Flow-form technology for production of rotationally symmetrical high precision parts from a variety of high-strength and hard-to-form thin-walled metals
For the Ariane rocket and satellites nose cones, exhaust nozzles and liner for pressure vessels with cylindrical or conical form are needed. The extremely thin and refractory parts are adapted as the basis of this technology from the aerospace industry. Here seamless cones etc. made of niobium, titanium or other heat-resistant materials are produced by different flow forming processes. Very thin wall thicknesses can be displayed with excellent surface quality and high contour accuracy.
In flow-forming, a cylindrical preform is fitted over a mandrel. After both are made to rotate, compression forces are applied to the outside diameter of the preform by three CNC-controlled rollers. The desired geometry is achieved when the outer diameter and the wall of the preform are decreased and the available material volume is forced, through plastic deformation, to flow longitudinally over the mandrel. Typically, the preform can be flow-formed four to six times compared to its starting length before needing re-annealing.
As a cold forming process, flow-forming often achieves mechanical properties and dimensional accuracies that are far closer to requirements than can be achieved by warm or hot forming manufacturing processes and chip removal forming process. The flow-form process causes the material's mechanical properties to increase while refining the microstructure, orienting the crystallographic texture, and in some cases causes desirable metallurgical phase transformations. The flow-form wall reduction is engineered to achieve specific, material properties thru the cold work.
The CNC (Computerized Numerical Control) controlled process offers consistent and repeatable accuracies. The precision of the flow-forming process often eliminates the need for finishing operations such as turning, grinding, honing, straightening, balancing or polishing with typically interior finishes of Ra 0,2 and exterior finishes of 1,6. Thus extremely thin and precise wall thicknesses can be generated economically and without difficulty. Furthermore, highest tolerance requirements are met.
Innovations & Advantages
The symmetric around components range in size from diameters of 25mm to 760mm, wall thickness of 0,2mm to 30mm with length up to 6 meters. Flow-form experience is with a large number of materials, from copper, aluminum, stainless steel over titanium, palladium, niobium to nickel, nickel alloys and beryllium copper. Corrosion-resistant-, acid-resistant- and heat-resistant steels can also be flow-formed as non-magnetic steels.
Finished flow-formed components tend to have superior mechanical properties compared to pre-formed materials, as the process realigns grain structure in a very uniform, axial direction. Flow-forming creates a uniformly oriented crystal texture, increasing the biaxial strength of the metal combined with a fine grain size.
Through its strain hardening of the base metal, flow-forming increases yield strength (up to 55 rockwell) and tensile strength (up to 2000 MPa) of the formed material, making it possible to design thinner walls that yield lighter components. Highest tolerance requirements are realized. Due to a higher fatigue strength a longer operating time of the flow-formed parts can be achieved. Flow-formed components can also be solution annealed or stress relieved to remove residual stresses, and heat treated or aged to alter levels of achieved strength, hardness and ductility.
Flow-forming reduces cost in a variety of ways. It is a chipless process with minimal material waste and labor cost. In almost all cases, we can flow-form to net shape, maximizing material utilization while eliminating post-forming machining. The seamless nature of flow-forming saves money by incorporating components like flanges into a single integrated design and eliminating welding. And flow-forming can eliminate the costs of finish-machining and/or grinding by forming net-shape components from pre-hardened metal.
Current and Potential Domains of Application
- industrial products
- specialty metals (including processes for working with metals)
- other specially materials
- machine tools, other metal working equipment
- power transmissions equipment (including generators and motors)
- other industrial equipment and machinery
Typical applications for this technology are:
- Retract Actuator Cylinders for main and nose landing gears, power door opening cylinders, thrust reverse cylinders, angle drive shafts for jet engines, various actuator and shafts for helicopter tail rotors for the aviation industry.
- Filling tubes, tank cylinder for rockets, diff. tank parts for spacelab and satellites, nose cones for boosters and rockets, satellites exhaust cones and composite pressure vessels for the space flight industry
- Motor case and intersection cone for air systems, diff. launch tubes and supporting tubes, various copper cones for sharped charges
- Clutch housing, planet carrier, piston brushes, guide tubes and exhaust turbo charger housings for passenger cars, commercial vehicles, agriculture and construction machinery
- Precise tubes for research drilling and artificial lift systems, MWD (Measurement While Drilling) housings and various tubes for tools in the gas & oil producing industry
- various tubes, housings cylinders and pressure vessels for different industrial applications and products