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송길호,박해두,김신일,Song, Gil-Ho,Park, Hae-Doo,Kim, Shin-Il 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.7
In the cold rolling mill, it is very important that a constrained static flow stress of rolled strip and rolling force calculation model be exactly considered to improve an prediction accuracy for rolling forces. Therefore, in this study, the values of the constrained static flow stress are used by deriving the regression equation which is a function of rolling conditions(FDT, CT) and chemical compositions(C, Si, Mn), previously applied by making the tables of yield strength for hot coils with size. And with the consideration that an elastic deformation part of an rolled strip appears at the entry and delivery side of the contacting area between the work roll and rolled strip is calculated. By applying these methods, the more accurate prediction for rolling force is obtained. As a results, the deviation of thickness is significantly reduced in the rolling direction.
초음파 냉간 단조가 SKD-61의 기계적 성질 변화에 미치는 영향
정대호(Jeong Dae-Ho),서창민(Suh Chang-Min),송길호(Song Gil-Ho),박해두(Park Hae-Doo) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Ultrasonic Cold Forging (UCF) technology is a method to induce intensive plastic deformation on a material surface, so that the structure of a material becomes very fine from surface to a certain depth. It improves the mechanical properties, hardness, compressive residual stress, wear and fatigue characteristics of the material surface. An application of UCF technology on a cutting tool on rolling process at steel mill industry is introduced in this study. At first, the ultrasonic cold forged specimens of SKD-61 are prepared and tested to verify the effects of UCF technology on the variation of mechanical properties, UCF is applied to the trimming knives of cold rolling process. It is found that UCF improves the mechanical properties effectively and is becoming a pratical method to improve service time of the trimming knives. Productivity of cold rolling process could have been increased by the application of the ultrasonic cold forged trimming knines.
열복사를 고려한 가열로 내 슬랩의 온도 예측에 관한 연구
이동은(Dong Eun Lee),김만영(Man Young Kim),박해두(Hae-Doo Park),김형진(Hyeong-Jin Kim),박윤범(Yun Beom Park) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
A mathematical heat transfer model for the prediction of heat flux on the slab surface and temperature distribution in the slab has been developed by considering the thermal radiation in the furnace and transient conduction governing equations in the slab, respectively. The furnace is modeled as radiating medium with spatially varying temperature and constant absorption coefficient. The slab is moved with constant speed through non-firing, charging, preheating, heating, and soaking zones in the furnace. Radiative heat flux calculated from the radiative heat exchange within the furnace modeled using the FVM by considering the effect of furnace wall, slab, and combustion gases is applied as the boundary condition of the transient conduction equation of the slab. Heat transfer characteristics and temperature behavior of the slab is investigated by changing such parameters as absorption coefficient and emissivity of the slab.