Macro-Segregation in Steel Ingots...

Macro-Segregation in Steel Ingots With the large scale reduction of the crude steel production through the ingot casting route, there is now-a-days a tendency of producing extremely heavy weight steel ingots weighing over 600 t and continuous cast strands with thickness over 450 mm and rounds with diameter over 800 mm. These large size crude steel products are mainly applied for retaining components like reaction vessels for nuclear power plant and rotating components such as drive shafts of gas turbines and generator rotors. These high value products require high quality of the as-cast crude steel products, and hence, the production of the heavy crude steel products with adequate control of the quality is a big concern for steelmakers worldwide. The macro-scale segregation of alloying elements during the casting of steel ingots continues to afflict the manufacturers of steel ingots, despite many decades of research into its prediction and elimination. Defects such as A-segregates are still common, and components are regularly scrapped due to their presence, leading to increased economic and environmental costs. With the growth of the nuclear power industry, and the increased demands placed on new pressure vessels, it is now more important than ever that today’s steel ingots are as chemically homogeneous as feasible. During the solidification of alloys (liquid steel), solute is partitioned between the solid and liquid to either enrich or deplete the inter-dendritic regions. This obviously leads to variations in the composition on the scale of micro-metres (micro-segregation). Macro-segregation is a composition inhomogeneity in the scale from several millimeters to centimeters or even meters. The effects of macro-segregation are critically important in the present day applications of steel ingots and hence the ability to predict segregation severity and location is very important and highly sought after these days. Almost...

Steel ingots and their Casting during Steelmaking...

Steel ingots and their Casting during Steelmaking Ingot casting is a conventional casting process for liquid steel. Production of crude steel through the ingot casting route constitutes a very small percentage of global crude steel production. However, the method of casting of the liquid steel in ingot moulds is still fundamental for specific low-alloy steel grades and for special forging applications, where products of large dimension, high quality or small lot size are needed. Typical application for conventional ingot casting includes the power engineering industry (e.g. shafts for power generation plants, turbine blades), the oil and gas industry (conveying equipment, seamless tubes), the aerospace industry (shafts, turbines, engine parts), ship building (shafts for engines and drives), tool making and mechanical engineering (heavy forgings, cold, hot and high-speed steels, bearing, drive gears) as well as automotive engineering (shafts, axes). As the demand of heavy ingot increases nowadays, especially from the power engineering industry and ship industry, there is a tendency of producing extreme large ingots over 600 t and continuous cast strands with thickness over 450 mm and rounds with diameter up to 800 mm, which are mainly applied for pressure retaining components such as reaction vessels for nuclear power plant and rotating components like drive shafts of gas turbines and generator rotors. The moulds used for casting of ingots are made of cast iron. Cast iron is used for the production of the mould since the thermal coefficient of cast iron is lower than that of steel. Because of this property of cast iron, liquid steel on solidification contracts more than cast iron which makes detachment of ingot easier from the mould. Inner walls of the mould are coated by either tar or fine carbon. The coated material decomposes during solidification and this prevents sticking...

Ferro-Chrome

Ferro-Chrome Ferro-chrome (Fe-Cr) is an alloy comprised of iron (Fe) and chromium (Cr).  Besides Cr and Fe, it also contains varying amounts of carbon (C) and other elements such as silicon (Si), sulphur (S), and phosphorus (P). It is used primarily in the production of stainless steel. The ratio in which the two metals (Fe and Cr) are combined can vary, with the proportion of Cr ranging between 50 % and 70 %. Fe-Cr is frequently classified by the ratio of Cr to C it contains. The vast majority of Fe-Cr produced globally is the ‘charge chrome’. It has a lower Cr to C ratio and is most commonly produced for use in stainless steel production. The charge chrome grade was introduced to differentiate it from the conventional high carbon Fe-Cr (HC Fe-Cr). The second largest produced Fe-Cr ferro-alloy is the HC Fe-Cr which has a higher content of Cr than charge chrome and is being produced from higher grade of the chromite ore. Other grades of Fe-Cr are ‘medium carbon Fe-Cr’ (MC Fe-Cr) and ‘low carbon Fe-C’ (LC Fe-Cr). MC Fe-Cr is also known as intermediate carbon Fe-Cr and can contain upto 4 % of carbon. LC Fe-Cr typically has the Cr content of 60 % minimum with C content ranging from 0.03 % to 0.15 %.  However C content in LC Fe-Cr can be upto 1 %. In international trade, Fe-Cr is classified primarily according to its C content. The common categories of Fe-Cr used in international trade are as follows. Charge chrome with a base of 52 % Cr. HC Fe-Cr with C content ranging from 6 % to 8 %, base of 60 % Cr, and a maximum of 1.5 % Si. HC Fe-Cr with C content ranging from 6...

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...

Ferro-Manganese

Ferro-Manganese Ferro-manganese (Fe-Mn) is a metallic ferro alloy which is added usually along with ferro-silicon (Fe-Si) as ladle addition during steelmaking. It is a ferroalloy composed principally of manganese (Mn) and iron (Fe), and normally contains much smaller proportions of minor elements, such as carbon (C), phosphorus (P), and sulphur (S). Fe-Mn is an important additive used as a deoxidizer in the production of steel. It is a master alloy of Fe and Mn with a minimum Mn content of 65 %, and maximum Mn content of 95 %. There are two families of Mn alloys. One is called Fe-Mn while the other is known as silico-manganese (Si-Mn). Around 93 % of all the Mn produced is in the form of Mn ferroalloys consists of the Fe-Mn grades and the Si-Mn grades. Mn plays an important role in the manufacturing of steel as deoxidizing, desulphurizing, and alloying agent. It is a mild deoxidizer than silicon (Si) but enhances the effectiveness of the latter due to the formation of stable manganese silicates and aluminates. Mn is used as an alloying element in almost all types of steel. Of particular interest is its modifying effect on the iron-carbon (Fe-C) system by increasing the hardenability of the steel. Fe-Mn is produced in a number of grades and sizes and is consumed in bulk form primarily in the production of steel as a source of Mn, although some Fe-Mn is also used as an alloying agent in the production of iron castings. Mn, which is intentionally present in nearly all steels, is used as a steel desulphurizer and deoxidizer. Mn improves the tensile strength, workability, toughness, hardness and resistance to abrasion. By removing S from steel, Mn prevents the steel from becoming brittle during the hot rolling process....

Silico- Manganese

Silico- Manganese Silico-manganese (Si-Mn) is a metallic ferro alloy which is being used to add both silicon (Si) and manganese (Mn) as ladle addition during steelmaking. Because of its lower carbon (C) content, it is a preferred ladle addition material during making of low carbon steels. Si-Mn is a ferroalloy composed principally of Mn, Si, and Fe (iron), and normally contains much smaller proportions of minor elements, such as C, phosphorus (P), and sulphur (S). The ferroalloy is also sometimes referred to as ferro-silicon-manganese. Both Mn and Si play an important role in the manufacturing of steel as deoxidizing, desulphurizing, and alloying agents. Si is the primary and more powerful deoxidizer. Mn is a milder deoxidizer than Si but enhances the effectiveness of the latter due to the formation of stable manganese silicates and aluminates. It also serves as desulphurizer. Mn is used as an alloying element in almost all types of steel. Of particular interest is its modifying effect on the iron-carbon (Fe-C) system by increasing the hardenability of the steel. There are two families of Mn alloys one is called Si-Mn while the other is known as ferro-manganese (Fe-Mn). Si-Mn adds additional silicon in liquid steel which is a stronger deoxidizer and which also helps to improve some mechanical properties of steel. In each family, content of C can be controlled and lowered when producing low C grades. Around 93 % of all the Mn produced is in the form of Mn ferroalloys consists of the Fe-Mn grades and the Si-Mn grades. The Fe-Mn grades are high carbon (HC), medium carbon (MC), low-carbon (LC) and very low carbon (VLC), whereas the Si-Mn grades include medium carbon (MC) and low carbon (LC). The steel industry is the only consumer of these alloys. However...