An impeller forging method, an impeller manufactured by using this method, and a centrifugal pump

Abstract

The present invention provides an impeller forging method, an impeller manufactured by using this method, and a centrifugal pump, relating to the technical field of centrifugal pump impeller manufacturing. The impeller forging method includes: pre-heating treatment before precision forging; precision forging the blank that has undergone the heating treatment to obtain an impeller forging with a diameter of D3, and a target protrusion and blade strips are provided on one surface of the impeller forging; wherein, the diameter of the blank is D2, which is equal to the diameter D3 of the impeller forging; at least one surface of the blank is provided with a pre-protrusion for forming the target protrusion during precision forging; during precision forging, it is forged at least twice, and at least during the first forging process, plastic deformation along the axial direction of the blank forms the target protrusion. The impeller forged by using this method has high strength, good surface flatness, a dense and smooth runner surface, and the material used is controllable, saving resources and being relatively environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of centrifugal pump impeller manufacturing, and particularly relates to an impeller forging method, an impeller manufactured by using this method, and a centrifugal pump. Background Art

[0002] The impeller of a centrifugal pump is a work part of the centrifugal pump. It relies on its high-speed rotation to do work on the liquid to achieve the transportation of the liquid, and is one of the important parts of the centrifugal pump.

[0003] The impeller generally consists of three parts: a hub, blades, and a cover plate. The cover plate of the impeller is divided into a front cover plate and a rear cover plate. The cover plate on the inlet side of the impeller is called the front cover plate, and the cover plate on the other side is called the rear cover plate. According to the structural form, the impeller can be divided into three forms: closed, semi-open, and open. Among them, the closed impeller has cover plates on both sides of the impeller; the semi-open impeller is generally divided into two types. One is the front semi-open type, which consists of the rear cover plate and the blades, and the other is the rear semi-open type, which consists of the front cover plate and the blades.

[0004] The impeller of the centrifugal pump is driven by the shaft of the motor during the working process. There is an annular boss in the middle of the cover plate. One side is used to connect the shaft of the motor, and the other side strings up the ends of multiple blades to support the blades. The annular boss is often centrally arranged in the middle of the cover plate. Looking from the side, the annular boss protrudes outward from both side surfaces (along the axial direction) of the cover plate.

[0005] There are several blades (or called blade strips) on one side surface of the cover plate (or both side edges). The blades are spirally arranged on the surface of the cover plate and radiate outward from the center. Multiple blades are evenly distributed around the boss in the middle of the cover plate.

[0006] The traditional manufacturing method of the centrifugal pump impeller generally uses copper alloy casting and sheet metal splicing processes. The impeller formed by splicing adopts a split design, and the two ends of the blades are respectively riveted to the upper cover plate and the lower cover plate with rivets. The impeller riveted with rivets has low strength and is prone to problems such as falling off due to low connection strength and weak joint force during use. In addition, due to factors such as production process and assembly error, the upper cover plate and the lower cover plate of the impeller riveted with rivets cannot ensure the flatness after splicing, which will cause rough and uneven problems, thereby affecting the performance of the impeller during daily use.

[0007] There are also impellers formed by sand casting in one piece. On the one hand, the flow channels of such impellers are relatively rough, which will affect the use performance of the water pump; on the other hand, the controllability of the weight of the impeller during the sand casting process is poor, which will cause waste of resources, and sand casting involves smelting and pouring processes, which is not conducive to environmental protection.

[0008] If the forging process is adopted, although it can solve some of the above problems to a certain extent, in the process of blanking, if sheet metal is used, the blanking is troublesome and the intermediate boss of the forging requires a lot of material. If the sheet is too thin, it is difficult to fill the middle. If the sheet is too thick, there is too much surplus material outside, resulting in waste, and the requirement for forging tonnage is very large.

[0009] In addition, in the national standard GB / T 20078-2006, there are clear regulations on the forgings of copper and copper alloys, which require the range of the ratio of the height to the width of the ribs on the general web. The impeller is not only thin at the edge, but also has a certain height above the cover plate. After calculation, the ratio of this height to the edge width has exceeded the range of the national standard. Therefore, using the conventional forging process, it is impossible to forge an impeller forging that meets the expectations. Summary of the Invention

[0010] The present invention aims to solve one of the technical problems in the related art to a certain extent. For this purpose, the present invention provides an impeller forging method, an impeller and a centrifugal pump manufactured by using this method, in which the forged impeller has a size that meets the expectations, high strength, good surface flatness, a dense and smooth flow passage surface, and controllable material consumption, saves resources, and is more environmentally friendly.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions in the first aspect:

[0012] An impeller forging method, comprising,

[0013] Pre-heating treatment before precision forging;

[0014] Precision forging the blank after heat treatment to obtain an impeller forging with a diameter of D 3 On one surface of the impeller forging, there are a target protrusion and blade strips;

[0015] Wherein, the diameter of the blank is D 2 , which is equal to the diameter D 3 of the impeller forging; at least one surface of the blank is provided with a pre-protrusion for forming the target protrusion during precision forging; during precision forging, it is forged at least twice and at least during the first forging process, the plastic deformation along the axial direction of the blank forms the target protrusion.

[0016] By selecting a blank with the same diameter as the target forging, during the forging process, the part stretched radially in the blank can be reduced, and the acting force can be mainly concentrated on forming the target convex part from the pre-convexity and forming qualified blade strips. After the target convexity is formed after the first forging, during the subsequent forging process, the plastic deformation of the blank can be completely concentrated on the formation of the blade strips. Additionally, prefabricating a pre-convexity on the blank in advance can appropriately reduce the extension amount of the pre-convexity during the forging process, and can also concentrate the acting force on the formation of the blade strips, thereby enabling the forging of dimensions far exceeding the national standards.

[0017] Optionally, the blank is obtained by the following steps:

[0018] Prepare a bar; the bar is cut from a copper alloy round bar with a diameter of D 1 and a thickness of H is cut off to form a section, and the diameter D of the bar 1 is smaller than the diameter D of the blank 1 ; 2 ;

[0019] Pre-forging heat treatment;

[0020] The bar after heat treatment is pre-forged to obtain the blank;

[0021] Among them, during the pre-forging process, it is forged at least twice; the diameter of the bar is sufficient to cover the pre-convexity, so that at least during the first forging process, the plastic deformation along the axial direction of the bar can form the pre-convexity, and during the subsequent forging process, the plastic deformation along the radial direction of the bar increases its diameter from D 1 to D 2 .

[0022] Optionally, the pre-forging heat treatment includes heat-treating the bar and the pre-forging equipment respectively; the finish-forging heat treatment includes heat-treating the blank and the finish-forging equipment respectively;

[0023] Among them, the temperature of the bar after heat treatment is the same as the temperature of the blank after heat treatment, and both are at 750 ± 50 °C.

[0024] Similarly, the blank is prefabricated by forging, and at the same time, the processing temperature during the pre-forging process is the same as the temperature during the finish-forging process. As much as possible, the temperature of the blank after pre-forging is restored to the degree before pre-forging, and then finish-forging is carried out. Because the temperature of the bar will gradually decrease during the pre-forging process, and its ductility will also decrease with the temperature, so it needs to be reheated before finish-forging to restore its ductility for convenient processing.

[0025] Optionally, in the pre-forging heat treatment and the finish-forging heat treatment, the temperature of the pre-forging equipment after heat treatment is the same as the temperature of the finish-forging equipment after heat treatment, and both are at 750 ± 50 °C.

[0026] Optionally, the impeller forging includes:

[0027] A forging body with a diameter of D 3 , having a third surface and a fourth surface;

[0028] A third recess provided in the middle of the third surface, the depth of the third recess relative to the third surface being H 34 ;

[0029] A third rib provided around the outside of the third recess;

[0030] A second convex portion provided in the middle of the fourth surface;

[0031] A fourth rib provided around the outside of the second convex portion; and,

[0032] A blade strip standing on the fourth surface, one end of the blade strip being connected to the fourth rib, and the other end of the blade strip extending outward in a spiral shape;

[0033] Wherein, the target convex portion is formed by the third rib and the fourth rib;

[0034] The blank includes:

[0035] A blank body in the shape of a circular plate with a diameter of D 2 , including a first surface and a second surface;

[0036] A first recess provided in the middle of the first surface, the depth of the first recess relative to the first surface being H 24 ;

[0037] A first rib provided around the outside of the first recess, the distance from the first rib to the first surface being less than the distance from the third rib to the third surface, for forming the third rib during precision forging;

[0038] A second recess provided around the outside of the first rib;

[0039] A first convex portion provided in the middle of the second surface, the distance from the first convex portion to the third surface being greater than the distance from the second convex portion to the first surface; and,

[0040] A second rib provided around the outside of the first convex portion, for forming the fourth rib during precision forging;

[0041] Wherein the pre-convex portion is formed by the first rib and the second rib; and H 24 =H 34, during the precision forging process, the first surface of the blank and the bottom surface of the first recess are attached to the cavity of the precision forging equipment as the support surface, and the blade strip is formed by forging the second surface of the blank with a punch.

[0042] Optionally, the diameter of the first rib is D 21 , the diameter of the second rib is D 22 , the diameter of the bar stock is D 1 ; where the diameter D 1 is greater than or equal to the diameter D 11 , the diameter D 1 is greater than or equal to the diameter D 22 , the diameter D 1 is less than or equal to the diameter D 2 .

[0043] Optionally, the diameter D of the first rib 21 is 76 ± 4 mm, the diameter D of the second rib 23 is 92.5 ± 15 mm, the diameter D of the blank 2 is 280 ± 50 mm; the diameter D of the bar stock 1 is between 107.5 mm and 330 mm; the forging pressure during the initial forging and precision forging processes is between 800T and 1600T.

[0044] Optionally, the copper alloy used is CuZn 4 OPb 2 .

[0045] In addition, in the second aspect, the present invention also provides an impeller. The impeller adopts the impeller forging method described in the first aspect. In the cross-section of the blade strip perpendicular to its extension direction, the height of the blade strip is h, and the minimum width at the end of the blade strip corresponding to this height is bmin; then the h and bmin on at least one cross-section of the blade strip satisfy the following conditions:

[0046] When 6 mm < h ≤ 12 mm, bmin = 2 mm;

[0047] Or when 12 mm < h ≤ 20 mm, bmin = 2.5 mm;

[0048] Or when 20 mm < h ≤ 32 mm, bmin = 3 mm;

[0049] Or when 32 mm < h ≤ 50 mm, bmin = 4 mm;

[0050] Or when 50 mm < h ≤ 80 mm, bmin = 6 mm;

[0051] Or when 80 mm < h ≤ 126 mm, bmin = 8 mm;

[0052] Or when h > 126 mm, bmin = 9 mm.

[0053] The beneficial effect inference process of the impeller provided by the present invention is similar to that of the aforementioned impeller forging method, and will not be elaborated here.

[0054] Meanwhile, the present invention provides a centrifugal pump in a third aspect, and the centrifugal pump uses the impeller described in the second aspect.

[0055] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments and the accompanying drawings. The best embodiments or means of the present invention will be elaborated in conjunction with the accompanying drawings, but it is not a limitation to the technical solution of the present invention. Additionally, these features, elements, and components appear multiple times in the following text and the accompanying drawings, and are marked with different symbols or numbers for convenience of representation, but all represent components with the same or similar structures or functions. Description of the Drawings

[0056] The present invention will be further described below in conjunction with the accompanying drawings:

[0057] Figure 1 It is a flowchart of the impeller forging method described in the present invention.

[0058] Figure 2 It is a structural schematic diagram of the impeller described in the present invention.

[0059] Figure 3 It is a cross-sectional view of the impeller described in the present invention in the radial direction.

[0060] Figure 4 It is a cross-sectional view of the blank described in the present invention in the radial direction.

[0061] Figure 5 It is a state schematic diagram of the initial forging process described in the present invention.

[0062] Figure 6 It is a state schematic diagram of the finish forging process described in the present invention.

[0063] Figure 7 It is an overlapping schematic diagram of the blank cross-section and the impeller cross-section described in the present invention, where the shaded part is the part of the blank that shrinks after forging.

[0064] Figure 8 It is a structural schematic diagram of the open web using copper and copper alloy for forging and forming ribs on its surface in the national standard.

[0065] Among them, 100 is a bar stock; 200 is a blank body; 210 is a first surface; 211 is a first recess; 212 is a first rib; 213 is a second recess; 220 is a second surface; 224 is a first protrusion; 225 is a second rib; 300 is a forging body; 310 is a third surface; 311 is a third recess; 312 is a third rib; 313 is a fourth recess; 314 is a fifth recess; 315 is a sixth recess; 320 is a fourth surface; 321 is a second protrusion; 322 is a fourth rib; 323 is a blade strip; 400 is a primary forging device; 500 is a finish forging device. Detailed implementation manners

[0066] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. Based on the embodiments in the implementation manners, it is intended to explain the present invention and should not be construed as a limitation to the present invention.

[0067] As used in this specification, the phrase "one embodiment" or "example" or "instance" means that a particular feature, structure, or characteristic described in connection with the embodiment itself may be included in at least one embodiment of the present patent disclosure. The appearances of the phrase "in one embodiment" in various positions in the specification do not necessarily refer to the same embodiment.

[0068] Before starting the detailed description of the embodiments of the present invention, a brief introduction to the national standards that appear in the background art will be given first.

[0069] As Figure 8 shown, in the national standard of GB / T 20078-2006, there are relevant regulations for forging with an open web made of copper and copper alloys and forming ribs on its surface. The standard for the minimum width b 1min allowed for the ribs on the open web and the height of the ribs corresponding to this minimum width are formulated as shown in Table 1:

[0070] Table 1 Minimum width b allowed for ribs on the open web 1min

[0071] Unit: millimeter

[0072]

[0073] When forging an impeller using a conventional forging process, the cover plate of the impeller is equivalent to an open web, and the blade strips (blades) on the surface of the impeller are equivalent to ribs. Therefore, as can be seen from the above table, for an impeller directly forged from an open-web plate, its relationship with the minimum width b 1minThe corresponding height h will not exceed the range of the above table either. At the same rotational speed, within a certain range, the effect of the impeller is closely related to the height of the blade strips. To improve the effect of the impeller, the height of the blade strips at the initial design may exceed the range of the above table. If the conventional forging process is used, the performance of the produced impeller will be limited. The present invention abandons the open-belly plate and uses a special blank to forge the impeller, so that the blade strips on the impeller have the same minimum width b min in the case where the corresponding height h can at least exceed the national standard by 1 time. The following will be described in detail with specific embodiments.

[0074] Embodiment:

[0075] As Figure 1 、 Figure 5 and Figure 6 shown, the embodiment of the present invention provides an impeller forging method, which includes the following steps.

[0076] S1: Cut a section with a thickness of H 1 from a copper alloy round bar with a diameter of D 1 to make a blank 100.

[0077] The blank 100 is made of a copper alloy with the grade CW617N, and this copper alloy is a CuZn 4 OPb 2 alloy, where Cu is 57 - 59, Al ≤ 0.05, Ni ≤ 0.3, Fe ≤ 0.3, Pb is 1.6 - 2.5, Sn < 0.3, and the balance is Zn.

[0078] S2: Perform the first heat treatment on the blank 100.

[0079] After the first heat treatment, the temperature of the blank 100 is at 750 ± 50 °C. At this temperature, the ductility of the blank 100 is improved, and it can be relatively easily forged and processed.

[0080] S3: Perform the second heat treatment on the initial forging equipment 400.

[0081] Among them, both the first heat treatment and the second heat treatment are performed before the initial forging. After the second heat treatment, the temperature of the initial forging equipment 400 is higher than the temperature of the blank 100 after the first heat treatment. Specifically, after the second heat treatment, the temperature of the initial forging equipment 400 is at 750 ± 50 °C.

[0082] During the forging process, the temperature of the blank 100 will decrease. Therefore, after heating the initial forging equipment 400 to a temperature higher than that of the blank 100, it can be avoided that the temperature of the blank 100 drops rapidly due to contact with the initial forging equipment 400 during the forging process, and to a certain extent, the temperature reduction of the blank 100 can be delayed.

[0083] S4: Use the primary forging equipment 400 to perform primary forging on the bar stock 100 placed in the mold cavity to obtain a blank. The forging pressure is between 800T - 1600T, and its magnitude needs to be determined according to the diameter of the blank, the number of forging passes, and the plasticity of the copper alloy at the corresponding temperature. The specific magnitude can be flexibly adjusted according to the situation. During this primary forging process, the punch of the primary forging equipment 400 is used to forge at least twice. In this embodiment, taking forging twice as an example, the forging pressure is 800T.

[0084] The blank obtained after primary forging has a diameter of D 2 , and an annular pre - protrusion is provided on at least one surface of the blank. This pre - protrusion overlaps with the target - impeller forging within a certain range, which can appropriately reduce the extension amount of the pre - protrusion during the forging process and can also concentrate the acting force on the formation of the blade bars 323 on the impeller, thereby enabling the forging of dimensions far exceeding the national standard.

[0085] As Figure 4 shown, a cross - sectional view of the blank in the direction of its diameter is shown, and the blank is a solid of revolution. Specifically, the blank includes a blank body 200, and a first recess 211, a first rib 212, a second recess 213, a first protrusion 224, and a second rib 225 provided on the blank body 200. Among them, the first rib 212 and the second rib 225 form the pre - protrusion.

[0086] In this embodiment, the blank body 200 is in the shape of a circular plate with a diameter of D 2 and a thickness of H 2 . The blank body 200 includes a first surface 210 and a second surface 220, that is, the upper surface and the lower surface, referring to the plane where the dotted line is located in Figure 4 .

[0087] Among them, the first recess 211 is provided in the middle of the first surface 210, and the depth of the first recess 211 relative to the first surface 210 is H 24 , and in this embodiment, taking H 24 as 3mm as an example. The first rib 212 surrounds the first recess 211, and the diameter of the first rib 212 is D 21 , and in this embodiment, taking D 21 as 76.5mm as an example, and its height relative to the bottom of the first recess 211 is H 21 , and in this embodiment, taking H 21 as 4mm as an example. The second recess 213 surrounds the first rib 212, and the second recess 213 has the same depth as the first recess 211 and they are on the same plane. The bottom of the second recess 213 is an annular plane, and the width of this annular plane is 11mm.

[0088] By respectively arranging a first concave part 211 and a second concave part 213 on the inner and outer sides of the first convex rib 212, during the forging process, the first concave part 211 and the second concave part 213 are in contact with the cavity of the initial forging device 400, which can provide sufficient support for both sides of the first convex rib 212, and helps the first convex rib 212 of the blank to form the third convex rib 312 of the impeller forging.

[0089] Wherein the first convex part 224 is arranged in the middle of the second surface 220. The second convex rib 225 is arranged around the first convex part 224, and the diameter of the second convex rib 225 is D 23 , in this embodiment, D 23 is taken as an example of 92.6 mm for illustration. The height H of the highest point of the second convex rib 225 relative to the first surface 210 23 is preferably 34 mm.

[0090] During the initial forging process, in order to quickly form the first convex rib 212 and the second convex rib 225, the diameter of the bar stock 100 should be greater than or equal to the former two. In this way, at the beginning of forging, the bar stock 100 can directly fill the cavity parts on the initial forging device 400 corresponding to the first convex rib 212 and the second convex rib 225. At the same time, in order not to waste the bar stock 100, its diameter should also be less than the diameter of the blank body 200.

[0091] In one embodiment, the diameter D of the blank body 200 2 is 280 ± 50 mm, preferably 280 mm, and the thickness H of the blank body 200 2 is preferably 15 ± 1 mm; the diameter D of the first convex rib 212 21 is 76 ± 4 mm, preferably 76 mm; the diameter D of the second convex rib 225 23 is 92.5 ± 15 mm, preferably 92.5 mm. Then, the diameter D of the bar stock 100 1 is between 107.5 mm and 330 mm. Since the second convex rib 225 is larger than the first convex rib 212 and the second convex rib 225 has a certain width, the diameter of the bar stock 100 is preferably completely covered by the second convex rib 225, so in this embodiment, it is preferably 120 mm.

[0092] In one embodiment, the first convex part 224 is cylindrical, and its height H relative to the first surface 210 22 is 23 mm. The second convex rib 225 is circular, and is concentrically arranged with the second surface 220 of the blank body 200. The second convex rib 225 is 11 mm higher than the first convex part 224, the diameter of the second convex rib 225 is 92.6 mm, and the inner side of the second convex rib 225 is smoothly connected with the edge of the first convex part 224 by an over-curved surface.

[0093] S5: Perform a third heat treatment on the blank to restore the plasticity of the blank and facilitate forging and forming.

[0094] Specifically, the temperature of the blank after the third heat treatment is 750 ± 50 °C.

[0095] S6: Perform a fourth heat treatment on the precision forging equipment 500.

[0096] Among them, both the third heat treatment and the fourth heat treatment are carried out before precision forging. The temperature of the precision forging equipment 500 after the fourth heat treatment is higher than the temperature of the blank after the third heat treatment. Specifically, the temperature of the precision forging equipment 500 after the fourth heat treatment is 750 ± 50 °C.

[0097] S7: Use the precision forging equipment 500 to perform precision forging on the blank that has undergone the third heat treatment and is placed in the cavity to obtain an impeller forging with a diameter of D 3 The forging pressure is between 800T - 1600T, and its magnitude needs to be determined according to the diameter of the impeller forging, the number of forging passes, and the plasticity of the copper alloy at the corresponding temperature. The specific magnitude can be flexibly adjusted according to the situation. During this precision forging process, the punch of the precision forging equipment 500 is used to forge at least twice. In this embodiment, taking forging twice as an example, the forging pressure is 800T.

[0098] During this precision forging process, after two forging passes, a target raised portion formed by the pre - raised portion and blade strips are provided on one surface of the impeller forging.

[0099] The diameter D of the impeller forging 3 and the diameter D of the blank 2 are equal. During precision forging, the part of the blank that is stretched radially can be reduced, and the acting force is mainly concentrated on forming the target raised portion from the pre - raised portion and forming qualified blade strips 323.

[0100] See Figure 2 、 Figure 3 and Figure 7 As shown, the impeller forging includes a forging body 300, a third concave portion 311, a third rib 312, a fourth concave portion 313, a second convex portion 321, a fourth rib 322, and blade strips 323. Among them, the outer contour of the forging body 300 is in the shape of a circular plate, with a diameter of D 3 , having a third surface 310 and a fourth surface 320, that is, the upper and lower surfaces. Among them, the target raised portion is formed by the third rib 312 and the fourth rib 322.

[0101] The third concave portion 311 is provided in the middle of the third surface 310, and the depth of the third concave portion 311 relative to the third surface 310 is H 34, and satisfy H34 = H24. Wherein, H 24 is the depth of the first concave portion 211 of the blank body 200 relative to its first surface 210.

[0102] With such a design, during the precision forging process (the second forging), the first surface 210 of the blank and the bottom surface of the first concave portion 211 are attached to the cavity of the precision forging device 500 as a support surface (see Figure 6 and Figure 7 ), and the blade strip 323 is formed by forging the second surface 220 of the blank with a punch.

[0103] The third rib 312 is disposed around the outside of the third concave portion 311. See Figure 7 , the distance from the third rib 312 to the third surface 310 is greater than the distance from the first rib 212 to the first surface 210, so that the third rib 312 can be formed by the first rib 212 during the precision forging process. The filled grid shadow in the figure is the part that needs to bulge out from the blank surface and fill into the cavity of the precision forging device 500 during the precision forging process. The filled oblique shadow in the figure is the amount of deformation that needs to be displaced by the inner wall of the cavity of the precision forging device 500 from the surface of the blank during the precision forging process.

[0104] The fourth concave portion 313 is disposed around the outside of the third rib 312 and can cooperate with the third concave portion 311 to form a support surface inside and outside the third rib 312 during precision forging.

[0105] The second convex portion 321 is disposed in the middle of the fourth surface 320, and the height of the second convex portion 321 relative to the fourth surface 320 is H 32 . As can be seen from the figure, H 32 < H 22 , where H 22 is the height of the first convex portion 224 relative to the second surface 220, that is, during the precision forging process, the first convex portion 224 is forged by the corresponding part on the punch of the precision forging device 500, so that the height is reduced to form the second convex portion 321. The copper alloy squeezed out during this process fills into the nearby cavity, which helps to form the third rib 312 and the blade strip 323.

[0106] The fourth rib 322 is disposed around the outside of the second convex portion 321. Moreover, the height of the fourth rib 322 relative to the third surface 310 is less than the height of the second rib 225 relative to the first surface 210, that is, the height of the second rib 225 is reduced during precision forging to form the fourth rib 322, and the excess part is filled into the adjacent blade strip 323.

[0107] The blade strip 323 is vertically arranged on the fourth surface 320. One end of the blade strip 323 is connected to the fourth rib 322, and the other end of the blade strip 323 extends outward in a spiral shape. The impeller forging is the highest at the fourth rib 322. The height of the end of the blade strip 323 connected thereto is flush with it. Along the extending direction of the blade strip 323, the height shows a trend of decreasing step by step. For blade strips 323 with different heights, on the cross-section perpendicular to the extending direction, the minimum width of the end of the blade strip 323 is different.

[0108] Specifically, in the cross-section of the blade strip 323 perpendicular to the extending direction, the height of the blade strip 323 is h, and the minimum width of the end of the blade strip 323 corresponding to this height is b min . The ratio of the height h of the blade strip 323 to the minimum width b of the end of the blade strip 323 min is k. When b min is the same as b in the aforementioned national standard 1min , the height h can reach at least twice the range specified by the national standard. That is, for the impeller forging in this solution, the k value corresponding to its blade strip 323 can easily reach and exceed the national standard, that is, at least one cross-section of the blade strip 323 has b min satisfying the following conditions:

[0109] When 6 mm < h ≤ 12 mm, b min = 2 mm;

[0110] Or when 12 mm < h ≤ 20 mm, b min = 2.5 mm;

[0111] Or when 20 mm < h ≤ 32 mm, b min = 3 mm;

[0112] Or when 32 mm < h ≤ 50 mm, b min = 4 mm;

[0113] Or when 50 mm < h ≤ 80 mm, b min = 6 mm;

[0114] Or when 80 mm < h ≤ 126 mm, b min = 8 mm;

[0115] Or when h > 126 mm, b min = 9 mm.

[0116] S8: Finally, put the impeller forging into an annealing furnace to remove stress. Keep the temperature at 300 °C and hold for at least half an hour, preferably 3 hours. After holding for 3 hours, cool in air in the furnace and take it out after the temperature is lower than 150 °C.

[0117] It should be noted that in the above steps, the thickness H of the bar stock 100 1 is determined by the weight of the final impeller forging. Since it is generated from some scrap during the forging process, the amount of the bar stock 100 can be deduced by adding the weight of the impeller and the weight of the scrap. Combining its density and diameter, the thickness H can be calculated 1 . In this embodiment, the finished weight of the impeller forging is 7.5 kg, and the bar stock 100 is 8.7 kg, with a margin of 1.2 kg. Then the corresponding H 1 is 92 mm.

[0118] In addition, in this embodiment, the blade strip 323 is formed by forging the second surface 220 of the blank under the forging of the precision forging equipment 500. After formation, the blade strip 323 is located on the fourth surface 320 of the impeller forging. In order to improve the strength of the impeller and save materials, in this embodiment, an annular fifth recess 314 and a sixth recess 315 are also provided on the third surface 310 of the impeller forging. Both are concentric rings with only different diameters, and are sequentially arranged outside the fourth recess 313. The fifth recess and the sixth recess play an effect similar to that of a reinforcing rib on the third surface.

[0119] Compared with the existing forging process, in the impeller forging method of the present invention, a bar stock with a diameter larger than the target protrusion is first used to forge a blank with a pre-protrusion, and the initial forging process is at least forged twice. During the first forging process, the copper alloy mainly fills the chamber of the initial forging equipment axially and forms a pre-protrusion. Only in the second forging does the excess copper alloy fill radially to form the blank body. By forging in batches, the moving direction of the plastic deformation of the copper alloy is single after being extruded during each forging, so that the force direction can be unified and the forging effect can be strengthened. After that, the blank with a pre-protrusion is put into the precision forging equipment for precision forging, and the precision forging process is also at least forged twice. During the first forging process, the copper alloy also mainly fills axially and forms the target protrusion (i.e., the boss in the background technology) and part of the blade strip, and then the complete blade strip on the impeller is formed only in the second forging. Such batch forging is also to complete different components in batches during each forging process as much as possible. The components completed by batch forging can maintain the flow direction of the copper alloy to a certain extent each time, avoiding the situation of chaos due to non-uniform internal flow when forming multiple components at one time. In addition, before initial forging and precision forging, the bar stock or the blank needs to be heated to improve its plasticity. Therefore, forgings higher than twice the national standard can be forged.

[0120] At the same time, this embodiment also provides an impeller, which is manufactured by using the above impeller forging method, and the impeller structure can be referred to Figure 2 .

[0121] Moreover, this embodiment also provides a centrifugal pump, which includes an impeller forged by the above impeller forging method.

[0122] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the content described in the drawings and the above specific implementation manner. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A method for forging an impeller, characterized in that, it includes, preparing a bar stock, which is made by cutting a section with a thickness of H1 from a copper alloy round bar with a diameter of D1; heating the bar stock and the primary forging equipment, and after the first heat treatment, the temperature of the bar stock is 750 ± 50 °C; performing a second heat treatment on the primary forging equipment, and after the second heat treatment, the temperature of the primary forging equipment is higher than the temperature of the bar stock after the first heat treatment, and after the second heat treatment, the temperature of the primary forging equipment is 750 ± 50 °C; performing primary forging on the heated bar stock to obtain a blank; wherein, during the primary forging process, it is forged at least twice; so that at least during the first forging process, plastic deformation along the axial direction of the bar stock can form a pre-protrusion, the diameter of the bar stock is sufficient to cover the pre-protrusion, and during the subsequent forging process, plastic deformation along the radial direction of the bar stock enlarges its diameter from D1 to D2, and the diameter D1 of the bar stock is smaller than the diameter D2 of the blank; heating the blank and the finish forging equipment, and after the third heat treatment, the temperature of the blank is 750 ± 50 °C; performing a fourth heat treatment on the finish forging equipment, and after the fourth heat treatment, the temperature of the finish forging equipment is higher than the temperature of the blank after the third heat treatment, and after the fourth heat treatment, the temperature of the finish forging equipment is 750 ± 50 °C; performing finish forging on the heated blank to obtain an impeller forging with a diameter of D3, and a target protrusion and blade strips are provided on one surface of the impeller forging; wherein, the diameter of the blank is D2, which is equal to the diameter D3 of the impeller forging; the blank is provided with a pre-protrusion for forming the target protrusion on at least one of its surfaces; during the finish forging process, it is forged at least twice and at least during the first forging process, plastic deformation along the axial direction of the blank forms the target protrusion; the impeller forging includes: a forging main body with a diameter of D3, having a third surface and a fourth surface, and the third surface and the fourth surface are respectively the upper and lower surfaces in its thickness direction; a third concave portion provided in the middle of the third surface, and the depth of the third concave portion relative to the third surface is H34; a third rib provided around the outside of the third concave portion; a second convex portion provided in the middle of the fourth surface; a fourth rib provided around the outside of the second convex portion; and, the blade strip, which is erected on the fourth surface, one end of the blade strip is connected to the fourth rib, and the other end of the blade strip extends outward in a spiral shape; wherein, the protrusion is formed by the third rib and the fourth rib; the blank includes: a blank main body, in the shape of a circular plate, with a diameter of D2, including a first surface and a second surface, and the first surface and the second surface are respectively the upper and lower surfaces in its thickness direction; a first concave portion provided in the middle of the first surface, and the depth of the first concave portion relative to the first surface is H24; a first rib provided around the outside of the first concave portion, and the distance from the first rib to the first surface is less than the distance from the third rib to the third surface, for forming the third rib during the finish forging process; a second concave portion provided around the outside of the first rib; A first convex portion disposed in the middle of the second surface, the distance from the first convex portion to the third surface being greater than the distance from the second convex portion to the first surface; and, A second convex rib disposed around the outside of the first convex portion for forming the fourth convex rib during the precision forging process; Wherein the first convex rib and the second convex rib form the pre-projection; and H24 = H34. During the precision forging process, the first surface of the blank and the bottom surface of the first recess are attached to the cavity of the precision forging equipment as a support surface, and the blade is formed by forging the second surface of the blank with a punch in the thickness direction of the blank.

2. The impeller forging method according to claim 1, Characterized in that, The diameter of the first convex rib is D 21 , the diameter of the second convex rib is D 23 , the diameter of the bar stock is D 1 ; among them, the diameter D 1 is greater than or equal to the diameter D 21 , the diameter D 1 is greater than or equal to the diameter D 23 , the diameter D 1 is less than or equal to the diameter D 2 .

3. The impeller forging method according to claim 2, Characterized in that, The diameter D of the first convex rib 21 is 76 ± 4 mm, and the diameter D of the second convex rib 22 is 92.5 ± 15 mm. The diameter D of the blank body 2 is 280 ± 50 mm; the diameter D of the bar stock 1 is between 107.5 mm and 330 mm; the forging pressure during the initial forging and finish forging is between 800 T and 1600 T.

4. The impeller forging method according to claim 1, Characterized in that, The copper alloy used is CuZn 4 OPb 2 .

5. An impeller manufactured by using the impeller forging method according to any one of claims 1-4, Characterized in that, In a cross-section of the blade strip perpendicular to its extending direction, the height of the blade strip is h, and the minimum width of the end of the blade strip corresponding to this height is b min ; then the h and b on at least one cross-section of the blade strip min meet the following conditions: When 6mm < h ≤ 12mm, b min = 2mm; or when 12mm < h ≤ 20mm, b min = 2.5mm; or when 20mm < h ≤ 32mm, b min = 3mm; or when 32mm < h ≤ 50mm, b min = 4mm; Or when 50mm < h ≤ 80mm, b min = 6mm; Or when 80mm < h ≤ 126mm, b min = 8mm; Or when h > 126 mm, b min = 9 mm.

6. A centrifugal pump, Characterized in that, The centrifugal pump includes the impeller described in claim 5.

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