JP2013181211A - Steel material excellent in compatibility with water-based coating - Google Patents
Steel material excellent in compatibility with water-based coating Download PDFInfo
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本発明は、水系塗料を塗装する際に下地鋼材として優れた塗装耐食性を発揮する水系塗料との適合性に優れた鋼材に関するものである。
特に本発明は、建築・土木構造物用に使用される鋼材であって、近年、環境問題の高まりと共に、塗料中のVOC削減および塗装環境改善を目的として開発された水系塗料によって主に防食される鋼材である。
The present invention relates to a steel material excellent in compatibility with a water-based paint that exhibits excellent coating corrosion resistance as a base steel material when a water-based paint is applied.
In particular, the present invention is a steel material used for construction and civil engineering structures, and has recently been protected mainly by water-based paints developed for the purpose of reducing VOCs in paints and improving the paint environment as environmental problems increase. Steel.
近年、世界的なオゾン層の保護や大気汚染環境の改善、さらには塗装する場合に塗装作業者のみならず近隣環境まで溶剤による臭気の問題を改善する目的で、水系塗料が塗料メーカーにおいて開発されている。
そのため、水系塗料について、その耐久性を調査する試みが日本各地で行われ、建築構造物については一部で水系塗料が使用され始めている。
In recent years, paint manufacturers have developed water-based paints for the purpose of protecting the global ozone layer, improving the air pollution environment, and improving the odor problem caused by solvents not only for painters but also for nearby environments when painting. ing.
For this reason, attempts have been made to investigate the durability of water-based paints in various parts of Japan, and some water-based paints have begun to be used for building structures.
しかしながら、水系塗料は、水を溶媒としていることから、以下に述べる問題を残していた。
(1) 従来使用されてきた、溶剤系塗料に比較して、相対的に耐用年数が短いと推定されること。この点については、実構造物での数十年の実績はないが、例えばクロスカット部からの塗装劣化を観察した場合、従来の溶剤系に比較して劣っている場合がある。
(2) 水を溶媒とする場合には、溶剤に比較して乾燥時間が相対的に長くなること、および水に鋼材が接触することから塗装後初期の段階で鋼の腐食から問題を起こす場合がある。例えば腐食した鉄イオンが表面に出てくるフラッシュラストの問題や腐食が原因で発生するふくれなどの不具合が起き易い。
そのため、塗料中の防錆顔料を増量することなどの処置を必要としていたことから、水系塗料についてはコスト的に高くついていた。
However, since water-based paints use water as a solvent, the following problems remain.
(1) It is estimated that the service life is relatively short compared to solvent-based paints that have been used in the past. In this regard, although there is no track record in actual structures for several decades, it may be inferior to conventional solvent systems, for example, when observing coating deterioration from a cross-cut portion.
(2) When water is used as the solvent, the drying time is relatively longer than that of the solvent, and the steel material comes into contact with the water, causing problems from corrosion of the steel at an early stage after painting. There is. For example, problems such as a flash last problem in which corroded iron ions appear on the surface and blisters caused by corrosion tend to occur.
For this reason, treatments such as increasing the amount of the anticorrosive pigment in the paint are required, and the water-based paint is expensive.
上記の問題を解決するものとして、例えば特許文献１では、水系塗料の防錆性を向上させるための顔料としてトリポリリン酸ナトリウムを推奨している。
また、特許文献２には、焼付け時間を制御することで、フラッシュラストを回避する方法が開示されている。
さらに、特許文献３には、亜硝酸系の腐食抑制剤を塗料中に添加することで同様にフラッシュラストを回避する方法が開示されている。
In order to solve the above problem, for example, Patent Document 1 recommends sodium tripolyphosphate as a pigment for improving the rust prevention property of the water-based paint.
Patent Document 2 discloses a method for avoiding flash last by controlling the baking time.
Further, Patent Document 3 discloses a method for avoiding flash last in the same manner by adding a nitrite-based corrosion inhibitor to the paint.
特許文献１に開示された亜鉛−ニッケルめっきは、耐食性の向上には有効であると考えられるが、溶接部を含む構造物へ適用するには，めっきによる溶接部の不具合やめっき消失部分の処置が容易ではない。また、顔料による腐食抑制は、顔料の溶出によるものであり、その持続期間が短いことおよび顔料が高価なことなどが問題である。
同様にフラッシュラストを回避する方法として、特許文献２に記載の方法は、工場製品には有効であるが、建築・土木構造物などでは加熱することが容易ではないので、現実的でない。
特許文献３に記載の方法では、特許文献１と同様に腐食抑制剤が高価な点と、これらが塗膜中に入ることで本来の塗膜性能の発現が妨害されることが問題である。
The zinc-nickel plating disclosed in Patent Document 1 is considered to be effective in improving corrosion resistance. However, in order to apply it to a structure including a welded part, treatment of a defect in the welded part or a plating disappeared part by plating. Is not easy. Moreover, the corrosion inhibition by the pigment is due to the elution of the pigment, and there are problems such as a short duration and an expensive pigment.
Similarly, as a method for avoiding flash last, the method described in Patent Document 2 is effective for factory products, but it is not practical because it is not easy to heat a building or civil engineering structure.
In the method described in Patent Document 3, as in Patent Document 1, the problem is that the corrosion inhibitors are expensive and that the original performance of the coating film is hindered by entering these into the coating film.
従って、常温で塗装ができる環境下で、前記(1)、(2)の問題を解決するためには、塗料側のアプローチの他に、鋼材側のアプローチもまた有効と考えられる。 Therefore, in order to solve the problems (1) and (2) in an environment where painting can be performed at room temperature, in addition to the paint side approach, the steel side approach is also considered effective.
本発明は、上記の要請に有利に応えるもので、鋼材そのものの耐食性を向上させることにより、水系塗料の大型構造物への適用を可能ならしめた水系塗料との適合性に優れた鋼材を提案することを目的とする。 The present invention advantageously responds to the above requirements, and proposes a steel material with excellent compatibility with water-based paints that can be applied to large structures of water-based paints by improving the corrosion resistance of the steel itself. The purpose is to do.
さて、発明者らは、上記の問題を解決すべく、水系塗料を塗布した鋼材の腐食現象について鋭意研究を重ねた。
その結果、水系塗料の腐食劣化（長期間および短期間とも）に対しては、主にＷ，Mo，Sn，Cu，NiおよびCrの添加が有効であることを見出した。
本発明は、上記の知見に立脚するものである。
Now, in order to solve the above-mentioned problems, the inventors have conducted intensive studies on the corrosion phenomenon of steel materials coated with a water-based paint.
As a result, it has been found that the addition of W, Mo, Sn, Cu, Ni and Cr is mainly effective for the corrosion deterioration (both long term and short term) of the water-based paint.
The present invention is based on the above findings.
すなわち、本発明の要旨構成は次のとおりである。
１．質量％で、
Ｃ：0.03〜0.30％、
Si：0.01〜1.0％、
Mn：0.10〜2.0％、
Ｐ：0.03％以下、
Ｓ：0.007％以下および
Sn：0.01〜0.05％
を含み、かつ
Cr：0.01〜0.10％、
Cu：0.05〜0.10％および
Ni：0.05〜0.10％
のうちから選んだ１種または２種以上を含み、さらに
Mo：0.01〜0.08％および
Ｗ：0.01〜0.08％
のうちから選んだ１種または２種を含有し、残部がFeおよび不可避的不純物からなることを特徴とする水系塗料との適合性に優れた鋼材。
That is, the gist configuration of the present invention is as follows.
1. % By mass
C: 0.03-0.30%
Si: 0.01 to 1.0%
Mn: 0.10 to 2.0%,
P: 0.03% or less,
S: 0.007% or less and
Sn: 0.01-0.05%
And including
Cr: 0.01-0.10%,
Cu: 0.05-0.10% and
Ni: 0.05-0.10%
Including one or more selected from among
Mo: 0.01-0.08% and W: 0.01-0.08%
A steel material excellent in compatibility with water-based paints, characterized in that it contains one or two selected from among them, and the balance consists of Fe and inevitable impurities.
２．前記鋼材が、さらに質量％で、
Ge：0.005〜0.010％、
Sb：0.005〜0.010％、
Bi：0.005〜0.010％および
Se：0.005〜0.010％
のうちから選んだ１種または２種以上を含有することを特徴とする前記１に記載の鋼材。
2. The steel material is further mass%,
Ge: 0.005-0.010%,
Sb: 0.005-0.010%,
Bi: 0.005-0.010% and
Se: 0.005-0.010%
The steel material according to 1 above, containing one or more selected from among the above.
３．前記鋼材が、さらに質量％で、
Nb：0.005〜0.10％、
Ｖ：0.005〜0.10％および
Ti：0.005〜0.10％
のうちから選んだ１種または２種以上を含有することを特徴とする前記１または２に記載の鋼材。
3. The steel material is further mass%,
Nb: 0.005-0.10%,
V: 0.005-0.10% and
Ti: 0.005-0.10%
The steel material according to 1 or 2 above, which contains one or more selected from among the above.
本発明によれば、建築・土木構造物用鋼材としての使用に際し、水系塗料による防食を図った場合に、従来の鋼材に比較してより長期間にわたる使用が可能で、また腐食による塗り替え削減や損傷による事故を回避することができ、さらにはこれらの諸施設を安価に提供することができる鋼材を得ることができ、産業上極めて有用である。 According to the present invention, when it is used as a steel material for a building / civil engineering structure, it can be used for a longer period of time compared to a conventional steel material when it is protected by a water-based paint. An accident due to damage can be avoided, and further, a steel material that can provide these facilities at low cost can be obtained, which is extremely useful in the industry.
以下、本発明を具体的に説明する。
まず、本発明において鋼材の成分組成を前記の範囲に限定した理由について説明する。なお、鋼材の成分組成における元素の含有量の単位はいずれも「質量％」であるが、以下、特に断らない限り単に「％」で示す。
Hereinafter, the present invention will be specifically described.
First, the reason why the component composition of the steel material is limited to the above range in the present invention will be described. In addition, although the unit of element content in the component composition of steel materials is “mass%”, hereinafter, unless otherwise specified, it is simply indicated by “%”.
Ｃ：0.03〜0.30％
Ｃは、鋼の強度確保に必要な元素であり、本発明で目標とする強度（400MPa以上）を確保するためには少なくとも0.03％の含有が必要であるが、0.30％を超えると溶接性が低下し、溶接の際に制限が加わるため、Ｃ量は0.03〜0.30％の範囲とする。
C: 0.03-0.30%
C is an element necessary for ensuring the strength of the steel, and in order to ensure the target strength (400 MPa or more) in the present invention, it is necessary to contain at least 0.03%, but if it exceeds 0.30%, the weldability is increased. The amount of C is in the range of 0.03 to 0.30% because it decreases and limits are applied during welding.
Si：0.01〜1.0％
Siは、脱酸のため添加するが、含有量が0.01％未満では脱酸効果に乏しく、一方1.0％ を超えると靭性や溶接性を劣化させるため、Si量は0.01〜1.0％の範囲とする。
Si: 0.01-1.0%
Si is added for deoxidation, but if the content is less than 0.01%, the deoxidation effect is poor. On the other hand, if it exceeds 1.0%, the toughness and weldability are deteriorated, so the Si content is in the range of 0.01 to 1.0%. .
Mn：0.10〜2.0％
Mnは、強度、靭性を改善するために添加するが、0.10％未満ではその効果が十分でなく、一方2.0％を超えると溶接性が劣化するため、Mn量は0.10〜2.0％の範囲とする。
Mn: 0.10 to 2.0%
Mn is added to improve strength and toughness. However, if it is less than 0.10%, the effect is not sufficient. On the other hand, if it exceeds 2.0%, weldability deteriorates, so the amount of Mn should be in the range of 0.10 to 2.0%. .
Ｐ：0.03％以下
Ｐは、不可避的不純物として含有されるが、靭性および溶接性を劣化させるため、Ｐ量は0.03％以下に抑制するものとした。
P: 0.03% or less P is contained as an inevitable impurity. However, in order to deteriorate toughness and weldability, the amount of P is suppressed to 0.03% or less.
Ｓ：0.007％以下
Ｓも、不可避的不純物として含有されるが、含有量が多くなると塗装耐食性が低下するだけでなく、MnＳなどの介在物が増加してSCCの起点となり塗装耐食性を低下させるので、極力低減することが望ましいが、0.007％以下であれば許容できる。
S: 0.007% or less S is also included as an inevitable impurity. However, as the content increases, not only coating corrosion resistance decreases, but also inclusions such as MnS increase, which causes SCC as a starting point and decreases coating corrosion resistance. It is desirable to reduce as much as possible, but 0.007% or less is acceptable.
Sn：0.01〜0.05％
Snは、塗装耐食性を改善する元素であり、どちらかと言えば長期間にわたる塗装耐食性に優れている。しかしながら、含有量が0.01％に満たないとその添加効果に乏しく、一方0.05％を超えると耐食性が飽和するだけでなく、製造上の制約が生じるので、Sn量は0.01〜0.05％の範囲とする。
Sn: 0.01-0.05%
Sn is an element that improves the coating corrosion resistance, and is rather excellent in coating corrosion resistance over a long period of time. However, if the content is less than 0.01%, the effect of addition is poor. On the other hand, if it exceeds 0.05%, not only the corrosion resistance is saturated, but also production restrictions occur, so the Sn content is in the range of 0.01 to 0.05%. .
Cr：0.01〜0.10％、Cu：0.05〜0.10％およびNi：0.05〜0.10％のうちから選んだ１種または２種以上
Cr：0.01〜0.10％
Crは、全面腐食量を低減する有用元素であり、フラッシュラストのような短期間の塗装耐食性のみならず、長期間にわたる塗装耐食性の改善に寄与する。しかしながら、含有量が0.01％に満たないと十分な効果が発現せず、一方0.10％超の添加では経済的な効果に見合わないため、Cr量は0.01〜0.10％の範囲とする。
One or more selected from Cr: 0.01-0.10%, Cu: 0.05-0.10% and Ni: 0.05-0.10%
Cr: 0.01-0.10%
Cr is a useful element that reduces the overall corrosion amount, and contributes not only to short-term paint corrosion resistance such as flash last but also to long-term paint corrosion resistance. However, if the content is less than 0.01%, a sufficient effect is not exhibited. On the other hand, addition of more than 0.10% does not meet the economic effect, so the Cr content is in the range of 0.01 to 0.10%.
Cu：0.05〜0.10％
Cuは、フラッシュラストのような短期間の塗装耐食性および長期間にわたる塗装耐食性の改善に有効な元素である。しかしながら、含有量が0.05％未満ではその効果に乏しく、一方0.10％を超えると鋼材製造上の面からの制約が生じるので、Cu量は0.05〜0.10％の範囲とする。
Cu: 0.05-0.10%
Cu is an element effective for improving paint corrosion resistance for a short period of time such as flash last and paint corrosion resistance for a long period of time. However, if the content is less than 0.05%, the effect is poor. On the other hand, if it exceeds 0.10%, there are restrictions in terms of steel production, so the Cu content is in the range of 0.05 to 0.10%.
Ni：0.05〜0.10％
Niも、Cuと同様に、フラッシュラストのような短期間の塗装耐食性および長期間にわたる塗装耐食性の改善に有効な元素である。しかしながら、含有量が0.05％未満ではその効果に乏しく、一方0.10％を超えると経済的な効果に見合わないので、Ni量は0.05〜0.10％の範囲とする。
Ni: 0.05-0.10%
Ni, like Cu, is an element that is effective for improving short-term paint corrosion resistance and long-term paint corrosion resistance, such as flash last. However, if the content is less than 0.05%, the effect is poor. On the other hand, if it exceeds 0.10%, the economic effect is not met, so the Ni content is in the range of 0.05 to 0.10%.
これら、Cr，CuおよびNiはいずれも、短期間の塗装耐食性、長期間の塗装耐食性の両方に有用であり、特にCuとNiを組み合わせると改善効果が高い。 These Cr, Cu and Ni are all useful for both short-term coating corrosion resistance and long-term coating corrosion resistance, and particularly when Cu and Ni are combined, the improvement effect is high.
Mo：0.01〜0.08％およびＷ：0.01〜0.08％のうちから選んだ１種または２種
Mo：0.01〜0.08％、
Moは、腐食生成物として酸素酸塩を形成するため、かかる腐食生成物が腐食抑制材として作用する。また鋼材中にあっては、不均一腐食を低減する効果も併せ持っている。塗装と組み合わせた場合には、これらの効果が高い。しかしながら、含有量が0.01％未満では耐食性の改善効果に乏しく、一方0.08％超ではコスト的に不利になるため、Mo量は0.01〜0.08％の範囲で含有させることが好ましい。より好ましくは0.03〜0.06％の範囲である。
One or two selected from Mo: 0.01-0.08% and W: 0.01-0.08%
Mo: 0.01-0.08%,
Since Mo forms an oxyacid salt as a corrosion product, the corrosion product acts as a corrosion inhibitor. In steel, it also has the effect of reducing uneven corrosion. These effects are high when combined with paint. However, if the content is less than 0.01%, the effect of improving the corrosion resistance is poor. On the other hand, if it exceeds 0.08%, the cost is disadvantageous. Therefore, the Mo content is preferably in the range of 0.01 to 0.08%. More preferably, it is 0.03 to 0.06% of range.
Ｗ：0.01〜0.08％
Ｗも、Moと同様な効果を有しているが、含有量が0.01％未満では耐食性の改善効果に乏しく、一方0.08％超ではコスト的に不利になるため、Ｗは0.01〜0.08％の範囲で含有させることが好ましい。より好ましくは0.03〜0.06％の範囲である。
Mo，Ｗについては、どちらも同様な効果を有することから、いずれか一方の元素でも効果を有する。しかしながら、MoとＷが共存することによって一層優れた効果を発揮するので、複合含有させることが好ましい。但し、その場合には、MoとＷの合計が0.12％を超えない範囲がコストの面からより好適である。
W: 0.01-0.08%
W has the same effect as Mo, but if the content is less than 0.01%, the effect of improving the corrosion resistance is poor, while if it exceeds 0.08%, it is disadvantageous in cost, so W is in the range of 0.01 to 0.08%. It is preferable to contain. More preferably, it is 0.03 to 0.06% of range.
Since both Mo and W have the same effect, any one of the elements has an effect. However, since more excellent effects are exhibited by the coexistence of Mo and W, it is preferable to contain them in a composite manner. However, in that case, a range in which the total of Mo and W does not exceed 0.12% is more preferable from the viewpoint of cost.
以上、基本成分について説明したが、本発明では、その他にも、以下に述べる成分を必要に応じて適宜含有させることができる。
Ge：0.005〜0.010％、Sb：0.005〜0.010％、Bi：0.005〜0.010％およびSe：0.005〜0.010％のうちから選んだ１種または２種以上
耐食性のさらなる向上を目的として、Ge，Sb，BiおよびSeのうちから選んだ１種または２種以上を含有させることができる。また、これらの元素は、弱酸性環境における耐食性の改善にも有効である。ここに、Ge量が0.005％未満では耐食性の改善効果に乏しく、一方0.010％超ではコスト的な不利を招く。Sb量が0.005％未満では耐食性の改善効果に乏しく、一方0.010％超では鋼材の機械的特性の低下を招く。Se量が0.005％未満では耐食性の改善効果に乏しく 、一方0.010％超ではコスト的な不利を招く。Bi量が0.005％未満では耐食性の改善効果に乏しく、一方0.010％超では鋼材の機械的特性の低下を招く。
The basic components have been described above, but in the present invention, other components described below can be appropriately contained as necessary.
One or more selected from Ge: 0.005-0.010%, Sb: 0.005-0.010%, Bi: 0.005-0.010% and Se: 0.005-0.010% For the purpose of further improving corrosion resistance, Ge, Sb, One or more selected from Bi and Se can be contained. These elements are also effective in improving the corrosion resistance in a weakly acidic environment. Here, if the Ge amount is less than 0.005%, the effect of improving the corrosion resistance is poor, while if it exceeds 0.010%, a cost disadvantage is caused. If the Sb content is less than 0.005%, the effect of improving the corrosion resistance is poor, while if it exceeds 0.010%, the mechanical properties of the steel material are deteriorated. If the amount of Se is less than 0.005%, the effect of improving the corrosion resistance is poor, while if it exceeds 0.010%, a cost disadvantage is caused. If the amount of Bi is less than 0.005%, the effect of improving the corrosion resistance is poor, while if it exceeds 0.010%, the mechanical properties of the steel are deteriorated.
Nb：0.005〜0.10％、Ｖ：0.005〜0.10％およびTi：0.005〜0.10％のうちから選んだ１種または２種以上
Nb，ＶおよびTiはいずれも、鋼材の機械的特性および塗装耐食性を向上させるために有用な元素である。これらの元素はいずれも、含有量が0.005％未満ではその添加効果に乏しく、一方0.10％を超えると溶接部の機械的特性が低下する。
One or more selected from Nb: 0.005-0.10%, V: 0.005-0.10% and Ti: 0.005-0.10%
Nb, V and Ti are all useful elements for improving the mechanical properties and paint corrosion resistance of steel. Any of these elements has a poor effect of addition when the content is less than 0.005%, while the mechanical properties of the weld deteriorate when the content exceeds 0.10%.
さらに、本発明の効果を損なわない範囲内であれば、上記以外の元素の含有を拒むものではない。例えば、上記した元素の他に、AlやREMを脱酸剤として少量添加することも できる。
なお、本発明の鋼材において、上記以外の成分は、Feおよび不可避的不純物である。
Furthermore, the content of elements other than the above is not rejected as long as the effects of the present invention are not impaired. For example, in addition to the above-described elements, a small amount of Al or REM can be added as a deoxidizer.
In addition, in the steel material of this invention, components other than the above are Fe and inevitable impurities.
次に、本発明鋼材の好適製造方法について説明する。
上記した好適成分組成になる溶鋼を、転炉や電気炉等の公知の炉で溶製し、連続鋳造法や造塊法等の公知の方法でスラブやビレット等の鋼素材とする。なお、溶製に際して、真空脱ガス精錬等を実施しても良い。
溶鋼の成分調整方法は、公知の鋼製錬方法に従えばよい。
Next, the suitable manufacturing method of this invention steel material is demonstrated.
The molten steel having the preferred component composition described above is melted in a known furnace such as a converter or an electric furnace, and is made into a steel material such as a slab or billet by a known method such as a continuous casting method or an ingot forming method. In addition, vacuum degassing refining or the like may be performed at the time of melting.
The component adjustment method of molten steel should just follow a well-known steel smelting method.
ついで、上記の鋼素材を所望の寸法形状に熱間圧延する際には、1000〜1350℃の温度に加熱する。加熱温度が1000℃未満では変形抵抗が大きく、熱間圧延が難しくなる。一方、1350℃を超えると、表面痕の発生原因となったり、スケールロスや燃料原単位が増加したりする。好ましくは1050〜1300℃の範囲である。なお、鋼素材の温度が、もともと1000〜1350℃の範囲の場合には、加熱せずに、そのまま熱間圧延に供してもよい。
また、熱間圧延では、熱間仕上圧延終了温度を適正化することが望ましく、600℃以上 850℃以下とすることが好ましい。熱間仕上圧延終了温度が600℃未満では、変形抵抗の増大により圧延荷重が増加し、圧延の実施が困難となる。一方、850℃超えだと所望の強度を得ることが難しくなる。熱間仕上圧延終了後の冷却は、空冷または冷却速度：150℃/ｓ以下の加速冷却とすることが好ましい。加速冷却する場合の冷却停止温度は300〜750℃の範囲とすることが好ましい。なお、冷却後、再加熱処理を施してもよい。
Next, when the steel material is hot-rolled to a desired size and shape, it is heated to a temperature of 1000 to 1350 ° C. When the heating temperature is less than 1000 ° C., the deformation resistance is large and hot rolling becomes difficult. On the other hand, if the temperature exceeds 1350 ° C, it may cause surface marks, increase scale loss and fuel consumption. Preferably it is the range of 1050-1300 degreeC. In addition, when the temperature of the steel material is originally in the range of 1000 to 1350 ° C., it may be subjected to hot rolling as it is without being heated.
In hot rolling, it is desirable to optimize the finish temperature of hot finish rolling, and it is preferable to set the temperature to 600 ° C. or higher and 850 ° C. or lower. When the finish temperature of hot finish rolling is less than 600 ° C., the rolling load increases due to an increase in deformation resistance, making it difficult to perform rolling. On the other hand, if it exceeds 850 ° C., it is difficult to obtain a desired strength. The cooling after the hot finish rolling is preferably air cooling or accelerated cooling with a cooling rate of 150 ° C./s or less. The cooling stop temperature for accelerated cooling is preferably in the range of 300 to 750 ° C. Note that, after cooling, reheating treatment may be performed.
次に、本発明の実施例について説明する。なお、本発明はこれらの実施例のみに限定されるものではない。
表１に示す成分組成になる溶鋼を、真空溶解炉で溶製後または転炉溶製後、連続鋳造によりスラブとした。ついで、1250℃に加熱後、仕上圧延終了温度：800℃の条件で熱間圧延を実施して、30mm厚の鋼板とした。
これらの鋼板について、次の塗装耐食性試験を実施した。
Next, examples of the present invention will be described. In addition, this invention is not limited only to these Examples.
The molten steel having the composition shown in Table 1 was made into a slab by continuous casting after melting in a vacuum melting furnace or after melting in a converter. Then, after heating to 1250 ° C., hot rolling was performed at a finish rolling finish temperature of 800 ° C. to obtain a 30 mm thick steel plate.
The following coating corrosion resistance tests were conducted on these steel plates.
(ａ) 模擬水系樹脂塗料による耐食試験（短期間における腐食試験）
鋼材を、長さ：100mm、幅：75mm、厚さ：６mmに切り出し、両面をグリットブラスト（表面仕上げ ISO Sa 2.5）で仕上げ、アセトン中で超音波脱脂を５分間行い、風乾して塗装耐食性の試験材とした。片面は塗装するための面とし、もう片面および端面は溶剤型のエポキシ樹脂塗料にてシールし、さらにシリコン系のシール剤にて被覆した。
一方、模擬水系塗料として、エポキシエマルジョン樹脂（固形分50％、溶媒：水；大日本インキ製）に対して、平均粒径：１μmのSiO2を樹脂固形分：100質量部に対して1.5質量部、および平均粒径：0.5μmのTiO2を樹脂固形分：100質量部に対して５重量部、また平均粒径：0.5μmのカーボンブラック粉を樹脂固形分：100質量部に対して0.2質量部添加したものを、塗料用ミキサーにて撹拌することにより、水系のエポキシ樹脂系塗料とした。
(a) Corrosion resistance test using simulated water-based resin paint (short-term corrosion test)
Steel material is cut into length: 100mm, width: 75mm, thickness: 6mm, both sides are finished with grit blast (surface finish ISO Sa 2.5), ultrasonically degreased in acetone for 5 minutes, air-dried and coated with corrosion resistance A test material was obtained. One side was used as a surface to be coated, and the other side and the end surface were sealed with a solvent-type epoxy resin paint and further covered with a silicon-based sealant.
On the other hand, as a simulated water-based paint, an epoxy emulsion resin (solid content: 50%, solvent: water; manufactured by Dainippon Ink) has an average particle size of 1 μm of SiO 2 and a resin solid content: 1.5 parts by mass for 100 parts by mass. Parts and average particle size: 0.5 μm of TiO 2 with respect to resin solid content: 100 parts by mass 5 parts by weight, and average particle size: 0.5 μm of carbon black powder with resin solid content: 0.2% with respect to 100 parts by mass What added mass part was stirred with the mixer for coating materials, and it was set as the water-based epoxy resin-type coating material.
このエポキシ系水系塗料を、エアレススプレーにて、先のブラスト表面上に塗布した。塗装膜厚は、乾燥後の膜厚が100μmとなるように調節して塗装した。これを24時間、23℃，60％RHの試験槽内に静置した。24時間経過後に、試験材を取り出し、降雨を想定して、毎分：0.3リットルの水をシャワーにて、ミストとして試験材の塗装表面を含む0.1m2の範囲に噴霧した。これを24時間連続で行い、その後表面に付着した水分を除去した後、塗装表面を観察した。塗装表面には、フラッシュラストに起因する黄〜白色の斑点模様が発生するが、この面積率を目視にて観察し、以下のように判定した。
◎：斑点模様 0.3％以下、
○：斑点模様 0.3％超、３％以下、
△：斑点模様 ３％超、10％以下、
×：斑点模様 10％超
This epoxy-based water-based paint was applied onto the blast surface by airless spraying. The coating film thickness was adjusted so that the film thickness after drying was 100 μm. This was left for 24 hours in a test bath at 23 ° C. and 60% RH. After the lapse of 24 hours, the test material was taken out, and assuming rain, every minute: 0.3 liters of water was sprayed as a mist in a range of 0.1 m 2 including the painted surface of the test material. This was carried out continuously for 24 hours, after which water adhering to the surface was removed, and then the painted surface was observed. A yellow to white spot pattern due to flash last is generated on the painted surface. This area ratio was visually observed and determined as follows.
◎: Spotted pattern 0.3% or less,
○: Spot pattern more than 0.3%, 3% or less,
Δ: speckled pattern more than 3%, 10% or less,
×: Spot pattern over 10%
(ｂ) 長期間にわたる塗装耐食性の調査
上記（ａ）のように塗装した各種鋼材を、35℃，50％RHの試験槽内で、7日間乾燥させた。その後、試験材の中央部に、幅：１mm、長さ：50mmの初期欠陥を、厚刃のカッターで設けた。この試験材を、塩水噴霧（SST：35℃，5％NaCl溶液)：１時間、湿潤 (40℃，95％RH)：３時間、乾燥（50℃，25％RH)：２時間の、合計６時間を１サイクルとする、複合サイクル腐食試験に供した。この試験を、49日間試験を行い、試験槽から取り出し水洗した後、クロスカット部からの最大膨れ（剥離）幅を計測した。その後膨れ幅の最大値測定結果から、以下のように判定した。
◎：膨れ幅５mm以下
○：膨れ幅５mm超、10mm以下
△：膨れ幅10mm超、15mm以下
×：膨れ幅15mm超
得られた結果を表２に示す。
(b) Investigation of long-term coating corrosion resistance Various steel materials coated as described in (a) above were dried for 7 days in a test bath at 35 ° C. and 50% RH. Thereafter, an initial defect having a width of 1 mm and a length of 50 mm was provided in the center of the test material with a thick blade cutter. The test material was sprayed with salt water (SST: 35 ° C, 5% NaCl solution): 1 hour, wet (40 ° C, 95% RH): 3 hours, dried (50 ° C, 25% RH): 2 hours in total. It was subjected to a combined cycle corrosion test with 6 hours as one cycle. This test was conducted for 49 days, taken out from the test tank, washed with water, and then measured for the maximum swelling (peeling) width from the crosscut portion. Thereafter, from the result of measuring the maximum value of the swollen width, it was determined as follows.
：: Swelling width 5 mm or less ○: Swelling width 5 mm or more, 10 mm or less △: Swelling width 10 mm or more, 15 mm or less ×: Swelling width 15 mm or less Table 2 shows the results obtained.
表２から明らかなように、発明例はいずれも、短期間の塗装耐食性のみならず、長期間の塗装耐食性が大幅に改善されていることが分かる。
これに対し、成分組成が発明範囲から外れた比較例はいずれも、短期間の塗装耐食性および長期間の塗装耐食性が共に劣っていた。特に長期間の耐食試験では、膨れの程度が大きかった。
従って、発明例と比較例の対比から、本発明の改善効果は明らかである。
As is clear from Table 2, it can be seen that not only the short-term paint corrosion resistance but also the long-term paint corrosion resistance are greatly improved in all the inventive examples.
On the other hand, all of the comparative examples whose component compositions deviated from the scope of the invention were inferior in both short-term coating corrosion resistance and long-term coating corrosion resistance. In particular, in the long-term corrosion resistance test, the degree of swelling was large.
Therefore, the improvement effect of the present invention is clear from the comparison between the inventive example and the comparative example.
Claims (3)
Ｃ：0.03〜0.30％、
Si：0.01〜1.0％、
Mn：0.10〜2.0％、
Ｐ：0.03％以下、
Ｓ：0.007％以下および
Sn：0.01〜0.05％
を含み、かつ
Cr：0.01〜0.10％、
Cu：0.05〜0.10％および
Ni：0.05〜0.10％
のうちから選んだ１種または２種以上を含み、さらに
Mo：0.01〜0.08％および
Ｗ：0.01〜0.08％
のうちから選んだ１種または２種を含有し、残部がFeおよび不可避的不純物からなることを特徴とする水系塗料との適合性に優れた鋼材。 % By mass
C: 0.03-0.30%
Si: 0.01 to 1.0%
Mn: 0.10 to 2.0%,
P: 0.03% or less,
S: 0.007% or less and
Sn: 0.01-0.05%
And including
Cr: 0.01-0.10%,
Cu: 0.05-0.10% and
Ni: 0.05-0.10%
Including one or more selected from among
Mo: 0.01-0.08% and W: 0.01-0.08%
A steel material excellent in compatibility with water-based paints, characterized in that it contains one or two selected from among them, and the balance consists of Fe and inevitable impurities.
Ge：0.005〜0.010％、
Sb：0.005〜0.010％、
Bi：0.005〜0.010％および
Se：0.005〜0.010％
のうちから選んだ１種または２種以上を含有することを特徴とする請求項１に記載の鋼材。 The steel material is further mass%,
Ge: 0.005-0.010%,
Sb: 0.005-0.010%,
Bi: 0.005-0.010% and
Se: 0.005-0.010%
The steel material according to claim 1, comprising one or more selected from among the above.
Nb：0.005〜0.10％、
Ｖ：0.005〜0.10％および
Ti：0.005〜0.10％
のうちから選んだ１種または２種以上を含有することを特徴とする請求項１または２に記載の鋼材。 The steel material is further mass%,
Nb: 0.005-0.10%,
V: 0.005-0.10% and
Ti: 0.005-0.10%
The steel material according to claim 1 or 2, comprising one or more selected from among the above.
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