A method for producing composite cast stone pipe fittings

Abstract

The present invention discloses a production method of composite cast stone pipe fittings. The method includes: 1) making spiral ribs; 2) press welding of spiral ribs: press welding the spiral ribs to the inner wall of steel pipe fittings with a press welding device; 3) fitting white modules: fitting white modules inside steel pipe fittings; 4) coating drying: sticking breathable paper on the surface of the white modules, brushing Class C fire-resistant oil, and brushing quartz powder coating after drying; 5) lost foam sand box modeling: fixing the steel pipe fittings with a mold in the lost foam sand box, inserting an induction coil, and placing an exhaust pipe inside the pipe fittings; 6) vacuum casting molding: vacuumizing the sand box, energizing the induction coil to induction heat the steel pipe fittings, gasifying the white modules, and forming a carbonized film on the inner surface of the coating; the induction coil is powered off, and the cast stone molten body is cast. The composite cast stone pipe fittings produced by the present invention have a steel pipe fitting and a cast stone lining as one body, and there is no gap between the two.

Description

Technical Field

[0001] The invention is applied to the wear-resistant or corrosion-resistant material conveying industry and relates to a cast stone composite pipe fitting, specifically using a cast stone lining as a wear-resistant layer or a corrosion-resistant layer for conveying materials. Background Art

[0002] Cast stone is a wear-resistant and corrosion-resistant material, and is often used as a lining material for wear-resistant pipes or corrosion-resistant pipes. Publication No. CN106764200A provides a cast stone wear-resistant pipe fitting, in which a cast stone plate is pasted on the inner wall of a curved pipe with furan glue. Announcement No. CN202868199U discloses a cast stone wear-resistant pipe fitting, in which Example 4 is also made by pasting a cast stone arc plate with glue, and Examples 1-3 are formed by forming a cavity with an inner and outer shell, and pouring a cast stone melt in the cavity. For pipe fittings in which cast stone plates are pasted on the inner wall, the bonding force gradually decreases over time, and the cast stone plates will peel off, which may cause pipeline blockage in severe cases. For pipe fittings in which cast stone melt is poured into the cavity, cast stone and steel are not infiltrated, and the two cannot be bonded. After the cast stone melt solidifies, it shrinks, forming a gap between the cast stone and the outer shell. When the inner layer of the pipe fitting is worn, the cast stone layer loses its support, and it is easy to break and fail. Therefore, the service life of these two types of pipe fittings is limited, and neither can give full play to the role of cast stone. The applicant has developed a new type of composite cast stone pipe fitting, the outer layer of which is a steel pipe fitting, and the inner layer is a cast stone lining. Spiral ribs are embedded in the cast stone lining, and the spiral ribs are press-welded to the inner wall of the steel pipe fitting, integrating the cast stone lining and the steel pipe fitting.

[0003] Announcement No. CN102764853B discloses an induction heating gasification EPS lost foam casting method, in which an induction coil is placed in the sand box, and a cold iron ring is pre-buried by induction heating to gasify the EPS white module, and the EPS is gasified before the metal liquid is poured to avoid the adverse effect of the gasification products of EPS on the quality of the casting. Announcements No. CN205236977U and CN206966592U respectively provide a vacuum lost foam sand box bottom leakage device and a vacuum lost foam sand box sealing insulation device, both of which constitute the prior art of the present invention. The present invention improves on the basis of the prior art and develops a new production method for composite cast stone pipe fittings. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a method for producing composite cast stone pipe fittings, which adopts multiple technologies such as pressure welding, lost foam, induction heating, etc. to produce composite cast stone pipe fittings integrating cast stone and steel pipe fittings. The composite cast stone pipe fittings will not peel off or fall off, thereby extending their wear-resistant service life.

[0005] The technical solution adopted by the present invention is: a composite cast stone pipe fitting production method, comprising the following steps: 1) Spiral rib production: the wire rod after stress relief annealing is coiled into a spiral rib with uniform pitch. 2) Spiral rib pressure welding: the spiral rib is pressure welded to the inner wall of the steel pipe fitting using a pressure welding device placed in the steel pipe fitting. 3) White module installation: the white module is installed in the steel pipe fitting, and an arched cavity is reserved on the white module at the position matching the spiral rib. 4) Paint drying: the adhesive is applied to the surface of the white module, and breathable paper is pasted, and Class C refractory oil is applied on the breathable paper, and the breathable paper is completely soaked with the Class C refractory oil and then dried, and quartz powder water-based paint is applied on the breathable paper, and the coating thickness after drying is not less than 2 mm. 5) Lost foam sand box molding: Fix the mold in the lost foam sand box in advance, fix the steel pipe with the mold, fix the temperature measuring plate on the outer surface of the steel pipe, put the induction coil on the outside of the steel pipe, add sand layer by layer for vibration molding, place the exhaust pipe inside the pipe, and connect the exhaust pipe to the vacuum system pipeline of the sand box. 6) Vacuum casting molding: The sand box is evacuated, the system vacuum is kept below -0.05Mpa, the induction coil is powered on to induction heat the steel pipe, gradually heating it to 600-700℃ and keeping it warm, the white module is gasified, and a carbonized film is formed on the inner surface of the coating; the induction coil is powered off, and the cast stone melt is poured. 7) Sand removal and cleaning: After the cast stone melt is completely solidified, the sand box is broken; sand is removed from the bottom opening of the sand box, the composite cast stone pipe is lifted out, and sent to the heat treatment furnace; the pouring system is cleaned after it is taken out of the furnace, and shot blasting is performed.

[0006] Further, the pressure welding device in step 2) includes a detachably connected pressure welding trolley, a support frame and a reaction frame, and the top view centers of the three are consistent. The pressure welding trolley is located at the bottom, the reaction frame is located at the top, and the support frame is located in the middle, connecting the pressure welding trolley and the reaction frame. The pressure welding trolley includes a frame, wheels, a frequency modulation motor, an arc plate and a cylinder; the wheels are evenly distributed on both sides of the frame, and each wheel is connected to a separate frequency modulation motor. The frequency modulation motor can adjust the wheel speed individually to achieve the straight or turning of the pressure welding trolley. The cylinder is fixed at the top view center of the frame, and the pressure welding block is fixedly connected to the lower end of the cylinder rod of the cylinder. The arc plate cooperates with the spiral rib, is fixed to the bottom of the frame, and is located in the middle of the wheelbase. The arc plate is processed with a pressure welding port at a position corresponding to the cylinder. The reaction frame includes a bottom plate connected to the support frame, and a fixed guide cylinder is welded and fixed at the top view center of the bottom plate. A freely sliding guide block is set in the guide cylinder, and the guide block and the guide cylinder stop are prevented from falling off. The top of the guide block is fixed with a support plate, and the pressure wheel is rotatably connected on the support plate. A compression spring is installed at the bottom of the guide block and inside the guide cylinder to adapt to the fluctuation of the inner diameter of the steel pipe fitting.

[0007] Furthermore, the Class C fire-resistant oil in step 4) is diesel, or engine oil, or lubricating oil, or transformer oil. If graphite powder coating is used in step 4) instead of quartz powder coating, the Class C fire-resistant oil may not be applied on the breathable paper.

[0008] Furthermore, the temperature measuring piece in step 5) transmits the temperature data to a display screen outside the sand box, and the induced current and power can be adjusted at any time to control the heating temperature of the steel pipe.

[0009] The beneficial effects of the present invention are as follows: the composite cast stone pipe fittings produced by the present invention are integrated with the steel pipe fittings and the cast stone lining, with no gap therebetween, the cast stone lining will not peel off or fall off, and the wear-resistant service life is greatly extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic diagram of the structure of the composite cast stone pipe fitting in Example 1;

[0011] Figure 2 This is a schematic diagram of the pressure-welded spiral ribs in Example 1;

[0012] Figure 3 This is the main view of the pressure welding trolley structure. Figure 4 BB cross-sectional view;

[0013] Figure 4 for Figure 3 AA cross-sectional view of ;

[0014] Figure 5 for Figure 3 A right view structural diagram of ;

[0015] Figure 6 This is a schematic diagram of the main view of the reaction frame structure. Figure 7 EE cross-sectional view;

[0016] Figure 7 for Figure 6 Right side schematic view;

[0017] Figure 8 for Figure 7 Schematic diagram from top view;

[0018] Fig. 9 This is a top view of the white module inserted into Example 1;

[0019] Fig.10 This is a cross-sectional schematic diagram of the white module inserted into Example 1;

[0020] Fig.11 This is a schematic diagram of lost foam sand box molding in Example 1;

[0021] Fig.12 This is a schematic diagram of the composite cast stone tee structure of Example 2;

[0022] Fig.13 This is a schematic diagram of lost foam sand box molding in Example 2;

[0023] Among them: 1-steel bent pipe, 2-spiral rib, 3-cast stone lining; 4-pressure welding trolley, 5-support frame, 6-reaction frame; 7-white module, 8-mold, 9-induction coil, 10-temperature measuring piece, 11-exhaust pipe, 12-pouring system, 13-molding sand; 14-steel tee pipe;

[0024] 41-frame, 42-wheel, 43-frequency modulation motor, 44-arc plate, 45-pressure welding block, 46-cylinder, 47-pressure welding port;

[0025] 61-bottom plate, 62-guide cylinder, 63-guide block, 64-support plate, 65-pressure wheel, 66-compression spring;

[0026] 71-22.5° elbow white module, 72-straight tube white module, 73-arched cavity. DETAILED DESCRIPTION

[0027] Among the types of composite cast stone pipe fittings, elbows and tees are the most numerous. The present invention is mainly described using elbows and tees, and other pipe fittings can be improved or modified on this basis.

[0028] Example 1: Composite cast stone elbow.

[0029] Attached Figure 1 It is a schematic diagram of the composite cast stone elbow structure. The outer layer is a steel elbow 1 made of low carbon steel or low alloy steel with good weldability. In terms of the wide range of steel types, Q215 or Q235 is the most suitable. The inner layer is a cast stone lining 3 with good wear resistance. Spiral ribs 2 are embedded in the cast stone lining 3. The spiral ribs 2 are fixedly welded to the inner wall of the steel elbow 1, which strengthens the cast stone lining 3, so that the cast stone lining 3 and the steel elbow 1 become one. Even if cracks occur in the cast stone lining, it will not peel off or fall off in pieces. Although there is no bonding force between the steel elbow 1 and the cast stone lining 3, the spiral ribs 2 combine the steel elbow 1 and the cast stone lining 3 into one.

[0030] Taking the DN300 composite cast stone elbow as an example, a DN350 welded pipe is selected to be bent into a steel elbow, the outer diameter of the welded pipe is Ø377mm, the wall thickness is 6mm, and the thickness of the cast stone lining 3 is about 32-33mm, which can meet the requirement of a diameter of Ø300mm. The manufacturing of this embodiment includes the following steps:

[0031] 1) Production of spiral ribs. After stress relief annealing treatment, the Ø5mm wire rod is coiled into spiral ribs to ensure consistent pitch. The outer diameter of the spiral ribs is Ø26mm and the pitch is 50mm.

[0032] 2) Spiral reinforcement pressure welding.

[0033] Spiral reinforcement is made of Figure 2The pressure welding device shown is pressure welded on the inner wall of the steel bent pipe. The pressure welding device includes a detachably mounted pressure welding carriage 4, a support frame 5, and a reaction frame 6. The pressure welding carriage 4 is located at the bottom, the reaction frame 6 is located at the top, and the support frame 5 is located in the middle, connecting the pressure welding carriage 4 and the reaction frame 6, and is used to adjust the height of the reaction frame 6.

[0034] The pressure welding carriage 4 includes a frame 41, wheels 42, a frequency modulation motor 43, an arc plate 44 and a cylinder 46. The four wheels 42 are evenly distributed on both sides of the frame 41. Each wheel 42 is connected to a separate frequency modulation motor 43. The frequency modulation motor 43 can drive the wheels 42 to rotate, and the rotation of the wheels 42 can drive the frame 41 to move. The frequency modulation motor 43 adjusts the rotation speed of the wheels on both sides. When the speeds are the same, the wheels can move in a straight line, and when the speeds are different, the wheels can turn. The shape and size of the arc plate 44 match the spiral rib 2 and are used to position the spiral rib. The arc plate 44 is fixedly welded to the bottom of the frame 41 and is located in the middle of the wheelbase. The cylinder 46 is fixed on the frame 41 and is located at the center of the frame 41, that is, the top view center of the frame 41 (the top view center refers to the center of the top view, the same below). At the lower end of the cylinder rod, a pressure welding block 45 is fixedly connected. The pressure welding block 45 is fixedly connected to the cable and is used to transmit large current and small voltage to meet the requirements of pressure welding process parameters. In order to reduce the resistance between the pressure welding block 45 and the spiral rib and increase the service life of the pressure welding block, the pressure welding block 45 is preferably made of graphite or pure copper. The downward extension of the cylinder rod can realize the pressure welding of the threaded rib. On the arc plate 44, at the position corresponding to the cylinder 46, a pressure welding port 47 is processed to facilitate the extension and contraction of the cylinder rod. The two ends of the arc plate 44 are designed as flared mouths with arc transitions, which is conducive to the pressure welding trolley to insert the threaded rib into the arc plate 44 during the movement to realize the positioning of the spiral rib.

[0035] The function of the reaction frame 6 is to provide a reverse force when the cylinder rod is extended by pressure welding. The reaction frame 6 includes a bottom plate 61 connected to the support frame 5, a guide cylinder 62 fixed by welding in the middle of the plane of the bottom plate 61, a guide block 63 is mounted inside the guide cylinder 62, and the guide block 63 can slide freely in the guide cylinder 62, and the two stoppers prevent slipping. A support plate 64 is fixed on the top of the guide block 63, and a pressure wheel 65 is rotatably connected to the support plate 64. A compression spring 66 is installed at the bottom of the guide block 63, and the compression spring 66 can be telescopically adjusted according to the change of the inner diameter of the steel curved pipe to ensure that the pressure welded vehicle can move smoothly in the steel curved pipe. After the reaction frame 6 is connected, its top view center is consistent with the top view center of the frame 41, ensuring that the cylinder rod and the pressure wheel 65 are subjected to force on an approximate straight line.

[0036] During pressure welding, the power supply cable and the cylinder air supply hose on the pressure welding trolley 4 are led out of the steel curved pipe, and the wheel 42 contacts the inner wall of the steel curved pipe. At the same time, the arc plate 44 corresponds to the spiral ribs at the bottom thereof, and the pressure wheel 65 of the reaction frame 6 contacts the inner wall. The travel direction of the pressure wheel 65 is consistent with the travel direction of the wheel 42. When the cylinder rod of the cylinder 46 extends downward for pressure welding, its reaction force comes from the reaction frame 6. When the cylinder rod extends downward, when the pressure welding block 45 contacts the threaded ribs, the cylinder body moves upward together with the guide cylinder 62 in the frame 41, the support frame 5, and the reaction frame 6. When the upper edge of the guide cylinder 62 of the reaction frame 6 contacts the bottom edge of the support plate 64, the support plate 64 cannot move upward, and the reaction force of the cylinder rod is transmitted to the inner wall of the steel curved pipe through the pressure wheel 65. At this time, the pressure of the cylinder 46 is fully applied to the pressure welding block 45 and the spiral rib 2, and the cable can be passed through a large current for welding.

[0037] The frequency modulation motor 43 can be automatically controlled by a chip, and a welding position of a spiral rib is pre-set. According to the inner diameter and wheelbase of the steel bend pipe, the linear velocity and angular velocity of the wheels on both sides of the pressure welding trolley are calculated according to the turning radius, and then the motor speed is set in the chip, and the travel distance of the pressure welding trolley is set according to the pitch of the spiral rib. After the first welding point of the steel bend pipe mouth is pressure welded, the chip automatically controls the travel distance of the next pressure welding point of the pressure welding trolley. After parking, the wireless control starts the cylinder and connects the cable current to realize automatic pressure welding. In this way, the automatic welding of the spiral rib can be realized. After the pressure welding is completed, the cylinder rod is retracted, the pressure welding trolley moves, and the next pressure welding operation is performed.

[0038] 3) Set white module.

[0039] After the spiral reinforcement positioning welding is completed, the white module 7 is installed in the steel elbow. Fig. 9 and attached Fig.10 As shown. Four 22.5° elbow white modules 71 are installed in the 90° elbow, and the straight section is installed with straight pipe white modules 72. Arched holes 73 are reserved on the white modules to match the threaded ribs. The outer diameter of the white module is slightly larger than the inner diameter of the steel elbow. The elastic deformation of the white module is used to fix the white module with the friction force of the inner wall of the steel elbow.

[0040] The 22.5° elbow white module 71 is adopted. Firstly, the white module is small and convenient for assembly. Secondly, it is convenient for assembly of 45° elbow and can also be used for manufacturing 45° elbow.

[0041] 4) Paint drying.

[0042] After installing the white module, apply adhesive on the surface of the white module, stick a layer of breathable paper, apply diesel on the breathable paper, soak the breathable paper with diesel and then dry it, apply quartz powder water-based paint on the breathable paper, dry it once each time the paint is applied, and the coating thickness should not be less than 2mm.

[0043] Graphite powder alcohol-based paint can also be used to replace quartz powder water-based paint. Since alcohol-based paint is more volatile than water-based paint, the coating drying time is short. However, since alcohol-based paint is a Class A flammable material, white module is a Class B flammable material, and diesel is a Class C flammable material, the fire hazard is much lower than that of alcohol and white module. For safe production, alcohol-based graphite powder paint is not recommended, and water-based quartz powder paint is suitable. If graphite powder paint is used, diesel does not need to be applied on the breathable paper. This method is to apply diesel or other oils to produce a carbon film to prevent the cast stone from bonding with the quartz powder paint. The graphite powder paint can directly isolate the cast stone melt and the quartz sand, so there is no need to apply diesel.

[0044] Diesel can also be replaced by other Class C fire-resistant oils such as engine oil, lubricating oil, transformer oil, etc.

[0045] 5) Lost foam sand box modeling.

[0046] After the white module is painted and dried, it is bonded with the pouring system 12 and placed in the lost foam sand box and molded with molding sand 13, as shown in the attached figure. Fig.11 As shown. During molding, a jig 8 is fixed in the lost foam sand box in advance, and the steel elbow 1 is fixed with the jig 8. A temperature measuring piece 10 is fixed on the outside of the steel elbow. The temperature measuring piece 10 can transmit the temperature data of the steel elbow to the display screen outside the sand box through a cable, so as to adjust the induced current and power and control the induced temperature of the steel elbow. Then, an induction coil 9 is inserted into the outside of the steel elbow 1, and sand is added layer by layer for vibration molding. At the same time, an exhaust pipe 11 is placed in the white module of the elbow, and the exhaust pipe 11 is connected to the vacuum system pipeline in the sand box. After the molding sand 13 is molded, the sand box is covered with agricultural film, covered with sand and waited for pouring.

[0047] 6) Vacuum casting.

[0048] Before pouring the cast stone melt, the sand box is evacuated, and the exhaust pipe 11 also evacuates the molding sand in the elbow pipe, and the vacuum degree is maintained below -0.05Mpa. The molding sand 13 in the sand box loses fluidity in the vacuum state and remains fixed. Then the induction coil 9 is energized to induction heat the steel elbow pipe 1, so that the steel elbow pipe 1 gradually heats up to about 600-700℃ and keeps warm. The white module is heated and vaporized at high temperature, and the vaporization product is drawn away by the exhaust pipe 11 through the breathable paper and coating. Since the vaporization product of the white module cannot enter the sand box from the steel elbow pipe, but can only enter the sand box through the breathable paper and coating, in order to prevent the vacuum degree of the molding sand in the elbow pipe from being insufficient, and the coating from being damaged and the box collapsing due to the fluidity of the molding sand, it is necessary to arrange the exhaust pipe 11 in the elbow pipe, so as to keep the vacuum degree of the molding sand in the elbow pipe from being destroyed by the vaporization product, so that the molding sand remains stable.

[0049] During the gasification process of the white module 7 of the steel elbow 1 set, the white module of the pouring system 12 is not gasified, so that the steel elbow 1 and the spiral rib 2 are kept at high temperature in a vacuum environment and will not be oxidized. Since the breathable paper is pre-coated with Class C fire-resistant oil such as diesel, the breathable paper is carbonized in a high-temperature vacuum environment, forming a carbonized film on the inner surface of the coating.

[0050] After about one minute of induction heating, the induction coil is powered off, and the cast stone melt is poured. After the white module of the pouring system 12 is gasified, it is poured quickly. The cast stone melt can be quickly filled into the mold under the action of atmospheric pressure to fill the cavity generated by the gasification of the white module 7. Since the cast stone melt is infiltrated with quartz sand but not with carbonized film or graphite, the graphite coating or carbonized film is used to separate the cast stone melt from the quartz sand coating or quartz molding sand to avoid sand adhesion defects, form a smooth surface, and improve the appearance quality of the cast stone.

[0051] The steel elbow 1 does not undergo phase change at 600-700° C., which does not adversely affect the performance of the steel elbow, and the thermal expansion basically reaches the maximum.

[0052] 7) Cleaning of falling sand.

[0053] After the cast stone melt is poured, the sand box is kept in vacuum for about 5 minutes. At this time, the cast stone melt is completely solidified, and the vacuum pump is turned off to break the vacuum in the sand box. After cooling in the sand box for more than four hours, the sand is dropped from the bottom opening of the sand box, and the induction coil 9 and the cast stone composite elbow gradually expose the molding sand. The cast stone composite elbow is lifted out of the induction coil 9 and sent to the heat treatment furnace for treatment, and the sand box enters the next elbow molding process. After the cast stone composite elbow comes out of the heat treatment furnace, the pouring system is cleaned, shot blasted, and the surface is sprayed to produce a finished composite cast stone elbow.

[0054] The purpose of induction heating is to obtain the maximum pre-expansion of the steel elbow. Since the expansion coefficient of steel is greater than that of cast stone, after the cast stone composite elbow is cooled, the larger shrinkage rate of the steel elbow is used to make the steel elbow produce prestress and tightly wrap the cast stone lining. There will be no gap between the two due to the shrinkage of the cast stone. Even if the prestress gradually decreases or even disappears with the increase of time, the steel elbow and the cast stone lining will not change in size or produce a gap. During the use of the composite cast stone elbow, the force of the cast stone lining can be transferred to the steel elbow. The cast stone lining can withstand the protection and support of the steel elbow, thereby preventing the cast stone lining from peeling or falling off, and increasing the service life of the cast stone lining.

[0055] Example 2: Composite cast stone tee pipe.

[0056] Attached Fig.12The structure diagram of the composite cast stone tee pipe is shown in FIG. The outer layer is a steel tee pipe 14 made of low carbon steel or low alloy steel with good weldability, and the inner layer is a cast stone lining 3 with good wear resistance. The spiral ribs 2 are embedded in the cast stone lining 3. The spiral ribs 2 are fixedly welded to the inner wall of the steel tee pipe 14, so that the cast stone lining 3 and the steel elbow pipe 1 are integrated. The manufacturing of this embodiment includes the following steps:

[0057] 1) Production of spiral ribs. After the wire rod is subjected to stress relief annealing, it is coiled into spiral ribs with uniform pitch.

[0058] 2) Spiral rib welding. The device for welding spiral ribs is the same as that in Example 1, except that when welding spiral ribs in a steel tee pipe, the welding trolley moves in a straight line without turning, and the control of the welding trolley is simpler.

[0059] 3) Installing white modules. After the spiral rib positioning welding is completed, install white modules in the steel tee pipe. The white modules in the tee pipe are all straight tube white modules, and the installation is simpler than that in Example 1. Only the arc transition at the connection of the tee pipe needs to make a separate white module.

[0060] 4) Paint drying. After the white module is installed, apply adhesive on the surface of the white module, paste a layer of breathable paper, apply diesel, engine oil, lubricating oil, transformer oil and other Class C fire-resistant oils on the breathable paper, soak the breathable paper completely and dry it, apply quartz powder water-based paint on the breathable paper, dry it once after each application of paint, and the coating thickness should not be less than 2mm. Graphite powder alcohol-based paint can also be used instead of quartz powder water-based paint, then there is no need to apply Class C fire-resistant oil on the breathable paper.

[0061] 5) Lost foam sand box molding. After the white module is painted and dried, it is bonded with the pouring system 12 and placed in the lost foam sand box and molded with molding sand 13, as shown in the attached Fig.13 As shown. During molding, a mold 8 is fixed in the lost foam sand box in advance, a steel three-way pipe 14 is fixed with the mold 8, a temperature measuring piece 10 is fixed on the outside, an induction coil 9 is inserted outside the steel three-way pipe 14, and sand is added layer by layer for vibration molding. At the same time, an exhaust pipe 11 is placed in the main pipe and branch pipe of the three-way pipe, and the exhaust pipe 11 is connected to the vacuum system pipeline in the sand box. After the molding sand 13 is molded, the sand box is covered with agricultural film and covered with sand to wait for pouring.

[0062] 6) Vacuum casting and molding. Before casting the cast stone melt, the sand box is evacuated, and the exhaust pipe 11 also evacuates the molding sand in the tee pipe, and the system vacuum is maintained below -0.05Mpa. The molding sand 13 in the sand box is fixed in a vacuum state, and then the induction coil 9 is powered on to induction heat the steel tee pipe 14, gradually heating it to 600-700℃ and keeping it warm. The gasification product of the white module 7 is drawn away by the exhaust pipe 11 through the breathable paper and the coating. Since the breathable paper is pre-coated with diesel, the breathable paper is carbonized in a high-temperature vacuum environment, and a carbonized film is formed on the inner surface of the coating. After about two minutes of induction heating, the induction coil is powered off, and the cast stone melt is quickly poured. The cast stone melt fills the cavity generated by the gasification of the white module 7 under the action of atmospheric pressure. The cast stone melt does not infiltrate the carbonized film or graphite, and the graphite coating or carbonized film separates the cast stone melt from the quartz sand coating or quartz molding sand to avoid sand adhesion defects and improve the appearance quality.

[0063] 7) Sand removal and cleaning. After the cast stone melt is poured, the sand box is kept in vacuum for about 5 minutes. At this time, the cast stone melt is completely solidified, and the vacuum pump is turned off to break the vacuum in the sand box. After cooling in the sand box for more than four hours, the sand is removed from the bottom opening of the sand box, and the induction coil 9 and the cast stone composite tee gradually expose the molding sand. The induction coil 9 is removed, the cast stone composite tee is lifted out, and sent to the heat treatment furnace for treatment. The sand box enters the next tee molding process. After the cast stone composite tee comes out of the heat treatment furnace, the pouring system is cleaned, shot blasted, and the surface is sprayed to produce a finished composite cast stone tee.

[0064] The present invention takes a 90° elbow and a tee pipe as examples to illustrate the production method of a composite cast stone pipe fitting. On this basis, the manufacturing method of a 45° elbow is basically the same as that of Example 1, and the manufacturing method of a cross pipe fitting is basically the same as that of Example 2, which will not be repeated.

[0065] The composite cast stone pipe fitting produced by the present invention utilizes the shrinkage of the steel pipe fitting to generate prestress in the steel pipe fitting, tightly wrapping the cast stone lining without generating a gap between the two. During use, the force of the cast stone lining can be transmitted to the steel pipe fitting, and the cast stone lining can withstand the protection and support of the steel pipe fitting. The spiral ribs connect the steel pipe fitting and the cast stone lining as a whole, effectively preventing the cast stone lining from peeling off or falling off, thereby increasing the service life of the cast stone lining.

Claims

1. A method for producing a composite cast stone pipe fitting, comprising the following steps: 1) Spiral reinforcement production; 2) Spiral rib pressure welding: The spiral rib is pressure welded to the inner wall of the steel pipe by a pressure welding device placed in the steel pipe; the pressure welding device comprises a detachably connected pressure welding carriage (4), a support frame (5) and a reaction frame (6), the centers of the three being consistent when viewed from above; the pressure welding carriage (4) is located at the bottom, the reaction frame (6) is located at the top, and the support frame (5) is located in the middle, connecting the pressure welding carriage (4) and the reaction frame (6); the pressure welding carriage (4) comprises a frame (41), an arc plate (44) and a cylinder (46); the cylinder (46) is fixedly located at the center of the frame (41) when viewed from above, and a pressure welding block (45) is fixedly connected to the lower end of the cylinder rod of the cylinder; the arc plate (44) cooperates with the spiral rib, is fixed to the bottom of the frame (41), and is located in the middle of the wheelbase, and a pressure welding opening (47) is processed on the corresponding arc plate (44) at a position corresponding to the cylinder (46); 3) Installing white module: Installing white module in steel pipe fittings, and reserving arched cavity on the white module at the position matching with spiral reinforcement; 4) Paint drying: Apply adhesive on the surface of the white module, stick breathable paper, apply Class C refractory oil on the breathable paper, soak the breathable paper with Class C refractory oil and then dry it, apply quartz powder water-based paint on the breathable paper, and the coating thickness after drying shall not be less than 2mm; 5) Lost foam sand box molding: Fix the mold in the lost foam sand box in advance, fix the steel pipe with the mold, fix the temperature measuring piece on the outer surface of the steel pipe, insert the induction coil on the outside of the steel pipe, add sand layer by layer for vibration molding, place an exhaust pipe inside the pipe, and connect the exhaust pipe to the vacuum system pipeline of the sand box; 6) Vacuum casting: The sand box is evacuated, and the system vacuum is maintained below -0.05Mpa. The induction coil is powered on to induction heat the steel pipe fittings, gradually heating up to 600-700℃ and keeping warm. The white module is vaporized and a carbonized film is formed on the inner surface of the coating. The induction coil is powered off and the cast stone melt is poured.

2. The method for producing a composite cast stone pipe fitting according to claim 1, characterized in that: The pressure welding device in step 2) further comprises wheels (42) and a frequency-modulated motor (43); the wheels (42) are evenly distributed on both sides of the vehicle frame (41), and each wheel (42) is connected to a separate frequency-modulated motor (43).

3. The method for producing a composite cast stone pipe fitting according to claim 1, characterized in that: The reaction frame (6) in step 2) comprises a bottom plate (61) connected to the support frame (5), the bottom plate (61) overlooking the center fixed guide cylinder (62), a freely sliding guide block (63) is mounted inside the guide cylinder (62), the guide block (63) and the guide cylinder (62) are prevented from falling off by stoppers, the top of the guide block (63) is fixed with a support plate (64), the support plate (64) is rotatably connected to a pressure wheel (65), and a compression spring (66) is installed at the bottom of the guide block (63) and inside the guide cylinder (62).

4. The method for producing a composite cast stone pipe fitting according to claim 1, characterized in that: The Class C fire-resistant oil in step 4) is diesel, lubricating oil, or transformer oil.

5. The method for producing a composite cast stone pipe fitting according to claim 1, characterized in that: In the step 4), graphite powder coating is used instead of quartz powder coating, and the breathable paper is not coated with Class C fire-resistant oil.

6. The method for producing a composite cast stone pipe fitting according to claim 1, characterized in that: The temperature measuring piece in step 5) transmits the temperature data to a display screen outside the sand box.

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