Construction steel types of low alloy high strength structural steel

The national standard ≤ low-alloy high-strength structural steel ≥ (GB/T11591) produces a total of five grades of steel Q295, Q345, Q390, Q420 and Q460, and the yield point of the corresponding grade of steel whose plate thickness is not more than 16mm is 295,345,390,420,460N/mm2, respectively. The carbon content of these steels is not more than 0.20%, and the strength improvement mainly depends on the addition of a small amount of alloying elements to achieve, and the total amount of alloying elements is less than 5%, so it is called low-alloy high-strength steel. Among them, Q345, Q390 and Q420 are divided into A, B, C, D and E total quality grades according to chemical composition and impact toughness, and the lower the alphabetical order of steel quality is higher. These three grades of steel have higher strength and better plasticity, toughness, welding performance, and are selected as load-bearing structural steel. The grades of these three kinds of low-alloy high-strength steel are similar to those of carbon structural steel, except that the A and B grades of the former are sedated steel, and the C, D and E grades are special sedated steel, so the symbols of the deoxidation method are not added. The chemical composition and tensile, impact and cold bending test results of these three grades of steel shall comply with the provisions of Table 2.4 and Table 2.5.