【発明の詳細な説明】
（産業上の利用分野）
本発明は、自動車、家電、鋼製家具、什器等の防錆鋼板
としての使用に好適な耐食性に優れた合金化処理溶融亜
鉛めっき鋼板に関する．（従来の技術）
溶融亜鉛めっき後に熱拡散処理されためっき鋼板、いわ
ゆる合金化処理溶融亜鉛めっき鋼板（以下、合金化溶融
亜鉛めっき＊Ｆｉという）は、塗装後耐食性、熔接性等
に比較的優れた防錆鋼板であるので、自動車をはじめ各
種の産業分野で広く利用されている．ところが、近年、
各種分野における腐食環境が益々厳しくなる傾向にあり
、それに伴い防錆能向上の要求が高まり、より耐食性に
優れた製品が望まれている．
従来から非合金化の溶融亜鉛めっき鋼板については、Ｎ
ｉＳＦｅＳＣｏ，等の各種元素を添加して耐食性を改善
する試みは種々行われているが、合金化溶融亜鉛めっき
鋼板については性能および作業性等に問題があるので、
今までに戒功した事例はほとんどない．例えば、溶融亜
鉛めっき鯛板については、特開昭５６−４１３５８号公
報に亜鉛中に加えるＡＩ２を適度に設定して、Ｍｇ，
Ｍｎを加える試みが開示され、また、特開昭５６ −
１ ２３３５９号公報には？ｌｇを添加して合金化処理
する方法が開示されている．しかし、これらの元素を亜
鉛浴中に添加すると次に述べるような問題が発生する．
？ち、Ｍ．は合金化溶融亜鉛めっき皮膜の耐食性向上に
効果があるものの、めっき浴の酸化が著しくなるという
問題がある．例えば、Ｎ，雰囲気中で熔融めっきしても
微量の０■、ＨｔＯによって浴面の酸化が発生する．さ
らにはＭｇの添加は大量の亜鉛蒸気を放散させるという
問題もある．この対策としては、めっき浴中のＡｌを増
量するのが有効である．例えば、浴中のＡＣ４度を０．
３重景％以上にすると浴の酸化や亜鉛の放散を抑制する
ことができる．しかし、Ａｌを多くすると合金化処理速
度が著しく低下し、インラインでの合金化処理が困難と
なるなど実用的でなくなる．
？Ｉｎも耐食性の向上に効果があるものの、Ｍｎを含む
めっき皮膜は脱亜鉛による耐食性の急速な低下が腐食環
境により生じる場合がある．また、Ｍｎは０．３重量％
未満までは合金化処理速度を大きく遅延化させるが、０
．４重量％を超えると逆に著しく促進させる．このＭｎ
の比界濃度は厳密には＾ｌ濃度によって異なる．従って
、Ｍｎ含有量の少ないものは合金化がしにくく、多いも
のは合金化速度が異常に促進され、その結果めっき層の
加工性が低下するという問題がある．
ＭｎおよびＭｇを複合添加すると、基本的に耐食性が向
上するものの、？’ｌｇによる浴面酸化、Ｍｎ添加によ
る合金化速度の過剰増大によるめっき皮膜の加工性低下
は避けらない．さらには鋼板からのＦｅの溶出によるド
ロスの発生が著しくなって、操業性が大きく低下する．
以上要するに、従来公知の事例においては操業性が著し
く低下したり、めっき皮膜の加工性が著しく劣る等の問
題があるので、これらの合金元素を含有する合金化溶融
亜鉛めっき鋼板は実用化に至っていないのが実状である
。Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an alloyed hot-dip galvanized steel sheet with excellent corrosion resistance and suitable for use as a rust-proof steel sheet for automobiles, home appliances, steel furniture, fixtures, etc. ．． (Prior art) Galvanized steel sheets subjected to heat diffusion treatment after hot-dip galvanizing, so-called alloyed hot-dip galvanized steel sheets (hereinafter referred to as alloyed hot-dip galvanized *Fi), have relatively excellent post-painting corrosion resistance, weldability, etc. As it is a rust-proof steel plate, it is widely used in various industrial fields including automobiles. However, in recent years,
Corrosive environments in various fields are becoming more and more severe, and as a result, there is a growing demand for improved anti-rust performance, and products with even better corrosion resistance are desired. Conventionally, for non-alloyed hot-dip galvanized steel sheets, N
Various attempts have been made to improve corrosion resistance by adding various elements such as iSFeSCo, but there are problems with performance and workability for alloyed hot-dip galvanized steel sheets.
To date, there have been very few cases of precepts. For example, regarding hot-dip galvanized sea bream plates, Japanese Patent Application Laid-Open No. 56-41358 discloses that AI2 added to zinc is set appropriately, and Mg,
An attempt to add Mn was disclosed;
1 What about Publication No. 23359? A method for alloying by adding lg is disclosed. However, when these elements are added to a zinc bath, the following problems occur. ? T-M. Although this method is effective in improving the corrosion resistance of alloyed hot-dip galvanized coatings, it has the problem of significant oxidation of the plating bath. For example, even if melt plating is performed in an atmosphere of N, oxidation of the bath surface occurs due to trace amounts of O and HtO. Furthermore, there is also the problem that the addition of Mg releases a large amount of zinc vapor. As a countermeasure to this problem, it is effective to increase the amount of Al in the plating bath. For example, set the AC4 degree in the bath to 0.
When the concentration is 3% or higher, oxidation of the bath and zinc dissipation can be suppressed. However, if the amount of Al is increased, the alloying processing speed will drop significantly, making in-line alloying processing difficult and thus impractical. ? Although In is also effective in improving corrosion resistance, a plating film containing Mn may experience a rapid decrease in corrosion resistance due to dezincing in a corrosive environment. In addition, Mn is 0.3% by weight
If it is less than 0, the alloying processing speed will be greatly delayed;
．． On the contrary, if it exceeds 4% by weight, it will be significantly accelerated. This Mn
Strictly speaking, the specific field concentration of differs depending on the ^l concentration. Therefore, if the Mn content is low, alloying is difficult, and if the Mn content is high, the alloying rate is abnormally accelerated, resulting in a problem that the workability of the plating layer is reduced. Adding Mn and Mg in combination basically improves corrosion resistance, but? Deterioration of workability of the plating film due to bath surface oxidation due to lg and excessive increase in alloying rate due to Mn addition is unavoidable. Furthermore, the production of dross due to the elution of Fe from the steel plate becomes significant, and the operability is greatly reduced. In summary, in the conventionally known cases, there are problems such as a marked decrease in operability and a markedly poor workability of the plating film, so alloyed hot-dip galvanized steel sheets containing these alloying elements have not been put into practical use. The reality is that there is none.
（発明が解決しようとする諜Ｂ）
本発明のｔｌＫ題は、上記Ｍｇおよび’ｆｌｎ添加にお
ける問題点を解消した操業性のよい耐食性に優れた合金
化溶融亜鉛めっき鋼板を提供することにある．〈課題を
解決するための手段〉
前掲のＭｇは耐食性の向上に有効な元素である．しかし
、めっき浴が酸化するという問題があるので、従来では
多量に添加することができなかった．しかし、本発明者
らは、下記の手段をとることで上記！Ｉａが達或される
ことを見出したー■ＭＨの大量添加による浴の酸化はＡ
ｆｆｉ濃度を高くすることで対処する．
■Ａｌの高濃度化による合金化速度低下をＭｎ添加によ
り対処する．
■Ｍｎの過剰な合金化促進作用にはＳ１添加によって対
処する．
上記■〜■の手段をとることで多量の？Ｉｇの添加が可
能となって、陶とＭｎの相乗効果により高耐食性が得ら
れ、しかも浴の酸化もなく、適正な合金化速度が達成さ
れるのである．
本発明は、上記知見を基に完成したものであって、その
要旨は「溶融めっき後、合金化処理されためっき鋼板で
あって、該めっき鋼板の皮膜中のＦｅは７〜１７重景％
で、このＰｅを除く他の成分が下記のとおりである合金
化溶融亜鉛めっき鋼板」にある．
ｌｊ２：Ｏ。３〜２。４重堡％、
ＰＩｇ：ｏ．ｓ〜２重量％、
門ｎ：ｏ．４〜０．８重量％、
Ｓｉ ： ０．００５〜０．３重量％、Ｚｎおよび不
可避不純物：残部．
上記本発明の合金化溶融亜鉛めっき鋼板は、例えば、下
記の方法で製造することができる．＾１！７０．１８〜
２．４重量％、Ｍｇ ： ０．５〜２重量％、旧： ０
．３８〜０．７５重量％、Ｓｔ ： ０．００５〜０．
３重量％を含有し、残部が亜鉛及び不可避不純物からな
るめっき浴に、通常の前処理を施した鋼板を浸漬して溶
融めっきを施し、次いで、付着量を調整した後、４５０
〜６００”Ｃの温度で合金化処理する方法。(Intelligence B to be Solved by the Invention) The object of the present invention is to provide an alloyed hot-dip galvanized steel sheet with good operability and excellent corrosion resistance, which solves the above-mentioned problems with the addition of Mg and 'fln. <Means for solving the problem> Mg mentioned above is an element effective in improving corrosion resistance. However, because of the problem of oxidation of the plating bath, it was not possible to add large amounts in the past. However, the inventors solved the above problem by taking the following steps. Ia was found to be achieved - oxidation of the bath by adding a large amount of MH was A.
This can be dealt with by increasing the ffi concentration. ■Address the decrease in alloying speed due to high Al concentration by adding Mn. ■The excessive alloying promoting effect of Mn can be countered by adding S1. Can you get a large amount by taking the above steps ■～■? By making it possible to add Ig, high corrosion resistance can be obtained due to the synergistic effect of porcelain and Mn, and an appropriate alloying rate can be achieved without oxidation of the bath. The present invention was completed based on the above knowledge, and the gist thereof is ``a plated steel sheet that has been subjected to an alloying treatment after hot-dipping, wherein the Fe content in the coating of the plated steel sheet is 7 to 17%.
The other components other than this Pe are as follows: Alloyed hot-dip galvanized steel sheet. lj2:O. 3 to 2.4%, PIg:o. s ~ 2% by weight, gate n: o. 4 to 0.8% by weight, Si: 0.005 to 0.3% by weight, Zn and inevitable impurities: remainder. The above-mentioned alloyed hot-dip galvanized steel sheet of the present invention can be manufactured, for example, by the following method. ^1!70.18～
2.4% by weight, Mg: 0.5-2% by weight, old: 0
．． 38-0.75% by weight, St: 0.005-0.
3% by weight, with the remainder consisting of zinc and unavoidable impurities, a steel plate that has been subjected to normal pretreatment is immersed for hot-dip plating, and then, after adjusting the coating amount, 450%
A method of alloying at a temperature of ~600"C.
なお、浴中のＡｊ！，Ｍｎの含有量がめつき層中の含有
量と若干異なるのは、めっき時に形威される拡散層中に
４１、旧の濃化を生じるためである．（作用）
以下、本発明の合金化熔融亜鉛めっき鋼板の皮膜組成を
前記のように限定する理由について説明する．
Ｆｅ：７〜１７重量％
めっき層中のＦｅは合金化処理することによって母材と
めっき皮膜との相互拡散により流入するものである．め
っき層中のＦｅが７重量％未満では未合金化亜鉛がかな
り残留するため、溶接性、塗装後耐食性が低下する．一
方、１７重量％を超えるとめっき皮膜の犠牲防食性が低
下し、特に塗装後の疵付部での耐孔あき性等の耐食性が
低下する．＾Ｚ：Ｏ．３〜２．４重景％、
＾ｌは過剰な合金化反応の抑制とＭｇの多量添加による
めっき浴面の酸化防止を目的として添加される．皮膜中
のＡｌ含有量が０．３重景％未満では浴面酸化抑止の効
果が乏しいので、Ｍｇの大量添加には耐えられない．一
方、２．４％を超えると合金化を促進するＭｎの添加が
あっても合金化がかなり抑制されるため合金化速度が小
さくなる．更に、合金化層中にＦｅＺｎベースの合金相
以外にＦｅＡｌ系ベースの合金相が共存し、局部電池を
形威して耐食性を低下させるので、ｉは０．３〜２．４
重量％の含有量とする．
ＰＩｇ ： ０．５〜２重置％、
陶は本発明では耐食性向上のための基本添加元素である
．皮膜中の含有量が０．５重量％未満では耐食性向上効
果に乏しい．高耐食性を確保するためには、Ｍ．を多く
含ませる方が有利であるが、２重量％を超えて含ませる
と合金化反応が抑制されるため、上限は２重量％とする
．
旧二〇．４〜０．８重量％、
ＭｎはＭ．と一緒に添加されて耐食性を高める効果があ
るが、本発明ではＭｎは寧ろＡ１の高濃度化による合金
化の遅延を防止するために添加する， Ｍｎは合金化処
理において特異な挙動を示す元素であり、濃度が低い場
合は合金化を抑制し、高濃度では合金化を促進（むしろ
過剰促進）する， Ｍｎ含有量が０．４重量％より少な
いと合金化促進作用がなく、Ａｌと共に合金化反応を抑
制する．従って、Ａｌを０．３重量％以上含有する本発
明の合金化熔融亜鉛めっき鋼板では、Ｍｎは少なくとも
０．４重景％以上含有させる必要がある．しかし、０．
８重量％を超えて含有させるとＭｎの浴面酸化促進作用
が現れるので、上限は０．８重量％とする．
Ｓｉ ： ０．００５〜０．３重量％
Ｓｉも本発明では不可欠な元素であり、Ｍｎの合金化促
進効果、特に過剰な促進を抑制して適正な合金化速度に
調整する作用がある．しかし、皮膜中の含有量がｏ．ｏ
ｏｓ重量％より少ないと、Ｓｉの合金化速度調整効果が
小さいので、Ｍｎの過剰な合金化を抑えることができな
い．一方、０．３重量％を超えて含有されると合金化の
抑制が過剰となる他に、不メ、ツキ点が現れる等の悪影
響がある．本発明の合金化溶融亜鉛めっき鋼板は、その
めっき皮膜が以上説明した成分を含み、残りがＺｎおよ
び不可避不純物からなる．不純物としてはｐｂ、Ｓｎ，
Ｃｄ等の低融点金属があるが、これらの不純物は可及
的に少ない方が望ましく、総量で１００ｐｐｍ以下に押
えるのがよい．
以下、実施例により本発明を更に説明する．（実施例）
重量％で、Ｃ：０．０３％、Ｓｉ ： ０．０１％、Ｍ
ｎ ： ０．２３％、Ｐ ： ０．００８％、ｓ ：
ｏ．ｏｏｓ％、Ｓｏｌ．Ａｉ ：０．２８％を含む、板
！０．７６一一のアルミキルド鋼板（未焼鈍材）を使用
し、この鋼板から幅０．７６−■×長さ２５〇一の供試
材を切り出し、有ｌ！溶剤で洗浄した後、竪型の熔融め
っきシξユレーターで、７４０゜Ｃの温度に６０秒間、
２６％Ｈｚ＋Ｎｘ混合ガス雰囲気中で焼鈍してから、浴
温か４６５℃の第１表に示す組威のめっき浴に３秒浸漬
し、溶融めっきを施した．次いで、ｔ４Ｍガスでワイピ
ングして付着量を６０１／ｓ”に調整した後、５００℃
の温度で合金化処理を行った．合金化処理後の試料は、
ＪＩＳ Ｚ ２８６７に準じる塩水噴霧試験に供し、赤
錆発生に至るまでの経過時間を測定し、耐食性を評価し
た．
この結果を第１表に、めっき浴組威、めっき皮膜組戒、
合金化所要時間とともに示す．なお、合金化所要時間は
別途実験によって測定したものであり、第１表の皮ｉ組
戒の合金化状態が達戒できる時間を示すものではない．
即ち、第１表における合金化所要時間とはＦｅ含有量が
８．５重量％となる時間である．
第１表に示すとおり、本発明例の合金化溶融亜鉛めっき
鋼板はいずれも合金化所要時間が短く、且つ耐食性が非
常に優れる．これに対して、比較例の合金化溶融亜鉛め
っき鋼板は、合金化に長時間を必要とするか、耐食性に
劣る．特に、比較例の階２、磁３、狙４はめっき時の浴
面の酸化が著し＜、Ｓｔ雰囲気中でも酸化物ドロスの浮
遊が顕著に認められた．
なお、弘８及び阻１７の比較例はめっき時の合金化反応
が非常に速く、このものについてはめっき時の付着量が
１００ｇ／ｍ”を超え、実用的なめっき付￥Ｉ！水準に
ワイピングできなかったので、第１表に示す合金化所要
時間は、別途厚目付の試料により測定した参考値である
．
（発明の効果）
以上説明した如く、本発明の合金化溶融亜鉛めっき鋼板
は耐食性に優れている．そして、この合金化溶融亜鉛め
っきｗ４板は、めっき浴の酸化や合金化速度の低下を招
くことなく製造することができる．In addition, Aj in the bath! The reason why the content of Mn is slightly different from that in the plating layer is that 41 and prior concentration occurs in the diffusion layer formed during plating. (Function) The reason why the coating composition of the alloyed hot-dip galvanized steel sheet of the present invention is limited as described above will be explained below. Fe: 7 to 17% by weight Fe in the plating layer flows through mutual diffusion between the base material and the plating film during alloying treatment. If the Fe content in the plating layer is less than 7% by weight, a considerable amount of unalloyed zinc remains, resulting in poor weldability and post-painting corrosion resistance. On the other hand, if it exceeds 17% by weight, the sacrificial corrosion resistance of the plating film decreases, particularly the corrosion resistance such as pitting resistance in the scratched area after painting. ^Z:O. 3 to 2.4%, ^l is added for the purpose of suppressing excessive alloying reactions and preventing oxidation of the plating bath surface by adding a large amount of Mg. If the Al content in the film is less than 0.3%, the effect of inhibiting bath surface oxidation is poor, and the addition of a large amount of Mg cannot be tolerated. On the other hand, when it exceeds 2.4%, alloying is considerably suppressed even with the addition of Mn, which promotes alloying, and the alloying rate decreases. Furthermore, in addition to the FeZn-based alloy phase, a FeAl-based alloy phase coexists in the alloyed layer, forming a local battery and reducing corrosion resistance, so i is 0.3 to 2.4.
The content is expressed as % by weight. PIg: 0.5 to 2%, ceramic is a basic additive element for improving corrosion resistance in the present invention. If the content in the film is less than 0.5% by weight, the effect of improving corrosion resistance is poor. In order to ensure high corrosion resistance, M. Although it is more advantageous to include more than 2% by weight, the alloying reaction will be suppressed if the content exceeds 2% by weight, so the upper limit is set at 2% by weight. Old twenty. 4 to 0.8% by weight, Mn is M. However, in the present invention, Mn is added to prevent delay in alloying due to high concentration of A1. Mn is an element that exhibits peculiar behavior during alloying treatment. When the concentration is low, alloying is suppressed, and when the concentration is high, alloying is promoted (or rather, excessively promoted).If the Mn content is less than 0.4% by weight, there is no effect of promoting alloying, and it is alloyed with Al. Suppresses chemical reaction. Therefore, in the alloyed galvanized steel sheet of the present invention containing 0.3% by weight or more of Al, it is necessary to contain at least 0.4% by weight or more of Mn. However, 0.
If the Mn content exceeds 8% by weight, Mn will promote bath surface oxidation, so the upper limit is set at 0.8% by weight. Si: 0.005 to 0.3% by weight Si is also an essential element in the present invention, and has the effect of accelerating Mn alloying, particularly suppressing excessive acceleration and adjusting the alloying rate to an appropriate level. However, the content in the film is o. o
If it is less than os weight %, the effect of adjusting the alloying rate of Si is small, so that excessive alloying of Mn cannot be suppressed. On the other hand, if the content exceeds 0.3% by weight, not only will alloying be excessively suppressed, but there will also be adverse effects such as the appearance of defects and sticking points. In the alloyed hot-dip galvanized steel sheet of the present invention, the plating film contains the above-described components, with the remainder consisting of Zn and inevitable impurities. Impurities include pb, Sn,
Although there are low melting point metals such as Cd, it is desirable that these impurities be as small as possible, and the total amount should be kept to 100 ppm or less. The present invention will be further explained below with reference to Examples. (Example) In weight%, C: 0.03%, Si: 0.01%, M
n: 0.23%, P: 0.008%, s:
o. oos%, Sol. Board containing Ai: 0.28%! A 0.76 mm aluminum killed steel plate (unannealed material) was used, and a test material with a width of 0.76 mm and a length of 25 mm was cut out from this steel plate. After cleaning with a solvent, it was heated to a temperature of 740°C for 60 seconds using a vertical melt plating simulator.
After annealing in a 26% Hz + Nx mixed gas atmosphere, it was immersed for 3 seconds in a plating bath with a bath temperature of 465°C and a composition shown in Table 1 to perform hot-dip plating. Next, after adjusting the adhesion amount to 601/s by wiping with t4M gas, 500°C
Alloying treatment was performed at a temperature of . The sample after alloying treatment is
The specimens were subjected to a salt spray test in accordance with JIS Z 2867, and the elapsed time until red rust appeared was measured to evaluate corrosion resistance. The results are shown in Table 1, plating bath composition, plating film composition,
It is shown along with the time required for alloying. Note that the time required for alloying was measured separately through experiments, and does not indicate the time required for the alloying state of the skin i-group precepts in Table 1 to reach the precepts.
That is, the required time for alloying in Table 1 is the time required for the Fe content to reach 8.5% by weight. As shown in Table 1, all of the alloyed hot-dip galvanized steel sheets of the present invention require a short alloying time and have excellent corrosion resistance. On the other hand, the alloyed hot-dip galvanized steel sheet of the comparative example requires a long time for alloying or has poor corrosion resistance. In particular, in Comparative Examples Floor 2, Magnetic 3, and Ani 4, the bath surface was significantly oxidized during plating, and floating oxide dross was observed significantly even in the St atmosphere. In addition, the alloying reaction during plating is very fast in the comparative examples of Ko 8 and Ii 17, and the coating weight exceeds 100 g/m'' during plating, making it possible to wipe to a practical plating ￥I! level. Therefore, the required alloying time shown in Table 1 is a reference value measured separately using a thick sample. (Effect of the invention) As explained above, the alloyed hot-dip galvanized steel sheet of the present invention has excellent corrosion resistance. This alloyed hot-dip galvanized W4 sheet can be manufactured without oxidizing the plating bath or reducing the alloying rate.