Hayriye Ertek Emre

HARDOKS400-AISI304 ÇELİK ÇİFTİNİN ELEKTRİK ARK VE MAG KAYNAĞI

Bu calismada asinmaya direncli hardoks celiginin, ostenitik paslanmaz celige elektrik ark kaynak (EAK) ve gaz alti ark kaynak (GMAK) yontemleri ile birlestirilebilirligi incelenmis, kaynak yontemi farkinin birlestirmenin mekanik ozelliklerine ve yapisina etkisi arastirilmistir. Standartlara uygun V kaynak agzi acilan HARDOKS 400–AISI 304 celik cifti EAK ve GMAK yontemleriyle cok pasolu olarak, yerde yatayda alin alina birlestirilmistir. Farkli cins celik birlestirmesinin mekaniksel ozellikleri; cekme, uc nokta egme ve darbe centik testi ile belirlenmistir. Ilave olarak birlestirmenin kesitinde sertlik olcumu ve mikroyapi incelemesi de gerceklestirilmistir. Elde edilen bulgulara gore; EAK yontemine gore GMAK yontemiyle birlestirilen numunelerin mekanik ozelliklerinin daha iyi oldugu tespit edilmistir.

Effect of static strain aging on the fatigue behavior of S275JRC steel

Abstract In this study, the effect of static strain aging on the fatigue behavior of a mild steel (S275JRC) was evaluated. For this purpose, the 5 % prestrained mild steel was aged at a temperature of 160 °C for different intervals. The aging behavior was determined primarily for the as-received (AR) as well as in the homogenization and normalizing heat treated (H+N heat treated) condition. The yield stresses before and after aging process as well as the hardness values of the aged steels were measured for the assessment of the strain aging progress. The dynamic mechanical behavior of strain aged samples was also determined by fatigue test under the dynamic loads. An increase in the yield strength due to strain aging and hardness induced improvement in fatigue strength of the steel were observed.

Effect of Post Weld Heat Treatment Process on Microstructure and Mechanical Properties of Friction Welded Dissimilar Drill Pipe

In this study, N80-42CrMo4 dissimilar drill pipes were welded by a roto-friction welding machine. A set of welded samples were tested as-welded condition. Another set of welded samples were post weld heat treated (stress relief annealing) at the temperature of 600 °C, for 20 min. and then tested. The microstructures of the as-welded and stress relief annealed samples were examined by optical microscope and SEM. The properties of the all welded samples were determined by hardness measurement, tension and V notch-impact tests. The high hardness especially in the weld interface resulted in low toughness. As a conclusion, the stress relief annealing treatment caused a little decrease in yield strength and ultimate tensile strength, but increase in the elongation. The ductility of samples also increased after annealing treatment which is very important for static and dynamic loads.