Tozaltı Ark Kaynağı Yöntemi Birleştirilen HSLA S960QL Çeliğinde Kaynak Parametrelerinin Mikroyapı ve Mekanik Özellikler Üzerinde Etkisi

Bu çalışmada; S960QL düşük karbonlu ve yüksek mukavemetli düşük alaşımlı çelikler, mikroyapı ve mekanik özelliklerinin araştırılması amacıyla tozaltı ark kaynağı yöntemi kullanılarak kaynak edilmişlerdir. Mikroyapısal incelemelerde tozaltı kaynak bölgeleri için mikroskobik muayene teknikleri uygulanmıştır. Kaynak ve ana metalden elde edilen farklı numunelerin mekanik özellikleri için çekme, darbe ve mikro sertlik testleri yapılmıştır. Yassı çekme numune mukavemet değerleri ana metale yakın değerler vermiştir. Fakat kaynak metalinden elde edilen yuvarlak tip çekme numune dayanımları ana metalden çok düşük çıkmıştır. Kopan parçaların kırılma yüzeyleri optik ve taramalı elektron mikroskobu ile incelenmiştir. Charpy darbe testleri; ana metal, kaynak metali merkez hattı, ergime hattı, kaynak metali merkez hattı ve ergime hattı arası bölgelerinden yapılmıştır. Kaynak metali ergime hattı darbe enerjisi ana metalden daha düşük ölçülmüştür. En düşük darbe enerjisi ergime hattında ölçülmüştür. Mikrosertlik testlerinde, en yüksek değer ısıdan etkilenmiş bölgeden ölçülmüştür. Mikroyapı analizlerinde, kaynak dikişi-ısıdan etkilenmiş bölge ara yüzeyi ve ısıdan etkilenmiş bölge mikroyapılarının ana malzemeye göre daha büyük taneli olduğu görülmüştür. Isıdan etkilenmiş bölge ortaya çıkan yüksek sıcaklık değerleri nedeniyle alaşım karbürleri çözünmüş ve tane büyümesi daha kolay bir şekilde gerçekleşmiştir.

The Effect of Welding Parameters on Microstructural and Mechanical Properties of HSLA S960QL Type Steel with Submerged Arc Welding

In this study, S960QL steels were welded with submerged arc welding process in order to examine microstructural and mechanical properties. For the microstructural investigation, microscopical examination methods were used for weld zones. Tensile, impact toughness and micro hardness tests were made for different samples obtained from the weld zone and the base metal. The examinations of fracture surfaces were made by using optical microscope and scanning electron microscope. The flat type tensile strength values were near to the base materials. Charpy impact toughness tests were made for the base metal, the weld metal center line, the fusion line, the zone between weld metal centerline and the fusion line. Impact energy of the weld metal was obtained lower than the base metal. The lowest impact energy was obtained at the fusion line. Heat affected zone had the highest value in micro hardness tests. In microstructure evaluation, the interface of the fusion zone-heat affected zone and heat affected zone had coarser grain structure than the base metal. Alloy carbides dissolved because of the high temperature values occurred at heat affected zone.

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