Method for welding impeller of primary helium fan

Abstract

The invention belongs to the technical field of primary helium fans, and particularly relates to a primary helium fan impeller welding method. The impeller welding method comprises the following steps that an impeller disc and a lower blade are integrally formed, an impeller cover and an upper blade are integrally formed, and grooves are machined in the two sides, close to an interface, of the upper blade and the two sides, close to the interface, of the lower blade; any section of the groove is provided with a large groove on the first surface welding side and a small groove on the back gouging side; in the streamline direction of the blade, the two sides of the blade are each of a crossed structure with a large groove and a small groove; a lengthened and slender welding torch is adopted, and welding is conducted on the groove of the blade through gas metal arc welding or tungsten inert gas arc welding; a vacuum furnace is adopted for heating during welding, and inert gas is adopted for cooling after welding. According to the welding method for the main helium fan impeller, welding deformation of a thin plate is controlled, the welding quality is guaranteed in a long, narrow and twisted runner, and the effect that the surface of the main impeller runner is not treated any more after heat treatment is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of main helium blower, and particularly relates to a main helium blower impeller welding method. BACKGROUND

[0002] The high-temperature gas cooled reactor is an advanced fourth generation nuclear power reactor technology, and has the advantages of good safety, high efficiency, good economy and wide application. The high-temperature gas cooled reactor primary loop device mainly includes four components of a reactor, a hot gas duct, a main helium blower and a steam generator. The main helium blower is a single-stage vertical centrifugal compressor, the driving motor is coaxial with the blower impeller, and is installed above the steam generator. The function of the main helium blower is to drive the helium gas of the high-temperature gas cooled reactor primary loop to flow through the reactor core, and to provide sufficient flow of helium through the primary loop system to carry away the heat generated by the reactor core under the conditions of normal start, power operation and shutdown of the reactor.

[0003] In order to realize the function of carrying away the heat generated by the reactor core, the pressure rise of the main impeller needs to reach 200kPa, and the operating parameters need to vary in a large range, including the primary loop pressure (1.0-7.0MPa), the inlet medium temperature (20-243℃) and the flow range (20-105%). The main impeller needs to continuously operate at any speed within 120% of the rated speed, and the breaking speed should be more than 140% of the rated speed.

[0004] In order to ensure the use requirements of the main impeller, the design, material and quality requirements are extremely high, and the welding manufacturing is extremely difficult, which is specifically embodied as follows: Firstly, the main impeller has 17 blades, the operation space is extremely small, the welding operation is difficult, and a very delicate welding structure needs to be used, and the blade is thin (the maximum thickness is 10mm) and easy to deform.

[0005] Secondly, the main impeller is made of martensitic precipitation hardening stainless steel, the strength is more than 1000MPa, the material weldability is poor, and the cracking risk is high.

[0006] Thirdly, the material has poor as-welded performance, and special heat treatment of solid solution + aging must be carried out after welding to ensure the performance, that is, the blade cannot be repaired after heat treatment, a new heat treatment process needs to be researched, and the polishing operation of the flow channel after heat treatment needs to be reduced as much as possible to avoid the generation of new defects.

[0007] Fourthly, the rated speed of the main impeller is 3800r / min, and the quality requirement of the welding seam is very high. The internal quality of the whole welding seam needs to be examined, and the existing radiographic testing (RT) and ultrasonic testing (UT) cannot meet the requirements, so a new detection method needs to be explored. SUMMARY

[0008] In order to solve the above problems existing in the prior art, the purpose of the present application is to provide a main helium fan impeller welding method, which controls the welding deformation of the thin plate, ensures the welding quality in the narrow and twisted flow channel, and achieves the effect that the surface of the main impeller flow channel does not need to be treated after heat treatment.

[0009] The technical scheme adopted by the present application is: A main helium fan impeller welding method, comprising the following steps: The impeller disc is integrally formed with the lower blade, and the impeller cover is integrally formed with the upper blade; the upper blade and the lower blade are both processed with a groove on both sides near the boundary surface; Any section of the groove is a large groove on the first welding side and a small groove on the root face; along the flow line direction of the blade, both sides of the blade are the intersection structure of the large groove and the small groove; A lengthened and slender welding torch is used to perform welding at the groove of the blade by using gas shielded welding or tungsten inert gas welding; A vacuum furnace is used for heating during welding, and inert gas is used for cooling after welding.

[0010] Any section of the groove of the present application is a large groove on the first welding side and a small groove on the root face; along the flow line direction of the blade, both sides of the blade are the intersection structure of the large groove and the small groove. The present application specially designs the form of the groove, and the residual stress is low and the dimensional accuracy is high after welding, which solves the problem of cracking of the weld in the welding process due to the extremely low toughness of the weld in the as-welded state (impact energy less than 10 J), solves the problem of difficult deformation control of the thin plate (the maximum thickness of the blade is 10 mm), and realizes the technical requirement of 1.3 mm dimensional tolerance of the main impeller welding.

[0011] The present application uses a light, slender and flexible welding torch and corresponding welding operation technology to solve the problem of long-time, long-distance and stable operation of the welding torch in the narrow and twisted flow channel, and realizes high-quality welding of the main impeller, with a one-time flaw detection qualified rate of 98%.

[0012] The present application uses the solid solution + aging heat treatment process of the super-large vacuum furnace to solve the problem of serious oxidation (the thickness of the oxidation layer can reach 1-2 mm) of the flow channel surface caused by high temperature (1040℃) during conventional solid solution treatment, solves the problem of difficult control of the furnace temperature of the super-large vacuum furnace (furnace size 1.5m) (quenching is necessary for solid solution, otherwise the material performance cannot meet the requirements), solves the problem of deformation of the main impeller caused by high-temperature softening of the material and quenching stress, and achieves the effect of ensuring the mechanical properties of the welded joint and the final size of the main impeller.

[0013] As a preferred scheme of the present application, the impeller disc and the impeller cover are positioned by positioning pins before welding. In order to ensure the accurate assembly position of the impeller disc and the impeller cover during assembly, the positioning pins are used for positioning. If the welding size of the impeller is larger than the machining size, the positioning pins are arranged at the position where the size is increased.

[0014] As a preferred scheme of the present application, the impeller is cubed or rotated by using a roller frame during welding at different positions, so as to ensure that the welding position is always in the flat welding or vertical welding position which is most beneficial to welding.

[0015] The present application adopts low-restraint welding, and the welding stress is released through welding deformation. The impeller is cubed or rotated by using a roller frame, so as to ensure that the impeller is always in the flat welding / vertical welding position which is most beneficial to welding during welding, and to reduce the influence of the self-weight of the main impeller. The toughness of the joint is very low in the as-welded state, and the impeller must be welded under low-restraint conditions, so no process materials such as supports are arranged, and only a positioning weld is arranged after assembly, and the positioning pins used for assembly will also be removed later.

[0016] As a preferred scheme of the present application, the axial deformation during welding is compensated by the reverse deformation amount, and the harmful deformation (such as the rotational angle deformation) is eliminated by a reasonable welding sequence. The welding sequence needs to consider the influence of the welding operation space, and the welding is performed as symmetrically as possible.

[0017] As a preferred scheme of the present application, the welding sequence is determined by considering the influence of the welding operation space and satisfying the symmetric welding.

[0018] As a preferred scheme of the present application, the deformation of welding and heat treatment during welding is compensated by the reverse deformation amount.

[0019] As a preferred scheme of the present application, the reverse deformation amount of 1 mm in the blade height direction is set during welding, and the actual profile tolerance requirement can be met at this time.

[0020] As a preferred scheme of the present application, a flexible welding torch is used for welding. The flexible welding torch has the characteristics that the angle between the tungsten electrode and the gun barrel is large enough, the tungsten electrode is short enough, the gun barrel is long enough, the gun barrel has a certain plasticity, can be bent in the runner according to the profile, and can maintain the shape after bending.

[0021] As a preferred scheme of the present application, after welding, the impeller is in an upside-down state with the impeller cover below the impeller disc during heat treatment, so as to reduce the influence of gravity.

[0022] As a preferred scheme of the present application, martensitic precipitation hardening stainless steel is used for equal strength matching welding during welding. The equal strength matching welding technology of martensitic precipitation hardening stainless steel solves the problem that the low matching technology is generally used for welding the martensitic precipitation hardening stainless steel in the industry, and realizes the mechanical properties of the welded joint which are equivalent to those of the parent material forging, and reaches the design index of 1029 MPa.

[0023] The beneficial effects of this invention are as follows: 1. In this invention, any segment of the bevel has a large bevel on the welding side and a small bevel on the root cleaning side; along the blade streamline direction, both sides of the blade have a cross structure of large and small bevels. This invention features a special design for the bevel form, resulting in low residual stress and high dimensional accuracy after welding. It solves the problem of weld cracking during welding due to the extremely low toughness of the weld in the weld state (impact energy not exceeding 10J), and solves the problem of difficult deformation control when welding thin plates (blade thickness maximum 10mm), achieving the technical requirement of a 1.3mm welding dimensional tolerance for the main impeller.

[0024] 2. This invention uses a lightweight, slender, and flexible welding torch and corresponding welding operation technology to solve the problem of stable operation of the welding torch for a long time and distance in narrow and twisted flow channels, and achieves high-quality welding of the main impeller with a first-pass flaw detection pass rate of 98%.

[0025] 3. This invention employs a solution treatment + aging heat treatment process in an ultra-large vacuum furnace, which solves the problem of severe oxidation on the flow channel surface (with an oxide layer thickness of 1-2 mm) caused by high temperature (1040℃) during conventional solution treatment. It also solves the problem of difficult temperature control in ultra-large vacuum furnaces (furnace chamber size 1.5m) (solution treatment requires rapid cooling, otherwise the material properties will not meet the requirements), and solves the problem of main impeller deformation caused by high-temperature softening and rapid cooling stress of the material. This achieves the effect of ensuring the mechanical properties of the welded joint and the final dimensions of the main impeller. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the blade structure; Figure 3 yes Figure 2 Sectional view at point A in the middle; Figure 4 yes Figure 2 Sectional view at point B; Figure 5 This is a schematic diagram of the blade welding sequence.

[0027] In the diagram: 1-Impeller disk; 2-Lower blade; 3-Impeller cover; 4-Upper blade; 5-Bevel. Detailed Implementation

[0028] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0030] As shown in Figure 1 The main helium blower impeller welding method of the present embodiment includes the following steps: the impeller disc 1 is integrally formed with the lower blade 2, the impeller cover 3 is integrally formed with the upper blade 4, and the upper blade 4 and the lower blade 2 are both processed with a bevel 5 on both sides near the boundary interface. The present application adopts a lengthened slender welding torch to perform welding at the bevel 5 of the blade by gas shielded welding or tungsten inert gas welding to meet the requirements of welding in the flow channel, and the welding method is GTAW. The vacuum furnace is used for heating during welding, and inert gas is used for cooling after welding to avoid oxidation of the surface of the impeller flow channel, so that the surface of the main impeller flow channel after heat treatment is no longer treated.

[0031] As shown in Figures 2-4 The bevel 5 of the blade is designed as an asymmetric size bevel, and any section of the bevel 5 is large on the first side for welding and small on the root face side to ensure uniform welding amount on both sides. The blade must be welded in sections, so along the flow line direction of the blade, both sides of the blade are the cross structure of large bevel and small bevel.

[0032] Any section of the bevel 5 of the present application is large on the first side for welding and small on the root face side, and along the flow line direction of the blade, both sides of the blade are the cross structure of large bevel and small bevel. The present application specially designs the form of the bevel 5, so that the residual stress after welding is low and the dimensional accuracy is high, solving the problem of cracking of the weld in the welding process due to the extremely low toughness of the weld in the as-welded state (impact energy not more than 10 J), solving the problem of difficult deformation control in thin plate (blade thickness maximum 10 mm) welding, and realizing the technical requirement of 1.3 mm dimensional tolerance of the main impeller welding.

[0033] The present application adopts light, slender, flexible welding torch and corresponding welding operation technology, solves the problem of long time, long distance and stable operation of welding torch in narrow and twisted flow channel, realizes high quality welding of main impeller, and the first time flaw detection qualified rate reaches 98%.

[0034] The present application adopts solid solution + aging heat treatment process of super large vacuum furnace, solves the problem of serious surface oxidation (the thickness of oxidation layer can reach 1-2mm) caused by high temperature (1040℃) during conventional solid solution treatment, solves the problem of difficult control of furnace temperature of super large vacuum furnace (furnace size 1.5m) (solid solution must be rapidly cooled, otherwise the material performance cannot meet the requirements), solves the problem of deformation of main impeller caused by high temperature softening and rapid cooling stress of material, and achieves the effect of guaranteeing the mechanical properties of welded joint and the final size of main impeller.

[0035] Further, before welding, the impeller disc 1 and the impeller cover 3 are positioned by positioning pins. In order to ensure the accurate assembly position of the impeller disc 1 and the impeller cover 3 during assembly, the positioning pins are used for positioning. The welding size of the impeller is larger than the machining size, and then the positioning pins are arranged at the increased position.

[0036] When welding different positions, the impeller is cubed or rotated by using a roller frame, so that the welding position is always in the flat welding or vertical welding position which is most beneficial to welding.

[0037] The present application adopts low restraint degree welding, and the welding stress is released through welding deformation. The roller frame is used to cube or rotate the impeller, so that the impeller is always in the flat welding / vertical welding position which is most beneficial to welding during welding, and the influence of the self weight of the main impeller is reduced. The toughness of the joint is very low in the as-welded state, and the impeller must be welded under low restraint condition, so no process materials such as supports are arranged, and only positioning welding is carried out after assembly. The positioning pins used for assembly will also be removed thereafter.

[0038] During welding, the axial deformation is compensated by the reverse deformation amount, and the harmful deformation (such as rotation angle deformation) is eliminated by reasonable welding sequence. The welding sequence needs to consider the influence of welding operation space and symmetrical welding as much as possible.

[0039] As shown in Figure 5 , the welding sequence considers the influence of welding operation space and meets the symmetrical welding. Figure 5 , welding is carried out in the order of a, b, c and d.

[0040] During welding, the deformation of welding and heat treatment is compensated by the reverse deformation amount. When the reverse deformation amount in the blade height direction is 1mm, the actual profile tolerance requirement can be met.

[0041] The present application adopts a flexible welding torch to carry out welding. The flexible welding torch meets the following characteristics: the angle between the tungsten electrode and the gun barrel is large enough, the tungsten electrode is short enough, the gun barrel is long enough, the gun barrel has a certain plasticity, can be bent in the flow channel, and can keep the shape after bending.

[0042] After welding, the impeller is in an upside-down state with the impeller cover 3 below the impeller disc 1 during heat treatment, so as to reduce the influence of gravity.

[0043] During welding, martensitic precipitation hardening stainless steel material is used for equal strength matching welding. The equal strength matching welding technology of martensitic precipitation hardening stainless steel solves the problem that the low matching technology is generally used to weld the martensitic precipitation hardening stainless steel in the industry, realizes the mechanical properties of the welded joint and the parent material forging, and reaches the design index of 1029 MPa.

[0044] The present application is not limited to the above optional embodiments, and anyone can derive other various forms of products under the inspiration of the present application, but regardless of any changes in shape or structure, any technical solution falling within the scope defined by the claims of the present application falls within the protection scope of the present application.

Claims

1. A method for welding the impeller of a main helium blower, characterized in that: Includes the following steps: The impeller disk (1) and the lower blade (2) are integrally formed, the impeller cover (3) and the upper blade (4) are integrally formed, and the upper blade (4) and the lower blade (2) are both beveled (5) on both sides near the interface. On any segment of the bevel (5), the welding side on the first surface is a large bevel and the root cleaning side is a small bevel; along the blade streamline direction, both sides of the blade are a cross structure of large bevel and small bevel. Welding was performed at the bevel (5) of the blade using an extended and thin welding torch and by gas metal arc welding or tungsten inert gas welding. A vacuum furnace is used for heating during welding, and an inert gas is used for cooling after welding.

2. The welding method for a main helium blower impeller according to claim 1, characterized in that: Before welding, the impeller disc (1) and impeller cover (3) are positioned by locating pins.

3. The welding method for a main helium blower impeller according to claim 1, characterized in that: When welding different positions, use a roller frame to make the impeller square or rotate to ensure that the welding position is always in the most favorable flat or vertical welding position.

4. The method for welding a main helium blower impeller according to claim 1, characterized in that: During welding, axial deformation is compensated by reverse deformation, and harmful deformation is eliminated by a set welding sequence.

5. The method for welding a main helium blower impeller according to claim 4, characterized in that: The welding sequence is determined by taking into account the influence of the welding operation space and ensuring symmetrical welding.

6. The welding method for a main helium blower impeller according to claim 1, characterized in that: During welding, the deformation caused by welding and heat treatment is compensated by the amount of reverse deformation.

7. The method for welding a main helium blower impeller according to claim 6, characterized in that: Set the welding anti-deformation amount in the blade height direction to 1mm.

8. The method for welding a main helium blower impeller according to claim 1, characterized in that: Welding is performed using a flexible welding torch.

9. The method for welding a main helium blower impeller according to claim 1, characterized in that: After welding, during heat treatment, the impeller is in an upside-down state with the impeller cover (3) below the impeller disk (1).

10. A method for welding a main helium blower impeller according to any one of claims 1 to 9, characterized in that: During welding, martensitic precipitation hardening stainless steel is used for equal strength matching welding.

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