KR19990063339A - Coated metal strip and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a continuous hot-dip coating apparatus of metal strips. The coating apparatus includes a first coating port for containing a molten bath of a first coating metal and a first metal heating means for heating the metal molten metal in the first coating port. The apparatus also includes a second coating port for containing the molten metal of the second coating metal and a second metal heating means operative to heat the metal molten metal in the second coating port. At this time, the second coating port is shallower than the first coating port, it is positioned so that it can be removed on top of the first coating port. The apparatus also includes a metal strip feeder, which, when the second coating port is removed, feeds the metal strip to and from the top of the first coating port to immerse the metal strip in the molten metal of the first coating metal. When the second coating port is positioned on top of the first coating port, the metal strip is fed into and out of the melt in the second coating port so that the metal strip is immersed in the molten metal of the second coating metal.

Description

Coated metal strip and method of manufacturing the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique of performing protective coating on a metal strip by hot-dip coating, and more particularly, to a protective metal coating of zinc or aluminum-zinc alloy. The present invention relates to a technology for continuous hot-dip coating of steel strips.

In a typical melt coating process, the steel strip passes through an annealing furnace and protects the reducing furnace atmosphere until it enters the bath of coating metal in the coating pot. Will be placed in a state. The coating metal is generally kept molten in the coating port using a heat treatment inductor.

The steel strip may pass through an exit chute or snout immersed in a molten furnace in a long furnace. In this melt the steel strip is conveyed upward from the melt after passing along the perimeter of one or more sink rolls that sink in the melt. After passing the coating bath, the steel strip can pass through a gas knife or a gas wiping station, where the coated surface is a jet of wiping gas. The coating thickness is controlled by the jets.

In a normal galvanizing treatment, the coating metal can be zinc or zinc with about 0.2% by weight of aluminum. This treatment produces a standard zinc-coated steel with a moderate degree of corrosion resistance, at a reasonable cost. Good coating can be achieved, for example, with an alloy of aluminum and zinc with an aluminum content of 25% to 70%.

To provide a highly corrosion resistant strip coated with a zinc-aluminum alloy with a high aluminum content, or to provide a hot-dip plating plant that can be operated in a different manner to date to provide a standard galvanized strip using a good zinc coating. Needs to be. In particular, it provides here a high corrosion resistant strip coated with a zinc-aluminum alloy in a location which is required for standard galvanized strips and thus needs to be in conventional existing plants to provide both types of strips. There are many worldwide plants.

This is not very attractive commercially or technically for using the same coating port to hold both types of coating metal. This inevitably damages the coating metal heating inductor and the refractory material at that port from one type of coating and requires a port to be pumped or emptied entirely upon conversion to another way. It also yields metals that are excessively time consuming and need to be improved. Moreover, it is very difficult to provide a bath of nearly pure zinc in a port pre-contained with a high proportion of aluminum. It is known to provide two stationary coated ports that stand side by side and to provide parts of a furnace and strip feeding line that are flexible for alternating one port or another port. However, this involves difficult technical engineering with excessive utility costs and flexible parts.

It is also known to replace and operate the coating port with a similar substitute port, but this is expensive. Particular arrangements of one of these types are disclosed in US Pat. No. 3,643,627 to Killen et al. This apparatus and method involves the use of a turntable capable of holding two coating ports, such that when a change in coating metal is required, the new coating port is synchronously rotated to an on-line position, where the on-line coating port is Such US patents are disclosed that are externally rotated. Another arrangement of this type is disclosed in US Pat. No. 3,130,068 to Wheattray. This U.S. patent provides for the conversion of one coating port to another coating port as the emptying of the first coating port of the molten coating metal, mounting the second coating port at the coating station, and in the second coating port It is disclosed to pump and continue the coating process again.

It is also disclosed to locate the second coating port in the first coating port. In particular, US Patent 4,645,695 to Gerrard discloses that a second coating port comprising a second metal that is shallower than a deeper first coating port containing a first metal is submerged in the first coating metal in the first port, whereby An arrangement is disclosed in which the metal strip can be coated using a second coating metal instead of the first coating metal without making substantial changes to the setting of the coating line. In this US patent, the second coating port is submerged in the first coating metal to use heating of the first coating metal to maintain the temperature of the second coating metal. There are many disadvantages to using a sinking port-in-port arrangement here. For example, it is difficult to avoid dripping of the first coating metal from the outer surface of the second coating port as it is removed from the first coating port after the coating operation. In addition, contact of the outer surface of the first coating metal with the second coating port accelerates the wear corrosion of the second coating port. In addition, submerging the second coating port in the first coating means introduces impurities on the outer surface of the second coating port in the first coating metal.

The present invention is used for coating strips with a primary coating port having a first coating metal and a second shallower coating port for coating with a second coating metal while the primary coating port retains a molten coating metal on its inductor. To the top of the main coating port.

The present invention relates to a method for coating a strip in a melt coating plant so that the type of coating applied to the strip can be changed.

A strip is applied to the molten metal of the first coating metal in a state in which the molten metal of the first coating metal is contained in the first coating port and the molten metal is kept in a molten state by induction heating means having a metal flow channel communicating with the molten metal. Passing through;

Stopping the coating process of the strip;

Lowering the level of the first coated metal melt in the first coating port to empty the top of the coating port while maintaining communication between the melt and the metal flow channel of the induction heating means;

The upper portion of the first coating port is relatively shallow relative to the first coating port, and the second coating port supported on the first coating port does not come into contact with the molten metal having a low level of the first coating metal. Positioning at;

Forming a molten metal of a second coating metal on the second coating port;

The strip is passed through a second coating metal melt in the second coating port to form a coating strip coated with the second coating metal to provide a method for coating the strip in a molten coating plant.

The metal flow channel of the induction heating means is connected to the inside of the first coating port so as to be located at or below the level of the lowered liquid level of the molten metal in the first coating port, thereby providing the first coating metal and the second coating metal. It is preferable to maintain the first coating port filled with the first coating metal molten metal throughout the strip coating process.

The molten metal of the second coating metal in the second coating port is preferably formed by melting the second coating metal in advance and pouring the molten molten metal into the second coating port.

While the molten coating of the strip is performed in the second coating port, the molten metal is heated by the electrical resistance heating means of the second coating port so that the molten metal in the second coating port is kept in a molten state. desirable.

The electrical resistance heating means includes one or more electrical resistance heating elements disposed in a housing submerged in the second coating metal melt, and is preferably shielded so that the electrical resistance heating elements do not come into contact with the molten metal.

The electric resistance heating element may be of an electric resistance heater type for external use of the second coating port.

While the molten coating of the strip is performed in the second coating port, it is preferable that the molten metal in the first coating port is maintained in a molten state by heating the molten metal by electric resistance heating means. .

Moved along the circumference of one or more first rolls immersed in the melt in the first coating port during coating with the first coating metal, and further immersed in the melt in the second coating port during coating with the second coating metal. It is preferred to move along the perimeter of at least one second roll.

In this case, it is preferable that the first one or more sink rolls are removed from the first coating port before the second coating port is positioned above the first coating port.

More specifically, it is preferable to remove the first sink roll from the first coating port before the step of lowering the liquid level of the molten metal of the first coating metal.

In addition, the present invention is a continuous melt coating apparatus of a metal strip,

A first coating port for containing a molten metal of the first coating metal;

First metal heating means for heating the molten metal in the first coating port;

A second coating port having a shallower depth than the first coating port and containing a molten second coating metal which can be positioned within the top of the first port and is removable therefrom;

Second metal heating means operable to heat the molten metal of the metal in the second coating port;

When the second port is removed, the strip is fed to and from the top of the first coating port so as to submerge the strip in the melt containing the first coating metal, or the second coating port is connected to the first coating port. A continuous strip of metal strip provided with strip feeding means operative to feed the strip into and out of the melt in the second coating port when positioned above the immersion of the strip in the melt of the second coated metal; Provided is a melt coating apparatus.

The apparatus preferably further comprises a furnace for heating the strip prior to being melt coated.

The further furnace, when the strip is fed by the strip feeding means into the melt of the first coating metal or into the melt of the second coating metal without being exposed to the atmosphere, e. It is preferred to include a spout.

The device preferably comprises sink roll means for guiding the strip in the coating melt.

The sink roll means may comprise one or more sink rolls or a pair of sink rolls positioned within the first coating port when the second port is removed to guide the strip in the melt in the first coating port, and the second coating port is When positioned on top of the first coating port, it may include an additional one or more sink rolls locable within the second coating port to guide the strip in the melt at the second coating port.

The one or more second sink rolls located in the second coating port may be smaller than the one or more first sink rolls located in the first port.

Here, a pair of further sink rolls may be located in the second coating port.

The pair of sink rolls is melted to and melted at the second coating port with the strip orientation substantially the same as the first sink roll or rolls when the strip is submerged in the melt at the first coating port. And may be positioned to receive entry and withdrawal of the strip from.

The first metal heating means may comprise an electric induction heater disposed around the first coating port.

The electric resistance heating means may be in the form of an electric resistance heater which is surrounded by the second coating port and extends.

The second coating port has a steel wall, and the electric resistance heater can be mounted on the outer surface of these walls.

The electrical resistance heating means may be in the form of one or more electrical resistance heating means which are used to sink in the molten metal of the second coating metal and are located in a housing that shields the heating element or elements from contact with the molten metal.

According to this arrangement, the electric resistance heating means preferably includes a plurality of heating elements.

The housing is preferably in the form of a plurality of tubes.

The one heating element is preferably located within each tube.

Each tube preferably extends from the sidewall of the port into the port.

Each tube preferably extends through an opening in the sidewall.

Here, a friction fit is made between the opening and the section of the tube located within the opening to function as a working seal in preparation for the escape of the melt from the port.

The opening is tapered inwardly towards the interior of the port, and the section of the tube located within the opening preferably has a corresponding taper.

Each tube preferably includes a flange welded to the outer surface of the side wall.

The electrical resistance heating means preferably comprises a terminal box connected to a power supply.

Preferably, the electric resistance heating means includes electric connection means for connecting the heating element to the terminal box.

Each tube extends from the sidewall of the port into the port, but does not reach the opposite sidewall of the port, so that it is adapted to accommodate thermal expansion of the tube.

In addition to preventing oxidation of the heating element, the tube has a structural malfunction of at least one tube, so that when a molten material penetrates inside the tube (s), a barrier to flow of the molten material ( It is preferred to be at least partially filled with particles, particulates or beads of appropriate material to form a barrier.

Preferably, the material is a ceramic material.

Preferably, the ceramic material is made of magnesium oxide (MgO).

The tube is preferably located adjacent to the base wall of the port.

Further, the tube is preferably located adjacent to the side wall connected to the tube or opposite side wall of the port perpendicular to the side walls.

The tubes are preferably in parallel.

Preferably, the tube is of two groups having a group extending from the first sidewall toward the second sidewall and a second group extending from the second sidewall toward the first sidewall. Do.

1 is a vertical sectional view of a portion of a molten coating plant having a main coating pot, which is used for hot dipping a steel strip with a zinc-aluminum alloy,

FIG. 2 is a plant section view similar to that of FIG. 1, showing a variant of a plant equipped with a second shallow coating port for dip coating a steel strip with a zinc coating, FIG.

3 is a cross-sectional view taken along the line 3-3 shown in FIG.

4 is a detailed plan view showing a first embodiment of a second coating port;

5 is a side view of the second coating port shown in FIG. 4;

6 is a longitudinal cross-sectional view of the second coating port of FIGS. 4 and 5;

7 is a detailed plan view showing another embodiment of the second coating port,

8 is a cross-sectional view of the second coating port cut along the line 8-8 of FIG.

9 is a side view seen from the operator side of the second coating port,

10 is a cross-sectional view taken along the line 10-10 of FIG. 9;

FIG. 11 is an enlarged view of the lower section of FIG. 10 showing the configuration of one of the tubes incorporating the electric resistance heating element and the configuration of positioning the tube in the opening of the side wall of the second coating port;

12 is a side view of the second coating port shown in FIGS. 7 to 11 from the driving side, with the side wall cover of the port removed to illustrate the electrical cable connecting the electric resistance heating element and the terminal box;

FIG. 13 is a side view of a second coating port similar to the elevation of FIG. 12 except that seen from the operator side.

Explanation of symbols for main parts of the drawings

12: molten metal 13: metal flow passage

14: induction heater 15: steel strip

16: furnace exit chute 17: sink roll

18 gas knife 19 support frame

20 loop inductor channel 21 second coating port

28: end support arm 61: heating element

63 tube 67 terminal box

69: opening 71, 73: side wall

77: flange 81: protective plate

85: cover 87: electrical cable / connector

One preferred embodiment will be described in more detail with reference to the accompanying drawings so that the present invention may be more fully described.

The illustrated melt coating plant for coating the steel strip 15 has a main coating port designated by the numeral '11' which contains the molten coating melt 12 of a zinc-aluminum alloy having an aluminum content of 25 to 70%. . The coating port 11 is configured as a large refractory material series having an outer circumferential metal flow passage 13 and an induction heater 14 for holding the molten metal 12 in the liquid state. This induction heater, in use, causes the excitation coil to be fixed such that the melt causes flow from the passages 13 around the loop inductor channels 20 such that it is induction heated and ejected into the melt throughout the passage 13. And a 'U' shaped metal flow channel 20 surrounded by a ring of ferromagnetic steel. An induction-heated pre-melting furnace (not shown) is located next to the coating port 11, and the melt 12 is initially secured by pumping the coating metal pre-melted from the pre-melting furnace into the coating port. After that, melting conditions are maintained by the operation of the induction heater 14.

The steel strip 15 is annealed prior to sinking and heating in the coating port to be flexible for good formability. The strip is removed from the aeration furnace through a furnace outlet chute or spout 16 submerged in the melt in the coating port so that the strip remains in the reducing atmosphere of the heated furnace gas without being exposed to the atmosphere until the time the strip enters the coating melt 12. Supplied.

FIG. 1 shows an apparatus under conditions for immersing and heating strip 15 in a molten metal 12 of zinc-aluminum alloy in coating port 11. For this mode of operation, a large diameter sink roll 17 is fixed to the coating port 11 and the melt 12 is at such a level as to actually fill the coating port so that the sink roll 17 is immersed in the melt. maintain. The strip 15 is passed through the interior of the melt near the sink roll 17 and pulled upward through the melt through a cooling spray (not shown) to ensure complete solidification of the metal coating prior to engagement with these rolls. It moves up and down around the roll (not shown) set to sufficient height.

Upon leaving this molten metal 12, the coated strip passes between a pair of gas knives 18 that eject a wiping gas on the coating side of the strip to control the coating thickness. This gas knife 18 is mounted on the support frame 19 and is easily moved to a retracted or remote position when the plant is inverted for zinc coating in the manner described below. The gas knives 18 are the same as in the conventional configuration. They can also be in the form of float pads fitted with gas knives in the manner disclosed in Australian patent 630281.

Thus, the melt coating plant as disclosed so far and illustrated in FIG. 1 is of conventional construction. However, according to the invention, the plant is switched to achieve a melt coating of the strip with a metal coating of another configuration. This modification results in the positioning of the second, relatively shallow coating port 21 within the upper portion of the main coating port 11 and the relatively large diameter of the sink roll 17 as shown in FIGS. 2 and 3. It includes replacing with the same pair of small diameter sink rolls 22.

The second coating port 21 is composed of a frame 23 around the top and a main tub portion 24 extending to the upper portion of the main coating port 11 so as to rest on the rim of the main coating port 11. The tub portion 24 is positioned at the top of the molten metal remaining in the main coating port 11 at a level sufficient to hold the gallery 13 and is shallow enough for the induction heater 14 to be submerged in the molten metal. The small diameter sink roll 22 can be rotated between the end support arms 28 hanging on the main frame of the device and is completely submerged in the melt 25 of zinc contained in the second coating port. The heated zinc melt can be initially achieved by pumping from a separate pre-melting furnace (not shown) installed next to the main coating port 11. This zinc pre-melting furnace is usually separated from the pre-melting furnace for zinc-aluminum alloys.

This small diameter sink roll 22 is small so as to enter and exit the molten metal 25 in the second coating port 21 with the same strip orientation as pre-applied during melt treatment in the molten metal in the main coating port. Spaced across the floor of the molten portion 24 of the coating pot. Thus, the strip is simply fed through the furnace spout 16 through the furnace spout 16 using the same strip means and is removed between the gas knives 18 in the longitudinal direction by the strip feeding means in the form of turning along the circumference of the roll. .

In order to maintain zinc under melting conditions, the second coating port 21 is provided with electric resistance heating means.

In the embodiment shown in Figs. 4 to 6, the electric resistance heating means is of a type in which the electric resistance heating means is attached to the outer surface of the steel wall of the molten portion 24 of the port. As shown in Figs. 5 and 6, the heater 31 is in the form of an electric resistance heater extending in a parallel configuration around the periphery of the molten portion 24. The second coating port is approximately 21 tonnes of zinc, which requires a heat capacity of up to 300 kilowatts (kWatts) to balance heat loss and maintain the molten zinc in molten state. 3.5m ³ Has a capacity of.

In the embodiment shown in FIGS. 7 to 13, the electrical resistance heating means is located in a tube 63 which is immersed in the melt 25 and extends through the melt 25 in a direction transverse to the direction of movement of the strip. And a continuous array of heating elements 61 (not shown) in parallel. The tube 63 is provided to mainly shield the heating element 61 from contact with the molten zinc of the molten metal 25.

The electrical resistance heating means comprises, for example, a plate 81 which protects the enclosed heating element 61 and the tube 63 from damage due to uncontrolled movement of the strip in the second coating port 21. do.

As shown in Figs. 9, 12 and 13, the heating means comprises a terminal box 67 connected to a power supply (not shown), and a series of electricity connecting the heating element 61 to the terminal box 67. Cable / connector 87.

The tube 63 is located adjacent to the inclined sidewall 83 of the base wall 65 and the second coating port 21. The tube 63 is a group extending through the opening 69 in the working side wall 71 of the coating port 21 and the opening 69 in the drive sidewall 73 of the coating port 21. It is arranged in two groups with other groups extending therethrough. Each tube 63 extends from sidewalls 71 and 73 connected substantially across the coating port 21 to a predetermined spaced position at the opposite side walls 71 and 73. This gap C (see FIG. 7) accommodates the axial thermal expansion of the tube 63 in the melt 25.

Each tube 63 is located in a sidewall opening 69 that is secured to seal between the tube 63 and the sidewalls 71, 73. In addition, this sidewall opening 63 is tapered, and the section 75 (see FIG. 11) of the tube 63 located in the opening 69 has a corresponding taper that contributes to the seal. Moreover, each tube 63 includes a flange 77 (see FIG. 8) welded to a position that contacts the outer surfaces of the side walls 71, 73, thereby contributing additional seals.

The tube 63 prevents the oxidation of the heating element 61, and fuses together upon contact with the molten metal, whereby the molten metal from the molten metal 25 penetrates into the inside of the tube. Filled with MgO granules (not shown) which constitute a barrier to flow.

This coating port 21 includes sidewall covers 81 (not shown) on sidewalls 71 and 73. This cover 85 is intended for contact with the zinc-aluminum alloy at the first coating port 11 and for accidental contact with other components of the plant as the coating port 25 moves into and out of the coating position. It shields the exposed end section of the tube from the resulting damage.

In a typical installation, the second coating port is approximately equivalent to approximately 21 tons of zinc, which requires a heat capacity of up to 300 kilowatts (kWatts) to balance heat loss and maintain the molten zinc in the molten state. 3.5m ³ Has a capacity of.

To switch the device from the state shown in FIG. 1, which is commonly used to coat the strip using a zinc-aluminum alloy, to the state shown in FIG. 2, which is operable to zinc coat the strip using zinc, the following steps are carried out: It is necessary to do

1. Stop dip coating of strip 15 using zinc-aluminum alloy in main coating port 11. The strip is separated and both ends of the isolated strip are supported on the outside of the coating port.

2. The plant withdraws all over the upper mouse of the main port 11, including the sink roll 17 and the gas knife 18.

3. The zinc-aluminum alloy is pumped or drained from the coating port 11 so that the level of the melt in the main coating port is reduced to the level shown in FIG. 2, and the furnace spout 16 is also removed.

4. The second coating port 21 is led to and supported within the top of the main coating port 11 with its lower end adjacent to it besides the excess melt top of the zinc-aluminum alloy in the main coating port.

5. A small diameter sink roll 22 is installed in the second coating port.

6. The furnace spout 16 and gas wiping knife 18 return to their operating position.

7. The molten zinc is pumped from the zinc pre-melting furnace into the second coating port 21.

8. The strip 15 passes through the molten metal through a feed roll and melted through a zinc coating procedure.

9. The electric resistance heating means of the coating port 21 is operated as necessary during the melt treatment to keep zinc in the molten state in the melt 25.

10. The induction heater 14 is operated throughout with reduced strength sufficient to keep the zinc-aluminum metal in the coating port 11 in the liquid state.

The present invention allows for a simple and rapid conversion of the molten coating plant in coatings using different metal or alloy coatings. Since separate coating ports are used for different coating metals, there are no two cross contaminations. Moreover, the present invention enables the conversion of existing plants for double coating operations at reasonable costs.

Claims (18)

In a method of coating a strip in a melt coating plant so as to change the type of coating applied to the strip, A strip is applied to the molten metal of the first coating metal in a state in which the molten metal of the first coating metal is contained in the first coating port and the molten metal is kept in a molten state by induction heating means having a metal flow channel communicating with the molten metal. Passing through; Stopping the coating treatment operation of the strip; Lowering the level of the first coated metal melt in the first coating port to empty the top of the coating port while maintaining communication between the melt and the metal flow channel of the induction heating means; The upper portion of the first coating port is relatively shallow relative to the first coating port, and the second coating port supported on the first coating port does not come into contact with the molten metal having a low level of the first coating metal. Positioning at; Forming a molten metal of a second coating metal on the second coating port; Passing the strip through a melt of a second coating metal in the second coating port to form a coating strip coated with the second coating metal. The metal coating channel of claim 1, wherein the metal flow channel of the induction heating means is connected with an inner side of the first coating port to be located at or below the level of the lowered liquid level of the molten metal in the first coating port. And maintaining the first coating port filled with the first coating metal melt during the entire process of coating the strip with the second coating metal. The method of claim 1 or 2, wherein the forming of the molten metal of the second coating metal in the second coating port comprises melting the second coating metal in advance and pouring the molten molten metal into the second coating port. Characterized in that the strip is coated in a melt coating plant. The method according to any one of claims 1 to 3, wherein the molten metal is heated by electric resistance heating means of the second coating port while the molten coating of the strip is performed in the second coating port. 2. The method of coating a strip in a melt coating plant, further comprising the step of maintaining the molten state in the coating port in a molten state. 5. The electric resistance heating means according to claim 4, wherein the electric resistance heating means includes at least one electric resistance heating element disposed in a housing submerged in the second coating metal melt, and the electric resistance heating element is shielded so as not to contact the melt. Coating the strip in a melt coating plant. The method of claim 4, wherein the electric resistance heating element comprises an electric heater for external use of the second coating port. The liquid level according to any one of claims 1 to 6, wherein the molten metal is heated by an electric resistance heating means while the molten coating of the strip is performed in the second coating port. The method of coating a strip in a molten coating plant, characterized in that it further comprises the step of allowing the lowered molten metal to remain molten. 8. A method according to any one of the preceding claims, wherein during coating with the first coating metal it is moved along the circumference of at least one first roll immersed in the molten metal in the first coating port and the second coating Moving along the circumference of at least one second roll immersed in the molten metal in the second coating port while being coated with the metal. The method of claim 8, further comprising removing the first roll from the first coating port prior to positioning the second coating port on top of the first coating port. How to coat the strips on. 10. The method of claim 9, wherein the first sink roll is removed from the first coating port prior to lowering the liquid level of the molten metal of the first coating metal. In the continuous melt coating apparatus of the metal strip, A first coating port for containing a molten metal of the first coating metal; First metal heating means for heating the molten metal in the first coating port; A second coating port having a shallower depth than the first coating port and containing a molten second coating metal which can be positioned within the top of the first port and is removable therefrom; Second metal heating means operable to heat the molten metal of the second port; When the second coating port is removed, the strip is fed to and from the top of the first coating port so as to submerge the strip in the melt containing the first coating metal, or the second coating port is the top of the first coating port. And a strip feeding means operable to feed the strip into and out of the melt in the second coating port when positioned in the melt to submerge the strip in the melt of the second coating metal. Device. The method of claim 11, And a sink roll means for guiding said strip in said coating melt. The method of claim 12, The sink roll means comprises one or more sink rolls or a pair of first sink rolls positioned within the first coating port when the second coating port is removed to guide the strip in the melt in the first coating port, and the second And when the coating port is located on top of the first coating port, an additional one or more second sink rolls positioned within the second coating port to guide the strip in the melt at the second coating port. Continuous melt coating apparatus for metal strip. The method of claim 13, Wherein said at least one second sink roll located in said second coating port is smaller than said at least one first sink roll located in said first port. The method according to any one of claims 11 to 14, And said first metal heating means comprises an electric induction heater disposed around said first coating port. The method according to any one of claims 11 to 15, And said second metal heating means comprises an electrical resistance heating means. The method of claim 16, The electrical resistance heating means is used by sinking in the molten metal of the second coating metal, characterized in that it comprises one or more electrical resistance heating means located in a housing that shields the heating element or elements from contact with the molten metal. Continuous melt coating of metal strips. The method of claim 16, And said second metal heating means comprises an electric resistance heater extending around said second coating port.