JPS5989791A - Method for modifying surface characteristic of cold rolled steel sheet - Google Patents

Abstract

PURPOSE:To prevent additive elements for improving the mechanical property of a cold- rolled steel sheet from thickening on the surface of said sheet to form an oxidized film and from deteriorating the surface characteristic by plating iron contg. a specific amt. of oxygen on the surface of said sheet prior to recrystallization annealing. CONSTITUTION:Elements such as Al, Si, Mn or the like are added to a cold-rolled steel sheet to be used for an automobile or the like in order to improve the mechanical property thereof. When such steel sheet is subjected to recrystallization annealing, these elements thicken on the surface of the steel sheet and form an oxidized film thus deteriorating the surface characteristic such as phosphatizability and paintability. The steel sheet is subjected to a plating treatment at a high current density in an electrolyte contg. a water soluble iron compd. whereby an iron plating layer contg. >=5,000ppm oxygen is formed on the surface thereof to 0.01-2.0mum thickness prior to the recrystallization annealing in order to prevent the above-mentioned deterioration. The Al, Si, Mn, etc. form fine Al2O3, SiO2, MnO, etc. with the O2 in the iron plating layer in the stage of recrystallization annealing thereby preventing the deteriorating in the surface characteristic occuring in the formation of said oxidized film.

Description

【発明の詳細な説明】 この発明は、冷間圧延鋼板（銅帯を含み、以下冷延鋼板
という）の表面性状改質方法に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for modifying the surface properties of cold rolled steel sheets (including copper strips, hereinafter referred to as cold rolled steel sheets).

冷延鋼板は、自動車や家庭電機製品など広い用途に用い
られる、最も一般的な鋼材の一つであるが、近年自動車
用鋼板の分野では車体の軽量化あるいは安全性の向上を
目的として、高張力を有する冷延鋼板の開発が推進され
、高強度と高加工性を兼備する材料を得るための成分設
計、製造プロセスの検討に多くの勢力が注がれている。Cold-rolled steel sheet is one of the most common steel materials used in a wide range of applications such as automobiles and home appliances.In recent years, however, in the field of automotive steel sheets, high-quality steel sheets have been developed to reduce the weight of car bodies and improve safety. The development of cold-rolled steel sheets with high tensile strength is being promoted, and much effort is being focused on studying component design and manufacturing processes in order to obtain materials that have both high strength and high workability.

また軟鋼板においても、鋼中の窒素や炭素をＡｔ　、　
Ｎｂなどの添加元素にて固定することにより、加工性の
一層の向上がはかられている。Also, in mild steel plates, nitrogen and carbon in the steel are replaced by At,
By fixing with an additive element such as Nb, workability is further improved.

しかしこのような冷延鋼板の機械的性質改良を目的とし
て使用される添加元素の中には、焼鈍時に鋼板表面に濃
化して酸化皮膜な形成し、冷延鋼板の重要な特性の一つ
である表面性状、すなわちりん酸塩化成処理性や塗装性
その他外観（テンパーカラー〕などを損うものが少なく
ない。However, some of the additive elements used for the purpose of improving the mechanical properties of cold-rolled steel sheets concentrate on the steel sheet surface during annealing and form an oxide film, which is one of the important properties of cold-rolled steel sheets. Many of them impair certain surface properties, such as phosphate conversion treatment properties, paintability, and appearance (temper color).

このような作用は、酸素との親和力の大きいＡｔＩ・・
Ｂｉ、　ｌ＋［ｎなど、鋼の機械的性質改良に関して重
要な元素でとくに顕著であるため、機械的性質改良のた
めの成分設計においてこの表面性状劣化の問題は、非常
に重大なものと言える。This action is caused by AtI, which has a high affinity for oxygen.
This problem of surface property deterioration can be said to be very serious in component design for improving mechanical properties, as it is particularly noticeable in elements important for improving the mechanical properties of steel, such as Bi and l+[n.

発明者らは、この表面性状劣化の問題を解決するため鋭
意検討を重ねた結果、冷間圧延終了後、再結晶焼鈍に先
立って高濃度の酸素を含有する鉄めっきをあらかじめ鋼
板表面に施しておくことにより、鋼中元素の焼鈍時にお
ける表面への拡散濃化を有効に防止する効果が得られる
ことを知見し、この発明の完成に至ったものである。As a result of intensive studies to solve this problem of surface quality deterioration, the inventors discovered that after cold rolling and prior to recrystallization annealing, iron plating containing a high concentration of oxygen was applied to the surface of the steel sheet in advance. The present invention was completed based on the finding that by keeping the steel in place, it is possible to effectively prevent the elements in the steel from diffusing and concentrating on the surface during annealing.

すなわちこの発明は、熱間圧延、脱スケールおよび冷間
圧延を施した鋼板に、再結晶焼鈍の前工程で、５０００
ｐ１）１１１以上の酸素を含有Ｔる鉄めっきを厚さ０．
０１４ｍ以上、２．０μｍ以下の範囲で施すことをもっ
て冷延鋼板の表面性状改質を有利に達成したものである
。In other words, the present invention provides a hot-rolled, descaled and cold-rolled steel plate that undergoes 5000
p1) Iron plating containing 111 or more oxygen to a thickness of 0.
By applying the coating in a range of 0.14 m or more and 2.0 μm or less, surface property modification of cold rolled steel sheets can be advantageously achieved.

鋼材に鉄めっきを施したのちに加熱処理を加えることに
より表面性状の改質を行った方法として公知のものに、
特公昭５４−２９９７６号公報の開示を見ることができ
るが、この場合鉄めっきを行なったのちに加熱処理を加
えることにより、母材の性状と無関係に鋼材の表面処理
性を一定とすることを目的とするにすぎず、これに従っ
て通常の条件で鉄めっきを施し、もって再結晶焼鈍時の
Ｓｌ、　Ｍｎなどの表面濃化を化成処理性や表面外観に
害のない程度まで減少させるには、鋼中のＳｌやＭｎの
添加量が多い場合において、鉄めっき厚さを２μｍ程度
またはそれ以上とする必要があったので、コストおよび
実施工程を考慮すると工業的に実施することは極めて困
難であった。A well-known method of modifying the surface properties by applying iron plating to steel and then applying heat treatment is
As disclosed in Japanese Patent Publication No. 54-29976, in this case, by applying heat treatment after iron plating, the surface treatment properties of the steel material can be made constant regardless of the properties of the base material. To reduce the surface concentration of Sl, Mn, etc. during recrystallization annealing to a level that does not harm chemical conversion properties or surface appearance, iron plating is performed under normal conditions according to this purpose. When the amount of Sl and Mn added to the steel is large, it is necessary to make the iron plating thickness about 2 μm or more, which is extremely difficult to implement industrially considering the cost and implementation process. Ta.

そこで鉄めっきの条件を植々変化させて表面濃化抑制効
果に及ぼす影響について検討したところ、鉄めっき中に
５０００　ｐｐｍ以上の酸素を含有させるような条件で
鉄めっきを行なうことにより、Ｈｎ。Therefore, we investigated the effect of varying the iron plating conditions on the surface concentration suppression effect, and found that by performing iron plating under conditions that contained 5000 ppm or more of oxygen in the iron plating, Hn.

Ｓｉなどの鋼中元素の表面濃化が著しく抑制されること
が判明した。It has been found that the surface concentration of elements in steel such as Si is significantly suppressed.

すなわちこのような条件で鉄めっきを行なった場合、鋼
中に相当量のＩｎ　、　Ｂ土などが添加さしていても０
．１〜０．５μｍ程度に薄い鉄めっき厚さで焼鈍時の表
面濃化を、十分なレベルまで減少させることが可能とな
る。In other words, when iron plating is carried out under these conditions, even if a considerable amount of In, B soil, etc. are added to the steel, no
．． With iron plating as thin as 1 to 0.5 μm, surface thickening during annealing can be reduced to a sufficient level.

高濃度の酸素を含有する鉄めっきにより再結晶焼鈍時に
おける１４ｎ　、　Ｓｉなどの鋼中元素の表面濃化が強
く抑制されるのは、鉄めっき中でこれらの元素が酸素に
よりトラップされることによる。すなわち、表面への濃
化が問題とされるＭｎ　、　ｓｉ、などの元素は％酸素
との親和力が強くこのため焼鈍時において鋼板表面で選
択的に酸化されることにより表面に濃化するわけである
が、高濃度の酸素を含む鉄めっきが焼鈍の前工程で施さ
れた場合、焼鈍過程においてこの鉄めっき中の酸素がｌ
ｄｎ、Ｓｉなどと結びついて鉄めっき層中に微細なＭｎ
　−？　ｓｉの酸化物を形成することにより、これらの
元素が表面まで拡散してくるの企有効に防ぐのである。The reason why iron plating containing a high concentration of oxygen strongly suppresses the surface concentration of elements in steel such as 14n and Si during recrystallization annealing is because these elements are trapped by oxygen in iron plating. . In other words, elements such as Mn and Si, whose concentration on the surface is a problem, have a strong affinity for oxygen, so they are selectively oxidized on the surface of the steel sheet during annealing, resulting in concentration on the surface. However, if iron plating containing a high concentration of oxygen is applied in the pre-annealing process, the oxygen in the iron plating will be released during the annealing process.
Fine Mn is combined with dn, Si, etc. in the iron plating layer.
−? Formation of Si oxide effectively prevents these elements from diffusing to the surface.

このような作用を持たせるためには、鉄めっき中の酸素
濃度は高いほど良く、少くとも５０００ｐｐｍの含有量
が必要である。すなわち鉄めっき中の酸素含有量が、５
ｏｏｏｐｐｍ未満では、鋼中元素の表面拡散防止効果に
おいて通常の鉄めっきに比し格別な差が認められない。In order to have such an effect, the higher the oxygen concentration in the iron plating, the better, and the content must be at least 5000 ppm. In other words, the oxygen content in iron plating is 5
At less than oooppm, no particular difference is observed in the effect of preventing surface diffusion of elements in steel compared to ordinary iron plating.

拡散防止効果が大きく、従って必要な鉄めっき厚さを小
さくできる効果を持たせるには５０００　ｐｐｍ以上の
酸素含有量が必要であり、この発明の方法における鉄め
っき中の酸素含有量の下限とする。An oxygen content of 5,000 ppm or more is required to have a large diffusion prevention effect and, therefore, the effect of reducing the required iron plating thickness, and this is the lower limit of the oxygen content in iron plating in the method of this invention. .

鉄めっき中にこのような高濃度の酸素を含有させるため
の条件は、鉄めっき液組成、めっき液温度などにより異
なるが、概して下記のことが言える〇 一般に鉄めっきは硫酸塩、塩化物、はうそ弗化物などを
用いた酸性のめつき液中での陰極電解により実施される
が、このめっき液中でのＨｅ　　イオンは、比較的不安
定であり、めっき液のｐＨ力５上昇すると水酸化物とし
て沈澱析出する傾向（こある０また鉄めっきにおいては
、陰極電流効率をま１００チではなく、陰極では金属Ｆ
ｅの電析反応とともに、Ｈ＋イオンの放電も起り、これ
に伴って陰極面（すなわち被めっき面）近傍でのｐＨ上
昇が起る。The conditions for containing such a high concentration of oxygen in iron plating vary depending on the composition of the iron plating solution, the temperature of the plating solution, etc., but in general, the following can be said. In general, iron plating is free from sulfates, chlorides, and It is carried out by cathodic electrolysis in an acidic plating solution using fluoride, etc., but He ions in this plating solution are relatively unstable, and if the pH of the plating solution increases by 5, it will be oxidized. Also, in iron plating, the cathode current efficiency is not 100%, and the metal F at the cathode tends to precipitate as a metal.
Along with the electrodeposition reaction of e, discharge of H+ ions also occurs, and this causes an increase in pH near the cathode surface (that is, the surface to be plated).

通常の鉄めっきでは、この陰極近傍でのｐＨ上昇により
水酸化鉄の沈澱析出が起るのを防ぐため、電流密度の比
較的低い範囲が採用さｎるカミ、この発明では、上述の
陰極近傍での水酸化鉄の発生を積極的へ木用へへへ鷲匁
水酸化跣曵発龜曝撰極色に利用して、この水酸化鉄の微
細析出物をめっき層中に取り込むことにより、高酸素濃
度の鉄めっきを得るものである。In normal iron plating, a relatively low current density range is adopted in order to prevent precipitation of iron hydroxide due to the pH increase near the cathode. By actively utilizing the generation of iron hydroxide in the wood coating process and incorporating the fine precipitates of iron hydroxide into the plating layer, This produces iron plating with a high oxygen concentration.

このためには、めっきの外観を損ねない範囲で電流密度
をできるだけ高くして鉄めっきを実施すればよい。To this end, iron plating may be carried out at a current density as high as possible within a range that does not impair the appearance of the plating.

表面性状の改質に必要な鉄めっき厚さ＆ま、鋼中の添加
元素の個類および量、再結晶焼鈍条件、鉄めっき中の酸
素含有量などにより異なるが、鉄めっき厚さ０．０１μ
ｍ未満では表面性状改質効果は全く認められないので、
これを鉄めっき厚さの下限とする。The iron plating thickness required to improve the surface properties varies depending on the type and amount of added elements in the steel, recrystallization annealing conditions, oxygen content in the iron plating, etc., but the iron plating thickness is 0.01μ.
If it is less than m, no surface property modification effect is observed.
This is the lower limit of iron plating thickness.

鋼中添加元素量および焼鈍の温度、時間の増大に伴ない
、必要な鉄めっき厚さは増し、また鉄めっき中の酸素含
有量が低いほど厚い鉄めっきを必要とするが、高張力鋼
で、通常使用される数パーセント以下の合金元素量およ
び８５０℃程度以下の焼鈍条件では０．１〜０．５μｍ
程度の鉄めっき厚さで実用上問題のない表面性状が得ら
れる。The required iron plating thickness increases as the amount of added elements in the steel and the annealing temperature and time increase, and the lower the oxygen content in the iron plating, the thicker the iron plating is required. , 0.1 to 0.5 μm under the commonly used alloying element content of several percent or less and annealing conditions of approximately 850°C or less.
A surface quality with no practical problems can be obtained with iron plating thickness of about

鋼中元素量や焼鈍条件がさらに厳しい場合や、表面性状
に対する要求の厳しい場合には、鉄めっき厚さをさらに
増してやｎば良いが、めっき厚さが２．０μｍを超える
と、めっき時の電着応力によると考えられる鉄めっき層
の密着性劣化が起る場合があるため、鉄めっき厚さの上
限は、２．０μｍとする。If the amount of elements in the steel or annealing conditions are more severe, or if the surface quality is more demanding, the thickness of the iron plating may be further increased, but if the plating thickness exceeds 2.0 μm, Since the adhesion of the iron plating layer may deteriorate due to the electrodeposition stress, the upper limit of the iron plating thickness is set to 2.0 μm.

この発明における素材鋼板の化学組成、焼鈍条件などに
は何ら規制を設ける必要はなく、それぞわの条件に応じ
て上記した規制範囲内で鉄めっき厚さ、鉄めっき中の酸
素含有量を適宜変化させることにより、良好な表面性状
を得ることができる。There is no need to set any restrictions on the chemical composition, annealing conditions, etc. of the raw steel sheet in this invention, and the iron plating thickness and oxygen content in the iron plating can be adjusted as appropriate within the above-mentioned regulatory range according to the respective conditions. By changing it, good surface quality can be obtained.

なおこの発明の鉄めっきは、通常の軟鋼板に対して実施
しても何ら弊害を与えないばかりでなく、鋼板表面に露
出している非金属介在物をおおい隠すことによる耐錆性
の向上という副次的な効果も得らｎるものである。The iron plating of the present invention not only does not cause any harmful effects when applied to ordinary mild steel plates, but also improves rust resistance by covering non-metallic inclusions exposed on the steel plate surface. Secondary effects can also be obtained.

この発明の鉄めっきを実施する工程としては、連続焼鈍
方式においては、入側の脱脂設備の後段で連続的に実施
できるよう電気めっき設備を設けることが好ましく、ま
た箱焼鈍方式においても電解洗浄工程設備で連続的に実
施を行うことが好ましい。As for the process of carrying out the iron plating of this invention, in the continuous annealing method, it is preferable to provide electroplating equipment after the degreasing equipment on the entry side, and also in the case of the box annealing method, the electrolytic cleaning step Preferably, the process is carried out continuously in a facility.

この発明では鉄めっき中に酸累を含有させることにより
鉄めっきの厚さを薄くできることが特徴であり、必要な
電気めっき設備もコンパクトなもので良いので、上述の
ようなインラインでの処理が可能となるような設備の設
置は比較的容易であるが、このような設備が設けられな
し１場合にＧま、焼鈍前に別工程で鉄めっきを実施する
方法をとってもかまわない。The feature of this invention is that the thickness of the iron plating can be made thinner by incorporating acid accumulation into the iron plating, and the required electroplating equipment can be compact, so in-line processing as described above is possible. Although it is relatively easy to install such equipment, if such equipment is not provided, a method of performing iron plating in a separate process before annealing may be used.

この発明の鉄めっきは、冷間圧延のままの活性化された
鋼板表面に施されるので、脱月旨後酸洗工程を省略して
実施することも可能であるカタ、脱月旨工程における鋼
板表面の鉄粉などの除去力（不十分であると鉄めっきの
効果が阻害される場合力５あるので、脱脂後に軽い酸洗
処理を実施すること力（望ましい。Since the iron plating of this invention is applied to the activated steel plate surface as it is cold rolled, it is also possible to omit the pickling process after the desaturation process. It is desirable to carry out a light pickling treatment after degreasing, since the removal power of iron powder, etc. from the surface of the steel sheet (if insufficient, the effect of iron plating will be inhibited).

以上述べたように、この発明を実施すること（こより、
冷延鋼板の表面性状の改質カタ可能となる力（、以下こ
の発明の実施例について説明する０実施例１ 表１に示す組成の供試鋼Ａを、スラブ加熱温度１２５０
℃、仕上温度８５０°Ｃ１巻取温度６８０°Ｃの条件で
８．２＝厚さまで熱間圧延したのち、酸洗工程を経て、
冷間圧延により１．２１８厚さとし、以下に示す条件で
鉄めっきを行った０ 表１ （１）脱脂：苛性ソーダ系脱、脂剤 ８０℃においてＩＯＡ／ｄｍ”Ｘ５秒陽極電解（２）酸
洗：２％塩酸水溶液（５０°Ｃ）に２秒浸漬■めつき液
温　　４０〜７０℃ ■陰極電流密度　５〜１００Ａ／ｄゼ このようにして槌々の酸素含有量およびめっき厚さの鉄
めっきを行なったのち、均熱温度８５０℃、均熱時間２
分の焼鈍をＮ、　＋　ｌ　Ｏ％Ｈ２雰Ｆ！！！気（露点
−４０℃）で施し、表面性状（外観および化成処理性）
への影響を調べた。As mentioned above, it is necessary to carry out this invention (from this).
Example 1 Test steel A having the composition shown in Table 1 was heated at a slab heating temperature of 1250
After hot rolling to a thickness of 8.2 at a finishing temperature of 850°C, a winding temperature of 680°C, and a pickling process,
It was cold rolled to a thickness of 1.218 mm and iron plated under the conditions shown below.Table 1 (1) Degreasing: caustic soda degreasing, lubricant IOA/dm" x 5 seconds anodic electrolysis at 80°C (2) Pickling : Immersed in 2% hydrochloric acid aqueous solution (50°C) for 2 seconds ■Plating solution temperature: 40~70℃ ■Cathode current density: 5~100A/dze In this way, the iron plating of the hammer was adjusted to the oxygen content and plating thickness. After that, the soaking temperature was 850℃ and the soaking time was 2.
Minute annealing in N, + l O% H2 atmosphere F! ! ! Surface quality (appearance and chemical conversion treatment properties)
We investigated the impact on

結果を表２に示す。The results are shown in Table 2.

表　　２ ※外観判定基準　　○　テンバカ２−なしム　わずかな
テンパーカラーあり ×　著しいテンパーカラー ※※化成処理性判定基準　○　５ｐｃａと同等ｘ　　５
ｐｃａに劣る 表２より明らかなように、鉄めっき中の酸素量６００お
よび２８００　ｐｐｍでは、表面性状の改質に８μｍの
鉄めっき厚さを必要とするが、鉄めっき中の酸素量を５
０００　ｐｐｍ以上とすることにより、必要な鉄めっき
厚さを０．１μｍと著しく薄くすることが可能となる。Table 2 *Appearance Judgment Criteria ○ Tenbaka 2-Nashimu Slight temper color × Significant temper color ※※Chemical conversion treatment property judgment criteria ○ Equivalent to 5 pca x 5
As is clear from Table 2, when the oxygen content in iron plating is 600 and 2800 ppm, an iron plating thickness of 8 μm is required to improve the surface texture, but when the oxygen content in iron plating is 5 μm,
000 ppm or more, it becomes possible to significantly reduce the necessary iron plating thickness to 0.1 μm.

実施例２ 表８に示す供試鋼Ｂを、スラブ加熱温度１１５０°Ｃ１
仕上温度８５０°Ｃ１巻取り温度６８０°Ｃの条件で厚
さ２．６賭まで熱間圧延し、脱スケールを行ったのち、
９．７ｍ厚さに冷間圧延したものに、実施例１のめっき
液（〜を用いて酸素含有量１５ＢＯＯｐｐｍ鉄めっきを
徳々の厚ざで施し、８００°Ｃ，１分間の焼鈍を行って
表面性状への影響を調べた。Example 2 Test steel B shown in Table 8 was heated at a slab heating temperature of 1150°C1.
After hot rolling to a thickness of 2.6 mm at a finishing temperature of 850°C and a winding temperature of 680°C, and descaling,
On a cold-rolled product having a thickness of 9.7 m, iron plating with an oxygen content of 15 BOOppm was applied using the plating solution of Example 1 (~), and annealing was performed at 800°C for 1 minute. The effect on surface properties was investigated.

表３ 結果を表４に示す。Table 3 The results are shown in Table 4.

表４ ※外観判定基準　　二〇　テンパーカラーなしΔ　わず
かなテンパーカラー ※化成処理性判定基準　二〇　５ＰＯ（３と同等ｘ　　
５ｐａａに劣る ※※※密　着　性　　　　：鉄めつき面な外側として０
７曲げを行ない、めっきの粉状化を判定 表４に示す結果より明かなように、鉄めっき厚さ０．０
１４ｍ未満では表面性状改質効果は全く認められない。Table 4 *Appearance Judgment Criteria 20 No temper color Δ Slight temper color *Chemical treatability judgment criteria 20 5PO (equivalent to 3 x
Inferior to 5paa※※※Adhesion: 0 for the outside iron-plated surface
As is clear from the results shown in Table 4, the iron plating thickness was 0.0.
If the length is less than 14 m, no surface property modification effect is observed at all.

０．０１μｍ以上では外観、化成処理性はいずれも良好
となるが、鉄めっき厚さが２μｍを超えて８μｍ。When the thickness is 0.01 μm or more, the appearance and chemical conversion treatment properties are both good, but the iron plating thickness exceeds 2 μm and is 8 μm.

５μｍの場合には、鉄めっきの密着性不良が認めらｎた
。In the case of 5 μm, poor adhesion of iron plating was observed.

以上、実施例１および２に示したとおり、　５０００ｐ
ｐｍ以上の酸素を含有Ｔる鉄めっきを０．０１μｍ以上
、２．０μｍ以下の範囲で実施することにより、冷延鋼
板の表面性状改質効果が得られる。As shown above in Examples 1 and 2, 5000p
By carrying out iron plating containing oxygen of pm or more in a range of 0.01 μm or more and 2.0 μm or less, the effect of improving the surface properties of cold rolled steel sheets can be obtained.

又、鋼板の防錆被覆として最も一般的な溶融亜鉛めっき
法は、再結晶焼鈍工程を同一ライン内で行なうため生産
性が高く、また容易にめっき付着量を増せるので犠牲防
食性を大きくしやすいという利点があり、アメリカ、カ
ナダなど塩害の著しい地域で自動車用鋼板に多く適用さ
ｎている。また、めっき後加熱処理によりめっき層を素
地鋼と合金化させた、いわゆる合金化溶融亜鉛めっき鋼
板は、さらに塗装性、溶接性にすぐれるという長所があ
り、自動車用表面処理鋼板の主流となりつつある。In addition, the hot-dip galvanizing method, which is the most common method for rust-preventing coating on steel sheets, has high productivity because the recrystallization annealing process is performed on the same line, and the coating weight can be easily increased, increasing sacrificial corrosion protection. It has the advantage of being easy to use, and is often applied to automotive steel sheets in areas where salt damage is severe, such as in the United States and Canada. In addition, so-called alloyed hot-dip galvanized steel sheets, in which the plating layer is alloyed with the base steel through heat treatment after plating, have the additional advantage of excellent paintability and weldability, and are becoming the mainstream of surface-treated steel sheets for automobiles. be.

しかしながら、高張力鋼板に溶融亜鉛めっきを適用しよ
うとする場合、　Ｍｎ　、　ｓｉ　、　（３ｒなど易酸
化性の合金元素を多く含有するとこれらが還元焼鈍工程
で選択的に酸化されることにより鋼板表面に濃化層を形
成して亜鉛めっき密着性を阻害し、ひどい場合には不め
っき発生の原因ともなるｏまた合金化亜鉛めっきでは、
素材成分が合金化反応の挙動に影響を及ぼすことも知ら
れる０ このため、通常の方法で溶融亜鉛めっきを行なうには、
　Ｍｎ　、　Ｂ土などの合金元素の添加量が制限され、
成分設計が著し〜く困難となる０特に昨今、・強度と延
性あるいは成形性のバランスの良い材料が要求され、こ
れに応えるため低温変態相の導入による強化（複合組織
強化）あるいは固溶強化を主体とした成分系にしようと
すると、ａｎ　、　ｓｉなどの添加ｉを多くすることが
必要となり、溶融亜鉛めっき性を阻害する結果となる。However, when hot-dip galvanizing is applied to a high-strength steel sheet, if it contains a large amount of easily oxidizable alloying elements such as Mn, Si, (3R), these will be selectively oxidized in the reduction annealing process, causing damage to the surface of the steel sheet. It forms a concentrated layer that impairs the adhesion of zinc plating, and in severe cases can cause unplatedness. Also, in alloyed zinc plating,
It is also known that material components affect the behavior of alloying reactions. Therefore, in order to carry out hot-dip galvanizing using the normal method,
The amount of alloying elements such as Mn and B soil added is limited,
Especially in recent years, it has become extremely difficult to design components. Materials with a good balance of strength and ductility or formability are required. If an attempt is made to create a component system based on , it is necessary to increase the amount of additives such as an and si, which results in inhibiting hot-dip galvanizing properties.

しかし、溶融亜鉛めっき前の還元焼鈍工程に先立ってこ
の発明ご適用し、あらかじめ鋼板表面に高濃度の酸素を
含有する鉄めっきを施すことにより、焼鈍時における鋼
中元素の表面への拡散濃化を有効に防止し、すぐれた亜
鉛めっき性が得らｎることも確認されている。However, by applying this invention prior to the reduction annealing process before hot-dip galvanizing, and applying iron plating containing high concentration of oxygen to the surface of the steel sheet in advance, the elements in the steel can be diffused and concentrated on the surface during annealing. It has also been confirmed that this method effectively prevents galvanizing and provides excellent galvanizing properties.

特許出願人　　川崎製鉄株式会社Patent applicant: Kawasaki Steel Corporation

Claims (1)

【特許請求の範囲】[Claims] Ｌ　熱間圧延、脱スケールおよび冷間圧延を施した鋼板
に、再結晶焼鈍の前工程で、５０００ｐｐｍ以上の酸素
を含有する鉄めっきを厚さ０．０１μｍ以上、２．０μ
ｍ以下の範囲で施すことを特徴とする、冷間圧延鋼板の
表面性状改質方法。L A hot-rolled, descaled, and cold-rolled steel plate is coated with iron plating containing 5000 ppm or more of oxygen to a thickness of 0.01 μm or more and 2.0 μm in the pre-process of recrystallization annealing.
1. A method for modifying the surface properties of a cold rolled steel sheet, the method comprising modifying the surface properties of a cold rolled steel sheet.