Electron Beam Welding Joints Research Articles

Numerical Simulation on Electron Beam Welding Temperature Field of Al-Li Alloy

The numerical simulation of electron beam welding temperature field for 2090 Al-Li alloy sheet of 2 mm thickness is conducted by using the ANSYS software. The combined model of Gauss surface heat source with cylindrical body heat source in linear attenuation is used according to the unique nail-shaped weld of electron beam welding joint, and the distribution cloud image of temperature field and the instantaneous weld thermal cycle curves of Al-Li alloy electron beam welding are obtained through calculation. The effect of welding parameters such as electron beam power and welding speed on the distribution of temperature field and weld width is investigated. Results show that electron beam welding has a very high rate of both temperature ascending and descending, and the rate of temperature ascending is higher than that of descending. With the increase of electron beam power or decrease of welding speed, the temperature of fusion zone elevates, and the weld width increases. The appearance of weld obtained through numerical simulation is greatly consistent with the practical welding.

Influence of Cooling Channel in First and Side Walls on Welding Residual Stress of Test Blanket Module for Iter

The cooling channels have to be installed in the first and side walls in current design of Japanese test blanket module for the international thermonuclear experimental reactor (ITER) and these walls are planned to be joined by electron beam (EB) welding. Since the EB weld joint is intended near the cooling channels in the first wall, thermal elastic-plastic finite element analyses were conducted to examine the influence of the cooling channels on the welding residual stress. From the computational results, it was found that there would be a risk of stress corrosion cracking (SCC) on the surface of the cooling channels, due to large tensile residual stress. As a result of serial numerical studies by using simplified model for examining the position of the weld joint, it was revealed that the residual stress on the surface of the channels would decrease by changing the distance between the weld line and the cooling channels from 10 to 16 mm. Also, the movement of the weld line would make the plastic strain distribution on the surface of channels uniform and let the distribution to the weld line symmetric. Then, it can be concluded that the uniformity and symmetrical distribution might make a selection of appropriate conditions for simpler post-weld heat treatment (PWHT).

Special features of the structure and properties of electron beam-welded joints in thick steel plates

Investigations were carried out on the special features of the structure and properties of electron beam welding joints in 150 mm thick plates of pearlitic steel 16GNMA and 160 mm plates of 12Kh2MFA steel. It is shown that using vacuum as the shielding medium results in the efficient removal of gases from the weld pool and reduces the content of alloying elements with high vapour tension.

Effects of the heterogeneity in the electron beam welded joint on fatigue crack growth in Ti–6Al–4V alloy

The heterogeneity of electron beam (EB)-welded joints in thick Ti–6Al–4V alloy plates is defined and described. The microstructure, hardness, and fatigue crack growth rate (FCGR) in the fuse zone (FZ) and the heat-affected zone (HAZ) of thick Ti–6Al–4V alloy EB-welded joint are studied using a new testing and interception method. The fatigue fractographs, crack growth paths and the microscopic deformation are observed through scanning and transmission electron microscopy. The effect mechanism of heterogeneity in the electron beam weld joint to FCGRs is discussed. The results reveal that FCGR is higher in the HAZ than in the FZ, mainly because of the effect of heterogeneity I of the welded joint. Heterogeneity II increases from the top to the root of the welding seam while the size of the α′ phase decreases. Consequently, FCGR is higher at the root of the welding seam. Heterogeneity in the joint is found to greatly influence the FCGR.

Effect of electron beam welding on the microstructures and mechanical properties of thick TC4-DT alloy

Electron beam welding (EBW) was applied to 50 mm thick damage-tolerant Ti–6Al–4V (TC4-DT) alloy, and microstructure, microhardness and tensile properties of the defect-free welded joints were examined. The results indicated that the microstructure of the base metal is composed of primary α phases and the lamellar (α + β) bimodal structure. For the EBW joint, martensite basketweave microstructure is formed in fusion zone (FZ). Moreover, the heat affected zone (HAZ) near FZ consists of acicular martensite and a small portion of primary α phase. The HAZ near base metal consists of primary α phase and transformed β containing aciculate α. It is found that the boundary of the two portions of the HAZ was dependent on the β phase transus temperature during weld cooling. Microhardness values for FZ and HAZ are higher than that of base metal, and there are the peak values for the HAZ near the weld metal. The fracture locations of all the EBW tensile specimens are in base metal, and the ultimate tensile strength of the joints may reach about 95% of the base metal. In addition, with the depth increasing along the weld thick direction, the grain size of the FZ decreases and microhardness increases.

Crack formation and control upon the electron beam welding of TiAl-based alloys

Electron beam welding experiments on 2.5-mm-thick as-forged Ti–43Al–9V–0.3Y intermetallic plates were carried out. Cold cracking occurred in the direct electron beam welding joints because of the brittleness of the microstructure and the residual stress. A crack-free electron beam welding joint was obtained by a new composite control method. This process can prolong the high temperature stage to promote the phase transformation and to give the expected microstructure of the joint. The microstructures and tensile strengths of the joints were examined by TEM, X-ray diffraction, electron back scattering diffraction and universal test machine. The weld obtained by the composite control method was characterized by an analysis of the combined phase structure of the γm grain and the γ/α2 colony microstructure. The tensile strength of the joint that was obtained by the composite control method was found to be 411.3 MPa, which is 20% higher than the direct welding joint.

Microstructures and high temperature mechanical properties of electron beam welded Inconel 718 superalloy thick plate

The microstructures and high temperature mechanical properties of whole and slices in Inconel 718 thick plate joint obtained by electron beam welding (EBW) were studied. The results show that, in the joint welded by full and cosmetic penetration, dendrites preserve in the top and bottom of welding center and columnar crystals emerge in the middle. The grain size in heat affected zone (HAZ) becomes smaller and smaller from top to bottom of welding line. The δ-phase precipitate in grain boundary and γ-phase is obtained inside the grain of EBW joint, which was heat-treated with solution and double aging. The most of δ-phases appear in the weld center and the less turn up in HAZ and base material zone (BMZ). The tensile strength σ b, yield strength σ s and elongation δ of the whole joint at 650°C are 1 100 MPa, 800 MPa and 18%, which reach 90%, 80% and 80% of base material's, respectively. The maximum σ b, σ s and δ lie in the bottom of joint and attain 1 170 MPa, 870 MPa and 18%, separately, while the minimum σ b, σ s and δ appear in the top of joint and reach 1 080 MPa, 780 MPa and 7%, respectively. The fracture of top weld is brittle; however, the ones of middle and bottom joint are flexible. The microhardness in HAZ and BMZ is higher than that in weld center. The value of microhardness tends to be lower as more δ-phase.

Effect of PWHT on the Mechanical and Metallographical Properties of a Dissimilar-Metal Weld Joint of F82H and SUS316L Steels

The effects of post-welding heat treatment (PWHT) at temperatures ranging from 640°C to 750°C for 1 h on the mechanical and metallographical properties of a dissimilar-metal electron beam weld (EBW) joint of reduced activation ferritic/martensitic steel, F82H, and SUS316L austenitic stainless steel were investigated. The EBW joint is demarcated into five regions: the base metal of F82H (F82H-BM), the heat-affected zone of F82H (F82H-HAZ), the interlayer at the edge of F82H-HAZ (IL), the weld metal (WM), and the base metal of SUS316L (SUS316L-BM). No hardening resulting from welding and no significant change in the hardness resulting from PWHT above 640°C were observed in the F82H-BM, SUS316L-BM and WM. However, a significantly higher hardness was observed in the as-welded F82H-HAZ and IL than in other regions, and a significant reduction in hardness occurred in F82H-HAZ and IL, as a result of PWHT above 640°C. Irradiation hardening after PWHT at 720°C was investigated using proton-irradiation at 300°C up to 0.1 and 1 dpa. The irradiation hardening of the WM, IL and SUS316L-BM, which was less than that of the as-received SUS316L, was much larger than that of F82H-HAZ and F82H-BM.

Study on Dissimilar-Material Welding with Vanadium and Austenitic Stainless Steel

The hardness distribution and the effect of post welding heat treatment (PWHT) at 600°C and 1000°C for 1 h and aging heat treatment at 600°C for 1000 h in the dissimilar-material electron beam weld (EBW) joint with pure-V and SUS316L austenitic stainless steel were investigated. The electron beam was positioned just on the butt joint (EB00), shifted by 0.2 mm (EB02) and 0.4 mm (EB04) on the pure-V side. The EBW joint was distinguished into the base metal of V (V-BM), weld metal (WM), interlayer at the edge of the WM of SUS316L side (IL) and base metal of SUS316L (SUS316L-BM). The IL was observed only in the EB02 and EB04 joints. The formation of macro-pore was observed in the EB04 joint. Much higher hardness was observed at the WM and IL of the as-welded EB00 and EB02 joints than the other regions of them. The hardness change in the WM was relatively small due to the PWHT at 600°C up to 1 h, whereas significant increment was observed due to the PWHT at 1000°C for 1 h regardless of the EB position. The hardness of the IL after the PWHT at 600°C was almost twice higher than that of the as-welded one, which showed slightly further increment at 1000°C. Rapid increment of the hardness due to the aging at 600°C for 1–10 h and slightly further increment of it due to the aging for 100–500 h occurred in the WM of the EB00 joint.

Influence of welding processes on microstructure, tensile and impact properties of Ti-6Al-4V alloy joints

Titanium alloys have been successfully applied for aerospace, ship and chemical industries because they possess many good characteristics such as high specific strength, superior corrosion resistance and excellent high temperature resistance. Though these alloys show reasonable weldability characteristics, the joint properties are greatly influenced by the welding processes. Weld thermal cycle of the processes will control the weld metal solidification and subsequent phase transformation and resultant microstructure. The welded joints of Ti-6Al-4V alloy were fabricated by gas tungsten arc welding (GTAW), laser beam welding (LBW) and electron beam welding (EBW) processes. The joints fabricated by EBW process exhibit higher strength compared with the GTAW and LBW joints; but the joints by GTAW process exhibit higher impact toughness compared with the LBW and EBW joints. The resultant tensile and impact properties of the welded joints were correlated with the weld metal microstructures.

Comparison of Electron Beam and Friction Stir Weldments of Modified 12 wt% Ferritic Stainless Steel

This article presents the comparative evaluation of microstructural features and mechanical properties of electron beam welded (high energy density fusion welding) and friction stir welded (FSW) (solid-state welding) 409 M grade ferritic stainless steel joints. Optical microscopy, microhardness testing, transverse tensile, and impact tests were performed. The coarser ferrite grains in the base material are changed to finer grains consisting duplex structure of ferrite and martensite due to the rapid cooling rate and high strain induced by severe plastic deformation caused by frictional stirring. On the other hand, columnar dendritic grain structure of alpha ferrite with grain boundary martensite was observed in fusion zone of electron beam welded (EBW) joints. Tensile testing indicates overmatching of the weld metal relative to the base metal irrespective of the welding processes used. The EBW joint exhibited superior impact toughness compared to the base metal and FSW joint.

Effect of welding processes on AA2219 aluminium alloy joint properties

AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding (GTAW), electron beam welding (EBW) and friction stir welding (FSW) processes. The effects of three welding processes on the tensile, fatigue and corrosion behaviour were studied. Microstructure analysis was carried out using optical and electron microscopes. The results show that the FSW joints exhibit superior tensile and fatigue properties compared to EBW and GTAW joints. It is also found that the friction stir welds show lower corrosion resistance than EB and GTA welds. This is mainly due to the presence of finer grains and uniform distribution of strengthening precipitates in the weld metal of FSW joints.

Prospective Design of Weld Joint between First and Side Walls in Test Blanket Module for ITER

The cooling channels have to be installed in the first and side walls in current design of Japanese test blanket module for the international thermonuclear experimental reactor (ITER) and these walls are planned to be joined by electron beam (EB). Since the EB weld joint is intended near the cooling channels in the first wall, thermal elastic-plastic finite element analyses were conducted to examine the influence of cooling channels on the welding residual stress. From these results, it was found that there would be a risk of stress corrosion cracking (SCC) on the surface of cooling channels due to large tensile residual stress. As a result of serial numerical studies by using simplified model for examining the position of weld joint, it was revealed that the residual stress on the surface of channels would decrease by changing the distance between weld line and cooling channels from 10 to 16 mm. Also, the movement of weld line would make the plastic strain distribution on the surface of channels uniform and let the distribution to weld line symmetric. Then, it can be concluded that the uniformity and symmetrical distribution might make a selection of appropriate condition for post weld heat treatment simpler.

Interfacial characteristics of electron beam welding joints of SiCp/Al composites

The electron beam welding of SiCp/101Al composites has been carried out. The influence of welding parameters on weldability and mechanical properties of the welded joints was discussed. The welding parameters were therefore optimised under the current experimental circumstance. Results show that only weak interfacial reaction between SiC particle and liquid aluminium occurred. Minute quantity brittle Al4C3 compounds and single phase Si were generated in the welded joint. The interfacial reaction between SiC particles and Al matrix could be greatly suppressed by adopting appropriate technique measures such as high welding speed and low heat input. The content of Al4C3 can be therefore greatly decreased in the welded joint. Moreover, modification welding and electron beam scanning could further improve the appearance of weld, and the welded joint with better quality could be obtained.

Fatigue crack growth resistance of gas tungsten arc, electron beam and friction stir welded joints of AA2219 aluminium alloy

AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding (GTAW), electron beam welding (EBW) and friction stir welding (FSW) processes. The effect of three welding processes on fatigue crack growth behaviour is reported in this paper. Transverse tensile properties of the welded joints were evaluated. Microstructure analysis was also carried out using optical and electron microscopes. It was found that the FSW joints are exhibiting superior fatigue crack growth resistance compared to EBW and GTAW joints. This was mainly due to the formation of very fine, dynamically recrystallised grains and uniform distribution of fine precipitates in the weld region.

Effects of Welding Processes and Post-Weld Aging Treatment on Fatigue Behavior of AA2219 Aluminium Alloy Joints

AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding (GTAW), electron beam welding (EBW), and friction stir welding (FSW) processes. The fabricated joints were post-weld aged at 175 °C for 12 h. The effect of three welding processes and post-weld aging (PWA) treatment on the fatigue properties is reported. Transverse tensile properties of the welded joints were evaluated. Microstructure analysis was also carried out using optical and electron microscopes. It was found that the post-weld aged FSW joints showed superior fatigue performance compared to EBW and GTAW joints. This was mainly due to the formation of very fine, dynamically recrystallized grains and uniform distribution of fine precipitates in the weld region.

Effects of beam offset on mechanical properties and corrosion resistance of Alloy 690–SUS 304L EBW joints for nuclear power plant

The current study investigates the effect of the beam offset (BOF) on the microstructure, mechanical properties, and the corrosion resistance of the fusion zone (FZ) of Alloy 690–SUS 304L stainless steel (SS) dissimilar metal butt joints formed by electron beam welding (EBW). The experimental results showed that as the value of the BOF increased from 0 to 0.30 mm, i.e. the electron beam shifted progressively toward the Alloy 690 base metal (BM), the tensile strength of the FZ fell from 582.1 to 541.2 MPa. However, the modified Huey test results indicated that the interdendritic corrosion resistance of the FZ was significantly enhanced. Pit nucleation potential value ( E np) was raised from 385 to 1050 mV. An offset of 0.30 mm appears to be the optimal BOF setting when fabricating Alloy 690–SUS 304L SS dissimilar metal butt joints using the EBW technique.

Creep property measurements of welded joint of reduced-activation ferritic steel by the small-punch creep test

The small-punch (SP) test and the SP creep test were carried out by using a further miniaturized plate-type specimen (3 mm diameter × 0.25 mm thick). Those tests were applied to the electron-beam welded joint of reduced-activation ferritic steel for evaluating the distribution of high-temperature strength in the joint. The experimental results revealed that the distribution of the maximum load measured by the SP test at 873 K was very similar to that obtained from Vickers hardness, and the fusion zone was relatively devoid of high-temperature ductility. In addition, the ratio of the load of SP creep test to the stress of standard uniaxial creep test was calculated so that both the creep rupture curves were overlapped to convert the results of SP creep test into those of standard test. As a result, the ratio was determined to be 0.43 for the base metal and this load-stress conversion coefficient is in good agreement with that obtained from finite element analysis.

Different Behavior in Electron Beam Welding of 18 Ni Co-free Maraging Steels

Microstructures of two different 18 Ni Co-free maraging specimens A and B and their electron beam (EB) weld joints were investigated comparatively by optical microscopy and scanning electron microscopy (SEM). It is shown that both of the steels are typical lath martensite; however, grain size of specimen A is about three times as large as that of specimen B. X-ray diffraction (XRD) reveals that the amount of the reverted austenitic phase in A is obviously less than that in B. Most of the austenite distributes in plate form along grain and lath boundaries while some of it distributes as fine particles within the matrix. The microstructural differences between the two specimens led to diverse behaviors in EB welding. The specimen A is weldable but B shows obvious welding defects of pits and burn-through holes in weld face. The welding microstructure exhibits a typical dendritic morphology, and the grains in the heat-affected zone recrystallized and grew because of high temperatures of welding EB. The weldablity of the examined materials is related to the microstructure characteristics that markedly affected thermal conduction performance.

High Strength 3D Non‐Vacuum Electron Beam Weld Joints ‐ Setting of Gradient Material Properties and Testing of Weld Quality

Highly loaded structures made of modern metallic materials are increasingly being placed under stringent standards with regard to the mechanical strength and deformation properties of their individual parts as well as with regard to the loading capacity of their joints. In order to create strain profiles in individual structural components, such components are heated with an electron beam at defined locations in order to bring in local microstructure changes and consequently the targeted local changes in the strength and deformation properties of the material with respect to a delayed crack growth. Additionally, components with specifically set tensile strength are welded to high quality structures. For this purpose the young but efficient non‐vacuum electron beam welding (NV‐EBW) method is used and further developed. Weld quality is examined especially in regard to an improved beam positioning, process control and weld joint defect detection.