How to distinguish between steel structure materials and structures, steel types and specifications?
According to the use can be divided into: structural steel, tool steel and special steel;According to smelting method can be divided into: converter steel and peace furnace steel;According to deoxidization methods can be divided into: boiling steel (F), semi killed steel (b), killed steel (Z) and special sedation steel (TZ), calm steel and special calm steel code can be omitted;According to the forming method can be divided into: rolled steel (hot rolling, Leng Zha), forged steel and cast steel;According to the chemical composition can be divided into: carbon steel and alloy steel.
Carbon structural steelAccording to the current national standard "carbon structural steel" (GB700) regulations, numerical grade carbon steel structural yield point represented by the letters Q, yield point (N/mm2), the quality grade of symbols and symbol deoxidization method four parts according to the order.Carbon structural steels are divided into five kinds: Q195, Q215, Q235, Q255 and Q275. The greater the yield strength, the greater the carbon content, strength and hardness of the carbon structure, the lower the plasticity. Among them, Q235 in use, processing and welding performance is better, is one of the steel commonly used in steel structure.Quality grade is divided into A, B, C, D four, from A to D that quality from low to high. Different quality grades of steel require different chemical composition and mechanical properties. A no impact on regulations, only in the cold test only when the carbon, silicon and manganese content can not as delivery conditions; the B level, C level and D level were required to ensure 20 C and 0 C, 20 C Charpy V notch impact energy is not less than 27J (longitudinal), were required to provide assurance of conformity of bending test, as well as carbon, manganese, silicon, sulfur and phosphorus content of warranty. When all steels are delivered, the supplier shall provide the quality assurance of mechanical properties such as yield point, ultimate strength and elongation.
Low alloy steels refer to steels whose total amount is less than 5% by adding one or more small amount of alloying elements during steelmaking. Low alloy steels have higher strength because they contain alloy elements. According to the current national standard "low alloy high strength structural steel" (GBT/l591) provisions, its brand and carbon structural steel grades of the same method, the commonly used low-alloy steel has Q345, Q390, Q420 and so on.The delivery of low alloy steel when the supplier should provide quality assurance of yield strength, ultimate strength, elongation and bending test of mechanical properties; to provide the content of chemical components of carbon, manganese, silicon, sulfur, phosphorus, vanadium, aluminum and iron quality.The quality grade of low alloy steel and carbon steel the same except A, B, C, D four grades, increased E level, which requires 40 DEG C when Charpy V notch power is not less than 27J (vertical). The requirements for the content of carbon, sulfur, phosphorus and aluminum in different quality grades are also different. The deoxidation method of low alloy steel is killed steel or special killed steel. Q345-B is a B grade killed steel with a yield strength of 345N / mm2; Q390 - D represents a D - grade special killed steel with a yield strength of 390N / mm2.
