Welding Position Research Articles

Effect of oscillation modes on weld formation and pores of laser welding in the horizontal position

The present paper systematically investigated the effect of oscillation modes on weld formation and pores of laser welding for high-strength low alloy (HSLA) steel in the horizontal position. The laser energy distributions with different oscillation modes were calculated and analyzed. The vapor plume, the molten pool characteristic, and the keyhole behavior with different oscillation modes were observed. The experimental results show that compared with non-oscillation laser welding and lateral oscillation laser welding, circular oscillation laser welding has more uniform energy distribution, less fluctuation of laser spot motion velocity, and more stable plume and keyhole. Circular oscillation laser welding decreases the depth-to-width ratio of the welds, reduces welding spatters, and improves weld formation. Circular oscillation of the laser beam increases keyhole size, and the oscillation keyhole formed is more likely to trap the bubbles in the molten pool, thus reducing the probability of pore formation. Finally, circular oscillation laser welding with an oscillation amplitude of 4 mm and an oscillation frequency of 60 Hz obtains high-quality weld with expected morphology and free of pores.

Investigations on the effect of standing ultrasonic waves on the microstructure and hardness of laser beam welded butt joints of stainless steel and nickel base alloy

Joining dissimilar metals with superior quality is important to provide tailored, lightweight, and cost-efficient components. Expensive and durable materials are exceptionally used where the cheaper material would not withstand the requirements. With laser beam welding, dissimilar metals can already be joined with high precision, low heat input, and a customizable mixing degree. Introducing ultrasonic excitation into the weld pool is a promising approach for further improvements like customizing the solidification morphology and avoiding weld defects. The experiments are carried out with round bars of 30 mm diameter made of 1.4301 steel alloy and 2.4856 nickel base alloy. Ultrasonic-assisted laser beam butt welding is conducted on rotating specimens with a laser beam power of 7.75 kW and a welding speed of 0.95 m/min. The specimens are evaluated by metallographic cross sections, hardness measurements, and energy-dispersive x-ray spectroscopy (EDX). The ultrasound is used to excite an eigenmode of the sample and the weld position is varied at stress- and displacement-nodes. Two different mechanisms of acoustic grain refinement are revealed. Heterogeneous nucleation is fostered in weld seams that are positioned in stress-nodes, and the fragmentation of dendrites is fostered in displacement-nodes. The welds' chemical compositions correspond to the change of solidification morphology.

Liquation cracking susceptibility of remelted and reheated weld metals in CM247LC superalloy using multi-bead Varestraint testing

The liquation cracking temperature range (LCTR) of CM247LC was evaluated, especially in remelted and reheated weld metals produced during multi-pass repair welding. The LCTR of the remelted weld metal was 282 K, and those of the reheated weld metals were 455–805 K depending on the testing position. In the multi-bead within the reheated weld metal, the LCTR increased from 455 K far from the inter-pass boundary to 805 K near this boundary. The mechanism underlying the varying LCTR for the remelted and reheated weld metals was the amount of MC carbide at each weld position. The single-mode fibre laser welding suppressed the carbide within both areas, and lowered the liquation cracking susceptibility.

Pengaruh variasi bevel pada proses pengelasan SMAW terhadap kekuatan tarik material

The strength of welded joints is influenced by a wide variety of factors. One of them is due to structural changes as a result of the heating process. In order for the connection between the two metal parts to have good quality, it is necessary to have a proper welding and the connection and the shape of the weld bevel are in accordance with the use of the results of the weld. Parameters in Shielded Metal Arc Welding (SMAW) welding include current strength, voltage, electrical polarity, and the angle of the joint used. These parameters make the basis for the right selection in order to get a good quality or connection quality. The purpose of this study was to determine the effect of bevel variations on the tensile strength test of the SMAW welding process connection on medium carbon steel material. The welding process is carried out using RB 26 type electrodes using a current of 100 A at 1 G welding position, welding is carried out on the material using V, I and double V bevel with 1 specimen per bevel. Based on the research that has been done, it can be concluded that the type of joint bevel has an important influence on the results of the weld. From the variation of the bevel that has the highest tensile strength value, it is V bevel rather than double V bevel and 1 bevel. Due to the variation of V bevel has a small distortion angle compared to double V bevel and I bevel. Optimal electric welding results depend on the welding process technique.

Influence of TIG welding process parameters on microstructure and mechanical properties of as-cast Mg–8Li–3Al–2Zn-0.5Y alloy

In this study, the feasibility of TIG welding of as-cast Mg–8Li–3Al–2Zn-0.5Y alloys was investigated, and the quality of welded joints using different welding currents was evaluated in terms of microstructural evolution and mechanical properties. The results showed that the welding position of plates was successfully welded with good formability and no obvious welding defects at the investigated processing parameters. Significant refinement of phase size was beneficial to improve the mechanical properties of the welded joints. Under the influence of heat input, the AlLi phase in the heat-affected zone dissolved into the matrix, which improved the mechanical properties of the welded joint. The ultimate tensile strength, yield strength and elongation of the welded joint at 100 A were 224.8 MPa, 177.4 MPa and 9.9%, respectively, which is 159.5%, 159% and 43.8% of the corresponding values of the base alloy in the as-cast state. The burning loss of Li element in the welded joint was effectively controlled, which confirmed the feasibility of this welding process for welding Mg–Li alloys.

Assessing and mitigating the distortion and stress during electron beam welding of a large shell-flange structure

Electron beam (EB) welding can efficiently join large-scale components using one single autogenous pass, but it still faces challenges associated with weld-induced distortion and stress. This study investigates EB welding in a low-alloy steel thick-section shell-flange structure for a small modular reactor. A 3D thermal-metallurgical-mechanical model is developed to assess the weld-induced distortion and stress, as well as the strategy to mitigate them. When no restraint is imposed on the circumferential weld plane, an opening and sliding gap develops during the EB welding, which can cause weld defects and even process failure. Restraint through tack welds can effectively mitigate the gapping distortion, but it generates high transient tensile stress in the tack weld. Circumferentially continuous tack weld is preferential over circumferentially discrete tack welds to minimise the tensile stress. The final residual stress is insensitive to the tack-weld restraint, and the stress distribution in the steady-state welding region is broadly similar to that found in plate butt welds. However, concentration of residual stresses with high triaxiality occurs in the weld stop region, with high tensile stresses generated just behind the beam stop location, which cannot be diminished by overlap welding or change of weld stop position. The mechanisms responsible for the distortion and the transient and residual stresses are analysed. This study could provide rational basis for designing weld restraint to control distortion and guiding stress mitigation strategy for crack-susceptible region in EB weldments.

The Effect of Temperature on Tensile Strength of Polypropylene Plate Material Using Hot Gas Welding (HGW) Method

This study focuses on plastic welding, a technique that employs polypropylene plastic material in 3600-litre reservoir applications. The liquid pressure within it causes hydrostatic pressure in the reservoir. The pressure in the reservoir is approximately 0.01 N/mm2. This study aimed to determine how frequently polypropylene joints leak or sustain damage as a result of welding. Hot gas welding (HGW) with a v-groove connection type is employed (v-grove). Specimens of polypropylene were prepared in accordance with ASTM D638-I. In this study, the input parameters were chosen by varying the welding position and the machine's setting temperature. The results indicated that the required welding temperature for 5 mm-thick polypropylene plastic ranged between 220 and 280 degrees Celsius. In the tensile test on samples S1, S2, and S3, the average decrease in tensile strength of the three test objects was 13.84 N/mm2, 15.98 N/mm2, and 15.21 N/mm2, respectively

Kajian Indikator Proses Pembelajaran Praktek Pengelasan Di SMK

<p> </p><p class="StyleAuthorBold"><em>Abstract </em></p><p><em>The objectives of the study are: (1) to find the indicators of welding teaching and learning process which is appropriate to the characteristics of welding ability, (2) to know the ideal magnitude of every indicator in qualified SMAW welding teaching and learning process.The approach of the survey which is used in this research is the combination of qualitative and quantitative with sequential exploratory model of descriptive method. The first step applied is qualitative method and the second step is quantitative method. The technique of collecting data were interview and questionnaire. The respondents of the study was chosen by certain consideration.The results of the study are: (1) the indicators of welding process in teaching and learning practice are teaching and learning model, students’ character, physical condition, psychological condition, duration of the practice session, and teaching and learning practice frequency. (2) Satisfied result was found when the teaching and learning held once in a week, one meeting is 8 teaching hours. (3) The material delivery within 16 meetings is enough to be understood by students. (4) The mastering position of welding is ideally for 1G or 1F needs 3 meetings, 2G or 2F needs 5 meetings, and 3G or 3F needs 8 meetings. (5) 16 meetings for welding teaching and learning practice is not enough to master the SMAW welding competency.</em></p>

Investigation on Weld Characteristic, Welding Position, Microstructure, and Mechanical Properties in Orbital Pulse Current Gas Tungsten Arc Welding of AISI 304L Stainless Steel Pipe

Orbital pipe welding is carried out in this study by Pulse Current Gas Tungsten Arc Welding (PC-GTAW) without metal filler (autogenous) of AISI 304L stainless steel pipe. The dimensions of the specimen are 114 mm outside diameter and the thickness of 3 mm. This study investigates the effect of pulse current parameters, weld position, and pulse width on the characteristics of weld geometry, mechanical properties, and microstructure. The welding method used in this study is the continuous current and pulse current. The mean current of each parameter is the same at 100 ± 0.5 Amperes, but in the pulse current, there are variations in peak current, base current, peak current time, and the base current time. The welding speed used is constant at 1.4 mm/s. The result of weld geometry on the outside of pipe has shown that the flat (0°) position is concave and the overhead (180°) position is convex due to the influence of gravity. The microstructure indicates that the fine cellular dendritic structures appear at PC-GTAW. The PC-GTAW can produce good mechanical properties such as the tensile strength and the micro-hardness. The tensile strength of the specimen is reduced 14.23 % from the base metal at parameter 65-B and the flat position.

Application of ISO 1999:2013 (E) model in risk assessment of hearing loss caused by industrial noise

To assess the risk of hearing loss caused by industrial noise exposure of welders and assemblers in a mechanical equipment manufacturing enterprise, and to explore the practical application and possible underestimation of ISO 1999∶2013(E) model. A total of 829 noise-exposed male workers from a mechanical equipment manufacturing enterprise were selected as study subjects. The questionnaire survey was administered, and individual noise exposure level(L_(Aeq.8 h)) and hearing loss level were measured. The risk assessment method of ISO 1999∶2013(E) was used to calculate the change of hearing threshold level and the risk of noise-induced hearing loss. By comparing the median of permanent hearing threshold shift caused by actual noise with the median of ISO1999 predicted value, the reason of the difference between the predicted value of ISO 1999∶2013(E) model and the actual value was analyzed. The L_(Aeq.8 h )was 89.5 dB(A), 77.4%(n=62)of the individual noise exposure levels exceeded 85 dB(A), and 24.6% of the participants(n=829) had different degrees of hearing loss. There was significant difference in hearing loss rate between welding and assembly positions(χ~2=10.07, P<0.01). The risk of noise-induced high-frequency hearing loss of 90% welders was 11.2% at the age of 50, and 14.0% at the age of 60. The risk of noise-induced deafness of 90% welders was 4.3% at the age of 60. The risk of high noise-induced frequency hearing loss of 90% assemblers was at the range of 4.0%-9.0% at the age of 40, 20.8% at the age of 50, and 22.5% at the age of 60. The risk of noise-induced deafness of 90% assemblers was at the range of 1.4%-6.4% at the age of 50, and 9.0% at the age of 60. Compared with actual median of permanent hearing threshold shift, ISO1999∶2013(E) predictions underestimated the median of permanent hearing threshold shift at 10.7 dB. The noise hazards of welding and assembly positions in mechanical equipment manufacturing enterprises are high relatively. ISO1999∶2013(E) can be used to predict the risk of noise-induced hearing loss in workers, but attention should be paid to the risk underestimation of this model.

A teaching-free welding position guidance method for fillet weld based on laser vision sensing and EGM technology

Position guidance plays an essential role in guaranteeing welding quality. However, the current position guidance methods usually rely on the teaching trajectory or a similarly designed weld path. The innovation of this manuscript is to establish a teaching-free position guidance method combining the position detected by laser vision with the data bidirectionally sent by externally guided motion (EGM) at a high rate. A feature point extraction method based on Steger algorithm and slope determination is proposed. A dense zig-zag path is generated according to the position guidance based on EGM. Meanwhile, the position guidance experiments for fillet weld (horizontal deflection angle α = 9.2°, 13.3° and vertical deflection angle β = 5.5°, 9.2°) are finished. The mean absolute error (MAE) of position guidance in the Y-axis and Z-axis can be controlled in 0.21 and 0.13 mm, respectively. Moreover, the robot welding experiments for fillet weld in three different horizontal and vertical deflection angles (α = 30°, β = 25°, α = 30° and β = 25°) show that this method can obtain good weld surface morphology and metallographic morphology, and have a potential application value in industrial automation.

Laser Spot Welding a Three-Layered Panel in Different Spatial Positions

The aim of the work is a comparative analysis of structural features and mechanical characteristics of spot welded joints of thin-sheet stainless steels 03Х11Н10М2T and 12Х18Н10Т, produced by laser welding in different welding positions. The change in the welding position from vertical to flat allowed extend the ranges of variation of welding modes from about ±5% to about ±10%, at which it is possible to produce a welded joint with satisfactory shape and mechanical characteristics. Higher strength is typical for welded joints obtained in a flat position. It also concerns the maximum value of the shear stress, which for the flat position is higher by approximately 10%, and the average value, which is higher by approximately 24%. In addition, the results of mechanical shear tests of these joints have a significantly lower dispersion.

Region-based path planning method with all horizontal welding position for robotic curved layer wire and arc additive manufacturing

For the curved layer deposition with wire and arc additive manufacturing on complex surface, the molten pool behavior and bead geometry are variant at different welding positions for the dragging effect of gravity, which lead to inconsistent layer appearance. A region-based path planning method for robotic curved layer wire and arc additive manufacturing (CL-WAAM) is developed, with which all horizontal welding position can be maintained at arbitrary region of the complex surface. The adverse effect of gravity is minimized and uniform bead appearance can be guaranteed. Firstly, with a two-stage clustering method , the complex surface was divided into a certain number of simple subregions . Then, the contour line across cluster centroid of each subregion was employed as initial path, and an adaptive bead overlapping model changed with local inclined angle was used to generate the offset curved path covering the subregion. Therefore, the overall welding paths were approximate to the contour line on the surface, and the horizontal welding position and consistent forming appearance can be achieved. Finally, three surface parts were designed to validate feasibility of the method, and the forming appearance was compared with traditional iso-parametric method and flat layer WAAM (FL-WAAM). The results suggested that the surface waviness and thickness were relatively consistent at arbitrary region of complex surface with the region-based method, and the stair-step effect appeared in FL-WAAM was significantly alleviated with the CL-WAAM. The proposed method helps achieve the uniform layer appearance deposited on complex surface, which could be widely used in the manufacturing or repairing of wear-resistant surface parts, such as the hot forging die and hydraulic turbine blade. • A framework of robotic curved layer wire and arc additive manufacturing (CL-WAAM) was proposed. • A region-based path planning method with all horizontal welding position for the CL-WAAM was implemented. • The complex surface was subdivided into simple patches with a two-stage clustering method. • The contour line across the cluster centroid was employed as the initial path, with which the all horizontal welding position could be ensured. • The uniform forming appearance was achieved through the proposed region-based path planning method.

Investigation of deposition welding in vertical and horizontal position with a coaxial laser wire welding head

Deposition welding of components using the laser metal deposition (LMD) process is a proven method of creating 3D structures. It is used for the manufacturing of components, the repair of machine parts and for cladding. Up to now, claddings have mainly been investigated in the flat welding position. Some investigations on deposition welding in vertical orientation are available with different processes. For the cladding of large components, welding in the vertical direction offers advantages. So far, there are no investigations on the LMD process with coaxial wire feeding when welding in vertical direction. Therefore, in this study, the influence of the welding direction, i.e., vertical down and vertical up weld seams, and the influence of the welding speed are investigated. Single weld seams, claddings and a wall are welded. A stable welding process could be achieved for a welding speed parameter window of 100 to 1000 mm/min. The results show that there is a statistical correlation between the welding direction and the waviness of the weld seams. Vertical up weld seams have a lower waviness. Another influence on the waviness is the welding speed. As the welding speed decreases, the waviness increases. The weld seam geometry is strongly dependent on the welding direction. With vertical down weld seams, the width and height of the weld seam vary depending on the distance welded. This can be attributed to the influence of the gravitational force. Vertical up weld seams, on the other hand, have a more uniform shape.

Gravity effects on temperature distribution and material flow in the keyhole pool of VPPA Al welding

This study investigated heat and mass transfer as well as the effect of gravity on keyhole formation in the molten pool of keyhole plasma arc welding. The flow trajectory of the molten pool was obtained via high-speed camera images illuminated by a laser light system, and the temperature distribution was obtained using an infrared thermal camera. The experimental results showed that the molten metal flowed rearward and downward at the top surface of the weld pool and thereafter to the rear side of the keyhole. There are two types of reverse flow of molten metal on the rear side of the keyhole. The different welding positions had minimal effect on the flow pattern; however, the flow velocities were different. Further, for the temperature distribution, although the keyhole front side yielded a similar high-temperature area under different welding positions, the area of the high temperature on the keyhole rear side in the vertical position welding was much larger than that in the flat position. Consequently, the influence of the force on the keyhole molten pool was evaluated, and the flow pattern of the molten pool was found to be dominated by the sheer force. Moreover, the flow velocity and solidification morphology of the molten pool were affected by the gravity at different welding positions. In addition, the correlation mechanism of the temperature distribution, flow, and solidification morphology of the keyhole molten pool was analyzed using the combined action of shear force and gravity, which further revealed the mechanism of the influence of gravity on the keyhole welding process.

Stress Analysis of the Effect of Additional Load on the Butt Weld of Suspended Pipeline With Variable Wall Thickness

Under the special geological environment of the buried pipe, the ground is lost at the bottom of the pipe, which is created by various kinds of external factors. The pipe in the suspended state would be greatly deformed due to its own weight, internal pressure, and other factors, resulting in the failure of the pipeline. When a variable wall thickness weld occurs in the suspended section of the pipeline, the change of the pipeline stress will be more complicated and changeable. In this study, ABAQUS software is used to establish a pipe–soil model of variable wall thickness butt welds of suspended pipelines. The axial stress distribution with different affected factors in the pipe, the change of curvature, and Mises stress change of the entire pipe along the axial direction are obtained by analyzing the internal pressure, wall thickness ratio, suspended length, weld position, and cone length. The results show that the stress at the root of the weld changes significantly; therefore, the weld has a greater impact on the stress of the entire pipeline. The change of internal pressure has little effect on the stress at the pipe weld. As the suspended length increases, the change in stress at the weld is more obvious. When the weld seam is close to the soil, the support of the soil will gradually shift the maximum stress position of the pipe from the top of the pipe to the bottom of the pipe. With the increase in cone length, it will reduce the sudden change of pipe section and the change in stress effectively. The places where the curvature greatly changes along the axial direction are at the pipe–soil separation and the middle of the pipeline, while the stress reaches the maximum at the pipe–soil separation, and the place with the largest stress change is the weld in the middle of the pipeline.

A real-time method for detecting weld deviation of corrugated plate fillet weld by laser vision sensor

In the process of arc welding of the corrugated plate fillet weld, both the modification of weld position and the change of welding torch attitude are required. In general, it is difficult to accurately detect the weld position with the advanced weld detection method, and there is short of real-time in advanced weld detection. In this paper, a unique new sensor and detection method were proposed. The laser vision sensor mainly includes a camera and two circular spot laser light sources. The two laser light sources are separately fixed at two sides of the welding torch clamping piece. The axes of the two laser sources and the axis of the welding torch are parallel and coplanar, and the laser spots on both sides of corrugated plate fillet weld are symmetrically distributed on both sides of welding point. When the welding torch moves horizontally or vertically, the image position of the two laser spots in the video camera will change. Through analysis and calculation, the direction of the welding torch migration was determined, and the offset was calculated to realize the real-time detection of the position of the corrugated plate fillet weld. The experimental results showed that when the welding torch moved ±4.5 mm horizontally or vertically, the detection accuracy of the weld was 0.5 mm.

Investigation on the influence of weld position on the deformation behavior of welded tube during free bending process

The plastic deformation behavior of welded tube is affected by the non-uniform distribution of the mechanical properties of welded tube during the free bending process. To explore the influence of weld position on the forming quality and axis dimensional accuracy of welded tube, the free bending experiment and numerical simulation of welded tube were conducted in this paper. First, the principle of free bending was theoretically deduced and the stress distribution of bent tube was analyzed. Then, the hardness test and uniaxial tensile test were conducted to obtain the mechanical properties of weld zone and parent zone of welded tube. The material strength in the weld zone of welded tube is significantly higher than that in the parent zone. Finally, the free bending experiment and numerical simulation with different weld positions were carried out, and the influence of weld position on the bending radius, cross-sectional distortion, and wall thickness of bent tube was discussed. All these findings advance the insight into the free bending deformation behavior of welded tube and help to improve the forming quality of welded tubes and facilitate the application of free bending technology in welded tube.

Pengaruh Metode Pengelasan TIG dan SMAW Terhadap Sifat Mekanik Baja Karbon SS400

Welding methods that greatly affect welding, heat input in a process that can affect the cooling rate, an increase in the amount of heat input used, the cooling rate will be slower, and vice versa increasing the heat input used, the cooling rate will be faster, the cooling rate is faster. will quickly increase the hardness value of the welding results. This research was conducted on 6 pieces of SS400 carbon steel plate with dimensions of 250x100x10mm. The welding method used is the TIG and SMAW method, with a welding position of 1G and the type of connection is single v butt joint, the electrode used is E6010 with a diameter of 2.6 mm. There are 3 welding samples, where sample 1 was welded by the TIG method, sample 2 by the SMAW method. and sample 3 using the combined TIG&SMAW method. Rockwell hardness testing uses the ASTM E-18 standard with area testing on weld metal, HAZ and Base metal. Tensile testing using the AWS D1.1 standard and the microstructure standard used ASTM E3. The highest average tensile strength value is found in the combined combined sample (sample 3) of 467.5 MPa. From the test results, it was found that the sample that had the highest hardness value was a combined sample of TIG and SMAW in the weld metal area of ​​34.5 HRC. The distribution of the perlitee phase in sample 1 was 15.39%. In sample 2 as much as 15.80%, and in sample 3 as much as 15.52%. The teaching method greatly affects the mechanical properties of the welding results.

Weld Fatigue Life Analysis of Truck Mixer Sub-frame Based on Equivalent Structural Stress Method

In order to accurately calculate the fatigue life of the sub-frame weld of the mixer truck during the design stage, fatigue analysis of the weld is carried out by equivalent structural stress method. Through the finite element analysis of the frame, the key weld position is researched. By using the inertial release method, the stress response of the frame under the single excitation of the unit load is obtained. Combined with the basic principle of equivalent structural stress, the stress at the weld position is calculated, and the main S-N curve with a survival rate of 50% is selected to predict the fatigue life of the weld. The results show that the fatigue life of the key weld is 105.803 cycles, which fails to reach the design target value. The equivalent structural stress method has the characteristics of grid insensitivity and can better predict the fatigue life of the sub-frame weld of the mixer truck.