A locomotive coupler crack welding repair method
By designing reasonable welding bevels and welding sequences for locomotive coupler cracks, and combining preheating and heat treatment, the problem of unqualified coupler crack repair in traditional welding methods has been solved, achieving efficient and reliable welding repair results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CRRC LUOYANG CO LTD
- Filing Date
- 2025-07-22
- Publication Date
- 2026-06-26
AI Technical Summary
Traditional welding methods are difficult to effectively repair cracks in locomotive couplers, resulting in poor weldability, which can easily lead to delayed cracking or crack propagation, increasing maintenance costs and time, and affecting train safety.
We employ appropriate welding grooves and welding sequences designed for different crack types, combined with preheating, post-weld heat treatment, and stress relief, and use suitable welding materials for welding repair.
It improved the quality and efficiency of coupler welding repair, avoided the occurrence of welding cracks, met the assembly and application process requirements, and reduced maintenance costs and cycle time.
Smart Images
Figure CN120901624B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of welding technology, specifically a method for welding repair of cracks in locomotive couplers. Background Technology
[0002] In locomotive traction, the interlocking of couplers enables locomotive coupling and traction. Couplers are crucial safety components of locomotives; malfunctions can range from affecting train efficiency to causing derailments and collisions, threatening operational safety. During locomotive coupling and traction, couplers are subjected to cyclic impact loads, frequently resulting in cracks. Traditional welding repair methods involve direct welding or grinding away the cracks before welding. However, because the coupler material is ZG25MnCrNi-Mo with a carbon equivalent of approximately 0.6%, its weldability is poor. Welded repairs often result in delayed cracking or crack expansion, causing significant difficulties for welders. Multiple repairs often fail to meet standards, and repeated welding increases heat input and stress concentration in the weld, ultimately necessitating coupler replacement to meet locomotive maintenance requirements, greatly increasing maintenance costs and timelines. To address these technological challenges, a welding repair process for couplers has been designed. Summary of the Invention
[0003] In response to the problems pointed out in the background art, the purpose of this invention is to propose a method for welding repair of locomotive coupler cracks, ensuring that the quality of the repaired coupler meets the requirements, avoiding the occurrence of welding cracks, and satisfying the process requirements for coupler assembly and operation.
[0004] To achieve the above objectives, the present invention adopts the following technical solution:
[0005] A method for welding repair of cracks in locomotive couplers includes the following steps:
[0006] S1. Select appropriate welding materials based on the coupler material;
[0007] S2. Mark the location of the coupler crack and determine the type of coupler crack based on the crack depth; the crack type is divided into through crack, shallow non-through crack and deep non-through crack.
[0008] S3. Determine the corresponding bevel type based on the type and location of the coupler crack, and process the bevel. Bevel types include shallow non-penetrating bevel, deep non-penetrating bevel, single-sided penetrating bevel, and double-sided penetrating bevel. Shallow non-penetrating bevel corresponds to shallow non-penetrating cracks, deep non-penetrating bevel corresponds to deep non-penetrating cracks, single-sided penetrating bevel corresponds to penetrating cracks in the non-open area of the coupler body, and double-sided penetrating bevel corresponds to penetrating cracks in the open area of the coupler body.
[0009] S4. Select the corresponding welding path according to the bevel type and weld in the following order: first weld the single-sided through bevel, then weld the double-sided through bevel, then weld the deep non-through bevel, and finally weld the shallow non-through bevel; the interpass temperature of each bevel must be preheated to 300-350℃ before welding, and the welding rod should be baked at 300-350℃ for 1-2 hours and placed in the welding rod heat preservation barrel so that the temperature of the welding rod before use is 100-150℃.
[0010] S5. After welding, hammer the weld and both sides of the weld to release welding stress;
[0011] S6. Post-weld heat treatment to eliminate internal stress in the weld;
[0012] S7. After cooling to room temperature for 24 hours, perform flaw detection. If the flaw detection is qualified, grind the weld.
[0013] In step S1, the coupler is made of ZG25MnCrNi-Mo, and the corresponding welding material is J857CrNi alkaline coated high-strength steel welding rod.
[0014] In step S2, shallow non-penetrating cracks and deep non-penetrating cracks are classified as follows: the crack is polished with a polishing device until it disappears, and the polishing depth is measured as the crack depth; when the crack depth is within 3 mm, it is a shallow non-penetrating crack, and when the crack depth is greater than 3 mm, it is a deep non-penetrating crack.
[0015] In step S3, the included angle between the two slopes of the shallow non-penetrating bevel, deep non-penetrating bevel, single-sided penetrating bevel, and double-sided penetrating bevel is not less than 20°, the included angle between the single slope and the horizontal is not more than 80°, the bottom width of the bevel is not less than 6mm, the depth of the shallow non-penetrating bevel is within 3mm, and the depth of the deep non-penetrating bevel is greater than 3mm.
[0016] In step S4, the following method is used to preheat each bevel before welding: within the bevel and within 100 mm around the bevel opening, heat to 300-350°C using oxyacetylene flame welding, and use an infrared thermometer to detect the temperature during the heating process.
[0017] In step S4, shallow non-penetrating bevels are welded using a single layer with φ3.2mm welding rods; deep non-penetrating bevels, single-sided penetrating bevels, and double-sided penetrating bevels are all welded using multi-layer, multi-pass welding. The first layer of weld uses welding rods with a diameter of φ2.5mm or less and a welding current of 70-90A. The remaining welds use φ3.2mm welding rods and a welding current of 90-120A.
[0018] When performing multi-layer, multi-pass welding, after each layer of weld is completed and before starting the next layer of weld, the weld is hammered to release stress.
[0019] In step S4, the same type of bevels are welded in the following order: according to the bevel depth, the deep bevel is welded first, and then the shallow bevel is welded; according to the bevel length, the long bevel is welded first, and then the short bevel is welded.
[0020] In step S6, the specific method of post-weld heat treatment is as follows: the weld and the surrounding area of the weld are heated to 600-650°C using an oxyacetylene flame for tempering treatment. The surrounding area of the weld is the area within 100mm of the weld perimeter.
[0021] The beneficial effects of this invention are as follows: Based on different crack states of the coupler, this invention designs a more reasonable welding bevel and welding sequence. Through preheating and post-weld heat treatment, welding stress is reduced, and the occurrence of welding cracks is avoided, resulting in high efficiency and good repair effect of coupler crack welding repair; the quality is qualified after welding flaw detection. It also provides a better process method for welding repair of similar cast steel parts. Attached Figure Description
[0022] Figure 1 This is a flowchart of the present invention.
[0023] Figure 2 This is a schematic diagram of a shallow, non-through bevel.
[0024] Figure 3 This is a schematic diagram of a deep, non-penetrating bevel.
[0025] Figure 4 This is a schematic diagram of a single-sided through bevel.
[0026] Figure 5 This is a schematic diagram of a double-sided through bevel.
[0027] Figure 6 This is a top view of the welding sequence for parallel welding.
[0028] Figure 7 This is a cross-sectional view of the welding sequence for parallel welding.
[0029] Figure 8 This is a top view showing the welding sequence for spiral welding.
[0030] Figure 9 This is a cross-sectional view showing the welding sequence of spiral welding.
[0031] Figure 10 This refers to the curved surface area inside the coupler body.
[0032] In the figure: D is the bottom width of the bevel, d is the opening width of the bevel, α is the angle between the single-sided slope and the horizontal, β is the angle between the two slopes of the bevel, B is the distance between the bottoms of the double-sided through bevel, and h is the crack depth. Detailed Implementation
[0033] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Example 1
[0034] Repair of cracks in the E-grade steel coupler of Harmony Locomotive 100.
[0035] like Figure 1 As shown, Example 1, which uses the locomotive coupler crack welding repair method provided by the present invention, includes the following steps:
[0036] S1. Welding material preparation; Select appropriate welding materials according to the coupler material; In Example 1, the material of the 100 type E grade steel coupler is ZG25MnCrNi-Mo, and J857CrNi alkaline coated high-strength steel welding rods with diameters of φ2.5 (root pass) and φ3.2 (cap pass) are selected.
[0037] S2. Mark the location of the coupler crack and determine the type of coupler crack based on the crack depth; the crack types are divided into through cracks, shallow non-through cracks and deep non-through cracks; the crack depth is determined by the following method: use a grinding wheel or rotary file to grind and remove the crack from the defective area, and when the crack is removed, the depth of the removed area is taken as the crack depth.
[0038] S3. Determine the corresponding bevel type based on the type and location of the coupler crack, and process the bevel. Bevel types include shallow non-penetrating bevels, deep non-penetrating bevels, single-sided penetrating bevels, and double-sided penetrating bevels. Shallow non-penetrating bevels correspond to shallow non-penetrating cracks, deep non-penetrating bevels correspond to deep non-penetrating cracks, single-sided penetrating bevels correspond to penetrating cracks in the non-open areas of the coupler body, and double-sided penetrating bevels correspond to penetrating cracks in the open areas of the coupler body. Specifically, such as... Figure 10 As shown, the non-open area of the coupler body refers to the curved surface area inside the coupler body (the two leader lines of the letter M in the figure indicate the range of this curved surface area), and the remaining area is the open area of the coupler body.
[0039] In Example 1, beveling can be carried out after the crack depth is determined. Mechanical methods are still used, employing a grinding wheel or rotary file to create a bevel of the corresponding type based on the crack depth. Crack depths h within 3 mm are considered shallow, non-penetrating cracks, while crack depths h greater than 3 mm are considered deep, non-penetrating cracks. The shape of the shallow, non-penetrating bevel is as follows: Figure 2 As shown, the shape of the deep non-penetrating bevel is as follows: Figure 3 As shown, the shape of the single-sided through bevel is as follows: Figure 4 As shown, the double-sided through bevel shape is as follows Figure 5As shown; the included angle β of the two sides of each type of bevel shall not be less than 20°, the included angle α of the single side of the bevel with the horizontal shall not exceed 80°, the bottom width D of the bevel shall not be less than 6mm, and the opening width d of the bevel shall not be less than 20mm; for double-sided through bevels, the distance B between the bottoms of the two sides of the bevel shall be ≥ 3mm, and a grinding wheel shall be used to groove so that the bottoms of the two sides of the bevel are connected to avoid hidden cracks; when processing the bevel, the surface of each bevel should expose the metal color, the transition between the bottom of the bevel and the sidewall should be smooth, and the oxide scale, oil stains, moisture, rust and other debris within 20cm around the bevel should be removed. After the defects are eliminated, magnetic particle testing can be performed to confirm that the defects are completely eliminated before proceeding to the next step;
[0040] S4. Select the corresponding welding path according to the bevel type and weld in the following order: first weld single-sided through bevels, then weld double-sided through bevels, next weld deep non-through bevels, and finally weld shallow non-through bevels; the interpass temperature for each bevel must be preheated to 300-350℃ before welding, and the welding rods must be baked at 300-350℃ for 1-2 hours. The electrodes are placed in a heat-insulating container to ensure they are at a temperature of 100–150°C before use. Before welding each bevel, preheating is performed using the following method: Within 100 mm of the bevel and surrounding area, heat to 300–350°C using an oxy-acetylene torch. During heating, the temperature is monitored using an infrared thermometer. Then, the electrodes are slowly cooled to the interpass temperature. In Example 1, welding is performed using a DC reverse polarity method. The welding position is a flat welding position. Shallow, non-penetrating bevels are welded using a single layer, and φ3.2 mm electrodes are selected. Deep, non-penetrating, single-sided, and double-sided penetrating bevels are all welded using multi-layer, multi-pass welding. For welding, the first layer of weld should use φ2.5 mm welding rods with a welding current of 70-90A, and the remaining welds should use φ3.2 mm welding rods with a welding current of 90-120A. This welding method can reduce the weld fusion ratio and prevent hot cracking. When performing multi-layer and multi-pass welding, after each layer of weld is completed and before starting the next layer, the weld should be hammered to release stress and the weld slag should be thoroughly removed (if new cracks or other defects are found, they should be removed in time). During welding, in order to prevent the arc from damaging the surface of the casting, the arc must not be struck on the non-welded surface of the workpiece.
[0041] For bevels of the same type, weld in the following order: based on bevel depth, weld the deep bevel first, then weld the shallow bevel; based on bevel length, weld the long bevel first, then weld the short bevel.
[0042] For shallow, non-through bevels, the welding path for single-layer welding can be either parallel welding or spiral welding. For deep, non-through bevels, single-sided through bevels, and double-sided through bevels, the welding path is multi-layer surfacing, and each layer can be either parallel welding or spiral welding. The sequences of parallel welding and spiral welding are existing technologies. The welding sequence for parallel welding is as follows: Figure 6 , Figure 7As shown, the welding sequence for spiral welding is as follows: Figure 8 , Figure 9 As shown. When welding, use short arcs and narrow weld beads as much as possible, and a small-toothed oscillating welding torch to reduce heat input and achieve low-heat-input welding. After each layer of welding, promptly remove the weld slag and hammer the repair area evenly outwards from the center of the defect, being careful not to apply excessive force to avoid creating new cracks. Figure 7 In the diagram, the numbers 1-7 represent the sequential numbering of the weld seams during parallel welding; Figure 9 In the diagram, the numbers 1-8 represent the sequential numbering of the weld seams during spiral welding;
[0043] S5. After welding, hammer the weld and both sides of the weld to release welding stress; in Example 1, use a round-headed hand hammer or a pneumatic rust remover to hammer the weld and both sides to release welding stress.
[0044] S6. Post-weld heat treatment to eliminate internal stress in the weld; Example 1: The weld and the surrounding area are heated to 600-650°C using an oxy-acetylene flame for tempering treatment. The surrounding area is the area within 100mm of the weld perimeter. After tempering and heat preservation, the weld is wrapped in an asbestos blanket for slow cooling (if conditions permit, it can be placed in a heating furnace for slow cooling with the furnace).
[0045] S7. After cooling to room temperature for 24 hours, perform flaw detection. If the flaw detection is qualified, grind the weld. After grinding, you can perform flaw detection again to ensure there are no cracks.
[0046] This invention marks the defect location, prepares welding bevels using different methods, and preheats and hammers before welding to fully release the original cracks and internal stress in the coupler. Then, welding is performed on the cracked defect according to a specific welding sequence and techniques. This effectively avoids problems such as delayed cracking and stress concentration caused by traditional welding repair methods. The weld bevel design facilitates welding and improves weld strength. Post-weld flaw detection confirms the weld is of acceptable quality.
[0047] The parts of this invention not described in detail are prior art.
Claims
1. A method for welding repair of cracks in locomotive couplers, characterized in that: Includes the following steps: S1. Select appropriate welding materials based on the coupler material; S2. Mark the location of the coupler crack and determine the type of coupler crack based on the crack depth; the crack type is divided into through crack, shallow non-through crack and deep non-through crack. S3. Determine the corresponding bevel type based on the type and location of the coupler crack, and process the bevel. Bevel types include shallow non-penetrating bevel, deep non-penetrating bevel, single-sided penetrating bevel, and double-sided penetrating bevel. Shallow non-penetrating bevel corresponds to shallow non-penetrating cracks, deep non-penetrating bevel corresponds to deep penetrating cracks, single-sided penetrating bevel corresponds to penetrating cracks in the non-open area of the coupler body, and double-sided penetrating bevel corresponds to penetrating cracks in the open area of the coupler body. S4. Select the corresponding welding path according to the bevel type and weld in the following order: first weld the single-sided through bevel, then weld the double-sided through bevel, then weld the deep non-through bevel, and finally weld the shallow non-through bevel; the interpass temperature of each bevel must be preheated to 300-350℃ before welding, and the welding rod should be baked at 300-350℃ for 1-2 hours and placed in the welding rod heat preservation barrel so that the temperature of the welding rod before use is 100-150℃. S5. After welding, hammer the weld and both sides of the weld to release welding stress; S6. Post-weld heat treatment to eliminate internal stress in the weld; S7. After cooling to room temperature for 24 hours, perform flaw detection. After passing the flaw detection, grind the weld. In step S2, shallow non-penetrating cracks and deep non-penetrating cracks are classified as follows: the crack is polished with a polishing device until it disappears, and the polishing depth is measured as the crack depth; when the crack depth is within 3 mm, it is a shallow non-penetrating crack, and when the crack depth is greater than 3 mm, it is a deep non-penetrating crack. In step S3, the included angle between the two slopes of the shallow non-penetrating bevel, deep non-penetrating bevel, single-sided penetrating bevel, and double-sided penetrating bevel is not less than 20°, the included angle between the single slope and the horizontal is not more than 80°, the bottom width of the bevel is not less than 6mm, the depth of the shallow non-penetrating bevel is within 3mm, and the depth of the deep non-penetrating bevel is greater than 3mm.
2. The method for welding repair of locomotive coupler cracks according to claim 1, characterized in that: In step S1, the coupler is made of ZG25MnCrNi-Mo, and the corresponding welding material is J857CrNi alkaline coated high-strength steel welding rod.
3. The method for welding repair of locomotive coupler cracks according to claim 1, characterized in that: In step S4, the following method is used to preheat each bevel before welding: within the bevel and within 100 mm around the bevel opening, heat to 300-350°C using oxyacetylene flame welding, and use an infrared thermometer to detect the temperature during the heating process.
4. The method for welding repair of locomotive coupler cracks according to claim 1, characterized in that: In step S4, shallow non-penetrating bevels are welded using a single layer with φ3.2mm welding rods; deep non-penetrating bevels, single-sided penetrating bevels, and double-sided penetrating bevels are all welded using multi-layer, multi-pass welding. The first layer of weld uses welding rods with a diameter of φ2.5mm or less and a welding current of 70-90A. The remaining welds use φ3.2mm welding rods and a welding current of 90-120A.
5. The method for welding repair of locomotive coupler cracks according to claim 4, characterized in that: When performing multi-layer, multi-pass welding, after each layer of weld is completed and before starting the next layer of weld, the weld is hammered to release stress.
6. The method for welding repair of locomotive coupler cracks according to claim 1, characterized in that: In step S4, the same type of bevels are welded in the following order: according to the bevel depth, the deep bevel is welded first, and then the shallow bevel is welded; according to the bevel length, the long bevel is welded first, and then the short bevel is welded.
7. The method for welding repair of locomotive coupler cracks according to claim 1, characterized in that: In step S6, the specific method of post-weld heat treatment is as follows: the weld and the surrounding area of the weld are heated to 600-650°C using an oxyacetylene flame for tempering treatment. The surrounding area of the weld is the area within 100mm of the weld perimeter.