Welding – a complex of several simultaneously occurring processes, the main ones are: the thermal effect on the metal in the weld areas, melting, metallurgical processes, mutual crystallization of metals in spot weld fusion and crystallization of the metal. Weldability – a feature of metal and metal to create a combination for a given welding compound, which meets the requirements stemming from the exploitation product and its device. The complexity of the concept of weldability of materials suggests that in assessing the weldability should take into account the relationship of welding technology in product design and welding of metals and materials. Weldability of many indicators. Measure of the weldability of alloy steels used for the production of chemical equipment, is the ability to produce welded joints that would ensure special qualities – strength at high or low temperatures, corrosion resistance. When welding dissimilar metals weldability criterion is the possibility of education in the United interatomic bonds. Homogeneous metals are joined by welding without the complexity, while some pairs of dissimilar metals are absolutely not form a compound of atomic bonds, for example, welded copper with a crown, or titanium with a carbon steel.
Significant indicator of the weldability of metals is the ability to avoid in the welded joints hardened areas, cracks and other defects that adversely affect the work of the welded product. All this suggests that no single criterion of weldability of the metal. Weldability of metals analyze the physical and technological points of view. Thermal effect on the metal in the weld areas, and the melting process expressed by the welding of his regime. Technological weldability is the ratio of metal to a specific method of welding and the regime. Physical weldability seen occurring in the area of fusion welded metals processes, so there-in-one weld.
Convergence of the particles and create favorable conditions for their interaction is the chosen method of welding, and the flow relevant chemical and physical properties of processes expressed in the joined metals. These properties of welded metals make them a physical weldability. Metals can be either the same or different features and chemical composition. In the first case in terms of chemical composition and properties, it will be homogeneous metals, in the second – mixed. All metals have homogeneous physical weldability. Properties of heterogeneous metals sometimes can not provide the necessary flow of chemical and physical processes in the fusion, so the metals do not have the physical weldability.