Circular seam robot welding method for ultrathin-wall and thick-wall components of nuclear reactor coolant pump

Abstract

The invention relates to a nuclear reactor coolant pump ultra-thin wall and thick wall part circular seam robot welding method, which comprises the following steps: establishing an ultra-thin wall and thick wall part circular seam welding unit, grabbing a welding head by adopting a six-axis robot arm, and matching with a purchased welding seam tightening tool and a mechanical tracking device; according to the method, welding of the through-welding groove of the annular part of the ultra-thin-wall and thick-wall component of the nuclear reactor coolant pump is completed, a six-axis robot arm is adopted to grab a welding machine head, and through-welding groove welding of the annular part of the stator shielding sleeve is completed in cooperation with a groove supporting tool and a welding seam tracking device according to reasonable process specifications. The brand-new ultra-thin-wall and thick-wall component circular seam robot welding unit is established, a great breakthrough is achieved on the basis of a circular seam welding method of the same type of structure, the row circle precision of a machine head is greatly improved, the operation difficulty is reduced, the construction period is shortened, and the welding quality stability is improved.

Description

[0001] Technical field: A robot welding method for annular seams of ultra-thin-wall and thick-wall components of a nuclear reactor coolant pump. Background technology:

[0002] The function of the nuclear main pump (RCP) is to force the coolant to circulate and transfer the heat generated in the reactor to the steam generator. The shielded RCP is a third-generation nuclear power manufacturing technology introduced by my country from the United States in 2008. It is a vertical, water-cooled, squirrel cage structure. The stator and rotor windings are isolated from the reactor coolant by the stator and rotor shielding sleeves. The chamber formed between the stator and rotor shielding sleeves is connected to the pump cavity to withstand the pressure of the reactor coolant system.

[0003] In recent years, nuclear main pump manufacturing technology has always been a reflection of the country's high-end manufacturing capabilities, and also represents the level of national strategic equipment manufacturing. In the manufacturing process of nuclear main pumps, high-precision, high-reliability, and high-safety precision thin-walled components are very critical, and the quality of welded joints needs to be improved.

[0004] As a key component of the shielded nuclear reactor coolant pump, the shielding sleeve has strict sealing performance and extremely high safety, stability and reliability requirements. The stator shielding sleeve ring seam is the most difficult weld among the shielding sleeve related welds, and it is urgent to optimize, upgrade and improve its process.

[0005] The stator shield ring seam is a typical ring seam structure of ultra-thin wall and thick wall parts. The traditional welding process is manual welding or special machine welding. The manual welding of ultra-thin wall parts is extremely difficult and the first-time pass rate is extremely low. The traditional special machine has a serious impact on the walking track of the welding head due to the track roundness accuracy problem, which is easy to cause welding problems such as welding deviation, incomplete penetration, and uneven weld width.

[0006] Invention content: The purpose of the present invention is to provide a method for robotic welding of annular seams of ultra-thin-wall and thick-wall components of a nuclear reactor coolant pump, which adopts a six-axis robot arm to grasp the welding head, and is matched with a groove support fixture and a weld tracking device to complete the groove welding of the annular part of the stator shield sleeve in accordance with reasonable process specifications.

[0007] The technical solution of the present invention is:

[0008] A method for robotic welding of annular seams of ultra-thin-wall and thick-wall components of a nuclear reactor coolant pump, (1) establishing an annular seam welding unit for ultra-thin-wall and thick-wall components, using a six-axis robot arm to grab a welding machine head, and using purchased weld seam tightening tooling and mechanical tracking devices to complete the penetration groove welding of annular portions of ultra-thin-wall and thick-wall components of a nuclear reactor coolant pump;

[0009] (2) The welding process uses a wire-filled pulse tungsten inert gas welding process to complete the welding;

[0010] (3) The weak-rigidity ultra-thin-walled parts made of nickel-based alloy with a thickness of less than 0.4 mm and the thick-walled parts made of stainless steel are tightly fitted by tightening the tooling to achieve an annular groove with no assembly gap, and the axial installation height difference between the ultra-thin-walled and thick-walled parts is controlled within 0.1 mm;

[0011] (4) Control of the circular motion accuracy of the welding head: A slide rail is installed at the end of the six-axis robot's terminal shaft. The slide rail is perpendicular to the terminal shaft. The welding head is installed on the slide rail. The head can adjust its position on the slide rail according to the diameter of the welded circumferential seam to meet the requirements of welds of different diameters. In order to further improve the circular motion accuracy of the head, a mechanical tracking device is installed on the head during the welding process. The top block on the mechanical tracking device contacts the inner wall processing surface of the thick-walled part and applies a part of the force. The circular motion trajectory of the head is further constrained during the welding process to ensure that the circular motion trajectory accuracy of the head is less than 0.3 mm when the robot's terminal shaft rotates.

[0012] (5) Carry out process evaluation and simulation test, formulate matching process parameters, and ensure stable arc combustion, good weld formation, and sufficient weld penetration. The specific parameters are pulse current 75-115A, base current 30-75A; welding voltage 7-12.5V; welding speed 50-152mm / min, base wire feeding speed 381-1016mm / min, and peak wire feeding speed 635-1270mm / min;

[0013] (6) Control of details such as arc starting current, arc ending current, tungsten electrode properties, relative position between welding wire and tungsten electrode, and overlap length of annular seam; the arc starting current is set to 20A to ensure arc starting while preventing the shielding sleeve from burning due to excessive instantaneous current; the arc ending current is set to 20A to facilitate a good transition with the arc starting end; the tungsten electrode is extended to 9.5mm in length and is deflected 10° from the vertical plane. At this angle, the arc has a stronger enveloping property on the shielding sleeve and the weld is smoother and fuller; the wire feeding position is 2.8mm away from the bottom of the tungsten electrode and is biased toward the outer circle on the tangent line of the circle. This feeding position can prevent the wire from slipping to the inner wall during welding; the robot's circle movement is set to 362° to compensate for the arc starting position.

[0014] Technical effects of the present invention:

[0015] The present invention innovatively adopts a unique method of driving the welding head to move in a circular motion by rotating the final shaft of the welding robot. In traditional special machine welding, due to the tolerance of the guide rail itself, this unavoidable factor will greatly reduce the circular motion accuracy of the head. The method of the present invention cleverly avoids this drawback. The rotation of the final shaft of the welding robot can more accurately control the motion trajectory of the head, and is no longer limited by the interference of the guide rail tolerance, thereby solving the problem of insufficient precision at the root, and greatly improving the accuracy of the head movement trajectory. This improvement in accuracy directly acts on the shielding sleeve annular seam welding process, significantly enhancing the stability of welding, and making the entire welding process more stable and reliable. Especially in the work of ultra-thin wall stator shielding sleeve annular seam welding, which requires extremely high precision, it can effectively prevent and control the risk of welding deviation, greatly reduce product quality problems caused by welding deviation, and provide a solid guarantee for the high-quality welding of products.

[0016] In addition, the present invention is also equipped with a mechanical tracking device. During the welding process, the walking stability of the machine head is precisely monitored and adjusted in real time. It can keenly sense any slight deviation of the machine head during its walking process, and make corrections in time to ensure that the machine head always moves along the predetermined optimal welding path. The use of this mechanical tracking device is another effective measure based on the precision improvement of the final axis rotation of the welding robot. It complements the former and jointly builds a dual guarantee system for welding quality. Under the protection of multiple lines of defense, the welding quality reaches a higher level.

[0017] Through the comprehensive application of the above series of innovative measures and technical means, the present invention has successfully explored and developed a new set of welding process technologies after repeated experiments, optimizations and improvements, reducing the welding defect rate to a minimum, and bringing major technological breakthroughs and innovations in the field of stator shield sleeve annular seam welding. It has extremely broad application prospects and significant economic and social benefits. Specific implementation method:

[0018] A method for robotic welding of annular seams of ultra-thin-wall and thick-wall components of a nuclear reactor coolant pump, (1) establishing an annular seam welding unit for ultra-thin-wall and thick-wall components, using a six-axis robot arm to grab a welding machine head, and using purchased weld seam tightening tooling and mechanical tracking devices to complete the penetration groove welding of annular portions of ultra-thin-wall and thick-wall components of a nuclear reactor coolant pump;

[0019] (2) The welding process uses a wire-filled pulse tungsten inert gas welding process to complete the welding;

[0020] (3) The weak-rigidity ultra-thin-walled parts made of nickel-based alloy with a thickness of less than 0.4 mm and the thick-walled parts made of stainless steel are tightly fitted by tightening the tooling to achieve an annular groove with no assembly gap, and the axial installation height difference between the ultra-thin-walled and thick-walled parts is controlled within 0.1 mm;

[0021] (4) Control of the circular motion accuracy of the welding head: A slide rail is installed at the end of the six-axis robot's terminal shaft. The slide rail is perpendicular to the terminal shaft. The welding head is installed on the slide rail. The head can adjust its position on the slide rail according to the diameter of the welded circumferential seam to meet the requirements of welds of different diameters. In order to further improve the circular motion accuracy of the head, a mechanical tracking device is installed on the head during the welding process. The top block on the mechanical tracking device contacts the inner wall processing surface of the thick-walled part and applies a part of the force. The circular motion trajectory of the head is further constrained during the welding process to ensure that the circular motion trajectory accuracy of the head is less than 0.3 mm when the robot's terminal shaft rotates.

[0022] (5) Carry out process evaluation and simulation test, formulate matching process parameters, and ensure stable arc combustion, good weld formation, and sufficient weld penetration. The specific parameters are pulse current 75-115A, base current 30-75A; welding voltage 7-12.5V; welding speed 50-152mm / min, base wire feeding speed 381-1016mm / min, and peak wire feeding speed 635-1270mm / min;

[0023] (6) Control of details such as arc starting current, arc ending current, tungsten electrode properties, relative position between welding wire and tungsten electrode, and overlap length of annular seam; the arc starting current is set to 20A to ensure arc starting while preventing the shielding sleeve from burning due to excessive instantaneous current; the arc ending current is set to 20A to facilitate a good transition with the arc starting end; the tungsten electrode is extended to 9.5mm in length and is deflected 10° from the vertical plane. At this angle, the arc has a stronger enveloping property on the shielding sleeve and the weld is smoother and fuller; the wire feeding position is 2.8mm away from the bottom of the tungsten electrode and is biased toward the outer circle on the tangent line of the circle. This feeding position can prevent the wire from slipping to the inner wall during welding; the robot's circle movement is set to 362° to compensate for the arc starting position.

Claims

1. A robot welding method for annular seams of ultra-thin-wall and thick-wall parts of a nuclear reactor coolant pump, characterized by: (1) Establish an ultra-thin-wall and thick-walled parts circumferential welding unit, use a six-axis robot arm to grab the welding head, and use the purchased weld tightening tooling and mechanical tracking device to complete the penetration groove welding of the annular part of the ultra-thin-wall and thick-walled parts of the nuclear reactor coolant pump; (2) The welding process uses a wire-filled pulse tungsten inert gas welding process to complete the welding; (3) The weak-rigidity ultra-thin-walled parts made of nickel-based alloy with a thickness of less than 0.4 mm and the thick-walled parts made of stainless steel are tightly fitted by tightening the tooling to achieve an annular groove with no assembly gap, and the axial installation height difference between the ultra-thin-walled and thick-walled parts is controlled within 0.1 mm; (4) Control of the circular motion accuracy of the welding head: A slide rail is installed at the end of the six-axis robot's terminal shaft. The slide rail is perpendicular to the terminal shaft. The welding head is installed on the slide rail. The head can adjust its position on the slide rail according to the diameter of the welded circumferential seam to meet the requirements of welds of different diameters. In order to further improve the circular motion accuracy of the head, a mechanical tracking device is installed on the head during the welding process. The top block on the mechanical tracking device contacts the inner wall processing surface of the thick-walled part and applies a part of the force. The circular motion trajectory of the head is further constrained during the welding process to ensure that the circular motion trajectory accuracy of the head is less than 0.3 mm when the robot's terminal shaft rotates. (5) Carry out process evaluation and simulation test, formulate matching process parameters, and ensure stable arc combustion, good weld formation, and sufficient weld penetration. The specific parameters are pulse current 75-115A, base current 30-75A; welding voltage 7-12.5V; welding speed 50-152mm / min, base wire feeding speed 381-1016mm / min, and peak wire feeding speed 635-1270mm / min; (6) Control of details such as arc starting current, arc ending current, tungsten electrode properties, relative position between welding wire and tungsten electrode, and overlap length of annular seam; the arc starting current is set to 20A to ensure arc starting while preventing the shielding sleeve from burning due to excessive instantaneous current; the arc ending current is set to 20A to facilitate a good transition with the arc starting end; the tungsten electrode is extended to 9.5mm in length and is deflected 10° from the vertical plane. At this angle, the arc has a stronger enveloping property on the shielding sleeve and the weld is smoother and fuller; the wire feeding position is 2.8mm away from the bottom of the tungsten electrode and is biased toward the outer circle on the tangent line of the circle. This feeding position can prevent the wire from slipping to the inner wall during welding; the robot's circle movement is set to 362° to compensate for the arc starting position.