High Carbon Steel Strip
High carbon steel strip is valued for its strength properties operating at significantly higher levels than the mild steel grades. It can be finished to meet a wide range of application needs.
A standard method for measuring the hardness of metals by applying a controlled load to the surface, the resultant indention being measured and a Vickers Hardness value read from a conversion table.
Mechanical Properties
High carbon steels are valued for their strength properties and operate at significantly higher White tempered steel strip levels than the mild steel grades. They can be through-hardened by heat treatment and we specialize primarily in the highest grades of this group, being those with carbon levels between 0.65% and 1.05% embracing BS 1449: Part 1 1991 standard specifications CS70, CS80 and CS95 as well as Euronorm EN 10132 grades C75S, C85S and C100S.
High-carbon steels are available in the hard cold-rolled or pre-hardened and tempered condition depending on the end-use component design and means of fabrication. The softened/annealed state allows maximum deformability to permit the component to be formed from complex shapes and results in lower relative wear on forming tools. The hardened and tempered condition can produce hardness levels up to 650 VPN (tensile strength of 2200 N/mm2) or harder.
This group of steels is difficult to weld as they readily enter the hard and brittle martensite phase, which also makes them difficult to machine. They possess good toughness and ductility and are used in applications such as Automobile Clutches, Tolerance Rings, Bulldog Clips and Circlips as well as hand tools and chain links. The hardness of this group of steels can be reliably measured by impact testing with a Vickers hardness gauge, where a pyramid shaped diamond is struck on the surface to create an indentation and the resulting Rockwell Hardness number read from a conversion table.
Chemical Composition
The chemical composition of steel depends on its iron content, which in turn affects its strength, ductility and resistance to corrosion. Carbon steels are divided into low, medium and high-carbon varieties, with the higher carbon levels giving rise to higher strengths, tensile properties and harder wear characteristics.
These steels are not readily weldable as they tend to form the hard and brittle martensite phase when exposed to heat. They are ideally suited for cold-forming techniques, and can be through-hardened to further improve their mechanical properties by the addition of alloy elements such as chromium, molybdenum, vanadium, tungsten, etc. Tool steels and die steels are a good example of this type of high-carbon grade, which typically contains 0.6% up to 2.0% carbon but also has significant amounts of manganese and nickel to provide toughness, machinability and hardwear.
The varying carbon levels in these grades produce different types of metallurgical microstructures and hence hardness levels. They are produced in soft spheroidized annealed condition for applications requiring maximum cold-forming or to achieve lower wear on component-forming tools. They can be through-hardened to achieve a wide range of tensile strength/hardness combinations as required by subsequent manufacturing processes. These steels are often used for various spring and coil applications or small washers such as those found in the backup sensor on your car, or in the COVID-19 pandemic where one of Three D Metals customers utilised our strip to make a metal version of the plastic ones they normally use.
Heat Treatment
Carbon steels get their hardness through heat treatment, which is a process of heating and cooling. The heating part is known as quenching, and the cooling part is called tempering.
Quenching involves the steel being heated to a high temperature and then rapidly cooled. This causes the atoms in the metal to “freeze” in an arrangement that leads to increased hardness. This is accomplished by immersing the steel in a liquid like oil or water.
When the steel is quenched, it becomes extremely hard, but this also increases its brittleness, which reduces the strength of the steel. Tempering is a process used to reduce this brittleness without affecting the hardness of the steel.
Carbon steels undergo heat treatments after being rolled or forged to give them their final shape, but they are usually annealed again before they’re put into production. This annealing is used to fix deformations in the metal and improve its machinability. It is usually done by heating the steel up to a specific temperature and then slowly letting it cool down. This process also helps to relieve any stress from the work-hardening of the steel. The result is a better quality product that is easier to work with and stronger than it would have been otherwise. This is especially important in applications that require a lot of force on the edges of the material.
Applications
High carbon steel strip can be produced in a large variety of tensile strengths/hardnesses to suit subsequent component-manufacturing processes and end uses. It can be used in the annealed condition or in either hard cold-rolled or pre-hardened and tempered condition depending on the design of the end-use component and its means of fabrication. The annealed condition provides maximum deformability for complex component shapes and lower relative wear on tooling. Hardness levels typically range from 240 – 320 VPN (equivalent to tensile strengths of 824 – 1090 N/mm2) and pre-hardened and tempered levels can be as high as 650 VPN.
Unlike low carbon steels that have lower strength, ductility and weldability after heat treatment, high-carbon steels have better mechanical properties in the hardened/tempered state. These properties include better fatigue resistance, higher workability, stronger cutting edges and greater abrasion resistance than mild or alloy steels.
In fact, you probably see our strip in action Tinplate steel plate manufacturer every day in automotive and manufacturing applications. Think of the backup sensor on your car, for example; a small high carbon steel clip holds it in place and keeps it from moving around during operation. Or the metal washers on fasteners, like screws, that hold things together. Our high carbon spring strip is ideal for these kinds of jobs because of its superior strength and hardness.
