JPH11335740A - Manufacture of cold rolled austenitic stainless steel sheet excellent in surface characteristic - Google Patents
Manufacture of cold rolled austenitic stainless steel sheet excellent in surface characteristicInfo
- Publication number
- JPH11335740A JPH11335740A JP14620798A JP14620798A JPH11335740A JP H11335740 A JPH11335740 A JP H11335740A JP 14620798 A JP14620798 A JP 14620798A JP 14620798 A JP14620798 A JP 14620798A JP H11335740 A JPH11335740 A JP H11335740A
- Authority
- JP
- Japan
- Prior art keywords
- heating
- slab
- ferrite
- austenitic stainless
- scale
- 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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- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、焼鈍酸洗後の冷延鋼板
に観察される帯状光沢ムラを熱延段階で防止し、美麗な
表面をもつオーステナイト系ステンレス冷延鋼板を製造
する方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an austenitic stainless steel cold-rolled steel sheet having a beautiful surface by preventing band-like gloss unevenness observed in a cold-rolled steel sheet after annealing and pickling at a hot rolling stage. .
【０００２】[0002]
【従来の技術】ステンレス冷延鋼板は、連鋳スラブを加
熱後に熱間圧延し、得られた熱延板を焼鈍酸洗し、冷間
圧延及び焼鈍酸洗を施すことにより製造されている。こ
のステンレス冷延鋼板は、外板としての用途が多いこと
から、板表面が美麗な外観をもつことが重要である。し
かし、通常の製造方法では、幅方向に関し光沢が異なる
箇所が連続的な帯状光沢ムラとして冷延鋼板の表面に発
生することがあり、特にオーステナイトステンレス冷延
鋼板では品質上の問題にされている。帯状光沢ムラは、
連続鋳造で得られた鋳片表層部のδフェライトの量，分
布等が影響している。δフェライトは、熱延→焼鈍酸洗
→冷延→仕上げ焼鈍酸洗を経た冷延鋼板の表面において
酸化膜の厚さを変動させる要因となり、結果として冷延
鋼板表面の反射率を部分的に相違させ、反射率の相違が
帯状光沢ムラとして観察されるものと考えられている。2. Description of the Related Art A cold-rolled stainless steel sheet is manufactured by heating a continuous cast slab and then hot-rolling the resulting hot-rolled sheet, annealing and pickling the obtained hot-rolled sheet, and performing cold rolling and annealing and pickling. Since this stainless steel cold-rolled steel sheet has many uses as an outer plate, it is important that the plate surface has a beautiful appearance. However, in a normal manufacturing method, a portion having a different gloss in the width direction may occur as a continuous band-shaped gloss unevenness on the surface of the cold-rolled steel sheet, which is a quality problem particularly in the austenitic stainless cold-rolled steel sheet. . The band-like gloss unevenness is
The amount and distribution of δ ferrite in the surface layer of the slab obtained by continuous casting have an effect. δ ferrite is a factor that causes the thickness of the oxide film to fluctuate on the surface of the cold-rolled steel sheet after hot rolling → annealing pickling → cold rolling → finish annealing pickling, and as a result, the reflectance of the cold rolled steel sheet surface partially It is considered that the difference in reflectance is observed as band-like gloss unevenness.
【０００３】そこで、鋳片表層部にあるδフェライトの
量や分布を均一化することにより、帯状光沢ムラを解消
し、美麗な表面をもつステンレス冷延鋼板を製造する方
法が種々提案されている。たとえば、特開平８−９０１
８０号公報では、δフェライトの量，大きさのバラツキ
を低減するため、鋳造速度との関係で粘性及び凝固温度
が規制されたパウダを用いて連鋳時にモールド内での抜
熱の不均一を小さくする方法を採用している。モールド
内での抜熱を均一化させることにより、スラブ幅方向に
関してδフェライトの量や大きさのバラツキが制御さ
れ、帯状光沢ムラはある程度まで低減される。しかし、
δフェライト量の多い鋼種を対象とするとき、モールド
内での抜熱の均一化では、δフェライトの量や大きさの
バラツキ抑制が十分でない。そのため、冷延鋼板段階で
帯状光沢ムラを完全に解消するまでには至っていない。Therefore, various methods have been proposed for producing a stainless steel cold-rolled steel sheet having a beautiful surface by eliminating the band-like gloss unevenness by making the amount and distribution of δ ferrite in the surface layer of the slab uniform. . For example, Japanese Patent Application Laid-Open No. 8-901
In Japanese Patent Publication No. 80, in order to reduce the variation in the amount and size of δ ferrite, use of powder whose viscosity and solidification temperature are regulated in relation to the casting speed reduces uneven heat removal in the mold during continuous casting. The method of making it smaller is adopted. By making the heat removal in the mold uniform, variation in the amount and size of δ ferrite in the slab width direction is controlled, and the band-like gloss unevenness is reduced to some extent. But,
When a steel type having a large amount of δ ferrite is targeted, it is not sufficient to suppress the variation in the amount and size of δ ferrite in making the heat removal in the mold uniform. For this reason, the strip-like gloss unevenness has not been completely eliminated at the cold-rolled steel sheet stage.
【０００４】[0004]
【発明が解決しようとする課題】δフェライトは、鋼材
が加熱雰囲気に曝されたとき、γ相よりも優先的に酸化
される。加熱される鋼板の表層部においてδフェライト
の量や大きさにバラツキがあると、このδフェライトと
γ相との間で異なる酸化現象が顕在化し、帯状光沢ムラ
の原因となるスケール層の厚み変動を来す。そこで、本
発明者等は、加熱炉に装入される鋼材の表面に酸化防止
剤を塗布することにより、δフェライトとγ相との酸化
のバラツキを抑制する方法を特願平９−７１００５号で
提案した。酸化防止剤の塗布は、δフェライトとγ相と
の間で相違する酸化現象を平均化させ、帯状光沢ムラの
原因となるスケール層の厚みの均一化に有効である。し
かし、スラブ等の鋼材に酸化防止剤を塗布するため、余
分な工程を必要とし、大量生産鋼種であるＳＵＳ３０４
等への適用にはコスト的な問題がある。The δ ferrite is oxidized preferentially over the γ phase when the steel is exposed to a heating atmosphere. If the amount and size of δ-ferrite vary in the surface layer of the steel sheet to be heated, different oxidation phenomena appear between this δ-ferrite and the γ-phase, and the thickness variation of the scale layer causes band-like gloss unevenness. Come. Therefore, the present inventors have applied a method of suppressing the variation in oxidation between δ ferrite and γ phase by applying an antioxidant to the surface of a steel material charged in a heating furnace, as disclosed in Japanese Patent Application No. 9-71005. Suggested. The application of the antioxidant is effective in averaging the oxidation phenomena different between the δ ferrite and the γ phase and making the thickness of the scale layer uniform causing band-like gloss unevenness. However, since an antioxidant is applied to a steel material such as a slab, an extra step is required, and SUS304 which is a mass-produced steel type is used.
However, there is a problem in terms of cost in application to such methods.
【０００５】[0005]
【課題を解決するための手段】本発明は、このような問
題を解消すべく案出されたものであり、スラブ加熱時の
加熱条件及び雰囲気中の酸素濃度を規制することによ
り、酸化防止剤の塗布を必要とすることなく、美麗な表
面をもつオーステナイト系ステンレス冷延鋼板を得るこ
とを目的とする。本発明の製造方法は、その目的を達成
するため、連続鋳造まま組織においてδフェライトを含
むオーステナイト系ステンレス鋼スラブを熱間圧延前に
加熱炉に装入して加熱する際、加熱温度Ｔ（℃）を１２
００℃以上，加熱時間を４０分以上とし、ＣO2≦０．０
６×Ｔ−７１．２又はＣO2≦５．０体積％の内の低い方
の条件を満足する酸素濃度ＣO2（体積％）の雰囲気中で
スラブを加熱することを特徴とする。本発明は、式
（１）で計算されるオーステナイト指数Ａ（γ）が０．
４以下のオーステナイトステンレス鋼に対して特に有効
である。 Ａ（γ）＝３０×（Ｃ％＋Ｎ％）＋０．５×Ｍｎ％＋Ｎｉ％ −１．３Ｃｒ％＋１１．８ ・・・・（１）DISCLOSURE OF THE INVENTION The present invention has been devised to solve such a problem. An antioxidant is provided by regulating the heating conditions during slab heating and the oxygen concentration in the atmosphere. It is an object of the present invention to obtain an austenitic stainless steel cold-rolled steel sheet having a beautiful surface without the need for coating. In order to attain the object, the production method of the present invention is characterized in that when an austenitic stainless steel slab containing δ ferrite in a continuous cast structure is charged into a heating furnace and heated before hot rolling, the heating temperature T (° C.) ) To 12
00 ° C or more, heating time is 40 minutes or more, and CO 2 ≦ 0.0
The slab is characterized in that the slab is heated in an atmosphere having an oxygen concentration C O2 (vol%) which satisfies the lower condition of 6 × T-71.2 or C O2 ≦ 5.0 vol%. In the present invention, the austenite index A (γ) calculated by the equation (1) is equal to 0.
It is particularly effective for austenitic stainless steels of 4 or less. A (γ) = 30 × (C% + N%) + 0.5 × Mn% + Ni% -1.3Cr% + 11.8 (1)
【０００６】[0006]
【作用】本発明者等は、δフェライト及びγ相の酸化状
況及び帯状光沢ムラへの影響を調査・研究し、以下に説
明する調査・研究結果から、熱間圧延に先立ってスラブ
を加熱する際に加熱条件を制御するときδフェライト及
びγ相の酸化が平均化され、帯状光沢ムラの原因となる
スケール層の膜厚変動が抑制されることを見出した。先
ず、帯状光沢ムラの発生状況は、熱延板と冷延焼鈍板と
の間では次の関係がある。熱延板段階で赤色及び黒色の
スケールムラが発生した熱延板を冷延し、焼鈍酸洗後の
鋼帯表面を観察すると帯状光沢ムラがみられる。他方、
熱延板段階でスケールムラのない熱延鋼板から得られた
冷延板では、焼鈍酸洗後においても帯状光沢ムラが検出
されない。この関係から、熱延板段階でスケールムラを
抑制することが、帯状光沢ムラの防止に有効であるとい
える。The present inventors have investigated and studied the oxidation of the δ-ferrite and γ-phase and the influence on the band-like gloss unevenness. Based on the results of the investigation and research described below, the slab is heated prior to hot rolling. It has been found that when controlling the heating conditions, the oxidation of the δ ferrite and the γ phase are averaged, and the thickness variation of the scale layer, which causes band-like gloss unevenness, is suppressed. First, the occurrence of the band-like gloss unevenness has the following relationship between the hot-rolled sheet and the cold-rolled annealed sheet. When the hot-rolled sheet in which red and black scale unevenness has occurred in the hot-rolled sheet stage is cold-rolled and the steel strip surface after annealing and pickling is observed, strip-shaped gloss unevenness is observed. On the other hand,
In a cold-rolled sheet obtained from a hot-rolled steel sheet having no scale unevenness in the hot-rolled sheet stage, no band-like gloss unevenness is detected even after annealing and pickling. From this relationship, it can be said that suppressing the scale unevenness at the hot-rolled sheet stage is effective for preventing the band-like gloss unevenness.
【０００７】そこで、熱延板に発生するスケールムラ
を、スラブ表層にあるδフェライト量のパターンと比較
検討した。その結果、δフェライト量が多い表面部分で
は赤色スケールが発生し、δフェライト量の少ない箇所
では黒色スケールが発生することが判った。更にδフェ
ライト量とスケールムラとの関係を明らかにするため、
加熱炉内での酸化現象を実験室的に再現した。すなわ
ち、２〜７体積％のδフェライトを含むＳＵＳ３０４ス
ラブをサンプルとして１２３０℃で６０分加熱し、加熱
後のサンプル表面に発生したスケールの断面を観察し
た。δフェライト量が多い表面部分では、図１の観察結
果にみられるように、断面が粗な構造になったスケール
層が生成した。また、この表面部分では、スケール層直
下のＣｒ濃度も大きく低下していた。これに対し、δフ
ェライト量が少ない表面部分では、図２に示すように、
緻密な構造をもつスケール層が発生しており、Ｃｒ濃度
の低下も少なかった。Therefore, the scale unevenness generated in the hot-rolled sheet was compared with the pattern of the amount of δ ferrite in the surface layer of the slab. As a result, it was found that a red scale was generated on the surface portion having a large amount of δ ferrite, and a black scale was generated on a portion having a small amount of δ ferrite. To further clarify the relationship between the amount of δ ferrite and scale unevenness,
The oxidation phenomenon in the heating furnace was reproduced in a laboratory. That is, a SUS304 slab containing 2 to 7% by volume of δ ferrite was heated at 1230 ° C. for 60 minutes as a sample, and the cross section of the scale generated on the sample surface after heating was observed. At the surface portion where the amount of δ ferrite is large, a scale layer having a rough cross section was formed, as can be seen from the observation results in FIG. In this surface portion, the Cr concentration immediately below the scale layer was also greatly reduced. On the other hand, in the surface portion where the amount of δ ferrite is small, as shown in FIG.
A scale layer having a dense structure was generated, and the decrease in the Cr concentration was small.
【０００８】以上の結果は、加熱により生成したスケー
ル層の形態やスケール直下のＣｒ濃度の変動がδフェラ
イト量の不均一分布に起因することを意味する。また、
スラブ加熱時に緻密なスケールがスラブ全面に生成する
と、スケール層の膜厚変動、ひいては帯状光沢ムラの抑
制に有効な表面状態に調整されることを示す。そこで、
スラブの加熱条件を再検討し、加熱温度及び加熱雰囲気
の酸素濃度が生成スケールの形態に及ぼす影響を実験室
的に調査した。その結果、加熱温度Ｔ（℃）を１２００
℃以上，加熱時間を４０分以上とし、更に加熱雰囲気の
酸素濃度ＣO2（体積％）をＣO2≦０．０６×Ｔ−７１．
２又はＣO2≦５．０体積％の内の低い方の値に設定する
とき、加熱されたスラブの全表面に緻密なスケールが生
成することを見出した。The above results indicate that the morphology of the scale layer generated by heating and the variation in the Cr concentration immediately below the scale are caused by the non-uniform distribution of the amount of δ ferrite. Also,
This shows that when a dense scale is formed on the entire surface of the slab during slab heating, the surface state is adjusted to an effective one for suppressing the fluctuation of the thickness of the scale layer and, consequently, the unevenness of the band-like gloss. Therefore,
The heating conditions of the slab were reexamined, and the effects of the heating temperature and the oxygen concentration of the heating atmosphere on the morphology of the formed scale were investigated in a laboratory. As a result, the heating temperature T (° C.) is set to 1200
C. or more, the heating time is 40 minutes or more, and the oxygen concentration C O2 (vol%) of the heating atmosphere is C O2 ≦ 0.06 × T−71.
It has been found that when set to the lower value of 2 or C O2 ≦ 5.0% by volume, a dense scale forms on the entire surface of the heated slab.
【０００９】制御された加熱条件下では、δフェライト
及びγ相の酸化現象におけるバラツキが小さくなり、δ
フェライトの量や分布に関係なく一次スケール形態が均
質化される。それに伴って、スケール層直下のＣｒ濃度
のバラツキも抑制される。したがって、加熱されたスラ
ブはスケールムラがなく、冷延焼鈍酸洗段階で帯状光沢
ムラが抑制される。なかでも、酸素濃度ＣO2は、加熱温
度がＴ＝１２００〜１２７０℃にあるときＣO2≦０．０
６×Ｔ−７１．２とし、Ｔ≧１２７０℃のときＣO2≦
５．０体積％とすることが好ましい。Under the controlled heating conditions, the variation in the oxidation phenomenon of the δ ferrite and the γ phase becomes small,
The primary scale morphology is homogenized regardless of the amount and distribution of ferrite. Accordingly, the variation in the Cr concentration immediately below the scale layer is also suppressed. Therefore, the heated slab has no scale unevenness, and the band-like gloss unevenness is suppressed in the cold rolling annealing pickling stage. Above all, the oxygen concentration C O2 is such that when the heating temperature is T = 1200 to 1270 ° C., C O2 ≦ 0.02.
6 × T-71.2, and when T ≧ 1270 ° C., C O2 ≦
It is preferable to be 5.0% by volume.
【００１０】以下、本発明で規定した加熱条件を説明す
る。 加熱温度：Ｔ（℃）≧１２００℃以上 δフェライトを消滅させ熱延に好適な均質組織にするた
め、１２００℃以上の加熱温度が必要である。スラブの
組織は、加熱温度が高くなるほど迅速に均質化される。
しかし、過度に高い温度では、スケール生成量が多くな
り、熱延歩留が低下するため、最高でも１３５０℃以下
にすることが好ましい。 加熱時間：４０分以上 δフェライトを消滅させ熱延に好適な均質組織にするた
め、４０分以上の加熱時間が必要である。加熱時間は、
加熱温度が高くなるほど短時間で済む。しかし、過度に
長い加熱時間は、生産性を低下させるばかりでなく、ス
ケール生成量を多くし熱延歩留を低下させる原因となる
ので、最長でも１２０分以内に設定することが好まし
い。なお、本件明細書では、スラブを昇温して目標温度
に加熱保持する時間をもって「加熱時間」という。Hereinafter, the heating conditions specified in the present invention will be described. Heating temperature: T (° C.) ≧ 1200 ° C. or more A heating temperature of 1200 ° C. or more is necessary in order to eliminate δ ferrite and obtain a homogeneous structure suitable for hot rolling. The structure of the slab is homogenized more quickly at higher heating temperatures.
However, if the temperature is excessively high, the amount of scale generated increases, and the hot rolling yield decreases. Heating time: 40 minutes or more Heating time of 40 minutes or more is required in order to eliminate δ ferrite and obtain a homogeneous structure suitable for hot rolling. The heating time is
The higher the heating temperature, the shorter the time. However, an excessively long heating time not only reduces the productivity, but also increases the scale generation amount and lowers the hot rolling yield. Therefore, it is preferable to set the heating time to 120 minutes or less at the longest. In the present specification, the time during which the slab is heated to the target temperature by heating is referred to as “heating time”.
【００１１】加熱雰囲気の酸素濃度：ＣO2≦０．０６×
Ｔ−７１．２ 又はＣO2≦５．０体積％の内の低い方の
値 加熱炉でスラブを加熱するとき、スラブ表面に形成され
るスケール層は、加熱雰囲気の酸素濃度に応じて形態が
異なったものとなる。一般的に、酸素濃度を低下するほ
ど酸化反応が遅くなり、緻密な構造をもつスケール層が
形成される。他方、酸素濃度が高い雰囲気下では、急激
な酸化反応によってスケール層の成長が促進され、粗い
構造になる。本発明者等の調査研究によるとき、後述す
る実施例でも説明しているように、ＣO2＝０．０６×Ｔ
−７１．２又はＣO2＝５．０体積％の低い方の値を境と
してスケール層が緻密構造又は粗い構造になることが判
った。なかでも、加熱温度が１２００〜１２７０℃の範
囲にあるときＣO2≦０．０６×Ｔ−７１．２を満足する
酸素濃度ＣO2とし、１２７０℃以上の加熱温度ではＣO2
≦５．０体積％とすると、スラブ表面に緻密な構造をも
つスケール層が形成される。このように酸素濃度ＣO2が
制御された雰囲気でスラブを加熱すると、δフェライト
とγ相との酸化のバラツキが小さくなり、δフェライト
の量や分布に影響されずに一次スケールの形態が均質化
され、スケール層直下のＣｒ濃度のバラツキも抑制され
る。Oxygen concentration in heating atmosphere: C O2 ≦ 0.06 ×
T-71.2 or the lower value of C O2 ≦ 5.0% by volume When a slab is heated in a heating furnace, the scale layer formed on the slab surface has a form depending on the oxygen concentration of the heating atmosphere. It will be different. Generally, as the oxygen concentration decreases, the oxidation reaction slows down, and a scale layer having a dense structure is formed. On the other hand, in an atmosphere having a high oxygen concentration, the growth of the scale layer is promoted by a rapid oxidation reaction, resulting in a rough structure. According to the investigation and research by the present inventors, C O2 = 0.06 × T
From the lower value of -71.2 or C O2 = 5.0 vol%, it was found that the scale layer had a dense structure or a coarse structure. Above all, when the heating temperature is in the range of 1,200 to 1,270 ° C. and the oxygen concentration C O2 satisfying the C O2 ≦ 0.06 × T-71.2 , C O2 is a heating temperature above 1270 ° C.
When ≦ 5.0% by volume, a scale layer having a dense structure is formed on the slab surface. When the slab is heated in an atmosphere where the oxygen concentration C O2 is controlled in this way, the variation in oxidation between the δ ferrite and the γ phase is reduced, and the morphology of the primary scale is homogenized regardless of the amount and distribution of the δ ferrite. Thus, variation in the Cr concentration immediately below the scale layer is also suppressed.
【００１２】オーステナイト指数：Ａ（γ）≦０．４ オーステナイト系ステンレス鋼の鋳造まま組織に存在す
るδフェライト量は、鋼成分及び含有量に応じて定ま
る。このδフェライト量は前掲した式（１）で定義した
オーステナイト指数Ａ（γ）で表され、指数Ａ（γ）が
高いほどδフェライト量が少なく、帯状光沢ムラの発生
率が低くなる。特に０．４を超える指数Ａ（γ）では、
本発明に従って条件制御した加熱を施さなくても、帯状
光沢ムラの発生がない。指数Ａ（γ）が０．４以下に低
下すると、帯状光沢ムラの発生率が高く、本発明に従っ
た加熱条件の制御が効果を発揮する。Austenite index: A (γ) ≦ 0.4 The amount of δ-ferrite present in the as-cast austenitic stainless steel structure is determined according to the steel composition and content. The amount of δ ferrite is represented by the austenite index A (γ) defined by the above-mentioned equation (1). The higher the index A (γ), the smaller the amount of δ ferrite and the lower the occurrence rate of band-like gloss unevenness. In particular, for an index A (γ) exceeding 0.4,
Even when heating under condition-controlled conditions is not performed in accordance with the present invention, there is no unevenness of the strip-like gloss. When the index A (γ) is reduced to 0.4 or less, the occurrence rate of the band-like gloss unevenness is high, and the control of the heating conditions according to the present invention exerts an effect.
【００１３】[0013]
【実施例】表１の組成をもつ各種オーステナイト系ステ
ンレス鋼７５トンを電気炉で溶製した後、転炉，真空脱
ガス工程を経て精錬，成分調整し、１０〜１２トンのス
ラブに連続鋳造した。これらのステンレス鋼は、組成バ
ランス上からすると、平均的には鋳造まま組織に７．０
体積％のδフェライトを含む鋼材である。EXAMPLE 75 tons of various austenitic stainless steels having the compositions shown in Table 1 were melted in an electric furnace, then refined through a converter and a vacuum degassing process, adjusted for components, and continuously cast into slabs of 10 to 12 tons. did. In view of the composition balance, these stainless steels have an average as-cast structure of 7.0.
It is a steel material containing volume% of δ ferrite.
【００１４】 [0014]
【００１５】各スラブから試験片を切り出し、加熱温度
Ｔ及び酸素濃度ＣO2を変化させて６０分加熱し、加熱炉
内の酸化現象を実験室的に再現させ、スケール層の形態
に及ぼす加熱温度Ｔ及び酸素濃度ＣO2の影響を調査し
た。図３の調査結果にみられるように、１２００〜１２
７０℃の温度域で試験片を加熱するとき、ＣO2≦０．０
６×Ｔ−７１．２を満足する酸素濃度ＣO2の雰囲気下で
緻密なスケール層が生成し、酸素濃度ＣO2が０．０６×
Ｔ−７１．２を超えるとスケール層が粗い構造になっ
た。また、１２７０℃以上の加熱温度では、ＣO2≦５．
０体積％の雰囲気下で緻密なスケール層が生成し、５．
０体積％を超えるとスケール層が粗い構造になった。緻
密なスケール層が生成したものでは、酸化による脱Ｃｒ
が抑えられ、スケール層直下のＣｒ濃度に実質的な変動
が検出されなかった。A test piece was cut out from each slab and heated for 60 minutes while changing the heating temperature T and the oxygen concentration C O2, and the oxidation phenomenon in the heating furnace was reproduced in a laboratory, and the heating temperature affecting the form of the scale layer was obtained. The effects of T and oxygen concentration CO2 were investigated. As can be seen from the survey results in FIG.
When the test piece is heated in a temperature range of 70 ° C., C O2 ≦ 0.0
A dense scale layer is formed in an atmosphere having an oxygen concentration C O2 satisfying 6 × T-71.2, and the oxygen concentration C O2 is 0.06 ×
When it exceeded T-71.2, the scale layer had a rough structure. At a heating temperature of 1270 ° C. or higher, C O2 ≦ 5.
4. A dense scale layer is formed under an atmosphere of 0% by volume.
If it exceeds 0% by volume, the scale layer has a coarse structure. In the case where a dense scale layer is formed, the removal of Cr by oxidation
Was suppressed, and no substantial change was detected in the Cr concentration immediately below the scale layer.
【００１６】加熱温度Ｔ及び酸素濃度ＣO2がスケール層
の粗密に及ぼす影響を前提にして、各スラブを加熱温度
及び加熱時間を変化させて各スラブを均熱した後で熱間
圧延した。熱間圧延に際し、各スラブから切り出された
試験片を加熱炉に同時に装入し、加熱炉から抽出された
スラブ表面に生成した一次スケールの形態を調査した。
熱間圧延後の鋼帯を焼鈍酸洗，冷間圧延，仕上げ焼鈍酸
洗し、得られた鋼帯の表面を観察した。帯状光沢ムラの
有無を目視判定し、帯状光沢ムラの発生程度が大きいも
のを×，中程度のものを△，帯状光沢ムラが観察されな
かったものを○として評価した。評価結果を、加熱条件
及び一次スケールの形態と併せて表２に示す。表２から
明らかなように、加熱温度Ｔ及び酸素濃度ＣO2が本発明
で規定した条件を満足する試験番号１〜６では、何れも
加熱後のスラブ表面に形成されたスケール層が緻密な構
造になっており、冷延鋼帯の表面に帯状光沢ムラが検出
されなかった。これに対し、酸素濃度ＣO2が高い試験番
号７〜１２では、粗い構造のスケールが混在したスケー
ル層が加熱後のスラブ表面に形成されており、冷延鋼帯
の表面にも帯状光沢ムラが観察された。On the premise that the heating temperature T and the oxygen concentration C O2 affect the density of the scale layer, each slab was heated at a different heating temperature and a different heating time, and then each slab was uniformly heated and then hot-rolled. During hot rolling, test pieces cut from each slab were simultaneously charged into a heating furnace, and the form of primary scale formed on the slab surface extracted from the heating furnace was investigated.
The steel strip after hot rolling was subjected to annealing pickling, cold rolling, and finish annealing pickling, and the surface of the obtained steel strip was observed. The presence or absence of the band-like gloss unevenness was visually judged, and those having a large degree of occurrence of the band-like gloss unevenness were evaluated as x, those of the medium degree were evaluated as Δ, and those without the band-like gloss unevenness were evaluated as ○. Table 2 shows the evaluation results together with the heating conditions and the form of the primary scale. As is clear from Table 2, in Test Nos. 1 to 6 in which the heating temperature T and the oxygen concentration C O2 satisfy the conditions specified in the present invention, the scale layer formed on the slab surface after heating has a dense structure. And no strip-like gloss unevenness was detected on the surface of the cold-rolled steel strip. On the other hand, in Test Nos. 7 to 12 in which the oxygen concentration C O2 was high, a scale layer in which a scale having a rough structure was mixed was formed on the slab surface after heating, and the band-shaped gloss unevenness was also present on the surface of the cold-rolled steel strip. Was observed.
【００１７】 [0017]
【００１８】[0018]
【発明の効果】以上に説明したように、本発明において
は、オーステナイト系ステンレス鋼スラブを熱間圧延に
先立って加熱する際、加熱温度及び雰囲気の酸素濃度を
規制することにより、δフェライト及びγ相の酸化進行
状況を平均化し、加熱後のスラブ全面に緻密なスケール
層を形成している。このようにして加熱されたスラブを
熱間圧延するとき、熱延後にスケールムラの発生が抑え
られ、焼鈍酸洗，冷延，仕上げ焼鈍酸洗を経て製造され
る冷延鋼帯にも帯状光沢ムラのない鋼帯となる。したが
って、商品価値の高いオーステナイト系ステンレス鋼板
として、各種機器，機械部品，構造材等として広範な分
野で使用される。As described above, in the present invention, when austenitic stainless steel slab is heated prior to hot rolling, δ ferrite and γ ferrite are controlled by regulating the heating temperature and the oxygen concentration in the atmosphere. The progress of the phase oxidation is averaged, and a dense scale layer is formed on the entire slab after heating. When hot-rolling the slab heated in this way, the occurrence of scale unevenness after hot rolling is suppressed, and the strip-like gloss is produced on the cold-rolled steel strip produced through annealing pickling, cold rolling and finish annealing pickling. A steel strip without unevenness. Therefore, as an austenitic stainless steel sheet having high commercial value, it is used in various fields such as various devices, machine parts, and structural materials.
【図１】 δフェライト量が多い部分で生成する粗なス
ケール層を示す熱延鋼帯表層部の金属組織を示す写真FIG. 1 is a photograph showing a metallographic structure of a surface layer of a hot-rolled steel strip showing a coarse scale layer formed in a portion having a large amount of δ ferrite.
【図２】 δフェライト量が少ない部分で生成する緻密
なスケール層を示す熱延鋼帯表層部の金属組織を示す写
真FIG. 2 is a photograph showing a metallographic structure of a surface layer portion of a hot-rolled steel strip showing a dense scale layer formed in a portion where the amount of δ ferrite is small.
【図３】 加熱温度及び雰囲気の酸素濃度がスラブ表面
に生成するスケールの粗密に及ぼす影響を示したグラフFIG. 3 is a graph showing the effect of the heating temperature and the oxygen concentration in the atmosphere on the density of the scale generated on the slab surface.
─────────────────────────────────────────────────────
────────────────────────────────────────────────── ───
【手続補正書】[Procedure amendment]
【提出日】平成１０年５月２８日[Submission date] May 28, 1998
【手続補正１】[Procedure amendment 1]
【補正対象書類名】図面[Document name to be amended] Drawing
【補正対象項目名】図１[Correction target item name] Fig. 1
【補正方法】変更[Correction method] Change
【補正内容】[Correction contents]
【図１】 FIG.
【手続補正２】[Procedure amendment 2]
【補正対象書類名】図面[Document name to be amended] Drawing
【補正対象項目名】図２[Correction target item name] Figure 2
【補正方法】変更[Correction method] Change
【補正内容】[Correction contents]
【図２】 FIG. 2
Claims (2)
を含むオーステナイト系ステンレス鋼スラブを熱間圧延
前に加熱炉に装入して加熱する際、加熱温度Ｔ（℃）を
１２００℃以上，加熱時間を４０分以上とし、ＣO2≦
０．０６×Ｔ−７１．２又はＣO2≦５．０体積％の内の
低い方の条件を満足する酸素濃度ＣO2（体積％）の雰囲
気中でスラブを加熱することを特徴とする表面性状に優
れたオーステナイト系ステンレス冷延鋼板の製造方法。1. When continuously heating an austenitic stainless steel slab containing δ ferrite in a continuous casting structure in a heating furnace before hot rolling, the heating temperature T (° C.) is 1200 ° C. or more, and the heating time is 40 minutes or more, C O2 ≦
A surface characterized in that the slab is heated in an atmosphere having an oxygen concentration C O2 (vol%) which satisfies the lower condition of 0.06 × T-71.2 or C O2 ≦ 5.0 vol%. Manufacturing method of austenitic stainless cold rolled steel sheet with excellent properties.
数Ａ（γ）が０．４以下のオーステナイトステンレス鋼
を使用する請求項１記載の表面性状に優れたオーステナ
イト系ステンレス冷延鋼板の製造方法。 Ａ（γ）＝３０×（Ｃ％＋Ｎ％）＋０．５×Ｍｎ％＋Ｎｉ％ −１．３Ｃｒ％＋１１．８ ・・・・（１）2. The method for producing an austenitic stainless steel cold-rolled steel sheet having excellent surface properties according to claim 1, wherein an austenitic stainless steel having an austenite index A (γ) calculated by the formula (1) of 0.4 or less is used. . A (γ) = 30 × (C% + N%) + 0.5 × Mn% + Ni% -1.3Cr% + 11.8 (1)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14620798A JPH11335740A (en) | 1998-05-27 | 1998-05-27 | Manufacture of cold rolled austenitic stainless steel sheet excellent in surface characteristic |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14620798A JPH11335740A (en) | 1998-05-27 | 1998-05-27 | Manufacture of cold rolled austenitic stainless steel sheet excellent in surface characteristic |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH11335740A true JPH11335740A (en) | 1999-12-07 |
Family
ID=15402551
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP14620798A Pending JPH11335740A (en) | 1998-05-27 | 1998-05-27 | Manufacture of cold rolled austenitic stainless steel sheet excellent in surface characteristic |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH11335740A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20030048810A (en) * | 2001-12-13 | 2003-06-25 | 주식회사 포스코 | Method for Manufacturing Hot-Rolled Ferrite Stainless Steel Sheet |
-
1998
- 1998-05-27 JP JP14620798A patent/JPH11335740A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20030048810A (en) * | 2001-12-13 | 2003-06-25 | 주식회사 포스코 | Method for Manufacturing Hot-Rolled Ferrite Stainless Steel Sheet |
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