Stock material or miscellaneous articles – Structurally defined web or sheet – Including variation in thickness
Patent
1996-03-04
1998-08-04
Loney, Donald
Stock material or miscellaneous articles
Structurally defined web or sheet
Including variation in thickness
428141, 428135, 428118, 428212, 428573, 428600, 428612, 428687, 428906, 72119, 72225, 723652, 29 171, 29 172, 29 33R, 292835, 29895, 298953, B32B 300, B21D 302, B32Q 100
Patent
active
057890668
DESCRIPTION:
BRIEF SUMMARY
OBJECT OF THE INVENTION
The present invention relates to a method and a device for manufacturing cold rolled metal sheets or strips, through a cold reduction operation in a rolling mill.
The present invention relates also to metal sheets or strips obtained through cold reduction mills preferably by using the method and the device of the present invention.
STATE OF THE ART
The cold rolling process consists essentially in pulling off the strip coming from the hot rolling mill to a cold reduction mill.
The cold reduction mill has the purpose to reduce the total thickness of the metal sheet or strip by an amount usually between 50 and 90%. This operation is performed in several steps and at least in three steps. Such cold reduction can be performed in one stand using a reversible mill or in several stands using a reduction mill called a `tandem mill` and wherein the several reduction steps are performed in one sequence.
The cold rolled sheet or strip is then heated up in a furnace, this process is known as annealing process. Afterwards, the annealed sheet or strip passes through a second cold roll mill called `skin pass` or `temper mill` in order to undergo a small cold deformation for improving mechanical properties and surface qualities of the metal sheet or strip.
During a cold reduction operation, the pressure applied to the rolls is higher than 10 kN/mm and the tension between two reduction steps is about 200 Pa, while during a temper rolling operation the normal pressure is less than 5 kN/mm and the tension between two reduction steps is about 25 MPa.
The physical properties of the metal sheet after a rolling operation in a reduction mill are completely different compared to the properties of the material after a skin pass or temper rolling operation.
Summarized hereunder are the main properties of the metal sheets or strips:
______________________________________ Reduction operation
Skin pass operation
______________________________________
Rockwell B hardness
min 80 (full hard)
30 to 60
(Euronorm A11-106
and A11-108)
Bend test no bending in bend flat on itself
(Euronorm 117-02)
either direction
in any direction
Yield strength
550 to 750 MPa
130 to 240 MPa
(Euronorm
EN10002-1)
Elongation in 50 mm
<10% 30 to 50%
(Euronorm EN10002-1
or ASTME8M)
______________________________________
It is a common practice in cold rolling devices to apply a certain roughness to the work rolls, preferably for the last step of the rolling operation in a cold reduction mill or for the only stand of a temper mill.
In the case of a cold reduction reversible mill, the mill work rolls are changed before the last step of the reduction operation for textured work rolls, and in the case of a tandem mill, only the last stand comprises textured work rolls.
To give such roughness to work rolls, several texturing technologies are known and are summarized in "Stahl und Eisen, Vol. 110 (1990), 14 March, No. 3, Dusseldorf, Del.".
Iron particles (grit) with a specific granulometry are sprayed on the surface of a work roll. The kinetic energy of the particles is sufficient to deform the surface plastically. The work roll roughness is function of the grit (angularity, mass, size), the velocity of rotation of the work roll, the hardness of the roll material, the number of passes along the roll and the rotating speed of the roll.
With SBT technology, roughness values (Ra) on the work roll comprised between 1.5 .mu.m and 6.0 .mu.m can be obtained.
The roughness profile shows a random distribution of peaks and valleys. No regular pattern can be distinguished.
Although SBT has a high productivity, this technology has major drawbacks:
Therefore the Ra value obtained on the roll after texturing shows a large scatter band. relatively softer rolls (hardness lower than 90 Shore C). Such rolls have only a shortlive service time. work rolls during a rolling campaign is always important. So there is a relationship between the roughness value (Ra) and the number of peaks/cm value (Pc) measured on the sh
REFERENCES:
patent: 5093180 (1992-03-01), Morgan
Hamilius, et al., La Revue de Metallurgie, vol. 89, No. 12, Dec. 1992, Paris, France, pp. 1083-1091.
Dolves, et al., "Electron beam texturing of rolls", Iron and Steel Engineer, vol. 68, No. 8, Aug. 1991, Pittsburg, USA, pp. 33-38.
Boppel, Optik, vol. 77, No. 2, Sep. 1987, Stuttgart, Germany, pp. 83-92.
Pankert, Stahl und Eisen, vol. 110, No. 3, Mar. 14, 1990, Dusseldorf, Germany, pp. 55-60.
De Mare Carl
De Soete Damien
Gadeyne Yves
Loney Donald
Sidmar N.V.
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