Welded connections The welding of structural weathering steels is similar to that of conventional structural steels, but such steels generally have higher CEV levels, which need to be considered when defining preheat levels. Note that Corus has recently developed a lower CEV weathering steel through the normalised rolled process route, details of which are included on page 13 of this brochure. For weathering steels, electrodes of matching chemical composition to the parent metal should be used for the capping runs of multi-run fillet and butt welds. However, conventional C-Mn electrodes may be used for the body of such welds. Conventional C-Mn electrodes may also be used for butt welds with a single run each side, and single run fillet welds of up to 8mm leg length, as there is sufficient dilution of the alloying elements from the parent metal in the weld pool to give the required corrosion resistance. For further details see references 9 and 10. One final aspect to consider on welded connections is that all joints, including fillet welds, should be continuously welded to avoid moisture and corrosion traps such as crevices. Bolted connections Weathering grade HSFG bolts, nuts and washers with chemical compositions complying with ASTM A325, Type 3, Grade A, or equivalent, should be used for all bolted joints. ‘Load-indicating’ washers should not be specified, as they are not readily available in weathering grades and would create crevices with the consequent risk of corrosion. Hence, other forms of tightening such as the ‘part-turn’ method should be used. Note that for the design of such bolted connections, the slip factor may be taken as that for conventional structural steel. Bolted connections inevitably introduce overlapping plates and the potential problem of crevices. However, careful detailing of the joint by adopting the following guidance will avoid the subsequent corrosion risks associated with crevices.
• Ensure good fit-up using flexible cover plates.
• Max. bolt spacing adjacent to an edge = 14t, but not > 180mm.
• Max. edge distance from bolt centreline = 8t, but not > 130mm. (Where t is the thickness of the thinner plate).
If this guidance cannot be met, the edges of the joint should be protected by a suitable sealant. Surface preparation Abrasive blast cleaning to a minimum standard of Sa2, should be carried out after fabrication and prior to delivery on site, to assist with the formation of a uniform rust 'patina'. The use of paint, wax, or crayon etc. for marking steelwork during fabrication and erection should be avoided, as these are difficult to remove, and will interfere with the weathering process. Installation Care should be taken on site with both storage and handling of the steelwork such that the developing rust ‘patina’ is not damaged. Although the ‘patina’ will re-form, it will appear nonuniform until that time. In addition, grout runs from deck concrete operations should be avoided, as they will adversely affect the steelwork, which may necessitate a final blast cleaning after site erection. During construction, piers and abutments should be protected from rust staining as the ‘patina’ forms by wrapping them in protective sheeting until the final construction inspection is made.
Fabrication and installation of weathering steel
Carbon Steel, Corten Steel, Stainless steel
Rust, Bare, Powder Coated, Polished, Black Heat-resisting Paint, Iron Oxide
Diameter : 320mm--1200mm
Thickness : 1.2mm--3.0mm
Inside : Anti-wear foam paper
Outside : Plywood box
Free (without any condition)
OEM & ODM
Customized service is available.