JP2015116575A - Press molding product and production method thereof - Google Patents
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- 238000000465 moulding Methods 0.000 title claims abstract description 36
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 11
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 59
- 239000010959 steel Substances 0.000 claims abstract description 59
- 238000000034 method Methods 0.000 claims abstract description 31
- 229910001335 Galvanized steel Inorganic materials 0.000 claims abstract description 30
- 239000008397 galvanized steel Substances 0.000 claims abstract description 30
- 239000011701 zinc Substances 0.000 claims description 16
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 14
- 229910052725 zinc Inorganic materials 0.000 claims description 14
- 239000007788 liquid Substances 0.000 claims description 9
- 229910052721 tungsten Inorganic materials 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 abstract description 37
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 abstract description 9
- 229910052742 iron Inorganic materials 0.000 abstract description 3
- 229910001338 liquidmetal Inorganic materials 0.000 abstract description 2
- 229910045601 alloy Inorganic materials 0.000 abstract 2
- 239000000956 alloy Substances 0.000 abstract 2
- 230000014759 maintenance of location Effects 0.000 abstract 1
- 238000007747 plating Methods 0.000 description 17
- 238000012360 testing method Methods 0.000 description 12
- 238000001816 cooling Methods 0.000 description 7
- 238000005275 alloying Methods 0.000 description 6
- 238000005260 corrosion Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 230000007797 corrosion Effects 0.000 description 5
- 229910001566 austenite Inorganic materials 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 239000010960 cold rolled steel Substances 0.000 description 3
- 238000005246 galvanizing Methods 0.000 description 3
- 230000006698 induction Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000002826 coolant Substances 0.000 description 2
- 238000005485 electric heating Methods 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910000905 alloy phase Inorganic materials 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 238000004881 precipitation hardening Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 230000037303 wrinkles Effects 0.000 description 1
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Abstract
Description
本発明は、自動車部品の構造部材に使用されるような強度および耐食性が必要とされるプレス成形品およびその製造方法に関する。特に亜鉛めっき鋼板または合金化溶融亜鉛めっき鋼板を加熱してから所定の形状にプレス成形加工する際に、形状付与と同時に焼入れて所定強度を得るプレス成形品、およびそのようなプレス成形品の製造方法に関するものである。 The present invention relates to a press-formed product that requires strength and corrosion resistance, such as those used for structural members of automobile parts, and a method for manufacturing the same. In particular, when a galvanized steel sheet or an alloyed hot-dip galvanized steel sheet is heated and then press-formed into a predetermined shape, a press-formed product that obtains a predetermined strength by quenching at the same time as forming the shape, and manufacture of such a press-formed product It is about the method.
近年、自動車軽量化のためにボディへの高強度鋼の適用が進み、引張強度が９８０ＭＰａを超える鋼板の適用が拡大している。その一方で、高強度化するにつれて部品加工時の金型寿命低下や、スプリングバックによる形状ばらつきが大きくなる問題がある。そこで低強度の鋼板を、プレス成形前にＡｃ1変態点以上の温度（約９００℃程度以上）に加熱して鋼板をオーステナイト化してから高温域で成形することによって変形抵抗を低減しつつスプリングバックをも低減し、なおかつ成形と同時に焼き入れを行って成形品の強度を確保する工法、いわゆる熱間プレス成形法（以下、「ホットスタンプ」と呼ぶことがある）が開発されている。こうしたホットスタンプは、特に引張強度で１４７０ＭＰａ以上級の高強度が必要される部品（プレス成形品）を製造するための工法として広まりつつある。 In recent years, application of high-strength steel to the body has progressed in order to reduce the weight of automobiles, and application of steel sheets having a tensile strength exceeding 980 MPa has been expanded. On the other hand, there is a problem that as the strength is increased, the die life during processing of the parts is reduced and the shape variation due to the spring back becomes larger. Therefore, a low strength steel plate is heated to a temperature above the Ac 1 transformation point (about 900 ° C. or higher) before press forming to austenite the steel plate, and then formed in a high temperature range to reduce deformation resistance and spring back. In addition, a so-called hot press molding method (hereinafter sometimes referred to as “hot stamping”) has been developed in which the strength of the molded product is ensured by quenching simultaneously with molding. Such a hot stamp is spreading as a construction method for manufacturing a part (press-molded product) that requires a high strength of 1470 MPa or more in particular.
一方、自動車構造材のうちで高耐食性が求められるサイドメンバ、サイドシル、クロスメンバ、ピラー下部などに適用される部品には、犠牲防食効果の付与が必須であり、従来から亜鉛めっき鋼板や合金化溶融亜鉛めっき鋼板の冷間加工部品が適用されてきた。現在、亜鉛めっき鋼板や合金化溶融亜鉛めっき鋼板をホットスタンププロセスで部品成形することにより、サイドメンバ、サイドシル、クロスメンバ、ピラー下部などに適用可能な高強度かつ高耐食性を持つプレス成形品が求められている。 On the other hand, sacrificial anti-corrosion effect must be imparted to parts applied to side members, side sills, cross members, pillar lower parts, etc. that require high corrosion resistance among automotive structural materials. Cold worked parts of hot dip galvanized steel sheets have been applied. At present, there is a need for press-formed products with high strength and high corrosion resistance that can be applied to side members, side sills, cross members, pillar lower parts, etc. by forming parts of galvanized steel sheets and galvannealed steel sheets by hot stamping processes. It has been.
図１は、上記のようなホットスタンプを実施するための金型構成を示す概略説明図であり、図中１はパンチ、２はダイ、３はブランクホルダー、４は鋼板（ブランク）、ＢＨＦはしわ押え力、ｒｐはパンチ肩半径、ｒｄはダイ肩半径、ＣＬはパンチ／ダイ間クリアランスを夫々示している。また、これらの部品のうち、パンチ１とダイ２には冷却媒体（例えば水）を通過させることができる通路１ａ，２ａが夫々の内部に形成されており、この通路に冷却媒体を通過させることによって、これらの部材が冷却されるように構成されている。
FIG. 1 is a schematic explanatory view showing a mold configuration for carrying out hot stamping as described above, in which 1 is a punch, 2 is a die, 3 is a blank holder, 4 is a steel plate (blank), and BHF is The wrinkle pressing force, rp is the punch shoulder radius, rd is the die shoulder radius, and CL is the punch / die clearance. Of these components, the punch 1 and the
こうした金型を用いてホットスタンプ（例えば、熱間深絞り加工）するに際しては、鋼板（ブランク）４を、（Ａｃ1変態点〜Ａｃ3変態点）の二相域温度またはＡｃ3変態点以上の単相域温度に加熱して軟化させた状態で成形を開始する。即ち、高温状態にある鋼板４をダイ２とブランクホルダー３間に挟んだ状態で、パンチ１によってダイ２の穴内（図１の２，２間）に鋼板４を押し込み、鋼板４の外径を縮めつつパンチ１の外形に対応した形状に成形する。また、成形と並行してパンチ１およびダイ２を冷却することによって、鋼板４から金型（パンチ１およびダイ２）への抜熱を行なうと共に、成形下死点（パンチ先端が最深部に位置した時点：図１に示した状態）で更に保持冷却することによって鋼板４の焼入れを実施する。こうしたプレス成形法を実施することによって、寸法精度の良い１４７０ＭＰａ以上級の成形品を得ることができ、しかも冷間で同じ強度クラスの部品を成形する場合に比較して、成形荷重が低減できることからプレス機の容量が小さくて済むことになる。
When hot stamping (for example, hot deep drawing) using such a mold, the steel plate (blank) 4 is set to the two-phase region temperature (Ac 1 transformation point to Ac 3 transformation point) or higher than the Ac 3 transformation point. Molding is started in a state of being softened by heating to a single phase temperature. That is, in a state where the steel plate 4 in a high temperature state is sandwiched between the
しかしながら、亜鉛めっき鋼板や合金化溶融亜鉛めっき鋼板をホットスタンプに供すると、９００℃の高温で液化（溶融）した亜鉛が鋼板の結晶粒界に浸入して鋼板が脆化する液体金属脆化（以下、「ＬＭＥ」と記載することがある）によりプレス成形時にクラックが発生し、部品（プレス成形品）としての耐衝撃特性や疲労強度が低下する問題がある。 However, when a galvanized steel sheet or an alloyed hot-dip galvanized steel sheet is subjected to hot stamping, liquid metal embrittlement occurs in which zinc liquefied (melted) at a high temperature of 900 ° C. enters the crystal grain boundaries of the steel sheet and embrittles the steel sheet. Hereinafter, there is a problem that cracks are generated during press molding due to “LME”), and impact resistance characteristics and fatigue strength as a part (press molded product) are lowered.
こうしたＬＭＥによるクラック（以下、「ＬＭＥクラック」と呼ぶことがある）を抑制するために、例えば特許文献１には、プレス成形前の加熱を２回行ったり、高温保持時間を比較的長くしたり（例えば１０００秒）することによって、めっき層の合金化を促進してプレス成形加工時に溶融する亜鉛を抑制し、クラックの発生を抑制する方法が提案されている。しかしながらこの方法では、ホットスタンプ工程において溶融した亜鉛をなくすために複数回の加熱や長時間の加熱保持が必要となり、生産性を損ねるという欠点がある。 In order to suppress such cracks due to LME (hereinafter sometimes referred to as “LME cracks”), for example, in Patent Document 1, heating before press molding is performed twice, or the high temperature holding time is relatively long. A method has been proposed in which, for example, 1000 seconds is used, the alloying of the plating layer is promoted to suppress the zinc melted during the press forming process, and the generation of cracks is suppressed. However, this method has a drawback in that productivity is deteriorated because heating and holding for a plurality of times are required in order to eliminate molten zinc in the hot stamping process.
本発明は上記事情に鑑みてなされたものであって、その目的は、亜鉛めっき鋼板または合金化溶融亜鉛めっき鋼板を用いて熱間プレス成形するに際し、成形前での加熱保持時間を短くしてもＬＭＥクラックの発生を回避しつつ高い強度を発揮するプレス成形品を製造するための有用な方法、およびこうした方法によって得られるプレス成形品を提供することにある。 The present invention has been made in view of the above circumstances, and its purpose is to shorten the heat holding time before forming when hot press forming using a galvanized steel sheet or an alloyed hot dip galvanized steel sheet. Another object of the present invention is to provide a useful method for producing a press-formed product exhibiting high strength while avoiding the occurrence of LME cracks, and a press-formed product obtained by such a method.
上記目的を達成することのできた本発明方法とは、亜鉛めっき鋼板または合金化溶融亜鉛めっき鋼板を、熱間プレス成形法によって成形してプレス成形品を製造する方法であって、前記鋼板を８８０℃以上、９２０℃以下の温度に６分未満保持した後、８００℃以上、９２０℃以下の温度範囲で成形を開始することを特徴とする。 The method of the present invention capable of achieving the above object is a method for producing a press-formed product by forming a galvanized steel sheet or an alloyed hot-dip galvanized steel sheet by a hot press forming method. After holding at a temperature of from ℃ .degree. C. to 920.degree. C. for less than 6 minutes, molding is started in a temperature range of from 800.degree. C. to 920.degree.
本発明方法においては、成形開始時に鋼板表面に液体亜鉛が存在していても、ＬＭＥクラックの発生を回避しつつプレス成形できるものとなる。 In the method of the present invention, even if liquid zinc is present on the steel sheet surface at the start of forming, press forming can be performed while avoiding the occurrence of LME cracks.
本発明で用いる亜鉛めっき鋼板または合金化溶融亜鉛めっき鋼板における素地鋼板は、Ｍｏ：１．５質量％未満およびＷ：０．７質量％未満に夫々抑制したものであることが好ましい。 The base steel sheet in the galvanized steel sheet or galvannealed steel sheet used in the present invention is preferably suppressed to Mo: less than 1.5 mass% and W: less than 0.7 mass%.
本発明においては、上記のような方法によって製造されるプレス成形品も包含する。 In this invention, the press-molded article manufactured by the above methods is also included.
本発明によれば、亜鉛めっき鋼板または合金化溶融亜鉛めっき鋼板を用いて熱間プレス成形するに際し、成形前の加熱条件（加熱温度、加熱保持時間）や、成形時の加熱温度を適切に制御することによって、成形前加熱時間を短くしてもＬＭＥクラックの発生を回避しつつ良好な特性を発揮するプレス成形品を製造することができる。 According to the present invention, when hot press forming using a galvanized steel sheet or an alloyed hot-dip galvanized steel sheet, the heating conditions (heating temperature, heat holding time) before forming and the heating temperature during forming are appropriately controlled. By doing this, even if the heating time before molding is shortened, it is possible to produce a press-molded product that exhibits good characteristics while avoiding the occurrence of LME cracks.
本発明者らは、亜鉛めっき鋼板または合金化溶融亜鉛めっき鋼板を所定の温度に加熱した後、熱間プレス成形してプレス成形品を製造するに際して、加熱保持時間を短くしても、プレス成形中にＬＭＥクラックの発生を回避しつつ良好な特性を発揮するプレス成形品を生産性良く製造すべく、様々な角度から検討した。 The inventors of the present invention, after heating a galvanized steel sheet or an alloyed hot dip galvanized steel sheet to a predetermined temperature and then producing a press-formed product by hot press forming, press forming In order to produce a press-molded product exhibiting good characteristics while avoiding the occurrence of LME cracks with good productivity, investigations were made from various angles.
その結果、亜鉛めっき鋼板または合金化溶融亜鉛めっき鋼板（これらを総括して「表面処理鋼板」と呼ぶことがある）を加熱した後、８００℃以上の高温を維持したままプレス成形を開始することによって、加熱保持時間を短時間にしてもＬＭＥクラックの発生を抑制できることを見出し、本発明を完成した。 As a result, after heating a galvanized steel sheet or a galvannealed steel sheet (sometimes collectively referred to as “surface-treated steel sheet”), press forming is started while maintaining a high temperature of 800 ° C. or higher. Thus, the inventors have found that the occurrence of LME cracks can be suppressed even when the heating and holding time is shortened, and the present invention has been completed.
ＬＭＥクラックは、溶融した液体亜鉛によって素地鋼板が脆化した状態でプレス成形を施すことによって発生する。液体亜鉛が付着した表面処理鋼板をプレス成形すると、結晶粒界に液体亜鉛が浸潤し、結晶粒界の耐力が失われるために、クラックが生じると考えられる。プレス成形前の加熱中において亜鉛めっき層は液化し、鋼板との界面においてＦｅ／Ｚｎの固体の合金相が生成する反応が進行し、めっき層中のＦｅ濃度が増加する。加熱してから一定以上の時間が経過すると、めっき層中の液体亜鉛がほぼなくなるため、プレス成形前に高温で長時間保持するほど、その後のプレス成形でＬＭＥクラックは発生しなくなることは知られている（前記特許文献１）。しかしながら、加熱後に長時間保持する必要があるため、生産性が低下する。 The LME crack is generated by performing press forming in a state where the base steel sheet is embrittled by molten liquid zinc. When the surface-treated steel sheet to which liquid zinc adheres is press-molded, liquid zinc infiltrates into the crystal grain boundary, and the proof stress of the crystal grain boundary is lost. During the heating before press forming, the galvanized layer is liquefied, and a reaction in which a solid alloy phase of Fe / Zn is generated at the interface with the steel sheet proceeds, and the Fe concentration in the plated layer increases. It is known that when a certain amount of time elapses after heating, the liquid zinc in the plating layer almost disappears, so that the longer the temperature is kept before press molding, the more LME cracks will not occur in subsequent press molding. (Patent Document 1). However, since it is necessary to hold | maintain for a long time after a heating, productivity falls.
通常の熱間プレスでは、鋼板を所定温度まで加熱した後に速やかにプレス成形を行うが、加熱が終わってからプレス成形に供するまでに鋼板の温度は大きく低下する。この低下温度は、通常の鋼板においてはたとえば約１００℃以上である。しかしながら、本発明者らは、高温を保ったままプレス成形を開始すれば、加熱保持時間を短時間にしてもＬＭＥクラックの発生を抑制できることを見出したのである。 In a normal hot press, press forming is performed immediately after heating the steel plate to a predetermined temperature. However, the temperature of the steel plate is greatly reduced from when the heating is finished until it is subjected to press forming. This lowering temperature is, for example, about 100 ° C. or more in a normal steel plate. However, the present inventors have found that if press molding is started while maintaining a high temperature, the occurrence of LME cracks can be suppressed even if the heating and holding time is shortened.
本発明者らが種々のプロセス条件の影響を検討したところ、鋼板の軟質化に必要な最小限の温度だけ加熱保持し、比較的高い温度でプレス成形することにより、プレス成形前の加熱工程で保持する時間を６分未満にしても、ＬＭＥによるクラックを抑制することを見出した。８８０℃以上、９２０℃以下の目標加熱温度に到達しさえすれば、その温度で必ずしも保持をしなくても（保持時間が０秒であっても）ＬＭＥによるクラックを抑制する効果が得られるが、成形性の観点、すなわちオーステナイト量を確保するという観点からは、この保持時間は１秒以上とすることが好ましく、より好ましくは５秒以上、更に好ましくは１０秒以上、特に好ましくは３０秒以上とするのが良い。しかしながら、この保持時間があまり長くなると生産性が低下することから、６分未満とする。好ましくは５分以下、より好ましくは４分以下、更に好ましくは３分以下である。 The present inventors examined the influence of various process conditions, and as a result, heated and held only at the minimum temperature necessary for softening the steel sheet, and by press forming at a relatively high temperature, the heating process before press forming was performed. It has been found that even if the holding time is less than 6 minutes, cracks due to LME are suppressed. As long as the target heating temperature of 880 ° C. or higher and 920 ° C. or lower is reached, the effect of suppressing cracks due to LME can be obtained even if the temperature is not necessarily held (even if the holding time is 0 second). From the viewpoint of moldability, that is, from the viewpoint of securing the amount of austenite, the holding time is preferably 1 second or longer, more preferably 5 seconds or longer, still more preferably 10 seconds or longer, particularly preferably 30 seconds or longer. It is good to do. However, if this holding time becomes too long, the productivity is lowered, so the time is less than 6 minutes. Preferably it is 5 minutes or less, More preferably, it is 4 minutes or less, More preferably, it is 3 minutes or less.
本発明方法においては、素地鋼板表面にめっき処理を施した表面処理鋼板を、金型を用いてプレス成形してプレス成形品を製造するに際して、表面処理鋼板を、８８０℃以上、９２０℃以下の温度に加熱する必要がある。熱間プレス法による効果を発揮させるためには、加熱温度は少なくとも８８０℃以上とする必要がある。加熱温度が８８０℃未満であると、加熱時に適切な量のオーステナイトが得られず、良好な成形性が確保できない。また、加熱温度が９２０℃を超えると、表面処理鋼板のめっき層中の亜鉛が沸騰および蒸発し、耐食性が劣化するため好ましくない。加熱温度の好ましい下限は８９０℃以上（全てをオーステナイトにする温度）であり、好ましい上限は９１０℃以下である。尚、本発明における加熱温度は、鋼板の表面温度によって測定した値である（以下の温度においても同じ）。 In the method of the present invention, when producing a press-formed product by press-molding a surface-treated steel sheet plated on the surface of the base steel sheet using a mold, the surface-treated steel sheet is 880 ° C. or higher and 920 ° C. or lower. Need to be heated to temperature. In order to exhibit the effect of the hot pressing method, the heating temperature needs to be at least 880 ° C. or higher. When the heating temperature is less than 880 ° C., an appropriate amount of austenite cannot be obtained during heating, and good moldability cannot be ensured. Moreover, when heating temperature exceeds 920 degreeC, since the zinc in the plating layer of a surface-treated steel plate will boil and evaporate and corrosion resistance will deteriorate, it is unpreferable. A preferable lower limit of the heating temperature is 890 ° C. or higher (a temperature at which all is austenite), and a preferable upper limit is 910 ° C. or lower. The heating temperature in the present invention is a value measured by the surface temperature of the steel sheet (the same applies to the following temperatures).
表面処理鋼板を上記の温度範囲に加熱した後は、比較的高い温度でプレス成形を開始する必要がある。こうした観点から、プレス成形開始温度は８００℃以上とすることが必要となる。プレス成形開始温度が８００℃よりも低くなると、ＬＭＥクラックが発生しやすくなる。この温度は、好ましくは８５０℃以上である。この温度範囲では、鋼板表面に液体亜鉛が多少存在する場合もあるが、本発明ではこうした状況であっても、良好なプレス成形性が確保できることになる。プレス成形開始温度の上限（および好ましい条件）は、鋼板加熱温度の上限と同じである。 After heating the surface-treated steel sheet to the above temperature range, it is necessary to start press forming at a relatively high temperature. From such a viewpoint, the press molding start temperature needs to be 800 ° C. or higher. When the press molding start temperature is lower than 800 ° C., LME cracks are likely to occur. This temperature is preferably 850 ° C. or higher. In this temperature range, there may be some liquid zinc on the steel sheet surface, but in the present invention, good press formability can be ensured even in such a situation. The upper limit (and preferred conditions) of the press forming start temperature is the same as the upper limit of the steel sheet heating temperature.
本発明によって上記効果が得られるメカニズムの詳細は明らかではないが、おそらく次のような現象が生じているものと推定される。即ち、プレス成形開始温度を８００℃以上の高温とすることにより、通常の熱間プレス成形よりも変形抵抗が小さくなるため、結晶粒界からクラックが発生する前に変形が進行するために、ＬＭＥクラックの発生が抑制されるものと考えられる。 Although the details of the mechanism by which the above-described effect can be obtained by the present invention are not clear, it is presumed that the following phenomenon is probably occurring. That is, by setting the press molding start temperature to a high temperature of 800 ° C. or higher, the deformation resistance becomes smaller than that of normal hot press molding, so that the deformation proceeds before cracks are generated from the crystal grain boundaries. It is thought that the occurrence of cracks is suppressed.
本発明で用いる表面処理鋼板は、亜鉛めっき鋼板または合金化溶融亜鉛めっき鋼板であるが、これらの表面処理鋼板の素材となる鋼板（素地鋼板）の鋼種については高強度鋼板としての通常の化学成分組成のものであれば良い（後記実施例の表１参照）。熱間プレス成形では、部品を成形する目的は主として高強度化であり、金型で冷却するプロセスにおいて焼き入れを行い、強度を確保するものである。このため一般にはＣに加えてＢやＭｎなど、焼き入れ性を向上させる元素が添加された鋼板を用いる。熱延鋼板または熱延鋼板を冷間圧延して得られる冷延鋼板を用いることができる。 The surface-treated steel sheet used in the present invention is a galvanized steel sheet or an alloyed hot-dip galvanized steel sheet. However, the steel type of the steel sheet (base steel sheet) that is the material of these surface-treated steel sheets is a normal chemical component as a high-strength steel sheet. Any composition may be used (see Table 1 in Examples below). In the hot press molding, the purpose of molding a part is mainly to increase the strength, and in the process of cooling with a mold, quenching is performed to ensure the strength. For this reason, in general, a steel sheet to which elements that improve hardenability such as B and Mn are added in addition to C is used. A hot-rolled steel sheet or a cold-rolled steel sheet obtained by cold rolling a hot-rolled steel sheet can be used.
鋼板の高強度化に有効な成分として、析出硬化作用のあるＭｏやＷ等が知られているが、熱間プレス成形時の変形抵抗を低下させて亀裂発生を抑制するために、Ｍｏ：１．５質量％未満およびＷ：０．７質量％未満に夫々抑制したものであることが好ましい。 Mo and W having a precipitation hardening effect are known as effective components for increasing the strength of the steel sheet. However, in order to reduce deformation resistance during hot press forming and suppress cracking, Mo: 1 It is preferable that they are suppressed to less than 0.5 mass% and W: less than 0.7 mass%, respectively.
本発明で用いる亜鉛めっき鋼板は、熱延鋼板または冷延鋼板にめっき処理することで得られる。亜鉛めっき層の望ましいめっき付着量は片面あたり３０〜２００ｇ／ｍ2程度にすることで、十分な耐食性を得ることができる。めっき処理の方法としては溶融めっき、電気めっきがある。めっき処理後に所定の温度（４７０℃〜５８０℃）で１分〜１０分間保持することで、めっき層と素地鋼板中の鉄とが合金化した合金化亜鉛めっき鋼板（通常、合金化溶融亜鉛めっき鋼板）とし、これを用いることもできる。 The galvanized steel sheet used in the present invention can be obtained by plating a hot-rolled steel sheet or a cold-rolled steel sheet. Sufficient corrosion resistance can be obtained by setting the desired coating amount of the galvanized layer to about 30 to 200 g / m 2 per side. Examples of the plating method include hot dipping and electroplating. An alloyed galvanized steel sheet (usually alloyed hot dip galvanized) in which the plating layer and iron in the base steel sheet are alloyed by holding at a predetermined temperature (470 ° C. to 580 ° C.) for 1 minute to 10 minutes after the plating treatment. Steel plate), which can also be used.
以下、本発明を実施例によって更に具体的に示すが、下記実施例は本発明を限定するものではなく、前・後記の趣旨に徴して設計変更することはいずれも本発明の技術的範囲に含まれるものである。 Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are not intended to limit the present invention, and any design changes in the spirit of the preceding and following descriptions are within the technical scope of the present invention. It is included.
下記表１に示した化学成分組成を有する鋼材をスラブ溶製し、熱間圧延を行なって板厚３．２ｍｍの熱延鋼板とした。これを冷間圧延することによって板厚：０．８ｍｍまたは１．４ｍｍの冷延鋼板を作製した。これらの鋼板に対してめっき処理を施し、亜鉛めっき鋼板とした。このとき、バッチ式雰囲気制御焼鈍めっき処理装置にて亜鉛めっき処理を行った。また一部の鋼板については、合金化処理を施し、合金化亜鉛めっき鋼板を作製した。亜鉛めっき処理および合金化処理は、雰囲気制御が可能で加熱冷却機構と亜鉛めっき浴となる坩堝を備え、めっき処理、合金化処理が一貫工程で可能な実験炉を用いた。 A steel material having the chemical composition shown in Table 1 below was melted by slab and hot-rolled to obtain a hot-rolled steel plate having a thickness of 3.2 mm. This was cold-rolled to produce a cold-rolled steel sheet having a thickness of 0.8 mm or 1.4 mm. These steel sheets were subjected to plating treatment to obtain galvanized steel sheets. At this time, the galvanization process was performed with the batch type atmosphere control annealing plating apparatus. Moreover, about some steel plates, the alloying process was performed and the alloyed galvanized steel plate was produced. For the galvanizing treatment and alloying treatment, an experimental furnace capable of controlling the atmosphere, equipped with a heating / cooling mechanism and a crucible serving as a galvanizing bath, and capable of performing plating treatment and alloying treatment in an integrated process was used.
めっき処理条件は、４６０℃のＺｎ浴（Ａｌ：０．１３％含有）に３秒間浸漬した。合金化処理は５％Ｈ2−Ｎ2（露点−４５℃）の雰囲気で５５０℃×２０秒間保持して行い、その後Ａｒガスの吹き付けにより冷却した。このときの平均冷却速度は１５℃／秒である。 The plating treatment conditions were immersed in a 460 ° C. Zn bath (Al: containing 0.13%) for 3 seconds. The alloying treatment was performed by holding at 550 ° C. for 20 seconds in an atmosphere of 5% H 2 —N 2 (dew point −45 ° C.), and then cooled by blowing Ar gas. The average cooling rate at this time is 15 ° C./second.
亜鉛めっき鋼板および合金化亜鉛めっき鋼板のめっき付着量は、断面ＳＥＭ（走査型電子顕微鏡）観察、およびめっき中のＦｅ濃度測定により評価した。 The coating amount of the galvanized steel sheet and the alloyed galvanized steel sheet was evaluated by cross-sectional SEM (scanning electron microscope) observation and measurement of Fe concentration during plating.
こうして得られた亜鉛めっき鋼板または合金化溶融亜鉛めっき鋼板から、平行部幅１５ｍｍ×長さ２０ｍｍの引張試験片（図２）を切り出し、一軸引張型の加工フォーマスタ装置を用いて、ホットスタンプ工程の温度履歴を模擬した上で加工を行い、その塑性変形部におけるＬＭＥクラック深さを評価する試験を行った。 From the galvanized steel sheet or galvannealed steel sheet thus obtained, a tensile specimen (FIG. 2) having a parallel part width of 15 mm and a length of 20 mm is cut out, and a hot stamping process is performed using a uniaxial tension type processing formaster device. The process was performed after simulating the temperature history, and a test for evaluating the LME crack depth in the plastically deformed portion was performed.
加熱方式は誘導加熱または通電加熱等が考えられるが、本試験では通電加熱で試験片平行部を加熱しながら、同時に試験片つかみ部付近を誘導加熱した。試験片の片面の亜鉛めっきを研磨除去し、めっき除去した側の面の平行部中央、およびつかみ部に設置した熱伝対によってそれぞれ通電加熱および誘導加熱を所定狙いの温度に制御した。 As the heating method, induction heating or electric heating can be considered. In this test, the parallel part of the test piece was heated by electric heating, and at the same time, the vicinity of the grip part of the test piece was induction heated. The galvanizing on one side of the test piece was polished and removed, and the energization heating and induction heating were controlled to a predetermined target temperature by thermocouples installed at the center of the parallel part of the surface on which the plating was removed and the grip part, respectively.
温度履歴は、室温から温度Ｔ１まで加熱し、所定時間ｔ１（分）保持した後に温度Ｔ２（成形開始時間）まで冷却し、その温度で所定の狙いひずみ量まで一定の歪み速度（秒-1）で加工した。加熱および加工中は、大気雰囲気にて行った。冷却プロセスのみＡｒガスの噴き付けによる冷却を行った。 In the temperature history, the temperature is heated from room temperature to T1, held for a predetermined time t1 (minute), then cooled to temperature T2 (molding start time), and at that temperature, a constant strain rate (second −1 ) up to a predetermined target strain amount. It was processed with. During heating and processing, it was performed in an air atmosphere. Only the cooling process was performed by cooling with Ar gas.
歪み量の実績値は、予め試験片平行部の裏面（めっきを除去した側）に標線を評点間距離２０ｍｍで刻印しておき、評点間距離の伸び率（％）を対数歪み量で測定した。一方、加工時の歪速度は、加工フォーマスタ試験機でロードセル間の距離の一秒当たりの増加率（ｓｅｃ-1）を制御した。 The actual amount of strain is measured in advance by marking the gauge line with a distance of 20 mm between the marks on the back of the parallel part of the test piece (the side from which the plating has been removed), and measuring the elongation (%) of the distance between the marks with the logarithmic strain. did. On the other hand, the strain rate at the time of machining was controlled by the rate of increase (sec −1 ) per second of the distance between load cells by a machining for master test machine.
［最大亀裂深さの測定］
試験片の外観、および断面ＳＥＭ観察によりクラックの有無の判断と最大深さを測定した。断面ＳＥＭ観察は、試験片平行部の幅方向の中央を引張方向と平行に切断し（図２）、樹脂埋め研磨試料を作製した。平行部長さ２０ｍｍ全体にわたって観察した。めっき層よりも下側（素地鋼板に亀裂が進展している箇所）において、進展深さが最大の亀裂の深さを測定した。
[Measurement of maximum crack depth]
The appearance of the test piece and the determination of the presence or absence of cracks and the maximum depth were measured by cross-sectional SEM observation. Cross-sectional SEM observation cut | disconnected the center of the width direction of the test piece parallel part in parallel with the tension | pulling direction (FIG. 2), and produced the resin embedding polished sample. The entire parallel part length of 20 mm was observed. On the lower side of the plating layer (the place where the crack has propagated in the base steel sheet), the depth of the crack with the maximum progress was measured.
そして素地鋼板表面に進展した最大亀裂深さが１０μｍ未満であれば部品の耐衝撃特性に影響が無いことから、最大亀裂深さが１０μｍ以上のものは、耐ＬＭＥクラック性（耐ＬＭＥ亀裂性）が悪いと判断した。またこの断面ＳＥＭ観察において、めっき層の一部に白色に見える亜鉛層の有無により、加工時における液体亜鉛の有無を確認した。 And, if the maximum crack depth developed on the surface of the base steel sheet is less than 10 μm, there is no effect on the impact resistance characteristics of the parts, so those with a maximum crack depth of 10 μm or more have LME crack resistance (LME crack resistance). Was judged bad. Moreover, in this cross-sectional SEM observation, the presence or absence of the liquid zinc at the time of a process was confirmed by the presence or absence of the zinc layer which looks white in a part of plating layer.
これらの結果を、板厚、めっき付着量、合金化処理の有無、加工条件［加熱温度、加熱保持時間、成形開始温度、歪み量（狙い、実績）、歪み速度］と共に、下記表２〜４に示す。 These results are shown in Tables 2 to 4 below together with the plate thickness, plating adhesion amount, presence / absence of alloying treatment, processing conditions [heating temperature, heating holding time, molding start temperature, strain amount (target, actual result), strain rate]. Shown in
これらの結果から、次のように考察できる。試験Ｎｏ．１〜３、６〜１０、１３〜１７、２０〜２８、３０、３４、３５、３７〜３９、４１、４２、４４、４５、４７、４８、５０、５２、５４、５６のものは、本発明で規定する要件を満足する実施例であり、ＬＭＥクラックの発生が抑制されており、良好な熱間プレス成形品が得られていることが分かる。 From these results, it can be considered as follows. Test No. 1-3, 6-10, 13-17, 20-28, 30, 34, 35, 37-39, 41, 42, 44, 45, 47, 48, 50, 52, 54, 56 It is an Example that satisfies the requirements specified in the invention, and it can be seen that the occurrence of LME cracks is suppressed and a good hot press-formed product is obtained.
これに対し、試験Ｎｏ．４、５、１１、１２、１８、１９、２９、３１、３６、４０、４３、４６、４９、５１、５３、５５のものは、本発明で規定する要件を外れる条件、即ち成形開始温度が低いため、最大亀裂深さが大きくなっている。尚、試験Ｎｏ．３２、３３のものは、加熱時の保持時間を長くした例であり、成形開始時点で液体亜鉛が残っておらず、成形開始温度が低くなっても、ＬＭＥクラックの発生が抑制された参考例である。但し、加熱保持時間が長時間となり、生産性が悪化する。 In contrast, test no. 4, 5, 11, 12, 18, 19, 29, 31, 36, 40, 43, 46, 49, 51, 53, 55 have conditions that deviate from the requirements defined in the present invention, that is, the molding start temperature. Since it is low, the maximum crack depth is large. Test No. Examples Nos. 32 and 33 are examples in which the holding time at the time of heating is extended, and liquid zinc does not remain at the start of molding, and even when the molding start temperature is low, the occurrence of LME cracks is suppressed. It is. However, the heating and holding time becomes long and productivity deteriorates.
１ パンチ
２ ダイ
３ ブランクホルダー
４ 鋼板（ブランク）
1
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016088296A1 (en) * | 2014-12-02 | 2016-06-09 | Ｊｆｅスチール株式会社 | Methods for evaluating and manufacturing hot-press formed article |
| JP2017064771A (en) * | 2015-10-01 | 2017-04-06 | 豊田鉄工株式会社 | Method of hot bending steel pipe |
| CN111434405A (en) * | 2019-06-12 | 2020-07-21 | 苏州普热斯勒先进成型技术有限公司 | Preparation method and device of hot stamping part |
| JP2022050246A (en) * | 2020-09-17 | 2022-03-30 | 日本製鉄株式会社 | Method for evaluating liquid metal embrittlement susceptibility |
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Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002102980A (en) * | 2000-07-28 | 2002-04-09 | Aisin Takaoka Ltd | Manufacturing method for collision reinforcing material for vehicle and collision reinforcing material |
| JP2009082992A (en) * | 2009-01-30 | 2009-04-23 | Nippon Steel Corp | Hot forming method |
| JP2009228134A (en) * | 2008-02-27 | 2009-10-08 | Nippon Steel Corp | Steel sheet excellent in strength and hydrogen embrittlement resistance characteristic after hot stamping, and hot stamping method |
| JP2012076100A (en) * | 2010-09-30 | 2012-04-19 | Kobe Steel Ltd | Method of manufacturing press-formed article |
| JP2013091099A (en) * | 2011-09-01 | 2013-05-16 | Kobe Steel Ltd | Hot press molded product and production method thereof |
| JP2013220449A (en) * | 2012-04-18 | 2013-10-28 | Mazda Motor Corp | Press forming method of steel sheet and formed article of the steel sheet |
| JP2013226599A (en) * | 2012-03-30 | 2013-11-07 | Kobe Steel Ltd | Manufacturing method for hot press-molded steel member, and hot press-molded steel member |
-
2013
- 2013-12-16 JP JP2013259412A patent/JP6043272B2/en not_active Expired - Fee Related
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002102980A (en) * | 2000-07-28 | 2002-04-09 | Aisin Takaoka Ltd | Manufacturing method for collision reinforcing material for vehicle and collision reinforcing material |
| JP2009228134A (en) * | 2008-02-27 | 2009-10-08 | Nippon Steel Corp | Steel sheet excellent in strength and hydrogen embrittlement resistance characteristic after hot stamping, and hot stamping method |
| JP2009082992A (en) * | 2009-01-30 | 2009-04-23 | Nippon Steel Corp | Hot forming method |
| JP2012076100A (en) * | 2010-09-30 | 2012-04-19 | Kobe Steel Ltd | Method of manufacturing press-formed article |
| JP2013091099A (en) * | 2011-09-01 | 2013-05-16 | Kobe Steel Ltd | Hot press molded product and production method thereof |
| JP2013226599A (en) * | 2012-03-30 | 2013-11-07 | Kobe Steel Ltd | Manufacturing method for hot press-molded steel member, and hot press-molded steel member |
| JP2013220449A (en) * | 2012-04-18 | 2013-10-28 | Mazda Motor Corp | Press forming method of steel sheet and formed article of the steel sheet |
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| WO2016088296A1 (en) * | 2014-12-02 | 2016-06-09 | Ｊｆｅスチール株式会社 | Methods for evaluating and manufacturing hot-press formed article |
| JP2017064771A (en) * | 2015-10-01 | 2017-04-06 | 豊田鉄工株式会社 | Method of hot bending steel pipe |
| CN111434405A (en) * | 2019-06-12 | 2020-07-21 | 苏州普热斯勒先进成型技术有限公司 | Preparation method and device of hot stamping part |
| JP2022050246A (en) * | 2020-09-17 | 2022-03-30 | 日本製鉄株式会社 | Method for evaluating liquid metal embrittlement susceptibility |
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