JP2007254766A - Steel sheet for deep drawing excellent in low-temperature baking hardenability and room-temperature non-aging property and method for producing the same - Google Patents
Steel sheet for deep drawing excellent in low-temperature baking hardenability and room-temperature non-aging property and method for producing the same Download PDFInfo
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本発明は、自動車のパネル部材、家電製品の内外板及び缶用材料の使途に好適な低温焼付硬化性と常温非時効性に優れた深絞り用鋼板及びその製造方法に関し、特に、引張強度が２５０〜４５０ＭＰａ程度の低温焼付硬化性と常温非時効性に優れた深絞り用鋼板及びその製造方法に関する。 The present invention relates to a steel sheet for deep drawing excellent in low-temperature bake hardenability and room temperature non-aging suitable for use in automobile panel members, inner and outer plates of home appliances, and can materials, and a method for producing the same, and in particular, has a tensile strength. The present invention relates to a steel sheet for deep drawing excellent in low-temperature bake hardenability of about 250 to 450 MPa and non-aging at room temperature, and a method for producing the same.
自動車用鋼板においては、車体重量軽減のニーズから高強度化の要請が高い。しかしながら、一般に、材料を高強度化すると、深絞り性低下による成形時の割れ及び形状凍結性の低下といったプレス成形性の劣化を伴うことが知られており、成形加工性を低下させずに自動車用鋼板を高強度化する方法が強く望まれている。 In automotive steel sheets, there is a strong demand for higher strength due to the need to reduce vehicle weight. However, it is generally known that increasing the strength of a material is accompanied by deterioration of press formability such as cracking during molding due to deep drawability reduction and reduction in shape freezing property. There is a strong demand for a method for increasing the strength of steel sheets for construction.
このような要望に対し、従来、成形加工性を確保した上で鋼板の高強度化を達成する技術として、成形加工時には軟質に保たれ、成形加工後の電着塗装焼付工程で生じる歪時効硬化現象を利用して降伏強度又は引張強度を増加させる焼付硬化性（Bake Hardenability：ＢＨ）を利用した技術が知られている。この技術は、成形加工時にはＣ原子又はＮ原子を固溶させて成形性を確保しておき、電着塗装焼付工程において、成形加工時に鋼板内に生じた転位にＣ原子若しくはＮ原子を固着させるか、又は転位上に炭化物若しくは窒化物を微細分散析出させることによって、鋼板の降伏強度又は引張強度の上昇を図っている。 In response to such demands, conventionally, as a technology to achieve high strength of steel sheets while ensuring formability, it is kept soft during forming and strain age hardening that occurs in the electrodeposition coating baking process after forming A technique using bake hardenability (BH) that increases the yield strength or tensile strength by utilizing a phenomenon is known. In this technique, C atoms or N atoms are dissolved in forming process to ensure formability, and in the electrodeposition coating baking process, C atoms or N atoms are fixed to dislocations generated in the steel sheet during forming process. Alternatively, the yield strength or tensile strength of the steel sheet is increased by finely dispersing and precipitating carbides or nitrides on the dislocations.
しかしながら、高いＢＨ量を得るために鋼板の固溶Ｃ量又は固溶Ｎ量を高めると、常温時効劣化が生じ、その結果、加工時にストレッチャーストレインと呼ばれる歪み模様が発生するという問題がある。このように、焼付硬化性と常温非時効特性とは二律相反するものと考えられており、実際、常温非時効性を確保した上で得られる最大のＢＨ量は高くても３０〜４０ＭＰａ程度であった。 However, when the solid solution C content or the solid solution N content of the steel sheet is increased in order to obtain a high BH content, there is a problem that normal temperature aging deterioration occurs, and as a result, a strain pattern called a stretcher strain occurs during processing. Thus, it is considered that the bake hardenability and the non-aging property at room temperature are contradictory, and in fact, the maximum amount of BH obtained after securing the non-aging property at room temperature is at most about 30 to 40 MPa. Met.
また、固溶Ｃ量又は固溶Ｎ量を意図的に残存させた焼付硬化型鋼板は、所謂ＩＦ鋼と呼ばれる固溶Ｃ及び固溶Ｎがほとんど存在しない鋼板に比べて、深絞り性が著しく低いという問題点もあり、鋼板の焼付硬化性の向上と深絞り性の向上とを両立することは難しいと考えられている。 In addition, the bake hardened steel sheet in which the amount of solid solution C or the amount of solid solution N intentionally remains is significantly deep-drawable compared to a steel sheet having almost no solid solution C and solid solution N called so-called IF steel. There is also a problem that it is low, and it is considered difficult to achieve both improvement in bake hardenability and deep drawability of the steel sheet.
そこで、従来、これらの問題点を解決するための方法が提案されている（例えば、特許文献１〜６参照）。例えば、特許文献１には、焼鈍後の組織を高温変態フェライト相と転位密度の高い低温変態フェライト相との複合組織とすることで、高ｒ値化、高ＢＨ化及び高延性化を図った常温非時効型絞り用高張力冷延鋼板が開示されている。また、特許文献２には、Ｎｂを添加した極低炭素冷延鋼板において、焼鈍後の冷却速度を制御することによって粒界中のＣ濃度を高めると、高ＢＨにしても、常温遅時効性及び深絞り性の両立が可能であることが示されている。更に、特許文献３には、フェライトの結晶粒界中のＮ濃度を所定の範囲内に定めることにより、高ＢＨと常温遅時効性との両立を可能にする技術が開示されている。 Therefore, conventionally, methods for solving these problems have been proposed (see, for example, Patent Documents 1 to 6). For example, in Patent Document 1, the structure after annealing is a composite structure of a high-temperature transformation ferrite phase and a low-temperature transformation ferrite phase having a high dislocation density, thereby achieving high r value, high BH, and high ductility. A high-tensile cold-rolled steel sheet for room temperature non-aging drawing is disclosed. Further, in Patent Document 2, in an ultra-low carbon cold-rolled steel sheet to which Nb is added, when the C concentration in the grain boundary is increased by controlling the cooling rate after annealing, even at a high BH, room temperature slow aging In addition, it is shown that both deep drawability can be achieved. Furthermore, Patent Document 3 discloses a technique that enables both high BH and room temperature slow aging by setting the N concentration in the crystal grain boundary of ferrite within a predetermined range.
特許文献４には、Ａｌ含有量とＮ含有量との比、及び固溶状態のＮの含有量を所定の値以上にすることにより、深絞り性及び歪時効硬化特性を向上させた深絞り用冷延鋼板が提案されている。また、特許文献５には、固溶Ｎの含有量を所定の範囲にすると共に、ミクロ組織の主相を平均結晶粒径が７．０μｍ以下のフェライトとすることにより、焼付け硬化性及び耐衝撃性に優れた高張力熱延鋼板及びその製造方法が提案されている。更に、特許文献６に記載の加工性及び歪み時効硬化特性に優れた高張力溶融亜鉛めっき鋼板では、Ａｌ含有量とＮ含有量との比及び固溶状態のＮの含有量を所定の値以上にすると共に、主相がフェライトで、第２相としてマルテンサイトを３体積％以上含む組織としている。 Patent Document 4 discloses a deep drawing in which the deep drawability and strain age hardening characteristics are improved by setting the ratio of Al content to N content and the content of N in a solid solution state to a predetermined value or more. Cold rolled steel sheets have been proposed. In Patent Document 5, the content of solute N is set within a predetermined range, and the main phase of the microstructure is ferrite having an average crystal grain size of 7.0 μm or less, whereby bake hardenability and impact resistance are disclosed. A high-tensile hot-rolled steel sheet having excellent properties and a method for producing the same have been proposed. Furthermore, in the high-tensile hot-dip galvanized steel sheet excellent in workability and strain age hardening characteristics described in Patent Document 6, the ratio between the Al content and the N content and the content of N in a solid solution state are a predetermined value or more. In addition, the main phase is ferrite and the second phase has a structure containing 3% by volume or more of martensite.
一方、近年の傾向として、電着塗装の焼付け温度の低温化が進みつつある。しかしながら、一般に、塗装焼付け温度を低温化すると、焼付け硬化（ＢＨ）量は減少するという問題点があり、低温でも焼付硬化する鋼板の開発が望まれている。この問題点を解決する手段として、従来、固溶Ｎが残存する鋼にＣｒ、Ｍｏ及び／又はＶ等を添加することにより、焼付け温度が低温の場合でも十分なＢＨ量が得られるようにした冷延鋼板が提案されている（例えば、特許文献７及び８参照。）。また、固溶Ｎの残存する鋼において、硫化物と母相鉄との界面の総面積を制御することにより、ＢＨ量を増加させると共に、常温非時効性を確保した歪時効硬化型鋼板が提案されている（例えば、特許文献９参照。）。 On the other hand, as a recent trend, the baking temperature of electrodeposition coating is decreasing. However, generally, when the coating baking temperature is lowered, there is a problem that the amount of bake hardening (BH) decreases, and development of a steel sheet that can be bake hardened even at a low temperature is desired. Conventionally, as a means for solving this problem, a sufficient amount of BH can be obtained even when the baking temperature is low by adding Cr, Mo and / or V, etc. to the steel in which the solid solution N remains. Cold-rolled steel sheets have been proposed (see, for example, Patent Documents 7 and 8). In addition, in the steel in which solute N remains, a strain age hardening type steel sheet is proposed in which the total area of the interface between the sulfide and the parent phase iron is controlled to increase the amount of BH and to ensure non-aging at room temperature. (For example, refer to Patent Document 9).
しかしながら、上述した従来の技術には以下に示す問題点がある。即ち、特許文献１に記載の技術は、複合組織を得るためには極めて高い温度の焼鈍が必須であるため、これが連続焼鈍時に板破断等のトラブルの原因となるという実操業上の問題点がある。また、特許文献２に記載の技術は、フェライトの再結晶抑制元素であるＮｂを利用するために、８５０℃以上の極めて高い温度の焼鈍が必須であるため、この高温での焼鈍が連続焼鈍時に板破断等のトラブルの原因となるという実操業上の問題点がある。更に、特許文献３に記載の技術は、ストレッチャーストレイン発生の原因となる降伏点伸び発生の抑制には配慮が無く、また深絞り性への配慮も無い。また、この方法によると、結晶粒が粗大になるほど常温遅時効を確保した上で得られるＢＨ量は減少する。従って、特許文献３の技術には、実鋼板への適用範囲は極めて限られるという問題点がある。更にまた、特許文献４〜６に記載の技術は、高いＢＨ特性を得ることは可能であるが、常温非時効性が得られないという問題がある。また、これらの技術では、平均ｒ値で１．５程度の深絞り性しか得られない。 However, the conventional techniques described above have the following problems. That is, since the technique described in Patent Document 1 requires extremely high temperature annealing in order to obtain a composite structure, there is a problem in actual operation that this causes troubles such as plate breakage during continuous annealing. is there. In addition, since the technique described in Patent Document 2 uses Nb, which is an element for suppressing recrystallization of ferrite, annealing at an extremely high temperature of 850 ° C. or higher is essential. Therefore, annealing at this high temperature is performed during continuous annealing. There is a problem in actual operation that causes troubles such as plate breakage. Furthermore, the technique described in Patent Document 3 has no consideration for suppression of yield point elongation, which causes stretcher strain, and no consideration for deep drawability. Also, according to this method, the amount of BH obtained after securing the normal temperature slow aging decreases as the crystal grains become coarser. Therefore, the technique of Patent Document 3 has a problem that the range of application to actual steel sheets is extremely limited. Furthermore, although the techniques described in Patent Documents 4 to 6 can obtain high BH characteristics, there is a problem that normal temperature non-aging cannot be obtained. Also, with these techniques, only a deep drawability of about 1.5 in average r value can be obtained.
一方、低温での焼付硬化性については、特許文献７〜９に記載の技術は、焼付硬化性と常温非時効特性との両立は実現できるが、成分及び製造方法が最適化されていないために、優れた深絞り特性を得ることが困難であるという問題点がある。 On the other hand, regarding the bake hardenability at low temperature, the techniques described in Patent Documents 7 to 9 can realize both the bake hardenability and the non-aging property at room temperature, but the components and the production method are not optimized. There is a problem that it is difficult to obtain excellent deep drawing characteristics.
本発明は、上述した問題点に鑑みてなされたものであって、常温非時効性を有すると共に、低温塗装焼付け処理でも高い焼付硬化性が得られ、更に深絞り性が良好な低温焼付硬化性と常温非時効性に優れた深絞り用鋼板及びその製造方法を提供することを目的とする。 The present invention has been made in view of the above-mentioned problems, and has low-temperature bake hardenability, which has a non-aging property at room temperature, a high bake hardenability even in a low-temperature paint baking process, and a good deep drawability. Another object is to provide a steel sheet for deep drawing excellent in non-aging properties at room temperature and a method for producing the same.
本発明に係る低温焼付硬化性と常温非時効性に優れた深絞り用鋼板は、質量％で、Ｃ：０．００４％以下、Ｓｉ：０．６％以下、Ｍｎ：０．１５〜１．２％、Ｐ：０．０５％以下、Ｓ：０．００３〜０．０３％、Ｃｕ：０．００２〜０．６％、Ｃｒ：０．３〜２．０％、及びＮ：０．００２〜０．００８％を含有すると共に、Ａｌ：０．０１５％以下、Ｎｂ：０．０１％以下及びＴｉ：０．０１％以下に規制し、残部がＦｅ及び不可避的不純物からなる組成を有し、固溶Ｎ：０．００１〜０．００４％を含有すると共に固溶Ｃ：０．００１５％以下に規制し、かつ硫化物とＦｅとの界面の単位体積あたりの総面積が２×１０−３μｍ２／μｍ３以上であることを特徴とする。 The steel sheet for deep drawing excellent in low-temperature bake hardenability and non-aging at room temperature according to the present invention is by mass%, C: 0.004% or less, Si: 0.6% or less, Mn: 0.15-1. 2%, P: 0.05% or less, S: 0.003-0.03%, Cu: 0.002-0.6%, Cr: 0.3-2.0%, and N: 0.002 In addition to containing 0.008%, Al: 0.015% or less, Nb: 0.01% or less, and Ti: 0.01% or less, with the balance being Fe and inevitable impurities , Solid solution N: 0.001 to 0.004% and solid solution C: restricted to 0.0015% or less, and the total area per unit volume of the interface between sulfide and Fe is 2 × 10 − 3 μm 2 / μm 3 or more.
この深絞り用鋼板は、更に、質量％で、Ｍｏ及びＷからなる群から選択された１種又は２種の元素を合計で０．０１〜０．２％含有していてもよく、また、Ｎｉ：０．０１〜３．０％を含有していてもよい。更に、質量％で、Ａｓ、Ｓｂ、Ｂｉ、及びＳｎからなる群から選択された１種又は２種以上の元素を合計で０．０００３〜０．００２％含有することもでき、Ｂ：０．０００３〜０．００２５％を含有していてもよい。更にまた、質量％で、Ｃａ、Ｍｇ、Ｚｒ及びＲＥＭからなる群から選択された１種又は２種以上の元素を合計で０．００１〜０．０１％含有することもできる。 The deep drawing steel sheet may further contain, in mass%, one or two elements selected from the group consisting of Mo and W in a total amount of 0.01 to 0.2%, Ni: 0.01 to 3.0% may be contained. Further, it may contain 0.0003 to 0.002% in total of one or more elements selected from the group consisting of As, Sb, Bi, and Sn in mass%, and B: 0.00. It may contain 0003-0.0025%. Furthermore, it is possible to contain 0.001 to 0.01% in total of one or more elements selected from the group consisting of Ca, Mg, Zr and REM in mass%.
また、本発明の深絞り用鋼板は、表面にめっき層が形成されていてもよい。 Moreover, the steel sheet for deep drawing of this invention may have the plating layer formed in the surface.
本発明に係る低温焼付硬化性と常温非時効性に優れた深絞り用鋼板の製造方法は、前述した深絞り用鋼板と同様の化学成分を有する鋼を溶製し、鋳造して得たスラブを、１２００℃以上に加熱し、仕上圧延温度が（Ａｒ３−５０）℃以上、１０００℃以上仕上圧延温度以下の温度範囲での板厚減少率が３０％以上、巻取り温度が６００〜７５０℃の条件で熱間圧延して熱延コイルを得る工程と、前記熱延コイルを、６０％以上の圧延率で冷間圧延して冷延コイルを得る工程と、連続焼鈍炉により、前記冷延コイルを、最高到達温度を７００〜８５０℃として焼鈍する工程とを有することを特徴とする。 The manufacturing method of the steel for deep drawing excellent in low temperature bake hardenability and non-aging at room temperature according to the present invention is a slab obtained by melting and casting steel having the same chemical composition as the steel for deep drawing described above. was heated to above 1200 ° C., the finish rolling temperature is (Ar 3 -50) ℃ or higher, 30% or more the thickness reduction rate in the temperature range of 1000 ° C. or higher finish rolling temperature below the coiling temperature is 600 to 750 A step of obtaining a hot-rolled coil by hot rolling under the condition of ° C, a step of obtaining a cold-rolled coil by cold-rolling the hot-rolled coil at a rolling rate of 60% or more, and a continuous annealing furnace. And a step of annealing the extended coil at a maximum temperature of 700 to 850 ° C.
本発明の深絞り用鋼板の製造方法では、前記冷延鋼板にめっきを施してもよく、また、前記冷延鋼板に伸び率が２％以下の調質圧延を施すこともできる。 In the method for producing a steel sheet for deep drawing according to the present invention, the cold-rolled steel sheet may be plated, and the cold-rolled steel sheet may be subjected to temper rolling with an elongation of 2% or less.
本発明によれば、鋼組成及び製造条件を適正化することにより、固溶Ｎ含有量を０．００１〜０．００４％及び固溶Ｃ含有量を０．００１５％以下にすると共に、鋼中に微細な硫化物粒子を高密度で析出させて、鋼中における硫化物とＦｅとの界面の単位体積あたりの総面積を２×１０−３μｍ２／μｍ３以上にしているため、常温非時効性を有し、低温塗装焼付け処理においても高い焼付硬化性を示し、更に深絞り性が良好な深絞り用鋼板が得られる。 According to the present invention, by optimizing the steel composition and production conditions, the solid solution N content is 0.001 to 0.004% and the solid solution C content is 0.0015% or less, and in the steel. Since fine sulfide particles are precipitated at a high density, the total area per unit volume of the interface between sulfide and Fe in steel is 2 × 10 −3 μm 2 / μm 3 or more. A steel sheet for deep drawing having aging properties, high bake hardenability even in a low temperature paint baking process, and good deep drawability is obtained.
以下、本発明を実施するための最良の形態について、詳細に説明する。本発明者は、上述した課題を解決するために、鋭意検討を重ねた結果、鋼成分及び製造プロセスを適正化し、かつ鋼中に微細な硫化物粒子を高密度で析出させ、固溶Ｎ及び固溶Ｃの含有量を最適化することにより、常温非時効性、低温塗装焼付け処理による高い焼付硬化性及び良好な深絞り性の全てを兼ね備える鋼板を製造できるという全く新しい事実を見出し、本発明に至った。 Hereinafter, the best mode for carrying out the present invention will be described in detail. As a result of intensive studies to solve the above-mentioned problems, the present inventor has optimized the steel components and the manufacturing process, and precipitated fine sulfide particles at a high density in the steel. By optimizing the content of solute C, we found a completely new fact that it is possible to produce a steel sheet that has all of high bake hardenability and good deep drawability by room temperature non-aging, low-temperature paint baking treatment, and the present invention It came to.
具体的には、本発明者は、前記課題を解決するために、以下に示す手段を講じた。即ち、焼付硬化温度が低温の場合でも高い焼付硬化量が得られやすい固溶Ｎ利用型の鋼板を中心に、常温非時効性、低温塗装焼付け処理における高い焼付硬化性、及び良好な深絞り性の３つの特性の全てが得られる方法について検討を重ねた。その結果、鋼中に微細な硫化物粒子を高密度で分布させ、更に成分及びプロセスを最適化することにより、適量の固溶Ｃ及び固溶Ｎを鋼中に含有させた場合に、常温非時効性を確保した上で、高ＢＨ及び良好な深絞り性を兼備する鋼板が製造できることを見出し、本発明に至った。鋼中に微細な硫化物粒子を高密度で分散させることにより、これらの特性を満足させることができる理由は定かではないが、微細な硫化物が存在すると、この硫化物上にＣｒ系の窒化物若しくは鉄系の炭化物の析出が助長されるか、又は硫化物と鉄との界面にＣ及びＮの偏析が助長され、これにより鋼中の固溶Ｃ含有量及び固溶Ｎ含有量が適正化されるものと考えられる。 Specifically, in order to solve the above-mentioned problems, the present inventor has taken the following means. That is, centering on solid solution N-use steel sheets that can easily achieve a high bake-hardening amount even when the bake-hardening temperature is low, non-aging at room temperature, high bake hardenability in low-temperature paint baking, and good deep drawability The method of obtaining all the three characteristics was studied repeatedly. As a result, fine sulfide particles are distributed at a high density in the steel, and further, by optimizing the components and process, when an appropriate amount of solute C and solute N is contained in the steel, The present inventors have found that a steel sheet having both high BH and good deep drawability can be manufactured while ensuring aging, and have led to the present invention. The reason why these characteristics can be satisfied by dispersing fine sulfide particles in steel at a high density is not clear, but when fine sulfide is present, Cr-based nitridation is performed on the sulfide. Precipitation of iron or iron-based carbides is promoted, or segregation of C and N is promoted at the interface between sulfide and iron, so that the solute C content and solute N content in steel are appropriate. It is thought that
なお、本発明の深絞り用鋼板において得られる特性は、２％の予歪付加後に１７０℃の温度条件下で２０分間の塗装焼付相当熱処理を行うことにより評価される焼付硬化（ＢＨ）量が５０ＭＰａ以上、２％の予歪付加後に１５０℃の温度条件下に１０分間の低温短時間熱処理を行うことにより評価されるＢＨ量が４０ＭＰａ以上であり、常温非時効性の指標として１００℃の温度条件下に１時間保持する促進処理後の鋼板の降伏点伸び量が０．３％以下、深絞り性の指標として平均ｒ値（ｒａｖｅ.）が１．５以上である。また、より好ましい条件としては、平均ｒ値が１．７以上、１００℃の温度条件下に１時間保持する促進処理後の鋼板の降伏点伸び量が０．２％以下である。 In addition, the characteristic obtained in the steel sheet for deep drawing of the present invention is that the amount of bake hardening (BH) evaluated by performing a heat treatment corresponding to paint baking for 20 minutes under a temperature condition of 170 ° C. after adding 2% pre-strain. The amount of BH evaluated by performing a low-temperature short-time heat treatment for 10 minutes under a temperature condition of 150 ° C. after applying a pre-strain of 50 MPa or more and 2% is 40 MPa or more, and a temperature of 100 ° C. as an index of normal temperature non-aging The yield elongation of the steel sheet after the accelerated treatment held for 1 hour under the conditions is 0.3% or less, and the average r value (r ave. ) Is 1.5 or more as an index of deep drawability. Further, as a more preferable condition, the yield point elongation of the steel sheet after the accelerated treatment which is maintained for 1 hour under the temperature condition of 100 ° C. and an average r value is 1.7% or less.
先ず、本発明の深絞り用鋼板における鋼成分の限定理由について説明する。なお、以下の説明においては、鋼組成における質量％は、単に％と記載する。 First, the reasons for limiting the steel components in the deep drawing steel sheet of the present invention will be described. In the following description, mass% in the steel composition is simply expressed as%.
Ｃ：０．００４％以下（０％は含まない）
Ｃは、鋼のミクロ組織制御及び焼付硬化性発現のために添加される元素である。しかしながら、Ｃ含有量が０．００４％を超えると、常温非時効性の確保及び良好な深絞り性を兼備することが困難となる。よって、本発明の深絞り用鋼板においては、Ｃ含有量を０．００４％以下に規制する。なお、Ｃ含有量の下限値は、特に限定しなくとも本発明の効果を奏することができるが、製鋼のコスト上からは、Ｃ含有量を０．０００１％以上とすることが好ましい。
C: 0.004% or less (excluding 0%)
C is an element added for controlling the microstructure of the steel and developing the bake hardenability. However, if the C content exceeds 0.004%, it becomes difficult to ensure the non-aging property at room temperature and the good deep drawability. Therefore, in the steel sheet for deep drawing according to the present invention, the C content is restricted to 0.004% or less. The lower limit of the C content is not particularly limited, but the effects of the present invention can be achieved. However, from the viewpoint of steelmaking cost, the C content is preferably 0.0001% or more.
Ｓｉ：０．６％以下（０％は含まない）
Ｓｉは、鋼板のミクロ組織及び強度を調整するために添加される元素である。しかしながら、Ｓｉ含有量が０．６％を超えると、化成処理性及びめっきの密着性が劣化する。よって、Ｓｉ含有量は０．６％以下に規制する。なお、Ｓｉは鋼中に不純物として不可避的に０．００１％以上含まれている場合が多く、この不純物として含まれている程度の量であっても本発明の効果を奏することができるため、本発明の深絞り用鋼板においてはＳｉ含有量の下限値を特に限定しない。但し、０％は含まないものとする。
Si: 0.6% or less (excluding 0%)
Si is an element added to adjust the microstructure and strength of the steel sheet. However, if the Si content exceeds 0.6%, chemical conversion treatment and plating adhesion deteriorate. Therefore, the Si content is restricted to 0.6% or less. Si is often unavoidably contained as an impurity in steel by 0.001% or more, and the effect of the present invention can be achieved even in an amount contained as an impurity. In the steel sheet for deep drawing of the present invention, the lower limit value of the Si content is not particularly limited. However, 0% is not included.
Ｍｎ：０．１５〜１．２％
Ｍｎは、鋼中に硫化物を形成させるために添加されると共に、強度の調整にも用いられる元素である。しかしながら、Ｍｎ含有量が０．１５％未満であると硫化物の析出量が十分ではなく、一方、Ｍｎ含有量が１．２％を超えると深絞り性の劣化を招く。従って、Ｍｎ含有量は０．１５〜１．２％の範囲に制限した。なお、より優れた深絞り性を得る観点からは、Ｍｎ含有量は１．０％以下とすることが好ましい。
Mn: 0.15 to 1.2%
Mn is an element that is added to form sulfides in steel and also used to adjust strength. However, if the Mn content is less than 0.15%, the precipitation amount of sulfide is not sufficient, while if the Mn content exceeds 1.2%, the deep drawability is deteriorated. Therefore, the Mn content is limited to the range of 0.15 to 1.2%. In addition, it is preferable that Mn content shall be 1.0% or less from a viewpoint of obtaining the more outstanding deep drawability.
Ｐ：０．０５％以下（０％は含まない）
Ｐは、熱延組織の微細化能を有し、また、強力な固溶強化元素であることから、鋼板の強度の調整に用いられる元素である。しかしながら、Ｐ含有量が０．０５％を超えると、２次加工性が劣化する場合があり、更に連続溶融亜鉛めっき時に合金化反応が極めて遅くなり生産性が低下する。よって、Ｐ含有量は０．０５％以下に規制する。なお、Ｐは鋼中に不純物として不可避的に０．００１％以上含まれている場合が多く、この不純物として含まれている程度の量であっても本発明の効果を奏することができるため、本発明の深絞り用鋼板においてはＰ含有量の下限値を特に限定しない。但し、０％は含まないものとする。
P: 0.05% or less (excluding 0%)
P is an element used for adjusting the strength of the steel sheet because it has the ability to refine a hot-rolled structure and is a strong solid solution strengthening element. However, if the P content exceeds 0.05%, the secondary workability may be deteriorated, and further, the alloying reaction becomes extremely slow during continuous hot dip galvanizing, and the productivity is lowered. Therefore, the P content is restricted to 0.05% or less. In many cases, P is unavoidably contained as 0.001% or more as an impurity in steel, and even if the amount is contained as an impurity, the effect of the present invention can be obtained. In the steel sheet for deep drawing of the present invention, the lower limit value of the P content is not particularly limited. However, 0% is not included.
Ｓ：０．００３〜０．０３％
Ｓは、硫化物を形成させるために添加される。しかしながら、Ｓ含有量が０．００３％未満であると、十分な量の硫化物を形成させることが困難になる。一方、Ｓ含有量が０．０３％を超えると、熱間脆性が生じる可能性がある。よって、Ｓ含有量は０．００３〜０．０３％に限定する。なお、硫化物の析出量を増大させるという観点からは、Ｓ含有量を０．００５％以上のとすることが望ましい。
S: 0.003-0.03%
S is added to form sulfides. However, when the S content is less than 0.003%, it becomes difficult to form a sufficient amount of sulfide. On the other hand, if the S content exceeds 0.03%, hot brittleness may occur. Therefore, the S content is limited to 0.003 to 0.03%. In addition, from the viewpoint of increasing the precipitation amount of sulfide, it is desirable that the S content is 0.005% or more.
Ａｌ：０．０１５％以下（０％を含む）
Ａｌは、脱酸及び固溶Ｎ量の調整に用いられる元素である。しかしながら、Ａｌ含有量が０．０１５％を超えると、硫化物上で安定なＡｌＮが形成され、その結果、適量の固溶Ｎを残存させることが困難になる。よって、Ａｌ含有量は０．０１５％以下に規制する。なお、ＡｌＮ生成を極力抑制し、安定した常温非時効性とＢＨとのバランスを得るという観点からは、Ａｌ含有量を０．００５％以下にすることが好ましい。また、本発明の深絞り用鋼板においては、Ａｌ含有量が０％（Ａｌを含まない）場合でも、同様の効果を奏することができるが、通常は、Ａｌを不可避的に０．００１％以上含むことが多い。
Al: 0.015% or less (including 0%)
Al is an element used for deoxidation and adjustment of the solute N amount. However, if the Al content exceeds 0.015%, stable AlN is formed on the sulfide, and as a result, it becomes difficult to leave an appropriate amount of solid solution N. Therefore, the Al content is restricted to 0.015% or less. In addition, it is preferable to make Al content 0.005% or less from a viewpoint of suppressing AlN production as much as possible and obtaining a stable normal temperature non-aging property and BH. Further, in the deep drawing steel sheet of the present invention, even when the Al content is 0% (not including Al), the same effect can be obtained, but usually Al is unavoidably 0.001% or more. Often included.
Ｃｕ：０．００２〜０．６％
Ｃｕは、本発明の深絞り用鋼板において重要な元素の１つであり、鋼中にＭｎＣｕＳ等からなる微細な硫化物を形成させるために添加される元素である。しかしながら、Ｃｕ含有量が０．００２％未満であると、析出する硫化物の量及び微細化分散効果が十分でない。一方、Ｃｕ含有量が０．６％を超えると、熱間加工割れが起こる。従って、Ｃｕ含有量は、０．００２％〜０．６％に限定する。なお、Ｃｕ含有量は０．００５％以上とすることがより好ましく、これにより、硫化物を微細化する効果が顕著となる。
Cu: 0.002 to 0.6%
Cu is one of the important elements in the steel sheet for deep drawing of the present invention, and is an element added to form fine sulfides made of MnCuS or the like in the steel. However, if the Cu content is less than 0.002%, the amount of sulfides to be precipitated and the effect of fine dispersion are not sufficient. On the other hand, when the Cu content exceeds 0.6%, hot working cracks occur. Therefore, the Cu content is limited to 0.002% to 0.6%. In addition, it is more preferable that Cu content shall be 0.005% or more, and, thereby, the effect of refining sulfide becomes remarkable.
Ｃｒ：０．３〜２．０％
Ｃｒは、本発明の深絞り鋼板において重要な元素の１つであり、熱延工程お及び焼鈍工程においてＣｒ系の窒化物を形成させることにより、鋼中の固溶Ｎ量を適正範囲にするために用いられる。しかしながら、Ｃｒ含有量が３％未満又は２．０％を超えると、固溶Ｎ量を適正範囲にすることが困難になる。よって、Ｃｒ含有量は０．３〜２．０％に制限する。なお、安定的な常温非時効性を得るためには、Ｃｒ含有量を０．４％以上とすることが好ましく、一方、延性劣化防止の観点からは、Ｃｒ含有量を１．５％以下とすることが望ましい。
Cr: 0.3-2.0%
Cr is one of the important elements in the deep-drawn steel sheet of the present invention. By forming Cr-based nitrides in the hot rolling process and the annealing process, the amount of solute N in the steel is within an appropriate range. Used for. However, when the Cr content is less than 3% or exceeds 2.0%, it is difficult to make the solid solution N amount within an appropriate range. Therefore, the Cr content is limited to 0.3 to 2.0%. In order to obtain stable room temperature non-aging properties, the Cr content is preferably 0.4% or more. On the other hand, from the viewpoint of preventing ductility deterioration, the Cr content is 1.5% or less. It is desirable to do.
Ｎｂ：０．０１％以下（０％を含む）
Ｎｂは、炭窒化物形成元素であり、鋼板のミクロ組織、集合組織、固溶Ｃ含有量及び固溶Ｎ含有量を調整するために用いられる。しかしながら、Ｎｂ含有量が０．０１％を超えると、高ＢＨを得ることが困難になると共に、焼鈍温度を高温しなければならず製造上好ましくないため、Ｎｂ含有量は０．０１％以下に規制する。なお、Ｎｂ含有量は０．００６％以下とすることが好ましく、これにより、高ＢＨ化に対してより顕著な効果が得られる。また、本発明の深絞り用鋼板においては、Ｎｂ含有量が０％（Ｎｂを含まない）場合でも、同様の効果を奏することができるため、Ｎｂ含有量が０％の場合も含むものとする。
Nb: 0.01% or less (including 0%)
Nb is a carbonitride forming element and is used to adjust the microstructure, texture, solute C content and solute N content of the steel sheet. However, if the Nb content exceeds 0.01%, it becomes difficult to obtain a high BH, and the annealing temperature must be increased, which is not preferable for production. Therefore, the Nb content should be 0.01% or less. regulate. In addition, it is preferable that Nb content shall be 0.006% or less, and by this, the more remarkable effect is acquired with respect to high BH. Further, in the deep drawing steel sheet of the present invention, even when the Nb content is 0% (not including Nb), the same effect can be obtained, so that the case where the Nb content is 0% is also included.
Ｔｉ：０．０１％以下（０％を含む）
Ｔｉは、炭窒化物形成元素であり、鋼板のミクロ組織、集合組織、固溶Ｃ量及び固溶Ｎ量を調整するために用いられる。しかしながら、Ｔｉ含有量が０．０１％を超えると、高ＢＨを得ることが困難になると共に、焼鈍温度を高温にしなければならず製造上好ましくないため、Ｔｉ含有量は０．０１％以下に規制する。なお、Ｔｉ含有量は０．００６％以下とすることがより好ましく、これにより、高ＢＨ化効果をより顕著にすることができる。また、本発明の深絞り用鋼板においては、Ｔｉ含有量が０％（Ｔｉを含まない）場合でも、同様の効果を奏することができるため、Ｔｉ含有量が０％の場合も含むものとする。
Ti: 0.01% or less (including 0%)
Ti is a carbonitride-forming element and is used to adjust the microstructure, texture, solute C content and solute N content of the steel sheet. However, if the Ti content exceeds 0.01%, it is difficult to obtain a high BH, and the annealing temperature must be set to a high temperature, which is not preferable for production. Therefore, the Ti content should be 0.01% or less. regulate. In addition, it is more preferable that Ti content shall be 0.006% or less, and this can make the high BH effect more remarkable. Further, in the deep drawing steel sheet of the present invention, even when the Ti content is 0% (not including Ti), the same effect can be obtained, and therefore the case where the Ti content is 0% is also included.
Ｎ：０．００２〜０．００８％
Ｎは、ＢＨを発現させるためには必須の添加元素である。しかしながら、Ｎ含有量が０．００２％未満であると、歪み時効硬化が得られない。また、Ｎ含有量が０．００８％を超えると、常温非時効性を確保することが困難になる。従って、Ｎ含有量は０．００２〜０．００８％とする。
N: 0.002 to 0.008%
N is an additive element essential for developing BH. However, when the N content is less than 0.002%, strain age hardening cannot be obtained. Moreover, when N content exceeds 0.008%, it will become difficult to ensure normal temperature non-aging property. Therefore, the N content is set to 0.002 to 0.008%.
固溶Ｎ含有量：０．００１〜０．００４％
固溶Ｎは、焼付け硬化性、深絞り性及び常温非時効性に強い影響を及ぼすため、その含有量は本発明の深絞り用鋼板において重要な要素の１つである。具体的には、固溶Ｎ含有量が０．００１％未満であると、十分な焼付硬化量が得られない。一方、固溶Ｎ含有量が０．００４％を超えると、常温非時効性及び深絞り性の確保が困難になる。従って、固溶Ｎ含有量は０．００１〜０．００４％とする。また、固溶Ｎ含有量は、０．００３％以下とすることがより好ましく、これにより、常温非時効性及び深絞り性を更に向上させることができる。なお、本発明の深絞り鋼板における固溶Ｎ含有量は、ＪＩＳ Ａ５５２３に規定されているＮ定量方法に準じて、ろ液を分析することにより求めることができる。
Solid solution N content: 0.001 to 0.004%
Since solute N has a strong influence on bake hardenability, deep drawability, and non-aging property at room temperature, its content is one of the important factors in the steel sheet for deep drawing of the present invention. Specifically, when the solute N content is less than 0.001%, a sufficient bake hardening amount cannot be obtained. On the other hand, if the solid solution N content exceeds 0.004%, it is difficult to ensure normal temperature non-aging and deep drawability. Therefore, the solute N content is set to 0.001 to 0.004%. Further, the solid solution N content is more preferably 0.003% or less, whereby the room temperature non-aging property and the deep drawability can be further improved. The solute N content in the deep-drawn steel sheet of the present invention can be determined by analyzing the filtrate according to the N quantification method defined in JIS A5523.
固溶Ｃ含有量：０．００１５％以下（０％を含む）
固溶Ｃは、焼付け硬化性、深絞り性及び常温非時効性に強い影響を及ぼすため、その含有量は本発明の深絞り用鋼板において重要な要素の１つである。具体的には、固溶Ｃ含有量が０．００１５％を超えると、常温非時効性の確保が困難になる。従って、固溶Ｃ含有量は０．００１５％以下に規制する。また、固溶Ｃ含有量は、０．００１０％以下とすることがより好ましく、これにより、常温非時効性を更に向上させることができる。なお、本発明の深絞り鋼板における固溶Ｃ含有量は、電解抽出法により析出物を採取した後でろ液を直接分析するか、又は全Ｃ量と電解抽出法により採取した析出物中のＣ量とを定量し、その差により評価することもできる。その際、不溶解残さをろ過するフィルターとしては、Ａｇを使用することが好ましい。
Solid solution C content: 0.0015% or less (including 0%)
Since the solute C has a strong influence on the bake hardenability, deep drawability and room temperature non-aging property, its content is one of the important factors in the deep drawing steel sheet of the present invention. Specifically, when the content of solute C exceeds 0.0015%, it is difficult to ensure normal temperature non-aging. Therefore, the solute C content is restricted to 0.0015% or less. Moreover, it is more preferable that the solid solution C content is 0.0010% or less, whereby the room temperature non-aging property can be further improved. In addition, the solid solution C content in the deep-drawn steel sheet of the present invention can be determined by analyzing the filtrate directly after collecting the precipitate by the electrolytic extraction method, or C in the precipitate collected by the total C amount and the electrolytic extraction method. The amount can be quantified and evaluated by the difference. In that case, it is preferable to use Ag as a filter which filters an insoluble residue.
本発明の深絞り用鋼板においては、上記各成分に加えて、更に、Ｍｏ及びＷからなる群から選択された１種又は２種の元素を含有していてもよい。 The steel sheet for deep drawing according to the present invention may further contain one or two elements selected from the group consisting of Mo and W in addition to the above components.
Ｍｏ，Ｗ：合計で０．０１〜１．０％
Ｍｏ及びＷは、Ｃに起因する常温非時効性低下を改善する効果がある。しかしながら、これらの元素の含有量が合計で０．０１％未満の場合、その効果が得られない。一方、これらの元素の含有量が合計で１．０％を超えると、Ｃ及びＮと結合して炭窒化物を形成してしまうため、固溶Ｎの残存量が減少する。従って、Ｍｏ及び／又はＷを添加する場合は、その総含有量が０．０１〜１．０％となるようにする。なお、炭窒化物を微細に分散させるためには、Ｍｏ及びＷの総含有量を０．２％以下とすることが好ましい。
Mo, W: 0.01 to 1.0% in total
Mo and W have the effect of improving the non-aging deterioration at room temperature caused by C. However, when the content of these elements is less than 0.01% in total, the effect cannot be obtained. On the other hand, when the content of these elements exceeds 1.0% in total, carbon and nitrides are formed by combining with C and N, so the residual amount of solid solution N decreases. Therefore, when adding Mo and / or W, the total content is made 0.01 to 1.0%. In order to finely disperse carbonitride, the total content of Mo and W is preferably 0.2% or less.
また、本発明の深絞り用鋼板においては、上記各成分に加えて、更に、Ｎｉを含有していてもよい。 Moreover, in the steel sheet for deep drawing of this invention, in addition to said each component, you may contain Ni further.
Ｎｉ：０．０１〜３．０％
Ｎｉは、Ｃｕに起因する熱間加工割れの発生を抑制する効果がある。しかしながら、Ｎｉ含有量が０．０１％未満であると、熱間割れを抑制することが難しく、一方、Ｎｉ含有量が３．０％を超えるとコスト的に割高となる。従って、Ｎｉを添加する場合は、その含有量が０．０１〜３．０％となるようにする。
Ni: 0.01-3.0%
Ni has the effect of suppressing the occurrence of hot working cracks due to Cu. However, if the Ni content is less than 0.01%, it is difficult to suppress hot cracking. On the other hand, if the Ni content exceeds 3.0%, the cost becomes high. Therefore, when adding Ni, the content is made 0.01 to 3.0%.
更に、また、本発明の深絞り用鋼板においては、上記各成分に加えて、更に、Ａｓ、Ｓｂ、Ｂｉ及びＳｎからなる群から選択された１種又は２種以上の元素が添加されていてもよい。 Furthermore, in the deep drawing steel sheet of the present invention, in addition to the above components, one or more elements selected from the group consisting of As, Sb, Bi and Sn are added. Also good.
Ａｓ，Ｓｂ，Ｂｉ，Ｓｎ：合計で０．０００３〜０．００２％
Ａｓ、Ｓｂ、Ｂｉ及びＳｎは、深絞り性を改善する効果がある。しかしながら、これらの元素の含有量が合計で０．０００３％未満の場合、その効果が得られない。一方、これらの元素の含有量が合計で０．００２％を超えると、２次加工性が低下する。よって、Ａｓ、Ｓｂ、Ｂｉ及び／又はＳｎを添加する場合は、その総含有量が０．０００３〜０．００２％になるようにする。
As, Sb, Bi, Sn: 0.0003 to 0.002% in total
As, Sb, Bi and Sn have the effect of improving deep drawability. However, when the content of these elements is less than 0.0003% in total, the effect cannot be obtained. On the other hand, when the content of these elements exceeds 0.002% in total, the secondary workability deteriorates. Therefore, when adding As, Sb, Bi and / or Sn, the total content is made 0.0003 to 0.002%.
更にまた、本発明の深絞り用鋼板においては、上記各成分に加えて、更に、Ｂを含有していてもよい。 Furthermore, the steel sheet for deep drawing of the present invention may further contain B in addition to the above components.
Ｂ：０．０００３〜０．００２５％
Ｂは、粒界に偏析し、Ｐに起因する２次加工割れを抑制する効果がある。しかしながら、Ｂ含有量が０．０００３％未満の場合、その効果が得られない。一方、Ｂ含有量が０．００２５％を超えると、ボロン窒化物を形成して固溶Ｎ量が減少するため、高ＢＨが得られなくなる。従って、Ｂを添加する場合は、その含有量が０．０００３〜０．００２５％になるようにする。
B: 0.0003 to 0.0025%
B segregates at the grain boundaries and has the effect of suppressing secondary processing cracks resulting from P. However, when the B content is less than 0.0003%, the effect cannot be obtained. On the other hand, if the B content exceeds 0.0025%, boron nitride is formed and the amount of dissolved N decreases, so that high BH cannot be obtained. Therefore, when adding B, the content is made 0.0003 to 0.0025%.
更にまた、本発明の深絞り用鋼板においては、上記各成分に加えて、更に、Ｃａ、Ｍｇ、Ｚｒ及びＲＥＭからなる群から選択された１種又は２種以上の元素を含有していてもよい。 Furthermore, the steel sheet for deep drawing according to the present invention may further contain one or more elements selected from the group consisting of Ca, Mg, Zr and REM in addition to the above components. Good.
Ｃａ，Ｍｇ，Ｚｒ，ＲＥＭ：合計で０．００１〜０．０１％
Ｃａ、Ｍｇ、Ｚｒ及びＲＥＭは、介在物の形態及び分布の制御に用いる元素である。しかしながら、これらの元素の含有量が合計で０．００１％未満の場合、その効果が得られない。一方、これらの元素の含有量が合計で０．０１％を超えると、深絞り性低下の原因となる。よって、Ｃａ、Ｍｇ、Ｚｒ及び／又はＲＥＭを添加する場合は、その総含有量が０．００１〜０．０１％になるようにする。なお、本発明の深絞り用鋼板において、「ＲＥＭ」とは、Ｌａ及びランタノイド系列の元素を指すものとする。
Ca, Mg, Zr, REM: 0.001 to 0.01% in total
Ca, Mg, Zr and REM are elements used for controlling the form and distribution of inclusions. However, when the content of these elements is less than 0.001% in total, the effect cannot be obtained. On the other hand, when the content of these elements exceeds 0.01% in total, it causes a decrease in deep drawability. Therefore, when adding Ca, Mg, Zr and / or REM, the total content is made 0.001 to 0.01%. In the deep drawing steel sheet of the present invention, “REM” refers to La and lanthanoid series elements.
本発明の深絞り用鋼板における上記以外の成分は、Ｆｅ及び不可避的不純物である。なお、本発明の深絞り用鋼板においては、不可避不純物のうち重要な元素として、Ｏが挙げられる。Ｏは脱酸の方法によりその残留量が大きく変化するが、不可避的に０．０００５％以上含有する場合が多い。特に、本発明の深絞り用鋼板ようにＡｌ含有量が少ない組成の場合には、Ｏの不可避的残留量は０．０１５％程度であり、これを不可避不純物としてのＯ含有量の上限とすることが望ましい。 Components other than the above in the deep drawing steel sheet of the present invention are Fe and inevitable impurities. In the deep drawing steel sheet of the present invention, O is an important element among the inevitable impurities. Although the residual amount of O varies greatly depending on the deoxidation method, it is unavoidably contained in an amount of 0.0005% or more. In particular, in the case of a composition having a low Al content as in the deep drawing steel sheet of the present invention, the unavoidable residual amount of O is about 0.015%, and this is the upper limit of the O content as an unavoidable impurity. It is desirable.
また、本発明の深絞り用鋼板においては、良好な深絞り性を得るため、任意の断面におけるフェライト面積率を９８％以上とすることが好ましい。このとき、フェライトの平均結晶粒径は、特に限定する必要はないが、フェライトが細粒である程、硫化物とＦｅとの界面（以下、硫化物／Ｆｅ界面という。）と総界面面積との比である粒界面積の割合が増大して、硫化物／Ｆｅ界面での析出・偏析挙動が変化し、主に深絞り性が低下する。このため、フェライトの結晶粒径は８μｍ以上であることが好ましく、より好ましくは１２μｍ以上である。 Moreover, in the steel sheet for deep drawing of this invention, in order to acquire favorable deep drawability, it is preferable that the ferrite area rate in arbitrary cross sections shall be 98% or more. At this time, the average crystal grain size of ferrite is not particularly limited, but the finer the ferrite, the more the interface between sulfide and Fe (hereinafter referred to as sulfide / Fe interface) and the total interface area. The ratio of the grain interface area, which is the ratio of the above, increases, the precipitation / segregation behavior at the sulfide / Fe interface changes, and the deep drawability mainly decreases. For this reason, it is preferable that the crystal grain diameter of a ferrite is 8 micrometers or more, More preferably, it is 12 micrometers or more.
更に、鋼中における硫化物／Ｆｅ界面の単位体積あたりの総面積が２×１０−３μｍ２／μｍ３未満であると、常温非時効性及び深絞り性が不十分となる。従って、硫化物／Ｆｅ界面の単位体積あたりの総面積は、２×１０−３μｍ２／μｍ３以上に制限する。また、硫化物／Ｆｅ界面の単位体積あたりの総面積は、４×１０−２μｍ２／μｍ３以上とすることがより好ましい。更に、硫化物／Ｆｅ界面の単位体積あたりの総面積における上限は、特に限定しなくても、本発明の効果を奏することができる。 Furthermore, when the total area per unit volume of the sulfide / Fe interface in the steel is less than 2 × 10 −3 μm 2 / μm 3 , the room temperature non-aging property and deep drawability become insufficient. Therefore, the total area per unit volume of the sulfide / Fe interface is limited to 2 × 10 −3 μm 2 / μm 3 or more. The total area per unit volume of the sulfide / Fe interface is more preferably 4 × 10 −2 μm 2 / μm 3 or more. Furthermore, even if the upper limit of the total area per unit volume of the sulfide / Fe interface is not particularly limited, the effects of the present invention can be achieved.
なお、硫化物／Ｆｅ界面の単位体積あたりの総面積を求める場合、硫化物／Ｆｅ界面の面積は硫化物の表面面積と等価であるため、抽出レプリカ法により硫化物を抽出し、これを分析透過電子顕微鏡により測定する方法が好適である。この方法により得られる単位面積あたりの分布密度及び界面面積を、溶解した試料の厚さで除することにより、単位体積当たりの界面面積を求めることができる。このとき、溶解試料の厚さが定かでないときは、一般的な値である０．１μｍを使用する。また、硫化物の測定限界は、１個の硫化物の最大長が０．０１μｍ以上とする。更に、硫化物の表面面積は、硫化物が球形状であると仮定し、４×π×（硫化物粒子径）２より求める。 When calculating the total area per unit volume of the sulfide / Fe interface, the sulfide / Fe interface area is equivalent to the surface area of the sulfide, so extract the sulfide by the extraction replica method and analyze it. A method of measuring with a transmission electron microscope is suitable. The interface area per unit volume can be determined by dividing the distribution density and interface area per unit area obtained by this method by the thickness of the dissolved sample. At this time, when the thickness of the dissolved sample is not clear, a general value of 0.1 μm is used. The measurement limit of sulfide is such that the maximum length of one sulfide is 0.01 μm or more. Further, the surface area of the sulfide is calculated from 4 × π × (sulfide particle diameter) 2 assuming that the sulfide is spherical.
一方、硫化物／Ｆｅ界面への単位界面面積あたりのＮの偏析量は、ＢＨ性、常温非時効性及び深絞り性と相関がある値であることがわかっている。単位界面面積あたりのＮの偏析量ｎｅｘｃｅｓｓが３原子／ｎｍ２を超えると、所望の焼付け硬化性が得られにくくなる。よって、硫化物／Ｆｅ界面へのＮの偏析量ｎｅｘｃｅｓｓは、３原子／ｎｍ２以下とすることが好ましい。この硫化物／Ｆｅ界面へのＮの偏析量は、アトムプローブ電界イオン顕微鏡法により測定する方法が簡易で好適である。また、硫化物種は、Ｍｎ、Ｃｕ、Ｃｒの硫化物、及び（Ｍｎ，Ｃｕ）Ｓ等のようにこれら元素を複合的に含有した硫化物のいずれでも同様に硫化物周囲へのＮ偏析能を有する。 On the other hand, it is known that the amount of segregation of N per unit interface area to the sulfide / Fe interface is a value correlated with BH property, room temperature non-aging property, and deep drawability. When segregation n excess of N per unit surface area exceeds 3 atomic / nm 2, the desired bake hardenability becomes difficult to obtain. Therefore, the amount of N segregation N excess to the sulfide / Fe interface is preferably 3 atoms / nm 2 or less. A method of measuring the amount of segregation of N at the sulfide / Fe interface by an atom probe field ion microscope is simple and suitable. In addition, any of the sulfide species, such as sulfides of Mn, Cu, Cr, and sulfides containing these elements in a complex manner, such as (Mn, Cu) S, similarly has N segregation ability around the sulfides. Have.
次に、上述の如く構成された本発明の深絞り用鋼板の製造方法について説明する。本発明の深絞り用鋼板を製造する際は、先ず、Ｃ：０．００４％以下、Ｓｉ：０．６％以下、Ｍｎ：０．１５〜１．２％、Ｐ：０．０５％以下、Ｓ：０．００３〜０．０３％、Ｃｕ：０．００２〜０．６％、Ｃｒ：０．３〜２．０％、及びＮ：０．００２〜０．００８％を含有すると共に、Ａｌ：０．０１５％以下、Ｎｂ：０．０１％以下及びＴｉ：０．０１％以下に規制し、残部がＦｅ及び不可避的不純物からなる組成のスラブを作製する。その作製方法は、特に限定されるものではなく、例えば、連続鋳造スラブ及び薄スラブキャスター等で製造されたスラブ等を使用することができる。 Next, the manufacturing method of the steel sheet for deep drawing of this invention comprised as mentioned above is demonstrated. When producing the steel sheet for deep drawing of the present invention, first, C: 0.004% or less, Si: 0.6% or less, Mn: 0.15-1.2%, P: 0.05% or less, S: 0.003-0.03%, Cu: 0.002-0.6%, Cr: 0.3-2.0%, and N: 0.002-0.008%, Al A slab having a composition in which the balance is composed of Fe and unavoidable impurities with the balance being restricted to: 0.015% or less, Nb: 0.01% or less, and Ti: 0.01% or less. The production method is not particularly limited, and for example, a slab manufactured by a continuously cast slab, a thin slab caster, or the like can be used.
次に、このようなスラブを、１２００℃以上に加熱し、仕上圧延温度が（Ａｒ３−５０）℃以上、１０００℃と仕上圧延温度との間での板厚減少率が３０％以上、巻取り温度が６００〜７５０℃の条件で熱間圧延して熱延コイルとする。この熱間圧延工程においては、スラブの温度が１２００℃よりも低い場合は、再加熱を行い、連続鋳造−直接圧延（ＣＣ−ＤＲ）のように鋳造後に直ちに熱間圧延を行うプロセスを適用する場合は、再加熱は行わずに、鋳造後のスラブを直接熱間圧延する。熱間圧延前のスラブ温度が１２００℃未満の場合、鋳造中又は粗圧延中に析出した硫化物が再溶解しないため、硫化物の微細化が不十分となる。 Then, such a slab, 1200 ° C. heated above, the finish rolling temperature is (Ar 3 -50) ℃ or higher, 1000 ° C. and the thickness reduction rate between the finish rolling temperature is more than 30%, the winding A hot-rolled coil is obtained by hot rolling under a temperature of 600 to 750 ° C. In this hot rolling process, when the temperature of the slab is lower than 1200 ° C., reheating is performed, and a process of performing hot rolling immediately after casting, such as continuous casting-direct rolling (CC-DR), is applied. In this case, the slab after casting is directly hot-rolled without reheating. When the slab temperature before hot rolling is less than 1200 ° C., sulfides precipitated during casting or rough rolling are not redissolved, so that the refinement of sulfides is insufficient.
また、熱間圧延する際は、１０００℃と仕上圧延温度との間（１０００℃〜仕上圧延温度）における板厚減少率を大きくする必要がある。具体的には、１０００℃〜仕上圧延温度での板厚減少率が３０％未満の場合、鋼中に硫化物が高密度で形成されにくくなる。よって、１０００℃〜仕上圧延温度における板厚減少率は３０％以上とする。なお、この温度範囲における板厚減少率は４０％以上にすることがより好ましい。また、硫化物を微細に分散させるためには、上述した条件を満足し、かつ１０５０〜１０００℃における板厚減少率も３０％以上であることがより好ましい。ここで、任意の温度Ｔａ（℃）及びＴｂ（℃）間における板厚減少率ΔｔＴａ〜Ｔｂ（％）は、下記数式（１）により求められる。なお、下記数式（１）におけるｔＴａはＴａ（℃）における板厚であり、ｔＴｂはＴｂ（℃）における板厚である。 Moreover, when hot-rolling, it is necessary to enlarge the plate | board thickness reduction | decrease rate between 1000 degreeC and finish rolling temperature (1000 degreeC-finish rolling temperature). Specifically, when the plate thickness reduction rate from 1000 ° C. to the finish rolling temperature is less than 30%, sulfides are hardly formed at high density in the steel. Therefore, the sheet thickness reduction rate at 1000 ° C. to the finish rolling temperature is 30% or more. The plate thickness reduction rate in this temperature range is more preferably 40% or more. Further, in order to finely disperse the sulfide, it is more preferable that the above-described conditions are satisfied and the thickness reduction rate at 1050 to 1000 ° C. is 30% or more. Here, any temperature Ta (° C.) and Tb (° C.) thickness between reduction rate Delta] t Ta to Tb (%) is calculated by the following equation (1). In addition, t Ta in the following mathematical formula (1) is a plate thickness at Ta (° C.), and t Tb is a plate thickness at Tb (° C.).
更に、熱間圧延時の仕上温度が（Ａｒ３−５０）℃未満であると深絞り性が低下するため、仕上圧延温度は（Ａｒ３−５０）℃以上に制限する。更にまた、熱延コイルの巻取温度が６００℃未満か又は７５０℃を超えると、Ｃｒ系窒化物が十分に形成されず、固溶Ｎ量が過大になり、常温非時効性及び深絞り性が劣化する。よって、仕上圧延温度は６００〜７５０℃に制限する。なお、ｒ値を確保する上では、仕上圧延温度は６５０℃以上とすることがより好ましい。 Furthermore, if the finishing temperature at the time of hot rolling is less than (Ar 3 -50) ° C., the deep drawability decreases, so the finishing rolling temperature is limited to (Ar 3 -50) ° C. or more. Furthermore, when the coiling temperature of the hot-rolled coil is less than 600 ° C. or exceeds 750 ° C., Cr-based nitrides are not sufficiently formed, the amount of solute N becomes excessive, room temperature non-aging property and deep drawability. Deteriorates. Therefore, the finish rolling temperature is limited to 600 to 750 ° C. In order to secure the r value, the finish rolling temperature is more preferably 650 ° C. or higher.
次に、巻取り後の熱延コイルを冷却し、引き続き酸洗等の通常公知の処理を行い、６０％以上の圧延率で冷間圧延を行う。このとき、冷間圧延率が６０％未満であると、良好な深絞り性を確保することが困難になる。また、冷間圧延率は７０％以上とすることが好ましく、これにより深絞り性をより向上させることができる。なお、冷間圧延率の上限は特に限定する必要はないが、圧延率が９０％を超えると、設備への負荷が過大となると共に、製品の機械的性質の異方性が大きくなる。よって、冷間圧延率は９０％以下とすることが好ましい。 Next, the hot-rolled coil after winding is cooled, and generally known treatment such as pickling is subsequently performed, and cold rolling is performed at a rolling rate of 60% or more. At this time, if the cold rolling rate is less than 60%, it is difficult to ensure good deep drawability. Moreover, it is preferable that a cold rolling rate shall be 70% or more, and, thereby, deep drawability can be improved more. The upper limit of the cold rolling rate is not particularly limited, but if the rolling rate exceeds 90%, the load on the equipment becomes excessive and the anisotropy of the mechanical properties of the product becomes large. Therefore, the cold rolling rate is preferably 90% or less.
次に、上述の方法で冷間圧延して得た冷延コイルを、連続焼鈍炉により、最高到達温度を７００〜８５０℃として焼鈍した後、必要に応じて表面にめっきを施す。焼鈍時の最高到達温度が７００℃未満の場合、再結晶が完了せず、深絞り性が劣悪となることがある。一方、焼鈍の最高到達温度が８５０℃を超えると、通板中に板破断を生じ生産性が大きく低下する。従って焼鈍の最高到達温度は、７００〜８５０℃に制限する。なお、深絞り性の観点からは、７５０℃以上で焼鈍することがより好ましい。 Next, the cold rolled coil obtained by cold rolling by the above-described method is annealed at a maximum temperature of 700 to 850 ° C. in a continuous annealing furnace, and then the surface is plated as necessary. If the maximum temperature reached during annealing is less than 700 ° C., recrystallization may not be completed and the deep drawability may be deteriorated. On the other hand, when the highest temperature reached in annealing exceeds 850 ° C., the plate breaks in the plate and the productivity is greatly reduced. Accordingly, the maximum annealing temperature is limited to 700 to 850 ° C. In addition, it is more preferable to anneal at 750 degreeC or more from a viewpoint of deep drawability.
また、上述の方法で作製しためっきが施されていない冷延鋼板は、各種めっき用原材としても好適である。そして、その表面にめっき層を形成する方法は、電気めっき法、溶融めっき法及び溶融−合金化めっき法のいずれでも良く、めっきの主成分としては、例えば亜鉛、アルミ、クロム、錫及びニッケル等が挙げられる。なお、めっき時の温度履歴については特に制限は無いが、６００℃以下の温度で行うことがより好ましい。 Moreover, the cold-rolled steel plate which is not plated by the above-described method is suitable as various plating raw materials. And the method of forming the plating layer on the surface may be any of electroplating, hot dipping, and hot-alloying plating, and the main components of plating are, for example, zinc, aluminum, chromium, tin, nickel, etc. Is mentioned. In addition, although there is no restriction | limiting in particular about the temperature history at the time of plating, It is more preferable to carry out at the temperature of 600 degrees C or less.
更に、連続焼鈍工程又は連続焼鈍−めっき（−合金化）工程における加熱速度については常法に従えばよく、また、連続焼鈍工程又は連続焼鈍−めっき（−合金化）工程における上記焼鈍後の熱履歴は特に限定する必要はない。但し、ＢＨ−常温非時効性バランスの観点からは、３５０〜５００℃での滞留時間が１０秒間以上の熱処理を行うことがより好ましい。なお、この熱処理を行なう場合、３５０〜５００℃の温度範囲となっている時間が１０秒間以上であれば、いかなる温度履歴を経ても構わない。更に、常温非時効性の向上及び形状矯正のために、調質圧延を行ってもよい。但し、圧下率が２％を超えると、焼付硬化量が低下する傾向があるため、調質圧延を行う場合は、圧下率を２％以下とする。 Furthermore, the heating rate in the continuous annealing step or the continuous annealing-plating (-alloying) step may be according to a conventional method, and the heat after the annealing in the continuous annealing step or the continuous annealing-plating (-alloying) step. The history need not be particularly limited. However, from the viewpoint of BH-room temperature non-aging balance, it is more preferable to perform a heat treatment at 350 to 500 ° C. for a residence time of 10 seconds or more. When this heat treatment is performed, any temperature history may be passed as long as the time in the temperature range of 350 to 500 ° C. is 10 seconds or longer. Furthermore, temper rolling may be performed in order to improve normal temperature non-aging and shape correction. However, if the rolling reduction exceeds 2%, the bake hardening amount tends to decrease. Therefore, when temper rolling is performed, the rolling reduction is set to 2% or less.
以上詳述したように、本発明の深絞り用鋼板においては、鋼組成及び製造条件を適正化することにより、固溶Ｎを０．００１〜０．００４％及び固溶Ｃを０．００１５％以下にすると共に、鋼中に微細な硫化物粒子を高密度で析出させて、硫化物／Ｆｅ界面の単位体積あたりの総面積を２×１０−３μｍ２／μｍ３以上にしているため、常温非時効性を有し、低温塗装焼付け処理においても高い焼付硬化性を示し、更に深絞り性が良好な深絞り用鋼板が得られる。この深絞り用鋼板は、常温保持中の品質劣化の少ない歪時効硬化型鋼板であり、電着塗装焼付処理を施す自動車用のパネル部材及び電器製品用内外板パネルの使途に好適である。また、引張強度で２５０〜４５０ＭＰａ程度の強度の鋼板に適用が可能である。更に、本発明の深絞り用鋼板の製造方法によれば、常温保持中の材質劣化が少なく、低温塗装焼付温度でも高い歪み硬化能を有する深絞り用鋼板を、安価に提供することができる。このため、本発明の深絞り用鋼板は、最終製品の軽量化への貢献と、低温の塗装焼付け温度でも硬化することから焼付処理中の使用エネルギー削減への貢献とが期待でき、産業上の効果は極めて高い。 As described in detail above, in the steel sheet for deep drawing according to the present invention, by optimizing the steel composition and manufacturing conditions, the solid solution N is 0.001 to 0.004% and the solid solution C is 0.0015%. In addition to the following, fine sulfide particles are precipitated in steel at a high density so that the total area per unit volume of the sulfide / Fe interface is 2 × 10 −3 μm 2 / μm 3 or more. A steel sheet for deep drawing having room temperature non-aging properties, high bake hardenability even in a low temperature coating baking process, and good deep drawability can be obtained. This steel sheet for deep drawing is a strain age hardening type steel sheet with little quality deterioration while being kept at room temperature, and is suitable for use as an automotive panel member subjected to electrodeposition coating baking treatment and an inner / outer panel panel for electrical appliances. Moreover, it can be applied to a steel sheet having a tensile strength of about 250 to 450 MPa. Furthermore, according to the method for manufacturing a deep drawing steel sheet of the present invention, a deep drawing steel sheet having little material deterioration during normal temperature holding and having a high strain hardening ability even at a low temperature coating baking temperature can be provided at low cost. For this reason, the steel sheet for deep drawing according to the present invention can be expected to contribute to reducing the weight of the final product and to reducing the energy used during the baking process because it hardens even at low coating baking temperatures. The effect is extremely high.
以下、本発明の効果を、実施例及び比較例を挙げて具体的に説明する。本実施例においては、下記表１に示す成分の鋼を溶製して作製したスラブを、下記表２に示す条件で再加熱した後、熱間圧延及び巻取処理を行い、熱延コイルとした。その際、熱間圧延時における１０５０〜１０００℃間の板厚減少率は、全て６０％とした。そして、この熱延コイルを、酸洗した後、７５〜８５％の冷延率で冷間圧延を行い、脱脂処理を行った。その後、焼鈍温度を８００℃、過時効温度を４００℃として連続焼鈍し、Ｎｏ．１〜Ｎｏ．７及びＮｏ．１３〜Ｎｏ．１７の鋼板を作製した。また、連続焼鈍−亜鉛めっき−合金化工程を連続して行って、Ｎｏ．８〜１２の鋼板を作製した。更に、連続焼鈍工程で鋼板を作製した後、別ラインにて亜鉛めっき及び合金化工程を行ってＮｏ．１４の鋼板を作製した。なお、下記表１に示す鋼組成における残部は、Ｆｅ及び不可避的不純物である。また、下記表２に示す「ＳＲＴ」はスラブ加熱温度（℃）であり、「Ｒｅｄ１」は１０５０〜１０００℃間の板厚減少率（％）であり、「Ｒｅｄ２」は１０００〜仕上圧延温度間の板厚減少率（％）であり、「ＦＴ」は仕上圧延温度（℃）であり、「ＣＴ」は巻取り温度（℃）である。更に、下記表１及び表２における下線は、本発明の範囲外であることを示す。 Hereinafter, the effects of the present invention will be specifically described with reference to Examples and Comparative Examples. In this example, a slab prepared by melting steels having the components shown in Table 1 below was reheated under the conditions shown in Table 2 below, followed by hot rolling and winding treatment, did. At that time, the plate thickness reduction rate between 1050 and 1000 ° C. during hot rolling was all 60%. And after pickling this hot-rolled coil, it cold-rolled with the cold rolling rate of 75 to 85%, and performed the degreasing process. Then, continuous annealing was performed with an annealing temperature of 800 ° C. and an overaging temperature of 400 ° C. 1-No. 7 and no. 13-No. Seventeen steel plates were produced. In addition, the continuous annealing-zinc plating-alloying process is continuously performed, and No. 8-12 steel plates were produced. Furthermore, after producing a steel plate by a continuous annealing process, a galvanizing and alloying process is performed in another line, and No. Fourteen steel plates were produced. The balance in the steel composition shown in Table 1 below is Fe and inevitable impurities. In addition, “SRT” shown in Table 2 below is a slab heating temperature (° C.), “Red 1 ” is a sheet thickness reduction rate (%) between 1050 and 1000 ° C., and “Red 2 ” is 1000 to finish rolling. The thickness reduction rate (%) between temperatures, “FT” is the finish rolling temperature (° C.), and “CT” is the coiling temperature (° C.). Furthermore, the underline in the following Table 1 and Table 2 indicates that it is outside the scope of the present invention.
このようにして得られた各鋼板について、引張試験、ＢＨ試験及び組織観察を行った。その条件を以下に示す。先ず、引張試験は、ＪＩＳ５号試験片を使用し、歪み速度が１×１０−３／秒の条件で行った。また、常温保持中の材質変化は、１００℃の温度条件下に６０分間保持する促進時効後の降伏点伸び量により評価した。更に、ＢＨ試験の予変形量は２％、塗装焼付処理に対応する時効条件は１７０℃の温度条件下で２０分間、及び１５０℃の温度条件下で１０分間とし、再引張時において上部降伏点で評価したＢＨ量を測定した。フェライトの平均結晶粒径測定は、ＪＩＳ Ｇ０５５２の試験方法に従って行った。平均ｒ値（ｒａｖｅ．）は、ＪＩＳ Ｚ２２５４に記載されている方法により測定した。調質圧延は、全て１．０％の伸び率で行った。また、透過電子顕微鏡法を用いてレプリカ法により抽出した硫化物を観察することにより、硫化物／Ｆｅ界面の単位体積あたりの総面積を測定した。更に、硫化物／Ｆｅ界面のＣ又はＮの偏析量の測定は、３次元アトムプローブ法により行った。以上の結果を下記表３にまとめて示す。なお、下記表３に示す「ｄ」は焼鈍後の平均結晶粒径であり、「Ｓ」は鋼中における単位体積あたりの硫化物／Ｆｅ界面の総面積であり、「ｎＮ ｅｘｃｅｓｓ」は硫化物／Ｆｅ界面におけるＮ偏析量（原子／ｎｍ２）であり、「１７０ＢＨ」は予歪量２％、１７０℃の温度条件下で２０分間の時効処理により評価した焼付硬化量、「１５０ＢＨ」は予歪量２％、１５０℃の温度条件下で１０分間の時効処理により評価した焼付硬化量、「時効後ＹＰＥ」は１００℃の温度条件下で６０分間の時効処理後の降伏点伸び量である。また、下記表３における下線は、本発明の範囲外であることを示す。 Each steel plate thus obtained was subjected to a tensile test, a BH test, and a structure observation. The conditions are shown below. First, the tensile test was performed using a JIS No. 5 test piece and a strain rate of 1 × 10 −3 / sec. The material change during normal temperature holding was evaluated by the yield point elongation after accelerated aging held at 100 ° C. for 60 minutes. Furthermore, the pre-deformation amount of the BH test is 2%, the aging conditions corresponding to the coating baking process are 20 minutes under the temperature condition of 170 ° C., and 10 minutes under the temperature condition of 150 ° C. The amount of BH evaluated in (1) was measured. The average crystal grain size of ferrite was measured according to the test method of JIS G0552. The average r value (r ave. ) Was measured by the method described in JIS Z2254. All temper rolling was performed at an elongation of 1.0%. Further, the total area per unit volume of the sulfide / Fe interface was measured by observing the sulfide extracted by the replica method using transmission electron microscopy. Further, the amount of C or N segregation at the sulfide / Fe interface was measured by a three-dimensional atom probe method. The above results are summarized in Table 3 below. “D” shown in Table 3 below is the average grain size after annealing, “S” is the total area of the sulfide / Fe interface per unit volume in steel, and “n N excess ” is sulfide N-segregation amount (atomic / nm 2 ) at the metal / Fe interface, “170BH” being a pre-strain amount of 2%, bake hardening amount evaluated by aging treatment for 20 minutes under a temperature condition of 170 ° C., “150BH” Bake-hardening amount evaluated by aging treatment for 10 minutes under a pre-strain amount of 2% and a temperature condition of 150 ° C., “post-aging YPE” is a yield point elongation after aging treatment for 60 minutes under a temperature condition of 100 ° C. is there. Moreover, the underline in the following Table 3 shows that it is outside the scope of the present invention.
上記表３に示すように、比較例Ｎｏ．３の鋼板は、スラブ加熱温度ＳＲＴが本発明の範囲外であったため、微細かつ多量の硫化物が得られず、その結果、常温非時効性及び良好なｒ値（ｒａｖｅ．）が得られなかった。また、比較例Ｎｏ．４及びＮｏ．５の鋼板は、熱延条件が本発明の範囲外であったため、微細かつ多量の硫化物が得られず、その結果、常温非時効性及び良好なｒ値（ｒａｖｅ．）が得られなかった。更に、比較例Ｎｏ．１３の鋼板はＳ含有量及びＣｕ含有量が本発明の範囲外であり、また、Ｎｏ．１４の鋼板はＳ含有量及びＣｒ含有量が本発明の範囲外であったため、微細かつ多量の硫化物が得られず、その結果、常温非時効性及び良好なｒ値（ｒａｖｅ．）が得られなかった。更にまた、比較例Ｎｏ．６の鋼板は、熱延巻取り条件が本発明の範囲から外れていたため、固溶Ｃ含有量が本発明の範囲を超え、常温非時効性及び良好なｒ値（ｒａｖｅ．）が得られなかった。更にまた、比較例Ｎｏ．１５の鋼板は、Ａｌ含有量が本発明の範囲から外れているため、固溶Ｎ含有量が本発明の範囲よりも少なく、高い焼付硬化特性が得られなかった。更にまた、比較例Ｎｏ．１６はＣ含有量が本発明の範囲を超えていたため、固溶Ｃ含有量が本発明の範囲を超えており、また、比較例Ｎｏ．１７の鋼板は、Ｎ含有量及びＣｒ含有量が本発明の範囲から外れていたため、固溶Ｎ含有量が本発明の範囲から外れていた。その結果、比較例Ｎｏ．１６及びＮｏ．１７の鋼板は、常温非時効性と及び良好なｒ値（ｒａｖｅ．）が得られなかった。 As shown in Table 3 above, Comparative Example No. Since the steel plate No. 3 had a slab heating temperature SRT outside the range of the present invention, fine and large amount of sulfide was not obtained, and as a result, room temperature non-aging property and good r value (r ave. ) Were obtained . There wasn't. Comparative Example No. 4 and no. As for the steel plate No. 5, since the hot rolling conditions were outside the scope of the present invention, a fine and large amount of sulfide could not be obtained, and as a result, room temperature non-aging property and good r value (r ave. ) Could not be obtained . It was. Further, Comparative Example No. No. 13 steel sheet has S and Cu contents outside the scope of the present invention. Steel sheet No. 14 had an S content and a Cr content outside the scope of the present invention, so that a fine and large amount of sulfide was not obtained. As a result, room temperature non-aging property and good r value (r ave. ) Were obtained. It was not obtained. Furthermore, Comparative Example No. As for the steel plate No. 6, the hot rolling coiling condition was out of the scope of the present invention, so the solid solution C content exceeded the scope of the present invention, and room temperature non-aging property and good r value (r ave. ) Were obtained . There wasn't. Furthermore, Comparative Example No. Since the steel plate No. 15 has an Al content outside the range of the present invention, the solid solution N content is less than the range of the present invention, and high bake hardening characteristics were not obtained. Furthermore, Comparative Example No. 16 had a C content exceeding the range of the present invention, so the solid solution C content exceeded the range of the present invention. In No. 17, the N content and the Cr content were out of the scope of the present invention, so the solute N content was out of the scope of the present invention. As a result, Comparative Example No. 16 and no. No. 17 steel plate did not have room temperature non-aging property and good r value (r ave. ).
これに対して、実施例Ｎｏ．１、Ｎｏ．２、Ｎｏ．７〜Ｎｏ．１２の鋼板は、常温非時効性を有すると共に、低温塗装焼付け処理でも高い焼付硬化性が得られ、更に、ｒ値（ｒａｖｅ．）も良好であった。 In contrast, Example No. 1, no. 2, no. 7-No. No. 12 steel sheet had non-aging properties at room temperature, high bake hardenability was obtained even by low-temperature coating baking treatment, and r value (r ave. ) Was also good.
本発明の深絞り用鋼板は、良好な深絞り性、常温非時効性及び良好な低温塗装焼付硬化特性を兼ね備えているため、電着塗装焼付処理を施す自動車用のパネル部材、電器製品用内外板パネル及び缶用材料の使途に好適である。 The steel sheet for deep drawing according to the present invention has good deep drawability, room temperature non-aging properties and good low temperature paint bake hardening properties, so that it can be applied to automobile panel members that are subjected to electrodeposition paint baking treatment, inside and outside electrical appliances. Suitable for the use of plate panels and can materials.
Claims (10)
Ｃ：０．００４％以下、
Ｓｉ：０．６％以下、
Ｍｎ：０．１５〜１．２％、
Ｐ：０．０５％以下、
Ｓ：０．００３〜０．０３％、
Ｃｕ：０．００２〜０．６％、
Ｃｒ：０．３〜２．０％及び
Ｎ：０．００２〜０．００８％を含有すると共に、
Ａｌ：０．０１５％以下、
Ｎｂ：０．０１％以下及び
Ｔｉ：０．０１％以下に規制し、
残部がＦｅ及び不可避的不純物からなる組成を有し、
固溶Ｎを０．００１〜０．００４％含有すると共に固溶Ｃを０．００１５％以下に規制し、
かつ硫化物とＦｅとの界面の単位体積あたりの総面積が２×１０−３μｍ２／μｍ３以上であることを特徴とする低温焼付硬化性と常温非時効性に優れた深絞り用鋼板。 % By mass
C: 0.004% or less,
Si: 0.6% or less,
Mn: 0.15 to 1.2%,
P: 0.05% or less,
S: 0.003-0.03%,
Cu: 0.002 to 0.6%,
Containing Cr: 0.3-2.0% and N: 0.002-0.008%,
Al: 0.015% or less,
Nb: 0.01% or less and Ti: 0.01% or less,
The balance has a composition consisting of Fe and inevitable impurities,
While containing 0.001 to 0.004% of solid solution N and restricting solid solution C to 0.0015% or less,
And the total area per unit volume of the interface between sulfide and Fe is 2 × 10 −3 μm 2 / μm 3 or more, and a deep drawing steel sheet excellent in low temperature bake hardenability and normal temperature non-aging .
前記熱延コイルを、６０％以上の圧延率で冷間圧延して冷延コイルを得る工程と、
連続焼鈍炉により、前記冷延コイルを、最高到達温度を７００〜８５０℃として焼鈍する工程とを有することを特徴とする低温焼付硬化性と常温非時効性に優れた深絞り用鋼板の製造方法。 Smelted steel having a chemical composition according to any one of claims 1 to 6, the obtained cast slab, heated above 1200 ° C., the finish rolling temperature is (Ar 3 -50) ℃ or higher , A step of obtaining a hot-rolled coil by hot rolling at a temperature reduction rate of 30% or more in a temperature range of 1000 ° C. or more and a finish rolling temperature or less and a winding temperature of 600 to 750 ° C .;
Cold rolling the hot rolled coil at a rolling rate of 60% or more to obtain a cold rolled coil;
A method of manufacturing a steel sheet for deep drawing excellent in low-temperature bake hardenability and non-aging at room temperature, characterized by having a step of annealing the cold-rolled coil at a maximum temperature of 700 to 850 ° C. by a continuous annealing furnace .
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| WO2009096314A1 (en) | 2008-01-31 | 2009-08-06 | Kabushiki Kaisha Kobe Seiko Sho | Copper alloy plate having excellent anti-stress relaxation properties |
| JP2011084786A (en) * | 2009-10-16 | 2011-04-28 | Sumitomo Metal Ind Ltd | Hot dip galvanized steel sheet |
| JP2011241414A (en) * | 2010-05-14 | 2011-12-01 | Sumitomo Metal Ind Ltd | Hot dip galvanized steel sheet |
| JP2011246767A (en) * | 2010-05-27 | 2011-12-08 | Sumitomo Metal Ind Ltd | Bake-hardenable cold rolled steel sheet and method for producing the same |
| KR101228701B1 (en) | 2009-03-24 | 2013-02-01 | 주식회사 포스코 | Bake Hardenable Steel Sheet with Excellent Strain Aging Resistance and Manufacturing Method Thereof |
| JP6202234B1 (en) * | 2016-03-31 | 2017-09-27 | Ｊｆｅスチール株式会社 | Thin steel plate and plated steel plate, method for producing hot rolled steel plate, method for producing cold rolled full hard steel plate, method for producing thin steel plate, and method for producing plated steel plate |
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| JP2004323925A (en) * | 2003-04-25 | 2004-11-18 | Nippon Steel Corp | Strain aging hardening type steel sheet having excellent cold elongation deterioration resistance, cold delayed aging property and low temperature bake hardenability, and its production method |
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|---|---|---|---|---|
| WO2009096314A1 (en) | 2008-01-31 | 2009-08-06 | Kabushiki Kaisha Kobe Seiko Sho | Copper alloy plate having excellent anti-stress relaxation properties |
| KR101228701B1 (en) | 2009-03-24 | 2013-02-01 | 주식회사 포스코 | Bake Hardenable Steel Sheet with Excellent Strain Aging Resistance and Manufacturing Method Thereof |
| JP2011084786A (en) * | 2009-10-16 | 2011-04-28 | Sumitomo Metal Ind Ltd | Hot dip galvanized steel sheet |
| JP2011241414A (en) * | 2010-05-14 | 2011-12-01 | Sumitomo Metal Ind Ltd | Hot dip galvanized steel sheet |
| JP2011246767A (en) * | 2010-05-27 | 2011-12-08 | Sumitomo Metal Ind Ltd | Bake-hardenable cold rolled steel sheet and method for producing the same |
| JP6202234B1 (en) * | 2016-03-31 | 2017-09-27 | Ｊｆｅスチール株式会社 | Thin steel plate and plated steel plate, method for producing hot rolled steel plate, method for producing cold rolled full hard steel plate, method for producing thin steel plate, and method for producing plated steel plate |
| WO2017168991A1 (en) * | 2016-03-31 | 2017-10-05 | Ｊｆｅスチール株式会社 | Thin steel sheet, plated steel sheet, hot-rolled steel sheet manufacturing method, cold-rolled full hard steel sheet manufacturing method, thin steel sheet manufacturing method, and plated steel sheet manufacturing method |
| US10961601B2 (en) | 2016-03-31 | 2021-03-30 | Jfe Steel Corporation | Steel sheet and plated steel sheet, method for producing hot-rolled steel sheet, method for producing cold-rolled full-hard steel sheet, method for producing steel sheet, and method for producing plated steel sheet |
| US11578379B2 (en) | 2017-12-26 | 2023-02-14 | Posco | Cold-rolled steel sheet having excellent high-temperature properties and room-temperature workability |
| CN113789506A (en) * | 2021-09-15 | 2021-12-14 | 西安隆基绿能建筑科技有限公司 | Metal plate, building and preparation method of metal plate |
| CN113789506B (en) * | 2021-09-15 | 2023-09-01 | 隆基乐叶光伏科技有限公司 | Metal plate, building and preparation method of metal plate |
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