Electron-beam welding method of heterogeneous metal materials

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.

2 dwg

 

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

There is a method of electron beam welding of dissimilar alloys (see Dragunov C. K., Chepurin M. C. ELS dissimilar alloys in terms of the generation of thermoelectric currents // Welding production. 2001. No. 12. C. 8-16), which is the variation of the spatial parameters of the electron beam, due to the displacement of the beam axis relative to the junction in the direction opposite to the deviation of the magnetic field of thermoelectric currents.

However, application of this method for materials of a thickness of > 15 mm not provide for the proper formation of the welds, as leads to poor penetration through the thickness of the welded connection.

Closest to the invention is a welding method in which carry out the simultaneous penetration of the joint welded parts of the electron beam and coaxially located with him arc discharge. When this electron beam is directed from the front side of the intersection, create a magnetic field of the arc discharge to form the desired geometry of the electron beam and Kahn is and penetration, moreover, the electron beam reject the thickness of the parts in the desired direction by a specified amount (see RF Patent №2174067, IPC WC 28/02, UK 15/00, publ. 27.09.2001). The magnetic field currents arc spreading on the product, changes the geometry of the electron beam, therefore, the channel shape of the penetration.

By adjusting the value and direction of these currents, it is possible to obtain the desired geometry of the electron beam, which allows welding spatial curvilinear joints, as well as to control the composition of the weld metal when welding dissimilar materials.

The disadvantage of this technical solution is: the complexity of the formation of the arc discharge and the direction its just butt welded products; the need to create the magnetic flux of the desired density by the thickness of the welded connection. Therefore not provided the required spatial beam parameters, and, therefore, does not reach the required degree of penetration of the edges of the welded materials and the quality of welded joints of greater thickness. Furthermore, the method is technically difficult in execution.

The feature of joining dissimilar materials, is that under the influence of heat at the junction of the formed thermoelectric currents, which create a magnetic field on the surface and in the field joint of the workpiece, changing the trajectory of the electron beam poolside interface, which leads to the formation of poor penetration in Shrivenham connection. Therefore, thermoelectric currents and the magnetic field formed by them, must be compensated, either pre-dispatch electron beam in the butt, so as to eliminate the deviation of the electron beam on the thickness of the joint.

The technical result of the invention is to improve the quality of welded joints of dissimilar metals and alloys during welding parts of great thickness, with no penetration through the thickness of the joint.

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 junction and the deviation in thickness of the workpiece in the desired direction by a specified amount, forming the necessary geometry of the electron beam and channel penetration, welding electron beam deflect in the direction of material with a negative thermoelectric potential at an acute angle φ(0) to the junction, which under the influence of a magnetic field of thermoelectric currents, the deviation of the beam axis from the intersection with the back side of the workpiece are the same, and the angle φ(0) vychislyayut of conditions:

φ(0)=(e2mU )0.5Bx(0)(1k+δ6),

whereeand m are the charge and mass of the electron, U is the accelerating voltage, Vx(0) is the magnetic induction on the surface of the interface, δ is the thickness of the workpiece, k is a coefficient determined experimentally, for each pair of dissimilar materials, parameters, interface and temperature settings.

The invention is illustrated by drawings, where Fig.1 shows the change in the axial trajectory of the electron beam in a magnetic field of thermoelectric currents flowing through the welded parts made of dissimilar materials, in 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 consider the variation of the spatial parameters of the beam under the influence of electric and magnetic fields, which are formed in the channel penetration and the drift space of the electron beam and due to thermoelectric and electromagnetic phenomena, occurring during the welding process. In the absence of high-current external sources is the ISR for the pre-razminochnyh materials thermoelectric currents are the main source of the magnetic field, the longitudinal component of which has an almost linear distribution along the depth of the gas-vapor channel (0≤z≤δ), reaches extreme values at its opposite ends and is determined from the relationship:

Bxm(z)Bxm(0)(1-2z/δ)(1)

Above the surface of the welded components in the drift space of electrons (z≤0) longitudinal joint component of the magnetic field decreases by the dependence is close to exponential:

Bxm(z)Bxm(0)ekz,(2)

where k=60... 70 m-1- coefficient, determined experimentally, for each pair of dissimilar materials, parameters, interface and temperature settings.

When the direction vector of the magnetic induction Bxm(z) the field of thermoelectric currents is determined by the sign of the relative thermoelectric power welded pairs m is materials.

When ELS heterogeneous materials the magnetic field of thermoelectric currents Bxm(z), changing its sign on the thickness of the welded joint deflects an electron beam to olutosin connection in the side of the material with a positive thermoelectric potential, and then in the opposite direction (see Fig.1). Thus the angles of deflection of the axis of the electron beam from its original direction in the top and root canal penetration equal to θ(0)=θ(δ), and the inflection point of its trajectory is at one-half the depth of the channel. Such spatial beam parameters, as a rule, lead to the formation of the weld through the thickness of the product. In this connection it is necessary to perform correction of these parameters.

The improvement of the correction is reduced to provide input into the product of such a tilt angle of the beam to the junction of φ(0), in which the beam deflection in the top and root of the weld (on the front and bottom interface) not present, i.e., ψ(0)=ψ(δ)≈0. This condition occurs when the rotation of the straight line CD, connecting the entry point in detail and exiting the axial electron beam, around point by angle α and the combination of straight line AB with the joint. In this case the angle α is equal to

αtg(α)=ψ(δ)-ψ(0)δ. (3)

To determine the values ψ(δ) and ψ(0) you can use the following relationship:

ψ(z)=(e2mU)0.5Bx(0)(1k2+zk+z22-z33δ),(4)

whereeis the electron charge; m is the electron mass, U is the accelerating voltage.

The angle of the axis of the electron beam gun to the intersection of φ(s) taking into account the deviation of the beam in the magnetic field above the workpiece is equal to the angle α (see Fig.2), if we neglect the slight change of the magnetic field along the axial trajectory of the electron beam, (3) subject to (4) can be obtained:

α=(e2mUmo> )0.5Bx(0)(1k+δ6)(5)

Thus, depending on welding conditions as the method for correcting the spatial position of the beam at ELS parts of great thickness, allowing to reduce the likelihood of penetration by the thickness of the welded products, you can use the change of angle of the beam axis relative to the interface.

If you cannot turn on the angle α of the electron beam gun or deflection of the beam, using the principle of relativity, unfolds the workpiece.

Installation for implementing the method of welding includes: the welded portion of the part 1 with positive thermoelectric potential, the welded portion of the part 2 with a negative thermoelectric potential, the thickness of the welded parts parts 1 and 2 is equal to δ, welding table 3 electronically-kluchevoi installation, which are welded parts parts 1 and 2 with minimal gap and form a welding joint 4, the vacuum chamber 5 electron-beam setup, which is equipped with electron beam gun 6, generating an electron beam with the axis 7, under the action of heat texts is rather dissimilar metals is formed thermoEMF with currents I Tcreating the direction of the induction Bxm(z) of the magnetic field 8, move the electron beam and workpiece relative to each other and produce a weld with velocity vStline connecting points of entry and exit of the electron beam of the product (CD) 9, z - considered product thickness, (0≤z≤δ), α is the angle of inclination of the straight line CD, connecting the entry point in detail and exiting the axial electron beam, θ is the deflection angle of the axis of the electron beam in a magnetic field of thermoelectric currents at the entrance to the product θ(0) and exit θ(δ), the thickness of the product θ(z), φ is the angle of inclination of the axis of the electron beam to the junction at the entrance in the product φ(0) and exit φ(δ), φ(s) is the angle of inclination of the axis of the electron beam gun over the surface, s is the distance from the surface to the electron beam gun, ψ is the distance between the joint and the axis of the electron beam from the front side of the intersection (at the entrance to product) ψ(0), on the bottom side of the junction (exit devices) ψ(δ), the thickness of the product ψ(z).

The invention is implemented as follows.

Part of the workpiece 1 and 2, mounted on a welding table 3 electron-beam system, with a minimum clearance of welding joint 4, are pumping out the vacuum chamber 5, form the electron beam, pre-aligned with the joint axis of the electron beam gun (electron beam 7), and then spend it in the penetration. In the welding process occur thermoelectric currents ITthat creates a magnetic field 8 with the magnitude and direction of the magnetic induction Bxm(z), which deflects an electron beam from the interface at an angle θ(0) in the direction of metal with a positive thermoelectric potential 1. To compensate for this deflection of the electron beam produces a rotation axis of the electron beam gun (electron beam 7) on the top seam at some angle φ(s). Turn the gun is carried out in the metal side with a positive thermoelectric potential so that the beam axis (the axial trajectory of the electron beam was directed towards a metal with a negative thermoelectric potential 2. The angle of the gun φ(s) to increase until the axis of the electron beam at the workpiece surface will not be with the intersection angle φ(0)≈θ(0), at which it will cross the junction from the opposite side in a straight CD 9.

The angle α of deflection of the beam from the interface is determined as follows. On a test sample, which consists of two parts of the same materials used in the workpiece, conduct preliminary welding for measuring the deflection of the beam from the joint and the angle α. The axis of the electron beam gun (electron beam) is combined with the interface, and then spend his penetration. In the welding process occur thermoelectric current is I Tmagnetic field Bxm(z) which deflects an electron beam from the interface at an angle φ(0) in the direction of metal with a positive thermoelectric potential. To compensate for this deviation of the beam, produces the rotation axis of the electron beam guns on top of the seam at some angle α. Or by deflecting system installation deflect the electron beam to the desired angle. Rotate the cannon (beam deflection) is carried out in the metal side with a positive thermoelectric potential 1 so that the beam axis (the axial trajectory of the electron beam was directed towards a metal with a negative thermoelectric potential 2. The angle of the gun α increases up until the axis of the electron beam at the workpiece surface will not be with the intersection angle φ(0)≈θ at which it will cross the junction from the opposite side.

If the angle of entry of the electron beam in the product will be more than θ(0), the axis of the electron beam at the exit of the products will be offset in the material with a negative thermal potential 2. On the contrary, if φ(0)<θ(0), the beam deflection will occur in the material with a positive thermoelectric potential 1. In each case in the weld will be observed defects in the form of weld thickness.

The use of the proposed method of welding allows p in order to obtain high-quality welded joints of dissimilar materials of greater thickness. In addition, the use of the invention will in ELS dissimilar steels and alloys to eliminate the education of poor penetration and to increase the degree of penetration of the welded edges of the part thickness, and consequently, to improve the structure and properties of welded joints associated with the spatial location of the electron beam relative to the interface.

The method of electron-beam welding of dissimilar metals or alloys, including the direction of the electron beam on the weld joint from the front of its sides and the deviation in the desired direction by a specified amount with the formation of the desired geometry of the electron beam and channel penetration, characterized in that in the process of welding electron beam deflect in the direction of material with a negative thermoelectric potential at an acute angle φ(0) to the junction, while delivering the deviation from the intersection of the beam axis from the back side of the workpiece under the influence of magnetic fields thermoelectric currents at an angle equal to the aforementioned angle φ(0), and the angle φ(0) is determined from the following equation:
,
whereand m are the charge and mass of the electron, U is the accelerating voltage, Vx(0) is the magnetic induction on the surface of the interface, δ is the thickness of the workpiece, k= (60-70)m-1- coefficient taking into account for the each pair of dissimilar materials parameters interface and temperature.



 

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