Repair welding repair method for box body defects of nodular cast iron gear box

Abstract

The invention relates to a spheroidal graphite cast iron gear box body defect repair welding repair method which comprises the following steps: S1, defect removal: removing rust and oil stains at the bottom corner defect and the periphery of a box body through an angle grinder to expose metallic luster; s2, assembling is conducted, specifically, an L-shaped surrounding plate is welded to the defect position of the bottom corner of the box body in a spot welding mode; s3, preheating is conducted, specifically, oxyacetylene flames are used for preheating the defects of the bottom corners of the box body; s4, defect part repair welding: according to the selected welding process parameters, firstly welding a transition layer at the defect part of the bottom corner of the box body, and then filling and welding a surfacing layer between the transition layer and the coaming; the surface of a weld joint is polished to be flush with the surface of an original gearbox body, and after weld joint metal is cooled to the room temperature, the weld joint and surrounding splashes are removed; and S6, flaw detection is conducted, specifically, dye flaw detection is conducted on the repaired area 24 hours after welding is conducted. The process problem that after the ink cast iron gearbox body is welded, a fusion area is prone to cracking or stripping is effectively solved, the welding quality and the production efficiency are improved, and the repairing cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of welding repair of a ductile iron gearbox housing, and in particular to a method for welding repair of defects in a ductile iron gearbox. Background Art

[0002] During the locomotive maintenance process, the base corners of the cast iron gearbox body are often missing along the installation holes, positioning holes or due to hoisting, disassembly and other reasons. Figure 1 shown.

[0003] Traditional repair welding uses nickel-based electrode cladding process, which has low efficiency, high cost and expensive welding rods, and the fusion zone is prone to cracks or peeling after welding. This requires a simple, efficient and low-cost welding method to meet the needs of repairing the cast iron gearbox housing. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for repairing defects in ductile iron gearboxes by welding, which effectively solves the process problem of cracks or peeling easily occurring in the fusion zone of the ductile iron gearbox body after welding, improves welding quality and production efficiency, and saves repair costs.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a method for repairing defects of a ductile iron gearbox housing by welding, comprising the following steps: S1. Defect removal: Use an angle grinder to remove rust and oil stains at the bottom corner defects and the surrounding areas of the box to reveal the metallic luster; S2. Assembly: spot weld the L-shaped enclosure at the bottom corner defect of the box; S3: Preheating: Preheat the bottom corner defects of the box with an oxyacetylene flame at a temperature of 500°C to 600°C; S4: Repair welding of defective parts: According to the selected welding process parameters, first weld the transition layer at the defective part of the bottom corner of the box. The thickness of the transition layer is 9-11mm, and then fill the welding cladding layer between the transition layer and the enclosure. S5: Post-weld treatment: Grind the weld surface to make it flush with the original gearbox housing surface. Secondary repair welding is required for areas with missing welds or poor fusion. After completion, use asbestos cloth to insulate the weld area. After the weld metal cools to room temperature, clean the weld and surrounding spatter. S6: NDT: Perform color NDT on the repaired area 24 hours after welding.

[0006] As a preferred solution, in step S2, a slot matching with the two ends of the enclosure is provided at the defect of the bottom corner of the box body.

[0007] As a preferred solution, in step S4, the welding process parameters are as follows: Transition layer: arc welding, power polarity: DC reverse connection; electrode diameter 3.2mm; current selection: I=70-90A; Surfacing layer: carbon dioxide gas shielded welding is adopted, power polarity: DC reverse connection; welding wire diameter 1.2mm; current selection: I=120-140A; voltage selection: U=19-21V.

[0008] As a preferred solution, multi-layer and multi-pass welding is adopted when welding the transition layer, and the interlayer temperature is controlled to be no less than 300°C.

[0009] As a preferred solution, the cladding layer is welded by performing multi-layer and multi-pass welding along the inner wall of the enclosure toward the cladding layer, controlling the interlayer temperature to be no less than 300°C, and performing interlayer cleaning after each layer of welding to clean oxides and spattering weld beans. At the same time, the weld is hammered to relieve stress after each layer of welding is completed.

[0010] As a preferred solution, when welding the transition layer, the angle between the welding rod and the cladding surface is controlled at 40° to 50°.

[0011] As a preferred solution, when welding the cladding layer, the angle between the welding wire and the cladding surface is controlled at 40° to 50°.

[0012] As a preferred solution, the enclosure is made of 2-3 mm low-carbon steel plate.

[0013] The beneficial effects of the present application are as follows: 1. The present application adopts the setting of enclosures, and welds transition layers and surfacing layers according to the selected welding process parameters, and repairs defects in the gear box body by welding through preheating before welding, multi-layer and multi-pass welding, controlling interlayer temperature, asbestos cloth insulation, color flaw detection and other measures.

[0014] 2. The present application uses a welding transition layer, and the transition layer adopts arc welding with electrodes, which has good bonding performance and can effectively prevent peeling or cracking while saving expensive welding materials.

[0015] 3. This application uses carbon dioxide gas shielded welding to weld the cladding layer, which saves costs, has a fast welding speed, makes it easy to observe the shape of the molten pool with a clear arc, and has high welding quality.

[0016] 4. This application makes welding operations easier by setting up enclosures, effectively saves the process of later appearance finishing, and greatly improves work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the bottom corner defect of the box body of the present invention; Figure 2 It is a schematic diagram of the bottom corner defect of the box body and the enclosure structure of the present invention; Figure 3 It is a schematic diagram of the structure of the surfacing layer of the present invention; Figure 4 It is a schematic diagram of the welding inclination structure of the present invention.

[0018] Markings in the figure: 1. gearbox housing, 2. housing bottom corner defect, 21. slot, 3. enclosure, 4. transition layer, 5. cladding layer, 6. cladding surface, 7. arc. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that in the description of the present invention, unless otherwise specified, the meaning of "multiple" is two or more; the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0020] See also Figure 1-4 The embodiment of the present invention provides a method for repairing defects of a ductile iron gearbox housing by welding, comprising the following steps: S1. Defect removal: Use an angle grinder to remove rust and oil stains within 30mm of the bottom corner defects of the box body to reveal the metallic luster; S2, assembly: spot weld an L-shaped enclosure 3 at the defect 2 at the bottom corner of the box; S3: Preheating: Preheat the two defects at the bottom corner of the box with an oxyacetylene flame at a preheating temperature of 500°C to 600°C; S4: Repair welding of defective parts: According to the selected welding process parameters, first weld the transition layer 4 at the defect 2 at the bottom corner of the box. The thickness of the transition layer 4 is 9-11mm, and then fill the welding cladding layer 5 between the transition layer 4 and the enclosure 3. S5: Post-weld treatment: Grind the weld surface to make it flush with the original gearbox housing surface. Secondary repair welding is required for areas with missing welds or poor fusion. After completion, use asbestos cloth to insulate the weld area. After the weld metal cools to room temperature, clean the weld and surrounding spatter. S6: NDT: Perform color NDT on the repaired area 24 hours after welding.

[0021] Among them, in step S2, a slot 21 is provided at the bottom corner defect 2 of the box body to match the two ends of the enclosure 3. Z308 welding rod is used for electric welding. The shape and size of the enclosure 3 are the same as the shape and size of the bottom corner defect of the box body. The enclosure 3 is made of 2-3mm low-carbon steel plate. It should be noted that the parts not described in detail in this application are all prior art.

[0022] In step S4, the welding process parameters are as follows: transition layer 4: arc welding, power polarity: reverse DC; electrode diameter 3.2 mm; current selection: I=70-90A; transition layer 4 uses Z308 electrode.

[0023] Surfacing layer 5: Carbon dioxide gas shielded welding is adopted, power polarity: DC reverse connection; welding wire diameter 1.2mm; current selection: I=120-140A; voltage selection: U=19-21V.

[0024] Specifically, the transition layer 4 is welded by multi-layer multi-pass welding, each layer is 2-3mm thick, and the interlayer temperature is controlled not less than 300°C. When welding the cladding layer 5, multi-layer multi-pass welding is performed along the inner wall of the enclosure 3 toward the cladding layer 5, each layer is 2-3mm thick, and the interlayer temperature is controlled not less than 300°C. After each layer of welding is completed, the interlayer cleaning is performed to clean the oxides and spattering weld beans, and the weld is hammered to relieve stress after each layer of welding is completed. The transition layer 4 and the cladding layer 5 of the present application are both welded by multi-layer multi-pass welding. On the one hand, it has the effect of heat treating the previous layer to eliminate the welding stress. On the other hand, compared with directly welding a single layer of welds, the welding stress is greatly reduced.

[0025] In addition, there is no ceramic pad or other non-metallic pad at the bottom, but a metal platform. When welding, in order to prevent the bottom layer from melting with the weld metal, such as Figure 4 As shown, when the transition layer 4 is welded, the angle between the welding rod and the surfacing surface is controlled at 40°~50°, and when the surfacing layer 5 is welded, the angle between the welding wire and the surfacing surface is controlled at 40°~50°, so that the center of the arc 7 burns at the surfacing surface 6 position 3~5mm upward from the bottom 1, and the molten iron is in contact with the platform surface by gravity (but not fused together).

[0026] Of course, the present invention is not limited to the above-described embodiments. Several other embodiments based on the design concept of the present invention are also provided below.

[0027] For example, in other embodiments, different from the above-described embodiments, in step S4, the thickness of the transition layer 4 is 10 mm.

[0028] For example, in other embodiments, different from the embodiments described above, when welding the cladding layer 5, the welding process parameters of the last layer adopt carbon dioxide gas shielded welding, power polarity: DC reverse connection; welding wire diameter 1.2mm; current selection: I=160-180A; voltage selection: U=22-24V, and the welding process parameters of other layers are: carbon dioxide gas shielded welding, power polarity: DC reverse connection; welding wire diameter 1.2mm; current selection: I=120-140A; voltage selection: U=19-21V.

[0029] For example, in other embodiments, different from the above-described embodiments, in step S3, the preheating temperature is 500°C.

[0030] For example, in other embodiments, different from the above-described embodiments, in step S3, the preheating temperature is 550°C.

[0031] For example, in other embodiments, different from the above-described embodiments, the preheating temperature is 600°C. It should be noted that the above embodiments are only used to illustrate the present invention, but the present invention is not limited to the above embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the present invention.

Claims

1. A method for repairing defects of a ductile iron gearbox housing by welding, characterized in that: The steps include: S1. Defect removal: Use an angle grinder to remove the rust and oil stains at and around the bottom corner defect (2) of the box body to reveal the metallic luster; S2, assembly: spot welding an L-shaped enclosure (3) at the bottom corner defect (2) of the box body; S3: Preheating: Preheat the bottom corner defect (2) of the box body with an oxyacetylene flame at a temperature of 500°C to 600°C; S4: Repair welding of defective parts: According to the selected welding process parameters, firstly weld the transition layer (4) at the defect (2) at the bottom corner of the box, the thickness of the transition layer (4) is 9-11mm, and then fill the gap between the transition layer (4) and the enclosure (3) with a welding cladding layer (5). S5: Post-weld treatment: Grind the weld surface to make it flush with the original gearbox housing surface. Secondary repair welding is required for areas with missing welds or poor fusion. After completion, use asbestos cloth to insulate the weld area. After the weld metal cools to room temperature, clean the weld and surrounding spatter. S6: NDT: Perform color NDT on the repaired area 24 hours after welding.

2. A method for repairing defects of a ductile iron gearbox housing by welding according to claim 1, characterized in that: In step S2, a slot (21) is provided at the bottom corner defect (2) of the box body to match the two ends of the enclosure (3).

3. The method for repairing defects of a ductile iron gearbox housing by welding according to claim 1, characterized in that: In step S4, the welding process parameters are as follows: Transition layer (4): arc welding, power polarity: DC reverse connection; electrode diameter 3.2 mm; current selection: I = 70-90 A; Welding layer (5): Carbon dioxide gas shielded welding is adopted, power polarity: DC reverse connection; welding wire diameter 1.2mm; current selection: I = 120-140A; voltage selection: U = 19-21V.

4. A method for repairing defects of a ductile iron gearbox housing by welding according to claim 3, characterized in that: The transition layer (4) is welded by multi-layer and multi-pass welding, and the interlayer temperature is controlled to be no less than 300°C.

5. The method for repairing defects of a ductile iron gearbox housing by welding according to claim 3 is characterized in that: When welding the cladding layer (5), multiple layers and multiple passes are welded along the inner wall of the enclosure (3) toward the cladding layer (5), and the interlayer temperature is controlled to be not less than 300° C. After each layer of welding is completed, the interlayer cleaning is performed to clean oxides and spattering weld beans, and at the same time, the weld is hammered to relieve stress after each layer of welding is completed.

6. A method for repairing defects of a ductile iron gearbox housing by welding according to claim 4, characterized in that: When welding the transition layer (4), the angle between the welding rod and the cladding surface is controlled to be between 40° and 50°.

7. A method for repairing defects of a ductile iron gearbox housing by welding according to claim 5, characterized in that: When welding the cladding layer (5), the angle between the welding wire and the cladding surface is controlled to be 40° to 50°.

8. The method for repairing defects of a ductile iron gearbox housing by welding according to claim 1, characterized in that: The enclosure plate (3) is made of 2-3 mm low-carbon steel plate.

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