Methods of technological strength evaluation.

One of the basic trial tasks, conducted during technological weldability of materials determination, is evaluation of its technological strength under conditions of any welding method, as with strength increasing the possibility of high-quality welded connection realization increases. Term “technological strength” was introduced by Prochorov N.N. in 1950. This term underlines, that we are speaking about the material ability for preservation interatomic forces of jointing in the process of their technological treatment (welding, forging, etc.). The experience shows, that strength of materials during their treatment is not proportional to their operation strength. The feedback is observed very often, especially during welding, forming and operations, connected with heating and cooling of item.

If item’s stress state during operation is determined as external load value and the size of item, then under conditions oftechnological treatment it is determined by chemical compound of material and treatment conditions. Increasing the size of item during welding increases stiffness and internal stresses, decreases technological safety factor.

Strength of materials conditions during welding harshly changes in time and determined by kinetics of phase transformation. In most cases the contraction (size shortening) of weld joint during welding proceeds with existence of tensile stresses that promote formation of cracks in metal of joint and in zone near weld joint. All these make the problem of increasing the technological strength of materials during welding urgent.

One of the basic factors of technological strength during welding is the ability of material to resist the formation of hot (crystallization) and cold (hardening) cracks. By increasing this ability one can obtain the improvement of technological strength of materials.

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