Welding repair method for high-strength stainless steel casting with narrow runner structure

Abstract

The invention discloses a welding repair method for a high-strength stainless steel narrow runner structure casting. The welding repair method comprises the steps that breakout foreign matter between blades in an inner cavity of a runner of the casting is removed, and the breakout foreign matter is eliminated; cleaning the surface of the casting; measuring the size of a to-be-repaired area of a second blade of the inner cavity of the casting runner, determining the shape and size of a welding gasket for welding repair, and manufacturing to obtain a copper gasket and a ceramic fiber blanket gasket; a ceramic fiber blanket liner is tightly attached to the outer side of a molded surface of a to-be-repaired area of a first blade of the inner cavity of the casting runner, then a copper liner is tightly attached to the outer side of the ceramic fiber blanket liner, and a to-be-repaired area of a second blade of the inner cavity of the casting runner is subjected to welding repair; the welding repair area is polished and smoothed, and it is guaranteed that the welding repair area is flat and smooth and is in smooth transition with the surrounding casting face; and the casting is subjected to destressing heat treatment.

Description

Technical Field

[0001] The invention relates to a welding repair method for a high-strength stainless steel narrow flow channel structure casting, belonging to the technical field of welding repair. Background Art

[0002] With the continuous development of modern manufacturing, green remanufacturing technology has developed rapidly. Among them, welding repair methods are widely used in industrial fields such as aerospace, petrochemicals, equipment machinery, etc. Among them, tungsten inert gas welding is an arc connection method that generates heat between non-consumable electrodes and workpieces under the protection of inert gas. It uses tungsten rods as electrodes and argon gas for protection. During welding, argon gas is continuously ejected from the nozzle of the welding gun to form a protective layer around the arc to isolate the air to prevent oxidation of the tungsten electrode, molten pool and adjacent heat-affected zone, thereby obtaining high-quality welds. Because tungsten inert gas welding has the advantages of easy to obtain high-quality welds, stable welding process, excellent protection performance, and a wide range of applications, it is the most widely used in actual production.

[0003] Pump guide housing castings are important flow-passing components widely used in the fields of petrochemicals, aerospace, equipment and machinery, etc. They are usually composed of complex curved shells, complex inner cavity flow channels and other structures, and the inner cavity of the flow channel usually contains several three-dimensional twisted blades evenly distributed along the circumferential direction. With the gradual improvement of the requirements for pump efficiency, head, flow rate and other indicators in the industrial field, the inner cavity of the flow channel of the pump guide housing casting designed by the designer is often narrow, and the blades are highly twisted and the cross-sectional space dimensions at both ends of the flow channel are small. Pump guide housing castings are often produced by investment casting technology. The production process mainly includes wax mold preparation, wax mold assembly, shell preparation, shell roasting, smelting and pouring, and casting post-processing. Among them, the shell preparation process is a cyclic repetition of slurry dipping, slurry control, sanding, drying and other processes. In the actual production process, the width of the inner cavity flow channel outlet is less than 10mm, and the space structure limitation makes the shell making process technically difficult, making the coating and sanding processes very difficult, resulting in uneven slurry and sanding processes in the module shell making process, and it is not easy to apply paint on the inside, which makes the shell strength insufficient after the subsequent dewaxing process, and easily leads to steel leakage (sparking) between the first blade of the flow channel cavity and the adjacent second blade. In the actual production process, when the above-mentioned casting defects are welded and repaired, in order to avoid the collapse of the molten pool in the welding repair area, a single copper pad is generally used as a welding pad for operation. However, if a single copper pad is used as a welding pad for repair, when the welding wire melts and adheres to the surface of the copper pad in sequence according to the arc movement route, the shrinkage of the molten pool will cause the copper pad to be clamped and unable to be removed, and ultimately the welding repair process cannot achieve the expected effect. Therefore, a welding repair method for the inner cavity structure of the flow casting of the guide shell is urgently needed to solve this production process problem to meet the needs of current production tasks. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to propose a welding repair method for a high-strength stainless steel narrow flow channel structure casting, and to solve the problem that when a single copper pad is used as a welding pad for welding repair operations, the copper pad is clamped and cannot be removed due to the shrinkage of the weld molten pool.

[0005] The technical solution of the present invention is: a welding repair method for a high-strength stainless steel narrow flow channel structure casting, comprising:

[0006] Remove the leaking foreign matter between the first blade and the second blade in the inner cavity of the casting flow channel and eliminate the leaking foreign matter; then clean the surface of the casting to ensure that the dirt on the surface of the casting is cleaned;

[0007] The dimensions of the second blade to be repaired area of ​​the casting flow channel inner cavity are measured, and the shape and size of the welding pad used for welding repair are determined according to the measurement data, and a copper pad and a ceramic fiber blanket pad are manufactured;

[0008] The ceramic fiber blanket liner is tightly fitted to the outer surface of the first blade to be repaired area of ​​the casting flow channel inner cavity, and then the copper liner is tightly fitted to the outer side of the ceramic fiber blanket liner, and then the tungsten inert gas arc welding method is used to weld and repair the second blade to be repaired area of ​​the casting flow channel inner cavity;

[0009] After the welding repair process is completed, the welding repair area is polished and smoothed to ensure that the welding repair area is flat and smooth and has a smooth transition with the surrounding casting surface;

[0010] The castings are subjected to stress relief heat treatment.

[0011] The copper liner is made of pure copper and has a thermal conductivity of 401 W·m-1·K-1.

[0012] The ratio of the copper liner thickness to the ceramic fiber blanket liner thickness is 3:1.

[0013] The ceramic fiber blanket liner has a refractory temperature of 950-1400°C.

[0014] When welding by tungsten inert gas arc welding, the welding wire material matches the chemical composition of the casting material. The welding wire grade is S-659 and the welding wire diameter is

[0015] The welding current is determined to be 110-130A according to the wire diameter.

[0016] According to the relationship between the welding gun porcelain nozzle diameter and the argon gas flow rate Q=(0.8-1.2)D, the required argon gas flow rate Q is determined, where D is the porcelain nozzle diameter.

[0017] The stress relief heat treatment includes solution cold treatment and aging treatment.

[0018] The solution cold treatment is as follows: in a vacuum environment with a pressure not exceeding 1.33 Pa, the temperature is kept at 1080±10°C for 120-125 minutes, the cooling method is air cooling, and the cooling medium is argon or high-purity nitrogen; cold treatment is performed within 4 hours after solution, and the cold treatment system is to keep the temperature at -70°C to -80°C for 120 to 130 minutes; and finally air cooling to room temperature.

[0019] The aging treatment comprises: keeping the temperature at 300±20° C. for 180 to 200 minutes, and finally cooling the mixture to room temperature in air.

[0020] The beneficial effects of the present invention compared with the prior art are:

[0021] (1) The present invention provides a welding repair method for a high-strength stainless steel narrow channel structure casting. By making a composite liner, a one-time overall repair can be achieved, which significantly improves the repair efficiency. In addition, the inner shape and contour size of the channel after repair can be guaranteed, providing a solution and idea for welding repair operations in narrow space areas of castings.

[0022] (2) The present invention provides a welding repair method for a high-strength stainless steel narrow flow channel structure casting. The composite gasket used in the method can support the molten pool. The copper trioxide oxide protective film generated on the surface of the copper gasket forms a physical isolation layer between the molten pool and the surface of the casting, thereby preventing the casting surface from fusing with the molten pool, and can significantly improve the repair quality of the welding repair area.

[0023] (3) The present invention provides a welding repair method for high-strength stainless steel narrow flow channel structure castings. In order to solve the bottleneck problem that the copper liner is clamped and cannot be removed due to the shrinkage of the weld pool after welding repair using traditional copper liner in the flow channel of the casting, an innovative method of using a composite liner is proposed, which uses the characteristics of high temperature resistance and fragility of ceramic fiber blanket liner to fit it tightly with the copper liner. During the welding repair operation, the quality of the weld is guaranteed, and the copper liner is extremely easy to remove after the welding repair is completed. The operation is convenient and there is no residue or excess. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the casting structure implemented by the present invention;

[0025] Figure 2 A schematic cross-sectional view of a blade portion of a casting implemented in the present invention;

[0026] Figure 3 A schematic diagram of the location of steel leakage foreign matter in a casting implemented by the present invention;

[0027] Figure 4 It is a schematic diagram of the blade structure after eliminating the steel foreign matter implemented in the present invention;

[0028] Figure 5 It is a schematic diagram of the spatial placement position of the ceramic fiber blanket liner, the spatial placement position of the copper liner, and the spatial position of the arc starting of the welding wire during the repair process implemented by the present invention;

[0029] Figure 6 A schematic diagram of the welding repair operation process implemented by the present invention; DETAILED DESCRIPTION

[0030] The three-dimensional model structure of a complex inner cavity structure guide shell casting is as follows Figure 1 As shown, it consists of a connecting flange, a second connecting flange, a connecting rib plate, a volute, a flow channel cavity, etc. The schematic diagram of the cross-section of the blade in the flow channel cavity is shown in Figure 2 As shown, they are the first blade, the second blade, the third blade, the fourth blade, the fifth blade, the sixth blade, the seventh blade, the eighth blade, the ninth blade, and the tenth blade, all of which are three-dimensional twisted blades with variable thickness and irregular shapes, and the blade thickness is about 3mm-10mm. The casting material is S-08 high-strength stainless steel, produced by investment casting process. Due to the very narrow space structure of the runner part, the shell strength is not enough after roasting, so that the molten metal liquid washes the shell during the pouring process, resulting in steel leakage. The schematic diagram of the location of the steel leakage foreign body is shown in Figure 3 As shown in the figure, the leaking foreign body exists in the gap between the first blade and the adjacent second blade in the inner cavity of the casting flow channel. Therefore, it is necessary to take measures to remove the leaking foreign body in the casting flow channel. However, due to the very narrow space structure, it is impossible to use existing tools to directly remove it. The only way is to first remove the second blade part structure that hinders the removal of the leaking foreign body, and then remove the leaking foreign body. The schematic diagram of the cross-section of the flow channel cavity after the second blade part structure and the leaking foreign body are removed is shown in Figure 4 Finally, the second blade was repaired by welding using tungsten inert gas welding.

[0031] like Figure 6 As shown, the method of the present invention is as follows:

[0032] First, the size of the area to be repaired of the second blade is measured, and a welding pad of a certain shape and size for welding repair is determined based on the measurement data. Welding pads are commonly used auxiliary devices for single-sided welding and double-sided forming. Their functions include supporting the molten pool and preventing the molten liquid metal from falling. They include ceramic pads, graphite pads, copper pads, ceramic fiber blanket pads, etc. If a graphite pad is used for welding pads, it is easy to break, and carbon combustion during welding will generate toxic carbon monoxide gas, which is not conducive to the quality of the weld and is also harmful to the health of the welder. If a ceramic pad is used, it cannot achieve surface fit with the area to be repaired. In actual production, a single copper pad is often used as a welding pad for operation. However, for the casting of the guide shell with a complex inner cavity structure, if a single copper pad is used for welding repair, when the welding wire melts and adheres to the surface of the copper pad in sequence according to the arc movement route, the shrinkage of the molten pool will cause the copper pad to be clamped and unable to be removed, which ultimately causes the welding repair process to fail to achieve the expected effect. Therefore, the welding pads are copper pads and ceramic fiber blanket pads (glass fiber pads). The thermal conductivity of the copper pad is 401 (W·m -1 ·K -1 ), Ceramic fiber blanket pads are widely used in aviation, aerospace, petrochemical and other fields. They have excellent chemical stability, excellent tensile strength, low thermal conductivity, and low heat capacity. They are excellent materials for thermal insulation refractory materials. It integrates fire resistance, heat resistance, and thermal insulation. It can maintain good tensile strength, toughness, and fiber structure when used for a long time in a neutral and oxidizing atmosphere. The refractory temperature is 950-1400℃. By combining copper pads with ceramic fiber blanket pads, the high temperature resistance and compressibility of ceramic fiber blanket pads can be fully utilized. At the same time, the copper pads have the characteristics of fast thermal conductivity and ability to withstand a certain pressure, which can ensure that the copper pads and ceramic fiber blanket pads are smoothly removed when the welding repair is completed. The final space dimensions of the copper pads and ceramic fiber blanket pads are 65mmX4mmX6mm and 65mmX3mmX2mm, respectively.

[0033] like Figure 5 As shown, first place the ceramic fiber blanket liner so that it fits tightly against the outer side of the first blade profile, then place the copper liner so that it fits tightly against the outer side of the ceramic fiber blanket liner. Then, use tungsten inert gas arc welding to weld and repair the second blade in the inner cavity of the casting flow channel. The arc starting position of the welding wire is shown in FIG. Figure 5 The diameter of the welding wire used is determined according to the welding repair area. The welding current is determined to be 110-130A according to the diameter of the welding wire. The argon flow rate is determined according to the relationship between the porcelain nozzle diameter and the argon flow rate Q = (0.8-1.2) D, where D is the porcelain nozzle diameter. Finally, the argon gas flow rate Q was calculated and determined to be approximately 15L / min.

[0034] When visual observation shows that the copper pad turns dark red, that is, the temperature of the copper pad is high, the welding repair operation needs to be stopped, and the welding repair operation can be continued after the copper pad cools down. After the welding repair operation is completed, use the elasticity of the ceramic fiber blanket pad to shake the ceramic fiber blanket pad back and forth several times with both hands, and then gently press the copper pad. The ceramic fiber blanket pad will produce a certain amount of deformation under the action of the compression force. There will be a certain gap between the copper pad and the second blade that has been repaired by welding, so that the copper pad can be smoothly removed at one time, and finally the ceramic fiber blanket pad can be removed.

[0035] After the welding repair process is completed, the welding repair area is polished and smoothed to ensure that the repair area is flat and smooth and has a smooth transition with the surrounding casting surface.

[0036] The casting is subjected to stress relief heat treatment. The stress relief heat treatment adopts the solid solution cold treatment aging method, in which the solid solution treatment system is to keep the temperature at 1080±10℃ for 120-125min in a vacuum environment with a pressure not exceeding 1.33Pa, and the cooling method adopts aeration cooling, and the cooling medium is argon or high-purity nitrogen. Cold treatment is carried out within 4 hours after solid solution, and the cold treatment system is to keep the temperature at -70℃~-80℃ for 120~130min, and then air cool to room temperature. Then aging treatment is carried out, and the aging treatment system is to keep the temperature at 300±20℃ for 180~200min, and finally air cool to room temperature.

[0037] The examples described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A welding repair method for a high-strength stainless steel narrow flow channel structure casting, characterized in that: include: Remove the leaking foreign matter between the first blade and the second blade in the inner cavity of the casting flow channel and eliminate the leaking foreign matter; then clean the surface of the casting to ensure that the dirt on the surface of the casting is cleaned; The dimensions of the second blade to be repaired area of ​​the casting flow channel inner cavity are measured, and the shape and size of the welding pad used for welding repair are determined according to the measurement data, and a copper pad and a ceramic fiber blanket pad are manufactured; The ceramic fiber blanket liner is tightly fitted to the outer surface of the first blade to be repaired area of ​​the casting flow channel inner cavity, and then the copper liner is tightly fitted to the outer side of the ceramic fiber blanket liner, and then the tungsten inert gas arc welding method is used to weld and repair the second blade to be repaired area of ​​the casting flow channel inner cavity; After the welding repair process is completed, the welding repair area is polished and smoothed to ensure that the welding repair area is flat and smooth and has a smooth transition with the surrounding casting surface; The castings are subjected to stress relief heat treatment.

2. A welding repair method for a high-strength stainless steel narrow flow channel structure casting according to claim 1, characterized in that: The copper liner is made of pure copper and has a thermal conductivity of 401 W·m-1·K-1.

3. The welding repair method for a high-strength stainless steel narrow flow channel structure casting according to claim 1 is characterized in that: The ratio of the copper liner thickness to the ceramic fiber blanket liner thickness is 3:

1.

4. The welding repair method for a high-strength stainless steel narrow flow channel structure casting according to claim 1 is characterized in that: The ceramic fiber blanket liner has a refractory temperature of 950-1400°C.

5. The welding repair method for a high-strength stainless steel narrow flow channel structure casting according to claim 1 is characterized in that: When welding by tungsten inert gas arc welding, the welding wire material matches the chemical composition of the casting material. The welding wire grade is S-659 and the welding wire diameter is 6. A welding repair method for a high-strength stainless steel narrow flow channel structure casting according to claim 5, characterized in that: The welding current is determined to be 110-130A according to the wire diameter.

7. The welding repair method for a high-strength stainless steel narrow flow channel structure casting according to claim 1, characterized in that: According to the relationship between the welding gun porcelain nozzle diameter and the argon gas flow rate Q=(0.8-1.2)D, the required argon gas flow rate Q is determined, where D is the porcelain nozzle diameter.

8. A welding repair method for a high-strength stainless steel narrow flow channel structure casting according to claim 1, characterized in that: The stress relief heat treatment includes solution cold treatment and aging treatment.

9. A welding repair method for a high-strength stainless steel narrow flow channel structure casting according to claim 8, characterized in that: The solution cold treatment is as follows: in a vacuum environment with a pressure not exceeding 1.33 Pa, the temperature is kept at 1080±10°C for 120-125 minutes, the cooling method adopts aeration cooling, and the cooling medium is argon or high-purity nitrogen; cold treatment is performed within 4 hours after solution, and the cold treatment system is to keep the temperature at -70°C to -80°C for 120 to 130 minutes; and finally air-cooling to room temperature.

10. A welding repair method for a high-strength stainless steel narrow flow channel structure casting according to claim 8, characterized in that: The aging treatment comprises: keeping the temperature at 300±20° C. for 180 to 200 minutes, and finally cooling the mixture to room temperature in air.

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