JP3569439B2 - Continuous hot-dip plating method and apparatus - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a continuous hot-dip plating method and apparatus for suppressing the amount of zinc fume generated in a snout in a hot-dip plating process.
[0002]
[Prior art]
In recent years, hot-dip galvanized steel sheets having excellent corrosion resistance have been increasingly used as surface-treated steel sheets for automobiles and home appliances. After the steel strip is annealed in a reducing atmosphere furnace, the steel strip is cooled, passed through a furnace called a snout connecting the annealing furnace and the plating bath, and immersed in the molten zinc bath. Further, thereafter, the wiping nozzle is adjusted to an appropriate plating adhesion amount. In the hot-dip galvanizing process, fumes have been generated from the zinc bath surface inside the snout, and the fume adheres and accumulates on the snout wall, partially peels and falls, and directly adheres to the steel plate before plating, It is known that the steel sheet falls to the bath surface and adheres to the steel strip while floating on the zinc bath surface, thereby impairing the appearance of the steel plate after plating.
[0003]
As a countermeasure, for example, as disclosed in JP-A-6-339346, the temperature distribution of the snout wall is applied to fumes generated from the surface of the zinc bath in the snout to generate natural convection, and the continuous furnace side is used. Forcibly transport to the upstream side from the snout mounting part, to suppress adhesion and growth on the inner wall of the snout, and to provide a low-temperature part in the turndown roll chamber to precipitate metal fume, furthermore, in the snout There has been proposed a method in which a plurality of electric heaters are sectioned on an outer wall of a snout to generate natural convection.
[0004]
[Problems to be solved by the invention]
However, when natural convection is generated inside the snout, the zinc fume concentration gradient on the surface of the snout bath increases, and the amount of generated fume is accelerated. As a result, the fume concentration inside the snout is almost the same as when natural convection does not occur, and since the amount of fume deposited in the low temperature part of the turndown roll chamber further increases, the production of the line is stopped and the furnace is opened, It becomes necessary to perform cleaning.
[0005]
[Means for Solving the Problems]
The present invention has been made in view of the above problems, and a steel strip is heated and annealed under a reducing atmosphere in a continuous annealing furnace, and a turndown roll chamber and a snout are separated from the surrounding atmosphere from the continuous annealing furnace. In the continuous hot-dip plating method of performing plating by introducing into a hot-dip metal plating bath through the above, the space between the inside of the snout and the inside of the annealing furnace was sealed, and the temperature deviation in the snout was set to 50 ° C. or less.
[0006]
Also, heating the steel strip in a reducing atmosphere, a continuous annealing furnace for annealing, in a continuous hot dipping apparatus comprising a snout for partitioning from the ambient atmosphere of the steel strip introduced from該連connection annealing furnace into the molten metal plating bath, on the upstream side or / and downstream side of the turndown roll, above and below the steel strip, by Rukoto provided a partition plate so that the distance between the steel strip and 30mm or less, and within 50 ° C. the temperature deviation in the snout Thus, the space between the snout and the inside of the annealing furnace was sealed.
Furthermore, a heating device is divided into a plurality of sections and installed on a steel shell of the snout and a turn-down roll chamber disposed above the snout, and a heat insulating material is installed outside the heating apparatus. Provided with a temperature detector, and a temperature controller for controlling an applied voltage to a plurality of divided heating devices based on a temperature measurement result input from the temperature detector.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a schematic diagram of an apparatus according to the present invention. FIG. 1A is an overall schematic view, FIG. 1B shows a case where partition plates are installed above and below a turndown roll, and FIG. 1C shows a partition plate upstream of a turndown roll portion. FIG. The steel strip 1 is annealed in an annealing furnace heating zone 2 and cooled in a cooling zone 3 to make the temperature of the hot dip galvanizing bath 5 and the steel strip 1 almost the same, and then passes through a snout 4 via a turndown roll 6. , it is immersed into the zinc bath 7. On the continuous annealing furnace side from the turndown rolls 6, a roll 8 that is in contact with both the upper and lower surfaces of the steel strip 1 is attached, and a partition plate 9 having a gap of 5 mm or less is provided between the roll 8 and the furnace body. An electric heater 5 is installed on the wall of the snout 4 so that the temperature difference from the zinc bath is within 50 ° C. The outside of the electric heater 5 is covered with a heat insulating material 10, and the outside of the heat insulating material 10 is further covered with a stainless steel plate 11.
[0008]
In addition, as a method for sealing the snout 4 and the continuous furnace side, as shown in FIG. 1B, a partition plate having a distance of 30 mm or less from the turndown roll 6 is installed above and below the turndown roll 6. In some cases, as shown in FIG. 1C, a partition plate having a distance of 30 mm or less from the steel plate is provided upstream or downstream of the turndown roll unit 6.
In the present apparatus, the reason why the temperature difference in the snout was set to 50 ° C. or less was to prevent convection in the snout, and when the snout wall temperature was changed in the experiment, the temperature difference in the snout exceeded 50 ° C. As it became larger, natural convection began to occur strongly, at which time the amount of zinc vapor leaking to the continuous furnace side increased.
[0009]
This is thought to be due to the fact that the zinc vapor in the snout was saturated, causing natural convection, which disrupted the vapor-liquid equilibrium on the surface of the zinc bath, resulting in an increase in the amount of zinc vapor generated. . In the case where the snout was not heated during the operation, the plate path portions on the upper and lower surfaces of the snout furnace body were heated to about 100 ° C. higher than the portion deviated from the plate path due to the radiation of the steel sheet holding heat. For this reason, it adjusted by the heating zone divided into several and made the snout wall temperature uniform.
Further, the gap between the cutting plate 9 and the steel strip 1 specification in claims 2 was 30mm below are to approximate as much as possible saturated zinc vapor inside the snout, the strip 1 and the partition plate 9 or turndown roll The thickness was set to 30 mm or less as a range where the contact trouble 6 and the partition plate 9 did not cause a contact trouble in actual operation.
[0010]
【Example】
FIG. 2 is a schematic diagram showing a turndown roll section of the device according to the present invention. The amount of fume moving from the turndown roll to the continuous furnace side when the temperature distribution was applied to the snout wall was measured in the snout 4 of the continuous hot-dip galvanizing with the apparatus as shown in FIG. For the measurement of the amount of fume generation, a measurement port 13 was attached to the furnace body on the upstream side of the turndown roll, the gas in the furnace was suctioned by the pump 14, the fume was collected by the filter paper 12, and the weight was measured. At that time, the piping from the furnace body to the filter paper 12 was heated so that the zinc fume did not dew. As a result, the temperature difference of the snout wall was added, and the fume generation increased. In addition, when a seal device having a gap of 10 mm with the steel strip is installed in the turndown roll, the amount of fume generated on the continuous furnace side from the seal device is reduced, and the temperature difference between the steel plate and the snout wall is set to 50 ° C or less. The fume volume in the case was reduced to 1/10 that of the case without the sealing device.
In addition, when the snout wall was heated by an electric heater, the amount of fume leakage to the continuous furnace side when the distance of the partition plate from the steel strip installed on the turndown roll was changed was investigated. The amount of fume leakage increased in proportion to the distance between the steel strip and the partition.
[0011]
【The invention's effect】
According to the present invention, the amount of zinc vapor generated from the zinc bath surface in the snout decreases, and a galvanized steel sheet having a good surface appearance can be manufactured without stopping production of a continuous hot-dip galvanizing line. .
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an apparatus according to the present invention.
FIG. 2 is a schematic diagram showing a turndown roll section of the device according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steel strip 2 Annealing furnace heating zone 3 Cooling zone 4 Snout 5 Electric heater 6 Turndown roll 7 Zinc bath 8 Roll 9 Partition plate 10 Insulation material 11 Stainless steel plate 12 Filter paper 13 Measurement port 14 Pump

Claims (3)

The steel strip is heated and annealed in a reducing atmosphere in a continuous annealing furnace, and is continuously introduced from the continuous annealing furnace into a molten metal plating bath through a turndown roll chamber and a snout partitioned from an ambient atmosphere to perform plating. A continuous hot-dip plating method, wherein the inside of the snout and the inside of the annealing furnace are sealed, and the temperature deviation in the snout is set to 50 ° C. or less . In a continuous hot-dip plating apparatus having a continuous annealing furnace for heating and annealing a steel strip under a reducing atmosphere, and a snout for separating a steel strip introduced from the continuous annealing furnace into a molten metal plating bath from an ambient atmosphere, on the upstream side or downstream side of the roll, snout above and below the steel strip, by Rukoto provided a partition plate so that the distance between the steel strip becomes 30mm or less, the temperature deviation within the snout to be within 50 ° C. A continuous hot-dip galvanizing apparatus characterized by sealing between the inside and the inside of the annealing furnace. A heating device is divided into a plurality of sections and placed on the skin of the snout and the turndown roll chamber disposed above the snout, and a heat insulating material is installed outside the heating apparatus. 3. The continuity according to claim 2, further comprising a detector, and a temperature controller configured to control an applied voltage to a plurality of divided heating devices based on a temperature measurement result input from the temperature detector. 4. Hot-dip plating equipment.

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