What are the differences among 304, 304H and 304L?

In fact, both are 304 stainless steel in terms of chromium and nickel content. The composition contains 18% chromium (Cr) and 8% nickel (Ni), but the main difference lies in the carbon content.

304L is an ultra-low carbon stainless steel with a carbon content reduced to less than 0.03%, which can avoid intergranular corrosion. In theory, the effect of resisting stress corrosion is stronger than that of 304, but the effect is not obvious in practical applications. The purpose of reducing carbon and adding titanium is the same, but the smelting cost of 321 with added titanium is higher, the molten steel is thick, and the price is also more expensive.

The "H" in 304H refers to high temperature. The high carbon content is the guarantee of high-temperature strength. GB150 requires that the carbon content of austenitic steel be not less than 0.04% when used above 525 degrees. Carbides are strengthening phases, especially the high-temperature strength is superior to pure austenite.

Among the three, 304H has the highest carbon content, 304L has the lowest carbon content, and the carbon content of 304 stainless steel is between the two. The higher the content, the worse the corrosion resistance of stainless steel and the easier it is to rust. The different carbon contents also lead to differences in their prices. As mentioned before, different uses have different requirements.