JPS6146526B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a surface-treated steel sheet, and more particularly to a method for manufacturing a surface-treated steel sheet obtained by passing a thin steel strip through an aqueous solution at high speed and subsequently introducing it into a heat treatment step. For example, when manufacturing surface-treated steel sheets used as can manufacturing materials, a continuous annealing line shown in FIG. 1 has recently been known. As shown in the figure, a degreased steel strip 1 is passed through an immersion bath 2 containing an aqueous nickel acetate solution containing Ni ⁺⁺ or an aqueous ammonium phosphate solution containing PO ₄ ^--- , and then pulled upward. The amount of adhesion is controlled to be thin by a wiping nozzle 3 that injects air, and then dried in a drying furnace 4, and then passed through a continuous annealing furnace 5 consisting of a heating zone, a soaking zone, a cooling zone, and an overaging zone. Annealed. By this annealing, a thin film consisting of a good Ni diffusion layer or Fe--P layer is formed on the surface of the strip 1. However, in the manufacturing process of the above-mentioned surface-treated steel sheets, the supplied steel sheets are thin (0.3 to 0.15 m/
m) and high line speed (maximum 500m/
Since the strip 1 between the dipping tank 2 and the drying oven 4 is subject to vibration and warping in the width direction (C warping),
Wiping nozzle 3 and strip 1
There is a problem that the distance from the surface varies, resulting in uneven adhesion amount. On the other hand, in the case of such a surface-treated steel sheet, the thickness of the treatment liquid deposited must be as thin as possible, and therefore the jetting pressure of the wiping nozzle 3 is high-pressure wiping, such as 1.0 to 2.0 kg/ ^cm2 , and The nozzle tip is required to be close to the strip surface. However, high pressure and close wiping increase the amount of splash and may cause undesirable contact between the nozzle tip and the strip due to vibration of the strip. In view of the above points, the present invention effectively suppresses vibrations and C warping of a steel plate that is run at high speed, immersed in an aqueous solution, and wiped, and forms a uniform film in the longitudinal and width directions of the steel plate after continuous annealing. The purpose of the present invention is to provide a method for manufacturing surface-treated steel sheets that allows for the production of surface-treated steel sheets. Another object of the present invention is to provide a method for manufacturing a surface-treated steel sheet that can provide a coat with a controlled and predetermined thin thickness. The contents of the present invention will be explained below with reference to the drawings. The present invention is characterized in that a fluid pressure pad is installed close to the top of the wiping nozzle to prevent vibration and correct C warpage when applying an aqueous solution in the process before continuous annealing, and to support the strip in a non-contact manner. It is said that That is, FIGS. 2 to 4 show examples in which static pressure pads 6 are arranged along the running line of the strip 1 drawn out from the aqueous solution immersion tank 2 before the continuous annealing process. In the arrangement example shown in FIG. 2, a pair of stationary pads 6 are arranged above the wiping nozzle 3 so as to be symmetrical with the strip 1 in between. In addition, in FIG. 3, at the upper position of the wiping nozzle 3,
The arrangement of the pair of static pressure pads 6 is the same as in FIG. 2, but a preliminary wiping roll 7 for sandwiching the strip 1 is provided at a position directly above or in contact with the bath surface of the dipping tank 2, and the preliminary wiping roll 7, the amount of adhesion to the strip is preliminarily suppressed so that a film with a thinner basis weight can be obtained. Furthermore, in the example of FIG. 4, the wiping nozzle 3
are arranged in a staggered manner instead of facing each other, and a static pressure pad 8 is provided at a position facing each wiping nozzle 3, and a pair of static pressure pads 6 are provided above the pads. In this example, static pressure support on one side of the strip at the wiping position makes it easier to move the wiping nozzle closer to the strip. Although an example is shown in which a pair of static pressure pads 6 are installed, in the present invention, not only one pair but also two or more pairs may be installed if necessary. When the static pressure pad 6 is installed within the area above the static pressure pad 6, this fluid flow is confined within the static pressure pad 6, and the synergistic effect with the fluid of the static pressure pad 6 creates a supporting force greater than the original static pressure. Therefore, it is desirable that the static pressure pad be as close to the wiping nozzle 3 as possible. Furthermore, in order to prevent air from entering the annealing furnace, a fifth
As shown in Figures 6 and 7, it is also possible to install the static pressure pad 6 close to the entrance side of the drying oven 4 (Fig. 5), built-in (Fig. 6), or built into the entrance side (Fig. 7). . If an inert gas such as nitrogen gas is used in either case, it is possible to prevent atmospheric air from entering the drying furnace 4 and annealing furnace 5 due to the gas curtain effect. Furthermore, the structure of the static pressure pad 6 that supports the strip 1 in a non-contact manner needs to be able to efficiently apply static pressure to the strip, and for example, a structure as shown in FIG. 8 is preferable. For example, as shown in FIG. 8, a pad main body 11 having a nozzle plate 10 on the front surface with a fluid blowing slit 9 inclined toward the center has a hollow box shape and functions as a fluid surge tank 12. A flexible hose 13 leading to a fluid supply source is attached to the back. The gap and angle of the slit 9 provided in the nozzle plate 10 may be appropriately determined in relation to the static pressure, and the configuration of the slit 9 may be such that two or more pairs of slits are provided in the width direction of the strip, or two or more pairs of slits are provided in the width direction of the strip. It is also possible to divide the slit into two or to form two or more multiple slits concentrically. Furthermore, when using split or multiple nozzles for the nozzle box, a partition plate is provided to control the fluid volume for each slit to efficiently prevent strip vibration and correct C warpage. Good too. In the present invention, a static pressure pad with an optimal structure may be selected by considering the line characteristics of the strip, the size of the strip, etc. Next, the operation of the present invention will be explained using the aqueous solution treatment and continuous annealing process shown in FIG. 1 as an example. After the steel strip 1 is degreased in a surface cleaning step, it is introduced into an aqueous solution tank 2, immersed, and pulled up in a substantially vertical direction, and air is blown at high pressure from a wiping nozzle 3 onto the strip surface for wiping.
In this case, as shown in Fig. 2, the wiping nozzle 3
Since at least one pair of static pressure pads 6 are provided close to the top, the strip 1 is held in a predetermined running line by its static pressure (the static pressure occurs in the area of FIG. does not occur. Further, even if a C warp occurs in the strip 1, a force is applied to the strip in the direction to correct it, and the warp is linearly corrected. Therefore, the strip 1 runs stably along a predetermined line, and there is no risk of contact even when the tip of the wiping nozzle approaches the strip surface, improving the wiping ability and improving control. A thin film can be obtained. In addition, since the distance between the wiping nozzle and the strip can be maintained constant at all times, and C warpage is corrected in the strip width direction, a uniform film can be formed over the entire surface of the strip without any variation in film thickness. Quality will be improved. In the conventional method, the wiping nozzle could not be placed too close to the strip in anticipation of vibrations, and therefore the wiping pressure had to be high in order to obtain a thin film, but increasing the pressure increased splash and noise. growing. On the other hand, in the present invention, since vibration of the strip is prevented, the wiping nozzle can be placed as close as possible, and a lower wiping pressure is sufficient to obtain the same film thickness as in the past, reducing the above problems. It is also effective in correcting C-curvature, for which no countermeasures have been taken in the past. Moreover, it is also possible to control a thinner film using the same wiping pressure as before. In this case, it is preferable to surround the wiping area with a box to prevent splashing and noise. In the example shown in FIG. 3, since the amount of adhesion can be reduced to some extent with the preliminary wiping roll 7, the thickness of the coating can be made even thinner as a result. Furthermore, in the example shown in FIG. 4, the static pressure of the static pressure pads 8 that face each other at the wiping nozzle 3 position acts, which can be said to be even more effective in preventing vibration of the strip. The strip 1 that has been wiped and raised enters the drying furnace 4, where its surface is dried, and then sent to the continuous annealing furnace 5, where it is heated to a predetermined temperature, soaked, and then cooled at a required cooling rate. Annealing treatment is applied. The strip 1 leaving the annealing furnace 5 is directly sent to the next process (for example, plating process). As described above, by performing the aqueous solution treatment and moving to the continuous annealing process, the surface of the steel plate, for example,
A Ni diffusion layer or a Fe--P layer is applied. As described above, according to the method of the present invention, it is possible to efficiently prevent and correct the vibration and C warping of the strip, which were major problems during conventional aqueous solution processing, and the strip surface after heat treatment has the desired controlled appearance. This makes it possible to uniformly apply a coated film, resulting in a high-quality surface-treated steel sheet.
Therefore, its industrial and practical merits are extremely large. Example 1 A 10% aqueous solution of nickel acetate was applied to a 3-foot-wide strip that had been electrolytically degreased in front of a continuous annealing furnace for cold-rolled steel sheets, followed by a drying process and annealing to produce a surface-treated steel sheet having a nickel diffusion layer. We compared the application methods of air wiping (AJC), air wiping with static pressure pad (P-AJC), and squeeze roll method (RC). Strip width direction (right,
Samples were cut out at three locations (middle, left) and the amount of Ni deposited was measured. The strip speed was 300 m/min. The results are shown in Table 1. 【table】

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram illustrating a continuous annealing line for a steel strip suitable for applying the present invention;
Figures 3, 4, 5, 6, and 7 are detailed views of main parts showing various types of equipment for carrying out the method of the present invention, and Figure 8 is the static pressure used in the present invention. A sectional view showing an example of a pad. 1...Steel strip, 2...Immersion tank, 3...Wiping nozzle, 4...Drying furnace, 5...Continuous annealing furnace, 6, 8...Static pressure pad, 7...Preliminary wiping roll, 9... Slit, 10... Nozzle plate,
11...pad body, 12...surge tank, 1
3...Flexible hose.

Claims (1)

[Scope of Claims] 1. A method for producing a surface-treated steel sheet, in which a high-pressure gas is sprayed from a wiping nozzle onto a thin steel sheet drawn out through an aqueous solution to control the coating amount, and then the thin steel sheet is heat-treated. A hydrostatic fluid pressure pad is installed against the surface of the steel plate in the vicinity of the pad, and the static pressure of the hydrostatic fluid pressure pad suppresses vibration and warpage in the width direction of the steel plate to ensure stable plate threading. 1. A method for producing a surface-treated steel sheet, which comprises passing the steel sheet in a continuous annealing furnace in such a state as to form a film on the surface of the steel sheet at the same time as heat treatment. 2. The manufacturing method according to claim 1, wherein a hydrostatic fluid pressure pad is provided near the outside or near the inside of the steel strip inlet of the continuous annealing furnace, or at the inlet, and the steel sheet is passed through the annealing furnace.