What is the difference between 304, 304H and 304L?
In fact, according to the content of chromium and nickel, they are all 304 stainless steels, which contain 18% chromium (Cr) and 8% nickel (Ni), but the main difference lies in the carbon content.
304L is an ultra-low carbon stainless steel, the carbon content is reduced to less than 0.03%, which can avoid intergranular corrosion, and the effect of stress corrosion resistance is stronger than 304 in theory, 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 321 with titanium is higher, the molten steel is thicker, and the price is more expensive.
The "H" in 304H refers to high temperature. 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%. Carbide is a strengthening phase, especially High temperature strength is better than that of 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 is between the two. The higher the carbon content, the worse the corrosion resistance of stainless steel and the easier it is to rust. The difference in carbon content also leads to differences in its price, or that sentence has different requirements for different uses.
In addition, it is wrong to think that 304L can be used instead of 304. Whether it can be used is related to the use occasion, and according to the regulations, we do not have the right to "material substitution", only the original design department has the right to "material substitution" "Work, please remember this.
