A welding method applied to long straight welds of main structural parts of mining excavators

Abstract

This invention discloses a welding method for long straight welds on the main structural components of mining excavators. A reverse-deformation hydraulic tool is used to hydraulically compress and reverse-deform the base plate of the main structural component by 7-9mm, offsetting the deformation of the base plate caused by the welding of the four long straight welds. This achieves the machining flatness requirement of less than or equal to 3mm for the base plate after welding, eliminating the need for a post-weld shaping process. The preheating temperature for each weld layer of the long straight welds is 100℃-150℃, and the interlayer temperature must be maintained above 100℃ during welding. A symmetrical welding sequence is used. After the main structural component is fully welded, it undergoes vibration aging treatment, followed by ultrasonic impact treatment of the weld toes of the long straight welds, and finally magnetic particle testing. This invention solves the problems of base plate deformation caused by welding long straight welds on the main structural components and the increased residual stress and significantly reduced fatigue life of the welds due to reverse-deformation welding.

Description

Technical Field

[0001] This invention relates to a novel welding method for long straight welds on the main structural components of mining excavators, applicable to the welding of main structural components of large mining excavators, and belonging to the field of welding technology in engineering machinery manufacturing. Background Technology

[0002] Large mining excavators are mainly used in open-pit coal mining, metal ore mining, and major project construction. The main structural components of the mining excavator are its core parts, and the material is primarily Q355 stainless steel.

[0003] The main structural components of mining excavators are complex and difficult to manufacture. In particular, the welding of the four composite welds between the base plate and the vertical plate causes significant deformation of the base plate, resulting in the main structural components failing to meet the machining requirements of a flatness of less than or equal to 3mm after welding. Currently, flame-backed shaping is used to address this issue. However, this flame-backed shaping significantly increases manufacturing time and costs, reduces production efficiency, and the high-temperature baking can alter the microstructure of the base material, increasing the risk of reduced service life for the main structural components. Therefore, a reasonable welding process must be adopted, employing techniques such as large base plate anti-deformation, preheating before welding, symmetrical welding, and post-weld stress removal to solve the problem of post-weld deformation of the main base plate, improve production efficiency, reduce residual stress in the welds, and enhance the quality and service life of the structural components. Summary of the Invention

[0004] To address the technical problems associated with welding long straight welds in the main structural components of mining excavators, this invention provides a novel welding method for long straight welds in the main structural components of mining excavators. This method results in minimal deformation of the base plate after welding, low residual stress in the weld, no cracks in the weld, good weld formation, good overall mechanical properties, high welding efficiency, and convenient and simple operation.

[0005] This invention is implemented according to the following technical solution:

[0006] A welding method for long straight welds applied to the main structural components of mining excavators includes the following steps:

[0007] S1: Place the assembled main structural components of the mining excavator onto the anti-deformation hydraulic clamp and tighten them. Press the pressure head down a predetermined distance on both sides and the front edge of the base plate, and mechanically press and fix the middle of the base plate.

[0008] S2: Four long straight welds are marked on the vertical plate and bottom plate of the main structural component of the mining excavator. All four welds are composite fillet welds. The front welds are numbered 1 and 2 respectively, and the back welds are numbered 3 and 4 respectively.

[0009] Welds 1 to 4 are designed as four layers and five passes. From bottom to top, the first layer is the root pass, with pass a; the second and third layers are the filler layers, with passes b and c respectively; and the fourth layer is the cover layer, also called the working layer, with passes d and e respectively.

[0010] S3: Welding sequence: The welding method of symmetrical root pass, symmetrical fill pass, and symmetrical cover pass is adopted. Welds 1-4-2-3 are welded in sequence, followed by root pass welding, fill pass welding, and finally cover pass welding.

[0011] S4: Preheating: Preheat to 100℃~150℃ before welding. Preheating is done by flame heating.

[0012] S5: Welding the root pass of the weld: Weld the straight weld seam 1-4-2-3 in sequence, a weld pass;

[0013] S6: Weld filler layer welding: Weld the b~c welds of straight weld seam 1-4-2-3 in sequence;

[0014] S7: Welding of the cover layer: Weld the d~e welds of straight welds 1-4-2-3 in sequence;

[0015] S8: Ensure the interpass temperature is above 100℃ during welding;

[0016] S9: Vibration aging treatment is carried out after the main structural components of the mining excavator are welded.

[0017] S10: After the vibration aging treatment of the main structural components of the mining excavator is completed, ultrasonic impact treatment is performed on the weld toe of the long straight weld.

[0018] S11: After the main structural components of the mining excavator are subjected to ultrasonic impact, they are placed still, and then the long straight weld is subjected to magnetic particle testing.

[0019] In some embodiments, the welding method used is metal arc welding (MAHW), the shielding gas composition is 84%Ar+16%CO2, the gas flow rate is 15-20L / min, the gas pressure is 0.4-0.6MPa, the root pass is welded using a deep penetration pulse function, and the filler and capping layers are welded using a DC reverse polarity function.

[0020] In some embodiments, the root pass, fill pass, and cover pass of the long straight weld seam are all welded using the ship-shaped weld position.

[0021] In some embodiments, a multi-layer, multi-pass symmetrical welding method is adopted, the welding thickness of each layer is controlled within 3.5mm, and the weld overlap is 25%~35%.

[0022] In some embodiments, when performing the root pass welding of the weld: the welding wire for the a pass of weld 1 to 4 is an ER50-6 welding wire with a diameter of 1.2mm, the current I=310±10A, and the voltage U=33±1V.

[0023] When welding the filler layer: for welds b to c of welds 1 to 4, use ER50-6 welding wire with a diameter of 1.2mm, current I = 280~290A, voltage U = 30~31V;

[0024] When welding the cover layer of the weld: for welds 1 to 4, the welding wire for d to e welds is ER50-6 with a diameter of 1.2mm, the current I = 270~280A, and the voltage U = 29~30V.

[0025] In some embodiments, after the main structural components of the mining excavator are welded, vibration aging treatment is performed. The vibration device is clamped at the peak position of the vibration frequency of the main structural component, and the eccentricity value of vibration parameters is 20 for steps 1-2, 40 for steps 3-4, and 20 for step 5. The vibration duration of each step is 8 minutes, and the total vibration duration is 40 minutes.

[0026] In some embodiments, after the vibration aging treatment of the main structural components of the mining excavator is completed, ultrasonic impact treatment is performed on the weld toe of the long straight weld. During the impact process, the impact gun head is perpendicular to the weld toe, and the impact parameters are set as follows: current: 1.6-2A, amplitude: 20-25μm, uniform vibration at the same position for 40-60mm for 2-3 times or more, and impact speed: 30-50mm / min.

[0027] In some embodiments, the assembled main structural components of the mining excavator are placed on the anti-deformation hydraulic clamp and tightened. The hydraulic pressure is set to 150MPa, and the pressure head presses down 7~9mm on both sides of the base plate and the front edge of the base plate.

[0028] In some embodiments, the anti-deformation fixture mainly consists of a fixture base, a hydraulic anti-deformation fixture, a mechanical clamping fixture in the middle of the base plate, a mechanical limiting clamping fixture in the base plate, and a mechanical limiting clamping fixture at the tail of the main body.

[0029] The beneficial effects of this invention are:

[0030] The main structural component's base plate is hydraulically clamped to counteract deformation, offsetting the deformation caused by the welding of the four long straight welds on the base plate. This composite residual stress removal treatment significantly reduces the high residual stress in the long straight welds caused by the counter-deformation constraint. The process is simple to operate, requires low technical skills from welding operators, results in minimal welding deformation of the base plate, low residual stress in the welds, and high welding quality and stability. Furthermore, this novel welding process for the long straight welds of the main structural component significantly improves production efficiency and reduces production costs. Attached Figure Description

[0031] The accompanying drawings, as part of this invention, are provided to further illustrate the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation thereof. Clearly, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0032] In the attached diagram:

[0033] Figure 1 This is a clamping diagram of the anti-deformation fixture of the present invention;

[0034] Figure 2 This is a structural diagram of the anti-deformation fixture of the present invention;

[0035] Figure 3 The diagram shows the weld seam type, numbering, and layer diagram of a single weld seam according to the present invention (a is a front view, b is a back view).

[0036] In the diagram, sequence Ⅰ is the main structural component of the mining excavator, sequence Ⅱ is the anti-deformation hydraulic clamp, sequence 5 is the clamp base, sequence 6 is the hydraulic anti-deformation clamp, sequence 7 is the mechanical clamping fixture in the middle of the large base plate, sequence 8 is the mechanical limit clamping fixture in the large base plate, and sequence 9 is the mechanical limit clamping fixture at the tail of the main body.

[0037] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this invention. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this invention, and should not be construed as limiting this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. The embodiments of this invention will be described in detail below with reference to the accompanying drawings.

[0039] To ensure welding of the main base plate in the reverse deformation position, this embodiment uses a reverse deformation hydraulic clamp, such as... Figure 2As shown, it mainly consists of a clamp base 5, a hydraulic anti-deformation clamp 6, a mechanical clamping fixture in the middle of the large base plate 7, a mechanical limit clamping fixture in the base plate 8, and a mechanical limit clamping fixture at the tail of the main body 9.

[0040] The main structural components of a mining excavator are its core parts. These components are complex and difficult to manufacture, especially during the welding of the four composite welds between the base plate and the vertical plate, which causes significant deformation of the base plate. To reduce the deformation of the large base plate caused by the welding of the long straight welds, a reverse deformation welding technique is used. This significantly reduces the deformation of the large base plate caused by the welding of the long straight welds. Combined with composite stress relief treatment, residual stress in the welds is reduced. The gas metal arc welding method and a reverse deformation welding fixture are used to position the workpiece's large base plate in the opposite direction of the long straight weld shrinkage during welding operations. (Refer to...) Figure 1 , Figure 2 , Figure 3 As shown, the welding process steps for the long straight weld seam of the mining body using the present invention are as follows:

[0041] S1: Place the assembled mining excavator main structural component I on the anti-deformation hydraulic clamp II and tighten it. Set the hydraulic pressure to 150Mpa. Press the pressure head down 7~9mm on both sides and the front edge of the base plate. Mechanically tighten and fix the middle of the base plate.

[0042] S2: Four long straight welds are marked on the vertical plate and bottom plate of the main structural component I of the mining excavator. All four welds are composite fillet welds. The welds on the front side are numbered 1 and 2, and the welds on the back side are numbered 3 and 4.

[0043] Welds 1 to 4 are designed as four layers and five passes. From bottom to top, the first layer is the root pass, with pass a; the second and third layers are the filler layers, with passes b and c respectively; and the fourth layer is the cover layer, also called the working layer, with passes d and e respectively.

[0044] S3: Welding sequence: The welding method of symmetrical root pass, symmetrical fill pass, and symmetrical cover pass is adopted. Welds 1-4-2-3 are welded in sequence, followed by root pass welding, fill pass welding, and finally cover pass welding.

[0045] S4: Preheating: Preheat to 100℃~150℃ before welding. Preheating is done by flame heating.

[0046] S5: Welding the root pass of weld seam: For weld seam 1 to 4, use ER50-6 welding wire with a diameter of 1.2mm, current I=310±10A, voltage U=33±1V, and weld the a pass of straight weld seam 1-4-2-3 in sequence.

[0047] S6: Weld filler layer welding: For welds 1-4, the b-c welds are welded with ER50-6 wire with a diameter of 1.2mm, current I=280~290A, voltage U=30~31V, and the b-c welds of straight welds 1-4-2-3 are welded in sequence.

[0048] S7: Welding of the cover layer of weld seam: For the d~e weld seams of weld seams 1~4, use ER50-6 wire with a diameter of 1.2mm, current I=270~280A, voltage U=29~30V, and weld the d~e weld seams of straight weld seams 1-4-2-3 in sequence.

[0049] S8: Ensure the interpass temperature is above 100℃ during welding;

[0050] S9: After the main structural component I of the mining excavator is welded, it undergoes vibration aging treatment. The vibration aging is performed using the LH spectrum vibration aging equipment produced by Beijing Xiangbo Technology Co., Ltd. The vibration equipment is clamped at the peak position of the main structural component's own vibration frequency, and the eccentricity value of vibration parameters is 20 for steps 1-2, 40 for steps 3-4, and 20 for step 5. The vibration duration of each step is 8 minutes, and the total vibration duration is 40 minutes.

[0051] S10: After the vibration aging treatment of the main structural component I of the mining excavator is completed, ultrasonic impact treatment is performed on the weld toe of the long straight weld. The ultrasonic impact is performed using the UIT125 ultrasonic impact equipment produced by Tianjin Yipu Technology Development Co., Ltd. During the impact process, the impact gun head is perpendicular to the weld toe, and the impact parameters are set as follows: current: 1.6-2A, amplitude: 20-25μm, uniform vibration at the same position for 40-60mm for 2-3 times or more, impact speed: 30-50mm / min.

[0052] S11: After ultrasonic impaction of the main structural component I of the mining excavator, it is left to stand still for 24 hours, and then magnetic particle testing is performed on the long straight weld.

[0053] In this embodiment, the welding method used is metal arc welding (MAHW), the shielding gas composition is 84% ​​Ar + 16% CO2, the gas flow rate is 15-20 L / min, and the gas pressure is 0.4-0.6 MPa. The root pass is welded using a deep penetration pulse function, while the filler and capping passes are welded using a DC reverse polarity function. The long straight weld is welded in a ship-shaped welding position for the root pass, filler, and capping passes. Residual welding stress is removed by combining vibration aging and ultrasonic waves. The weld is welded in a multi-layer, multi-pass symmetrical manner, with the thickness of each weld pass controlled within 3.5 mm and the weld overlap being 25%~35%.

[0054] Practice has shown that using hydraulic clamping to counteract deformation of the main structural component's base plate effectively offsets the deformation caused by the welding of the four long straight welds on the base plate. This composite residual stress removal treatment significantly reduces the high residual stress in the long straight welds caused by the counteracting deformation constraint. The process is simple to operate, requires low technical skills from welding operators, results in minimal welding deformation of the base plate, low residual stress in the welds, and high welding quality and stability. Furthermore, this novel welding process for the long straight welds of the main structural component significantly improves production efficiency and reduces production costs.

[0055] In summary, this invention utilizes the hydraulic pressure head of a reverse deformation hydraulic clamp to reverse deform the base plate by 7-9 mm under a force of 150 MPa before welding the long straight welds. This counteracts the deformation of the base plate caused by the welding of the four long straight welds of the main structural component, achieving the machining flatness requirement of less than or equal to 3 mm for the base plate after welding of the main structural component, thus eliminating the post-weld shaping process of the base plate. Preheating to 100℃-150℃ before welding and ensuring the interpass temperature is above 100℃ during welding reduces residual welding stress and welding deformation. The welds are produced using multi-layer, multi-pass welding. A reasonable welding sequence and different welding positions reduce heat input and welding deformation, improve stress distribution during the welding process, and reduce stress magnitude. After the main structural components are fully welded, a vibration aging device is used to perform a 40-minute vibration aging treatment on the main body. Then, an ultrasonic stress relief device is used to subject the weld toe of the long straight weld to ultrasonic impact. After standing still for 24 hours, the long straight weld is subjected to magnetic particle inspection. This solves the problems of deformation of the base plate caused by welding the long straight weld of the main structural components and increased residual stress and significantly reduced fatigue life of the weld caused by reverse deformation welding. The reverse deformation welding method for the long straight weld of the main body of this invention is simple to operate, requires low technical skills from welding operators, produces an aesthetically pleasing weld, and has low residual stress and high fatigue life. Furthermore, the use of this long straight weld welding process eliminates the post-weld base plate straightening process, significantly improving production efficiency and reducing production costs.

[0056] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0057] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features found in other embodiments but not others, combinations of features from different embodiments are also within the scope of protection of this invention and form different embodiments. For example, in the embodiments described above, those skilled in the art can use them in combination based on known technical solutions and the technical problems to be solved by this application.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A welding method for long straight welds applied to the main structural components of mining excavators, characterized in that, Includes the following steps: S1: Place the assembled main structural components of the mining excavator onto the anti-deformation hydraulic clamp and clamp them in place. Press the pressure head down a predetermined distance on both sides and the front edge of the base plate, and mechanically press and fix the middle of the base plate. S2: Four long straight welds are marked on the vertical plate and bottom plate of the main structural component of the mining excavator. All four welds are composite fillet welds. The front welds are numbered 1 and 2 respectively, and the back welds are numbered 3 and 4 respectively. Welds 1 to 4 are designed as four layers and five passes. From bottom to top, the first layer is the root pass, with pass a; the second and third layers are the filler layers, with passes b and c respectively; and the fourth layer is the cover layer, also called the working layer, with passes d and e respectively. S3: Welding sequence: The welding method of symmetrical root pass, symmetrical fill pass, and symmetrical cover pass is adopted. Welds 1-4-2-3 are welded in sequence, followed by root pass welding, fill pass welding, and finally cover pass welding. S4: Preheating: Preheat to 100℃~150℃ before welding. Preheating is done by flame heating. S5: Welding the root pass of the weld: Weld the straight weld seam 1-4-2-3 in sequence, a weld pass; S6: Weld filler layer welding: Weld the b~c welds of straight weld seam 1-4-2-3 in sequence; S7: Welding of the cover layer: Weld the d~e welds of straight welds 1-4-2-3 in sequence; S8: Ensure the interpass temperature is above 100℃ during welding; S9: Vibration aging treatment is carried out after the main structural components of the mining excavator are welded. S10: After the vibration aging treatment of the main structural components of the mining excavator is completed, ultrasonic impact treatment is performed on the weld toe of the long straight weld. S11: After the main structural components of the mining excavator are subjected to ultrasonic impact, they are placed still, and then the long straight weld is subjected to magnetic particle testing. When performing the root pass welding of the weld: for the a pass of welds 1 to 4, use ER50-6 welding wire with a diameter of 1.2mm, current I=310±10A, voltage U=33±1V. When welding the filler layer: for welds b to c of welds 1 to 4, use ER50-6 welding wire with a diameter of 1.2mm, current I = 280~290A, voltage U = 30~31V; When welding the cover layer of the weld: the welding wire for the d~e welds of welds 1~4 is ER50-6 welding wire with a diameter of 1.2mm, the current I=270~280A, and the voltage U=29~30V.

2. The welding method for long straight welds applied to the main structural components of mining excavators according to claim 1, characterized in that: The welding method used is metal arc welding (MAHW), the shielding gas composition is 84%Ar+16%CO2, the gas flow rate is 15-20L / min, and the gas pressure is 0.4-0.6MPa. The root pass is welded using a deep penetration pulse function, while the fill and cap passes are welded using a DC reverse polarity function.

3. The welding method for long straight welds applied to the main structural components of mining excavators according to claim 1, characterized in that: For long straight welds, the root pass, fill pass, and cap pass are all welded using the ship-shaped weld position.

4. The welding method for long straight welds applied to the main structural components of mining excavators according to claim 1, characterized in that: Multi-layer, multi-pass symmetrical welding is adopted, with the welding thickness of each layer controlled within 3.5mm and the weld overlap of 25%~35%.

5. The welding method for long straight welds applied to the main structural components of mining excavators according to claim 1, characterized in that: After the main structural components of the mining excavator are welded, vibration aging treatment is carried out. The vibration device is clamped at the peak position of the vibration frequency of the main structural component, and the eccentricity value of vibration parameters is 20 for steps 1-2, 40 for steps 3-4, and 20 for step 5. The vibration duration of each step is 8 minutes, and the total vibration duration is 40 minutes.

6. The welding method for long straight welds applied to the main structural components of mining excavators according to claim 1, characterized in that: After the vibration aging treatment of the main structural components of the mining excavator is completed, ultrasonic impact treatment is performed on the weld toe of the long straight weld. During the impact process, the impact gun head is perpendicular to the weld toe, and the impact parameters are set as follows: current: 1.6-2A, amplitude: 20-25μm, uniform back and forth vibration at 40-60mm at the same position for 2-3 rounds, impact speed: 30-50mm / min.

7. The welding method for long straight welds applied to the main structural components of mining excavators according to claim 1, characterized in that: Place the assembled main structural components of the mining excavator onto the anti-deformation hydraulic clamp and clamp them in place. Set the hydraulic pressure to 150MPa and press the pressure head down 7-9mm at both sides and the front edge of the base plate.

8. The welding method for long straight welds applied to the main structural components of mining excavators according to claim 1, characterized in that: The anti-deformation hydraulic clamp mainly consists of a clamp base, a hydraulic anti-deformation clamp, a mechanical clamping fixture in the middle of the base plate, a mechanical limit clamping fixture in the base plate, and a mechanical limit clamping fixture at the tail of the main body.

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