TABLE OF CONTENTS Note: Many metal forming operations can be performed with the workpiece metal either hot or cold. The operations discussed in this section are normally - but not always - performed on workpiece material that has been heated to make it more malleable for the operation involved. Metals that are to be hot formed are heated above their recrystallization temperature, one that varies with each material but is normally about 0.6 times the melting temperature on the Kelvin (absolute temperature) scale. For example, steels require a temperature above about 1800 F (980 C). Warm forming involves heating to a temperature 30 to 60 percent of the melting point, while cold forming takes place when the metal temperature is below 30% of the melting temperature2.
Is commonly applied to convert steel ingots to blooms, billets, or slabs, and to make these shapes into salable forms. In the process, heated metal is passed between two rollers whose spacing is less than the thickness of the metal. The rotation of the rollers moves the metal forward, squeezing and elongating it. Fig. 2A1 illustrates the process. The process extends and refines the grain structure of the rolled material. A number of passes may be required, depending on the thickness desired and the thickness of the entering material. Reversing rollers are often used to facilitate multiple passes. Thin sheet or foil is best rolled with small-diameter rollers that are backed up with larger rollers to provide the necessary rolling...
