M. Fonte, Tufts University, Medford, MA
Flowforming is an advanced, net shape, cold metal forming process employed for the manufacturing of dimensionally precise, rotationally symmetrical, hollow components. Precise tubular components that have large length to diameter ratios, made with thin walls and require high degree of dimensional accuracies are excellent flowformed parts. Titaniums, nickel based alloy, high strength carbon steels, Maraging Steels, high strength aluminums, Tantalum Tungsten alloys are routinely flowformed. Well known for its efficiency and economical benefits, flowforming has been widely accepted as the process of choice in the fabrication of difficult-to-manufacture military and aerospace components requiring superior metallurgical and dimensional controls. Flowforming is currently employed for the production of missile outer shells and nose cones, housings for flight and launch motors, casings for rocket motors, large caliber cartridge casings, thin wall mortar tubes, projectiles, warheads, projectiles, bomb bodies; as well as tubulars for the nuclear, petrochemical and aerospace industries. A cylindrical work piece is attached to a rotating mandrel; 3 rollers hydraulically compress against the outer diameter of the preform. The desired geometry of the flowformed tube is achieved when the preform wall thickness is compressed above its yield strength and plasticized “made to flow” in the longitudinal direction onto the surface of the inner, rotating mandrel. As the preform material is thinned out and lengthened onto the mandrel, preforms are formed into seamless, thin wall, very round and concentric tubular-shaped products; with increased mechanical properties from the cold work, refined microstructure, oriented crystallographic texture and excellent surface finishes, all with repeatable accuracy.
www.flowform.com “In recent years, the rapid increase in the cost of raw materials and the growing appreciation of their finite availability has caused many industries to examine their manufacturing techniques and consider alternatives to traditional methods, with the aim of making economical use of the materials available. One of these ‘new’ techniques is that of metal spinning and its derivatives, shear forming and flow forming. ” So, wrote C. L. Packham back in 1976.
Thirty years later, we once again face the rising costs of materials. In the last 18 months alone, titanium and nickel prices have tripled. Making the problem worse, these materials are not readily available in tubular form. Therefore, when cylindrical components are needed in titanium or Inconel, more often than not they are machined from solid bar; which wastes material and are expensive operations. By flowforming these expensive materials, the customer keeps their components’ costs down. First, as flowforming begins with a short preform, usually a fourth the length of the over all finished component’s length; there is minimal material waste when machining the short preform. Second, because the piece is flowformed to either net shape or near net shape, costly machining operations which are conventionally employed to produce cylindrical components such as trepanning, gun drilling and boring are eliminated.
