Welding Flux Research Articles

Reliability of Neural Implants-Effective Method for Cleaning and Surface Preparation of Ceramics.

Neural implants provide effective treatment and diagnosis options for diseases where pharmaceutical therapies are missing or ineffective. These active implantable medical devices (AIMDs) are designed to remain implanted and functional over decades. A key factor for achieving reliability and longevity are cleaning procedures used during manufacturing to prevent failures associated with contaminations. The Implantable Devices Group (IDG) at University College London (UCL) pioneered an approach which involved a cocktail of reagents described as “Leslie’s soup”. This process proved to be successful but no extensive evaluation of this method and the cocktail’s ingredients have been reported so far. Our study addressed this gap by a comprehensive analysis of the efficacy of this cleaning method. Surface analysis techniques complemented adhesion strengths methods to identify residues of contaminants like welding flux, solder residues or grease during typical assembly processes. Quantitative data prove the suitability of “Leslie’s soup” for cleaning of ceramic components during active implant assembly when residual ionic contaminations were removed by further treatment with isopropanol and deionised water. Solder and flux contaminations were removed without further mechanical cleaning. The adhesive strength of screen-printed metalisation layers increased from 12.50 ± 3.83 MPa without initial cleaning to 21.71 ± 1.85 MPa. We conclude that cleaning procedures during manufacturing of AIMDs, especially the understanding of applicability and limitations, is of central importance for their reliable and longevity.

Effect of SAW fluxes on electrochemical corrosion & microstructural behavior of API X70 weldments

High-performance pipeline steels are frequently used for storage, transportation and energy development applications. Submerged arc welding finds its application to weld thick pipes. Design and development of appropriate welding fluxes provide good structural integrity properties in severe service environments. The present study aims to investigate the effect of laboratory-developed SAW fluxes on the electrochemical corrosion behavior of SAW weldments in different environments. Electrochemical corrosion behavior of weld specimens in different environments was performed using Linear Sweep Voltammetry. Different mediums such as seawater and sodium thiosulphate solution (10−2 Mol/l, pH = 3, and 10−3 Mol/l, pH = 5) were taken for the corrosion study. The microstructure of the weld specimen reveals the presence of acicular ferrite structure. F3RA and F19RA weld specimen shows a higher corrosion rate in seawater and sodium thiosulphate medium (pH = 3 or 5).

Agglomerated flux for welding of corrosion-resistant high-strength nitrogen-containing steels

ABSTRACT The problems of Russian welding materials for welding highly alloyed austenitic steels that are not inclined to intergranular corrosion are considered. A new agglomerated flux for welding with austenitic welding materials is developed. Slag composition is selected that ensures a stable welding process, good separation of the slag crust and the formation of a seam. The possibility of introducing ferroalloys and metal powders through the flux ensures the necessary level of mechanical characteristics of the weld metal, and increases also the resistance of the weld metal to hot cracks and pore formation.

Activated flux TIG welding of austenitic stainless steels

The tungsten (W) inert gas (TIG) welding process that is applied with an active flux deposited on the workpiece surface just before welding is called activated flux TIG (A-TIG) welding. Layer deposition can be achieved by brushing or spraying over the surface, and welding is carried out after the surface dries out. This process has shown that it is possible to increase weld penetration and productivity up to three times higher or more compared with the TIG process in steels. In this review paper, A-TIG welding applications of steels were examined. The chemical composition and thickness of the flux and welding parameters (welding current, welding speed, arc length and shielding gas composition and its flow rate) affect the weld geometry. The activated flux welding mechanisms, effects of flux and welding parameters on weld geometry and microstructure and properties of A-TIG welds were explained.

Use of barium-strontium modifier for the manufacturing of welding flux based on silicomanganese slag

The possibility of using a barium-strontium modifier as a gasprotective and refining additive for welding the fluxes based on crushed slag from the production of ferrosilicomanganese is presented. The barium-strontium modifier BSK-2 produced by JSC “NPK Metalltekhnoprom” according to TU 1717-001-75073896–2005 was used as a material for the study. The base of the welding flux was silicomanganese slag produced by the West Siberian Electrometallurgical Plant. The research work on new welding fluxes and flux-additives was carried out using the equipment of the Scientific and Production Center “Welding Processes and Technologies” and the Center for Collective Use “Materials Science”. The use of barium-strontium flux additive was carried out in two ways. In the first option, the flux-additive was made by grinding barium-strontium to a dust-like fraction of less than 0.2 mm with further mixing with liquid sodium glass, drying in a furnace, crushing and separating a fraction of 0.45 – 3.00 mm. In the second option, the flux additive was used in the form of dust with a fraction of less than 0.2 mm. The additives were mixed at a ratio of 2 – 10 % of mass of the slag produced by silicomanganese. Surfacing of the samples was carried out with a welding wire of the sv-08GA grade on a substrate of steel grade 09G2S with a thickness of 20 mm. Quality of the deposited metal was studied, the chemical compositions (deposited layers, slag crusts, the used flux) were investigated by X-ray fluorescence method on XRF-1800 spectrometer and by atomic emission method on DFS-71 spectrometer. The degree of contamination with non-metallic inclusions (non-deforming silicates, point oxides, sulfides) was studied using OLYMPUS GX-51 optical microscope in the magnification range from 100 to 1000. The laboratory studies on the surfacing of steel samples have shown that due to introduction of a flux additive made from barium-strontium modifier, the metal is refined, and the concentration of sulfur and phosphorus decreases. The use of a mixture of a barium-strontium modifier with liquid glass as an additive is preferable to the use of an additive in the form of a dust. It was revealed that the best samples from the point of view of the degree of contamination of the deposited metal with nonmetallic inclusions are samples made using no more than 8 % of barium-strontium flux additive.

New submerged arc welding flux for hardfacing of Hardox steels

Abstract In this study, the usability of a new submerged arc welding flux was investigated to develop the surface properties of Hardox steels. In the hardfacing welding processes for Hardox 400 steel, four welding speeds resulting in varied heat inputs were applied. Through an analysis of the chemical composition, microstructure examinations, hardness measurements and wear tests, the possibility of hardfacing properties control due to the change of process parameters were determined. In the experimental studies, the hardness of the hardfacing obtained at a welding speed of 30 cm × min-1 was measured as 42 HRC while the hardness of the hardfacing obtained at a welding speed of 48 cm × min-1 was measured as 57 HRC. Moreover, in the wear tests, results consistent with the hardness values were obtained. It was understood in the light of the results that the use of high carbon ferro-chromium 20 wt.-% in a submerged arc welding flux mixture may be useful in improving hardness and wear properties of Hardox steels through hardfacing welding processes.

Investigations of Surface Properties of SAW Fluxes Using CaO-SiO2-TiO2 & Al2O3-CaO-SiO2 Ternary Phase Systems

In the present paper, investigation on wettability and contact angle measurement of twenty-one SAW fluxes for CaO-SiO2-TiO2 & Al2O3-CaO-SiO2 welding flux system at a temperature of 1300 °C was studied. Wettability observed by measuring the contact angle properties of twenty-one SAW fluxes. The purity of flux constituents determined by the XRF technique. Si-O-Si and Al-O-Al symmetric bond behaviour and various crystalline phases observed using FTIR and XRD techniques. Lower contact angle gives higher wetting and spreading properties. The contact angle increased with the increase of TiO2/SiO2 ratio. For the composition range 1.5 to 2.0, there is a higher value of contact angle observed. A maximum increase of contact angle noticed for the composition range 1.5 to 2.0. There is a constant rise in the amount of contact angle for the composition that varies from 1.0 to 1.2.

Influence of gas saturation on physical and mechanical properties of welded hidden seam with the flux made of the slag, obtained at manganese-silicon production

Hidden building-up under a flux layer is a perspective way for restoration of equipment. For production of welding fluxes, wastes of metallurgical production are widely used as components. In this work new results of a study of influence of gas saturation on physical and mechanical properties of hidden welding seam are represented. The seam was made under laboratory conditions with a flux, obtained at production of manganese-silicon. Concentration of oxygen and nitrogen were measured according to GOST 17745‒90 “Steels and alloys. Methods of measuring gases” by a gas analyzer TC-600 of LECO, USA. The dependences of indices of physical and mechanical properties of welded seam metal on content of nitrogen, free oxygen and oxygen compounds were determined. The carried out study showed, that oxygen and nitrogen content in the welded seam decreases the whole spectrum of physical and mechanical properties of the welded seam. Based on the obtained dependences, by the degree of harmful influence, complex oxide inclusions of silicate of alumina and magnesium spinels are most dangerous from the point of view of physical and mechanical properties decrease.

New submerged arc welding flux for hardfacing of Hardox steels

Abstract In this study, the usability of a new submerged arc welding flux was investigated to develop the surface properties of Hardox steels. In the hardfacing welding processes for Hardox 400 steel, four welding speeds resulting in varied heat inputs were applied. Through an analysis of the chemical composition, microstructure examinations, hardness measurements and wear tests, the possibility of hardfacing properties control due to the change of process parameters were determined. In the experimental studies, the hardness of the hardfacing obtained at a welding speed of 30 cm × min-1 was measured as 42 HRC while the hardness of the hardfacing obtained at a welding speed of 48 cm × min-1 was measured as 57 HRC. Moreover, in the wear tests, results consistent with the hardness values were obtained. It was understood in the light of the results that the use of high carbon ferro-chromium 20 wt.-% in a submerged arc welding flux mixture may be useful in improving hardness and wear properties of Hardox steels through hardfacing welding processes.

Microstructure and properties of nano-SiO2 activated flux TIG (A-TIG) welding of Incoloy 925 joints

• Improved depth of penetration with the use of activated, nano-oxide flux welding for Incoloy 925. • The yield and tensile strengths of the weld joints were considerably increased when subjected to direct ageing. • The occurrence of γ′, M 7 C 3 , η, and σ phases were noticed along the grain boundaries in the direct aged condition. • High angle grain boundaries (HAGBs) were dominated in the jointed regions after subjecting to ageing. Precipitation strengthened Ni based alloy, Incoloy 925 is widely used in the H 2 S-containing hot sour environments because of its excellent properties. Metallurgical properties, which is known to affect the performace of this alloy greatly depends on the welding technique adopted, ageing condition, formation of inter-metallic phases and hardness. Hence, in this research work, the joints of Incoloy 925 are accomplished in a single pass with the use of nano-SiO 2 activtated flux tungsten inert gas (A-TIG) welding process. Further, the A-TIG welded joints were subjected to direct ageing for 4 h and 8 h at 732 °C and air-cooled. Recrystallized grains were observed in the fusion region in the as-welded (AW) condition. The grain boundaries of the weld seams were precipitated with M 7 C 3 carbides, discrete amounts of η (Eta) and σ (Sigma) phases after subjecting to DA. The tensile strength of the weld seams was increased to ∼ 41 % and 31 % after having exposed to DA for 4 and 8 h respectively. The failures due to tension occurred in the fusion zone of Incoloy 925 irrespective of the DA conditions. The formation of η phase and high angle grain boundaries (HAGBs) resulted in a lower percentage of elongation and impact toughness when aged for 8 h.

Experimental investigation of structural integrity behavior of High strength low alloy steel – Study of mechanical, microstructural and corrosion behavior of Submerged arc welding weldments

The present study aims at investigating the effect of submerged arc welding fluxes for enhanced corrosion resistance of structural steel welds. By varying the basicity index of submerged arc welding fluxes the corrosion resistance and mechanical properties of weld metal such as tensile strength, impact strength, microhardness in submerged arc weldments were evaluated. The result shows that with the increase in bascity index tensile strength of weld specimen reduced while impact strength and microhardness value increased. Maximum microhardness (288 HV) was observed for flux 2 while base metal show minimum microhardness value (205 HV). Flux 5 gives maximum impact strength (94.17 J) as compared to the base metal (80 J). This is due to the reduced content of oxygen in weld metal which increases the weld metal impact toughness. Corrosion resistance of weld specimen increased as compared to the base metal. Ductile fracture mode and shear lip or tears were observed in the weld zone. Shear dimples and shear lips were more severe in base metal as well as weld metal impact specimens due to the rapid effect of external forces on the impact test. The banded microstructure of delta ferrite and austenite was observed in the base metal. Fine grains of ferrite and pearlite at the center and edges were present in the weld zone.

Structural Roles of TiO2 in CaF2-SiO2-CaO-TiO2 Submerged Arc Welding Fluxes

A series of fused CaF2-SiO2-CaO-based fluxes geared towards submerged arc welding has been prepared with incremental TiO2 additions. Through systematic investigation on physical properties, quantitative relationship between TiO2 content and corresponding structural information has been established, and the roles played by TiO2 have been profiled. It is found that TiO2 has been introduced into the silicate network by acting as network-former, increasing the degree of polymerization while lowering the strength of the flux.

Review on the use of activated flux in arc and beam welding processes

Improvement in penetration capabilities is an important issue in many welding processes. One of the most emerging trends to improve penetration capabilities is the utilization of activated flux with welding processes. A thin coating of activated flux is applied on the area to be welded with the help of brush or spray. This paper represents a review of the use of activated fluxes in different arc welding and beam welding processes. Arc welding processes are most commonly employed for various manufacturing applications and hence most applications are considered for utilization of oxide fluxes with these processes. The most common mechanisms responsible for deeper penetration due to flux application in arc welding processes are Reverse Marangoni and arc constriction. EBW Process is considered for thick plates owing to its higher fusion zone depth to width ratio. Use of activation flux concentrates electron beam which creates a narrow and deep fusion zone due to keyhole mechanism. A combination of laser with activated flux improves penetration due to exothermic reaction in the weld pool, welding quality, welding efficiency significantly and reduces cost.

OXIDATIVE REFINING OF MOLTEN STEEL USING THE WELDING FLUX WASTE

The possibility of using welding flux of the Volga pipe plant (VTZ) to improve the process of oxide refining of steel was considered.

Grain size and viscosity behaviour of developed agglomerated fluxes during submerged arc welding

The present paper studies the physical properties such as viscosity and grain size of the newly formed submerged arc welding (SAW) fluxes. The response surface methodology (RSM) was applied to formulate the design of experiments (DOE) and fluxes were developed. These properties of developed agglomerated fluxes were used to identify their effect on weld bead appearance and quality of weld. The results were found satisfactory.

Improvement of low temperature impact toughness through flux modification for submerged arc welded low carbon steel E350 plates

Objectives: To analyse the effects of rutile (TiO2) and Alumina (Al2O3) on impact toughness properties of Submerged arc welded joints for low temperature applications. Methods: Al2O3 and TiO2 have been added to F7AZ/PZ-EL8 Submerged arc welding (SAW) flux in varying quantities and the base material used for joining is low carbon structural steel having E350 grade. To verify the effect of these elements by flux modification, the Charpy V-Notch impact tests, scanning electron microscope (SEM) fractography and visible light microscopy (VLM) have been conducted. Findings: Charpy V-Notch impact testing and analysis have shown that there is considerable improvement in the impact properties of welds with the addition of 20% TiO2 and 20% Al2O3 in the 80% of flux as separate constituents i.e., when these elements have been added in the flux in separate form or two new modified fluxes were prepared, where one is doped with alumina and other is with rutile. Fractography of welds with addition of 20% alumina in 80% F7AZ/PZ-EL8 SAW fluxes are having best impact properties at lower temperature and addition of 20% rutile also as almost effective as alumina in flux. consequently, mode of failure is ductile fracture with dimples as a result of good amount of acicular ferrite microstructure. Novelty: Analysis of previous studies implicated that there is lack of significant studies in the low temperature impact properties of low carbon steel submerged arc welds. Present study shows that the significant improvement in the toughness properties of welds at lower temperature of -40◦C can be achieved through flux modification, it would ensure the application of Low carbon steel structures at lower working temperature. The applications may be pressure vessels, ships or containers. Keywords: Submerged arc welding (SAW); low temperature impact toughness; flux modification; low carbon steels

Study of Mechanical Behavious and Characterization of a Steel Joints in MIG Welding under Varying Fluxes

A lot of research work has been carried out varying welding parameters and studying its effects but rare work has been done on application of fluxes in MIG welding. Two different FeO based fluxes; Nano-flux and easy- flo flux powder were applied to the joints of 10 pcs each of 50 x 50 mm stainless and mild steel rods, galvanized and mild steel plates using MIG welding process. The samples used were welded under three categories; includes without flux (control), with nano-flux and easy-flow type-flux powder. The weld of the joints were subjected to mechanical test; hardness, tensile and morphological test; SEM and TEM examinations. The weld joints produced using the fluxes were found to have higher average values of hardness and tensile (stress and strain) of 222.73 BHN, 0.03125 and 199.97 BHN, 0.02785 respectively compare to samples without flux having lowest value of 131.36 BHN, 0.01323. The Microstructural analysis results with the use of SEM and TEM were found to have a better ordered grain structure and improved the structure, surface and pattern of the weld than those produced without flux.. The results obtained has revealed the impact of flux in MIG welding for joining steel gave better joint hardness and the structure of the weld.

Development and characterization of nano- flux welding powder from calcined coconut shell ash admixture with FeO particles

This work presents a novel nanoparticle flux powder Iron Oxide (FeO) developed from coconut shell through the chemical reduction. The analysis and the characterization of morphology and chemical properties of the developed flux powder and control were examined using Scanning Electron Microscopy, Elemental Dispersive X-ray, Transmission Electron Microscopy, and X-ray Powder Diffraction. From the results, the powder was found to contain 45.82% Iron, 44.38% carbon, 8.86% oxygen and trace amounts of manganese, Aluminum, and silicon while the control flux powder was found to contain 57.1% Fe, 23.3% O and 7.3% C which confirmed the flux powder as Iron Oxide based type. Digitizer image confirmed that the area of the particle’s sizes was in the nanometric range with the largest particle being 240 nm2 and the smallest being 9 nm2 and areas ranging from 1.319 to 490.57 nm2 compare to control. The X-Ray diffraction contains various phases of Fe with the most prominent groups wavelength 9.26. For the developed nano-flux welding powder, at 2ϑ = 38°, the value of FWHM, i.e. ∝ was found to be 0.275°, and the Dislocation density (δ) value was found to be 9.8269 × 1014 (Lines/m2), the d spacing was computed to be 2.355 Å, the Micro Strain (ε) value was 6.497 × 10−2 while the Crystallite size was 31.9 nm at hkl (111). The results confirmed that flux powder can be produced from agro-waste with better properties and applications.

Study of weld bead chemical, microhardness & microstructural analysis using submerged arc welding fluxes for linepipe steel applications

Linepipes above 16″ diameter are often submerged arc welded. Weld mechanical as well as metallurgical properties are widely affected by the flux composition. Flux composition and welding parameters play an important role in determining the good bead quality and mechanical properties of the welded joint. In present study submerged arc welding fluxes were formulated using constrained mixture design approach. Twenty one submerged arc welding flux compositions based on CaF2–CaO–SiO2 and Al2O3–CaO–SiO2 flux system were designed using extreme vertices design approach. Regression models were developed in terms of individual, binary and ternary mixture flux constituents for submerged arc series of bead on plate weld deposits (API 5 L X70 pipeline steel). By using F-test regression mathematical models have been checked for 95% significance level. Effect of formulated fluxes on silicon, copper, molybdenum, titanium and chromium content was studied using a multi-layer weld deposits. All binary mixtures C·Al, S·CF, S·Al and C·Al have significant increasing effect on silicon content in a bead on plate weld deposits while S·Al is the most effective synergistic binary mixture. Individual and binary flux mixtures tend to decrease the copper content in a bead on plate weld deposits.

Organic adhesive assisted underwater submerged-arc welding

Abstract Underwater welding technology has become indispensable to the construction, maintenance, and repair of many offshore structures in oceanographic engineering industry. However, the existing disadvantages of current underwater welding technologies make them be unpopular and limited. An innovative organic adhesive assisted underwater submerge-arc welding was proposed to avoid the water disturbances to the maximum extent in wet condition. The mixture composed of bisphenol-A epoxy resin (EP) and welding flux in a weight ratio of 4:6 was placed on the metal surface before welding. Welding arc totally submerged in the mixture and maintained stable burning between the wire and base metal. The coverage effectively isolated the serious direct disturbances from surrounding water and greatly reduced the cooling rate of the welded joints to 19.57 °C/s. High-performance and defect-free welded joints were achieved with fine microstructures. The average tensile strength and maximum bending angle of the welded joints obtained by underwater submerged arc welding reached 463 MPA and 180°, respectively. Especially, low temperature impact toughness still keep 63 J/cm2 in 0 °C, which means far better mechanical properties compared with underwater wet welding. For the wet condition, this provides a possibility to acquire high-quality underwater welded joints comparable to that in air.