Investigation of The Effect of Accelerated Quenching Process and Quenching Parameters on The Strength of Low-Carbon Railway Forged Steel

Yıl 2025, Cilt: 25 Sayı: 6, 1439 - 1446

Halime Kirtiş , Levent Elen , Yunus Türen

Öz

This study examined the impact of the 'Accelerated Cooling and Self-Tempering (AC-ST)' heat treatment on the mechanical and microstructural properties of S355J2 grade steel forgings, specifically the component known as the 'Lower Side Bearer.' The AC-ST heat treatment was conducted under 12 bar air pressure for a specific cooling duration. In the microstructure of untreated samples, a Ferrite+Pearlite phase was observed. With an increase in the cooling rate, the structure transformed into polygonal ferrite and/or acicular ferrite, followed by the formation of sorbite and/or upper bainite, and finally, martensite and/or lower bainite phases. It was noted that with an increasing cooling rate, martensite and bainite phases coexisted within the structure. At even higher cooling rates, the structure fully transformed into martensite. Additionally, the applied heat treatment was found to enhance the mechanical properties of the material. Especially, the highest value was obtained with 377 HB hardness value in the edge region of the sample with the highest cooling rate (1-fold distance). Similarly, the highest tensile strength (1002 N/mm²) and yield strength (663.93 N/mm²) were obtained in the 1-fold distance sample. However, in the 2-fold distance sample with lower hardness, the impact energy exhibited the highest value as 81.22 J at room temperature and 95.38 J at -20°C.

Anahtar Kelimeler

Accelerated cooling , Mechanical properties , Steel , Self-tempering

Destekleyen Kurum

Karabuk University

Proje Numarası

KBÜBAP-21-YL-046

Teşekkür

This study was financially supported by Karabük University, Scientific Research Projects Unit (KBÜBAP) with the number KBÜBAP-21-YL-046

Düşük Karbonlu Demiryolu Dövme Çeliğine Uygulanan Hızlandırılmış Su Verme İşlemi ve Su Verme Parametrelerinin Dayanıma Etkisinin İncelenmesi

Öz

Bu araştırmada, S355J2 kalite çelikten üretilen ve “Alt Oturma” olarak adlandırılan dövme parçaya, üretim sonrası uygulanan “Hızlandırılmış Soğutma ve Kendi Kendini Temperleme (HS-KT)” ısıl işleminin mikroyapısal ve mekanik özellikler üzerindeki etkisi değerlendirilmiştir. HS-KT ısıl işlemi, 12 bar hava basıncı altında belirli bir soğutma süresi boyunca gerçekleştirilmiştir. Isıl işlem uygulanmamış numunelerin mikroyapısında Ferrit+Perlit fazları tespit edilirken, soğutma hızı etkisi ile yapı, önce poligonal ferrit ve/veya iğnemsi ferrit, ardından sorbit ve/veya üst beynit, son olarak ise martenzit ve/veya alt beynit fazlarına dönüşmüştür. Soğutma hızının artmasıyla birlikte martenzit ve beynit fazlarının birlikte oluştuğu gözlemlenmiştir. Daha yüksek soğutma hızlarında ise yapının tamamen martenzite dönüştüğü belirlenmiştir. Ayrıca uygulanan ısıl işlemin, malzemenin mekanik özellikleri üzerinde olumlu yönde etkiler meydana getirdiği tespit edilmiştir. Özellikle en yüksek soğuma hızına (1 kat mesafe) sahip numunenin kenar bölgesinde 377 HB sertlik değeri ile en yüksek değer elde edilmiştir. Aynı şekilde en yüksek çekme dayanımı (1002 N/mm²) ve akma dayanımı (663,93 N/mm²) 1 kat mesafeli numunede elde edilmiştir. Fakat, daha düşük sertliğe sahip 2 kat mesafeli numunede darbe enerjisi oda sıcaklığında 81,22 J, -20°C'de 95,38 J olarak en büyük değeri sergilemiştir.

Anahtar Kelimeler

Çelik , Hızlandırılmış soğutma , Kendi kendini temperleme , Mekanik özellikler

Destekleyen Kurum

Karabük Üniversitesi

Proje Numarası

KBÜBAP-21-YL-046

Teşekkür

Bu çalışma Karabük Üniversitesi Bilimsel Araştırma Projeleri Birimi (KBÜBAP) tarafından KBÜBAP-21-YL-046 numarasıyla finansal olarak desteklenmiştir.

Kaynakça

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