Abstract
Welding thermomechanically-strengthened materials is accompanied with certain difficulties in terms of loss of strength characteristics in the zone of thermal influence. This issue can be resolved by using the technological welding schemes that include fusion of materials in a narrow contact area. One such technological scheme is electron beam welding, which is currently widely used to fabricate structures from refractory and chemically active materials. One of the main advantages of the electron beam welding process is a small quantity of heat input, which leads to the formation of narrow zones of melting and thermal influence and, as a result, minor deformities in the structure of the material. The welded joint can structurally be divided into several zones, which differ in the morphological characteristics of the structure. The most interesting, in terms of ensuring the quality of the joint, are the boundaries between the zones. It has been shown that the use of local heating sources, which is the case at electron beam welding, leads to the migration of the boundaries of grains. As a result, clear intersections, fusion lines, form at the boundaries between zones of the welded joint. The formation of the structural state of a welded joint is predetermined by the simultaneous course of several processes. First, a crystallization from the liquid state – the formation of a welded joint structure, as well as the boundary between a welded joint and the zone of thermal influence. Second, the phase-structural transformations in the solid state – a thermal impact zone, the boundary between a thermal impact zone and the main metal. Given this, one should note that the geometry and quality of joints at electron beam welding are more interrelated than in other welding techniques. Thus, one of the main parameters that ensure the quality of a welded joint is the structural state of the material that forms during welding
Highlights
Low-carbon sheet structural steel of strength class C490 is mostly used at present as a material for welding construction structures
On the other hand, according to the results reported in work [10], the features of physical and mechanical processes that occur during the formation of a welded joint during electron beam welding lead to the formation of specific defects that can reduce the operational characteristics of the joints
Our set of studies into the structure of the steels 09G2S, 10HSND, and 10G2FB, which were produced according to the technological scheme of controlled rolling, has shown that the structural state is characterized by the presence of a dispersed ferrite-perlite structure
Summary
Low-carbon sheet structural steel of strength class C490 is mostly used at present as a material for welding construction structures. 3/12 ( 111 ) 2021 properties of the material for welding construction structures and analyzing the manufacturability and energy efficiency of production of the structures themselves (welding, installation modes, etc.) [3]. Improving the manufacturability and energy efficiency of production and the use of welding construction structures by advancing the structural state and welding regimes is relevant both from a scientific and the economic and national point of view. It should be noted that the application of welding adds factors that are associated with both the design of welded joints and the technology of their manufacture These factors, first of all, include the presence of stress concentrators associated with abrupt transitions from the main metal to the joint’s metal, or from one element to another, which could reduce the reliability of a welded joint. It follows from above that ensuring the reliability of structures, which is to be understood as the likelihood of trouble-free operation before the onset of the limit state of destruction, is a relevant task for modern materials science
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