Rolling control method for metal strip, rolling control apparatus, and manufacturing method for rolled metal strip

Patent metadata

Field	Value
Publication number	US-10307806-B2
Application number	US-201515505394-A
Country	US
Kind code	B2
Filing date	Aug 11, 2015
Priority date	Sep 16, 2014
Publication date	Jun 4, 2019
Grant date	Jun 4, 2019

Abstract

A provisional elongation strain difference distribution Δε(x) of a metal strip during rolling is found under conditions in which out-of-plane deformation of the metal strip is restrained. A critical buckling strain difference distribution Δε cr (x) is found based on the provisional elongation strain difference distribution Δε(x), a strip thickness and strip width of the metal strip, and tension acting on the metal strip at exit from a rolling mill. When the provisional elongation strain difference distribution Δε(x) exceeds the critical buckling strain difference distribution Δε cr (x), the difference between the provisional elongation strain difference distribution Δε(x) and the critical buckling strain difference distribution Δε cr (x) is found, and added to the provisional elongation strain difference distribution Δε(x) to find a true elongation strain difference distribution Δε′(x). Rolling conditions are set based on the true elongation strain difference distribution Δε′(x), and the metal strip is rolled, thereby controlling the metal strip's profile.

First claim

The invention claimed is:

1. A rolling control method comprising:
finding a critical buckling strain difference distribution, which is a distribution in a strip width direction of differences in a critical strain at which a metal strip will buckle, based on a strip thickness of the metal strip, a strip width of the metal strip, tension acting on the metal strip at exit from a rolling mill, and a provisional elongation strain difference distribution which is a distribution of differences in the strip width direction of elongation strain along a rolling direction of the metal strip during rolling under specific rolling conditions and which is found under conditions in which out-of-plane deformation of the metal strip is restrained by using an up-down asymmetrical model that permits displacement of a strip-thickness center of the metal strip within a plane of a reference plane, the reference plane being parallel to a strip surface of the metal strip and passing through a center point of a line that joins respective rotational centers of upper and lower rolls, and does not permit displacement of the strip-thickness center of the metal strip outside of the plane of the reference plane;
in cases in which the provisional elongation strain difference distribution exceeds the critical buckling strain difference distribution, finding a true elongation strain difference distribution by adding the difference between the provisional elongation strain difference distribution and the critical buckling strain difference distribution to the provisional elongation strain difference distribution; and
rolling the metal strip without changing the specific rolling conditions in cases in which the provisional elongation strain difference distribution does not exceed the critical buckling strain difference distribution, and rolling the metal strip under rolling conditions set based on the true elongation strain difference distribution in cases in which the provisional elongation strain difference distribution exceeds the critical buckling strain difference distribution.

2. The rolling control method of claim 1 , further comprising finding the provisional elongation strain difference distribution.

3. The rolling control method of claim 1 , wherein, when finding the true elongation strain difference distribution, a converted tension is found by converting a difference between the provisional elongation strain difference distribution and the critical buckling strain difference distribution into tension acting on the metal strip at exit from the rolling mill, and the true elongation strain difference distribution is found by adding an elongation strain difference distribution corresponding to the converted tension to the provisional elongation strain difference distribution.

4. The rolling control method of claim 3 , wherein, when finding the true elongation strain difference distribution, a second order differential with respect to the strip width direction of a rolling load difference distribution in the strip width direction of the metal strip corresponding to the converted tension is found as an elongation strain difference distribution corresponding to the converted tension.

5. The rolling control method of claim 1 , wherein the metal strip undergoes out-of-plane deformation at entry to the rolling mill.

6. The rolling control method of claim 1 , further comprising:
employing a profile meter installed at exit from the rolling mill to measure the profile of the metal strip after rolling; and
correcting the provisional elongation strain difference distribution based on a difference between an actual elongation strain difference distribution that has been transformed into out-of-plane deformation found from a measured profile of the metal strip, and an elongation strain difference distribution predicted to be transformed into out-of-plane deformation.

7. A rolling control method comprising:
under conditions in which out-of-plane deformation of a metal strip is restrained, finding a provisional rolling load difference distribution, which is a distribution of differences in rolling load in a strip width direction of the metal strip during rolling under specific rolling conditions, and finding a provisional elongation strain difference distribution, which is a distribution of differences in the strip width direction in elongation strain along a rolling direction of the metal strip during rolling, by using an up-down asymmetrical model that permits displacement of a strip-thickness center of the metal strip within a plane of a reference plane, the reference plane being parallel to a strip surface of the metal strip and passing through a center point of a line that joins respective rotational centers of upper and lower rolls, and does not permit displacement of the strip-thickness center of the metal strip outside of the plane of the reference plane;
finding a critical buckling strain difference distribution, which is a distribution in the strip width direction of differences in a critical strain at which the metal strip will buckle, based on the provisional elongation strain difference distribution, a strip thickness of the metal strip, a strip width of the metal strip, and tension acting on the metal strip at exit from a rolling mill;
in cases in which the provisional elongation strain difference distribution exceeds the critical buckling strain difference distribution, finding an out-of-plane deformation load difference distribution corresponding to an out-of-plane deformation strain difference distribution, which is a difference between the provisional elongation strain difference distribution and the critical buckling strain difference distribution, from a correlation between the provisional rolling load difference distribution and the provisional elongation strain difference distribution, deriving a new rolling load difference distribution by superimposing the out-of-plane deformation load difference distribution on the provisional rolling load difference distribution, finding a new elongation strain difference distribution based on the new rolling load difference distribution under the assumption that there is a change in a crown ratio of the metal strip, and further finding a new critical buckling strain difference distribution based on the new elongation strain difference distribution, the strip thickness and the strip width of the metal strip, and tension acting on the metal strip at exit from the rolling mill;
finding a difference between the new elongation strain difference distribution and the new critical buckling strain difference distribution, and finding a true elongation strain difference distribution by adding this difference to the new elongation strain difference distribution; and
rolling the metal strip without changing the specific rolling conditions in cases in which the provisional elongation strain difference distribution does not exceed the critical buckling strain difference distribution, and rolling the metal strip under rolling conditions that are set based on the true elongation strain difference distribution in cases in which the provisional elongation strain difference distribution exceeds the critical buckling strain difference distribution.

8. The rolling control method of claim 7 , wherein finding the out-of-plane deformation load difference distribution is performed a plurality of times by taking the new elongation strain difference distribution as the provisional elongation strain difference distribution, and taking the new critical buckling strain difference distribution as the critical buckling strain difference distribution.

9. A rolling control method comprising:
under conditions in which out-of-plane deformation of a metal strip is rest

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Akashi Tooru
• Ogawa Shigeru
• Yamada Kenji

Classifications

• B21B37/28

  Control of flatness or profile during rolling of strip, sheets or plates · CPC title

• B21B2263/08

  Centre buckles · CPC title

• B21B37/16 Primary

  Control of thickness, width, diameter or other transverse dimensions (B21B37/58 takes precedence) · CPC title

• B21B2265/10

  Compression, e.g. longitudinal compression · CPC title

• B21B1/16

  for rolling {wire rods, bars, merchant bars, rounds} wire or material of like small cross-section · CPC title