JP3058229B2 - Method for producing thin cast chromium stainless steel slab with excellent toughness - Google Patents
Method for producing thin cast chromium stainless steel slab with excellent toughnessInfo
- Publication number
- JP3058229B2 JP3058229B2 JP4294387A JP29438792A JP3058229B2 JP 3058229 B2 JP3058229 B2 JP 3058229B2 JP 4294387 A JP4294387 A JP 4294387A JP 29438792 A JP29438792 A JP 29438792A JP 3058229 B2 JP3058229 B2 JP 3058229B2
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- Prior art keywords
- slab
- toughness
- stainless steel
- less
- 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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- Heat Treatment Of Sheet Steel (AREA)
- Metal Rolling (AREA)
- Continuous Casting (AREA)
- Heat Treatment Of Steel (AREA)
Description
【0001】[0001]
【産業上の利用分野】近年溶鋼から板厚10mm以下の薄
鋳片を直接鋳造する技術が開発され、すでに工業的規模
での実施も行われている。新しいこの技術は、熱間圧延
工程が省略され、薄鋳片を直接冷延して冷間圧延薄板製
品を製造するプロセスであり、省エネルギー、省コスト
の点で大きく期待され、注目を集めている。以後、本発
明のプロセスをSTCプロセス(Strip Cast
ing Process)と称し、連続鋳造によって板
厚100mm以上のスラブを鋳造し、熱間圧延を行って板
厚数mm程度の熱延板とし、熱延板から冷間圧延薄板製品
を製造するプロセスを現行熱延プロセスと称する。本発
明は、STCプロセスでNbを含むCr系ステンレス鋼
薄鋳片を製造する際に、良好な靱性を有する薄鋳片を製
造する方法に関するものである。2. Description of the Related Art In recent years, a technique for directly casting a thin slab having a plate thickness of 10 mm or less from molten steel has been developed, and has already been practiced on an industrial scale. This new technology eliminates the hot-rolling process and is a process that directly cold-rolls thin slabs to produce cold-rolled sheet products. . Hereinafter, the process of the present invention is referred to as an STC process (Strip Cast Process).
The process of casting a slab with a thickness of 100 mm or more by continuous casting, performing hot rolling to a hot-rolled sheet having a thickness of about several mm, and manufacturing a cold-rolled sheet product from the hot-rolled sheet. Called the current hot rolling process. The present invention relates to a method for producing a thin cast slab having good toughness when producing a Cr-based stainless steel thin cast containing Nb by an STC process.
【0002】[0002]
【従来の技術】従来、Cr系のステンレス鋼はスラブを
鋳造し、熱間圧延を経て製造する所謂現行熱延プロセス
で製造していた。このプロセスでは熱延時に発達した集
合組織によって冷間圧延薄板製品にリジング(ローピン
グ)が発生する問題があった。そこで、STCプロセス
で薄鋳片を鋳造し、リジングの無い薄板製品を製造する
試みが行われている。例えば、特開昭62−17664
9号公報で「ローピングのないフェライト系ステンレス
鋼薄板帯の製造方法」が述べられている。しかし、この
発明においてはNbを0.2〜1.0wt%含有するCr
系のステンレス鋼において発生する靱性の劣化現象につ
いては述べられておらず、Nbを0.2〜1.0wt%含
有するCr系のステンレス鋼を鋳造した場合、鋳片の靱
性が劣化し、その後の冷間圧延が行えないと言う問題が
あった。2. Description of the Related Art Conventionally, Cr-based stainless steel has been manufactured by a so-called current hot rolling process in which a slab is cast and subjected to hot rolling. In this process, there was a problem that ridging (roping) occurred in the cold-rolled sheet product due to the texture developed during hot rolling. Therefore, an attempt has been made to produce a thin product without ridging by casting a thin slab by the STC process. For example, Japanese Patent Application Laid-Open No. Sho 62-17664
No. 9 describes "a method for producing a ferritic stainless steel sheet strip without roping". However, in the present invention, Cr containing 0.2 to 1.0 wt% of Nb is used.
No mention is made of the phenomenon of toughness degradation occurring in stainless steels of the system type. When a Cr type stainless steel containing 0.2 to 1.0 wt% of Nb is cast, the toughness of the slab deteriorates. Cannot be cold rolled.
【0003】また特開昭64−4458号公報「靱性に
優れるフェライト系ステンレス鋼急冷帯」では鋳片の柱
状晶率を70%以上にする事によって、靱性の良い鋳片
を製造する事が出来ると述べられているが、Nbを含有
するCr系ステンレス鋼の鋳片の靱性と鋳片の温度履歴
についての、技術的な検討は全く行われていない。Further, in Japanese Patent Application Laid-Open No. 64-4458, "Quenching zone of ferritic stainless steel excellent in toughness", a slab having good toughness can be manufactured by setting the columnar crystal ratio of the slab to 70% or more. However, no technical study has been conducted on the toughness of the cast slab of Cr-based stainless steel containing Nb and the temperature history of the cast slab.
【0004】[0004]
【発明が解決しようとする課題】本発明者らはSTCプ
ロセスでNb添加型Cr系ステンレス鋼薄鋳片の製造試
験を行って来たが、その結果、Nb添加型Cr系ステン
レス鋼薄鋳片は鋳片靱性が低く、鋳片を冷間圧延する事
が出来ないと言う問題が発生した。この問題は鋳片の組
織(柱状晶率 等)に関係無く発生し、Nbを0.2wt
%以上含有するCr系ステンレス鋼においてのみ発生し
た。一方、現行熱延プロセスにおいては、熱延焼鈍板の
靱性に関する問題はなく、本課題がSTCプロセスに特
有な課題である事が判った。The present inventors have conducted a production test of Nb-added Cr-based stainless steel thin slabs by the STC process. Has a problem that the slab has low toughness and cannot be cold rolled. This problem occurs regardless of the structure of the slab (columnar crystal ratio, etc.).
% Only in Cr-based stainless steels containing more than 1%. On the other hand, in the current hot rolling process, there was no problem regarding the toughness of the hot rolled annealed sheet, and it was found that this problem was a problem peculiar to the STC process.
【0005】[0005]
【課題を解決するための手段】本発明は、上記課題を解
決するために次の様な構成とした。すなわち、本発明は
Cr:16〜25wt%,Nb:0.2wt〜1.0wt%,
Ti:0.01〜0.5wt%を含むCr系ステンレス鋼
から板厚10mm以下の薄鋳片を鋳造する方法において、
鋳造直後に1250〜900℃の温度域で機内保温処
理、すなわち20℃/sec 以下の緩冷却又は保温、或い
は20℃/s以下の加熱のいずれも一つの処理を4秒以
上行い、その後鋳片を650℃以下の温度で巻き取る事
からなるCr系ステンレス鋼薄鋳片の製造方法を特徴と
するものである。以下、本発明を詳細に説明する。Means for Solving the Problems The present invention has the following structure to solve the above-mentioned problems. That is, the present invention provides Cr: 16 to 25 wt%, Nb: 0.2 to 1.0 wt%,
In a method of casting a thin slab having a plate thickness of 10 mm or less from a Cr-based stainless steel containing Ti: 0.01 to 0.5 wt%,
Immediately after casting, in-machine heat treatment in a temperature range of 1250 to 900 ° C, that is, one of slow cooling or heat keeping at 20 ° C / sec or less, or heating at 20 ° C / s or less is performed for 4 seconds or more, and then slabs. Is rolled at a temperature of 650 ° C. or less. Hereinafter, the present invention will be described in detail.
【0006】[0006]
【作用】Cr:16〜25wt%,Nb:0.2〜1.0
wt%,Ti:0.01〜0.5wt%を含むCr系ステン
レス鋼から鋳造した薄鋳片の靱性は鋼中の析出物の挙動
に大きく影響される。鋳片の析出物サイズと量が靱性に
及ぼす影響を図1に模式的に示す。最も靱性を劣化させ
る析出物はFe3 Nb3 C(M6 C),Fe2 Nb(L
aves)である。これらの析出物は鋼中に多量にかつ
粗大に析出するので極端に靱性を劣化する。この2種の
析出物は700〜1000℃の温度域で析出するので、
この温度域で鋳片を巻き取ると鋳片靱性は著しく劣化す
る。[Action] Cr: 16 to 25 wt%, Nb: 0.2 to 1.0
The toughness of a thin slab cast from a Cr-based stainless steel containing 0.1% by weight and 0.01% by weight of Ti is greatly affected by the behavior of precipitates in the steel. FIG. 1 schematically shows the effect of the size and amount of the slab precipitate on the toughness. The precipitates which deteriorate the toughness most are Fe 3 Nb 3 C (M 6 C) and Fe 2 Nb (L
aves). Since these precipitates precipitate in a large amount and coarsely in steel, the toughness extremely deteriorates. Since these two kinds of precipitates precipitate in a temperature range of 700 to 1000 ° C.,
When the slab is wound in this temperature range, the slab toughness is significantly degraded.
【0007】次に靱性を劣化させる析出物としては(N
b,Cr)Nがある。(Nb,Cr)Nは凝固時のNb
偏析部に非常に微細に析出し、母地の強度を上げるため
靱性が劣化する。また、その次に靱性を劣化させる析出
物としてはNb(C,N),Ti(C,N)がある。N
b(C,N),Ti(C,N)は凝固温度から約120
0℃の間に析出しており、大変安定している。[0007] Next, as precipitates that deteriorate toughness, (N
b, Cr) N. (Nb, Cr) N is Nb during solidification
It precipitates very finely in the segregated part, and the toughness deteriorates because the strength of the base material is increased. Next, there are Nb (C, N) and Ti (C, N) as precipitates which deteriorate toughness. N
b (C, N) and Ti (C, N) are about 120
It precipitates during 0 ° C and is very stable.
【0008】従って、鋳片の靱性を向上させるために
は、これら種々の析出物の析出を防止しなければならな
い。そこで、本発明では1200〜900℃の温度域で
機内保温処理、すなわち20℃/sec 以下の冷却速度の
緩冷却、又は保温、或いは20℃/s以下の加熱を4秒
以上行う事によって、Nbの偏析を拡散させ、その後、
700℃以下の温度で巻き取る事によって、Fe3 Nb
3 C,Fe2 Nbや(Nb,Cr)Nが無い良好な靱性
を有する薄鋳片の製造を可能にした。但し、Nb(C,
N),Ti(C,N)は残存しており、Nb無添加材に
比べれば靱性は低くなっているが、ほぼ問題無いレベル
である。Therefore, in order to improve the toughness of the slab, it is necessary to prevent the precipitation of these various precipitates. Therefore, in the present invention, Nb is kept in a temperature range of 1200 to 900 ° C., that is, by performing slow cooling at a cooling rate of 20 ° C./sec or less, or keeping the temperature, or heating at 20 ° C./s or less for 4 seconds or more. Diffuse the segregation of
By winding at a temperature of 700 ° C. or less, Fe 3 Nb
It is possible to produce a thin cast piece having good toughness without 3 C, Fe 2 Nb or (Nb, Cr) N. However, Nb (C,
N) and Ti (C, N) remain, and the toughness is lower than that of the Nb-free material, but at a level that is almost no problem.
【0009】Cr濃度を16wt%以上とした理由は16
wt%未満にすると鋳片の冷却中にγループを横切るため
γから変態したマルテンサイトが室温においても残存
し、鋳片の靱性を劣化させるためである。又、25wt%
以下とした理由はCrが増えたことによって靱性の劣化
が生じるため、鋳造後の鋳片の温度履歴を制御しても、
鋳片靱性を向上出来なかったためである。The reason for setting the Cr concentration to 16 wt% or more is 16
If the content is less than wt%, the slab crosses the γ loop during cooling of the slab, so that martensite transformed from γ remains even at room temperature and deteriorates the toughness of the slab. Also, 25wt%
The reason given below is that the toughness deteriorates due to the increase in Cr, so even if the temperature history of the cast slab is controlled,
This is because the slab toughness could not be improved.
【0010】Nbの量を0.2wt%以上とした理由は
0.2wt%未満ではこの様な析出物による靱性の劣化が
発生しなかったためであり、1.0wt%以下とした理由
は、1.0wt%超のNbを含むと鋳造後の鋳片の温度履
歴を制御しても、鋳片靱性を改善出来なかったためであ
る。The reason why the amount of Nb is set to 0.2 wt% or more is that if the content is less than 0.2 wt%, the toughness does not deteriorate due to such precipitates. This is because if Nb exceeds 0.0 wt%, the slab toughness cannot be improved even if the temperature history of the slab after casting is controlled.
【0011】Tiの量を0.01wt%以上にした理由
は、Tiを0.01wt%以上添加する事によって、鋳片
の表面性状が改善されるためであり、1.0wt%以下と
した理由は1.0wt%超のTiを含むとTi系の大型析
出物(介在物)によって鋳片の靱性が著しく劣化するた
めである。[0011] The reason why the amount of Ti is set to 0.01 wt% or more is that by adding 0.01 wt% or more of Ti, the surface properties of the slab are improved. The reason is that if more than 1.0 wt% of Ti is contained, the toughness of the slab is significantly deteriorated by large Ti-based precipitates (inclusions).
【0012】図2に鋳片の巻取り温度と鋳片靱性の関係
を示す。700℃超で巻き取る事によって、鋳片靱性が
劣化する事が判る。図3には、1250〜900℃の温
度範囲における機内保温条件が鋳片靱性に及ぼす影響を
示した。機内保温として鋳片を20℃/sec 以下の緩冷
却又は保温或いは20℃/sec 以下の加熱を4秒以上処
理すれば、鋳片靱性が向上する事が判る。図4には機内
保温の設備を示す。鋳造後の鋳片Sの温度履歴を巻取り
までの搬送ラインにおいて制御する設備である。図中、
1は双ドラム式鋳造機、2は機内保温装置、3は2次冷
却装置、4はコイラーである。FIG. 2 shows the relationship between the slab winding temperature and the slab toughness. It turns out that the slab toughness is deteriorated by winding at a temperature exceeding 700 ° C. FIG. 3 shows the effect of in-machine heat retention conditions in a temperature range of 1250 to 900 ° C. on slab toughness. It can be seen that the slab toughness is improved if the slab is slowly cooled or kept at 20 ° C./sec or less or heated at 20 ° C./sec or less for 4 seconds or more as the heat retention in the machine. FIG. 4 shows equipment for keeping the temperature in the machine. This is a facility for controlling the temperature history of the cast slab S after casting in a transport line up to winding. In the figure,
1 is a twin-drum casting machine, 2 is an in-machine warming device, 3 is a secondary cooling device, and 4 is a coiler.
【0013】[0013]
【実施例】表1に示す18%のCr鋼を基本とするNb
を0.15〜0.64wt%含有する本発明範囲内の成分
の各種Cr系ステンレス鋼を10トン溶製し、内部水冷
式の双ドラム鋳造機によって板厚3mmの薄鋳片に鋳造
し、1250〜900℃の温度域で種々の保定又は緩冷
却、又は加熱を行った後、650℃以下の温度域で巻き
取った。また比較法として同様の成分(表1)のCr系
ステンレス鋼から同様の方法で薄鋳片を鋳造し、鋳造
後、1250〜900℃の冷却速度、又は巻取り温度が
本発明の範囲外になる様にして冷却した。以上の方法で
製造した各鋳片の靱性を表2に示す。この表で示すよう
に、本発明の方法で製造した薄鋳片は20℃で2kgfm/
cm2 以上の良好な靱性を示したが、比較法で製造した薄
鋳片は20℃での靱性が2kgfm/cm2 以下で、冷延が出
来ないほど靱性が低かった。EXAMPLE Nb based on 18% Cr steel shown in Table 1
10 tons of various Cr-based stainless steels containing 0.15 to 0.64 wt% of the components within the range of the present invention and cast into a thin slab having a thickness of 3 mm by an internal water-cooled twin-drum casting machine. After performing various holding, slow cooling, or heating in a temperature range of 1250 to 900 ° C, winding was performed in a temperature range of 650 ° C or less. As a comparative method, a thin slab is cast from a Cr-based stainless steel having the same composition (Table 1) by the same method, and after the casting, the cooling rate of 1250 to 900 ° C or the winding temperature is out of the range of the present invention. It was cooled as it was. Table 2 shows the toughness of each slab produced by the above method. As shown in this table, the thin slab produced by the method of the present invention was 2 kgfm / 20 ° C.
Although good toughness of not less than 2 cm 2 was exhibited, the thin slab produced by the comparative method had a toughness at 20 ° C. of 2 kgfm / cm 2 or less, and was so low that cold rolling was impossible.
【0014】[0014]
【表1】 [Table 1]
【0015】[0015]
【表2】 [Table 2]
【0016】[0016]
【発明の効果】本発明によりSTCプロセスによって良
好な靱性を有するNb添加型Cr系ステンレス鋼薄鋳片
を製造する事が出来る。従って、経済性の点でその技術
的効果は極めて大きい。According to the present invention, an Nb-added Cr-based stainless steel thin slab having good toughness can be manufactured by the STC process. Therefore, the technical effect is extremely large in terms of economy.
【図1】鋳片の析出物と鋳片靱性の関係を示す図であ
る。FIG. 1 is a view showing the relationship between precipitates of a slab and slab toughness.
【図2】鋳片の巻取り温度と鋳片靱性の関係を示す図で
ある。FIG. 2 is a diagram showing a relationship between a slab winding temperature and a slab toughness.
【図3】鋳片の機内保温条件と鋳片靱性との関係を示す
図である。FIG. 3 is a diagram showing a relationship between in-machine heat retention conditions of a slab and slab toughness.
【図4】機内保温の設備的イメージを示す概略図であ
る。FIG. 4 is a schematic diagram showing an equipment image of in-machine heat retention.
1…双ドラム式鋳造機 2…機内保温装置 3…2次冷却装置 4…コイラー DESCRIPTION OF SYMBOLS 1 ... Twin drum type casting machine 2 ... In-machine heat insulation apparatus 3 ... Secondary cooling apparatus 4 ... Coiler
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 FI C22C 38/00 302 C22C 38/00 302Z 38/50 38/50 (72)発明者 桐原 端史 山口県光市大字島田3434番地 新日本製 鐵株式会社光製鐵所内 (72)発明者 岡 秀毅 山口県光市大字島田3434番地 新日本製 鐵株式会社光製鐵所内 (56)参考文献 特開 平2−258931(JP,A) 特開 平1−197046(JP,A) 特開 平5−293595(JP,A) 特開 昭60−2628(JP,A) 特開 昭62−176649(JP,A) 特開 昭64−4458(JP,A) (58)調査した分野(Int.Cl.7,DB名) B22D 11/06 330 B21B 3/02 C21D 6/00 102 C21D 8/02 C21D 9/46 C22C 38/00 302 C22C 38/50 ──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. 7 Identification code FI C22C 38/00 302 C22C 38/00 302Z 38/50 38/50 (72) Inventor Katsuhara Kishihara 3434 Shimada, Oaza, Hikari-shi, Yamaguchi Nippon Steel Corporation Hikari Works (72) Inventor Hideki Oka 3434 Shimada, Hikari-shi, Yamaguchi Prefecture Nippon Steel Corporation Hikari Works (56) References JP-A-2-258931 (JP, A JP-A-1-197046 (JP, A) JP-A-5-293595 (JP, A) JP-A-60-2628 (JP, A) JP-A-62-176649 (JP, A) JP-A 64-64 4458 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) B22D 11/06 330 B21B 3/02 C21D 6/00 102 C21D 8/02 C21D 9/46 C22C 38/00 302 C22C 38/50
Claims (2)
1.0wt%,Ti:0.01〜0.5wt%を含むCr系
ステンレス鋼から板厚10mm以下の薄鋳片を鋳造する方
法において、鋳造直後に1250〜900℃の温度域で
機内保温処理を4秒以上行い、その後鋳片を700℃以
下の温度で巻き取る事を特徴とする靱性の優れたCr系
ステンレス鋼薄鋳片の製造方法。1. Cr: 16-25 wt%, Nb: 0.2-
In a method of casting a thin slab having a plate thickness of 10 mm or less from a Cr-based stainless steel containing 1.0 wt% and Ti: 0.01 to 0.5 wt%, the in-machine heat treatment is performed in a temperature range of 1250 to 900 ° C. immediately after casting. For 4 seconds or more, and then winding the slab at a temperature of 700 ° C. or less.
速度の緩冷却、保温又は20℃/s以下の加熱の内のい
ずれか一つの処理である請求項1記載の製造方法。2. The method according to claim 1, wherein the in-machine heat-retaining treatment is any one of slow cooling at a cooling rate of 20 ° C./sec or less, heat keeping or heating at 20 ° C./s or less.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP4294387A JP3058229B2 (en) | 1992-11-02 | 1992-11-02 | Method for producing thin cast chromium stainless steel slab with excellent toughness |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP4294387A JP3058229B2 (en) | 1992-11-02 | 1992-11-02 | Method for producing thin cast chromium stainless steel slab with excellent toughness |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH06142712A JPH06142712A (en) | 1994-05-24 |
JP3058229B2 true JP3058229B2 (en) | 2000-07-04 |
Family
ID=17807073
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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JP4294387A Expired - Fee Related JP3058229B2 (en) | 1992-11-02 | 1992-11-02 | Method for producing thin cast chromium stainless steel slab with excellent toughness |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP3058229B2 (en) |
-
1992
- 1992-11-02 JP JP4294387A patent/JP3058229B2/en not_active Expired - Fee Related
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JPH06142712A (en) | 1994-05-24 |
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