KR20190078330A - Plated steel wire and manufacturing method for the same - Google Patents

Abstract

According to an embodiment of the present invention, a plated steel wire comprises a base steel wire and a zinc alloy plated layer. The zinc alloy plated layer comprises: 1.0-3.0 wt% of AI; 1.0-2.0 wt% of Mg; 0.5-5.0 wt% of Fe; and the remainder of Zn and unavoidable impurities. The zinc alloy plated layer further comprises Zn / MgZn_2 / AI ternary process structure, Zn single-phase structure, and Fe-Zn-AI-based crystal structure. The Fe-Zn-AI-based crystal structure is formed adjacent to the base steel wire, and can have average thickness of 1/5 to 1/2 with respect to average thickness of the zinc alloy plated layer.

Description

[0001] DESCRIPTION [0002] Plated steel wire and manufacturing method for the same [

The present invention relates to a plated steel wire and a method of manufacturing the same, and more particularly, to a plated steel wire with effective workability and corrosion resistance and a method of manufacturing the same.

The zinc plating method is widely used for manufacturing a steel material having excellent corrosion resistance and economic performance. Particularly, the hot dip galvanized steel having a plated layer formed by immersing steel in a molten zinc plating bath has a simpler manufacturing process than that of an electro-galvanized steel, and its product price is inexpensive, and its demand is increasing in various fields.

The hot-dip galvanized steel sheet formed with the zinc-plated layer has Sacrificial Corrosion Protection characteristic in which the Zn having lower oxidation-reduction potential than the Fe is first corroded by corrosion exposure to suppress the corrosion of the steel, and the Zn of the zinc- Thereby forming a dense corrosion product on the surface of the steel material to block the steel material from the oxidizing atmosphere. Thus, corrosion resistance of the steel material can be effectively improved.

However, the increase in air pollution and the deterioration of the corrosive environment are accelerating due to the advancement of industry, and due to strict regulation related to resource and energy saving, the necessity of development of steel having better corrosion resistance than conventional zinc plated steel is increasing to be.

Zn-Al alloy plated steel wires have been developed to meet these demands. The Zn-Al alloy plated steel wire is generally flux-treated to activate the interface reaction with zinc after cleaning, such as pickling, washing and degreasing, and can be manufactured by dipping in a Zn-based plating bath containing Al.

Korean Patent Publication No. 10-2016-0078670 (published on Jul.

According to one aspect of the present invention, there can be provided a coated steel wire and a method of manufacturing the same, effectively securing workability and corrosion resistance.

The object of the present invention is not limited to the above description. Those of ordinary skill in the art will have no difficulty understanding the further subject of the present invention from the general context of this specification.

The coated steel wire according to one embodiment of the present invention includes a base steel wire and a zinc alloy plating layer. The zinc alloy plating layer contains 1.0 to 3.0% of Al, 1.0 to 2.0% of Mg, Zn-Al-based crystal structure includes Zn / MgZn ₂ / Al ternary system structure, Zn single-phase structure and Fe-Zn-Al system crystal structure, And may have an average thickness of 1/5 to 1/2 of the average thickness of the zinc alloy plating layer.

The area fraction of the Zn / MgZn ₂ / Al ternary system structure and the area occupied by the single-phase Zn structure in the cross-section of the zinc alloy plating layer may be 60% or more.

The main phase average interval of the Zn single phase structure in the cross section of the zinc alloy plating layer may be 1 to 5 탆.

A method of manufacturing a galvanized steel wire according to an embodiment of the present invention includes: firstly dipping a steel wire into a molten zinc plating bath to provide a galvanized steel wire; The primary dipped galvanized steel wire is secondarily immersed in a molten copper alloy gold plating bath to provide a galvanized gold wire; Wherein the molten alloy gold plating bath is cooled at a cooling rate of 15 to 50 DEG C / s, wherein the molten alloy gold plating bath comprises 1.0 to 3.0% of Al, 1.0 to 2.0% of Mg, Zn and unavoidable impurities.

The base steel wire may be first immersed in the molten zinc plating bath at 440 to 460 DEG C for 10 to 20 seconds.

The primary dipped galvanized steel wire may be cooled to a temperature range lower than the melting point of Zn and then secondarily immersed in the molten alloy gold plating bath.

The galvanized steel wire can be secondarily immersed in the molten solder gold plating bath at 440 to 460 DEG C for 10 to 20 seconds.

A coated steel wire according to an embodiment of the present invention and a method of manufacturing the same can provide a coated steel wire with improved workability and corrosion resistance and a method of manufacturing the same.

1 is an FE-SEM image of a section of Inventive Example 1 observed.
2 is an FE-SEM image of the surface of the plating layer of Inventive Example 1 observed.
3 is an FE-SEM image of the cross section of Comparative Example 1 observed.
4 is an FE-SEM image of the surface of the coating layer of Comparative Example 1. FIG.
5 is a SEM image of the surface after the freshness of the inventive example 1 is observed.
Fig. 6 is a SEM image of the surface after freshness of Comparative Example 1 observed. Fig.

The present invention relates to a plated steel wire and a manufacturing method thereof, and a preferred embodiment of the present invention will be described below. The embodiments of the present invention can be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments are provided to explain the present invention to a person having ordinary skill in the art to which the present invention belongs.

The plated steel wire according to an embodiment of the present invention may include a base steel wire and a zinc alloy plating layer. The base steel wire of the present invention is not limited to a specific kind of steel wire but can be interpreted to include all types of steel wire used in hot dip galvanizing or molten zinc alloy plating.

In addition, the zinc alloy plating layer of the coated steel wire according to an embodiment of the present invention may contain 1.0 to 3.0% of Al, 1.0 to 2.0% of Mg, 0.5 to 5.0% of Fe, the remaining Zn and unavoidable impurities can do.

Hereinafter, the composition of the zinc alloy plating layer of the present invention will be described in more detail.

Mg: 1.0 to 2.0%

Mg plays an important role in improving the corrosion resistance of the zinc alloy plating layer. Mg is contained in the zinc alloy plating layer and can inhibit the formation of zinc oxide based corrosion products which are less effective in improving the corrosion resistance in a severe corrosive environment and can stabilize the zinc hydroxide based corrosion products which are dense and have a great effect of improving the corrosion resistance on the surface of the plating layer . Therefore, in order to achieve this effect, the Mg content of the present invention may be 1.0% or more. However, when the content of Mn is excessively added, the effect of improving the corrosion resistance by the addition of Mg is saturated, and the oxidative dross formed by oxidation of Mg rapidly increases on the surface of the molten alloy gold plating bath, The Mg content of the present invention may be 2.0% or less.

Al: 1.0 to 3.0%

Al is an element added to reduce the dross generated by the oxidation reaction of Mg in a molten alloy gold plating bath containing Mg. Further, Al is an element capable of improving the corrosion resistance of the plated steel wire in combination with Zn and Mg. Therefore, in order to achieve this effect, the Al content of the present invention may be 1.0% or more. The preferred Al content may be at least 1.5%. However, when the Al content is excessively added, the amount of Fe elution in the steel wire immersed in the molten alloy gold plating bath rapidly increases, so that Fe alloy type dross can be formed. In addition, the Al-Zn metal structure is formed in the molten alloy gold plating bath to raise the temperature of the plating bath, and the Al-Zn metal structure formed in the zinc alloy plating layer may hinder the workability of the zinc alloy plating layer. Therefore, the Al content of the present invention can be 3.0% or less. The preferred Al content may be up to 2.8%.

Fe: 0.5 to 5.0%

Fe contained in the zinc alloy plating layer of the present invention is an element which flows into the zinc alloy plating layer by Fe of the base steel and the Zn of the molten alloy-bonded gold plating bath react to form Fe-Zn. The present invention attempts to secure the adhesion of the plating layer by forming an Fe-Zn-Al system crystal structure in the interface portion of the zinc alloy plating layer. The Fe content of the zinc alloy plating layer of the present invention may be 0.5% or more, The content may be at least 0.8%. On the other hand, if the Fe content flowing into the zinc alloy plating layer is excessive, the hardness of the zinc alloy plating layer may be excessively increased and the local corrosion resistance may be lowered. Therefore, the Fe content of the zinc alloy plating layer of the present invention may be 5.0% or less, and the preferable Fe content may be 4.3% or less.

The zinc alloy plating layer of the present invention may contain the remaining Zn and other unavoidable impurities. Unintended impurities from the raw material or the surrounding environment can be inevitably incorporated in the ordinary steel manufacturing process, and this can not be totally excluded. These impurities can be known to any person skilled in the art of steel manufacturing, so that the present invention does not particularly mention all of the impurities.

Hereinafter, the metal structure of the zinc alloy plating layer of the present invention will be described in more detail.

The zinc alloy plating layer of the present invention may include Zn / MgZn ₂ / Al ternary system structure, Zn single phase structure, and Fe-Zn-Al system crystal structure. The Fe-Zn-Al-based crystal structure is formed adjacent to the base steel wire and can be formed to have an average thickness of 1/5 to 1/2 of the average thickness of the zinc alloy plating layer. That is, the Fe-Zn-Al-based crystal structure is formed from the interface with the base steel wire to the area of 1/5 to 1/2 thickness of the average thickness of the zinc alloy plating layer, and the adhesion between the zinc alloy plating layer and the base steel wire It can be ensured effectively. Therefore, cracking in the zinc alloy plating layer or peeling of the zinc alloy plating layer during the processing of the coated steel wire of the present invention can be effectively prevented, so that the coated steel wire of the present invention can secure excellent workability.

The area fraction occupied by Zn single-phase structure in the Zn / MgZn ₂ / Al ternary system structure and the area occupied by the Zn single-phase structure in the cross section of the zinc alloy plating layer may be 60% or more, %. ≪ / RTI > In addition, the mean spacing of the single phase of Zn single phase can be uniformly distributed at a level of 1 ~ 5 ㎛, and thus the Zn / MgZn ₂ / Al ternary system can be uniformly distributed among the Zn single phase tissues. Therefore, the zinc alloy plating layer of the present invention can have a uniform corrosion resistance as well as a uniform Zn single phase structure and a Zn / MgZn ₂ / Al ternary system process structure.

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

A method of manufacturing a galvanized steel wire according to an embodiment of the present invention includes: firstly dipping a steel wire into a molten zinc plating bath to provide a galvanized steel wire; The primary dipped galvanized steel wire is secondarily immersed in a molten copper alloy gold plating bath to provide a galvanized gold wire; The second submerged galvanized gold-plated steel wire can be cooled at a cooling rate of 15 to 50 DEG C / s.

The hot dip galvanizing bath of the present invention means a plating bath containing Zn as a main component, but may contain impurities inevitably flowing in the plating bath production process. However, the hot-dip galvanizing bath of the present invention may mean a plating bath close to pure Zn, in which an alloy component such as Al and Mg is not artificially added. Therefore, the hot-dip galvanizing bath of the present invention may contain at least 95% Zn, preferably at least 98% Zn, more preferably at least 99% Zn.

The compositional content of the molten zinc alloy plating bath of the present invention corresponds to the reason for limiting the compositional content of the above-mentioned zinc alloy plating layer, and the reason for restricting the compositional content of the molten zinc alloy plating bath of the present invention is not limited to the zinc alloy The reason for restricting the compositional content of the plated layer is to be substituted. The description of the compositional content of the above-mentioned zinc alloy plating layer as a component of the Fe component of the zinc alloy plating layer, that is, the composition of the above-mentioned zinc alloy plating layer, is the same as that of the composition of the gold alloy gold plating bath of the present invention Can be excluded.

Pretreatment and primary immersion

It is possible to purify the base steel wire by a process such as pickling, washing and degreasing, and to perform flux treatment. The galvanized steel wire can be prepared by immersing the pre-treated steel wire in a hot-dip galvanizing bath at 440 to 460 ° C for 10 to 20 seconds. Therefore, a galvanized layer having Zn as a main component may be formed in the first-dipped galvanized steel wire.

Preparation of hot dip galvanizing bath

1.0 to 3.0% of Al, 1.0 to 2.0% of Mg, and the balance of Zn and Inevitable Zn-Al composite oxide ingots of a predetermined Zn-Al-Mg composite ingot or Zn- It is possible to produce a molten zinc alloy gold plating bath containing impurities. The temperature range suitable for melting these ingots may be from 440 to 520 캜. As the melting temperature of the ingot is higher, the fluidity in the plating bath can be ensured and a uniform composition can be obtained, and the amount of floating dross can be reduced, so that the ingot can be heated and melted in a temperature range of 440 캜 or higher. However, when the temperature of the molten alloy gold plating bath is higher than 520 ° C, it is highly likely that ash surface defects are caused by the evaporation of Zn, and the melting temperature of the ingot is also preferably limited to 520 ° C or lower . Preferably, in the initial stage of melting of the ingot, the temperature of the gold alloy gold plating bath is maintained at a level of from 500 to 520 DEG C to initiate melting, and then the stabilization of the gold alloy gold plating bath is performed at a temperature range of 440 to 480 DEG C It is desirable to complete the process.

Secondary immersion

The first immersed galvanized steel wire can be cooled to a temperature below the melting point of Zn, and then immersed in the molten zinc alloy plating bath prepared as described above.

Generally, if the content of Al in the plating bath is increased, the melting point is increased, so that the plating facility is eroded and the life of the equipment is shortened. In addition, the Fe alloy dross in the plating bath is increased and the surface of the plating material becomes poor . However, the content of Al in the molten zinc plating bath of the present invention is 1.0 to 2.0%, which is relatively low, and it is not necessary to set the temperature of the molten alloy gold plating bath higher than necessary. Therefore, a conventional plating bath temperature can be used as the temperature of the molten gold plating bath provided in the second immersion, and a temperature range of preferably 440 to 480 캜 can be applied. Also, the secondary immersion time can be suitably applied in consideration of the thickness of the zinc alloy plating layer and the like, and the secondary immersion can proceed preferably for 10 to 20 seconds.

The galvanized layer formed on the surface of the base steel sheet by the first immersion can be dissolved again or partially when the second base is immersed, so that the Al component contained in the Au alloy gold plating solution can diffuse to the interface side with the base steel sheet.

Cooling

The gold-plated steel wire after the second immersion is completed can be cooled at a cooling rate of 15 to 50 ° C / s. Preferably, immediately after the completion of the second immersion, the galvanized gold wire is cooled at a cooling rate of 15 to 50 ° C / Can be cooled. That is, cooling can be started from the bath surface of the molten gold coin plating bath. In order to prevent coarsening of the Zn single phase structure and prevent the formation of Zn / MgZn ₂ binary system structure, the cooling rate of the present invention may be higher than 15 ° C / s. If the mean spacing of the Zn single-phase structure main phase exceeds 5 占 퐉, uniform corrosion resistance can not be secured since the Zn single-phase tissue pores are excessively coarsened. In addition, Zn / MgZn ₂ ternary step 2 tissue may be harmful to the bar, a uniform corrosion resistance and workability, which leads to cracking during processing of the coated steel wire formed in the plating layer. On the other hand, when the cooling rate is excessive, the main phase of the Zn single phase structure becomes excessively fine and local uneven corrosion resistance can be manifested, and the diffusion of Fe-Zn-Al system is insufficient, It is impossible to expect a sufficient bonding force between the molten zinc alloy plating layer and the base steel wire so that the workability of the plated steel wire can be lowered.

The cooling of the present invention can be carried out by supplying an inert gas such as nitrogen, argon and helium, but relatively inexpensive nitrogen may be preferable in terms of production cost reduction.

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

(Example)

A steel wire containing 0.82% of C, 0.2% of Mn, 0.5% of Mn, 0.003% of P, 0.003% of P, and the balance of Fe and unavoidable impurities and having a diameter of 5 mm was prepared as test pieces and then subjected to degreasing and pickling , And subjected to flux treatment using a flux mainly containing zinc chloride (ZnCl ₂ ) and ammonium chloride (NH ₄ Cl). Then, the steel wire was first immersed in a hot dip galvanizing bath at 460 占 폚 for 15 seconds to adjust the average thickness of the hot dip galvanized layer to 20 占 퐉 and then cooled to a temperature equal to or lower than the melting point of Zn. Thereafter, a plated steel wire was prepared by immersing in a Zn-Mg-Al system plating bath having a composition corresponding to the composition of the plating layer shown in Table 1 below (except for the Fe component) at 460 ° C for 15 seconds, .

Each of the prepared coated steel wires was cut in a direction perpendicular to the longitudinal direction, and then a cross section was photographed with a scanning electron microscope (FE-SEM, Field Emission Scanning Electron Microscope). Based on the result of the photographing, The area ratio of the tissue, the mean spacing of the Zn single phase structure and the ternary system of Zn / MgZn ₂ / Al and the binary system of Zn / MgZn ₂ were measured. The area ratio of the Zn single phase structure means the ratio of the area occupied by the Zn single phase structure to the area occupied by the Zn single phase structure and the ternary system structure of Zn / MgZn ₂ / Al in the plating layer section.

For the evaluation of workability, each plated steel wire was cut into a 1 mm plated steel wire with a diameter reduction rate of 80%, and the surface appearance and corrosion resistance of the treated plated steel wire were evaluated. The surface appearance of the freshly plated steel sheet was measured using SEM, and it was judged based on the presence or absence of cracks in the image. The corrosion resistance was evaluated by performing a salt spray test on each of the freshly plated steel wires. Specifically, each of the coated steel wires was charged into a salt spray tester and then the time of occurrence of red rust was measured by an international standard (ASTM B117-11). Specifically, in a salt spray tester, a salt concentration of 5% 6.8) was sprayed with an injection volume of ² ml / 80 cm ² per hour. &Quot;",""," X ", and " X ", respectively, for each of the plated steel wires. . Generally, when the time for generating red rust is 300 hours or more in the salt spray test, it means that excellent corrosion resistance can be secured even in a severe oxidizing environment.

division Plating layer composition
(wt%) Cooling
speed
(° C / s) Zn single phase
Tissue area
Fraction
(%) Zn single phase
Tissue columnar mean
interval
(탆) The ratio of thickness of Fe-An-Al type crystal structure
(t: plating layer
thickness) Crack after freshness Evaluation of salt water spray after freshness Al Mg Fe time
(h) evaluation Inventory 1 2.0 1.7 0.8 30 85 3 t / 5 Not occurring 350 ◎ Inventory 2 1.5 1.5 3.5 25 90 3.5 t / 3 Not occurring 320 ◎ Inventory 3 2.5 2.0 2.5 40 75 2 t / 4 Not occurring 400 ◎ Honorable 4 2.8 1.2 4.3 20 70 4 t / 2 Not occurring 370 ◎ Comparative Example 1 2.5 3.0 2.4 5 50 15 t / 6 Occur 130 △ Comparative Example 2 1.8 3.0 2.2 10 70 10 t / 8 Occur 80 X Comparative Example 3 5.0 2.0 0.2 15 50 8 t / 7 Occur 75 X Comparative Example 4 1.0 0.9 1.5 20 80 6 t / 9 Not occurring 150 △

Inventive Examples 1 to 4 satisfied the conditions of the present invention, and it was confirmed that cracking did not occur after freshness, and 300 hours elapsed in the evaluation of the salt spray, indicating that redness occurred. On the other hand, Inventive Examples 1 to 4 do not satisfy the conditions of the present invention, and it can be confirmed that cracking occurs after freshness, and redness occurs within 200 hours in the evaluation of salt spray.

Fig. 1 is an FE-SEM image showing a section of Inventive Example 1, and Fig. 2 is an FE-SEM image of a surface of a coating layer of Inventive Example 1 observed.

As shown in FIGS. 1 and 2, in the case of Inventive Example 1, the area fraction of the Zn single phase structure is about 85%, and the main phase average interval of the Zn single phase structure is about 3 μm, and the main phase of the Zn single phase structure is finely As shown in FIG. In the case of Inventive Example 1, the Fe-Zn-Al-based crystal structure was formed at about 1/5 level from the interface with respect to the thickness of the entire plating layer, and the Zn / MgZn ₂ / Minute.

Fig. 3 is an FE-SEM image of the cross section of Comparative Example 1, and Fig. 4 is an FE-SEM image of the surface of the coating layer of Comparative Example 1. Fig.

As shown in FIG. 3 and FIG. 4, in the case of Comparative Example 1, the area fraction of the Zn single phase structure is about 50%, and the main phase average interval of the Zn single phase structure is about 15 μm. As shown in FIG. Further, in the case of Comparative Example 1, the Fe-Zn-Al-based crystal structure was thinly formed to about 1/6 level from the interface with respect to the thickness of the entire plating layer, and the Zn / MgZn ₂ 2 raw coarse- It can be confirmed that the minute includes nonuniformity.

FIG. 5 is a SEM image of the surface after the freshness of Inventive Example 1, and FIG. 6 is a SEM image of the surface after freshness of Comparative Example 1 observed.

As shown in Fig. 5, in Inventive Example 1, it can be confirmed that cracks do not occur on the surface of the plated layer after the drawing. On the other hand, as shown in FIG. 6, in the case of Comparative Example 1, it can be confirmed that a crack occurred on the surface of the plated layer after the drawing.

Therefore, the coated steel wire according to one embodiment of the present invention and the method for producing the same can provide a coated steel wire with effective workability and corrosion resistance, and a method of manufacturing the same.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, Therefore, the technical idea and scope of the claims set forth below are not limited to the embodiments.

Claims (7)

A base steel wire and a zinc alloy plating layer,
The zinc alloy plating layer is, in weight%, Al: 1.0 ~ 3.0% , Mg: 1.0 ~ 2.0%, Fe: 0.5 ~ 5.0%, remainder Zn and unavoidable including impurities, Zn / MgZn ₂ / Al 3 alloy process tissue , Zn single phase structure and Fe-Zn-Al type crystal structure,
Wherein the Fe-Zn-Al system crystal structure is formed adjacent to the base steel wire and has an average thickness of 1/5 to 1/2 of an average thickness of the zinc alloy plating layer. The method according to claim 1,
Wherein an area fraction occupied by the Zn single phase structure in the cross section of the zinc alloy plating layer, of the area occupied by the Zn / MgZn ₂ / Al ternary system structure and the Zn single phase structure is 60% or more. The method according to claim 1,
Wherein the main phase average interval of the Zn single phase structure in the cross section of the zinc alloy plating layer is 1 to 5 占 퐉. Firstly immersing the steel wire in a hot dip galvanizing bath to provide a galvanized steel wire;
The primary dipped galvanized steel wire is secondarily immersed in a molten copper alloy gold plating bath to provide a galvanized gold wire;
The second submerged galvanized gold-plated steel wire is cooled at a cooling rate of 15 to 50 ° C / s,
Wherein said molten alloy gold plating bath comprises 1.0 to 3.0% of Al, 1.0 to 2.0% of Al, and the balance of Zn and unavoidable impurities, in weight%. 5. The method of claim 4,
Wherein the base steel wire is first immersed in the molten zinc plating bath at 440 to 460 DEG C for 10 to 20 seconds. 5. The method of claim 4,
Wherein the zinc dipped galvanized steel wire is cooled to a temperature not higher than the melting point of Zn and is secondarily dipped in the molten zinc alloy plating bath. 5. The method of claim 4,
Wherein the galvanized steel wire is secondarily immersed in the molten alloy gold plating bath at 440 to 460 DEG C for 10 to 20 seconds.

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