Abstract: Round steel is a solid strip of steel with a circular cross-section. Its specifications are generally expressed in terms of diameter in mm. There are many ways to classify round steel, which can be based on process, chemical composition, steel quality, usage, etc.
Compared to other steel bars, round steel has a smooth and rounded appearance with no grain or ribs, resulting in a low adhesion of round steel to concrete, while other steel bars have a high adhesion to concrete.
Round steel is a long, solid bar of steel with a round cross-section. Its specification is expressed in millimetres of diameter, e.g. “50” means a round steel with a diameter of 50 mm. Round steel is divided into three types: hot rolled, forged and cold drawn. Hot-rolled round steel is available in sizes from 5.5 to 250 mm. Most of the 5.5-25 mm small round steel is supplied in bundles in straight strips and is commonly used for reinforcement, bolts and various mechanical parts; round steel greater than 25 mm is mainly used for the manufacture of mechanical parts or for seamless steel pipe billets.
W = 0.006165 * D * D (d = diameter mm)
I. Classification by process
Round steel is divided into hot-rolled, forged and cold-drawn. Hot-rolled round steel specifications for 5.5-250mm, of which 5.5-25mm small round steel more in a bundle of straight supply, commonly used as reinforcement, bolts and a variety of mechanical parts; more than 25mm round steel is mainly used in the manufacture of mechanical parts, seamless steel pipe billets, etc..
(1) Low carbon steel
Also known as low carbon steel, the carbon content of 0.10% to 0.30% of low carbon steel, easy to accept forging, welding, cutting and other kinds of processing. Commonly used in the manufacture of chains, rivets, bolts, shafts, etc.
(2) Medium carbon steel
Carbon steel with carbon content of 0.25% to 0.60%. There are calming steel, semi-calming steel, boiling steel and other products. In addition to carbon, can also contain a small amount of manganese (0.70% ~ 1.20%).
It is divided into ordinary carbon structural steel and high quality carbon structural steel according to product quality. It has good hot working and cutting properties, but poor welding performance.
Its strength and hardness is higher than low carbon steel, while plasticity and toughness is lower than low carbon steel. It can be used directly without heat treatment, hot-rolled and cold-drawn materials, or after heat treatment. Tempered medium carbon steel has good overall strength mechanical properties.
The maximum hardness achievable is approximately HRC55 (hb538) and σB is 600-1100 mpa. Therefore, medium carbon steel is most widely used in various applications of medium strength grades. In addition to being used as a construction material, it is also widely used in the manufacture of various mechanical parts.
Commonly known as tool steel, with a carbon content of 0.60% to 1.70%, it can be quenched and tempered. Hammers and crowbars are made of steel with a carbon content of 0.75%; drills, taps, reamers and other cutting tools are made of steel with a carbon content of 0.90% to 1.00%.
(1) Common carbon structural steel, also known as ordinary carbon steel, has extensive restrictions on carbon content, range of properties and residual element content such as phosphorus and sulphur.
In China and some countries, there are three categories according to the guaranteed conditions of delivery.
Class A steel (class a steel) is a steel with guaranteed mechanical properties. class B steel (class B steel) is a steel with guaranteed chemical composition. Special steel (class C steel) is a steel with guaranteed mechanical properties as well as chemical composition.
Commonly used in the manufacture of important structural components. The most produced and used in China is A3 steel with a carbon content of about 0.20% (A grade 3 steel), mainly used for engineering structures.
Some carbon structural steels also add small amounts of aluminium or niobium (or other carbide forming elements) to form nitride or carbide particles to limit grain growth, strengthen the steel and save steel.
In China and some countries, the chemical composition and properties of ordinary carbon structural steels have been adjusted to meet the special requirements of specialist steels, resulting in the development of a range of ordinary carbon structural steels (e.g. for bridges, buildings, reinforcing steel, pressure vessels, etc.).
(2) Compared with ordinary carbon structural steel, high-quality carbon structural steel has a lower content of non-metallic inclusions such as sulphur and phosphorus.
According to the carbon content and use of different, this steel is broadly divided into three categories.
① low carbon steel with a carbon content of less than 0.25%, especially with a carbon content of less than 0.10% 08F and 08Al. Because of its good deep-drawing and weldability, it is widely used as deep-drawing parts, such as cars, steel tanks …… etc. 20G is the main material for manufacturing ordinary boilers. In addition, low carbon steel is also widely used as carburizing steel in the machinery manufacturing industry.
② 0.25 ~ 0.60% C is medium carbon steel, mostly used in a tempered state for the manufacture of mechanical manufacturing parts.
③ 0.6% C or more for high carbon steel, more for 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 high manganese content (0.7 ~ 1.0% and 0.9 ~ 1.2%) two categories. Manganese can improve the hardenability of steel, strengthen the ferrite, improve the yield strength, tensile strength and wear resistance of steel.
Usually high manganese steel grades are marked with “Mn”, such as 15mn, 20Mn, to distinguish it from the ordinary manganese content of carbon steel
Round steel can be divided into carbon structural steel and carbon tool steel. The carbon content of carbon tool steel is between 0.65 and 1.35%.
High hardness and high wear resistance can be obtained after heat treatment. It is mainly used for the manufacture of various tools, edge tools, moulds and gauges.
Carbon structural steel is divided into five grades according to the yield strength of the steel.
Each grade is divided into three grades A, B, C and D depending on the quality. There are up to four grades, some of which have only one.
(1) ordinary carbon structural steel a wider range of ordinary carbon steel, on carbon steel, performance, as well as phosphorus, and other elements of the country content more. For three categories: Class A steel (Class A steel) is to ensure the mechanical properties of the steel. Category B steel (B steel) is to ensure the chemical composition of the steel. Special category steel (C steel) is the steel that guarantees both the mechanical properties and the chemical composition of the steel composition, commonly used in the manufacture of more important structural components. The most produced and used in China is A3 steel (Class A 3 steel) with a carbon content of around 0.20%, the main engineering structures.
There are elements of the elemental structure also add trace amounts of niobium (other aluminium elements formed by carbon or carbon content steel) , the formation of alkaline matter or carbon or carbon elements to grain formation, in steel to strengthen, steel. To adapt to the ordinary carbon structure and properties of steel for adjustment, special development of specific steel specialised structure (such as to adapt to the construction of vegetal structure, steel with chemical composition, the general composition of steel, steel for pressure, etc.) ).
(2) according to the carbon content and use of different, carbon structural steel and ordinary carbon steel, compare and other non-metallic inclusions of low content. (1) 0.25% C for carbon steel, which is particularly low carbon content of 08F, 08Al, etc. system steel, due to the deep punching and weldability of the car is widely used in 10% of the processing of deep punching parts such as, cans 20G manufacturing ordinary furnace of the main material transfer use. In addition, in low carbon steel is also widely carburized steel, machinery manufacturing field. ② 0.25 ~ 0.60% C for medium carbon steel …… multi-mass state use, the production of mechanical industry parts. ③ greater than 0.6%C for high steel, mostly used in the manufacture of springs, carbon gears, rolls, etc. According to the different amounts of manganese content, can also be divided into ordinary manganese content (0.25 ~ 0.8%). ) and contains contains the amount of vegetation (0.71.0% and 0.71.0% ~ 1.2%) two steel groups. Manganese improves hardenability, strengthens and improves the performance strength, tensile strength and wear resistance of steel. After the grade of steel with high manganese content is usually additionally marked “Mn”, such as 15Mn, 20Mn to distinguish it from the normal amount of manganese carbon steel.
In the stainless steel round steel automatic production control system, in the mode of operation, according to the different operating environment and work purposes, the mode of operation is increasingly refined, mainly divided into the following four types.
1, automatic mode: only in this mode can steel be rolled, generally the only condition for normal steel rolling production.
2, simulated operation mode: its main purpose is to provide the operator with the opportunity to verify that the operation of each live set of lifting rolls, shear and other action actuators before rolling is normal, that the initial state is correct and that the rolling control is Not normal ;
3. machine-side mode: in machine-side working mode, some equipment movements can be completed at the operating site by manual control, such as crawling, turning shears, changing rolls, etc.
4、Stack repair mode: The repair mode is not used for rolling, but only for checking the equipment and its operation, featuring minimal electrical and mechanical connections.
Stainless steel round steel (≤ 40mm bar) is produced by continuous process of Morgan type 45 ° two high or Cox three high (Y-type) rolling mill. The general product specification is 5.5 ~ 40mm coil.
The finish rolling speed is 50 ~ 60m / S (ferritic stainless steel) or 70 ~ 60m / S (austenitic stainless steel).
Due to non torsion rolling, the surface quality of stainless steel round steel products is smooth and high dimensional accuracy. ≤? The diameter deviation of 20mm wire and bar can reach ± 0.1mm,? 40mm bar can reach ± 0.2mm, and the disc weight can reach 2T.
Specific production process steps: billet preparation, heating, descaling, rough rolling, head cutting, medium rolling, head cutting, finish rolling, coiling, heat treatment, pickling and human warehouse.
1. Sand blasting (shot) method: the method of spraying micro glass beads is mainly used to remove the black oxide scale on the surface.
2. Chemical method: use a pollution-free pickling passivation paste and normal temperature non-toxic cleaning solution with inorganic additives for leaching.
So as to achieve the purpose of whitening the natural color of stainless steel. After treatment, it basically looks like a dull color. This method is suitable for large and complex products.
The difference between round steel and other steel bars.
1. Appearance is not the same, round steel appearance light round, no grain without rib, other steel surface appearance has carved patterns or rib, which causes the bond between round steel and concrete is small, while other steel and concrete bonding force is large.
2. Ingredients are not the same, round steel (first class steel) belongs to the ordinary low carbon steel, other steel bars are mostly alloy steel.
3. Strength is not the same, round steel strength is low, other steel strength is high, that is, the diameter of the same size of round steel compared with other steel, round steel can withstand the tension than other steel, but the plasticity of round steel than other steel, that is, round steel before being pulled off a large deformation, while other steel before being pulled off the deformation is much smaller
Materials of round steel: Q195, Q235, 10#, 20#, 35#, 45#, Q215, 15CrMo, 40Cr, 20CrMo, 50Cr, 3Cr2W8V, 5CrMnMo, etc.