Rolling (metalworking)

Rollers is a forming method in which the (usually metallic ) material between two or more rotating tools, namely, rolling, is formed. Is the deformation above the recrystallization temperature of the material take place, it is called hot rolling, or cold rolling. The work of the waltz is now mostly automated.

Based on the deformation of the rolling material is a Forging and closely related to the hammering or forging.

4.1 Circular cross rolling
4.2 flat baking transverse rolling

6.2 Special Procedures
6.3 Related Topics

Roll

In the classification system of Druckumformverfahren according to DIN 8583, a distinction is longitudinal, transverse and oblique rolls.

A run of the rolling stock through the rollers is called down.

Longitudinal rolling

The longitudinal rolling the rolling stock is moving perpendicular to the roll axes without rotation about its own axis through the nip. It emerges as a strand of the oppositely rotating rollers. The strand with uniform cross-section is usually semi-finished, which is further processed. The products can be divided into flat and profile products according to their geometry. The tools can be called flat or profiled rollers.

Breit-/Flachprodukte

As flat products (hot - rolled and cold ) those rolled products are designated, the width of the thickness (height) exceeds by a multiple. You are quantitatively the largest proportion of the required global rolled products dar.

Sheets and strips of steel and non-ferrous metals are produced by rolling between two nearly parallel cylindrical rollers. So that, the roll gap can be changed ( setting of the strip profile ), some rolls are ground to a special, not exactly cylindrical shape. There are different manufacturers of different proposals. By displacement of individual rolls in the processing direction, the strip crown is controlled ( in the longitudinal direction).

The load applied to the rollers bend by the rolling process. To produce perfectly flat strip products, it is necessary to compensate for these rolling deformation accurately. To this end, work roll bending, work roll contour and local cooling or warming be tailored. In most cases, each work roll in the roll stand of a support roller of larger diameter and thus a much higher bending stiffness is supported ( see Figure ).

A specific method for flat products is the round rollers for the production of curved panels. This method is often used for tank construction.

Long Products

Long products are wire, rods, tubes and profiles made of steel and non-ferrous metals. They are produced by rolling between two or four rollers in the caliber is cut.

Roller assemblies

In the course of technological development or for special products various mill types for the longitudinal rolls have been developed which are still in use today.

Duo- roll mill

A two-high rolling mill consists of two parallel rollers, between which the rolling stock is rolled. To repeat the rolling process to further reduce the thickness of the rolled or for rerolling the next caliber you have to get back on the other side of the scaffold or the direction of rotation at a Duowalzwerk ( engl. "Two- High Rolling Mill " ) either the rolling stock of the rolls reversed ( reverse ). The former was dissolved by the fact that it was able to increase the horizontal roller table, in which the rolled stock runs upstream and downstream of the nip, on the side of the roll stand ( Fritz'scher roller table after the inventor George Fritz) and the rolled over the top roller to the other transported back side, the roller supported by friction. By improving the transmission Reversiermethode but gained more and more importance since the lifting of the upper roller as idle cycle is always associated with a cooling of the rolled material. With the advent of the electric drive, the reversal was again technically easier and also arranging a plurality of rolling mills in succession, the advance by the consistent as possible drive shaft of the drive ( steam ) was machine too expensive, could be realized.

Trio - rolling mill

Another method weiterzuwalzen the rolling stock with the same skeleton, without over lift or need to reverse, is to use a so-called trio - rolling mill (English " Three High Rolling Mill "). The trio arrangement with three rolls, the rolling stock is eg in one direction only, and then rolled between the lower and the middle between the middle and the upper roller in the other direction. The design of the caliber of a progressive profile of the rolled stock is however more complicated arrangement in the trio. Furthermore, the middle roll is mechanically very heavily loaded, since it is used in both rolling cycles and must therefore be relatively frequently replaced.

Universal rolling mill

In 1848, Reiner Daelen invented a rolling mill, in which the two horizontal rolls of a two - stand are supplemented by two vertical suffixes or rollers and a wide variety of rectangular profiles could be produced without roll changes through the adjustment of the roll gap. The universal rolling mill was first used in Piepenstock & Co. in Dortmund- Horde.

Quarto, Sendzimir and cluster frameworks

In order to reduce the deflection of which is in contact with the rolling work rolls, they are often back-up rolls - usually of large diameter - supported. For a total of four rollers mounted in a rolling mill, one speaks of a four-high configuration. Scaffolding with six rollers may be built in vertical or Sendzimir assembly. In the latter each work roll is supported by two rollers, which engage at an angle of about 120 degrees on the work roll in order to reduce vertical and horizontal bending. For rolls of very thin or very resistant materials, scaffolds with up to 20 rollers are used.

Stretching rolls

Stretching rolls is a section longitudinal rolls in the the emerging cross-section does not remain constant. The rolls are formed so as to change the cross-sectional profile in the circumferential direction. This method is often used to produce intermediate forms with cheaper mass distribution for forging the die.

Cross rolling

The cross-rolling, also called cross-wedge rolling, is the transformation of a rotationally symmetrical blank between two oppositely moving flat or round baking rolls. It can differ in circular cross-rolling and cross rolling flat die.

Circular cross rolling

For rotary cross rolling the rolled between two or more in the same direction rotating tool rolls around its axis rotates. By sending at least one tool roller, the workpiece is deformed.

Feasible are graded, rotationally symmetrical workpieces (eg, axles, shafts, gear shift blocks ) and preforms with optimal mass distribution for subsequent die forging ( eg levers, cranks, connecting rods, ball housing, turbine blades ). The following, shaping by escapes most completely or is reduced considerably due to near net shape forming.

Characteristic features of the Rundquerwalzens are:

High shape and dimensional accuracy of workpieces
Higher piece episode compared to removal processes
Economy due to high material utilization and very high production rate
Preservation of the molecular chain structure in the workpiece ( undisturbed grain )
Long tool life, a very low proportion of the tooling costs to the manufacturing costs
Environmentally friendly, as no lubrication; low noise, shock and vibration

Flat Back transverse rolling

In shallow baking cross rolling the rolled between two against each other horizontally or vertically running tool plates is formed. The flat design of the tools is characterized by the design and manufacturing technology simpler structure as opposed to a curved roller, but has the same design parameters.

Ring rolling

In ring rolling are seamless rings, for example tires of railway wheels manufactured. The starting material is a swamped and concentric perforated front ring, which is expanded on ring rolling machines. By reducing the wall thickness ( radial) and the ring height ( axial) takes the ring diameter to according to the volume constancy.

Skew rolling

When cross-rolling the roller axes are crossed. This creates a longitudinal feed in the rotating about its longitudinal axis workpiece. The workpiece is held by the support guide rollers or ruler in the nip. The roll pass is configured so as to narrow the nip. Cross rolling is used as a method for manufacturing of cast iron or Hochreduzierwalzwerk for long products.

By rolling seamless tubes can be manufactured. For this purpose, various methods are applied. One must distinguish three basic process steps, punching, elongation ( stretching) and reducing ( finish rolling ). The punching is done on cross-rolling mills or hole punching. The elongation is done in several steps. These include, for example, rolling mills and the longitudinal helical rolling mills can be used. Reducing to the desired outer diameter is the final shaping step.

Hole method: oblique rolling mills for punching:

The Mannesmann piercing rolls ( Max and Reinhard Mannesmann 1885) used two obliquely arranged mutually driven rollers and a non-driven support roller. The rolled material is a solid round blank ( called billets), which moves the piercing spirally through the nip. By fiddling (change between compressive and tensile stresses ), the core is loosened and then rolled over a mandrel. Absolutely but an inner tearing of the block in front of the mandrel tip should be avoided because the rolling stock may otherwise have internal errors. The result is a hollow block ( also called tube blank ), so a thick-walled tube.
The barrel piercer is an evolved by Ralph Charles boots type of Mannesmann piercing mill. It consists of two helical rollers which are calibrated doppeltkonisch, and two guiding rulers which limit the deformation zone. The mechanism of action is the same as the Mannesmann piercing mill.
The Diescher -rolling mill is an altered tons of punch. Samuel Diescher replaced the rigid guide rulers of tons of punch by rotating guide discs.

Elongierverfahren All Elongierverfahren are characterized in that a previously perforated insert block is only reduced in wall thickness and, optionally, changed in diameter.

Cross-rolling method of elongation:

The Assel rolling process is a cross-rolling method, which was named after its inventor, Walter J. Assel. It is a three-roller cross-rolling process are used in the rollers of a so-called shoulder calibration. When Assel rolling process, the wall thickness is reduced and changed the diameter. It is possible divergently, neutral and reducing to roll. Aufweitendes rollers means that the diameter of the formed cavity block is larger than the diameter of the input material. At a neutral rollers input material and emerging hollow block have the same diameter, meaning it will only reduces the wall thickness. The reducing rolling the hollow block diameter is smaller than the diameter of the input material.

The RRM ( Kock - rotation - Mill ) is designed as a planetary skew rolling mill Elangator convergent with four rollers, which is similar to the Assel rolling mill. A hollow block is reduced by a rolling bar in the diameter and wall thickness. Since the rolling mill is not adjustably, the diameter reduction results from the spacing of the rollers and the wall thickness reduction of the distance between the rollers and the roller bar. To allow for different wall thickness reductions, the roll bars have to be used with different diameters.

Longitudinal rolling method of elongation:

The push bench process used as a starting material a perforated stick with the ground or a tube blank with a angekümpelten end. In the rolled stock a mandrel bar is inserted, with which it is then pushed by a plurality of sequentially arranged roll stands not driven. Characterized the wall thickness of the billet is reduced. The internal diameter is determined by the mandrel. The mandrel is referred to by a small rolling mill, rolling mill or reeler solvent dissolved and can then be removed and reintroduced into the circuit.
Reducing the expanded using a tube blank as the starting material, which is rolled at the same time in a plurality of thornless a unifying underlying roll stands. The wall thickness reduction is accomplished by superimposing a Längszugs. Since the longitudinal tension on the tube top is up and taken down again at the end of the pipe, the wall thickness along the tube length is not constant. The thickened ends have to be cropped.
The pilgrim rolling can be carried out cold or warm. By hot rolling large seamless tubes are manufactured and cold rolling the hot-rolled blanks are finish-rolled. The rolling mill consists of two rollers that rotate opposite to the direction of rolling. In the caliber rolls is cut, which is designed so that one half of the roller periphery, the rolling stock can be moved in the roll gap and by further rotation of the nip closes continuously. For rolling, a mandrel is inserted into the rolled stock on which it is rolled. The rolled material is then inserted in the idle step into the nip and then moving backward with the roller rotation. In the next step, the empty rolling is rotated 90 degrees and again pushed forward a little in the nip. The process is repeated cyclically until the entire tube is rolled. The name comes from the typical feed motion that resembles a pilgrim.

Special Procedures

The casting summarizes the archetypes and the first stage of forming together in one process step. In this case, the molten metal e.g. solidifies between two internally cooled rollers and compressed, which prevents segregation.
Thread rolling is used to produce threads in larger numbers, for example, screws.
The axial feed - cross rolling is a flexible cross-rolling process for the production of remote axles and shafts for smaller quantities.
The Roll forming is a continuous bending process is transformed gradually to the desired final cross-section in the sheet.
The gap profiling is a method for massive forming of sheet metal, can be incorporated with the branches in metal profiles.
By roll-bonding composites can be made of metals to coat as aluminum with a lower melting solder alloy.