KR940000086B1 - Method for producing mg and galvanized two-layer plating steel sheet with an excellant corrosion resistance and adhesion - Google Patents

Abstract

The steel sheet having excellent corrosion resistance and adhesion property, comprises a lower electroplated Zn layer and an upper Mg layer. The plating method comprises (a) placing Mg vaporising source charged with Mg in a vacuum chamber; (b) evacuating the vacuum chamber to below 1 x 10-4 torr; (c) heating the Zn-plated substrate in a range of 220 to 270 deg.C; (d) degassing the Mg vaporising source by introducing a current; and (f) vacuum depositing the Mg onto the Zn-plated substrate in the region of deposition amt. of from 2 g/m2 to 50 % of Zn-deposition amount.

Description

Manufacturing method of magnesium and zinc alloyed two-layer plated steel with excellent corrosion resistance and adhesion

1 is a cross-sectional view of a zinc-magnesium alloy plated steel sheet.

2 is a cross-sectional view of a magnesium-zinc two-layer coated steel sheet.

3 is a cross-sectional view of a magnesium-zinc alloyed two-layer plated steel sheet according to the present invention.

The present invention relates to a plated steel sheet used as a structural material for automobiles, home appliances, and building materials, and more particularly, to a method for manufacturing magnesium and zinc alloyed two-layer plated steel sheets excellent in corrosion resistance and adhesion.

Steel plate is widely used as structural material of automobiles and home appliances because of its excellent mechanical strength, good workability, and abundant resources. However, steel plate itself is extremely poor in corrosion resistance. Galvanized steel sheet and alloyed galvanized steel sheet have been widely used as structural materials for automobiles. Recently, in order to further improve paintability and corrosion resistance after painting, double layer electroplating steel sheet and flash plating steel sheet were developed. In order to further improve the method, an organic coating is applied on a zinc-nickel alloy plated steel sheet. On the other hand, electroplated steel sheets for home appliances, and hot dip galvanized steel sheets for building materials are generally used.

Electro galvanized steel sheet mainly used for home appliances has the advantage of simple manufacturing process, no restriction on the steel plate and beautiful appearance after painting, but when used as a non-painting material, corrosion resistance is poor. In addition, hot-dip galvanized steel sheet, which is widely used for building materials, is mainly a post-plating material with a coating weight of 40 g / m 2 or more, so it has better corrosion resistance than electro-galvanized steel sheet, but also has poor corrosion resistance when used as a non-painting material. Since the plating is performed by immersing the steel plate in the zinc bath at a high temperature or higher, it affects the mechanical properties of the steel sheet, which leads to the selection of the steel sheet. Therefore, in recent years, research has been made to develop a new plating system that can obtain high corrosion resistance with a smaller adhesion amount.

In the case of automotive materials as well, in recent years, as the anti-rust regulation of the body to extend the service life of automobiles becomes stricter, the high corrosion resistance of the surface-treated steel sheet used as the exterior plate material of automobiles is required, and the new plating system with better corrosion resistance is required. Attempts to find are actively being made. Since the existing hot dip plating method or the electroplating method has a limitation in developing and operating a new plating system, the vacuum deposition method has emerged as a new plating method. Zinc-magnesium alloy plated steel sheet is remarkable as a highly corrosion-resistant surface treated steel sheet for automobiles, home appliances, and building materials using vacuum deposition. Since zinc-magnesium alloy plated steel shows excellent corrosion resistance with a small amount of adhesion compared to conventional alloy plated steel sheets, it is considered that the zinc-magnesium alloy plated steel sheet can greatly contribute to the extension of the service life of the product used for exterior plates of automobiles.

However, in order to apply new surface-treated steel sheet to automobiles, home appliances, structural materials for building materials, etc., not only the corrosion resistance should be excellent, but also the adhesion of the plating layer should be good so that the plating layer does not peel during processing. It should be easy. Zinc-magnesium alloy plated steel sheet has a very good corrosion resistance but has a defect in poor adhesion with the steel sheet.

In order to improve this, it is necessary to form an intermediate plating layer between the zinc-magnesium alloy plating layer and the base steel sheet, and a method of somewhat improving adhesion defects by electroplating zinc having an adhesion amount of about 2 g / m 2 has been developed. To this end, however, the manufacturing process involves the production of a thinly deposited zinc electroplated steel sheet that is not currently produced, and the zinc electroplated steel sheet as a base plate to maintain the optimum composition range of zinc-magnesium and vacuum deposition. There is a disadvantage.

In the present invention, zinc-magnesium vacuum-deposited alloy plated steel sheet is extremely excellent in corrosion resistance but poor adhesion to form an electroplated zinc layer in the lower layer to improve the adhesion, the focus is difficult to stabilize the manufacturing process due to the nature of alloy plating As proposed by the above, vacuum deposition plating magnesium on ordinary galvanized steel plate or zinc vacuum deposition plated steel plate, it has very low corrosion resistance with relatively small adhesion amount, excellent adhesion and processability of plating layer, and easy manufacturing process. To provide a method for producing a magnesium and zinc alloyed two-layer plated steel sheet, the object is.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention provides a method for producing a two-layer plated steel sheet by a vacuum deposition method (vacuum evaporation method), in which a magnesium evaporation source containing magnesium is placed in a vacuum vessel, and an electrogalvanized steel sheet is mounted on the magnesium evaporation source as a small substrate. Evacuating the inside of the vacuum vessel to 1 × 10 ^-4 Torr or less; Heating the substrate to a temperature range of 200-300 ° C. after evacuating as described above; When the heating of the substrate is completed as described above, supplying power to the magnesium evaporation source to degas the evaporation source, and then open the shutter of the evaporation source to open the zinc electrolytic galvanized steel sheet with an adhesion amount ranging from 2 g / m 2 to 50% of the zinc plating layer adhesion. The present invention relates to a method for producing a magnesium and zinc alloyed two-layer coated steel sheet excellent in corrosion resistance and adhesion, comprising the step of depositing on a phosphorus substrate.

In addition, the present invention is a method for producing a two-layer plated steel sheet by a vacuum deposition method (vacuum evaporation method), in which a magnesium and zinc evaporation source loaded with magnesium and zinc are placed in a vacuum vessel, and a cold rolled steel sheet as a substrate is placed on the evaporation source. Mounting, and then evacuating the inside of the vacuum vessel to 1 × 10 ^-4 Torr or less; Heating the substrate to a temperature range of 150-250 ° C. after evacuating as described above; When the substrate is heated as described above, power is supplied to each evaporation source to degas the evaporation source, then the zinc evaporation source is opened, the zinc is vacuum deposited, the zinc evaporation source is closed, and the zinc deposited substrate is removed. Magnesium having excellent corrosion resistance and adhesion, comprising the step of depositing magnesium at an adhesion amount in the range of 2 g / m 2 to 50% of the zinc plating layer deposition on the zinc deposition layer by maintaining the shutter of the magnesium evaporation source after maintaining at 200-300 ℃ A method for producing a galvanized bilayer coated steel sheet.

The present invention also includes a method for producing a magnesium and zinc alloyed two-layer plated steel sheet excellent in corrosion resistance and adhesion by ion plating.

Hereinafter, the method of manufacturing the alloyed two-layer plated steel sheet of the present invention will be described.

Magnesium is a very active metal and cannot be plated by electroplating using an aqueous solution. It can be plated by hot dip, but magnesium alone has excellent corrosion resistance but is not used because of poor weather resistance. In the present invention, since the base plate is not a steel sheet but a galvanized steel sheet, it is difficult to apply the hot dip plating method to the upper layer plating. Therefore, the present inventors used the vacuum evaporation method as a method for plating magnesium in a temperature range in which zinc is not lost through melting or sublimation.

There are various methods of vacuum evaporation, but in the present invention, vacuum evaporation (commonly referred to as ″ vacuum evaporation ″) and ion plating are used. The vacuum evaporation method is the most economical vacuum evaporation method due to its simple manufacturing facilities and high productivity. Compared to the vacuum evaporation method, the ion plating method has a merit in that a manufacturing facility is complicated and productivity is low, but a high quality plating film is obtained.

The present invention is implemented by a conventional vacuum deposition apparatus. In the method for producing an alloyed two-layer plated steel sheet of the present invention by a vacuum evaporation method, firstly, a magnesium-evaporated source loaded with magnesium is placed in a vacuum container and subjected to electric zinc as a base plate. After the plated steel sheet is mounted on the magnesium evaporation source, the vacuum chamber is evacuated to 1 × 10 ^-4 Torr or less.

Examples of the evaporation source include electron beam heating or resistance heating.

Preferably, the small substrate is subjected to ultrasonic cleaning using alkali degreasing and an organic solvent before mounting in a vacuum container. In addition, the argon gas was introduced into the vacuum chamber to maintain an argon gas atmosphere of about 1 × 10 ^{-2 to} 1 × 10 ^-1 Torr, and then a negative voltage of 500-1000 V was applied to the substrate to form a substrate by glow discharge. It is desirable to correct. After evacuating as described above, the substrate is heated to a temperature range of 200 to 300 캜, preferably 220 to 270 캜.

If the temperature of the substrate is 200 ° C or less, the upper plated magnesium does not alloy with the zinc of the lower layer and is present separately. Therefore, the corrosion resistance is not greatly improved, and the adhesion of the upper layer magnesium is poor, and the temperature of the substrate is 300 ° C. In this case, since zinc, which is the main component of the lower layer coating, is not sublimed in the upper layer plating and the effect of the two-layer plating cannot be obtained, it is preferable to maintain the small substrate temperature at 200 to 300 占 폚.

When the heating of the substrate is completed as described above, supply an appropriate amount of power to the magnesium evaporation source to degas the evaporation source, and then open the shutter of the evaporation source to open magnesium in an amount of 20 g / m 2 to 50% of the zinc plating layer adhesion. By depositing on a substrate, the magnesium and zinc alloyed two-layer plated steel sheet of the present invention is produced.

On the other hand, also in the method of manufacturing the magnesium and zinc alloyed two-layer plated steel sheet of the present invention by the ion plating method, a small substrate is mounted in the same manner as the vacuum evaporation method and the inside of the vacuum container is evacuated. Next, after heating the substrate to 200 ° C, the magnesium evaporation source is degassed, the shutter of the evaporation source is opened to evaporate magnesium, and at the same time, a glow discharge plasma is generated by using a hot electron emission filament and an ionizing anode located directly on the evaporation source. By ion plating in the deposition amount range as in the evaporation method, the magnesium and zinc alloyed two-layer plated steel sheets of the present invention are produced.

In the ion plating method, the substrate heating error is kept below 200 ° C and the bias voltage applied to the substrate is from -100V to -600V. Since the temperature of the small substrate increases, the alloy plating layer can be obtained by adjusting the ionization conditions and the bias voltage. If the temperature of the small substrate is set to 250 ° C or higher, the zinc of the lower plating layer may be sublimed and lost during the upper plating. . If the bias voltage applied to the substrate is less than -100V, the ion collision effect is insufficient and alloying is not sufficiently performed, and the adhesion of the upper coating film may be far off. If the bias voltage is higher than -60V, the ion collision effect is extremely severe and the lower coating layer Zinc is likely to be lost due to the sputtering effect.

Phase, in the case of producing the lower layer by the evaporation method has a mode to insert the zinc and magnesium, zinc, and magnesium in the evaporation source in the vacuum chamber, respectively, and then, cold-rolled steel sheet to hold the substrate mounted on the evaporation source, and then, the vacuum chamber 1 × 10 ^-4 Evacuate to under vacuum.

Subsequently, the substrate is heated to 150-250 ° C. when forming the zinc-deposited plating layer, which is the lower layer, and the substrate is heated to 200-300 ° C., preferably 220-270 ° C., when the upper magnesium deposition plated layer is formed. By doing so, various characteristics including adhesiveness are shown well.

Next, power is supplied to each evaporation source to degas the gas, and then a zinc evaporation source is opened to deposit zinc on the substrate, and a zinc evaporation source is shuttered, and a magnesium evaporation source is opened to open the shutter. By depositing magnesium in the deposition amount range, such as magnesium and zinc alloyed two-layer plated steel sheet of the present invention is produced.

In this method, if the deposition temperature of the upper layer of magnesium and the deposition temperature of the lower layer of zinc are set equal, the manufacturing process can be further simplified. Examples of the evaporation source of zinc and magnesium include electron beam heating or resistance heating.

As described above, according to the present invention, an electrogalvanized layer or a zinc deposition plated layer is used as a lower layer, and a magnesium deposition plated layer having an adhesion amount of 2 g / m 2 to 50% of the zinc plated layer deposition amount is an upper layer, and a part of the magnesium deposition plated layer which is an upper layer. Or magnesium and zinc alloyed two-layer plated steel sheet excellent in corrosion resistance and adhesion that is alloyed with a zinc-plated layer of the lower layer is manufactured.

When the alloyed two-layer plated steel sheet prepared according to the present invention is placed in a corrosion atmosphere, the alloying layer of magnesium and zinc is first corroded, and as the alloy layer is corroded, a passivation layer is formed to suppress the progress of corrosion. However, when the adhesion amount of the upper layer of the magnesium deposition plating layer is 2 g / m 2 or less, due to the nonuniformity of the upper plating itself, the alloying layer becomes thinner at the place where the film thickness is thin, and not only an effective passivation film is formed, but also the adhesion of the plating layer is reduced. Therefore, it is preferable that the adhesion amount of the magnesium vapor deposition plating layer which is an upper layer is 50% of the adhesion amount of the zinc plating layer which is 2 g / m <2>-lower layer.

The characteristics of the magnesium and zinc alloyed double coated steel sheets produced according to the present invention will be described in comparison with conventional zinc-magnesium alloy plated steel sheets and magnesium / zinc two-layer coated steel sheets.

The zinc FIG. 1 - for the magnesium alloy plated steel sheet there is the magnesium is most and exists as MgZn ₂ form a MgZn ₂ O ₄ as corrosion in a corrosive atmosphere in progress, MgZn ₂ O _4, once as a dense oxide of styryl Fresnel structure When this is formed, it has a passive role of suppressing further corrosion and thus greatly improves the corrosion protection effect of protecting the substrate. However, the manufacturing process is complicated.

On the other hand, in the magnesium / zinc double layered steel sheet of FIG. 2, zinc and magnesium are present separately, so that the corrosion rate of the plating layer is faster than that of the alloy plated steel sheet, and the adhesion of the upper layer magnesium is poor, but the manufacturing process is an alloy plated steel sheet. It is easier than the manufacturing process of.

Magnesium and zinc alloyed two-layer plated steel sheet prepared according to the present invention, as shown in FIG. 3, when the upper plating temperature, that is, the temperature of the substrate during vacuum deposition is properly controlled, most magnesium is alloyed with zinc, the lower layer zinc-magnesium As a new two-layer plating layer of the alloy layer and the pure zinc layer is formed, not only the adhesion but also the corrosion resistance is as good as that of the zinc-magnesium alloy steel plate, and moreover, only a constant temperature is maintained as compared with the manufacture of the alloy plate steel which must maintain a constant composition. If so, the manufacturing process is easy and the electroplating and vacuum deposition method can be used in combination when necessary to manufacture the lower layer zinc plated layer.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

[Inventive Example 1-3 and Comparative Example 1-2]

An electrogalvanized steel sheet prepared by electroplating zinc on a cold rolled steel sheet having a thickness of 0.7 mm was used as a base plate for alloyed two-layer plating, and the zinc plating amount was 20 g / m 2. The substrate was ultrasonically degreased with acetone and alcohol, charged in a vacuum bath, and evacuated to 1 × 10 ^-5 Torr.

The substrate was heated to 250 ° C. with a resistance heater, and vacuum evaporated plating was carried out by heating and evaporating magnesium having a purity of 99.99% with an electron beam heating evaporation source of 0.05 kw. The deposition rate of magnesium was 0.16㎛ / min, the coating weight was changed in the range of 1-12g / ㎡ as shown in Table 1.

Invention Example 4-5

Both upper and lower layers were manufactured by vacuum evaporation, and the cold rolled steel sheets having a thickness of 0.7 mm were alkali-degreased, ultrasonically washed with acetone and alcohol, charged in a vacuum bath, and evacuated to 1 × 10 ^-5 Torr. The substrate is heated to 200 ° C with a resistance heater, and zinc vapor of 99.9% purity is heated and evaporated by a tantalum resistance heating evaporation source, followed by vacuum evaporation by heating and evaporating magnesium with a purity of 99.99% with an electron beam heating evaporation source of 0.05kw. Plated. As shown in Table 1 below, the coating amount of zinc was 20 g / m 2, and the coating amount of magnesium was 2-4 g / m 2.

Comparative Example 3-4

Comparative Example 3 is a single-layer plated steel sheet vacuum-deposited zinc-magnesium alloy on a cold rolled steel sheet of 0.7 mm thickness, Comparative Example 4 is a two-layer plated steel sheet with a zinc-magnesium alloy vacuum deposition layer as an upper layer and a zinc electroplating layer as a lower layer. .

To evaluate the corrosion resistance of the plated steel sheet prepared according to Inventive Example 1-5 and Comparative Example 1-4 prepared as described above by the salt spray test, after the Ot, 180 ° bend test, the adhesiveness through the tape test, The evaluation results are shown in Table 1 below.

TABLE 1

(Note) Optimal occurrence time: Time until proper occurrence of more than 5% of the total surface area

Evaluation criteria for adhesion: ○ -No bending of plating layer during tape test after bending

Part of the plating layer peeled off during tape test after ×

As shown in Table 1, it can be seen that the inventive example (1-5) is superior in corrosion resistance and adhesion compared to the comparative example (1-4).

Example 2

An electrogalvanized steel sheet prepared by electroplating zinc on a cold rolled steel sheet having a thickness of 0.7 mm was used as a base plate for two-layer plating, and the zinc plating amount was 20 g / m 2. The substrate was ultrasonically degreased with acetone and alcohol, charged in a vacuum bath, and evacuated to 1 × 10 ^-5 Torr. As shown in Table 2, the resistance heating path substrate was heated in a room temperature of −350 ° C. and vacuum-deposited by heating and evaporating magnesium having a purity of 99.99% with an electron beam heating evaporation source of 0.05 kw. The deposition rate of magnesium was 0.16 탆 / min, and the plating deposition amount was 4 g / m 2. The prepared specimens were evaluated for corrosion resistance by the brine section test, and the adhesiveness was also evaluated through the tape test after the Ot, 180 ° bending test, and the evaluation results are shown in Table 2 below.

TABLE 2

(Note) Optimal occurrence time: Time until proper occurrence of more than 5% of the total surface area

Evaluation criteria for adhesion: ○ -No bending of plating layer during tape test after bending

Part of the plating layer peeled off during tape test after ×

As shown in Table 2 above, the inventive example (1-3) in which the magnesium deposition temperature falls within the scope of the present invention is compared with the comparative example (1-5) deposited at a temperature outside the scope of the present invention. It can be seen that excellent.

As described above, the present invention is not only excellent in adhesion and corrosion resistance, but also easy to manufacture process, magnesium and zinc alloyed two-layer also steel plate, which can be formed zinc plating layer of the lower layer by electroplating or vacuum deposition method, if necessary By providing it, there is an effect that can be used more appropriately for products requiring high corrosion resistance and adhesion in automobiles, home appliances and building materials.

Claims (2)

In the method for producing a two-layer plated steel sheet by the vacuum evaporation method, a magnesium-evaporated source loaded with magnesium is placed in a vacuum container, and an electrogalvanized steel sheet is mounted on the magnesium evaporation source as a small substrate, and then the inside of the vacuum vessel is 1 × 10. Evacuating to less than ^-4 Torr; After evacuating as described above, the substrate is degassed at a temperature in the range of 220-270 ° C., and when the substrate is heated as described above, the gas is degassed by supplying power to the magnesium evaporation source. Magnesium and zinc alloyed two-layer plating having excellent corrosion resistance and adhesion, comprising the step of depositing magnesium on a base plate, which is an electro-galvanized steel sheet, by opening the shutter at a deposition amount ranging from 2 g / m 2 to 50% of the zinc-plated layer deposition amount. Method of manufacturing steel sheet. In the method for producing a two-layer plated steel sheet by the vacuum evaporation method, magnesium and zinc evaporation sources loaded with magnesium and zinc are placed in a vacuum vessel and a cold rolled steel sheet is mounted on the evaporation source as a base plate. Evacuating to less than 10 &lt; ^-4 &gt; Heating the substrate to a temperature range of 150-250 ° C. after evacuating as described above; When the heating of the substrate is completed as described above, power is supplied to each evaporation source to degas the evaporation source, and then the zinc evaporation source is opened, the zinc is vacuum-deposited, the zinc evaporation source is closed, and the zinc deposited substrate is removed. After maintaining at 220-270 ° C., opening the shutter of the magnesium evaporation source and depositing magnesium on the zinc deposition layer in an amount of deposition in the range of 50% of the adhesion amount of 2 g / m 2 to the zinc plating layer. Method for producing excellent magnesium and zinc alloyed two-layer plated steel sheet.