ASTM F593
ASTM F593 covers the chemical and mechanical requirements for stainless steel bolts, hex cap screws and studs in diameters ranging from 1/4" to 1 1/2".
Austinitic Stainless - 300 Series
Most common grades of stainless fasteners. Offers good corrosion resistance, low heat conductivity, and good strength at higher temperatures. Often non-magnetic unless cold-worked.
NOTE: 18-8 is a general term that applies to 300 series stainless and is not a actual grade. It implies 18% Chromium and 8% Nickel, so a few different grades can be considered 18-8. 304 is the most common type of 18-8.
| Grade | Chromium % | Nickel % | Max Carbon % | Molybd % | Tensile KSI | Yield KSI | Hardness | Notes |
|---|---|---|---|---|---|---|---|---|
| 302 | 17-19 | 8-10 | .15 | - | 90-125 | 40 | B85-95 | Higher carbon content than 304. It is ductile. Used in flat washers. |
| 303 | 17-19 | 8-10 | .15 | .6 Max | 90-125 | 40 | B85-95 | Good machinability. Higher in sulfur content. Lower corrosion resistance. |
| 304 | 18-20 | 8-10.5 | .08 | - | 85-150 | 40 | B85-95 | Most popular grade. Good corrosion resistance and strength. |
| 304L | 18-20 | 8-10.5 | .03 | - | 85-150 | 40 | B85-95 | Lower carbon than 304. Increased corrosion resistance and welding capacity. |
| 305 | 17-19 | 10.5-13 | .12 | - | 80-140 | 40 | B85-95 | Higher nickel content lowers work hardening during severe cold forming and keeps non-magnetic. |
| 316 | 16-18 | 10-14 | .08 | 2-3 | 85-140 | 40 | B85-95 | Addition of molybdenum increases corrosion resistance to chloride and sulfides. Used often in salt water conditions. |
| 316L | 16-18 | 10-14 | .03 | 2-3 | 85-140 | 40 | B85-95 | Lower carbon than 316. Increased corrosion resistance and welding capacity. |
| 309 | 22-24 | 12-15 | .2 | - | 100-120 | 60-80 | B85-95 | Higher chromium and nickel give better corrosion resistance at high temperatures. |
| 321 | 17-19 | 9-12 | .08 | - | 100-120 | 60-80 | B85-95 | Titanium improves the intergranular corrosion resistance by avoiding carbide precipitation. Good for intermittent heating applications. |
| 347 | 17-19 | 9-13 | .08 | - | 100-120 | 60-80 | B85-95 | Same as 321 except Niobium(Columbium) and Tantalum are used instead of Titanium. |
Martensitic Stainless - 400 Series
Not as good of corrosion resistance. Higher carbon makes it much harder and stronger. Material will be slightly magnetic. There is no Nickel in the 400 series materials.
| Grade | Chromium % | Max Sulfur % | Max Carbon % | Tensile KSI | Yield KSI | Hardness | Notes |
|---|---|---|---|---|---|---|---|
| 410 | 11.5-13.5 | .03 | .15 | 180 | 150 | C34 | Higher carbon gives good strength. Most common of the 400 series. Commonly used in screws. |
| 416 | 12-14 | .06 | .15 | 180 | 150 | C34 | Higher sulfur content helps machinability but lowers corrosion resistance. |
| 420 | 12-14 | .03 | .15-.30 | 250 | 200 | C45 | Higher carbon gives greater strength but lowers corrosion resistance. |