Round steel

Round steel is divided into three types: hot-rolled, forged, and cold drawn.

 The specification of hot-rolled round steel is 5.5-250 millimeters.

 Among them, 5.5-25mm small round steel is mostly supplied in bundles of straight bars, commonly used as steel bars, bolts, and various mechanical parts;

 Round steel larger than 25 millimeters is mainly used for manufacturing mechanical parts, seamless steel pipe blanks, etc.

Round steel

Classified by chemical composition

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

(1) Low carbon steel

Also known as soft steel, low-carbon steel with carbon content ranging 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

Round steel

Carbon steel with a carbon content of 0.25% to 0.60%.

 There are various products such as killed steel, semi killed steel, boiling steel, etc.

 In addition to carbon, it may also contain a small amount of manganese (0.70% to 1.20%).

 According to product quality, it is divided into ordinary carbon structural steel and high-quality carbon structural steel.

 Good thermal processing and cutting performance, but poor welding performance.

 Strength and hardness are higher than low carbon steel, while plasticity and toughness are lower than 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 achievable hardness is approximately HRC55 and HB538, with a σ b of 600-1100MPa.

 So among various applications with moderate strength, medium carbon steel is the most widely used, not only as a building material, but also extensively used in the manufacture of various mechanical parts.

(3) High carbon steel

Commonly known as tool steel, with a carbon content ranging from 0.60% to 1.70%, it can be quenched and tempered.

 Hammer, pry bar, etc. are made of steel with a carbon content of 0.75%;

 Cutting tools such as drill bits, wire taps, reamers, etc. are made of steel with a carbon content of 0.90% to 1.00%.

Classified by the quality of steel

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

(1) Ordinary carbon structural steel, also known as ordinary carbon steel, has wide limitations on carbon content, performance range, and phosphorus, sulfur, and other residual element content.

 In China and some countries, it is divided into three categories based on delivery guarantee conditions: Class A steel (Class A steel) is steel that guarantees mechanical properties.

Round steel

 Class B steel is a steel with a guaranteed chemical composition.

 Special grade steel C-grade steel is a type of steel that ensures both mechanical properties and chemical composition, commonly used in the manufacture of important structural components.

 The most commonly produced and used steel in China is A3 steel (Class A Grade 3 steel) with a carbon content of around 0.20%, 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, in order to limit grain growth, strengthen the steel, and save steel.

Round 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, thus developing a series of professional steels for ordinary carbon structural steel (such as bridge, construction, steel reinforcement, pressure vessel steel, etc.).

(2) Compared with ordinary carbon structural steel, high-quality carbon structural steel has lower content of sulfur, phosphorus, and other non-metallic inclusions.

 According to their carbon content and usage, this type of steel can be roughly divided into three categories: