Metalworking I: Rolling

Beryllium Manufacturing Processes

“…An example of the effect of strain rate on formability is illustrated in Figure II-3, which shows that for a given thickness, smaller bend radii or for a given radius, larger thicknesses are attainable at the slower bending speed. 10 It appears that the two slow-rate and high-rate curves would tend to merge at the higher temperatures. Figure II-4 gives the forming speed as a function of the minimum bend ratio, r/t.…”

“…The optimum temperature range for forming was given as between 600 and 750 O C 8 and above 700 O C. 9 Other factors affecting its formability are composition and prior thermomechanical history; for example the ductility of vacuum-hot-pressed block can be improved by hot working. 10 The iron-to-aluminum ratio must be controlled to prevent hot shortness c due to aluminum precipitating along the grain boundaries.…”

“…8,10 Deep drawing, also referred to as cupping, involves both deep drawing and stretching deformations. A successful deep-drawing operation involves proper control of friction and hold-down pressure, which is affected by the die design and lubricant selection.…”

“…The location of the lubricated asbestos paper on the workpiece blank in a double-action tool for deep drawing of beryllium is pointed out in Figure II-3-1. 8,10 The double-action provides a restraint on the workpiece (blank or preform) to prevent wrinkling, which may occur when using a single-action tool. The restraint is applied by the blank holder and is developed by a lower (additional) ram in the hydraulic press.…”

“…8 The safe reduction (formability) limits, R, as a function of d/t for both with and without blank restraint are shown in Figure II- 8 Deep drawing of simple hemispherical shells are done at punch speeds from 760 to 1270 mm/min. 10 The primary cause of failure in deep-drawn shapes was observed to be due to localized tensile strains induced by stresses from the punch. The strains are most severe in the early stages of the draw when the contact areas are small.…”