JPS6348959B2 - - Google Patents

Description

【発明の詳細な説明】[Detailed description of the invention]

本発明は、加工性、耐衝撃性にすぐれた亜鉛−
ニツケル電気合金めつき鋼板に関するものであ
る。 従来、鋼板の耐食性向上のための金属めつきと
して、亜鉛めつきが広く一般に行われてきた。亜
鉛めつきは溶融めつきあるいは電気めつきによつ
て処理され、その製品は広範な分野で数多くの用
途に使用されている。しかし、亜鉛めつきは亜鉛
の犠牲防食によつて鋼板の腐食を防止するもので
あり、耐食性は亜鉛の付着量に依存する。すなわ
ち、高耐食性を得ようとすれば亜鉛付着量を増加
しなければならず、その場合、必要亜鉛量の増加
によるコストアツプあるいは溶接性の低下など、
いくつかの問題を避けることができない。 近年、耐食寿命向上のための自動車車体への防
錆用めつき鋼板の適用の拡大にともない、少ない
めつき付着量で耐食性の良好なめつきが改めて
種々検討されている。このような中で、亜鉛−ニ
ツケル合金電気めつきが、ニツケル含有率約10〜
16％のγ単相の領域で耐食性に優れ、同じ目付量
の亜鉛めつきに比べ数倍の耐食性を示すことか
ら、既に実用の域を拡大しつつある。しかし、亜
鉛−ニツケル合金めつきは、耐食性の優れるNi
含有率10〜16％においてはめつき層の内部応力が
大きく、硬度もHvで約300〜600と極めて硬く脆
い。このため、プレスなどの加工や塗装後に石は
ね等によつて衝撃を受けると、めつき皮膜に大き
い亀裂を生じたり、めつき剥離が起り易い。この
ような亀裂やめつき剥離を生じた部分は、当然の
ことながら耐食性も劣化する。 本発明はこの問題点を解決し、加工性、耐衝撃
性に優れた亜鉛−ニツケル合金電気めつき鋼板を
得ることを目的とする。 本発明によれば、鋼板の少なくとも片面に５
ｇ／m²以上の亜鉛−ニツケル合金めつき層を有
し、かつそのめつき層のNi含有率が鋼板界面で
は７％以下、めつき表面では10〜16％であり、鋼
板界面からめつき表面に向つてニツケル含有率を
少なくとも４層に漸増させることにより、上記目
的を達成することができる。 以下に本発明による方法の具体的効果、適正範
囲等につき詳細に説明する。第１ａ図は亜鉛−ニ
ツケル合金めつき鋼板のめつき層のNi含有率と
硬度の関係を示したものである。また、第１ｂ図
はそれぞれNi含有率の異なる目付量20ｇ／m²の
亜鉛−ニツケルめつき鋼板に、カチオン電着塗装
（20μ）を行つた後、デユポン衝撃試験（1/2″、
500ｇ、50cm）を行い、セロテープでめつき剥離
の有無を調べた結果である。これらの図から、
Ni含有率の上昇とともにめつき層の硬度は大幅
に上昇し、それに伴つてめつき皮膜の耐衝撃性が
劣化することがわかる。また、第１ｂ図からNi
含有率が７％以下の場合に耐衝撃性が優れている
ことがわかる。第１ｂ図の実験に用いたのと同じ
鋼板をエリクセン加工し、表面を電子顕微鏡観察
したところ、めつき層中Ni含有率が低くなると
めつき層の亀裂が明らかに少なくなることが認め
られた。従つて、Ni含有率の低下による耐衝撃
性、加工性の向上は、めつき層の硬度の低下、延
性の増大に起因するものと判断される。 一方、亜鉛−ニツケル合金めつきの耐食性は
Ni含有率が10〜16％の時に最も優れていること
が知られている。すなわち、Ni含有率が10％未
満ではη＋μの、また16％を超えるとα＋γの、
いずれも２相析出となり、２相間で局部電池を形
成するので耐食性が劣化するといわれている。従
つて、いかに加工性、耐衝撃性が良好であつて
も、Ni含有率が７％未満の亜鉛−ニツケル合金
めつきは耐食性が劣るので、耐食材料としての利
用価値は少ないと思われる。 本発明者等は、以上の事実に基づき、加工性、
耐衝撃性および耐食性のいずれも満足する亜鉛−
ニツケル合金めつき鋼板について検討した結果、
めつき層中のNi含有率が鋼板界面では７％以下、
めつき表面では10〜16％であり、鋼板界面からめ
つき表面に向つてNi含有率を少くとも４層に漸
増させることによつて、本目的を達成できること
を見出したものである。 鋼板界面側を低いNi含有率にするのは、加工
性、耐衝撃性を確保するためであり、この部分の
Ni含有率が７％を超えると加工性、耐衝撃性が
劣化する。また、めつき表面側のNi含有率を10
〜16％としたのは耐食性を確保するためであり、
この範囲以外のNi含有率では前述したく如く十
分な耐食性が得られない。 めつき層中のNi含有率を少くとも４層に漸増
させる理由は、これによりNi含有率の低いめつ
き層の耐食性劣化が起こらず、全体としてNi10
〜16％の耐食性を維持するからである。この理由
は不明であるが、例えば、めつき層がNi含有率
の異なる２層あるいは３層のような単純な階段構
造とした場合には、加工部の耐食性は十分でな
い。これは、加工によつて生じためつき層の亀裂
がその境界に到達た時に、電位の差に基づくめつ
き層内の腐食反応が激しくなり、耐食性を悪くす
るものと考えられる。Ni含有率が連続的に変化
していることによつて、２相間の局部電池の形成
はなくなるし、表面層で形成された保護皮膜が常
に効果的に働くものと考えられる。なお、工業的
に本発明のZn−Ni合金めつき鋼板を製造する場
合、後述するように多数のめつき槽を配置し、順
次Ni含有率が高くなるように各槽の条件を設定
し、めつきするが、めつき層中のNi含有率を４
層以上の漸増層にしておけば、確実に本発明の目
的を達することがわかつた。さらに２層めつきで
の問題として、例えば下地に亜鉛−ニツケル合金
より卑な金属をめつきするという考えがあるが、
亜鉛などを下地めつきした場合には、腐食環境に
よつては下地層の腐食が激しく、上層を剥離する
現象があるので好ましくない。 なお、めつき目付量は５ｇ／m²以上必要であ
り、これ未満の場合は耐食性が不十分である。 次に、本発明のNi含有率が鋼板界面からめつ
き表面にかけて連続的に増加する亜鉛−ニツケル
合金電気めつき鋼板の製造方法につき説明する。 本発明において用いる鋼材の種類等は限定され
ず、常法に従つて脱脂、酸洗、水洗などの前処理
を行なう。これらの前処理に続いて順次Ni含有
率が上昇していくようにZn−Ni合金めつき処理
をする。その一つの方法は、多数のめつき槽を配
置し、そのめつき槽中のNiモル濃度（Ni²⁺／
Ni²⁺＋Zn²⁺、モル濃度百分率）が順次高くなる
ように設定して、めつきを行うものである。めつ
き方式としては、水平式、縦型式、ラジアルセル
式などの既知の方式を適用できる。めつき浴とし
ては、硫酸塩浴、塩化物浴またはこれらの混合浴
などが用いられ、硫酸塩浴では例えば、Niモル
濃度10〜80％、PH１〜４、浴温40〜70℃、電流密
度５〜150A／ｄm²、液流速５〜150ｍ／minの条
件でめつきされる。また、塩化物浴では例えば、
Niモル濃度10〜60％、PH２〜４、浴温40〜70℃、
電流密度５〜200A／ｄm²、液流速５〜150ｍ／
minの条件でめつきされる。さらに硫酸塩と塩化
物の混合浴でも、Niモル濃度10〜80％でめつき
条件は上記硫酸塩浴や塩化物浴とほぼ同様な条件
でめつきすることができる。いずれの場合におい
ても、めつき層のNi含有率が、鋼板界面では７
％以下、めつき表面では10〜16％となるように、
鋼板界面からめつき表面に向つてNi含有率が少
くとも４層に漸増するように、任意の条件を選択
することができる。 上述しためつき方法は、各めつき槽の浴組成を
個別に管理しなければならず、そのため装置費、
作業費の増大を招くという問題がある。そこで、
本発明においては、以下に述べる他の方法により
Ni含有率がめつき表面にかけて逓増するNi−Zn
合金めつき鋼板を製造することもできる。第２図
は、硫酸ニツケルおよび硫酸亜鉛を主成分とする
めつき浴で、鋼板に目付量20ｇ／m²の亜鉛−ニツ
ケル合金めつきを行つた場合の、電流密度とめつ
き層中のNi含有率を示したものである。この図
から、めつき層中のNi含有率は電流密度と明ら
かな相関を示し、電流密度を低くすることにより
Ni含有率を容易に下げうることがわかる。従つ
て、複数のめつき槽を用いて亜鉛−ニツケル合金
めつき処理するに当り、各めつき槽の電流密度を
順次高くしていけば良いことが判つた。上述した
処から明らかなように、初期にめつきを行うめつ
き槽の電流密度はNi含有率が７％以下になるよ
う設定し、めつき表面層を形成するめつき槽の電
流密度はNi含有率が10〜16％となるよう設定す
る必要がある。めつき条件等は最初に述べためつ
き方法とほぼ同様で良い。 以下、本発明を、浴濃度を変えてめつきを行う
場合の好適実施例および比較例を挙げて説明す
る。 実施例 １ 脱脂、酸洗、水洗等の前処理を行つた0.8mm厚
のSPCC鋼板に、10槽からなるめつき槽を用い、
下記条件でZn−Ni合金めつきを施した。 (1) めつき浴： The present invention is a zinc-based material with excellent workability and impact resistance.
This relates to nickel electric alloy plated steel sheets. Conventionally, zinc plating has been widely used as a metal plating to improve the corrosion resistance of steel sheets. Galvanizing is done by hot dipping or electroplating, and the products are used in many applications in a wide range of fields. However, galvanizing prevents corrosion of steel sheets through sacrificial corrosion protection of zinc, and corrosion resistance depends on the amount of zinc deposited. In other words, in order to obtain high corrosion resistance, it is necessary to increase the amount of zinc deposited, and in this case, the increase in the required amount of zinc will increase costs or reduce weldability.
Some problems cannot be avoided. In recent years, with the expansion of the application of anti-rust galvanized steel sheets to automobile bodies to extend their corrosion-resistant lifespan, various types of plating with good corrosion resistance with a small amount of plating have been investigated. Under these circumstances, zinc-nickel alloy electroplating has a nickel content of about 10~10%.
It has excellent corrosion resistance in the 16% γ single phase region, and is several times more corrosion resistant than zinc plating with the same basis weight, so it is already expanding its range of practical applications. However, zinc-nickel alloy plating uses Ni, which has excellent corrosion resistance.
At a content of 10 to 16%, the internal stress of the plating layer is large, and the hardness is approximately 300 to 600 Hv, making it extremely hard and brittle. For this reason, if the plated film is subjected to impact from stone splashes or the like after processing such as pressing or painting, large cracks may occur in the plated film or peeling of the plated layer may easily occur. Naturally, corrosion resistance deteriorates in areas where such cracks and peeling occur. The object of the present invention is to solve this problem and obtain a zinc-nickel alloy electroplated steel sheet with excellent workability and impact resistance. According to the present invention, at least one side of the steel plate has 5
It has a zinc-nickel alloy plating layer of g/ ^m2 or more, and the Ni content of the plating layer is 7% or less at the steel plate interface and 10 to 16% on the plated surface, and the Ni content of the plated layer is 7% or less at the steel plate interface and 10 to 16% on the plated surface. The above object can be achieved by gradually increasing the nickel content to at least four layers. The specific effects, appropriate range, etc. of the method according to the present invention will be explained in detail below. Figure 1a shows the relationship between the Ni content and hardness of the plating layer of a zinc-nickel alloy plated steel sheet. Figure 1b shows zinc-nickel plated steel sheets with different Ni content and area weight of 20g/m ² after cationic electrodeposition coating (20μ) and Dupont impact test (1/2'',
500g, 50cm) and examined the presence or absence of plating peeling using cellophane tape. From these figures,
It can be seen that as the Ni content increases, the hardness of the plating layer increases significantly, and the impact resistance of the plating film deteriorates accordingly. Also, from Figure 1b, Ni
It can be seen that impact resistance is excellent when the content is 7% or less. When the same steel plate used in the experiment shown in Figure 1b was subjected to Erichsen processing and the surface was observed using an electron microscope, it was found that as the Ni content in the plating layer decreased, the number of cracks in the plating layer clearly decreased. . Therefore, it is considered that the improvement in impact resistance and workability due to the decrease in Ni content is due to the decrease in hardness and increase in ductility of the plated layer. On the other hand, the corrosion resistance of zinc-nickel alloy plating is
It is known that the best performance is achieved when the Ni content is 10 to 16%. In other words, when the Ni content is less than 10%, η + μ, and when it exceeds 16%, α + γ,
In both cases, two-phase precipitation occurs, forming a local battery between the two phases, which is said to deteriorate corrosion resistance. Therefore, no matter how good the workability and impact resistance are, zinc-nickel alloy plating with a Ni content of less than 7% has poor corrosion resistance and is therefore considered to have little utility as a corrosion-resistant material. Based on the above facts, the present inventors have determined that processability,
Zinc satisfies both impact resistance and corrosion resistance.
As a result of studying nickel alloy plated steel sheets,
The Ni content in the plating layer is 7% or less at the steel plate interface.
The Ni content is 10 to 16% on the plated surface, and it has been found that this objective can be achieved by gradually increasing the Ni content to at least four layers from the steel plate interface toward the plated surface. The purpose of lowering the Ni content on the steel plate interface side is to ensure workability and impact resistance.
When the Ni content exceeds 7%, workability and impact resistance deteriorate. In addition, the Ni content on the plated surface side was increased to 10
The reason for setting it to ~16% is to ensure corrosion resistance.
If the Ni content is outside this range, sufficient corrosion resistance cannot be obtained as described above. The reason why the Ni content in the plating layer is gradually increased to at least 4 layers is that this prevents the corrosion resistance of the plating layer with a low Ni content from deteriorating, and the overall Ni10
This is because it maintains ~16% corrosion resistance. Although the reason for this is unknown, for example, when the plating layer has a simple step structure such as two or three layers with different Ni contents, the corrosion resistance of the processed part is not sufficient. This is thought to be due to the fact that when the cracks in the plating layer caused by processing reach their boundaries, the corrosion reaction within the plating layer becomes intense due to the difference in potential, resulting in poor corrosion resistance. It is believed that the continuous change in Ni content eliminates the formation of local batteries between the two phases, and that the protective film formed in the surface layer always works effectively. In addition, when manufacturing the Zn-Ni alloy plated steel sheet of the present invention industrially, a large number of plating tanks are arranged as described later, and the conditions of each tank are set so that the Ni content increases sequentially. When plating, the Ni content in the plating layer is set to 4.
It has been found that the object of the present invention can be certainly achieved by increasing the number of layers. Furthermore, there is a problem with two-layer plating, for example, the idea of plating a base metal with a base metal than a zinc-nickel alloy.
If the base layer is plated with zinc or the like, the base layer may be severely corroded depending on the corrosive environment, and the upper layer may peel off, which is not preferable. The plating weight should be 5 g/m ² or more, and if it is less than this, the corrosion resistance will be insufficient. Next, a method of manufacturing a zinc-nickel alloy electroplated steel sheet according to the present invention in which the Ni content increases continuously from the steel sheet interface to the plating surface will be explained. The type of steel used in the present invention is not limited, and pretreatments such as degreasing, pickling, and water washing are performed according to conventional methods. Following these pre-treatments, a Zn--Ni alloy plating treatment is performed so that the Ni content increases sequentially. One method is to arrange a large number of plating tanks and adjust the Ni molar concentration (Ni ²⁺ /
Ni ²⁺ + Zn ²⁺ , molar concentration percentage) is set to increase sequentially, and plating is performed. As a plating method, known methods such as a horizontal method, a vertical method, and a radial cell method can be applied. As the plating bath, a sulfate bath, a chloride bath, or a mixed bath thereof is used. For example, a sulfate bath has a Ni molar concentration of 10 to 80%, a pH of 1 to 4, a bath temperature of 40 to 70°C, and a current density. Plating is carried out under conditions of 5 to 150 A/dm ² and a liquid flow rate of 5 to 150 m/min. Also, in chloride baths, e.g.
Ni molar concentration 10-60%, PH2-4, bath temperature 40-70℃,
Current density 5-200A/ ^dm2 , liquid flow rate 5-150m/
Plated with min condition. Further, even in a mixed bath of sulfate and chloride, plating can be carried out at a Ni molar concentration of 10 to 80% under almost the same conditions as the sulfate bath and chloride bath. In either case, the Ni content in the plating layer was 7.
% or less, and 10 to 16% on the plated surface.
Any conditions can be selected so that the Ni content gradually increases to at least four layers from the steel plate interface toward the plated surface. In the above-mentioned plating method, the bath composition of each plating tank must be managed individually, which reduces equipment costs,
There is a problem in that the work cost increases. Therefore,
In the present invention, other methods described below are used.
Ni-Zn whose Ni content increases gradually towards the plated surface
It is also possible to produce alloy plated steel sheets. Figure 2 shows the current density and Ni content in the plating layer when zinc-nickel alloy plating with a basis weight of 20 g/m ² is applied to a steel plate using a plating bath mainly composed of nickel sulfate and zinc sulfate. This is what is shown. From this figure, the Ni content in the plating layer shows a clear correlation with the current density, and by lowering the current density,
It can be seen that the Ni content can be easily lowered. Therefore, it has been found that when plating a zinc-nickel alloy using a plurality of plating tanks, it is sufficient to sequentially increase the current density in each plating tank. As is clear from the above, the current density of the plating bath that initially performs plating is set so that the Ni content is 7% or less, and the current density of the plating bath that forms the plating surface layer is set so that the Ni content is 7% or less. It is necessary to set the rate to be between 10 and 16%. The plating conditions etc. may be almost the same as the plating method described at the beginning. The present invention will be described below with reference to preferred examples and comparative examples in which plating is performed with varying bath concentrations. Example 1 A plating tank consisting of 10 tanks was used to coat a 0.8 mm thick SPCC steel plate that had been pretreated by degreasing, pickling, water washing, etc.
Zn-Ni alloy plating was performed under the following conditions. (1) Glazing bath:

【表】 なお、いずれの槽にもNa₂SO₄を40ｇ／添
加し、浴PHは1.8、浴温は60℃で一定とした。 (2) 電流密度：80A／ｄm² (3) 液流速：70ｍ／min (4) めつき付着量：20ｇ／m² （各槽で２ｇ／m²ずつ析出） (5) めつき層中のNi含有率：第１槽で析出した
めつき層は７％、第８槽以降で析出しためつき
層は13％であり、その間は、鋼板界面およびめ
つき表面を含み少なくとも４層に漸増して分布
していた。 上記めつき条件で得られた亜鉛−ニツケル合金
めつき鋼板を、エリクセン７mm加工およびデユポ
ン衝撃試験（1/2″、1000ｇ、50cm）に供し、この
加工部の耐食性を塩水噴霧試験（JIS Ｚ 2371）
によつて調べた。また、アニオン電着塗装20μ、
カチオン電着塗装20μおよびカチオン電着塗装＋
中塗り＋上塗りの３コート（全膜厚120μ）をそ
れぞれ行つた後、デユポン衝撃試験（1/2″、500
ｇ、50cm）および石はね試験（大理石約３ｇ／個
を300個、10秒間５Kg／cm²の圧力であてる）に供
し、試験部分のめつき剥離の有無をセロテープ剥
離テストによつて調べた。これらの結果は、他の
実施例および比較例の場合とともに第１表に示
す。 実施例 ２ 実施例１と同様にして、下記の条件でZn−Ni
合金めつきを施した。 (1) めつき浴：[Table] In addition, 40 g of Na ₂ SO ₄ was added to each bath, and the bath pH was kept constant at 1.8 and the bath temperature at 60°C. (2) Current density: 80A/dm ² (3) Liquid flow rate: 70 m/min (4) Plating deposition amount: 20 g/m ² (2 g/m ² deposited in each tank) (5) Ni content: The deposited layer precipitated in the first tank is 7%, and the deposited layer deposited in the eighth tank and onwards is 13%.In between, it gradually increases to at least 4 layers, including the steel plate interface and the plated surface. It was distributed as follows. The zinc-nickel alloy plated steel sheet obtained under the above plating conditions was subjected to Erichsen 7mm processing and Dupont impact test (1/2", 1000g, 50cm), and the corrosion resistance of this processed part was evaluated by salt spray test (JIS Z 2371). )
It was investigated by. In addition, anion electrodeposition coating 20μ,
Cationic electrodeposition coating 20μ and cationic electrodeposition coating +
After applying 3 coats (intermediate coat + top coat) (total film thickness 120μ), the Dupont impact test (1/2″, 500
g, 50 cm) and a stone splash test (applying 300 pieces of marble, approximately 3 g/piece, with a pressure of 5 kg/cm ² for 10 seconds), and the presence or absence of peeling of the plating on the test area was examined using a Sellotape peel test. . These results are shown in Table 1 along with other Examples and Comparative Examples. Example 2 In the same manner as in Example 1, Zn-Ni was prepared under the following conditions.
Alloy plating was applied. (1) Glazing bath:

【表】 なお、いずれの槽にもNa₂SO₄を40ｇ／添
加し、浴PHは3.0、浴温は50℃で一定とした。 (2) 電流密度：120A／ｄm² (3) 液流速：80ｍ／min (4) めつき付着量：20ｇ／m² （各槽で２ｇ／m²ずつ析出） (5) めつき層中のNi含有率：第１槽で析出した
めつき層は５％、第８槽以降のめつき槽で析出
しためつき層は12％であり、その間は、鋼板界
面およびめつき表面を含み少なくとも４層に漸
増して析出していた。 実施例 ３ 実施例１と同様にして下記の条件でZn−Ni合
金めつきを施した。 (1) めつき浴：[Table] In addition, 40 g of Na ₂ SO ₄ was added to each bath, the bath pH was kept constant at 3.0, and the bath temperature was kept constant at 50°C. (2) Current density: 120A/dm ² (3) Liquid flow rate: 80 m/min (4) Plating deposition amount: 20 g/m ² (2 g/m ² deposited in each tank) (5) Ni content: The deposited layer precipitated in the first tank is 5%, and the deposited layer deposited in the plating tanks after the eighth tank is 12%. It was precipitated gradually in layers. Example 3 Zn--Ni alloy plating was performed in the same manner as in Example 1 under the following conditions. (1) Glazing bath:

【表】 なお、いずれの槽にもNa₂SO₄を40ｇ／添
加し、また浴PHは1.8、浴温は55℃で一定とし
た。 (2) 電流密度：60A／ｄm² (3) 液流速：70ｍ／min (4) めつき付着量：20ｇ／m² （各槽で２ｇ／m²ずつ析出） (5) めつき層中のNi含有率：第１槽で析出した
めつき層は４％、第８槽以降で析出しためつき
層は11％であり、その間は、鋼板界面およびめ
つき表面を含み少なくとも４層に漸増して分布
していた。 比較例 １ ２槽からなるめつき槽を用い、実施例１と同じ
鋼板に下記の条件でZn−Ni合金めつきを施した。 (1) めつき浴：[Table] In addition, 40 g of Na ₂ SO ₄ was added to each bath, and the bath pH was kept constant at 1.8 and the bath temperature at 55°C. (2) Current density: 60A/dm ² (3) Liquid flow rate: 70 m/min (4) Plating amount: 20 g/m ² (2 g/m ² deposited in each tank) (5) Ni content: The deposited layer precipitated in the first tank is 4%, and the deposited layer deposited in the eighth tank and later is 11%, and gradually increases to at least 4 layers including the steel plate interface and the plated surface. It was distributed as follows. Comparative Example 1 Zn-Ni alloy plating was applied to the same steel plate as in Example 1 under the following conditions using a plating tank consisting of two tanks. (1) Glazing bath:

【表】 なお、いずれの槽にもNa₂SO₄を40ｇ／添
加し、浴PHは4.0、浴温は55℃で一定とした。 (2) 電流密度：80A／ｄm² (3) 液流速：70ｍ／min (4) めつき付着量：20ｇ／m² （各槽で10ｇ／m²ずつ析出） (5) めつき層中のNi含有率：第１槽で析出した
めつき層は７％、第２槽で析出しためつき層は
13％であつた。 比較例 ２ 実施例１と同じ鋼板に１槽のめつき槽で下記条
件でZn−Ni合金めつきを施した。 (1) めつき浴：NiSO₄・6H₂O300ｇ／、
ZnSO₄・7H₂O190ｇ／、Na₂SO₄40ｇ／、
Niモル濃度63.3％、PH1.8、浴温55℃ (2) 電流密度：80A／ｄm² (3) 液流速：70ｍ／min (4) めつき付着量：20ｇ／m² (5) めつき層中のNi含有率：13％ さらに、本発明を電流密度を変えてめつきを行
う場合の好適実施例および比較例を挙げ、このよ
うにして得られたZn−Ni合金めつき鋼板を実施
例１に記載した種々の試験に供し、その結果をま
とめて第２表に示した。 実施例 ４ 10槽からなるめつき槽を用い、実施例１と同じ
鋼板に下記条件でZn−Ni合金めつきを施した。 (1) めつき浴：NiSO₄・6H₂O300ｇ／、
ZnSO₄・7H₂O190ｇ／、Na₂SO₄40ｇ／、
Niモル濃度63.3％、浴PH1.8、浴温60℃ (2) 電流密度（Ａ／ｄm²）： 第１槽 20 第６槽 60 第２槽 20 第７槽 70 第３槽 30 第８槽 80 第４槽 40 第９槽 90 第５槽 50 第10槽 90 (3) 液流速：70ｍ／min (4) めつき付着量：20ｇ／m² （各槽で２ｇ／m²ずつ析出） (5) めつき層中のNi含有率：第１、２槽で析出
しためつき層は５％、第９槽以降で析出しため
つき層は13％であり、その間は、鋼板界面およ
びめつき表面を含み少なくとも４層に漸増して
分布していた。 実施例 ５ 実施例４と同じめつき槽で、電流密度以外は実
施例４と同じ条件でZn−Ni合金めつきを施した。 (1) 電流密度（Ａ／ｄm²）： 第１槽 30 第６槽 45 第２槽 30 第７槽 50 第３槽 30 第８槽 60 第４槽 35 第９槽 70 第５槽 40 第10槽 70 (2) めつき層中のNi含有率：第１〜３槽で析出
しためつき層は６％、第９、10槽で析出しため
つき層は11％であり、その間は、鋼板界面およ
びめつき表面を含み少なくとも４層に漸増して
分布していた。 実施例 ６ 実施例４と同様にして下記条件でZn−Ni合金
めつきを施した。 (1) めつき浴：NiCl₂・6H₂O200ｇ／、
ZnCl₂170ｇ／、Niモル濃度40.2％、浴PH3.0、
浴温50℃ (2) 電流密度（Ａ／ｄm²）： 第１槽 30 第６槽 90 第２槽 30 第７槽 105 第３槽 45 第８槽 120 第４槽 60 第９槽 120 第５槽 75 第10槽 120 (3) 液流速：80ｍ／min (4) めつき付着量：20ｇ／m² (5) めつき層中Ni含有率：第１、２槽で析出し
ためつき層は５％、第８槽以降で析出しためつ
き層は12％であり、その間は、鋼板界面および
めつき表面を含み少なくとも４層に漸増して分
布していた。 比較例 ３ 実施例１と同じ鋼板に１槽のめつき槽で下記条
件でZn−Ni合金めつきを施した。 (1) めつき浴：NiSO₄・6H₂O300ｇ／、
ZnSO₄・7H₂O190ｇ／、Na₂SO₄40ｇ／、
Niモル濃度63.3％、浴PH1.8、浴温55℃ (2) 電流密度：90A／ｄm² (3) 液流速：70ｍ／min (4) めつき付着量：20ｇ／m² (5) めつき層中のNi含有率：13％ これらの結果をまとめて示した第１表および第
２表から、本発明によるZn−Ni合金めつき鋼板
が加工後も良好な耐食性を示し、かつ塗装後の耐
衝撃性にも優れていることが明らかである。従つ
て、自動車用鋼板のように、プレス、ベンドなど
の厳しい加工を受け、塗装後も石はね等による衝
撃を受ける可能性のある部所に使用される表面処
理鋼材として極めて有望である。なお、本発明は
実施例で示したような鋼板以外に各種の鋼板に適
用しても優れた効果を発揮するのは勿論のことで
ある。[Table] In addition, 40 g of Na ₂ SO ₄ was added to each bath, the bath pH was kept constant at 4.0, and the bath temperature was kept constant at 55°C. (2) Current density: 80A/dm ² (3) Liquid flow rate: 70 m/min (4) Plating deposition amount: 20 g/m ² (10 g/m ² deposited in each tank) (5) Ni content: 7% for the deposited layer precipitated in the first tank, and 7% for the deposited layer deposited in the second tank.
It was 13%. Comparative Example 2 Zn-Ni alloy plating was applied to the same steel plate as in Example 1 in one plating tank under the following conditions. (1) Plating bath: NiSO ₄・6H ₂ O 300g/,
ZnSO ₄・7H ₂ O 190g/, Na ₂ SO ₄ 40g/,
Ni molar concentration 63.3%, PH1.8, bath temperature 55℃ (2) Current density: 80A/dm ² (3) Liquid flow rate: 70m/min (4) Plating deposition amount: 20g/m ² (5) Plating Ni content in layer: 13% Furthermore, preferred examples and comparative examples are given in which the present invention is plated by changing the current density, and the Zn-Ni alloy plated steel sheets obtained in this way are implemented. It was subjected to the various tests described in Example 1, and the results are summarized in Table 2. Example 4 Using a plating tank consisting of 10 tanks, Zn-Ni alloy plating was applied to the same steel plate as in Example 1 under the following conditions. (1) Plating bath: NiSO ₄・6H ₂ O 300g/,
ZnSO ₄・7H ₂ O 190g/, Na ₂ SO ₄ 40g/,
Ni molar concentration 63.3%, bath pH 1.8, bath temperature 60℃ (2) Current density (A/dm ² ): 1st tank 20 6th tank 60 2nd tank 20 7th tank 70 3rd tank 30 8th tank 80 4th tank 40 9th tank 90 5th tank 50 10th tank 90 (3) Liquid flow rate: 70m/min (4) Plating deposition amount: 20g/m ² (2g/m ² deposited in each tank) ( 5) Ni content in the plating layer: The plating layer precipitated in the 1st and 2nd tanks is 5%, and the plating layer precipitated in the 9th tank and onward is 13%. It was distributed in at least four layers, including the surface. Example 5 Zn--Ni alloy plating was performed in the same plating tank as in Example 4 under the same conditions as in Example 4 except for the current density. (1) Current density (A/ ^dm2 ): 1st tank 30 6th tank 45 2nd tank 30 7th tank 50 3rd tank 30 8th tank 60 4th tank 35 9th tank 70 5th tank 40 10th tank Tank 70 (2) Ni content in the plating layer: The plating layer precipitated in the 1st to 3rd tanks is 6%, and the plating layer precipitated in the 9th and 10th tanks is 11%. It was gradually distributed in at least four layers, including the interface and the plated surface. Example 6 Zn-Ni alloy plating was performed in the same manner as in Example 4 under the following conditions. (1) Plating bath: NiCl ₂ 6H ₂ O 200g/,
ZnCl ₂ 170g/, Ni molar concentration 40.2%, bath PH3.0,
Bath temperature 50℃ (2) Current density (A/dm ² ): 1st tank 30 6th tank 90 2nd tank 30 7th tank 105 3rd tank 45 8th tank 120 4th tank 60 9th tank 120 5th tank Tank 75 Tank 10 120 (3) Liquid flow rate: 80 m/min (4) Plating amount: 20 g/m ² (5) Ni content in the plating layer: The plating layer precipitated in the 1st and 2nd tanks 5%, and 12% of the plating layer precipitated from the 8th tank onwards, and the distribution gradually increased to at least 4 layers including the steel plate interface and the plating surface. Comparative Example 3 Zn-Ni alloy plating was applied to the same steel plate as in Example 1 in one plating tank under the following conditions. (1) Plating bath: NiSO ₄・6H ₂ O 300g/,
ZnSO ₄・7H ₂ O 190g/, Na ₂ SO ₄ 40g/,
Ni molar concentration 63.3%, bath pH 1.8, bath temperature 55℃ (2) Current density: 90A/dm ² (3) Liquid flow rate: 70m/min (4) Plating deposition amount: 20g/m ² (5) Me Ni content in the coating layer: 13% From Tables 1 and 2, which summarize these results, it can be seen that the Zn-Ni alloy plated steel sheet according to the present invention shows good corrosion resistance even after processing, and shows good corrosion resistance after painting. It is clear that it also has excellent impact resistance. Therefore, it is extremely promising as a surface-treated steel material for use in parts such as automotive steel sheets that undergo severe processing such as pressing and bending, and may be exposed to impact from stone chips and the like even after painting. It goes without saying that the present invention exhibits excellent effects even when applied to various steel plates other than those shown in the examples.

【表】【table】

【表】【table】 【図面の簡単な説明】[Brief explanation of the drawing]

第１図はめつき層中Ni含有率とめつき層硬度
との関係(a)およびめつき層中Ni含有率と耐衝撃
性との関係(b)を示すグラフ、第２図は電流密度と
めつき層中Ni含有率との関係を示すグラフであ
る。 Figure 1 is a graph showing the relationship between the Ni content in the plating layer and the hardness of the plating layer (a) and the relationship between the Ni content in the plating layer and impact resistance (b), and Figure 2 is a graph showing the relationship between the current density and the hardness of the plating layer. It is a graph showing the relationship with the Ni content in the layer.

Claims (1)

【特許請求の範囲】[Claims] １ 鋼板の少なくとも片面に５ｇ／m²以上の亜鉛
−ニツケル合金めつき層を有し、かつそのめつき
層のNi含有率が鋼板界面では７％以下、めつき
表面では10〜16％であり、鋼板界面からめつき表
面に向つてニツケル含有率が少なくとも４層に漸
増していることを特徴とする加工性、耐衝撃性に
すぐれた亜鉛−ニツケル合金めつき鋼板。1 At least one side of the steel plate has a zinc-nickel alloy plating layer of 5 g/m ² or more, and the Ni content of the plating layer is 7% or less at the steel plate interface and 10 to 16% on the plated surface. A zinc-nickel alloy plated steel plate having excellent workability and impact resistance, characterized in that the nickel content gradually increases to at least four layers from the steel plate interface toward the plated surface.