Physicochemical Characterization of Simulated Welding Fumes from a Spark Discharge System

Figures & data

TABLE 1 Elemental and compositional specification of test electrodes (Hobart 2008)

Element	Core rod	Coating layer
Fe	Balance	60–70%
C	<0.15%	0.1–2.1%
Si	<0.7%	0.1–2.1%
Mn	<1.0%	0.1–2.0%
V	—	0.1–2.1%
Cr	—	5–15%
Mo	—	1–11%
TiO2	—	1–11%
W	—	1–11%
Calcium Carbonate (CaCO3)	—	1–11%
Chromium Fluoride (CrF3)	—	1–11%
Sodium Silicate (Na2O3Si)	—	1–11%
Potassium Silicate (K2O3Si)	—	1–11%

FIG. 1. Experimental setup. Sampling ports #1 and #2 are located before and after the coagulation chamber, respectively.

TABLE 2 Sample current and particle characteristics (size, total number concentration, and total mass concentration) for generated welding fume particles

					Total mass concentration (μg/m^3)
	Loading current (mA)	NMD (nm)	σg	Total number concentration (particles/cm^3)	SMPS	Gravimetric
Fresh fume	0.25	10 (±0.1)	1.52 (±0.01)	3.1×10^7 (±6.6×10^5)	282 (±26)	85 (±4)
	0.5	14 (±0.2)	1.59 (±0.01)	5.1×10^7 (±2.5×10^5)	1418 (±108)	220 (±5)
	1	23 (±0.1)	1.64 (±0.01)	6.0×10^7 (±8.9×10^5)	7196 (±172)	760 (±70)
Aged fume	1	81 (±1.1)	2.16 (±0.01)	1.5×10^6 (±1.8×10^4)	4.5×10^4 (±4.0 ×10^2)	730 (±40)
	3	154 (±3.0)	1.95 (±0.02)	2.7×10^6 (±7.0×10^4)	2.4×10^5 (±2.9×10^3)	2700 (±550)

NMD: Number median diameter; σ_g: geometric standard deviation. Particle density was assumed as 7870 kg/m³ (bulk iron density) for the SMPS.

FIG. 2. Size distributions of fresh (a) and aged (b) fume particles and continuous generation data (c) of fresh fume particles at 0.25 and 0.5 mA. TNC: Total number concentration; NMD: number median diameter; σ_g: geometric standard deviation.

FIG. 3. TEM images of fresh (a) and aged (b) fume particles, projected area diameters (d_PA) of fresh and aged fume particles (c) and primary single particles (d).

FIG. 4. EDX spectrum (a) and elemental maps (b) of aged fume particles. These maps are for Fe, O, Si, Cr and Ni. For EDX spectrum, the square region in the top left image of Figure 5b was analyzed. Particles were sampled on the Ni grid.

FIG. 5. XRD patterns of aged fume particles and reference powders; Fe₃O₄ and Fe₂O₃.

TABLE 3 O₃ and NO_X concentrations measured for spark discharge system (SDS) under different operating conditions

Loading current (mA)	O3 (ppm)	NOX (ppm)
0.25	0.07 (±0.01)	1 (±0)
0.5	0.26 (±0.01)	3 (±0)
1	0.62 (±0.01)	7 (±1)
3	2.22 (±0.01)	20 (±1)

Hobart. (2008). Material Safety Data Sheet #230 by Selectrode Industries, Inc.

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