International Journal of Iron & Steel Society of Iran
Year:2015 | Volume:12 | Issue:2|Papers Count:7

In this study, the effect of cold rolling process on the microstructure and texture evolution in 1wt. % Si non-oriented electrical steel was investigated. For this purpose, all samples were processed through single-stage hot rolling at 1100 ° C and two-stage cold rolling (cross rolling and unidirectional rolling) with intermediate annealing at 650 °C for 35 seconds. Finally, all of them were fully annealed for 3 min at 900 ° C. The results showed that cold rolling process could affect shear band formation, deformation texture and annealing texture. Shear band and {322} grains were decreased and {100} grains were increased by the cross rolling method. These observations showed the weakening of the {110}<001>and {111}<112>components and the strengthening of the {001}<110>component after final annealing for the cross rolled sample. On the other hand, shear band formation in the unidirectional rolling sample caused the development of annealing Goss texture component ({110}<001>).

In the present study, the effects of growth defects and chromium content loss on the degradation of corrosion and passivation of cathodic arc evaporation (CAE-PVD) of stainless steel coating were investigated in 2 M sulphuric acid solution. EDS analysis indicated that the micro-particles were obtained during the coating growth. In addition, it was detected that the growth defects had poor adhesion to the coating matrix and in the open circuit potential (OCP), they were detached from the coating, providing appropriate conditions for the penetration of the solution. In addition, loss of chromium during evaporation was found to be detrimental to the passivation of the stainless steel coating and the formation of a porous oxide layer. The average percent of the main elements of the coating, according to EDS area analysis, was Fe-13Cr-6Ni. Moreover, the lower semicircle diameter of the coating in electrochemical impedance spectroscopy (EIS) measurements revealed the lower polarization resistance of it, in comparison to that of the bulk 304 stainless steel.

The aim of the present study was to investigate the effect of quenching and tempering temperatures on the microstructure, mechanical properties and the wear characteristics of medium carbon-high chromium wear resistant steel. In addition, the dominant wear mechanisms were studied. For this purpose, austenitizing and tempering temperatures were selected in the ranges of 900- 1000oC and 300- 500oC, respectively. Mechanical properties were evaluated through hardness and impact tests as well as wear test (by dry sand/rubber wheel apparatus). Microstructure and wear and fracture surface appearances were investigated using scanning electron microscopy (SEM). Moreover, the measurement of retained austenite was done through X-Ray diffraction (XRD) analysis. The obtained results revealed that the best wear properties were achieved by tempering at 450oC due to the reduction of tendency to micro-cracking, the decrease in internal stresses, and the improvement of the impact energy. Observing the wear surfaces showed that the wear mechanism for the specimen tempered at 400 °C was a combination of abrasive, adhesive and fatigue wear. However, abrasive wear was the only active wear mechanism for the specimen tempered at 450oC.

Deep cryogenic heat treatment is assumed as a supplementary heat treatment performed on steels before the final tempering treatment to enhance the wear resistance and hardness of the steels. In this study, the effects of the deep cryogenic heat treatment on the wear behavior and corrosion resistance of the 1.2080 tool steel were studied using the wear testing machine and polarization and impedance spectroscopy tests. Moreover, the microstructural changes of the deep cryogenically treated samples were clarified via the scanning electron microscope (SEM) and X-ray diffraction testing machine. The results showed that the deep cryogenic heat treatment eliminated the retained austenite and made a more uniform carbide distribution with higher percentages. Beyond this, it was clarified that the deep cryogenic heat treatment increased the hardness and improved the wear behavior of the 1.2080 tool steel, as well as decreasing the corrosion resistance, due to the higher chromium carbides produced during the deep cryogenic heat treatment.

AISI 304L austenitic stainless steel with different grain sizes of 0.5 -12 μm was obtained through the martensitic process. Corrosion behavior of different samples was investigated in a 0.5M HCl solution using open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy tests. Also, the correlation between the grain size and pitting corrosion resistance was assessed by cyclic polarization experiments and immersion tests combined with optical microscopy. The potentiodynamic polarization results demonstrated that grain refinement had little influence on the corrosion potential and corrosion current density. However, cyclic polarization tests showed that the ultrafine grained steel (500 nm grain size) exhibited superior pitting resistance, as compared to the steel with the larger grain size (1- 12 μm). This behavior was confirmed by immersion tests in the 0.5M HCl for 48 hours, thereby showing that the size and the number of pits were decreased by increasing the grain size. The electrochemical impedance spectroscopy results also revealed that grain refinement enhanced the stability of the passive film of 304L stainless steel.

The aim of conducting this research was to evaluate the viscosity change in the continuous casting of steel mold powders by altering their chemical compositions, using hot stage microscope analysis.4 low-fluorine samples containing such compositions as MnO, Fe2O3, Li2O, TiO2 and ZnO, as well as another fluorine-free sample containing a combination of Fe2O3 and TiO2, were prepared in this research. The viscosity of the reference powder (the mold powder applied in high-speed continuous casting in steel industry), as well as the viscosity of the above-mentioned samples, was evaluated using hot stage microscope analysis. The results of hot stage microscope analysis revealed that the viscosity of the reference powder was similar to that of low-fluorine and fluorine-free samples. Finally, a fluorine-free sample containing a combination of Fe2O3 and TiO2 was introduced as an optimized composition which could be a substitute for the currently-used mold powder applied in the continuous casting of steel with high speed, considering its similar viscosity to be that of the reference powder

Low stacking fault energy face centered cubic (FCC) materials contain characteristic defect structures. Stacking fault tetrahedral are one of those rare structures that occur under special experimental conditions. For the first time, stacking fault tetrahedral were observed in Fe-30Mn-3Al-3Si twinning induced plasticity (TWIP) steel. Their presence resulted from a quenching heat treatment.