JP3465729B2 - Manufacturing method and manufacturing apparatus for hot-dip galvanized steel sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a hot-dip galvanized steel sheet, and more particularly to a method and an apparatus for manufacturing a hot-dip galvanized steel sheet capable of adjusting a spangle (flower pattern) of a plating layer.

[0002]

2. Description of the Related Art Hot-dip galvanized steel sheets have excellent corrosion resistance, and by coarsening the zinc crystals in the plating layer, a flower pattern can be produced to obtain a beautiful appearance.
It is used as a building material. A hot-dip galvanized steel sheet that shows a flower pattern with coarsened zinc crystal grains is called a regular spangle-coated steel sheet, while a hot-dip galvanized steel sheet with fine crystal grains is called a minimum spangle-coated steel sheet (zero spangle-coated steel sheet). , Both of them are made differently depending on the Pb content in the hot dip galvanizing bath, the solidification rate of the plating layer, the control of solidification nuclei, and the like.

With respect to the Pb content in the plating layer and the spangle formation state, in particular, galvanizing with a high Pb content facilitates the production of regular spangled steel sheets, and galvanizing with a low Pb content produces minimum spangled steel sheets. It is known to be easy to do. For this reason, a method has been used in which a regular spangle-coated steel sheet and a minimum spangle-coated steel sheet are separately produced by adjusting the Pb content in the zinc plating bath.

On the contrary, since Pb in the plating layer causes a decrease in the adhesiveness of the plating layer over time, the Pb content in the plating layer is reduced when a minimum spangle-coated steel sheet without coarse spangles is manufactured. Had to let.
However, in order to adjust the Pb content in the plating bath, it is necessary to pump the plating bath or prepare a dedicated plating bath according to the required Pb content.
There was a problem in terms of equipment and economy.

When adjusting the Pb content in the plating bath, during the production of the minimum spangled steel sheet, the plating bath tub and the wall of the snout, the sink roll in the plating bath,
It was difficult to reduce the Pb content in the plating layer because the Pb that remained or adhered to the support rolls and other auxiliary equipment was mixed into the plating bath and eventually into the plating layer. As a method to solve the problem in making such spangles separately, in the plating layer which is still in a molten state after being pulled out from the zinc bath.
Although a method of dissolving Pb (Japanese Patent Laid-Open No. 59-118869) and a nucleation treatment method in the solidification process of the plated layer (Japanese Patent Laid-Open No. 62-149861) are disclosed, the Pb content of the plated layer is Fluctuation was unavoidable, leaving some problems to solve.

[0006]

DISCLOSURE OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present invention is to adjust the spangle accurately by a simple method without adjusting the Pb content in the plating bath. A hot-dip galvanized steel sheet manufacturing method and a manufacturing apparatus are provided.

[0007]

According to the present invention, a steel sheet is immersed in a hot dip galvanizing bath and then pulled up to control the amount of coating deposit, and then the coating layer is brought into contact with a roll having at least a surface layer containing Pb. A method for producing a hot-dip galvanized steel sheet, which is characterized in that the steel sheet is immersed in a hot-dip galvanizing bath, pulled up, and a hot-dip galvanized steel sheet manufacturing apparatus for performing hot-dip galvanizing, a hot-dip galvanizing bath (2) A coating amount control device (3) is provided on the steel plate outlet side of, and after the device, at least the surface layer in contact with the plated steel plate contains Pb (7), and the surface temperature control device of the roll (1
6), and a plated steel plate temperature control device (17) before and after the roll,
An apparatus for producing a hot-dip galvanized steel sheet is provided with (18).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. FIG. 1 shows a hot-dip galvanized steel sheet manufacturing apparatus according to the present invention. In FIG. 1, 1 is a plated steel sheet, 2 is a hot dip galvanizing bath, 3 is a coating amount control device (gas wiping nozzle), 4 and 5 and 6 are heating devices by radiant heat, and 7 is at least a surface layer containing Pb. Rolls (hereinafter referred to as lead rolls), 8 and 9 are cooling devices that are air blowing devices, 1
0 and 11 are radiation thermometers, 12 is a thermocouple, 13 and 14 and 15 are control devices, 16 is a heating device 5, a cooling device 8, a radiation thermometer 11, and a roll surface temperature control device including a control device 17, Is a steel plate temperature controller in front of the lead roll consisting of a heating device 4, a radiation thermometer 10 and a controller 14, 18 is a heating device 6, a cooling device 9,
A steel plate temperature control device after the lead roll, which is composed of a thermocouple 12 and a control device 15, 19 indicates a traveling direction of the plated steel plate.

The coated steel sheet 1 pulled up from the hot-dip galvanizing bath 2 is adjusted to a predetermined coating coating amount by a coating coating amount control device (a pair of gas wiping nozzles) 3, and then in the direction 19 of the coated steel sheet moving direction. It is passed.
This is because by controlling the Pb addition and the Pb addition amount after controlling the plating deposition amount, it is possible to prevent the final variation of the plating deposition amount.

The roll having at least the surface layer containing Pb in the present invention is preferably one having at least the surface layer containing lead as a main component, and the remaining component is, for example, Z.
It is preferable that one or more selected from n, Fe, Al and the like, that is, a component in the intended plating layer. Further, a roll in which at least the components of the surface layer are lead and inevitable impurities is also preferably used.

At the time of manufacturing the regular spangle plated steel sheet, the zinc coating layer of the plated steel sheet 1 adjusted to a predetermined coating weight by the coating weight control device 3 comes into contact with the lead roll 7 and Pb is added to the zinc coating layer. It In this case, the following methods are exemplified as preferred embodiments. Further, in the present invention, the following method is more preferable in terms of productivity and the ease of making the regular spangle-plated steel sheet and the minimum spangle-plated steel sheet separately.

At least the surface layer of the lead roll 7 is heated to a melting point of the surface layer or more by the roll surface temperature control device 16 to bring it into a molten state, and the surface layer is brought into contact with the galvanized layer,
A method of adding Pb to the galvanized layer by diffusion alloying. : At least the surface layer of the lead roll 7 is heated to a melting point of the surface layer or more by the roll surface temperature control device 16 to be in a molten state, and the surface layer is brought into contact with the galvanized layer heated by the steel plate temperature control device 17 to diffuse. A method of adding Pb to the galvanized layer by alloying.

A method of heating the zinc plating layer of the steel plate to a melting point or higher of the plating layer by the steel plate temperature control device 17 to bring it into a molten state, bringing the plating layer into contact with the lead roll 7, and adding Pb to the zinc plating layer. . In this case, it is preferable that the surface layer of the lead roll 7 is heated by the roll surface temperature control device 16.

A method in which the lead roll surface layer, which is in a molten state, is brought into contact with the galvanized layer by the roll surface temperature control device 16 and the steel plate temperature control device 17, and Pb is added to the galvanized layer. As a method for controlling the amount of Pb added to the galvanized layer, it is also preferable to combine it with a lead roll load adjusting device (not shown) for adjusting the load on the steel plate of the lead roll.

In the present invention, in the case of the above, it is preferable that the plated steel sheet 1 in which Pb is added to the plated layer is then solidified by controlling the cooling rate by the steel sheet temperature control device 18. As described above, in adjusting the spangle, the Pb content in the molten zinc and the solidification rate of the molten zinc are important, but according to the present invention, the addition amount of Pb and the solidification rate can be adjusted very easily. Therefore, it is possible to prevent the variation of the plating layer Pb content and the variation of the spangle formation condition under the same manufacturing conditions.

In the present invention, the steel plate temperature control device 17,
The roll surface temperature control device 16 is preferably a device that can accurately control the surface temperature of the steel plate and the surface temperature of the lead roll. For this purpose, for example, as shown in FIG. 1, radiation thermometers 10 and 11 for measuring the steel plate surface temperature and the roll surface temperature are installed, and based on the measurement results, the heating device 4 by radiant heat,
Heating the steel plate surface temperature and the roll surface temperature by 5,
It is preferable to control and add Pb to the plating layer under the conditions.

Further, in the roll surface temperature control device 16, it is preferable to adjust the roll surface temperature quickly and accurately by using the blowing of gas such as air from the cooling device 8 together. Further, the production method of the present invention, the production apparatus, by adjusting the Pb content in the plating layer, as a method of adjusting the spangle, as a method of independently controlling the surface temperature other than the method described above Installation, multi-stage installation of lead rolls with different Pb contents in the surface layer, multi-stage installation of lead rolls with different roll diameters, adjustment of load applied to the steel plate of the lead rolls, adjustment of roll diameter, heating device after lead rolls 6
It is possible to adopt various adjustment methods such as setting the length of the heating part of the.

Therefore, according to the present invention, in the plating layer
It is possible to accurately control the Pb content, and accordingly, the spangle formation state can be accurately controlled.

[0019]

EXAMPLES The present invention will be specifically described below based on examples. Using the apparatus for producing hot-dip galvanized steel sheet shown in FIG. 1, hot-dip galvanizing is applied to an ultra-low carbon steel sheet, the surface temperature of the steel sheet before the lead roll, the surface temperature of the roll, and the ambient temperature of the heated portion of the steel sheet after the lead roll. , The line speed was variously changed, and hot-dip galvanized steel sheets were prototyped (Examples 1 to 1 of the present invention)
8, Comparative Examples 1 and 2). In this embodiment, a lead roll whose entire material is Pb (Pb and inevitable impurities) was used.

Further, as a comparative sample, a hot-dip galvanized steel sheet was prototyped under the condition that the lead roll and the plated steel sheet were not heated and the lead roll was not in contact with the plated steel sheet (Comparative Example 3).
The Pb content in the plating bath was 0.01 wt% and was constant. Table 1 shows the production conditions and the spangle formation state of the obtained galvanized steel sheet. The symbols in Table 1 indicate the experimental order (experiment number).

The formation of spangles was visually observed. From Table 1, according to the present invention, spangle is developed even in a low Pb plating bath by adjusting the surface temperature of the plated steel sheet before the lead roll, the surface temperature of the lead roll, the atmospheric temperature of the heated portion of the plated steel sheet after the lead roll, and the line speed. It is possible to
Furthermore, it is clear that it is possible to make regular spangle plated steel sheets and minimum spangle plated steel sheets separately.

Next, in order to investigate whether the plating layer Pb content of the hot-dip galvanized steel sheet and the spangle formation condition by the manufacturing method and apparatus of the present invention varied, the manufacturing conditions were set to Experiment No. 7, The hot-dip galvanized steel sheet was prototyped by setting the same manufacturing conditions as in Example 8 (Invention Example 9,
Ten). Table 1 shows the production conditions and the spangle formation state of the obtained hot-dip galvanized steel sheet together with the above-mentioned examples.

It can be seen from Table 1 that according to the manufacturing method and the manufacturing apparatus of the present invention, it is possible to prevent the fluctuation of the plating layer Pb content of the hot dip galvanized steel sheet and the fluctuation of the spangle formation condition.

[0024]

[Table 1]

[0025]

According to the present invention, the hot-dip galvanizing of the steel sheet is performed, the coating amount is adjusted, and then the roll having at least the surface layer containing Pb is brought into contact with the plating layer. It became possible to make regular spangle-plated steel sheets and minimum spangle-plated steel sheets separately without changing.

Furthermore, since the plating layer is in a molten state and the cooling rate when the plating layer is solidified is also controlled, it is easier to make different parts. Further, according to the present invention, it is possible to form the spangle formation state of the hot dip galvanized steel sheet with high accuracy without causing fluctuation. Furthermore, it is not necessary to add Pb to the plating bath to form spangles, and as a result, it is possible to avoid the inclusion of Pb as an impurity during the production of minimum spangle-coated steel sheets, and the Pb content in the plating layer can be reduced. , Pb also has the effect of preventing a decrease in adhesiveness over time.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a hot dip galvanizing apparatus according to the present invention.

[Explanation of symbols]

1 plated steel sheet 2 Hot dip galvanizing bath 3 Plating amount control device 4, 5, 6 heating device Roll containing 7 Pb (lead roll) 8, 9 Cooling device 10, 11 radiation thermometer 12 thermocouple 13, 14, 15 controller 16 Roll surface temperature controller 17 Steel plate temperature controller 18 Steel plate temperature controller 19 Plated steel sheet traveling direction

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-263254 (JP, A) JP-A-7-292482 (JP, A) JP-A-59-118869 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C23C 2/00-2/40

Claims (2)

(57) [Claims] 1. After immersing the steel sheet in a hot dip galvanizing bath,
A method for producing a hot-dip galvanized steel sheet, which comprises pulling up and controlling an amount of deposited plating, and then bringing a roll having at least a surface layer containing Pb into contact with the plating layer. 2. A hot-dip galvanized steel sheet manufacturing apparatus for immersing a steel sheet in a hot-dip galvanizing bath, pulling it up, and performing hot-dip galvanizing, in a hot-dip galvanizing bath (2) at the steel sheet outlet side. ) Is provided, and at least the surface layer that comes into contact with the plated steel sheet after the device contains Pb.
(7), a surface temperature control device (16) for the roll, and a galvanized steel plate temperature control device (17), (18) provided in front of and behind the roll, respectively.