SU1301614A1 - Method of welding metals - Google Patents

Abstract

The invention relates to welding production, in particular to methods of welding metals, and can be used in various sectors of the national economy in the manufacture of welded structures. The purpose of the invention is to reduce the level of residual welding stresses, increasing the technological and operational strength of the welded joint. The method includes heating, melting and forming a weld, passing a pulsed electric current through the weld metal during its crystallization in a mode that ensures the occurrence of an electroplastic effect in the temperature range, mainly from the onset temperature of crystallization to the temperature at which plastic deformations. In doing so, they affect the dislocation structure of the weld metal, ensuring the rearrangement of the dislocations into a more energetically favorable state, controlling the diffusion processes at the interface and in the crystallizing weld metal. This makes it possible to obtain a weld metal with a lower level of chemical heterogeneity. 1 hp f-ly. 2 tab. i (L so O 35

Description

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The invention relates to the welding industry, in particular to the method of arc welding, and to be used in various areas of the national economy in the production of welded structures, I

The purpose of the invention is to reduce

level of residual welding voltage

Research institutes, the technological and operational strength of the welded joint.

The method is carried out as follows.

In the process of welding metals, including heating, melting of the metal and the formation of the weld through the weld metal in the process of its crystallization, a pulsed electric current is passed in a mode that ensures the appearance of an electroplastic effect in the temperature range from the temperature of the onset of crystallization to the temperature at which the seam ends with plastic deformations.

When welding metals, the dislocations are rearranged to a more energetically favorable state (decrease in the level of residual welding stresses) by direct action of an electron flow, which is imparted to the drift velocity (electric current in a pulse) on the dislocations of the weld metal in a mode that ensures the appearance of an electroplastic in which the dislocations are supplied with sufficient energy to overcome the energy barrier. M1 Nim; sh. At a current density in a pulse, at which an electroplastic effect occurs, is 10–10 A / mm for metallics. In this case, an increase in the current density in a pulse is equivalent to an increase in the voltage acting on the dislocations. This provides for the overcoming of the energy barrier by dislocations and the rearrangement into the state with the minimum Hbw free energy level, i.e. decrease in the level of residual welding stresses.

Efficient process flow contributes to the fact that the transmission of a pulsed electric current through the weld metal in a mode that ensures the occurrence of electroplastic effect

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in the process of crystallization of the weld metal, t, e, since the formation and start of movement of dislocations. The activation energy (the energy required to overcome the energy barrier by dislocations) is minimal at this moment. This is due to the fact that the mutual braking of the dislocations is minimal, since the dislocation density at this moment is much lower than in the remaining weld metal that has undergone cooling deformation (the density of dislocations in the metal subjected to deformation is much higher than in the non-deformed metal),

In addition, in the process of crystallization of the weld metal, the atoms of the diffusion sites and the surrounding atoms are thermally activated, which increases the mobility of dislocations and reduces the required activation energy.

When the temperature of the onset of crystallization of the weld metal, it contains the maximum number of vacancies, which also facilitate the rearrangement of dislocations.

The possibility of the formation of residual welding stresses during the welding process exists as long as plastic deformation occurs in the weld (the dislocations are carriers), I

When welding metals, electrons interact, which are communicated to the drift velocity (by passing an electric current pulse through the weld metal in a mode that gives rise to an electroplastic effect) with impurity atoms in the weld. This results in acceleration of the diffusion of impurity atoms (electric transfer phenomenon), which ensures more diffusion processes at the interface, as well as in the solid phase (crystallizing weld metal), and provides a weld with a lower level of chemical heterogeneity and higher strength properties. . The effective process is facilitated by the fact that the interaction of electrons, which are imparted to the drift velocity, with impurity atoms is carried out in the process of crystallization of the weld metal, i.e. in the moment.

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when the impurity atoms are thermally activated.

Example. Low-alloyed sheet steel, UHSND grade 2 mm thick, is welded in carbon dioxide, welding current 150 A, voltage 19 V, welding speed 18 m / h, pulsed electric current is passed through the weld metal in the crystallization rtpouecce mode: current density in pulse

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5x10 A / mm (current amplitude in a pulse 10 A), duration of one pulse 10 s, pulse frequency 1 Hz Pulsed electric current is supplied from a capacitor block through moving contacts, moving along the weld with a welding speed: one along the tail edge parts of the weld pool (in the zone where the metal begins to crystallize), the other part 40 mm away from it, i.e. in the zone where the temperature of the weld corresponds to the end of plastic deformations.

Welding is also carried out at other values of current densities and pulse frequencies, the data are given in Table 1,

Conduct mechanical testing. The results are summarized in table 2.

Samples welded by the proposed method have the best mechanical properties.

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Claims (1)

The use of the proposed method. In the manufacture of welded structures, the welding of metals ensures a decrease in the level of residual welding stresses, an increase in the technological and operational strength of the welded joints and, consequently, an increase in the reliability of operation of the welded structures as a whole. Invention Formula 1, A method of welding metals, including heating, melting a metal, forming a weld, and passing an electric current through it, characterized in that, in order to reduce the level of residual stresses, increase technological and operational strength. a welded joint; a pulsed electric current is passed through the forming weld in the electroplastic effect mode in the temperature range from the onset of crystallization to the temperature at which plastic deformations end in the weld, 2, the method according to claim 1, characterized by the fact that a pulsed electric current with a density of 10 - 10 A / mm is transmitted, continuous 4 5 The pulse duration is 10–10 s, i the pulse repetition frequency is 1–20 s. Table 1 eleven j 6 five 4.7 11 Editor I.Rogulich Compiled by L.Nazarova Tehred N.Glushchenko Order 1183/15 Circulation 976. Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab ,, d.4 / 5 Production and printing company, Uzhgorod, Projecto st., 4 37 40 41 41.2 37 51 55 56 56 51 Proofreader L. Patay