Welding Metallurgy of

Investigation of TiO2–SiO2–CaO–CaF2 based electrode coatings on weld metal chemistry and mechanical behaviour of bimetallic welds

Fluxes in submerged arc welding of high-strength low-alloy steels are not readily available, flux compositions are not clear and compositions are patented. This study aims at the design, development and optimization of flux for submerged arc welding of high-strength low-alloy steel. Extreme vertices design suggested by McLean and Anderson is used to formulate twenty-one fluxes to study the effect of flux constituents on tensile strength, percentage elongation, impact strength, diffusible hydrogen content and microstructure of the weld metal. Mathematical models for ultimate tensile strength, percentage elongation, impact strength and diffusible hydrogen content for welded specimens versus flux constituents have been developed. From the experiments, it is found that tensile strength and elongation are affected the most with Al2O3 content, whereas CaO and CaF2 contents have significant effect on impact strength. Synergic binary effect of CaO·CaF2, CaO·MgO and Al2O3·CaF2 mixtures is more than other binary mi...

Investigation on flux design for submerged arc welding of high-strength low-alloy steel:

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...

Investigating the effect of electrode preheating in novel water-cooled advanced submerged arc welding process:

Investigating the physicochemical and thermophysical properties of submerged arc welding fluxes designed using TiO2-SiO2-MgO and SiO2-MgO-Al2O3 flux systems for linepipe steels

The bimetallic welds between ferritic low alloy steels and austenitic stainless steels are widely used in the heat piping transport systems of nuclear power plants for connecting the heavy section low alloy steel components with those of high temperature stainless steel pipes. The operating experience of major nuclear power plant components has recently shown that bimetallic joints can jeopardize the plant availability and safety because of increased incidences of failure. In shielded metal arc welding process, the occurrence and severity of weld defects mainly depend upon the type of electrode filler wire and the electrode coating ingredients used. The use of nickel based filler metals is no longer considered as the final solution for unexpected failures of bimetallic welds due to incidences of hot cracking. In the present paper, an attempt has been made to design and develop an intermediate electrode based on CaO–CaF2–SiO2 ternary phase diagram system and nickel as an additional electrode coating ingred...

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

Bimetallic welds (BMWs) have been a necessity within the steam generators of nuclear power plants, where the heavy section low alloy steel components are usually connected to stainless steel primary piping systems. These welds represent zones with metallurgical discontinuities, which tend to localize the strains and cause failures. The other critical issues which must be taken care of while welding of bimetallic joints include solidification cracking, thermal fatigue and residual stresses in welds. The occurrence and severity of all these problems associated with bimetallic welds depend upon the type of welding process used along with the other variables like welding consumables, heat input etc. In shielded metal arc welding (SMAW), welding electrode consumables/coatings play an important role in deciding the weld metal quality. The development of welding electrode coatings is quite difficult due to very rapid complex reactions taking place during welding and the involvement of many controlled process variables. The present paper is an effort to highlight the general issues and challenges for the systematic and scientific development of welding electrode coatings for bimetallic welds. The experimental procedure contains three sets of coated electrodes having varying ferro-alloys, silica and carbon content. In the first set of electrodes, non-ferrous elements are also introduced into the weld metal through flux addition. Further, the welded joints are subjected to various tests and then evaluated to ascertain their mechanical as well as metallurgical behaviour.

Effect of Electrode Coatings on Diffusible Hydrogen Content, Hardness and Microstructures of the Ferritic Heat Affected Zones in Bimetallic Welds

The bimetallic welds (BMWs) between ferritic low alloy steels and austenitic stainless steel are used widely in steam generators of the power plants. The adoption of these welds in wide industrial applications provides feasible solutions for the flexible design of the products by using each material efficiently and economically. The present paper is an effort towards studying the development of austenitic stainless steel buttering filler material for bimetallic weld joint. The work aims at the design and development of buttering layer electrode coatings for shielded metal arc welding process using extreme vertices design methodology suggested by McLean and Anderson to study the effect of electrode coating ingredients on the buttering layer metal composition and delta ferrite content to prevent solidification cracking.

Investigations on Design and Formulation of Buttering Layer Electrode Coatings for Bimetallic Welds

ii TABLE OF CONTENTS iii-vii LIST OF TABLES viii-x LIST OF FIGURES xi-xv CHAPTER

Deepak Bhandari

Papers

Investigation of TiO2–SiO2–CaO–CaF2 based electrode coatings on weld metal chemistry and mechanical behaviour of bimetallic welds

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

Effect of Electrode Coatings on Diffusible Hydrogen Content, Hardness and Microstructures of the Ferritic Heat Affected Zones in Bimetallic Welds

Investigations on Design and Formulation of Buttering Layer Electrode Coatings for Bimetallic Welds

Design of Electrode Coatings for Bimetallic Welds