KR940000081B1 - Mn-zn two-layer plating steel sheet with an excellent corrosion resistance, adhesion and plating properties and process therefor - Google Patents

Abstract

The steel sheet having excellent corrosion resistance and adhesion property comprises a lower Zn layer of above 5 g/m2 and a upper Mn layer of 2-50 g/m2. The plating method comprises; (a) placing Mn vaporising source charged with Mn in a vacuum chamber; (b) evacuating the vacuum chamber to less than 1 x 10-4 torr; (c) heating the conventional Zn- plated steel sheet as a substrate in a range of 50 to 300 deg.C; (d) degassing the vaporising source by introducing a current; and (e) vacuum depositing the Mn onto the Zn-plated substrate by opening the covered shutter of Mn vaporising source.

Description

Manganese / Zinc-Layer Plated Steel Sheet with Excellent Corrosion Resistance, Adhesiveness and Paintability and Manufacturing Method Thereof

The present invention relates to a surface-treated steel sheet used as structural materials for automobiles, home appliances, and building materials, and more particularly, to a manganese / zinc two layer plated steel sheet excellent in corrosion resistance, adhesion, and paintability, and a method of manufacturing the same. Steel plate is widely used in structural materials such as automobiles, home appliances, and building materials because of its excellent mechanical strength, good workability, and abundant resources. However, the steel plate itself is extremely poor in corrosion resistance, so it often covers zinc to prolong its life. . 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, two-layer electroplating steel sheet and flash plating steel sheet have been developed. In order to improve, it is often used by coating an organic coating on a zinc-nickel alloy plated steel sheet. In addition, electro-galvanized steel sheet for home appliances, and hot-dip galvanized steel sheet 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. Hot-dip galvanized steel sheet, which is widely used for building materials, is mainly a post-plating material with a coating weight of more than 40 g / m ^2, 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 plating is performed by immersing the steel plate in the above-described high temperature zinc bath, it affects the mechanical properties of the base steel sheet, thereby limiting the selection of the base 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 amount of adhesion.

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 or electroplating method has a limitation in developing and applying a new plating system, vacuum deposition has emerged as a new plating method.

In order to effectively protect the steel plate and secure high corrosion resistance, it should be a plating system capable of sacrificial anode action on the steel sheet under corrosion atmosphere like zinc. The research to develop a new high corrosion resistance plating system using vacuum deposition method is mainly to find a plating system having excellent corrosion resistance and other characteristics by plating alloys between various metals. However, alloy plating has a disadvantage in that it is difficult to accurately maintain the alloy composition over time in the case of actual industrialization. In addition, although the alloy plating layer may form a single phase metallically, at least two phases may form a mixed phase in many cases. In such a case, setting of image processing conditions for coating after plating becomes difficult, and there is a problem in uniformity of the chemical film.

These problems can be solved by a two-layer plated steel sheet using a combination of appropriate single-small plating system. The two-layer plated steel sheet has a very simple manufacturing process, and since a single layer of upper metal film exists on the surface of the plating layer, it is necessary to select an appropriate plating system. The chemical conversion treatment is also good. Under the corrosion atmosphere, the angular metal frame forming the two layers can complement each other to effectively protect the steel sheet similarly to alloy plating. The most suitable for this two-layer plating manufacturing process is to apply vacuum deposition to the upper layer or both layers. Applying vacuum deposition can produce an upper coating layer without affecting the lower layer, and if necessary, some alloying layers can be formed by adjusting deposition conditions such as deposition temperature.

Therefore, according to the present invention, the conventional zinc plated layer is used as the lower layer, and the manganese layer is formed by vacuum deposition as the upper layer, or the upper and lower layers are formed by vacuum deposition. It is to provide a manganese / zinc bilayer plated steel sheet excellent in corrosion resistance, and its purpose is to provide a high quality corrosion resistant coating.

Hereinafter, the present invention will be described.

The present invention is a manganese excellent in corrosion resistance, adhesion and coating properties composed of a conventional zinc plating layer having a plating deposition amount of 5g / m ² or more as a lower layer and a vacuum deposition manganese plating layer having a plating deposition amount of 2-50 g / m ² as a lower layer. It relates to a zinc two-layer plated steel sheet and a method of manufacturing the same.

Hereinafter, the reason for numerical limitation will be described.

The two-layer plated steel sheet of the present invention exhibits the effect of inhibiting the progress of corrosion by forming a passivation layer of gamma -Mn ₂ O ₃ as the surface of the manganese coating is corroded at the beginning of corrosion, and even if the manganese layer is lost by the progress of corrosion, The coating is supported to protect the steel sheet. However, when the plating deposition amount of the upper manganese plating layer is 2g / m ² or less, due to the nonuniformity of the upper plating itself, an effective passivation film may not be formed in the place where the film thickness is thin, thereby causing local corrosion. On the other hand, when the deposition amount of the upper manganese plating layer is 50 g / m ² or more, there is a possibility that the upper layer peels off due to excessive accumulation of residual stress during deposition, thereby degrading adhesion. Therefore, the deposition amount of the upper manganese plating layer is preferably 2-50 g / m ² .

On the other hand, the adhesion amount of the lower zinc plated layer is preferably 5g / m ² or more, because the protective effect of the steel sheet is significantly reduced when it is 5g / m ² or less. As said lower zinc plating layer, a normal vacuum deposition zinc plating layer, an electro zinc plating layer, or a hot dip galvanizing layer is mentioned.

Manganese / zinc double layered steel sheet with upper layer of manganese forms gamma -Mn ₂ O ₃ in the early stage of corrosion in the corrosion atmosphere, and this gamma -Mn ₂ O ₃ is a very dense film of brown color. Since it greatly inhibits the diffusion of oxygen and the like, and serves as a passive film to suppress further corrosion progress, the corrosion resistance protecting the base steel sheet is greatly improved. In addition, the zinc-based manganese vacuum deposition film is not significantly affected by the deposition conditions and forms a high quality film having excellent adhesion and coverage, so that it is easy to control and control the manufacturing process. Since manganese is an electrochemical metal than zinc, its activity is very high. Therefore, the formation of the chemical conversion film by chemical conversion is very easy. In particular, since the plating surface layer is composed of a single metal of manganese, it is easy to set and control the chemical conversion treatment conditions.

Hereinafter, the manufacturing process of the manganese / zinc double layered steel sheet of the present invention will be described in detail.

There are various methods of vacuum evaporation, but vacuum evaporation and ion plating may be preferably applied to the present invention. The vacuum evaporation method is the most economical vacuum evaporation method because of its simple manufacturing equipment and high productivity, and the ion plating method has the advantage of obtaining a high quality plating film while the manufacturing equipment is more complicated and less productive than the vacuum evaporation method. These methods will be described in more detail.

The present invention is implemented by a conventional vacuum evaporation apparatus. In the case of manufacturing the manganese / zinc bilayer plated steel sheet of the present invention by a vacuum evaporation method, first, a manganese evaporation source loaded with manganese is placed in a vacuum container and used as a base plate. An electrogalvanized glass or hot dip galvanized steel sheet having a plating weight of 5 g / m ² or more is mounted on the manganese evaporation source, and the vacuum chamber is evacuated to 1 × 10 ⁻⁴ Torr or less.

Examples of the evaporation source include electron beam heating or resistance heating. It is preferable that the small substrate is subjected to ultrasonic cleaning using an alkali degreasing agent and an organic solvent before mounting in the vacuum container.

In addition, argon gas is introduced into the vacuum chamber to maintain an argon atmosphere of about 1 × 10 ^-2 -1 × 10 ^-1 Torr, and a negative voltage of 500-1000 V is applied to the substrate to clean the substrate by glow discharge. It is preferable.

After evacuating as described above, the substrate is heated to a temperature range of 50-300 ℃. Although adhesion is good even if vacuum is deposited without heating the substrate, manganese heating is required to desorb water vapor adsorbed to the surface layer of the zinc film, which is the lower layer.When the substrate is heated to 300 ℃ or higher, the lower zinc plated layer Zinc is sublimed, evaporated and lost, so the effect of two-layer plating cannot be obtained. Therefore, the heating temperature of the small substrate is preferably 50-300 ° C.

When the heating of the substrate is completed as described above, by supplying an appropriate amount of power to the manganese evaporation source to degas the evaporation source and then open the evaporation source shutter to deposit the manganese on the substrate to the deposition amount range of 2-50g / m ² , The manganese / zinc two layer plated steel sheet of this invention is manufactured.

On the other hand, in the case of manufacturing the manganese / zinc bilayer plated steel sheet of the present invention by the ion plating method, the 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 a temperature range of 50-300 ° C., degassing the manganese evaporation source and opening the shutter of the evaporation source to evaporate manganese while simultaneously discharging the glow using a hot electron emission filament and an ionizing anode located on the evaporation source. The manganese / zinc bilayer plated steel sheet of the present invention is produced by generating plasma and ion plating manganese in the deposition amount range as in the vacuum evaporation method.

In the ion plating method, a small amount of argon gas may be introduced into the vacuum vessel to stabilize the glow discharge. Phase, in the case of manufacture by both the lower layer in a vacuum vapor deposition method include the following, a vacuum container mounted on, insert the manganese and zinc to the manganese and zinc evaporation source in the vacuum chamber, respectively, to the cold-rolled steel sheet to hold the substrate evaporation source 1 × 10 ^- Evacuate to less than ⁴ torr.

After evacuating as described above, the substrate is heated to a temperature range of 150-250 ° C.

Next, power is supplied to each evaporation source to degas the evaporation source, the shutter of the zinc evaporation source is opened, the vacuum is evaporated to a deposition amount of 5 g / m ² or more on the substrate and the shutter of the zinc evaporation source is closed.

Next, after heating the base plate without heating or at a temperature range of 50-300 ° C., the manganese evaporator is opened with a shutter to remove the manganese by vacuum depositing manganese in an adhesion amount range of 2-50 g / m ² on the deposited zinc plated layer. The manganese / zinc two layer plated steel sheet of the present invention is produced. If the deposition temperature of the upper manganese is set equal to the deposition temperature of the lower zinc plated layer, the manufacturing process is simplified. The reason why the substrate is heated to a temperature range of 150-250 ° C. during the deposition of the zinc plated layer is because the plated characteristics including adhesiveness are good by vacuum deposition in this temperature range.

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

Example 1

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 coating 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 ⁻⁶ Torr. The test piece was prepared by heating the substrate to 150 ° C. with a resistance heater, and heating and evaporating a manganese having a purity of 99.99% with an electron beam heating evaporation source having an output of 0.45 kW. The deposition rate of manganese was 0.4 μm / min, and the deposition amount was changed in the range of 1-60 g / m ² as shown in Table 1 below. As shown in Table 1, Comparative Examples 3 and 4 represent specimens coated with monolayers of manganese and zinc, respectively.

Corrosion resistance, adhesiveness and paintability of each specimen prepared as described above were measured, and the measurement results are shown in Table 1 below. Here, the corrosion resistance was evaluated by the time of occurrence of red blue water when spraying 5% saline, and the adhesion was evaluated by the tape test after the Ot, 180 bending test.

TABLE 1

(Red) Red blue time: Time until red blue color occurs over 5% of the total surface

Evaluation criteria for adhesion: No plating layer peeling during tape test after O-bending

Partial peeling of plating layer during tape test after x-bending

Paintability: The coating film adhesion was evaluated by cross-cut and tape test after chemical conversion treatment and electrodeposition coating under normal conditions.

○-no peeling

△-part peeling

× -detachment

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

Example 2

The cold rolled steel sheet having a thickness of 0.7 mm was alkali-degreased, ultrasonically washed with acetone and alcohol, charged in an electrolytic bath, and evacuated to 1 × 10 ⁻⁵ Torr. The substrate is heated to 200 ° C with a resistance heater, and zinc is vaporized by heating and evaporating 99.9% pure zinc with a tantalum resistive heating evaporator, and then vacuuming by heating and evaporating manganese with a purity of 99.99% with an electron beam heating evaporation source of 0.45 kW. Specimens were prepared by deposition plating. At this time, the coating weight of zinc, as shown in Table 2 was in the range of 2-20g / m ^2, coating weight of the manganese was set to 10g / m ^2.

Corrosion resistance, adhesion and paintability of the specimens prepared as described above were measured, and the measurement results are shown in Table 2 below. Here, the corrosion resistance was evaluated by the time of occurrence of red blue water when spraying 5% saline, and the adhesion was evaluated by the tape test after Ot, 180 ° bending test.

TABLE 2

(Red) Red blue time: Time until red blue color occurs over 5% of the total surface

Evaluation criteria for adhesion: No plating layer peeling during tape test after O-bending

Partial peeling of plating layer during tape test after x-bending

Paintability: The coating film adhesion was evaluated by cross-cut and tape test after chemical conversion treatment and electrodeposition coating under normal conditions.

○-no peeling

△-part peeling

× -detachment

As shown in Table 2, the inventive example (1-3) is excellent in corrosion resistance, adhesiveness and paintability compared to the comparative example (1).

As described above, the present invention provides a manganese / zinc double layer coated steel sheet excellent in corrosion resistance, adhesion and paintability by a simple manufacturing process, thereby providing high corrosion resistance, adhesion and paintability in structural materials for automobiles, home appliances and building materials. There is an effect that can be used more appropriately for the required product.

Claims (3)

A galvanized layer having a plating deposition amount of 5 g / m ² or more is used as a lower layer; Manganese / zinc two layer plated steel sheet with excellent corrosion resistance, adhesion and paintability, comprising a vacuum deposited manganese plated layer having a plating deposition amount of 2-50 g / m ² as an upper layer. The manganese evaporation source loaded with manganese is placed in a vacuum vessel, and an electrogalvanized steel sheet having a plating deposition amount of 5 g / m ² or more as a small substrate is fixed to the manganese evaporation source, and the vacuum vessel is then subjected to 1 × 10 ^-4 Torr or less. Evacuating the furnace; Heating the substrate to a temperature range of 50-300 ° C. after evacuating as described above; When the heating of the base plate is completed as described above, supplying power to the manganese evaporation source to degas the evaporation source, and opening the shutter of the evaporation source and depositing manganese on the base plate with a deposition amount of 2-50 g / m ² . Method of producing a manganese / zinc two-layer plated steel sheet excellent corrosion resistance, adhesion and paintability, characterized in that comprising a. In a method of manufacturing a plated steel sheet by vacuum deposition by placing a manganese and zinc evaporation source loaded with manganese and zinc in a vacuum vessel and mounting a substrate on the evaporation source, the cold rolled steel sheet is mounted on the evaporation source as a substrate. Evacuating the vacuum vessel to less than 1 × 10 ⁻⁴ Torr; 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, the power is supplied to each evaporation source to degas the evaporation source, and then the zinc evaporation source is opened to vacuum-deposit zinc on the substrate to the deposition amount of 5 g / m ² or more. Closing the shutter of the evaporation source and maintaining the temperature of the substrate at 50-300 ° C .; If the temperature of the substrate is maintained as described above, by opening the shutter of the manganese evaporation source and depositing manganese in the deposition amount range of 2-50g / m ² on the deposited zinc plating layer, corrosion resistance, adhesion and coating Manufacturing method of manganese / zinc two layer plated steel sheet with excellent properties.