What's the difference between 304, 304H and 304L stainless steel?

In fact, according to the content of chromium nickel is 304 Stainless Steel, the composition is containing 18% chromium (Cr), 8% nickel (Ni), but the main difference is the different carbon content.

304L is an ultra-low carbon stainless steel, carbon content reduced to 0.03% or less, can avoid intergranular corrosion, and in theory, the effect of stress corrosion resistance is stronger than 304, but the effect is not obvious in practical application. The purpose of reducing carbon and adding titanium is the same, but the smelting cost of titanium 321 is higher, the steel is thick, and the price is more expensive.

H in 304H refers to high temperature, high carbon content is the guarantee of high temperature strength, GB150 requires austenitic steel used in 525 degrees above, carbon content is not less than 0.04%, carbide is a strengthening phase, especially high temperature strength is better than pure austenite.

Among the three, the highest carbon content is 304H, the lowest carbon content is 304L, and the carbon content of 304 stainless steel in between the two. The higher the carbon content of stainless steel, the worse the corrosion resistance and rust. Different carbon content also leads to its price will be different, or that word use of different requirements are different.