Rolling (metalworking)

The earliest rolling mills in crude form but the same basic principles were found in Middle East and South Asia as early as 600 BCE.

[citation needed] The invention of the rolling mill in Europe may be attributed to Leonardo da Vinci in his drawings.

The slitting mill was adapted to producing hoops (for barrels) and iron with a half-round or other sections by means that were the subject of two patents of c. 1679.

The use of steam engines considerably enhanced the production capabilities of the mills, until this form of power was displaced by electric motors soon after 1900.

[7] Modern rolling practice can be attributed to the pioneering efforts of Henry Cort of Funtley Iron Mills, near Fareham in Hampshire, England.

After the grains deform during processing, they recrystallize, which maintains an equiaxed microstructure and prevents the metal from work hardening.

The starting material is usually large pieces of metal, like semi-finished casting products, such as ingots, slabs, blooms, and billets.

While the finished product is of good quality, the surface is covered in mill scale, which is an oxide that forms at high temperatures.

Hot rolling is used mainly to produce sheet metal or simple cross-sections, such as rail tracks.

During shape rolling, an initial billet (round or square) with edge of diameter typically ranging between 100 and 140 mm is continuously deformed to produce a certain finished product with smaller cross section dimension and geometry.

Different approaches have been achieved, including empirical knowledge, employment of numerical models, and Artificial Intelligence techniques.

Lambiase et al.[13][14] validated a finite element model (FE) for predicting the final shape of a rolled bar in round-flat pass.

Because of the smaller size of the workpieces and their greater strength, as compared to hot rolled stock, four-high or cluster mills are used.

It is used to produce a smooth surface, a uniform thickness, and reduce the yield point phenomenon (by preventing Lüders bands from forming in later processing).

To avoid the formation of Lüders bands it is necessary to create substantial density of unpinned dislocations in ferrite matrix.

Common applications include railway tyres, bearings, gears, rockets, turbines, airplanes, pipes, and pressure vessels.

Types of heat treatments include the production of a fine grain structure; controlling the nature, size, and distribution of various transformation products (such as ferrite, austenite, pearlite, bainite, and martensite in steel); inducing precipitation hardening; and, controlling the toughness.

Common variables in controlled rolling include the starting material composition and structure, deformation levels, temperatures at various stages, and cool-down conditions.

Forge rolling is mainly used to preform long-scaled billets through targeted mass distribution for parts such as crankshafts, connection rods, steering knuckles and vehicle axles.

Merchant or bar mills produce a variety of shaped products such as angles, channels, beams, rounds (long or coiled) and hexagons.

Mills are designed in different types of configurations, with the most basic being a two-high non-reversing, which means there are two rolls that only turn in one direction.

At the exit end of the mill there is normally a flying shear (to cut the strip at or near the weld) followed by two coilers; one being unloaded while the other winds on the current coil.

In hot rolling, if the temperature of the workpiece is not uniform the flow of the material will occur more in the warmer parts and less in the cooler.

This file was analyzed separately for each frequency/wavelength from 5 m to 60 m in steps of 0.1 m. To improve the accuracy, care was taken to use a full multiple of each wavelength (100*).

The deviation from complete flatness is the direct result of the workpiece relaxation after hot or cold rolling, due to the internal stress pattern caused by the non-uniform transversal compressive action of the rolls and the uneven geometrical properties of the entry material.

In the case of metal strips and sheets, the flatness reflects the differential fiber elongation across the width of the workpiece.

This property must be subject to an accurate feedback-based control in order to guarantee the machinability of the metal sheets in the final transformation processes.

Another way to overcome deflection issues is by decreasing the load on the rolls, which can be done by applying a longitudinal force; this is essentially drawing.

is final thickness, then the draught d is given by The maximum draught that can be achieved via rollers of radius R with coefficient of static friction f between the roller and the metal surface is given by This is the case when the frictional force on the metal from inlet contact matches the negative force from the exit contact.

Methods of scarfing have included hand-chipping with chisels (18th and 19th centuries); powered chipping and grinding with air chisels and grinders; burning with an oxy-fuel torch, whose gas pressure blows away the metal or slag melted by the flame;[30] and laser scarfing.