Modern steel is made of a variety of metal alloys different mixtures for different purposes. Carbon steel is composed of iron and carbon and accounts for about 90% of all steel production. High Strength low alloy steel has some additions usually less the 2% by weight of other elements, most typically 1.5% manganese, to provide additional strength for a small price increase. Low alloy steel is alloyed with other elements, usually molybdenum, manganese, chromium, or nickel, in amounts of up to 10% by weight to improve the harden ability of thick sections. Stainless steel and Surgical stainless steel contains a minimum of 10% chromium, often combined with nickel, to resist Rust (corrosion). Some steels are magnetic while others are not we will talk more about Stainless steel in another article.
Other modern steels include Tool steels, which are alloyed with large amounts of cobalt & tungsten or other elements to maximize hardening solutions. This allows the use of precipitation hardening & improves the alloy’s temperature resistance. Tool steel is usually used in drills, axes & other devicesthat need sharp, long lasting cutting edges. Other special-purpose alloys include weathering steels such as Cor-ten, which weather by acquiring a stable, rusted surface, and so can be used un-painted
Many more high-strength alloys exist, such as dual-phase steel. which is heat treated so that it contains both a ferrite & martensic microstructure for extra strength. Another is TRIP steel (Transformation Induced Plasticity) involves special alloying and heat treatments to stabilize amounts of austenite at room temperature in normally austenite-free low-alloy ferritic steels. By applying a strain to the metal, the austenite goes through a transition phase to martensite with out the additional heat. Maraging steel is alloyed with nickel and other elements, but unlike most steel contains almost no carbon at all. This creates metal that has a malleable property but that is still strong. (TWIP) steel or Twinning Induced Plasticity steel uses a specific type of strain to increase the effectiveness of work hardening on the alloy. Eglin steel uses over a dozen different elements in different amounts to create a relatively low-cost metal for use in bunker buster weapons. Hadfield steel which was named after Sir Robert Hadfield also called manganese steel it contains between 12-14% manganese that when abraded forms an incredibly hard skin which resist wearing. A few examples of Hadfield steel include bulldozer blades, tank tracks, edges and cutting blades on the jaws of life. A special class of high-strength alloy, the superalloys, retain their mechanical properties at extreme temperatures while minimizing creep. These are commonly used in applications such as jet engine blades where temperatures can reach levels at which most other alloys would become weak.
Most of the more commonly used steel alloys are categorized into grades by standards organizations. An example, the American Iron and Steel Institute has a series of grades defining many types of steel ranging from standard carbon steel to HSLA and stainless steel. The American Society for Testing and Materials has a separate set of standards, which define alloys such as A36 steel, the most commonly used structural steel in the United States. Though not an alloy, galvanized steel is a commonly used variety of steel which has been hot-dipped or electroplated in zinc for protection against corrosion (rust).
