JP7406100B2 - Plated wire and its manufacturing method - Google Patents
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- 238000004519 manufacturing process Methods 0.000 title claims description 21
- 238000007747 plating Methods 0.000 claims description 165
- 239000013078 crystal Substances 0.000 claims description 127
- 238000001816 cooling Methods 0.000 claims description 103
- 229910000831 Steel Inorganic materials 0.000 claims description 51
- 239000010959 steel Substances 0.000 claims description 51
- 239000000203 mixture Substances 0.000 claims description 32
- 229910017706 MgZn Inorganic materials 0.000 claims description 29
- 229910052782 aluminium Inorganic materials 0.000 claims description 27
- 229910052751 metal Inorganic materials 0.000 claims description 26
- 239000002184 metal Substances 0.000 claims description 26
- 229910052749 magnesium Inorganic materials 0.000 claims description 19
- 239000012535 impurity Substances 0.000 claims description 17
- 239000011248 coating agent Substances 0.000 claims description 15
- 238000000576 coating method Methods 0.000 claims description 15
- 230000008021 deposition Effects 0.000 claims description 3
- 239000011701 zinc Substances 0.000 description 114
- 239000010410 layer Substances 0.000 description 91
- 238000005260 corrosion Methods 0.000 description 49
- 230000007797 corrosion Effects 0.000 description 49
- 230000000694 effects Effects 0.000 description 23
- 238000000034 method Methods 0.000 description 23
- 229910052725 zinc Inorganic materials 0.000 description 20
- 238000005259 measurement Methods 0.000 description 16
- 230000005496 eutectics Effects 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 11
- 230000007423 decrease Effects 0.000 description 11
- 230000006872 improvement Effects 0.000 description 8
- 230000008569 process Effects 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- 229910002056 binary alloy Inorganic materials 0.000 description 6
- 229910002058 ternary alloy Inorganic materials 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 238000005491 wire drawing Methods 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 239000000314 lubricant Substances 0.000 description 4
- 238000005554 pickling Methods 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 238000005452 bending Methods 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000007598 dipping method Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 238000009661 fatigue test Methods 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 229910001335 Galvanized steel Inorganic materials 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- 229910000611 Zinc aluminium Inorganic materials 0.000 description 2
- 229910007570 Zn-Al Inorganic materials 0.000 description 2
- HXFVOUUOTHJFPX-UHFFFAOYSA-N alumane;zinc Chemical compound [AlH3].[Zn] HXFVOUUOTHJFPX-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 239000008397 galvanized steel Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- VKYKSIONXSXAKP-UHFFFAOYSA-N hexamethylenetetramine Chemical compound C1N(C2)CN3CN1CN2C3 VKYKSIONXSXAKP-UHFFFAOYSA-N 0.000 description 2
- 238000009616 inductively coupled plasma Methods 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 238000010583 slow cooling Methods 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 230000004580 weight loss Effects 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910000677 High-carbon steel Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- CJZGTCYPCWQAJB-UHFFFAOYSA-L calcium stearate Chemical compound [Ca+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O CJZGTCYPCWQAJB-UHFFFAOYSA-L 0.000 description 1
- 239000008116 calcium stearate Substances 0.000 description 1
- 235000013539 calcium stearate Nutrition 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 230000000376 effect on fatigue Effects 0.000 description 1
- 238000001887 electron backscatter diffraction Methods 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- 238000004993 emission spectroscopy Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000005246 galvanizing Methods 0.000 description 1
- 235000010299 hexamethylene tetramine Nutrition 0.000 description 1
- 239000004312 hexamethylene tetramine Substances 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 238000010301 surface-oxidation reaction Methods 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
- LRXTYHSAJDENHV-UHFFFAOYSA-H zinc phosphate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LRXTYHSAJDENHV-UHFFFAOYSA-H 0.000 description 1
- 229910000165 zinc phosphate Inorganic materials 0.000 description 1
Landscapes
- Coating With Molten Metal (AREA)
Description
本開示は、めっき線及びその製造方法に関するものである。 The present disclosure relates to a plated wire and a method for manufacturing the same.
溶融めっき線の一般的な製造工程は熱間圧延線材を原材料とし、熱間圧延線材表面のスケールを除去し、表面に被膜処理した後、ダイスにより、目的の線径まで冷間加工し、被めっき線とする。この後に、めっき前処理工程で酸洗やフラックス処理等による表面の活性化処理後、溶融金属の浴に浸漬し、被めっき線表面に金属の被膜を形成し、製造される。 The general manufacturing process for hot-dip galvanized wire uses hot-rolled wire as raw material, removes scale from the surface of the hot-rolled wire, coats the surface, and then cold-works the wire to the desired wire diameter using dies. Use plated wire. Thereafter, in a plating pretreatment process, the wire is activated by pickling, fluxing, etc., and then immersed in a bath of molten metal to form a metal film on the surface of the wire to be plated.
亜鉛を含む成分皮膜を有する溶融めっき線は、めっき皮膜層の亜鉛の犠牲防食作用により、地鉄の腐食を抑制することで、耐食性を改善することが大きな目的である。特に、亜鉛－アルミニウム二元合金、さらには亜鉛－アルミニウムに加え、微量のＭｇを含む三元合金めっきは、より高い耐食性が得られる。 The major purpose of hot-dip galvanized wire having a component film containing zinc is to improve corrosion resistance by suppressing corrosion of the base steel through the sacrificial anticorrosive action of zinc in the plating film layer. In particular, zinc-aluminum binary alloy, and even ternary alloy plating containing a small amount of Mg in addition to zinc-aluminum, can provide higher corrosion resistance.
一方、溶融めっきにより、疲労特性が低下する課題がある。このため、めっき線に繰り返し負荷が作用する、架線等に使用する溶融めっき線には耐食性とともに、疲労特性も要求される。
そこで、従来、溶融めっき線の疲労特性を改善するための方法について検討されている。
On the other hand, hot-dip plating poses a problem in that fatigue properties deteriorate. For this reason, hot-dip plated wires used in overhead wires and the like, where repeated loads are applied to the plated wires, are required to have not only corrosion resistance but also fatigue properties.
Therefore, methods for improving the fatigue characteristics of hot-dip plated wires have been studied.
特許文献１には、Ａｌ：２～１２％と、残余が実質的にＺｎからなる組成のめっき浴組成を用いて鋼線に溶融めっきを施した後、２５０℃から１００℃の温度範囲において、Ｔ（ｌｏｇｔ＋８．９）≧４９００で表わされる関係式を満足する加熱（温度：Ｔ°Ｋ）、保持（保持時間：ｓ）を行なう製造方法により疲労特性が改善することが記載されている。 Patent Document 1 describes that after hot dipping a steel wire using a plating bath composition of Al: 2 to 12% and the remainder substantially consisting of Zn, in a temperature range of 250°C to 100°C, It is described that fatigue properties are improved by a manufacturing method that performs heating (temperature: T°K) and holding (holding time: s) that satisfies the relational expression expressed by T (logt+8.9)≧4900.
また、特許文献２には、めっき層の成分が、質量％で、 Ｍｇ：０．１０％以上１．００％未満、Ａｌ：５．０％以上１５．０％以下、残部がＺｎ及び不純物からなり、 めっき層の組織は、質量％でＺｎを９０％以上含むＺｎ相を面積率で２５～７０％有し、Ｚｎ相に占める、円換算した結晶粒径が２～５μｍの粒径を有するＺｎ相の面積率が２０～１００％である溶融めっき鋼線が開示されている。 Furthermore, Patent Document 2 states that the components of the plating layer are, in mass%, Mg: 0.10% or more and less than 1.00%, Al: 5.0% or more and 15.0% or less, and the balance is Zn and impurities. The structure of the plating layer has a Zn phase containing 90% or more of Zn by mass in an area ratio of 25 to 70%, and the crystal grain size in terms of yen occupied by the Zn phase has a grain size of 2 to 5 μm. A hot-dip galvanized steel wire having a Zn phase area ratio of 20 to 100% is disclosed.
特許文献１に記載されている合金めっき鋼線の製造方法は、ＺｎとＡｌの二元合金めっきの共析変態応力低減のため、加熱温度範囲を共析温度以下の１００～２５０℃としている。
しかし、より耐食性に優れる、Ｚｎ、Ａｌに、Ｍｇを含む三元合金めっきでは、めっき層による疲労特性の悪化影響が大きいために、共析変態応力制御のみでは改善効果が小さく、さらに疲労特性を改善することが望ましい。
また、特許文献２に記載されている三元合金めっき層を有する溶融亜鉛めっき鋼線は、Ｚｎめっき鋼線又はＺｎ－Ａｌ溶融めっき鋼線に比べ耐食性が高いとされているが、疲労特性は考慮されていない。
In the method for manufacturing an alloy-plated steel wire described in Patent Document 1, the heating temperature range is set to 100 to 250° C. below the eutectoid temperature in order to reduce the eutectoid transformation stress of binary alloy plating of Zn and Al.
However, in the case of ternary alloy plating containing Zn, Al, and Mg, which has better corrosion resistance, the plating layer has a large effect of deteriorating fatigue properties, so controlling eutectoid transformation stress alone has a small improvement effect, and further improving fatigue properties. Improvement is desirable.
Further, the hot-dip galvanized steel wire having a ternary alloy plating layer described in Patent Document 2 is said to have higher corrosion resistance than Zn-plated steel wire or Zn-Al hot-dip coated steel wire, but the fatigue properties are Not considered.
本開示は、上記事情に鑑みてなされたもので、Ｚｎ、Ａｌ、及びＭｇを含むめっき層を有し、疲労特性と耐食性に優れためっき線とその製造方法を提供することを課題とする。 The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a plated wire that has a plated layer containing Zn, Al, and Mg and has excellent fatigue properties and corrosion resistance, and a method for manufacturing the same.
本発明者は、上記課題を解決するために、Ｚｎ、Ａｌ、及びＭｇを含む三元合金めっき組成において、めっき線の疲労特性及び耐食性に及ぼすめっき層組織の影響について鋭意検討した。その結果、めっき層の母相であるＺｎ相（Ｚｎ結晶）の結晶粒径、初晶として晶出する、共晶相のＡｌ相（Ａｌ結晶）の結晶粒径が疲労強度に大きく影響することを知見した。また、そのようなめっき組織を得るための冷却条件を見出した。
すなわち、本開示の要旨は以下のとおりである。
In order to solve the above-mentioned problems, the present inventors have intensively studied the influence of the plating layer structure on the fatigue properties and corrosion resistance of the plating wire in a ternary alloy plating composition containing Zn, Al, and Mg. As a result, the crystal grain size of the Zn phase (Zn crystal), which is the parent phase of the plating layer, and the crystal grain size of the eutectic Al phase (Al crystal), which crystallizes as primary crystals, have a large effect on fatigue strength. I found out. We also discovered cooling conditions to obtain such a plating structure.
That is, the gist of the present disclosure is as follows.
＜１＞ 鋼線と、前記鋼線の表面を被覆するめっき層と、を含み、
前記めっき層の組成が、質量％で、
Ａｌ：５．０％超～１２．０％、
Ｍｇ：０．３０％超～１．００％、並びに
残部：Ｚｎ及び不純物、からなり、
前記めっき層の組織が、Ｚｎ相、Ａｌ相、及びＭｇＺｎ２相を含み、ＥＢＳＤ（電子線後方散乱解析：Ｅｌｅｃｔｒｏｎ Ｂａｃｋ Ｓｃａｔｔｅｒｅｄ Ｄｉｆｆｒａｃｔｉｏｎ Ｐａｔｔｅｒｎ）により、Ｚｎ結晶とＡｌ結晶を測定したときの結晶の方位差１５度以上を結晶粒界と定義し、前記Ｚｎ結晶のうち５μｍ以上の円相当結晶粒径の平均円相当結晶粒径をｄＺｎμｍ、前記Ａｌ結晶の平均円相当結晶粒径をｄＡｌμｍとしたとき、前記ｄＺｎが３０μｍ以下であり、かつ下記（１）式の値Ｄが６４以上、１０８以下である、めっき線。
Ｄ＝２．４×ｄＺｎ＋２４．２×ｄＡｌ ・・・（１）
＜２＞ 前記めっき層を前記ＥＢＳＤにより測定した前記Ａｌ相、前記Ｚｎ相、及び前記ＭｇＺｎ２相の相マップにおいて、前記ＭｇＺｎ２相の面積率が０．３～３．５％である＜１＞に記載のめっき線。
＜３＞ 組成が、質量％で、Ａｌ：５．０％超～１２．０％、Ｍｇ：０．３０％超～１．００％、並びに残部：Ｚｎ及び不純物からなる溶融金属のめっき浴に鋼線を浸漬して引き上げることにより、前記鋼線の表面に前記溶融金属の被膜を付着させる溶融金属被膜付着工程と、
前記溶融金属被膜が付着した鋼線を、４００℃から３３０℃までの範囲で冷却速度５．０～１５．０℃／ｓで２５℃以上１次冷却し、３３０℃から２００℃までの範囲で冷却速度０．３～３．０℃／ｓで１０℃以上２次冷却する冷却工程と、
を含む、めっき線の製造方法。
<1> Including a steel wire and a plating layer covering the surface of the steel wire,
The composition of the plating layer is in mass%,
Al: more than 5.0% to 12.0%,
Mg: more than 0.30% to 1.00%, and the balance: Zn and impurities,
The structure of the plating layer includes a Zn phase, an Al phase, and two MgZn phases, and the crystal orientation difference when Zn crystal and Al crystal are measured by EBSD (Electron Back Scattered Diffraction Pattern) 15 degrees or more is defined as a grain boundary, the average circle-equivalent crystal grain size of the circle-equivalent crystal grains of 5 μm or more among the Zn crystals is d Zn μm, and the average circle-equivalent crystal grain size of the Al crystals is d Al μm A plated wire in which the d Zn is 30 μm or less, and the value D of the following formula (1) is 64 or more and 108 or less.
D=2.4×d Zn +24.2×d Al ...(1)
<2> In a phase map of the Al phase, the Zn phase, and the MgZn two phases measured by the EBSD of the plating layer, the area ratio of the MgZn two phases is 0.3 to 3.5%. <1 Plated wire described in >.
<3> In a molten metal plating bath whose composition is, in mass%, Al: more than 5.0% to 12.0%, Mg: more than 0.30% to 1.00%, and the balance: Zn and impurities. a molten metal coating deposition step of attaching the molten metal coating to the surface of the steel wire by dipping the steel wire and pulling it up;
The steel wire to which the molten metal coating has been attached is firstly cooled at a cooling rate of 5.0 to 15.0°C/s at a cooling rate of 25°C or more in a range from 400°C to 330°C, and then cooled in a range from 330°C to 200°C. A cooling step of secondary cooling of 10°C or more at a cooling rate of 0.3 to 3.0°C/s,
A method of manufacturing plated wire, including
本開示によれば、Ｚｎ、Ａｌ、及びＭｇを含むめっき層を有し、疲労特性と耐食性に優れためっき線とその製造方法が提供される。 According to the present disclosure, a plated wire having a plated layer containing Zn, Al, and Mg and having excellent fatigue properties and corrosion resistance, and a method for manufacturing the same are provided.
以下、本開示の実施形態について説明する。
本開示において、「鋼線」とは、めっき線の素材である鋼線を意味し、「めっき線」とは、鋼線の表面（外周）にめっき層が形成されたもの、すなわち、鋼線とめっき層が含まれる。
化学組成の元素の含有量について、「％」は「質量％」を意味する。
化学組成の元素の含有量は、元素量（例えば、Ｃ量、Ｓｉ量等）と表記する場合がある。
また、「工程」との用語は、独立した工程だけではなく、他の工程と明確に区別できない場合であってもその工程の所期の目的が達成されれば、本用語に含まれる。
本開示において、「～」を用いて表される数値範囲は、「～」の前後に記載される数値を下限値及び上限値として含む範囲を意味する。ただし、「～」の前後に記載される数値に「超」又は「未満」が付されている場合の数値範囲は、これら数値を下限値又は上限値として含まない範囲を意味する。
本明細書中に段階的に記載されている数値範囲において、ある段階的な数値範囲の上限値又は下限値は、他の段階的な記載の数値範囲の上限値又は下限値に置き換えてもよく、また、実施例に示されている値に置き換えてもよい。
Embodiments of the present disclosure will be described below.
In the present disclosure, a "steel wire" refers to a steel wire that is a material for a plated wire, and a "plated wire" refers to a steel wire with a plating layer formed on the surface (outer periphery), that is, a steel wire. and plating layer.
Regarding the content of elements in the chemical composition, "%" means "% by mass".
The content of an element in a chemical composition may be expressed as an element amount (for example, C amount, Si amount, etc.).
Furthermore, the term "process" is used not only to refer to an independent process but also to include a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.
In the present disclosure, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as lower and upper limits. However, a numerical range in which "more than" or "less than" is attached to the numerical value written before and after "~" means a range that does not include these numerical values as the lower limit or upper limit.
In the numerical ranges described stepwise in this specification, the upper limit or lower limit of one stepwise numerical range may be replaced with the upper limit or lower limit of another stepwise numerical range. , may also be replaced with the values shown in the examples.
［めっき線］
本開示に係るめっき線は、鋼線と、前記鋼線の表面を被覆するめっき層と、を含み、
めっき層の組成（本開示において「めっき組成」と記す場合がある。）が、質量％で、
Ａｌ：５．０％超～１２．０％、
Ｍｇ：０．３０％超～１．００％、並びに
残部：Ｚｎ及び不純物、からなり、
めっき層の組織（本開示において「めっき組織」と記す場合がある。）が、Ｚｎ相、Ａｌ相、及びＭｇＺｎ２相を含み、ＥＢＳＤ（電子線後方散乱解析：Ｅｌｅｃｔｒｏｎ Ｂａｃｋ Ｓｃａｔｔｅｒｅｄ Ｄｉｆｆｒａｃｔｉｏｎ Ｐａｔｔｅｒｎ）により、Ｚｎ結晶とＡｌ結晶を測定したときの結晶の方位差１５度以上を結晶粒界と定義し、Ｚｎ結晶のうち５μｍ以上の円相当結晶粒径の平均円相当結晶粒径をｄＺｎμｍ、Ａｌ結晶の平均円相当結晶粒径をｄＡｌμｍとしたとき、ｄＺｎが３０μｍ以下であり、かつ下記（１）式の値Ｄが６４以上、１０８以下である。
Ｄ＝２．４×ｄＺｎ＋２４．２×ｄＡｌ ・・・（１）
[Plated wire]
The plated wire according to the present disclosure includes a steel wire and a plating layer covering the surface of the steel wire,
The composition of the plating layer (sometimes referred to as "plating composition" in this disclosure) is in mass%,
Al: more than 5.0% to 12.0%,
Mg: more than 0.30% to 1.00%, and the balance: Zn and impurities,
The structure of the plating layer (sometimes referred to as "plating structure" in the present disclosure) includes a Zn phase, an Al phase, and two MgZn phases, and is determined by EBSD (Electron Back Scattered Diffraction Pattern). When measuring a Zn crystal and an Al crystal, the crystal orientation difference of 15 degrees or more is defined as a grain boundary, and the average circle equivalent crystal grain size of the circle equivalent crystal grain size of 5 μm or more in the Zn crystal is d Zn μm, Al When the average circular equivalent crystal grain size of the crystal is d Al μm, d Zn is 30 μm or less, and the value D of the following formula (1) is 64 or more and 108 or less.
D=2.4×d Zn +24.2×d Al ...(1)
本開示におけるめっき層のめっき組織は、例えば、ＺｎＡｌ共晶組織である初晶部分とその周囲を取り囲むＺｎ相、及びＭｇＺｎ２相からなり、ＭｇＺｎ２相の生成によりめっき層の耐食性を改善する効果を有する。一方、ＭｇＺｎ２相がめっき層を硬くし、疲労亀裂の進展パスとして作用し、疲労強度を低下させることがある。 The plating structure of the plating layer in the present disclosure consists of, for example, a primary crystal part that is a ZnAl eutectic structure, a Zn phase surrounding it, and two MgZn phases, and the formation of the two MgZn phases has the effect of improving the corrosion resistance of the plating layer. has. On the other hand, the MgZn two phase hardens the plating layer, acts as a propagation path for fatigue cracks, and may reduce fatigue strength.
本発明者は、めっき組織と疲労強度の関係、疲労亀裂の進展状況を詳細に調査、観察した結果、めっき線の疲労強度は、めっき層に生成した亀裂が地鉄とめっき界面に達し、地鉄に進展することで、切り欠きとして作用するためにめっき線の疲労強度を低下させることがわかった。
この疲労強度低下の影響は、めっきの組成によって異なり、純ＺｎめっきよりＺｎＡｌ二元合金めっきが大きく、さらにＺｎＡｌＭｇ三元合金めっきは、より疲労強度を低下させることが明らかになった。
As a result of detailed investigation and observation of the relationship between the plating structure and fatigue strength and the progress of fatigue cracks, the inventor found that the fatigue strength of the plating wire is due to the fact that the cracks generated in the plating layer reach the interface between the base steel and the plating. It was found that by progressing into the steel, it acts as a notch and reduces the fatigue strength of the plated wire.
It has been revealed that the influence of this reduction in fatigue strength varies depending on the composition of the plating, and is greater in ZnAl binary alloy plating than in pure Zn plating, and further, that ZnAlMg ternary alloy plating reduces fatigue strength more.
そこで、本発明者は、Ｚｎ、Ａｌ、Ｍｇを含む三元合金めっきにおいて、耐食性を維持しつつ、疲労強度の低下を抑制する方法について検討を行った。
特に、めっき層の組織に着目してめっき層の結晶粒径と疲労強度の関係を鋭意調査したところ、共晶部分のＡｌ相の結晶粒径とその周囲のＺｎ相の結晶粒径が大きくなるほどめっき中に発生した疲労亀裂の停留効果を発揮し、疲労強度が改善されることを知見した。
一方、Ｚｎ相の結晶粒径が大きくなると、めっき線を加工したときに、粒界に沿って割れが発生しやすくなることも明らかにし、Ｚｎ結晶粒径に上限を設けることで疲労強度が改善されることも見出した。
さらに、Ｚｎ相、Ａｌ相の各結晶粒径を大きくしても、めっき線の耐食性は変化しないことも確認された。
Therefore, the present inventor investigated a method for suppressing the decrease in fatigue strength while maintaining corrosion resistance in ternary alloy plating containing Zn, Al, and Mg.
In particular, we focused on the structure of the plating layer and investigated the relationship between the crystal grain size of the plating layer and fatigue strength, and found that the larger the crystal grain size of the Al phase in the eutectic part and the crystal grain size of the surrounding Zn phase, the more It has been found that this has the effect of arresting fatigue cracks that occur during plating and improves fatigue strength.
On the other hand, it was also revealed that as the crystal grain size of the Zn phase increases, cracks are more likely to occur along the grain boundaries when processing a plated wire, and fatigue strength can be improved by setting an upper limit on the Zn crystal grain size. We also found that
Furthermore, it was also confirmed that even if the crystal grain sizes of the Zn phase and the Al phase were increased, the corrosion resistance of the plated wire did not change.
そして、本発明者は、めっき線の素材である鋼線を、Ｍｇ、Ａｌ、Ｚｎをそれぞれ所定量含む溶融金属のめっき浴に浸漬してめっき浴から引き上げた後の高温域での１次冷却によりＺｎ相の結晶粒を制御し、めっき層が凝固後の低温域での２次冷却によりＡｌ相の結晶粒を制御することにより、疲労強度と耐食性が良好なめっき線を製造することができることも見出した。 The present inventor then immersed the steel wire, which is the material of the plated wire, into a plating bath of molten metal containing predetermined amounts of Mg, Al, and Zn, and after pulling it out of the plating bath, performed primary cooling in a high temperature range. It is possible to manufacture a plated wire with good fatigue strength and corrosion resistance by controlling the crystal grains of the Zn phase by controlling the crystal grains of the Zn phase and by controlling the crystal grains of the Al phase by secondary cooling in a low temperature range after the plated layer solidifies. I also found
＜鋼線＞
本開示に係るめっき線の素材となる鋼線の鋼成分は特に限定されないが、高い疲労強度を得るために、炭素含有量が０．６２％以上の高炭素鋼線の適用が好ましい。Ｓｉ、Ｍｎはめっき線の強度を調整するために適宜選択できる。さらにＣｒ、Ｔｉ、Ｂ、Ａｌ、Ｃｕ、Ｍｏ、Ｓｎ等を含む鋼線も適用可能である。
本開示に係るめっき線の素材となる鋼線は、通常、熱間圧延線材を伸線により加工した伸線材を用いることが出来る。
<Steel wire>
Although the steel composition of the steel wire that is the raw material for the plated wire according to the present disclosure is not particularly limited, in order to obtain high fatigue strength, it is preferable to use a high carbon steel wire with a carbon content of 0.62% or more. Si and Mn can be selected as appropriate to adjust the strength of the plated wire. Furthermore, steel wires containing Cr, Ti, B, Al, Cu, Mo, Sn, etc. are also applicable.
As the steel wire that is the raw material for the plated wire according to the present disclosure, a drawn wire material obtained by processing a hot rolled wire material by wire drawing can be used.
鋼線の直径も特に限定されず、用途に応じて選択すればよい。例えば、２．０ｍｍ～５．０ｍｍの直径を有する鋼線を用いることができる。 The diameter of the steel wire is not particularly limited either, and may be selected depending on the application. For example, a steel wire with a diameter of 2.0 mm to 5.0 mm can be used.
＜めっき層＞
本開示に係るめっき線は、鋼線の表面に、前述した組成及び組織を有するめっき層が形成されている。以下、めっき層の組成及び組織について説明する。
<Plating layer>
In the plated wire according to the present disclosure, a plated layer having the composition and structure described above is formed on the surface of the steel wire. The composition and structure of the plating layer will be explained below.
（めっき組成）
Ｍｇ：０．３０％超～１．００％
Ｍｇはめっき層にＺｎＭｇ金属間化合物を形成し、腐食環境下で生成した腐食生成物を安定化させ、めっき線の腐食の進行を抑制させる作用がある。しかし、Ｍｇ量が０．３０％以下ではその効果が小さく、耐食性改善効果が小さくなるため、めっき層におけるＭｇ含有量は０．３０％超とする。一方、めっき層が１．００％超のＭｇを含むと硬質なＺｎＭｇ金属間化合物相が多く生成し、めっき層が硬くなり、本開示におけるめっき組織に制御しても、疲労強度の改善効果が得にくくなる。そのため、めっき層におけるＭｇ含有量は１．００％を上限とする。めっき層におけるＭｇ含有量は、好ましくは０．５０～０．８０％である。
(Plating composition)
Mg: more than 0.30% to 1.00%
Mg forms a ZnMg intermetallic compound in the plating layer, stabilizes corrosion products generated in a corrosive environment, and has the effect of suppressing the progress of corrosion of the plating wire. However, if the amount of Mg is 0.30% or less, the effect is small and the effect of improving corrosion resistance is reduced, so the Mg content in the plating layer is set to exceed 0.30%. On the other hand, if the plating layer contains more than 1.00% Mg, a large amount of hard ZnMg intermetallic compound phase will be generated, the plating layer will become hard, and even if the plating structure is controlled to the one according to the present disclosure, the fatigue strength will not be improved. It becomes difficult to obtain. Therefore, the upper limit of the Mg content in the plating layer is 1.00%. The Mg content in the plating layer is preferably 0.50 to 0.80%.
Ａｌ：５．０％超～１２．０％
ＡｌもＭｇと同様に腐食環境下で生成した腐食生成物を安定化させる効果があり、５．０％以下ではその効果が小さくなり、耐食性改善効果が得にくくなるため、めっき層におけるＡｌ含有量を５．０％超とする。一方、１２．０％を超えると、Ａｌ初晶領域が増加し、優先して腐食が進行するために耐食性が低下することがある。また、めっき浴の融点が高くなり表面の酸化が進行しやすくなり、表面性状が低下し、疲労強度が低下することがある。そのため、めっき層におけるＡｌ含有量は１２．０％を上限とする。めっき層におけるＡｌ含有量は、好ましくは７．０％～１２．０％、より好ましくは８．０～１２．０％である。
Al: more than 5.0% to 12.0%
Like Mg, Al also has the effect of stabilizing corrosion products generated in a corrosive environment, and if it is less than 5.0%, this effect decreases and it becomes difficult to obtain the effect of improving corrosion resistance. Therefore, the Al content in the plating layer shall be over 5.0%. On the other hand, if it exceeds 12.0%, the Al primary crystal region increases and corrosion preferentially progresses, so that corrosion resistance may decrease. In addition, the melting point of the plating bath becomes high, making it easier for surface oxidation to progress, resulting in a decrease in surface quality and fatigue strength. Therefore, the upper limit of the Al content in the plating layer is 12.0%. The Al content in the plating layer is preferably 7.0% to 12.0%, more preferably 8.0 to 12.0%.
残部：Ｚｎ及び不純物
めっき層の組成の残部はＺｎ及び不純物である。
不純物は、めっき浴に含まれるＺｎ、Ｍｇ、Ａｌ以外の元素であって、めっき工程において意図してめっき浴中に添加した成分ではなく、原料、製造工程に起因して意図せず混入する成分（元素）であり、めっきの耐食性、疲労特性に影響を及ぼさない元素および含有量である。めっき層に不純物として含まれる含有量は、不純物元素にもよるが、成分（元素）単独の含有量は０．１％以下であることが好ましい。また、めっき層に含まれる不純物元素の合計含有量の上限は、本開示の効果に悪影響を及ぼさない範囲とし、具体的には１．０％以下であることが好ましく、０．１％以下であることがより好ましく、０．０１％未満であることが特に好ましい。
Remainder: Zn and impurities The remainder of the composition of the plating layer is Zn and impurities.
Impurities are elements other than Zn, Mg, and Al contained in the plating bath, and are not components intentionally added to the plating bath during the plating process, but components that are unintentionally mixed in due to raw materials or manufacturing processes. (element), which is an element and content that does not affect the corrosion resistance and fatigue properties of the plating. Although the content of impurities contained in the plating layer depends on the impurity element, the content of each component (element) alone is preferably 0.1% or less. Further, the upper limit of the total content of impurity elements contained in the plating layer is set within a range that does not adversely affect the effects of the present disclosure, and specifically, it is preferably 1.0% or less, and 0.1% or less. More preferably, it is present, and particularly preferably less than 0.01%.
めっき層の組成分析は、ＪＩＳ Ｈ０４０１：１９９９「溶融亜鉛めっき試験方法」に準じてめっき線を１０００ｍｌの塩酸溶液に浸漬してめっき層を溶解し、溶解前重量をＷ１、溶解後重量をＷ２として、小数点以下５桁のｇ重量でめっき層の溶解重量を求め、ＩＣＰ（Ｉｎｄｕｃｔｉｖｅｌｙ Ｃｏｕｐｌｅｄ Ｐｌａｓｍａ）発光分光分析により溶解液中のＡｌ量、Ｚｎ量、Ｍｇ量をそれぞれｇ／ｌ濃度で定量し、
Ａｌ濃度（％）は分析値のＡｌ／（Ｗ１－Ｗ２）×１００として、
Ｍｇ濃度（％）は分析値のＭｇ／（Ｗ１－Ｗ２）×１００として、
Ｚｎ濃度（％）は分析値のＺｎ／（Ｗ１－Ｗ２）×１００として、
それぞれ求めることができる。
The composition analysis of the plating layer was performed according to JIS H0401:1999 "Hot dip galvanizing test method" by immersing the plating wire in 1000 ml of hydrochloric acid solution to dissolve the plating layer, and calculating the weight before dissolution as W 1 and the weight after dissolution as W. 2 , the dissolved weight of the plating layer was determined in g weight to 5 decimal places, and the amount of Al, Zn, and Mg in the solution was determined in terms of g/l concentration using ICP (Inductively Coupled Plasma) emission spectrometry. ,
Al concentration (%) is the analytical value Al/(W 1 - W 2 ) x 100,
Mg concentration (%) is the analytical value Mg/(W 1 - W 2 ) x 100,
The Zn concentration (%) is the analysis value of Zn/(W 1 - W 2 ) x 100,
You can ask for each.
（めっき組織）
本開示におけるめっき層は、鋼線の表面（外周）に付着した溶融金属が、冷却、凝固により形成される。
Ａｌ：５．０％超～１２．０％、Ｍｇ：０．３０％超～１．００％、残部：Ｚｎ及び不純物からなるめっき組成は、鋼線の表面にめっき膜として付着した溶融金属が冷却して凝固する際に、ＺｎとＡｌの共晶が初晶として晶出し、次いで、ＭｇＺｎ２相が晶出し、その後で共晶部分を取り囲んで、Ｚｎ相が生成する。
図２は、本開示に係るめっき線のめっき層の断面についてＳＥＭで観察した組織を示し、ＺｎＡｌ共晶領域、ＭｇＺｎＡｌ三元共晶領域、及びＺ相領域を含むめっき層の一例を示している。図２において、ＺｎＡｌ共晶領域における白っぽい部分がＺｎ相であり、黒っぽい部分がＡｌ相である。ＭｇＺｎＡｌ三元共晶領域は、ＭｇＺｎ２相とＡｌ相で構成されている。
一方、図３は、本開示に係るめっき線のめっき層の断面をＥＢＳＤで測定した他の一例を示している。図３に示すめっき層は、図２に示すめっき層には見られない比較的大きなＡｌ相の組織が存在するほか、Ｚｎ相、ＭｇＺｎ２相（モザイク状領域）が存在している。すなわち、図２に示すめっき層と図３に示すめっき層は、各相の形態及び大きさが異なるが、いずれも、Ａｌ相、Ｚｎ相、ＭｇＺｎ２相が存在しており、主に、ＭｇＺｎ２相によって耐食性が改善される。
なお、図２に示すめっき層及び図３に示すめっき層は、いずれも後述するめっき線の製造方法によって形成したものである。図２に示すめっき層は、１次冷却速度が８．０℃／ｓ、２次冷却速度が２．８℃／ｓで製造した場合に得られたものであり、図３に示すめっき層は１次冷却速度が１０．０℃／ｓ、２次冷却速度が０．３℃／ｓで製造した場合に得られたものである。図３に示すめっき層では、図２に示すめっき層に比べ、Ａｌ相が成長して大きくなっている。
本開示に係るめっき線は、めっき層におけるＺｎ相の結晶粒径とＡｌ相の結晶粒径を適正に制御することで、めっき線の疲労強度が改善される。
(Plating structure)
The plating layer in the present disclosure is formed by cooling and solidifying molten metal adhering to the surface (outer periphery) of the steel wire.
The plating composition consists of Al: more than 5.0% to 12.0%, Mg: more than 0.30% to 1.00%, and the balance is Zn and impurities. During cooling and solidification, a eutectic of Zn and Al crystallizes as a primary crystal, then two MgZn phases crystallize, and then surround the eutectic portion to form a Zn phase.
FIG. 2 shows a structure observed by SEM on a cross section of a plating layer of a plated wire according to the present disclosure, and shows an example of a plating layer including a ZnAl eutectic region, a MgZnAl ternary eutectic region, and a Z phase region. . In FIG. 2, the whitish portion in the ZnAl eutectic region is the Zn phase, and the dark portion is the Al phase. The MgZnAl ternary eutectic region is composed of two MgZn phases and an Al phase.
On the other hand, FIG. 3 shows another example in which the cross section of the plating layer of the plating wire according to the present disclosure was measured by EBSD. The plating layer shown in FIG. 3 has a relatively large Al phase structure which is not seen in the plating layer shown in FIG. 2, and also has two phases of Zn phase and MgZn (mosaic region). That is, although the plating layer shown in FIG. 2 and the plating layer shown in FIG. The two phases improve corrosion resistance.
Note that the plating layer shown in FIG. 2 and the plating layer shown in FIG. 3 are both formed by a method for manufacturing a plated wire, which will be described later. The plating layer shown in Figure 2 was obtained when the primary cooling rate was 8.0°C/s and the secondary cooling rate was 2.8°C/s. This was obtained when the primary cooling rate was 10.0°C/s and the secondary cooling rate was 0.3°C/s. In the plating layer shown in FIG. 3, the Al phase has grown and is larger than that in the plating layer shown in FIG.
In the plated wire according to the present disclosure, the fatigue strength of the plated wire is improved by appropriately controlling the crystal grain size of the Zn phase and the crystal grain size of the Al phase in the plated layer.
Ｚｎ相の平均円相当結晶粒径ｄＺｎ：３０μｍ以下
Ｚｎ相はＺｎＡｌ共晶部を取り囲むように（図２参照）又はＡｌ相部を取り囲むように（図３参照）生成し、結晶粒径が大きくなると、めっき線を曲げたりしてめっき層にひずみが入ると、結晶粒界から亀裂が発生することがある。特にＺｎ相の結晶粒径ｄＺｎが３０μｍ超となると粒界部分から亀裂が発生しやすくなり、めっき線の加工性が低下するためＺｎ相の平均円相当結晶粒径は、３０μｍを上限とする。より好ましいＺｎ相の平均円相当結晶粒径の上限は２８μｍである。
一方、疲労強度向上の観点から、Ｚｎ相の平均円相当結晶粒径の下限は、１５μｍであることが好ましい。
Average circular equivalent crystal grain size d of Zn phase Zn : 30 μm or less The Zn phase is generated so as to surround the ZnAl eutectic part (see Fig. 2) or the Al phase part (see Fig. 3), and the crystal grain size is If it becomes large, cracks may occur from the grain boundaries when the plating layer is strained by bending the plating wire. In particular, when the crystal grain size d of the Zn phase exceeds 30 μm, cracks are likely to occur from the grain boundary portion, and the workability of the plated wire decreases. . A more preferable upper limit of the average circular equivalent crystal grain size of the Zn phase is 28 μm.
On the other hand, from the viewpoint of improving fatigue strength, the lower limit of the average circular equivalent crystal grain size of the Zn phase is preferably 15 μm.
Ｚｎ相の平均円相当結晶粒径ｄＺｎ（μｍ）及びＡｌ相の平均円相当結晶粒径ｄＡｌ（μｍ）の関係： ６４≦２．４×ｄＺｎ＋２４．２×ｄＡｌ≦１０８
疲労強度に影響を及ぼすＺｎ相の結晶粒径とＡｌ相の結晶粒径はいずれも、大きくなると疲労強度を高める作用を有する。
一方、Ｚｎ相の結晶粒径が小さい場合でもＡｌ相の結晶粒径が大きい場合は疲労強度は高くなり、逆にＡｌ相の結晶粒径が小さくてもＺｎ相の結晶粒径が大きくなると疲労強度が高くなる。
しかし、疲労強度に及ぼすＺｎ粒径とＡｌ粒径の影響度は異なり、本発明者が実験を重ねた結果、Ｚｎ相の結晶粒径が１μｍ大きくなったときの疲労強度の改善は２．４ＭＰａで、Ａｌ相の結晶粒径が１μｍ大きくなったときの疲労強度の改善は２４．２ＭＰａである。この関係から、
Ｄ＝２．４×ｄＺｎ＋２４．２×ｄＡｌ ・・・（１）
として、上記（１）式の値Ｄが６４以上である場合、本開示におけるめっき組成の三元めっきの疲労強度がＺｎＡｌの二元合金めっき線の疲労強度と同等以上となることから、（１）式の結晶粒径から求めた値Ｄを６４以上とする。
一方、（１）式の結晶粒径から求めた値Ｄが１０８を超えると、結晶粒粗大化による疲労強度改善効果が飽和すると共に、著しく遅い冷却速度で冷却する必要があり、生産性の低下及び設備の増大を招くため、上限を１０８とする。上記（１）式の値Ｄは、好ましくは、７０～１００である。
なお、Ａｌ相の平均円相当結晶粒径ｄＡｌは、上記（１）式の値Ｄが６４～１０８の範囲であれば特に限定されないが、疲労強度向上の観点から、０．５～２．０μｍが好ましい。
Relationship between the average circular equivalent crystal grain size d Zn (μm) of the Zn phase and the average circular equivalent crystal grain size d Al (μm) of the Al phase: 64≦2.4×d Zn +24.2×d Al ≦108
Both the crystal grain size of the Zn phase and the crystal grain size of the Al phase, which influence fatigue strength, have the effect of increasing fatigue strength when they become large.
On the other hand, even if the grain size of the Zn phase is small, the fatigue strength will be high if the grain size of the Al phase is large, and conversely, even if the grain size of the Al phase is small, if the grain size of the Zn phase is large, the fatigue strength will increase. Increases strength.
However, the degree of influence of Zn grain size and Al grain size on fatigue strength is different, and as a result of repeated experiments by the present inventor, the improvement in fatigue strength when the crystal grain size of the Zn phase increases by 1 μm is 2.4 MPa. The improvement in fatigue strength when the crystal grain size of the Al phase increases by 1 μm is 24.2 MPa. From this relationship,
D=2.4×d Zn +24.2×d Al ...(1)
If the value D of the above formula (1) is 64 or more, the fatigue strength of the ternary plating with the plating composition of the present disclosure is equal to or higher than the fatigue strength of the ZnAl binary alloy plated wire. ) The value D obtained from the crystal grain size of the formula is 64 or more.
On the other hand, if the value D calculated from the crystal grain size in equation (1) exceeds 108, the fatigue strength improvement effect due to crystal grain coarsening will be saturated, and cooling will need to be performed at an extremely slow cooling rate, resulting in a decrease in productivity. The upper limit is set to 108 because it also causes an increase in equipment. The value D in the above formula (1) is preferably 70 to 100.
Note that the average equivalent circular grain size dAl of the Al phase is not particularly limited as long as the value D in the above equation (1) is in the range of 64 to 108, but from the viewpoint of improving fatigue strength, it is 0.5 to 2. 0 μm is preferable.
（めっき層の結晶粒径の求め方）
めっき線のＣ断面（めっき線の長手方向に垂直な断面）、すなわち、めっき層と地鉄（鋼線）を含む断面をＣＰ（クロスセクションポリッシャー）で加工し、走査型電子顕微鏡（ＳＥＭ）で、加速電圧２５ｋＶの条件でめっき層を観察し、めっき層部分を電子線後方散乱回折法（ＥＢＳＤ：Ｅｌｅｃｔｒｏｎ ＢａｃｋＳｃａｔｔｅｒ Ｄｉｆｆｒａｃｔｉｏｎ）によりＺｎ相の結晶とＡｌ相の結晶についてそれぞれ測定する。
Ｚｎ相及びＡｌ相のＥＢＳＤ測定領域は、めっき層の厚さ（付着量）にもよるが、極力めっき層の厚さ全体が入るようにして領域を決定する。
例えば、めっき付着量が３００ｇ／ｍ２以上で、めっき厚さが４０μｍ以上の場合はＺｎ結晶の測定は、倍率２０００倍で、４０μｍ×８０μｍの領域を測定ステップ０．１μｍでＡｌとＺｎの結晶を測定する。Ａｌ結晶の測定は、倍率５０００倍で、２０μｍ×２０μｍの領域を測定ステップ０．０５μｍで、ＡｌとＺｎの結晶を測定する。なお、共晶部に存在するＡｌ結晶は微細なため、Ｚｎ結晶の測定よりも観察倍率を高くして測定する。
測定対象結晶データとして、Ｚｎは、ｈｅｘｉａｇｏｎａｌ結晶で、格子定数ａ＝ｂ＝ｃ＝２．６０５Å、ｃ＝４．９４７Å、Ａｌは、ｃｕｂｉｃ結晶で、格子定数ａ＝ｂ＝ｃ＝３．６６Åとすることが好ましい。
なお、めっき付着量が３００ｇ／ｍ２未満の場合にはＥＢＳＤ測定領域は小さくなるものの、測定条件は上記と同様にして測定する。
(How to determine the crystal grain size of the plating layer)
The C cross section of the plated wire (a cross section perpendicular to the longitudinal direction of the plated wire), that is, the cross section including the plating layer and the base iron (steel wire), is processed with a CP (cross section polisher) and polished with a scanning electron microscope (SEM). , the plating layer was observed under the conditions of an accelerating voltage of 25 kV, and the plating layer portion was measured for Zn phase crystals and Al phase crystals by electron backscatter diffraction (EBSD).
Although the EBSD measurement area for the Zn phase and the Al phase depends on the thickness (adhesion amount) of the plating layer, the area is determined so as to include the entire thickness of the plating layer as much as possible.
For example, when the coating weight is 300 g/ m2 or more and the plating thickness is 40 μm or more, Zn crystals are measured at a magnification of 2000 times over an area of 40 μm x 80 μm. Al and Zn crystals are measured at a step of 0.1 μm. Measure. Al crystals are measured at a magnification of 5,000 times, with a measurement step of 0.05 μm in an area of 20 μm×20 μm, and the crystals of Al and Zn are measured. Note that since the Al crystals present in the eutectic region are fine, the observation magnification is higher than that for the measurement of Zn crystals.
As the crystal data to be measured, Zn is a hexagonal crystal with lattice constants a=b=c=2.605 Å and c=4.947 Å, and Al is a cubic crystal with lattice constants a=b=c=3.66 Å. It is preferable to do so.
Note that when the amount of plating deposited is less than 300 g/m 2 , the EBSD measurement area becomes smaller, but the measurement conditions are the same as above.
Ｚｎ相及びＡｌ相の各結晶粒径は、ＥＢＳＤで測定したそれぞれの結晶について、結晶方位の角度差が１５度以上の大角粒界を結晶粒界として、ＴＳＬ社のＯＩＭ解析ソフトで、粒径分布を求め、面積率が５０％となる粒径を平均結晶粒径として求めることができる。
ＺｎとＡｌの共晶組織である初晶領域にも微細なＺｎ相が存在するため、母相Ｚｎの結晶粒径は、初晶領域の微細なＺｎ結晶を除いて求めることが好ましい。具体的には粒径測定の対象下限粒径を５μｍとすることで、初晶領域のＺｎ相を除いた、母相Ｚｎ相（Ｚｎ相組織領域）の結晶粒径を求めることが可能である。なお、Ａｌ結晶粒径及びＺｎ結晶粒径は、いずれも円相当径として算出される。
めっき層の上記結晶粒径の測定は、加工した１断面で、めっき線の中心軸を中心として１８０度反対側となる２ヵ所で測定し、かつ、めっき線の長手方向に２ヵ所のＣ断面で測定し、合計４ヵ所でそれぞれ測定した平均結晶粒径の平均値とする。
The grain size of each of the Zn phase and Al phase was calculated using TSL's OIM analysis software, using large-angle grain boundaries with an angular difference of 15 degrees or more as grain boundaries for each crystal measured by EBSD. The distribution can be determined, and the grain size at which the area ratio is 50% can be determined as the average crystal grain size.
Since fine Zn phases also exist in the primary crystal region, which is a eutectic structure of Zn and Al, it is preferable to determine the crystal grain size of the mother phase Zn excluding the fine Zn crystals in the primary crystal region. Specifically, by setting the target lower limit grain size for grain size measurement to 5 μm, it is possible to determine the crystal grain size of the matrix Zn phase (Zn phase texture region) excluding the Zn phase in the primary crystal region. . Note that the Al crystal grain size and the Zn crystal grain size are both calculated as equivalent circle diameters.
The above-mentioned crystal grain size of the plating layer is measured at two places on one processed cross section, which are 180 degrees opposite to each other about the central axis of the plating wire, and at two C cross-sections in the longitudinal direction of the plating wire. This is the average value of the average crystal grain diameters measured at a total of four locations.
（ＭｇＺｎ２相の比率）
ＭｇＺｎ２相は耐食性改善効果を有する。ＭｇＺｎ２相の生成比率（断面内の面積率）が０％超であれば耐食性改善効果が得られるが、耐食性改善効果を高める観点から、０．２％以上が好ましく、０．３％以上とすることがより好ましく、０．５％以上とすることがさらに好ましい。一方、ＭｇＺｎ２相が、面積率で３．５％を越えて存在すると、めっき層が硬くなり疲労特性が低下するため、３．５％以下とすることが好ましい。ＭｇＺｎ２相の比率はさらに好ましくは０．５～２．５％である。
ＭｇＺｎ２相の測定は結晶粒径測定と同じサンプルの断面においてＥＢＳＤで、Ｚｎ結晶、Ａｌ結晶を測定すると同時に、ＭｇＺｎ２結晶も測定し、ＯＩＭ解析ソフトによる相マップによりＺｎ相、Ａｌ相、ＭｇＺｎ２相の各面積率を求めることができる。
ＭｇＺｎ２結晶は、ＭｇＺｎ２、Ｈｅｘａｇｏｎａｌ結晶とし、格子常数ａ＝ｂ＝５．２２１Å、ｃ＝８．５６７Åとして求める。
(MgZn two -phase ratio)
The MgZn two- phase has the effect of improving corrosion resistance. If the production ratio (area ratio in the cross section) of MgZn two phases exceeds 0%, an effect of improving corrosion resistance can be obtained, but from the viewpoint of increasing the effect of improving corrosion resistance, it is preferably 0.2% or more, and 0.3% or more. The content is more preferably 0.5% or more, and even more preferably 0.5% or more. On the other hand, if the area ratio of the MgZn 2 phase exceeds 3.5%, the plating layer becomes hard and the fatigue properties deteriorate, so it is preferably 3.5% or less. The ratio of MgZn two phases is more preferably 0.5 to 2.5%.
The MgZn 2 -phase measurement was performed using EBSD on the same cross-section of the sample used for the grain size measurement. At the same time, the Zn crystal and Al crystal were measured, and the MgZn 2- crystal was also measured, and the Zn phase, Al phase, and MgZn phase were determined using a phase map using OIM analysis software. Each area ratio of the two phases can be determined.
The MgZn 2 crystal is MgZn 2 , Hexagonal crystal, and the lattice constants a=b=5.221 Å and c=8.567 Å.
本開示においては、めっき付着量は必ずしも制限はされないが、めっき付着量が好ましくは２００ｇ／ｍ２以上とすることで、良好な耐食性が得られる。
めっき付着量の測定は、ＪＩＳ Ｇ ３５４８：２０１１「溶融めっき線」記載の方法に準じて実施する。具体的な手順は以下の通りである。
ヘキサメチレンテトラミン３．５ｇを、質量分率３５％の塩酸５００ｍｌに溶かし、その溶液を１Ｌに希釈した溶液に、長さ３００ｍｍ～６００ｍｍに切断した溶融めっき線を、気泡の発生がなくなるまで浸漬する。
浸漬前の溶融めっき線の重量（即ち、試験片のめっき層を除去する前の質量）Ｗ１（ｇ）、めっき層溶解後の鋼線の重量（即ち、試験片のめっき層を除去した後の質量）Ｗ２（ｇ）、及びめっき層溶解後の鋼線の線径ｄ（ｍｍ）を測定する。
これらの数値を以下の計算式に代入することで、めっき付着量Ａ（ｇ／ｍ２）を求めることができる。
Ａ＝（（Ｗ１－Ｗ２）／Ｗ２）×ｄ×１９６０
In the present disclosure, although the amount of plating is not necessarily limited, good corrosion resistance can be obtained by setting the amount of plating to preferably 200 g/m 2 or more.
The amount of plating deposited is measured according to the method described in JIS G 3548:2011 "Hot-dip plated wire". The specific steps are as follows.
Dissolve 3.5 g of hexamethylenetetramine in 500 ml of hydrochloric acid with a mass fraction of 35%, dilute the solution to 1 L, and immerse a hot-dip plated wire cut into lengths of 300 mm to 600 mm until no air bubbles are generated. .
The weight of the hot-dipped wire before immersion (i.e., the mass before the plating layer of the test piece is removed) W 1 (g), the weight of the steel wire after the plating layer has been melted (i.e., after the plating layer of the test piece is removed) (mass) W 2 (g) and the wire diameter d (mm) of the steel wire after dissolving the plating layer.
By substituting these values into the following calculation formula, the plating adhesion amount A (g/m 2 ) can be determined.
A=((W 1 - W 2 )/W 2 )×d×1960
［めっき線の製造方法］
本開示に係るめっき線の製造方法は特に限定されないが、以下の製造方法が挙げられる。すなわち、本開示に係るめっき線の製造方法は、
組成が、質量％で、Ａｌ：５．０％超～１２．０％、Ｍｇ：０．３０％超～１．００％、並びに残部：Ｚｎ及び不純物からなる溶融金属のめっき浴に鋼線を浸漬して引き上げることにより、前記鋼線の表面に前記溶融金属の被膜を付着させる溶融金属被膜付着工程と、
前記溶融金属被膜が付着した鋼線を、４００℃から３３０℃までの範囲で冷却速度５．０～１５．０℃／ｓで２５℃以上１次冷却し、３３０℃から２００℃までの範囲で冷却速度０．３～３．０℃／ｓで１０℃以上２次冷却する冷却工程と、を含む、めっき線の製造方法である。
[Method for manufacturing plated wire]
Although the method for manufacturing the plated wire according to the present disclosure is not particularly limited, the following manufacturing methods may be mentioned. That is, the method for manufacturing a plated wire according to the present disclosure includes:
A steel wire is placed in a plating bath of molten metal whose composition is, in mass%, Al: more than 5.0% to 12.0%, Mg: more than 0.30% to 1.00%, and the balance: Zn and impurities. a molten metal coating deposition step of attaching the molten metal coating to the surface of the steel wire by dipping and pulling it up;
The steel wire to which the molten metal coating has been attached is firstly cooled at a cooling rate of 5.0 to 15.0°C/s at a cooling rate of 25°C or more in a range from 400°C to 330°C, and then cooled in a range from 330°C to 200°C. This is a method for producing a plated wire, which includes a cooling step of performing secondary cooling to 10° C. or more at a cooling rate of 0.3 to 3.0° C./s.
図１は、本開示に係るめっき線の製造工程の一例を概略的に示している。
まず、めっきを施す鋼線を用意する。例えば、熱間圧延線材の表面に生成したスケール（酸化鉄）を除去し、更に被膜処理した後、ダイスによる伸線加工で目的の線経に加工して鋼線（被めっき線）１とする。
この鋼線を、めっき前処理装置２で脱脂、酸洗、電気Ｚｎめっきによる１次めっきを行い、さらに、本開示におけるめっき組成のめっき金属が溶融した２次めっき浴３に浸漬し、鋼線１の表面に溶融金属の被膜を形成し、浴３の外に引き出した後に冷却凝固させてめっき層を形成する。
溶融金属（２次めっき浴）３に浸漬したときに、１次めっきの電気亜鉛めっき層は溶解し、浴３から引き上げることで、地鉄（鋼線）１の表面に溶融金属３が形成される。これにより、鋼線とめっき層の間にＺｎ、Ａｌ、Ｆｅ、及びＭｇを含む硬質な合金層の生成は抑制される。
なお、１次めっきは必須ではなく、電気Ｚｎめっきによる１次めっきを行わずに、鋼線１に溶融めっきを施してもよい。
FIG. 1 schematically shows an example of a manufacturing process for a plated wire according to the present disclosure.
First, prepare the steel wire to be plated. For example, after removing the scale (iron oxide) generated on the surface of a hot-rolled wire rod and further applying a coating treatment, the steel wire (plated wire) 1 is produced by drawing the wire with a die to the desired wire diameter. .
This steel wire is subjected to primary plating by degreasing, pickling, and electrolytic Zn plating in a plating pretreatment device 2, and then immersed in a secondary plating bath 3 in which a plating metal having a plating composition according to the present disclosure is melted. A coating of molten metal is formed on the surface of 1, and after being drawn out of the bath 3, it is cooled and solidified to form a plating layer.
When immersed in the molten metal (secondary plating bath) 3, the electrogalvanized layer of the primary plating is dissolved, and by pulling it out of the bath 3, molten metal 3 is formed on the surface of the base iron (steel wire) 1. Ru. This suppresses the formation of a hard alloy layer containing Zn, Al, Fe, and Mg between the steel wire and the plating layer.
Note that primary plating is not essential, and hot-dip plating may be applied to the steel wire 1 without performing primary plating by electrolytic Zn plating.
めっき層のめっき組織の制御は、溶融金属３から引き上げて、１次冷却装置４で表面の溶融金属を凝固させ、Ｚｎの結晶粒径を制御し、その後に備える、２次冷却装置５でＡｌの結晶粒径の制御を行う。これにより、本開示に係る溶融めっき線６が得られる。
以下、鋼線をめっき浴から引き上げた後の１次冷却及び２次冷却について説明する。
The plating structure of the plating layer is controlled by pulling the molten metal from the molten metal 3, solidifying the molten metal on the surface in the primary cooling device 4, controlling the crystal grain size of Zn, and then cooling the Al in the secondary cooling device 5. control the crystal grain size. Thereby, the hot-dip plated wire 6 according to the present disclosure is obtained.
Hereinafter, primary cooling and secondary cooling after the steel wire is pulled up from the plating bath will be explained.
１次冷却温度域：４００～３３０℃の範囲で２５℃以上
１次冷却温度域では主にＺｎ相の結晶粒径の制御を行う。めっき表層に薄い凝固層が生成する前に冷却を行うと、表面が乱れ、きれいな溶融めっき線を得にくくなるために、４００～３３０℃の範囲で２５℃以上冷却する１次冷却制御を行う。好ましくは、表面に凝固層が生成する温度である４００℃以下から冷却制御を行う。一方、温度が低くなるとＺｎ相の結晶粒が制御できなくなるために、１次冷却温度域の下限温度は３３０℃とすることが好ましい。
Primary cooling temperature range: 25°C or higher in the range of 400 to 330°C In the primary cooling temperature range, the crystal grain size of the Zn phase is mainly controlled. If cooling is performed before a thin solidified layer is formed on the plating surface layer, the surface will be disturbed and it will be difficult to obtain a clean hot-dip plating line, so primary cooling control is performed to cool the plate by 25°C or more in the range of 400 to 330°C. Preferably, cooling is controlled from 400° C. or below, which is the temperature at which a solidified layer is formed on the surface. On the other hand, since the crystal grains of the Zn phase cannot be controlled when the temperature becomes low, it is preferable that the lower limit temperature of the primary cooling temperature range is 330°C.
１次冷却速度：５．０～１５．０℃／ｓ
Ｚｎ相の結晶粒径を制御するためには１次冷却温度範囲で、冷却速度５．０～１５．０℃／ｓで冷却することが好ましい。
１次冷却温度域における１次冷却速度が５．０℃／ｓより遅い場合は、Ｚｎ相の結晶粒が粗大化し、めっき線を加工したときにＺｎ相の結晶粒界に割れが発生し、加工性が低下することがある。一方、１次冷却速度が１５．０℃／ｓより大きい場合は、Ｚｎ相の結晶が微細になり、めっき線の疲労強度が低下することがある。１次冷却温度域における１次冷却速度は、より好ましくは、８．０～１２．０℃／ｓである。
Primary cooling rate: 5.0 to 15.0°C/s
In order to control the crystal grain size of the Zn phase, it is preferable to cool at a cooling rate of 5.0 to 15.0° C./s within the primary cooling temperature range.
If the primary cooling rate in the primary cooling temperature range is slower than 5.0°C/s, the crystal grains of the Zn phase will become coarse and cracks will occur at the grain boundaries of the Zn phase when processing the plated wire. Processability may decrease. On the other hand, if the primary cooling rate is higher than 15.0° C./s, the crystals of the Zn phase become fine and the fatigue strength of the plated wire may decrease. The primary cooling rate in the primary cooling temperature range is more preferably 8.0 to 12.0°C/s.
めっき層の冷却速度の制御方法は特に限定されないものの、一般的な水冷ノズルを用いて水量、水冷時間を制御することで調整可能である。また、水冷温度を調整することによっても、冷却速度の制御が可能である。
また、冷却ノズルを２流体、気水、水膜等のノズルを用いる方法や特定のガスを噴射することでも強制冷却における平均冷却速度を制御してもよい。
さらにめっき線の冷却は一方向のみではなく、円周の少なくとも４方向から冷却を行うことにより、めっき層組織のばらつきが低減可能となる。
Although the method of controlling the cooling rate of the plating layer is not particularly limited, it can be adjusted by controlling the amount of water and water cooling time using a general water cooling nozzle. The cooling rate can also be controlled by adjusting the water cooling temperature.
Furthermore, the average cooling rate in forced cooling may be controlled by using a cooling nozzle of two fluids, air/water, water film, or the like, or by injecting a specific gas.
Furthermore, by cooling the plated wire not only in one direction but from at least four directions around the circumference, variations in the structure of the plated layer can be reduced.
２次冷却温度域：３３０℃から２００℃までの範囲で１０℃以上
１次冷却後、３３０℃から２００℃までの範囲で１０℃以上冷却する２次冷却制御を行う。
共析温度より高温ではＺｎ相の結晶粒径が変化することがあるため、Ａｌ相を含む共晶組織部分は共析温度以下の温度域で制御するのが好ましい。しかし、共析温度の２８０℃では連続冷却によるＡｌ相の組織制御を行うのが困難な場合があるため、短時間では実質的にＺｎ相の結晶粒径変化が起きにくい、３３０℃以下から２次冷却の制御を行うのが好ましい。
しかし、２００℃より低下してしまうと、冷却制御の影響が得にくいため、２００℃を２次冷却制御温度の下限とするのが好ましい。
Secondary cooling temperature range: 10°C or more in the range from 330°C to 200°C After the primary cooling, perform secondary cooling control to cool the temperature by 10°C or more in the range from 330°C to 200°C.
Since the crystal grain size of the Zn phase may change at a temperature higher than the eutectoid temperature, it is preferable to control the eutectic structure portion containing the Al phase in a temperature range below the eutectoid temperature. However, at the eutectoid temperature of 280°C, it may be difficult to control the structure of the Al phase by continuous cooling. It is preferable to control the subsequent cooling.
However, if the temperature falls below 200°C, it is difficult to obtain an effect of cooling control, so it is preferable to set 200°C as the lower limit of the secondary cooling control temperature.
２次冷却速度：０．３～３．０℃／ｓ
２次冷却温度域である、３３０℃～２００℃の間で１０℃以上冷却する際の冷却速度は０．３～３．０℃／ｓであることが好ましい。
３３０℃以下の温度域でめっき線を連続して２次冷却する場合、冷却速度を０．３℃／ｓより遅くしてもＡｌの結晶粒径の組成制御効果が得にくくなる場合があるとともに、めっき線を巻き取るための装置でのハンドリング可能な低温まで冷却するのに長時間かかり、連続処理できなくなる場合があるため、０．３℃／ｓを２次冷却速度の下限とするのが好ましい。
一方、２次冷却速度が３．０℃／ｓより速いとＡｌ相の平均結晶粒径が小さくなるため疲労特性の改善効果が十分に得られないことがある。そのため、２次冷却では、３．０℃／ｓ以下の冷却速度とすることが好ましい。
Secondary cooling rate: 0.3-3.0℃/s
The cooling rate when cooling by 10°C or more in the secondary cooling temperature range of 330°C to 200°C is preferably 0.3 to 3.0°C/s.
In the case of continuous secondary cooling of the plated wire in a temperature range of 330°C or lower, even if the cooling rate is lower than 0.3°C/s, it may be difficult to obtain the effect of controlling the Al crystal grain size composition. , it takes a long time to cool the plated wire to a low temperature that can be handled by a device for winding it, and continuous processing may not be possible. preferable.
On the other hand, if the secondary cooling rate is higher than 3.0° C./s, the average crystal grain size of the Al phase becomes small, so that a sufficient effect of improving fatigue properties may not be obtained. Therefore, in the secondary cooling, it is preferable to set the cooling rate to 3.0° C./s or less.
２次冷却速度の制御方法は特に限定されないが、めっき線に高温のガスを吹き付けることや、２次冷却装置５の雰囲気温度を制御したボックス内を通過させることにより冷却速度の制御が可能となる。
さらに冷却速度を遅くする場合は、単線では２次冷却ゾーンが長くなりすぎるため、めっき線を巻き取った状態で徐冷しても同様に組織の制御は可能である。この場合、より徐冷速度を遅くできる。
The method of controlling the secondary cooling rate is not particularly limited, but it is possible to control the cooling rate by blowing high temperature gas onto the plated wire or by passing it through a box in which the ambient temperature of the secondary cooling device 5 is controlled. .
If the cooling rate is further slowed down, the secondary cooling zone will be too long in the case of a single wire, so the structure can be similarly controlled even if the plated wire is slowly cooled in a wound state. In this case, the slow cooling rate can be made slower.
以上説明したように、めっき層の組成及び組織を本開示の範囲に制御することでめっき線の疲労強度の低下を抑制することが可能となり、Ｍｇを含まない、Ｚｎ－Ａｌの二元合金めっきに比べ良好な耐食性が得られることから、耐食性と疲労特性が良好なめっき線を得ることができる。 As explained above, by controlling the composition and structure of the plating layer within the range of the present disclosure, it is possible to suppress a decrease in the fatigue strength of the plating wire, and the Zn-Al binary alloy plating does not contain Mg. Since better corrosion resistance can be obtained compared to the above, it is possible to obtain a plated wire with good corrosion resistance and fatigue properties.
本開示に係るめっき線の用途は特に限定されないが、良好な耐食性及び良好な疲労耐久性が得られることから、特に架線用途に適用することで、産業上の貢献が極めて顕著である。 Although the use of the plated wire according to the present disclosure is not particularly limited, since good corrosion resistance and good fatigue durability can be obtained, the industrial contribution will be extremely significant especially when applied to overhead wire use.
以下、本開示の実施例について説明する。なお、本開示は、必ずしも本実施例に記載の方法に限定されるものではない。 Examples of the present disclosure will be described below. Note that the present disclosure is not necessarily limited to the method described in this example.
［めっき線の製造］
鋼線（被めっき線）の素材として用いた線径が５．５ｍｍの熱間圧延線材の鋼材成分を表１に示す。なお、表１に記載の成分以外の残部はＦｅ及び不純物である。
[Manufacture of plated wire]
Table 1 shows the steel components of the hot rolled wire rod with a wire diameter of 5.5 mm used as the material for the steel wire (wire to be plated). Note that the remainder other than the components listed in Table 1 is Fe and impurities.
熱間圧延線材は酸洗でスケールを除去した後、リン酸亜鉛被膜処理を行い、ステアリン酸カルシウムを主体とした乾式潤滑剤（伸線潤滑剤）を用いて１パス減面率が１６％～２４％で４～６回繰り返し伸線を行い、３．２ｍｍまで加工し、鋼線とした。
次に、めっき前処理として、鋼線をアルカリ溶液で脱脂して伸線潤滑剤を除去した。伸線潤滑剤を除去後、酸洗を行い、１次めっきとして、厚さ２μｍの電気亜鉛めっきを施した。
１次めっきに引き続き、Ｚｎ、Ａｌ、及びＭｇを含む２次めっきの４５０℃の溶融金属のめっき浴に１次めっき線を浸漬し、浴から連続して垂直に引き上げて、表面にＺｎ、Ａｌ、及びＭｇを含む被膜（めっき層）を形成した。
After removing scale from hot-rolled wire rods by pickling, a zinc phosphate coating treatment is applied, and a dry lubricant (wire drawing lubricant) mainly composed of calcium stearate is used to achieve a one-pass area reduction of 16% to 24%. %, repeated wire drawing 4 to 6 times and processed to 3.2 mm to obtain a steel wire.
Next, as a plating pretreatment, the steel wire was degreased with an alkaline solution to remove the wire drawing lubricant. After removing the wire drawing lubricant, pickling was performed, and electrogalvanizing with a thickness of 2 μm was performed as primary plating.
Following the primary plating, the primary plating wire is immersed in a 450°C molten metal plating bath containing Zn, Al, and Mg, and is continuously pulled up vertically from the bath to coat the surface with Zn, Al, and Mg. , and a coating (plating layer) containing Mg was formed.
２次めっきの溶融金属のＡｌ、Ｍｇの各濃度、浴から引き上げた後の１次冷却温度範囲、及び冷却速度を変えることで、めっき層の組成、Ｚｎ相の結晶粒径を制御した。また、通線速度を調整して、めっき付着量を２００～３２０ｇ／ｍ２に制御した。 The composition of the plating layer and the crystal grain size of the Zn phase were controlled by changing the respective concentrations of Al and Mg in the molten metal for secondary plating, the temperature range of the primary cooling after being pulled from the bath, and the cooling rate. In addition, the wire passing speed was adjusted to control the coating weight to 200 to 320 g/m 2 .
更に１次冷却後に２次冷却を行い、２次冷却温度範囲、冷却速度を変えて、Ａｌ相の平均結晶粒径を調整した。 Furthermore, secondary cooling was performed after primary cooling, and the average crystal grain size of the Al phase was adjusted by changing the secondary cooling temperature range and cooling rate.
１次冷却温度域は、１次冷却ゾーンの冷却開始温度と、１次冷却ゾーン出口温度を測定して求め、１次冷却速度は、温度差を通線時間で割って平均冷却速度として求めた。
２次冷却温度域は、２次冷却ゾーンの冷却開始温度と、１次冷却ゾーン出口温度を測定して求め、２次冷却速度は、温度差を通線時間で割って、平均冷却速度として求めた。
The primary cooling temperature range was determined by measuring the cooling start temperature of the primary cooling zone and the primary cooling zone outlet temperature, and the primary cooling rate was determined as the average cooling rate by dividing the temperature difference by the line time. .
The secondary cooling temperature range is determined by measuring the cooling start temperature of the secondary cooling zone and the primary cooling zone exit temperature, and the secondary cooling rate is determined as the average cooling rate by dividing the temperature difference by the line time. Ta.
［めっき層の分析］
＜組成分析＞
上記のようにして製造しためっき線のめっき層の組成について、前述した方法により分析した。表２に、Ｍｇ量、Ａｌ量を記載した。残部はＺｎ及び不純物であり、溶解しためっき層の総量からＭｇ量、Ａｌ量、及びＺｎ量を差し引いた不純物量は０．０１％未満であった。
[Analysis of plating layer]
<Composition analysis>
The composition of the plating layer of the plated wire produced as described above was analyzed by the method described above. Table 2 shows the amount of Mg and the amount of Al. The remainder was Zn and impurities, and the amount of impurities obtained by subtracting the amount of Mg, the amount of Al, and the amount of Zn from the total amount of the dissolved plating layer was less than 0.01%.
＜組織分析＞
Ｚｎ相の平均円相当結晶粒径、Ａｌ相の平均円相当結晶粒径は先に記載の通り、まず、めっき層のＣ断面（溶融めっき線の長手方向に垂直な断面）をＣＰで加工して、走査型電子顕微鏡（ＳＥＭ）で観察し、電子線後方散乱回折法（ＥＢＳＤ）により、めっき層部分を測定領域として、ＺｎとＡｌの結晶データを測定した。
Ｚｎ相の結晶粒径は倍率２０００倍の測定データから結晶方位差が１５度以上を粒界として結晶粒径分布をＯＩＭの解析ソフトで求めた。初晶内の微小なＺｎ結晶を測定対象から除くために、最小結晶粒径（最小円相当結晶粒径）を５μｍとして面積平均結晶粒径をＺｎ相の平均円相当結晶粒径とした。
Ａｌ相の平均円相当結晶粒径は倍率５０００倍の測定データから、結晶方位の角度差が１５度以上の境界を結晶粒界とみなしてＯＩＭ解析ソフトの粒径分布グラフから平均結晶粒径を求めた。
各測定領域及び測定ステップは、前述したとおりである。
各めっき線について、１つのＣ断面につき、中心軸を中心として１８０度反対側となる２ヵ所で測定し、かつ、めっき線の長手方向に１ｍ間隔の２ヵ所のＣ断面で測定し、合計４ヵ所でそれぞれ平均円相当結晶粒径を測定した。そして、４ヵ所におけるＺｎ相の平均円相当結晶粒径の平均値、Ａｌ相の平均円相当結晶粒径の平均値を、それぞれ各めっき層における各相の平均円相当平均結晶粒径とした。
<Organizational analysis>
As described above, the average equivalent circular crystal grain size of the Zn phase and the average equivalent circular crystal grain size of the Al phase are determined by first processing the C cross section of the plating layer (the cross section perpendicular to the longitudinal direction of the hot-dip plated wire) using CP. Then, observation was made using a scanning electron microscope (SEM), and crystal data of Zn and Al were measured by electron beam backscatter diffraction (EBSD) using the plating layer portion as a measurement region.
The crystal grain size distribution of the Zn phase was determined from measurement data at a magnification of 2000 times using OIM analysis software, with a crystal orientation difference of 15 degrees or more defined as a grain boundary. In order to exclude minute Zn crystals within the primary crystal from the measurement target, the minimum crystal grain size (minimum circle equivalent crystal grain size) was set to 5 μm, and the area average crystal grain size was taken as the average circle equivalent crystal grain size of the Zn phase.
The average circular equivalent crystal grain size of the Al phase is determined from the measurement data at a magnification of 5000 times, and the average crystal grain size is determined from the grain size distribution graph of OIM analysis software, regarding boundaries where the angular difference in crystal orientation is 15 degrees or more as grain boundaries. I asked for it.
Each measurement area and measurement step are as described above.
For each plated wire, measurements were taken at two locations 180 degrees on opposite sides of each C cross-section around the central axis, and at two C cross-sections spaced 1 m apart in the longitudinal direction of the plated wire, resulting in a total of 4 measurements. The average circular equivalent crystal grain size was measured at each location. Then, the average value of the average equivalent circular crystal grain size of the Zn phase and the average value of the average equivalent circular crystal grain size of the Al phase at the four locations were defined as the average equivalent circular crystal grain size of each phase in each plating layer.
［評価］
＜疲労強度＞
めっき線の疲労強度は、中村疲労試験により評価した。めっき線の引張り強さの０．１～０．５倍の曲げ応力をかけて、回転曲げ疲労試験を行い、それぞれの応力での破断寿命を求め、１０７回で破断しなかった応力をめっき線の疲労強度とし、疲労強度を引張り強さで除し、疲労限耐久比を求めた。
疲労限耐久比が０．２３以上であれば、疲労強度が極めて良好と判断し、◎とした。疲労限耐久比が０．２１～０．２３未満であれば良と判断し、○とした。疲労限耐久比が０．２１未満の場合は疲労強度が劣位と判断し、×とした。
[evaluation]
<Fatigue strength>
The fatigue strength of the plated wire was evaluated by the Nakamura fatigue test. A rotating bending fatigue test was performed by applying a bending stress of 0.1 to 0.5 times the tensile strength of the plated wire, the fracture life at each stress was determined, and the stress that did not cause fracture in 107 cycles was applied to the plated wire. The fatigue strength of the wire was taken as the fatigue strength, and the fatigue strength was divided by the tensile strength to obtain the fatigue limit durability ratio.
If the fatigue limit durability ratio was 0.23 or more, the fatigue strength was judged to be extremely good, and it was rated ◎. If the fatigue limit durability ratio was less than 0.21 to 0.23, it was judged as good and marked as ○. When the fatigue limit durability ratio is less than 0.21, the fatigue strength is judged to be inferior and it is marked as ×.
＜耐食性＞
溶融めっき線の耐食性は以下の方法で評価した。種々のめっき組成、結晶サイズのめっき線を、ＪＩＳ Ｚ ２３７１：２０１５「塩水噴霧試験方法」に記載の塩水噴霧試験を実施し、１０００ｈ後の溶融めっき層の腐食減量を測定した。
比較例のＮｏ．１８、Ｚｎ－１０．５％Ａｌめっき線の腐食減量を１００とし、腐食減量がＺｎ－１０．５％Ａｌめっき線の２５％以下の場合は、耐食性が極めて良好と判断し、◎とした。腐食減量がＺｎ－１０．５％Ａｌめっき線の２５％超～５０％の場合は、耐食性が良好で、○と判断した。腐食減量がＺｎ－１０．５％Ａｌめっき線の５０％超の場合は、耐食性改善効果が小さく、×と判断した。
<Corrosion resistance>
The corrosion resistance of the hot-dip plated wire was evaluated by the following method. Plated wires with various plating compositions and crystal sizes were subjected to a salt spray test described in JIS Z 2371:2015 "Salt water spray test method", and the corrosion loss of the hot-dip plated layer after 1000 hours was measured.
Comparative example No. 18. The corrosion weight loss of the Zn-10.5% Al plated wire is set as 100, and if the corrosion weight loss is 25% or less of the Zn-10.5% Al plated wire, the corrosion resistance is judged to be extremely good and it is marked as ◎. If the corrosion loss was more than 25% to 50% of the Zn-10.5% Al-plated wire, the corrosion resistance was good and it was judged as ○. If the corrosion loss was more than 50% of that of the Zn-10.5% Al-plated wire, the corrosion resistance improvement effect was small, and it was judged as ×.
表２に発明例と比較例の溶融めっき線の特性評価結果を示す。 Table 2 shows the characteristics evaluation results of the hot-dip plated wires of the invention examples and comparative examples.
表２において、本開示の範囲外の値には下線を付した。 In Table 2, values outside the range of the present disclosure are underlined.
比較例のＮｏ．１８はＺｎ－１０．５％Ａｌの二元合金溶融めっき線で、１次冷却のみを行っためっき線であり、耐食性評価の基準めっき線である。
発明例のＮｏ．２～４，６，９，１１～１３，１５は極めて良好な疲労強度と、耐食性が得られた。
Ｍｇ量が本開示の下限近傍及び／又はＡｌ量が本開示の上限近傍の組成であるＮｏ．５，７はＭｇＺｎ２相が比較的少なく耐食性改善効果は良好レベルであった。Ｎｏ．１６もＭｇＺｎ２相が比較的少なく、耐食性改善効果は良好レベルであった。
（１）式の値Ｄが、７０未満のＮｏ．１，１４，１７は疲労強度が良好で、Ｍｇが高めのＮｏ．８もＭｇＺｎ２相が増加し、疲労強度レベルは良であった。
Ａｌ結晶粒径０．６μｍであり、発明例の中で最も小さいＮｏ．１０も疲労強度レベルは良であった。
Comparative example No. 18 is a binary alloy hot-dip plated wire of Zn-10.5% Al, which is a plated wire that has undergone only primary cooling, and is a standard plated wire for corrosion resistance evaluation.
Invention example No. Samples 2 to 4, 6, 9, 11 to 13, and 15 had extremely good fatigue strength and corrosion resistance.
No. 1 whose composition has a Mg content near the lower limit of the present disclosure and/or an Al content near the upper limit of the present disclosure. Nos. 5 and 7 had a relatively small amount of MgZn two phases, and the corrosion resistance improvement effect was at a good level. No. No. 16 also had a relatively small amount of MgZn two phases, and the corrosion resistance improvement effect was at a good level.
No. 1 whose value D in formula (1) is less than 70. No. 1, 14, and 17 have good fatigue strength and a high Mg content. No. 8 also had an increase in MgZn 2 phase, and the fatigue strength level was good.
The Al crystal grain size is 0.6 μm, which is the smallest among the invention examples. No. 10 also had a good fatigue strength level.
比較例のＮｏ．１９は、めっき組成のＭｇが本開示の下限未満のため、耐食性の改善効果が見られなかった例である。 Comparative example No. No. 19 is an example in which the effect of improving corrosion resistance was not observed because Mg in the plating composition was less than the lower limit of the present disclosure.
比較例のＮｏ．２０は、めっき組成のＭｇが上限を越えて、多いために、耐食性は良好であるが、疲労強度が低下した例である。 Comparative example No. No. 20 is an example in which the amount of Mg in the plating composition exceeds the upper limit, so the corrosion resistance is good, but the fatigue strength is reduced.
比較例のＮｏ．２１は、めっき組成のＡｌが本開示の下限未満のため、初晶がＺｎ相となるとともに、ＭｇＺｎ２相が低下し、耐食性が改善しなかった例である。 Comparative example No. No. 21 is an example in which the primary crystals became a Zn phase and the MgZn 2 phase decreased because Al in the plating composition was less than the lower limit of the present disclosure, and the corrosion resistance was not improved.
比較例のＮｏ．２２は、めっき組成のＡｌが本開示の上限を超えているためにＡｌ初晶が増加し、初晶部の腐食が進行するとともにＭｇＺｎ２相が少なく耐食性低下すると共に溶融金属の融点が高くなり、良好な表面性状が得られなかった例である。 Comparative example No. In No. 22, since Al in the plating composition exceeds the upper limit of the present disclosure, Al primary crystals increase, corrosion of the primary crystal portion progresses, MgZn 2 phase is small, corrosion resistance decreases, and the melting point of the molten metal increases. This is an example in which good surface quality was not obtained.
比較例のＮｏ．２３は、１次冷却速度が速く、１次冷却でめっき線表面の温度が低下したために、Ｚｎ結晶が小さくなるとともに、Ａｌ結晶粒の制御が出来ず、（１）式の値Ｄが本開示の下限に満たなかったために疲労強度が低下した例である。 Comparative example No. In No. 23, the primary cooling rate was fast and the temperature of the surface of the plated wire was lowered by the primary cooling, so the Zn crystal became smaller and the Al crystal grains could not be controlled, so the value D in equation (1) was lower than the value D of the present disclosure. This is an example where the fatigue strength decreased because the lower limit of was not met.
比較例のＮｏ．２４は、１次冷却速度が遅いために、Ｚｎ結晶粒が本開示の上限を超え、３４μｍと粗大化したため、疲労試験で割れが発生し疲労強度が低下した例である。 Comparative example No. No. 24 is an example in which the Zn crystal grains exceeded the upper limit of the present disclosure and became coarse to 34 μm due to the slow primary cooling rate, resulting in cracking in the fatigue test and a decrease in fatigue strength.
比較例のＮｏ．２５は、２次冷却速度温度が低温かつ、冷却速度が速かったためにＡｌの結晶粒径が微細となり、疲労強度が低下した例である。 Comparative example No. No. 25 is an example in which the secondary cooling rate temperature was low and the cooling rate was fast, so the Al crystal grain size became fine and the fatigue strength decreased.
比較例のＮｏ．２６は、１次冷却のみを実施し、低温まで冷却してめっき線を製造し、２次冷却制御を行なわなかったため、Ａｌ結晶粒径が微細になり、（１）式の値Ｄが本開示の下限に満たなかったために疲労強度が低かった例である。 Comparative example No. In No. 26, only the primary cooling was performed to produce a plated wire by cooling to a low temperature, and the secondary cooling control was not performed, so the Al crystal grain size became fine and the value D in equation (1) was lower than that disclosed in the present disclosure. This is an example where the fatigue strength was low because it did not meet the lower limit of .
本開示に係るめっき線は、疲労特性と耐食性に優れるために、架線等、動的負荷が作用する各種用途への適用が可能となり、産業上の利用可能性が極めて高い。 Since the plated wire according to the present disclosure has excellent fatigue properties and corrosion resistance, it can be applied to various applications where dynamic loads are applied, such as overhead wires, and has extremely high industrial applicability.
１ 鋼線（被めっき線）
２ 前処理装置
３ ２次めっき浴
４ １次冷却装置
５ ２次冷却装置
６ 溶融めっき線
1 Steel wire (plated wire)
2 Pretreatment device 3 Secondary plating bath 4 Primary cooling device 5 Secondary cooling device 6 Hot dip plated wire
Claims (3)
前記めっき層の組成が、質量％で、
Ａｌ：５．０％超～１２．０％、
Ｍｇ：０．３０％超～１．００％、並びに
残部：Ｚｎ及び合計１．０％以下の不純物、からなり、
前記めっき層の組織が、Ｚｎ相、Ａｌ相、及びＭｇＺｎ２相を含み、ＥＢＳＤ（電子線後方散乱解析：Ｅｌｅｃｔｒｏｎ Ｂａｃｋ Ｓｃａｔｔｅｒｅｄ Ｄｉｆｆｒａｃｔｉｏｎ Ｐａｔｔｅｒｎ）により、Ｚｎ結晶とＡｌ結晶を測定したときの結晶の方位差１５度以上を結晶粒界と定義し、前記Ｚｎ結晶のうち５μｍ以上の円相当結晶粒径の平均円相当結晶粒径をｄＺｎμｍ、前記Ａｌ結晶の平均円相当結晶粒径をｄＡｌμｍとしたとき、前記ｄＺｎが３０μｍ以下であり、かつ下記（１）式の値Ｄが６４以上、１０８以下である、めっき線。
Ｄ＝２．４×ｄＺｎ＋２４．２×ｄＡｌ ・・・（１） comprising a steel wire and a plating layer covering the surface of the steel wire,
The composition of the plating layer is in mass%,
Al: more than 5.0% to 12.0%,
Mg: more than 0.30% to 1.00%, and the balance: Zn and impurities of a total of 1.0% or less ,
The structure of the plating layer includes a Zn phase, an Al phase, and two MgZn phases, and the crystal orientation difference when Zn crystal and Al crystal are measured by EBSD (Electron Back Scattered Diffraction Pattern) 15 degrees or more is defined as a grain boundary, the average circle-equivalent crystal grain size of the circle-equivalent crystal grains of 5 μm or more among the Zn crystals is d Zn μm, and the average circle-equivalent crystal grain size of the Al crystals is d Al μm A plated wire in which the d Zn is 30 μm or less, and the value D of the following formula (1) is 64 or more and 108 or less.
D=2.4×d Zn +24.2×d Al ...(1)
前記溶融金属被膜が付着した鋼線を、４００℃から３３０℃までの範囲で冷却速度５．０～１５．０℃／ｓで２５℃以上１次冷却し、３３０℃から２００℃までの範囲で冷却速度０．３～３．０℃／ｓで１０℃以上２次冷却する冷却工程と、
を含む、めっき線の製造方法。 A molten metal whose composition is, in mass%, Al: more than 5.0% to 12.0%, Mg: more than 0.30% to 1.00%, and the balance: Zn and impurities of a total of 1.0% or less a molten metal coating deposition step of attaching the molten metal coating to the surface of the steel wire by immersing the steel wire in a plating bath and pulling it up;
The steel wire to which the molten metal coating has been attached is firstly cooled at a cooling rate of 5.0 to 15.0°C/s at a cooling rate of 25°C or more in a range from 400°C to 330°C, and then cooled in a range from 330°C to 200°C. A cooling step of secondary cooling of 10°C or more at a cooling rate of 0.3 to 3.0°C/s,
A method of manufacturing plated wire, including
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011214145A (en) | 2010-03-17 | 2011-10-27 | Nippon Steel Corp | Plated steel material and steel pipe having high corrosion resistance and excellent workability, and method for producing the same |
| WO2018169084A1 (en) | 2017-03-17 | 2018-09-20 | 新日鐵住金株式会社 | Plated steel sheet |
| WO2019124485A1 (en) | 2017-12-20 | 2019-06-27 | 日本製鉄株式会社 | Hot-dip plated steel wire and manufacturing method therefor |
| JP2021508779A (en) | 2017-12-26 | 2021-03-11 | ポスコＰｏｓｃｏ | Zinc alloy plated steel with excellent corrosion resistance and surface smoothness and its manufacturing method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2011214145A (en) | 2010-03-17 | 2011-10-27 | Nippon Steel Corp | Plated steel material and steel pipe having high corrosion resistance and excellent workability, and method for producing the same |
| WO2018169084A1 (en) | 2017-03-17 | 2018-09-20 | 新日鐵住金株式会社 | Plated steel sheet |
| WO2019124485A1 (en) | 2017-12-20 | 2019-06-27 | 日本製鉄株式会社 | Hot-dip plated steel wire and manufacturing method therefor |
| JP2021508779A (en) | 2017-12-26 | 2021-03-11 | ポスコＰｏｓｃｏ | Zinc alloy plated steel with excellent corrosion resistance and surface smoothness and its manufacturing method |
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