فهرست مطالب

Iron and steel society of Iran - Volume:5 Issue: 2, Summer and Autumn 2008

International Journal of iron and steel society of Iran
Volume:5 Issue: 2, Summer and Autumn 2008

  • 46 صفحه،
  • تاریخ انتشار: 1388/07/25
  • تعداد عناوین: 6
|
  • M.Alizadeh, S.A.Jenabali Jahromi Page 1
    In the present work, a meshless method called Finite Point Method (FPM) is developed to simulate the solidification process of a continuously cast steel bloom in both primary and secondary cooling regions. The method is based on the use of a weighted least-square interpolation procedure. A transverse slice of the bloom moving at casting speed is considered as the computational domain and two dimensional heat transfer equations are solved in the computational domain. The present FPM-thermal analysis is coupled with the microsegregation model and used to investigate the capability of the FPM for use in hot tearing study. This hypothesis is verified by comparing surface temperatures simulated by both FPM (the method proposed in this study) and finite volume method (FVM) (the conventional method). Also the simulated surface temperatures are compared with thermography measurements. The results reveal that the proposed FPM can be used successfully both for the simulation of steel bloom to determine its temperature field and for hot tearing study.
  • S.M.H.Modarresi, M.Kashefi, J.Vahdati Khaki Page 8
    Simulation of metallurgical processes has been the subject of intense research due to the reduced number of experiments required for controlling the process as well as time and energy savings it allows. In gas carburizing of steel parts, the amount of carbon at the surface of carburized parts is the most important specification of the process in terms of achieving the desired metallurgical properties. In the present research, the gaseous reactions in an endothermic gas generator have been simulated using MATLAB software where the equilibrium surface carbon percentage was obtained by solving the equilibrium constant equations. The effects such variables as air-to-fuel ratio in the endothermic gas generator, carburizing temperature, pressure inside the furnace, relative humidity, and ambient temperature have been investigated. Besides, working conditions of the furnace have been investigated to obtain the desired carbon potential. Finally, the results of the simulation have been compared with experimental results obtained from a gas carburizingfurnace.
  • A.R.Ebrahimi, A.Abyazi, S.M.Abbasi Page 14
    Thermomechanical control process steel produced by rolling has a significant anisotropy. The elongated grains and inclusions formed during hot rolling of ferrite and low carbon HSLA steels directly influence the anisotropy of the steel’s mechanical properties as a result of microstructural anisotropy. The present research deals with this anisotropy, and particular attention has been paid to the tensile and Charpy V-notched behavior and microscopic properties. The mechanical response of a 25 mm thick rolled plate of S355N steel was characterized. The results of Charpy tests of V-notched specimens of the through-thickness direction were found o be considerably temperature-dependent and also to vary in the longitudinal and the transverse directions. arked anisotropy effects were observed, with the through-thickness orientation exhibiting a tensile response ower than that of the longitudinal and transverse ones. These experimental findings were ationalized using the orrelation holding among inclusion distribution, reduction area ercent, nd banding of the microstructure.
  • M.Eskandari, A.Najafizadeh, A.Kermanpur, M.Karimi Page 21
    In this work, effects of homogenization time of 3 to 13 h at 1200 °C on the grain refinement of as-cast AISI 301 stainless steel after different hot rolling conditions were investigated. The results showed that the minimum grain size of 16±7 μm was achieved when homogenization took place at 1200 °C for 9 h followed by hot rolling at temperature range of 1000–1200 °C with strain of 0.8 and strain rate of 1.2 s-1 and annealing at 1050 °C for 3 min. Effect of Nb element on the retardation of recrystallization was pronounced. It seems that there is an optimum solute segregation below which retardation and above which grain growth of recrystallized grains is dominant. It was also found that this optimum homogenization condition was dependent upon the hot rolling parameters; higher the strain and strain rate resulted in lower homogenizing time at 1200 °C.
  • S.R.Hosseini, F.Ashrafizadeh Page 29
    Diffusion of nitrogen in plasma nitrided iron and structural evolution during the nitriding process were evaluated by several characterization techniques including optical microscopy (OM), microhardness depth profiling (HDP), scanning electron microscopy (SEM), x-ray diffraction (XRD), glow discharge optical emission spectroscopy (GDOES), and secondary ion mass spectroscopy (SIMS). Plasma nitriding was carried out on high purity iron substrate at a temperature of 550oC in an atmosphere of 75%H2-25%N2. Case depth, thickness of the compound layer, micro-hardness profile, nitrogen depth profile, and characteristics of intermediate nitrides including epsilon, gamma prime, and Fe16N2 were studied. The results of characterization of plasma nitrided iron indicated a good agreement with experimental findings; thus, the techniques confirmed one another. For accurate measurement of nitrogen within the diffusion zone, where concentration was below 0.1wt%, secondary ion mass spectroscopy technique was used. The extent of nitrogen diffusion detected by secondary ion mass spectroscopy in this work was greater than 1800 μm; a value which is not reported in the iterature.
  • S.M.Siadati, A.Monshi, E.Karamian, S.Alikhani, A.Salehian Page 36
    Plasters are produced from a light refractory material, mainly MgO (M.P. 2800ºC), a binder, and a void forming substance for insulating purposes. Different oxides from the slag penetrate into these voids and provide low melting-point phases such as rhodonite (MnSiO3) (1290ºC), tephorite (Mn2SiO4) (1345ºC), merwinite (Ca3MgSi2O8) (1575ºC), monticellite (CaMgSiO4) (1490ºC), and enstatite (MgSiO3) (1560ºC). XRF, XRD, and microanalysis by EDX were used to investigate and evaluate the penetration of different oxides to distances below the slag-plaster interface. Results show that SiO2 and MnO are the most deteriorating while alumina and calcite are the least harmful. It is suggested that rice husk cover on melt, which is rich in SiO2, be replaced with insulating powders rich in Al2O3 and CaO, and that slag basicity be increased in order to decrease the slag line hot corrosion of plaster.