Centrifugal casting pipe die for double-flange straight pipe

Abstract

The utility model discloses a double-flange straight pipe centrifugal casting pipe die which is characterized in that an upper half die and a lower half die are buckled in a stepped inclined plane mode, and a rolling belt ring inclined plane is sleeved on a half convex ring of the upper half die and a half convex ring of the lower half die in a matched mode and is matched with a retaining ring on a centrifugal riding wheel. And balance blocks capable of being circumferentially adjusted are mounted on the outer surfaces of the upper half die and the lower half die. Inner and outer sand cores are installed on spigot sections at the two ends of the pipe die, the back faces of the inner sand cores are matched with inner spigots to form receding spaces, and shrinkage of the cast pipe is prevented from being blocked. The balance blocks are fastened on the semi-rings on the outer walls of the upper half die and the lower half die or fastened between the semi-baffle rings and the semi-convex rings and in gaps between the semi-convex rings and the rolling belt rings, and dynamic balance of the pipe die is achieved through circumferential adjustment. The pipe die is simplified in structure, waste products cannot be generated due to casting shrinkage, the pipe die can adjust dynamic balance, and the equipment failure rate is reduced.

Description

Technical Field

[0001] The utility model is applied to the field of centrifugal casting, relates to the production of ductile iron double-flange straight pipes, and specifically is a pipe mold for centrifugally casting double-flange straight pipes. Background Art

[0002] Since ductile iron has good corrosion resistance, water pipelines mostly use centrifugal ductile iron pipes, which are basically in the form of socket joints. Since the double-flange ductile iron pipe has flanges at both ends, it cannot be pulled out from the pipe mold, which seriously restricts its application. To solve this problem, CN1923410A provides a manufacturing process for a double-flange ductile iron pipe, first centrifugally casting a single-flange ductile iron pipe, and then melting and casting the other end flange. The quality of melting and casting directly determines the quality of the double-flange ductile iron pipe. In order to ensure that the double-flange straight pipe can be taken out of the pipe mold, CN111496215A discloses a centrifugal casting mold and manufacturing process patent for a double-flange pipe fitting, in which a combined mold is set in a centrifugal drum, and the combined mold and the double-flange pipe are pulled out from the centrifugal drum after centrifugal casting, but casting shrinkage is not considered, and cracks will occur after the molten iron solidifies. In order to take into account the removal and shrinkage of the double flange pipe, CN106735045B provides a double-disc flange straight pipe centrifugal integral casting metal mold, which is composed of multiple pipe mold sections and is designed as two half molds with horizontal parting. The bolt connection structure not only seriously restricts production efficiency, but also does not consider the dynamic balance of the pipe mold during centrifugal rotation. CN107127316A provides a device and method for full-mold centrifugal casting of double-disc flange straight pipes and through-wall flange straight pipes. The pipe mold is integrated and has good dynamic balance, but the process is complicated. It combines two special casting processes, lost foam and centrifugal casting. Its disadvantages are that the process preparation time is long, the production efficiency is low, and the resin sand between the double flanges has no retreat space, which is also easy to produce casting shrinkage cracks. CN113231613A discloses a horizontal combined pipe mold for centrifugal casting of double flange straight pipes. Although casting shrinkage and dynamic balance are considered, the structure is complicated, and the installation gap of the module in the pipe end directly affects the solidification speed of the molten iron, which is easy to produce casting cracks. Utility Model Content

[0003] The technical problem solved by the utility model is to provide a double-flange straight pipe centrifugal casting pipe mold, simplify the structure, fully consider the casting shrinkage and dynamic balance, meet the centrifugal casting requirements, and improve the qualified rate of cast pipes.

[0004] The technical solution adopted by the utility model is: a double flange straight tube centrifugal casting pipe mold comprises an upper half mold, a lower half mold, and a rolling ring. The stepped inclined surfaces of the upper and lower half molds are buckled to form a centrifugal casting pipe mold. Semi-convex rings corresponding to the positions are arranged on the outer surfaces of the upper and lower half molds, and the inclined surface of the rolling ring fits on the upper and lower half convex rings to ensure that the rolling ring is concentric with the center line of the pipe mold. Balance blocks that can be adjusted circumferentially are installed on the outer surfaces of the upper and lower half molds.

[0005] Furthermore, the stopper sections at both ends of the pipe mold are installed with an outer sand core, an inner sand core and a baffle. The core support on the back of the inner sand core cooperates with the inner stopper to form a retreat space. The outer sand core is assembled in the concave cavity of the baffle, and the outer stopper is positioned. The hole core on the outer sand core fixes the inner sand core to prevent the inner sand core from moving axially. The number of the hole cores is consistent with the flange hole, and the bolt holes are directly cast, or two are symmetrical, which is convenient for the operation of sealing the gap with refractory mud. The size of the retreat space is larger than the space volume of the cast pipe shrinkage retreat.

[0006] Furthermore, the core support is in contact with the inner stop conical surface, and when the casting pipe shrinks, the radial force borne by the core support is conducive to the collapse of the sand core.

[0007] Furthermore, the balancing block is fastened on a half ring, and the half ring is respectively fixed on the outer wall of the upper and lower half molds at corresponding positions; an arc-shaped through hole is processed on the half ring to facilitate the circumferential adjustment of the balancing block.

[0008] Furthermore, a half retaining ring is welded on the outer surface of the upper and lower half molds, and a balancing block is placed in the gap between the half retaining ring and the half convex ring, and in the gap between the half convex ring and the rolling ring. The hook head of the balancing block cooperates with the circumferential groove of the rolling ring, and can move circumferentially in the groove to adjust the dynamic balance. The balancing block is threadedly connected to a set screw, and the set screw fastens the balancing block.

[0009] Furthermore, the rolling ring cooperates with the stop ring on the centrifugal support wheel, and the stop ring applies a force on the rolling ring to prevent the axial movement of the tube mold, so that the rolling ring and the semi-convex ring are firmly matched.

[0010] The beneficial effects of the utility model are as follows: the utility model utilizes the retreat space to avoid shrinkage cracks of the cast pipe, and realizes the dynamic balance of the rapid rotation of the pipe mold by adjusting the position of the balance block, and is particularly suitable for the centrifugal casting of a long fixed-length double-flange straight pipe. The pipe mold structure is simplified, the operation is fast, no waste is generated due to casting shrinkage, the vibration of the pipe mold is eliminated, and the failure rate of the pipe mold and the centrifuge is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a front view schematic diagram of Example 1;

[0012] Figure 2 for Figure 1 Schematic diagram of top view;

[0013] Figure 3 for Figure 1 Schematic diagram of the left side;

[0014] Figure 4 for Figure 1 AA cross-sectional diagram of ;

[0015] Figure 5for Figure 1 A partial enlarged view of E;

[0016] Figure 6 for Figure 1 A partial enlarged view of F;

[0017] Figure 7 This is a partial schematic diagram of the tube mold of Example 2;

[0018] Figure 8 This is a schematic diagram of the installation of the balancing block in Example 3;

[0019] Among them: 1-upper mold, 2-lower mold, 3-roller ring, 4-support wheel, 5-balance block, 6-baffle, 7-inclined iron, 8-outer sand core, 9-inner sand core, 10-retreat space, 11-fastener, 12-set screw, 13-lifting ring, 14-semi-baffle ring, 15-semi-convex ring, 16-hole core, 17-stop section, 18-core support, 19-semi-ring. DETAILED DESCRIPTION

[0020] The structure described in the utility model is mainly the structure of the stopper section and the rolling belt at the end of the pipe mold. The following inside and outside installation habits are different for the directions of the two positions. At the end of the pipe mold, the inside and outside refer to the inside and outside relative to the cavity of the molded cast pipe; at the rolling belt position, the inside and outside refer to the rotation center line of the pipe mold, and the outside is far away from the center line.

[0021] The cast pipe of the utility model refers to a centrifugally cast double flange straight pipe. The upper half mold and the lower half mold are only used to distinguish the two half molds in the figure, and are not the upper and lower position relationship when the actual pipe mold is used. Example 1

[0022] The structure of the double flange straight tube centrifugal casting pipe mold in this embodiment is as shown in the attached figure. Figure 1-6 As shown, it includes an upper mold 1, a lower mold 2, and a rolling ring 3. The upper mold 1 and the lower mold 2 are buckled with stepped inclined surfaces. Figure 4 As shown, the advantages of step-type bevel buckling are: 1) when the upper and lower molds are buckled and installed, the bevel plays a guiding role, which can increase the assembly speed; 2) it is conducive to sealing, and prevents the accident of molten iron being thrown through the matching gap; 3) it is conducive to reducing the cooling gradient of the molten iron at the gap, avoiding the generation of casting cracks. The outer surfaces of the upper and lower molds 1 and 2 are provided with corresponding semi-convex rings 15. After the upper and lower molds are buckled, the rolling ring 3 is inserted into the upper and lower semi-convex rings 15 and fixed with fasteners 11, as shown in the attached figure. Figure 1 and attached Figure 5As shown, the upper and lower molds are fixed together to form a pipe mold for centrifugal casting. The mating surfaces of the semi-convex ring 15 and the rolling ring 3 are inclined surfaces, that is, the outer surface of the semi-convex ring 15 and the inner surface of the rolling ring 3 are mutually matched inclined surfaces, which facilitates the insertion and installation of the rolling ring 3 and ensures that the center line of the rolling ring 3 is consistent with the center line of the pipe mold. In addition, after the fastener 11 is tightened, the friction between the semi-convex ring 15 and the matching inclined surfaces of the rolling ring 3 can drive the pipe mold to rotate, thereby reducing the shear force of the fastener. The matching method of the rolling ring 3 and the supporting wheel 4 is shown in the attached figure. Figure 1 and attached Figure 5 As shown, the stop ring of the support wheel 4 applies a force on the rolling ring 3 to prevent the tube mold from moving axially, so that the rolling ring 3 and the semi-convex ring 15 are firmly matched, increasing the friction between the two without affecting the stress state of the fastener 11.

[0023] A half retaining ring 14 is welded on the inner surface of the rolling ring 3 and the outer surface of the upper and lower half molds, or it is an integrated structure. A balancing block 5 is placed in the gap between the half retaining ring 14 and the half convex ring 15, and in the gap between the half convex ring 15 and the rolling ring 3. Figure 5 As shown, the hook of the balancing block 5 cooperates with the circumferential groove of the rolling ring 3, and can move circumferentially in the groove and be relatively fixed in the radial direction. The dynamic balance of the pipe mold is adjusted by the circumferential movement of the balancing block 5. A threaded hole is processed on the balancing block 5, and the threaded hole is threadedly connected to the set screw 12. When the set screw 12 is tightened, the pre-tightening force is applied to the semi-convex ring 15. The balancing block 5 is fixed by the friction generated by the rolling ring 3 and the semi-retaining ring 14. Even under the action of centrifugal force, since the hook is in the groove, no radial relative displacement will occur, so it will not affect the dynamic balance.

[0024] The stopper sections 17 at both ends of the tube die are provided with inner sand cores 9, outer sand cores 8 and baffles 6, as shown in the attached Figure 1 and attached Figure 6 As shown. On the back of the inner sand core 9, that is, the surface that matches the inner stopper of the pipe mold, a retreat space 10 is designed. The retreat space 10 is prepared to adapt to the casting shrinkage of the cast pipe. After the molten iron is centrifugally poured, the liquid shrinkage of the molten iron is a shrinkage compensation process, and the solidification mode of ductile iron is paste solidification. When solidification begins, if there is shrinkage resistance, casting shrinkage cracks will occur. At this time, the inner sand core 9 has been heated and is in a collapsed state. When the cast pipe drives the flange to shrink, the inner sand core is filled and retreated unprecedentedly, and no shrinkage resistance will be generated. On the outer sand core 8, a hole core 16 is provided. One function of the hole core 16 is to form the bolt holes on the flange, and the second function is to fix the inner sand core 9 when the sand core is installed to prevent the axial movement of the inner sand core 9. The outer sand core 8 is assembled in the concave cavity of the baffle 6, the surface is flush with the flange, the outer stopper is positioned, and the inclined iron 7 is fixedly installed in cooperation with the mounting hole on the pipe mold.

[0025] In order to facilitate the opening and closing of the half molds, lifting rings 13 are designed on the upper and lower half molds to facilitate the overhead crane lifting.

[0026] The double flange straight pipe adopts the hot mold centrifugal casting process, and its main steps include: 1) After the upper and lower half molds are buckled on the auxiliary support wheel, the roller ring and the balance block are installed. 2) Lift it to the support wheel of the centrifuge, first rotate slowly, then quickly, and then slowly, use the measuring instrument to measure the dynamic balance of the pipe mold, then adjust the position of the balance block, and tighten it with the set screw to meet the requirements of the rapid rotation dynamic balance of the pipe mold. 3) The pipe mold rotates slowly, and the gas bakes the pipe mold to 200-300℃. After that, the inner wall of the pipe mold is sprayed with paint, and the coating thickness is 2-5mm. In order to reduce the influence of the pipe mold joint on the cooling rate of the cast pipe, the coating thickness should be taken as the upper limit. 4) Use sandpaper to clean the stop coating, and the pipe mold is statically installed with the inner sand core and the outer sand core (the coating thickness is usually measured by measuring the coating thickness of the stop section). Before installing the sand core, apply a small amount of refractory mud on the matching surface of the sand core, such as the joint between the inner sand core and the inner stop, and the joint between the outer sand core and the outer stop to prevent large gaps. During centrifugal pouring, molten iron will enter the gap due to the centrifugal force. After the molten iron in the gap solidifies, the shrinkage of the cast pipe is hindered and thermal cracks are generated. Finally, the excess refractory mud is manually cleaned. When cleaning the refractory mud at the outer stop joint, be careful not to damage the core of the hole. 5) Centrifugal pouring, water-cooled pipe mold. The pipe mold rotates rapidly, and molten iron is poured from the short chute at one end of the pipe mold. Due to the high superheat of the molten iron and good fluidity, the whole centrifugal mold can be filled before solidification begins. After filling, turn on the cooling water, and the cooling water sprays the pipe mold to cool it, increase the solidification speed of the molten iron, and improve production efficiency. 6) Separation of pipe and mold. After solidification, remove the baffles at both ends, clean the sand core, transfer it to the auxiliary support wheel, remove the rolling ring, separate the upper and lower molds, and take the cast pipe out of the pipe mold. After cleaning the coating in the upper and lower molds, the upper and lower molds are buckled together to prepare for the centrifugal production of the next cast pipe.

[0027] In order to facilitate the cleaning of the excess refractory mud at the joint between the outer sand core and the outer stop, the hole core 16 can be two symmetrical ones, which can be used to fix the inner sand core 9. After the cast pipe is cast, the other bolt holes are processed using special tooling based on the two casting bolt holes. Although the bolt hole processing process is increased, the efficiency of centrifugal casting is improved, and the waste of cast pipes caused by damage to the hole core is avoided. Example 2

[0028] This embodiment is an improvement on the above embodiment, and the main improvement is the structure of the inner sand core 9, as shown in the attached Figure 7 As shown, the force-matching contact surface between the core support 18 and the inner stopper that forms the retreat space in the inner sand core 9 is not a flat surface, but a conical surface. When the cast pipe shrinks in the cast state, the core support 18 generates a component force in the radial direction due to the force on the conical surface, so that the core support 18 is subjected to shear force. When the inner sand core 9 collapses at high temperature, the shear force makes it easier for the core support 18 to collapse, thereby making it easier for the inner sand core 9 to retreat, thereby reducing the casting shrinkage stress and avoiding cracks. Example 3

[0029] In the above embodiment, the balancing block 5 needs to be installed and removed each time the rolling ring 3 is installed and removed, which adds unnecessary operations. In this embodiment, the balancing block is installed separately from the rolling ring. Figure 8 shown.

[0030] The belt rolling ring is still mounted on the upper and lower half convex rings 15 and fixed with fasteners 11, so as to achieve the concentricity of the belt rolling ring and the tube mold. The balancing block 5 is fixed on the half ring 19 with fasteners 11. The half ring 19 is welded to the outer wall of the upper and lower half molds, or is integrated with the upper and lower half molds, and the positions of the upper and lower half rings 19 are corresponding. An arc-shaped through hole is processed on the half ring 19, and the fastener passes through the arc-shaped through hole to fix the balancing block 5 on the half ring 19. The balancing block 5 can only move circumferentially along the arc-shaped through hole to adjust the dynamic balance.

[0031] Compared with the above-mentioned embodiments, the balancing block in this embodiment is relatively fixed, and the number of balancing blocks can be increased according to the actual situation of the tube mold, so that the adjustment of dynamic balance is freer and more convenient.

[0032] The utility model utilizes the retreat space formed by the inner sand core to avoid the shrinkage of the cast pipe being blocked. The size of the retreat space is larger than the volume of the space for the cast pipe to shrink and retreat, ensuring that the inner sand core does not affect the shrinkage of the cast pipe, thereby avoiding shrinkage thermal cracks in the cast pipe. The dynamic balance of the rapid rotation of the pipe mold is achieved by circumferentially adjusting the position of the balance blocks on the upper and lower molds. Although measuring instruments and operator experience are required, the adjustment of dynamic balance is a necessary step to ensure safe production and equipment safety. If the pipe mold rotates without dynamic balance, vibration will occur, affecting the service life of the support wheel bearing and the pipe mold, and increasing the failure rate of the pipe mold and the centrifuge.

[0033] The utility model is particularly suitable for centrifugal casting of a long fixed-length double flange straight pipe, such as 4-6m in length, but it is also suitable for casting pipes shorter than 4m. If the PN value of the flange is adjusted, resulting in changes in the thickness of the flange and the number of bolt holes, the thickness of the sand core and the number of hole cores can be changed, while the pipe mold remains unchanged.

[0034] From the production point of view, compared with the prior art, the utility model has a simplified tube mold structure, quick operation, full consideration of casting shrinkage and dynamic balance, meets the requirements of centrifugal casting, does not produce waste due to casting shrinkage, eliminates tube mold vibration, and reduces the failure rate of the tube mold and the centrifuge.

Claims

1. A double-flange straight tube centrifugal casting mold, comprising an upper mold (1), a lower mold (2), and a rolling ring (3); characterized in that: The upper mold (1) and the lower mold (2) are buckled together with stepped inclined surfaces to form a tube mold; the outer surfaces of the upper mold (1) and the lower mold (2) are provided with semi-convex rings (15) at corresponding positions, and the inclined surface of the rolling ring (3) is fitted on the upper and lower semi-convex rings (15); and the outer surfaces of the upper mold (1) and the lower mold (2) are installed with circumferentially adjustable balance blocks (5).

2. A double flange straight tube centrifugal casting pipe mold according to claim 1, characterized in that: The stop sections at both ends of the tube mold are provided with an outer sand core (8), an inner sand core (9), and a baffle (6); a core support (18) on the back of the inner sand core (9) cooperates with the inner stop to form a retreat space (10); the outer sand core (8) is assembled in the concave cavity of the baffle (6) and the outer stop is positioned; and the hole core (16) on the outer sand core (8) fixes the inner sand core (9).

3. A double flange straight tube centrifugal casting pipe mold according to claim 2, characterized in that: The size of the retreat space (10) is greater than the volume of the space for shrinkage and retreat of the casting pipe.

4. A double flange straight tube centrifugal casting pipe mold according to claim 2, characterized in that: The core support (18) is in contact with the inner stop conical surface.

5. The double flange straight tube centrifugal casting pipe mold according to claim 2, characterized in that: The number of the hole cores (16) is the same as the number of the flange holes, or is two symmetrical ones.

6. The double flange straight tube centrifugal casting tube mold according to claim 1, characterized in that: The balancing block (5) is fastened to a half ring (19), and the half ring (19) is respectively fixed to the outer wall of the upper and lower half molds at corresponding positions; an arc-shaped through hole is processed on the half ring (19) to facilitate circumferential adjustment of the balancing block (5).

7. The double flange straight tube centrifugal casting pipe mold according to claim 1, characterized in that: A half retaining ring (14) is welded on the outer surface of the upper half mold (1) and the lower half mold (2), and the balancing block (5) is placed in the gap between the half retaining ring (14) and the half convex ring (15), and in the gap between the half convex ring (15) and the rolling ring (3); the hook head of the balancing block (5) cooperates with the circumferential groove of the rolling ring (3), and the balancing block (5) is threadedly connected to the fixing screw (12), and the fixing screw (12) fixes the balancing block (5).

8. The double flange straight pipe centrifugal casting pipe mold according to claim 1, characterized in that: The rolling belt ring (3) cooperates with the stop ring on the centrifugal support wheel.

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