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Hot rolling

Rollingin technologythe principal method of forming molten metals, glass, or other substances into shapes that are small in cross-section in comparison with their length, such as bars, sheets, rods, rails, girders, and wires.

Rolling is the most widely used method of shaping metals and is particularly important in the manufacture of steel for use in construction and other industries. Rolling may be done while the steel is hot hot-rolling or cold cold-rolling.

The process consists of passing the metal between pairs of rollers revolving at the same speed but in opposite directions and spaced so that the distance between them is slightly less than the thickness of the metal.

hot rolling

The degree of change that can be made in the thickness of the steel depends on its temperature, with higher heat increasing the plasticity of the steel. Cold-rolling, in which unheated bars, sheets, or strips of steel are sent through the rollers, usually requires several rollings to achieve the desired shape. Cold-rolling often follows hot-rolling and is done to gain better mechanical properties, better machinability, special size, a bright surface, or a thinner gauge than hot-rolling can.

Rolling was introduced to steel production in by Henry Cortwho successfully improved on earlier primitive attempts to use this technique.

STEEL: From Start to Finish

Modern mills have as many as four sets of rollers, one above the other, and steel is rolled in a continuous process through one set, into another, and then back again, until the desired shape is achieved. Semifinishing mills roll the steel into rectangular shapes to be further refined; finishing mills produce steel ready for use in manufacturing.

Rolling is also an important process in glassmaking. A continuous stream or ribbon of molten glass is passed between a pair of rollers that are so spaced as to control the thickness of the glass sheet. Rolling is a very rapid way to produce glass, but the glass produced is not high in surface quality owing to its contact with the metal rollers. Article Media. Info Print Cite. Submit Feedback. Thank you for your feedback. Rolling technology. See Article History.

Read More on This Topic. Rolling is the most common metalworking process. More than 90 percent of the aluminum, steel, and copper produced is rolled…. Learn More in these related Britannica articles:. More than 90 percent of the aluminum, steel, and copper produced is rolled at least once in the course of production—usually to take the metal from a cast ingot down to a sheet or bar.

The most…. In this process, the rolls, working always in pairs, are driven in opposite directions with the same peripheral velocity and are held at a specific distance from each other by heavy bearings and mill housings.

The steel workpiece is pulled by friction into the…. This was first done in the steel industry, but similar processing is also accomplished with aluminum and other metals. In a modern steel plant, hot-rolling is performed under computer control. The rolling….When approaching your project, it is crucial to know the type of steel that is best suited for your needs.

Different types of steel manufacturing can produce material that performs better for the specific applications. The hot and cold rolled steel manufacturing methods specifically have a great effect on the overall performance of the steel. Prior knowledge of distinctions between the two methods can help your company save on time, raw material cost, and additional processing.

NOTE: Hot-rolling and cold-rolling should not be mistaken for different grades of steel.

hot rolling

Steels of different grades can be produced as hot-rolled or cold-rolled. When steel is heated past its recrystallization point, it becomes more malleable and can be properly formed and shaped.

It also allows for the ability to produce larger quantities of steel. When the steel cools off, it will shrink non-uniformly, which gives slightly less control on the overall size and shape of a finished hot-rolled product. Hot-rolled steel typically has a scaly surface finish. For situations in which the appearance of the material is a concern, the scales can be removed by several techniques: pickling, grinding, or sand-blasting.

hot rolling

These properties make hot-rolled steel most suitable for structural components and other applications where incredibly precise shapes and tolerances are of less importance, such as:.

As you might suspect, the manufacturing process behind cold-rolled steel is a bit different. Despite the name, this process refers to steel that is pressed with the pressure of a roller at room temperature. Cold-rolling steel allows for the creation of very precise shapes. Since the process is performed at room temperature, the steel will not shrink as it cools, as it does in the hot-rolled process. The exterior finish of cold-rolled steel is very desirable when aesthetics and visual appeal are a priority in your project.

However, the applications of cold-rolled steel are somewhat limited to a couple of shapes — square, round, flat, and variations thereof.

If you require large structural components, you will most likely need the hot-rolled steel process to create the parts. For smaller parts that require more precise and durable qualities, then the cold-rolled steel process is the way to go. If you have questions about which mill process you need for your project, feel free to call National Material at and ask for one of our skilled customer representatives.

These properties make hot-rolled steel most suitable for structural components and other applications where incredibly precise shapes and tolerances are of less importance, such as: Railroad tracks I-beams Agricultural equipment Sheet metal Automotive frames COLD-ROLLED STEEL As you might suspect, the manufacturing process behind cold-rolled steel is a bit different.

Related Posts. Galvanizing vs.Stop wasting time on admin! Order your sheet metal fabrication online. Immediate pricing and short lead times all over the UK. Hot rolled steel or cold rolled steel — which to choose? Each with its own advantages and uses. Some types of steel make an excellent fit for home appliances, others for the automotive or marine industry, gas tanks, constructions, etc. A material grade with the same chemical composition may have varying qualities depending on the manufacturing method.

Our customers have asked for the difference. So here it is. Hot working is more widely used compared to cold working because it needs less force and energy.

It is used in compressive forming methods like rolling, extrusion, forging, etc. The starting material is usually steel billets or slabs. First, they are heated above the aforementioned temperature. The next step is feeding them to the rolling machinery. Continuous rolling gives the desired final shape — a metal sheet 3 mm and upwards or profile.

As it is easy to form metal in high temperatures without any extra delays, it is possible to produce it in larger quantities than cold rolled steel. This keeps the market price of hot rolled steel lower. The steel cools at room temperature. This is known as normalising. Ductility is especially important when forming the material e.

It shrinks slightly during the cooling process. This leaves the metal with internal stresses. The results are non-uniform measurements and some distortions.

Also, the surface has a scaly finish. This is a kind of oxide that forms at high temperatures, known as mill scale. It is easy to identify hot rolled products by touching the surface because of the uneven finish but it is also lacking an oily film.

With steel bars, the corners are rounded. Hot rolled steel is a good choice when tight tolerances are not of utmost importance. There are many fields where that is the case. Its great advantage in price matters more than precision. Some common uses for hot rolled steel are:. Cold working is a metal forming method that has many advantages over hot working. Technically, cold working includes cold rolling and cold drawing. The former is a process used with sheet metal.Jump to navigation.

To those on the outside, the rolling process is an unknown. The average person may be completely unaware of what rolling is, but it is something that is extremely important to know in the steel industry.

Rolling is a fabricating process in which metal is passed through a pair of rolls. Rolling has 2 main classifications. Flat rolling, in which the product is typically a sheet, or profile rolling, in which the product is typically a rod or bar. Rolling is also classified according to the recrystallization temperature of the metal.

Rolling processes date back to The first rolling mill was built in Fontley, Hampsire where Henry Cort developed and received patents for his ideas. The two types of temperature-dependent rolling processes are hot rolling and cold rolling, and they each have their own specific use. The metal pieces are then deformed between rollers creating thin cross sections. These cross sections are thinner than those formed by cold rolling processes with the same number of stages.

Hot rolling also reduces the average grain size of metal but maintains an equiaxed microstructure. This increases the yield strength and hardness of the metal. This is done by introducing defects into the crystal structure of the metal creating a hardened microstructure which prevents further slip.

This makes cold rolling a more labor intensive and expensive process than hot rolling. Cold rolling can also reduce the grain size of the metal resulting in Hall-Petch Hardening.

Both hot rolling and cold rolling are used to create sheet metal. However, cold rolling produces thinner sheets. Hot rolling is also commonly used to create railroad rails, and cold rolling is often used to make beverage cans. This was only a caveat of rolling info highlighting two very important rolling processes — hot and cold. Employment Opportunities.

Hot rolling

All Rights Reserved.Hot rolling is more common than cold rolling as it is cheaper and less time consuming. Hot rolling has less manufacturing delays due to the fact steel does not need to be reheated, as is the case with cold rolled steel. When cooling steel after hot rollingyou should expect the steel to shrink slightly.

You may find that you have less control over the final size and shape of your steel when using a hot rolling method. Hot rolling, however, allows steel to be formed into much larger sizes than cold rolling. Cold rolling involves a similar process to hot rolling, however the steel is subjected to further processing. After being rolled, the steel is cooled at room temperature in cold reduction mills.

Cold rolled steel is often erroneously used to refer to all products, when the product name refers specifically to flat rolled sheet and coil products.

Generally speaking, cold treated steel and metals have a superior surface finish, tolerance, concentricity, and rigidity when compared to hot rolled products. If you need help with metal processing or machining for your next project, why not utilise our network of trusted metal processing providers?

Hot and Cold Rolling Explained

At ShapeCUT we use plate rollers that can roll steel up to 3,mm wide and 32mm thick. If you require fast and reliable steel rolling servicescontact ShapeCUT today.

Cold rolling Cold rolling involves a similar process to hot rolling, however the steel is subjected to further processing.Metal rolling is one of the most important manufacturing processes in the modern world. The large majority of all metal products produced today are subject to metal rolling at one point in their manufacture. Metal rolling is often the first step in creating raw metal forms. The ingot or continuous casting is hot rolled into a bloom or a slab, these are the basic structures for the creation of a wide range of manufactured forms.

Blooms typically have a square cross section of greater than 6x6 inches. Slabs are rectangular and are usually greater than 10 inches in width and more than 1. Rolling is most often, particularly in the case of the conversion of an ingot or continuous castingperformed hot. At a rolling millblooms and slabs are further rolled down to intermediate parts such as plate, sheet, strip, coil, billets, bars and rods.

Many of these products will be the starting material for subsequent manufacturing operations such as forging, sheet metal working, wire drawing, extrusion, and machining. Blooms are often rolled directly into I beams, H beams, channel beams, and T sections for structural applications. Rolled bar, of various shapes and special cross sections, is used in the machine building industry, as well as for construction.

Rails, for the production of railroad track, are rolled directly from blooms.

STATE-OF-THE-ART SOLUTIONS FOR HOT ROLLING FLAT PRODUCTS

Plates and sheets are rolled from slabs, and are extremely important in the production of a wide range of manufactured items. Plates are used in heavy applications like boilers, bridges, nuclear vessels, large machines, tanks, and ships.

Sheet is used for the production of car bodies, buses, train cars, airplane fuselages, refrigerators, washers, dryers, other household appliances, office equipment, containers, and beverage cans, to name a few.

It is important to understand the significance of metal rolling in industry today, as well as its integration with other manufacturing processes. Most metal rolling operations are similar in that the work material is plastically deformed by compressive forces between two constantly spinning rolls.

These forces act to reduce the thickness of the metal and affect its grain structure. The reduction in thickness can be measured by the difference in thickness before and after the reduction, this value is called the draft. In addition to reducing the thickness of the work, the rolls also act to feed the material as they spin in opposite directions to each other. Friction is therefore a necessary part of the rolling operation, but too much friction can be detrimental for a variety of reasons.

It is essential that in a metal rolling process the level of friction between the rolls and work material is controlled, lubricants can help with this. A basic flat rolling operation is shown in figure, this manufacturing process is being used to reduce the thickness of a work piece. During a metal rolling operation, the geometric shape of the work is changed but its volume remains essentially the same. The roll zone is the area over which the rolls act on the material, it is here that plastic deformation of the work occurs.

An important factor in metal rolling is that due to the conservation of the volume of the material with the reduction in thickness, the metal exiting the roll zone will be moving faster than the metal entering the roll zone.

The rolls themselves rotate at a constant speed, hence at some point in the roll zone the surface velocity of the rolls and that of the material are exactly the same. This is termed the no slip point. Before this point the rolls are moving faster than the material, after this point the material is moving faster than the rolls.Hot rolling can greatly reduce energy consumption and costs.

The metal-plastic deformation is high during hot rolling, and the deformation resistance is low, which reduces the energy consumption of metal deformation. Hot rolling can improve the processing performance of metals and alloys. Hot rolling usually uses large ingots and large reduction rolling, which not only improves production efficiency but also creates conditions for increasing rolling speed and achieving the continuous and automated rolling process. After hot rolling, non-metallic inclusions mainly sulfides and oxides, as well as silicates inside the steel are pressed into thin sheets, causing delamination sandwich.

The delamination greatly deteriorates the tensile properties of the steel in the thickness direction, and it is possible that interlaminar tearing occurs when the weld is shrunk. The local strain induced by weld shrinkage often reaches several times the yield point strain and is much larger than the strain caused by the load.

Residual stress caused by uneven cooling. The residual stress is the internal self-phase equilibrium stress without external force. The hot-rolled steel of various sections has such residual stress. The larger the section size of the general section steel, the larger the residual stress. Although the residual stress is self-phase-balanced, it still has some influence on the performance of steel members under external force.

Such as deformation, stability, fatigue and other aspects may have adverse effects. Hot rolling does not control the mechanical properties required for the product accurately, and the microstructure and properties of the hot rolled product are not uniform.

The strength index is lower than that of the cold work hardened product and higher than the fully annealed product, the plasticity index is higher than that of the cold work hardened product and lower than the fully annealed product.

The thickness of the hot rolled product is difficult to control and the control precision is relatively poor; the rough Ra value of the surface of the hot rolled product is generally 0. Therefore, hot rolled products are generally used as blanks for cold rolling. If you are interested in our hot rolling mills, such as wire rod rolling mill machine or TMT rebar rolling mill machine, please kindly contact us.

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comments so far

Zujar Posted on 10:12 pm - Oct 2, 2012

Ich entschuldige mich, es gibt den Vorschlag, nach anderem Weg zu gehen.