Bearings for Rolling mill Rolls...

Bearings for Rolling mill Rolls Rolling mills for rolling of steel differ in many aspects with each other. The rolling mills are of different sizes and capacities. The mills roll steel materials of different cross-sections, sizes and qualities and in material conditions which are either hot or cold. The mills have different configurations and speeds of rolling. The configurations of the mills can vary from cross country, reversing, semi continuous to continuous. The equipments of rolling mills can have manual operations, mechanical operations, electro-mechanical operations, pneumatic operations, hydraulic operations, or a combination of all of these. The controls provided in the mills can be manual controls, remote controls, instrumented controls, or fully automated controls. Further in many types of mills even heat treatment processes are integrated. In spite of the so many differences, all the rolling mills have in common some basic technologies and equipments. All the rolling mills have rolls for the rolling of materials which are fitted in roll stands. Rolls are either driven by electric power or friction driven and are to resist many forces for normal rolling. The roll stands can have two rolls, three rolls, four rolls, six rolls, or a set of multiple rolls mounted on them depending on the types of mills. During rolling, the load on the rolls gets transferred to the roll neck bearings and their assembly (chocks). Rolls for their smooth rotation as well as for resistance to different forces need ‘bearings’.  Roll bearings are to meet the basic need of the rolling mill which is the smooth rolling of the steel products. They are friction reducing devices which provide support to the rolls for effective rolling with minimum of energy loss. The bearings are designed to withstand high rolling loads, heavy shocks, varying...

Rolling mill Rolls and Roll Shop Dec10

Rolling mill Rolls and Roll Shop...

Rolling mill Rolls and Roll Shop Rolls are the main and very costly consumables in a rolling mill. They are used to roll steel in the rolling mill and their performance depend on many factors which include the materials used and the loads to which they are subjected to during service. The roll design is influenced by the limitations applied by the rolling load, the roll strength and the torque available for rolling. In case of flat rolling it is also influenced by the allowance made for roll bending and by cambering of the rolls. The roll design is to take-care the load and torque required for any pass. In addition it must ensure that the physical dimensions and material of the roll are capable of withstanding the heaviest loads arising during the rolling sequence. Another important factor where roll life is concerned is the wear properties of the roll material. Roll materials In the rolling of steels, the material of the rolls is to be capable of withstanding loads which plastically deforms the rolling stock without itself being plastically deformed. In the rolling of hot steel this is not a difficult problem and iron or steel rolls are suitable if they are operated at a temperature considerably lower than that of the rolling stock. Whether iron or steel rolls are used in any particular case depends on the specific duty they have to perform and whether toughness, resistance to thermal cracking or shock loading or hard wearing properties is most important. Rolls can be classified according to the roll materials (Fig 1) and the method of manufacture, the first main subdivision being (i) iron rolls, and (ii) steel rolls. This division depends on the carbon content of the material. In the case of...

Understanding Rolling Process in Long Product Rolling Mill Nov27

Understanding Rolling Process in Long Product Rolling Mill...

Understanding Rolling Process in Long Product Rolling Mill  Steel rolling 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 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 working processes, because of its higher productivity 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. 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 stock gradually approach to the desired profile. Rolling accounts for about 90 % of all materials produced by metal working process. It was first developed in the late 1500s. Hot Rolling is carried out at elevated temperature above the re-crystallization temperature. During this phase, the coarse-grained, brittle, and porous structure of the continuously cast steel is broken down into a wrought structure having finer grain size and improved properties. A long product rolling mill comprised of equipment for reheating, rolling and cooling. The primary objectives of the rolling stage are to reduce the cross section of the incoming stock and to produce the planned section profile, mechanical properties and microstructure of the product. Major parameters in the three...

Roll Pass Design Jun18

Roll Pass Design

Roll Pass Design  Long products are normally rolled in several passes, whose numbers are determined by the ratio of the initial input steel material (square or round billet or bloom) and final cross section of finished product. The cross section area is reduced in each pass and form and size of the steel material being rolled gradually approach to the desired profile. Rolling is carried out between grooved rolls. Two opposite grooves in the collaborating rolls form a pass, which corresponds to a work piece’s cross section shape expected after the pass. After every pass, the cross section decreases and its shape becomes closer to a shape of the final product. Development of subsequent pass shapes and its proper location on the rolls is called the roll pass design. Roll pass design is an essential part of long product rolling process, since the long products are rolled between the shaped rolls in the long product rolling mills. Roll pass design generally means the cutting of grooves in the roll body through which steel to be rolled is made to pass sequentially to get the desired contour and size. The primary objective of the roll pass design is to ensure production of a product of correct profile within the tolerance limits, free of defects, with good surface quality and the required mechanical properties. In addition, economic condition must be achieved while rolling the product, for example, maximum productivity at the lowest cost, optimum energy utilization, easy working conditions for the rolling crew and minimum roll wear. Roll pass design is a set of methods for determining the dimensions, shape, number, and type of arrangement of rolling mill passes. Roll pass design also includes the calculation of pressing forces and their distribution on the roll passes. Several   passes are made for each section; a square or round billet or bloom acquires a specified form on each successive pass. The roll passes are designed to avoid excessive stresses in the steel being rolled, since such stresses can lead to the formation of cracks and other flaws. Roll pass design is based on the characteristics of initial input...

Rolling Process for Steel Mar27

Rolling Process for Steel...

Rolling Process for Steel Rolling is the process of plastically deforming steel by passing it between rolls. Rolling is defined as the reduction of the cross sectional area of the steel piece being rolled, or the general shaping of the steel products, through the use of the rotating rolls. Rolling of steel is one of the most important manufacturing processes for steel. It is usually the first step in the processing of steel after it is made and cast either in Ingot or continuous cast product in a steel melting shop. The initial rolling of steel is done in a hot rolling mill where blooms and slabs are rolled down to various rolled products such as plate, sheet, strip, coil, billet, structures, rails, bars and rods. Cold rolling of steel is also carried out for some products. Many of these rolled products such as rails and reinforcement bars etc. are directly used by the consumers while the other rolled products are the starting raw materials for subsequent manufacturing operations such as forging, sheet metal working, wire drawing, extrusion, machining, and fabrication industry. Steel rolling can produce a wide range of products. The width of a rolled product can vary from a few millimeters to several meters while the thickness can vary from 0.1 mm to more than 200 mm. The rolled section can be square, rectangular, round or shaped sections. Different rolling processes for steel are shown in Fig 1 Fig 1 Rolling processes of steels Principle of rolling steel During rolling, steel work piece is subjected to high compressive stresses as a result of the friction between the rolls and the surface of work piece being rolled. The work piece is plastically deformed by the compressive forces between two constantly rotating rolls. These...