JP2005125402A

JP2005125402A - Method for continuously casting cast block, and method for judging quality of cast block

Info

Publication number: JP2005125402A
Application number: JP2003366298A
Authority: JP
Inventors: Noriyuki Nomoto; 詞之野本
Original assignee: Hitachi Cable Ltd
Current assignee: Hitachi Cable Ltd
Priority date: 2003-10-27
Filing date: 2003-10-27
Publication date: 2005-05-19

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for continuously casting a cast block which controls and manages the casting conditions by directly utilizing the measured result of the internal temperature of a mold without calculating heat flux from the measured value of the internal temperature of the mold to catch the heat transferring state between the surface in the mold and the surface of the cast block and also, a method for judging the quality of the cast block, guarantees the cast block quality over the whole length of the cast block with non-destructive means. <P>SOLUTION: The method for continuously casting the cast block, is performed as the followings, with which in the case of continuously casting the cast block, the internal temperature of the mold is measured at the lapse of time with a thermocouple 15 disposed at the prescribed position on the inner wall 12 of the mold, and in the case that the difference between the maximum value and the minimum value is out of the control value decided by beforehand gathering data related to the relation between the internal temperature of the mold and the cast block quality, after correcting the casting condition, the casting is performed while keeping the casting condition in the control values. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、鋳型内部温度の測定結果を利用して鋳造条件を制御、管理する鋳塊の連続鋳造方法及び、鋳型内部温度の測定結果を利用した鋳塊の品質判定方法に関する。 The present invention relates to an ingot continuous casting method for controlling and managing casting conditions using the measurement result of the mold internal temperature, and an ingot quality determination method using the measurement result of the mold internal temperature.

図６に、従来より用いられている鋳塊の縦型連続鋳造装置の概略を示す。この縦型連続鋳造装置は、銅や銅合金若しくはカーボンでできた中空の鋳型１と、鋳型１の下方に配置され水をシャワー状またはスプレー状に放水して鋳型１から取り出される鋳塊４を冷却する２次冷却部２と、鋳型１から取り出された鋳塊４を更に冷却する水槽３とを備えている。この装置により銅や銅合金を連続鋳造する場合は、銅あるいは所定比率の銅合金となるように配合された所定の金属の溶湯を鋳型１内に流し込み、充分な厚みの凝固鋳塊４を形成させ、これを下方から連続的に引き抜き、鋳型１下に配置したシャワー若しくはスプレー等の２次冷却部２、更に水槽３で直接水冷して冷却する。 FIG. 6 shows an outline of an ingot vertical continuous casting apparatus conventionally used. This vertical continuous casting apparatus includes a hollow mold 1 made of copper, a copper alloy or carbon, and an ingot 4 which is disposed below the mold 1 and is discharged from the mold 1 by discharging water into a shower or spray. A secondary cooling unit 2 for cooling and a water tank 3 for further cooling the ingot 4 taken out from the mold 1 are provided. When continuously casting copper or a copper alloy with this apparatus, a molten metal of a predetermined metal blended to become copper or a predetermined ratio of copper alloy is poured into the mold 1 to form a solidified ingot 4 having a sufficient thickness. Then, it is continuously pulled out from below and cooled by direct water cooling in the secondary cooling part 2 such as a shower or spray disposed under the mold 1 and the water tank 3.

このような連続鋳造時に、鋳型１内においては、鋳型１内表面と鋳塊４表面の間に、鋳塊４の収縮によって隙間（以下「エアー・ギャップ」という）が生じる。通常、エアー・ギャップは発生と消滅を繰り返し、エアー・ギャップが発生している場合は鋳塊４と鋳型１間の熱伝達は放射熱伝達となり、発生していない場合に比べて鋳塊４の抜熱が著しく悪化する。よって、エアー・ギャップの発生と消滅に従って、抜熱状態は周期的に変化する。エアー・ギャップの発生の様相は、鋳造する合金種、鋳型材質、鋳型表面状態等によって大きく異なる。また、連続鋳造中に鋳型１の表面状態や長辺５と短辺６とを有する鋳型１の形状等が変化するといった制御・管理しきれない因子によっても抜熱状態が経時変化する。鋳型における抜熱状態の変化は鋳塊表面や内部の割れ等の品質に影響を与え、その影響度も合金種によっても大きく異なる。従って、特に鋳型内での抜熱状態の把握および制御・管理が、鋳塊品質安定のために重要となる。 During such continuous casting, in the mold 1, a gap (hereinafter referred to as “air gap”) is generated between the inner surface of the mold 1 and the surface of the ingot 4 due to contraction of the ingot 4. Normally, the air gap is repeatedly generated and disappeared. When the air gap is generated, the heat transfer between the ingot 4 and the mold 1 is radiant heat transfer. Heat removal is significantly worsened. Therefore, the heat removal state changes periodically as the air gap is generated and disappeared. The appearance of the air gap varies greatly depending on the type of alloy to be cast, mold material, mold surface condition, and the like. Also, the heat removal state changes over time due to factors that cannot be controlled and managed, such as the surface state of the mold 1 and the shape of the mold 1 having the long side 5 and the short side 6 during continuous casting. Changes in the heat removal state in the mold affect the quality of the ingot surface and internal cracks, and the degree of influence varies greatly depending on the alloy type. Therefore, in particular, grasping, controlling and managing the heat removal state in the mold is important for stable ingot quality.

鋳型の抜熱能力を低下させることなく、表面欠陥のない鋳片を高速で鋳造しようとする連続鋳造方法として、特許文献１に示すものがある。この連続鋳造方法は、鋳型内部に複数の温度センサを設け、該温度センサにより測定された熱流束の差に基づき、冷却体及び発熱体の印加電流を制御して、熱流束を均一にしようとするものである。ここで、溶融金属の鋳型内の熱流束ｑは、鋳型材質の熱伝導率λ、２点の温度センサ（熱電対）の距離ｄと熱電対による温度計測値から得られる温度差ΔＴから、
ｑ＝（λ／ｄ）・ΔＴの式により求められる。（特許文献２、３参照）
特開平１１−１０４７８７号公報特開２０００−３１７５９４号公報特開２００１−２３９３５３号公報 As a continuous casting method for casting a slab having no surface defect at a high speed without lowering the heat removal capability of the mold, there is one disclosed in Patent Document 1. In this continuous casting method, a plurality of temperature sensors are provided inside the mold, and based on the difference in heat flux measured by the temperature sensors, the current applied to the cooling body and the heating element is controlled to make the heat flux uniform. To do. Here, the heat flux q in the mold of the molten metal is obtained from the temperature difference ΔT obtained from the thermal conductivity λ of the mold material, the distance d of the two temperature sensors (thermocouples) and the temperature measurement value by the thermocouple,
It is calculated by the equation q = (λ / d) · ΔT. (See Patent Documents 2 and 3)
JP-A-11-104787 JP 2000-317594 A JP 2001-239353 A

しかしながら、温度センサにより測定された熱流束の差により冷却体や発熱体の印加電流を制御する上記方法では、鋳型内温度分布が定常状態にあることを前提として熱流束が算出されるため、非定常状態の程度が大きくなるにつれ、実際の熱流束値に対する推定誤差が大きくなってしまうという問題がある。 However, in the above method of controlling the applied current of the cooling body and the heating element based on the difference in heat flux measured by the temperature sensor, the heat flux is calculated on the assumption that the temperature distribution in the mold is in a steady state. There is a problem that the estimation error with respect to the actual heat flux value increases as the degree of steady state increases.

従って、本発明の目的は、鋳型内部温度の測定値から熱流束を算出することなく、鋳型内部温度の測定結果を直接利用して鋳型内表面と鋳塊表面との熱伝達状態を把握し、鋳造条件の制御、管理する鋳塊の連続鋳造方法を提供することにある。 Therefore, the purpose of the present invention is to directly understand the heat transfer state between the mold inner surface and the ingot surface by directly using the measurement result of the mold internal temperature without calculating the heat flux from the measured value of the mold internal temperature, An object of the present invention is to provide a method for continuously casting an ingot to control and manage casting conditions.

一方、このような連続鋳造によって得られた大断面鋳塊の品質管理項目として、従来は外観目視観察による湯ジワの程度、溶湯被覆剤等の表層への巻き込みの有無、表層付近の割れの有無、両端から採取した試料による内部の割れの有無、組織観察による組織異常の有無、化学成分等があった。しかしながら、連続鋳造のような大断面の鋳塊では調査試料の採取や調整に多大な時間を要する。更に、鋳塊内部の品質を鋳塊全長にわたって保証するには、これらのような鋳塊表層および両端の調査のみでは不十分であった。超音波探傷試験、Ｘ線透過試験等が内部の空孔、割れ等のチェックに利用された例も見られるが、鋳塊の表面状態や結晶粒界の影響を強く受けること、浸透深さの問題等により、精度良く調査することは困難であった。 On the other hand, as a quality control item of the large-section ingot obtained by such continuous casting, conventionally, the degree of hot wrinkles by visual observation, presence of entrainment in the surface of the molten coating, etc., presence of cracks near the surface The presence or absence of internal cracks in samples collected from both ends, the presence or absence of tissue abnormalities by tissue observation, chemical components, and the like. However, in the case of a large-section ingot such as continuous casting, it takes a lot of time to collect and adjust the investigation sample. Furthermore, in order to guarantee the quality of the inside of the ingot over the entire length of the ingot, it has been insufficient to investigate only the surface of the ingot and both ends. There are cases where ultrasonic flaw detection tests, X-ray transmission tests, etc. were used to check internal vacancies, cracks, etc., but they were strongly affected by the surface condition of the ingot and crystal grain boundaries, and the penetration depth Due to problems, it was difficult to conduct a precise survey.

従って、本発明の他の目的は、鋳型内部温度を経時測定した結果を利用して鋳塊の品質判定に要する時間を軽減させるとともに、非破壊的手法により鋳塊品質を鋳塊全長にわたって保証する鋳塊品質の判定方法を提供することにある。 Therefore, another object of the present invention is to reduce the time required for ingot quality judgment by using the result of measuring the mold internal temperature over time, and to guarantee the ingot quality over the entire length of the ingot by a non-destructive method. An object of the present invention is to provide a method for determining ingot quality.

上記目的を達成するため、本発明に係る鋳塊の連続鋳造方法は、鋳塊を連続鋳造する際に、鋳型内部の所定箇所に配置した温度計測手段により鋳型内部温度を経時測定し、測定温度の極大値と極小値との差が、予め鋳型内部温度と鋳塊品質との関係についてデータを採取して定めた管理値から外れた場合に、鋳造条件を修正して該管理値内に維持しつつ鋳造を行うことを特徴とする。この場合、前記管理値を３０℃とすることができる。 In order to achieve the above object, the continuous casting method of the ingot according to the present invention, when continuously casting the ingot, the temperature inside the mold is measured over time by means of temperature measuring means arranged at a predetermined location inside the mold, and the measurement temperature If the difference between the local maximum value and the local minimum value deviates from the control value obtained by collecting data on the relationship between the mold internal temperature and the ingot quality in advance, the casting conditions are corrected and maintained within the control value. However, it is characterized by performing casting. In this case, the management value can be set to 30 ° C.

また、本発明に係る鋳塊の連続鋳造方法は、鋳塊を連続鋳造する際に、鋳型内部で鋳造方向の異なる位置の２ヶ所以上に配置した温度計測手段により鋳型内部温度を経時測定し、鋳型内部温度の鋳造方向における差が、予め鋳型内部温度と鋳塊品質との関係についてデータを採取して定めた管理値から外れた場合に、鋳造条件を修正して該管理値内に維持しつつ鋳造を行うことを特徴とする。この場合、前記管理値を２０℃とすることができる。 Further, in the continuous casting method of the ingot according to the present invention, when continuously casting the ingot, the internal temperature of the mold is measured with time by means of temperature measuring means arranged at two or more locations in the casting direction in the mold, When the difference in the casting direction of the mold internal temperature deviates from the control value determined by collecting data on the relationship between the mold internal temperature and the ingot quality in advance, the casting conditions are corrected and maintained within the control value. It is characterized by performing casting. In this case, the management value can be set to 20 ° C.

更に、本発明に係る鋳塊の品質判定方法は、鋳塊を連続鋳造する際に、鋳型内部の所定箇所に配置した温度計測手段により鋳型内部温度を経時測定し、測定温度の極大値と極小値との差と、予め鋳型内部温度と鋳塊品質との関係についてデータを採取して定めた管理値とを比較することにより鋳塊品質を判定することを特徴とする。 Furthermore, in the ingot quality judging method according to the present invention, when continuously casting an ingot, the temperature inside the mold is measured over time by means of temperature measuring means arranged at a predetermined location inside the mold, and the maximum and minimum values of the measured temperature are measured. The ingot quality is determined by comparing a difference between the value and a management value obtained by collecting data on the relationship between the mold internal temperature and the ingot quality in advance.

前記極大値と極小値との差が３０℃以下の場合に、鋳塊内部に割れが無いと判定することができる。 When the difference between the maximum value and the minimum value is 30 ° C. or less, it can be determined that there is no crack in the ingot.

また、本発明に係る鋳塊の品質判定方法は、鋳塊を連続鋳造する際に、鋳型内部で鋳造方向の異なる位置の２ヶ所以上に配置した温度計測手段により鋳型内部温度を経時測定し、鋳型内部温度の鋳造方向における差と、予め鋳型内部温度と鋳塊品質との関係についてデータを採取して定めた管理値とを比較することにより鋳塊品質を判定することを特徴とする。 In addition, the ingot quality determination method according to the present invention, when continuously casting the ingot, the temperature inside the mold is measured over time by means of temperature measuring means arranged at two or more locations in the casting direction in the mold, The ingot quality is determined by comparing a difference in the casting direction of the mold internal temperature with a management value obtained by collecting data on the relationship between the mold internal temperature and the ingot quality in advance.

前記鋳型内部温度の鋳造方向における差が２０℃以下の場合に、鋳塊内部に割れが無いと判定することができる。 When the difference in the casting direction of the mold internal temperature is 20 ° C. or less, it can be determined that there is no crack in the ingot.

更に、他の品質調査項目と組み合わせて前記鋳塊品質を判定することもできる。 Furthermore, the ingot quality can be determined in combination with other quality inspection items.

本発明に係る鋳塊の連続鋳造方法は、鋳型内部の測定温度の極大値と極小値との差を調べ、予め鋳型内部温度と鋳塊品質との関係についてデータを採取して定めた管理値と比較して鋳造条件を修正しているので、鋳型内部温度の測定結果を直接利用して鋳型内表面と鋳塊表面との熱伝達状態を把握でき、鋳造条件の迅速、正確な制御、管理が可能となる。このため、鋳造期間の短縮、鋳塊の歩留まり向上といった効果が期待される。 The ingot continuous casting method according to the present invention examines the difference between the maximum value and the minimum value of the measured temperature inside the mold, and collects and determines the relationship between the mold internal temperature and the ingot quality in advance. Since the casting conditions have been modified compared to, the heat transfer state between the mold inner surface and the ingot surface can be grasped by directly using the measurement result of the mold internal temperature, and the casting conditions can be controlled quickly and accurately. Is possible. For this reason, the effects of shortening the casting period and improving the yield of the ingot are expected.

また、鋳型内部の測定温度の鋳造方向における差を調べ、予め鋳型内部温度と鋳塊品質との関係についてデータを採取して定めた管理値と比較することによっても、同様に、鋳型内部温度の測定結果を直接利用して鋳型内表面と鋳塊表面との熱伝達状態を把握でき、鋳造条件の迅速、正確な制御、管理が可能となり、鋳造期間の短縮、鋳塊の歩留まり向上といった効果が期待される。 Similarly, by examining the difference in the casting direction of the measured temperature inside the mold and comparing the control value determined by collecting data on the relationship between the mold internal temperature and the ingot quality in advance, By directly using the measurement results, it is possible to grasp the heat transfer state between the mold inner surface and the ingot surface, making it possible to quickly and accurately control and manage the casting conditions, shortening the casting period, and improving the ingot yield. Be expected.

更に、本発明に係る鋳塊の品質判定方法は、鋳型内部の測定温度の極大値と極小値との差を調べ、予め鋳型内部温度と鋳塊品質との関係についてデータを採取して定めた管理値と比較することにより鋳塊品質を判定しているので、鋳型内部温度の測定結果を直接利用して鋳塊の品質判定に要する時間を短縮させるとともに、非破壊的手法により鋳塊品質を鋳塊全長にわたって保証することが可能となる。 Further, the ingot quality judging method according to the present invention is to determine the difference between the maximum value and the minimum value of the measured temperature inside the mold, and to collect and determine the relationship between the mold internal temperature and the ingot quality in advance. Since the ingot quality is judged by comparing with the control value, the measurement result of the mold internal temperature is directly used to reduce the time required for ingot quality judgment, and the ingot quality is improved by a non-destructive method. It is possible to guarantee over the entire length of the ingot.

また、鋳型内部の測定温度の鋳造方向における差を調べ、予め鋳型内部温度と鋳塊品質との関係についてデータを採取して定めた管理値とを比較することによっても、同様に、鋳型内部温度の測定結果を直接利用して鋳塊の品質判定に要する時間を短縮させるとともに、非破壊的手法により鋳塊品質を鋳塊全長にわたって保証することが可能となる。 Similarly, by examining the difference in the casting direction of the measured temperature inside the mold and comparing the control value determined by collecting data on the relationship between the mold internal temperature and the ingot quality in advance, This measurement result can be directly used to reduce the time required for ingot quality judgment, and the ingot quality can be guaranteed over the entire length of the ingot by a non-destructive method.

図１に、本発明の実施の形態に用いられる連続鋳造用鋳型を示す。この連続鋳造用鋳型は内部に所定の金属の溶湯が流し込まれるための中空部１１が形成された鋳型内壁１２と該鋳型内壁１２の外側に設けられた冷却用の鋳型冷却体１３とを備えており、かかる鋳型内壁１２と鋳型冷却体１３とにより鋳型を構成している。また、鋳型冷却体１３の内部には、鋳型を冷却するための冷却水を流せる構造になっている。更に、鋳型冷却体１３の外表面には熱電対１５を差し込むための熱電対挿入孔１４が少なくとも１ヶ所以上設置されており、熱電対１５が鋳型冷却体１３を貫通して鋳型内壁１２内部の温度を測定できる構造になっている。中空部１１の形状は、図示された矩形状のみならず、溶湯を流し込むために適した所望の形状とすることができる。鋳型内壁１２は、銅、銅合金またはカーボン等で形成することができる。また、鋳型内壁１２は一体であっても、数個に分割されたブロックを組み合わせたものでもよく、特に規定するものではない。更に、鋳型内壁１２と鋳型冷却体１３とについても、一体であっても、組み合わせたものでもよく、特に規定するものではない。なお、鋳型冷却体１３の材質については特に規定するものではない。この連続鋳造用鋳型は、図６に示した縦型連続鋳造装置の鋳型１の部分に用いることができる。 FIG. 1 shows a continuous casting mold used in the embodiment of the present invention. This continuous casting mold includes a mold inner wall 12 in which a hollow portion 11 is formed for pouring a molten metal of a predetermined metal therein, and a cooling mold cooling body 13 provided outside the mold inner wall 12. The mold inner wall 12 and the mold cooling body 13 constitute a mold. The mold cooling body 13 has a structure in which cooling water for cooling the mold can flow. Further, at least one thermocouple insertion hole 14 for inserting the thermocouple 15 is provided on the outer surface of the mold cooling body 13, and the thermocouple 15 penetrates the mold cooling body 13 and is located inside the mold inner wall 12. It has a structure that can measure temperature. The shape of the hollow portion 11 is not limited to the illustrated rectangular shape, but can be a desired shape suitable for pouring molten metal. The mold inner wall 12 can be formed of copper, a copper alloy, carbon, or the like. Further, the mold inner wall 12 may be integrated or may be a combination of several divided blocks, and is not particularly defined. Further, the mold inner wall 12 and the mold cooling body 13 may be integrated or combined, and are not particularly defined. Note that the material of the mold cooling body 13 is not particularly specified. This continuous casting mold can be used in the mold 1 portion of the vertical continuous casting apparatus shown in FIG.

熱電対１５からの信号は図示しない記録計にモニターされ、鋳型内部温度の経時変化が連続鋳造時に監視可能となっている。本実施形態においては、予め、鋳造条件の制御因子と鋳型内部温度および鋳塊品質との関係についてデータを採取し、これをもとに鋳型内部温度の管理値を定めておく。連続鋳造中に、鋳型内部温度がこのようにして定めた管理値からはずれた場合、鋳型冷却体１３の水流量、２次冷却部２の水流量、鋳造速度等の制御因子を手動または自動で修正する。 A signal from the thermocouple 15 is monitored by a recorder (not shown), and a change in the mold internal temperature with time can be monitored during continuous casting. In this embodiment, data is collected in advance on the relationship between the control factor of casting conditions, the mold internal temperature, and the ingot quality, and the management value of the mold internal temperature is determined based on this data. If the mold internal temperature deviates from the control value determined in this way during continuous casting, control factors such as the water flow rate of the mold cooling body 13, the water flow rate of the secondary cooling unit 2, and the casting speed are manually or automatically set. Correct it.

図２は所定の銅合金の連続鋳造時における鋳型内部温度の経時変化の測定例を示したものである。予め管理値として例えば鋳型内部温度の極大値と極小値の差等を定めておくことにより、万が一管理値を超えた場合、鋳型冷却体１３の水流量、２次冷却部２の水流量等の鋳造条件制御因子を手動または自動で修正することにより、鋳型内部温度の経時変化を図３に示す測定例のように修正することができる。 FIG. 2 shows an example of measurement of changes over time in the mold internal temperature during continuous casting of a predetermined copper alloy. For example, by setting a difference between the maximum value and the minimum value of the mold internal temperature as a control value in advance, if the control value exceeds the control value, the water flow rate of the mold cooling body 13, the water flow rate of the secondary cooling unit 2, etc. By manually or automatically correcting the casting condition control factor, the time-dependent change in the mold internal temperature can be corrected as in the measurement example shown in FIG.

また、図１に示すように、連続鋳造用鋳型の鋳造方向の異なる位置の２ヶ所以上に熱電対１５を設置することにより、鋳型内部温度の鋳造方向での差を経時測定する。この温度差を予め管理値として定めておくことにより、万が一管理値を超えた場合、鋳型冷却体１３の水流量、２次冷却部２の水流量等の鋳造条件制御因子を手動または自動で修正することにより、温度差を管理値内に修正可能である。 Further, as shown in FIG. 1, the thermocouples 15 are installed at two or more positions in the casting direction of the continuous casting mold, so that the difference in the casting direction in the casting mold is measured over time. By setting this temperature difference as a control value in advance, in the unlikely event that the control value is exceeded, the casting condition control factors such as the water flow rate of the mold cooling body 13 and the water flow rate of the secondary cooling unit 2 are corrected manually or automatically. By doing so, the temperature difference can be corrected within the control value.

図４は、所定の銅合金の矩形断面鋳塊を連続鋳造した際の、鋳型長辺中央上部と下部の内部温度の経時変化の測定例である。上部と下部に温度差が見られる。これは上述のように、鋳型下部においてエア・ギャップが発生し、抜熱不良が生しているためと考えられる。このような場合、ある種の合金においては、組織の粗大化や粗大結晶粒界での割れが見られることがある。このように、鋳型下部でのエア・ギャップの状態は鋳塊品質に大きく影響するが、本実施形態によれば鋳型上部と下部の温度差からこれを判断可能である。つまり、割れが発生すると判定する温度差の臨界値を予め定めておくことにより、スライス試料を採取しての割れの調査に要する時間を省くことが可能であるとともに、鋳塊全長にわたる品質保証も可能となる。 FIG. 4 is a measurement example of changes over time in the internal upper and lower portions of the mold long side when a rectangular cross-section ingot of a predetermined copper alloy is continuously cast. There is a temperature difference between the top and bottom. As described above, this is probably because an air gap is generated at the lower part of the mold, resulting in poor heat removal. In such a case, in a certain type of alloy, coarsening of the structure or cracking at a coarse grain boundary may be observed. As described above, the state of the air gap at the lower part of the mold greatly affects the ingot quality, but according to the present embodiment, this can be determined from the temperature difference between the upper part and the lower part of the mold. In other words, by predetermining the critical value of the temperature difference at which it is determined that cracks will occur, it is possible to save the time required for investigating cracks by taking slice samples, and quality assurance over the entire length of the ingot. It becomes possible.

図５は、所定の銅合金の矩形断面鋳塊を連続鋳造した際の、鋳型長辺中央下部の鋳型内部温度の経時変化の測定例である。鋳型内部温度に周期的な変化が見られ、極大値と極小値が存在する。これは鋳型下部においてエア・ギャップが鋳造方向に周期的に生じているためである。このような場合、ある種の合金においては、粒界偏析や粒界割れが鋳型温度の変化の周期と等しい周期で鋳造方向に断続的に見られることがある。従って、鋳型内部温度変化にこのような周期的変化が見られた場合、鋳塊両端から採取したスライス試料で割れが見られなくても内部には割れがある可能性があり、従来の調査方法では全長にわたる品質保証が不可能である。しかし、本実施形態によれば、鋳型長辺中央下部の鋳型内部温度の経時変化からこれを判断可能である。つまり、割れが発生すると判定する鋳型内部温度の極大値と極小値の差を予め定めておくことにより、スライス試料を採取しての割れの調査に要する時間を省くことが可能であるとともに、鋳塊全長にわたる品質保証も可能となる。なお、本実施形態の品質保証方法と他の品質調査項目と併せることにより、より精度の高い品質保証が可能となることはいうまでもない。 FIG. 5 is a measurement example of changes over time in the mold internal temperature at the lower center of the mold long side when a rectangular cross-section ingot of a predetermined copper alloy is continuously cast. Periodic changes are observed in the mold internal temperature, and there are local maximum and minimum values. This is because air gaps are periodically generated in the casting direction at the lower part of the mold. In such cases, in certain alloys, grain boundary segregation and grain boundary cracking may be seen intermittently in the casting direction with a period equal to the period of mold temperature change. Therefore, when such a periodic change is seen in the mold internal temperature change, there is a possibility that there is a crack inside the slice sample taken from both ends of the ingot, even if there is no crack, the conventional investigation method Therefore, quality assurance over the entire length is impossible. However, according to the present embodiment, this can be determined from the temporal change in the mold internal temperature at the lower center of the mold long side. In other words, by predetermining the difference between the maximum value and the minimum value of the mold internal temperature at which it is determined that cracks will occur, it is possible to save time required for investigating cracks by taking slice samples. Quality assurance over the entire length of the mass is also possible. Needless to say, by combining the quality assurance method of the present embodiment with other quality survey items, quality assurance with higher accuracy becomes possible.

図１に示す連続鋳造用鋳型を用いて、所定の銅合金の溶湯を下降管から鋳型内に供給し、鋳造速度１５０ｍｍ／ｍｉｎで連続鋳造した。湯面は鋳型内壁１２と鋳型冷却体１３とで構成される鋳型の上端から５０ｍｍとし、湯面には溶湯酸化防止のための被覆を施した。鋳型の断面サイズは１８０ｍｍ×６２０ｍｍ、長さは４００ｍｍで、矩形断面を有し、鋳造方向に長辺側で１５’、短辺側で３０’のテーパー加工を施してある。鋳型材質は銅合金である。鋳型には合計２４箇所に熱電対挿入孔１４が設けられており、このうち合計１２箇所の位置にクロメル・アルメル熱電対１５を差し込み、鋳塊との接触面から１０ｍｍの位置の鋳型内部温度を経時測定した。この結果、いずれの位置でも鋳型内部温度の経時変化はほとんどなかったが、鋳型長辺中央の上部と下部での温度差が約１００℃となった（条件Ｅ）。これは、長辺中央の下方にエア・ギャップが生成し、抜熱不良が起こっているためと考えられる。そこで、鋳型冷却体１３の水流量、２次冷却部２の水流量を調整した結果、鋳型長辺中央の上部と下部での温度差は約２０℃となった（条件Ａ）。鋳造終了後、これらの鋳塊から調査試料を切り出し、鋳塊内部の割れのチェックを実施した。このようにして、鋳型冷却体１３の水流量、２次冷却部２の水流量の組み合わせにおいて、鋳型長辺中央の上部と下部での温度差と鋳塊内部の割れの発生率との関係を調査したところ、表１の結果が得られた。 Using the continuous casting mold shown in FIG. 1, a predetermined copper alloy melt was supplied from the downcomer into the mold and continuously cast at a casting speed of 150 mm / min. The molten metal surface was 50 mm from the upper end of the mold composed of the mold inner wall 12 and the mold cooling body 13, and the molten metal surface was coated to prevent molten metal oxidation. The cross-sectional size of the mold is 180 mm × 620 mm, the length is 400 mm, has a rectangular cross-section, and is taped 15 ′ on the long side and 30 ′ on the short side in the casting direction. The mold material is a copper alloy. The mold is provided with thermocouple insertion holes 14 at a total of 24 locations. Among them, a chromel-alumel thermocouple 15 is inserted at a total of 12 locations, and the mold internal temperature at a position 10 mm from the contact surface with the ingot is set. It was measured over time. As a result, there was almost no temporal change in the mold internal temperature at any position, but the temperature difference between the upper part and the lower part of the mold long side center was about 100 ° C. (Condition E). This is presumably because an air gap is generated below the center of the long side and heat extraction failure occurs. Therefore, as a result of adjusting the water flow rate of the mold cooling body 13 and the water flow rate of the secondary cooling unit 2, the temperature difference between the upper part and the lower part of the center of the long side of the mold was about 20 ° C. (Condition A). After the completion of casting, the investigation samples were cut out from these ingots and checked for cracks inside the ingots. In this way, in the combination of the water flow rate of the mold cooling body 13 and the water flow rate of the secondary cooling unit 2, the relationship between the temperature difference between the upper part and the lower part of the center of the long side of the mold and the occurrence rate of cracks inside the ingot. When investigated, the result of Table 1 was obtained.

表１の結果より、条件Ｅのように温度差が１００℃ある場合は、粗大結晶粒が見られ、これらの粒界に沿って割れが発生しており、割れの発生率は８０％であった。温度差の減少に従って割れの発生率は減少し、条件Ａのように温度差が２０℃以下の場合では割れの発生率は０．１％以下となった。このように、鋳型内部温度の経時測定における長辺中央上部と下部の温度差と鋳塊内部の割れの発生率とには大きな相関が見られ、鋳型長辺中央の上部と下部での温度差が２０℃以下の鋳塊では、割れがないと判定することとした。従って、鋳型内部温度の管理値として、鋳型長辺中央の上部と下部での温度差を２０℃以下となるように鋳造条件を制御することとし、標準鋳造条件を条件Ａとした。その後、条件Ａで連続鋳造していたところ、鋳型長辺中央の上部と下部での温度差が２０℃を超えた。直ちに、条件を微調整した結果、温度差を２０℃以下に抑えることができた。この鋳塊の内部の割れの調査を実施したところ、割れは一切見られなかった。その後も、条件Ａでの割れの発生率は０．１％であった。 From the results in Table 1, when the temperature difference is 100 ° C. as in Condition E, coarse crystal grains are observed, cracks are generated along these grain boundaries, and the crack generation rate is 80%. It was. As the temperature difference decreased, the crack generation rate decreased. When the temperature difference was 20 ° C. or less as in Condition A, the crack generation rate was 0.1% or less. Thus, there is a large correlation between the temperature difference between the upper and lower center of the long side and the incidence of cracks in the ingot in the time-dependent measurement of the mold internal temperature. However, ingots of 20 ° C. or lower were determined to have no cracks. Therefore, as a control value of the mold internal temperature, the casting conditions are controlled so that the temperature difference between the upper part and the lower part in the center of the long side of the mold is 20 ° C. or less. Thereafter, continuous casting was performed under condition A, and the temperature difference between the upper part and the lower part of the center of the mold long side exceeded 20 ° C. Immediately after fine-tuning the conditions, the temperature difference could be suppressed to 20 ° C. or less. As a result of investigating the cracks in the ingot, no cracks were found. Even after that, the incidence of cracking under Condition A was 0.1%.

比較例１Comparative Example 1

実施例１と同じ銅合金の溶湯を、鋳型内部温度を測定せずに、それ以外は実施例１と同様にして連続鋳造した。各鋳塊の両端からスライス試料を採取し、割れのチェックを実施したが多大な時間を要した。また、鋳型冷却体１３の水流量、２次冷却部２の水流量の適性値を導出するにあたり、これらと鋳塊品質との関係を調査したが多大な時間を要した。その後、導出した適性条件で連続鋳造したが、鋳塊内部の割れの発生率は５％程度であった。割れの発生率が実施例１より多い原因として、導出した適性条件が本来の最適条件より若干ずれていること、連続鋳造中に何らかの要因で抜熱状態が変化した際に条件の微調整ができなかったことが考えられる。更に、鋳塊内部が両端と同一であるかについての明確な根拠がないため、鋳塊両端の判定を鋳塊全長にわたって保証するには無理が生じた。 The same copper alloy melt as in Example 1 was continuously cast in the same manner as in Example 1 except that the mold internal temperature was not measured. Slice samples were taken from both ends of each ingot and checked for cracks, but it took a lot of time. Moreover, in deriving the appropriate value of the water flow rate of the mold cooling body 13 and the water flow rate of the secondary cooling section 2, the relationship between these and the ingot quality was investigated, but it took a lot of time. Thereafter, continuous casting was performed under the derived suitability conditions, but the rate of occurrence of cracks in the ingot was about 5%. The reason why the occurrence rate of cracks is higher than in Example 1 is that the derived suitability conditions are slightly different from the original optimum conditions, and the conditions can be finely adjusted when the heat removal state changes for some reason during continuous casting. It is thought that there was not. Furthermore, since there is no clear ground as to whether the inside of the ingot is the same as both ends, it has become impossible to guarantee the judgment of both ends of the ingot over the entire length of the ingot.

図１に示す連続鋳造用鋳型を用いて、所定の銅合金の溶湯を、下降管から鋳型内に供給し、鋳造速度９０ｍｍ／ｍｉｎで連続鋳造した。湯面は鋳型上端から５０ｍｍとし、湯面には溶湯酸化防止のための被覆を施した。鋳型の断面サイズは１８０ｍｍ×６２０ｍｍ、長さは４００ｍｍで、矩形断面を有し、鋳造方向に長辺側で５’、短辺側で１０’のテーパー加工を施してある。鋳型材質は銅合金である。鋳型には合計２４箇所に熱電対挿入孔１４が設けてあり、このうち合計１２箇所の位置にクロメル・アルメル熱電対１５を差し込み、鋳塊との接触面から１０ｍｍの位置の鋳型内部温度を経時測定した。この結果、長辺中央下部で鋳型内部温度が周期的に変化した。その極大値と極小値の差は約１００℃であった（条件Ｅ）。そこで、鋳型冷却体１３の水流量、２次冷却部２の水流量を調整した結果、鋳型内部温度変化の極大値と極小値の差は約３０℃となった（条件Ａ）。鋳造終了後、これらの鋳塊から調査試料を切り出し、鋳塊内部の割れのチェックを実施した。条件Ｅの鋳塊では、中心付近に鋳造方向で周期的に微小な割れが発生した。この周期は鋳型温度変化の周期と同一であった。一方、条件Ａの鋳塊では、割れは一切見られなかった。このようにして、鋳型冷却体１３の水流量、２次冷却部２の水流量の組み合わせにおいて、鋳型内部温度の経時変化と内部の割れの発生率との関係を調査したところ、表２の結果が得られた。 Using the continuous casting mold shown in FIG. 1, a predetermined copper alloy melt was supplied from the downcomer into the mold and continuously cast at a casting speed of 90 mm / min. The molten metal surface was 50 mm from the upper end of the mold, and the molten metal surface was coated to prevent oxidation of the molten metal. The cross-sectional size of the mold is 180 mm × 620 mm, the length is 400 mm, has a rectangular cross-section, and is tapered 5 ′ on the long side and 10 ′ on the short side in the casting direction. The mold material is a copper alloy. The mold is provided with thermocouple insertion holes 14 at a total of 24 locations, of which chromel-alumel thermocouples 15 are inserted at a total of 12 locations, and the temperature inside the mold at a position 10 mm from the contact surface with the ingot is changed over time. It was measured. As a result, the mold internal temperature periodically changed at the lower part of the center of the long side. The difference between the maximum value and the minimum value was about 100 ° C. (Condition E). Accordingly, as a result of adjusting the water flow rate of the mold cooling body 13 and the water flow rate of the secondary cooling unit 2, the difference between the maximum value and the minimum value of the mold internal temperature change was about 30 ° C. (Condition A). After the completion of casting, the investigation samples were cut out from these ingots and checked for cracks inside the ingots. In the ingot of Condition E, minute cracks periodically occurred in the casting direction near the center. This period was the same as the mold temperature change period. On the other hand, in the ingot of condition A, no cracks were observed. Thus, when the relationship between the time-dependent change of the mold internal temperature and the occurrence rate of internal cracks was investigated in the combination of the water flow rate of the mold cooling body 13 and the water flow rate of the secondary cooling section 2, the results shown in Table 2 were obtained. was gotten.

表２の結果より、条件Ｅのように極大値と極小値の差が１００℃の場合では、鋳塊表面に周期的な窪みが見られ、内部にも同一の周期で断続的に割れが発生し、割れの発生率は５０％であった。極大値と極小値の差の減少に従って割れの発生率は減少し、条件Ａのように極大値と極小値の差が３０℃以下では、割れの発生率は０．１％以下となった。このように、鋳型内部温度の経時測定における長辺中央下部での極大値と極小値の差と鋳塊内部の割れの発生率とには大きな相関が見られ、極大値と極小値の差が３０℃以下の鋳塊では、割れがないと判定することとした。従って、鋳型内部温度の管理値として、極大値と極小値の差を３０℃以下とすることとし、標準鋳造条件を条件Ａとした。その後、条件Ａで連続鋳造していたところ、鋳型内部温度の極大値と極小値の差が３０℃を超えた。直ちに、条件を微調整した結果、極大値と極小値の差を３０℃以下に抑えることができた。この鋳塊の内部の割れの調査を実施したところ、割れは一切見られなかった。その後も、条件Ａでの割れの発生率は０．１％であった。 From the results in Table 2, when the difference between the maximum value and the minimum value is 100 ° C as in Condition E, periodic indentations are seen on the ingot surface, and internal cracks occur intermittently at the same cycle. The occurrence rate of cracks was 50%. As the difference between the maximum value and the minimum value decreased, the occurrence rate of cracks decreased. When the difference between the maximum value and the minimum value was 30 ° C. or less as in Condition A, the occurrence rate of cracks was 0.1% or less. In this way, there is a large correlation between the difference between the maximum value and minimum value at the center lower part of the long side and the incidence of cracks in the ingot in the measurement of the mold internal temperature over time, and the difference between the maximum value and the minimum value is In the ingot of 30 ° C. or less, it was determined that there was no crack. Therefore, as the control value of the mold internal temperature, the difference between the maximum value and the minimum value is set to 30 ° C. or less, and the standard casting condition is set to Condition A. Thereafter, when continuous casting was performed under condition A, the difference between the maximum value and the minimum value of the mold internal temperature exceeded 30 ° C. Immediately after fine-tuning the conditions, the difference between the maximum value and the minimum value could be suppressed to 30 ° C. or less. As a result of investigating the cracks in the ingot, no cracks were found. Even after that, the incidence of cracking under Condition A was 0.1%.

比較例２Comparative Example 2

実施例２と同じ銅合金の溶湯を、鋳型内部温度を測定せずに、それ以外は実施例２と同様にして連続鋳造した。各鋳塊の両端からスライス試料を採取し、割れのチェックを実施したが多大な時間を要した。鋳型冷却体１３の水流量、２次冷却部２の水流量の適性値を導出するにあたり、これらと鋳塊品質との関係を調査したが多大な時間を要した。その後、導出した適性条件で連続鋳造したが、鋳塊内部の割れの発生率は３％程度であった。割れの発生率が実施例２より多い原因として、導出した適性条件が本来の最適条件より若干ずれていること、連続鋳造中に何らかの要因で抜熱状態が変化した際に条件の微調整ができなかったことが考えられる。更に、鋳塊両端でのチェックで割れがなくても、内部に割れが発生することがあり、鋳塊全長にわたる保証は不可能であった。 The same copper alloy melt as in Example 2 was continuously cast in the same manner as in Example 2 except that the mold internal temperature was not measured. Slice samples were taken from both ends of each ingot and checked for cracks, but it took a lot of time. In deriving the appropriate value of the water flow rate of the mold cooling body 13 and the water flow rate of the secondary cooling unit 2, the relationship between these and the ingot quality was investigated, but a great deal of time was required. Thereafter, continuous casting was performed under the derived suitability conditions, but the rate of occurrence of cracks in the ingot was about 3%. The reason why the occurrence rate of cracks is higher than in Example 2 is that the derived suitability conditions are slightly different from the original optimum conditions, and the conditions can be fine-tuned when the heat removal state changes for some reason during continuous casting. It is thought that there was not. Furthermore, even if there is no crack in the check at both ends of the ingot, a crack may occur inside, and it was impossible to guarantee the entire length of the ingot.

本発明の実施の形態に用いられる連続鋳造用鋳型を示す斜視図である。It is a perspective view which shows the casting mold for continuous casting used for embodiment of this invention. 所定の銅合金の連続鋳造時における鋳型内部温度の経時変化の測定例を示すグラフである。It is a graph which shows the example of a measurement of the time-dependent change of the mold internal temperature at the time of continuous casting of a predetermined copper alloy. 鋳造条件制御因子を手動または自動で修正することにより、鋳型内部温度の経時変化を図２の測定例から修正した例を示すグラフである。It is a graph which shows the example which corrected the time-dependent change of mold internal temperature from the measurement example of FIG. 2 by correcting a casting condition control factor manually or automatically. 所定の銅合金の矩形断面鋳塊を連続鋳造した際の、鋳型長辺中央上部と下部の内部温度の経時変化の測定例を示すグラフである。It is a graph which shows the example of a measurement of the time-dependent change of internal temperature of a mold long side center upper part at the time of continuously casting the rectangular cross-section ingot of a predetermined copper alloy. 所定の銅合金の矩形断面鋳塊を連続鋳造した際の、鋳型長辺中央下部の鋳型内部温度の経時変化の測定例を示すグラフである。It is a graph which shows the example of a measurement of the time-dependent change of the mold internal temperature of the mold lower side center lower part at the time of continuously casting the rectangular cross-section ingot of a predetermined copper alloy. 従来の縦型連続鋳造装置の概略を示す斜視図である。It is a perspective view which shows the outline of the conventional vertical continuous casting apparatus.

符号の説明Explanation of symbols

１鋳型
２２次冷却部
３水槽
４鋳塊
５長辺
６短辺
１１中空部
１２鋳型内壁
１３鋳型冷却体
１４熱電対挿入孔
１５熱電対 DESCRIPTION OF SYMBOLS 1 Mold 2 Secondary cooling part 3 Water tank 4 Ingot 5 Long side 6 Short side 11 Hollow part 12 Mold inner wall 13 Mold cooling body 14 Thermocouple insertion hole 15 Thermocouple

Claims

鋳塊を連続鋳造する際に、鋳型内部の所定箇所に配置した温度計測手段により鋳型内部温度を経時測定し、測定温度の極大値と極小値との差が、予め鋳型内部温度と鋳塊品質との関係についてデータを採取して定めた管理値から外れた場合に、鋳造条件を修正して該管理値内に維持しつつ鋳造を行うことを特徴とする鋳塊の連続鋳造方法。 When continuously casting an ingot, the temperature inside the mold is measured over time by means of temperature measurement arranged at a predetermined location inside the mold, and the difference between the maximum and minimum values of the measured temperature is determined in advance by the mold internal temperature and the ingot quality. When the data is deviated from the control value determined by collecting data with respect to the relationship, the casting condition is corrected and casting is performed while maintaining the control value within the control value.

前記管理値が３０℃であることを特徴とする請求項１記載の鋳塊の連続鋳造方法。 The ingot continuous casting method according to claim 1, wherein the control value is 30 ° C.

鋳塊を連続鋳造する際に、鋳型内部で鋳造方向の異なる位置の２ヶ所以上に配置した温度計測手段により鋳型内部温度を経時測定し、鋳型内部温度の鋳造方向における差が、予め鋳型内部温度と鋳塊品質との関係についてデータを採取して定めた管理値から外れた場合に、鋳造条件を修正して該管理値内に維持しつつ鋳造を行うことを特徴とする鋳塊の連続鋳造方法。 When continuously casting an ingot, the temperature inside the mold is measured over time by two or more temperature measuring means located at different positions in the casting direction inside the mold. Ingot continuous casting, characterized in that, when the data is out of the control value determined by collecting data on the relationship between the control value and the ingot quality, the casting condition is corrected and maintained within the control value. Method.

前記管理値が２０℃であることを特徴とする請求項３記載の鋳塊の連続鋳造方法。 The ingot continuous casting method according to claim 3, wherein the control value is 20 ° C.

鋳塊を連続鋳造する際に、鋳型内部の所定箇所に配置した温度計測手段により鋳型内部温度を経時測定し、測定温度の極大値と極小値との差と、予め鋳型内部温度と鋳塊品質との関係についてデータを採取して定めた管理値とを比較することにより鋳塊品質を判定することを特徴とする鋳塊の品質判定方法。 When continuously casting an ingot, the temperature inside the mold is measured over time by means of temperature measurement arranged at a predetermined location inside the mold, the difference between the maximum and minimum values of the measured temperature, the mold internal temperature and the ingot quality in advance. The ingot quality judgment method is characterized in that the ingot quality is judged by comparing data with a management value determined by collecting data on the relationship between

前記極大値と極小値との差が３０℃以下の場合に、鋳塊内部に割れが無いと判定することを特徴とする請求項５記載の鋳塊の品質判定方法。 6. The ingot quality determination method according to claim 5, wherein when the difference between the maximum value and the minimum value is 30 ° C. or less, it is determined that there is no crack inside the ingot.

鋳塊を連続鋳造する際に、鋳型内部で鋳造方向の異なる位置の２ヶ所以上に配置した温度計測手段により鋳型内部温度を経時測定し、鋳型内部温度の鋳造方向における差と、予め鋳型内部温度と鋳塊品質との関係についてデータを採取して定めた管理値とを比較することにより鋳塊品質を判定することを特徴とする鋳塊の品質判定方法。 When continuously casting an ingot, the temperature inside the mold is measured over time by means of temperature measuring means placed at two or more locations in the casting direction in the mold, and the difference in the casting temperature between the casting direction and the temperature inside the mold in advance. A method for determining the quality of an ingot, wherein the quality of the ingot is determined by comparing the control value determined by collecting data on the relationship between the ingot quality and the ingot quality.

前記鋳型内部温度の鋳造方向における差が２０℃以下の場合に、鋳塊内部に割れが無いと判定することを特徴とする請求項７記載の鋳塊の品質判定方法。 The ingot quality judgment method according to claim 7, wherein when the difference in the casting temperature of the mold internal temperature is 20 ° C or less, it is determined that there is no crack in the ingot.

他の品質調査項目と組み合わせて前記鋳塊品質を判定することを特徴とする請求項５乃至請求項８のいずれか１項記載の鋳塊の品質判定方法。

The ingot quality determination method according to any one of claims 5 to 8, wherein the ingot quality is determined in combination with other quality inspection items.