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Shielding gas oxygen and nitrogen content effects in the case of duplex stainless steel welding

Varbai Balázs

Advances in Materials Science

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2024

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Vol. 24, nr 3(81)

111--123

EN

The duplex stainless steels show improved localized corrosion resistance and strength comparing to the austenitic stainless steels. All of the duplex stainless steels solidify as pure ferrite and the double microstructure is evolving during the solid-state, diffusion driven phase transformation. In this research nitrogen and oxygen containing argon-based shielding gases were used. It was found that the nitrogen and oxygen addition significantly increased the weld metal austenite content, up to +27%. The oxygen addition also improved the weld dissolved oxygen content with up to +0.09%, and the weld penetration depth with up to +3.3 mm.

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Application of regression models on the prediction of corrosion degradation of a crude oil distillation unit

Varbai Balázs, Wéber Richárd, Farkas Balázs, Danyi Péter, Krójer Antal, Locskai Roland, Bohács György, Hős Csaba

Advances in Materials Science

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2024

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Vol. 24, nr 1(79)

72--85

EN

The crude distillation unit is the most critical elements in the refining process. Moreover, most of the equipment in the distillation unit are made of general carbon steels. Data analysis models, machine learning techniques can predict corrosion degradation rates. We used Pearson’s correlation coefficient and multiple linear regression, to predict the impact of process parameters. Altogether, we have analysed 84 channels of technological parameters, and 22 different types of crude oils. Among the corrosion agents, the chloride content strongly affected the weight loss of coupons, where the highest coefficient was 0.68. The most influential parameter is found to be the pH value. Thus, an estimation method of the pH value is set up to predict the corrosion degradation rate. The regression correlation for estimating the pH value is 0.53 if the corrosion agents are not used, which can be improved to 0.76 if the corrosion agents are also used in the regression analysis.

3

The effects of arc voltage and shielding gas type on the microstructure of wire arc additively manufactured 2209 duplex stainless steel

Kemény Dávid Miklós, Sándor Bence, Varbai Balázs, Katula Levente Tamás

Advances in Materials Science

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2023

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Vol. 23, nr 4(78)

62--82

EN

Duplex stainless steels (DSSs) are widely used due to their corrosion resistance. Austenite and ferrite determine the excellent properties. Ferrite provides strength and good corrosion resistance, while austenite provides toughness and weldability. During our research,samples were producedwith ER 2209 duplex steel wire using wirearc additive manufacturing (WAAM). Two different 17V and 19V arc voltages were used during the production. Two shielding gases were used for each voltage: M12-ArC-2.5 and M12-ArHeC-20/2. The research aimed to determine the ferrite ratio as a function of the welding parameters. The ferrite(or austenite)content must be between 30% and 70% for duplex stainless steel welds, according to the ISO 17781 standard.Based on our research, it can be stated that the austenite ratio increases as the voltage increases, thus failing to fulfill the standard's requirements. The helium content reduced the ferrite ratio even when the 17V voltage was used due to the gas's higher ionizationpotential. During the metallographicexamination, our welded samples met the standardrequirements for the austenite content for17V arc voltage and M12-ArC-2.5 shielding gas. The ferrite content in the entire sample cross-sectionfell between 30-42% duringferitscopeand image analysis measurements. These welding parameters can be recommended for industrial applications.