In the rolling process and subsequent handling stages—such as cooling, transportation, and further processing—rolled products often develop bending or twisting deformation. These defects can arise from external forces, temperature variations, and internal stress redistribution during processing.
For long products whose length is much greater than their width or thickness, deformation of the longitudinal fibers is particularly noticeable. In wider products, such as strip or plate, transverse fiber deformation can also occur.
Typical examples include:
- Rails, sections, and pipes may develop arc-shaped bending.
- Structural sections such as I-beams may experience flange distortion, inward or outward spreading, and torsion.
- Plates and strips can show defects like longitudinal waves, transverse curvature, edge waves, dish-shaped deformation, or camber.
To remove these defects and obtain straight products, the longitudinal and transverse fibers must be restored from a curved state to a straight condition.
The process used to correct these deformations is called straightening, and the equipment used for this purpose is known as a straightening machine (also called a straightener).
Straightening machines are widely used in rolling mills and downstream processing lines to ensure that finished steel products meet dimensional and shape requirements.
Types of Straightening Machines
Because different steel products and deformation conditions require different correction methods, straightening machines are available in many forms. They can be classified according to working principle, application, and structural characteristics.
1. Classification by Working Principle
Based on how the deformation is corrected, straightening machines can be divided into several categories:
- Repeated Bending Straighteners
Examples include press straighteners and roller straightening machines, which repeatedly bend the material to eliminate residual curvature. - Rotary Bending Straighteners
Machines such as inclined-roll straighteners and rotary drum straighteners correct deformation through rotational bending action. - Stretch Straighteners
These machines apply tensile force to the material, including clamp-type stretch straighteners and continuous stretch straightening machines. - Stretch-Bending Straighteners
These combine tensile force with controlled bending to achieve higher straightening accuracy. - Casting Strand Straighteners
Used in continuous casting processes to straighten the solidifying strand.
2. Classification by Application
Different rolled products require specialized straightening equipment. Common application-based categories include:
- Section Straightening Machines
Used for structural sections such as beams and channels. - Plate Straightening Machines
Applied to steel plates using roller or stretch straightening methods. - Strip Straightening Machines
Often used in strip processing lines, including continuous stretch or stretch-bending systems. - Pipe and Bar Straightening Machines
Typical examples include inclined-roll straighteners and rotary drum straighteners. - Wire Straightening Machines
Used for wire products with rotary or combined vertical-horizontal roll arrangements. - Straighteners for Thin-Walled or Special-Shaped Tubes
- Continuous Casting Strand Straighteners
- Special-Purpose Straightening Machines
Designed for specific products such as corrugated plates, circular saw blades, or steel wire ropes.
3. Classification by Structural Characteristics
From a structural perspective, straightening machines commonly include:
- Press Straighteners
- Parallel Roller Straighteners (Roller Straightening Machines)
- Inclined-Roll Straighteners
- Rotary Drum Straighteners
- Stretch Straighteners
- Stretch-Bending Straighteners
- Casting Strand Straighteners
- Specialized Straighteners, such as planetary straighteners or translational straightening machines.
