SU1750891A1 - Electron-beam welding method - Google Patents

Abstract

The invention relates to electron beam welding, in particular to scanning beam welding technology, and can be used in welding of hard-to-weld alloys. The purpose of the invention is to improve the quality of welded joints of alloys with a high teloconductive ratio. The invention relates to electron-beam welding, in particular to welding technology of a scanning beam, and can be used in welding of weldable alloys. The purpose of the invention is to improve the quality of welded joints of alloys with a high thermal conductivity coefficient by means of the stable formation of a welding rod, with non-penetration, reducing root defects. Fig. 1 shows a diagram of the electron beam scanning trajectory; Fig. 2 shows diagrams of the variation of currents of a deflecting electromagnetic system of an electron beam gun, its power and amplitude using stable formation of a weld pool with non-penetration and reduction of root defects. The method consists in scanning the electron beam on the surface of the metal being welded along an arcuate trajectory 5 (arc of a circle or ellipse, parabola) located symmetrically relative to the plane of the joint 6 and concave inside the weld pool 4, and simultaneously smoothly changing the power of the electron beam. The minimum value of the beam power is reached on the axis of symmetry of the scanning trajectory, and the maximum - at its ends. The maximum value of the beam power corresponds to the specified value according to the welding conditions, i.e. determined by the depth of penetration. With a gradual decrease in the power of the beam at point B, the melting front does not advance the movement of the beam along the scanning trajectory. This is a condition for obtaining the required melting front curvature 3 sludge. changes during the scanning period of the beam; on fig.Z - block diagram of the device that implements the method of electron beam welding. The method consists in scanning the electron beam along an arcuate path located symmetrically with respect to the joint plane and a welding bath concave inward, and simultaneously smoothly changing the power of the electron beam so that the minimum is reached on the axis of symmetry of the scanning path, and the maximum is at its ends. Moreover, the maximum value of the beam power corresponds to the specified value according to the welding conditions, i.e. determined by the depth of penetration. Ј V4 SL O 00 CHE

Description

The parts 1 and 2 are welded by an electron beam with the formation of a weld 3 and a bath 4, in which the beam is scanned along an arc-shaped trajectory 5 symmetrically located relative to the junction 6 of parts 1 and 2. In this case, a heat flux 7 occurs in the direction of the center of curvature of the scan trajectory 5 (FIG. .one). The scanning trajectory 5 is set by moving the electron beam along and across junction 6 (x and y axes) in accordance with the relevant laws of changing currents 1x and 1y in the windings of the deflecting electromagnetic system of the electron gun. The beam power is simultaneously synchronously modulated according to the P-Ro-L P cosa rotation, where P and P0 are the current and the specified beam power values determined by the beam current at a constant accelerating voltage (Fig. 2), with a gradual decrease power of the beam to the point of symmetry of the scanning trajectory 5 (point B) the melting front does not advance the beam movement, which is a condition for obtaining the necessary melting front curvature.

The direction of the maximum heat sink from the melting front (the ABC line at each point coincides with the normal to the front line at the same points. The solid metal in the ABCD region thus receives additional heating, with the greatest heating having a metal adjacent to the symmetry axis (line BD), since heat comes in from two sides. From this it follows that the heat input on the Melting Front as the electron beam approaches the point of symmetry of the scanning trajectory (point B) needs to be reduced. Melting not ahead of the scanning electron beam trajectory. Reduced heat input in the middle of the scanning path can be obtained either by increasing the speed of movement of the electron beam, which is unacceptable because of hydrodynamic disturbances in the welding bath, or decrease of its power.

. The law of change in the power of the electron beam during its scanning period depends on the shape of the scanning trajectory. When scanning along an arc (parabola, arc of a circle or ellipse), the power of the beam P along the scanning trajectory must be changed according to the cosine law (Fig. 2). which ensures uniform heating before the melting front. The amplitude of the change in the power of the beam D P depends inversely on the magnitude of the chord connecting the ends of the scanning path.

electron beam, but does not exceed the magnitude of the PO, Thus, K / b. Pol. where K is the proportionality coefficient determined by the welding speed and heat by the conductivity of the metal being welded:

b is the chord length of the scan path.

To enable the formation of a melting front with a reverse curvature, it is necessary that the condition b de be fulfilled, where de is the diameter of the electron beam on the surface of the welded metal.

The value of the maximum power of the beam PO is chosen from the condition of reaching the required projection depth. Angle a between the longitudinal axis of symmetry, the weld pool and normal to the surface of the scanning trajectory varies from 0 to 90 ((Fig. 1). When the electron beam scanning method is used, the condition for preventing the formation of root weld defects is simultaneously realized. electron beam with a dip in the paraxial region.

The method of electron-beam welding is implemented with the help of (device, block diagram of which is shown in Fig. 3. The device contains: a welding gun 8 equipped with a deflecting electromagnetic system 9, blocks 10 of amplifiers and digital-analogue converters 11 of programmable storage blocks 12, control unit 13, modulator 14. Also shown in Fig. 3. 3 - weld. 4 - welding pan

The device works as follows.

In the programmable memories 12, the programs for setting the displacement of the radii 15 along and across the junction 6 of parts 1 and 2, as well as the normalized function of varying the power of the beam 15 (for example, cos a), are entered. In block 13, the operator sets the scan amplitude by issuing a digital-to-analog converter of the reference signal to block 11; scanning frequency by issuing address codes of reproduced information from block 13 to the input of block 12; welding current by issuing a control signal to the input of the modulator unit 14, the second input of which receives the codes of the normalized coefficients of change in the current (power) of the electron beam.

With a sampling frequency, block 12 provides codes for the control signals for shifting the beam 15 and modulating its current. Block 11 converts

the codes of the beam bias and through the amplifiers 10, are set to currents 1x and 1u in the winding of the deflecting electromagnetic system 9, the magnetic field of which moves the electron beam 15 along the trajectory 5 relative to the junction 6 Block 14 modulates the signal setting the current of the electron beam from block 13 according to the module code The adjustment of the modulation depth in block 14 makes it possible to set the gradient of variation of the power of the electron beam when approaching the axis of symmetry of the scanning trajectory 5. The signal from the output of block 14 is supplied to the stabilization circuit of the current of the electron beam gun 8.

Thus, the operator, skidding the program in block 12, can change the beam scanning path 5, as well as control its frequency and scan amplitude, set the amplitude of the beam power variation in accordance with its movement along the scan path.

Implementing the device according to the block diagram of FIG. 3 allowed to work out the welding technology of previously difficult-to-weld materials.

Samples of aluminum alloy AMgb were welded with a vertical electron beam at a speed of 0.75 cm / s in the continuous penetration mode to a depth of 5 cm. The beam was scanned along an arc of a circle with a diameter of 0.15 cm with a frequency of 90 Hz. The amplitude of the change in beam power AR was (5 .. 20)% of the maximum beam power P0 equal to 18 kW. The optimal results for the formation of the seam obtained at D, 16 PO. That is, the beam power varied from 18 to 15.1 kW. Metallographic analysis revealed that root defects in the root of the joint are absent, and amplitude

0

five

0

five

0

five

0

fluctuations in depth of propagation

Compared with the base prototype, the proposed prototype, the proposed method of electron beam welding provides a reduction in scrap at joint venture alloys and a reduction in the cost of repairing defects in welds,

Claims (1)

Formula of inventions Electron beam pairing method in which the beam is scanned along an arcuate path with an axis of symmetry that coincides with the plane of the joint, characterized in that, in order to improve the quality of welded joints of alloys with a high thermal conductivity by sustainably forming a weld pool with non-penetration and reduction the root defects, the beam scanning trajectory with the convex side is oriented towards the weld pool, and the beam power is varied according to the cone-shaped Р Ro-L P cos a, where RO is the maximum beam power, W; D P is the amplitude of the change in beam power, W, even min K / b, PO; K - coefficient of proportionality. determined by welding speed and heat conductivity of the metal being welded: b is the chord length of the scanning path, mm,, de is the diameter of the electron beam on the surface of the metal being welded, mm; a is the angle between the longitudinal axis of symmetry of the weld pool and the normal to the surface of the scanning path. X 1 FIG. 2 Fig.Z