Method for improving welding quality and efficiency of hydraulic support push rod

Abstract

The invention relates to a method for improving the welding quality and efficiency of a hydraulic support push rod, the method comprises pretreatment before tack solidification, push rod assembly preheating, assembly welding and postweld heat treatment, and meanwhile, compared with the prior art, the lap joint mode of a cover plate and a main rib plate is changed. According to the method, the machining and assembling difficulty of the push rod tailor-welded part can be greatly reduced, the production period is shortened, and meanwhile the welding quality of the robot for welding the push rod is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mechanical welding, in particular to a method for improving the welding quality and efficiency of a hydraulic support push rod. BACKGROUND

[0002] The push rod, also known as a push moving rod or a push moving frame, is a connecting carrier and a key force transmission component in a hydraulic support push moving and moving mechanism of a fully mechanized coal mining face. The push rod mainly completes the push moving and moving functions through the extension and retraction of a push moving jack. The push rod is mostly made of high-strength medium-thick steel plates (generally Q890) and is spliced and welded. Therefore, the welding quality and efficiency are very important. In recent years, with the popularization of welding robots, a seat type welding robot is widely used in the welding of the push rod. During the welding of the steel plate, the workpiece processing error, the assembly error and the thermal deformation during the welding process will inevitably cause a certain deviation between the teaching trajectory of the robot and the actual welding trajectory. How to compensate for the trajectory deviation of the robot and complete the accurate welding process is the key to ensuring the welding quality.

[0003] In the production site, some schemes do not compensate for the welding trajectory deviation of the robot, but rely on the processing accuracy and the assembly accuracy of the spliced parts to ensure the welding quality. However, this will increase the production cost and greatly reduce the production efficiency. Some other schemes rely on visual tracking to obtain the relative position of the welding part and the welding seam and the relevant information of the bevel and the molten pool. However, the visual tracking obtains a large amount of information, the system is complex, the cost is high, the scanned range is not the actual welding point, and the information such as magnetic deviation, welding wire bending interference and the like cannot be obtained.

[0004] During the welding of the push rod, the preheating temperature before welding is 150-200℃, and the final welding temperature should not be lower than 100℃. Most of the existing technologies use a heating furnace for heating or flame heat compensation. The energy consumption is large, and the construction period is long. In order to release the welding stress, the Q890 base material level push rod needs to be subjected to overall heat treatment after welding. The heating temperature is high, and the production cycle is long. SUMMARY

[0005] In view of the above shortcomings of the prior art, the purpose of the present application is to provide a method for improving the welding quality and efficiency of a hydraulic support push rod. The method can greatly reduce the processing and assembly difficulty of the push rod spliced parts, shorten the production period, and improve the welding quality of the push rod welded by the robot.

[0006] In order to achieve the above purpose, the present application provides a method for improving the welding quality and efficiency of a hydraulic support push rod. The process after the assembly of the push rod includes point fixing, preheating, welding and post-welding heat treatment. The method comprises the following steps:

[0007] (1) heating the area with a diameter of 150mm around the point fixing welding joint to 100-150℃ and then performing point fixing;

[0008] (2) using electromagnetic induction heating to preheat the push rod assembly after tack welding to 150-180°C;

[0009] (3) welding the preheated push rod assembly, during the welding process, using multi-layer and multi-pass welding, controlling the interlayer temperature <200°C, timely slag removal between layers, the temperature before welding is not less than 150°C, the final welding temperature is not less than 100°C, and the welding area is covered with asbestos for heat preservation;

[0010] (4) the post-weld heat treatment is to put the workpiece into the furnace for hydrogen removal treatment after each weld is completed: furnace temperature 250°C, holding time 2 hours,

[0011] The push rod is a rectangular cross-section box structure spliced from a medium-thick steel plate, including a bottom plate, two main rib plates, and a cover plate, wherein one end face of each main rib plate is partially overlapped on both ends of the bottom plate, the lower surface of the cover plate is smaller in width than the upper surface, and both ends of the lower surface of the cover plate are partially overlapped on the other end face of the two main rib plates.

[0012] Further, the mutual connection of the bottom plate, the main rib plate and the cover plate forms an angular gap for the fillet weld.

[0013] Further, the medium-thick steel plate is a Q890 medium-thick steel plate with a thickness of 12-50mm, preferably 20-30mm; at least one side length of the triangular cross-section of the angular gap is not less than 2 / 3 of the thickness of the steel plate, preferably not less than 3 / 4. For example, the gap length is 8mm or 15mm.

[0014] Further, the heating in step (1) is performed using a baking gun, flame or resistance heater. Using a baking gun, flame or resistance heater for heating has the advantage of convenient and flexible operation, and the preheating before tack welding has met the requirements.

[0015] The tack welding is to temporarily fix the parts of the push rod together according to the drawing position with a very short weld (usually 5-15mm) to form a movable assembly, to ensure that the parts are not misaligned during subsequent handling and clamping, so as to facilitate subsequent complete welding, and to provide a stable and repeatable reference for welding robot parameter setting.

[0016] Q890 used in the present application is a high-strength steel, and the high carbon equivalent leads to high hardenability of the material. Therefore, even if the spot welding operation is performed, the heat affected zone is prone to generate hard and brittle martensite, and becomes a micro-crack source, which brings hidden troubles of crack propagation in subsequent formal welding or service. The technical scheme of the present application heats the whole circle with a diameter of 150 mm around the welding spot to 100-150 DEG C before spot welding, so that the heat is sufficient to cover the spot welding seam and the heat affected zone thereof, and the region can still be transformed at a relatively slow cooling speed after the spot welding is completed, so as to inhibit the martensite. Meanwhile, the preheating temperature range of the spot welding is not high, and is just below the lower limit of the preheating window of Q890, so that the structure is not coarsened.

[0017] Further, in step (2), the preheating time of the push rod assembly is 50-80 min, preferably 55-65 min. The electromagnetic induction heating has the advantages of high heat efficiency, fast heating speed, safety, energy saving and the like, as compared with the traditional heating modes such as heating furnace or torch heating. The preheating time of the push rod box body by the traditional mode is about 4 h, while the preheating time by the electromagnetic induction heating is about 1 h, which greatly reduces the preparation time before welding, and saves a lot of time for formal welding.

[0018] Further, in step (3), the welding seam area is heated to the preheating temperature again by the electromagnetic induction heating when each welding seam is welded to 1 / 2-2 / 3 thickness. The long welding seam is continuously welded, and the heat is dissipated, so that the temperature between layers can drop below the critical value. The heat supplement can stabilize the temperature between layers in the process window, and prevent cracks. Meanwhile, the heat supplement is equivalent to "small tempering", which can reduce the bending deformation caused by the temperature gradient, and improve the dimensional accuracy.

[0019] Further, in step (3), the arc tracking function is applied in the welding process. The arc tracking function can automatically detect the position of the welding seam, find the center of the welding seam, correct the track deviation in the welding process in real time, and can automatically compensate according to the groove width and depth, so as to ensure that the welding process is continuous.

[0020] Meanwhile, due to the deformation of the spliced parts (main rib plate, cover plate) and the non-uniform groove size of the cover plate, the groove width and depth are often not uniform after the push rod is assembled. The use of the arc tracking function can make the overall welding seam not affected by the assembly gap and the non-uniform size, and the appearance is full and uniform, and the reinforcement is consistent.

[0021] Further, the arc tracking function is realized by setting the arc tracking parameters of the welding robot. The arc tracking parameters are a key welding preparation work, and need to be combined with the actual situation, and through continuous testing and adjustment, the most suitable parameter setting can be found. It is generally recommended to use the default value for trial welding, and then to fine-tune according to the welding seam quality.

[0022] In one embodiment, the arc tracking parameters include: an extension length of 18-21 mm, a real-time current deviation from the set welding current of ±20 A, and an arc tracking speed of 65-75% of the welding speed; preferably, the extension length is 20 mm, the real-time current deviation from the set welding current is ±15 A, and the arc tracking speed is 70% of the welding speed.

[0023] Arc tracking identifies the weld center by detecting minute changes in arc voltage / current in real time. Among the parameters mentioned above, wire extension refers to the length of the welding wire from the tip of the contact tip to the workpiece surface. During welding, the wire extension must remain constant throughout the entire weld pass. The deviation between the real-time current and the set welding current represents the allowable current fluctuation range during welding: as long as the difference between the real-time current and the set welding current does not exceed this range, the welding robot considers the position correct. A deviation that is too wide will result in sluggish tracking, while a deviation that is too narrow will easily lead to malfunctions. Arc tracking speed is the response speed of the welding robot's lateral oscillation or trajectory adjustment. For the aforementioned 65-75% arc tracking speed, when the welding speed is fast and the bevel is narrow, the tracking speed can be faster; when the welding speed is slow and the bevel is wide, the tracking speed should be slower to prevent back-and-forth oscillation.

[0024] Furthermore, in step (4), the workpiece is heated to at least 100°C before entering the furnace and then cooled naturally after exiting the furnace. Additionally, holding at 250°C for 2 hours is sufficient to allow diffusible hydrogen in the weld to escape without causing secondary hardening or grain growth in the high-strength steel Q890. Post-weld heat treatment of the push rod is a crucial step in ensuring its durability. Traditionally, all welds are subjected to heat aging treatment: the heating temperature is generally around 550°C, and the holding time is 8-10 hours or more, resulting in a long construction period and high energy consumption. Through experimental research, the technical solution of this invention replaces heat aging treatment with timely hydrogen removal treatment after each weld. Compared to the traditional solution, this significantly reduces the heating temperature, saves construction time, and thus improves production efficiency.

[0025] The beneficial effects of this invention include:

[0026] 1. The present invention provides a method for improving the welding quality and efficiency of hydraulic support push rods. Compared with traditional manufacturing methods, it uses electromagnetic induction equipment for preheating before welding and supplemental heating during welding, which improves heating efficiency and reduces energy consumption.

[0027] 2. The overlapping method between the cover plate and the main stiffening plate was adjusted, and arc tracking was reasonably adopted during welding, which reduced the assembly difficulty and improved the quality and appearance consistency of the weld.

[0028] 3. Timely hydrogen removal treatment after welding greatly reduces the heating temperature, saves time, and thus improves production efficiency. Attached Figure Description

[0029] Figure 1This is an existing method for connecting push rod box structures.

[0030] Figure 2 This is an example of an overlapping scheme for the push rod box structure in one embodiment of the present invention.

[0031] [Explanation of Labels in the Attached Image]

[0032] 1-Base plate; 2-Main stiffener plate; 3-Cover plate (existing technology); 3'-Adjusted cover plate (this invention). Detailed Implementation

[0033] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings.

[0034] While exemplary embodiments of the invention are shown in the accompanying drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention can be understood more clearly and thoroughly, and that the scope of the invention can be fully conveyed to those skilled in the art.

[0035] In the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0036] Example 1

[0037] In this embodiment, a method for improving the welding quality and efficiency of hydraulic support push rods is provided. The push rod undergoes tack welding, preheating, welding, and post-weld heat treatment after assembly. The method includes:

[0038] (1) Heat the area with a diameter of 150mm around the tack weld to 120℃ with a heat gun before tack welding;

[0039] (2) Electromagnetic induction heating is used to preheat the solidified push rod assembly to 160°C;

[0040] (3) Weld the preheated push rod assembly. During the welding process, multi-layer and multi-pass welding is adopted, and the interlayer temperature is controlled to be <200℃. Slag is removed in time between layers. The temperature before welding is not lower than 150℃, and the final welding temperature is not lower than 100℃. The part to be welded is covered with asbestos blanket for insulation.

[0041] (4) The post-weld heat treatment is to put the workpiece into the furnace for hydrogen removal after each weld is completed: furnace temperature 250℃, heat preservation for 2 hours.

[0042] like Figure 2 As shown, the push rod is a box structure with a rectangular cross-section, spliced ​​from medium-thickness Q890 steel plates. It includes a base plate 1, two main stiffening plates 2, and a cover plate 3'. The lower end face of each main stiffening plate 2 partially overlaps the two ends of the upper surface of the base plate 1. The width of the lower surface of the cover plate 3' is smaller than the width of its upper surface. The cross-section of the cover plate 3' is essentially an inverted trapezoid, and the two ends of the lower surface of the cover plate 3' partially overlap the upper end faces of the two main stiffening plates 2. The connections between the base plate 1, the main stiffening plates 2, and the cover plate 3' form corner gaps for fillet welds. The triangular cross-sections of these corner gaps are all isosceles right triangles, with the right-angled side being 3 / 4 of the steel plate thickness.

[0043] Relatively speaking, such as Figure 1 The diagram shows the overlapping joint scheme of the push rod's box structure in the prior art. The most obvious difference is that the cover plate 3 is located between the two main stiffening plates 2. Although, like this invention, a corner gap for fillet welds is formed between the cover plate and the main stiffening plates, this structure often results in cracking of the cover plate welds during actual use. The improved solution is to... Figure 2 The overlapping joint scheme shown greatly improves the welding quality of the push rod.

[0044] Example 2

[0045] Based on Example 1, in step (2), the preheating time of the push rod assembly is 60 minutes. Due to the use of electromagnetic induction heating, the preparation time before welding is greatly reduced compared to existing preheating methods, thus saving a lot of time for the actual welding.

[0046] In step (3), when each weld is welded to 2 / 3 of its thickness, the weld area is reheated to a preheating temperature of 160°C using an electromagnetic induction device. The temperature before welding should not be lower than 150°C to avoid cold cracking; the final welding temperature should not be lower than 120°C to prevent martensitic cracks from forming in the arc-closing zone due to rapid cooling. The area to be welded is covered with an asbestos blanket for insulation.

[0047] Example 3

[0048] Based on Example 2, in step (3), the arc tracking function is achieved by setting the arc tracking parameters of the welding robot. The arc tracking parameters include: a wire extension of 20 mm, a deviation between the real-time current and the set welding current of ±15 A, and an arc tracking speed of 70% of the welding speed.

[0049] In step (4), the workpiece is not less than 120°C before entering the furnace and is naturally cooled after exiting the furnace.

[0050] In existing technologies, all welds on the entire push rod must be completed before it undergoes 8-10 hours of "thermal aging" in a large furnace at, for example, 550°C. This process is characterized by high temperature, long processing time, high energy consumption, and significant furnace occupancy. In this proposed solution, each weld (or section) is immediately placed in the furnace after completion, without waiting for the entire process to finish. Holding at 250°C for 2 hours is sufficient to allow diffusible hydrogen in the weld to escape without causing secondary hardening or grain growth in the high-strength Q890 steel. The goal is solely to "eliminate hydrogen," removing the hydrogen most likely to cause delayed cracking. Simultaneously, compared to existing technologies, the heating temperature is reduced from 550°C to 250°C, resulting in a significant decrease in energy consumption. A single-section processing time of 2 hours is reduced by more than 70% compared to the original 8-10 hours. Furthermore, each section's processing furnace is smaller, and the workpiece is lighter, allowing for parallel operation of multiple furnaces, thereby shortening the overall project time and improving production efficiency.

[0051] In summary, the technical solution of this invention improves welding quality and efficiency, significantly reduces energy consumption and costs, and saves time by using electromagnetic induction equipment for preheating during the tack welding stage and adjusting the overlap between the cover plate and the main stiffener plate, applying arc tracking function during welding and automatically achieving tracking function by setting the working parameters of the welding robot, and performing hydrogen removal treatment on each weld segment in a timely manner after welding and parallel processing by multiple processing devices.

[0052] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for improving the welding quality and efficiency of hydraulic support push rods, characterized in that, The push rod undergoes the following processes after assembly: tack welding, preheating, welding, and post-weld heat treatment. The methods include: (1) Heat the area with a diameter of 150mm around the tack weld to 100℃~150℃ and then tack weld it. (2) Electromagnetic induction heating is used to preheat the solidified push rod assembly to 150℃~180℃; (3) Weld the preheated push rod assembly. During the welding process, multi-layer and multi-pass welding is adopted, and the interlayer temperature is controlled to be <200℃. Slag is removed in time between layers. The temperature before welding is not lower than 150℃, and the final welding temperature is not lower than 100℃. The part to be welded is covered with asbestos blanket for insulation. (4) The post-weld heat treatment involves placing the workpiece in a furnace for hydrogen removal after each weld is completed: furnace temperature 250℃, holding for 2 hours. The push rod is a box structure with a rectangular cross section spliced ​​from medium-thick steel plates, including a bottom plate, two main stiffening plates and a cover plate. One end face of each main stiffening plate partially overlaps the two ends of the bottom plate. The width of the lower surface of the cover plate is smaller than the width of the upper surface, and the two ends of the lower surface of the cover plate partially overlap the other end face of the two main stiffening plates.

2. The method according to claim 1, characterized in that, The connection points of the base plate, main stiffening plate, and cover plate respectively form corner gaps for fillet welds.

3. The method according to claim 2, characterized in that, The medium-thick steel plate is a Q890 medium-thick steel plate with a thickness of 12-50mm; at least one side of the triangular cross-section of the corner gap is not less than 2 / 3 of the thickness of the steel plate.

4. The method according to claim 1, characterized in that, In step (1), heating is performed using a torch, flame, or resistance heater.

5. The method according to claim 1, characterized in that, In step (2), the preheating time for the push rod assembly is 50-80 minutes.

6. The method according to claim 1, characterized in that, In step (3), when each weld is welded to 1 / 2 to 2 / 3 of its thickness, the weld area is heated again to the preheating temperature using electromagnetic induction heating.

7. The method according to claim 6, characterized in that, In step (3), the arc tracking function is applied during the welding process.

8. The method according to claim 7, characterized in that, Arc tracking functionality is achieved by setting the arc tracking parameters of the welding robot.

9. The method according to claim 8, characterized in that, The arc tracking parameters include: an extension length of 18-21 mm, a real-time current deviation of ±20 A from the set welding current, and an arc tracking speed of 65-75% of the welding speed.

10. The method according to claim 1, characterized in that, In step (4), the workpiece is not less than 100°C before entering the furnace and is naturally cooled after exiting the furnace.

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