JPH08277423A - Production of austenitic stainless steel thin sheet excellent in surface quality - Google Patents
Production of austenitic stainless steel thin sheet excellent in surface qualityInfo
- Publication number
- JPH08277423A JPH08277423A JP7081473A JP8147395A JPH08277423A JP H08277423 A JPH08277423 A JP H08277423A JP 7081473 A JP7081473 A JP 7081473A JP 8147395 A JP8147395 A JP 8147395A JP H08277423 A JPH08277423 A JP H08277423A
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- Japan
- Prior art keywords
- rolling
- slab
- hot rolling
- stainless steel
- casting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Links
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- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Metal Rolling (AREA)
- Continuous Casting (AREA)
- Control Of Metal Rolling (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、鋳片と鋳型内壁面の間
に相対速度差のない、所謂双ロール法等の同期式連続鋳
造プロセスにおいて、表面品質の優れたオーステナイト
系ステンレス鋼薄板の製造方法に関するものである。BACKGROUND OF THE INVENTION The present invention relates to an austenitic stainless steel thin plate excellent in surface quality in a synchronous continuous casting process such as a so-called twin roll method in which there is no relative speed difference between a slab and a mold inner wall surface. The present invention relates to a manufacturing method.
【０００２】[0002]
【従来の技術】同期式連続鋳造プロセスとは、例えば
「鉄と鋼」’８５−Ａ１９７〜Ａ２５６に特集された論
文に紹介されているような、双ロール法、双ベルト法、
単ロール法等、鋳片と鋳型内壁面の間に相対速度差のな
い同期式連続鋳造プロセスである。これら同期式連続鋳
造プロセスの一つである双ロール式連続鋳造法は、平行
または傾斜配置した一対の同径あるいは異径冷却ドラム
とその両端面をシールするサイド堰とによって構成され
た連続鋳造鋳型内に溶鋼を注入し、両冷却ドラムの周面
上にそれぞれ凝固殻を生成させ、回転する両冷却ドラム
の最接近位置（所謂「キッシングポイント」）付近で凝
固殻同士を合体させて一体の薄帯状鋳片とする連続鋳造
法である。2. Description of the Related Art Synchronous continuous casting processes include twin roll method, twin belt method, as described in, for example, a paper featured in "Iron and Steel"'85 -A197 to A256.
It is a synchronous continuous casting process such as a single roll method in which there is no relative speed difference between the slab and the inner wall surface of the mold. The twin-roll continuous casting method, which is one of these synchronous continuous casting processes, is a continuous casting mold composed of a pair of parallel or inclined cooling drums of the same or different diameter and side dams that seal both end surfaces of the cooling drums. Molten steel is poured into the inside of the two cooling drums to form solidified shells on the peripheral surfaces of both cooling drums. It is a continuous casting method for forming strip cast pieces.
【０００３】例えば、双ロール式連続鋳造法により鋳造
される薄帯状鋳片は、厚さ数mm（通常２〜５mm程度）で
あり、従来の熱間圧延を経ずに冷間圧延を行って薄板製
品を製造することができる。そのため、振動鋳型等を用
いる連続鋳造により厚さ１００mm超の熱間圧延用スラブ
を鋳造し、これを熱間圧延してから冷間圧延する従来の
製造方法（スラブ鋳造−熱間圧延プロセス）に比べて、
生産効率およびコストが格段に有利となる。For example, a thin strip slab cast by a twin roll type continuous casting method has a thickness of several mm (usually about 2 to 5 mm), and is cold-rolled without the conventional hot rolling. Thin sheet products can be manufactured. Therefore, the conventional manufacturing method (slab casting-hot rolling process) in which a hot-rolling slab having a thickness of more than 100 mm is cast by continuous casting using a vibration mold or the like, hot-rolled and then cold-rolled Compared to,
The production efficiency and cost will be significantly improved.
【０００４】しかし、双ロール式連続鋳造法等により鋳
造した薄帯状鋳片を熱間圧延を経ずに冷間圧延した製品
には、種々の表面欠陥が発生する場合がある。例えば、
特開平２−１９４２６号公報に述べられているように、
冷間圧延後の表面に鋳片の粗大な結晶粒が原因するロー
ピング（表面肌荒れ）が発生する。また、鋳造割れ等を
安定的に防止するために冷却ドラム周面にディンプルを
形成させた双ロール式連続鋳造法等で製造された製品に
は、特開平４−１５８９５７号公報に述べられているよ
うに、鋳造組織のδフェライト残存むらに対応する最終
焼鈍後の粗粒・細粒組織が色調むらとなる光沢むらが発
生する。However, various surface defects may occur in a product obtained by cold-rolling a thin strip-shaped slab cast by a twin roll type continuous casting method or the like without hot rolling. For example,
As described in JP-A-2-19426,
Roping (rough surface) caused by coarse crystal grains of the slab occurs on the surface after cold rolling. Further, a product manufactured by a twin roll type continuous casting method or the like in which dimples are formed on the peripheral surface of the cooling drum in order to stably prevent casting cracks and the like, is described in JP-A-4-158957. As described above, uneven glossiness, which is uneven in color tone, occurs in the coarse-grained / fine-grained structure after the final annealing, which corresponds to the residual unevenness of δ ferrite in the cast structure.
【０００５】これらの課題の内、ローピング対策とし
て、特開平３−７１９０２号公報に鋳片を圧延率（％）
≧８．５１×１０-3×圧延温度（℃）＋４．７９を満た
す条件で直接熱間圧延した後、焼鈍−冷間圧延−最終焼
鈍を施すことによってローピングを防止することが提案
されている。しかしながら、鋳造割れを防止する目的で
冷却ドラム周面に配置されたディンプルが鋳片に転写さ
れ、熱間圧延時に凹部に倒れ込む疵、あるいは熱延ロー
ルのヒートクラックによるロール肌荒れが鋳片表面へ転
写された疵、さらには熱延ロールにビルドアップしたス
ケールの熱間圧延時の噛込み疵等が発生し、これらは形
態の違いはあるものの冷延板製品に微小なヘゲ状疵とな
って残存し、表面品質を著しく損ねる。このように、熱
間圧延を付加させた双ロール鋳造プロセスは、ローピン
グを改善する反面、冷延製品表面に疵が発生しやすくな
ると言う問題があった。Among these problems, as a countermeasure for roping, the rolling ratio (%) of a cast piece is disclosed in Japanese Patent Laid-Open No. 3-71902.
It has been proposed to prevent roping by directly performing hot rolling under conditions satisfying ≧ 8.51 × 10 −3 × rolling temperature (° C.) + 4.79 and then performing annealing-cold rolling-final annealing. . However, dimples arranged on the peripheral surface of the cooling drum are transferred to the slab for the purpose of preventing casting cracks, and defects that fall into recesses during hot rolling or roll surface roughness due to heat cracks of hot rolling rolls are transferred to the slab surface. Defects, and further, biting defects during hot rolling of the scale built up on the hot rolling rolls, etc. It remains and significantly deteriorates the surface quality. As described above, the twin roll casting process to which hot rolling is added has a problem that defects are likely to occur on the surface of the cold rolled product while improving the roping.
【０００６】また、光沢むら対策として、特開平４−１
５８９５７号公報では冷却ドラム周面に設けたディンプ
ルすべての隣接間隔を０．３５mm以下とすることで、デ
ィンプル凹凸に対応する不均一冷却を緩和して凝固組織
を均一化するとともに、δ−Ｆｅcal.（％）を５〜９％
に調整することで、凝固組織むら感受性を下げる方法が
提案されている。しかし、所定のディンプルを加工する
ための方法が高価なフォトエッチ法等に限定され、安価
なショットブラスト等の加工方法を用いることが出来
ず、不慮のトラブルに備えて冷却ドラムの予備を多く持
つことが必要となり、経済的でなく、品質的にもδ−Ｆ
ｅcal.の成分規定のみでは安定した凝固組織を得ること
ができなかった。As a measure against uneven gloss, Japanese Patent Laid-Open No. 4-1 is used.
In Japanese Patent No. 58957, by setting the adjacency of all the dimples provided on the peripheral surface of the cooling drum to 0.35 mm or less, uneven cooling corresponding to the dimple irregularities is alleviated and the solidified structure is made uniform, and δ-Fe cal . (%) of 5-9%
A method of reducing the sensitivity to unevenness of coagulation tissue by adjusting the amount to 1 has been proposed. However, the method for processing the predetermined dimples is limited to the expensive photo-etching method and the like, and the inexpensive processing methods such as shot blasting cannot be used, and there are many spares for the cooling drum in case of unexpected trouble. Is necessary, and it is not economical and δ-F in terms of quality.
It was not possible to obtain a stable coagulated tissue only by defining the components of e cal .
【０００７】以上のように、従来技術には表面疵、ロー
ピングおよび光沢むらの課題を同時に解決する手段につ
いて何ら開示されていない。As described above, the prior art does not disclose any means for simultaneously solving the problems of surface defects, roping, and uneven gloss.
【０００８】[0008]
【発明が解決しようとする課題】本発明は、冷却ドラム
周面にディンプルを形成させた双ロール法等の所謂同期
式連続鋳造プロセスにおいて、特定の成分と鋳造後の熱
間圧延と冷間圧延の合計圧延率を所要の条件範囲とする
ことによって、表面疵、ローピングおよび光沢むらを同
時に改善した表面品質の優れたオーステナイト系ステン
レス鋼薄板の製造方法を提供することを目的とする。DISCLOSURE OF THE INVENTION The present invention, in a so-called synchronous continuous casting process such as a twin roll method in which dimples are formed on the peripheral surface of a cooling drum, has specific components and hot rolling and cold rolling after casting. It is an object of the present invention to provide a method for producing an austenitic stainless steel sheet having excellent surface quality in which surface defects, roping, and uneven gloss are simultaneously improved by setting the total rolling ratio of the above in the required condition range.
【０００９】[0009]
【課題を解決するための手段】上記課題を解決するため
に、本発明は以下の手段によって構成される。ショット
ブラスト法によってランダムなディンプルを多数散在さ
せた冷却ドラムの周面に同期して鋳片が移動する連続鋳
造機により、オーステナイト系ステンレス鋼薄帯状鋳片
を鋳造する製造方法において、重量％で、Ｃｒ＋Ｍｏ＋
１．５Ｓｉで定義されるＣｒ当量とＮｉ＋３０（Ｃ＋
Ｎ）＋０．５（Ｍｎ＋Ｃｕ）で定義されるＮｉ当量が下
記（１）式を満足する成分組成とし、鋳造に続いて圧延
率１５％以下の１パス熱間圧延を行い、続いて水冷後６
００℃以下で巻き取って薄帯状鋳片とし、続いて該薄帯
状鋳片をデスケーリングし、続いて前記熱間圧延におけ
る圧延率との累積圧下率が２５〜４０％となる圧延率で
１パスの冷間圧延を行い、必要に応じて中間の焼鈍・冷
間圧延を行い、続いて焼鈍・酸洗または光揮焼鈍を行う
ことを特徴とする表面品質の優れたオーステナイト系ス
テンレス鋼薄板の製造方法。In order to solve the above problems, the present invention comprises the following means. By a continuous casting machine in which the slab moves in synchronization with the peripheral surface of the cooling drum in which a large number of random dimples are scattered by the shot blast method, a manufacturing method for casting an austenitic stainless steel thin strip slab, in weight%, Cr + Mo +
Cr equivalent defined by 1.5Si and Ni + 30 (C +
N) +0.5 (Mn + Cu), and the equivalent weight of Ni satisfies the following formula (1). Casting is followed by 1-pass hot rolling with a rolling reduction of 15% or less, followed by water cooling.
The strip-shaped slab is wound up at a temperature of 00 ° C. or less to subsequently descale the strip-shaped slab, and then the rolling reduction in the hot rolling is 25 to 40%, and the rolling reduction is 1 to 1. Austenitic stainless steel sheet with excellent surface quality characterized by cold rolling in a pass, intermediate annealing / cold rolling if necessary, followed by annealing / pickling or light volatility annealing. Production method.
【００１０】 Ｎｉ当量≦０．６３×Ｃｒ当量−１．２９ ………（１）Ni equivalent ≦ 0.63 × Cr equivalent−1.29 (1)
【００１１】[0011]
【作用】本発明者らはオーステナイト系ステンレス鋼を
双ロール鋳造等によって鋳造して得た急冷凝固組織まま
の鋳片を直接冷間圧延するときに発生するローピング現
象を詳細に解析した。その結果、ローピングの程度は冷
間圧延前の結晶粒径の大小に依存することを突き止め
た。結晶粒径の大小の評価については、従来から便宜的
に用いられている結晶粒の個数頻度の期待値として定義
するＤn （＝Σ２×ＳＱＲ（３×Ｓi ／２π）／ｎ）が
急冷凝固組織およびそれを圧延−熱処理した再結晶組織
においては、それらの混粒状態を代表する指標値とは成
りえないことが分かり、結晶粒の面積率（実際には体積
率を考える必要があるが、体積を実測することは不可能
であり、便宜上面積率をもって体積率とする）に対する
期待値であるＤave （＝Σ２×ＳＱＲ（３×Ｓi ／２
π）×Ｓi ／Ｓ）を新たな指標値として定義した。The present inventors have made a detailed analysis of the roping phenomenon that occurs when a slab obtained by casting austenitic stainless steel by twin roll casting or the like, which has a rapidly solidified structure, is directly cold-rolled. As a result, it was found that the degree of roping depends on the size of the crystal grain size before cold rolling. Regarding the evaluation of the crystal grain size, D n (= Σ2 × SQR (3 × S i / 2π) / n), which is conventionally used for convenience and is defined as the expected value of the number frequency of crystal grains, is rapidly cooled. It was found that the solidified structure and the recrystallized structure obtained by rolling and heat treating it cannot be the index value representing the mixed grain state, and it is necessary to consider the area ratio of crystal grains (actually it is necessary to consider the volume ratio). However, it is impossible to actually measure the volume, and for the sake of convenience, an area ratio is an expected value for D ave (= Σ2 × SQR (3 × S i / 2)
π) × S i / S) was defined as a new index value.
【００１２】当然のことながら、従来指標のＤn は結晶
粒の個数頻度の期待値であるため、混粒組織では細粒側
に平均値が現れる。しかしながら、ローピング現象は一
つ一つの結晶粒、あるいは粗大粒と細粒コロニー（群）
の存在に応じた板厚方向の変形差の総和が表面に現出す
る現象と理解され、等軸かつ細粒ほど板厚方向の累積変
形差が平均化され、ローピングは良好となる。したがっ
て、非常に粒径差の大きい混粒組織における平均結晶粒
径の定義は面積率に対する期待値であるＤaveによって
表現することが、組織の実態を表した指標となる。事
実、本発明者らは、双ロール鋳造材を２０〜４０％の圧
延率で熱間圧延した後の再結晶組織は現行ＣＣスラブ−
熱間圧延材ほど等軸粒ではなく、表層が細粒で中心部は
粗粒傾向となることや、さらに、隣接する結晶粒とはか
け離れた粗大粒が出現することがあり、このような粗大
粒は再結晶しても隣接する粒よりも大きいか、甚だしい
場合は未再結晶として残存した混粒組織となり、ローピ
ングの改善が不十分であることを観察している。As a matter of course, since the conventional index D n is an expected value of the number frequency of crystal grains, an average value appears on the fine grain side in the mixed grain structure. However, the roping phenomenon is caused by individual crystal grains, or coarse and fine grain colonies (groups).
It is understood that the sum of the deformation differences in the plate thickness direction according to the presence of the is manifested on the surface, and the more equiaxed and finer the particles are, the more the accumulated deformation differences in the plate thickness direction are averaged, and the better the roping is. Therefore, the definition of the average crystal grain size in a mixed grain structure with a very large difference in grain size is expressed by D ave which is an expected value for the area ratio, which is an index representing the actual state of the structure. In fact, the present inventors have found that the recrystallization structure after hot rolling the twin roll cast material at a rolling rate of 20 to 40% is the current CC slab-
Rather than equiaxed grains as in the hot-rolled material, the surface layer may have fine grains and the central portion tends to have coarse grains.In addition, coarse grains that are far from adjacent crystal grains may appear. It has been observed that the grains are larger than the adjacent grains even if recrystallized, or if they are extremely large, they have a mixed grain structure that remains as unrecrystallized, and the improvement of roping is insufficient.
【００１３】以上から本発明者らは、等軸粒の場合はＤ
n に近い値になり、混粒の場合はその程度に応じてＤn
からの乖離が大きくなり、ローピングに有害な粗大粒の
影響が正しく反映できる指標値として平均粒径Ｄave を
定義した。この定義で規定される再結晶粒径Ｄave を７
０μｍ以下に確保すれば、ローピングランク（１〜５ラ
ンクの官能評価）が２以下の合格レベルとすることがで
きる（表２参照）。From the above, the present inventors have found that in the case of equiaxed grains, D
It becomes a value close to n , and in the case of mixed particles, D n
The average particle diameter D ave was defined as an index value that can accurately reflect the influence of coarse particles that are harmful to roping. The recrystallized grain size D ave defined by this definition is 7
If it is ensured to be 0 μm or less, the roping rank (sensory evaluation of 1 to 5 ranks) can be a pass level of 2 or less (see Table 2).
【００１４】ローピングを防止するには、凝固組織をで
きるだけ等軸かつ細粒化することが必要であり、圧延−
熱処理による再結晶を利用することが有効な方法であ
る。熱間圧延による再結晶を利用するには、鋳片の初期
粒径に対応した熱延率を確保する必要があり、本発明者
らが検討した結果では、引き続く熱処理条件にも依存す
るが、約２０〜４０％の熱間圧延率を確保する必要があ
る。しかしながら、２０％以上の熱間圧延を１パス圧延
で行うと、鋳造割れを防止する目的で冷却ドラム周面に
設けたディンプルの鋳片への転写部が熱間圧延時に倒れ
込む疵、あるいは熱延ロールのヒートクラックによるロ
ール肌荒れが鋳片表面へ転写された疵、さらには圧延ロ
ールにビルドアップしたスケールの噛込み疵等が発生す
る問題があり、冷間圧延前のコイルグラインダー等の機
械的研削を省略した場合に、表面疵のない冷延板を製造
することが困難である。そこで、本発明では鋳造機に直
結した熱間圧延機により軽度な熱間圧延を行い、デスケ
ーリングに引き続いて軽度な冷間圧延を実施することで
圧延疵の発生を防止し、その後の焼鈍によって再結晶組
織を得ることでローピングを防止することを同時に達成
する手段を主要件としている。In order to prevent roping, it is necessary to make the solidified structure equiaxed and fine-grained as much as possible.
Utilizing recrystallization by heat treatment is an effective method. In order to utilize the recrystallization by hot rolling, it is necessary to secure a hot rolling rate corresponding to the initial grain size of the slab, and the results of the present inventors' investigations also depend on the subsequent heat treatment conditions, It is necessary to secure a hot rolling rate of about 20-40%. However, if hot rolling of 20% or more is performed by one-pass rolling, the dimples transferred to the slab on the peripheral surface of the cooling drum for the purpose of preventing casting cracks may be damaged during hot rolling, or may be hot rolled. There is a problem that roll roughness caused by heat crack of the roll is transferred to the surface of the slab, and further, build-up scale scratches on the rolling roll occur, and mechanical grinding of coil grinder etc. before cold rolling. When is omitted, it is difficult to manufacture a cold-rolled sheet without surface flaws. Therefore, in the present invention, a mild hot rolling is performed by a hot rolling mill directly connected to a casting machine, the occurrence of rolling flaws is prevented by performing a mild cold rolling following the descaling, and the subsequent annealing is performed. The main subject is to simultaneously achieve the prevention of roping by obtaining a recrystallized structure.
【００１５】熱間圧延による表面疵発生の機構について
は次のように考えられる。圧延油を用いない熱間圧延で
は表層の歪が圧延油を用いる冷間圧延よりも大きく、圧
延率の影響がより大きくなると考えられる。図１に山田
他；Ｓ６１年塑性加工春期講演論文集、Ｐ２３５に発表
されている剛塑性有限要素法による非対称圧延の解析モ
デルを用いて計算した板厚方向の相当歪（剪断歪＋圧縮
歪で表層ほど剪断歪が大きくなる）分布におよぼす圧延
率の影響を示す（ここで、ロール径：φ６５０／３７５
mm、下駆動、摩擦係数：上下とも０．３、入板厚：３．
０mmである）。同図から、圧延率とともに表層／中心の
相当歪の比は大きくなることがモデル計算から検証され
ている。The mechanism of surface flaw generation due to hot rolling is considered as follows. It is considered that in the hot rolling without using rolling oil, the strain in the surface layer is larger than that in the cold rolling with rolling oil, and the influence of the rolling rate becomes larger. Fig. 1 Yamada et al .; Equivalent strain (shear strain + compressive strain) in the plate thickness direction calculated using the analysis model of asymmetric rolling by the rigid-plastic finite element method published in P235, S61 Spring Working Session The influence of the rolling ratio on the distribution in which the shear strain increases as the surface layer increases (here, roll diameter: φ650 / 375)
mm, downward drive, friction coefficient: 0.3 at both top and bottom, entry plate thickness: 3.
0 mm). From the figure, it is verified from the model calculation that the ratio of the equivalent strain of the surface layer / center increases with the rolling rate.
【００１６】本発明者らは、圧延によるこのような現象
が、ディンプル転写部の倒れ込み疵、ロール肌荒れの転
写・倒れ込み疵、さらにはスケール噛込み疵に影響して
いるとの考えから、特に、表層での相当歪、即ち剪断歪
が大きい熱間圧延での圧延率の上限を明らかにした。そ
の結果、上記熱間圧延疵の発生を完全に防止するには、
熱圧延率を１５％以下に制限する必要があることを見い
出した。The inventors of the present invention have considered that such a phenomenon due to rolling has an influence on the falling flaws of the dimple transfer portion, the transfer / falling flaws of the rough surface of the roll, and the scale biting flaws. The upper limit of the rolling ratio in hot rolling with a large equivalent strain in the surface layer, that is, a large shear strain was clarified. As a result, in order to completely prevent the occurrence of the hot rolling flaw,
It has been found that it is necessary to limit the hot rolling rate to 15% or less.
【００１７】しかしながら、１５％以下の熱延率ではそ
の後の熱処理によって再結晶組織を得るための歪量とし
ては十分でない。この対策として、本発明では熱間圧延
後直ちに水冷して巻き取り、可能な限り熱間圧延時の加
工歪を凍結維持し、さらに冷間圧延で加工歪を補填して
再結晶に必要なエネルギーを確保した後、焼鈍によって
完全な再結晶組織を得る方法を提案するものである。冷
間圧延時の冷延率は熱間圧延時よりも上限の圧延率が大
きくても圧延による倒れ込み現象は発生しにくいが、冷
間での変形抵抗や圧延形状の安定化を考慮すると１パス
圧延で２５％以上が望ましく、また再結晶に必要な歪量
を確保するには熱間圧延との累積圧延率で２５〜４０％
確保されていれば十分である。なお、累積圧延率が４０
％以上ではローピングへの改善効果が飽和し、かつ熱間
圧延と冷間圧延のそれぞれの上限圧延率からも４０％が
上限となる。However, a hot rolling ratio of 15% or less is not sufficient as the amount of strain for obtaining a recrystallized structure by the subsequent heat treatment. As a countermeasure against this, in the present invention, water cooling is immediately performed after hot rolling and winding is performed, and the processing strain during hot rolling is frozen and maintained as much as possible, and the energy required for recrystallization is compensated for by the cold rolling. After securing the above, a method for obtaining a complete recrystallized structure by annealing is proposed. The cold rolling ratio during cold rolling is less likely to cause the collapse phenomenon due to rolling even if the upper limit rolling ratio is higher than during hot rolling, but considering the deformation resistance during cold rolling and the stabilization of the rolled shape, 1 pass 25% or more is desirable in rolling, and in order to secure the strain amount necessary for recrystallization, the cumulative rolling rate with hot rolling is 25 to 40%.
It is enough if it is secured. The cumulative rolling rate is 40
% Or more, the improvement effect on roping is saturated, and 40% is the upper limit from the respective upper limit rolling rates of hot rolling and cold rolling.
【００１８】次に、光沢むらについて述べる。双ロール
法等の連続鋳造法において、冷却ドラム周面にディンプ
ルをランダムに散在させる目的は、エヤーギャップによ
って緩冷された未だ剛性の低い状態にある部分（ディン
プル中央部）を、冷却ドラムと直接接触することによっ
て十分に冷却された剛性の高い部分（ディンプルエッジ
部）が取り囲むことによって生じる熱応力をディンプル
の分散によって小さくし、かつ凝固シェルの収縮に伴う
割れが複数の剛性低下部にまたがって発生することを防
止することである。しかしながら、このディンプルの形
成によって生じる不均一冷却が表層の凝固組織の均一性
の面からは悪影響し、ディンプル凹凸に対応した残留δ
フェライトのむらが発生する。この残留δフェライトむ
らの発生は、オーステナイト系ステンレス鋼特有の現象
である。Next, uneven gloss will be described. In the continuous casting method such as the twin roll method, the purpose of randomly distributing the dimples on the peripheral surface of the cooling drum is to directly cool the part (dimple center part) which is still cooled by the air gap and has low rigidity. The thermal stress generated by surrounding a highly rigid part (dimple edge part) that is sufficiently cooled by contacting is reduced by dimple dispersion, and cracks due to shrinkage of the solidified shell are spread over multiple reduced rigidity parts. It is to prevent it from occurring. However, the uneven cooling caused by the formation of the dimples adversely affects the uniformity of the solidified structure of the surface layer, and the residual δ corresponding to the dimple unevenness is generated.
Irregularity of ferrite occurs. The occurrence of the residual δ-ferrite unevenness is a phenomenon peculiar to austenitic stainless steel.
【００１９】本発明者らは、ショットブラスト法によっ
てディンプル間隔、大きさ等を規制することなくランダ
ムな配置のディンプルを冷却ドラム周面に形成させたド
ラムを用いた双ロール鋳造機から、種々の成分に調整し
たオーステナイト系ステンレス鋼を鋳造し、鋳片の凝固
組織および冷延後の光沢むらを評価した。その結果を図
２に示す。重量％で、Ｃｒ＋Ｍｏ＋１．５Ｓｉで定義さ
れるＣｒ当量とＮｉ＋３０（Ｃ＋Ｎ）＋０．５（Ｍｎ＋
Ｃｕ）で定義されるＮｉ当量の関係において、Ｎｉ当量
≦０．６３Ｃｒ当量−１．２９を満足する成分限定によ
って、鋳片の凝固形態はＦモード凝固となり、冷延板に
も残存δフェライト起因の光沢むらはまったく発生しな
かった。The inventors of the present invention have developed various twin roll casting machines using a drum in which dimples having random arrangement are formed on the cooling drum peripheral surface without regulating the dimple spacing, size, etc. by the shot blast method. Austenitic stainless steel adjusted to the composition was cast, and the solidification structure of the slab and the uneven gloss after cold rolling were evaluated. The result is shown in FIG. In weight%, Cr equivalent defined by Cr + Mo + 1.5Si and Ni + 30 (C + N) +0.5 (Mn +
In the relationship of Ni equivalent defined by Cu), due to the component limitation satisfying Ni equivalent ≦ 0.63 Cr equivalent−1.29, the solidification morphology of the slab becomes F mode solidification, and the residual δ ferrite is also caused in the cold rolled sheet. No gloss unevenness occurred.
【００２０】本発明者らは、δフェライト起因の光沢む
らは、凝固時のδ＋γ相の共晶組織で発生するバーミキ
ュラーδよりもδ単相で完全凝固し、γに変態した場合
に発生するアシュキュラー状δは凝固組織の残留フェラ
イトむらが軽減されることを多くの双ロール鋳造剤の凝
固組織観察から見い出しているが、従来知見からはディ
ンプル間隔を小さくすることが必要であった。しかし、
ショットディンプルの場合、ディンプル間隔が必ずしも
必要十分条件ではないことが明らかになった。この理由
は、図３に示すように、以下のように考えられる。The present inventors have found that the gloss unevenness caused by δ ferrite is completely solidified in δ single phase rather than vermicular δ generated in the eutectic structure of δ + γ phase at the time of solidification, and ash generated when transformed into γ. It has been found from observation of the solidification structure of many twin roll casting agents that the residual ferrite unevenness of the solidification structure is reduced in the curular δ, but it was necessary to reduce the dimple spacing from the conventional knowledge. But,
In the case of shot dimples, it became clear that the dimple spacing is not always a necessary and sufficient condition. The reason for this is considered as follows, as shown in FIG.
【００２１】フォトエッチ加工図３（ａ）のディンプル
エッジはほぼ直角であることから表面張力によってディ
ンプル中央部まで溶鋼が入らず、その部分のエアギャッ
プ層が厚くなるのに対して、ショット加工で形成された
ディンプル図３（ｂ）はエッジの傾斜が緩やかなため、
エッジ部の傾斜に沿って溶鋼がディンプル中央部まで入
る結果、エアギャップ層が薄く、ディンプル中央部とデ
ィンプルとディンプルの間の部分の凝固冷速差が軽減さ
れる。さらに、ショットディンプルでは大きなディンプ
ルの中に小さなディンプルが存在し、冷却ドラムとの直
接接触が面から点へと変化する効果がディンプルの各部
位における凝固冷速差を分散させる。これらの効果が、
フォトエッチディンプルで言うところのディンプル間隔
を狭くすることの作用を少なからず代替し、特定の成分
を限定するのみで実質上製品の光沢むらが改善されるも
のとみられる。Photo-etching process Since the dimple edge in FIG. 3 (a) is almost right angle, the molten steel does not enter the dimple center part due to the surface tension, and the air gap layer in that part becomes thicker. The formed dimples in FIG. 3B have a gentle edge,
As a result of the molten steel entering the dimple center along the inclination of the edge portion, the air gap layer is thin, and the solidification cold speed difference between the dimple center and the portions between the dimples is reduced. Further, in the shot dimple, small dimples are present in large dimples, and the effect of direct contact with the cooling drum changing from surface to point disperses the solidification cold speed difference in each part of the dimple. These effects
It is considered that the effect of narrowing the dimple spacing, which is the so-called photo-etched dimple, is substituted to some extent, and the unevenness of gloss of the product is substantially improved only by limiting the specific components.
【００２２】なお、巻取り温度を６００℃以下に限定し
た理由は、鋭敏化による酸洗時のミクロブルーブ（結晶
粒界に沿った腐食溝）が冷間圧延後に網目模様として残
存し、冷延板表面の光沢が低下することを防止するため
である。但し、コイルグラインダー等の機械的研削を実
施すれば問題はないが、この工程を省略するためには、
鋳造時あるいは中間焼鈍時の鋭敏化を防止する必要があ
る。The reason why the winding temperature is limited to 600 ° C. or lower is that the micro-blobs (corrosion grooves along the crystal grain boundaries) during pickling due to sensitization remain as a mesh pattern after cold rolling, This is to prevent the gloss of the surface of the rolled sheet from decreasing. However, there is no problem if mechanical grinding such as a coil grinder is performed, but in order to omit this step,
It is necessary to prevent sensitization during casting or during intermediate annealing.
【００２３】本発明は、フォトエッチ加工法等によら
ず、ディンプル加工および補修等が容易であるショット
ブラスト法による冷却ドラムのディンプル形成ととも
に、成分を特定の範囲に限定することによってδフェラ
イトの残存むらが緩和された良好な凝固組織が得られ、
光沢むらが防止される。また、鋳造機に直結した熱間圧
延機により軽度な熱間圧延を行い、直ちに水冷し、巻取
り後デスケーリングし、引き続いて軽度な冷間圧延によ
る補填を行って焼鈍することで、圧延疵を防止し、かつ
十分な再結晶組織を得ることでローピングが防止され
る。The present invention forms dimples on the cooling drum by the shot blasting method, which facilitates dimple processing and repair, without relying on the photoetching method or the like, and at the same time limits the components to a specific range so that the δ ferrite remains. A good solidified structure with less unevenness is obtained,
Uneven gloss is prevented. In addition, a hot rolling mill directly connected to the casting machine performs light hot rolling, immediately water cooling, descaling after winding, followed by light cold rolling compensation and annealing, which results in a rolling defect. And the sufficient recrystallized structure is obtained to prevent roping.
【００２４】[0024]
【実施例】表１および２に示すオーステナイト系ステン
レス鋼を、ショットブラスト法によりランダムな配置の
ディンプルを冷却ドラム周面に形成させた双ロール鋳造
機で、鋳造厚３〜５mm鋳造し、約１０００〜１２００℃
の温度範囲で鋳造機後面に配置した２Ｈｉの熱間圧延機
により３５％以下の１パス圧延を行い、直ちに水冷して
６００℃以下で巻取ることにより薄帯状鋳片を製造し
た。EXAMPLE Austenitic stainless steels shown in Tables 1 and 2 were cast at a casting thickness of 3 to 5 mm by a twin roll casting machine in which randomly arranged dimples were formed on the peripheral surface of a cooling drum by a shot blasting method, and cast to a thickness of about 1000 mm. ~ 1200 ° C
A single pass rolling of 35% or less was carried out by a 2Hi hot rolling mill arranged on the rear surface of the casting machine in the temperature range of 1, and immediately water-cooled and wound at 600 ° C or less to produce a strip-shaped slab.
【００２５】[0025]
【表１】 [Table 1]
【００２６】[0026]
【表２】 [Table 2]
【００２７】圧延率は途中ででミル圧下力を変化させる
こと、および事前に冷却ドラムから圧延機の間に設置さ
れた保温カバーの断熱材を調整して鋳造速度との関連で
圧延温度を変化させる組み合わせによって上記範囲に調
整した。なお、圧延温度は圧延率の影響が小さいことか
ら、チャージ間の平均値を採用して示した。その後、冷
間圧延によって圧延率を補填し、焼鈍によって再結晶さ
せ、冷間圧延を行い、最終焼鈍・酸洗仕上げと光輝焼鈍
仕上げとした。The rolling rate is changed on the way to change the mill rolling force, and the rolling temperature is changed in relation to the casting speed by adjusting the heat insulating material of the heat insulating cover installed between the cooling drum and the rolling mill in advance. The above range was adjusted depending on the combination. Since the rolling temperature is less affected by the rolling ratio, the average value between charges is used. After that, the rolling rate was compensated by cold rolling, recrystallization was performed by annealing, and cold rolling was performed to obtain final annealing / pickling finish and bright annealing finish.
【００２８】品質評価として鋳片の凝固モード、熱間圧
延と冷間圧延の累積圧延後の焼鈍によって得られた再結
晶粒径Ｄave を中間指標として調査し、光輝焼鈍材のロ
ーピングと最終焼鈍、酸洗材の光沢むらおよび表面疵状
況をそれぞれ官能評価した。その結果を表３および４に
示す。As a quality evaluation, the solidification mode of the slab and the recrystallized grain size D ave obtained by annealing after cumulative rolling of hot rolling and cold rolling were investigated as an intermediate index, and roping and final annealing of the bright annealed material were conducted. , The uneven glossiness of the pickling material and the surface flaw condition were sensory evaluated. The results are shown in Tables 3 and 4.
【００２９】[0029]
【表３】 [Table 3]
【００３０】[0030]
【表４】 [Table 4]
【００３１】本発明による製造方法（No. １〜No. １
３）によって得られたものは、ローピングランクが２以
下でローピングは合格であった。また、光沢むらも表面
疵の発生もない良好な表面品質を示した。一方、比較例
No. １４〜２１は凝固モードがＦで冷延板の光沢むらは
良好であったが、累積圧延率が不足してローピングが不
合格となったもの（比較例No. １４）や熱延率が１５％
超で実施したため、冷延板にヘゲ状の表面疵が散発し、
ローピング自身は合格レベルであったが総合的な表面品
質としては不合格となった（比較例No. １５〜２１）。
また、比較例No. ２２は累積圧延率の不足および成分外
れによってローピングと光沢むらが発生し、不合格とな
った。Manufacturing method according to the present invention (No. 1 to No. 1
The product obtained in 3) had a roping rank of 2 or less and passed the roping. In addition, it showed good surface quality with neither uneven gloss nor surface defects. On the other hand, a comparative example
In Nos. 14 to 21, the solidification mode was F and the gloss unevenness of the cold rolled sheet was good, but the cumulative rolling rate was insufficient and roping failed (Comparative Example No. 14) and hot rolling rate. Is 15%
Since it was carried out at a temperature over the surface of the cold-rolled sheet, there were scattered bald surface defects.
Although the roping itself was at a passing level, it failed as a comprehensive surface quality (Comparative Example Nos. 15 to 21).
In addition, Comparative Example No. 22 was rejected because roping and uneven gloss occurred due to lack of the cumulative rolling rate and component deviation.
【００３２】さらには、比較例No. ２３〜２５は全ての
条件が本発明の範囲から外れたため、ローピング、光沢
むらおよび表面疵ともに不合格であった。なお、ローピ
ング合格材は中間指標として定義した平均粒径Ｄave 値
が７０μｍ以下となっており、官能評価ランクを良い対
応がみられる。Further, in Comparative Examples Nos. 23 to 25, all the conditions were out of the range of the present invention, and therefore, roping, uneven gloss and surface defects were all unacceptable. In addition, the average particle diameter D ave value defined as an intermediate index is 70 μm or less in the roping passing material, and the sensory evaluation rank shows good correspondence.
【００３３】[0033]
【発明の効果】以上説明したように、本発明によれば、
スラブ鋳造−熱間圧延プロセスによる従来の製造方法と
同等の表面品質のオーステナイト系ステンレス鋼薄帯状
冷延鋼板を、安価にしてかつ短納期で製造することがで
きる。As described above, according to the present invention,
An austenitic stainless steel thin strip cold-rolled steel sheet having a surface quality equivalent to that of the conventional production method by the slab casting-hot rolling process can be manufactured at low cost and in a short delivery time.
【図１】剛塑性有限要素法による非対称圧延の解析モデ
ルで計算した板厚方向の相当歪分布におよぼす圧延率の
影響を示した図である。FIG. 1 is a diagram showing the effect of a rolling ratio on the equivalent strain distribution in the plate thickness direction calculated by an analytical model for asymmetric rolling by the rigid-plastic finite element method.
【図２】光沢むらの発生有無におよぼすＣｒ当量とＮｉ
当量の関係を示した図である。[Fig. 2] Cr equivalent and Ni depending on the occurrence of uneven gloss
It is a figure showing a relation of equivalent.
【図３】フォトエッチ（ａ）およびショットディンプル
（ｂ）形状により溶鋼の入込み状況を示す模式図であ
る。FIG. 3 is a schematic view showing a molten steel intrusion state by photoetching (a) and shot dimple (b) shapes.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｂ２２Ｄ 11/00 Ｂ２２Ｄ 11/04 ３１１Ｇ 11/04 ３１１ 11/06 ３３０Ｂ 11/06 ３３０ 11/12 Ａ 11/12 Ｚ Ｂ２４Ｃ 1/06 Ｂ２４Ｃ 1/06 9270−4Ｋ Ｃ２１Ｄ 8/02 Ｄ Ｃ２１Ｄ 8/02 Ｃ２２Ｃ 38/00 ３０２Ｚ Ｃ２２Ｃ 38/00 ３０２ 38/44 38/44 8315−4Ｅ Ｂ２１Ｂ 37/00 １３２Ａ ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI Technical display location B22D 11/00 B22D 11/04 311G 11/04 311 11/06 330B 11/06 330 11/12 A 11/12 Z B24C 1/06 B24C 1/06 9270-4K C21D 8/02 D C21D 8/02 C22C 38/00 302Z C22C 38/00 302 38/44 38/44 8315-4E B21B 37/00 132A
Claims (1)
ディンプルを多数散在させた冷却ドラムの周面に同期し
て鋳片が移動する連続鋳造機により、オーステナイト系
ステンレス鋼薄帯状鋳片を鋳造する製造方法において、
重量％で、Ｃｒ＋Ｍｏ＋１．５Ｓｉで定義されるＣｒ当
量とＮｉ＋３０（Ｃ＋Ｎ）＋０．５（Ｍｎ＋Ｃｕ）で定
義されるＮｉ当量が下記（１）式を満足する成分組成と
し、鋳造に続いて圧延率１５％以下の１パス熱間圧延を
行い、続いて水冷後６００℃以下で巻き取って薄帯状鋳
片とし、続いて該薄帯状鋳片をデスケーリングし、続い
て前記熱間圧延における圧延率との累積圧下率が２５〜
４０％となる圧延率で１パスの冷間圧延を行い、必要に
応じて中間の焼鈍・冷間圧延を行い、続いて焼鈍・酸洗
または光輝焼鈍を行うことを特徴とする表面品質の優れ
たオーステナイト系ステンレス鋼薄板の製造方法。 Ｎｉ当量≦０．６３×Ｃｒ当量−１．２９ ………（１）1. A method of casting an austenitic stainless steel thin strip cast by a continuous casting machine in which the cast moves in synchronization with the peripheral surface of a cooling drum in which a large number of random dimples are scattered by a shot blast method. ,
In weight%, the Cr equivalent defined by Cr + Mo + 1.5Si and the Ni equivalent defined by Ni + 30 (C + N) +0.5 (Mn + Cu) satisfy the following formula (1), and the rolling ratio is 15 after casting. % Or less 1-pass hot rolling, followed by water cooling and winding at 600 ° C. or less to obtain a strip-shaped slab, followed by descaling of the strip-shaped slab, followed by rolling rate in the hot rolling. The cumulative rolling reduction of
Excellent surface quality characterized by performing 1-pass cold rolling at a rolling rate of 40%, performing intermediate annealing / cold rolling as required, and then performing annealing / pickling or bright annealing. Method for producing austenitic stainless steel sheet. Ni equivalent ≦ 0.63 × Cr equivalent −1.29 ………… (1)
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| Application Number | Priority Date | Filing Date | Title |
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| JP8147395A JP3595369B2 (en) | 1995-04-06 | 1995-04-06 | Method for producing austenitic stainless steel sheet with excellent surface quality |
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| JP8147395A JP3595369B2 (en) | 1995-04-06 | 1995-04-06 | Method for producing austenitic stainless steel sheet with excellent surface quality |
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| JPH08277423A true JPH08277423A (en) | 1996-10-22 |
| JP3595369B2 JP3595369B2 (en) | 2004-12-02 |
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| JP8147395A Expired - Fee Related JP3595369B2 (en) | 1995-04-06 | 1995-04-06 | Method for producing austenitic stainless steel sheet with excellent surface quality |
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|---|---|---|---|---|
| WO2009145347A1 (en) | 2008-05-27 | 2009-12-03 | 新日鐵住金ステンレス株式会社 | Flux-cored wire for welding of duplex stainless steel which enables the miniaturization of solidified crystal particles |
| US20120073778A1 (en) * | 2009-06-26 | 2012-03-29 | Hyundai Steel Company | Method for predicting surface quality of thin slab hot rolled coil and method for producing thin slab hot rolled coil using the same |
| CN103966521A (en) * | 2013-01-25 | 2014-08-06 | 宝山钢铁股份有限公司 | Method for producing atmosphere corrosion resistance thin strip steel through short process |
| CN110669986A (en) * | 2019-10-17 | 2020-01-10 | 浦项(张家港)不锈钢股份有限公司 | 310S stainless steel preparation method and 310S stainless steel |
-
1995
- 1995-04-06 JP JP8147395A patent/JP3595369B2/en not_active Expired - Fee Related
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009145347A1 (en) | 2008-05-27 | 2009-12-03 | 新日鐵住金ステンレス株式会社 | Flux-cored wire for welding of duplex stainless steel which enables the miniaturization of solidified crystal particles |
| US8878099B2 (en) | 2008-05-27 | 2014-11-04 | Nippon Steel & Sumikin Stainless Steel Corporation | Flux cored wire for welding duplex stainless steel which refines solidified crystal grains |
| US20120073778A1 (en) * | 2009-06-26 | 2012-03-29 | Hyundai Steel Company | Method for predicting surface quality of thin slab hot rolled coil and method for producing thin slab hot rolled coil using the same |
| CN102458717A (en) * | 2009-06-26 | 2012-05-16 | 现代制铁株式会社 | Method for predicting surface quality of thin slab hot rolled coil and method for producing thin slab hot rolled coil using same |
| US8220525B2 (en) * | 2009-06-26 | 2012-07-17 | Hyundai Steel Company | Method for predicting surface quality of thin slab hot rolled coil and method for producing thin slab hot rolled coil using the same |
| JP2012528723A (en) * | 2009-06-26 | 2012-11-15 | ヒュンダイ スチール カンパニー | Method for predicting surface quality of thin slab hot rolled coil and method for manufacturing thin slab hot rolled coil using the same |
| CN103966521A (en) * | 2013-01-25 | 2014-08-06 | 宝山钢铁股份有限公司 | Method for producing atmosphere corrosion resistance thin strip steel through short process |
| CN103966521B (en) * | 2013-01-25 | 2016-08-24 | 宝山钢铁股份有限公司 | A kind of short route produces the method for atmospheric corrosion resistance Thin Strip Steel |
| CN110669986A (en) * | 2019-10-17 | 2020-01-10 | 浦项(张家港)不锈钢股份有限公司 | 310S stainless steel preparation method and 310S stainless steel |
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|---|---|
| JP3595369B2 (en) | 2004-12-02 |
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