Modeling and simulation of arc: Laser and hybrid welding process

Cho, D.W.,Cho, W.I.,Na, S.J. Society of Manufacturing Engineers 2014 Journal of manufacturing processes Vol.16 No.1

Welding is a fabrication process to join two different materials. Among the many welding processes, the arc and laser welding processes are the most widely used. Great effort is required to understand the physical phenomena of arc and laser welding due to the complex behaviors which include liquid phase, solid phase and, gas phase. So it is necessary to conduct numerical simulation to understand the detailed procedures of welding. This paper will present the various numerical simulation methods of the arc welding processes such as arc plasma, gas tungsten arc welding, gas metal arc welding, laser welding, and laser-arc hybrid welding. These simulations are conducted by the finite element method, finite differential method and volume of fluid method to describe and analyze the various welding processes.

차체 플러그 용접품질에 영향을 미치는 아크 위치에 대한 실험적 기초 연구

이경민,김재성,이보영,Lee, Kyung-Min,Kim, Jae-Seong,Lee, Bo-Young 대한용접접합학회 2012 대한용접·접합학회지 Vol.30 No.3

Welding is an essential process in the automotive industry. Most welding processes that are used for auto body is spot welding. And $CO_2$ arc welding is used in a small part. In production field, $CO_2$ arc welding process is decreased and spot welding process is increased due to welding quality is poor and defects are occurred in $CO_2$ arc welding process frequently. But $CO_2$ arc welding process should be used at robot interference parts and closed parts where spot welding couldn't. $CO_2$ welding is divided into lap welding and plug arc spot welding. In case of plug arc spot welding, burn through and under fill were caused in various welding environment such as different thickness combinations of base metal, teaching point, over the two steps welding and inconsistent voltage/current. It makes some problem like poor quality of welding area and decrease the productivity. In this study, we will evaluate the effect of teaching point through the weld pool behavior and bead geometry in the arc spot welding at the plut hole. Welding position is horizontal position. And galvanized steel sheet of 2.0mm thickness that has plug hole of 6mm diameter was used. Teaching point was changed by center, top, bottom, left and right of the plug hole. At each condition, the phenomenon of weld pool behavior was confirmed using a high-speed camera. As the result, we find the center of plug hole is the most optimal teaching point. In the other teaching point, under fill was occurred at the plug hole. This phenomenon is caused by gravity and surface tension. For performance of arc spot welding at the plug hole, the teaching condition should be controlled at a center of plug hole.

새 국제표준규격에 의한 수용성 유해금속의 평가

윤충식 ( Chung Sik Yoon ) 한국산업위생학회 2003 한국산업보건학회지 Vol.13 No.3

This study was performed to investigate the total (insoluble + soluble) metal contents and soluble metal contents in flux cored arc welding fumes. A well designed fume collection chamber for welding operations was used for flux-cored arc welding with CO2gas. Nine different products of 1.2 mm diameter flux-cored wires, five of which were for stainless steel welding applications and the others were for non-stainless welding. Ashing for total metal compositions were treated by NIOSH 7300 method and soluble metals were extracted by newly developed ISO 15202-2(Annex B). Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) was used to analyze 13 different metal components. The contents of all metals were 47.6% in the non-stainless welding fumes whereas 36.4% in the stainless welding fumes. But the soluble contents of all metals were higher in stainless welding fume than in non-stainless welding fumes(15.% vs 8.3%). The reason that soluble fractions are higher in stainless welding fumes is that there are high levels of potassium and sodium, which contribute other metals to be solubles. Hexavalent chromium, A known human carcinogen, can easily be soluble by combining with potassium and sodium. Total chromium content in stainless welding fumes were 3.8 (2.8-5.2)% and soluble content was 0.8(0.4-1.2)%. So, the soluble fraction of chromium was 21.3% in stainless flux cored arc welding fumes. The content of aluminum was exceptionally high in self-shielded flux cored wire fume(product `D`). The reason is that aluminum is added as a de-gassing agent that protect the melting part from the nitrogen and oxygen. It was found that soluble chromium concentration should be evaluated for stainless flux cored arc welding. This study revealed that how to use the fume concentration and/or total(insoluble + soluble) metal concentration to estimate soluble concentration of occupational exposure limit designated metals. The metal compositions of flux cored arc welding fumes were similar to those of shielded metal arc welding whereas welding method of flux cored arc welding were similar to that of metal gas arc welding(MIG or MAG), which were mainly explained by flux existed in both flux cored arc welding and shielded metal arc welding.

GMA용접에서 콘택트 팁 재질에 따른 용접특성 평가

김동윤,황인성,김동철,강문진,Kim, Dong Yoon,Hwang, In Sung,Kim, Dong Cheol,Kang, Moon Jin 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.6

The contact tip for gas metal arc welding has important functions to transmit the welding current to the wire and to guide the wire to molten pool. If the contact tip is damaged, it is a cause of lowering the welding productivity due to removal of welding defects and replacement of contact tip. In case of the use of a contact tip for a long time the arc is unstable because the processed hole in the contact tip center is larger, and the variation of aiming position of the welding wire causes a seam tracking error. In this study, gas metal arc welding experiments using contact tip of three different materials were performed. The contact tips with Cu-P, Cu-Cr, and Cu-ODS were used at the experiments, and the welding characteristics by each contact tip were evaluated. After welding contact tip appearance, welding spatter adhesion amount of the nozzle, and weld bead appearance were evaluated. The welding current and welding voltage were measured to verify arc stability during arc welding.

아크용접 작업 중 발생하는 자외선 노출에 관한 연구

최상준(Sang Jun Choi),백남원(Nam Won Paik),윤충식(Chung Sik Yoon),김정한(Jeong Han Kim),채현병(Hyun Byung Chae) 한국환경보건학회 1999 한국환경보건학회지 Vol.25 No.4

This study was conducted to investigate workers´ exposure levels to ultraviolet radiation(UVR) in shipbuilding industry and constriction equipment manufacturing industry which utilized CO_2-arc welding, shielded metal arc welding (SMAW) and tungsten inert gas(TIG) welding, and to evaluate the effects of various variables on the UVR intensity. The UVR inadiance by welding type, measured in the front of welders with shielding helmet, were highest in CO_2-Arc welding and followed by SMAW and TIG welding. UVR irradiance decreased by distance from welding operations. But at same distance, UVR irradiance showed various values by direction of measurements. Especially UVR irradiance was highest at right side of workers. The most important variable, in determining the UVR irradiace, was heat energy(kW) combined with arc current and arc voltage. In laboratory test, heat energy was positively correlated with UVR irradiance(r=0.90, p<0.01) in the condition of local ventilation. As the proportion of CO_2 in shielding gas mixed with pure Ar and CO_2 increased from 5% to 13%, the irradiance of UVR was decreased by 49.5%. In conclusion, to evaluate correctly the exposure level to UVR irradiance, various variables affecting UVR irradiance such as arc current and voltage, wire type, shielding gas, distance and direction of measurement should be considered. Especially not to underestimate workers´ exposure to UVR in arc welding environment, we should measure UVR irradiance in direction of right side which has the lowest possibility of arc-interception.

아크 출력과 동저항의 통계적 분석을 활용한 아크 안정성 및 비드 품질에 따른 용접 건전성 평가

박주용(Ju-Yong Park),송상호(Sang-Ho Song) 대한용접·접합학회 2019 대한용접·접합학회지 Vol.37 No.6

The goal of this study was to evaluate weld soundness based on arc stability and bead quality using a statistical analysis of the arc power and the arc dynamic resistance. To achieve this, 50 passes of welding experiments were carried out. The welding current and voltage for every pass were obtained at a sampling rate of 5,000 Hz. The weld beads were classified into 4 quality levels by visual inspection and X-ray tests. The measured arc current and voltage were converted to a dimensionless value that was independent of the value itself, and then mapped onto a non-dimensional current-voltage plane. The welding data in the non-dimensional current-voltage plane were grouped into 50 areas (A0 ~ A49) surrounded by the lines of constant arc power and arc dynamic resistance, which changed every ±2% of mean value. The number of welding data points (N0 ~ N49) in each group were distributed in a quasi-lognormal distribution form. When this distribution skewed more leftward, the data in the center became denser and the arc became more stable. The statistical analysis of the entire welding data distribution of 50 passes showed that the cumulative probability=0.8 at the percentile α = 0.22 was an indication of weld soundness. The cumulative probability for a good bead was higher than 0.8, and was lower for a poor bead. This tendency remained consistent in a piecewise analysis of 125 sections of each bead. The sections with irregular bead or pores showed a much lower cumulative probability than 0.8, while sound bead sections had higher than 0.8, that is, a higher arc stability. The piecewise analysis makes it possible to evaluate weld quality in real time during welding.

Development of Plasma Arc Spot Welding Process and Finite Element Method Analysis Model for Predicting Fracture Strength: Part 1—Development of Plasma Arc Spot Welding Process

Geonho Lee,Hansol Kim,Jongho Jeon,Sangjun Han,Sang-Woo Han,Jung Ho Cho 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.1

Resistance spot welding is widely used in automobiles and ships, and especially, it accounts for 70% of the body welding process. However, resistance spot welding is limited when welding the closed structure of a vehicle body. As welding is performed by placing a spot gun in a closed structure, a passage is required for the insertion of the spot gun. This passage is called a “passing hole”, and the structural design of the passing hole and the cover that is installed to block the passing hole is complicated, resulting in durability problems as the weight of the vehicle body increases. This study aims to develop a plasma arc spot welding (PASW) process that can replace resistance spot welding. “Part 1 - Development of Plasma Arc Spot Welding Process” determines whether this process can replace the resistance spot welding process through experiments by adjusting the existing process variables of the plasma arc welding process as well as additional process variables. The experimental results of applying the PASW process are then applied to the development of a finite element analysis model for predicting the fracture strength of the PASW process in Part 2.

Plasma Arc Welding of 780CP High Strength Steel Sheet Lap Joint for Tensile Strength of 100% Compared to Base Metal

Sang-Woo Han,Seungcheol Shin,Hansol Kim,Geonho Lee,Jongho Jeon,Sangjun Han,Gyuyeol Bae,Jung-Ho Cho 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.25 No.5

Homogeneous and heterogeneous PAW (plasma arc welding) experiments were conducted to obtain weld beads with tensile strength of 100% or more compared to that of the base metal in lap joint fillet welding of CP (complex phase) 780 MPa grade high strength steel sheet. Homogeneous and heterogeneous welding mean welding technic without and with welding wire in each. Common basic welding parameters of both homogeneous and heterogeneous PAW wire were applied, including welding speed of 21 cm/min, arc length of 3.5 mm, weaving amplitude of 3 mm, work angle of 30°, and Ar 99.99% shielding gas with 12 L/min. In homogeneous PAW, the optimized additional welding conditions were a welding current of 90 and 95 A, push angle of 20°, and weaving frequency of 5 Hz. The fracture strengths of all the samples were less than that of the base metal, and all fractures occurred at the weld bead fusion zone due to insufficient reinforcement. In heterogeneous PAW, the optimized additional welding conditions were a welding current of 125 A, push angle of 0°, weaving frequency of 4 Hz, and wire feed speeds of 1.53 and 1.38 m/min. Moreover, the welding wire was fed from behind the arc. The fracture strengths of all the samples were greater than that of the base metal, and fractures occurred at the base metal or fusion zone boundary. The reason for higher tensile in heterogeneous PAW wire is deduced as the large cross-section area of reinforcement provided by the welding wire comparing to homogeneous welding. It is well known that small radius of welding heat source clearly produces narrow heat affected zone. Therefore, the PAW produces relatively narrower heat affected zone, then resulted as fully enough strength of weldment. This is another reason of the current achievement.

GTA용접용 텅스텐 전극팁의 형상과 연마 상태가 아크특성에 미치는 영향

조상명,서상균 대한용접접합학회 2001 대한용접·접합학회지 Vol.19 No.1

The welding quality by Gas Tungsten Arc Welding shows very high level, but the welding speed is lower than that of gas metal arc welding. Also, the welding quality by automatic GTAW is variable as the arc characteristics is changed by the consumption of electrode tip. The purpose of this study is to investigate the relation between the properties of tungsten electrode tip and the various arc characteristics at high current region. In this study, the high welding current 200A was applied to the repeated arc start test and long term arcing test using the $\phi$3.2 tungsten electrodes with cone angle 30$^{\circ}$, 45$^{\circ}$, 60$^{\circ}$sharp tip, and 60$^{\circ}$surface polished (S.P.) sharp tip. It was confirmed that the maximum arc pressure by the initial electrode condition was highest in 45$^{\circ}$sharp tip, and the next in 60$^{\circ}$sharp tip, the last was in 30$^{\circ}$sharp tip and 60$^{\circ}$S.P.. But, the maximum arc pressure after the repeated arc start test and long term arcing test was decreased considerably. But, the maximum arc pressure was highest also in 45$^{\circ}$ sharp tip after the tests, the next was in 30$^{\circ}$sharp tip, and the last was in 60$^{\circ}$sharp tip and 60$^{\circ}$S.P.. The arc start characteristics was the most excellent in 60$^{\circ}$S.P., By long term arcing test, the lanthania included in tungsten electrode was extinguished at tip surface preferentially, therefore the arc characteristics of electrode tip got worse.

Study of optimal weld design for arc plug welding of advanced high strength steels

ARUN LALACHAN,SIVA PRASAD MURUGAN,김경영,신지영,김두영,공호영,박영도 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.11

The incorporation of Advanced high strength steels (AHSS) into the automotive architecture have led to reduction of the vehicle weight and improve the crash worthiness. Majorly Resistance spot welding and laser welding have been employed for joining car-body joining. However, these joining techniques poses an issue of reachability in chassis part. To resolve this issue, arc plug welding was introduced as a novel method. The transition of the welding process to arc welding process requires knowledge of the weldability of the arc plug welding. In this study, an experimental method for the selection of the optimal plug welding shape in 1180MPa AHSS with the equivalent effective weld area to the 6.0mm nugget diameter in spot welds was performed. The arc plug welding was performed with 3 different plug hole shapes namely circle plug (6φ) and elliptical plug (4x9 and 3x12mm) to define the optimum weld shape design for plug welding. The optimized welded sample were subjected for mechanical characterization like hardness and Tensile shear performance. The experimental results confirm that the Elliptical plug welding of 4x9 hole showed 68% increase in TSS performance with the low strength wire (ER70S-6) than the resistance spot welding counterparts and poses a possible replacement for securing weld robustness.