Optimization of Weld Pitch on Overlay Welding using Mathematical Method

Kim, Ji-Sun,Kim, In-Ju,Kim, Young-Gon 한국정밀공학회 2014 International Journal of Precision Engineering and Vol.15 No.6

It is important to overlap the even bead continuously to automate the overlay welding process. To obtain the even surface bead on overlay welded product, optimization of pitch distance between the each pass is one of the methods. Therefore, this study determines the optimal second pass pitch distance with respect to welding parameter such as torch position and welding speed. Variety of welding experiments was carried out with different welding parameters using Central Composite Rotatable Design (CCRD) method. Based on the experimental results, empirical models were developed after analyzing correlation between welding parameters and bead height, width and decentration of overlay welding. Finally, optimized empirical models were developed for predicting bead height and width by analyzing the main effect of each factor which affects bead geometry and their influence on interaction. In addition, a mathematical model was developed which determines the bead profile for visualizing the bead shapes using the Matlab curve fitting tool. These two models were combined for one of the overlay bead shape model. Furthermore, the mathematical model is then used to determine the second pass pitch distance, by allowing the same area above and below the point of interaction between two overlay weld pass.

Mn-Ni-Cr-Mo강에 대한 Inconel 690 오버레이 용접부에서의 고온균열의 발생거동

양병일,김정태,신용범,안용식,박화순 대한용접접합학회 2002 대한용접·접합학회지 Vol.20 No.2

In order to clarify hot cracking phenomena occurred in Inconel 690 welds and it's prevention, in this study, the cracking behavior and the influence of welding variables on cracking in Inconel 690 overlay welds on Mn-Ni-Cr-Mo steel(SA 508 cl.3) for pressure vessel were investigated by using mock-up test. The main results are as follows: The cracks in Inconel 690 overlay welds were mainly generated near the start and the end part of welding beads adjacent to STS 309L welded outside of Inconel 690 welds. Most of the cracks showed typical solidification crack, and also it was assumed that there was possibility of liquation cracking in HAZ. The existence of Nb constituents or concentration of Nb was recognized on the fracture facets of the solidification cracks in the welds by SMAW. Therefore Nb was considered to be the main factor of the solidification cracking. As the weld heat input was more increased and the weld bead length was longer, the extent of cracking was more increased. Moreover the extent of cracking was considerably decreased by changing of welding sequence to the start and the end part of welds. Hot cracking in welds by GTAW was considerably decreased as compared with that of SMAW. And cracks were well generated in the Inconel 690 overlay welds adjacent to 575 309L welds. This means that the hot cracking susceptibility of Inconel 690 welds was largely varied by chemical components and/or compositions of filter metals, base metals and neighboring welds.

Numerical investigation on welding residual stresses in a PWR pressurizer safety/relief nozzle

SONG, TAE-KWANG,BAE, HONG-RYUL,KIM, YUN-JAE,LEE, KYUNG-SOO Blackwell Publishing Ltd 2010 Fatigue & Fracture of Engineering Materials and St Vol.33 No.11

<P>ABSTRACT</P><P>This paper presents finite element simulation results of residual stresses in dissimilar metal welds of a PWR pressurizer safety/relief nozzle. The present results are believed to be significant in two aspects. The first one is to consider the effect of the presence of similar metal welds on resulting residual stresses. The second one is the mitigation effect of the overlay welding thickness on residual stresses. After dissimilar metal welding, tensile residual stresses are present both at the inner surface and at the outer surface of dissimilar metal welds. Adjacent similar metal welding, however, decreases residual stresses to compressive ones at the inner surface of dissimilar metal welds, possibly due to the bending mechanism caused radial contraction of the weld. At the outer surface of dissimilar metal welds, similar metal welding increases residual stresses. Overlay welding further decreases residual stresses at the inner surface of dissimilar and similar metal welds, but increases slightly residual stresses at the outer surface.</P>

복합 크롬 분말에 의한 철계 용접 오버레이의 내마모 특성

김종철,박경채,최창옥 대한용접접합학회 2001 대한용접·접합학회지 Vol.19 No.5

Weld overlay has been developed to improve the property of material surface which is used in the severe environment. Weld overlay is the process which uses an arc heat and welds different composition of alloy on the substrate for the improvements of heat resistance and wear resistance. Weld overlay has a lot of advantages which are high hardness, good processing efficiency, easy controlling of layer thickness, good quality and low cost. In this study, weld overlay was performed by MAG welding on the base metal(SS400) with filler metal which contain composite powders(Cr+C+Mn+Mo+NbC) and solid wire(JIS-YGW11). Characterization of hardness and wear resistance were analyzed by EDS, EPMA, XRD and observations of microstructure were performed to investigate characteristics of overlays. The experimental results of overlaid specimens manufactured with Cr+C+Mn+Mo+NbC powders were obtained as fellows. ${\alpha}-phase$, M(Fe, Cr)3C and NbC of overlays were increased with decreasing the wire feed rates and increasing powder feed rates. Also the hardness of overlays were increased and the specific wear were decreased.

Optimization of Weld Pitch on Overlay Welding using Mathematical Method

김지선,김인주,김영곤 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.

It is important to overlap the even bead continuously to automate the overlay welding process. To obtain the even surface bead onoverlay welded product, optimization of pitch distance between the each pass is one of the methods. Therefore, this study determinesthe optimal second pass pitch distance with respect to welding parameter such as torch position and welding speed. Variety of weldingexperiments was carried out with different welding parameters using Central Composite Rotatable Design (CCRD) method. Basedon the experimental results, empirical models were developed after analyzing correlation between welding parameters and beadheight, width and decentration of overlay welding. Finally, optimized empirical models were developed for predicting bead height andwidth by analyzing the main effect of each factor which affects bead geometry and their influence on interaction. In addition, amathematical model was developed which determines the bead profile for visualizing the bead shapes using the Matlab curve fittingtool. These two models were combined for one of the overlay bead shape model. Furthermore, the mathematical model is then usedto determine the second pass pitch distance, by allowing the same area above and below the point of interaction between two overlayweld pass.

Inconel 690 오버레이용접부의 고온균열 발생에 미치는 용접금속의 화학조성 및 용접조건의 영향

양병일,지병하,김정태,박광식,최해수,박화순 대한용접접합학회 2002 대한용접·접합학회지 Vol.20 No.3

In order to investigate the hot cracking phenomena of the Inconel 690 overlay welds, the hot cracking test(modified Varestraint test) was performed by varying augmented strain and welding speed in GTAW. A total of five kinds of specimens was used in the hot cracking test. The specimens used were two kinds of one layer specimens that were composed of just Inconel 690 deposited metal and three kinds of double layer specimens that were composed with as upper part of Inconel 690 weld metal and lower part of SA508 cl.3 or STS 309L. The main results are as fo11ows: In the welds composed of just Inconel 690, as the augmented strain was more increased and the welding speed was more decreased, the extent of cracking was more increased. And these cracks were mainly solidification cracks, and liquation cracks were also observed partially in HAZ. And hot cracking susceptibily of Inconel 690 welds by using filler metals containing Nb were higher than that of the welds with Nb free. The hot cracking susceptibility of Inconel 690 weld metal was increased with dilution of SA 508 cl.3 and STS 309L, and the influence of SA 508 cl.3 was higher than that of 575 309L. The results of calculation of $TSC\Delta$ and $TLC\Delta$ in Inconel 690 weld metal changed by dilution with base metal or neighboring welds were agreed well with the results of hot cracking test in this study. Therefore, it was expected that the hot cracking was considerably decreased or prevented by using proper welding conditions such as lower heat input, filler metals, base metal and neighboring welds.

대구경 상수관로의 기존 부분 보수보강 기술 성능평가

이호민,배철호,박정수,정기문 대한상하수도학회 2022 상하수도학회지 Vol.36 No.6

In this study, as the proportion of aged pipelines increases rapidly, in the event of an accident caused by corrosion and structural deterioration of metal pipes, appropriate overlay welding is applied in the field to partially repair it. The size of the base steel plate and the selection of a stable welding method were evaluated, and possible problems caused by the overlay welding were identified, and improvement measures were proposed. For the test, a new steel pipe coated with epoxy lining on the inner surface and polyethylene on the outer surface was subjected to a tensile test by processing the repaired specimen through overlay welding with a steel plate after artificial cracking, and structural safety was evaluated after repair. Furthermore, the influences of the size of the throat and the size of the steel plate were analyzed. As a result of the tensile test by dividing the repaired steel plate overlay into a constraint and non-constraint conditions, the tensile load was concentrated in the welded part and damage occurred in the welded part. It was found that the maximum load leading to breakage increases as the size of the welding throat increases. In addition, it was found that the resistance to load increased slightly as the size of the overlaid steel plate increased, but the effect was not significant, confirming the need for repair in consideration of the site conditions. As a result of evaluating the damage to the coating material on the back side of the welding, it was confirmed that the coating material on the opposite side of the welding burned black(epoxy) or was greatly deformed by heat(polyethylene). Therefore, it is necessary to secure structural stability through repainting, etc. in order to prevent damage to the coating material on the opposite side during overlay welding.

Thermal Deformation Analysis Methodology Development for Inconel Overlaying

Rajesh S.R.,Yoo JinSun,Park JungGoo,Choi DooJin 대한용접·접합학회 2022 대한용접·접합학회지 Vol.40 No.2

Overlaying of Inconel on carbon steel base material is widely used in offshore and shipbuilding. The prediction of the overlay related deformation is important to accurately carry out this work with minimum loss and maximum profit. So, in this research, a detailed experimental study on the variation of the weld deposit and the HAZ area while overlay FCAW welding with carbon steel wire as well as Inconel wire on carbon steel plate was carried out and finally, with Inconel Strip to observe the material related and heat input related factor associated with overlay welding. Using this modified heat input and material related values as scale factor is applied to (Strain as Direct Boundary condition) SDB method which is presently applied for welding deformation analysis of large ship block in our shipyard. Based on this research outcome, the overlay welding related deformation was accurately predicted. By predicting the deformation accurately, optimum thickness (always above design thickness) of overlay could be ap- plied and thus reduce the grinding related man-hour to a great extend in this process.

Cr 및 Nb 복합탄화물에 의한 철계 MAG용접 오버fp이의 내마모 특성

김종철,박경채 대한용접접합학회 2002 대한용접·접합학회지 Vol.20 No.3

Overlays is a treatment of the surface and near-surface regions of a material to allow the surface to perform functions that are distinct from those frictions demanded far the bulk of the material. Welding, thermal spray, quenching, carburizing and nitration have been used as the surface treatment. Especially, weld overlay is a relatively thick layer of filler metal applied to a carbon or low-alloy steel base metal for the purpose of providing a wear resistant surface. In this study, weld overlay was performed by MAG welding on the base metal(SS400) with filler metal which contain composite powders($Cr_3C_2+Mn+Mo+NbC$) and solid wire(JIS-YGW11). Characteristics of hardness and wear resistance on overlays were analyzed by EDS, EPMA, XRD and microstructures. Carbide formations were $M(Cr, Fe)_7C_3$ and NbC phases. And carbide volume fraction, hardness and specific wear resistance of overlays were increased with increasing powder feed rate and decreasing wire fred rate. Hardness and wear resistance were almost proportioned to carbide volume fraction of overlay.

오버레이 용접부에 대한 초음파검사 훈련용 시험편 개발 및 결함 신호 검증

정남두(Nam-Du Jung),문용식(Yong-Sik Moon),이승표(Seung-Pyo Lee) 한국비파괴검사학회 2017 한국비파괴검사학회지 Vol.37 No.5

국내 원자력발전소에는 탄소강과 스테인리스강 용접을 위해 Alloy600 용접재를 적용한 이종금속용접부가 존재하며, 전 세계적으로 이종금속용접부에서 결함 발생이 보고되고 있다. 국내 원전의 경우 예방 정비 차원으로 가압기 노즐 이종금속용접부에 대해 오버레이 용접을 수행하였다. 국내 원전 오버레이 용접부는 테이퍼 형상이며, 기량 검증된 위상배열초음파 기법으로 검사되고 있다. 검사에 대한 신뢰성을 강화하기 위하여 오버레이 용접부와 동일한 크기 및 재질의 훈련용 결함시험편을 제작하고 결함 검출 실험 및 검증을 수행하였다. 연구 결과, 결함 검출이 가능하였으며, 이들 훈련용 시험편이 현장검사 전 훈련용으로 적용 가능함을 확인하였다. Alloy600 welding material a dissimilar metal weld used in domestic nuclear power plant (NPP) for welding carbon steel with stainless steel. Many defects have been reported in dissimilar metal welds. Consequently, as a preventive maintenance measure, overlay welding was performed on the dissimilar metal welds of the pressurizer nozzles in a domestic NPP. These overlay welds have a tapered shape, and are inspected by a phased array ultrasonic test technique whose performance has been preven experimentally. To reinforce the reliability of the examination, training specimens with similar-sized flaws were fabricated in the same material for the domestic overlay welds, and the experiment and verification for flaw detection was performed. As a result, all flaws in the specimens were detected by the phased array ultrasonic technique, and these specimens were confirmed to be suitable for application in pre-field examinations.