Ferro-Silicon

Ferro-Silicon Ferro-silicon (Fe-Si) is a metallic ferro-alloy having iron (Fe) and silicon (Si) as its main elements. In commercial terminology It is defined as a ferro-alloy containing 4 % or more of Fe, more than 8 % but not more than 96 % of Si, 3 % or less phosphorus (P), 30 % or less of manganese (Mn), less than 3 % of magnesium (Mg), and 10 % or less any other element. However, the regular grades of the ferro-alloy normally contain Si in the range of 15 % to 90 %. The usual Si contents in the Fe-Si available in the market are 15 %, 45 %, 65 %, 75 %, and 90 %. The remainder is Fe and minor elements. The minor elements, such as aluminum (Al), calcium (Ca), carbon (C), manganese (Mn), phosphorus (P), and sulphur (S) are present in small percentages in Fe-Si. Commercially, Fe-Si is differentiated by its grade and size. Fe-Si grades are defined by the percentages of Si and minor elements contained in the product. The principal characteristic is the percentage of Si contained in the ferro-alloy and the grades are referred to primarily by reference to that percentage. Hence 75 % Fe-Si contains around 75 % of Si in it. Fe-Si grades are further defined by the percentages of minor elements present in the product. ‘Regular grade 75 % Fe-Si’ denote that the product containing the indicated percentages of Si and recognized maximum percentages of minor elements. Other grades of Fe-Si differ from regular grades by having more restrictive limits on the content of elements such as Al, titanium (Ti), and/or Ca in the ferro-alloy. Fe-Si is also produced in a grade that contains controlled amounts of minor elements for the purpose of adding them to...

Iron and Types of Iron...

Iron and Types of Iron Iron is a chemical element with symbol Fe (from Latin word Ferrum). Its atomic number is 26 and atomic mass is 55.85. It has a melting point of 1538 deg C and boiling point of 2862 deg C. The density of iron is 7.87 grams/cu cm. It is a metal in the first transition series. Like the elements of other group 8 elements (ruthenium and osmium), iron exists in a wide range of oxidation states, ?2 to +6, although +2 and +3 are the most common. Iron as a common metal is mostly confused with other metals such as different types of steels. Iron is by mass the most common element on the earth, forming much of earth’s outer and inner core. It is the fourth most common element and the second most common metal in the earth crust. Steels contain over 95 % Fe. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen and water. Fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. Unlike the metals which form passivating oxide layers, iron oxides occupy more volume than the metal and thus flake off, exposing fresh surfaces for corrosion. Iron objects have been found in Egypt dating from around 3500 BCE (Before Common Era). They contain around 7.5 % nickel, which indicates that they were of meteoric origin. The ancient Hittites of Asia Minor (today’s Turkey) were the first to smelt iron from its ores around 1500 BCE. The ‘Iron Age’ had begun at that time. The first person to explain the various types of iron was René Antoine Ferchault de Réaumur who wrote a book on the subject in 1722. This explained how steel, wrought iron, and cast iron, were to be distinguished by the amount of charcoal (carbon) they contained. The...

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,...

Corrosion of Cast Irons...

Corrosion of Cast Irons Cast iron is a standard term which is used for a large family of alloys of ferrous materials. Cast iron is mainly alloy of iron (Fe) which contains higher than 2 % of carbon (C) and more than 1 % of silicon (Si). Low cost of raw materials and relative ease of production make cast iron the last cost engineering material. Cast iron can be cast into intricate shapes since it has excellent fluidity and comparatively low melting point. It can also be alloyed for improvement of corrosion resistance and strength. With suitable alloying, the corrosion resistance of cast iron can equal to or exceed that of stainless steel and nickel (Ni) based alloy. Since outstanding properties are obtained with this low cost engineering material, cast iron finds extensive use in atmospheres which need good corrosion resistance. Services in which cast iron can be used for its good corrosion resistance include water, soils, acids, alkalis, saline solutions, organic compounds, sulphur compounds, and liquid metals. In some cases, alloyed cast iron is the only economical choice for the equipment manufacture. Cast iron and the basic metallurgy The metallurgy of cast iron is similar to that of steel except that Si in sufficient quantities is present to necessitate use of the Fe-Si-C ternary phase diagram rather than the simple Fe-C binary diagram. A section of the Fe- Fe3C (iron carbide)-Si ternary diagram at 2 % Si is shown in Fig 1. Iron carbide is also known as cementite. The eutectic and eutectoid points in the Fe-Si-C diagram are both affected with the introduction of Si into the system. With normal Si in the range of 1 % to 3 % in cast irons, eutectic C percentage is related to Si percentage as...

Alloy Cast Irons

Alloy Cast Irons Alloy cast irons are the casting alloys which are based on the iron (Fe) – carbon (C) – silicon (Si) system. They contain one or more alloying elements intentionally added to improve one or more properties. The addition to the ladle of small amounts of substances such as ferrosilicon (Fe-Si), cerium (Ce), or magnesium (Mg)) that are used to control the size, shape, and/or distribution of graphite particles is termed as inoculation. The quantities of material used for inoculation neither change the basic composition of the solidified cast iron nor alter the properties of individual constituents. Alloying elements, including Si when it exceeds about 3 %, are usually added to increase the strength, hardness, hardenability, or corrosion resistance of the basic iron and are often added in quantities sufficient to affect the occurrence, properties, or distribution of constituents in the microstructure. In gray and ductile cast irons, small amounts of alloying elements such as chromium (Cr), molybdenum (Mo), or nickel (Ni) are added primarily to achieve high strength or to ensure the attainment of a specified minimum strength in heavy sections. Otherwise, alloying elements are used almost exclusively to enhance resistance to abrasive wear or chemical corrosion or to extend service life at elevated temperatures. Classification of alloy cast irons Alloy cast irons can be classified as (i) white cast irons, (ii) corrosion resistant cast irons, and (iii) heat resistant cast irons (Fig 1). Fig 1 Classification of alloy cast irons White cast irons White cast irons are so named because of their characteristically white fracture surfaces. They do not have any graphite in their microstructures. Instead, the C is present in the form of carbides, mainly of the types Fe3C and Cr7C3. Frequently, complex carbides such as (Fe,Cr)3C and (Cr,Fe)7C3,...