JP5304122B2 - Method for evaluating corrosion resistance of surface-treated steel sheets - Google Patents
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Description
本発明は、自動車フードパネルに用いられる表面処理鋼板の耐食性評価方法に関するものである。 The present invention relates to a method for evaluating corrosion resistance of a surface-treated steel sheet used for an automobile food panel.
自動車用表面処理鋼板の開発では、実際に自動車用外板として表面処理鋼板を使用した場合を想定して、塩水噴霧試験（以下、SSTと称す）、複合サイクル腐食試験（以下、CCTと称す）、暴露試験などの腐食試験により、表面処理鋼板の耐食性評価が行われている。しかし、SSTやCCTに代表される腐食促進試験の場合は、塩水濃度、温度、湿度、および時間割合などによって材料間の相対的な耐食性が変化するため、腐食試験結果が実際に自動車用外板として鋼板を用いた場合の耐食性能と異なり、実際の自動車の腐食との相関性が課題とされている。
そこで、上記課題を解決するために、例えば、実際の環境における腐食を再現するため、暴露試験や自動車に試験片を取り付けて走行するOn Vehicle Test などが行われている。
また、環境条件だけでなく、自動車の形状を模擬して加工した試験片を腐食試験に用いる場合もある。例えば、自動車のプレス成形を模擬して、表面処理鋼板に張出し加工や深絞り加工を付与した試験片が腐食試験に供されている（例えば特許文献１）。
その他、外板向け表面処理鋼板においては、チッピングなどによる塗膜損傷を起点とする外観腐食に対する耐食性が要求されることから、塗装した表面処理鋼板に、人工的に傷を付与した試験片が用いられる。また、鋼板合わせ部の穴あき腐食に対する耐食性は、合わせ内部特有の腐食環境を模擬するために、試験片として、鋼板を重ね合わせた試験片やヘミング形状に加工した試験片が用いられる。
In order to solve the above problems, for example, in order to reproduce corrosion in an actual environment, an exposure test or an On Vehicle Test in which a test piece is mounted on a vehicle is performed.
Further, not only environmental conditions but also test pieces processed by simulating the shape of an automobile may be used for the corrosion test. For example, a test piece obtained by impressing press forming of an automobile and imparting an extension process or a deep drawing process to a surface-treated steel sheet is used for a corrosion test (for example, Patent Document 1).
In addition, for surface-treated steel sheets for outer panels, corrosion resistance to appearance corrosion starting from coating film damage due to chipping, etc. is required, so test pieces with artificially scratched coated surface-treated steel sheets are used. It is done. Moreover, in order to simulate the corrosion environment peculiar to the inside of the laminated portion, the corrosion resistance against perforated corrosion of the steel plate mating portion is a test piece obtained by superimposing steel plates or a test piece processed into a hemming shape.
現在、自動車用途には多くの種類の亜鉛系めっき鋼板が用いられている。また、摺動性や耐食性の向上を目的として、めっき上に有機、無機皮膜を形成した化成処理鋼板も用いられている。
これらのめっき皮膜や化成処理皮膜（これらをまとめて表面処理皮膜と称す）は、鋼板の製造時においては、均一に鋼板表面に被覆されているが、加工を付与することで表面処理皮膜が損傷する場合がある。場合によってはパウダリングやフレーキングなどの剥離現象を引き起こす。特に自動車部品の多くは形状が複雑で、難成形な形状のものが多く、加工による変形や摺動が大きいためめっきや化成処理皮膜は損傷を受け易い。このように表面処理皮膜が損傷を受けた場合、該皮膜が有する防錆効果が損なわれる可能性がある。
Currently, many types of galvanized steel sheets are used for automotive applications. In addition, for the purpose of improving slidability and corrosion resistance, a chemically treated steel sheet in which an organic or inorganic film is formed on the plating is also used.
These plating films and chemical conversion coatings (collectively referred to as surface treatment films) are uniformly coated on the steel sheet surface during the production of the steel sheet, but the surface treatment film is damaged by the processing. There is a case. In some cases, it causes peeling phenomena such as powdering and flaking. In particular, many automotive parts are complicated in shape, often in difficult-to-mold shapes, and are greatly deformed and slid by processing, so that plating and chemical conversion coatings are easily damaged. Thus, when the surface treatment film is damaged, the rust prevention effect of the film may be impaired.
このような加工による表面処理皮膜への影響をシミュレートする方法として、深絞り加工などの加工を付与した試験片を用いて評価することもできるが、実際の自動車の腐食箇所と加工様式は必ずしも一致していていない。また、同じ目的で実プレス加工した自動車部品が耐食性評価に用いられる場合もあるが、実際の自動車成形部品は寸法が大きく、サンプル調達性の面、腐食試験機のスペースの面からも、一様に評価することは困難であった。このように、現在の耐食性評価方法では、表面処理鋼板を適用する部材の実際の皮膜損傷とそれに伴う耐食性劣化の程度を再現できておらず、従って、適正な耐食性を評価することが困難であった。
本発明は、かかる事情に鑑みなされたもので、実際の自動車フードパネル材の腐食に対して相関性が高い、表面処理鋼板の耐食性評価方法を提供することを目的とする。
As a method of simulating the effect of such processing on the surface treatment film, it can also be evaluated using a test piece with processing such as deep drawing, but the actual corrosion location and processing mode of an automobile are not necessarily the same. Does not match. In addition, automotive parts that have been actually pressed for the same purpose may be used for corrosion resistance evaluation, but actual automotive molded parts are large in size, uniform in terms of sample availability and corrosion tester space. It was difficult to evaluate. As described above, the current corrosion resistance evaluation method cannot reproduce the actual film damage of the member to which the surface-treated steel sheet is applied and the degree of the corrosion resistance deterioration associated therewith. Therefore, it is difficult to evaluate the appropriate corrosion resistance. It was.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for evaluating the corrosion resistance of a surface-treated steel sheet having a high correlation with the corrosion of an actual automobile hood panel material.
本発明者らは、上記課題を解決すべく検討を重ねた。その結果、以下の知見を得た。
自動車は部位毎に異なる様式でプレス成形されるため、ひずみの変形分布が異なる。したがって表面処理鋼板が受ける損傷の形態や程度もそれぞれの部位によって異なる。ゆえに、自動車フードパネルなどの腐食の厳しい部位に用いられる表面処理鋼板の耐食性を評価するにあたっては、各部位の特徴的な成形様式の加工を表面処理鋼板に付与したものを試験片として、前記試験片を腐食環境に供して耐食性を評価することが重要となる。
The present inventors have repeatedly studied to solve the above problems. As a result, the following knowledge was obtained.
Since an automobile is press-molded in a different manner for each part, the strain distribution differs. Therefore, the form and degree of damage that the surface-treated steel sheet undergoes vary depending on each part. Therefore, in evaluating the corrosion resistance of surface-treated steel sheets used in severely corroded parts such as automobile hood panels, the above-mentioned test was conducted using the surface-treated steel sheets treated with the characteristic forming style of each part. It is important to subject the pieces to a corrosive environment and evaluate the corrosion resistance.
さらに、自動車において、腐食が激しい代表的な部位としては、フードパネル、ドア、クオーター、ホイールハウス、サイドシルなどの鋼板合わせ部が挙げられることから、合わせ部形状で評価することが必要となる。 Furthermore, typical parts of automobiles that are severely corroded include steel plate mating parts such as hood panels, doors, quarters, wheel houses, and side sills. Therefore, it is necessary to evaluate the mating part shape.
本発明は、以上の知見に基づき、鋭意研究を重ねた結果完成されたもので、その要旨は以下のとおりである。
［１］自動車フードパネルに用いられる表面処理鋼板の耐食性評価方法であって、表面処理鋼板に張出し加工、ドロービード加工、平面摺動加工のいずれか１種類以上の加工を付与し、前記加工付与後の異種又は同種の表面処理鋼板を重ね合わせて鋼板合わせ部を形成し、次いで、前記鋼板合わせ部を形成した鋼板を試験片として腐食環境に供して耐食性を評価することを特徴とする表面処理鋼板の耐食性評価方法。
［２］前記［１］において、鋼板合わせ部は、前記異種又は同種の表面処理鋼板を接合して形成されることを特徴とする耐食性評価方法。
［３］前記［２］において、前記接合が抵抗溶接による接合であることを特徴とする耐食性評価方法。
［４］前記［１］〜［３］において、前記試験片は、前記鋼板合わせ部を形成したのち、化成処理および電着塗装を施したものであることを特徴とする表面処理鋼板の耐食性評価方法。
The present invention has been completed as a result of intensive studies based on the above findings, and the gist thereof is as follows.
[1] A method for evaluating the corrosion resistance of a surface-treated steel sheet used for an automobile hood panel, wherein the surface-treated steel sheet is subjected to any one or more of overhanging, draw beading, and plane sliding processing, and after the processing is applied A surface-treated steel sheet characterized by superposing different kinds or the same kind of surface-treated steel sheets to form a steel sheet mating part, and then subjecting the steel sheet on which the steel sheet mating part is formed to a corrosive environment as a test piece to evaluate corrosion resistance Corrosion resistance evaluation method.
[2] The corrosion resistance evaluation method according to [1], wherein the steel sheet mating portion is formed by joining the different or the same kind of surface-treated steel sheets.
[3] The corrosion resistance evaluation method according to [2], wherein the joining is joining by resistance welding.
[4] In the above [1] to [3], the test piece is subjected to chemical conversion treatment and electrodeposition coating after forming the steel plate mating portion, and the corrosion resistance evaluation of the surface-treated steel plate, Method.
本発明の表面処理鋼板の耐食性評価方法によれば、実際の自動車フードパネル材の腐食に対して相関性が高い評価を簡便に実施することができる。その結果、材料開発の効率化および腐食試験による材料選定の精度向上が期待される。 According to the corrosion resistance evaluation method for a surface-treated steel sheet of the present invention, it is possible to easily carry out an evaluation having a high correlation with the corrosion of an actual automobile hood panel material. As a result, it is expected to improve the efficiency of material development and improve the accuracy of material selection through corrosion tests.
本発明は実際の自動車部位に即して自動車用表面処理鋼板の耐食性評価を行う方法であり、本発明では自動車フードパネルに用いられる表面処理鋼板を対象とする。そして、その特徴は、自動車フードパネルの成形様式で表面処理鋼板を加工した試験片を腐食が発生しやすい合わせ部形状にし、腐食試験に供する耐食性評価方法である。
本発明の耐食性評価の対象である自動車フードパネル材の場合は、張出し加工の要素が強く、Ｘ方向、Ｙ方向ともに材料が伸び変形を受ける。また、材料を固定し、金型側へ材料を流入させないようにビードが設けてあるが、材料の一部がビードを通過してパネルが成形される可能性がある。ゆえに、フードパネル材の耐食性評価試験を行うに際し、実際の自動車フードパネル材の腐食に対して相関性が高い評価結果を得るためには、自動車フードパネル材の特徴的な成形様式の加工、すなわち張出し加工、ドロービード加工、平面摺動加工のいずれか1種類以上の加工を表面処理鋼板に付与したものを試験片とすることが重要となる。特に好ましいのは、表面処理鋼板に、張出し加工を付与し、またはさらにドロービード加工、平面摺動加工のいずれか１種類以上の加工を付与するものである。
ここで、深絞り加工は張出し加工とは異なり、金型側へ材料を流入させる加工であり、フードパネル材の成形様式として用いるのは好ましくない。
そして、このように、自動車フードパネル材の加工を模擬して、事前に表面処理鋼板を加工しておき、加工後の表面処理鋼板を試験片として腐食試験を行うことにより、実際の自動車フードパネル材の腐食を高い精度で再現することができる。
具体的には、まず、表面処理鋼板に張出し加工、ドロービード加工、平面摺動加工のいずれか１種類以上の加工を付与し、前記加工付与後の異種又は同種の表面処理鋼板を重ね合わせて鋼板合わせ部を形成する。次いで、前記鋼板合わせ部を形成した鋼板を試験片として腐食環境に供して耐食性を評価することを特徴とする。
この時、鋼板合わせ部は、前記異種又は同種の表面処理鋼板を接合して形成されることが好ましい。また、特に抵抗溶接により接合されることが好ましい。
また、前記試験片は、鋼板合わせ部を形成したのち、化成処理および電着塗装を施したものであることが好ましい。
以下、詳細に説明する。
The present invention is a method for evaluating the corrosion resistance of a surface-treated steel sheet for automobiles according to an actual automobile part. In the present invention, a surface-treated steel sheet used for an automobile hood panel is targeted. And the feature is the corrosion-resistance evaluation method which makes the test piece which processed the surface treatment steel plate with the shaping | molding style of the automobile food panel into the joint part shape which is easy to generate | occur | produce corrosion, and uses for a corrosion test.
In the case of the automobile food panel material which is the object of the corrosion resistance evaluation of the present invention, the overhanging element is strong, and the material is stretched and deformed in both the X direction and the Y direction. Moreover, although the material is fixed and the bead is provided so that the material does not flow into the mold side, a part of the material may pass through the bead and the panel may be molded. Therefore, when performing the corrosion resistance evaluation test of the hood panel material, in order to obtain an evaluation result having a high correlation with the corrosion of the actual automobile hood panel material, It is important to use a surface-treated steel sheet that has been subjected to at least one of overhang processing, draw bead processing, and plane sliding processing. Particularly preferably, the surface-treated steel sheet is subjected to an overhanging process, or further subjected to any one or more processes of a draw bead process and a plane sliding process.
Here, unlike the overhanging process, the deep drawing process is a process in which a material is allowed to flow into the mold side, and it is not preferable to use it as a molding mode of the hood panel material.
And, in this way, by simulating the processing of the automobile hood panel material, processing the surface-treated steel plate in advance, and performing the corrosion test using the processed surface-treated steel sheet as a test piece, the actual automobile hood panel The corrosion of the material can be reproduced with high accuracy.
Specifically, first, the surface-treated steel sheet is subjected to any one or more kinds of processing such as overhanging, draw beading, and plane sliding, and the different or same type of surface-treated steel sheets after the processing are overlaid are overlapped. A mating part is formed. Next, the steel plate on which the steel plate mating portion is formed is used as a test piece in a corrosive environment to evaluate the corrosion resistance.
At this time, it is preferable that the steel plate mating portion is formed by joining the different or same kind of surface-treated steel plates. Moreover, it is preferable to join especially by resistance welding.
Moreover, it is preferable that the test piece is subjected to chemical conversion treatment and electrodeposition coating after forming a steel plate mating portion.
Details will be described below.
表面処理鋼板に張出し加工、ドロービード加工、平面摺動加工のいずれか１種類以上の加工を付与する。
自動車フードパネル材を模擬するために、例えば、表面処理鋼板に対して円筒または円錐台張出し加工を行う。加工の方法はエリクセン試験（JIS Z2247）や液圧バルジ試験など張出し加工性能を評価するための試験機を使用して加工してもよい。
また、表面処理鋼板に対してドロービード加工、平面摺動加工を行うこともできる。加工の方法は、摺動試験機（しごき）やドロービード試験機により、材料の変形に加えて摺動を付与することができ、より厳しい加工条件での加工を受けたフードパネルの耐食性を模擬することができる。そして、上記加工は１回だけでなく、複数種、複数回の加工を付与しても構わない。なおこの時の加工方法、回数等は特に限定されず、実際に用いられる自動車フードパネル材の加工方式を考慮して選択することが好ましい。
Any one or more types of overhang processing, draw bead processing, and plane sliding processing are applied to the surface-treated steel sheet.
In order to simulate an automobile hood panel material, for example, a cylindrical or truncated conical overhanging process is performed on the surface-treated steel sheet. The processing method may be performed using a testing machine for evaluating overhang processing performance such as Erichsen test (JIS Z2247) or hydraulic bulge test.
Moreover, a draw bead process and a plane sliding process can also be performed with respect to a surface treatment steel plate. The processing method can be applied to sliding in addition to material deformation by a sliding tester (ironing machine) or a draw bead tester, simulating the corrosion resistance of food panels that have been processed under more severe processing conditions. be able to. And the said process may give not only one time but multiple types and multiple times of process. In addition, the processing method, the number of times, and the like at this time are not particularly limited, and are preferably selected in consideration of the processing method of the automobile food panel material actually used.
加工付与後の異種又は同種の表面処理鋼板を重ね合わせて鋼板合わせ部を形成する。
自動車では、完全に塗装された外面よりも、複数の鋼板が重なり合った鋼板合わせ部が腐食し易く、防錆対策の中心となっている。このため、自動車フードパネルに用いられる表面処理鋼板の耐食性を評価するにあたっては、フードパネル内外板の合わせ部やフードパネルと他部品とで構成される合わせ部における腐食を再現するため、表面処理鋼板に加工を付与した後、表面処理鋼板を重ね合わせて鋼板合わせ部を形成することとする。この時の鋼板合わせ部を形成する鋼板は同種であっても異種であってもどちらでもよい。
また、鋼板合わせ部は、異種又は同種の表面処理鋼板を接合して形成することができる。例えば、スポット溶接等の抵抗溶接で接合して形成することができる。抵抗溶接は自動車の製造工程で使用されている接合方法であり、実験室においても溶接機を用いることにより簡便に接合することができる方法のため、鋼板合わせ部の形成に際し、好適に使用される。しかし、鋼板合わせ部の接合方法は上記に限定されず、他には、シーム溶接等の抵抗溶接の他に、トックス接合などのかしめ、ロウ付け、摩擦攪拌接合等が挙げられる。
The different or the same kind of surface-treated steel sheets after processing are overlapped to form a steel sheet mating portion.
In automobiles, the steel plate mating portion where a plurality of steel plates overlap is more likely to corrode than the completely painted outer surface, which is the center of rust prevention measures. For this reason, when evaluating the corrosion resistance of surface-treated steel sheets used in automobile hood panels, the surface-treated steel sheets are used to reproduce the corrosion at the mating parts of the hood panel inner and outer plates and the mating parts composed of the hood panel and other parts. After processing, the surface treated steel plates are overlapped to form a steel plate mating portion. The steel plates forming the steel plate mating portion at this time may be the same type or different types.
Moreover, the steel plate mating portion can be formed by joining different or the same type of surface-treated steel plates. For example, it can be formed by joining by resistance welding such as spot welding. Resistance welding is a joining method used in the manufacturing process of automobiles, and it is a method that can be easily joined by using a welding machine even in a laboratory, so it is preferably used when forming a steel sheet mating part. . However, the joining method of the steel sheet mating portion is not limited to the above, and other than resistance welding such as seam welding, caulking such as Tox joining, brazing, friction stir welding, and the like can be given.
鋼板合わせ部を形成した表面処理鋼板を試験片として腐食環境に供して耐食性を評価する。
試験片を、例えば、複合サイクル試験などの腐食環境に供し、所定期間後の腐食の状態を観察する、若しくは塗膜の膨れ幅、赤錆の発生頻度などを定量的に測定することによって耐食性を評価する。
耐食性を評価する方法は特に限定しない。自動車用外観腐食試験法として国内外で規格化されている試験法、例えば、国内では、JASO M 609-91で規格された試験法、米国では、米国自動車技術者協会で定めたSAE J2334などの複合サイクル試験法を用いることができる。
また、自動車の生産工程に従い、鋼板合わせ部を形成した鋼板に対して、化成処理および電着塗装を施し試験片として、この試験片に対して腐食環境に供して耐食性を評価することが好ましい。このように鋼板合わせ部に対して電着塗装までの一連の処理を施した試験片を用いることで、より実際の自動車構造を模擬することができる。
なお、化成処理および電着塗装の条件は特に限定しないが、以下に化成処理および電着塗装の条件の一例を示す。
日本パーカラインジング（株）製PB-3080りん酸塩化成処理液を用いて、りん塩皮膜量が1.8〜2.2ｇ/ｍ2になるように化成処理を行った後、関西ペイント（株）製自動車用電着塗料を用いて、焼付け後の膜厚が18〜24μｍになるように塗装する。その後、170℃の雰囲気で20分間焼付け処理する。また、化成処理前に脱脂処理、表面調整処理を行ってもよい。
また、試験片には、鋼板合わせ内部だけを腐食させ、外面からの腐食の影響を除くために、合わせ部を形成した鋼板の外表面（合わせ開口部を除く）にシールを施すことが好ましい。
The surface-treated steel sheet on which the steel sheet mating part is formed is used as a test piece in a corrosive environment to evaluate the corrosion resistance.
Evaluate the corrosion resistance by subjecting the test piece to a corrosive environment such as a combined cycle test and observing the state of corrosion after a predetermined period of time, or by quantitatively measuring the swelling width of the coating film, the occurrence frequency of red rust, etc. To do.
The method for evaluating the corrosion resistance is not particularly limited. Test methods standardized at home and abroad as exterior corrosion test methods for automobiles, such as the test methods specified in JASO M 609-91 in Japan, SAE J2334 established by the American Automobile Engineers Association in the United States, etc. A combined cycle test method can be used.
Moreover, according to the production process of a motor vehicle, it is preferable to perform chemical conversion treatment and electrodeposition coating on the steel sheet on which the steel sheet mating portion is formed, and to use the test specimen in a corrosive environment to evaluate the corrosion resistance. Thus, the actual vehicle structure can be simulated more by using the test piece that has been subjected to a series of processes up to electrodeposition coating on the steel sheet mating portion.
In addition, although the conditions of chemical conversion treatment and electrodeposition coating are not specifically limited, an example of the conditions of chemical conversion treatment and electrodeposition coating is shown below.
After performing chemical conversion treatment using PB-3080 phosphate chemical treatment solution manufactured by Nippon Parker Lines Co., Ltd. so that the amount of the phosphate film is 1.8 to 2.2 g / m 2 , manufactured by Kansai Paint Co., Ltd. Using an electrodeposition paint for automobiles, the film thickness after baking is 18-24 μm. Thereafter, baking is performed for 20 minutes in an atmosphere of 170 ° C. Moreover, you may perform a degreasing process and a surface adjustment process before chemical conversion treatment.
Moreover, it is preferable to seal the test piece on the outer surface (excluding the mating opening) of the steel sheet on which the mating portion is formed in order to corrode only the inside of the mating steel plate and eliminate the influence of corrosion from the outer surface.
なお、本発明で用いる表面処理鋼板とは、特に限定されず、使用される目的に応じて適宜選択することができる。中でも、電気亜鉛めっき鋼板、溶融亜鉛めっき鋼板および合金化溶融亜鉛めっき鋼板は好適に使用される。 The surface-treated steel sheet used in the present invention is not particularly limited and can be appropriately selected depending on the purpose of use. Among these, an electrogalvanized steel sheet, a hot dip galvanized steel sheet, and an alloyed hot dip galvanized steel sheet are preferably used.
＜参考試験片の作製＞
板厚0.75mmでめっき付着量45g／m2、及び60g／m2の合金化溶融亜鉛めっき鋼板（GA45およびGA60）2種と、板厚0.75mmでめっき付着量50g／m2の電気亜鉛めっき鋼板（EG50）ならびに冷延鋼板の計4種に対して、図１に示すドロービード加工と図２に示す張出し加工をそれぞれ施した。張出し加工後の鋼板各２枚はそのままサンプルとした。一方、ドロービード加工を受けた鋼板は加工を受けた箇所からサンプルとして各２枚切り出し採取した。次いで、同種の鋼板の上記サンプルをスポット溶接で接合して合わせ部を形成し、図３に示すドロービード加工による試験片(参考例１；ｎ＝３)と図４に示す張出し加工による試験片（参考例２；ｎ＝３）を作製した。次いで、作製した試験片の評価面の腐食に影響を及ぼす部位にポリエステル製粘着テープ（日東電工（株）製リビック（登録商標））でシールした。なお、上記ドロービード加工は、押しつけ荷重3923N（400kgf）、引き抜き速度1m/minの条件にて行い、上記張出し加工は、しわ押さえ147100N（15tf）、速度1m/minの条件にて高さ20mmの張出し加工を行った。
<Preparation of reference specimen>
Two types of alloyed hot-dip galvanized steel sheets (GA45 and GA60) with a plating thickness of 45 g / m 2 and 60 g / m 2 at a plate thickness of 0.75 mm, and electrogalvanizing with a plating thickness of 50 g / m 2 at a plate thickness of 0.75 mm A total of four types of steel plate (EG50) and cold-rolled steel plate were subjected to draw bead processing shown in FIG. 1 and overhang processing shown in FIG. Each of the two steel sheets after the overhang processing was used as a sample. On the other hand, two steel plates that were subjected to the draw bead processing were cut out and collected as samples from the processed portions. Next, the above-mentioned samples of the same type of steel plate were joined by spot welding to form a mating portion, and a test piece by draw bead processing ( Reference Example 1; n = 3) shown in FIG. 3 and a test piece by overhang processing shown in FIG. Reference Example 2; n = 3) was produced. Subsequently, the part which affects the corrosion of the evaluation surface of the produced test piece was sealed with a polyester adhesive tape (Ribik (registered trademark) manufactured by Nitto Denko Corporation). The draw bead processing is performed under the conditions of pressing load 3923N (400kgf) and pulling speed 1m / min. Processing was performed.
＜比較試験片の作製＞
比較サンプルとして、上記本発明と同様に4種の鋼板を用いて、加工を行わず、それ以外は上記本発明例１と同じ方法で作製した試験片(比較例１；ｎ＝３)を準備した。また、上記本発明の加工方法（ドロービード加工および張出し加工）の代わりに図５に示す深絞り加工を行い、図６に示す試験片とした以外は上記本発明例と同じ方法で作製した試験片(比較例２；ｎ＝３)を準備した。なお、上記深絞り加工は、ブランク径110mmφ、ポンチ径50mmφ、しわ押さえ29420N（3tf）、速度2mm/secの条件にて深さ30mmの深絞り加工を行った。
以上により得られた、参考試験片と比較試験片をSAE J2334腐食試験に供した。
また、本試験の評価のために、各めっきをフードパネルに使用し、北米を8〜12年走行した車両（各めっきについて3台）のフードパネルの鋼板合わせ部の腐食深さ測定データを用いた。なお、これら車両のフードパネルの鋼板合わせ部には、シーラー、ワックス等の副資材は使用されていない。
腐食試験は、全ての試験片について、上記の冷延鋼板と実車データの最大腐食深さの比が約１になるサイクルで終了とした。試験後、鋼板合わせ部の溶接部に穴をあけて分解し、内部の腐食生成物を除錆剤により溶解除去した後、ポイントマイクロメーターを用いて板厚を測定し、各試験片の健全部に対する板厚減少値（腐食深さ）の最大値を求めた。また、各試験片の最大腐食深さ（ｎ＝３）は、同種のめっき材を使用した実車フードパネル材の最大腐食深さ（ｎ＝３）それぞれを1とした場合の比を求めて評価した（全評価値としてｎ＝９となる）。
以上の方法により得られた結果を図７に示す。
<Production of comparative specimen>
As a comparative sample, a test piece (Comparative Example 1; n = 3) prepared by the same method as that of Invention Example 1 except that no processing was performed using four types of steel plates as in the present invention. did. Moreover, the test piece produced by the same method as the said invention example except performing the deep drawing process shown in FIG. 5 instead of the processing method (draw bead processing and overhanging process) of the said invention, and making it the test piece shown in FIG. (Comparative Example 2; n = 3) was prepared. Note that the deep drawing was performed with a depth of 30 mm under the conditions of a blank diameter of 110 mmφ, a punch diameter of 50 mmφ, a crease presser 29420N (3 tf), and a speed of 2 mm / sec.
The reference test piece and the comparative test piece obtained as described above were subjected to the SAE J2334 corrosion test.
In addition, for the evaluation of this test, the corrosion depth measurement data of the steel plate mating part of the hood panel of a vehicle (3 units for each plating) used for 8-12 years in North America was used for each hood panel. It was. In addition, secondary materials such as sealers and waxes are not used in the steel plate mating portions of the hood panels of these vehicles.
The corrosion test was completed for all the test pieces in a cycle in which the ratio of the maximum corrosion depth of the cold-rolled steel sheet and the actual vehicle data was about 1. After the test, a hole was made in the welded part of the steel plate mating part to disassemble and the internal corrosion products were dissolved and removed with a rust remover, then the plate thickness was measured using a point micrometer, and the healthy part of each test piece The maximum value of the thickness reduction value (corrosion depth) with respect to was obtained. In addition, the maximum corrosion depth (n = 3) of each test piece is evaluated by determining the ratio when the maximum corrosion depth (n = 3) of an actual vehicle hood panel material using the same kind of plating material is set to 1. (N = 9 as the total evaluation value).
The results obtained by the above method are shown in FIG.
図７より、加工せずに鋼板合わせ部を形成した試験片（比較例１）、および深絞り加工して鋼板合わせ部を形成した試験片（比較例２）では、冷延鋼板が実際の自動車と同じ程度の腐食深さに達しても、めっき鋼板（GA45、EG50、GA60）では、実際の自動車の腐食深さと大きく異なり傾向が一致していないことがわかる。
これに対して、参考のドロービード加工または張出し加工を付与し鋼板合わせ部を形成した試験片（参考例１および２）では、全てのめっき鋼板（GA45、EG50、GA60）について冷延鋼板と同様に実際の自動車の最大腐食深さとの比が0.5〜1.5の範囲であり、実際の自動車におけるフードパネル材の耐食性を高い精度で再現した。
From FIG. 7, in the test piece (Comparative Example 1) in which the steel sheet mating part is formed without processing, and in the test piece (Comparative Example 2) in which the steel sheet mating part is formed by deep drawing, the cold-rolled steel sheet is an actual automobile. Even when the corrosion depth reaches the same level as in Fig. 1, it can be seen that the tendency of the plated steel sheets (GA45, EG50, GA60) does not agree with the actual car corrosion depth.
On the other hand, in the test pieces ( Reference Examples 1 and 2) in which the reference draw bead processing or the overhang processing was applied to form the steel sheet mating portion, all the plated steel sheets (GA45, EG50, GA60) were the same as the cold-rolled steel sheets. The ratio of the maximum corrosion depth of the actual automobile is in the range of 0.5 to 1.5, and the corrosion resistance of the food panel material in the actual automobile is reproduced with high accuracy.
板厚0.75mmでめっき付着量45g／m2の合金化溶融亜鉛めっき鋼板（GA45）に対して、図８に示す平面摺動加工を付与した後、図2と同様に張出し加工を施し、加工を受けた箇所からサンプルを切断採取した。平面摺動加工は、ビードの先端5mmr、平工具の肩5mmRとし、潤滑油に一般洗浄油（スギムラＲ325Ｌ）を使用し、押し付け圧2452N（250kgf）とし、引き抜き速度を1mm/minとした。次いで、同種の鋼板の上記サンプルをスポット溶接で接合して合わせ部を形成し、試験片（本発明例３；ｎ＝３）を作製した。また、試験片に、アルカリ脱脂を行い、以下に示すように化成処理および電着塗装を施した後、さらに、本発明例１と同様に、評価面の腐食に影響を及ぼす部位にシールした。
リン酸塩化成処理液（日本パーカライジング（株）製ＰＢ−３０８０）を用いて、りん酸塩皮膜量が１．８〜２．２g/m2となるように化成処理を行った後、関西ペイント（株）製自動車用電着塗料を用いて電着塗装した。その後、１７０℃の雰囲気で20分間焼付け処理し、膜厚が１８〜２４μmの電着塗膜を形成した。
After applying the flat sliding process shown in Fig. 8 to the alloyed hot-dip galvanized steel sheet (GA45) with a plate thickness of 0.75mm and a coating weight of 45g / m 2 , the overhanging process is performed in the same way as in Fig. 2 A sample was cut and collected from the place where the test was received. In the flat sliding process, the tip of the bead was 5 mmr, the flat tool shoulder was 5 mmR, general cleaning oil (Sugimura R325L) was used as the lubricating oil, the pressing pressure was 2452 N (250 kgf), and the drawing speed was 1 mm / min. Next, the above-mentioned samples of the same type of steel plate were joined by spot welding to form a mating portion, and a test piece (Invention Example 3; n = 3) was produced. Further, the test piece was subjected to alkali degreasing and subjected to chemical conversion treatment and electrodeposition coating as shown below, and then, in the same manner as in Example 1 of the present invention, the test piece was sealed to a site that affected the corrosion of the evaluation surface.
After performing chemical conversion treatment using a phosphate chemical treatment solution (PB-3080 manufactured by Nihon Parkerizing Co., Ltd.) so that the amount of phosphate film is 1.8 to 2.2 g / m 2 , Kansai Paint Electrodeposition coating was performed using an electrodeposition paint for automobiles. Then, it baked for 20 minutes in 170 degreeC atmosphere, and formed the electrodeposition coating film with a film thickness of 18-24 micrometers.
上記のようにして、平面摺動加工および張出し加工後、化成処理、電着塗装した試験片（本発明例３；ｎ＝３）を作製した。これを試験片としてSAE J2334腐食試験に供し、実施例１と同じ試験期間で試験片を取り出した。取り出した試験片は、実施例１と同様の方法により各試験片の健全部に対する板厚減少値（腐食深さ）の最大値を求めた。また、各試験片の最大腐食深さ（ｎ＝３）は、同種のめっき材を使用した実車フードパネル材の最大腐食深さ（ｎ＝３）それぞれを1とした場合の比を求めて評価した（全評価値としてｎ＝９となる）。
以上の方法により得られた結果を実施例1の結果と併せて図７に示す。
As described above, a test piece (Invention Example 3; n = 3) prepared by chemical conversion treatment and electrodeposition coating after plane sliding and overhanging was produced. This was subjected to SAE J2334 corrosion test as a test piece, and the test piece was taken out in the same test period as in Example 1. The taken-out test piece calculated | required the maximum value of the plate | board thickness reduction | decrease value (corrosion depth) with respect to the healthy part of each test piece by the method similar to Example 1. FIG. In addition, the maximum corrosion depth (n = 3) of each test piece is evaluated by determining the ratio when the maximum corrosion depth (n = 3) of an actual vehicle hood panel material using the same kind of plating material is set to 1. (N = 9 as the total evaluation value).
The results obtained by the above method are shown in FIG. 7 together with the results of Example 1.
図７より、本発明の平面摺動加工後張出し加工を付与し鋼板合わせ部を形成した試験片（本発明例３）のめっき鋼板（GA45）では、冷延鋼板と同様に実際の自動車との腐食比が0.75〜1.25の範囲であり、実際の自動車におけるフードパネル材の耐食性をより高い精度で再現した。 From FIG. 7, in the plated steel sheet (GA45) of the test piece (Example 3 of the present invention) which was provided with the post-sliding process after the flat sliding process of the present invention and formed the steel sheet mating part, the same as the cold rolled steel sheet, The corrosion ratio is in the range of 0.75 to 1.25, and the corrosion resistance of the hood panel material in an actual automobile is reproduced with higher accuracy.
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