RU2277988C1 - Method for forming coil of etched hot rolled steel strip and apparatus for performing the same - Google Patents

Abstract

FIELD: methods and apparatuses for shaping coils of etched hot rolled steel at preparation of rolled piece for further cold rolling of strips.

SUBSTANCE: method comprises steps of successively coiling strip including several butt welded strips for forming coil with predetermined outer diameter and mass; before coiling subjecting strip portions with welded seams to lengthwise sign-variable bending at plastic tension of metal; setting bending radius values Ru consisting of 0.04 -0.05 of maximum width of coiled strip and setting number of bending operations n = [( 0.4 - 0.5)E x Ru]/h where E - percentage reduction value in first stand of cold rolling mill; h - strip thickness, mm; Ru -bending radius, mm. Apparatus for performing the method includes successively mounted along motion direction of metal pairs of upper and lower cylindrical bending rollers. Four pairs of rollers with diameter 2Ru are mounted in initial position respectively over and under moving strip and in each pair they are mutually spaced by distance l = (3 - 4)Ru. Value l is inversely proportional to value h. Upper rollers are driving ones. Lower rollers are mounted with possibility of moving along arc of circle whose center coincides with axis of upper roller by means of lever mounted in axles of both rollers till they achieve vertical axial plane of said rollers and position over upper roller. Distance between driving rollers of each pair consists (5 -6)Ru. Circular motion of lower rollers is realized with use of gear wheels; one of said gear wheels is rigidly joined with lever. Gear wheels for rotating lever are arranged at side opposite to roller drive unit.

EFFECT: lowered labor consumption due to reduced number of welded strip breaking at rolling them.

5 cl, 1 dwg, 1 ex

Description

The invention relates to technology and equipment for finishing and processing of strip steel (rolled) and can be used in the preparation of rolling for subsequent cold rolling of strips.

To increase the productivity of modern continuous cold rolling mills, coiling of a billet (rolling), usually 2 ... 6 mm thick, is carried out, the weight of the coils, which reaches 50 ... 60 tons, by butt welding of individual hot-rolled strips. In this regard, the problem arises of creating welds of sufficient strength, excluding breaks during cold rolling, which lead to additional mill stops and labor costs. Said strip welding is carried out on continuous pickling units (NTA) of the hot rolling workshops.

The preparation of hot rolled strips for cold rolling (including NTA) is described, for example, in the reference manual, under the editorship of Ed. V.I. Zyuzina and A.V. Tretyakov "Technology of rolling production", book 2, Moscow, Metallurgy, 1961, pp. 632-640.

There is a method of winding a cold-rolled strip into a roll on a reel drum with a change in the current average specific tension along the width of the strip along its entire length and inversely proportional to the inter-turn pressure in the wound roll with a decrease in this tension at the edges (see USSR AS No. 1311806, class. At 21 C 47/00, published in BI No. 19, 1987). However, this method is unsuitable for forming rolls of hot rolled strips.

Known roller machine for straightening sheets, in which one row of rollers performing alternating bending of the moving strip is mounted in a cassette with the possibility of rotation in the pressure beam, on which the rotation mechanism is located (see USSR AS No. 156920, publ. 25.09.63 g.). This machine is unsuitable for plastic bending of heat-affected sections of welded strips with a relatively large stretching thereof.

The closest analogue to the claimed method is the method of forming a roll of hot-rolled strip steel, described in the book by A.I. Tselikov and others. Machines and assemblies of metallurgical plants, t.3, M., Metallurgy, 1988, p. 480.

This method consists in sequentially folding (winding) the strip and is characterized in that the winding is carried out by a winder drum that creates tension of the strip without pressing the roll forming rollers to the strip. The disadvantage of this method is its unacceptability to create a given tension in individual sections of the rolled strip.

The closest analogue to the claimed device is the correct machine for editing thin sheets, given in the book of A.A. Korolev. Design and calculation of machines and mechanisms of rolling mills, M., Metallurgy, 1985, p.309-310 and Fig. IX.6.

This device contains a pair of successively installed in the direction of movement of the metal upper and lower cylindrical bending rollers and is characterized by the presence of support rollers located in a checkerboard pattern with respect to the working (bending) rollers. However, such a device does not provide bending of the strip at large angles (up to 180 ... 185 °), necessary for the implementation of the proposed method.

An object of the present invention is to reduce labor costs in the production of cold rolled strip steel by reducing breaks in welded strips obtained from a hot rolled pickled billet.

To solve this problem, in a method for forming a coil of pickled hot-rolled steel, which consists in sequentially folding a strip consisting of several butt-welded strips to form a roll of a predetermined external diameter and weight, before folding, sections of the strip with welds are subjected to alternating longitudinal bending with plastic stretching of the metal, taking the bending radii Ru equal to 0.04 ... 0.05 of the maximum width of the strip rolled up into a roll, and the number of bends equal to n = (0.4 ... 0.5) E Ru / h, where E is the ratio compression in the first stand of the cold rolling mill, h - strip thickness, mm, Ru - in mm.

A device for plastic bending of pickled hot rolled steel, rolled into a roll and consisting of several butt welded strips, containing pairs of successively installed upper and lower cylindrical bending rollers in the direction of metal movement, contains four pairs of rollers with a diameter of 2Ru located in the initial position, respectively, under the moving strip and below it at a distance l = (3 ... 4) Ru from each other in each pair and the value of l is inversely proportional to the value of h, while the upper rollers are driven, and the lower ones are made with the possibility of moving along an arc of a circle, the center of which coincides with the axis of the upper roller, using the lever mounted on the axes of both rollers, until the vertical axial plane of these rollers reaches the position above the upper roller; the distance between the drive rollers of each pair can be equal to (5 ... 6) Ru, and the circular movement of the lower rollers can be carried out using gears, one of which is rigidly connected to the lever and the gears for turning the lever are located on the side opposite to the drive of the rollers.

The above mathematical relationships are obtained as a result of experiments and are empirical.

The essence of the claimed technical solution consists in bending with plastic tension of the metal of the heat-affected zone of the moving strip, and the number of strip bendings when passing the bending-stretching device is determined not only by the radius of the bending rollers and the thickness of the metal, but also by the relative compression in the first stand of the cold rolling mill. As a result of this, the weld is subjected to transverse stretching, which, if the quality of the welding is unsatisfactory, will cause the strip to break immediately before winding onto the NTA (and not on the mill) with less negative consequences. In addition, a decrease in the thickness of the heat-affected area during its longitudinal tension will reduce the load on the rolls when the weld passes through them, which also reduces the likelihood of strip breaks.

The proposed method and device are illustrated in the drawing, which schematically shows the implementation of the technical solution found; I and II pairs of bending rollers are shown in the working position (with double bending of the strip), III and IV pairs - in the initial position.

The upper rollers 1 of each pair are connected to the lower rollers 2 by means of levers 3 that rotate the rollers 2 in a vertical plane (coinciding with the plane of the drawing) 90 ° clockwise (in our case) until they reach one vertical axis yy passing through the centers both rollers 1 and 2. At the end of each lever 3, located on the axis of the upper roller 1, a gear 4 is fixed, driven in rotation from a gear 5 connected to an engine (not shown). The distance between the lower rollers of each pair is L, and the distance between the upper and lower rollers in the working position is -l.

Strip 6 (the direction of its movement is shown by arrows) is stretched through the bending rollers using two pairs of pulling rollers 7 and 8, as well as using the upper drive rollers 1, which prevents mutual sliding of the surfaces of the rollers and the metal with known negative consequences.

The total angle of coverage of the strip of one pair of bending rollers, obviously, is equal to:

The magnitude of the plastic longitudinal tension during double bending by one pair of rollers is equal to:

, где

,

where

,

Therefore, the radius of the bending rollers is determined by the quantities h and λ.

Before starting the operation of the device, the required strain value of the heat-affected area of the hot-rolled pickled strip is determined, which should be about half the strain (compression) of this strip in the first stand of the cold rolling mill. The found value determines the number of pairs of bending rollers. Then, in these pairs, the lower rollers using the drive levers 3 (see Fig. 1) are installed (if there is a strip between them) in the position shown in the diagram for pairs I and II, moreover, the strip is fed into the rollers or when the second one stops (by the movement of the metal) pairs of pulling rollers 7 and 8, or by properly reducing the speed of rotation of these rollers. Plastic stretching of the heat-affected area, as shown by experiments (see below), is enough to carry out at a length of 1 ... 2 m, which can be more when the strip is bent, for example, with three or four pairs of bending rollers.

After the strip passes through the device, the lower bending rollers can be returned to their original position (as in pairs III and IV in the diagram) without stopping the metal: by increasing the speed of the second pulling rollers to “select the loop” near the strip.

An experimental verification of the proposed technical solution was carried out at the NTA sheet rolling shop No. 5 of OJSC "Magnitogorsk Iron and Steel Works". For this purpose, the main device parameters (Ru, l, and L) and the number of strip bends (n) for strip steel of various thickness h and width B were varied. The test results were evaluated by the “rolling” of the joints, i.e. the advent of a strip blank without breaks through the stands of a cold rolling mill.

The best result (rolling without breaks of strips at the seams, ie 100% "rolling") was obtained when implementing the proposed method and device. Deviations from the recommended parameters worsened this indicator, as well as the quality of hot-rolled etched metal.

Thus, a decrease in Ru to (0.025 ... 0.035) B led to the appearance of transverse kink lines on the strips, and an increase in Ru to slippage of the strips in the rollers and scratches) due to a decrease in the angle of coverage φ of the rollers. A decrease in l and L led to similar consequences, and their increase does not change the quality indicators of the process, but leads to an increase in the dimensions of the device and its cost.

The location of the upward bending roller in front of the same drive roller (in the direction of the strip) facilitates the lifting of the rollers with a moving strip. The direct dependence of Ru on strip width B, confirmed by experiments, is due to the fact that an increase in the barrel length of the bending rollers leads to an increase in their normal bending force, which requires an increase in the diameter of the rollers.

In the experimental device, all the drive bending rollers had a common chain drive, and the pivot arm was moved using gears mounted on the control side, which facilitates the operation of the device.

The method and device, selected as the closest analogues, were not subjected to comparative tests due to their unsuitability for the implementation of the goal. Thus, the pilot test confirmed the acceptability of the claimed technical solution to achieve the goal and its advantage over known objects.

According to the Central Control Laboratory of OJSC MMK, the use of the invention in the production of rolled products with a thickness of 2 ... 6 mm for cold rolling mills will reduce the cost of cold rolled strip steel by at least 5% due to the prevention of strip breaks during rolling with a corresponding increase in profit from the sale of finished products.

Concrete example

The device for plastic bending of pickled hot rolled steel, welded into a roll, has the form shown in the drawing, and contains four pairs of bending, and stationary (non-moving) rollers of each pair are driven.

The maximum width of the passing strip B = 2000 mm, its thickness h = 4 mm. The value of Ru = 0.045 · 2000 = 90 mm, and the diameter of the bending rollers d = 2Ru = 2 · 0.045 · B = 2 · 0.045 · 2000 = 180 mm. The value of E = 20% = 0.2.

The number of bends (and the rollers rotated in the vertical plane) n = 0.45 · E · Ru / h = 0.45 · 0.2 · 90/4 = 2.

The value of l = 3.5Ru = 3.5 · 90 = 315 mm, L = 5.5 Ru = 5.5 · 90 = 445 mm.

Coverage:

Claims (5)

1. A method of forming a pickled hot-rolled steel coil serving as a rolling stock for subsequent cold rolling, comprising sequentially folding a strip consisting of several butt-welded strips to form a roll of a predetermined external diameter and weight, characterized in that prior to folding sections of the strip with welds are subjected to longitudinal alternating bending with plastic stretching of the metal, taking the bending radius Ru equal to 0.04 ... 0.05 of the maximum width of the strip, rolled into a roll, and the number of bending equal

where E is the value of the relative compression in the first stand of the cold rolling mill, h is the strip thickness, mm, Ru - in mm. 2. Device for plastic bending of pickled hot rolled steel, rolled into a roll and consisting of several butt welded strips, containing pairs of successively installed upper and lower cylindrical bending rollers in the direction of the metal, characterized in that it contains four pairs of rollers with a diameter of 2Ru, located in the initial position, respectively, above and below the moving strip at a distance l = (3 ... 4) Ru from each other in each pair and the value of l is inversely proportional to the value of h, while the upper rollers are pr and the lower ones are made with the possibility of moving along an arc of a circle, the center of which coincides with the axis of the upper roller, with the help of a lever mounted on the axes of both rollers, until these rollers reach the vertical axial plane and in a position above the upper roller. 3. The device according to claim 2, characterized in that the distance between the drive rollers of each pair is (5 ... 6) Ru. 4. The device according to claim 2, characterized in that the circular movement of the lower rollers is carried out using gears, one of which is rigidly connected to the lever. 5. The device according to claim 2, characterized in that the lever rotation gears are located on the side opposite to the drive of the rollers.