Investigation of Metallurgical and Mechanical Properties for Refractory Materials

Öz

Refractory materials involved in most metallurgical processes are often exposed to thermal stresses exceeding their mechanical strength, but this does not cause well-designed refractory linings to fail causing major material damage. On the contrary, they are partially subjected to a gradual wear process and maintain their structural stability despite damage. For this reason, classical mechanical tests performed by considering tensile strength are not sufficient to measure the resistance of refractory products to damage. Despite significant advances in the determination of the fracture process and the resistance of refractory materials to damage, empirical data and scientific studies on the fracture behavior of typical refractory materials, especially at high temperatures, have still not reached a sufficient level. The aim of this study is to contribute to literature an article detailing the academic and technical applications that will eliminate the mentioned deficiency. For this purpose, wedge splitting tests, which have proven to be quite effective for investigating the fracture behavior of refractory materials, were carried out up to 1500°C on four typical refractory materials commonly used, and the findings were supported by microscopic examinations. As a result of the study, it was determined that high alumina bricks remained stable up to at least 1500°C. It has been observed that the mechanical strength of cement-bonded high-alumina castable bricks decreases above 1400°C and shows a significant increase in specific fracture energy above 1100°C. It was supported by data that Andalusite and silica bricks have a brittle feature even at lower temperatures than high-alumina castable bricks. It has been determined that the specific fracture energy of Andalusite bricks weakens significantly with the formation of the liquid phase above 1100°C, while the specific fracture energy of silica bricks increases strongly at 1000°C, and shows a brittle fracture character at temperatures above 1100°C.

Anahtar Kelimeler

• Refractory materials
• failure analysis
• metallurgical properties
• mechanical strength

Refrakter Malzemelerin Metalurjik ve Mekanik Özelliklerinin İncelenmesi

Öz

Metalurjik süreçlerin büyük bir kısmında yer alan refrakter malzemeler genellikle mekanik dayanımlarını aşan termal gerilimlere maruz kalır ancak bu durum iyi tasarlanmış refrakter astarların büyük maddi hasarlar oluşturacak şekilde başarısız olmasına yol açmaz. Tam aksine kısmen kademeli bir aşınma sürecine tabi tutulur ve hasara rağmen yapısal stabilitelerini korurlar. Bu nedenle çekme mukavemeti dikkate alınarak gerçekleştirilen klasik mekanik testler refrakter ürünlerin hasara karşı direncini ölçmek için yeterli değildir. Kırılma sürecinin ve refrakter malzemelerin hasara karşı direncinin tespitindeki önemli ilerlemelere rağmen tipik refrakter malzemelerin özellikle yüksek sıcaklıktaki kırılma davranışına ilişkin ampirik veriler ve bilimsel çalışmalar halen yeterli seviyeye ulaşamamıştır. Bu çalışmanın amacı bahsi geçen eksikliği giderecek akademik ve teknik uygulamaların detaylarının aktarıldığı bir makalenin literatüre kazandırılmasıdır. Bu amaçla yaygın olarak kullanılan dört tipik refrakter malzeme üzerinde refrakter malzemelerin kırılma davranışını araştırmak için oldukça etkili olduğu kanıtlanan kama yarılma testleri 1500°C'ye kadar gerçekleştirilmiş ve bulgular mikroskobik incelemelerle desteklenmiştir. Çalışma neticesinde yüksek alüminalı tuğlaların en az 1500°C'ye kadar stabil durumda kaldığı tespit edilmiştir. Çimento bağlı yüksek alüminalı dökülebilir tuğlaların ise 1400°C'nin üzerinde mekanik dayanımında azalma meydana geldiği ve 1100°C'nin üzerinde spesifik kırılma enerjisinde ciddi bir artış gösterdiği gözlenmiştir. Andaluzit ve silika tuğlalar ise yüksek alüminalı dökülebilir tuğlalara göre daha düşük sıcaklıklarda bile kırılgan bir özelliğe sahip olduğu verilerle desteklenmiştir. Andaluzit tuğlaların özgül kırılma enerjisi 1100°C'nin üzerinde sıvı fazın oluşmasıyla önemli ölçüde zayıfladığı, silika tuğlalarının özgül kırılma enerjilerinin ise 1000°C'de güçlü bir şekilde yükseldiği gözlenirken, 1100°C'nin üzerindeki sıcaklıklarda gevrek bir kırılma karakteri gösterdiği tespit edilmiştir.

Anahtar Kelimeler

• Refrakter malzemeler
• hasar analizi
• metalurjik özellikler
• mekanik dayanım

Kaynakça

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