용접구조용강재의 기계적 성질에 관한 통계적 분석

장동일,경갑수,홍성욱,남왕현,Chang, Dong-Il,Kyung, Kab-Soo,Hong, Sung-Wook,Nam, Wang-Hyone 한국강구조학회 2000 韓國鋼構造學會 論文集 Vol.12 No.3

본 연구에서는 강구조물에 자주 사용되고 있는 용접구조용강재를 대상으로 강재검사성적증명서를 수집하고 이를 통계적으로 분석, 정리해서 기계적 성질의 특성을 정량적으로 평가하였다. 본 연구결과 현재 국내에서 생산되는 용접구조용강재의 기계적 성질은 현행 KS에서 규정하고 있는 기준값을 만족하였으며, 판두께 및 강도등급과 일정한 상관관계가 있음을 알 수 있었다. 강종별 판두께 및 강도등급과 기계적 성질 사이에는 선형적인 비례관계가 성립, 본 연구결과는 기존 연구결과와 유사한 경향이 있음을 알 수 있었다. 현행 KS에서는 강재의 기계적 성질 중 항복점 응력에 대한 상한값이 규정되어 있지 않는데, 강재의 변형성능을 충분하게 확보하기 위해서는 항복비 (또는 항복강도)의 상한값을 규정 할 필요가 있을 것으로 생각된다. In this study, we have quantitatively estimated the mechanical properties of structural welding steels widely used in steel structures after correcting the millsheets of the steels using statistical technique. From this result, in present, the mechanical properties of the steels produced in domestics have satisfied the prescribed values in Korean Standards. The mechanical properties of the steels were dependent upon the plate thickness & class of the steels. Also, there have been linear relations between the plate thickness & class of the steels and the mechanical properties of the steels. And the results of this study have shown the similar tendencies with the existing results. Because the upper limit value of yield strength is not prescribed at Korean Standards in present, it is necessary to prescribe the upper limit value of yielding ratio(or yield strength) in order to assure the deformation performance of the steels.

선체구조용 A급 강재의 하이브리드 용접에 대한 열 및 역학적 특성에 관한 연구

오종인,김영표,박호경,방한서 한국해양공학회 2007 韓國海洋工學會誌 Vol.21 No.1

Recently, there has been considerable research in the field of application of Laser-Arc hybrid welding for superstructures, such as ship-structures, transport vehicles etc. However, the study on heat distribution and welding residual stress of hybrid weld by numerical simulation leaves much to be desired. Therefore, in this study,an optimized welding condition and numerical simulation for hybrid welding, using previous numerical analysis to calculate the heat source for hybrid welding, has been analyzed. For this purpose, fundamental welding phenomena of the hybrid process, using Laser and, is investigated. In order to calculate temperature and residual stress distribution in hybrid welds, a finite element heat sourcemodel is developed on the basis of experimentalresults and characteristics of temperature. Residual stress distribution in hybrid welds are understood from the result of simulation, and compared with the experimental values.1. 서 론일반적으로 CO2 레이저 또는 Nd:YAG 레이저에 MIG, MAG, TIG 및 Plasma 용접법을 복합하여 사용하는 하이브리드 용접법은 레이저 용접의 깊은 용입과 빠른 용접속도의 장점과 아크용접의 저렴한 가격과 고출력, 가공 허용오차(Fit-up)정도를 완화시키는 장점을 가진 용접법이다 (방한서와 김영표 등, 2003). 최근 선박과 같은 대형 구조물 제조 공정에 하이브리드 용접법을 적용하려는 노력이 이루어지고 있고 이에 대한 지속적인 연구를 하고 있으나 현재까지 하이브리드 용접부에 대한 용접성을 파악할 수 있는 수치해석 연구가 아크용접에 비해 매우 미흡한 실정이다. 따라서, 본 연구에서는 선박 제조시 사용되고 있는 조선용 강재 A급(A-grade) 강판에 대하여 하이브리드 용접 시험편을 제작하고 시험편 제작시 사용된 용접조건과 하이브리드 용접 특성을 고려하여 선정한 용접열원모델을 이용하여 열적 특성 및 용접잔류응력을 수치 해석하였으며 용접 시험편에 잔류응력 및 기계적 강도 특성(인장, 충격 등)을 측정하여 비교 검토함으로써 하이브리드 용접부의 최적의 용

복합거동을 고려한 구조용 강재 용접부의 등가탄성계수 산정

김정중 한국복합신소재구조학회 2017 복합신소재구조학회 학술발표회 Vol.2017 No.04

구조용 강재의 용접부는 강재(Base metal, BM), 용접모재(Weld metal, WM), 열영향부(Heat affected zone, HAZ)로 구성된다. 용접부를 구성하는 이들 세 부분의 구조적 성질은 서로 다를 것이므로, 강재의 용접부의 구조 거동은 BM, WM, HAZ로 구성된 복합체의 거동으로 고려할 수 있다. 본 연구에서는 용접부를 구성하는 BM, WM, HAZ 각각의 탄성계수를 나노압입으로 도출하고, 이들의 복합거동(composite action)을 고려한 용접부의 등가탄성계수(equivalent elastic modulus)를 산정하였다.

피복아크 용접봉의 직경에 따른 용접봉 소요량, 용접시간, 용접 경제성에 관한 비교 연구

오상철(Sang-Cheol Oh) 한국산업기술융합학회(구. 산업기술교육훈련학회) 2024 산업기술연구논문지 (JITR) Vol.29 No.1

본 연구에서는 용접에 많이 사용되는 피복아크용접에서 용접봉의 직경에 따른 용접봉 소요량, 용접시간, 용접 경제성에 따른 특징을 알고 이해하여 구조물에 적합한 용접방법을 선택하고자 하였으며 용접 시험편 1개를 용접하는데 소요되는 용접봉 사용량은 ø3.2mm 용접봉이 평균 3.5개 소모되었고 ø4mm 용접봉은 평균 1.93개가 소모되었으며 용접봉값으로 환산하면 ø3.2mm 용접봉 사용시 약 601원이며 ø4mm 용접봉 사용시 약 560.3원으로 직경이 큰 ø4mm 용접봉을 사용 하면 40.7원이 감소되어 약 7.3%의 용접봉 값이 절약 되었다. 용접에 소요되는 시간은 ø3.2mm 용접봉 사용시 평균 440 초 정도 소요되었고, ø4mm 용접봉 사용시 용접에 소요된 시간은 평균 355초 정도의 용접 시간이 소요되어 직경이 큰 ø4mm 용접봉을 사용하면 약 85초를 단축하여 19.3%의 용접 시간을 절약할 수 있었다. 이러한 결과로 직경이 큰 용접봉을 사용하면 용접시간 단축에 따른 인건비 절약 및 용접봉값 절약과 전기세 등의 직, 간접비까지 포함하면 ø4mm 용접봉의 사용이 경제적으로 많은 이익이라는 결론을 얻었으며 이상적인 용접방법이라 판단된다. This study compared the characteristics of welding rod consumption, welding time, and welding economy of welding rods of various diameters commonly used in shielded metal arc welding to select an appropriate welding method for structures. The results of the study revealed that for welding a test piece, an average of 3.5 rods was consumed for ø3.2-mm welding rods, while an average of 1.93 rods was consumed for ø4-mm welding rods. Converting the consumption to the cost of welding revealed approximately 601 KRW for ø3.2-mm welding rods and approximately 560.3 KRW for ø4-mm welding rods. Using larger ø4-mm welding rods reduced the cost by 40.7 KRW, which is equivalent to a 7.3% savings in rod welding expenses.

TIG용접에서 실드가스 종류의 변화에 따른 용접부의 변화상태 고찰

김진수,김법헌,이칠순,김용조,박용환 한국기계가공학회 2015 한국기계가공학회지 Vol.14 No.2

Tungsten inert gas (TIG) welding is commonly used in industries that require airtightness, watertightness, oiltightness, and precision. It is a non-consumable welding method that is commonly used for the welding of non-ferrous metals, but it can be used to weld most metals. The methods of TIG welding can be divided into three types. The first, manual welding is done directly on the metal by a welder with a torch. The second, semi-automatic welding, gets help from a material supplying machine, but it is conducted by a welder. Lastly, automated welding is conducted fully by a machine during its process and operation. Depending on the selection of electrode, the amount of heat that is applied to the base material and the electrode rod changes and makes the shape of welded parts different. A direct-current positive electrode was used for this study. Through the change of shielding gas type on a structural steel (SS-400) that is commonly used in industry, the composition and shape changes in welded parts were detected after welding. The heat-affected area, hardness value, and tensile strength were also identified through hardness testing and tensile testing. In this study, it was found that the higher hardness value of the heat-affected is, the weaker the tensile strength becomes.

용접구조용 강재 적용 부정정 보부재의 해석적 내화성능 연구

권인규 대한건축학회지회연합회 2015 대한건축학회연합논문집 Vol.17 No.5

용접 구조용 강재(SM 490)로 제작된 보부재가 양단 고정단인 부정정 구조물이라 하더라도 화재와 같은 고온에서의 내력 유지성능 평가는 한단 자유, 타단 힌지단인 단순보의 조건으로 이루어지고 있는 것이 현재의 실정이다. 따라서 본 논문에서는 실제 강구조 건축물의 양단 고정단 조건인 부정정 보부재의 내화시험에 적용되고 있는 단순보 조건과의 내화성능 차이를 해석적으로 평가함으로써 화재 안전성을 확인하고, 향후 해석적인 내화설계의 기본 자료 제공을 목적으로 한다. Structural beams plays a role to carry the applied load on the floor into columns and the typical boundary conditions of the beams would be designed as a fixed. This is regarded as an indeterminate structure, for it cannot be solved by condition of equilibrium forces. A fixed boundary condition has a better performance than that of simple beam in aspects of sustaining of applied loads or it is possible to design with a smaller section. However when the fire resistance performance of a beam made of a submarined structural steels and with a fixed boundary is required, the fire test of it is done as a simple beam by a Korean standard. In this paper, an analytic method is used to know the fire resistance performance of statistically indeterminate beams made of a submarine structural steels(SM 490) and to clarify that it is resonable to test by simple beam condition instead of a fixed boundary condition.

SS400 압연강재의 용접방법에 따른 기계적 성질 연구

오상철(Sang Cheol Oh) 산업기술교육훈련학회 2017 산업기술연구논문지 (JITR) Vol.22 No.4

This study aims to figure out and understand mechanical properties and features of shielded metal arc welding, CO₂ gas solid wire arc welding, and CO₂ gas flux cored wire arc welding which are commonly used, in order to choose and utilize the most suitable welding method according to different structures. As a result of the study, CO₂ gas solid wire arc welding showed the largest tensile strength value, while CO₂ gas flux cored wire arc welding showed the intermediate value, and shielded metal arc welding did the lowest value. In case of CO₂ gas solid wire arc welding, it had the largest tensile strength because of weld zone hardening caused by quenching due to the absence of slag, and the lowest elongation rate. CO₂ gas flux cored wire arc welding, a semiautomatic welding method, had the intermediate value in terms of mechanical properties. Shielded metal arc welding showed the relatively low tensile strength because a weld metal zone was not quenched due to slag formed by flux melting, while its elongation rate was large. For these reasons, in case of a structure under impact loading, welding with slag which slow cooling of weld zone is available is considered to be more advantageous. Particularly when taking the mechanical properties into account, a semiautomatic welding, CO₂ gas flux cored wire arc welding, is regarded as the most ideal welding method in terms of work efficiency, tensile strength, and elongation rate.

용접한 건축구조용 강재의 고온 시 기계적 특성에 관한 연구

조범연(Cho Bum-Yean),지남용(Jee Nam-Yong) 대한건축학회 2009 大韓建築學會論文集 : 構造系 Vol.25 No.12

This research is to show the mechanical properties of structural steels by welding at high temperature. Welding parts are divided with weld metal and HAZ(Heat Affected Zone). HAZ is formed by interval from welding heat source and heating and cooling rates. Then, the change of both microstructure and mechanical properties occurs. Discontinuity of mechanical and chemical property at HAZ is the cause of safety decrease of structure. At this point, in this research, tensile tests at high temperature with test pieces of base metal and weld metal of SS400 and SM490 are accomplished. Furthermore, the effect on steel by welding throughout the microstructure's observation at welding parts and fractural parts. From the results, the mechanical properties of both SS400 and SM490 are standardized without welding or non-welding. Moreover, after tensile tests, The volume fraction of ferrite and pearlite is analyzed with microstructure of fractural parts of test pieces of weld metal. As a result, it is verified that the fragility parts of test pieces of weld metal are base metal.

SM45C강의 용접·열처리후 피로 크랙에 미치는 잔류응력의 영향

최순철(Soon-Cheol Choi) 산업기술교육훈련학회 2010 산업기술연구논문지 (JITR) Vol.15 No.2

Structural steels are usually welded by butt submerged arc. After effects of residual stress are considered about welding materials and PWHT materisls, the main conclusions obtained arc as follows 1. Althougth both the welding materials and the PWHT materials have a little difference at the initial crack tip, it is presented that compression residual stress exists. 2. The hardness distribution two-sided specimens has difference by the heat treatment effect of weld penetration heat in two-fold welding, but the hardness distribution of welding materials and PWHT materials were observed to be always the same thing.

FCAW에 의한 고장력압력용기강의 초층편면용접부 균열에 관한 연구

문성실(Sung-Sil Moon) 산업기술교육훈련학회 2012 산업기술연구논문지 (JITR) Vol.17 No.1

It is well known that solidification cracking often occurs in welds of root pass for one-side welding under the conditions of high welding currents and speeds. In this study, the solidification cracking in SPPV490 was investigated by using FCAW with 4 types of welding wires and welding conditions of 200~280A and 2.8~ 4.2mm/sec. In order to compare the result of cracking in SPPV490, the experiments were also conducted with SWS400 and SM45C as base compared metals. As the results, all the cracks formed in some welding conditions were observed near the center of weld bead. The cracking tendency with bead was extended under the condition of higher welding currents.