Weld Line Direction Research Articles

Effect of weld line direction and paint orientation on corrosion and paint deterioration characteristics of welded part of steel

ABSTRACTOne thousand two hundred cycles of accelerated exposure experiment with combined salt water spray simulating atmospheric corrosion was performed for investigating the effect of weld line direction and paint orientation on the corrosion and paint deterioration characteristics of welded part of the steel. The corrosion depth of the weld toe of transverse weld line became 1.35 times as large as that of the base metal part because of the remained salt water on the weld toe. The coating thickness at the weld toe became thin by vertically painting on the transverse weld line. When the scribe line was installed at the thin painted weld toe under the transverse weld line, the paint blister area became 15% larger than that of the base metal part. The paint coating thickness at the weld toe in different weld line directions and paint orientations should be confirmed and ensured from the viewpoints of manufacturing and maintaining steel structures.

Effect of Weld Line Direction on Tensile Deformation Behavior

The stretch flangeability of tailor-welded blank depends on the angle between weld line and the tangential line of blank edge, which is generally the tensile direction in stretch flanging. This effect was studied by uniaxial tensile testing of tailor-welded high-strength-steel specimens with a weld line at 45, 60, or 90 degrees from the tensile direction. The 60-degree-weld-line specimen provides the highest elongation at the maximum load. This is the angle at which the strain component in the weld-line direction is close to zero. At the other angles, the weld lines, of which hardness sufficiently increases by welding, play a role as a constraint for vicinal base metal. This leads to early strain localization and low elongation. Furthermore, the elongation at the maximum load can, in some cases, exceed the uniform elongation of base metal. This is pronounced by a base metal with a low n-value.

Mechanical Behaviour Investigation Of Aluminium Alloy Tailor Welded Blank Developed By Using Friction Stir Welding Technique

The objective on the research was to investigate the mechanical properties and microstructure of tailor welded blank (TWB) made from AA6061-T6 and AA1100 using friction stir welding (FSW) process. Due to the dissimilar mechanical properties of the two aluminium alloys, microhardness test was conducted to measure the hardness distribution across the weld nugget. The mixing of two distinct materials was influenced by tool rotation speed. Therefore, microstructure analysis was carried out to investigate the grain size and shape. The grain size of AA6061-T6 has increased in the heat affected zone (HAZ) while for AA1100 has decreased. In the weld nugget, it has found a hook defects in the dissimilar aluminium joining. By using monotonic tensile load, the different weld line direction was observed with the expansion in tool rotation. The joints failure were consistently on the area of AA1100 series. Furthermore, two specimens were investigated, one through the dissimilar aluminium and the other through similiar material. Inspection of the weld nugget hardness was shown that nonhomogen material intermixing during the stiring process as confirmed by microhardness measurement.

Deep-Drawing Process Simulation for Tailor-Welded Blanks with an Elastic Blankholder

Application of tailor-welded blanks is proved to be very effective in the current trend of body parts construction. However, their formability is limited to the differences of mechanical properties of individual tailor-welded blanks parts. These differences result in non-constant material flow and a deflection of the weld line. This article is focused on the elimination of uneven material flow and weld line instability. The results have been obtained by means of laboratory measurements on the drawing tool as well as material simulation computed by LS-DYNA code. According to acquired results, it can be claimed that the blankholder force values and force distribution have a significant influence on the deep-drawing process of tailor-welded blanks. The weld line direction in consideration of the blankholder area size has influence on the deflection value. The simulation provided a reliable prediction of tailor-welded blank formability.

Thermomechanical numerical analysis of hot cracking during laser welding of 6XXX aluminum alloys

The finite element method is applied to study the mechanisms inducing hot cracking during laser welding of 6xxx aluminum alloys. The welding process of a single-sheet plate is modeled by adopting a three dimensional fully coupled thermomechanical finite element formulation, where the energy distribution due to a fiber laser heat source and the motion trajectory of the moving laser beam are specified. The temperature dependent material behavior of aluminum alloys is described by a thermo-elastic-plastic constitutive law which assumes isotropic hardening, and the plastic strain history is reinitialized during the melting and solidification process. With this numerical model, the critical mechanical and thermal responses in the welded metal sheet are used to investigate potential hot cracking mechanisms. It is found that the heat flux vector field obtained through simulation is consistent with the grain orientation in the weld bead observed experimentally. The large tensile stress in the semisolid mushy zone near the fusion line is used as an indicator for identification of hot crack initiation, which is shown to be in the direction normal to the welding line. As the crack grows from the fusion line into the weld centerline, due to the high transverse tensile thermal stress developed inside the weld central region, the crack propagation then shifts to the weld line direction. Furthermore, the effects of several manufacturing process parameters on hot cracking susceptibility are investigated. The results reveal that a smaller weld line-to-edge distance would result in a higher tensile stress state near the fusion line in the mushy zone, and thus increase the possibility of crack formation which is consistent with the experimental observations. Preliminary results also suggest that higher laser power or slower welding speed could increase the hot cracking susceptibility.

Numerical and Experimental Investigation of Influence of Weld Line Orientation on Formability in Deep Drawing of Tailor-Welded Blanks

Application of tailor welded blanks (TWBs) in automobile industry and aircraft manufacturing have been increased during past few years. Efficient material distribution and decreasing weight of the final part are some of the most important advantages of TWBs. Since tailor welded blanks are produced with at least two dissimilar and uniform or non-uniform thickness materials, they show different behavior than uniform materials during deep drawing process. In this research, the effect of weld line orientation on formability in deep drawing of tailor-welded blanks is examined using finite element simulation and experiments. The thinning behavior of the circular TWBs during a deep drawing in a square die is studied for different weld line orientations between two mild-steel blanks with different thicknesses. The numerical and experimental results indicate that the orientation of the weld line direction of the blank sheet has significant influence on the deformation behaviour. It is seen that thinning behavior is similar for two sections of TWB for the same weld line orientation. In addition, the most thinning occurs at 45 degree rotation of weld line, thus appropriate weld line orientation or the tailor blank sheets direction orientation can improve the formability of the tailor-welded blank in a deep-drawing of square cup.

Effect of Weld Line Direction and Its Position on Drawing Performance of Tailor-Welded Blanks

Nowadays, the tailor-welded blanks (TWBs) technology has been developing very rapidly in China. The quality of tailor-welded blanks becomes more and more important for the stable manufacturing of automotive panels. therefore, it’s very necessary to find out the key factors that influence the forming performance of tailor-welded blanks. This paper experimentally studies the effect of weld line direction on drawing performance. The tailor-welded blanks with the same material pair were used in the experiment, in which the weld line is straight and forms a certain angle with drawing force. The drawing tests were done with the different angles and values of relative position. The results show that the forming performance is related to the relative position of weld line and the angle between weld line and drawing force.

장력법을 적용한 필릿용접변형 제어에 관한 연구

As it has been well appreciated, the weld-induced deformation control is one of the most important issues from view point of efficiency in ship production. The weld-induced deformation is more serious in the case of thin plate block than in the case of relatively thick plate block, since, for example, heat affect zone of thin plates is wider than that of thick plates for the same heat input. Among weld-induced deformation, buckling deformation due to shrinkage and residual stress in weld line direction is one of the most serious deformation type. This paper is concerned with the controling the buckling deformation of thin plate fillet weld by applying the tensioning method. Weld experiments have been carried out for specimens with varying the magnitude and direction of tension load. The results are graphically represented to show the effect of tensioning method upon reducing the weld-induced deformation. From the present findings, its has been seen that tensioning method is one of the useful ways to control the weld-induced deformation of fillet weld of thin plates.

장력법을 적용한 박판블록의 변형제어에 관한 연구

The weld-induced deformation is more serious in thin plates than in thick plates because heat affect zone of thin plates is wider than that of thick plates and in addition internal and external constraints have much more influence upon weld-induced deformation of thin plates. This paper deals with the application of the mechanical tensioning method to butt weld of thin plates to reduce the transverse and longitudinal deformation. In order to investigate the quantitative effect of tensioning method upon the reduction of angular deformation and shrinkage in longitudinal and transverse direction of weld line, butt welding test has been carried out for several thin plate specimens with varying plate thickness and magnitude of tensile load. From the present experimental study, it has been found that the tensioning method is very effective in reducing the weld-induced residual stress as well as the weld-induced deformation.

선체 박판구조의 용접변형 제어에 관한 연구(I)

Although weld-induced deformation is inevitable in shipbuilding, it is important to reduce it as low as possible during fabrication for a more efficient production of ships' blocks. The weld-induced deformation is more serious in thin plates than in thick plates because heat affect zone of thin plates is wider than that of thick plates, and in addition internal and external constraints much more influence upon weld-induced deformation of thin plates. This paper deals with the application of the mechanical tensioning method to butt weld of thin plates to reduce the transverse and longitudinal deformation. in order to investigate the quantitative effect of tensioning method upon the reduction of angular deformation and shrinkage in longitudinal and transverse direction of weld line, butt welding test have been carried out for several thin plate specimens with varying plate thickness and magnitude of tensile load. Numerical simulation has been also carried out to compare the weld-induced deformation and residual stress. From the present study, it has been found that the tensioning method is very effective on reduction of weld-induced residual stress as well as weld-induced deformation.

Characteristics of High Temperature Tensile Properties and Residual Stresses in Weldments of High Strength Steels

In this study, high temperature tensile properties of high strength steels, POSTEN60 and POSTEN80, whose tensile strengths were 600 and 800 MPa respectively, were investigated through the elevated temperature tensile test. Residual stress measurements were also carried out to estimate the residual stress relaxation due to phase transformation (martensite transformation) in the process of cooling after welding. A finite element (FE) model which was able to include the volumetric changes due to the austenite ! martensite phase transformation was developed on the basis of the experimental results. The three-dimensional thermal elastic-plastic FE analyses using the FE model were conducted to determine residual stresses in weldments of the high strength steels. The results show that the extents of residual stress relaxation due to the austenite ! martensite phase transformation in the process of cooling after welding are approximately 0.85 � x=� Y0 and 0.75 � x=� Y0 in the FZ and HAZ of POSTEN60 and POSTEN80, respectively. And residual stresses of weld line direction in the base metal (BM) which is adjacent to HAZ, therefore, do not undergo martensitic transformation increase (655 MPa < 870 MPa) with increasing tensile strength of the high strength steels (POSTEN60 < POSTEN80).

再熱割れ感受性評価試験片が具備すべき条件

Investigating the general conditions which the specimen to evaluate the susceptibility of reheat cracking must have, a series of processes from welding to PWHT (Post Weld Heat Treatment) were modeled by 3D thermal elastic-plastic-creep analysis based on FEM for the reheat cracking test specimen used in this study.Noting the components of the welding residual stress owing to the test bead itself, the component in the direction of weld line, σx, was remarkably large and another two components perpendicular to weld line, σy, and thickness direction, σz, were small. Performing the third layer of restraint beads, σy, on the position where the reheat cracking was anticipated was large because the bending moment in the cross section became large due to the shrinkage of the following restraint beads. After the fourth layer restraint beads, σy, was not changed. This is because the bending stiffness in the cross section of the specimen became large. Performing the PWHT without whole restraint beads, σy was largely relaxed without accumulation of creep strain because the bending moment in the cross section was released. So, the evaluation of the reheat cracking susceptibility using the specimen should be performed after the whole restraint beads was laminated. When the susceptibility of the reheat cracking caused by PWHT is evaluated by the specimen used in this study, the test bead welding should be done remained the stress concentration in coarse grained HAZ but the restraint bead welding which is performed from back side should be full penetration. The plate thickness of restraint beads side should be at least four layers, which become to be full penetration.

Recognition and Tracking of Weld Line by Visual Sensing System Using Artificial Neural Network.

In order to develop a robust control system to detect a weld line and to track the weld line automatically by means of a welding robot with a visual sensor, a new control system applying the artificial neural network was constructed. Before the image taken was input to the neural network, the LOG filter was applied to the original image to enhance the weld line image, and then a binary image was generated. The binary image was input to the artificial neural network, and the weld line direction was detected. Then seam tracking was performed using the weld line direction. Because the neural network was used for detecting the weld line, a more robust control system was obtained. Moreover, as the result of seam tracking simulation, the applicability of the system to automatic welding was confirmed.

On the Robust Control of Seam Tracking Applied Observing System of Weld Line Position and Direction in Welding Robot with Visual Sensor.

In order to improve the robustness of the visual sensing system of on intelligent welding robot against noise, a new control system is constructed. In this paper, some robust control systems to track a weld line with disappeared portion are proposed. One of them is the sequential linear estimation (SLE) method, in which the weld line positions are estimated on the assumption that the weld line is linear. Another method is the position detecting observer (PDO) method, in which a scanning line is set at a front position of the image and the positions of the weld line are estimated. Furthermore, the direction detecting observer (DDO) method, in which two scanning lines to detect the weld line direction are set at a front position of the image, is proposed. As the result of tracking experiments, the effectiveness of these systems are confirmed.

厚板80kg/mm&lt;SUB&gt;2&lt;/SUB&gt;高張力鋼溶接部の脆性破壊発生特性(第3報)

Effects of residual stress and repair welding on the brittle fracture initiation in weld fusion line of the manual arc welded joints for 80kg/mm2 high strength steel were investigated using the wide plate tension test specimen with an angular distortion and a surface notch. And the results were analyzed by application of the fracture mechanics. The main results are summarized as follow:(1) The maximum residual stress of T-shaped welded joints is about 50kg/mm2 in the direction of weld line. That of repair weld zone is about 35kg/mm2 in the direction of right angle with weld line and is about 50kg/mm2 in the direction of weld line.(2) The brittle fracture strength of the T-shaped welded wide plate specimen with a surface notch, is lower than that of the transversely welded W(1) specimen. The test results with the specimen in which residual stress is superimposed can be adjusted quantitatively by taking stress intensity factor KR of Eq. (4) into consideration. The fracture toughness obtained by the above procedure agrees with that of a transversely welded W(1) specimen without residual stress.(3) The fracture toughness of the repair welded wide plate specimen almost equals to the minimum values of stress relieved welded joints when the notch tip is heated to the temperature range, 300-550°C, in repair welding. Therefore, the fracture stress of the repair welded joints is extremely lowered if defects remain in the fusion line. But it is as high as the fracture stress of the transversely welded W(1) joints as welded, when the maximum temperature of notch tip is below 250°C in repair welding.(4) It is important that the maximum heat temperature of fusion line is below 250°C in repair welding. Removal ofhydrogen by heating is effective, but its temperature should be below 250°C.(5) We calculated relation between fracture stress and crack length of T-shaped welded joint and repair weld zone for welded structure.