Publication: Recyclig of investment casting shell mold sands ın ceramic industry
Abstract
HASSAS DÖKÜM KALIP KUMLARININ SERAMİK SANAYİNDE YENİDEN DEĞERLENDİRİLMESİ Bu çalışmada, hassas döküm kalıp kumlarının geri dönüşümü incelenmiştir. Öncelikli olarak, dökümde kullanılmamış ve dökümde kullanılmış kalıp kumlarının kompozisyonu ve mikroyapı özelliklerinin tespit edilebilmesi için XRF, XRD, EDS, SEM ve DTA-TG analizleri yapıldı. Literatürde yer alan çalışmalar ve analiz sonuçları doğrultusunda, sinterlemeye yardımcı olması için 1,2 ve 3 ağ%‘e kadar MgO ilavesi ile 4 farklı kompozisyonda numuneler hazırlandı. 1450, 1475 ve 1500 °C sıcaklık değerlerinde 3 saat sinterlenerek özellikleri incelenmek üzere karakterize edildi. Numunelerin kimyasal ve mikroyapı özellikleri için XRD, EDS ve SEM analizleri yapıldı.Ayrıca kaba yoğunluk, görünür porozite, sertlik, su emme, ağırlık kaybı ve pişme küçülmesi gibi fiziksel özellikleri de ölçüldü. Yapılan analizler sonucunda, MgO ilavesinin müllit-zirkon yapısında sinterlenme özelliğini arttırdığı, bu sebeple de hacimsel küçülme oranlarında düşüşe, kaba yoğunlukta artışa sebep olduğu gözlemlendi. Pişme küçülmesi oranlarının tüm ilavelerde sıcaklığa bağlı olarak, aynı sıcaklıkta MgO ilavesine bağlı olarak arttığı, görünür porozitenin de azaldığı tespit edildi. Kaba yoğunluğun MgO ile artışı, su emme oranlarında düşüşe, dolayısı ile numune sertliğinin artışına yol açtığı gözlemlendi. Kalıp kumlarına yapılan MgO ilavesinin, malzemenin mekanik özelliklerinin iyileştirilmesine yardımcı olmasının yanında, düşük sinterlenme sıcaklıklarında çalışması nedeniyle proses ve geri dönüşüm maliyetlerinin düşük olması açısından da avantaj sağlamaktadır. MgO ilaveli hassas döküm kalıp kumları 1500 °C’nin altındaki sıcaklıklarda, bazı refrakter uygulamalarında takviye amaçlı olarak kullanılabilir. Aralık, 2013Sevnur ÖZDEMİR
RECYCLING OF INVESTMENT CASTING SHELL MOLD SANDS IN CERAMIC INDUSTRY In this study recycling of mould sand was investigated. Firstly, to determine the compositions and microstructures of the used and unused mould wastes, XRF, XRD, EDS, SEM and DTA-TG analysis were performed. With the help of the literature survey and the analysis results, samples with 4 different compositions were prepared. MgO addition was attempted between 0-3 wt % for densification. The compacted powder mixtures were sintered with 3 different sintering temperature at 1450, 1475 and 1500 °C for 3 hours. Sinterability of the samples were investigated and explored. Microstructural evaluation and chemical analysis were carried out by XRD, EDS, SEM, and physical properties such as bulk density, apparent porosity, hardness, water absorbtion, loss on ignition and shrinkage were also measured. MgO addition was found to promote sinterability of mullite-zirconia composite leading to an increment in shrinkage of the samples thus bulk density increased.The shrinkage rate increased with increasing magnesia addition at all temperatures, resulted in decreasing apparent porosity.Bulk density increase with increasing magnesia addition at all temperatures caused to decrease water absorption and improvement in hardness. MgO addition into mould sand can provide improved or better mechanical properties and reduces the sintering temperature for cost effective processing and recycling of the mould sand. MgO added investment casting waste mould sand can be partially used in some refractory applications for reinforcement purposes where operation temperature should be lower than 1500 °C. December, 2013Sevnur ÖZDEMİR
RECYCLING OF INVESTMENT CASTING SHELL MOLD SANDS IN CERAMIC INDUSTRY In this study recycling of mould sand was investigated. Firstly, to determine the compositions and microstructures of the used and unused mould wastes, XRF, XRD, EDS, SEM and DTA-TG analysis were performed. With the help of the literature survey and the analysis results, samples with 4 different compositions were prepared. MgO addition was attempted between 0-3 wt % for densification. The compacted powder mixtures were sintered with 3 different sintering temperature at 1450, 1475 and 1500 °C for 3 hours. Sinterability of the samples were investigated and explored. Microstructural evaluation and chemical analysis were carried out by XRD, EDS, SEM, and physical properties such as bulk density, apparent porosity, hardness, water absorbtion, loss on ignition and shrinkage were also measured. MgO addition was found to promote sinterability of mullite-zirconia composite leading to an increment in shrinkage of the samples thus bulk density increased.The shrinkage rate increased with increasing magnesia addition at all temperatures, resulted in decreasing apparent porosity.Bulk density increase with increasing magnesia addition at all temperatures caused to decrease water absorption and improvement in hardness. MgO addition into mould sand can provide improved or better mechanical properties and reduces the sintering temperature for cost effective processing and recycling of the mould sand. MgO added investment casting waste mould sand can be partially used in some refractory applications for reinforcement purposes where operation temperature should be lower than 1500 °C. December, 2013Sevnur ÖZDEMİR