RU2644491C2 - Method of electron-beam welding of titanium alloy ring compounds - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to a method of electron-beam welding (EBW) of annular seams in a vacuum of titanium alloys. The method includes preparing the edges for welding, assembling them end to end, melting with an electron beam of the welded seam. Edge preparation is carried out with ensuring a radial gap between the backing element and the welded seam. The gap is formed by the preliminary groove of the parts to be seamed, and the backing element is a part of one of the seamed parts after its groove. Electron-beam welding is then performed using a circular sweep of the beam. The sharp focus of the electron beam is located above the surface of the welded article. The gap between the welded edges and the backing element is between 0.5 and 1 times the thickness of the seam to be welded. Electron beam with circular sweep is focused above the surface of the article at a distance from the surface of the welded edges to the point of sharp focus of beam not less than 2 and not more than 3 thickness of the welded seam.

EFFECT: invention allows to get the smooth formation of the reverse roller, to exclude ingress of welding products in the internal cavity of article, and electron beam - on the surface of parts behind the welded seam, thereby improving ring welding seam.

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Description

The invention relates to a method of electron beam welding (ELS) of annular welds in a vacuum of titanium alloys, in particular to an ELS using an electron beam scan.

Known welding technology with full penetration of the welded joint ("Electron beam welding", edited by academician B.E. Paton, Academy of Sciences of the Ukrainian SSR, Institute of Electric Welding named after E.O. Paton, 1987, pp. 57-62). This the most reliable and easiest way to eliminate root defects, reduce the likelihood of pores and shells, and minimize deformation conditions.

The disadvantage of this method is the possibility of displacing the metal into the internal cavity, hit by an electron beam (EL) passing through the joint, on the back surface of the part.

A known method of electron beam welding of pipes, in which welding is performed with oscillations of the electron beam across and along the joint. This method provides a reduction in the volume of the weld pool, which eliminates the sagging of the weld, the formation of burns and fistulas, facilitates the adjustment of EL to the welded joint by using a reamer (Patent No. 2259906, IPC B23K 15/04).

The disadvantage of this method of ELS is the use of a focused heating spot, the formation of a narrow vapor-gas-dynamic channel, leading to spraying of the weld metal. In addition, a butt joint without a liner does not preclude the electron beam from entering the internal surfaces of the parts.

The closest analogue of the claimed invention is a method of ELS pipes, in which an annular protrusion with a cross section in the form of an isosceles triangle is made on the lateral surface of one of the pipes. The ends at the end of the pipes are cut at an angle and joined. Then, in one revolution of the joint, welding with a concentrated beam is performed. This method reduces the cost of the ELS process of thick-walled pipes due to the rejection of the additive, and also increases the strength and corrosion properties (Patent No. 2285599, IPC B23K 31/02, B23K 15/02, B23K 33/00, B23K 101/06).

However, since when welding, a concentrated electron beam is used, the welded metal is sprayed and gets into the internal cavities of the assembly unit, which, provided that stripping is not available along the internal contour of the connection, is unacceptable.

The technical result, the achievement of which the present invention is directed, is to obtain a smooth formation of the reverse roller and to prevent the ingress of welding products into the internal cavities of the product, and the electron beam on the surface of the parts behind the welded joint, improving the quality of the ring welded joint.

This technical result is achieved by electron beam welding of ring compounds of titanium alloys. The method includes preparing the edges for welding, assembling them end-to-end, melting the welded joint with the electron beam. The preparation of the edges is carried out with a radial clearance between the backing element and the welded joint. Moreover, the gap is formed by a preliminary groove of the joined parts, and a part of one of the joined parts after its groove serves as a backing element.

Then carry out electron beam welding using a circular scan of the beam. In this case, the sharp focus of the electron beam is located above the surface of the welded product. The gap between the welded edges and the backing element is from 0.5 to 1 thickness of the welded joint c). The electron beam with a circular scan focus above the surface of the product at a distance from the surface of the welded edges to the point of sharp focus of the beam of not less than 2 and not more than 3 thicknesses of the welded joint.

Using the sweep of the electron beam allows you to expand the root of the weld pool. Refocusing the beam and, as a consequence of this, expanding the weld pool and reducing the pressure in the melting channel preclude the exit of the concentrated electron beam into the internal cavity of the product.

The invention is illustrated by drawings. In FIG. 1 shows a weldable joint; FIG. 2 - location of the point of sharp focus of the beam.

The method is as follows.

An annular joint is assembled without cutting edges and with a gap of not more than 0.1 mm. Under the welded joint there is a backing element, which eliminates the formation of technological lack of penetration and provides the possibility of smooth formation of the root bead. A pre-machined part of one of the joined parts serves as a backing element. The size of the gap between the welded edges and the underlay element a) is determined empirically to exclude the influence of the underlay element on the formation of the weld pool.

Welding of the assembled joint is performed by an electron beam using a circular scan with a frequency of 600-800 Hz. In this case, a sharp focus is located above the surface of the product, which allows for smooth formation of the root bead (melt). The beam focusing distance h for optimal connection was also determined empirically.

An example implementation of the method.

Welding of parts, for example, of VT6-S titanium alloy, is performed on an ELU-9 industrial electron-beam installation with ELTA 60/15 technological equipment. The welded diameter is 25.5 mm, the thickness of the joined edge is 2.7 mm.

Set the following welding parameters: U _St. = 60 kW, I _St. = 12 mA, V _St. = 17 m / h, beam scan ∅1.0 mm with a frequency of 800 Hz. After welding, quality control of the welded joint is performed:

- a method of visually measuring control (VIC);

- x-ray control;

- water strength test;

- air tightness test in an aquarium;

- permeability test with air-helium mixture (HCV).

According to the test results, the quality of the welded joint meets the established requirements.

Thus, the present invention allows to obtain a smooth formation of the reverse roller, to prevent the ingress of welding products into the internal cavities of the product, and the electron beam on the surface of the parts behind the welded joint, thereby improving the quality of the ring welded joint.

Claims (1)

A method of electron beam welding of a ring joint of a titanium alloy, including cutting edges for welding, assembling a joint and welding with an electron beam with the sharp focus of the electron beam above the surface of the welded product and using a circular scan of the electron beam, characterized in that the edges are cut by grooving a part of the edges with the formation of a backing element, which serves as part of one of the joined parts after its groove, and a radial clearance between the part of one of the joined parts and the welded joint, while the gap between the welded edges and the backing element is from 0.5 to 1 the thickness of the welded joint, and the electron beam with a circular scan is focused at a distance from the surface of the welded edges to the point of sharp beam focusing of at least 2 and no more 3 thicknesses of the welded joint.

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