Steel Quality Grade

1. Carbon structural steel:
Q235. The quality grade of the steel grade is from A to D, indicating the low to high quality. The quality is mainly distinguished by the requirements of impact toughness (Charpy V-notch test), and the requirements for cold bending test are also different.
For Class A steel, the impact toughness is not required, and the cold bending test is only carried out when required by the purchaser. At the B, C, and D levels, the Akv value is not less than 27J, but the test temperatures of the three are different. The B grade requires a normal temperature (25+-5 oC) impact value, and the C and D grades respectively require 0 oC and -20 oC impact value. Class B, C, and D also require a cold bend test. In order to meet the above performance requirements, the chemical elements of different grades of Q235 steel are slightly different.

2. Alloy high strength structural steel
Q345 steel also includes five grades of quality grades A, B, C, D and E, which are the same as carbon structural steels. Different grades are distinguished by the requirements for impact toughness (Charpy V-notch test). Class A has no impact requirements; Class B requires 20 oC impact energy Akv>=34J (longitudinal); Class C requires 0 oC impact work Akv>=34J (longitudinal); Class D requires -20 oC impact work Akv>= 34J (longitudinal); Class E requires -40 oC impact work Akv>=327J (longitudinal). Different quality grades also have different requirements for carbon, sulfur, phosphorus, aluminum and other requirements.