JPS6173879A - Plating method by vacuum deposition - Google Patents

Abstract

PURPOSE:To reduce considerably the cost of plating by refining an inert gas and reutilizing the same without discarding the inert gas to the outside of a system. CONSTITUTION:A steel strip 1 is annealed and reduced by gaseous H2 in an annealing furnace 2 and enters an inlet side nitrogen replacing chamber 3 where the strip passes through a vacuum sealing device 5 constituted of sealing rolls 4 and is subjected to the pressure reduction during this time. The strip passes through turn-down rolls 6 and is plated in a vacuum deposition chamber 7. The strip passes again through the device 5 and is led out into the atm. air through an outlet side nitrogen replacing chamber 8. The device 5 has plural vacuum chambers 9 from which the gas is evacuated through discharge lines 11 consisting of vacuum pumps 10. The discharged gaseous N2 is fed to a nitrogen refining line 12. The gas is thereupon refined to <=60ppm oxygen concn., 0.2-2% hydrogen concn. and <=-50 deg.C dew point. The refined gaseous N2 is fed to the chamber 26 under the atm. pressure of the device 5. The gaseous N2 is thus cyclically used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for vacuum evaporation plating of steel strips, and more particularly to an improvement in the method for vacuum evaporation plating of steel strips sent through an annealing furnace.

(Prior art) Conventionally, in vacuum evaporation plating, a steel strip is annealed in an annealing furnace in a reducing atmosphere using hydrogen gas (T3m3m gas 5 refs) to obtain an active steel strip surface that can be plated at the same time. The molten metal was evaporated and plated by evacuating the chamber and creating a vacuum in the evaporation plating chamber. In this case, when the gas was evacuated, there was a risk that the vacuum would break and oxygen gas (haegas) would enter the exhaust system, causing an explosion. Therefore, a nitrogen substitution chamber was installed between the annealing furnace and the vacuum chamber, and nitrogen gas (island gas) was introduced to replace the gas with N gas, and the horse gas was evacuated to avoid the risk of explosion.

However, in the conventional method, the gas was exhausted and disposed of outside the system, which resulted in a disadvantage in terms of cost due to the difference in unit consumption.

(Problems to be Solved by the Invention) The present invention solves the drawbacks of the prior art and provides a vacuum evaporation plating method that can purify and reuse inert gas without disposing of it outside the system. This is what I am trying to do.

(Means for Solving the Problems) The present invention provides an inert gas exchange chamber between an inlet side vacuum sealing device in front of a vacuum evaporation plating chamber and an annealing furnace, and an inert gas exchange chamber at an inlet side after the vacuum evaporation plating chamber. An outlet side inert gas exchange chamber is provided between the side vacuum sealing device and the atmosphere, and an atmospheric pressure exchange chamber is provided from the two vacuum sealing devices between the two vacuum sealing devices and the atmospheric pressure chambers of the two vacuum sealing devices. Purification is carried out in an inert gas circulation purification device of a vacuum evaporation plating equipment equipped with an inert gas circulation purification device that circulates inert gas into the chamber and removes water, oil, and oxygen from the inert gas. Oxygen concentration f in the inert gas after 60 ppm or less, hydrogen concentration cL2
~2.0%, and is a vacuum evaporation plating method characterized by controlling the dew point to -50°C or less.

Hereinafter, the present invention will be explained in detail with reference to FIG. 1 showing one embodiment of the present invention.

In FIG. 1, a steel strip 1 is annealed in an annealing furnace 2 and reduced by hydrogen gas (% + 5 to 75%), enters a nitrogen purge chamber 3 on the inlet side while retaining its active surface, and is made up of a seal roll 4. The molten metal (not shown) is evaporated in a vacuum deposition chamber 7 and plated onto a steel strip. Ru. Thereafter, it passes through the vacuum sealing device 5 again and is led out into the atmosphere via the nitrogen substitution chamber 8 on the exit side.

A vacuum sealing device 5 consisting of a plurality of seal rolls has a plurality of vacuum chambers 9, each of which has a plurality of vacuum pumps 10.
It is evacuated by a vacuum evacuation system 11 consisting of.

The nitrogen substitution chamber 3, the vacuum sealing device 5, the vacuum deposition chamber 7, and the outlet side nitrogen substitution chamber 8 are filled with nitrogen gas.

The evacuated nitrogen gas is sent from the vacuum evacuation system 11 to the nitrogen purification system 12. Nitrogen gas that has entered the nitrogen purification system passes through the vacuum tank 13 and Roots blower 14 before being transferred to the heat exchanger 15.
It is further cooled in a cooler 17 using the refrigerant produced by the refrigerator 16, and after water in the nitrogen gas is removed, oil is removed in an oil remover 18. It is then heated and sent to the deoxidizing tower 19.

Hydrogen gas 20 is put into the mixer 21 to remove the enzyme component from the nitrogen gas, the hydrogen gas is mixed with the nitrogen gas, oxygen is removed by the action of the catalyst placed in the deoxidizer tower 19, and the dryer Sent to 22nd. Moisture is further removed by a dryer, the dew point of the nitrogen gas is lowered, and purified nitrogen gas is obtained.

Two dryers may be installed; one operates to lower the dew point, and the remaining dryer is inactive, and performs regeneration work to remove moisture inside the dryer during the downtime. In this regeneration operation, a part of the outlet gas of the deoxidizing tower 19 is used as a regeneration gas, and the moisture-containing nitrogen gas obtained in this operation has its moisture removed in a cooler 25, and is sent under pressure by a Roots blower 23. The dryer is dried by the heater 24, and moisture in the dryer is removed while the dryer is inactive. By continuously circulating the nitrogen in the regeneration circulation circuits of these regeneration devices, idle dryers are regenerated and can be alternately switched, allowing continuous operation of the nitrogen purification system. Further, the moisture accumulated in the cooler 25 is discharged from the system through a drain (tincture valve seal) 32.

The nitrogen gas 27 purified by the nitrogen purification system is sent to the atmospheric pressure chamber 26 of the vacuum sealing device, passes through each stage of the vacuum sealing device 5 again, and is exhausted by the vacuum exhaust system 11, forming a closed cycle. .

Moisture in the nitrogen gas purified by the nitrogen purification system is measured using a moisture meter 28.
, the oxygen concentration is controlled by a fake meter 29, and the temperature is controlled by a thermometer 30. The fake is about 111 ppm or less, and the dew point is about -50.
It is automatically controlled to keep the temperature below ℃.

The purified nitrogen gas contacts the steel strip as it passes through the vacuum sealing device.

In order to introduce the steel strip into the vacuum deposition chamber while maintaining the surface quality that has been reduced and activated with hydrogen gas (4; 5 to 75%) in the annealing furnace and ready for plating, purified nitrogen gas must be used. This is not sufficient in this state, and it is necessary to make it weakly reducing. Therefore, it is necessary to inject extra hydrogen gas into the mixer 21 and manage the hydrogen gas concentration within the range of α2 to 2.0%, and the hydrogen meter 31 controls the amount of hydrogen.

(Functions and effects) (1) By creating a closed cycle circulation circuit in which the evacuated nitrogen gas is not directly discarded into the atmosphere, but is guided to the nitrogen purification system and the purified nitrogen gas is returned to the inlet of the vacuum evacuation device. Since the amount of nitrogen gas consumed is almost zero, the plating cost of vacuum evaporation plating can be significantly reduced.

(2) By adding extra hydrogen gas into the purified nitrogen gas and controlling the amount of hydrogen gas to [1L2~2-0%], the steel strip passing through the vacuum sealing device is able to absorb nitrogen gas and hydrogen gas. It passes through the weakly reducing atmosphere of the mixed gas, thereby maintaining the surface quality that was reduced and activated in the annealing furnace.As a result, vacuum evaporation plating is performed, so the plating It is effective to ensure the plating adhesion strength between the metal and the steel strip.

(Specific example) Plate thickness of steel strip Q, Plate of 84 strip steel @ saa ■ Threading speed 2 o / min Number of vacuum stages of vacuum sealing device 200)' A = /70 j--1 /10 to-L
/1 To-L/at To-z/a, a 1 Toll vacuum displacement 78ONm"/h Nitrogen purification system inlet gas property amount 270 ppm Oil content 1007 hr Water content 205 Yu/hr As a result of circulating purification under the following conditions, An outlet gas with the following properties was obtained.

Nitrogen purification system exit gas property false amount IIL 7 ppm ~ 60 ppm oil amount
O (too small to be measured) moisture content Dew point -50
°C to -70 °C Hydrogen content Q: 2 to 1.5% The steel strip was passed through a vacuum sealing device in a weakly reducing atmosphere containing a mixture of purified nitrogen gas and hydrogen gas, and vacuum evaporation plating was performed.

In the above, FIG. 2 shows the relationship between the adhesion strength of the plated metal (zinc) when the oxygen concentration in the purified nitrogen gas and the temperature of the steel strip are changed. In addition, in order to examine the influence of only oxygen concentration, FIG. 2 shows the results obtained by setting the hydrogen concentration to 0, and the dew point was set to -50°C. In the diagram, the ○ mark is 180'o
A peel test in which Scotch tape was pasted on the t-bent portion resulted in good adhesion strength with no peeling of the plated surface at all, and the mark X indicates poor adhesion that caused peeling in the same test.

As shown in Figure 2, without mixing hydrogen gas into the circulating nitrogen gas,
By changing the oxygen concentration, the adhesion strength between the vacuum-deposited zinc film and the steel strip at each strip temperature was determined as follows:
It can be seen that good results are obtained if the false concentration is controlled to be about j Oppm or less at temperatures between 250'C and 250'C.

When 0.7% hydrogen is mixed under the conditions of the circulating nitrogen gas properties shown in Figure 3 (the dew point is -50°C), the false concentration is 60%.
Even at ppm, the adhesion strength of the zinc film was good. In other words, even if the false concentration is somewhat high, if a weakly reducing atmosphere is created by mixing a small amount of hydrogen gas, zinc plating by vacuum evaporation can provide a sufficient adhesion strength of the film. O1X in the diagram
The marks have the same meaning as in Figure 2.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of an embodiment of the method of the present invention, Fig. 2.5
The figure is a diagram showing the results obtained in Examples of the present invention. Sub-agents 1) Clearance agent Ryo Hagiwara - Procedural amendment June 1985) 7 a

Claims (1)

[Claims] An inert gas exchange chamber is provided between the inlet side vacuum sealing device in front of the vacuum evaporation plating chamber and the annealing furnace, and an inert gas exchange chamber is provided at the inlet side between the outlet side vacuum sealing device after the vacuum evaporation plating chamber and the atmosphere. A gas exchange chamber is provided, and an inert gas is circulated from both vacuum sealing devices to the atmospheric pressure chamber between the two vacuum sealing devices and the atmospheric pressure chamber of the two vacuum sealing devices, and the inert gas is In the inert gas circulation purification device of the vacuum evaporation plating equipment, which is equipped with an inert gas circulation purification device that removes water, oil, and oxygen in the inert gas, the oxygen concentration in the purified inert gas is 60 ppm or less, and the hydrogen concentration is 0. .2 to 2.0%, and a vacuum evaporation plating method characterized by controlling the dew point to -50°C or lower.