Curved tubing is becoming increasingly popular in building design, and the introduction of a new grade of tubing may increase its usefulness.
As you know, HSS refers to hollow structural sections – round, square and rectangular. A new HSS specification, ASTM A1085, was announced at the North American Steel Construction Conference (NASCC) in St. Louis on April 16, 2013.
The new grade will have a more consistent wall thickness: previous specifications allowed 10% variation; the new standard is 5%. The corner radii will be larger. (Engineers joked that the developers of the new standards were trying to make the square and rectangular tubes round.) The new material has a defined upper and lower yield stress which will make it better-suited for seismic applications. Finally, having standard requirements for Charpy notch toughness will make it more suitable for dynamic loading as in bridge applications.
In summary, the new spec should make HSS more economical and more efficient. Read more on this new steel specification.
From the viewpoint of a bender/roller who will be curving this new material, greater consistence in the raw material should lead to greater consistency in the curved members. To a greater degree than previously, each straight piece should roll more similarly than the last. And that contributes to productivity and reduced costs.
Some tube mills plan on producing this product. It will be interesting to see which other mills follow and which service centers stock it.