Stainless Steel Grades 304, 304H, 304L, and 316: Key Differences

Stainless steel is a widely used material across various industries. Among the many grades, 304, 304H, 304L, and 316 are some of the most common, all of which are defined under the ASTM A240/A240M standard for chromium and chromium-nickel stainless steel plates, sheets, and strips for pressure vessels and general applications.

 

All four grades 304, 304H, 304L, and 316 belong to the same category of austenitic stainless steels and are classified as 3-series chromium-nickel stainless steels based on their composition. Their main differences lie in chemical composition, corrosion resistance, heat resistance, and typical applications.

 

What is 304 Stainless Steel?

304 stainless steel contains approximately 18–20% chromium, 8–10.5% nickel, and a small amount of carbon (≤0.08%). It offers good tensile strength (minimum 515 MPa as per standards) and elongation (around 40% or higher). Its corresponding grade in Chinese standards is 06Cr19Ni10 (formerly 0Cr18Ni9). The chemical composition ranges are generally consistent between Chinese (GB) and American (ASTM) standards.

 

What is 304L Stainless Steel?

304L stainless steel has a composition similar to 304, but with a lower carbon content, limited to ≤0.03%. Due to the reduced carbon, its tensile strength is slightly lower than 304 (minimum 485 MPa), while elongation remains similar. The low carbon content improves weldability and effectively prevents intergranular corrosion.

 

What is 304H Stainless Steel?

304H stainless steel has similar chromium and nickel content to 304, but with a defined carbon range of 0.04–0.10%. It exhibits excellent strength and toughness at high temperatures and is specifically designed for high-temperature applications. At elevated temperatures (above 550°C), carbon forms small carbide precipitates, which pin grain boundaries and hinder deformation under stress, significantly improving creep strength and long-term high-temperature performance.

 

What is 316 Stainless Steel?

316 stainless steel primarily contains 16–18% chromium, 10–14% nickel, and 2–3% molybdenum, with a carbon content usually ≤0.08%. Its tensile strength is 515 MPa, and elongation is greater than 40%. The addition of molybdenum provides enhanced corrosion resistance, especially in reducing media and marine environments.

 

304, 304H, 304L, and 316: Chemical Composition

 

 

304, 304H, 304L, and 316: Corrosion Resistance

316 Stainless Steel: Due to its 2–3% molybdenum content, its corrosion resistance is significantly superior to that of the 304 series; it performs particularly well in resisting corrosion and pitting caused by chlorides (such as those found in seawater and saline environments).
304L Stainless Steel: Thanks to its ultra-low carbon content, it effectively prevents sensitization (intergranular corrosion), making it suitable for use in corrosive environments following welding. Its resistance to uniform corrosion is comparable to that of 304, but its resistance to intergranular corrosion is superior to that of standard 304.
304H: Its corrosion resistance is slightly lower than that of 304L; due to its higher carbon content, potential issues regarding intergranular corrosion must be carefully considered after welding. Consequently, it is generally not recommended for use in highly corrosive environments.

 

304, 304H, 304L, and 316: Heat Resistance

304H Stainless Steel: Due to its high carbon content (0.04–0.10%), it exhibits superior creep strength and rupture strength at elevated temperatures. Among the four materials, it offers the best high-temperature performance and is suitable for environments exceeding 500°C.
316 Stainless Steel: Thanks to the inclusion of molybdenum and a higher nickel content, its high-temperature oxidation resistance and heat resistance are superior to those of standard 304; however, its overall heat resistance is slightly lower than that of 304H.
304/304L: Due to its low carbon content, 304L possesses relatively poor high-temperature strength and is generally not recommended for high-temperature pressure-bearing structures operating above 400°C.

 

304, 304H, 304L, and 316: Applications

304 Stainless Steel: The most economical and versatile basic grade, widely used in fields such as architectural decoration, food processing equipment, general chemical equipment, and household appliances.
304L Stainless Steel: Suitable for welded components in industries such as chemicals, petroleum, and textiles, as well as in applications where resistance to intergranular corrosion is required.
304H Stainless Steel: Used in applications such as superheaters and reheaters in large-scale boilers, steam piping, and high-temperature heat exchangers in the petrochemical industry-fields that demand materials with excellent high-temperature creep strength.
316 Stainless Steel: Commonly utilized in pulp and paper mills, coastal facilities, heavy industry, chemical processing and storage equipment, oil refineries, medical surgical instruments, and pharmaceutical equipment. High-end cookware and tableware also frequently employ 316 stainless steel to ensure superior corrosion resistance.