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Knowledge of development trend of square tube

Knowledge of development trend of square tube

December 9,2022
Square tube is a kind of hollow square section shape steel tube, also known as square tube, rectangular tube. Its specification is expressed in mm of outer diameter * wall thickness. It is made of hot rolled steel strip by cold rolling or cold drawing.
Use of seamless square pipe:
Seamless square and yuantai rectangular tube are widely used. It is commonly used to manufacture structural parts and mechanical parts, such as oil drill pipe, automobile transmission shaft, bicycle frame and steel scaffolding used in construction, which are made of high-quality carbon structural steel by hot rolling or cold drawing, and are mainly used as pipes or structural parts to transport fluids.
Type of seamless rectangular tube:
1. According to the material, it can be divided into ordinary carbon structure steel and low alloy high strength structural steel. The carbon content of the former shall not exceed 4.5%; sulfur ≤ 0.035; phosphorus ≤ 0.005; chromium ≤ 0.15; nickel content<0.25; copper ≤ 0.30; The latter contains a small amount of silicon, manganese and vanadium in addition to carbon, sulfur, phosphorus and chromium.
2. According to surface quality:
(1) Finish:
1 The internal and external surfaces of the seamless square tube shall be smooth and flat without bubbles and wrinkles.
2 When the internal surface area is less than 100 mm2, the allowable tolerance of the internal surface area is ± 0.2 mm.
3 When the internal surface area is greater than 100 mm2, the allowable tolerance of the internal surface area is ± 0.5 mm.
4 No cracks or folds are allowed on the inner surface; 5 There shall be no scar 6 No obvious scratch and bruise marks.
(2) Flatness:
1 The internal and external surfaces of seamless square tubes shall be flat and smooth.
2 There should be no obvious unevenness when observed with a 10X magnifying glass.
3 The end face of the nozzle is perpendicular to the centerline of the pipe.
4 The end face of pipe orifice shall be free of burrs.
5 There shall be no wrinkle at the bend of the pipe.
6 Both ends of the pipe shall be parallel.
7 No obvious bulge is allowed at the weld after rust removal.
8 There should be no obvious pits.
9 No defects affecting the use are allowed.
10 When the plate rolling machine is used for welding, the fillet radius at the weld shall not be less than the thickness of the base metal.
(3) Dimensional accuracy:
1 The roundness error shall not exceed the maximum deviation specified in the corresponding standard by more than 2 mm/m2.
2 The straightness and angle deviation shall not exceed 1/20 of the maximum deviation specified in the corresponding standard.
3 The limit deviation of length shall not be greater than 1.5 times of the corresponding specified value.

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