US3121019A - Galvanizing one side of a strip of metal - Google Patents
Galvanizing one side of a strip of metal Download PDFInfo
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- US3121019A US3121019A US90365A US9036561A US3121019A US 3121019 A US3121019 A US 3121019A US 90365 A US90365 A US 90365A US 9036561 A US9036561 A US 9036561A US 3121019 A US3121019 A US 3121019A
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- strip
- metal
- zinc
- galvanizing
- coating
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- 238000005246 galvanizing Methods 0.000 title claims description 19
- 229910052751 metal Inorganic materials 0.000 title description 29
- 239000002184 metal Substances 0.000 title description 29
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 27
- 229910052725 zinc Inorganic materials 0.000 claims description 27
- 239000011701 zinc Substances 0.000 claims description 27
- 238000000034 method Methods 0.000 claims description 20
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 13
- 239000000463 material Substances 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 9
- 239000001569 carbon dioxide Substances 0.000 claims description 8
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 8
- 238000002844 melting Methods 0.000 claims description 5
- 230000008018 melting Effects 0.000 claims description 5
- 238000000576 coating method Methods 0.000 description 25
- 239000011248 coating agent Substances 0.000 description 24
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 11
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 11
- 239000000920 calcium hydroxide Substances 0.000 description 11
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 11
- 235000011116 calcium hydroxide Nutrition 0.000 description 11
- 238000001816 cooling Methods 0.000 description 6
- 238000004140 cleaning Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 4
- 239000011575 calcium Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000002485 combustion reaction Methods 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 3
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical group [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 3
- 239000000347 magnesium hydroxide Substances 0.000 description 3
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 3
- 230000000873 masking effect Effects 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 239000007921 spray Substances 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 229910000019 calcium carbonate Inorganic materials 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 150000004679 hydroxides Chemical class 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical class [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/003—Apparatus
- C23C2/0038—Apparatus characterised by the pre-treatment chambers located immediately upstream of the bath or occurring locally before the dipping process
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/003—Apparatus
- C23C2/0038—Apparatus characterised by the pre-treatment chambers located immediately upstream of the bath or occurring locally before the dipping process
- C23C2/004—Snouts
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
- C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
- C23C2/0222—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating in a reactive atmosphere, e.g. oxidising or reducing atmosphere
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
- C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
Definitions
- the present invention relates to galvanizing, and more particularly to a method of galvanizing one side only of a sheet of steel.
- the process can be carried out either as a batch process on individual sheets, or it can be carried out as a continuous process on strip. In either case, the steps performed on the material are the same.
- the metal is first cleaned so that its surface is suitable for the reception of zinc. Those portions or" the metal not to be galvanized are then coated with a solution of masking material which is dried. Thereafter the metal is heated and dipped in zinc, and when the zinc coating has solidified, the masking material is removed. The surface that was previously covered with masking material is clean and ready for whatever further treatment may be required.
- the single figure of the drawing shows diagrammatically apparatus that can be used for practicing the method.
- the invention can be used with any metal capable of being galvanized, but will be described herein as being used in connection with the continuous galvanizing of low carbon steel in the form of strip.
- a supply roll 1 of strip material that passes over a series of guide rolls, defining a path through which the strip travels to a take-up roll 2.
- a take-up roll 2 Between the supply and take-up rolls that are driven at a suitable speed are located the various instrumentalities that act upon the strip to perform the method.
- the strip After leaving the supply roll, the strip passes through a cleaning tank 3 in which oil, dirt and oxides are removed from its surfaces.
- the side of the strip that is not to be alvanized is then coated with a solution of material which will prevent zinc from adhering to said surface.
- the coating material is one of the alkaline earth hydroxides which include calcium, magnesium, strontium and barium.
- Each of the hydroxides has the same properties as far as the present invention is concerned, and reacts in the same way at substantially the same temperatures.
- the method will be described as being carried out with a solution of calcium hydroxide or slaked lime (Ca(OH) Commercially this is the most, desirable material because it is readily available, easily handled and inexpensive.
- the calcium hydroxide is made in a thin solution with Water so that it can be sprayed in a thin coating on the strip.
- the coating needs only to be thick enough to cover the strip surface. Thicker coatings are not detrimental to the process, they merely require more material than is actually necessary.
- the so-coated strip is then dried. This drying can take place in the air if convenient.
- the strip is passed through an oven 5 at a temperature of about 250 B, which is above the boiling point of the water that is used as a carrier for the lime.
- the strip is then moved through a furnace to bring it to the desired preheat temperature, and simultaneously to react the calcium hydroxide to a dense, hard coating.
- Furnace 6 is preferably of the type shown in Bloom Patent 2,869,846 in which heat in the form of radiant heat is produced by open, cup-shaped burners. Some convention heat is also provided by the hot products of combustion that are liberated in the furnace chamber. The CO released in the products of combustion reacts with the calcium hydroxide on the strip to form CaCO which makes a dense, hard coating on the strip.
- the temperature of the furnace will be maintained at 2200 F. or higher, depending upon the speed of the strip and the temperature to which the strip is to be heated, and with an atmosphere having no free oxygen.
- the temperature to which the strip is raised will depend upon the final properties desired. If the strip is being normalized, it will be heated to about 1600" F.; if annealed, to about 1300 F. If, however, the strip is being heated only for galvanizing, it will be heated slightly above 900 F., since the strip is introduced into the zinc pot at that temperature. This tem perature is sufficiently high to maintain the zinc bath at 850 F. while providing heat to melt pig additions, and to offset radiation pot losses. The amount above 900 F. the strip is heated in furnace 6 must be at least enough to allow for radiation losses between the time the strip leaves the furnace and the time it enters the zinc pot.
- the reaction between Ca(OH) and CO in the products of combustion to form CaCO will take place at about 825 F., so the strip is heated enough to produce this reaction even if it is only being heated for galvanizing.
- the reaction is apparently speeded in the presence of water vapor, which is also present in the products of combustion.
- the decomposition temperature of CaCO appears to be in the neighborhood of 1500 F. Since, however, some time is required for the decomposition to take place, and the strip is cooled as soon as it leaves the furnace, the coating of CaCO is not harmed by the temperature of the strip or the furnace before the cooling takes place.
- the strip When the strip leaves furnace 6, it travels through a housing or duct 7 that is filled with a non-oxidizing atmosphere to protect the strip surface.
- This duct extends into a zinc pot 3 through which the hot strip passes, so that the unprotected side will be galvanized. If the strip Was heated to annealing or normalizing temperature, this housing also acts as a cooling duct to bring the strip temperature down to about 900 F. before entering pot 8.
- the strip After leaving zinc pot 8, the strip is wiped, if necessary, to regulate the thickness of the zinc coating, and is permitted to cool at least sufiiciently for the zinc to freeze. Thereafter the CaCO coating may be left on the strip to protect its surface, or it may be removed from the strip to present a clean surface for further treatment.
- the coaing on the strip may be removed in any suitable manner, such as by washing the strip in water and brushing the coating from the strip.
- a washing tank is shown diagrammatically at 9. It has been found that this coating of CaCO and any oxide that may have been formed on the strip surface beneath the coating on cooling after leaving the zinc pot can readily be removed by passing it through the tank 9, having a cleaning fluid in it which is vibrated by electrical transducers to produce ultrasonic vibrations with a frequency in the neighborhood of 38,000 cycles per second. Upon discharge from the cleaning bath, the strip is wound upon roll 2 or sheared to required sheet lengths for such disposition as is desired.
- metal sheets can be coated on one side with the Ca(OH) or on selected areas of both sides prior to the time they are dipped in a galvanizing pot.
- Tubes can be coated with the solution by suitably shaped spray nozzles on either the inside or outside before being dipped in zinc.
- Castings of various shapes can be coated in selected areas by a spray or brush before being galvanized. Thus the selected areas can be kept zinc-free to facilitate further assembling or finishing operations.
- the method of galvanizing one side of a strip of metal having a melting point above that of zinc which comprises placing on one side of the strip of metal a layer of material comprising an alkaline earth hydroxide, heating said metal to a temperature above the melting point of zinc in the presence of carbon dioxide, moving said metal through a bath of molten zinc, reducing the temperature of the metal to freeze the zinc, removing the layer of material placed on said metal, and continuously performing the above mentioned steps in sequence.
- the method of preparing a carbonate of the class of magnesium carbonate and calcium carbonate which comprises coating a continuously moving strip of metal with a solution of hydroxide of the group consisting of a calcium hydroxide and magnesium hydroxide, heating said coated strip in the presence of CO to a temperature at which the reaction from hydroxide to carbonate takes place, and removing the carbonate from said strip as it is moving.
- the method of coating a desired portion of a metal object with a second metal having a melting point lower than that of said object which comprises covering the portion of the object that is not to be coated with a thin solution of an alkaline earth hydroxide, drying said solution, heating the object in the presence of carbon dioxide sufficiently to cause the hydroxide to react with the carbon dioxide to form an alkaline earth carbonate on the covered portion of the object, dipping the object in a molten bath of the second metal, cooling the object to freeze the second metal, and removing the carbonate.
- the method of galvanizing a portion only of a ferrous metal object which comprises cleaning the object, applying a solution of alkaline earth hydroxide in a thin layer to the portion of the object which is not to be galvanized, drying said coating, heating said object in a nonoxidizing atmosphere in the presence of carbon dioxide to a temperature above 900 F. to react said hydroxide with said carbon dioxide into a hard dense coating of alkaline earth carbonate, moving the object directly from the place of heating through a non-oxidizing atmosphere into a galvanizing bath, and removing the carbonate coating from the object.
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Coating With Molten Metal (AREA)
Description
Feb. 11, 1964 J. 5. BLAY GALVANIZING om: SIDE OF A STRIP OF METAL Filed Feb. 20. 1961 IN V EN TOR. Jw/m J? 5/0 22 443 ATTORNEY.
United States Patent 3,121,019 GALVANIZTNG ONE SIDE (BF A S 0F METAL Justin S. Blay, Ambler, Pa., assignor to Selas Corporation of America, Dresha, Pa, a corporation of Pennsylvania Filed Feb. 29, 1961, Ser. No. 99,365 Claims. (Cl. 117-55) The present invention-relates to galvanizing, and more particularly to a method of galvanizing one side only of a sheet of steel.
There are many applications in which it is desirable to have corrosion resistant properties of zinc on one side of a sheet of metal, while the other side has its original, uncoated surface, to permit paint adherence, for example. In addition, when galvanized sheet is to be spot welded, the zinc adheres to the electrode tips, producing a roughened sheet surface that must be ground to smooth it before further treatment. Presently, however, most gflvanizing of sheet is accomplished by conveying through a pot of molten zinc so that both sides are coated. It is then expensive and dificult, if not impossible, to remove the zinc coating from one side. Therefore, it has not been practical to use galvanized sheet in many applications where its properties would be advantageous.
It is an object of the invention to provide a method of galvanizing one side only of sheet metal. The process can be carried out either as a batch process on individual sheets, or it can be carried out as a continuous process on strip. In either case, the steps performed on the material are the same.
It is a further object of the invention to provide a process by means of which a selected portion or portions only of a metal piece can be galvanized.
In practicing the invention, the metal is first cleaned so that its surface is suitable for the reception of zinc. Those portions or" the metal not to be galvanized are then coated with a solution of masking material which is dried. Thereafter the metal is heated and dipped in zinc, and when the zinc coating has solidified, the masking material is removed. The surface that was previously covered with masking material is clean and ready for whatever further treatment may be required.
The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.
The single figure of the drawing shows diagrammatically apparatus that can be used for practicing the method.
The invention can be used with any metal capable of being galvanized, but will be described herein as being used in connection with the continuous galvanizing of low carbon steel in the form of strip. Referring to the drawing, there is shown a supply roll 1 of strip material that passes over a series of guide rolls, defining a path through which the strip travels to a take-up roll 2. Between the supply and take-up rolls that are driven at a suitable speed are located the various instrumentalities that act upon the strip to perform the method.
After leaving the supply roll, the strip passes through a cleaning tank 3 in which oil, dirt and oxides are removed from its surfaces. The side of the strip that is not to be alvanized is then coated with a solution of material which will prevent zinc from adhering to said surface. This coating can be appli-=d in any usual manner. It is preferred, however, to spray the coating on the strip from a series of nozzles 4 located across the strip.
The coating material is one of the alkaline earth hydroxides which include calcium, magnesium, strontium and barium. Each of the hydroxides has the same properties as far as the present invention is concerned, and reacts in the same way at substantially the same temperatures. For purposes of this description, however, the method will be described as being carried out with a solution of calcium hydroxide or slaked lime (Ca(OH) Commercially this is the most, desirable material because it is readily available, easily handled and inexpensive.
The calcium hydroxide is made in a thin solution with Water so that it can be sprayed in a thin coating on the strip. The coating needs only to be thick enough to cover the strip surface. Thicker coatings are not detrimental to the process, they merely require more material than is actually necessary. The so-coated strip is then dried. This drying can take place in the air if convenient. Preferably, however, the strip is passed through an oven 5 at a temperature of about 250 B, which is above the boiling point of the water that is used as a carrier for the lime. The strip is then moved through a furnace to bring it to the desired preheat temperature, and simultaneously to react the calcium hydroxide to a dense, hard coating.
Furnace 6 is preferably of the type shown in Bloom Patent 2,869,846 in which heat in the form of radiant heat is produced by open, cup-shaped burners. Some convention heat is also provided by the hot products of combustion that are liberated in the furnace chamber. The CO released in the products of combustion reacts with the calcium hydroxide on the strip to form CaCO which makes a dense, hard coating on the strip.
in operation, the temperature of the furnace will be maintained at 2200 F. or higher, depending upon the speed of the strip and the temperature to which the strip is to be heated, and with an atmosphere having no free oxygen. The temperature to which the strip is raised will depend upon the final properties desired. If the strip is being normalized, it will be heated to about 1600" F.; if annealed, to about 1300 F. If, however, the strip is being heated only for galvanizing, it will be heated slightly above 900 F., since the strip is introduced into the zinc pot at that temperature. This tem perature is sufficiently high to maintain the zinc bath at 850 F. while providing heat to melt pig additions, and to offset radiation pot losses. The amount above 900 F. the strip is heated in furnace 6 must be at least enough to allow for radiation losses between the time the strip leaves the furnace and the time it enters the zinc pot.
The reaction between Ca(OH) and CO in the products of combustion to form CaCO will take place at about 825 F., so the strip is heated enough to produce this reaction even if it is only being heated for galvanizing. The reaction is apparently speeded in the presence of water vapor, which is also present in the products of combustion. The decomposition temperature of CaCO appears to be in the neighborhood of 1500 F. Since, however, some time is required for the decomposition to take place, and the strip is cooled as soon as it leaves the furnace, the coating of CaCO is not harmed by the temperature of the strip or the furnace before the cooling takes place.
When the strip leaves furnace 6, it travels through a housing or duct 7 that is filled with a non-oxidizing atmosphere to protect the strip surface. This duct extends into a zinc pot 3 through which the hot strip passes, so that the unprotected side will be galvanized. If the strip Was heated to annealing or normalizing temperature, this housing also acts as a cooling duct to bring the strip temperature down to about 900 F. before entering pot 8.
After leaving zinc pot 8, the strip is wiped, if necessary, to regulate the thickness of the zinc coating, and is permitted to cool at least sufiiciently for the zinc to freeze. Thereafter the CaCO coating may be left on the strip to protect its surface, or it may be removed from the strip to present a clean surface for further treatment.
The coaing on the strip may be removed in any suitable manner, such as by washing the strip in water and brushing the coating from the strip. Such a washing tank is shown diagrammatically at 9. It has been found that this coating of CaCO and any oxide that may have been formed on the strip surface beneath the coating on cooling after leaving the zinc pot can readily be removed by passing it through the tank 9, having a cleaning fluid in it which is vibrated by electrical transducers to produce ultrasonic vibrations with a frequency in the neighborhood of 38,000 cycles per second. Upon discharge from the cleaning bath, the strip is wound upon roll 2 or sheared to required sheet lengths for such disposition as is desired.
it will be apparent from the above description that the method described herein is applicable to the galvanizing of other metal objects as well as strip. For example, metal sheets can be coated on one side with the Ca(OH) or on selected areas of both sides prior to the time they are dipped in a galvanizing pot. Tubes can be coated with the solution by suitably shaped spray nozzles on either the inside or outside before being dipped in zinc. Castings of various shapes can be coated in selected areas by a spray or brush before being galvanized. Thus the selected areas can be kept zinc-free to facilitate further assembling or finishing operations.
While the present invention is described in connection with the galvanizing of strip, and is particularly applicable therewith, it will be apparent that it can be used in the coating of one metal with another when the coating metal will not adhere to the alkaline earth carbonate that is formed in furnace 6. An example of such a coating metal is aluminum.
While in accordance with the provisions of the statutes, I have illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit and scope of the invention set forth in the appended claims, and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.
What is claimed is:
1. The method of galvanizing one side of a strip of metal having a melting point above that of zinc which comprises placing on one side of the strip of metal a layer of material comprising an alkaline earth hydroxide, heating said metal to a temperature above the melting point of zinc in the presence of carbon dioxide, moving said metal through a bath of molten zinc, reducing the temperature of the metal to freeze the zinc, removing the layer of material placed on said metal, and continuously performing the above mentioned steps in sequence.
2. The method of claim 1 in which the alkaline earth hydroxide is calcium hydroxide.
3. The method of claim 1 in which the alkaline earth hydroxide is magnesium hydroxide.
4. The method of galvanizing selected portions only of a ferrous metal object which comprises coating all .of said object but said selected portions with a solution 4 of a hydroxide of the group consisting of magnesium hydroxide and calcium hydroxide, heating said coated object in the presence of CO and water vapor to change the hydroxide to a carbonate, immersing the object in molten zinc, the zinc adhering to all portions of the object except those coated with said solution, and removing the carbonate from said selected portions.
5. The method of preparing a carbonate of the class of magnesium carbonate and calcium carbonate which comprises coating a continuously moving strip of metal with a solution of hydroxide of the group consisting of a calcium hydroxide and magnesium hydroxide, heating said coated strip in the presence of CO to a temperature at which the reaction from hydroxide to carbonate takes place, and removing the carbonate from said strip as it is moving.
6'. The method of coating a desired portion of a metal object with a second metal having a melting point lower than that of said object which comprises covering the portion of the object that is not to be coated with a thin solution of an alkaline earth hydroxide, drying said solution, heating the object in the presence of carbon dioxide sufficiently to cause the hydroxide to react with the carbon dioxide to form an alkaline earth carbonate on the covered portion of the object, dipping the object in a molten bath of the second metal, cooling the object to freeze the second metal, and removing the carbonate.
7. The method of continuously galvanizing one side of a strip of steel which comprises moving the strip through a path, spraying a coat of calcium hydroxide on the surface of the strip not to be galvanized, heating the strip to at least 900 F. in the presence of carbon dioxide, moving said strip through a molten zinc bath, and cooling said strip.
8. The method of continuously galvanizing one side of a strip of ferrous metal which comprises moving said strip through a path, and while it is traveling performing the following operations on it in succession, placing a solution of calcium hydroxide on the side of the strip that is not to be galvanized, drying said solution, heating the strip to at least 900 F. in the presence of carbon dioxide, moving the strip directly and without appreciable loss of heat through a non-oxidizing atmosphere into a galvanizing bath, cooling the strip to freeze the zinc and cleaning the side of the strip that was not galvanized.
9. The method of galvanizing a portion only of a ferrous metal object which comprises cleaning the object, applying a solution of alkaline earth hydroxide in a thin layer to the portion of the object which is not to be galvanized, drying said coating, heating said object in a nonoxidizing atmosphere in the presence of carbon dioxide to a temperature above 900 F. to react said hydroxide with said carbon dioxide into a hard dense coating of alkaline earth carbonate, moving the object directly from the place of heating through a non-oxidizing atmosphere into a galvanizing bath, and removing the carbonate coating from the object.
10. The process of claim 9 in which said alkaline earth hydroxide is calcium hydroxide, and in which said alkaline earth carbonate is calcium carbonate.
References Cited in the file of this patent UNITED STATES PATENTS Re. 23,794 Schur et al Mar. 2, 1954 235,231 Gutzkow Dec. 7, 1880 911,116 CoWper-Coles Feb. 2, 1909 2,559,969 Kennedy July 10, 1951 2,894,850 Greene et al. July 14, 1959
Claims (1)
1. THE METHOD OF GALVANIZING ONE SIDE OF A STRIP OF METAL HAVING A MELTING POINT ABOVE THAT OF ZINC WHICH COMPRISES PLACING ON ONE SIDE OF THE STRIP OF METAL A LAYER OF MATERIAL COMPRISING AN ALKALINE EARTH HYDROXIDE, HEATING SAID METAL TO A TEMPERATURE ABOVE THE MELTING POINT OF ZINC IN THE PRESENCE OF CARBON DIOXIDE, MOVING SAID
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US90365A US3121019A (en) | 1961-02-20 | 1961-02-20 | Galvanizing one side of a strip of metal |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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US90365A US3121019A (en) | 1961-02-20 | 1961-02-20 | Galvanizing one side of a strip of metal |
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US3121019A true US3121019A (en) | 1964-02-11 |
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US90365A Expired - Lifetime US3121019A (en) | 1961-02-20 | 1961-02-20 | Galvanizing one side of a strip of metal |
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Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3398010A (en) * | 1964-08-17 | 1968-08-20 | United States Steel Corp | Masking composition for galvanized metal |
US3647497A (en) * | 1968-11-29 | 1972-03-07 | Gen Electric | Masking method in metallic diffusion coating |
US3928661A (en) * | 1973-06-01 | 1975-12-23 | Phillips Petroleum Co | Selective coating of a substrate with poly(arylene sulfide) |
JPS5310329A (en) * | 1976-07-15 | 1978-01-30 | Nisshin Steel Co Ltd | Oneeside molten plating method and apparatus therefor |
US4177303A (en) * | 1977-04-22 | 1979-12-04 | Dominion Foundries And Steel, Limited | Method of galvanizing a portion only of a ferrous metal article |
US4246865A (en) * | 1977-02-15 | 1981-01-27 | Asahi Glass Company Limited | One side surface molten metallic coating apparatus |
EP0026005A1 (en) * | 1979-07-24 | 1981-04-01 | HODIGAL s.a.s. di Luciano Moroni | Selective hot-dip zinc galvanizing process and chemical product therefor |
US4264652A (en) * | 1978-09-13 | 1981-04-28 | Desire Danese | Method for locally galvanizing a piece of metal |
US4404030A (en) * | 1981-03-27 | 1983-09-13 | Kawasaki Steel Corporation | Anti-plating agent for one-side hot-dip plating process |
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US235231A (en) * | 1880-12-07 | Feedeeick gutzkow | ||
US911116A (en) * | 1907-05-20 | 1909-02-02 | Sherard Osborn Cowper-Coles | Process of inlaying, ornamenting, and case-hardening metallic surfaces. |
US2559969A (en) * | 1950-02-16 | 1951-07-10 | Pittsburgh Plate Glass Co | Method of applying a masking composition to a glass base |
USRE23794E (en) * | 1954-03-02 | Process of producing calcium | ||
US2894850A (en) * | 1958-05-14 | 1959-07-14 | Gen Motors Corp | Method of galvanizing ferrous metal strip |
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Patent Citations (5)
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US235231A (en) * | 1880-12-07 | Feedeeick gutzkow | ||
USRE23794E (en) * | 1954-03-02 | Process of producing calcium | ||
US911116A (en) * | 1907-05-20 | 1909-02-02 | Sherard Osborn Cowper-Coles | Process of inlaying, ornamenting, and case-hardening metallic surfaces. |
US2559969A (en) * | 1950-02-16 | 1951-07-10 | Pittsburgh Plate Glass Co | Method of applying a masking composition to a glass base |
US2894850A (en) * | 1958-05-14 | 1959-07-14 | Gen Motors Corp | Method of galvanizing ferrous metal strip |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3398010A (en) * | 1964-08-17 | 1968-08-20 | United States Steel Corp | Masking composition for galvanized metal |
US3647497A (en) * | 1968-11-29 | 1972-03-07 | Gen Electric | Masking method in metallic diffusion coating |
US3928661A (en) * | 1973-06-01 | 1975-12-23 | Phillips Petroleum Co | Selective coating of a substrate with poly(arylene sulfide) |
JPS5310329A (en) * | 1976-07-15 | 1978-01-30 | Nisshin Steel Co Ltd | Oneeside molten plating method and apparatus therefor |
JPS5624030B2 (en) * | 1976-07-15 | 1981-06-03 | ||
US4246865A (en) * | 1977-02-15 | 1981-01-27 | Asahi Glass Company Limited | One side surface molten metallic coating apparatus |
US4177303A (en) * | 1977-04-22 | 1979-12-04 | Dominion Foundries And Steel, Limited | Method of galvanizing a portion only of a ferrous metal article |
US4264652A (en) * | 1978-09-13 | 1981-04-28 | Desire Danese | Method for locally galvanizing a piece of metal |
EP0026005A1 (en) * | 1979-07-24 | 1981-04-01 | HODIGAL s.a.s. di Luciano Moroni | Selective hot-dip zinc galvanizing process and chemical product therefor |
US4421793A (en) * | 1979-07-24 | 1983-12-20 | Hodigal S.A.S. Di Luciano Moroni | Selective galvanizing process using a calcium carbonate masking composition |
US4404030A (en) * | 1981-03-27 | 1983-09-13 | Kawasaki Steel Corporation | Anti-plating agent for one-side hot-dip plating process |
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