A method of centrifugal casting of a flanged tube

Abstract

The application discloses a flange pipe centrifugal casting method. The production steps of the method mainly comprise the following steps: 1) the upper and lower half molds are assembled on a supporting wheel station and a turnover machine respectively, the flange inner mold blocks embedded in a concave ring are respectively positioned by springs and compressed by foam blocks, the flange inner mold blocks are compressed by pipe end inner mold blocks, and the flange inner mold blocks are assembled with the upper and lower half molds and the pipe end inner mold blocks by using inclined surfaces. 2) pipe mold assembly: the assembled upper pipe mold is hoisted to the supporting wheel station and positioned and combined with the lower pipe mold, and the pipe mold is sleeved with roller belt rings at both ends. 3) coating cleaning and dynamic balance detection. 4) coating spraying and centrifugal pouring. 5) disassembly of the pipe mold, hoisting of the flange pipe, disassembly of the pipe end inner mold blocks and the flange inner mold blocks. The flange pipe can be cast at one time by adopting the application, the welding process is saved, welding defects are eliminated, and the consistency of the quality of the flange pipe is ensured.

Description

Technical Field

[0001] This invention is applied in the field of centrifugal casting, specifically relating to a horizontal pipe mold for hot mold centrifugal casting, which can be combined to produce flange pipes. Background Technology

[0002] Flange pipe refers to a pipe with flanges welded to both ends, as shown in the attached image. Figure 1 As shown, flange 1 has bolt holes machined on it for bolting the flanged pipe. For some austenitic stainless steel or nickel-based alloy steel cast pipes, welding the flange can cause coarse grains in the heat-affected zone, thus affecting the pipe's performance, such as corrosion resistance and fatigue resistance. If the flange and pipe are centrifugally cast together, the flange will hinder the shrinkage of the cast pipe, resulting in cracks and scrap. Furthermore, the flanges at both ends prevent the pipe mold from being demolded. Therefore, flanged pipes are mostly manufactured using welding. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a centrifugal casting method for flanges, which makes it possible to centrifugally cast flanges using a hot mold method, eliminating the flange welding process and removing welding defects.

[0004] The technical solution adopted in this invention is as follows: The centrifugal casting method for flanged pipes employs a cylindrical pipe mold composed of a semi-circular upper and lower mold halves. Symmetrical semi-convex rings are machined on the left and right sides of both the upper and lower mold halves, and a secondary roller belt is machined between the middle of the upper and lower mold halves and the semi-convex rings. The upper and lower semi-convex rings, which cooperate with each other, are fitted with roller belt rings. Concave rings are designed at both ends of the upper and lower mold halves, and flange inner modules, springs, foam blocks, and pipe end inner modules are assembled within these concave rings. The flange inner modules consist of four symmetrical pieces, embedded within the concave rings of the upper and lower mold halves. Springs and foam blocks are assembled on the back of the flange inner modules and within the cavity of the concave rings. The foam blocks are made of polypropylene composite material with a softening temperature of 180-220℃. The centrifugal casting method mainly includes the following steps:

[0005] 1) Assembly of upper and lower mold halves: The lower mold halves are assembled on the roller support station, and the upper mold halves are assembled on the turning machine; the assembly method of the upper and lower mold halves is the same. The flange inner modules embedded in the concave rings of the upper and lower mold halves are respectively positioned by springs and clamping foam blocks. The two flange inner modules are clamped by semi-circular pipe end inner modules. Fasteners are used to connect the pipe end inner modules and the upper and lower mold halves, so that the concave arc surface of the pipe end inner module is flush with the inner surface of the pipe mold; the flange inner modules are assembled with the upper and lower mold halves and the pipe end inner modules using a frustum inclined plane with an inclination angle of 15°.

[0006] 2) Tube mold assembly: The tilting machine flips the assembled upper half mold, and the overhead crane lifts the upper half mold to the support roller station to position and combine it with the lower half mold. Roller belt rings are fitted at both ends of the tube mold, and fasteners are used to secure the roller belt rings and the tube mold semi-convex rings.

[0007] 3) Coating cleaning, dynamic balance detection.

[0008] 4) Tube mold baking, paint spraying, upper baffle, centrifugal casting.

[0009] 5) Disassemble the tube mold: after cooling, the tube mold and the flange pipe are hoisted to the roller support station, the auxiliary roller belt is placed on the roller support, and the tube mold is rotated and aligned; the tube mold end baffle and the roller belt ring are disassembled, the upper mold is hoisted away from the turnover machine, the flange pipe is hoisted away, the tube end inner mold and the flange inner mold are disassembled, and the concave rings of the upper and lower molds are cleaned.

[0010] The beneficial effects of the present application are: the flange pipe can be cast at one time, the welding process is saved, the welding defects are eliminated, and the consistency of the quality of the flange pipe is ensured. The flange and the pipe body produced are simultaneously heat treated, the organization is uniform and consistent, the corrosion resistance and thermal fatigue resistance of austenitic stainless steel or nickel-based alloy steel are ensured, the service life of some key parts is improved, and the safe operation of the pipeline is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a schematic view of the flange pipe structure;

[0012] Figure 2 is a schematic view of the main view of the present application;

[0013] Figure 3 is a schematic view of the present application from the top;

[0014] Figure 4 is the A-A sectional view of Figure 2 ;

[0015] Figure 5 is the E-E sectional view of Figure 2 ;

[0016] Wherein: 1-flange, 2-upper mold, 3-inclined iron, 4-baffle, 5-flange inner mold, 6-spring, 7-lower mold, 8-foam block, 9-tube end inner mold, 10-auxiliary roller belt, 11-lifting lug, 12-sand core, 13-inner baffle, 14-outer baffle, 15-roller belt ring, 16-semi-convex ring. DETAILED DESCRIPTION

[0017] Reference is made to the accompanying Figure 2 --the accompanying Figure 5 The present application is described in detail, and the following up and down, left and right are based on the accompanying Figure 2 , which refers to the up and down, left and right of the accompanying Figure 2 . The following inside and outside refers to the inside and outside of the tube mold, the axial direction refers to the direction of the rotating shaft of the tube mold, and the radial direction refers to the direction of the diameter of the tube mold. The tube mold is a cylindrical structure, and part of the center line is omitted for the convenience of displaying the structure.

[0018] The tube mold used in this invention includes an upper mold 2 and a lower mold 7, both of which are semi-circular and symmetrical. When combined, they form a single cylindrical tube mold. Steps are machined at the mating points of the upper mold 2 and the lower mold 7, as shown in the attached figure. Figure 4 As shown, this structure serves two purposes: first, it enables the positioning and assembly of the upper and lower mold halves; second, it prevents steel spillage accidents. From a precise positioning perspective, the optimal combination of matching conical positioning pins and holes for the upper and lower mold halves is to prevent collisions between the steps during assembly and to protect the steps. During the pouring of molten steel, if the coating peels off, there is a risk of the molten steel being centrifugally thrown out through the assembly gap. This structure has a relatively long assembly gap channel, allowing any molten steel that leaks into the assembly gap to solidify and seal it, thus preventing steel spillage accidents.

[0019] Semi-convex rings 16 are machined symmetrically at the left and right proximal ends of the upper half mold 2, and auxiliary roller belts 10 are machined near the middle of the left and right sides of the upper half mold 2. Similarly, semi-convex rings 16 and auxiliary roller belts 10 are machined at the same positions as the upper half mold 2 in the lower half mold 7. Roller belt rings 15 are fitted onto the two semi-convex rings 16 of the upper and lower half molds and connected with fasteners. The roller belt rings 15 can fix the upper and lower half molds into one piece, forming a cylindrical tube mold, while eliminating deviations in the machining and assembly of the upper and lower half molds, ensuring the concentricity of the upper and lower half molds, thereby ensuring the dynamic balance of the tube mold during high-speed centrifugal rotation and preventing large vibrations. To facilitate the assembly and disassembly of the roller belt rings 15, the annular mating surfaces of the semi-convex rings 16 and the roller belt rings 15 are designed as truncated cones with the same angle. The function of the auxiliary roller belts 10 is to lift the tube mold off the centrifuge, place it on the support rollers, rotate it slowly, and straighten the tube mold, facilitating the assembly and disassembly of the tube mold. A lifting lug 11 is machined between the semi-convex ring 16 and the auxiliary roller belt 10 to facilitate the hoisting, assembly, and disassembly of the tube mold.

[0020] At both ends of the inner surface of the tube mold, concave rings are designed. Inside these concave rings are assembled flange inner module 5, spring 6, foam block 8, and tube end inner module 9. The tube end inner module 9 is semi-circular and connects to the upper and lower mold fasteners respectively. The concave arc surface of the tube end inner module 9 is flush with the inner surface of the tube mold. Whether the semi-circular end face of the tube end inner module 9 has a mating step depends on its thickness and the size of the step. The flange inner module 5 is divided into four symmetrical pieces, as shown in the attached figure. Figure 5As shown, the flange inner module 5 is assembled with the upper and lower half molds and the pipe end inner module 9 conical surface, and the inclination angle determines the force of the axial movement, the inclination angle of the embodiment is 15°, and the spring 6 and the foam block 8 are assembled in the cavity of the concave ring on the back of the flange inner module 5 (not visible from the outside), the foam block 8 is a polypropylene composite material, and the softening temperature is 180-220℃, the foam block 8 positions the flange inner module 5 before pouring the molten steel, and the flange inner module 5 is fixed when the pipe mold rotates at high speed, and after pouring the high-temperature molten steel, the heat of the molten steel is transferred to the foam block 8, the foam block 8 is softened by heat, and when the flange plate 1 on the flange pipe shrinks, the flange inner module 5 can be displaced in the direction of the flange pipe shrinkage, without affecting the shrinkage of the flange pipe. The purpose of the spring 6 is to stabilize the flange inner module 5 after the foam block 8 is softened, to avoid irregular movement of the flange inner module 5 in the concave ring, thereby affecting the dynamic balance of the high-speed rotation of the pipe mold. That is, even if the softening speed of the foam block 8 is inconsistent, the position of the eight flange inner modules 5 at both ends of the pipe mold is still relatively consistent, and the force is relatively balanced, so as not to destroy the dynamic balance of the pipe mold. During the movement of the flange inner module 5, the flange inner module 5 is radially moved outward due to sliding along the conical surface, and a cavity is formed between the flange inner module 5 and the outer surface of the flange pipe, the cavity is communicated with the cavity in the concave ring, and the coating peeled off due to the shrinkage of the flange pipe can be collected, so as to avoid the shrinkage caused by the peeling of the coating.

[0021] The pipe mold is provided with a stopper at both ends, the baffle 4 is installed close to the stopper after the pipe mold is combined and coated, the baffle 4 is fixed by knocking the inclined iron 3 on the stopper, and then pouring is performed. If it is required to cast the bolt hole on the flange plate together, the flange plate can be provided with a recess, and the recess is provided with a sand core. Figure 1 The right end is assembled in the same way, the recess for installing the sand core 12 is processed on the flange inner module 5, the sand core 12 is crushed to form the bolt hole, and the baffle is divided into the inner baffle 13 and the outer baffle 14, the inner baffle 13 is mainly used for fixing the sand core 12, and the outer baffle 14 is mainly used for fixing the inner baffle 13.

[0022] The steps of the horizontal combined pipe mold hot mold method centrifugal production flange pipe are as follows:

[0023] 1. The upper and lower half molds are assembled. The lower half mold 7 is assembled on the supporting wheel, and the upper half mold 2 is assembled on the turnover machine. The assembly methods of the upper and lower half molds are consistent, two flange inner modules 5 are positioned by springs 6 and compressed foam blocks 8, the two flange inner modules 5 are compressed by the semicircular pipe end inner module 9, and the pipe end inner module 9 and the upper and lower half molds are connected by fasteners, so that the concave arc surface of the pipe end inner module 9 is flush with the inner surface of the pipe mold. The flange inner module 5 is assembled with the upper and lower half molds and the pipe end inner module 9 by using a conical surface, in order to reduce the sliding resistance of the flange inner module 5, high-temperature lubricating grease can be applied on the conical surface.

[0024] 2. Tube mold assembly. The assembled upper half mold 2 is turned over by the turnover machine, hoisted by the overhead crane to the roller support station, positioned by the steps or positioning pins, and the upper and lower half molds are combined, the roller belt rings 15 are sleeved on both ends of the tube mold, cooperated with the half convex rings 16 of the upper and lower half molds, and the roller belt rings 15 and the half convex rings 16 are fastened by the fasteners.

[0025] 3. Coating cleaning and dynamic balance detection. The assembled tube mold is hoisted to the centrifugal machine station, the coating is cleaned at a low speed first, and then dynamic balance detection is performed at a high speed. The dynamic balance can be adjusted by adding gaskets or nuts on the fasteners or other methods.

[0026] 4. Tube mold baking and coating spraying. The tube mold baking temperature is not more than 150-170℃, which is appropriate to maintain the strength of the foam block 8, and the coating is sprayed in a hot mold. Before the coating is sprayed, the recesses of the fasteners of the tube end inner module 9 are filled with the coating to be flush.

[0027] 5. Upper baffle and centrifugal casting. The baffles are installed on both ends of the tube mold, and the molten steel is centrifugally cast. Before the molten steel is cast, the tube mold is rotated at a high speed, the flange inner module 5 is mainly positioned by the foam block 8, and after the molten steel is cast, before the foam block 8 softens, part of the molten steel has already solidified, but at this time, the high-temperature cast steel organization is high-temperature austenite, which has very good plasticity and will not produce cracks. Shrinkage cracks are mostly produced when the solidification is blocked, and before the solidification, the foam block 8 has already softened, and the spring 6 is not enough to resist the shrinkage of the flange tube, so that the shrinkage of the flange tube is not hindered, thereby eliminating the shrinkage cracks.

[0028] 6. Cooling and disassembly of the tube mold. After the molten steel is cast, water spraying is used for cooling to control the temperature of the tube mold to be not more than 300℃ (the temperature is a computer simulation temperature, not an infrared temperature gun measured temperature). After the tube mold and the flange tube are cooled, the tube mold is hoisted to the roller support station, the auxiliary roller belt 10 is placed on the roller support, the tube mold is rotated to be aligned, so that the mating surface of the upper half mold 2 and the lower half mold 7 is nearly horizontal. The baffles on both ends of the tube mold are disassembled, then the roller belt ring 15 is disassembled, hoisted away from the upper half mold 2 to the turnover machine, hoisted away from the flange tube, the tube end inner module 9 and the flange inner module 5 are disassembled, the coating and the foam block residues in the concave rings of the upper and lower half molds are cleaned by compressed air, and then step 1 is executed, the foam block 8 is installed, the half mold assembly is performed, and the cycle is repeated.

[0029] The centrifugal casting production flange tube needs the cooperation of the centrifugal station, the roller support station and the turnover machine, the production efficiency of a single tube mold is low, and two tube molds and three stations need to work simultaneously. The flange tube can be cast at one time by using the present application, the welding process is saved, the welding defects are eliminated, and the consistency of the quality of the flange tube is ensured.

[0030] The flange pipe adopting the centrifugal casting method of the application has flange plates and pipe bodies simultaneously heat treated, uniform and consistent structure, guaranteed corrosion resistance and thermal fatigue resistance of austenitic stainless steel or nickel-based alloy steel, and the service life is improved for some key parts in petrochemical plants, thereby ensuring safe operation of the pipeline.

Claims

1. A centrifugal casting method for flanged pipes, comprising a cylindrical pipe mold composed of a semi-circular upper mold (2) and a lower mold (7) for centrifugal casting. The upper mold (2) and lower mold (7) are symmetrically machined with semi-convex rings (16) on their left and right sides. A secondary roller belt (10) is machined between the middle of the upper and lower molds and the semi-convex rings (16). The two mutually cooperating semi-convex rings (16) are fitted with roller belt rings (15). Concave rings are designed at both ends of the upper mold (2) and lower mold (7). Flange inner modules (5), springs (6), foam blocks (8), and pipe end inner modules (9) are assembled within the concave rings. The flange inner modules (5) consist of four symmetrical pieces, embedded within the concave rings of the upper mold (2) and lower mold (7). Springs (6) and foam blocks (8) are assembled on the back of the flange inner modules (5) and within the cavity of the concave rings. The centrifugal casting method mainly includes the following steps: 1) Assembly of upper and lower mold halves: The lower mold halves (7) are assembled on the roller station, and the upper mold halves (2) are assembled on the turning machine; the flange inner module (5) embedded in the concave ring of the upper and lower mold halves is positioned by spring (6) and pressed by foam block (8), and the two flange inner modules (5) are pressed by semi-circular pipe end inner module (9). Fasteners connect the pipe end inner module (9) and the upper and lower mold halves, so that the concave arc surface of the pipe end inner module (9) is flush with the inner surface of the pipe mold; the flange inner module (5) and the upper and lower mold halves, and the flange inner module (5) and the pipe end inner module (9) are assembled by frustum inclined surface; 2) Mold assembly: The rotating machine flips the assembled upper half mold (2), the overhead crane lifts the upper half mold (2) to the support roller station and positions it with the lower half mold (7). Roller belt rings (15) are fitted at both ends of the mold, and fasteners connect the roller belt rings (15) and the semi-convex rings (16). 3) Coating cleaning and dynamic balancing test; 4) Mold baking, paint spraying, baffle plate installation, centrifugal casting; 5) Disassemble the tube mold: hoist the cooled tube mold and flange tube to the support roller station, place the auxiliary roller belt (10) on the support roller, rotate the tube mold to align; disassemble the baffles at both ends of the tube mold and the roller belt ring (15), hoist the upper half mold to the turning machine, hoist the flange tube, disassemble the inner module (9) of the tube end and the inner module (5) of the flange, and clean the concave rings of the upper and lower half molds.

2. The centrifugal casting method for flanged pipes according to claim 1, characterized in that: The foam block (8) is a polypropylene composite material with a softening temperature of 180-220℃.

3. The centrifugal casting method for flanged pipes according to claim 1, characterized in that: The inclination angle of the truncated cone of the inner module (5) of the assembly flange is 15°.

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