The main difference lies in the carbon content:
304L has very low carbon (≤ 0.03%), which makes it ideal for welded applications because it minimizes sensitization and intergranular corrosion.
304H has a higher carbon content (≈ 0.04–0.10%), which improves its high-temperature strength, making it suitable for pressure and heat applications.
304 (standard) is a balance between the two – good strength, corrosion resistance, and weldability for general-purpose use.
