Steels and Cast irons and their Essential and Incidental Elements...

Steels and Cast irons and their Essential and Incidental Elements Steels and cast irons are basically alloys of iron and different other elements in the periodic table. The vast majority of steels and all cast irons contain carbon as a principal alloying element. As a general definition, steel is an alloy of iron, carbon (less than 2 % C), and other alloying elements which is capable of being hot and/or cold deformed into various shapes. On the other hand, cast iron is an alloy of iron, carbon (higher than 2 % C), and other alloying elements and is not generally capable of being hot and/or cold deformed. A cast iron is used in its cast form. Steels and cast irons are the most widely used and least expensive metallic materials. There are several thousands of different steel compositions presently available. A vast variety of terminology is used to differentiate different types of steels. In fact, the way the steels are classified sometimes is quite confusing even to the regular user of steels. However, in many cases, the steels fall into a limited number of well-defined classes. Generally, the carbon and low alloy steels come under a classification system based on composition. The high alloy steels (the stainless, heat resistant, and wear resistant steels, etc.) are being classified according to many different systems, including composition, microstructure, application, or specification. The easiest way to classify steels is by their chemical composition. Different alloying elements are normally added to iron for the purpose of attaining certain specific properties and characteristics. These elements include, but are not limited to, carbon, manganese, silicon, nickel, chromium, molybdenum, vanadium, niobium, copper, aluminum, titanium, tungsten, and cobalt. The general category of carbon and low alloy steels encompasses plain carbon steels, alloy steels,...

Carbon and low alloy steels...

Carbon and low alloy steels  The definition of the carbon steels by American Iron and Steel Institute (AISI) is as follows: “Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, columbium [niobium], molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.40 %; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65 %, silicon 0.60 %, copper 0.60 %.” Steels can be classified based on different systems depending upon: The composition: Carbon, micro alloy, low alloy, high alloy or stainless steel. The manufacturing processes: Open hearth furnace, basic oxygen process, energy optimizing furnace or electric arc furnace. The finishing methods: Hot rolling, cold rolling or forging etc. The type of product: Flat such as plate, sheet, strip, long such as wire rods, reinforcement bars, rounds and shapes, pipes and tubes or forged products. The de oxidation method: Killed, semi-killed, rimmed or capped steel The microstructure: Ferritic, austenitic, pearlitic, bainitic or martensitic The strength levels: HSS, HSLA or normal strength to meet standard requirement The heat treatment process: Annealing, normalizing, thermo mechanical treatment, quenching and tempering etc. Quality defining designations: Forging quality, commercial quality, drawing quality or welding quality etc. Carbon steels As a group carbon steels are the most frequently produced and used steels. More than 85 % of the steels produced presently are carbon steels. Variations in the carbon content of the steels have the greatest impact on the mechanical properties of steels. Increase in the carbon content also results into increase in the hardness of the steels as well as their strengths. Hence carbon steels are generally...