![]() Since this specification notes that … “For square and rectangular tubing, the wall thickness requirements shall apply only to the centers of the flats” (which would not be construed as including a weld location), the amount of required through-thickness weld fusion is not specified. ASTM A500-13, however, only requires that … “The longitudinal butt joint of welded tubing shall be welded across its thickness in such a manner that the structural design strength of the tubing section is assured”. HSS manufacturers also generally concur that the longitudinal weld should fuse the HSS across the complete wall thickness. If all HSS faces are to be connected then shims, either side of the seam weld, could be employed.įigure 2: Lack of complete weld fusion through the HSS thickness This potential problem (where a splice plate cannot lie flat on the inside HSS surface due to a raised weld) can be overcome by the fabricator paying attention to the seam weld location and avoiding bolting to that wall, if not all four faces are to be connected. Sometimes the protruding inside weld flash may complicate the execution of a particular bolted connection, such as a splice connection using interior splice plates where the intention is to place the bolts in double shear (see Figure 1). Inside flash removal is most commonly stipulated for round HSS where one tube must fit snugly inside another (e.g. Some manufacturers are able to provide HSS with inside flash removal, but this needs to be requested and confirmed prior to production. However, welded tubing is normally furnished without removal of the inside flash, as noted by both A500 (ASTM, 2013a) and A1085 (ASTM, 2013b). The “flash” (protruding weld metal) of the longitudinal seam weld is always removed, during the manufacturing process, on the outside of HSS, thus making the exterior of the HSS surface smooth and flush. Both methods of HSS manufacture involve forming a closed section by continuous “welding”, using an induction heating process, without the use of any additional weld consumable. The static properties of these two HSS products have been compared by Sun and Packer (2014). Both production methods are used in North America, although the latter (continuous-forming) is much more common. The continuous-forming process includes: (1) roll-forming a coil strip first into a circular open tube (2) joining the edges of the open tube by welding to form a closed circular shape and (3) flattening the circular tube to form the desired rectangular shape. The cold-working in this case is concentrated at the four corners. The direct-forming process includes: (1) roll-forming a coil strip directly into an open section with the desired rectangular shape and (2) joining the edges of the open section by welding to form a closed rectangular shape. There are two principal manufacturing methods internationally for cold-forming square and rectangular HSS: direct-forming and continuous-forming. 1Bahen/Tanenbaum Professor of Civil Engineering, University of Toronto, Ontario, Canada
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