JP3699691B2 - High corrosion resistance hot dipped steel wire and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a highly corrosion-resistant hot-dip galvanized steel wire having improved corrosion resistance and workability in plated steel wires used outdoors such as wire nets, rockfall prevention nets, reed mats for wire protection works, wire ropes, and steel stranded wires, and a method for producing the same About.
[0002]
[Prior art]
As a method for imparting corrosion resistance to a steel wire, Zn plating is generally performed. Recently, Zn-6% Al alloy plating or Zn-11% Al alloy plating is performed by a two-bath method in which hot-dip Zn plating is performed first and then Zn-Al alloy plating is performed a second time.
On the other hand, in the field of steel sheets, Zn-6% Al-3% Mg alloy plating in which 3% by weight of Mg is added as a method for making the corrosion resistance of Zn-Al alloy plating higher corrosion resistance is a plating manufacturing method for steel sheets. This is proposed in Japanese Patent Laid-Open No. 10-306357.
In order to apply Zn—Al—Mg alloy plating in the steel sheet field to steel wires, trial production of Zn-6% Al-3% Mg and Zn-11% Al-3% Mg alloy plating has been performed. However, although the corrosion resistance is good, the plating layer has a high hardness, and therefore, when bent, peeling and cracks frequently occur on the surface defects such as thick portions and unevenness due to uneven thickness of the plating layer. In practice, the plated steel wire always has some of the surface defects described above, so that there is a problem that it cannot be applied to the plated steel wire, which is a product that cannot be bent.
Also, regarding the amount of plating adhesion, even if the appearance and uneven thickness are good, peeling of the plating part at the time of bending processing, cracks occur, so there is a limit to the plating thickness that combines the alloy layer and the plating layer, There was a problem that a thick plating of 300 g / m 2 or more could not be produced stably.
Further, the Zn—Al-3% Mg alloy has a surface roughness larger than that of the Zn—Al alloy, the surface is textured, has poor smoothness, and has a problem in appearance.
In addition, in the manufacturing method using a known normal manufacturing apparatus, the uneven thickness ratio deteriorates to about 3 to 5, and there is a problem that peeling of the plating and cracking occur.
[0003]
[Problems to be solved by the invention]
The problem to be solved is, firstly, a Zn-Al-Mg alloy that has corrosion resistance, and at the same time, has solved the problem of peeling and cracking of the plated portion during bending, which is a required quality peculiar to steel wires. High corrosion resistance hot dip galvanized steel wire having a composition, and secondly, a high corrosion resistance hot dip galvanized steel wire having a Zn-Al-Mg alloy composition that is excellent in corrosion resistance and workability, and has a smooth plating surface and low surface roughness. Thirdly, a highly corrosion-resistant hot-dip galvanized steel wire consisting of a plating layer that is less prone to peeling and cracking at the time of bending, has a small thickness deviation, and has a good appearance without surface defects such as bumps and roughness. 4th is providing the manufacturing method of the high corrosion-resistant hot-dip galvanized steel wire which can mass-produce the above-mentioned high corrosion-resistant hot-dip steel wire efficiently and stably.
[0004]
[Means for Solving the Problems]
In order to achieve the above-mentioned problems, the present invention is a two-stage air-cooled Zn— which is hot-plated by a two-bath method and is cooled by a relatively high-speed air flow after low-speed air-flow cooling. In an Al-Mg alloy plated steel wire, the plating layer has a Vickers hardness of 60 to 90, the alloy layer has a Vickers hardness of 100 to 140, the plating layer is mainly composed of Zn, and the composition ratio of the plating layer and the entire alloy layer is Mg: 0.03 to 0.15%, Al: 8 to 15%, Zn: the balance, and the maximum thickness on the cross section is the minimum thickness with respect to the total plating thickness of the plating layer and the alloy layer. The average thickness deviation ratio is 2.0 or less .
Further, in the high corrosion resistance hot-dip galvanized steel wire of the present invention, a two-stage air-cooled Zn—Al—Mg alloy-plated steel that is hot-dip plated by a two-bath method and cooled by a relatively high-speed air flow after low-speed air-flow cooling. In the wire, the Vickers hardness of the plating layer is 60 to 90, the Vickers hardness of the alloy layer is 100 to 140, the plating layer is mainly composed of Zn, and the composition ratio in the entire plating layer and the alloy layer is Mg: 0.03 About 0.15%, Al: 8-15%, Zn: The balance, the surface roughness in the circumferential direction of the plating surface is Ra: 1.0 μm or less, and the plating thickness of the combined plating layer and alloy layer The average thickness deviation ratio obtained by dividing the maximum thickness on the cross section by the minimum thickness is 2.0 or less, and the plating thickness is 553 to 740 g / m ² .
And in the manufacturing method of the high corrosion resistance hot dip galvanized steel wire of the present invention, in the manufacturing method of the high corrosion resistance hot dip galvanized steel wire by the two-bath method, after performing hot dip Zn plating mainly containing Zn on the wire, the composition ratio is , Mg: 0.03 to 0.15%, Al: 8 to 15%, Zn: Molten Zn-Al-Mg alloy plating consisting of the remainder, and from the Zn-Al-Mg alloy plating bath surface through the plating throttle part A plurality of rising wires are passed through an air cooling device comprising a lower cooling part at the lower part of the pressurized air part and an upper cooling part at the upper part of the pressurized air part, and from the air outlet of the pressurized air part into the upper cooling part. High-speed main cooling air that flows into each rectification space portion of each wire formed in and flows out from the upper cooling portion upper end outlet, and is sucked into the main cooling air flow from the lower cooling portion lower end inlet Formed in the lower cooling part Wherein the produced air-cooled in two steps in the air cooling in the secondary cooling air relatively low speed flows into the rectifying space merges into the main cooling air per timber.
[0005]
About Al weight ratio in this invention, it confirmed that high corrosion resistance was ensured by making a minimum into 8% or more, and it can be made into a thick plating product by making an upper limit into 15%, and set it as 8 to 15%. It is confirmed that the Mg weight ratio is 0.15% or less and the passing rate of the winding test is 100%, the hardness is lowered, the workability is improved, and high corrosion resistance is obtained. 0.03 to 0.15 % did. Regarding the plating thickness of the plating layer and the alloy layer, setting the average value of the uneven thickness ratio with the maximum thickness on the cross section as the minimum thickness is set to 2.0 or less, while having high corrosion resistance, This is an important item for improving the workability of a Zn-Al-Mg alloy-plated steel wire having high half-surface hardness and low workability. In the two-bath method, the primary plating and the secondary plating may be performed either continuously or intermittently.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
8 to 13 exemplify a production apparatus employed for producing the highly corrosion-resistant hot-dip galvanized steel wire of the present invention, and a hot-dip Zn plating tank 1 as primary plating and Zn-- as secondary plating. The Al—Mg plating tank 2 is continuously arranged, and an air cooling device 4 is provided above the plating throttle portion 3 on the plating bath surface 2 a of the Zn—Al—Mg plating tank 2. Are provided with water cooling devices 8, respectively, and after a plurality of wire rods L have passed through the molten Zn plating tank 1, the plating bath surface 2 a passes through the sinker roller 9 in the Zn—Al—Mg plating tank 2. The plate passes through the diaphragm 3 covered with the non-oxidizing atmosphere gas and rises at the same time. In the process of passing through the air-cooling device 4 and the water-cooling device 5, the plating layer L1 is air-cooled and water-cooled, and then the drum passes through the top roller 10. (Not shown ) In it is then to be wound simultaneously. The water cooling device 8 may not be used depending on the application.
The air cooling device 4 includes a pressurized air unit 5, a lower cooling unit 6 below the pressurized air unit 5, and an upper cooling unit 7 above the pressurized air unit 5. The wire L flows naturally into the main cooling air flow and the high-speed main cooling air a that flows into the upper cooling portion 7 from the air outlet 5a of the pressurized air portion 5 and flows out from the outlet 7a at the upper end of the upper cooling portion 7. The low-speed sub-cooling air b that is sucked and flows into the lower-side cooling unit 6 from the inlet 6a at the lower end of the lower-side cooling unit 6 and merges with the main cooling air a is simultaneously cooled in two stages. It is.
[0007]
The pressurized air portion 5 is formed with a long hole-like wire rod passage portion 5c through which a plurality of parallel wire rods L can pass simultaneously in the front and rear between the bifurcated left and right tip portions 5b, and the left and right tip portions. A pair of left and right air jets 5a are formed in the upper surface of the part 5b so as to communicate with the respective rectifying spaces 7b in the upper cooling part 7, and main cooling at a wind speed of about 20 to 50 m / s from each air jet 5a. Air a is ejected to the rectifying space 7b.
[0008]
The lower cooling section 6 has a plurality of turbulent flow prevention plates 6b for suppressing the turbulent flow of the sub-cooling air b inside the cylindrical body having a substantially rectangular cross section along the side of the trajectory of each wire L. And a plurality of rectifying space portions 6c separated by the respective turbulent flow prevention plates 6b adjacent to each other in the front-rear direction and the left-right direction are formed, and are sucked by the main cooling air flow flowing in the upper cooling portion 7. Then, the sub cooling air b having a wind speed of 5 to 15 m / S flows into the rectifying space 6c from the inlet 6a and is rectified while suppressing the turbulent flow. The plating layer L1 is cooled at the same time.
[0009]
The upper cooling section 7 has a plurality of turbulent flow prevention plates 7c for suppressing the turbulent flow of the main cooling air a inside the cylindrical body having a substantially long rectangular cross section so as to be opposed to each other along the side of the passing track of each wire L. A plurality of rectifying space portions 7b separated by the respective turbulent flow prevention plates 7c adjacent to each other are formed, and the main cooling air a ejected from the air outlet 5a serves as the rectifying space portion. The plating layer L1 in the plurality of wires L immediately after cooling by the sub cooling air b is cooled at the same time in a state where the turbulent flow is suppressed and rectified while flowing into the 7b.
[0010]
And the pressurized air part 5, the lower cooling part 6, and the upper cooling part 7 in the air cooling device 4 are formed integrally by being positioned with respect to each other, and at the time of maintenance of the air cooling device 5 or the wire L In case of disconnection, etc., it is possible to respond quickly by attaching and detaching.
[0011]
As a result, the rectified air, that is, the main cooling air a and the sub-cooling air b having two different speeds of low speed and high speed are generated in one air cooling device 4, so that uneven thickness is likely to occur immediately after passing through the plating throttle portion 3. The high-temperature plating layer is cooled with the rectified air called the low-speed sub-cooling air b, and then the low-temperature plating layer L1 that is relatively free from uneven thickness immediately after being cooled by the sub-cooling air b is called the high-speed main cooling air a. By cooling with rectified air, the plating layer L1 is efficiently cooled while preventing uneven thickness.
[0012]
Next, an example of the high corrosion resistance hot-dip galvanized steel wire of the present invention manufactured by the manufacturing apparatus described above will be described.
After performing Zn plating as primary plating in the molten Zn plating bath 1 under normal conditions on a wire rod (soft steel wire JIS G3505 SWRM6K, 4 mm) L, for comparison, under the conditions of FIGS. Each comparative product plated with% Al alloy and a product according to the present invention plated with Zn-11% Al—Mg alloy as secondary plating in the Zn—Al—Mg plating tank 2 were obtained. Regarding the Mg weight ratio, 9 kinds of 3%, 2%, 1.5%, 0.8%, 0.3%, 0.15%, 0.08%, 0.03%, and 0% were used. . The comparative product and the product of the present invention were comprehensively confirmed for each item of corrosion resistance, workability, plating layer hardness, alloy layer hardness, and plating layer surface roughness.
[0013]
Corrosion resistance evaluation: After performing a salt spray test shown in JIS Z2371 continuously for 500 hours, a corrosion product was removed with an ammonium acetate solution based on the JIS, and a corrosion raw material was determined from a weight difference before and after the test. The results are shown in FIG. 1, FIG. 2, and FIG.
As a result, as shown in FIGS. 1, 2, and 4, the corrosion resistance of the Zn-6% Al—Mg alloy layer and the Zn-11% Al—Mg alloy layer is between 3.0% and 0.8%. Is good without much difference. In addition, when Mg is between 0.8 and 0.03%, the corrosion resistance gradually decreases in proportion to the amount of Mg, but the corrosion resistance is approximately twice that of 0.08% Mg and 0% Mg. 0.03% Mg has an effect of improving the corrosion resistance of about 1.7 compared with 0% Mg, and a large effect of Mg was recognized even in a small amount. If the amount of Mg is the same, the corrosion resistance of the Zn-11% Al-Mg alloy layer is higher than that of the Zn-6% Al-Mg alloy layer. There is a large trend. And about Al weight ratio, it confirmed that high corrosion resistance was ensured by making a minimum into 8% or more, and it can be made into a thick plating product by making an upper limit into 15%.
[0014]
Workability evaluation: The wire L was wound around a 6 mm (1.5 × d) steel wire 6 times, and the surface of the plating layer was visually confirmed and judged. The absence of peeling and the absence of large cracks where the steel wire could be seen were regarded as acceptable conditions for the winding test, and each comparative product and the present invention product were tested for 20 each. The results are shown in FIGS. Since the workability is affected by the hardness of the plating layer, the measurement of the hardness of the plating layer and the alloy layer for each test product was performed together (see FIGS. 1, 2, 5, and 6).
As for the evaluation results of workability, both the hardness of the plating layer and the alloy layer are lowered and the acceptance rate is improved as the amount of Mg is lowered. It was confirmed that the acceptance ratio was significantly improved when the Mg weight ratio was 1.5% or less, and the acceptance ratio was 100% when it was 0.8% or less. The Mg weight ratio was 0.03 to 1.5% at which the hardness decreased, the workability improved, and high corrosion resistance was obtained. In particular, Mg of 0.03 to less than 0.8%, which improves workability, is suitable for thick plating. FIG. 5 shows the change in hardness of the plated layer depending on the Mg weight ratio, and FIG. 6 shows the change in hardness of the alloy layer.
[0015]
Evaluation of plating layer surface roughness: Based on JIS B0601, the center line average roughness Ra in the circumferential direction of the Zn—Al—Mg alloy layer was measured, and the results are shown in FIG.
As a result, Ra is decreased with decreasing Mg weight ratio, and Mg is an additive element that decreases the fluidity of the molten metal in the alloy bath. It is occurring.
In the case of a Zn-11% Al—Mg alloy layer, Mg is 1.5%, the center line average roughness Ra is 1.0 μm or less, Mg is 0.8%, and Ra is 0.8 μm or less. Considering a variation of about 2 μm, Mg is 1.5% and Ra is 1.2 μm or less, Mg is 0.8% and Ra is 1.0 μm or less.
[0016]
Thick Plating Results and Corrosion Resistance Evaluation: Corrosion resistance decreases with decreasing Mg weight ratio, but conversely, with the decrease in plating layer hardness, the workability of the plating layer is improved and thick plating is possible. Even those having a low Mg weight ratio of 0.03% to 1.5% exhibit corrosion resistance equivalent to or higher than that of a high Mg weight ratio of 1.6 to 3% (see FIG. 3).
[0017]
【The invention's effect】
A. According to claim 1, there is no fear of peeling and cracking of the plating part at the time of bending, which is corrosion-resistant, and at the same time, the required quality peculiar to steel wire, and the corrosion resistance is Zn-Al alloy plated steel wire It has a high corrosion resistance of about 1.5 to 3 times that of the steel plate , is less uneven , and is useful as a plated steel wire that requires good corrosion resistance and bending workability.
B. According to claim 2, there is corrosion resistance, and at the same time, there is no fear of peeling of the plating part and occurrence of cracks at the time of bending, which is the required quality peculiar to the steel wire, and the corrosion resistance is Zn-Al alloy plated steel wire. Compared to the above, it has a high corrosion resistance of about 1.5 to 3 times, good corrosion resistance, bending workability, surface roughness, peeling and cracking hardly occur in the plated part during bending, and uneven thickness At least, it is useful as a plated steel wire for which a plating layer having a good appearance free from surface defects such as bumps and roughness is desired.
C. According to the third aspect, the plating layer which has high fluidity and is likely to cause uneven thickness at a high temperature in the wire just after passing through the plating throttle portion is cooled by the rectified low-speed subcooling air, and cooling by the subcooling air is performed. Since the plating layer that has low fluidity at the low temperature immediately after and is not easily uneven is cooled by the rectified high-speed main cooling air, efficient cooling with suppressed unevenness is possible. Therefore, it is possible to efficiently and stably mass-produce a highly corrosion-resistant hot-dip galvanized steel wire having an uneven thickness ratio that is equal to or less than that of the conventional product, and having a good appearance and high workability.
[Brief description of the drawings]
FIG. 1 is a data table showing a salt spray test result, a winding test result, a plating layer hardness, and an alloy layer hardness of a comparative product.
FIG. 2 is a data table showing salt spray test results, winding test results, plating layer hardness, and alloy layer hardness of the highly corrosion resistant hot-dip steel wire of the present invention and a comparative product.
FIG. 3 is a data table showing the winding test and thick plating results of the highly corrosion-resistant hot-dip galvanized steel wires of the present invention and comparative products.
FIG. 4 is a graph showing a salt spray test result of the high corrosion resistance hot-dip steel wire of the present invention and a comparative product.
FIG. 5 is a graph showing the plating layer hardness of the high corrosion resistance hot-dip steel wire of the present invention and a comparative product.
FIG. 6 is a graph showing the alloy layer hardness of the high corrosion resistance hot-dip galvanized steel wire of the present invention and a comparative product.
FIG. 7 is a graph showing the surface roughness of the highly corrosion-resistant hot-dip galvanized steel wire of the present invention and a comparative product.
FIG. 8 is a schematic view illustrating a production apparatus employed for producing the high corrosion resistance hot-dip galvanized steel wire of the present invention.
FIG. 9 is a side view.
10 is a longitudinal sectional view of (10)-(10) in FIG. 9. FIG.
11 is a longitudinal sectional view of (11)-(11) in FIG. 9;
12 is a longitudinal sectional view of (12)-(12) in FIG. 9;
13 is a longitudinal sectional view of (13)-(13) in FIG. 9;
[Explanation of symbols]
L Wire rod L1 Plating layer 1 Molten Zn plating bath 2 Zn-Al-Mg plating bath 2a Plating bath surface 3 Plating throttle portion 4 Air cooling device 5 Pressurized air portion 5a Air outlet 5b Bifurcated left and right tip portion 5c Wire rod passage portion 6 Lower cooling part 6a Inlet 6b Turbulence prevention plate 6c Rectification space part 7 Upper cooling part 7a Outlet 7b Rectification space part 7c Turbulence prevention plate 8 Water cooling device 9 Sinker roller 10 Top roller a Main cooling air b Sub cooling air

Claims (3)

In a two-stage air - cooled Zn—Al—Mg alloy-plated steel wire that is hot-dip plated by a two-bath method and cooled by a relatively high-speed air flow after low-speed air-flow cooling , the plating layer has a Vickers hardness of 60 to 90 The alloy layer has a Vickers hardness of 100 to 140, the plating layer is mainly composed of Zn, and the composition ratio of the plating layer and the entire alloy layer is Mg: 0.03 to 0.15%, Al: 8 to 15%, Zn: It consists of the remainder, and with respect to the plating thickness of the plating layer and the alloy layer, the average thickness deviation ratio obtained by dividing the maximum thickness on the cross section by the minimum thickness is 2.0 or less. High corrosion resistance hot dipped steel wire. In a two-stage air-cooled Zn—Al—Mg alloy-plated steel wire that is hot-dip plated by a two-bath method and cooled by a relatively high-speed air flow after low-speed air-flow cooling, the plating layer has a Vickers hardness of 60 to 90 The alloy layer has a Vickers hardness of 100 to 140, the plating layer is mainly composed of Zn, and the composition ratio of the plating layer and the entire alloy layer is Mg: 0.03 to 0.15%, Al: 8 to 15%, Zn: the remainder, the surface roughness in the circumferential direction of the plating surface is Ra: 1.0 μm or less, and the maximum thickness on the cross section is the minimum thickness with respect to the total plating thickness of the plating layer and the alloy layer. A high corrosion-resistant hot-dip galvanized steel wire having an average thickness deviation ratio of 2.0 or less and a plating thickness of 553 to 740 g / m ² . In the method for producing a highly corrosion-resistant hot-dip galvanized steel wire by the two-bath method, the composition ratio is Mg: 0.03-0.15%, Al: 8- 15%, Zn: The remaining Zn-Al-Mg alloy plating is performed, and a plurality of wires rising from the Zn-Al-Mg alloy plating bath surface through the plating throttle portion are cooled below the pressurized air portion. Passing through an air cooling device composed of an upper cooling part at the upper part of the pressurized air part and flowing into each rectifying space part for each wire formed in the upper cooling part from the air outlet of the pressurized air part, High-speed main cooling air that flows out from the upper cooling unit upper end outlet, and each rectification space portion for each wire rod that is sucked into the main cooling air flow and formed in the lower cooling unit from the lower cooling unit lower end inlet Into the main cooling air Method for producing a high corrosion resistance hot dip coating steel wire, characterized in that prepared by cooling in two steps in the air cooling in the secondary cooling air relatively slow.

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