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The difference between normal carbon steel and high quality carbon steel

The difference between normal carbon steel and high quality carbon steel

2020-06-04

Ordinary carbon steel number labeled with "Q", on behalf of the steel yield strength, the number after the yield strength value (MPa).For example, Q235 steel has a yield strength of 235MPa.When necessary, the steel number can be followed by a symbol indicating the quality grade and the method of deoxidation during smelting.The quality grade symbols are A, B, C, D.The notation of the deoxidization method is F, B, Z, TZ.Deoxidization method symbol F refers to the boiling steel with incomplete deoxidization only using weak deoxidizer Mn.After pouring the liquid steel into the ingot, the liquid steel has self-deoxidation reaction in the ingot mold, and a large amount of CO gas is released in the liquid steel, which results in "boiling" phenomenon, so it is called rimming steel.If strong oxidants such as silicon and aluminum are added in the smelting process, and the molten steel is completely deoxidized, then it is called dead steel, denoted by Z.When the deoxidation condition is between the above two, it is called semi-killed steel, with symbol B;Special deoxidization process is adopted in smelting, which is called special dead steel, denoted by the symbol TZ.Killed steel is generally used for chemical pressure vessels.There are five types of ordinary carbon steel: Q195, Q215, Q235, Q255 and Q275.The quality grade of each steel can be seen in GB700-88.Among them, Q235 A with yield strength of 235MPa has good plasticity, toughness and processing property, and its price is relatively cheap. It is widely used in chemical equipment manufacturing.Q235-a plate is used as the shell and parts of room temperature and low pressure equipment, Q235-A bar and section steel are used as bolts, nuts, supports, gaskets, bushings and other parts, as well as valves and pipe fittings.

The high quality steel contains less harmful impurity elements of sulfur and phosphorus, its smelting process is strict, the steel structure is uniform, the surface quality is high, and the chemical composition and mechanical properties of the steel are guaranteed, but the cost is high.The number of high-quality carbon steel is represented by two digits only, the steel number sequence is 08, 10, 15, 20, 25, 30, 35, 40, 45, 50...80, etc.Steel Numbers represent parts per million of the average carbon content in steel.For example, no.45 steel means that the average carbon content in steel is 0.45%(0.42% ~ 0.50%).For example, no.45 steel means that the average carbon content in steel is 0.45%(0.42% ~ 0.50%).High quality unalloyed steel with high manganese content should be marked with manganese elements such as 45Mn.According to the different carbon content, it can be divided into high quality low carbon steel (containing C < 0.25%), such as 08, 10, 15, 20, 25;High quality medium carbon steel (containing 0.3% ~ 0.60% C), such as 30, 35, 40, 45, 50 and 55;High quality carbon steel (containing C > 0.6%), e.g. 60, 65, 70, 80.High quality low carbon steel has low strength but good plasticity and welding performance.In the manufacture of chemical equipment, it is often used as the gasket cover (08, 10) for heat exchangers, equipment nozzles and flanges.High quality medium carbon steel has high strength and good toughness, but poor welding performance, so it is not suitable for the shell of chemical equipment.But can be used as heat exchange equipment tube plate, high strength requirements of bolts and nuts, etc.No.45 steel is commonly used as a driving shaft (stirring shaft) in chemical equipment.High grade carbon steel has higher strength and hardness.60, 65 steel is mainly used to make spring, 70, 80 steel is used to make wire rope and so on.


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