What is Grade S355JR steel?

Grade S355JR is a structural steel that is widely used in construction and manufacturing industries. S355JR steel is a low carbon steel grade with a minimum yield strength of 355 N/mm² and has good weldability and machinability. S355JR structural steel is popularly known for its high tensile strength and good impact resistance, which makes it suitable for various applications that require strength and durability. 

Properties of Grade S355JR steel:

Chemical composition:

The chemical composition of S355JR structural steel includes carbon, manganese, phosphorus, sulfur, silicon, and copper. The carbon content is 0.24%, while the manganese content ranges from 1.60% to 1.70%. The presence of manganese improves the strength and toughness of the steel. The phosphorus and sulfur contents are limited to 0.035% each to improve the machinability of the steel. The silicon content ranges from 0.50% to 0.60%, while the copper content is 0.55%. The presence of copper improves the corrosion resistance of the steel.

Mechanical properties:

The mechanical properties of S355JR steel are as follows:

1. Tensile strength: The ultimate tensile strength of this steel is between 470 N/mm² and 630 N/mm².

2. Yield strength: The yield strength of this steel is between 355 N/mm² and 510 N/mm².

3. Elongation: The elongation of this steel is between 14% and 22%.

4. Impact resistance: The impact strength of this steel is between 27 J at 20°C and 40 J at -20°C.

Applications of Grade S355JR steel:

S355JR steel is used in various construction and manufacturing applications, including:

1. Structural engineering: S355JR steel is widely used in structural engineering applications such as buildings, bridges, and tunnels. Its high strength and durability make it suitable for withstanding heavy loads and harsh weather conditions.

2. Industrial manufacturing: S355JR steel is used in the manufacturing of various industrial equipment such as cranes, lifting equipment, offshore structures, and material handling equipment.

3. Automotive industry: S355JR steel is used in the production of automobile frames and structural components due to its excellent strength, corrosion resistance, and low weight.

4. Wind power generation: S355JR steel is used in the manufacturing of wind turbine towers due to its high strength and ability to withstand extreme weather conditions.

5. Mining industry: S355JR steel is used in the mining industry for the construction of mining equipment and processing plants.

Variants of Grade S355JR steel:

There are different grades and variants of S355JR steel available in the market, including:

1. S355J2: This grade has similar properties to S355JR, but with higher impact resistance and lower carbon content.

2. S355K2: This grade has higher strength than S355JR and S355J2 and is suitable for heavy-duty applications.

3. S355NL: This grade has low-temperature impact resistance and is used in applications that require resistance to brittle fracture at low temperatures.

4. S355MC: This grade is a high-strength low-alloy steel that is used in construction and manufacturing applications where weight reduction is required.

5. S355G10: This grade is used in the oil and gas industry for the fabrication of offshore drilling platforms and other installations.

Heat treatment of Grade S355JR steel:

S355JR steel can be heat treated to improve its mechanical properties. The following heat treatment processes are commonly used for this steel:

1. Normalizing: S355JR steel is heated to a temperature of 900°C and held at this temperature for a period of time before cooling in air. This process improves the strength and toughness of the steel.

2. Annealing: S355JR steel is heated to a temperature of 650°C and held at this temperature for a period of time before cooling to room temperature. This process improves the machinability of the steel.

3. Tempering: S355JR steel is heated to a temperature of 600°C and held at this temperature for a period of time before cooling in air. This process improves the ductility and toughness of the steel.

4. Quenching and tempering: S355JR steel is heated to a temperature of 900°C and held at this temperature for a period of time before quenching in oil or water. This process improves the strength and hardness of the steel, which is then tempered to improve its ductility and toughness.