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(11) | EP 0 317 841 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method of rolling bar sections, such as beams |
| (57) A method of rolling bar sections, such as beams or girders, in a rolling mill including
a reversing roughing or blooming stand and downstream universal stands, universal
stand groups or two-high stands. Initially, the bar sections are pre-rolled in n-passes
into beam-blank sections in the reversing blooming stand. Subsequently, the pre-rolled
bar sections are cropped at one or both ends. The cropped ends of the bar sections
are then introduced into the universal stand, the universal stand group, or the two-high
stands located downstream where they are finish-rolled. Cropping of one or both ends
of the bar sections takes place after n-1 or less passes in the reversing blooming
stand followed by additional passes in the same reversing blooming stand until the
n-passes have been completed. |
BACKGROUND OF THE INVENTION
[0001] The present invention is directed to a method of rolling bar sections, particularly beams or girders, in a rolling mill including reversing roughing or blooming stands and downstream universal mill stands, universal stand groups or two-high stands. Initially, the bar sections are pre-rolled for n-passes in reversing blooming stands to form beam-blank sections. The beam-blank sections are cropped on one or both ends and, subsequently, are finished rolled by inserting the cropped bar end into the finishing groove of the downstream stands.
[0002] Cropping the ends of bar section is especially necessary when rolling girders, because a more or less long web tongue forms at the end when rolling the bar section in the blooming stand. The end must be removed prior to introducing the bar section into the universal stands. The ends to be cropped have lengths of 500mm or more, depending on the size of the bar section. If the cropping operation is performed with a circular saw, the introduction of the bar section ends into the universal stands presents no particular difficulties. The sawing process, however, requires a comparatively long time, and the wear developed is so great that a saw-blade change must be performed after a short period of time, for instance, eight hours. Since an extraordinary amount of noise is generated during the sawing operation, special noise protection means have to be installed.
[0003] If the bar ends are cropped by shears, there is the disadvantage that the bar ends are bent upwardly or downwardly from the rolling direction out of the section mid-axis. As a result, the lower edge of the cropped bar section strikes against the circumferential roll surfaces as it is conveyed on the rolling table and moves toward the entry groove of the downstream universal stand or two-high stand with a skipping and chattering action. The introduction of the bent end into the groove in the universal stand provides considerable difficulty, particularly because of the comparatively narrow pre-set guide passages.
SUMMARY OF THE INVENTION
[0004] Therefore, the primary object of the present invention is to modify the known method so that the difficulties and disadvantages mentioned above are avoided. In accordance with the present invention, the improvement involves that after performing n -1 or less passes through the reversing blooming stands, the bar sections are cropped at one or both ends and subsequently are rolled in the same reversing blooming stands until n-passes are completed.
[0005] In carrying out the method embodying the present invention, the ends of the bars shaped in the manner described above by the cropping shear cut are rolled in the same reversing blooming stands after the cropping cut, whereby the bends are removed and the cropped end is returned to its original position with respect to the central axis of the bar. The increased expenditure of time resulting from the introduction of the bar ends into the shears, which increases the time period required for performing the total number of passes, does not have a disadvantageous effect, because, under any circumstances, more time is required for the finish rolling of the bar in the downstream universal stands, universal stand groups or two-high stand than for the pre-rolling of the bar into the beam-blank section.
[0006] As compared to the bar ends cropped by saw, the method of the present invention involves an additional significant advantage. While the bar, with its bar ends cropped in accordance with the present invention, every now and then falls behind when entering the downstream universal stand, because the vertical rolls engage the flanges of the bar and the rolls are not driven, however, the driven horizontal rolls do not engage the flanges. When utilizing the method of the invention, a short tongue portion of the web projected from the bar section surface in the course of the passes through the reversing blooming stand following the cropping cut, are first engaged by the driven horizontal rollers as the bar section moves into the universal stand, thereby aiding the passage of the bar section into the roll gap of the universal stand without any difficulty.
[0007] The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
DESCRIPTION OF THE DRAWINGS
[0008] In the drawings:
Figure 1 is a diagrammatic plan view of a rolling mill used in carrying out the method of the present invention; and
Figure 2 is a plan view and front end view of the bar section being rolled in the rolling mill of Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The bar or rod to be rolled, not shown, is introduced into the reversing blooming stand l in the direction of the arrow S in Figure 1. After completing n -2 passes, the bar is moved with its front end on the rolling table 2 into the shears 3. The front end is cropped by the shears and the bar is returned into the reversing blooming stand opposite to the direction of he arrow S and is rolled for two additional passes to form the desired beam-blank section. As a result of the shearing action, the bending deflection at the end T′ of the bar T from the central plan M of the bar is indicated in dashed lines in Figure 2. The deflected end, developed during the cropping step, is for practical purposes eliminated and the end T′ of the bar is in the form shown in solid lines in Figure 2.
[0010] The bar can be prematurely cropped in the appropriate manner at its rear end while passing through the shears 3 and can be rolled in the manner indicated above. The insertion of the cropped rear end of the bar T into the reversing blooming stand 1 does not present any difficulties, because the rolls of the stand 1 can be moved away from one another to facilitate the insertion in a manner differently from for the universal stands 5, 6 in Figure 1, since at the reversing blooming stand there is no rolling equipment which has to be adjusted to a narrow dimension.
[0011] After completing the rolling operation in the reversing blooming stand 1, as described above, the bar is fed by the transverse conveyor 8 into the rolling line of the universal rolling stand group made up of the universal stands 5 and 6 with a two-high edging stand 7 located between them. The drives 9, 10 and 11 are connected, respectively, to the universal stand 5, the two-high edging stand 7, and the universal stand 6. As the bar passes through the universal rolling stand group, it is finish rolled in the usual manner.
A method of rolling bar sections, such as girders, in a rolling mill including a reversing
blooming stand and downstream therefrom at least one of universal stands, universal
stand groups and two-high stands, comprising the steps of prerolling the bar section
in the reversing blooming stand for n-passes for forming a beam-blank section, and
cropping the bar section pre-rolled in the reversing blooming stand at least at one
end thereof and subsequently finish rolling the cropped bar section by introducing
the cropped end into finishing grooves of the at least one of the universal stand,
the universal stand group, and the two-high stands, wherein the improvement comprises
the step of cropping the at least one end of the bar section pre-rolled in the reversing
blooming stand at least after n -1 or less passes and continuing rolling the cropped
bar section in the reversing blooming stand until completing the n-passes.