JP6480132B2 - Al-plated steel sheet - Google Patents
Al-plated steel sheet Download PDFInfo
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- JP6480132B2 JP6480132B2 JP2014190406A JP2014190406A JP6480132B2 JP 6480132 B2 JP6480132 B2 JP 6480132B2 JP 2014190406 A JP2014190406 A JP 2014190406A JP 2014190406 A JP2014190406 A JP 2014190406A JP 6480132 B2 JP6480132 B2 JP 6480132B2
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- 229910000831 Steel Inorganic materials 0.000 title claims description 91
- 239000010959 steel Substances 0.000 title claims description 91
- 238000007747 plating Methods 0.000 claims description 87
- 239000012535 impurity Substances 0.000 claims description 7
- 239000010935 stainless steel Substances 0.000 claims description 2
- 229910001220 stainless steel Inorganic materials 0.000 claims description 2
- 230000007797 corrosion Effects 0.000 description 68
- 238000005260 corrosion Methods 0.000 description 68
- 239000011248 coating agent Substances 0.000 description 44
- 238000000576 coating method Methods 0.000 description 44
- 229910045601 alloy Inorganic materials 0.000 description 16
- 239000000956 alloy Substances 0.000 description 16
- 239000000203 mixture Substances 0.000 description 15
- 239000003973 paint Substances 0.000 description 11
- 238000011156 evaluation Methods 0.000 description 9
- 238000010422 painting Methods 0.000 description 9
- 239000000126 substance Substances 0.000 description 9
- 239000000463 material Substances 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 7
- 239000000047 product Substances 0.000 description 6
- 150000001875 compounds Chemical class 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 239000004566 building material Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000004070 electrodeposition Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 229910018191 Al—Fe—Si Inorganic materials 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 229910000765 intermetallic Inorganic materials 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 230000006641 stabilisation Effects 0.000 description 3
- 238000011105 stabilization Methods 0.000 description 3
- 230000008961 swelling Effects 0.000 description 3
- 239000013585 weight reducing agent Substances 0.000 description 3
- 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 3
- 229910000165 zinc phosphate Inorganic materials 0.000 description 3
- 229910018125 Al-Si Inorganic materials 0.000 description 2
- 229910018520 Al—Si Inorganic materials 0.000 description 2
- 229910001335 Galvanized steel Inorganic materials 0.000 description 2
- -1 Mg 2 Si Chemical class 0.000 description 2
- 238000000137 annealing Methods 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 239000010960 cold rolled steel Substances 0.000 description 2
- 238000005097 cold rolling Methods 0.000 description 2
- 239000004035 construction material Substances 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 239000008397 galvanized steel Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910052718 tin Inorganic materials 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 1
- 206010053759 Growth retardation Diseases 0.000 description 1
- 229910019018 Mg 2 Si Inorganic materials 0.000 description 1
- 229910019021 Mg 2 Sn Inorganic materials 0.000 description 1
- 229910017706 MgZn Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000013527 degreasing agent Substances 0.000 description 1
- 238000005237 degreasing agent Methods 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000004993 emission spectroscopy Methods 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000002828 fuel tank Substances 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000002987 primer (paints) Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000010183 spectrum analysis Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
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Description
本発明は、塗装後耐食性に優れた溶融Ａｌ系めっき鋼板に関するものである。 The present invention relates to a hot-dip Al-based plated steel sheet which is excellent in post-paint corrosion resistance.
溶融Ａｌ系めっき鋼板は、通常の溶融Ｚｎめっき鋼板と比較して、耐食性及び耐熱性に優れる。
一般的に、溶融Ａｌ系めっき鋼板は、鋼スラブを熱間圧延若しくは冷間圧延した薄鋼板を下地鋼板として用い、該下地鋼板を連続式溶融めっきラインの焼鈍炉にて再結晶焼鈍及び溶融めっき処理を行うことによって製造される。この形成されたＡｌ系めっき層は、下地鋼板との界面に存在する合金層と、その上に存在する上層とを備えている。さらに、上層は、主としてＡｌがめっき皮膜の膜厚方向に積層するようにデンドライト凝固した部分（α−Ａｌ相）と、残りのインターデンドライトの部分からなり、インターデンドライトの一部には、後述するＦｅやＳｉなどの金属間化合物や単体が存在する。この上層の特徴的な皮膜構造により、表面からの腐食進行経路が複雑になり腐食が容易に下地鋼板に到達しにくくなるため、溶融Ａｌ系めっき鋼板は、優れた耐食性を有することが可能である。
さらに、めっきの主成分であるＡｌは、本来熱力学的には活性な金属であるが、大気中などの有酸素雰囲気では表面に酸化膜を形成し、この酸化膜の安定性に起因して優れた耐食性を有する。
The hot-dip Al-based plated steel sheet is superior in corrosion resistance and heat resistance as compared to a normal hot-dip galvanized steel sheet.
Generally, a hot-dip Al-based plated steel sheet uses a thin steel sheet obtained by hot rolling or cold rolling a steel slab as a base steel sheet, and the base steel sheet is recrystallization annealing and hot-dip plating in an annealing furnace of a continuous hot-dip plating line Manufactured by performing processing. The formed Al-based plating layer includes an alloy layer present at the interface with the base steel plate and an upper layer present thereon. Further, the upper layer is mainly composed of a portion (α-Al phase) solidified with dendrite so that Al is laminated in the film thickness direction of the plating film, and a portion of the remaining interdendrite. There exist intermetallic compounds such as Fe and Si and simple substances. The characteristic film structure of the upper layer complicates the path of corrosion from the surface and makes it difficult for the corrosion to easily reach the substrate steel sheet, so the hot-dip Al-based plated steel sheet can have excellent corrosion resistance. .
Furthermore, Al, which is the main component of plating, is a metal that is inherently thermodynamically active, but forms an oxide film on the surface in the presence of an oxygen-containing atmosphere such as in the air, which is attributed to the stability of this oxide film. Has excellent corrosion resistance.
なお、めっき浴には、不可避的不純物、鋼板やめっき浴中の機器等から溶出するＦｅが含まれており、その他、過度の合金層成長を抑制するためのＳｉが通常添加される。このＳｉは合金層に金属間化合物の形、あるいは上層に金属間化合物、固溶体若しくは単体の形で存在している。そして、このＳｉの働きにより、溶融Ａｌ系めっき鋼板の界面の合金層成長が抑えられ、合金層厚さは約１〜５μｍ程度となっている。めっき層厚が同一ならば、合金層が薄いほど耐食性向上に効果のある上層が厚くなるので、合金層の成長を抑制することは耐食性の向上に寄与することになる。また、合金層は上層よりも固く、加工時にクラックの起点として作用することから、合金層の成長抑制はクラックの発生を減少させ、曲げ加工性を向上させる効果をもたらすことにもなる。そして、発生したクラック部は下地鋼板が露出しており耐食性に劣るので、合金層の成長を抑制し、クラックの発生を抑制することは曲げ加工部耐食性をも向上させることになる。 The plating bath contains unavoidable impurities, Fe eluted from steel plates, equipment in the plating bath, etc. In addition, Si is usually added to suppress excessive alloy layer growth. The Si is present in the form of an intermetallic compound in the alloy layer, or in the form of an intermetallic compound, a solid solution or a simple substance in the upper layer. And, by the function of this Si, the growth of the alloy layer at the interface of the hot-dip Al-based plated steel sheet is suppressed, and the thickness of the alloy layer is about 1 to 5 μm. If the plating layer thickness is the same, the thinner the alloy layer, the thicker the upper layer effective for improving the corrosion resistance. Therefore, suppressing the growth of the alloy layer contributes to the improvement of the corrosion resistance. In addition, since the alloy layer is harder than the upper layer and acts as a crack starting point during processing, suppressing the growth of the alloy layer reduces the occurrence of cracks and also has an effect of improving the bending workability. And since the base steel plate is exposed and the crack part which generate | occur | produced is inferior to corrosion resistance, suppressing the growth of an alloy layer and suppressing generation | occurrence | production of a crack will also improve the bending part corrosion resistance.
このように耐食性に優れる溶融Ａｌ系めっき鋼板は、長期間屋外に曝される屋根や壁などの建材分野を中心に需要が伸び、近年は、自動車分野においても、優れた耐熱性を活かしてマフラー、燃料タンクなどの特定部品で使用されている。特に、自動車分野においては、地球温暖化対策の一環で車体を軽量化して燃費を向上させＣＯ2排出量を削減することが求められている。このため、現在、高強度鋼板の使用による軽量化と、鋼板の耐食性向上によるゲージダウンが強く望まれている。 In this way, the hot-dip Al-based plated steel sheet, which has excellent corrosion resistance, has increased demand mainly in the building materials field such as roofs and walls exposed to the outside for a long time, and in recent years It is used in certain parts such as fuel tanks. In the automobile field, in particular, it is required to reduce the weight of the vehicle body, to improve the fuel efficiency, and to reduce the CO 2 emission as part of the measures against global warming. For this reason, weight reduction by use of a high strength steel plate and gauge down by corrosion resistance improvement of the steel plate are strongly desired at present.
しかしながら、溶融Ａｌ系めっき鋼板を自動車分野、特に外板パネルに用いようとした場合には、次の問題があった。
溶融Ａｌ系めっき鋼板を自動車外板パネルとして使用する場合、該めっき鋼板は連続式溶融めっき設備でめっきまで施した状態で自動車メーカー等に供される。そこでパネル部品形状に加工された後に化成処理、さらに電着塗装、中塗り塗装、上塗り塗装の自動車用３コート塗装が施されることが一般的である。ただし、溶融Ａｌ系めっき鋼板を用いた外板パネルは、塗膜に損傷が生じた際に傷部からの塗膜膨れが生じ易いという問題があった。
塗装後腐食の一つである塗膜膨れは、下地鋼板が露出する傷部がカソード、腐食先端部がアノード、腐食最先端部がカソードのような塗膜下で局部電池を形成するために起こる事象である。Ａｌ系めっき鋼板は、めっき層中のインターデンドライトに形成した針状のＳｉやＡｌ−Ｆｅ−Ｓｉ化合物がいずれもＡｌよりも貴な電位を示し、局部的にカソードサイトとして働くため、塗膜下で局部電池を形成する。これにより、傷部を起点にインターデンドライトの選択腐食が塗膜／めっき界面で発生する。これが進行して大きな塗膜膨れを起こす結果、十分な塗装後耐食性を確保できなくなる。
However, in the case where it is intended to use a molten Al-based plated steel sheet for the automotive field, particularly an outer panel, there are the following problems.
When using a hot-dip Al-based plated steel plate as an automobile outer panel, the plated steel plate is provided to a car maker or the like in a state where the plating is performed in a continuous hot-dip plating facility. Therefore, after being processed into a panel part shape, it is general to apply a chemical conversion treatment, and further an automotive 3-coat coating such as electrodeposition coating, middle coat coating and top coat coating. However, the outer panel using the hot-dip Al-based plated steel sheet has a problem that the coating film is easily blistered from the flaw when the coating film is damaged.
Coating film blistering, which is one of corrosion after coating, occurs because a scratch where the substrate steel plate is exposed forms a local cell under a coating such as the cathode, the corrosion tip as the anode, and the corrosion tip as the cathode. It is an event. In the Al-based plated steel sheet, needle-like Si or Al-Fe-Si compound formed on interdendrite in the plating layer exhibits a potential higher than Al and works locally as a cathode site. Form a local battery. As a result, selective corrosion of interdendrite occurs at the coating / plating interface starting from the flaw. As this progresses to cause a large coating film blister, sufficient corrosion resistance after coating can not be secured.
一方、溶融Ａｌ系めっき鋼板を建屋の屋根材や壁材として建材分野で用いた場合もまた、塗装後耐食性が問題となっている。屋根材や壁材として使用される場合は、溶融めっき鋼板は一般的に下塗り塗装、上塗り塗装を施した状態で建築会社等に供され、必要なサイズに剪断してから使用される。このため、必然的に塗装がされていない鋼板端面が露出する。ここを起点にエッジクリープと呼ばれる塗膜膨れが発生することがある。溶融Ａｌ系めっき鋼板を建材分野で用いた場合、自動車外板パネルの場合と同様に、鋼板端面部を起点に塗膜／めっき界面におけるインターデンドライトの選択腐食が起こる。この結果、溶融Ｚｎめっきに比べて著しく大きなエッジクリープを生じて塗装後耐食性が劣ることがあった。 On the other hand, corrosion resistance after painting is also a problem when using a molten Al-based plated steel sheet as a roofing material or wall material of a building in the building material field. When used as a roofing material or a wall material, the hot-dip galvanized steel sheet is generally provided to a building company or the like in a state of being subjected to primer coating and top coating, and is used after being sheared to a required size. For this reason, the steel plate end surface which is not necessarily painted is exposed. From this point, coating film blister called edge creep may occur. When a hot-dip Al-based plated steel sheet is used in the construction material field, selective corrosion of interdendrite occurs at the coating / plating interface starting from the end face of the steel sheet, as in the case of automobile outer panel. As a result, as compared with hot dip galvanization, edge creep may occur significantly and corrosion resistance after coating may be inferior.
上記問題を解決すべく、例えば特許文献１には、めっき組成にＭｇ、又はさらにＳｎ等を添加し、めっき層中にＭｇ2Ｓｉ、ＭｇＺｎ2 、Ｍｇ2Ｓｎ等のＭｇ化合物を形成させることで、鋼板端面からの赤錆発生を改善した溶融Ａｌ系めっき鋼板が開示されている。
しかしながら、特許文献１に開示される溶融Ａｌ系めっき鋼板に塗装を施した場合、塗装後の塗膜に損傷が生じたときの耐食性（塗装後耐食性）は、依然として解消できていなかった。
In order to solve the above problems, for example, in Patent Document 1, Mg or Sn or the like is added to the plating composition, and a Mg compound such as Mg 2 Si, MgZn 2 , or Mg 2 Sn is formed in the plating layer. Also, a hot-dip Al-based plated steel sheet has been disclosed in which the occurrence of red rust from the end face of the steel sheet is improved.
However, when the hot-dip Al-based plated steel sheet disclosed in Patent Document 1 is coated, the corrosion resistance (corrosion after coating) when the coating film after the coating is damaged has not been resolved yet.
また、溶融Ａｌ系めっき鋼板は、建材や家電分野に塗装を施さず使用される場合もある。なかでも、壁材や家電製品の背面板等に使用される場合には、めっき鋼板の表面が人目に曝されることになるので、高い外観品位が求められる。外観品位とは、主に、異物付着や不めっき、傷等の欠陥有無の他に、模様や色調のムラのないことをいう。後者の模様や色調については、溶融Ａｌ系めっき鋼板が無塗装で使用される場合により強く求められる品位である。そのため、塗装鋼板として使用する溶融Ａｌ系めっき鋼板の全てが、無塗装で用いられる用途（壁材、家電製品の背面板等）に適用できるわけではなく、外観品位のさらなる向上についても望まれていた。
さらに、溶融Ａｌ系めっき鋼板の場合、めっきの成分組成によって、めっき後の表面が徐々に黒色に変化（黒変）することがあった。例えば、特許文献１に示されたＳｎを添加した溶融Ａｌ系めっき鋼板でも、黒変が発生する場合がある。このように、無塗装で使用する用途に全ての溶融Ａｌ系めっき鋼板を適用することができないという問題があった。
In addition, the molten Al-based plated steel sheet may be used without being painted in the construction materials and home appliance fields. Among them, when used as a wall material or a back plate of a home appliance, the surface of the plated steel sheet is exposed to the human eye, so a high appearance quality is required. The appearance quality mainly means that there is no unevenness in the pattern or the color tone, in addition to the presence of defects such as foreign matter adhesion, non-plating, and scratches. The latter pattern or color tone is a grade that is strongly required when the hot-dip Al-based plated steel sheet is used without coating. Therefore, not all of the Al-coated steel sheet used as a coated steel sheet can be applied to applications (wall materials, back plates of household appliances, etc.) used without coating, and further improvement in appearance quality is also desired. The
Furthermore, in the case of a hot-dip Al-based plated steel sheet, the surface after plating may gradually turn black (black) depending on the component composition of the plating. For example, even in the case of a molten Al-based plated steel sheet to which Sn is added as shown in Patent Document 1, blackening may occur. As described above, there is a problem that it is not possible to apply all of the hot-dip Al-based plated steel sheet to the application used without coating.
本発明は、かかる事情に鑑みてなされたものであって、優れた塗装後耐食性を有する溶融Ａｌ系めっき鋼板を提供することを目的とする。 The present invention has been made in view of such circumstances, and an object thereof is to provide a hot-dip Al-based plated steel sheet having excellent post-paint corrosion resistance.
本発明者らは、上記の課題を解決すべく、鋭意研究を重ねた。その結果、Ａｌ系めっき層中に、特定量のＳｎを含有させることにより、従来にない優れた塗装後耐食性が得られることを見出した。 The present inventors have intensively studied to solve the above-mentioned problems. As a result, it has been found that by containing a specific amount of Sn in the Al-based plating layer, it is possible to obtain an excellent post-paint corrosion resistance which has not been achieved heretofore.
本発明は、上記知見に基づきなされたものであり、その要旨は以下の通りである。
［１］下地鋼板（ただし、ステンレス鋼板を除く）上に、Ｓｎを０．０１〜１質量％、Ｓｉを０．１〜１０質量％含有し、残部がＡｌ及び不可避的不純物からなるめっき層を有することを特徴とする溶融Ａｌ系めっき鋼板。
The present invention has been made based on the above findings, and the summary thereof is as follows.
[1] A plated layer containing 0.01 to 1% by mass of Sn and 0.1 to 10% by mass of Si on the base steel plate (but excluding the stainless steel plate) , the balance being Al and unavoidable impurities A molten Al-based plated steel sheet characterized by having:
［２］前記めっき層が、さらにＭｇ及び／又はＣａを、合計で０．０１〜１０質量％含有することを特徴とする上記［１］に記載の溶融Ａｌ系めっき鋼板。 [2] The hot-dip Al-based plated steel sheet according to the above [1], wherein the plating layer further contains 0.01 to 10% by mass in total of Mg and / or Ca.
［３］前記めっき層のＳｉ含有量が、３質量％以下であることを特徴とする上記［１］又は［２］に記載の溶融Ａｌ系めっき鋼板。 [3] The molten Al-based plated steel sheet according to the above [1] or [2] , wherein the Si content of the plating layer is 3% by mass or less.
［４］前記めっき層のＳｉ含有量が、２質量％以下であることを特徴とする上記［３］に記載の溶融Ａｌ系めっき鋼板。 [4] The hot-dip Al-based plated steel sheet according to the above [3] , wherein the Si content of the plating layer is 2% by mass or less.
［５］前記めっき層のＡｌ含有量が、９０質量％を超えることを特徴とする上記［１］〜［４］のいずれかに記載の溶融Ａｌ系めっき鋼板。 [5] The hot-dip Al-based plated steel sheet according to any one of the above [1] to [4] , wherein the Al content of the plating layer exceeds 90% by mass.
本発明によれば、耐食性、特に塗装後耐食性に優れた溶融Ａｌ系めっき鋼板が得られる。そして、本発明の溶融Ａｌ系めっき鋼板を高強度鋼板とすることによって、自動車分野において、軽量化と優れた耐食性の両立が可能となる。また、建材分野で屋根材や壁材として使用することにより、建屋寿命の延命が可能となる。 According to the present invention, it is possible to obtain a hot-dip Al-based plated steel sheet which is excellent in corrosion resistance, particularly corrosion resistance after painting. And, by making the molten Al-based plated steel sheet of the present invention a high strength steel sheet, it is possible to achieve both weight reduction and excellent corrosion resistance in the automotive field. In addition, by using it as a roofing material or wall material in the building materials field, it is possible to prolong the life of the building.
以下、本発明について具体的に説明する。尚、以下の説明において、めっき層、及びめっき浴の組成を示す各元素の含有量の単位はいずれも「質量％」であり、以下、特に断らない限り単に「％」で示す。 Hereinafter, the present invention will be specifically described. In the following description, the unit of the content of each element indicating the composition of the plating layer and the plating bath is “mass%”, and hereinafter, it is simply indicated as “%” unless otherwise specified.
先ず始めに、本発明で最も重要である、溶融Ａｌ系めっき鋼板による塗装後耐食性の改善方法について説明する。
本発明の溶融Ａｌ系めっき鋼板は、めっき層中に、Ａｌに加えて、Ｓｎ：０．０１〜１０％を含有することを特徴とする。めっき層中にＳｎを含有することで、本発明で課題とする塗装後耐食性の改善が可能となる。
First of all, the method of improving the corrosion resistance after coating with a hot-dip Al-based plated steel sheet, which is the most important in the present invention, will be described.
The molten Al-based plated steel sheet of the present invention is characterized in that the plating layer contains, in addition to Al, Sn: 0.01 to 10%. By containing Sn in the plating layer, it is possible to improve the post-paint corrosion resistance to be addressed in the present invention.
めっき層中に特定量のＳｎを含まない、従来の溶融Ａｌ系めっき鋼板のめっき層が大気に触れると、α−Ａｌ相の周囲に緻密、且つ安定なＡｌ2Ｏ3の酸化膜が直ぐに形成される。この酸化膜による保護作用によってα−Ａｌ相の溶解性は低くなる。一方、インターデンドライトに形成した針状のＳｉやＡｌ−Ｆｅ−Ｓｉ化合物は、いずれもα−Ａｌ相よりも貴な電位を示し、局部的にカソードサイトとして働くため、塗膜下で局部電池を形成することになる。これにより、傷部を起点としたインターデンドライトの選択腐食が、塗膜／めっき界面で発生する。これが進行して大きな塗膜膨れを起こすことで、塗装後耐食性が低下することとなる。
ここで、塗装鋼板の下地として、Ｓｎを含有した溶融Ａｌ系めっき鋼板を用いた場合には、Ｓｎが、上述したα−Ａｌ相の周囲に形成するＡｌ酸化膜を破壊し、α−Ａｌ相の溶解性を上げる。これによって、α−Ａｌ相の均一腐食が可能となり、従来のＡｌ系めっき鋼板を下地に用いた場合に問題となるインターデンドライトの選択腐食を抑制できる。その結果、本発明の溶融Ａｌ系めっき鋼板は、優れた塗装後耐食性を示す。
When the plating layer of a conventional hot-dip Al-plated steel sheet containing no specific amount of Sn in the plating layer is exposed to the atmosphere, a dense and stable Al 2 O 3 oxide film is immediately formed around the α-Al phase. Be done. The protective action by the oxide film reduces the solubility of the α-Al phase. On the other hand, the needle-like Si or Al-Fe-Si compound formed in interdendrite exhibits a potential nobler than that of the α-Al phase, and acts locally as a cathode site. It will be formed. Thereby, selective corrosion of the interdendrite starting from the flaw occurs at the coating / plating interface. As this progresses to cause a large coating film blister, corrosion resistance after coating will be reduced.
Here, in the case where a molten Al-based plated steel sheet containing Sn is used as a base of the coated steel sheet, the Sn destroys the Al oxide film formed around the above-described α-Al phase, and the α-Al phase Increase the solubility of As a result, uniform corrosion of the α-Al phase becomes possible, and selective corrosion of interdendrite, which is a problem when a conventional Al-based plated steel sheet is used as a base, can be suppressed. As a result, the hot-dip Al-based plated steel sheet of the present invention exhibits excellent post-paint corrosion resistance.
次に、本発明の対象とする溶融Ａｌ系めっき鋼板のめっき層の組成について説明する。
前記めっき層中のＳｎ含有量を、０．０１〜１０％としたのは次の理由からである。それぞれ、Ｓｎが０．０１％未満の場合は、上記に示したインターデンドライトの選択腐食を抑制可能とするＡｌ酸化膜の破壊が起こらないため、塗装後耐食性の向上は望めない。逆に、Ｓｎが１０％を超える場合には、Ａｌ酸化膜の破壊が激しく起こり、めっき層全体の溶解性が過度に上昇する。その結果、めっき層を均一腐食させても、その溶解速度が大きくなる。このため、大きな膨れ幅を生じ、塗装後耐食性が劣化する。よって、優れた塗装後耐食性を安定的に得るためには、Ｓｎの含有量を０．０１〜１０％の範囲とする必要がある。
Next, the composition of the plating layer of the hot-dip Al-based plated steel sheet to which the present invention is applied will be described.
The reason for setting the Sn content in the plating layer to 0.01 to 10% is as follows. When each of Sn is less than 0.01%, since the destruction of the Al oxide film which can suppress the selective corrosion of the interdendrite described above does not occur, the improvement of the corrosion resistance after coating can not be expected. On the contrary, when Sn exceeds 10%, the destruction of the Al oxide film occurs violently, and the solubility of the entire plating layer is excessively increased. As a result, even if the plating layer is uniformly corroded, the dissolution rate is increased. As a result, a large bulging width is produced, and the corrosion resistance after painting is deteriorated. Therefore, in order to stably obtain excellent post-paint corrosion resistance, the content of Sn needs to be in the range of 0.01 to 10%.
また、前記めっき層中のＳｎ含有量は、０．１％以下とすることで、めっき表面が黒色化することがなく、外観品位に優れる。さらに、１％以下であれば塗装を施さず使用する場合でも表面外観が問題となることがない。そのため、塗装後耐食性と優れためっき外観とを両立する観点からは、前記めっき層中のＳｎ含有量を、０．０１〜１％とし、０．０１％〜０．１％とすることが好ましい。 Moreover, by setting the Sn content in the plating layer to 0.1% or less, the plating surface does not become black, and the appearance quality is excellent. Furthermore, if it is 1% or less, the surface appearance does not become a problem even in the case of using without applying a coating. Therefore, from the viewpoint of making the post-paint corrosion resistance and the excellent plating appearance compatible with each other, the Sn content in the plating layer may be 0.01% to 1% and 0.01% to 0.1%. preferable.
さらに、前記めっき層は、Ｍｇ及び／又はＣａを、合計で０．０１〜１０％含有することが好ましい。Ｍｇ及びＣａは、腐食により生成した腐食生成物中に取り込まれることで、腐食生成物の安定化を図り、鋼板の腐食進行を早期に抑えることができる。Ｍｇ及び／又はＣａの合計含有量を０．０１％以上としたのは、前記腐食生成物に取り込まれるＭｇやＣａの量を十分に確保でき、腐食生成物の安定化を望めるためである。また、前記含有量を１０％以下としたのは、腐食生成物の安定化効果を確保しつつ、製造コストの上昇を抑えることができるからである。 Furthermore, it is preferable that the said plating layer contains 0.01 to 10% of Mg and / or Ca in total. Mg and Ca can be taken into the corrosion product generated by the corrosion to stabilize the corrosion product and to suppress the progress of corrosion of the steel plate at an early stage. The total content of Mg and / or Ca is set to 0.01% or more, because the amount of Mg and Ca to be incorporated into the corrosion product can be sufficiently secured, and stabilization of the corrosion product can be expected. Moreover, the reason for setting the content to 10% or less is because an increase in manufacturing cost can be suppressed while securing the stabilization effect of the corrosion product.
また、前記めっき層中の、Ｍｇ及び／又はＣａの合計含有量は、めっき浴中の成分管理によって調整される。なお、めっき浴中のＭｇ及び／又はＣａの含有量が３％を超えるとドロスの生成量が多くなり、成分管理が難しくなるといった問題が生じる。よって、めっき浴の組成管理の観点からは、前記含有量を０．０１〜５％の範囲とすることが好ましく、０．０１〜３％の範囲とすることがより好ましい。 In addition, the total content of Mg and / or Ca in the plating layer is adjusted by component control in the plating bath. When the content of Mg and / or Ca in the plating bath exceeds 3%, the amount of dross generated increases, which causes a problem that component control becomes difficult. Therefore, from the viewpoint of composition control of the plating bath, the content is preferably in the range of 0.01 to 5%, and more preferably in the range of 0.01 to 3%.
なお、前記めっき層中にＭｇとＣａを複合で含有する場合も、単独で含有する場合と同じ効果が得られるが、実際の操業の点から、めっき浴組成を安定かつ容易に管理するべく、含有させる元素数を少なくすること、具体的には、Ｍｇ又はＣａを単独で含有させることが好ましい。 In the case where the plating layer contains Mg and Ca in combination, the same effect as in the case of containing Mg and Ca alone can be obtained, but from the point of actual operation, in order to stably and easily control the plating bath composition. It is preferable to reduce the number of elements to be contained, specifically, to contain Mg or Ca alone.
さらに、本発明の溶融Ａｌ系めっき鋼板は、前記めっき層中にＳｉを０．１〜１０％含有する。Ｓｉは、下地鋼板との界面に形成する界面合金層の成長を抑制し、耐食性や加工性の向上を目的にめっき浴中に添加され、めっき層に含有される。具体的には、溶融Ａｌ系めっき鋼板の場合、Ｓｉを含有させためっき浴中に鋼板を浸漬すると、鋼板表面のＦｅと浴中のＡｌやＳｉが合金化反応し、Ｆｅ-Ａｌ系及び／又はＦｅ−Ａｌ−Ｓｉ系の化合物を形成する。このＦｅ-Ａｌ系及び／又はＦｅ−Ａｌ−Ｓｉ系界面合金層の形成により、界面合金層の成長が抑制される。そして、めっき浴中のＳｉ含有量は、０．１％以上とすることで界面合金層の十分な成長抑制が可能となる。
なお、界面合金層に取り込まれない余剰のＳｉはめっき上層のインターデンドライトに単体又はＡｌ-Ｆｅ-Ｓｉなどの化合物として析出する。これらは前述のとおり、いずれもα−Ａｌ相よりも貴な電位を示し、局部的にカソードサイトとして働くため、インターデンドライトの選択腐食を引き起こす。この選択腐食を抑制するためには、可能な限り余剰のＳｉ量を減らすことが必要であり、めっき浴中のＳｉ含有量を３％以下にすることが好ましく、２％以下にすることがより好ましい。よって、めっき浴中のＳｉ含有量の好適範囲は、０．１〜１０％であり、より好ましい範囲は０．１〜３％、されに好ましい範囲は０．１〜２％である。Ａｌ系めっき鋼板の場合、めっき層の組成がめっき浴組成とほぼ同等となるため、めっき層中のＳｉ含有量の好適範囲はめっき浴中のＳｉ含有量の好適範囲と同等の０．１〜１０％であり、より好ましい範囲は０．１〜３％、さらに好ましい範囲は０．１〜２％である。
Furthermore, the molten Al-based plated steel sheet of the present invention contains 0.1 to 10% of Si in the plating layer . Si is added to the plating bath for the purpose of suppressing the growth of the interface alloy layer formed at the interface with the base steel plate and improving the corrosion resistance and the workability, and is contained in the plating layer. Specifically, in the case of a molten Al-based plated steel sheet, when the steel sheet is immersed in a plating bath containing Si, the Fe on the surface of the steel sheet and the Al and Si in the bath cause an alloying reaction, and the Fe-Al and / or Or form a compound of Fe-Al-Si system. The formation of the Fe-Al-based and / or Fe-Al-Si-based interfacial alloy layer suppresses the growth of the interfacial alloy layer. When the Si content in the plating bath is 0.1% or more, sufficient growth suppression of the interfacial alloy layer can be achieved.
Excess Si not taken into the interface alloy layer precipitates as a single substance or a compound such as Al-Fe-Si on the interdendrite of the plating upper layer. As described above, they all exhibit nobler potentials than the α-Al phase, and act locally as cathode sites, thereby causing selective corrosion of interdendrite. In order to suppress this selective corrosion, it is necessary to reduce the amount of excess Si as much as possible, and the Si content in the plating bath is preferably 3% or less, more preferably 2% or less preferable. Therefore, the preferable range of the Si content in the plating bath is 0.1 to 10%, more preferably 0.1 to 3%, and still more preferably 0.1 to 2%. In the case of an Al-based plated steel sheet, the composition of the plating layer is almost the same as that of the plating bath, so the preferable range of the Si content in the plating layer is 0.1 to the same as the preferable range of the Si content in the plating bath 10%, more preferably 0.1 to 3%, still more preferably 0.1 to 2%.
本発明の溶融Ａｌ系めっき鋼板のめっき層は、Ａｌを主成分としており、より優れた耐食性及び耐熱性を確保する観点から、好ましくは９０％超え、より好ましくは９５％超えの含有量で含有する。なお、めっき層中には、鋼板やめっき浴中の機器等から溶出するＦｅや、Ａｌ合金原料中に含有した不可避的不純物が含まれる。不可避的不純物の種類としては、例えば、Ｃｒ、Ｃｕ、Ｍｏ、Ｎｉ、Ｔｉ、Ｚｒ等が挙げられる。前記、Ｆｅ及び不可避的不純物の総含有量は特に限定はしないが、めっき層の耐食性と均一な溶解性を維持するという観点から、１％以下であることが好ましい。
なお、前記めっき層は、溶融Ａｌ系のめっきであり、Ｚｎについては、不可避的不純物である場合を除いて含有しない。
The plating layer of the hot-dip Al-based plated steel sheet of the present invention contains Al as a main component, and from the viewpoint of securing better corrosion resistance and heat resistance, the content is preferably more than 90%, more preferably more than 95%. Do. The plating layer contains Fe eluted from steel plates, equipment in the plating bath, and the like, and unavoidable impurities contained in the Al alloy raw material. As types of unavoidable impurities, for example, Cr, Cu, Mo, Ni, Ti, Zr and the like can be mentioned. Although the total content of Fe and unavoidable impurities is not particularly limited, it is preferably 1% or less from the viewpoint of maintaining the corrosion resistance and uniform solubility of the plating layer.
In addition, the said plating layer is plating of molten Al type, and does not contain about Zn except the case of being an unavoidable impurity.
本発明の溶融Ａｌ系めっき鋼板に用いられる下地鋼板の種類については、特に限定はされない。例えば、酸洗脱スケールした熱延鋼板若しくは鋼帯、又は、それらを冷間圧延して得られた冷延鋼板若しくは鋼帯を用いることができる。 There is no particular limitation on the type of the base steel sheet used for the hot-dip Al-based plated steel sheet of the present invention. For example, it is possible to use a pickled-descaled hot-rolled steel plate or strip, or a cold-rolled steel plate or strip obtained by cold rolling them.
なお、めっき層の成分組成は、例えば、めっき層を塩酸等の水溶液に浸漬して溶解させ、その溶液をＩＣＰ発光分光分析や原子吸光分析を行うことで確認することができる。この方法はあくまでも一例であり、めっき層の成分組成を正確に定量できる方法であればどのような方法でも良く、特に限定するものではない。 In addition, the component composition of a plating layer can be confirmed by, for example, immersing and dissolving a plating layer in aqueous solutions, such as hydrochloric acid, and performing the solution by ICP emission spectral analysis or atomic absorption analysis. This method is merely an example, and any method may be used as long as it can accurately determine the composition of the plating layer, and it is not particularly limited.
なお、本発明の溶融Ａｌ系めっき鋼板のめっき層の付着量は片面あたり３５〜１５０ｇ／ｍ2であることが好ましい。３５ｇ／ｍ2以上であれば優れた耐食性が得られ、１５０ｇ／ｍ2以下であれば優れた加工性が得られるからである。また、より優れた耐食性及び加工性を得る点からは、前記付着量を、４０〜１１０ｇ／ｍ2とすることが好ましく、４０〜８０ｇ／ｍ2とすることがより好ましい。 In addition, it is preferable that the adhesion amount of the plating layer of the hot dip Al-based plated steel plate of this invention is 35-150 g / m < 2 > per single side | surface. If it is 35 g / m 2 or more, excellent corrosion resistance can be obtained, and if 150 g / m 2 or less, excellent processability can be obtained. Further, more excellent from the viewpoint of obtaining a corrosion resistance and workability, the adhesion amount is preferably to 40~110g / m 2, and more preferably to 40 and 80 g / m 2.
次に、本発明の溶融Ａｌ系めっき鋼板の製造方法について説明する。
本発明の溶融Ａｌ系めっき鋼板は、連続式溶融めっき設備で製造され、めっき浴の組成管理以外は、全て常用の方法で行うことができる。
Next, the method for producing the hot-dip Al-based plated steel sheet of the present invention will be described.
The hot-dip Al-based plated steel sheet of the present invention is manufactured in a continuous hot-dip plating facility and can be carried out by a commonly used method except for composition control of the plating bath.
めっき浴中に、Ａｌに加え、Ｓｎを０．０１〜１０％含有させる。このような組成のめっき浴を用いることにより、上述しためっき層の構成を具える溶融Ａｌ系めっき鋼板を製造できる。その際、前述の通り、界面合金層の成長を抑制するために、めっき浴中にＳｉを０．１〜１０％含有させることが好ましい。また、腐食生成物の安定化効果を確保する点からは、Ｍｇ及び／又はＣａを、合計で０．０１〜１０質量％含有させることが好ましい。さらに、製造される溶融Ａｌ系めっき鋼板が安定的に優れた耐食性を得るために、Ａｌ含有量を９０％超えとすることが好ましい。 In addition to Al, the plating bath contains 0.01 to 10% of Sn. By using a plating bath having such a composition, it is possible to manufacture a molten Al-based plated steel sheet having the above-described configuration of the plating layer. At that time, as described above, in order to suppress the growth of the interfacial alloy layer, it is preferable to contain 0.1 to 10% of Si in the plating bath. Moreover, it is preferable to contain 0.01-10 mass% of Mg and / or Ca in total from the point which ensures the stabilization effect of a corrosion product. Furthermore, in order to stably obtain excellent corrosion resistance in the produced molten Al-based plated steel sheet, it is preferable to set the Al content to more than 90%.
上記のように、めっき浴の組成管理を行うことで、塗装後耐食性に優れる溶融Ａｌ系めっき鋼板を、連続的な溶融めっき設備で効率的に製造することができる。 As described above, by performing composition control of the plating bath, it is possible to efficiently manufacture a molten Al-based plated steel sheet which is excellent in post-paint corrosion resistance in a continuous hot-dip plating facility.
次に、本発明を実施例に基づき具体的に説明する。
（サンプル１〜２７）
サンプルとなる全ての溶融Ａｌ系めっき鋼板について、常法で製造した板厚０．８ｍｍの冷延鋼板を下地鋼板として用い、連続式溶融めっき設備によって、めっき浴の浴温を６００℃、めっき付着量を片面あたり５０ｇ／ｍ2、すなわち両面で１００ｇ／ｍ2の条件で製造した。
Next, the present invention will be specifically described based on examples.
(Samples 1 to 27)
A cold-rolled steel plate with a thickness of 0.8 mm manufactured by a conventional method is used as a base steel plate for all of the hot-dip aluminum-based plated steel plates to be samples. The amount was produced at 50 g / m 2 per side, ie 100 g / m 2 on both sides.
（１）めっき層の組成
サンプルとなる溶融Ａｌ系めっき鋼板を、それぞれ１００ｍｍΦに打ち抜き、３５％の塩酸水溶液に浸漬してめっき層を溶解させた後、溶解液の組成をＩＣＰ発光分光分析で定量化することで確認した。各サンプルの組成を表１に示す。
(1) Composition of plating layer A sample of a molten Al-based plated steel plate to be a sample is punched out in 100 mm diameter and immersed in a 35% hydrochloric acid aqueous solution to dissolve the plating layer, and then the composition of the solution is quantified by ICP emission spectroscopy. Confirmed by The composition of each sample is shown in Table 1.
（２）塗装後耐食性の評価
サンプルとなる溶融Ａｌ系めっき鋼板をそれぞれ９０ｍｍ×７０ｍｍのサイズに剪断後、自動車外板用塗装処理と同様に、化成処理としてリン酸亜鉛処理を行った後、電着塗装、中塗り、及び上塗り塗装を施した。ここで、リン酸亜鉛処理、電着塗装、中塗り塗装及び上塗り塗装は以下に示す条件で行った。
○リン酸亜鉛処理：日本パーカライジング社製の脱脂剤：ＦＣ−Ｅ２００１、表面調整剤：ＰＬ−Ｘ、及び化成処理剤：ＰＢ−ＡＸ３５Ｍ（温度：３５℃）を用いて、化成処理液のフリーフッ素濃度を２００質量ｐｐｍ、化成処理液の浸漬時間を１２０秒の条件で化成処理を施した。
○電着塗装：関西ペイント社製の電着塗料：ＧＴ−１００を用いて、膜厚が１５μｍとなるように電着塗装を施した。
○中塗り塗装：関西ペイント社製の中塗り塗料：ＴＰ−６５−Ｐを用いて、膜厚が３０μｍとなるようにスプレー塗装を施した。
○上塗り塗装：関西ペイント社製の中塗り塗料：Ｎｅｏ６０００を用いて、膜厚が３０μｍとなるようにスプレー塗装を施した。
その後、図１に示すとおり、評価面の端部５ｍｍ、及び非評価面（背面）をテープでシール処理を行った後、評価面の中央にカッターナイフでめっき鋼板の地鉄に到達する深さまで、長さ６０ｍｍ、中心角９０°のクロスカット傷を加えたものを塗装後耐食性の評価用サンプルとした。
上記評価用サンプルを用いて図２に示すサイクルで腐食促進試験を実施した。腐食促進試験を湿潤からスタートし、６０サイクル後まで行った後、傷部からの塗膜膨れが最大である部分の塗膜膨れ幅（最大塗膜膨れ幅：傷部を中央にした片側の最大塗膜膨れ幅）を測定し、塗装後耐食性を下記の基準で評価した。評価結果を表１に示す。
○：最大塗膜膨れ幅≦１．５ｍｍ
△：１．５ｍｍ＜最大塗膜膨れ幅≦２．０ｍｍ
×：最大塗膜膨れ幅＞２．０ｍｍ
(2) Evaluation of corrosion resistance after coating After shearing the hot-dip Al-based plated steel sheet to be a sample to a size of 90 mm × 70 mm, and after performing zinc phosphate treatment as a chemical conversion treatment in the same manner as painting processing for automobile outer plates, Coating, middle coating and top coating were applied. Here, the zinc phosphate treatment, electrodeposition coating, middle coat coating and top coat coating were performed under the following conditions.
○ Zinc phosphate treatment: Degreasing agent manufactured by Nippon Parkerizing Co., Ltd .: FC-E 2001, surface conditioner: PL-X, and chemical conversion treatment agent: PB-AX 35 M (temperature: 35 ° C.), free fluorine of the chemical conversion solution The chemical conversion treatment was performed under the conditions of a concentration of 200 mass ppm and the immersion time of the chemical conversion treatment solution for 120 seconds.
○ Electrodeposition coating: Electrodeposition coating made by Kansai Paint Co., Ltd .: GT-100 was applied to a film thickness of 15 μm.
○ Middle coat coating: The middle coat paint made by Kansai Paint Co., Ltd .: TP-65-P was spray-coated so that a film thickness might be 30 micrometers.
Top coating: A mid-coating paint manufactured by Kansai Paint Co., Ltd .: Neo 6000 was applied by spray coating to a film thickness of 30 μm.
Thereafter, as shown in FIG. 1, after the end 5 mm of the evaluation surface and the non-evaluation surface (rear surface) are sealed with a tape, the cutter knife to the center of the evaluation surface to a depth reaching the ground steel of the plated steel plate A crosscut scratch with a length of 60 mm and a central angle of 90 ° was used as a sample for evaluation of corrosion resistance after coating.
The accelerated corrosion test was performed in the cycle shown in FIG. 2 using the above-mentioned evaluation sample. Accelerated corrosion test starts from wet and after 60 cycles, the film blister width of the part where the film blister from the flaw is the largest (maximum film blister width: maximum of one side centered on the wound The coating film swelling width was measured, and the corrosion resistance after painting was evaluated according to the following criteria. The evaluation results are shown in Table 1.
○: Maximum film blister width ≦ 1.5 mm
Δ: 1.5 mm <maximum coating film swelling width ≦ 2.0 mm
X: Maximum film blister width> 2.0 mm
（３）めっきの外観品位
サンプルとなる溶融Ａｌ系めっき鋼板について、めっき処理を施した後１時間以内に、雰囲気：大気、温度：２０℃、相対湿度：５０％に調節した恒温恒湿槽内に入れた。以後、９０日間放置した後、サンプルを取り出しめっき表面の目視観察を行い、下記の基準で外観品位を評価した。評価結果を表１に示す。
○：黒変が認められない
△：黒変は認められるが、塗装を施さない用途で特に問題にならない
×：黒変が塗装を施さない用途で問題になる
(3) Appearance grade of plating Within 1 hour after plating treatment, the temperature of the atmosphere: atmosphere, temperature: 20 ° C., relative humidity: 50%, for the molten Al-based plated steel sheet to be a sample. Put in. Thereafter, after standing for 90 days, the sample was taken out, the plating surface was visually observed, and the appearance quality was evaluated according to the following criteria. The evaluation results are shown in Table 1.
:: no blackening is observed :: blackening is recognized but not particularly problematic in applications not to be coated ×: blackout is problematic in applications not to be coated
表１より、本発明例のサンプルでは、比較例のサンプルとは異なり、最大塗膜膨れ幅が２．０ｍｍ以下であったことから、塗装後耐食性に優れた溶融Ａｌ系めっき鋼板が得られたことがわかる。
また、本発明例のサンプルの中において、めっき層中のＳｎ含有量をそれぞれ適切な範囲に制御することで、塗装後耐食性に加えて、優れた外観品位が得られることがわかる。
さらに、本発明例のサンプルの中において、めっき層中のＭｇ含有量及び／又はＣａ含有量を適切な範囲に制御することで、より優れた塗装後耐食性が得られることがわかる。
From Table 1, in the sample of the present invention example, unlike the sample of the comparative example, the maximum coating film swelling width was 2.0 mm or less, so a hot-dip Al-based plated steel sheet excellent in corrosion resistance after painting was obtained I understand that.
Further, it can be seen that, by controlling the Sn content in the plating layer to an appropriate range among the samples of the invention example, it is possible to obtain excellent appearance quality in addition to the corrosion resistance after painting.
Furthermore, it is understood that by controlling the Mg content and / or the Ca content in the plating layer in the appropriate range in the sample of the invention example, it is possible to obtain more excellent post-paint corrosion resistance.
本発明の溶融Ａｌ系めっき鋼板は、塗装後耐食性に優れ、自動車、家電、建材の分野等、広範な分野で適用できる。特に自動車分野において、高強度鋼板に適用すると、自動車の軽量化と高耐食性を達成する表面処理鋼板として使用できる。 The hot-dip Al-based plated steel sheet of the present invention is excellent in corrosion resistance after painting, and can be applied to a wide range of fields such as automobiles, home appliances, and building materials. In particular, in the automotive field, when applied to a high strength steel plate, it can be used as a surface-treated steel plate that achieves weight reduction and high corrosion resistance of the vehicle.
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