Development of Nano – flux powder from bio-waste for welding application

. Oxyacetylene welding is a fast-growing means of joining metals that were developed to address the drawbacks of other welding techniques. The use of chemical compounds known as fluxes in the welding process does this, resulting in improved weld characteristics and increased weld depth. Chemical synthesis was used to create a new nanoparticle flux powder from Egg shell powder for this research. The powder was studied micro-structurally and spectroscopically using SEM, TEM, FTIR, and EDS techniques, and it was discovered to be a compound made up of 57.31 % calcium, 12.31 % sodium, and 6.86 % carbon. The flux was tested on, 8 mm mild steel rods, 3 pcs each of 10 x 10 mm and 50 x 50 mm galvanized steel plates, utilizing oxyacetylene welding techniques. 50 x 50 mm mild steel plates and galvanized steel plates Control samples were made utilizing the oxyacetylene welding techniques with and without the use of a flux (Easy-Flo powder). The mild steel welds generated with the created flux were found to be harder, with hardness values of 98.45 and 115.78 BHN for oxyacetylene welding procedures, respectively. Welds produced without flux powder were able to withstand higher loads than the welds produced using the other methods of welds produced with the developed flux.


Introduction
Welding is a method of joining materials, typically metals when heat is applied to the materials to form a pool of welded joints [1].It is a common way of manufacturing and upgrading metal goods in all sectors, large and small because it is generally cost-effective, efficient, and reliable.There are various techniques used nowadays for the welding process among which is TIG.Arc welding has become a widely acknowledged welding standard and the parameters that regulate it have been changed to create several variants for use in the industry.The primary principle of GMAW, SMAW, GTAW, FCAW, and Autogenous TIG welding is to create an electrical arc between the electrode and the workpiece, and then use the heat generated to melt a filler metal or fuse the workpiece without the use of a filler metal [2,3].Welding fluxes, which vary from oxides to fluorides, can significantly improve the welding operations' characteristics [4].Welding fluxes are chemical substances that enhance the welded joints' characteristics, utilized to join different ferrous and non-ferrous metals in several welding methods, including GMAW, GTAW, plasma is welding (PAW), laser beam welding (LBW), and EBW.Among the several forms of welding used, TIG welding is the most crucial.Tungsten Inert Gas (TIG) welding [5] (Figure 1), also known as Gas Tungsten Arc (GTA) welding, is a process of joining metal parts using heat generated by an arc formed between the workpieces and a non-replaceable Tungsten electrode [6].Low weld penetration during a single pass, high cost owing to precise edge preparation, and the requirement for additional filler metal to fill the welds are only a few of the drawbacks of TIG welding that prevent it from being used more widely in the industry [8].Some of the challenges that can develop when using TIG welding are as follows: Because TIG welding cannot produce deep penetration joints, the workpiece must be smaller than 3mm in diameter to be joined reliably.For workpieces thicker than 3 mm, joint edge preparation and multiple passes to fill in the joint were required [9].The flux is a material that is nearly inert at ambient temperature but quickly degrades when exposed to higher temperatures, preventing metal oxide development.for wetting to solder by dissolving the metal surface oxides that help in melting the metal, which acts as a barrier to oxygen [10][11].
Many researchers have attempted the study the use of biowastes for the enhancement of steel.Leman et al. [12] conducted a preliminary investigation on the physical and chemical properties of SP for use as concrete filler.Shredded coconut shells were collected and processed to a fine powder, which was then subjected to a range of tests, including density, X-Ray Fluorescence (XRF), Particle Size Distribution, and Scanning Electron Microscopic analysis.The chemical and physical characteristics of the coconut shell were determined using scanning electron microscopy (SEM) and specific gravity.The elements with the highest detectable percentages were C and K203, which were 10.0 percent and 1.21 percent, respectively, according to the XRF.About 1% of the total was made up of the new components found in CSP.The percentage of silicon oxide in concrete is 0.98 percent, which is a critical ingredient in the mixing process.The coconut shell powder was found to include particles with diameters of 600um and below, with the majority of the particles being smaller than 150um, which is required for its usage as a filler in concrete, using the sieve analysis method.Mohamed et al. [13] investigated whether coconut shell powder and composites made of coconut shell-activated carbon could be used to block electromagnetic interference.In this work, basic materials such as coconut shell powder (SP) and coconut shell activated carbon (SAC) were combined with an amine hardener and an epoxy resin composite to capture microwave signals with frequencies ranging from 1 to 8 GHz.The composition of the raw materials was analyzed using CHNS Elemental Analysis to investigate their use as EMI absorption materials and Scanning Electron Microscope (SEM) was used also.The goal of this study is to explore if biowaste can be used to develop flux and improve the weld joint of Oxyacetylene welding.Ikumapayi et al. [14] investigated the effect of the use of Palm Kernel Shell Ash (PKSA) on the strength of the processed aluminium based composite.The study focused majorly on the wear pattern of the metal matrix composite, its corrosion behavior, and the total strength and friction pattern of the composite.They captured their results using a tribometer, surface roughness tester, scanning electron microscope, energy dispersive x-ray, x-ray fluorescence, and x-ray diffraction analysis.Their results show that the introduction of the PKSA generally improved the strength of the aluminium composite and as well resulted in a reduced corrosion pattern.

Nanoparticles production process
Four pairs each from the specimens made from the various heat treated and unheated control samples were joined together using lap welding technique (See Figure 1).A Shielded Metal Arc Welding (SMAW) was employed at a current of 90A and a voltage of 220V.Two samples were placed one over another and then welded on both sides with gauge 10 arch welding electrode for mild steel; welding titanium type.The E6013 electrode was used for this welding process.The devices used for the lap welding and their classifications are as shown in Table 3. Figure 1 shows the welded samples at different quenching and cooling media.

Pulverization of the Egg Shell
The eggshells shown in Figure 2(a) were sourced from a locally source, sun dried for 72 hours, crushed and grounded into powdered form as shown in Figure 2(b).The powdery shell was burned in a Muffle furnace at 900°C for around 2 hours, yielding eggshell ashes, which were used as a raw material in the synthesis process (Figure 3a & 3b).

Synthesis of Nanoparticle Powder from the eggshell powder ash
The reaction, centrifugation, and calcination steps were all part of the synthesis process.The method included using metal chemistry knowledge to obtain Calcium carbonate nanoparticle flux powder from eggshell ash.In 1.5 liters of water, 195g of sodium hydroxide pallets were combined with 65g of eggshell ashes.The solution was then agitated for 1 hour using the magnetic flit bar and a hot plate with a magnetic stirrer.To allow the reactions to take place, the stirred solution was then left on sand for 24 hours (Figure 4).

Centrifugation process
The reaction was completed after 24 hours, and iron nanoparticles were formed within the fluid.A centrifuge was used to separate the mixture, with the powder settled at the base of the 10 ml tube while the liquid float after spinning spun for 15 minutes.

Calcination process
After centrifugation, the nanoparticle powder was removed with a spatula and place in a furnace for 2 hours to remove any leftover nanofluid.The nanoparticle powder was then calcined in an oven for roughly 2 hours at high temperatures.As illustrated in figure 3.7, the resultant powder was completely pulverized into fine powder.

Characterization of nanoparticle flux powder
Scanning Electron Microscopy (SEM) as well as the FIR and X-ray Diffractometer, were used to characterize the nanoparticle powder.This was done to look at the microstructure of the powder, check its constituent parts, and figure out what phases it contains.

Experimental Application of Developed Flux Powder
After the powder was developed, it was applied in the Oxyacetylene welding process with the setup shown in Figure 5, the weld produced was tested to identify the mechanical properties which have been improved by the application of the produced flux powder Mild steel (MS) rods and galvanized steel (GS) plates were cut into 3 by 50 mm x 50 mm and 4 by 10mm x 10mm plates, as well as 6 pieces of 50 mm long 16 mm diameter rods, using a disc cutter.Flux was added to the joints during the course welding using the Oxyacetylene welding process.MS-MS rod GS-GS plate, were the joints manufactured.Three samples of each were made, one as a control without any flux powder, one with control Flux powder, and the third with the Nano flux powder developed for the purpose of this research.

Microstructural Examination
The SEM micrograph in Figure 6(a) was taken within a space of 9.9 mm, magnified 7000x, an HFW of 110 nm, and a pressure of 90 Pa, revealing that the generated flux powder is made up of finely scattered particles with black spots.Carbon particles stayed on the graph as a result of the flux powder development procedure, whereas the other Ca particles were evenly scattered.The micrograph demonstrated no aggregation between the powder's numerous particles, and the particles themselves exhibited very high transparency.The micro-image of the control sample in Figure 8(a), is made up of a dark spot with white parchments dispersed throughout, forming a group in a stream-like manner.Figure 7 showed that there is agglomeration in the structures clogging in bond.Micrographs were evaluated using the Digimizer TM image analysis application which is shown in Figure 8(b).According to the SEM, the particle sizes for the control flux powder ranged from 1.475 to 1235.154 nm, with an average particle size of 69.08 nm.The particle sizes of the produced flux powder range from 1.451 nm to 490.547 nm, with an average particle size of 54.216 nm, as shown in Figures 6 and 7. Figure 7 showed SEM and TEM micrographs of the generated flux powder, which reveal the darker-colored carbon particles uniformly scattered throughout the compound.In the evolved flux, there was also a sort of particle agglomeration, as visible in the TEM image.
The principal constituents of the flux powder, as indicated in the EDS graph of the produced flux in Figure 9, are Ca, C, and Na, with concentrations of 57.30, 6.80, and 12.31 percent, respectively, with large phases of Ca visible owing to the parent material's properties being high in C, with Ca and O coming from the synthesis process, as demonstrated in the Xray diffractogram of the generated flux powder.The principal ingredients of the control flux powder utilized in comparison to this flux were Ca, O, C, and Al, with concentrations of 57.30, 6.8, 12.31, and 6%, respectively, with two peaks of Quartz at 20 = 25° and Hematite at 20 = 28 percent, as shown in Figure 9.
When comparing the two powders, the created powder has a higher proportion of carbon and a lower percentage of iron than the control flux, and the weld joint with flux powder was harder due to the strengthening qualities supplied by carbon particles.

Hardness Test
The welds were evaluated using a Brinell hardness device at the base materials, weld zone, and heat-affected zone, and the results are presented in Table 1.As demonstrated in Table 2, the mild steel control sample welded without flux using the oxyacetylene welding procedure was harder than the ones made with the produced flux and the control flux.The finding revealed the joint made with the produced flux and oxyacetylene welding techniques had much greater Brinell hardness values than those made with the control flux.Also, the hardness of the heat-affected zone was determined to be the highest in the welded region made by the developed flux and those formed without any powder.This implies that the created flux performed satisfactorily in enhancing the hardness and ductility of the welded zone.
Table 2 showed that in the base material, the welded joint of the mild steel without flux using oxyacetylene welding was harder than the joint made by the developed flux and the control flux; while the welded region of the galvanized steel using oxyacetylene with the developed flux was harder than then all.

Conclusion
The eggshell was employed in this research work to generate Ca nanoparticle flux powder for use as flux in Oxyacetylene welding procedures, to improve the qualities of the weld joint.The findings showed that: the created flux increased the hardness of the weld when used in the oxyacetylene welding processes on galvanized plates and mild steel rods in comparison to joints made with the powdered flux control and those made without the use of welding flux, chemical reduction was used to creating Ca nanoparticle powder from eggshell, and the powder particles generated range from 1.319 to 490.57nm which is a quite a satisfactory range of nanometers, and when compared to welds made with powdered flux control and those made without flux powder, the welds made with the developed flux were found to be ductile, with a greater maximum tensile strength and increased ability to tolerate higher loads and finally weld constructed with the developed flux had a superior grain structure and microstructural layout than the control weld made without flux.

Fig. 5 .
Fig. 5. Oxyacetylene welding of various steel types (a) mild steel using control flux powder (b) galvanized steel using nano flux powder (c) mild steel using nano flux powder.

Fig. 8 .Fig. 10 .
Fig. 8. SEM Micrograph of control flux powder /doi.org/10.1051/e3sconf/202343001212212 430 The main idea behind fluxes is that they are used to generate a surface

Table 1 :
Brinell hardness test results for galvanized steel weld

Table 2 :
Brinell hardness test results for Mild steel weld