KR101002628B1 - Apparatus for automatically overlay welding, inspecting and processing nozzzle part having different kind metals of pressurizer in nuclear power plant and method thereof - Google Patents

Abstract

The present invention relates to a welding, inspection and processing apparatus and a method thereof, which are fixed to a pressurizer and a nozzle of a nuclear power plant through a fixing member to automatically overlay weld, inspect, and process dissimilar metal joints of a nozzle. Work tools for welding and machining dissimilar metal joints; An inspection and measurement tool to remove the oxide layer on the bead surface of the weld and measure the temperature; A three-axis manipulator capable of rotating the tool 360 in the circumferential direction of the dissimilar metal joint in a fixed state; A camera integrated with the work tool for monitoring and recording work status; And a control unit for controlling the work tool, the inspection and measurement tool, the three-axis manipulator, and the camera. The welding unit for dissimilar metal joining of the nozzle of the pressurizer of the nuclear power plant contaminated with radioactivity by the method as described above. Allows stress corrosion cracking prevention maintenance or inspection to be performed automatically.

Nuclear Power Plant, Pressurizer Nozzle, Stress Corrosion Cracking, Dissimilar Metals, Overlay Welding

Description

Apparatus for automatically overlay welding, inspecting and processing nozzzle part having different kind metals of pressurizer in nuclear power plant and method

The present invention relates to an automatic overlay welding, inspection and processing apparatus of the nozzle portion of the pressurizer and a method thereof, and more particularly to a heterogeneous metal welded portion of a nozzle having a defect caused by PWSCC or a heterogeneous nozzle of a nuclear power plant pressurizer. The present invention relates to an automatic overlay welding, inspection and processing apparatus of a nozzle part made of dissimilar metal of a nuclear power plant pressurizer for preventing PWSCC of a metal welding part, and a method thereof.

In general, as shown in FIG. 1, the nozzle 3 of the nuclear power plant pressurizer is made of low alloy steel, and a stainless steel pipe of a separate pipe 2 is connected to the nozzle 3, and the nozzle 3 is connected to the nozzle 3. The welding part which is the dissimilar metal joining part 4 of the piping 2 is formed.

The welding part is welded with a welding rod made of Alloy 600.

However, defects are generated by PWSCC (Primary Water Stress Corrosion Cracking) for a long time in the welded portion, which is the dissimilar metal junction 4, and the defects continue to grow as time passes, causing a safety problem. Therefore, maintenance is required.

In addition, the nozzle shape with the dissimilar metal welding part of the pressurizer is all formed differently, that is, the shape of the nozzle part is a straight line, a "b" shape or a shape bent at 45 degrees.

In the shape of the nozzle as described above, in order to prevent maintenance, it is necessary to be welded to the bent portion, the equipment that fits the specific shape is required.

In addition, since the vicinity of the nozzle portion of the pressurizer is a region contaminated by radioactivity, it is difficult to repair by hand by a human because it has a significant influence on the safety of the worker.

Therefore, the automatic overlay welding device is required for the maintenance of the weld, which is the dissimilar metal junction 4 of the pressurizer nozzle of the nuclear power plant.

As a prior art of such a device, US Pat. No. 6,678,833 proposes an overlay welding apparatus and method for pipes or piping, but it is impossible to apply it to a nuclear power plant site because it is an overlay welding apparatus while rotating a pipe or piping. .

In addition, US Patent No. 6013890 is made of a device in the form of a pipe or pipe is rotated like US Patent 6678890 is very difficult to apply to the nuclear power plant site.

In addition, US Patent No. 5,999,333 is a device for processing an overlay welded surface of a pipe or a pipe, and a method of processing by finding a center of a pipe by using a dial gauge, which is not applicable to welding.

In addition, US Patent 4484123 is a device for welding the outer surface of the T-shaped pipe or pipe in the form of a saddle, which is difficult to apply to a nuclear power plant pressurizer dissimilar metal welding nozzle that requires a circular welding.

Therefore, an apparatus for automatically overlay welding and processing a welded portion for dissimilar metal bonding of a pressurizer nozzle and a pipe is not found until now, and it is at a time when the safety of the operator is desperately necessary.

An object of the present invention for solving the above problems, maintenance, processing and inspection work for the prevention of PWSCC generated in the welding portion for dissimilar metal bonding of the nuclear power plant pressurizer nozzle portion contaminated with radiation without harming the safety of the operator Provides an automatic overlay welding, inspection and processing device for nozzle part made of dissimilar metal of nuclear power plant pressurizer which can be performed automatically and can also be applied to automatic overlay welding of pipes and pipes that are difficult to access. It's there.

Welding, inspection and processing apparatus for automatically overlay welding, inspecting and processing the dissimilar metal joint of the nozzle is fixed to the pressurizer and the nozzle of the nuclear power plant according to an embodiment of the present invention for achieving the object as described above The work tool is transported from side to side along the dissimilar metal joint by a left and right drive motor and a transfer guide, and is welded and processed while moving up and down along the dissimilar metal joint by a vertical drive motor; An inspection and measurement tool for removing the oxide layer on the surface of the weld bead by measuring the temperature after the dissimilar metal junction of the nozzle is welded one pass through the work tool, and then rotating along the dissimilar metal junction via a rotary drive motor; A three-axis manipulator which rotates 360 degrees in the circumferential direction of the dissimilar metal joint of the nozzle and moves the work tool in a fixed state while being transferred in a direction parallel and perpendicular to the central axis of the dissimilar metal joint; A camera integrated with the work tool for monitoring and recording work status; And a controller for controlling a work tool, an inspection and measurement tool, a three-axis manipulator, and a camera having a controller and a motor controller in which a shape measurement control program and a machine part control program are embedded.

According to an embodiment of the present invention, a welding method for automatically overlay welding a dissimilar metal joint of a nozzle of a nuclear power plant pressurizer includes: installing a welding, inspecting, and processing apparatus by using a fixing member in the pressurizer and the nozzle; Installing a welding tool in the welding, inspection and processing apparatus; Receiving a wire from a wire feeder and overlay welding the dissimilar metal joint of the nozzle using the welding tool; Removing the oxide layer of the weld using a brush when overlay welding of the dissimilar metal joint is completed; Confirming whether the overlay welding is made to a predetermined thickness or more; Measuring the weld by replacing the welding tool with an LVDT when the overlay welding is completed over a predetermined thickness; Setting a profile of the welded portion measured by the LVDT; Replacing the LVDT with a machining tool when the profile of the weld is set; Machining based on the weld shape using the replaced machining tool; And disassembling the overlay welding device when the overlay welding, measuring, and processing of the dissimilar metal joint is completed.

In the method of inspecting a welded portion in which the dissimilar metal junction of the nozzle of the nuclear power plant pressurizer according to the present invention is automatically overlay-welded, when welding the dissimilar metal joint of the nozzle, the shape of each last layer weld is sensed using LVDT, The temperature sensor, a measuring tool, measures the temperature between each pass during welding, and the welding condition of the weld is monitored by a camera.

Method for processing a weld welded dissimilar metal joint of the nozzle of the nuclear power plant pressurizer according to the invention automatically overlay welded, measuring the shape welded through the LVDT to generate data through a shape program; Setting a processing range and a processing area of the welded part based on the data; Sending the data to the three-axis manipulator to process the weld.

By using the automatic overlay welding, inspection, and processing apparatus of the nozzle part made of dissimilar metal of the nuclear power plant pressurizer according to the present invention, and a method thereof, the welding part for joining the dissimilar metal of the nuclear power plant pressurizer nozzle part contaminated with radiation is safe for the operator. It enables automated maintenance, machining, and inspection work without compromising safety, and enables applications for automatic overlay welding of pipes and pipes that are difficult to access.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the automatic overlay welding, inspection and processing apparatus and the method of the nozzle portion made of dissimilar metal of the nuclear power plant pressurizer according to the present invention.

1 is a cross-sectional view showing a nuclear power plant pressurizer applied to the present invention, Figure 2 is a cross-sectional view showing an automatic overlay welding, inspection and processing apparatus of the nozzle unit made of dissimilar metal of the nuclear power plant pressurizer according to the present invention, Figure 3 4 is a cross-sectional view showing a portion AA, Figures 4a and 4b is a view showing a holding member for fixing the device according to the invention, Figure 5 is a cross-sectional view showing a machining tool of the device according to the invention, Figure 5 7A and 7B are cross-sectional views showing inspection and measurement tools of a device according to the present invention, and FIG. 8 is a welding state of a dissimilar metal joint according to an embodiment of the present invention. 9 is a flowchart illustrating an overlay welding method according to an embodiment of the present invention, and FIG. 10 is a flowchart illustrating an overlay weld inspection method according to an embodiment of the present invention. 11 is a flowchart showing the overlay weld processing method according to an embodiment of the invention.

The pressurizer 1 of the nuclear power plant as shown in FIG. 1 has a spray nozzle 3-1 on top, a relief nozzle 3-2, and a safety nozzle on top. (3-3) It consists of six nozzles (3) for joining dissimilar metals with three and one surge nozzle (3-4) at the bottom. The welding part, which is the dissimilar metal joint 4, is for connecting the nozzle 3 mounted on the pressurizer 1 and the pipe 2 of stainless steel.

 Welding, inspection, which is fixed to the pressurizer 1 and the nozzle 3 of the nuclear power plant according to the present invention through the fixing member 5 to automatically overlay weld, inspect, and process the dissimilar metal joint 4 of the nozzle 3. And the processing apparatus 100, the work tool 10, the inspection and measurement tool 20, three axes, as shown in Figs. 2 and 3 in which the apparatus is installed in the pressurizer 1 and the nozzle 3, respectively. It consists of a manipulator 30, a camera 40, and a control part.

The work tool 10 is conveyed from side to side along the dissimilar metal joint 4 of the nozzle 3 by the left and right driving motor 11 and the transfer guide 12, and the dissimilar metal by the vertical driving motor 13. The dissimilar metal joint 4 is welded and machined while moving up and down along the joint 4.

The work tool 10 senses a welding tool 17 for welding the dissimilar metal joint 4 to a predetermined thickness, a machining tool 17 for processing the weld part according to the shape of the welding bead, and a welding part. It consists of Linear Variable Differential Transformer (LVDT) 19 for measurement.

The welding tool 17 receives the filler metal wire 15 wound on the spool 14 separately installed in the pressurizer 1 from the wire feeder 16 to weld the dissimilar metal joint 4.

The machining tool 18 as shown in FIG. 5 is provided separately, and if necessary, that is, the dissimilar metal joint 4 is welded and then replaced with the welding tool 17 to process based on the weld shape. Do it.

The LVDT 19 as shown in FIG. 6 serves to sense and measure the shape of the welded portion and transmit it to the control unit. The LVDT 19 is provided separately and used to be replaced with the welding tool 17 or the processing tool 18 when necessary. .

The inspection and measurement tool 20 serves to remove the oxide layer on the weld bead surface and measure the temperature, after the dissimilar metal junction 4 of the nozzle 3 is welded one pass through the work tool 10. The inspection and measurement are performed while rotating along the welded portion of the dissimilar metal joint 4 through the rotation drive motor 21.

The inspection and measurement tool 20 includes an inspection tool 23 equipped with a brush 22 for removing an oxide layer formed on a surface when welding a welding portion that is a dissimilar metal junction 4 of a nozzle 3, and It consists of the measuring tool 25 with which the temperature sensor 24 which measures the weld part temperature between each path | pass is mounted.

Here, the removal of the oxide layer of the weld bead and the weld temperature measurement are preferably performed for each pass of the weld in order to increase the weldability of the next pass.

The brush 22 is installed to be movable up and down by the operation of the moving member 27 as the temperature sensor 24 described below (see FIGS. 7A and 7B).

That is, when the temperature sensor 24 for measuring the temperature of the welded part restores the original position after measuring the temperature, the moving member 27 moves downward and the brush 22 also moves downward to remove the scale of the bead part. do.

The measuring tool 25 is provided with a cylinder 26 to guide the front and rear movement of the temperature sensor 24, which can freely move the sensor 24 to the near area for measuring the temperature. At the same time, it prevents damage due to contact with the weld.

As shown in FIGS. 7A and 7B, a method of driving the brush 22 of the inspection tool 23 and the temperature sensor 24 of the measurement tool 25 is described. The thermocouple, the sensor 24, is brought into contact with the weld bead by the cylinder 26 to measure the temperature, and the removal of the oxidized layer of the weld bead is caused by the temperature sensor 24 being returned to its original position by the cylinder 26. At the same time, the brush 22 is lowered to remove the oxide scale while contacting the weld bead surface.

2 and 3, the inspection tool 23 and the measurement tool 25 are integrally formed, but may be provided separately from each other.

The three-axis manipulator 30 rotates 360 degrees in the circumferential direction of the welded portion, which is the dissimilar metal junction 4 of the nozzle 3, and is transported in a direction parallel and perpendicular to the central axis of the dissimilar metal junction 4. While serving to transport the work tool 10 in a fixed state.

The camera 40 serves to monitor and record the welding and processing work conditions, and is integrally formed with the work tool 10.

The controller (not shown) includes a controller and a motor controller in which a shape measurement control program and a machine control program are embedded, so that the work tool 10, the inspection and measurement tool 20, the three-axis manipulator 30, and a camera are provided. 40 is controlled.

The controller also controls a welding path and a welding condition by the work tool 10 through a built-in control program, and sets and controls conditions for each welding section.

In addition, the fixing member 5, as shown in Figures 4a and 4b, consists of two semi-circular rotating body (5-1) coupled by the hinge member (5-4), the welding, inspection And a fixing jig 5-2 for fixing the processing apparatus 100 to the pressurizer 1 and the nozzle 3, and a connector 5-3 for connecting the two rotary bodies 5-1 to each other. Is made of.

That is, the fixing member 5 has two semi-circular rotating bodies 5-1 connected to one side and the other opposite side thereof, and the rotating body 5-1 is used for the pressurizer 1 nozzle 3. After wrapping, the connector 5-3 is connected, and the device 100 is installed on the pressurizer 1 and the nozzle using the fixing jig 5-2.

Through the welding, inspection and processing apparatus 100 as described above, as shown in FIG. 8, first, a buttering welding of the nozzle 3 side of the low alloy steel is performed, and then a pipe of the buttering welding side and the stainless steel ( 2) Overlay welding is performed with Alloy 690 to prevent the PWSCC of the dissimilar metal connection 4 between the nozzle 3 and the pipe 2 of the dissimilar metal, which is groove welded therebetween.

9 illustrates a welding method for automatically overlay welding the dissimilar metal joint 4 of the nozzle 3 of the nuclear power plant pressur 1 according to the embodiment of the present invention having the above configuration, and the inspection and processing method of the welded part. Looking briefly through the following.

First, the welding, inspection and processing apparatus 100 is installed using the fixing member 5 in the pressurizer 1 and the nozzle 3 (S11).

The welding tool 17 is installed in the welding, inspection and processing apparatus 100 (S12), and at the same time, the spool 14 and the wire feeder 16 on which the filler metal wire 15 is wound are installed in the pressurizer 1.

The wire 15 is supplied from the feeder 16 on which the wire 15 installed in the subscriber 1 is wound, and overlay welding is performed on the dissimilar metal joint 4 of the nozzle 3 using the welding tool 17. (S13).

At this time, each time the overlay welding of the dissimilar metal joint 4 is completed, the oxide layer of the weld is removed using the iron brush 22 installed in the inspection tool 23 (S14).

It is confirmed whether the overlay welding is made to be greater than or equal to a predetermined thickness, and if the thickness is less than or equal to a predetermined thickness, re-welding is performed (S15).

When the overlay welding is completed to a predetermined thickness or more, the welding tool 17 is replaced with the LVDT 19 to measure the shape of the weld (S16).

The profile of the welded part measured by the LVDT 19 is set (S17).

When the welding profile is set, the LVDT 19 is replaced with the machining tool 18 (S18).

The machining is performed based on the weld shape data measured using the replaced machining tool 18 (S19). At this time, the work is performed in the area contaminated with radiation, so the work process is monitored using a CCD camera, a monitoring and recording device, and recorded when necessary.

When the overlay welding, measuring and processing of the dissimilar metal joint 4 is completed, the overlay welding apparatus is dismantled (S20).

Next, referring to FIG. 10, a method of automatically inspecting a welded portion in which the dissimilar metal junction 4 of the nozzle 3 of the nuclear power plant pressurizer 1 according to the embodiment of the present invention is overlay welded is as follows.

First, when welding the dissimilar metal joint 4 of the nozzle 3, the shape of the last layer weld is sensed by using the LVDT 19 to be measured. Through the above measurement, the weld shape data is formed by the shape program. To be created, and the machining range and the machining area are set based on this.

Then, the temperature between each pass is measured during welding through the temperature sensor 24 of the measuring tool 25.

Finally, the welding state of the welded portion is monitored through the camera 40.

This method of inspection allows follow-up to be taken when a weld is found to be defective.

Next, a method of automatically processing the weld welded with the dissimilar metal junction 4 of the nozzle 3 of the nuclear power plant pressurizer 1 according to the embodiment of the present invention will be briefly described with reference to FIG. 11.

The shape welded through the LVDT 19 is measured to generate data through a shape program (S51).

On the basis of the data generated as described above to set the processing range and the processing area of the weld (S52).

When the machining range and the machining area are set, the data is transmitted to the three-axis manipulator 30 to process the welded part (S53).

If a defect occurs in the welded part during the machining operation as described above, it is possible to immediately follow up through monitoring by the monitoring camera 40.

Welding, inspection and processing apparatus 100 according to the present invention and the method therewith are as described above spray nozzle (3-1), relief nozzle (3-2), safety nozzle (3-3) and surge nozzle ( It can be applied to 3-4), and only the size of the automatic device is changed according to the nozzle outer diameter depending on the situation.

Moreover, it is comprised so that application is possible even in the state in which the said nozzle 3 shape was bent at 90 degree | times.

In particular, although the apparatus of the present invention is limited to a three-axis automatic apparatus to prevent maintenance of a nuclear power plant pressurizer dissimilar metal weld nozzle, it is possible to apply the apparatus and method of the present invention to automatic welding of any pipes and pipes that are difficult to access. Do.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation in the scope of the appended claims. It will be understood by those skilled in the art that various modifications may be made and equivalents may be resorted to without departing from the scope of the appended claims.

1 is a cross-sectional view showing a nuclear power plant pressurizer applied to the present invention.

Figure 2 is a cross-sectional view showing an automatic overlay welding, inspection and processing apparatus of the nozzle unit made of dissimilar metal of the nuclear power plant pressurizer according to the present invention.

3 is a cross-sectional view showing a portion A-A of FIG.

4a and 4b show a holding member for holding a device according to the invention;

5 is a cross-sectional view showing a machining tool of the apparatus according to the present invention.

6 is a cross-sectional view of an LVDT of an apparatus according to the present invention.

7A and 7B are cross-sectional views showing inspection and measurement tools of the device according to the invention.

Figure 8 is a side cross-sectional view showing a welding state of dissimilar metal joints in accordance with an embodiment of the present invention.

9 is a flow chart showing an overlay welding method according to an embodiment of the present invention.

10 is a flowchart showing an overlay weld inspection method according to an embodiment of the present invention.

11 is a flowchart showing a method for processing an overlay welded portion according to an embodiment of the present invention.

* Brief description of symbols for the main parts of the drawings *

1: pressurizer 2: piping

3: Nozzle 3-1: Spray Nozzle

3-2: relief nozzle 3-4: surge nozzle

4: dissimilar metal joint 5: fixing member

5-1: Rotating Body 5-2: Fixing Jig

5-3: connector 5-4: hinge member

10: Work tool 11: left and right drive motor

12: Moving guide 13: Up and down drive motor

14: Spool 15: Wire

16: wire feeder 17: welding tool

18: Machining Tool 19: LVDT

20: Inspection and measurement tool 21: Rotary drive motor

22: Brush 23: Inspection Tool

24: temperature sensor 25: measuring tool

26: cylinder 27: moving member

30: 3-axis manipulator 40: camera

100: welding, inspection and processing equipment

Claims (12)

A welding, inspection and processing device which is fixed to the pressurizer 1 and the nozzle 3 of the nuclear power plant through the fixing member 5 to automatically overlay weld, inspect and process the dissimilar metal joint 4 of the nozzle 3 ( 100), The left and right drive motor 11 and the transfer guide 12 is moved to the left and right along the dissimilar metal junction (4), by the vertical drive motor 13 while moving up and down along the dissimilar metal joint (4) welding And a work tool 10 for processing; After the dissimilar metal joint 4 of the nozzle 3 is welded one pass through the work tool 10, it is rotated along the dissimilar metal joint 4 via the rotary drive motor 21 to form a weld bead surface. An inspection and measurement tool 20 for removing the oxide layer and measuring the temperature; The work tool 10 may be transported in a fixed state while being rotated 360 degrees in the circumferential direction of the dissimilar metal joint 4 of the nozzle 3 and being transferred in a direction parallel and perpendicular to the central axis of the dissimilar metal joint 4. A three-axis manipulator 30; A camera 40 integrated with the work tool 10 for monitoring and recording work status; And A controller and a motor controller in which a shape measurement control program and a machine control program are embedded are provided to control the work tool 10, the inspection and measurement tool 20, the three-axis manipulator 30, and the camera 40. Automatic overlay welding, inspection and processing apparatus of the nozzle unit made of dissimilar metal of the nuclear power plant pressurizer, characterized in that consisting of. The work tool 10 according to claim 1, A welding tool 17 which receives the filler metal wire 15 wound on the spool 14 from the wire feeder 16 and welds the dissimilar metal joint 4 to each other; Automatic overlay of the nozzle part made of dissimilar metal of the nuclear power plant pressurizer, characterized in that the dissimilar metal joint 4 is welded and then replaced with the welding tool 17 to be processed based on the weld shape. Welding, inspection and processing equipment. The nuclear power plant according to claim 2, wherein the work tool (10) is further provided with a linear variable differential transformer (LVDT) 19, which is replaced with the welding tool 17 to sense and measure the shape of the welded part. Automatic overlay welding, inspection and processing device of nozzle part made of dissimilar metal of pressurizer. The inspection and measurement tool 20 according to claim 1 or 2, An inspection tool 23 equipped with a brush 22 for removing a weld surface oxide layer, It consists of a measuring tool 25 equipped with a temperature sensor 24 for measuring the weld temperature between each pass, The inspection tool (23) and the measuring tool (25) is an automatic overlay welding, inspection and processing device of the nozzle portion made of a dissimilar metal of the nuclear power plant pressurizer, characterized in that formed in one piece. 5. The automatic overlay welding and inspection of the nozzle unit of claim 4, wherein the inspection tool 23 includes a moving member 27 for moving the brush 22 up and down. And processing equipment. The method of claim 4, wherein the measuring tool 25 is provided with a cylinder 26 for guiding the forward and backward movement of the temperature sensor 24, automatic overlay welding of the nozzle unit made of a dissimilar metal of the nuclear power plant pressurizer, Inspection and processing equipment. The heterogeneous nuclear power plant pressurizer of claim 1, wherein the controller controls a welding path and a welding condition by the work tool 10 and sets a condition for each welding section through a built-in control program. Automatic overlay welding, inspection and processing equipment for metal nozzles. The method of claim 1, wherein the fixing member 5, Rotating body (5-1) consisting of two semi-circular shape is coupled by the hinge member (5-4), A high stopper 5-2 for fixing the welding, inspection and processing apparatus 100 to the pressurizer 1 and the nozzle 3; Automatic overlay welding, inspection and processing apparatus of the nozzle unit made of a dissimilar metal of the nuclear power plant pressurizer, characterized in that consisting of a connector (5-3) connecting the two rotating bodies (5-1) to each other. In the welding method for automatically overlay welding the dissimilar metal joint 4 of the nozzle 3 of the nuclear power plant pressurizer 1, Installing a welding, inspection, and processing device (100) using the fixing member (5) on the pressurizer (1) and the nozzle (S10); Installing a welding tool (17) in the welding, inspection and processing apparatus (100) (S12); Receiving a wire (15) from a wire feeder (16) and overlay welding the dissimilar metal joint (4) of the nozzle (3) using the welding tool (S13); When the overlay welding of the dissimilar metal joint 4 is completed, removing the oxide layer of the weld using the brush 22 (S14); Confirming whether the overlay welding is made to have a predetermined thickness or more (S15); Measuring the weld by replacing the welding tool 17 with the LVDT 19 when the overlay welding is completed to a predetermined thickness or more (S16); Setting a profile of the welded part measured by the LVDT (S17); Replacing the LVDT (19) with a machining tool (18) when the profile of the weld is set (S18); Machining based on the weld shape using the replaced tool 18 (S19); And Dismantling the overlay welding device when the overlay welding, measurement and processing of the dissimilar metal junction (4) is completed (S20); Automatic overlay welding method of the nozzle unit made of a dissimilar metal of the nuclear power plant pressurizer. 10. The method of claim 9, wherein the overlay welding, using the lobster wire for Alloy690 to prevent the PWSSC prevention of the nozzle (3), the pipe (2) and the buttering weld and groove weld between the nozzle (3) and the pipe (2) An automatic overlay welding method for a nozzle unit made of dissimilar metal of a nuclear power plant pressurizer, characterized in that welding. delete delete

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