The “best” stainless steel for springs depends heavily on the specific application requirements, particularly regarding corrosion resistance, temperature, strength, and cost.

Here’s a breakdown of commonly used stainless steel grades for springs:

• AISI 302/304 (Austenitic): These are the most common and cost-effective stainless steel spring materials. They offer excellent corrosion resistance in many environments and good strength when cold worked. Type 302 was traditionally preferred, but Type 304 is often used interchangeably due to availability and similar properties in the spring temper condition. Ideal for general-purpose springs where moderate corrosion resistance is sufficient.
• AISI 316 (Austenitic): Offers superior corrosion resistance compared to 302/304, especially against chlorides and marine environments, due to the addition of molybdenum. It’s chosen when higher resistance to pitting and crevice corrosion is needed. It also maintains strength well at moderately elevated temperatures. Typically more expensive than 304.
• 17-7PH (Precipitation Hardening): This grade offers significantly higher strength and hardness compared to the 300 series austenitic grades, approaching the strength of carbon steel spring wires while retaining good corrosion resistance (generally better than 302/304 but less than 316). It achieves its properties through heat treatment (precipitation hardening) after forming. Excellent for high-stress applications or where minimal size/weight is crucial. It also performs well at higher temperatures (up to ~650°F or 343°C).

Comparison Summary:

Ultimately, Type 302/304 is often the best balance for general use, Type 316 is best for corrosive environments, and 17-7PH is best for high-strength and higher-temperature spring applications.