Byung-Chul Lim

Study of the welding monitor and characteristics according to a change in Gas mixture by FCAW

In this study, the effect of varying the mixture gas during FCA welding was studied for an Atos 60 test piece. To examine the characteristics of welding, the weldability of the material was checked before welding and online monitoring was performed to examine the mechanical properties after welding. The mixture Ar 80% + 20% at low speed gave very elegant beads with very little spatter. 100% gave rise to high spatter generation. For Ar 80% + 20%, the low current region due to the normal short circuits created spatter, which was more than double for 100% . This peak distribution occurred due to the instability of the arc. The tensile test result for Ar 80% + 20%, Ar 90%+ 10% and 100% at 511MPa, 507MPa, and 469MPa showed that the yield strength was improved by 8.1 and 8.9% for 80%+ 20% and Ar 90%+ 10%, respectively, compared to 100% . The tensile test result at 622MPa, 609MPa, and 581MPa showed that the yield strength was improved by 7.0% for both the mixture gas compared to 100% .

Heat Flow Analysis of Inner Groove Tube for Latent Heat Exchanger in Condensing Gas Boiler

Abstract These days, household condensing gas boilers are an obligatory trend. The use of environmentally-friendlyboilers that emit less pollutant, such as CO and NOx, are strongly recommended. In this paper, heat flow analysisof the additional inner groove in the tube of the secondary latent heat exchanger was studied to increase the efficiency. A 20% difference in the heat transfer area was obtained with the addition of an inner grove, which showedan increase in the amount of heat transferred. This was confirmed using three-dimensional numerical analysis. Withthe addition of an inner groove, the exit temperature increased by 1 ℃ . This increase in exit temperature was considered to be a substantial increase in the efficiency of the condensing gas boiler. Key Words : Condensing Gas Boiler, Latent Heat Exchanger, Inner Groove, Gas Boiler Efficiency, Heat Flow 이 논문은 충남테크노파크의 2013년도 지역특화산업육성사업의 지원을 받아 수행하였으며 이에 감사드립니다. * Corresponding Author : Sang-Heup Park(Kongju National Univ.)Tel: +82-10-8380-2400 email: weldpark@kongju.ac.krReceived March 31, 2013 Revised (1st April 29, 2014, 2nd May 9, 2014, 3rd May 16, 2014, 4th May 26, 2014) Accepted July 10, 2014

A Study on the Stress and Deformation of Vertical Steel grating

The grating is the main purpose of drainage in civil engineering, architecture. This study examined the change and stress distribution by simulating three models of Vertical type grating structures that reduced the resistibility in respect of velocity rather than horizontal type grating and to design a grating with the optimal grating gap. The vertical type and horizontal type grating were compared in terms of the maximum stress and strain to identify the better product.

A Process Optimization of HVOF on ALBC3 by Experiments Design

Abstract Erosion and abrasion caused by cavitation damage occur in fluid equipment, such as ships or impellers. Similarly, the equipment damage from noise and vibration can shorten its life. This study analyzed the importance of the parameter characteristics of the process optimization of HVOF (High Velocity Oxygen Fuel spraying), which is generally used in a variety of industries for enhancing the resistibility from the cavitation phenomenon. The surfaceof the ALBC3 substrate was coated with an amorphous powder as a filler metal according to the experimental designusing the Taguchi method, and then the characteristics with each parameter were analyzed using a porosity measurement test. The optimal process conditions was a combustion pressure of 80psi, coating distance of 270mm,gun speed of 200mm/s, and powder feed rate of 25g/min as a result of the HVOF coating by applying the experimental design. The combustion pressure, coating distance and powder feed rate were more than 25% and indicated a similar contribution rate, but the contribution rate of the gun speed was 19%, which was slightly less thanthe others. The contribution rate with each parameter was only slightly significant. On the other hand, all four parameters were found to be important in the contribution rate aspects of the HVOF coating process.

Failure Behavior of Laser Cladding Layer used by Fe-based Bulk Metallic Glass

In this study, Fe-based bulk amorphous alloy powder manufactured using gas atomization fabrication was used for laser welding. the fracture behavior of welding layer were analyzed. Tensile test results show that the destruction occurred immediately after the elastic deformation, After plastic deformation of the substrate, the destruction occurred. The actual maximum tensile strength of the welding layer and the substrate are 959.9MPa and 220.4MPa. welding layer were each 485.5±21 and 197.4±21 to the substrate and the actual microhardness, The welding layer has very high hardness. The welding layer showed a very weak fine acicular structure. The base material was shown in the micro structure appear a coarse grain. SEM observations of the fracture after the tensile test. Fracture morphology of the base metal and the welding layer showed ductile fracture and brittle fracture,

A study on the hard surfacing Characteristics of STS420J2 by using Diode laser

In this study, a variety of industrial gears, shafts, chains, rollers, mold, etc. are widely used inautomotive steel carbon steel for machine structural SM45C typical material used for the experiments. In order to cure the surface of the test piece after the rough grinding and fine grinding was performed in order polishing. Perform the surface hardening of SM45C lacal area by using a diode laser. The output of the laser diode and the feed rate to the process variable. Micro-hardness testing, microstructure testing, scanning electron microscope testing(SEM), the heat input to the analysis. After analyzing the experiment to compare the mechanical properties of the material. When using a diode laser to assess the soundness of the surface hardening. Accordingly, the process for deriving the optimum demonstrate the feasibility.