Even though the automotive industry shapes people’s thought of Usa manufacturing, and metal manufacturing especially, 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 methods to reduce the volume of seamless steel pipe a structure needs, in addition to reduce on-site erection time. One design avenue that has been far more popular within the past two decades is to utilize options to the regular wide-flange beam.
These beams have become an effective building material of choice. But when it comes to strength, the shape of the wide-flange beam pre-sents difficult. It can span merely a certain distance (or “unbraced length”) before requiring support. From the purely strength perspective, it will be far more efficient for beams to take on a circular, square, or rectangular shape, which would extend the maximum unbraced length. The more distance these structural members can span, the fewer braces and supports a building needs. Ultimately, this simply means 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 that provide inherently higher strength and may span greater lengths between braces. A square steel tube with a 3/16-in.-thick wall thickness has a allowable load of 79 kips spanning a column time period of 32 ft., while the same wide flange (ASTM designation of W12 x 40) has an allowable load of 64 kips on the same column length (see Figure 2).
For many years HSS have been utilized for their dramatic effect. Builders and architects have used these to make an artistic statement, not to save cash, and this remains true oftentimes today. But because HSS are so strong, architects can design buildings with less material. HSS also save money on finishing costs, because compared to hollow steel pipe, tubular sections have less area to color or fireproof. Combine this with the point that tube production costs have fallen lately, and building with HSS begins to make real economic sense. This is certainly one major reason that need for HSS has become rising considering that the recession, and it’s with this environment how the tube cutting laser is commencing to unlock new opportunities.
HSS represent a departure from many tube laser cutting applications that tend to work with relatively thin-walled workpieces. Shops providing HSS often must handle workpiece weights (called “stick weights”) approximately 2,000 pounds. These workpieces are not just long, but also large; 14-, 16-, and 20-in. diagonal cross sections aren’t uncommon.
To produce such large workpieces cost-effectively on the tube laser requires careful planning. It’s a lot more complicated than using a cutoff saw, it also adds a lot more value to the workpiece. Modern tube lasers have load/unload functions that may handle mill-length pipe and structural material.
This capability gives designers stainless steel seamless tube when it comes to designing for mated sections. Mating a round tube to a different one round tube seems simple, nevertheless the bevel required dexopky12 create a tight fit-up involving the two sections can be hugely complicated, especially when tubes are of several diameters or shapes, or if they intersect at unusual angles.
From an architectural engineering perspective, such angles may make the best transfer of loads and many efficient consumption of HSS. But for the welder and fabricator, such a complicated joint can be quite a nightmare.