RU2032509C1 - Method for electron-beam welding of circular joints - Google Patents

Abstract

FIELD: welding of parts such as fuel manifolds of gas turbine engines consisting of a circular part and radially-disposed parts. SUBSTANCE: method involves welding in two passes from the opposite sides with beam scanning across the joint and monitoring the alignment of beam with joint plane. Beam scanning amplitude is set not to exceed the permissible thermal expansion of circular joint. Alignment of beam with joint plane is monitored in the course of welding by the presence of splashes in blind holes along the outside diameter of ring. The depth of holes is made to be equal to circle diameter of circular joint and the upper side of each hole is disposed at a certain preset depth of fusion from the part surface at the beam entry side. EFFECT: higher efficiency. 2 dwg

Description

 The invention relates to the technology of electron beam welding and can be used in aircraft, ship and engine manufacturing in the manufacture of annular parts such as fuel manifolds of gas turbine engines (GTE) having nozzle elements radially arranged on it that are joined to the ring.

 A feature of such designs is the need to weld intermittent joints located in a circle, formed by relatively rigid nozzles installed in grooves along the outer diameter of the non-rigid ring.

 The closest in technical essence to the proposed method is a welding method, which consists in the fact that the circular joints to be welded are welded with a scanning beam across the joint. In this case, before welding, the alignment of the beam path with the joint plane is controlled.

 Welding in one pass on one side is carried out to a predetermined depth. If necessary, welding can be carried out on the other opposite side of the joint.

 This method is used mainly for welding circular joints of small length, which allows one-time preliminary control of combining a low-power beam with the plane of the joint, and this guarantees a high degree of accuracy of the welding quality of the product. However, in the manufacture of large-sized products with a large seam length, such control of the combination of the beam with the butt plane cannot be carried out, the quality of the product cannot be guaranteed due to significant possible leashes due to large heat input during welding.

 In addition, the lack of control during the welding process of the entire joint height, carried out in two passes, each time to an incomplete height with the occurring wheel deformations, can lead to lack of penetration in the middle of the product, which reduces its quality and, in addition, requires additional control after welding and subsequent correction of product defects. Responsibility and high cost of the product make high demands on the quality of welding associated with the absence of lack of fusion along the entire height and length of the joint.

 The aim of the invention is to improve the quality of welding products such as fuel manifolds of gas turbine engines due to the exclusion of intermittent joints.

 In FIG. 1 shows a top view of the welded product; Fig. 2 is the same side view.

 The parts to be welded ring 1 and nozzles 2, the number of which reaches 40 pieces, are assembled in the fixture by installing nozzles 2 in grooves 3 made along the outer diameter D of ring 1.

 The joints 4 to be welded between the bottom of the grooves 3 and the nozzles 2 are arranged in a circle with a diameter d1 and form a circular discontinuous joint.

 Due to the design features of the product having a rigid ring 1 and sufficiently rigid nozzles 2, in order to reduce its leash during the welding process, it is carried out in two passes from two opposite sides in series. The welding depth in one pass h is set not less than 1/2 of the thickness H of the welded product and not more than 2/3 N for guaranteed penetration over the entire joint height. In the second pass, under these conditions, all possible root defects of the first pass are penetrated.

 At the same time, during the welding process, the electron beam is moved across the joint with a certain frequency, providing for scanning it. The magnitude of the scanning amplitude is set based on the condition of a possible displacement of the joint from the path of the beam due to heat input and its deformation. The penetration zone obtained by the scanning beam across the seam is greater than the width of the zone obtained by passing the beam along the joint without scanning and captures simultaneously with the joint on the theoretically specified trajectory the portions of the acceptable movement of the joint from the center. It is precisely at the departure of the zone of the joint being welded from the center that the control principle was built, which is implemented for the beam deviation from the joint.

 The control is carried out by the presence of spatter in specially made holes 5. These holes 5 are performed before welding the parts in the ring 1 along the outer diameter D not to its full width. They are located between the nozzles 2 in the body of the ring 1. The depth of the blind holes 5 is set to the diameter d of the joint circumference, i.e. up to the theoretical trajectory of the electron beam. This is due to the fact that it is this line of a circle with a diameter dst that is average, with respect to which the admissible value of the possible deviation of the joint from the beam path is set. Performing the beam scanning amplitude of not more than the specified permissible value of the thermal expansion of the circular joint, when the bottom of the blind hole is placed along this midline, the maximum permissible displacement is controlled. A decrease in the scanning amplitude accordingly increases the accuracy of alignment of the beam with the joint, since it more strictly limits the limit of their permissible discrepancy.

 For guaranteed tracking penetration of the selected depth h, the level of placement of holes along the height H of the ring is strictly limited. Holes 5 are positioned so that its upper face is located at a given depth h of penetration of the joint from the surface of the ring from the side of the beam inlet. The penetration depth h is selected taking into account the penetration peaks by their smallest value.

 Technologically, it is advisable to perform the holes in a cylindrical shape, then the upper face is the upper generatrix of the cylinder. It is possible to make holes and a rectangular shape, but their dimensions should be small so as not to reduce even more the rigidity of the welded structure. Since the holes are located in the wheel between the grooves for the nozzles, their number is determined either by the number of gaps between the nozzles, or they can be less, which depends on the degree of the leash along the length of the welded joint.

 During welding in the selected modes, when an electron beam passes around a circle with a diameter d in the case of a complete coincidence of the joint with the trajectory of the joint or withdrawal of the joint as a result of welding deformations, sprays will be observed indicating the fulfillment of the circular expansion in the corresponding hole welding along the joint and to the entire specified penetration depth in one pass. In the absence of splashes in the hole, which indicates the departure of the joint from the beam path by an unacceptable value, the operator increases the welding current, thereby expanding the root part of the weld being welded, capturing the joint. It is possible to install collectors opposite the holes 5, which will automatically adjust the beam output to the joint that changed position by relative movement of the gun and the product, which also ensures penetration of the joint.

 As an example, the results of testing this method by ELS of a gas turbine engine manifold made of a ring of heat-resistant nickel alloy VZh 98 with a diameter of 800 mm and 40 nozzles located along its perimeter installed in the grooves of the ring are given. The diameter of the annular interrupted joint for welding turned out to be 600 mm. The joint thickness is 30 mm, the width of the wheel rim is 18 mm.

 Welding was carried out on the ELU-20 installation, equipped with a VEP 60/15 power unit in the following modes: Vsv = 45 m / h, Isv = 75-80 mA, Uus = 60 kV.

 Various modes were preliminarily tested on the samples and one was selected in which the resulting joint width at half the joint height is 1.8 mm. For guaranteed penetration over the entire height (thickness) while ensuring the alignment of the beam with the junction plane, the penetration depth was selected in one pass 2/3 of the thickness of the product.

It was experimentally established that the assembled unit during welding heats up under these conditions on average to 200 ° C. Proceeding from this, for this material, the possible deformation of the circular joint L = t dst = 1.5x10-6x200x600 = 1.8 mm, where the coefficient of thermal volume expansion, deg. -1;
t is the difference between the initial and final temperatures of the product, deg.

 dst diameter of a circular joint, mm.

 Welding was carried out in two passes from opposite sides of the product. In one pass, the welding of the product is carried out to a depth of h = 18-20 mm. Holes with a diameter of 4 mm for control were performed by placing its center at a height of 20 mm from the upper end of the ring from the side of the beam inlet. A beam scan was performed at a frequency of 280 Hz. During the welding process, when the product was turned, the operator observed the occurrence of “sprinkling” (spray) in the control holes.

 After boiling the entire circuit on one side of the product, we turned it along with the fixture and produced a similar welding process on the other side of the product with a second pass. The repeatability of the welding process eliminated the use of control holes in the second welding pass. The study of the obtained samples showed that at the specified modes of welding and scanning the beam, a weld with almost parallel walls with an average width of 1.8 mm was obtained. Radiographic inspection did not reveal lack of penetration at the joint, i.e. the quality of welding corresponded to the high quality of the product.

 On one of the cooked products, almost half of the length to be welded showed the disappearance of “sprinkling” of spray in the control hole. A slight increase in the welding current brought the scanning beam to the joint zone, with the help of which the possibility of defective products was excluded, which was established as a result of radiographic inspection of the product.

 Thus, the proposed method made it possible to obtain a series of high-quality products, to completely eliminate lack of fusion at the joint, thereby eliminating the possibility of marriage in the manufacture of complex and expensive products.

Claims (1)

 METHOD OF ELECTRON BEAM WELDING OF CIRCLE JOINTS, in which welding is performed by a beam scanning along the joint and the beam is aligned with the joint plane, characterized in that, in order to improve the quality of welding of parts such as fuel collectors consisting of a ring and radially located parts, by eliminating lack of penetration , welding is carried out in two passes from two opposite sides, the beam scanning amplitude is set no more than the permissible value of the thermal expansion of the circular joint, and the beam alignment control with the plane of the joint, they are guided by the presence of splashes in the blind radial holes, which are carried out in depth from the outer diameter of the ring to the circumference of the circular joint, and the upper face of the hole is placed at a predetermined penetration depth from the surface of the radial part from the side of the beam inlet.

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