| Title of Invention | A METHOD FOR CONTINUOUS ANNEALING AND HOT DIP PLATING |
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| Abstract | A dual-purpose installation for continuous annealing and hot dip plating wherein at least a continuous annealing furnace, a coating pot, a coating device and a water quenching device are arranged in the form of a processing line along the traveling direction of a steel sheet, characterized by having a baypass device enabling a steel sheet to be led from the continuous annealing furnace directly to the water quenching device without being exposed to the outside atmosphere and the interior of the bypass device is kept filled with an non-oxidizing atmosphere composed of H2: 5 — 10%, and N2: 95 — 90%; the coating pot and the coating device are installed beneath the bypass device; and means for transporting the coating device and/or equipment in the coating pot during simultaneously producing annealed product by the continuous annealing installation of the dual purpose installation thereby enabling repair of the coating device and/or equipment in the coating pot during the simultaneous producing of the continuously annealed product, wherein said means for transporting the coating device and/or equipment in the coating pot is installed beneath the bypass device. |
| Full Text | The present invention relates to a method for continuous annealing and hot dip plating. BACKGROUND ART While a continuously annealed steel sheet and a hot dip plated steel sheet, especially a hot dip galvanized steel sheet, have so far been produced, in general practice, using different installations designed for the respective purposes, a dual-purpose installation for continuous annealing and hot dip plating or hot dip galvanizing to produce a continuously annealed steel' sheet as well as a hot dip plated steel sheet in.the single installation is proposed in Japanese Unexamined Patent Publication No. S55—6469 or Japanese Patent Application No. H11-5298. ' Japanese Unexamined Patent Publication No. S55-6469 discloses a dual-purpose installation used for a hot dip plating line and a continuous annealing line, wherein a steel sheet coming out from a continuous annealing furnace is cooled in the normal atmosphere without being dipped into a plating pot when producing a continuously annealed, steel sheet. However, since a steel sheet just coming out from a continuous annealing furnace has a. high temperature, there is a problem in that the surfaces of the steel sheet will become oxidized if no countermeasures are taken. An idea has' been proposed of installing a pickling apparatus for removing the oxide films on the surfaces. However, this requires additional equipment investment, the necessity of newly installing a waste liquor treatment facility and increased operational loads. Japanese Patent Application No. Hll-5298 discloses an apparatus to sufficiently lower the temperature of a steel sheet at the exit from a continuous annealing furnace so as to prevent the steel sheet from oxidizing when it comes out from the continuous annealing furnace and is exposed to the outside atmosphere. However, cooling a steel sheet to a temperature where it does not become oxidized when exposed to the normal atmosphere requires a larger cooling apparatus in the continuous annealing furnace and resultant increased equipment investment. SUMMARY OF THE INVENTION The present invention proposes measures to solve the above problems and make a dual-purpose installation for continuous annealing and hot dip plating or hot dip galvanizing to produce a steel sheet without incurring a large increase in equipment costs. The gist of the present invention to solve the above problems is as follows: (1) A dual-purpose installation for continuous annealing and hot dip plating wherein at least a continuous annealing furnace, a coating pot, a coating facility and a water quenching facility are arranged in the form of a processing line along the travelling direction of a steel sheet, characterized by having a bypass facility enabling a steel sheet to be led from the continuous annealing furnace directly to the water quenching facility without being exposed to the outside atmosphere and the interior of the bypass facility being kept filled with a non-oxidizing atmosphere. (2) A dual-purpose installation for continuous annealing and hot dip plating characterized by having an alloying furnace, a steel sheet cooling unit, or both of them proceeding to a coating pot and a coating facility and being equipped with the bypass facility according to the item (1). (3) A dual-purpose installation for continuous annealing and hot dip plating according to the item (1) or (2), enabling the coating facility and the equipment in the coating pot to be transported and repaired and the production efficiency to be improved by installing the coating pot, the coating facility and a crane beneath the bypass facility. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic illustration showing a dual-purpose installation for continuous annealing and hot dip plating to which the present invention is applied. THE MOST PREFERRED EMBODIMENTS The present invention is explained in detail hereafter based on an example. Fig. 1 is a schematic illustration of the annealing furnace portion of a dual-purpose installation for continuous annealing and hot dip plating or hot dip galvanizing to which the present invention is applied. A steel sheet 1 is annealed in a continuous annealing furnace 2. When producing a plated or galvanized product, the steel sheet 1 is fed to a coating pot 3 and plated after going through the continuous annealing furnace 2 as shown by dotted lines. Then, after the coating weight is controlled by a coating facility 4, the steel sheet is subjected to alloying treatment in an alloying furnace 5, as required, cooled by steel sheet cooling units 6, and then cooled further to near room temperature in a water quenching facility 7. The above sequence of process steps is exactly the same as the normal process sequence for producing a hot dip plated or hot dip galvanized product. When producing a continuously annealed steel sheet, the steel sheet 1 has to be cooled to near room temperature by the water quenching facility 7, without going through the coating pot 3, the coating facility 4, the alloying furnace 5 and the cooling units 6. However, if the steel sheet 1 is exposed to the outside atmosphere after going through the continuous annealing furnace 2, the surfaces of the steel sheet become oxidized. To avoid oxidization, a bypass facility 8 is installed in the present invention so that the steel sheet can travel from the continuous annealing furnace 2 directly to the water quenching facility 7 without being exposed to the outside atmosphere. Since the interior of the bypass facility 8 is kept filled with a non-oxidizing atmosphere having, for example, a composition of 5 to 10% of H2 and 95 to 90% of N2, which is the same atmosphere as that in the continuous annealing furnace, the steel sheet 1 can be transferred to the water quenching facility 7 and cooled without being oxidized. Further, by installing the coating pot 3, the coating facility 4 and a crane 9 beneath the bypass facility 8, it becomes possible to transport and repair the coating pot, the coating facility or the equipment in the coating pot during the production of a continuously annealed product, thus enhancing production efficiency. INDUSTRIAL AVAILABILITY As explained above, by applying the present invention to a dual-purpose installation for continuous annealing, hot dip plating and hot dip galvanizing, it becomes possible to eliminate a pickling facility for removing oxide films on the surfaces of a steel sheet after annealing. Further, it is also possible to transport and repair a coating pot, a coating facility and the equipment in the coating pot using a crane during the production of a continuously annealed product, and thus enhance production efficiency. We Claim: 1. A method for continuous annealing and hot dip plating comprising the steps of: - arranging at least a continuous annealing furnace (2), a coating pot (3), a coating device (4) and a water quenching device (7) in the form of a processing line along the traveling direction of a steel sheet (1), characterized by having a bypass device (8) enabling a steel sheet to be led from the continuous annealing furnace (2) directly to the water quenching device (7) without being exposed to the outside atmosphere and the interior of the bypass device (8) is kept filled with an non-oxidizing atmosphere composed of H2: 5-10%, and N2: 95-90%; - placing the coating pot (3) and the coating device (4) beneath the bypass device (8); and - transporting the coating device (4) in the coating pot during simultaneously producing annealed product by the continuous annealing apparatus of the dual purpose apparatus thereby enabling repair of the coating device (4) in the coating pot (3) during the simultaneous producing of the continuously annealed product; and - transporting the coating device (4) by a crane (9) placed beneath the bypass device (8), the coating device in the coating pot (3) being installed beneath the bypass device (8). |
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159-delnp-2003-complete specification (as filed).pdf
159-delnp-2003-complete specification (granted).pdf
159-delnp-2003-correspondnece-others.pdf
159-delnp-2003-correspondnece-po.pdf
159-delnp-2003-description (complete).pdf
159-delnp-2003-petition-137.pdf
159-delnp-2003-petition-138.pdf
| Patent Number | 243470 | |||||||||||||||
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| Indian Patent Application Number | 159/DELNP/2003 | |||||||||||||||
| PG Journal Number | 43/2010 | |||||||||||||||
| Publication Date | 22-Oct-2010 | |||||||||||||||
| Grant Date | 19-Oct-2010 | |||||||||||||||
| Date of Filing | 13-Feb-2003 | |||||||||||||||
| Name of Patentee | NIPPON STEEL CORPORATION | |||||||||||||||
| Applicant Address | 6-3, OTEMACHI 2-CHOME, CHIYODA -KU TOKYO 100-8071 JAPAN | |||||||||||||||
Inventors:
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| PCT International Classification Number | C21D 9/56 | |||||||||||||||
| PCT International Application Number | PCT/JP01/07969 | |||||||||||||||
| PCT International Filing date | 2001-09-13 | |||||||||||||||
PCT Conventions:
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