Difference between SPV235 and SPV450

SPV235 and SPV450 are pressure vessel quality steel plates manufactured to Japanese Industrial Standard JIS G3115, specifically designed for intermediate temperature service in welded pressure vessels, boilors, and storage tanks. The "SPV" designation stands for Steel Plate for Vessels, and the number indicates either the minimum tensile strength (for SPV450) or the minimum yield strength (for SPV235) . These grades are widely used in oil refineries, chemical plants, and power generation facilities where reliable performance at elevated temperatures is required.

Key Differences:

The fundamental distinction is their strength level and designation basis. SPV235 specifies a minimum yield strength of 235 MPa (with tensile strength typically 410 MPa or higher), while SPV450 specifies a minimum tensile strength of 450 MPa (with corresponding yield strength typically ≥ 245 MPa or higher depending on thickness). This makes SPV450 a significantly higher-strength material, capable of withstanding greater internal pressures and enabling thinner vessel wall designs.

This strength difference is achieved through substantially different chemical compositions. SPV235 is a mild steel with very low carbon (typically ≤ 0.18%) and manganese content, offering excellent weldability and formability. SPV450 requires a higher carbon and manganese content, often with micro-alloying elements, resulting in a considerably higher carbon equivalent (Ceq) . Consequently, fabrication requirements differ dramatically. SPV235 can be welded with minimal preheating and simple procedures, while SPV450 demands strict welding controls: mandatory low-hydrogen consumables, precise preheating, controlled heat input, and mandatory post-weld heat treatment (PWHT) for most thicknesses to prevent hydrogen-induced cracking. 

Chemical Composition

Mechanical Property