Metal deforming – With use of control means energized in response to activator... – Metal deforming by use of roller or roller-like tool element
Patent
1982-03-15
1985-03-26
Husar, Francis S.
Metal deforming
With use of control means energized in response to activator...
Metal deforming by use of roller or roller-like tool element
72 13, 72248, 72366, B21B 3712
Patent
active
045065314
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a method for automatic control of the screwing-down of reeling rolls in a reeling mill. More particularly, the invention relates to a method for automatically controlling the screwing-down of rolls in the process of reeling in the production of seamless steel pipes by the Mannesman plug mill method.
BACKGROUND OF THE INVENTION
The reeling mill (reeler) is layed between the plug mill and sizing mill in the process for manufacture of seamless steel pipes. In this mill, the pipe is "reeled" by reducing its wall thickness for various purposes among which are the correction of the thickness deviation that has developed in the previous rolling mills (i.e. piercer, elongator and plug mill), elimination of the flaws developed by abrasion with the plug in the plug mill rolling, and ensuring a suitable amount of pipe expansion for the sizing mill in the subsequent step. It is the most important feature of the reeling mill that the greater part of the amount of reduction in wall thickness changes into the expansion of the outside diameter of the pipe, so if a variation occurs in the amount of reduction of the wall thickness during reeling, the outside diameter of the reeled pipe also changes in its longitudinal direction and the following disadvantages result: if the amount of reduction in wall thickness during reeling is small, the degree of increase in the outside diameter is small and the desired outside diameter of the pipe cannot be achieved, and vice versa. If the outside diameter of the reeled pipe is smaller than a predetermined value, not all parts of the pipe is rolled in the subsequent sizing mill, which has a very adverse effect on the outside diameter of the final product. If the outside diameter of the reeled pipe is larger than the predetermined value, a flaw such as one due to the roll edges develops during rolling in the sizing mill, which is also detrimental to the quality of the final product. So, the operation in the reeling mill has great effect on the accuracy of the dimensions of the final product, hence its yield, and it is mandatory in the reeling mill to roll the pipe to have the desired outside diameter.
Several methods are known for controlling the operation of reeling mills. One of them is described in Japanese Patent Application (OPI) No. 37568/78 (the symbol OPI as used herein means an unexamined published Japanese Patent Application), and to provide a pipe of constant outside diameter on the leaving side of the mill, the electric power for rolling is kept constant for each lot and for the entire length of each pipe to be rolled. Another method is described in Japanese Patent Application (OPI) No. 86663/78, and to provide a pipe of constant wall thickness on the leaving side, the pattern of electrical power outputs is determined for each pipe on the basis of information of the cross section and temperature of the pipe on the entry side so that the cross section of the pipe on the leaving side is kept constant for each lot and for the entire length of each pipe, and the electric power for rolling is changed after this pattern.
The method of Japanese Patent Application (OPI) No. 37568/78 disregards the change in the temperature of each pipe to be rolled as well as the change in the temperature in the longitudinal direction of the pipe. So, if the reeling operation is performed with the electric power held constant, the reduction in the wall thickness at the low temperature portion of pipe where occurs the larger resistance to deformation is so small that the pipe on the leaving side cannot be expanded to the predetermined value of outside diameter. What is more, the outside diameter of the pipe on the entry side of the mill is also varied in longitudinal direction by the rolling force and by the set of roll gap in the plug mill rolling, so this adds to the variation in the outside diameter of the pipe that is leaving the reeling mill under the control of constant electric power.
The method of Japanese Patent Application (OPI) No. 86663/
REFERENCES:
patent: 4087859 (1978-02-01), Anbe
patent: 4365496 (1982-12-01), Shiozaki
Napadajlo, I. T., East German Patent 134,305, English Translation.
Yu, B., Lots, Russian Inventor's Certificate 395,138, English Translation.
Funyu Yutaka
Kanno Toyoji
Masuda Toshikazu
Sakurada Kazuyuki
Togashi Fusao
Husar Francis S.
Rosenberg Charles
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