Morozov

Existence of oscillatory mechanism of solidification of metal welded bath in the form of recurrent formation isotherms of crystallization is characteristic for different metals and alloys. It was found that under the influence of heat from an external periodically active source with the frequency corresponding to natural frequency of crystallization of weld material, resonance conditions which contribute to crushing the cast structure of seam and heat-affected zone are created. Fine structure of the welded joint obtained by effective control of the oscillatory mechanism of the crystallization front, can significantly improve hot cracking resistance and, probably, cold cracking due to changes in conditions of structural transformations, unachievable by conventional welding. Frequency of external action which creates conditions for parametric resonance can have several meanings according to the theory of oscillations.

Oscillations in the process of molten metall crystallization appears when welding as a periodic formation of cristallization isotherms; this is a characteristic of different metals and alloys. Cycling of commercial pure metal crystallization process is caused by temperature oscillations when hidden heat evaluating on the phase boundary. Frequency mechanism of hidden heat evaluation grouped with concentration subcooling mechanism appeared to be significantly difficult including both non-equilibrium cooling conditions and cycling. External thermal factors’ influence on the frequency of heat evaluation when welding pure metals and alloys allowed to increase the capabilities of structure forming. It was found out that thermal influence from external periodic source with the frequency corresponding to the natural frequency of welded seam crystallization created conditions for resonance that led to the increasing of penetration, interval of temperature oscillation and also to the reduction os welded seam’s cast structure. 

The process of metal melt during welding with subsequent crystallization is characterized by several features. Transition of liquid melt to solid state occurs simultaneously at the interface in the so-called germ band. It is in the embryonic area that during crystallization there appears an oscillatory mechanism which is considered within the framework of a phenomenological model. Modeling the dynamics of particle motion in simple liquids confirms transition from the chaotic state of the particles into the ordered one with preliminary formation of clusters of several particles. The mechanism of layer-wise phased transition of the particles occurs at establishing a specific frequency and mode of unstable equilibrium or breakdown. Using an external source of fluctuations synchronous with the process of crystallization rate, you can control the formation of the structure by creating a resonance condition. This would be a significant improvement in the properties of welded joints by grinding the cast structure of the weld metal.

 Existence of the oscillatory mechanism of hardening of metal of a welded bath in the form of formation of periodically repeating isotherms of crystallization, is characteristic for different metals and alloys. Periodicity of process of crystallization of metal is connected with fluctuations of speed of crystallization of interphase border at its movement with accelerations both the subsequent delays and a stop.It is established that at influence of heat from an external periodically operating source with frequency to corresponding own frequency of crystallization of metal of a seam conditions of a resonance which promote not only to crushing of cast structure of metal of a seam and HEZ are created, but also causes influence of the growth of mechanism the direction heat.                 The fine-grained structure of welded connection received for the account of efficient control by the oscillatory mechanism of moving of front of crystallization, allows to raise essentially resistibility to formation of hot cracks at the expense of periodic changes of temperature in a germinal zone, overcooling of liquid metal and the subsequent changes of rate of internal shrinkable deformations in a temperature interval of fragility.

Process of crystallization of metal of a bath after continuous welding is characterized by a number of physical and chemical laws which have the general character without dependence from a mode of influence of a source of heating. Existence of the oscillatory mechanism of hardening of metal of a welded bath in the form of formation of periodically repeating isotherms of crystallization, is characteristic for different metals and alloys. It is established that at influence of heat from an external periodically operating source with frequency to corresponding own frequency of crystallization of metal of a seam conditions of a resonance which promote crushing of cast structure of a seam and a zone of thermal influence are created.  The fine-grained structure of welded connection received for the account of efficient control by the oscillatory mechanism of moving of front of crystallization, allows to raise essentially resistibility to formation of hot cracks and, possibly, cold cracks at the expense of change of conditions of the structural transformations unattainable at usual welding

Existence of the oscillatory mechanism of hardening of metal of a welded bath in the form of formation of periodically repeating isotherms of crystallization, is characteristic for different metals and alloys.  Without dependence from a mode of influence of a source of heating a number of the physical and chemical laws connected with a heredity of properties of metal in a liquid state, are closely connected with transition not only to microlevel, but also to the macroscale sizes of elements of structure of a welded seam at its formation. Periodicity of process of crystallization of metal is connected with fluctuations of speed of crystallization of interphase border at its movement with accelerations both the subsequent delays and a stop.It is established that at influence of heat from an external periodically operating source with frequency to corresponding own frequency of crystallization of metal of a seam conditions of a resonance which promote crushing of cast structure of welded connection are created.  The fine-grained structure of welded connection received for the account of efficient control by the oscillatory mechanism of moving of front of crystallization, allows to raise essentially resistibility to formation of hot cracks at the expense of periodic changes of temperature in a germinal zone, overcooling of liquid metal and the subsequent changes of rate of internal shrinkable deformations in a temperature interval of fragility.

Process of crystallisation of metal of a bath after pulse welding is characterised by a number of physical and chemical laws which have the general character without dependence from a mode of influence of a source of heating. Existence of the oscillatory mechanism of hardening of metal of a welded point in the form of formation of periodically repeating isotherms of the crystallisation having various density is experimentally confirmed. It is established, that own frequency of crystallisation of metal of a welded point remains a constant at moving from a line сплавления to the bath centre. The various density of isotherms allows to judge character of change of volume speed of crystallisation which according to a number of researchers can coincide with linear speed of moving of interphase border or carry the excellent tendency.  The account of heat conductivity of metal which нелинейно changes at temperature growth, allows to explain changing density of isotherms of crystallisation.                Possibility of regulation of frequency of hardening allows to operate effectively the oscillatory mechanism of moving of the interphase border, the dominating role in which is played by the internal reasons of periodicity. Achievement of resonant conditions at coincidence of frequency of action of an arc source and own frequency of crystallisation of welded metal, will allow to achieve substantial improvement of technological durability of welded connection for the account of crushing of cast structure of metal of a seam

Process of fusion of metal at welding with its subsequent crystallisation is characterised by a number of features. Transition liquid расплава in the firm condition, occurring on interphase border in a so-called germinal zone, has a number of physical and chemical laws.                 A number of experimentally received facts allows to testify really to the existence, arising metal of a welded seam. In a germinal zone where there is an oscillatory mechanism at crystallisation, many processes influencing formation of a microstructure of a seam, mechanical properties of welded connection and especially the properties of technological durability defining reliability of work of a welded product as a whole originate.                 Management possibility the oscillatory mechanism of difficult and ambiguous process of the hardening, a dominating role in which is played by the internal reasons of periodicity, will allow to achieve substantial improvement of properties of welded connection for the account of crushing of cast structure of metal of a seam.                 Modelling of dynamics of movement of particles in simple liquids confirms transition of particles from a chaotic condition in ordered with preliminary formation кластеров from several particles.                 The mechanism of level-by-level stage-by-stage transition of particles is carried out at an establishment of a certain frequency mode of unstable balance or failure. Using an external source of fluctuations with synchronous to process of crystallisation by frequency, it is possible to operate structure formation, creating resonance conditions