JP2522074B2 - Ultra-thin Sn-plated steel sheet for can and method for producing the same - Google Patents

Description

【発明の詳細な説明】 ［産業上の利用分野］ この発明は、食缶など製缶に際して缶胴の継ぎ目を溶
接によってシームする缶用材で、Snめっき層が極めて薄
くても、塗装後耐食性や加工後の耐食性など缶用材とし
ての諸特性に加えて溶接性にも優れた缶用鋼板に関す
る。DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is a can material for seaming seams of a can body by welding when making a can such as a food can. Even if the Sn plating layer is extremely thin, the corrosion resistance after coating and The present invention relates to a steel sheet for a can having excellent weldability in addition to various properties as a can material such as corrosion resistance after processing.

［従来技術］ 現在、缶用材として最も大量に用いられているものに
Snめっき鋼板とティンフリースチールとがある。Snめっ
き鋼板は前世紀から用いられて来たもので、缶用材とし
てのSnめっき鋼板の持つ特性は極めて優れたものであ
る。しかしながら、よく知られているように、Snは資源
的に限られたものであることから、Snめっき鋼板開発の
歴史は又Snを節約する技術の歴史でもある。缶胴は、缶
用材めっき鋼帯に耐食塗料を塗布したのち、その寸法に
切断した四角形の缶用材を丸めてその両端をシームして
作られる。このシーム技術もSnめっき鋼板のSnの節約に
応じて開発され、半田付けに始まり現在では溶接法、溶
着法等が実用されている。[Prior Art] Currently the most widely used can material
There are Sn-plated steel plate and tin-free steel. The Sn-plated steel sheet has been used since the last century, and the characteristics of the Sn-plated steel sheet as a can material are extremely excellent. However, as is well known, since Sn is limited in resources, the history of Sn plated steel sheet development is also the history of Sn saving technology. The can body is made by applying a corrosion-resistant paint to a can material-plated steel strip, then rolling a rectangular can material cut into that size and seaming both ends thereof. This seam technology was also developed according to the saving of Sn in the Sn-plated steel sheet, and starting from soldering, the welding method, welding method, etc. are now in practical use.

ティンフリースチールはCrめっき鋼板であり、全くSn
を用いないものであるが、残念ながら、有機材料を用い
た接着法によるシームしか行えず、溶接法が実用できな
い。接着法では、接着剤に耐熱性の限界や接着時間に伴
う生産性の低下等があり、使用上、工程上の制限を受け
る。溶接法では、継ぎ目部を重ねて銅線電極の間に挟
み、ロールによって加圧しながら電気抵抗加熱溶接を行
う。このとき、ティンフリースチールでは被膜表面に絶
縁体である酸化物が多く、溶接面同士の接触電気抵抗が
大き過ぎて高電圧を印加しなければならない。高電圧を
かけると局部的に過剰電流が流れチリと呼ばれるスプラ
ッシュが発生し良好な溶接が得られない。現在では、め
っき最表層に少量のSnを存在させることで、これが解消
されることが判り、このSnの最小量は0.05g/m²であると
いわれている。即ち、缶用極薄Snめっき鋼板の開発で
は、缶用材としての耐食性や加工性等の諸特性に加え
て、溶接時に最小量のSnを残すことに力が注がれてい
る。Tin-free steel is a Cr-plated steel plate, and is entirely Sn
However, unfortunately, only the seam by the bonding method using the organic material can be performed, and the welding method cannot be practically used. In the bonding method, there is a limit in heat resistance of the adhesive and a decrease in productivity due to bonding time. In the welding method, the seam portion is overlapped and sandwiched between the copper wire electrodes, and electric resistance heating welding is performed while pressing with a roll. At this time, in tin-free steel, the oxide film, which is an insulator, is often present on the coating surface, and the contact electric resistance between the welding surfaces is too large, so that a high voltage must be applied. When a high voltage is applied, excess current flows locally and a splash called dust occurs, which makes it impossible to obtain good welding. At present, it has been found that this can be solved by allowing a small amount of Sn to exist in the outermost surface layer of plating, and the minimum amount of Sn is said to be 0.05 g / m ² . That is, in the development of an ultra-thin Sn-plated steel sheet for cans, in addition to various characteristics such as corrosion resistance and workability as a can material, efforts have been made to leave a minimum amount of Sn during welding.

一般には、溶接前に缶内塗料が焼き付けられ、この際
に鋼板上にめっきされたSnは拡散するFeと合金化し金属
Snの特性を失う。Snのみをめっきしその上に化成処理を
施したSnめっき鋼板では、この点を考慮しSnを1.1g/m²
まで減じたいわゆる＃10ぶりきまでが実用されている。
これに対して、更にSn量を減じても前記した他の諸特性
とともに溶接性を損なわないめっき被膜構成として、Sn
層の下にNiやCrのめっき層を設けることが検討されてい
る。例えば、特開昭63-499では、鋼板表面にCr或はCr−
Niを拡散させ、この拡散層によって塗料焼き付け時のSn
−Fe合金の生成を抑制し、Snめっき量を0.1g/m²まで節
減することが提案されている。Generally, the paint in the can is baked before welding, and the Sn plated on the steel plate is alloyed with the diffusing Fe to form a metal.
It loses the characteristics of Sn. Considering this point, Sn-plated steel sheet plated with only Sn and chemical-treated on top of Sn has a Sn content of 1.1 g / m ²
The so-called # 10 tinplate, which has been reduced to, is in practical use.
On the other hand, even if the Sn content is further reduced, as a plating film configuration that does not impair the weldability together with the other various properties described above, Sn
Providing a Ni or Cr plating layer under the layer is under consideration. For example, in Japanese Patent Laid-Open No. 63-499, Cr or Cr-
Ni is diffused, and this diffusion layer causes Sn during paint baking.
-It has been proposed to suppress the formation of Fe alloy and reduce the Sn plating amount to 0.1 g / m ² .

［発明が解決しようとする課題］ しかしながら、CrとFeとの拡散層或はCrとNiとFeとの
拡散層は、Sn−Fe合金の生成を抑制することはできる
が、抑制度合いに限界がありSn量の半分近くは合金化さ
れてしまう。このため、溶接性を損なうことなくSn量を
更に節減することが困難であった。[Problems to be Solved by the Invention] However, the diffusion layer of Cr and Fe or the diffusion layer of Cr, Ni and Fe can suppress the formation of Sn-Fe alloy, but the degree of suppression is limited. Yes Nearly half of the Sn content is alloyed. Therefore, it has been difficult to further reduce the Sn content without impairing the weldability.

この発明はこの問題を解決するためになされたもの
で、更にSn量を節約しても、溶接性その他の缶用材とし
ての諸特性を損なうことのない缶用極薄Snめっき鋼板の
提供を目的とするものである。The present invention has been made to solve this problem, and an object of the present invention is to provide an ultra-thin Sn-plated steel sheet for cans that does not impair the weldability and other properties of the material for cans, even if the Sn content is further saved. It is what

［課題を解決するための手段］ この目的を達成するための手段は、鋼板の表面がCr換
算で0.02g/m²以上0.2g/m²以下の付着量のCr熱拡散層で
覆われ、この熱拡散層の上に付着量0.05g/m²以上1.0g/m
²以下のSnめっき層を有し、このSnめっき層の上に金属C
r量が3mg/m²以上30mg/m²以下で且つ１μm²当たり10個以
上の突起を有し、該突起部とその他の部分で厚みの異な
るクロメート層を有する缶用極薄Snめっき鋼板、及びこ
の缶用極薄Snめっき鋼板を製造するに適した方法で、こ
の方法は鋼板の表層にCr熱拡散層を生成し、調質圧延を
行った後、付着量0.05g/m²以上1.0g/m²以下のSnめっき
を施し、その後、クロメート処理液中で電流密度5A/dm²
以上30A/dm²以下で0.3秒以上0.5秒以下の陽極処理に引
き続いて陰極処理を行い、突起を形成するとともに金属
Cr量が3mg/m²以上30mg/m²以下のクロメート層を生成す
る缶用極薄Snめっき鋼板の製造方法である。[Means for Solving the Problem] A means for achieving this object is that the surface of the steel sheet is covered with a Cr thermal diffusion layer having an adhesion amount of 0.02 g / m ² or more and 0.2 g / m ² or less in terms of Cr, Adhesion amount 0.05g / m ² or more 1.0g / m ² on this thermal diffusion layer
^It has a Sn plating layer of ² or less, and metal C is placed on this Sn plating layer.
An ultrathin Sn-plated steel sheet for cans having an r amount of 3 mg / m ² or more and 30 mg / m ² or less and 10 or more protrusions per 1 μm ² , and a chromate layer having different thicknesses in the protrusions and other portions, And a method suitable for producing an ultra-thin Sn-plated steel sheet for cans, this method produces a Cr thermal diffusion layer on the surface layer of the steel sheet, and after temper rolling, the adhesion amount is 0.05 g / m ² or more 1.0 Sn plating of g / m ² or less is applied, and then the current density is 5 A / dm ^{2 in the} chromate treatment solution.
Anodizing at 30 A / dm ² or less for 0.3 s or more and 0.5 s or less, followed by cathodic treatment to form protrusions and metal
This is a method for producing an ultrathin Sn-plated steel sheet for a can, which produces a chromate layer having a Cr content of 3 mg / m ² or more and 30 mg / m ² or less.

［作用］ 鋼素地とSnめっき層との間に、Crめっき層やCr熱拡散
層が存在すると、めっき鋼板に耐食性を与えると共に塗
装焼き付け時のSn−Fe合金化を抑制することは、よく知
られている。これらの作用に加えて、この熱拡散層が存
在すると、加工後も良好な耐食性を保つことが出来る。
厳しい加工を受けるとめっき被膜に亀裂が生じ、拡散し
ていないCrめっき層では、この亀裂の下では鋼素地が露
出してしまうが、熱拡散層では深部にまでCrが拡散して
おり、層の上部に亀裂が生じても亀裂の下には未だCrが
存在して鋼の露出を防ぐ。このため、製缶時の巻き締め
加工や絞り加工の後も被膜の連続性を保ち耐食効果を維
持する。[Operation] It is well known that the presence of a Cr plating layer or a Cr thermal diffusion layer between the steel substrate and the Sn plating layer provides corrosion resistance to the plated steel sheet and suppresses Sn-Fe alloying during paint baking. Has been. In addition to these functions, the presence of this thermal diffusion layer makes it possible to maintain good corrosion resistance even after processing.
Cracking occurs in the plating film when subjected to severe processing, and in the Cr plating layer that has not diffused, the steel base is exposed under this crack, but in the thermal diffusion layer Cr diffuses deeply Even if cracks occur in the upper part of the steel, Cr still exists under the cracks to prevent the steel from being exposed. For this reason, the continuity of the coating is maintained and the corrosion resistance effect is maintained even after the winding tightening process and the drawing process during can making.

Snめっき層は、シーム溶接の際はSn特有の軟らかさと
低い融点のために電気抵抗加熱溶接時の接触抵抗を減じ
て良好な溶接を可能にする、又、缶内容物充填後は耐食
被膜として機能する。Snめっき量は溶接性を確保するだ
けは必要であり、この必要Sn量を確保するために、Cr熱
拡散層の合金化抑制作用を利用する。しかし、このCr熱
拡散層があっても、缶用塗料の焼き付け時にSnとFeとの
拡散を十分に防ぐことは困難である。第１表は、Cr熱拡
散層とSn−Fe拡散の関係を示すもので、Crめっき量を変
えて熱拡散層を形成し、その上にSnをめっきし、これを
205℃に10分間保って空焼きした後、合金化せずに残っ
ている金属錫の量を測定した結果である。The Sn plating layer reduces the contact resistance during electric resistance heating welding to enable good welding due to the softness and low melting point peculiar to Sn during seam welding, and as a corrosion-resistant coating after filling the can contents. Function. The Sn plating amount is required only to secure the weldability, and in order to secure the required Sn amount, the alloying suppressing effect of the Cr thermal diffusion layer is utilized. However, even with this Cr thermal diffusion layer, it is difficult to sufficiently prevent the diffusion of Sn and Fe during baking of the can coating material. Table 1 shows the relationship between the Cr thermal diffusion layer and Sn-Fe diffusion. The thermal diffusion layer was formed by changing the Cr plating amount, Sn was plated on it, and
It is the result of measuring the amount of metallic tin remaining without alloying after air-baking at 205 ° C. for 10 minutes.

Cr熱拡散層の合金化抑制効果は明瞭である。この効果
はCr量が0.01g/m²でも現れるが、実用上加工条件のバラ
ツキを考慮すると、巻き締め加工後の耐食性を確実に維
持するためには、0.02g/m²以上のCr量が望ましい。又、
耐食性に関してはこの熱拡散層は厚いほど良いが、この
層の硬度は鋼やNiに較べて高く、余りに厚すぎると溶接
面を接触させたとき柔軟性を欠き、溶接性にとって好ま
しくない。 The effect of suppressing alloying of the Cr thermal diffusion layer is clear. This effect appears even when the Cr amount is 0.01 g / m ² , but in consideration of variations in working conditions in practical use, a Cr amount of 0.02 g / m ² or more is required in order to reliably maintain the corrosion resistance after the tightening process. desirable. or,
With respect to corrosion resistance, the thicker this heat diffusion layer is, the better, but the hardness of this layer is higher than that of steel and Ni. If it is too thick, it lacks flexibility when brought into contact with the welding surface and is not preferable for weldability.

0.2g/m²を超えて厚くしてもその効き方は緩慢となる
ので、経済性を勘案すると、その量は0.2g/m²以下であ
ることが望ましい。Even if the thickness exceeds 0.2 g / m ² , the effect will be slow, so in consideration of economic efficiency, the amount is preferably 0.2 g / m ² or less.

しかしながら、このようなCr熱拡散層があっても、30
〜40％のSnは空焼きにより合金化されてしまう。Sn量を
節減していくと、この合金化量は無視できなくなり、特
に、Snめっき量が0.1g/m²以下ともなると、Sn残量が溶
接に必要であると言われている量即ち0.05g/m²未満とな
るおそれもある。しかし、この溶接に必要なSn量は、ク
ロメート層の存在を前提とする量であり、クロメート層
を工夫することによって更に低減することが可能であ
る。缶用材では缶の内容物に対応して塗装を施すことに
よって耐食性を確保するが、これら塗料の付着性や塗膜
下耐食性を確保するため、クロメート層は欠かせないも
のとなっている。クロメート層は金属Crとこれを覆うCr
の酸化物或いは水酸化物からなるが、酸化物或いは水酸
化物は金属に較べ電気抵抗の大きい絶縁材であり、又、
酸化物は極めて硬くしかも両者とも融点は極めて高く、
これらが溶接面の接触電気抵抗を大きくしている。この
ような、クロメート層が一般にはCr換算で５〜30mg/m²
存在し、溶接時にこの存在を補う量として50mg/m²のSn
量が必要となる。しかしながら、１μm²当たり10個以上
の突起を有し、該突起部とその他の部分で厚みの異なる
クロメート層であると、溶接時に圧下力がかかり、この
突起の先端に局部的に大きな力を受けたとき、この部分
の酸化物或いは水酸化物の膜は破壊され、金属Crが露出
してくる。金属Cr同士が接触すれば、電気抵抗は10^-12
倍以下にも下がるので、溶接面の接触抵抗は低下する。
このため、Sn量は溶接時に0.02g/m²以上あれば容易に溶
接することが出来、そのためには、0.05g/m²以上のめっ
き量でよい。Sn量は多い程溶接性が向上することは当然
であるが、増量の効果は徐々に小さくなるので、Sn節約
の観点からも、1.0g/m²を上限とすることが妥当であ
る。However, even with such a Cr thermal diffusion layer,
~ 40% Sn is alloyed by baking. As the Sn amount is reduced, this alloying amount cannot be ignored, and in particular, when the Sn plating amount is 0.1 g / m ² or less, the amount of Sn remaining is said to be necessary for welding, namely 0.05. It may be less than g / m ² . However, the amount of Sn required for this welding is based on the existence of the chromate layer, and can be further reduced by devising the chromate layer. For can materials, the corrosion resistance is secured by applying a coating to the contents of the can, but the chromate layer is indispensable in order to secure the adhesion of these paints and the corrosion resistance under the coating film. Chromate layer is metallic Cr and Cr covering it
The oxide or hydroxide is an insulating material having a higher electric resistance than a metal, and
Oxides are extremely hard and both have extremely high melting points,
These increase the contact electric resistance of the welding surface. Such a chromate layer is generally 5 to 30 mg / m ^{2 in} terms of Cr.
50 mg / m ² of Sn that is present and supplements this presence during welding.
You need the amount. However, if the chromate layer has 10 or more protrusions per 1 μm ^{2 and} the protrusions and other portions have different thicknesses, a pressing force is applied during welding and a large local force is locally applied to the tip of the protrusion. At this time, the oxide or hydroxide film in this portion is destroyed and the metal Cr is exposed. If the metal Crs contact each other, the electrical resistance will be 10 ^-12.
The contact resistance on the welded surface is reduced because the contact resistance decreases to less than double.
Therefore, Sn amount can be readily welded if 0.02 g / m ² or more at the time of welding, in order thereof may be 0.05 g / m ² or more coating weight. It is natural that the weldability improves as the amount of Sn increases, but the effect of increasing the amount gradually decreases. Therefore, from the viewpoint of Sn saving, it is appropriate to set 1.0 g / m ² as the upper limit.

クロメート層の突起の数は多いほど接触抵抗が減じ、
μm²当たり10個以上存在すると確実にその効果が得られ
る。第１図は、Cr熱拡散の上に0.05g/m²のSnをめっき
し、後に述べる方法で突起の形成されるクロメート処理
を施した試料について、突起数と接触抵抗値との関係を
表わしたものである。縦軸は接触抵抗値、横軸は突起数
で数の平方根の間隔で目盛っある。応力勾配は突起間の
距離に反比例し応力差の生じる箇所は突起数に比例する
と考えられる。図は、突起数が少ないと接触抵抗値が大
きくなってくること、又、突起数が10個／μm²以上では
接触抵抗値は非常に小さいことを示している。このよう
に接触抵抗を低下させる突起を作るためにクロメート層
は金属Cr量で3mg/m²以上存在することが望ましい。金属
Cr量が少なく1mg/m²程度では、突起形成ばかりでなく塗
膜下耐食性を維持することも困難である。又、30mg/m²
を超えた場合でも突起は形成されるが、酸化物等が増え
ることの負の効果を考慮すると30mg/m²を超えないこと
が望ましい。The larger the number of protrusions on the chromate layer, the lower the contact resistance,
If 10 or more particles exist per μm ² , the effect is surely obtained. Fig. 1 shows the relationship between the number of protrusions and the contact resistance value for a sample in which 0.05 g / m ² of Sn was plated on Cr thermal diffusion and subjected to chromate treatment to form protrusions by the method described later. It is a thing. The vertical axis represents the contact resistance value, and the horizontal axis represents the number of protrusions at intervals of the square root of the number. It is considered that the stress gradient is inversely proportional to the distance between the protrusions, and the location where the stress difference occurs is proportional to the number of protrusions. The figure shows that when the number of protrusions is small, the contact resistance value becomes large, and when the number of protrusions is 10 / μm ² or more, the contact resistance value is very small. In order to form the protrusions that lower the contact resistance, it is desirable that the chromate layer is present in an amount of 3 mg / m ² or more in terms of metallic Cr. metal
When the Cr content is low and about 1 mg / m ² , it is difficult not only to form protrusions but also to maintain the corrosion resistance under the coating film. Also, 30 mg / m ²
Even if the amount exceeds 50 mg / m ² , the protrusions are formed, but considering the negative effect of the increase in oxides, it is desirable that the amount does not exceed 30 mg / m ² .

上記の缶用極薄Snめっき鋼板を製造するためには、先
ず、Cr熱拡散層を形成する必要がある。これには、熱処
理前の鋼板の表面にCrを付着させておくと、この鋼板を
熱処理するときに、Crが熱拡散される。この方法は、一
般に行われているように、熱処理及び調質圧延を施され
機械的性質の調整された鋼板にめっきを施すよりも、工
程が少なく且つ省エネルギー的であり、又、鋼板は二度
目の処理による材質への影響を受けないで済む。熱処理
が冷間圧延後に行う焼鈍処理の場合、缶用鋼板では一般
に700℃付近に加熱され、又、過時効処理では500℃前後
に加熱される。何れの処理でも、Cr熱拡散層が十分に形
成されるので、どちらの熱処理を利用してもよい。Crを
鋼板に付着させる方法はここに述べる以外に何通りもあ
る。Crをめっきするのが最も簡単な方法であるが、拡散
層の上層でCr濃度が高くなり、後に行うSnめっきで付着
効率が低下する傾向がある。これは、Crの酸素親和性に
因し、濃度が高いと酸化物や水酸化物が生成し易く、Sn
めっき中に還元電流が消費されるためと考えられる。Cr
をめっきしその上にFeをめっきすると、工程は増える
が、熱拡散層の中層でCr濃度が最も高く上層では稀釈さ
れているので、Snめっきの付着効率の向上に寄与し、
又、亀裂の先端のCr濃度も確保される。Cr・Feの合金め
っきを施すと、熱処理温度が低かったり或いは熱処理時
間が短くても十分に拡散が行われ、拡散層内のCr濃度も
比較的一定である。Crをめっきしその上にCr・Fe合金を
めっきすると、Crめっきの上にFeをめっきした場合より
も拡散層内のCr濃度勾配は緩和する。このようなCrの付
着方法は、用途や鋼板の厚さ、熱処理条件等によって選
択されるが、何れの方法で付着させても前記した加工後
耐食性に優れたCr熱拡散層が得られる。In order to manufacture the above-mentioned ultra-thin Sn-plated steel sheet for cans, it is first necessary to form a Cr thermal diffusion layer. To this end, if Cr is adhered to the surface of the steel sheet before heat treatment, Cr is thermally diffused when the steel sheet is heat treated. This method has a smaller number of steps and is more energy-saving than plating a steel sheet that has been heat-treated and temper-rolled and whose mechanical properties have been adjusted, as is generally done. The material does not have to be affected by the treatment. When the heat treatment is an annealing treatment performed after cold rolling, the steel sheet for cans is generally heated to about 700 ° C, and the overaging treatment is heated to about 500 ° C. In either case, either heat treatment may be used because the Cr thermal diffusion layer is sufficiently formed. There are many ways to attach Cr to the steel sheet other than those mentioned here. Plating with Cr is the simplest method, but the Cr concentration in the upper layer of the diffusion layer becomes high, and the adhesion efficiency tends to decrease with Sn plating performed later. This is due to the oxygen affinity of Cr, and when the concentration is high, oxides and hydroxides are easily generated, and Sn
It is considered that the reduction current is consumed during plating. Cr
However, if the Fe layer is plated with Fe, the number of steps increases, but since the Cr concentration is highest in the middle layer of the thermal diffusion layer and diluted in the upper layer, it contributes to the improvement of the Sn plating adhesion efficiency.
Also, the Cr concentration at the tip of the crack is secured. When Cr / Fe alloy plating is performed, diffusion is sufficiently performed even if the heat treatment temperature is low or the heat treatment time is short, and the Cr concentration in the diffusion layer is relatively constant. When Cr is plated and then a Cr / Fe alloy is plated thereon, the Cr concentration gradient in the diffusion layer is more relaxed than when Fe is plated on the Cr plating. The Cr deposition method is selected depending on the application, the thickness of the steel sheet, the heat treatment conditions, etc., but the Cr thermal diffusion layer having excellent corrosion resistance after processing as described above can be obtained by any method.

クロメート処理液中で陽極電解を短時間行った後引き
続いて陰極電解を行うと、微細な突起が無数にできる。
クロメート処理液は周知のクロム酸或いは重クロム酸系
のものでよい。短時間の陽極電解によって処理面を不均
質状態にし、その後陰極電解を行うことによってCrの不
均一析出を起こさせるものであり、析出量の多い所が突
起となる。陽極電解の時間は極く短くてよく0.5秒に至
らなくても十分に効果が得られる。If anodic electrolysis is carried out for a short time in a chromate treatment solution and then cathodic electrolysis is carried out, innumerable fine projections can be formed.
The chromate treatment liquid may be a well-known chromic acid or dichromic acid type. The treated surface is brought into a non-homogeneous state by anodic electrolysis for a short period of time, and then non-uniform deposition of Cr is caused by performing cathodic electrolysis. The time of anodic electrolysis can be extremely short and sufficient effect can be obtained even if it does not reach 0.5 seconds.

［実施例］ 冷延鋼板の表面にCr及びNiを付着してから熱処理を施
し、伸張率２％の調質圧延を行った後、Snをめっきし、
これにクロメート処理液中で陽極処理に引き続いて陰極
処理を施した。これらの試験片について、耐食性、塗料
付着性、溶接性を調べた。試験は、この発明の範囲外の
比較例及び従来の技術による従来例とについても行い、
これらを比較した。なお、従来例では実施例と同様にCr
・Niめっき、熱処理及びSnめっきを施し、又、熱拡散層
がCr・Ni熱拡散層の場合も含めたが、クロメート処理で
は陽極電解を行わず陰極電解処理のみを施した。[Example] After Cr and Ni were attached to the surface of a cold rolled steel sheet, heat treatment was performed, temper rolling was performed at an elongation rate of 2%, and then Sn was plated,
This was subjected to anodizing in a chromate treatment solution followed by cathodic treatment. These test pieces were examined for corrosion resistance, paint adhesion and weldability. The test is also carried out on a comparative example outside the scope of the present invention and a conventional example according to the prior art,
These were compared. In the conventional example, Cr
・ Ni plating, heat treatment, and Sn plating were performed, and the case where the thermal diffusion layer was Cr / Ni thermal diffusion layer was included, but in the chromate treatment, anodic electrolysis was not performed, and only cathodic electrolysis treatment was performed.

試験片作製の処理条件は次のようであった。 The processing conditions for producing the test piece were as follows.

Crめっき： CrO₃ 200g/l (NH₄)F 3g/l 浴温 50℃ 電流密度 40A/dm² Cr・Fe合金めっき： CrO₃ 200g/l FeCl₂ 150g/l 浴温 50℃ pH 1.7 電流密度 40A/dm² Snめっき： Sn⁺⁺ 30g/l フェノールスルフォン酸 70g/l 光沢剤 5g/l 浴温 50℃ 電流密度 20A/dm² これらの処理条件は何れも一般的に用いられているめ
っき条件である。Cr plating: CrO ₃ 200g / l (NH ₄ ) F 3g / l Bath temperature 50 ° C Current density 40A / dm ² Cr ・ Fe alloy plating: CrO ₃ 200g / l FeCl ₂ 150g / l Bath temperature 50 ° C pH 1.7 Current density 40A / dm ² Sn plating: Sn ⁺⁺ 30g / l Phenolsulfonic acid 70g / l Brightener 5g / l Bath temperature 50 ℃ Current density 20A / dm ² All of these treatment conditions are commonly used plating conditions Is.

クロメート処理A: CrO₃ 50g/l (NH₄)F 1g/l 浴温 40℃ 陰極処理電流密度 20〜50A/dm² 陽極処理電流密度 5〜30A/dm² 陽極処理時間 0.3〜0.4秒 クロメート処理B: Na₂Cr₂O₇ 50g/l pH 5.5 浴温 40℃ 陰極処理電流密度 5〜10A/dm² 陽極処理電流密度 5〜30A/dm² 陽極処理時間 0.3〜0.4秒 耐食性試験としては、加工後耐食性、塗膜下耐食性、
鉄溶出試験を行ない、塗料付着性試験としてＴピール試
験を、溶接性は接触電気抵抗を調べた。Chromate treatment A: CrO ₃ 50g / l (NH ₄ ) F 1g / l Bath temperature 40 ° C Cathodic treatment Current density 20 to 50A / dm ² Anodizing current density 5 to 30A / dm ² Anodizing time 0.3 to 0.4 seconds Chromate treatment B: Na ₂ Cr ₂ O ₇ 50 g / l pH 5.5 Bath temperature 40 ° C Cathodic treatment current density 5 to 10 A / dm ² Anodizing current density 5 to 30 A / dm ² Anodic treatment time 0.3 to 0.4 seconds As a corrosion resistance test, processing Post-corrosion resistance, under-coat corrosion resistance,
An iron elution test was carried out, a T-peel test was conducted as a paint adhesion test, and a contact electric resistance was examined for weldability.

加工後耐食性は、製缶時の巻き締め加工後の耐食性を
調べるもので、試験片を二つに折り曲げ、これを食塩1.
5％、クエン酸1.5％を含む水溶液に38℃で96時間浸漬し
た後、鉄の発錆を調べた。二つに折り曲げるとき、その
間にスペーサーを全く挿まないいわゆる密着折り曲げを
OT,試験片と同じ厚さの板を挿んだ場合の1T,以下5Tまで
の折り曲げ方により、どの折り曲げ方まで発錆がなっか
ったかによりＴ値で判定する。ここでは、試料30枚につ
いて試験し、全てが1Tより良かった場合を○、2Tが混じ
た場合を△、3Tが混じた場合を×で評価した。Corrosion resistance after processing is to check the corrosion resistance after the tightening processing during can making.Fold the test piece in two and use salt 1.
After immersing in an aqueous solution containing 5% and 1.5% citric acid at 38 ° C for 96 hours, iron rusting was examined. When folding in two, so-called close folding without inserting a spacer at all
OT, 1T when a plate with the same thickness as the test piece is inserted, and depending on the bending method up to 5T, the T value is used to judge which rusting did not occur. Here, 30 samples were tested, and when all were better than 1T, ◯ was evaluated, when 2T was mixed, Δ was evaluated, and when 3T was mixed, × was evaluated.

鉄溶出試験は、果実やジュースなどの缶内容物による
腐食の耐性を調べるもので、供試材にエポキシ系缶内塗
料を20μｍ塗り、205℃で10分間焼き付けた後、クエン
酸1.5％と食塩1.5％含む水溶液に、38℃で96時間浸漬
し、この浸漬液に溶出した鉄の量を測定した。The iron elution test examines the resistance to corrosion by the contents of cans such as fruits and juice. After coating the test material with 20 μm of epoxy-based paint inside the can and baking at 205 ° C for 10 minutes, use 1.5% citric acid and salt. It was immersed in a 1.5% aqueous solution at 38 ° C. for 96 hours, and the amount of iron eluted in this immersion liquid was measured.

塗膜下耐食性試験としては、UCC試験とブリスター試
験とを行い、両試験のうち悪い方の結果で塗膜下耐食性
を評価した。UCC試験では、鉄溶出試験と同様に缶内塗
料を焼き付けたのち、塗膜にナイフで十字に下地に達す
る傷を付け、これを鉄溶出試験と同じ条件で浸漬した
後、傷の周囲の劣化状況を観察した。劣化の状況は、塗
膜めくれ状況、素地の腐食状況を目視観察し、腐食が認
められない状態を○、腐食が若干認められるが実用に耐
える状態を△、一見して腐食が認められ状態を×で評価
した。As the under-coating corrosion resistance test, a UCC test and a blister test were performed, and the worse result of both tests was used to evaluate the under-coating corrosion resistance. In the UCC test, as in the iron elution test, the paint in the can is baked, and then the coating is scratched with a knife to reach the base in a cross shape, and after soaking it under the same conditions as in the iron elution test, the surroundings of the scratch are deteriorated. I observed the situation. The deterioration is visually observed by observing the coating turn-up condition and the corrosion condition of the substrate. ○ is a condition where no corrosion is observed, Δ is a condition in which some corrosion is observed but is acceptable for practical use, and is a condition where corrosion is recognized at a glance. It evaluated by x.

ブリスターでは、鉄溶出試験と同様に缶内塗膜を焼き
付けた試片を、先ず、0.1％食塩中で120℃に加温し、2k
g/cm²の加圧下に1.5時間曝す。この後更に、0.1％の食
塩水に38℃で96時間浸漬し、塗膜の劣化状況を観察す
る。観察は、塗膜にふくれの発生している部分の面積が
全体に占める率を判定する。率が５％未満を○、５〜20
％を△、20％を越えた場合を×で評価した。In the blister, the test piece on which the coating film inside the can was baked as in the iron elution test was first heated to 120 ° C in 0.1% sodium chloride and
Expose under pressure of g / cm ² for 1.5 hours. After that, it is further immersed in 0.1% saline solution at 38 ° C. for 96 hours, and the deterioration state of the coating film is observed. In the observation, the ratio of the area of the part where the coating film is blistered to the whole is judged. A rate of less than 5% is ○, 5 to 20
% Was evaluated as Δ, and when more than 20% was evaluated as x.

Ｔピール試験では、缶用のエポキシフェノール樹脂を
50mg/m²塗布し、205℃で10分間焼き付けた後、5mm幅の
試験片となし、この試験片２枚の塗装面をナイロンフィ
ルムを接着媒体として熱圧着した後、20mm/分の速度で
引き剥がし、塗膜の付着強度を測定した。In the T-peel test, epoxy phenolic resin for cans
After applying 50 mg / m ² and baking at 205 ° C for 10 minutes, a test piece with a width of 5 mm was prepared. The coated surfaces of these two test pieces were thermocompression bonded with a nylon film as an adhesive medium, and then at a speed of 20 mm / min. It was peeled off and the adhesion strength of the coating film was measured.

溶接性は同種の材料同士の接触電気抵抗を測定するこ
とで評価した。試験片を二枚重ねて直径5mmの銅電極間
に挿み込み、4000kg/cm²の圧力下で通電し、このときの
通電電流と試験片間の電位差とから接触抵抗を求めた。Weldability was evaluated by measuring the contact electrical resistance between materials of the same type. ^Two test pieces were stacked and inserted between copper electrodes having a diameter of 5 mm, and current was applied under a pressure of 4000 kg / cm ² , and the contact resistance was determined from the current supplied and the potential difference between the test pieces.

なお、Cr熱拡散層の形成については、試験No.1、２で
はCrめっきを施して700℃で20秒間の熱処理を行い、試
験No.3、10及び11ではCr・Fe合金めっきを施して530℃
で１時間の熱処理を行い、試験No.4、12及び13ではCrを
めっきした後Feめっきを施して670℃で50秒間の熱処理
を行い、並びに、試験No.5ではCrをめっきした後Cr・Fe
合金めっきを施して430℃で10時間の熱処理を行った。
又、クロメート処理は試験No.1〜４、10及び11について
はクロメート処理Ａの条件で、試験No.5、12及び13につ
いてはクロメート処理Ｂの条件で行い、試験No.14〜16
についてはクロメート処理Ａの陰極処理条件で行った。Regarding the formation of the Cr thermal diffusion layer, in Test Nos. 1 and 2, Cr plating was performed and heat treatment was performed at 700 ° C. for 20 seconds, and in Test Nos. 3, 10 and 11, Cr / Fe alloy plating was performed. 530 ° C
1 hour heat treatment. In Test Nos. 4, 12 and 13, Cr plating, then Fe plating, heat treatment at 670 ° C for 50 seconds, and in Test No. 5 Cr plating, then Cr・ Fe
Alloy plating was performed and heat treatment was performed at 430 ° C. for 10 hours.
Chromate treatment was performed under the conditions of chromate treatment A for Test Nos. 1 to 4, 10 and 11, and under the conditions of chromate treatment B for Test Nos. 5, 12 and 13, and test Nos. 14 to 16
Was performed under the cathode treatment condition of chromate treatment A.

なお、突起数については、20万倍の走査型電子顕微鏡
を用いて、一枚の試験片につき10箇所を測定しその平均
値を求めた。Regarding the number of protrusions, a scanning electron microscope with a magnification of 200,000 was used to measure 10 points on one test piece, and the average value was obtained.

供試材及び試験の結果を第２表に示す。 Table 2 shows the test materials and the test results.

実施例では、全項目で満足な結果が得られた。 In the example, satisfactory results were obtained for all items.

これに対して、比較例では、Snめっき量の少ない試験
No.10及びCrめっき量の少ない試験No.11ではＴピール試
験以外の項目で劣り、Crめっき量が極端に多い試験No.1
2では、接触抵抗が大きい。又、クロメート層中の金属C
rが少なく突起数の少ない試験No.13では、塗膜の付着性
が悪く塗膜下耐食性に劣り、溶接性にも劣る。陽極電解
を行わなかった試験No.14では、突起数が少なく溶接性
に劣る。 On the other hand, in the comparative example, a test with a small amount of Sn plating
No. 10 and test No. 11 with a small amount of Cr plating are inferior in items other than the T-peel test, and test No. 1 with an extremely large amount of Cr plating
In 2, the contact resistance is high. Also, the metal C in the chromate layer
In Test No. 13 with a small number of r and a small number of protrusions, the adhesion of the coating film was poor, the corrosion resistance under the coating film was poor, and the weldability was also poor. In Test No. 14 in which anodic electrolysis was not performed, the number of protrusions was small and the weldability was poor.

従来例では、熱拡散層がCrであっても、Cr・Niであって
も、陽極電解を行っていないので、溶接性に劣る。In the conventional example, even if the thermal diffusion layer is Cr or Cr / Ni, anodic electrolysis is not performed, and thus the weldability is poor.

［発明の効果］ 以上のように、この発明によればCr熱拡散層の上にSn
めっき層が存在し、その上を多数の突起を持つクロメー
ト層が覆う被膜構造となっている。このため、Snが大幅
に節減されているにもかかわらず、溶接性を始め缶用鋼
板としての諸特性を満たすことができた。このように、
性能に優れ且つ省資源を実現したこの発明の効果は大き
いと言わざるを得ない。As described above, according to the present invention, Sn is deposited on the Cr thermal diffusion layer.
There is a plating layer, and a chromate layer having a large number of protrusions covers the plating layer to form a coating structure. Therefore, despite the significant reduction in Sn, it was possible to satisfy various properties as a steel sheet for cans, including weldability. in this way,
It must be said that the effect of the present invention, which has excellent performance and saves resources, is great.

【図面の簡単な説明】[Brief description of drawings]

第１図はこの発明の原理を説明するための突起数と接触
抵抗との関係を示す図である。FIG. 1 is a diagram showing the relationship between the number of protrusions and contact resistance for explaining the principle of the present invention.

Claims (2)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】鋼板の表面がCr換算で0.02g/m²以上0.2g/m
²以下の付着量のCr熱拡散層で覆われ、この熱拡散層の
上に付着量0.05g/m²以上1.0g/m²以下のSnめっき層を有
し、このSnめっき層の上に金属Cr量が3mg/m²以上30mg/m
²以下で且つ１μm²当たり10個以上の突起を有し、該突
起部とその他の部分で厚みの異なるクロメート層を有す
ることを特徴とする缶用極薄Snめっき鋼板。1. The surface of the steel sheet is 0.02 g / m ² or more in terms of Cr and 0.2 g / m ^2.
Covered with Cr heat diffusion layer ² below the adhesion amount, has a coating weight 0.05 g / m ² or more 1.0 g / m ² or less of the Sn-plated layer on the thermal diffusion layer, on the Sn plated layer Metal Cr content is 3 mg / m ² or more 30 mg / m
An ultra-thin Sn-plated steel sheet for a can, which has ² or less and 10 or more protrusions per 1 μm ² , and has a chromate layer having different thicknesses in the protrusions and other portions. 【請求項２】鋼板の表層にCr熱拡散層を生成し、調質圧
延を行った後、付着量0.05g/m²以上1.0g/m²以下のSnめ
っきを施し、その後、クロメート処理液中で電流密度5A
/dm²以上30A/dm²以下で0.3秒以上0.5秒以下の陽極処理
に引き続いて陰極処理を行い、突起を形成するとともに
金属Cr量が3mg/m²以上30mg/m²以下のクロメート層を生
成することを特徴とする缶用極薄Snめっき鋼板の製造方
法。2. A generates Cr thermal diffusion layer in the surface layer of the steel sheet, after the temper rolling, coating weight 0.05 g / m ² or more 1.0 g / m ² subjected to the following Sn plating, then a chromate treatment liquid Current density in 5A
/ dm ² or more and 30 A / dm ² or less, followed by anodizing for 0.3 seconds or more and 0.5 seconds or less, followed by cathodic treatment to form protrusions and a chromate layer with a metal Cr content of 3 mg / m ² or more and 30 mg / m ² or less. A method for producing an ultra-thin Sn-plated steel sheet for cans, which is characterized by the generation.