What are the properties of high-quality carbon steel 20# seamless steel pipe

20# seamless steel pipe is a high-quality steel pipe product made of high-quality carbon structural steel, possessing high strength and excellent processing performance. 20# seamless steel pipe is produced by piercing to form a rough tube, followed by hot rolling, cold rolling, or cold drawing to create the finished product. 20# seamless steel pipe belongs to low-carbon steel pipe. Carbon steel is classified into low-carbon steel, medium-carbon steel, and high-carbon steel based on carbon content. 20# seamless steel pipe has a relatively low carbon content and is widely used in structural pipes, fluid pipes, and low- and medium-pressure boiler tubes. Unless otherwise specified, 20# seamless steel pipe is generally used.

20# seamless steel pipe is made of 20 steel and is a high-quality seamless steel pipe product. Standards for 20# seamless steel pipes include GB/T8162-2008, GB/T8163-2008, GB3087-2008, GB6479-2000, and GB9948-2006, etc., and they are widely used in the transportation of oil, natural gas, coal gas, water, and certain solid materials. Compared with 15# steel, 20# seamless steel pipes have slightly higher strength and higher cold deformation plasticity, making them suitable for bending, rolling, flanging, and hammering processes. 20# seamless steel pipes have good weldability, suitable for arc welding and contact welding processes. When gas welding, they are suitable for thinner sections and can be used to manufacture parts with strict shape requirements or complex shapes. Furthermore, 20# seamless steel pipes also have good machinability, making them suitable for manufacturing products with low stress but high toughness requirements. Their hardness is slightly lower than that of 45# seamless steel pipes.

The chemical composition of 20# seamless steel pipes includes elements such as carbon, silicon, manganese, sulfur, phosphorus, chromium, nickel, and copper. The carbon content is 0.17–0.24%, the silicon content is 0.17–0.37%, the manganese content is 0.35–0.65%, the sulfur and phosphorus content are both no higher than 0.035%, and the chromium, nickel, and copper content are all no higher than 0.25%.

The mechanical properties of 20# seamless steel pipe are also quite good. The tensile strength σb (MPa) of 20# seamless steel pipe is not less than 410 (42), the yield strength σs (MPa) is not less than 245 (25), the elongation δ5 (%) is not less than 25, and the reduction of area ψ (%) is not less than 5. The hardness without heat treatment does not exceed 156HB, and the sample size is 25mm. Therefore, 20# seamless steel pipe is a high-quality steel pipe product with high strength and toughness, widely used in various fields.

The heat treatment specification is the key to ensuring the quality of 20# seamless steel pipe. According to the specification, the normalizing temperature should be 910℃, and air cooling is required. Furthermore, the metallographic structure should include ferrite and pearlite. Regarding delivery condition, 20# seamless steel pipes can be delivered in either untreated or heat-treated (annealed, normalized, or high-temperature tempered) condition. However, the contract must specify that the 20# seamless steel pipes must be delivered in a heat-treated condition; otherwise, they will be delivered untreated. The formula for calculating the weight of 20# seamless steel pipes is [(outer diameter - wall thickness) wall thickness] 0.02466 = kg/meter (weight per meter). In terms of the manufacturing process, the processes for sanitary mirror-finish pipes and industrial pipes are largely the same, including billet inspection, peeling, heating, piercing, pickling, grinding, lubrication and drying, welding, cold drawing, solution treatment, pickling and passivation, inspection, cold rolling, degreasing, cutting, drying, internal and external polishing, marking, and finished product packaging. Strict adherence to the above specifications and processes will ensure the quality and performance of the 20# seamless steel pipes.