Clean Steels

Clean Steels There are various definitions of clean steel. The term clean steel is also vague. Clean steels are generally those steels that have low levels of the solute elements sulfur, phosphorus, nitrogen, oxygen and hydrogen; controlled levels of the residual elements copper, lead, zinc, nickel, chromium, bismuth, tin, antimony and magnesium; and, a low level of non metallic or oxide inclusions. The requirements vary with the steel grade and its end use. Clean steels used for one application may be often not acceptable for a different use. Steels with low levels of solutes are sometimes termed as ‘high purity steels’ while steels with low percentage of tramp elements are often called ‘low residual steels’. Sometimes steels with a low frequency of product defects that can be related to the presence of oxide inclusions are called clean steels. Hence the definition of ‘clean’ is not absolute. Instead it is based upon the product formed from the casting and the in-service use or life of the product. In addition, the definition ‘clean’ is comparative since the cleanliness standard desired by the customer is continuously changing as a function of time and technological improvements. The term ‘clean steel’ is therefore continually variable depending upon the application. Effect of solute elements on steels The individual or combined effect of solute elements such as carbon (C), phosphorus (P), sulphur (S), nitrogen (N), hydrogen (H) and total oxygen (T.O.) is known to have a remarkable influence on the steel’s properties, such as tensile strength, formability, toughness, weldability, cracking resistance, corrosion resistance, and fatigue resistance etc. The extent of control of the solute elements needed in the steels depends on the performance expected from the steel. The influence of the solute elements on the properties of steels is given in...

Rewards and Incentives...

Rewards and Incentives One effective way of motivating employees is to provide rewards and incentives for their excellent performance and also for recognition of a job well done. Sometimes management in several organizations forgets these tools since it is felt by them that employees are paid the wages to do a good job. Management of these organizations should keep in mind that employees respond to recognition for good performance. This recognition can be given in the form of either rewards or incentives or both. These recognitions can be given in monetary as well as in non monetary form. The tools of rewards and incentives are used by the management of several organizations to motivate employees for carrying out of a task, for learning of new skills and for changing of behaviour patterns. Though the terms ‘rewards’ and ‘incentives’ are used for the purpose of motivating employees, yet both the terms are distinct terms. The distinction between rewards and incentives is sometimes get blurred and people generally can think that the two terms are one and the same. However this is not the case – far from it in fact. A reward is something that celebrates success once an action has been tried or completed. It is a thing that is given to an employee in recognition of service, effort, good behaviour, and/or achievement. It is something which is actually given to an employee after his effort or achievement. On the other hand an incentive is something that motivates an employee to perform an action. It is a thing that encourages the employee to do something. In fact incentive is a motivating factor for an employee to exceed expectations. Employee rewards and incentives can both be very effective motivators when used appropriately. In case they...

Electromagnetic Stirring in Continuous Casting Process Nov29

Electromagnetic Stirring in Continuous Casting Process...

Electromagnetic Stirring in Continuous Casting Process Since the first application of the principle of continuous casting to steel in the test continuous casting machine of Junghans of former West Germany, the quality of the continuous cast product has been paid more and more attention. In recent years with the stress on the production of clean steels, there are higher requirements for the microstructure and the composition homogenization of the cast product. The chemical composition, solidification conditions and the nature of the liquid steel flow in the mould affects the surface quality and the inner structure of the cast product. The application of electromagnetic stirring (EMS) technique promotes the formation of an equiaxed crystallic zone in the strand. It causes the refinement of the solidification structure, the reduction in the content of inclusions and improvement in the quality of the surface, sub surface and the inner structure of the cast product. Principle of electromagnetic stirring It is well known that an alternating magnetic field (B) (either single phase, two phase or three phase) applied to a conductor, whether solid or fluid, will induce electric current (j) in the conductor, and hence there is a force (F = j x B). This force is known as Lorentz force. Due to the Lorentz force there is a generation of a torque that gives the liquid steel a rotational movement.  The generated torque depends on the following factors. Intensity of supply current Number of windings forming a coil Frequency System geometry These parameters change depending on the stirrer type. Thus the magnetic field acts as a non intrusive stirring device and it can, in principle, be engineered to provide any desired pattern of stirring. The stirrer design, size and position etc. depend on the continuous casting machine data,...

Wear Resistant Structural Steels...

Wear Resistant Structural Steels Wear is described as ‘the phenomenon of metal surfaces that are moving relative to each other getting worn out due to the surfaces scratching each other or due to metallic adhesion’. Wear resistance can be said to be the property in which such a phenomenon is difficult to occur. The properties of wear resistant steels enable them to resist wear, due to rubbing, impact or compressive loads from external agents such as cement, sand, stones etc., and are intended for use in equipment construction and for replacement of wearing parts. Numerous structures, such as dump bodies, materials handling equipment and crushing machines, for instance, are exposed to continuous, abrasive and impact wear, which is costly. As a solution, special structural steels have been developed that are highly resistant to wear and abrasion. Factors affecting wear resistance of steels There are four main factors which have considerable effect on the wear resistance of steels. These are (i) heat treatment, (ii) alloying additions, (iii) influence of carbon content, and (iv) effects of carbides, both primary and secondary. A big factor affecting wear resistance is ‘hardness’. In general, the wear resistance increases as the material becomes harder. There is a direct relationship between hardness and wear resistance. The resistance of a steel surface against wear is primarily a function of the ‘effective hardness’ resulting from the destructive action of the abrasive particles and depend on the strain hardening rate of the steel under the applied conditions. Factors affecting plastic deformation, such as grain size, recrystallization temperature, hardness, strain rate etc. also affect the wear of steels. Unlike single crystals which have free boundaries, the grains of a polycrystalline steel are influenced by their neighours during deformation, their constraining action on deformation is least...

Quality Management System...

Quality Management System Quality management system (QMS) is a set of coordinated activities to direct and control an organization with regard to quality in order to continually improve the effectiveness and efficiency of its performance. QMS is structured around interlinked processes that provide the necessary implementation controls to ensure customer and regulatory requirements are met, and continual process improvement occurs. The main thrust of a QMS is in defining the processes, which result in the production of quality products and services, rather than in detecting defective products or services after they have been produced. QMS is a business asset to an organization since it has a major impact on the financial performance of a business, its exposure to risks, and employee’s morale. It also gives confidence to an organization with respect to its ability to produce and provide products that fulfill the needs and expectations of customers and external stakeholders. QMS follows process approach as shown in Fig 1. Fig 1 Process approach to QMS QMS principles Quality management system is based on eight quality management principles. These principles are used as a guide for an organization to improve its performance. These eight principles are described below. Principle 1: Customer focus –  Organizations depend on their customers and therefore should understand current and future customer’s needs. They should meet customer requirements and strive to exceed customer expectations. The key benefits of customer focus are (i) increased revenues and market share obtained through flexible and fast responses to market opportunities, (ii) increased effectiveness in the use of the organizational resources to enhance customer’s satisfaction and (iii) improved customer loyalty to repeat business. Principle 2: Leadership –  Leaders establish unity of purpose and direction of the organization. They create and maintain the internal environment in which...