JP5476676B2 - Hot-pressed member and manufacturing method thereof - Google Patents
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本発明は、ホットプレス部材及びその製造方法に関し、特に、塗装後耐食性及び生産性に優れるホットプレス部材及びその製造方法に関する。 The present invention relates to a hot press member and a manufacturing method thereof, and more particularly, to a hot press member excellent in post-coating corrosion resistance and productivity and a manufacturing method thereof.
近年、自動車用鋼板の用途（例えば、自動車のピラー、ドアインパクトビーム、バンパービーム等）などにおいて、高強度と高成形性を両立する鋼板が望まれており、これに対応するものの１つとして、残留オーステナイトのマルテンサイト変態を利用したＴＲＩＰ（Ｔｒａｎｓｆｏｒｍａｔｉｏｎ Ｉｎｄｕｃｅｄ Ｐｌａｃｉｔｉｃｉｔｙ）鋼がある。このＴＲＩＰ鋼により、成形性の優れた１０００ＭＰａ級程度の強度を有する高強度鋼板を製造することは可能であるが、さらに高強度、例えば１５００ＭＰａ以上といった超高強度鋼で成形性を確保することは困難である。 In recent years, in steel plate applications for automobiles (for example, automobile pillars, door impact beams, bumper beams, etc.) and the like, steel plates that have both high strength and high formability have been desired. There is TRIP (Transformation Induced Privacy) steel using martensitic transformation of retained austenite. With this TRIP steel, it is possible to produce a high-strength steel sheet having excellent formability and a strength of about 1000 MPa, but it is possible to secure formability with ultra-high-strength steel having higher strength, for example, 1500 MPa or more. Have difficulty.
このような状況で、高強度及び高成形性を両立するものとして最近注目を浴びているのが、ホットプレス（熱間プレス、ホットスタンプ、ダイクエンチ、プレスクエンチ等とも呼称される。）である。このホットプレスは、鋼板を８００℃以上のオーステナイト域で加熱した後に熱間で成形することにより高強度鋼板の成形性を向上させ、成形後の冷却により焼きを入れて所望の材質を得るというものである。 Under such circumstances, hot press (also referred to as hot pressing, hot stamping, die quenching, press quenching, etc.) has recently been attracting attention as having both high strength and high formability. This hot press improves the formability of a high-strength steel sheet by heating it in an austenite region at 800 ° C. or higher and then forming it hot, and after it is formed, it is baked to obtain a desired material. It is.
ホットプレスは、超高強度の部材を成形する方法として有望であるが、通常は大気中で鋼板を加熱する工程を有しており、この際、鋼板表面に酸化物（スケール）が生成するため、スケールを除去する工程が必要であった。ところが、このような後工程には、スケールの除去能や環境負荷等の観点からの対応策の必要性等の問題があった。 Hot press is promising as a method of forming ultra-high strength members, but usually has a step of heating the steel plate in the atmosphere, and at this time, oxide (scale) is generated on the steel plate surface. The process of removing the scale was necessary. However, such post-processes have problems such as the necessity of countermeasures from the viewpoints of scale removal ability and environmental load.
これを改善する技術として、ホットプレス用の鋼板としてＡｌめっき鋼板を使用することにより、加熱時のスケールの生成を抑制する技術が提案されている（例えば、特許文献１〜３を参照）。 As a technique for improving this, a technique for suppressing the generation of scale during heating by using an Al-plated steel sheet as a steel sheet for hot pressing has been proposed (see, for example, Patent Documents 1 to 3).
しかしながら、上記特許文献１〜３に記載された技術は、炉加熱のような昇温速度が緩やかな加熱条件を前提としている。このような加熱条件の場合、塗装後耐食性を確保するためには、高めっき付着量とすることが必要であった。付着量が多過ぎると熱間での成形時にめっきが剥離する懸念があり、また、金型にＡｌ−Ｆｅ粉が付着する場合もあり、これらによりホットプレス工程自体の生産性が低下する、という問題があった。 However, the techniques described in Patent Documents 1 to 3 presuppose heating conditions such as furnace heating with a slow temperature increase rate. In the case of such heating conditions, in order to ensure the corrosion resistance after coating, it was necessary to make the coating amount high. If the amount of adhesion is too large, there is a concern that the plating may be peeled off during hot molding, and Al-Fe powder may adhere to the mold, which reduces the productivity of the hot press process itself. There was a problem.
また、炉加熱の場合には、通常、鋼板の昇温速度３〜５℃／秒程度であり、ホットプレスにより成形できる鋼板は２〜４個／分程度と非常に生産性が低い。これに対して、ホットプレスの生産性を向上させるために、通電加熱や誘導加熱等のような電気を使用する加熱方式で急速加熱を行うと、所謂ピンチ効果が働く。このピンチ効果により、めっき鋼板表面において、溶融しためっきが局部的に盛り上がるような現象（以降、この現象を「寄り」と称する。）が発生して局部的にめっき厚みが厚くなるなど、めっき厚みが不均一になる、という問題があった。このようなめっき厚みが不均一なめっき鋼板は、プレス時に型に噛みこんだり、凝着したりするため、生産性を阻害していた。 Further, in the case of furnace heating, the temperature rise rate of the steel sheet is usually about 3 to 5 ° C./second, and the productivity of the steel sheet that can be formed by hot pressing is about 2 to 4 pieces / minute, which is very low in productivity. On the other hand, in order to improve the productivity of the hot press, when rapid heating is performed by a heating method using electricity such as energization heating or induction heating, a so-called pinch effect works. This pinch effect causes a phenomenon that the molten plating locally swells on the surface of the plated steel sheet (hereinafter, this phenomenon is referred to as “slip”), and the plating thickness increases locally. There was a problem of non-uniformity. Such a plated steel sheet with a non-uniform plating thickness bites into or adheres to the mold during pressing, which hinders productivity.
そこで、本発明は、このような問題に鑑みてなされたもので、ホットプレス部材及びその製造方法において、低めっき付着量でも優れた耐食性を確保するとともに、生産性を向上させることを目的とする。 Therefore, the present invention has been made in view of such problems, and it is an object of the present invention to ensure excellent corrosion resistance even with a low plating adhesion amount and improve productivity in a hot press member and a manufacturing method thereof. .
本発明者らは、上記課題を解決するために鋭意研究を重ねた結果、めっき付着量、めっき鋼板の加熱速度及びプレス前のめっき鋼板の最高到達板温を適切に制御することにより、低めっき付着量でも優れた耐食性を確保するとともに、生産性を向上させることができることを見出し、この知見に基づいて本発明を完成するに至った。 As a result of intensive studies to solve the above problems, the present inventors have achieved low plating by appropriately controlling the amount of plating coating, the heating rate of the plated steel sheet, and the maximum temperature of the plated steel sheet before pressing. The present inventors have found that excellent corrosion resistance can be ensured even with an adhesion amount and productivity can be improved, and the present invention has been completed based on this finding.
すなわち、本発明の要旨とするところは、以下の通りである。
（１） 鋼成分として質量％でＣ：０．１〜０．４％、Ｓｉ：０．０１〜０．６％、Ｍｎ：０．５〜３％、Ｔｉ：０．０１〜０．１％、Ｂ：０．０００１〜０．０１％、Ｃｒ：０．０１〜１％、Ｐ：０．０５％以下、Ｓ：０．０２％以下、Ａｌ：０．１％以下及びＮ：０．０１％以下を含有し、残部がＦｅ及び不可避的不純物からなり、付着量が片面６０ｇ／ｍ２以下となるようにＡｌめっきが施されたＡｌめっき鋼板をホットプレスすることにより、当該Ａｌめっき鋼板の表面にＦｅＡｌ２、Ｆｅ２Ａｌ５、ＦｅＡｌ３、ＦｅＡｌ及びＦｅＡｌＳｉ化合物からなる群より選択される少なくとも２種以上の金属間化合物を含有する被覆層を形成させ、前記被覆層は、Ａｌ濃度が４０質量％超の領域中に、Ａｌ濃度が４０質量％以下の領域が分散された単層構造であることを特徴とする、ホットプレス部材。
（２） 前記被覆層の厚みは、１０μｍ以上２５μｍ以下であることを特徴とする、（１）に記載のホットプレス部材。
（３） 加熱は、６００℃から最高到達板温より１０℃低い温度までの平均昇温速度が５０℃／秒以上となるような条件で行われることを特徴とする、（１）または（２）に記載のホットプレス部材。
（４） 前記最高到達板温は、９００℃以上であることを特徴とする、（３）に記載のホットプレス部材。
（５） Ａｌめっき鋼板を加熱後にホットプレスすることにより、ホットプレス部材を製造する方法であって、鋼成分として質量％でＣ：０．１〜０．４％、Ｓｉ：０．０１〜０．６％、Ｍｎ：０．５〜３％、Ｔｉ：０．０１〜０．１％、Ｂ：０．０００１〜０．０１％、Ｃｒ：０．０１〜１％、Ｐ：０．０５％以下、Ｓ：０．０２％以下、Ａｌ：０．１％以下及びＮ：０．０１％以下を含有し、残部がＦｅ及び不可避的不純物からなり、付着量が片面６０ｇ／ｍ２以下となるようにＡｌめっきが施されたＡｌめっき鋼板を、６００℃から最高到達板温より１０℃低い温度までの平均昇温速度が５０℃／秒以上となる条件で加熱することを特徴とする、ホットプレス部材の製造方法。
（６） 前記最高到達板温は、９００℃以上であることを特徴とする、（５）に記載のホットプレス部材の製造方法。
（７） 前記加熱は、通電加熱または誘導加熱により行われることを特徴とする、（５）または（６）に記載のホットプレス部材の製造方法。
That is, the gist of the present invention is as follows.
(1) C: 0.1 to 0.4%, Si: 0.01 to 0.6%, Mn: 0.5 to 3%, Ti: 0.01 to 0.1% in mass% as steel components , B: 0.0001 to 0.01%, Cr: 0.01 to 1% , P: 0.05% or less, S: 0.02% or less, Al: 0.1% or less, and N: 0.01 % Of the Al-plated steel sheet by hot-pressing the Al-plated steel sheet, the balance of which is Fe and inevitable impurities, and the Al plating is performed so that the adhesion amount is 60 g / m 2 or less on one side. A coating layer containing at least two kinds of intermetallic compounds selected from the group consisting of FeAl 2 , Fe 2 Al 5 , FeAl 3 , FeAl and FeAlSi compounds is formed on the surface, and the coating layer has an Al concentration of 40 The region where the Al concentration is 40% by mass or less in the region of more than mass%. Characterized in that but a single layer structure that is dispersed, hot pressing member.
(2) The hot press member according to (1), wherein the coating layer has a thickness of 10 μm or more and 25 μm or less.
(3) pressurized heat, characterized in that the average heating rate from 600 ° C. to peak metal 10 ° C. lower temperature than the temperature is carried out under conditions such that 50 ° C. / sec or more, (1) or ( The hot press member as described in 2).
(4) The hot pressed member according to (3), wherein the maximum plate temperature is 900 ° C. or higher.
(5) A method of manufacturing a hot-pressed member by hot-pressing an Al-plated steel sheet after heating, wherein C: 0.1 to 0.4%, Si: 0.01 to 0 by mass% as a steel component .6%, Mn: 0.5-3%, Ti: 0.01-0.1%, B: 0.0001-0.01%, Cr: 0.01-1% , P: 0.05% Hereinafter, S: 0.02% or less, Al: 0.1% or less, and N: 0.01% or less , the balance is made of Fe and inevitable impurities, and the adhesion amount is 60 g / m 2 or less on one side. In this way, the Al-plated steel sheet subjected to Al plating is heated under the condition that the average rate of temperature increase from 600 ° C. to a temperature 10 ° C. lower than the maximum attained plate temperature is 50 ° C./second or more. The manufacturing method of a press member.
(6) The method for producing a hot press member according to (5), wherein the maximum plate temperature is 900 ° C. or higher.
(7) The method for manufacturing a hot press member according to (5) or (6), wherein the heating is performed by energization heating or induction heating.
本発明によれば、ホットプレス部材及びその製造方法において、めっき付着量、めっき鋼板の加熱速度及びプレス前のめっき鋼板の最高到達板温を適切に制御して、鋼板表面に所定の単層構造を有する被覆層を形成することにより、低めっき付着量でも優れた耐食性を確保するとともに、生産性を向上させることが可能となる。 According to the present invention, in a hot press member and a method for manufacturing the same, a predetermined single-layer structure is formed on the surface of the steel sheet by appropriately controlling the coating amount, the heating rate of the plated steel sheet, and the maximum temperature of the plated steel sheet before pressing. By forming the coating layer having, it is possible to ensure excellent corrosion resistance even with a low plating adhesion amount and improve productivity.
以下に添付図面を参照しながら、本発明の好適な実施の形態について詳細に説明する。なお、本明細書及び図面において、実質的に同一の機能構成を有する構成要素については、同一の符号を付することにより重複説明を省略する。 Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.
［本発明に係るホットプレス部材の概要］
上述したように、上記特許文献１〜３に記載された技術では、塗装後耐食性を確保するためには、高めっき付着量とすることが必要であるが、めっき付着量が多過ぎると加工性が低下するという問題があった。また、ホットプレスの生産性を向上させるために、通電加熱等により急速加熱を行うと、所謂ピンチ効果により、鋼板表面に溶融しためっきの寄りが発生するという問題もあった。ここで、ピンチ効果とは、フレミング左手の法則（Ｆｌｅｍｉｎｇ’ｓ ｌｅｆｔ ｈａｎｄ ｒｕｌｅ）などの電磁気の法則から判るように、電流が同一方向に流れる導体には、一般的に相互に引き寄せ合う力が働く。この力により電流の導通電路が収縮する現象のことをいう。溶融したアルミめっき層のように、電流を流す導体が流動体であると、相互引力により、流動体が電路の収縮位置に収縮される。その結果、アルミめっき層の厚みは、収縮位置では厚くなり、他の部位では薄くなり、均一でなくなる。すなわち、ピンチ効果により、めっき鋼板表面において、溶融しためっきが局部的に盛り上がるような現象（寄り）が発生して局部的にめっき厚みが厚くなるなど、めっき厚みが不均一になる。
[Outline of Hot Press Member According to the Present Invention]
As described above, in the techniques described in Patent Documents 1 to 3, in order to ensure the corrosion resistance after coating, it is necessary to use a high plating adhesion amount. There was a problem that decreased. Further, when rapid heating is performed by energization heating or the like in order to improve the productivity of the hot press, there is a problem that a molten plating shift occurs on the steel sheet surface due to a so-called pinch effect. Here, the pinch effect means that, as can be seen from electromagnetic laws such as the Fleming's left hand rule (Fleming's left hand rule), forces that attract each other generally act on conductors that flow in the same direction. . This refers to a phenomenon in which the current conduction circuit contracts due to this force. If the conductor through which an electric current flows is a fluid, such as a molten aluminum plating layer, the fluid is contracted to the contracted position of the electric circuit by the mutual attractive force. As a result, the thickness of the aluminum plating layer becomes thicker at the contracted position and becomes thinner at the other portions, and is not uniform. That is, due to the pinch effect, the plating thickness becomes non-uniform, for example, a phenomenon (displacement) in which the molten plating locally rises on the surface of the plated steel sheet and the plating thickness locally increases.
本発明者らの検討の結果によれば、このめっきの寄りを防止するためには、めっき付着量を減らせば良いことがわかっている。例えば、Ａｌめっき鋼板を使用して昇温速度を５０℃／秒以上で昇温温度９００〜１２００℃とした場合には、めっき付着量が片面で３０ｇ／ｍ２では、めっきの寄りが発生せずに平滑な表面となるが、めっき付着量が片面で７０ｇ／ｍ２では、ピンチ効果により溶融しためっきの寄りが発生するという実験例が得られている。一方、めっきの寄りを防止するために、めっき付着量を減らすと、十分な塗装後耐食性を確保することができない。すなわち、生産性の向上と耐食性の確保とはトレードオフの関係にあるため、従来は、優れた耐食性と優れた生産性を兼ね備えるホットプレス部材は得られていなかった。 According to the results of the study by the present inventors, it is known that the amount of plating adhesion may be reduced in order to prevent the deviation of the plating. For example, when an Al plated steel sheet is used and the temperature rising rate is 50 ° C./second or higher and the temperature rising temperature is 900 to 1200 ° C., if the amount of plating is 30 g / m 2 on one side, the plating may be shifted. However, when the amount of plating adhesion is 70 g / m 2 on one side, an experimental example has been obtained in which a molten plating shift occurs due to the pinch effect. On the other hand, if the amount of plating adhesion is reduced in order to prevent shifting of the plating, sufficient post-coating corrosion resistance cannot be ensured. That is, since there is a trade-off between improving productivity and ensuring corrosion resistance, conventionally, a hot press member having excellent corrosion resistance and excellent productivity has not been obtained.
ここで、本発明者らは、比較的めっき付着量が少なくても良好な塗装後耐食性を得ることができるホットプレス部材を得るために鋭意検討を行っている。その結果、特許文献４（特開２００７−３１４８７４号公報）に記載されているように、加熱条件を適切に制御することにより、Ａｌめっき鋼板を加熱した際の適正な合金層の構造として、表面にＦｅＡｌ２、Ｆｅ２Ａｌ５、ＦｅＡｌ３、ＦｅＡｌ及びＡｌ固溶α−Ｆｅから成る被覆層を有し、この被覆層の組織が３層構造であるめっき鋼板が、比較的めっき付着量が少なくても良好な塗装後耐食性を得ることができるという知見を既に得ている。 Here, the present inventors have conducted intensive studies in order to obtain a hot press member that can obtain good post-coating corrosion resistance even if the amount of plating adhesion is relatively small. As a result, as described in Patent Document 4 (Japanese Patent Application Laid-Open No. 2007-314874), by appropriately controlling the heating conditions, the surface of the appropriate alloy layer structure when heating the Al-plated steel sheet, Has a coating layer composed of FeAl 2 , Fe 2 Al 5 , FeAl 3 , FeAl, and Al solid solution α-Fe, and a coated steel sheet having a three-layer structure of the coating layer has a relatively small amount of coating adhesion. However, it has already been found that good post-coating corrosion resistance can be obtained.
しかしながら、この特許文献４に記載された技術においても、実施例等に示すように、６００℃〜８５０℃の間の昇温速度が２．５〜５．５℃／秒程度と低く、生産性の向上という観点からは不十分なものであり、また、ピンチ効果によるめっきの寄り等によるめっき厚みの不均一性については検討されていない。従って、上記特許文献４に記載された技術においても、優れた耐食性と優れた生産性を兼ね備えるホットプレス部材を得ることはできていない。 However, even in the technique described in Patent Document 4, as shown in Examples and the like, the rate of temperature increase between 600 ° C. and 850 ° C. is as low as about 2.5 to 5.5 ° C./second, and the productivity This is insufficient from the viewpoint of improving the thickness, and the nonuniformity of the plating thickness due to the shift of the plating due to the pinch effect has not been studied. Therefore, even in the technique described in Patent Document 4, a hot press member having both excellent corrosion resistance and excellent productivity cannot be obtained.
そこで、本発明者らは、優れた耐食性と優れた生産性を兼ね備えるホットプレス部材を得るために鋭意検討を行った結果、めっき付着量及びめっき鋼板の加熱条件を適切に制御することにより、上記特許文献４に記載された被覆層とは異なる構造を有する合金層の構造を得ることができる、という知見を得た。 Therefore, as a result of intensive studies to obtain a hot press member having both excellent corrosion resistance and excellent productivity, the present inventors have appropriately controlled the amount of plating adhesion and the heating condition of the plated steel sheet, as described above. The knowledge that the structure of the alloy layer which has a structure different from the coating layer described in patent document 4 can be obtained was acquired.
［本発明に係るホットプレス部材の構成］
すなわち、本発明によれば、表面に、ＦｅＡｌ２、Ｆｅ２Ａｌ５、ＦｅＡｌ３、ＦｅＡｌ及びＦｅＡｌＳｉ化合物からなる群より選択される少なくとも２種以上の金属間化合物を含有する被覆層を有し、この被覆層が、Ａｌ濃度が４０質量％超の相中に、Ａｌ濃度が４０質量％以下の相が分散された単層構造であるホットプレス部材を得ることができる。以下、このような本発明に係るホットプレス部材の構成について詳細に説明する。
[Configuration of Hot Press Member According to the Present Invention]
That is, according to the present invention, the surface has a coating layer containing at least two kinds of intermetallic compounds selected from the group consisting of FeAl 2 , Fe 2 Al 5 , FeAl 3 , FeAl and FeAlSi compounds, A hot press member having a single layer structure in which the coating layer has a phase with an Al concentration of 40% by mass or less dispersed in a phase with an Al concentration of more than 40% by mass can be obtained. Hereinafter, the configuration of the hot press member according to the present invention will be described in detail.
（鋼板について）
ホットプレスが金型によるプレスと焼入を同時に行うものであることから、本発明に係るホットプレス部材の母材となる鋼板としては、焼入されやすい成分である必要がある。具体的には、鋼板中の鋼成分として、質量％で、Ｃ：０．１〜０．４％、Ｓｉ：０．０１〜０．６％、Ｍｎ：０．５〜３％、Ｔｉ：０．０１〜０．１％、Ｂ：０．０００１〜０．０１％、Ｃｒ：０．０１〜１％であることが好ましい。Ｃ量については、焼入性の向上という観点から０．１％以上であることが好ましく、また、Ｃ量が多過ぎると鋼板の靭性の低下が著しくなるため、０．４質量％以下であることが好ましい。また、Ｓｉを０．６％超添加するとＡｌめっき性が低下し、０．０１％未満とすると疲労特性が劣るため好ましくない。また、Ｍｎは焼入性に寄与する元素で０．５％以上の添加が有効であるが、焼入後の靭性の低下という観点からは３％を超えることは好ましくない。また、Ｔｉはアルミめっき後の耐熱性を向上させる元素で０．０１％以上の添加が有効であるが、過剰に添加するとＣやＮと反応して鋼板強度を低下させてしまうため、０．１％を超えることは好ましくない。また、Ｂは焼入性に寄与する元素で０．０００１％以上の添加が有効であるが、熱間での割れの懸念があるため、０．０１％を超えることは好ましくない。Ｃｒは強化元素であるとともに焼入れ性の向上に有効である。しかし、０．０１％未満ではこれらの効果が得られ難い。逆に、１％超含有すると製造時および熱延時の製造性に悪影響を及ぼすため好ましくない。また、鋼板中の成分として、他に、Ｐ、Ｓ、Ａｌ、Ｎ、Ｍｏ、Ｎｂ、Ｎｉ、Ｃｕ、Ｖ、Ｓｎ、Ｓｂ等が含有されうる。通常は、質量％で、Ｐ：０．０５％以下、Ｓ：０．０２％以下、Ａｌ：０．１％以下、Ｎ：０．０１％以下である。
(About steel plate)
Since hot pressing is performed simultaneously with pressing with a mold and quenching, the steel plate that is the base material of the hot press member according to the present invention needs to be a component that is easily quenched. Specifically, as steel components in the steel sheet, in mass%, C: 0.1 to 0.4%, Si: 0.01 to 0.6%, Mn: 0.5 to 3%, Ti: 0 0.01 to 0.1%, B: 0.0001 to 0.01%, and Cr: 0.01 to 1% are preferable. The amount of C is preferably 0.1% or more from the viewpoint of improving hardenability, and if the amount of C is too much, the toughness of the steel sheet is remarkably lowered, so that it is 0.4% by mass or less. It is preferable. Further, if Si is added in excess of 0.6%, the Al plating property is lowered, and if it is less than 0.01%, fatigue characteristics are inferior, which is not preferable. Mn is an element that contributes to hardenability, and it is effective to add 0.5% or more, but it is not preferable to exceed 3% from the viewpoint of lowering toughness after quenching. Ti is an element that improves the heat resistance after aluminum plating, and it is effective to add 0.01% or more. However, if it is added excessively, it reacts with C and N to lower the steel sheet strength. It is not preferable to exceed 1%. B is an element that contributes to hardenability, and it is effective to add 0.0001% or more. However, since there is a concern of hot cracking, it is not preferable to exceed 0.01%. Cr is a strengthening element and is effective in improving hardenability. However, if it is less than 0.01%, it is difficult to obtain these effects. On the other hand, if the content exceeds 1%, the manufacturability during production and hot rolling is adversely affected. In addition, P, S, Al, N, Mo, Nb, Ni, Cu, V, Sn, Sb, and the like may be included as components in the steel sheet. Usually, in mass%, P: 0.05% or less, S: 0.02% or less, Al: 0.1% or less, N: 0.01% or less.
（一般的な合金層の構造について）
次に、上述したような鋼板表面に形成される被覆層の構造について説明する前に、その前提として、図１を参照しながら、一般的な合金層の構造について説明する。なお、図１は、Ａｌめっき鋼板を加熱合金化した後の断面組織の構造の一般的な例を示す光学顕微鏡写真である。
(General alloy layer structure)
Next, before explaining the structure of the coating layer formed on the surface of the steel sheet as described above, as a premise, the structure of a general alloy layer will be explained with reference to FIG. FIG. 1 is an optical micrograph showing a general example of the structure of a cross-sectional structure after heat-alloying an Al-plated steel sheet.
ホットプレス前のＡｌめっき鋼板のめっき層は、表層よりＡｌ−Ｓｉ層及びＦｅＡｌＳｉ合金層から成る。このめっき層は、ホットプレス工程で９００℃程度に加熱されることでＡｌ−Ｓｉと鋼板中Ｆｅとの相互拡散が起こり、全体がＡｌ−Ｆｅ化合物へ変化する。このとき、Ａｌ−Ｆｅ化合物中に部分的にＳｉを含有する相も生成する。 The plated layer of the Al-plated steel sheet before hot pressing is composed of an Al—Si layer and a FeAlSi alloy layer from the surface layer. When this plating layer is heated to about 900 ° C. in a hot pressing process, interdiffusion between Al—Si and Fe in the steel sheet occurs, and the whole changes to an Al—Fe compound. At this time, a phase partially containing Si is also generated in the Al—Fe compound.
ここで、図１に示すように、Ａｌめっき鋼板を加熱合金化した後のＦｅ−Ａｌ合金層は、一般に５層構造となることが多い。これら５層を図１では、めっき鋼板表面から順に、１層〜５層で表している。第１層、第３層の層中のＡｌ濃度は約５０質量％、第２層中のＡｌ濃度は約３０質量％、第４層、第５層中のＡｌ濃度はそれぞれ１５〜３０質量％、１〜１５質量％の幅を持つ組成となる。残部はＦｅ及びＳｉである。第４層と第５層の界面付近にボイドの生成が観察されることもある。このような合金層の耐食性はＡｌ含有量にほぼ依存し、Ａｌ含有量が高いほど耐食性に優れる。従って、第１層、第３層が最も耐食性に優れている。なお、第５層の下部の組織は鋼素地であり、マルテンサイトを主体とする焼入組織となっている。 Here, as shown in FIG. 1, the Fe—Al alloy layer after heat-alloying an Al-plated steel sheet generally has a five-layer structure in many cases. In FIG. 1, these five layers are represented by 1 to 5 layers in order from the surface of the plated steel sheet. The Al concentration in the first and third layers is about 50% by mass, the Al concentration in the second layer is about 30% by mass, and the Al concentrations in the fourth and fifth layers are 15 to 30% by mass, respectively. The composition has a width of 1 to 15% by mass. The balance is Fe and Si. Void formation may be observed near the interface between the fourth layer and the fifth layer. The corrosion resistance of such an alloy layer substantially depends on the Al content, and the higher the Al content, the better the corrosion resistance. Therefore, the first layer and the third layer are most excellent in corrosion resistance. In addition, the structure below the fifth layer is a steel base, which is a hardened structure mainly composed of martensite.
図２に、Ｆｅ−Ａｌの二元系状態図を示す。この図２を参照すれば、第１層、第３層はＦｅＡｌ２を主成分とし、第４層、第５層はそれぞれＦｅＡｌ、αＦｅに対応するものと判断できる。また、第２層はＦｅ−Ａｌ二元系状態図から説明できないＳｉを含有する層でその詳細な組成は明らかではないが、本発明者らは、ＦｅＡｌ２とＦｅ−Ａｌ−Ｓｉ化合物が微細に混じりあったようなものであると推定している。 FIG. 2 shows a binary phase diagram of Fe—Al. Referring to FIG. 2, it can be determined that the first layer and the third layer have FeAl 2 as a main component, and the fourth layer and the fifth layer correspond to FeAl and αFe, respectively. In addition, the second layer is a layer containing Si that cannot be explained from the Fe—Al binary phase diagram, and its detailed composition is not clear, but the present inventors have found that the FeAl 2 and Fe—Al—Si compounds are fine. It is presumed that it was mixed.
（本発明に係る被覆層の構造について）
一方、本発明に係る被覆層は、上述したように、ＦｅＡｌ２、Ｆｅ２Ａｌ５、ＦｅＡｌ３、ＦｅＡｌ及びＦｅＡｌＳｉ化合物からなる群より選択される少なくとも２種以上の金属間化合物を含有し、Ａｌ濃度が４０質量％超の領域中に、Ａｌ濃度が４０質量％以下の領域が分散された単層構造を有するものである。
(About the structure of the coating layer according to the present invention)
On the other hand, as described above, the coating layer according to the present invention contains at least two kinds of intermetallic compounds selected from the group consisting of FeAl 2 , Fe 2 Al 5 , FeAl 3 , FeAl, and FeAlSi compounds, and Al It has a single layer structure in which a region having an Al concentration of 40% by mass or less is dispersed in a region having a concentration of more than 40% by mass.
ここで、上記被覆層における組織の構造としては、プレス工程前の加熱工程において生成する合金層の組織の構造を規定する。この組織は、プレス工程によって変化しないため最終的な部材の組織と一致する。 Here, the structure of the structure in the coating layer defines the structure of the structure of the alloy layer generated in the heating process before the pressing process. Since this structure is not changed by the pressing process, it matches the structure of the final member.
上記被覆層は、上述した一般的な合金層と同様に、表面にＡｌめっきが施されたＡｌめっき鋼板を加熱することにより生成される（ただし、加熱条件は全く異なる）。すなわち、上記被覆層は、加熱工程前にはＡｌめっきであるが、加熱工程において表面までＦｅが拡散して金属間化合物に変化することにより生成される。この場合、部材表面の被覆層中には金属Ａｌは存在しないが、このことは、例えば、表面からＸ線回折でのＡｌのピークを検出することにより容易に確認することができる。 The coating layer is generated by heating an Al-plated steel sheet having a surface plated with Al, as in the general alloy layer described above (however, the heating conditions are completely different). That is, although the said coating layer is Al plating before a heating process, it is produced | generated when Fe diffuses to the surface and changes to an intermetallic compound in a heating process. In this case, metal Al is not present in the coating layer on the surface of the member, but this can be easily confirmed, for example, by detecting an Al peak by X-ray diffraction from the surface.
また、「単層構造」とは、図１に示すような５層構造とは異なるもので、代表的な組織の構造を図３に示す。図１と図３との対比から判るように、図３の組織は、図１の第２層及び第４層の双方が分断され、５つの層が積層された層状構造から単層構造へと変化したものである。ここで、塗装後耐食性を担保するという観点から、本発明に係る被覆層は、図１の第２層及び第４層が単に分断されただけの構造ではなく、図１の第２層及び第４層の分断が進み（さらには体積分率も低下し）、図１の第１層及び第３層に相当するＡｌ濃度が高い海状の領域（以下、「高Ａｌ領域」という。）中に、図１の第２層及び第４層に相当するＡｌ濃度が低い島状の領域（以下、「低Ａｌ領域」という。）が分散された海島構造を有することが必要である。この高Ａｌ領域は、Ａｌの濃度が４０質量％超の領域であり、低Ａｌ領域は、Ａｌ濃度が４０質量％以下の領域である。また、高Ａｌ領域中の組成としては、４５〜５５質量％であり、低Ａｌ領域中の組成としては、１５〜３５質量％であることが多い。このような被覆層の組成や結晶構造は、電子線マイクロアナライザ（ＥＰＭＡ）、走査型電子顕微鏡−エネルギー分散型Ｘ線分析装置（ＳＥＭ−ＥＤＳ）、透過型電子顕微鏡（ＴＥＭ）等を用いて分析することにより特定することができる。なお、図４に示すように、加熱条件によっては図３に示した合金層と鋼板の界面に層状のα−Ｆｅ層を有する場合もある。 The “single layer structure” is different from the five layer structure as shown in FIG. 1, and a typical structure of the structure is shown in FIG. As can be seen from the comparison between FIG. 1 and FIG. 3, the structure of FIG. 3 is changed from a layered structure in which both the second layer and the fourth layer in FIG. 1 are divided and five layers are laminated to a single layer structure. It has changed. Here, from the viewpoint of ensuring post-coating corrosion resistance, the coating layer according to the present invention is not a structure in which the second layer and the fourth layer in FIG. 1 are simply divided, but the second layer and the second layer in FIG. The division of the four layers progresses (and the volume fraction also decreases), and the sea-like region (hereinafter referred to as “high Al region”) having a high Al concentration corresponding to the first layer and the third layer in FIG. In addition, it is necessary to have a sea-island structure in which island-like regions having a low Al concentration (hereinafter referred to as “low-Al regions”) corresponding to the second layer and the fourth layer in FIG. 1 are dispersed. The high Al region is a region where the Al concentration exceeds 40% by mass, and the low Al region is a region where the Al concentration is 40% by mass or less. Further, the composition in the high Al region is 45 to 55% by mass, and the composition in the low Al region is often 15 to 35% by mass. The composition and crystal structure of such a coating layer are analyzed using an electron beam microanalyzer (EPMA), a scanning electron microscope-energy dispersive X-ray analyzer (SEM-EDS), a transmission electron microscope (TEM), or the like. Can be specified. As shown in FIG. 4, depending on the heating conditions, there may be a layered α-Fe layer at the interface between the alloy layer and the steel plate shown in FIG.
このような本発明に係る被覆層の組織を得るためには、合金層の構造を律する６００℃から最高到達板温より１０℃低い温度（例えば、８５０℃程度）までの温度域において、所定の速度以上で昇温することにより、海状の高Ａｌ領域中に、島状の低Ａｌ領域が分散された海島構造を有することができる。加熱方式については特に限定しないが、本発明では、例えば５０℃／秒以上の昇温速度で急速加熱を行うことが必要であるため、通電加熱や高周波誘導加熱等の電気を用いる加熱方式を使用することが好ましい。本発明者らは、従来のような炉加熱や特許文献４に記載されたような近赤外線を用いた加熱等とは異なり、通電加熱や高周波誘電加熱等では熱が鋼板内部から発生するため、この熱の発生の仕方が影響して上述したような海島構造をとりやすくなるものと推定している。 In order to obtain the structure of the coating layer according to the present invention, in a temperature range from 600 ° C. that regulates the structure of the alloy layer to a temperature that is 10 ° C. lower than the maximum plate temperature (for example, about 850 ° C.), By raising the temperature at a speed higher than the speed, it is possible to have a sea-island structure in which island-like low Al regions are dispersed in a sea-like high Al region. The heating method is not particularly limited, but in the present invention, for example, since it is necessary to perform rapid heating at a temperature rising rate of 50 ° C./second or more, a heating method using electricity such as energization heating or high frequency induction heating is used. It is preferable to do. Unlike the conventional furnace heating or the heating using near infrared rays as described in Patent Document 4, the present inventors generate heat from the inside of the steel sheet in the electric heating or high frequency dielectric heating, It is presumed that this heat generation will affect the sea-island structure as described above.
なお、本発明における被覆層の厚みは、例えば、加熱工程後のめっき鋼板の断面の電子顕微鏡写真を画像解析する等の手法により測定することができる。また、被覆層と鋼板（母材）との界面は、例えば、２〜３体積％のナイタールエッチングをすることで容易に判別することができる。 In addition, the thickness of the coating layer in this invention can be measured by methods, such as image-analyzing the electron micrograph of the cross section of the plated steel plate after a heating process, for example. Further, the interface between the coating layer and the steel plate (base material) can be easily identified by performing, for example, 2-3% by volume of nital etching.
（Ａｌめっきについて）
本発明に係るホットプレス部材は、表面にＡｌめっきが施されたＡｌめっき鋼板を加熱することにより製造されるが、本発明における鋼板へのＡｌめっきの方法については特に限定するものでなく、溶融めっき法を初めとして電気めっき法、真空蒸着法、クラッド法等が可能である。現在工業的に最も普及しているのは溶融めっき法であり、通常、めっき浴として、Ａｌに３質量％〜１５質量％のＳｉを含有するものを使用することができ、これに不可避的不純物のＦｅ等が混入している。これ以外の添加元素として、Ｍｎ、Ｃｒ、Ｍｇ、Ｔｉ、Ｚｎ、Ｓｂ、Ｓｎ、Ｃｕ、Ｎｉ、Ｃｏ、Ｉｎ、Ｂｉ、ミッシュメタル等があり得るが、めっき層がＡｌを主体とする限り、適用可能である。Ｚｎ、Ｍｇの添加は赤錆を発生し難くするという意味で有効であるが、蒸気圧の高いこれら元素の過剰な添加はＺｎ、Ｍｇのヒューム発生、表面へのＺｎ、Ｍｇ起因の粉体状物質の生成等があり、Ｚｎ：６０質量％以上、Ｍｇ：１０質量％以上の添加は好ましくない。
(About Al plating)
The hot-pressed member according to the present invention is manufactured by heating an Al-plated steel sheet having a surface plated with Al, but the method of Al plating on the steel sheet in the present invention is not particularly limited, and is melted. An electroplating method, a vacuum deposition method, a clad method, etc. are possible starting with a plating method. Currently, the most widely used industrially is the hot dipping method. Usually, a plating bath containing 3% by mass to 15% by mass of Si can be used as an inevitable impurity. Fe and the like are mixed. Other additive elements may be Mn, Cr, Mg, Ti, Zn, Sb, Sn, Cu, Ni, Co, In, Bi, Misch metal, etc., but as long as the plating layer is mainly Al. Is possible. Addition of Zn and Mg is effective in terms of making red rust unlikely to occur, but excessive addition of these elements having a high vapor pressure causes generation of fumes of Zn and Mg, Zn on the surface, and powdery substances derived from Mg The addition of Zn: 60% by mass or more and Mg: 10% by mass or more is not preferable.
また、本発明において、Ａｌめっきのめっき前処理、後処理等については特に限定するものではない。めっき前処理としてＮｉ、Ｃｕ、Ｃｒ、Ｆｅプレめっき等もありうるが、これも適用可能である。また、めっき後処理としては一次防錆、潤滑性を目的としてクロメート処理、樹脂被覆処理等を施してもよい。ただし、クロメート処理については、近年の６価クロム規制を考慮すると、電解クロメート等の３価の処理皮膜が好ましい。その他、無機系のクロメート以外の後処理も適用可能である。潤滑性を付与するため、アルミナ、シリカ、ＭｏＳ２等を用いて予め表面処理することも可能である。 Moreover, in this invention, it does not specifically limit about the plating pre-processing and post-processing of Al plating. Ni, Cu, Cr, Fe pre-plating and the like may be used as the plating pretreatment, but this is also applicable. Further, as a post-plating treatment, chromate treatment, resin coating treatment, or the like may be performed for the purpose of primary rust prevention and lubricity. However, with regard to the chromate treatment, a trivalent treatment film such as electrolytic chromate is preferable in consideration of recent hexavalent chromium regulations. In addition, post-treatment other than inorganic chromate is also applicable. In order to impart lubricity, it is also possible to perform surface treatment in advance using alumina, silica, MoS 2 or the like.
本発明において、加熱工程前のＡｌめっき鋼板は、表層に位置するＡｌめっき層と、このＡｌめっき層と鋼板（母材）との界面に存在するＦｅ−Ａｌ合金層とを有する。このとき、Ａｌめっき層とＦｅ−Ａｌ合金層との界面の平均粗さＲａが０．５μｍ以上３μｍ以下であることが好ましい。Ａｌめっき層とＦｅ−Ａｌ合金層との界面の粗度をこの範囲とすることにより、物理的な合金層の凹凸形状が溶融したＡｌの移動を阻害することで、加熱工程において、ピンチ効果による溶融しためっきの寄りを防止して、被覆層の厚みが不均一となることを防止することができる。 In the present invention, the Al-plated steel sheet before the heating step has an Al-plated layer located on the surface layer and an Fe—Al alloy layer present at the interface between the Al-plated layer and the steel sheet (base material). At this time, the average roughness Ra of the interface between the Al plating layer and the Fe—Al alloy layer is preferably 0.5 μm or more and 3 μm or less. By setting the roughness of the interface between the Al plating layer and the Fe—Al alloy layer within this range, the uneven shape of the physical alloy layer inhibits the movement of the molten Al, thereby causing a pinch effect in the heating process. It is possible to prevent the plating from being melted and prevent the coating layer from becoming uneven in thickness.
［本発明に係るホットプレス部材の製造方法］
以上、本発明に係るホットプレス部材の構成について詳細に説明したが、続いて、このような構成を有する本発明に係るホットプレス部材の製造方法について詳細に説明する。
[Method for Producing Hot Press Member According to the Present Invention]
The configuration of the hot press member according to the present invention has been described in detail above. Subsequently, the method for manufacturing the hot press member according to the present invention having such a configuration will be described in detail.
本発明に係るホットプレス部材は、鋼成分として、上述したように、質量％でＣ：０．１〜０．４％、Ｓｉ：０．０１〜０．６％、Ｍｎ：０．５〜３％、Ｔｉ：０．０１〜０．１％、Ｂ：０．０００１〜０．０１％を含有し、付着量が６０ｇ／ｍ２以下となるようにＡｌめっきが施されたＡｌめっき鋼板を、６００℃から最高到達板温より１０℃低い温度までの平均昇温速度が５０℃／秒以上となる条件で加熱することにより製造する。付着量を６０ｇ／ｍ２以下とするのは、上述したように、ピンチ効果によるめっきの寄りを防止するためである。なお、めっき付着量が６０ｇ／ｍ２とは、平均のめっき厚みで約２２μｍに相当する。重量換算の付着重量とめっき厚みとは比例関係にあり、本願発明でのめっき厚みとは付着厚みの平均値を言う。 As described above, the hot press member according to the present invention is C: 0.1 to 0.4% in mass%, Si: 0.01 to 0.6%, Mn: 0.5 to 3 as a steel component. %, Ti: 0.01-0.1%, B: 0.0001-0.01%, Al-plated steel sheet on which Al plating is applied so that the adhesion amount is 60 g / m 2 or less, It manufactures by heating on the conditions that the average temperature increase rate from 600 degreeC to the temperature 10 degreeC lower than the maximum attainment board temperature becomes 50 degreeC / second or more. The reason why the adhesion amount is set to 60 g / m 2 or less is to prevent the shifting of the plating due to the pinch effect as described above. The plating adhesion amount of 60 g / m 2 corresponds to an average plating thickness of about 22 μm. The attached weight in terms of weight and the plating thickness are in a proportional relationship, and the plating thickness in the present invention means an average value of the attached thickness.
鋼組成については上述したので、その説明を省略する。以下、Ａｌめっき鋼板の加熱条件について詳細に説明する。 Since the steel composition has been described above, the description thereof is omitted. Hereinafter, the heating conditions for the Al-plated steel sheet will be described in detail.
本発明者らは、本発明に係る被覆層（合金層）の構造を主に律するのは、６００℃から最高到達板温より１０℃低い温度までの温度域における昇温速度（℃／秒）であると考えている。到達板温よりも１０℃低い温度としたのは、到達板温近傍では昇温速度が小さくなることから、終点を正確に定めるのが困難なためである。本発明では、この温度域において、５０℃／秒以上の昇温速度で急速加熱を行う。このような加熱を行うことにより、上述したような海島構造を有する被覆層の組織を生成することができる。加熱方式については特に限定しないが、本発明では５０℃／秒以上の昇温速度で急速加熱を行うことが必要であるため、通常の炉加熱や輻射熱を用いる近赤外線方式の加熱方式ではなく、昇温速度５０℃／秒以上の急速加熱を行うことが可能な、通電加熱や高周波誘導加熱等の電気を用いる加熱方式を使用することが好ましい。昇温速度の上限は特に規定しないが、上記の通電加熱や高周波誘導加熱等の加熱方式を使用する場合には、その装置の電源容量、つまりは初期コストに依存するが、通常３００℃／秒程度が上限となることが多い。 The present inventors mainly determine the structure of the coating layer (alloy layer) according to the present invention. The rate of temperature increase in the temperature range from 600 ° C. to 10 ° C. lower than the maximum plate temperature (° C./second) I believe that. The reason why the temperature is 10 ° C. lower than the ultimate plate temperature is that it is difficult to accurately determine the end point because the rate of temperature rise is small in the vicinity of the ultimate plate temperature. In the present invention, rapid heating is performed at a temperature increase rate of 50 ° C./second or more in this temperature range. By performing such heating, the structure of the coating layer having the sea-island structure as described above can be generated. The heating method is not particularly limited, but in the present invention, it is necessary to perform rapid heating at a temperature rising rate of 50 ° C./second or more. Therefore, it is not a near-infrared heating method using normal furnace heating or radiant heat, It is preferable to use a heating method using electricity, such as energization heating or high-frequency induction heating, capable of rapid heating at a temperature rising rate of 50 ° C./second or more. The upper limit of the rate of temperature rise is not particularly specified, but when using the heating method such as the above-mentioned current heating or high frequency induction heating, although it depends on the power source capacity of the apparatus, that is, the initial cost, it is usually 300 ° C./second. The degree is often the upper limit.
最高到達温度については、熱間プレスの原理より、少なくともオーステナイト領域で加熱する必要がある。８５０℃以下では十分な焼入れ硬度が得られない可能性があり好ましくない。また、Ａｌめっき層はＡｌ−Ｆｅ合金層に変化する必要があり、この意味からも８５０℃以下は好ましくない。１０００℃を超える温度で合金化が進行し過ぎると、Ａｌ−Ｆｅ合金層中のＦｅ濃度が上昇して塗装後耐食性の低下を招くことがある。これは昇温速度、Ａｌめっき付着量にも依存するため一概には言えないが、経済性を考慮しても１１００℃以上の加熱は好ましくない。ホットプレス部材の最高到達板温を９００℃以上とすれば、鋼板を確実にオーステナイト域まで変態させるとともに、表面まで十分に合金化を進行させることができる。 Regarding the maximum temperature reached, it is necessary to heat at least in the austenite region based on the principle of hot pressing. If it is 850 ° C. or less, there is a possibility that sufficient quenching hardness may not be obtained, which is not preferable. Further, the Al plating layer needs to be changed to an Al—Fe alloy layer, and from this point of view, 850 ° C. or lower is not preferable. If alloying proceeds excessively at a temperature exceeding 1000 ° C., the Fe concentration in the Al—Fe alloy layer may increase, resulting in a decrease in corrosion resistance after coating. Since this depends on the rate of temperature rise and the amount of Al plating deposited, it cannot be said unconditionally, but heating at 1100 ° C. or higher is not preferable in consideration of economy. If the maximum plate temperature of the hot pressed member is 900 ° C. or higher, the steel plate can be reliably transformed to the austenite region and alloying can be sufficiently advanced to the surface.
ホットプレス後の部材は、溶接、化成処理、電着塗装等を経て最終製品となる。通常は、カチオン電着塗装が用いられることが多く、その膜厚は１〜３０μｍ程度である。電着塗装の後に中塗り、上塗り等の塗装が施されることもある。 The member after hot pressing becomes a final product through welding, chemical conversion treatment, electrodeposition coating, and the like. Usually, cationic electrodeposition coating is often used, and the film thickness is about 1 to 30 μm. After electrodeposition coating, coating such as intermediate coating and top coating may be applied.
以下、実施例を用いて本発明をさらに具体的に説明する。 Hereinafter, the present invention will be described more specifically with reference to examples.
（実施例１：参考例）
通常の熱延工程及び冷延工程を経た、表１に示すような鋼成分の冷延鋼板（板厚１．２ｍｍ）を材料として、溶融Ａｌめっきを行った。溶融Ａｌめっきは無酸化炉−還元炉タイプのラインを使用し、めっき後ガスワイピング法でめっき付着量を調節し、その後冷却した。この際のめっき浴組成としてはＡｌ−９％Ｓｉ−２％Ｆｅであった。浴中のＦｅは、浴中のめっき機器やストリップから供給される不可避のものである。めっき外観は不めっき等がなく良好であった。この鋼板を大気中で加熱し、約７００℃の温度まで大気中で冷却して、その後、厚さ５０ｍｍの金型間で圧着することで急冷した。このときの金型間での冷却速度は約１５０℃／秒であった。Ａｌめっきのめっき付着量と、鋼板の加熱条件を変えて試料を作成して、これらの試料の塗装後耐食性を評価した。なお、加熱速度の影響を見るために加熱方法としては通電加熱、高周波誘導加熱法、近赤外線加熱、電気炉輻射加熱という４種類の方法を使用した。合金層構造を確認するため３％ナイタールエッチング後の断面からの光学顕微鏡組織を観察した。
(Example 1 : Reference example )
Using a cold-rolled steel sheet (thickness: 1.2 mm) having a steel component as shown in Table 1 that has undergone a normal hot-rolling process and cold-rolling process, hot-dip Al plating was performed. For the molten Al plating, a non-oxidation furnace-reduction furnace type line was used, and after plating, the amount of plating was adjusted by a gas wiping method, followed by cooling. The plating bath composition at this time was Al-9% Si-2% Fe. Fe in the bath is inevitable supplied from plating equipment or strips in the bath. The plating appearance was good with no unplating. The steel sheet was heated in the air, cooled to a temperature of about 700 ° C. in the air, and then rapidly cooled by pressure bonding between molds having a thickness of 50 mm. The cooling rate between the molds at this time was about 150 ° C./second. Samples were prepared by changing the coating amount of Al plating and the heating conditions of the steel sheet, and the corrosion resistance after coating of these samples was evaluated. In order to see the influence of the heating rate, four types of heating methods were used: energization heating, high frequency induction heating method, near infrared heating, and electric furnace radiation heating. In order to confirm the alloy layer structure, an optical microscope structure was observed from the cross section after 3% nital etching.
加熱した後の鋼板について、ピンチ効果によるめっきの厚みの不均一性を評価するため加熱前後の板厚変化を測定した。 In order to evaluate the nonuniformity of the plating thickness due to the pinch effect, the plate thickness change before and after heating was measured for the heated steel plate.
塗装後耐食性の評価に当たっては、日本パーカライジング（株）製化成処理液ＰＢ−ＳＸ３５Ｔで化成処理を施し、その後、日本ペイント（株）製カチオン電着塗料パワーニクス１１０を約２０μｍ厚みで塗装した。その後、カッターで塗膜にクロスカットを入れ、自動車技術会で定めた複合腐食試験（ＪＡＳＯ−Ｍ６０９）を１８０サイクル（６０日）行ない、クロスカットからの膨れ幅（片側最大膨れ幅）を測定した。 In the evaluation of the corrosion resistance after coating, chemical conversion treatment was performed with a chemical conversion treatment solution PB-SX35T manufactured by Nippon Parkerizing Co., Ltd., and then cationic electrodeposition paint Powernics 110 manufactured by Nippon Paint Co., Ltd. was applied with a thickness of about 20 μm. After that, a cross cut was put into the coating film with a cutter, a composite corrosion test (JASO-M609) determined by the automobile engineering association was performed for 180 cycles (60 days), and the swollen width from the cross cut (maximum swollen width on one side) was measured. .
表２に、加熱条件と組織並びに特性評価結果をまとめた。番号１のように電気炉加熱よりも、番号２、３のように近赤外線を用いた方が塗装後耐食性は改善される傾向があるが、番号４〜７、９のように本発明を用いることで、より塗装後耐食性は改善される。本発明において、めっき厚が大きいとピンチ効果によりめっきの寄りが若干認められた。この意味から付着量は上限３０μｍとすることが好ましい。また、番号８は昇温速度が速く、かつ到達温度が低いために表面に合金化していないＡｌが残存した場合である。このときには、残存したＡｌが優先的に腐食するために塗装後耐食性は大きく低下した。番号９はやや到達温度が高く、単層の底部に２μｍ程度のα−Ｆｅ生成が認められたものである。このときにも特に問題のない特性が得られた。 Table 2 summarizes the heating conditions, structure, and property evaluation results. Corrosion resistance after painting tends to be improved by using near infrared rays as in Nos. 2 and 3 rather than heating in an electric furnace as in No. 1, but the present invention is used as in Nos. 4 to 7 and 9. Thus, the corrosion resistance after painting is further improved. In the present invention, when the plating thickness is large, a slight shift of the plating is recognized due to the pinch effect. In this sense, the upper limit is preferably 30 μm. No. 8 is a case where Al that is not alloyed remains on the surface because the temperature rising rate is high and the temperature reached is low. At this time, since the remaining Al was preferentially corroded, the corrosion resistance after coating was greatly reduced. No. 9 has a slightly high reached temperature, and α-Fe production of about 2 μm was observed at the bottom of the single layer. Even at this time, a characteristic with no particular problem was obtained.
（実施例２）
第３表に示した様々な鋼成分を持つ冷延鋼板（板厚１．２ｍｍ）に実施例１と同じ要領で溶融Ａｌめっきを施した。めっき付着量は片面４０ｇ／ｍ２とした。これらのＡｌめっき鋼板を、通電加熱により６００〜８９０℃間の昇温速度７５℃／秒，到達温度９００℃で加熱し、その後金型焼入した。焼入後の硬度（ビッカース硬度、荷重１０ｋｇ）を測定した結果も第３表に示しているが，鋼中Ｃ量が低いと焼入後の硬度が低下するため，Ｃ量として０．０５質量％以上あることが好ましいことがわかる。
(Example 2)
Cold-rolled steel sheets (plate thickness 1.2 mm) having various steel components shown in Table 3 were subjected to hot Al plating in the same manner as in Example 1. The amount of plating was 40 g / m 2 on one side. These Al-plated steel sheets were heated at a heating rate of 75 ° C./second between 600 to 890 ° C. and an ultimate temperature of 900 ° C. by energization heating, and then subjected to die quenching. The results of measuring the hardness after quenching (Vickers hardness, load 10 kg) are also shown in Table 3. However, if the C content in the steel is low, the hardness after quenching decreases, so the C content is 0.05 mass. % Is preferable.
以上、添付図面を参照しながら本発明の好適な実施形態について説明したが、本発明はかかる例に限定されないことは言うまでもない。当業者であれば、特許請求の範囲に記載された範疇内において、各種の変更例または修正例に想到し得ることは明らかであり、それらについても当然に本発明の技術的範囲に属するものと了解される。 As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.
Claims (7)
前記被覆層は、Ａｌ濃度が４０質量％超の領域中に、Ａｌ濃度が４０質量％以下の領域が分散された単層構造であることを特徴とする、ホットプレス部材。 As steel components, C: 0.1 to 0.4%, Si: 0.01 to 0.6%, Mn: 0.5 to 3%, Ti: 0.01 to 0.1%, B: 0.0001 to 0.01%, Cr: 0.01 to 1% , P: 0.05% or less, S: 0.02% or less, Al: 0.1% or less, and N: 0.01% or less contained, the balance being Fe and unavoidable impurities, the Al-plated steel sheet Al-plated so that the amount of deposition becomes one-sided 60 g / m 2 or less by hot pressing, FeAl on the surface of the Al plated steel sheet 2 , forming a coating layer containing at least two kinds of intermetallic compounds selected from the group consisting of Fe 2 Al 5 , FeAl 3 , FeAl and FeAlSi compounds;
The hot-press member according to claim 1, wherein the coating layer has a single layer structure in which a region having an Al concentration of 40% by mass or less is dispersed in a region having an Al concentration of more than 40% by mass.
鋼成分として質量％でＣ：０．１〜０．４％、Ｓｉ：０．０１〜０．６％、Ｍｎ：０．５〜３％、Ｔｉ：０．０１〜０．１％、Ｂ：０．０００１〜０．０１％、Ｃｒ：０．０１〜１％、Ｐ：０．０５％以下、Ｓ：０．０２％以下、Ａｌ：０．１％以下及びＮ：０．０１％以下を含有し、残部がＦｅ及び不可避的不純物からなり、付着量が片面６０ｇ／ｍ２以下となるようにＡｌめっきが施されたＡｌめっき鋼板を、６００℃から最高到達板温より１０℃低い温度までの平均昇温速度が５０℃／秒以上となる条件で加熱することを特徴とする、ホットプレス部材の製造方法。 A method of manufacturing a hot press member by hot pressing an Al-plated steel sheet after heating,
As steel components, C: 0.1 to 0.4%, Si: 0.01 to 0.6%, Mn: 0.5 to 3%, Ti: 0.01 to 0.1%, B: 0.0001 to 0.01%, Cr: 0.01 to 1% , P: 0.05% or less, S: 0.02% or less, Al: 0.1% or less, and N: 0.01% or less Contain Al-plated steel sheet containing Al and plated with Al and inevitable impurities remaining, with an adhesion amount of 60 g / m 2 or less on one side, from 600 ° C. to a temperature 10 ° C. lower than the maximum plate temperature A method for producing a hot press member, characterized in that heating is carried out under the condition that the average temperature rise rate is 50 ° C./second or more.
The method for manufacturing a hot press member according to claim 5, wherein the heating is performed by energization heating or induction heating.
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