304 Stainless Steel
In fact, according to the content of chromium and nickel, all of them are 304 stainless steel, and all of them contain 18% chromium (Cr) and 8% nickel (Ni), but the main difference lies in the different carbon content.
304L Stainless Steel
304L is an ultra-low carbon stainless steel, the carbon content is below 0.03%, which can avoid intergranular corrosion, and the effect of stress corrosion resistance is stronger than that of 304 in theory, but the effect is not obvious in practical application. The purpose of reducing carbon is the same as adding titanium, but the smelting cost of 321 with titanium is higher, the molten steel is thicker and the price is more expensive.
304H Stainless Steel
H in 304H refers to high temperature, and high carbon content is the guarantee of high-temperature strength. GB150 requires that when austenitic steel is used above 525 degrees, the carbon content is not less than 0.04%, and carbide is the strengthening phase, especially the high-temperature strength is better than pure austenite.
Among the three, the highest carbon content is 304H, the lowest is 304L, and the carbon content of 304 stainless steel is between them. The higher the carbon content, the worse the corrosion resistance of stainless steel and the easier it is to rust. Different carbon content also leads to different prices and different requirements for different purposes.