Q17Basic Mechanical Engineering
Question
Q.7 Explain rolling and extrusion processes.
Answer
Rolling is a bulk deformation process that aggressively reduces material thickness by squeezing metal directly between massive rotating cylinders, whereas extrusion is a severe shaping process that violently forces a heated metal billet strictly through a shaped die to create continuous, complex cross-sections.
In manufacturing engineering, bulk deformation processes are systematically utilized to fundamentally alter the geometric shape of solid metal billets or ingots strictly through the application of massive compressive plastic yielding. Two of the most dominant and economically vital deformation processes are Rolling and Extrusion.
1. The Rolling Process
Rolling is an absolutely continuous, high-volume manufacturing process predominantly used to drastically reduce the exact cross-sectional thickness of a metal workpiece while proportionally extending its length. The process rigorously involves passing a massive, thick metallic slab or ingot directly between two (or more) extremely heavy, rigid cylindrical rollers that are physically rotating in strictly opposite directions.
The exact geometric gap firmly established between these massive rollers is rigorously set to be distinctly less than the incoming thickness of the unworked metal. As the immense friction from the rotating rollers actively bites and pulls the metal completely through the gap, massive compressive forces physically squeeze and plastically deform the crystalline structure, ejecting a significantly thinner, elongated strip. It is universally employed to mass-produce massive structural I-beams, extensive railroad rails, heavy steel plates, and enormous rolls of thin aluminum foil.
2. The Extrusion Process
Extrusion is a highly specialized, severe compressive deformation process utilized explicitly to manufacture long, completely continuous, straight metallic products possessing highly intricate, complex, and unvarying cross-sectional profiles (such as hollow tubes or star shapes). The physical process is conceptually identical to squeezing thick toothpaste entirely out of a small geometric nozzle.
A massive, solid cylindrical billet of raw metal (often heated to a highly plastic state) is securely placed completely inside a massive, enclosed strong steel container. An immensely powerful hydraulic ram rigorously applies astronomical compressive pressure directly to the back of the billet, violently forcing the plasticized metal to flow completely out through a very specifically shaped, high-strength steel die located at the opposite end. The emerging metal strictly adopts the exact geometric profile of the die opening.