RU2300577C2 - Method and the device for the product coating by its immersing into the melt - Google Patents

Abstract

FIELD: building industry; metallurgy industry; methods and the devices for the product coating by its immersing into the melt.

SUBSTANCE: the invention is pertaining to the method and the device for coating on the surface of the strip made out of the non-ferrous metals or the steel strip of the metallic coating. The method provides for the strip passing through reservoir with the melt, at that the melt is introduced from the receiving reservoir into the gap between the rotors rotating in the opposite directions, and the strip is passing top-down through the melt and between the rotors. At that the gap from its lower side is hermetically sealed by means of the spinning permanent magnets fixed on the lateral side of the spinning rollers, which are located inside the rotors. The device includes the reservoir containing the melt which is formed by the upper and middle space between the two rotors rotating in the opposite directions with the gap hermetically sealed in the lower part by means of the rotating permanent magnets fixed on the lateral surface of the rotating rollers, which are located inside of the rotors. The technical result of the invention is: the good opportunity to coat the product by its immersing into the melt without the refrigerating column, the combination of the minimally possible volume of the construction with the optimal investment input and the high efficiency at the high quality of the products.

EFFECT: the invention ensures the good opportunity to coat the product by its immersing into the melt without the refrigerating column, the combination of the minimally possible volume of the construction with the optimal investment input and the high efficiency at the high quality of the products.

9 cl, 5 dwg

Description

The invention relates to a method for applying to a surface, in particular a strip-like material, for example, strips of non-ferrous metals or a steel strip, at least one metal coating when passing through at least one container containing molten coating material. The invention also relates to a device for implementing the method.

Conventional hot strip coating (called method 1) of Zn, Zn-Al, Al or Al-Si alloys in the coating area is characterized by the fact that the strip from the heating furnace is introduced without air into the melt and is rejected by a different arrangement of irreducible rollers in a vertical plane and stabilizes, as shown in Fig.1. This applies to all metals or alloys used as coatings when applied by immersion in a melt.

The disadvantage of method 1 is that the rollers and the roller bearings are inside the melt and all materials are exposed to the chemical action of the melt. The life of all parts inside the melt is limited. In addition, a large volume of melt and, accordingly, a large capacity are required to accommodate the rollers or, accordingly, all the submersible equipment. Typically, hot dip galvanizing uses between 200 and 400 tons of liquid zinc. Quick control of the temperature and composition of the melt is not possible due to the large volume. It is necessary to take into account the large spacing of the above parameters, which lead to deterioration in the given conditions, since in one tank the technological methods of alloying affect the quality of the strip and vice versa.

Another disadvantage is that it is impossible to increase the processing speed, in particular of thin strips <0.5 mm, in order to achieve a cost-effective installation performance (approximately 180 m / min). The reason for this is that the movement between the rollers in the bath and the strip is relative. If the pulling forces are increased to solve this problem, there will be a danger of a strip breaking. The consequence of this is scrap production and long installation downtime.

Another limitation of the maximum speed of the strip of the hot dip galvanizing plant is due to the system of cleaning nozzles located above the mirror of molten zinc, see Figure 1. The thickness of the coating layer is controlled by air or nitrogen, and with increasing strip speed increases the minimum possible coating thickness. This means that thin coatings are not possible at high strip speeds. However, it is thin coatings (<25 g / m ² on one side of a thin hot dip galvanized strip) that are most in demand.

As a more advanced coating method by immersion in a melt of a ferrite steel strip from mild non-alloy steels, the so-called vertical hot dip galvanizing method is known, which is described in various patents such as EP 0630421 B1, EP 0630420 B1 and EP 0673444 B1.

In this method (called method 2), the strip passes from bottom to top through a working vessel filled with molten metal of Zn and / or Al alloys, the strip being first subjected to heat treatment, and the strip enters the melt without air. Compared with method 1, the melt volume is substantially less than about 2-5 tons of liquid zinc. Also, the above-mentioned quality problems are absent, since alloying techniques are carried out in a receiving tank located near the line, and the strip quality is achieved in a separate working tank.

The connection between the working tank and the furnace chamber below is through a gas-tight ceramic channel with a height of approximately 800 mm and a passage width for a strip of a maximum of 20 mm. Hermetic sealing of the working capacity from below and preventing leakage of the melt into the furnace space is carried out inside this channel using the inductors located on the side of the channel or, accordingly,. These inductors create a traveling electromagnetic field, causing a force directed from above, preventing the leakage of the melt down. This induction system works like a pump, so that a melt exchange is also provided in the channel.

Method 2 is characterized in that at least in the area of coating to the level of the bathtub mirror also for the thin steel strip, significantly higher strip speeds of the order of 300 m / min can be obtained without problems, since there are no rollers in the coating tank.

After the strip passes from bottom to top, the coating unit with a temperature, for example, hot dip galvanizing at 460 ° C, regulates the desired thickness of the applied metal coating layer, compared to method 1, slightly above the level of the bath mirror, using blowing nozzles. It is carried out in comparison with method 1 by blowing off with compressed air or nitrogen.

In method 2, in the case of thin coatings, compared to method 1, the wiper nozzle method also limits the maximum possible strip speed. However, method 2 provides greater freedom of variation affecting the thickness of the layer, the parameters of galvanizing - temperature, melt viscosity and alloy composition. For this reason, it should be expected that at the same layer thickness, the strip speed in method 2, compared with method 1, can be selected higher. Compared to method 1, method 2 has not yet been tested on a large scale production. So far, only experiments have been carried out on experimental installations with a narrow strip, which have been completed successfully.

However, the fact that during the upward movement to the first deviation the strip is cooled down to a temperature below 300 ° C counteracts the increased speed. If the temperature is higher, there is a danger that metal particles will accumulate on the first contact or deflecting roller in the cooling column and create irreparable surface defects on the material.

Cooling usually takes place using several successive air cooling sections. However, the cooling effect, or rather, the cooling intensity is limited depending on the cooling medium and cannot be increased as desired when using air in a certain area as a cooling medium (for example, 2 × 15 m). With an increase in strip speed or an increase in mass productivity, the cooling sections should be lengthened. This, however, requires lifting the upper deflecting roller in the cooling column of the melt dip coating unit.

In installations for method 1, the upper deflecting roller is usually at a height of between 30 and 60 m. For method 2, at higher speeds of the strip, the cooling sections must be accordingly lengthened so that the height of the cooling column is possibly increased to 89-90 m. This leads to high investment costs on buildings and foundations.

This would cause a lengthening of the indefinite, unstabilized portion of the strip movement in the cooling column and deterioration of the strip passage, which could cause the appearance of vibrations and adversely affect the quality of the product. The use of other cooling media in the upper part is controversial and has not yet been technologically solved in mass production.

Another problem associated with the electromagnetic seal according to method 2 is that the forces acting on the liquid melt also act, in particular, on the ferrite strip. Elimination of unwanted contact of the strip with the channel due to the magnetic forces of the sealing inductors is possible only by additional measures. This requires additional stabilizing spirals and expensive automatic control technology.

The objective of the present invention is to eliminate the above disadvantages of methods 1 and 2 and the creation of a high-speed installation of coating by immersion in a melt without a cooling column, which combines the minimum possible volume of construction with optimal investment costs and high productivity of the installation with high quality products.

This problem is solved by a method of applying to the surface of a strip of non-ferrous metals or a steel strip of at least one metal coating when passing through at least one container containing a melt, according to which the melt is introduced from the receiving tank into the gap between the rotors rotating in the opposite direction, and the strip is passed from top to bottom through the melt and between the rotors, while the gap on the bottom side is hermetically sealed with rotating permanent magnets fixed to the sides th surface rotating rollers which are arranged within the rotors.

The hermetic container seal by means of rotating permanent magnets is significantly more reliable and cost-effective than the electromagnetic solution and, in addition, much less energy is required for rotation than for electromagnetic seal, which is of particular advantage in the case of blackout.

In a preferred embodiment, it is provided that the rotors are pipes made of heat-resistant, melt-resistant materials, preferably ceramic.

It is also preferable if the melt is fed into the gap by means of a pump for pumping molten metal in a metered amount from a receiving tank.

It may further be provided that the regulation of the thickness of the coating on the metal strip is carried out using rotating permanent magnets.

In addition, it is provided that the strip after turning in a heating furnace without access to air, preferably in a protective gas atmosphere, is directed vertically downward through the melt.

In an improved embodiment of the method, it is provided that the coated strip is stabilized with air and / or cooled with water.

Also proposed is a device and its construction for implementing the method, the device for applying to the surface of a strip of non-ferrous metals or a steel strip of at least one metal coating, comprising at least one vessel containing a melt, characterized in that the vessel is formed by the upper and middle spaces between two opposite-rotating rotors with a gap hermetically sealed at the bottom with rotating permanent magnets fixed to the side the surface of the rotating rollers that are located inside the rotors.

Preferably, the rotors are surrounded by a casing to form a protective gas atmosphere.

It is also preferable if the rotor casing is connected to the upper chamber in order to supply a metal strip from above to the rotor casing, as well as to a receiving tank for the melt, while devices for stabilizing the air and water cooling of the strip and a water bath are located below the rotor casing.

The invention is described on the basis of a number of drawings.

Figure 1 is a conventional method for coating a strip.

Figure 2 is an improved coating method according to the prior art.

Figure 3 - method of coating according to the invention, as well as a suitably made high-speed installation for coating by immersion in the melt in action.

Figure 4 - installation of figure 3 in a start state.

Figure 5 - installation of Figure 3 in a stopped state after completion of work.

According to FIG. 3, after deflection in a furnace without air access, the strip moves vertically downward into the vessel in which the melt is located. This container is hermetically sealed from below. For this, forces are necessary, which, however, are not of electromagnetic origin, but are produced using rotating permanent magnets. Hermetic sealing of the melt with permanent magnets is known per se. But only for the case of rectangular channels. This type of channel cannot vary in distance and shape.

In turn, the present invention provides two adjacent rotors 5, 5 ′. The rotors are tubes 6, 6 ′ of heat-resistant, melt-resistant material, preferably ceramic. Inside these pipes 6, 6 ′, the diameter of which can be selected as desired, the rollers rotate, on the side surface of which permanent magnets 4 are fixed. The rotors 5, 5 'can be connected to the melt or, respectively, to the strip. In the state of stopping or starting the installation, the gap 7 can also be closed.

Permanent magnets are significantly more cost-effective than electromagnetic compaction with spirals or inductors, and much less energy is required for rotation than electromagnetic compaction, which is a particular advantage in the event of a blackout.

With permanent magnets, in addition, significantly higher field intensities (factor 3) are possible compared to the electromagnetic method. These higher field strengths or the resulting higher forces are necessary for the cleaning process by adjusting the desired coating thickness on the steel strip. Cleaning in known methods is carried out using additional cleaning nozzles.

In the method according to the invention, additional measures are no longer needed in the framework of magnetic sealing and cleaning, since the region of the narrowest passage of strip 1 through the sealing block is only a few millimeters. Further, the stretch of the strip 1 can be much shorter than in the known methods 1 and 2, since immediately below the sealing block the strip can be immediately cooled in the water bath 9 and retracted. The length of the tension section in the present invention is preferably about 5000 mm, in method 1 it is about 8-10 times longer and in method 2 it is even greater.

Another advantage of the method according to the invention is that the mirror of the molten metal, preferably of the zinc bath, is in the coating region inside the atmosphere of a protective gas, preferably consisting of a mixture of nitrogen and hydrogen, and liquid zinc cannot be oxidized. In the known methods 1 and 2, this can be achieved only through additional measures. In addition, known methods require that the surface of the zinc melt be accessible for certain handicrafts. In the present invention, access to the melt mirror in order to remove oxide particles is not required.

In the exemplary embodiment of FIG. 3, the apparatus for coating a non-ferrous metal strip or steel strip 1 by immersion in a melt is in a state of operation.

The strip 1 arriving for processing passes in the furnace 2 through a tension roller 17 and then through a lock gate 18, which hermetically cuts off the atmosphere of the protective gas from the ambient atmosphere with oxygen, which is immersed in the melt by coating by immersion in the melt.

In the subsequent galvanizing chamber 14, the strip 1 by the guide roller 13 is deflected in a vertical plane relative to the coating section 19. Upon entering the coating section 19, the strip 1 passes vertically from top to bottom through the melt bath 3 held vertically in the gap 7 between the rotors 5, 5 ′ and is thus provided with the necessary coating.

Magnetic forces generated due to magnetic fields or traveling magnetic fields of rotating permanent magnets 4 do not allow the melt 3 to leak down into the gap formed between the spaced apart rotors 5, 5 ′. The rotors 5, 5 ′ are located inside the pipes 6, 6 ′ surrounding them in a coating section 19 surrounded by an outer casing in the form of a channel, in which the rotors 5, 5 ′ are placed with the possibility of changing the distance between them. The rotors are enclosed in pipes 6, 6 ′ of heat-resistant, melt-resistant, in particular non-magnetic material, preferably ceramic.

Permanent magnets 4 rotate inside these tubes 6, 6 ′.

The necessary and constantly replenished melt from the receiving tank 8, where it is brought to the working condition, is pumped into the gap 7 between the rotors 5, 5 ′ using a pump 12 for pumping liquid metal. The strip 1 on which the coating is applied passes through the gap 7 and then the air stabilization device 15, and also thereafter the water cooling device 16.

After passing the water bath 9 and the tension roller 20, the strip 1 is pulled out of the installation for further use or processing.

The remaining figures 4 and 5 show the methods according to the invention

a) in a start-up state and

b) in a state of stop after completion of work.

a) Start state:

- the strip is

- rotors rotate

- the gap between the rotors is closed

- the melt is fed

- The furnace chamber is closed.

b) Stop status after completion of work:

- return of the melt

- rotors rotate

- clearance is closed

- The furnace chamber is open.

Claims (9)

1. The method of applying to the surface of a strip of non-ferrous metals or steel strip (1) of at least one metal coating when passing through at least one container containing the melt (3), characterized in that the melt is introduced from the receiving tank (8) into the gap (7) between the rotors (5, 5 ′) rotating in the opposite direction, and the strip (1) is passed from top to bottom through the melt (3) and between the rotors (5, 5 ′), while the gap (7) tightly sealed on the underside with rotating permanent magnets (4) fixed to the side oh the surface of rotating rollers which are arranged within the rotors (5, 5 '). 2. The method according to claim 1, characterized in that the rotors (5, 5 ′) are pipes (6, 6 ′) of heat-resistant, melt-resistant materials, preferably ceramic. 3. The method according to claim 1 or 2, characterized in that the melt (3) is fed into the gap (7) using a pump (12) for pumping molten metal in a metered amount from a receiving tank (8). 4. The method according to claim 1 or 2, characterized in that the regulation of the thickness of the coating on the metal strip (1) is carried out using rotating permanent magnets. 5. The method according to claim 1 or 2, characterized in that the strip (1) after turning in the furnace (2) for heating without access of air, preferably in a protective gas atmosphere, is directed vertically downward through the melt (3). 6. The method according to claim 1 or 2, characterized in that the strip (1) coated is stabilized by air and / or cooled by water. 7. A device for applying to the surface of a strip of non-ferrous metals or steel strip (1) of at least one metal coating, comprising at least one vessel containing a melt (3), characterized in that the vessel is formed by the upper and middle the space between two counter-rotating rotors (5, 5 ′) with a gap (7) hermetically sealed at the bottom with rotating permanent magnets (4) mounted on the side surface of the rotating rollers that are located inside the rotors (5, 5 ′). 8. The device according to claim 7, characterized in that the rotors (5, 5 ′) are surrounded by a casing with the formation of a protective gas atmosphere. 9. The device according to claim 7 or 8, characterized in that the rotor casing is connected to the upper chamber (14) for the purpose of supplying a metal strip (1) from above to the rotor casing, as well as to a receiving tank (8) for the melt, while below Devices for stabilization by air (15) and water cooling (16) of the strip (1) and a water bath (9) are located on the rotor casing.

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