JP2002047521A - Highly corrosion resistant plated steel and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide plated steel having increased corrosion resistance and workability and used outdoors, e.g., in buildings, shore protection works, fishing nets and fences and to provide its production method. SOLUTION: This plated steel has a plating layer having the average composition containing, by mass, 4 to 20% Al, 0.8 to 5% Mg and 0.01 to 2% Si, if required, containing one or more plural elements selected from one or plural groups of the following (a), (b), (c) and (d), and the balance Zn and moreover having a solidified structure of columnar crystals, in which Mg2Si is dispersedly present: (a) Ti, Li, Be, Na, K, Ca, Cu, La and Hf of 0.01 to 1.0%, (b): Mo, W, Nb and Ta of 0.01 to 0.2%, (c) Pb and Bi of 0.01 to 0.2% and (d) Sr, V, Cr, Mn and Sn of 0.01 to 0.5%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plated steel material having excellent corrosion resistance and workability of a steel material used by being exposed outdoors such as a building, seawall construction, a fish net, a fence and the like, and a method for producing the same. Here, the plated steel material is an iron wire for wire mesh,
Includes bridge wires, PWS wires, PC steel wires, plated steel wires such as ropes, structural steel materials such as H-shaped steel, steel sheet piles, mechanical parts such as screws, bolts, springs, and steel products such as steel plates. is there.

[0002]

2. Description of the Related Art Conventionally, galvanized steel wires and zinc-aluminum alloy-plated steel wires having better corrosion resistance have been used as plated steel materials, particularly as plated steel wires.
This zinc-aluminum alloy-plated steel wire is generally subjected to cleaning treatment by cleaning, degreasing, etc., the steel wire, and then performing a flux treatment, and then, as a first step, performing hot-dip plating mainly using zinc, As the second stage, the amount of Al
Hot-dip plating in a 0% Zn-Al alloy bath, or plating directly in a Zn-Al alloy bath containing 10% Al, then pulling up vertically from the plating bath, cooling, and winding. Being manufactured.

[0003] Steel wires plated with this zinc-aluminum alloy have good corrosion resistance, but there is a method of increasing the plating thickness in order to further increase the corrosion resistance. One of the methods to secure the required plating thickness is to increase the moving speed (linear speed) of the steel wire, pull up the steel wire from the plating bath at a high speed, and the amount of plating alloy adhering to the steel wire due to the viscosity of the hot-dip alloy. There is a way to increase. However, this method has a problem in that, due to the increase in speed, the plating thickness is likely to be non-uniform in a section perpendicular to the longitudinal direction of the plated steel wire. Thus, there is a limit in improving the corrosion resistance of plated steel in terms of plating equipment. Therefore, in the galvanizing with the current plating equipment or the hot-dip galvanizing with the Zn-Al alloy, it cannot be said that the corrosion resistance is sufficiently imparted to the steel wire. However, this technique has a problem that this demand cannot be completely satisfied.

[0004] In order to address this problem, Mg in a plating bath is used.
JP-A-10-226865 proposes a Zn-Al-Mg alloy-based plating composition in which the corrosion resistance is increased by adding Cu. The plating method based on this plating composition is based on the premise that thinning for steel sheets is used, and thick plating steel wires represented by steel wires used by exposing this method to buildings, seawalls, fish nets, fences, etc. When it is applied to a steel sheet, there is a problem that a crack occurs in a plated layer when processing a plated steel wire.

Japanese Patent Application Laid-Open No. 7-207421 discloses a method of thickening Zn-Al-Mg alloy plating. However, when this method is directly applied to steel wire plating, Fe -There is a problem that the Zn alloy layer becomes thick and the Fe-Zn alloy layer cracks or peels off during processing of the plated steel wire.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned various problems, and has been made based on the following problems. It is an object of the present invention to provide a plated steel wire excellent in workability in which cracking and peeling do not occur in a plated layer and / or an alloy layer, and a method for producing the same.

[0007]

Means for Solving the Problems The present inventors have conducted various studies on means for solving the above problems, and as a result, have reached the present invention. The gist of the present invention is as follows. (1) In a plated steel material, the average composition is
l: 4 to 20%, Mg: 0.8 to 5%, Si: 0.01
~ 2%, Fe: 2% or less, with the balance being Zn
A highly corrosion-resistant plated steel material characterized by having a solidified structure having a granular crystal structure and having a plated layer in which Mg ₂ Si is dispersed and present in the structure. (2) In the plated steel material, the average composition is A
l: 4 to 20%, Mg: 0.8 to 5%, Si: 0.01
~ 2%, Fe: 2% or less, and the following a, b,
It contains one or more elements selected from one or more of the groups c and d, is composed of the balance Zn, and has a columnar crystal structure, and Mg ₂ S in the structure.
A highly corrosion-resistant plated steel material having a plating layer in which i is dispersed. a: 0.01 to 1.0% by mass of each of Ti, Li, and B
e, Na, K, Ca, Cu, La, and Hf b: 0.01 to 0.2% by mass of Mo, W, and N, respectively.
b and Tac: 0.01 to 0.2% by mass of Pb and
Bid: 0.01 to 0.5% by mass of each of Sr, V, and C
r, Mn, and Sn

(3) Al—Zn is added to the structure of the plating layer.
(1) or (1) or (3), wherein an α phase containing Zn as a main component, a β phase composed of a Zn single phase or an Mg—Zn alloy phase, and a Zn—Al—Mg ternary eutectic phase are present. 2) The highly corrosion-resistant plated steel according to the above. (4) In the structure of the plating layer, β composed of an α-phase mainly composed of Al—Zn, a single phase of Zn, or a Mg—Zn alloy phase is used.
(1), (2) or (3), wherein each of the phase and the Zn-Al-Mg ternary eutectic phase exists, and the volume fraction of the β phase is 20% or less. High corrosion resistance plated steel material as described. (5) The high corrosion resistance according to (1), (2), (3) or (4), wherein the plated steel material is further coated with any one of a paint coating and a heavy corrosion protection coating. Plated steel. (6) The heavy duty anticorrosion coating is made of vinyl chloride, polyethylene,
The highly corrosion-resistant plated steel material according to the above (5), which is coated with at least one polymer compound selected from polyurethane and fluororesin. (7) The highly corrosion-resistant plated steel material according to (1), (2), (3), (4), (5) or (6), wherein the plated steel material is a plated steel wire. (8) In the method for producing a plated steel material, the steel material is subjected to hot-dip galvanizing mainly composed of zinc as a first step, and then, as a second step, the average composition is Al: 4 to
20%, Mg: 0.8-5%, Fe: 0-2%, balance Z
The method for producing a highly corrosion-resistant plated steel material according to the above (1), wherein a hot-dip zinc alloy plating comprising n is applied, and thereafter, the solidification structure of the plating layer is changed to a columnar crystal structure by cooling.

(9) The method for producing a highly corrosion-resistant plated steel material according to (8), wherein the cooling after the galvanizing alloy plating is performed at a cooling rate of 300 ° C./sec or more. (10) The hot-dip galvanizing as the first step is performed by mass%
Wherein the hot-dip galvanized steel contains Al: 3% or less and Mg: 0.5% or less. (11) In the step of applying the hot-dip galvanizing as the first step and then applying the hot-dip galvanized alloy plating as the second step, a portion where the plated steel material is pulled up from the plating bath is purged with nitrogen gas, and the surface of the plating bath is purged. And the method for producing a highly corrosion-resistant plated steel material according to (8), wherein oxidation of the plated steel material is prevented. (12) The hot-dip galvanizing as the first step is performed with a plating bath immersion time of 20 seconds or less, and then the hot-dip zinc alloy plating as the second step is performed with a plating bath immersion time of 20 seconds or less. The method for producing a highly corrosion-resistant plated steel material according to the above (8). (13) Immediately after applying the hot-dip zinc alloy plating as the second step, and immediately after pulling the coated steel wire out of the hot-dip zinc alloy plating bath, by direct cooling by any one of water spray, air-water spray and water flow The method for producing a highly corrosion-resistant plated steel material according to the above (8) or (9), wherein the plating alloy is solidified. (14) The production of a highly corrosion-resistant plated steel material according to (8), (9) or (13), wherein a cooling start temperature at the time of cooling the plated steel wire is set to be equal to or lower than a melting point of the plated alloy + 20 ° C. Method.

(15) In a method for producing a plated steel material,
As a first step, the steel is subjected to hot-dip galvanizing mainly composed of zinc, and then, as a second step, the average composition is
And Al: 4 to 20%, Mg: 0.8 to 5%, Si:
0.01 to 2%, Fe: 2% or less, and one or more elements selected from one or more of the following groups a, b, c, d, and the balance The method for producing a highly corrosion-resistant plated steel material according to the above (2), wherein the solidification structure of the plating layer is changed to a columnar crystal structure by subjecting to a hot-dip zinc alloy plating of Zn and then cooling. a: 0.01 to 1.0% by mass of each of Ti, Li, and B
e, Na, K, Ca, Cu, La, and Hf b: 0.01 to 0.2% by mass of Mo, W, and N, respectively.
b and Tac: 0.01 to 0.2% by mass of Pb and
Bid: 0.01 to 0.5% by mass of each of Sr, V, and C
r, Mn, and Sn (16) The high corrosion resistant plating according to (15), wherein the cooling performed after the galvanized zinc alloy plating as the second step is performed at a cooling rate of 300 ° C./sec or more. Method of manufacturing steel. (17) The hot-dip galvanizing as the first step is performed by mass%
, Wherein the hot-dip galvanizing method includes Al: 3% or less and Mg: 0.5% or less. (18) In the step of applying the hot-dip galvanizing as the first step and then applying the hot-dip zinc alloy plating as the second step, a portion of the steel plate pulled up from the plating bath is purged with nitrogen gas, and the surface of the plating bath is purged. And (1) wherein oxidation of the surface of the plated steel material is prevented.
5) The method for producing a highly corrosion-resistant plated steel material according to the above. (19) The hot-dip galvanizing as the first step is performed with a plating bath immersion time of 20 seconds or less, and then the hot-dip zinc alloy plating as the second step is performed with a plating bath immersion time of 20 seconds or less. The method for producing a highly corrosion-resistant plated steel material according to the above (15). (20) Immediately after applying the hot-dip zinc alloy plating as the second stage, and immediately after pulling the plated steel material out of the plating bath, plating is performed by direct cooling by any one of water spray, air-water spray, or water flow. The method for producing a highly corrosion-resistant plated steel material according to the above (15) or (16), wherein the alloy is solidified. (21) The method for producing a highly corrosion-resistant plated steel material according to the above (15), (16) or (20), wherein the cooling start temperature is set to be equal to or lower than the melting point of the plated alloy + 20 ° C. when cooling the plated steel material.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the plated steel material of the present invention will be described. The plated steel wire of the present invention has an average composition of mass%
And Al: 4 to 20%, Mg: 0.8 to 5%, Si:
0.01 to 2%, Fe: 2% or less, with the balance being Zn, and the solidification structure is a columnar crystal structure.
_It has a plating layer in which 2Si is dispersed. The average composition of the plated steel wire of the present invention is
And Al: 4 to 20%, Mg: 0.8 to 5%, Si:
0.01% to 2%, Fe: 2% or less, in addition to one or more of corrosion resistance improving element, plating hardness improving element, plating structure refinement element, plating workability improving element, and the balance It has a plating layer made of Zn and having Mg ₂ Si dispersed in the layer. First,
The role of the alloy element forming the plating layer and the content thereof will be described.

Al enhances corrosion resistance and has an antioxidant effect of preventing oxidation of other elements in the plating layer.
If the addition is less than 4%, the effect of preventing the oxidation of Mg in the plating bath cannot be obtained. Further, when Al is added in excess of 20%, the formed plating layer becomes hard and brittle, so that processing cannot be performed. Therefore, Al in the plating layer
The range of the addition amount is 4 to 20%. When plating a steel wire, the thickness is preferably set to 9 to 14% because the steel wire is thickened. A stable plating layer can be obtained with the Al content in this range.

[0013] Mg uniformly produces a corrosion product of plating, and the corrosion product containing Mg has an effect of inhibiting the progress of corrosion. Therefore, Mg has an effect of improving the corrosion resistance of the plating layer. is there. However, if the addition is less than 0.8%, the effect of improving corrosion resistance cannot be obtained, while 5%
If added in excess of the above, oxides are likely to be formed on the surface of the plating bath, and a large amount of dross is generated, making the plating operation difficult. In order to achieve both improvement in corrosion resistance and suppression of the amount of dross, the range of the added amount of Mg is set to 0.8 to 5%.

Si forms Mg ₂ Si in the plating layer,
Further, it is an element added to enhance corrosion resistance. Mg ₂ Si
Has a size of about 0.1 to 20 μm, is uniformly dispersed in the plating layer, and contributes to improvement of corrosion resistance.
If less than 0.01% is added, a sufficient amount of Mg to improve corrosion resistance
₂ Si is not generated, not the required corrosion resistance improving effect is obtained.
Si acts more effectively as the amount of Al added increases, and when the amount of Al added is at most 20%, the maximum amount of Si added is 2%. Therefore, the addition amount range of Si is set to 0.01 to 2%.

[0015] Fe may be eluted from steel during plating or may be present as an impurity in the plated metal. However, since Fe exceeding 2% causes a decrease in corrosion resistance, the upper limit is set. 2%. Although there is no particular lower limit on the amount of Fe added, Fe may not be included in some cases. Ti has an effect of improving corrosion resistance, and other elements having the same effect include Li, Be, and N.
a, K, Ca, Cu, La, Hf and the like. 0.01 to 0.5% of one or more of these elements
The addition can increase the corrosion resistance.
No effect is observed with the addition of less than 0.01%, while
If the addition exceeds 1.0%, phase separation may occur when the plating is solidified. Therefore, the addition amount range of these elements is set to 0.01 to 0.5%.

Mo has the effect of increasing the hardness of the plating layer and making it less likely to be damaged, and other elements having the same effect include W, Nb, Ta and the like. Of those elements, one
By adding one or more elements in an amount of 0.01 to 0.2%, the hardness of the plating layer can be increased and the plating layer can be hardly damaged. Pb and Bi have the effect of making the crystals on the plating surface finer. In a plated steel material such as a plate with a large plated surface or a shaped steel, a crystal of a plated alloy may grow large on the plated surface and look like a pattern. In order to avoid this phenomenon, Pb which does not form a solid solution with Zn and Fe,
Add Bi. Pb and Bi serve as nuclei for solidification during plating, promote fine crystal growth, and suppress generation of patterns. The range of the added amount of Pb and Bi to obtain this effect is
It is 0.01 to 0.2%.

Sr, V, Cr, Mn, and Sn have an effect of improving workability. If the addition amount is less than 0.01%, no effect is recognized, and if it exceeds 0.5%, segregation becomes remarkable and cracks easily occur during processing of the plated steel material. 0.01 to 0.5%. Furthermore, in the plated steel material of the present invention, plating is performed so that the solidification structure of the plating layer applied to the plated steel material has columnar crystals. The purpose of columnarizing the solidification structure of the plating layer is to impart corrosion resistance to the plated steel material.
After hot-dip galvanizing, hot-dip zinc alloy plating is further performed, and then, a cooling treatment is performed at a cooling rate of 300 ° C./sec or more, so that the solidified structure of the plated layer can be columnarized.

FIGS. 1A and 1B show the solidified structure of the plating layer. The cooling rate in the cooling treatment after the plating was 350 ° C./sec in FIG. 1A and 1 in FIG.
50 ° C./sec. The solidified structure of the plating layer shown in FIG. 1A is the columnar structure according to the present invention, and a fine granular structure is formed between the dendritic structures developed during solidification. Since the structure is fine and the structure having low corrosion resistance is not continuous, the structure is such that corrosion hardly proceeds from the surface layer into the inside of the layer. As a result, in the plated steel material of the present invention, the corrosion resistance of the plated layer is high. On the other hand, FIG.
The solidification structure of the plating layer shown in (b) has a granular crystal structure. In this granular crystal structure, since the grains of the solidification structure unit are large, when a structure having low corrosion resistance is present, corrosion easily proceeds from the surface layer into the inside of the layer, and the corrosion resistance is lower than that of the columnar crystal structure.

Further, in the plated steel material of the present invention, A
Since l and Mg are the main components, by cooling after plating,
In the plating alloy layer (plating layer) outside the alloy layer existing at the plating-ground iron interface, an α phase mainly composed of Al—Zn, a β phase composed of a Zn single phase or a Mg—Zn alloy phase, and , Zn-Al-Mg ternary eutectic phase can coexist. The presence of the Zn-Al-Mg ternary eutectic phase in the plating layer provides the uniform generation of corrosion products and the effect of preventing the corrosion products from progressing. The β phase is inferior to other phases in corrosion resistance, and thus is liable to cause local corrosion. If the volume ratio of the β phase exceeds 20%, the corrosion resistance is reduced, so the volume ratio is set to 20% or less.

After the steel material is plated, the steel material is rapidly cooled by, for example, water cooling, and the solidification structure of the plating alloy layer (plating layer) outside the Fe-Zn-based alloy layer existing at the plating-ground iron interface is removed. As shown in FIG. 1A, a columnar crystal structure can be obtained. However, when the plating layer has a columnar crystal structure, each structure generated during plating becomes fine, and the workability is somewhat sacrificed. Even so, the improvement in corrosion resistance is remarkable.

The method for producing the plated steel material of the present invention includes:
Adopt the two-step plating method. As a first step, hot-dip galvanizing mainly comprising zinc is formed to form an Fe-Zn alloy layer, and then, as a second step, hot-dip zinc alloy plating having an average composition defined in the present invention is performed. Thus, the plated steel material of the present invention can be obtained efficiently. As hot-dip zinc used in hot-dip galvanizing as the first stage,
A molten zinc alloy containing Al: 3% or less and Mg: 0.5% or less can also be used. When the Fe—Zn alloy layer is obtained by hot-dip galvanizing as the first step, if the Fe—Zn alloy layer contains Al and Mg, A
There is an effect that l and Mg can easily enter.

In the method for producing a plated steel material according to the present invention, a portion where the plated steel material is pulled up from the plating bath is purged with nitrogen gas to prevent oxidation of the surface of the plating bath and the surface of the plated steel material, thereby improving workability. Can be.
Immediately after plating, if an oxide is generated on the plating surface or an oxide generated on the plating bath surface adheres to the plating surface, the plating may crack with the oxide as a nucleus during processing of the plated steel material. is there. Therefore, preventing oxidation of the surface of the plating bath and the surface of the plated steel material in a portion where the plated steel material is pulled up from the plating bath is an important factor in maintaining a desired material of the plated steel material.

FIG. 2 shows the plating alloy composition (Zn-
Surface cracks during winding test (number of wires) of plated steel wire of 11% Al-3Mg-0.1% Si) with or without gas
Are compared. If the gas is not cut off, cracks may occur on the surface exceeding the allowable limit. In order to prevent oxidation, it is possible to use an inert gas such as argon or helium in addition to nitrogen. However, nitrogen is the best in terms of cost.

In the case where the plated steel material of the present invention is obtained by the two-step plating method, in order to make the growth of the plated alloy appropriate, the hot-dip galvanizing mainly composed of zinc as the first step is carried out by dipping in a plating bath. 20 seconds or less, and then hot-dip zinc alloy plating as the second step
It is necessary to apply it in 0 seconds or less. In any case, if plating is performed for a long time exceeding 20 seconds, the thickness of the entire alloy layer becomes large and exceeds 35 μm, which is not preferable. Therefore,
As a first stage, hot-dip plating mainly composed of zinc is applied for a plating bath immersion time of 20 seconds or less, and then, as a second stage,
Hot-dip zinc alloy plating is performed with a plating bath immersion time of 20 seconds or less.

Further, after the steel material is plated, when cooling the plated steel material, the steel is cooled at a cooling rate of 300 ° C./sec or more so that the solidification structure of the plating layer is refined and columnarized. What is necessary is just to employ | adopt the cooling means which can achieve the said cooling rate as a cooling means. For example, the plating alloy is solidified by direct cooling by any one of water spray, air-water spray, and water flow, but preferably water spray or air-water spray is used. A stable plating layer can be obtained by adopting this water spray or air-water spray and setting the cooling start temperature at the time of the cooling to be equal to or lower than the melting point of the plating alloy + 20 ° C.

As the plated steel material used in the present invention, a low carbon steel containing 0.01% by mass of carbon to a high carbon steel containing about 1% by mass is generally used without any limitation as long as it is a steel material. It is possible, and the component composition is typically, in mass%, C: 0.02 to 0.25%, Si: 1%
Hereinafter, Mn: 0.6% or less, P: 0.04% or less, S:
It is a steel material containing 0.04% or less, with the balance being Fe and unavoidable impurities.

In the present invention, the surface of the plated steel material is finally coated or coated with at least one polymer compound selected from vinyl chloride, polyethylene, polyurethane and fluororesin. By applying the anticorrosion coating, the corrosion resistance can be further improved. Although the present invention has been described centering on plated steel materials, particularly steel wires, the present invention can be applied to steel plates, steel pipes, steel structures, and other steel products. Of course.

[0028]

EXAMPLES (Example 1) A 4 mm diameter steel wire obtained by applying pure Zn plating to the surface of a steel wire rod "JIS G 3505 SWRM6" was subjected to Zn-Al-Mg zinc plating under the conditions shown in Table 1. And various characteristics were evaluated. As comparative examples, the plating composition and F
What changed the e-Zn alloy layer was evaluated similarly. Observation of the plating structure was carried out by polishing the C section of
A. Regarding the composition analysis of the alloy layer, quantitative analysis was performed with a beam diameter of 2 μm. For corrosion resistance,
A continuous salt spray test for 250 hours was performed, and the amount of corrosion of the plating per unit area was calculated from the difference in weight before and after the test to determine the corrosion loss. In this test, a pass / fail was determined as a corrosion weight loss of 20 g / m ² or less.

The workability was evaluated by using the prepared plated steel wire for 6 times.
It is wound around a steel wire with a diameter of 6 mm six times, and its surface is visually observed.
The presence or absence of cracks was determined. In addition, a cellophane tape was attached to the sample after crack determination, and the presence or absence of peeling of the plating when the sample was peeled was observed. One or less cracks or no peeling was regarded as a pass condition. Table 1 shows the relationship between the average plating composition, the thickness, the structure, and the β phase volume ratio of the plating layer, and the corrosion resistance, workability, and dross generation of the plating bath. All of the invention examples exhibited good corrosion resistance and workability, and produced little dross.
In Comparative Examples 1 to 7, the plating alloy composition was out of the range of the present invention. In Comparative Examples 1 to 3, the amount of Al, Mg or Si is lower than the lower limit of the range of the present invention, and as a result, the corrosion resistance is inferior. In Comparative Examples 4 to 7, the amount of Al, Mg, or Si was higher than the upper limit of the range of the present invention, and as a result, corrosion resistance was poor, and the amount of dross generated in the plating bath was large, which hindered the operation. In Comparative Examples 8 and 9, the thickness of the plating alloy was out of the range of the present invention, resulting in poor workability. Comparative Examples 10 to 12
Is that the β phase in the plating structure is out of the range of the present invention, and as a result, the corrosion resistance is poor. Table 2 shows a plated steel wire obtained by plating a steel wire with a plating alloy having the same composition, changing the cooling rate, and changing the solidification structure of the plating layer to a granular crystal structure, and
This is a comparison of differences in corrosion resistance (corrosion loss) by producing plated steel wires having the same columnar crystal structure. The plated steel wire having each solidification structure was subjected to a continuous salt spray test for 250 hours. From the results shown in Table 2, it can be seen that both the granular crystal structure and the columnar crystal structure satisfy the required standards, but the columnar crystal structure has better corrosion resistance.

[0030]

[Table 1]

[0031]

[Table 2]

(Example 2) A steel wire rod of JIS G 3505 SWRM6 having a diameter of 4 mm and having a surface of pure Zn plated with Zn-Al-Mg based zinc alloy plated under the conditions shown in Table 3 The properties were evaluated. As comparative examples, plating composition,
What changed the Fe-Zn alloy layer was evaluated similarly. Observation of the plating structure was carried out by polishing the C section of the plating wire, followed by EP
Performed at MA. Regarding the composition analysis of the alloy layer, quantitative analysis was performed with a beam diameter of 2 μm. Regarding the corrosion resistance, a continuous salt spray test for 250 hours was performed, and the amount of corrosion of the plating per unit area was calculated from the difference in weight before and after the test to determine the corrosion loss. In this test, the corrosion loss was 20 g / m ²
The following were accepted as pass / fail.

The workability was evaluated by using the prepared plated steel wire for 6 times.
It was wound around a steel wire having a diameter of 6 mm six times, and its surface was visually observed to determine the presence or absence of cracks. In addition, a cellophane tape was attached to the sample after the crack determination, and the presence or absence of peeling of the plating when peeling the cellophane tape was observed. Table 3 shows the average plating composition,
Further, the relation between the thickness, the structure, and the β phase volume ratio of the plating layer and the corrosion resistance, workability, and dross generation of the plating bath are shown. The invention examples are all good corrosion resistance, and
It showed processability and dross generation was small.

In Comparative Examples 13 to 19, the plating alloy composition was out of the range of the present invention. Comparative Examples 13 to 15
The amount of l, Mg or Si is lower than the lower limit of the present invention, resulting in poor corrosion resistance. Comparative Examples 16 to 19
The amount of Al, Mg or Si is higher than the upper limit of the range of the present invention. As a result, corrosion resistance is deteriorated, and dross generation in the plating bath is large, which hinders operation. In Comparative Examples 20 and 21, the thickness of the plating alloy layer was out of the range of the present invention, resulting in poor workability. In Comparative Examples 22 to 24, the volume ratio of the β phase in the plating structure was out of the range of the present invention, and as a result, the corrosion resistance was poor.

Table 4 compares differences in corrosion resistance due to wire drawing. By changing the cooling rate for the plating having the same composition, a plated steel wire having a granular structure and a plated steel wire having a columnar crystal were produced, and a continuous salt spray test was performed for 250 hours. As a result, it was shown that the plating with the columnar crystal structure was more excellent in the corrosion resistance than the plating with the granular crystal structure, although all of the samples satisfied the acceptance criteria.

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

As described above, according to the present invention,
A plated steel material having high corrosion resistance and excellent workability, in particular, a plated steel wire having high corrosion resistance and excellent workability can be obtained.
Therefore, the present invention greatly contributes particularly to the development of the industry using steel wires.

[Brief description of the drawings]

FIG. 1 is a view showing a cross section of the structure of a plated steel wire.
(A) is a figure which shows the cross section of the columnar crystal structure in a plating layer, (b) is a figure which shows the cross section of the granular crystal structure in a plating layer.

FIG. 2 is a diagram comparing surface cracks (number) during a winding test with respect to plated steel wires plated with a Zn-11% Al-3Mg-0.1% Si alloy, with or without gas deflation.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Seiji Nishida 1 Kimitsu, Kimitsu City, Chiba Prefecture Inside Nippon Steel Corporation (72) Inventor Akira Takahashi 1 Kimitsu, Kimitsu City, Chiba Prefecture Nippon Steel Corporation (72) Inventor Atsuhiko Yoshie 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Kazumi Nishimura 1 Fujimachi, Hirohata-ku, Himeji-shi, Hyogo New Japan 4K027 AA05 AA06 AA22 AB02 AB05 AB33 AB34 AB42 AB44 AC72 AE03 AE33

Claims (21)

[Claims] In a plated steel material, the average composition is, in mass%, Al: 4 to 20%, Mg: 0.8 to 5%, Si:
0.01 to 2%, Fe: 2% or less, with the balance being Zn, and the solidification structure is a columnar crystal structure.
_2. A highly corrosion-resistant plated steel material having a plating layer in which Si is dispersed. 2. The plated steel material has an average composition of 4 to 20% Al, 0.8 to 5% Mg, and Si:
0.01 to 2%, Fe: 2% or less, and one or more elements selected from one or more of the following groups a, b, c, d, and the balance In addition to being composed of Zn, the solidification structure is a columnar crystal structure, and M
A highly corrosion-resistant plated steel material having a plating layer in which g ₂ Si is dispersed. a: 0.01 to 1.0% by mass of each of Ti, Li, and B
e, Na, K, Ca, Cu, La, and Hf b: 0.01 to 0.2% by mass of Mo, W, and N, respectively.
b and Tac: 0.01 to 0.2% by mass of Pb and
Bid: 0.01 to 0.5% by mass of each of Sr, V, and C
r, Mn, and Sn 3. The structure of the plating layer includes an α phase mainly composed of Al—Zn, a β phase composed of a Zn single phase or a Mg—Zn alloy phase, and a Zn—Al—Mg ternary eutectic phase. The highly corrosion-resistant plated steel material according to claim 1, wherein each of the steel materials is present. 4. The structure of the plating layer includes an α phase mainly composed of Al—Zn, a β phase composed of a single phase of Zn or an Mg—Zn alloy phase, and a ternary eutectic phase of Zn—Al—Mg. 4. The highly corrosion-resistant plated steel material according to claim 1, wherein each of them is present and the volume fraction of the β phase is 20% or less. 5. The highly corrosion-resistant plated steel material according to claim 1, wherein the plated steel material further has any one of a coating and a heavy corrosion protection coating. 6. The highly corrosion-resistant plated steel material according to claim 5, wherein said heavy corrosion protection coating is a coating of at least one polymer compound selected from vinyl chloride, polyethylene, polyurethane, and fluororesin. 7. The highly corrosion resistant plated steel material according to claim 1, wherein the plated steel material is a plated steel wire. 8. A method for producing a plated steel material, wherein the steel material is subjected to hot-dip galvanizing mainly comprising zinc as a first step, and then to a second step, wherein the average composition is A
l: 4 to 20%, Mg: 0.8 to 5%, Fe: 0 to 2
2. A method for producing a highly corrosion-resistant plated steel material according to claim 1, wherein the solidification structure of the plating layer is changed to a columnar crystal structure by subjecting to a hot-dip zinc alloy plating comprising a% and a balance of Zn, followed by cooling. 9. The cooling after the hot-dip zinc alloy plating is performed by 3
The method for producing a highly corrosion-resistant plated steel material according to claim 8, wherein the cooling is performed at a cooling rate of 00 ° C / sec or more. 10. The method according to claim 8, wherein the hot-dip galvanizing as the first stage is hot-dip galvanizing containing Al: 3% or less and Mg: 0.5% or less by mass%. Manufacturing method of high corrosion resistant plated steel. 11. A step of applying hot-dip galvanizing as the first step and then applying a hot-dip zinc alloy plating as the second step, by purging a portion of the steel plate to be pulled up from a plating bath with nitrogen gas, The method for producing a highly corrosion-resistant plated steel material according to claim 8, wherein oxidation of the bath surface and the plated steel material is prevented. 12. The hot-dip galvanizing as the first step is performed with a plating bath immersion time of 20 seconds or less, and then the hot-dip zinc alloy plating as the second step is performed with a plating bath immersion time of 20 seconds or less. The method for producing a highly corrosion-resistant plated steel material according to claim 8, characterized in that: 13. The hot-dip zinc alloy plating as the second stage is performed, and immediately after the coated steel wire is lifted from the hot-dip zinc alloy plating bath, it is directly sprayed by one of water spray, steam-water spray and water flow. The method for producing a highly corrosion-resistant plated steel material according to claim 8, wherein the plating alloy is solidified by cooling. 14. The method for producing a highly corrosion-resistant plated steel material according to claim 8, wherein the cooling start temperature at the time of cooling the plated steel wire is equal to or lower than the melting point of the plated alloy + 20 ° C. 15. A method for producing a plated steel material, wherein the steel material is subjected to hot-dip galvanizing mainly composed of zinc as a first step, and then, as a second step, the average composition is
Al: 4 to 20%, Mg: 0.8 to 5%, Si: 0.0
1 to 2%, Fe: 2% or less, and the following a, b,
a solidification structure of a plating layer containing one or more elements selected from one or more of the groups c and d, and performing hot-dip zinc alloy plating comprising the balance of Zn, and then cooling; 3. The method for producing a highly corrosion-resistant plated steel material according to claim 2, wherein the steel has a columnar crystal structure. a: 0.01 to 1.0% by mass of each of Ti, Li, and B
e, Na, K, Ca, Cu, La, and Hf b: 0.01 to 0.2% by mass of Mo, W, and N, respectively.
b and Tac: 0.01 to 0.2% by mass of Pb and
Bid: 0.01 to 0.5% by mass of each of Sr, V, and C
r, Mn, and Sn 16. The method for producing a highly corrosion resistant plated steel material according to claim 15, wherein the cooling performed after the galvanized zinc alloy plating as the second stage is performed at a cooling rate of 300 ° C./sec or more. 17. The hot-dip galvanizing as the first step is a hot-dip galvanizing containing Al: 3% or less and Mg: 0.5% or less by mass%.
The method for producing a highly corrosion-resistant plated steel material according to the above. 18. A step of applying the hot-dip galvanizing as the first stage and then performing the hot-dip galvanizing alloy plating as the second stage, purging a portion where the plated steel material is pulled up from a plating bath with nitrogen gas, The method for producing a highly corrosion-resistant plated steel material according to claim 15, wherein oxidation of the bath surface and the surface of the plated steel material is prevented. 19. The hot-dip galvanizing as the first step is performed with a plating bath immersion time of 20 seconds or less, and then the hot-dip zinc alloy plating as the second step is performed with a plating bath immersion time of 20 seconds or less. The method for producing a highly corrosion-resistant plated steel material according to claim 15, characterized in that: 20. The hot-dip zinc alloy plating as the second stage is performed, and immediately after the plated steel material is pulled out of the plating bath, water cooling, air-water spraying, or direct cooling by any one of means of water flow is performed. 17. The method according to claim 15, wherein the plating alloy is solidified. 21. The method for producing a highly corrosion-resistant plated steel material according to claim 15, wherein the cooling start temperature is set to be equal to or lower than the melting point of the plated alloy + 20 ° C. when cooling the plated steel material.