JP2505518B2 - Continuous vacuum vapor deposition plating method for strip steel - Google Patents

Description

TECHNICAL FIELD The present invention relates to a continuous vacuum vapor deposition plating method for strip steel, and more particularly to the above apparatus connected to a continuous annealing furnace for strip steel, such as zinc, aluminum, and ceramics. The present invention relates to a method suitable for continuously vacuum-depositing a steel strip on a strip immediately after annealing.

[Conventional technology]

A conventional zinc plating line has been a line in which a coil cold-rolled by a cold rolling mill is unwound by a rewinding machine, passed through a looper, and then an annealed reduction furnace is used for galvanizing.

Further, by improving this molten zinc plating line, a vacuum deposition zinc plating line in which a vacuum sealing device and a vapor deposition device are provided on the rear surface of the annealing reduction furnace of the molten zinc plating line via an inert gas replacement chamber is industrialized. Has been done.

As described above, conventionally, there is no facility for directly introducing a vacuum deposition zinc plating device from a continuous annealing furnace, and an annealing reduction furnace (H ₂ = 15% to 75%, N ₂ = 85 to 25%) in a molten zinc plating line. , Steel strip temperature was 500 ℃ to 800 ℃).

[Problems to be Solved by the Invention]

However, the above-mentioned vacuum deposition zinc plating line that passes the annealing reduction furnace has a slow stripping speed, while the strip steel does not pass through the annealing reduction furnace with a slow stripping speed, which causes vacuum deposition zinc plating. Since suitable steel strip surface properties could not be obtained, productivity was low and cost was high.

In order to solve this, it is considered that the vacuum deposition plating line should be connected to the continuous annealing line having a high sheet passing speed, but this connection technique has the following problems.

(1) Recently, ultra-low carbon steel has been produced, and the continuous annealing furnace can be composed of only heating zone and cooling zone, so there is no need for soaking zone, slow cooling zone and quenching zone. And the processing time is becoming unlimited. However, the heating zone and the cooling zone of the ultra-low carbon steel also have a hydrogen concentration of 2 to 3%, a nitrogen concentration of 98 to 97%, and a dew point of about -20 ° C, so that they have been annealed in the atmosphere of the furnace. Iron oxide on the surface of steel is not sufficiently reduced by hydrogen gas, and when vacuum deposition plating is applied, the adhesion between the plating metal and the strip steel is not sufficient, and there is a problem of peeling of the plating metal. It was

(2) The continuous annealing furnace for strip steel has an enormous capacity and consumes a large amount of hydrogen gas as an atmospheric gas. When the hydrogen gas concentration is increased to 10% or more, the basic unit of hydrogen gas increases. However, the cost will increase. Further, in consideration of prevention of explosion of hydrogen gas, the atmosphere gas in the furnace is usually operated at a concentration of 2-3% of hydrogen within the explosion limit of hydrogen. When operating at a hydrogen gas concentration that exceeds the explosion limit, and if air (oxygen) intrudes and explodes, the capacity of the furnace will be large and the damage to the equipment will be enormous. Therefore, the hydrogen gas concentration cannot be increased above the explosion limit.

The present inventors have solved the above problems and have high productivity,
In addition, as a continuous vacuum vapor deposition plating device that can perform zinc plating etc. at low cost, we replaced the technology that previously connected the vacuum deposition zinc plating equipment to the exit of the conventional annealing reduction furnace. We proposed a device in which a reduction zone for reducing the surface of the strip is additionally provided at the exit of the continuous annealing furnace and a vacuum deposition zinc plating equipment is connected to the continuous annealing furnace (Japanese Patent Application No. 62-300069 (Japanese Patent Application Laid-Open No. 1-300069). 142082)}.

The present invention eliminates the drawbacks of the conventional continuous vapor deposition method for strip steel, suppresses leakage of hydrogen from the reducing chamber, and controls dilution so that the hydrogen concentration in the adjacent chamber does not exceed the explosion limit. Thus, it is intended to provide a highly productive strip vacuum vapor deposition plating method that enables high concentration reduction of hydrogen and, as a result, makes it possible to increase the strip-passing speed of the strip.

[Means for solving the problem]

The present invention provides (1) continuous vacuum vapor deposition plating by sequentially passing (1) a strip steel through a heating zone for annealing, a first cooling zone, a reduction zone, a second cooling zone, an inert gas replacement chamber, a sealing means and a vacuum vapor deposition apparatus. In the above method, the reduction zone is allowed to contain a high concentration of hydrogen of 15% or more, and sealing means for strip steel is provided before and after the reduction zone, and the pressure in the first and second cooling zones is set to When the pressure is always kept higher than the pressure and the hydrogen concentration in the first and second cooling zones exceeds the explosion limit in either case,
Nitrogen gas is supplied to dilute the gas in the first and / or second cooling zones, and a continuous vacuum vapor deposition plating method for strip steel, and (2) heating strip for annealing a strip steel, In a method of performing continuous vacuum deposition plating by sequentially passing through a first cooling reduction zone, a second cooling zone, an inert gas displacement chamber, a sealing means and a vacuum vapor deposition device, a high concentration hydrogen of 15% or more in the first cooling reduction zone. And a means for sealing the steel strip before and after the first cooling / reduction zone to keep the pressures in the heating zone and the second cooling zone higher than the pressures in the first cooling / reduction zone, and And the hydrogen concentration in the second cooling zone exceeds the explosion limit in either case, nitrogen gas is supplied to dilute the gas in the heating zone and / or the second cooling zone. It is a continuous vacuum deposition plating method.

The method of the present invention can be applied not only to zinc plating but also to vacuum deposition of aluminum, ceramics or the like.

[Action]

To reduce the strip steel to a surface texture suitable for deposition plating,
A strip steel temperature of 500 ° C or higher is required, and this strip steel temperature can be secured in the cooling zone of the continuous annealing furnace described above. If the holding zone in the middle of this cooling process is used as a reduction zone, the strip steel is subjected to a reduction treatment in a continuous annealing furnace at a temperature of about 600 ° C. in a high hydrogen concentration atmosphere, and a surface suitable for vapor deposition plating. It becomes a property.

Therefore, in the present invention, the cooling zone essential to the continuous annealing furnace for the strip steel is the first cooling zone, and the reduction zone is provided so as to be located inside the continuous annealing furnace at the first cooling zone outlet, or The cooling zone essential to the above continuous annealing furnace is provided with a reducing function to form the first cooling reduction zone.

In the present invention having such a configuration, in the continuous annealing furnace, the steel strip heated to a high temperature in the heating zone of the furnace,
In the above-mentioned first cooling zone, it is cooled to, for example, about 500 to 550 ° C, and then it is held in the above-mentioned reduction zone for about 10 to 7 seconds, or in the above-mentioned first cooling and reduction zone, for example, to about 500-550 ° C. Meanwhile, the oxide film on the surface of the steel strip is reduced by being treated with a reducing gas for about 10 to 7 seconds.

As described above, in the present invention, since the reduction of the strip steel is performed in the continuous annealing furnace, not only the thermal efficiency is better than that of the device provided with the reduction zone at the outlet of the previously proposed continuous annealing furnace, but also the reduction zone is reduced. It can be shortened (In the previously proposed device where the reduction zone is outside the annealing furnace, in order to maintain the strip steel at the temperature required for reduction, heating of the reducing high hydrogen concentration gas and the zone by the heating gas It may be necessary to secure a heating zone for steel).

Also, in connection with this shortening, it is possible to maintain the reducing function in the cooling zone essential for the continuous annealing furnace.

Further, the present invention in which the reduction zone or the first cooling reduction zone is provided inside the continuous annealing furnace can be preferably applied when the furnace is newly installed or when the existing furnace has a space on the outlet side.

The strip steel from which the oxide film on the surface is reduced and removed as described above is cooled by the gas jet in the second cooling zone provided at the exit of the continuous annealing furnace. Then, after passing through an inert gas substitution chamber and a plurality of vacuum sealing devices, it is guided to one or more vacuum vapor deposition devices, the surface oxide film is reduced, and the surface state suitable for vacuum vapor deposition is applied to the strip steel. Is vapor-deposited on one side or both sides.

〔Example〕

An embodiment of the device of the present invention in which a first cooling zone and a reduction zone are provided will be described with reference to FIG.

In the apparatus of the present invention, as shown in FIG. 1, the cooling zone 2 on the rear surface of the heating zone 1 essential to the continuous annealing furnace is used as the first cooling zone, and the rear surface of the first cooling zone 2 is also the continuous annealing. A reduction zone 3 is provided in the furnace. A gas-tight seal device 4 is provided at the inlet of the reduction zone 3. A gas-tight sealing device 4 is also provided at the outlet of the continuous annealing furnace, that is, at the outlet of the reduction zone 3 described above. Together with the sealing device 4 on the inlet side, the atmosphere gas of the reduction zone 3 having a high hydrogen concentration is First cooling zone 2 above
Also, consideration is given so that a large amount does not flow into the second cooling zone 5 provided on the rear surface of the outlet of the continuous annealing furnace.

An outlet is provided above the second cooling zone 5, a furnace atmosphere gas sealing device 4 ′ and a bridle 6 are connected, and a sealing device 7
The inert gas replacement chamber 8 is provided via the above, and further connected to the vacuum sealing device 10 via the sealing device 7 and the centering roll 9, and the first vapor deposition device 11 and the second vapor deposition device 12 are connected to the rear surface thereof.

After that, vacuum seal device 10, cooling device 13, alloying treatment furnace
A winding device of a known means is connected via 14 and the cooling tower 15. That is, water quench 17, squeeze roll
A winder 27 is connected via 18, a dryer 19, a looper 23, a skin pass mill 25, and the like.

20 is a centering roll, 21 and 28 are deflector rolls, 22 and 24 are bridles, and 26 is a shear.

Next, the operation of the device of the present invention configured as described above will be described.

By passing through the atmosphere gas having a high hydrogen concentration in the reduction zone 3 after passing through the heating zone 1 and the first cooling zone 2 which are essential for annealing,
The iron oxide on the surface of the steel strip is reduced and adjusted to an active surface texture suitable for deposition plating. Next, the strip steel 16 'is guided to the sealing device 4'from the upper part of the final pass of the second cooling zone 5, and the bridle 6, the sealing device 7, the inert gas replacement chamber 8, the sealing device 7, the centering roll 9, the vacuum sealing device are provided. After passing through 10, the first vapor deposition device 11 performs vapor deposition plating on one surface of the strip steel 16 ′, and the second vapor deposition device 12 performs vapor deposition plating on the remaining surface, and then the vacuum sealing device 10, the cooling device 13, Deflector roll
28, through the alloying treatment furnace 14, the cooling tower 15, and the deflector roll 28, it is led to the water quench 17. afterwards,
It is wound by a winder 27 through a squeezing roll 18 to a shear 26 of a known means.

When the strip steel is only annealed continuously without vapor deposition plating, the heating zone 1 as the annealing furnace, the first cooling zone 2,
The sealing device 4, the reduction zone 3 (in this case, the atmosphere gas in the reduction zone 3 is used at a hydrogen concentration of 2 to 3% or less), the sealing device 4, and the strip steel 16 passed through the second cooling zone 5 , Sealing device 4 ″, water quench 17, squeeze roll 18, dryer
19, centering roll 20, deflector roll 21, bridle 22,24, looper 23, skin pass mill 25, shear 26
After that, the winder 27 may wind up.

Further, each part of the device of the present invention shown in FIG. 1 will be specifically described.

(1) Reduction zone 3 Atmosphere of reduction zone 3 is hydrogen gas H ₂ = 15% or more, strip steel temperature
10 seconds or more at 550 ° C or more, H ₂ = 30% or more, strip steel temperature 5
When the temperature is 00 ° C. or higher, a reduction treatment for 7 seconds or more reduces the surface of the steel strip satisfactorily, and the activity suitable for vapor deposition plating is finished in the surface texture. To secure this kind of holding time,
When the line speed is 400m / min, the length of reduction zone 3 is 45-70
About m is enough.

The dew point of the atmospheric gas supplied to the reduction zone 3 is -60.
C. or less and the oxygen concentration is preferably 10 ppm or less.

Further, the atmosphere gas in the reduction zone 3 may be circulated through a blower (not shown) or may be injected from a nozzle (not shown) onto the strip steel. In this case, it is not necessary to cool the circulating gas. Further, in order to control the dew point of the atmospheric gas, it may be circulated through a drier (not shown), but it is preferable to cool the circulated gas to about 100 ° C. or less at the drier inlet in order to improve the drier efficiency.

(2) Gas sealing function Since the hydrogen gas concentration in the reduction zone 3 exceeds the explosion limit of 3%, a sealing device 4 is provided at the inlet and outlet of the reduction zone 3 to separate the reduction zone 3 from other parts. and the first cooling zone 2, the furnace pressure P ₃ of the reducing zone 3, furnace pressure P ₂ of the furnace pressure P ₁ reduction zone 3 of the furnace pressure in the second cooling zone 5 first cooling zone 2 second cooling zone 5 Then, the pressure of each furnace is controlled so that the relationship of 0 <P ₁ > P ₂ <P ₃ > 0 can be maintained.

That is, the device of the present invention is designed so that the hydrogen gas having a high concentration in the reduction zone 3 does not flow into the first cooling zone 2 and the second cooling zone 5, and the hydrogen in the first cooling zone 2 and the second cooling zone 5 is hydrogenated. The concentration is controlled to be 3% or less. In addition, if the hydrogen concentration exceeds 3% and there is a danger of explosion, nitrogen gas is added to dilute it, and when the furnace pressure rises, an atmospheric valve that releases atmospheric gas to the atmosphere (not shown) Is provided.

Moreover, the continuous annealing furnace itself has a gas tight structure.

(3) Second cooling zone 5 The second cooling zone 5 is for adjusting the strip steel temperature to a temperature suitable for vapor deposition plating. That is, the strip steel temperature has a range in which vacuum deposition is possible depending on the kind of the plated metal (for example, zinc is about 190 to 420 ° C., preferably 190 to 420 ° C.).
~ 350, about 200-600 ° C for aluminum, preferably about 200-400 ° C, about 200-1000 ° C for ceramics, preferably about 200-500 ° C). Raise and peel. This cooling device is provided to prevent this.

(4) Inert gas substitution chamber 8 The inert gas substitution chamber 8 is reduced and activated in the reduction zone 3 to maintain the strip steel surface having a surface texture suitable for plating to the surface texture as it is. A weakly reducing atmosphere is preferable, and the hydrogen concentration is maintained at 2% or less.

The pressure of the inert gas substitution chamber 8, when the pressure to P _4, and is controlled to be P ₃ ≧ P _4> 0.

Further, when the hydrogen concentration in the inert gas substitution chamber 8 exceeds 2%, nitrogen gas is added to dilute it, and when the pressure in the inert gas substitution chamber 8 becomes P ₃ ≦ P ₄ , atmospheric gas is released to the atmosphere. An automatic valve (not shown) for that purpose is provided.

The inert gas replacement chamber 8 is connected to the vacuum chambers 11 and 12 via the sealing devices 7 and 10, and if a problem should occur on the vacuum chambers 11 and 12 side, a large amount of hydrogen gas will be generated in the vacuum chambers. 11,12
On the other hand, the pressure in the vacuum chambers 11 and 12 is lower than the atmospheric pressure, the air intrusion rate is higher than in the first cooling zone 2 and the second cooling zone 5, and the explosion risk may be high. It is essential to control the hydrogen concentration in the active gas substitution chamber 8 to be 2% or less as described above.

Next, an embodiment of the device of the present invention in which the cooling zone of the continuous annealing furnace is the first cooling reduction zone will be described with reference to FIG.

As shown in FIG. 2, this apparatus uses a cooling zone 2 ′ on the rear surface of the heating zone 1 essential for a continuous annealing furnace as a first cooling reduction zone,
A gas-tight sealing device 4 is provided at the inlet of the first cooling reduction zone 2 '. A gas-tight sealing device 4 is also provided at the outlet of the continuous annealing furnace, that is, the outlet of the first cooling / reduction zone 2 ', and together with the sealing device 4 on the inlet side, the first cooling / reduction having a high hydrogen concentration is provided. Care is taken to prevent large amounts of the atmosphere gas in the zone 2'from flowing into the heating zone 1 essential to the continuous annealing furnace and the second cooling zone 5 provided on the rear surface of the outlet of the continuous annealing furnace.

Since the device configuration after the second cooling zone 5 is the same as that of the device shown in FIG. 1, the description thereof will be omitted.

However, the first cooling reduction zone 2'and the gas sealing function are slightly different from those in FIG. 1, and thus will be specifically described.

(1a) First cooling reduction zone 2'The atmosphere gas composition of the first cooling reduction zone 2'is H ₂ gas concentration 15
% N ₂ -H ₂ mixed gas, this atmosphere gas is circulated through a jet cooler, injected from a nozzle (not shown) to the steel strip, and the temperature of the steel strip at the outlet of the first cooling reduction zone 2 ′ is increased. Is controlled at 500 to 550 ° C. If the treatment time in the first cooling / reduction zone 2'is 7 to 10 seconds or more, the surface of the strip steel is finished to have an active surface texture suitable for deposition plating.

Further, the above N ₂ —H ₂ mixed gas supplied as an atmospheric gas to the first cooling / reduction zone 2 ′ preferably has a dew point of −60 ° C. or lower and an oxygen concentration of 10 ppm or lower.

(2a) Gas sealing function The hydrogen gas concentration in the first cooling reduction zone 2'is at the explosion limit of 3
%, The sealing device 4 is provided at the inlet and the outlet of the first cooling / reduction zone 2'to separate the first cooling / reduction zone 2'from the other parts, and the heating zone 1 and the first cooling / reduction zone are provided. 2 When the furnace pressure P _3a of the furnace pressure P _2a second cooling zone 5 ', second the furnace pressure of the cooling zone 5 furnace pressure P _1a first cooling reduction zone 2 of the heating zone 1', 0 <P _1a> The pressure of each furnace is controlled so that the relationship of P _2a <P _3a > 0 can be maintained.

As described above, even when the first cooling / reduction zone 2'of FIG. 2 is provided, as in the case of FIG. The gas is designed not to flow into the heating zone 1 and the second cooling zone 5, and the concentration of hydrogen in the heating zone 1 and the second cooling zone 5 is controlled to be 3% or less. If the hydrogen concentration exceeds 3% and there is a danger of explosion,
An automatic valve (not shown) is provided to release nitrogen gas into the atmosphere when nitrogen gas is introduced to dilute it and the furnace pressure rises.

Moreover, the continuous annealing furnace itself has a gas tight structure.

Hereinafter, experimental examples for demonstrating the effect of the present invention will be described.

Experimental Example 1 Using the apparatus shown in FIG. 1, a degreased steel plate (extremely low carbon steel) of 0.8 mm thickness and 100 mm square was exposed to atmospheric gas (hydrogen 3%, nitrogen 97%, dew point -20 ° C) After heating to 750 ℃ for 90 seconds, and then cooling to 550 ℃ in atmosphere gas (hydrogen 3%, nitrogen 97%, dew point -20 ℃), atmosphere gas (hydrogen 15%, nitrogen 85
%, Dew point −40 ° C.) for about 10 seconds at 550 ° C.

After that, the atmosphere gas (hydrogen 3%, nitrogen 97%, dew point-
25 ℃) to 250 ℃, then vacuum pressure 0.05 Torr
Then, zinc was vacuum-deposited on the above to obtain a sample having an adhesion amount of zinc of 30 g / m ² .

This sample was subjected to 180 ° Ot contact bending (the sample was folded in two for close contact), and a Scottish tape was attached to the bent portion to perform an adhesion test. The results of the adhesion test were good, and no peeling of the plating was observed.

Experimental Example 2 After heating and cooling under the same conditions as in Experimental Example 1 using the apparatus shown in FIG. 1, atmospheric gas (30% hydrogen, 70% nitrogen)
%, Dew point −40 ° C.) and the steel plate was kept at a temperature of 560 ° C. for 7 seconds. Then, it was cooled to 250 ° C. under the same conditions as in Experimental Example 1, and zinc was vacuum-deposited at a vacuum pressure of 0.05 Torr.
A sample having a deposited amount of zinc of 60 g / m ² was obtained.

As a result of a peeling test on this sample after 180 ° Ot contact bending as in Experimental Example 1, good adhesion was obtained.

Experimental Example 3 After degreasing 0.8 mm thick x 100 mm square ultra-low carbon steel using the apparatus shown in Fig. 2, the temperature was raised to 90 ° C at about 720 ° C in atmospheric gas (3% hydrogen, 97% nitrogen, -20 ° C dew point). It was heated for 2 seconds and then cooled to 550 ° C. in an atmosphere gas (hydrogen 15%, nitrogen 85%, dew point −45 ° C.) for about 10 seconds.

After that, the atmosphere gas (hydrogen 3%, nitrogen 97%, dew point-
25 ℃) to 250 ℃, then vacuum pressure 0.05 Torr
Then, zinc was vacuum-deposited on the above to obtain a sample with an attached amount of zinc of 20 g / m ² .

As a result of a peeling test on this sample after 180 ° Ot contact bending as in Experimental Example 1, peeling of the plating layer was not observed at all and it was good.

〔The invention's effect〕

As described above in detail, according to the method of the present invention, as compared with the vacuum deposition zinc plating line in which the vacuum sealing device and the vapor deposition device are provided through the inert gas replacement chamber on the rear surface of the conventional annealing reduction furnace, The threading speed can be increased 2 to 4 times.

Therefore, in the method of the present invention, the productivity is improved by 2 to 4 times as compared with the above-mentioned conventional zinc plating line, and there is an effect that the manufacturing cost of the plated steel plate can be greatly reduced.

Further, in the case of the device of the present invention in which the cooling zone essential for continuous annealing is the first cooling zone, the temperature required for reducing the strip steel to an active surface texture suitable for vapor deposition plating is 500 ° C. or higher. It can be easily adjusted simply by cooling in the first cooling zone.

Moreover, since the reduction zone following the first cooling zone is located in the continuous annealing furnace, it is easy to keep the strip steel at the temperature of 500 ° C. or higher, and as a result, the surface properties of the strip steel are increased. Can be reliably maintained in a state suitable for vapor deposition plating.

Thus, in the case of the device of the present invention in which the cooling zone essential for continuous annealing is the first cooling zone and the reduction zone is located in the continuous annealing furnace, it is easy to maintain the strip steel temperature at the above reduction temperature. The thermal efficiency is good, and the reduction zone does not need to be too long, which reduces the installation space and equipment cost.

Further, in the apparatus of the present invention in which the cooling zone essential to the continuous annealing furnace is provided with a reducing function, and this cooling zone is used as the first cooling / reduction zone, it is easy to adjust to the strip steel temperature necessary for the reduction as in the above. Therefore, it is possible to surely make the surface of the strip steel suitable for vapor deposition plating, and it is not necessary to make the length of the first cooling reduction zone too long, and the installation space and the equipment cost are reduced. To do.

In addition, in the present invention, even if an explosion should occur, the damage to the equipment is small, so that the reduction zone or the first cooling reduction zone can be made a highly accurate hydrogen gas atmosphere above the explosion limit. Can improve the activation effect of
Due to its excellent adhesion, a steel strip can be obtained.

In addition, in the method of the present invention, the cooling steel plate and the plated steel plate can be separately manufactured on a single line.

[Brief description of drawings]

1 and 2 are schematic views showing an embodiment of the present invention. 1 ... Heating zone of continuous annealing furnace, 2 ... First cooling zone, 3 ...
Reduction zone, 2 '... 1st cooling reduction zone, 4 ... Sealing device,
5 ... Second cooling zone, 8 ... Inert gas replacement chamber, 10 ... Vacuum seal device, 11 ... First vapor deposition chamber, 12 ... Second vapor deposition chamber

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Nakamura 5 Ishizu Nishi-machi, Sakai City, Osaka Prefecture Nisshin Steel Co., Ltd. Sakai Works (72) Inventor Takehiko Ito 3-4-1, Marunouchi, Chiyoda-ku, Tokyo Nisshin Steel Co., Ltd. (72) Inventor Takuya Aiko 5th Ishizu Nishimachi, Sakai City, Osaka Prefecture Nisshin Steel Co., Ltd. Sakai Works (56) References JP 62-270770 (JP, A) JP 50 -39208 (JP, A) JP 61-250117 (JP, A) JP 54-121242 (JP, A) JP 63-145773 (JP, A)

Claims (2)

(57) [Claims] 1. Continuous vacuum vapor deposition plating is performed by sequentially passing the strip steel through a heating zone for annealing, a first cooling zone, a reduction zone, a second cooling zone, an inert gas replacement chamber, a sealing means and a vacuum vapor deposition apparatus. In the method, the reduction zone contains a high concentration of hydrogen of 15% or more, and a strip steel sealing means is provided before and after the reduction zone,
Nitrogen gas is supplied when the pressure in the first and second cooling zones is always kept higher than the pressure in the reduction zone, and when the hydrogen concentration in the first and second cooling zones exceeds the explosion limit in any one of them. Then, the gas in the 1st and / or 2nd cooling zone is diluted, The continuous vacuum evaporation plating method of the strip steel characterized by the above-mentioned. 2. A method of performing continuous vacuum vapor deposition plating by sequentially passing a strip steel through a heating zone for annealing, a first cooling reduction zone, a second cooling zone, an inert gas replacement chamber, a sealing means and a vacuum vapor deposition apparatus. , Having a high concentration of 15% or more of hydrogen in the first cooling / reduction zone, and providing steel strip sealing means before and after the first cooling / reduction zone to cool the pressure in the heating zone and the second cooling zone to the first cooling When the pressure in the reduction zone is always kept higher and the hydrogen concentration in either the heating zone or the second cooling zone exceeds the explosion limit, nitrogen gas is supplied to supply the heating zone and / or
Alternatively, a continuous vacuum vapor deposition plating method for a strip steel, which comprises diluting a gas in the second cooling zone.