What are the differences between 304, 304H, and 304L?

Thread Content

What are the differences between 304, 304H, and 304L? In fact, all 304 stainless steels have the same chromium and nickel content; they all contain 18% chromium (Cr) and 8% nickel (Ni). The main difference lies in their carbon content. Table of chemical compositions (%) for 304, 304L, and 304H – Image. 304L is an ultra-low carbon stainless steel; its carbon content is reduced to below 0.03%, which helps to prevent intergranular corrosion. Theoretically, it has a better resistance to stress corrosion than 304, but this advantage is not very noticeable in practical applications. The purpose of reducing carbon and adding titanium is the same, but the production cost of 321 steel with titanium addition is higher; the molten steel is thicker, and its price is also more expensive. The ‘H’ in 304H refers to high temperature; a high carbon content ensures high-temperature strength. GB150 requires that for austenitic steels to be used at temperatures above 525 degrees, their carbon content must be at least 0.04%. Carbides are strengthening phases, and materials with these carbides exhibit better high-temperature strength than pure austenitic steels. Among the three, 304H has the highest carbon content, 304L has the lowest carbon content, while the carbon content of 304 stainless steel lies between the two. The higher the carbon content, the worse the corrosion resistance of stainless steel, and it becomes more prone to rusting. Different carbon contents also result in varying prices; once again, different uses imply different requirements.