A method and system for forging and welding a center seat of a movable arm of an excavator

Abstract

The present application relates to the field of engineering machinery forging and welding processing technology, and discloses a kind of excavator arm center seat mother and child split type forging and welding forming method and system.The method includes obtaining two half-ring forgings symmetrical to left and right, and machining mutually matched mother and child socket positioning structures on the butt joint end faces of the two half-ring forgings, respectively, and machining symmetrical V-shaped welding grooves on the outside of the butt joint seam;the mother end forging in the two half-ring forgings is heated, and the child end forging is press-fitted into the mother end forging, to form an interference positioning assembly through the mother and child socket positioning structures;the V-shaped welding groove of the interference positioning assembly is fully penetrated welded to obtain a welded forming piece;the welded forming piece is stress relief annealed to obtain an excavator arm center seat.The present application can realize high-precision positioning, high-strength welding and low-stress forming, to ensure the coaxial precision and overall structural reliability of the ring-shaped workpiece.

Description

Technical Field

[0001] This invention relates to the field of forging and welding processing technology for engineering machinery, specifically to a method and system for forging and welding a split-type mother-daughter joint for the center seat of an excavator boom. Background Technology

[0002] The boom center is a critical load-bearing component connecting the slewing platform of the excavator and the boom, bearing heavy loads and alternating impact loads. There are currently two main manufacturing methods for boom center: one is integral forging, but due to the complex structure and uneven wall thickness of the workpiece, forging is difficult, yield is low, and processing costs are extremely high, making integral forging impossible for large parts; the other is direct butt welding of two halves, where the two halves are only welded together at their end faces without a positioning structure. This makes it difficult to ensure coaxiality during welding, leading to eccentric deformation, slag inclusions and incomplete fusion at the weld root, poor overall rigidity, low fatigue life, and the lack of pre-tightening, making the weld prone to cracking under heavy load conditions.

[0003] Therefore, how to provide a forming process that can guarantee both high-precision positioning and high-strength welding is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] To address the problems of poor coaxiality, numerous weld defects, insufficient structural strength, and susceptibility to deformation and cracking in existing split-welded ring parts, this invention provides a split forging and welding method and system for the center seat of an excavator boom, achieving high-precision positioning, high-strength welding, and low-stress forming, thus ensuring the coaxial accuracy of the ring workpiece and the reliability of the overall structure.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0006] In a first aspect, the present invention proposes a method for forging and welding a split-type mother-daughter joint for the center seat of an excavator boom, comprising the following steps:

[0007] Two symmetrical semi-ring forgings are obtained, and matching male and female socket positioning structures are machined on the mating end faces of the two semi-ring forgings respectively, and symmetrical V-shaped welding grooves are machined on the outside of the mating joint.

[0008] The female end forging of the two semi-ring forgings is heated, and the male end forging is press-fitted into the female end forging, forming an interference-fitted assembly through the male-female socket positioning structure.

[0009] Full penetration welding is performed on the V-shaped welding groove of the interference fit assembly to obtain a welded part;

[0010] The welded part is subjected to stress-relieving tempering treatment to obtain the center seat of the excavator boom.

[0011] Further, the female end forging of the two semi-ring forgings is heated, and the male end forging is press-fitted into the female end forging, forming an interference fit assembly through the male-female socket positioning structure, including:

[0012] The female end forging is heated to 220-350°C;

[0013] Under heating conditions, the male end forging is axially pressed into the female end forging, so that the mating surfaces of the male and female socket positioning structure form an interference fit with a single-sided interference of 0.12 to 0.18 mm. After cooling, the interference positioning assembly is obtained.

[0014] Further, the V-shaped weld bevel of the interference fit assembly is subjected to full penetration welding to obtain a welded formed part, including:

[0015] Preheating is performed on the interference fit assembly before welding;

[0016] An all-position automatic gas shielded welding equipment with a track is used, along with the automatic lateral oscillation of the welding torch, to weld the V-shaped weld bevel with low heat input. The interpass temperature is controlled during the welding process to obtain the welded part.

[0017] Furthermore, preheating the interference fit assembly before welding includes preheating the interference fit assembly to 80-150°C.

[0018] Controlling the interpass temperature during welding includes maintaining the interpass temperature between 150 and 200°C during the welding process.

[0019] Further, the V-shaped weld bevel of the interference fit assembly is subjected to full penetration welding to obtain a welded formed part, including:

[0020] The V-shaped weld bevel is segmented and symmetrically welded using gas shielded welding to obtain the welded part.

[0021] Furthermore, before performing full penetration welding on the V-shaped weld bevel of the interference fit assembly, the method further includes:

[0022] The V-shaped weld bevel and the area within at least 20mm around it are ground to remove oil and oxide scale until the metal luster is exposed.

[0023] Further, the welded part is subjected to stress-relieving tempering treatment to obtain the excavator boom center seat, comprising:

[0024] The welded part is placed in a heating furnace and subjected to stress-relieving tempering at a temperature of 500-580°C, and then naturally cooled to room temperature to obtain the excavator boom center seat.

[0025] Furthermore, machining mutually matching male and female socket positioning structures on the mating end faces of the two semi-ring forgings includes:

[0026] An annular inner step is machined on the mating end face of the female end forging, and an annular outer boss matching the annular inner step is machined on the mating end face of the male end forging.

[0027] The inner annular step and the outer annular protrusion are used as the female-female socket positioning structure to form a bidirectional positioning mating surface in the axial and radial directions during press fitting.

[0028] Furthermore, machining a symmetrical V-shaped welding bevel on the outer side of the butt joint includes:

[0029] The V-shaped welding bevel is machined on the outer side of the butt joint, and the total angle of the V-shaped welding bevel is 45° to 60°.

[0030] Secondly, this invention proposes a split-type forging and welding forming system for the center seat of an excavator boom, employing the aforementioned split-type forging and welding forming method for the center seat of an excavator boom, including:

[0031] The processing module is used to obtain two symmetrical semi-ring forgings, and to process matching male and female socket positioning structures on the mating end faces of the two semi-ring forgings, and to process symmetrical V-shaped welding grooves on the outside of the mating joint.

[0032] The assembly module is used to heat the female end forging of the two semi-ring forgings and press the male end forging into the female end forging, forming an interference-fit assembly through the male-female socket positioning structure.

[0033] A welding module is used to perform full penetration welding on the V-shaped welding groove of the interference fit assembly to obtain a welded part.

[0034] A heat treatment module is used to perform stress-relieving tempering on the welded parts to obtain the center seat of the excavator boom.

[0035] The present invention has the following beneficial effects:

[0036] (1) The present invention adopts a bidirectional positioning structure with male and female joints, and achieves high-precision coaxial positioning of the two halves through hot fitting interference fit, which solves the problem of eccentric deformation that is easy to occur in traditional split welding, thereby meeting the requirements of high-precision assembly.

[0037] (2) The present invention achieves full penetration of the weld by setting a V-shaped bevel on the outside of the butt joint and matching the sealing surfaces of the male and female parts. At the same time, the mating surfaces of the male and female parts are high-precision machined surfaces. After heat fitting, they achieve complete interference fit and form an annular sealing barrier to prevent welding slag from seeping into the mating gap and eliminate internal welding defects. This ensures stable weld quality, no internal slag inclusions or leakage, and a significant increase in overall strength.

[0038] (3) The present invention adopts a hot-fitting pre-tightening + welding composite structure, which combines interference fit rigidity and overall welding strength. At the same time, it combines preheating and stress relief processes to effectively reduce the risk of stress cracking and effectively solve the cracking risk caused by double stress superposition. It is suitable for heavy load, impact and alternating working conditions.

[0039] (4) The split forging process used in this invention is easy to manufacture and has a high yield, which greatly reduces the manufacturing cost of large ring forgings. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the process for a split forging and welding method for the center seat of an excavator boom according to the present invention.

[0041] Figure 2 This is a front view of the assembly of the female end forging and the female end forging in this invention;

[0042] Figure 3 This is a cross-sectional view of the assembly of the female end forging and the male end forging in this invention;

[0043] The attached figures are labeled as follows: 1-mother end forging, 2-daughter end forging, 3-annular inner step, 4-annular outer boss, 5-V-shaped welding bevel. Detailed Implementation

[0044] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0045] like Figure 1 As shown, the present invention provides a method for forging and welding a split-type center seat for an excavator boom, comprising the following steps S1 to S4:

[0046] S1. Obtain two symmetrical semi-ring forgings, and machine matching male and female socket positioning structures on the mating end faces of the two semi-ring forgings respectively, and machine symmetrical V-shaped welding grooves 5 on the outside of the mating joint.

[0047] S2. Heat the female end forging 1 of the two semi-ring forgings, and press the male end forging 2 into the female end forging 1 to form an interference-fit assembly through the male-female socket positioning structure.

[0048] S3. Perform full penetration welding on the V-shaped welding groove 5 of the interference positioning assembly to obtain a welded part;

[0049] S4. Perform stress-relieving tempering treatment on the welded part to obtain the center seat of the excavator boom.

[0050] This embodiment achieves bidirectional positioning in both the axial and radial directions by machining matching male and female socket positioning structures on the mating end faces of the two half-ring forgings. After hot fitting, the male and female socket positioning structures form an interference fit, ensuring high-precision coaxial positioning of the two half-ring forgings and avoiding welding eccentric deformation. At the same time, symmetrical V-shaped welding grooves 5 are machined on the outer side, which is conducive to full weld penetration and improves welding strength. Furthermore, the male end forging 2 is pressed into the female end forging 1 through hot fitting to form an interference positioning assembly, which combines the rigidity of the interference fit with the overall strength of the weld. Then, full penetration welding and stress-relief tempering are performed to eliminate residual stress generated by hot fitting and welding, reduce the risk of cracking, and finally obtain a boom center seat with high coaxiality, good strength, and high reliability.

[0051] In an optional embodiment of the present invention, step S1, which involves machining mutually matching male and female socket positioning structures on the mating end faces of the two semi-ring forgings, includes:

[0052] An annular inner step 3 is machined on the mating end face of the female end forging 1, and an annular outer boss 4 matching the annular inner step 3 is machined on the mating end face of the male end forging 2.

[0053] The inner annular step 3 and the outer annular protrusion 4 are used as the male and female socket positioning structure to form a bidirectional positioning mating surface in the axial and radial directions during press fitting.

[0054] Step S1 involves machining a symmetrical V-shaped welding bevel 5 on the outer side of the butt joint, including:

[0055] The V-shaped welding bevel 5 is machined on the outer side of the butt joint, and the total angle of the V-shaped welding bevel 5 is 45° to 60°.

[0056] In this embodiment, two semi-ring forgings are forged and rough-machined separately, and the mating surfaces, butt joint surfaces, and outer V-shaped welding bevels 5 are precision-machined. The butt joint surfaces of the two semi-ring forgings are equipped with matching mating socket positioning structures. The female forging 1 has an inner annular step 3, and the male forging 2 has an outer annular boss 4, forming a bidirectional positioning mating surface with axial and radial directions. Axial positioning prevents relative axial displacement between the two semi-rings, while radial positioning ensures coaxiality. After heat fitting, the bidirectional positioning surfaces form an interference fit, providing strong resistance to shear and torsion, ensuring the stability of the assembly during welding and service.

[0057] In this embodiment, a symmetrical V-shaped welding groove 5 is machined on the outer side of the butt joint of the two semi-ring forgings. The groove angle is 45° to 60°. This angle range ensures sufficient filler metal to achieve full weld penetration while avoiding excessive groove size, which could lead to welding deformation and material waste. Furthermore, the V-shaped welding groove 5 can be combined with an appropriate blunt edge, such as 1 mm to 2 mm, to effectively prevent burn-through and obtain a high-quality weld joint.

[0058] In an optional embodiment of the present invention, step S2, before performing full penetration welding on the V-shaped weld groove 5 of the interference fit assembly, further includes:

[0059] The V-shaped welding groove 5 and its surrounding area within at least 20 mm are ground to remove oil and oxide scale until a metallic luster is exposed. This pretreatment promotes stable arc combustion and molten pool flow, reduces defects such as porosity and slag inclusions, and improves the internal quality and mechanical properties of the weld.

[0060] Step S2 involves heating the female end forging 1 of the two semi-ring forgings and pressing the male end forging 2 into the female end forging 1, forming an interference fit assembly through the male-female socket positioning structure, including:

[0061] The female end forging 1 is heated to 220-350°C;

[0062] Under heating conditions, the male end forging 2 is axially pressed into the female end forging 1, so that the mating surfaces of the male and female socket positioning structure form an interference fit with a single-sided interference of 0.12 to 0.18 mm. After cooling, the interference positioning assembly is obtained.

[0063] This embodiment employs induction heating to heat the female forging 1 to 220–350°C, expanding its inner bore using the principle of thermal expansion. The male forging 2 is then axially pressed in, creating an interference fit with a unilateral interference of 0.12–0.18 mm. After natural cooling to room temperature, it is locked, forming an interference-fit assembly. This embodiment utilizes a heating temperature range of 220–350°C to ensure sufficient expansion for assembly without excessively affecting material properties. Furthermore, the 0.12–0.18 mm unilateral interference range ensures sufficient preload after assembly, resulting in a tight bond between the two ring forging halves. This improves overall coaxiality and rigidity, and avoids stress concentration caused by excessive interference.

[0064] In an optional embodiment of the present invention, step S3 involves full penetration welding of the V-shaped weld groove 5 of the interference fit assembly to obtain a welded part, including:

[0065] Preheating is performed on the interference fit assembly before welding;

[0066] An all-position automatic gas shielded welding equipment with a track is used, along with the automatic lateral oscillation of the welding torch, to weld the V-shaped welding groove 5 with low heat input. During the welding process, the interpass temperature is controlled to obtain the welded part.

[0067] Preheating the interference fit assembly before welding includes preheating the interference fit assembly to 80-150°C.

[0068] Controlling the interpass temperature during welding includes maintaining the interpass temperature between 150 and 200°C during the welding process.

[0069] This embodiment employs a preheating method to preheat the entire weld area to 80–150°C. Then, a track-type, all-position automatic gas-shielded welding process is used for the five-ring V-groove weld. The welding torch is equipped with automatic lateral oscillation, and welding parameters are adaptively adjusted in all positions. The bevel angle is 25°–30° on each side, and the assembly gap and misalignment are strictly controlled. The weld area is thoroughly cleaned before welding, and preheating and interpass temperature control are performed according to specifications. Low heat input is used throughout the welding process to prevent excessively high local temperatures and shortened heating time in the weld area. This method reduces thermal stress by preheating before welding, thereby minimizing the risk of cold cracking. Setting the preheating temperature to 80–150°C effectively reduces the hardening tendency and cold cracking sensitivity of the weld joint. Simultaneously, the use of a track-type, all-position automatic gas-shielded welding system, coupled with automatic lateral oscillation of the welding torch, ensures uniform welding, guaranteeing the consistency and stability of the weld formation. Furthermore, welding with low heat input and controlling the interpass temperature avoids localized overheating, reduces the heat-affected zone and welding deformation, and ensures full penetration and high quality of the weld. Controlling the interpass temperature at 150–200°C ensures sufficient microstructural transformation of the weld metal and the heat-affected zone, preventing hydrogen-induced cracking due to excessively low temperatures or grain coarsening due to excessively high temperatures.

[0070] In this embodiment, a V-shaped bevel 5 is set on the outside of the butt joint, which, together with the sealing surface of the male and female parts, achieves full penetration of the weld. At the same time, the mating surface of the male and female parts is a high-precision machined surface, which achieves complete interference fit after heat fitting, forming an annular sealing barrier to prevent welding slag from seeping into the mating gap and to eliminate internal welding defects.

[0071] In an optional embodiment of the present invention, step S3 involves full penetration welding of the V-shaped weld groove 5 of the interference fit assembly to obtain a welded part, including:

[0072] The V-shaped weld bevel 5 is segmented and symmetrically welded using gas shielded welding to obtain the welded part.

[0073] This embodiment uses a segmented symmetrical welding method to make the welding heat distribution more uniform, reduce thermal deformation caused by local overheating, and ensure the overall dimensional accuracy of the welded parts.

[0074] In an optional embodiment of the present invention, step S4 involves stress-relieving tempering of the welded part to obtain the excavator boom center seat, comprising:

[0075] The welded part is placed in a heating furnace and subjected to stress-relieving tempering at a temperature of 500-580°C, and then naturally cooled to room temperature to obtain the excavator boom center seat.

[0076] In this embodiment, the entire assembly undergoes stress-relieving tempering at 500–580℃ to eliminate assembly stress and residual welding stress, and the datum surface is then precision-machined to complete the finished product. The 500–580℃ tempering temperature range effectively releases residual stress generated during assembly and welding, without affecting the mechanical properties of the base material. Natural cooling avoids secondary stress generation, thus improving the dimensional stability and fatigue life of the workpiece.

[0077] Secondly, this invention proposes a split-type forging and welding forming system for the center seat of an excavator boom, employing the aforementioned split-type forging and welding forming method for the center seat of an excavator boom, including:

[0078] The processing module is used to obtain two symmetrical semi-ring forgings, and to process matching male and female socket positioning structures on the mating end faces of the two semi-ring forgings, and to process symmetrical V-shaped welding grooves 5 on the outside of the mating joint.

[0079] The assembly module is used to heat the female end forging 1 of the two semi-ring forgings and press the male end forging 2 into the female end forging 1, forming an interference-fit assembly through the male-female socket positioning structure.

[0080] The welding module is used to perform full penetration welding on the V-shaped welding groove 5 of the interference positioning assembly to obtain a welded part.

[0081] A heat treatment module is used to perform stress-relieving tempering on the welded parts to obtain the center seat of the excavator boom.

[0082] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0083] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1The function specified in one or more boxes.

[0084] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0085] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

[0086] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for forging and welding a split-type center seat for an excavator boom, characterized in that, Includes the following steps: Two symmetrical semi-ring forgings are obtained, and matching male and female socket positioning structures are machined on the mating end faces of the two semi-ring forgings respectively, and symmetrical V-shaped welding grooves are machined on the outside of the mating joint. The female end forging of the two semi-ring forgings is heated, and the male end forging is press-fitted into the female end forging, forming an interference-fitted assembly through the male-female socket positioning structure. Full penetration welding is performed on the V-shaped welding groove of the interference fit assembly to obtain a welded part; The welded part is subjected to stress-relieving tempering treatment to obtain the center seat of the excavator boom.

2. The method for forging and welding a split-type center seat for an excavator boom according to claim 1, characterized in that, The female end forging of the two semi-ring forgings is heated, and the male end forging is press-fitted into the female end forging, forming an interference fit assembly through the male-female socket positioning structure, including: The female end forging is heated to 220-350°C; Under heating conditions, the male end forging is axially pressed into the female end forging, so that the mating surfaces of the male and female socket positioning structure form an interference fit with a single-sided interference of 0.12 to 0.18 mm. After cooling, the interference positioning assembly is obtained.

3. The method for forging and welding a split-type center seat for an excavator boom according to claim 1, characterized in that, The V-shaped weld bevel of the interference fit assembly is subjected to full penetration welding to obtain a welded part, including: Preheating is performed on the interference fit assembly before welding; An all-position automatic gas shielded welding equipment with a track is used, along with the automatic lateral oscillation of the welding torch, to weld the V-shaped weld bevel with low heat input. The interpass temperature is controlled during the welding process to obtain the welded part.

4. The method for forging and welding a split-type center seat for an excavator boom according to claim 3, characterized in that, Preheating the interference fit assembly before welding includes preheating the interference fit assembly to 80-150°C. Controlling the interpass temperature during welding includes maintaining the interpass temperature between 150 and 200°C during the welding process.

5. The method for forging and welding a split-type center seat for an excavator boom according to claim 1, characterized in that, The V-shaped weld bevel of the interference fit assembly is subjected to full penetration welding to obtain a welded part, including: The V-shaped weld bevel is segmented and symmetrically welded using gas shielded welding to obtain the welded part.

6. The method for forging and welding a split-type center seat for an excavator boom according to claim 1, characterized in that, Before performing full penetration welding on the V-shaped weld bevel of the interference fit assembly, the process further includes: The V-shaped weld bevel and the area within at least 20mm around it are ground to remove oil and oxide scale until the metal luster is exposed.

7. The method for forging and welding a split-type center seat for an excavator boom according to claim 1, characterized in that, The welded part is subjected to stress-relief tempering treatment to obtain the excavator boom center seat, comprising: The welded part is placed in a heating furnace and subjected to stress-relieving tempering at a temperature of 500-580°C, and then naturally cooled to room temperature to obtain the excavator boom center seat.

8. The method for forging and welding a split-type center seat for an excavator boom according to claim 1, characterized in that, The process of machining mutually matching male and female socket positioning structures on the mating end faces of the two semi-ring forgings includes: An annular inner step is machined on the mating end face of the female end forging, and an annular outer boss matching the annular inner step is machined on the mating end face of the male end forging. The inner annular step and the outer annular protrusion are used as the female-female socket positioning structure to form a bidirectional positioning mating surface in the axial and radial directions during press fitting.

9. The method for forging and welding a split-type center seat for an excavator boom according to claim 1, characterized in that, The symmetrical V-shaped welding bevel is machined on the outer side of the butt joint, including: The V-shaped welding bevel is machined on the outer side of the butt joint, and the total angle of the V-shaped welding bevel is 45° to 60°.

10. A split-type forging and welding forming system for the center seat of an excavator boom, using the split-type forging and welding forming method for the center seat of an excavator boom as described in any one of claims 1 to 9, characterized in that... include: The processing module is used to obtain two symmetrical semi-ring forgings, and to process matching male and female socket positioning structures on the mating end faces of the two semi-ring forgings, and to process symmetrical V-shaped welding grooves on the outside of the mating joint. The assembly module is used to heat the female end forging of the two semi-ring forgings and press the male end forging into the female end forging, forming an interference-fit assembly through the male-female socket positioning structure. A welding module is used to perform full penetration welding on the V-shaped welding groove of the interference fit assembly to obtain a welded part. A heat treatment module is used to perform stress-relieving tempering on the welded parts to obtain the center seat of the excavator boom.

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