Welded Portion Research Articles

Evaluation and Prediction of Formation of Heat-Affected Zone and Mechanical Properties According to Welding Method of STS 316L/A516-70N Clad Plates

Two welding methods of FCAW (Flux-cored arc welding) + FCAW, and FCAW + GTAW (Gas tungsten arc welding) were compared to identify effective routes for STS 316L/A516-70N clad stainless steel. Since the welding speed of the FCAW + GTAW welding method is slower than that of the FCAW + FCAW welding method, the amount of heat input is large, the size of the heat-affected zone formed is larger, and the amount of angular deformation is also large. The microstructure and deformation of the welding specimens were investigated by computational simulation, and the results were compared with calculated results for actual specimens. The results were very similar, thus confirming the high accuracy of the calculation. After measuring the hardness value of the actual welded specimens, the specimen welded by the FCAW + FCAW welding method was found to have a higher hardness value. The hardness of the welded portion of the FCAW + GTAW specimen tests tended to remain at nearly the same value throughout the specimen, indicating that the FCAW + GTAW hardness profile is desirable. In the computer simulation, butt welding was used to set the optimal heat source conditions for the two welding methods, and the effect of heat formed during welding was confirmed using the thermal analysis results according to the conditions. Based on the butt welding conditions, the residual stress and strain for the two welding methods are discussed, using calculations for the welding of C-seam (circumferential seam) and L-seam (longitudinal seam) used in the manufacture of pressure vessels.

Investigating the redundancy of steel truss bridges composed of modular joints

The objective of this paper is to present a numerical investigation of the redundancy of steel truss bridges composed of novel modular joints when subjected to the sudden loss of diagonal members. The modular joint - a prefabricated steel nodal connector composed of flat web plate welded to flat and curved cold bent flange plates - represents a new approach to the construction of steel truss bridges in which the connector is a module that joins member that are standard rolled wide flange sections. A unique feature of this approach is that a moment-resisting connection is achieved in a truss topology by joining webs and flanges independently through bolted splice connections. This, in combination with orienting members in strong axis bending, provides the potential for the system to tolerate the loss of a diagonal member through load redistribution in flexure. The response of a 119-m (390-ft) simply supported vehicular bridge following the abrupt loss of a diagonal is numerically investigated considering three behaviors: (1) instantaneous dynamic behavior, focusing on the effect of the high-velocity stress wave, with its associated high strain rates and impact on fracture toughness particularly in the cold bent and welded portion of the modular joint, (2) short-term dynamic behavior of the structure, and (3) static behavior of the faulted structure. Results show that the modular joint is able to redistribute load after sudden member loss, demonstrating the redundancy of this new approach to modular construction.

Characteristic Study of Friction Stir Welding of Aluminium Alloy AA7075 Using H13 Surface Hardened Tool Steel with Variable Tool Pin Design

Friction Stir Welding is a solid-state process where a tool which is not consumable rotates between two metals or alloy. In FSW process heat is generated because of the friction that is developed between the tool and the work piece below the melting point of the material. Compared to conventional welding this FSW process can be used for welding alloys such as aluminium, copper, etc. In this process, we can even weld two different types of alloy together which is not possible in conventional welding. Aluminium alloy AA7075 (Al-Zn-Mg-Cu) is a type of alloy which shows high strength and corrosive resistant because of the zinc content in the alloy. This zinc act as a sacrificial anode for the alloy which forms a outer covering on the surface of the alloy which is the one which gets corroded first and then followed by the alloy. In this FSW the parameters play the significant role that determines the weld characteristics. Here, aluminium alloy of series AA7075 of thickness 6mm is welded by Friction Stir Welding Process. This alloy contains zinc with a minimum amount of 5.8%. This zinc acts as a sacrificial-anode in sub-marines application, where this zinc forms like an outer covering layer on the surface of the submarine. So, this zinc gets corroded first keeping the sub-marine safe for a long period. After the Friction Stir Welding Process is completed, different tests are performed in the welded portion of the alloy. The test starts with the Ultimate Tensile Test followed by the Impact hardness test and the microstructure of the welded portion is studied. The welding parameter such as rotational speed, transverse speed is optimized in this process by using the Taguchi analysis. Taguchi method greatly improves the design and engineering productivity. This method is very effective on regard of its simple experimental design and systematic approach to produce better quality at lower costs. The optimum results can be obtained by providing the input functions and can easily produce better results. By this effect of input variables the results can be formed by S/N ratio and response means. The Larger is better criteria is employed to our problems.

Optimization of a Welded Portion of the High Pressure Compressor Rotor

An integrated method for optimization of a welded portion of a high pressure compressor rotor as a single object is developed. The minimum mass criterion is used in the optimization method; limitations are imposed in accordance with strength and stiffness requirements. An example is given of optimization of a typical welded portion of a high pressure compressor rotor resulting in mass reduction and increase of cyclic durability.

Microstructure Evaluation on Friction Stir Welding of Cryorolled 2219 Aluminum Alloy

Abstract This article presents a study of friction stir welding (FSW) on cryorolled (CR) AA2219 alloy using a hexagonal pin tool with different set of process parameters. Normally, AA2219 alloy is difficult to weld, but it is possible to get a defect-free, sound weldment with a solid-state welding technique (FSW) compared to traditional welding methods. Here, among the 9 weld joints, the weld made on CR AA2219 by the hexagonal pin tool with 1,000 r/min tool rotational speed at 25 mm/min welding speed and 3° axis inclination exhibited better tensile strength, impact toughness, hardness, and corrosion resistance. It was confirmed by microscopy analysis that the ultrafine grains structure and dissolution of Al2Cu were present at the weld zone. The fine dimple morphology was found at the fracture surface area of weldment. Also, the X-ray Diffraction (XRD) and energy-dispersive X-ray results showed that the intensity of Al2Cu was decreased at the weld portion for the CR AA2219. Dissolution of precipitates resisted the flow of electrons and delivered good resistance against corrosion. Corroded portion surface topography was analyzed, and pit details were measured.

Prediction of weld porosity (pit) in gas metal arc welds

Recently, in the automobile industry, the use of zinc-plated high-strength steels has been increasing to lighten vehicles and improve safety. In this scenario, gas metal arc welding (GMAW) processes are applied to automobile bodies and chassis parts. However, porosity defects occur in the welds because of the zinc vapor formed in the zinc coating layer during the GMAW process. This causes a decrease in the strength of the welded portion. These porosity defects have internal porosity and external pits, but in the actual production line, the quality of the welds is assessed by the occurrence of defects in external pits. In this study, using arc voltage and a system based on the waveform of the welding current, feature variables were extracted to characterize the sizes of external pits formed in high tensile strength galvanized steel during the GMAW process. Subsequently, a size prediction model was applied to predict the sizes of the external defects in the pits, and the results were verified using a multiple linear regression model and an artificial neural network.

Corrosion behavior of Friction stir welded aluminum alloys: A review

A review on corrosion behavior of Friction Stir Welded aluminum alloys has been presented. Objective of the work is to discuss the behavior of Friction Stir Welded aluminum alloys under chloride environment. The variation of corrosion potential and corrosion rate for the welded portion and base metal and within the welded region for various zones like weld nugget, HAZ and TMAZ has been studied. Alloys of series 2XXX, 5XXX, 6XXX & 7XXX are considered and a comparison is made in between heat treatable and non-heat treatable alloys on basis of their response to chloride atmosphere. The effect of tool rotational speed, traverse speed & tool profile on and are investigated. It is concluded that 5XXX series alloy exhibit better corrosion resistance compared to other series whereas 2XXX & 7XXX are most susceptible to corrosion. It is found that except for hexagonal tool profile corrosion rates of welded joints are higher than the parent metal for both heat treatable as well as non-heat treatable alloys.

Modified Coring Tool Designs Reduce Iceberg Lettuce Cross-Contamination

Contaminated coring tools may transfer bacteria to iceberg lettuce. The efficiency of coring tool design modifications in reducing bacterial transfer to lettuce heads was evaluated under simulated field operations. The standard coring tool consists of a stainless steel cylindrical tube welded to a tab that is inserted into a plastic handle. Design modifications included removal of the welded portion, incorporation of a shorter front straight bottom edge, or an angled bottom edge toward the front. In the first study, coring tools of four different designs were inoculated by dipping in a tryptic soy broth (TSB) suspension that contained 8.85 Log CFU/mL of Escherichia coli K-12 and then were used to core 100 lettuce heads, consecutively. Use of the standard tool resulted in 91% ± 9% positive lettuce heads. Removing the welded surface from the standard tool resulted in the highest reduction of E. coli transfer (44% ± 11.9% positive lettuce heads, P < 0.05), whereas incorporation of a short front straight edge with no welding resulted in 65.6% ± 5.6% of the cored lettuce heads being positive for E. coli. Removal of the welded surface resulted in a 40% decrease in E. coli contamination among the last 20 cored lettuce heads (81 to 100), which indicates that coring tool design modifications resulted in reduced cross-contamination. In the second study, the transfer of Salmonella to coring tools after their immersion in rinsing solutions was evaluated using imaging. The tools were dip inoculated for 2 min in water, water with lettuce extract, or TSB containing 7 Log CFU/mL bioluminescent Salmonella Newport; they were then imaged to observe spatial distribution of bacteria. There was greater retention and spatial distribution of Salmonella on the surface of tools immersed in water containing lettuce extract than in TSB and water. The results of the second study indicate that rinsing solutions that contain lettuce particulate and organic load could facilitate cross-contamination of Salmonella Newport to tool surfaces.

Use of morphing techniques within weld distortion analysis to simulate the size customization of parts during assembly and welding of the vacuum vessel PS3 outer shell

During welding of large, massive and complex assemblies, the accumulated shrinkage of parallel welds may cause a cumulative distortion effect which significantly varies the dimensions and geometry of the welded portion while still unfinished. The subsequent parts to be added require customization to fit in the space to allocate them.When welding distortion analysis (WDA) is carried out, the process described of part size customization needs to be taken into account; otherwise it would be a relevant source of inexactitude for the prediction of distortion. A methodology is presented to include in WDA the size customization of the parts being added to fit into a distorted assembly.

Effects of various tool pin profiles on mechanical and metallurgical properties of friction stir welded joints of cryorolled AA2219 aluminium alloy

Friction stir welding (FSW) process was conducted on cryorolled (CR) AA2219 plate using different tool pin profiles such as cylindrical pin, threaded cylindrical pin, square pin and hexagonal pin profiles. The FSW was carried out with pairs of 6 mm thick CR aluminium plates with different tool pin profiles. The different tool pin profile weld portions' behaviors like mechanical (tensile strength, impact and hardness) and metallurgical characteristics were analyzed. The results of the mechanical analysis revealed that the joint made by the hexagonal pin tool had good strength compared to other pin profiles. This was due to the pulsating action and material flow of the tool resulting in dynamic recrystallization in the weld zone. This was confirmed by the ultra fine grain structure formation in Weld Nugget (WN) of hexagonal pin tool joint with a higher percentage of precipitate dissolution. The fractograph of the hexagonal tool pin weld portion confirmed the finer dimple structure morphology without having any interior defect compared to other tool pin profiles. The lowest weld joint strength was obtained from cylindrical pin profile weld joint due to insufficient material flow during welding. The Transmission Electron Microscope and EDX analysis showed the dissolution of the metastable θ″, θ′ (Al2Cu) partial precipitates in the WN and proved the influence of metastable precipitates on enhancement of mechanical behavior of weld. The XRD results also confirmed the Al2Cu precipitation dissolution in the weld zone.

Influences of metastable θ″, θ′ and stable θ intermetallics formed during cryorolling and friction stir welding process on AA2219

This paper presents a detailed investigation on the formation of θ′ and θ″ precipitates in the Cryorolled (CR) material of AA2219 alloy and the Friction Stir (FS) welded portion of CR AA2219 and their influence on material characterizations. The ultrafine grain formation and precipitate dissolutions in CR AA2219 and FS weld were characterized using optical, Scanning Electron (SEM) and Transmission Electron Microscopes (TEM). X-Ray Diffraction (XRD) was carried out to distinguish the phase changes of base AA2219, CR AA2219 and FS weld portion.

Control of Microstructures and the Practical Properties of API X80 Grade Heavy-Wall High-Frequency Electric Resistance-Welded Pipe with Excellent Low-Temperature Toughness

This paper describes development of heavy-walled API X80 grade high-frequency electric resistance-welded (HFW) line pipes and conductor-casing pipes with wall thicknesses up to 20.6 mm. A fine bainitic–ferrite microstructure, which is preferable for low-temperature toughness, was obtained by optimizing the carbon content and applying the thermomechanical controlled hot-rolling process. As a result, the Charpy ductile–brittle transition temperature (DBTT) was well below 227 K (−46 °C) in the base metal of the HFW line pipe. When the controlled hot-rolling ratio (CR) was increased from 23 to 48 pct, the area average grain size decreased from 15 to 8 μm. The dependence of CTOD properties on CR was caused by the largest grain which is represented by the area average grain size. No texture development due to the increase of CR from 23 to 48 pct was observed. In addition, because controlled in-line heat treatment of the longitudinal weld seam also produced the fine bainitic–ferrite microstructure at the weld seam, DBTT was lower than 227 K (−46 °C) at the weld portion. The developed pipes showed good girth weldability without preheat treatment, and fracture in the tensile test initiated from the base metal in all cases.

Effect of PWHT on the Hardness and fractured microstructure of IS-103Cr1 welded joint

During the welding process change of chemical and physical properties takes place due to uneven heating and cooling for improving regaining their properties heat treatment processes is one of the best methods. In the similar or dissimilar welded joints, at the welded portion it can be exist in more than one crystalline form and the carbon atom is only 1/30th size of the iron atom.In this weldment phase changes occurs in solid state due to heating or cooling (allotropic transformation).At welded portion liquid metals cools and solidification temperature approaches initial crystals are formed. These are grown in to large solid grains and each grain acts as different crystallization with the atom. A random grain growth again takes place within the melt boundary, results in a low strength. Within HAZ the grain become coarse only possible to PWHT processes.The weldments are underlying their properties so to achieve the better results that are possible through heat treatment processes.

The Effects of SiC Particle Addition as Reinforcement in the weld Zone during Friction Stir Welding of Magnesium Alloy AZ31B

&lt;div&gt;&lt;p&gt;&lt;em&gt;Welding of magnesium alloys influence a great effect on magnesium application expansion, especially in marine and aerospace where large-size, complex components are required. Due to specific physical properties of magnesium, its welding requires great control. In general, the solid-state nature of friction stir welding (FSW) process has been found to produce a low concentration of defects. Mechanical properties of friction stir welded joints are decreases than base material, so to enhance the mechanical properties of welded portion, In the present research additional SiC particulates were incorporated in the weld interface of friction stir welding of Magnesium alloy AZ31B. Silicon Carbide has been added as reinforcement by creating separate geometry, at the edges where the welding is interface with 4 different volume proportions such as 10%, 15%, 25% and 30%. Tool Steel of H13 grade has been used as friction stir welding tool. Rotational Speed of 1400 RPM and Transverse Speed of 25 mm/min were selected. Joined Mg Alloy AZ31B alloy plates were evaluated for their mechanical properties under two different conditions, i.e in the un-reinforced welded condition and reinforced welded conditions. The results of the study revealed that the mechanical properties of the SiC particulates added Mg alloy AZ31B welded joints are superior in all four proportions of SiC, compared to un-reinforced Mg alloy AZ31B welded joints. Microstructural examination of the welded joints was conducted using Optical microscope and revealed that distribution of SiC particles producing increased weld strength. The comparison of the microstructures and mechanical properties of unreinforced Friction stir welded AZ31 with those of SiC reinforced FS-welded joints showed that the addition of SiC particles decreased the grain size and increased the strength.&lt;/em&gt;&lt;/p&gt;&lt;/div&gt;

Effects of PWHT on the Hardness and Fractured Microstructure of IS-103Cr1 Welded Joint

During the welding process change of chemical and physical reactions due to the flow of heat in the weldments are varied with respect to rate of cooling time and weld axis. In the dissimilar welded joints, at the welded portion it can be exist in more than one crystalline form and the carbon atom is only 1/30th size of the iron atom. The weldments are underlying their properties so to achieve the better results that are possible through heat treatment processes.

荷重伝達型片側すみ肉溶接構造物における疲労き裂進展挙動の観察

Hydraulic excavators and cranes are major heavy equipment with numerous one-sided welded joints. Although fillet weld joints are easily implemented and economical, the unwelded portion frequently initiates crack propagation. Therefore, the welded portion is reduced by side welding and by adding a groove. However, attachments with box like structures are difficult to weld at both sides, and grooving cannot completely remove the welded portion because high-quality full penetration welds are difficult to achieve. Despite the need for an accurate evaluation method of crack propagation, the fatigue fracture mechanism and the fatigue damage in practical fillet joints with one-sided welding remains poorly understood. In this study, the fatigue properties and the fracture mechanism of the load carrying type fillet joints with one-sided welding were investigated experimentally to evaluate its fatigue damage with high accuracy based on the experimental results. As the results, fatigue cracks in the test piece initiated from the tip of the unwelded portion and propagated into the welding materials. The three-dimensional observations revealed that fatigue cracks initiate at an early stage of the fatigue development. So, we infer that the fatigue lifetime is chiefly governed by the crack propagation lifetime. Furthermore, from the three-dimensional observation results, cracks were initiated at multiple sites in the test piece. As the number of cycles increased, these cracks propagated and combined.

Ultrasonic Welding of Amorphous and Semi Crystalline Materials

Ultrasonic welding have been studied using Polycarbonate (amorphous) and Polypropylene (semi-crystalline) in presence and absence of polymeric compatibilizer. A solution phase compatibilization has been used using Polycaprolactone, Polymethylmethacrylate and Maleic anhydride grafted Polypropylene. Cylindrical samples were used in the near and far field ultrasonication in order to achieve the better weldability. The welding strength was increased while utilizing the compatibilizer than that of un-compatibilized samples. Mixture of Polycarbonate and Polymethylmethacrylate on the PC phase enhanced the weld strength tremendously. The XRD analysis revealed the increase in crystallinity during the ultrasonication process resulting the enhanced weldability. The phase fusion is quite prominent from the SEM study of the fractured surface and also from the SEM of the welded portion. The FTIR study indicated the phase interaction through the compatibilizer thus enhancing the ultrasonic weldability of the thermoplastics.

Local Deformation Behavior of Inconel 718 TIG Weldment at Room Temperature and at 550°C

The weld portion will have different mechanical properties in weld bead, HAZ and fusion boundary due to variation in the microstructure, chemistry and internal stresses that arise in the welding process. Inconel 718 TIG welded samples are tested to study the deformation behavior of the weld constituents with the help of non contact laser extensometer. Stress-strain curves for the individual constituents of weld, parent, fusion boundary and HAZ are evaluated at room temperature and at 550°C. Test results show that the welded samples exhibited 50% lower tensile properties compared to the parent material. Parent metal remains elastic through out the test. The proof stress of the weld alone is 100 MPa lower than the average proof stress of the welded sample when considered standard gauge length.

Characterization of Gas Metal Arc Welded Hot Rolled DP600 Steel

AbstractDual‐phase (DP) steels are suitable candidates for automotive applications due to their high strength and ductility. These advanced mechanical properties result from the special microstructure of the DP steel with 5∼20% martensite phase in a soft ferrite matrix. However, during welding, which is an important process in automotive industry, this special microstructure is destroyed. In this research the characterization of Gas Metal Arc (GMA) welded joining zones was performed by optical microscopy and hardness mapping. Tensile tests were also performed keeping the welded portion in the gauge length. Scanning Electron Microscopy (SEM) was used for the fracture investigation. From the characterization and tensile tests, the soften zones were found, which are caused by the tempered martensite and larger ferrite grain size than that in base metal. Furthermore, GMA welding make a large Heat Affected Zone (HAZ).

Analysis of the Influence of the Heat Input and Bead Volume on HAZ Hardness for Submerged Arc Welding Process of Mild Steel Plates

In Submerged Arc Welding process involves critical set of variables which are needed to control. An attempt has been made in this paper to find out- the influence of the heat input and bead volume on HAZ Hardness for Submerged Arc Welding Process of Mild steel plates. Mild steel plates are welded by changing input variables (current, voltage, travel speed, i.e. heat input) and Rockwell hardness no. has been observed on welded portion and at the zone adjacent to the welded portion. A detailed analysis of the microstructure changes is carried out to understand the HAZ softening phenomenon.