JP5716376B2 - Method for determining surface cracks in slabs in continuous casting - Google Patents
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- JP5716376B2 JP5716376B2 JP2010281560A JP2010281560A JP5716376B2 JP 5716376 B2 JP5716376 B2 JP 5716376B2 JP 2010281560 A JP2010281560 A JP 2010281560A JP 2010281560 A JP2010281560 A JP 2010281560A JP 5716376 B2 JP5716376 B2 JP 5716376B2
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- 238000000034 method Methods 0.000 title claims description 21
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- 238000004458 analytical method Methods 0.000 description 5
- 238000005452 bending Methods 0.000 description 5
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- 238000009864 tensile test Methods 0.000 description 2
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Description
本発明は、連続鋳造機の矯正帯(上部、下部)における、鋳片にかかる応力状態や高温での延性低下に起因して発生する鋳片の表面割れを判定する有効な方法について提案する。 The present invention proposes an effective method for determining a surface crack of a slab caused by a stress state applied to a slab and a ductility decrease at a high temperature in a straightening band (upper and lower) of a continuous casting machine.
連続鋳造鋳片の表面に発生する横割れ(以下、「表面割れ」という)は、連続鋳造鋳片の代表的な欠陥の一つであり、鋼板の品質低下の一因であり、このような表面割れは阻止しなければならない。なお、この鋳片の表面割れ発生原因については、一般に、連続鋳造機の矯正帯における鋳片表面温度が、鋳造鋳片の延性低下温度(以下、「脆化温度」という)域にあるときに、発生するものと考えられている。 Transverse cracks (hereinafter referred to as “surface cracks”) generated on the surface of continuous cast slabs are one of the typical defects of continuous cast slabs and contribute to the deterioration of steel sheet quality. Surface cracks must be prevented. As for the cause of the surface cracking of the slab, generally, when the slab surface temperature in the straightening zone of the continuous casting machine is in the ductility lowering temperature (hereinafter referred to as “embrittlement temperature”) region of the cast slab. , Is considered to occur.
連続鋳造鋳片の表面割れの発生を阻止する方法に関して、特許文献1には、鋳片に大きな変形が加わる矯正域における鋳片の表面温度分布を、二次冷却帯の冷却水量の調整により制御し、この領域内での鋳片表面温度を脆化温度域外に導くことにより、表面割れを防止する方法が開示されている。
Regarding a method for preventing the occurrence of surface cracks in a continuous cast slab,
特許文献2には、Ar3点未満のオーステナイト相の変態が完了しない温度域で冷却を停止し、その後、鋳片の表面温度を950〜1200℃まで復熱させた連続鋳造鋳片に対して、鋳片の厚さに応じて定められる表面割れ発生の限界歪よりも鋳造鋳片に負荷されている矯正歪の方を小さくすることにより、鋳片表面割れの発生を防止するという、鋼の連続鋳造方法が開示されている。
また、特許文献3には、鋳片の表面割れ予測方法として、連続鋳造機の二次冷却帯における鋳片表面の幅方向温度分布を測定し、鋳片表面温度の高低差(山谷差)によって定まる鋼の表面熱応力が、表面割れ臨界応力を上回ると同時に、その高低差(山谷差)区間内に熱間延性低下温度域が存在するような場合に、鋳片に表面割れが発生したとする割れ予測方法を開示している。
しかしながら、鋳片表面温度を延性温度域に復熱させる、特許文献lおよび2に開示されているような方法は、連続鋳造の能率を著しく低下させるという問題があり、生産性の向上には不向きである。
However, methods such as those disclosed in
また、特許文献3では、矯正帯における鋳片の幅方向表面温度の高低山谷区間の温度差の大きさと、脆化温度がその山谷区間に含まれるようなときをもって表面割れを判定しているが、鋳片の幅方向表面温度分布等の温度偏差以外、例えば、鋳片の厚さ方向の温度偏差に起因する表面割れについては考慮されていない。
Moreover, in
本発明の目的は、表面割れ発生については連続鋳造機の矯正帯に到達するまでの鋳片表面の温度偏差だけでなく、矯正帯における鋳片の厚さ方向(断面)温度分布およびその温度分布に起因する熱応力の状態をも考慮して、表面割れの発生を推定するという、連続鋳造鋳片の表面割れ判定方法を提案することにある。 The object of the present invention is not only the temperature deviation of the slab surface until reaching the straightening zone of the continuous casting machine, but also the thickness direction (cross-section) temperature distribution of the slab and its temperature distribution in the straightening zone. Another object is to propose a method for determining surface cracks in a continuous cast slab in which the occurrence of surface cracks is estimated in consideration of the state of thermal stress caused by the above.
従来技術が抱えている上述した課題を解決し、上記目的を達成する方法につき鋭意研究を重ねた結果、発明者らは、少なくとも少なくとも下部矯正帯を有する連続鋳造機によって、鋼の連続鋳造を行うにあたり、その下部矯正帯における連続鋳造鋳片表面の線膨張率αsと該鋳片断面方向の平均温度での線膨張率αtとの線膨張率比αt/αsが、限界線膨張率比αt/αs(cri)を上回ったときに、該鋳片表面に横割れが生じたものと判定することを特徴とする、連続鋳造における鋳片表面の割れ判定方法を開発した。 As a result of earnestly researching how to solve the above-mentioned problems of the prior art and achieving the above object, the inventors perform continuous casting of steel by a continuous casting machine having at least a lower correction band. In this case, the linear expansion coefficient ratio αt / αs between the linear expansion coefficient αs of the continuous cast slab surface in the lower straightening zone and the linear expansion coefficient αt at the average temperature in the cross section direction of the slab is the critical linear expansion coefficient ratio αt / A method for determining cracks on the slab surface in continuous casting has been developed, characterized in that it is determined that transverse cracks have occurred on the slab surface when αs (cri) is exceeded.
また、本発明において、前記限界線膨率比αt/αs(cri)Hとは、連続鋳造機の下部矯正帯において、連続鋳造鋳片表面に割れが発生し始める時の、該鋳片にかかる静水圧応力σmとそのときの降伏応力σoとの比で示される限界応力比σm/σo(cri)が最小値を示す値に相当する線膨張率比であって、該矯正帯における鋳片の線膨張率比αt/αsがこの限界線膨張率比αt/αs(cri)を上回るか否かをもって、該鋳片の表面割れ発生の有無を推定することが好ましい。 In the present invention, the critical linear expansion ratio αt / αs (cri) H is applied to the slab when cracks start to occur on the surface of the continuous cast slab in the lower straightening zone of the continuous casting machine. The linear expansion coefficient ratio corresponding to the value at which the critical stress ratio σm / σo (cri) indicated by the ratio between the hydrostatic stress σm and the yield stress σo at that time is a minimum value, It is preferable to estimate the occurrence of surface cracks in the slab depending on whether or not the linear expansion coefficient ratio αt / αs exceeds the limit linear expansion coefficient ratio αt / αs (cri).
さらに、本発明において、前記連続鋳造鋳片は、0.01〜36mass%のNiを含有する鋼を処理対象とすることが好ましい。 Furthermore, in the present invention, the continuous cast slab is preferably treated with steel containing 0.01 to 36 mass% Ni.
前記のような構成を有する本発明によれば、矯正帯での連続鋳造鋳片に生じる限界応力比(鋳片表面および断面平均温度の推定値)から求められる応力比に基づいて算出される線膨張率αt、σsを所定の限界線膨張率と対比することによって、鋳片の表面割れを判定する方法であるから、鋳片の表面のみならず断面の応力状態を考慮したものになるため、鋳片の表面割れの発生を正確に判定することができる。 According to the present invention having the above-described configuration, a line calculated based on a stress ratio obtained from a critical stress ratio (estimated value of slab surface and cross-section average temperature) generated in a continuous cast slab in a straightening band. By comparing the expansion coefficients αt and σs with the predetermined critical linear expansion coefficient, it is a method for determining the surface crack of the slab, so that it takes into account the stress state of the cross section as well as the surface of the slab, Generation | occurrence | production of the surface crack of a slab can be determined correctly.
以下、本発明の構成の詳細を説明する。
図1に本発明方法を適用するのに好適な連続鋳造機の断面図を示す。この図において、符号1は、連続鋳造機を示す。この連続鋳造機1において、取鍋2内溶鋼はタンディッシュ3を経て、連続鋳造用モールド4に注出され冷却されることにより、凝固シェルを生成する。その凝固シェルはそのモールド4を出た後鋳片支持ロール5によって支持されながら、二次冷却帯(二次冷却装置6)により冷却され、凝固シェルの厚みを次第に増加させながら連続的に引き抜かれる。その間、図示のような垂直曲げ型連続鋳造機においては、凝固シェルが肥厚化して形成される鋳片10が、上部矯正帯7(曲げ帯)にて垂直方向から次第に湾曲しながら、下部矯正帯8(曲げ矯正帯)にまで達し、やがて湾曲状態から水平状態に矯正される。なお、図示した垂直曲げ型連続鋳造機は、少な
Details of the configuration of the present invention will be described below.
FIG. 1 shows a cross-sectional view of a continuous casting machine suitable for applying the method of the present invention. In this figure, the code |
発明者らの経験によれば、一般に、Niを含有する鋼(以下、「Ni含有鋼」という)の連続鋳造鋳片は、連続鋳造機1の下部矯正帯8において表面割れが頻繁に発生することがわかっている。この表面割れ発生原因としては、下部矯正帯8において、特に鋳片の表面に熱間延性低下部が存在する場合に、その箇所に引張り応力や歪が負荷され、表面割れとなって現われるものと考えられている。しかも、Ni含有鋼というのは、Niが粒界に偏析しやすく、この偏析部から粒界酸化やAlN等の介在物の析出により粒界が著しく脆化し、表面割れが発生しやすい鋼種である。
According to the experiences of the inventors, generally, in a continuous cast slab of steel containing Ni (hereinafter referred to as “Ni-containing steel”), surface cracks frequently occur in the lower straightening zone 8 of the
また、発明者らの知見によれば、連続鋳造時の二次冷却パターンが強冷却のときには、連続鋳造鋳片の表面割れが多く発生していた。これは、強冷却により鋳片表面温度が一時的に大きく低下して、鋳片内部との温度差が大きくなるため、該鋳片表面に発生する熱膨張率差に起因した熱応力が大きくなり、このことと前記の脆化した粒界の影響とが相俟って、表面割れを発生しやすい状態になったものと考えられる。 Further, according to the knowledge of the inventors, when the secondary cooling pattern during continuous casting is strong cooling, many surface cracks of the continuous cast slab occurred. This is because the slab surface temperature temporarily decreases greatly due to strong cooling, and the temperature difference from the inside of the slab increases, so the thermal stress due to the difference in thermal expansion coefficient generated on the surface of the slab increases. It is considered that this fact and the influence of the above-mentioned embrittled grain boundaries are in a state where surface cracks are likely to occur.
このような鋳片表面割れの現象は、例えば大入熱材である0.01mass%Ni鋼、LNGタンク材である9mass%Ni鋼あるいは、36mass%Ni鋼等の、Niを少なくとも0.01〜36mass%含有している鋼種においてよく見られる。下記表1は、表面割れを起こしやすいNi含有鋼種代表的な化学成分を示す。 Such slab surface cracking is caused by, for example, 0.01 mass% Ni steel, which is a large heat input material, 9 mass% Ni steel, which is an LNG tank material, or 36 mass% Ni steel. It is often found in steel types containing 36 mass%. Table 1 below shows typical chemical components of Ni-containing steel types that are prone to surface cracking.
ところで、発明者らの研究によると、Ni含有鋼などによく見られる鋳片の表面割れ現象は、鋳片表面での静水圧応力σmとその温度における降伏応力σoとの関係で示すことができることを突き止めた。即ち、鋳片の表面割れ現象は、鋳片表面でのこうした2つの応力の比σm/σo(以下、「応力比」という)で表わすことができることがわかる。 By the way, according to the research of the inventors, the surface cracking phenomenon of the slab often seen in Ni-containing steel can be shown by the relationship between the hydrostatic stress σm on the slab surface and the yield stress σo at that temperature. I found out. That is, it can be seen that the surface cracking phenomenon of the slab can be expressed by the ratio σm / σo (hereinafter referred to as “stress ratio”) of these two stresses on the slab surface.
図2は、熱間3点曲げ試験時の試験片表面に発生した表面割れ深さと鋳片表面の応力比との関係を示す。この図において、実線および破線で示す近似線と横軸の交点が限界応力比になる。この図からわかるように、表面割れは、応力比σm/σoがある一定値(この場合、応力比:1.8〜1.9)を超えると発生している。このような割れが発生する限界を、限界応力比σm/σo(cri)とする。 FIG. 2 shows the relationship between the surface crack depth generated on the surface of the test piece during the hot three-point bending test and the stress ratio of the slab surface. In this figure, the intersection of the approximate line indicated by the solid line and the broken line and the horizontal axis is the critical stress ratio. As can be seen from this figure, the surface crack occurs when the stress ratio σm / σo exceeds a certain value (in this case, the stress ratio: 1.8 to 1.9). The limit at which such cracking occurs is defined as a critical stress ratio σm / σo (cri).
また、発明者らは、連続鋳造機内の鋳造鋳片の温度分布、熱応力、歪状態についても調査した。そのために、まず、鋳片の伝熱・凝固計算および熱応力解析を行った。その結果、鋳片断面方向の平均温度での線膨張率αtおよび鋳片表面の線膨張率αsとの比αt/αsと、前記応力比σm/σoとは、連続鋳造機および鋳片の厚みが固定されている条件下では一定の関係があることがわかった。このことから、前記応力比のσm/σoから線膨張率比αt/αsへの推測が可能であることがわかる。なお、αは常温を基準とした線膨張率であり、例えば、それぞれの鋳片温度における熱線膨張率α(−)は、図3に示すように、熱機械分析(TMA)[JIS G 0202]により求めることができる。なお、以下の説明では、熱線膨張率を含めて、単に「線膨張率」と略記する。 The inventors also investigated the temperature distribution, thermal stress, and strain state of the cast slab in the continuous casting machine. For this purpose, first, heat transfer / solidification calculation and thermal stress analysis of the slab were performed. As a result, the ratio αt / αs between the linear expansion coefficient αt at the average temperature in the cross-section direction of the slab and the linear expansion coefficient αs of the slab surface, and the stress ratio σm / σo are the thicknesses of the continuous casting machine and the slab. It was found that there is a certain relationship under the condition that is fixed. From this, it can be seen that the stress ratio σm / σo can be estimated to the linear expansion coefficient ratio αt / αs. Α is a linear expansion coefficient based on normal temperature. For example, as shown in FIG. 3, the thermal linear expansion coefficient α (−) at each slab temperature is thermomechanical analysis (TMA) [JIS G 0202]. It can ask for. In the following description, the thermal expansion coefficient is simply abbreviated as “linear expansion coefficient”.
次に、発明者らは、厚さが258mm、幅が2100mmのNi含有鋼の連続鋳造鋳片について、連続鋳造機の二次冷却帯における二次冷却水量および熱伝達係数を仮定し、周知の伝熱・凝固計算を行うことで、前記矯正帯における鋳片の断面平均温度および鋳片の表面温度をそれぞれ計算し、これらの値から前記線膨張率比αt/αsを算出した。 Next, the inventors assumed a secondary cooling water amount and a heat transfer coefficient in a secondary cooling zone of a continuous casting machine for a Ni-containing steel continuous cast slab having a thickness of 258 mm and a width of 2100 mm. By performing heat transfer / solidification calculations, the cross-sectional average temperature of the slab and the surface temperature of the slab in the straightening zone were calculated, and the linear expansion coefficient ratio αt / αs was calculated from these values.
即ち、図4は、前記計算結果に基づいて算出した線膨張率比αt/αsと、そのときの鋳片表面の応力比σm/σoとの関係を示したものである。なお、図中破線は近似線、点線は表面割れが発生するときの限界応力比σm/σo(cri)と、そのときの線膨張率比αt/αsを示す。 That is, FIG. 4 shows the relationship between the linear expansion coefficient ratio αt / αs calculated based on the calculation result and the stress ratio σm / σo of the slab surface at that time. In the figure, the broken line indicates the approximate line, and the dotted line indicates the critical stress ratio σm / σo (cri) when the surface crack occurs and the linear expansion coefficient ratio αt / αs at that time.
この図4から、応力比σm/σoは線膨張率比αt/αsにほぼ比例した強い相関関係があり、鋳片表面の応力比から線膨張率比αt/αsの推測が可能であることがわかる。このことはまた、限界応力比σm/σo(cri)から限界線膨張率比をαt/αs(cri)を求めることができることも意味している。従って、この限界線膨張率比αt/αs(cri)を限界値(規定値)とし、矯正帯における連続鋳造鋳片の線膨張率比αt/αsが上記限界線膨張率比(cri)を上回るときに、鋳片に表面割れが発生したと推定(判定)することができ、このことによって鋳片表面の割れ判定を行うことが可能になる。この例においては、図4より、限界応力比σm/σo(cri)の最小値が1.7の場合、線膨張率比αt/αsは2.4であると推定できる。 From FIG. 4, the stress ratio σm / σo has a strong correlation substantially proportional to the linear expansion coefficient ratio αt / αs , and the linear expansion coefficient ratio αt / αs can be estimated from the stress ratio of the slab surface. Recognize. This also means that the limit linear expansion coefficient ratio αt / αs (cri) can be obtained from the limit stress ratio σm / σo (cri). Therefore, this limit linear expansion coefficient ratio αt / αs (cri) is set as a limit value (specified value), and the linear expansion coefficient ratio αt / αs of the continuous cast slab in the straightening zone exceeds the above limit linear expansion coefficient ratio (cri). Sometimes it can be estimated (determined) that a surface crack has occurred in the slab, and this makes it possible to determine the crack on the surface of the slab. In this example, it can be estimated from FIG. 4 that the linear expansion coefficient ratio αt / αs is 2.4 when the minimum value of the critical stress ratio σm / σo (cri) is 1.7.
このように本発明によれば、応力解析をするまでもなく、連続鋳造鋳片表面、断面の温度分布から、前記線膨張率比αt/αsを求めることにより、連続鋳造機の下部矯正帯における連続鋳造鋳片の応力状態に基づいて鋳片表面の割れの有無を判定することが可能になる。 As described above, according to the present invention, the linear expansion coefficient ratio αt / αs is obtained from the temperature distribution of the continuous cast slab surface and cross section without performing stress analysis. It is possible to determine the presence or absence of cracks on the surface of the slab based on the stress state of the continuous cast slab.
本発明の適用にあたって、前記応力比σm/σoを求める方法としては、鋳片に表面割れが発生した時の鋳片表面の静水圧応力σmを、その鋳片から切り出した試験片を熱間3点曲げ試験や熱間引張試験等の割れ再現試験を行って求めることができる。例えば、割れ再現試験に当たって、応力解析により試験片表面に発生した各開口割れ位置における静水圧応力σmを算出し、また、鋳片(鋼種)の降伏応力σoについては、熱間引張試験をして得られる。 In the application of the present invention, the stress ratio σm / σo is obtained by measuring the hydrostatic stress σm on the surface of the slab when surface cracks occur in the slab, and hot-testing the test piece cut out from the slab. It can be determined by performing a crack reproduction test such as a point bending test or a hot tensile test. For example, in the crack reproduction test, the hydrostatic pressure stress σm at each opening crack position generated on the surface of the test piece is calculated by stress analysis, and the yield stress σo of the slab (steel type) is subjected to a hot tensile test. can get.
このようにして得られる前記限界応力比σm/σo(cri)と、割れ再現試験片温度との関係について、図5に示した。この図に示すように、割れ再現試験を行うことによって、鋳片表面温度に応じた該鋳片表面の限界応力比σm/σo(cri)(図中の破線で示す)を求めることができ、これを鋳片の表面に割れが発生する否かの基準値(クライテリア)として採用することができる。
なお、クライテリアとは、鋳片割れについての判断基準であり、基準値を超えるσm/σo(cri)が該鋳片表面に生じる時、その箇所に表面割れが発生する可能性が極めて高いことを示す。
FIG. 5 shows the relationship between the critical stress ratio σm / σo (cri) thus obtained and the crack reproduction test piece temperature. As shown in this figure, by performing a crack reproduction test, the critical stress ratio σm / σo (cri) (shown by a broken line in the figure) of the slab surface according to the slab surface temperature can be obtained, This can be adopted as a reference value (criteria) as to whether or not cracking occurs on the surface of the slab.
Criteria is a criterion for slab cracking. When σm / σo (cri) exceeding the standard value is generated on the surface of the slab, it indicates that the possibility of surface cracking at that location is extremely high. .
なお、連続鋳造鋳片の伝熱・凝固計算については、一般的に実用されている鋳片の凝固過程における伝熱計算を行うことで、また、鋳片断面の温度分布は差分法に基づいて計算をする。 Regarding the heat transfer and solidification calculation of continuous cast slabs, the heat transfer calculation in the solidification process of slabs that is generally used is performed, and the temperature distribution of the cross section of the slab is based on the difference method. Calculate.
この実施例は、厚み:258mm、幅:2100mmの前述の表1に示すNi含有鋼鋳片について、垂直曲げ連続鋳造機の下部矯正帯における鋳片表面の幅方向温度分布が、図6に示すようになる鋳片の表面割れについて評価したものである。なお、この図において、幅位置における横軸の0は幅方向センターを示し、1000mmは片側端部を示す。また、表2は、このときの鋳造条件を示しており、一方は、二次冷却帯の下部曲げ矯正帯までの冷却水量を増加させた強冷却パターンの連続鋳造鋳片をもう一方は、その二次冷却帯の水量を低減させた緩冷却パターンの連続鋳造鋳片を示している。各冷却パターンの鋳片断面の平均温度は、伝熱・凝固計算により、強冷却パターンでは1219℃、緩冷却パターンでは1234℃であることがわかった。これら温度から鋳片幅中央部の線膨張率比αt/αsを算出した結果、強冷却パターンではその値が2.6、緩冷却パターンでは2.0であった。そして、このときの本発明で説明した前記限界線膨張率比αt/αs(cri)は、それぞれ2.48である。 In this example, the Ni-containing steel slab shown in Table 1 having a thickness of 258 mm and a width of 2100 mm is shown in FIG. This is an evaluation of the surface cracks of the cast slab. In this figure, 0 on the horizontal axis at the width position indicates the center in the width direction, and 1000 mm indicates one end. Table 2 shows the casting conditions at this time. One is a continuous casting slab with a strong cooling pattern in which the amount of cooling water up to the lower bending straightening zone of the secondary cooling zone is increased. The continuous casting slab of the slow cooling pattern which reduced the water quantity of the secondary cooling zone is shown. The average temperature of the slab section of each cooling pattern was found to be 1219 ° C. for the strong cooling pattern and 1234 ° C. for the slow cooling pattern by heat transfer and solidification calculations. As a result of calculating the linear expansion coefficient ratio αt / αs at the center of the slab width from these temperatures, the value was 2.6 for the strong cooling pattern and 2.0 for the slow cooling pattern. At this time, the limiting linear expansion coefficient ratio αt / αs (cri) described in the present invention is 2.48, respectively.
そこで、本発明方法に従い、前記線膨張率比αt/αsと、前記限界線膨張率比αt/αs(cri)とを対比したところ、表2に示したようになり、前記冷却パターンで連続鋳造した鋳片の表面割れを調査したところ、強冷却パターンにおいては幅中央部に表面割れが発生していた。一方、緩冷却パターンでは、下部矯正帯における鋳片の表面温度は800℃程度であり、該鋳片の熱間延性低下温度域が700〜900℃であったにもかかわらず、表面割れは発生していなかった。 Therefore, according to the method of the present invention, the linear expansion coefficient ratio αt / αs and the limiting linear expansion coefficient ratio αt / αs (cri) are compared, and as shown in Table 2, continuous casting with the cooling pattern is performed. When the surface crack of the cast slab was investigated, the surface crack occurred at the center of the width in the strong cooling pattern. On the other hand, in the slow cooling pattern, the surface temperature of the slab in the lower straightening zone is about 800 ° C., and the surface crack occurs even though the hot ductility lowering temperature range of the slab is 700 to 900 ° C. I did not.
このように、本発明に適合する判定方法を採用すれば、連続鋳造における鋳片の応力解析を行わなくとも、連続鋳造鋳片の矯正帯付近における鋳片断面の温度分布を伝熱・凝固計算により計算し、鋳片の線膨張率比αt/αsを算出し、これを表面割れが発生するときの限界熱線膨張率比αt/αs(cri)と比較することで、正確な表面割れの判定が可能になる。 As described above, if the determination method suitable for the present invention is adopted, the temperature distribution of the slab cross section near the straightening zone of the continuous cast slab can be calculated by heat transfer / solidification calculation without performing stress analysis of the slab in continuous casting. Calculate the ratio of thermal expansion coefficient αt / αs of the slab and compare it with the critical thermal expansion coefficient ratio αt / αs (cri) when surface cracks occur, so that the accurate determination of surface cracks Is possible.
本発明に係る前述の技術は、下部に矯正帯をもつ連続鋳造機のみならず、上部にも矯正帯をもつ湾曲型連続鋳造機等の幅広い設備での割れ判定方法への適用が可能である。 The above-described technique according to the present invention can be applied not only to a continuous casting machine having a straightening band at the bottom but also to a crack determination method in a wide range of equipment such as a curved continuous casting machine having a straightening band at the top. .
1 連続鋳造機
2 取鍋
3 タンデッシュ
4 モールド
5 鋳片支持ロール
6 二次冷却装置
7 上部矯正帯
8 下部矯正帯
9 表面温度計
10 鋳片
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