Method of operating a rolling line for wire or light sections

Abstract

A method of operating a mill for wire or fine sections in which control of the rolling gap is limited only to selected stands of a multiple stand intermediate line of the mill for changeover of the product to be rolled, for example, as the composition or diameter.

Description

FIELD OF THE INVENTION

[0001] Our present invention relates to a method of operating a rolling mill line for the rolling of wire or light sections and, more particularly, to a method of controlling such a line upon the feed of a new stock with respect to the characteristics of its material and the inlet cross section.

BACKGROUND OF THE INVENTION

[0002] In rolling of wire and light sections, especially of steel, it is a common practice to provide a rolling line consisting of a preliminary rolling line or stretch, an intermediate rolling line or stretch and a finish rolling line or stretch through which the workpiece is fed in succession.

[0003] Each of these stretches normally comprises a multiplicity of rolling mill stands each having at least two rolls between which the workpiece is deformed so as to alter its dimensions and/or cross sectional shape.

[0004] The intermediate rolling line especially comprises a large number of rolling mill stands which successively engage the workpiece and usually have adjustable rolls, the settings of which are controlled, for example, with respect to the rolling gap individually, i.e. for individual roll stands, so as to be varied for different inlet and outlet cross sections and different workpiece materials for the rolled wire. In addition, the settings will depend on the loading values and modulus of elasticity of the individual mill stands in the sense that the loading characteristics of the mill stand are considered in calculating the setting of the rolling gap for the individual pair of rolls.

[0005] As a consequence in the operation of this intermediate rolling line, a relatively large number of individual rolling stands, successively engageable with the workpiece, requires individual adjustment and especially in the case of thermomechanical rolling (TM rolling) with different rolling temperatures over the rolling line, the controlled system for setting the roll, variation of the settings of the gap for the many roll stands, temperature regulation, monitoring and after-regulation, is exceedingly complex and expensive.

[0006] In the past it was standard practice to adjust substantially all of the stands of at least the intermediate rolling line for a change to rolling of a workpiece with a different wire diameter and/or for a different composition of the workpiece.

OBJECTS OF THE INVENTION

[0007] It is, therefore, the principal object of the present invention to provide an improved method of controlling a rolling line whereby the cost of controlling that line in the case of a change of the wire diameter or workpiece material can be significantly reduced and the maintenance and service operation can be limited.

[0008] Another object of the invention is to provide a method of operating a rolling mill line of the type described at the outset for rolling wire and light sections, especially to minimize the efforts hitherto used in resetting the rolling stands of the intermediate stretch or line.

[0009] A further object of this invention is to provide a method of operating a rolling mill line, especially for the production of wire, whereby drawbacks of earlier systems are reduced or avoided.

SUMMARY OF THE INVENTION

[0010] These objects and others which will become apparent hereinafter are attained, in accordance with the invention which is based upon our finding that, contrary to previous approaches to the control of the intermediate stretch or line in the rolling especially of wire but also of light sections, it is no longer necessary to reset the rolling gap of all of the stands of the intermediate rolling line but rather it is possible to reset the entire rolling mill line for a different wire diameter or composition by adjusting only the rolling gaps of a limited number of stands of the intermediate line by appropriate selection of the locations of those controlled stands along the lien and their number. In particular, it has been found that control of the first two or four stands and of the last two or four stands of the intermediate line will suffice.

[0011] In other words, when there is a changeover from the rolling of one workpiece to another workpiece of a different diameter or composition or there is a need to change over from a previous strand cross section to another cross section and that workpiece is to pass through all of the mill stands of the intermediate line, it is only necessary to reset the rolls of certain of these stands of the intermediate lien and vary the gap width only for these selected stands, the tolerances being maintained for the rolled product:in passing through all of the stands of the intermediate line.

[0012] The intermediate line can be located upstream of the finishing line and in that case it suffices to control the rolling gap of the first two or four mill stands and the last two or four mill stands immediately upstream of the finishing line.

[0013] The number of stands which are controlled and their position along the intermediate line are determined by the production palette (dimensions, composition and rolling product temperature, for example in the case of temperature controlled rolling).

[0014] The method of the invention can then comprise the steps of:

[0015] (a) passing an original workpiece having characterizing workpiece properties including cross-sectional shape, cross-sectional dimensions and composition in succession through a preliminary rolling line, an intermediate rolling line and a finishing rolling line to produce a rolled product, at least the intermediate rolling line comprising a multiplicity of rolling stands each having at least a pair of rolls defining a rolling gap between them;

[0016] (b) setting the rolling gaps of all individual stands of the intermediate line to produce the product based upon inlet and outlet cross sections and composition of the workpiece, and calculated based upon a loading property of the respective stand; and

[0017] (c) changing the workpiece passed in step (a) through the lines to a workpiece having at least one characterizing workpiece property different from those of the original workpiece, and modifying the rolling gap settings of only selected ones of the rolling stands of the intermediate line at locations along the intermediate line enabling tolerance-maintaining rolling of the workpiece through all of the stands of the intermediate line.

[0018] The invention thus eliminates the need for expensive motorized controls of those stands which need not be readjusted and limits the need for such controls only to the more limited number of stands at which the readjustment is effected.

BRIEF DESCRIPTION OF THE DRAWING

[0019] The sole FIGURE of the drawing is a diagram of a rolling mill for the rolling of wire in accordance with the invention.

SPECIFIC DESCRIPTION

[0020] The rolling mill shown in the drawing comprises a preliminary rolling line 10 with multiple rolling stands and temperature-controlled rolls for rolling the workpiece 11 to produce the prerolled product 12. The latter is fed to the intermediate rolling line 13 with a multiplicity of rolling stands 141, 142, 143, 144 . . . 14n and 14n−1. The additional rolling stands between the penultimate rolling stand 14n−1 and the rolling stand 144 have been represented only by a dated line. The intermediate rolled product 15 is delivered directly to the finishing units of a finishing rolling line 16 having multiple rolling stands and temperature controlled rolls.

[0021] As can be seen from the drawing, only selected rolling stands 14-144 and 14n−1, 14n of the intermediate rolling line 13 have their rolling gaps reset by the controller 17 when the stock to be rolled is changed and the prerolled product 12 entering the intermediate rolling line has a different diameter or composition.

[0022] The system of the invention thus enables the expensive servomotor control of only the aforementioned selected stands for changeover of workpieces and eliminates the need for such control for the remainder of the stands of the intermediate lines.

Claims

1. A method of operating a rolling mill for producing wire or light sections, comprising the steps of:

(a) passing an original workpiece having characterizing workpiece properties including cross-sectional shape, cross-sectional dimensions and composition in succession through a preliminary rolling line, an intermediate rolling line and a finishing rolling line to produce a rolled product, at least said intermediate rolling line comprising a multiplicity of rolling stands each having at least a pair of rolls defining a rolling gap between them;

(b) setting the rolling gaps of all individual stands of said intermediate line to produce said product based upon inlet and outlet cross sections and composition of said workpiece, and calculated based upon a loading property of the respective stand; and

(c) changing the workpiece passed in step (a) through said lines to a workpiece having at least one characterizing workpiece property different from those of the original workpiece, and modifying the rolling gap settings of only selected ones of the rolling stands of the intermediate line at locations along the intermediate line enabling tolerance-maintaining rolling of the workpiece through all of the stands of the intermediate line.

2. The method defined in claim 1, further comprising the step of controlling temperatures of the rolls of said intermediate line.

3. The method defined in claim 2 for the rolling of wire wherein the finishing line has finishing mills directly following said intermediate line, and wherein a first two or four stands and a last two or four stands of the intermediate line have their rolling gap settings modified in step (c).