Martensitic Stainless Steels...

Martensitic Stainless Steels Martensitic grades of stainless steel were developed in order to provide a group of stainless steels which are corrosion resistant and hardenable by heat treatment. Martensitic stainless steels are essentially Fe-Cr-C alloys and are similar to carbon or low alloy steels with a structure similar to the ferritic steels. However, due the addition of carbon, they can be hardened and strengthened by heat treatment, in a similar way to carbon steels. The main alloying elements are chromium (10.5 % to 18 %), molybdenum (0.2 % to 1 %), no nickel (except for two grades), and carbon (0.1 % to 1.2 %). Major grades in the family of martensitic group of stainless steels are given in Fig 1. Fig 1 Major grades of martensitic stainless steels History The characteristic body centered tetragonal martensitic microstructure was first observed by German microscopist Adolf Martens around 1890. In 1912, Elwood Haynes applied for a U.S. patent on a martensitic stainless steel alloy. This patent was not granted until 1919. Also in 1912, Harry Brearley of the Brown – Firth research laboratory in Sheffield, England, while seeking a corrosion resistant alloy for gun barrels, discovered and subsequently industrialized a martensitic stainless steel alloy. The discovery was announced two years later in a January 1915 newspaper article in The New York Times. Brearley applied for a US patent during 1915. Properties The structures of martensitic stainless steels are body centered tetragonal (bct) and they are classified as a hard ferro magnetic group. In the annealed condition, these steels have tensile yield strengths of around 275 N/sq mm and hence they can be machined, cold formed, or cold worked in this condition. These stainless steels have good ductility and toughness properties, which decrease as strength increases. Martensitic stainless steels can be moderately hardened by...

Branding, Brand and Brand Management...

Branding, Brand and Brand Management Branding is assembling of various marketing mix medium into a whole so as to give an organization or a product an identity. It is nothing but capturing the minds of the customers with the name of the brand. Brand gives an image of an experienced, huge and reliable organization. It is all about capturing the niche market for the product / service of the organization and about creating a confidence in the current and prospective customers’ minds that the organization or the product is the unique solution to their problem. The aim of branding is to convey brand message vividly, create customer loyalty, persuade the buyer for the product, and establish an emotional connectivity with the customers. Branding forms customer perceptions about the product and raises customer expectations about the product. The primary aim of branding is to create differentiation with the competition. Hislop defined branding in the year 2001 as ‘the process of creating a relationship or a connection between a company’s product and emotional perception of the customer for the purpose of generating segregation among competition and building loyalty among customers’. Kapferer and Keller have defined branding as a fulfillment in customer expectations and consistent customer satisfaction. Branding can also be defined as ‘a seller’s promise to provide consistently a unique set of characteristics, advantages, and services to the buyers/consumers. It is a name, term, sign, symbol or a combination of all these planned to differentiate the goods/services of one seller or group of sellers from those of the competitors’. Branding normally precedes and underlies any marketing effort. Branding is not push, but pull. Branding is the expression of the essential truth or value of the organization, the product, or the service. It is the communication of...

Argon Oxygen Decarburization Process Apr28

Argon Oxygen Decarburization Process...

Argon Oxygen Decarburization Process Argon oxygen decarburization (AOD) is a process primarily used in production of stainless steel and other high grade alloys such as silicon steels, tool steels, nickel-base alloys and cobalt-base alloys with oxidizable elements such as chromium and aluminum. AOD was invented in 1954 by the Lindé division of The Union Carbide Corporation, which became Praxair in 1992. An AOD converter is shown in Fig 1. Fig 1 AOD converter Today, over 75 % of the world’s stainless steel is made using the AOD process. The process is very popular because it combines higher metallic yields with lower material costs. It provides an economical way to produce stainless steel with a minimum loss of precious elements. It is part of a duplex process in which scrap or virgin raw materials are first melted in an electric arc furnace (EAF) or induction furnace (IF). The molten metal is then decarburized and refined in an AOD converter to less than 0.05 % carbon. The key feature in the AOD converter is that oxygen for decarburization is mixed with inert gas such as argon or nitrogen and injected through submerged tuyeres. This argon dilution of oxygen minimizes unwanted oxidation of precious elements contained in specialty steels, such as chromium. Other benefits of AOD process include pinpoint accuracy in chemistry control down to 0.01 % carbon and lower, rapid desulfurization to less than 0.001 %, and lead removal to less than 0.001 %. The end result is a cleaner metal coupled with increased productivity. AOD process uses dilution technique for the decarburization of steel bath. The injection of inert gas (argon or nitrogen) lowers the partial pressure of CO in the bath, thus allowing  higher chromium content to be in equilibrium with lower carbon contents. The amount...

Austenitic Stainless Steels...

Austenitic Stainless Steels Austenitic stainless steels are the most common and widely known types of stainless steels. They make up over 70 % of total stainless steel production. These steels contain around 16 % to 25 % chromium and sufficient nickel and/or manganese to retain an austenitic structure at all temperatures from cryogenic region to the melting point of the stainless steel. Austenitic stainless steels can also contain nitrogen in solution.  Although nickel is the alloying element most commonly used to produce austenitic stainless steels, nitrogen can also be used to produce austenitic stainless steels. The austenitic stainless steels are more easily recognized because of their non magnetic properties. Austenitic steels are non magnetic since the face centered cubic structure of austenite is non magnetic. They are extremely formable and weldable, and they can be successfully used from cryogenic temperatures to the jet engines and red hot temperatures of furnaces. The austenitic stainless steels can have compositions anywhere in the portion of the Schaeffer- Delong diagram labeled austenite shown in Fig. 1. Fig 1 Schaeffer- Delong diagram The family of austenitic stainless steels is shown in Fig 2. Fig 2 Family of austenitic stainless steels Austenitic stainless steels are mainly segregated into the following two series 200 series – Stainless steels with a low nickel and high nitrogen content are classified as 200 series. These are chromium-nickel-manganese austenitic stainless steels. Grade 201 is hardenable through cold working while the grade 202 is a general purpose stainless steel. Decreasing nickel content and increasing manganese results in weak corrosion resistance. 300 Series – The most common austenitic stainless steels are iron-chromium-nickel steels and are widely known as the 300 series. In this series the most widely used austenitic stainless steel is the grade 304, also known...

Disaster Management

Disaster Management Disaster is defined as an event or series of events, which gives rise to causalities and damage or loss of properties, infrastructures, environment, essential services or means of livelihood on such a scale which is beyond the normal capacity of the affected community to cope with. Disaster is also described as a ‘catastrophic situation in which the normal pattern of life or eco system has been disrupted  and extra ordinary emergency interventions are required to save and preserve lives and/or environment’. Disasters are characterized by some or all of the following issues. They are disruptive to individuals and communities. They are not part of day to day experience and are outside normal life expectations. They are unpredictable in occurrence and effects can be of sudden onset. They require a response for which normal local resources may not be adequate. They have a wide range of effects and impacts on the human and physical environment. For reducing the impact of a disaster, a comprehensive disaster management programme is necessary in every organization which is aiming at the following activities. Development of an efficient disaster management system which improves the effectiveness of the management of disasters. Mainstreaming of disaster risk reduction in order to reduce the impact of disasters. To ensure that effective disaster preparedness measures are in place in order to cope with the disasters when they occur. There is an effective emergency response and recovery when disaster strikes Disaster management cycle recognizes four major functional areas which are considered as necessary components of a comprehensive approach. These are (i) prevention and mitigation, (ii) preparation, (iii) response, and (iv) recovery. Further to these functional areas, the key responsibilities of agencies connected with the disaster management include the following. Planning – The analysis of...