IE370Lecture16 - BULK DEFORMATION PROCESSES IN METALWORKING...

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1 BULK DEFORMATION PROCESSES IN METALWORKING • Rolling • Other Deformation Processes Related to Rolling • Forging • Other Deformation Processes Related to Forging • Extrusion • Wire and Bar Drawing Bulk Deformation Metal forming operations which cause significant shape change by deformation in metal parts whose initial form is bulk rather than sheet • Starting forms: cylindrical bars and billets, rectangular billets and slabs, and similar shapes • These processes work by stressing metal sufficiently to cause plastic flow into desired shape • Performed as cold, warm, and hot working operations Importance of Bulk Deformation • In hot working, significant shape change can be accomplished • In cold working, strength can be increased during shape change • Little or no waste - some operations are near net shape or net shape processes - The parts require little or no subsequent machining Four Basic Bulk Deformation Processes 1. Rolling – slab or plate is squeezed between opposing rolls 2. Forging – work is squeezed and shaped between between opposing dies 3. Extrusion – work is squeezed through a die opening, thereby taking the shape of the opening 4. Wire and bar drawing – diameter of wire or bar is reduced by pulling it through a die opening
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2 Rolling Deformation process in which work thickness is reduced by compressive forces exerted by two opposing rolls Figure 19.1 - The rolling process (specifically, flat rolling) The Rolls The rotating rolls perform two main functions: • Pull the work into the gap between them by friction between workpart and rolls • Simultaneously squeeze the work to reduce cross section Types of Rolling • By geometry of work: - Flat rolling - used to reduce thickness of a rectangular cross-section - Shape rolling - a square cross-section is formed into a shape such as an I-beam • By temperature of work: - Hot Rolling – most common due to the large amount of deformation required - Cold rolling – produces finished sheet and plate stock Figure 19.2 - Some of the steel products made in a rolling mill
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3 Figure 19.3 - Side view of flat rolling, indicating before and after thicknesses, work velocities, angle of contact with rolls, and other features Flat Rolling – Terminology Draft = amount of thickness reduction f o t t d - = where d = draft; t o = starting thickness; and t f = final thickness Flat Rolling – Terminology Reduction = draft expressed as a fraction of starting stock thickness: o t d r = where r = reduction Shape Rolling Work is deformed into a contoured cross-section rather than flat (rectangular) • Accomplished by passing work through rolls that have the reverse of desired shape • Products include: - Construction shapes such as I-beams, L-beams, and U-channels - Rails for railroad tracks - Round and square bars and rods
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4 Flowchart of Rolling Operations Figure 16-1 Flow chart for the production of various finished and semifinished steel shapes. Note the abundance of rolling operations. (Courtesy of
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This note was uploaded on 09/23/2009 for the course IE 370 taught by Professor Chunghorng,r during the Spring '08 term at Purdue University-West Lafayette.

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IE370Lecture16 - BULK DEFORMATION PROCESSES IN METALWORKING...

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