Main Features of a modern Hot Strip Mill Dec22

Main Features of a modern Hot Strip Mill...

Main Features of a modern Hot Strip Mill The objective of a hot strip mill (HSM) is to reheat and roll thick slabs into thin strip with a wide range of thickness. Because of its huge size and large investment a hot strip mill need to have a life time of several decades. The mill must be capable of meeting the market demands for a wide range of steel grades, in particular, high strength and advanced high strength steels (AHSS) with good cold formability and with superior strip properties. The mill should be able to meet the following requirement High mill availability coupled with high productivity and high yields. Meeting the need of low maintenance. Meeting the need of lower energy consumption. Improved product quality by meeting close thickness and profile tolerances as needed by the modern day customers, through powerful controls and adjustments. These tolerances may be much closer than specified in various international standards. More flexible rolling schedules to ensure short delivery times and economical rolling of smaller lot sizes. For achieving these demanding requirements, many important features are incorporated in the modern conventional hot strip mills. Some of these are described below. Reheating furnace – Modern hot strip mills are equipped with energy efficient walking beam furnaces which are normally computerized controlled. These reheating furnaces uniformly heat the slabs to the target temperatures at the required production rates and without skid marks and without cold spots. These furnaces are capable of receiving cold or hot slabs as the charge material in the furnace. Descalers – Descalers are a must in hot strip mills for attaining good surface quality. Present day descalers employ state of the art nozzle technology with highly effective application of high pressure water (upto 400 bars). Descalers are...

Direct Reduced Iron

Direct Reduced Iron Direct reduced iron (DRI) is also known as sponge iron. It is produced by the reduction of iron ore (in the form of lumps or pellets) by either non-coking coal or a reducing gas produced by reforming of natural gas. The reducing gas can also be produced by the gasification of coal. The reducing gas is normally a mixture. The majority gases in this mixture are hydrogen (H2) and carbon mono oxide (CO). These gases act as reducing agents. The reduction process is conducted at high temperature but substantially below the melting point of iron. Since the reduction reaction takes place in solid state, the lump or pellet retain their original shape, but are considerably lighter due to the removal of the oxygen from the ore. Hence the produced direct reduced iron has a highly porous structure. This porous structure gives DRI an appearance of a sponge and because of it, DRI is also known as sponge iron. Iron content in the DRI is in two forms. One is in metallic form which is known as metallic iron, Fe (M), and the second form is iron present in residual iron oxides, Fe (O). The total iron Fe (T) in DRI is the sum of these two iron components. Metallic iron is the aggregate quantity of iron, either free or combined with carbon (as cementite) present in DRI. Metallization of DRI is a measure of the conversion of iron oxides into metallic iron (either free or in combination with carbon as cementite) by removal of oxygen due to the action of the reductant used. Degree of metallization of DRI is the extent of conversion of iron oxide into metallic iron during reduction. It is defined in percentage of the mass of metallic iron divided by the mass of...

Organizational Discipline...

Organizational Discipline Discipline is required for any activity where people work together toward a common objective. The opposite of discipline is anarchy, where each person does what he wants without concern for others. Any organization depends on group cooperation, and cooperation cannot be achieved without discipline. Discipline is the structure and order within an individual or within a group that allows for true cooperation, real support of the mission and the members of the team or organization. Organizational discipline is the orderly and systematically conducting the affairs of the organization by the organizational members who strictly adhere to the essential rules and regulations. These employees/organizational members work together and cooperate harmoniously with each other as a team so as to achieve organizational vision and mission as well as organizational goals and objectives and they truly understand that the individual and group aims and desires must be matched so as to ensure organizational success. While punishment plays a role in maintaining discipline, such usage does not help in an organization which has a mission to succeed. Disciplinary authorities in an organization should know that an employee motivated by fear would not perform efficiently in his job and may not perform well under conditions of emergency. Hence emphasis on training in place of punishment is a better way to achieve organizational discipline. The objectives of the organizational discipline are (i) to obtain a willing acceptance of the rules, regulations and procedures of an organization by its employees so that organizational goals can be achieved, (ii) to impart an element of certainty despite several differences in informal behaviours pattern and other related changes in an organization, and (iii) to develop among the employees a spirit of tolerance and a desire to make adjustments. Organizational discipline is an...

Discharge options for Direct Reduced Iron and its Hot Transport Dec14

Discharge options for Direct Reduced Iron and its Hot Transport...

Discharge options for Direct Reduced Iron and its Hot Transport The two main methods of producing direct reduced iron (DRI) are (i) gas based process in a vertical shaft furnace and (ii) coal based process in a rotary furnace.  In both the processes the reduction reactions take place in solid state and the maximum furnace temperatures are in the range of 850 deg C to 1050 deg C. In the coal based process, the produced DRI is mixed with char that is needed to be separated from DRI. Hence DRI-char mixture is cooled in a rotary cooler and then char is separated from DRI by the magnetic separation process. In the case of vertical shaft furnace processes, since char is not present along with DRI, there are three discharge options available. These are cold DRI (CDRI), hot briquetted iron (HBI), and hot DRI (HDRI). Most of the vertical shaft DRI furnaces have been built for the production of CDRI. In these furnaces the DRI produced after reduction is cooled in the lower part of the furnace to about 50 deg C. CDRI is temporarily stored in Silos for passivation before it is transported to a nearby steel melting shop for its use later. CDRI has got the property of auto ignition and need special precautions during transport and storages as required by the International Maritime Organization (IMO). CDRI is most suited material for the continuous charging in the EAF. HBI is now being produced since more than 30 years. It is the desirable method of preparing DRI for storage and transporting it by sea going vessels. For the production of HBI, hot DRI is discharged from the vertical shaft furnace at a temperature of around 700 deg C. The hot DRI is sent to...

Rolling Mills Rolls

Rolling Mills Rolls Rolling had assumed importance in the industrialized world during the nineteenth century. Profiles and flats are hot rolled while some flat products are also cold rolled. Rolls are tools in the rolling mill. The weight of the rolls can vary from a few kilograms to as high as 250 tons. Rolls are required to carry out the heavy work of reduction of the cross section of the steel being rolled.  Rolls have to take all kind of stresses, loads from normal and abnormal rolling and which are changing with the roll wear during a rolling campaign. Roll should never break, spall or wear. They are expected to give excellent performance without causing any problems. Under the conditions of rolling, the contact area of the roll that comes in contact with the steel suffers wear, while other parts of the roll body and roll necks does not experience plastic deformation or fatigue but are under high loads. In the recent past rolling technology was improved and changed but rolls have always remained the critical part of the rolling mills. Hence the development of roll quality and roll making technology had followed the development of rolling technology. Historical developments In the nineteenth century basically non alloy grey iron and forged steel was used for rolls. The cast iron grades varied from mild hard to clear chill, where the barrel showed a white iron layer with grey iron core and necks. These rolls were used for flat rolling without any roll cooling in the sheet mills. Later cast steel rolls were developed. These rolls are still produced today. Around 1930 ICDP (Indefinite chill double pour) rolls were developed for hot rolling. In late 1990s ICDP enhanced with carbide rolls were developed. Around 1950 nodular...