US3722250A

US3722250A - Rolling mills and methods

Info

Publication number: US3722250A
Application number: US00145220A
Authority: US
Inventors: W Demny
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-04-22
Filing date: 1971-05-20
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27
Also published as: GB1339030A; DE2019292C2; DE2019292A1

Abstract

A multi-roller stand, e.g. three roller, for a rolling line in a rolling mill, e.g. a rod mill, has journalled therein rollers of slightly different diameter. When the rollers become worn the worn larger roller can be refinished and used in the same stand as a replacement for the worn smaller roller. The latter can then be refinished or reground and can replace a still smaller worn roller in the same stand or in another stand, in the latter case as a replacement for a larger roller in said other stand. Alternatively the worn larger roller, after refinishing or reprofiling can be moved to a similar position in another stand higher up the line. In this case a worn larger roller from the first stand can, after refinishing or reprofiling, be used to replace a smaller roller in the last stand.

Description

United States Patent [191 Demny Mar. 27, 1973 ROLLING MILLS AND METHODS Primary E.mminer--Milton S. Mehr [75] Inventor: Werner Demny, Dusseldrof, Ger- Att0mey Bueu Blenko & zlesenhelm many [ ABSTRACT [73] Assignee: Friedrich Kocks A multi-roller stand, e.g. three roller, for a rolling line Filedl y 1971 in a rolling mill, e.g. a rod mill, has journalled therein [21] Appl. No; 145,220 rollers of slightly different diameter. When the rollers become worn the worn larger roller can be refinished and used in the same stand as a replacement for the [52] U.S. Cl ..72/224 worn smaller roller The latter can then be refinished [5 l] Int. Cl. or reground and can replace a till maller worn roller Field Of Search 199 in the same tand or in another stand in the latter case as a replacement for a larger roller in said other References Cimd stand. Alternatively the worn larger roller, after refinishing or reprofiling can be moved to a similar UNITED STATES PATENTS position in another stand higher up the line. In this 2,139,872 12/1938 Worthington ..72/203 case a worn larger roller from the first stand can, after 3,584,490 6/1971 Bindemagel ..72/249 refinishing or reprofiling, be used to replace a smaller 3,618,354 11/1971 Bindernagel et al ..72/224 ll i h l d 1,810,167 6/1931 George ..72/234 X 11 Claims, 1 Drawing Figure ROLLING MILLS AND METHODS The invention relates to a rolling mill and method and particularly to rolling mills having at least one stand with two or more rollers journalled therein to define a sizing gap, wherein the rolls are refinished and moved to a next position.

In the operation of a rolling mill, the cost of the rollers represents a very important factor. The roller costs can be lowered appreciably by refinishing or reprofiling the worn rollers and reusing them several times.

In some known multi-stand rolling mills the rollers journalled non-adjustably in one stand are of equal diameter, and after experiencing a maximum amount of wear with consequential reduction of the ideal diameter, are reprofiled and can be reused by fitting them in a replacement stand having a smaller spacing between the roller axes either in the same position or in another part of the rolling line. The possibility of reuse of the rollers is in this case limited by the number of available interchangeable stands provided with different spacings between the roller axes. It is normally regarded as economic to provide one set of replacement stands.

In other multi-stand rolling mills with non-adjustable rollers the spacing between the roller axes in the stands of a given row is uniform, so that the rollers which are re-profiled with retention of the ideal diameter, can with their stand be progressively transferred along the whole row from the output end to the input end. The possibility of reuse depends in this case on the number of stands in one row. After one passage through the row these rollers cannot be re-used;

The invention is concerned with the problem of procuring still further reductions in roller costs in rolling mills of the above-mentioned kind.

According to the invention, the rollers defining one sizing gap comprise at least two rollers of slightly different diameters, such that the larger of two rollers of different diameters, after experiencing a specified degree of wear and an appropriate refinishing operation, is further usable in the same stand in place of the smaller roller.

In rolling mills of this kind, the rollers, quite apart from the known multiple reutilization in different stands after reprofiling, are reusable several times, after the required refinishing, in one and the same stand, depending on the number of rollers defining one sizing In this case the rollers can be progressively transferred from the positions of rollers of the largest diameter to the positions of rollers of the smallest diameters in the same stands. In order to have optimum conditions for refinishing, the difference in diameter between different-sized, newly installed or unworn rollers in one stand may correspond at least to the sum of the degree of wear permissible for the larger roller and the grinding loss incurred on refinishing. This ensures satisfactory conditions for re-finishing to the same roller profile.

In the case of rolling mills having several stands arranged one after the other in a rolling line, the difference in diameter between two different-sized, newly installed or unworn rollers of the stand at the output end of the line may alternatively be so chosen that it corresponds at least to the sum of the difference in diameter between the larger roller of this stand and the corresponding larger roller of the stand positioned at the input end, the permissible degree of wear of this roller in the input stand and the grinding loss thereof. In such rolling mills the sizing gap after reaching the permissible wear limits, may for example be ground to the next sized sizing gap and the whole stand, along with the refinished rollers, can be moved along the rolling line by one rolling station in a direction opposite the direction of rolling. The rollers are then, only after the stand has passed along the whole row, themselves interchanged.

In the case of a frequently used type of rolling mill which has several three-roller stands in a row, it is advisable to have all three rollers of each stand of different diameters. In stands of this kind the rollers, after the required refinishing can be used three times.

In order to facilitate the refinishing of the rollers, the differences in diameter between the smallest and the middle-sized roller, and between the middle-sized and the largest roller are preferably equal.

As a rule, the rollers in a three-roller stand are arranged at relative to each other, one of the rollers being journalled about an horizontal axis. The stands, which are located one behind the other, can be alternately inverted by about their horizontal stand axis, so that the roller which is rotatable about the horizontal axis is in one stand above the material being rolled and in the adjoining stands below it. In such stands, in which the axes of the three rollers form an equilateral triangle, the roller displacement of the middle-sized roller is preferably equal to the quotient of the semi-diameter difference and cos 30, while the roller displacement of the largest and the smallest rollers is equal to the product of the roller displacement of the middle-sized roller and sin 30. This ensures that the height of the rolling center remains on the horizontal line through the center of the equilateral triangle formed by the axes of the three rollers, and therefore lies at the same height as for the case of the symmetrical arrangement of three equal-diameter rollers.

In order to ensure that when the stand is inverted the roll-center always remains in the same position, the rolling center can be made coincident with the standcenter.

The invention is further described, by way of example, with reference to the accompanying drawing, which is a schematic representation of a three-roller stand in accordance with the invention.

The drawing shows one of a number of three-roller stands of a rod mill. The illustrated stand has three disclike rollers l, 2, 3 whose axes l', 2' and 3 form an equi-lateral triangle, with one vertex pointing downwardly. The peripheries of the rollers l, 2 and 3 are suitably profiled to perform the desired working operation on the rod or wire passing through the mill along the rolling axis. Reference may be made to copending US. Pat. No. 3,618,354 filed May 6, I970 by Bindernagel and Demny for examples of suitable profiles which may be applied to the

rollers

1, 2 and 3. However, according to the present invention the diameters of the

rollers

1, 2 and 3 differ in length, so that the rolling center WM is displaced from the center DM of the triangle.

The middle-sized roller 2 is in the vertical position and in the position of the stand shown in the drawing it is at the top, while the largest and smallest rollers 1 and 3 are at 120 to either side and below the roller 2. The diameter differences A between the largest and the middle-sized rollers, and between the middle-sized and the smallest rollers are made equal, so that the rolling center is at the same height as the center of the triangle.

In order to be able to make unhampered use of the stands in the normal manner, i.e., according to their position in the rolling line to be able to turn them upside-down, the rolling center is made the center of the stand, so that on inverting the stand the sizing gap always remains at the rolling center.

The diameter of the middle-sized roller is called the nominal diameter and has the same magnitude as in the normal symmetrical arrangement, in which the three roller diameters are the same. The so-called ideal roller diameters for the

rollers

1, 2 and 3 are denoted by WD 1, WD 2, WD 3. Let the displacement of roller 1 from the center DM of the triangle be denoted by a, the displacement of roller 2 by b, and the displacement of roller 3 by c. In the example shown in the drawing, in which the diameter differences are equal, theroller displacement a of roller 1 and the roller displacement c of roller 3 are equal.

As can be seen from the drawing, the following geometrical relationships apply:

A/2=b.cos 30 (1) a=c=b. sin 30 (2) WDi=WD2+A 3 WG WD DT (5) The following relationship therefore holds for the i" stand:

WG2,= WD2, DT; (7)

Wc3,= W03, DT,= W02,- A 0T, (8)

The respective values are given a dash if they refer to the worn state, in which case the following relationships hold:

WGl,'= WD2,+A,DT,' (9

WG2 WD2, DT, (10) The magnitude of the maximum permissible wear V is defined as the difference of the inscribed circles:

V=DT|""DTOI' (l2) A basis for the maximum permissible wear is the difference of the inscribed circle of two successive sizing gaps multiplied by a factor smaller than unity. The grinding loss S,- must also be taken into account.

The case in which the rollers are interchanged within a given stand has also to be considered. The procedure is that, after refinishing, roller 1 moves into the place of roller 2 and roller 2 into the place of roller 3. Roller 3, which can no longer be reused in this particular stand, is reprofiled and is moved to the next stand in the direction opposite the rolling direction,-into which it is fitted as the new roller 1. Similarly, roller 1 of the stand in question is replaced by the reprofiled roller 3 of the stand next in line. The reprofiling of the rollers when they are transferred from one stand to the next may comprise a mere refinishing with the same profile but smaller diameter or may comprise a change in profile as well as a diameter reduction.

In a row consisting of several stands one behind the other, it follows that only one roller is set free by the stand at the input end and this roller is no longer usable in the row. At the same time only one completely new roller is required by the stand at the output end. In the known rolling mills at the same point of time three rollers are rejected at the first stand while three new rollers have to be introduced into the last stand, so that, with the present invention, the roller costs can be reduced to one third of the previousamount. If two parallel rows with different ideal diameters are used, the rollers released from the first stand of the first row can subsequently be passed through the second row, thus again reducing the roller costs by one half.

The diameter differences A of the rollers'at a given sizing gap need only be very small, so that the rolling performance as compared with that of rolling mills with equal diameter rollers is not at all or unappreciably impaired. If for example roller 1 is to take the place of roller 2, the effective diameter of roller 1 in the worn condition must be greater than that of roller 2 in the unworn condition by an amount equal to the grinding loss, i.e.,

WGl WG21+ S,

Using equations (7) and (9):

W02, A DT, W02, DT, 3,

Using equation (13) I WD2,+A,DT, V= WD2,DT,+S,

From this we obtain for the diameter difference for the i-th stand:

The diameter difference is determined solely by the permissible wear and the loss due to the grinding required. For roller 2, which is to be put in the place of roller 3, the same holds good. Therefore the diameter differences of the rollers in each of the successive stands in the row can be equal.

If in the above equations we substitute actual values,

we obtain values for the diameter differences which are smaller than 1.5 mm. The resulting displacements a, b and c of the roller axes turn out to be less than mm.

The peripheral velocities of the three rollers at one sizing gap differ from each other only by about 0.5 percent. This amount is so small that it does not require compensation by differences in the speeds of rotation of the rollers.

According to another method, according to the invention, the rollers are not interchanged within a single stand, but they are transferred, after refinishing or reprofiling, first of all to the same position in the preceding stand in the direction of rolling. Thus, the roller 1 from the final stand is progressively transferred along all of the stands of the row, whereby in each case it takes the place of the former roller 1, until it reaches the stand at the input end of the row. If roller 1 in the first stand is worn, it is placed, after refinishing or reprofiling in the place of roller 2 of the final stand and is again progressively transferred along the whole row of stands in the position of roller 2. Finally, the roller is progressively transferred along the row as roller 3.

If in a rolling mill of this kind the stands in a row have the same ideal roller diameters, the stands are interchangeable among themselves. This makes it possible, when the wear limit has been reached, for the sizing gap, as usual in the past, to be ground down to the next larger sizing gap. The stand, together with the refinished rollers, is then moved to the next position. In the first sizing gap the rollers must however be changed round in the stand, whereby roller 1 is put in place of roller 2 and roller 2 in place of roller 3. Roller 3 is withdrawn from the stand and is no longer usable in the row. A new roller has to be fitted in place of roller 1 of the first sizing gap. This stand, to which the new roller has been fitted, now has the smallest sizing gap and is transferred to the output end of the row. In this embodiment, the diameter of roller 1 at the sizing gap of the input end, in the worn condition, must exceed the diameter of roller 2 at the sizing gap at the output end by an amount equal to the grinding loss, i.e., the sizing gap with the smallest inscribed circle. In general the following equation holds:

Using equations (9) and (7) and putting k for i in equation (7) we have:

- WD2 +A,-DT,'= WD2,,DT +S Using equation (13):

In this equation we substitute WD2 WD2 giving the following value for the diameter difference:

It is also however possible to choose different values for the nominal diameters.

If normal values are substituted in the equations, we have for example in the case of an eight or l0-stand rolling mill, diameter differences of less than mm. Under these conditions the peripheral velocities of the rollers at identical rotational speeds can differ by more than 3 percent. Since differences of this order in the peripheral velocities can under certain conditions have an unfavorable effect on the performance of the rolling mill, it may be desirable to compensate for the differences in peripheral velocity by altering the gear ratios in the drives for the rollers.

The same is true for rolling mills, in which, within a row, individual groups of stands or individual stands have different idea] diameters. The rollers then in the first place pass according to the above-described method through the stand group on the output end which has constant ideal diameters, and are then put in the place of the largest roller in the last stand of the preceding group, through which they can then pass three times. If the group consists only of a single stand, the rollers move through all of the places in this stand, before they are taken to the next stand.

The invention can of course also advantageously be applied to rolling mills having adjustable rollers.

For example, the diameter difference between two different diameter rollers in a given stand which has adjustable rollers, in analogy with the first abovedescribed method in which the rollers are first interchanged in the stand itself, can be equal to the sum of twice the adjustment path of the larger roller plus the wear and grinding losses. In this way the worn large roller, after utilizing the whole adjustment path, can in the refinished condition take the place of the smaller roller.

With suitable choice of the diameter differences the rollers may also, by analogy with the second abovedescribed method, be transferred first of all between each of the stands of a row, or through a group in the row in a specified position, before being placed in the stand at the output end in place of the smaller rollers.

The invention is useful in many kinds of rolling mills, e.g. for rolling wire, rods, profiled bars and tubes.

While I have in the foregoing specification set out certain preferred embodiments and practices of my invention, it will be understood that this invention may be otherwise embodied within the scope of the following claims.

I claim:

1. In a rolling mill having at least one stand and at least two rollers journaled therein to define a sizing gap, the improvement comprising at least two rollers of different diameters in said stand, said different diameters being selected so that the larger of said two different diameter rollers, after suffering a predetermined loss due to wear, and the consequential further loss on refinishing, can be used in place of the worn smaller roller.

2. In a rolling mill having at least one stand and at least two rollers journalled therein to define a sizing gap, the improvement comprising at least two rollers of different diameters in said stand so that the larger of said two different diameter rollers, after suffering a predetermined loss due to wear, and the consequential further loss on refinishing, can be used in place of the worn smaller roller and wherein the diameter difference between said two different diameter unwo'rn rollers is at least equal to the sum of the permissible loss due to wear and the grinding loss on refinishing.

3. A rolling mill comprising a plurality of stands arranged one after the other from an input end to an output end, at least two rollers journalled in each said stand defining a sizing gap, said two rollers in each stand having different diameters so that the larger of said two different diameter rollers, after suffering a predetermined loss due to wear, and the consequential further loss on refinishing, can be used in place of the worn smaller roller, and in which the diameter difference between said two different diameter unworn rollers of the stand at said output end is at least equal to the sum of the diameter difference between the larger of said two rollers of the said stand at said output end and the corresponding larger of the different diameter rollers of the stands at said input end, the permissible wear of the said larger roller in the stand at said input end, and the grinding loss on refinishing thereof.

4. A rolling mill according to claim 3 in which each of said stands has three rollers journalled therein, all three rollers of each stand having different diameters.

5. In a rolling mill having at least one rolling mill stand and at least three rollers journalled therein, the improvement comprising at least three rollers, all of different diameters, journalled in said stand to define a sizing gap, said different diameters being selected so that the larger of said three different diameter rollers, after suffering a predetermined loss due to wear and the consequential further loss on refinishing, can be used in place of the intermediate diameter roller ofthe three different diameter rollers and the intermediate diameter roller after suffering a predetermined loss due to wear, and the consequential further loss on refinishing, can be used in place of the worn smallest roller of the three different diameter rollers.

6. A rolling mill stand according to claim 5 in which the difference in diameter between the smallest and the middle-sized of said three rollers is substantially equal to the diameter difference between the middle-sized and the largest of said three rollers.

7. A rolling mill stand according to claim 6 in which the axes of said three rollers define an equilateral triangle.

8. A rolling mill stand according to claim 7 in which one of said roller axes is substantially horizontal.

9. A rolling mill stand according to claim 5 including means for inverting said stand about a stand axis coincident with the axis of said sizing gap.

10. In a rolling mill having at least one stand and at least two rollers journalled therein to define a sizing gap, the improvement comprising at least two rollers of different diameters in said stand so that the larger of said two different diameter rollers, after suffering a predetermined loss due to wear, and the consequential further loss on refinishing, can be used in place of the worn smaller roller, and in which said rollers are journalled non-adjustably in said stand.

11. A method of rolling comprising the steps of:

lpassing a metal strand through a rolling mill having at least one stand with at least two rollers journalled therein of different diameters until the rollers are worn to a predetermined extent, refinishing the larger of said rollers to'replace the smaller roller, and 3. inserting a new roller of the original diameter of said larger roller in place of the refinished larger roller and continuing the rolling operation.

Claims

2. In a rolling mill having at least one stand and at least two rollers journalled therein to define a sizing gap, the improvement comprising at least two rollers of different diameters in said stand so that the larger of said two different diameter rollers, after suffering a predetermined loss due to wear, and the consequential further loss on refinishing, can be used in place of the worn smaller roller and wherein the diameter difference between said two different diameter unworn rollers is at least equal to the sum of the permissible loss due to wear and the grinding loss on refinishing.

2. refinishing the larger of said rollers to replace the smaller roller, and

3. inserting a new roller of the original diameter of said larger roller in place of the refinished larger roller and continuing the rolling operation.

5. In a rolling mill having at least one rolling mill stand and at least three rollers journalled therein, the improvement comprising at least three rollers, all of different diameters, journalled in said stand to define a sizing gap, said different diameters being selected so that the larger of said three different diameter rollers, after suffering a predetermined loss due to wear and the consequential further loss on refinishing, can be used in place of the intermediate diameter roller of the three different diameter rollers and the intermediate diameter roller after suffering a predetermined loss due to wear, and the consequential further loss on refinishing, can be used in place of the worn smallest roller of the three different diameter rollers.

11. A method of rolling comprising the steps of: