US3924428A - Method of and apparatus for descaling and leveling a metal strip - Google Patents

Abstract

A metal strip is passed continuously through three succeeding roller-tensioning devices. Between the upstream and central tensioning device the strip is elongated by between 0.5 and 1.3 percent so as to descale this strip. Between the central tensioning device and the downstream tensioning device the strip is elongated by between 2 and 2.5 percent so as to level the strip and prevent end bowing thereof.

Description

United States Patent [1 1 [111 3,924,428

Noe [4 Dec. 9, 1975 METHOD OF AND APPARATUS FOR [56] References Cited DESCALING AND LEVELING A METAL I UNITED STATES PATENTS STRIP 2,163,504 6/1959 Thomas.... 29/81 A [75] Inventor: Oskar No, Mulheim (Ruhr), 3,261,191 7/1966 Wasson 72/161 Germany 3,559,431 2/1971 Noe et a1. 72/8 3,626,735 12/1971 Lebourg et a]. 72/205 X [73] Assrgnee: Firma BWG Bergwerkund @lzwerkMaschinenbau GmbH, Primary Examiner-Milton S. Mehr Dulsburg, Germany Attorney, Agent, or Firm1(arl F. Ross; Herbert 22 Filed: Oct. 7, 1974 'Dubno [21] Appl. No.: 512,604 [57] ABSTRACT A metal strip is passed continuously through three [30] Forelgn Apphcatlon Pnonty Dam succeeding roller-tensioning devices. Between the up- Oct. 8, 1973 Germany 2350503 stream and central tensioning device the strip is elongated by between 0.5 and 1.3 percent so as to descale [52] US. Cl. 72/40; 29/81 A; 72/ 161; this strip. Between the central tensioning device and 3; 6 /3 P the downstream tensioning device the strip is elon- [51] Int. C1. B21B 45/06;B21D 1/04 gated by between 2 and 2.5 percent so as to le el th [58] Field of Search 72/39, 40, 205, 161, 160, strip and prevent end bowing thereof.

4 Claims, 3 Drawing Figures LEVELING 4 O'S'CAL/NG TEQBQ METHOD OF AND APPARATUS FoR DESCALING AND LEVELING A MET L STRIP FIELD OF THE INVENTION The present invention relates to a method of and an apparatus for descaling and leveling a metal strip. More particularly this invention concerns a roller-levelerthrough which a metal strip is passed beforepickling.

BACKGROUND OF THEINVENTION Prior to thepickling of a metal strip, in particular a steel strip, it is necessary toldescale the strip. This;is done in a so-called roller-leveler which stretches the sheet longitudinally to a limited extent while alternately and reverse bending it soas to remove all ;of the scale thereon. At the same time the stripis flattened 2 The apparatus according to the present invention comprises three roller ten'sioners separating two reverse bending devices. The strip is descaledbetween the extreme upstream and the central roller tensioner and is leveled between the central and the extreme downstream roller tensioner.

BRIEF DESCRIPTION OF THE DRAWING of operation of the system according to the present in- Experiments have shown that the amount of elongation necessary to descale the strip adequately does not eliminate lateral bowing, that is a deformation of the strip in its own plane toward one side caused by hotworking of the strip. This lateral bowing occurs at the ends of the strip most often so that it is necessary to cut off these ends before the strip can be further processed, as it is impossible to pass the strip through conventional treatment apparatus when it is bowed in this manner.

It has been suggested that this lateral bowing can be eliminated by stretching the strip longitudinally to a relatively large extent. At this high degree of stretch however the descaling is usually insufficient so that the known systems usually employ a degree of stretch that is a middle ground between the two levels, so that the descaling is usually inadequate while the lateral bowing is also inusfficiently suppressed.

OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide an improved method of an apparatus treating a metal strip.

Another object is the provision of improved system for descaling and leveling a metal strip.

Yet another object is to provide such an apparatus which in one simple operation both effectively descales the strip and leveling it perfectly, thereby eliminating any lateral bowing at the ends thereof.

SUMMARY OF THE INVENTION These objects are attained accordingto the present invention in a system wherein the strip is passed through a pair of succeeding stretching assemblies. In the upstream assembly the strip is subjected to a relatively low degree of longitudinal elongation, equal to the maximum-descaling stretch (MDS). At the downstream assembly the extent of stretch is considerably greater so as to completely eliminate lateral bowing of the strip. Thus in accordance with the present invention the strip in a single pass is both completely descaled and perfectly leveled, both of these operations being carried out at levels which correspond to the ideal stretch for that operation.

In accordance with the present invention the maximum-descaling stretch in the upstream device is between 0.5 percent and 1.3 percent for removal of scale on the strip.

In accordance with yet another feature of this invention the extent of stretch in the downward stream assembly serving to level the strip is greater than 2 percent, advantageously between 2 and 2.5 percent.

vention.

' SPECIFIC DissCRIPIIoN As shown in FIG. 1 asteel strip 1 is passed in adirection 8 through three succeeding roller-tensioners 2a, 2b, and 20 each having two respective driventension rollers 3a, 3b, and 3c. Between theupstream roller assembly 2a and thecentral roller assembly 2b there is provided a reverse-bending device 4 having threereversing rollers 9 much as described in my US. Pat. No. 3,777,532 issued on Dec. 11, 1973.Idler rollers 5 are employed to either side of this reverse bender 4 for proper feeding of thestrip 1.

A similar reverse bender 4" havingrollers 9" is provided between thecentral tensioning assembly 2b and thedownstream tensioning assembly 20. After exiting from thedownstream assembly 20 thestrip 1 is pickled.

It has been found that a maximum amount of g/m of scales is removed as illustrated in FIG. 2 when theupstream assembly 2a and thecentral assembly 2b are so driven as to elongate thestrip 1 by an extent equal to the maximum-descaling stretch (MDS) of between 0.5 percent and 1.3 percent. Thus thedrive motors 10a and 10b for theassemblies 2a and 2b are so controlled that they stretch the strip between these assemblies by approximately 0.8 percent.

Similarly as shown in FIG. 3 it has been found that the lateral deflection h in mm/m of thestrip 1 is reduced greatly when thestrip 1 is stretched greater than 2 percent. Between 2 and 2.5 percent has been found advantageous. To this end the drive motor of theassembly 2c is driven at a rate relative to the drive speed of the motor 10b of theassembly 2b to stretch thestrip 1 between these twoassemblies 2b and 2c by an extent equal to between 2 percent and 3 percent.

Thus the band section 6 between theupstream assembly 2a andsecond assembly 2b is subjected to a longitudinal tension of approximately 10 tons while the ;tension on the section 7 between theassembly 2b and theassembly 20 is equal to approximately 20 tons.

The system and apparatus according to the present invention is equally usable with nonferrous metal sheets. It is also possible to provide in the system according to the present invention various metal working machines between the rolling-tensioning assemblies 2a 20. Four such assemblies could also be provided as could only two to carry out the present invention.

I claim:

1. A method of treating a metal strip comprising the steps of:

longitudinally stretching said strip to a relatively small extent between 0.5 and 1.3 percent corre- 3 sponding to maximum-descaling stretch while reverse bending the strip to remove scale from the strip; thereafter longitudinally stretching said strip to a relatively large extent sufficient'to level said strip; and

pickling said strip after leveling same. 2. The method defined inclaim 1 wherein said strip is leveled by stretching more than 2 percent.

3. An apparatus for treating a metal strip and comprising:

descaling means for longitudinally stretching said strip to a relatively small extent between 0.5 and 1.3 percent to remove scale therefrom; reverse bending means for reverse bending said strip simultaneously with the longitudinal stretching thereof by said descaling means;

4 leveling means downstream from said descaling means for stretching said strip to a relatively large extent sufficient to level said strip; and

means for pickling said strip downstream of said levcling means.

4. The apparatus defined inclaim 3 wherein said descaling means includes an upstream roller-tensioner, said leveling means includes a downstream roller-tensioner, and said apparatus includes a central roller tensioner between said upstream and downstream roller tensioners, an upstream reverse bender being provided between said upstream roller-tensioner and said central roller-tensioner and a downstream reverse bender being provided between said central roller-tensioner and said downstream roller-tensioner, each of said reverse benders including a plurality of succeeding and parallel rollers defining a sinusiodal path for said strip.

Claims (4)

1. A method of treating a metal strip comprising the steps of: longitudinally stretching said strip to a relatively small extent between 0.5 and 1.3 percent corresponding to maximumdescaling stretch while reverse bending the strip to remove scale from the strip; thereafter longitudinally stretching said strip to a relatively large extent sufficient to level said strip; and pickling said strip after leveling same.

2. The method defined in claim 1 wherein said strip is leveled by stretching more than 2 percent.

3. An apparatus for treating a metal strip and comprising: descaling means for longitudinally stretching said strip to a relatively small extent between 0.5 and 1.3 percent to remove scale therefrom; reverse bending means for reverse bending said strip simultaneously with the longitudinal stretching thereof by said descaling means; leveling means downstream from said descaling means for stretching said strip to a relatively large extent sufficient to level said strip; and means for pickling said strip downstream of said leveling means.

4. The apparatus defined in claim 3 wherein said descaling means includes an upstream roller-tensioner, said leveling means includes a downstream roller-tensioner, and said apparatus includes a central roller tensioner between said upstream and downstream roller tensioners, an upstream reverse bender being provided between said upstream roller-tensioner and said central roller-tensioner and a downstream reverse bender being provided between said central roller-tensioner and said downstream roller-tensioner, each of said reverse benders including a plurality of succeeding and parallel rollers defining a sinusiodal path for said strip.

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