RU2570145C1 - Method of pulse arc welding - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to welding of metals and alloys by consumable electrode in argon or in the mix of at least 80% of argon with carbon dioxide. Claimed process comprises the generation of the train of welding current pulses. Basic arc current I_b is set at pauses between said pulses which corresponds to globular metal transfer from the electrode to molten pool. Arc current in the pulse is increased to the peak current with amplitude I_p = (1.5-2.0)I_cr where I_cr is critical current and the pulse current is maintained for time required for fine spray metal transfer. Note here that pause duration equals the pulse duration.

EFFECT: higher quality of the weld, expanded welding range for welding with fine controlled electrode metal transfer from control supply source with inverter converter.

4 cl, 2 dwg

Description

The invention relates to electric arc welding of metals and alloys with a consumable electrode in argon and a mixture of argon at least 80% of the rest is carbon dioxide and can be used in aviation, shipbuilding, chemical engineering and other engineering industries.

A known method of pulse-arc welding of non-ferrous metals and stainless steels and alloys with a consumable electrode in an argon protective medium, which consists in applying short-term current pulses of 1.5-3.0 ms duration to a base arc current from a special pulse generator connected in parallel with a welding power source with the purpose of obtaining controlled metal transfer is a current pulse of one drop [N. Dyurgerov. Equipment for pulsed arc welding with a consumable electrode. / N.G. Dyurgerov, H.N. Sagirov, V.A. Lenivkin, Moscow: Energoatomizdat, 1985. - 80 p.].

The disadvantage of this method is the relatively narrow range of regulation of the parameters of the current pulses, providing a stable welding process due to the redistribution of current during the cycle.

The closest to the implementation, technical nature and the achieved result is a method of pulsed arc welding with a consumable electrode [Copyright certificate No. 440863, V23K 9/16, 1974], which concludes that current pulses are applied to a continuously burning arc at the base current with the current the same polarity lasting 4-10 ms with a repetition rate of 50 or 100 pulses / sec, with a pulse current rise rate of 250-500 kA / sec, in order to obtain a process with controlled metal transfer, in which a few drops of electron are transferred under the action of a current pulse metal-stand.

The disadvantage of this method is that jet intermittent transfer of electrode metal is possible in a relatively narrow range of regulation of the parameters of the current pulses, providing continuous arc burning and a stable welding process. The pulse-arc welding process is carried out from two power sources connected in parallel to the arc: the main one is a welding power source with a rigid current-voltage characteristic of the power source (I – V characteristic) and an additional special pulse generator that affects the operation of the main power source. An increase in the pulse current of their duration and repetition rate leads to a decrease in the magnitude of the base current I _b due to the principle of self-regulation of the welding process. This is especially evident during the termination of the current pulse, when due to the transient in the power supply circuit of the welding arc I _b decreases to a value less than the minimum permissible arc burning current. This leads to a break in the burning of the arc, a violation of the uniformity of the formation of the weld. The pulse repetition rate is set in steps, which reduces the flexibility of controlling the welding process.

The technical result of the invention is to improve the formation of the seam and the expansion of the ranges of the welding mode with a small droplet controlled transfer of electrode metal from a controlled power source with an inverter converter.

, где t_и - длительность импульса,

- увеличение длины дуги за время действия импульса тока, Δυ_э1 - увеличение скорости плавления электрода при переходе с базового тока на ток импульса, затем понижают ток импульса до базового тока, выдерживают его в течение времени

, где t_п - длительность паузы, обеспечивающей сокращение длины дуги до длины дуги, соответствующей базовому току,

- сокращение длины дуги за время паузы, Δν_э2=υ_п-υ_э2 - уменьшение скорости плавления электрода при переходе на сварку базовым током в паузе, при которой производят сокращение длины дугового промежутка до длины, соответствующей длине дуги крупнокапельного переноса, и процесс повторяют.The technical result is achieved in that the method pulsed arc welding with consumable electrode is characterized in that the process is carried out in argon or an argon mixture at least 80% carbon dioxide, establish a base arc current I _b corresponding globular transferring metal from the electrode to the weld pool, and then the arc current is increased to a peak current with a pulse amplitude of I _p = (1.5-2.0) I _cr, where I _cr is the critical current and the pulse current is maintained for the time that ensures the metal jet transfer, according to the formula

where t _and is the pulse duration,

- increase in the length of the arc during the action of the current pulse, Δυ _e1 - increase in the melting rate of the electrode during the transition from the base current to the pulse current, then lower the pulse current to the base current, maintain it for time

where t _p - the duration of the pause, providing a reduction in the length of the arc to the length of the arc corresponding to the base current,

- reduction of the arc length of the pause, Δν = υ _{n A2} -υ _A2 - reduction rate of melting electrode when switching to weld the base current in the interval at which produce a reduction of length of the arc gap to a length corresponding to the length of the arc globular transfer, and the process is repeated.

, где k_ст, k_{сн -} коэффициент саморегулирования по току и по напряжению соответственно, k_д - градиент потенциала столба дуги, I_п и I_б - ток импульса и базы соответственно.The value Δυ _e1 can be determined by the formula

, where k _st , k _{sn -} coefficient of self-regulation by current and voltage, respectively, k _d - gradient of the arc column potential, I _p and I _b - pulse current and base, respectively.

The basic arc current I _b can be set by a controlled power source with an inverter converter, mainly with a combined current-voltage characteristic with a bayonet section in the range of operating currents.

The transition from the base current to the peak current and vice versa is preferably carried out discretely, for example, by switching the bayonet section of the current-voltage characteristic of the power source.

The process is repeated mainly with a smooth change in frequency from 10 to 110 imp / s.

The principle of implementation of the proposed method of welding with rectangular pulses during discrete switching of the bayonet section of the current-voltage characteristics of the power source is shown in FIG. 1, where 1 is the current-voltage characteristic of the power source, providing welding at subcritical current, 1 ₁ is the current-voltage characteristic of the power source, providing welding at supercritical current; 2 - characteristic of self-regulation of the arc; 3 and 3 ₁ - static current-voltage characteristics of the arc before and after the action of the current pulse, respectively.

The welding mode corresponding to the process with large-droplet metal transfer I _b <I _cr is determined by the intersection of the I – V characteristic of the FE (curve 1) with the welding self-regulation curve (2) point (a), while the voltage drop across the arc U _yes must ensure its length no more than 1.5-2.5 mm. At this point, the independent electrode feed rate (ν _p ) is equal to its melting rate (ν _e ), which is determined by the formula (1)

where k _dt - steepness of the natural static characteristics of the arc.

остается постоянной и через точку (а) проходит вольтамперная характеристика дуги (ВАХ Д) кривая 3.The length of the arc gap

remains constant and through the point (a) the current-voltage characteristic of the arc (CVC D) curve 3 passes.

а скорость плавления электрода в ней (ν_эа1) определяется уравнением 2When the discrete switching VAC SP from position 1, which provides globular metal transfer point a to 1 _1, which provides spray transfer of metal, the current and the arc voltage (I _n, U _yes1) in this case determines the point a ₁ intersection VAC A (curve 3 ) and IV characteristics of IP 1 ₁ at constant arc length

and the melting rate of the electrode in it (ν _ea1 ) is determined by equation 2

Since ν _p remains unchanged (self-regulation curve of arc 2), then ν _ea1 for I _{p is} greater than ν _p by Δν _e

выбирается из условия обеспечения СПМ при постоянном токе импульса I_п и займет положение 3₁.In this case, the arc length begins to increase, the overhang of the electrode decreases, and the I – V characteristic D 3 is equidistantly displaced upward from point a ₁ to point (b ₁ ), obtained by the intersection of the characteristics of the I – V characteristic I with the I – V characteristic IP 1 ₁ . Arc length

is selected from the condition for providing PSD at a constant pulse current I _p and will occupy position 3 ₁ .

Based on the permissible length of the arc, provides MTA when I _n, the current pulse duration determined by the time _{t, and} the arc between the points a ₁ and b ₁

,

,

- скорость плавления электрода при I_п,

, k_д - градиент потенциала столба дуги.Where

,

,

- the melting rate of the electrode at I _p

, k _d - the gradient of the potential of the arc column.

и меньше разность между величинами тока в импульсе и паузе, тем больше длительность импульса, во время которого происходит интенсивное плавление электродной проволоки и струйный перенос металла.From equation 7 it follows that the more

and the smaller the difference between the values of the current in the pulse and the pause, the longer the pulse duration, during which there is intense melting of the electrode wire and metal jet transport.

When the I – V characteristic of the switchgear is switched from position 1 ₁ point b ₁ to position 1 point b, a pause t _p begins, the duration of which is determined by the time of burning of the arc between points b and a .

,

.Where

,

.

Since the increment in the melting rate of the electrode wire under the action of a current pulse Δν _ei is equal in absolute value to the melting rate at Δν _ep , the pulse duration is equal to the duration of the pause.

. Частота следования импульсов выбирается из условия обеспечения равномерности формирования ширины шва по его длине и не должна превышать 10 имп/с.The minimum pulse duration, providing PSPM, is (4.5 ... 5.0) · 10 ^-3 s at I _p = (1.5 ... 2.0) I _cr . In this case, the pulse repetition rate is maximum - 110 ... 100 imp / s. The largest pulse duration is determined from the condition for providing PSD at a constant value of I _p and the maximum allowable

. The pulse repetition rate is selected from the condition of ensuring the uniformity of the formation of the seam width along its length and should not exceed 10 imp / s.

The following is an example embodiment of the invention.

Example

For welding taken: plates of low-carbon structural steel St20, 6 mm thick, welding wire Sv-08G2S with a diameter of 1.2 mm.

The method of pulsed arc welding with a consumable electrode was carried out in a mixture of 80% Ar + 20% CO ₂ . The welding mode was preliminarily set corresponding to the region of modes with large-drop metal transfer from the electrode to the weld pool [V. Lenivkin Technological properties of a welding arc in shielding gases / V.A. Lenivkin, N.G. Dyurgerov, H.N. Sagirov. - 2nd ed. add. - M .: 368 pp.], The base current of the arc I _b , equal to 160 A, and the voltage drop across the arc is 23.4 V. In this case: the external component length of the arc is 2.5 mm, the arc is spatially stable, liquid metal at the end of the electrode has a spherical shape, the active spot of the arc is located under the drop, the transfer of metal is large droplet of 6-10 drops / s.

, где

- увеличение длины дуги за время действия импульса тока - 2,0 мм, Δυ_эи - увеличение скорости плавления электрода при переходе с базового тока на ток импульса - 6,6 мм/с, рассчитанной по формуле (3).Then the arc current was increased to a peak current with an pulse amplitude I _p equal to 375A, which was 1.87 I _cr - (I _cr - the critical current for Sv-08G2S wire with a diameter of 1.2 mm in a mixture of protective gases is 190-210A [Lenivkin V.A. Technological properties of a welding arc in shielding gases / V.A. Lenivkin, N.G. Dyurgerov, H.N. Sagirov. - 2nd ed. Supplement. - M .: 368 p.], And supported by flow of time t _and equal to 30 ms calculated by the formula

where

- increase in the length of the arc during the action of the current pulse - 2.0 mm, Δυ _ei - increase in the melting rate of the electrode when switching from the base current to the pulse current - 6.6 mm / s, calculated by the formula (3).

During the action of the pulse, the arc covers the side surface of the electrode and the liquid metal located at the end of the electrode wire is drawn under the action of electromagnetic forces into a cone (trickle). Small drops with a diameter of up to 0.4 mm with a frequency of 400 ÷ 200 drops per second are separated from the top of the cone. The length of the arc increases to 4.5 mm, the voltage drop across the arc rises to 25.8 V.

, где t_п - длительность паузы, равная 30 мсек, которая обеспечивала сокращение длины дуги

до 2,5 мм, соответствующей базовому току, Δυ_зп=υ_п-υ_э2 - уменьшение скорости плавления электрода при переходе на сварку базовым током во время паузы. Перенос металла с электрода в сварочную ванну во время паузы отсутствовал.Then, the pulse current was discretely reduced to a base current of 160 A and held for a time

Where t _p - pause time equal to 30 ms, which reduce the arc length

2.5 mm corresponding to the base current, Δυ _sn = υ _n -υ _A2 - reduction rate of melting electrode when switching to the welding base current during the pause. There was no transfer of metal from the electrode to the weld pool during a pause.

до нуля ток дуги вновь повышали до I_п, равного 375 А, и процесс повторялся. Время цикла t_ц=t_и+t_п составляет 60 мсек, частота следования импульсов f=1/t_ц-16,6 имп/с.When decreasing

to zero, the arc current was again increased to I _p equal to 375 A, and the process was repeated. The cycle time t _c = t _and + t _p is 60 ms, the pulse repetition rate f = 1 / t _c -16.6 imp / s.

In FIG. Figures 2a and b show the portion of the waveform of the voltage and current changes during a pulse and pause in time, from which it follows that the current I _b and I _p in time remain unchanged.

The resulting seam is formed uniformly along the width and height of the seam convexity.

Thus, the use of the inventive method of pulse-arc welding can provide improved weld formation and expand the range of the welding mode with intermittent jet transfer of electrode metal from controlled power sources with an inverter converter with combined current-voltage characteristics with a bayonet section in the range of operating currents.

Claims (4)

1. A method of pulsed arc welding of metals with consumable electrode under shielding gas in the form of an argon or a mixture of at least 80% of argon and carbon dioxide, comprising forming a welding current pulse sequence, in the pauses between which is set the arc base current I _b, characterized in that the set arc base current I _b, corresponding globular metal transfer from the electrode to the weld pool, and the amplitude of pulses of said set corresponding to the peak arc current I _p = (1,5 - 2,0) I _kr, where I _cr - a critical current OJEC echivayuschy inkjet transfer of metal from the electrode to the weld pool, and maintain said peak current for a time t _and = Δℓ _di / ΔV _A1 where t _and - the duration of the pulse welding current, Δ ℓ _di - increasing the arc length of the duration of said pulse equal Δℓ _di = (U _db1 - U _da1 ) / k _d , where U _db1 is the voltage determined by the point of intersection of the static current-voltage characteristic (CVC) of the arc after the action of the current pulse and the CVC of the power source during the jet transfer of the electrode metal, U _yes1 is the voltage determined intersection point stat cal CVC arc to the current pulse action and VAC power source when the jet transfer electrode metal, k _d - potential gradient of arc column, ΔV _A1 -increase electrode melting speed when moving from the base current for the pulse current, equal ΔV _A1 = (k _CT (I _p - I _b ) - k _cn · (U _yes1 - U _yes )), where k _ct , k _cn are the coefficients of self-regulation by current and voltage, respectively, U _yes is the voltage determined by the point of intersection of the static I – V characteristic of the arc before the action of the current pulse and CVC of the power source during a large-drop transfer of the metal of the electrode, while the duration of the pause t _p between the mentioned pulses, at which the length of the arc gap decreases to the length corresponding to the length of the large droplet transfer arc, is set equal to the duration of the mentioned pulse. 2. The method according to claim 1, characterized in that the basic arc current I _{b is} set by means of a controlled power source with an inverter converter. 3. The method according to claim 1, characterized in that the transition from the base current to the peak current and vice versa is carried out discretely. 4. The method according to claim 1, characterized in that the pulse repetition rate of the welding current is set in the range from 10 to 110 imp / s.

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