JP3094804B2 - Bake-hardened steel sheet with excellent surface properties - Google Patents
Bake-hardened steel sheet with excellent surface propertiesInfo
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- JP3094804B2 JP3094804B2 JP06227193A JP22719394A JP3094804B2 JP 3094804 B2 JP3094804 B2 JP 3094804B2 JP 06227193 A JP06227193 A JP 06227193A JP 22719394 A JP22719394 A JP 22719394A JP 3094804 B2 JP3094804 B2 JP 3094804B2
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、焼付け硬化性に優れた
鋼板（鋼帯、表面処理鋼板用の原板、表面処理鋼板、鋼
帯を含む）、例えば自動車の外板などの優れた耐デント
性が要求される薄鋼板に利用するのに好適な鋼板に関す
るものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel plate having excellent bake hardenability (including a steel strip, a base sheet for a surface-treated steel sheet, a surface-treated steel sheet, and a steel strip), for example, an excellent dent resistance such as an outer panel of an automobile. TECHNICAL FIELD The present invention relates to a steel sheet suitable for use in a thin steel sheet requiring a property.
【０００２】[0002]
【従来の技術】今日の製鋼脱ガス技術の進歩により、鋼
中の炭素量を30ppm以下まで低減した極低炭素鋼が比較
的安価でかつ大量に製造されるようになり、自動車部品
などの用途に広く使用されている。2. Description of the Related Art With the progress of steelmaking degassing technology today, ultra-low carbon steels in which the amount of carbon in steel has been reduced to 30 ppm or less have become relatively inexpensive and mass-produced. Widely used for.
【０００３】また、近年、地球環境問題が注目されるよ
うになり、自動車の排気ガスを低減することが重要な課
題になっている。排気ガスの低減策の一つとして、自動
車の外板パネルなどが高強度化され、部材の薄肉化によ
る車体の軽量化によって燃費の向上が進められている。
鋼板の薄肉化は製品をへこみやすくするため、外板パネ
ルなどの外観が重要視される部材では降伏点を上げて耐
デント性（鋼板のへこみにくさ）を確保する必要があ
る。しかし、プレス成形を考慮すると面ひずみを抑制す
るためには降伏点を低くする必要がある。In recent years, global environmental problems have been attracting attention, and reducing exhaust gas from automobiles has become an important issue. As one of the measures for reducing the exhaust gas, the outer panel of an automobile has been strengthened, and the fuel consumption has been improved by reducing the weight of the vehicle body by making the members thinner.
In order to reduce the thickness of the steel sheet, it is necessary to secure the dent resistance (resistance to the dent of the steel sheet) by increasing the yield point of members whose appearance is regarded as important, such as an outer panel, in order to make the product easily dent. However, in consideration of press molding, it is necessary to lower the yield point in order to suppress surface distortion.
【０００４】このニーズに対応できる鋼板として、極低
炭素鋼にNb、Tiなどの炭窒化物形成元素を添加すること
によって、成形時に降伏点が低いがその後の塗装焼付け
の際に降伏点が高くなる所謂焼付け硬化型の極低炭素冷
延鋼板が自動車の外板パネルなどに広く使用されるよう
になってきている。[0004] As a steel sheet that can meet this need, by adding a carbonitride forming element such as Nb or Ti to ultra-low carbon steel, the yield point is low at the time of forming, but the yield point is high during the subsequent baking of paint. 2. Description of the Related Art A so-called bake hardening type ultra low carbon cold rolled steel sheet has been widely used for an outer panel of an automobile.
【０００５】例えば、特公昭60-17004号公報等は、極低
炭素鋼にNbを添加した焼付け硬化型冷延鋼板に関するも
のであり、成形性および焼付け硬化性の向上に焦点を当
てたものである。For example, Japanese Patent Publication No. Sho 60-17004 relates to a bake hardening type cold rolled steel sheet in which Nb is added to an ultra-low carbon steel, and focuses on improvement of formability and bake hardenability. is there.
【０００６】特開平4-323345号公報、特公昭61-45689号
公報、特公平3-72134号公報は、Nb系あるいはNb-Ti系極
低炭素焼付け硬化型鋼板に関するものであり、同様に成
形性及び焼付け硬化性の向上を目的とするものである。
これらの技術においては、0.010%以下の低Si材のデータ
を開示しているものの、SiとO 両元素の低減の重要性を
開示したものは見当たらない。また、いずれも、後で述
べるような表面性状の改善を目的とする本発明とは技術
内容が異なるものである。JP-A-4-323345, JP-B-61-45689, and JP-B-3-72134 relate to an Nb-based or Nb-Ti-based ultra-low carbon bake hardening steel sheet. The purpose is to improve the properties and bake hardenability.
In these technologies, although data on low Si materials of 0.010% or less are disclosed, there is no disclosure of the importance of reducing both Si and O 2 elements. Further, each of them has a different technical content from the present invention for the purpose of improving surface properties as described later.
【０００７】[0007]
【発明が解決しようとする課題】ところで、極低炭素冷
延鋼板等の極低炭素鋼板は鋼が高純度であること等に起
因して表面欠陥が発生しやすいという問題点がある。こ
の薄鋼板に発生しやすい表面欠陥の一つにスケール性欠
陥がある。However, ultra-low carbon steel sheets such as ultra-low carbon cold-rolled steel sheets have a problem that surface defects are likely to occur due to the high purity of the steel. Scale defects are one of the surface defects that easily occur in this thin steel sheet.
【０００８】このスケール性欠陥は熱延鋼板のみなら
ず、酸洗後、冷間圧延後、あるいはさらに施されるめっ
き、化成処理等の表面処理後も鋼板表面に残存し、表面
外観不良となる。[0008] This scale defect remains on the steel sheet surface not only in hot-rolled steel sheets, but also after pickling, cold rolling, or after further surface treatment such as plating or chemical conversion treatment, resulting in poor surface appearance. .
【０００９】とくに，焼付け硬化型鋼板はその多くが自
動車の外板として用いられるために、表面欠陥がある
と、例え焼付け硬化性などの内質特性に優れていても、
商品価値が著しく低下する。[0009] In particular, since most of bake hardening type steel sheets are used as outer plates of automobiles, even if they have surface defects, even if they have excellent internal properties such as bake hardenability, even if they have excellent surface properties,
The product value is significantly reduced.
【００１０】本発明はこのような実情を鑑み、極低炭素
焼付け硬化型鋼板で多く発生するスケール性欠陥の低減
を目的とし、表面性状を向上させるうえで好ましい成分
組成の極低炭素焼付け硬化型鋼板を提供するものであ
る。In view of such circumstances, the present invention aims at reducing scale defects which often occur in ultra-low carbon bake hardening type steel sheets, and has an extremely low carbon bake hardening type having a preferable component composition for improving surface properties. Provide steel sheet.
【００１１】[0011]
【課題を解決するための手段】本発明者らは、極低炭素
焼付け硬化型鋼板のスケール剥離性について、鋭意研究
を重ねた結果、このスケール性欠陥の原因が、熱間圧延
時のスラブ加熱段階で粒界の優先酸化により楔状に形成
されたファイアライト（SiO2-FeO）がスケール剥離性を
阻害すること、さらに、鋼中のSiおよびO を低減するこ
とにより、スケール剥離性を阻害する粒界酸化が抑制さ
れることを見出した。Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the scale peelability of an ultra-low carbon bake hardening type steel sheet. As a result, the cause of this scale defect was slab heating during hot rolling. Firelite (SiO 2 -FeO) formed in a wedge shape by preferential oxidation of grain boundaries at the stage inhibits scale exfoliation, and further reduces scale exfoliation by reducing Si and O 2 in steel It has been found that grain boundary oxidation is suppressed.
【００１２】本発明はこのような知見に基づきなされた
ものであり、その特徴とする構成は以下の通りである。The present invention has been made on the basis of such knowledge, and the characteristic configuration thereof is as follows.
【００１３】（１）重量％で、C:0.001〜0.003%、Mn:0.
05〜2.2%、P:0.1%以下、S:0.015%以下、sol.Al:0.01〜
0.08%、N:0.003%以下、Nb:0.002〜0.01%、Si:20〜80pp
m、O:5〜20ppmを含み、かつ前記のSi、O が、[ppmO]≦
−0.1 × [ppmSi] ＋25なる関係を満足し、残部が鉄お
よび不可避不純物からなる表面性状に優れた焼付け硬化
型鋼板。(1) By weight%, C: 0.001 to 0.003%, Mn: 0.
05 to 2.2%, P: 0.1% or less, S: 0.015% or less, sol.Al: 0.01 to
0.08%, N: 0.003% or less, Nb: 0.002-0.01%, Si: 20-80pp
m, O: contains 5 to 20 ppm, and the Si, O 2 is [ppmO] ≦
A bake hardening steel sheet that satisfies the relationship of -0.1 x [ppmSi] +25 and the balance is iron and inevitable impurities and has excellent surface properties.
【００１４】（２）重量％で、C:0.001〜0.003%、Mn:0.
05〜2.2%、P:0.1%以下、S:0.015%以下、sol.Al:0.01〜
0.08%、N:0.003%以下、Nb:0.002〜0.01%、Si:20〜80pp
m、O:5〜20ppmを含み，かつ前記のSi、O が[ppmO]≦−
0.1 × [ppmSi]＋25なる関係を満足し、さらにTi:0.002
%〜(48/14) ×[%N]＋(48/32)×[%S]を含み、残部が鉄お
よび不可避不純物からなる表面性状に優れた焼付け硬化
型鋼板。(2) By weight%, C: 0.001 to 0.003%, Mn: 0.
05 to 2.2%, P: 0.1% or less, S: 0.015% or less, sol.Al: 0.01 to
0.08%, N: 0.003% or less, Nb: 0.002-0.01%, Si: 20-80pp
m, O: contains 5 to 20 ppm, and said Si and O are [ppmO] ≦ −
0.1 × [ppmSi] +25 is satisfied and Ti: 0.002
A bake hardened steel sheet containing% to (48/14) × [% N] + (48/32) × [% S], the balance being iron and unavoidable impurities, and excellent in surface properties.
【００１５】[0015]
【作用】以下に本発明の詳細についてその限定理由とと
もに説明する。The details of the present invention will be described below, together with the reasons for its limitation.
【００１６】まず、粒界酸化について説明する。図２
は、スラブ加熱後の極低炭素鋼に認められる母材の粒界
酸化の状態を示す写真で、Siが0.02% の極低炭素鋼スラ
ブを加熱炉で加熱後のスラブ断面の金属の酸化組織を示
す顕微鏡写真である。母材の粒界に沿ってスケールが楔
状に食い込んでいる。この粒界酸化はファイアライト
（SiO2-FeO）生成によるものであり、Siが0.01〜0.04%
と比較的低い含有量であっても、1100〜1300℃の広い加
熱温度範囲で観察される。極低炭素鋼の場合、Siが0.01
〜0.04％と比較的低い含有量であっても、粒界へのSiの
濃化が起こり、鋭利で深い粒界酸化が生成するため、そ
のアンカー効果によりデスケーリング時のスケール剥離
性が阻害され、低炭素鋼に比較してスケール性欠陥発生
率が高くなる。First, the grain boundary oxidation will be described. FIG.
Is a photograph showing the state of intergranular oxidation of the base metal observed in the ultra-low carbon steel after heating the slab.The oxidation structure of the metal in the cross section of the slab after heating the ultra-low carbon steel slab with 0.02% Si in the heating furnace FIG. The scale is wedge-shaped along the grain boundaries of the base metal. This grain boundary oxidation is due to the formation of firelite (SiO 2 -FeO), and the content of Si is 0.01 to 0.04%.
Is observed in a wide heating temperature range of 1100 to 1300 ° C even if the content is relatively low. For ultra low carbon steel, Si is 0.01
Even at a relatively low content of ~ 0.04%, the concentration of Si at the grain boundaries occurs, and sharp and deep grain boundary oxidation is generated. As a result, the scale defect generation rate is higher than that of low carbon steel.
【００１７】本発明は鋼板中のSi、O を低減することに
より、スケールの剥離性を改善し、鋼板のスケール性欠
陥を低減するものである。図１によりこの点について説
明する。図１は、鋼中のSi量、O 量とスケール性欠陥発
生率との関係を示す図である。The present invention is intended to improve the peelability of scale by reducing Si and O in a steel sheet, and to reduce the scale defect of the steel sheet. This will be described with reference to FIG. FIG. 1 is a diagram showing the relationship between the amounts of Si and O in steel and the rate of occurrence of scale defects.
【００１８】図１に示すようにSiが80ppm以下になる
と、欠陥発生率が激減する。Siが80ppm以下では粒界酸
化個数がそれを超える場合と変わらないものの、粒界酸
化の深さが大幅に減少する。このためにデスケーリング
時のスケール剥離性が改善され、スケール性欠陥の発生
率が激減する。しかし、Siが20ppm 未満になると、スケ
ールが薄くて緻密になり、逆にスケール剥離性が低下
し、スケール性欠陥発生率が増加する。従って、Siは20
ppm 以上、80ppm 以下にする必要がある。なお、欠陥発
生率は、最終工程での長さ15cm以上の欠陥１個当たりを
1.5mとし、合計欠陥長さをコイル長さで除した値であ
る。As shown in FIG. 1, when the content of Si is 80 ppm or less, the defect generation rate is drastically reduced. When the content of Si is 80 ppm or less, the depth of the grain boundary oxidation is greatly reduced although the number of grain boundary oxidation numbers is not different from the case where the number exceeds the limit. For this reason, the scale exfoliation at the time of descaling is improved, and the incidence of scale defects is drastically reduced. However, when the content of Si is less than 20 ppm, the scale becomes thin and dense, and conversely, the scale releasability decreases and the scale defect rate increases. Therefore, Si is 20
It is necessary to be more than ppm and less than 80ppm. In addition, the defect occurrence rate is the defect per 15cm or more in the final process.
The value is 1.5 m, and the total defect length is divided by the coil length.
【００１９】また、図１に示されるように、O は5ppm以
上、20ppm 以下にする必要がある。O は鋼中で酸化物と
して存在するが、これが表層に分布する場合は、スラブ
加熱段階での内部酸化の核となり、内部酸化の生成物が
表層に延びて表層の酸化物と連結し、粒界酸化と同様の
形態を呈するようになる。O が20ppm を超えると表層で
の酸化物の分布が増え、内部酸化の生成物が多数表層に
延びて表層の酸化物と連結し、粒界酸化と同様の形態を
呈するようになり、デスケーリング時のスケール剥離性
が低下し、スケール性欠陥発生率が増加する。O を20pp
m以下に低減することにより、このスケール性欠陥の発
生率を抑制することができる。Further, as shown in FIG. 1, O 2 needs to be 5 ppm or more and 20 ppm or less. O exists as an oxide in the steel, but if it is distributed in the surface layer, it becomes the core of internal oxidation during the slab heating step, and the products of internal oxidation extend to the surface layer and connect with the surface oxide to form particles. It takes on a form similar to field oxidation. When O exceeds 20 ppm, the distribution of oxides in the surface layer increases, and many products of internal oxidation extend to the surface layer and connect with the surface layer oxides, exhibiting a morphology similar to grain boundary oxidation, resulting in descaling. In this case, the scale releasability decreases, and the scale defect occurrence rate increases. O to 20pp
By reducing it to m or less, the rate of occurrence of this scale defect can be suppressed.
【００２０】また、オーステナイト粒が大きいと熱間圧
延時に粒界割れによるスケール性欠陥が発生しやすい。
O はオーステナイトの粒成長を抑制し、熱間圧延時の粒
界割れによるスケール性欠陥の発生を抑制する。O が5p
pm未満になると、オーステナイトの粒成長を抑制する作
用が低下し、熱間圧延時の粒界割れによるスケール性欠
陥の発生が増加する。したがって、O は5ppm以上にする
必要がある。If the austenite grains are large, scale defects due to grain boundary cracks are likely to occur during hot rolling.
O suppresses the grain growth of austenite and suppresses the generation of scale defects due to grain boundary cracks during hot rolling. O is 5p
When it is less than pm, the effect of suppressing austenite grain growth is reduced, and the occurrence of scale defects due to grain boundary cracks during hot rolling increases. Therefore, O needs to be 5 ppm or more.
【００２１】また、SiおよびO が上記の範囲内であって
も、両者が上限近傍の場合は、欠陥発生率が高くなる。
欠陥発生率を低減するためには、SiとO との間で、[ppm
O]≦−0.1 ×[ppmSi]＋25なる関係をさらに満足させる
必要がある。Further, even when Si and O 2 are within the above ranges, when both are near the upper limit, the defect occurrence rate becomes high.
In order to reduce the defect rate, [ppm
It is necessary to further satisfy the relationship of O] ≦ −0.1 × [ppmSi] +25.
【００２２】その他の元素の成分限定範囲は以下のとお
りである。C はその含有量が少ないほど成形性に有利で
ある。しかし、焼付け硬化性を確保するには0.001%以上
が必要である。また、その量が0.003%を超えると成形性
が低下する。したがって，その範囲は0.001〜0.003%に
限定する。The ranges of the other elements are as follows. The smaller the content of C, the more advantageous the moldability. However, 0.001% or more is required to secure bake hardenability. On the other hand, if the amount exceeds 0.003%, the moldability decreases. Therefore, its range is limited to 0.001 to 0.003%.
【００２３】Mnは熱間圧延時の割れを抑制し表面性状向
上に寄与するので添加する必要がある。その量が0.05%
未満では前記の効果を十分に発揮できなくなる。また、
過剰のMnは成形性を低下するので、その量を2.2%以下に
する必要がある。したがって、Mnは0.05〜2.2%に限定す
る。Mn must be added because it suppresses cracking during hot rolling and contributes to improving the surface properties. The amount is 0.05%
If it is less than the above, the above-mentioned effects cannot be sufficiently exhibited. Also,
Excessive Mn lowers the formability, so the amount must be 2.2% or less. Therefore, Mn is limited to 0.05 to 2.2%.
【００２４】P は粒界脆化元素であり、熱間圧延時の表
面割れ抑制の点からは低い方が望ましく、その上限を0.
1%とする。P is a grain boundary embrittlement element, and is desirably low from the viewpoint of suppressing surface cracking during hot rolling.
1%.
【００２５】S は多すぎると粒界を脆弱化し、熱間圧延
時の割れを引き起こすので、少ない方がのぞましく、そ
の上限を0.015%とする。If S is too large, it weakens the grain boundaries and causes cracking during hot rolling. Therefore, a smaller amount is preferable, and the upper limit is made 0.015%.
【００２６】Alは溶鋼の脱酸のために添加する必要があ
る。その量が鋼中のsol.Alとして、0.01% 未満になると
その目的が十分に達成できない。また、その量が0.08%
を超えるようになるとAl2O3が増加し、スケールの剥離
性を阻害する。したがって、sol.Alとして0.01〜0.08%
に限定する。Al must be added for deoxidizing molten steel. If the amount is less than 0.01% as sol.Al in steel, the purpose cannot be sufficiently achieved. In addition, the amount is 0.08%
When the value exceeds the limit, Al 2 O 3 increases and inhibits the peelability of the scale. Therefore, 0.01-0.08% as sol.Al
Limited to.
【００２７】N は常温時効性および成形性の点で低い方
が望ましく、その上限を0.003%とする。N is desirably low in terms of aging at room temperature and moldability, and its upper limit is made 0.003%.
【００２８】Nbは極低炭素ベースで成形性を向上させる
働きを有するので添加する必要がある。Nbが0.002%未満
ではその目的を十分に達成できなくなる。また、0.01%
を超えて過剰に添加すると焼付け硬化性が得られなくな
る。したがって、Nbは0.002〜0.01%とする。Nb must be added because it has a function of improving formability on a very low carbon basis. If Nb is less than 0.002%, the purpose cannot be sufficiently achieved. Also, 0.01%
If the amount exceeds the range, baking hardenability cannot be obtained. Therefore, Nb is set to 0.002 to 0.01%.
【００２９】以上を本発明の基本成分範囲とするが、常
温時効性の抑制のためにTiを適量添加してもよい。Tiは
N と結合し，N による常温時効性を抑制する効果があ
る。目的とする効果を発揮するためには0.002%以上にす
る必要がある。しかし、過剰に添加するとS 、次いでC
と結合する。C と結合すると焼付け硬化性が低下するの
で、目的とする焼付け性を得るためには、Tiは(48/14)
×[%N]＋(48/32) ×[%S]を超えないようにする必要があ
る。したがって、Ti: 0.002%〜(48/14) ×[%N]＋(48/3
2) ×[%S]に限定する。The above is the basic component range of the present invention, but an appropriate amount of Ti may be added to suppress the aging at room temperature. Ti is
It combines with N and has the effect of suppressing normal-temperature aging caused by N. In order to achieve the desired effect, the content needs to be 0.002% or more. However, when added in excess, S and then C
Combine with When combined with C, bake hardenability decreases, so to obtain the desired bakeability, Ti should be (48/14)
X [% N] + (48/32) x [% S] must not be exceeded. Therefore, Ti: 0.002% ~ (48/14) × [% N] + (48/3
2) Limited to × [% S].
【００３０】本発明の鋼板は、熱間圧延ままの鋼板、こ
れを熱処理した鋼板、酸洗など脱スケールした鋼板、脱
スケールした鋼板を熱処理した鋼板、熱処理後に酸洗な
ど脱スケールした鋼板、あるいはこれらの鋼板にめっき
などの表面処理を施した鋼板を含む。The steel sheet of the present invention may be a hot-rolled steel sheet, a heat-treated steel sheet, a steel sheet descaled by pickling, a steel sheet heat-treated from a descaled steel sheet, a steel sheet descaled by pickling after heat treatment, or These include steel sheets that have been subjected to surface treatment such as plating.
【００３１】また、本発明の鋼板は、熱間圧延後、酸
洗、冷間圧延した後に再結晶焼鈍を行った冷延鋼板を含
む。Further, the steel sheet of the present invention includes a cold-rolled steel sheet which has been subjected to recrystallization annealing after hot rolling, pickling and cold rolling.
【００３２】また、本発明の鋼板は、表面処理鋼板を含
み、熱間圧延鋼板あるいは冷間圧延鋼板のいずれに処理
を行ったものでもよい。The steel sheet of the present invention includes a surface-treated steel sheet and may be a hot-rolled steel sheet or a cold-rolled steel sheet.
【００３３】なお、本発明の鋼板は常法によって製造す
ることができる。即ち、鋼を溶製、鋳造し、熱間圧延し
て、熱延鋼板を製造することができる。鋼の溶製は転
炉、電気炉のいずれでもよい。また、炉外精錬も必要に
より適用できる。鋳造は普通造塊あるいは連続鋳造のい
ずれでもよい。熱間圧延は冷スラブを再加熱後、または
鋳造後の熱スラブを軽い再加熱（保熱、保定を含む）後
に行ってもよい。また、熱間粗圧延を行わない場合であ
ってもよい。The steel sheet of the present invention can be manufactured by a conventional method. That is, it is possible to produce a hot-rolled steel sheet by melting, casting and hot rolling steel. The smelting of steel may be performed by either a converter or an electric furnace. Out-of-pile refining can also be applied if necessary. Casting may be either ordinary ingot or continuous casting. Hot rolling may be performed after reheating the cold slab or after slightly reheating (including heat holding and holding) the hot slab after casting. Moreover, the case where hot rough rolling is not performed may be sufficient.
【００３４】熱間圧延後の鋼板に、必要に応じて、熱処
理、酸洗など脱スケール、脱スケールした鋼板を熱処
理、熱処理後に酸洗など脱スケール等の処理を行うこと
ができる。あるいは、さらに、これらの鋼板にめっきな
どの表面処理を施すことができる。The steel sheet after hot rolling can be subjected to heat treatment, descaling such as pickling, heat treatment of the descaled steel sheet as required, and descaling processing such as pickling after the heat treatment. Alternatively, these steel sheets can be further subjected to a surface treatment such as plating.
【００３５】また、熱間圧延後、酸洗、冷間圧延した後
に再結晶焼鈍を行い、冷延鋼板を製造することができ
る。この場合、特に限定するものではないが、加熱温度
を1150℃以上、仕上げ温度をAr3 点以上として熱間圧延
を行い、さらに圧下率50% 以上の冷間圧延をすること
で、本発明の効果を最大限に発揮することができる。ま
た、再結晶焼鈍は、箱型焼鈍炉、連続焼鈍炉、連続焼鈍
炉を有する溶融めっきラインの何れで行ってもかまわな
い。Further, after hot rolling, pickling and cold rolling, recrystallization annealing is performed to produce a cold-rolled steel sheet. In this case, although not particularly limited, the hot rolling is performed at a heating temperature of 1150 ° C. or higher, the finishing temperature is set to an Ar 3 point or higher, and the cold rolling is performed at a reduction ratio of 50% or higher. The effect can be maximized. The recrystallization annealing may be performed in any of a box annealing furnace, a continuous annealing furnace, and a hot-dip plating line having a continuous annealing furnace.
【００３６】本発明の表面処理鋼板は、熱間圧延鋼板あ
るいは冷間圧延鋼板のいずれに処理を行ったものでもよ
い。表面処理としては、溶融金属めっき（亜鉛、アル
ミ、亜鉛−アルミ合金）や合金化溶融亜鉛めっき、電気
亜鉛めっき、電気亜鉛合金めっき、化成処理、有機複合
めっき、塗装、錫めっき等の常法による処理を単独ある
いは適宜複合して施すことができる。これらの処理を施
しても本発明の効果を損なうことがない。The surface-treated steel sheet of the present invention may be one obtained by treating a hot-rolled steel sheet or a cold-rolled steel sheet. The surface treatment is performed by a conventional method such as hot-dip metal plating (zinc, aluminum, zinc-aluminum alloy), alloyed hot-dip galvanization, electro-zinc plating, electro-zinc alloy plating, chemical conversion treatment, organic composite plating, painting, tin plating, etc. The treatment can be performed alone or in combination as appropriate. These effects do not impair the effects of the present invention.
【００３７】[0037]
【実施例】表１にそれぞれ本発明鋼および比較鋼の組成
およびスケール欠陥の発生率を示す。なお、表中、成分
の表示は重量％、但し、C 、N 、Si、0 、25−0.1Si は
ppm 表示である。また、欠陥発生率の表示は％である。
また、比較鋼中の太線枠は本発明の範囲外であることを
示しているEXAMPLES Table 1 shows the compositions of the steels of the present invention and the comparative steels and the incidence of scale defects. In the table, the indication of the components is% by weight, provided that C, N, Si, 0, and 25-0.1Si are
It is expressed in ppm. The indication of the defect occurrence rate is%.
Also, the thick line frame in the comparative steel indicates that it is outside the scope of the present invention.
【００３８】[0038]
【表1 】 【table 1 】
【００３９】基本的な製造条件としては、連続鋳造後、
600℃から室温まで冷却した鋳片を1150〜1280℃に再加
熱して熱間圧延−ランナウトテーブル上での冷却−巻き
取り処理により、2.8〜3.6mm板厚の熱延鋼板を得た。な
お、デスケーリングは粗圧延および仕上げ圧延前にそれ
ぞれ２回ずつ、衝突圧：3kgf/cm2の高圧水を噴射するこ
とにより実施し、平均的な仕上げ温度は900℃、巻き取
り温度は660℃とした。さらに、酸洗後冷間圧延を行い
(板厚0.6〜1.6mm)、800〜870℃の連続焼鈍−1.4%の調質
圧延を施した（鋼1〜5 、8〜10、14 〜19、23 〜26）。
なお、溶融亜鉛めっき鋼板については、前記と同様に冷
間圧延後、連続溶融亜鉛めっきラインで850℃の焼鈍を
施し、ただちに460℃まで冷却した段階で片面あたり55g
/m2の溶融亜鉛をめっきし、引き続き500℃で合金化処理
を行い、1.4%の調質圧延を行った（鋼6）。一部につい
て、さらに片面あたり3g/m2の80%Fe-Zn合金の上層電気
めっきを施して溶融めっきと電気めっきの二層めっき鋼
板とした（鋼7 、11、20、21）。電気めっき鋼板につい
ては、冷間圧延−焼鈍−調質圧延後、片面あたり20g/m2
の88%Zn-Ni合金電気めっきを行い（鋼12、22）、有機被
覆鋼板については、電気めっきの上にさらに金属クロム
換算で50mg/m2 のクロメート被覆、樹脂層1 μmの複合
被覆を行った（鋼13）。The basic manufacturing conditions are as follows:
The cast slab cooled from 600 ° C. to room temperature was reheated to 1150 to 1280 ° C., and hot-rolled—cooled on a run-out table—rewinded to obtain a hot-rolled steel sheet having a sheet thickness of 2.8 to 3.6 mm. The descaling was performed twice before each of the rough rolling and the finish rolling by injecting high-pressure water having a collision pressure of 3 kgf / cm 2. The average finishing temperature was 900 ° C and the winding temperature was 660 ° C. And Furthermore, cold rolling is performed after pickling.
(Sheet thickness: 0.6 to 1.6 mm), continuous annealing at 800 to 870 ° C-temper rolling of 1.4% (steel 1 to 5, 8 to 10, 14 to 19, 23 to 26).
The hot-dip galvanized steel sheet was cold-rolled in the same manner as above, then annealed at 850 ° C. in a continuous hot-dip galvanizing line, and immediately cooled to 460 ° C. at a stage of 55 g per side.
/ m 2 of hot-dip zinc, followed by alloying at 500 ° C. and temper rolling of 1.4% (Steel 6). Some parts were further subjected to upper layer electroplating of 80% Fe-Zn alloy at 3 g / m 2 per side to obtain double-layer plated steel sheets of hot-dip plating and electroplating (steel 7, 11, 20, 21). For electroplated steel sheets, after cold rolling-annealing-temper rolling, 20 g / m 2 per side
Of performed 88% Zn-Ni alloy electroplating (steel 12, 22), for the organic coated steel sheet, chromate coating of 50 mg / m 2 in addition reckoned as metal chromium on the electroplating, the composite coating of the resin layer 1 [mu] m Went (steel 13).
【００４０】スケール性欠陥発生のパラメーターとして
は、最終段階での15cm以上の欠陥１個を1.5mとして、そ
の総和を冷間圧延コイル長で除した値をスケール欠陥発
生率とし、この発生率により表面性状を評価した。ま
た、焼付け硬化性は2%の引張歪み付加後、145℃で20分
の低温焼付け処理を実施し、歪み付加前に対する焼付け
後の降伏強度の上昇量（BH量）で評価した。As a parameter of the scale defect generation, one defect of 15 cm or more at the final stage is set to 1.5 m, and a value obtained by dividing a total thereof by a cold-rolled coil length is defined as a scale defect generation rate. The surface properties were evaluated. The bake hardenability was evaluated by performing a low-temperature baking treatment at 145 ° C. for 20 minutes after applying 2% tensile strain, and evaluating the increase in yield strength (BH amount) after baking before applying strain.
【００４１】比較鋼のSi量が適正でない鋼17、23、24、
O 量が適正でない鋼18〜20、22 およびSi-Oバランスが
適正でない鋼20、21 はスケール性欠陥による不良率が
0.61%以上であるのに対し、本発明鋼1〜16は発生率が0.
39%以下となっている。また、NbまたはTi添加量が適正
でない鋼25、26はBH量が13〜16MPaと本発明鋼の35〜53M
Paに比較して低くなっている。Steels 17, 23, 24, in which the amount of Si in the comparative steel is not appropriate
Steels 18-20 and 22 with inappropriate O content and Steels 20 and 21 with improper Si-O balance have a poor defect rate due to scale defects.
In contrast to 0.61% or more, the steels 1 to 16 of the present invention have an incidence of 0.
It is less than 39%. In addition, steels 25 and 26 where the Nb or Ti addition amount is not appropriate have a BH amount of 13 to 16 MPa and 35 to 53 M of the steel of the present invention.
It is lower than Pa.
【００４２】[0042]
【発明の効果】以上のごとく本発明によれば、焼付け硬
化型極低炭素鋼板で問題となるスケール性欠陥が新たな
設備の設置あるいは製造プロセスの変更をすることなく
低減でき、表面性状に優れた鋼板を得ることができる。As described above, according to the present invention, scale defects, which are a problem in bake hardening type ultra-low carbon steel sheets, can be reduced without installing new equipment or changing the manufacturing process, and the surface properties are excellent. Steel sheet can be obtained.
【図１】Si量およびO 量とスケール性欠陥不良率の関係
を示す図である。FIG. 1 is a diagram showing the relationship between the amounts of Si and O 2 and the defect rate of scale defects.
【図２】Siが0.02% の極低炭素鋼スラブの加熱後の粒界
酸化の状態を示すスラブ断面の金属の酸化組織の図面代
用写真である。FIG. 2 is a photograph substituted for a drawing of an oxidation structure of a metal in a cross section of a slab, showing a state of grain boundary oxidation of a very low carbon steel slab containing 0.02% of Si after heating.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 沖本 一生 東京都千代田区丸の内一丁目１番２号 日本鋼管株式会社内 (72)発明者 松浦 俊暁 東京都千代田区丸の内一丁目１番２号 日本鋼管株式会社内 (72)発明者 田辺 治良 東京都千代田区丸の内一丁目１番２号 日本鋼管株式会社内 (56)参考文献 特開 平５−255807（ＪＰ，Ａ) 特開 昭58−110659（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) C22C 38/00 - 38/14 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuo Okimoto 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Inventor Toshiaki Matsuura 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Inside of Kokan Co., Ltd. (72) Inventor Jira Tanabe 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Kokan Co., Ltd. (56) References JP-A-5-255807 (JP, A) JP-A-58-110659 ( JP, A) (58) Field surveyed (Int. Cl. 7 , DB name) C22C 38/00-38/14
Claims (2)
2.2%、P:0.1%以下、S:0.015%以下、sol.Al:0.01〜0.08
%、N:0.003%以下、Nb:0.002〜0.01%、Si:20〜80ppm、O:
5〜20ppmを含み、かつ前記のSi、O が、[ppmO]≦−0.1
× [ppmSi] ＋25なる関係を満足し、残部が鉄および不
可避不純物からなる表面性状に優れた焼付け硬化型鋼
板。[Claim 1] By weight%, C: 0.001-0.003%, Mn: 0.05-
2.2%, P: 0.1% or less, S: 0.015% or less, sol.Al: 0.01 to 0.08
%, N: 0.003% or less, Nb: 0.002 to 0.01%, Si: 20 to 80 ppm, O:
5 to 20 ppm, and the above-mentioned Si, O 2 is [ppmO] ≦ −0.1
× Baking hardened steel sheet that satisfies the relationship of [ppmSi] +25 and the balance is iron and inevitable impurities and has excellent surface properties.
2.2%、P:0.1%以下、S:0.015%以下、sol.Al:0.01〜0.08
%、N:0.003%以下、Nb:0.002〜0.01%、Si:20〜80ppm、O:
5〜20ppmを含み，かつ前記のSi、O が、[ppmO]≦−0.1
× [ppmSi]＋25なる関係を満足し、さらにTi:0.002%〜
(48/14) ×[%N]＋(48/32)×[%S]を含み、残部が鉄およ
び不可避不純物からなる表面性状に優れた焼付け硬化型
鋼板。2. In% by weight, C: 0.001 to 0.003%, Mn: 0.05 to
2.2%, P: 0.1% or less, S: 0.015% or less, sol.Al: 0.01 to 0.08
%, N: 0.003% or less, Nb: 0.002 to 0.01%, Si: 20 to 80 ppm, O:
5 to 20 ppm, and the above-mentioned Si, O 2 is [ppmO] ≦ −0.1
× [ppmSi] +25 was satisfied, and Ti: 0.002% or more
A bake hardened steel sheet containing (48/14) × [% N] + (48/32) × [% S], with the balance consisting of iron and unavoidable impurities having excellent surface properties.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06227193A JP3094804B2 (en) | 1994-08-01 | 1994-08-01 | Bake-hardened steel sheet with excellent surface properties |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06227193A JP3094804B2 (en) | 1994-08-01 | 1994-08-01 | Bake-hardened steel sheet with excellent surface properties |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0841587A JPH0841587A (en) | 1996-02-13 |
| JP3094804B2 true JP3094804B2 (en) | 2000-10-03 |
Family
ID=16856956
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP06227193A Expired - Lifetime JP3094804B2 (en) | 1994-08-01 | 1994-08-01 | Bake-hardened steel sheet with excellent surface properties |
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| Country | Link |
|---|---|
| JP (1) | JP3094804B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4177478B2 (en) * | 1998-04-27 | 2008-11-05 | Ｊｆｅスチール株式会社 | Cold-rolled steel sheet, hot-dip galvanized steel sheet excellent in formability, panel shape, and dent resistance, and methods for producing them |
| JPH11305987A (en) | 1998-04-27 | 1999-11-05 | Matsushita Electric Ind Co Ltd | Text voice converting device |
| WO2016170794A1 (en) * | 2015-04-21 | 2016-10-27 | Ｊｆｅスチール株式会社 | Alloyed hot-dip galvanized sheet, production method therefor and alloyed hot-dip galvanized steel sheet |
-
1994
- 1994-08-01 JP JP06227193A patent/JP3094804B2/en not_active Expired - Lifetime
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| Publication number | Publication date |
|---|---|
| JPH0841587A (en) | 1996-02-13 |
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