Stainless steel is typically graded based on its composition and properties. The most commonly used grading system for stainless steel is the SAE steel grades, also known as the AISI (American Iron and Steel Institute) grading system. This system uses a three-digit number to designate different grades of stainless steel.

Here are some common grades of stainless steel along with their characteristics:

1. Austenitic Stainless Steel:

   - Grade 304 (A2): This is the most common type of stainless steel, often referred to as "18-8" stainless steel. It contains 18% chromium and 8% nickel, providing good corrosion resistance and excellent formability.

   - Grade 316 (A4): This grade contains 16-18% chromium, 10-14% nickel, and 2-3% molybdenum. It offers increased resistance to corrosion, especially in marine environments.

2. Ferritic Stainless Steel:

   - Grade 430: This grade contains 16-18% chromium and is known for its good corrosion resistance in mildly corrosive environments. It has lower formability compared to austenitic stainless steels.

3. Martensitic Stainless Steel:

   - Grade 410: This grade contains 11.5-13.5% chromium and is often used in applications requiring high strength, hardness, and moderate corrosion resistance.

4. Duplex Stainless Steel:

   - Grade 2205: This grade contains approximately 22% chromium, 5-6% nickel, and 3% molybdenum. It offers a combination of high strength and excellent corrosion resistance, making it suitable for demanding applications.

5. Precipitation-Hardening Stainless Steel:

   - Grade 17-4 PH: This grade contains about 17% chromium, 4% nickel, and 3% copper. It can be heat treated to achieve high strength and hardness while maintaining good corrosion resistance.

It's important to note that there are numerous other stainless steel grades available, each with its own specific composition and properties. The choice of grade depends on the intended application and the desired characteristics such as corrosion resistance, strength, formability, and cost.