Stainless, 18-8 & 316
Hex Cap Screw Mechanical and Performance Data
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18-8 and 316 stainless steel cap screws are both made from austenitic alloys as described below. |
| Applications/Advantages | 18-8: Used in products that require
general atmospheric corrosion resistnace, such as chemical and food-processing
equipment. Some chemical environments may require special corrosion
resistant materials and precautions. 316: The molybdenum content gives this type of stainless even greater corrosion resistance than 18-8 as well as superior strength at high temperatures. |
| Heat Treatment | The austenitic alloys develop their strength through work hardening during the fastener manufacturing process, as seen from the hardness properties below. The only heat treatment normally available on austenitic stainless alloys is annealing, which is done at approximately 1900 F to a dead soft condition and is not nomrally thermally reversible. |
| Material | 18-8: A cap screw made from one of
the following austenitic alloys: 303, 303Se, 304, XM7, all of which
are characterized as having a chromium content of 17-19% and nickel
content of 8-10%. 316: A cap screw made from 316 stainless steel, an austenitic alloy which differs from 18-8 by its molybdenum content (2-3%) and a higher nickel content (10-14%). |
| Hardness | 1/4 through 5/8 in. diameter: Rockwell
B95-C32. 3/4 through 1 in. diameter: Rockewll B80-C32 |
| Yield Strength* | 1/4 through 5/8 in. diameter, 2.25D and longer: 65,000 psi. minimum. 3/4 in. (2.25D & longer) & 7/8 through 1 in. diameter (3D & longer); 85,000-140,000 |
| Tensile Strength | 1/4 through 5/8 in. diameter, 2.25D
and longer; 65,000 psi. minimum. 3/4 in. (2.25D & longer) & 7/8 through 1 in. diameter (3D & longer); 85,000-140,000 |
| Elongation in 4D* | 1/4 through 5/8 in. diameter: 20% minimum; 3/4 through 1 in. diameter: 24% minimum. |
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