黒皮生成実験 2 1 実験方法 Fig.1 19 SKH51 S45C SUS310S Table 1 24 mm 30 mm 27 mm 20 mm YAMATO FO h30 Fig.1 50 MPa ml/mm

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1 735 論文熱延ロールに生じる黒皮の熱伝達に及ぼす影響 Influence of Work Roll Surface Oxide Scale on Interface Thermal Transfer Shohei Fujiwara, Eiji Abe and Nobuki Yukawa Synopsis : In hot rolling processes, an accurate prediction of thermal expansion of work rolls is necessary because it affects profile of strips. A precise calculation of thermal expansion requires an accurate heat transfer coefficient between the roll and the strip, and the oxide scale on the surface of the work roll (mill scale) is one of the important factor that affects the heat transfer coefficient. Although clear relation between the mill scale and the heat transfer coefficient is required, it has not clarified because forming mill scale in a laboratory is difficult. In this study, first, we developed a generating method of the mill scale of hot rolling mill in a laboratory. Uniaxial compression contact experiments are used to simulate the contact between the work roll and the strip during the hot rolling. An oxide scale layer that simulates the mill scale was obtained on the surface of punch. The thickness of mill scale which was generated from the different kinds of strips material was measured. Second, the interface heat transfer coefficient for various thickness of mill scale are measured. Heat transfer coefficient is obtained from comparing the measured temperature of punch and the results of computer simulation by FEM. From these results, the relation between the thickness of mill scale and the heat resistance is clarified. Key words: hot rolling; thermal expansion; heat transfer coefficient; mill scale. 1. 緒言 1,2 Cr Mo W V 3 4, , Received on Apr. 6, 2018 ; Accepted on Sep. 6, Department of Materials Science and Engineering, Nagoya University, Furo-cho Chikusa-ku Nagoya Corresponding author : yukawa@numse.nagoya-u.ac.jp DOI : 15

736 2. 黒皮生成実験 2 1 実験方法 Fig.1 19 SKH51 S45C SUS310S Table 1 24 mm 30 mm 27 mm 20 mm 10 1180 YAMATO FO310 20 1 30 h30 Fig.1 50 MPa 0.0018 ml/mm 2 9.

2 黒皮生成実験 2 1 実験方法 Fig.1 19 SKH51 S45C SUS310S Table 1 24 mm 30 mm 27 mm 20 mm YAMATO FO h30 Fig.1 50 MPa ml/mm MPa MARUI Table t2 mm XRD X SEM ImageJ 実験結果考察 Table 1. Chemical compositions (mass%). Grade C Mn Ni Cr Mo V W SKH S45C SUS310S Contact time Table 2. Experiment condition. Number of contacts sec 4 sec 5 sec Fig. 1. Experiment configuration (a) schematic of actual rolling, (b) photo of experiment and (c) schematic of experiment. (Online version in color.) 16

737 S45C SUS310S Fig.2 a b XRD S45C SUS310S Fe 3 O 4 Fe 3 O 4 Fig.3 S45C 3 40 XRD FeO Fe 3 O 4 15,20 23 Fig.4 a b SEM Fig.4 S45C SUS310S SEM Fig.5 Fig.5 S45C SUS310S 15 Fig. 3. XRD results of punch surface.

3 737 S45C SUS310S Fig.2 a b XRD S45C SUS310S Fe 3 O 4 Fe 3 O 4 Fig.3 S45C 3 40 XRD FeO Fe 3 O 4 15,20 23 Fig.4 a b SEM Fig.4 S45C SUS310S SEM Fig.5 Fig.5 S45C SUS310S 15 Fig. 3. XRD results of punch surface. Experiment without water. Fig. 2. XRD results of punch surface in experiment condition (a) workpiece S45C (b) workpiece SUS310S. Fig. 4. SEM results of cross section mill scale in experiment condition (a) workpiece S45C (b) workpiece SUS310S. 17

738 が水や水蒸気と反応して Fe OH 2 などの中間生成物が生面の熱伝達係数の関係を調査した接触界面の熱伝達係数成しそれが圧縮時にパンチ材側で反応し Fe3O4 が主成分を決定するためまずパンチ材に熱電対を挿入し被圧延材の黒皮になるとする考えを支持していると思われる S45C/SUS310S を接触させ温度履歴を測定する実験を 15,23 SUS304S の場合

4 738 が水や水蒸気と反応して Fe OH 2 などの中間生成物が生面の熱伝達係数の関係を調査した接触界面の熱伝達係数成しそれが圧縮時にパンチ材側で反応し Fe3O4 が主成分を決定するためまずパンチ材に熱電対を挿入し被圧延材の黒皮になるとする考えを支持していると思われる S45C/SUS310S を接触させ温度履歴を測定する実験を 15,23 SUS304S の場合被圧延材表面は強固な Cr 系酸化物で覆わ行った続いて温度測定実験を再現した有限要素解析を行れていると考えられ 22 接触時に SUS310S からパンチ材とい校正曲線を作成し実験値と解析値の誤差が小さくなるの界面への Fe の拡散が S45C より少ないことにより中間生よう解析を繰り返すことで接触界面の熱伝達係数を同定成物の生成が少なくそのため黒皮厚さが薄くなったと考したえられる 3 1 温度履歴測定実験高温の被圧延材にパンチ材を接触させパンチ材内部に 3. 熱伝達係数測定実験挿入した 3 本の熱電対からパンチ材内部の温度上昇量と時間の関係を測定する被圧延材からパンチ材への熱伝達に黒皮が及ぼす影響を調査するため黒皮の厚さと被圧延材とパンチ材の接触界実験試料実験に用いるパンチ材は SKH51 で形状は直径φ24 mm 高さ h17 mm とした被圧延材は 2 章の黒皮生成実験と同じ形状と組成であるダイスは窒化ケイ素で 2 章と同じ形状と組成であるパンチ材には 3 本のφ1.6 のシース型 K 熱電対を埋め込むため端面の中心から半径 5 mm の円周上に 120 毎に上部から直径 1.7 mm の穴を 3 か所にあけたそれぞれ深さを下端から 0.5 mm 1.0 mm 1.5 mm としたパンチ材に穴を空ける加工を行ったあと続いて黒皮生成実験を行いパンチ材表面に黒皮を生成させた黒皮を生成するための接触保持時間と接触回数は Table 2 の通りで被圧延材が S45C と SUS310S の場合で 16 種類の実験条件でパンチ材に黒皮を生成させたパンチ材の穴と熱電対の位置さらに実験の概略図を Fig.6 に示す温度履歴測定実験に使用したシース直径φ1.6 mm の K 熱電対の応答速度は 63.2% で 0.9 sec 99.9% で 2.1 sec である実験装置は 2 章の黒皮生成実験に用いたものと同じである実験方法まず被圧延材 S45C または SUS310S を大気炉 Fig. 5. R elation between number of contact and thickness of scale. (Online version in color.) YAMATO 科学社製大気炉 FO310 で温度 1080 保持時 Fig. 6. E xperiment configuration (a) photo of experiment, (b) schematic of experiment configuration and (c) scope of punch and thermocouple. (Online version in color.) 18

5 S45C S45C SUS310S SUS310S 50 MPa MPa 3 2 有限要素解析 Scientific Forming Technologies DEFORM-2D TM kwm 2 K kwm 2 K Fig.7 Fig.7 b Fig.7 S45C kwm 2 K 1 Fig.8 SUS310S Fig. 7. (a) Temperature change of punch and fitting curves (b) enlarged view between s. (Online version in color.) 19

740 4. 考察 Fig.9 5 R workpiece-scale R oxide scale Fig. 8. Relation between thickness of oxide scale and heat transfer. (Online version in color.

6 考察 Fig.9 5 R workpiece-scale R oxide scale Fig. 8. Relation between thickness of oxide scale and heat transfer. (Online version in color.) R interface R mill scale R mill scale-punch R 1 1 R workpiece-scale R mill scale-punch R oxide scale R interface R mill scale R workpiece-scale R mill scale-punch R oxide scale R interface Fig.10 0 Fig.11 S45C SUS304S Fig. 9. Schematic of heat transfer from workpiece to punch. (Online version in color.) 20

7 741 Fig. 10. Relation between thickness of mill scale and total heat resistance. Fig. 11. Relation between thickness of mill scale and heat resistance. (Online version in color.) 5. 結言 1 S45C SUS310S Fe 3 O 4 2 S45C SUS310S Fe Fe 3 4 文 1 ) 31(1995), ) R.Nawata, Y.Sugimura and Y.Sano: J. Jpn. Soc. Technol. Plast., 36(1995), ) J.Ikeda: J. Jpn. Soc. Technol. Plast., 40(1999), ) K.Goto, Y.Matsuda, K.Sakamoto and Y.Sugimoto: ISIJ Int., 32(1992), ) Y.Sano, T.Hattori and M.Haga: ISIJ Int., 32(1992), ) A.Ishikawa: Nisshin steel Tech. Rep., 73(1996), ) M.Hashimoto, T.Kawakami, T.Oda, R.Kurahashi and K.Hokimoto: Nippon Steel Tech. Rep., 356(1995), ) T.Tsuchihashi, J.Satoh, T.Shiraishi, K.Kawashima, K.Hirata and Y.Ooike: CAMP-ISIJ, 9(1996), ) J.D.Fletcher and J.H.Beynon: Ironmaking Steelmaking, 23(1996), ) S.Araya: CAMP-ISIJ, 10(1997), ) H.Okada: Nippon Steel & Sumitomo Metal Tech. Rep., 401(2015), ) T.Fukawa: Tetsu-to-Hagané, 82(1996), ) K.Fukuda: Tetsu-to-Hagané, 84(1998), ) 20(2008), ) Y.Sekimoto, M.Tanaka and T.Yoshimura: Tetsu-to-Hagané, 61(1975), ) T.Oohata, T.Hattori, G.Sano and J.Kihara: CAMP-ISIJ, 3(1990), ) S.Araya, T.Inoue and S.Uchida: CAMP-ISIJ, 10(1997), ) K.C.Hwang, L.Sunghak and L.Eonsik: Tetsu-to-Hagané, 83(1997), ) S.Fujisaki: CAMP-ISIJ, 28(2015), 451, CD-ROM. 20) K.Kusabiraki, T.Sugihara and T.Ooka: Tetsu-to-Hagané, 77(1991), ) H.Hori: Tetsu-to-Hagané, 55(1969), ) M.Kikuchi: Sanyo Tech. Rep., 21(2014), 1, ) H.H.Kim, J.W.Lim and J.J.Lee: ISIJ Int., 43(2003), ) Y.Nakashima: J. Jpn. Soc. Technol. Plast., 55(2014), 献 21

Photo. 1. Scale banding in roughing mill work roll. Photo. 2. Etched micro-structure of alloyed grain iron roll. Photo. 3. Etched micro-structure of a

Photo. 1. Scale banding in roughing mill work roll. Photo. 2. Etched micro-structure of alloyed grain iron roll. Photo. 3. Etched micro-structure of a Work Rolls in Hot Strip Mills Hidemaro KAWAHARA Synopsis: The work roll materials in hot strip mills and the damages of rolls which arise in rolling operation are discussed in this paper. As for the rolls