DE2313207C3 - Method and device for wiping and equalizing coating metal of a wire or strip coated in the hot dip process - Google Patents

Description

The invention relates to a method and a device for wiping and equalizing Coating metal of a hot-dip coated, in particular hot-dip galvanized, wire or Strip that goes up from the weld pool through one floating on top of the pool, through one to the side Housing limited, possibly flushed by means of a non-oxidizing gas wiping bed Gravel or other hard and inert material pulled through it in the form of free tumbling bodies or grains will.

It was common practice for many years to have zinc coatings on a wire or strip to produce that 4 wire or strip from a bath of molten zinc upwards through tin floating on the bath wiping bed of oil-soaked, Crushed charcoal was pulled through, with the zinc coating then over the bed solidified by cooling in air and / or by a water quench. There were to date, to some extent, various other discrete wiping materials including sand, vermiculite and coke, have been used, but charcoal has generally proven to be more advantageous in this regard proven; accordingly, for many years charcoal was used almost unchanged as a wiping material.

However, the use of a conventional charcoal mop bed has a number of disadvantages, one of which is that coatings of acceptable quality are only relatively slow throughput speeds can be generated; this has the consequence that the weight of the the zinc coating applied to the wire or strip is only controlled to a limited extent can be.

In the applicant's British patent specification 12 56 928 a method is described which involves wiping a hot-dip galvanized wire or strip allows using this method can be used at considerably higher throughput speeds are generated compared to the zinc coatings below Using a conventional charcoal mop bed produced zinc coatings of the same weight and weight generally of better quality. In the cited patent, the application of Mop beds described, which are formed from hard, inert and freely movable bodies, in particular from washed and sorted river sand or river gravel; the air is excluded from these beds that a suitable non-oxidizing gas is continuously passed up through the bed that contains at least a small amount of hydrogen sulfide.

This act of wiping using a non-oxidizing gas containing at least one contains a small amount of hydrogen sulfide or another suitable sulfur-forming gas hereinafter referred to as "gas wiping".

Hot-dip galvanized wires with zinc coatings of various grades are used for various purposes required, whereby each quality class is usually defined as the minimum weight of zinc per unit area Wire surface.

In order to rationalize the use of zinc, the prescribed minimum coating weight are exceeded as little as possible, regardless of the type of coating that should be generated.

It is known that the speed of the Bed conducted wire is the main factor in determining the weight of the zinc coating, though it is It has been shown that when using the gas wiping method mentioned above, the influence of the speed is significantly lower than with the conventional charcoal wiping process. Both procedures will however, increasing the speed also creates a coating of greater weight. However, it is with the conventional wiping method or wiping using charcoal normally not possible to form good quality coatings at high speeds.

The invention is therefore based on the problem - in order to be able to produce coatings of different prescribed weights using a mopping bed made of discrete material - to determine and use other factors which influence the average coating weight and - which is perhaps even more important - the make it possible to reduce the fluctuations in coating weight; such fluctuations are found in practice generally along each wire and on corresponding parts of similar wires which run side by side through the same mopping bed. Therefore, if equals ^; If more shaped coatings can be formed, the average coating weight could also be reduced without individual test results falling below a prescribed minimum. Since zinc is relatively expensive, a reduction in the average coating weight would also result in significant savings in terms of zinc consumption and therefore also in terms of costs.

According to the invention, experiments have now shown that another factor for controlling the coating weight, namely the relevant factor for the present invention, the pressure is - in the following as "Wiping pressure" means - that is exerted by the mopping bed on the coated wire when this emerges from the zinc bath. Namely, an increase in the wiping pressure has a decrease in the Coating weight result, which also applies in reverse.

The wiping pressure can therefore be varied in that a discrete, d. h .. a non-cohesive and individual material with different specificities Weight is used. If, therefore, heavier coatings at a constant drawing speed are required, a material with a lower specific weight can be used, what also applies in reverse. In the same way, when using a material with a higher specific weight, e.g. gravel or coarse sand, coatings with the same average weight, like the coatings produced in a conventional charcoal bed, at increased drawing speeds are generated when the gas wiping method according to the aforementioned pre-publication is applied.

On the other hand, the wiping pressure can also be varied by turning on "of the depth of the bed. According to the invention, however, changes to the bed rail have so far exercised only limited control based on the effects of internal friction between the granules themselves and / or between the granules and the walls of the housing containing the mop bed.

If the depth of the bed is increased in a housing with given dimensions, has it has been shown that the wiping pressure is not adequate increases, but also assumes scattering values, which is perhaps much more characteristic is. It is believed that these frictional effects tend to pull the granules together to connect, are responsible for ensuring that the desired uniformity and density in the arrangement and filling of the granules forming the bed and that these frictional effects contribute to the coating weight Show fluctuations that have arisen in practice under apparently similar conditions.

The invention is therefore also very generally based on the object of eliminating these disadvantages and to provide a method and apparatus to measure the size and fluctuations of the Wiping pressure of such mopping beds to be able to control or control, the fire metallizing, in particular in hot-dip galvanizing.

The characteristics of the method and the device created to solve this problem result from the claims.

In the method according to the invention, the housing delimiting the wiping bed is continuous or vibrated intermittently, thereby making the bodies or grains in dense and uniform State to be maintained.

In addition to this, the top of the housing can also be pressed down by the fact that on the Housing top mounted parts by weight or a pressure plate can be used, which by means of springs or Fluid pressure is operated.

When the invention is used to produce a hot-dip galvanized wire or strip, it comes to pass they are preferably used in combination with the aforementioned gas wiping process.

According to a preferred embodiment of the invention, the bed is a spring-loaded one Enclosed box or other housing that vibrates by means of a corresponding device is displaced; But it is also possible to make the bed vibrate by means of vibrator devices, which have been inserted into the bed or are in engagement with the bed top.

The shaking or swinging of the bed reduces the friction effects in the bed and between the bed and the enclosing housing, so that the bed becomes denser, more uniform and settles in to a greater extent by floating on the molten metal; this has the consequence that the bottom of the bed is pushed further into the bath, increasing the wiping pressure causes.

The reduction in friction between the bed and the housing also enables it to develop of a desired wiping pressure to effectively utilize a greater bed depth. So if a static or stationary mop bed is initially set in vibration, it turns out that the Bed surface is lowered until it reaches a certain

constant lower level at which it remains. It has also been shown that the bed is under such conditions can be set in vibration, in which the material forming the bed after and is carried out from the bottom of the bed at a limited speed which the bed remains largely uniform and tight, the material thus discharged thereby is replaced that either continuously or at appropriate intervals fresh material from the Is added from the top of the bed.

This gradual discharge or pushing out at the bottom of the bed has proven to be extremely beneficial proven to keep the bottom of the bed in a clean condition and thus energetic contributes to the steady maintenance of uniform coating weights; at the same time the Avoid the usual periodic cleaning process in which the material that is on the bottom of the Bed has accumulated must be scraped away. Since the bed, when it is vibrating, is in Is supported or supported to a greater extent by swimming on the bath, is for this reason the Bed bottom depressed. It has been shown, for example, that the bed in this way largely, for example by about 5 cm, can be depressed when river gravel or coarse river sand with the specific gravity of about 2.3 is used. Therefore, if the bottom of the wiper housing in one smaller distance, for example about 1.25 to 1.875 cm, arranged below the bathroom level and the bath level is kept at or near a constant height can affect the bottom layers of the bed to be acted upon to be carried out under the housing and to the surface to swim. This process is followed by a continuous, gradual downward movement of the whole Bed, which in this way is kept constantly in a clean and mobile condition.

The preferred discharge speed for a gravel bed is in the size range from about 25 to 50 mm Bed depth / h as this has been found to be sufficient to keep the bed in a clean condition, though of course, higher discharge speeds can also be used, but without this has a noticeable effect on the filling of the bed When using gravel, however, discharge speeds which were considerably above 100 mm / h, in some cases a reduction in the filling space resulted in "■ - - ·

Experiments have shown that both the compression of the bed and the questioning within white? 'Frequency and amplitude ranges' can be achieved £ Thus, with gravel beds with a frequency in the range of 20 to 160 Hz and with small amplitudes of around 35 to 60 ounces, advantageous results can be achieved with regard to bed compaction and limited discharge .-7 * "% '" - · -Zweckmäßigerweise be jedochaus reasons of control and a constant for obtaining results in a presently preferred Schwingungshönen Prodükfionseinheit, the frequencies in the order of between 50 to 110 Hz "and amplitudes have to ven-15OaMn -. ^l '- - ~ * "■ ^r * There has been no indication that the Schwinguhgsnchtuhg represents a critical or significant value," although it does not "exclude the possibility that a certain value might arise for various reasons in special cases Direction of oscillation proves to be more suitable compared to other directions of oscillation. At the present stage, however, beneficial results could be obtained with vertically or laterally disposed single-directional vibrators and also with centrifugal vibrators.

The invention is explained in more detail below with reference to the drawing. This shows in

Fig. 1 shows a device for wiping a hot-dip galvanized Of the wire in a partially cut-open front view,

Fig. 2 in side view as well

is Fig. 3 in plan view, partially cut away according to Line 3-3 in Fig. 2, and

Fig. 4 in diagram the relationships between the vibration strength and the bed compaction and the Deliver.

The device shown in the drawing has a wiper housing 10 which is rectangular in shape and expediently has a height of about 38 to 60 cm, a width or depth of about 10 cm as well as any desired length.

This wiper housing 10, which is open on its upper side and on its underside, extends over a bath 12 of molten zinc, with the lower end of the wiper housing 10 in the zinc bath 12 is immersed. The wiper housing 10 is mounted in such a way that it vibrates in the required manner can be moved. For this purpose, each end of the wiper housing 10 is at the free ends of support arms 13 attached, which is arranged approximately horizontally and in turn with its other opposite end are each attached to a rigid support 130. The wiper housing 10 contains a Wisrhbett 14 from a suitable discrete material, preferably washed and sorted river gravel, on the melted Zinc floats When the device is in operation, it will be spaced a desired number of times wires 16 arranged to one another at constant speed vertically upwards through the Mop bed 14 pulled, by means of a conventional, not shown winding or winch frame.

For this purpose, the wires 16 run from wheels, not shown, to rollers 18, which in the usual way are immersed in the zinc bath 12 below the wiper housing 10.

The wiper housing 10 shown is designed in such a way that that the above-mentioned gas wiping process

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For this purpose, the rear wall 10 of the wiper housing lOjpinen inner 'cavity 20 on which at its underWErideTnitnäem interior., the wiping

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entire length deVWschgehäuseslO A horizontal extending to der.-Mfebirand'iqioberhälb ^ there cavity 20 mounted rotor ¹ is engaged with the HiM space 20 via a "-in def wall of the pipe 22 provided in slot connection; at least one end of the tube 22 is oflen so that it can be connected to a gas supply source.

The design of the wiper housing 10 in such a way that a gas is worked into the interior of the housing can, but is not essential to the invention.

As can be seen from FIGS. 1 and 3, there is a device provided, by means of which the wiper housing 10 can be made to vibrate. To this end can any suitable vibrator device can be used. In the illustrated embodiment, for example, a rotary vibrator device driven by means of compressed air is used 30 are provided, which are attached to a center on a side wall of the wiper housing 10 Bracket 32 is arranged. Instead, however, various other commercially available, Unidirectional electromagnetic. Vibrators have been used.

The wiper housing 10 can be made to vibrate either vertically and / or horizontally, specifically in its longitudinal direction and / or in the lateral direction, with no indication whatsoever that the direction of vibration is important up to now. For example, horizontal vibrations of 50 Hz with an amplitude of about 150 μ-m in the longitudinal direction of the wiper housing have proven to be very effective.

If the wiper blade 14, regardless of whether it is made of charcoal, gravel or some other discrete material is composed in this way is subjected to vibration, the granules pack themselves closer together, and the level of the top of the mop bed 14 lowers. This lowering is based partly on the fact that the mop bed 14 is more compact, and partly on the fact that the The bottom of the mopping bed 14 is further lowered below the level of the zinc bath 12, whereby it is then in this Zinc bath 12 almost completely supported. In the absence of any vibration, the mop bed 14 is in contrast to a greater extent due to the friction between the granules of the bed 14 as well as due to the friction supported between the granules and the walls of the housing 10.

In the practice of the invention, several different conditions of the bed become at different Vibration strengths are generated which in turn differ for different materials forming the bed and of various factors such as shape, size, surface character and specific Depend on the weight of the material used. As an example of the individual stages required for the invention are relevant are in Fig. .4 .. different. Test results have been plotted in context with a mop bed made of washed and sorted river pebbles with the specific Weight of approximately 2.3 and the size -6.35mm + 3.175mm was composed.

The apparent from FIG. 4 line A shows the relationship between the frequency and the amplitude at which the compaction of the bed begins, while the curve B indicates those connection, wherein the discharge from the bottom of the bed begins in the shaded area between A and B found the bed therefore in the desired, compressed state, but no discharge of material took place.

From the diagram according to Fi g. 4 it is clear that at very low frequencies or small amplitudes below the lines no noticeable influence on the bed results in At or near this line of represented by A frequencies and amplitudes, however, a lowering of the surface and the top of the bed shows that the bed sits down and becomes thicker. If the frequency and / or amplitude is increased further, little, if any, change can be observed in the bed until curve B is reached, whereupon discharge begins, resulting in a gradual decrease in the bed surface and discharged bed-forming material the surface of the zinc melt in the vicinity of the wiper housing 10 can appear.

If the frequency and / or amplitude is increased even further, the discharge speed also increases, until it becomes too big for practical purposes, and so does the bed becomes less dense.

Therefore, within the hatched area of the diagram according to FIG. 4, there is a wide range of frequencies and amplitudes, which leads to a yield of coatings which, characteristically, have a lower weight and are more uniform ^. nd as such coatings produced under similar conditions without any vibration. It is possible by adjusting the frequency and the amplitude to a point on or above curve B. To set conditions in which the advantage of a lower coating weight can be combined with a certain discharge rate or rate that keeps the bed clean without, however, at the same time emptying it too quickly. A sufficient discharge rate or rate is, for example, that which results in a lowering of the top of the bed at a rate of about 2.5 to 5.0 cm / h.

In addition, a modified method was used according to the invention, which is also known as has proven extremely effective. Here, the housing is within the hatched area of the diagram according to FIG. 4 a continuous oscillation

4c embossed. The level or strength of this Vibration has the advantage of a reduced coating weight, but does not ensure that it is the automatic discharge results in the self-cleaning effect. However, if this vibration an intermittent oscillation with a higher amplitude is superimposed, for example with an amplitude of about 1 mm, the gravel can be carried out through this. The results achieved hereby are generally similar to those that result when the bed vibrates under conditions

"· ': Is offset, which are represented by a point above and near the" curve B. Depending on the particular arrangement, this method using a mixed oscillation may be more expedient than there; first method described above.

Table 1 below shows the coating weight results obtained when ver different bundles of wires with a diameter of 1.47 mm after the gas wiping process were treated with the mopping bed subjected to various vibration conditions. All" other investment conditions have been kept constant and are as follows:

Zinc temperature 455 ° C

Immersion length 3.05 m

Height of the gravel bed 200 cm

Throughput speed ....... 76.1 m / min

609 685/258

fr

10

Table j;

Fre- Ainpli- coating weight (g / m ² ) quenz tude

(Hz) (μτη) max.min. Through- loading standard-

nice rich deviation frequency

Ampli coating weight (g / m ² ) tude

(i " ^m )

^max

^min -

through-

Area stan-

deviation

552.3 292.9 384.5 259.4 54.9

332.6 207.5 277.7 125.1 27.5

360.1 231.9 308.2 128.2 35.7

375.3 250.2 295.9 125.1 27.5

320.4 250.2 292.9 70.2 15.5 350.9 222.8 289.9 128.1 37.2

56 200 381.4 283J 320.4 97.7 20.1

20th 800 32 60 44 150 55 120 72 100

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16Q
10 ()}

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₄ i ₈ , 0

₄₂₇₂

3 ^ 5
_4g2J

286.8

308.2

₃₂₉₅

_3O2 , l
₃₃₅₆

341.7

369.2 3753

350.9

122.1 109.8

88.4

27.7 27.6

23.4 ₂ 5.6

The following Table II contains the results obtained when using different bundles of Wires with a diameter of 2.64 mm in gleieher Were treated with a throughput speed of 45.7 m / min, with the other conditions, apart from the vibration strengths, remained constant, namely:

Zinc temperature 455 ° C

Immersion length 3.05 m

Height of the gravel bed 200 cm

The standard deviation s for η individual observations is usually defined as the mean square deviation of the individual values X ₁ from their arithmetic mean X as follows:

Table 11

Friday Ampli Coating weight min. (g / m ² ) Area Stan- quenz dude dard- (Hz) (/ xrn) Max. through- From white nice chung 396.6 198.4 32.9 369.2 192.3 38.4 595.0 268.5 491.3 97.6 19.8 - - 561.5 268.5 448.6 79.3 21.6 20th 800 366.1 302.1 56 140 34 ⁷ 8 308.2

From the two Tables I and II it is clear that in each case by the fact that the bed under the specified Conditions vibrated, the average coating weight, the The size range between the maximum and minimum coating weight and the Stardard deviation are significant were reduced.

In connection with the described vibration of the mopping bed, a desired wiping pressure can be achieved also achieve that a material with a suitable specific weight to form the mopping bed is selected or that the bed is smaller at its top, for example by applying Pieces of metal, is loaded.

For example, if an unloaded bed composed of gravel of the aforementioned order of magnitude is used, it has been found that changing the throughput rate on a wire of 3.42 mm diameter will produce coatings with a weight in the size range of 240 to 490 g zinc / m « Surface can be formed. If, on the other hand, the top of the same bed was loaded with pieces of cut half-inch steel plate, the size range of the coating weights obtained under the same wiping speeds was 180 to 430 g zinc / m ² surface, which is essentially the same value as it is with results in a non-fumigated mop bed of the same depth, which is composed of zinc sinter

^The invention is used primarily in the production ^{of hot-} dip galvanized wires or strips; however, it is of course also applicable to other metal coatings which can be formed in the same way.

Claims (7)

Claim: L Method for wiping off and leveling off coating metal by a hot dip method coated, especially hot-dip galvanized, wire or strip that comes out of the weld pool upwards through a floating on the bath, laterally limited by a housing, if necessary by means of a non-oxidizing gas ι ο flushed wiping bed made of gravel or another hard and inert material in the form of free tumbling bodies or grains is pulled through, thereby characterized in that the housing delimiting the mop bed is vibrated continuously or intermittently and thereby the bodies or grains are kept in a dense and uniform state. 2. The method according to claim 1, characterized in that the housing of the bed in such a way Vibrations is caused that the materials making up the bed gradually at the bottom of the The bed must be discharged at such a limited speed that the bed is tight and uniform remains, with the discharged material being replaced by new material, which is continuous or intermittent is added at the top of the bed. 3. The method according to claim 2, characterized in that the housing of the bed is continuous vibrated at a frequency and amplitude sufficient to keep the bed dense and uniform To hold the condition without there being any material discharge at the bottom of the bed, and that it is subjected to intermittent vibrations of greater amplitude around those forming the bed Gradually discharge materials. 4. The method according to any one of claims 1 to 3, characterized in that the housing within a frequency range from 20 to 160Hz and within an amplitude range of 35 up to 600 μηι is set in vibrations. 5. The method according to any one of claims 1 to 3, characterized in that the housing is made to vibrate within a frequency range of 50 to 110 Hz and within an amplitude range of 35 to 150 μτα. 6. Processor according to claim 1, characterized in that that the top of the housing by means of a device such as mounted on its top Parts by weight or a pressure plate actuated by springs or by means of fluid pressure, continuously is pressed down. 7. Device for performing the method according to one of claims 1 to 6, with a vertically arranged housing, open on the top and bottom, enclosing the mopping bed, that with its lower end into a bath of molten metal! immersed, marked by a device (13, 130) for the resiliently elastic mounting of the housing (10) and by an oscillating device (T ') for the housing (10).