Spinning is a deformation process for forming sheet metal or tubing into seamless hollow cylinders, cone hemispheres, or other symmetrical circular shapes, by a combination of rotation and force. There are two basic forms, known as manual spinning and power (or shear) spinning. In the former method, no appreciable thinning of the metal occurs, whereas in the latter, metal is thinned as a result of shear forces.
Nearly all HAYNES® and HASTELLOY® alloys can be spin formed, generally at room temperature. The control of quality, including freedom from wrinkles and scratches, in addition to dimensional accuracy, is largely dependent upon operator skill. The primary parameters that should be considered when spinning these alloys are:
- Feed Rate
- Strain Hardening Characteristics
- Tool Material, Design, and Surface Finish
- Power of the Machine
Optimum combinations of speed, feed, and pressure are normally determined experimentally when a “new job” is set up. During continuous operation, changes in the temperature of the mandrel and spinning tool may necessitate the adjustment of pressure, speed, and feed to obtain uniform results.
Lubrication should be used in all spinning operations. The usual practice is to apply lubricant to the blank prior to loading of the machine. It may be necessary to add lubricants during operation. During spinning, the work-piece and tools should be flooded with a coolant, such as an emulsion of soluble oil in water.
Sulfurized or chlorinated lubricants should not be used, since the spinning operation might burnish the lubricant into the surface, resulting in detrimental surface effects (due to diffusion of sulfur and/or chlorine) during any subsequent annealing treatments. If these types of lubricant are used accidentally, they should be thoroughly removed (by grinding, polishing, or pickling) prior to any intermediate or final anneal.
The tool material, work-piece design, and surface finish are all very important in achieving trouble-free operation. Mandrels used in spinning must be hard, wear-resistant, and resistant to the fatigue resulting from normal eccentric loading.
As is the case for other cold-forming operations, parts produced by cold spinning should be intermediate and final annealed in accordance with the recommendations in the Heat-Treatment section of this guide.