What is the difference between SM490C and SM490B?

SM490B and SM490C are Japanese structural steel grades under JIS G3106 standard, with the main difference being their toughness requirements, especially impact energy at low temperatures, with SM490C having stricter low-temp impact standards (e.g., 47J at 0°C) than SM490B (e.g., 27J at 20°C), making SM490C generally better for colder applications or critical welded structures needing higher reliability. Both offer similar tensile strength (490 MPa minimum), but the suffix (B or C) denotes varying chemical compositions and required impact toughness tests for different service conditions.

Key Differences Summarized:

Toughness/Impact Test: This is the biggest differentiator. SM490C requires a more rigorous impact test, often at lower temperatures (e.g., 0°C), demanding higher impact energy absorption than SM490B, which tests at 20°C.

Chemical Composition: SM490C typically has slightly lower carbon content (e.g., around 0.18% max) compared to SM490B (e.g., 0.18-0.20%), contributing to better weldability and toughness.

Applications: While both are for welded structures (bridges, buildings, ships), SM490C's superior low-temperature performance suits more demanding environments or critical structural parts needing enhanced weldability and mechanical properties.

In simple terms: Think of the letters A, B, C as increasing levels of quality/toughness for the same base strength steel. SM490C is a higher-grade version of SM490B.

Chemical Composition

Mechanical Property