as cold drawing, cold stretching, or precision drawing. They are typically based on extruded or rolled blanks and undergo secondary processing to achieve excellent dimensional accuracy, surface finish, and mechanical properties. This contrasts sharply with “hot-worked” or “extruded” bars, which are processed at high temperatures and generally have lower precision.
Main Features |
Explanation |
| High Dimensional Accuracy & Good Surface Quality | Cold working, achieved through die drawing, allows for dimensional tolerances of ±0.05 mm or even higher, far superior to ordinary extruded bars. It also results in better surface finish and straightness, enabling direct use in high-precision assembly and reducing subsequent machining. |
| Mechanical Performance Improvement | Cold working produces a “work hardening” effect, which increases the tensile strength and hardness of a material while decreasing its plasticity. For alloys that cannot be strengthened by heat treatment (such as 3003 and 5083), this is the primary strengthening method. |
| Good Overall Performance | It retains the inherent advantages of aluminum alloys, such as corrosion resistance, oxidation resistance, thermal and electrical conductivity, lightweight and high strength. By selecting different alloys (such as 5xxx, 6xxx, 7xxx series), various requirements can be met, ranging from general structures to high strength and high corrosion resistance. |
| Changes in Processing Performance | Cold working hardens the material, slightly increasing tool wear during cutting. However, good surface finish aids in chip removal and results in a smoother machined surface. Some alloys (such as 3003) exhibit a significant decrease in plasticity after cold work hardening, necessitating careful planning of both cold and hot working processes. |
| Cost and Delivery Time | Because of the added cold working process, its unit price is usually higher than that of ordinary extruded bars. However, high precision can reduce subsequent processing, which may result in a lower overall cost. Delivery time is also relatively longer. |
Common Alloy Grades and Tempers
Cold-worked finished aluminum bars are available in a variety of alloys, and their temper is usually indicated by the suffix “CF” (cold-worked).
|
Alloy Series |
Common Tempers |
Key Properties & Applications |
|
T3, T4, T351, T6, T651 |
High Strength. Used in aerospace (aircraft structures, landing gear), automotive (high-strength fasteners), and military components. | |
|
T4, T6, T651 |
Good Strength, Corrosion Resistance, Weldability. Widely used for general engineering, automotive parts, and architectural components. | |
|
O, H111, H14, H16, H32 |
Excellent Corrosion Resistance (esp. marine). Used in marine hardware, chemical equipment, and transportation. | |
|
O, H12-H18 |
High Corrosion Resistance, Good Formability, Conductivity. Used for electrical conductors, decorative trims, and general fabrication. |
Manufacturing Process
The production of cold finished aluminum bar typically involves two main steps:
Hot Working (Pre-processing): The process begins by heating an aluminum billet and then forming it into a rough bar or rod through extrusion or hot rolling. At this stage, the product has a relatively rough surface and loose dimensional tolerances.
Cold Finishing (Final Processing): The hot-worked bar is then processed at room temperature using methods like cold drawing or cold rolling. This step may be repeated multiple times through progressively smaller dies to achieve the final desired size and properties.
Common Shapes & Sizes
Cold finished (CF) aluminum bar is produced in a variety of standard shapes and dimensions:
Shapes: Round, square, rectangular (flat), hexagonal, and custom profiles (e.g., T-bar, I-beam, channel).
Sizes: Diameters for round bars can range from a few millimeters to over 600 mm. Lengths are typically supplied in standard mill lengths (e.g., 1-6 meters) but can be custom cut.
Relevant Standards
Cold finished (CF) aluminum bar is manufactured to meet various international and national standards, ensuring quality and consistency. Key specifications include:
ASTM B211 / B211M: Covers rolled or cold-finished bar, rod, and wire.
AMS 4xxx Series: Aerospace Material Specifications for high-performance alloys (e.g., AMS 4118 for 2017 alloy).
EN 755-2 / EN 573-3: European standards for wrought aluminum products.
GB/T 3880, GB/T 3191: Chinese national standards for aluminum alloy plates, strips, and bars.
Typical Applications
The combination of high precision, excellent surface quality, and enhanced mechanical properties makes cold finished aluminum bars ideal for demanding applications:
- Aerospace: Aircraft structural components, landing gear, fasteners, and fittings.
- Automotive & Transportation: High-strength fasteners, shafts, and suspension components.
- Precision Machinery: Shafts, pins, and other parts requiring tight tolerances and smooth finishes for CNC machining.
- Marine & Offshore: Components requiring high corrosion resistance, such as marine hardware and fittings.
- Electrical & Electronics: Conductors, busbars, and precision-machined parts where surface quality is critical.