Papers by Keyword: Hypoeutectoid Steel

Abstract: The present paper deals with the influence of the duration of isothermal spheroidization annealing on the evolution of pearlite bands in various initial states. In this study, two initial conditions of the steel 16MnCrS5 are considered: a) industrially hot-rolled pearlite structures in their ferritic matrix and b) a specifically adjusted microstructure in the lab condition. Based on the experimental investigations and quantitative microstructural analyses, an empirical model for the prediction of pearlite banding within a broad range of annealing durations could be derived. Both, experiment and model, agree that pronounced pearlite bands in the initial state almost disappear after 25 h of spheroidization annealing. On the other hand, a marginal degree of pearlite banding in the initial state increases slightly during annealing. This fact could be explained by inhomogeneous cementite formation inside and outside the primary segregation regions of manganese.

Abstract: Three different Fe-C alloys were prepared in vacuum using the arc melting method: hypereutectoid (1.4% C), eutectoid (0.76% C) and hypoeutectoid (0.4% C). Unlike commercial steels, which they always contain Mn and other impurities, our samples were prepared by using high quality powders (99.999 wt.%). The samples were heat-treated and then observed with optical and scanning electronic microscopy (Zeiss EVO MA10). Selected samples were tested by microidentation (microhardness test). After isothermal transformation at 350 °C fine bainite nanostructures were observed in the hypoeutectoid sample, the mean size of which was found to be 50 nm. With the eutectoid sample, following different heat treatment procedures different micro-and nanostructures were measured: pearlite lamellar spacing, spheroidized cementite particles, and martensite needles, whose mean size is 145 nm, 290 nm and 200 nm respectively. The nanostructure of hypereutectoid sample after isothermal transformation at 650 °C, reveals the eutectoid and proeutectoid cementite lamellas with a mean spacing of 390 nm. X-ray diffraction pattern of eutectoid sample indicated the existence of cementite (Fe₃C) content which is also confirmed by carbon mapping of pearlite colonies performed with Energy Dispersive X-ray Spectroscopy. The Vickers hardness of the samples compares well to the one of corresponding commercial steels.

Abstract: The results of a microstructure, energy dispersive X-ray spectroscopy (EDS) analysis and hardness investigations of the hypoeutectoid steels with 1% Ni, imitating by its chemical composition toughening steels, are presented in the paper. According to PN-EN 10027 standard this steel should have a symbol 37NiMo4-3.The kinetic of phase transformation of undercooled austenite of investigated steel was presented on CCT diagram (continuous cooling transformation). The CCT diagram of tested steel is characterized in that the curves of beginning of the diffusion transitions form a letter "C" and are not separated from bainitic transformation by the stability range of the undercooled austenite.The EDS analysis performed for the selected cooling rates did not reveal any changes in the distribution of alloying elements of hypoeutectoid 37NiMo4-3 steel. However, these studies, from the point of view of the effect of alloying elements (acting jointly) are only the preliminary assessment analysis (beginning) of the impact of the chemical composition gradient in micro-scale in iron-based alloys.

Abstract: Cavitation is an important factor in many areas of science and engineering, including acoustics, chemistry and hydraulics. In this paper the authors analyze the structural analysis of cavitation damages in two steel. The cavitation erosion tests were carried out in a magnetostrictive facility, in Timisoara Hydraulic Machinery Laboratory, in according with ASTM G32-85, using as cavitant liquid drink water at 20 10C. After quantitative and qualitative investigations structural features were put in evidence on experimental steel

Abstract: The fracture surfaces of SAE-1018 steel tension and impact test specimens with different grain sizes are analyzed in order to explore the possible relations between the microstructure and the self-affine fracture surface parameters such as the roughness exponent, ζ, and the correlation length, ξ. The topography of the fracture surfaces was observed and quantified by means of scanning electron microscopy, atomic force microscopy, optical microscopy and optical digitizer. It is confirmed that the fracture surfaces exhibit a self-affine behavior extending over six decades of length scale, from nanometers up to a few millimeters. The roughness exponent exhibits a value of ζ∼0.82 for all the cases regardless of the microstructural condition.