Method of arc welding

 

(57) Abstract:

Usage: the invention relates to the field of arc welding and can be used in industry, which uses welding seams in different spatial positions. The inventive when implementing the method on the arc and the metal molten weld pool impose external longitudinal industrial frequency (50 Hz) magnetic field. For generating a magnetic field using a simple, reliable in operation and inexpensive equipment. Arc welding perform a constant current of either polarity. The magnitude of induction of the alternating electromagnetic field of industrial frequency is determined from the expression:

< / BR>
where Loand L are the length of the molten metal weld pool without magnetic field and when welding in a magnetic field; K - coefficient of proportionality. 3 table.

The invention relates to the field of arc welding and can be used in industry, which uses welding seams in different spatial positions and other structures having annular seams (e.g., pipelines).

There is a method of welding of girth joints of pipes of small diameter, in which the water of reduced diameter (Akulov A. I. Belchak, A. Demyanovich VP Technology and equipment for fusion welding.- M Engineering. 1977. 432 C.). However, the use of such modes reduces the productivity of welding. In addition, increases the probability of formation of defects such as incomplete fusion, reduced depth of penetration, etc.

A known method of controlling the formation of a seam using pulse welding (Erokhin, A. A. fundamentals of fusion welding. M. engineering, 1973, 448 C. ), wherein due to the periodic cooling and fractional crystallization of the melt bath creates conditions that prevent runoff of liquid metal.

However, when pulse welding experience significant dynamic effects on the metal melt in the momentum, and there is a risk of disruption in the formation of a seam. In addition, for pulse welding requires a special power supply of the welding arc, which are expensive and require specially trained personnel to maintain and work on them.

Known also closest in the combination of features of the method of arc welding of aluminum alloys.with. USSR N 1703325, CL 23 To 9/167, 1989), including welding TIG electroelectronic field served at the moment of the polarity of the half cycles of the welding current.

However, in the known method perform welding only aluminum alloys non-consumable electrode, which limits its technological capabilities. In addition to the implementation of the welding method, you must use a special sophisticated equipment generators to negotiate electromagnetic pulses with straight polarity welding current. The known method does not effectively act on the regulation of the length of the weld pool, which limits its wide use in welding seams in different spatial positions of the structures of ferrous and non-ferrous metals and alloys.

The task to be solved by the invention is the ability to ensure effective regulation of the length of the weld pool in arc welding in various positions of metals and alloys and the use to implement conventional industrial equipment for welding consumable and non-consumable electrodes.

In the method of arc welding with arc and metal weld pool effect longitudinal alternating electee field of industrial frequency imposed regardless of the polarity of the welding current, the magnitude of the magnetic induction (B) the electromagnetic field is determined from the expression

< / BR>
where Loand L the length of the molten metal weld pool when welding without magnetic field and magnetic field, respectively;

To the coefficient of proportionality.

It is known that in arc welding of heat and mass transfer in metal molten weld pool depends on the direction and intensity of convective flows, which determine, in particular, the geometrical dimensions of the weld pool (length, width, depth).

Convection is mainly the result of mechanical action of the arc flow (dynamic forces) and three-dimensional electromagnetic force (Lorentz force) resulting from the expansion of the flow field in the liquid metal.

When exposed to the welding zone of the outer longitudinal industrial frequency (50 Hz) magnetic field changes in the character of motion of the liquid molten metal weld pool and the arc column.

Such changes caused by the emergence of additional surround the electromagnetic force (F), which is defined by the expression

< / BR>
where j is the current vector;

In the range of complete vector is of the form (consumable or non-consumable) and the brand of the electrode material or product, and is determined only by the magnitude and direction of the current density in the electrode and the magnetic induction vector. When changing the polarity of direct current on the welding current changes only the direction of the force. When welding with direct current of a given polarity, the direction of the force F will be determined by the direction of the vector of magnetic induction, the frequency of change of direction is equal to the frequency of the magnetic field (50 Hz).

In the electromagnetic effects in the melt occurs vibration associated with periodic changes in the direction of the force F. however, due to the relatively large inertia of the liquid metal melt, appreciable reverse flow in the weld pool is not observed.

Such vibration, first, reduces the intensity of the natural axial flows from the head to the tail of the welding bath; second, it allows disperse heat flux, to reduce the temperature gradient in the volume of the bath, to cool the metal, to reduce the degree of fluidity and, therefore, reduce the length of the bath.

In addition, the magnetic field influences the shape and motion of the pole of an electric welding arc. Arc is almost instantaneous pravah this leads to a spatial change in position of the arc and the dispersal of heating spot on the surface of the product. This reduces the length of the molten metal weld pool.

In the proposed method for generating the electromagnetic field of industrial frequency (50 Hz) does not require special frequency converters, which significantly increases the economic efficiency of the method compared to the prototype. The use of a constant (in magnitude and direction) of the welding current can impose a magnetic field on the arc and the metal of the weld pool during the whole cycle, not according to its direction, frequency, and pulse duration of the welding current, and greatly simplifies the implementation of the method.

When implementing the method used the following equipment and materials:

welding automat ADP-1002

the power source of the welding arc BKSM-1000

the power supply of the electromagnet TD-300

a tungsten electrode with a diameter of 3 mm VL

electrode wire SV-A

flux an-348A

shielding gas argon

Submerged arc welding with consumable electrode was carried out on plates of low-alloy 10HSND and stainless HTM steels with thicknesses of 20 and 10 mm, respectively. Welding with a consumable tungsten electrode in argon were performed on plates of became nawiliwili the feed speed of the electrode, the speed of welding current and arc voltage. Was napravlyali seam and not armored crater was determined by the length of the weld pool. After complete cooling plate repeated the surfacing of the same modes, but using an external longitudinal magnetic field at different inductions and measured the length of the bath.

Modes of welding, and electromagnetic welding processing baths in the table.

Notes. 1. The length of the liquid molten metal weld pool was determined according to five independent measurements. 2. Increased induction of more than 100 MT in some cases led to the disruption of stable protection of the weld metal.

Based on the experimental data (see tab. 1), it is easy to determine the equation of the length of the bath (PL. 2), for each experiment, respectively.

As follows from the obtained experimental results, the length of the weld pool in a magnetic field, with increasing induction decreases linearly and is described by the equation L=Lo-kB. Constant coefficient (k) depends on the parameters of the welding mode.

The length of the bath (Lo), the corresponding welding without magnetic field, you can determine experimentally (as in our the ke. M. the motor cycle", 1951 296 S.).

Was welded pipes with a diameter of 100 mm with a wall thickness of 2 mm of steel HTM. Swivel ring butt joints in the underlying technology performed a tungsten electrode with a diameter of 3 mm in argon filler wire diameter 1.2 mm HAS on the modes presented in table 3. For welding used the following equipment: rectifier VD-306, welding head STS-220.

Note. The argon consumption for all modes of welding 8 10 l/min

Thus, to reduce the length of the liquid bath, to keep it from draining when welding in various positions, including welding circumferential seams, you can not only due to changes in thermal power of the arc, but due to overlay on a metal melt of the external longitudinal magnetic field of industrial frequency (50 Hz).

Method of arc welding with arc and metal weld pool effect longitudinal alternating electromagnetic field, characterized in that the welding are at a constant current of either polarity and use the electromagnetic field of industrial frequency, the value of B induction electromagnetic fields are selected according to the formula

< / BR>
where Lis responsible;

K is the proportionality coefficient.

 

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