Rolling of Steel in a Modern Long Product Rolling Mill Jun19

Rolling of Steel in a Modern Long Product Rolling Mill...

Rolling of Steel in a Modern Long Product Rolling Mill Long product is a common name for (i) reinforcement steel bars, (ii) shaped steel bar products such as rounds, flats, squares, and hexagon etc., (iii) sectional products such as angles (equal and unequal), channels, beams, tees, and special profiles etc., and (iv) wire rods. Mills which roll long products are known as long product mills. Based on the product being rolled these mills are called, merchant bar mill, bar and rod mill, light section mill, rebar mill, light merchant mill, special bar quality (SBQ) mill, and wire rod mill etc. The product range of these mills usually consists of those shaped and sectional products whose cross-section is smaller than the cross section of the products rolled in medium and heavy section rolling mills. Wire rod mills produces steel wire rods of diameters 5 mm to 12.5 mm in coil form with the weight of the coil upto 2.5 tons. The qualities of steels being rolled in these mills can range from low carbon, mild steel, medium carbon, high carbon, and micro and low alloyed steels. The design of the long product rolling mill is required to provide right solutions for the required performance requirements which include high speed production, microstructure qualities of the product, and shortest changeover time from one product to other product etc. Large amount of flexibility is available in modern long products rolling mills. These mills are normally continuous mills consisting of three sets of rolling stands namely (i) roughing group of stands, (ii) intermediate group of stands and (iii) finishing group of stands. The input material for these mills is normally billet. A billet mill can be combined with the long product rolling mill through a roller hearth furnace in...

Rolling of Steel in small and medium sized Rolling Mills Jun09

Rolling of Steel in small and medium sized Rolling Mills...

Rolling of Steel in small and medium sized Rolling Mills Rolling of steel consists of passing the material, usually termed as rolling stock, between two rolls driven at the same peripheral speed in opposite directions (i.e. one clockwise and the second anti-clockwise) and so spaced that the distance between them is somewhat less than the thickness of the steel section entering them. In these conditions, the rolls grip the material and deliver it reduced in thickness, increased in length and probably somewhat increased in width. This is one of the most widely used processes among all the metal forming processes, because of its higher productivity, close control of the rolled product, and lower operating cost. Rolling is able to produce a product which is having constant cross section throughout its length. Many shapes and sections are possible to roll by the steel rolling process. Rolling of steel is a metal forming process used for plastic deformation of the steel. Plastic deformation is caused by the compressive forces applied through the rotating rolls. High compressive stresses are as a result of the friction between the rolls and the surface of the steel material. The steel material gets squeezed between the pair of rolls mounted in a roll stand, as a result of which the thickness of the steel being rolled gets reduced and the length is increased. Steel sections are generally rolled in several passes, whose number is determined by the ratio of initial input material and final cross section of finished product. The cross section area is reduced in each pass and form and the size of the rolling stock gradually approach to the desired profile. Mostly, rolling is done at high temperature, which is called hot rolling, because of requirement of large deformations....

Heating of Steel in Reheating Furnace Jun01

Heating of Steel in Reheating Furnace...

Heating of Steel in Reheating Furnace Reheating furnace is important equipment in the process of hot rolling. It is the heart of any hot rolling mill. Reheating of steel is a continuous process. The steel material to be rolled is charged at the entrance of the reheating furnace. The steel material is pushed forward on the hearth of the furnace by means of a pusher machine whose ram is in direct contact with the steel material. The steel material is pre-heated, heated and soaked as it passes through pre-heating, heating and soaking zone of the reheating furnace. At the end of the soaking zone of the furnace, the steel material is discharged from the furnace by ejector for rolling in the rolling mill. The temperature of the heated steel material at the time of discharged depends on several factors and it can vary in the range of 1100 deg C to 1250 deg C. The size of the reheating furnace is normally expressed as the capacity to supply the rolling mill with sufficiently hot steel, in tons per hour. Steel materials with different material compositions, dimensions, and charging temperatures can reside in the furnace simultaneously. The reheating furnace used for heating the steel materials is normally considered to be having high energy consumption. It also emits good amount pollutants in the atmosphere because the process used for heat generation is the combustion process. Reheating process has considerable influence on the economics of the working of the rolling mill. There are usually three types of continuous reheating furnaces used in the rolling mills. These are (i) pusher type furnace, (ii) walking hearth furnace, and (iii) walking beam furnace. Pusher type furnaces have some disadvantages which includes (i) frequent damage of refractory hearth, (ii) skid marks...

Scale Formation in Reheating Furnace May25

Scale Formation in Reheating Furnace...

Scale Formation in Reheating Furnace  Reheating furnaces constitute an important element in the rolling of steels, in which the semi-finished steel products are heated to a desired temperature for achieving the plastic properties in the products for rolling. The basic purposes of heating the semi-finished steel products for rolling include (i) to soften the steel for making it suitable for rolling, and (ii) to provide a sufficiently high initial temperature so that rolling process is completed in fully austenitic temperature region. During reheating in the reheating furnace, steel is passed through the furnace along which the temperature is gradually increased up to the soak zone. In there, the temperature is kept constant for thermal and chemical homogeneity of the steel. The reheating furnace is a direct fired furnace which uses either of the gaseous, liquid, or solid fuel and air. The composition of the atmosphere within the furnace generally consists mainly of nitrogen (N2), Carbon di-oxide (CO2), water vapour (H2O) and free oxygen (O2). The atmosphere composition can vary drastically during the operation. These variations are functions of the air/fuel ratio, which in turn, depends on furnace and mill operating conditions. Reheating furnace for the reheating of steel is conceptually divided into three zones. Starting from the discharge end of the reheating furnace, these zones are (i) soaking zone, (ii) heating zone/zones, and (iii) pre-heating zone. In the soaking zone, fuel and air is fired through the furnace burners at normal or reduced primary fuel stoichiometry. This zone has high furnace temperature. The temperature of steel is equalized through its cross section in this zone. The exhaust gases from this zone travel to heating zones. The heating zones, which are between preheating zone and the soaking zone, require high radiant heat transfer for increasing...

Ironmaking in Rotary Hearth Furnace May17

Ironmaking in Rotary Hearth Furnace...

Ironmaking in Rotary Hearth Furnace Ironmaking in the rotary hearth furnace (RHF) is a direct reduction process which utilizes non-coking coal for the reduction of iron ore. The RHF is the process reactor which consists of a flat, refractory hearth rotating inside a stationary, circular tunnel kiln. Inside the RHF, direct reduction of iron ore or iron-bearing waste materials occurs, using coal as the reductant. RHF is not a new technology. It has been used successfully in a range of industrial applications which includes heat treatment, calcination of petroleum coke, waste treatment, and non-ferrous high-temperature metal recovery. The history of ironmaking in RHF goes back to the mid-1960s with the development of the ‘Heat Fast’ process by Midrex. Since then several ironmaking processes based on RHF have been developed. These include ‘Fastmet’ process/‘Fastmelt’ process, and ITmk3 process which were brought into commercial operation. These processes have been described in separate articles having links    http://ispatguru.com/fastmet-and-fastmelt-processes-of-ironmaking/, and http://ispatguru.com/itmk-3-process-of-making-iron-nuggets/. Other RHF processes are ‘Redsmelt’ process, ‘Inmetco’ process, ‘Iron Dynamics’ process, ‘DRyIron’ process, ‘Comet’ and ‘SidComet’ processes and Hi-QIP process. Redsmelt process The Redsmelt process technology has been developed to meet the growing demand for a low cost environmental friendly ironmaking alternative to the traditional blast furnace route. The plant with this process can be designed for a production capacity of 0.3 million tons per year to 1.0 million tons per year of hot metal. The process can treat a wide range of iron ore fines and waste materials from the steel plant. The Redsmelt process is based upon a RHF which reduces green pellets made out of iron ore, reductant fines and binders to produce hot, metallized direct reduced iron (DRI) which is charged to a submerged arc furnace (SAF). The process operates at high temperature and...

Tecnored Process for Ironmaking Apr30

Tecnored Process for Ironmaking...

Tecnored Process for Ironmaking Tecnored process was developed by ‘Tecnored Desenvolvimento Tecnológico S.A.’ of Brazil and is based upon a low pressure moving bed reduction furnace which reduces cold bonded, carbon bearing, self-fluxing, and self-reducing pellets. Reduction is carried out in a short height shaft furnace of distinct design at typical reduction temperatures. The process produces hot metal (liquid iron). Tecnored technology has been conceived and developed to be a ‘coke-less’ ironmaking process, thus avoiding the investment and operation of environmentally harmful  coke ovens besides significantly reducing green-house gas emissions in the production of hot metal. Tecnored process uses a combination of hot and cold blast and requires no additional oxygen. It eliminates the need for coke plants, sinter plants, and tonnage oxygen plants. Hence, the process has much lower operating and investment costs than those of traditional ironmaking routes. Tecnored process is flexible with regard to the type of iron bearing and carbon bearing raw materials which it can process. The ability of the process to smelt either pellets or briquettes, or even mixed charges of both, provides means of using a wide range of alternative feed materials. The process has got good productivity and high energy efficiency. Tecnored process is also being claimed to be suitable for producing ferro alloys such as ferro manganese. History of development The history of the development of the Tecnored process comprises different phases with different goals, testing a wide range of raw materials and using distinct sizes and concepts of the reactor. During the period 1979 to 1985, development activities were carried out regarding the use of pyrite cinder containing self-reducing pellets as metallic burden in cupola furnaces. This concept of self-reduction was adapted to develop the new process.  In 1985 the concept of the Tecnored...