Types of Rolling Operations

Definition

Rolling is a metal forming process in which metal stock is passed through one or more pairs of rollers to reduce thickness, make the thickness uniform, or impart a desired mechanical property and surface finish. It is the most widely used metal-forming process in industrial manufacturing.

Main Content

1. Flat Rolling

• This is the most basic form of rolling, where the metal stock is passed between two cylindrical rolls rotating in opposite directions.
• The primary goal is to reduce the thickness of the workpiece while slightly increasing its length and width.

2. Shape Rolling

• Unlike flat rolling, the rolls used in shape rolling have grooves or contours cut into them.
• This process is used to create structural shapes such as I-beams, channels, rails, and angles by deforming the cross-section of the metal.

3. Ring Rolling

• This is a specialized process used to increase the diameter of a ring-shaped workpiece.
• A smaller thick-walled ring is placed between two rolls; as they rotate, the wall thickness decreases, and the diameter of the ring increases.

Working / Process

1. Feed Preparation

• The raw metal (billet or slab) is prepared and usually heated to a high temperature (hot rolling) to increase ductility.
• The surfaces are cleaned to prevent defects from being pressed into the finished product.

2. Rolling Deformation

• The material is fed into the rotating rolls, which exert a compressive force (rolling pressure).
• The friction between the rolls and the metal pulls the material forward, causing the internal structure to deform and the dimensions to change.

       Force
         ↓
    [  Roll 1  ]
  –––––––––––––––––––  ← Workpiece
    [  Roll 2  ]
         ↑
       Force

Visual representation of material passing between two rolls

3. Cooling and Finishing

• After exiting the rollers, the material is cooled, which affects its final grain structure and strength.
• Final processes like shearing or coiling are performed to prepare the metal for distribution or further manufacturing.

Advantages / Applications

• High production rates and efficiency for large-scale manufacturing.
• Excellent control over the final dimensions and surface finish of the product.
• Used extensively in the construction industry for structural steel, in the automotive sector for car body panels, and for manufacturing railway tracks and metal foil.

Summary

Rolling operations involve passing metal through rotating rolls to alter its shape or reduce its thickness. It is categorized into flat, shape, and ring rolling based on the desired geometry of the final product. Key terms to remember include reduction, rolling pressure, ductility, and cross-section.