Low alloy steel pipe is: low alloy high strength structural steel: carbon content is 0.1% - 0.25%, adding main alloy elements such as manganese, silicon, vanadium, niobium and titanium; Its total alloy content is less than 3%. According to the strength, it is divided into four levels: 300, 350, 400 and 450MPa. There are mainly q295, Q345, Q390, Q420 and Q460 "Q" is the Chinese Pinyin capital prefix of the yielding "Qu", and the subsequent number is the minimum yield point of the brand（ σ s) The subsequent symbols are divided into a, B, C and d according to the content of impurity elements (sulfur and phosphorus) in the steel from high to low and with the change of carbon and manganese elements. Among them, Grade A and B steels are usually called 16Mn Chemical composition of 16Mn low alloy steel pipe: C：0.12~0.20； Mn:1.20~1.60； Si:0.20~0.55； Tensile strength: 470 ~ 660 n / mm2; Yield strength: 275 ~ 345 n / mm2; Elongation: 21%. The specific value shall be based on the thickness or diameter of steel. The thickness or diameter of steel corresponding to the above data is 16 ~ 100mm Application of 16Mn low alloy steel pipe: The special steel for bridge is "16Mnq", the special steel for automobile girder is "16MnL", and the special steel for pressure vessel is "16MnR". 16Mn low alloy steel pipe standard: Seamless steel pipe for chemical fertilizer (gb8179-1999) 16Mn low alloy steel pipe specification: 32mm -- 426mm hot expanded non-standard steel pipe