API 강재의 가스 절단 시 물성변화에 관한 연구

강민석,송우현 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5

가스 절단은 강재 절단 시 가장 널리 사용되는 방법 중 하나이며, 강재와 산소가스의 반응열에 의해 형성되는 절단부 주변의 열영향은 절단 후 강재 물성의 변화에 영향을 미칠 수 있다. 본 연구에서는 가스 절단이 API 강재 물성에 미치는 영향을 분석하기 위하여 산소/LPG 가스 절단 시 절단부 주변의 온도 분포의 변화를 고려한다. 절단부 폭의 변화에 따른 온도 분포의 변화를 분석하였다. 또한, 가스 절단 시 API 강재의 사전변형률의 유무에 절단 후 강재 물성에 미치는 영향을 분석하였다. 사전변형률이 부가된 API 강재의 경우 가스 절단 시 변형시효에 의하여, 가스 절단에 의한 열영향에 의해 항복강도 및 항복비가 증가하는 반면 균일연신율을 감소하는 결과를 나타내었다.

수직 충격파 이론을 이용한 레이저 절단용 초음속 보조 가스의 효과 분석

김두승,이승헌,박병훈,강성원 대한기계학회 2019 大韓機械學會論文集B Vol.43 No.4

The behavior of the assist gas in a laser cutting process affects the cutting quality. In this study, numerical analysis was conducted to analyze the trend in cutting quality with respect to the nozzle design and stand-off distance. For this purpose, a supersonic nozzle was designed based on the method of characteristics to maintain the cutting quality regardless of the stand-off distance. For a simplified laser cutting process with a minimum length nozzle or conical nozzle, numerical simulations were performed for a set of stand-off distances using a Reynolds-averaged Navier–Stokes model. Finally, based on the structural similarity between flows, the normal shock theory was examined to predict the trend in cutting quality from a free jet simulation. 레이저 절단 과정에서 보조 가스의 거동은 절단 품질에 영향을 준다고 알려져 있다. 본 연구에서는 노즐 형상과 절단 거리에 따른 절단 품질의 경향성을 분석하고자 수치 해석을 수행하였다. 이를 위해 먼저 특성곡선법을 이용하여 절단 거리와 무관하게 절단 품질을 유지할 수 있는 초음속 노즐의 형상을 설계하였다. 다음으로 레이저 절단 과정을 축대칭 조건을 사용하여 모사하였다. RANS 기법을 이용하여 최소 길이 노즐과 원뿔형 노즐에 대해 절단 거리에 따른 수치 해석을 수행하였고, 유동의 구조적 유사성을 바탕으로 수직 충격파 이론을 도입하여 절단 거리에 따른 절단 품질의 경향성을 예측했으며, free jet 해석 결과로부터 절단 성능 예측의 가능성을 확인하였다.

강판의 CNC 가스 절단시 절단면특성에 관한 연구

김성일 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.1

In the gas cutting of plate steel, the quality of the quality of the cut surfaces and sections is strongly dependent on the cutting conditions such as cutting speed, kerf width, plate thickness, material, distance between tip and specimen, and cutting oxygen pressure etc. The cutting tests of plate steel were carried out using CNC gas cutting machine. This paper deals with cut surface and section characteristics of plate steel in CNC gas cutting. Both top and bottom widths of kerf, the surface roughness(Ra, Rmax) of cutting surfaces are measured under various cutting conditions such as cutting speed, material, distance between tip and specimen, and cutting thickness. The photographs of cut surface and cut section are also analyzed under various cutting conditions.

철근 가스압접의 접합조건에 대한 연구

이철구,서성원,채병대,남복현 한국공작기계학회 2001 한국생산제조학회지 Vol.10 No.6

Recently, it has increased that the importance of gas pressure weldment of steel bars in large construction bars. But there has hardly been any studies about it. Therefore we need more research. SD40 steel bar (32mm in diameter) which has been practically used at construction sites are tested about tension, bending, fatigue, a macro structure and micro structure at longitudinal section and hardness to find out the mechanical property and best welding ranges in some cases of mechanical cut and gas cut before gas pressure welded. It is that a gas-pressure welded zone of steel bar where was cleaned of impurities in way of two-upsetted method is more excellent bending and tension property than the regulation of KS D 0244. Also gas cut bars gained hardness from the heat affected zone so. In conclusion, to improve the weldability of steel bars, it is considered best to clean mechanically cut surfaces and then weld them by a method of 2 step upset way.

Dynamic Analysis and Mathematical Modeling of a Gas Cutting Process

이재인,고병수,이준엽,유인근,문도영,박민원 한국정밀공학회 2023 한국정밀공학회지 Vol.40 No.1

In this paper, the relationship between various physical and chemical dynamics included in a gas cutting process was analyzed and a mathematical model was presented. To express the gas cutting process in a formula that could reflect the physics and chemical reaction dynamics, the entire process was classified into three stages: flame spurt, metal oxidation, and metal oxide melting. Flame spurt is caused by combustion of fuel gas and oxygen. It was modeled through fluid dynamics, chemical species transport, and reaction kinetics. Metal oxidation was modeled as a chemical reaction of surface oxidation and oxide growth based on temperature and concentration of species of the metal surface obtained through flame and cutting oxygen spurt results. Finally, the melting of metal oxide was expressed as a rate equation based on melting conditions, heat flux obtained in the previous two stages, and changed properties of the metal. The presented mathematical model could analyze dynamic relationships for each stage of a gas cutting process and connect them into one process. Results of this study can be used as basic data for future finite element analysis and simulations.

Hydrox Gas 절단과 LPG 절단의 열적특성에 관한 연구

김홍건,곽이구,Kim, Hong-Gun,Kwac, Lee-Ku 한국생산제조학회 2010 한국생산제조학회지 Vol.26 No.2

Cutting procedures where qualities are determined by various demand factors largely influences shipbuilding productivity. Particularly, defects in cutting shapes and cutting surface results in delay for post shipbuilding stages such as in welding and assemblage lines which could become factors for reduced economic viability of the project. Existing cutting procedures utilize fossil fuels such as propane or ethylene as the main fuel component and these methods applied particularly to ship plate cutting gives relatively slow cutting speed and generates large quantities of harmful and sometimes poisonous polluting fumes of which warrants an urgent need to look for alternative cutting methods. Recent introduction of hydrox gas generated by electrically dissociating water into hydrogen and oxygen components to be utilize as an alternative cutting fuel has resulted not just in visible improvement on cutting quality and speed over the existing methods but it has also been welcomed as an environmentally friendly clean fuel source. This paper has been prepared to serve as the basis for accommodating this environmentally friendly hydrox gas cutting method into actual working environment by observing and recording hydrox gas cutting thermal characteristics.

Hydrox Gas 절단과 LPG 절단의 열적특성에 관한 연구

김홍건(Hong Gun Kim),곽이구(Lee Ku Kwac) 한국생산제조학회 2010 한국생산제조학회지 Vol.19 No.2

Cutting procedures where qualities are determined by various demand factors largely influences shipbuilding productivity. Particularly, defects in cutting shapes and cutting surface results in delay for post shipbuilding stages such as in welding and assemblage lines which could become factors for reduced economic viability of the project. Existing cutting procedures utilize fossil fuels such as propane or ethylene as the main fuel component and these methods applied particularly to ship plate cutting gives relatively slow cutting speed and generates large quantities of harmful and sometimes poisonous polluting fumes of which warrants an urgent need to look for alternative cutting methods. Recent introduction of hydrox gas generated by electrically dissociating water into hydrogen and oxygen components to be utilize as an alternative cutting fuel has resulted not just in visible improvement on cutting quality and speed over the existing methods but it has also been welcomed as an environmentally friendly clean fuel source. This paper has been prepared to serve as the basis for accommodating this environmentally friendly hydrox gas cutting method into actual working environment by observing and recording hydrox gas cutting thermal characteristics

신개념 저 탄소 절단의 열적특성에 관한 연구

김홍건(Hong Gun Kim),곽이구(Lee Ku Kwac),강영우(Young Woo Kang) 한국생산제조학회 2009 한국생산제조시스템학회 학술발표대회 논문집 Vol.2009 No.10

Hydrox gas which is the mixed gas of hydrogen and oxygen gained fromwater electrolysis is one of the new clean energy sources and thus is researched and commercialized actively. Especially, it can be replaced the fossil energy and shows the better quality compared to the conventional energy such as LPG or acetylene gas. The mixed gas of hydrogen and oxygen is gained from water electrolysis reaction. It has constant volume ratio 2:1 of hydrogen and oxygen, and it is used as a source of thermal energy by combustion reaction. Further, hydrox gas is nearly a mixed ideal gas com busting itself completely and its combustion shows anunique characteristics of implosion.

신개념 저 탄소 절단의 열적특성에 관한 연구

김홍건(Hong Gun Kim),곽이구(Lee Ku Kwac),강영우(Young Woo Kang) 한국생산제조학회 2009 한국공작기계학회 추계학술대회논문집 Vol.2009 No.-

Hydrox gas which is the mixed gas of hydrogen and oxygen gained fromwater electrolysis is one of the new clean energy sources and thus is researched and commercialized actively. Especially, it can be replaced the fossil energy and shows the better quality compared to the conventional energy such as LPG or acetylene gas. The mixed gas of hydrogen and oxygen is gained from water electrolysis reaction. It has constant volume ratio 2:1 of hydrogen and oxygen, and it is used as a source of thermal energy by combustion reaction. Further, hydrox gas is nearly a mixed ideal gas com busting itself completely and its combustion shows anunique characteristics of implosion.

철근 가스압접의 접합조건에 대한 연구

이철구,서성원,채병대,남복현 한국생산제조학회 2001 한국생산제조학회지 Vol.12 No.1

Recently, it has increased that the importance of gas pressure weldment of steel bars in large construction bars. But there has hardly been any studies about it. Therefore we need more research. SD40 steel bar (32mm in diameter) which has been practically used at construction sites are tested about tension, bonding, fatigue, a macro structure and micro structure at foil gitudinal section and hardness to fed out the mechanical property and best welding ranges in some cases of mechanical cut and gas cut before gas pressure welded. It is that a gas-pressure welded zone of steel bar where was cleaned of impurities in way of two-upsetted method is more excellent bending and tension property than the regulation of KD D 0244. Also gas cut bars gained hardness from the heat affected zone so. In conclusion, to improve the weldability of steel bars, it is considered best to clean mechanically cut sutra- faces and then weld them by a method of 2 step upset way.