JP2002246171A - Artificial graphite electrode for steel making with superior spalling resistance - Google Patents
Artificial graphite electrode for steel making with superior spalling resistanceInfo
- Publication number
- JP2002246171A JP2002246171A JP2001041579A JP2001041579A JP2002246171A JP 2002246171 A JP2002246171 A JP 2002246171A JP 2001041579 A JP2001041579 A JP 2001041579A JP 2001041579 A JP2001041579 A JP 2001041579A JP 2002246171 A JP2002246171 A JP 2002246171A
- Authority
- JP
- Japan
- Prior art keywords
- voids
- electrode
- area
- average
- artificial graphite
- 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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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Ceramic Products (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
- Discharge Heating (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、電気製鋼アーク炉
に用いられる直径が２４インチ以上の人造黒鉛電極で、
操業中に先端部の欠け落ち、ネジ底横割れなどの発生が
抑制された耐スポーリング性に優れた製鋼用人造黒鉛電
極に関する。TECHNICAL FIELD The present invention relates to an artificial graphite electrode having a diameter of 24 inches or more used in an electric steelmaking arc furnace.
The present invention relates to an artificial graphite electrode for steel making which is excellent in spalling resistance and in which the occurrence of chipping at the tip portion and occurrence of lateral cracks at the screw bottom during operation is suppressed.
【０００２】[0002]
【従来の技術】電気製鋼アーク炉に用いられる人造黒鉛
電極は、原料コークスにバインダーピッチを混捏し、押
出成形後、一次焼成、含浸、再焼成、黒鉛化し、所定の
寸法に加工することにより製造される。2. Description of the Related Art Artificial graphite electrodes used in electric steelmaking arc furnaces are manufactured by kneading a raw material coke with a binder pitch, extruding, primary firing, impregnation, refiring, graphitization, and processing to a predetermined size. Is done.
【０００３】電極には、操業中に折損事故を生じること
があるため、これまで、その防止法として、ネジ部など
の形状、設計を改善する手段が講じられてきた。また、
原料コークスやバインダーピッチの配合を調整し、熱膨
張係数、弾性率、曲げ強度、その他の特性の改善を図る
ことも提案されている（特公平１−２１０８５号公報、
特公平２−２０５９１号公報）。[0003] Since the electrode may be broken during operation, measures to improve the shape and design of the screw portion and the like have been taken as a method of preventing the breakage. Also,
It has also been proposed to adjust the blending of raw coke and binder pitch to improve the thermal expansion coefficient, elastic modulus, bending strength, and other properties (Japanese Patent Publication No. 1-21085,
Japanese Patent Publication No. 2-20591.
【０００４】近年の大形高負荷電気製鋼アーク炉の普及
に伴って、電極についても、例えば直径２６インチ、２
８インチのような大径のものが主流となってきている。
電極の大形化に伴い電極に要求される品質性能も厳しく
なっており、折損防止対策がこれまで以上に強く要求さ
れている。[0004] With the recent widespread use of large high-load electric steelmaking arc furnaces, electrodes are also required to have a diameter of, for example, 26 inches.
Large diameters such as 8 inches are becoming mainstream.
As the size of the electrode has increased, the quality performance required for the electrode has become stricter, and breakage prevention measures have been more strongly required than ever.
【０００５】大径化された電気製鋼アーク炉用電極の折
損防止に対処するために、曲げ強度、弾性率、固有抵
抗、熱膨張係数の４項目の特性値を特定範囲に調整する
よう品質設計された黒鉛電極が提案されている（特開平
９−２７３９０号公報）が、これらの諸特性のみでは、
電気製鋼アーク炉における電極の耐スポーリング性を予
測するための指標として十分でなく、必ずしも信頼の置
けるものではない。[0005] In order to prevent breakage of an electrode for an electric steel arc furnace having a large diameter, quality design is performed so that four characteristic values of bending strength, elastic modulus, specific resistance and thermal expansion coefficient are adjusted to specific ranges. The proposed graphite electrode has been proposed (Japanese Patent Laid-Open No. 9-27390).
It is not sufficient as an index for predicting the spalling resistance of an electrode in an electric steel arc furnace, and is not always reliable.
【０００６】発明者は、少なくとも直径２４インチ、さ
らに２６〜２８インチ以上の直径をそなえた大形の製鋼
アーク炉用人造黒鉛電極の折損防止対策として、上記の
諸特性とともに、電極内部の組織性状、とくに空隙の形
態などと電極の耐スポーリング性との関連について実
験、検討を加えた結果、電極内部の空隙が耐スポーリン
グ性に対する重要な因子となることが知見し、耐スポー
リング性を左右する内部空隙の形態についての評価方法
を見出した。The inventor of the present invention has taken measures to prevent breakage of a large-sized artificial graphite electrode for a steel-making arc furnace having a diameter of at least 24 inches and further having a diameter of 26 to 28 inches or more. In particular, after conducting experiments and studies on the relationship between the morphology of the voids and the spalling resistance of the electrode, we found that the voids inside the electrode are an important factor for the spalling resistance. A method for evaluating the shape of the internal voids which influences was found.
【０００７】[0007]
【発明が解決しようとする課題】本発明は、上記の知見
に基づいてなされたものであり、その目的は、電気製鋼
アーク炉に用いられる直径が２４インチ以上の人造黒鉛
電極であり、耐スポーリング性に優れ、操業中に先端部
の欠け落ち、ネジ底横割れなどの発生が抑制された製鋼
用人造黒鉛電極を提供することにある。SUMMARY OF THE INVENTION The present invention has been made based on the above findings, and an object of the present invention is to provide an artificial graphite electrode having a diameter of 24 inches or more used in an electric steel arc furnace and having a resistance to dust. It is an object of the present invention to provide an artificial graphite electrode for steelmaking which has excellent poling properties and is free from chipping at the tip during operation and occurrence of lateral cracks at the screw bottom.
【０００８】[0008]
【課題を解決するための手段】上記の目的を達成するた
めの本発明の請求項１による製鋼用人造黒鉛電極は、電
気製鋼アーク炉に用いられる直径が２４インチ以上の人
造黒鉛電極であって、該電極の長さ方向と平行な方向に
採取した直径２０ｍｍ、長さ１００ｍｍの試片の嵩比重
が１．６６以上、固有抵抗が５．２μΩｍ以下、弾性率
が１７０００ＭＰａ以下、三点曲げ強度が９．８０ＭＰ
ａ以上、石英ガラスを基準とした０℃から１００℃まで
の熱膨張係数が０．５×１０-6／℃以下であり、前記電
極内部の空隙の平均形状係数が５００〜３０００である
ことを特徴とする。但し、電極内部の空隙の平均形状係
数は、電極の長さ方向と直角な断面を、画像解析を用い
て計測面積を２８００±３００ｍｍ2 とし縮尺が１ｍｍ
当たり８〜１０画素となるよう読み込み、読み込んだ画
像を、空隙と空隙以外の部分の色調の違いにより空隙と
空隙以外の部分に二値化し、二値化した二値化画像を画
像解析して個々の空隙の周囲長さと面積を計測し（電極
内のコークス内空隙は計測から省く）、計測した個々の
空隙のうち周囲長さの長い順に５０個の空隙を選出し、
選出した空隙から面積が１５ｍｍ2 以上の空隙を除く空
隙の周囲長さの平均値を求め、空隙長さが該平均値を越
える空隙について、周囲長さ（Ｌ）と面積（Ｓ）を求
め、下記の式により形状係数を算出し、その平均を求め
て平均形状係数とする。形状係数＝〔（周囲長さＬ）2
／｛４π×（面積Ｓ）｝〕×１００According to a first aspect of the present invention, there is provided an artificial graphite electrode for steelmaking, which is used in an electric steelmaking arc furnace and has a diameter of 24 inches or more. A sample having a diameter of 20 mm and a length of 100 mm taken in a direction parallel to the length direction of the electrode has a bulk specific gravity of 1.66 or more, a specific resistance of 5.2 μΩm or less, an elastic modulus of 17000 MPa or less, and a three-point bending strength. Is 9.80MP
a, the coefficient of thermal expansion from 0 ° C. to 100 ° C. based on quartz glass is 0.5 × 10 −6 / ° C. or less, and the average shape factor of voids inside the electrode is 500 to 3000. Features. However, the average shape factor of the void inside the electrode is such that the cross-section perpendicular to the length direction of the electrode is measured using image analysis, the measurement area is 2800 ± 300 mm 2, and the scale is 1 mm.
Read to be 8 to 10 pixels per pixel, the read image is binarized into gaps and parts other than gaps due to the difference in the color tone of the gaps and parts other than the gaps, and the binarized binarized image is subjected to image analysis. The perimeter and area of each void were measured (voids in the coke in the electrode were omitted from the measurement), and 50 voids were selected from the measured voids in descending order of the perimeter,
The average value of the peripheral lengths of the voids excluding the voids having an area of 15 mm 2 or more from the selected voids is determined. For the voids whose void lengths exceed the average value, the peripheral length (L) and the area (S) are determined. The shape factor is calculated by the following equation, and the average is calculated to be the average shape factor. Shape factor = [(perimeter L) 2
/ {4π × (area S)}] × 100
【０００９】請求項２による耐スポーリング性に優れた
製鋼用人造黒鉛電極は、前記周囲長さの長い順に選出し
た５０個の空隙から、面積が１５ｍｍ2 以上の空隙を除
く空隙の周囲長さおよび面積の平均値がそれぞれ３〜２
０ｍｍおよび１〜５ｍｍ2 で、削除率が６０〜９０％で
あることを特徴とする。但し、削除率とは、前記電極内
部の空隙の平均形状係数を求めるに当たり、周囲長さの
長い順に５０個の空隙を選出し、選出した空隙から面積
が１５ｍｍ2 以上の空隙を除く空隙の周囲長さの平均値
を求めるとき、面積が１５ｍｍ2 以上の空隙を除く空隙
の数（Ｎ）に対する空隙の周囲長さが該平均値以下の空
隙の数（ｎ）の割合（（ｎ／Ｎ）×１００％をいう）。[0009] The artificial graphite electrode for steelmaking having excellent spalling resistance according to claim 2 is a peripheral length of a void excluding a void having an area of 15 mm 2 or more from the 50 voids selected in the descending order of the peripheral length. And the average value of the area is 3 to 2 respectively.
0 mm and 1 to 5 mm 2 , and the deletion rate is 60 to 90%. However, the elimination rate means that, when calculating the average shape factor of the voids inside the electrode, 50 voids are selected in ascending peripheral length, and the area around the voids excluding the voids having an area of 15 mm 2 or more from the selected voids. When calculating the average value of the lengths, the ratio of the number of voids (n) whose peripheral length is less than the average value to the number of voids (N) excluding the voids having an area of 15 mm 2 or more ((n / N) × 100%).
【００１０】[0010]
【発明の実施の形態】本発明は、電気製鋼アーク炉に用
いられる直径が２４インチ以上の人造黒鉛電極、さらに
例えば直径が２６〜２８インチ、３０インチの大径の人
造黒鉛電極に適用される。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is applied to an artificial graphite electrode having a diameter of 24 inches or more used in an electric steel arc furnace, and further to a large-diameter artificial graphite electrode having a diameter of, for example, 26 to 28 inches or 30 inches. .
【００１１】本発明の電極においては、電極の長さ方向
と平行な方向に採取した直径２０ｍｍ、長さ１００ｍｍ
の試片の嵩比重が１．６６以上、固有抵抗が５．２μΩ
ｍ以下、弾性率が１７０００ＭＰａ以下、三点曲げ強度
が９．８０ＭＰａ以上、石英ガラスを基準とした０℃か
ら１００℃までの熱膨張係数が０．５×１０-6／℃以下
の特性をそなえている。In the electrode of the present invention, a diameter of 20 mm and a length of 100 mm sampled in a direction parallel to the length direction of the electrode.
Has a bulk specific gravity of 1.66 or more and a specific resistance of 5.2 μΩ.
m, an elastic modulus of 17000 MPa or less, a three-point bending strength of 9.80 MPa or more, and a thermal expansion coefficient of 0.5 × 10 −6 / ° C. or less from 0 ° C. to 100 ° C. based on quartz glass. ing.
【００１２】固有抵抗が５．２μΩｍを越えると、ジュ
ール発熱量が増加して熱応力が大きくなり、弾性率が１
７０００ＭＰａを越えると、吸収エネルギーが低下して
衝撃エネルギーを吸収し難くなる。曲げ強度が９．８０
ＭＰａ未満では、耐折損モーメントが十分でない。ま
た、熱膨張係数が０．５×１０-6／℃を越えると、ジュ
ール発熱による耐熱応力性が低下する。When the specific resistance exceeds 5.2 .mu..OMEGA.m, the Joule heat generation increases, the thermal stress increases, and the elastic modulus becomes 1
If it exceeds 7000 MPa, the absorbed energy decreases, making it difficult to absorb impact energy. Flexural strength of 9.80
If it is less than MPa, the breaking moment is not sufficient. If the coefficient of thermal expansion exceeds 0.5 × 10 −6 / ° C., the heat stress resistance due to Joule heat decreases.
【００１３】本発明における最も重要な品質特性は、電
極内部の空隙の平均形状係数を５００〜３０００の範囲
に特定することである。電極内部の空隙の平均形状係数
は、つぎのようにして求める。すなわち、電極の長さ方
向と直角な断面を、画像解析を用いて計測面積を２８０
０±３００ｍｍ2 とし縮尺が１ｍｍ当たり８〜１０画素
となるよう読み込み、読み込んだ画像を、空隙と空隙以
外の部分の色調の違いにより空隙と空隙以外の部分に分
ける。この操作を二値化という。つぎに二値化した画像
（二値化画像）を画像解析して、個々の空隙の周囲長さ
と面積を計測する。この場合、電極内のコークス内空隙
は計測から省く。The most important quality characteristic in the present invention is to specify the average shape factor of the void inside the electrode in the range of 500 to 3000. The average shape factor of the void inside the electrode is determined as follows. That is, a cross section perpendicular to the length direction of the electrode is measured using image analysis to obtain a measurement area of 280
The image is read so as to be 0 ± 300 mm 2 and the scale is 8 to 10 pixels per 1 mm, and the read image is divided into a gap and a part other than the gap according to a difference in color tone between the gap and the part other than the gap. This operation is called binarization. Next, the binarized image (binary image) is subjected to image analysis to measure the peripheral length and area of each gap. In this case, the void in the coke in the electrode is omitted from the measurement.
【００１４】計測した個々の空隙のうち周囲長さの長い
順に５０個の空隙を選出し、選出した空隙から面積が１
５ｍｍ2 以上の空隙を除く空隙の周囲長さの平均値を求
め、空隙周囲長さが該平均値を越える空隙について、周
囲長さ（Ｌ）と面積（Ｓ）を求め、下記の式により形状
係数を算出し、その平均値を求めて平均形状係数とす
る。真円の場合、形状係数は１００となる。 形状係数＝〔（周囲長さＬ）2 ／｛４π×（面積
Ｓ）｝〕×１００From the measured individual voids, 50 voids are selected in ascending order of the perimeter, and an area having an area of 1 from the selected voids.
The average value of the peripheral lengths of the voids excluding the voids of 5 mm 2 or more is determined. For the voids whose peripheral length exceeds the average value, the peripheral length (L) and the area (S) are determined, and the shape is calculated by the following formula. The coefficient is calculated, and the average value is determined to be the average shape coefficient. In the case of a perfect circle, the shape factor is 100. Shape factor = [(perimeter L) 2 / {4π × (area S)}] × 100
【００１５】前記電極内部の空隙の平均形状係数を求め
るに当たり、前記のように、周囲長さの長い順に５０個
の空隙を選出し、選出した空隙から面積が１５ｍｍ2 以
上の空隙を除く空隙の周囲長さの平均値を求めるとき、
面積が１５ｍｍ2 以上の空隙を除く（すなわち、面積が
１５ｍｍ2 未満の）空隙の数（Ｎ）に対する空隙の周囲
長さがこの平均値以下の空隙の数（ｎ）の割合（（ｎ／
Ｎ）×１００％）を削除率という。また、空隙周囲長さ
がこの平均値を越える空隙についての、周囲長さ（Ｌ）
と面積（Ｓ）の平均値をそれぞれ平均周囲長さおよび平
均面積という。In obtaining the average shape factor of the voids inside the electrode, as described above, 50 voids are selected in ascending order of the perimeter, and the voids excluding the voids having an area of 15 mm 2 or more are selected from the voids. When calculating the average value of the perimeter,
The ratio of the number of voids (n) whose peripheral length is equal to or less than the average value to the number of voids (N) excluding voids having an area of 15 mm 2 or more (that is, having an area of less than 15 mm 2 ) ((n /
N) × 100%) is called a deletion rate. In addition, the perimeter (L) of a gap whose gap perimeter exceeds this average value
And the average value of the area (S) are referred to as an average peripheral length and an average area, respectively.
【００１６】電極内部の空隙の平均形状係数は７００以
上とするのがさらに好ましい。また、好ましい平均周囲
長さおよび平均面積は、それぞれ３〜２０ｍｍおよび１
〜５ｍｍ2 、好ましい削除率は６０〜９０％、さらに好
ましい平均周囲長さ、平均面積および削除率は、それぞ
れ５〜２０ｍｍ、１〜３ｍｍ2 および６５〜９０％の範
囲である。The average shape factor of the voids inside the electrode is more preferably 700 or more. In addition, the preferable average peripheral length and average area are 3 to 20 mm and 1 respectively.
５5 mm 2 , a preferred removal rate is 60-90%, and more preferred average perimeter, average area and removal rate are in the range of 5-20 mm, 1-3 mm 2 and 65-90%, respectively.
【００１７】本発明の好ましい平均形状係数を有する電
極は、電気製鋼アーク炉用人造黒鉛電極の製造におい
て、例えば、原料コークスおよびバインダーピッチの種
類とその配合割合及び捏合中の雰囲気を調整することに
より得ることができる。The electrode having a preferred average shape factor of the present invention can be produced by, for example, adjusting the types of raw coke and binder pitch, the mixing ratio thereof, and the atmosphere during kneading in the production of artificial graphite electrodes for electric steel arc furnaces. Obtainable.
【００１８】[0018]
【実施例】本発明によれば、嵩比重、固有抵抗値、弾性
率、曲げ強度および熱膨張係数の諸特性を特定範囲に調
整するとともに、電極内部の空隙を評価する方法として
形状係数を導入し、平均形状係数を特定することによっ
て、耐スポーリング性に優れた電極を得るものであり、
以下、実施例を比較例と対比して説明し、本発明の効果
を実証する。なお、これらの実施例は本発明の一実施態
様を示すものであり、本発明はこれに限定されるもので
はない。DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, various characteristics such as bulk specific gravity, specific resistance, elastic modulus, bending strength and thermal expansion coefficient are adjusted to specific ranges, and a shape factor is introduced as a method for evaluating voids inside an electrode. Then, by specifying the average shape factor, to obtain an electrode with excellent spalling resistance,
Hereinafter, examples will be described in comparison with comparative examples to demonstrate the effects of the present invention. These examples show one embodiment of the present invention, and the present invention is not limited thereto.
【００１９】実施例１〜３、比較例１〜３ 電極の長さ方向と平行な方向に採取した直径２０ｍｍ、
長さ１００ｍｍの試片の嵩比重が１．６６〜１．７５、
固有抵抗が４．４〜５．０μΩｍ、弾性率が１００００
〜１４０００ＭＰａ、三点曲げ強度が９．８０〜１４．
０ＭＰａ、石英ガラスを基準とした０℃から１００℃ま
での熱膨張係数が０．１×１０-6〜０．３×１０-6／℃
で、表１に示す平均形状係数、平均面積、平均周囲長さ
および削除率を有する人造黒鉛電極を製造した。なお、
固有抵抗、弾性率、三点曲げ強度は、ＪＩＳ Ｒ７２２
２−１９９７に従って測定した。Examples 1 to 3 and Comparative Examples 1 to 3 A diameter of 20 mm taken in a direction parallel to the length direction of the electrode,
The bulk specific gravity of the test piece having a length of 100 mm is 1.66 to 1.75,
Specific resistance is 4.4 to 5.0 μΩm, elastic modulus is 10,000
-14000 MPa, three-point bending strength 9.80-14.
0 MPa, the coefficient of thermal expansion from 0 ° C. to 100 ° C. based on quartz glass is 0.1 × 10 −6 to 0.3 × 10 −6 / ° C.
Then, an artificial graphite electrode having an average shape factor, an average area, an average peripheral length, and a deletion rate shown in Table 1 was manufactured. In addition,
The specific resistance, elastic modulus, and three-point bending strength are based on JIS R722.
Measured according to 2-1997.
【００２０】固有抵抗の測定方法：電圧降下法により４
端子法を用いて測定した。サンプル（直径２０ｍｍ、長
さ１００ｍｍ）の端部に電流端子を当てて直流５Ａを通
電し、円筒部の表面に電圧端子を当てて電位差を測定し
た。電圧端子間距離は６６ｍｍとする。サンプルの断面
積Ｓと電位差Ｖ、電流Ｉ、端子間距離Ｌと固有抵抗Ｒの
関係は次式であらわされる。 Ｒ＝ＶＳ／（ＩＬ）Measurement method of specific resistance: 4 by voltage drop method
It was measured using the terminal method. A current terminal was applied to an end of the sample (diameter: 20 mm, length: 100 mm), a direct current of 5 A was applied, and a potential difference was measured by applying a voltage terminal to the surface of the cylindrical portion. The distance between the voltage terminals is 66 mm. The relationship between the cross-sectional area S of the sample, the potential difference V, the current I, the distance L between the terminals and the specific resistance R is expressed by the following equation. R = VS / (IL)
【００２１】弾性率の測定方法：弾性率Ｅは共振周波数
ｆを測定して算出する。 Ｅ＝４．０８ρｆ2 Ｌ2 ｘ１０-10 （ｋｇｆ／ｍｍ2 ） ９．８１（ＭＰａ）＝１（ｋｇｆ／ｍｍ2 ） ここで ρ：嵩密度（ｇ／ｃｃ）、Ｌ：サンプルの長さ
（ｍｍ）、ｆ：共振周波数（Ｈｚ）Method of measuring elastic modulus: Elastic modulus E is calculated by measuring resonance frequency f. E = 4.08ρf 2 L 2 × 10 −10 (kgf / mm 2 ) 9.81 (MPa) = 1 (kgf / mm 2 ) where ρ: bulk density (g / cc), L: sample length ( mm), f: resonance frequency (Hz)
【００２２】曲げ強度の測定方法：曲げ強度Ｓｔは３点
曲げにて測定した。支点間距離ＬはＬ＝４ｘＤ＝８ｃ
ｍ、クロスヘッドの下降スピードは加荷重速度５．０±
２（ｋｇ／ｓ）になるよう、約３（ｍｍ／ｍｉｎ）に設
定した。荷重Ｐはロードセルにて測定し、サンプル直径
Ｄ（ｃｍ）はマイクロメータで測定した。 Ｓｔ＝８ＰＬ／（πＤ3 ） （ｋｇ／ｃｍ2 ） ９．８１ｘ１０4 （Ｐａ）＝１（ｋｇｆ／ｃｍ2 ）Measuring method of bending strength: The bending strength St was measured by three-point bending. The distance L between fulcrums is L = 4 × D = 8c
m, crosshead descent speed is loading speed 5.0 ±
It was set to about 3 (mm / min) so as to be 2 (kg / s). The load P was measured with a load cell, and the sample diameter D (cm) was measured with a micrometer. St = 8PL / (πD 3 ) (kg / cm 2 ) 9.81 × 10 4 (Pa) = 1 (kgf / cm 2 )
【００２３】平均形状係数、平均面積、平均周囲長さお
よび削除率は、以下の方法により測定した。すなわち、
電極を長さ方向と直角な方向に切断して、その切断面を
研磨し、研磨面を観察面とする。この場合、研磨に当た
っては、電極内の空隙が埋没しないように、また、研磨
表面が鏡面のように著しく光を反射しないように研磨す
ることが重要である。The average shape factor, average area, average perimeter and elimination rate were measured by the following methods. That is,
The electrode is cut in a direction perpendicular to the length direction, the cut surface is polished, and the polished surface is used as an observation surface. In this case, it is important that the polishing is performed so that the voids in the electrode are not buried, and that the polishing surface does not significantly reflect light like a mirror surface.
【００２４】観察面の写真を撮影し、写真のコークス部
分を白色に塗りつぶし、これを画像解析装置（株式会社
ニレコ製、ＬＵＺＥＸ ＦＳ）に読み込む。読み込み
は、写真を２５６階調の白黒画像として、観察面積２８
００ｍｍ2 、縮尺は１ｍｍが９画素（Ｐｔ）となるよう
取り込む。A photograph of the observation surface is taken, the coke portion of the photograph is painted in white, and this is read into an image analyzer (Luzex FS, manufactured by Nireco Co., Ltd.). The reading is performed by converting the photograph into a black-and-white image of 256 gradations,
00 mm 2 , and the scale is captured so that 1 mm becomes 9 pixels (Pt).
【００２５】取り込まれた画像においては、空隙部分は
空隙以外の部分よりも濃い色で示されており、コークス
部分は白色で塗りつぶされているので、空隙部分や空隙
以外の部分より淡い色となっている。In the captured image, the void portion is shown in a darker color than the portion other than the void, and the coke portion is filled with white, so that the color becomes lighter than the void portion and the portion other than the void. ing.
【００２６】この画像を、ある階調の色調を境界にし
て、濃い部分を着色、淡い部分を無色に分ける。この操
作を二値化処理といい、二値化処理では、空隙の部分だ
けが着色されるようにする。二値化処理により、コーク
ス内空隙を除いた空隙部分だけとなった画像について、
前記画像解析装置により空隙の周囲長さ、面積を計測
し、形状係数を求め、前記の方法に従って平均形状係
数、平均面積、平均周囲長さおよび削除率を計算する。In this image, a dark part is colored and a light part is colorless with a certain tone color as a boundary. This operation is called a binarization process, and in the binarization process, only the void portions are colored. Due to the binarization process, for the image only the void portion excluding the void in the coke,
The image analyzer measures the peripheral length and area of the void, determines the shape factor, and calculates the average shape factor, average area, average peripheral length, and deletion rate according to the method described above.
【００２７】この電極を製鋼用電気炉において使用し
た。この製鋼用電気炉においては、操業中における電極
の折損は少ない反面、電極の先端の欠け落ち、ネジ底の
横割れの発生に起因する先端脱落（操業中に上側接続部
のネジ底に発生した横割れに起因して電極が落下するこ
と）の有無（耐スポーリング性）が使用結果の善し悪し
を決めている。This electrode was used in an electric furnace for steelmaking. In this steelmaking electric furnace, the electrode breakage during operation was small, but the tip of the electrode dropped off, and the tip fell off due to the occurrence of a lateral crack in the screw bottom. The presence or absence (spalling resistance) of the electrode (dropping of the electrode due to a lateral crack) determines the quality of use.
【００２８】使用した結果としての耐用回数を表１に示
す。耐用回数とは、バッチ式で運転される製鋼用電気炉
において、１本の人造黒鉛電極が使用できたバッチ数で
あり、製鋼用人造黒鉛電極の使用成績を示す指標として
一般的に用いられる数値である。The service life as a result of use is shown in Table 1. The service life is the number of batches in which a single artificial graphite electrode could be used in a steelmaking electric furnace operated in a batch system, and is a numerical value generally used as an index indicating the performance of the artificial graphite electrode for steelmaking. It is.
【００２９】[0029]
【表１】 [Table 1]
【００３０】表１に示すように、嵩比重、固有抵抗値、
弾性率、曲げ強度、熱膨張係数が本発明の範囲内にあ
り、平均形状係数も本発明の範囲にある実施例１〜３の
電極は、平均形状係数が本発明の範囲を外れている比較
例１〜３の電極に比べて、いずれも優れた耐用回数をそ
なえている。As shown in Table 1, bulk specific gravity, specific resistance,
The electrodes of Examples 1 to 3 whose elastic modulus, bending strength, and coefficient of thermal expansion are within the range of the present invention, and whose average shape factor is also within the range of the present invention, have the average shape factor outside the range of the present invention. As compared with the electrodes of Examples 1 to 3, all of them have excellent service life.
【００３１】[0031]
【発明の効果】本発明によれば、耐スポーリング性に優
れ、使用中における先端の欠け落ち、ネジの横割れの発
生が顕著に抑制される製鋼用電気アーク炉用人造黒鉛電
極が提供される。According to the present invention, there is provided an artificial graphite electrode for an electric arc furnace for steelmaking, which is excellent in spalling resistance and in which occurrence of chipping of a tip and occurrence of a lateral crack in a screw during use is remarkably suppressed. You.
Claims (2)
４インチ以上の人造黒鉛電極であって、該電極の長さ方
向と平行な方向に採取した直径２０ｍｍ、長さ１００ｍ
ｍの試片の嵩比重が１．６６以上、固有抵抗が５．２μ
Ωｍ以下、弾性率が１７０００ＭＰａ以下、三点曲げ強
度が９．８０ＭＰａ以上、石英ガラスを基準とした０℃
から１００℃までの熱膨張係数が０．５×１０-6／℃以
下であり、前記電極内部の空隙の平均形状係数が５００
〜３０００であることを特徴とする耐スポーリング性に
優れた製鋼用人造黒鉛電極。但し、電極内部の空隙の平
均形状係数は、電極の長さ方向と直角な断面を、画像解
析を用いて計測面積を２８００±３００ｍｍ2 とし縮尺
が１ｍｍ当たり８〜１０画素となるよう読み込み、読み
込んだ画像を、空隙と空隙以外の部分の色調の違いによ
り空隙と空隙以外の部分に二値化し、二値化した二値化
画像を画像解析して個々の空隙の周囲長さと面積を計測
し（電極内のコークス内空隙は計測から省く）、計測し
た個々の空隙のうち周囲長さの長い順に５０個の空隙を
選出し、選出した空隙から面積が１５ｍｍ2 以上の空隙
を除く空隙の周囲長さの平均値を求め、空隙長さが該平
均値を越える空隙について、周囲長さ（Ｌ）と面積
（Ｓ）を求め、下記の式により形状係数を算出し、その
平均を求めて平均形状係数とする。形状係数＝〔（周囲
長さＬ）2 ／｛４π×（面積Ｓ）｝〕×１００1. The diameter used for an electric steelmaking arc furnace is 2
An artificial graphite electrode of 4 inches or more, having a diameter of 20 mm and a length of 100 m sampled in a direction parallel to the length direction of the electrode.
m has a bulk specific gravity of 1.66 or more and a specific resistance of 5.2 μm.
Ωm or less, elastic modulus of 17000 MPa or less, three-point bending strength of 9.80 MPa or more, 0 ° C. based on quartz glass
A coefficient of thermal expansion from 0.5 to 100 ° C. is 0.5 × 10 −6 / ° C. or less, and an average shape factor of voids inside the electrode is 500
An artificial graphite electrode for steelmaking having an excellent spalling resistance of from 3,000 to 3,000. However, the average shape factor of the voids inside the electrode is read and read so that the cross-section perpendicular to the length direction of the electrode is measured using image analysis, the measurement area is 2800 ± 300 mm 2, and the scale is 8 to 10 pixels per mm. The image is binarized into gaps and parts other than the gaps based on the difference in color tone between the gaps and the parts other than the gaps, and the binarized binarized image is image-analyzed to measure the perimeter and area of each gap. (The voids in the coke in the electrode are omitted from the measurement.) From the measured voids, 50 voids are selected in ascending order of the perimeter, and the voids except the voids having an area of 15 mm 2 or more from the voids selected are selected. The average value of the lengths is determined, and for the voids having a void length exceeding the average value, the peripheral length (L) and the area (S) are determined, the shape coefficient is calculated by the following formula, and the average is determined. The shape factor is used. Shape factor = [(perimeter L) 2 / {4π × (area S)}] × 100
の空隙から、面積が１５ｍｍ2 以上の空隙を除く空隙の
周囲長さおよび面積の平均値がそれぞれ３〜２０ｍｍお
よび１〜５ｍｍ2 で、削除率が６０〜９０％であること
を特徴とする請求項１記載の耐スポーリング性に優れた
製鋼用人造黒鉛電極。但し、削除率とは、前記電極内部
の空隙の平均形状係数を求めるに当たり、周囲長さの長
い順に５０個の空隙を選出し、選出した空隙から面積が
１５ｍｍ2 以上の空隙を除く空隙の周囲長さの平均値を
求めるとき、面積が１５ｍｍ2 以上の空隙を除く空隙の
数（Ｎ）に対する空隙の周囲長さが該平均値以下の空隙
の数（ｎ）の割合（（ｎ／Ｎ）×１００％をいう）。2. An average value of the peripheral length and the area of the voids, excluding the voids having an area of 15 mm 2 or more, from the 50 voids selected in the descending order of the peripheral length are 3 to 20 mm and 1 to 5 mm 2 , respectively. 2. The artificial graphite electrode for steelmaking having excellent spalling resistance according to claim 1, wherein a deletion rate is 60 to 90%. However, the elimination rate means that, when calculating the average shape factor of the voids inside the electrode, 50 voids are selected in ascending peripheral length, and the area around the voids excluding the voids having an area of 15 mm 2 or more from the selected voids. When calculating the average value of the lengths, the ratio of the number of voids (n) whose peripheral length is less than the average value to the number of voids (N) excluding the voids having an area of 15 mm 2 or more ((n / N) × 100%).
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|---|---|---|---|
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| Application Number | Priority Date | Filing Date | Title |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2017065962A (en) * | 2015-09-30 | 2017-04-06 | クアーズテック株式会社 | Carbon electrode for quartz glass melting |
| WO2020203825A1 (en) | 2019-03-29 | 2020-10-08 | 日鉄ケミカル＆マテリアル株式会社 | Method for manufacturing high-density artificial graphite electrode |
-
2001
- 2001-02-19 JP JP2001041579A patent/JP2002246171A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2017065962A (en) * | 2015-09-30 | 2017-04-06 | クアーズテック株式会社 | Carbon electrode for quartz glass melting |
| WO2020203825A1 (en) | 2019-03-29 | 2020-10-08 | 日鉄ケミカル＆マテリアル株式会社 | Method for manufacturing high-density artificial graphite electrode |
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