Chemical composition

Gr.3: Carbon content ≤0.19%, silicon content 0.18%-0.37%, manganese content 0.31%-0.64%, phosphorus and sulfur content ≤0.025%, and also contains 3.18%-3.82% nickel.

Gr.6: Carbon content ≤0.30%, silicon content ≥0.10%, manganese content 0.29%-1.06%, phosphorus and sulfur content All ≤0.025%.

Mechanical properties

Gr.3: tensile strength ≥450MPa, yield strength ≥240MPa, elongation ≥30% longitudinally, ≥20% transversely, low impact test temperature is -150°F (-100°C).

Gr.6: tensile strength ≥415MPa, yield strength ≥240MPa, elongation ≥30% longitudinally, ≥16.5% transversely, low impact test temperature is -50°F (-45°C).

Production process

Smelting: Use electric furnace or converter and other equipment to deoxidize, remove slag and alloy the molten steel to obtain Pure molten steel.

Rolling: Inject molten steel into the tube rolling mill for rolling, gradually reduce the tube diameter and obtain the required wall thickness, and at the same time, smooth the surface of the steel tube.

Cold processing: Through cold processing such as cold drawing or cold rolling, the precision and surface quality of the steel tube can be further improved.

Heat treatment: Generally, it is delivered in normalizing or normalizing and tempering state to eliminate the residual stress inside the steel tube and improve its comprehensive performance.

Application field

Petrochemical: Used to manufacture low-temperature pressure vessel pipelines and low-temperature heat exchanger pipelines in the fields of petroleum, chemical industry, etc., which can meet the use requirements in low-temperature environments, such as liquefied natural gas Natural gas storage tanks, low-temperature transmission pipelines, etc.

Natural gas: Suitable for natural gas transmission pipelines and gas storage tanks and other equipment to ensure safe operation in low-temperature environments.

Other fields: It is also used in power, aerospace, and shipbuilding, such as the main structural materials for condensers, boilers and other equipment in power equipment, and the main structural materials for hydraulic systems, fuel systems and other equipment in the aerospace field.

Specifications and dimensions

Common specifications and dimensions have a wide range, such as outer diameter 21.3-711mm, wall thickness 2-120mm, etc.
Gr.6 seamless steel pipe, especially ASTM A333/A333M GR.6 or SA-333/SA333M GR.6 low-temperature seamless steel pipe, is an important industrial material, widely used in various occasions requiring low-temperature toughness and high strength. The following is a detailed introduction to Gr.6 seamless steel pipe:

1. Implementation standards and materials

Implementation standards: Gr.6 seamless steel pipe implements ASTM A333/A333M or ASME SA-333/SA333M standards, which are issued by the American Society for Testing and Materials (ASTM) and the American Society of Mechanical Engineers (ASME) and are specifically used to specify the technical requirements for seamless steel pipes and welded steel pipes for low temperature.

Material: Gr.6 seamless steel pipe is a nickel-free low-temperature steel pipe, which uses aluminum-deoxidized fine-grained low-temperature toughness steel, also known as aluminum-killed steel. Its metallographic structure is body-centered cubic ferrite.

2. Chemical composition

The chemical composition of Gr.6 seamless steel pipe mainly includes:

Carbon (C): The content is low, generally not exceeding 0.30%, which helps to reduce the brittleness of steel.

Manganese (Mn): The content is between 0.29% and 1.06%, which can improve the strength and toughness of steel.

Silicon (Si): The content is between 0.10% and 0.37%, which helps the deoxidation process of steel and can enhance the strength of steel to a certain extent.

Phosphorus (P) and sulfur (S): As impurity elements, their content is strictly limited, generally not exceeding 0.025%, because high content of phosphorus and sulfur will reduce the toughness and weldability of steel.

Other alloying elements: such as chromium (Cr), nickel (Ni), molybdenum (Mo), etc., their content is also controlled at a low level to ensure the low temperature performance and comprehensive performance of steel.

3. Mechanical properties

Gr.6 seamless steel pipe has excellent mechanical properties, mainly including:

Tensile strength: Generally between 415 and 655 MPa, which ensures that the steel pipe can maintain structural integrity and prevent rupture when under pressure.

Yield strength: The minimum value is about 240 MPa (it can also reach more than 200 MPa), so that it will not produce excessive deformation under certain external forces.

Elongation: not less than 30%, which means that the steel pipe has good plastic deformation ability and can produce a certain deformation without breaking when stretched by external force. This is especially important for use in low temperature environments, because low temperature may make the material brittle, and good plasticity can alleviate the risk of such embrittlement.

Impact toughness: At a specified low temperature (such as -45°C), the impact energy must meet certain numerical requirements through Charpy impact test verification to ensure that the steel pipe will not brittle fracture under low temperature impact.