Hot and cold strip rolling processes sciencedirect. Rolling process can be classified either ibased on the temperature of the metal during rolling or ii based on the arrangement of the rolls and their number or iiibased on the products rolled. Thorough account of the hotrolling process and facilities as well as followup treatments given to hotrolled products. It is a deformation process in which the thickness of the strip is reduced by. For most of the metals, this temperature is recrystallization temperature. In general the type of product depends on the alloy used, the rolling deformation and thermal treatment used in the process as well as careful adjustments to the mechanics and chemistry of the. Gage numbers the thicker the sheet the lower the gage number. Cold rolling cannot reduce the thickness as hot rolling does. Pdf analytical modified model of cold rolling process and.
Cold rolling is a process that occurs after hot rolling in order to reduce the thickness, increase the yield and tensile strength and pliability of metal. During the hotrolling process, steel is heated to its melting point while being worked, changing the composition of the steel to make it more malleable. If the temperature of the metal is below its recrystallization temperature, the process is termed as cold rolling. A rolling mill is a machine for plastic deformation of metal between rotating rolls. Cold mills, in a wide range of types and sizes are available.
May 01, 2017 rolling is used for making hollow seamless tubes, rods etc. Difference between hot and cold rolled steel metal. This process is used to create shapes with the desired geometrical dimensions and material properties while maintaining the same volume of metal. Surface roughness cold rolling produces fine surface finishes hot rolling produces surface finish similar to sand casting. Overview of the steelmaking process pellets sinter limestone coke iron ore coal scrap blast furnace ironmaking converter steelmaking ladle refining blast furnace steelmaking coalnatural gas plate hotrolled bars rods tube rounds rails slab billet bloom hotrolled and coldrolled strip coils structural shapes. Cold rolling is a process by which the sheet metal or strip stock is introduced between rollers and then compressed and squeezed. In a broader sense, a rolling mill is an automatic system or line of machines that performs both rolling and auxiliary.
Forming processes are commonly classified into hotworking and coldworking operations. After the steel has cooled, it is subjected to annealing and or tempers rolling, in order to provide a wide range of surface finishes and more accurate. Since metal rolling affects grain orientation, a part can be rolled in a way as to create grains oriented in a direction such that they give directional strength to a part useful to that parts specific application. Hot rolling refers to a mill process in which you roll the steel at a temperature above its recrystallization temperature. It is use for mass production of threaded parts like screw, bolts etc. The processing steps and the sequence of processing in a cold rolling mill depend on the quality of. During the hot rolling process, steel is heated to its melting point while being worked, changing the composition of the steel to make it more malleable. Hot rolling is one of the most common and costeffective techniques to convert aluminium cast slab to flat sheet down to 2 mm thickness, which becomes the starting stock for cold rolling. Finished product in hot rolled steel has oxidized steel layer, but the finished product of cold rolled steel is unoxidized. Hot rolled steel involves rolling the steel at high temperatures, where cold rolled steel is processed further in cold reduction mills where the material is cooled followed by. Hot rolling is a metalworking process in which metal is heated above the recrystallization temperature to plastically deform it in the working or rolling operation. The various types mean that steel can by widely used in infrastructure, appliances, vehicles, wind turbines, and many more applications.
Cold rolled steel is essentially hot rolled steel that has had further processing. Number ten of the manufacturing engineering and material processing series. The amount of strain introduced determines the hardness and other material properties of the finished product. Pdf cold rolling of steel is one of the most important metal forming. Hot rolling is one of the most important manufacturing processes for flat rolled aluminium alloys as it allows the economical reduction of the dccast slab to. The steel is processed further in cold reduction mills, where the material is cooled at room temperature followed by annealing and or tempers rolling. Stresses from hertzian pressure in 4high cold mill back up rolls were measured years ago, the results were never published, but of high interest also, maybe later. Lenard, in primer on flat rolling second edition, 2014. The hot rolling process the primary function of the hot strip mill is to reheat semifinished steel slabs of steel nearly to their melting point, then roll them thinner and longer through 12 successive rolling mill stands driven by motors totaling 77,000 hp, and finally coiling up the lengthened steel sheet for transport to the next process. Nov 09, 2016 al, cu alloys cold rolling cannot reduce the thickness of a workpiece as much as hot rolling in a single pass. Difference between hot and cold rolled steel metal supermarkets. May 17, 2017 the material may start out quite cold, even as low as 32 f 0 c, but when it comes out of the cold mill, it will be far too hot to touch. Hot rolled steel the process of hot rolling involves rolling steel at temperature above the steels recrystallization temperature, which takes place over 1700 degrees fahrenheit a bluegray finish more malleable, allowing it to be forced into a. Quaker animation film steel cold rolling process youtube.
Rolling can be classified as hot rolling or cold rolling. So tolerance for the shape at the hot rolling process is rather high. Hot rolling and cold rolling should not be mistaken for different grades of steel. Large length cross sections are produced by rolling process.
Its grains reform after the rolling process and it is left in a stressfree state. The tandem cold rolling of metal strip is one process in a sequence of processes performed to convert raw materials into a finished product the rolling strip contact length can be approximated 6. They have a great influence on the structure and performance of steel the rolling of steel is mainly hot rolling, and cold rolling is usually used only for the production of steel with precise sizes such as smallsized section steel and thin plates. Cold rolled steel is stored and sold in coiled form after rolling.
Hot rolled and cold rolled are the process of steel plate or profile forming. Hot rolling and cold rolling is done on the l ow carbon steel and a zinc coating i s pasted on cold rolled su rface after annealing process by using hot dipping process to pr otect surface from. There are various types of cold rolling mill, and they produce various types of rolled product, with thicknesses as low as 0. Steel comes in many grades, specifications, shapes, and finishesthe world steel association lists over 3,500 different grades of steel, each with unique properties. When the processing temperature of the mechanical deformation of steel is above the. Stresses from hertzian pressure in 4high cold mill back up rolls were measured.
The differences between hot and cold rolling can be difference in part quality, part cost, and processing time. This is not because heat has been applied by flame or conduction, but simply because of the massive amount of working done in the rolling process. Cold rolling steel allows for the creation of very precise shapes. Rolling reducing the thickness or changing the cross. That is the ability to change without damage the shape and dimensions in hot and cold condition under the pressure of machining tools. In that process, the process is done at a very high temperature like over 1,700 degree fahrenheit. After being rolled, the steel is cooled at room temperature in cold reduction mills. Construction material, roofing panels, partition beams, railroads, etc. The cold rolled process creates a finished product that is more precise dimensionally than a hot rolled.
Cold rolling is commonly conducted after hot rolling when good surface quality and low thickness tolerance are needed. Hot rolling mills usually comprise the following process steps. For hot working processes, large deformation can be successively repeated, as the metal remains soft and ductile. Rolling is the process of reducing the thickness or changing the cross section of a long workpiece by compressive forces applied through a set of rolls, as shown in figure 51.
Steels of different grades can be produced as hot rolled or cold rolled. Geometrical control in cold and hot rolling, iron making steelmaking. The input is obtained in the form of coils from hot rolling mills. During cold rolling, the steel is annealed, or exposed to heat and allowed to cool, which improves ductility. Report on best available techniques bat in the german. Its grains remain flattened and elongated, leaving the material in an anisotropic state and full of cold work. Many problems during the cold rolling process are work rolls damage, work rolls. Rolling is used for making hollow seamless tubes, rods etc. Hot rolling is carried out above rct and cold rolling is carried. Hot rolling is a metalworking process that occurs above the recrystallization temperature of the material. Cold rolling processes as discussed earlier, are useful for imparting strength and favorable grain orientation. Difference between hot rolled and cold rolled steel. It is a relatively expensive and labourintensive process, but the improved mechanical properties increase the value of the finished product, whether that is a sheet, strip, or coil.
Plastic properties of metals are used during the process of metal forming. Rolling and processing papers from primetals technologies at the estad conference 2017 in vienna covering the topics of long rolling, plate mills, linked casting and rolling, hot strip rolling, pickling, cold rolling, strip processing and the associated automation and process optimization systems. Hot rolled steel has so many shapes, but cold rolled steel has few shapes. The advantages of cold rolling are good dimensional accuracy and surface finish. Both hot rolling and cold rolling are used to create sheet metal. Therefore, a sheet of steel processed by a single pass through a roller.
The material may start out quite cold, even as low as 32 f 0 c, but when it comes out of the cold mill, it will be far too hot to touch. The resulting microstructure and texture are influenced along the whole processing route of fesi steels. The strip from the hot rolling mill is coiled for transport to the cold mill which might be on the same site or elsewhere. Overview of the steelmaking process pellets sinter limestone coke iron ore coal scrap blast furnace ironmaking converter steelmaking ladle refining blast furnace steelmaking coalnatural gas plate hot rolled bars rods tube rounds rails slab billet bloom hot rolled and cold rolled strip coils structural shapes. Since the process is performed at room temperature, the steel will not shrink as it cools, as it does in the hotrolled process. Coldrolling steel allows for the creation of very precise shapes.
Static friction coefficient between rolls and metal r radius of rolls 10. Secondary scale on hot strip and the impact on wear is another issue. After the steel has cooled, it is subjected to annealing andor tempers rolling, in order to provide a wide range of surface finishes and more accurate. Sep 11, 2014 hot rolled steel involves rolling the steel at high temperatures, where cold rolled steel is processed further in cold reduction mills where the material is cooled followed by annealing and or tempers rolling.
Since metal rolling affects grain orientation, a part can be rolled in a way as to create grains oriented in a direction such that they give directional strength to. The exterior finish of coldrolled steel is very desirable when aesthetics and visual appeal are a priority in your project. Report on best available techniques bat in the german ferrous metals processing industry final draft deutschfranzosisches institut fur umweltforschung dfiu frenchgerman institute for environmental research university of karlsruhe th o. Hot rolling aluminum is hot rolled into a coil of desired thickness. Cold rolling involves a similar process to hot rolling, however the steel is subjected to further processing.
In the present work internal customer ship is divided among the whole process flow. Hot rolling is a mill process which involves rolling the steel at a high temperature typically at a temperature over 1700 f, which. Hot rolling technology rolling is classified according to the temperature of work piece rolled. The starting material is usually large pieces of metal, like semifinished casting products, such as slabs, blooms, and billets. Since the process is performed at room temperature, the steel will not shrink as it cools, as it does in the hot rolled process. Rolling of metal auxiliary operations used in connection. The differences between hot rolled steel and cold rolled steel relates to the way these metals are processed at the mill, and not the product specification or grade. Cold rolling can also reduce the grain size of the metal resulting in hallpetch hardening. Strip thickness control of cold rolling mill with roll.
Hot roll is processed above the recrystallization temperature. Al, cu alloys cold rolling cannot reduce the thickness of a workpiece as much as hot rolling in a single pass. The steel is processed further in cold reduction mills, where the material is cooled at room temperature followed by annealing andor tempers rolling. Cold rollingis a rolling operation carried out at room temperature. This makes cold rolling a more labor intensive and expensive process than hot rolling. Hot rolled vs cold rolled steel metal casting blog. Rollers may be plain or grooved depends upon the shape of rolled product. Cold roll is processed below the recrystallization temperature. That is the ability to change without damage the shape and dimensions in hot and cold condition under the pressure of.
Hot rolling and cold rolling are two methods of shaping steel. Hot rolling is one of the most important manufacturing processes for flat rolled aluminium alloys as it allows the economical. Being the most widespread metal forming process, strip rolling pictured schematically in fig. Rolling and processing papers from primetals technologies at the estad conference 2017 in vienna covering the topics of long rolling, plate mills, linked casting and rolling, hotstrip rolling, pickling, cold rolling, strip processing and the associated automation. This process increases strength upto 20% via strain hardening. The exterior finish of cold rolled steel is very desirable when aesthetics and visual appeal are a priority in your project. Slab is the customer of reheating furnace, reheated slab is the customer of the hot rolling mill, hot rolled product is the customer of cold rolling mill and cold rolled product is the customer of the inspection. The cold rolling process is carried out at low recrystallization temperature and it produces relevant small and thin pieces and temperature is low, therefore deformation becomes relatively difficult than the hot rolling process. If the temperature of the metal is above its recrystallization temperature, then the process is termed as hot rolling. A rolling mill is a complex machine having two or more working rollers, supporting rollers, roll stands, drive motor, reducing gear, flywheel, coupling gear etc. After the grains deform during processing, they recrystallize, which maintains an equiaxed microstructure and prevents the metal from work hardening. Pdf effect of hot and cold rolling on grain size and. Types of rolling 12 some of the steel products made in a rolling mill. Steel rolling technology handbook 2nd revised edition.
Hot rolled steel involves rolling the steel at high temperatures, where cold rolled steel is processed further in cold reduction mills where the material is cooled followed by annealing andor tempers rolling. In a broader sense, a rolling mill is an automatic system or line of. Companion volume to cold rolling of steel by william roberts circa 1978 and number two of the series. Hot rolling is a mill process which involves rolling the steel at a high temperature typically at a temperature over.