JP2017074597A - Hot press molding method of steel plate - Google Patents

Hot press molding method of steel plate Download PDF

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JP2017074597A
JP2017074597A JP2015202637A JP2015202637A JP2017074597A JP 2017074597 A JP2017074597 A JP 2017074597A JP 2015202637 A JP2015202637 A JP 2015202637A JP 2015202637 A JP2015202637 A JP 2015202637A JP 2017074597 A JP2017074597 A JP 2017074597A
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galvanized steel
hot press
steel plate
iron powder
galvanized
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児玉 幸多
Kota Kodama
幸多 児玉
林 義之
Yoshiyuki Hayashi
義之 林
修 中嶋
Osamu Nakajima
修 中嶋
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Toyota Motor Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a hot press molding method of a steel plate capable of enhancing strength of a molding product molded by a hot press, while restraining a melting zinc embrittlement crack of mutual galvanized steel plates.SOLUTION: In a hot press molding method of a steel plate, hot press molding is executed in a state of overlapping mutual galvanized steel plates 11 and 12. First of all, iron powder 14 of a maximum grain size of 100 μm or less is sprayed on a surface of one galvanized steel plate 11, and the other galvanized steel plate 12 is overlapped with a surface of spraying the iron powder 14 of the one galvanized steel plate 11, and the mutual galvanized steel plates 11 and 12 are partially welded, and the hot press molding is executed to the welded galvanized steel plate.SELECTED DRAWING: Figure 1

Description

本発明は、亜鉛メッキ鋼板同士を重ね合わせて熱間プレス成形する鋼板の熱間プレス成形方法に関する。   The present invention relates to a hot press forming method of a steel plate in which galvanized steel plates are overlapped and hot press formed.

従来から、自動車の車体を構成する骨格部分である、たとえば、Aピラー、Bピラー、またはサイドシルなどの部品は、熱間プレス成形により製造されている。自動車の軽量化および衝突安全性の向上の観点から、このような部品(成形品)は、高強度であることが必要とされており、レインフォース部品(補強部材)で補強されることが多い。レインフォース部品は、成形品にスポット溶接等により溶接されて、成形品と一体化される。   Conventionally, parts such as an A pillar, a B pillar, or a side sill, which are skeleton parts constituting a vehicle body, are manufactured by hot press molding. From the viewpoint of reducing the weight of automobiles and improving collision safety, such parts (molded products) are required to have high strength, and are often reinforced with reinforcement parts (reinforcing members). . The reinforcement component is welded to the molded product by spot welding or the like and integrated with the molded product.

レインフォース部品で成形品を補強する以外の方法として、例えば、熱間プレス成形される鋼板の補強すべき部分に、補強用の鋼板を重ね合わせて溶接し、これを補強用の鋼板と共に熱間プレス成形により成形する方法が利用されている。この方法によれば、成形品の補強すべき部分に、もう一枚の補強用の鋼板が一体化されているので、成形品の耐力を向上させることができる。   As a method other than reinforcing a molded product with reinforcement parts, for example, a reinforcing steel plate is overlapped and welded to a portion to be reinforced in a hot-pressed steel plate, and this is hot-bonded together with the reinforcing steel plate. A method of molding by press molding is used. According to this method, since another reinforcing steel plate is integrated with the portion of the molded product to be reinforced, the yield strength of the molded product can be improved.

ここで、熱間プレス成形を行う鋼板に、非めっき鋼板を用いることが多い。しかしながら、熱間プレス成形時に、加熱された非めっき鋼板の表面には、酸化スケールが形成されてしまう。このため、酸化スケールが形成された鋼板を、金型で成形した際には、酸化スケールが起因して金型が摩耗することがあった。さらに、成形された成形品の溶接性および塗装性を確保するために、成形品に形成された酸化スケールを、ショットブラスト等により、除去する作業することがあった。   Here, a non-plated steel sheet is often used as a steel sheet for hot press forming. However, during hot press forming, an oxide scale is formed on the surface of the heated non-plated steel sheet. For this reason, when the steel plate in which the oxide scale was formed was shape | molded with the metal mold | die, the metal mold | die sometimes abraded due to the oxide scale. Furthermore, in order to ensure the weldability and paintability of the molded product, there has been a case where the oxide scale formed on the molded product is removed by shot blasting or the like.

このような点を鑑みて、熱間プレス成形を行う鋼板に、亜鉛メッキ鋼板を用いた熱間プレス成形方法が提案されている(たとえば、引用文献1参照)。この熱間プレス成形方法では、熱間プレスにより1.5%以上の歪が付与される亜鉛メッキ鋼板の部分において、もう一枚の亜鉛メッキ鋼板と0.03〜2.0mmの隙間が形成されるように、亜鉛メッキ鋼板同士を重ね合わせて溶接し、これを熱間プレス成形している。   In view of such a point, a hot press forming method using a galvanized steel plate as a steel plate to be hot press formed has been proposed (see, for example, cited document 1). In this hot press forming method, a gap of 0.03 to 2.0 mm is formed with another galvanized steel sheet in a portion of the galvanized steel sheet to which a strain of 1.5% or more is applied by hot pressing. As shown, the galvanized steel sheets are overlapped and welded, and this is hot press formed.

特開2013−184221号公報JP 2013-184221 A

特許文献1に係る熱間プレス成形方法によれば、亜鉛メッキ鋼板を重ね合わせた状態で、これらの鋼板の間に隙間が形成されるので、熱間プレス成形時に、亜鉛メッキ鋼板の亜鉛メッキ層の液化した溶融亜鉛が鋼板の母材(鉄組織)の粒界に侵入することはない。これにより、熱間プレス成形時に、鋼板の溶融亜鉛脆化割れ(表面割れ)を抑えることができる。   According to the hot press forming method according to Patent Document 1, since a gap is formed between these steel plates in a state where the galvanized steel plates are overlapped, a galvanized layer of the galvanized steel plate is formed during hot press forming. The liquefied molten zinc does not enter the grain boundary of the base material (iron structure) of the steel sheet. Thereby, the hot zinc embrittlement crack (surface crack) of a steel plate can be suppressed at the time of hot press forming.

しかしながら、この熱間プレス成形方法により成形された成形品には、上述した隙間が形成されている。このため、この隙間が形成された亜鉛メッキ鋼板製の成形品は、隙間が形成されていない非メッキ鋼板製の成形品よりも、強度が低くなるおそれがある。   However, the gap described above is formed in a molded product molded by this hot press molding method. For this reason, there exists a possibility that the intensity | strength of the molded product made from a galvanized steel plate in which this clearance gap was formed may become lower than the molded product made from the non-plated steel plate in which the clearance gap is not formed.

本発明は、このような点を鑑みてなされたものであり、その目的とするところは、亜鉛メッキ鋼板同士の溶融亜鉛脆化割れを抑えつつ、熱間プレスにより成形された成形品の強度を確保することができる鋼板の熱間プレス成形方法を提供することにある。   The present invention has been made in view of these points, and the object of the present invention is to reduce the strength of a molded product formed by hot pressing while suppressing hot-dip zinc embrittlement cracks between galvanized steel sheets. An object of the present invention is to provide a hot press forming method for a steel sheet that can be secured.

前記課題を鑑みて、本発明に係る鋼板の熱間プレス成形方法は、亜鉛メッキ鋼板同士を重ね合わせた状態で、熱間プレス成形する鋼板の熱間プレス成形方法であって、一方の亜鉛メッキ鋼板の表面に最大粒径100μm以下の鉄粉を散布し、前記一方の亜鉛メッキ鋼板の前記鉄粉が散布された表面に、他方の亜鉛メッキ鋼板を重ね合わせて、前記亜鉛メッキ鋼板同士を部分的に溶接し、溶接された亜鉛メッキ鋼板に対して熱間プレス成形を行うことを特徴とする。   In view of the above problems, a hot press forming method of a steel sheet according to the present invention is a hot press forming method of a steel sheet that is hot press formed in a state in which galvanized steel sheets are overlapped, and one of the galvanized steel sheets. Sprinkle iron powder having a maximum particle size of 100 μm or less on the surface of the steel sheet, and overlap the other galvanized steel sheet on the surface of the one galvanized steel sheet on which the iron powder has been dispersed. And hot press forming is performed on the welded galvanized steel sheet.

本発明によれば、熱間プレス成形を行う前に、重ね合わせて部分的に溶接された亜鉛メッキ鋼板同士の間には、最大粒径100μm以下の鉄粉が介在する。これにより、熱間プレス成形の際に、亜鉛メッキ鋼板の亜鉛メッキ層の亜鉛を鉄粉に拡散させ、鉄粉の鉄を亜鉛メッキ鋼板の亜鉛メッキ層に拡散させることができる。このようにして、亜鉛メッキ層の亜鉛と、鉄粉の鉄とが相互拡散し、亜鉛メッキ層の亜鉛の液化を低減することができる。   According to the present invention, iron powder having a maximum particle size of 100 μm or less is interposed between galvanized steel sheets that are overlapped and partially welded before hot press forming. Thus, during hot press forming, zinc in the galvanized layer of the galvanized steel sheet can be diffused into the iron powder, and iron in the iron powder can be diffused into the galvanized layer of the galvanized steel sheet. In this manner, zinc in the galvanized layer and iron in the iron powder can be diffused to reduce liquefaction of zinc in the galvanized layer.

特に、本発明では、最大粒径100μm以下の微細な鉄粉を用いたので、亜鉛メッキ層の亜鉛が鉄粉に接触する面積が増加する。これにより、亜鉛メッキ層の亜鉛と、鉄粉の鉄との相互拡散が促進され、短時間でこれらが固溶体化するので、亜鉛メッキ層の亜鉛の液化を低減することができる。   In particular, in the present invention, since fine iron powder having a maximum particle size of 100 μm or less is used, the area in which the zinc of the galvanized layer contacts the iron powder increases. Thereby, mutual diffusion of zinc in the galvanized layer and iron in the iron powder is promoted, and these are solid solution in a short time, so that liquefaction of zinc in the galvanized layer can be reduced.

このようにして、熱間プレス成形の際に、液化した溶融亜鉛が鋼板の鉄母材の粒界に侵入することを抑えることができる。これにより、亜鉛メッキ鋼板同士の溶融亜鉛脆化割れ(表面割れ)を抑えることができる。   In this way, it is possible to prevent the liquefied molten zinc from entering the grain boundaries of the iron base material of the steel plate during hot press forming. Thereby, the hot-dip zinc embrittlement crack (surface crack) of galvanized steel plates can be suppressed.

これに加え、熱間プレスにより成形された成形品には、従来のように表面割れのための隙間を形成する必要がないので、熱間プレス成形により成形された成形品の強度を確保することができる。   In addition to this, it is not necessary to form gaps for surface cracking in molded products molded by hot pressing as in the past, so ensure the strength of molded products molded by hot pressing. Can do.

(a)〜(e)は、本発明の実施形態に係る鋼板の熱間プレス成形方法を説明するための模式図である。(A)-(e) is a schematic diagram for demonstrating the hot press forming method of the steel plate which concerns on embodiment of this invention. (a)は、鉄粉を介在させずに重ね合わせた状態の亜鉛メッキ鋼板の断面図である。(b)は、鉄粉を介在させて重ね合わせた状態の亜鉛メッキ鋼板の断面図である。(A) is sectional drawing of the galvanized steel plate of the state piled up without interposing iron powder. (B) is sectional drawing of the galvanized steel plate of the state piled up with iron powder interposed. は、Zn−Feの2元状態図である。These are the binary phase diagrams of Zn-Fe.

以下に本発明の実施形態に係る鋼板の熱間プレス成形方法を説明する。
図1(a)〜(e)は、本発明の実施形態に係る鋼板の熱間プレス成形方法を説明するための模式図である。
Hereinafter, a hot press forming method for a steel sheet according to an embodiment of the present invention will be described.
Fig.1 (a)-(e) is a schematic diagram for demonstrating the hot press forming method of the steel plate which concerns on embodiment of this invention.

本実施形態に係る鋼板の熱間プレス成形方法は、亜鉛メッキ鋼板同士を重ね合わせて熱間プレス成形する方法である。図1(a)に示すように、まず、2枚の亜鉛メッキ鋼板11,12を準備する。ここで、本実施形態では、一方の亜鉛メッキ鋼板11が、成形品の骨格部分となり、他方の亜鉛メッキ鋼板12が、成形品の補強部分となる。   The hot press forming method of a steel sheet according to the present embodiment is a method of hot press forming by superimposing galvanized steel sheets. As shown in FIG. 1A, first, two galvanized steel plates 11 and 12 are prepared. Here, in the present embodiment, one galvanized steel plate 11 serves as a skeleton portion of the molded product, and the other galvanized steel plate 12 serves as a reinforced portion of the molded product.

次に、図1(b)に示すように、一方の亜鉛メッキ鋼板11の表面に、最大粒径100μm以下の鉄粉14を散布する。ここで、鉄粉14の最大粒径は、JIS−Z8801に規定する試験用篩いを用いて、鉄粉を測定した粒径であり、本明細書でいう「最大粒径」とは、この方法で測定した値をいう。このような最大粒径を有する鉄粉14は、その比表面積が大きいので、亜鉛メッキ層11b,12b(図2参照)の亜鉛との接触面積を大きくすることができる。   Next, as shown in FIG. 1 (b), iron powder 14 having a maximum particle size of 100 μm or less is sprayed on the surface of one galvanized steel sheet 11. Here, the maximum particle size of the iron powder 14 is a particle size obtained by measuring the iron powder using a test sieve specified in JIS-Z8801, and the “maximum particle size” referred to in this specification is this method. The value measured in. Since the iron powder 14 having such a maximum particle size has a large specific surface area, the contact area of the galvanized layers 11b and 12b (see FIG. 2) with zinc can be increased.

さらに、鉄粉14は、純鉄粉であることが好ましく、鉄粉14に含有する炭素量は、0.01質量%以下であることが好ましい。鉄粉14に含有する炭素量を制限することにより、後述する亜鉛メッキ鋼板11,12の熱間プレス成形時に、鉄粉14が変形し易い。   Furthermore, the iron powder 14 is preferably pure iron powder, and the amount of carbon contained in the iron powder 14 is preferably 0.01% by mass or less. By limiting the amount of carbon contained in the iron powder 14, the iron powder 14 is easily deformed during hot press forming of the galvanized steel plates 11 and 12 described later.

次に、一方の亜鉛メッキ鋼板11の鉄粉14が散布された表面に、他方の亜鉛メッキ鋼板12を重ね合わせる。本実施形態では、一方の亜鉛メッキ鋼板11のうち、他方の亜鉛メッキ鋼板12が重なった部分が、熱間プレス成形後に得られた成形品15Aの補強される部分となる。   Next, the other galvanized steel sheet 12 is overlaid on the surface of the galvanized steel sheet 11 on which the iron powder 14 is dispersed. In the present embodiment, the portion of one galvanized steel plate 11 on which the other galvanized steel plate 12 overlaps is the portion to be reinforced of the molded product 15A obtained after hot press forming.

これにより、一方の亜鉛メッキ鋼板11と、他方の亜鉛メッキ鋼板12との間に、鉄粉14が介在される。より具体的には、図2(b)に示すように、一方の亜鉛メッキ鋼板11には、鋼からなる母材11aの表面に、亜鉛メッキ層11bが形成されており、他方の亜鉛メッキ鋼板12にも、鋼からなる母材12aの表面に、亜鉛メッキ層12bが形成されている。そして、亜鉛メッキ層同士11b,12bの間に、鉄粉14が配置(挿入)される。   Thereby, the iron powder 14 is interposed between one galvanized steel sheet 11 and the other galvanized steel sheet 12. More specifically, as shown in FIG. 2 (b), one galvanized steel sheet 11 has a galvanized layer 11b formed on the surface of a base material 11a made of steel, and the other galvanized steel sheet. 12 also has a galvanized layer 12b formed on the surface of a base material 12a made of steel. And the iron powder 14 is arrange | positioned (inserted) between galvanized layers 11b and 12b.

次に、図1(c)に示すように、一方の亜鉛メッキ鋼板11と、他方の亜鉛メッキ鋼板12とを重ね合わせた状態で、載置台31に載置し、溶接機32を用いて、亜鉛メッキ鋼板同士11,12を部分的に溶接する(スポット溶接する)。これにより、鉄粉14を挟んで、亜鉛メッキ鋼板同士11,12が、溶接により部分的に接合された接合体15を得ることができる。   Next, as shown in FIG. 1 (c), one galvanized steel sheet 11 and the other galvanized steel sheet 12 are placed on the mounting table 31 in a state of being overlapped, and a welding machine 32 is used. The galvanized steel plates 11 and 12 are partially welded (spot welded). Thereby, it is possible to obtain a joined body 15 in which the galvanized steel plates 11 and 12 are partially joined by welding with the iron powder 14 interposed therebetween.

次に、図1(d)に示すように、亜鉛メッキ鋼板11,12が溶接された接合体15を、一対のヒータ41,42を有した加熱装置40で加熱する。ここで、接合体15の加熱温度は、850〜905℃の範囲にあることが好ましく、本実施形態では、接合体15を900℃で加熱する。   Next, as shown in FIG. 1 (d), the joined body 15 to which the galvanized steel plates 11 and 12 are welded is heated by a heating device 40 having a pair of heaters 41 and 42. Here, the heating temperature of the bonded body 15 is preferably in the range of 850 to 905 ° C. In this embodiment, the bonded body 15 is heated at 900 ° C.

最後に、図1(e)に示すように、加熱された接合体15をプレス機50内に配置し、接合体15を、プレス機50の上型51と下型52の間に挟み込んで、接合体15を熱間プレス成形する。   Finally, as shown in FIG. 1 (e), the heated joined body 15 is disposed in the press machine 50, and the joined body 15 is sandwiched between the upper mold 51 and the lower mold 52 of the press machine 50, The joined body 15 is hot press-molded.

ここで、本実施形態では、図3に示すように、亜鉛メッキ層11b,12bには、90質量%程度の亜鉛が含有しているため、図1(d)に示す加熱装置40の加熱により一定時間加熱すると、亜鉛メッキ層11b,12bの亜鉛の一部は、液化する。   Here, in this embodiment, as shown in FIG. 3, since the zinc plating layers 11b and 12b contain about 90% by mass of zinc, the heating device 40 shown in FIG. When heated for a certain time, a part of zinc in the galvanized layers 11b and 12b is liquefied.

図2(a)に示すように、亜鉛メッキ鋼板11,12の間に、鉄粉を配置(挿入)していない場合、加熱装置40の加熱により、鉄と亜鉛との固溶体化が完了する前に、亜鉛メッキ層11b,12bの亜鉛が液化する。これにより、液化した溶融亜鉛が、熱間プレス成形時に、母材11a,12aに侵入し、鋼板の溶融亜鉛脆化割れが発生することがある。   As shown to Fig.2 (a), when the iron powder is not arrange | positioned (inserted) between the galvanized steel plates 11 and 12, before the solid solution formation of iron and zinc is completed by heating of the heating device 40 Further, the zinc in the galvanized layers 11b and 12b is liquefied. Thereby, the liquefied molten zinc may penetrate | invade into the base materials 11a and 12a at the time of hot press molding, and the molten zinc embrittlement crack of a steel plate may generate | occur | produce.

しかしながら、本実施形態では、図2(b)に示すように、亜鉛メッキ鋼板11,12の間に、鉄粉14が挿入されているので、加熱装置40の加熱により、亜鉛メッキ層11b,12bの亜鉛は、鉄粉14に拡散する。一方、鉄粉14の鉄も、亜鉛メッキ層11b,12bに拡散する。このようにして、亜鉛メッキ層11b,12bの亜鉛と鉄粉14の鉄とが相互拡散する。これにより、鉄と亜鉛が短時間で固溶体化するので、加熱による亜鉛メッキ層の亜鉛の液化を低減することができる。   However, in this embodiment, as shown in FIG. 2B, since the iron powder 14 is inserted between the galvanized steel plates 11 and 12, the galvanized layers 11b and 12b are heated by the heating device 40. The zinc diffuses into the iron powder 14. On the other hand, the iron of the iron powder 14 also diffuses into the galvanized layers 11b and 12b. In this way, the zinc of the galvanized layers 11b and 12b and the iron of the iron powder 14 are interdiffused. Thereby, since iron and zinc form a solid solution in a short time, liquefaction of zinc in the galvanized layer due to heating can be reduced.

特に、本実施形態では、最大粒径100μm以下の微細な鉄粉14を用いたので、鉄粉14と、亜鉛メッキ層11b,12bの亜鉛との接触面積が増加する。これにより、亜鉛と鉄の相互拡散が促進され、短時間で、これらの固溶体化が可能となる。   In particular, in the present embodiment, since the fine iron powder 14 having a maximum particle size of 100 μm or less is used, the contact area between the iron powder 14 and zinc in the galvanized layers 11b and 12b increases. Thereby, the mutual diffusion of zinc and iron is promoted, and these can be formed into a solid solution in a short time.

このような結果、亜鉛メッキ層11b,12bの亜鉛−鉄合金の亜鉛の含有量は低減され(図3の合金化経路参照)、熱間プレス成形時に、亜鉛メッキ層11b,12bに由来する液化した溶融亜鉛が母材11a,12aの粒界に侵入することを抑制することができる。これにより、熱間プレス時に、鋼板の溶融亜鉛脆化割れを抑えることができる。   As a result, the zinc content of the zinc-iron alloy in the galvanized layers 11b and 12b is reduced (see the alloying path in FIG. 3), and liquefaction derived from the galvanized layers 11b and 12b during hot press forming. It is possible to suppress the molten zinc from entering the grain boundaries of the base materials 11a and 12a. Thereby, the molten zinc embrittlement crack of a steel plate can be suppressed at the time of hot pressing.

また、本実施形態では、亜鉛メッキ鋼板11,12同士に隙間を形成することなく、熱間プレス成形で成形品15Aを成形したので、成形品15Aの高強度化を図ることができる。   Moreover, in this embodiment, since the molded product 15A was formed by hot press molding without forming a gap between the galvanized steel plates 11, 12, the strength of the molded product 15A can be increased.

<確認試験>
以下に本発明の一部を実施した確認試験を行った。
<Confirmation test>
The confirmation test which implemented a part of this invention below was done.

(参考例1〜8)
板厚1.4mmの2枚の合金化溶融亜鉛メッキ鋼板(亜鉛メッキ付着量45〜50g/cm)を準備した。鋼板の母材の組成は、C:0.21質量%、Si:0.03質量%、Mn:1.3質量%、P:0.01質量%、S:0.07質量%、Cr:0.2質量%、Ti:0.02質量%、残部はFeおよび不可避不純物である。
(Reference Examples 1-8)
Two alloyed hot-dip galvanized steel sheets with a thickness of 1.4 mm (zinc-plating amount of 45 to 50 g / cm 2 ) were prepared. The composition of the base material of the steel plate is as follows: C: 0.21% by mass, Si: 0.03% by mass, Mn: 1.3% by mass, P: 0.01% by mass, S: 0.07% by mass, Cr: 0.2% by mass, Ti: 0.02% by mass, the balance being Fe and inevitable impurities.

次に、一方の亜鉛メッキ鋼板の表面に、表1に示す、最大粒径の還元鉄粉(炭素含有量0.01質量%以下)を散布した。例えば、参考例1は、最大粒径180μm以下の鉄粉を、亜鉛メッキ鋼板の表面に159g/m散布した例である。 Next, reduced iron powder having a maximum particle size (carbon content of 0.01% by mass or less) shown in Table 1 was sprayed on the surface of one galvanized steel sheet. For example, Reference Example 1 is an example in which iron powder having a maximum particle size of 180 μm or less is applied to the surface of a galvanized steel sheet at 159 g / m 2 .

次に、鉄粉が散布された表面に、他方の亜鉛メッキ鋼板を重ね合わせ、亜鉛メッキ鋼板同時の間に散布した鉄粉を挟み込んだ。この状態の鋼板を、900℃に加熱した電気炉で、加熱時間4分間の条件で加熱した後、電気炉内から取り出して、室温で放冷した。   Next, the other galvanized steel sheet was superposed on the surface on which the iron powder was dispersed, and the dispersed iron powder was sandwiched between the galvanized steel sheets at the same time. The steel plate in this state was heated in an electric furnace heated to 900 ° C. under the condition of a heating time of 4 minutes, then taken out from the electric furnace and allowed to cool at room temperature.

得られた亜鉛メッキ鋼板の断面を、走査型電子顕微鏡で観察し、亜鉛と鉄の固溶体化の完了の有無を確認した。この結果を表1に示す。   The cross section of the obtained galvanized steel sheet was observed with a scanning electron microscope, and it was confirmed whether or not solid solution of zinc and iron was completed. The results are shown in Table 1.

(参考例9,10)
参考例1〜8と同様に、重ね合わせた2枚の亜鉛メッキ鋼板を、電気炉で加熱後、亜鉛メッキ鋼材の断面を、走査型電子顕微鏡で観察した。参考例9が、参考例1〜8と相違する点は、表1に示すように、亜鉛メッキ鋼板の間に鉄粉を挟み込まなかった点である。一方、参考例10が、参考例1〜8と相違する点は、表1に示すように、亜鉛メッキ鋼板の間に鉄粉を挟み込まなかった点と、電気炉の加熱時間を、10分間にした点である。得られた亜鉛メッキ鋼材の断面を、走査型電子顕微鏡で観察した結果を、表1に示す。
(Reference Examples 9 and 10)
In the same manner as in Reference Examples 1 to 8, the two galvanized steel sheets that were overlapped were heated with an electric furnace, and then the cross section of the galvanized steel material was observed with a scanning electron microscope. Reference Example 9 is different from Reference Examples 1 to 8 in that iron powder is not sandwiched between galvanized steel sheets as shown in Table 1. On the other hand, Reference Example 10 differs from Reference Examples 1 to 8 in that, as shown in Table 1, the iron powder was not sandwiched between galvanized steel sheets, and the heating time of the electric furnace was 10 minutes. This is the point. Table 1 shows the results of observation of the cross section of the obtained galvanized steel with a scanning electron microscope.

Figure 2017074597
Figure 2017074597

参考例1,2、および9では、鉄と亜鉛の固溶体化が未完了であったが、参考例3〜8、および10では、鉄と亜鉛の固溶体化が完了していた。参考例3〜8で、固溶体化が完了したのは、最大粒径が小さい鉄粉を用いたからであると考えられる。   In Reference Examples 1, 2, and 9, solid solution formation of iron and zinc was incomplete, but in Reference Examples 3-8, and 10, solid solution formation of iron and zinc was completed. In Reference Examples 3 to 8, it is considered that the solid solution was completed because iron powder having a small maximum particle size was used.

このように、参考例3〜8の条件で鉄粉を散布すれば、加熱時に、鉄と亜鉛が短時間で相互に拡散するため、亜鉛の液化を抑制でき、熱間プレス成形時に、鋼板の溶融亜鉛脆化割れを回避することができると考えられる。一方、参考例1または2の条件で鉄粉を散布すれば、鉄と亜鉛の固溶体化が遅いため、亜鉛が液化し、溶融亜鉛が母材の粒界に侵入するおそれがあると考えられる。   Thus, if iron powder is sprinkled under the conditions of Reference Examples 3 to 8, since iron and zinc diffuse each other in a short time during heating, liquefaction of zinc can be suppressed, and during hot press forming, It is thought that molten zinc embrittlement cracking can be avoided. On the other hand, if the iron powder is dispersed under the conditions of Reference Example 1 or 2, it is considered that the solid solution of iron and zinc is slow, so that zinc is liquefied and molten zinc may enter the grain boundaries of the base material.

さらに、参考例9では、鉄粉を用いてないため、鉄と亜鉛の固溶体化は完了していなかったと考えられるが、参考例10の如く、加熱時間10分間にすることにより、固溶体化が完了したと考えられる。しかしながら、参考例10の加熱条件では、鉄と亜鉛の固溶体化が完了するまでの時間が長いため、亜鉛が液化し、熱間成形時には、溶融亜鉛が母材の粒界に侵入するおそれがあると考えられる。   Furthermore, in Reference Example 9, it is considered that the solid solution of iron and zinc was not completed because no iron powder was used. However, as in Reference Example 10, the solid solution was completed by setting the heating time to 10 minutes. It is thought that. However, in the heating conditions of Reference Example 10, since it takes a long time to complete the solid solution of iron and zinc, zinc is liquefied, and during hot forming, molten zinc may enter the grain boundaries of the base material. it is conceivable that.

以上、本発明の実施の形態を詳述してきたが、具体的な構成はこの実施形態に限定されるものではなく、本発明の要旨を逸脱しない範囲における設計変更があっても、それらは本発明に含まれるものである。   Although the embodiment of the present invention has been described in detail above, the specific configuration is not limited to this embodiment, and even if there is a design change within a scope not departing from the gist of the present invention, they are not limited to this embodiment. It is included in the invention.

11:一方の亜鉛メッキ鋼板、11a:母材、11b:亜鉛メッキ層、12:他方の亜鉛メッキ鋼板、12a:母材、12b:亜鉛メッキ層、14:鉄粉、15:接合体、15A:成形品。 11: one galvanized steel sheet, 11a: base material, 11b: galvanized layer, 12: other galvanized steel sheet, 12a: base material, 12b: galvanized layer, 14: iron powder, 15: joined body, 15A: Molding.

Claims (1)

亜鉛メッキ鋼板同士を重ね合わせた状態で、熱間プレス成形する鋼板の熱間プレス成形方法であって、
一方の亜鉛メッキ鋼板の表面に最大粒径100μm以下の鉄粉を散布し、
前記一方の亜鉛メッキ鋼板の前記鉄粉が散布された表面に、他方の亜鉛メッキ鋼板を重ね合わせて、前記亜鉛メッキ鋼板同士を部分的に溶接し、
溶接された亜鉛メッキ鋼板に対して熱間プレス成形を行うことを特徴とする鋼板の熱間プレス成形方法。
In a state where galvanized steel sheets are overlapped with each other, a hot press forming method of a steel sheet to be hot press formed,
Sprinkle iron powder with a maximum particle size of 100 μm or less on the surface of one galvanized steel sheet,
The surface of the one galvanized steel sheet on which the iron powder is dispersed is overlapped with the other galvanized steel sheet, and the galvanized steel sheets are partially welded to each other,
A hot press forming method for a steel sheet, characterized by performing hot press forming on a welded galvanized steel sheet.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020105325A1 (en) * 2018-11-19 2020-05-28 株式会社神戸製鋼所 Joined structure and method for manufacturing joined structure
WO2022215425A1 (en) * 2021-04-09 2022-10-13 日本製鉄株式会社 Method for manufacturing press-molded article

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020105325A1 (en) * 2018-11-19 2020-05-28 株式会社神戸製鋼所 Joined structure and method for manufacturing joined structure
WO2022215425A1 (en) * 2021-04-09 2022-10-13 日本製鉄株式会社 Method for manufacturing press-molded article
JP7477810B2 (en) 2021-04-09 2024-05-02 日本製鉄株式会社 Manufacturing method of press-molded products

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