A welded joint structure of a closed impeller of a martensitic stainless steel

Abstract

The utility model relates to closed type impeller technical field, concretely is a kind of martensitic stainless steel closed type impeller welded joint structure. Including the hub of integrally forming several blades, the front cover assembled with hub, and the reserved bevel corresponding with several blades one-to-one is equipped on front cover;Blade bottom is integrally formed on hub, and the top of blade is equipped with the plug-in boss for clamping into reserved bevel;Reserved bevel includes root straight slot and U-shaped bevel, the width of the bottom of U-shaped bevel is greater than the width of root straight slot, and the width of the top of U-shaped bevel is greater than the width of the bottom of U-shaped bevel;And the clearance fit between plug-in boss and root straight slot, the height of plug-in boss is consistent with the height of root straight slot;The width of plug-in boss is less than the width of blade.The utility model designs reserved bevel on front cover, and plug-in boss is designed on blade corresponding with reserved bevel;The welding structure greatly reduces the heat input of electric arc welding, reduces the problems such as blade deflection, front and rear disc eccentricity caused by welding.

Description

Technical Field

[0001] This utility model relates to the field of closed impeller technology, specifically a welded joint structure for a martensitic stainless steel closed impeller. Background Technology

[0002] Closed stainless steel impellers include a cover plate and a hub. The common method is to process a stainless steel forged billet into a hub, and the hub has blades integrally formed. The cover plate has a pre-reserved welding bevel. After the cover plate and hub are assembled, the parts are welded together by arc welding. During the arc welding process, the pre-reserved welding bevel will be filled.

[0003] Closed impellers have complex structures and limited welding space. Furthermore, different impeller models have different impeller covers and blade profiles, which can easily lead to large assembly gaps. Welding closed impellers is prone to defects such as weld misalignment, weld burn-through, undercut, and porosity, making welding quite difficult. Additionally, when the cover plate wall thickness is large, the depth of the weld bevel and the excessively large openings on both sides result in excessive heat input during arc welding. This easily causes angular deformation during welding, which can lead to blade misalignment and front / rear disc eccentricity, affecting the impeller's balance and performance.

[0004] Specifically, such as Figure 1 The diagram shows a schematic of a welding structure in the prior art. The existing blade 20 is integrally formed on the hub. The existing cover plate 30 has a cover plate bevel 40. After the existing cover plate 30 is assembled with the hub, the interior of the cover plate bevel 40 is filled with weld metal using arc welding. The thickness of the existing cover plate 30 is H, the width of the existing blade 20 is d, and the cover plate bevel 40 is trapezoidal with an included angle β between the two sides of the trapezoid. β typically ranges from 30° to 50°. When the wall thickness H of the existing cover plate 30 is large, the depth of the filler weld in the cover plate bevel 40 is also large, and the base c of the trapezoid also increases. The main reason for the excessive heat input during the aforementioned arc welding is the increase in the filling cross-sectional area S. Figure 1 It can be seen from the middle , As can be seen from the above formula, the larger the wall thickness H of the existing cover plate 30, the larger the value of c will be, the larger the openings on both sides of the top of the cover plate bevel 40, and the larger the area S of the arc welding filler section. The larger the area S, the larger the arc welding heat input will be. During the welding process, the excessive welding heat input will easily cause angular deformation, resulting in problems such as the existing blade 20 being skewed and the existing cover plate 30 being eccentric with the hub, affecting the balance and performance of the impeller.

[0005] Therefore, it is urgent to find a solution to the problems of blade misalignment and wheel hub eccentricity caused by excessive heat input from arc welding. Utility Model Content

[0006] The problem to be solved is to propose a solution to address the issues of blade misalignment and wheel hub eccentricity caused by excessive heat input during arc welding.

[0007] To achieve the above objectives, this utility model provides the following technical solution: a martensitic stainless steel closed impeller welding joint structure, comprising a hub integrally formed with several blades, a front cover assembled with the hub, and a pre-reserved bevel corresponding to each of the blades on the front cover; the bottom of the blades is integrally formed on the hub, and the top of the blades is provided with an insertion boss for engaging the pre-reserved bevel; the pre-reserved bevel includes a root straight groove and a U-shaped bevel, the bottom width of the U-shaped bevel is greater than the width of the root straight groove, and the top width of the U-shaped bevel is greater than the bottom width of the U-shaped bevel; and the insertion boss is clearance-fitted with the root straight groove, the height of the insertion boss is the same as the height of the root straight groove; the width of the insertion boss is less than the width of the blade.

[0008] Preferably, the height of the insertion boss is 3~10mm.

[0009] Preferably, the included angle between the two sides of the U-shaped bevel is 20~30°.

[0010] Preferably, the gap between the insertion boss and the root straight groove is no more than 1mm.

[0011] Preferably, the width of the blade is 4~20mm.

[0012] Preferably, the height of the insertion boss is 6~8mm.

[0013] Preferably, the height of the insertion boss is 6~8mm.

[0014] Preferably, the bottom two sides of the U-shaped bevel are rounded chamfers.

[0015] Preferably, the radius of the rounded chamfer is 1~2mm.

[0016] Compared with existing technologies, this utility model provides a closed-loop welded joint structure for martensitic stainless steel impellers, which has the following advantages: This utility model features a pre-reserved bevel on the front cover, and a corresponding insertion boss on the blade; the original bevel on the front cover is replaced with a root straight groove and a U-shaped bevel. The root straight groove is responsible for engaging with the insertion boss, while the U-shaped bevel is used for filler electrode welding to ensure weld strength. The relevant dimensional parameters of the insertion boss, root straight groove, and U-shaped bevel are designed according to the equipment power and product dimensions, ensuring welding quality while reducing welding heat input, thereby reducing blade deformation caused by welding heat. This utility model's welding structure significantly reduces the heat input of arc welding, effectively reducing problems such as blade misalignment and front / rear disc eccentricity caused by welding, greatly improving the impeller's balance and performance. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an existing welded structure in the background art;

[0018] Figure 2 This is a schematic diagram of the welding structure of this utility model;

[0019] Figure 3 This is a schematic diagram of the impeller after assembly according to this utility model;

[0020] Figure 4 This is a schematic diagram of the front cover structure involved in this utility model;

[0021] Figure 5 for Figure 4 An enlarged schematic diagram of point A in the middle;

[0022] Figure 6 This is a schematic diagram of the wheel hub structure involved in this utility model;

[0023] Explanation of reference numerals in the attached drawings: 20, existing blade; 30, existing cover plate; 40, cover plate bevel; 1, hub; 2, blade; 21, insertion boss; 3, front cover; 31, reserved bevel; 32, root straight groove; 33, U-shaped bevel. Detailed Implementation

[0024] The technical solutions of the present utility model will now be described with reference to the accompanying drawings in the embodiments of the present utility model:

[0025] As described in the background section, the purpose of this invention is to solve the problem of excessive heat input during arc welding. The root cause of excessive heat input lies in the excessively large arc weld filler cross-sectional area S. Therefore, this invention considers reducing the arc weld filler cross-sectional area S while keeping the front cover thickness constant. This invention provides a martensitic stainless steel closed impeller welding joint structure, such as... Figures 2-6As shown, the device includes a hub 1 and a front cover 3. The hub 1 and the front cover 3 are assembled and welded together. Several blades 2 are integrally formed on the hub 1, and several reserved bevels 31 are provided on the front cover 3. Each reserved bevel 31 corresponds to a blade 2. The bottom of the blade 2 is integrally formed on the hub 1, and the top of the blade 2 is provided with an insertion boss 21, which is used to fit into the reserved bevel 31. The reserved bevel 31 includes a root straight groove 32 and a U-shaped bevel 33. The bottom width a of the U-shaped bevel 33 is greater than the width of the root straight groove 32. Preferably, a = (b + 2) mm, where b is the cross-sectional width of the blade 2. The width b of the blade 2 is preferably 4~20 mm. Common blade 2 widths are 6 mm, 8 mm, and 12 mm. The width b of the blade 2 in this invention can be selected according to the customer's drawings. The top width n of the U-shaped bevel 33 is greater than the bottom width a of the U-shaped bevel 33; and the insertion boss 21 and the root straight groove 32 are fitted with a clearance. The clearance between the insertion boss 21 and the root straight groove 32 is no greater than 1mm. After assembly, the clearance can be checked with a feeler gauge. If the feeler gauge cannot be inserted into the clearance, the clearance is less than or equal to 1mm, which proves that it is qualified. If the feeler gauge can be inserted into the clearance, the clearance is greater than 1mm, which proves that it is unqualified.

[0026] The height of the insertion boss 21 is the same as the height of the root straight groove 32. Considering machining errors, the height difference between the insertion boss 21 and the root straight groove 32 is no more than 0.1mm. The height of both the insertion boss 21 and the root straight groove 32 is m, where m is 3~10mm. The value of m (3~10mm) is determined based on the thickness of the front cover 3. If the front cover 3 is thin, a smaller value for m is chosen; if the front cover 3 is thick, a larger value for m is chosen.

[0027] The height m of the insertion boss 21 is preferably 6~8mm. The insertion boss 21 and the root straight groove 32 are laser welded together; the U-shaped bevel 33 is filled with filler electrode by arc welding. The value of m as 6~8mm is based on the power of the laser welding head equipment. Generally, the equipment can weld to a depth of 10mm. That is, within the capacity of the equipment, 6~8mm can weld as deep as possible. The greater the laser welding depth, the less filler electrode is used by arc welding, and the less heat input is required, which can reduce the deformation of the blade 2. Therefore, the height m of the insertion boss 21 is preferably 6~8mm, which also takes into account the welding depth that the laser welding head can achieve. The width of the insertion boss 21 is less than the width b of the blade 2. Generally, the width of the insertion boss 21 is (b-2)mm. The included angle between the two sides of the U-shaped bevel 33 is α, which is 20~30°. If the α angle is too large, more filler metal is needed for arc welding, and the heat input will also increase. That is, the deformation of blade 2 is positively correlated with the α angle. However, if the α angle is too small, the welding quality cannot be guaranteed. Therefore, the α value of 20~30° is determined based on experience. This angle can minimize the amount of filler metal in arc welding while ensuring welding quality. The preferred α angle is 25°. b is a data that varies with different cross-sections. The width b value of blade 2 varies depending on the impeller model. The width of the insertion boss 21 of blade 2 is b-2: a 1mm step is left on each side of the insertion boss 21. The 1mm step is to prevent laser welding penetration.

[0028] The bottom sides of the U-shaped bevel 33 are rounded chamfers 34. The radius of the rounded chamfers 34 is 1~2mm. Based on actual processing experience, rounded chamfers 34 are set on both sides of the bottom of the U-shaped bevel 33; the radius R of the rounded chamfers 34 is preferably 1.5mm. The advantage of the rounded chamfers 34 is that they can prevent incomplete fusion defects during arc welding filling, ensuring the quality of arc welding.

[0029] In this invention, the root straight groove 32 and the insertion boss 21 are connected by laser welding. Laser welding offers advantages such as high welding quality, high speed, low heat input, and high automation, making it suitable for welding closed stainless steel impellers. This results in well-formed welds with fine microstructure, narrow heat-affected zones, and excellent joint microstructure and mechanical properties. After laser welding, the U-shaped groove 33 is filled using arc welding. The area S1 filled by arc welding is the location of the U-shaped groove 33, and the cross-section... , In the formula, α is less than β in the background technology. Equal to H in the background technology, If t is less than H, then n is equivalent to c in the background technology. It can be seen that when t is equal to H, S1 is less than S, and the heat input of arc welding will be greatly reduced.

[0030] Figure 3This is a schematic diagram of the impeller assembly after the cut-off part involved in this utility model. As can be seen from the figure, the insertion bosses 21 on the blade 2 have all been inserted into the root straight groove 32 of the reserved bevel 31. The U-shaped bevel 33 of the reserved bevel 31 serves as the filling position for subsequent arc welding. Figure 4 This is a schematic diagram of the structure of the front cover 3 after a portion has been removed, which relates to this utility model. Figure 5 for Figure 4 The enlarged schematic diagram at point A clearly shows the straight groove 32 and U-shaped groove 33 at the root of the reserved bevel 31. Figure 6 This is a schematic diagram of the hub structure involved in this utility model. It can be clearly seen from the figure that several blades 2 are provided with insertion bosses 21.

[0031] During processing, the hub 1 is integrally forged, and several blades 2 are machined together. After machining, the blades 2 have insertion bosses 21. The insertion bosses 21 are shorter than the blades 2 in the arc length direction and narrower than the blades 2 in the radial direction. A pre-reserved bevel 31 is machined on the front cover 3 after machining. The root straight groove 32 of the pre-reserved bevel 31 is located at the lower part of the front cover 3, and the U-shaped bevel 33 of the pre-reserved bevel 31 is located at the upper part of the front cover 3. During assembly, the insertion bosses 21 are inserted into the root straight groove 32. If there are 20 blades 2, they are assembled symmetrically. First, laser welding is used to connect the root straight groove 32 and the insertion bosses 21, and then arc welding is used to fill the U-shaped bevel 33. The welding process of this utility model structure can reduce the heat input of arc welding, avoid angular deformation of the blades 2, and thus avoid problems such as blade skew and front and rear disc eccentricity, ensuring the performance of the impeller. The welding structure of this utility model greatly reduces the heat input of arc welding, effectively reduces problems such as blade misalignment and front and rear disc eccentricity caused by welding, and greatly improves the balance and performance of the impeller.

[0032] The above embodiments are merely some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the scope of protection of this utility model.

Claims

1. A martensitic stainless steel closed impeller welded joint structure, comprising a hub (1) integrally formed with a plurality of blades (2), and a front cover (3) assembled with the hub (1), characterized in that: The front cover (3) is provided with reserved bevels (31) corresponding to several blades (2); the bottom of the blade (2) is integrally formed on the hub (1), and the top of the blade (2) is provided with a plug-in boss (21) for inserting into the reserved bevel (31); the reserved bevel (31) includes a root straight groove (32) and a U-shaped bevel (33), the bottom width of the U-shaped bevel (33) is greater than the width of the root straight groove (32), and the top width of the U-shaped bevel (33) is greater than the bottom width of the U-shaped bevel (33); and the plug-in boss (21) is in clearance fit with the root straight groove (32), and the height of the plug-in boss (21) is consistent with the height of the root straight groove (32); the width of the plug-in boss (21) is less than the width of the blade (2).

2. The martensitic stainless steel closed impeller welded joint structure according to claim 1, characterized in that: The height of the plug boss (21) is 3~10mm.

3. The martensitic stainless steel closed impeller welded joint structure according to claim 1, characterized in that: The included angle between the two sides of the U-shaped bevel (33) is 20~30°.

4. The martensitic stainless steel closed impeller welded joint structure according to claim 1, characterized in that: The gap between the insertion boss (21) and the root straight groove (32) is no more than 1 mm.

5. The martensitic stainless steel closed impeller welded joint structure according to claim 1, characterized in that: The width of the blade (2) is 4~20mm.

6. The martensitic stainless steel closed impeller welded joint structure according to claim 2, characterized in that: The height of the insertion boss (21) is 6~8mm.

7. The martensitic stainless steel closed impeller welded joint structure according to claim 2, characterized in that: The height of the insertion boss (21) is 6~8mm.

8. The martensitic stainless steel closed impeller welded joint structure according to claim 1, characterized in that: The bottom sides of the U-shaped bevel (33) are rounded chamfers (34).

9. The martensitic stainless steel closed impeller welded joint structure according to claim 8, characterized in that: The radius of the rounded chamfer (34) is 1~2mm.

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