Influence of Titanium-Containing Inoculants on the Structure of Metal in the Welds of High-Strength Low-Alloy Steels
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INFLUENCE OF TITANIUM-CONTAINING INOCULANTS ON THE STRUCTURE OF METAL IN THE WELDS OF HIGH-STRENGTH LOW-ALLOY STEELS G. M. Grigorenko,1, 3 L. I. Markashova,1 V. V. Golovko,1 E. N. Berdnikov,1,2 T. A. Alekseenko,1 and V. V. Zhukov1
UDC: 621.791, 669.14.018.2/.8-194.2
We study the influence of titanium-containing refractory inoculants (nitrides, carbides, and intermetallic materials) on the structure of metal in the welds of high-strength low-alloy steels. The character of structural-and-phase transformations and the specific features of fine structures are determined by the method of transmission electronic microscopy with regard for the dislocation density distribution. The influence of structural components formed as a result of introduction of various types of inoculants on the mechanical properties of welded joints is investigated. The roles played by the structural factors (phase composition, subgrain structure, and the distribution of dislocations) in the behavior of local internal stresses and stress concentrators in the process of crack initiation are analyzed. For the case of welding of high-strength low-alloy steels, we determine the optimal compositions of applied inoculants guaranteeing the possibility of getting of high-quality and reliable welded joints with high mechanical characteristics and crack-growth resistance. Keywords: high-strength steel, arc welding, welded joints, refractory inoculants, structure, phase composition, dislocations, mechanical properties, local internal stresses, crack resistance.
In order to improve the technology of production of welded metal structures, it is necessary to create new materials with a complex of physicochemical and operating characteristics guaranteeing their in-service reliability and durability [1–4]. As one of promising directions in their creation, we can mention the development of the technologies of modification of metals by introducing refractory admixtures (inoculants) in the melts [5–7]. These inoculants are used in the production of high-strength low-alloy steels in order to get the required structural composition [8]. It is also necessary to mention the work [9] dealing with the prospects of the introduction of inoculants in the welding bath. In [10], the processes of structure formation in the weld metal of welded joints were investigated by using powder inoculants of several types (oxides, carbides, and nitrides). It was established that the presence of these inoculants (containing titanium, zirconium, and magnesium oxides) guarantees high values of the ultimate strength and impact toughness at negative temperatures due to the formation of fine-grained bainite or acicular structures. The effects of TiN, TiC, and TiO 2 admixtures on the sizes, distribution, and volume fractions of nonmetallic inclusions, as well as on the growth of dendrites and phase composition of the weld metal were determined in [11, 12]. It is worth noting that the contemporary scientific and technical literature contains insufficient amount of data on the influence of refra
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