JP3535377B2 - Oil storage tanks with tank roofs with internal corrosion protection by hot-dip Zn-Mg plating - Google Patents
Oil storage tanks with tank roofs with internal corrosion protection by hot-dip Zn-Mg platingInfo
- Publication number
- JP3535377B2 JP3535377B2 JP07228498A JP7228498A JP3535377B2 JP 3535377 B2 JP3535377 B2 JP 3535377B2 JP 07228498 A JP07228498 A JP 07228498A JP 7228498 A JP7228498 A JP 7228498A JP 3535377 B2 JP3535377 B2 JP 3535377B2
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- tank
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- welding
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Description
【発明の詳細な説明】
【０００１】
【発明の属する技術分野】本発明は、溶融Zn-Mg めっき
で内面防食を施したタンク屋根を有する石油貯蔵タンク
に関するものである。
【０００２】
【従来の技術】従来、石油貯蔵タンクの屋根は、熱延黒
皮鋼板を外側で溶接し、外面は手塗り塗装、内面は黒皮
材のまま使用することが一般的であった。特開平7-1127
92号公報に記載されているように、このような従来の黒
皮材よりなるタンクにおいては、タンク内面の石油に接
していない部分、即ち屋根の内面の腐食が進行しやすい
問題があることが指摘されている。
【０００３】ここでタンク屋根の全体図を図１に示す。
石油貯蔵タンクの屋根は、板厚4.5mm の長方形からなる
鋼板を用い、その縁部が重ね合わせされ外面側から重ね
すみ肉溶接することより固定される。
【０００４】また、その溶接部の断面の模式図を図２に
示す。図２（ａ）は、熱延黒皮鋼板を用いた場合であ
り、この場合、外面側から板重ね部分で溶接作業を行う
ことになる。その後、外面については全面塗装を行って
塗装部４を形成し防食するが、内面については、実際、
ガソリン上に船を浮かべるなどの塗装方法しかなく、コ
ストが高いため、防食処理なしで使われている。また、
図２（ｂ）は溶融亜鉛めっき鋼板を用いた場合である。
同様な溶接により固定されるがこの場合、外面側から板
重ね部分で溶接作業を行うことになる。当然ながら内面
部に熱影響部３があり、溶接時の条件で融点の低いめっ
き層はダメージを受けることになる。外面部は、ジンク
リッチペイントなどの補修を行って補修層７を形成する
ことが前提となる。
【０００５】特開平7-112792号公報には、本分野へ溶融
Ｚｎめっき鋼板を適用することにより、寿命延長が可能
になったことが開示されている。また、そのＺｎ付着量
が300g/m2 の鋼板を利用した場合には、熱影響部が小で
あれば約２０年以上の寿命延長が可能であることも開示
される。
【０００６】
【発明が解決しようとする課題】これに対して本発明者
らは、更に２０年以上の寿命延長を目的に、まず特開平
7-112792号公報記載の板厚4.5mm の溶融Znめっき鋼板の
付着量を500g/m2 まで高くして、寿命延長可能か検討し
た。
【０００７】図３には、付着量225g/m2 と400g/m2 の溶
融亜鉛めっき鋼板を溶接し、その内面の熱影響部のめっ
き損傷程度を損傷した幅を測定することにより評価した
結果を示す。尚、本試験では、通常使用される被覆アー
ク溶接棒（イルミナイト系：JIS Z3211 D4301 、棒
系4.0mm ）による溶接法を用いた。
【０００８】その結果、入熱量を10.5kJ/cm 以上で溶接
した場合に内面側に伝わる熱が大きすぎるため熱影響部
でめっきが、蒸発してなくなるということが明らかにな
った。付着量225g/m2 と400g/m2 はどちらも同じ結果が
得られた。
【０００９】更に検討を進めた結果、入熱量8KJ/cm以上
で熱影響部に関しては、めっき層は残存しているものの
Feが拡散して合金層が生成しており、溶接部以外と比較
すると、耐食性が劣ることも明らかになった。
【００１０】一方、図４には、板厚4.5mm の付着量を変
えたＺｎめっき鋼板の溶接性の評価を行った結果を示
す。図中の黒い部分が適正電流範囲である。適正電流範
囲とは溶接強度を確保できる最低入熱量から、スパッタ
等が発生して実現的に溶接作業ができなくなくなるまで
の範囲である。
【００１１】耐食性を向上するために付着量を400 、50
0g/m2 と高くすると溶接強度を確保するための適正電流
範囲が狭く、更に Zn 融解のための入熱を高くせざるを
得ないことが明らかになった。
【００１２】前述したように入熱量10.5kJ/cm 以上で溶
接した場合に内面側に伝わる熱が大きすぎるため熱影響
部でめっきが、蒸発してなくなる。つまり、溶接熱影響
部に関して、Ｚｎめっきが存在しないため、部分的に腐
食が進行し、その部分のみがタンク全ての寿命を決定し
てしまうことが明らかである。すなわち、単にZnの付着
量を上げるのみでは寿命延長はできなく、溶接作業を考
慮すると付着量の限界は、片面当たり300g/m2 以下であ
ることが判明した。
【００１３】ここで特に問題となるのが、内面の防食で
ある。外面の防食は、樹脂系の選択により高価な塗装を
行えば、寿命延長も期待できるし、タンク外面であるた
め補修作業も容易である。しかしながら、内面塗装は、
タンク内に船を浮かべて塗装する方法しかなく、実際に
は不可能である。つまり、実用上、塗装などによる内面
補修は、できないという問題がある。
【００１４】このように内面補修をせずに、熱影響部の
耐食性寿命延長が望まれるようになってきた。つまり、
特に溶接熱影響による防食皮膜の蒸発を防ぎ、かつ２０
年以上の寿命延長できる手段が望まれていた。
【００１５】
【課題を解決するための手段】本発明者らは、上述した
課題を解決し、優れた防食能を優した貯蔵タンクを提供
するために誠意研究を重ねた。その結果、Zn浴中に特定
の量のMgを添加した溶融浴を用いて製造した溶融Ｚｎ−
Ｍｇ鋼板が、タンク内の腐食性環境において飛躍的に防
食性能が向上されることを確認した。しかも本鋼板を用
いれば薄目付で十分であるため問題であった熱影響部の
溶融Ｚｎ−Ｍｇめっき層が融解せず、残存し、優れた防
食性を維持できることが判明した。
【００１６】さらに、８ｋJ/cm以上１０.5ｋJ/cm未満の
入熱の場合、Znめっきを用いると熱影響によりZn-Fe 層
が形成され、熱影響部の耐食性が劣るのに対し、本鋼板
を用いれば、溶接による熱影響のためにめっき中のMgが
熱により優先的に拡散し、MgO 層が生成され、さらに防
食性が向上することを見いだした。
【００１７】すなわち、本発明は、縁部が重ね合わせさ
れ、片面から隅肉溶接された複数枚の鋼板からなるタン
ク屋根を有する石油貯蔵タンクにおいて、上記鋼板とし
てＭｇ 0.1 〜 3.0 ％、Ａｌ 0.1 〜 0.2 ％、残部がＺｎと
不可避的不純物よりなり、その付着量が片面当たり６０
〜３００ｇ／ｍ 2 の溶融Ｚｎめっき鋼板を用い、上記隅
肉溶接を上記めっき付着量で決まる適正電流範囲で、か
つ溶接入熱量が１０．５ＫＪ／ｃｍ未満で行なうことに
より、上記タンク屋根内面の溶接熱影響部をＺｎ−Ｆｅ
−Ｍｇ合金層を介してＭｇＯ層で覆うと共に、溶接熱影
響部以外をＭｇ0.1 〜3.0 ％、Ａｌ 0.1 〜 0.2 ％、残部
がＺｎと不可避的不純物よりなる６０〜３００ｇ／ｍ２
の溶融めっき層で覆ってタンク屋根内面に防食を施し
たことを特徴とする石油貯蔵タンクであることを要旨と
し、溶接に伴う、熱影響部においても石油貯蔵タンクの
防錆能を向上させる。
【００１８】図５には、通常使用される被覆アーク溶接
棒（イルミナイト系：JIS Z3211D4301 、棒系4.0mm
）による溶接法を用いて、Zn-Mg めっき鋼板を用いた
場合の結果を参考に示す。素材が変わっても溶接強度な
どの特性が変わらないことが明らかである。
【００１９】なお、本発明に関わる溶接法としては、ソ
リッドワイヤ、フラックス入りワイヤ及び被覆アーク溶
接棒による方法が適することを実験により確かめてい
る。特に風の影響を受ける屋外での施工となるため、ブ
ローホール等の溶接欠陥の少ない被覆アーク溶接棒が最
適であり、イルミナイト系（ＪＩＳ Ｚ３２１１ Ｄ４
３０１）、ライムチタニア系（Ｄ４３０３）、高酸化Ｔ
ｉ系（Ｄ４３１３）等の溶接棒を用いることが望まし
い。
【００２０】石油タンク屋根の場合、消防法により板厚
４．５ｍｍと規定されているために本評価に用いた鋼板
は、4.5mm の鋼板を用いたが、板厚が変化しても本製品
性能に関する考え方は全く変わらない。板厚が例えば0.
8 ｍｍ以下などであれば熱の伝わり方が早くなるため若
干であるが熱影響によるダメージが大きくなるが、通常
種々のタンク材料に用いられる鋼板は、３ｍｍ以上であ
る場合が多いのでその場合はその影響は無視できるもの
と容易に推定できる。
【００２１】
【発明の実施の形態】以下、図面を用いて本発明を詳細
に説明する。本発明において、耐食性を特に必要とする
対象部位であるタンク屋根内面は、石油に接しておら
ず、気相部となっており、本部位での腐食環境は、ｐＨ
５、35℃の硫酸酸性水溶液噴霧試験で簡便な腐食シュミ
レーションができることが、前述した特開平７―１１２
７９２号公報に記載されている。
【００２２】そこで我々は、本腐食シミュレート試験を
用いて、溶融Ｚｎ−Ｍｇ鋼板の耐食性を調査した。その
結果を図６に示す。本試験においては、(1) 正常部評価
として鋼板ままと、(2) 溶接熱影響部として付着量別に
それぞれの適正範囲内で溶接した後の熱影響部の耐食性
を調査した。
【００２３】尚、試験時間は、６ヶ月（4320Hr）であ
り、特開平７―１１２７９２号公報記載の図２にあるよ
うに、本試験時間で10μｍの残存Ｚｎめっき量の時、約
４０年の寿命となり、黒皮材＋塗装が約２０年の寿命延
長であるため、約２０年の寿命延長ができることが開示
されており、本試験で残存めっき量が10μｍ以上である
ことを合格の基準とした。
【００２４】溶融Ｚｎ−Ｍｇ鋼板は、タンク内腐食シミ
ュレート試験において、従来のＺｎめっき鋼板に比較し
て非常に優れた耐食性を示し、わずか60g/m2でも溶融Ｚ
ｎめっきの300g/m2 に相当することがわかる。
【００２５】また、 Zn めっき鋼板300g/m2 以下でも、
溶接熱影響部では、平板ままに比べて耐食性が劣ること
が判明した。その原因について調査した結果から得た模
式図を図７（ａ）に示す。図中の上部がタンク屋根の内
面側になり、図に示すように熱影響部３は、Ｚｎめっき
層にＦｅが拡散したＺｎ−Ｆｅ層９になっており、その
ために耐食性が劣化していることが判明した。
【００２６】これに対してZn-Mg めっき鋼板を用いた場
合は、めっき層が完全に蒸発しない条件では、ほとんど
耐食性が劣化しなかった。
【００２７】この原因について調査した結果、溶接部は
図７（ｂ）に示すような構造になっていることが判明し
た。下地はFeが拡散したＺｎＦｅＭｇ層１１になってい
るが、上層にＭｇＯ層１２が析出しており、この構造の
ために溶接熱影響部３においても耐食性が劣化しないこ
とを確認した。
【００２８】また、めっき付着量の下限を60g/m2以上と
したのは、前述したように従来の溶融Ｚｎめっきの実用
上の限界（約２０年以上）同程度の寿命延長を図るため
である。
【００２９】また、めっき付着量上限を300g/m2 以下と
したのは、溶接性を考慮したためであり、これ以上のめ
っきを用いても溶接熱影響により、めっきが蒸発するた
めに意味がない。
【００３０】また、タンク屋根外面の試験法としては従
来法である塩水噴霧試験（以下，ＳＳＴと略す）を用い
るが、本環境でのZn-Mg 鋼板の優位性は、特開平４−１
４７９５５号公報に記載されるように約５倍の耐食性を
有するため外面の寿命延長が可能であることは公知であ
る。
【００３１】本発明のＭｇ濃度は０．１〜３％である
が、これは、０．１％以下の添加では効果がなく、３％
からその効果が飽和するためにそれ以上の添加はコスト
的無駄であるためである。望ましいＭｇ濃度は、0.3 〜
0.5g％である。
【００３２】加工性改善のために本めっきにAlを0.1 〜
10% 添加しても耐食性・溶接性に影響を与えない。これ
は、0.1 ％未満では、加工性改善にあまり効果がなく、
10% 以上添加すると溶接性が劣化するためである。
【００３３】さらにＺｎ−Ｍｇめっき鋼板の製造に関し
ては、特に限定されず種々の方法を適用できるが、寿命
延長のためには付着量60g/m2以上必要であり、コストを
考慮すると、溶融Zn-Mg めっき鋼板を用いるのが良い。
【００３４】また、石油タンクの種類についても限定さ
れず、屋根固定型石油タンクのみならず、屋根浮揚式タ
ンク等、他の種々のタンクにも適用可能である。その他
に、浮屋根タンク付着物の屋根シール 部の雨よけ板及びシー
ル 材取り付け部の部材等にも適用が可能である。
【００３５】
【実施例】次に本発明を表１に実施例によって説明す
る。下地原板として熱延黒皮材（板厚４．５ｍｍ）を用
い、酸洗した後、Al0.2%を含む溶融Zn-Mg めっき浴及び
比較としてＺｎ単独浴により付着量を変化させて、サン
プルを作製した。(1) 正常部評価として鋼板ままと、
(2) 溶接熱影響部として付着量別にそれぞれの適正範囲
内で溶接した後の熱影響部の耐食性を調査した。
【００３６】尚、溶接入熱条件は、表中に記載した。溶
接は、前述したイルミナイト棒を用いた重ねすみ肉溶接
である。
【００３７】内面評価としては、前述したpH=5, 硫酸水
噴霧試験を用いた。尚、試験時間は、６ヶ月（4320Hr）
である。尚、評価項目の評価基準は表２に示す通りであ
り、３点以上を合格とした。
【００３８】参考に、外面評価として上述した(1) 正常
部評価として鋼板ままのものを用いて、ＳＳＴ４３２０
Ｈｒ後の地鉄浸食量を測定した結果を示す。
【００３９】
【表１】
【００４０】
【表２】
【００４１】No１−４，７に示すように、本発明の溶融
Ｚｎめっき鋼板製タンクは、内面（正常部、熱影響
部）、外面共に、耐食性が従来例に比べて、良好であ
り、更なる寿命延長ができることが明らかである。
【００４２】No５は、入熱量が高いため、熱影響部に関
して基準を満足できない。No６は、Mg濃度が本発明範囲
外であるため耐食性が不足している。また、No９は、正
常部の耐食性は良好であるが、前述してきたように溶接
の熱影響部の耐食性が不足している。
【００４３】
【発明の効果】以上のように、本発明によれば、従来に
ない内面高耐食性を有したタンク屋根を有する石油タン
クが得られることから、その工業的意義は大きい。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a petroleum storage tank having a tank roof provided with internal corrosion protection by hot-dip Zn-Mg plating. 2. Description of the Related Art Conventionally, the roof of an oil storage tank is generally welded with a hot-rolled black scale steel plate on the outside, the outer surface is hand-painted, and the inner surface is generally used as a black scale material. . JP 7-1127
As described in Japanese Patent Publication No. 92, there is a problem that such a conventional tank made of black scale material has a problem that the corrosion of the portion of the tank inner surface that is not in contact with oil, that is, the inner surface of the roof, is likely to progress. It is pointed out. FIG. 1 shows an overall view of a tank roof.
The roof of the oil storage tank is made of a rectangular steel plate with a thickness of 4.5 mm, the edges of which are overlapped and fixed by fillet welding from the outside. FIG. 2 shows a schematic view of a cross section of the welded portion. FIG. 2A shows a case in which a hot-rolled black-scaled steel plate is used. In this case, welding work is performed from the outer surface side at the plate overlap portion. Thereafter, the outer surface is entirely coated to form a coated portion 4 to prevent corrosion, but the inner surface is actually
Because of the high cost of painting methods such as floating a ship on gasoline, it is used without anticorrosion treatment. Also,
FIG. 2B shows a case where a hot-dip galvanized steel sheet is used.
It is fixed by similar welding, but in this case, welding work is performed at the plate overlap portion from the outer surface side. Naturally, the heat affected zone 3 is present on the inner surface, and the plating layer having a low melting point will be damaged under welding conditions. The outer surface portion is premised on forming the repair layer 7 by repairing zinc-rich paint or the like. [0005] Japanese Patent Application Laid-Open No. Hei 7-112792 discloses that the service life can be extended by applying a hot-dip galvanized steel sheet to this field. It is also disclosed that when a steel sheet having a Zn adhesion amount of 300 g / m 2 is used, the life can be extended for about 20 years or more if the heat-affected zone is small. [0006] On the other hand, the inventors of the present invention first disclosed in Japanese Unexamined Patent Application Publication No.
The adhesion of the hot-dip galvanized steel sheet having a thickness of 4.5 mm described in JP-A-7-112792 was increased to 500 g / m 2 , and it was examined whether the life could be extended. [0007] FIG. 3 is a result of adhesion amount 225 g / m 2 and welded galvanized steel sheet 400 g / m 2, was evaluated by measuring the damaged width approximately plating damage of the heat-affected zone of the inner surface Is shown. In this test, a welding method using a commonly used coated arc welding rod (illuminite type: JIS Z3211 D4301, rod type 4.0 mm) was used. As a result, it has been found that when welding with a heat input of 10.5 kJ / cm or more, the heat transferred to the inner surface is too large, so that the plating does not evaporate in the heat affected zone. The same results were obtained for both the adhesion amounts of 225 g / m 2 and 400 g / m 2 . As a result of further study, the heat-affected zone was found to have a heat input of 8 KJ / cm or more, although the plated layer remained
It was also clarified that the alloy layer was formed by the diffusion of Fe, and the corrosion resistance was inferior to those other than the weld. On the other hand, FIG. 4 shows the results of evaluation of the weldability of a Zn-plated steel sheet having a thickness of 4.5 mm and varying the amount of adhesion. The black part in the figure is the appropriate current range. The appropriate current range is a range from a minimum heat input amount at which welding strength can be ensured to a point at which welding work cannot be practically performed due to generation of spatter or the like. [0011] In order to improve the corrosion resistance, the adhesion amount is 400, 50
It has been clarified that, when it is increased to 0 g / m 2 , the appropriate current range for securing the welding strength is narrow, and the heat input for melting Zn must be increased. As described above, when welding is performed at a heat input of 10.5 kJ / cm or more, the heat transmitted to the inner surface side is too large, so that the plating does not evaporate in the heat affected zone. In other words, it is clear that since the Zn plating does not exist in the heat affected zone, corrosion progresses partially, and only that portion determines the life of the entire tank. That is, it was found that the service life could not be extended only by simply increasing the amount of Zn deposited, and that the limit of the amount deposited was 300 g / m 2 or less per side in consideration of welding work. What is particularly problematic here is anticorrosion of the inner surface. As for the corrosion prevention on the outer surface, if an expensive coating is performed by selecting a resin system, the service life can be expected to be extended, and the repair work is easy because the outer surface is the tank. However, the inner coating is
There is no other way than painting a ship floating in a tank. That is, in practice, there is a problem that the inner surface cannot be repaired by painting or the like. As described above, it has been desired to extend the corrosion resistance life of the heat-affected zone without repairing the inner surface. That is,
In particular, it prevents evaporation of the anticorrosion film due to the influence of welding heat, and
Means that can extend the life of more than one year have been desired. Means for Solving the Problems The present inventors have conducted sincere research to solve the above-mentioned problems and to provide a storage tank having excellent corrosion protection. As a result, molten Zn- produced using a molten bath in which a specific amount of Mg was added to a Zn bath.
It was confirmed that the Mg steel sheet dramatically improved the anticorrosion performance in a corrosive environment in the tank. In addition, it was found that the use of the steel sheet was sufficient for thinning, so that the molten Zn-Mg plating layer in the heat-affected zone, which was a problem, did not melt, remained, and excellent corrosion resistance could be maintained. Further, in the case of a heat input of 8 kJ / cm or more and less than 10.5 kJ / cm, the use of Zn plating forms a Zn—Fe layer due to the heat effect, and the corrosion resistance of the heat-affected zone is poor. It has been found that, when Mg is used, Mg in the plating is preferentially diffused by heat due to the thermal effect of welding, an MgO layer is generated, and the corrosion resistance is further improved. That is, the present invention relates to an oil storage tank having a tank roof composed of a plurality of steel plates whose edges are overlapped and whose one side is fillet welded ,
0.1 to 3.0 % of Mg , 0.1 to 0.2 % of Al and the balance of Zn
It consists of unavoidable impurities, and the attached amount is 60 per side.
~ 300 g / m 2 Using the hot-dip galvanized steel sheet
In the appropriate current range determined by the above coating weight,
The welding heat input is less than 10.5KJ / cm
More, the weld heat affected zone of the tank roof inner surface Zn-Fe
-Covered with an MgO layer via a Mg alloy layer, and other than the heat affected zone by welding, 0.1 to 3.0% of Mg, 0.1 to 0.2 % of Al , the balance being 60 to 300 g / m 2 consisting of Zn and unavoidable impurities.
And summarized in that covered by the molten plating layer petroleum storage tanks, characterized in that subjected to corrosion protection to the tank roof inner surface, due to the welding, Ru also improve the anticorrosive performance of oil storage tanks in the heat affected zone . FIG. 5 shows a commonly used coated arc welding rod (illuminite type: JIS Z3211D4301, rod type 4.0 mm).
The results for the case where Zn-Mg plated steel sheet is used by using the welding method described in (1) are shown for reference. It is clear that properties such as welding strength do not change even if the material changes. It has been confirmed by experiments that the method using a solid wire, a flux-cored wire and a covered arc welding rod is suitable as the welding method according to the present invention. In particular, since the construction is performed outdoors under the influence of wind, a coated arc welding rod having few welding defects such as blow holes is optimal, and an illuminite-based (JIS Z3211 D4)
301), lime titania (D4303), high oxidation T
It is desirable to use a welding rod such as i-type (D4313). In the case of petroleum tank roofs, the steel sheet used in this evaluation was 4.5 mm because the firefighting law stipulates a sheet thickness of 4.5 mm. The way of thinking about performance remains the same. The thickness is, for example, 0.
If it is 8 mm or less, the heat is transmitted more quickly, so the damage due to the thermal effect is slightly increased, but the steel sheet used for various tank materials is usually 3 mm or more. The effects can easily be estimated to be negligible. Hereinafter, the present invention will be described in detail with reference to the drawings. In the present invention, the inner surface of the tank roof, which is a target site particularly requiring corrosion resistance, is not in contact with petroleum but is in a gas phase, and the corrosive environment at this site is pH
5. It was found that a simple corrosion simulation can be performed by a sulfuric acid aqueous solution spray test at 35 ° C.
No. 792. Then, we investigated the corrosion resistance of the molten Zn-Mg steel sheet using the present corrosion simulation test. FIG. 6 shows the result. In this test, the corrosion resistance of the heat-affected zone after welding within the appropriate range for each of the (1) the steel plate as a normal part evaluation and the (2) welding heat-affected zone according to the amount of adhesion was investigated. The test time is 6 months (4320 hours). As shown in FIG. 2 of JP-A-7-112792, when the residual Zn plating amount is 10 μm in the test time, it is about 40 years. It is disclosed that the service life can be extended by about 20 years since black-skin material + coating is about 20 years longer, and in this test, the remaining plating amount must be 10 μm or more as a passing criterion. did. The molten Zn-Mg steel sheet, in the corrosion simulated test tank, in comparison with the conventional Zn-plated steel sheet exhibits very good corrosion resistance, only 60 g / m 2, even molten Z
It turns out that it is equivalent to 300 g / m 2 of n plating. In addition, even if the Zn-coated steel sheet is 300 g / m 2 or less,
It was found that the corrosion resistance of the heat affected zone was inferior to that of the flat plate. FIG. 7A is a schematic diagram obtained from the result of investigating the cause. The upper part in the figure is the inner surface side of the tank roof, and as shown in the figure, the heat-affected zone 3 is a Zn-Fe layer 9 in which Fe is diffused in the Zn plating layer, and therefore, the corrosion resistance is deteriorated. It has been found. On the other hand, when the Zn-Mg plated steel sheet was used, the corrosion resistance hardly deteriorated under the condition that the plating layer did not completely evaporate. As a result of investigating the cause, it was found that the welded portion had a structure as shown in FIG. Although the base was a ZnFeMg layer 11 in which Fe was diffused, an MgO layer 12 was deposited on the upper layer, and it was confirmed that the corrosion resistance did not deteriorate even in the weld heat affected zone 3 due to this structure. The reason why the lower limit of the coating weight is set to 60 g / m 2 or more is to extend the life as much as the practical limit (about 20 years or more) of the conventional hot-dip Zn plating as described above. is there. The reason why the upper limit of the coating weight is set to 300 g / m 2 or less is that the weldability is taken into consideration. . As a test method for the outer surface of the tank roof, a conventional salt spray test (hereinafter abbreviated as SST) is used. The superiority of the Zn-Mg steel sheet in this environment is described in Japanese Patent Laid-Open No. 4-1.
It is known that the life of the outer surface can be extended because it has about five times the corrosion resistance as described in JP-A-47955. The Mg concentration of the present invention is 0.1 to 3%.
This is because the effect is saturated and further addition is wasteful in cost. Desirable Mg concentration is 0.3 to
0.5 g%. In order to improve workability, Al is added to the plating in an amount of 0.1 to 0.1%.
Addition of 10% does not affect corrosion resistance and weldability. This means that if it is less than 0.1%, there is not much effect on improving processability,
This is because the addition of 10% or more deteriorates the weldability. Further, with respect to the production of the Zn—Mg plated steel sheet, various methods can be applied without any particular limitation. However, in order to extend the service life, an adhesion amount of 60 g / m 2 or more is required. -Mg plated steel sheet is recommended. The type of the oil tank is not limited, and the present invention can be applied not only to a fixed-roof oil tank, but also to various other tanks such as a roof floating tank. In addition, the present invention can be applied to a rain shield plate on a roof seal portion of a floating roof tank deposit and a member for a seal material attaching portion. Next, the present invention will be described with reference to Table 1 by way of Examples. A hot-rolled black scale material (4.5 mm thick) was used as the base plate, and after pickling, the amount of adhesion was changed using a hot-dip Zn-Mg plating bath containing 0.2% Al and a Zn single bath for comparison. Was prepared. (1) As a normal part evaluation,
(2) We investigated the corrosion resistance of the heat-affected zone after welding within the appropriate range for each adhesion amount as the welding heat-affected zone. The welding heat input conditions are described in the table. The welding is lap fillet welding using the aforementioned illuminite rod. For the inner surface evaluation, the above-mentioned pH = 5, sulfuric acid water spray test was used. The test time is 6 months (4320Hr)
It is. In addition, the evaluation criteria of the evaluation items are as shown in Table 2, and three or more points were accepted. For reference, the evaluation of the outer surface was carried out as described above (1) The evaluation of the normal portion was performed using the steel plate as it was.
The result of measuring the amount of ground iron erosion after Hr is shown. [Table 1] [Table 2] As shown in Nos. 1-4 and 7, the tank made of the hot-dip galvanized steel sheet of the present invention has better corrosion resistance on both the inner surface (normal portion, heat affected zone) and the outer surface than the conventional example. Obviously, a longer life can be achieved. In No. 5, since the heat input is high, the standard cannot be satisfied for the heat affected zone. No. 6 has insufficient corrosion resistance because the Mg concentration is outside the range of the present invention. In addition, No. 9 has good corrosion resistance in the normal part, but has insufficient corrosion resistance in the heat-affected zone of welding as described above. As described above, according to the present invention, a petroleum tank having a tank roof having an unprecedented inner surface with high corrosion resistance can be obtained, and its industrial significance is great.
【図面の簡単な説明】
【図１】石油貯蔵タンク屋根の構造を示す平面図であ
る。
【図２】タンク屋根の鋼板設置の模式図であり、（ａ）
は熱延黒皮鋼板を用いた場合、（ｂ）は溶融亜鉛めっき
鋼板を用いた場合である。
【図３】Znめっき鋼板の溶接入熱量とめっき層の損傷度
合いの関係を示したものである。
【図４】Znめっき鋼板の溶接における適正電流範囲と目
付量の関係を示したものである。
【図５】Zn-Mg めっき鋼板の溶接における適正電流範囲
と目付量の関係を示したものである。
【図６】タンク内面に溶融めっき鋼板を用いた場合の耐
食性を示したものである。
【図７】熱影響部のめっき層構造を図示したものであ
り、（ａ）は従来のＺｎめっき鋼板の溶接熱影響部、
（ｂ）は本発明のＺｎ−Ｍｇめっき鋼板の溶接熱影響部
の模式図である。
【符号の説明】
１ 黒皮鋼板
２ 溶接部
３ 熱影響部
４ 塗装部
５ 鋼板
６ めっき層
７ 補修層
８ Ｚｎ層
９ Ｚｎ−Ｆｅ層
１０ ＺｎＭｇ層
１１ ＺｎＦｅＭｇ層
１２ ＭｇＯ層BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing a structure of an oil storage tank roof. FIG. 2 is a schematic view showing the installation of a steel plate on a tank roof, and FIG.
(B) is the case where a hot-dip galvanized steel sheet is used. FIG. 3 shows the relationship between the welding heat input of a Zn-plated steel sheet and the degree of damage to a plating layer. FIG. 4 shows a relationship between an appropriate current range and a basis weight in welding of a Zn-plated steel sheet. FIG. 5 shows a relationship between an appropriate current range and a basis weight in welding of a Zn-Mg plated steel sheet. FIG. 6 shows the corrosion resistance when a hot-dip coated steel sheet is used for the inner surface of the tank. FIG. 7 is a diagram illustrating a plating layer structure of a heat-affected zone, where (a) shows a welding heat-affected zone of a conventional Zn-plated steel sheet,
(B) is a schematic diagram of a welding heat affected zone of the Zn-Mg plated steel sheet of the present invention. [Description of Signs] 1 Black scale steel plate 2 Welded part 3 Heat affected part 4 Painted part 5 Steel plate 6 Plating layer 7 Repair layer 8 Zn layer 9 Zn-Fe layer 10 ZnMg layer 11 ZnFeMg layer 12 MgO layer
───────────────────────────────────────────────────── フロントページの続き (72)発明者 山根 国秀 富津市新富20−１ 新日本製鐵株式会社 技術開発本部内 (72)発明者 石本 裕保 千葉県千葉市中央区新田町37番24号 (72)発明者 屋敷 孝志 愛知県知多市南浜町11番地 (56)参考文献 特開 平７−112792（ＪＰ，Ａ) 特開 平２−85346（ＪＰ，Ａ) 特開 平２−73954（ＪＰ，Ａ) 特開 平４−246193（ＪＰ，Ａ) 特開 平５−214544（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) B65D 90/22 C23C 2/06 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kunihide Yamane 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technology Development Division (72) Inventor Yuho Ishimoto 37-24 Nittacho, Chuo-ku, Chiba-shi, Chiba (72) Inventor Takashi Yashiki 11 Minamihama-cho, Chita-shi, Aichi (56) References JP-A-7-1112792 (JP, A) JP-A-2-85346 (JP, A) JP-A-2-73954 (JP) JP-A-4-246193 (JP, A) JP-A-5-214544 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) B65D 90/22 C23C 2/06
Claims (1)
接された複数枚の鋼板からなるタンク屋根を有する石油
貯蔵タンクにおいて、上記鋼板としてＭｇ 0.1 〜 3.0
％、Ａｌ 0.1 〜 0.2 ％、残部がＺｎと不可避的不純物よ
りなり、その付着量が片面当たり６０〜３００ｇ／ｍ 2
の溶融Ｚｎめっき鋼板を用い、上記隅肉溶接を上記めっ
き付着量で決まる適正電流範囲で、かつ溶接入熱量が１
０．５ＫＪ／ｃｍ未満で行なうことにより、上記タンク
屋根内面の溶接熱影響部をＺｎ−Ｆｅ−Ｍｇ合金層を介
してＭｇＯ層で覆うと共に、溶接熱影響部以外をＭｇ0.
1 〜3.0 ％、Ａｌ 0.1 〜 0.2 ％、残部がＺｎと不可避的
不純物よりなる６０〜３００ｇ／ｍ2 の溶融めっき層で
覆ってタンク屋根内面に防食を施したことを特徴とする
石油貯蔵タンク。(57) [Claims] 1. Edges are overlapped, and fillet filling is performed from one side.
Petroleum with a tank roof consisting of several steel sheets in contact
In the storage tank,Mg as the above steel sheet 0.1 ~ 3.0
%, Al 0.1 ~ 0.2 %, Balance is Zn and inevitable impurities
And the adhesion amount is 60 to 300 g / m per side. Two
Using the hot-dip Zn-plated steel sheet
Within the appropriate current range determined by the amount of adhesion and the welding heat input is 1
By performing at less than 0.5 KJ / cm,Above tank
The heat affected zone on the inner surface of the roof is interposed through a Zn-Fe-Mg alloy layer
And covered with MgO layer, and Mg0.
1 ~ 3.0%,Al 0.1 ~ 0.2 %,The remainder is inevitable with Zn
60 to 300 g / m consisting of impuritiesTwo With hot-dip plating layer
Covered and covered with anti-corrosion on the tank roof
Oil storage tank.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07228498A JP3535377B2 (en) | 1998-03-20 | 1998-03-20 | Oil storage tanks with tank roofs with internal corrosion protection by hot-dip Zn-Mg plating |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07228498A JP3535377B2 (en) | 1998-03-20 | 1998-03-20 | Oil storage tanks with tank roofs with internal corrosion protection by hot-dip Zn-Mg plating |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11268794A JPH11268794A (en) | 1999-10-05 |
| JP3535377B2 true JP3535377B2 (en) | 2004-06-07 |
Family
ID=13484842
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP07228498A Expired - Fee Related JP3535377B2 (en) | 1998-03-20 | 1998-03-20 | Oil storage tanks with tank roofs with internal corrosion protection by hot-dip Zn-Mg plating |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3535377B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108444190A (en) * | 2018-04-08 | 2018-08-24 | 中山市新顺翔电器制造有限公司 | A kind of evaporator and the refrigerator of pipe protection |
-
1998
- 1998-03-20 JP JP07228498A patent/JP3535377B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH11268794A (en) | 1999-10-05 |
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