Square and rectangular tube, also known as square and rectangular cold-formed hollow steel, referred to as square tube and rectangular tube, codenamed F and J respectively.

1. The allowable deviation of the wall thickness of the square and rectangular pipe shall not exceed plus or minus 10% of the nominal wall thickness when the wall thickness is not greater than 10mm, and shall be plus or minus 8% of the wall thickness when the wall thickness is greater than 10mm. Except for wall thickness.

2. The usual delivery length of the square tube is 4000mm-12000mm, mostly 6000mm and 12000mm. The square rectangular tube is allowed to deliver short-length and non-fixed-length products not less than 2000mm, and it can also be delivered in the form of an interface tube, but the buyer should cut off the interface tube when using it. The weight of short-length and non-fixed-length products shall not exceed 5% of the total delivery quantity, and for square and rectangular pipes with a theoretical weight greater than 20kg/m, shall not exceed 10% of the total delivery quantity

3. The curvature of the square tube shall not be greater than 2mm per meter, and the total curvature shall not be greater than 0.2% of the total length.