JPS60223694A - Airtight welding device by laser light - Google Patents

Abstract

PURPOSE:To obtain good weld penetratability by providing a condensing optical system which focuses the laser light made incident on the inside of a hermetic chamber to the desired position of a part to be welded into a welding chamber. CONSTITUTION:The aperture end of a coated pipe 1 is inserted into a welding chamber 11 and the air in the chamber 11 is evacuated via a vacuum evacuating pipe 30. An inert gas is fed through a supply pipe 32 to maintain a high pressure atm. in the chamber 11 via a relief valve 29. An end plug 6 is press-fitted into the aperture end of the pipe 1 by a mechanism 21 for press-fitting the end plug and a condenser lens 25 is moved forward and backward together with a shielding cap 24 by a driving device 26 for the optical system so that the focus of the laser light is brought to the desired position on the surface of the weld zone or near the same. An inert gas is supplied into the gap 24 and is blown from a gas nozzle 34 to the surface of the weld zone. The laser light is fed from a laser light generator 16 and is condensed via the lens 25 to the joint part between the plug 6 and the pipe 1. Welding is executed by rotating the pipe 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an airtight welding device using laser light, which welds objects to be welded, such as nuclear fuel rods or spacers for fuel assemblies, using laser light.

[Technical background of the invention and its problems] Generally, nuclear fuel rods used in power reactors, etc., have an end plug 2 at one end of a cladding tube 1 made of zirconium alloy or stainless steel, as shown in FIG. After welding, a pellet 3 made of a nuclear fuel material such as uranium dioxide UO2 is loaded into the cladding tube 1, and a spring 5 is inserted into the space 4 formed between the pellet 3 and the open end of the cladding tube 1. The cladding tube 1 is then filled with an inert gas at a pressure higher than atmospheric pressure, the end plug 6 is fitted to the open end, and the end plug 6 is placed in a welding chamber under a high pressure atmosphere. Manufactured by hermetic welding.

On the other hand, in a fuel assembly constructed by assembling a large number of nuclear fuel rods manufactured as described above, spacers for maintaining the spacing between each nuclear fuel rod are as shown in FIGS. 2 and 3. , a bar 7, a divider 8, a spring 9, a band 10, etc., and the intersection of the bar 7 and the divider 8, or the intersection of the bar 7, etc. and the band 10, etc. are welded. By the way, when performing these types of welding, in order to prevent oxidation and nitridation of the welded part, part or all of the workpiece to be welded is inserted into an airtight welding chamber, and the inside of the welding chamber is filled with inert gas. Welding of the above-mentioned parts to be welded is performed in an atmosphere.

FIG. 4 is a partially sectional side view schematically showing a welding device for welding nuclear fuel rods, spacers, etc. as described above;
A laser beam introduction window 12 is provided on one side wall of the sealed welding chamber 11, and an exhaust pipe 13 for evacuation is provided at appropriate locations in the welding chamber 11. Conduit 1 feeding the
4 is connected.

On the other hand, on the outside of the welding chamber 11, a laser beam generator 16 is provided that irradiates the welding portion of the workpiece 15 with a laser beam through the laser beam window 12,
The laser beam irradiated from the laser beam generator 16 is focused on the welding portion through the condensing lens 17, and the welding portion is welded.

Therefore, when welding the welded portion 15,
The workpiece 15 to be welded is inserted into the welding chamber 11, the air inside the welding chamber 11 is exhausted through the exhaust pipe 13, and then an inert gas is sent through the conduit 14 to create a pressure atmosphere higher than atmospheric pressure. do. Then, the laser beam from the laser beam generator 16 is focused on the welding part of the workpiece through the condensing lens 17 and the laser beam introduction tH12,
Weld the welded part.

However, in such a device, the thickness of the window material needs to be increased for structural strength because the laser light introduction window is required to withstand vacuum pressure and pressurize inert gas. Therefore, a thick plate of transparent material is interposed between the condensing lens and the object to be welded, which deteriorates the convergence of the laser beam and
There are problems such as a decrease in energy density and the inability to obtain the deep penetration characteristic of laser welding. Furthermore, since welding is performed with an inert gas sealed in the welding chamber, there are also problems such as plasma being generated by metal vapor and the energy of the laser beam being absorbed, resulting in poor weld seepage.

[Purpose of the invention]

In view of these points, it is an object of the present invention to provide a gas-tight welding device using a laser beam that can achieve good weld permeability.

[Summary of the Invention] The present invention is directed to a laser welding process in which part or all of a workpiece is inserted into an airtight welding chamber, and the workpiece is welded in a high-pressure inert gas atmosphere within the welding chamber. The airtight welding device using light is characterized in that a condensing optical system is provided in the welding chamber to focus the laser beam incident on the welding chamber onto the surface of the welded part or its vicinity. do.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

FIG. 5 shows a welding device for welding nuclear fuel rods, in which an opening 20 is provided in one side wall of the welding chamber 11 into which the end of the cladding tube 1 of the nuclear fuel rod can be inserted. An end plug press-fitting mechanism 21 is provided at a position facing the end plug 20 for holding the end plug 6 and making it possible to press it against the end of the cladding tube.

On the other hand, a laser beam introducing window 12 is provided on a side wall perpendicular to the side wall in which the opening 20 is provided, and furthermore, a laser beam introducing window 12 is provided on the outside of the welding chamber 11 through the laser beam introducing window 12. A laser beam generator 16 is provided that irradiates the welded portion with a laser beam. Further, a guide tube 22 is provided in the welding chamber 11 so as to protrude concentrically with the laser beam introduction window 12, and a condensing optical system 23 is slidably adjusted in the axial direction within the guide tube 22. It is installed.

That is, a shield cap 24 having a truncated conical cylinder portion at the tip is provided in the guide tube 22 so as to be slidable in the axial direction of the guide tube 22, and a shield cap 24 is provided within the shield cap 24 concentrically with the shield cap 24. A condensing lens 25 is provided at. In addition, the shield cap 24 is an optical system drive@
1126, and is moved along a guide rod 27 protruding into the welding chamber 11 by the operation of the optical system drive device 26, so that the condensing lens 25 moves toward the welded part. It is designed to advance and retreat.

Further, a vacuum exhaust pipe 30 having a solenoid valve 28 and a relief valve 29 is installed at an appropriate location in the welding chamber 11.
．． and an inert gas supply pipe 32 that supplies inert gas at a pressure higher than atmospheric pressure into the welding chamber 11 via a solenoid valve 31. The inert gas supply pipe 32 is connected to the shield cap 24 through a pipe 33.
It is connected to a gas nozzle 34 that opens in the vicinity of the welding point.

Therefore, when welding the end plug 6 to the open end of the cladding tube 1, the open end of the cladding tube 1 is inserted into the welding chamber 11 through the opening 2°, and the solenoid valve 28 is opened. The air in the welding chamber 11 is exhausted through the vacuum exhaust pipe 30, and then the solenoid valve 31 is opened to send inert gas into the welding chamber 11, and the inside of the welding chamber 11 is lowered from atmospheric pressure through the relief valve 29. Also create a high pressure atmosphere.

Then, the end plug press-fitting mechanism 21 press-fits the end plug 6 into the open end of the cladding tube 1, and the optical system drive device 26 advances and retreats the condensing lens 25 together with the shield cap 24, so that the focus of the laser beam is on the surface of the welded part. or to a desired position near the shield cap 24, and continue to supply inert gas into the shield cap 24, and the gas nozzle 3
4, while blowing inert gas onto the surface of the welded part, the laser beam from the laser beam generator 16 is passed through the laser beam introduction window 12.
The light is then focused through the condensing lens 25 onto the junction between the end plug and the covering, and the junction is welded by rotating the covering tube 1.

In this way, welding is carried out by concentrating the laser beam into an arbitrary micro-diameter and setting the energy density to an appropriate state for weldability, and at the same time, the metal vapor generated by welding is removed by inert gas, and plasma is generated during welding. It is prevented from doing so.

In addition, when welding the spacer, please use the spacer.

By moving and rotating, each welding part can be positioned. Further, the condensing optical system is not limited to a condensing lens, and for example, a concave mirror may be used.

(Effects of the Invention) As explained above, in the present invention, the condensing optical system for focusing the laser beam incident into the welding chamber on the surface of the welded part or its vicinity is attached to the welding chamber. Since it is installed inside the welding area, there is no thick transparent material between the condensing optical system and the part to be welded, which prevents deterioration of light convergence and energy density, and achieves the deep penetration unique to laser welding. This makes it possible to obtain sound welding quality.

In addition, if the condensing optical system is made to move forward and backward relative to the part to be welded, it is possible to more reliably condense the laser beam into a sufficiently small spot diameter, ensure sufficient energy density, and furthermore, the inert gas When welding the surface of the welded part while blowing repeatedly, the metal vapor is prevented from turning into plasma in the laser beam path, and deterioration of weld retention due to plasma can be further prevented.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view showing an example of a nuclear fuel rod for a nuclear reactor;
3 is a side view of the spacer, FIG. 4 is a partially sectional side view of the already proposed laser beam welding device, and FIG. 5 is a partially sectional side view of the welding device of the present invention. It is. DESCRIPTION OF SYMBOLS 1... Covering tube, 2,6... End plug, 11... Welding chamber, 12... Laser light introduction window, 16... Laser light generator, 23... Condensing optical system, 24... Shield cap, 25... Condensing lens, 30... Vacuum exhaust pipe, 32... Inert gas supply pipe, 34... Gas nozzle. Applicant's agent Kiyoshi Inomata Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. Part or all of the workpiece is inserted into an airtight welding chamber, and the workpiece is welded by laser light in a high-pressure inert gas atmosphere inside the welding chamber. The airtight welding apparatus is characterized in that a condensing optical system is provided in the welding chamber to focus the laser beam incident on the welding chamber at or near the surface of the welded part. Airtight welding equipment using laser light. 2. The hermetic welding apparatus using a laser beam according to claim 1, wherein the condensing optical system is a condensing lens. 3. The hermetic welding device using a laser beam according to claim 1, wherein the condensing optical system is a concave mirror. 4. The laser beam according to any one of claims 1 to 3, wherein the focusing optical system is adjustable in its position so as to change the focal position of the laser beam. Airtight welding equipment by. 5. The airtight welding bag by laser light according to claim 1, wherein the inert gas is supplied into the airtight chamber from a gas nozzle that opens at least in the vicinity of the part to be welded.