Metal Rolling Mills and Extrusion Processes

Rolling Mill Configurations

Rolling mills are categorized by the arrangement of their cylinders. Common configurations include:

• Duo: These consist of two horizontal axis cylinders. They can be reversible or non-reversible, depending on whether the rotation direction of the cylinders can be changed to allow processing in both directions.
• Trio: This setup features three horizontal axis cylinders placed in the same vertical plane. The cylinders may have the same diameter with movements synchronized by gears, or a smaller middle cylinder may turn via friction with the two geared outer cylinders.
• Duo Alternate: In these cases, one of the cylinders is replaced by a trio train shaft.
• Double Duo: This configuration consists of two boxes, each containing two pairs of cylinders with their axes set in two parallel vertical planes.
• Quarto (Four-High): These boxes utilize four cylinders in the same vertical plane. The two inner cylinders have a smaller diameter and perform the actual rolling, while the two larger external cylinders provide support.
• Multiple Cylinders: Systems utilizing 6, 12, or more cylinders for specialized applications.

Rolling Mill Trains

A rolling mill train refers to a set of several rolling mills or boxes arranged to process material sequentially to obtain a specific profile.

Types of Rolling Trains

• Open or online
• Continuous
• Semi-continuous
• Cross-country

Metal Extrusion Processes

Extrusion is a process used for forming metals and alloys by forcing them to flow under high pressure. This system allows for the production of tubes or profiles with perfectly uniform sections and excellent finishes.

Cold Extrusion

Cold extrusion is performed by forcing the material, placed at the bottom of a matrix, to flow between the walls of the matrix and a punch press. For the operation to be successful, two conditions must be met:

1. The material used must be highly ductile.
2. The pressure from the punch must be very powerful and applied via impact, as the impact energy generates heat that facilitates the extrusion process.

Hot Extrusion

In hot extrusion, pressure is applied to metal heated to a temperature range between recrystallization and melting. The metal flows through matrices with nozzles shaped to the desired profile section. Hot extrusion has a much wider range of applications than cold extrusion. Unless otherwise specified, the term "extrusion" generally refers to the hot extrusion process.