Abstract: round steel refers to the solid strip steel with circular section. Its specification is generally expressed in diameter, and the unit is mm. There are many classification methods for round steel, which can be classified according to process, chemical composition, steel quality, purpose, etc.
compared with other reinforcement, round steel has a smooth and round appearance, no grain and no rib, resulting in low adhesion between round steel and concrete, and high adhesion between other reinforcement and concrete.
W = 0.006165 * D * D (d = diameter mm)
1. Classification by process
Round steel is divided into hot rolling, forging and cold drawing. The specification of hot rolled round steel is 5.5-250mm. Among them, 5.5-25mm small round steel is mostly supplied in bundles of straight bars, which is often used as reinforcement, bolts and various mechanical parts; Round steel larger than 25mm is mainly used for manufacturing mechanical parts, pipe blank of seamless steel pipe, etc.
(1) Low carbon steel
Also known as mild steel, low carbon steel with carbon content from 0.10% to 0.30% is easy to accept various processing, such as forging, welding and cutting. It is commonly used in the manufacture of chains, rivets, bolts, shafts, etc.
(2) Medium carbon steel
Carbon steel with carbon content of 0.25% ~ 0.60%. There are killed steel, semi killed steel, boiling steel and other products. In addition to carbon, it can also contain a small amount of manganese (0.70% ~ 1.20%).
According to the product quality, it is divided into ordinary carbon structural steel and high-quality carbon structural steel. It has good hot working and cutting performance and poor welding performance.
Its strength and hardness are higher than that of low carbon steel, while its plasticity and toughness are lower than that of low carbon steel. It can be used directly without heat treatment, hot rolled and cold drawn materials, or after heat treatment. The quenched and tempered medium carbon steel has good comprehensive strength Mechanical properties.
The maximum hardness that can be achieved is about HRC55 (hb538), σ B is 600 ~ 1100mpa. Therefore, medium carbon steel is the most widely used in various applications with medium strength level. In addition to being used as building materials, it is also widely used to manufacture various mechanical parts.
Commonly known as tool steel, the carbon content ranges from 0.60% to 1.70%, which can be hardened and tempered. Hammer, crowbar, etc. are made of steel with 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%.
(1) Ordinary carbon structural steel, also known as ordinary carbon steel, has wide restrictions on carbon content, performance range and content of phosphorus, sulfur and other residual elements.
In China and some countries, it is divided into three categories according to the guarantee conditions of delivery:
class a steel (class a steel) is the steel to ensure mechanical properties. Class B steel (class B steel) is the steel to ensure chemical composition. Special steel (Class C steel) is a steel that ensures both mechanical properties and chemical composition.
It is often used to manufacture important structural parts. A3 steel (class a No. 3 steel) with carbon content of about 0.20% is produced and used most in China, which is mainly used for engineering structures.
Some carbon structural steels also add a small amount of aluminum or niobium (or other carbide forming elements) form nitrides or carbide particles to limit grain growth, strengthen steel and save 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 have been adjusted, so as to develop a series of professional steel of ordinary carbon structural steel (such as bridges, buildings, steel bars, steel for pressure vessels, etc.).
(2) Compared with ordinary carbon structural steel, high-quality carbon structural steel has lower contents of sulfur, phosphorus and other non-metallic inclusions.
① low carbon steel with less than 0.25% C, especially 08F and 08Al with carbon content less than 0.10%. Due to its good deep drawing and weldability, it is widely used as deep drawing parts, such as automobile and steel Can… Etc. 20G is the main material for manufacturing Ordinary boilers. In addition, low carbon steel is also widely used as carburized steel in machinery manufacturing industry.
② 0.25 ~ 0.60% C is medium carbon steel, which is mostly used in quenched and tempered state to make parts for machinery manufacturing industry.
③ More than 0.6% C is high carbon steel, which is mostly used to manufacture springs, gears, rolls, etc.
According to the different manganese content, it can be divided into two groups: ordinary manganese content (0.25 ~ 0.8%) and high manganese content (0.7 ~ 1.0% and 0.9 ~ 1.2%). Manganese can improve the hardenability of steel, strengthen ferrite and improve the yield strength, tensile strength and wear resistance of steel.
Usually, the brand of steel with high manganese content is marked with “Mn”, such as 15mn and 20Mn, to distinguish it from carbon steel with normal manganese content.
Round steel can be divided into carbon structural steel and carbon tool steel. The carbon content of carbon tool steel is between 0.65 ~ 1.35%.
After heat treatment, it can obtain high hardness and high wear resistance. It is mainly used to manufacture all kinds of tools, cutting tools, molds and measuring tools.
Carbon structural steel is divided into five grades according to the yield strength of steel.
Each grade is divided into grades A, B, C and D due to different quality. There are four at most, and some have only one.
In the automatic production control system of stainless steel round steel, in terms of operation mode, the operation mode is more and more detailed according to different operation environment and work purpose, which is mainly divided into the following four types:
1. Automatic mode: steel can be rolled only in this mode, which is generally the only condition for normal steel rolling production;
2. Simulated operation mode: its main purpose is to provide it to the operator to verify whether the operation of each looper lifting roll, shear and other action actuators is normal before steel rolling, whether the initial state is correct and whether the rolling control is abnormal;
3. Machine side mode: under the machine side working mode, some equipment actions can be completed through manual control at the operation site, such as crawling, rotating shear, roll change, etc;
4. Heap repair mode: the maintenance mode is not used for steel rolling, but only to check the equipment and its operation, and has the characteristics of minimum connection between electrical appliances and machinery.
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.