20# seamless steel pipe is a high-quality steel pipe product. It is made of high-quality carbon structural steel material with high strength and excellent processing performance. The steel pipe is made into a rough pipe by perforation process, and then hot rolling, cold rolling or cold drawing are processed into finished products. 20# seamless steel pipe belongs to low-carbon steel pipe. Carbon steel can be divided into three categories according to carbon content: low-carbon steel, medium-carbon steel and high-carbon steel. The carbon content of 20# seamless steel pipe is low, and it is widely used in structural pipes, fluid pipes, low and medium pressure boiler pipes and other fields. If there is no special requirement, 20# seamless steel pipe is generally used.
20# seamless pipe is made of 20 steel and is a high-quality steel pipe product. The standards of 20# seamless pipe include GB/T8162-2008, GB/T8163-2008, GB3087-2008, GB6479-2000 and GB9948-2006, etc., which are widely used in the fields of transporting oil, natural gas, coal gas, water and certain solid materials. Compared with No. 15 steel, the strength of 20# seamless pipe is slightly higher, and it has higher cold deformation plasticity, which is suitable for processing technologies such as bending, rolling, bending and hammering. The welding performance of 20# seamless pipe is good, which is suitable for processes such as arc welding and contact welding. The thickness is small during gas welding, and it can be used to manufacture parts with strict appearance requirements or complex shapes. In addition, the cutting processability of 20# seamless pipe is also good, which is suitable for manufacturing products with low force but high toughness requirements. Its hardness is slightly lower than that of 45# seamless steel pipe.
The chemical composition of 20# seamless pipe includes elements such as carbon, silicon, manganese, sulfur, phosphorus, chromium, nickel and copper. Among them, 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 contents are not higher than 0.035, and the chromium, nickel and copper contents are not higher than 0.25.
The mechanical properties of 20# seamless pipe are also relatively good. Its tensile strength σb (MPa) is not less than 410 (42), yield strength σs (MPa) is not less than 245 (25), elongation δ5 (%) is not less than 25, and cross-sectional shrinkage ψ (%) is not less than 5. The hardness does not exceed 156HB without heat treatment, and the sample size is 25mm. It can be seen that 20# seamless pipe is a high-quality steel pipe product with high strength and toughness, which is widely used in various fields.
Heat treatment specifications are the key to ensuring the quality of 20# seamless pipe. According to the specifications, the normalizing temperature should be 910℃, and air cooling is required. In addition, the metallographic structure should include ferrite and pearlite. In terms of delivery status, 20# seamless pipe can be selected as non-heat treated or heat treated (annealing, normalizing or high temperature tempering) state. However, it is necessary to indicate in the contract that the heat treated state is required for delivery, otherwise it will be treated as non-heat treated delivery. The formula for calculating the weight of 20# seamless pipe is [(outer diameter-wall thickness)*wall thickness]*0.02466=kg/meter (meter weight). In terms of process flow, the process flow of sanitary mirror pipe and industrial pipe is roughly the same, including tube blank inspection, peeling, heating, perforation, pickling, grinding, lubrication and air drying, welding head, cold drawing, solution treatment, pickling and passivation, inspection, cold rolling, degreasing, cutting, air drying, internal and external polishing, marking and finished product packaging. Strict implementation of the above specifications and process flow will ensure the quality and performance of 20# seamless pipe.
