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....

Synthetic Slag for Secondary Steelmaking...

Synthetic Slag for Secondary Steelmaking Synthetic slag consists of prepared mixture of several individual oxides which is used during secondary steelmaking to assist the steel treatment in the ladle from the viewpoint of effective refinement. Synthetic slag practice is normally used to obtain clean steels and also for the desulphurization of the liquid steel. Secondary steelmaking is a critical quality control step between the primary steelmaking and the continuous casting of the liquid steel. A key feature for success with the secondary steelmaking processes is the slag control. Use of synthetic slag which is specifically designed to have the required chemical composition and physical properties helps in the slag control. The  desirable properties of the synthetic slag include (i) slag is to have high sulphide capacity, (ii) it is to be basic in nature, (iii) it is to be fluid to obtain faster reaction rates, and (iv) it is not to cause excessive refractory wear. The secondary steelmaking slag is in liquid form in the ladle and floats on the surface of liquid steel which is usually at temperature of 1,600 deg or higher. It acts like a sponge to absorb the impurities consisting mainly of sulphur and non-metallic inclusions. The design of the slag is a critical step impacting the efficiency of the steel refining processes during the secondary steelmaking. Slag regime in secondary steelmaking significantly influences the final quality of the produced steel, particularly with respect to the achieved desulphurization of steel. One of the possibilities for influencing the slag regime is the application of synthetic slags to the ladle slag, formed from slag-making additions during the liquid steel tapping. Synthetic slag practice during secondary steelmaking maximizes the efficiency of the steel refining process by (i) improving steel quality, (ii) improving productivity,...

Lead in Steels

Lead in Steels  Lead (Pb) (atomic number 82 and atomic weight 207.21) has density of 11.34 gm/cc. Melting point of Pb is 327.5 deg C and boiling point is 1749 deg C. The phase diagram of the Fe-Pb binary system is at Fig 1. Pb has a face centered cubic (f.c.c.) crystal structure.  Fig 1 Fe-Pb binary system Pb is only slightly soluble in liquid or solid steel. When added , Pb does not remain in the metal but it remains separate from and mechanically dispersed in the steel  as submicroscopic metallic inclusions when it solidifies. It does not change the mechanical properties of the steel appreciably. The sole function of Pb is to improve the machinability of steel. This accounts for the wide use of Pb for high strength steel for which machinability is required. Also, Pb only slightly influences mechanical properties of steel. However, with the growing consciousness of environmental issues in recent years, there is a tendency toward eliminating Pb because it is seen to be one of the pollutants of the environment. Addition agents and addition practice Elemental Pb is available as cored wire (Pb micro shots), pellets and fine shots suitable for addition in the continuous casting tundish, ladle metallurgical furnace, or degassing furnace. Alloys containing bismuth (bi) are also available for addition. Addition of Pb in liquid steel is carefully controlled to ensure its even dispersion in the solidifying steel. Segregation of Pb can be an issue. Pb segregation in steel  can lead to problems during cold working and machining of steel. Due to this Pb bearing steels are normally checked for segregation. The steel sample is usually heated at 700 deg C and is examined for uniform distribution of Pb. This test is known as sweat test. Pb does not...

Zirconium in Steels

Zirconium in Steels  Zirconium (Zr) (atomic number 40 and atomic weight 91.22) has density of 6.52 gm/cc. Melting point of Zr is 1855 deg C and boiling point is 4377 deg C. Zr  has a hexagonal close pack crystal structure. The phase diagram of the Fe-Zr binary system is given at Fig 1. Fig 1 Fe-Zr binary phase diagram Zr is being used as a alloying element in steels since the early 1920s, but has never been universally employed, as have niobium (Nb), titanium(Ti), and vanadium (V). Historically, the main use of additions of Zr to steel was for combination preferentially with sulphur, to avoid the formation of manganese sulphide (MnS), known to have a deleterious influence of the impact toughness of wrought and welded steel. These days there has been a renewed interest in the addition of Zr to the micro alloyed steels. Zr is highly reactive and has a strong affinity, in decreasing order, for oxygen (O), nitrogen (N), sulphur (S), and carbon (C). Its affinity for O, S, and N is the primary reason for its use in steelmaking. Due to this property it controls  the nonmetallic inclusions of sulphides and oxy-sulphides. it is also used for the fixation of N mainly in boron (B) steels. Zr also inhibits grain growth and prevents strain aging but its use for either of these reasons is limited. Because of its relatively high price and also due to the availability of cheaper replacements, general acceptance of Zr for use as an alloying element in steels is limited. Addition agents Te Zr addition agents in the liquid steel are iron-silicon-zirconium (FeSiZr) alloy, ferrozirconium (Fe-Zr) alloy, Zr alloy scrap and pure Zr sponge. Out of these the most popular addition agent is FeSiZr since it is...