Comprehensive knowledge of round steel

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• Tag: chemical composition , round steel , use
Comprehensive knowledge of round steel Round steel refers to a solid long strip of steel with a circular cross-section. The material of round steel is generally made of first-grade steel, which has...

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Comprehensive knowledge of round steel

Round steel refers to a solid long strip of steel with a circular cross-section. The material of round steel is generally made of first-grade steel, which has very good plasticity. It is used in a large amount in industry and is used less in construction projects. The specifications of round steel are mainly expressed in millimeters of diameter, for example, "50" means a round steel with a diameter of 50 mm.The material of round steel is generally made of first-grade steel, which has very good plasticity. It is used in a large amount in industry and is used less in construction projects. The specifications of round steel are mainly expressed in millimeters of diameter, for example, "50" means a round steel with a diameter of 50 mm.

1. Classification of round steel

Classification by production process: divided into three types: hot rolling, forging and cold drawing;

Hot-rolled round steel: The metal billet is passed through the gap (various shapes) of a pair of rotating rolls, and the cross-section of the material is reduced and the length is increased due to the compression forming and rolling of the rolls. This is the most commonly used production method for steel production. It is mainly used to produce profiles, plates and pipes. Divided into hot-rolled and cold-rolled. The size of hot rolled round bar is 5.5-250 mm. Among them: small round bars of 5.5-25 mm are mostly supplied in bundles of straight strips, which are often used as steel bars, bolts and various mechanical parts in construction projects; round bars larger than 25 mm are mainly used for the manufacture of mechanical parts or seamless steel pipe raw materials .

Forged round steel: refers to round steel that can be shaped by forging. In general, the quality of the round steel produced by the free forging rolling method is better under the conditions of the same deformation ratio, because forging to achieve the same deformation amount of rolling requires repeated forging to elongate (forging is free deformation and rolling It is constrained deformation), so the same billet produces the same finished round steel forging is equivalent to an increase in the deformation ratio of rolling by more than 50%. In addition, in general, forging is the overall deformation of the steel from the surface to the interior and the rolling surface is deformed first, so The internal structure, segregation degree, metal flow line, etc. of the round bars produced by the two are completely different, and the quality of forged round bars is generally better than that of rolled round bars. Therefore, key components such as crane hook heads must be forged parts.

Cold-drawn round steel: also known as cold-drawn round steel, cold-drawn element steel, cold-drawn round steel, and smooth round steel, it is a kind of cold-drawn section steel. Whether it is cold-drawn round steel or round steel, its shape is round, but the surface of cold-drawn round steel is very smooth, its dimensional accuracy is high, and its mechanical properties are high. Because of its high dimensional accuracy, it can be used directly without processing.

2. Round steel material

Round steel materials are mainly divided into carbon steel and low alloy steel, such as Q195, Q235, 10#, 20#, 35#, 45#, Q215, Q235, 304, 316, 20Cr, 40Cr, 20CrMo, 35CrMo, 42CrMo, 40CrNiMo , GCr15, 65Mn, 50Mn, 50Cr, 3Cr2W8V, 20CrMnTi, 5CrMnMo, etc.

3. Chemical composition of round steel

Carbon steel can be divided into low carbon steel, medium carbon steel and high carbon steel according to chemical composition (that is, carbon content).

Low carbon steel: also known as mild steel, carbon content from 0.10% to 0.30% low carbon steel is easy to accept various processing such as forging, welding and cutting, commonly used in the manufacture of chains, rivets, bolts, shafts, etc., because of its high elongation It is not easy to break and is also used in construction projects.

Medium carbon steel: carbon steel with a carbon content of 0.25% to 0.60%, and a small amount of manganese (0.70% to 1.20%) in addition to carbon. Good thermal processing and cutting performance, poor welding performance. The strength and hardness are higher than those of low carbon steel, while the plasticity and toughness are lower than those of low carbon steel. Hot-rolled and cold-drawn materials can be used directly without heat treatment, or they can be used after heat treatment. The quenched and tempered medium carbon steel has good comprehensive mechanical properties. The highest hardness that can be achieved is about HRC55 (HB538), and σb is 600-1100MPa. Therefore, among various uses of medium strength level, medium carbon steel is the most widely used, in addition to being used as construction engineering materials, it is also widely used in the manufacture of various mechanical parts.

High carbon steel: often called tool steel, carbon content from 0.60% to 1.70%, can be quenched and tempered. Hammers, crowbars, etc. are made of steel with a carbon content of 0.75%; cutting tools such as drills, taps, reamers, etc. are made of steel with a carbon content of 0.90% to 1.00%.

4. Use of round steel

Ordinary carbon round steel is used for structures with low tensile strength requirements, such as ordinary construction projects, ordinary standard parts, hot-rolled steel, etc.; high-quality carbon structural steel, which contains low content of harmful elements sulfur and phosphorus (≤ 0.035%), of which 08, 10, 15, 20, 25 and other grades are low carbon steels, which have good plasticity and are easy to draw, extrude, stamp, forge and weld;

Medium carbon round steel, after quenching and tempering, can obtain excellent mechanical properties, and is often used for more important shafts, fasteners, etc.;

High carbon round steel to make springs and wear parts;

Other alloy round steels, such as 20CrMnTi, are important carburized steels, suitable for important gears, etc. 27SiMn is a high-strength, easy-to-weld steel used where welding is important. 35CrMo, 42CrMo are high-strength steels used for very important parts, such as engine connecting rod screws, cylinder head screws. Heavy duty car tire screws, etc.