What is the difference between 304L and 304H and 304 stailess steel

According to the content of chromium and nickel, 304L stailess steel and 304H stailess steel and 304 stailess steel are all 304 stainless steel. Their composition of chromium (Cr) is 18%, nickel (Ni) is 8%. The main difference between 304L stailess steel and 304H stailess steel and 304 stailess steel lies in the different carbon content.

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

H in 304H stainless steel refers to high temperature. High carbon content is the guarantee of high temperature strength. When austenitic steel is used above 525 degrees, the carbon content should not be less than 0.04%. Carbide is the strengthening phase, its high temperature strength is especially superior to pure austenite.

Among 304L stailess steel and 304H stailess steel and 304 stailess steel, the highest carbon content steel is 304H stailess steel, the lowest carbon content steel is 304L stailess steel, and the carbon content of 304 stainless steel is between the two. The higher the carbon content is, the worse the corrosion resistance of stainless steel is and the easier it is to rust. The difference in carbon content will also lead to differences in prices.

In addition, there are different requirements for different uses. It is wrong to think that 304L stailess steel can replace 304 stailess steel, and which steel it can be used in relation to the occasion of use.