Investigations on weld metal chemistry and mechanical behaviour of bimetallic welds using CaO–CaF2–SiO2–Ni based electrode coatings

Abstract: In this paper, a novel developed water-cooled advanced submerged arc welding (WASAW) process has been designed and established. The developed WASAW process can be utilized for higher preheating cur...

Abstract: Submerged arc welding is widely used for manufacturing of pipelines. In the present study physicochemical and thermophysical properties of TiO2-SiO2-MgO and SiO2-MgO-Al2O3 based rutile acidic SAW fluxes were studied. Twenty one flux formulations were designed based on the extreme vertices design methodology. Fluxes were analyzed using x-ray fluorescence (XRF), TGA, DSC, Hot-disc and XRD techniques. Bond length behavior of different fluxes were analyzed using Fourier transform infrared spectroscopy. For finding the thermal stability and enthalpy change of fluxes TGA and DSC was performed in the range 25–900 °C. Hot disc technique was used to estimate the thermophysical behavior such as specific heat, thermal diffusivity and thermal conductivity of each flux. Density and grain fineness number of flux was investigated at room temperature. Multi response optimization was carried out to derive the optimized flux combinations.

Abstract: Submerged arc welding is widely used in pipeline manufacturing due to higher efficiency as compared to the other welding processes In present study, TiO2-SiO2-CaO and SiO2-CaO-Al2O3–based submerge

Abstract: Pipeline welding is an integral part of oil and gas exploration industries. Often the weld failures are observed due to lack of weld quality, improper heat treatment and poor workmanship. Further, the use of new materials in pipeline industry puts focus on a better understanding of requirements for welding and reducing the failures in future. This necessitates the need for development and design of suitable welding fluxes for joining of these materials. In this paper an attempt is made to analyse the effect of commercial submerged arc welding flux and laboratory prepared agglomerated submerged arc welding fluxes (of basic, rutile basic and rutile acidic type) on the weldability, microstructural evolution as well as the structural integrity issues in API X70 line pipe steel welds. The mechanical and microstructural behaviour of weld joints was observed for submerged arc welding fluxes. The maximum tensile strength of 613 N/mm2 was observed for weld joint prepared using commercial flux (C.F). While in case of agglomerated fluxes the maximum value of tensile strength observed was 561 N/mm2 for F15B basic flux. Impact toughness for all the weld joints was evaluated both at room temperature and at −65 °C. For the weld as well as the heat-affected zone, the maximum impact toughness (160 J and 436 J) was observed for basic flux F5B at room temperature while at −65 °C (16 J and 30 J) impact toughness was obtained which was similar to that obtained with commercial flux. Microhardness of commercial weld joint (232 HV) is maximum as compared to the other weld joints. Maximum microhardness of 222 HV was observed for weld joint fabricated with flux F15B. Flux F15B shows a maximum value of microhardness (218 HV) for the heat-affected zone. Weld joints fabricated by using F3RA and F19RA fluxes exhibit high susceptibility to hydrogen induced cracking as compared to the remaining weld joints. The crack sensitivity ratio (CSR %) is high for weld specimen F3RA (54.64%) and F19RA (50.26%) while weld specimen fabricated using (F5B and C.F) fluxes show minimum crack sensitivity ratio (27.54% & 30.97%) respectively. The high susceptibility towards hydrogen induced cracking may be attributed to the very low value of carbon equivalent as compared to the remaining weld joints.

Abstract: A problem facing the product development community is the selection of a set of conditions which will result in a product with a desirable combination of properties. This essentially is a problem i...

Abstract: Desirability functions have been used extensively to simultaneously optimize several responses. Since the original formulation of these functions contains non-differentiable points, only search methods can be used to optimize the overall desirability response. Furthermore, all responses are treated as equally important. We present modified desirability functions that are everywhere differentiable so that more efficient gradient-based optimization methods can be used instead. The proposed functions have the extra flexibility of allowing the analyst to assign different priorities among the responses. The methodology is applied to a wire bonding process that occurs in semiconductor manufacturing, an industrial process where multiple responses are common.

Abstract: First introduced in 1965, the concept of a "desirability function" has gained wide acceptance as a method of determining parameter settings to optimize a process with multiple output measurements. Unfortunately, little attention has been paid to the underlying assumptions of decision theory on which the procedure is based. This paper demonstrates critical issues that can arise from blind adherence to this procedure.

Abstract: The current work was carried out to characterize welding of AISI 310 austenitic stainless steel to Inconel 657 nickel–chromium superalloy. The welds were produced using four types of filler materials; the nickel-based corresponding to Inconel 82, Inconel A, Inconel 617 and 310 austenitic stainless steels. This paper describes the selection of welding consumables for the joint. The comparative evaluation was based on hot-cracking tests (Varestraint test) and estimation of mechanical properties. According to Varestraint tests, Inconel A showed the least susceptibility to hot cracking. In tension tests, all weldments failed in the weaker parent metals (i.e., Inconel 657). Moreover, Inconel A weldment had the highest strength and total elongation. On the other hand, the weld metals failed by ductile fracture except Inconel 617, which exhibited mixed fracture mode. At last, it was concluded that Inconel A filler material offered the best compromise for the joint between Inconel 657 and 310 stainless steel.