1. What is 20# seamless steel pipe?
20# seamless steel pipe is made of 20# steel, which has a slightly higher strength than 15# steel. It is rarely quenched and has no temper brittleness. It has high cold deformation plasticity and is generally used for bending, rolling, bending and hammering. It has good welding performance for arc welding and contact welding. It has a small thickness during gas welding and is prone to cracks on parts with strict appearance requirements or complex shapes.
2. 20# Material Standard
The material of 20# seamless steel pipe is: high-quality carbon structural steel
Grade: 20#
Standard: GB8162-2018, GB/T8163-2018, GB3087-2008, GB9948-2013, GB5310-2017
3. Chemical composition
Carbon C: 0.17%~0.20%
Silicon Si: 0.17%~0.37%
Manganese Mn: 0.35%~0.65%
Sulfur S: ≤0.035%
Phosphorus P: ≤0.035%
Chromium Cr: ≤0.25%
Nickel Ni: ≤0.25%
Copper Cu: ≤0.25%
4. Introduction to mechanical properties
Tensile strength σb (MPa): ≥410 (42)
Yield strength σs (MPa): ≥245 (25)
Elongation δ (%): ≥25
Sectional shrinkage ψ (%): ≥5,
5. What are the process flows?
Hot rolling (extruded seamless steel pipe): round tube billet → heating → perforation → three-roller oblique rolling, continuous rolling or extrusion → tube removal → sizing (or reducing diameter) → cooling → billet tube → straightening → quality inspection of wall thickness → water pressure test (or flaw detection) → marking → 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 tube → heat treatment → straightening → quality inspection of wall thickness → water pressure test (flaw detection) → marking → storage.
