Stainless Steel Grades Chart: 304, 316, 321, 347, 410 & 430

Stainless steel is not a single metal; it is rather a group of alloys. The grade designation indicates the contents of stainless steel. The grades are based on the content of chromium, nickel and molybdenum, and fall into four groups: austenitic, ferritic, martensitic and duplex.  Aashish Metals stocks and supplies these six grades, and this chart reflects the composition questions our buyers ask most often when matching a grade to a drawing. This stainless steel grades and composition chart covers 304, 316, 321, 347, 410 and 430. 

Chemical Composition of 304, 316, 321, 347, 410 and 430, ASTM A240 Limits

Table A. Chemical composition by grade in percent by weight, 304 vs 316 vs 321 composition with L grades

Read the table with two cautions in mind. First, a single value is a maximum, so 304 allows up to 0.07 percent carbon and no more. Second, many older tables still in circulation show 304 with chromium 18.0 to 20.0 and carbon 0.08. Those are superseded limits. The current ASTM A240 limits for 304 are carbon 0.07 max and chromium 17.5 to 19.5, and this stainless steel grades chart uses the current figures.

A few notes on numbering help when you read other documents. The three digit number is the AISI or SAE designation, and the S number is the UNS, the Unified Numbering System. ASTM A240 covers plate, sheet and strip, ASTM A312 covers pipe, and ASTM A276 covers bar. Each product form has its own standard, so check the one that matches what you are buying. In Europe the same grades carry numbers under EN 10088, which Table C lists beside the UNS and the national names.

304 vs 316 vs 321 Composition at a Glance

Think of 304 as the baseline, roughly 18 percent chromium and 8 percent nickel. Grade 316 keeps that base and adds 2 to 3 percent molybdenum with more nickel. Grade 321 stays close to 304 but adds titanium. The L grades, 304L and 316L, cut carbon to 0.030 max. For the full two grade story, read our SS 304 vs SS 316 differences guide.

Stainless Steel Grade Comparison, Mechanical Properties and Physical Data

Table B. Mechanical and physical data for annealed material

Treat the strength values as annealed minimums from the standard, not typical test results. Real mill material usually exceeds them. The 400 series is different, because its strength depends on heat treatment. Densities are approximate and rounded, and our metal density chart lists other metals for comparison. Annealed austenitic grades can become slightly magnetic after heavy cold work.

Yield strength is the stress at which the metal starts to deform for good, and tensile strength is the stress at which it fails. Elongation shows how far the metal can stretch before it breaks, which is why the austenitic grades form so well at 40 percent. Hardness is given as a maximum, which keeps annealed material soft enough to form and machine.

Stainless Steel Types and Grades, The Families Explained

Grades behave the way they do because of the structure their chemistry produces. Four families matter most for the six grades in this guide.

Austenitic Stainless Steel, 304, 316, 321 and 347

The 300 series is non magnetic when annealed, carries high nickel, and gives the best formability and weldability. Grade 304 is the general purpose workhorse, and our page on stainless steel in the food industry shows where it earns that reputation. Grade 316 adds molybdenum for chlorides, and for harsher conditions you can compare it with 904L in the SS 904L vs SS 316 guide. The L grades, 304L and 316L, keep the same base but hold carbon to 0.030 max, which helps in welded work. Grades 321 and 347 are the stabilised versions, explained below.

Ferritic Stainless Steel, 430

Ferritic grades rely on chromium alone. They are magnetic and lower in cost, but welding and toughness are limited, which is why 430 is used for trim and appliance work rather than pressure parts. It also resists stress corrosion cracking better than the austenitic grades in some conditions, a point to check against the service.

Martensitic Stainless Steel, 410

Martensitic grades can be hardened by heat treatment. They are magnetic and give up some corrosion resistance in return for strength and wear performance. Typical parts include shafts, valve trim and cutlery blades, where an edge or a wear surface counts for more than corrosion resistance.

Duplex and Other Families

Duplex grades mix austenite and ferrite for high strength and strong chloride resistance, and precipitation hardening grades reach very high strength after ageing. Neither is covered by a table here. Read our guides to duplex stainless steel grades and duplex vs super duplex stainless steel for detail.

Why 321 and 347 Exist, Sensitisation and Stabilised Grades

Hold an austenitic grade between roughly 425 and 860 degrees C and chromium carbides can form along the grain boundaries. That pulls chromium out of the surrounding metal, and the weakened edges corrode. This is called sensitisation, and the damage is called intergranular corrosion. Welding passes through this temperature range, so it is a real concern.

There are two ways around it. Stabilised grades add a strong carbide former, which is titanium in 321 and niobium in 347. These bind the carbon first, so chromium stays where it should. Low carbon grades, 304L and 316L, simply leave less carbon to react. Grade 321 suits repeated heating, and 347 suits welded high temperature service. For wider guidance, see our page on metal alloy selection for high temperatures. Stabilisation only helps if the welding and heat exposure suit the grade, so a stabilised grade still needs a sound weld procedure.

A practical example shows why this matters. A welded 304 tank held at 600 degrees C for hours can sensitise along the weld, while a 321 tank in the same service resists it, because titanium has already taken the carbon.

Stainless Steel Equivalent Grades, UNS, EN, JIS and GB

Buyers often work across drawings written to different standards. Table C lines up the six grades by UNS, EN number, JIS and GB name, so you can read a drawing from another region without guessing.

Table C. Equivalent grades by national and international standard

Use equivalents as a guide. Two grades with matching names can differ slightly in limits, so the project specification decides what is acceptable.

The 400 Series Pair, Choosing Between Two Magnetic Grades

410 vs 430 Stainless Steel

Both grades are magnetic and both sit in the 400 series, so they are often confused. They are not interchangeable.

• Hardenability. 410 hardens by heat treatment. 430 does not.
• Corrosion resistance. 430 has higher chromium and resists corrosion better in mild environments.
• Formability. 430 forms more easily, while 410 is chosen for strength and wear.

In practice the choice follows the job. A decorative trim strip or an appliance panel suits 430, and a pump shaft or a valve stem suits 410.

How to Choose the Right Stainless Steel Grade

Table D. Quick selection guide

A short decision list gets most selections right. The stainless steel grades chart above supplies the numbers, and these four steps supply the order.

1. Check the environment. If chlorides are present, choose 316 or above.
2. Check temperature and welding. Heat or welded service points to 321, 347 or an L grade.
3. Check the strength or wear need. 410 is the one that hardens.
4. Check cost and appearance. 430 and 304 cover most mild duty and decorative work.

The choice between an L grade and a stabilised grade deserves a closer look. An L grade, such as 304L, suits welded work at ordinary temperatures, because low carbon limits carbide formation. A stabilised grade, such as 321 or 347, suits parts that sit in the 425 to 860 degrees C range for long periods, where even low carbon steel can sensitise over time.

Remember what the chart cannot tell you. It gives chemistry and annealed properties, but not the surface finish, the product form or the exact requirements of your project. A grade can be right on paper and still wrong if the finish, thickness or heat treatment condition does not match the job. When in doubt, go back to the specification and the mill test certificate.

For a close look at the most common choice, read our SS 304 vs SS 316 differences comparison.