JP5263258B2 - Manufacturing method of high-strength automobile parts and high-strength parts - Google Patents
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Description
本発明は、自動車の構造部材・補強部材に使用されるような強度が必要とされる部材に関し、特に高温成形後の強度に優れた高強度自動車部品の製造方法および高強度部品に関するものである。 The present invention relates to a member that requires strength such as that used for a structural member / reinforcing member of an automobile, and more particularly, to a method for manufacturing a high-strength automobile part excellent in strength after high-temperature molding and a high-strength part. .
地球環境問題に端を発する自動車の軽量化のためには、自動車に使用される鋼板をできるだけ高強度化することが必要となるが、一般に鋼板を高強度化していくと伸びやｒ値が低下し、成形性が劣化していく。このような課題を解決するために、例えば温間で成形し、その際の熱を利用して該温度域での析出強化を利用して強度を上昇させるような考え方が提示されてきた。一方、より高強度を得る目的で、鋼板をオーステナイト単相域に加熱し、その後プレス成形過程にて冷却を施す技術が、非特許文献１や特許文献1に開示されている。この工法は熱間プレス、ホットプレス、ホットスタンプ、ダイクエンチ等、種々の呼び方がされている。 In order to reduce the weight of automobiles that originate in global environmental problems, it is necessary to increase the strength of steel sheets used in automobiles as much as possible. Generally, as steel sheets are increased in strength, the elongation and r value decrease. However, the moldability deteriorates. In order to solve such a problem, for example, an idea has been proposed in which molding is performed warm, and the strength is increased by utilizing precipitation strengthening in the temperature range by using heat at that time. On the other hand, Non-Patent Document 1 and Patent Document 1 disclose a technique in which a steel sheet is heated to an austenite single phase region and then cooled in a press forming process for the purpose of obtaining higher strength. This method is called various methods such as hot pressing, hot pressing, hot stamping, die quenching and the like.
この工法を使用することで1500MPa級の超高強度の部材を成形性よく製造することが可能となったが、鋼板をオーステナイト単相域まで加熱すると表面に厚い鉄の酸化物が生成し、これをショットブラストや酸洗等の手法で除去する必要があり、これは工程増となるばかりでなく、ショットブラストにより形状が崩れたり、酸洗の廃液処理が必要となるなどの問題がある。これらの問題を避けるために、耐熱性に優れたAlめっきを適用することで酸化物の発生を抑制する技術が下記特許文献１に開示されている。 By using this construction method, it became possible to produce a 1500 MPa class ultra-high strength member with good formability, but when the steel sheet was heated to the austenite single phase region, a thick iron oxide was formed on the surface. Is required to be removed by a method such as shot blasting or pickling, which not only increases the number of processes, but also causes problems such as the shape being deformed by shot blasting and the waste liquid treatment for pickling being required. In order to avoid these problems, a technique for suppressing the generation of oxide by applying Al plating excellent in heat resistance is disclosed in Patent Document 1 below.
近年ではこのようなAlめっき材のホットスタンプ工法への適用が進んできた。しかしこの工法の有する問題点として、プレスの生産性が低く、部品コストとしては従来の冷間プレスに比べて増大する点が挙げられる。プレスの生産性を向上させるためには、加熱方法を急速にする必要があり、また金型冷却速度も増大させなければならない。前者の加熱方法を急速にする方法として、下記特許文献２には放射光のエネルギー密度の高い近赤外線(NIRとも称される)加熱による急速加熱技術、また下記特許文献３には直接通電加熱を用いた急速加熱技術が開示されている。しかし近赤外線加熱の場合、非めっき材の昇温測度は上昇するものの、Alめっき材の昇温測度は非めっき材に比べると上昇し難い。これはAlめっき表面の放射率が低いためであると考えられる。更に近赤外線加熱ヒーターは一般的に高価であり、適用は経済的に見合わなくなる場合も多い。一方直接通電加熱を使用する際にはAlめっき鋼板では電磁力による溶融Alの局部的な凝集(寄り)が発生し、Alめっき付着量を厳しく制限する必要がある。また直接通電加熱の場合には電極と接触させる部位が必要であり、この部位は加熱することが難しく、Alめっき鋼板を使用する場合にはこの部位のスポット溶接性や塗装後耐食性が低下する課題がある。 In recent years, the application of such an Al plating material to the hot stamping method has been advanced. However, the problem of this method is that the productivity of the press is low, and the part cost is increased compared to the conventional cold press. In order to improve the productivity of the press, the heating method needs to be rapid, and the mold cooling rate must also be increased. As a method for making the former heating method rapid, the following Patent Document 2 discloses a rapid heating technique using near-infrared (also referred to as NIR) heating having a high energy density of radiant light, and the following Patent Document 3 directly conducts electric heating. The rapid heating technique used is disclosed. However, in the case of near-infrared heating, the temperature rise measure of the non-plated material is increased, but the temperature rise measure of the Al plated material is less likely to be increased than that of the non-plated material. This is probably because the emissivity of the Al plating surface is low. Furthermore, near-infrared heaters are generally expensive and their application is often not economically appropriate. On the other hand, when direct current heating is used, the Al-plated steel sheet causes local agglomeration (shift) of molten Al due to electromagnetic force, and it is necessary to strictly limit the amount of Al-plated adhesion. In addition, in the case of direct current heating, a part to be in contact with the electrode is necessary, and this part is difficult to heat, and when using an Al-plated steel sheet, the spot weldability and corrosion resistance after coating are reduced. There is.
本発明は上記課題を解決する方法を提供するものである。すなわち本発明は、必ず加熱しない部位が生じる直接通電加熱ではなく、輻射加熱によりAlめっき鋼板の急速加熱を実現する高強度自動車部品の製造方法および高強度部品を提供することを課題とする。 The present invention provides a method for solving the above problems. That is, an object of the present invention is to provide a method for manufacturing a high-strength automobile part and a high-strength part that realize rapid heating of an Al-plated steel sheet by radiant heating rather than direct current heating in which a part that is not necessarily heated is generated.
本発明者らは、上記課題を解決するために種々の検討を実施した。その結果、特定の化合物を含有する皮膜をAlめっき鋼板の表面に形成し、その化合物が吸収しやすい波長の電磁波による輻射加熱との着想を得るに至った。具体的には近赤外線よりも波長の長い中赤外線あるいは遠赤外線を用い、この波長域を吸収しやすい酸化物をAlめっき鋼板上に塗布することでAlめっき鋼板であっても急速に加熱することが可能となる。このような中赤外線、遠赤外線を放射するヒーターは一般に近赤外線ヒーターよりも廉価であり、より経済的な効果も得られる。これら酸化物は近赤外線域の波長は中赤外線や遠赤外線より吸収し難いが、酸化物を付与しない場合よりも吸収効率は増大することを見出した。 The present inventors have conducted various studies to solve the above problems. As a result, a film containing a specific compound was formed on the surface of the Al-plated steel sheet, and the idea of radiation heating by electromagnetic waves having a wavelength that the compound easily absorbs was obtained. Specifically, by using mid-infrared rays or far-infrared rays having a wavelength longer than that of near-infrared rays, an oxide that easily absorbs this wavelength region is coated on the Al-plated steel plate to rapidly heat even the Al-plated steel plate. Is possible. Such a heater that emits mid-infrared rays and far-infrared rays is generally less expensive than a near-infrared heater and can provide more economical effects. It has been found that these oxides are less likely to absorb near-infrared wavelengths than mid-infrared rays and far-infrared rays, but the absorption efficiency is higher than when no oxide is added.
すなわち、本発明の要旨とするところは下記の通りである。
（１）化学成分が質量%で、C:0.1〜0.5%、Mn:0.1%〜3%、Si:0.7%以下、Al:0.005〜0.1%、S:0.02%以下、P:0.03%以下、B:0.0002%〜0.0050%、Ti:0.01〜0.1%、N:0.02%以下を含有し、残部Feおよび不可避的不純物である熱延鋼板または冷延鋼板の表面に、めっき層中に５〜１２％の濃度のＳｉを含有するAlめっき層を有し、更にその表面に粒径10〜300nmの酸化物微粒子からなる膜厚0.1〜3μmの皮膜を有する鋼板を加熱する際に、波長0.5μm〜100μmの赤外線ヒーターを用いて加熱し、しかる後にプレス成形し、プレス金型内で冷却して焼入することを特徴とする高強度部品の製造方法。
（２）前記赤外線ヒーターの波長が2μm〜100μmであることを特徴とする、（１）に 記載の高強度部品の製造方法。
（３）前記酸化物粒子がZnO、SiO2、あるいはその混合物であることを特徴とする、（１）または（２）請求項２に記載の高強度部品の製造方法。
（４）前記鋼板の化学成分として質量%で、更にCr:0.01〜2%、Mo:0.01〜0.5%の1種または2種を含有することを特徴とする、（１）乃至（３）のいずれか一項に記載の高強度部品の製造方法。
（５）前記Alめっき層が表面まで合金化されていることを特徴とする、（１）乃至（４）のいずれか一項に記載の高強度部品の製造方法。
（６）（１）乃至（５）のいずれか一項に記載の方法で製造されたことを特徴とする高強 度部品。
That is, the gist of the present invention is as follows.
(1) The chemical composition is mass%, C: 0.1 to 0.5%, Mn: 0.1% to 3%, Si: 0.7% or less, Al: 0.005 to 0.1%, S: 0.02% or less, P: 0.03% or less, B: 0.0002% to 0.0050%, Ti: 0.01 to 0.1%, N: 0.02% or less, the remaining Fe and unavoidable impurities on the surface of hot or cold rolled steel sheet , 5-12 in the plating layer When heating a steel sheet having an Al plating layer containing Si at a concentration of% and having a film having a film thickness of 0.1 to 3 μm made of oxide fine particles having a particle diameter of 10 to 300 nm on the surface thereof, a wavelength of 0.5 μm to A method for producing a high-strength part, characterized by heating using a 100 μm infrared heater, then press-molding, cooling in a press mold and quenching.
(2) The method for producing a high-strength part according to (1), wherein the wavelength of the infrared heater is 2 μm to 100 μm.
(3) The method for producing a high-strength part according to (1) or (2), wherein the oxide particles are ZnO, SiO 2 , or a mixture thereof.
(4) As a chemical component of the steel sheet, the steel composition further comprises one or two of Cr: 0.01-2% and Mo: 0.01-0.5% as a chemical component of (1) to (3) The manufacturing method of the high intensity | strength components as described in any one.
(5) The method for producing a high-strength part according to any one of (1) to (4), wherein the Al plating layer is alloyed to the surface.
(6) A high-strength component manufactured by the method according to any one of (1) to (5).
本発明により、ホットスタンプ工法の生産性を高めることが可能となり、その結果高強度かつ形状安定性に優れた部品を安価に製造することができるようになり、高温成形後の強度に優れた高強度自動車部品の製造方法および高強度部品を提供することができる。これにより車体が軽量で衝突安全性に優れた自動車が製造できるため、社会的貢献が大きいものである。 According to the present invention, it becomes possible to increase the productivity of the hot stamping method, and as a result, it becomes possible to manufacture a high-strength and excellent shape-stable component at a low cost, resulting in high strength after high-temperature molding. A manufacturing method of high-strength automobile parts and high-strength parts can be provided. This makes it possible to manufacture automobiles that are light in weight and excellent in collision safety, which greatly contributes to society.
以下に本発明について詳細に説明する。本発明の特徴は、焼入後に高強度となる鋼成分を有するAlめっき鋼板の表面に波長0.5〜100μm程度の赤外線を吸収しやすい酸化物微粒子を含有する皮膜を形成し、当該波長域の赤外線を発する赤外線加熱ヒーターにより加熱し、しかる後に金型で成形し、金型内で急冷、焼入することである。特に波長2〜100μm程度の領域において酸化物の放射率が上昇するため、この波長の赤外線を使用することが特に有効である。 The present invention is described in detail below. A feature of the present invention is that a film containing oxide fine particles that easily absorb infrared rays having a wavelength of about 0.5 to 100 μm is formed on the surface of an Al-plated steel sheet having a steel component that has high strength after quenching, and infrared rays in the wavelength region It heats with the infrared heater which emits, and after that, it shape | molds with a metal mold | die, quenches and quenches in a metal mold | die. In particular, since the emissivity of the oxide rises in a region of a wavelength of about 2 to 100 μm, it is particularly effective to use infrared rays having this wavelength.
ここで赤外線について記述する。赤外線は可視光よりも長波長の電磁波であり、その波長により近赤外線、中赤外線、遠赤外線に分けられる。近赤外線は0.5〜2μm、中赤外線は2〜4μm、遠赤外線は4〜1000μm程度の波長と言われている。近赤外線が最も低波長、高周波数であり、電磁波の有するエネルギーが大きいため、急速加熱との観点からは有利とされている。 Here, infrared is described. Infrared rays are electromagnetic waves having a longer wavelength than visible light, and are classified into near infrared rays, middle infrared rays, and far infrared rays depending on the wavelength. It is said that near infrared rays have a wavelength of 0.5 to 2 μm, mid infrared rays have a wavelength of 2 to 4 μm, and far infrared rays have a wavelength of about 4 to 1000 μm. Near-infrared rays have the lowest wavelength and high frequency, and the electromagnetic wave has a large energy, which is advantageous from the viewpoint of rapid heating.
その一方で金属表面はこれら赤外線に対する放射率が小さいことが知られており、特にAlはこれらの放射率は0.1程度とされている。このためAlめっき鋼板を輻射加熱で急速加熱することは困難で、近赤外線を用いて、出力の大きいヒーターをできるだけ近づけて加熱することで900℃までの平均昇温測度が20℃/秒あるいはそれ以上を達成できるが、鋼板はヒーターから出し入れする必要があり、ヒーターと鋼板を近接させるにも限界があり、かつ出力の大きい近赤外線ヒーターは高価で上記を工業的に実現させることは困難であった。 On the other hand, it is known that the emissivity for these infrared rays is small on the metal surface, and in particular, the emissivity of Al is about 0.1. For this reason, it is difficult to rapidly heat an Al-plated steel sheet by radiant heating. By using near-infrared rays and heating a heater with a large output as close as possible, the average temperature rise measure up to 900 ° C is 20 ° C / second or more. Although the above can be achieved, the steel plate needs to be taken in and out of the heater, the heater and the steel plate are limited, and the near infrared heater with a large output is expensive and difficult to realize the above industrially. It was.
これに対して本発明は中赤外線〜遠赤外線に対する放射率の高い物質をAlめっき表面に付与することで加熱効率の改善を図ったものである。この領域の波長に対して一般に酸化物の放射率が高いことは知られているが、放射率は実際には表面形状の影響も大きく受ける。本発明においては特に酸化物の微細粒を使用することで膜厚は薄くても赤外線の吸収効果を大幅に改善し、昇温特性の改善を達成できたところに特徴がある。この皮膜は近赤外線に対しても効果を有する。 On the other hand, the present invention aims to improve the heating efficiency by applying a substance having a high emissivity for mid-infrared to far-infrared to the Al plating surface. Although it is known that the emissivity of oxides is generally high with respect to wavelengths in this region, the emissivity is actually greatly influenced by the surface shape. The present invention is characterized in that, by using fine oxide particles, the effect of absorbing infrared rays can be greatly improved and the temperature rise characteristics can be achieved even when the film thickness is small. This film also has an effect on near infrared rays.
次に、本発明に用いる鋼板の成分について説明する。 Cは冷却後の組織をマルテンサイトとして材質を確保するために添加する元素であり、強度1000MPa以上を確保するためには0.1％以上添加することが望ましい。ところが、添加量が多すぎると、衝撃変形時の強度確保が困難となるため、その上限は0.5％とする。 Next, the components of the steel sheet used in the present invention will be described. C is an element added to secure the material with the structure after cooling as martensite. It is desirable to add 0.1% or more in order to secure a strength of 1000 MPa or more. However, if the addition amount is too large, it is difficult to ensure the strength during impact deformation, so the upper limit is made 0.5%.
Mnは強度および焼入れ性を向上させる元素であり、0.1％未満では焼入れ時の強度を十分に得られず、また、3％を超えて添加しても効果が飽和し、また焼入性が向上しすぎて熱延後の冷却過程あるいは冷延再結晶後の冷却過程で焼きが入ってしまい、製造性を損なう可能性がある。このため、0.1〜3％の範囲が望ましい。 Mn is an element that improves strength and hardenability. If it is less than 0.1%, sufficient strength during quenching cannot be obtained, and if added over 3%, the effect is saturated and hardenability is improved. If it is too much, baking may occur in the cooling process after hot rolling or the cooling process after cold rolling recrystallization, which may impair the productivity. For this reason, the range of 0.1 to 3% is desirable.
Siは固溶強化型の合金元素であるが、0.7%を超えると、表面スケールの問題が生じる。また、特に鋼板表面にAlめっきする際に、CGL内の焼鈍炉において鋼板表面にSi酸化物を形成してAlめっき性が劣化する。このため上限を0.7%とすることが好ましい。 Si is a solid solution strengthened alloy element, but if it exceeds 0.7%, a problem of surface scale occurs. In particular, when Al plating is performed on the surface of the steel plate, Si plating is formed on the surface of the steel plate in the annealing furnace in the CGL, and the Al plating performance is deteriorated. For this reason, the upper limit is preferably set to 0.7%.
Alは溶鋼の脱酸剤として使われる必要な元素であり、またNを固定する元素でもあり、その量は結晶粒径や機械的性質に影響を及ぼす。このような効果を有するためには0.005%以上の含有量が必要であるが、0.1%を超えると非金属介在物が多くなり製品に表面疵が発生しやすくなる。このため、Alは0.005〜0.1%の範囲が望ましい。 Al is a necessary element used as a deoxidizer for molten steel, and is also an element that fixes N, and its amount affects the crystal grain size and mechanical properties. In order to have such an effect, a content of 0.005% or more is necessary. However, if it exceeds 0.1%, nonmetallic inclusions increase and surface defects are likely to occur in the product. For this reason, Al is preferably in the range of 0.005 to 0.1%.
Sは鋼中の非金属介在物に影響し、加工性を劣化させるとともに、靱性劣化、異方性および再熱割れ感受性の増大の原因となる。このため、Sは0.02%以下が望ましい。なお、さらに好ましくは、0.01%以下である。更にはSを0.005%以下に規制することにより、衝撃特性が飛躍的に向上する。 S affects non-metallic inclusions in steel and degrades workability, and causes toughness deterioration, anisotropy and increased reheat cracking sensitivity. For this reason, S is preferably 0.02% or less. More preferably, it is 0.01% or less. Furthermore, by restricting S to 0.005% or less, impact characteristics are dramatically improved.
Pは溶接割れ性および靱性に悪影響を及ぼす元素であるため、Pは0.03%以下が望ましい。なお、好ましくは、0.02%以下である。また、更に好ましくは0.015%以下である。 Since P is an element that adversely affects weld cracking and toughness, P is preferably 0.03% or less. In addition, Preferably, it is 0.02% or less. Further, it is more preferably 0.015% or less.
Bはプレス成形中あるいはプレス成形後の冷却での焼入れ性を向上させるために添加すると良い。この効果を発揮させるためには0.0002%以上の添加が必要である。しかしながら、この添加量がむやみに増加すると熱間での割れの懸念があることや、その効果が飽和するためその上限は0.0050%が望ましい。 B is preferably added in order to improve the hardenability during press molding or cooling after press molding. In order to exert this effect, 0.0002% or more must be added. However, if this amount increases excessively, there is a concern of hot cracking, and the effect is saturated, so the upper limit is preferably 0.0050%.
TiはBの効果を有効に発揮させるため、Bと化合物を生成するNをTiNとして固定する目的で添加してもよい。この効果を発揮させるためには、Nと結合していないTiが0.01%以上添加させることが望ましいが、Ti量がむやみに増加するとTiと結合していないC量が減少し冷却後に十分な強度が得られなくなる。このため、Tiは0.1%以下とした方がよい。 Ti may be added for the purpose of fixing N which forms B and a compound as TiN in order to effectively exhibit the effect of B. In order to exert this effect, it is desirable to add 0.01% or more of Ti that is not bonded to N. However, if the amount of Ti increases excessively, the amount of C that is not bonded to Ti decreases and sufficient strength is obtained after cooling. Cannot be obtained. Therefore, Ti should be 0.1% or less.
Nは0.02%を超えると窒化物の粗大化および固溶Nによる時効硬化により、靱性が劣化する傾向がみられる。このため、Nは0.02%以下の含有が望ましい。 When N exceeds 0.02%, the toughness tends to deteriorate due to the coarsening of nitride and age hardening due to solid solution N. For this reason, the N content is desirably 0.02% or less.
その他、必要に応じて以下の元素を添加しても良い。 CrはMnと共に焼入れ性を向上させる元素であり、またマトリックス中へM23C6型炭化物を析出させる効果を有し、強度を高めるとともに、炭化物を微細化する作用を有する。0.01%未満ではこれらの効果が十分期待できない。またCrはAlめっきと鋼素地との反応(合金化反応)に影響する元素で、Crを1%以上添加することでAlめっきをボックス焼鈍する際の合金化反応を均一に進めることができる。その一方でCr添加量が2%を超えると、Siと同様に焼鈍炉内で表面にCr酸化物を形成してAlめっき性を低下させる。このためCrは0.01〜2%の範囲が望ましい。より望ましくは、0.05〜1.5%である。 In addition, the following elements may be added as necessary. Cr is an element that improves the hardenability together with Mn, and has the effect of precipitating M 23 C 6 type carbide into the matrix, and has the effect of increasing the strength and miniaturizing the carbide. If it is less than 0.01%, these effects cannot be expected sufficiently. Cr is an element that affects the reaction (alloying reaction) between the Al plating and the steel substrate. By adding 1% or more of Cr, the alloying reaction can be promoted uniformly when box-annealing the Al plating. On the other hand, if the amount of Cr added exceeds 2%, similarly to Si, Cr oxide is formed on the surface in the annealing furnace, and the Al plating property is lowered. For this reason, Cr is desirably in the range of 0.01 to 2%. More desirably, it is 0.05 to 1.5%.
MoもCrと同様焼入れ性を向上させる元素である。0.01%未満ではこの効果が十分期待できない。またMoもAlめっきと鋼素地との反応(合金化反応)に影響する元素で、Moを0.01%以上添加することでAlめっきをボックス焼鈍する際の合金化反応を均一に進めることができる。その一方でMoは効果な元素であるため0.5%を超えないことが望ましい。 Mo, like Cr, is an element that improves hardenability. If it is less than 0.01%, this effect cannot be expected sufficiently. Mo is also an element that affects the reaction (alloying reaction) between Al plating and the steel substrate, and by adding Mo in an amount of 0.01% or more, the alloying reaction at the time of box annealing of the Al plating can be promoted uniformly. On the other hand, since Mo is an effective element, it is desirable not to exceed 0.5%.
Oについては特に規制しないが、過度の添加は靱性に悪影響を及ぼす酸化物の生成の原因となるとともに、疲労破壊の起点となる酸化物を生成するため、0.015%以下の含有が望ましい。 Although there is no particular restriction on O, excessive addition causes generation of an oxide that adversely affects toughness, and also generates an oxide that becomes the starting point of fatigue fracture. Therefore, its content is preferably 0.015% or less.
その他、不可避的に含まれる不純物が含有しても特に問題は生じない。スクラップ から混入すると考えられるNi, Cu, Snなどの元素が含有してもよい。また介在物の形状 制御のため、Ca, Mg, Y, ,As, Sb, REMを添加してもよい。またさらに強度を向上する 目的で、Nb, Zr, Mo, V、Wを添加してもよいが、むやみに増加するとこれらの元素と 結合していないC量が減少し、冷却後に十分な強度が得られなくなる。 In addition, even if impurities inevitably contained, no particular problem occurs. Elements such as Ni, Cu, and Sn that may be mixed from scrap may be contained. Ca, Mg, Y, As, Sb, and REM may be added to control the shape of inclusions. In addition, Nb, Zr, Mo, V, and W may be added for the purpose of further improving the strength. However, if the amount is increased unnecessarily, the amount of C not bonded to these elements decreases, and sufficient strength is obtained after cooling. It can no longer be obtained.
以上の成分からなる鋼片を熱間圧延し、またはさらに酸洗した熱延鋼板にＡｌめっきを施す。または、更に冷間圧延、焼鈍を行った冷延鋼板にＡｌめっきを施す。これらの工程条件はいずれも常法で良い。 A steel slab composed of the above components is hot-rolled or further subjected to Al plating on a pickled hot-rolled steel sheet. Alternatively, Al plating is applied to a cold-rolled steel sheet that has been further cold-rolled and annealed. Any of these process conditions may be a conventional method.
次にAlめっきの条件について説明する。Alめっきを施す場合、めっき浴中Si濃度は5〜12%が適している。また、Alめっき層中に0.1〜8%のMgやZnを混在させても、特に問題なく同様の特性の鋼板を製造することができる。めっき付着量は片面当たり30〜100g/m2とする。Alめっきの付着量が大きい方が化成処理、電着塗装後の耐食性が優れるが、加
熱する際には放射熱をより吸収し難くなる傾向がある。
Next, conditions for Al plating will be described. When Al plating is applied, the Si concentration in the plating bath is suitably 5 to 12%. Moreover, even if 0.1 to 8% of Mg or Zn is mixed in the Al plating layer, a steel plate having the same characteristics can be produced without any particular problem. The amount of plating is 30-100 g / m 2 per side. The larger the amount of Al plating attached, the better the corrosion resistance after chemical conversion treatment and electrodeposition coating, but it tends to be difficult to absorb radiant heat when heating.
Alめっき材をそのまま使用することもできるし、Alめっき後に合金化処理することも可能である。合金化処理はボックス焼鈍炉において行うものとする。このときボックス炉内での合金化時にAlめっき表面にAlNが生成しやすいことが知られており、この抑制のために鋼中へのCr、Mo添加が有効である。従ってボックス焼鈍で合金化する際には、鋼中にCrを1%以上添加、あるいはCrを0.5%以上でMoを複合添加し、Mn、B量で焼入性を調整することが望ましい。なお、ボックス焼鈍炉内で合金化することで表面の色調は黒色に近くなり、これだけでも合金化しないAlめっきよりも昇温特性に優れるが、この表面に更に微細な酸化物皮膜を形成させることで更に昇温特性が優れることも知見された。 The Al plating material can be used as it is, or it can be alloyed after the Al plating. The alloying process is performed in a box annealing furnace. At this time, it is known that AlN is likely to be generated on the surface of the Al plating during alloying in the box furnace, and it is effective to add Cr and Mo to the steel to suppress this. Therefore, when alloying by box annealing, it is desirable to add 1% or more of Cr to the steel, or to add Mo in combination with 0.5% or more of Cr, and adjust the hardenability by the amount of Mn and B. By alloying in a box annealing furnace, the color tone of the surface becomes close to black, and even this alone has better temperature rise characteristics than Al plating that does not alloy, but a finer oxide film should be formed on this surface It was also found that the temperature rise characteristics were even better.
Alめっき工程における焼鈍炉については、無酸化炉を有する連続式めっき設備でも、無酸化炉を有しない連続式めっき設備でも、通常の条件でめっき可能であり、本鋼板だけ特別な制御を必要としないことから、生産性を阻害することもない。 また、Alめっきに先立ってNiプレめっきやFeプレめっき、その他めっき性を向上させる金属プレめっきを施しても特に問題は無い。 The annealing furnace in the Al plating process can be plated under normal conditions, whether it is a continuous plating facility with a non-oxidizing furnace or a continuous plating facility without a non-oxidizing furnace, and only this steel plate needs special control. It does not impede productivity. Further, there is no particular problem even if Ni pre-plating, Fe pre-plating or other metal pre-plating for improving the plating property is performed prior to Al plating.
次にAlめっき表面の皮膜について述べる。先述したように、Alめっき表面に微細な酸化物の被膜を形成させることとする。この際の酸化物粒径は10〜300nmとする。本発明において酸化物粒径を小さくすることで赤外線に対する放射率が向上する知見が得られ、この意味から粒径は小さい方が望ましく、上限を300nmとする。しかし微細になるほど工業的に生産することが困難になり、工業生産性の観点から10nmを下限とする。 Next, the film on the Al plating surface will be described. As described above, a fine oxide film is formed on the Al plating surface. The oxide particle size at this time is 10 to 300 nm. In the present invention, knowledge that the emissivity with respect to infrared rays is improved by reducing the oxide particle diameter is obtained. In this sense, the smaller particle diameter is desirable, and the upper limit is set to 300 nm. However, the finer it becomes, the more difficult it is to produce industrially, and the lower limit is 10 nm from the viewpoint of industrial productivity.
酸化物皮膜の膜厚は0.1〜3μmとする。当然皮膜が厚い方が赤外線を吸収しやすくなるがその一方で酸化物は通常絶縁体のため、厚すぎるとスポット溶接性が低下する可能性がある。この意味から赤外線吸収特性確保の観点から下限を0.1μm、スポット溶接性確保のために上限を3μmとする。なお、酸化膜の厚みはFE-SEMで直接観察して測定するか、あるいは皮膜付着量をg/m2で測定し、比重、かさ密度より膜厚に換算するものとす
る。
The thickness of the oxide film is 0.1 to 3 μm. Naturally, the thicker the film, the easier it is to absorb infrared rays. On the other hand, the oxide is usually an insulator, and if it is too thick, the spot weldability may be lowered. In this sense, the lower limit is set to 0.1 μm from the viewpoint of securing infrared absorption characteristics, and the upper limit is set to 3 μm to ensure spot weldability. Note that the thickness of the oxide film is measured by directly observing with FE-SEM, or the coating amount is measured by g / m 2 and converted to the film thickness from the specific gravity and bulk density.
酸化物の種類としてはアルミナ、シリカ、ムライト、チタニア、ジルコニア等が考えられるが、特にZnO、SiO2、あるいはその混合物が好適である。SiO2(シリカ)は赤外線域での放射率が高いことに特徴があり、少ない量で放射率を発揮できる。一方ZnOはプレス時の潤滑性や化成処理性を向上させる効果がある。これらの混合物を使用することで、両方の特性を得ることも可能である。塗布液は水系の溶液が望ましく、酸化物の微細粒は場合により水溶性樹脂のバインダー、粘度、表面張力、分散性を調整するための樹脂成分を添加することが望ましい。これら樹脂成分も赤外線に対する放射率は大きく、赤外線を吸収しやすいが、200〜300℃で分解してしまい、それよりも高い温度域では昇温に対して寄与することはできない。 As the type of oxide, alumina, silica, mullite, titania, zirconia and the like can be considered, and ZnO, SiO 2 or a mixture thereof is particularly preferable. SiO 2 (silica) is characterized by high emissivity in the infrared region, and can exhibit emissivity in a small amount. On the other hand, ZnO has the effect of improving the lubricity and chemical conversion treatment during pressing. By using these mixtures, it is possible to obtain both properties. The coating solution is preferably an aqueous solution, and in the case of fine oxide particles, a water-soluble resin binder, a resin component for adjusting the viscosity, surface tension, and dispersibility may be preferably added. These resin components also have high emissivity with respect to infrared rays and easily absorb infrared rays, but decompose at 200 to 300 ° C. and cannot contribute to temperature rise in a temperature range higher than that.
液の塗布はロールコーター、スプレー等の手法でAlめっき鋼板上に塗布され、80℃程度で水分を蒸散させると共にバインダー樹脂を架橋させる。 The liquid is applied on the Al-plated steel sheet by a roll coater, spraying, or the like to evaporate moisture at about 80 ° C. and crosslink the binder resin.
こうして製造した酸化物皮膜を付与したAlめっき鋼板を赤外線加熱するが、このときの赤外線の波長は0.5〜100μmとする。下限の0.5μmは近赤外線と可視光との境界付近に相当し、これ以下の波長では赤外線とは言えず、加熱効率が低下する。一方波長が大きくなると赤外線の有するエネルギー自体は小さくなり、やはり加熱効率は低下する。この意味から波長の上限を100μmとする。近赤外線と中赤外線の境界に相当し、本発明は中赤外線よりも長波長側を利用するものとする。特に波長2〜100μmとすることが好ましく、この時の2μmは近赤外線と中赤外線の境界に相当し、酸化物はこの領域の波長の赤外線に対する放射率が高い。一般的な遠赤外線加熱ヒーターの波長域は2〜30μmの分布を持つとされており、このようなヒーターを使用することが好ましい。 The Al-plated steel sheet provided with the oxide film thus manufactured is heated with infrared rays, and the wavelength of infrared rays at this time is 0.5 to 100 μm. The lower limit of 0.5 μm corresponds to the vicinity of the boundary between near-infrared light and visible light, and at wavelengths shorter than this, it cannot be said to be infrared light, and the heating efficiency decreases. On the other hand, when the wavelength is increased, the energy itself of the infrared ray is decreased, and the heating efficiency is also decreased. In this sense, the upper limit of the wavelength is 100 μm. This corresponds to the boundary between the near infrared ray and the mid infrared ray, and the present invention uses the longer wavelength side than the mid infrared ray. In particular, the wavelength is preferably 2 to 100 μm, and 2 μm at this time corresponds to the boundary between the near-infrared ray and the mid-infrared ray, and the oxide has a high emissivity with respect to infrared rays having a wavelength in this region. The wavelength range of a general far-infrared heater is supposed to have a distribution of 2 to 30 μm, and it is preferable to use such a heater.
こうして酸化物皮膜層は赤外線を吸収してAlめっき鋼板の昇温測度を増大させる。このとき皮膜中のZnOやSiO2は熱により焼結されてやや粒径が増大する。従って本発明においては加熱前の皮膜における粒径、厚みを規定するものとする。 Thus, the oxide film layer absorbs infrared rays and increases the temperature measurement measure of the Al-plated steel sheet. At this time, ZnO and SiO 2 in the coating are sintered by heat and the particle size is slightly increased. Therefore, in this invention, the particle size and thickness in the film before heating shall be prescribed | regulated.
表１に示された鋼成分を有する鋼帯を通常の熱延、酸洗、冷延工程を経て板厚1.4mmに調整した後に無酸化炉型の連続溶融めっきラインにおいてAlめっきした。このときのAlめっき浴は約9%Si、約2%のFeを含有していた。付着量は両面80〜160g/m2に調整した。 A steel strip having the steel components shown in Table 1 was adjusted to a sheet thickness of 1.4 mm through normal hot rolling, pickling, and cold rolling processes, and then subjected to Al plating in a non-oxidizing furnace type continuous hot dipping line. The Al plating bath at this time contained about 9% Si and about 2% Fe. The adhesion amount was adjusted to 80 to 160 g / m 2 on both sides.
次に種々の付着量を有するAlめっき材にロールコーターで微細な酸化物を含有する水溶性塗布液を塗布し、乾燥炉内で板温80℃まで昇温させた。このときの塗布液と酸化物種類、粒径、膜厚を表２にまとめる。酸化物の混合比は質量比を意味する。比較として酸化物皮膜のないAlめっきも評価した。 Next, a water-soluble coating solution containing fine oxides was applied to an Al plating material having various adhesion amounts with a roll coater, and the temperature was raised to 80 ° C. in a drying furnace. Table 2 summarizes the coating solution, oxide type, particle size, and film thickness at this time. The mixing ratio of oxides means mass ratio. As a comparison, Al plating without an oxide film was also evaluated.
次に製造した鋼板を150×150mmに剪断し、遠赤外線ヒーターで加熱した。遠赤外線ヒーターは２つのゾーンに分かれ、１つは1100℃に、もう１つは900℃に保定されていた。いずれのヒーターも赤外線の波長は2〜20μmの分布をもっていた。このヒーターの1100℃のゾーンで急速に加熱し、850℃に達した段階で900℃のゾーンに移動させて1分間保定した後に取出して板厚40mmのSUS製金型に挟んで冷却した。このとき試料に熱電対を取付け、昇温測度、冷却速度を実測した。昇温速度は室温〜890℃までの平均速度、冷却速度は金型冷却開始温度〜150℃までの平均速度で、金型冷却開始温度は670〜720℃の間であった。得られた昇温測度を表２に示す。冷却速度はいずれも約70℃/秒であった。 Next, the produced steel plate was sheared to 150 × 150 mm and heated with a far infrared heater. The far infrared heater was divided into two zones, one at 1100 ° C and the other at 900 ° C. All heaters had an infrared wavelength distribution of 2 to 20 μm. The heater was rapidly heated in the 1100 ° C. zone, moved to the 900 ° C. zone when it reached 850 ° C., held for 1 minute, taken out, and cooled by being sandwiched between 40 mm thick SUS molds. At this time, a thermocouple was attached to the sample, and a temperature rise measure and a cooling rate were measured. The heating rate was an average rate from room temperature to 890 ° C, the cooling rate was an average rate from mold cooling start temperature to 150 ° C, and the mold cooling start temperature was between 670 to 720 ° C. The resulting temperature elevation measure is shown in Table 2. The cooling rate was about 70 ° C./sec.
表２に酸化物種類、酸化物粒径、皮膜厚の昇温速度への影響が表されている。シリカの昇温速度への影響は大きく、次いでZnOであった。しかしそれ以外の酸化物(アルミナ、チタニア等)も効果は認められた。ZnOの酸化物粒径、膜厚を変更したときの昇温速度についても評価した。酸化物粒径を小さくした方が昇温速度が増大する、つまり表面の放射率が大きくなることが確認された。ZnO粒径370nmでは昇温速度に対して大きな効果は得られなかった。また粒径が70nmと微細であっても膜厚が0.05μmでは同様に大きな効果は得られず、粒径と膜厚の制御が重要であることが分かる。またNo.15については、昇温速度は得られたものの、この材料のスポット溶接適正電流範囲を評価すると、0.9kAの適正範囲しか得られず、チリ発生しやすい傾向が認められた。このため膜厚を増大すると表面抵抗が大きくなり、スポット溶接性が低下すると考えられる。なおこのときの溶接条件は、加圧力500kgf、溶接時間15サイクル(60Hz)で、下限を4.25√t(tは板厚)、上限をチリ発生電流とした。No.14を同様の方法で評価すると適正範囲は1.5kAで合格レベルであった。 Table 2 shows the influence of the oxide type, oxide particle size, and film thickness on the rate of temperature rise. The influence of silica on the heating rate was large, followed by ZnO. However, other oxides (alumina, titania, etc.) were also effective. The temperature rise rate when the oxide particle size and film thickness of ZnO were changed was also evaluated. It was confirmed that the temperature rising rate increases when the oxide particle size is reduced, that is, the emissivity of the surface increases. When the ZnO particle size was 370 nm, no significant effect on the rate of temperature increase was obtained. In addition, even when the particle size is as fine as 70 nm, a large effect cannot be obtained if the film thickness is 0.05 μm, and it is understood that control of the particle size and film thickness is important. As for No. 15, although the rate of temperature increase was obtained, when the appropriate spot welding current range of this material was evaluated, only an appropriate range of 0.9 kA was obtained, and a tendency to easily generate dust was recognized. For this reason, it is considered that when the film thickness is increased, the surface resistance is increased and the spot weldability is lowered. The welding conditions at this time were a pressure of 500 kgf, a welding time of 15 cycles (60 Hz), a lower limit of 4.25√t (t is the plate thickness), and an upper limit of dust generation current. When No. 14 was evaluated by the same method, the appropriate range was 1.5 kA, which was an acceptable level.
鋼成分の焼入性等諸特性への影響を確認するために表３に示された種々の成分を持つ鋼塊を溶製し、常法に従い熱延、酸洗、冷延して板厚1.2mmとした。この鋼帯を還元炉方式でAlめっきした。めっき浴組成は、Al-8%Si-2%Fe、浴温は650℃とし、めっき付着量をガスワイピング法により両面120g/m2に調整した。このAlめっき鋼板の表面に約70nmのZn
Oと約50nmのSiO2を重量比で80：20で混合し、さらに水溶性アクリル樹脂をバインダーとしてZnOとSiO2の合計量に対して20%含有する皮膜を約0.7μm形成させた。次にこの鋼板を実施例１と同様の要領で遠赤外線加熱装置を用いて加熱し、金型内に挟んで急冷した。このときの昇温速度は約25℃/sであった。実施例１に比べて板厚が薄い分だけ温度が上がりやすかったと考えられる。一方冷却速度は約80℃/sで実施例１よりもやはり少し冷却されやすかった。冷却後の鋼板硬度を板厚中心付近、荷重10kgfで5点測定し、平均値を算出した。この時の硬度も表３に示す。C量が約0.077%と低すぎるときには十分な硬度が得られず、同様にMn量が0.05%と低すぎる場合にも焼入性が低下してこの冷却速度では焼入がされていなかった。従ってこのような条件では高強度の部材を得ることはできない。これに対して鋼成分が適正である場合にはほぼC量に応じた硬度が得られた。
In order to confirm the effects of steel components on hardenability, etc., steel ingots with various components shown in Table 3 were melted and hot rolled, pickled and cold rolled according to conventional methods. 1.2 mm. This steel strip was Al plated by a reduction furnace method. The plating bath composition was Al-8% Si-2% Fe, the bath temperature was 650 ° C., and the plating adhesion was adjusted to 120 g / m 2 on both sides by the gas wiping method. About 70nm Zn on the surface of this Al plated steel sheet
O and SiO 2 of about 50 nm were mixed at a weight ratio of 80:20, and a film containing about 20 μm of the total amount of ZnO and SiO 2 with a water-soluble acrylic resin as a binder was formed to about 0.7 μm. Next, this steel sheet was heated using a far-infrared heating apparatus in the same manner as in Example 1, and was quenched in a mold. The temperature rising rate at this time was about 25 ° C./s. It is considered that the temperature was likely to rise by the amount that was thinner than in Example 1. On the other hand, the cooling rate was about 80 ° C./s, which was a little easier to cool than Example 1. The steel plate hardness after cooling was measured at five points near the center of the plate thickness at a load of 10 kgf, and the average value was calculated. The hardness at this time is also shown in Table 3. When the amount of C was too low at about 0.077%, sufficient hardness could not be obtained. Similarly, when the amount of Mn was too low at 0.05%, the hardenability was lowered and quenching was not performed at this cooling rate. Therefore, a high-strength member cannot be obtained under such conditions. On the other hand, when the steel components were appropriate, hardness corresponding to the C content was obtained.
表４に示す鋼成分を持つ鋼塊を溶製し、常法に従い熱延、酸洗、冷延して板厚1.2mmとした。この鋼帯を還元炉方式でAlめっきした。めっき浴組成は、Al-10%Si-2%Fe、浴温は650℃とし、めっき付着量をガスワイピング法により両面160g/ｍ2に調整した。このAl
めっき鋼板の表面に約100nmのZnOとバインダー成分として水溶性ポリエステル樹脂をZnO量に対して30%含有する皮膜を約0.5μm形成させた。
Steel ingots having the steel components shown in Table 4 were melted and hot rolled, pickled and cold rolled according to conventional methods to obtain a plate thickness of 1.2 mm. This steel strip was Al plated by a reduction furnace method. The plating bath composition was Al-10% Si-2% Fe, the bath temperature was 650 ° C., and the amount of plating was adjusted to 160 g / m 2 on both sides by the gas wiping method. This Al
About 0.5 μm of a film containing about 100 nm of ZnO and 30% of water-soluble polyester resin as a binder component with respect to the amount of ZnO was formed on the surface of the plated steel sheet.
Alめっき鋼板をボックス焼鈍炉内で加熱し、合金化した。このときの焼鈍炉の条件は650℃とし、昇温速度は約100℃/時間、保定時間は約6時間であり、大気を炉内に導入した。その結果、表４のLにおいては焼鈍後鋼帯の幅方向中央付近に黒色物が生成し、分析の結果AlNが同定された。一方鋼帯の端に近い部位はAlNが生成せず、合金化していた。合金化後の色も黒色に近いが、AlNが生成した部位の方がより黒色であり、不均一な反応をしており、このような状態では評価に値しなかった。大気中の酸素が届く端部付近は合金化するが、中央は酸素が十分届かずにAlNが生成したものと推定した。符号M〜Oの場合には同様の条件でボックス焼鈍した後鋼帯のほぼ全面で均一に合金化していた。従ってAlN生成には鋼成分も影響したと考えられた。合金化が可能であった3鋼種を用いて実施例１と同様の要領で遠赤外線加熱装置を用いて加熱し、金型内に挟んで急冷した。このときの昇温速度は約42℃/sが得られた。なお冷却速度は約80℃/sであった。比較のために鋼成分符号MでZnOを付与せずにボックス焼鈍炉で合金化させ、遠赤外線加熱装置で加熱し、金型冷却した。このときの昇温速度は15℃/sであった。 The Al-plated steel sheet was heated and alloyed in a box annealing furnace. At this time, the annealing furnace was set to 650 ° C., the heating rate was about 100 ° C./hour, the holding time was about 6 hours, and the atmosphere was introduced into the furnace. As a result, in Table 4 L, a black product was generated near the center in the width direction of the steel strip after annealing, and AlN was identified as a result of analysis. On the other hand, AlN was not formed in the part near the end of the steel strip, and it was alloyed. The color after alloying is also close to black, but the site where AlN is generated is blacker and reacts more unevenly. In such a state, it was not worthy of evaluation. It is presumed that AlN was formed in the middle of the edge where oxygen in the atmosphere reaches, but oxygen did not reach the center sufficiently. In the case of codes M to O, after box annealing under the same conditions, alloying was almost uniform over almost the entire surface of the steel strip. Therefore, it was considered that the steel component also influenced AlN formation. The three steel types that could be alloyed were heated using a far-infrared heating device in the same manner as in Example 1, and then rapidly cooled by being sandwiched in a mold. The rate of temperature increase at this time was about 42 ° C./s. The cooling rate was about 80 ° C./s. For comparison, steel component code M was alloyed in a box annealing furnace without adding ZnO, heated with a far-infrared heating device, and mold cooled. The temperature rising rate at this time was 15 ° C./s.
以上の結果より、ボックス焼鈍により合金化することで、より昇温速度が向上することが知見された。 From the above results, it has been found that the temperature rising rate is further improved by alloying by box annealing.
実施例１に記載の鋼成分を有する、表２のNo.１、３、４に記載のAlめっき鋼板を用いて、150×150mmのブランクに対して0.5〜1.5μm程度の波長を有する近赤外線加熱炉を用いて加熱試験を行った。この際の近赤外線ヒーターは試料の片面から放射し、温度ムラが出にくいように試料を10mm程度の振幅で振動させながら加熱した。温度が900℃に達した段階で近赤外線ヒーターの出力を弱め、20秒程度保定し、その後実施例１に記載した方法で冷却した。このときの室温〜890℃までの平均昇温速度を熱電対を用いて実測したところ、下の値が得られた。
No.１：19℃/秒
No.３：22℃/秒
No.４：27℃/秒
Near-infrared rays having a wavelength of about 0.5 to 1.5 μm with respect to a blank of 150 × 150 mm using the Al-plated steel sheets described in No. 1, 3, and 4 of Table 2 having the steel components described in Example 1. A heating test was performed using a heating furnace. The near-infrared heater at this time radiated from one side of the sample, and was heated while vibrating the sample with an amplitude of about 10 mm so that temperature unevenness was less likely to occur. When the temperature reached 900 ° C., the output of the near infrared heater was weakened, held for about 20 seconds, and then cooled by the method described in Example 1. When the average temperature increase rate from room temperature to 890 ° C. at this time was measured using a thermocouple, the following values were obtained.
No.1: 19 ℃ / sec
No.3: 22 ℃ / second
No.4: 27 ℃ / second
実施例１の数値と比較すると、皮膜を付与しないAlめっき材に置いて近赤外線による加熱効率増大が認められる。酸化物皮膜の効果は実施例１に比べると小さいが、SiO2はこの波長領域においても放射率増大効果が大きいことが認められた。 Compared with the numerical value of Example 1, the heating efficiency increase by near infrared rays is recognized by placing on the Al plating material to which no film is applied. Although the effect of the oxide film is smaller than that of Example 1, it was confirmed that SiO 2 has a large emissivity increasing effect even in this wavelength region.
実施例１に記載の鋼成分を有する、表２に記載の数種類のAlめっき鋼板を用いて、150×150mmのブランクに対して実施例１と同様の条件で遠赤外線加熱、金型冷却を施した。次に７０×１５０ｍｍに剪断し、日本パーカライジング（株）社製化成処理液（ＰＢ−ＳＸ３５Ｔ）で化成処理後、日本ペイント（株）社製電着塗料（パワーニクス１１０）を２０μｍ狙いで塗装し、１７０℃で２０分間焼き付けた。 Using several types of Al-plated steel sheets listed in Table 2 having the steel components described in Example 1, far-infrared heating and mold cooling were performed on a 150 × 150 mm blank under the same conditions as in Example 1. did. Next, it is sheared to 70 x 150 mm, and after chemical conversion treatment with Nihon Parkerizing Co., Ltd. chemical conversion treatment liquid (PB-SX35T), an electrodeposition paint (Powernics 110) made by Nihon Paint Co., Ltd. is applied for 20 μm. And baked at 170 ° C. for 20 minutes.
塗装後耐食性評価は自動車技術会制定のＪＡＳＯ Ｍ６０９に規定する方法で行った。塗膜に予めカッターでクロスカットを入れ、腐食試験１８０サイクル（６０日）後のクロスカットからの塗膜膨れの幅（片側最大値）を計測した。
＜塗装後耐食性評価基準＞
○：膨れ幅4mm未満、△：膨れ幅4〜6mm、×：膨れ幅6mm超
Evaluation of corrosion resistance after painting was carried out by the method prescribed in JASO M609 established by the Automotive Engineering Association. A crosscut was put in advance in the coating film with a cutter, and the width of the film swelling (maximum value on one side) from the crosscut after 180 cycles (60 days) of corrosion test was measured.
<Evaluation criteria for corrosion resistance after painting>
○: Swelling width less than 4mm, △: Swelling width 4-6mm, ×: Swelling width over 6mm
表５に評価結果を示す。このときの昇温速度、冷却速度は実施例１及び表２に示されている。塗装後耐食性との観点からはZnOの効果が大きく、ZnOを塗布した試料には化成処理皮膜の生成が認められた。SiO2やAl2O3に関しては化成処理皮膜の生成は認められず、塗装後耐食性もこれら皮膜のないものと同等であった。これらの皮膜は耐食性を必要としない部品に対して適用する、あるいはAlめっき付着量を増大させて塗装後耐食性を確保することが必要となる。番号８(表２のNo.１９)のようにZnOとSiO2を複合させることで塗装後耐食性と加熱時の昇温特性を両立させることも可能である。 Table 5 shows the evaluation results. The heating rate and cooling rate at this time are shown in Example 1 and Table 2. From the standpoint of post-coating corrosion resistance, the effect of ZnO was great, and the formation of a chemical conversion coating was observed in the sample coated with ZnO. With respect to SiO 2 and Al 2 O 3 , no chemical conversion treatment film was formed, and the corrosion resistance after coating was equivalent to that without these films. It is necessary to apply these coatings to parts that do not require corrosion resistance, or to increase the amount of Al plating adhesion to ensure post-coating corrosion resistance. By combining ZnO and SiO 2 as in No. 8 (No. 19 in Table 2), it is possible to achieve both post-coating corrosion resistance and temperature rise characteristics during heating.
実施例１に記載の鋼成分を有する、表２のNo.１３に記載のAlめっき鋼板を用いて、250×300mmのブランクに対して実施例１と同様の条件で遠赤外線加熱を施した。その後図１に示すようなハット形状に成形した。昇温速度は約20℃/sであった。冷却速度は部位により異なるため正確には不明であるが、断面から各部位の硬度を測定したところ全ての位置でHv430以上の値が得られた。 Far-infrared heating was performed on a 250 × 300 mm blank under the same conditions as in Example 1 using the Al-plated steel sheet described in No. 13 of Table 2 having the steel components described in Example 1. Thereafter, it was formed into a hat shape as shown in FIG. The heating rate was about 20 ° C / s. Although the cooling rate differs depending on the part, it is not exactly known, but when the hardness of each part was measured from the cross section, a value of Hv430 or more was obtained at all positions.
Claims (6)
C:0.1〜0.5%、
Mn:0.1%〜3%、
Si:0.7%以下、
Al:0.005〜0.1%、
S:0.02%以下、
P:0.03%以下、
B:0.0002%〜0.0050%、
Ti:0.01〜0.1%、
N:0.02%以下を含有し、残部Feおよび不可避的不純物である熱延鋼板または冷延鋼板の表面に、めっき層中に５〜１２％の濃度のＳｉを含有するAlめっき層を有し、更にその表面に粒径10〜300nmの酸化物微粒子からなる膜厚0.1〜3μmの皮膜を有する鋼板を加熱する際に、波長0.5μm〜100μmの赤外線ヒーターを用いて加熱し、しかる後にプレス成形し、プレス金型内で冷却して焼入することを特徴とする高強度部品の製造方法。 Chemical component is mass%,
C: 0.1-0.5%
Mn: 0.1% to 3%
Si: 0.7% or less,
Al: 0.005-0.1%,
S: 0.02% or less,
P: 0.03% or less,
B: 0.0002% to 0.0050%,
Ti: 0.01-0.1%,
N: 0.02% or less, the remaining Fe and inevitable impurities on the surface of the hot-rolled steel sheet or cold-rolled steel sheet has an Al plated layer containing Si at a concentration of 5 to 12% in the plated layer , Furthermore, when heating a steel sheet having a film thickness of 0.1 to 3 μm made of oxide fine particles having a particle diameter of 10 to 300 nm on its surface, it is heated using an infrared heater with a wavelength of 0.5 μm to 100 μm, and then press-molded. A method for producing a high-strength part, characterized by cooling in a press mold and quenching.
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