Modular laser additive repair method for shell-type casting defects

Abstract

The present application relates to the technical field of additive manufacturing, and discloses a modular laser additive repair method for defects of a shell type martensitic stainless steel casting, comprising the following steps: performing nondestructive testing on the casting, designing a modular repair process according to the detected defects, determining the standardized repair size, parameters, strategy and repair sequence of the defects, removing the material within the repairable size by using a machining center, drawing a three-dimensional model of each repair area by using modeling software, and checking the correctness of the scanning path and strategy. According to the process scheme, the repairable areas of the casting are repaired on a metal component repair device. Finally, the inner and outer surfaces of the repair area are finely polished or machined according to the required size and surface quality of the component. The present application provides a rapid defect repair method suitable for batch production, standardization and low cost and high reliability for high-value-added shell type castings with frequent defects by means of laser melting deposition repair technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of additive manufacturing, and in particular to a modular laser additive repair method for defects of a shell type casting. BACKGROUND

[0002] Metal shell is one of the important components on liquid rocket engine. For metal shell with complex contoured surface structure, precision casting method is often used for manufacturing. Due to the influence of alloy smelting process, material wide crystallization characteristics, and large shell structure complexity, the internal quality of the product is often difficult to control, and casting defects such as shrinkage, shrinkage hole, and porosity often occur in shell type castings, and the defect area and quantity are large. In order to meet the delivery schedule and the demand for high quality and reliability of aerospace products, efficient and high quality repair of defects in non-critical parts of the shell casting is one of the important methods to ensure the quality of the product. The common methods for defect repair are manual repair welding and single-point laser melting deposition repair.

[0003] The traditional manual repair welding operation is greatly affected by human factors and has low repair efficiency, which leads to low quality consistency and reliability of the repaired products, and it is difficult to meet the stable and reliable delivery demand of batch product repair.

[0004] Single-point laser melting deposition repair is an advanced laser processing technology that uses a high-energy concentrated laser beam to melt metal powder material, thereby repairing the damaged parts of the component. It is considered to be an efficient repair method to replace traditional manual repair welding. The main repair process is as follows: non-destructive testing and marking of defects-manual polishing to remove defects-mechanical processing of bevel-three-dimensional scanning reverse modeling-single area laser additive repair-manual polishing of the repaired area. However, the traditional single-point laser melting deposition repair method for defect repair of metal shell castings mainly has the following problems:

[0005] (1) Low repair process efficiency. In order to ensure as little repair filling as possible, manual contour polishing is used to remove the defect site, which takes a long time. The shape of each position defect is irregular, so three-dimensional scanning reverse modeling and repair scheme design are required for each position. Repair operation can only be carried out in single area. Due to the above reasons, the automation degree in the process is low, which consumes time and labor, and is not conducive to standardized operation management in batch repair.

[0006] (2) Poor adaptability. The defects of complex castings in liquid rocket engines often occur in contoured surface parts and are mostly penetrating. The existing laser melting deposition repair method is mainly used for size restoration repair of planar components or rotary components, or non-penetrating defect repair of planar or rotary parts in shell components, which is difficult to meet the demand of all defect types repair of the engine. SUMMARY

[0007] The application overcomes the shortcomings of the prior art, adopts a laser melting deposition repair technology, and proposes a modular laser additive repair method for defects of a complex casting shell in a liquid rocket engine, which are mostly located in a special-shaped curved surface part and are mostly in a penetrating form, thereby providing a low-cost, high-reliability, and rapid defect repair method suitable for batch and standardized industrial production for complex metal shell castings with frequent defects. The specific process is as follows: nondestructive testing and defect marking-modular process design-repair area machining-establishment of a three-dimensional repair model-modular laser additive repair-repair area post-processing.

[0008] In a first aspect, a modular laser additive repair method for defects of a shell casting is provided, including the following steps:

[0009] Nondestructive testing is performed on the internal quality of the metal shell casting, and defects are marked;

[0010] The standardized repair zone size of each defect is determined according to the nondestructive testing result;

[0011] The material in the standardized repair size is removed by using a machining center to obtain a repair area;

[0012] The repair area is repaired on a metal member repair device, and the repaired area is subjected to surface treatment.

[0013] In combination with the first aspect, in some implementations of the first aspect, the method further includes:

[0014] A three-dimensional model of each repair area in each module is drawn by using modeling software according to the size and position of the standardized repair area;

[0015] The three-dimensional model is processed according to the process scheme, and the correctness of the scanning path and scanning strategy is checked through process simulation and on-machine trajectory checking.

[0016] In combination with the first aspect, in some implementations of the first aspect, the nondestructive testing adopts an X-ray perspective method, and different perspective voltages are selected to detect the internal quality of the metal casting,

[0017] When the wall thickness is 5-10 mm, a tube voltage of 110-130±5 kV is used; when the wall thickness is 10-20 mm, a tube voltage of 130-180±5 kV is used; when the wall thickness is 20-30 mm, a tube voltage of 180-240 kV is used; and when the wall thickness is more than 30 mm, a tube voltage of 240-300±5 kV is used.

[0018] In combination with the first aspect, in some implementations of the first aspect, the determination of the standardized repair zone size of each defect according to the nondestructive testing result includes:

[0019] The maximum outer circle of the defect size is determined by circumscribing the identified defect range with a circle, and then a standardized repair size of the defect is determined according to a modular process design standard.

[0020] In combination with the first aspect, in some implementations of the first aspect, a diameter of the envelope circle of the defect is d, and the repair region size D satisfies at least one of the following:

[0021] When d < 20 mm, the repair region size D is 20 mm;

[0022] When 20 mm ≤ d < 50 mm, the repair region size D is 50 mm;

[0023] When 50 mm ≤ d < 100 mm, the repair region size D is 100 mm;

[0024] When 100 mm ≤ d < 150 mm, the repair region size D is 150 mm;

[0025] When 150 mm ≤ d, the repair region is first processed according to D150, and the remaining region is re-partitioned and graded according to the foregoing method.

[0026] In combination with the first aspect, in some implementations of the first aspect, the shell is divided into different modules according to the structure of the component and the repair process characteristics, and then the repair parameters of each standardized repair region in each module are determined.

[0027] In combination with the first aspect, in some implementations of the first aspect, the shell casting includes a vortex wall region, a flange outlet section, a vortex and outlet section transition region, a U-shaped groove, and a rib plate root region.

[0028] In combination with the first aspect, in some implementations of the first aspect, the repair parameters satisfy at least one of the following:

[0029] At the vortex wall or a position with a thickness of 5 mm, the laser repair parameters of the penetrating defect are as follows: for a primer layer, a laser power is 1300-1500 W, a scanning speed is 300-350 mm / s, a path interval is 1.0-1.4 mm, a spot scale is 1-3, a slice thickness is 0.3-0.5 mm, and a phase angle is 67°; for a filling layer, a laser power is 1300-1800 W, a scanning speed is 300-500 mm / s, a path interval is 1.0-1.4 mm, a spot scale is 1-3, a slice thickness is 0.3-0.5 mm, and a phase angle is 67°.

[0030] The laser repair parameters of the penetrating defect at the flange outlet section or the position with a thickness of 12 mm are as follows: the primer layer: laser power 2000-2300 W, scanning speed 400-500 mm / s, path interval 1.6-2.0 mm, spot scale 4-6, slice thickness 0.5-0.6 mm, and phase angle 67°; and the filling layer: laser power 2000-2500 W, scanning speed 400-600 mm / s, path interval 1.6-2.0 mm, spot scale 4-6, slice thickness 0.5-0.6 mm, and phase angle 67°.

[0031] The laser repair parameters of the penetrating defect at the transition zone of the vortex and the outlet section are as follows: the primer layer: laser power 1500-2000 W, scanning speed 350-450 mm / s, path interval 1.4-1.6 mm, spot scale 2-5, slice thickness 0.4-0.5 mm, and phase angle 67°; and the filling layer: laser power 1600-2200 W, scanning speed 400-500 mm / s, path interval 1.4-1.6 mm, spot scale 2-5, slice thickness 0.4-0.5 mm, and phase angle 67°.

[0032] The laser repair parameters of the non-penetrating defect at the U-shaped groove and root area or the position with a thickness of 15-23 mm are as follows: the primer layer: laser power 3000-3300 W, scanning speed 800-900 mm / s, path interval 2.0-2.3 mm, spot scale 6-8, slice thickness 0.6-0.9 mm, and phase angle 67°; and the filling layer: laser power 3000-3500 W, scanning speed 800-1000 mm / s, path interval 2.0-2.3 mm, spot scale 6-8, slice thickness 0.6-0.9 mm, and phase angle 67°.

[0033] With reference to the first aspect, in some implementations of the first aspect, the angle between the machining head axis and the normal of the repair site section is 30°-70°.

[0034] With reference to the first aspect, in some implementations of the first aspect, before laser repair, a bevel structure with an angle of 45°-60° is machined around the repair area.

[0035] With reference to the first aspect, in some implementations of the first aspect, a conformal support backing plate and / or a support top rod are arranged on the back side of the penetrating repair area before repair to assist repair forming.

[0036] Compared with the prior art, the scheme provided in the application has at least the following beneficial technical effects:

[0037] (1) Repair efficiency and product quality are more reliable. The modular laser additive repair technology has less manpower and material cost investment than the manual repair welding technology, higher repair efficiency, and the core processing parameters and process control mainly rely on mechanical equipment to ensure that the influence of human factors on the repair quality is excluded, and the product quality reliability is more reliable.

[0038] (2) The operation process is more standard. Compared with the existing single laser melting deposition repair operation process, the modular laser additive repair technology standardizes the defect elimination and determination method of the repair area size, simplifies the establishment process of the three-dimensional repair model, and clearly defines the repair strategy and parameter selection principle of the shell type component. It makes up for the limitation of the existing single melting deposition repair technology which can only face non-penetrating defect repair.

[0039] (3) The application of modular laser additive repair technology in complex metal shell type casting defect elimination verifies the feasibility of the technology in liquid rocket engine shell type component defect repair, and also accumulates a lot of technical experience for the engineering application research of engine plane type, rotary type and shell type component / position integrity repair. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 It is a schematic diagram of the modular partition of the turbine oxygen pump shell whole repair.

[0041] Figure 2 It is the position of the machining head and the repair area of the penetrating defect.

[0042] Figure 3 It is the position of the support pad of the penetrating defect.

[0043] Figure 4 It is the position of the equivalent circle of the defect of the repair area groove structure and the structure schematic diagram.

[0044] Figure 5 It is the schematic diagram of the groove angle of the repair area groove structure.

[0045] Figure 6 It is a schematic diagram of the defect form of the shell type component. DETAILED DESCRIPTION

[0046] The application will be described in further detail below in combination with the drawings and specific embodiments.

[0047] The embodiment of the application provides a modular laser additive repair method for a penetrating defect of a turbine oxygen pump shell. The turbine oxygen pump shell is made of aerospace special martensitic age stainless steel, and the modular repair method is as follows. Figure 1

[0048] ​(1) Use X-rays to perform non-destructive testing on the turbine oxygen pump housing casting to relatively accurately identify the size range and location of all out-of-standard defects on the casting housing.

[0049] In some embodiments, the pump housing is divided into multiple (e.g., 66) sub-sections according to its structural characteristics. X-ray fluoroscopy is used, and an appropriate fluoroscopy voltage is selected based on the housing wall thickness to inspect the internal quality of the metal casting. In one embodiment, the tube voltage is 110-130±5kV for a wall thickness of 5-10mm; 130-180±5kV for a wall thickness of 10-20mm; 180-240kV for a wall thickness of 20-30mm; and 240-300±5kV for a wall thickness greater than 30mm.

[0050] (2) Process design for modular defect repair. Based on X-ray fluoroscopy partitioning, combined with the distribution location of defects in the turbine oxygen pump housing casting and the characteristics of laser additive repair technology, the entire turbine oxygen pump housing can be divided into 8 repair modules according to factors such as process, interference, tooling fixation, and ease of disassembly. The specific partitioning is shown in Table 1 below, and the regional schematic diagram is attached. Figure 1 As shown in the diagram. The U-shaped groove A and the riser are located on opposite sides of the turbine oxygen pump casing vortex channel. The vortex channel walls are divided into three sections according to orientation: the U-shaped groove side vortex channel wall C, the riser side vortex channel wall D, and the central vortex channel wall E. The rib root is divided into two sections according to orientation: the U-shaped groove side rib root F and the riser side rib root G. The transition zone between the vortex channel and the flange outlet section B is H.

[0051] Table 1 Modular Partitioning Table for Turbo-Oxygen Pumps

[0052] Serial number Region code Position 1 A U-channel 2 B Flange exit section 3 C U-channel side vortex wall 4 D Riser side vortex wall 5 E Vortex wall center 6 F U-channel side rib root 7 G Riser side rib root 8 H Vortex and exit section transition zone

[0053] For the identified defect area, use circles to enclose it according to the following principles (e.g. Figure 2 As shown in the figure, the dimensions of the defect repair area are determined, and the diameter of the defect's envelope circle can be assumed to be d. The repair shape is circular, which allows for matching the annular filling path during repair, ensuring a smoother transition between the repair area and the base material to form a strong metallurgical bond. The dimensions can be determined with reference to the following standards:

[0054] 1) When d < 20mm, the size of the repair area is D20 (Note: D20 represents that the size D of the repair area is a circle with a diameter of 20mm, the same below);

[0055] 2) When 20mm ≤ d < 50mm, the size of the repair area is D50;

[0056] 3) When 50mm≤d<100mm, the size of the repair area is D100;

[0057] 4) When 100mm≤d<150, the repair area size is D150;

[0058] 5) When 150mm≤d, the repair area is first processed according to D150, and the remaining area is then re-partitioned and graded according to the foregoing method.

[0059] (3) Repair area processing. The material within the standardized repair size is removed using a machining center. If new defect points are exposed during processing and need to be further enlarged, the processing range is ensured to be large enough to completely exclude the defects, and the repair area is processed into a bevel structure with an angle of 45°-60° (as shown in Figure 6 ) around the repair area to ensure good metallurgical bonding between the repair area and the base material.

[0060] (4) Establishment of a three-dimensional repair model. According to the size and position of the standardized repair area, a three-dimensional model of each repair area in each module is established using modeling software. The establishment of the repair three-dimensional model requires the use of professional modeling software, combined with the three-dimensional model of the component to be repaired, to establish a three-dimensional model of each repair area in each module, ensuring that the three-dimensional models of each repair area in each module have a fixed relative positional relationship and can be sequentially repaired during the repair process.

[0061] (5) Preparation and checking of repair program files. According to the process scheme, the repair three-dimensional model of each module is processed, and according to the characteristics of S-04 high-strength stainless steel material and each module repair area, the repair parameters are set on the slicing software platform, and the three-dimensional repair model is imported. The center of the model bottom surface is placed on the machining platform origin, the scanning strategy is selected as the "zigzag" scanning mode, the phase angle between layers is 67°, and the machining program obtained after the model is divided is obtained. Through process simulation and on-machine trajectory checking, the correctness of the scanning path and strategy is checked.

[0062] (6) Modular repair of casting defects. The turbine oxygen pump shell to be repaired is fixed using a clamping tool, and a repair support tool is installed on the back side of the repair module with penetrating defects. Open the device cleaning function, and when the oxygen content in the forming cabin is less than 1000 PPM, turn on the laser enable. According to the process scheme, the repair area of the metal component is sequentially repaired on the metal component repair device, and the argon gas is continuously supplied during the forming process to ensure that the oxygen content in the forming cabin is always within 1000 PPM.

[0063] According to the minimum wall thickness of the defect location, the repair processing parameters are selected as follows in the following typical areas of the vortex wall, flange outlet segment B, U-shaped groove A, and root.

[0064] 1) The thickness of the vortex wall (C, D, E) is 5mm, mainly for penetrating defects, and the selected laser repair parameters are:

[0065] Base layer (first 2 layers): laser power 1300-1500 W, scanning speed 300-350 mm / s, path interval 1.0-1.4 mm, spot scale 1-3, slice thickness 0.3-0.5 mm, phase angle 67°;

[0066] Filler layer (above the second layer): laser power 1300-1800 W, scanning speed 300-500 mm / s, path interval 1.0-1.4 mm, spot scale 1-3, slice thickness 0.3-0.5 mm, phase angle 67°.

[0067] 2) The wall thickness of the flange outlet section B is 12 mm, mainly for penetrating defects, and the selected laser repair parameters are:

[0068] Base layer (first 2 layers): laser power 2000-2300 W, scanning speed 400-500 / s, path interval 1.6-2.0 mm, spot scale 4-6, slice thickness 0.5-0.6 mm, phase angle 67°;

[0069] Filler layer (above the second layer): laser power 2000-2500 W, scanning speed 400-600 mm / s, path interval 1.6-2.0 mm, spot scale 4-6, slice thickness 0.5-0.6 mm, phase angle 67°.

[0070] 3) The wall thickness of the vortex and outlet section transition zone H is between the vortex wall and the flange outlet section B, and the selected laser repair parameters are, for example:

[0071] Base layer (first 2 layers): laser power 1500-2000 W, scanning speed 350-450 mm / s, path interval 1.4-1.6 mm, spot scale 2-5, slice thickness 0.4-0.5 mm, phase angle 67°;

[0072] Filler layer (above the second layer): laser power 1600-2200 W, scanning speed 400-500 mm / s, path interval 1.4-1.6 mm, spot scale 2-5, slice thickness 0.4-0.5 mm, phase angle 67°.

[0073] 4) The wall thickness of the U-shaped groove A and the root area (F, G) is 15-23 mm, mainly for non-penetrating defects, and the selected laser repair parameters are:

[0074] Base layer (first 2 layers): laser power 3000-3300 W, scanning speed 800-900 mm / s, path interval 2.0-2.3 mm, spot scale 6-8, slice thickness 0.6-0.9 mm, phase angle 67°;

[0075] Filler layer (2nd layer or more): laser power 3000-3500 W, scanning speed 800-1000 mm / s, path spacing 2.0-2.3 mm, spot scale 6-8, slice thickness 0.6-0.9 mm, phase angle 67°.

[0076] The determination of the defect repair sequence is based on the mutual interference between each repair area. The defect form of the shell type defect generally includes penetrating defects and non-penetrating defects, such as Figure 3 As shown. For the repair of non-penetrating defects, conventional in-situ continuation additive repair can be used. The repair strategy for penetrating defects is to set a random support pad plate, a support top rod and other auxiliary repair forming at the bottom of the shell penetrating repair area, as shown in the accompanying Figure 4 As shown. The pad plate material can be red copper or chromium zirconium copper and other materials, which have good thermal conductivity and are not compatible with the powder material used for repair. During repair, the angle between the machining head axis and the normal of the repair part section can be ensured to be 30°-70° (as shown in Figure 5 As shown), which is achieved by program control in the equipment.

[0077] (7) Post-processing of the repair area. After all areas are repaired, the repaired turbine oxygen pump shell is taken out of the chamber and sent to the post-processing area to process the outer surface of the repair area by using a machining center according to the required size and surface quality of the component, and the inner surface of the repair area is polished.

[0078] Although the present application is disclosed with the above preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application should be defined by the scope of the claims of the present application.

Claims

1. A method of modular laser additive repair of defects in a shell-type casting, characterized in that, The method comprises the following steps: Nondestructive testing is performed on the internal quality of the metal shell casting, and defects are identified. The nondestructive testing is performed by using X-ray perspective method, and different perspective voltages are selected to detect the internal quality of the metal casting. When the wall thickness is [5, 10) mm, a tube voltage of 110-130 kV is used; when the wall thickness is [10, 20) mm, a tube voltage of 130-180 kV is used; when the wall thickness is [20, 30) mm, a tube voltage of 180-240 kV is used; and when the wall thickness is more than 30 mm, a tube voltage of 240-300 kV is used. The standardized repair zone size of each defect is determined according to the nondestructive testing result, which comprises the following steps: the maximum outer circle of the defect size is determined by using a circle to envelope the identified defect range, and then the standardized repair size of the defect is determined according to the modular process design standard. The diameter of the envelope circle of the defect is d, and the repair zone size D satisfies: when d < 20 mm, the repair zone size D is 20 mm; when 20 mm ≤ d < 50 mm, the repair zone size D is 50 mm; when 50 mm ≤ d < 100 mm, the repair zone size D is 100 mm; when 100 mm ≤ d < 150 mm, the repair zone size D is 150 mm; and when 150 mm ≤ d, the repair area is first processed according to D = 150 mm, and then the remaining area is re-zoned and graded according to the aforementioned method of determining the standardized repair zone size of each defect according to the nondestructive testing result. The material in the standardized repair size is removed by using a machining center to obtain a repair area to be repaired. The repair area to be repaired is repaired on a metal component repair equipment, and the repaired area is subjected to surface treatment.

2. The method of claim 1, wherein, The method further comprises the following steps: A three-dimensional model of each repair area in each module is drawn by using modeling software according to the size and position of the standardized repair area to be repaired. The established three-dimensional model is processed according to the process scheme, and the correctness of the scanning path and scanning strategy is checked through process simulation and machining trajectory checking.

3. The method of claim 1, wherein, The shell is divided into different modules according to the structure of the component and the repair process characteristics, and the repair parameters of each standardized repair zone in each module are determined.

4. The method of claim 3, wherein, The shell casting comprises a vortex wall area, a flange outlet section, a vortex and outlet section transition area, a U-shaped groove and a rib plate root area.

5. The method of claim 4, wherein, The repair parameters satisfy at least one of the following conditions: The laser repair parameters for the penetrating defects at the vortex wall or the position with a thickness of 5 mm are as follows: for the primer layer, the laser power is 1300-1500 W, the scanning speed is 300-350 mm / s, the path interval is 1.0-1.4 mm, the light spot scale is 1-3, the slice thickness is 0.3-0.5 mm, and the phase angle is 67°; and for the filling layer, the laser power is 1300-1800 W, the scanning speed is 300-500 mm / s, the path interval is 1.0-1.4 mm, the light spot scale is 1-3, the slice thickness is 0.3-0.5 mm, and the phase angle is 67°. The laser repair parameters of the penetrating defect at the flange outlet section or the position with a thickness of 12 mm are as follows: the base layer: laser power 2000-2300 W, scanning speed 400-500 mm / s, path spacing 1.6-2.0 mm, spot scale 4-6, slice thickness 0.5-0.6 mm, and phase angle 67°; and the filling layer: laser power 2000-2500 W, scanning speed 400-600 mm / s, path spacing 1.6-2.0 mm, spot scale 4-6, slice thickness 0.5-0.6 mm, and phase angle 67°. The laser repair parameters of the penetrating defect at the transition zone between the vortex and the outlet section are as follows: the base layer: laser power 1500-2000 W, scanning speed 350-450 mm / s, path spacing 1.4-1.6 mm, spot scale 2-5, slice thickness 0.4-0.5 mm, and phase angle 67°; and the filling layer: laser power 1600-2200 W, scanning speed 400-500 mm / s, path spacing 1.4-1.6 mm, spot scale 2-5, slice thickness 0.4-0.5 mm, and phase angle 67°. The laser repair parameters of the non-penetrating defect at the U-shaped groove and root area or the position with a thickness of 15-23 mm are as follows: the base layer: laser power 3000-3300 W, scanning speed 800-900 mm / s, path spacing 2.0-2.3 mm, spot scale 6-8, slice thickness 0.6-0.9 mm, and phase angle 67°; and the filling layer: laser power 3000-3500 W, scanning speed 800-1000 mm / s, path spacing 2.0-2.3 mm, spot scale 6-8, slice thickness 0.6-0.9 mm, and phase angle 67°.

6. The method of claim 1, wherein, The angle between the axis of the machining head and the normal of the section of the repair part is 30°-70°.

7. The method of claim 1, wherein, Before laser repair, a bevel structure with an angle of 45°-60° is machined around the repair area.

8. The method of claim 1, wherein, A profiled support pad and / or a support top rod are arranged on the back side of the penetrating repair area before repair to assist in repair forming.

Images