Difference between SPV315 and SPV450

SPV315 and SPV450 are pressure vessel quality steel plates manufactured to Japanese Industrial Standard JIS G3115, specifically intended for intermediate temperature service in welded pressure vessels, boilers, and storage tanks. The "SPV" designation stands for Steel Plate for Vessels, and the number indicates either the minimum yield strength (for SPV315) or the minimum tensile strength (for SPV450) . These grades are commonly used in oil refineries, chemical plants, and thermal power stations where reliable performance at elevated temperatures is essential.

Key Differences:

The fundamental distinction lies in their strength level and designation basis. SPV315 specifies a minimum yield strength of 315 MPa (with tensile strength typically 490 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 means SPV315 actually possesses higher yield strength than SPV450, despite the latter having a higher numerical designation. This is a common point of confusion in the SPV series.

This strength inversion is explained by their different metallurgical designs. SPV315 is a higher-carbon, higher-manganese steel formulated to achieve superior yield strength through a normalized or normalized-rolled delivery condition. SPV450 achieves its tensile strength specification through a different balance of chemistry and processing, but its yield strength requirement is lower than SPV315. Consequently, SPV315 generally has a higher carbon equivalent (Ceq) compared to SPV450, making its welding more demanding. SPV315 requires stricter preheating, more careful heat input control, and mandatory post-weld heat treatment (PWHT) for most thicknesses. 

Chemical Composition

Mechanical Property