Cam ambalaj üretiminde kullanılan kalıplar, havada yüksek sıcaklıktaki ergimiş camla temas ederek ürüne şekil verirler. Ergimiş cam ile temas eden kalıpların çalışma yüzeyleri, mekanik gerilmelere ve ısıl çevrimlere maruz kalırlar. Bu etkilerle kalıp yüzeylerinde meydana gelen hasarlar, kalıpların kullanım ömürlerini sınırlar ve mamul kalitesini bozar. Cam ambalaj üretimi kalıbı malzemelerinden beklenen özellikleri sağlayan kalıp metalleri arasında en ucuz ve kolay şekil verilebilen malzemeler gri dökme demirlerdir. Bu çalışmada, alaşımlı gri dökme demir kalıp malzemesi örneklerinin, üretim koşullarına benzer koşullar altındaki davranışı laboratuvar ortamında incelenmiştir. Metal-sıvı cam etkileşmesini sağlamak amacıyla, hazırlanan deney düzeneğinde taşıyıcı kola bağlı olan dökme demir örnekler, fırın içerisine aşağıya doğru hareket ettirilerek ergimiş cam banyosuna temas ettirilmiş ve bir süre bekletildikten sonra fırın dışına çıkarılarak üflenen basınçlı hava ile soğutulmuştur. Çevrimsel olarak tekrarlanan bu hareketle oluşturulan performans deneyleri süresince oluşan hasarlar; oksidasyon ve ısıl yorulmanın bir arada olduğu hasarlardır. Yüzeyde, ilerleyen oksitlenme ile poroz yapıda yoğun oksit fazları oluşmaktadır. Isıl gerilmeler ve cama temasla oluşan gerilmeler, hasar oluşumunda ikincil etki olarak, mikro çatlaklar oluşturmakta ve adhesif aşınmada yüzeyden malzeme kaybını hızlandıran kırılma ve ayrılmalara neden olmaktadır. Cam örneklerin yüzeyine kalıp metalinden, adhesif aşınma ile metaloksit kalıntıları geçmekte ve cam yüzeyini kirletmektedir. Hava atmosferi koşullarında yapılan deneylerde camın köpürmeye başladığı sıcaklıklar inert gaz atmosferindeki sıcaklıklardan daha düşüktür Yüksek sıcaklıklarda argon gaz atmosferinde alaşımlı dökme demir ile temas halindeki cama zamana bağlı olarak metal-cam arayüzeyinden demir geçişleri olmaktadır. Anahtar Kelimeler: Alaşımlı dökme demir, cam ambalaj üretimi, kalıp. The mould materials used in the glass container production form the glass product by contacting with molten glass in air at elevated temperatures. The performing surfaces, which contact with molten glass, are subjected to the mechanical stresses and the thermal cyclic operations. These failures at the mould surfaces limit the service life of the moulds and affect the quality of glass products. Production of high-quality glass with smooth surface is related with the contact behaviour of the hot glass towards the mould. Therefore, beside cost and rate of production, the selection of a mould material has significant importance in the glass industry. Cast irons are commonly used as a mould material in the production of glass materials. One of the most inexpensive and easily machinable materials is grey cast iron for the mould materials, which meet the desirable properties in the glass container production. However, these materials require further surface treatment applications to improve the surface properties. In this study, behaviour of alloyed grey cast iron mould material under the production conditions simulated in the laboratory and the effects of the hot glass contact and failure formation mechanisms on the glass forming mould surfaces were investigated. The tests were carried out using a combined furnace with a pneumatic movable plunger set-up. The vertically movable holder was mounted on a plunger, to provide the interactions between hot glass and metal. The cast iron samples were attached at the tip of the holder of the experimental set-up. The plunger was moved up and down periodically. At the lower end position, the sample surface and hot glass contact in an exact immersion depth at certain time. Then the plunger lifted out of the furnace immediately, and compressed air was blown against the specimen surface through a nozzle. After the cooling with blown air, the same movement periods were cyclically repeated. This movement carried on until desired cycle number was reached. Then samples were pulled up from the plunger. After the cyclic experimental studies, the surface of the samples was investigated and characterised. The surface hardness of alloyed cast iron decreases during the experimental processes. Thermal and contact stresses create micro cracks and cause the acceleration of material losses from the surface of the material by adhesion, as a secondary factor. The wear tracks, especially through the graphite flakes obtained on the surface of alloyed cast iron. The formation of decarburised pitting at the surface that growth through the graphite flakes, due to the oxidation and the adhesion, propagates material losses causing intensive adhesive wear at the surface. Failures in alloyed cast iron were oxidation and thermal fatigue failures. Adhesive wear occurred on the surfaces because of the formation of micro holes, tracks that molten glass penetrates. The dense oxide phases occurred with the oxidation progressing on the surface. Metal oxides transferred into the glass from mould surface and contaminated the glass surface. The surface of alloyed cast iron was rapidly oxidised at elevated temperatures and thicker oxide layer occurred at the surfaces. The oxide layer pulled out from the surface by molten glass and the surface smoothness decreased. The oxide phases, which occurred at the sample surfaces during the performance experiments, were characterised by x-ray analyses. After 5000 cycle both Fe3O4 and Fe2O3 phases occurred at the alloyed cast iron surface. TG-DTA analyses were carried out in air atmosphere. At about 400 °C oxidation began and the maximum oxidation peak in the DTA curve was recorded at about 750 °C. Decarburisation reaction, which started with mass loss, occurred after 765 °C. The rate of decarburisation increased with rise in temperature from 920 to 973°C. The wetting tests were carried out for determination of the contact angles and the wetting behaviour of alloyed cast iron and glass ball at elevated temperature. The oxygen at the glass-metal interface caused gasification and foaming during the wetting experiments. The glass foaming temperature for the experiments done in air atmosphere was lower then the experiments done in Ar atmosphere for alloyed cast iron. Iron diffusion occurred on the glass-metal interfaces depending on the time in Ar atmosphere. The iron diffusion from alloyed cast iron to the glass increased with time. The contamination occurred at the glass surface by iron diffusion. Keywords: Alloyed cast iron, glass container production, mould
