Impact-resistant large ceramic impeller and machining method thereof

Abstract

The invention discloses an impact-resistant large ceramic impeller and a machining method thereof.The impact-resistant large ceramic impeller comprises a hub and an impeller body arranged on the hub; the impeller body is provided with a plurality of groups of outer lining plates on the radial outer side of the front cover plate or / and the rear cover plate of the impeller; the splicing position of every two adjacent sets of outer lining plates is arranged at the combination position of the blades and the front cover plate or the rear cover plate, and the two sides of each set of outer lining plates are arranged at the combination position of the blades and the front cover plate or the rear cover plate. A connecting part which is made of a silicon carbide material and is used for combining the outer lining plate into a whole is arranged between the blades and the inner side part of the front cover plate or / and the rear cover plate. The large ceramic impeller is better in structural performance and lower in production cost.

Description

Technical Field

[0001] The invention belongs to the technical field of functional ceramic materials, and more specifically, relates to an impact-resistant large-scale ceramic impeller and a processing method thereof. Background Art

[0002] The impeller of a slurry pump is the most severely worn component of a slurry pump, and is generally made of wear-resistant alloy or wear-resistant rubber. However, in some working conditions with severe wear, wear-resistant alloy impellers and wear-resistant rubber impellers often cannot meet the use requirements. In order to improve the life of the impeller, silicon carbide ceramic materials with good wear resistance are currently being tried to be used to make the impeller. Depending on the process and raw materials, common silicon carbide ceramics mainly include pressureless sintered silicon carbide, hot-pressed sintered silicon carbide, reaction-sintered silicon carbide, silicon nitride bonded silicon carbide, and oxide bonded silicon carbide. Among them, pressureless sintered silicon carbide and hot-pressed sintered silicon carbide can only manufacture some simple-shaped workpieces due to the complex molding and sintering processes, and cannot manufacture complex large parts such as slurry pump impellers; while reaction-sintered silicon carbide, silicon nitride bonded silicon carbide, and oxide bonded silicon carbide can be formed by casting or grouting processes, so complex-shaped workpieces can be manufactured. At present, almost all silicon carbide ceramic impellers are made of reaction-sintered silicon carbide, silicon nitride bonded silicon carbide, and oxide bonded silicon carbide materials.

[0003] Silicon nitride bonded with silicon carbide and oxide bonded with silicon carbide can be cast, which is easy to manufacture workpieces with complex shapes such as impellers. The basic production process of silicon nitride bonded with silicon carbide and oxide bonded with silicon carbide is: mix α-SiC particles with metal silicon powder, binder, water, etc. evenly, inject into the mold for molding, demold and dry; heat the blank to 1420℃ under high-purity nitrogen, then the metal silicon powder and nitrogen in the blank react to form silicon nitride, and finally obtain silicon nitride bonded with silicon carbide; place the blank in oxygen or air and heat to 1420℃, then the metal silicon powder and oxygen in the blank react to form silicon oxide, and finally obtain oxide bonded with silicon carbide. The porosity of silicon nitride bonded with silicon carbide is generally 8%-15%, and the α-Si C content is generally 65%-80%. The flexural strength is generally 30-60Mpa. The porosity of oxide bonded with silicon carbide is generally 15%-20%, and the α-Si C content is generally 75%-85%. The flexural strength is generally 20-30Mpa.

[0004] Reaction-bonded silicon carbide ceramics generally refer to reaction-bonded silicon carbide. There is also reaction-formed silicon carbide, sometimes also called reaction-bonded silicon carbide, that is, the material is all β-SiC generated by carburization reaction, but this material has poor processability and high cost, and there is no report on its commercial application in manufacturing impellers. When manufacturing workpieces with complex shapes such as impellers, they are all reactively bonded silicon carbide, and grouting molding is generally used. The manufacturing process is: raw materials containing α-SiC micropowder and carbon black micropowder are mixed with water, binders, dispersants, etc. to form a slurry, which is then injected into the cavity of a gypsum mold (or other water-absorbing mold). The gypsum mold absorbs the water in the slurry. After the slurry loses some of its moisture, the binder gives the blank a certain strength. The gypsum mold is removed to obtain the blank. After the ceramic blank is dried and trimmed, the blank and excess metal silicon particles are stacked in a reaction sintering furnace, and the temperature is raised to about 800°C in a vacuum or inert gas. The binder and dispersant are completely carbonized. The temperature is further raised to 1500-1700°C, and the metal silicon is liquefied or vaporized. Under the action of capillaries, it penetrates into the blank and reacts with the carbon in the blank to form β-SiC, and the α-SiC in the blank is formed. C powder is combined together, and excess metallic silicon fills the pores in the blank at the same time. After cooling, a ceramic material with very low porosity (generally less than 0.1%) is obtained, and the main components are silicon carbide (generally containing α-SiC+β-SiC of 85-93%) and free silicon (also called residual silicon, generally containing 7-15%).

[0005] In recent years, 3D printing technology has also been applied to the manufacture of reaction sintered blanks. Reaction sintered silicon carbide not only has much higher wear resistance than silicon nitride combined with silicon carbide and oxide combined with silicon carbide, but also has much higher mechanical strength than the latter two, and its general bending strength can reach 250-500Mpa. Therefore, the reaction sintered silicon carbide material is significantly superior to silicon nitride combined with silicon carbide and oxide combined with silicon carbide in terms of wear resistance and strength. However, there are also many problems with the reaction sintered silicon carbide technology. At present, the reaction sintered silicon carbide impeller manufactured by conventional grid technology can only achieve a diameter of about 500mm. For example, the utility model patent with authorization announcement number CN209687784U discloses "an integral ceramic impeller", and some models of the integral ceramic impeller have been put into commercial use. However, the current market use is successful only in some small models of reaction sintered silicon carbide impellers whose diameters generally do not exceed 500mm. When manufacturing reaction-sintered silicon carbide impellers with larger diameters, it was found that the yield rate was very low, which led to a sharp increase in manufacturing costs. In addition, the manufactured reaction-sintered silicon carbide impellers had poor impact resistance and were prone to cracking not only when used under strong impact conditions, but also under slight impact conditions, the probability of cracking was also high.

[0006] Through in-depth research on the above phenomenon, we found that for silicon nitride bonded silicon carbide ceramics, oxide bonded silicon carbide, sialon bonded silicon carbide and other ceramics, due to their high porosity, these tiny pores can greatly reduce the internal stress generated during the ceramic sintering process and absorb the stress caused by external impact, so the residual stress of the workpiece is small and the impact resistance is strong. However, due to the high porosity, its wear resistance and resistance to large particle erosion are significantly lower than those of low-porosity ceramic materials such as reaction-sintered silicon carbide.

[0007] The invention patent application with application publication number CN118407930A discloses a large silicon carbide ceramic impeller proposed by the applicant, which is formed by bonding several parts including multiple ceramic impeller bodies. Since the size of the ceramic body is much smaller than the size of the impeller, the internal stress of the workpiece can be significantly reduced, and the impact resistance of the impeller can be greatly improved. However, the technical solution has the following major problems: whether it is a grouting molded workpiece or a 3D printed workpiece, there is a large shrinkage during the drying and sintering process, so that the sintered impeller body has a low dimensional accuracy, and it is difficult to meet the accuracy requirements during splicing. If mechanical processing is required to make its accuracy meet the requirements, the processing cost will be very high. If mechanical processing is not performed, it is easy to form a large dislocation at the splicing point, and at the same time, a large splicing seam is left during splicing, so that the adhesive filled in the splicing seam is easily worn, which not only reduces the life and strength of the impeller, but also leads to a decrease in the efficiency of the pump.

[0008] The utility model patent with application publication number CN 219197703 U discloses another ceramic impeller solution proposed by the applicant, wherein the impeller is provided with an impeller body of silicon nitride combined with silicon carbide, and a liner of reaction-sintered silicon carbide is provided on the surface of the impeller flow channel which is severely worn, and the liner and the impeller body are integrally formed and sintered as a whole. This technical solution can improve the wear resistance of the surface of the impeller flow channel, but this solution also has some shortcomings. First, when the impeller is enlarged, the area of ​​the flow channel is large, and the number of liner plates has to be increased to reduce the outer dimensions of the liner plates. Otherwise, during sintering, due to the difference in expansion coefficients between silicon carbide combined with silicon carbide and reaction-sintered silicon carbide, a high probability of liner plates falling off will occur, which makes the flow channel surface of the impeller have more joints, resulting in a decrease in the hydraulic performance of the impeller. Second, many other areas of the impeller are also in severely worn areas, and it is difficult to reliably set liner plates in these areas, which shortens the life of the impeller.

[0009] When the impeller is enlarged, there is another problem that is difficult to solve, that is, the strength of the rough is low. At the same time, during the manufacturing process of the rough, cracks are easy to occur in certain parts (especially the front cover and the rear cover). The larger the impeller, the more prominent the problem. When the impeller diameter exceeds 1000mm, the weight of the impeller rough often reaches more than 1000kg. During the process of trimming, drying, and kiln loading, it needs to be hoisted and moved. The strength of the rough is difficult to support its own weight and it is very easy to break, resulting in a significant decrease in the yield rate and extremely high production costs. Summary of the invention

[0010] In order to solve the deficiencies and shortcomings of the prior art, the object of the present invention is to provide a large impact-resistant ceramic impeller.

[0011] The second object of the present invention is to provide a method for processing a large impact-resistant ceramic impeller.

[0012] The technical solution of the present invention to solve the above technical problems is:

[0013] A large impact-resistant ceramic impeller comprises a hub and an impeller body arranged on the hub, wherein the impeller body is provided with a plurality of groups of outer lining plates at the radial outer side of the front cover plate or / and the rear cover plate of the impeller; the joint between two adjacent groups of outer lining plates is arranged at the joint between the blade and the front cover plate or the rear cover plate, and the two sides of each group of outer lining plates are arranged at the joint between the blade and the front cover plate or the rear cover plate; a connecting portion made of silicon carbide material is provided between the blade and the inner side of the front cover plate or / and the rear cover plate for combining the outer lining plates into a whole.

[0014] Preferably, the impeller body is an integral sintered structure.

[0015] Preferably, the head and working surface of the blade are both provided with a blade liner, and the blade liner and the impeller body are an integral sintered structure.

[0016] Preferably, a front frame is provided on the front cover plate, and a front lining plate is provided on the axial outer side of the front frame; an outer lining plate provided on the front cover plate is provided with a groove for accommodating the front frame on its axial outer side, and the front frame, the impeller body and the front lining plate are bonded into a whole by an adhesive.

[0017] Preferably, a rear frame is provided on the rear cover plate, and a rear lining plate is provided on the axial outer side of the rear frame; an outer lining plate provided on the rear cover plate is provided with a groove for accommodating the rear frame on its axial outer side, and the rear frame, the impeller body and the rear lining plate are bonded into a whole by an adhesive.

[0018] Preferably, one or more outer anti-slip structures which are narrow on the outside and wide on the inside are arranged on the radial inner side of the outer lining plate, and an inner anti-slip structure which is compatible with the anti-slip structure is also arranged on the connecting portion.

[0019] Preferably, an air gap filled with adhesive is provided between the outer anti-slip structure on the outer lining plate and the inner anti-slip structure on the connecting portion adapted thereto.

[0020] Preferably, an axial protrusion is provided on the outer lining plate, and a mounting hole matching with the protrusion is provided on the front frame or the rear frame.

[0021] Preferably, the radial dimension of the outer lining plate is 0.1-0.2 times the diameter of the impeller body.

[0022] Preferably, a flow channel lining plate is provided on the surface of the flow channel on the radial inner side of the outer lining plate.

[0023] Preferably, a bonding silicon carbide layer is provided between the front skeleton and the outer lining plate, the bonding silicon carbide layer and the outer lining plate are sintered into one piece, and the average axial thickness of the bonding silicon carbide layer is less than 40% of the axial thickness of the outer lining plate; or a bonding silicon carbide layer is provided between the rear skeleton and the outer lining plate; the average axial thickness of the bonding silicon carbide layer between the rear skeleton and the outer lining plate is less than 40% of the axial thickness of the outer lining plate.

[0024] Preferably, after two adjacent sets of outer lining plates are joined together, a gap corresponding to the blade is formed at the joint, and the width S2 of the gap is smaller than the thickness S of the blade but larger than the width S3 of the gap at the outer edge of the gap.

[0025] A method for processing a large impact-resistant ceramic impeller comprises the following steps:

[0026] (1) injecting grout into a gypsum mold for one-time molding to obtain the blanks of the outer lining plate, the blade lining plate and the flow channel lining plate;

[0027] (2) trimming and drying the blanks of the outer lining plate, blade lining plate and flow channel lining plate, and placing them in a vacuum sintering furnace, stacking metal silicon in proportion outside the blanks, heating to 1500-1700° C. under vacuum conditions for primary sintering, and obtaining the outer lining plate, blade lining plate and flow channel lining plate of reaction sintering material;

[0028] (3) positioning the obtained reaction sintered material outer lining plate, blade lining plate and flow channel lining plate on the corresponding positions of the impeller body outer mold or the impeller body mud core, filling the mold cavity with a mixture of silicon nitride and silicon carbide from the impeller body pouring port for secondary molding, and obtaining the impeller body blank after demolding;

[0029] (4) After the impeller body blank is dried, it is placed in a nitriding furnace, nitrogen is introduced, and secondary sintering is performed, and it is heated to about 1400° C. to obtain the impeller body;

[0030] (5) Assemble the impeller body onto the hub.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] 1. The impeller body in the large ceramic impeller of the present invention is obtained by secondary molding and secondary sintering; that is, before the impeller body is molded, a primary molding is first performed to obtain a blank such as an outer lining plate, and a primary sintering is performed to obtain a primary sintered part such as an outer lining plate; the primary sintered part is then placed in the molding mold of the impeller body for secondary molding, and then the secondary molded impeller body blank is subjected to secondary sintering to obtain the impeller body. When manufacturing large impellers with current technology, the strength of the blank after molding generally does not exceed 3MPa. Due to the large dead weight of the impeller, the blank is very easy to be damaged during trimming, drying, and kiln loading operations of the impeller blank, especially the outer edge of the front cover plate or the rear cover plate between adjacent blades, which is easy to break and become scrapped due to insufficient strength. After the secondary molding of the impeller body in the present invention, since the outer lining plate therein has been sintered once, its bending strength is very high, generally reaching about 100 MPa. Since the joint between the outer lining plates is located at the joint between the blades and the front cover plate or the rear cover plate, the force on the outer lining plate is similar to that of a simply supported beam, with the fulcrums being the blades at both ends. The outer lining plate is similar to the steel bars in a reinforced concrete structure. This structure greatly improves the strength of the secondary molded blank, especially the front cover plate or the rear cover plate of the impeller body blank at the outer edge between the blades, thereby greatly reducing the breakage rate of the impeller body blank and reducing production costs.

[0033] 2. Since the existing ceramic impeller is severely worn at the outer edge in the radial direction, a plurality of outer lining plates are arranged at the outer edge of the front cover plate or / and the rear cover plate through the impeller body; the joint between two adjacent outer lining plates is arranged at the joint between the blade and the front cover plate or the rear cover plate, and is strengthened by arranging the outer lining plates, so that the wear resistance of the impeller body can be better. In addition, since the outer dimensions of the outer lining plate are much smaller than the overall dimensions of the impeller body, the internal stress of the outer lining plate after the first sintering is much smaller than the internal stress of the reaction sintered impeller sintered as a whole. The joint between the outer lining plates is arranged at the joint between the blade, the front cover plate or / and the rear cover plate, so that the larger internal stress area generated by the secondary sintering can be distributed at the tail of the blade. Even if the probability of cracks in the impeller body due to sintering stress at the joint part increases, the cracks on the joint part generally do not cause the impeller body to be scrapped because the stress condition of the joint part is good, and most of the stress can be released, thereby improving the impact resistance of the impeller body.

[0034] 3. The present invention can well solve the problem that multiple impeller bodies in the large silicon carbide ceramic impeller with application publication number CN118407930A are difficult to correct due to insufficient precision and misalignment. When the outer lining plate after primary sintering is positioned in the impeller body molding mold for secondary molding, even if the outer lining plate and the mold do not completely match, the filling process of secondary molding can correct the misalignment caused by the splicing of the primary sintering workpiece, so that the secondary molded and secondary sintered impeller body has higher dimensional accuracy, thereby reducing subsequent processing and manufacturing costs, and also improving the hydraulic efficiency of the impeller. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a cross-sectional view of a first specific embodiment of the impact-resistant large-scale ceramic impeller of the present invention.

[0036] Figure 2 for Figure 1 Section view at AA.

[0037] Figure 3 A cross-sectional view of the impeller body.

[0038] Figure 4 for Figure 3 A cross-sectional view of the BB.

[0039] Figure 5 for Figure 3 Sectional view of CC.

[0040] Figure 6 This is the main view of the outer lining.

[0041] Figure 7 for Figure 6 A cross-sectional view of the EE.

[0042] Figure 8 This is the main view after the outer lining panels are assembled.

[0043] Fig. 9 for Figure 3 Sectional view in DD.

[0044] Fig.10 Schematic diagram of secondary molding of impeller body.

[0045] Fig.11 It is a cross-sectional view of the impeller body in the second specific embodiment of the impact-resistant large-scale ceramic impeller of the present invention.

[0046] Fig.12 for Fig.11 Cross-sectional view of FF.

[0047] Fig.13 This is the main view of the outer lining.

[0048] Fig.14 for Fig.13 Cross-sectional view of GG.

[0049] Fig.15 It is a cross-sectional view of a third specific embodiment of the impact-resistant large-scale ceramic impeller of the present invention.

[0050] Fig.16 This is the main view of the outer lining.

[0051] Fig.17 for Fig.16 Sectional view of HH.

[0052] Fig.18 This is the front view of the rear frame.

[0053] In the figure: 1-outer lining, 2-connecting part, 3-rear frame, 4-front frame, 5-flow channel lining, 6-front lining, 7-rear lining, 8-hub, 9-blade frame, 10-adhesive, 11-blade lining, 12-blade cavity, 13-empty gap, 14-impeller body outer mold, 15-impeller body mud core, 16-impeller body pouring port, 101-groove, 102-outer anti-slip structure, 103-axial protrusion, 104-bonded silicon carbide layer, 202-inner anti-slip structure, 303-mounting hole. DETAILED DESCRIPTION

[0054] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0055] Example 1

[0056] like Figure 1-Figure 9 As shown, the large impact-resistant ceramic impeller of the present invention has a diameter of 1430 mm, including a hub 8 and an impeller body arranged on the hub 8, wherein the impeller body is provided with 5 outer lining plates 1 at the radial outer sides of the front cover plate and the rear cover plate of the impeller; the joint between two adjacent groups of outer lining plates 1 is arranged at the junction of the blade and the front cover plate or the rear cover plate, and the two sides of each group of outer lining plates 1 are arranged at the junction of the blade and the front cover plate or the rear cover plate; a connecting portion 2 made of silicon carbide material for combining the outer lining plates 1 into a whole is provided between the blade and the inner side of the front cover plate or / and the rear cover plate.

[0057] like Figure 3As shown, the impeller body is an integral sintered structure, so that the joint seams between the outer lining plates 1 can be filled with bonded silicon carbide material; the so-called bonded silicon carbide refers to a material with a silicon carbide content of more than 60% formed by high-temperature sintering at more than 1000°C, such as silicon nitride bonded silicon carbide, oxide bonded silicon carbide, sialon bonded silicon carbide, reaction bonded silicon carbide, etc. Since bonded silicon carbide has better wear resistance than adhesives, the impeller body will not cause early damage to the ceramic impeller due to wear of the joint seams.

[0058] like Figure 2 , Figure 4 As shown, blade liners 11 are provided on the head and working surface of the blade, and the blade liners 11 and the impeller body are an integral sintered structure; since the head and working surface of the blade are the parts with more severe wear, the blade liners 11 are provided at these parts, which can significantly improve the life of the impeller.

[0059] like Figure 2 , Figure 3 , Figure 6 , Figure 7 , Figure 8 As shown, the front cover plate is provided with a front frame 4, which can significantly improve the impact resistance of the front cover plate. The front liner plate 6 is provided on the axial outer side of the front frame 4; the outer liner plate 1 provided on the front cover plate is provided with a groove 101 for accommodating the front frame 4 on its axial outer side, and the front frame 4, the impeller body and the front liner plate 6 are bonded into a whole by an adhesive. By providing the outer liner plate 1 provided on the front cover plate with a groove 101 for accommodating the front frame 4 in the axial direction, and bonding the front frame 4, the impeller body and the front liner plate 6 into a whole by an adhesive, the outer liner plate 1 can be bonded to the front frame 4 to prevent the outer liner plate 1 from falling out of the impeller body.

[0060] like Figure 1 , Figure 3 As shown, the rear cover plate is provided with a rear frame 3, which can significantly improve the impact resistance of the rear cover plate, and a rear lining plate 7 is provided on the axial outer side of the rear frame 3; the outer lining plate 1 arranged on the rear cover plate is provided with a groove 101 for accommodating the rear frame 3 on its axial outer side, and the rear frame 3, the impeller body and the rear lining plate 7 are bonded into a whole by an adhesive; in this way, the outer lining plate 1 can be bonded to the rear frame 3 to prevent the outer lining plate 1 from escaping from the impeller body.

[0061] like Figure 6The radial dimension S1 of the outer lining plate 1 is 168 mm, and the diameter of the impeller body is 1430 mm, that is, the radial dimension S1 of the outer lining plate 1 is 0.117 times the diameter of the impeller. This makes the outer lining plate 1 rupture in the direction of the cross-section with smaller bending strength of the workpiece under stress, that is, pointing to the axial direction of the impeller body. Therefore, even if the outer lining plate 1 is ruptured by impact, since both ends of the fracture are bonded to the front frame 4 / rear frame 3 and the front lining plate 6 / rear lining plate 7 as a whole, the probability of falling off from the impeller body is very low, and the reliability of the impeller is improved.

[0062] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, a flow channel lining plate 5 is provided on the flow channel surface on the radial inner side of the outer lining plate 1 to improve the wear resistance of the impeller; in this embodiment, two flow channel lining plates 5 are provided on each flow channel surface, so a total of 10 flow channel lining plates 5 are provided.

[0063] like Figure 2 and Figure 4 As shown, a blade lining 11 is arranged on the head and working surface of the blade. On each blade, the connecting portion 2 connects the front cover plate and the rear cover plate into one body. A blade cavity 12 for accommodating the blade skeleton 9 and the adhesive 10 is arranged on the connecting portion 2 of the blade.

[0064] In this embodiment, the material of the outer lining plate 1 and the flow channel lining plate 5 is reaction-sintered silicon carbide, and the material of the connecting part 2 is silicon nitride combined with silicon carbide; and the material of the front frame 4, the rear frame 3, the blade frame 9 and the hub 8 is carbon steel, among which the rear frame 3, the blade frame 9 and the hub 8 are welded into a whole.

[0065] See also Figure 1-Figure 9 The specific manufacturing process of the impeller body of this embodiment is:

[0066] (1) injecting grout into a plaster mold to form blanks of the outer lining plate 1, the blade lining plate 11 and the flow channel lining plate 5;

[0067] (2) After trimming and drying the blanks of the outer lining plate 1, the blade lining plate 11 and the flow channel lining plate 5, the blanks are placed in a vacuum sintering furnace, metal silicon is stacked in proportion outside the blanks, and the blanks are heated to 1500-1700° C. under vacuum conditions for primary sintering to obtain the outer lining plate 1, the blade lining plate 11 and the flow channel lining plate 5 of reaction sintered material;

[0068] (3) Position the outer lining plate 1, the blade lining plate 11, etc. at the corresponding positions of the impeller body outer mold 14 and the impeller body mud core 15, and fill the mold cavity with a mixture of silicon nitride and silicon carbide from the impeller body pouring port 16 for secondary molding. After demolding, the impeller body blank (such as Fig.10 shown);

[0069] (4) After the impeller body blank is dried, it is placed in a nitriding furnace, high-purity nitrogen is introduced, and secondary sintering is performed, and it is heated to about 1400° C. to obtain the impeller body;

[0070] The impeller body manufactured according to the above process, during the secondary molding, due to the gap between the outer lining plate 1 and the secondary molding mold, a layer of silicon nitride combined with silicon carbide layer mixture will be formed on the surface of part of the outer lining plate 1, and after sintering, it will become a silicon nitride combined with silicon carbide layer (i.e. Figure 7 When the impeller is bonded, the adhesive with lower viscosity can penetrate through the pores of the silicon nitride bonded silicon carbide layer to bond the outer lining plate 1 and the front frame 4 / rear frame 3 into a whole. To improve the bonding strength to the outer lining plate 1, the average axial thickness of the silicon nitride bonded silicon carbide layer is less than 40% of the axial thickness of the outer lining plate 1.

[0071] In this embodiment, the axial thickness of the outer lining plate 1 is 62 mm, the axial thickness of the silicon nitride bonded silicon carbide layer between the front skeleton 4 and the outer lining plate 1 is 2 mm, and the thickness of the silicon nitride bonded silicon carbide layer between the rear skeleton 3 and the outer lining plate 1 is 1 mm.

[0072] like Figure 5 , Figure 8 As shown, when the five outer lining plates 1 are assembled, a gap 13 corresponding to the blade is formed at the joint. The width S2 of the gap 13 is less than the thickness S of the blade but greater than the width S3 of the gap at the outer edge of the gap 13. This structure can use the silicon nitride combined with silicon carbide material filled in the relatively large gap in the gap 13 as a binder to improve the strength of the impeller body blank and the impeller body, while ensuring that the outer edge of the impeller body between the outer lining plates 1 has a smaller gap, so that the silicon nitride combined with silicon carbide filled therein is not easy to be worn, thereby improving the wear resistance of the impeller body. The pores in the silicon nitride combined with silicon carbide material in the gap 13 can release the stress generated by the secondary sintering, thereby reducing the probability of impeller rupture and improving the impact resistance of the impeller. At the same time, the silicon nitride combined with silicon carbide in this part will also be protected by the blade lining plate 11 to prevent it from being worn quickly. In this embodiment, the thickness S of the blade at the corresponding position is 70 mm, the gap S2 of the empty gap 13 is 30-40 mm, and the gap S3 at the outer edge of the empty gap 13 is 0.5-2 mm.

[0073] In this embodiment, the material of the front lining plate 6 and the rear lining plate 7 is pressureless sintered silicon carbide, and the adhesive is acrylic resin.

[0074] Example 2

[0075] This embodiment is substantially the same as Embodiment 1, and the main differences are as follows:

[0076] like Fig.11 , Fig.12 , Fig.13 , Fig.14 As shown, the diameter of the impeller in this embodiment is 1620 mm, 5 outer lining plates 1 are arranged on the front cover plate of the impeller body, and 5 outer lining plates 1 are also arranged on the rear cover plate. Two outer anti-slip structures 102 with narrow outer sides and wide inner sides are arranged on the radial inner side of each outer lining plate 1, as shown in FIG. Fig.12 , 13 In the figure, the inner width B1 of the outer anti-slip structure is 55 mm, and the outer width B2 is 52 mm. The inner anti-slip structure 202 which is adapted to the outer anti-slip structure 102 is naturally formed on the connecting portion 2 during the secondary molding. The radial dimension S4 of the outer lining plate 1 is 162 mm, that is, the radial dimension of the outer lining plate 11 is 0.1 times the impeller diameter.

[0077] By arranging one or more outer anti-slip structures which are narrow on the outside and wide on the inside on the radial inner side of the outer lining plate 1, an inner anti-slip structure 202 which is adapted to the outer anti-slip structure 102 will be naturally formed on the connecting portion 2 during casting, thereby preventing the outer lining plate 1 from escaping from the impeller body under the action of centrifugal force.

[0078] In this embodiment, the material of the outer lining plate 1 is pressureless sintered silicon carbide, and the material of the connecting portion 2 is oxide-bonded silicon carbide.

[0079] The manufacturing process of the impeller body in this embodiment is substantially the same as that in Embodiment 1, and the main differences are:

[0080] After the primary sintering, before the secondary molding, a 0.1-0.5 mm thick organic glue is applied to the surface of the outer anti-stripping structure 102 of the outer lining plate 1. When the secondary sintering is performed after the secondary molding, the organic glue is burned. After the secondary sintering is completed, an air gap is left between the outer anti-stripping structure 102 and the inner anti-stripping structure 202, thereby preventing cracking or generating large residual stress due to the difference in expansion coefficients between the two. In the subsequent bonding process, the adhesive is infiltrated into the air gap to improve the strength and impact resistance of the impeller.

[0081] Example 3

[0082] like Figure 15-18 As shown, this embodiment is substantially the same as Embodiment 1, and the main differences are:

[0083] The impeller has a diameter of 950 mm, the outer lining plate 1 is made of pressureless sintered silicon carbide or reaction sintered silicon carbide, and the connecting portion 2 is made of reaction sintered silicon carbide.

[0084] Each outer lining plate 1 has two axial protrusions 103 and is embedded in corresponding mounting holes 303 on the front frame 4 / rear frame 3, so as to improve the bonding force between the outer lining plate 1 and the front frame 4 / rear frame 3 and prevent the outer lining plate 1 from falling off the impeller body.

[0085] After the first sintering and the second sintering, the distribution of internal stress and the direction of the impact rupture of the outer lining plate 1 are related to its shape. When the outer lining plate 1 is larger in radial direction, the outer lining plate 1 can cover a wider area and the wear resistance of the impeller is better. However, the stress distribution of the outer lining plate 1 of this shape makes the direction of its rupture after impact and the tangent angle of the outer circle smaller, so that the broken part after rupture is easy to fall off, thereby causing the impeller to fail and the reliability of the impeller to decrease. On the contrary, when the outer lining plate 1 is smaller in radial direction, the stress distribution of the outer lining plate 1 makes the direction of its rupture and the tangent angle of the outer circle larger, that is, the crack extends toward the center of the circle. After the outer lining plate 1 is broken, the stress is released and the crack no longer extends toward the connecting part 2 of the center of the circle. Since the outer lining plate 1 after rupture can still be fixed to the front frame 4 or the rear frame 3 by the adhesive, the impeller can continue to be used, which can improve the reliability of the impeller. However, if the coverage area of ​​the outer lining plate 1 is too small, the overall wear resistance of the impeller will decrease or the difficulty of setting the flow channel lining plate 5 will increase. When the radial dimension of the outer lining plate 1 is 0.1-0.2 times of the impeller diameter, the above contradiction can be balanced.

[0086] Therefore, after the impeller body of this embodiment is bonded with the adhesive, the outer lining plate 1 can be prevented from falling off after cracks appear in the outer lining plate 1. The radial dimension S5 of the outer lining plate 1 is 130 mm, which is 0.126 times the diameter of the impeller.

[0087] The above is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited to the above content. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A large impact-resistant ceramic impeller, characterized in that: It comprises a hub and an impeller body arranged on the hub, wherein the impeller body is an integral sintered structure, and the impeller body is provided with a plurality of groups of outer lining plates at the radial outer side of the front cover plate or / and the rear cover plate of the impeller; the joint between two adjacent groups of outer lining plates is arranged at the joint between the blade and the front cover plate or the rear cover plate, and the two sides of each group of outer lining plates are arranged at the joint between the blade and the front cover plate or the rear cover plate; a connecting portion made of silicon carbide material is arranged between the blade and the inner side of the front cover plate or / and the rear cover plate for combining the outer lining plates into a whole; a flow channel lining plate is arranged on the surface of the flow channel on the radial inner side of the outer lining plate.

2. The impact-resistant large ceramic impeller according to claim 1, characterized in that: The head and working surface of the blade are both provided with blade liners, and the blade liners and the impeller body are an integral sintered structure.

3. The impact-resistant large ceramic impeller according to claim 1, characterized in that: A front frame is arranged on the front cover plate, and a front lining plate is arranged on the axial outer side of the front frame; an outer lining plate arranged on the front cover plate is provided with a groove for accommodating the front frame on its axial outer side, and the front frame, the impeller body and the front lining plate are bonded into a whole by an adhesive.

4. The impact-resistant large ceramic impeller according to claim 3, characterized in that: A rear frame is arranged on the rear cover plate, and a rear lining plate is arranged on the axial outer side of the rear frame; an outer lining plate arranged on the rear cover plate is provided with a groove for accommodating the rear frame on its axial outer side, and the rear frame, the impeller body and the rear lining plate are bonded into a whole by an adhesive.

5. The impact-resistant large ceramic impeller according to claim 1, characterized in that: One or more outer anti-slip structures which are narrow outside and wide inside are arranged on the radial inner side of the outer lining plate, and an inner anti-slip structure which is adapted to the anti-slip structure is also arranged on the connecting portion.

6. The impact-resistant large ceramic impeller according to claim 5, characterized in that: An air gap filled with adhesive is arranged between the outer anti-slip structure on the outer lining plate and the inner anti-slip structure on the connecting part adapted thereto.

7. The impact-resistant large ceramic impeller according to claim 4, characterized in that: The outer lining plate is provided with an axial protrusion, and the front frame or the rear frame is provided with a mounting hole that matches the protrusion.

8. The impact-resistant large ceramic impeller according to claim 1, characterized in that: The radial dimension of the outer lining plate is 0.1-0.2 times the diameter of the impeller body.

9. The impact-resistant large ceramic impeller according to claim 4, characterized in that: A bonding silicon carbide layer is provided between the front frame and the outer lining plate, the bonding silicon carbide layer and the outer lining plate are sintered into one body, and the average axial thickness of the bonding silicon carbide layer is less than 40% of the axial thickness of the outer lining plate; or a bonding silicon carbide layer is provided between the rear frame and the outer lining plate; the average axial thickness of the bonding silicon carbide layer between the rear frame and the outer lining plate is less than 40% of the axial thickness of the outer lining plate.

10. The impact-resistant large ceramic impeller according to claim 1, characterized in that: After two adjacent sets of outer lining plates are joined together, a gap corresponding to the blade is formed at the joint, and the width S2 of the gap is smaller than the thickness S of the blade but larger than the width S3 of the gap at the outer edge of the gap.

11. A method for processing the impact-resistant large-scale ceramic impeller according to any one of claims 1 to 10, characterized in that: The following steps are involved: (1) injecting grout into a gypsum mold for one-time molding to obtain the blanks of the outer lining plate, the blade lining plate and the flow channel lining plate; (2) trimming and drying the blanks of the outer lining plate, blade lining plate and flow channel lining plate, and placing them in a vacuum sintering furnace, stacking metal silicon in proportion outside the blanks, heating to 1500-1700° C. under vacuum conditions for primary sintering, and obtaining the outer lining plate, blade lining plate and flow channel lining plate of reaction sintering material; (3) positioning the obtained reaction sintered material outer lining plate, blade lining plate and flow channel lining plate on the corresponding positions of the impeller body outer mold or the impeller body mud core, filling the mold cavity with a mixture of silicon nitride and silicon carbide from the impeller body pouring port for secondary molding, and obtaining the impeller body blank after demolding; (4) After the impeller body blank is dried, it is placed in a nitriding furnace, nitrogen is introduced, and secondary sintering is performed, and it is heated to 1400° C. to obtain an impeller body; (5) Assemble the impeller body onto the hub.

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