A welding process for lining a liquid outlet with a tetrafluoroethylene sheet

Abstract

This invention relates to the field of PTFE plate lining processing technology, and discloses a welding process for the liquid outlet of a PTFE plate lining, including the following steps: S1, plate lining preparation: (1) Removing impurities: Thoroughly clean the storage tank that needs to be lined, remove impurities and dirt from the inner wall, and ensure that the inner surface is clean and smooth; (2) Spraying primer: The primer is the first step in the PTFE lining process, which can fill the red sesame and irregular surfaces. The welding process for the liquid outlet of the PTFE plate lining adopts a gasket sealing welding method for the welding joint of the liquid outlet of the small and medium diameter PTFE plate lining. The weld joint assembly is simple and easy to perform, and has strong operability. Moreover, the welding is completed in one step by CO2+Ar mixed gas MIG welding or FCAW semi-automatic welding for the root filling. The weld formation is beautiful, and the back of the weld is not prone to defects such as burn-through, collapse, and oxidation. The welding efficiency is high and the weld quality is stable and reliable. Practice has proven that it can significantly reduce welding costs and improve welding efficiency.

Description

Technical Field

[0001] This invention relates to the field of PTFE sheet lining processing technology, specifically a welding process for the liquid outlet of a PTFE sheet lining. Background Technology

[0002] PTFE-lined pipes use ordinary carbon steel pipes as the base material and are lined with thermoplastic pipes with excellent chemical stability. They are formed by cold drawing or rotational molding. PTFE-lined pipes have both the mechanical properties of steel pipes and the corrosion resistance, scale inhibition, and microbial growth resistance of plastic pipes.

[0003] Currently, with the advancement of PTFE lining technology and the widespread use of new materials, this material is increasingly widely used in liquid transportation. Therefore, it can be used as a liquid outlet. However, due to the limitation of pipe diameter, welding cannot be performed from the inside, which easily leads to incomplete welding of the pipe composite layer, thus preventing the composite layer from performing its function and reducing the mechanical properties of the joint. In addition, the incomplete welding of the internal composite layer creates new corrosion points, which greatly reduces the service life of the pipe and becomes a bottleneck restricting the widespread use of stainless steel composite pipes.

[0004] Therefore, it is necessary to propose a new welding process for small-diameter PTFE linings to improve pipe processing efficiency. Thus, a welding process for the liquid outlet of PTFE linings is proposed to solve the above problems. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a welding process for a PTFE-lined liquid outlet, which has advantages such as improved welding efficiency and solves the problem of poor welding efficiency.

[0007] (II) Technical Solution

[0008] To achieve the aforementioned goal of improving welding efficiency, the present invention provides the following technical solution: a welding process for a PTFE-lined liquid outlet, comprising the following steps:

[0009] S1. Lining preparation: (1) Remove impurities: Thoroughly clean the storage tank that needs to be lined, remove impurities and dirt from the inner wall, and ensure that the inner surface is clean and smooth.

[0010] (2) Applying primer: The primer is the first step in the PTFE lining process. It can fill the red sesame and irregular surfaces, provide good adhesion and protection so that the final PTFE coating adheres well.

[0011] (3) Spraying PTFE: This is the last step of the process and must be carried out under dry and ventilated conditions. The quality of the coating is related to factors such as the cleanliness of the storage tank, the quality of the primer, and the adhesion of the coating.

[0012] (4) Drying: After the PTFE coating is applied, it needs to be dried. Hot air drying is usually used to ensure that the coating is completely dry and to form the PTFE plate lining liquid outlet.

[0013] S2. Pipe segment cutting: Pipe segments are cut using a plasma cutting machine;

[0014] S3. Pipe end preparation: Use an angle grinder to grind the bevel, with a V-shaped bevel of 30° on one side and a 1mm blunt edge reserved until the metal luster is exposed. To ensure the flatness of the cut, a pipe end milling machine should be used if conditions permit.

[0015] S4. Gasket fabrication: The bottom gasket material is made of the same material as the cladding material. The perimeter is ground into a rounded bevel or a 30° chamfer. In order to facilitate the effective formation of the weld pool of the stainless steel cladding on the inner wall, a small arc-shaped groove is milled downward at the corresponding position in the middle 1 / 2 of the outer ring of the bottom gasket.

[0016] S5. Assembly: Assembly welding is carried out using three specifications of pipes: Φ325×5(4+1), Φ426×5(4+1), and Φ529×6(4.5+1.5) as welding representatives.

[0017] S6. Assembly: Align the inner opening of the pipe with the inner opening, make it straight and round, and weld 2 to 4 hot-rolled equal angle steels at both ends of the pipe opening. Depending on the site conditions, hot-rolled round steel, square steel or flat steel or other miscellaneous materials can also be used instead. The tack welding method adopts the same process parameters as the formal welding.

[0018] S7. Root pass welding: CO2+Ar mixed gas MIG automatic welding is used for root pass filling. Different current adjustment values ​​are set according to the different flat, vertical and overhead welding. The welding method is DC reverse polarity method, that is: the pipe is connected to the negative pole and the welding gun is connected to the positive pole. The short-circuit transition welding arc process with less spatter is used. There is almost no oxidation and burn-off during the welding process.

[0019] S8. Filler welding: CO2+Ar mixed gas shielding or FCAW welding is used. Compared with traditional shielded metal arc welding, FCAW welding has a larger weld formation coefficient, lower spatter rate, and smoother weld. It can be completed together with the root pass welding, which can significantly improve the first pass rate of the weld and ensure the pass rate of non-destructive testing. The electrode baking temperature is 250℃ and the holding time is 2h.

[0020] S9. Cover weld: Use manual arc welding or FCAW welding for the cover weld. The weld reinforcement should be 2-3mm. The weld should have a smooth transition with the base material and a beautiful shape.

[0021] Preferably, in step S4, the height of the liner groove does not exceed 1 / 3 of the liner thickness, and in step S5, the liner is inserted into the inner wall of the composite pipe and spot-welded before the pipe assembly is assembled, ensuring that the spot-welding position is consistent with the direction of the medium being transported inside the pipe.

[0022] Preferably, in step S5, the pipe assembly requires a flatness of ≤2mm, a weld gap of approximately 3-4mm, a misalignment of less than 2mm, and a pipe straightness of ≤5°.

[0023] Preferably, in step S7, the welding current is 110-130A, the welding voltage is 19-21V, the shielding gas flow rate is 15L / min, and the welding speed is 14-21cm / min.

[0024] (III) Beneficial Effects

[0025] Compared with the prior art, the present invention provides a welding process for a PTFE-lined liquid outlet, which has the following advantages:

[0026] The welding process for the PTFE-lined liquid outlet utilizes a gasket-sealed welding method for the weld joints of small and medium-diameter PTFE-lined liquid outlets. This method is simple, easy to perform, and highly operable. Furthermore, the welding process employs CO2+Ar mixed gas MIG welding or FCAW semi-automatic welding to complete the root pass and filler in one step, resulting in aesthetically pleasing weld formation. Defects such as burn-through, collapse, and oxidation are less likely to occur on the back of the weld. The welding efficiency is high, and the weld quality is stable and reliable. Practical experience has shown that this process can significantly reduce welding costs and improve welding efficiency. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] To improve the welding efficiency of PTFE lining, a welding process for the liquid outlet of the PTFE lining is proposed, including the following steps:

[0029] S1. Lining preparation: (1) Remove impurities: Thoroughly clean the storage tank that needs to be lined, remove impurities and dirt from the inner wall, and ensure that the inner surface is clean and smooth.

[0030] (2) Applying primer: The primer is the first step in the PTFE lining process. It can fill the red sesame and irregular surfaces, provide good adhesion and protection so that the final PTFE coating adheres well.

[0031] (3) Spraying PTFE: This is the last step of the process and must be carried out under dry and ventilated conditions. The quality of the coating is related to factors such as the cleanliness of the storage tank, the quality of the primer, and the adhesion of the coating.

[0032] (4) Drying: After the PTFE coating is applied, it needs to be dried. Hot air drying is usually used to ensure that the coating is completely dry and to form the PTFE plate lining liquid outlet.

[0033] S2. Pipe segment cutting: Pipe segments are cut using a plasma cutting machine;

[0034] S3. Pipe end preparation: Use an angle grinder to grind the bevel, with a V-shaped bevel of 30° on one side and a 1mm blunt edge reserved until the metal luster is exposed. To ensure the flatness of the cut, a pipe end milling machine should be used if conditions permit.

[0035] S4. Gasket fabrication: The bottom gasket material is made of the same material as the cladding material. The perimeter is ground into a rounded bevel or a 30° chamfer. In order to facilitate the effective formation of the weld pool of the stainless steel cladding on the inner wall, a small arc groove is milled downward at the corresponding position in the middle 1 / 2 of the outer ring of the bottom gasket. The height of the gasket groove does not exceed 1 / 3 of the gasket thickness.

[0036] S5. Assembly: Pipes of three specifications, Φ325×5(4+1), Φ426×5(4+1), and Φ529×6(4.5+1.5), are used as welding representatives for assembly welding. Before the pipes are assembled, the gasket is inserted into the inner wall of the composite pipe for spot welding, and the spot welding position is consistent with the direction of the medium being transported in the pipe. The pipe assembly requires a flatness of ≤2mm, a weld gap of about 3-4mm, a misalignment of less than 2mm, and a pipe straightness of ≤5°.

[0037] S6. Assembly: Align the inner opening of the pipe with the inner opening, make it straight and round, and weld 2 to 4 hot-rolled equal angle steels at both ends of the pipe opening. Depending on the site conditions, hot-rolled round steel, square steel or flat steel or other miscellaneous materials can also be used instead. The tack welding method adopts the same process parameters as the formal welding.

[0038] S7. Root pass welding: CO2+Ar mixed gas MIG automatic welding is used for root pass filling. Different current adjustment values ​​are set according to the different flat, vertical and overhead welding. The welding method is DC reverse polarity, that is: the pipe is connected to the negative pole and the welding gun is connected to the positive pole. The short-circuit transition welding arc process with less spatter is adopted. There is almost no oxidation loss during the welding process. The welding current is 110~130A, the welding voltage is 19~21V, the shielding gas flow rate is 15L / min, and the welding speed is 14~21cm / min.

[0039] S8. Filler welding: CO2+Ar mixed gas shielding or FCAW welding is used. Compared with traditional shielded metal arc welding, FCAW welding has a larger weld formation coefficient, lower spatter rate, and smoother weld. It can be completed together with the root pass welding, which can significantly improve the first pass rate of the weld and ensure the pass rate of non-destructive testing. The electrode baking temperature is 250℃ and the holding time is 2h.

[0040] S9. Cover weld: Use manual arc welding or FCAW welding for the cover weld. The weld reinforcement should be 2-3mm. The weld should have a smooth transition with the base material and a beautiful shape.

[0041] The beneficial effects of this invention are as follows: By using a gasket-sealed welding method for the weld joint of the liquid outlet of the PTFE plate with small and medium diameter, the weld joint assembly is simple and easy to perform, and highly operable; moreover, the welding is completed in one step by CO2+Ar mixed gas MIG welding or FCAW semi-automatic welding for root filling, resulting in a beautiful weld formation, and the back of the weld is less prone to defects such as burn-through, collapse, and oxidation. The welding efficiency is high, and the weld quality is stable and reliable. Practice has proven that it can significantly reduce welding costs and improve welding efficiency.

[0042] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A welding process for a PTFE-lined liquid outlet, characterized in that, Includes the following steps: S1. Lining preparation: (1) Remove impurities: Thoroughly clean the tank that needs to be lined, remove impurities and dirt from the inner wall, and ensure that the inner surface is clean and smooth. (2) Spraying primer: The primer is the first step in the PTFE lining process. It can fill the red sesame and irregular surfaces, provide good adhesion and protection so that the final PTFE coating adheres well. (3) Spraying PTFE: This is the last step of the process and must be carried out under dry and ventilated conditions. The quality of the coating is related to the cleanliness of the storage tank, the quality of the primer, and the adhesion of the coating. (4) Drying: After the PTFE coating is applied, it needs to be dried. Hot air drying is usually used to ensure that the coating is completely dry and forms the liquid outlet of the PTFE plate lining. S2. Pipe segment cutting: Pipe segments are cut using a plasma cutting machine; S3. Pipe end preparation: Use an angle grinder to grind the bevel, with a V-shaped bevel of 30° on one side and a 1mm blunt edge reserved until the metal luster is exposed. To ensure the flatness of the cut, a pipe end milling machine should be used if conditions permit. S4. Gasket fabrication: The bottom gasket material is made of the same material as the cladding material. The perimeter is ground into a rounded bevel or a 30° chamfer. In order to facilitate the effective formation of the weld pool of the stainless steel cladding on the inner wall, a small arc-shaped groove is milled downward at the corresponding position in the middle 1 / 2 of the outer ring of the bottom gasket. S5. Assembly: Assembly welding is carried out using three specifications of pipes: Φ325×5(4+1), Φ426×5(4+1), and Φ529×6(4.5+1.5) as welding representatives. S6. Assembly: Align the inner opening of the pipe with the inner opening, align it with the circle, and weld 2 to 4 hot-rolled equal angle steels at both ends of the pipe opening. Depending on the site conditions, hot-rolled round steel, square steel or flat steel can also be used as substitutes. The tack welding method adopts the same process parameters as the formal welding. S7. Root pass welding: CO2+Ar mixed gas MIG automatic welding is used for root pass filling. Different current adjustment values ​​are set according to the different flat, vertical and overhead welding. The welding method is DC reverse polarity method, that is: the pipe is connected to the negative pole and the welding gun is connected to the positive pole. The short-circuit transition welding arc process with less spatter is used. There is almost no oxidation and burn-off during the welding process. S8. Filler welding: CO2+Ar mixed gas shielding or FCAW welding is used. Compared with traditional shielded metal arc welding, FCAW welding has a larger weld formation coefficient, lower spatter rate, and smoother weld. It can be completed together with the root pass welding, which can significantly improve the first pass rate of the weld and ensure the pass rate of non-destructive testing. The electrode baking temperature is 250℃ and the holding time is 2h. S9. Cover weld: Use manual arc welding or FCAW welding for the cover weld. The weld reinforcement should be 2-3mm. The weld should have a smooth transition with the base material and a beautiful shape.

2. The welding process for a PTFE-lined liquid outlet according to claim 1, characterized in that, In step S4, the height of the liner groove does not exceed 1 / 3 of the liner thickness. In step S4, the liner is inserted into the inner wall of the composite pipe and spot-welded, ensuring that the spot-welding position is consistent with the direction of the medium being transported inside the pipe.

3. The welding process for a PTFE-lined liquid outlet according to claim 1, characterized in that, In step S5, the pipe assembly requires a flatness of ≤2mm, a weld gap of 3~4mm, a misalignment of less than 2mm, and a pipe straightness of ≤5°.

4. The welding process for a PTFE-lined liquid outlet according to claim 1, characterized in that, In step S7, the welding current is 110~130A, the welding voltage is 19~21V, the shielding gas flow rate is 15L / min, and the welding speed is 14~21cm / min.