RU2534183C1 - Electron-beam welding method of heterogeneous metal materials - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves the direction of an electron beam to a welded joint on its face side. The electron beam is diverted during welding towards the material with a negative thermoelectric potential at an acute angle φ(0) to the joint. A provision is made for the diversion from the joint of a beam axis on the reverse side of the welded part under an action of magnetic fields of thermoelectric currents at an angle equal to the above angle φ(0). The value of the angle φ(0) is determined depending on a charge and mass of an electron accelerating voltage, magnetic induction on the joint surface, thickness of the welded part and a coefficient considering parameters of the joint and heating temperature for each pair of heterogeneous materials.

EFFECT: invention allows improving the quality of weld joints from heterogeneous metals and alloys of large thickness with no lacks of penetration throughout the joint thickness.

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Description

The invention relates to the field of engineering, and is intended for the creation of permanent joints by electron beam processing, in particular to the technology of electron beam welding of butt joints of dissimilar metals or alloys and can be used in various industries.

A known method of electron beam welding of dissimilar alloys (see Dragunov V.K., Chepurin M.V. ELS of dissimilar alloys under conditions of thermoelectric current generation // Welding production. 2001. No. 12. P.8-16), which consists in changes in the spatial parameters of the electron beam due to the displacement of the beam axis relative to the joint in the direction opposite to its deflection by the magnetic field of thermoelectric currents.

However, the application of this method for materials with a thickness of more than 15 mm does not provide high-quality formation of welds, as it leads to the formation of imperfections in the thickness of the welded joint.

Closest to the invention is a welding method in which the joint of the welded parts is simultaneously melted by an electron beam and an arc discharge coaxially located with it. In this case, the electron beam is directed from the front side of the joint, an magnetic field of the arc discharge is created and the specified geometry of the electron beam and the penetration channel is formed, and the electron beam is deflected by the thickness of the parts in the required direction by the specified value (see RF Patent No. 2174067, IPC V23K 28 / 02, V23K 15/00, publ. 09/27/2001). The magnetic field of the arc currents spreading over the product changes the geometry of the electron beam, and therefore, the shape of the penetration channel.

By adjusting the magnitude and direction of these currents, it is possible to obtain the required geometry of the electron beam, which makes it possible to weld spatial curved joints, as well as to control the composition of the weld metal when welding dissimilar materials.

The disadvantage of this technical solution is: the difficulty of forming an arc discharge and directing it exactly to the joint of the welded products; the need to create a magnetic flux of the required density over the thickness of the welded joint. Therefore, the required spatial parameters of the beam are not provided, and, therefore, the required degree of penetration of the edges of the welded materials and the quality of the welded joints of large thickness are not achieved. In addition, the method is technically difficult to perform.

A feature of welding dissimilar materials is that under the influence of heating, thermoelectric currents are formed in the joint, which create a magnetic field on the surface and in the joint area of the welded part, which changes the path of the beam electrons along the joint thickness, which leads to the formation of imperfections in the welded joint. That is why, thermoelectric currents and the magnetic field formed by them, it is necessary to compensate, or first send the electron beam to the joint, so as to eliminate the deviation of the electron beam along the thickness of the joint.

The technical result of the invention is to improve the quality of welded joints of dissimilar metals and alloys when welding parts of large thickness, with the absence of lack of penetration in the joint thickness.

This is achieved by the fact that in the known method of electron beam welding, including the direction of the electron beam from the front side of the joint and its deviation through the thickness of the part to be welded in the desired direction by a predetermined amount, forming the necessary geometry of the electron beam and the penetration channel, the electron beam is rejected during welding towards the material with negative thermoelectric potential at an acute angle φ (0) to the joint, at which the beam axis deviates under the influence of magnetic fields of thermoelectric currents from a junction with the reverse side of the same workpiece, and the angle φ (0) vychislayut of conditions:

, $$\varphi \left(0\right)={\left(\frac{\overline{e}}{2mU}\right)}^{0.5}{B}_x\left(0\right)\left(\frac{\mathrm{one}}{k}+\frac{\delta }{6}\right)$$

,

и m - заряд и масса электрона, U - ускоряющее напряжение, В_х(0) - магнитная индукция на поверхности стыка, δ - толщина свариваемой детали, k -коэффициент, определяемый экспериментально, для каждой пары разнородных материалов, параметров стыка и температуры нагрева.Where $$\overline{e}$$

and m is the charge and mass of the electron, U is the accelerating voltage, V _x (0) is the magnetic induction on the surface of the joint, δ is the thickness of the part to be welded, k is the coefficient determined experimentally for each pair of dissimilar materials, the parameters of the joint and the heating temperature.

The invention is illustrated by drawings, in which Fig. 1 shows a change in the trajectory of an axial electron beam in a magnetic field of thermoelectric currents flowing through parts to be welded from dissimilar materials, Fig. 2 is a diagram showing the technical implementation of this welding method.

To ensure the required quality of welded joints of dissimilar steels and alloys, it is necessary to take into account the change in the spatial parameters of the beam under the influence of electric and magnetic fields, which are formed in the penetration channel and the space of electron beam drift and are caused by thermoelectric and electromagnetic phenomena that occur during the welding process. In the absence of high-current external sources for pre-demagnetized materials, thermoelectric currents are the main source of magnetic field, the longitudinal component of which has an almost linear distribution over the depth of the vapor-gas channel (0≤z≤δ), reaches extreme values at its opposite ends and is determined from the relation:

$$B_{xm}\left(z\right)\cong B_{xm}\left(0\right)\left(\mathrm{one}-2z/\delta \right)\left(\mathrm{one}\right)$$

Above the surface of the welded parts in the electron drift space (z≤0), the longitudinal junction of the field induction component decreases according to an exponential dependence:

$$B_{xm}\left(z\right)\cong B_{xm}\left(0\right)e^{k\cdot z},\left(2\right)$$

where k = 60 ... 70 m ^-1 is the coefficient determined experimentally for each pair of dissimilar materials, joint parameters and heating temperature.

The direction of the magnetic induction vector B _xm (z) of the field of thermoelectric currents is determined by the sign of the relative thermopower of the welded pair of materials.

When ELS of dissimilar materials, the magnetic field of thermoelectric currents B _xm (z), changing its sign along the thickness of the welded joint, deflects the electron beam to half the thickness of the joint in the direction of the material with positive thermoelectric potential, and then in the opposite direction (see figure 1). In this case, the angles of deviation of the axial electron of the beam from the initial direction at the apex and in the root of the penetration channel are θ (0) = θ (δ), and the inflection point of its path is half the channel depth. Such spatial parameters of the beam, as a rule, lead to the formation of imperfections along the thickness of the product. In this regard, it is necessary to carry out the correction of these parameters.

Improving the correction is reduced to providing at the entrance to the product such an angle of inclination of the beam to the joint φ (0), at which there is no beam deviation at the top and root of the seam (on the front and bottom surfaces of the joint), i.e. ψ (0) = ψ (δ) ≈0. This condition is satisfied when the straight line CD connecting the entry points into the part and the exit of the axial electron of the beam around point C is rotated around point C by an angle α and the line AB is aligned with the joint. Moreover, the angle α is equal to

$$\alpha \approx tg\left(\alpha \right)=\frac{\psi \left(\delta \right)-\psi \left(0\right)}{\delta }.\left(3\right)$$

To determine the values of ψ (δ) and ψ (0), we can use the following relation:

$$\psi \left(z\right)={\left(\frac{\overline{e}}{2mU}\right)}^{0.5}{B}_x\left(0\right)\left(\frac{\mathrm{one}}{{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="00000009.png"\; state="\{\{state\}\}">k</figure-callout>}}^2}+\frac{z}{k}+\frac{{\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="00000009.png"\; state="\{\{state\}\}">z</figure-callout>}}^2}{2}-\frac{{\mathrm{<figure-callout\; id="3"\; label="z"\; filenames="00000009.png"\; state="\{\{state\}\}">z</figure-callout>}}^3}{3\delta }\right),\left(\mathrm{four}\right)$$

- заряд электрона; m - масса электрона; U - ускоряющее напряжение.Where $$\overline{e}$$

- electron charge; m is the mass of the electron; U is the accelerating voltage.

The angle of inclination of the axis of the electron beam gun to the junction φ (s), taking into account the beam deflection in the magnetic field above the welded part, will be equal to the angle α (see Fig. 2), if we neglect a slight change in the magnetic field induction along the path of the axial electron of the beam, from 3) taking into account (4), one can obtain:

$$\alpha ={\left(\frac{\overline{e}}{2mU}\right)}^{0.5}{B}_x\left(0\right)\left(\frac{\mathrm{one}}{k}+\frac{\delta }{6}\right)\left(5\right)$$

Thus, depending on the welding conditions, as a way of correcting the spatial position of the beam during EBW of large-thickness parts, which reduces the likelihood of lack of penetration through the thickness of the welded products, one can use a change in the angle of inclination of the beam axis relative to the joint.

If it is impossible to rotate the angle of the electron beam gun or deflect the electron beam, using the principle of relativity, the welded part is deployed.

The installation for implementing the welding method comprises: a welded part of a part 1 with a positive thermoelectric potential, a welded part of a part 2 with a negative thermoelectric potential, the thickness of the welded parts of a part 1 and 2 is equal to δ, a welding table 3 of an electron-beam installation on which the parts to be welded are installed 1 and 2 with a minimum gap and form a joint for welding 4, a vacuum chamber 5 of an electron beam installation, in which an electron beam gun 6 is installed, generating an electron beam with axis 7, p Under the influence of heating the joint of dissimilar metals, a thermoelectric power is formed with currents I _T creating the direction of induction B _xm (z) of the magnetic field 8, the electron beam and the part are moved relative to each other, and welding is performed at a speed v _sv , a line connecting the entry and exit points of the electron beam from the product (CD) 9, z is the thickness of the product under consideration, (0≤z≤δ), α is the angle of inclination of the straight line CD connecting the entry points of the part and the exit of the axial electron of the beam, θ is the angle of deviation of the axis of the electron beam in the magnetic field of thermoelectric currents at the entrance to the product θ (0) and at the exit from it θ (δ), along the thickness of the product θ (z), φ is the angle of inclination of the axis of the electron beam to the joint at the entrance to the product φ (0) and at the exit φ ( δ), φ (s) is the angle of inclination of the axis of the electron beam gun above the surface of the part, s is the distance from the surface of the part to the electron beam gun, ψ is the distance between the joint and the axis of the electron beam from the front of the joint (at the entrance to the product) ψ (0), on the lower side of the joint (exit from the product) ψ (δ), along the thickness of the product ψ (z).

The invention is implemented as follows.

Parts of the welded part 1 and 2 are installed on the welding table 3 of the electron beam installation, with a minimum joint gap for welding 4, the vacuum chamber 5 is pumped out, an electron beam is formed, having previously aligned the axis of the electron beam gun (electron beam 7) with the joint, and then carry out its penetration. In the welding process, thermoelectric currents I _T arise, creating a magnetic field 8 with the magnitude and direction of magnetic induction B _xm (z), which deflects the electron beam from the junction by an angle θ (0) in the direction of the metal with positive thermoelectric potential 1. To compensate for this deviation electron beam rotate the axis of the electron beam gun (electron beam 7) relative to the top of the seam at a certain angle φ (s). The rotation of the gun is carried out in the direction of the metal with positive thermoelectric potential so that the beam axis (the trajectory of the axial electron of the beam) is directed towards the metal with negative thermoelectric potential 2. The angle of rotation of the gun φ (s) is increased until the axis of the electron beam at the surface the part will not make an angle φ (0) ≈θ (0) with the joint at which it will intersect the joint from the back side in a straight line CD 9.

The angle α of the deviation of the beam from the junction is determined as follows. On the test sample, which consists of two parts of similar materials used in the welded part, preliminary welding is carried out to measure the deviation of the beam from the joint and angle α. The axis of the electron beam gun (electron beam) is combined with the joint, and then its penetration is carried out. In the welding process, thermoelectric currents I _T arise, the magnetic field B _xm (z) of which deflects the electron beam from the junction at an angle φ (0) in the direction of the metal with positive thermoelectric potential. To compensate for this deviation of the beam, the axis of the electron beam gun is rotated relative to the top of the seam by a certain angle α. Or, with the help of a deflecting system, the electron beam is deflected by the required angle. The rotation of the gun (deflection of the beam) is carried out in the direction of the metal with positive thermoelectric potential 1 so that the axis of the beam (the trajectory of the axial electron of the beam) is directed towards the metal with negative thermoelectric potential 2. The angle of rotation of the gun α is increased until the axis of the electron beam near the surface of the part, the angle φ (0) ≈θ at which it will intersect the joint from the back side will not make a junction.

If the angle of entry of the electron beam into the product is greater than θ (0), then the axis of the electron beam at the exit from the product will be displaced into the material with negative thermoelectric potential 2. Conversely, if φ (0) <θ (0), the beam will deviate into a material with positive thermoelectric potential 1. In both cases, defects in the form of lack of penetration in thickness will be observed in the welded joint.

Using the proposed welding method allows to obtain high-quality welded joints of dissimilar materials of large thickness. In addition, the use of the invention in ELS of dissimilar steels and alloys eliminates the formation of imperfections and increases the degree of penetration of the welded edges along the thickness of the part, and therefore, improves the structure and properties of welded joints associated with the spatial arrangement of the electron beam relative to the joint.

Claims (1)

A method of electron beam welding of dissimilar metals or alloys, including the direction of the electron beam to the welded joint from its front side and its deviation in the desired direction by a predetermined amount with the formation of the specified geometry of the electron beam and the penetration channel, characterized in that the electron beam is rejected during welding towards the material with negative thermoelectric potential at an acute angle φ (0) to the joint, while providing a deviation from the joint of the beam axis from the back side of the welded parts under the influence of magnetic fields of thermoelectric currents at an angle equal to the aforementioned angle φ (0), and the value of the angle φ (0) is determined from the following relation:

,
Where

and m is the charge and mass of the electron, U is the accelerating voltage, V _x (0) is the magnetic induction at the interface, δ is the thickness of the welded part, k = (60-70) m ^-1 is a coefficient that takes into account for each pair of dissimilar materials joint parameters and heating temperature.

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