FR2488913A1 - FERROUS LAMINATE COATING BY DIPPING - Google Patents

Abstract

IN A HOT BATH 6 COATING A CONTINUOUS LAMINATE IN FERROUS METAL WITH AN ALUMINUMZINC ALLOY OR OTHER METAL COATING PRODUCT OF THE SAME KIND, THE CONTINUOUS LAMINATE 3 IS SENT FROM AN OVEN UNTIL A GALVANIZING BATH BY PASSING A SHEATH 4 THAT ENDS IN A HOOD 5 WHICH IMMERSES IN THE BATH. WHILE THE CONTINUOUS LAMINATE IS IN THE SHEATH AND IN THE HOOD, IT IS SUBJECT TO A REDUCING GASEOUS ATMOSPHERE. THE GAS CONSISTS OF NITROGEN AND MAY CONTAIN UP TO 15 HYDROGEN. THE GAS TEMPERATURE MAY BE THE ROOM TEMPERATURE. THE GAS PRESSURE IS JUST SUFFICIENT TO ESTABLISH A SLIGHT OVERPRESSION IN THE SHEATH SO THAT THE GAS CAN DIFFUSER THROUGH THE HOOD AND BE QUIET THERE AND IS KEPT SENSITIVELY CONSTANT IN QUANTITY AND COMPOSITION.

Description

The present invention relates to the coating of

  continuous ferrous, strip, metal wire-

  bar or bar, in a way comparable to what was exhibited

  Seen in prior Australian patent 481,508.

  The hot soaking process, subject of said patent

  previous, has largely proven that it satisfies the use

  tion; however, this method is relatively storytelling and sometimes complicated in execution, because it requires the use of a gas heated to at least 400 C; moreover, although the aim of the prior invention is to provide a coating of

  continuous laminate "free from defects, punctures and

  uncoated placement ", and that, by comparison with the methods

  still anterior coating, it contributes very effectively

  For this purpose, experience has shown that the invention

  is not entirely satisfactory to prevent

  punctures and other similar defects from areas not recognized

  clothed. In fact, we find it doubtful whether it is pos-

  able to absolutely eliminate pitting defects.

  Another weak point of the prior invention is that the hood (marked 16 on the drawings of the earlier patent) has a tendency to accumulate, on its internal surface, deposits of zinc and zinc oxide and that it is necessary regularly clean these deposits at relatively frequent intervals (for example, approximately every month). In addition, it is desirable

  use heating elements to heat the laminate

  kept in an annealing oven preceding the hood and these elements

  heaters are usually on. So another in-

  convenient is that the deposits mentioned frequently shorten the heating elements thus requiring

  reparations, which is detrimental in itself and, im

  planned, discontinues a laminate processing process

  tinu which in modern practice. precisely needs to be continuous. The object of the present invention is to overcome or

  to improve the faults mentioned in a simple way, by

  as a method of coating the continuous laminate which eliminates the need for a hot reducing atmosphere, which reduces the volume of gas required, which further reduces pitting and other defects, compared to the results obtained by the practice of the prior invention; and which prevents the formation of zinc or other deposits in the hood

  used either completely or enough to be without

  sequence. The invention consists of a process for coating a continuous laminate, made of ferrous metal, heated in the oven, with an alloy

  aluminum / zinc, or other metallic coating

  maple, comprising the following phases: (a) moving the continuous laminate longitudinally to pass through a protective hood, the end of which exits the continuous laminate plunges into a bath of metal coating product in the molten state, in such a way

  that said outlet end contains a fraction of the over-

  upper side of the coating product,

  (b) maintain inside said hood an atmosphere

  substantially calm reducing gas sphere at least in the vicinity of said outlet end,

  (c) introducing a reducing gas into an outlet sheath

  tie from the oven from which the continuous laminate arrives, sheath arranged upstream

  from said hood and through which said continuous laminate pro-

  sticks in its path towards said hood and in such a way that said gas diffuses into said hood and,

  (d) limit the rate of diffusion of said gas outside the

  said sheath and towards said hood at a rate substantially

  not greater than that which is necessary to maintain sensitive-

  the quantity and composition of the gas in said hood are constant.

  The invention also provides a device for monitoring

See the process described.

  The accompanying drawings represent examples of this device.

  Figure 1 is a side sectional elevation

  trating the outlet duct of a continuous laminate oven, a hood associated with this duct and a bath of coating product at

the molten state.

  Figure 2 essentially shows the right end

  of Figure 1 on a larger scale and with a slight mo-

  dification. -3 - If we refer to Figure 1, a continuous laminate to be coated is identified by the number 3. It progresses through the outlet duct of the oven 4 towards the hood 5 then in the bath 6 of product of molten coating, then in a wiping zone 7 o depositing a coating product in

  excess can be removed by the wiping action of a gas or

  very conventionally. The hood 5 includes an ex-

  exit end of the continuous laminate 5a which plunges into the

  melt of coating which is in the bath 6.

  While the continuous laminate is in the sheath

  4 (the oven itself is not shown, being of

  conventional concept), it is subject to a reduced atmosphere

  gas whose experience has shown that it can be a

  gas mixture composed mainly of nitrogen but which can coel-

  take hydrogen in a proportion not exceeding 15% ej volume of the mixture. Preferably this gas is dehumidified. The reducing gas can be brought into the sheath 4 in any convenient manner; for example by means of a series of inlet nozzles 8 supplied from a supply distributor (9). The gas used or the excess gas can also be led out of the sheath 4 in any convenient way, for example by means of outlets 10 leading to a bypass manifold 11. The gas can be brought into the sheath 4 at any suitable temperature ;

  the ambient temperature is completely satisfactory.

  The sheath 4 contains a certain number of partitions with passages like 12, 13 and 14. The continuous laminate which goes from the oven to the bath, passes through the passages in the partitions, where it is

  enclosed as close as it is compatible with the mechanical game

  sufficient picnic necessary for its passage.

  It will be recognized that there may be a certain loss of gas by countercurrent through the passages of the walls 12 and

  13. This loss is not significant.

  The gas will also diffuse through the wall 14 and

  enter the hood 5 o it serves as make-up gas for

  keep the gas content of the hood and its composition substantially constant. Of course, a certain amount of gas will be lost by entrainment with the continuous laminate when it leaves the hood and there may be very slight gas losses in - 4 -

the hood due to its oxidation.

  Preferably, the gas which enters the outlet duct of the furnace 4 is sufficiently exactly above atmospheric pressure to be sufficient to maintain the overpressure conditions in the outlet duct, but in all cases

  it is possible to control both the arrival and the evacuation

  tion of the gas not only to obtain the mentioned overpressure effect, but at the same time guarantee that the gas which enters the hood is at least sufficient to compensate for the losses

  gas due to leaks or otherwise.

  The gas flow rate introduced into the hood 5 must be

  the minimum input flow which ensures the booster function of-

  in the hood, while preserving the calm state of the gas in the hood, at least in the vicinity of the outlet end of the hood. Arrived at this end, the gas which is about to pass from the duct 4 into the hood 5 is preferably prevented in any convenient manner, for example by using conventional sealing rollers as indicated in 15 or in using deflectors or the like located in the furnace outlet duct near its outlet end of the

continuous laminate.

  Referring to FIG. 2, the arrangement represented therein is virtually the same as that already described, with the exception of the deflectors situated in the vicinity of the junction

sheath 4A and hood 5A.

  Experimental practice of the invention has shown that maintaining the necessary gas conditions in the hood

  is actually obtained, especially when the laminate

  tinu to treat is in the form of a continuous strip whose width is very close to the interior width of the hood, by means of a pair of deflectors as those indicated

in 16 and 17.

  The deflector 16 is an incorporated wall of refractory material which extends transversely to the inlet end of the hood and extends upwards from the floor of the

  hood up to a level just below that of the

mined continuously.

  The deflector 17 can be in the form of a

  beam made of a suitable ceramic fiber material-

  reinforced or other refractory material. This beam can be incorporated but it is preferable that it be mounted on a rotating shaft 18 so as to allow it to be rotated in the position indicated by the dashed lines 17A to make

  cilitate the initial threading of the head end of the laminate oEr-

  held in and through the hood. For the same purpose it is preferred-

  able to provide an access opening in the hood 19. When

  the appliance is in service this opening is closed by a cover

removable key as indicated in 20.

-6 -

Claims (9)

  1. A method of coating a continuous laminate, made of ferrous metal heated in an oven, with a metallic coating product, comprising the following phases: (a) moving the continuous laminate (3) longitudinally to pass through a protective hood (5) whose end (5a) through which the continuous laminate leaves is immersed in a bath of metal coating product in the molten state (6),   in such a way that said outlet end contains a frac-   tion of the upper surface of the coating product, (b) maintain inside said hood (5) a reducing gaseous atmosphere substantially calm at least in the vicinity of said outlet end,   (c) introducing a reducing gas into an outlet sheath   tie from the oven (4) from which the continuous laminate arrives, sheath arranged   upstream of said hood and through which said laminate con-   tinu progresses along its path towards said hood and in such a way that said gas diffuses into said hood and, (d) limit the rate of diffusion of said gas outside of   said duct and towards said hood at a significant rate   no greater than that necessary to keep the quantity and composition of the gas substantially constant in said hood.   2. Method according to claim. 1, characterized by   the fact that said product is an aluminum / zinc alloy.   3. Method according to any one of the claims   1 and 2, characterized in that said reducing gas is a   dehumidified mixture of nitrogen and hydrogen, the amount of hy-   drogen not exceeding 15% by volume of said mixture.   4. Device for implementing the method according to claim 1, characterized in. that it comprises: (a) a continuous laminate heating furnace comprising an outlet sheath (4) of continuous laminate which ends in a hood (5) whose end remote from said sheath (5a)   immersed in a bath (6) of metallic coating product of.   (b) means for advancing said contiguous laminate   bare longitudinally from said furnace, through said sheath, -7-   through said hood and through said bath.   (c) means (9) for supplying said sheath with   reducing gas to maintain an overpressure condition there.   (d) deflector means (16,17) located, for 1'-   essential, at the junction where said duct meets said hood to control the amount of gas entering it the hood.   5. Device according to claim 4, characterized   by the fact that said sheath has a number of partitions   internal sounds (12, 13, 14) arranged transversely relative   port to the sheath, each of said partitions having a passage   to allow said continuous laminate to pass freely through it.   6. Device according to claim 5, characterized in that said deflector means comprise a pair   sealing rollers (15) between which said laminate   tinu advances by moving through said hood and one of the say partitions.   7. Device according to claim 5, characterized in that said deflector means (16,17) comprise a refractory wall (16) which extends across said hood and which extends from the floor of said hood to at a level close to, but below that of a continuous laminate which advances through the hood, as well as a refractory beam (17) which extends across the hood and which extends from   the upper part of the hood down to a level   close calf, but located above that of said laminate   tinu. 8. Device according to claim 7, characterized   by the fact that said beam (17) is mounted on a rotating shaft   nant (18) which extends transversely with respect to said   hood to allow the rotation of said beam and increase   thus ter the distance between said beam and said laminate   tinu. 9. Device according to claim 8, characterized in that said hood has an access orifice (19) formed on it, near said beam, said orifice being provided with a removable cover (20).