INTRODUCTION

In Russia, much attention is paid to the development of novel welding and surfacing fluxes with the use of wastes taken from metallurgical production [1‒3]. In the manufacturing of welding and surfacing materials, various slag systems have recently been used, including the use of wastes from metallurgical production [4–21], in order to reduce their production costs. A number of studies conducted earlier were devoted to improving the compositions of welding fluxes based on slag from silicomanganese production. Novel welding fluxes based on silicomanganese slag with a carbon-and-fluorine-containing additive made of dust taken from gas purification facilities of aluminum industry have been proposed in [22, 23].

In the present work, a further study of welding flux based on slag taken from the production of silicomanganese mixed with a carbon-and-fluorine-containing flux additive is presented.

EXPERIMENTAL

For the welding of samples, an ASAW-1250 welding tractor was used. The chemical composition of the studied welded samples was determined according to GOST (State Standard) 10543–98 using a DFS-71 spectrometer (atomic emission method), and an XRF-1800 spectrometer (X-ray fluorescence method). The welded samples were tested for the value of impact strength (KCV) in the positive and negative temperature range and carried out using a pendulum shock testing machine according to GOST (State Standard) 9454–78. The fractional gas analysis was performed using a LECO TC-600 analyzer.

In this work, the welding-and-technological properties of the welding flux made of silicomanganese slag and the flux additive based on the dust taken from gas purification facilities involved in aluminum industry were studied. In addition, the following effects appeared: the introduction of the carbon-and-fluorine-containing additive exerted on the content of total oxygen and hydrogen in the welding seam’s metal, as well as this additive on the physicomechanical properties of the welding seam’s metal (impact strength in the positive and negative temperature range).

As the components for the welding flux preparation, silicomanganese slag was used as the base, and dust taken from electrostatic precipitators involved in aluminum industry was used as the flux additive. The components exhibited the following chemical compositions:

—silicomanganese slag produced at the West Siberian electrometallurgical plant: 6.91–9.62 wt % of Al2O3; 22.85–31.70 wt % of CaO; 46.46–48.16 wt % of SiO2; 0.27–0.81 wt % of FeO; 6.48–7.92 wt % of MgO; 8.01–8.43 wt % of MnO; 0.28–0.76 wt % of F; 0.26–0.36 wt % of Na2O; up to 0.62 wt % of K2O; 0.15–0.17 wt % of S; 0.01 wt % of P;

—dust of electrostatic precipitators of aluminum industry (carbon-and-fluorine-containing additive) of the RUSAL combined company: 21.00–46.23 wt % of Al2O3; 18–27 wt % of F; 8–15 wt % of Na2O; 0.4–6.0 wt % of K2O; 0.7–2.3 wt % of CaO; 0.5–2.48 wt % of SiO2; 2.1–3.27 of Fe2O3; 12.5–30.2 wt % of total C; 0.07–0.90 wt % of MnO; 0.06–0.90 wt % of MgO; 0.09–0.19 wt % of S; 0.1–0.18 wt % of P.

The flux additive was performed according to a technique described in [22, 23].

The composition of the studied welding fluxes is presented below in Table 1.

Table 1.   The amount of components in the welding flux, %
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The submerged arc welding was carried out line-to-line on both sides using the samples made of 09G2S steel sheets with a size of 500 × 75 mm, 16 mm thick. The process was performed with the use of Sv-08GA wire with a diameter of 4 mm. In the welding experiments, an ASAW1250 welding tractor in an operating mode at welding current strength Iw = 700 A was used; welding voltage Uw = 30 V; and welding speed Vw = 35 m/h.

RESULTS AND DISCUSSION

After the welding, the samples have been examined for the content of total oxygen and hydrogen in the welding seam’s metal, and the impact strength in the positive and negative temperature range has been determined (see Table 2).

Table 2.   Impact strength of welded samples
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The oxygen concentration in the welding seam’s metal exhibits a decrease with an increase in the content of the carbon-and-fluorine-containing additive in the flux (Fig. 1). In the case of submerged arc welding without any additive, comparing to the samples with a 6% carbon-and-fluorine-containing additive, the oxygen’s mass fraction decreases from 759.5 to 236.5 ppm on the average.

Fig. 1.
figure 1

Fractional gas analysis of the samples containing 0, 2, 4, and 6% of carbon-and-fluorine-containing additives and the amount of oxygen, ppm: (1) total and surface content; (2) in silicates; (3) in aluminates; (4) in calcium aluminosilicates, in calcium silicates, and in magnesium spinels.

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Upon fractional gas analysis, increasing additive content in the flux, the oxygen’s mass fraction in silicates has changed upon submerged arc welding without additives comparing to the samples with a 6% content of carbon-and-fluorine-containing additives from 628.25 to 155.1 ppm on the average. No significant changes have been found in the case of aluminates, calcium aluminosilicates, calcium silicates and magnesium spinels.

The oxygen distribution in silicates, aluminates, and aluminosilicates could be, to all appearance, connected with the oxidation level of the obtained slag and the assimilation of nonmetallic inclusions by the slag, depending on the slag’s resulting viscosity.

The analysis of the mechanical properties (impact strength in the positive and negative temperature range) has shown that the impact strength level increases when the amount of carbon-and-fluorine-containing additive increases. Upon introducing 6% of carbon-and-fluorine-containing additive into the flux, the impact strength KCV exhibits an 88% increase at a temperature of –20°C, and a 37% increase at a temperature of +20°C.

Figure 2 shows the amount of total oxygen and the impact strength in the negative and positive temperature range depending on the added amount of the flux additive.

Fig. 2.
figure 2

Impact strength (KCV) (1) at +20°C, (2) at –20°C, and (3) total oxygen amount in the metal of the welding seam depending on the amount of the flux additive; (4, 5, 6) linear dependences.

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Figure 3 shows the impact strength in the negative and positive temperature range depending on the total oxygen content in the welding seam’s metal.

Fig. 3.
figure 3

Impact strength depending on total oxygen amount in the metal of the welding seam: (a) at a temperature of ‒20°C, and (b) at a temperature of +20°C.

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Upon changing data concerning oxygen, a correlation is observed between the impact strength and the oxygen content (see Fig. 3).

Figure 4 shows the amount of hydrogen in the welding seam and the impact strength in the negative and positive temperature range depending on the added amount of the flux additive.

Fig. 4.
figure 4

Impact strength (KCV) depending on the amount of flux additive: (1) at +20°C and (2) at –20°C, and (3) total hydrogen amount in the metal of the welding seam; (4, 5, 6) linear dependences.

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Figure 5 shows the impact strength in the negative and positive temperature range depending on the amount of hydrogen in the welding seam’s metal.

Fig. 5.
figure 5

Impact strength depending on hydrogen amount of in metal of the welding seam: (a) at –20°C and (b) at +20°C.

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The analysis has revealed that the hydrogen content in the welding seam’s metal exhibits a decrease from 2.0 cm3/100 g of metal to 1.3 cm3/100 g of metal (submerged arc welding without any additive, and with 6% of a carbon-and-fluorine-containing additive).

CONCLUSIONS

Upon using a carbon-and-fluorine-containing flux additive to the welding flux based on silicomanganese slag, the amount of oxygen and hydrogen in the welding seam’s metal exhibits a decrease, and at the same time, the impact strength increases both at positive and negative temperature values.