Telescopic cranes stronger and lighter at the same time

Any mobile telescopic crane is a compromise between lifting weight, height and reach, not to mention all-up weight. High-strength steel with hybrid laser-arc welding gives a stronger boom, able to lift greater weights higher and further, without increasing the weight of the vehicle.
Hybrid laser-arc welding performed at OCAS

A producer of mobile telescopic cranes wanted to find ways of increasing the reach and capacity. At the same time, he wanted to reduce the all-up weight of the vehicle, so as to use less energy during transport.

"The only way to achieve greater strength with lower weight is to use high-strength steel," says Christoph Gerritsen, Research Engineer Welding at OCAS. "Because it is stronger, you can reduce the weight by using thinner steel. But since the boom sections have to fit closely into one another and slide in and out smoothly, the welding has to be even more precise, with the weld bead being kept as small as possible. Furthermore, deformation and weakening of the steel in the heat affected zone must be reduced to the absolute minimum, in order to preserve the strength of the boom. The obvious solution to these requirements is hybrid laser-arc welding."

Section of a hybrid weld

We know welding matters

"We carried out welding tests on various kinds of high-strength steel in order to find the optimum combination of welding process and type of steel, including optimisation of the microstructure and mechanical properties of the steel. We also took the safety-critical standards for mobile cranes into account in our research."

"Hybrid laser-arc welding is more suitable for this application than either arc welding or laser welding. The welding speed can be much higher, with corresponding benefits for productivity. Moreover, less filler is needed than with arc welding, which makes the bead smaller and requires less heat input. And the process is much more tolerant to joint fit-up variations than laser welding, whilst maintaining its deep penetration. Our research enabled the customer to build mobile telescopic cranes that can lift heavier loads, with a greater reach, while weighing less overall."