The Properties of Spring Steel Strip
When it comes to springs, you need a material that offers the right balance of properties. 301 stainless steel is the ideal choice because of its excellent tensile strength, high elasticity, and corrosion resistance.
The material is cold drawn as wire or rolled into flat strip before being heat-treated. This process results in work-hardened tensile strengths of up to 1700 MPa and total elongations of >2%.
High tensile strength
The high tensile strength of spring steel strip makes it an excellent choice for applications that require significant deformation without permanent loss of elasticity. For example, it is used in the retractor springs of car seat belts. Similarly, it is also used in the brakes of heavy vehicles. The special fine pearlitic microstructure of this material makes it particularly durable, even under high stress.
The tensile strength of spring steel is defined by its yield strength, which is the ability of the material to be twisted, bent, compressed spring steel strip or extended and then return to its original shape. This characteristic is what makes it a good material for forming hardware tools and other mechanical components that must withstand cyclical stresses. While it is possible to make tools out of other types of steel, they may not have the elasticity and resilience of spring steel.
There are several different grades of spring steel, with varying metallurgical qualities and properties. Some common spring steels include carbon and alloy steels. These steels are generally cold rolled and heat treated to achieve their desired mechanical properties. They can be annealed or hardened, depending on their intended use and environmental conditions.
Stainless steel spring wires are often chosen for their ductility and corrosion resistance. Typical examples include type 301, which has excellent formability at full and extra-hard tempers. It is available in diameters from 0.031 to 0.500 inch, and can be tempered to achieve a variety of tensile strengths.
High elongation
A high elongation is an important property of spring steel strip as it allows the material to bend and return to its original shape after the load is removed. This is especially important for springs that have to absorb energy before they deform plastically (like crash barriers or car bumpers). A high elongation also helps the spring to keep its shape and resist buckling during use, as well as prevent stress from being induced in the material during bending.
To achieve a high elongation, the strip is first hot-formed to give it its initial shape and then hardened through a process of heating within or above the transformation range and quenching in oil. This hardening Tinplate Sheet supplier leaves the metal with a distinctive needle like structure called acicular martensite. The acicular structure is much tougher and has greater ductility than the tempered martensite found in ordinary low carbon steels.
To eliminate randomly trapped internal stress and produce flat material that will stay flat, the strip is further elongated through temper mills in cut-to-length lines past its yield point. This “stress equalizing” process also ensures that all the fibers in the strip are elongated equally. This process is not to be confused with the stretching that occurs during a tensile test, as the forces involved are considerably less. This is why temper mills are often referred to as “stress equalizers.” The resulting material is then annealed, which further increases the elongation and tensile strength of the strip.
High toughness
Spring steel is a specific type of metal that has been engineered for its high yield strength and elasticity. It also has a higher resilience than regular steels. It is suitable for many applications that require a high level of durability, including retaining clips and tabs. In order to achieve the required tensile strengths, spring steel undergoes extensive heat treatment processes. These include tempering, which is used to relieve stress and achieve a more controlled tensile strength.
In addition to being highly durable, spring steel is also versatile. It can be used in a wide variety of manufacturing applications and has great formability. This allows it to be shaped into the desired shape without damaging its integrity. It is also easier to weld and machine than most other types of steel.
Stainless spring steel is available in a range of grades and tempers. The most common is 301, which is ideal for compression spring applications. Other options include 301Si, which is tempered to high-strength room temperature tempers and has greater ductility than traditional 301. The choice of grade and temper depends on the desired application.
301 spring steel is typically annealed, then hardened by long continuous furnace and oil quenching. This process results in better uniformity than hardened strips produced by batch hardening. 301 spring steel strip is available with various edges, such as deburred or skived, and can be passivated for corrosion resistance.
High corrosion resistance
A spring is exposed to a lot of stress, so it is important that the material can handle it. It must have a high combination of strength and elasticity to prevent damage and breakage. It is also useful if it can resist corrosion in harsh environments. There are many types of steel that can be used for springs, but some have better characteristics than others.
The most commonly used spring steel is 304 stainless steel. It has good corrosion resistance and can be used without plating. It can withstand exposure to most oxidising acids, and is able to work in temperatures down to 150 degC. However, it has a lower tensile strength than other metals in the same class of elasticity, so it is not as suitable for flat stamping and sharp bends. It is also weakly magnetizable, and it is not recommended for use in contact with magnetic objects.
Another option is nickel-chromium alloys such as Nimonic 90 and Inconel 718. These alloys have excellent mechanical properties at both high and low temperatures, and they are resistant to corrosion fatigue and pitting. They can be tempered to achieve high levels of ductility while maintaining their fatigue resistance. In addition, they can be passivated to remove iron deposits from the surface of the steel strip. Ulbrich can perform this service to improve the lifespan of your springs.
