RU2159171C1 - Method for electric arc double-layer welding-on - Google Patents

Abstract

FIELD: electric arc welding of parts of carbon, medium-alloy quenchable steels, for example in lock joints of drilling pipes, crank shafts of engines and so on. SUBSTANCE: welding-on is realized by means of main electrode while feeding into crystallized zone of bath heated wire spaced from main electrode by distance consisting 0.35-0.4 of length of welding bath. Additive wire is heated by electric current pulses. Main electrode and additive wire are subjected to cross oscillations with frequency depending upon width of welding bath. EFFECT: enhanced formation of bead at simultaneous reduction of length of welding bath. 1 tbl

Description

 The invention relates to the field of electric arc surfacing of parts from carbon, medium alloy hardened steels, for example tool joints of drill pipes, crankshafts of engines, cold rolls, etc.

 The method of arc welding with a consumable electrode (AS USSR No. 633688, 23K 9/18), in which vibrations along its axis are reported to the consumable electrode, transverse vibrations are used for the additional filler wire, is an analog of the two-layer arc welding method.

 The disadvantage of this method is that it does not change the shape of the weld, and therefore, the reinforcement of the roller and its other geometric dimensions remain large.

 The closest analogue of the claimed invention can be considered the method of two-layer arc welding (RU 97104641 A1, MPK7 V 23 K 9/04, 05/10/1999), in which the process is carried out with the main electrode and at the same time a heated filler wire is placed into the crystallizing part of the bath with its location at a distance from the main electrode, determined by the length of the weld pool.

 The disadvantages of the method selected as a prototype include the increased thickness of the weld bead due to the displacement of the flows of molten metal in the head of the bath filler wire. The increased height of the shaft is not always acceptable, for example, when surfacing drill pipe joints, at which the maximum height of the shaft should not exceed 4 mm, because otherwise, the washing of boreholes with clay mud is disrupted (the gap between the hardened lock and casing is sharply reduced, which affects the circulation of mud).

 The objective of the invention is to provide a method of two-layer arc surfacing, which provides improved formation of the roller by reducing its height.

This problem is solved by the fact that during the process of two-layer arc welding with the main electrode and feeding a heated filler wire into the crystallized part of the bath at a distance from the main electrode, determined by the length of the weld pool, the filler wire is heated by current pulses, the distance between the filler wire and the main electrode is 0 , 35-0.4 lengths of the weld pool, while the filler wire reports lateral vibrations with a frequency f _CR and an amplitude equal to 0.6-0.7 of the width of the weld pool transverse vibrations with the frequency f _e , component (0.9-4) f _pr , (Hz).

 The proposed method is as follows. In the crystallized part of the weld pool serves filler wire, heated by short-term pulses of constant current low voltage. To ensure the formation of a stable layer along the entire length of the fusion line of the filler wire, vibrations across the roller are reported. The oscillation frequency of the filler wire is selected from the conditions for the formation of a continuous sublayer and determined depending on the speed of surfacing.

To improve the formation of the roller by reducing its height, the main electrode is informed of transverse vibrations that increase the width of the seam and, due to the constant cross-sectional area, reduce its height. This reduces the length of the weld pool. The oscillation frequency of the main electrode is determined by the formula:
f _e = (0.9-4) f _ol ,
where: f _CR - the oscillation frequency of the filler wire, Hz;
f _e - oscillation frequency of the main electrode, Hz.

 At minimum values of the oscillation frequency of the main electrode, a wavy shape of the side surface of the roller is observed, and at maximum values, chaotic wandering of the arc spot on the product and disturbance of the bath mirror are observed.

Example. Surfacing of samples made of Steel 45 with flux-cored wire PP-AN-122 with a diameter of 2.6 mm was carried out. Surfacing mode: welding current I _st = 350 A, arc voltage U _d = 36 V, electrode wire feed speed V _p = 220 m / h. The mode parameters were kept constant during surfacing of all samples. Deposition speed V _n = 20 m / h.

An austenitic filler wire Sv-04X19N11MZ with a diameter of 2 mm was fed into the weld pool at a distance of 14 mm from the cored wire. The filing speed of the filler wire V _PP = 135 m / h It was heated from the GIDS-1 pulse generator by passing DC pulses of duration (2.0-2.5) • 10 ^-3 s, amplitude 900-1000 A and frequency 50 Hz.

To obtain comparative data, two batches of samples were surfaced:
The 1st batch was surfaced with an oscillation of the filler wire with a frequency f _pr = 2.8 Hz and an amplitude equal to 0.6-0.7 of the width of the bath and at a distance between the cored wire and the filler 0.37 of the length of the weld pool.

The 2nd batch was surfaced with oscillations of the main electrode with a frequency f _{e min} = 2.5 Hz, f _{e opt} = 6.9 Hz and f _{e max} = 11.2 Hz and with a frequency of vibrations of the filler wire f _pr = 2.8 Hz with an amplitude equal to 0.6-0.7 of the width of the bath, and at a distance between the cored wire and filler 0.37 of the length of the weld pool.

 After surfacing, the samples were tested for the resistance of the deposited metal to cold cracks.

The criterion for evaluating the resistance to cold crack formation was the critical tensile stress σ _pmin , causing crack formation.

 The criterion for assessing the height of the weld bead is the reinforcement of the seam g.

The criterion for assessing the wear resistance is the coefficient of relative wear resistance K _{and the} test deposited metal in relation to Steel 45.

 Surfacing parameters and test results are presented in the table.

 As can be seen from the table, the use of oscillations of the main electrode, changing the shape and size of the weld pool, practically does not affect the resistance to cracking and the wear resistance of the deposited metal within the data spread.

 When surfacing with the optimal combination of the oscillation frequency of the main electrode and filler wire according to the proposed method (batch 2), ceteris paribus, the height of the deposited bead does not exceed 4 mm, which does not violate the process of washing wells with clay mud.

 The mismatch of the relationship between the oscillation frequency of the main electrode and the oscillation frequency of the filler wire does not provide the required height of the weld bead, all other things being equal.

Claims (1)

The method of two-layer arc welding, including the process using the main electrode and feeding the heated filler wire to the crystallized part of the bath at a distance from the main electrode, determined by the length of the weld pool, characterized in that the filler wire is heated by current pulses, the distance between the filler wire and the main electrode is 0 , 35 - 0,4 weld puddle length, wherein the filler wire reported transverse vibrations with a frequency f and an amplitude _Ave of 0.6 - 0.7 welded width -bath, and the main electrode report transverse vibrations with frequency f _e, component (0,9 - 4,0) f _ave Hz.

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