Twinned Steel

What is twinned steel?

Twinned steel is a unique type of steel that exhibits a twinning phenomenon, where regions of the crystal lattice are mirrored or “twinned” across specific planes. This twinning leads to distinct mechanical properties, such as enhanced strength, toughness, and ductility, making it highly desirable for various industrial applications.

The origin of twinned steel can be traced back to the early 20th century when researchers discovered that certain metallic alloys could undergo deformation twinning under specific conditions. However, the precise understanding and controlled production of twinned steel took further materials science and metallurgy advancements.

Production of twinned steel has continued to evolve, with modern techniques focusing on controlled alloy compositions, heat treatment processes, and advanced characterisation methods. Today, twinned steel remains an intriguing area of research and valuable material for industrial applications requiring high strength and toughness.

Steelwork

When it comes to constructing a structural steel project, sometimes a single beam or column just won’t suffice. There are instances where the height of a room presents restrictions. For example, limited vertical space may not accommodate a deep beam in a loft or a basement. When a single beam or column falls short in size or length or space constraints come into play, twinning becomes an advantageous alternative.

By combining two smaller beams, which can be easily manufactured and transported, structural engineers can create a composite beam that possesses the required strength and dimensions. These beams are connected through welding or bolting, ensuring a secure and seamless joint. This technique allows for a more flexible and efficient design process, accommodating specific project requirements.

Similarly, twinning can be applied to columns or parallel flange channels, enabling the construction of larger and sturdier support structures. The use of twinned steel enhances load-bearing capacity and provides versatility in adapting to architectural designs that necessitate unconventional heights or space utilisation. Moreover, the composite nature of twinned steel enhances structural performance by redistributing forces, resulting in improved load resistance and durability. This construction method offers an economical solution by optimising material usage while maintaining structural integrity. 

Fabrication

To prevent the steel from buckling and to keep them stable, the two pieces need to be bolted together. One of the beams/columns/PFCs will usually have a joining mechanism welded to one of them.

Universal beams can be twinned with one another with a spacer, which is one of the more frequent mechanisms to join. It’s also usual to see universal beams twinned with a circular hollow section between them. An accurately measured PFC can act as a robust join that will sit snugly and provide some extra strong reinforcement. The same methods can apply to universal columns as well.

Parallel flange channels can be joined together with spacers, and due to the C shape of the channels, there is greater flexibility with how far the backs can be sat from each other. They can be very closely twinned together or have the distance of the entire spacer to separate them, depending on the brand. PFC twinning is usually done to give strength to walls where they need support above or around an opening.

Twinned steel is fabricated through a two-step process. First, by heating and slowly cooling the steel, a crystal structure creates twinning planes. In the second step, the steel is subjected to a plastic deformation process, such as rolling or drawing, which activates the twinning planes.

This leads to the formation of nanoscale twin boundaries within the steel, enhancing its strength and ductility. The twinning process allows for improved mechanical properties compared to conventional steel. The resulting twinned steel exhibits increased strength, higher energy absorption capacity, and improved resistance to deformation.

See for yourself

Have a look at some of the fantastic projects we have created for our clients here.