Production of tubes and profiles out of high-strength steels
Light metal and composite materials are revolutionizing car body construction. The materials alone promise advantages in vehicle construction because of their low weight.
With 90 percent market share, steel still dominates the material battle of the coachbuilder. So-called "high-strength", "ultra-high-strength" or even "ultra-high-strength" steel grades offer so much potential for slimming down the bodywork that steel will continue to shape the car industry for a long time to come.
Body steel must meet very different requirements. For the passenger compartment, for example, the highest strength is required. In contrast, the material in the defined deformation zones in the front and rear of the vehicle must be so flexible that it can compensate for the energy at impact. No matter how different the requirement for the respective area is defined, for weight reasons, the steel used must be processed as thin as possible.
The different properties of the steel sheets are caused by variable amounts of carbon (between 0.01 and 2.06 percent) or by so-called "micro alloys". These micro alloys define the properties of the categories "high strength", "highest strength" or "ultra-high strength" in steel.
Low additions of niobium, titanium or vanadium increase the tensile and compressive strength of steel by up to four times in ultra-high-strength steel. That is, a one millimeter thick ultra-high strength steel component has the same strength against tension and compression, as the same part made of four millimeters thick conventional steel.
Ever since crash safety has become a top priority for manufacturers, ultra-high-strength steel has become the material of choice for components such as bumper reinforcements, side impact beams, seat frames and mechanisms, and chassis components. Using this material, the weight of the components has been reduced by up to 40 percent, costs reduced, production efficiency increased and a variety of innovations developed that would not have been possible in the past.
Forming high-strength steel sheets into tubes in a continuous tube production process using dual-phase materials creates high stresses in the tube. If these tubes are cut, the diameter stability decreases and the diameter increases.
weil technology relies on a roll-forming technique that allows the material to be formed with a roundness of ± 0.125 mm and laser welded with a longitudinal seam. With a cycle time of 24 sec, monitoring of the welding quality and automated ejection of the good and bad parts, it is possible to produce structural tubes for the automotive industry or instrument carriers with high roundness and rigidity: Material: spring steel, wall thickness 1.2 mm, tube length 2,000 mm, Ø 70 mm.
weil technology offers an alternative with a flexible, highly productive investment concept (Tubestar) at the point where the processing of high-strength steels becomes technically disadvantageous in a continuous pipe production process. Low tool changeover times and costs, lower scrap costs when setting up the system and high process reliability (welding sensor) make it possible to compensate for cycle time disadvantages compared to Conti systems.
Dual phase steels combine all the positive properties of stronger steel in a thinner and weight-saving version.