KR100293187B1 - METHOD FOR MANUFACTURING Zn-Fe ALLOY ELECTROPLATED STEEL SHEETS WITH EXCELLENT SURFACE APPEARANCE AND BEAUTIFUL COLORS - Google Patents

Abstract

PURPOSE: Provided is a method for manufacturing Zn-Fe alloy electroplated steel sheets with excellent surface appearance and beautiful colors by adjusting the ratio of KCl/NH4Cl in a plating solution. CONSTITUTION: In the manufacturing method of Zn-Fe alloy electroplated steel sheets by plating a plating solution comprising Zn ion, Fe ion, 220-260g/L of Cl ion, and 1.5-2.5ml/L of organic additive in the temperature range of 45 to 65°C at pH 4-6 on the surface of steel sheets, the plating solution is characterized by comprising KCl and NH4Cl and its formulation is determined by the follow equation: KCl/£KCl+NH4Cl|=0.004+0.61{Fe/£Fe+Zn|}-0.99{Fe/£Fe+Zn|}¬2 where Fe/£Fe+Zn| is less than 0.3.

Description

Manufacturing method of zinc-iron alloy plated steel sheet with excellent surface shape

The present invention relates to a method of electroplating a zinc-iron alloy on a steel sheet, and more particularly to a zinc-iron alloy plated steel sheet having excellent surface shape by controlling the content ratio of KCl content and NH ₄ Cl in the electroplating solution. It relates to a manufacturing method.

At present, zinc and zinc-based alloy plated steel sheets are produced in various plating lines, and the composition of commercially produced zinc-iron alloy plated products is 15-20 wt.% Fe for electroplating, and 10- for alloyed hot dip plating. It is about 15% by weight Fe.

Since the alloy composition of the plating layer is generally closely related to workability, coating property, corrosion resistance after coating, and the like, it is necessary to perform plating of an appropriate composition depending on the application. In addition, in order to manufacture a standard sample for setting the calibration curve of the composition measuring equipment, manufacturing of plating layers having various compositions is required. Therefore, the control of the plating bath components for obtaining a desired plating layer composition is complicated and detailed. .

In electroplating, the plating solution mainly uses a chloride bath or a sulfuric acid bath. When the chloride bath is used, high current density operation is possible, power consumption is reduced, and the color of the plating layer is excellent. However, if the composition range of the alloy is large, the surface shape of the plating layer is changed rapidly and the surface color is black, there is a problem that the operation only in a constant composition.

In addition, even when plating is performed by obtaining an optimum process condition for a certain composition, since the composition of the plating layer for the optimum process condition is changed, plating causes a color of the plated layer to be black and a poor surface shape.

Accordingly, the present inventors conducted research and experiments to solve the above problems, and based on the results, the present invention proposes the present invention, and the present invention changes the plating layer when the zinc-iron alloy composition is changed in various ways. By appropriately controlling the concentration of the plating solution according to the present invention is to provide a method for producing a zinc-iron alloy plated steel sheet to form a zinc-iron alloy electroplating layer having an excellent surface shape and beautiful color, an object thereof.

1 is a schematic diagram of an electroplating apparatus applied to the method of the present invention.

2 is a graph showing the results obtained by visually observing the surface shape of the plated steel sheet according to the present invention.

The present invention for achieving the above object, Zn ions, Fe ions, 220 to 260 g / L Cl ions, 1.5 to 2.5 ml / L of an organic additive, the sum of the Zn ions and Fe ions concentration is 60 ~ A method for producing a zinc-iron alloy electroplated steel sheet by electroplating in a chloride plating bath having a temperature of 80 g / l, a temperature of 45 to 65 DEG C, and a pH of 4 to 6, wherein KCl and NH ₄ Cl are added to the plating bath. Is included; The composition of the KCl and NH ₄ Cl is a summary of a method for producing a zinc-iron alloy plated steel sheet having an excellent surface shape, characterized in that determined by the following relation 1.

[Relationship 1]

KCl / [KCl + NH ₄ Cl] = 0.004 + 0.61 {Fe / [Fe + Zn]}-0.99 {Fe / [Fe + Zn]} ²

Hereinafter, the present invention will be described in more detail.

In manufacturing the plated steel sheet according to the present invention, in order to examine the relationship between the appropriate plating layer and the plating bath composition, a simple apparatus such as FIG. 1 was used. The electroplating apparatus of FIG. 1 is largely comprised by the plating tank 1 and the storage tank 2, The component adjustment of the plating bath was performed in the storage tank 2. As shown in FIG. The plating solution in the reservoir 2 usually contains FeCl ₂ · 4H ₂ O, ZnCl ₂ , KCl, or NH ₄ Cl as a chloride plating solution. In the case of Fe ions and Zn ions, the sum of the concentrations is 60 to 80 g / L, Cl ions (where Cl ions means total Cl ions) are preferably from 220 to 260 g / l, and the organic additive is from 1.5 to 2.5 ml / l. The reason for this is that if the sum of the Fe ions and the Zn ion concentrations is less than 60 g / l, the plating yield is lowered, and if it exceeds 80 g / l, the surface shape is bad. In addition, if the total Cl ions contained less than 220g / ℓ poor plating appearance due to poor plating state, when the total Cl ions are more than 260g / ℓ there is a problem that the surface is not uniform and the pits occur when staining occurs. In addition, when the organic additive is contained at 1.5 ml / l, there is no glossiness, and when the organic additive is contained at 2.5 ml / l, a problem of poor adhesion occurs.

In addition, the plating solution is preferably heated by a heater 3 impregnated in the reservoir 2 and maintained at a constant temperature, specifically 45 to 65 ° C. The reason is that if the temperature is lower than 45 ° C, there is no gloss, and if the temperature is higher than 65 ° C, the surface shape is not good. At this time, the temperature is configured to be adjusted by the temperature controller 5 attached to the thermometer (4) on one side.

And, the pH of the plating solution is preferably adjusted to the range of 4-6 by the pH adjuster (6). If the pH is out of the 4 to 6 range, there is a problem that the surface shape is poor and the plating state is poor.

The plating solution adjusted as described above is filtered through the filter 10 and then supplied into the plating bath 1 through the hydraulic system 11, the circulation pump 12 and the valve 13, the plating machine (1) Inside, plating is performed while a direct current is applied to the positive electrode steel sheet 8 and the negative electrode zinc plate 7 by the power supply device 9.

On the other hand, in general, when plating a zinc-iron alloy on the steel plate in the chloride bath, KCl in the reservoir (2) or NH ₄ Cl is used, in the present invention KCl and NH ₄ Cl as the Cl source of the chloride bath. By using a mixture of and controlling the composition range according to the composition of the desired plating layer, it was possible to obtain an electroplated steel sheet with a beautiful color and surface shape in the composition of the desired plating layer.

In other words, the inventors of the present invention, while obtaining a good surface shape in the coated steel sheet, while studying the relationship between the KCl and NH ₄ Cl and Fe and Zn composition, KCl / [KCl + NH ₄ Cl] value and Fe / It was found that the relationship between the [Fe + Zn] values influences the surface shape of the plated steel sheet, and as shown in Fig. 2, the KCl / [KCl + NH ₄ Cl] and Fe / [Fe + Zn] values were changed. While observing the surface shape of the steel sheet, the following relational expression 1 was derived based on the result. At this time, Fe / [Fe + Zn] in the following relational formula 1 represents the Fe content ratio on the zinc-iron plating layer, and the value thereof is preferably 0.3 or less. This is because, from the following relation 1, when the Fe / [Fe + Zn] value becomes 0.3 or less and the composition of Fe in the plating layer is increased, the content of KCl in the solution must be increased by a certain amount.

[Relationship 1]

KCl / [KCl + NH ₄ Cl] = 0.004 + 0.61 {Fe / [Fe + Zn]}-0.99 {Fe / [Fe + Zn]} ²

As described above, the present invention can produce a zinc-iron alloy electroplating steel sheet having a desired plating layer by determining the optimum content of KCl according to the plating composition.

Hereinafter, the present invention will be described through examples.

EXAMPLE

Zinc-iron alloy plating was performed on the steel plate using the electroplating apparatus as shown in FIG. At this time, a cold rolled steel sheet having a thickness of 0.4mmt was used, the temperature of the plating liquid is 60 ℃, Zn + Fe ion concentration of 70g / ℓ, Fe / [Fe + Zn] is less than 0.3, the total Cl concentration is 240g / 1, the organic additive (brand name USS-P) was 2 ml / l, and pH was 6. Then, KCl / [KCl + NH ₄ Cl] was electroplated for 2 minutes at 0.004 to 0.1. Electroplating is started at the same time as the DC power is applied to the steel sheet and the zinc plate from the power supply device, and when plating by the desired plating amount, the power supply is cut off, the plated steel sheet is taken out, washed and dried.

After washing and drying the plated steel sheet, the surface shape and color were measured and evaluated, and the results are shown in FIG. 2.

As shown in FIG. 2, the most excellent surface shape was shown in the content range of KCl / [KCl + NH ₄ Cl] satisfying the condition of relation 1, and when the condition of the present invention was not satisfied, the surface shape was poor. And the color appeared black.

As can be seen from the above, according to the manufacturing method of the zinc-iron alloy plated steel sheet of the present invention, even if the zinc-iron alloy composition range is changed to less than 30% by weight Fe, excellent surface shape, zinc- having a beautiful color An iron alloy electroplated steel sheet can be obtained.

Claims (2)

Zn ion, Fe ion, 220-260 g / l Cl ion, 1.5-2.5 ml / l organic additive, The sum of said Zn ion and Fe ion concentration is 60-80 g / l, The temperature is 45- A method for producing a zinc-iron alloy electroplated steel sheet by electroplating in a chloride plating bath having a pH of 4 to 6 at 65 ° C., wherein the plating bath contains KCl and NH ₄ Cl; The composition of the KCl and NH ₄ Cl is a zinc-iron alloy plated steel sheet having a good surface shape, characterized in that determined by the following equation 1. [Relationship 1] KCl / [KCl + NH ₄ Cl] = 0.004 + 0.61 {Fe / [Fe + Zn]}-0.99 {Fe / [Fe + Zn]} ² The method of manufacturing a zinc-iron alloy plated steel sheet having excellent surface shape according to claim 1, wherein the Fe / [Fe + Zn] value of the relational formula 1 is 0.3 or less.