Welding Of Stainless Steel Plates Research Articles

Real-time tracking method for motion spatter in high-power laser welding of stainless steel plate based on a lightweight deep learning model

The high-power laser welding of stainless steel is prone to spatter defects. The dynamic behavior of motion spatter is closely related to the welding state, but the relevant features are difficult to obtain. This paper extensively describes a motion spatter tracking method based on a lightweight deep learning model and a multi-target tracking algorithm. Firstly, an in-situ observation platform with a high-speed camera-based high spatiotemporal resolution for motion spatters is established. This platform can record the generation and motion process of different spatters during welding. To reduce the interferences and highlight the spatter characteristics, a linear point operation-based image low-brightness metal vapor plume removal method is also proposed. Then, a deep learning-based lightweight spatter detection model is established, and an automatic spatter label generation method is proposed to quickly obtain a sufficient amount of highly discriminative training data to train the established model comprehensively. Compared with the basic model, the validation results show that the lightweight spatter detection model runs 5.11 times faster, with a spatter detection accuracy of 96.71%. Finally, a motion spatter tracking method based on the DeepSORT algorithm is proposed to distinguish different spatters and associate the same spatters. The spatter size, velocity, quantity, and other features are also able to be accurately extracted via this method, achieving spatter defect monitoring. In summary, this study describes a novel and robust method for motion spatter real-time tracking during laser welding and this method can provide reliable data support for accurate and fast process condition monitoring as well as weld quality assessment.

Simulation of hybrid (LASER-TIG) welding of stainless steel plates using design of experiments

A solid drive for the improvement of higher productivity welding forms lead to the advancement of Hybrid welding process. This research combines arc and laser welding processes providing more robust joints. Hybrid laser welding is a perfect combination of the advantages of laser and arc welding processes. It provides high welding depth at high welding speeds and also good gap bridging capability. This process finds potential applications in shipbuilding, pipeline and automotive industries where high productivity and quality are important. Many researches are in progress to analyze the effect of process variables. This present work is mainly carried out to study the effect of various process parameters like laser beam power, arc power, welding speed on the weld bead dimensions, i.e., bead width and depth of penetration. A three-dimensional transient thermal analysis has been performed for the hybrid welding (LASER + TIG) process using ANSYS. The computed results of width and depth of fusion zone indicates the weld pool shapes. Good agreement was achieved between computed and experimental weld bead dimensions. Mathematical equations were developed using a three factor 5-level factorial technique to predict the geometry of the weld bead. These equations were used to correlate the hybrid welding process parameters with the bead geometry. From these mathematical equations the response of weld bead dimensions with the variation of various hybrid welding parameter were predicted.

Simulation of keyhole laser welding of stainless steel plates with a gap

The presence of a gap (from tens to hundreds of microns) between two components may cause defects during laser-welding processes. Within this paper the process is investigated for two stainless steel plates in overlap configuration by means of multiphysyical CFD modeling. As a first step modeling results are compared with experimental data. Then the gap influence on the fluid dynamics and on the appearance of welding defects are analyzed. Based on the results adapted beam shapes are proposed that allow for an optimized energy distribution and thus an improved weld quality.

Investigation of Clamping Effect on the Welding Sub-surface Residual Stress and Deformation by Using the Ultrasonic Stress Measurement and Finite Element Method

In this study, sub-surface residual stress and deformations, produced by the welding process, are investigated by using ultrasonic stress measurement method and finite element (FE) simulation. The FE analysis is employed to evaluate the residual stresses and deformations caused by the tungsten inert gas welding of 304L stainless steel plates. Residual stresses obtained from the FE analysis are then used to validate results of the ultrasonic stress measurement method, which is fulfilled by employing longitudinal critically refracted ( $$L_{CR})$$ waves. By using four different frequencies of ultrasonic probes, the sub-surface residual stress fields are mapped in four different depths of the examined material. Two different plates are welded with and without the use of clamp to investigate the clamping effect on the residual stress and deformation. By employing the through-thickness measurement of residual stresses, the clamping effect on the sub-surface distribution of the residual stresses is also studied. As a result, the $$L_{CR}$$ ultrasonic method is accurate enough to distinguish the surface and sub-surface residual stresses in the clamped and non-clamped welding plate. Consequently, the longitudinal residual stresses have been increased by using the clamp during the welding of stainless steel plates. However, using the clamp significantly influences the amount and distribution of longitudinal residual stress in the base metal. Regarding the welding deformation results, it has been concluded that employing the clamp considerably decreases the deformations of the stainless steel plates.

Roadmap proposal for determining the variables of pulsed TIG welding process applied to welding of thin plates

In pulsed TIG welding, the current varies between two well-defined energy levels in a given frequency, thus being necessary to regulate a set of variables consisting of the peak current, peak time, background current, background time and the welding speed. Yet despite being a widespread technique, in practice, these welding variables are often regulated arbitrarily. This can lead to inefficient use of the pulsed current regarding the end result of the weld and aspects of productivity. This paper aims to present a roadmap developed in order to meet the practical need to establish criteria to assist in the determination of pulsed TIG welding variables, taking as its premise the desired width of the weld bead, overlap between the weld points comprising the weld bead and the welding speed. Finally, one application of this roadmap is presented in bead on plate welding of stainless steel plates with 1.2-mm thickness.

Modeling of the thermal fluid flow and keyhole shape in stationary plasma arc welding

A three dimensional transient model has been developed to investigate the fluid flow and heat transfer in the weld pool with a dynamic-variation keyhole during stationary plasma arc welding (PAW). The level set method is used to track the moving boundary of the keyhole, and the evolution of both keyhole and weld pool in stationary keyhole PAW process are quantitatively analyzed. The thermal fluid flow of the molten metal surrounding the keyhole inside the weld pool is numerically simulated, and its effect on the keyhole shape is considered. The establishing time of an open keyhole is calculated for the stationary plasma arc welding of stainless steel plates with thickness 6mm. The stationary keyhole PAW experiments are conducted to measure the keyhole shape, the fusion zone, and the establishment time of the keyhole. The predicted results, such as the keyhole length and width at bottom-side, the weld width at top- and bottom-side, and the establishment time of the keyhole, are in agreement with the experimental measurement.

STUDY ON THE THERMAL LAG EFFECT OF KEYHOLE IN CONTROLLED PULSE KEY--HOLING PLASMA ARC WELDING

The behaviors of keyhole formation determine to a great degree the deep penetration welding process and the weld depth-width ratio in welding of medium and large thickness plates. Obtaining a deep insight into the dynamic keyholing process in the weld pool in plasma arc welding is of great significance for widening the process parameter-widow and improving the process robustness as well as weld quality stability. Based on the Level-Set theory, a numerical model is developed to describe the keyhole behaviors in the weld pool in stationary plasma arc welding (PAW), and employed to track the evolution process of keyhole boundary. In this paper, the fluid flow fields in both the plasma and the keyhole regions are constructed according to the experimental and simulation data in the previous literatures. The combined volumetric heat source model is used to numerically analyze the transient temperature field and then to determine the weld pool geometry. The algorithm of Level-Set theory combined with the transient thermal conduction model is used to determine the evolution of both keyhole and weld pool geometry at different time steps. The dynamic information on the weld pool and keyhole geometry and sizes under a few process conditions is obtained by the numerical simulation of keyholing phenomena in welding of stainless steel plates. It is found that a complete keyhole is established at 2.7 and 2.5 s for the current levels of 170 and 180 A, respectively. During the stationary PAW process, the cross-section geometry of keyhole transforms from U-shape at initial stage to V- shape later and shows finally a hyperbola shape after a complete keyhole is formed. The numerical analysis of keyhole formation is verified by measuring the efflux plasma voltage signals at the moment of keyholing.

A simplified 2-D model for the linear GTA welding of stainless steel plates

A simplified heat and fluid flow model has been used to solve the Gas Tungsten Arc (GTA) linear welding problem for austenitic stainless steel. In this study, an equivalent 2-D (two-dimensional) transient heat and fluid flow model has been used to study the effect of controlled boundary conditions with free bottom surface and with bottom insulation. The governing equations have been solved by a finite volume method. The peak temperature, maximum velocity in the weld pool, weld bead width and depth get reduced when the bottom surface of the stainless steel plate is insulated.

An experimental and theoretical study of gas tungsten arc welding of stainless steel plates with different sulfur concentrations

During fusion welding, the presence of sulfur in steel often affects heat and fluid flow in the weld pool and its geometry. While the role of sulfur during welding of stainless steel plates with the same sulfur content is well understood, welding of stainless steel plates containing different concentrations of sulfur has not yet received proper attention. Here we report an experimental and modeling investigation of gas tungsten arc butt welding of stainless steel plates containing different sulfur concentrations. The main variables studied were sulfur concentrations in the two plates, welding current and welding speed. The results show significant shift of the fusion zone toward the low sulfur steel. The asymmetric fusion zone profile with respect to the original joint interface could be quantitatively explained through numerical modeling of heat transfer and fluid flow considering a bead shift observed experimentally.

Nd:YAG 레이저 맞대기 용접의 비드형상 예측에 관한 유한요소해석

Nd:YAG pulse laser welding of stainless steel plate was simulated to find welding condition by using commercial finite element code MARC. Due to geometric symmetry, a half model of AISI 304 stainless steel plate was considered and user subroutines were applied to boundary condition for the heat transfer. Material properties such as conductivity, specific heat, mass density and latent heat were given as a function of temperature. As results, Three dimensional heat source model for pulse laser beam conditions of butt welding has been designed by the comparison between the finite element analysis results and experimental data on AISI 304 stainless steel plate. Nd:YAG laser welding for AISI 304 stainless steel was successfully simulated and it should be useful to determine optimal welding condition.

Nd:YAG 레이저 필렛 용접의 비드형상 예측에 관한 유한요소해석

Nd:YAG pulse laser fillet welding of stainless steel plate was simulated to find welding condition by using commercial finite element code MARC. Full model of AISI 304 stainless steel plate was considered and user subroutines were applied to boundary condition for the heat transfer. Material properties such as conductivity, specific heat, mass density and latent heat were given as a function of temperature. As results, Three dimensional heat source model for pulse laser beam conditions of fillet welding has been designed by the comparison between the finite element analysis results and experimental data on AISI 304 stainless steel plate. Nd:YAG laser welding for AISI 304 stainless steel was successfully simulated and it should be useful to determine optimal welding condition.

Thin-Plate Welding by a High-Power Density Small Diameter Plasma Arc

High-power-density plasma arc of 10 4 W/mm 2 (10 6 W/cm 2 ) is applied to welding of stainless steel plate of 0.1 and 0.3 mm in thickness. Practical conditions required for successful welding and welding capability of this new equipment are discussed. Welding capability does not depend on the working distance defined as the distance between exit of nozzle and workpiece surface. Furthermore, even though the plasma torch is deviated from the right position, appropriate welding can be successfully carried out because the workpiece is the anode in this process and thus all power is supplied to the workpiece.

金属材料のレーザ溶接(第2報)

In CO2 laser welding of stainless steel plate, correlation between travelling velocity and dimensions of the weld bead is examined over a wide range of 0 2-200 m/min. The interaction between the cavity and the incident beam is analyzed. The penetration depth and joining rate are estimated on the basis of this correlation and the heat conduction theory. Results obtained are summerized as follows:(1) Under fixed focussing condition, cyclic change in the beam intensity at the bottom of the cavity occurs, producing step-like change in the dimensions of the bead with the travelling velocity.(2) Under optimal focussing condition, the ratio of penetration depth to mean bead width is almost constant in a wide travelling speed range of 1-40 m/min. In this range, the penetration depth is inversely proportional to the square root of the travelling velocity.(3) The maximum joining rate, 320 mm/kJ, has been obtained at a penetration depth about 0.5 mm. The joining rate is inversely proportional to the penetration depth.

ステンレス鋼のプラズマ溶接の研究

Recently, plasma process has been applied to such industrial uses as cutting and spraying. Arc plasma is constricted by the gas flow and/or metallic wall of nozzle in a plasma process. The temperature and the thermal energy intensity of the constricted arc plasma are much higher than those of ordinary open arc. In the cutting and welding applications, it will be expected that the plasma stream has a property of line heat source similar to the one as observed in Electrlon Beam Welding.In this report the experimental results on the plasma welding of stainless steel plate are described briefly. The electric capacity of plasma welding torch used in these experiments is about 8 KW. The plasma welding is capable of producing a narrow and deep weld bead by the action of "Key Hole". And a sound weld is obtained by one pass of torch even for a 15 mm thick plate. With the above welding energy source, optimum welding conditions are established for various thickness of plate. Welding speed in plasma process is much higher than that in TIG welding and others at the same welding energy.Various tests on the microstructure, mechanical property and the deformation of weld specimen are carried out with satisfactory results.It was confirmed that the formation of key hole in crater of bead had much influence upon the welding results. When the key hole is not formed, porosity is contained in most weld beads. The formation of key hole is sensitive to the travelling speed.