Chinas General Structure Steel Grades
In China, structural steel grades are defined by the Chinese standard GB/T700-2006. This standard specifies a series of general-purpose structural steel grades that are often used as the basis for steel production. The basic composition of the general structure steel grades is characterized by the addition of a certain amount of alloying elements and a very small amount of impurities, so that the steel has better physical and performance properties.
GB/T700-2006 specifies seven categories of steel grades including Q235A, Q235B, Q235C, Q235D, Q235E, Q235F and Q235G. The grades of these steel categories differ in terms of chemical composition, mechanical properties and application.
The chemical composition of Q235A, Q235B and Q235C is basically the same, the only difference is that the mass fraction of carbon content varies slightly. Q235A has a carbon content of 0.20-0.30%, Q235B has 0.30-0.35%, and Q235C has 0.35-0.40%. Q235A, Q235B and Q235C are also of equal tensile strength, but the yield strength of Q235A requires a slightly higher value than that of Q235B and Q235C.
Q235D, Q235E and Q235F have a higher vacancy rate than Q235A, Q235B and Q235C. Q235D’s mass fraction of carbon content is 0.18-0.20%, Q235E is 0.17-0.20%, and Q235F is 0.15-0.20%. Q235D, Q235E and Q235F also require a slightly lower tensile strength than Q235A, Q235B and Q235C, but the yield strength values are higher.
Q235G is a general structure steel grade with a lower carbon content than that of Q235C. Its mass fraction of carbon is 0.14-0.22%, and its yield strength is higher than that of Q235C.
In addition to the fundamental physical and mechanical properties of general structure steel, corrosion resistance and welding performance are also important.Q235A, Q235B and Q235C have good corrosion resistance, but not so good when it comes to welding. Q235D, Q235E and Q235F have better welding performance, but it is not recommended to use them as large-scale structural components because of their lower strength. Q235G has good corrosion resistance but also possesses a good welding performance.
In conclusion, Chinas general structure steel grades are divided into seven categories according to their chemical compositions, all of which have different physical and mechanical properties, corrosion resistance and welding performance. Knowing the characteristics and grades of the general structure steel grade will help you use them more effectively in your work.
