Mini Blast Furnace and Iron making Oct10

Mini Blast Furnace and Iron making...

Mini Blast Furnace and Iron making Mini blast furnaces (MBF) are generally viewed as miniature versions of the conventional large blast furnaces (BF). These furnaces are ideally suited for small scale operations. In fact, they are basically the forerunner to modern conventional last blast furnaces and hence they have operated for a longer period of time. MBFs are located in many countries but the majority of the MBFs are located in China, India, Brazil and Indonesia. Plant availability as well as the perfection achieved in this technology has made MBF an accepted route for iron making. Further, these days, most of the technologies of design, burdening and operation which have become the norm for today’s modern large furnaces have also been adopted in MBFs. MBF is a vertical shaft furnace with a crucible like hearth. Burden materials consisting of iron ore, coke or charcoal used as a reducing agent as well as fuel, and fluxes, usually limestone or dolomite, are charged into the top of the furnace. The furnace works on the principle of a counter current reactor. As the burden descends through the shaft, it is preheated and pre-reduced by the hot gases ascending from the furnace bottom. The gases are generated by introducing hot air blast enriched with oxygen through tuyeres. The hot blast burns the reducing agent, producing reducing gases and heat required for the reduction process taking place in the furnace. The reduced burden material melts to form HM (liquid iron) which becomes saturated with carbon and descends to the hearth. The fluxes combine with the impurities in the burden materials to produce a molten slag which accumulates on top of the liquid iron in the hearth. Liquid iron and liquid slag are periodically tapped from the furnace. MBF exhibits...

Classification of Steel Products produced in Steel Plants...

Classification of Steel Products produced in Steel Plants Steel products in general are classified as (i) castings, (ii) forged products, (iii) stamped products, (iv) bright products, (v) cold formed products, (vi) welded sections, (vii) wire and wire products, (viii) pipes, tubes, hollow sections and hollow bars, and (ix) powder metallurgy products. Steel products produced in steel plants are classified as per (i) stage of manufacture of the product, (ii) shape and dimensions of the product, and (iii) the product appearance. As per the stage of manufacture, the range of steel products produced in the steel plants are usually grouped into three main categories (Fig 1) namely (i) crude steel products, (ii) semi-finished steel products, and (iii) finished rolled steel products. Finished rolled steel products can be (i) hot rolled products, (ii) cold rolled products, and (iii) coated products.  Fig 1 Categories of steel products Crude steel products Crude steel products are either in the liquid state or in solid state. Liquid steel is normally used for the production steel castings. Crude steel in solid form was earlier considered as steel ingots which are produced by pouring liquid steel into iron moulds of a shape appropriate to the subsequent processing into semi-finished or finished steel products normally by hot rolling or forging. The shape of steel ingots usually resembles a truncated pyramid or truncated cone with the side surfaces may be corrugated and the corners more or less rounded. Steel ingots may be dressed and/or hot scarfed or cropped depending on the subsequent conversion requirements. Steel ingots can be distinguished based on their cross sections as (i) having a cross-section which can be square, rectangular (of width less than twice the thickness), polygonal, round, oval or shaped according to the profile to be rolled, (ii)...

Quality of Products and Process Control...

Quality of Products and Process Control A product is said to be of desired quality when it complies with the specification as well as customer’s requirements and expectations and when it displays basic, performance and excitement functionalities. Products are produced by manufacturing processes. Also, quality cannot be tested into the product. It is to be built in the product by the manufacturing process during its manufacturing. One of the main factors which affect the quality of the product is the quality of the manufacturing process which produces the product. Sound and reliable processes produce quality products. Hence improving the quality of the manufacturing processes is a precondition for better product quality at an acceptable cost. Process as used in the terms process control and process industry, refers to the methods of changing or refining raw materials to create end products. Process control refers to the methods that are used to control process variables when manufacturing a product. Organization controls the production process for three reasons namely (i) reduce variability, (ii) increase efficiency, and (iii) ensure safety. Process control can reduce variability in the end product, which ensures a consistently high-quality product. Manufacturing processes have the many features which fall into one of the following categories Procedures – These are a series of steps followed in a regular, definite order. Methods – These are an orderly arrangement of a series of tasks, activities, or procedures. Equipment and supplies – These are physical devices and other hard goods which are needed to perform the process Materials – These are tangible elements, data, facts, figures, or information needed which along with equipment and supplies make up inputs required. People – They are numbers of individuals, skills they require, goals, and tasks they perform. Training – It is...

Heat Affected Zone and Weld Metal Properties in Welding of Steels Oct01

Heat Affected Zone and Weld Metal Properties in Welding of Steels...

Heat Affected Zone and Weld Metal Properties in Welding of Steels There are many factors which control the properties of the weld metal and heat affected zone (HAZ) while welding of carbon (C) and low alloy steels. The weld metal and HAZ are frequently referred as steel weldments. The welding processes, welding consumables, and welding parameters have also influence on these properties. Properties of steel weldments are also influenced by the corrosive atmospheres and cyclic loading to which they are frequently being subjected. Heat affected zone During the selection of steels, the characteristics of the HAZ are more important than the weld metal. This is since the metallurgical and mechanical properties of the HAZ are directly linked to the selected steel. However, these properties can be adjusted by welding parameters and post weld heat treatment (PWHT). Also the metallurgical and/or weldability issues related with the HAZ characteristics are more difficult to tackle than those connected with the weld metal. Welding issues which usually occur in the weld metal can frequently be overcome by changing the welding electrode and/or other welding consumables. In comparison, difficulties with the HAZ can often be resolved only by changing the base steel, which is generally a very costly measure, or by changing the heat input. Different empirical C equivalents (CE) have been developed and utilized to evaluate the weldability and the tendency of hydrogen (H2) induced cracking (HIC) of the base steels. The most frequently used equation for CE which is also being used by the International Institute of Welding (IIW) is CE = % C + % Mn/6 + (% Cu + % Ni)/15 + (% Cr + % Mo + % V)/5. In Japan, the Ito-Bessyo composition characterizing parameter, Pcm, is more widely used. Pcm is considered...