PSI - Issue 36

Victor Shapovalov et al. / Procedia Structural Integrity 36 (2022) 262–268 V. Shapovalov, I. Protokovilov, V. Porokhonko / Structural Integrity Procedia 00 (2021) 000 – 000

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1. Introduction Electroslag welding (ESW) is an effective way of joining thick-walled products made of various metals and alloys, as shown in the works of Paton B. et al. (1999, 2017), Yushchenko K. et al. (2014, 2018), Kaluc E. et al. (2006). One of the main advantages of ESW is high performance and the ability to join products up to 500 mm thick and more in one pass without cutting edges. The technological advantages of ESW also include the simplicity and reliability of the used equipment, which does not require the use of bulky vacuum chambers, the absence of evaporation of alloy components with high vapor pressure and protective and refining effect of slag on the liquid metal. ESW is most widely used when joining steelworks. However, ESW can also be effective when joining thick walled components made of titanium alloys, including high- strength (α+β) alloys , as shown in the works of Shcherbinin and Kompan (2005), Devletian et al. (1990), Protokovilov et al. (2013). In this case, an important task is to ensure the required properties of the welded joint. Titanium at high temperatures actively interacts with atmospheric gases that cause its embrittlement. Therefore, when ESW of titanium, it is necessary to apply additional measures to prevent the interaction of titanium with atmospheric gases and to ensure the required gas composition of the weld metal. (  +  ) titanium alloys are heat-hardening alloys whose properties are significantly dependent on heat treatment. Therefore, during ESW of (  +  ) titanium alloys, there can be a danger of undesirable structural transformations in the heat-affected zone (HAZ) under the influence of the thermal welding cycle, which negatively affects on the properties of welded joints. In general, ESW should provide the absence of surface and internal defects such as pores, slag inclusions, cracks while it is desirable that mechanical properties (tensile strength) of the welded joint was not lower than 90% of the strength of the base metal. The aim of this work was to develop the conditions of electroslag welding of Ti-6Al-4V slabs with a thickness of 100 mm and to investigate properties of welded joint. 2. Experiment Initial specimens for welding were plats with dimensions 100  150  150 mm of Ti-6AI-4V alloy which was received in the annealed condition (Fig. 1). Two welded joints were made. The wire with a diameter of 5 mm of the SPT2 alloy was used as the welding wire. The consumable nozzle was made of Ti-6AI-4V alloy. The chemical and gas composition of the used materials are shown in Table 1.

Fig. 1. View of slabs of Ti-6Al-4V alloy to be welded.

The schematic view of the ESW process is shown in Fig. 2. Welding was carried out using a consumable nozzle with two wires. The welding gap was 26 mm. An oxygen-free fluoride-chloride flux was used. The welding area was protected by supplying an inert gas to the welding gap. The main welding parameters were as follows: voltage – 22...25 V, current – 2600...3000 A, welding rate – 2.4 m/h.