Although the automotive industry shapes people’s perception of U.S. manufacturing, and metal manufacturing specifically, it isn’t the nation’s largest consumer of metal-not from a long shot. It’s commercial construction.
To lower cost, builders have trusted design solutions to reduce the quantity of stainless steel seamless tube a structure needs, as well as to reduce on-site erection time. One design avenue that has become far more popular throughout the past two decades has become to utilize choices to the standard wide-flange beam.
These beams have evolved into a reliable building material of preference. But when it comes to strength, the contour from the wide-flange beam pre-sents an issue. It might span merely a certain distance (or “unbraced length”) before requiring support. From a purely strength perspective, it might be far more efficient for beams to consider a circular, square, or rectangular shape, which would extend the utmost unbraced length. The more distance these structural members can span, the fewer braces and supports a building needs. Ultimately, what this means is builders are able to use less of what’s often their biggest expense: the structural metal itself.
Enter hollow structural sections, or HSS (see Figure 1). These round, rectangular, or square tubes have shapes which provide inherently higher strength and may span greater lengths between braces. A square steel tube using a 3/16-in.-thick wall thickness has a allowable load of 79 kips spanning a column duration of 32 ft., while the same wide flange (ASTM designation of W12 x 40) has an allowable load of 64 kips over the same column length (see Figure 2).
For years HSS have already been used for their dramatic effect. Builders and architects have used those to make an artistic statement, not to save money, and this remains true on many occasions today. But because HSS are so strong, architects can design buildings with less material. HSS also save on finishing costs, because in comparison to hollow section steel, tubular sections have less surface area to paint or fireproof. Combine this with the truth that tube production costs have fallen lately, and building with HSS starts to make real economic sense. This is one major reason that requirement for HSS continues to be going up since the recession, and it’s in this environment that the tube cutting laser is commencing to unlock new opportunities.
HSS represent a departure from many tube laser cutting applications that tend to do business with relatively thin-walled workpieces. Shops providing HSS often must deal with workpiece weights (called “stick weights”) approximately 2,000 pounds. These workpieces are not only long, but also large; 14-, 16-, and 20-in. diagonal cross sections aren’t uncommon.
To create such large workpieces cost-effectively on a tube laser requires meticulous planning. It’s a lot more complicated than employing a cutoff saw, additionally it adds far more value for the workpiece. Modern tube lasers have load/unload functions that could handle mill-length pipe and structural material.
This capability gives designers seamless steel pipe with regards to designing for mated sections. Mating a round tube to a different one round tube seems simple, however the bevel required dexopky12 develop a tight fit-up in between the two sections can be hugely complicated, especially when tubes are of several diameters or shapes, or maybe if they intersect at unusual angles.
From an architectural engineering perspective, such angles may produce the best transfer of loads and the majority of efficient use of HSS. But to the welder and fabricator, such a complicated joint might be a nightmare.