Papers by Keyword: Dissimilar Metal Welding

Abstract: The performance of dissimilar activated tungsten inert gas (A-TIG) welding on the welds morphology, angular distortion, and mechanical properties in dissimilar metal plates were investigated. Autogenous TIG welding process was applied to the JIS G3131 mild steel and type 316L stainless steel through a thin layer of activating flux to produce a butt-joint weld. CaO, SiO₂, Fe₂O₃, and Cr₂O₃ fluxes were used as the activating fluxes. The experimental results indicated that the SiO₂, Fe₂O₃, and Cr₂O₃ fluxes can increase joint penetration in both of the 316L stainless steel and the JIS G3131 mild steel. The CaO flux only can increase the joint penetration of the mild steel. The reversed Marangoni convection are considered to the main factors for increasing penetration of A-TIG on dissimilar welds in this study. Furthermore, TIG welding with SiO₂ powder can significantly reduce the angular distortion and increase the tensile strength of the dissimilar weldment.

Abstract: The use of temper bead technique in an attempt to eliminate the conventional postweld heat treatment (PWHT) in welding of A508 steel with Alloy 52 filler metal was evaluated. A PWHT at 621°C for 24 h reduced hardness in the heat-affected zone (HAZ) of the conventional welds but led to forming a carbon-denuded zone near the weld interface. The temper bead welding process not only softened the hardness in the HAZ but also diminished the carbon-denuded zone of A508-Alloy 52 welds. Apparently, the temper bead technique provides a convenient and time- saving process for welding/repairing large structural components.

Abstract: DE-GMAW (Double-Electrode Gas Metal Arc Welding) is a new welding technology. It is possible to change the melting current while the base metal current still be controlled at a desired level because the changed part of the melting current would be bypassed without flowing through the workpiece. So the heat input of base metal can be controlled accurately in DE-GMAW, and this welding method is suitable for dissimilar metal welding which has strict requirements for heat input of base metal, such as joining of steel and aluminum. On the basis of heat source model of DE-GMAW, numerical simulation and analysis on temperature field and residual stress for DE-GMAW in bonding steel and aluminum were done. The results show that residual stress after welding changed sharply from close 0 MPa to about 130 MPa at the interface of aluminum and steel. This value is greater than the binding force of steel, aluminum interface.

Abstract: Spot welding between Al alloy and some kinds of steels by friction stirring was conducted. In the process, a rotating tool was plunged into the Al alloy which was overlapped onto the steel plate, and held at the plunge depth for a few seconds with rotating condition. In this welding, friction stirring was adopted only inside of the Al alloy, and welding between Al alloy and steel is performed by an interaction of stirred Al alloy to the fixed steel surface. Mechanical strength of the joints was evaluated by both tensile shear test and cross tensile test. From the observation results on the microstructure of the weld interface, it was found that Fe/Al intermetallic compound with a few m thickness was formed at the interface. It was found that Zinc coated layer intrinsically has a role to protect the steel materials at a static condition, however, in the stirring condition of Al alloy, Zinc layer easily moved toward the outside of stirring zone and resultant fresh surface of the steel enables formation of the higher mechanical strength of the joint.

Abstract: Laser welding process is widely used in the industrial field due to its numerous advantages: a small heat affected zone(HAZ), deep penetration, high welding speed, ease of automation, single-pass thick section capability, enhanced design flexibility, and small distortion after welding. In this paper, the laser weldability of Austenite stainless steel and INCONEL600 at dissimilar metal welds using a continuous wave Nd:YAG laser are experimentally investigated. INCONEL600 is being used in a steam generator tubing of pressurized water reactor(PWR) exposed to some corrosion. Therefore stress corrosion cracking can occur on this material. A research work is conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, laser power and welding speed were tested.

Abstract: Fatigue crack propagation behavior near the fusion line between SA508 ferritic steel and Ni-based buttering metal was studied to assess the integrity of dissimilar metal welded zone in reactor pressure vessels. Ni-based filler metal has been used as a buttering or filler metal to weld the ferritic steel to the Ni-alloy or austenitic stainless steel. The J integral value and stress field at the crack tip in a simulated small-CT welded specimen model was calculated by using the commercial FE calculation code to anticipate the effect of the yield strength differences between dissimilar metals. If the Ni-based buttering metal has lower yield strength, which means the decrease of material constraint by the weld metal, the J integral value of the crack tip in the base metal near the fusion line was calculated higher than that of the base metal. The fatigue crack propagation behavior near the fusion line was measured by using the small-CT welded specimens of 5 mm thickness. The relationships between da/dN and )K were measured in the base metal and the HAZ near fusion line. The yield strength of the weld metal including microstructure at the joint can be considered more effective than the material constraint on explaining the behavior of fatigue crack propagation near the fusion line.

Abstract: Dissimilar metal welding (DMW) are used widely in various industrial applications due to the practical importance from the technical and economic aspect. However, DMW have several fabricative and metallurgical drawbacks that can often lead to in-service failures. For example, the most pronounced fabrication faults are hot cracks. Recently, DMW have used the several of heat source to decrease such as faults. Laser welding process has, in recent years, attracted more attention due to its special features: a small heat-affected zone and narrow weld bead due to the low heat input; welding at high speed; welding can be carried out in areas of difficult access; contactless energy transfer; welding in an exact and reproducible manner; possibilities for automation and robotization, and welding performed in various atmospheres. In this paper, the weldability on dissimilar metal welding of austenite stainless steel and carbon steel using Nd:YAG laser with a continuous wave was experimentally investigated.