Conveying elbow and preparation method thereof

Abstract

The invention relates to the technical field of concrete conveying, and discloses a conveying elbow pipe and a preparation method thereof.The conveying elbow pipe comprises an outer pipe layer (4) and an inner pipe layer (2), the outer pipe layer (4) and the inner pipe layer (2) make contact with each other and form metallurgical bonding, the contact interface is of a mutually-embedded concave-convex structure, and a wear-resisting part (3) is embedded in a wear-resisting area of the inner pipe layer (2); the thickness of the wear-resisting part (3) is gradually reduced from the center to the periphery, the maximum thickness of the wear-resisting part (3) is smaller than that of the inner pipe layer (2), the inner surface of the wear-resisting part (3) is flush with the inner surface of the inner pipe layer (2), a plurality of meshes are formed in the wear-resisting part (3), and chemical components of the inner pipe layer (2) permeate into the meshes to form metallurgical bonding. According to the conveying elbow provided by the invention, the zero clearance of the elbow is fully realized, the problem of early rupture failure caused by insufficient shock resistance of the inner pipe of the elbow due to the clearance between the pipes is avoided, and the wear resistance and the shock resistance are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of concrete transportation, and in particular to a transportation elbow and a preparation method thereof. Background Art

[0002] Concrete delivery pipe is used as a pipeline for concrete pumping equipment such as pump trucks, vehicle-mounted pumps and trailer pumps to pump concrete to the destination. Among them, the end bend is an arc-shaped pipe located at the end of the delivery pipe, which is mainly used to change the flow direction of concrete. During the actual pumping operation, the end bend must withstand the pumping pressure and resist the strong wear of concrete.

[0003] At present, the terminal elbow of concrete delivery in the market mainly adopts a double-layer metal pipe composite structure. The outer pipe is generally Q345 alloy steel, which mainly plays a supporting role, and the inner pipe is generally high-chromium cast iron, which mainly plays an anti-wear role. There is a gap between the inner and outer pipes. As the pumping height gradually increases, the terminal elbow has to withstand higher pumping pressure and concrete wear. The posture of the end boom is generally tilted downward, resulting in greater impact and wear on the terminal elbow than other elbows, and it is more likely to fail early than other elbows. Improving the service life of the terminal elbow is a difficult problem that needs to be solved urgently for concrete delivery pipes.

[0004] CN214222366U discloses a ceramic elbow, in which cylindrical ceramics matching with the inner tube are inserted into the tapered holes on the back and neck of the inner tube to improve wear resistance. However, this scheme has the following disadvantages: (1) In this technology, the tapered ceramic is arranged in the tapered hole of the inner tube, which has high requirements on the ceramic size accuracy and the size of the tapered hole of the inner tube, and the process is complicated, the production efficiency is low, and the production cost is high; (2) When the inner tube is compounded with the tapered ceramic material, a step is easily formed in the tapered ceramic area of ​​the inner tube, which increases the resistance of the concrete pumping process and aggravates the wear of the inner tube; (3) When the gap between the inner and outer tubes is filled with fillers, it is still impossible to achieve a gapless gap. When the inner tube is impacted by concrete, it is still possible that the inner tube is insufficiently supported due to the gap between the inner and outer tubes, and thus it is broken and fails early. Summary of the invention

[0005] The purpose of the present invention is to provide a concrete conveying elbow pipe having excellent wear resistance and impact resistance.

[0006] In order to achieve the above-mentioned object, a first aspect of the present invention provides a conveying elbow pipe, comprising an outer pipe layer and an inner pipe layer, wherein the outer pipe layer and the inner pipe layer contact each other and form a metallurgical bond, and have a concave-convex structure embedded in each other at the contact interface.

[0007] The wear-resistant area of ​​the inner tube layer is inlaid with a wear-resistant portion, the wear-resistant area has a central angle of 30° to 90° corresponding to the cross section of the conveying elbow, and a central angle of 100° to 180° corresponding to the cross section of the conveying elbow.

[0008] The thickness of the wear-resistant part gradually decreases from the center to the periphery, and the maximum thickness of the wear-resistant part is less than the maximum thickness of the inner tube layer. The inner surface of the wear-resistant part is flush with the inner surface of the inner tube layer. The wear-resistant part is provided with a plurality of mesh holes, and the chemical components of the inner tube layer penetrate into the mesh holes to form a metallurgical bond.

[0009] A second aspect of the present invention provides a method for preparing a conveying elbow, the method comprising:

[0010] S1: subjecting the material containing the ceramic composition to compression molding and sintering in sequence to obtain a wear-resistant portion containing a plurality of meshes, wherein the thickness of the wear-resistant portion gradually decreases from the center to the periphery;

[0011] S2: manufacturing a lost foam model according to the shape of the conveying elbow, wherein the lost foam model comprises an outer mold layer and an inner mold layer, fixing the wear-resistant portion on the wear-resistant region of the inner mold layer, and providing a wire mesh having a concave-convex structure on the contact interface between the outer mold layer and the inner mold layer of the lost foam model,

[0012] The inner surface of the wear-resistant portion is flush with the inner surface of the inner mold layer, and the maximum thickness of the wear-resistant portion is less than the maximum thickness of the inner mold layer; the central angle of the wear-resistant area in the cross section of the lost foam model is 30° to 90°, and the central angle of the wear-resistant area in the cross section of the lost foam model is 100° to 180°;

[0013] S3: Injecting the molten first metal material and the molten second metal material into the outer mold layer and the inner mold layer of the lost foam model at the same time; the molten first metal material and the molten second metal material penetrate into the depressions and protrusions of the wire mesh, presenting a mutually embedded concave-convex structure on the contact interface, and the molten second metal material penetrates into several meshes of the wear-resistant part, forming a metallurgical bond with the wear-resistant part, and cooling to obtain a conveying elbow.

[0014] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0015] (1) The inner tube of the elbow in the present invention adopts a casting process, and the inner tube layer and the wear-resistant part are combined with high strength at high temperature, and a plurality of mesh holes are provided on the wear-resistant part, which is conducive to the molten second metal material (the chemical component of the inner tube layer) to penetrate into the mesh holes, so that the second metal material and the wear-resistant part can be contacted and combined with a large area, and a metallurgical bond is formed at the contact point, thereby improving the bonding strength between the wear-resistant part and the inner tube layer in the finished elbow, avoiding the wear-resistant part from falling off under high impact and wear conditions, and reducing the risk of early failure. The contact interface between the inner tube layer and the outer tube layer of the elbow of the present invention is a concave-convex structure embedded in each other, which is conducive to increasing the intersection interface area of ​​the outer tube layer and the inner tube layer, further enhancing the metallurgical bonding strength between the outer tube layer and the inner tube layer, and relatively increasing the thickness of the outer tube layer and the inner tube layer, which is conducive to improving the wear resistance of the elbow while ensuring the strength of the elbow. In addition, the overall thickness of the structural design of the inner tube layer and the outer tube layer is effectively controlled, and the lightweight of the elbow is achieved.

[0016] (2) The present invention adopts a special casting process, and adds a wire mesh with a special concave-convex structure during the lost foam casting process, so as to realize the integrated manufacturing of the inner and outer tubes of the elbow, and effectively control the thickness of the structural design of the inner tube layer and the outer tube layer. At the same time, the very limited blending of the two molten metal materials in a large number of fine pores and the gear-shaped mutual embedding structure of the outer tube layer and the inner tube layer after casting and condensation greatly improve the bonding strength between the outer tube layer and the inner tube layer, and improve the wear resistance of the conveying elbow to a certain extent.

[0017] (3) The present invention adopts the lost foam casting process to directly combine the inner and outer tubes of the traditional double-layer elbow pipe, and at the same time combines them with wear-resistant ceramics to form a metallurgically bonded composite pipe layer, that is, there is no gap between the multiple layers of pipes, and the gap-free nature of the pump truck elbow pipe is fully realized, avoiding the problem of early rupture and failure caused by insufficient impact resistance of the inner tube of the pump truck elbow pipe due to the gap between the tubes; compared with the traditional double-layer elbow pipe, the filler between the inner and outer tubes does not increase the weight of the elbow pipe, and the low-density and high-wear-resistant ceramic material realizes the lightweight of the concrete elbow pipe.

[0018] (4) The integrated manufacturing of the inner and outer tubes of the conveying elbow provided by the present invention optimizes the manufacturing process, simplifies the manufacturing process, and reduces the manufacturing cost, compared with the traditional method of independently manufacturing the outer tube and the inner tube and then performing the inner and outer tube composite process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a cross-sectional view of the conveying elbow;

[0020] Figure 2 yes Figure 1 Cross-sectional view in the AA direction;

[0021] Figure 3 It is a three-dimensional schematic diagram of the wear-resistant part.

[0022] Description of reference numerals:

[0023] 1-flange, 2-inner tube layer, 3-wear-resistant part, 4-outer tube layer, 5-wear-resistant sleeve, 6-composite layer. DETAILED DESCRIPTION

[0024] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0025] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first" and "second" in the terms "first metal material" and "second metal material" are only used to distinguish different metal materials and have no special meaning.

[0026] The "section" of the present invention refers to Figure 1 The axial section shown; the "cross section" refers to the Figure 2 shown Figure 1 Cross-sectional view in the AA direction; the "cross-sectional center axis" refers to the vertical center axis.

[0027] like Figure 1 , Figure 2 As shown, a conveying elbow comprises an outer tube layer 4 and an inner tube layer 2. The outer tube layer 4 and the inner tube layer 2 are in contact with each other and form a metallurgical bond, and a concave-convex structure embedded in each other is formed at the contact interface.

[0028] A wear-resistant portion 3 is embedded in the wear-resistant area of ​​the inner tube layer 2, and the wear-resistant area has a central angle of 30° to 90° in the cross section of the conveying elbow and a central angle of 100° to 180° in the cross section of the conveying elbow.

[0029] The thickness of the wear-resistant part 3 gradually decreases from the center to the periphery, and the maximum thickness of the wear-resistant part 3 is less than the maximum thickness of the inner tube layer 2. The inner surface of the wear-resistant part 3 is flush with the inner surface of the inner tube layer 2. The wear-resistant part 3 is provided with a plurality of mesh holes, and the chemical components of the inner tube layer 2 penetrate into the mesh holes to form a metallurgical bond.

[0030] Preferably, the area of ​​the concavo-convex structure has a central angle of 70° to 90° in the cross section of the conveying elbow and a central angle of 140° to 180° in the cross section.

[0031] More preferably, the area of ​​the concavo-convex structure has a central angle of 90° in the cross section of the conveying elbow and a central angle of 180° in the cross section, that is, the range of 0° to 90° inward from the elbow port and 0° to 180° along the circumferential direction of the cross section.

[0032] Preferably, the central angle of the wear-resistant portion 3 corresponding to the cross section of the conveying elbow is 40° to 70°.

[0033] More preferably, the central angle of the wear-resistant portion 3 corresponding to the cross-section of the conveying elbow is selected from at least one of 45°, 50°, 55°, 60° and 65°.

[0034] Preferably, the wear-resistant portion 3 has a central angle corresponding to a cross section of the conveying elbow of 120° to 160°.

[0035] More preferably, the central angle of the wear-resistant portion 3 corresponding to the cross section of the conveying elbow is selected from at least one of 125°, 130°, 135°, 140°, 145°, 150° and 155°.

[0036] More preferably, the wear-resistant portion 3 is symmetrically arranged along the cross-sectional center axis and the cross-sectional center axis of the conveying elbow.

[0037] In the present invention, according to the actual wear data of the elbow, it is particularly preferred that the wear-resistant part 3 is symmetrically arranged along the cross-sectional central axis and the cross-sectional central axis of the conveying elbow, and a raised wear-resistant part is used at the central angle of 50° corresponding to the cross-section and the central angle of 140° corresponding to the cross-section, that is, at a position 20° to 70° into the elbow port and 20° to 160° along the circumferential direction of the cross-section. The wear-resistant part is designed to be the thickest raised part of the wear-resistant part at the position of the cross-sectional central axis, and gradually becomes thinner around. The progressive raised mesh design of the wear-resistant part makes the wear-resistant ceramics evenly distributed on the easily worn surface. The present invention preferably places the wear-resistant part at the most easily worn position to increase the service life of the pipe fittings, and arranges the most rational use of wear-resistant ceramics for the most severely worn parts of the pump truck. The wear resistance of the inner pipe is maximized when the amount of wear-resistant ceramics used is small, and the cost performance is high.

[0038] According to a preferred specific implementation manner, the thickness of the composite layer 6 formed by the inner tube layer 2 and the wear-resistant portion 3 gradually decreases from the middle of the conveying elbow to both ends of the conveying elbow.

[0039] The “two ends of the conveying elbow” mentioned in the present invention refers to the direction extending from the middle of the conveying elbow to the two pipe openings.

[0040] Preferably, the maximum thickness of the composite layer 6 is 18-22 mm, and the minimum thickness is 5-7 mm.

[0041] Preferably, the maximum thickness of the wear-resistant portion 3 is 12-15 mm, and the minimum thickness is 0-3 mm.

[0042] The thickness of the composite layer 6 described in the present invention refers to the thickness calculated from the starting plane of the concave or convex part of the contact interface of the concave-convex structure, and does not include the height of the concave or convex part.

[0043] Preferably, the heights of the concave and convex parts of the concave-convex structure are independently selected from 0.5 to 1.5 mm.

[0044] Preferably, the distance between the concave part and the convex part of the concave-convex structure is greater than 0.

[0045] According to another preferred specific embodiment, the conveying elbow further comprises flanges 1 and wear-resistant sleeves 5 arranged at both ends of the conveying elbow, wherein the wear-resistant sleeves 5 are mounted on the inner ring of the flange and the flanges 1 are welded to both ends of the pipe.

[0046] Preferably, the wear-resistant part 3 is made of ceramic, more preferably wear-resistant ceramic. The present invention uses low-density and high-wear-resistant ceramic materials, which avoids the filler between the inner and outer pipes increasing the weight of the elbow and realizes a lightweight design of the elbow compared to the traditional double-layer elbow.

[0047] Preferably, the outer tube layer 4 is made of low carbon steel.

[0048] Preferably, the inner tube layer 2 is made of high chromium cast iron.

[0049] Preferably, the flange 1 is made of low alloy steel.

[0050] Preferably, the wear-resistant sleeve 5 is made of high-chromium cast iron.

[0051] As mentioned above, the second aspect of the present invention provides a method for preparing a conveying elbow, the method comprising:

[0052] S1: subjecting the material containing the ceramic composition to compression molding and sintering in sequence to obtain a wear-resistant portion containing a plurality of meshes, wherein the thickness of the wear-resistant portion gradually decreases from the center to the periphery;

[0053] S2: manufacturing a lost foam model according to the shape of the conveying elbow, wherein the lost foam model comprises an outer mold layer and an inner mold layer, fixing the wear-resistant portion on the wear-resistant region of the inner mold layer, and providing a wire mesh having a concave-convex structure on the contact interface between the outer mold layer and the inner mold layer of the lost foam model,

[0054] The inner surface of the wear-resistant portion is flush with the inner surface of the inner mold layer, and the maximum thickness of the wear-resistant portion is less than the maximum thickness of the inner mold layer; the central angle of the wear-resistant area in the cross section of the lost foam model is 30° to 90°, and the central angle of the wear-resistant area in the cross section of the lost foam model is 100° to 180°;

[0055] S3: Injecting the molten first metal material and the molten second metal material into the outer mold layer and the inner mold layer of the lost foam model at the same time; the molten first metal material and the molten second metal material penetrate into the depressions and protrusions of the wire mesh, presenting a mutually embedded concave-convex structure on the contact interface, and the molten second metal material penetrates into several meshes of the wear-resistant part, forming a metallurgical bond with the wear-resistant part, and cooling to obtain a conveying elbow.

[0056] Preferably, step S1 comprises: mixing materials containing a ceramic composition to obtain a mixture I, adding the mixture I into a mold for compression molding, drying the preform that has been pressed and demolded, and then sintering the dried preform at a temperature of 1450°C to 1600°C, preferably at a temperature of 1480°C to 1600°C, to obtain a wear-resistant portion containing a plurality of meshes, wherein the thickness of the wear-resistant portion gradually decreases from the center to the periphery.

[0057] Preferably, in step S1, based on the total weight of the ceramic composition, the ceramic composition contains 88-96 wt% of ceramic raw materials, 3-11 wt% of active additives and 0.2-1.0 wt% of binder.

[0058] Preferably, the ceramic raw material is selected from at least one of alumina ceramics, zirconia toughened alumina ceramics, titanium carbide ceramics, and tungsten carbide ceramics.

[0059] Preferably, the active additive is selected from at least one of Ti, Ni and B4C. Preferably, the active additive is used in the form of powder.

[0060] Preferably, the binder is selected from at least one of polyvinyl alcohol, epoxy resin, polyaldehyde resin and acrylic polymer.

[0061] Preferably, in step S1, the hardness of the wear-resistant part is above 88HRA.

[0062] In the present invention, HRA refers to the hardness obtained by a 60 kg load and a 120° diamond cone indenter.

[0063] Preferably, in step S1, the material of the lost foam model is foam and / or paraffin.

[0064] More preferably, the material of the lost foam model is foam, and the foam is selected from at least one of expandable polystyrene resin (EPS), expandable methyl methacrylate and styrene copolymer resin (STMMA), and expandable polymethyl methacrylate (EPMMA).

[0065] The specific type of foam preferably used in the present invention has the characteristics of low density, rapid gasification, good strength and surface rigidity, etc., which can ensure that the lost foam maintains the stability of size and shape, reduces surface scratches, and has sufficient gasification capacity to support the metal melt to penetrate and fill the corresponding position.

[0066] According to a preferred specific implementation manner, the method described in step S1 further includes: coating a thermal insulation coating in the inner cavity of the lost foam model, and the thickness of the thermal insulation coating is 1 to 3 μm.

[0067] Preferably, in step S2, the center angle of the wear-resistant area in the cross section of the lost foam model is 40° to 70°, and the center angle of the wear-resistant area in the cross section of the lost foam model is 120° to 160°.

[0068] More preferably, in step S2, the center angle of the wear-resistant area corresponding to the cross-section of the lost foam model is selected from at least one of 45°, 50°, 55°, 60°, and 65°, and the center angle of the wear-resistant area corresponding to the cross-section of the lost foam model is selected from at least one of 125°, 130°, 135°, 140°, 145°, 150°, and 155°.

[0069] Particularly preferably, the wear-resistant area has a central angle of 50° corresponding to the section of the lost foam model, and a central angle of 140° corresponding to the cross section, that is, a position within 20° to 70° from the model elbow port and 20° to 160° along the circumferential direction of the cross section. Placing the wear-resistant part at the most easily worn position increases the service life of the pipe fittings, and the most reasonable amount of wear-resistant ceramics is arranged for the most severely worn parts of the actual pump truck, which maximizes the wear resistance of the inner pipe when the amount of wear-resistant ceramics is small, and has a high cost-effectiveness.

[0070] Preferably, in step S2, the setting area of ​​the screen on the contact interface has a central angle of 70° to 90° in the cross section of the lost foam model and a central angle of 140° to 180° in the cross section of the lost foam model.

[0071] More preferably, in step S2, the area where the screen is set on the contact interface has a central angle of 90° in the cross section of the lost foam model and a central angle of 180° in the cross section of the lost foam model, that is, the range of 0° to 90° inward from the elbow of the lost foam model and 0° to 180° along the circumferential direction of the cross section.

[0072] Preferably, the heights of the concave and convex parts of the concave-convex structure in the screen are independently selected from 0.5 to 1.5 mm.

[0073] Preferably, the distance between the concave and convex parts of the concave-convex structure in the screen is greater than 0.

[0074] Preferably, the mesh has an aperture of 1 to 100 μm, preferably 20 to 80 μm. The inventors found in their research that by controlling the mesh aperture within the preferred range, the two molten metal materials of the inner and outer tube layers can be blended in a limited manner in a large number of pores during the lost foam casting process, further improving the bonding strength between the outer and inner tube layers of the conveying elbow.

[0075] According to a preferred specific implementation manner, the thickness of the combined layer formed by the inner mold layer and the wear-resistant portion gradually decreases from the middle of the lost foam model to both ends of the lost foam model.

[0076] Preferably, the maximum thickness of the combined layer is 18 to 22 mm, and the minimum thickness is 5 to 7 mm.

[0077] Preferably, the maximum thickness of the wear-resistant portion is 12 to 15 mm, and the minimum thickness is 0 to 3 mm.

[0078] The present invention has no particular restriction on the material of the wire mesh, as long as it can remain unmelted during the casting of the molten first metal material or the molten second metal material. However, in order to obtain a conveying elbow with stronger bonding between the inner and outer pipe layers, the present invention preferably uses a material selected from at least one of iron and steel.

[0079] The present invention has no particular limitation on the preparation method of the screen, and those skilled in the art can obtain it according to the actual form requirements using preparation methods known in the art. The present invention will not go into details herein, and those skilled in the art should not interpret this as a limitation on the present invention.

[0080] Preferably, the first metal material is low carbon steel.

[0081] Preferably, the second metal material is high chromium cast iron.

[0082] Preferably, the hardness of the inner tube layer of the conveying elbow is 63-66HRC.

[0083] In the present invention, HRC refers to Rockwell hardness.

[0084] According to a preferred specific implementation, the method further comprises: fitting the wear-resistant sleeve to the inner ring of the flange, and fixing the wear-resistant sleeve to the conveying elbow described in step S3 by welding.

[0085] Preferably, the flange is made of low alloy steel.

[0086] Preferably, the wear-resistant sleeve is made of high-chromium cast iron.

[0087] The method described in the present invention may also include post-processing means known in the art such as cleaning and coating the conveying elbow. The present invention exemplarily provides a preferred specific implementation method in the following text, which should not be understood by those skilled in the art as a limitation of the present invention.

[0088] According to a particularly preferred embodiment, the method for preparing the conveying elbow of the present invention comprises the following steps:

[0089] SS1: Preparation of the wear-resistant part: Mix the materials containing the ceramic composition by a vertical three-dimensional mixer to obtain a mixture I, add the mixture I into a steel mold for compression molding, dry the preform that has been pressed and demolded, and then sinter the preform after drying at a temperature of 1450°C to 1600°C to obtain a wear-resistant part containing a plurality of meshes, wherein the thickness of the wear-resistant part gradually decreases from the center to the periphery; the mesh diameter of the wear-resistant part is 5 to 20 mm, and the maximum thickness of the wear-resistant part is 12 to 15 mm;

[0090] SS2: A lost foam model is manufactured according to the shape of the conveying elbow, wherein the lost foam model comprises an outer mold layer and an inner mold layer, the wear-resistant portion is fixed to the wear-resistant area of ​​the inner mold layer, and a wire mesh with a concave-convex structure is arranged on the contact interface between the outer mold layer and the inner mold layer of the lost foam model.

[0091] The inner surface of the wear-resistant portion is flush with the inner surface of the inner mold layer, and the maximum thickness of the wear-resistant portion is less than the maximum thickness of the inner mold layer; the wear-resistant area is 20° to 70° into the elbow port of the lost foam model and 20° to 160° along the circumferential direction of the cross section; the setting area of ​​the wire mesh on the contact interface is 0° to 90° into the elbow port of the lost foam model and 0° to 180° along the circumferential direction of the cross section.

[0092] SS3: Injecting a molten first metal material and a molten second metal material at 1450°C to 1600°C into the outer mold layer and the inner mold layer of the lost foam model at the same time; the molten first metal material and the molten second metal material penetrate into the depressions and protrusions of the wire mesh, presenting a mutually embedded concave-convex structure on the contact interface, and the molten second metal material penetrates into a plurality of meshes of the wear-resistant part, forming a metallurgical bond with the wear-resistant part, and cooling to obtain a conveying elbow; the first metal material is low carbon steel, and the second metal material is high chromium cast iron;

[0093] SS4: Put the wear-resistant sleeve onto the inner ring of the flange and fix it to the conveying elbow described in step SS3 by welding; the material of the wear-resistant sleeve is high-chromium cast iron; the material of the flange is low-alloy steel.

[0094] When preparing the conveying elbow, the wire mesh provided in the present invention plays at least the following four roles:

[0095] Function 1: The fine structure can almost isolate the molten first metal material and the molten second metal material from penetrating and blending with each other, preventing the molten liquid from condensing into a layer of the same material.

[0096] The second function is to control the structural thickness design of each layer of casting.

[0097] Function three: although the fine structure almost isolates the two molten metals from blending, the specific aperture design of the fine wire mesh is conducive to the very limited blending of the two molten metals at the countless fine pores at the intersection interface, thereby strengthening the metallurgical bonding strength between the outer tube layer and the inner tube layer.

[0098] Function four: the concave-convex design of the wire mesh at a specific position of the intersection interface is conducive to increasing the intersection interface area of ​​the outer tube layer and the inner tube layer. The outer tube layer and the inner tube layer present a gear-like embedded structure, which further enhances the metallurgical bonding strength between the outer tube layer and the inner tube layer, and relatively increases the thickness of the outer tube layer and the inner tube layer, which is conducive to improving the wear resistance of the bent tube while ensuring the strength of the bent tube.

[0099] In addition, the wear-resistant part of the present invention adopts a mesh design. During the casting process, the molten second metal material penetrates into the mesh holes of the wear-resistant part, and further penetrates into the gaps on the rough surface of the wear-resistant part, thereby completing a tight bond with the wear-resistant part. This bonding method has a very strong bonding strength, avoiding the problem of insufficient bonding strength caused by traditional ceramic mechanical bonding and adhesive adhesion.

[0100] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, the raw materials are all commercially available.

[0101] Ceramic composition: 95 wt% of ceramic raw material, 4.5 wt% of active additives and 0.5 wt% of binder.

[0102] The ceramic raw material is alumina ceramic.

[0103] The active additive is titanium powder.

[0104] The binder is polyvinyl alcohol.

[0105] The thermal insulation coating is made of quartz powder.

[0106] The high chromium cast iron material of the inner tube layer and the wear-resistant sleeve are purchased from Changsha Maike Bearing Co., Ltd. The grade of the high chromium cast iron material of the inner tube layer and the wear-resistant sleeve is Cr26.

[0107] The outer tube layer is low carbon steel, using 20 steel.

[0108] Flange, made of Q345 low alloy steel.

[0109] The material of the wire mesh is steel wire mesh.

[0110] The material of the lost foam model is expandable polystyrene resin (EPS).

[0111] Example 1

[0112] The first step is the production of wear-resistant parts:

[0113] The ceramic raw materials are washed with distilled water and alcohol in succession, and then placed in an ultrasonic cleaning machine for ultrasonic treatment to clean the surface of the ceramic raw materials, and then placed in a 120°C oven for drying. The ceramic raw materials, active additives and binders are fully and evenly mixed using a vertical three-dimensional mixer. According to the mesh design of the wear-resistant part, the fully mixed ceramic composition is injected into a gypsum mold with a cavity designed with the same mesh shape as the wear-resistant part through a powder metallurgy grouting molding method. Since the gypsum mold absorbs moisture relatively quickly, the slurry solidifies quickly in the gypsum mold. The demolded prefabricated blank is then placed in a drying oven for drying, and then placed in a sintering furnace for sintering at 1500°C. It is cooled and dried in the furnace to obtain a wear-resistant part containing several meshes (the maximum thickness is 15 mm, the minimum is 1 mm, and the mesh diameter is 10 mm), and its shape is as follows: Figure 3 shown.

[0114] The second step is to make the lost foam model and fix the wear-resistant part and the screen:

[0115] A lost foam model is manufactured according to the shape of the conveying elbow, the lost foam model comprising an outer mold layer and an inner mold layer, the inner cavity of the lost foam model is coated with a layer of coating with heat insulation performance, the coating thickness is 2 μm, and the lost foam model cavity wraps the entire elbow (except the flange wear-resistant sleeve); the wear-resistant part is fixed to the wear-resistant area of ​​the inner mold layer (20° to 70° inward from the elbow port of the lost foam model and 20° to 160° along the circumferential direction of the cross section), and a wire mesh with a concave-convex structure is arranged on the contact interface between the outer mold layer and the inner mold layer of the lost foam model (the setting area of ​​the wire mesh is the outermost layer at 0° to 90° inward from the elbow port of the lost foam model and 0° to 180° along the circumferential direction of the cross section, the aperture of the wire mesh is 50 μm, the height of the depression and the protrusion is 1 mm, and the distance between the depression and the protrusion is 8 mm).

[0116] The third step is casting:

[0117] The lost foam casting method is adopted, and 1500℃ molten high-chromium cast iron is poured between the inner tube layer and the wear-resistant part. The high-chromium cast iron penetrates into the inner mold layer and gradually replaces the foam plate. The high-chromium cast iron penetrates into the space where the wire mesh protrudes toward the outer mold layer, and penetrates into the mesh holes and the gaps on the rough surface of the wear-resistant part. At the same time, molten low-carbon steel is injected into the outer mold layer to gradually replace the foam plate. The low-carbon steel penetrates into the pit where the wire mesh is recessed toward the inner mold layer, and bent pipe fittings are obtained after cooling (the maximum thickness of the composite layer is 20mm and the minimum is 6mm).

[0118] Step 4: Wear-resistant sleeve flange installation:

[0119] The wear-resistant sleeve and flange are assembled, and then fixed to the pipe by welding. The pipe is then painted. The outer surface of the pipe is cleaned before painting. The appropriate painting temperature is controlled at 120°C and kept warm for 2 hours to allow the paint to be fully and evenly distributed on the outer surface of the pipe to obtain a conveying elbow.

[0120] Through wear resistance test, the wear resistance of the conveying elbow obtained in Example 1 of the present invention was compared with that of the conventional high chromium cast iron test block. The wear resistance of the former was more than twice that of the latter while ensuring the impact strength.

[0121] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A conveying elbow, comprising an outer tube layer (4) and an inner tube layer (2), characterized in that: The outer tube layer (4) and the inner tube layer (2) are in contact with each other and form a metallurgical bond, and a concave-convex structure that is embedded in each other is present at the contact interface. A wear-resistant portion (3) is embedded in the wear-resistant area of ​​the inner tube layer (2); the wear-resistant area has a center angle of 30° to 90° corresponding to the cross section of the conveying elbow and a center angle of 100° to 180° corresponding to the cross section of the conveying elbow. The thickness of the wear-resistant portion (3) gradually decreases from the center to the periphery, and the maximum thickness of the wear-resistant portion (3) is less than the maximum thickness of the inner tube layer (2). The inner surface of the wear-resistant portion (3) is flush with the inner surface of the inner tube layer (2). The wear-resistant portion (3) is provided with a plurality of mesh holes, and the chemical components of the inner tube layer (2) penetrate into the mesh holes to form a metallurgical bond.

2. The conveying elbow according to claim 1, characterized in that: The area of ​​the concavo-convex structure has a central angle of 70° to 90° in the cross section of the conveying elbow and a central angle of 140° to 180° in the cross section.

3. The conveying elbow according to claim 1, characterized in that: The center angle of the wear-resistant portion (3) corresponding to the cross section of the conveying elbow is 40° to 70°; The center angle of the wear-resistant portion (3) corresponding to the cross section of the conveying elbow is 120° to 160°.

4. The conveying elbow according to claim 1, characterized in that: The thickness of the composite layer (6) formed by the inner tube layer (2) and the wear-resistant portion (3) gradually decreases from the middle of the conveying elbow to both ends of the conveying elbow; And / or, the maximum thickness of the composite layer (6) is 18 to 22 mm, and the minimum thickness is 5 to 7 mm; and / or, the maximum thickness of the wear-resistant portion (3) is 12 to 15 mm, and the minimum thickness is 0 to 3 mm; And / or, the heights of the concave and convex parts of the concave-convex structure are independently selected from 0.5 to 1.5 mm; And / or, the distance between the concave part and the convex part of the concave-convex structure is greater than 0.

5. The conveying elbow according to claim 1, characterized in that: The conveying elbow further comprises flanges (1) and wear-resistant sleeves (5) arranged at both ends of the conveying elbow, wherein the flanges (1) are welded to both ends of the pipe fitting and the wear-resistant sleeves (5) are sleeved onto the inner ring of the flange.

6. The conveying elbow according to claim 5, characterized in that: The material of the wear-resistant part (3) is ceramic; And / or, the material of the outer tube layer (4) is low carbon steel; And / or, the material of the inner tube layer (2) is high chromium cast iron; And / or, the flange (1) is made of low alloy steel; And / or, the wear-resistant sleeve (5) is made of high-chromium cast iron.

7. A method for preparing a conveying elbow, characterized in that: The method includes: S1: subjecting the material containing the ceramic composition to compression molding and sintering in sequence to obtain a wear-resistant portion containing a plurality of meshes, wherein the thickness of the wear-resistant portion gradually decreases from the center to the periphery; S2: manufacturing a lost foam model according to the shape of the conveying elbow, wherein the lost foam model comprises an outer mold layer and an inner mold layer, fixing the wear-resistant portion on the wear-resistant region of the inner mold layer, and providing a wire mesh having a concave-convex structure on the contact interface between the outer mold layer and the inner mold layer of the lost foam model, The inner surface of the wear-resistant portion is flush with the inner surface of the inner mold layer, and the maximum thickness of the wear-resistant portion is less than the maximum thickness of the inner mold layer; the central angle of the wear-resistant area in the cross section of the lost foam model is 30° to 90°, and the central angle of the wear-resistant area in the cross section of the lost foam model is 100° to 180°; S3: Injecting the molten first metal material and the molten second metal material into the outer mold layer and the inner mold layer of the lost foam model at the same time; the molten first metal material and the molten second metal material penetrate into the depressions and protrusions of the wire mesh, presenting a mutually embedded concave-convex structure on the contact interface, and the molten second metal material penetrates into several meshes of the wear-resistant part, forming a metallurgical bond with the wear-resistant part, and cooling to obtain a conveying elbow.

8. The method according to claim 7, characterized in that Step S1 includes: The materials containing the ceramic composition are mixed to obtain a mixture I, and the mixture I is added into a mold for compression molding. The compression-molded and demolded preform is dried, and then the dried preform is sintered at a temperature of 1450°C to 1600°C to obtain a wear-resistant portion containing a plurality of meshes, wherein the thickness of the wear-resistant portion gradually decreases from the center to the periphery.

9. The method according to claim 7, characterized in that: In step S2, the setting area of ​​the screen on the contact interface has a central angle corresponding to a cross section of the lost foam model of 70° to 90°, and a central angle corresponding to a cross section of the lost foam model of 140° to 180°; And / or, the heights of the concave and convex parts of the concave-convex structure in the screen are independently selected from 0.5 to 1.5 mm; And / or, the distance between the concave part and the convex part of the concave-convex structure in the screen is greater than 0; And / or, the mesh has an aperture of 1 to 100 μm.

10. The method according to any one of claims 7 to 9, characterized in that: The thickness of the combined layer formed by the inner mold layer and the wear-resistant portion gradually decreases from the middle of the lost foam model to both ends of the lost foam model; And / or, the maximum thickness of the combined layer is 18 to 22 mm and the minimum thickness is 5 to 7 mm; And / or, the maximum thickness of the wear-resistant portion is 12 to 15 mm, and the minimum thickness is 0 to 3 mm.

11. The method according to claim 7, characterized in that The method further comprises: fitting the wear-resistant sleeve onto the inner ring of the flange, and fixing the wear-resistant sleeve to the conveying elbow described in step S3 by welding.

12. The method according to claim 11, characterized in that The material of the wire mesh is selected from at least one of iron and steel; And / or, the first metal material is low carbon steel; And / or, the second metal material is high chromium cast iron; And / or, the flange is made of low alloy steel; And / or, the wear-resistant sleeve is made of high chromium cast iron.

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