Difference Between 316 Stainless Steel and 304 Stainless Steel

304 stainless steel is an austenitic stainless steel, primarily composed of nickel (Ni) and chromium (Cr), with chromium content typically ranging between 18% and 20%, and nickel content between 8% and 10.5%. It also contains small amounts of carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), as well as trace elements like nitrogen (N), titanium (Ti), and molybdenum (Mo).

Nickel plays a crucial role in 304 stainless steel:

It strengthens and stabilizes the austenitic structure, ensuring a fully austenitic microstructure, which provides a good balance of strength, plasticity, and toughness.

It enhances hot and cold workability.

It improves thermodynamic stability, making 304 stainless steel more resistant to rust and oxidizing media compared to ferritic or martensitic stainless steels with similar chromium and molybdenum content.

It helps stabilize the protective oxide layer on the steel's surface, further enhancing corrosion resistance.

316 stainless steel is also an austenitic stainless steel, but it contains an additional key element—molybdenum (Mo). Its typical composition includes:

Plus small amounts of carbon, silicon, manganese, phosphorus, sulfur, etc.

Molybdenum significantly influences 316 stainless steel's properties:

It greatly improves resistance to reducing media, such as sulfuric acid and acetic acid, making 316 superior to 304 in such environments.

It enhances resistance to pitting and crevice corrosion, especially in chloride (Cl⁻)-containing environments (e.g., seawater, saltwater exposure).

It increases high-temperature strength, improving creep and stress-rupture resistance.

However, the addition of molybdenum makes 316 harder to hot-work compared to 304, and higher molybdenum content further increases processing difficulty.

Key Differences Summary