Metalotermik Prosesle Titanyum-bor-alüminyum Alaşımlarının Üretimi

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Tarih
1998
Yazarlar
Gözkaman, Çiğdem
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Fen Bilimleri Enstitüsü
Institute of Science and Technology
Özet
Titanyum-Bor-Alüminyum alaşımları, alüminyum ve alaşımlarının tane boyutunu küçülterek mekanik özelliklerinin geliştirilmesinde ön alaşım olarak kullanılmaktadır. Bu ön alaşımlar, titanyum ve borun çeşitli kimyasal tuzlarının ergimiş alüminyumla reaksiyonu ile üretilmektedir. Ancak klor, flor, gibi kimyasal bileşikler içeren malzemeler kullanımında kaçınmak gerekliliği yeni yöntemler geliştirme zorunluluğunu ortaya çıkarmıştır. Bu çalışmanın konusu %30-60 titanyum- %5-15 bor ve geri kalan alüminyum olan ön alaşımların metalotermik yöntemle üretimine ısı verici ve curuflaştırıcı maddelerin etkisinin araştırılması olmuştur. TİO2, B203 ve alüminyum tozlarından oluşan şarj karışımlarına KCIO3 gibi ısı verici ve CaO gibi cüruf yapıcı maddeler değişen oranlarda ilave edilerek elde edilen alaşımlardaki titanyum, bor ve alüminyum konsantrasyonları ve bu metallerin alaşıma kazanım verimleri araştırılmıştır. Belirli miktarlarda hazırlanan TİO2 (Titanyum dioksit), B2O3 (Boroksit), toz alüminyum gibi şarj numuneleri karıştırılarak alüminotermik redüksiyon deneyleri MgO astarlı bir pota içerisinde yapılmıştır. Reaksiyon ısısının alaşımın cüruftan ayrılmasına yetmediği durumlarda gerekli ısıyı sağlamak için şarja %10 kadar KCIO3 ve optimum şartların sağlandığı şarj bileşimine şarjın %50 'si kadar da CaO ilave edilmiştir. Deneyler sonucunda elde edilen cüruf ve metal numuneleri ayrı ayrı kırılıp öğütüldükten sonra kimyasal ve x-ışınlan teknikleri incelenmiştir. Uygulanan metalotermik yöntemde TİO2 ve B2O3yi redüklemek amacıyla redükleyici madde olarak alüminyum kullanılmıştır. Sadece metalotermik redüksiyon esnasında açığa çıkan ısılar kullanılarak metal-curuf ayırımı yapılması amaçlanmışta'. Termodinamik hesaplamalar ve literatür karşılaştırmaları reaksiyon ısının redüksiyon ve metal-curuf ergitmesi ayırımına yeterli olduğunu göstermiştir. Ancak deneyler ısı verici madde olarak adlandırılan KClO3 + Al tozu karışımının şarja % 40 oranından az ilave edildiği şartlarda metal-curuf ayırımı yeterli seviyede yapılamamıştır. Bu amaçla B203, Ti02 ve bu oksidleri stokiometrik oranda redükleyecek kadar alüminyumdan oluşan şarja ağırlığının % 60'ına kadar ısı verici madde karışımı ilave edilmiştir. Bu şartlarda % 52.89 Ti, % 7.73 B ve % 38.38 Al'dan oluşan alaşım üretilmiştir. Bu elementlerin metale kazanım verimleri de sırasıyla % 55.00 Ti, % 47.70 B ve % 25.23 Al olmuştur. Daha düşük sıcaklıkta ergiyen bir cüruf eldesi için CaO katkısı ile yapılan deneylerde, açığa çıkan ısının yetersiz kalması nedeniyle özellikle verim değerlerinde her üç metal için de düşüş gözlenmiştir. B2O3 / TİO2 oranının 0.22 olması durumunda alaşımda bor konsantrasyonunun % 6'yı aşmaması nedeni ile 0.33 oranında da ısı verici madde ilavesi ile deneyler yapılmıştır. Ancak bu durumda şarja ilave edilmesi gereken ısı verici madde miktarının şarjın en az % 50 olması gerektiği saptanmıştır. Bu şartlarda alaşım kompozisyonu % 54.98 Ti, % 7.93 B, % 36.52 Al şeklinde oluşurken metal kazanım verimleri sırasıyla % 60.00 Ti, % 50.73 B ve % 44. 16 Al olarak gerçekleşmiştir. Elde edilen sonuçlar metalotermik yöntemin karakteristik özelliği olan % 50 civarındaki metal kazanım verimleri dışında tatminkardır. Verim arttırıcı yöntem olarak bu işlemlerin elektro alüminotermik yöntem şeklinde elektrik ark fırınında yapılması ile daha tatminkar verim değerlerine ulaşılabilecektir.
In Ti-B-Al ternary system, commonly used alloys are TİB2 and AI-Ti-B. Titaniumdiboride is a refractory material which has extreme hardness (2300-2800 kg/mm2) good electricial and thermal conductivity, good wear resistance good thermal shock resistance (better than most oxides), high melting point (2980°C). It is used for the manufacture of high-speed cutting instruments. Because of chemically inert behaviour to molten metals, it is also used for metal evaporation boots and cathodes for aluminium electrolise cell. TİB2 however, is an expensive material to produce and form commercially and the extreme processing and fabrication conditions, only small and expensive shapes are available. In the aluminium production which take place in the Hall-Harould cell titaniumdiboride can be used as the cathode material instead of carbon cathodes. Titanium-boride alloys are used as high temperature materials and cutting instruments, x-ray and transmission tubes lamp flament supports, heating elements for high temperature furnaces. The thermite reaction is a self sustain reaction which generates its own thermal energy. There are a number of advantages in using the thermite reaction for the synthesis of materials: low cost materials, low ignition temperatures, high reaction temperatures, and a potential for synthesizing a wide range of refractory compounds. The objective of this research effort is to produce TİB2 by using the thermite reaction and to understand the effects of selected process parameters on the ignition behavior. In the first study, the synthesis of TİB2 was done by using TiCK B4C. B2O3 and C raw materials via carbothermic reduction method. The reaction was completed at high temperatures (1500. 1600. 1700°C) under argon atmosphere. The reaction products were investigated by x-ray di fraction. It was found that, the amount of TiBi is increased with the increasing temperature. A small grain promoting aluminum-titanium-boron master alloy contents 3.5 to 7.5 wt % of titanium and 0.1 to 0.3 wt % of born in a ratio by weight of boron/titanium of 1:20-40. The alloy is preferably prepared by admixing finely divided titanium alkali fluoride and alkali borofluoride to molten aluminum at temperatures not exceeding 900°C. the aluminum reducing the titanium and boron in such fluorides to get free metal. The mother alloy can be dispersed into the mass of molten aluminum VII to be improved which is then ready to be cast into a desired shape. What is the claimed is: An aluminum-titanium-boron mother alloy for addition to molten casting aluminum to promote the formation in the solid castings of a uniform small grain crystalline structure, said mother alloy consisting essentially of aluminum containing from about 3.5 up to about 7.5 % by weight titanium and from about 0.1 up to about 0.3 % by weight boron in a weight ratio of titanium to boron of 20-40:1 and being substantially free of acicular crystals. An aluminum-titanium-boron master alloy is provided that is characterized by an optimum promotion of fine grain together with sufficient ductility for it to be produced in the form of a wrought product, for example, continuous rod. The alloy of this invention preferably contains about 8 weight percent titanium, about 0.4 weight percent boron and the balance essentially aluminum and incidental impurities normally found in alloys of this class. A method for producing a master alloy for use in aluminum casting processes in which an aluminum melt containing 0.02-6 percent by weight titanium and 0.01-2 percent by weight boron is produced under conditions under which the boron is bound to titanium in the form of titanium diboride. whereafter the melt containing titanium diboride is under agitation at the temperature ranging from the melting point of material to 900° AITİ3B1 is as effective as AITİ5B1 in many applications. Use AlTi.?B| as a means of limiting titanium build-up when your furnace charge contains recycled material. Aluminum titanium boron alloys with a 1% born content are effective grain refiners. However, boride related defects are a potential problem. Lower boron alloys such as AITİ5B0.6 and AITİ5B00 have been developed to reduce this problem. By using this lower boron containing alloys effective grain refinement can be achieved and boride related problems reduced. Titanium-boron can be produced by metalothermic prosess. Since high temperature is needed for good metal / slag seperation. alumina based slag can have large amount of metallic parts. Because of this, metalothermic prosess can also be used for producing metal / ceramic composites. The aim of this study is investigate the effects of heat generating and fluxing materials on the manufacture the alloy 30-60% titanium. 5-15% boron and the rest, with aluminum. Experimental study was carried out by using a mixture TiOi. B2O3 and reductant aluminum powder. Chemically analysis of these materials are given in the Table 1. VIII Table 1. Chemical analysis of charge materials Charge mixture was prepared in a lurhila mixer, then poured to the Mg() lined crucible and initiated remotely by passing current through the coil which embeded in KOOji + Al powder mixture placed on top of the packed charge. Once initiated the reaction quickly proceeds to completion. After cooling, the reactor discharge and the alloy which has solidified beneath a solidified slag layer was removed. Since good metal / slag seperalion was not obtained, different amount of heat generating material (K.CIO3) was added to the charge. Then CaO as a fluxing material was also used to obtain good metal/slag seperation. To increase boron content of alloy, higher B2O3 / TiOi ratio in charge was also tried. After experiments metal and slag samples were examined by X-ray difraction. scanning electron microscoby technic and wet chemical prosess. Results obtained by the experiments are shown in the Table 2-3-4-5. The experiments to determine the effect of heat generating materials on metal concentretion and metal yield were carried out with a charge having B203 / Tİ02 = 0.22 and with out CaO addition by varying heat generating material / total charge amount ratio from 0 to 60. Up to 30 % heat generating material / total charge amount, metal formation was not observed and increasing heat generating material / total charge ratio to 50 % increases total metal amount, but higher heat generating material / total concentration ratio then 50 % causes to reduce metal amount. By changing heat generating materials / total concentration ratio from 30 % to 60 %. Titanium and aluminum content of alloy and titanium and aluminum reduction yield increase: but boron concentration and boron reduction yield decreases by increasing heat generating material / total concentration ratio higher then 50 %. The effect of fluxing material on the titanium, boron and aluminum concentrations and titanium, boron and aluminum reduction yield was studied by adding different amount of CaO 70 the charge al 40 % and 50 % heal generating material / total concentration ratio. Reduction yield of three metals decreased by increasing CaO / total concentration ratio because of lack of expose heat, by the reactions for both heat generating material / total concentration ratios. To obtain higher boron content then 6 % in alloy. B2O3 / TİO2 ratio was increased to 0.33 in charge and three different heal generating material / total concentration ratios was applied. The best result is obtained al 50 % heat generating materials / total concentration ratio and alloy containing 54.98 % Ti. 7.93 % B and 36.5 %A1 is produced by 60 % Ti. 50.73 % B and 4.16 % Al yield. IX Table 2. Devation of total metal amount, as Ti, B, Al concentrations and recovery as a function of heat generating material. Table 3. Devation of total metal amount, as Ti, B, Al concentrations and recovery as a function of CaO / Total metal amount under the conditions of 40 % KCIO3 Table 4. Devation of total metal amount, as Ti, B, Al concentrations and recovery as a function of CaO / Total metal amount under the conditions of SO % KCIO3 Table 5. Devation of total metal amount, as Ti, B, Al concentrations and recovery as a function of CaO / Total metal amount (B203 / Ti02 = 0.33) It has been demonstrated that To obtain higher boron content then 6 % in alloy. B2O3 / Ti02 ratio was increased to 0.33 in charge and three different heat generating material / total concentration ratios was applied. Results at 40 % CaO / Total metal amount there is no metal amount and concentration ratio and alloy containing. The best result is obtained at 50 % heat generating materials / total concentration ratio and alloy containing 54.98 % Ti, 7.93 % B and 36.5 %A1 is produced by 60 % Ti, 50.73 % B and 4. 16 % Al yield.
Açıklama
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1998
Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 1998
Anahtar kelimeler
Alaşımlar, Alüminyum, Bor, Titanyum, Alloys, Aluminum, Boron, Titanium
Alıntı