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Stainless Steel Square Tubes EN 1.4301
Austenitic steels with designations 1.4301 and 1.4307 are the commonest stainless types and contain about 18% chromium and 9% nickel. The difference between the two grades is that in 1.4301, the maximum allowed carbon content is higher than for 1.4307 which can mean that 1.4301 has marginally higher strength. However, in critical situations, 1.4307 is the preferred alternative since corrosion resistance in the vicinity of the weld could be impaired for 1.4301.
In relation to the base steel, hollow sections of 1.4301/1.4307 are standardised in EN 10088-2 and 10088-4 while tolerances and section properties are as stipulated in EN 10219-2. Tibnor’s programme covers sections with width 15-400 mm, height 10-300 mm and thickness 1.2-12.5 mm. The starting material for manufacture of hollow sections is cold-or hot-finished strip (annealed and pickled, surface 1D or 2B) which is slit, shaped to a square or rectangular format and welded longitudinally. Welding methods vary, examples being plasma/TIG, laser or butt resistance welding. As a final operation, the appearance of the welded area is improved by grinding.
Grades 1.4301 and 1.4307 exhibit good resistance to corrosion in neutral water both indoors and outdoors. The steels are also fairly immune to atmospheric corrosion. However, they are less suitable if the environment is acidic or contains chlorides. In such instances, higher alloyed grades will be needed.
Both 1.4301 and 1.4307 are characterised by excellent formability and weldability so that if needed, welding, bending or other cold-forming of hollow sections is seldom an issue. Extensive testing guarantees weld quality so that risk for cracking in the vicinity of the weld in connection with bending or cold forming is minimal.
Hollow sections in grades 1.4301/1.4307 are offered with two surface executions: untreated with the welded area ground to remove oxide but the weld still completely visible, or with the entirety of the flat faces ground (grit 220, Ra 1.0-1.4 µm). Tolerances are stipulated in detail in EN 10219-2 but are at most ±0.6-1.0% for width and breadth (depending on dimension) and ±10% or ±0.5 mm for thickness. Straightness is good with the allowed height of arc at most 0.0015 times length.