Automatic Welding, 2016, №01



2016 №01 (04)

DOI of Article 10.15407/as2016.01.05

2016 №01 (06)

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Avtomaticheskaya Svarka (Automatic Welding), #1, 2016, pp. 38-41

Investigation of conditions for providing low content of diffusion hydrogen in welding using electrodes of basic type

A.P. Paltsevich

E.O. Paton Electric Welding Institute, NASU 11 Kazimir Malevich Str., 03680, Kiev, Ukraine. E-mail: office@paton.kiev.ua
 
 
Abstract
In this work the mechanisms for prevention of hydrogen absorption at the participation of CaF₂ and SiO₂ in submerged arc welding and welding with covered electrodes resulting in formation of HF, based on thermodynamic calculations, are considered. The formation of SiF₄ and HF was experimentally established in the air samples in the arc zone. In the opinion of researchers, HF is a thermally resistant compound in the arc gap and, thus, it facilitates the decrease of P_H in the arc zone. As the criterion for the efficiency of this mechanism the reduction and elimination of weld porosity in submerged arc welding were served. The further works and accurate data on thermal properties of HF, H₂, H₂O, N₂ and other gases at high temperatures, as well as the results of experiments with measurement of [H]_diff content in welds showed that the above-mentioned mechanism does not provide the ultra-low [H]_diff content. In the present work the investigations on the influence of CaF₂ and moisture content in the coating on [H]_diff content were carried out, the content of water impurities was determined in the components of electrode coatings at heating up to 1000 °C. It is shown that the preliminary heat treatment of the components provides reduction of the level of [H]_diff to ≤3–2 ml/100 g depending on the coating composition. 19 Ref., 3 Tables, 5 Figures.
 
Keywords: arc welding, covered electrodes, potential hydrogen, diffusion hydrogen, silicon fluoride, hydrogen fluoride, dissociation of gases, components of electrode coatings, chromatographic analysis of hydrogen, investigations
 
 
Received:                29.12.15
Published:               15.03.16
 
 
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