JPH06234048A - Production of austenitic stainless steel cast strip - Google Patents
Production of austenitic stainless steel cast stripInfo
- Publication number
- JPH06234048A JPH06234048A JP2274093A JP2274093A JPH06234048A JP H06234048 A JPH06234048 A JP H06234048A JP 2274093 A JP2274093 A JP 2274093A JP 2274093 A JP2274093 A JP 2274093A JP H06234048 A JPH06234048 A JP H06234048A
- Authority
- JP
- Japan
- Prior art keywords
- austenitic stainless
- stainless steel
- solidified slurry
- temp
- cast strip
- 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.)
- Pending
Links
Abstract
Description
【0001】[0001]
【産業上の利用分野】この発明は、表面割れなどの品質
劣化を伴うことなしにオーステナイト系ステンレス薄鋳
片を得ようとするものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to obtain an austenitic stainless thin slab without quality deterioration such as surface cracking.
【0002】[0002]
【従来の技術】一般に、オーステナイト系ステンレス鋼
はフェライト系ステンレス鋼に比較して熱間加工時の割
れ感受性が大きいため、かかる鋼の薄板は、鋼塊を一た
ん分塊圧延してスラブとしたのち、スラブ表面に生じた
割れきずを研削加工によって除去し、次いで熱間圧延、
冷間圧延を施すことによって製造するのが通例とされて
いた。ところが、スラブ表面のきず取り作業は、製品歩
留りを大きく低下させる不利があり、作業のうえでも著
しい負荷となっているのが現状であった。2. Description of the Related Art Generally, austenitic stainless steels have a higher cracking susceptibility during hot working than ferritic stainless steels. After that, cracks generated on the slab surface are removed by grinding, then hot rolling,
It was customary to manufacture by cold rolling. However, the flaw removal work on the surface of the slab has a disadvantage that the product yield is significantly reduced, and it is a current situation that the work is significantly burdened.
【0003】上記のような問題の解決を図ることに関し
ては、スラブに相当する鋳片を連続鋳造によって直接製
造しようとする試みもあるが、このような方法を適用し
ても表面割れを回避することは困難であって、割れきず
の研削除去作業を省略するまでには至っていない。In order to solve the above problems, there is an attempt to directly produce a slab corresponding to a slab by continuous casting, but even if such a method is applied, surface cracks can be avoided. This is difficult, and the work of grinding and removing cracks has not been omitted.
【0004】[0004]
【発明が解決しようとする課題】この発明の目的は、オ
ーステナイト系ステンレス鋼の薄板を製造する際に生じ
ていた従来の問題を解消できる新規な方法を提案すると
ころにある。SUMMARY OF THE INVENTION An object of the present invention is to propose a new method capable of solving the conventional problems that have occurred when manufacturing austenitic stainless steel sheets.
【0005】[0005]
【課題を解決するための手段】この発明は、液相線温度
以下、固相線温度以上の温度域で強く攪拌して得たオー
ステナイト系ステンレス鋼の半凝固スラリーを、互いに
間隔をおいて対向配置した一対の冷却ロールを備えた双
ロール式連続鋳造機で鋳造することによって薄鋳片とす
ることを特徴とするオーステナイト系ステンレス薄鋳片
の製造方法であり、上記半凝固スラリーの固相率は1%
以上、40%以下であるのが好ましい。また、鋳片の厚さ
については10mm以下のものを対象とするのが望ましい。SUMMARY OF THE INVENTION According to the present invention, semi-solidified austenitic stainless steel slurries obtained by vigorous stirring in a temperature range below the liquidus temperature and above the solidus temperature are opposed to each other at intervals. It is a method for producing an austenitic stainless thin slab, which is characterized by forming a thin slab by casting with a twin roll type continuous casting machine having a pair of cooling rolls arranged, and the solid fraction of the semi-solidified slurry. Is 1%
It is preferably 40% or less. Further, it is desirable that the thickness of the slab is 10 mm or less.
【0006】[0006]
【作用】オーステナイト系ステンレス鋼の熱間加工時に
おける割れは、鋼中の不純物であるPとSの偏析がフェ
ライト系ステンレス鋼に比べてはるかに大きいことが原
因になっている。すなわち、オーステナイト系ステンレ
ス鋼では、その凝固過程において形成される凝固殻の前
面にPやSの濃化層が形成されやすく、凝固の進行にと
もなって該濃化層はPやSの濃度を上昇させながら最終
的には結晶粒界に濃厚偏析が生成されることになる。The cracking of austenitic stainless steel during hot working is caused by segregation of P and S, which are impurities in the steel, being much larger than that of ferritic stainless steel. That is, in austenitic stainless steel, a concentrated layer of P or S is easily formed on the front surface of the solidified shell formed in the solidification process, and the concentrated layer increases the concentration of P or S as the solidification progresses. Ultimately, dense segregation will be generated at the crystal grain boundaries while allowing it.
【0007】ここに、上記濃厚偏析部は凝固点が低く、
熱間加工温度に再加熱された場合に部分的に溶融し、こ
れが熱間加工において破断の起点となる。Here, the dense segregation portion has a low freezing point,
When it is reheated to the hot working temperature, it partially melts, which becomes the starting point of fracture during hot working.
【0008】このようなオーステナイト系ステンレス鋼
に特有の熱間割れは、いわゆる液膜脆化に起因するもの
であるから、熱間加工のみならず連続鋳造時の鋳片のバ
ルジングやベンド部、アンベンド部などでの変形によっ
ても生じるものである。Since the hot cracking peculiar to such austenitic stainless steel is caused by so-called liquid film embrittlement, not only the hot working but also the bulging of the slab during continuous casting, the bend portion, and the unbend. It is also caused by deformation of parts.
【0009】以上のような割れ発生原因から推測する
と、オーステナイト系ステンレス鋼の連続鋳造において
はかかる鋼の溶湯を急冷凝固させることによって偏析を
軽減し割れの発生を抑制するとこができるものと考えら
るが、実際にもある程度の改善はみられるものの、溶湯
の凝固速度を単に大きくするだけでは表面割れを完全に
回避することはできない。Inferring from the causes of cracking as described above, it is considered that in continuous casting of austenitic stainless steel, segregation can be reduced and cracking can be suppressed by quenching and solidifying the molten metal of such steel. Although there is some improvement in practice, surface cracking cannot be completely avoided by simply increasing the solidification rate of the molten metal.
【0010】これは、鋳造された薄鋳片の凝固組織が、
鋳片の表層から厚さ方向の中心へ伸びた粗大な柱状晶組
織をなしていること、そしてその結晶粒界に生成する液
膜が全体的には大きく軽減されるものの局部的には大き
な液膜が発生するとこに起因している。This is because the solidified structure of the cast thin slab is
It has a coarse columnar crystal structure extending from the surface layer of the slab to the center in the thickness direction, and the liquid film formed at the crystal grain boundaries is greatly reduced as a whole, but it is a large liquid locally. This is due to the occurrence of the film.
【0011】この発明においては、液相線温度以下、固
相線温度以上の温度域で攪拌して得た半凝固スラリー
を、双ロール式連続鋳造基を用いて鋳造するようにした
ので、粗大な柱状晶組織の生成が抑えられ、微細な粒状
の固相粒 (以下これを初晶粒という) と粒状晶からなる
混合組織とすることができるのでオーステナイト系ステ
ンレス鋼に特有の表面割れは有利に回避される。In the present invention, the semi-solidified slurry obtained by stirring in the temperature range below the liquidus temperature and above the solidus temperature is cast using a twin roll type continuous casting base, so that it is coarse. The formation of a large columnar crystal structure is suppressed, and a mixed structure composed of fine granular solid-phase grains (hereinafter referred to as primary crystal grains) and granular crystals can be formed, so surface cracking peculiar to austenitic stainless steel is advantageous. To be avoided.
【0012】また、オーステナイト系ステンレス鋼の半
凝固スラリーを用いた連続鋳造においては鋳片の表面割
れが回避できる他、溶湯を用いる場合に比較し以下のよ
うな利点もある。 (1) 凝固速度が大きいので生産性を高くできる。 (2) 凝固潜熱の一部を放出しているため冷却ロールに
対する熱負荷が軽減されロールの寿命延長が可能であ
る。 (3) スラリーが適度の粘性を有するので表面性状を改
善することができる。 また、(1) 〜(3) の他に、半凝固スラリーは、液相中に
初晶粒を懸濁したものであるから、鋳造組織としてはス
ラリー中で固相として存在していた初晶粒と鋳造時に生
成される微細粒状晶の混合組織からなり、溶湯を使った
連続鋳造で生成するような粗大柱状晶組織は全く生成し
ない。Further, in continuous casting using a semi-solidified slurry of austenitic stainless steel, surface cracks of slabs can be avoided, and there are the following advantages as compared with the case of using molten metal. (1) Since the solidification rate is high, productivity can be increased. (2) Since part of the latent heat of solidification is released, the heat load on the cooling roll is reduced and the life of the roll can be extended. (3) The surface property can be improved because the slurry has an appropriate viscosity. In addition to (1) to (3), the semi-solidified slurry is a suspension of primary crystal grains in the liquid phase. It is composed of a mixed structure of grains and fine granular crystals generated during casting, and does not form a coarse columnar crystal structure, which is generated in continuous casting using a molten metal.
【0013】連続鋳造に使用する半凝固スラリーは、そ
の製法についてはとくに指定はなく、固相が極微量であ
ってもそれなりの効果は期待できるものである。しかし
ながら、固相率が1%未満では部分的に粗大柱状晶組織
となることがあるので、この発明においてその下限を1
%とする。スラリーの固相率が40%を超えるとオーステ
ナイト系ステンレス鋼の場合においては粘度が急激に高
くなり取扱が困難となるので、注入作業などを考慮して
上限については40%とするのが望ましい。The semi-solidified slurry used in continuous casting is not specified in its manufacturing method, and some effects can be expected even if the amount of solid phase is extremely small. However, if the solid fraction is less than 1%, a coarse columnar crystal structure may be partially formed.
%. If the solid phase ratio of the slurry exceeds 40%, the viscosity becomes abruptly increased in the case of austenitic stainless steel and it becomes difficult to handle. Therefore, it is desirable to set the upper limit to 40% in consideration of the injection work.
【0014】鋳片の板厚に関しては、10mmを超えると凝
固速度が小さくなるため凝固時に生成する粒状晶が粗大
して結晶粒界に液膜を生成し表面割れが発生しやすくな
る。このため、鋳造すべき鋳片の板厚は10mm以下が最適
である。With respect to the plate thickness of the slab, if the thickness exceeds 10 mm, the solidification rate becomes small, so that the granular crystals formed during solidification become coarse and a liquid film is formed at the crystal grain boundaries, and surface cracking is likely to occur. Therefore, the thickness of the cast piece to be cast is optimally 10 mm or less.
【0015】[0015]
【実施例】SUS310S(21%Ni-25 %Cr) とSUS316L (14 %
Ni-17 %Cr-2.5%Mo) のオースナイト系ステンレス鋼に
ついて、まず電磁攪拌式半凝固金属製造装置を用いて固
相率が0〜45%になる半凝固スラリーを製造し、次いで
このスラリーを、水冷式銅製ロール (ロールの直径:40
0 mm, ロールの幅:205 mm, ロールの間隔:0〜30mm、
ロール回転数:5〜50rpm)を備えた双ロール式薄板製造
装置を用いて鋳造し、得られた鋳片の組織、表面割れの
程度、鋳造性(作業性)について調査した。その結果を
表1に示す。[Example] SUS310S (21% Ni-25% Cr) and SUS316L (14%
Ni-17% Cr-2.5% Mo) austenitic stainless steel, first, using an electromagnetic stirring type semi-solidifying metal manufacturing equipment, a semi-solidifying slurry with a solid fraction of 0-45% is manufactured, and then this slurry A water-cooled copper roll (roll diameter: 40
0 mm, Roll width: 205 mm, Roll spacing: 0-30 mm,
Casting was performed using a twin roll type thin plate manufacturing apparatus equipped with a roll rotation number: 5 to 50 rpm), and the structure of the obtained slab, the degree of surface cracking, and the castability (workability) were investigated. The results are shown in Table 1.
【0016】[0016]
【表1】 [Table 1]
【0017】表1においてNo. 2,3,4,6および7
(適合例)は鋳造組織が初晶粒と微細粒状晶の混合組織
からなり、鋳片表面における割れの発生は全くみられ
ず、鋳造性も良好であった。これに対し、固相率が0%
(完全溶湯)になるNo. 1のものについては鋳造組織が
粗大な柱状晶からなっていて、表面割れも大量に発生し
た。また、固相率が45%になるNo. 4のものは半凝固ス
ラリーの流動性が悪いために鋳造することができず、さ
らにNo. 8のもの (板厚10mm超え) は鋳造組織が初晶粒
と粗大粒状晶の混合組織となって少量ながら表面割れが
みられた。In Table 1, Nos. 2, 3, 4, 6 and 7
In (Compatible example), the cast structure was composed of a mixed structure of primary crystal grains and fine granular crystals, no cracks were observed on the surface of the slab, and the castability was good. On the other hand, the solid fraction is 0%
For No. 1 (completely melted), the cast structure was composed of coarse columnar crystals, and a large amount of surface cracks also occurred. In addition, No. 4 with a solid fraction of 45% could not be cast due to the poor fluidity of the semi-solidified slurry, and No. 8 (thickness exceeding 10 mm) had the first cast structure. Surface cracks were observed in a small amount with a mixed structure of crystal grains and coarse granular crystals.
【0018】なお、この発明に従う適合例については、
極少量の表面研削 (表面きずを除去するための研削では
ない) を行ってから従来法に従い冷間圧延、焼鈍処理を
施して最終製品としたところ、品質的には、鋼塊〜分塊
〜熱延を経る従来材とほぼ同水準にあることが確かめら
れた。Incidentally, regarding the conforming example according to the present invention,
After performing a very small amount of surface grinding (not grinding to remove surface flaws), cold rolling and annealing were performed according to the conventional method to obtain the final product. It was confirmed that it is almost at the same level as the conventional material that has undergone hot rolling.
【0019】[0019]
【発明の効果】この発明によれば、表面割れのないオー
ステイナト系ステンレス鋼の薄板を製造することができ
るようになり、製品歩留りの低減によって大幅なコスト
ダウンが実現できる。According to the present invention, it becomes possible to manufacture a thin plate of austenato stainless steel without surface cracks, and a significant cost reduction can be realized by reducing the product yield.
Claims (3)
域で強く攪拌して得たオーステナイト系ステンレス鋼の
半凝固スラリーを、互いに間隔をおいて対向配置した一
対の冷却ロールを備えた双ロール式連続鋳造機で鋳造す
ることによって薄鋳片とすることを特徴とするオーステ
ナイト系ステンレス薄鋳片の製造方法。1. A pair of cooling rolls, which are opposed to each other with a semi-solidified slurry of austenitic stainless steel obtained by vigorous stirring in a temperature range below the liquidus temperature and above the solidus temperature. A method for producing an austenitic stainless thin cast piece, which comprises forming a thin cast piece by casting with a twin roll type continuous casting machine.
%以下である請求項1記載の方法。2. The solid fraction of the semi-solidified slurry is 1% or more, 40
The method according to claim 1, which is at most%.
又は2記載の方法。3. The thin cast piece has a thickness of 10 mm or less.
Or the method described in 2.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2274093A JPH06234048A (en) | 1993-02-10 | 1993-02-10 | Production of austenitic stainless steel cast strip |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2274093A JPH06234048A (en) | 1993-02-10 | 1993-02-10 | Production of austenitic stainless steel cast strip |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH06234048A true JPH06234048A (en) | 1994-08-23 |
Family
ID=12091118
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP2274093A Pending JPH06234048A (en) | 1993-02-10 | 1993-02-10 | Production of austenitic stainless steel cast strip |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH06234048A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7963136B2 (en) * | 2004-10-13 | 2011-06-21 | Siemens Vai Metals Technologies Gmbh & Co | Process and apparatus for the continuous production of a thin metal strip |
-
1993
- 1993-02-10 JP JP2274093A patent/JPH06234048A/en active Pending
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7963136B2 (en) * | 2004-10-13 | 2011-06-21 | Siemens Vai Metals Technologies Gmbh & Co | Process and apparatus for the continuous production of a thin metal strip |
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