JPS62205257A - Continuous hot dipping method - Google Patents

Abstract

PURPOSE:To enable alloying and unalloying by changing over the amount of cooling water fed to touch rolls placed above wiping nozzles from a high flow rate to a low flow rate. CONSTITUTION:A metallic strip 4 pulled up from a hot dipping bath 2 is sent to cooled touch rolls 10 placed above a pair of wiping nozzles 6 at <=5m interval after the extent of sticking is regulated to a prescribed value with the wiping nozzles 6. Cooling water is fed to each of the touch rolls 10 in two systems and the amount of cooling water fed can be changed over from a high flow rate to a low flow rate through solenoid valves 18. When an alloyed steel sheet is manufacture, cooling water is fed at a low flow rate and alloying is carried out in an alloying furnace 14. When an unalloyed steel sheet is manufactured, cooling water is fed at a high flow rate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a continuous hot-dip plating method, in particular, enables high-speed, thin plating, and also enables non-alloyed metal strip (
For example steel sheet) to alloyed metal strip or vice versa! This invention relates to a continuous hot-dip plating method that can be switched between two types.

(Prior art) In recent years, hot-dip plating has become faster and more uniformly thinner.
What is important is whether the strip can be made flat and how close the distance between the strip and the wiping nozzle can be.

In the conventional line, after melt plating, there is no connection to the strip from the time it is lifted out of the bath to the top roll, and the strip vibrates freely at intervals of about 50,111 mm in length.

Therefore, the amplitude of the strip at the wiping nozzle portion is large, and the nozzles cannot be placed close to each other.

Furthermore, even if warpage occurs in the strip, the warp is as smooth as possible, resulting in uneven adhesion and the wiping nozzle being unable to approach the strip.

By the way, there are 21 types of hot-dip plating methods: those that involve alloying treatment and those that do not. When alloying treatment is carried out, it is passed through a wiping nozzle section and then put into a heat treatment furnace, but these processes are usually carried out continuously.
It is necessary to be able to switch between alloying and non-alloying treatments on the same production line.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a method of preventing strip warpage and vibration as much as possible in order to achieve high-speed, thin-area continuous hot-dip plating. .

Another object of the present invention is to provide a continuous hot-dip plating method that allows production of alloyed steel sheets and non-alloyed steel sheets to be switched on the same production line.

Another object of the present invention is to provide a continuous hot-dip plating method that can switch between alloying treatment and non-alloying treatment on the same production line while thinning the coating weight at high speed.

(Means for Solving the Problems) Therefore, the inventors of the present invention conducted various studies, focused on the advantage of providing a touch roll, and continued research and development.

In the past, when manufacturing alloyed steel sheets, touch rolls were sometimes used directly above the nozzle to prevent vibration of the strip. However, in this case, if a cooled touch roll is used, the strip will be cooled too much and the efficiency of the alloying furnace will be reduced, so the roll surface temperature cannot be lowered. However, when a non-alloyed steel sheet is manufactured using such a touch roll, there are problems such as striped patterns on the plating surface, making it difficult to put it into practical use.

In addition, JP-A No. 59-85853 discloses that a rolling roll driven in synchronization with the processing speed of the strip is provided above the plating bath in order to prevent uneven plating thickness. It has been suggested that the vibrations of the strip can also be suppressed. However, this device is for rolling solidified plated metal, and the purpose of cooling the rolls is to prevent the plated metal from adhering to the rolling rolls.

JP-A-50-3926 discloses a temperature-adjustable pinch roll arranged in an S-shape. This is because conventional touch rolls are provided to prevent vibrations of the strip caused by wiping gas or vibrations caused by poor shape of the metal strip, and the temperature of the touch roll increases. If the touch roll is placed in a pinch roll type, scratches will occur on the product, so a touch roll with the above-mentioned configuration is used.

Therefore, the present inventors first used a cooled touch roll to completely prevent not only the vertical vibration of the strip but also the horizontal warpage, thereby making it possible to achieve a thin touch roll at high speed. We came up with the idea of limiting the mounting position of the roll and using a switching system for the cooling lid of the water-cooled touch roll, and obtained the following knowledge.

(1) By installing the touch roll at a distance within 5m above the wiping nozzle, it is possible to completely prevent not only vertical vibration but also horizontal warping of the strip, and reduce the plating thickness in the width direction. There was almost no decrease in the plating thickness, especially at the edges.

(2) Both alloying and non-alloying treatments are installed within a distance of 5 or less from the wiping nozzle, and at the touch roll stage, they simply adjust the cooling capacity of the touch roll, that is, the surface temperature. For example, when producing alloyed steel sheets, water cooling of the touch roll should be kept to a minimum. If the roll is cooled too strongly, the strip will be cooled too much, which will reduce the efficiency of heating for alloying. Cooling Mercury
For example, the water temperature on the exit side of the roll may be suppressed to below the boiling point. Surface properties that may be problematic due to contact with the rolls are reheated in the alloying furnace and reflowed, resulting in a problem-free finish.

(3) On the other hand, when manufacturing non-alloyed steel sheets, it is necessary to keep the roll surface temperature below 100°C due to surface quality issues, and the angle of each touch roll to be kept below 10°. To do this, it is necessary to flow a large amount of cooling water (1) to prevent the roll surface temperature from rising.

If the roll surface temperature exceeds 100°C, problems such as roughening of the plating surface and pinking up of Zn on the roll will occur.

Thus, the present inventors have completed the present invention based on the above-mentioned knowledge, and the gist of the present invention is to provide a metal strip that is continuously pulled up from a molten metal plating bath. In the continuous molten metal plating method in which plated M1k is controlled by spraying gas through a wiping nozzle, at a position within 5 m above the wiping nozzle,
A cooling type touch roll is provided in contact with the metal strip from at least one side, and the amount of refrigerant can be switched between a large flow rate and a small flow rate, and the flow rate can be used selectively for alloying processing and non-alloying processing. This is a continuous hot-dip plating method.

As described above, according to the present invention, in order to be able to manufacture alloyed and non-alloyed metal strips, the amount of cooling water supplied to the touch roll provided within 5 m above the wiping nozzle is increased to a large flow rate. The flow rate may be changed to a small flow rate, and at that time, a small flow (2) is used when producing an alloyed steel plate, and a large flow rate is used when producing a non-alloyed steel plate, and each flow rate may be determined in advance. Naturally, the taft roll may be rotated by an appropriately connected roll drive device following the running speed of the strip, and the roll surface material is not limited at all.

According to the present invention, a water-cooled touch roll is provided within 5 m directly above the wiping nozzle.
You can use more than one roll, but it is preferable to have two rolls, one on each side.If this roll is more than 51m away from the wiping nozzle, it will be too far away from the snuff roll in the plating bath, which will cause strip vibration and warping. The suppressive effect is halved.

Furthermore, according to another aspect of the present invention, when performing the non-alloying treatment, the roll surface temperature is set to 100° C. or less. For this purpose, it is common to cool the inside of the tafty roll with water. When the surface temperature exceeds 100 °C, Zn is deposited on the roll surface.
The adhesion of powder, etc. becomes intense, which not only damages the plating surface but also deteriorates the surface quality of the product. The surface temperature is preferably 50'C or less.

Then, set the wrapping angle of the strip to the touch roll to 1
Keep it below 0°. If the angle exceeds 10°, a mottled pattern will appear on the plating surface. Preferably, the angle is 5° or less. The smaller the wrapping angle is, the better; however, if it is too small, the rotation of the roll and the stripping speed will not be synchronized when the Taft roll is allowed to freely rotate, resulting in defects on the product surface. Preferably, the touch roll is appropriately connected to a roll drive device and rotated in synchronization with the stripping speed, so that this drawback can also be avoided.

There are no particular restrictions on the material of the roll surface.

In addition to regular steel rolls, C-plated or thermally sprayed rolls may also be used.

In order to lower the roll surface temperature, not only internal water cooling but also cooling by blowing compressed air or the like onto the roll surface may be used.

(effect) The invention will now be further described with reference to the accompanying drawings.

FIG. 1 is an explanatory diagram of the method according to the present invention, and in the figure,
The metal strip 4 pulled up from the plating bath 2 is made to have a predetermined basis weight by a pair of wiping nozzles 6, passes through a water-cooled touch roll 10, and, when alloying is performed, enters the alloying process 14.

As shown in an enlarged view in FIG. 2, the structure of this water-cooled touch roll 10 is such that two systems of cooling water are supplied, and each system is configured to supply a large flow rate and a small flow rate. The switching between them may be performed using the solenoid valves 18 and 18. Note that the internal cooling structure of the cooled touch roll 1o is not particularly limited and may be the same as that of a normal chilled roll. The coolant is typically water.

The optimum flow rate for alloying treatment and non-alloying treatment is determined in advance, and after setting this flow rate, adjustment during operation is performed simply by switching the valves for large flow rate and small flow (2).

Further, according to the present invention, by arranging the cooling type touch roll directly above the wiping nozzle, the occurrence of vibration and warping of the strip is suppressed. Thereby,
It is possible to prevent uneven coating amount due to warpage and uneven spangles during zero spangle production due to warpage. Also, since the wiping nozzle can be placed close to each other,
Thin plating can be done at high speed.

This situation is schematically shown in FIG. 3, and it can be seen that warping of the metal strip at the wiping nozzle portion is significantly suppressed compared to the case where no touch roll is provided.

Therefore, the amount of adhesion is substantially uniform at the ends of the strip in the width direction.

Next, the present invention will be further explained by examples.

Example 1 Using the apparatus shown in FIG. 1, a steel strip was hot-dip galvanized under the treatment conditions shown in Table 1.

,L! J- Plate 1zo: 0.8IllI+ Line speed: 100IIl/win Nozzle spacing 2 30+
++s Wiping pressure crab 0.8kg/c+j attached Fir
: 80 g/rd Alloying furnace temperature: 1050° C. Alloyed steel sheets and non-alloyed steel sheets were manufactured, but for comparison, the cooling water flow rate was changed significantly in each case.

The results are summarized in Table 2 below.

The maximum flow rate of the cooling type touch roll used in this example is 5 rrr/hr, and the Q small flow rate is 0.5 n? /hr
Met.

Example 2 In this example, hot-dip galvanizing was carried out by non-alloying treatment under the same conditions as in Example 1, but in this example, the winding angle of the steel strip around the touch roll and the surface temperature of the taft roll were varied. The results are summarized in Table 3.

The angle at which the touch roll is wound around the steel strip is the angle from the center of the roll that covers the length of contact between the two, as shown in FIG.

33 tables

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram for explaining the present invention in detail; Fig. 2 is a schematic explanatory diagram of the structure of the touch roll used in the present invention; Fig. 3 is a vibration of the metal strip according to the present invention. FIG. 4 is an explanatory diagram of the winding angle of the touch roll with respect to the strip.

Claims (3)

[Claims] (1) In a continuous molten metal plating method in which the amount of plating is controlled by spraying gas through a wiping nozzle onto a metal strip that is continuously pulled up from a molten metal plating bath, the metal strip is placed within 5 m above the wiping nozzle. A cooling type touch roll is provided in contact with at least one side of the refrigerant, and the amount of refrigerant can be switched between a large flow rate and a small flow rate, and the flow rate can be used selectively for alloying processing and non-alloying processing, Continuous hot-dip plating method. (2) When performing the non-alloying treatment, the cooled touch roll is made of metal so that the roll surface temperature of the cooled touch roll is 100°C or less and the winding angle around the metal strip is within 10°. 2. The method of claim 1, wherein the strip is contacted from at least one side. (3) The method according to claim 1 or 2, wherein the cooled touch roll is driven by a roll drive device to follow the running speed of the metal strip.