Folyo haddeleme proses parametrelerinin 8XXX alüminyum alaşımlarında derin çekmeye etkisi
The effects of foil rolling parameters on deep drawing behaviour of 8XXX aluminum alloy
Yazar: SERHAT AKCAN
Danışman: PROF. DR. SEBAHATTİN GÜRMEN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Metalurji ve Malzeme Mühendisliği Ana Bilim Dalı / Malzeme Bilimi ve Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2019
Konu: Metalurji Mühendisliği = Metallurgical Engineering

Özet:
Alüminyum (Al) 8XXX serisi mekanik işlem alaşımları, sahip oldukları korozyon direnci, elektrik iletkenliği ve mekanik özellikleri gibi nedenlerle birçok alanda kullanılmaktadır. Alüminyum 8XXX alaşımları folyo olarak özellikle esnek ambalaj endüstrisinde en çok tercih edilen malzeme grubudur.
Folyo haddeleme işlemi sırasında birçok proses parametresi 8XXX alaşım serisinin mekanik özelliklerini belirlemektedir. Haddeleme sırasında kullanılan iş merdaneleri de alüminyum folyonun özelliklerini değiştirebilmektedir. 
Bu çalışmada 8XXX alüminyum folyo malzemelerinin folyo haddelemesi sırasında farklı pürüzlülükte iş merdaneleri kullanılarak, iş merdanesinin alüminyum folyo üzerindeki etkileri incelenmiştir.
Yapılan çalışmalarda 330 µm kalınlığında olan alüminyum folyolar 2 kere soğuk haddelenerek 105 µm kalınlığa indirilmiştir. Farklı pürüzlülükte (0,14 – 0,16 Ra, 0,20 – 0,25 Ra, 0,30 – 0,35 Ra ve 0,55 – 0,60 Ra) iş merdaneleri kullanılarak folyoların derin çekme kabiliyetinin arttırılması hedeflenmiştir.
Deneysel çalışmalar Assan Alüminyum Sanayi ve Ticaret A.Ş. şirketinde TRC döküm tekniği ile üretilen ve soğuk haddeleme işlemi görerek 330 µm kalınlığa indirilen 8XXX alüminyum malzemeler ile gerçekleştirilmiştir. 
Numuneler Assan Alüminyum Sanayi ve Ticaret A.Ş. şirketinde Achenbach markalı intermediate-foil mill tezgahlarında 2 kere üst üste soğuk haddelenmiştir. Nihai kalınlık olarak 105 µm sahip numunelerde optik mikroskop ile tane yapısı incelenmiş, numune ve iş merdaneleri arasındaki pürüzlülük bağlantıları araştırılmıştır. Malzemenin derin çekme kabiliyetlerindeki değişimi görebilmek için numunelere Erichsen testi yapılmıştır.
Deneysel çalışmalar sonucunda her iki soğuk haddeleme işleminde de kullanılacak olan parlak merdaneler ile daha iyi derin çekilebilir malzemeler üretildiği gözlenmiştir. Derin çekme üzerinde oluşan durum malzemelere yapılan çekme deneyleri sonucuna yansımamıştır. Deneysel çalışmalarda, iş merdanelerinin pürüzlülüğünün mikro yapıda herhangi bir değişikliğe sebep olmadığı görülmüştür. Ancak, malzeme yüzeyi ile iş merdanesi yüzeyi arasında bir bağlantı olduğu; iş merdane Ra değerleri düştükçe bu benzerliğin daha da yakın olduğu tespit edilmiştir.

Abstract:
Aluminum is preferred in different areas thanks to its special properties. One of the most significant properties of aluminum is being light metal. This property provides energy conservation, which also decreases environmental pollution. Aluminum can be used as alloy by the addition of different metals. Aluminum can have more strengths thanks to other alloy metals. In addition, the property of ductility provides design flexibility in many areas such as construction and transportation. Furthermore, due to having natural oxide film layer, aluminum has perfect corrosion resistance. Thus, the life cycle of aluminum is much more with respect to other many materials. Moreover, aluiminum is used in the applications of electric dispersion and heat transfer because of its electrical and heat conductivity. In addition to all these, aluminum is perfect impermeable materials. Even if aluminum is chosen as the thinnest foil, 6,35 micrometers, this property still exist. All properties aluminum has can develop by means of other metals. Developing and adaptation of aluminum alloys according to area it is used still continue.  
Aluminum 8XXX alloy series is used in lots of areas by means of their special properties like corrosion resistance, electrical conductivity, mechanical properties etc. These serie is mainly favored in flexible packaging area as foil.
There are lots of areas where aluminum foil is used like automotive, finstock, housohold foils, smooth-wall and flexible packaging. Nowadays, aluminum sheets are generally produced through twin-roll casting methods. Aluminum sheets produced by twin roll casting are cold rolled in order to obtain thin materials like aluiminum foil.
Process parameters of cold rolling of 8XXX aluminum series specify mechanical properties of these materials. The work rolls used during rolling operation also have effects on properties of materials. The diameter of work rolls, the roughness of work rolls can affect properties of cold-rolled materials. For this reason, selection of work rolls is important. 
In this study, the work rolls having different roughness (0,14 – 0,16 Ra, 0,20 – 0,25 Ra, 0,30 – 0,35 Ra ve 0,55 – 0,60 Ra) properties were used in order to observe the effect of work rolls on the properties of aluminum foil. Firstly, the relation between surface of work rolls and cold-rolled aluminum foils were investigated. According to this relation, other mechanical properties were investigated. In comparison with surface relation and difference of mechanical properties, these results were compared.
In these experimental studies, the materials having thickness of 0.3 mm were cold rolled twice in order to make the materials thickness as 105 microns. Improving the deep drawing capability of aluminum foils is aimed through using of the work rolls having varied surface roughness properties.
Experimental studies were done with the materials which have been obtained from Assan Alüminyum Sanayi ve Ticaret A.Ş. factory. These 8XXX aluminum sheets were firstly produced via twin roll casting method; then they were cold rolled and have several annealing processes in order to get 0.33 mm aluminum sheets.
In order to observe the effect of surface roughness of work rolls on the deep drawability of aluminum foils, three different process were designated. Aluminum sheets having 0.33 mm thickness were cold rolled two times. Firstly, three different 0.21 mm aluminum sheets were obtained. In order to get these sheets two different work rolls were used. Two of them were rolled with work rolls having surface roughness of 0,30-0,35 Ra; the other one was rolled with work rolls having surface roughness of 0,55-0,60 Ra. Secondly, three different 105 µm aluminum foils were obtained. In order to get these aluminum foils two different work rolls were used. The aluminum sheet which was rolled with work rolls having surface roughness of 0,55-0,60 Ra was rolled again with work rolls having surface roughness of 0.20-0,25 Ra. Other aluminum sheets were cold rolled with work rolls having surface roughness of 0.20-0,25 Ra and 0.14-0,16 Ra. As a result, in order to observe differences of both cold rolling passes; for first passes two similar one different work rolls were used; for second passes two similar one different work rolls were used.
Firstly, the properties of aluminum sheets having thickness of 330 µm were investigated. According to surface roughness measurements, results of Erichsen tests, tensile tests and images of microstructure there were no difference between starting materials.
During both cold rolling passes, the similar rolling force were applied to materials. The rolling speed were differentiated according to work rolls. Cold rolling with work rolls having high surfaces has much more speed with respect to other ones. 
When surface roughness tests were analyzed, it was determined that there was relation between surface roughness of work rolls and aluminum sheets and foils which had been cold rolled. However, the similarity of first passes were less than second passes. It was observed that the aluminum sheets cold rolled by work rolls having high surface roughness had similar surface roughness with work rolls; but these sheets also gave more reaction against work rolls with respect to aluminum foils which gave less reaction against work rolls. Shortly, surface roughness of aluminum sheets have less similarity with work rolls with respect to aluminum foils.
When erichsen tests were analyzed, work rolls having high surface roughness affected unfavorably. At the end of the first passes, aluminum sheets having thickness of         210 µm had been cold rolled with two different work rolls. Aluminum sheets colled rolled by 0,30-0,35 Ra has better elongation with respect to other aluminum sheet which was cold rolled with work rolls having surface roughness of 0,50-0,55 Ra. At the end of the second passes, aluminum foils having thickness of 105 µm had been cold rolled with two different work rolls. Two of them were cold rolled with work rolls having surface roughness 0,20-0,25 Ra and also these sheets had been cold rolled at the first passes with different work rolls. Thus, the effect of first passes on the behavior of deep drawability of aluminum foils could been analyzed. It was seen that although surface roughness of work rolls that had been used at second passes were similar, the erichsen test results were different. The effect of first pass was still exist. Aluminum foil which were cold rolled at first step with work rolls having higher surface roughness had less elongation around 15%. Other aluminum foils which were cold rolled with work rolls having low surface roughness both passes gave better elongation. When it was compared with 105 µm aluminum foils cold rolled by work rolls having higher surface roughness at both passes, there was certain difference on elongation which was about 35%. 
According to tensile test results, there were no significant difference between aluminum foils and sheets. As mentioned before, firstly starting materials were investigated. The results of tensile tests of aluminum sheets having 330 µm were similar. After first passes, the similary were still observed; however, work hardening of cold rolling was seen clearly. Then by, aluminum foils having thickness of 105 µm were examined and the results were similar with previous aluminum sheets. 
When microstructures of all materials were analyzed, inequality of grain orientation were gained. Even though grain orientatin of starting materials were similar, after cold rolling processes, materials having same thickness had different grain orientation. Frequency of grain orientation of aluminum materials cold rolled with work rolls having high surface roughness were much more. Aluminum foils having more grain orientation gave less elongation at the end of the Erichsen tests.
As a result of experimental studies, aluminum foils that have better deep drawing capability were gathered associated with work rolls having low surface roughness. The same effect which has seen on the deep drawing properties have not observed on the results of tensile tests. In addition, it was observed that there is no influence of work rolls properties on the microstructure of foils. However, it is obvious that roughness of foils and roughness of work rolls were directly related each other. When the roughness of work rolls is lower, the similarity between foils and work rolls becomes significant.