Seamless steel pipes for structural use are seamless steel pipes for general structure and mechanical structure.Used for manufacturing pipelines, containers, equipment, fittings and mechanical structures.The main grades of steel pipes are 10, 20, 35, 45, Q345, 15CrMo, 12Cr1MoV, A53A, A53B, SA53A,SA53B,etc.
Classification: seamless steel pipes for structure can be divided into carbon steel pipes and low alloy steel pipes with high strength according to the material.
1.Carbon steel pipes:
Carbon steel pipes are generally smelted by converter or open hearth furnace, and its main raw material is molten iron plus scrap steel. The content of sulfur and phosphorus in steel is higher than that of high-quality carbon structural steel pipes, with general sulfur ≤0.050% and Phosphorus ≤0.045%.The content of other alloy-elements, such as chromium, nickel and copper, brought into the steel by raw materials generally does not exceed 0.30%. According to the composition and performance requirements, the steel grades of such structural steel pipes are Q195, Q215A, Q215B, Q235A, Q235B, Q235C, Q235D, Q255A,Q255B,Q275 and other steel grades.
Note :”Q” is the Chinese phonetic capital character of “qu”in yield strength, followed by the number of the minimum yield points value of the brand, followed by the symbol of the steel impurities (sulfur, phosphorus) from high to low content with carbon, can be divided into four grades: A, B, C and D.
Carbon steel pipe is the largest in output and has a wide range of uses. It is mainly used in building structures such as workshops, bridges, ships and general pipelines for conveying fluids.This kind of steel is generally used directly without heat treatment.
2.Low alloy high strength steel pipes:
In addition to some basic elements of silicon or manganese, low alloy high strength steel pipes also contain other elements suitable for China’s resources.Such as vanadium (V), niobium (Nb), titanium (Ti), aluminum (Al), molybdenum (Mo), nitrogen (N), and rare earth (RE) trace elements.According to the chemical composition and performance requirements, the steel grades are Q295A, Q295B, Q345A,Q345B, Q345C, Q345D, Q345E, Q390A, Q390B, Q390C, Q390D, Q390E, Q420A, Q420B, Q420C, Q420D, Q420E,Q460C, Q460D, Q460E and other steel grades, which have the same meaning as carbon steel tubes.
In the steel grades C, D and E,at least one of V, Nb, Ti, Al and other refined grain trace elements shall be contained in low alloy high strength steel pipes.In order to improve the performance of the steel, one of them can also be added into grade A and B .In addition, the content of Cr, Ni and Cu residual elements in such steel is no more than 0.30%.Q345A, Q345B, Q345C,Q345D and Q345E are the representative grades of this type of steel, among which grade A and B steel are usually called 16Mn.More than one trace elements shall be added to the steel pipes of grade C and above, and one low-temperature impact property test shall be added in the mechanical property test.
Compared with carbon steel pipes, low alloy steel pipes with high strength has the advantages of good comprehensive performance, long service life, wide application range and relatively economic.They are widely used in bridges, ships, boilers, vehicles and important building structures.
Application of structural steel pipes:
- Used for manufacturing seamless steelpipelines, containers, equipment, fittings and mechanical structures.
- Construction: hall structure, sea trestle structure, airport structure, dock, safety door frame, garage door, reinforced steel lining doors and windows, interior partition wall, cable bridge structure and expressway safety guard, railing, decoration, residence, decorative piping.
- Auto parts: automobile and bus manufacturing, transportation.
- Agriculture: agricultural equipment.
- Industry: machinery, solar energy support, offshore oil field, mining equipment, mechanical and electrical hardware, engineering, mining, heavy and resources, process engineering, material processing, machinery parts.
- Traffic: pedestrian railing, guardrail, square structure, guide sign, road equipment, fence.
- Logistics warehousing: supermarket shelves, furniture, school appliances.