Düşük Karbonlu Çeliklerde Metalurjik Yapının Elektrik Direncin Etkisi
Düşük Karbonlu Çeliklerde Metalurjik Yapının Elektrik Direncin Etkisi
Dosyalar
Tarih
1998
Yazarlar
Samer, Şebnem
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Fen Bilimleri Enstitüsü
Institute of Science and Technology
Institute of Science and Technology
Özet
Düşük karbonlu çelik teller güç ve enerji kablolarında mekanik koruma amaçlı olarak kullanılırlar. Aynı zamanda düşük karbonlu çelik teller yeraltında topraklama amacıyla da kullanılırlar. Bu amaçla bu teller kullanıldığı zaman mekanik özelliklerine ilave olarak elektriksel bazı özellikler gerekmektedir. İletkenlik enerji nakil hatlarında toprak teli olarak kullanılan düşük karbonlu çeliklerde önem kazanmaktadır. BS 1442 standardında kablo zırhlamasında kullanılan çelik tellere ait direnç değerleri tanımlanmıştır. Bu tez çalışmasında; piyasa teli (balya bağ teli, cıvata teli, süpürge teli, yay teli), elektrodluk tel (kaynak teli) ve kablo sektöründe (güç ve kontrol kablolarının zırhlanmasında) kullanılan düşük karbonlu çelik teller ile çalışılmıştır. Bu çalışmada tellerin elektrik dirençlerinin kimyasal kompozisyonla, sertlik, çekme mukavemeti, mikroyapı ve ısıl işlem ile nasıl değiştiğini ve bu değişimi etkileyen parametreler araştırılmıştır. Karbon, kükürt, alüminyum, silisyum ve mangan gibi alaşım elementi miktarının artması elektrik direnci artırmaktadır buna bağlı olarak elektrik iletkenliği düşmektedir. Bunun için alaşım elementi miktarı düşük olmalıdır. Sertlik arttıkça elektrik direnç artmaktadır, iletkenlik düşmektedir. Çekme mukavemetinin artması ile elektrik direnç artmaktadır, iletkenlik düşmektedir. Optik mikroskop incelemeler sonucu numuneler içinde, % 0.017 karbon içeren telin yapısı ferritikdir. 400 °C ve 500 °C' lerde, 5-10-20-40-60 dakikalarda yapılan ısıl işlemler sonucunda elektrik direnç değerlerinin bu sıcaklıklarda değişmediği saptanmıştır. Bu sıcaklık değerleri ve süreleri elektrik iletkenliği artırıcı, elektrik direnci düşürücü yönde etkili olmamıştır.
In this study, effect of metallurgical structure on the electrical conductivity was examined at low carbon steel. The armouring wires are used for earthing purpose so in addition to the mechanical properties of it, it should have electrical properties. The wire armour will serve as the sole earth continuity conductor for certain purposes and types of cables, the electrical 'resistance of the armour becomes important. According to standard BS 1442 - 1969, Tab. 1 shows steel wire for armouring cable of dimensions, electrical resistivities and conductivities at 20 °C. The tensile strength of the low carbon steel wires shall be between 34 kg/mm2 and 50 kg/mm2. Tab. 1. Electrical resistivities of low carbon steel Diameter Max. DC resistance Electrical conductivity (mm) at 20°C (ohm/km) at 20°C (l/ohm) 0.80 286.20 6.95 0.81 279.28 6.95 0.82 272.35 6.95 0.88 230.78 7.12 0.89 223.85 7.18 0.90 216.92 7.25 0.91 213.94 7.19 0.92 210.95. 7.13 1.22 121.40 7.05 1.23 118.42 7.11 1.24 115.43 7.17 1.25 112.45 7.25 1.26 111.20 7.21 1.27 109.95 7.18 1.28 108.69 7.15 1.51 79.91 6.99 1.52 78.65 7.01 1.53 77.40 7.03 1.54 76.15 7.05 1.55 74.90 7.08 2.00 43.93 7.25 2.50 28.11 7.25 3.15 17.71 7.25 IX Also low carbon steel is mainly used as an armouring for multi cores power and control cables as a mechanical protection. And low carbon steel wire forms for usage include industrial or standard - quality wire, annealed low carbon manufacturers' wire, and merchant wire. The reduction in conductivity associated with increasing temperature is due to the electron scatter caused by lattice vibrations. In addition, crystal imperfections such as vacancies, dislocations, stacking faults, foreign atoms, a -» y transformation is accompanied by a sudden change in electrical resistance. The y - phase exhibits an approximately 0.5 % lower resistivity value. Increasing the amount of silicon in either a pearlite or ferritic matrix also increases electrical resistivity (Fig. 1). Increasing the amount of graphite tends to increase electrical resistivity because graphite has a high resistance, but the graphitization of pearlite or cementite to produce a ferritic matrix often results in a net decrease in resistance because of the lower electrical resistivity of ferrite. Alloying elements that dissolve in the matrix normally increase resistance, but reversals of this tendency may be observed when the relative amounts of various microconstituents are changed by the presence of the alloying element. Effect of alloying elements on the electrical resistance of iron is shown in Fig. 2. Using wires are defined with chemical composition in Tab.2. 2.5. 3.0 Silicon content. % Fig. 1. The influence of the matrix structure and silicon content on the electrical resistivity of ductile iron at room temperature X O 4 8 10 20 Alloying element, % Fig. 2. Effect of alloying elements on the electrical resistance of iron Tab. 2. Samples with chemical composition Sample No Diameter %C %S %A1 %Si %Mn %Total Alloying (mm) Elements Electrical resistivity values were found by Thomson bridge method (Tab. 3). Vickers hardness values are shown in Tab. 4 and tensile strength values are shown in Tab. 5. XI Tab 3. Electrical resistivity values of samples at 20 °C Sample No Electrical resistivity at 20 °C. miliohm/cm 1 135 2 160 3 0.057 4 203 5 79 6 259 7 150 8 303 9 276 10 220 11 321 12 252 13 92 14 115 Tab. 4. Vickers hardness values of samples Sample No Hardness (Vickers) (kg/mm2) 1 96.7 2 111 3 60 4 102 5 56.8 6 287 7 79 8 210 9 93 10 201 11 294 12 75 13 64 14 83 XII Tab. 5. Tensile strength values of samples Sample No Tensile Strength (kg/mm2) 1 34 2 37 3 41 4 40.5 5 32 6 42 7 34.5 8 44 9 42.5 10 39 11 45 12 Ml 13 33 14 33J Haet treatment was done at 400 °C and 500 °C for 5, 10, 20, 40 and 60 minutes. Results of heat treatment are given in Tab. 6, 7, 8, and 9. Tab. 6. Effect of heat treatment on the electrical resistance of sample 4 (electrical resistivity is 203 miliohm/m at 20°C) Time (minute) Electrical resistivity Electrical resistivity at 400°C. miliohm/m at 500°C. miliohm/m 5 201 200 10 201 201 20 200 201 40 204 203 60 203. 203 Tab. 7. Effect of heat treatment on the electrical resistance of sample 8 (electrical resistivity is 303 miliohm/m at 20°C) Time (minute) Electrical resistivity Electrical resistivity at 400°C. miliohm/m at 500°C. miliohm/m 5 300 300 10 300 300 20 301 301 40 303 302 60 302 303 XIII Tab. 8. Effect of heat treatment on the electrical resistance of sample 9 (electrical resistivity is 276 miliohm/m at 20°C) Time (minute) Electrical resistivity Electrical resistivity at 400°C. miliohm/m at 500°C. miliohm/m 5 280 276 10 278 277 20 275 276 40 274 275 60 279 276 Tab. 9. Effect of heat treatment on the electrical resistance of sample 10 (electrical resistivity is 220 miliohm/m at 20°C) Time (minute) Electrical resistivity Electrical resistivity at 400°C. miliohm/m at 500°C. miliohm/m 5 221 219 10 219 219 20 220 220 40 218 220 60 219 220
In this study, effect of metallurgical structure on the electrical conductivity was examined at low carbon steel. The armouring wires are used for earthing purpose so in addition to the mechanical properties of it, it should have electrical properties. The wire armour will serve as the sole earth continuity conductor for certain purposes and types of cables, the electrical 'resistance of the armour becomes important. According to standard BS 1442 - 1969, Tab. 1 shows steel wire for armouring cable of dimensions, electrical resistivities and conductivities at 20 °C. The tensile strength of the low carbon steel wires shall be between 34 kg/mm2 and 50 kg/mm2. Tab. 1. Electrical resistivities of low carbon steel Diameter Max. DC resistance Electrical conductivity (mm) at 20°C (ohm/km) at 20°C (l/ohm) 0.80 286.20 6.95 0.81 279.28 6.95 0.82 272.35 6.95 0.88 230.78 7.12 0.89 223.85 7.18 0.90 216.92 7.25 0.91 213.94 7.19 0.92 210.95. 7.13 1.22 121.40 7.05 1.23 118.42 7.11 1.24 115.43 7.17 1.25 112.45 7.25 1.26 111.20 7.21 1.27 109.95 7.18 1.28 108.69 7.15 1.51 79.91 6.99 1.52 78.65 7.01 1.53 77.40 7.03 1.54 76.15 7.05 1.55 74.90 7.08 2.00 43.93 7.25 2.50 28.11 7.25 3.15 17.71 7.25 IX Also low carbon steel is mainly used as an armouring for multi cores power and control cables as a mechanical protection. And low carbon steel wire forms for usage include industrial or standard - quality wire, annealed low carbon manufacturers' wire, and merchant wire. The reduction in conductivity associated with increasing temperature is due to the electron scatter caused by lattice vibrations. In addition, crystal imperfections such as vacancies, dislocations, stacking faults, foreign atoms, a -» y transformation is accompanied by a sudden change in electrical resistance. The y - phase exhibits an approximately 0.5 % lower resistivity value. Increasing the amount of silicon in either a pearlite or ferritic matrix also increases electrical resistivity (Fig. 1). Increasing the amount of graphite tends to increase electrical resistivity because graphite has a high resistance, but the graphitization of pearlite or cementite to produce a ferritic matrix often results in a net decrease in resistance because of the lower electrical resistivity of ferrite. Alloying elements that dissolve in the matrix normally increase resistance, but reversals of this tendency may be observed when the relative amounts of various microconstituents are changed by the presence of the alloying element. Effect of alloying elements on the electrical resistance of iron is shown in Fig. 2. Using wires are defined with chemical composition in Tab.2. 2.5. 3.0 Silicon content. % Fig. 1. The influence of the matrix structure and silicon content on the electrical resistivity of ductile iron at room temperature X O 4 8 10 20 Alloying element, % Fig. 2. Effect of alloying elements on the electrical resistance of iron Tab. 2. Samples with chemical composition Sample No Diameter %C %S %A1 %Si %Mn %Total Alloying (mm) Elements Electrical resistivity values were found by Thomson bridge method (Tab. 3). Vickers hardness values are shown in Tab. 4 and tensile strength values are shown in Tab. 5. XI Tab 3. Electrical resistivity values of samples at 20 °C Sample No Electrical resistivity at 20 °C. miliohm/cm 1 135 2 160 3 0.057 4 203 5 79 6 259 7 150 8 303 9 276 10 220 11 321 12 252 13 92 14 115 Tab. 4. Vickers hardness values of samples Sample No Hardness (Vickers) (kg/mm2) 1 96.7 2 111 3 60 4 102 5 56.8 6 287 7 79 8 210 9 93 10 201 11 294 12 75 13 64 14 83 XII Tab. 5. Tensile strength values of samples Sample No Tensile Strength (kg/mm2) 1 34 2 37 3 41 4 40.5 5 32 6 42 7 34.5 8 44 9 42.5 10 39 11 45 12 Ml 13 33 14 33J Haet treatment was done at 400 °C and 500 °C for 5, 10, 20, 40 and 60 minutes. Results of heat treatment are given in Tab. 6, 7, 8, and 9. Tab. 6. Effect of heat treatment on the electrical resistance of sample 4 (electrical resistivity is 203 miliohm/m at 20°C) Time (minute) Electrical resistivity Electrical resistivity at 400°C. miliohm/m at 500°C. miliohm/m 5 201 200 10 201 201 20 200 201 40 204 203 60 203. 203 Tab. 7. Effect of heat treatment on the electrical resistance of sample 8 (electrical resistivity is 303 miliohm/m at 20°C) Time (minute) Electrical resistivity Electrical resistivity at 400°C. miliohm/m at 500°C. miliohm/m 5 300 300 10 300 300 20 301 301 40 303 302 60 302 303 XIII Tab. 8. Effect of heat treatment on the electrical resistance of sample 9 (electrical resistivity is 276 miliohm/m at 20°C) Time (minute) Electrical resistivity Electrical resistivity at 400°C. miliohm/m at 500°C. miliohm/m 5 280 276 10 278 277 20 275 276 40 274 275 60 279 276 Tab. 9. Effect of heat treatment on the electrical resistance of sample 10 (electrical resistivity is 220 miliohm/m at 20°C) Time (minute) Electrical resistivity Electrical resistivity at 400°C. miliohm/m at 500°C. miliohm/m 5 221 219 10 219 219 20 220 220 40 218 220 60 219 220
Açıklama
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1998
Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 1998
Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 1998
Anahtar kelimeler
Elektriksel direnç,
Karbon çeliği,
Electrical resistance,
Carbon steel