Flow turning is a metal forming process that plastically deforms thick gauge material to create components with significantly reduced wall thickness.
Understanding Flow Turning
Often referred to as shear forming or power spinning, flow turning is an advanced metalworking technique used to produce rotationally symmetrical hollow components. This process leverages the principle of plastic deformation under precisely controlled conditions.
How Flow Turning Works
At its core, flow turning involves the following mechanics:
- Material Deformation: A thick gauge material blank (often a pre-formed preform or disk) is securely mounted onto a rotating mandrel.
- Pressure Rolling: One or more rollers apply substantial pressure to the surface of the material. A key characteristic of this process is that these rollers travel in the same direction as the material's rotation, guiding the material's flow.
- Plastic Flow: Under this immense pressure and the synchronized movement of the rollers, the material is forced to flow plastically along the mandrel. This controlled axial flow causes the material to stretch and elongate.
- Wall Thickness Reduction: The most significant outcome of this process is that the component produced has a wall thickness much less than that of the original blank. The material is efficiently redistributed, resulting in a longer, thinner-walled part with enhanced material properties.
Key Characteristics and Advantages
Flow turning offers several notable benefits and features that distinguish it from other forming methods:
- Significant Wall Reduction: It excels at achieving substantial reductions in wall thickness while maintaining high material integrity and often improving grain structure.
- Enhanced Automation: Compared to traditional methods like metal spinning, flow turning is a more automated process. This leads to greater precision, consistency, reduced human error, and higher production rates.
- Improved Material Properties: The intense cold working involved in flow turning can significantly improve the mechanical properties of the material, such as increasing its tensile strength, hardness, and fatigue resistance.
- Near-Net Shape Production: Components are often produced to near-net shape, which minimizes the need for extensive subsequent machining, thereby reducing material waste and production time.
- Versatility: This process is suitable for a wide range of materials, including various steels, aluminum alloys, and high-strength superalloys, and is used to produce components like rocket motor casings, cones, cylinders, and specialized nozzles.
Flow Turning vs. Metal Spinning
While both processes create rotationally symmetrical parts, a key distinction lies in their operational mechanics and level of automation:
| Feature | Flow Turning | Metal Spinning |
|---|---|---|
| Process | Material is made to flow plastically and axially under pressure rolling, leading to significant wall thickness reduction. | Material is progressively formed over a rotating mandrel by a roller or tool, typically without significant wall thinning. |
| Automation | More automated process | Often less automated, frequently relying on skilled manual control to guide the tool. |
| Wall Thickness | Deliberate and substantial reduction from the original blank thickness. | Wall thickness typically remains relatively constant or experiences only slight reduction. |
| Material State | Thick gauge material undergoes controlled plastic flow. | Material deforms incrementally by bending and stretching. |
