Papers by Keyword: Micro-Alloyed Steel

Abstract: The present research focuses on the hot forging of 38MnSiVS5 micro-alloyed steel, examining the impact of key process variables, such as working temperature, deformation percentage and rate of cooling on mechanical properties, notably the ultimate tensile strength and impact energy. To optimize the process, Taguchi's parametric design, utilizing an orthogonal array in combination with grey relational analysis and fuzzy logic analysis, has been implemented. By applying grey-fuzzy logic analysis, the optimization of complex multiple responses is streamlined into a single grey-fuzzy reasoning grade. The study employs the Grey fuzzy logic method to concurrently optimize both responses. The grey-fuzzy reasoning grade serves as a performance index, aiding in the determination of the optimal process parameter settings for both the ultimate tensile strength and impact energy responses simultaneously.

Abstract: Normalizing is an effective heat treatment in improving the microstructure and developing the mechanical properties of micro-alloyed steel. The normalizing parameters such as temperature and holding time are the main keys to microstructure and mechanical properties controlling. Therefore, obtaining an optimum combination of mechanical properties must be subjected to an ideal combination of these parameters. Furthermore, adjusting the optimum normalizing parameters must be considered for every chemical composition depending on the critical transformation temperatures. In this work, four micro-alloyed steel alloys containing V (0.008-0.1wt %) and Ti (0.002-0.072) were held on different normalizing temperatures for 30 minutes. The first holding temperature was carried out just above the Ac3 temperature and the second was carried out above the Ac3 by 100°C (Ac3+100°C). With the controlled normalizing condition, V-Ti-micro-alloyed steel alloy has produced an ultra-fine structure of grain size 2.2 microns and combined high strength of 725 MPa YS, 1058 MPa UTS and good ductility of 20%.

Abstract: Current study deals with the microstructural characterization of five different plates of steel with carbon concentration ranging from ultra-low to moderately high. Phase analysis was carried out using XRD technique. The XRD results were analyzed through Rietveld refinement and Williamson Hall plots. Rietveld refinement was carried out to understand the effect of carbon concentration on the lattice parameters of the above steel samples in as-received condition and also after deformation under uni-axial tensile loading. Lattice parameters obtained from refinement showed the strong dependence on carbon concentration of the given steels. But the failed specimens showed somewhat complex results as Spheroidized high carbon steel, Low carbon steel and IF steel showed an increase in lattice parameter whereas Medium carbon steel and Microalloyed steel showed a contraction in lattice parameter. Williamson Hall plot gave the crystallite size, microstrain and dislocation density in the steels. For IF and Microalloyed steels the dislocation density in the material is found to be higher after deformation whereas dislocation density decreased in Spheroidized high carbon steel, Medium carbon steel and Low carbon steel.

Abstract: Three medium carbon Cr-Mn-Mo structural steels with different content of alloying elements were studied. The austenite transformation during continuous cooling was investigated using dilatometer and metallographic analysis. The CCT diagrams were plotted showing the effect of the increased alloying elements content and B and Nb micro-alloying on the hardenability of the studied steels. The hardness dependences on the cooling rate were obtained.

Abstract: Recrystallization is a major means for controlling the grain size of steel during hot deformation. Usually, small grain sizes deliver superior mechanical properties. To aid the grain size controlling effect of recrystallization, small precipitates of carbo-nitride particles can be utilized to hinder the movement of grain boundaries. Interestingly, these particles are not only effective during grain growth, but also during recrystallization. In the present work, a recently developed state-parameter based model is introduced that is capable of describing both, the individual processes of static recrystallization, dynamic and static recovery and precipitation as well as the mutual interaction of these mechanisms in the course of elevated temperature processing. The evolution of state parameters within the model is discussed and the simulation results are compared to experimental information. Within our approach, a vast amount of experimental data for microalloyed steel is reproduced on basis of a single set of input parameters

Abstract: In the automotive industry, grinding of round diameters is an important process, to achieve desired tolerances and finish. While the effect of grinding parameters namely cutting velocity, work velocity and infeed (or downfeed) on grinding forces and surface integrity (that includes finish, residual stresses and subsurface damage) have been studied extensively in the literature, the effect on material removal rate (MRR) and dimensional accuracies has been given very limited attention. This work involves the analysis of effect of grinding parameters namely cutting velocity, work speed and infeed on MRR, surface finish (R_a) and dimensional accuracies by performing experiments on micro-alloyed steel bars. A series of cylindrical plunge grinding experiments were performed on round bar using CBN grinding wheel. The results show that, to achieve minimum surface roughness (R_a), infeed is the most influencing input parameter, whereas to achieve maximum MRR, work speed influences the most. An increase in infeed and a reduction in cutting velocity and work speed, leads to an increase in finish on ground surface. Also, an increase in infeed and cutting velocity, and a reduction in work speed results into an increase in MRR. The results show that, dimensional accuracies such as diameter, ovality and taper of ground surfaces have not been affected significantly.

Abstract: Currently, the automotive industry used sheets of different qualities. The most common include IF (inter Interstitial Free) steel and alloyed steel. Use the sheet quality depends on the point of application in the production car. Testing and product testing is a standard part of the process of innovation and production itself. Testing of automotive steels under dynamic conditions is increasingly important. Changing the hardness HV 1 was performed on the fractured bars on the static and dynamic loading conditions. Tests were made on steel IF and S 460.

Abstract: In the production process of sheet metal parts, oil is widely used as lubricant, not only in sheet metal forming but also in shearing and blanking. Due to environment, health and cost reasons, the absence of lubricants is an aim for future production as it has initiated for machining in the last years. For lubricant-free shearing, it has to be known if there is an influence on the process itself when using oil or not. To find this out, experiments are carried out with a small testing device installed in a tensile testing machine and a blanking tool installed in a servo press. With the small device it is possible to make a piercing process with a circle punch of 16 mm diameter. The blanking tool produces a larger cut part with different holes and open cuts. Without lubricant, there is no difference in the maximum shearing force for the small device while the stripping force is higher and the cut edge zones differs slightly. Using oil or not has a small effect on the force using the blanking tool.

Abstract: Abstract. The main aim of this paper is to assess the quality of newly produced, alloyed flux-cored wire with increased thickness of the steel cover compared to traditional according to AWS A5.29 standard, alloyed with Ni and Mo, and designed for welding of fine-grained HSLA steel. Flux-cored wire was produced on a pilot production line that allows calibration of steel band of higher thickness and production of flux-cored wire. Quality assessment of the alloyed flux-cored wire was based on the analysis of the results of tests of mechanical properties and microstructure mainly of the weld metal. Variation of chemical composition and microstructure were analyzed along weld metal (for each welding pass) and heat affected zone (HAZ) using SEM and EDS. Based on the results of the quality assessment of flux-cored wire, the conclusions about the feasibility of industrial application of selected metallurgical grade of flux-cored wire designed for welding of fine-grain HSLA steel were presented.

Abstract: This paper analyzes the effect of the punch-die gap on blanked edge quality in fine blanking. The objective is to determine basic mechanical properties of galvanized multiphase steel sheets with a thickness of 0.75, 0.80 and 0.85 mm by a single-axis tensile test, determine the effect of the punch-die gap on plastic phase depth [h_v] expressed as the relation of h_v to a₀, and, finally, determine the effect of material properties of blanked sheet metal on blanked edge quality expressed as the relation of h_v to a₀.