Forming process of steel lining polytetrafluoroethylene concentric reducing pipe

Abstract

The invention discloses a forming process of a steel lining polytetrafluoroethylene concentric reducing pipe. The forming process comprises the following specific steps that S1, pretreatment is conducted, specifically, after a steel pipe is cut, laser rust removal is conducted, and primer containing a silane coupling agent is sprayed on the surface; s2, powder filling is conducted, specifically, a mold is placed in the center of the steel pipe, and then PTFE-containing powder is added into modified powder according to 1.3 times of the volume between the steel pipe and the mold; the steel pipe enters a sintering area after the temperature of the steel pipe reaches 200 DEG C in a preheating area, PTFE powder is melted at the temperature of 380 DEG C and is subjected to roll coating forming, gradient cooling is conducted in a slow cooling area at the speed of 5 DEG C / min, the temperature is stabilized at 260 DEG C, internal stress is eliminated, an electromagnetic induction coil is arranged in the preheating area, and microwave heating is adopted in a forming area; s4, static pressure forming; s5, reducing forming is carried out; and S6, post-treatment. The forming process of the steel lining PTFE concentric reducing pipe has the effects that the phenomenon that the lining layer is cracked or stripped after cooling is avoided, and the yield is increased.

Description

Technical Field

[0001] This invention relates to the field of PTFE-lined steel tubing technology, and more particularly to a forming process for a PTFE-lined concentric reducer. Background Technology

[0002] Steel-lined PTFE concentric reducers are reducing pipes that use a seamless steel pipe lined with polytetrafluoroethylene (PTFE). The PTFE and steel pipe are bonded together through a molding process, forming a corrosion-resistant and high-temperature-resistant composite structure. Because they combine the structural strength of metal with the corrosion resistance of PTFE, they are mainly used in chemical, power, and environmental protection fields for connecting pipelines transporting corrosive media of different diameters.

[0003] Traditional processes use integral heating of the steel pipe and PTFE powder, resulting in a significant difference in their coefficients of thermal expansion. This leads to lining cracking or peeling after cooling, resulting in a yield of less than 70%. While existing technologies improve processing efficiency through segmented heating, they do not solve the problem of thermal stress at the material interface. Summary of the Invention

[0004] This invention discloses a molding process for a steel-lined PTFE concentric reducer, which aims to solve the technical problem that the traditional process uses integral heating of the steel pipe and PTFE powder, resulting in a significant difference in their expansion coefficients, which easily leads to cracking or peeling of the lining after cooling, and insufficient yield.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A forming process for a steel-lined PTFE concentric reducer includes the following specific steps: S1: Pretreatment: After cutting the steel pipe, laser rust removal is performed, and the surface is sprayed with a primer containing a silane coupling agent; S2: Powder filling: A mold is placed in the center of the steel pipe, and PTFE-containing powder is added at 1.3 times the volume between the steel pipe and the mold to improve thermal conductivity uniformity; S3: Gradient forming: After the steel pipe reaches 200°C in the preheating zone, it enters the sintering zone, where the PTFE powder is melted at 380°C and rolled into shape. The slow cooling zone cools down at a gradient of 5°C / min and stabilizes at 260°C to eliminate internal stress. An electromagnetic induction coil is installed in the preheating zone, and microwave heating is used in the forming zone; S4: Static pressure forming: Axial and radial pressure are applied simultaneously and pressure is maintained; S5: Reduction forming: Diameter change is completed using a flaring device; S6: Post-treatment: Cooling to 80°C at a rate of 2°C / min, and aging heat treatment is performed to eliminate residual stress;

[0007] In S2, the filling powder is a mixture of PTFE powder and 5% graphene nanotubes;

[0008] In step S4, a pressure of 35 MPa in the axial direction and 25 MPa in the radial direction are applied simultaneously and maintained for 40 minutes.

[0009] By employing a three-stage temperature control heating device, the steel pipe and PTFE powder are heated synchronously, eliminating the material expansion coefficient difference caused by traditional overall heating. An electromagnetic induction coil is set in the preheating zone to eliminate the oxide layer on the inner wall of the steel pipe. Microwave heating is used in the forming zone to increase the melting rate of PTFE powder by 40%, avoiding lining cracking or peeling after cooling and improving the yield.

[0010] In a preferred embodiment, the mold in S2 includes: a base, with a steel pipe placed on the top outer wall of the base; multiple uprights, equidistantly fixed to the circumferential outer wall of the base, and each upright having a connecting buckle at its top; and a limiting ring, fixedly connected to the bottom inner wall of the base.

[0011] The mold in S2 further includes: an inner layer, the bottom of which is fixedly connected to the inner wall of the bottom of the base, and multiple hollow connecting frames are fixedly connected at equal intervals to the outer periphery of the top of the inner layer, the multiple hollow connecting frames being movably fitted to the outer wall of the top of the steel pipe; a vibration mechanism, movably connected to the center position of the inner layer; and an inner support mechanism, movably connected to the center position of the inner layer.

[0012] The inner layer includes: a heat-resistant rubber layer, the bottom of which is fixedly connected to the inner wall of the top of the base, and the top of which is fixedly connected to multiple connecting hollow frames; and multiple elastic metal sheets, which are fixedly surrounded by the inner wall of the heat-resistant rubber layer at equal intervals. The elastic metal sheets provide support while also providing rebound and deformation.

[0013] The internal support mechanism includes: a top plate, covering the top outer wall of the steel pipe, with multiple inserts and sealing blocks fixedly connected to its bottom end. The inserts and sealing blocks are staggered, and the inserts are movably inserted into multiple connecting hollow frames. Inserting the inserts into the corresponding connecting hollow frames enhances the connection between the internal support mechanism and the inner layer, while the sealing blocks fill the gaps between adjacent connecting hollow frames to ensure sealing. Multiple connecting holes are provided through the top inner wall of the top plate for connecting external hoisting equipment for transferring the mold and steel pipe.

[0014] The internal support mechanism also includes: multiple uprights two, which are equidistantly and fixedly connected to the outer circumference of the top plate; and multiple latches, which are fixedly installed at the bottom ends of the multiple uprights two and simultaneously connected to the corresponding connecting latches.

[0015] The inner support mechanism further includes: an inner support rod, which is fixedly connected to the bottom outer wall of the top plate and inserted into the inner layer, with its outer diameter being larger than the outer diameter of the inner vibration guide tube; and a chamfer, which is set at the bottom end of the inner support rod. The chamfer facilitates the insertion of the inner support rod into the inner layer.

[0016] By incorporating an internal support mechanism, after filling with powder, the vibration mechanism is removed, and then the internal support mechanism is inserted from above. Since the diameter of the internal support rod is larger than that of the internal guide tube, it can drive the inner layer to expand outward during the embedding process, squeezing the filled powder, thereby achieving pre-pressing, which is beneficial to improving the subsequent molding efficiency and quality.

[0017] In a preferred embodiment, the vibration mechanism includes: an inner guide tube, the outer circumferential wall of which is movably attached to the inner wall of the inner layer; a handle, which is fixedly connected to the top outer wall of the inner guide tube; and a vibrator, the bottom end of which is movably inserted into a limiting ring, and multiple output ends of which are respectively fixedly connected to vibration heads, with multiple vibration heads simultaneously attached to the inner wall of the inner guide tube.

[0018] By incorporating a vibration mechanism, a steel pipe is placed on the mold before powder filling, and then the vibration mechanism is installed from the top of the inner layer. While filling the powder, the vibration mechanism generates vibration by activating the vibrator. The generated vibration acts between the powder particles, which can replace manual vibration, ensuring the density of the powder filling. Moreover, compared with manual vibration, the powder injection efficiency is higher.

[0019] As can be seen from the above, the forming process of a steel-lined PTFE concentric reducer includes the following specific steps: S1: Pretreatment: After the steel pipe is cut, laser rust removal is used, and the surface is sprayed with a primer containing silane coupling agent; S2: Powder filling: A mold is placed in the center of the steel pipe, and then PTFE-containing powder is added at a ratio of 1.3 times the volume between the steel pipe and the mold; S3: Gradient forming: After the steel pipe reaches 200°C in the preheating zone, it enters the sintering zone. The PTFE powder is melted at 380°C and rolled into shape. The slow cooling zone cools down at a gradient of 5°C / min and stabilizes at 260°C to eliminate internal stress. An electromagnetic induction coil is set in the preheating zone, and microwave heating is used in the forming zone; S4: Static pressure forming: Axial and radial pressure are applied simultaneously and pressure is maintained; S5: Reduction forming: The diameter is changed using a flaring device; S6: Post-treatment: The pipe is cooled to 80°C at a rate of 2°C / min and subjected to aging heat treatment to eliminate residual stress. The forming process of the steel-lined PTFE concentric reducer provided by the present invention has the technical effect of avoiding cracking or peeling of the lining after cooling and improving the yield. Attached Figure Description

[0020] Figure 1 This is an overall flow chart of the molding process of a steel-lined PTFE concentric reducer proposed in this invention.

[0021] Figure 2 This is a schematic diagram of the overall mold structure for the molding process of a steel-lined PTFE concentric reducer proposed in this invention.

[0022] Figure 3 This is a schematic diagram of the internal structure of the mold for the molding process of a steel-lined PTFE concentric reducer proposed in this invention.

[0023] Figure 4 This is a cross-sectional view of the top inner layer of the mold for the molding process of a steel-lined PTFE concentric reducer proposed in this invention.

[0024] Figure 5 This is a schematic diagram of the mold inner support mechanism for the molding process of a steel-lined PTFE concentric reducer proposed in this invention.

[0025] In the diagram: 2. Vibration mechanism; 3. Inner layer; 4. Connecting hollow frame; 5. Upright pole one; 6. Base; 7. Connecting buckle; 8. Limiting ring; 9. Internal support mechanism; 201. Handle; 202. Inner vibration guide tube; 203. Vibration head; 204. Vibrator; 301. Heat-resistant rubber layer; 302. Elastic metal sheet; 901. Top plate; 902. Sealing block; 903. Insert block; 904. Upright pole two; 905. Lock; 906. Internal support rod; 907. Chamfer; 908. Connecting hole. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0027] The forming process of the steel-lined PTFE concentric reducer disclosed in this invention is mainly applied to the manufacturing of steel-lined PTFE pipes.

[0028] Reference Figure 1A forming process for a steel-lined PTFE concentric reducer includes the following specific steps: S1: Pretreatment: After cutting the steel pipe, laser rust removal is performed, and the surface is sprayed with a primer containing a silane coupling agent; S2: Powder filling: A mold is placed in the center of the steel pipe, and then PTFE-containing powder is added at 1.3 times the volume between the steel pipe and the mold to improve thermal uniformity; S3: Gradient forming: After the steel pipe reaches 200°C in the preheating zone, it enters the sintering zone, where the PTFE powder melts at 380°C and is rolled into shape. The slow cooling zone cools down at a gradient of 5°C / min and stabilizes at 260°C to eliminate internal stress. An electromagnetic induction coil is installed in the preheating zone, and microwave heating is used in the forming zone; S4: Static pressure forming: Simultaneous application of axial... S5: Radial and lateral pressure, followed by pressure holding; S6: Diameter changing: diameter change is achieved using flaring equipment; S7: Post-treatment: cooling to 80℃ at a rate of 2℃ / min, followed by aging heat treatment to eliminate residual stress. A three-stage temperature-controlled heating device is used, with a preheating zone of 200℃, a forming zone of 380℃, and a stabilization zone of 260℃, to ensure that the steel pipe and PTFE powder are heated synchronously, eliminating the material expansion coefficient difference caused by traditional overall heating. An electromagnetic induction coil is set in the preheating zone to eliminate the oxide layer on the inner wall of the steel pipe. Microwave heating is used in the forming zone to increase the melting rate of PTFE powder by 40%. At the same time, through the gradient heating-isostatic pressing integrated process, the traditional multi-step process is integrated into continuous production, and the forming cycle can be shortened to a great extent.

[0029] Reference Figure 1 In a preferred embodiment, in S2, the filling powder is a mixture of PTFE powder and 5% graphene nanotubes.

[0030] Reference Figure 1 In a preferred embodiment, in S4, an axial pressure of 35 MPa and a radial pressure of 25 MPa are applied simultaneously and held for 40 minutes.

[0031] Reference Figure 2 In a preferred embodiment, the mold in S2 includes: a base 6, with a steel pipe placed on the top outer wall of the base 6; a plurality of uprights 5, which are fixedly connected at equal intervals to the circumferential outer wall of the base 6, and each upright 5 is provided with a connecting buckle 7 at its top; and a limiting ring 8, which is fixedly connected to the bottom inner wall of the base 6.

[0032] Reference Figure 2 In a preferred embodiment, the mold in S2 further includes: an inner layer 3, the bottom of which is fixedly connected to the inner wall of the bottom of the base 6, and a plurality of connecting hollow frames 4 are fixedly connected at equal intervals to the outer periphery of the top of the inner layer 3, the plurality of connecting hollow frames 4 being movably attached to the outer wall of the top of the steel pipe; a vibration mechanism 2, which is movably connected to the center position of the inner layer 3; and an inner support mechanism 9, which is movably connected to the center position of the inner layer 3.

[0033] Reference Figure 3In a preferred embodiment, the vibration mechanism 2 includes: an inner guide tube 202, the outer circumference of which is movably attached to the inner wall of the inner layer 3; a handle 201, fixedly connected to the top outer wall of the inner guide tube 202; and a vibrator 204, the bottom end of which is movably inserted into the limiting ring 8, and multiple output ends of which are respectively fixedly connected to vibration heads 203. The multiple vibration heads 203 are simultaneously attached to the inner wall of the inner guide tube 202. Before powder filling, the steel pipe is placed on the mold, at which time the inner layer 3 is located at the center of the steel pipe. Then, the vibration mechanism 2 is installed from the top of the inner layer 3. While filling the powder, the vibration mechanism 2 starts the vibrator 204, and the multiple vibration heads 203 drive the inner guide tube 202 to vibrate. The vibration is also driven by the inner layer 3 through the attachment with the inner layer 3. The generated vibration acts between the powder particles, which can replace manual vibration, ensure the density of the powder filling, and the powder injection efficiency is higher than that of manual vibration. The vibration mechanism 2 can be disassembled by lifting the handle 201, which is easy and convenient for daily operation.

[0034] Reference Figure 4 In a preferred embodiment, the inner layer 3 includes: a heat-resistant rubber layer 301, the bottom end of which is fixedly connected to the inner wall of the top of the base 6, and the top end of which is fixedly connected to a plurality of connecting hollow frames 4; a plurality of elastic metal sheets 302, which are fixedly surrounded by the inner wall of the heat-resistant rubber layer 301 at equal intervals. The elastic metal sheets 302 provide support while also providing rebound and deformation.

[0035] Reference Figure 5 In a preferred embodiment, the inner support mechanism 9 includes: a top plate 901, covering the top outer wall of the steel pipe, and having a plurality of insert blocks 903 and sealing blocks 902 fixedly connected to its bottom end. The plurality of insert blocks 903 and sealing blocks 902 are arranged in an alternating manner. The plurality of insert blocks 903 are respectively movably inserted into a plurality of connecting hollow frames 4. The insertion of the plurality of insert blocks 903 into the corresponding connecting hollow frames 4 can enhance the connectivity between the inner support mechanism 9 and the inner layer 3, while the sealing blocks 902 can fill the gaps between adjacent connecting hollow frames 4 to ensure sealing. A plurality of connecting holes 908 are provided through the top inner wall of the top plate 901 for connecting external hoisting equipment for transferring the mold and the steel pipe.

[0036] Reference Figure 5 In a preferred embodiment, the inner support mechanism 9 further includes: a plurality of uprights 904, which are equidistantly and fixedly connected to the outer circumference of the top plate 901; and a plurality of latches 905, which are fixedly installed at the bottom ends of the plurality of uprights 904 and simultaneously connected to the corresponding connecting latches 7.

[0037] Reference Figure 5In a preferred embodiment, the inner support mechanism 9 further includes: an inner support rod 906, fixedly connected to the bottom outer wall of the top plate 901, and inserted into the inner layer 3, with its outer diameter being larger than the outer diameter of the inner guide tube 202; and a chamfer 907, provided at the bottom end of the inner support rod 906. The chamfer 907 facilitates the insertion of the inner support rod 906 into the inner layer 3. Based on the elastic metal sheet 302 and the heat-resistant rubber layer 301 of the inner layer 3, it has resilience. When the vibration mechanism 2 is installed, the circumferential diameter of the inner layer 3 is smaller than the required processing diameter, thereby temporarily expanding the volume and facilitating the filling of excess powder. After filling the powder, the vibration mechanism 2 is removed, and then the inner support mechanism 9 is placed in from above. Since the diameter of the inner support rod 906 is larger than that of the inner guide tube 202, it can drive the inner layer 3 to expand outward during the embedding process, squeezing the filled powder, thereby achieving pre-pressing, which is beneficial to improving the subsequent molding efficiency and quality.

[0038] Working principle: By adopting a three-stage temperature control heating device, with a preheating zone of 200℃, a forming zone of 380℃, and a stabilization zone of 260℃, the steel pipe and PTFE powder are heated synchronously, eliminating the material expansion coefficient difference caused by traditional overall heating. The preheating zone is equipped with an electromagnetic induction coil to eliminate the oxide layer on the inner wall of the steel pipe. The forming zone uses microwave heating to increase the melting rate of PTFE powder by 40%. At the same time, through the gradient heating-isostatic pressing integrated process, the traditional multi-step process is integrated into continuous production, and the forming cycle can be shortened to a great extent.

[0039] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A forming process for a steel-lined PTFE concentric reducer, characterized in that, The specific steps include the following: S1: Pretreatment: After the steel pipe is cut, laser rust removal is performed, and the surface is sprayed with a primer containing silane coupling agent; S2: Powder filling: Place the mold in the center of the steel pipe, and then add PTFE-containing powder at a ratio of 1.3 times the volume between the steel pipe and the mold to the modified powder; S3: Gradient forming: After the preheating zone brings the steel pipe to 200°C, it enters the sintering zone. PTFE powder melts at 380°C and is rolled into shape. The slow cooling zone cools down at a gradient of 5°C / min and stabilizes at 260°C to eliminate internal stress. An electromagnetic induction coil is installed in the preheating zone, and microwave heating is used in the forming zone. S4: Static pressure forming: Simultaneous application of axial and radial pressure, followed by pressure holding; S5: Different diameter forming: Diameter change is completed using flaring equipment; S6: Post-treatment: Cool to 80°C at a rate of 2°C / min and perform aging heat treatment to eliminate residual stress.

2. The forming process of a steel-lined PTFE concentric reducer according to claim 1, characterized in that, In S2, the filling powder is a mixture of PTFE powder and 5% graphene nanotubes.

3. The forming process of a steel-lined PTFE concentric reducer according to claim 1, characterized in that, In step S4, a pressure of 35 MPa in the axial direction and 25 MPa in the radial direction are applied simultaneously and maintained for 40 minutes.

4. The forming process of a steel-lined PTFE concentric reducer according to claim 1, characterized in that, The mold in S2 includes: The base (6) has a steel pipe placed on the top outer wall of the base (6); Multiple uprights (5) are fixedly connected to the outer circumference of the base (6) at equal intervals, and each upright (5) is provided with a connecting buckle (7) at its top. The limiting ring (8) is fixedly connected to the inner wall of the bottom end of the base (6).

5. The forming process of a steel-lined PTFE concentric reducer according to claim 4, characterized in that, The mold in S2 also includes: The inner layer (3) is fixedly connected to the bottom inner wall of the base (6), and multiple hollow connecting frames (4) are fixedly connected at equal intervals on the top outer periphery of the inner layer (3). The multiple hollow connecting frames (4) are movably attached to the top outer wall of the steel pipe. The vibration mechanism (2) is movably connected to the center of the inner layer (3); The inner support mechanism (9) is movably connected to the center of the inner layer (3).

6. The forming process of a steel-lined PTFE concentric reducer according to claim 5, characterized in that, The vibration mechanism (2) includes: The inner guide tube (202) has its outer circumferential wall movably attached to the inner wall of the inner layer (3); The handle (201) is fixedly connected to the outer wall of the top end of the inner vibration guide tube (202); The vibrator (204) has its bottom end movably inserted into the limiting ring (8), and its multiple output ends are respectively fixedly connected to the vibrating head (203), and the multiple vibrating heads (203) are simultaneously attached to the inner wall of the inner guide tube (202).

7. The forming process of a steel-lined PTFE concentric reducer according to claim 5, characterized in that, The inner layer (3) includes: The heat-resistant rubber layer (301) is fixedly connected at its bottom end to the inner wall of the top end of the base (6), and its top end is fixedly connected to multiple connecting hollow frames (4); Multiple elastic metal sheets (302) are fixedly and equidistantly around the inner wall of the heat-resistant rubber layer (301).

8. The forming process of a steel-lined PTFE concentric reducer according to claim 6, characterized in that, The internal support mechanism (9) includes: The top plate (901) covers the top outer wall of the steel pipe, and its bottom end is fixedly connected with multiple inserts (903) and sealing blocks (902). The multiple inserts (903) and sealing blocks (902) are arranged in an alternating manner, and the multiple inserts (903) are movably inserted into multiple connecting hollow frames (4); Multiple connection holes (908) are provided through the top inner wall of the top plate (901).

9. The forming process of a steel-lined PTFE concentric reducer according to claim 8, characterized in that, The internal support mechanism (9) also includes: Multiple uprights (904) are equidistantly and fixedly connected to the outer circumference of the top plate (901); Multiple latches (905) are fixedly installed at the bottom of multiple uprights (904) and simultaneously connected to the corresponding connecting latches (7).

10. The forming process of a steel-lined PTFE concentric reducer according to claim 9, characterized in that, The internal support mechanism (9) also includes: The inner strut (906) is fixedly connected to the bottom outer wall of the top plate (901), and the inner strut (906) is inserted into the inner layer (3), and its outer diameter is larger than the outer diameter of the inner vibration guide tube (202); A chamfer (907) is provided at the bottom end of the inner strut (906).

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