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Redükleyici ergitme yöntemiyle kobaltlar ve nikelbor ön alaşımlarının DC ARK fırınlarında üretim şartlarının belirlenmesi

Başlık çevirisi mevcut değil.

  1. Tez No: 46258
  2. Yazar: İSMAİL KARACAN
  3. Danışmanlar: PROF.DR. İSMAİL KARACAN
  4. Tez Türü: Yüksek Lisans
  5. Konular: Metalurji Mühendisliği, Metallurgical Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1995
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 65

Özet

ÖZET Kobaltbor ve nikeltror elektrik/elektronik sanayinde kul lanılan trafo saçlarının imalinde kullanılan ön alaşımlardır. Bu ön alaşımlar yarı iletken, lehim vs sızdırmazlık malzemesi, traş bıçağı vs refrakter malzeme üretiminde de kullanıl - maktadır. Bu çalışmada barikasit ve kobalthidroksit/nikelksit hammaddeleriyle odun kömürü ve tahta talaşı ilavelerinden oluşan şarj harmanı, yaklaşık 40 kg. şarj alabilen 270 kVA'lık tek fazlı, daldırmalı tip doğru akım elektrik ark fırınında ergitilerek farklı konsantrasyonlarda kobaltbor/nikelbor üretilmiştir. Deneylerde ölçülen elektriksel değerler bilgisayar da ta toplama sistemi yardımıyla depolanmıştır. Şarj içindeki sabit karbon miktarının ve barikasit miktarının artırılmasıyla kobaltbor/nikelbor alaşımlarında bor kon santrasyonunu artarken, karbon konsantrasyonu ve enerji tüke timi azalmıştır.H B0 /Co(OH) oranının 0.79; ve şarjda sabit karbonun % 14 alddğujşarj bileşiminde, % 17.60 B, % D. 06 G, % 0.3 Si ve % 0 B içeren alaşım 59.1 klılh/kg B enerji tüketi - miyle üretilmiştir.Elektrot tüketimi 250 g/kg kobaltbor ' dur. H B0 /l\IİQ oranının 1.1 olduğu ve şarjda sabit karbon miktarlnıd % 10.02 olduğu deneyde % 15.02 B, % 0.018 C, % 0.2 Si ve % 0 S içeren alaşım 55.4 klılh/kg B değerinde enerji tüketimi ve 61 g /kg nikelbor elektrot tüketimiyle üretilmiştir. Redüksiyon reaksiyonunun elektrodun ark yaptığı bölgede toplanan sığ bir cüruf fazı üzerinden gerçekleştiği görülmüştür. Kobaltbor deneylerinde voltajın 25-40 V, akımın 1300-2100 A ve direncin 0.015-0.025 ohm arasında salındığı görülmüştür. Nikelbor deneylerinde voltaj 25-45 V, akım 1100-1800 A ve direncin 0.02-0.04 ohm arasında değiştiği görülmüştür.Ortalama direnci 0.03 ohm alan nikelboratlı cürufun spesifik iletkenliği 1.46 ohm" cm- olarak saptanmıştır. Kobaltbor/nikelbor üretiminde kısa devre voltajının 5-8 V arasında oluştuğu görülmüştür.

Özet (Çeviri)

THE DETERMINATIDN DF PRODUCTION CONDITIONS FOR REDUCTION SMELTING METHOD OF COBALTBORON AND NICKELBORON MASTER ALLOYS IN DC ARC FURNACES SUMMARY Cobaltboron and nickelbaron are master alloys used in the manufacture af metallic glass and, xn the produc tion of semiconductor, refractares, razor blade, and soldering materials. Owing to improvements in the magnetic properties of transormer sheets, cobaltboron and nickelbaron has become important role the electrical/ electronic sector. The replacement of conventional silicon sheets by nickelboron/cobaltboron sheets has resulted in reduction of BO % in the are core lasses af transformers, making a big impact an energy conservation. Since elemental boran is an expensive chemical, boron is usually introduced into cabaltbaron/nickelboron in the farm af cheaper compounds such as H,B0,, B“0,, etc. Cabaltboran/nickelboron master allays can be produced three main process; aluminothermic, silicothermic and corbothermic methods. Production of cobaltboron/nickelboron with either aluminothermic method or silicothermic method, concent ration of Al or Si impurities exceed limits for manufac ture of metallic glass in products. The carbothermic method of cobaltbaron/nickelboron production yields a better product, which satisfies the impurity limits set by the metallic glass industry. Thermodynamic consideration of the reduction of NiO/ CoO and BpO”in the presence of carbon shows that reduc tion sequence with solid carbon includes NiO/CoO, B“D3(g), and Bgügfl). Nickel/cobalt is reduced prior te boron, vixand the reduction of gaseous boron starts at 1 650 K. Reduction of the liquid phase starts at 190QDK. Under these conditions, vapour pressure of B”0_ is 10 mm Hg. For this reason, it can be concluded that the reduction of boric oxide with solid carbon take place preferen tially in the gaseous phase. The affinity of boron far nickel/cobalt is also higher than its affinity for carbon. Consequently, at a high nickel/cobalt concent ration, the possibility of the formation of nickelboron/ cobaltboron is higher than the passible formation of boron carbide. The charcoal and wood chips in selected ratios of H-BQ, and Co(0H)p (or IMiO) were mixed in a rotary mixer for 60 minutes, and the mixture was fed to furnace which open heated arc. After 30-100 minutes from start of experimental run, the liquid metal was removed from the tap hole at the bottom and the arc was stopped. When the liquid metal was removing the furnace, its tem perature was measured with a optic pyrometer. The furnace left to cool for inspection. In the experimental, evalua tion, the metal and boron that remained in the furnace were taken into consideration. The energy consumption was also evaluated accordingly. The changes in the elect rodes such as consumption, erosion, shape and dimension were carefully inspected and quantified. Two H2B03 to Co(0H)2 ratios were used 0.79 and 1.18, and two HUSO., to Nİ0 ratios were used 1 and 1.1. These ratios changed the content of carbon in the furnace. Generally, the addition of the increased amount of fix carbon ratio in the charge increased the concentration of baron in the allays. Concentration of aluminium and silicon in cobaltboron/ nickelboron master alloy were controlled with initial raw materials and characol: Raw materials were high purity and charcoal have very law ash contenent. The carbon contenent of the alloys decreased with increasing boron concentration and, far cobaltboron alloy containing 17. B0 % boron, the carbon content decreased to 0.06 %,and for nickelboron alloy containing 15.02 % boron, the carbon concentration decreased to 0.018 %. In this study cobaltboron/nickelboran allay was produced from boric acid, cobalt hydroxide/nickel oxide characoal and wood chips. The mixture was smelted in a vixx270 kVA monophase DC arc furnace» Production conditions of cobaltboran/nickelbaron mere determined, with the charge composition, applied voltage and current, resis tance, energy and electrode consumption. The boric acid used uas 99.5 % pure and contained Fe, Si, Mg, Ca and Na as impurities. The cobalt hydroxide was more than 99 % pure and contained Ni,Fe,Cu,Pb, Mn, Mg,Ca as impurities. The nickel oxide uas more than 99 % pure and contained Co, Fe,Na,Mg,Ca as imprutions. The particle size of the charcoal and mood chips were 1 to 3 mm and 5 to 20 mm respecively. The laboratory type monophase resistant arc furnace has a 40 kg charge capacity. The smelting process uas conducted with a dc power supply of 270 kVA. The inner surface of the furnace was lined with graphide and, to provide the necessary heat insulation, refractory bricks were used as a backing for the graphide. The voltage and current readings were fed to a computer-control system for the acquisition of data that were used in the control of the position of the upper electrode. The energy consumption per kilogram of alloy dec reased with increasing boron concentration. The produc tion of cobaltboron alloy containing 17. BO % boron, consumed 10.52 külh/kg cobaltboron. The production of nickelboron alloy having 15.02 % boron, energy consump tion was 8.32 ktdh/kg nickelboron. In all the experiment, curves of voltage-time, current-time, power-time and resistance-time were obtained _during the cobaltboron production experiments, the voltage fluctuated between 25-40 V, the amper fluctuated between 1300-2100 A. During the nickelboron production experiments, the voltage fluctuated between 24-45 V, the amper fluctualted between 11 00-1 B00 A. Both of cobaltboron and nickelboron production experiments, the system was short-circuited between 5 -B V. The choice of initial voltage was critical. If voltage was less than 20 \l. The arc was lost owing to a short-circuit. Far this reason, the electrode spacing was adjusted to ensure the arc and to keep the voltage above 25 V. ixThe movement of the upper electrode was controlled during the experiments by the use of a photocell. It bias observed that electrodes were under the influence of two process: electrad erosion and the accumulation of metals. When the metal has formed, the electrod movement mas aluiays towards the bottom. The errosion of the electrode was not from the sides, but from the bottom. Far this reason the charged reagents were observed to be relatively unreactive during contact with tha sides of the electrode and most of the reaction took place at the arc tip of the electrode. In cobaltbaron experiments, at the best conditon» electrad erosion rate was 7.31 cm/h and the consump tion was 250 g/kg cobaltbaron. In nickelbaran experiments, at the best condition (continous experiment) electrode erosion rate was 3.31 cm/h and the consumption was 61 g/kg nikelboron. The nickelbarate were formed by drying of H^BO^ in the furnace and they flow continued downward coming to arc zone. n_au, until This nickelbarate slag is reduced under the electrode, to from nickelbaran which accumulated at the bottom of the furnace. The overall electric resistance, in a slag resitance electric arc furnace, is an important factor in furnace design and performance, and it can be expressed as a function of slag conductivity and furnace geometric factor. Geometric factor is function of electrode dia meter, depth of electrode immersion, electrode spacing, and overall depth of the slag leyer.In this study, they hava.been found that geometric factor were 0.044 cm“, avarage resis tance of nickelborate slag was 0.03 ohm. As a result, the electrical conductivitiy of the nickelborate slag has been determined as 1.46 ohm”.cm". xx

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