Structural seamless pipe

Structural seamless pipe (GB/T8162-2008) is a kind of seamless steel pipe used for general structure and mechanical structure. The fluid seamless steel pipe standard applies to seamless steel pipes that transport fluids.

In addition to carbon (C) elements and a certain amount of silicon (Si) (generally no more than 0.40%) and manganese (Mn) (generally no more than 0.80%, higher up to 1.20%) alloy elements for deoxidation, structural steel pipes , without other alloying elements (except residual elements).

Such structural steel pipes must guarantee both chemical composition and mechanical properties. The content of sulfur (S) and phosphorus (P) impurity elements is generally controlled below 0.035%. If it is controlled below 0.030%, it is called high-grade high-quality steel, and “A” should be added after its grade, such as 20A; if P is controlled below 0.025% and S is below 0.020%, it is called super high-quality structural steel pipe, and its grade should be followed by Add “E” to distinguish. For other residual alloying elements brought into structural steel pipes from raw materials, the content of chromium (Cr), nickel (Ni), copper (Cu), etc. is generally controlled at Cr≤0.25%, Ni≤0.30%, Cu≤0.25%. Some grades of manganese (Mn) content reach 1.40%, called manganese steel.

The difference between structural seamless pipe and fluid seamless pipe:

The main difference between it and the structural seamless steel pipe is that the fluid seamless steel pipe is subjected to hydraulic test one by one or ultrasonic, eddy current and magnetic flux leakage inspection. Therefore, in the standard selection of pressure pipeline steel pipes, fluid seamless steel pipes should not be used. The representation method of seamless steel pipe is outer diameter, wall thickness, and thick-walled seamless steel pipe is mainly used for machining, coal mine, hydraulic steel, and other purposes. The material of thick-walled seamless steel pipe is divided into 10#, 20#, 35#, 45#, 16Mn, 27SiMn, 12Cr1MoV, 10CrMo910, 15CrMo, 35CrMo and so on.

Structural stainless steel seamless pipe (GB/T14975-1994) is a hot-rolled (extruded, expansion) and cold drawn (rolled) seamless steel pipes.

Due to their different manufacturing processes, seamless steel pipes are divided into hot-rolled (extruded) seamless steel pipes and cold-drawn (rolled) seamless steel pipes. Cold drawn (rolled) tubes are divided into two types: round tubes and special-shaped tubes.

Process flow overview:
Hot rolling (extruded seamless steel pipe): round tube billet → heating → perforation → three-roller skew rolling, continuous rolling or extrusion → tube removal → sizing (or diameter reduction) → cooling → billet tube → straightening → water pressure Test (or flaw detection) → mark → storage.

Cold drawn (rolled) seamless steel pipe: round tube billet → heating → perforation → heading → annealing → pickling → oiling (copper plating) → multi-pass cold drawing (cold rolling) → billet → heat treatment → straightening → Hydraulic test (flaw detection)→marking→warehousing.