US3513679A

US3513679A - Method and apparatus for after-sizing hot-rolled bar stock

Info

Publication number: US3513679A
Application number: US661613A
Authority: US
Inventors: Walter Dechene; Kurt Rothert
Original assignee: Stahlwerke Suedwestfalen AG
Current assignee: Krupp Stahl AG
Priority date: 1966-08-24
Filing date: 1967-08-18
Publication date: 1970-05-26
Anticipated expiration: 1987-05-26
Also published as: GB1192462A; BE702914A; LU54349A1; CH454778A; FR1549270A; NL6711525A; DE1527725A1

Description

May 26, 1970 w, DECHENE ET AL 3,513,679

METHOD AND APPARATUS FOR AFTERSIZING HOT-ROLLED BAR STOCK i Filed Aug. 18, 1967 FIG. 7 FIG. 2

Inventom WA L'FER Z EcHF/VE KURT 2011-1591- ATTO'RIVEVS 3,513,679 METHOD AND APPARATUS FOR AFTER-SIZING HOT-ROLLED BAR STOCK Walter Dechne, Hagen, and Kurt Rothert, Duesseldorf, Germany, assignors to Stahlwerke Sudwestfalen A.G., Huttental-Geisweid, Germany, a corporation of Germany Filed Aug. 18, 1967, Ser. No. 661,613 Int. Cl. BZlb 15/00 US. Cl. 72225 5 Claims ABSTRACT OF THE DISCLOSURE The controlling of variations in the cross-sectional dimensions of rolled bar stock from a hot-rolling mill by directly ramming the hot-rolled stock emerging from the last stand of the mill through a plurality of opposed post rolls freely driven by the ramming of the bar stock therethrough and so spaced apart to correct cross-sectional variations in the stock without substantial overall change in the cross-sectional dimensions thereof. An apparatus comprising the combination of such a post-rolling stand having freely driven rolls with the hot-rolling mill.

This invention relates to a method and apparatus for post-rolling hot-rolled bar stock.

Bar stock, as for example lengths of steel bar having rectangular, polygonal, circular, or oval cross-sectional shape is commonly fabricated in a hot-rolling mill. The uniformity of the cross-sectional shape and dimensions of the stock produced in this manner cannot always be controlled within the tolerances desired. Thus, for example, the deviations in the side dimensions, side-to-side thicknesses and diameters over a rolled length, and the differences between the maximum and minimum profile dimensions, as measured in a cross-sectional plane, may be so great that the stock is not suitable for the purpose intended and must be considered as a reject. Often the dimensions and profile tolerances required for specific purposes or customers which are some times narrower than those of such standards as DIN 59,130, are not met by a considerable portion of the material produced. The deviations in the cross-sectional shape and dimensions of the stock are often particularly pronounced when the stock is hot-rolled on two-high mills due, for example, to olf-center entry of the stock into the finishing pass of the mill, wandering of the stock as it passes therethrough, off-centering passage, and the like. This variation in the cross-sectional shape and dimension of the stock and the rejections necessitated thereby considerably increase the cost of manufacture of hot-rolled bar stock.

One object of this invention is a method for controlling variations in the cross-sectional shape and dimensions of hot-rolled bar stock.

A further object of this invention is a method and apparatus for improving the dimensional accuracy, the geometric shape and the profile of the hot-rolled stock emerging from a rolling mill.

A still further object of this invention is to overcome the piror art difficulties in maintaining the accuracy of the cross-sectional shape and dimensions of bar stock produced in a hot-rolling mill.

These and still further objects will become apparent from the description read in conjunction with the draw ings wherein:

FIG. 1 is a end view showing a rod emerging from the last finishing stand of a two-high hot-rolling mill through the after-sizing device of this invention, and

FIG. 2 is a longitudinal section'of the finishing stand and after-sizing device shown in FIG. 1.

United States Patent Q In accordance with the invention variations in the cross-sectional shape and dimensions of hot-rolled bar stock are controlled by directly ramming the hot-rolled stock emerging from the last stand of the hot-rolling mill, such as a two-high mill, through opposed post-rolls which are freely driven by the ramming of the bar stock therethrough and spaced apart at a distance to correct crosssectional variations in the stock without substantial overall change in the cross-sectional dimensions thereof.

While the improved method and apparatus in accordance with the invention may be used in connection with any hot-rolling mill for hot-rolling bar stock, the same is preferably used in combination with the conventional twohigh mills.

The bar emerging from the last stand of the mill, as for example, the finishing stand of a two-high mill, is rammed while still at its rolling temperature by the action of this last stand through the opposed post-rolls which are nondriven i.e. idler rolls and which are freely driven by the ramming action of the bar stock therethrough.

Preferably a plurality, and most preferably at least four of the freely driven post-rolls are provided which surround the periphery of the stock being passed therethrough. The axes of the rolls preferably extend in a com mon plane which is normal to the feed or conveying direction of the stock.

As mentioned, the rolls should be so spaced apart i.e. provided with a gap therebetween, which will correct variations in the cross-sectional shape and dimensions without substantial overall change in the cross-sectional dimensions of the stock. The post-rolls will thus only remedy dimension and cross-sectional deviations from the specifications in the bar stock emerging from the rolling mill without any substantial change and/or reduction in the cross-section and thus the deformation and ramming forces are only slight.

The diameter of the rolls of the post-rolling system in accordance with the invention may be relatively small since they are not powered, i.e. driven at least while the stock is being passed therethrough, and consequently they may be positioned relatively closely adjacent the rolls of the final stand of the rolling mill even when a plurality of these post-rolls is provided. These post-rolls may thus have a diameter which is only a fraction of the diameter of the rolls of the final stand of the rolling mill, but the diameter should not be so small as to substantially impair the ramming action. With a positioning of the postrolling rolls in accordance with the invention closely adjacent the rolls of the final stand of the mill, only a short length of the stock emerges from the mill before entry into these final rolls, avoiding any likelihood of fluttering or deflection of the stock.

Referring to the embodiment shown in the drawing, 1 represents the final finishing stand on a conventional twohigh hot-rolling mill for bar stock. This final finishing stand 1 is provided with the conventional rolls 2. In accordance with the invention a post-rolling apparatus is mounted on the roll beam 3 of the finishing stand 1. This post-rolling apparatus consists of four rolls 5 which are of substantially smaller diameter than the rolls 2 and which are freely rotatable, i.e. are not driven. The rolls 5 are so positioned with respect to the rolls 2 of the stand 1 of the mill that the hot rolled stock 8 emerging from the rolls 2 while still at the rolling temperature will be directly rammed through the gap of the rolls 5, the rotation of the rolls 5 being caused by this ramming action. To ensure an accurate guiding the guide means 6 are provided and a further guide 7 is provided for the finished roll stock leaving the stand. The gap between the rolls 5 is so dimensioned that the same will correct cross-sectional variations in the dimension and shape of the stock without any substantial overall change therein, such as an overall rolling out of the stock.

While the rolls 5 of the post-rolling apparatus may be adjustable, either individually or together, it has been found preferable that the entire post-rolling arrangement be made as a complete unit removable and exchangeable as such. With such an arrangement, among other things, it is possible to prepare a set of rolls with great precision and to provide an exchangeable unit of equal precision when it is necessary to roll a bar stock with a different size or profile. In the same manner, if it is necessary to repair the unit, this can be done with a restoration of the same to its precision adjustment.

It is desirable to make the entire unit adjustable with respect to the rolls 2 so as to obtain a very accurate alignment. Thus, for example, the unit may be made so that the same can be adjusted upwardly and downwardly with the roll beam and may be laterally displaceable.

In operation the post-rolling apparatus is simply adjusted so that the guide 6 is in alignment and receives the stock 8 as it emerges from the rolls 2. As the roll stock emerges from the rolls 2, it will be rammed through the rolls 5, this ramming action driving the rolls and remedying dimension and cross-sectional shape deviations in the bar stock so that the emerging bar stock falls within the dimensions an dprofile tolerances permitted.

The method and apparatus in accordance with the invention shows many advantages. The ramming of the bar stock through the post-roll arrangement has advantages over pulling it through a drawing die or driving it through the powered rolls of a further finishing stand. The ramming force and thus the tension and deformation conditions in the pass are always the same and an output that is uniform with respect to dimensions is assured without the use of special regulating devices even in the case of incorrect rolling speeds.

Since in the case of the ramming through the nondriven rolls in accordance with the invention, the speed of the rolls automatically adapts to the feed speed of the bar, none of the regulating systems are necessary which are required in the case of drawing systems or driven finishing rolls for adapting the speed of the bar during the pass to the speed at which the bar enters.

Furthermore, with the use of the post-rolling arrangement in accordance with the invention, in which the rolls are not driven, there is no possibility of damage to the bar surface by drawing force as may occur in drawing systems, and no possibility of damage by slippage of the rolls on the bar as may occur when using driven finished rolls. These conventional causes of trouble which can result in unacceptable dimensional or profile deviations are thus eliminated in accordance with the invention.

With the use of a plurality of rolls in accordance with the invention, the rolls will act on the material simultaneously in a single plane and uniformly over its entire periphery so that the material will scarcely spread out and will run lengthwise more than it would using fewer rolls. This is especially beneficial in the case of closed finishing passes consisting of a plurality of rolls, as for example, rolls distributed around the periphery of the bar stock with their axes extending in a common plane normal to the path of travel of the stock.

Another advantage obtained with the use of such a plurality of rolls is that the speed of the roll surface coming in contact with the stock is the same over the entire width of the roll, as for example, in the case of bar stock having a polygonal cross-sectional shape. This is also true for all practical purposes in the case of stock having a round cross-section. In the case of stock having a round cross-section a further advantage is achieved in that the forming action and thus forming efi'ects of the stock are distributed uniformly about the circumference according to the number of rolls used and are not produced in only one direction as in the case where only two opposed rolls are used.

While the invention has been described with reference to the specific embodiments shown, various changes and modifications which fall within the spirit of the invention will become apparent to the skilled artisan. The invention therefore is only intended to be limited by the appended claims or their equivalent wherein we have endeavored to claim all inherent novelty.

The ratio diameter of the rolls in the last stand to that of the post-rolls is not critical, only the difference between the hot rolled cross section and the corrected finished cross-sectional shape and consequently the pressure of rolling determined thereby are the base for the minimum diameter of the rolls and the roll bearings in the post-roll stand.

EXAMPLE Hot rolling stock having a diameter of 23 mm. with an off-size of $0.3 mm. when emerging from the last stand of the hot rolling mill, was rammed immediately through the post rolls. The temperature of the stock was 800-950 C. and the rolling speed 6 meters per second. The distance between the center of the rolls in the last stand of the hot rolling mill and the center of the post-rolls was 600 mm. (in general 600 to 700 mm.). After the postrolls the diameter of the stock was 23 mm.:0.1 mm.

We claim:

1. In the hot-rolling of bar stock in arolling mill, the method of after-sizing the just rolled bar material which comprises directly ramming the hot rolled stock emerging from the last stand of the rod mill through opposed post-rolls, all positioned so that their axes extend through a common plane substantially normal to the direction of travel of the stock, freely driven by the ramming of the bar stock therethrough, substantially surrounding the periphery of the stock and spaced apart at a distance to correct cross-sectional variations in the stock without substantial overall change in the cross-sectional dimension thereof.

2. Improvement according to claim 1 in which said last stand is a final two-high finishing stand.

3. In combination with a hot-rolling mill for hot-rolling bar stock; a after-sizing apparatus comprising a stand of at least four freely rotatable rolls positioned directly behind the rolls of the last stand of the mill aligned therewith for the direct ramming of stock emerging from said last stand therethrough, the rolls of said post-rolling apparatus having their axes in a common plane extending substantially normal to the feed direction of the mill and being spaced apart at a distance to correct cross-sectional variations in the stock being passed therethrough without substantial overall change in the cross-sectional dimension thereof.

4. Combination according to claim 3 in which said post-rolling apparatus is removable and replaceable as a unit.

5. Combination according to claim 3 in which the rolls of said post-rolling apparatus are of substantially smaller diameter than the diameter of the rolls of the last stand of said mill.

References Cited UNITED STATES PATENTS 328,591 10/1885 Lenox 72-224 1,808,752 6/1931 Banner 72-225 LOWELL A. LARSON, Primary Examiner US. Cl. X.R. 72-234