SU1065119A1 - Method of arc welding by consumable electrode - Google Patents

Abstract

THE METHOD OF THE ARCED CBAPICH PLANE ELECTROD OF CLUSTERING STRAINS OF WIDE-CUTTED STAINLESS STEEL STEELS, Predominantly Type 18-8, in which the mixture of Ar 4–3.5% 02 is used as a zapadatnoy environment, characterized in that, in order to increase welding productivity and quality of welded seams by reducing the number of passes and preventing the occurrence of crystallization cracks in the root of the seam, from the moment the arc was stabilized and the jet transfer of the molten metal of the melting electrode was established. increase 3-3.5 times while Nala-s ait the arc of the reversible axial pulsed magnetic field of 8-15 MLT and reversal interval 0,02-0,24 with. (L

Description

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The invention relates to the welding industry, namely to welding with a melting electrode, advantageously from steels of the type 18-8 of joints assembled with a narrow gap. A known method of welding in a mixture of gases (Ar + 5.0% 62), in which the process is conducted in the following modes, the welding current is Lsv 300–1500 L, the diameter of the electrode is 3–6.4 MT.I; welding speed 300-1500 mm / min; gas consumption 50 200 l / min ClJ. The disadvantage of this method is the high probability of embrittlement and local destruction of metal due to significant overheating during welding in shielding gas at high currents, as well as a large protective gas flow rate. The closest to the proposed is a method of welding plav psms electrode in a mixture of protective gases Ar + 3-5.0% 02 of connections with narrow deep cutting of stainless steels 2. The disadvantage of this method is low productivity, since for welding large metals Thickness requires a multi-pass process that requires a considerable amount of time. In addition, multiple thermal effects during multipass welding are undesirable because of the embrittlement of the weld metal, and the narrow and stretched shape of the weld cross section when welding with a narrow-groove creates unfavorable conditions for the crystallization of the weld metal, since as a result of limited heat sink From the base of the weld pool, columnar crystallites grow towards each other, which leads to the appearance of crystallization cracks. The aim of the invention is to increase the productivity of welding and the quality of welds by reducing the number of passes and preventing the appearance of crystallization cracks in the root of the seam. The goal is achieved by agreeing to the method of arc welding by fusible electrode of joints with narrow separation of stainless steels, mainly of the type 18-8, in which the mixture of Ar + 3-5% 02 is used as a protective medium, s. for setting the jet transfer of the molten metal of the melting electrode, the speed of supplying the melting electrode increases by 3-3.5 aza and simultaneously impose on the arc an axial pulsed reversible magnetic field with an induction of 8-15 mlT and a reversing interval of 0.02-0.24 s . When the oxygen content in argon is less than 3%, a sufficiently complete removal of hydrogen from the austenitary seam is not provided, which leads to increased pore formation and a decrease in the quality of the seam; with an increase in the oxygen content in argon by more than 5%, the risk of damage to the seams increases due to oxidation of ferritization and possible austenization seam structures. Since the welding process begins at a wire feed speed sufficient to form a jet transfer of the metal of the wire to the base metal (200 m / h), and after initiating the arc from the moment it is stabilized and establishing the jet transfer of the molten metal of the melting electrode 5 seconds after ignition of the arc, the wire feed rate is increased by 3, 3, 5 times, then the jet of molten metal presses on the preheated main mass and the arc is immersed in a bath of molten metal. In this case, there is the effect of a keyhole and a sharp increase in the depth of penetration (by 1.52 times compared with the method of the prototype). This reduces the number of weld passes, i.e. to increase the productivity of the welding process and the associated terglycic cycles acting on the previously welded grooves and the adjacent heat-affected zone. The interval of increasing the feed rate of the melting electrode (33, 5 times) was determined experimentally. With an increase in the feed rate of less than 3 times, there is no effect of an immersion of the arc, and with an increase in the feed rate of more than 3.5 times, the welding current dramatically increases. Which leads to overheating of the base metal. After 3-5 seconds after initiating the arc (i.e., together with an increase in the wire feed speed), the control reversing magnetic field with an induction of 815 mlT and a reversal interval of 0.02-0.24 sec, ensures the mixing of the weld pool melt and therefore, an intensive heat removal from the base of the weld pool, grinding of the crystallites and their orientation in one direction. The indicated ranges of intensity and reversal intervals of the axial magnetic field are determined experimentally. These induction ranges and reversal intervals of the magnetic field provide the optimal form of penetration at elevated wire feed speeds (weld coefficient | 3-4 K

When using a magnetic field with an induction of less than 8 mlT and a reversal interval of less than 0.02 s, the necessary intensive heat removal from the base of the weld pool is not provided, and when using an NI magnetic field with an induction higher than 15 mlT and a reversal interval of more than 0.24 s, an excessive rotation of the molten metal in the weld pool, resulting in metal splashes (splashing and disturbing the jet transfer of the metal.

At magnetic induction values of 8–15 mlT, welded joints are characterized by better mechanical properties as compared to welded joints obtained by welding without electromagnetic stirring.

Example. Weld plates from steel 08Kh18N10T 10 mm thick with wire 08Kh19N10G2B f 1.6 mm in the gas mixture Ar + 5% C in the following mode.

Arc ignition: welding current 250 A, arc voltage 26 V, welding speed 35 m / h, wire feed speed 250 m / h; 5 seconds after the ignition of the arc: welding current 380 A, arc voltage 30 V, welding speed 35 m / h, wire feed speed 860 m / h.

At the same time, the arc is subjected to a magnetic field with induction, 12 mlT, reversing interval 0.02 s;

The results of mechanical and metallographic tests show that welding of the samples according to the proposed method has the highest performance - metal 10 mm thick is welded in one pass instead of three passes (without a magnetic field or without an increase in welding speed y.

The form of penetration of seams is most favorable from the point of view of preventing the occurrence of crystallization cracks (coefficient of seam shape is K 3-4).

Compared to the base object, the proposed method improves the quality and productivity of welding by reducing the number of passes and their associated thermal heating cycles, and also reduces the likelihood of crystallization cracks.

Claims (1)

METHOD OF ARC WELDING BY MELTING ELECTRODE of compounds with narrow cutting of stainless steels, mainly of type 18-8, in which Ar + 3-5% 02 mixture is used as a protective medium, characterized in that, in order to increase welding productivity and quality of welds by reducing the number of passes and preventing the appearance of crystallization cracks in the root of the weld, from the moment of stabilization of the arc burning and the establishment of the jet transfer of molten metal of the melting electrode, the feed rate of the melting electrode was increased Chiva dissolved in 3-3.5 times and simultaneously nala- ₃ ait the arc of the reversible axial pulsed magnetic field of 8-15 MLT and reversal interval 0,02-0,24 seconds.