R260 KALİTE RAY ÇELİĞİNİN ISIL İŞLEM SONRASI MİKROYAPI VE MEKANİK ÖZELLİKLERİNİN İNCELENMESİ
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Tarih
2021-08
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info:eu-repo/semantics/openAccess
Özet
Bu çalışmada, labaratuvar ortamında R260 kalite ray çeliğine uygulanan mantar sertleştirme işleminin mekanik özellikler ve mikroyapı üzerinde etkileri araştırılmıştır. Isıl işlem görmüş raylara sertlik ve basma deneyleri yapılmıştır. Optik ışık mikroskobu ve taramalı elektron mikroskobunda (SEM) mikroyapı görüntüleri incelenmiştir. Rayın östenitleşme sıcaklığı 800 °C olarak belirlenmiştir. Soğutma yöntemi olarak daldırma metodu seçilmiştir. Soğutma süreleri 1,10 saniye ve tam soğuma olarak belirlenmiştir. Soğutma ortamı sadece su ve su+hava olarak belirlenmiştir. İki numune 800 °C’de 1 ve 10 saniye sürelerle suda bekletildikten sonra havada soğumaya bırakılmıştır. Diğer numune ise 800 °C’de uç kısımları suya daldırılarak tam su verme ısıl işlemi gerçekleştirilmiştir. Sertlik değerleri, mantar sertleştirme yönteminde artan ısıl işlem süresi ile artış göstermektedir.10 sn süreyle su verilen ray numunesi R350HT kalite ray için gerekli olan sertlik değerlerini karşılama eğilimindedir. Tam su verme ısıl işleminde ise yapı artık martenzit olmuştur. SEM görüntülerinde, su verme süresi arttıkça mikro yapıların inceldiği gözlemlenmiştir. Isıl işlem uygulanmayan ray kaba perlit yapıdayken, 1 ve 10 sn sürelerle ısıl işlem uygulanan raylarda ince perlitik yapı gözlemlenmiştir. Basma deneyinde en gevrek malzeme tam su verilen ray numunesidir. Tam su verilen ray numunesi en yüksek mukavemet değerine ulaşmıştır. Diğer su verilen numuneler ise sünek özellik göstermişlerdir.
In this study, the effects of cork hardening applied to R260 quality rail steel on the mechanical properties and microstructure were investigated in the laboratory environment. Hardness and compression tests were carried out on the heattreated rails. Microstructure images were examined under optical light microscope and scanning electron microscope (SEM). The austenitization temperature of the rail was determined as 800 °C. The immersion method was chosen as the cooling method. Cooling times were determined as 1.10 seconds and full cooling. The cooling medium is determined as water and water+air only. Two samples were kept in water at 800 °C for 1 and 10 seconds and then allowed to cool in air. In the other sample, full quenching heat treatment was carried out by immersing the ends in water at 800 °C. The hardness values increase with increasing heat treatment time in the cork hardening method. The rail sample, which is quenched for 10 seconds, meets the hardness values required for the R350HT quality rail. In the complete quenching heat treatment, the structure is now martensite. In the SEM images, it was observed that the microstructures became thinner as the quenching time increased. While the rail that is not heat treated is in coarse perlite structure, the rails that are heat treated for 1 and 10 seconds are in fine pearlitic structure. The most brittle material in the compression test is the fully quenched rail sample. The fully quenched rail sample reached the highest strength value. Other quenched samples showed ductile properties."
In this study, the effects of cork hardening applied to R260 quality rail steel on the mechanical properties and microstructure were investigated in the laboratory environment. Hardness and compression tests were carried out on the heattreated rails. Microstructure images were examined under optical light microscope and scanning electron microscope (SEM). The austenitization temperature of the rail was determined as 800 °C. The immersion method was chosen as the cooling method. Cooling times were determined as 1.10 seconds and full cooling. The cooling medium is determined as water and water+air only. Two samples were kept in water at 800 °C for 1 and 10 seconds and then allowed to cool in air. In the other sample, full quenching heat treatment was carried out by immersing the ends in water at 800 °C. The hardness values increase with increasing heat treatment time in the cork hardening method. The rail sample, which is quenched for 10 seconds, meets the hardness values required for the R350HT quality rail. In the complete quenching heat treatment, the structure is now martensite. In the SEM images, it was observed that the microstructures became thinner as the quenching time increased. While the rail that is not heat treated is in coarse perlite structure, the rails that are heat treated for 1 and 10 seconds are in fine pearlitic structure. The most brittle material in the compression test is the fully quenched rail sample. The fully quenched rail sample reached the highest strength value. Other quenched samples showed ductile properties."
Açıklama
Anahtar Kelimeler
R260 quality rail steel, heat treatment, microstructure and mechanical properties, hardness test, compression test., R260 kalite ray çeliği, ısıl işlem, mikroyapı ve mekanik özellikler, sertlik deneyi, basma deneyi.
