고장력강(HT50) 레이저용접부의 용접잔류응력 및 파괴인성 특성

노찬승,오종인,방희선,방한서 한국해양공학회 2007 韓國海洋工學會誌 Vol.21 No.3

Recently, many industries have been employing the application of laser beam welding, due to the resulting high welding quality, such as smaller width of melting and heat affective zone, smaller welding deformation, and fine grains of weldment, compared to arc welding. However, in order to appropriately utilize this welding process with steel structure, the characteristics of welding residual stresses and fracture toughness in welded joints are to be investigated for reliability. Therefore, in this study, the mechanical properties of weldments by arc and laser welding are investigated using FEM to confirm the weldability of laser welding to the general structural steel (HT50). The Charpy impact test and 3-points bending CTOD test are carried out in the range of temperatures between -60℃and 20℃, in order to understand the effect on the fracture toughness of weldments. From the research results, it has been found that the maximum residual stress appears at the center of plate thickness, and that the fracture toughness is influenced by strength mis-match.1. 서 론 레이저빔 용접법은, 아크용접법에 비하여 역사가 짧고, 비교적 새로운 용접법이지만, 여러가지 장점을 가지고 있어 폭넓은 분야에 적용이 기대되어지고 실용화를 향한 연구개발이 활발히 진행되고 있다(Yasuda and Kitani, 2000).레이저빔 용접법은 고에너지 밀도를 가지고 있기 때문에 용융부가 좁고 깊은 용입이 얻어지고, 용접입열에 의한 열전도가 적기 때문에 아크용접법에서 문제로 되고있는 용접변형을 저감할 수가 있다. 또한 기계화, 자동화가 비교적 쉬운 특징을 가지고 있다. 반면, 초기 설비비가 고가이고, 재료에 정밀한 개선가공 등을 필요로 하기 때문에 그 적용은 한정된 분야에 국한되어 왔었지만, 최근 기술이 향상되어 고출력화, 비용감소, 고속 후판의 용접이 가능하게 되고, 자동차, 기계, 및 이화학분야 등의 작은 부품뿐만 아니라 대형구조물의 적용이 진행되고 있다. 강구조물에 대하여 레이저빔 용접법을 유효하게 활용하기 위해서는 용접부의 역학적 제특성에 대하여 검토할 필요가 있다. 따라서 본 연구에서는 50kg급 고장력강의 레이저빔 용접부에 대하여 수치해석을 통하여 용접잔류응력 및 소성변형도 교신저자 오종인: 광주광역시 동구 서석동 375062-230-7137 chong1015@hotmail.com특성을 고찰하였고, 3점굽힘 CTOD시험 및 샤르피충격시험을 통하여 용접부의 파괴인성 특성을 고찰하였다.

금속분말재료의 사출 성형해석에 관한 연구

노찬승(Chan-Seung Ro),박종남(Jong-Nam Park),정한별(Han-Byul Jung) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.10

본 연구는 광통신용 아답타의 필수품인 플랜지 개발을 위한 금속분말 사출성형해석에 관한 내용이다. 금속분말 사출성형법은 세라믹 또는 스테인레스 분말과 바인더를 혼합하여 복잡한 형상의 사출성형품을 제조하는 기술로써, 지금까지 가공기술로 제작이 복잡하거나 생산성이 저조한 제품들에 대한 생산을 대체 할 수 있는 기술로 관심을 받고 있다. 연구 목적은 기존의 기계가공을 통해 제작했던 제품에 대해 공정을 최소화하기 위함이다. 사출성형해석을 위해 먼저 스테인레스 계 STS316 금속분말과 바인더를 6대4 비율로 혼합하여 과립형 펠렛의 사출 성형재료를 완성하여 해결하였다. 이후, 3차원 모델링, 모델의 메시화 작업 등을 수행하여 최적의 사출성형 해석조건(금형 온도, 용융 온도, 사출 시간, 사출 온도, 사출 압력, 충진 시간 및 냉각 시간 등)을 도출하였다. 해석결과 성형품은 최초 사출 후 13.29초가 경과되면 취출이 가능하였다. 또한 용융수지는 스프루, 러너, 게이트를 거쳐 금형 내부까지 유동 및 충전이 안정적으로 진행되어 양호한 성형품의 제조가 기대되었다. In this study,we conducted an injection molding analysis of metal powder materials for the development of flanges, which are necessary adapters for optical communication. The metal powder injection molding process is a technique for producing an injection molded article having a complicated shape by mixing ceramic or stainless powder and binders. It is used to produce products which require complex processing technology or for which the productivity is low. The purpose of this study is to minimize the manufacturing processing of products which aremanufactured through existing mechanical processing procedures. For the injection molding analysis, we mixed stainless STS316 metal powder with binders at a ratio of 6 to 4 to make molding materials consisting of granular pellets. Then, three-dimensional modeling and meshing were carried out to obtain the optimal injection molding analysis conditions(molding temperature, melting temperature, injection time, injection temperature, injection pressure, packing time and cooling time). As a result of the analysis, it was discovered that the inlet became available 13.29 seconds after the first injection. Also, as the flowing and packing in the melt through the sprue, runner and gate were stable, it is expected that good molds canbe manufactured.

극후판 Box-Column의 Lamellar 균열 감수성 평가

노찬승(CHAN-SEUNG RO),박창수(CHANG-SOO PARK),김흥주(HEUNG-JU KIM),방한서(HAN-SUR BANG),이창우(CHANG-WOO LEE) 한국해양공학회 2003 韓國海洋工學會誌 Vol.17 No.4

In case of the thick rolling-steel for a multistory building, a large oil-drilling structure, a large vessel, a bridge and so on, Lamella Tearing around the welded joint zone is the one of the most serious problems. In order to prevent Lamella Tearing, not only is choice of material important, but also the comprehensive investigation for the structural design and the construction. The Lamella Tearing that is a staircase-shape occurs due to the contraction stress to the thickness direction of the plate and has the character that the cracks progress along the elongated inclusion by rolling. In general, because cracks occur at the heat affected zone and around HAZ, it is necessary to establish the safety and the confidence of the welded structure to restrain the welding defect such as Lamella Tearing. The mechanical approaches are the easier and more economical than the approaches of the material and the construction method. In addition, the appropriate welding profile and the optimum welding condition contribute toward the improvement of the productivity and influence on the standardization of the manufacturing technology.

적외선 열화상 카메라를 이용한 용접부의 온도 측정 방법

노찬승(Chan-Seung Ro),김경석(Kyeong-Suk Kim),장호섭(Ho-Seob Chang) 한국비파괴검사학회 2014 한국비파괴검사학회지 Vol.34 No.4

본 연구에서는 적외선 열화상 카메라와 열원 사이에 유리를 설치하여 측정기기의 보호 및 온도 보정을 통하여 고온의 용접부 온도를 실시간으로 측정하고자 하였다. 먼저 할로겐램프의 열에 대한 온도 차이를 실시간으로 촬영하고 온도를 측정한 결과, 카메라와 열원 사이의 거리별 온도는 거의 동일하게 측정되었음을 확인할 수 있었고, 유리 두께와 측정 거리의 상관관계를 통하여 온도 범위를 예측할 수 있다는 것을 알 수 있었다. 이를 바탕으로 용접열원에 대한 실험을 수행하여 열화상 카메라를 이용한 용접부의 온도 측정의 타당성을 제시하였다. In this paper, a method is tested to measure temperatures in high-temperature welds. Protective glass was installed between an infrared thermal imaging camera and a heat source, and temperature compensation was applied to the measuring instruments. When the temperature of halogen lamps was taken in real-time and measured by the thermal camera, the temperature was found to be almost invariant with the distance between the camera and heat source. The temperature range could be predicted, through correlations with the thickness of the protective glass and the measured distance. This study suggests that the temperature measurement of welds obtained by using an infrared thermal imaging camera is valid, through experimental testing of heat sources.

Analysis of Residual Stress on Dissimilar Butt Joint by TIG Assisted Hybrid Friction Stir Welding

방희선,노찬승,엠 에스 비조이,방한서,이윤기,Bang, Hee-Seon,Ro, Chan-Seoung,Bijoy, M.S.,Bang, Han-Sur,Lee, Yoon-Ki The Korean Welding and Joining Society 2012 대한용접·접합학회지 Vol.30 No.2

This paper aimed to study and understand the mechanical phenomena of thermal elasto-plastic behavior on the dissimilar butt joint (Al 6061-T6 and STS304) by TIG assisted Friction Stir Welding. Heat conduction and residual stress analysis is carried out using in-house solver. Two-dimensional results of the heat distribution and residual stresses in dissimilar joint for particular tool geometry and material properties are presented. The predicted stress along longitudinal direction in Al 6061-T6 and STS304 are approximately between 12-15% of their respective yield strengths. A comparison is made between experimentally measured and numerically predicted equivalent residual stress values.

2¼Cr-1Mo강 압력용기 용접이음부의 재열균열에 관한 역학적 연구

권영섭,노찬승,방한서 朝鮮大學校 機械技術硏究所 1999 機械技術硏究 Vol.2 No.2

구조물에 사용되는 각종 압력용기들의 재질은 고온 및 고압에 견딜 수 있도록 요구되고 있다. 따라서, 내열, 내압 및 내부식성이 뛰어난 2¼Cr-1Mo강의 수요가 향후 증대될 전망이다 용접잔류응력은 일반적으로 응접구조물에 각종 악영향을 미치는 것으로 알려져 있다. 이 때문에 용접잔류응력. 확산성 수소제거 및 용접 열영향부의 연화등을 목적으로 용접후열처리(PWHT)를 수행하나, PWHT를 행하면 사용 강재의 종류에 따라 재열균열이 발생하고 있다. 본 연구에서는 2¼Cr-1Mo강에 대하여 실험과 수치해석 기법을 통하여 용접이음부의 재열균열 감수성평가 및 상당크리프 변형율의 재열균열 발생에 판정에 대한 역학적 지표로서의 적용성을 검토하였다. 2¼Cr-1Mo steels are widely used to fabricate pressure vessels. Residual stresses, in general, are known to be harmful to the soundness of the welded structures. PWHT is release residual stresses, which may cause cracks. But, in those PWHT process, 2¼Cr-1Mo steels are apt to occur reheat crack frequently. In this reason, it is strongly needed to analysis and examine the mechanical behavior of welded joints through welding to PWHT process. So, in this study, welded nozzle parts of pressure vessel where reheat cracks are frequently occur are selected for examine the crack-occurrence mechanism.

외력이 작용하는 용접구조물에 용접잔류응력이 미치는 영향

방희선,박창수,노찬승,오종인,방한서,Bang, Hee-Seon,Park, Chang-Soo,Ro, Chan-Seung,Oh, Chong-In,Bang, Han-Sur 대한용접접합학회 2007 대한용접·접합학회지 Vol.25 No.6

유한요소법을 이용한 하이브리드 용접부의 열 및 용접잔류응력 해석

방희선,오종인,노찬승,박창수,방한서,Bang, Hee-Seon,Oh, Chong-In,Ro, Chan-Seung,Park, Chang-Soo,Bang, Han-Sur 대한용접접합학회 2007 대한용접·접합학회지 Vol.25 No.6

Influence of Preheating Source on Mechanical Properties and Welding Residual Stress Characteristics in Ultra Thin Ferritic Stainless Steel Hybrid Friction Stir Welded Joints

김경학,방희선,방한서,노찬승 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.4 No.4

The joining of ultra thin ferritic stainless steel (STS) with thickness of 0.5 mm has been carried out by Hybrid Friction Stir Welding (HFSW) without pin method using additional Gas Tungsten Arc Welding (GTAW) as preheating source. The influence of preheating source on mechanical properties and welding residual stress characteristics has been investigated through mechanical test and numerical analysis. The ultimate tensile strength of HFSWelded joints is approximately 103% of base metal tensile strength which is higher than that of FSWelded joints. From the result of numerical analysis for thermal elastic-plastic analysis, it is founded that the magnitude of residual stress component (σx) of welding direction is in following order: HFSWelded joints (470 MPa) > FSWelded joints (400 MPa). For the stress component (σy) of perpendicular direction to welding line, there is no great difference for maximum tensile residual stress of FSWelded joints (180MPa) and HFSWelded joints (200 MPa). On the other hand, the area of residual stress distributions in HFSW is smaller than FSW method. The overall results obtained in mechanical test and numerical analysis confirmed that HFSW is a distinct possibility to join ultra thin STS.

배면 3D 패턴 구현을 위한 고광택 표면 사출 금형 시스템 개발

강형선 ( Hyung-sun Kang ),노찬승 ( Chan-seung Ro ),백종진 ( Jong-jin Baek ),오형종 ( Hyung-jong Oh ) 조선대학교 공학기술연구원 2017 공학기술논문지 Vol.10 No.3

The injection Mould products of the vehicle interior decoration and interior are applied to many post-processing techniques such as fusing, painting, plating, etc. in order to achieve various effects. As a result, this increases the price of the product, but it is having difficulty in securing the necessary quality for mass production. Therefore, this study is to test the results of applying a high-gloss 3D pattern to the back of the product. a green mold system, which is a technology to control the temperature of the mold in a short time, is used to realize a high-gloss surface of the product. Through the research, it is possible to remove the defects on the surface of the product produced by the injection molding, by rapidly heating to a high temperature and precisely controlling the cooling rate to make the resin density of the injection product uniform.