Chapter 15 Introduction to Nonferrous Metals 341 Rolling Hot-rolling nonferrous metals proceeds very much like hot-rolling steel, discussed in Chapter 7. The rolling mills, runout tables, and other equipment are sized to match the size of the ingots or continuous slabs of the metals being worked. Cast ingots are broken down on reversing mills and reduced to plate or 3/8″ (1 cm) strip in coils. Just as for steel, metal 3/8″ (1 cm) or thicker is called plate. Thinner metal is called strip if it is coiled, or sheet if it is cut to flat rectangles. Forging Many nonferrous alloys are forged to obtain the improved properties of a forged part. The forging temp erature, lubricants, and other conditions all depend on the alloy, but otherwise each forging operation is very much like steel forging. Extrusion In extrusion, the workpiece metal, heated to the hot-work temperature, is pushed through a die. The metal dynamically recrystallizes and forms the cross section dictated by the die. Many nonferrous metals can be extruded into long lengths of complex cross sections and hollow shapes, because steel dies can handle the hot- work temperature of the workpiece without undue wear. For example, a tube for a heat exchanger with internal ribs, Figure 15-23, can only be made by extrusion. For some alloys, the part can be made by back extrusion. In this process, the workpiece is placed in a cavity in a machine tool, and a ram presses down on the workpiece, Figure 15-24, extruding the metal back over the ram. Drawing Nonferrous alloys with good ductility can be drawn, or pulled, into round or oval shapes. Just as for st eel, the amount of reduction in a single draw is limited Jay Warner Figure 15-23. Extruded tube with internal ribs is designed to support high internal fluid pressures, such as the one found in this air conditioner condenser. This tube, approximately 2.5″ (6.35 cm) wide, has nine webs plus small fins to improve heat transfer. It can only be made by extrusion. Punch Mandrel Die Workpiece metal Extruded part Goodheart-Willcox Publisher Figure 15-24. In back extrusion, a ram coming down forces the workpiece metal to extrude around the edge of the ram and up around it. The finished part is a cylinder and base. Copyright Goodheart-Willcox Co., Inc.