JP3052780B2 - Method for producing hot rolled steel sheet with excellent hole expansion uniformity - Google Patents
Method for producing hot rolled steel sheet with excellent hole expansion uniformityInfo
- Publication number
- JP3052780B2 JP3052780B2 JP7110592A JP11059295A JP3052780B2 JP 3052780 B2 JP3052780 B2 JP 3052780B2 JP 7110592 A JP7110592 A JP 7110592A JP 11059295 A JP11059295 A JP 11059295A JP 3052780 B2 JP3052780 B2 JP 3052780B2
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- Japan
- Prior art keywords
- steel sheet
- less
- rolled steel
- hole expansion
- width direction
- Prior art date
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- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Metal Rolling (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は、安価で幅方向にわたっ
て材質が均一で、特に孔拡げ性の均一性に優れた熱延鋼
板の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hot-rolled steel sheet which is inexpensive, has a uniform material in the width direction, and has particularly excellent uniformity of hole expansion.
【０００２】[0002]
【従来の技術と問題点】従来、高加工性を有する鋼とし
ては主に高張力鋼を中心として検討されているが (例え
ば特開昭57−47828 号公報、特公昭61−22007 号公報、
同63−39647 号公報、特開平４−224635号公報) 、軟鋼
における検討は少ない。2. Description of the Related Art Hitherto, steels having high workability have been studied mainly on high-tensile steels (for example, JP-A-57-47828, JP-B-61-22007,
No. 63-39647, Japanese Unexamined Patent Publication No. 224635/1992, and studies on mild steel are few.
【０００３】軟鋼において高成形性を持たせるには炭素
量を100 ppm 以下に抑えるいわゆる極低炭素鋼の採用が
考えられるが、薄物の場合、冷え易いエッジ部で熱間圧
延中にAr3 点以下の温度になりその結果、鋼板の表裏面
の組織が粗大化し成形性が著しく損なわれる。また、エ
ッジ部でAr3 点以上が確保できても幅方向においてエッ
ジ部分はセンタ部に比し冷え易くセンタ部と熱履歴が異
なるため、どうしても幅方向について特性がバラツクと
いった問題を有している。[0003] To give a high formability in mild steel is considered to employ a so-called ultra low carbon steel to reduce the carbon content to below 100 ppm, when the thin, Ar 3 point during hot rolling in cold liable edge portion As a result, the structure on the front and back surfaces of the steel sheet becomes coarse and the formability is significantly impaired. In addition, even if three or more Ar points can be secured at the edge portion, the edge portion is more likely to cool in the width direction than the center portion and has a different thermal history from the center portion, so that there is a problem that the characteristics inevitably vary in the width direction. .
【０００４】これに対しては特開昭53−22850 号公報、
特公平５−77728 号公報に代表されるように、Ar3 点以
下で熱間圧延を施しその後再結晶をさせ高成形性を得る
方法が提示されているが、この方法では温度を低下させ
るために製造ライン上でアイドリングが必要となり、生
産性が低下するに加えて、Ar3 点以下の低温度で圧延す
るために相当な圧下負荷が加わるという問題を有してい
る。[0004] On the other hand, Japanese Patent Application Laid-Open No. Sho 53-22850 discloses
As represented by Japanese Patent Publication No. Hei 5-77728, a method has been proposed in which hot rolling is performed at an Ar point of 3 or less and then recrystallization is performed to obtain high formability. In addition, idling is required on a production line, and in addition to a decrease in productivity, there is a problem that a considerable reduction load is applied because rolling is performed at a low temperature of not more than the Ar 3 point.
【０００５】[0005]
【発明が解決しようとする課題】ここに、本発明の目的
は、安価な手段でもって品質の均一性および高い成形性
を確保する熱延鋼板の製造方法を提供することである。SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a hot-rolled steel sheet which ensures uniform quality and high formability by inexpensive means.
【０００６】より具体的には、本発明の目的は、センタ
とエッジ部との孔拡げ率の差異が18％以内である、孔拡
げ性の均一性に優れた引張強度30〜45キロ級の熱延鋼板
の製造方法を提供することである。[0006] More specifically, an object of the present invention is to provide a material having a tensile strength of 30 to 45 kg class having excellent uniformity of hole expansion, wherein the difference in hole expansion ratio between the center and the edge portion is within 18%. An object of the present invention is to provide a method for manufacturing a hot-rolled steel sheet.
【０００７】[0007]
【課題を解決するための手段】本発明者は、上記問題を
解決すべく研究を行った結果、Ｃ、Mn、Si、Ｐ、Ｓ、Cr
の含有量を調整した上に、かつ粗圧延前にスラブを適正
な条件下で幅方向に圧下することにより、安価で幅方向
に材質が均一で孔拡げ性に優れる熱延鋼板が得られるこ
とを見い出し、本発明を完成した。Means for Solving the Problems The present inventor has conducted studies to solve the above problems, and as a result, has found that C, Mn, Si, P, S, Cr
By adjusting the content of slab and rolling down the slab in the width direction under appropriate conditions before rough rolling, it is possible to obtain a hot-rolled steel sheet that is inexpensive, has uniform material in the width direction, and has excellent hole expansion properties. And completed the present invention.
【０００８】よって、本発明は、重量％で、Ｃ：0.03〜
0.12％、Mn：0.1 〜1.0 ％以下、Si：0.1 ％以下、Ｐ：
0.035 ％以下、Ｓ：0.010 ％以下、sol.Al：0.005 〜0.
04％、Cr：0.08〜1.0 ％、残部がFeおよび不可避不純物
から成る鋼組成を有する鋼スラブを粗圧延開始前に幅方
向に10〜35％の圧下を加え、幅方向への圧下開始後45秒
以内に粗圧延を開始し、Ar3 点以上で熱間圧延を終了
し、その後400 〜550 ℃で巻取ることを特徴とする孔拡
げ性に優れた熱延鋼板の製造方法である。Accordingly, the present invention relates to a method for preparing C:
0.12%, Mn: 0.1 to 1.0% or less, Si: 0.1% or less, P:
0.035% or less, S: 0.010% or less, sol.Al: 0.005-0.
04%, Cr: 0.08 to 1.0%, balance of steel slab having a steel composition consisting of Fe and unavoidable impurities is subjected to 10-35% reduction in the width direction before starting rough rolling, and 45% after starting reduction in the width direction. This is a method for producing a hot-rolled steel sheet having excellent hole expandability, in which rough rolling is started within seconds, hot rolling is completed at an Ar temperature of 3 or more points, and then winding is performed at 400 to 550 ° C.
【０００９】[0009]
【作用】次に、この発明において、素材の鋼の成分組成
および製造条件を上記の通りに限定した理由をその作用
とともに説明する。なお、本明細書において特にことわ
りがない限り、「％」は「重量％」である。Next, the reason why the composition of the steel material and the manufacturing conditions in the present invention are limited as described above will be described together with the operation thereof. In this specification, “%” is “% by weight” unless otherwise specified.
【００１０】まず、それに先立って本発明において達成
される特性についてに説明すると、孔拡げ性が均一であ
ることは、センタとエッジ部との孔拡げ率の差が18％以
下の場合をいい、このような差は通常平均で20〜25％程
度であることを考えれば、本発明の達成する効果が如何
に顕著であるかは十分に理解されよう。First, the characteristics achieved in the present invention will be described prior to that. The fact that the hole expandability is uniform means that the difference in hole expansion ratio between the center and the edge portion is 18% or less. Considering that such a difference is usually on the order of 20 to 25% on average, it is well understood that the effect achieved by the present invention is remarkable.
【００１１】本発明の対象とする鋼板は、通常自動車足
廻り部品用に使用され、バーリング加工によって目的製
品とするため、孔拡げ率の均一性は不可欠である。しか
も安価であるという要請もあるため、冷間圧延を行うこ
とことなく熱延鋼板として利用できるように成分調整を
するのである。[0011] The steel sheet which is the object of the present invention is usually used for undercarriage parts of automobiles and is made into a target product by burring. Therefore, uniformity of the hole expansion rate is indispensable. In addition, since there is a demand for inexpensiveness, the components are adjusted so that they can be used as hot-rolled steel sheets without performing cold rolling.
【００１２】(1) Ｃ：Ｃは鋼の成形加工性に対して悪影
響を及ぼす成分である。成形加工性の面からＣの含有量
は低い方が望ましいが、その含有量が0.03％未満では脱
炭にコストが掛かる上、Ar3 点が上昇すること、かつ、
スラブを幅方向に圧下するとスラブと圧下金型の接触に
よる抜熱が加工熱より大きくなることより、熱間圧延中
にエッジ部がAr3 点以下の温度になることがあり、その
結果鋼板の表裏面の組織が粗大化し成形性が著しく損な
われる。一方、0.12％超では材質が過剰に硬化し加工性
が劣化するようになることから、Ｃの含有量は0.03〜0.
12％と定めた。好ましくは、0.03〜0.10％である。(1) C: C is a component that adversely affects the formability of steel. It is desirable that the content of C is low from the viewpoint of moldability, but if the content is less than 0.03%, decarburization requires cost and increases the Ar 3 point, and
When the slab is reduced in the width direction, the heat removal due to the contact between the slab and the reduction mold becomes larger than the processing heat, so that the edge portion may reach a temperature of 3 points or less during hot rolling, and as a result, The structures on the front and back surfaces are coarsened, and the formability is significantly impaired. On the other hand, if it exceeds 0.12%, the material is excessively hardened and the workability deteriorates, so the C content is 0.03 to 0.3.
It was set at 12%. Preferably, it is 0.03 to 0.10%.
【００１３】(2) Mn：Mnは赤熱脆化を防止する観点から
0.1 ％以上添加する必要がある。しかし、1.0 ％超では
硬化し加工性が劣化するようになることからMnの含有量
の上限を1.0％と定めた。好ましくは、0.1 〜0.8 ％で
ある。(2) Mn: Mn is used from the viewpoint of preventing red heat embrittlement.
It is necessary to add 0.1% or more. However, if it exceeds 1.0%, it hardens and the workability deteriorates, so the upper limit of the Mn content is set to 1.0%. Preferably, it is 0.1-0.8%.
【００１４】(3) Si：Siは、脱酸成分として0.003 ％以
上が添加されるが、0.1 ％超では熱延鋼板の表面に島状
スケールが生成し、表面性状が悪化することから、Siの
含有量を0.1％以下と定めた。特に脱酸成分として添加
しない場合は、不純物として好ましくは、0.04％以下に
制限する。(3) Si: Si is added in an amount of 0.003% or more as a deoxidizing component. If it exceeds 0.1%, island scale is formed on the surface of the hot-rolled steel sheet, and the surface properties are deteriorated. Was determined to be 0.1% or less. Especially when not added as a deoxidizing component, it is preferably limited to 0.04% or less as an impurity.
【００１５】(4) Ｐ：Ｐは不純物として可及的に少なく
することが好ましく、特に偏析しやすい元素であるた
め、その含有量が0.035 ％超では加工性を劣化させるこ
とからＰの含有量を0.035 ％以下と定めた。好ましく
は、0.020 ％以下に制限する。(4) P: It is preferable to reduce P as an impurity as much as possible. Particularly, since P is an element which is easily segregated, if its content exceeds 0.035%, workability is deteriorated. Is set at 0.035% or less. Preferably, it is limited to 0.020% or less.
【００１６】(5) Ｓ：Ｓも不純物の一つであり、偏析し
やすくかつ、MnS を生成し加工性を劣化させるために極
力低減することが望ましいが、0.010 ％以下程度の範囲
で許容できる。好ましくは0.008 ％以下に制限する。(5) S: S is also one of the impurities, and it is desirable to reduce as much as possible in order to easily segregate and to form MnS and deteriorate the workability, but it is allowable within a range of about 0.010% or less. . Preferably, it is limited to 0.008% or less.
【００１７】(6) sol.Al：Alは脱酸作用により鋼の清浄
性を高めるが、0.005 ％未満ではその添加効果に乏し
く、一方、0.04％超ではかえって結晶粒の成長性を妨げ
加工性が劣化するため0.04％以下とした。好ましくは、
0.005 〜0.025 ％である。(6) sol.Al: Al enhances the cleanliness of the steel by deoxidation, but if it is less than 0.005%, the effect of its addition is poor. On the other hand, if it exceeds 0.04%, the growth of crystal grains is hindered rather than the workability. Is reduced to 0.04% or less. Preferably,
0.005 to 0.025%.
【００１８】(7) Cr：Crは炭化物を分散化させる効果が
認められる。また、炭化物を生成し固溶Ｃを減じ加工性
を向上させる。その添加効果は0.08％未満では発揮され
ず、一方、1.0 ％超では硬化が起こり加工性を劣化させ
ること、合金コストが高くなることから1.0 ％以下とし
た。好ましくは、0.1 〜0.4 ％である。(7) Cr: Cr has an effect of dispersing carbides. In addition, carbides are formed to reduce solid solution C and improve workability. If the addition effect is less than 0.08%, the effect is not exhibited. On the other hand, if it exceeds 1.0%, hardening occurs to deteriorate the workability and the alloy cost is increased, so that the content is set to 1.0% or less. Preferably, it is 0.1-0.4%.
【００１９】(8) スラブ幅方向圧下率 粗圧延前のスラブに圧下を加えることが、幅方向に均一
な加工性を持たせる上で特に効果的である。幅方向に均
一になるのは下記の〜の３つの作用の重畳効果と推
定される。(8) Reduction rate in slab width direction Applying a reduction to the slab before rough rolling is particularly effective in providing uniform workability in the width direction. The uniformity in the width direction is presumed to be the superimposition effect of the following three functions.
【００２０】スラブエッジ部のオーステナイトの細粒
化作用 粗圧延においてオーステナイトの再結晶温度以下の温度
域の圧下では変形帯が導入されるが、オーステナイトが
細粒化された場合、変形帯の均一性が良好となりこれが
集合組織のランダム化に寄与し加工性が向上するものと
考えられる。Austenite grain refinement at slab edge Deformation bands are introduced under roughening rolling at a temperature lower than the austenite recrystallization temperature, but when austenite is refined, the uniformity of the deformation bands is reduced. Is considered to be good, which contributes to the randomization of the texture and improves the workability.
【００２１】スラブエッジ部の温度低下防止作用 圧下による加工熱が発生し、その結果、エッジを加熱す
るのと同じ効果がありセンター部と温度履歴が近づくと
考えられる。The effect of preventing the temperature of the slab edge from lowering is generated, and as a result, the processing heat is generated due to the reduction, and as a result, it is considered that the same effect as the heating of the edge is obtained and the temperature history becomes closer to the center portion.
【００２２】スラブエッジ部のＣの拡散促進による偏
析抑制作用 ミクロ組織的に、炭化物が凝集している場合、その凝集
した炭化物とフェライトの界面に応力が集中しやすくな
り加工性が劣化してしまう。従って良好な加工性を得る
ためにはこの炭化物を微細に分散させることが有効な手
段となる。スラブ幅方向への圧下は少なからずＣの拡散
を促す効果があり、ひいては炭化物凝集化の抑制に寄与
し加工性を向上させると考えられる。Segregation Suppressing Effect by Promoting C Diffusion at Slab Edge When carbides are agglomerated microscopically, stress tends to concentrate on the interface between the agglomerated carbides and ferrite, thereby deteriorating workability. . Therefore, in order to obtain good workability, it is an effective means to finely disperse the carbide. It is considered that the reduction in the slab width direction has an effect of promoting the diffusion of C to some extent, and further contributes to the suppression of carbide agglomeration and improves the workability.
【００２３】上述のような効果は圧下量が10％未満では
発揮されず、35％超ではスラブと圧下金型の接触時間が
長くなり結果として、圧下により発生する加工熱より抜
熱の方が大きくなりエッジの温度が過度に低下し、後続
の熱間圧延中にエッジ部がAr3 点以下の温度になってし
まうことがある。好適圧下率は15〜25％である。The above-mentioned effects are not exhibited when the amount of reduction is less than 10%, and when it exceeds 35%, the contact time between the slab and the reduction die becomes longer, and as a result, the heat removal is more effective than the processing heat generated by the reduction. The temperature of the edge may be excessively lowered, and the temperature of the edge portion may be lower than the Ar 3 point or less during the subsequent hot rolling. The preferred reduction is 15 to 25%.
【００２４】(9) スラブ幅方向圧下後粗圧延開始までの
時間 45秒超ではオーステナイト粒の成長が生ずるため、上記
(8) のの細粒化作用が効かなくなるため、45秒以内と
した。(9) The time from the reduction in the slab width direction to the start of rough rolling exceeds 45 seconds, because austenite grains grow.
Since the grain refining action of (8) becomes ineffective, the time was set within 45 seconds.
【００２５】(10)仕上温度 熱間圧延の際に、Ar3 点より低い温度域で仕上げると組
織が加工フェライトとなり、得られる熱延鋼板の加工性
が著しく劣化することから仕上温度はAr3 点以上とし
た。好ましくはAr3 点超10〜50℃の温度範囲である。[0025] (10) finish in a temperature hot rolling, finish at a temperature range lower than the Ar 3 point and the tissue becomes deformed ferrite, temperature finish since the workability of hot-rolled to obtain steel sheet is remarkably deteriorated Ar 3 Scored. Preferably, the temperature is in the range of 10 to 50 ° C. exceeding the Ar 3 point.
【００２６】(11)巻取温度 巻取温度が400 ℃未満では残存した固溶炭素による延性
や歪み時効の劣化の恐れがある。また、550 ℃超では鋼
帯の幅方向、長手方向で冷却にムラが生じ易くなる。従
って、巻取温度を400 〜550 ℃と定めた。好ましくは42
0 〜500 ℃である。(11) Winding temperature If the winding temperature is lower than 400 ° C., there is a possibility that ductility and strain aging may be deteriorated due to remaining solid solution carbon. On the other hand, when the temperature exceeds 550 ° C., unevenness is likely to occur in cooling in the width and longitudinal directions of the steel strip. Therefore, the winding temperature was set at 400 to 550 ° C. Preferably 42
0-500 ° C.
【００２７】圧延後の冷却速度については特に定めない
が、炭化物を微細分散化させるには急冷が有利であり、
できるだけ冷却の前段主体で冷却することが望ましい。
次に、実施例により本発明の作用効果をさらに具体的に
説明する。The cooling rate after rolling is not particularly specified, but rapid cooling is advantageous for finely dispersing carbides.
It is desirable to perform cooling mainly in the former stage of cooling as much as possible.
Next, the operation and effect of the present invention will be described more specifically with reference to examples.
【００２８】[0028]
【実施例】表１に化学成分値 (レードル値wt％) を示す
本発明範囲の成分組成を有する鋼と本発明以外の成分組
成を有する鋼とについて表２中に表示の各々の熱延条件
で製造し熱延鋼板を得た。EXAMPLES The hot rolling conditions indicated in Table 2 for steel having a composition within the range of the present invention and steel having a composition other than the present invention, the chemical composition of which is shown in Table 1 (ladle value wt%). To obtain a hot-rolled steel sheet.
【００２９】得られた熱延鋼板についての各機械的特性
を表２に示した。但し、表２における引張試験はJIS 5
号試験片によって行った。表２の結果からわかるように
に本発明の範囲内でのみ目標とする特性が得られること
がわかる。Table 2 shows the mechanical properties of the obtained hot rolled steel sheet. However, the tensile test in Table 2 is based on JIS 5
No. test pieces were used. As can be seen from the results in Table 2, it is understood that the target characteristics can be obtained only within the range of the present invention.
【００３０】孔拡げ率は以下の式を用いて評価した。 孔拡げ率 (HEL)＝ (Ｄ−Ｄo ) ／Ｄo ×１００ （％） Ｄ：亀裂発生時の径、 Ｄo : 打抜き孔径The hole expansion rate was evaluated using the following equation. Hole expansion ratio (HEL) = (D−D o ) / D o × 100 (%) D: diameter at the time of crack occurrence, D o : punched hole diameter
【００３１】[0031]
【表１】 [Table 1]
【００３２】[0032]
【表２】 [Table 2]
【００３３】[0033]
【発明の効果】以上説明したように、本発明によれば孔
拡げ性が幅方向に均一である30〜45キロ級の熱延鋼板が
安価な手段で製造されるため、例えば、従来鋼板エッジ
側が孔拡げ加工を受けないように板取りを考慮していた
自動車足廻り部品用途において、板取りの制約がなくな
るようになり、その実用上の意義は大きい。As described above, according to the present invention, a 30 to 45 kg hot-rolled steel sheet having uniform hole expansion properties in the width direction can be manufactured by inexpensive means. In applications for car undercarriage parts, in which plate trimming is taken into consideration so that the side is not subjected to hole expanding processing, there is no longer any restriction on plate trimming, and its practical significance is great.
Claims (1)
以下、 Ｐ：0.035 ％以下、Ｓ：0.010 ％以下、sol.Al：0.005
〜0.04％、 Cr：0.08〜1.0 ％、 残部がFeおよび不可避不純物から成る鋼組成を有する鋼
スラブを粗圧延開始前に幅方向に10〜35％の圧下を加
え、幅方向への圧下開始後45秒以内に粗圧延を開始し、
Ar3 点以上で熱間圧延を終了し、その後400 〜550 ℃で
巻取ることを特徴とする孔拡げ性の均一性に優れた熱延
鋼板の製造方法。C. 0.03 to 0.12%, Mn: 0.1 to 1.0% or less, Si: 0.1% by weight%
P: 0.035% or less, S: 0.010% or less, sol. Al: 0.005
0.00.04%, Cr: 0.08 to 1.0%, balance of steel slab having a steel composition consisting of Fe and unavoidable impurities is reduced by 10 to 35% in the width direction before starting rough rolling, and after rolling in the width direction is started. Start rough rolling within 45 seconds,
A method for producing a hot-rolled steel sheet having excellent uniformity of hole expansion, wherein hot rolling is completed at three or more points of Ar, and thereafter, winding is performed at 400 to 550 ° C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7110592A JP3052780B2 (en) | 1995-05-09 | 1995-05-09 | Method for producing hot rolled steel sheet with excellent hole expansion uniformity |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7110592A JP3052780B2 (en) | 1995-05-09 | 1995-05-09 | Method for producing hot rolled steel sheet with excellent hole expansion uniformity |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08302426A JPH08302426A (en) | 1996-11-19 |
| JP3052780B2 true JP3052780B2 (en) | 2000-06-19 |
Family
ID=14539772
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7110592A Expired - Fee Related JP3052780B2 (en) | 1995-05-09 | 1995-05-09 | Method for producing hot rolled steel sheet with excellent hole expansion uniformity |
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| Country | Link |
|---|---|
| JP (1) | JP3052780B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP6720504B2 (en) * | 2015-11-06 | 2020-07-08 | 日本製鉄株式会社 | High-strength steel sheet and method of manufacturing the same |
| EP3575426A4 (en) * | 2017-01-27 | 2020-05-27 | Nippon Steel Corporation | Steel sheet and plated steel sheet |
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1995
- 1995-05-09 JP JP7110592A patent/JP3052780B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08302426A (en) | 1996-11-19 |
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