The art of designing smarter crane booms

Benefits of Strenx^® Tube 700QLH and hot-finished hollow sections

Everywhere around us, you’ll find structural hollow sections in various applications. In fact, they are one of the most common forms of steel product used. Sectors like construction, transportation, lifting, agriculture, energy and recycling are typical examples where structural hollow sections play an essential role in our daily life. Hollow sections come in different shapes, sizes, steel grades and wall thicknesses. They are manufactured by either cold or hot forming, and come seamless or welded. Different manufacturing methods result in various types of hollow section products, even if the dimensions and yield strength are exactly same.

Hot-finished welded hollow sections combine some of the best characteristics of both cold formed and seamless tubes in a unique way. Our Strenx^® Tube 700QLH hollow sections are made of steel strip, which is roll formed to a circular shape and then continuously seam welded. Using Strenx^® steel strip as a raw base material results in an extremely low variation in steel thickness tolerance, both from tube-to-tube and particularly the tube’s circumference. Unlike cold-formed welded tubes yet similar to hot-formed seamless tube properties, Strenx^® welded and hot-finished QLH tubes do not have any residual stresses thanks to a subsequent heat treatment process. This is a huge benefit in the workshop.

Strenx^® Tube 700QLH hot-finished hollow sections are made of SSAB’s own high-performance steel. Thanks to its advanced metallurgy, hollow sections offer good weldability and machinability along with an excellent combination of mechanical properties. With a minimum yield strength of 700 MPa (100 ksi) and elongation A5 minimum 14%, this makes them ideal for a wide range of applications. Our hot-finished hollow sections deliver exceptional impact toughness at low temperatures: 40 J at -40°C. This means that Strenx^® products perform reliably when they’re needed the most.

Strenx^® Tube 700QLH hot-finished hollow sections are delivered in tempered condition, so they are allowed to be used in load-bearing structures. This brings great benefits in lifting applications, such as cranes, where high strength combined with low weight is essential.

How Strenx^® steel helps cranes extend reach while maintaining strength

By using higher strength steel, you can increase the lifting capacity of a crane without increasing the overall boom weight. Or, using a higher strength steel within the boom section gives a design engineer the possibility to use a thinner steel section without compromising the crane’s lifting capacity. This reduces the weight of the boom section, allowing you to increase the overall reach of the boom. Using high-strength steels is possible as long as the standards and design parameters for cranes are met, especially taking into account any deflection limitations.

For many years, Strenx^® Tube 700QLH hot-finished hollow sections have been successfully used in lattice boom sections in state-of-the-art cranes. Their high strength, good weldability, dimensional accuracy and surface quality have benefitted customers around the world – not only for their ability to improve the design of crane booms, delivering end user benefits, but also increased boom manufacturing efficiencies. Strenx^® Tube 700QLH hot-finished hollow sections are available in many different diameters and wall thicknesses. Tailor-made wall thicknesses are also available upon request. This offers design engineers the flexibility to choose the optimal section needed, while minimizing boom weight. And as an extra bonus, less steel needs to be purchased.

For available dimensions and delivery conditions in your area, contact SSAB sales.