SA662 Grade C is a low-alloy, high-strength carbon steel plate specified by the American Society for Testing and Materials (ASTM), primarily engineered for low-temperature service applications where excellent toughness and structural integrity are critical at subzero temperatures. This grade features a controlled chemical composition and is typically supplied in the normalized or thermomechanically processed condition, delivering a favorable balance of tensile strength, yield strength, and notch toughness to resist brittle fracture in cold environments. It is widely used in the fabrication of pressure vessels, storage tanks, and structural components for industries such as petrochemical, liquefied gas handling, and cryogenic processing, complying with the stringent mechanical and metallurgical requirements of ASTM SA662 standard for low-temperature carbon and low-alloy steel plates.
Chemical Composition and Mechanical Property
|
Grade |
Chemical Composition(%) |
||||
|
C |
Mn≥ |
Si |
P |
S |
|
|
SA662 Grade C(SA662GR C) |
0.24 |
0.13-0.45 |
0.79-1.62 |
0.035 |
0.035 |
|
Grade |
Mechanical Property |
|
|||
|
Tensile Strength(MPa) |
Yield Strength(MPa) |
% Elongation in 2 in.(50mm) min |
Impacting Test Temperature(°C) |
|
|
|
SA662 Grade C(SA662GR C) |
480-620 |
295 |
20 |
-20,40,-60 |
|
Applications
SA662 Grade C, as a low-alloy high-strength steel plate for low-temperature service, is widely used in industries requiring excellent low-temperature toughness and structural reliability. Its main applications are as follows:
Petrochemical Industry: It is used to fabricate low-temperature pressure vessels, such as storage tanks and pipelines for ethylene, propylene and other low-boiling petrochemical intermediates. These components need to maintain structural integrity in low-temperature working environments to avoid brittle fracture caused by medium cooling.
Liquefied Gas Handling: It is applied in the manufacturing of storage and transportation equipment for liquefied natural gas (LNG), liquefied petroleum gas (LPG) and other cryogenic media, including tank bodies, pipe fittings and support structures, which can withstand the low temperature of -40℃ and below.
Cryogenic Processing Equipment: It is used to produce cryogenic separators, coolers and heat exchangers in air separation plants and refrigeration systems. These devices need to resist the erosion of low-temperature media and ensure stable operation for a long time.
Marine and Offshore Engineering: It is used to make low-temperature-resistant structural parts and pressure components of offshore platforms and LNG transport ships, adapting to the harsh low-temperature marine environment and ensuring the safety of marine operations.
Power Industry: It is applied in the fabrication of low-temperature auxiliary equipment for thermal power plants and nuclear power plants, such as low-temperature flue gas treatment devices and cryogenic storage tanks for auxiliary media, meeting the strict safety and performance requirements of the power industry.
Application Conditions
To ensure the safe and stable operation of SA662 Grade C, it must be used under the following specific conditions, which are closely related to its material properties and standard requirements:
Temperature Condition: It is mainly suitable for low-temperature service environments with a minimum working temperature of -40℃. It shall not be used in environments lower than this temperature, otherwise its toughness will decrease sharply and brittle fracture may occur. The maximum working temperature shall not exceed 350℃ to avoid the decline of material strength due to high temperature.
Medium Condition: It is applicable to neutral or weakly corrosive media, such as low-temperature hydrocarbons, liquefied gas and dry gas. It shall not be in direct contact with strong corrosive media (such as strong acid, strong alkali and chloride ions with high concentration) for a long time, unless effective anti-corrosion treatment is carried out.
Pressure Condition: It shall be used within the pressure range specified by the design standard. The maximum working pressure shall match its tensile strength and yield strength. Generally, it is suitable for medium and low pressure equipment (working pressure ≤10MPa), and shall not be overloaded to avoid structural damage.
Fabrication and Welding Condition: Strict welding procedures must be followed during fabrication. Preheating (preheating temperature 80-150℃) and post-weld heat treatment (tempering temperature 550-620℃) are required to eliminate welding stress and ensure welding joint toughness. Welding materials shall be matched with the base metal (such as E7018 electrode) to avoid welding defects.
Inspection and Maintenance Condition: Regular non-destructive testing (such as ultrasonic testing, radiographic testing) shall be carried out during service to check for internal defects and surface damage. Routine anti-corrosion maintenance shall be done to avoid rust and corrosion, and the service environment shall be inspected regularly to ensure that it is consistent with the designed application conditions.
Advantages
SA662 Grade C boasts prominent advantages tailored to low-temperature service scenarios, core strengths are as follows:
Excellent Low-Temperature Toughness: Maintains high toughness at -40℃ and below, effectively resists brittle fracture, ensuring structural safety in cryogenic environments.
Balanced Mechanical Properties: Combines high tensile and yield strength with good ductility, meeting the load-bearing requirements of industrial equipment.
Good Fabricability: Easy to weld and process under standard procedures, with stable welding joint performance, reducing fabrication difficulty and cost.
Strong Environmental Adaptability: Resists erosion from neutral/weakly corrosive low-temperature media, suitable for multiple harsh industrial scenarios.
Compliance with Strict Standards: Meets ASTM SA662 specifications, with reliable quality and traceability, widely recognized in global industries.
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What is SA662 Grade C?
SA662 Grade C is a low-alloy carbon steel plate specified by ASTM/ASME standards. It is mainly used for pressure vessels and structural components, featuring good weldability, moderate strength and toughness, suitable for low-temperature service environments.
What are the main chemical components of SA662 Grade C?
The main chemical components include C (≤0.20%), Mn (0.70-1.00%), Si (0.15-0.40%), P (≤0.035%), S (≤0.035%), and trace amounts of other elements, ensuring its mechanical and chemical properties.
What is the minimum tensile strength of SA662 Grade C?
The minimum tensile strength of SA662 Grade C is 485 MPa (70 ksi). This strength level enables it to withstand certain pressure and load, making it suitable for pressure vessel manufacturing and related structural applications.
What is the minimum yield strength of SA662 Grade C?
SA662 Grade C has a minimum yield strength of 290 MPa (42 ksi). This yield strength ensures the material has good load-bearing capacity and deformation resistance under working conditions.
What is the applicable temperature range of SA662 Grade C?
SA662 Grade C is suitable for service temperatures ranging from -29°C (-20°F) to 343°C (650°F). It maintains stable mechanical properties within this range, avoiding brittle fracture or performance degradation.
What are the common heat treatment processes for SA662 Grade C?
Common heat treatments for SA662 Grade C include normalizing and tempering. Normalizing refines grain structure, while tempering reduces internal stress, improving the material's toughness and machinability.
Is SA662 Grade C weldable?
Yes, SA662 Grade C has excellent weldability. It can be welded using common methods such as shielded metal arc welding (SMAW), gas metal arc welding (GMAW), and submerged arc welding (SAW) without preheating in most cases.
What are the main applications of SA662 Grade C?
SA662 Grade C is widely used in manufacturing low-temperature pressure vessels, boilers, storage tanks, pipelines, and structural components in petrochemical, power generation, and chemical industries due to its good comprehensive properties.
What standard does SA662 Grade C comply with?
SA662 Grade C complies with the ASTM A662/A662M standard, which is formulated by the American Society for Testing and Materials (ASTM) for low-alloy carbon steel plates for pressure vessels and structural purposes.
What is the elongation requirement of SA662 Grade C?
SA662 Grade C requires a minimum elongation of 22% in the tensile test. This high elongation indicates good ductility, allowing the material to undergo plastic deformation without breaking under external force.