Nitriding Process and Nitriding Steels...

Nitriding Process and Nitriding Steels  According to DIN EN 10052:1994-01, nitriding is defined as the thermo-chemical treatment of a work piece in order to enrich the surface layer with nitrogen. Carbo-nitriding involves enriching the surface layer with nitrogen and carbon. The nitriding process, which was first developed in the early 1900s, continues to play an important role in many industrial applications. It often is used in the manufacture of aircraft, bearings, automotive components, textile machinery, and turbine generation systems. It remains the simplest of the case hardening techniques. The basic of the nitriding process is that it does not require a phase change from ferrite to austenite, nor does it require a further change from austenite to martensite. In other words, the steel remains in the ferrite phase (or cementite, depending on alloy composition) during the complete procedure. This means that the molecular structure of the ferrite (bcc) does not change its configuration or grow into the face-centered cubic (fcc) lattice characteristic of austenite, as occurs in more conventional methods such as carburizing. Also, since only free cooling takes place, rather than rapid cooling or quenching, no subsequent transformation from austenite to martensite occurs. Again, there is no molecular size change and, more importantly, no dimensional change, only slight growth due to the volumetric change of the steel surface caused by the nitrogen diffusion. What can (and does) produce distortion are the induced surface stresses being released by the heat of the process, causing movement in the form of twisting and bending. The purpose of nitriding is to enrich the surface layer of a work piece with nitrogen in order to increase the hardness in the surface. The process of nitriding takes advantage of the low solubility of nitrogen in the ferritic crystal structure...

Management of Uncertainties...

Management of Uncertainties  Donald Rumsfield, US defence secretary at a press briefing during 2002 has stated “There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – the ones we don’t know we don’t know”. Uncertainties are the things that are unknown unknowns. Uncertainty can be defined as unpredictable events in manufacturing environment that disturb operations and performance of an organization. Presently organizations are functioning in environments which combine known knowns, known unknowns and unknown unknowns. The growth of the last category presents organizational management with a new and little charted management challenge. The fast changing and uncertain environments these days brings a lot of uncertainties for the organization. These uncertainties require management to be agile and responsive for facing the conditions of change and uncertainty. The timing of uncertainty often causes a greater challenge response from the management than the uncertainty itself. “All of management’s value is derived from managing uncertainty.” Sometimes risks are equated with uncertainties. But uncertainty is much more than risk and it encompasses risk in it as shown in Fig 1. Fig 1 Risk and uncertainty  Every organization has to pass through several periods or many situations of uncertainties. Periods of uncertainties are an inevitable aspect of most organizations, but even the most proficient managements have difficulty in handling these periods. They use decision milestones to anticipate outcomes, risk management to prevent disasters and sequential iteration to make sure everyone is making the desired product, yet the organization still ends up the periods of uncertainties with unfulfilled plans, overflowing budgets and compromised outcomes. Uncertainties may exist in practically all decision making situations....

Refractories for Basic Oxygen Furnace Aug28

Refractories for Basic Oxygen Furnace...

Refractories for Basic Oxygen Furnace  The main objective in the development of refractories for basic oxygen furnace (BOF) is to get a useful lining life of the wear lining so as to obtain maximum availability of the BOF. Longer lining life not only results in lower refractories cost but it also enables higher productivity through increased furnace availability. The following are the basic requirements from the refractories of BOF. Thermal spalling resistance Corrosion resistance Abrasion resistance Oxidation resistance Hot modulus of rupture BOF is lined normally with a permanent lining and above it there is a wear lining. Permanent lining thickness may vary from 100 mm to 120 mm and is made of chrome-magnesite permanent lining which is given on the full height of the BOF. The refractories available for use in wear linings of BOF range from tar or pitch bonded dolomite or magnesia (MgO), chrome magnesite, or magnesium chrome refractories to the advanced refractories that are made with resin bonds, metallics, graphites, and sintered and/or fused magnesia that can be with a purity of 99 %. Bricks are designed with a combination of critical physical properties to withstand the high temperatures and rapidly changing conditions/environment throughout the BOF heat cycle. A balance of different properties such as hot strength, oxidation resistance, and slag resistance is necessary from the BOF refractories for good performance. When BOF process of steelmaking was introduced in 1950s, converters were lined with tar dolomite bricks and stabilized burnt dolomite bricks. These refractories were then replaced by semi stabilized burnt dolomite bricks and tar bonded and fired bricks made of synthetic magnesia dolomite clinker. Chrome magnesite, or magnesium chrome refractories were used for lining of some BOFs.  High purity burnt magnesia bricks were also used in some of BOF...

Malleable Cast Iron

Malleable Cast Iron  Malleable cast iron is essentially white cast iron which has been modified by heat treatment. It is formed when white cast iron is heated to around 920 deg C and then left to cool very slowly. Graphite separates out much more slowly in this case, so that surface tension has time to form it into spheroidal particles rather than flakes. Due to their lower aspect ratio, spheroids are relatively short and far from one another, and have a lower cross section vis-a-vis a propagating crack. They also have blunt boundaries, as opposed to flakes, which alleviates the stress concentration problems faced by the gray cast iron. In general, the properties of malleable cast iron are more like mild steel. There is a limit to how large a part can be cast in malleable cast iron, since it is made from white cast iron. The white cast iron is converted to malleable cast iron by a two stage heat treatment process to a condition having most of its carbon content in the form of irregularly shaped nodules of graphite, called temper carbon. The structure of malleable cast iron consists of ferrite, pearlite and tempered carbon as compared to the fracture inducing lamellar structure of gray cast iron. Malleable cast irons are a class of cast irons with mechanical strength properties that are intermediate to those of gray or ductile cast irons. The microstructure provides it properties that make malleable cast irons ideal for applications where toughness and machinability are required, and for components that are required to have some ductility or be malleable so that they can be bent or flexed into position without cracking. Malleable cast iron besides less sensitive to cracking has a range of features, such as higher values of...

Negotiation skills for effective negotiations...

Negotiation skills for effective negotiations  It is inevitable that, from time-to-time, conflict and disagreement can arise due to the differing needs, wants, aims and beliefs of the people who are brought together.  Without negotiations, such conflicts may lead to argument and resentment resulting in one or all the parties feeling dissatisfied. Negotiation is normally done so as to reach agreement without causing future barriers to communications. Negotiation takes place when two or more people/parties, with differing views, come together to attempt to reach agreement on an issue. It is persuasive communication or bargaining. Negotiation is a cooperative process whereby participants try to find a solution which meets the legitimate interests of the negotiating parties. It is the process between two or more parties to settle differences. In the process of negotiation parties try to reach compromise or agreement while avoiding argument and dispute. In case of any disagreement, parties understandably aim to achieve the best possible outcome for their position (or perhaps an organization they represent). However, the principles of fairness, seeking mutual benefit and maintaining a relationship are the keys to a successful outcome. The word ‘negotiation’ originated from the Latin expression, ‘negotiatus’, which means ‘to carry on business’.  Negotiating is the process of communicating back and forth, for the purpose of reaching a joint agreement about differing needs or ideas. It is a collection of behaviours that involves negotiation skills, communication, sales, marketing, psychology, sociology, assertiveness and conflict resolution. A method of negotiation is usually judged by three criteria namely (i) it should produce wise agreement if agreement is possible, (ii) it should be efficient, and (iii) it should improve or at least not damage the relationship between the parties. Negotiations are viewed ‘hard’ where the participants are adversaries, the goal is victory, there is...