RU1810258C - Method of electron-beam welding of difficult-to-weld steels and alloys - Google Patents

Abstract

The essence of the invention: the reconciliation of details of labor-steppe steppes and alloys of large thickness is performed by a cross-section of the joint at an accelerating voltage of 60-120 kV with a horizontal beam, deployed along a circular path with a diameter of 0.8-1.5 mm with a frequency of 150-2000 Hz welding is carried out at a working range of 150-220 mm at a speed of 9 mm / h for horizontal joints and 4.510 / N, mm / h for vertical joints, where H is the thickness of the joint, mm, at a beam current of U-1.2 1nom mA , where (nom is the nominal value of the beam current in mA. necessary for through penetrations; and ensuring its stability during welding is not worse than ± 5%, and the beam focus in the operating mode is buried under the surface of the parts by 5/8 N, mm for horizontal seams and 5/12 N for vertical seams and ensuring its stability during welding is not worse, ± 20%. 2 silt, 1 tab. S IS

Description

The invention relates to electron beam welding, and in particular, to a technology for welding hard-to-weld steels and alloys that are prone to the formation of metallurgical defects in the form of cracks, fusion, shells and can be used in any engineering industry.

The purpose of the invention is to improve the quality of welded joints by reducing internal and external defects in the form of cracks, shells, non-fusion.

In FIG. 1 shows a diagram of an ELS process; in Fig, 2 is a diagram of the sweep of the electron beam along a circular path: - optimal 1ph, II 1F.OPT., MNF 1F.6PT.

The method consists in orienting the electron beam 1 in the horizontal plane, and the product 2 in the vertical plane, setting the working distance A 150-220 mm between the end of the electron beam gun 3 and the surface of the product 2, scanning the electron beam 1 along a circular path with a diameter: , 8-1.5 mm and a frequency f of 150-2000 Hz. setting the beam current, 2 i, IHOM, mA, where 1nom is the nominal value of the beam current required for the through hole & the joint and beam focus under the surface of the product 2 at a distance Л p / QH, mm for horizontal seams p) N . mm for vertical joints (Fig. 1), welding of the i joint at a speed of 10 / N, mm / h for horizontal joints and 5 10 / N, mm / h for vertical joints, where N is the thickness of the joint, 30-150 mm and ensuring stability during the welding process of 1 liter and not worse than ± 5% and not worse than A ± 20%.

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The main difficulty in ELS of promising high-alloy steels and heat-resistant alloys is the formation of cracks during welding in the weld metal and the weld joint, shells and non-fusion in the weld of a metallurgical nature. The number and length of these defects increases with increasing thickness of the compound N. It has been established that the formation of these defects is influenced by the thermo-deformational welding cycle and weld geometry, determined by the beam convergence angle (working distance), and the focal spot deepening into the metal (focusing current) ), beam current (power), local scan geometry in the product plane, welding speed. Moreover, these patterns are general and independent of the equipment used and are determined by the physical and metallurgical properties of the material being welded.

The optimal mode was selected in which through penetration of the compound is obtained on a vertical plane with minimal heat input and the crystallization rate of the weld metal and optimal formation and shape of the weld. The conditions - minimum heat input and crystallization rate are necessary for difficult to weld materials and are determined by the choice of such mode parameters as beam current and focusing and their stability, sweep diameter, welding speed and working distance (beam diameter in the focal plane). Also, these mode parameters affect the weld geometry, its formation, and the thermodeformational welding cycle. Therefore, all mode parameters are interconnected and not separable.

In the welding experiments being conducted, the accelerating voltage and the source were chosen in the range of 60–120 kV, and the input power was controlled by a beam current of 1 l. High UycK was selected from the condition of increasing the specific power of the electron beam, and 1 L was set from a ratio of 2 IHOM. At, 2 IHOM, heat input to the seam increases and defects form in the form of cracks. Moreover, the deviation of 1L in the welding process from the nominal value should not be more than ± 5%. This is due to the fact that the optimal focusing current is 1F.OPT. is determined by a value of 1 L. (see the article by Nazarenko O.K. et al. Regularities of focus control of welding electron beam, beam. International Conference on Electron Beam Technology, Sophie, 1985, p. 112-118). With increasing or decreasing I /, the focusing current becomes more or less than optimal, which leads to either un-focusing (Fig. 2, P) or to refocusing the beam (Fig. 2. III). The deterioration of stability (l compared with the specified limit leads to a significant decrease in the quality of the weld metal. At 1 l, 1, stable through penetration is not provided due to local magnetic deflections of the beam and elimination of root defects. The absence of through penetration increases the vapor pressure and gas in the penetration channel and increases the likelihood of destruction of the cast weld metal during crystallization.

For ELS of steels and alloys of large thicknesses of 5 thicknesses (more than 30 mm), the working distance A of 150-220 mm is optimal. With decreasing A, the angle of convergence of the beam on the product increases and the negative effect on the beam of steam and ion increases

0 losses from the penetration channel, the seam geometry becomes wedge-shaped, the seam Iirin increases on the front side of the joint, which increases the likelihood of surface cracks. With an increase in A of more than 220 mm, the aberration of the beam affects, its diameter increases and the power density in the focal spot decreases and the length of the beam of the beam increases. This leads to an increase in width

.0 weld along its entire depth and the formation of shrinkage cracks and.

The local beam sweep geometry affects the power density distribution in the heating zone and the weld geometry. The local scan of the beam was varied along different trajectories - along a circle, an ellipse, an arc of a circle and an ellipse, X and T - shaped trajectories, along and across the junction. Beam Scan Welding Technology

0 were tested on equipment equipped with SU-165 and SU-177 instruments at different beam oscillation frequencies. It is established that the beam path along one coordinate does not provide stabilization of the structure

5 of the beam in the transverse and longitudinal directions, and the reproducibility of the welding conditions is reduced. For complex local scan paths (second-order curves, intersecting straight lines) welding

0 metals of large thicknesses with through melt of the joint do not significantly affect the weld geometry and the tendency of weld metal to form cracks. Therefore, the basis chosen is simple.

5 circular beam paths.

The optimal frequency range is f 150-2000 Hz, when the electron beam acts as a linear hollow heat source. At f = 2F0 ° Hz, the ring energy distribution in the heating spot is blurred, the heat source circuit approaches evenly distributed and the power density in the heating spot decreases. This leads to a decrease in the penetration depth and a violation of the optimal welding mode. At f 150 Hz, the frequency of the natural oscillations of the weld pool does not coincide with the oscillations of the beam and the stability of the weld formation process is violated, which also increases the likelihood of discontinuities in the weld.

The diameter of the sweep of the beam dp should not be less than 0.8 mm, because the effect of stabilization of the beam structure is reduced, and more than 1.5 mm due to an increase in the volume of the weld metal and the length of the heat affected zone. In addition, the 5-mm vapor-gas channel is not blocked by liquid metal and is blown out, which leads to an increase in undercuts from the front and root sides of the seam.v

It has been experimentally established that in order to ensure high-quality welds with an increase in the joint thickness H, the welding speed must be proportionally reduced. The need to reduce VCB is due to maintaining a high beam power density and lowering the crystallization rates of the weld metal and temporary deformations in the weld zone. On the other hand, small VCBs increase the metal consumption of the weld pool and make it difficult to transfer and hold the molten metal in horizontal position. Therefore, the optimum vce is determined by the thickness of the joint. With the horizontal position of the joint, the speed sv is 9-105 / N. Satisfactory quality of vertical joints is achieved at lower optimum speeds, 54d5 / H. This is explained by the fact that during through penetration of vertical joints, the processes of transfer of liquid metal are more stable, since the gravity of the molten metal, the speed of movement of the welded product and thermocapules p-force are directed in one direction. Proportionality factors of 10 mm2 / hr and 5 -10 mm2 / hr relate the size between ev m / h and N mm. At 4.5-10 / N for vertical seams and vCs9 10 / N for horizontal seams, the heat affected zone of the HAZ and the volume of the weld pool metal, which becomes difficult to hold on a vertical plane, increase and drain. It leads to

an increase in the strain concentration and the tendency of the weld metal to form longitudinal cracks in the crystallization center. With VCB 4.5-105 / N for vertical

joints and VCB 9 105 / N for horizontal joints, the likelihood of formation of transverse (relative to the axis of the joint) cracks in the joint and the joint welded joint, shells and non-fusion in the joint increases

The optimal position of the focal spot relative to the surface of the part corresponds to its penetration into the part by a value of A (5/8) N for horizontal

joints and A (5/12) H for vertical joints. Moreover, the deviation A in the welding process should not exceed ± 20%, i.e. the beam focus should fluctuate within (1 / 2- 3/4) N for horizontal joints and

(1 / 3-1 / 2) B for vertical seams. When the focal spot is located below (3/4) N for the horizontal joint and (1/2) N for the vertical joint, the seam expands significantly on the front side, increase its wedge-shaped (width ratio

top of the seam to the width of the bottom

is 2-6). Molten metal

the weld pool begins to drain from the front and the likelihood increases

formation of cracks in the weld metal and non-fusion at the center of crystallization. When the focal spot is located above (1/2) H for the horizontal joint and (1/3) H for the vertical joint, the melting channel expands as it deepens and the shape of the seam takes a barrel-shaped cross-section; In the enlarged part of the weld at a depth of (0.6-0.7) N, shrinkage shells and cracks form. For vertical joints, the optimal focal spot position should be higher than for horizontal joints. This is due to the need to squeeze the beam from the front of the connection to prevent overheating of the front

Walls of the penetration channel. With an increase in the working distance A, the region with the minimum beam cross section (waist) and its diameter increase, and with a change in φ and p, the focal spot shifts, which changes the value of A, the shape of the weld, and the probability of formation of discontinuities in the weld metal. Therefore, the tolerance for changing A must be regulated during the welding process. From FIG. 2 that the position of the focal spot of a converging resultant electron beam and its angle of convergence are determined by the focal distance A and the working distance A of the individual beam. Estimate the effect of fn and f

on beam geometry is possible using the expressions given in O.K. Nazarenko et al. (See above link). The calculation results show that at A 150-220 iyiM. And Yu, 5H a change in the value of f within 1% or l And within 10% leads to a change in A within 45%. The experimental results in a facility equipped with a U-843 power source and a UL-141 gun are fully confirmed. When changing f by ± 0.4mA (± 0.5%), 1l by ± 25mA (± 5.0%), and from 150 to 220 mm, high-quality seams while maintaining the given geometry are ensured with the stability of the value A at the level of ± 20% from the optimal position. Thus, the focus of the beam during welding should be in the range A (1 / 3-1 / 2) N for vertical joints and A (1 / 2-3 / 4) N for horizontal joints.

Example. The power elements were made of high-strength steel 12Kh2NChMD, heat-resistant chromium steel 15X11MF with a thickness of 40-150 mm and heat-resistant nickel alloy KhN73MBTY with a thickness of 30-90 mm with a horizontal beam on a vertical plane on U-570 units equipped with power complexes of 30.60 and 120 kW. For these purposes, electron beam guns, UL-141 guns (60 kV), ELA 60/60, (60 kV), respectively, were used; U-858 (120 kV). The effect of the mode parameters on the weld quality of 15.Kh2NChMD steel and KhN73MBTYu alloy is presented in the table. In these experiments, a beam scan system with one deflecting coil was used, which provides a circular scan shape. Since the sweep frequency in the range of 150-2000 Hz has a special effect on the shape ...

does not have a seam and the formation of defects, the experiments are presented at -f 1000 Hz.

Application of the proposed welding method allows preventing defects in welded joints, which increases the yield by 100%.

Claims (1)

The claims A method of electron beam welding of difficultly welded steels and alloys of large thicknesses, in which the parts are welded at an accelerating voltage of 60-120 kV with a horizontal beam with through penetration of the joint, deployed along a circular path with a diameter of 0.8-1.5 mm with a frequency of 150 -2000 Hz, with the exception that, in order to improve the quality of welded joints by reducing internal and external defects in the form of cracks, sinks, non-fusion, welding is carried out at a working distance of 150-220 mm at a speed of 9-105 / N, mm / h for horizontal joints and 4.5 105 / N mm / h for vertical joints, where H is the joint thickness, mm, at a beam current of 21 Nom. where 1nom the nominal value of the beam current, mA, necessary for through penetration of the joint and ensuring its stability during welding is not worse than ± 5%, and the beam focus in the operating mode is buried under the surface of the parts by 5/8 N for horizontal joints and 5 / 12 N for vertical welds and ensuring its stability during welding is not worse than ± 20%. microcracks root defects no defects -t - no to the center. crystallization of cracks and non-fusion shrink shells and cracks no defects . surface cracks shrinkage cracks and non-fusion transverse cracks, shells, non-fusion longitudinal cracks; defects; no root defects; microt; cracks; defects. are absent in areas of microcracks