Difference between SPV355 and SPV450 steel plate

SPV355 and SPV450 are pressure vessel quality steel plates manufactured to the Japanese Industrial Standard JIS G3115. This standard specifically governs steel plates for intermediate temperature service in pressure vessels. The designation "SPV" stands for Steel Plate for Vessels, and the number indicates the minimum tensile strength in MPa. These grades are engineered for the fabrication of welded pressure vessels, boilers, and storage tanks operating at elevated temperatures, such as in oil refineries, petrochemical plants, and thermal power stations.

Key Differences:

The fundamental distinction is their strength level. SPV355 has a minimum tensile strength of 355 MPa (with yield strength typically ≥ 205 MPa depending on thickness), while SPV450 offers a higher minimum tensile strength of 450 MPa (with yield strength typically ≥ 245 MPa or higher). This makes SPV450 capable of withstanding greater internal pressures, allowing for reduced wall thickness in vessel design.

To achieve this higher strength, SPV450 requires a more refined chemical composition with higher carbon and manganese content, and often micro-alloying additions. Consequently, SPV450 has a higher carbon equivalent (Ceq) compared to SPV355. This results in more demanding fabrication requirements, particularly regarding welding. SPV450 necessitates stricter control of preheating temperatures, mandatory use of low-hydrogen welding consumables, careful management of heat input, and often more rigorous post-weld heat treatment (PWHT) to prevent hydrogen-induced cracking and ensure the integrity of welded joints in pressure vessel construction. 

Chemical Composition

Mechanical Property