Küresel Grafitli Dökme Demirin Mikroyapısı ve Mekanik Özellikleri Üzerinde Döküm Modülünün Değerlendirilmesi

Öz

Küresel grafitli (Sfero) dökme demir, çift aşamalı bir işlemle üretilmektedir: **Nodülerizasyon / Küreselleştirme** (Mg ve/veya Nadir Toprak Elementleri ile işlem) ve **Aşılama** (FeSiX alaşımı ile işlem, X = Ca, Ba, Sr, Ce, La, Zr vb.). Her aşama belirli amaçlara hizmet etmektedir. Grafitin küreselleşmesi, kalıp kalınlığına bağlı olup, bu nedenle soğuma hızı önemli bir faktördür. Bu çalışmada, **GGG70L alaşımı**, farklı kesit kalınlıklarına sahip plakalar halinde dökülmüştür. Modül değişimi, mikroyapı ve mekanik özellikler açısından incelenmiştir. Nodule boyutu küçüldükçe çekme gerilmesi ve kırılma uzaması azalırken, sertliğin arttığı gözlemlenmiştir. Sonuç olarak, kesit kalınlığının, **küresel grafitli dökme demirlerin mikroyapısını ve mekanik özelliklerini belirleyen önemli bir parametre olduğu** sonucuna varılmıştır.

Anahtar Kelimeler

• küresel graift
• mikroyapı
• mekanik özellik

Evaluation of Casting Modulus on the Microstructure and Mechanical Properties of Spheroidal Graphite Cast Iron

Abstract

Nodular graphite (Ductile) cast iron is produced by a double treatment; Nodularization / Spheroidization (Mg and/or Rare Earth) treatment + Inoculation (FeSiX-alloy treatment, with X = Ca, Ba, Sr, Ce, La, Zr etc.). Each step has specific objectives. The spheroidization of the graphite depends on the thickness of the mould and thus cooling rate is an important factor. In this work, GGG70L alloy was cast into plates that had different cross-sections. The change in the modulus has been investigated by means of microstructure and mechanical properties. It turned out that as nodule size was decreased, tensile stress and elongation at fracture were decreased however hardness was increased. It was concluded that the section thickness was an important parameter that determines the microstructure and mechanical properties of spheroidal cast irons.

Keywords

• spherodal cast iron
• microstructure
• mechanical properties

Kaynakça

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