Weldability, Structural Alloys Systems

There is hardly a metal that cannot, or has not, been joined by some welding process. From a practical standpoint, however, the range of alloy systems that may be welded is more restricted. The term weldability specifies the capacity of a metal, or combination of metals, to be welded under fabrication conditions into a suitable structure that provides satisfactory service. It is not a precisely defined concept, but encompasses a range of conditions, eg, base- and filler-metal combinations, type of process, procedures, surface conditions, and joint geometries of the base metals (12). A number of tests have been developed to measure weldability. These tests generally are intended to determine the susceptibility of welds to cracking. 

In addition to requirements for the steels and alloys used in cryogenic structures, good weldability requires (1) resistance to metallurgical defects in the weld and heat-affected zone (HAZ), (2) stability of structural and physical-mechanical properties during welding, (3) the development of a special weld alloying system, and (4) the possibility of application of welding joints without post-heat treatment. 

In the USSR, the E. O. Paton Institute of Electrowelding carries out systematic studies of the weldability of structural steels and alloys for cryogenic use and the development of new materials and technological processes for welding. In recent years, data have been obtained and summarized on the main types of steels and alloys, distinguished by their specific strength, structural composition, and alloying system. 

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