OBRABOTKAMETALLOV Vol. 26 No. 2 2024 technology composition (type) of the coating, but also on the calcination temperature of the electrodes [18]. According to Russian regulatory documents [18], the group with the H5 index includes electrodes that provide a hydrogen content in the weld overlaid metal of up to 5 cm3/100 g, in H10 from 5 to 10 cm3/100 g, in H15 from 10 to 15 cm3/100 g, and the most critical group over 15 cm3/100 g. All electrode suppliers should adhere to the new marking of welding materials with a mandatory indication of the hydrogen content in the weld overlaid metal [18]. The manufacturer has a great responsibility for implementing appropriate hydrogen cracking protection measures in welding procedures. In addition to prescribing properly processed basic type welding consumables with low hydrogen content, manufacturers rely on preheating, temperature control between passes, strict control of heat input and post-welding heat treatment to reduce the risk of cracking during welding. These traditional hydrogen control measures are expensive and time-consuming. According to the ISO 3690 standard [15], various methods can be used to determine and measure hydrogen content: (1) the mercury method; two carrier gas methods: (2) gas chromatography (CG) and (3) hot extraction (HE). The mercury method is widely discussed critically [8, 14, 19–23], since the use of mercury is associated with health risks, as well as from the point of view of environmental protection. Consequently, it is increasingly being replaced by other safer methods [8, 14]. Using CG method, hydrogen is collected from a weld specimen in a closed chamber for a specified period of exposure at elevated temperatures. For this reason, collection time can be reduced to several hours [14]. After this, the chamber is purged with carrier gas and the gas mixture is transferred to the CG unit. Typically, a gas chromatograph consists of a heated column to separate individual gases. Separation is achieved by different retention time of the carrier gas and hydrogen due to interaction with the column wall. The HE method (regardless of the use of vacuum or carrier gas) is based on the thermal activation of hydrogen atoms in a solid specimen and subsequent thermal desorption. Recent discussions [13, 14, 19–23] on the standardization of hydrogen determination in welds according to ISO 3690 [16] have shown that a discussion of experimental effects is necessary for the used method of carrier gas hot extraction (CGHE) from the point of view of a device for collecting and extracting hydrogen. In particular, important factors affecting the results of hydrogen extraction and collection are specimen temperature, extraction time, and its interdependencies. It is worth noting that additional boundary conditions may have an impact, for example, the size and surface of the specimen. All presented methods have advantages and disadvantages. It is also a matter of the available budget, as well as the number of specimens to be analyzed (and time per specimen), and what equipment is used to determine hydrogen in welds. Russia has adopted a standard for the determination of hydrogen in welds [24], which cannot always be used on industrial sites for operational control of welding materials. For the purpose of operational control in workshop conditions, the “pencil test” method is used [25], the advantage of which is the use of simple, inexpensive equipment, clarity and the ability to assess the effect on the kinetics of hydrogen evolution at negative temperature. Thus, the growing demand for high-strength steels in the energy sector has led to an increased need for low-hydrogen welding technologies to reduce the risk of cold cracking. Therefore, moisture control of the base coating of the electrodes is the key to obtaining high-quality welds by observing handling conditions and storage methods to prevent moisture absorption, as well as calcining the electrodes at temperatures in the range of 340–400 °C [8]. The quality of the weld is influenced by the quality of the metal, which in turn is influenced by various factors of its production [26–36]. At the same time, the factor affecting the quality of the welded joint when using electrodes with a basic coating is the manufacturer of the welding electrodes itself. Currently, the market offers electrodes with a basic coating from various Russian and foreign manufacturers under the well-known brands UONI, TMU, etc., which do not always meet the requirements of regulatory documents on welding technological parameters [37–39], which poses a serious danger for use in conditions of thermal power plants. Replacing the recipe of the main components of the coating, failure to maintain the recipe, violations in the electrode production technology – all these factors can have an important impact on the quality of the weld [40, 41]. As consumers, we buy a ready-made product that externally complies with regulatory documents, but we can determine compliance with the claimed properties only after purchase and welding operation.
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