RU2641940C1 - Method of arc-mechanized pulse welding - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: negative pole of the DC power supply is connected to a non-consumable electrode, and its positive pole is connected to the product and to two consumable electrodes having different chemical composition. Arc between nonconsumable electrode and product is lighted, and then periodically the product is turned off from the positive pole of the power supply by connecting to it consumable electrodes with indirect arc ignition between each of them and nonconsumable electrode. The duration of the current flow in each of the consumable electrodes and the value of current in the period of burning of indirect arc are regulated. Periodic connection of the positive pole of power source is carried out in the sequence "product - first consumable electrode - product - second consumable electrode - product". Consumable electrodes of different diameters can be used.

EFFECT: method ensures the chemical composition of seam with a specified content of alloying elements.

3 cl, 3 dwg, 2 tbl

Description

The invention relates to the field of welding and can be used in mechanical engineering for surfacing layers with special properties and welding of difficultly welded steels and alloys.

There is a method of plasma arc welding, in which the negative pole of the welding power source is connected to the non-consumable electrode, and the positive pole is connected to the product, a melting electrode is used, connected to the positive pole of the power source, a direct-action arc of direct polarity between the non-consumable electrode and the product and an indirect arc are ignited actions between a non-consumable and a consumable electrode (see article by I.E. Taver, M.Kh. Shorshorov “Welding of steel with a double plasma jet”, Welding production, 1971, No. 10, S. 26-28).

The disadvantages of this method is the interaction of the intrinsic magnetic fields of the arcs, leading to instability of the spatial position of the arcs and the transfer of electrode metal into the weld pool, and limited technological capabilities for regulating the chemical composition of the weld.

There is also a known method of pulsed plasma surfacing, in which two phases are connected to the electrodes, and the third to the filler wire or to the fused product, the filler wire is fed into a column of a compressed arc of direct action, the product is periodically disconnected from the power source and during this period the filler wire is connected to power source (see "The method of pulsed plasma surfacing." SU Copyright certificate No. 1693808, MKI ² V23K 9/16 - Zareg. 07.22.91.). This method is adopted as a prototype.

The application of this method is possible when welding with a free arc. This method provides adjustment of the ratio of the amount of molten and deposited metals. However, with this method it is difficult to obtain the chemical composition of the weld with a wide range of alloying elements, since the number and content of alloying elements in one welding wire is limited.

In the known method of arc mechanized pulsed surfacing in an inert gas medium, the negative pole of the DC power source is connected to the non-consumable electrode, and the positive pole is connected to the product and the electrode wire, the electrode wire is fed continuously between the non-consumable electrode and the product, the arc is ignited between the non-consumable electrode and product and then periodically disconnect the product from the positive pole of the power source and periodically connect the electrode wire to it Oka.

Unlike the prototype, the second electrode wire of a different chemical composition is connected to the positive pole of the power source and continuously fed into the gap between the non-consumable electrode and the product, the arc of indirect action from the non-consumable electrode is periodically ignited on it, the ratio of the duration of the current flow in each of the electrode wires is set within 0.2 ... 0.4 with respect to the current flow cycle, and the magnitude of the currents of the arcs to the melting electrodes during periods of current flow through them is determined by the formula

where d _E is the diameter of the melting electrode, cm;

V _e - the required rate of melting of the electrode, cm / s;

ρ is the density of the consumable electrode, g / cm ³ ;

t _C - the total cycle time of the current flow in the melting electrodes and the product, s;

t _e - current flow time in this consumable electrode, s;

α _P is the melting coefficient of the consumable electrode when welding by a direct-acting arc on the reverse polarity of the arc at a current I _D = I _E ⋅t _I / t _C ,

moreover, the connection of the positive pole of the power source and the ignition of the arcs between the non-consumable electrode and the remaining electrodes are performed in the sequence: "product - first wire - product - second wire - product.

In many cases, it is advisable to use electrode wires of various diameters.

The duration of the currents in the electrode wires can be selected different.

The technical result of the proposed method lies in the fact that at the same time the independence of the penetration rate of the base metal and the melting rates of the two electrode wires is ensured with the possibility of wide regulation of the chemical composition of the weld metal by a large number of alloying elements. This is ensured by alternating periodic burning of one of the three arcs from one power source, which creates the possibility of stable ignitions of indirect arcs between a non-consumable electrode and wires and direct-action arcs between a non-consumable electrode and a product, despite their rather long interruptions in burning. Stable ignition of the arc on the product is ensured by the fact that the electrode wires are fed into the gap between the product and the non-consumable electrode continuously and play the role of duty arcs in relation to the product. The stability of repeated ignitions of indirect arcs is ensured by the constant supply of electrode wires to the arc column, the penetration of wires into the arc column and the connection of a sufficiently high open circuit voltage to one DC power source.

The use of electrode wires of various diameters significantly expands the technological capabilities of the method for regulating the ratio of productivity of their surfacing and, accordingly, the possibility of additional regulation of the chemical composition of the weld metal and weld.

The choice of different durations of the flow of currents in the electrodes serves to obtain the necessary rate of melting of the electrodes with a difference in their thermophysical properties.

In FIG. 1 shows a diagram of the implementation of the method, FIG. 2 is a current flow diagram in a non-consumable electrode; FIG. 3 - dependences of the coefficient of fusion of the electrode wire on the arc current of reverse polarity.

In FIG. 1 presents a diagram of the implementation of the proposed welding method. A non-consumable tungsten electrode 2 is permanently connected to the negative pole of the power source 1 of the DC arc, located in the welding torch 3. The torch 3 moves relative to the product at a speed of V _C. An inert gas argon, helium or a mixture thereof is supplied to the nozzle of the burner 3. To the positive pole of the power source 1 is connected surfaced product 4 and consumable electrodes 5 and 6 of different chemical composition. The electrodes 5 and 6 with two different feeding devices are supplied with constant speeds in the gap between the non-consumable electrode 2 and the product 4. The electrodes 5 and 6 can be of different diameters. An electronic key 7 is installed in the electric conductor connecting the melting electrode 5 to the positive pole of the power source 1, which enables connecting and disconnecting the electrode 5 and ignition and extinction of the arc between the electrode 2 and electrode 5. In the electric conductor connecting the melting electrode 6 to the positive pole of the source 1, an electronic key 8 is also installed, providing connection and disconnection of the electrode 6 and ignition and extinction of the arc between the non-consumable electrode 2 and electrode 6. In the electrical conductor, an enclosing article 4 with a positive pole of the power supply 1, an electronic key 9 is installed, which enables the connection and disconnection of the product 4 with respect to the positive pole of the power supply 1.

The electronic control circuit controls the electronic keys in such a way that only one welding arc burns at any given time. In FIG. 1 it is shown that an indirect arc 10 is burning between the consumable electrode 5 and the nonconsumable 2. In this case, the electronic key 6 is turned on, and the electronic keys 8 and 9 are turned off.

At the initial moment of surfacing, an arc is ignited between the non-consumable electrode 2 and the product 4 with the electronic key 9 turned on, which burns for a time t _AND . Electronic keys 7 and 8 are disabled during this period. After that, the electrode wire 5 is turned on, the electronic key 9 is disconnected by connecting the electrode 5 with the electronic key 7. Thus, the arc 10 between the electrodes 2 and 5 is ignited. After a while t _{Э1, the} electronic key 7 is disconnected, disconnecting the arc between the electrodes 2 and 5 and _turned on again the key 9, again igniting the arc between the electrode 2 and the product 4 at a time t _AND . The burning time of the arc between the non-consumable electrode 2 and the product 4 is of time t _And in the interval between the burning of the arcs on the melting electrodes 5 and 6, the same is selected.

After that, the electrode wire 6 is turned on and the electronic key 9 is turned off, and the electronic key 8 is turned on, igniting an indirect arc between the electrodes 2 and 6 for a time t _E2 . This completes one cycle of all three arcs. Time arcs burning melting at electrodes may be the same as t = t _{A1 A2 A1} or different t ≠ t _A2. The total cycle time t _C is equal to the sum of the duration of the arcing between the non-consumable electrode, the product and the melting electrodes

t _C = 2t _I + t _E1 + t _E2 .

A new cycle begins by extinguishing the arc between the electrodes 2 and 6 by opening the electronic key 8 and turning on the arc between the electrode 2 and the product 4 with the electronic key 9. Between the connections of the electrodes 5 and 6, the arc between the non-consumable electrode 2 and the product 4 is switched on each time. sufficiently high frequency, providing continuous melting and supply of electrodes 5 and 6 with constant speeds. The characteristics of the power source 1 provide separate regulation of the current in the electrodes 5 and 6 and the product 4. The arc current "non-consumable electrode 2 - product 4" provides the necessary penetration of the product 4. Arc currents "non-consumable electrode 2 - consumable electrode 5" and "non-consumable electrode 2 - 6 ”melting electrode provides the necessary surfacing performance to ensure alloying of the seam with the necessary alloying elements contained in the electrode wires of various chemical composition. Stable ignition of arcs is ensured by high speed electronic keys and good ignition conditions for all three arcs. Indirect arcs are well ignited due to their supply to the pole of a direct-acting arc in the gap between the electrode 2 and the product 4. The direct-arc is reliably excited by blowing the pillars of indirect arcs with their own magnetic field in the direction of the part and good ionization of the arc gap “non-consumable electrode 2 - product four".

In FIG. 2 shows a current flow diagram in a non-consumable electrode. Current in a non-consumable electrode flows continuously. The total cycle time in FIG. 2 t _C coincides with the duration of the current flow in the non-consumable electrode. The cyclogram shows the duration of the current flow in the product and in the melting electrodes. The cyclogram contains sections 1, 2, 3, 4, representing the dependence of the arc currents on the burning time. Section 1 of the direct current I _{And the} arc of direct polarity is located between the non-consumable electrode and the product. Line 2, parallel to the time axis, shows the arc current I _E1 to the first consumable electrode in the second part of the cycle, the duration of which is t _E1 . Line 3, parallel to the time axis, shows the arc current I _and to the product during the third part of the cycle, the duration of which t _AND . Line 4, parallel to the time axis, shows the current in the second electrode I _{E2 of the} arc between the non-consumable electrode and the second consumable electrode, the duration of which is t _E2 .

In FIG. 2 in the general case, the duration of the flow of currents and currents in the melting electrodes are not equal to each other: I _E1 ≠ I _E2 ; t _E1 ≠ t _E2 . Arc current I _and the product takes place in two times higher than in each of the electrodes. This is necessary to increase the stability of repeated ignitions of arcs. The duration of the flow of currents in each of the melting electrodes t _E1 and t _E2 should be 0.2 ... 0.4 period t _C. The total time of current flow in the two melting electrodes is t _A1 + t _A2 = 0.4 ... 0.8 t _C. The current flow in the product t _And = 0.2 ... 0.6 t _C. This allows you to adjust the ratio of the productivity of surfacing and melting of the base metal within the necessary limits, depending on whether the process of surfacing or welding. The duration of the flow of arc currents in the electrodes t _E1 and t _E2 and currents I _E1 and I _E2 can be chosen equal to each other: I _E1 = I _E2 , I _E1 = I _E2 ;

In FIG. Figure 3 shows the dependences of the melting coefficient α _{P of the} aluminum electrode wire on the arc current of the opposite polarity. Curve 1 represents the dependence for the wire brand SvAMts with a diameter d _e = 1.6 mm, curve 2 - for wire SvAMg6 with a diameter d _e = 2.0 mm. Curve 1 for a smaller diameter electrode is located above curve 2 for a larger diameter. Therefore, at the same currents, the melting coefficient and the melting performance of a smaller diameter electrode wire are greater. Similar dependences hold for steel wires in an arc of reverse polarity in inert gases.

The deposition performance of P electrode wire is determined by the formula

where α _H is the surfacing coefficient, g / (A⋅h);

I _D - arc current, A.

Melting factors α _P and deposition coefficient α _H are related by

where ψ _P is the loss coefficient, data on which are available in the specialized literature.

The performance of surfacing simultaneously with two electrode wires according to the proposed method can be determined by the formula

where P ₁ and P ₂ - respectively, the deposition rate of the first and second arcs on the melting electrodes;

α _H1 - deposition coefficient for the first arc;

I _C1 is the average current value of the first arc per cycle (period);

α _H2 - deposition coefficient for the second arc;

I _C2 - the average value of the current of the second arc per cycle (period).

Then the content of the weld metal of any alloying elements _E, present in the electrode wire

where β ₁ is the content of this element in the first electrode wire;

β ₂ - the content of this element in the second electrode wire.

The arcs between the non-consumable and the melting electrodes, which in the proposed method are always anodes, burn intermittently with a certain frequency. In this case, their melting performance α _P can be determined using the dependencies of the form shown in FIG. 3, by the average arc current in the electrode. The average value of the arc current for the period for each of the electrodes I _C can be determined by the formula

where I _E is the value of direct current during the burning of the arc "non-consumable electrode - melting electrode", A;

t _e - the duration of the current flow in the pulse for a period, s;

t _C - the duration of the period in the cycle, C.

From the average current value in the consumable electrode, the melting coefficient is determined using dependencies similar to those in FIG. 3, and melt flow rate and the electrode wires on the basis of the formula that links the melting rate of the wire to melt the coefficient α _F.

where ρ is the density of the electrode wire, g / cm ³ ;

j _C is the average value of the arc current density in the electrode section, A / cm ² .

The average current density at the electrode per cycle (period) is determined by the formula

After considering jointly the formula (6), (7) and (8) yields a formula for determining the arc current in a consumable electrode arc during combustion indirect actions depending on the desired speed V _e of its melting

The inclusion of arcs in the sequence "product - first wire - product - second wire - product" provides high stability of ignition of arcs of both direct and indirect action.

The use of electrode wires of various diameters, as well as the use of various durations of burning of indirect arcs on melting electrodes, expand the technological capabilities of the method.

Example

Surfacing was carried out on a plate of steel 20 with a thickness of 10 mm by two surfacing wires with diameters d _E = 1.0 and d _E = 1.2 mm according to the proposed method. The power source was a direct current source VDU-500U3 together with a specially designed electronic switch. The deposition rate was V _C = 0.3 cm / s. A wire with a diameter of d _E = 1.0 mm grade Np-40X13. A wire with a diameter of d _E = 1.2 mm grade Np-G13A. The chemical composition of the wires according to GOST 10543-98.

The Np-40X13 wire contains chemical elements: carbon C = 0.4%, chromium Cr = 13.0%, manganese Mn = 0.6%, silicon Si = 0.6%.

The Np-G13A wire contains chemical elements: carbon C = 1.1%, chromium Cr = 0.5%, manganese Mn = 13%, silicon Si = 0.3%, nickel Ni = 0.5%.

Surfacing was carried out in the following modes: current of the first pulse in the product I _И1 = 400 A, pulse duration t _И1 = 0.002 s, current of the second pulse in the product I _И2 = 500 А, duration of the second pulse t _И2 = 0.002 s. The current in the wire Np-40X13 I _E1 = 400 A, the pulse duration t _E1 = 0.004 s, the current in the wire Np-G13A I _E2 = 500 A, the pulse duration t _E2 = 0.002 s. The total cycle time is t = 0.01 _D c. Cycle frequency f = 100 Hz.

The average value of current in the product for the period

I _IP = (400⋅0.002 + 500⋅0.002) /0.01 = 180 A.

The average value of current in the wire Np-40X13 for the period

I _SE1 = 400⋅0.004 / 0.01 = 160 A.

The average value of the current in the wire Np-G13A for the period

I _SE2 = 500⋅0,002 / 0,01 = 100 A.

The average current in the non-consumable electrode I _H for the period will be the sum of the currents

I _H = I _IS + I _SE1 + I _SE1 = 180 + 160 + 100 = 440 A.

Thus, the power of the welding power source is fully utilized.

The melting coefficients of the electrode wires when connecting the positive pole of the power source when they are anodes were α _P = 17 g / (Ah) for the Нп-40Х13 wire, α _P = 15 g / (А⋅ for the Нп-Г13А wire h).

Using formula (7), we determine the melting rate of wires for average currents

For wire Нп-40Х13

V _E1 = 17⋅20382 / (7.8⋅3600) = 12.3 cm / s.

For wire Np-G13A

V _E2 = 15⋅24880 / (7.8⋅3600) = 13.3 cm / s.

We determined the productivity of surfacing P with wires, taking the loss factor for fumes and spatter ψ _P = 0.1. Coating coefficient of wire Np-40X13

α _H = 17 (1-0.1) = 15.3 g / Ah.

Deposition performance of the first wire Np-40X13

P _E1 = 15.3⋅160 = 2448 g / h.

Coating ratio Np-G13A

α _H = 15 (1-0.1) = 13.5 g / Ah.

Deposition performance of the second wire Np-G13A

P _E2 = 13.5-100 = 1350 g / h.

Two wire surfacing performance was determined.

P _N = P ₁ + P ₂ = 3798 g / h.

The formula (5) was used to determine the content of chemical elements in the deposited metal C _EN presented in table 1. The table also shows the content of elements in electrode wires.

Using a macro section, the cross-sectional area of the penetration of the base metal F _O = 0.3 cm ² was determined.

The melting performance of the base metal was determined by the formula

П _О = F _О ⋅ρ⋅V _C = 0.2⋅7.8⋅0.3⋅3600 = 1685 g / h

where V _C - Welding speed cm / s, 3600 - the number of seconds in one hour to convert the dimension P _O g / h.

The share of the base metal in the weld metal

ψ _O = P _O / (P _N + P _O ) = 1685 / (1685 + 3798) = 0.31.

The content of chemical elements in the weld С _{ES was} calculated using a formula similar to formula (5)

С _ES = (П _Н ⋅С _ЭН + П _О ⋅С _ЭО ) / (П _Н + П _О ),

where C _EN - element content in the weld metal,%;

With _EO - element content in the base metal,%.

The content of chemical elements in the weld with _ES is summarized in table 2. It also presents the content of elements in the weld metal C _en and the base metal C _EO steel 20.

In the seam there are three chemical elements that are absent in one of the wires: Cr, Mn, Ni.

Using chemical analysis, the content of elements in the seam was determined. It was found that the maximum relative deviation of the calculated content of chemical elements from the experimental values does not exceed 5%.

The method allows, using known electrode wires, to select their optimal combination and obtain a wide range of alloying elements in the weld and to determine by calculation the surfacing and welding modes that provide the required content of alloying elements in the weld metal and weld. The method can be widely used not only in surfacing, but also in welding to fill the cutting edges.

The method can be implemented using semi-automatic machines and machines for mechanized and automatic welding in inert gases produced by the industry with filler wire feeding together with used welding power sources. Such installations must be supplemented with a similar feed mechanism for feeding the second wire and a device for switching current between the electrodes. The latter does not present a problem for the current level of development of electronic and microprocessor technology. Therefore, the method has industrial applicability.

Claims (13)

1. The method of arc mechanized pulsed surfacing in an inert gas medium, characterized in that the negative pole of the DC power source is connected to a non-consumable electrode, and its positive pole is connected to the product and to two melting electrodes having different chemical composition, which are fed continuously in the gap between the non-consumable electrode and the product, while igniting the arc between the non-consumable electrode and the product, and then periodically disconnect the product from the positive pole of the power source when connecting to it melting electrodes with ignition of an indirect arc between each of them and a non-consumable electrode, and the duration of the current flow in each of the consumable electrodes is set within 0.2 ... 0.4 with respect to the full current flow in the consumable electrodes and the product, and the value of the current during the burning of an indirect arc is determined by the formula I _Э = (πd _Э ² V _Э ρt _Ц ) / (4t _Э α _Р ), where d _E is the diameter of the melting electrode, cm, V _e - the melting rate of the electrode, cm / s, ρ is the density of the consumable electrode, g / cm ³ , t _C - the total cycle time of the current flow in the melting electrodes and the product, s, t _e - current flow time in the consumable electrode, s, α _P is the melting coefficient of the consumable electrode when welding by a direct-acting arc on the reverse polarity of the arc at a current of I _D = I _E ⋅t _I / t _C , where I _D - arc current, A, t _And - current flow time in the product, s, moreover, the periodic connection of the positive pole of the power source is carried out in the sequence "product - the first consumable electrode - product - the second consumable electrode - product". 2. The method according to p. 1, characterized in that they use melting electrodes of different diameters. 3. The method according to claim 1 or 2, characterized in that establish a different duration of the current flow in the melting electrodes.

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