Stainless Steel Springs
Stainless steel springs are used for their ability to resist high temperatures, moisture, and chemicals. They are also known for their smooth and attractive surface finish. Made of steel alloyed with at least 12% chromium and often nickel, stainless steel is a strong metal that fares well in a wide variety of environments and conditions.
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Manufacturing Stainless Steel Springs
Most stainless steel springs are fabricated from austenitic stainless steel, which is unaffected by heat treatment. Grades 302 (18% chromium, 9% nickel), 304 (18% chromium, 8% nickel) and 316 (17% chromium, 12% nickel, 2.5% molybdenum) are used to manufacture springs, all of which offer different properties. They are able to withstand temperatures up to 650ºF, a property that no other spring metal exhibits. These grades have a small degree of magnetism, a coefficient of thermal expansion 15% less than carbon steel, and thermal conductivity of only 30% of standard steel. While stainless springs are not likely to oxidize and rust, they sometimes become discolored when stress relieves the spring wire. This yellow-brown color only affects the spring's aesthetics, not the function, life span, or mechanical properties. In order to resume and maintain the spring's appearance, passivation, which is a coating method, is applied. It improves tarnish resistance as well as removes any discoloration.
Applications of Stainless Steel Springs
Springs made of stainless steel are preferred in outdoor and water applications and environments where sanitation is necessary. The aerospace, semiconductor, heat exchanging, medical, food and beverage processing, marine, boat manufacturing, industrial manufacturing and oil industries all use stainless steel springs as components within machinery, equipment, and vehicles. They always have a shiny, gray finish and can be fabricated into many different sizes and types of spring, including coil, compression, extension, and torsion springs. Small spring sizes generally have higher tensile strengths, which are similar to hard drawn carbon steel. They are made from cold drawn flat or round wire with varying nickel degrees. Springs that exhibit lower nickel content have better formability and flexibility but lower strength than those that have high amounts. Like all stainless steel parts and products, heat treatment will not strengthen the metal. Instead, cold working, like cold extrusion to fabricate wire, strengthens the steel's properties. After cold working, a low temperature heat treatment improves the spring properties, some of which are lost during cold working.