Q345 steel pipe is an alternative to several steel grades such as 12MnV, 14MnNb, 18Nb, 16MnRE, 16Mn, etc. Although in terms of historical evolution, the predecessor of Q345 is based on the 16Mn grade in the standard YB13-69 of the Ministry of Metallurgy (which can be traced back to the ST52 of the German standard even earlier), its chemical composition is not identical with that of the 16Mn steel pipe.
16Mn steel belongs to the carbon-manganese steel, the carbon content of about 0.16%, yield point is equal to 345MPa (strength level belongs to the 345MPa level). 16Mn steel has less alloy content, weldability is good, and generally do not have to preheat before welding.
Q345 steel mechanical properties include tensile strength, yield strength and elongation. National standard Q345B hot rolled steel coil, for example, its mechanical properties are: tensile strength 470-630MPa, yield strength ≥ 345MPa, elongation ≥ 20%.
In general the comprehensive mechanical properties and low temperature performance of Q345 steel is better than 16Mn steel, in most cases it is not recommended to use 16Mn to replace Q345.
