Vermiküler grafitli dökme demir ile üretilen motor blokların özelliklerini etkileyen faktörlerin alternatif dökme demirler ile karşılaştırmalı analizi
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Dosyalar
Tarih
2021
Yazarlar
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Yayıncı
Bursa Teknik Üniversitesi, Lisansüstü Eğitim Enstitüsü
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Dökme demirler ailesinin yeni üyesi olan vermiküler grafitli dökme demirler başta otomotiv sanayi olmak üzere son yıllarda artan tonajlarda kullanılmaktadır. Bu dökme demir tipi mühendislik özellikleri olarak gri dökme demirler ile sfero dökme demirler arasında yer almakta olup her iki dökme demir tipinin iyi mühendislik özelliklerini tek bir malzemede toplamaktadır. Otomotiv sanayinde başta motor blok ve kafalar olmak üzere birçok döküm parçanın imalatında kullanılmaktadır. Bu çalışmada vermiküler grafitli dökme demirler ile üretilmiş motor blokların özelliklerini etkileyen faktörlerin alternatif dökme demirler ile karşılaştırması yapılmıstır. Farklı analiz ve mikroyapıya sahip gri ve sfero dökme demirlerden motor bloklar dökülerek, bu motor bloklardan mekanik testler, ses hızı ölçümleri, mikroyapı incelemeleri ve iç sağlamlık kontrolleri yapılmıştır. Mekanik testlerde kopma ve akma mukavemeti, %uzama değeri ve sertlik sonuçları değerlendirilmiştir. Mikroyapı incelemesinde ise %küresellik ve matrikste %ferrit, perlit oranları incelenmiştir. Deneysel çalışma sonuçlarına göre vermiküler grafitli dökme demirden üretilen parçaların malzeme özelliklerinin gri ve sfero döküm özelliklerinin arasında olduğu tespit edilmiştir. Vermiküler grafitli dökme demirlerin mukavemet özelliklerinin gri dökümlere kıyasla oldukça yüksek olduğu görülmüştür. Gevrek olan gri döküme kıyasla nispeten sünek olmakla birlikte sferoya göre süneklik miktarı nispeten düşüktür. Vermiküler grafitli dökme demirlerde %küresellik değeri arttıkça mukavemet ve %uzama değerlerinin de arttığı ve diğer malzeme özelliklerinin de sfero dökme demire doğru yaklaştığı görülmüştür. İç sağlamlık için yapılan X-ray kontrollerinde ise hem sayıca hem de boyut olarak en düşük süreksizliğe sahip parçaların gri dökme demir malzeme ile dökülen, adet ve boyutsal olarak en fazla süreksizliğe sahip motor bloğun ise sfero dökme demir ile dökülen parca oldugu tespit edilmiştir. Vermiküler grafitli motor bloğun iç süreksizlik seviyesi ise diğer malzeme özelliklerinde olduğu üzere gri döküm ile sfero döküm arasında olduğu görülmüştür.
New member of cast iron family, compacted graphite iron has been used with an incresaing volume especially in automotive industry in recent years. It has material properties varying between gray and ductile iron grades and is a hybrid material which collects good material properties of both grades in a single material. It is used in the production of many casting parts, especially engine blocks and heads in automotive industry. In this study, the factors affecting the properties of engine blocks produced with compacted graphite cast iron were compared with alternative cast iron types. Engine blocks were cast from gray and ductile cast iron with different analysis and microstructures, and then mechanical tests, sound velocity measurements, microstructure examinations and internal soundness controls were performed from these engine blocks. Tensile and yield strength, % elongation value and hardness results were evaluated in mechanical tests. In microstructural analysis, nodularity and ferrite and pearlite distribution ratios in the matrix were examined. According to the experimental study results, it has been determined that all material properties of the parts produced from compacted graphite cast iron are between the gray and ductile cast irons' material properties. It has been observed that the strength properties of compacted graphite cast irons are considerably higher than gray cast iron. It is relatively ductile compared to the brittle gray cast iron but has lower ductility than ductile iron. It has been observed that as the nodularity increases in compacted graphite cast iron, the strength and the elongation values also increase and the material properties approach towards ductile cast iron properties. In X-ray controls performed for internal soundness it was determined that the parts poured with gray cast iron have the lowest discontinuity in terms of both number and defect size, while the engine blocks poured with ductile cast iron have the highest number and defect size.
New member of cast iron family, compacted graphite iron has been used with an incresaing volume especially in automotive industry in recent years. It has material properties varying between gray and ductile iron grades and is a hybrid material which collects good material properties of both grades in a single material. It is used in the production of many casting parts, especially engine blocks and heads in automotive industry. In this study, the factors affecting the properties of engine blocks produced with compacted graphite cast iron were compared with alternative cast iron types. Engine blocks were cast from gray and ductile cast iron with different analysis and microstructures, and then mechanical tests, sound velocity measurements, microstructure examinations and internal soundness controls were performed from these engine blocks. Tensile and yield strength, % elongation value and hardness results were evaluated in mechanical tests. In microstructural analysis, nodularity and ferrite and pearlite distribution ratios in the matrix were examined. According to the experimental study results, it has been determined that all material properties of the parts produced from compacted graphite cast iron are between the gray and ductile cast irons' material properties. It has been observed that the strength properties of compacted graphite cast irons are considerably higher than gray cast iron. It is relatively ductile compared to the brittle gray cast iron but has lower ductility than ductile iron. It has been observed that as the nodularity increases in compacted graphite cast iron, the strength and the elongation values also increase and the material properties approach towards ductile cast iron properties. In X-ray controls performed for internal soundness it was determined that the parts poured with gray cast iron have the lowest discontinuity in terms of both number and defect size, while the engine blocks poured with ductile cast iron have the highest number and defect size.
Açıklama
Anahtar Kelimeler
Metalurji Mühendisliği, Metallurgical Engineering
