Some basics about steel quality grades

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I. For carbon structural steel of grade Q235, the quality grades range from A to D, indicating a decrease in quality from lowest to highest. The difference in quality is mainly determined by the requirements regarding impact toughness (Charpy V-notch test), and there are also differences in the requirements for cold bending tests. * B’ y- c( H6 u) k1 @8 w: I! q! Y For grade A steel, no requirements are specified regarding impact toughness; the cold bending test is carried out only when required by the purchaser. Levels B, C, and D all require an AKV value of not less than 27 J; however, the test temperatures for these three levels are different. Level B requires an impact value at room temperature (25 ± 5 °C), while levels C and D require impact values at 0 °C and –20 °C respectively. Levels B, C, and D also require a successful cold bending test. To meet the above performance requirements, the chemical elements of different grades of Q235 steel vary slightly. , j9 Q2 r’ D9 n. w II. Alloy high-strength structural steel 1 g$ |+ f6 @) D5 B0 ] The Q345 steel is also available in five quality grades: A, B, C, D, and E. Similar to carbon structural steel, these different quality grades are distinguished by the requirements regarding impact toughness (Charpy V-notch test). Class A, no shock requirements ； Class B requires an impact energy AKV of >=34 J at 20°C (longitudinal) ； Class C requires an impact energy at 0°C of AKV >= 34 J (longitudinal) ； Grade D requires an impact energy AKV of >=34 J at -20°C (longitudinal) ； Class E requires an impact energy AKV of >=327 J at –40°C (longitudinal). Different quality grades also have varying requirements for the contents of carbon, sulfur, phosphorus, aluminum, etc.