• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.228-232
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• 2001

Fatigue strength, electrical conductivity and stress-corrosion-cracking resistance are considered as important factors at aircraft Al alloys, therefore Al7050 alloy has been developed to improve such properties. However, hammer-forged Al7050 parts showed the undesirable structures such as severe local grain coarsening and inhomogeneous material flow, resulted in the degraded mechanical properties. In this paper, process conditions are investigated for elimination of the grain coarsening and improved material flow during forging process by both of experiments and FEM analysis. Particular interest has been given to understand role of preform shape on the grain coarsening behavior and magnitude of the hammer forging load The use of preform has been beneficial for reduction of the forging load and elimination of the grain coarsening. However, in the cases of as received bar and the round bar, which was machined to 2.5mm thickness in surface layer, some degree of local grain coarsening behavior has been observed. The optimized preform shape could be properly designed by applying the FEM simulation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.216-220
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• 2003

Most important for meaningful forging simulation is the determination of correct process parameters. In addition a check and a compensation of the data base after the comparison between experiments and the computation of the developed process is necessary. The existence of a systematic process parameter data bank for special kinds of forming process in combination with forging specific simulation lifts the value of the products. Finite volume method is applied to simulate the hot forging process to investigate the defects for the automobile product. Three typical forging processes have been investigated; Extrusion by hydrolic press, Upsetting by crank press and Inclined upsetting by hammer press. Simulated result has compared with the experiment and provided a direction to improve the process.

• Journal of Conservation Science
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• v.34 no.2
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• pp.87-96
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• 2018

This study analyzed the influence of folding time on the forge welded bar and hammer scale produced using the traditional refining and forge welding reproduction experiment. In the case of the forge welded bar, increasing the forging time decreased the percentage of impurities and porosity from 26.09% to 1.8%. Additionally, the hardness increased by an average of 36.88 HV. In other words, the microstructure gradually became more precise. For the hammer scale, the amount of T Fe increased with forging time. X-ray diffraction analysis revealed the presence of quartz, fayalite, $w{\ddot{u}stite$, and magnetite. The amount of quartz decreased as the forging time increased. In addition, as the forging time increased, the granular $w{\ddot{u}stite$ changed into a cohesive, long, white band. The results provide information on the characteristics of the forge welded bar and hammer scale produced in the refining and forging process. This information can be used as technical data for ancient steel making processes as well as for future technological systems.

• Journal of Conservation Science
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• v.37 no.6
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• pp.738-747
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• 2021

This study attempted to investigate the metallurgical characteristic through material scientific analysis of hammer scale produced as a direct smelting method restoration experiment for each raw material of iron. To this end, four hammer scale groups were set up, respectively, by experimenting with Gyeongju-Gampo Iron sand and Yangyang Iron ore. For the analysis, principal component analysis, compound analysis, microstructure observation, and chemical composition were confirmed. As a result of principal component analysis, as forging and refining progressed, the content of Fe increased and the content of non-metallic objects decreased. As a result of compound analysis, iron oxide-based compounds were identified. As a result of confirming microstructure and chemical composition, Wüstite and Fayalite were observed overall, and agglomerated Wüstite were observed in some. Magnetite on shape of polygon and pillar was observed. In addition, it was confirmed that internal defects, impurities, and non-metallic interventions gradually decreased. In the future, it is necessary to investigate the metallurgical characteristic through material scientific analysis of hammer scale produced through restoration experiments using various raw material of iron, and compare them with those excavated from Iron manufacture ruins.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.47-50
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• 2003

Grain size of the $\alpha$ phase is computed during isothermal forging of the TC6 aerofoil blade, by combining FE with the Yada's model of grain size. The present results illustrate the grain size and distribution of the $\alpha$ phase during isothermal forging of the TC6 aerofoil blade' in detail. The computed results show that height reduction, deformation temperature, hammer velocity and friction have significant effect on distribution of the equivalent strain, and that height reduction, deformation temperature and hammer velocity have more significant effect on grain size of the $\alpha$ phase than friction between billet and die.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.39-45
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• 2012

In this paper, process conditions are investigated for elimination of the grain coarsening and improved material flow during forging process by both of experiments and FEM analysis. Particular interest has been given to understand role of preform shape on the grain coarsening behavior and magnitude of the hammer forging load. As the results of FEM simulation by using DEFORM-3D, the simulated forging loads were 2,200ton in the case of a machined bar which is machined from 65mm to 60mm diameter, and below 1,900ton in the case of machined preform, respectively. The use of preform has been beneficial for reduction of the forging load and elimination of the grain coarsening. However, in the case of as received bar and the round bar, which was machined to 2.5mm thickness in surface layer, some degree of local grain coarsening behavior has been observed. The optimized preform shape could be properly designed by applying the FEM simulation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.154-158
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• 2002

The mechanical properties of Al 6061 excluded bar were deformed in high temperature with the variable deformation conditions and characterized by the tensile test. Three types of different strain rate were experimentally performed by using hydraulic press, crank press and hammer and two types of the nominal strain 0.5 and 0.8 were achieved. To decide optimum forging process, the relationship among the strain rate, strain and mechanical properties was explained by analyzing the microstructures of the forged and heat heated parts. The strength was deeply related with the strain rate due to the dynamic recrystallization (DRX) in hot forging, and the best forging condition was presented in Al 6061 alloy.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.223-226
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• 1995

A three-dimensional elastic-plastic finite element analysis using the explicit time integration method has been performed for the characterization of theimpact forming machines. The block upsetting using a forging hammer has been analyzed. The effects of machine type, work capacity of equipment and the mass ratio in an anvil-type hammer have been studied through the analysis.

• Journal of Power System Engineering
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• v.16 no.5
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• pp.70-75
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• 2012

In mechanical industries, forging is one of the basic process. But comparing the other developed industries, forging industries can not reach at the level of that development. In forging industries, the quality of the products totally depends on the skills of workers and also the precision of the equipments. Particularly because the open die forging industry is unable to deviate from the past method of production and all works are manually progressed, the operator is always exposed to the danger. In the regard some additional device has been made especially. Thus, in this research, by using the forklift as the means for the manipulation of the development object system, it tries to be comprised the process automation. After than it is fitted with the forklift for safe and easy handling of jobs and products during open die forging process. First of all, development system mold has been assembled to the system, after than it is assembled with forklift. This development system has been applied for handling of large scale products more than 300kg, and the satisfactory result with uniform quality of the products have been achieved due to this mechanical setup.

• Journal of Conservation Science
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• v.38 no.1
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• pp.33-44
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• 2022

The study, iron-making process was examined through the scientific analysis of six by-products that were obtained during iron making at the Songdu-ri site in Jincheon. The total Fe content of the slags excavated from the Songdu-ri site was 36.29-54.61 wt%, whereas the deoxidation agent was 26.48-49.08 wt%. The compound analysis result indicated that fayalite and wüstite are the main compounds in slag. Furthermore, the microstructure analysis result confirmed the presence of fayalite and wüstite in the slag. It can be inferred from the flat shape in a bright matrix structure of the hammer scales that forging was performed in the latter stage. The Raman micro-spectroscopy results confirmed that the surface was hematite (Fe₂O₄), middle layer was magnetite (Fe₃O₄), and inner layer was wüstite (FeO). The presence of smelting and smithing slags, spheroid hammer scales, and flake hammer scales suggests that at the Songdu-ri site, iron-making process is carried out by division of labor into producing iron bloom through direct smelting, refining and forge welding, and ingot production.