Round steel is a long solid steel with a circular cross-section. Its specification is expressed in diameter, unit millimeter (mm), such as "50mm" that means the diameter of 50 mm round steel.

Classification by process

Round steel is divided into hot-rolled, forged and cold-drawn three. Hot-rolled round steel specifications for 5.5-250 mm. Among them: 5.5-25 mm of small round steel mostly supplied in bundles of straight bars, commonly used as reinforcing bars, bolts and various mechanical parts; more than 25 mm of round steel, mainly used in the manufacture of mechanical parts, seamless steel pipe billets, etc..

 

Classification by chemical composition

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

 

(1) low carbon steel

 

Also known as soft steel, carbon content from 0.10% to 0.30% low carbon steel is easy to accept a variety of processing such as forging, welding and cutting, commonly used in the manufacture of chains, rivets, bolts, shafts, etc.

 

(2) Medium carbon steel

 

Carbon steel with 0.25% to 0.60% carbon. There are a variety of products such as quiescent steel, semi-quiescent steel, boiling steel. In addition to carbon can also contain a small amount of manganese (0.70% ~ 1.20%). According to product quality is divided into ordinary carbon structural steel and high quality carbon structural steel. Good hot working and cutting performance, poor welding performance. Strength, hardness than low carbon steel, while plasticity and toughness is lower than low carbon steel. Can be used directly without heat treatment, hot-rolled, cold-drawn material, or after heat treatment. Quenched and tempered medium carbon steel has good overall mechanical properties. Can achieve the highest hardness of about HRC55 (HB538), σb for 600 ~ 1100MPa. so in the medium strength level of a variety of uses, medium carbon steel is the most widely used, in addition to construction materials, but also a large number of mechanical parts for the manufacture of various.

 

(3)High-carbon steel

 

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

 

Classification by steel quality

According to the quality of steel can be divided into ordinary carbon steel and high quality carbon steel.

 

(1) ordinary carbon structural steel, also known as ordinary carbon steel, the carbon content, performance range, as well as phosphorus, sulfur and other residual elements content of the wider restrictions. In China and some countries according to the delivery conditions of the guarantee is divided into three categories: Class A steel (Class A steel) is to ensure the mechanical properties of steel. Class B steel (Class B steel) is to ensure the chemical composition of the steel. Special category steel (C steel) is to ensure both the mechanical properties and chemical composition of the steel, commonly used in the manufacture of more important structural components. The most produced and used in China is A3 steel (Class A, No. 3 steel) with carbon content around 0.20%, which is mainly used for engineering structures.

 

Some carbon structural steels also add trace amounts of aluminum or niobium (or other carbide forming elements) to form nitride or carbide particles to limit grain growth, so that steel strengthening, saving steel. In China and some countries, in order to meet the special requirements of professional steel, the chemical composition and properties of ordinary carbon structural steel to adjust, thus developing a series of ordinary carbon structural steel professional steel (such as bridges, construction, reinforcing steel, pressure vessel steel, etc.).

 

(2) high-quality carbon structural steel and ordinary carbon structural steel, compared with the content of sulfur, phosphorus and other non-metallic inclusions is lower. According to the carbon content and use of different, these steels are broadly divided into three categories: ① less than 0.25% C for low carbon steel, especially with carbon content of less than 0.10% of 08F, 08Al, etc., because of the good deep-drawing and weldability and is widely used as deep-drawing parts such as cars, cans ......, etc. 20G is the manufacture of ordinary boilers 20G is the main material for the manufacture of general boilers. In addition, low carbon steel is also widely used as carburizing steel for machinery manufacturing. ②0.25~0.60%C is medium carbon steel, mostly used in tempered condition to make parts for mechanical manufacturing industry. ③ greater than 0.6%C for high-carbon steel, mostly used in the manufacture of springs, gears, rolls, etc.. According to the different content of manganese, can be divided into ordinary manganese content (0.25 ~ 0.8%) and higher manganese content (0.7 ~ 1.0% and 0.9 ~ 1.2%) two steel groups. Manganese can improve the hardenability of steel, strengthen the ferrite, and improve the yield strength, tensile strength and wear resistance of steel. Usually in the high manganese content of the steel grade after the additional mark "Mn", such as 15Mn, 20Mn to distinguish from the normal amount of manganese content of carbon steel.

 

Classification by use

According to the use can be divided into carbon structural steel, carbon tool steel.

 

Carbon tool steel carbon content between 0.65~1.35%, after heat treatment can get high hardness and high wear resistance, mainly used in the manufacture of a variety of tools, cutting tools, molds and gauges (see tool steel).

 

Carbon structural steel is divided into 5 grades according to the yield strength of steel:

 

Q195, Q215, Q235, Q255, Q275

 

Each grade is divided into A, B, C, D grade due to different quality, up to four, some only one; in addition there are steel smelting deoxidation method difference.

 

Deoxidation method symbols:

 

F - boiling steel

 

b - semi-sedated steel

 

Z--Sedimentation steel

 

TZ--Special sedimentation steel

 

Material

Materials of round steel:Q195, Q235, 10#, 20#, 35#, 45#, Q215, Q235, Q345, 12Cr1Mov, 15CrMo, 304, 316, 20Cr, 40Cr, 20CrMo, 35CrMo, 42CrMo, 40CrNiMo, GCr15, 65Mn, 50Mn 50Cr, 3Cr2W8V, 20CrMnTi, 5CrMnMo, etc.