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Grit와 Air의 혼합비 최적화를 통한 블라스팅 효율 향상
배한진(Han-Jin Bae),백재진(Jae-Jin Baek),김을현(Eul-Hyun Kim),정몽규(Mong-Ku Chung),신칠석(Chil-Seok Shin),백광기(Kwang-Ki Baek) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
Achieving the maximum blasting efficiency with minimum abrasive consumption is a critical concern in surface preparation stage of shipbuilding and offshore industry. Increasing the abrasive flow rate beyond the optimum point results in a major reduction in productivity even though the amount of abrasive used is larger. So, this study is intend to find out the optimum abrasive-to-air mixing ratio which can make a significant improvement in blasting efficiency and remarkably reduce the amount of abrasive used. From the test results, it can be identified that as the abrasive feeding rate is increased linearly, blasting efficiency is increased to a maximum point and then gradually decreased in the form of a bell-shaped.
AA 7019 알루미늄 합금 용접부의 기계적 성질 및 응력부식귀열 저항성에 관한 연구
김희진,백광기 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.11
To study the weldability of the newly developed AA7019 aluminum alloy, both mechanical and corrosion resistant properties of its Gas Metal Arc (GMA) weldment were evaluated. GMA butt welds with A5356 filler metal were made in the flat and vertical positions of 30㎜ thick plates. The results of mechanical tests performed on test coupons, which were removed from the welded plates (natural1y aged at least 30 days), were correlated directly with softening and subsequent recovery of the strength in the HAZ(Heat Affected Zone) whereas the strength of the weld metal was not significantly affected The susceptibility to the corrosion and stress-corrosion cracking in an aqueous salt solution (3.5wt.% NaCl) was also evaluated in each weldment. A combination of susceptible microstructure and galvanic coupling was determined as the cause of SCC(Stress-Corrosion Cracking) failure, which occurs preferentially in the HAZ adjacent to the weld bead. Results of this study suggest that development of new filler metals higher in s rength and avoiding severe corrosion environment be considered for the optimum application of GMAW of AA7019 alloy.
임계확산성 수소의 농도측정에 의한 수소유기귀열 (水素誘起龜裂) 의 감수성에 대한 평가
최기영,백광기 대한금속재료학회(대한금속학회) 1987 대한금속·재료학회지 Vol.25 No.4
An evaluation of Hydrogen Induced Cracking (HIC) susceptibility of low alloyed high tensile strength steels with different microstructure were conducted both in a synthetic seawater saturated with H₂S (BP solution) and in an acidified chloride solution saturated with H₂S (NACE solution) at room temperature according to standard test method (NACE TM-02-84). Threshold diffusible hydrogen content (C_(th)) value of each steel was also determined, which was shown to be a consistent indicator in the determination of HIC susceptibility Standard HIC test showed comparatively low reliability due to a wide allowable range of H₂S concentration for the 'saturated condition'(2300-3500ppm), which could be compensated by incorporating C_(th) value. Moreover, the C_(th) values determined from cathodic charging of hydrogen agreed well with those determined from the standard test; the method, therefore, is proposed as an easy, reliable method for measuring HIC susceptibility of steels for sour service.
용접조건에 따른 고장력강 용접부의 기계적 성질 및 수소유기 응력부식귀열 (應力腐食龜裂) 저항성 변화
박동환,권해욱,백광기,서창교 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.10
The effect of welding condition on mechanical properties and Hydrogen Induced Stress Corrosion Cracking (HISCC) resistance of Heat Affected Zone (HAZ) in high strength steel weldment was studied. Multi-pass Submerged Arc Welding of A5l6 Grade 70 steel plate with different heat input of 30, 40, 50 KJ/㎝ were carried out, which were followed by Post Weld Heat Treatment (PWHT) for 2 hrs at 630 ℃. As the heat input during welding was increased, the impact energy and hardness at HAZ were decreased, on the other hand, the hardness was decreased and both the impact energy and the resistance of HISCC were increased. With proper selection of welding heat input and PWHT, better results of the resistance of HISCC and Charpy V notch impact energy of HAZ can be obtained.