Alloy Steels and Steel Alloys
Steel is a metal alloy consisting mostly of iron and a small amount of carbon, which improves the steel fabricator‘s strength and fracture resistance. It may also contain other elements, such as chromium, which increases its corrosion resistance. In the case of stainless steels, 11% chromium is used to produce the steel.
Alloy steels are steels with various elements added to them to improve various properties. In low quantities, the elements increase the strength and hardenability of the steel, while in large quantities, they increase corrosion resistance and temperature stability. The effects of each element on the steel’s properties are summarized in the table below. In general, alloy steels have increased strength, but have lower machinability, weldability, and formability.
Alloy steels are used to create a variety of construction products. They are used for large structures and steel skeletons, and for many small items in building and construction. These materials also work well as reinforcement in concrete structures. The use of alloy steels for building and construction projects can make them stronger than conventional steels and reduce overall structure weight.
Alloy steels can also be case-hardened. Several types of alloy steels are used for cutting and forming tools. Their alloy content varies from about 0.25 to more than 38 percent. These alloys are useful for high-quality drills, reamers, milling cutters, punches, and plastic moulds. Generally, these types of steels are oil or air hardened.
The most common steel is carbon steel. It is inexpensive and machinable. Moreover, carbon steels can be case-hardened. This process adds carbon to the surface, making a hard outer layer and a soft core. Carbon steel contains between 0.29% and 0.54% carbon and a small amount of manganese.
According to the American Iron and Steel Institute, carbon steels are those with carbon content of 0.05 to 2.1 percent by weight. This makes them extremely strong and durable. As a result, carbon steels are a great choice for many applications. However, they are not the only steels available for construction.
Carbon steels have a variety of physical properties that vary based on their composition. The alloying elements can also influence the oxidation rate. Carbon steels are usually slow to oxidize compared to iron. For example, a steel with a high carbon content will oxidize 10 to 20 percent slower than one that is low in carbon content.
Carbon steels come in many different grades. For example, plain carbon steels are labelled 10xx. The first two numbers are the carbon content, while the last two are the proportion of phosphorus, silicon, and manganese. The alloy composition determines the hardness and strength of a steel.
Carbon steels fall into three categories: low carbon steels, medium carbon steels, and high carbon steels. Low-carbon steels are used in automotive body components, construction materials, and food cans. Medium-carbon steels are used for general industrial applications and have high strength and resistance to wear. High-carbon steels are used for cutting tools, high-strength wire, and dies.
When exposed to seawater, carbon steels may experience pitting of various depths. This is often much higher than general corrosion rates. However, it is often difficult to determine how deep carbon steels can be attacked by pitting, and pitting rates are not linear with exposure time. Typical methods for calculating pitting rates rely on the measurements of different pits on different test samples.