Definition and Classification of Spring Steel
Spring steel is a term that is used to refer to a variety of steels which have a high elastic limit and are highly resistant to ambient temperature changes. The steel is also characterized by a high degree of resilience, the capacity to absorb and release energy, giving it several applications in industries such as automotive and aerospace. The steel must possess a combination of properties such as high strength, ductility and elasticity to be used as a spring steel.
The most common spring steel used is carbon steel, a medium/low-carbon alloy that is formed as an alloy composed of iron and carbon. Carbon steel spring steel is also known as tempered steel as this steel is heat-treated to give a greater corrosion resistance and higher tensile strength. Its hardness also increases with higher heat treatment temperatures. Carbon spring steel is typically supplied in annealed, hardened and tempered and even in pre-cap form with the use of a vapor degreasing process that creates a clean surface free from oil and other surface impurities.
Spring steel can be classified into two main categories: carbon spring steel and alloy spring steel. Carbon spring steel is made up of a single material and has what is called a shallow hardening response. Alloy spring steel, however, is composed of multiple materials and has a deep hardening response. As a general rule, carbon spring steel is used in applications that require strength and abrasion resistance, while alloy spring steel is preferred where increased resilience and flexibility is desired.
Within the spring steel family, several different grades exist to meet different performance needs. The most common grades are 1095, 1075, 1074, 1045, and 1060. Additionally, there is also medium carbon silicon steel (or Music Wire) which is superior to carbon steel in mechanical properties due to the silicon content and is more resistant to the effects of corrosion.
Grade 1095 is a high carbon steel with relatively low yield strength and can be used to create springs and other parts requiring high toughness and high wear resistance. Typical applications for this grade are agricultural discs, blades, and flat springs. Grade 1075 spring steel is a higher carbon steel with higher yield and tensile strengths than 1095, but with less elasticity. This material is used in applications requiring resilience and superior wear resistance, such as railway wheels, large agricultural machinery, and high load springs.
Grade 1074 is a high carbon steel with a deeper hardening response than 1075. This material is used in springs that need superior strength and fatigue resistance, such as automobile suspension systems and machinery springs and gears. Grade 1045 is a medium carbon steel with slightly lower yield strength than 1075 and is used in similar applications but requires a slightly more elastic material. Grade 1060 is a medium carbon steel with less yield strength than 1074 and is used in applications requiring higher toughness than 1074 and 1045 can offer, such as springs and precision machinery.
Finally, there is also a newer grade of spring steel known as 17-7 stainless steel that is highly corrosion resistant and can be used to create springs for parts used in the presence of water. While this material does not have the sheer strength and resilience of the other spring steel grades, it does provide superior corrosion and stress-corrosion cracking resistance, making it ideal for parts needing to be exposed to moisture.
In summary, spring steel is a special type of alloy steel that has greater elasticity and resilience than other steel grades. It can be made up of one or multiple materials and is typically classified as either carbon steel or alloy steel. There are several grades of spring steel available, each with its own unique properties and performance benefits to fit different applications.
