Electric heating – Inductive heating – Metal working
Patent
1995-12-29
1999-09-14
Leung, Philip H.
Electric heating
Inductive heating
Metal working
219617, 219670, 219671, 72202, 228158, 2282352, H05B 610, B21B 4500
Patent
active
059519037
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a metal piece joining method useful for continuous hot rolling, by which a preceding metal piece and a succeeding metal piece are heated and joined with each other at their ends to continuously carry out hot finishing rolling, and also to a joining apparatus which is directly used for carrying out the method.
BACKGROUND ART
Conventionally, in a hot rolling line for metal pieces (for example, steel, aluminum or copper), since the metal pieces have been extracted one by one from a heating furnace, there occurred various problems particularly in the finishing rolling process, as follows.
1) A biting failure at the front end of a metal piece.
2) A defective stamping at the rear end of a metal piece (a phenomenon that a corner at the rear end of a thin metal piece is bent).
3) A traveling problem of the front end of a metal piece occurring on a run-out table.
4) A defective dimension at the front and rear ends of metal pieces.
As means for solving the above-mentioned problems, there has been proposed a so-called endless rolling in which metal pieces to be rolled are joined at their rear and front ends before the finishing rolling, and continuously supplied to the fomoshinh rolling line to carry out the hot rolling.
As prior documents in this regard, a number of propositions can be found, for example, in Japanese Patent Laid-open Publication Nos. 60-244401, 61-144203, 62-234679, 4-89109, 4-89115 and 4-89110.
When carrying out the endless rolling of metal pieces, the following process has been generally performed. That is, firstly, on the entry side of a rolling equipment, a small gap is provided between a preceding metal piece and a succeeding metal piece at the ends thereof and these metal pieces are opposed substantially in parallel with each other. Further, a portion in the vicinity of the end of each metal piece is clamped and supported by clamps, and the end regions on the opposed faces of the metal pieces, which are portions to be joined, are heated by a heating means. The both metal pieces are then pressed against each other to be joined. In the joining method for metal pieces using such a process, various disadvantages which will be described below have still remained and an improvement in this regard has been desired.
1) In the joining form of this type, there is provided an inductor having a pair of magnetic poles vertically sandwiching the portions to be joined in the metal pieces. With the inductor, an alternating magnetic field running through the metal pieces in the thickness direction thereof is applied, and a surface layer at the portions to be joined, or on the opposed surfaces in particular is intensively heated by the induced current generated at this time. The induced current is, however, hard to flow at corners of the front and rear ends of the metal pieces, and the heating temperature at the portions to be joined thus gradually lowers toward the wide ends. Thus, there is such a disadvantage that the portions to be joined cannot be joined over the full width thereof when pressing the metal pieces against each other.
In this case, the wide ends having a low temperature function as a resistance when pressing the metal pieces against each other, if the temperature at the portions to be joined does not reach a target heating temperature, so that a pressing apparatus having a capacity above a necessary level must be installed. Also, since a sufficient joining strength cannot be secured, the joined portions are gradually separated as the rolling proceeds and the metal plate are ruptured so that a serious accident may occur. In order to solve such a problem, it is most effective to continue the heating until the temperature at the corners of the steel pieces reaches a target value. However, since the temperature in regions other than the corners (i.e., central regions in the plate width direction) reaches a melting temperature and the metal pieces are melted down in these regions, excellent joined portions cannot be obtained. In addition, such a
REFERENCES:
patent: 4300031 (1981-11-01), Reboux et al.
patent: 4795872 (1989-01-01), Hagisawa et al.
patent: 5510600 (1996-04-01), Jackson
Patent Abstracts of Japan, vol. 095, No. 003, Apr. 28, 1995 & JP 06 339705 A (Kawasaki Steel Corp.; Others: 01), Dec. 13, 1994.
Patent Abstracts of Japan, vol. 017, No. 379 (M-1447), Jul. 16, 1993 & JP 05 069024 A (Ishikawajima Harima Heavy Ind. Co. Ltd.), Mar. 23, 1993.
Amagasa Toshiaki
Amanuma Shuji
Eguchi Toshinobu
Hashimoto Michio
Hayashi Kanji
Kawasaki Steel Corporation et al.
Leung Philip H.
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