JPS6048586B2 - Double-sided hot dip galvanizing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a double-sided hot-dip galvanizing apparatus.

In the case of conventional double-sided hot-dip galvanizing equipment for steel strips, the steel strip to be plated is completely immersed in the galvanizing layer using a zinc roll, and the galvanizing layer is passed through the galvanizing layer for a certain period of time.
The structure is such that galvanization is applied to both sides of the steel strip.

A typical device will be explained based on FIG. The steel strip S, which has been pretreated to a suitable surface condition for plating, is immersed in a plating bath 2 through a chute 1 maintained in a protective atmosphere.

A zinc roll 3 is installed in the plating bath 2 via hangers and bearings (not shown), and the steel strip S changes its traveling direction during plating by the zinc roll 3 and swings upward. Stabilizer roll 4 for stopping
Then, at the same time as leaving the country, the amount of plating deposited is adjusted by the wiper 5 for wiping away the molten metal, a plating coating layer of a predetermined thickness is formed on the steel strip S, and then the usual method is applied. The product is made by post-processing. In such a conventional plating device, the shaft 6 for holding the zinc roll is completely immersed in the plating and rotates in the plating, so the bearing part and the bearing body of the shaft are particularly prone to wear and melting. It is extremely hot, and the replacement work is actually difficult due to the high heat.

Moreover, since the gap between the bearing and the shaft 6 is made larger in advance in anticipation of thermal expansion, this creates causes such as lateral vibration of the steel strip S, causing uneven wear of the device operating system, and feeding. There was a drawback that the steel strip S meandered. In addition, there were various problems in hot-dip galvanizing production, such as the generation of a large amount of dross due to the iron content leached from the zinc roll 3, its hanger/bearing, or the stabilizer roll hanger. 1
This invention is capable of providing sufficient plating adhesion even if the contact with the molten galvanized steel sheet is for a short time, and that the contact time has little effect on the plating thickness, such as wiper adjustment or bath temperature. This article relates to a detergent method developed to overcome the various obstacles mentioned above, based on useful knowledge such as the fact that

The details of the configuration will be explained below. FIG. 2 shows a preferred embodiment of the present invention, in which the reference numeral S indicates a steel strip, and this steel strip S is fed through the chute 1 after being pretreated.

The inside of this chute 1 is maintained in a reducing atmosphere to prevent oxidation of the steel strip S, and in particular, the tip of the chute 1 is kept in contact with outside air by blowing inert gas such as nitrogen gas through the buffer plate 7. is completely sealed. 2 is a plating bath of molten zinc, and 3 is a guide roll.

This guide roll 3 has a roll shaft 6 that supports it.
is rotatably supported above the bath surface via a hanger and a bearing (not shown), while only a part of the outer peripheral surface of the guide roll 3 itself is connected to the plating bath 2.
It is supported in a submerged state. The steel strip S introduced into the plating bath 2 at a certain angle through the chute 1 is guided by the guide roll 3 on the side immersed in the plating bath 2 as described above, and is once fitted into the plating bath 2. As it passes through the soaking bath 2, it changes direction and exits above the bath, and after adjusting the plating thickness with the gas wiper 5, it is sent to the post-treatment process. At the tip of the chute 1 are fixed partition plates 8a and 8b whose lower ends (free ends) protrude into the bath or contact the peripheral wall of the guide roll 3, and the steel strip S remains in a reducing atmosphere. A defining structure is provided for introduction into the plating bath 2. The guide roll 3 is heated from the inside by a necessary means until the roll surface temperature reaches 35.
It is preferable to maintain the temperature at 0 to 550°C to improve the wettability of molten zinc to the copper strip S. As mentioned above, unlike the conventional method, by positioning the roll shaft 6 above the bath surface, the guide roll 3 is in a state in which only a portion thereof is immersed in the plating 2. Therefore, depending on the entering angle θ of the steel strip S into the plating bath 2, one surface of the steel strip S, that is, the upward facing surface may not come into contact with the plating bath 2.

Therefore, in order to perform double-sided plating with the apparatus of the present invention, the angle θ of the steel strip S entering the plating bath 2 with respect to the bath surface is adjusted appropriately. By appropriately selecting the steel strip 3, a V-shaped gap 9 is formed across the width direction of the steel strip S at the position where the steel strip 3 starts to contact the guide roll 3, and the molten zinc in the bath is filled in this gap 9. The structure is such that both sides of the steel strip S are galvanized by flowing the steel strip S into the steel strip S. That is, when the steel strip approach angle θ is set to 20 to 40 degrees, an appropriate shape gap 9 can be formed.
This upper limit of θ=40° means that the v-shaped gap 9 formed between the steel strip S and the guide roll 3 becomes smaller, so the amount of molten zinc flowing into this gap 9 decreases, and the entrainment is insufficient. If foreign matter is floating on the surface of the plating bath 2, there is a risk that a defective part may be caused by foreign matter being trapped. On the other hand, if the approach angle θ is smaller than 20°, there is a problem in terms of the equipment structure; in particular, it becomes difficult to implement the equipment in relation to the tip of the chute. Furthermore, when the approach angle θ becomes 35° or more, the flow of molten zinc from the plating bath 2 into the gap 9 decreases, so as shown in FIG. A tank 10 is provided, and molten zinc is poured into the gap 9 from this holding tank 10.
This is a type of device that stores the amount of molten zinc necessary for plating by letting it fall into the tank.

It should be noted that these devices described above can be easily converted into single-sided plating devices by lifting the roll shaft further upward or by eliminating the gap 9 mentioned above. The following shows the results obtained using the apparatus according to the present invention.

Example 1 A normal cold rolled steel strip 0.57WL x 300TWL was degreased and placed in a weakly reducing atmosphere (H.

The temperature of the steel strip at the snout outlet was reduced to 490'C. 10% of molten zinc at 470℃ from the holding tank
Both sides were plated at a flow rate of 00gr/min. The guide roll is made of Ni-Cr steel and is internally heated to maintain a roll surface temperature of 47.
The temperature was set to 0°C, and the sample was immersed in a plating bath with a diameter of 215 mm. The plating bath temperature was 473°C, and the A1 concentration in the plating bath was 0.
The plating speed was set at 18%, the plating speed was 35n/min, and air was used for the plating amount control nozzle. The amount of zinc deposited at this time was 67 gr/d on the guide roll side and 73 gr/d on the other side.
/I was at a loss.

Example 2 A normal cold-rolled steel strip of 0.5 TWL x 30- was degreased, reduced by sintering in a weakly reducing atmosphere (H2L 5%, N2 85%), and the temperature of the steel strip at the snout exit was cooled to 495°C. The approach angle to the galvanized bath surface is 60°, and the temperature is 470° from the funnel-shaped plating bath holding tank on the upper surface of the steel strip at the entrance of the guide roll.
molten zinc was flowed down at 1,200 gr/min to plate both sides.

The guide roll was internally heated with Ni-Cr steel, the roll surface temperature was set at a target of 450°C (actual measurement not possible), and the roll diameter was immersed in a 3110 plating bath. The plating bath temperature is 47
2'C, and the Al concentration in the plating bath was 0.18%. The atmosphere in the plating chamber was a nitrogen gas atmosphere, and the cooling chamber was cooled by blowing liquid nitrogen.

The plating rate was 35 TrL/Min, and nitrogen gas was used for the plating amount control nozzle.

At this time, the amount of zinc deposited was 63 gr on the guide roll side and 80 gr on the other side.

As explained above, according to the present invention, the life of the roll shaft bearing can be significantly extended, and since the roll is not immersed in the plating bath, the difference in thermal expansion can be reduced, and therefore the play By eliminating the space, it is possible to prevent sideways movement of the steel strip, and it is possible to obtain a high-quality plating film.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional hot-dip galvanizing apparatus, FIG. 2 is a sectional view of the apparatus of the present invention, and FIG. 3 is a sectional view of an embodiment of the present invention. S...Steel strip, 1...Chute, 2.
...Plating bath, 3...Guide roll, 4
...Stabilizer roll, 5. ．．゜゜゜゜Wiper, 6゜゜゜゜゜゜Roll shaft, 7...
...Buffer plate, 8...Partition plate, 9...
...Gap, 10...Holding tank.

Claims (1)

[Claims] 1. In an apparatus that galvanizes both sides of a steel strip fed into a protective atmosphere by introducing it into a molten zinc bath via guide rolls and immersing it, one part of the outer peripheral surface is immersed in the plating bath. A guide roll is provided such that only a portion of the steel strip is immersed in the plating bath, and a roll shaft supporting the guide roll is installed on the surface of the plating bath. A double-sided hot-dip galvanizing apparatus characterized in that a gap is provided in the width direction of the steel strip at a position where it starts to come into contact with the steel strip, through which molten zinc in the bath or prepared separately flows.