Metal deforming – By use of roller or roller-like tool-element – With cleaning or conditioning of tool – or lubrication of...
Reexamination Certificate
2002-03-26
2004-03-23
Tolan, Ed (Department: 3725)
Metal deforming
By use of roller or roller-like tool-element
With cleaning or conditioning of tool, or lubrication of...
C072S007600, C072S011100, C072S011600, C072S365200, C451S005000, C451S049000
Reexamination Certificate
active
06708547
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plate rolling mill. More particularly, the invention relates to a rolling mill including a grinder installed in a rolling stand to grind the surface of each of working rolls, and a rolling method, the rolling mill being suited for rolling a plate requiring good quality, especially a metal plate, and the working rolls being movable in axial directions.
2. Description of the Related Art
In the field of plate rolling, there has been a demand for a plate quality improvement. The profile of a working roll surface has been improved in an effort to increase the accuracy of plate dimensions, and various types of rolling mills have been developed. For example, Conventional Technology 1 (JP-B-51-7635) discloses a 4-high rolling mill having working rolls and reinforcing rolls provided in its rolling stand. The working rolls are movable in axial directions, and working rolls bender is installed. According to the Conventional Technology 1, the controllability of plate thickness distribution can be improved by changing an axial position of each of the working rolls, and by using the working roll bender in combination. In addition, according to the Conventional Technology 1, by changing the axial position of the working roll, the surface region of the working roll brought into contact with a plate is changed in the axial direction, the wear of the working roll surface being uniformed, and local uneven wear is minimized. Thus, there is obtained an advantage in manufacturing cost because of a prolonged time of using the working roll. Moreover, according to the Conventional Technology 1, a thermal crown and a wear crown occurring on the working roll surface are cancelled each other, and a coffin type limitation hitherto occurring regarding the plate width order of a rolling schedule is relaxed. Thus, it is possible to make a rolling schedule more freely. For the foregoing reasons, the Conventional Technology 1 has been widely accepted in a plate manufacturing field, and still used.
Another Conventional Technology 2 (JP-B-2708351) discloses a rolling mill including an on-line roll grinder. According to the Conventional Technology 2, a grindstone brought into contact with a working roll is formed to have a highly elastic thin disk-like structure, so that the effect of whirling caused by the vibration of the working roll or the eccentricity of a shaft center line is absorbed for good grinding, whereby even in an actual rolling mill, stable grinding is performed. In addition, according to the Conventional Technology 2, there is provided such a function as to detect a profile of the working roll while pressure-contacting the grindstone onto the surface of the working roll with a constant force so that the movement of the grindstone may be detected to thereby obtain irregularity on the working roll surface. Thus, it is possible to grind in an on-line manner each of the working rolls by detecting the profile of the working roll. In the Conventional Technology 2, a period of time for using the working roll can be further prolonged by performing grinding during the rolling. As in the case of the Conventional Technology 1, it becomes possible to obtain a considerably free rolling schedule, and the rolling mill has been used in the plate manufacturing field.
Still another Conventional Technology 3 (JP-A-61-296910) discloses a method of making a wide wear profile by using both of roll-shifting and grinding a roll surface region of each of the working rolls which region is located outside of a plate to be rolled (, which grinding is referred to as “plate-outside-grinding” hereinafter). According to the Conventional Technology 3, as in the case of the Conventional Technology 1, since the changing of the axial position of the working roll makes the uniform wear on the working roll surface and minimize local uneven wear, there is such an advantage to make the manufacturing cost low because of a prolonged period of time regarding the use of the working rolls. Moreover, a working roll region located outside a plate width is ground by an amount equal to the amount of working roll center wear so that the abrupt change of the wear profile may occur outside of the plate width. Thus, any contact is prevented from occurring between the plate to be rolled and the working roll region having a considerably changed wear profile. In this way, since the transfer of the abruptly changed wear profile portion of the working roll to the plate is prevented, the influence of the wear profile of the working roll surface on the plate to be rolled is deemed to become small.
SUMMARY OF THE INVENTION
However, in any of the foregoing Conventional Technologies 1 to 3, no specific means has been disclosed from the viewpoint of keeping a good profile of the working roll surface over the whole of rolling cycles in order to prevent the defects of a plate surface from occurring which defects are considered to be the problem of plate quality. As the result of the researches of the inventors of the invention, the inventors discovered that when rolling was performed by any one of the Conventional Technologies 1 to 3, deterioration of plate quality occurred with the progress of rolling, making it difficult to perform many times of plate-rolling. This problem will now be explained while referring to the drawings.
FIGS. 2A and 2B
illustrate working roll surface profiles and thermal expansion and wear profiles which constitute the working roll surface profile, in a case where plates equal in width are subjected to hot rolling by using a rolling mill having no working roll shifting. The working roll surface profiles shown in
FIGS. 2A and 2B
indicate change per roll radius. In the case of usual rolling of a plate, a temperature of plate end portions are lower than that of a plate center, and plate surface scales and hardness are different between the plate center and the plate end portions. The wear amount of a working roll region brought into contact with each of the plate end portions is larger than that of another working roll region brought into contact with the plate center (larger by 1.05 to 1.25 times than center wear). In other words, working roll wear takes a peak shape at the working roll end region. The thermal expansion profile of the working roll surface becomes a constant, gently-sloping profile saturated after the rolling of 40 or more pieces of rolled plates. Accordingly, as shown, the working roll surface profile constituted by the wear and thermal expansion profiles receives the great influence of the shape of the end portion peak wear, and is suddenly changed near the plate end portions. When such a suddenly changed working roll region is brought into contact with and transferred to the plate, flaws or defects occur on the plate surface. Thus, the contact of this region with the plate must be avoided. For this reason, there has been used such a so-called “coffin schedule” of rolling as the rolling is performed by a process having the steps of: sequentially changing plate widths so that the width of each of the plates to be rolled is increased sequentially till such a period of time of small wear as to correspond to about 10 to 20 pieces of rolled plates to thereby make the thermal expansion profile dispersed; and then changing the plate width so that the width of each of the plates to be rolled becomes narrow sequentially to prevent the working roll end regions having the peaks of the wear profile from contacting with the plates.
FIGS. 3A and 3B
illustrate working roll surface profiles and thermal expansion and wear profiles which constitute each of the working roll surface profiles, in a case where the working roll shifting of the Conventional Technology 1 is performed and plates equal in width are subjected to hot rolling. Each of the working roll surface profiles shown in the drawings indicates a change per roll radius. In the case of the profiles, the working roll is moved 10 mm axially every two pieces of rolled plates, and a maximum
Kaga Shinichi
Kamoshita Takashi
Narita Kenjiro
Nihei Mitsuo
Saito Takehiko
Crowell & Moring LLP
Tolan Ed
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