KR101511931B1 - Tin-zinc alloy coated steel sheet and method for preparing the same - Google Patents

Abstract

The tin-zinc alloy coated steel sheet of the present invention comprises a steel sheet; And a tin-zinc alloy layer formed on the steel sheet, wherein the tin-zinc alloy layer forms a concentration gradient in which the concentration of tin and zinc is changed according to the thickness. The tin-zinc alloy plated steel sheet is excellent in corrosion resistance, paintability and solderability.

Description

TECHNICAL FIELD [0001] The present invention relates to a tin-zinc alloy coated steel sheet and a method for manufacturing the same,

The present invention relates to a tin-zinc alloy coated steel sheet and a method of manufacturing the same. More particularly, the present invention relates to a tin-zinc alloy plated steel sheet excellent in corrosion resistance, paintability and solderability, and a method for producing the same.

As a method of preventing corrosion of steel products, zinc plating has been widely known to be the most economical and effective. The galvanized steel sheet has been widely used for automotive exterior panels, household appliances, and building materials. Recently, however, regulations on rustproofing have become more stringent, failing to fully satisfy the requirements of the demanders. Zn-Al, Zn-Al-Si, Zn-Fe, Zn-Ni, Zn-Mn, and Zn-Co films by the electroplating method for the purpose of improving the corrosion resistance, Al-Mg, and Zn-Al-Sn. However, the steel sheets obtained by the electroplating process are liable to be peeled off after processing, or may easily cause redness (Zn-Fe) or hydrogen generation during plating, resulting in poor current efficiency (Zn-Mn). In addition, the hot-dip galvanized steel sheet also has an alloy phase at its interface portion, resulting in deteriorated processability or an oxidized film on the surface, resulting in deteriorated chemical conversion properties and poor coat adhesion.

 As a result, a tin-zinc (Sn-Zn) alloy coated steel sheet excellent in corrosion resistance and workability which is obtained by plating zinc and tin on a steel sheet at a predetermined ratio has been developed. Methods for producing conventional tin-zinc alloy plated steel sheets include electro-tin-zinc alloy plating methods and molten tin-zinc alloy plating methods.

In the electro-tin-zinc alloy plating method, a plating solution contains a certain amount of tin ions and zinc ions, and a tin-zinc alloy metal is used as a cathode as a method of supplying metal ions. This electro-alloy plating method can maintain the alloy ratio of the two metals only when the ratio of the ions and the pH in the plating liquid are kept constant at the time of plating. If the plating solution is not appropriately controlled, the alloy ratio is changed and desired physical properties can not be maintained. Also, when changing the alloy ratio, it is difficult to prepare the plating solution. Actually, the working current density capable of electro-tin-zinc alloy plating is considerably low, making it difficult to perform high-speed plating work.

Another method, the molten tin-zinc alloy plating method, is a method in which a material is charged by melting two metals at a predetermined ratio, and it is difficult to economically manage the amount of plating adhered to the equipment. In addition, considerable time and cost loss is also caused when the alloy ratio is changed.

In addition, although Sn-Zn alloy coated steel sheet excellent in corrosion resistance and workability, in which zinc and tin are deposited on a steel sheet at a constant ratio by using a vacuum deposition method and an ion plating method, has been developed, it is still required to improve the corrosion resistance, paintability and solderability There is room.

An object of the present invention is to provide a tin-zinc alloy plated steel sheet excellent in corrosion resistance, paintability and solderability and a method for producing the same.

Another object of the present invention is to provide a tin-zinc alloy coated steel sheet excellent in appearance gloss and a method of manufacturing the same.

One aspect of the present invention relates to a tin-zinc alloy coated steel sheet. The tin-zinc alloy plated steel sheet is a steel plate; And a tin-zinc alloy layer formed on the steel sheet, wherein the tin-zinc alloy layer forms a concentration gradient in which the concentration of tin and zinc is changed according to the thickness.

In embodiments, the tin-zinc alloy layer may have an adhesion amount of 1 to 100 g / m ² and the weight ratio of tin and zinc (tin: zinc) in the total tin-zinc alloy layer may be 70 to 80:20 to 30 .

In an embodiment, the tin-zinc alloy layer is divided into a first zone and a second zone in order from the first face being the outermost layer to the second face facing the steel plate, and the concentration of tin in the first zone And the concentration of zinc increases, and in the second zone, the concentration of tin increases and the concentration of zinc decreases.

Preferably, the tin content in the first zone is reduced from 90 to 95 wt.% To 60 to 70 wt.%, The zinc content is increased from 5 to 10 wt.% To 30 to 40 wt.%, The content of tin in the region may increase from 60 to 70 wt% to 90 to 100 wt%, and the content of zinc may decrease from 30 to 40 wt% to 0 to 10 wt%.

Preferably, the first zone is 40 to 60% of the total thickness of the tin-zinc alloy layer, and the second zone is 40 to 60% of the total thickness of the tin-zinc alloy layer.

Another aspect of the present invention relates to a method of manufacturing the tin-zinc alloy plated steel sheet. Forming a zinc plating layer on a surface of the tin plating layer; Treating the surface of the zinc plating layer with a metal salt aqueous solution containing chlorine ions having a pH of 4 to 6 as a flux solution and then performing heat treatment to form a tin-zinc alloy layer from the tin plating layer and the zinc plating layer; And subjecting the steel sheet formed with the tin-zinc alloy layer to a quenching treatment in an acidic solution.

In a specific example, the total adhesion amount of the tin plating layer and the zinc plating layer is 1 to 100 g / m ² , and the weight ratio (tin plating layer: zinc plating layer) of the tin plating layer and the zinc plating layer is 70 to 80:20 to 30 days have.

In an embodiment, the tin-zinc alloy layer has a concentration gradient in which the concentration of tin and zinc varies with the thickness, the deposition amount is 1 to 100 g / m ² , and the tin- The weight ratio (tin: zinc) may be 70 to 80: 20 to 30.

In an embodiment, the flux solution is an aqueous solution containing a metal salt containing chlorine ions containing at least one of zinc chloride, tin chloride, ammonium chloride, sodium chloride and hydrochloric acid at a concentration of 1 to 500 g / L, Can be carried out at 200 to 300 < 0 > C.

In an embodiment, the acidic solution is an aqueous solution containing 0.01 to 10% by weight of an acid comprising at least one of hydrochloric acid, sulfuric acid, nitric acid and hydrofluoric acid, and the quenching treatment may be performed at 25 to 50 ° C.

The present invention has the effect of providing a tin-zinc alloy plated steel sheet excellent in corrosion resistance, paintability, solderability and appearance gloss and a method for producing the same. The tin-zinc alloy plated steel sheet may be variously used for general containers, household appliances, or parts, depending on the thickness of the steel sheet and the plating amount of the tin-zinc alloy layer.

1 is a graph showing the concentration gradient of tin and zinc according to the depth of a tin-zinc alloy layer of a tin-zinc alloy coated steel sheet according to an embodiment of the present invention.
2 is a schematic cross-sectional view for explaining a first zone and a second zone of a tin-zinc alloy layer of a tin-zinc alloy coated steel sheet according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

The tin-zinc alloy coated steel sheet according to the present invention comprises a steel sheet and a tin-zinc alloy layer formed on the steel sheet, wherein the tin-zinc alloy layer has a concentration gradient in which the concentration of tin and zinc is varied .

As the steel sheet used in the present invention, a steel sheet used for a conventional coated steel sheet can be used without limitation. For example, as the steel sheet, a material having a surface for rust prevention coated with a black plating material or a cold-rolled steel sheet (CR) can be used. When the alloy is plated, it can be used after proper pretreatment . The pretreatment furnace may be a conventional degreasing process, a water washing process, or a pickling process, but is not limited thereto.

The thickness of the steel sheet may vary depending on the intended use, and may be, for example, 0.1 to several mm, but is not limited thereto.

The tin-zinc alloy layer of the present invention has a concentration gradient. In the outermost layer, the tin concentration is higher than the zinc concentration, and when entering the plating layer, the zinc concentration increases and then decreases again. Thus, excellent gloss appearance, paintability, solderability, corrosion resistance, and the like can be obtained.

FIG. 1 is a graph showing a concentration gradient of tin and zinc according to a depth of a tin-zinc alloy layer of a tin-zinc alloy coated steel sheet according to an embodiment of the present invention. Sectional view for explaining the first zone and the second zone of the tin-zinc alloy layer of the alloy-plated steel sheet. As shown in Figures 1 and 2, the tin-zinc alloy layer 20 has an outermost layer first surface 22 and a second surface 24 facing it against the steel sheet 10, A1 and the second zone A2. When the concentration gradient is analyzed by GDS (Glow Discharge Spectrometer), the concentration of tin is decreased and the concentration of zinc is increased in the first zone A1, In the second zone (A2), the concentration of tin increases and the concentration of zinc decreases. In this case, the first zone A1 is 40 to 60%, preferably 45 to 55% of the total thickness of the tin-zinc alloy layer, and the second zone A2 is a thickness of the entire tin- 40 to 60%, preferably 45 to 55%. In the above range, the tin-zinc alloy plated steel sheet has excellent corrosion resistance, paintability, solderability and appearance gloss.

In one embodiment, the tin content in the first zone (A1) is reduced from 90 to 95 wt% to 60 to 70 wt%, the zinc content is from 5 to 10 wt% to 30 to 40 wt% , The tin content in the second zone (A2) increases from 60 to 70 wt% to 90 to 100 wt%, the zinc content decreases from 30 to 40 wt% to 0 to 10 wt% can do. In the above range, the tin-zinc alloy plated steel sheet has excellent corrosion resistance, paintability, solderability and appearance gloss.

In addition, the tin-coating weight of the zinc alloy layer, but may vary depending on the intended use, for example, 1 to 100 g / m ^2, preferably from 3 to 70 g / m ^2, overall tin-zinc alloy layer The weight ratio of tin and zinc (tin: zinc) is 70-80: 20-30, preferably 72-78: 22-28.

For example, when a corrosion resistance equivalent to that of an electro-galvanized product is required, the adhesion amount of the tin-zinc alloy layer may be about 4 g / m ^{2. For} applications requiring high corrosion resistance such as an automobile fuel tank, The adhesion amount of the tin-zinc alloy layer may be about 100 g / m < ² > but is not limited thereto.

However, when the weight ratio (tin: zinc) of tin and zinc in the entire tin-zinc alloy layer is out of the above range, there is a fear that the corrosion resistance is lowered irrespective of the adhesion amount of the tin-zinc alloy layer.

A method of manufacturing a tin-zinc alloy plated steel sheet according to the present invention includes the steps of: (a) forming a tin plating layer on a steel sheet; (b) forming a zinc plated layer on the surface of the tin plating layer; (c) forming a tin-zinc alloy layer from the tin plating layer and the zinc plating layer by treating an aqueous metal salt solution containing chlorine ions having a pH of 4 to 6 as a flux solution on the surface of the zinc plating layer; And (d) subjecting the steel sheet formed with the tin-zinc alloy layer to a quenching treatment in an acidic solution.

The step of forming the tin plating layer (step (a)) can be performed by a conventional electroplating method using a conventional electrolytic tin plating bath (plating bath). For example, the electrolytic tin plating solution may be an acidic plating solution containing tin and an acid such as methane sulfonic acid (MSA), phenol sulfonic acid (PSA) or the like, tin and halogen containing a halogen ion as a main component A plating solution or the like may be used, and an acidic plating solution may preferably be used. The acid plating solution may contain, for example, 18 to 22 g / L of tin, 50 to 70 cc / L of an acid, 30 to 50 cc / L of a surface conditioner, 10 to 20 cc / L of an antioxidant, But is not limited to, water.

In forming the tin plating layer, the temperature of the tin plating solution (plating bath) may be, for example, 30 to 50 ° C, and the cathode current density may be 10 to 30 A / dm ² , but is not limited thereto.

The step of forming the zinc plating layer (step (b)) may be performed by a conventional electroplating method using a conventional electrolytic zinc plating solution (plating bath). For example, as the electrolytic zinc plating solution, a zinc sulfate plating solution, a zinc chloride plating solution, a zinc cyanide plating solution and the like can be used, and a zinc sulfate plating solution can be preferably used. The zinc sulfate plating solution may contain, for example, from 250 to 300 g / L of zinc sulfate (ZnSO ₄ ), from 20 to 30 g / L of ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) H ₂ SO ₄ ) 10 to 20 g / L, and the balance water.

In forming the zinc plating layer, the temperature of the zinc plating solution (plating bath) may be, for example, 40 to 60 캜, and the cathode current density may be 5 to 30 A / dm ² , but is not limited thereto.

In an embodiment, the total amount of deposition of the tin plating layer and the zinc plating layer may be the same as the deposition amount of the tin-zinc alloy layer to be obtained and may be varied depending on the intended use, for example, 1 to 100 g / m ² , Preferably 3 to 70 g / m ² , and the weight ratio (tin plating layer: zinc plated layer) of the tin plating layer and the zinc plating layer is 70 to 80:20 to 30, preferably 72 to 78:22 to 28. A tin-zinc alloy plated steel sheet having excellent corrosion resistance in the above range can be obtained.

The adhesion amount between the tin plating layer and the zinc plating layer can be easily controlled by adjusting the amount of current. For example, when the tin plating is performed at 3 g / m ² and the zinc is coated at 1 g / m ² and the weight ratio of the tin plating layer and the zinc plating layer is A tin plating layer and a zinc plating layer having a total adhesion amount of 4 g / m < ² >, which is 75:25, can be formed.

The step of forming the tin-zinc alloy layer (step (c)) is a step for melting and alloying the tin-plated layer and the zinc-plated layer, wherein the tin-zinc alloy layer is coated with a flux solution and alloyed by heat treatment . When the heat treatment is performed without coating the flux solution, the zinc plating layer in the surface layer is oxidized by heat to cause discoloration or the like, and the zinc plating layer can be unmelted according to the melting point deviation of tin and zinc, There is a fear that excessive dissolution and evaporation may occur and the alloy layer may not be formed or may not have appearance characteristics that can be commercialized.

The flux solution used in the present invention is a metal salt aqueous solution containing chlorine ions having a pH of 4 to 6, preferably 4 to 5. If the pH of the flux solution is less than 4, corrosion or etching may occur in the zinc plated layer, resulting in deterioration in appearance and corrosion resistance. If the pH is more than 6, the flux effect is insufficient, And alloying may not be achieved.

In an embodiment, the flux solution may be a metal salt containing a chloride ion including at least one kind of zinc chloride, tin chloride, ammonium chloride, sodium chloride, hydrochloric acid, etc., depending on the coating method of the flux solution. 1 to 500 g / L, preferably 5 to 400 g / L. The pH of the flux solution may be 4 to 6, preferably 4 to 5 in the above concentration range, and alloying of the tin plating layer and the zinc plating layer can be made without deteriorating appearance and corrosion resistance.

The coating of the flux solution may be performed through a conventional flux solution coating method. For example, the flux solution may be deposited on the steel sheet on which the tin plating layer and the zinc plating layer are formed and then maintained in a wet state, After the dipping, the coating thickness of the flux solution can be controlled to about 10 탆 by a squeeze roll, and the flux solution may be coated using a spray or the like, but is not limited thereto.

In a specific example, when the coating of the flux solution is maintained in a wet state, the concentration of the metal salt including the chloride ion may be 1 to 20 g / L, and the thickness of the flux solution may be about 10 탆 When adjusted, the concentration of the metal salt including the chloride ion may be 300 to 500 g / L. In the above range, excellent appearance and corrosion resistance are excellent.

The tin plating layer and the zinc plating layer may be alloyed by flux during the coating of the flux solution, and the melting point of the tin and zinc alloy metal in the weight ratio ranges of the tin plating layer and the zinc plating layer is 200 to 300 占 폚, Lt; / RTI > Thus, for the alloying after coating the flux solution, the heat treatment may be performed at 200 to 300 占 폚, preferably 200 to 250 占 폚. In the above range, a tin-zinc alloy layer excellent in appearance characteristics, corrosion resistance and the like can be obtained.

The quenching step (step (d)) is for preventing the occurrence of blue stain due to surface oxidation of the tin-zinc alloy layer and maintaining the alloy state uniformly. In a specific example, The steel sheet on which the tin-zinc alloy layer is formed is quenched at a temperature of 25 to 50 占 폚, preferably 40 to 50 占 폚 in an acidic solution of pH 0.5 to 5, preferably pH 1 to 3. It is possible to obtain a tin-zinc alloy plated steel sheet having excellent appearance without occurrence of a blue coat or the like in the temperature and pH range.

In an embodiment, the acidic solution comprises from 0.01 to 10% by weight of an acid comprising at least one of hydrochloric acid, sulfuric acid, nitric acid and hydrofluoric acid. And preferably 0.1 to 5% by weight. It is possible to obtain a tin-zinc alloy plated steel sheet having excellent appearance without occurrence of a blue coat in the above range.

The tin-zinc alloy coated steel sheet according to the present invention may be subjected to conventional chemical treatment or paint coating, if necessary, after the alloying heat treatment and quenching treatment.

Hereinafter, the present invention will be described in more detail by way of examples, but these examples are for illustrative purposes only and should not be construed as limiting the present invention.

Example

Example  One

Brush degreasing and electrolytic degreasing (current density: 15 A / min) in a composite degreasing solution containing 2 to 3% caustic soda and a surfactant in a black plate or a cold rolled steel plate (CR) coated with oil for anti- dm < ² >), washed with water, and then subjected to a pickling treatment with a 5 to 10 wt% sulfuric acid solution. The pretreated material (steel plate) was treated with 40 g of methane sulfonic acid (MSA) tin plating solution (20 g / L of tin, 70 cc / L of methane sulfonic acid, surface conditioner (manufactured by DOW CHEMICAL, Product: the TP-SR) 40 cc / L , an antioxidant 15 cc / L and the balance including water) tin by electrolysis for 0.9 seconds with a current density of 20 a / dm ² in a plating layer 1.0 g / m ² was formed. The tin-plated material was then subjected to a water treatment, and then the tin-plated material was immersed in a zinc sulfate plating solution of 60 占 폚 (30 g / L of zinc sulfate (ZnSO ₄ ), ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) , sulfuric acid (H ₂ SO ₄₎ was a 15 g / L, and the rest of the water delivered during included) 1 seconds at a current density 10 a / dm ² to form in the galvanizing layer 0.3 g / m ² and washed. Next, a flux solution containing zinc chloride at a concentration of about 400 g / l was coated on the tin-zinc double-plated material surface to a thickness of about 10 [mu] m using a roll coating method. The flux-treated material was heated to about 250 ° C so that the two metals could be alloyed and melted by an induction heater. Finally, the material in which the tin-zinc plating layer was melted was rapidly cooled in a 1 wt.% Hydrochloric acid solution at 50 占 폚 to prepare a tin-zinc alloy plated steel sheet of good gloss free from a blue oxide film.

Example 2

Tin plated, and to be delivered for 1.8 seconds galvanized during a current density of 20 A / dm ² of 2 g / m delivered to 0.7 g / m ² to form a tin plating layer ² and for 2.2 seconds with a current density of 10 A / dm ² A tin-zinc alloy plated steel sheet was produced in the same manner as in Example 1 except that a zinc plated layer was formed.

Example 3

Tin-plated and zinc-plated City, zinc plating layer having a current density of 20 A / to be delivered for 2.7 seconds dm ² 3 g / m to be delivered for 3.3 seconds, tin plating layer ² and a current density of ^{10 A / dm 2 1 g /} m 2 A tin-zinc alloy plated steel sheet was produced in the same manner as in Example 1 above.

Example 4

Tin-plated and zinc-plated City, zinc plating layer having a current density of 20 A / to be delivered for 3.6 seconds dm ² 4 g / m delivered to 1.4 g / m ² for 4.6 seconds, tin plating layer ² and a current density of 10 A / dm ² A tin-zinc alloy plated steel sheet was produced in the same manner as in Example 1 above.

Example 5

Tin-plated and zinc-plated City, zinc plating layer having a current density of 20 A / to be delivered for 4.5 seconds dm ² 5 g / m delivered to 1.7 g / m ² for 5.6 seconds, tin plating layer ² and a current density of 10 A / dm ² A tin-zinc alloy plated steel sheet was produced in the same manner as in Example 1 above.

Comparative Example 1

Brush degreasing and electrolytic degreasing (current density: 15 A / min) in a composite degreasing solution containing 2 to 3% caustic soda and a surfactant in a black plate or a cold rolled steel plate (CR) coated with oil for anti- dm < ² >), washed with water, and then subjected to a pickling treatment with a 5 to 10 wt% sulfuric acid solution. The pretreated material (steel sheet) was coated with a zinc sulfate plating solution (zinc sulfate plating solution, zinc sulfate (ZnSO ₄ ) 300 g / L, ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) 30 g / H ₂ SO ₄ ) 15 g / L, and the remainder of water) at a current density of 10 A / dm ² for 33 seconds to produce a galvanized steel sheet having a zinc plated layer of 10 g / m ² .

Comparative Example 2

A galvanized steel sheet was prepared in the same manner as in Comparative Example 1, except that zinc plating was carried out at a current density of 10 A / dm ² for 66 seconds to form a zinc plated layer of 20 g / m ² .

Comparative Example 3

A galvanized steel sheet was prepared in the same manner as in Comparative Example 1, except that zinc plating was carried out at a current density of 10 A / dm ² for 99 seconds to form a 30 g / m ² zinc plated layer.

Comparative Example 4

Brush degreasing and electrolytic degreasing (current density: 15 A / min) in a composite degreasing solution containing 2 to 3% caustic soda and a surfactant in a black plate or a cold rolled steel plate (CR) coated with oil for anti- dm < ² >), washed with water, and then subjected to a pickling treatment with a 5 to 10 wt% sulfuric acid solution. The pretreated material (steel sheet) was treated with 40 g of methane sulfonic acid (MSA) tin plating solution (20 g / L of tin, 70 cc / L of methane sulfonic acid, surface conditioning agent (manufacturer: DOW CHEMICAL) 50 to cc / L, an antioxidant 15 cc / L and the balance including water) tin by electrolysis for 1.3 seconds with a current density of 20 a / dm ² in a plating layer 1.4 g / m ² was formed. Next, a tin-plated steel sheet was produced by melting the tin-plated layer using an induction heater and performing a chromate treatment.

Comparative Example 5

A tin-plated steel sheet was prepared in the same manner as in Comparative Example 4, except that tin plating was conducted at a current density of 20 A / dm ² for 2.5 seconds to form a tin plating layer of 2.8 g / m ² .

Comparative Example 6

A tin-plated steel sheet was prepared in the same manner as in Comparative Example 4, except that tin plating was carried out at a current density of 20 A / dm ² for 5 seconds to form a tin plating layer of 5.6 g / m ² .

Comparative Example 7

A tin-plated steel sheet was prepared in the same manner as in Comparative Example 4, except that tin plating was carried out at a current density of 20 A / dm ² for 7.5 seconds to form a tin plating layer of 8.4 g / m ² .

Comparative Example 8

A tin-zinc plated steel sheet was produced in the same manner as in Example 5 except that the flux treatment was not performed.

In the tin-zinc alloy coated steel sheet of Comparative Example 8, the tin-plated layer and the zinc plated layer were not formed with a tin-zinc alloy layer, and the zinc layer on the surface was oxidized and discolored severely,

Comparative Example 9

A zinc-tin alloy coated steel sheet was prepared in the same manner as in Example 5 except that the quenching treatment (the material in which the tin-zinc plating layer was melted at 50 캜 and quenched in 1 wt% hydrochloric acid solution) was not performed.

The tin-zinc alloy plated steel sheet of Comparative Example 9 was not separated from tin and zinc or formed a crystal phase, so that it was impossible to obtain a good appearance such as a fine pearl surface.

Property evaluation method

(1) Tin and Zinc plating amount (unit: g / m ² ) measurement

Using a fluorescent X-ray spectrometer, the amounts of tin and zinc plated were measured from the weight calibration curve of Sn and Zn prepared in advance.

(2) Measurement of concentration gradient

Was measured using a calibration curve obtained from Sn, Zn and Sn-Zn alloys previously prepared by using a GDS (Glow Discharge Spectrometer).

As a result of the measurement, it was confirmed that the tin-zinc alloy plating layers of Examples 1 to 5 exhibited a concentration gradient similar to the concentration gradient graph of FIG.

(3) Evaluation of corrosion resistance

The test was carried out for 72 hours with spraying of brine (5% NaCl) prescribed in JIS Z 2371, and the point at which the generation of red rust became 5% or more of the area of the steel sheet was measured.

The measurement results are shown in Table 1 below.

division Plating amount (g / m ² ) When red rust occurs Example 1 Tin-zinc alloy coated steel sheet Sn: 1, Zn: 0.3 5 hr Example 2 Sn: 2, Zn: 0.7 30 hr Example 3 Sn: 3, Zn: 1.0 48 hr Example 4 Sn: 4, Zn: 1.4 74 hr or more Example 5 Sn: 5, Zn: 1.7 74 hr or more Comparative Example 1 galvanized steel Zn: 10 20 hr Comparative Example 2 Zn: 20 48 hr Comparative Example 3 Zn: 30 72 hr Comparative Example 4 Tin-plated steel sheet Sn: 1.0 3 hr Comparative Example 5 Sn: 2.8 5 hr Comparative Example 6 Sn: 5.6 10 hr Comparative Example 7 Sn: 8.4 15 hr

From the results shown in Table 1, it can be seen that the tin-zinc alloy plated steel sheet of the present invention (Examples 1 to 5) is superior in corrosion resistance to a single metal plated steel sheet at a similar overall plating amount. In particular, in Example 2 in which the total amount of plating is 2.7 (Sn: 2, Zn: 0.7) g / m ² , the time point of occurrence of redness is 6 times longer than that of Comparative Example 5 in which the total amount of plating is 2.8 g / m ² . It can also be seen that the tin-zinc alloy plated steel sheet of the present invention can achieve a result equal to or greater than the corrosion resistance of the galvanized steel sheet having a total plating amount of not less than 10 g / m ² even at a small total plating amount of not more than 10 g / m ² .

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (10)

Steel plate; And
And a tin-zinc alloy layer formed on the steel sheet,
The tin-zinc alloy layer forms a concentration gradient in which the concentration of tin and zinc varies depending on the thickness,
The tin-zinc alloy layer is divided into a first zone and a second zone in order from the first face of the outermost layer to the second face opposite to the steel plate, and in the first zone from the first face to the second face The concentration of tin is decreased and the concentration of zinc is increased in the direction of the first surface, the concentration of tin is increased and the concentration of zinc is decreased in the direction from the first surface to the second surface in the second region,
Wherein the tin-zinc alloy layer has an adhesion amount of 1 to 100 g / m ² and a weight ratio of tin and zinc (tin: zinc) in the total tin-zinc alloy layer is 70 to 80: 20 to 30. Zinc alloy coated steel sheet.
delete delete The method of claim 1, wherein the tin content in the first zone is reduced from 90 to 95 wt% to 60 to 70 wt%, the zinc content is increased from 5 to 10 wt% to 30 to 40 wt% , The tin content in the second zone increases from 60 to 70 wt% to 90 to 100 wt%, and the content of zinc decreases from 30 to 40 wt% to 0 to 10 wt% Zinc alloy coated steel sheet.
The tin-zinc alloy sheet of claim 1, wherein the first zone is 40-60% of the total thickness of the tin-zinc alloy layer and the second zone is 40-60% of the total thickness of the tin- - Zinc alloy coated steel sheet.
Forming a tin plating layer on the steel sheet;
Forming a zinc plated layer on the surface of the tin plating layer;
Treating the surface of the zinc plating layer with a metal salt aqueous solution containing chlorine ions having a pH of 4 to 6 as a flux solution and then performing heat treatment to form a tin-zinc alloy layer from the tin plating layer and the zinc plating layer; And
And rapidly cooling the steel sheet on which the tin-zinc alloy layer is formed in an acidic solution.
7. The method according to claim 6, wherein the total adhesion amount of the tin plating layer and the zinc plating layer is 1 to 100 g / m ² , and the weight ratio (tin plating layer: zinc plating layer) of the tin plating layer and the zinc plating layer is 70 to 80: 20 to 30 Zinc alloy-coated steel sheet.
The method of claim 6, wherein the tin-zinc alloy layer is formed a concentration gradient of the tin and the concentration of zinc varies with the thickness and a coating weight of 1 to 100 g / m ^2, the entire tin-tin in the zinc alloy layer and Wherein the weight ratio of zinc (tin: zinc) is 70 to 80: 20 to 30.
7. The method according to claim 6, wherein the flux solution is an aqueous solution containing a metal salt comprising chloride ions containing at least one of zinc chloride, tin chloride, ammonium chloride, sodium chloride and hydrochloric acid at a concentration of 1 to 500 g / L, Wherein the heat treatment is performed at 200 to 300 占 폚.
The method according to claim 6, wherein the acidic solution is an aqueous solution containing 0.01 to 10% by weight of an acid including at least one of hydrochloric acid, sulfuric acid, nitric acid and hydrofluoric acid, and the quenching treatment is performed at 25 to 50 캜 Wherein the tin-zinc alloy plated steel sheet is produced by a method comprising the steps of:

Images