Corrosion of Cast Steels...

Corrosion of Cast Steels Cast steels are generally classified into the categories of (i) carbon (C) steels, (ii) low alloy steels, (iii) corrosion resistant steels, and (iv) heat resistant steels, depending on the alloy content and the planned usage. Steel castings are categorized as corrosion resistant if they are capable of sustained operation when exposed to attack by corrosive agents at operating temperatures which are generally below 300 deg C. The high alloy iron base compositions are generally given the name ‘stainless steels’, though this name is not recognized universally. Actually, these steels are widely referred to as cast stainless steels. Some of the high alloy steels (e.g. 12 % chromium steel) show many of the familiar physical characteristics of C steels and low alloy steels, and some of their mechanical properties, such as hardness and tensile strength (TS), can be altered by suitable heat treatment. The alloy steels of higher chromium (Cr) content (20 % to 30 % Cr), Cr-Ni (nickel)  steels and Ni-Cr steels do not show the changes in phase observed in ordinary C steel when heated or cooled in the range from room temperature to the melting point. Consequently, these steels are non hardenable, and their mechanical properties depend on the composition instead of heat treatment. The high alloy steels (stainless steels) differ from C steels and low alloy steels in other respects, such as their production and properties. Special attention is required to be given to each grade with regard to casting design and casting practice in the foundry. For example, such elements as Cr, Ni, C, N2 (nitrogen), Si (silicon), Mo (molybdenum), and Nb (niobium) can exert a deep impact on the ultimate structure of these complex steels. Hence, balancing of the alloy compositions is normally required to...

Digitization Process

Digitization Process The information contained in traditional print materials such as important records, minutes of important meetings, original drawings, and other similar documents cannot be preserved for a very long time due to several reasons. As the time pass by, the information contained in these materials fades out, the medium becomes brittle and finally the document becomes unusable. These documents can be lost forever unless there are alternative arrangements for recapturing and reproducing them. Fortunately, technological advances have provided suitable alternatives for the preservation of such valuable documents. Digitization process is of crucial importance for data processing, storage and transmission, because it “allows information of all kinds in all formats to be carried with the same efficiency and also intermingled”. Unlike analog data, which typically suffers some loss of quality each time it is copied or transmitted, digital data can, in theory, be propagated indefinitely with absolutely no degradation. This is why it is a favoured way of preserving information in an organization in the present day environment. Digitization process in an organization deals with strategies, methods and tools used to capture, manage, store, preserve, and deliver content and documents related to organizational processes. It deals with tools and strategies which streamlines the unstructured information of the organization. Digitization is the process of converting information into a digital format. In this format, information is organized into discrete units of data (called bits) that can be separately addressed (usually in multiple-bit groups called bytes). This is the binary data that computers and many devices with computing capacity can process. Text and images can also be digitized.  Similarly digitization of audio and video presentations is also possible. Digitization process is also known as imaging or scanning and is the means of converting hard-copy, or non-digital, records into digital...

Desulphurization of Liquid Steel Jul30

Desulphurization of Liquid Steel...

Desulphurization of Liquid Steel Solubility of sulphur (S) in liquid iron (Fe) is quite high. But the solubility of S in solid iron is limited. It is 0.002 % in ferrite at room temperature and 0.013 % in austenite at around 1000 deg C. Hence, when liquid steel cools down, sulphur is liberated from the solution in the form of iron sulphide (FeS) which forms a eutectic with the surrounding iron. The eutectic is segregated at the iron grain boundaries. The eutectic temperature is comparatively low at around 988 deg C. Fe-FeS eutectic weakens the bonding between the grains and causes sharp drop in the properties of steel at the temperatures of hot deformation. During the continuous casting of liquid steel, sulphur present in liquid steel (i) causes the formation of undesirable sulphides which promotes granular weaknesses and cracks in steel during solidification, (ii) lowers the melting point and inter-granular strength, (iii) contributes to the brittleness of steel and thus acts as stress raiser in steel, and (iv) results in the hot shortness. Sulphur, present in solid steel as FeS inclusions, has several detrimental effects on steel processing. During deformation, FeS inclusions act as crack initiation sites and zones of weakness. Such inclusions from sulphur adversely affect the toughness, ductility, formability, weldability, and corrosion resistance of steel. An increase in manganese (Mn) content (not less than 0.2 %) however, helps prevent formation of FeS. Sulphur is thus an undesirable element in steel. Manganese actively reacts with iron sulphides during solidification of steel transforming FeS to MnS according to the following reaction. FeS (slag) + Mn (steel) = MnS (slag) + Fe The melting temperature of manganese sulphide (MnS) is comparatively high (around 1610 deg C). Hence steel containing manganese can be deformed in hot state. However...

Corrosion of Stainless Steels...

Corrosion of Stainless Steels Stainless steels (SS) are alloys of iron (Fe) which containing a minimum of 10.5 % chromium (Cr). With increasing content of Cr and with the presence or absence of many of other elements, SS can provide an extraordinary range of corrosion resistance. Different grades of SS are being used since several years in atmospheres which are mild (open air, in architectural applications) as well as extremely severe (chemical-processing industries). Stainless steels are classified in five families as per the crystal structures and the strengthening precipitates. Each family of SS shows its own general features in terms of mechanical properties and corrosion resistance. Within each family, there is a range of specifications which varies in composition, corrosion resistance, and cost. Stainless steels are vulnerable to several types of localized corrosive attack. The avoidance of such localized corrosion is the focus of most of the efforts made in the selection of SS. Also, the corrosion performance of SS is strongly influenced by practices of design, fabrication, surface conditioning, and maintenance. The selection of a grade of SS for a specific application involves the consideration of several factors, but the main factor remains corrosion resistance. It is the first necessity to specify the likely service environment. Besides considering the design conditions, it is also necessary to consider the reasonably anticipated exposures or upsets in service conditions. The suitability of a specific specification can be assessed from laboratory tests or from the documented field experience in similar atmospheres. Once the specification with satisfactory corrosion resistance has been identified, it is then appropriate to consider other factors such as mechanical properties, ease of fabrication, the types and degree of risk present in the application, the availability of the necessary product forms, and cost. Families of...

Customer Segmentation – A Technique for Effective Marketing...

Customer Segmentation – A Technique for Effective Marketing Customer segmentation is also known as market segmentation. It is the practical division of potential customers in a given market into discrete groups. The division is based on customers having similar appearing needs and buying characteristics so that a common market approach can be used by an organization for the marketing of its products to them in a competitive and economical manner. Also when the organization plans for expansion, then executing a marketing strategy without any knowledge of how the target market is segmented is similar to firing shots at a target blindfolded. In such case the likelihood of hitting the target is a matter of luck more than anything else. Without a deep understanding of how best the current customers of the organization are segmented, the organization often lacks the market focus needed to allocate and spend its precious human and capital resources efficiently. Furthermore, a lack of best current customer segment focus can cause diffused go-to-market and product development strategies that hamper the ability of the organization to fully engage with its target segments. All of these factors when combine together, can ultimately obstruct the growth of the organization. All markets are heterogeneous and all the customers are not the same. The different customers have got different needs. Also customers’ behaviours towards a product vary based on their requirements as well as on the environment in which they are working. Hence marketing strategy of ‘one size that fits all’ does not work in present day situation. Therefore, effective marketing strategies requires a segmentation of the market into smaller and homogeneous customers’ segments, the understanding of needs and wants of these segments, the design of the products and services to meet these needs, and development of...