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研究生:董志宏
研究生(外文):Zhi-Hong Dong
論文名稱:高鋁與硫化錳複合添加方向性電磁鋼片再結晶行為之研究
論文名稱(外文):A Study of Recrystallization Behaviors in Grain Oriented Electrical Steels Added with high Aluminum and MnS
指導教授:侯春看侯春看引用關係
指導教授(外文):Chun-kan Hou
學位類別:碩士
校院名稱:國立雲林科技大學
系所名稱:機械工程系碩士班
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2003
畢業學年度:91
語文別:中文
論文頁數:159
中文關鍵詞:方向性電磁鋼片
外文關鍵詞:Grain Oriented Electrical Steels
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方向性電磁鋼片是一種機能性鋼鐵材料,用來製作變壓器的鐵心,它的磁特性直接影響到電機機械的能源效率。介在物的大小及分佈型態可用來抑制方向性電磁鋼片的一次結晶晶粒成長,使方向性電磁鋼片再二次再結晶退火時,產生有益於磁特性的(110)<001>優選方位。而其前製程條件,如精軋再加熱溫度、熱軋板退火溫度、中間退火溫度都直接影響其介在物種類與大小。因此,本研究主要是在探討介在物對方向性電磁鋼片不同二次再結晶溫度的微觀組織與優選方位效應,和不同二次再結晶溫度的再結晶行為。將改變方向性電磁鋼片中的硫含量,其碳含量為0.034 wt﹪與複合添加MnS及AlN抑制劑。
結果顯示當精軋再加熱溫度為1200℃時,低硫的試片因為MnS大多已固溶,所以看到的大部分為AlN介在物,而高硫的試片大多存在著MnS與AlN兩種介在物。且當方向性電磁鋼片經過1200℃的精軋再加熱退火及二次再結晶退火熱處理後,會發生較多異常的晶粒成長現象,而採用熱軋板退火溫度為900℃及中間退火900℃製程,其介在物大小與分佈情形,能較有效抑制不利於磁性的晶粒再結晶成長,作為最有效的抑制劑,促使二次再結晶效應能發展的更完全。
對低硫條件而言,當精軋再加熱溫度1200℃、熱軋板退火900℃的條件下,由於有較多且細小的介在物析出而抑制一次再結晶晶粒成長,使得基地的晶粒維持在較細小的狀態,這將有利於二次再結晶的成長。對於高硫材料而言,當精軋再加熱溫度1200℃、熱軋板退火900℃和1000℃的條件下,也因為基地晶粒獲得較好的抑制效果因而有較大的二次再結晶比例。經過800℃、持溫5分鐘的一次再結晶脫碳退火處理製程,複合添加MnS與AlN作為抑制劑的低碳方向性電磁鋼片其碳含量皆小於16ppm,已達到工業上所需要之數值。
在不同爐氛下作二次再結晶退火的製程,發現當通以全氮氣的條件下能得到較完整的二次再結晶晶粒和較好的磁特性。而以不同升溫速率的二次再結晶退火製程,發現在速率1℃/min條件的晶粒尺寸最大,也有較好的磁特性,而0.5℃/min條件之性質較差。
Grain oriented electrical steel is an important function magnetic material. It has no magnetism but has excellent permeability after magnetization. Grain oriented electrical steel is usually used to be the core of transformers and it’s magnetic properties affect the energy efficiency of electric machinery. Proper size and distribution of inclusions can impede the normal grain growth during primary annealing and let the preferred Goss grain grow during secondary recrystallization. This study will investigate the effect of inclusion on texture , microstructure and secondary recrystallization behaviors of grain oriented electrical steels added with MnS and AlN inclusions at various temperature.
It is found that when the steels were reheated to 1200℃, low sulfur sample has AlN inclusions because many of MnS had dissolved. And high sulfur sample has both MnS and AlN inclusions. Those steels reheated to 1200℃ occurred abnormal grain growth after secondary annealing. Hot band annealing at 900℃ can get optimum distribution and size of inclusions and let secondary recrystallization occur. Intermediate annealing at 900℃ can also get proper amount and size of inclusions that are suitable for development of secondary recrystallization.
For low sulfur sample reheated to 1200℃ and hot band annealing at 900℃, there are many fine inclusions precipitated and impede normal grain growth. That will maintain matrix grain size to be small and let abnormal grain growth occur. For high sulfur sample reheated to 1200℃ and hot band annealing at 900℃ and 1000℃, because of matrix grain be impeded well that there are more secondary recrystallization grains to grow. After decarburized five minutes at 800℃, the carbon level of low carbon electrical steels added with MnS and AlN reduced to less than 16 ppm. It meets the demand of industry.
It is found that when the steels are annealing at 100% nitrogen atmosphere, the better secondary recrystallization grains and magnetic properties will occur. For different rate of raising temperature, it is found that better secondary recrystallization grains and magnetic properties will appear at the rate of 1℃/min.
中文摘要 …………………………………………………………………….. i
英文摘要 …………………………………………………………………….. ii
誌 謝 ………………………………………………………………………… iii
目 錄 ………………………………………………………………………… iv
表目錄 ………………………………………………………………………. viii
圖目錄 ……………………………………………………………………….. ix
符號說明 …………………………………………………………………….. xviii

第一章 緒 論…………………………………………………………………. 1
1.1前言………………………………………………………………………….. 1
1.2方向性電磁鋼片的發展……………………………………………………. 2
1.2.1方向性電磁鋼片的製造流程…………………………………………. 3
1.2.2方向性電磁鋼片的特點………………………………………………. 4
1.2.3近年來方向性電磁鋼片之發展趨勢………………………………… 4
1.3影響電磁鋼片電磁特性的因素…………………………………………… 5
1.3.1 鐵損值(Core loss)…………………………………………………. 6
1.3.2 導磁率(Permeability)……………………………………………… 7
1.3.3 優選方位(Texture)………………………………………………… 7
1.3.4 結晶粒大小……………………………………………….…………… 8
1.4方向性電磁鋼片中二次再結晶機制的因素和理論…………………….. 8
1.4.1合金元素的添加量與種類……………………………………………. 9
1.4.2鑄錠的產生方式……………………………………………………….. 10
1.4.3熱軋時Goss優選方位的形成……………………………………….. 11
1.4.4熱軋時微觀組織的變化………………………………………………. 13
1.4.5熱軋時抑制劑析出的控制……………………………………………. 14
1.4.6冷軋和退火製程……………………………………………………….. 14
1.4.7二次再結晶退火製程…………………………………………………. 15
1.5近年來國內方向性電磁鋼片之研究現況………………………………… 18
1.6本論文研究的課題…………………………………………………………. 19

第二章 實驗方法……………………………………………………………... 32
2.1材 料………………………………………………………………………… 32
2.2熱 軋………………………………………………………………………… 32
2.3熱軋板退火…………………………………………………………………. 33
2.4熱軋板表面�蚰皏h除………………………………………………………. 33
2.5第一道冷軋………………………………………………………………….. 34
2.6中間退火…………………………………………………………………….. 34
2.7第二道冷軋………………………………………………………………….. 34
2.8一次再結晶退火和二次再結晶退火……………………………………… 35
2.9碳成分分析和試片準備……………………………………………………. 36
2.10 金相試片準備與觀察………………………………………………….. 36
2.11 晶粒尺寸的量測………………………………………………………… 37
2.12 介在物觀察與量測………………………………………………………. 37
2.13 優選方位試片準備與量測………………………………………………. 37
2.14 磁特性量測……………………………………………………………….. 38
2.15 二階段再結晶退火實驗流程與分析方法……………………………… 38
第三章 結果與討論…………………………………………………………... 45
3.1 熱軋板的微觀組織與優選方位………………………………………….. 45
3.1.1成分與再加熱溫度對熱軋板中介在物種類與大小的影響………. 45
3.1.2 成分與再加熱溫度對熱軋板金相組織的影響…………………….. 46
3.1.3 成分與再加熱溫度對熱軋板優選方位的影響…………………….. 48
3.2 熱軋板退火的微觀組織與優選方位…………………………….………. 48
3.2.1 成分與熱軋板退火溫度對熱軋板金相組織的影響………………. 48
3.2.2 成分與熱軋板退火溫度對熱軋板優選方位的影響………………. 49
3.3 中間退火冷軋板的微觀組織……………………………………………... 50
3.4 一次再結晶脫碳退火製程對低碳方向性電磁鋼片的影響效應……… 51
3.4.1 一次再結晶脫碳退火製程條件的影響…………………………….. 51
3.4.2 一次再結晶脫碳退火製程狀態下對複合添加MnS和AlN的低碳方向性電磁鋼片的微觀組織效應關係……………………………. 51
3.4.3 一次再結晶脫碳退火製程狀態下對複合添加MnS和AlN的低碳方向性電磁鋼片優選方位的效應關係……………………………. 52
3.5 二次再結晶退火溫度對方向性電磁鋼片二次再結晶之微觀組織、介在物及優選方位的效應關係…………………………………………….. 53
3.5.1 一次再結晶脫碳退火後以1℃/min速率升溫至不同溫度下之介在物和微觀組織之效應關係………………………………………. 53
3.5.2 一次再結晶脫碳退火後以1℃/min速率升溫至不同溫度下之微觀組織和優選方位效應關係………………………………………. 56
3.5.2.1 A、B材料在精軋再加熱1200℃、熱軋板退火1000℃及中間退火900℃製程下,升溫至不同溫度下之微觀組織和優選方位效應關係……………………………………………….. 56
3.5.2.2 A、B材料在精軋再加熱1200℃、熱軋板退火900℃及中間退火900℃製程下,升溫至不同溫度下之微觀組織和優選方位效應關係……………………………………………….. 57
3.5.2.3 A、B材料在精軋再加熱1100℃、熱軋板退火1000℃及中間退火900℃製程下,升溫至不同溫度下之微觀組織和優選方位效應關係……………………………………………….. 57
3.5.2.4 A、B材料在精軋再加熱1100℃、熱軋板退火900℃及中間退火900℃製程下,升溫至不同溫度下之微觀組織和優選方位效應關係……………………………………………….. 58
3.6 不同爐氛之二次再結晶效應對低碳方向性電磁鋼片的微觀組織與磁特性影響…………………………………………………………………… 59
3.7 不同升溫速率之二次再結晶效應對低碳方向性電磁鋼片的微觀組織與磁特性影響……………………………………………………………... 60
3.8 成分與製程對二階段再結晶退火之微觀組織與優選方位之效應…… 61
3.8.1 成分與製程條件對一次再結晶脫碳退火後微觀組織之影響……. 61
3.8.2 成分與製程條件對一次再結晶脫碳退火後優選方位之影響……. 61
3.8.3 一次再結晶脫碳退火冷卻後再以1℃/min速率升溫至不同溫度下持溫四小時之介在物和微觀組織效應關係………………. 62
3.8.4 一次再結晶脫碳退火冷卻後再以1℃/min速率升溫至不同溫度下持溫四小時之優選方位效應關係………………………………. 63
3.8.4.1 A、B材料在精軋再加熱1200℃、熱軋板退火1100℃及中間退火1000℃製程下,升溫至不同溫度下之優選方位效應關係……………………………………………………………... 63
3.8.4.2 A、B材料在精軋再加熱1200℃、熱軋板退火1000℃及中間退火1000℃製程下,升溫至不同溫度下之優選方位效應關係……………………………………………………………... 64
第四章 結論…………………………………………………………………. 152
參考文獻 ……………………………………………………………………… 154

作者簡歷 .…………………………………………………………………….. 159
參考文獻
1.N.P.Goss, 1934,U.S.Patent 1965559.
2.K.Honda, S.Kaya, 1926, Sci. Reports, Tohoku Univ., vol. 15, pp.721-753.
3.鄭振東,1999,”實用磁性材料”,pp3-56~3-58.
4.R.A.Hadfield, 1903, U.S. Patent 745829.
5.張永輝、吳志昌,1999,” 中鋼對電磁鋼片開發之演進及市場需求之消長”,磁性技術協會會訊,22期,pp.17-24,十月。
6.Y. Ushigami, H. Masui, Y. Okazaki, Y. Suga, N. Takahashi: J. Mater. Eng. Perfomance 5 (1996),pp. 310-315.
7.S.Taguchi, A.Sakakura, U.S. Patent 3287183.
8.S.Taguchi, A.Sakakura, T.Wada, K.Ueno, T.Yamamoto, U.S.Patent 3636579.
9.松本文夫,黑木克郎,日本特許 54-138468。
10.金中拓一,佐籐徹,日本特許 昭51-13469。
11.I. Goto, I.Matoba, T.Imanaka, T.Gotoh, T.Kan, 1975, Proc. Soft Mag. Mat., vol.2, pp.262.
12.Nippon. Steel Corp., U.S.Patent 385668.
13.H.Shimanaka. T.Ichida, S.Kobayashi, T.Funahashi, 1979,IEEE. Trans.Mag., MAG-15, no.6, pp.1595.
14.14.

15.T.Sashio, B.Fukada., 1990, "Development of Grain-Oriented Silicon Steel Sheets with Low Iron Loss", Kawasaki Steel Technical Report, no.22, pp.84-91.
16.Y. Ushigami, H. Masui, Y. Okazaki, Y. Suga, N. Takahashi: J. Mater. Eng. Perfomance 5 (1996),pp. 310-315.
17.Nobuyuki Takahashi, Yozo Suga, Hisashi Kobayashi: J. Mag. Mag. Mater. 160 (1996), pp.98.
18.鄭振東,1999,”實用磁性材料”,pp3-62~3-64.
19.N. Takahashi and J.Harase, Proc. 2nd Int. Conf. On Grain Growth in Polycrystalline Material, Trans. Tech. Publications, to be published.
20.ASTM A665-84, Flat-Rolled, Grain-Oriented, Silican Iron, Electrical Steel, Fully Processed Types. 23G048, 27G053, 30G058 and 35G066.
21.ASTM A677-84, Nonoriented Electrical Steel, Fully Processed Types.
22.ASTM A683-84, Nonoriented Electrical Steel, Semiprocessed Types.
23.ASTM A725-84, Flat-Rolled, Grain-Oriented, Silicon Iron., Electrical Steel, Fully Processed Types. 23H048, 27H053, 30H058 and 35H066.
24.ASTM A726-85. Cold-Rolled Carbon Steel, Magnetic Lamination Quality, Types l,2 and 2S.
25.AISI, 1983, Electrical Steel.
26.JIS C2552, Non-Oriented Magnetic Steel Sheet and Strip.
27.JIS C2553, Grain-Oriented Magnetic Steel Sheet and Strip.
28.DIN 41301, Electro Sheets, Magnetic Materials for Tramformers.
29.DIN 46400, Steel Flat Product with Special Magnetic Properties, Cold-Rolled, Non-Oriented, Finally Annealed Magnetic Sheet and Strips, Technical Delivery Condition.
30.G.Lyudkovsky, P.K. Rastogi and M.Bala, 1986, Jour. of Met., pp.18-26.
31.Y. Ushigami, H. Masui, Y. Okazaki, Y. Suga, N. Takahashi: J. Mater. Eng. Perfomance 5 (1996),pp. 310-315.
32.E.W.Golding, 1963, Electrical Measurement and Measuring Instruments, 5th.ed. (London, Pitman).
33.B.D.Cullity, 1972, Introduction to Magnetic Materials, Reading, Mass., Addison-Wesley Publishiag Co., pp.493-508.
34.F.Brailsford, 1966, Physical principles of Magnetsm, F. Vannostrand, pp.238-240.
35.H.Sato and B.S.Chandrasekhar, "Phys. and Chem. Solids, vol.1, 1957, pp.228.
36.P.R.Morris and J.W.Flowers, Texture of Crystalline Solid, vol. 4, 1981,pp.129-141.
37.J.A.Szpunar, Jour. Textures and Microstructure, vol.11, 1989, pp.93-105.
38.J.A.Szpunar and M.Ojanen, Metall. Trans., vol.6A, 1975, pp.561.
39.J.A.Szpunar, Jour. Appl. Phys., vol.55, 1984, pp.2133.
40.B.Szpunar and J.A.Szpunar, Jour. Magn. Mag. Mat., vol.43, 1984, pp.317.
41.M.Shiozaki and Y.Kurosaki, Jour. Textures and Microstructures, vol.11, 1989, pp.159-170.
42.H.J.Bunge, Jour. Textures and Microstructures, vol.11, 1989, pp.75-91.
43.H.J.Bunge, Jour. Magn. Mag. Mat., vol. 4, 1977, pp.305-320.
44.T.D.Yensen and N.A.Ziegler, 1936, Trans. ASM, vol.24, pp.337-358.
45.T.D.Yensen and N.A.Ziegler, 1936, Trans. ASM, vol.23, pp.556.
46.M.F.Littmann, 1967, Jour. Appl. Phys., vol.38, pp.1104-1108.
47.H.Shimanaka, Y.Ito, T.Irie, K.Natsumura, H.Nakamura and Y.Shono, "Non-Oriented Si-Steels Useful for Energy", in "Energy Efficient Electrical Steels", ed. by A.R.Marder and E.T.Stephenson, AIME, 1980, pp.193-204.
48.E.T.Stephenson and A.R.Marder, IEEE Trans. on Mag., vol.MAG-22, 1986, pp.101-105.
49.J.Degauque, B.Astie, J.L.Porteseil and R.Vergne, Jour. Magn. Mag. Mat., vol.26, 1982, pp.261-263.
50.B.D.Cullity, 1972, Introduction to Magnetic Materials, Reading, Mass., Addison-Wesley Publishing Co, pp.264.
51.T.Gladman, 1986, "Grain Growth and Secondary Recrystallization", Encyclopedia of Materials Science and Engineering, ed. M.M.Bever, pp.2405-2051.
52.G.Abbruzzese, I.Ciancaglioni, A.Campopiano, 1988, " On the Mechanism of Secondary Recrystallization in Grain Oriented Silicon Iron", Texture and Microstructure, vol.8&9, pp.401-412.
53.J.Harase, R.Shimizu, N.Takahashi, 1990, " Prediction of Secondary Recrystalliza-ion Texture by Three Dimensional Texture Analysis", Recrysiallization '90, ed. T.Chandra, The Minerals, Metals & Materials Society, pp.801-806.
54.H.C.Fiedler, 1958, J. Appl. Phys., vol.29, pp.361.
55.J.W.Schoen. 1986,"High Temperature Grain Grorth during Slab Reheating of oriented 3 Pct Si-Fe Made Using Continuous Casting", Met. Tran., vol.l7a, pp. 1335-1346.
56.Y.Kawamo, T.Wada, S.Hayami, 1990, "Secondary Recrystallization of 3﹪Si-Fe Alloy in the Case of Using α Single Phase 3﹪Si-Fe Slab for the Material", Recrystallization '90, ed. T.Chandra, The Minerals, Metals & Materials Society, pp.801-806.
57.H.A.Wriedt. Hsun.Hu, 1976, "The Solubility Product of Manganese Sulfide in 3Pct Silicon-Iron at 1270 to 1670K", Met. Trans., vol.7a, pp.711-718.
58.H.A.Wriedt, 1980,"Solibility product of Aluminum Nitride in 3Percent Silicon Iron", Met. Trans., vol. 11a, pp.1731-1738.
59.T.H.Shen, 1986, "The Study of Desulfurization Kinetics in Grain Oriented 3 Person Silicon Iron", Met. Trans., vol.17a, pp.1347-1351.
60.T.Gladman, D.Dulieu, 1974, Metal Science, vol.8, pp.167.
61.T.Gladman, 1992, "Grain Refinement in Multiple Micro-alloyed Steel", HSLA Steel: Processing, Properties and Applications, ed. by G.Tither and Z.Shouhua, The Minerals, Metals & Materials Society, pp.3-14.
62.M.F.Littmann, 1975, Met. Trans., vol.6a, pp.1041.
63.K.Kumal, M.Motoyoshi, K.Tanaka, Y.Hakiwara, 1972, U. S. Patent 3671337.
64.1973, U. S. Patent 3764406.
65.A.Sakakura, F.Matsumoto, K.Ueno, 1974, U. S. Patent 3841924.
66.Y.Inokuti, C.Maeda, Y.Ito, H.Shimanaka, 1983, "Transmission Kossel Study of Origin of Goss Texture in Grain Oriented Silicon Steel", Tran. ISIJ, vol.23, pp.440-449.
67.H.Hu, 1974, "Texture of Metals", Texture, vol.1, pp.233-258.
68.Y.Inokuti, 1984, "Mechanism of Secondary Recrystallization in Grain Oriented Silicon Steel", ISIJ., vol.15, pp.243-250.
69.M.Matsuo, T.Sakai, Y.Suga, 1986, "Origin and Development of Through the Thickness Variations of Texture in the Processing of Grain Oriented Silicon Steel", Met. Trans., vol.l7a, pp.1313-1322.
70.Y.Shimizu, Y.Ito, Y.Iida, 1986, "Formation of the Goss Orientation near the Surface of 3 Pct Silicon Steel during Hot Rolling", Met. Trans., vol.17a, pp.1323-1334.
71.M.Matsuo, T.Sakai, Y.Suga, 1986, "Origin and Development of Trough the Thickness Variations of Texture in the Processing of Grain Oriented Silicon Steel", Met. Trans., vol.l7a, pp.1313-1322
72.M.Matsuo, S.Hayami, S.Nagashima, 1971, Trans. Iron Steel Inst. Jpn., suppl. to vol.11, pp.867-871.
73.I.Gokyu, M.Matsuo, 1967. J. Jpn. Inst. Met., vol.31, pp.374-380.
74.

75.91.

76.M.Manabe, T.Obara, T. Kan, 1993, "Recrystallization Behavior of 3﹪ Si Steel after High Temperature Deformation", Materials Science Forum, vol.113-115, pp.491-496.
77.M.Muraki, T.Obara, M.Satoh, T.Kan, 1995,"Control of Recrystallization during High-Temperature Hot-Rolling of Grain Oriented Silicon Steel", JMEPEG, vol.4, pp.413-417.
78.W.P.Sun, W.J.Liu, J.J.Jonas,1989,"A Creep Technique for Monitoring MnS Pre-cipatation in Si Steels", Met. Trans., vol.20a, pp.2707-2715.
79.W.P.Sun, M.Militzer, J.J.Jonas, 1992, "Strain-Induced Nucleation of MnS in Electrical Steel", Met. Trans., vol.23a, pp.821-830.
80.L.Seidel, M.Holscher, K.Lucke, 1989, "Rolling and Recrystallization Texture in Iron 3﹪Silicon", Texture and Microstructures, vol.11, pp.171-185.
81.B.F.Decker, D.Harker, 1950, "Relations between Initia 1 and Final Orientations in Rolling and Annealing of Silicon Ferrite", Journal of Applied Physics, vol.22, pp.900-905.
82.C.G.Dunn, 1953, "Secondary Recrystallization Textures and their Origin in Cold-Rolled Single Crystals of Silicon Iron", Acta Metall., vol.1, pp.163-175.
83.長嵨晉一,1984,集合組織,丸善株式會社,pp.65-125。
84.W.R.Hibbard, Jr.W.R.Tully, 1961, "The Effect of Orientation on the Recrystallizat-ion Kinetics of Cold-Rolled Single Crystals", Trans. of the Metall. Society of AIME, vol.221, pp.336-343.
85.G.Abbruzzese, 1985, "Computer Simulated Grain Growth Staganation", Acta Metall., vol.33, no.7, pp.1329-1337.
86.G.Abbruzzese, S.Fortunati, 1989, "Development of Goss Texture during Grain Growth in Fe-3﹪Si", Physica Scripta, vol.39, pp.624-625.
87.G.Abbruzzese, A.Campopiano, 1990. "On the Role of Grain Boundary Energy in Secondary Recrystallization of Grain Oriented Silicon Iron", Recrystallization '90, ed. by T.Chandra, The Minerals, Metals & Materials Society, pp.667-672.
88.S.Taguchi, A.Sakakura, U.S. Patent 3287183.
89.LEE,Kitae, "Quantitative analysis of texture development in iron-3% Si during secondary recrystallization", UMI Dissertation Services,1993.
90.Jae Young Park, Kyu Seok Han, Sam Kyu Chang, N.Rajmohan, Jerzy A.Szpunar, 2002, "Influence of primary annealing condition on texture development in grain oriented electrical steels" Acta Materialia 50, pp.1825-1834.
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