Automatic welding method for sealing welds of control rod drive mechanism and upper and lower components thereof

Abstract

The present invention provides a method for automatically welding sealed welds of a control rod drive mechanism and its upper and lower components, belonging to the field of nuclear power technology. The present invention sets the angle and distance between the welding wire and the tungsten electrode to 65-75° and 2mm, respectively, and the wire retraction distance to 8-10mm to ensure the one-time forming requirement of the weld. The back-side forming requirement of the weld is ensured by the delivery of back-side shielding gas. The back-side shielding gas supply is stopped when the welding torch rotates to 300° to prevent a large amount of gas at the root of the weld from affecting the final forming quality of the weld, thereby achieving single-layer, single-pass welding of the weld. Furthermore, the welding current is attenuated when the welding torch rotates to 361° to ensure good overlap at the arc closing portion, thereby achieving single-layer, single-pass welding of the weld, reducing the difficulty of welding forming, improving the weld quality, and realizing automatic wire-filling welding of Canopy sealed welds between drive tube seats.

Description

Technical Field

[0001] The present invention relates to the field of nuclear power technology, and in particular to an automatic welding method for sealing welds of a control rod drive mechanism and upper and lower components thereof. Background Art

[0002] The reactor's control rod drive mechanism (CRDM) is a crucial servo mechanism in the reactor's control and protection system. Its primary function is to drive the control rod assembly up and down within the reactor core according to command, maintaining it at the commanded height. It also releases the assembly upon power failure, allowing it to quickly re-enter the core under gravity. This allows the reactor to start up, regulate power, maintain power, and perform normal and emergency shutdowns.

[0003] CRDM is generally composed of dozens of control rod assemblies, which are distributed on the top cover of the pressure vessel in a closely arranged manner, and the space between the control rod assemblies is very narrow, such as Figure 1 、 Figure 2 The spacing between adjacent control rod assemblies shown is only 114mm. The upper and lower parts of the control rod assembly are also called the upper assembly and the lower assembly. The upper and lower assemblies are connected by a sealing weld, and the sealing weld adopts a specially designed structure, called a canopy sealing weld or Ω weld. This type of Ω sealing weld is a nuclear safety level I weld and is an integral part of the reactor primary circuit system pressure boundary, which is related to the safe operation of the entire reactor. The canopy sealing weld is located in the middle of the upper and lower assemblies of each drive mechanism, and the welding space is small. Figure 1 、 Figure 2 At the same time, the groove thickness of the Canopy sealed weld is 2.35mm±0.05mm, and the groove gap is 1.2mm. Due to structural limitations, the welding difficulty of single-pass double-sided welding is relatively large. Figure 3 shown.

[0004] On other welds of pressure vessels, the difference in weld bead formation may not directly affect the welding quality, and subsequent welding can generally be adjusted by cleaning the weld bead. However, due to the thin thickness of the base material of the Canopy sealing weld, in order to prevent the base material from thinning, the weld bead cannot generally be trimmed after welding. Of course, there are technologies for surfacing and repairing sealing welds, but post-weld repair is not only complicated but also seriously affects the welding quality. Therefore, it is best for the sealing weld to be formed to pass in one go. In the past, Canopy sealing welds used a metal ring made of the same material as the base material pre-placed in the weld groove as filler metal, but the prefabricated filling ring needs to be customized, and is difficult to process and install. It is also difficult to adjust the weld bead formation, which affects the welding quality. Summary of the Invention

[0005] The problem solved by the present invention is the welding of the sealing weld between the upper and lower components of the control mechanism. The existing technology uses a method of pre-setting a metal ring made of the same material as the parent material in the weld groove as the filler metal for welding. However, the filling ring is difficult to process and install, and it is not easy to meet the one-time forming requirements.

[0006] To address at least one aspect of the above-mentioned problems, the present invention provides a method for automatically welding the sealed welds of the upper and lower components of a control rod drive mechanism. The method is based on a welding device comprising a welding gun, a filler wire device, and a backside protection device. The filler wire device is used to output welding wire, and the backside protection device is used to output shielding gas from the root of the drive tube seat. The method comprises:

[0007] Set the angle between the welding wire and the tungsten electrode of the welding gun to 65-75 degrees, the distance between the welding wire and the tungsten electrode to 2 mm, and the welding wire retraction distance to 8-10 mm;

[0008] After the welding gun supplies gas for 30 seconds, the back protection device supplies gas;

[0009] The back protection device starts arcing after supplying air for 200s;

[0010] Rotating the welding gun, increasing the welding current in a slowly varying current form, and performing welding along the circumferential direction of the surface to be welded to form an annular weld;

[0011] When the welding current increases to a preset value, the wire filling device starts feeding wire, and when the welding gun rotates to 300°, the back protection device stops supplying gas, and after the welding gun rotates to 357°, the welding current is increased to continue welding;

[0012] After the welding gun rotates to 361 degrees, the welding current is controlled to decay, and the wire filling device is controlled to retract the welding wire;

[0013] The welding gun stops rotating;

[0014] The welding gun stops supplying gas.

[0015] Preferably, when the arc is struck, the arc striking speed is 300 mm / min, the arc striking current is 30 A, the welding gun is lifted to a height of 2.5 mm, the lifting speed is 500 mm / min, and the arc striking current is 65 A.

[0016] Preferably, the welding gun rotates at a speed of 110 mm / min.

[0017] Preferably, the total time of the slowly varying current is 3s, the peak pulse current after 3s is 114A, the peak pulse time is 400ms, the base pulse current is 58A, and the base pulse time is 400ms.

[0018] Preferably, the peak wire feeding speed of the wire filling device is 1800 mm / min, and the base wire feeding speed is 1000 mm / min.

[0019] Preferably, during the welding process, the welding gun maintains a swinging state. When the welding gun deflects downward, the relative lateral deviation distance is 1.6 mm, and the relative lateral deviation speed is 500 mm / min; when the welding gun deflects upward, the relative lateral deviation distance is 0.8 mm, and the relative lateral deviation speed is 500 mm / min.

[0020] Preferably, the increasing of the welding current after the welding gun rotates to 357° includes: a peak pulse current of the welding current is 128A, a peak pulse time is 400ms, a base pulse current is 68A, and a base pulse time is 400ms.

[0021] Preferably, the welding current decay time is 8s and the cut-off current is 15A.

[0022] Preferably, the welding gun stops supplying gas 20 seconds after the welding gun stops rotating.

[0023] The advantages of the automatic welding method for sealing welds of upper and lower components of the control rod drive mechanism of the present invention over the prior art are:

[0024] The present invention sets the angle and distance between the welding wire and the tungsten electrode to 65-75° and 2mm respectively, and the welding wire retraction distance to 8-10mm to ensure the one-time forming requirement of the weld, and delivers welding gas in advance to avoid oxidation of the welding material, and ensures the back forming requirement of the weld by delivering the back shielding gas, and stops the supply of the back shielding gas when the welding gun is rotated to 300° to prevent the gas volume at the root of the weld from being large, which affects the final forming quality of the weld, thereby realizing single-layer single-pass welding of the weld, and starts to attenuate the welding current when the welding gun is rotated to 361°, and welds 1.4mm more at the arc closing part to ensure good overlap at the arc closing part. Therefore, this embodiment not only realizes the automatic filling wire welding of the Canopy sealing weld between the driving tube seats by adjusting the welding wire angle and setting the distance, setting the welding program, and setting the back protection device and the gas supply timing, but also reduces the difficulty of welding forming, and can realize single-layer single-pass welding of the weld with high weld quality.

[0025] The present invention also provides a control rod drive mechanism, comprising a drive mechanism upper assembly and a drive mechanism lower assembly, wherein the sealing weld between the drive mechanism upper assembly and the drive mechanism lower assembly is welded using the automatic welding method for sealing welds of upper and lower assemblies of the control rod drive mechanism.

[0026] The advantages of the control rod drive mechanism of the present invention over the prior art are the same as the advantages of the automatic welding method for sealing welds of upper and lower components of the control rod drive mechanism over the prior art, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a distribution diagram of the control panel drive mechanism of the reactor pressure vessel in an embodiment of the present invention;

[0028] Figure 2 Schematic diagram of the distance between the drive mechanisms in an embodiment of the present invention;

[0029] Figure 3 Schematic diagram of the sealing welds of the upper and lower components of the drive mechanism in an embodiment of the present invention;

[0030] Figure 4 This is a flow chart of an automatic welding method for sealing welds of upper and lower components of a control rod drive mechanism according to an embodiment of the present invention;

[0031] Figure 5 Schematic diagram of the angle and distance between the welding wire and the tungsten electrode in an embodiment of the present invention;

[0032] Figure 6 Schematic diagram of the inflation of the back protection device in an embodiment of the present invention;

[0033] Figure 7 This is a welding flow chart of the Canopy sealing weld in an embodiment of the present invention.

[0034] Description of reference numerals:

[0035] 1- upper assembly of the driving mechanism; 2- lower assembly of the driving mechanism; 3- sealing weld. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0037] like Figure 4 As shown, an embodiment of the present invention provides a method for automatically welding the sealed welds of the upper and lower components of a control rod drive mechanism, based on a welding device, the welding device including a welding gun, a wire filler device, and a back protection device, the wire filler device being used to output welding wire, and the back protection device being used to output shielding gas from the root of the drive tube seat; the method comprising:

[0038] Set the angle between the welding wire and the tungsten electrode of the welding gun to 65-75 degrees, the distance between the welding wire and the tungsten electrode to 2 mm, and the welding wire retraction distance to 8-10 mm;

[0039] After the welding gun supplies gas for 30 seconds, the back protection device supplies gas;

[0040] The back protection device starts arcing after supplying air for 200s;

[0041] Rotating the welding gun, increasing the welding current in the form of a slowly varying current, and welding along the circumferential direction of the surface to be welded to form an annular weld; it can be understood that the surface to be welded is the area between the upper component of the control mechanism and the lower component of the control mechanism;

[0042] When the welding current increases to a preset value, the wire filling device starts feeding wire, and when the welding gun rotates to 300°, the back protection device stops supplying gas, and after the welding gun rotates to 357°, the welding current is increased to continue welding;

[0043] After the welding gun rotates to 361 degrees, the welding current is controlled to decay, and the wire filling device is controlled to retract the welding wire;

[0044] The welding gun stops rotating;

[0045] The welding gun stops supplying gas.

[0046] This embodiment utilizes welding equipment equipped with a wire-feeding device. Based on the welding program settings, this device automatically fills the sealant welds of the upper and lower components of the control rod drive mechanism with wire-feeding. Parameters such as the wire feed position angle and speed can be adjusted to meet weld formation requirements. This welding equipment can meet the requirements of welding in small spaces, and its pneumatic clamping ensures stability.

[0047] Through the welding process of this embodiment, especially the various parameters involved, the effect of single-layer, single-pass welding of the sealing welds of the upper and lower components of the control rod drive mechanism can be achieved. Specifically, Figure 5 As shown in the figure, first set the angle and spacing parameters between the welding wire and the tungsten electrode, where the angle between the welding wire and the tungsten electrode is as follows: Figure 5 As shown in C, it is 65-75 degrees, the distance between the welding wire and the tungsten electrode is 2mm, and the welding wire retraction distance is 8-10mm. The so-called welding wire retraction distance refers to the distance between the welding wire output by the wire filling device and the surface to be welded or the welding point to be welded. Figure 5 As shown in S, the distance between the welding wire and the tungsten electrode refers to the distance between the end of the welding wire and the tip of the tungsten electrode above the surface to be welded when the welding wire is extended to the surface to be welded. Figure 5 As shown in D.

[0048] In this embodiment, the welding gun pre-sends gas 30 seconds in advance to blow away the air at the welding position and prevent oxidation of the material during welding. At the same time, in order to ensure the back-side shaping requirements of the weld and avoid oxidation at the weld root, this embodiment also introduces shielding gas from the root of the driver tube seat to ensure the quality of the weld process. The process of using the back protection device to deliver shielding gas from the root of the driver tube seat is as follows: Figure 6In addition, in order to prevent a large amount of gas at the weld root from forming a positive pressure inside the weld and affecting the final quality of the weld, the back shielding gas supply is stopped when the welding torch rotates to 300°.

[0049] In this embodiment, since the sealing weld between the upper and lower components of the control rod drive mechanism is annular, the welding of a 360° annular weld is completed by rotating the welding gun. However, since the thickness of the base material is only 2.35 mm, the impact of the arc starting current can easily cause a gap in the arc starting position. Therefore, in this embodiment, when the welding gun is rotated to 361°, the welding current begins to decay. As a result, the arc ending position can be welded 1.4 mm more, thereby ensuring a good overlap at the arc ending position.

[0050] In summary, in order to solve the problem of difficulty in forming the double-sided weld in a single pass due to structural limitations of the sealing weld between the upper and lower components of the control rod drive mechanism, this embodiment sets the angle and distance between the welding wire and the tungsten electrode to 65-75° and 2mm respectively, and the welding wire retraction distance is set to 8-10mm to ensure the one-time formation requirement of the weld. The welding gas is delivered in advance to avoid oxidation of the welding material, and the back-side shielding gas is delivered to ensure the back-side formation requirement of the weld. The back-side shielding gas supply is stopped when the welding torch rotates to 300° to prevent the gas volume at the root of the weld from accumulating. It is large, which affects the final forming quality of the weld, thereby realizing single-layer and single-pass welding of the weld, and by starting to attenuate the welding current when the welding gun is rotated to 361°, 1.4mm more is welded at the arc closing part to ensure good overlap at the arc closing part. Therefore, this embodiment adjusts the angle of the welding wire and sets the distance, sets the welding program, and sets the back protection device and the gas supply timing, etc., not only realizes the automatic filling wire welding of the Canopy sealing weld between the drive tube seats, but also reduces the difficulty of welding forming, can realize single-layer and single-pass welding of the weld, and improves the weld quality.

[0051] In some of the embodiments, the method further comprises: cleaning the surface to be welded so that there are no welding impurities on the surface of the surface to be welded and the surrounding area.

[0052] In some of the embodiments, the back protection device mainly supplies protective gas, and the arc is struck 200s after the gas is supplied, wherein the relevant parameters of the arc striking are as follows: the arc striking speed is 300mm / min, the arc striking current is 30A, the welding gun lifting height is 2.5mm, the lifting speed is 500mm / min, and the arc striking current is 65A.

[0053] In some embodiments, during welding, the welding gun remains in a swinging state. When the welding gun deflects downward, the relative lateral deviation distance is 1.6 mm, and the relative lateral deviation speed is 500 mm / min; when the welding gun deflects upward, the relative lateral deviation distance is 0.8 mm, and the relative lateral deviation speed is 500 mm / min.

[0054] In some embodiments, the welding gun rotates at a speed of 110 mm / min.

[0055] In some embodiments, the total time of the ramp current is 3 seconds, and after 3 seconds, the peak pulse current is 114A, the peak pulse time is 400ms, the base pulse current is 58A, and the base pulse time is 400ms. In this embodiment, the peak pulse current and the base pulse current are alternated, each lasting 400ms for a total of 3 seconds, that is, after 3 seconds, the peak pulse current and the base pulse current increase to 14A and 58A, respectively.

[0056] In some embodiments, the peak wire feeding speed of the wire filling device is 1800 mm / min, and the base wire feeding speed is 1000 mm / min.

[0057] In some embodiments, the welding torch stops supplying gas 20 seconds after the torch stops rotating. In this embodiment, the delayed shutoff of the welding gas is primarily due to the fact that the weld material is at a high temperature after welding. If the welding gas is shut off immediately, air may come into contact with the weld material, causing oxidation. Therefore, in this embodiment, the welding gas is shut off 20 seconds after welding to prevent the high-temperature weld material from coming into contact with air, which could affect weld quality.

[0058] In some embodiments, increasing the welding current after the welding gun rotates to 357° includes: the peak pulse current of the welding current is 128A, the peak pulse time is 400ms, the base pulse current is 68A, and the base pulse time is 400ms.

[0059] In some implementation methods, the welding current decay time is 8s and the cut-off current is 15A.

[0060] In some of the embodiments, the welding equipment is also equipped with a video monitoring system and a data acquisition system to achieve remote welding quality control and meet the welding requirements of the Canopy sealing weld between the drive tube sockets.

[0061] For detailed procedures of Canopy sealing weld, see Figure 7As shown in the figure, the welding equipment is first installed and aligned. The welding gun is then pre-delivered with welding gas to purge the air around the welding position to prevent oxidation of the weld material. Back shielding gas is then supplied through the back shielding device. After 200 seconds of gas supply, the arc is struck and the workpiece is brought into contact with the weld surface at a speed of 300 mm / min. Arc initiation is achieved at a starting current of 30A, with the torch lift height and speed controlled at 2.5 mm and 500 mm / min, respectively. Arc initiation is completed at a starting current of 65A. The torch is then swung downward, with a lateral deviation of 1.6 mm and a speed of 500 mm / min. After 1.5 seconds, the welding current is increased in a slowly varying manner. The torch is then swung upward, with a lateral deviation of -0.8 mm and a speed of 500 mm / min, respectively. The -0.8 mm here refers to the position of the torch when it is deflected downward. The two offsets are opposite, hence the negative sign to distinguish them. Rotate the welding gun at a speed of 110mm / min, and start to increase the welding current. Weld along the circumferential direction of the surface to be welded. The welding current increases slowly in a pulsed manner. The peak pulse time and base pulse time are both 400ms. After 3s, the peak pulse current and base pulse current increase to 114A and 58A respectively. After the welding current reaches the preset value, wire feeding begins. That is, wire feeding begins after the peak pulse current and base pulse current reach 114A and 58A respectively. When feeding wire, the peak wire feeding speed and base wire feeding speed are controlled to be 1800mm / min and 1000mm / min respectively. The so-called peak wire feeding speed refers to the wire feeding speed of 1800mm / min when the welding current is the peak pulse current, and the so-called base wire feeding speed refers to the wire feeding speed of 1000mm / min when the welding current is the base pulse current. Start AVC (automatic voltage control) tracking and control the arc voltage to 10.2V. After rotating to 357°, the current increased, reaching a peak current of 128A with a peak pulse duration of 400ms and a base current of 68A with a base pulse duration of 400ms. AVC was stopped, and at 361°, the welding current began to decay, decreasing to 15A within 8 seconds. At 15A, the current was cut off, and wire retraction was controlled. No pulse current was applied during wire retraction, and the wire feed speed was 2500mm / min with a displacement of 12mm. Finally, the welding torch was stopped, and gas supply to the torch was stopped after 20 seconds.

[0062] This embodiment provides a method for automatic wire-filling welding of the sealing welds of the upper and lower components of a control rod drive mechanism, which can implement automatic wire-filling welding of the Canopy sealing welds between the drive tube seats, and reduce the difficulty of welding and improve the quality of the welds by adjusting the angle and distance of the welding wire, setting the welding program, and setting the back protection device and the gas supply timing.

[0063] An embodiment of the present invention also provides a control rod drive mechanism, comprising a drive mechanism upper assembly and a drive mechanism lower assembly, wherein the sealing weld between the drive mechanism upper assembly and the drive mechanism lower assembly is welded using the automatic welding method for sealing welds of upper and lower assemblies of the control rod drive mechanism.

[0064] Although the present invention is disclosed as above, the scope of protection disclosed by the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for automatically welding the sealing seams of the upper and lower components of a control rod drive mechanism, characterized in that: Based on the welding equipment, the welding equipment includes a welding gun, a wire filling device and a back protection device, the wire filling device is used to output welding wire, and the back protection device is used to output shielding gas from the root of the driving pipe seat; The automatic welding method for sealing welds of upper and lower components of the control rod drive mechanism comprises: The angle between the welding wire and the tungsten electrode of the welding gun is set to 65-75 degrees, the distance between the welding wire and the tungsten electrode is set to 2 mm, and the welding wire retraction distance is set to 8-10 mm; After the welding gun supplies gas for 30 seconds, the back protection device supplies gas; The back protection device starts arcing after supplying air for 200s; Rotating the welding gun, increasing the welding current in a slowly varying current form, and performing welding along the circumferential direction of the surface to be welded to form an annular weld; When the welding current increases to a preset value, the wire filling device starts feeding wire, and when the welding gun rotates to 300°, the back protection device stops supplying gas, and after the welding gun rotates to 357°, the welding current is increased to continue welding; After the welding gun rotates to 361 degrees, the welding current is controlled to decay, and the wire filling device is controlled to retract the welding wire; The welding gun stops rotating; The welding gun stops supplying gas.

2. The automatic welding method for sealing welds of upper and lower components of a control rod drive mechanism according to claim 1, characterized in that: When the arc is struck, the arc striking speed is 300 mm / min, the arc striking current is 30 A, the welding gun is lifted to a height of 2.5 mm, the lifting speed is 500 mm / min, and the arc striking current is 65 A.

3. The automatic welding method for sealing welds of upper and lower components of a control rod drive mechanism according to claim 1, characterized in that: The welding gun rotates at a speed of 110 mm / min.

4. The automatic welding method for sealing welds of upper and lower components of a control rod drive mechanism according to claim 1, characterized in that: The total time of the slowly varying current is 3s, the peak pulse current after 3s is 114A, the peak pulse time is 400ms, the base pulse current is 58A, and the base pulse time is 400ms.

5. The automatic welding method for sealing welds of upper and lower components of a control rod drive mechanism according to claim 1, characterized in that: The peak wire feeding speed of the wire filling device is 1800 mm / min, and the base wire feeding speed is 1000 mm / min.

6. The automatic welding method for sealing welds of upper and lower components of a control rod drive mechanism according to claim 1, characterized in that: During the welding process, the welding gun remains in a swinging state. When the welding gun deflects downward, the relative lateral deviation distance is 1.6 mm, and the relative lateral deviation speed is 500 mm / min; when the welding gun deflects upward, the relative lateral deviation distance is 0.8 mm, and the relative lateral deviation speed is 500 mm / min.

7. The automatic welding method for sealing welds of upper and lower components of a control rod drive mechanism according to claim 1, characterized in that: The increasing of the welding current after the welding gun rotates to 357° includes: the peak pulse current of the welding current is 128A, the peak pulse time is 400ms, the base pulse current is 68A, and the base pulse time is 400ms.

8. The automatic welding method for sealing welds of upper and lower components of a control rod drive mechanism according to claim 1, characterized in that: The welding current decay time is 8s and the cut-off current is 15A.

9. The automatic welding method for sealing welds of upper and lower components of a control rod drive mechanism according to claim 1, characterized in that: After the welding gun stops rotating for 20 seconds, the welding gun stops supplying gas.

10. A control rod drive mechanism, characterized in that: The control rod drive mechanism comprises an upper assembly and a lower assembly, wherein the sealing weld between the upper assembly and the lower assembly is welded by the automatic welding method for sealing welds of upper and lower assemblies of the control rod drive mechanism according to any one of claims 1 to 9.

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