Automatic robot welding method for high-strength medium-carbon quenched and tempered steel for planet carrier

Abstract

The invention relates to an automatic robot welding method for high-strength medium-carbon quenched and tempered steel for a planet carrier. The automatic robot welding method comprises the following steps that firstly, the welding performance of a forge piece is analyzed; 2, welding material selection, wherein a gas shielded welding wire with the diameter being 1.2-1.4 mm is selected; step 3, tool installation; 4, pre-welding heat treatment is conducted, specifically, the whole workpiece is preheated to 150-300 DEG C before welding; 5, welding is conducted, specifically, gas shield welding and multi-layer and multi-pass welding are adopted during welding, and the interlayer temperature is controlled to range from 150 DEG C to 300 DEG C; 6, postweld heat treatment is conducted, specifically, postweld dehydrogenation treatment is conducted for 8-22 hours at the temperature of 490 DEG C; step 7, detecting after welding; according to the characteristics of the 34CrNi1Mo forge piece, reasonable welding materials are preferably selected, process parameters such as temperatures before welding, during welding and after welding are accurately regulated and controlled, material deterioration caused by overheating is effectively avoided, it is ensured that the organization structure around a welding seam is uniform and stable, the welding quality is effectively improved, and the reject ratio is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of planetary carrier welding, and in particular to a robot automatic welding method for high-strength medium-carbon quenched and tempered steel for a planetary carrier. Background Art

[0002] The wind power platform lifting system is the core basic working system of the entire platform. The reduction gearbox is the key component that connects the lifting system transmission parts with the lifting frame, and the planetary carrier is the most important load-bearing structural component of the reducer.

[0003] In the production of planetary carriers for reducers, in order to ensure the position accuracy and structural strength of the planetary gears, the planetary carrier material must have a high structural strength so that it can bear the large load of the reduction gear in a large load environment. Therefore, forgings and castings are often used. Since the mechanical properties of castings are worse than forgings and the size and weight of products such as reducers are required to be as small as possible, castings are only suitable for environments where strength requirements or volume and weight requirements are not high. Forging materials for high-strength and small-volume environments have a high cost-effectiveness. 34CrNi1Mo forgings are a material with high strength and good processing performance and are mostly used as structural materials in high-strength environments. In the selection of planetary carrier materials, various factors such as material strength, processability, weldability, etc. are considered and applied in practice, and finally 34CrNi1Mo forgings are used as the main structural material of the planetary carrier.

[0004] 34CrNi1Mo forging welding is a very critical technology. This technology involves high temperature, high pressure and complex chemical reactions, and has been widely used in many fields. However, the existing 34CrNi1Mo forging planetary carrier welding technology still has some defects and shortcomings, which not only affect the efficiency and quality of production, but also restrict the development of the entire industry. First of all, the existing 34CrNi1Mo forging planetary carrier welding technology often causes deformation and cracking of parts. This is because in this process, the metal material will be subjected to strong thermal shock and mechanical stress, and if it is not handled properly, it will cause the parts to deform or produce tiny cracks. This is very dangerous for precision equipment because these defects may cause serious failures or even catastrophic accidents. Secondly, the existing 34CrNi1Mo forging planetary carrier welding technology has very high requirements for operators. Since this process requires precise control of parameters such as temperature, pressure and time, experienced welders are required to operate. However, with the increasing speed of modern production lines, many companies find it difficult to find enough skilled welders to meet production needs. This greatly increases the production cost of enterprises and limits the expansion of production capacity. In summary, although the 34CrNi1Mo forging planetary carrier welding technology has made great progress, it still faces many challenges and difficulties in practice.

[0005] Therefore, the present invention proposes a robot automatic welding method for high-strength medium-carbon quenched and tempered steel for planetary carriers to solve the above problems. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a robot automatic welding method for high-strength medium-carbon quenched and tempered steel for planetary frames, so as to improve the welding quality of products, reduce the unqualified rate, shorten the production cycle and save costs.

[0007] In order to solve the above technical problems, the technical solution of the present invention is: a robot automatic welding method for high-strength medium-carbon quenched and tempered steel for a planetary frame, the planetary frame includes a planetary frame flange and a planetary frame pin, the planetary frame flange has two and is arranged in parallel, the planetary frame pin is arranged between the two planetary frame flanges, the planetary frame flange is provided with a plurality of flange holes, the flange holes on the two planetary frame flanges are arranged in pairs, the planetary frame flange and the planetary frame pin are both 34CrNi1Mo forgings, and the innovation point is: the automatic welding method comprises the following steps: Step 1: Analysis of forging welding performance: According to the chemical composition of 34CrNi1Mo forging material, calculate the Ceq value of 34CrNi1Mo and evaluate the weldability of the forging; Step 2, welding material selection: According to the welding material selection principle, considering the factors of crack resistance and welding production efficiency, choose gas shielded welding wire with a diameter of 1.2-1.4mm; Step 3, tooling installation: Use the fastening tooling to clamp the two planetary carrier flanges on both sides of the planetary carrier pin to form an integral workpiece; Step 4: Heat treatment before welding: preheat the entire workpiece to 150~300℃ before welding; Step 5, welding: gas shielded welding, multi-layer and multi-pass welding, control the interlayer temperature at 150~300℃, negative DC electrode, welding current at 250~320A, arc voltage at 26~32V, welding speed at 230~350cm / min, heat input ≤2.5kJ / cm; Step 6, post-weld heat treatment: remove the fastening fixtures and perform post-weld dehydrogenation treatment at 490°C for 8 to 22 hours; Step 7, post-weld inspection: Perform a macroscopic inspection of the planet carrier's appearance quality, and perform a flaw detection inspection after the planet carrier has cooled to room temperature for 48 to 72 hours.

[0008] Furthermore, the model of the gas shielded welding wire is GB / T 17493 E761T1-K3CJ or AWS A5.29E111T1-K3CJ or AWS A5.36 E111T1-C1A4-K3.

[0009] Furthermore, during the welding process of step 5, after each welding pass is completed, it is necessary to check whether the temperature of the entire workpiece is between 150 and 300° C. If it is lower than 150° C., it is preheated again.

[0010] Furthermore, the planetary carrier pin is welded in two passes. The first pass is a gas shielded welding base weld. After welding, the welding slag must be removed and a careful visual inspection must be performed to ensure there are no cracks, pores, or slag inclusions. The second pass is a robot automatic welding fill and cover weld. During welding, the current is increased by 5 to 10 A based on the first welding current.

[0011] Furthermore, the final arc-ending welding position of the planet carrier pin welding must lead out the weld bead by 5 to 10 mm.

[0012] Furthermore, the fastening tool comprises two clamping plates, bolts and nuts matching the bolts, and both clamping plates are provided with through holes for the bolts to pass through.

[0013] Furthermore, the planetary carrier pin includes a pin body, each side of the pin body has a reduced diameter section, the reduced diameter section includes a cylindrical section and a truncated cone section, the truncated cone section is located on the side of the cylindrical section away from the pin body, the outer diameter of the cylindrical section matches the inner diameter of the flange hole, the outer diameter of the truncated cone section gradually decreases from the joint with the cylindrical section, and the side of the pin body close to the cylindrical section has an inclined surface, and the inclined surface is inclined from the side away from the cylindrical section toward the direction close to the central axis of the cylindrical section.

[0014] Furthermore, the detailed process of the tooling installation in step 3 is as follows: The two planetary carrier flanges are respectively installed on both sides of the planetary carrier pin, and the reduced diameter sections on both sides of the planetary carrier pin enter the flange holes at the corresponding positions of the planetary carrier flange on the same side, and the two clamping plates are respectively set on the outsides of the two planetary carrier flanges. The bolts pass through the through holes of one clamping plate, the flange holes on the two planetary carrier flanges where the planetary carrier pins are not installed, and the through holes of the other clamping plate in turn, and are threadedly connected with the nuts. The nuts are tightened to achieve relative fixation of the planetary carrier flange and the planetary carrier pin. At this time, the end face of the frustum section is flush with the outer wall of the planetary carrier flange, and a first weld groove is formed between the side face of the frustum section and the flange hole wall. The end face of the pin body is against the inner wall of the planetary carrier flange, and a second weld groove is formed between the inclined surface on the pin body and the inner wall of the planetary carrier flange.

[0015] The advantages of the present invention are: (1) The automatic welding method of the present invention uses a fastening tool to connect the planetary carrier pin and the planetary carrier flange to form a whole in advance before welding. According to the characteristics of the 34CrNi1Mo forging, reasonable welding materials are selected, and process parameters such as temperature before, during and after welding are accurately controlled, which effectively avoids material degradation caused by overheating, ensures that the microstructure around the weld is uniform and stable, effectively improves the welding quality, and reduces the unqualified rate.

[0016] (2) In the automatic welding method of the present invention, after each welding pass is completed, it is necessary to detect whether the temperature of the entire workpiece is between 150 and 300°C. If it is lower than 150°C, it is preheated again. This effectively avoids the situation in which a hardened zone is easily generated in the range of the fusion line and the heat-affected zone when the weldment is cooled to below 150°C due to the high rigidity of the 34CrNi1Mo forging and then cold cracks are generated.

[0017] (3) The model of the gas shielded welding wire of the present invention is preferably GB / T 17493 E761T1-K3CJ or AWS A5.29E111T1-K3CJ or AWS A5.36 E111T1-C1A4-K3. The base material composition of these three models is more in line with the characteristics of 34CrNi1Mo forgings, thereby improving the welding quality.

[0018] (4) The planetary carrier pin of the present invention is welded in two passes. The second pass increases the current by 5 to 10 A based on the first pass, which can effectively ensure the depth of penetration and fusion quality.

[0019] (5) The final arc-ending welding position of the planetary carrier pin welding of the present invention must lead out the weld bead by 5 to 10 mm, which can effectively avoid the possible arc-ending cracks from affecting the quality of the weld in the groove.

[0020] (6) The fastening tool of the present invention is composed only of a clamping plate, bolts and nuts, has a simple structure, and is easy to install and disassemble.

[0021] (7) The present invention utilizes the structural characteristics of the planet carrier pin itself. After the planet carrier pin is assembled, a welding groove is automatically formed between the planet carrier flange and the planet carrier pin, thereby effectively reducing welding residual stress, thereby reducing the risk of cracking and making subsequent processing more convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0023] Figure 1 It is a schematic structural diagram of the planet carrier of the present invention.

[0024] Figure 2 It is a cross-sectional view of the planet carrier of the present invention along the AA direction.

[0025] Figure 3 It is a layout diagram of the fastening fixture of the present invention on the planet carrier.

[0026] Figure 4 This is a partial cross-sectional view of the fastening tool of the present invention installed on the planet carrier.

[0027] Figure 5 It is a schematic diagram of the final arc-ending welding position of the planet carrier pin welding of the present invention. DETAILED DESCRIPTION

[0028] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0029] Example like Figure 1-2 As shown, the planet carrier involved in this embodiment includes a planet carrier flange 1 and a planet carrier pin 2. The planet carrier flange 1 has two and is arranged in parallel. The planet carrier pin 2 has three and is arranged in a triangular shape between the two planet carrier flanges 1. Six flange holes are opened on each planet carrier flange 1. The flange holes on the two planet carrier flanges 1 are arranged in pairs. The planet carrier pin 2 includes a pin body 21. The pin body 21 has a reduced diameter section on both sides. The reduced diameter section includes a cylindrical section 22 and a truncated cone section 23. The truncated cone section 23 is located on the side of the cylindrical section 22 away from the pin body 21. The outer diameter of the cylindrical section 22 matches the inner diameter of the flange hole. The outer diameter of the truncated cone section 23 gradually decreases from the joint with the cylindrical section 22. The side of the pin body 21 close to the cylindrical section 22 has an inclined surface 24. The inclined surface 24 is inclined from the side away from the cylindrical section 22 to the direction close to the central axis of the cylindrical section 22. Both the planet carrier flange and the planet carrier pin are 34CrNi1Mo forgings.

[0030] The above-mentioned robot automatic welding method of high-strength medium-carbon quenched and tempered steel for planetary carriers comprises the following steps: Step 1: Analysis of forging welding performance: According to the chemical composition of 34CrNi1Mo forging material, calculate the Ceq value of 34CrNi1Mo and evaluate the weldability of the forging; The chemical composition of 34CrNi1Mo forging materials is shown in Table 1, and the mechanical properties of 34CrNi1Mo forging materials are shown in Table 2. The calculation formula recommended by the International Welding Society is used to calculate the Ceq value of 34CrNi1Mo. The calculation formula is as follows: Ceq=C+Mn / 6+(Cu+Ni) / 15+(Cr+Mo+V) / 5=0.81-1.06% Table 1 Chemical composition of 34CrNi1Mo forging materials Table 2 Mechanical properties of 34CrNi1Mo materials 34CrNi1Mo forging material is a high chromium nickel-molybdenum alloy steel with the advantages of high strength, wear resistance and corrosion resistance. These advantages make 34CrNi1Mo forging material an ideal choice for manufacturing planetary carriers. Due to the characteristics of its chemical composition, hardening tendency may occur during welding, resulting in increased hardness of the welded joint. To avoid this problem, appropriate heat treatment methods are required to reduce the degree of hardening, thereby ensuring welding quality.

[0031] Step 2, welding material selection: According to the principle of welding material selection, that is, the alloy composition and strength properties of the weld metal basically meet the lower limit values ​​specified in the parent material standard, or meet the minimum performance indicators specified in the product technical conditions, to ensure that the strength, plasticity, toughness, etc. of the weld meet the technical requirements of the product, considering the factors of crack resistance and welding production efficiency, select gas shielded welding wire with a diameter of 1.2-1.4mm, model GB / T 17493 E761T1-K3CJ or AWS A5.29 E111T1-K3CJ or AWSA5.36 E111T1-C1A4-K3, the chemical composition and mechanical properties of the welding wire are shown in Table 3 and Table 4 respectively.

[0032] Table 3 Chemical composition of welding wire materials Table 4 Mechanical properties of welding wire materials Step 3, tooling installation: Use the fastening tooling to clamp the two planetary carrier flanges on both sides of the planetary carrier pin to form an integral workpiece; like Figure 3-4 As shown, the fastening tool comprises two clamping plates 3, bolts 4 and nuts 5 matching the bolts 4, and through holes for the bolts 4 to pass through are provided on the two clamping plates 3.

[0033] During the tooling installation, the two planetary frame flanges 1 are respectively installed on both sides of the planetary frame pin 2, and the reduced diameter sections on both sides of the planetary frame pin 2 enter the flange holes at the corresponding positions of the planetary frame flanges on the same side. Through the cooperation between the cylindrical section on the planetary frame pin 2 and the flange hole, the installation position of the planetary frame pin 2 on the planetary frame flange 1 is positioned to improve the accuracy; then, the two clamping plates 3 are respectively arranged on the outside of the two planetary frame flanges 1, and the bolts 4 are successively passed through the through hole of one clamping plate, the flange holes on the two planetary frame flanges where the planetary frame pins are not installed, and the through hole of the other clamping plate, and then tightened with the nuts 5. Threaded connection, tighten the nut 5 to achieve relative fixation between the planetary carrier flange 1 and the planetary carrier pin 2. At this time, the end face of the conical section 23 is flush with the outer wall of the planetary carrier flange 1, and a first weld groove W01 is formed between the side of the conical section 23 and the flange hole wall. The end face of the pin body 21 is against the inner wall of the planetary carrier flange 1, and a second weld groove W02 is formed between the inclined surface 24 on the pin body 21 and the inner wall of the planetary carrier flange 1. This optimized groove design can effectively reduce welding residual stress, thereby reducing the risk of cracking and making subsequent processing more convenient.

[0034] In order to improve the fastening strength, at least two fastening tools are used. In this embodiment, three fastening tools are used and are arranged at intervals from the planet carrier pins to be welded.

[0035] Step 4: Heat treatment before welding: Preheat the entire workpiece to 150~300℃ before welding. Preheating before welding can reduce the cooling rate of welding, reduce or avoid the formation of hardened martensite, and promote the escape of hydrogen in the weld, effectively preventing the formation of cracks.

[0036] Step 5, welding: weld the connection between the planetary frame pin and each planetary frame flange, use gas shielded welding GMAW or FCAW, multi-layer multi-pass welding, control the interlayer temperature at 150~300℃, the current type and polarity are DCEN direct current electrode connected to negative, welding current 250~320A, arc voltage 26~32V, welding speed 230~350cm / min, heat input ≤2.5kJ / cm, this precise control operation can avoid material degradation caused by overheating and ensure uniform and stable structure around the weld; Due to the high rigidity of 34CrNi1Mo forgings, when the weldment is cooled to below 150℃, a hardened zone is easily generated in the range of the fusion line and the heat-affected zone, thereby generating cold cracks. Therefore, during the welding process, after each welding pass, the temperature of the entire workpiece must be checked to see if it is between 150 and 300℃. If it is lower than 150℃, it must be preheated again; In this embodiment, two passes are used for welding the planetary carrier pin. The first pass is gas shielded welding for base welding. After welding, the welding slag must be removed and carefully visually inspected for cracks, pores, and slag inclusions. During the welding process, welders must record the welding parameters of their welds and sign for quality traceability. After base welding, the welder and the team leader must conduct self-inspection and inspection of the base weld appearance. After the base welding self-inspection is completed, the temperature of the entire workpiece is detected. If it is lower than 150°C, it is put into the furnace for re-preheating; The second welding is robot automatic welding filling and capping. During welding, the current is increased by 5~10A based on the first welding current to ensure the depth of penetration and fusion quality. During the filling and capping welding process, the welding temperature, welding current, welding voltage, welding speed are monitored and the welding record sheet is filled in. After each weld is completed, the welder must record the welding parameters of the weld he welded and sign for quality traceability. The final arc end welding position of the planetary frame pin welding must lead out the weld by 5~10mm, such as Figure 5 As shown, this operation can effectively avoid the possible arc closing cracks affecting the quality of the weld in the groove.

[0037] Step 6, post-weld heat treatment: remove the fastening tooling and perform post-weld dehydrogenation treatment at 490°C for 8 to 22 hours. Timely dehydrogenation heat treatment after welding can accelerate the escape of diffused hydrogen in the weld metal, reduce the hydrogen content in the weld and heat-affected zone, and effectively avoid hydrogen-induced cracks.

[0038] Step 7, post-weld inspection: Perform a macroscopic inspection on the appearance quality of the planetary frame, and after the planetary frame cools to room temperature for 48 to 72 hours, perform a radiographic flaw detection test in accordance with the national standard GB3323-2005. If the level I test is qualified, the next machining process will be entered after the flaw detection is qualified.

[0039] In order to verify the 34CrNi1Mo alloy quenched and tempered steel and the selected welding materials, the welding process qualification test was carried out to verify the matching of steel and welding materials, the feasibility of welding conditions and welding parameters. After the welded planet carrier passed the flaw detection inspection, the welded joint was subjected to tensile, bending and impact tests in accordance with national standards. The welding test results are shown in Table 5.

[0040] Table 5 Welding test results The results of the mechanical test show that the tensile strength of the welded joint meets the requirements, and the bending specimens are qualified when bent 180° under the pressure head with a bending center diameter of d=6t. The impact values ​​of all impact specimens are higher than those of the parent material. The welded joint can meet the technical requirements, indicating that the welding process of the process test is reasonable.

[0041] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A robot automatic welding method for high-strength medium-carbon quenched and tempered steel for a planetary carrier, the planetary carrier comprising a planetary carrier flange and a planetary carrier pin, the planetary carrier flange having two and arranged in parallel, the planetary carrier pin arranged between the two planetary carrier flanges, the planetary carrier flange having a plurality of flange holes, the flange holes on the two planetary carrier flanges being arranged in pairs, the planetary carrier flange and the planetary carrier pin are both 34CrNi1Mo forgings, characterized in that: The automatic welding method comprises the following steps: Step 1: Analysis of forging welding performance: According to the chemical composition of 34CrNi1Mo forging material, calculate the Ceq value of 34CrNi1Mo and evaluate the weldability of the forging; Step 2, welding material selection: According to the welding material selection principle, considering the factors of crack resistance and welding production efficiency, choose gas shielded welding wire with a diameter of 1.2-1.4mm; Step 3, tooling installation: Use the fastening tooling to clamp the two planetary carrier flanges on both sides of the planetary carrier pin to form an integral workpiece; Step 4: Heat treatment before welding: preheat the entire workpiece to 150~300℃ before welding; Step 5, welding: gas shielded welding, multi-layer and multi-pass welding, control the interlayer temperature at 150~300℃, negative DC electrode, welding current at 250~320A, arc voltage at 26~32V, welding speed at 230~350cm / min, heat input ≤2.5kJ / cm; Step 6, post-weld heat treatment: remove the fastening fixtures and perform post-weld dehydrogenation treatment at 490°C for 8 to 22 hours; Step 7, post-weld inspection: Perform a macroscopic inspection of the planet carrier's appearance quality, and perform a flaw detection inspection after the planet carrier has cooled to room temperature for 48 to 72 hours.

2. The robot automatic welding method for high-strength medium-carbon quenched and tempered steel for planetary carriers according to claim 1 is characterized in that: The model of the gas shielded welding wire is GB / T 17493 E761T1-K3CJ or AWS A5.29 E111T1-K3CJ or AWSA5.36 E111T1-C1A4-K3.

3. The robot automatic welding method for high-strength medium-carbon quenched and tempered steel for planetary carriers according to claim 1 is characterized in that: During the welding process of step 5, after each welding is completed, it is necessary to check whether the temperature of the entire workpiece is between 150 and 300° C. If it is lower than 150° C., it is preheated again.

4. The robot automatic welding method for high-strength medium-carbon quenched and tempered steel for planetary carriers according to claim 1 is characterized in that: The planetary carrier pin is welded in two passes. The first pass is a gas shielded welding base weld. After welding, the welding slag must be removed and a careful visual inspection must be carried out to ensure there are no cracks, pores, or slag inclusions. The second pass is a robot automatic welding fill and cover weld. During welding, the current is increased by 5 to 10 A based on the first welding current.

5. The robot automatic welding method for high-strength medium-carbon quenched and tempered steel for planetary carriers according to claim 1 is characterized in that: The final arc-ending welding position of the planet carrier pin welding must lead out the weld bead by 5 to 10 mm.

6. The robot automatic welding method for high-strength medium-carbon quenched and tempered steel for planetary carriers according to claim 1, characterized in that: The fastening tool comprises two clamping plates, bolts and nuts matching the bolts, and through holes for the bolts to pass through are provided on the two clamping plates.

7. The robot automatic welding method for high-strength medium-carbon quenched and tempered steel for planetary carriers according to claim 6, characterized in that: The planetary carrier pin includes a pin body, each of which has a reduced diameter section on both sides, the reduced diameter section including a cylindrical section and a truncated cone section, the truncated cone section is located on the side of the cylindrical section away from the pin body, the outer diameter of the cylindrical section matches the inner diameter of the flange hole, the outer diameter of the truncated cone section gradually decreases from the joint with the cylindrical section, and the side of the pin body close to the cylindrical section has an inclined surface, and the inclined surface is inclined from the side away from the cylindrical section toward the direction close to the central axis of the cylindrical section.

8. The robot automatic welding method for high-strength medium-carbon quenched and tempered steel for planetary carriers according to claim 7, characterized in that: The detailed process of the tooling installation in step 3 is as follows: The two planetary carrier flanges are respectively installed on both sides of the planetary carrier pin, and the reduced diameter sections on both sides of the planetary carrier pin enter the flange holes at the corresponding positions of the planetary carrier flange on the same side, and the two clamping plates are respectively set on the outsides of the two planetary carrier flanges. The bolts pass through the through holes of one clamping plate, the flange holes on the two planetary carrier flanges where the planetary carrier pins are not installed, and the through holes of the other clamping plate in turn, and are threadedly connected with the nuts. The nuts are tightened to achieve relative fixation of the planetary carrier flange and the planetary carrier pin. At this time, the end face of the frustum section is flush with the outer wall of the planetary carrier flange, and a first weld groove is formed between the side face of the frustum section and the flange hole wall. The end face of the pin body is against the inner wall of the planetary carrier flange, and a second weld groove is formed between the inclined surface on the pin body and the inner wall of the planetary carrier flange.

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