JP6187028B2 - Alloyed hot-dip galvanized steel sheet with excellent productivity and press formability and manufacturing method thereof - Google Patents
Alloyed hot-dip galvanized steel sheet with excellent productivity and press formability and manufacturing method thereof Download PDFInfo
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Description
本発明は、自動車、家電製品、建築材料等へプレス成形して用いられる合金化溶融亜鉛めっき鋼板およびその製造方法に関するもので、特に、摺動性（耐フレーキング性）、耐パウダリング性及び化成処理性に優れた合金化溶融亜鉛めっき鋼板およびその製造方法に関するものである。 The present invention relates to an alloyed hot-dip galvanized steel sheet used for press molding to automobiles, home appliances, building materials, and the like, and a method for producing the same. In particular, the present invention relates to slidability (flaking resistance), powdering resistance and The present invention relates to an alloyed hot-dip galvanized steel sheet excellent in chemical conversion treatment and a method for producing the same.
合金化溶融亜鉛めっき鋼板は亜鉛めっき鋼板と比較して溶接性および塗装性に優れることから、自動車車体用途をはじめとして、家電製品、建築材料等の広範な用途分野で多用されている。このような用途に用いられる合金化溶融亜鉛めっき鋼板は、プレス成形を施されて使用に供されるのが通常である。ところが、合金化溶融亜鉛めっき鋼板は、鋼板表面に溶融亜鉛めっきを施した後、直ちに亜鉛の融点以上に加熱保持して、鋼板中のＦｅをめっき層中のＺｎ中に拡散させる合金化反応を生じさせて、Ｚｎ−Ｆｅ合金相を形成させたものであるが、冷延鋼板に比べてプレス成形性が劣るという欠点を有する。 Alloyed hot-dip galvanized steel sheets are widely used in a wide range of application fields such as automobile body applications, home appliances, and building materials because they are superior in weldability and paintability compared to galvanized steel sheets. The alloyed hot-dip galvanized steel sheet used for such applications is usually subjected to press forming and used. However, the alloyed hot-dip galvanized steel sheet, after hot dip galvanizing on the surface of the steel sheet, is immediately heated and held above the melting point of zinc to cause an alloying reaction to diffuse Fe in the steel sheet into Zn in the plating layer. Although it is made to form a Zn—Fe alloy phase, it has a disadvantage that press formability is inferior to that of a cold-rolled steel sheet.
このようにプレス成形性が劣る原因としては、合金化溶融亜鉛めっき層の組織に起因するものである。即ち、鋼板中のＦｅをめっき層中のＺｎ中に拡散させる合金化反応によって生成させたＺｎ−Ｆｅ合金めっき層は、通常、Γ相、δ1相、ζ相からなるめっき皮膜層であり、Ｆｅ濃度が低くなるに従い、Γ相→δ1相→ζ相の順で、硬度ならびに融点が低下し、鋼板表面に近いめっき層領域（めっき鋼板界面）には硬質で脆いΓ相が生成し、めっき層上部領域には軟質のζ相が生成する。ζ相は軟質でプレス金型と凝着しやすく摩擦係数が高く、摺動性が悪いので、厳しいプレス成形を行なったときにめっき層が金型に凝着し剥離する現象（フレーキング）を引き起こす原因となり、そして、Γ相は硬質で脆いためプレス成形時にめっき層が粉状になって剥離（パウダリング）する原因となる。 The reason why the press formability is inferior is due to the structure of the alloyed hot-dip galvanized layer. That is, the Zn-Fe alloy plating layer produced by an alloying reaction that diffuses Fe in the steel sheet into Zn in the plating layer is usually a plating film layer composed of a Γ phase, a δ 1 phase, and a ζ phase. As the Fe concentration decreases, the hardness and melting point decrease in the order of Γ phase → δ 1 phase → ζ phase, and a hard and brittle Γ phase is generated in the plated layer region (plated steel plate interface) close to the steel plate surface. A soft ζ phase is generated in the upper region of the plating layer. Since the ζ phase is soft and easily adheres to the press mold and has a high coefficient of friction and poor slidability, the plating layer adheres to the mold and flakes when severe press molding is performed (flaking). In addition, since the Γ phase is hard and brittle, the plating layer becomes powdery and peels (powdering) during press molding.
合金化溶融亜鉛めっき鋼板をプレス成形する際には、摺動性が良好なことが重要である。このため、摺動性の観点では、めっき皮膜は高合金化して高硬度で、融点が高く凝着の起こりにくい高Ｆｅ濃度の皮膜が有効であるが、パウダリングを引き起こすこととなる。一方、パウダリングを防止するために低合金化し、Γ相の生成を抑制した低Ｆｅ濃度のめっき皮膜とすると摺動性が劣りフレーキングを引き起こすこととなる。 When press-molding a galvannealed steel sheet, it is important that the slidability is good. For this reason, from the viewpoint of slidability, it is effective to use a high-concentration, high-hardness, high-melting-point, high-Fe coating with a high melting point, but it causes powdering. On the other hand, if the alloy is made low in order to prevent powdering and the plating film has a low Fe concentration in which the formation of the Γ phase is suppressed, the sliding property is inferior and flaking is caused.
合金化溶融亜鉛めっき鋼板のプレス成形性を良好なものとするためには、摺動性とバウダリングとの相反する性質を両立させることが要求される。 In order to improve the press formability of the alloyed hot-dip galvanized steel sheet, it is required to satisfy both the slidability and the contradictory properties of the bow ring.
これまで、合金化溶融亜鉛めっき鋼板のプレス成形性を改善する技術として、高Ａｌ浴において、該Ａｌ濃度との関係で規定される高侵入板温でめっきを行なうことにより合金化反応を抑制し、その後、高周波誘導加熱方式の合金化炉で出側板温が４９５℃超〜５２０℃となるように合金化処理することによりδ1主体の合金化溶融亜鉛めっき鋼板を製造する方法（例えば、特許文献１参照）や、溶融Ｚｎめっきを施し、直ちに４６０〜５３０℃の温度域で２〜１２０秒保持後、５℃／秒以上の冷却速度で２５０℃以下に冷却してδ1単相の合金化めっき層を形成する合金化溶融亜鉛めっき鋼板の製造方法（例えば、特許文献２参照）や、表面摺動性と耐パウダリング性を両立させるために、合金化溶融亜鉛めっき鋼板の製造時の合金化処理で加熱・冷却中の温度（Ｔ）と時間（ｔ）とを掛け合わせて積算した温度分布に基づいて、合金化処理の温度パターンを決定する合金化溶融亜鉛めっき鋼板の製造方法（例えば、特許文献３参照）が提案されている。 Until now, as a technology to improve the press formability of alloyed hot-dip galvanized steel sheets, in a high Al bath, the alloying reaction is suppressed by performing plating at a high intrusion plate temperature specified in relation to the Al concentration. Thereafter, a method of producing a δ 1 main alloyed hot-dip galvanized steel sheet by alloying in an alloying furnace of a high frequency induction heating method so that the outlet side plate temperature is over 495 ° C. to 520 ° C. (for example, patent Reference 1) or hot-dip Zn plating, immediately hold in a temperature range of 460 to 530 ° C. for 2 to 120 seconds, cool to 250 ° C. or less at a cooling rate of 5 ° C./second or more, and a δ 1 single-phase alloy In order to achieve both the surface slidability and the powdering resistance in the manufacturing method of the galvannealed steel sheet for forming the galvanized layer (see, for example, Patent Document 2), With alloying treatment A method for producing an alloyed hot-dip galvanized steel sheet that determines the temperature pattern of the alloying treatment based on the temperature distribution obtained by multiplying the temperature (T) and time (t) during heat / cooling and integrating the temperature (T) 3) has been proposed.
これらの従来提案されている技術は、何れも合金化の度合いを制御して、合金化溶融亜鉛めっき層の硬質化を図り、合金化溶融亜鉛めっき鋼板のプレス成形時の欠点となる耐パウダリング性と耐フレーキング性）との両立を図るものである。 All of these conventionally proposed technologies control the degree of alloying to harden the alloyed hot-dip galvanized layer, and are resistant to powdering, which is a drawback when press-forming alloyed hot-dip galvanized steel sheets. Compatibility and anti-flaking property).
また、表面平坦部が摺動性に大きな影響を与えるので、表面平坦部を制御して、表層にζ相が多く存在するめっき皮膜においても良好な耐パウダリング性、摺動性に優れた合金化溶融亜鉛めっき鋼板とすること（例えば、特許文献４参照）が提案されている。 In addition, since the surface flat part has a great influence on the slidability, the surface flat part is controlled, and an alloy excellent in powdering resistance and slidability even in a plating film having a lot of ζ phases on the surface layer. It has been proposed to use a galvannealed steel sheet (see, for example, Patent Document 4).
この技術は、合金化度を低くして表層にζ相が多く存在するめっき皮膜においても良好な耐パウダリング性、摺動性に優れた合金化溶融亜鉛めっき鋼板としたものであるが、耐フレーキング性（耐摺動性）をさらに改善することが必要であると考えられる。 This technology is an alloyed hot-dip galvanized steel sheet with excellent powdering resistance and slidability even in a plating film having a low degree of alloying and a large amount of ζ phase on the surface layer. It is considered necessary to further improve the flaking property (sliding resistance).
さらに、この他に、亜鉛系めっき鋼板のプレス成形性を向上させる方法としては、高粘度の潤滑油を塗布する方法が広く用いられているが、潤滑油の高粘性のために塗装工程で脱脂不良による塗装欠陥が発生したり、また、プレス時の油切れにより、プレス性能が不安定になったりする等の問題がある。このため、亜鉛系めっき鋼板の表面にＺｎＯを主体とする酸化膜を形成させること（例えば、特許文献５参照）や、Ｎｉ酸化物の酸化膜を形成すること（例えば、特許文献６参照）が提案されているが、これらの酸化膜は化成処理性が劣るという問題がある。そこで化成処理性を改善した皮膜としてＭｎ系酸化物皮膜を形成すること（例えば、特許文献７参照）が提案されている。しかし、これらの酸化物系皮膜を形成する技術は、いずれも合金化溶融亜鉛めっき層の構造との関係については具体的に検討されていない。 In addition, as a method for improving the press formability of galvanized steel sheets, a method of applying a high-viscosity lubricating oil is widely used. There are problems such as coating defects due to defects and press performance becoming unstable due to oil shortage during pressing. For this reason, forming an oxide film mainly composed of ZnO on the surface of a galvanized steel sheet (for example, refer to Patent Document 5) or forming an oxide film of Ni oxide (for example, refer to Patent Document 6). Although proposed, these oxide films have the problem of poor chemical conversion properties. Therefore, it has been proposed to form a Mn-based oxide film as a film with improved chemical conversion properties (see, for example, Patent Document 7). However, none of these techniques for forming an oxide-based film has been specifically studied in relation to the structure of the alloyed hot-dip galvanized layer.
本発明は、かかる事情に鑑み、プレス成形時の表面摺動性（耐フレーキング性）、耐パウダリング性を両立させた生産性に優れた合金化溶融亜鉛めっき鋼板およびその製造方法を提供することを課題とする。 In view of such circumstances, the present invention provides an alloyed hot-dip galvanized steel sheet excellent in productivity that achieves both surface slidability (flaking resistance) and powdering resistance during press forming, and a method for producing the same. This is the issue.
合金化溶融亜鉛めっきの合金化処理で高合金化処理をすれば、Γ相が多く生成してプレス成形時の表面摺動性（耐フレーキング性）は良好となるが、耐パウダリング性が劣ることとなる。一方、合金化処理で低合金化処理をすれば、Γ相の生成が少なくなってζ相が多くなり、プレス成形時の耐パウダリング性は良好となるが、表面摺動性（耐フレーキング性）が劣ることとなる。合金化溶融亜鉛めっき鋼板においてはΓ相の生成は避けることができない。そこで、本発明者らは、上工程である熱延、冷延、焼鈍条件の溶融亜鉛めっきの合金化に及ぼす影響を鋭意研究した。その結果、冷間圧延時の冷延率と合金化速度に関係があることを見出し、鋼中の成分により冷延率を変化させることにより、合金化条件を大きく変化させることなく、好適なめっき層を形成させ、耐パウダリング性と耐フレーキング性とを両立できることを知見して、本発明を完成した。 If a high alloying treatment is performed in the alloying hot dip galvanizing process, a large amount of Γ phase is generated and the surface slidability (flaking resistance) during press forming is improved, but the powdering resistance is improved. It will be inferior. On the other hand, if a low alloying treatment is performed in the alloying treatment, the generation of Γ phase is reduced and the ζ phase is increased, and the powdering resistance during press forming is improved, but the surface sliding property (flaking resistance is prevented). Property) is inferior. In the alloyed hot-dip galvanized steel sheet, the formation of the Γ phase cannot be avoided. Therefore, the present inventors have intensively studied the influence of the above-described hot rolling, cold rolling, and annealing conditions on the alloying of hot dip galvanizing. As a result, it has been found that there is a relationship between the cold rolling rate during cold rolling and the alloying speed, and by changing the cold rolling rate depending on the components in the steel, suitable plating without greatly changing the alloying conditions. The present invention was completed by forming a layer and finding that powdering resistance and flaking resistance can be compatible.
本発明の要旨は、次の通りである。 The gist of the present invention is as follows.
（１）合金化溶融亜鉛めっき鋼板であって、鋼板（地鉄）が、質量％で、
Ｃ：０．０００５〜０．０１％、
Ｓｉ：０．００１〜１．０％、
Ｍｎ：０．５３〜２．５％、
Ｐ：０．００１〜０．１％、
Ｓ：０．０２％以下、
Ａｌ：０．０３５〜０．１０％、
Ｔｉ：０．０００１〜０．１％、
Ｎ：０．００１〜０．００３７％
を含有し、残部がＦｅおよび不可避的不純物からなる成分組成で、鋼板（地鉄）中のＰ濃度を［Ｐ］とし、Ｔｉ濃度を［Ｔｉ］としたときにＥＢＳＰ法により測定される鋼板表面の結晶方位｛１１１｝と｛１００｝の面積比である｛１１１｝／｛１００｝が（１−０．０１６×［Ｐ］／［Ｔｉ］）以上（３．２−０．０１６×［Ｐ］／［Ｔｉ］）以下であることを特徴とする生産性とプレス成形性に優れた合金化溶融亜鉛めっき鋼板。ただし、鋼板がＣ：０．００２５％、Ｓｉ：０．１６％、Ｍｎ：１．１０％、Ｐ：０．００４％、Ｓ：０．０１２％、Ａｌ：０．０４４％、Ｔｉ：０．０４０％、Ｎ：０．００２２％を含有し、残部がＦｅおよび不可避的不純物からなる場合を除く。
(1) An alloyed hot-dip galvanized steel sheet, in which the steel sheet (ground iron) is in mass%,
C: 0.0005 to 0.01%
Si: 0.001 to 1.0%,
Mn: 0.53-2.5%,
P: 0.001 to 0.1%,
S: 0.02% or less,
Al: 0.035 to 0.10%,
Ti: 0.0001 to 0.1%,
N: 0.001 to 0.0037%
Steel plate surface measured by the EBSP method when the P concentration in the steel sheet (ground iron) is [P] and the Ti concentration is [Ti] {111} / {100}, which is the area ratio between the crystal orientations {111} and {100}, is (1−0.016 × [P] / [Ti]) or more (3.2−0.016 × [P ] / [Ti]) An alloyed hot-dip galvanized steel sheet excellent in productivity and press formability. However, the steel plate is C : 0.0025%, Si: 0.16%, Mn: 1.10%, P: 0.004%, S: 0.012%, Al: 0.044%, Ti: 0.00. 040%, N: 0.0022% to have free and unless the balance being Fe and unavoidable impurities.
（２）前記鋼板（地鉄）の前記成分組成がさらに質量％で、
Ｂ：０．００５％以下、
Ｎｂ：０．１％以下、
Ｍｏ：０．１％以下の１種または２種以上を含有することを特徴とする（１）に記載の生産性とプレス成形性に優れた合金化溶融亜鉛めっき鋼板。ただし、鋼板がＣ：０．００２０％、Ｓｉ：０．０１％、Ｍｎ：１．０６％、Ｐ：０．０４７％、Ｓ：０．００８％、Ａｌ：０．０４０％、Ｔｉ：０．０１８％、Ｎ：０．００２６％、Ｎｂ：０．０２２％を含有し、残部がＦｅおよび不可避的不純物からなる場合を除く。
(2) The said component composition of the said steel plate (base iron) is further mass%,
B: 0.005% or less,
Nb: 0.1% or less,
Mo: An alloyed hot-dip galvanized steel sheet excellent in productivity and press formability as described in (1), containing one or more of 0.1% or less. However, the steel plate is C: 0.0020%, Si: 0.01%, Mn: 1.06%, P: 0.047%, S: 0.008%, Al: 0.040%, Ti: 0.00. Excluding the case of containing 018%, N: 0.0026%, Nb: 0.022%, the balance being Fe and inevitable impurities.
（３）上記（１）または（２）に記載の成分組成の溶鋼（ただし、Ｃ：０．００２０％、Ｓｉ：０．０１％、Ｍｎ：１．０６％、Ｐ：０．０４７％、Ｓ：０．００８％、Ａｌ：０．０４０％、Ｔｉ：０．０１８％、Ｎ：０．００２６％、Ｎｂ：０．０２２％を含有し、残部がＦｅおよび不可避的不純物からなる場合、および、Ｃ：０．００２５％、Ｓｉ：０．１６％、Ｍｎ：１．１０％、Ｐ：０．００４％、Ｓ：０．０１２％、Ａｌ：０．０４４％、Ｔｉ：０．０４０％、Ｎ：０．００２２％を含有し、残部がＦｅおよび不可避的不純物からなる場合を除く）を連続鋳造してスラブを得る工程と、前記スラブを１１００〜１３００℃で加熱する工程と、加熱スラブを仕上げ温度８００℃以上１０５０℃以下、巻取り温度５００℃以上８００℃以下の条件で熱間圧延して熱延コイルを得る工程と、塩酸または硫酸を用いてスケールを除去する酸洗をして酸洗コイルを得る工程と、前記酸洗コイルを、鋼板中のＰ濃度を［Ｐ］とし、Ｔｉ濃度を［Ｔｉ］としたときに（６０−０．４５×［Ｐ］／［Ｔｉ］）％以上（１００−０．４５×［Ｐ］／［Ｔｉ］）％以下の冷延率で冷間圧延して冷延コイルとする工程と、前記コイルを再結晶温度以上の温度で焼鈍するとともに、その後コイル表面に溶融めっきを施す工程を実施することにより、
ＥＢＳＰ法により測定される鋼板表面の結晶方位｛１１１｝と｛１００｝の面積比である｛１１１｝／｛１００｝が（１−０．０１６×［Ｐ］／［Ｔｉ］）以上（３．２−０．０１６×［Ｐ］／［Ｔｉ］）以下とすることを特徴とする生産性とプレス成形性に優れた合金化溶融亜鉛めっき鋼板の製造方法。
(3) Molten steel having the composition described in (1) or (2) above (however, C: 0.0020%, Si: 0.01%, Mn: 1.06%, P: 0.047%, S : 0.008%, Al: 0.040% , Ti: 0.018%, N: 0.0026%, Nb: a 0.022% has free, if the balance of Fe and unavoidable impurities, and C: 0.0025%, Si: 0.16%, Mn: 1.10%, P: 0.004%, S: 0.012%, Al: 0.044%, Ti: 0.040%, N: 0.0022% to a free, a step of the balance to obtain a slab by continuous casting excluding) the case of Fe and unavoidable impurities, heating the slab at 1100 to 1300 ° C., heated slab Finishing temperature 800 ° C or higher and 1050 ° C or lower, winding temperature 500 ° C or higher and 800 ° C A step of obtaining a hot-rolled coil by hot rolling under the following conditions, a step of obtaining a pickled coil by pickling to remove scale using hydrochloric acid or sulfuric acid, When the concentration is [P] and the Ti concentration is [Ti], (60−0.45 × [P] / [Ti])% or more (100−0.45 × [P] / [Ti])% By carrying out the step of cold rolling at the following cold rolling rate to form a cold rolled coil, and annealing the coil at a temperature equal to or higher than the recrystallization temperature, and then subjecting the coil surface to hot dip plating,
{111} / {100}, which is the area ratio between the crystal orientations {111} and {100} on the steel sheet surface measured by the EBSP method, is (1−0.016 × [P] / [Ti]) or more (3. 2-0.016 × [P] / [Ti]) or less, a method for producing an galvannealed steel sheet having excellent productivity and press formability.
本発明によれば、プレス成形時の耐パウダリング性、表面摺動性（耐フレーキング性）を両立させ、かつ生産性に優れた合金化溶融亜鉛めっき鋼板を得ることができる。 According to the present invention, it is possible to obtain an alloyed hot-dip galvanized steel sheet having both powdering resistance and surface slidability (flaking resistance) during press molding and excellent productivity.
以下本発明を詳細に説明する。 The present invention will be described in detail below.
金化溶融亜鉛めっき鋼板の製造プロセスでは、焼鈍炉にて焼鈍された鋼板（以下単に地鉄ということがある）は、溶融亜鉛浴（ポット）に浸漬されて表面にめっきが施された後、加熱炉にて最高到達温度まで加熱された後、保熱炉にて徐冷され、冷却帯にて急冷されて、合金化溶融亜鉛めっき鋼板が製造される。この場合、この合金化処理時の合金化温度等により合金化度が決まる。 In the manufacturing process of the metallized hot-dip galvanized steel sheet, the steel sheet annealed in an annealing furnace (hereinafter sometimes simply referred to as “base iron”) is immersed in a hot-dip zinc bath (pot) and plated on the surface. After being heated to the maximum temperature in the heating furnace, it is gradually cooled in a heat-retaining furnace and quenched in a cooling zone to produce an alloyed hot-dip galvanized steel sheet. In this case, the degree of alloying is determined by the alloying temperature during the alloying process.
図１の合金化度と生成するΓ相及びζ相との関係の概略図に示すように、合金化度が低いとζ相の生成が多くなり、Γ相の生成は抑制され、ζ相が厚くΓ相が薄くなる。一方、合金化度が高いとΓ相の生成が多くなり、ζ相の生成は抑制され、Γ相が厚くζ相は薄くなる。 As shown in the schematic diagram of the relationship between the degree of alloying and the Γ phase and ζ phase generated in FIG. 1, when the degree of alloying is low, the formation of ζ phase increases, the generation of Γ phase is suppressed, and the ζ phase is reduced. Thick and Γ phase becomes thinner. On the other hand, when the degree of alloying is high, the generation of the Γ phase increases, the formation of the ζ phase is suppressed, the Γ phase is thick, and the ζ phase is thin.
そして、合金化度が高いとΓ相の生成量が多くなり、鋼板とめっき層との界面に厚く成長して合金化溶融亜鉛めっき鋼板のプレス成形時にパウダリングが発生する原因となる。即ち、合金化度が高く、Ｆｅ濃度が１１％以上となるとΓ相が厚く成長してパウダリングが発生する原因となる。一方、合金化度が低いとζ相の生成量が多くなり、めっき層表面に成長してプレス成形時にフレーキングが発生する原因となり、さらにＦｅ濃度が下がると溶接性が劣化し自動車の生産工程に悪影響が出る。 When the degree of alloying is high, the amount of Γ phase generated increases, and grows thick at the interface between the steel sheet and the plating layer, causing powdering during press forming of the alloyed hot-dip galvanized steel sheet. That is, when the degree of alloying is high and the Fe concentration is 11% or more, the Γ phase grows thick and causes powdering. On the other hand, if the degree of alloying is low, the amount of ζ phase generated increases, causing flaking on the surface of the plating layer and causing flaking during press forming. Further, when the Fe concentration decreases, the weldability deteriorates and the automobile production process Adversely affected.
本発明では、合金化条件をなるべく変化させずに種々の鋼種を製造するために、より上工程である熱延、冷延、焼鈍の条件を鋭意検討した。その結果、本願発明者は、Ｔｉ含有量（［Ｔｉ］）とＰ含有量（［Ｐ］）と冷間圧延時の冷延率を特定の関係に制御することにより、耐フレーキング特性、耐パウダリング特性および生産性に優れた合金化溶融亜鉛めっき鋼板の製造方法を知見した。 In the present invention, in order to produce various steel types without changing the alloying conditions as much as possible, the conditions of hot rolling, cold rolling, and annealing, which are higher steps, have been intensively studied. As a result, the inventor of the present application controls the anti-flaking property, anti-flaking property by controlling the Ti content ([Ti]), the P content ([P]), and the cold rolling ratio during cold rolling to a specific relationship. A method for producing galvannealed steel sheets with excellent powdering characteristics and productivity was discovered.
以下、本願発明者がこの事実を知見した実験内容について説明する。本願発明者は、先ず、Ｃ：０．０００５〜０．０１％、Ｓｉ：０．００１〜１．０％、Ｍｎ：０．０１〜１．５％、Ｐ：０．００１〜０．１２％、Ｓ：０．０２％以下、Ａｌ：０．０１〜０．１０％、Ｔｉ：０．００１〜０．１％、Ｎ：０．００１〜０．０１０％の範囲で組成を変化させた鋼を、真空溶解炉で溶製し、１２００℃で１時間に加熱保持した後、仕上げ温度を８８０〜９３０℃で熱間圧延して熱延板とした。次に、この熱延板を酸洗した後、冷延率２０〜９７％で冷間圧延し冷延板とした。この冷延板を窒素９５％水素５％の雰囲気で８００℃の温度で６０秒間保持するサイクルで焼鈍し、冷却中４６０℃において浴組成Ｚｎ−０．１３５％Ａｌ−０．０４％Ｆｅでめっきを施し、その後４９０℃〜５３０℃にて合金化処理を行い、溶融亜鉛めっき鋼板（ＧＡ）とした。その後、製作したＧＡ鋼板を用いプレス実験を行い、パウダリング性とフレーキング性を評価した。プレスはクランクプレスを用い、幅４０ｍｍ×長さ２５０ｍｍを供試材とし、ｒ＝５ｍｍの半丸ビードの金型にてパンチ肩半径５ｍｍ、ダイ肩半径５ｍｍで成形高さ６５ｍｍに加工した。 Hereinafter, the experiment contents in which the present inventor has found this fact will be described. The inventor of the present application firstly C: 0.0005 to 0.01%, Si: 0.001 to 1.0%, Mn: 0.01 to 1.5%, P: 0.001 to 0.12% , S: 0.02% or less, Al: 0.01 to 0.10%, Ti: 0.001 to 0.1%, N: 0.001 to 0.010%, steel whose composition was changed Was melted in a vacuum melting furnace, heated and held at 1200 ° C. for 1 hour, and then hot-rolled at a finishing temperature of 880 to 930 ° C. to obtain a hot-rolled sheet. Next, the hot-rolled sheet was pickled and then cold-rolled at a cold rolling rate of 20 to 97% to obtain a cold-rolled sheet. This cold-rolled sheet was annealed in a cycle of holding at a temperature of 800 ° C. for 60 seconds in an atmosphere of 95% nitrogen and 5% hydrogen, and plated with a bath composition Zn—0.135% Al—0.04% Fe at 460 ° C. during cooling. After that, alloying treatment was performed at 490 ° C. to 530 ° C. to obtain a hot dip galvanized steel sheet (GA). Thereafter, a press experiment was performed using the manufactured GA steel sheet, and the powdering property and flaking property were evaluated. The press was a crank press using a test piece having a width of 40 mm and a length of 250 mm, and was processed into a mold shoulder height of 5 mm, a die shoulder radius of 5 mm, and a molding height of 65 mm using a half round bead mold of r = 5 mm.
図２〜図４にＴｉが０．０００５％の場合、０．００１％の場合、０．０８％の場合の結果を示す。図中、横軸にＰ量をとり、縦軸に冷間圧延時の冷延率をとり、パウダリングが生じた水準を×で、フレーキングが生じた水準を△で、いずれも生じなかった水準を○で示した。図２〜図４に示すように、パウダリング性とフレーキング性とを確保するには、Ｐ濃度が高くなるにしたがって、延伸率を低下させる必要があるが、Ｔｉ濃度が高くなるとＰ濃度が高くなっても延伸率の程度を下げなくてもよいことが分る。なお、パウダリング性とフレーキング性はいずれも目視で判断し、めっき層が粉状になって剥離したものをパウダリングが生じた水準とし、めっき層が剥離して金型に凝着していたものをフレーキングが生じた水準とした。以上の実験から、本発明者は、図２〜図４をまとめると、鋼板中のＰ濃度を０．１％以下にし、かつ、Ｐ濃度を［Ｐ］とし、Ｔｉ濃度を［Ｔｉ］としたときに、図５に示すように、冷間圧延時の冷延率を（６０−０．４５×［Ｐ］／［Ｔｉ］）％以上で（１００−０．４５×［Ｐ］／［Ｔｉ］）以下にすることにより、耐フレーキング特性、耐パウダリング特性および生産性に優れた合金化溶融亜鉛めっき鋼板が製造できることを知見した。 2 to 4 show the results when Ti is 0.0005%, 0.001%, and 0.08%. In the figure, the amount of P is taken on the horizontal axis, the cold rolling ratio during cold rolling is taken on the vertical axis, the level at which powdering occurs is indicated by x, and the level at which flaking occurs is indicated by Δ. The level is indicated by ○. As shown in FIGS. 2 to 4, in order to ensure powdering properties and flaking properties, it is necessary to decrease the stretching rate as the P concentration increases. However, as the Ti concentration increases, the P concentration increases. It turns out that even if it becomes high, it is not necessary to reduce the extent of a draw ratio. Both powdering and flaking properties are judged visually, and the plating layer is powdered and peeled to the level where powdering occurs, and the plating layer peels off and adheres to the mold. The level of flaking occurred. From the above experiment, the present inventor summarized FIG. 2 to FIG. 4, the P concentration in the steel sheet was 0.1% or less, the P concentration was [P], and the Ti concentration was [Ti]. Sometimes, as shown in FIG. 5, the cold rolling rate during cold rolling is (60−0.45 × [P] / [Ti])% or more (100−0.45 × [P] / [Ti). ]) It was discovered that an alloyed hot-dip galvanized steel sheet excellent in anti-flaking property, anti-powdering property and productivity can be produced by the following.
更に本発明者は、上述した現象のメカニズムを検討するために、製作したＧＡ鋼板を発煙硝酸でめっきを剥離して表面組織を調査した。その結果の一例を図６、図７に示す。図６には表面粒径に及ぼす冷間圧延時の冷延率の影響を、図７には表面方位に及ぼす冷間圧延時の冷延率の影響を示す図である。図６、図７とも横軸は冷間圧延時の冷延率（％）であり、縦軸はそれぞれ表面の平均粒径（μｍ）と表面方位｛１１１｝と｛１００｝の割合を示す。図６に示すように表面平均粒径は冷間圧延時の冷延率によってほとんど変化しないが、図７に示すように表面方位は冷間圧延時の冷延率によって大きく変化し、冷延率が小さいほど｛１００｝が多く、冷延率が大きいほど｛１１１｝が多い。図２〜図４において冷間圧延時の冷延率によって、パウダリング性やフレーキング性が変化しているが、この現象は合金化速度の影響によりめっき層構造が変化していることに起因しているが、この合金化速度の変化には、図７に示すように表面の結晶方位が影響していると推察される。この理由は明確ではないが、表面方位によって、Ｆｅの分離し易さが異なり、｛１００｝の方が｛１１１｝より分離し易いために、合金化速度が速いと推定される。 Furthermore, in order to examine the mechanism of the phenomenon described above, the present inventor examined the surface texture of the manufactured GA steel sheet by peeling the plating with fuming nitric acid. An example of the result is shown in FIGS. FIG. 6 shows the influence of the cold rolling ratio during cold rolling on the surface grain size, and FIG. 7 shows the influence of the cold rolling ratio during cold rolling on the surface orientation. 6 and 7, the horizontal axis represents the cold rolling ratio (%) during cold rolling, and the vertical axis represents the average particle diameter (μm) of the surface and the ratio of the surface orientations {111} and {100}, respectively. As shown in FIG. 6, the surface average particle diameter hardly changes depending on the cold rolling rate during cold rolling, but as shown in FIG. 7, the surface orientation greatly changes depending on the cold rolling rate during cold rolling, and the cold rolling rate Is smaller, the more {100}, and the larger the cold rolling rate, the more {111}. 2 to 4, the powdering property and flaking property change depending on the cold rolling rate during the cold rolling. This phenomenon is caused by the change in the plating layer structure due to the influence of the alloying speed. However, it is presumed that the change in alloying rate is influenced by the crystal orientation of the surface as shown in FIG. The reason for this is not clear, but the ease of separation of Fe differs depending on the surface orientation, and {100} is easier to separate than {111}.
本発明者は、以上のようにＴｉ含有量（［Ｔｉ］）とＰ含有量（［Ｐ］）と冷間圧延時の冷延率を特定の関係に制御すること、すなわち換言すれば、図５〜図７より鋼板（地鉄）中のＰ濃度を［Ｐ］とし、Ｔｉ濃度を［Ｔｉ］としたときに鋼板表面の結晶方位｛１１１｝と｛１００｝の比である｛１１１｝／｛１００｝が（１−０．０１６×［Ｐ］／［Ｔｉ］）以上（３．２−０．０１６×［Ｐ］／［Ｔｉ］）以下に制御することにより、耐フレーキング特性、耐パウダリング特性に優れた合金化溶融亜鉛めっき鋼板が得られることを知見した。 As described above, the inventor controls the Ti content ([Ti]), the P content ([P]), and the cold rolling ratio during cold rolling to have a specific relationship, that is, in other words, FIG. 5 to 7, the P concentration in the steel sheet (base metal) is [P] and the Ti concentration is [Ti], which is the ratio of the crystal orientation {111} to {100} on the steel sheet surface {111} / By controlling {100} to be (1−0.016 × [P] / [Ti]) or more and (3.2−0.016 × [P] / [Ti]) or less, anti-flaking property, It has been found that an alloyed hot-dip galvanized steel sheet having excellent powdering characteristics can be obtained.
本発明は、これらの知見に基づいて完成したものである。 The present invention has been completed based on these findings.
以下、本発明で鋼板の成分を限定した理由について説明する（なお、ここで記載の％は、特別の断りがなければ質量％を意味する）。 Hereinafter, the reason why the components of the steel sheet are limited in the present invention will be described (% described here means mass% unless otherwise specified).
自動車用鋼板としては、軟鋼あるいは高張力化しても深絞り性等のプレス成形性を満足するものでなければならない。本発明では、鋼板成分として、加工性を向上させるために、極低炭素鋼を基本成分とし、高張力化する場合は強化元素であるＳｉ、Ｍｎ、Ｐ等を添加した鋼板を用いるものである。以下に本発明の鋼板の各成分の添加理由および各成分の成分範囲を限定した理由を説明する。ここで、成分についての「％」は質量％を意味する。 The steel sheet for automobiles must satisfy mild formability or press formability such as deep drawability even when the tension is increased. In the present invention, as a steel plate component, in order to improve workability, a very low carbon steel is used as a basic component, and a steel plate to which a strengthening element such as Si, Mn, P or the like is added is used when increasing the tension. . The reason for adding each component of the steel sheet of the present invention and the reason for limiting the component range of each component will be described below. Here, “%” for a component means mass%.
Ｃ：０．０００５〜０．０１％、
Ｃは、プレス加工性に関する伸び及びｒ値を低減させる元素であり、少ないほうが好ましいが、０．０００５％未満に低減させるためには製鋼プロセスからしてコストがかかり操業上現実的でない。一方、０．０１％を超えると加工性を害することとなるので、上限を０．０１％とした。好ましくは、上限は０．００８％である。
C: 0.0005 to 0.01%
C is an element that reduces the elongation and r value related to press workability, and it is preferable that the amount be smaller. However, in order to reduce it to less than 0.0005%, it is costly from the steelmaking process and is not practical in operation. On the other hand, if it exceeds 0.01%, workability will be impaired, so the upper limit was made 0.01%. Preferably, the upper limit is 0.008%.
Ｓｉ：０．００１〜１．０％、
Ｓｉは、鋼の強度を改善する元素であるが、Ｓｉが多くなると鋼板表面にＳｉ酸化物が形成され溶融めっきの際に不めっきやめっき密着性を低下させることとなるので、Ｓｉの上限を１．０％とした。一方、０．００１％未満にするには精錬コストが高くなるため、下限を０．００１％とする。また、高張力化する場合は強度確保の観点から０．１％以上の含有量とすることが好ましい。
Si: 0.001 to 1.0%,
Si is an element that improves the strength of steel. However, if Si is increased, Si oxide is formed on the surface of the steel sheet, and unplating and plating adhesion are reduced during hot dipping. 1.0%. On the other hand, since refining cost becomes high to make it less than 0.001%, the lower limit is made 0.001%. Moreover, when making high tension | tensile_strength, it is preferable to set it as 0.1% or more content from a viewpoint of ensuring intensity | strength.
Ｍｎ：０．０１〜２．５％、
Ｍｎは、鋼の強度を改善する元素であり、他の強化元素と組み合わせて使用するが、０．０１％未満では精錬コストが高くなるため、下限を０．０１％とする。一方、２．５％を超えて含有すると鋼板が硬化して加工性を低下させることとなり、また鋼板の表面にＭｎ酸化物が生成し、溶融めっき性が損なわれるので、Ｍｎの上限を２．５％とした。
Mn: 0.01 to 2.5%
Mn is an element that improves the strength of steel, and is used in combination with other strengthening elements. However, if it is less than 0.01%, the refining cost increases, so the lower limit is made 0.01%. On the other hand, if the content exceeds 2.5%, the steel sheet is hardened and the workability is lowered, and Mn oxide is generated on the surface of the steel sheet and the hot dipping property is impaired. 5%.
Ｐ：０．００１〜０．１％、
Ｐは、鋼の強度を改善する元素であり、他の強化元素と組み合わせて使用するが、０．００１％未満では精錬コストが高くなるため、下限を０．００１％とする。高張力化する場合は強度確保の観点から０．００５％以上の含有量とすることが好ましい。一方、Ｐは溶融亜鉛めっきの合金化反応を遅くさせる元素であり、めっき表面に線状模様を発生させ表面性状を劣化させたり、フレーキングの原因となる。更にスポット溶接性にも悪影響を与える元素であるので、その上限を０．１％とした。好ましくは０．０７％以下が良い。
P: 0.001 to 0.1%,
P is an element that improves the strength of steel, and is used in combination with other strengthening elements. However, if less than 0.001%, the refining cost increases, so the lower limit is made 0.001%. When increasing the tension, the content is preferably 0.005% or more from the viewpoint of securing the strength. On the other hand, P is an element that slows the alloying reaction of hot dip galvanizing, and causes a linear pattern on the plating surface to deteriorate surface properties or cause flaking. Furthermore, since it is an element that adversely affects spot weldability, the upper limit was made 0.1%. Preferably it is 0.07% or less.
Ｓ：０．０２％以下、
Ｓは、鋼中に不可避的に含有される不純物であり、深絞り性の観点からも少ないほうが好ましいが、０．０２％以下であれば、実質的な悪影響はなく、許容できる範囲である。
S: 0.02% or less,
S is an impurity inevitably contained in the steel, and is preferably less from the viewpoint of deep drawability. However, if it is 0.02% or less, there is no substantial adverse effect and is an acceptable range.
Ａｌ：０．０１〜０．１％、
Ａｌは、鋼の脱酸元素として含有される元素であって、０．０１％未満では十分な脱酸効果が得られない。しかし、０．１％を超えると加工性の低下を招くので、上限を０．１％とした。
Al: 0.01 to 0.1%,
Al is an element contained as a deoxidizing element of steel, and if it is less than 0.01%, a sufficient deoxidizing effect cannot be obtained. However, if it exceeds 0.1%, the workability is reduced, so the upper limit was made 0.1%.
Ｔｉ：０．０００１〜０．１％、
Ｔｉは、鋼中のＮをＴｉＮとして固定し、固溶Ｎ量を低減することにより、加工性を改善する元素であり、０．１％を超えて添加してもその効果は飽和し、むしろＴｉＣを形成して加工性を劣化させる。Ｔｉを添加する場合には０．０００１％以上添加することが加工性改善のためには好ましい。更にＴｉは合金化を促進させるため、過剰な添加はパウダリングの原因となる。一方、Ｔｉを０．０００１％未満にするには精錬コストが高くなるため下限を０．０００１％とした。また、加工性改善のためには０．００１％以上添加することが好ましい。
Ti: 0.0001 to 0.1%,
Ti is an element that improves the workability by fixing N in steel as TiN and reducing the amount of solute N, and even if added over 0.1%, the effect is saturated, rather TiC is formed to deteriorate workability. When adding Ti, adding 0.0001% or more is preferable for improving workability. Furthermore, since Ti promotes alloying, excessive addition causes powdering. On the other hand, if the Ti content is less than 0.0001%, the refining cost increases, so the lower limit was made 0.0001%. Moreover, it is preferable to add 0.001% or more for workability improvement.
Ｎ：０．００１〜０．０１０％、
Ｎは、鋼の精錬時に不可避的に混入する元素であり、加工性や溶接部靭性を劣化させる。このため、Ｎ含有量は０．０１％以下に規制する必要がある。一方、Ｎ含有量を０．００１％未満に低減するには、製造コストが高くなる。よって、Ｎ含有量は０．００１〜０．０１０％とする。
N: 0.001 to 0.010%,
N is an element that is inevitably mixed during steel refining, and deteriorates workability and weld toughness. For this reason, it is necessary to regulate N content to 0.01% or less. On the other hand, to reduce the N content to less than 0.001%, the manufacturing cost increases. Therefore, the N content is set to 0.001 to 0.010%.
本発明の鋼板で必要に応じて添加する成分について以下に説明する。 The components added as necessary in the steel sheet of the present invention will be described below.
Ｂ：０．００５％以下、
Ｂは、Ｎとの親和力が強く、凝固時または熱間圧延時に窒化物を形成し、鋼中に固溶しているＮを低減して加工性を高める効果がある。その効果を得るためには０．０００１％以上の含有量とすることが好ましい。しかしながら含有量が０．００５％を超えると溶接時に溶接部及びその熱影響部が硬質化し靭性が劣化する。また、熱延板での強度も高くなり、冷間圧延時の負荷が高くなる。更に、再結晶温度が高くなることにより、加工性の指標であるｒ値の面内異方性が大きくなりプレス成形性が劣化する。よってＢ含有量は０．００５％以下とする。
B: 0.005% or less,
B has a strong affinity for N, and has the effect of forming a nitride during solidification or hot rolling, reducing N dissolved in the steel and improving workability. In order to obtain the effect, the content is preferably 0.0001% or more. However, if the content exceeds 0.005%, the welded part and its heat-affected zone become hard during welding and the toughness deteriorates. In addition, the strength of the hot-rolled sheet is increased, and the load during cold rolling is increased. Furthermore, as the recrystallization temperature increases, the in-plane anisotropy of the r value, which is an index of workability, increases and press formability deteriorates. Therefore, the B content is 0.005% or less.
Ｎｂ：０．１％以下、
Ｎｂは、Ｃ及びＮとの親和力が強く、凝固時または熱間圧延時に炭窒化物を形成し、鋼中に固溶しているＣ及びＮを低減して加工性を高める効果がある。その効果を得るためには０．００１%以上の含有量とすることが好ましい。しかしながら含有量が０．１％を超えると再結晶温度が高くなることにより、加工性の指標であるｒ値の面内異方性が大きくなりプレス成形性が劣化する。また、溶接部の靭性も劣化する。よって、Ｎｂ含有量は０．１％以下とする。
Nb: 0.1% or less,
Nb has a strong affinity with C and N, and forms carbonitrides during solidification or hot rolling, and has the effect of reducing workability by reducing C and N dissolved in the steel. In order to obtain the effect, the content is preferably 0.001% or more. However, if the content exceeds 0.1%, the recrystallization temperature increases, and the in-plane anisotropy of the r value, which is an index of workability, increases, and the press formability deteriorates. Moreover, the toughness of the welded portion is also deteriorated. Therefore, the Nb content is 0.1% or less.
Ｍｏ：０．００１〜０．１％
Ｍｏは、微量添加することにより時効が抑制され、遅時効性を得ることができる元素である。この効果を得るためには、Ｍｏの含有量は、０．００１％以上であることが好ましい。しかし、Ｍｏの含有量が０．１％を超えて添加してもその効果は飽和するばかりか、鋼板が硬化して加工性が低下する。よって、Ｍｏ含有量は０．００１〜０．１％であることが好ましい。
上記に述べた含有成分の残部はＦｅおよび不可避的不純物である。
Mo: 0.001 to 0.1%
Mo is an element capable of obtaining delayed aging by suppressing the aging by adding a small amount. In order to obtain this effect, the Mo content is preferably 0.001% or more. However, even if the Mo content exceeds 0.1%, the effect is not only saturated, but the steel sheet is hardened and the workability is lowered. Therefore, the Mo content is preferably 0.001 to 0.1%.
The balance of the components described above is Fe and inevitable impurities.
次に本発明の製造方法について説明する。 Next, the manufacturing method of this invention is demonstrated.
スラブを１１００〜１３００℃で加熱する理由は、１１００℃未満では、熱延での負荷が高くなり、また所望する熱延仕上げ温度を確保できない。一方で、１３００℃を超える加熱はエネルギーを過剰に使用しコスト増を招く。 The reason for heating the slab at 1100 to 1300 ° C is that if it is less than 1100 ° C, the load in hot rolling becomes high and the desired hot rolling finishing temperature cannot be ensured. On the other hand, heating exceeding 1300 ° C. uses excessive energy and increases costs.
熱間圧延で仕上温度が８００℃未満となると、混粒組織となり、材質バラツキ原因となる。一方で１０５０℃以上の仕上がり温度にするためには、加熱温度を高温にする必要があり、コスト増につながる。また、強度低下原因ともなる。よって、熱延仕上げ温度は８００℃以上１０５０℃以下に限定した。 When the finishing temperature is less than 800 ° C. by hot rolling, a mixed grain structure is formed, which causes material variation. On the other hand, in order to obtain a finishing temperature of 1050 ° C. or higher, it is necessary to increase the heating temperature, leading to an increase in cost. It also causes a decrease in strength. Therefore, the hot rolling finishing temperature is limited to 800 ° C. or higher and 1050 ° C. or lower.
巻取り温度は５００℃未満だと形状不良の原因となる。一方で、８００℃を超えて巻き取るとスケール疵が生成し易くなる。また冷延焼鈍後の強度低下につながる。したがって、本発明では、巻取り温度を５００℃以上８００℃以下と限定した。 When the coiling temperature is less than 500 ° C., it causes a shape defect. On the other hand, when it winds over 800 degreeC, it will become easy to produce | generate a scale flaw. Moreover, it leads to the strength fall after cold rolling annealing. Therefore, in the present invention, the winding temperature is limited to 500 ° C. or higher and 800 ° C. or lower.
本発明では、酸洗コイルを、鋼板中のＰ濃度を［Ｐ］とし、Ｔｉ濃度を［Ｔｉ］としたときに（６０−０．４５×［Ｐ］／［Ｔｉ］）％以上（１００−０．４５×［Ｐ］／［Ｔｉ］）％以下の冷延率で冷間圧延して冷延コイルとするが、この理由は前述の通り、耐パウダリング性と耐フレーキング性を両立させるためであり、これによりめっき直前の鋼板(地鉄)表面の結晶方位｛１１１｝と｛１００｝の比である｛１１１｝／｛１００｝が（１−０．０１６×［Ｐ］／［Ｔｉ］）以上（３．２−０．０１６×［Ｐ］／［Ｔｉ］）以下となり耐パウダリング性と耐フレーキング性の両立が可能となる。更には１．４−０．０１６×［Ｐ］／［Ｔｉ］）以上（２．８−０．０１６×［Ｐ］／［Ｔｉ］）以下が好ましい。なお、地鉄表面の結晶方位は、地鉄最表層の結晶粒毎の情報を得るために、めっき鋼板のめっきを発煙硝酸を使い剥離した後に、表面をＥＢＳＰ法（Ｅｌｅｃｔｒｏｎ Ｂａｃｋｓｃａｔｔｅｒ Ｄｉｆｆｒａｃｔｉｏｎ Ｐａｔｔｅｒｎ：電子後方散乱回折像法）によって結晶方位解析することによって測定することができる。また、冷延コイルを再結晶温度以上の温度で焼鈍することによって圧延によって生じた歪が除去され、軟質化して加工性を向上させることができる。焼鈍後に鋼板表面に溶融めっきを施し、合金化処理を行なって合金化溶融亜鉛めっき鋼板とする。この焼鈍と溶融めっき工程は、連続焼鈍炉を用いて行なうことが好ましい。 In the present invention, the pickling coil is (60−0.45 × [P] / [Ti])% or more (100−) when the P concentration in the steel sheet is [P] and the Ti concentration is [Ti]. 0.45 × [P] / [Ti])% or less, and cold-rolled into a cold-rolled coil. This is because, as described above, both powdering resistance and anti-flaking resistance are achieved. Therefore, {111} / {100} which is the ratio of the crystal orientation {111} to {100} on the surface of the steel plate (base metal) immediately before plating is (1−0.016 × [P] / [Ti ]) (3.2-0.016 × [P] / [Ti]) or less, it is possible to achieve both powdering resistance and anti-flaking resistance. Furthermore, 1.4-0.016 * [P] / [Ti]) or more and (2.8-0.016 * [P] / [Ti]) or less are preferable. The crystal orientation of the surface of the ground iron is obtained by peeling the plated steel sheet using fuming nitric acid to obtain information for each crystal grain of the outermost surface layer of the ground steel, and then the surface is subjected to the EBSP method (Electron Backscatter Diffraction Pattern: back of the electron). It can be measured by analyzing the crystal orientation by the scattering diffraction image method. Further, by annealing the cold-rolled coil at a temperature equal to or higher than the recrystallization temperature, distortion caused by rolling can be removed and softened to improve workability. After annealing, the surface of the steel sheet is hot dip plated and alloyed to obtain an alloyed hot dip galvanized steel sheet. It is preferable to perform this annealing and hot dipping process using a continuous annealing furnace.
以下実施例に基づいて本発明を詳細に説明する。 Hereinafter, the present invention will be described in detail based on examples.
連続鋳造により表１に示す鋼組成の供試材鋳片（スラブ）を製造した。このスラブを加熱炉で１２３０℃に加熱保持した後、抽出して脱スケール（デスケ）を行ない、熱延仕上げ温度が８８０〜９２０℃、巻き取り温度が６３０〜６７０℃での条件で熱間圧延に供した。熱間圧延後の熱延鋼板の表面を酸洗によってスケールを除去した後、表２に示す冷延率で冷間圧延して冷延コイルとした後、連続焼鈍炉で７８０〜８５０℃の焼鈍を行ない、溶融亜鉛めっき浴に浸漬して溶融めっきをし、合金化処理を行なって合金化溶融めっき鋼板を得た。その後、製作した合金化溶融めっき鋼板を用いプレス実験を行い、パウダリング性とフレーキング性を評価した。プレスはクランクプレスを用い、幅４０ｍｍ×長さ２５０ｍｍを供試材とし、ｒ＝５ｍｍの半丸ビードの金型にてパンチ肩半径５ｍｍ、ダイ肩半径５ｍｍで成形高さ６５ｍｍに加工した。なお、パウダリング性とフレーキング性はいずれも目視で判断し、めっき層が粉状になって剥離したものをパウダリングが生じた水準とし、めっき層が剥離して金型に凝着していたものをフレーキングが生じた水準とした。 Test piece slabs (slabs) having the steel compositions shown in Table 1 were produced by continuous casting. This slab is heated and held at 1230 ° C. in a heating furnace, extracted, descaled, and hot-rolled under conditions of a hot rolling finishing temperature of 880 to 920 ° C. and a winding temperature of 630 to 670 ° C. It was used for. After removing the scale from the surface of the hot-rolled steel sheet after hot rolling by pickling, it was cold-rolled at a cold rolling rate shown in Table 2 to form a cold-rolled coil, and then annealed at 780 to 850 ° C. in a continuous annealing furnace. Then, it was immersed in a hot dip galvanizing bath to perform hot dip plating, and an alloying treatment was performed to obtain an galvannealed steel sheet. After that, a press experiment was performed using the manufactured alloyed hot-dip steel sheet, and the powdering property and flaking property were evaluated. The press was a crank press using a test piece having a width of 40 mm and a length of 250 mm, and was processed into a mold shoulder height of 5 mm, a die shoulder radius of 5 mm, and a molding height of 65 mm using a half round bead mold of r = 5 mm. Both powdering and flaking properties are judged visually, and the plating layer is powdered and peeled to the level where powdering occurs, and the plating layer peels off and adheres to the mold. The level of flaking occurred.
表２に冷間圧延の冷延率に関する結果を、そして、表３に地鉄表面の結晶方位｛１１１｝と｛１００｝の比に関する結果を示す。そして、表２に示す冷間圧延の冷延率と表１に記載の鋼板中のＰ濃度とＴｉ濃度との関係を図８に示し、また、表３に示す地鉄表面の結晶方位｛１１１｝と｛１００｝の比と表１に記載の鋼板中のＰ濃度とＴｉ濃度との関係を図９に示した。なお、図８及び図９において、表示した番号は比較例の鋼Ｎｏ．２４〜３３を示し、その他の番号の表示がないものは発明例である。 Table 2 shows the results relating to the cold rolling ratio of cold rolling, and Table 3 shows the results relating to the ratio between the crystal orientations {111} and {100} on the surface of the ground iron. FIG. 8 shows the relationship between the cold rolling ratio of cold rolling shown in Table 2, the P concentration and the Ti concentration in the steel sheet shown in Table 1, and the crystal orientation {111 of the surface iron surface shown in Table 3 } And the ratio of {100} and the relationship between the P concentration and Ti concentration in the steel sheet described in Table 1 are shown in FIG. 8 and 9, the displayed numbers are the steel numbers of comparative examples. 24 to 33 are shown as examples of the invention without other numbers.
表２及び図８に示すように、冷間圧延の冷延率が、鋼板（地鉄）中のＰ濃度を［Ｐ］とし、Ｔｉ濃度を［Ｔｉ］としたときに（６０−０．４５×［Ｐ］／［Ｔｉ］）％以上（１００−０．４５×［Ｐ］／［Ｔｉ］）％以下であった発明例の鋼Ｎｏ．１〜２３は、表３及び図９に示すように、地鉄表面の結晶方位｛１１１｝と｛１００｝の比である｛１１１｝／｛１００｝が（１−０．０１６×［Ｐ］／［Ｔｉ］）以上（３．２−０．０１６×［Ｐ］／［Ｔｉ］）以下となりパウダリングもフレーキングも生じず良好であった。一方、冷間圧延の冷延率が（６０−０．４５×［Ｐ］／［Ｔｉ］）％以上（１００−０．４５×［Ｐ］／［Ｔｉ］）％以下の範囲外であった比較例の鋼No.２４〜３１は地鉄表面の結晶方位｛１１１｝と｛１００｝の比である｛１１１｝／｛１００｝が（１−０．０１６×［Ｐ］／［Ｔｉ］）以上（３．２−０．０１６×［Ｐ］／［Ｔｉ］）以下の範囲外となりパウダリングまたはフレーキングが生じた。また、比較例３２と比較例３３は、冷間圧延の冷延率が（６０−０．４５×［Ｐ］／［Ｔｉ］）％以上（１００−０．４５×［Ｐ］／［Ｔｉ］）％以下の範囲内であったが、比較例３２はＴｉ含有量が過剰であったためにパウダリングが生じ、発明例３３はＰの含有量が過剰であったためにフレーキングが生じた。
As shown in Table 2 and FIG. 8, when the cold rolling ratio of the cold rolling is P concentration in the steel sheet (base iron) is [P] and Ti concentration is [Ti] (60-0.45). × [P] / [Ti])% or more (100-0.45 × [P] / [Ti])% or less of the steel No. of the invention example. 1 to 23, as shown in Table 3 and FIG. 9, {111} / {100} which is the ratio of the crystal orientation {111} and {100} on the surface of the ground iron is (1−0.016 × [P]) / [Ti]) to (3.2-0.016 × [P] / [Ti]) and below, and no powdering or flaking occurred, which was good. On the other hand, the cold rolling ratio of the cold rolling was outside the range of (60−0.45 × [P] / [Ti])% or more and (100−0.45 × [P] / [Ti])% or less. Steel Nos. 24-31 of the comparative examples have {111} / {100} (1-0.016 × [P] / [Ti]), which is the ratio of the crystal orientation {111} and {100} on the surface of the ground iron Above or below (3.2-0.016 × [P] / [Ti]) or less, powdering or flaking occurred. Further, in Comparative Example 32 and Comparative Example 33, the cold rolling ratio of cold rolling is (60−0.45 × [P] / [Ti])% or more (100−0.45 × [P] / [Ti]). However, in Comparative Example 32, powdering occurred because the Ti content was excessive, and in Example 33, flaking occurred because the P content was excessive.
Claims (3)
Ｃ：０．０００５〜０．０１％、
Ｓｉ：０．００１〜１．０％、
Ｍｎ：０．５３〜２．５％、
Ｐ：０．００１〜０．１％、
Ｓ：０．０２％以下、
Ａｌ：０．０３５〜０．１０％、
Ｔｉ：０．０００１〜０．１％、
Ｎ：０．００１〜０．００３７％
を含有し、残部がＦｅおよび不可避的不純物からなる成分組成で、鋼板（地鉄）中のＰ濃度を［Ｐ］とし、Ｔｉ濃度を［Ｔｉ］としたときにＥＢＳＰ法により測定される鋼板表面の結晶方位｛１１１｝と｛１００｝の面積比である｛１１１｝／｛１００｝が（１−０．０１６×［Ｐ］／［Ｔｉ］）以上（３．２−０．０１６×［Ｐ］／［Ｔｉ］）以下であることを特徴とする生産性とプレス成形性に優れた合金化溶融亜鉛めっき鋼板。ただし、鋼板がＣ：０．００２５％、Ｓｉ：０．１６％、Ｍｎ：１．１０％、Ｐ：０．００４％、Ｓ：０．０１２％、Ａｌ：０．０４４％、Ｔｉ：０．０４０％、Ｎ：０．００２２％を含有し、残部がＦｅおよび不可避的不純物からなる場合を除く。 In the alloyed hot-dip galvanized steel sheet, the steel sheet (ground iron) is in mass%,
C: 0.0005 to 0.01%
Si: 0.001 to 1.0%,
Mn: 0.53-2.5%,
P: 0.001 to 0.1%,
S: 0.02% or less,
Al: 0.035 to 0.10%,
Ti: 0.0001 to 0.1%,
N: 0.001 to 0.0037%
Steel plate surface measured by the EBSP method when the P concentration in the steel sheet (ground iron) is [P] and the Ti concentration is [Ti] {111} / {100}, which is the area ratio between the crystal orientations {111} and {100}, is (1−0.016 × [P] / [Ti]) or more (3.2−0.016 × [P ] / [Ti]) An alloyed hot-dip galvanized steel sheet excellent in productivity and press formability. However, the steel plate is C : 0.0025%, Si: 0.16%, Mn: 1.10%, P: 0.004%, S: 0.012%, Al: 0.044%, Ti: 0.00. 040%, N: 0.0022% to have free and unless the balance being Fe and unavoidable impurities.
Ｂ：０．００５％以下、
Ｎｂ：０．１％以下、
Ｍｏ：０．１％以下の１種または２種以上を含有することを特徴とする請求項１に記載の生産性とプレス成形性に優れた合金化溶融亜鉛めっき鋼板。ただし、鋼板がＣ：０．００２０％、Ｓｉ：０．０１％、Ｍｎ：１．０６％、Ｐ：０．０４７％、Ｓ：０．００８％、Ａｌ：０．０４０％、Ｔｉ：０．０１８％、Ｎ：０．００２６％、Ｎｂ：０．０２２％を含有し、残部がＦｅおよび不可避的不純物からなる場合を除く。 The component composition of the steel sheet (base iron) is further mass%,
B: 0.005% or less,
Nb: 0.1% or less,
The alloyed hot-dip galvanized steel sheet having excellent productivity and press formability according to claim 1, comprising Mo: 0.1% or less. However, the steel plate is C: 0.0020%, Si: 0.01%, Mn: 1.06%, P: 0.047%, S: 0.008%, Al: 0.040%, Ti: 0.00. Excluding the case of containing 018%, N: 0.0026%, Nb: 0.022%, the balance being Fe and inevitable impurities.
ＥＢＳＰ法により測定される鋼板表面の結晶方位｛１１１｝と｛１００｝の面積比である｛１１１｝／｛１００｝が（１−０．０１６×［Ｐ］／［Ｔｉ］）以上（３．２−０．０１６×［Ｐ］／［Ｔｉ］）以下とすることを特徴とする生産性とプレス成形性に優れた合金化溶融亜鉛めっき鋼板の製造方法。 Molten steel having the composition according to claim 1 or 2 (however, C: 0.0020%, Si: 0.01%, Mn: 1.06%, P: 0.047%, S: 0.008%, al: 0.040%, Ti: 0.018 %, N: 0.0026%, Nb: a 0.022% has free, if the balance of Fe and unavoidable impurities, and, C: 0.0025 %, Si: 0.16%, Mn: 1.10%, P: 0.004%, S: 0.012%, Al: 0.044%, Ti: 0.040%, N: 0.0022% the a free, unless the balance being Fe and inevitable impurities) obtaining a continuous casting to slabs, heating the slab at 1100 to 1300 ° C., a temperature 800 ° C. or higher finishing the heating slab Under the conditions of 1050 ° C or lower and the coiling temperature of 500 ° C or higher and 800 ° C or lower The step of hot rolling to obtain a hot rolled coil, the step of pickling by removing the scale using hydrochloric acid or sulfuric acid to obtain the pickled coil, and the pickling coil with the P concentration in the steel plate [P , And when the Ti concentration is [Ti], the cold rolling is (60−0.45 × [P] / [Ti])% or more and (100−0.45 × [P] / [Ti])% or less. By carrying out a step of cold rolling at a rate to form a cold-rolled coil, and annealing the coil at a temperature equal to or higher than the recrystallization temperature, and then subjecting the coil surface to hot-dip plating,
{111} / {100}, which is the area ratio between the crystal orientations {111} and {100} on the steel sheet surface measured by the EBSP method, is (1−0.016 × [P] / [Ti]) or more (3. 2-0.016 × [P] / [Ti]) or less, a method for producing an galvannealed steel sheet having excellent productivity and press formability.
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| CN107794445A (en) * | 2017-10-23 | 2018-03-13 | 攀钢集团攀枝花钢铁研究院有限公司 | Hot-dip galvanizing sheet steel and preparation method thereof |
| CN107739981A (en) * | 2017-10-23 | 2018-02-27 | 攀钢集团攀枝花钢铁研究院有限公司 | Baking hardening hot-dip galvanizing sheet steel and preparation method thereof |
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| JP2600528B2 (en) * | 1991-07-29 | 1997-04-16 | 住友金属工業株式会社 | Galvannealed steel sheet |
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