JP2003328101A - Hot dip coated steel wire and production method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated steel wire which has fatigue resistance and excellent corrosion resistance. <P>SOLUTION: In the coated steel wire having fatigue resistance and excellent corrosion resistance, an Fe-Zn-Al-Mg quaternary intermetallic compound is present in a thickness of 2 to 20 μm on the boundary of ferrite in the plating. Residual strain is present by ≥0.01% in the intermetallic compound layer. A Zn-Al-Mg based alloy layer consisting of, by mass, 8 to 15% Al and 0.1 to 3% Mg, and the balance Zn is present by ≥5 μm on the outside thereof. Alternatively, ≥4% Al and ≥0.1% Mg are contained in the Fe-Zn-Al-Mg alloy layer present on the boundary of ferrite in the coating as for the coated steel wire. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plated steel wire for supporting power lines and signal lines, a wire for a bridge, a wire used for being exposed to the outdoors such as a wire net, etc., and a method for manufacturing the same. It is a thing.

[0002]

2. Description of the Related Art Conventionally, a galvanized steel wire or a zinc-aluminum alloy-plated steel wire having better corrosion resistance than that has been used as a galvanized steel wire. This zinc-aluminum alloy-plated steel wire is generally treated by cleaning the steel wire by cleaning, degreasing, etc., then performing flux treatment, hot-dip galvanizing as the first step, and then adding Al as the second step. It is produced by hot dip plating in a 10% Zn-Al alloy bath or by directly plating in a 10% Zn-Al alloy bath, pulling it up vertically from the plating bath, cooling and winding. To be

[0003]

Since the zinc-aluminum alloy-plated steel wire has good compatibility between the base iron and the Fe-Zn-Al alloy layer, cracks generated on the surface of the plated wire easily propagate to the base iron. However, there is a drawback that the fatigue resistance is inferior to that of the Zn-plated steel wire. Zn-plated steel wire is Fe-Z
Since the n-alloy layer is harder than the Zn layer and stops the development of cracks, the fatigue strength is higher than that of the zinc-aluminum alloy-plated steel wire. However, the corrosion resistance of Zn-plated steel wire is inferior to that of zinc-aluminum alloy-plated steel wire. To increase the corrosion resistance of the Zn-plated steel wire, there is a method of increasing the plating thickness. However, there is a limit to the thickness because the plating is likely to peel off when the plating thickness is increased.

[0004]

Therefore, the first aspect of the present invention is to provide a plated steel wire with Fe-Zn-Al at the interface of the plated base iron.
-Mg quaternary intermetallic compound exists in a thickness of 2 to 20 [mu] m, residual strain exists in the intermetallic compound layer in an amount of 0.01% or more, and Al: 8 to 15% by mass% and Mg: outside thereof.
A plated steel wire having fatigue resistance and excellent corrosion resistance, characterized in that a Zn-Al-Mg-based alloy layer consisting of 0.1 to 3% and the balance Zn is present at 5 µm or more.

Secondly, in the plated steel wire, A is contained in the Fe-Zn-Al-Mg alloy layer existing at the interface of the plated base iron.
The galvanized steel wire according to claim 1, wherein the galvanized steel wire includes 1: 4% or more and Mg: 0.1% or more, and has fatigue resistance and excellent corrosion resistance. The third is a plated steel wire characterized in that the above plating alloy composition contains Si: 2% or less in mass%. Fourthly, a plated steel wire is characterized in that the plating alloy composition described above contains 0.001 to 0.1% of sodium in mass%.

The fifth is a plated steel wire characterized by containing Ti: 0.01 to 0.2% in mass% in the above-mentioned plating alloy composition. Sixth, in a galvanized steel wire, an α phase containing Al—Zn as a main component and a Zn single phase or a Mg—Zn alloy in an outer plating layer of an Fe—Zn-based alloy layer present at the galvanized base iron interface. The plated steel wire is characterized by the presence of a β phase and a Zn / Al / Zn-Mg ternary eutectic phase.

Seventh, in a galvanized steel wire, an α phase containing Al—Zn as the main component and a Zn single phase or Mg— in the plating phase outside the Fe—Zn-based alloy layer present at the interface of the galvanized base iron. Β phase consisting of Zn alloy phase and Zn / Al / Zn
-Mg ternary eutectic phase is present, and the volume ratio of α phase is 20% or less. Eighth, when producing a galvanized steel wire, hot-dip galvanizing mainly zinc is applied as the first step, and then the second step is that the average composition of the hot-dip zinc alloy is the above-mentioned plating composition 1-5. And a method for producing a plated steel wire.

Ninth, in the production of plated steel wire,
As the first stage, in mass% Al: 3% or less, Mg: 0.1%
A method for producing a galvanized steel wire is characterized in that hot-dip galvanizing including the following is performed, and then, as a second step, the mean composition of the hot-dip zinc alloy is the plating composition of the above 1 to 5. The tenth is that the first step is hot-dip galvanizing, and then the second step is hot-dip zinc alloy plating. The method for producing a plated steel wire is characterized by preventing oxidation of the bath surface and the plated steel wire.

In the eleventh step, hot-dip galvanizing mainly containing zinc is performed as a first step with a plating bath immersion time of 20 seconds or less, and then as a second step, hot-dip zinc alloy plating is performed with a plating bath immersion time of 20 seconds or less. It is a characteristic method for producing a plated steel wire. In the twelfth, in the process for producing a plated steel wire in which hot-dip galvanizing mainly zinc is applied as the first step and then hot-dip zinc alloy plating is performed as the second step, water spray or immediately after pulling the plated steel wire from the plating alloy is performed. A method for producing a plated steel wire, characterized in that the plating alloy is solidified by direct water cooling with steam spray or water flow.

In the thirteenth, in the galvanized steel wire manufacturing process in which hot-dip plating mainly containing zinc is applied as the first step, and then hot-dip zinc alloy plating is performed as the second step, the cooling start temperature when cooling the galvanized steel wire. Is a melting point of the plating alloy to a melting point + 20 ° C., a method for producing a plated steel wire. The fourteenth is that the steel component of the plated steel wire is C by mass:
0.25 to 1.05%, Si: 1% or less, Mn: 0.9
%, P: 0.04%, S: 0.04% or less. A plated steel wire and a method for producing the same.

The details will be described below. The wire used for plating in the present invention is a steel wire obtained by cleaning the steel wire by cleaning, degreasing, etc., and then performing a flux treatment, or the first wire.
The galvanized wire is hot-dip galvanized as a step.
In conventional zinc plating or Zn-Al alloy plating, Zn-Fe or Zn-Fe-A is present at the interface between the base iron and the plating.
l alloy layers are formed. In addition, Fe-Zn- of the present invention
The alloy layer of the Al-Mg quaternary alloy has a function of strengthening the adhesion between the base iron and the plating layer. Peeling does not occur even if the plated wire is wound around a wire having the same diameter and subjected to severe processing. As a result of various experiments, it was found that the minimum required thickness of the alloy layer is 2 μm, and if it exceeds 20 μm, cracks are likely to occur in the alloy layer.
And Further, it is desirable that this thickness be thin, 10 μm
Is desirable.

The composition of the plating alloy is Zn based on Al,
Mg is added. Al has the effect of increasing corrosion resistance. When Al is less than 8%, the effect of improving corrosion resistance is low, and 15
%, Al on the surface of the plating bath is oxidized by air and the yield of the plated alloy deteriorates, so it is set to 8% to 15%. Further, Al enters the Fe-Zn alloy layer and Fe-Z
The n-Al ternary system has an effect of improving workability. However, it is impossible to prevent the propagation of fatigue cracks.

[0013] Mg has the effect of preventing the progress of corrosion by the uniformly formed corrosion product and the effect of hardening the plating layer and preventing the development of fatigue cracks. The range of Mg is 0.1
If it is less than%, it is not effective in preventing crack growth due to hardening and is 3%.
If it exceeds, the plating layer is too hard to withstand processing such as wire drawing, so the content is set to 0.1 to 3%. In order to improve the workability, it is desirable that the content of Mg be 1% or less. In the present invention, the amount of Mg is determined from the viewpoint of fatigue strength, but the corrosion resistance is sufficiently high in this range.

The above-mentioned Zn-Al-Mg-based alloy layer existing outside the Fe-Zn-Al-Mg quaternary alloy layer exerts an anticorrosive action while producing a corrosion product, and thus the thicker it is, the more excellent the corrosion resistance is. In general industrial production, the plating thickness is usually uneven in the circumferential direction, and if the average thickness is 5 μm, the Fe—Zn—Al—Mg alloy layer is not exposed even in a thin place, In order to maintain the corrosion resistance, 5 μm or more is necessary.

Fatigue failure of a galvanized steel wire leads to cracking from the occurrence of cracks in plating under repeated stress through the progress of cracks. In the case of a galvanized steel wire, the strength of plating is much smaller than that of steel, so that it does not occur from steel, but occurs from the surface of the plating to which the greatest stress is applied or the hard and brittle alloy layer. Since the alloy layer of the Al-added alloy has ductility, it was found that cracks generated on the surface propagate as they are from the plating layer to the base iron. As a result of examining countermeasures, it is necessary to increase the hardness of the alloy layer by adding Mg, and to impart compressive strain to the alloy layer existing at the interface between the plating and the base iron in order to mitigate the effect of becoming brittle by hardening. It was found that can be prevented by. When the residual strain of 0.01% or more is given by the cooling control at the time of producing the plated steel wire, the effect is great, so the lower limit is made 0.01%.

It is also effective to add Si to the plating layer in order to further improve the corrosion resistance. It is more effective to add Si when the amount of Al added is large. In the case where the maximum amount of Al added in the present invention is 20%, the maximum amount that the effect of Si can be obtained is 2%, so the range of Si is set to 2%. Further, dross is generated on the surface of the plating bath during plating, but addition of a small amount of Na is effective for suppressing dross generation. By suppressing the generation of dross, the plating surface can be improved and the yield of plating alloy can be improved. When Na exceeds 0.1%, oxidation of Na occurs, so the range of Na was made 0.001 to 0.1%. Further, addition of Ti is effective for suppressing the formation of dross, and its effective range is 0.0
It is 1 to 0.1%.

In addition to the above Si, Na, and Ti, addition of antimony, misch metal, etc. can improve the surface quality of plating. In the galvanized steel wire described so far, the corrosion resistance is improved by including Al: 4% or more and Mg: 1% or more in the Fe—Zn alloy layer existing at the galvanized base iron interface. If the Al content in the alloy layer is 4% or more, the effect of improving corrosion resistance cannot be obtained, so the Al content is 4%.
That is all. Further, the addition of Mg produces a uniform corrosion product, but if it is less than 1%, the effect cannot be obtained. Therefore, the amount of Mg is set to 1% or more.

In the plated steel wire of the present invention, Al, M
Since g is contained as a component, cooling after the plating causes Al-Z in the plating layer outside the alloy layer existing at the interface of the plating base iron.
An α phase containing n as a main component, a β phase consisting of a Zn single phase or a Mg—Zn alloy phase, and a Zn / Al / Zn—Mg ternary eutectic phase can coexist. Of these, Zn / Al / Zn
The presence of the —Mg ternary eutectic phase provides the uniform formation of corrosion products and the effect of preventing the progress of corrosion by the corrosion products. Further, the α phase crystallizes as a primary crystal in the solidification process, but when the cooling rate is slow, the α phase becomes coarse and almost no residual strain of plating occurs. If the deposition rate of the α phase exceeds 20%, residual strain does not occur and the fatigue characteristics are deteriorated. Therefore, the volume ratio is 20% or less.

As a method for obtaining the plated steel wire of the present invention, there is a two-step plating method. The first step is hot-dip galvanizing to form a Fe-Zn alloy layer, and then the second step is to make the average composition of the hot-dip zinc alloy within the scope of the present invention. It can be obtained efficiently. As the first stage molten zinc alloy, A in mass%
It is also possible to include 1: 3% or less and Mg: 0.5% or less. When the Fe-Zn alloy layer is obtained in the first step, Al,
The inclusion of Mg has the effect of making it easier for Al and Mg to enter the alloy layer.

In order to produce the plated steel wire of the present invention, the portion pulled up from the plated alloy is purged with nitrogen gas,
Workability can be improved by preventing oxidation of the bath surface and the plated steel wire. If oxides are formed on the plating surface or formed on the bath surface immediately after plating,
The plating may crack with the oxide as a nucleus during processing.
Therefore, it is important to prevent oxidation of the takeout part. In addition to nitrogen, an inert gas such as argon or helium can be used for preventing oxidation, but nitrogen is the best in terms of cost.

When the plated wire of the present invention is obtained by two-step plating, in order to properly grow the plating alloy, hot-dip plating mainly containing zinc is applied as the first step with a plating bath immersion time of 20 seconds or less, Next, as the second step, it is necessary to perform hot dip zinc alloy plating with a plating bath immersion time of 20 seconds or less.
If plating is performed for a longer time than this, the thickness of the alloy layer becomes thicker and exceeds 20 microns. Therefore, as the first step, hot dip plating mainly consisting of zinc is applied for a plating bath immersion time of 20 seconds or less, and then the second step. As a step, hot dip zinc alloy plating is performed with a plating bath immersion time of 20 seconds or less. A Zn-plated wire having a Fe—Zn alloy layer thickness of 15 μm formed by first-stage Zn plating (immersion time: 20 seconds) had a bath composition of Zn-10% A.
As a result of investigating the relationship between the immersion time of the plating bath and the thickness of the Fe—Zn alloy layer in the case of plating with 1-1% Mg, the thickness of the alloy layer in the second-stage alloy plating was 20 times the immersion time of the plating alloy bath. If it is less than a second, the growth is small and the alloy layer thickness is 20 μm or less.

By quickly cooling the plated alloy of the plated steel wire after plating from a molten state, the plating can be cooled rapidly and residual strain can be imparted by solidification shrinkage. As a method therefor, there is a method in which the plated alloy is solidified by water spray, steam spray or direct water cooling by a water flow immediately after the plated steel wire is pulled out from the plated alloy. The compressive stress generated by this cooling is caused by residual strain and improves fatigue characteristics.

When cooling the plated steel wire, it is necessary to start cooling while the plating is in a molten state. When solidified by air cooling or the like, the residual strain generated during solidification of each phase is relaxed, and the effect of improving fatigue characteristics is reduced. Therefore, the cooling start temperature needs to be equal to or higher than the melting point of the plated alloy. Further, when cooling water hits the hot-dip galvanizing having a low viscosity, the plating surface becomes rough, so the upper limit is made the melting point + 20 ° C.

The components of the steel of the galvanized steel wire are C: 0.25 to 1.05% by mass, Si: 1% or less, and Mn:
0.6% or less, P: 0.04%, S: 0.04% or less. C is an element that determines the strength of steel, and is required to be 0.25% or more in order to realize the strength of ordinary plated steel wire. On the other hand, if it exceeds 1.05%, martensite is generated immediately after rolling and subsequent processing cannot be performed.
5% or less. Si has the effect of improving plating adhesion and at the same time having the effect of increasing strength. If Si exceeds 1%, the strength will increase too much, so the upper limit is 1%.
And Mn has the effect of increasing the toughness of steel and at the same time the effect of increasing the strength. If Mn exceeds 0.6%, the strength increases too much, so the upper limit is made 0.6%.
P and S cause embrittlement of steel, so the upper limit is 0.04.
%.

[0025]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. In addition,% in each example means the mass%. Steel wire JIS
Under the conditions shown in Table 1, Zn-A was applied to a steel wire having a diameter of 4 mm in which the surface of G 3506 SWRH62A was plated with pure Zn.
1-Mg-based zinc alloy plating was applied. For comparison, a plating composition of Zn-Al alloy plating was also performed. The plating structure was observed by EPMA after polishing the cross section of the plated wire. For the corrosion resistance, the amount of corrosion of the plating per unit area was determined as the corrosion weight loss from the weight difference before and after the test by continuous salt water spray for 250 hours.

The workability was evaluated by processing the prepared plated wire to a diameter of 2 mm by wire drawing, winding the steel wire with a diameter of 3 mm 6 times, and visually observing the surface of the steel wire for the presence or absence of cracks.
Further, after the cellophane tape was attached to the sample after the crack determination, the presence or absence of peeling of the plating was observed when the sample was peeled off.
Fatigue characteristics are evaluated by using the Nakamura-type fatigue tester with a fatigue limit of 9% or more of the fatigue limit of the unplated steel wire when the fatigue limit is the stress that achieves a repetition number of 10 million times or more. I passed.

As shown in Table 1, No. Nos. 1 to 11 are examples of the present invention. 12 to 21 are comparative examples. No.
The invention examples 1 to 11 all showed good workability, fatigue properties and corrosion resistance. Comparative Example No. Nos. 12 to 16 have a plating composition outside the scope of the present invention and are inferior in corrosion resistance. Comparative Example No. Nos. 17 and 18 were cases where the thickness of the plating alloy layer was out of the range of the present invention, resulting in poor workability. Comparative Example N
o. In Nos. 19 to 21, the plating structure is out of the range of the present invention, and the corrosion resistance is poor.

[0028]

[Table 1]

[0029]

As described above, according to the present invention, it is possible to obtain a plated steel wire having fatigue resistance and excellent corrosion resistance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22C 38/00 301 C22C 38/00 301Y C23C 2/06 C23C 2/06 2/26 2/26 F term ( Reference) 4K027 AA06 AA23 AB02 AB05 AB33 AB34 AB42 AB43 AB44 AC02 AC32 AC51 AC64 AC72 AC86 AE03 AE23 4K032 AA05 AA06 AA07 AA16 AA31 BA02 CH04 4K043 AA02 AB04 AB05 AB06 AB16 AB27 BB04 CA06 EA02 FA03 FA12 FA12

Claims (16)

[Claims] 1. In a galvanized steel wire, Fe-Zn-Al-Mg quaternary intermetallic compound is contained in an interface of the galvanized iron in an amount of 2 to 20 μm.
The residual strain exists in the intermetallic compound layer in an amount of 0.01% or more, and Al: 8 to
Zn- consisting of 15%, Mg: 0.1 to 3%, balance Zn
A plated steel wire excellent in corrosion resistance and having fatigue resistance, characterized in that an Al-Mg based alloy layer is present at 5 μm or more. 2. In a galvanized steel wire, Al: 4% in the Fe—Zn—Al—Mg alloy layer present at the galvanized base iron interface.
As described above, the plated steel wire having the fatigue resistance and the excellent corrosion resistance according to claim 1, wherein Mg: 0.1% or more is contained. 3. The plating alloy composition according to claim 1, wherein Si: 2% or less by mass% is contained.
~ A plated steel wire having fatigue resistance according to claim 2 and excellent in corrosion resistance. 4. The fatigue resistance according to claim 1, wherein the plating alloy composition according to claim 1 contains sodium: 0.001 to 0.1% in mass%. Plated steel wire with excellent corrosion resistance. 5. The fatigue resistance according to claim 1, wherein the plating alloy composition according to claim 1 contains Ti: 0.01 to 0.2% in mass%. A plated steel wire with excellent corrosion resistance. 6. In a plated steel wire, an α phase containing Al—Zn as a main component and a Zn single phase or Mg—Z in a plating layer outside an Fe—Zn-based alloy layer existing at an interface of a plated base iron.
The β phase consisting of an n alloy phase and the Zn / Al / Zn-Mg ternary eutectic phase are present respectively.
~ A plated steel wire having fatigue resistance according to claim 5 and excellent in corrosion resistance. 7. In a galvanized steel wire, an α phase containing Al—Zn as a main component and a Zn single phase or Mg—Z in the plating phase outside the Fe—Zn-based alloy layer present at the galvanized base iron interface.
7. A β phase consisting of an n alloy phase and a Zn / Al / Zn—Mg ternary eutectic phase are present, and the volume ratio of the α phase is 20% or less. A plated steel wire with the described fatigue resistance and excellent corrosion resistance. 8. When producing a galvanized steel wire, hot-dip galvanizing mainly zinc is applied as the first step, and then the mean composition of the hot-dip zinc alloy is second step and the average composition of the hot-dip zinc alloy is the plating composition according to any one of claims 1 to 5. The method for producing a plated steel wire having fatigue resistance and excellent corrosion resistance according to any one of claims 1 to 7. 9. When manufacturing a galvanized steel wire, hot-dip galvanizing containing Al: 3% or less and Mg: 0.1% or less by mass% is performed as a first step, and then a second step is a hot-dip zinc alloy. The method for producing a plated steel wire having fatigue resistance and excellent corrosion resistance according to any one of claims 1 to 8, wherein the average composition is the plating composition according to claims 1 to 5. 10. In a galvanized steel wire manufacturing process in which hot-dip galvanizing mainly zinc is applied as the first step and then hot-dip galvanizing alloy plating is performed as the second step, a portion for pulling the galvanized steel wire out of the galvanized alloy is filled with nitrogen gas. The method for producing a plated steel wire having fatigue resistance and excellent corrosion resistance according to any one of claims 8 to 9, characterized by purging to prevent oxidation of the bath surface and the plated steel wire. 11. As a first step, hot-dip galvanizing mainly comprising zinc is applied with a plating bath immersion time of 20 seconds or less, and then a second step.
The method for producing a galvanized steel wire having fatigue resistance and excellent corrosion resistance according to claim 8, wherein hot-dip zinc alloy plating is performed as a step for 20 seconds or less in a plating bath immersion time. 12. A galvanized steel wire manufacturing process in which hot-dip galvanizing is mainly performed as a first step and then hot-dip zinc alloy plating is performed as a second step, and a water spray is applied immediately after pulling the galvanized steel wire from the galvanized alloy. Alternatively, the method for producing a plated steel wire having fatigue resistance and excellent corrosion resistance according to any one of claims 8 to 11, wherein the plating alloy is solidified by direct water cooling with steam spray or water flow. 13. In a galvanized steel wire manufacturing process in which hot-dip galvanizing is mainly performed as a first step and then hot-dip zinc alloy plating is performed as a second step, a cooling start temperature is plated when the galvanized steel wire is cooled. From melting point of alloy to melting point +20
The method for producing a plated steel wire having fatigue resistance and excellent corrosion resistance according to any one of claims 8 to 12, wherein the temperature is set to ° C. 14. The composition of the steel of the plated steel wire is C by mass:
0.25 to 1.05%, Si: 1% or less, Mn: 0.9
% Or less, P: 0.04%, S: 0.04% or less, the plated steel wire having fatigue resistance and excellent corrosion resistance according to claims 1 to 13, and the production thereof. Method. 15. The plated steel wire according to claim 14, wherein the structure of the steel wire is pearlite by patenting, and the manufacturing method thereof. 16. The steel wire before plating of the plated steel wire is immersed in lead or a molten salt at 500 to 600 ° C. immediately after rolling to transform into pearlite.
The described plated steel wire and a method for producing the same.