JP2917641B2 - Steel continuous casting method - Google Patents

Steel continuous casting method

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Publication number
JP2917641B2
JP2917641B2 JP4002837A JP283792A JP2917641B2 JP 2917641 B2 JP2917641 B2 JP 2917641B2 JP 4002837 A JP4002837 A JP 4002837A JP 283792 A JP283792 A JP 283792A JP 2917641 B2 JP2917641 B2 JP 2917641B2
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JP
Japan
Prior art keywords
strain
slab
steel
continuous casting
zdt
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JP4002837A
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Japanese (ja)
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JPH05185183A (en
Inventor
章裕 山中
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Nippon Steel Corp
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Sumitomo Metal Industries Ltd
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Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【0001】[0001]

【産業上の利用分野】本発明は、鋳片の内部割れを発生
させずに鋼を連続鋳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 continuously casting steel without causing internal cracks in a slab.

【0002】[0002]

【従来の技術】鋼の連続鋳造法は、その発祥以来たゆみ
なく改良が加えられ、ほぼ完成に近い形になっている
が、それでもなお、いくつかの未解決の問題を残してい
る。その一つが鋳片の内部に発生する“内部割れ”であ
る。
BACKGROUND OF THE INVENTION Continuous casting of steel has been continuously improved since its inception and is nearing completion, but nonetheless still has some unsolved problems. One of them is "internal cracking" that occurs inside the slab.

【0003】連続鋳造においては、鋳型内に供給された
溶融金属が鋳型によって冷却され、凝固殻を成形した
後、支持ロールによってサポートされながら、水スプレ
ー等による二次冷却を受けて徐々に凝固が進行し、最終
的に完全凝固した鋳片を所定長さに切断する方式が採ら
れている。この間鋳片内部に未凝固部が存在しており、
連続鋳造中の鋳片の曲げ、曲げ矯正、バルジング、ミス
アラインメント、熱応力等により、引張歪が生じて凝固
界面が裂けることにより、前記の内部割れが発生するも
のと考えられる。近年生産性の向上を図るため、鋳造の
高速化が進められているが、鋳造速度を大きくすること
により、内部割れ発生頻度が大きくなり、内部割れの発
生が鋳造速度を律する一要因となっている。
[0003] In continuous casting, molten metal supplied into a mold is cooled by the mold to form a solidified shell, and then, while being supported by a support roll, is subjected to secondary cooling by water spray or the like to gradually solidify. A method of cutting a slab that has progressed and finally completely solidified to a predetermined length is adopted. During this time, there is an unsolidified part inside the slab,
It is considered that the above-mentioned internal cracks occur due to the occurrence of tensile strain due to bending, straightening, bulging, misalignment, thermal stress, and the like of the slab during continuous casting, causing the solidification interface to tear. In recent years, casting has been accelerated to improve productivity.However, by increasing the casting speed, the frequency of occurrence of internal cracks has increased, and the occurrence of internal cracks is a factor that determines the casting speed. I have.

【0004】また、線材、管材向けのブルーム、ラウン
ド、ビレットあるいは厚板向けのスラブなどを対象とす
る連続鋳造において、中心偏析、センターポロシティを
改善するために鋳片の未凝固圧下技術が採用されつつあ
る。鋳片を圧下すると凝固界面に引張歪が生じ、この際
圧下量、圧下時期等を誤ると内部割れの発生を招くこと
になる。これらに関し、以下の技術が公知である。
[0004] In continuous casting for blooms, rounds, billets for wires and pipes, and slabs for thick plates, etc., a technique of unsolidifying and reducing the slab is adopted to improve center segregation and center porosity. It is getting. When the slab is rolled down, tensile strain is generated at the solidification interface. At this time, if the rolling amount, the rolling timing and the like are wrong, internal cracks will be caused. Regarding these, the following techniques are known.

【0005】鉄と鋼、73(1987)、S909「オンライン内
部割れ診断、防止システムの開発」 これは、鋳造中の操業情報を取り込んだ歪計算により限
界歪と対比して、内部割れを診断し、防止システムをコ
ントロールするものである。
Iron and steel, 73 (1987), S909 "Development of on-line internal crack diagnosis and prevention system" This is to diagnose internal cracks by comparing with limit strain by strain calculation incorporating operation information during casting. , To control the prevention system.

【0006】材料とプロセス、Vol.4(1991)、297
「強圧下による中心偏析改善結果」 これは、大径のロールを用いて未凝固圧下を行うことに
より、凝固界面歪を極力小さくして、圧下時の内部割れ
を防止するものである。
Materials and Processes, Vol. 4 (1991), 297
"Improvement of center segregation by strong reduction" This is to reduce the solidification interfacial strain as much as possible by performing unsolidification reduction using a large-diameter roll, thereby preventing internal cracking during reduction.

【0007】特開平3−174962号公報「鋼の連続鋳造
法」 これは、本発明者らが提案した方法であるが、その骨子
はZST〜ZDTの間で鋳片に加わる歪の蓄積を考慮し
て、その歪の総和がある一定限界値(限界歪)を超えな
いように鋳造条件および装置の設計条件を定めるという
ものである。しかし、この限界歪を鋼の組成成分から導
き出すことはある程度可能であるが鋼の成分と歪量総和
限界値との関係についての知見は未だ不十分である。
Japanese Unexamined Patent Publication No. Hei 3-174962, "Continuous casting of steel" This is a method proposed by the present inventors, but its main feature is to consider the accumulation of strain applied to the slab between ZST and ZDT. Then, the casting conditions and the design conditions of the apparatus are determined so that the sum of the strains does not exceed a certain limit value (limit strain). However, although it is possible to derive this critical strain from the composition of the steel to some extent, knowledge on the relationship between the steel composition and the total strain limit is still insufficient.

【0008】すなわち、鋼片の内部割れ発生の感受性に
大きく影響を与える成分として、Mnがあることは経験的
には知られているが、上記の発明においても、限界歪
とZST〜ZDTの間の加わる歪の総和との関係につい
てMn成分を考慮しておらず、また他の従来技術において
も、鋼の必須成分であるC、Mn、P、Sを考慮の上、総
合的かつ定量的に検討し、広範囲で実用に供することが
できるようにした知見は見当たらない。
That is, it is empirically known that Mn is a component that greatly affects the susceptibility of a steel slab to the occurrence of internal cracks. Does not consider the Mn component in relation to the sum of the strains added, and also in other conventional technologies, comprehensively and quantitatively, taking into account the essential components C, Mn, P, and S of steel. There is no finding that has been examined and made practical for a wide range.

【0009】[0009]

【発明が解決しようとする課題】連続鋳造鋳片の内部割
れに対して、前記のように種々の防止対策が提案されて
いるが、未だいずれも実用上十分なものではない。
Various measures have been proposed to prevent internal cracks in continuous cast slabs, as described above, but none of them is practically sufficient.

【0010】本発明の目的は、鋼の必須成分であるC、
Mn、P、Sを実用的な広い含有量の範囲で総合的に考慮
して、これらの成分から、加わる歪量の総和限界値を直
接定量的に求め、ZST〜ZDTの間の歪量の総和がこ
の値を超えない条件で鋳造して、内部割れの発生を防止
すると共に、高品質の鋳片を高速度で鋳造できる連続鋳
造方法を提供することにある。
It is an object of the present invention to provide C, an essential component of steel,
Considering Mn, P, and S comprehensively in a practically wide range of contents, the total limit value of the applied strain is directly and quantitatively determined from these components, and the strain of ZST to ZDT is determined. An object of the present invention is to provide a continuous casting method in which casting is performed under a condition that the sum does not exceed this value to prevent the occurrence of internal cracks and to cast a high-quality slab at a high speed.

【0011】[0011]

【課題を解決するための手段】本発明者らは、前記の発
明を基礎として更に、従来経験的にしか知られていなか
った、Mnの割れ感受性に与える影響を広い範囲で実験的
に種々検討した。その結果、特にSとの関係について、
互いに独立に影響を与えるのではなく、MnSを形成する
ために相互的に影響を与え合うことおよびMnとSの比
(〔Mn〕/〔S〕)とC含有量とが割れ感受性と密接な
係わりがあることを見い出した。また、内部割れ発生に
及ぼす歪み総和量限界値はこのMnとSの比およびC含有
量といくつかの定数を組み合わせることによって含有成
分から簡便な数式によって導き出せることも見い出し
た。本発明はこれらの知見に基づいてなされたものであ
り、その要旨は下記の連続鋳造方法にある。
Means for Solving the Problems Based on the above-mentioned invention, the present inventors have further experimentally studied a wide range of effects on Mn cracking susceptibility, which have been known only empirically. did. As a result, especially regarding the relationship with S,
Instead of affecting each other independently, they influence each other to form MnS, and the ratio of Mn to S ([Mn] / [S]) and C content are closely related to crack susceptibility. We found that there was relation. It has also been found that the limit value of the total amount of strain exerted on the occurrence of internal cracks can be derived from the contained components by a simple mathematical formula by combining the ratio of Mn and S and the C content with some constants. The present invention has been made based on these findings, and its gist lies in the following continuous casting method.

【0012】重量%で、C:0.85%以下、P:0.03%以
下、Mn: 2.5%以下、S: 0.001〜0.1 %の成分範囲に
ある鋼の連続鋳造において、鋼片の各部が、少なくとも
抗張力出現温度(ZST)と延性出現温度(ZDT)の
間の温度域にある間に、加わる歪量の総和が、次式で規
定されるεC (%) の値を超えない条件で鋳造すること
を特徴とする連続鋳造方法である。
[0012] In the continuous casting of steel in a component range of C: 0.85% or less, P: 0.03% or less, Mn: 2.5% or less, S: 0.001 to 0.1% by weight, each part of the billet has at least tensile strength. Casting under the condition that the total amount of applied strain does not exceed the value of ε C (%) defined by the following equation while in the temperature range between the appearance temperature (ZST) and the ductility appearance temperature (ZDT) It is a continuous casting method characterized by the following.

【0013】 εC =K1 ×{〔Mn〕/〔S〕}−K2 〔C〕+K3 ・・・(イ) ただし、〔Mn〕、〔S〕および〔C〕は、溶鋼中のMn、
SおよびCの含有量(重量%)であり、K1 、K2 およ
びK3 は下記〜の定数である。
Ε C = K 1 × {[Mn] / [S]} − K 2 [C] + K 3 (B) where [Mn], [S] and [C] are Mn,
It is the content (% by weight) of S and C, and K 1 , K 2 and K 3 are the following constants.

【0014】 〔Mn〕/〔S〕≦ 100で〔C〕≦0.22のとき: K1 =0.012 、K2 =7.5 、K3 =2.1 〔Mn〕/〔S〕> 100で〔C〕≦0.22のとき: K1 =0.004 、K2 =7.5 、K3 =3.0 〔Mn〕/〔S〕≦ 100で0.22<〔C〕≦0.85のとき: K1 =0.012 、K2 =1.4 、K3 =0.86 〔Mn〕/〔S〕> 100で0.22<〔C〕≦0.85のとき: K1 =0.004 、K2 =1.4 、K3 =1.6[Mn] / [S] ≦ 100 and [C] ≦ 0.22: K 1 = 0.012, K 2 = 7.5, K 3 = 2.1 [Mn] / [S]> 100 and [C] ≦ 0.22 When: K 1 = 0.004, K 2 = 7.5, K 3 = 3.0 [Mn] / [S] ≦ 100 and 0.22 <[C] ≦ 0.85: K 1 = 0.012, K 2 = 1.4, K 3 = 0.86 [Mn] / [S]> 100 and 0.22 <[C] ≦ 0.85: K 1 = 0.004, K 2 = 1.4, K 3 = 1.6

【0015】[0015]

【作用】連続鋳造中の鋳片の各部は、最初液体の状態か
ら固液共存状態を経て、完全凝固、冷却に到る間に抗張
力出現温度(ZST)、延性出現温度(ZDT)を経る
ことが知られている。このZSTとZDTは鋼種によっ
て定まる値で、その値は例えば Arch.Eisenhuttenwesen
54(1983).357 によって公知の方法で測定することがで
きる。また、ZSTとZDTの値は固相率とよく対応す
ることも知られており、ZSTは固相率 0.8の点に、Z
DTは固相率0.99の点にそれぞれほぼ一致する(「鉄と
鋼」’87−S896) 。
Each part of the slab during continuous casting first undergoes a tensile strength appearance temperature (ZST) and a ductile appearance temperature (ZDT) from complete liquid state to solid-liquid coexistence state to complete solidification and cooling. It has been known. ZST and ZDT are values determined by the type of steel, and the values are, for example, Arch. Eisenhuttenwesen
54 (1983) .357 by a known method. It is also known that the values of ZST and ZDT correspond well with the solid fraction.
DT almost coincides with the point of the solid phase ratio of 0.99 ("Iron and steel"'87 -S896).

【0016】図1は、連続鋳造における鋳片の凝固過程
を模式的に示す図である。同図において、モールドMに
注入された溶鋼は、下方に引き抜かれて行くに従って冷
却され、凝固層(シェル)Sが次第に厚くなって行く。
この凝固層Sと中心部の液相(L)の間には、固液共存
層(S+L)がある。今、鋳片の長手方向(引抜方向)
の一定位置P1 においてA1 点を固相率 0.8の点とすれ
ば、ここから抗張力が現れ始める。即ち、A1 点の温度
がZSTである。同じ位置P1 においてB1 点を固相率
0.99の点とすれば、ここから延性が現れこの温度がZD
Tである。
FIG. 1 is a view schematically showing a solidification process of a slab in continuous casting. In the figure, the molten steel injected into the mold M is cooled as it is drawn downward, and the solidified layer (shell) S gradually becomes thicker.
There is a solid-liquid coexistence layer (S + L) between the solidified layer S and the liquid phase (L) at the center. Now, the longitudinal direction of the slab (drawing direction)
If at a certain position P 1 and the point of the solid fraction 0.8 1 point A, tensile strength begins to appear here. That is, the temperature at point A 1 is ZST. The solid fraction a point B at the same position P 1
Assuming a point of 0.99, ductility appears from this and this temperature is ZD
T.

【0017】先のA1 点を鋳片の引抜方向に追っていく
と、A2 点でZDTに達し、延性が現れることになる。
ZSTは応力が加わり歪を生じ始める最高温度であり、
ZDTは、これ以下の温度であれば歪が生じても延性が
あるために割れは生じない限界の温度である。鋳片の各
部は、連続鋳造中、曲げ、バルジング、矯正、熱応力等
により、ZSTからZDTを経る間に前記のような様々
な歪を受けることになる。
If the point A 1 is followed in the direction of drawing the slab, ZDT is reached at the point A 2 and ductility appears.
ZST is the maximum temperature at which stress is applied and strain begins to occur,
ZDT is a limit temperature at which the cracking does not occur due to ductility even if strain occurs at a temperature lower than this. Each part of the slab is subjected to various strains as described above during the continuous casting, due to bending, bulging, straightening, thermal stress, and the like, while passing from ZST to ZDT.

【0018】本発明者らは、特開平3−17496 号公報に
記載のように、鋳片各部がZSTからZDTまでの温度
域にある間に受けた歪が、歪を受けるたびに緩和しない
で、そのまま蓄積するとして、その蓄積した歪の総量
(Σε、ただし範囲はZST〜ZDT、以下Eと記す)
が或る限界値(限界歪εC )を越えると割れが発生し、
それ以下であれば割れが発生しないことを種々の実験を
繰り返すことによって確認した。図2は、その実験の一
つで、割れ発生限界歪の測定方法を説明するものである
(詳細は本発明者らの論文、材料とプロセス、Vol.1(1
988)、P.1229参照)。
As described in Japanese Patent Application Laid-Open No. 3-17496, the inventors of the present invention do not reduce the strain received while each part of the slab is in the temperature range from ZST to ZDT each time it receives the strain. Is stored as it is, the total amount of the stored strain (Σε, where ZST to ZDT, hereinafter referred to as E)
Exceeds a certain limit (critical strain ε C ), cracks occur,
It was confirmed by repeating various experiments that cracking did not occur if it was less than that. FIG. 2 illustrates one of the experiments, which describes a method of measuring the critical strain for crack initiation (for details, see the papers of the present inventors, Materials and Processes, Vol.
988), p.1229).

【0019】内部割れ発生限界歪は、連続鋳造鋳片とほ
ぼ同一の条件となる様に鋳造した小型の鋳塊に種々の変
形を加えて、その歪量の大小と割れの発生の有無を調べ
る事により求めた。即ち、図2に示すような中央部が未
凝固の状態である鋳塊に一軸の引張変形を与えて歪を生
じさせた。変形量、変形回数、変形と変形の間の時間間
隔を種々変え、これらを組み合わせて変形を与えた。ま
た鋳塊の内部に温度測定用の熱電対をセットしておき、
温度を確認しながら、全歪量のうちZST〜ZDTの間
で加わる歪量を求めた。
The critical strain for the occurrence of internal cracks is determined by applying various deformations to a small ingot cast under the same conditions as in a continuous cast slab, and examining the magnitude of the strain and the occurrence of cracks. Asked by the thing. That is, a uniaxial tensile deformation was applied to an ingot whose center portion was in an unsolidified state as shown in FIG. 2 to generate strain. The amount of deformation, the number of deformations, and the time interval between deformations were variously changed, and these were combined to give a deformation. Also, set a thermocouple for temperature measurement inside the ingot,
While confirming the temperature, the amount of strain applied between ZST and ZDT in the total amount of strain was determined.

【0020】冷却条件を連続鋳造鋳片で考え得る範囲で
変化させる事により、温度測定点の冷却速度を変えて、
各点がZST〜ZDTの間にある時間を変化させた。
By changing the cooling conditions within a range that can be considered for continuous cast slabs, the cooling rate at the temperature measurement point is changed,
The time during which each point was between ZST and ZDT was varied.

【0021】図3は、C:0.15%、Mn: 0.6%、S:
0.012%、P:0.02%の成分の鋼を対象として、横軸に
冷却条件、縦軸に生じた歪量の総和をとって内部割れの
発生の有無を調べた結果を示す。歪量は、生じた歪量の
総和(Σε)とZST〜ZDTの間に加わった歪量の総
和(E)とに区別して示してある。
FIG. 3 shows that C: 0.15%, Mn: 0.6%, S:
For steel having a composition of 0.012% and P: 0.02%, the abscissa indicates the cooling conditions and the ordinate indicates the sum of the amount of strain generated, and the result of examining the occurrence of internal cracks is shown. The amount of distortion is shown separately from the total amount of generated distortion (Σε) and the total amount of distortion added between ZST and ZDT (E).

【0022】図3に示すとおり、Eが本発明の式で求め
た限界歪εC である約 1.6%を越えると内部割れが発生
しており、これが限界歪となる。またこの限界歪は、冷
却条件によって変化していないことがわかる。一方、生
じた総歪量Σεによって判定される割れ発生限界値は、
上記の約 1.6%よりも大きい。これは、ZDT以下で加
えられた歪もカウントされているからであり、その歪は
凝固シェルのもつ延性により伸びとなって吸収され割れ
発生の要因にはならない。また、生じた総歪量Σεによ
る割れ発生限界値は、冷却条件によって変化し、冷却速
度が大きくなるほど大きくなっている。
As shown in FIG. 3, when E exceeds the critical strain ε C obtained by the equation of the present invention, which is about 1.6%, internal cracks occur, and this is the critical strain. It can also be seen that this critical strain has not changed with cooling conditions. On the other hand, the crack initiation limit value determined by the total strain
Greater than about 1.6% above. This is because the strain applied below the ZDT is also counted, and the strain is absorbed as elongation due to the ductility of the solidified shell and does not cause cracking. Further, the limit value of crack generation due to the generated total strain Δε changes depending on the cooling conditions, and increases as the cooling rate increases.

【0023】Eは、先に述べた様々の加わった歪の組合
せであるが、変形の種類によらず、この総歪量が限界値
を越えると割れが発生する。連続鋳造において鋳片に加
わる歪の主要なものは、曲げ歪、矯正歪、バルジング
歪、ミスアラインメント歪および熱歪である。これらそ
れぞれの歪のうち、鋳片各部がZST〜ZDT間にある
ときに加わる歪の和を、それぞれΣεr 、Σεu 、Σε
b 、Σεm およびΣεt とすれば、これらの総和、即ち
Eは下記のようになる。
E is a combination of the various added strains described above, but cracks occur when the total strain exceeds the limit value regardless of the type of deformation. The main types of strain applied to a slab in continuous casting are bending strain, straightening strain, bulging strain, misalignment strain, and thermal strain. Of these strains, the sum of the strains applied when the cast slab is between ZST and ZDT is represented by Σε r , Σε u , and Σε, respectively.
b, if Shigumaipushiron m and Shigumaipushiron t, the sum of these, i.e. E is as follows.

【0024】 Σεr +Σεu +Σεb +Σεm +Σεt =E このEが、ある限界値εC (先の図3では約 1.6%)を
超えれば内部割れが発生することになる。従って、鋳片
が完全強固に到るまで、少なくとも、E≦εC の条件を
維持して鋳造を行うことが必要である。なお、鋼種によ
ってZDT以下の温度域でも延性が極く小さい温度域が
存在する場合には、延性が十分に大きくなる温度範囲ま
で拡大して、その間の総合歪を限界歪以下に抑えること
が好ましい。
Σε r + Σε u + Σε b + Σε m + Σε t = E If E exceeds a certain limit value ε C (about 1.6% in FIG. 3 described above), internal cracks occur. Therefore, it is necessary to perform the casting while maintaining at least the condition of E ≦ ε C until the slab is completely solid. If there is a temperature range where ductility is extremely small even in a temperature range equal to or lower than ZDT depending on the type of steel, it is preferable that the temperature range is expanded to a temperature range where ductility becomes sufficiently large and the total strain during that time is suppressed to a limit strain or less. .

【0025】次いで、上述のような知見を、実用的に広
い成分組成範囲にまで拡張適用するために、高Cおよび
高Mnの範囲まで図2に示す方法によって同様の試験を実
施して組成と内部割れ発生の感受性との関係を調査し
た。すなわちC:0.85%以下、P:0.03%以下、Mn:
2.5%以下、S: 0.1%以下の範囲で、鋼の組成を種々
変更した鋳塊に異なる変形量を加え、その時の歪量の総
和と割れ発生との関係を調査することにより、組成に応
じた内部割れ発生の限界歪を求めた。その結果を図4に
示す。縦軸E(%)は、鋳塊のZST〜ZDTの間に加
わった歪量の総和であり、横軸εC (%)は、鋼の組成
毎に求めた限界歪である。なお、図4において斜めの線
がE=εC を、εC =13の縦線が前記(イ)式で求まる
εC の値のとりうる最大値、すなわち適用限界をそれぞ
れ示す。
Next, in order to extend the above knowledge to a practically wide range of component composition, a similar test was conducted by the method shown in FIG. The relationship with the susceptibility of internal cracking was investigated. That is, C: 0.85% or less, P: 0.03% or less, Mn:
In the range of 2.5% or less and S: 0.1% or less, different deformations are added to the ingot with various steel compositions, and the relationship between the total strain and the occurrence of cracks at that time is investigated. The critical strain for the occurrence of internal cracking was determined. FIG. 4 shows the results. The vertical axis E (%) is the total amount of strain applied between the ZST and ZDT of the ingot, and the horizontal axis ε C (%) is the limit strain obtained for each steel composition. In FIG. 4, the oblique line indicates E = ε C , and the vertical line of ε C = 13 indicates the maximum possible value of ε C obtained by the above equation (a), that is, the applicable limit.

【0026】各成分のうち、Pは0.03%以下では内部割
れに対し無関係であり、またMnとSは独立して影響を与
えるのではなく、内部割れの起点となる非金属介在物Mn
S生成との関連において、〔Mn〕/〔S〕と更に〔C〕
に応じて限界歪εC に影響を与え、前記(イ)式によっ
て規定されることがわかった。なお、定数K1 〜K3
〜に示すように、成分毎に決まる数字であるが、こ
れらは、図4の結果から前記(イ)式の構造を仮定して
多重回帰分析を行って求めたものである。
Of the components, if P is 0.03% or less, P is irrelevant to internal cracking, and Mn and S do not independently affect each other, but nonmetallic inclusions Mn that serve as starting points for internal cracking.
In relation to S generation, [Mn] / [S] and further [C]
It affects the critical strain ε C in accordance with the equation (1), and is determined to be defined by the equation (A). The constants K 1 to K 3 are numbers determined for each component as shown in the following. These are obtained from the results of FIG. 4 by performing multiple regression analysis on the assumption of the structure of the above equation (A). It is a thing.

【0027】本発明の方法によれば、鋳込み開始前に鋼
の組成が明らかになった時点で、簡便な式により直ちに
その組成成分毎に決まる限界歪みを算出することができ
る。
According to the method of the present invention, when the composition of the steel becomes clear before the start of casting, the critical strain determined for each composition component can be immediately calculated by a simple formula.

【0028】[0028]

【実施例】鋼の成分を本発明の範囲で変更し、下記条件
で連続鋳造を実施した。
EXAMPLES Continuous casting was carried out under the following conditions while changing the composition of steel within the scope of the present invention.

【0029】連続鋳造機 :垂直曲げ(V−B)型 曲 げ :5点 矯 正 :4点 スラブサイズ:2000mm幅×250mm 厚 溶鋼過熱度 :40〜50℃(タンディッシュ内) 鋳造速度 : 0.5〜2.5m/min 冷却水(比水)量: 1.0〜2.5l/kg(鋼) なお、各ロール配置は、鋳片の中心部の固相率が0.3 〜
0.8となる凝固末期に鋳片に対して最大4mmの圧下が加
わるようにした。また鋳造中に、鋳片の表面温度とロー
ル圧力を鋳造初期から末期に至るまで連続測定し、鋳片
内部の歪量を応力解析により連続的に算出するようにし
た。このようにして、本発明の限界歪量を求める式によ
るεC を鋼の成分毎に算出し、鋳片内部の歪量と常時比
較しながら運転を監視し、この歪量が限界εC 値を超え
る場合は、二次冷却水量の増加、鋳造速度の低下、もし
くは圧下量の低下などの手段を自動的に採れるよう配慮
した。
Continuous casting machine: Vertical bending (V-B) type Bending: 5 points Straightening: 4 points Slab size: 2000 mm width x 250 mm thickness Molten steel superheat degree: 40-50 ° C (in a tundish) Casting speed: 0.5 ~ 2.5m / min Cooling water (specific water) volume: 1.0 ~ 2.5l / kg (steel) In addition, in each roll arrangement, the solid fraction at the center of the slab is 0.3 ~
In the final stage of solidification at 0.8, a maximum reduction of 4 mm was applied to the slab. During casting, the surface temperature and roll pressure of the slab were continuously measured from the initial stage to the final stage, and the strain inside the slab was continuously calculated by stress analysis. In this way, the epsilon C according to formula to obtain the limit strain of the present invention calculated for each component of the steel, to monitor the operation while constantly compared with the strain amount of the internal slab, the amount of distortion limit epsilon C value In the case of exceeding, a measure was taken to automatically take measures such as increasing the amount of secondary cooling water, decreasing the casting speed, or decreasing the rolling reduction.

【0030】一方、比較例は、本発明の式によるεC
を用いず、他条件は同じとして実施した。
On the other hand, the comparative example was carried out under the same conditions without using the ε C value according to the formula of the present invention.

【0031】これらの結果を、鋼の成分から求めた〔M
n〕/〔S〕で層別し、表1に総括的に示す。表1から
明らかなように、本発明の方法による場合は、内部割れ
の発生頻度は0.04〜0.3 回/チャージに対し、εC 値を
使用しない比較例は0.4 〜 1.3回/チャージであり、本
発明方法の内部割れ防止効果は明らかである。
These results were obtained from the steel composition [M
n] / [S] and the results are shown in Table 1. As apparent from Table 1, the case according to the method of the invention, the frequency of occurrence of internal cracks is to 0.04 to 0.3 times / charge, Comparative Examples not using the epsilon C value is 0.4 to 1.3 times / charging, the The effect of the invention method for preventing internal cracks is clear.

【0032】[0032]

【表1】 [Table 1]

【0033】[0033]

【発明の効果】本発明の方法により、鋳造する鋼の組成
成分に応じて加わる歪の総和限界値と計算によって求め
内部割れ発生の危険性を予測し、事前にあるいは鋳造中
に鋳片に加わる内部歪みをこの限界値を超えない範囲に
留めるように鋳込条件を設定することにより、内部割れ
発生を効果的に防止することが可能である。
According to the method of the present invention, the total limit value of the strain applied according to the composition of the steel to be cast is calculated and calculated, and the risk of internal cracking is predicted, and the risk of internal cracking is added to the slab before or during casting. By setting the casting conditions so that the internal strain does not exceed the limit value, it is possible to effectively prevent the occurrence of internal cracks.

【図面の簡単な説明】[Brief description of the drawings]

【図1】ZSTとZDTを説明する連続鋳造鋳片の断面
模式図である。
FIG. 1 is a schematic cross-sectional view of a continuous cast slab illustrating ZST and ZDT.

【図2】内部割れ発生限界歪みを求める実験方法の説明
図である。
FIG. 2 is an explanatory diagram of an experimental method for obtaining an internal crack generation limit strain.

【図3】図2の方法によって求めた鋳塊に加わる歪の総
和と内部割れ発生との関係を示す一例である。
FIG. 3 is an example showing the relationship between the sum of strain applied to an ingot and the occurrence of internal cracks obtained by the method of FIG. 2;

【図4】同じく鋳塊に加わる歪の総和および本発明方法
による限界歪みと内部割れ発生との関係を示す図であ
る。
FIG. 4 is a graph showing the sum of strain applied to an ingot and the relationship between critical strain and the occurrence of internal cracks according to the method of the present invention.

Claims (1)

(57)【特許請求の範囲】(57) [Claims] 【請求項1】重量%で、C:0.85%以下、P:0.03%以
下、Mn: 2.5%以下、S: 0.001〜0.1 %の成分範囲に
ある鋼の連続鋳造において、鋼片の各部が、少なくとも
抗張力出現温度(ZST)と延性出現温度(ZDT)の
間の温度域にある間に、加わる歪量の総和が、次式で規
定されるεc (%) の値を超えない条件で鋳造すること
を特徴とする連続鋳造方法。 εC =K1 ×{〔Mn〕/〔S〕}−K2 〔C〕+K3 ・・・(イ) ただし、〔Mn〕、〔S〕および〔C〕は、溶鋼中のMn、
SおよびCの含有量(重量%)であり、K1 、K2 およ
びK3 は下記〜の定数である。 〔Mn〕/〔S〕≦ 100で〔C〕≦0.22のとき: K1 =0.012 、K2 =7.5 、K3 =2.1 〔Mn〕/〔S〕> 100で〔C〕≦0.22のとき: K1 =0.004 、K2 =7.5 、K3 =3.0 〔Mn〕/〔S〕≦ 100で0.22<〔C〕≦0.85のとき: K1 =0.012 、K2 =1.4 、K3 =0.86 〔Mn〕/〔S〕> 100で0.22<〔C〕≦0.85のとき: K1 =0.004 、K2 =1.4 、K3 =1.6
In a continuous casting of steel having a composition of C: 0.85% or less, P: 0.03% or less, Mn: 2.5% or less, S: 0.001 to 0.1% by weight, each part of a billet is Casting under the condition that the total amount of applied strain does not exceed the value of ε c (%) defined by the following equation at least in the temperature range between the tensile strength appearance temperature (ZST) and the ductility appearance temperature (ZDT) A continuous casting method. ε C = K 1 × {[Mn] / [S]} − K 2 [C] + K 3 (B) where [Mn], [S] and [C] are Mn in molten steel,
It is the content (% by weight) of S and C, and K 1 , K 2 and K 3 are the following constants. [Mn] / [S] ≦ 100 and [C] ≦ 0.22: K 1 = 0.012, K 2 = 7.5, K 3 = 2.1 [Mn] / [S]> 100 and [C] ≦ 0.22: K 1 = 0.004, K 2 = 7.5, K 3 = 3.0 [Mn] / [S] ≦ 100 and 0.22 <[C] ≦ 0.85: K 1 = 0.012, K 2 = 1.4, K 3 = 0.86 [Mn ] / [S]> 100 and 0.22 <[C] ≦ 0.85: K 1 = 0.004, K 2 = 1.4, K 3 = 1.6
JP4002837A 1992-01-10 1992-01-10 Steel continuous casting method Expired - Lifetime JP2917641B2 (en)

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JP2917641B2 true JP2917641B2 (en) 1999-07-12

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JP4949052B2 (en) * 2007-02-06 2012-06-06 新日本製鐵株式会社 Continuous casting method of steel preventing internal cracking
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