What is the difference between 304, 304H and 304L?

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, the carbon content is reduced to below 0.03%, can avoid intergranular corrosion, and in theory the stress corrosion resistance effect 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 321 smelting cost of adding titanium is higher, the molten 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 the 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, the worse the corrosion resistance of stainless steel and the easier it is to rust. The carbon content will also lead to a difference in the price, or the use of different requirements.