Advanced Materials Research Vols. 690-693

Abstract: The effects of a 2 T pulsed magnetic field primary annealing process on microstructure evolution and grain boundary characteristics in two-stage cold-rolled silicon steel were examined. Pulsed magnetic annealing increased grain size through the application of relatively smaller intensity of magnetic fields (2 T), compared to steady magnetic annealing. The effect of increasing grain size may be attributed to the magnetic acceleration effect of boundary motion under magnetic pulse conditions. Pulsed magnetic annealing may serve to enhance the relative intensity of the {111} component and decrease the frequency of low-angle misorientations. Repeated magnetostriction induced by pulsed magnetic field applications may accelerate overall dislocation motion. These findings suggest that pulsed magnetic fields require relatively lower intensities than steady magnetic fields to achieve superior results, providing a potentially viable alternative for industrial annealing processes for electrical steels.

Abstract: The effect of electric current pulse (ECP) on the solidification structure of hypereutectic high chromium cast iron was studied. The orthogonal array L9 was used to determine the effect of three process parameters of ECP, which were electric voltage, pulse frequency, pulse width. According to the experimental results, the solidification structure of hypereutectic high chromium cast iron was modified from large grains to finer grains with equiaxed crystals, by allowing the ECP to act on liquid.

Abstract: In view of the equipment and process conditions of some enterprise, simulate its production process through the laboratory to do systematic experimental research, to the recrystallization law of steel austenitic contained the niobium Q345. The purpose is to explore the recrystallization behavior of this type of steel austenitic, as is expected to lay the foundation for formulation controlled rolling and cooling process parameters which are suitable for this kinds of steel.

Abstract: In the traditional Norton-Bailey model, the stress exponent is a constant value when the temperature keeps constant, But for some materials, this situation can’t be suitable. Based on the analysis of the experimental data, a secondary creep constitutive model which can be used in the stress exponent changing situation has been proposed. By introducing Kachanov-Rabotnov damage equation, the modified creep model has been established for P92 steel at 610°C and 670°C, which can describe the second and tertiary stage. And the method to determine creep parameters of tertiary stage has been derived. The new model was embedded into ANSYS interface program, and used for calculating the creep life of P92 steel. The results show that the model is in agreement with the experimental data.

Abstract: This paper present that experimental research on the fatigue behavior of beam with Q345c steel corrugated webs. There are four test specimens with different structural feature will be tested in three-point bending to load by Shinmadzu 4890 fatigue testing machine. Moreover, the finite-element analysis will be used to simulate the fatigue behavior of common beam with corrugated steel web. Weld will be our focus on importance object.

Abstract: The method of numerical simulation and experiment were adopted to research the molten steel flow with electromagnetic stirring(EMS). Woods metal was used to simulate molten steel flow by changing electromagnetic parameters in laboratory.The results of numerical simulation was verified. The results showed that the velocity of round mold is larger than rectangle in same EMS conditions. In order to play a fully stirring ,the EMS current and frequencies shouldn't too high in round mold, but the current is as big as possible in rectangle mold.

Abstract: High nitrogen Fe-18Cr-12Mn-3Mo-xN austenitic stainless steels were prepared by mechanical alloying and powder metallurgical pressing-sintering techniques. The microstructures, nitrogen contents and sintering properties of the milled powders and sintered bodies had been also investigated. The results show that high nitrogen and nearly spherical composite powders with good compressibility can be obtained by high-energy vibration ball milling and high temperature nitriding. It is also found that the sintering temperature has a significant effect on the density and the nitrogen content of sintered specimens, and the optimal sintering temperature are determined to be 1250°C, at which a favorable combination of the relative density as high as 97.1% and the final nitrogen content of 0.79wt% in sintered specimens can be obtained. The sintered bodies mainly consist of γ-austenite, α-ferrite and the lamellar Cr₂N phase. After solution-annealing at 1150°C for 1.5h followed by water-quenching, high nitrogen austenitic stainless steels reveal a fully austenitic structure.

Abstract: In this paper, the influence of finish rolling temperature during hot rolling on microstructure and mechanical properties of ferritic stainless steel containing vanadium was investigated. It showed that with the rolling temperature increasing, the tensile strength and hardness value fell down, while the value of ductility rising and less precipitates appearing. If the finish rolling temperature was set too high, the grain would get coarsened and the α-fiber get strengthened, which had an adverse effect on the formability and wrinkle resistance of the production sheet. 850°C was a reasonable finish rolling temperature.

Abstract: A high deformation pipeline steel X70 with low yield ratio of 74% was achieved has been processed on an industrial scale. The impact toughness of the investigated steel is 388.3 J/cm2 at -20°C and the shear area is 97% in drop weight tear test at -15°C. The microstructure of the steel constisted of primarily acicular ferrite, polygonal ferrite and a small proportion of scattered martensite-austenite constituents. The high deformation pipeline steel had low yield ratio and good toughness, which was attributed to high Nb microalloying and rapid cooling in the TMCP process.

Abstract: This study concerned the influence of the material strength, ductility and impact energy and the relationship of the broken section profile vs. ductile transition brittle where the steel material was treated under different tempering temperature and hardness. Generally after the steel materials, 10B35 coil wire materials which was generally applied to form screws, was treated by quenching and tempering, its hardness ranged from HRC30 to HRC45. The results showed that the elongation rate beyond 20.4% would be proportional to the impact energy with linear relation, but with reverse proportion to the hardness value. The brittle-tough point of the hardness was set around HRC37 after heat treatment in order to balance the strength and the toughness. In addition, the coil wire materials were analyzed from broken section materials showing good toughness; this represented that the area of the cross section radiation layer due to ductile fracture would largely increase. On the contrary, the wire material test fragment with bad toughness represented that the area of the shear layer due to brittle fracture would largely increase as well. As to that material, if its hardness was greater than or equal to HRC37, that material would have an excellent turning danger from transition. At the same time, when the tempering temperature of the wire steel material was set under 4600C and its corresponding central hardness was about HRC37, the distance between two cementite phase layers suddenly increased. This result leaded to the reason why the wire material test fragment was turned into brittleness from ductility. Therefore, when the fastener was manufactured under tempering treatment, avoiding the tempering brittleness temperature range was necessary.