Contradictions between small-section steel materials and procurement
Thread Content
When steel sections are used in environments with temperatures exceeding 350 degrees, Q345 or a higher-grade material is required. However, small-section steel sections often use only Q235; for example, angle bars with a side length of 100 millimeters or less, channel bars of grade 20 or lower, and I-beams of the same grade 20. It is often difficult to find Q345 material on the market. How do you address this issue? One can’t just use steel plates welded together as a substitute for shaped steel, right? The amount used is relatively small, what should I do?
If the amount used is small, it is recommended to use steel plates for assembly; angle iron can also be made by bending and pressing steel plates. If angle iron is used for assembly, it is best to choose a design that results in minimal welding deformation, with as small weld angles as possible, and it may be preferable to use a T-shaped structure.
It’s very difficult to do this on-site; the necessary equipment may not even be available, and it’s hard to ensure the quality of welding
There may be no bending equipment on site, but a small factory nearby can be found to bend the angle steel. Plate welding structures are also feasible. Welding Q345 is not difficult; it is only necessary to control the welding process in order to minimize welding deformation. Support components that must withstand high temperatures typically use plate welding structures.
Welding is also no problem, as long as welding deformation is well controlled; if necessary, post-weld correction can be carried out.
Replacing angle steel structures with T-shaped steel is better in terms of assembly and control of welding deformation.
Of course, if the structure permits, it is better to use a bent form.
What are the quality acceptance standards for steel sections formed by welding steel plates together, or for steel sections created by bending steel plates into angle shapes?
For the dimensional tolerances of welded or bent steel sections, if control is required, they can be inspected in accordance with the dimensional tolerance standards for rolled steel sections. For ordinary welded parts, surface non-destructive testing of the welds is sufficient. For special cases, the designer shall specify specific acceptance requirements based on the operating conditions.
If dimensional tolerances are based on hot rolling, the standards are likely to be too high. For welded structures, it’s very difficult to achieve such high precision; this leads to higher costs and creates problems