PERLİTİK RAYLARIN MANTAR SERTLEŞTİRME İŞLEMLERİNDE FARKLI SOĞUTMA ORTAMLARININ MİKROYAPI VE MEKANİK ÖZELLİKLERE ETKİSİ
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Tarih
2021-08
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info:eu-repo/semantics/openAccess
Özet
Ülkemizde, demiryolu projelerinin artmasıyla birlikte, kullanılan malzemelerde kaliteli ürün ihtiyacı doğmuştur. Bununla birlikte, maliyeti de düşürmek adına mantarı sertleştirilmiş demiryolu raylarının, yerli kaynaklarla geliştirilmesi ve üretilmesi için pek çok proje üzerinde çalışmalar yapılmaktadır. Raylarda kırılma meydana gelmesinin en önemli sebeplerinden bazıları; rayların içyapısı, yüzeyde meydana gelen aşınmalar ve kalıcı bozulmalardır. Meydana gelen bu hasarları en aza indirmek için mantar sertleştirme süreci uygulanmaktadır. Bu uygulama diğer raylara göre, rayın içyapısında ince perlit oluşturarak, daha sert bir yapıyla aşınmayı azaltır. Aşınmaların ve hasarların çoğu ray mantarı üstünde olduğundan dolayı mantar sertleştirme prosesine önem verilmiştir. Bu çalışmada kullanılan başlangıç malzemesi R260 kalite demiryolu rayıdır. Mantar sertleştirme işleminde, literatürdeki kaynaklardan yararlanarak optimum östenitleme sıcaklığı olarak 825°C belirlenmiştir. Bu östenitleme sıcaklığında östenitlenen raylar 2 farklı soğutma ortamında farklı sürelerde soğutularak mantar sertleştirme işlemi gerçekleştirilmiştir. Soğutma ortamı olarak oda sıcaklığındaki su ve oda sıcaklığındaki Quenchoıl MB serisi ısıl işlem yağı kullanılmıştır. Soğutma işlemi olarak, suda 10 saniye ve tam soğutma, yağda 10 saniye ve tam soğutma ortamı uygulanmıştır. EN 13674 standardında belirtilen değerler incelendiğinde, mikroyapı ve mekanik testler sonucunda optimum soğutma ortamı, numunenin suda 10 saniye süreyle soğutulması işlemi olduğu gözlemlenmiştir.
With the increase in railway projects in our country, the need for quality products has arisen in the materials used. In addition, studies are being carried out on many projects to develop and produce head hardened rails with domestic resources in order to reduce the cost. Some of the most important causes of breakage in the rails; The internal structure of the rails are the abrasions and permanent deteriorations that occur on the surface. In order to minimize these damages, the head hardening process is applied. Compared to other rails, this application creates fine perlite in the inner structure of the rail, reducing wear with a harder structure. Most of the wear and damage is on the rail head, so the head hardening process has been given importance. The starting material used in this study is R260 quality railway rail. In the head hardening process, 825°C was determined as the optimum austenitizing temperature, using the resources in the literature. The head hardening process was carried out by cooling the rails austenitized at this austenitizing temperature at different times in 2 different cooling environments. Water at room temperature and Quenchoil MB series heat treatment oil at room temperature were used as cooling medium. As the cooling process, 10 seconds in water and full cooling, 10 seconds in oil and full cooling medium were applied. When the values specified in the EN 13674 standard are examined, it has been observed that the optimum cooling environment is the process of cooling the sample in water for 10 seconds as a result of microstructure and mechanical tests."
With the increase in railway projects in our country, the need for quality products has arisen in the materials used. In addition, studies are being carried out on many projects to develop and produce head hardened rails with domestic resources in order to reduce the cost. Some of the most important causes of breakage in the rails; The internal structure of the rails are the abrasions and permanent deteriorations that occur on the surface. In order to minimize these damages, the head hardening process is applied. Compared to other rails, this application creates fine perlite in the inner structure of the rail, reducing wear with a harder structure. Most of the wear and damage is on the rail head, so the head hardening process has been given importance. The starting material used in this study is R260 quality railway rail. In the head hardening process, 825°C was determined as the optimum austenitizing temperature, using the resources in the literature. The head hardening process was carried out by cooling the rails austenitized at this austenitizing temperature at different times in 2 different cooling environments. Water at room temperature and Quenchoil MB series heat treatment oil at room temperature were used as cooling medium. As the cooling process, 10 seconds in water and full cooling, 10 seconds in oil and full cooling medium were applied. When the values specified in the EN 13674 standard are examined, it has been observed that the optimum cooling environment is the process of cooling the sample in water for 10 seconds as a result of microstructure and mechanical tests."
Açıklama
Anahtar Kelimeler
Demiryolu Rayı, Mantar Sertleştirme, Mikroyapı, Mekanik Özellik, : Railroad Track, Head Hardening, Microstructure, Mechanical Properties