1. Ordinary carbon structural steel
Q195 steel has low strength, good plasticity, toughness, processing performance and welding performance, and is mainly used for rolling thin plates and wire rods.
Q215 steel is mainly used to make pipe billets, bolts, etc..
Q235 steel has moderate strength, good load-bearing capacity, good plasticity and toughness, good weldability and processability, and is a commonly used grade for steel structures. It is made into steel bars, steel sections and steel plates in large quantities for building houses and bridges.
Q275 steel has high strength and hardness, good wear resistance, but poor plasticity, impact toughness and weldability. It is mainly used to manufacture shafts, agricultural tools, wear-resistant parts and pads.

2. Fine carbon structural steel, fine carbon structural steel is carbon steel with a carbon content of less than 0.8%. This steel contains less sulfur, phosphorus, and non-metallic inclusions than carbon structural steel. Compared with ordinary carbon structural steel, high-quality carbon structural steel has higher plasticity and toughness, and can be strengthened by heat treatment. It is mostly used for more important parts and is widely used in machinery manufacturing.

According to the different carbon content, high-quality carbon steel is divided into low carbon steel, medium carbon steel and high carbon steel. Low carbon steel has low strength and hardness, but high plasticity and toughness, excellent processing and welding properties, and is used to manufacture parts with small loads and high toughness requirements, as well as small carburized parts; medium carbon steel has high strength and hardness, low plasticity and toughness, good cutting performance, but poor welding performance, good cold and hot deformation ability, and is mainly used to manufacture mechanical parts with large loads. Commonly used medium carbon steels are 40#, 45# and 50# steels, but because the hardenability of carbon steel is not high, the larger the size of the part, the worse the strengthening effect of the quenching and tempering treatment.

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