Liquid inlet and return elbow pipe for coal mine and production method thereof

Abstract

The invention discloses a liquid inlet and return elbow for a coal mine and a production method of the liquid inlet and return elbow, and belongs to the technical field of liquid inlet and return elbows. When the blank pipe is blanked, under the condition that it is guaranteed that the bent pipe section and the body section of the liquid inlet and return bent pipe are not changed, the lengths of the pipe ends on the two sides are symmetrically increased, the pipe ends on the two sides are subjected to repeated heating and upsetting treatment through upsetting equipment, and the integrated end of the liquid inlet and return bent pipe is formed; in order to overcome the defects in the prior art, at least one purpose of the invention is to provide the liquid inlet and return bent pipe for the coal mine and the production method thereof, the heading process is adopted to replace the traditional welding process, the liquid inlet and return bent pipe is integrally formed, and the production cost is reduced. The risk of liquid leakage of the liquid inlet and return pipe is solved, and the professional requirement for operators is lowered.

Description

Technical Field

[0001] This invention relates to the field of inlet and return fluid bend technology, specifically to an inlet and return fluid bend for coal mines and its manufacturing method. Background Technology

[0002] Comprehensive mechanization of coal mining is an important measure to accelerate the development of my country's coal industry and realize its modernization. During the process of comprehensive mechanization of coal mining, hydraulic supports are needed to support large equipment. These supports require hydraulic oil during their extension and retraction, and the inlet and outlet of the hydraulic oil requires inlet and outlet hydraulic bend assemblies, which are connected to the hydraulic supports.

[0003] The bent pipe structure is generally constructed by welding a main inlet or return pipe with fittings and other accessories. The welding process for the bent pipe is relatively complex, requiring high-quality welds, strict control over welding parameters, and demanding skilled personnel for production and operation. Furthermore, due to the high pressure of the hydraulic support system (around 40 MPa), the fittings are prone to leakage, posing a risk of fluid leakage, and repairs are difficult after the welded pipe deforms.

[0004] A search revealed several existing technologies addressing the issues of leakage and high welding requirements in inlet / return fluid bend structures. For example, Chinese patent literature, entitled "Connector for Main Inlet, Main Return, and Water Inlet Pipes of Hydraulic Supports" (application number 201410325493.6), discloses a connector that integrates the traditional bend structure and function onto a polygonal distribution plate. This results in a compact structure and simple manufacturing. The connector's compact design uses a welded joint only at the connection between the joint and the distribution plate (for low pressure), while other joints are machined directly through drilling on the polygonal plate. This ensures high precision in sealing surface machining and significantly reduces welding work compared to traditional structures, minimizing high-pressure fluid leakage caused by welding deformation and defects. However, this solution still faces challenges in welding processes and leakage issues.

[0005] For example, a Chinese patent document, titled "A Support-Type Inlet / Return T-Connector for Coal Mines and Its Usage Method," application number 202011007578.1, discloses a support-type inlet / return t-connector for coal mines. This t-connector distributes emulsion from a hydraulic pump station to various hydraulic supports, allowing for individual control of each support group's movement and enabling coordinated action. This makes the emulsion distribution simpler, clearer, and more precise. However, this solution addresses the emulsion distribution problem but does not resolve issues such as the difficulty of welding the inlet / return bends or leakage.

[0006] After years of research, the inventors of this application have broken with traditional thinking and adopted an upsetting process to replace the traditional welding process, forming an integrated inlet and outlet liquid bend. This solves the problems of difficult welding processes, high welding requirements, and easy leakage under long-term pulse pressure. Summary of the Invention

[0007] In order to overcome the defects and deficiencies of the existing technology, at least one objective of the present invention is to provide a coal mine inlet and return liquid bend and its production method. The method adopts the roughing process to replace the traditional welding process and integrally forms the inlet and return liquid bend, which not only solves the risk of leakage of the inlet and return liquid pipe, but also reduces the professional requirements of the operators.

[0008] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for producing a coal mine inlet and return fluid bend. When the blank tube is cut, while ensuring that the bend section and the main body section of the inlet and return fluid bend remain unchanged, the length of the ends of the tubes on both sides is symmetrically increased, and the ends of the tubes on both sides are heated and thickened multiple times using a thickening device to form an integrated end of the inlet and return fluid bend. The mandrel structures used in the multiple thickening processes are all different.

[0009] The first aspect can be achieved by including the following steps: S1: One heating process is used to heat the end of the blank tube. The heating temperature is 900℃~950℃ and the heating time is 5min~8min. S2: First-stage upsetting: The heated pipe is quickly sent to the upsetting equipment for fixing, and the first mandrel is embedded into the heated end for first-stage upsetting. The thickness and shortening amount of the first-stage upsetting is 85mm~100mm. S3: Reheat the end of the pipe after the first upsetting, with a heating temperature of 950-1000℃ and a heating time of 5-10 minutes; S4: Quickly feed the heated pipe into the overlaying equipment for fixing, and then insert the second mandrel into the heated end for secondary overlaying. The thickness and shortening amount of the secondary overlaying is 50mm to 65mm.

[0010] The first aspect can be achieved by including the following steps: S1: One heating process is used to heat the end of the blank tube. The heating temperature is 900℃~950℃ and the heating time is 5min~8min. S2: First-stage upsetting: The heated pipe is quickly sent to the upsetting equipment for fixing, and the first mandrel is embedded into the heated end for first-stage upsetting. The thickness and shortening amount of the first-stage upsetting is 60mm~70mm. S3: Reheat the end of the pipe after the first upsetting, with a heating temperature of 950-1000℃ and a heating time of 5-10 minutes; S4: Quickly feed the heated pipe into the overlaying equipment for fixing, and then insert the second mandrel into the heated end for secondary overlaying. The thickness and shortening amount of the secondary overlaying is 40mm to 50mm. S5: The ends of the pipe after the second upsetting are reheated at a temperature of 1000℃~1100℃ for 3min~8min. S6: Quickly feed the heated pipe into the overlaying equipment for fixing, and after embedding the second mandrel into the heated end, perform three overlaying operations. The thickness and shortening amount of the three overlaying operations is 35mm to 45mm.

[0011] In the first aspect of the feasible method, the end of the pipe after secondary or tertiary upsetting is annealed and then formed into an integral end. The annealing temperature is 800℃~850℃ and the holding time is 30min~45min. And / or, the increase in the wall thickness at the end of the pipe remains consistent before and after each upsetting.

[0012] In the manner achievable in the first aspect, the mechanical properties of the rear end of the inlet and outlet bend are: tensile strength ≥ 800 MPa, yield strength > 500 MPa, elongation after fracture A > 40%, and reduction of area Z > 53%.

[0013] In the first aspect, the upsetting equipment includes a punch and a die that cooperate with each other. The punch is equipped with a fixed seat, and the fixed seat is equipped with a slot, which is used to fix the pipe to be thickened; A limiting groove is provided on the die corresponding to the slot position. In use, the limiting groove and the slot are respectively attached to the outer surfaces of the radial sides of the tube.

[0014] In the first aspect of the implementation, the upsetting equipment also includes a mandrel, one end of which is embedded into the end of the pipe to be upset during upsetting, and the other end of which is connected to a power mechanism to provide power for upsetting. The mandrel is provided with an embedding section, a reducing section and an overlaying section in sequence along the axial direction. The embedding section is used to embed into the end of the pipe to be overlayed, and the outer diameter of the overlaying section is the same as the outer diameter of the end of the pipe after overlaying.

[0015] In the manner achievable in the first aspect, the core rod includes a first core rod and a second core rod: The first mandrel is used to be embedded in the end of the pipe to be thickened during the first thickening process. It includes a first embedding section, a first diameter changing section and a first thickening section arranged sequentially along the axial direction. The outer diameter of the first thickening section is the same as the outer diameter of the end of the pipe after the first thickening. The second mandrel is used to be embedded in the end of the pipe to be thickened during the second thickening process. It includes a second embedding section, a second diameter changing section and a second thickening section arranged sequentially along the axial direction. The outer diameter of the second thickening section is the same as the outer diameter of the end of the pipe after the second thickening.

[0016] In the first aspect of the implementation, the mandrel also includes a third mandrel for embedding into the end of the pipe to be uptaken during the second uptake. The third mandrel includes a third embedding section, a third diameter-changing section and a third uptake section arranged sequentially along the axial direction. The outer diameter of the third uptake section is the same as the outer diameter of the end of the pipe after the third uptake.

[0017] In the first aspect of the possible implementation, the end diameter of the first variable diameter section near the first thickening section is the same as the maximum inner diameter of the pipe end after the first thickening. The diameter of the end of the second reducing section near the second thickening section is the same as the maximum inner diameter of the end of the pipe after the second thickening. The diameter of the end of the third diameter-reducing section near the third thickening section is the same as the maximum inner diameter of the pipe end after the second thickening.

[0018] Secondly, the present invention provides a coal mine inlet and return fluid bend, which is manufactured using the above-mentioned coal mine inlet and return fluid bend production method, wherein the two bend ends of the inlet and return fluid bend are integrally formed.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. This invention uses an upsetting process to replace the traditional welding process, resulting in an integrated molding of the inlet and return liquid bends. This not only eliminates the risk of leakage in the inlet and return liquid pipes but also reduces the professional requirements for operators.

[0020] 2. This invention utilizes a multi-stage heating and overlaying process to form the pipe end into an integrated structure, avoiding the use of traditional welding methods to form the pipe end. The multi-stage overlaying process allows for staged overlaying, ensuring precise shaping of the required pipe end dimensions and preventing single-stage overlaying from causing the pipe end to fail to meet dimensional and quality requirements. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the blank tube in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the first overlay tube obtained after the first overlay process of the blank tube in an embodiment of the present invention; Figure 3 This is a schematic diagram of the first upsetting process in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the first upsetting die in an embodiment of the present invention. The concave die is not shown in this schematic diagram. Figure 5This is a three-dimensional structural diagram of the first core rod in an embodiment of the present invention; Figure 6 This is a schematic cross-sectional view of the first core rod in an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of the second overlay tube obtained after the second overlay process in an embodiment of the present invention; Figure 8 This is a schematic diagram of the second upsetting process in an embodiment of the present invention; Figure 9 This is a schematic diagram of the structure of the second upsetting die in an embodiment of the present invention. The concave die is not shown in this schematic diagram. Figure 10 This is a three-dimensional structural diagram of the second core rod in an embodiment of the present invention; Figure 11 This is a schematic cross-sectional view of the second core rod in an embodiment of the present invention; Figure 12 This is a schematic diagram of the structure of the third-stage thickened pipe obtained after the third thickening process in an embodiment of the present invention; Figure 13 This is a schematic diagram of the third upsetting process in an embodiment of the present invention; Figure 14 This is a schematic diagram of the third upsetting die in an embodiment of the present invention. The concave die is not shown in this schematic diagram. Figure 15 This is a three-dimensional structural diagram of the third core rod in an embodiment of the present invention; Figure 16 This is a schematic cross-sectional view of the third core rod in an embodiment of the present invention; Figure 17 This is a three-dimensional structural diagram of the punch in the upsetting mold according to an embodiment of the present invention; Figure 18 This is a three-dimensional structural diagram of the concave die in the upsetting mold according to an embodiment of the present invention; Figure 19 These are data charts of tensile tests performed on the specimens in Examples 1-2. The longitudinal direction represents the tensile force borne by the specimen, and the transverse direction represents the length of the specimen stretched. Figure 20 These are data charts of tensile tests performed on the specimens in Examples 3-4. The longitudinal direction represents the tensile force borne by the specimen, and the transverse direction represents the length of the specimen stretched.

[0022] The numbers on the map are: 100. Blank pipe blank; 110. Blank end; 120. Blank bend section; 130. Blank body section; 200. First pier thick pipe; 210. First pier thick end; 220. First pier thick bend section; 230. First pier thick body section; 300. Second pier thick pipe; 310. Second pier thick end; 320. Second pier thick bend section; 330. Second pier thick body section; 400. Third pier thick pipe; 410. Third pier thick end; 420. Third pier thick bend section; 430. Third pier thick body section; 510. First mandrel; 511. First insert section; 512. First diameter changing section; 513. First thickening section; 514. First positioning section; 515. First limiting section; 520. Second mandrel; 521. Second embedded section; 522. Second variable diameter section; 523. Second thickening section; 524. Second positioning section; 525. Second limiting section; 530. Third mandrel; 531. Third embedded section; 532. Third variable diameter section; 533. Third thickening section; 534. Third positioning section; 535. Third limiting section; 600, punch; 601, support groove; 610, fixing seat; 611, slot; 612, limiting component; 700. Power connection components; 800, Die cavity; 810, Mating groove; 811, Limiting groove. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. 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.

[0025] Example 1: Since both ends of the traditional coal mine inlet and return liquid bends are formed by welding, it not only requires high welding skills from the operators and is difficult to weld, but also is prone to leakage under long-term pulse pressure.

[0026] To address the aforementioned problems, this invention provides a method for producing inlet and outlet fluid bends for coal mines. During the blanking of the pipe 100, while ensuring that the bend section and body section of the inlet and outlet fluid bend remain unchanged, the lengths of the pipe ends on both sides are symmetrically increased. The pipe ends on both sides are then subjected to multiple heating and upsetting processes using an upsetting device to form an integrated end of the inlet and outlet fluid bend. The mandrel structures used in these multiple upsetting processes are all different; "multiple" here can be understood as two or more times. By utilizing multiple heating and upsetting processes, the pipe ends are upset into an integrated structure, avoiding the use of traditional welding methods to form the pipe ends. The multiple upsetting process allows for staged upsetting to precisely form the required pipe end dimensions, preventing single upsetting from causing the pipe end dimensions and quality to fail to meet requirements.

[0027] Furthermore, existing upsetting processes are mostly applied to thin-walled components, with minimal change in wall thickness before and after upsetting. This merely increases the outer diameter of the pipe, representing a simple upsetting process with low requirements. Moreover, the performance often changes after upsetting. For applications like coal mine inlet and return pipes, where system pressure is high, the altered performance after upsetting often makes it difficult to meet usage requirements. Additionally, those skilled in the art typically use end welding to form the ends, which reflects a relatively fixed technical mindset. Improvements are generally limited to the welding process and fail to fundamentally solve the problem.

[0028] Therefore, the production method of the coal mine inlet and return fluid bend in this embodiment adopts an upsetting process to prepare an integrally formed coal mine inlet and return fluid bend, which can effectively solve the above problems. Specifically, it includes the following steps: S1: A single heating process is used to heat the end of the blank tube 100 at a temperature of 900℃ for 5 minutes. Maintaining the heating temperature above 900℃ facilitates subsequent upsetting and forming. Too low a temperature makes upsetting difficult, while too high a temperature can cause deformation during the upsetting process. Simultaneously, the heating time should not be too long to avoid affecting the internal structure of the tube end and causing quality problems later.

[0029] Figure 1 The diagram shows a cross-sectional view of the blank tube 100, in which the inner diameter, outer diameter, and wall thickness of the blank body section 130, the blank bend section 120, and the blank end 110 are all consistent, and its outer diameter R0 is 68mm. The blank end 110 has a relatively large reserved length during blanking to facilitate subsequent upsetting and thickening forming; its length is L3, which is 200mm. The length of the blank tube 100 along the first direction is L1, and the length of the blank tube 100 along the first direction is L2. In some embodiments, L1 and L2 are consistent.

[0030] In this embodiment, the arc angle of the blank bending section 120 is α, which is 45°. The specific angle can be set according to actual conditions and is not intended to limit the invention. The length L5 of the blank body section 130 is 320mm. During the subsequent upsetting process, the dimensions and angles of the blank bending section 120 and the blank body section 130 remain unchanged; only the ends on both sides are upset to avoid affecting the body section and the bending section.

[0031] S2: First-stage upsetting. The heated pipe is quickly fed into the upsetting equipment and fixed. The first mandrel 510 is then embedded into the heated end for first-stage upsetting. The thickness reduction of the first-stage upsetting is 60mm, and the outer diameter R1 of the end after the first-stage upsetting is 78mm. The reduction of the first-stage upsetting should not be too large to avoid excessive compression of the end and causing quality damage.

[0032] Figure 2 The diagram shows a cross-sectional view of the first-stage thickened pipe 200, which is the pipe formed after a single thickening process. It includes a first-stage thickened body section 230 and first-stage thickened bent pipe sections 220 located at both ends of the first-stage thickened body section 230. Each of the first-stage thickened bent pipe sections 220 has a first-stage thickening end 210 on its outer side. The first-stage thickening end 210 and the first-stage thickened bent pipe sections 220 are connected by a first-stage thickening step to form an integral structure. The length L31 of the first-stage thickening end 210 is 130m.

[0033] S3: The end of the pipe after the first upsetting is reheated at a temperature of 950°C for 5 minutes to facilitate the subsequent second upsetting.

[0034] S4: The heated pipe is quickly fed into the overlaying equipment and fixed. After the second mandrel 520 is embedded into the heated end, a second overlay is performed. The thickness reduction of the second overlay is 40mm, and the outer diameter R2 of the end after the second overlay is 85mm. The reduction of the second overlay is smaller than that of the first overlay. The first overlay can be understood as rough machining, the second overlay as finish machining, and the third overlay as a fine adjustment stage.

[0035] Because the pipe end is heated before the second upsetting, and the heating temperature is higher than that before the first upsetting, it can be quickly upsetting and formed during the second upsetting, avoiding changes in its internal structure.

[0036] Figure 7The diagram shows a cross-sectional view of the second-stage thickening pipe 300, which represents the pipe after secondary thickening. It includes a second-stage thickening body section 330 and second-stage thickening bend sections 320 symmetrically located at both ends of the second-stage thickening body section 330. A second-stage thickening end section 310 is also provided on the outer side of the second-stage thickening body section 330. At this point, the second-stage thickening end section 310 and the second-stage thickening bend section 320 are connected by a second-stage thickening step to form an integral structure. The length L32 of the second-stage thickening end section 310 is 130m.

[0037] S5: The ends of the pipe after the second upsetting are reheated at a temperature of 1000℃ for 3 minutes.

[0038] S6: Quickly feed the heated pipe into the overlaying equipment and fix it. After embedding the second mandrel 520 into the heated end, perform three overlaying operations. The thickness and shortening amount of the three overlaying operations is 35mm to 45mm. The outer diameter R3 of the end after the three overlaying operations is 96mm.

[0039] In the above-mentioned single-stage, double-stage, and triple-stage overlay processes, the increase in pipe end wall thickness remains consistent after each overlay. That is, the maximum wall thickness at the pipe end increases by 5mm with each overlay, from the initial 12mm to 27mm after three overlays. The outer diameter changes from the initial 68mm to 96mm. In other words, the minimum inner diameter at the pipe end is 42mm, which is basically not much different from the initial inner diameter of 44mm and does not affect the liquid inlet and outlet performance.

[0040] It is understandable that the purpose of using three upsetting processes in this embodiment is to reasonably thicken the pipe wall. If the pipe wall is directly upset in one go, it is very easy to cause the pipe wall to tear. Therefore, the material is extruded by three upsetting processes to ensure that the wall thickness increases uniformly by 5mm each time, preventing defects such as tearing. In addition, the tensile strength of the material can be gradually increased to meet the strength requirements of the inlet and outlet pipes.

[0041] In some feasible embodiments, the pipe ends after each upsetting process are annealed and then integrally formed. The annealing temperature is 800°C, and the holding time is 60 minutes, followed by air cooling to room temperature. During annealing, dislocations within the material rearrange and decrease, allowing grain recrystallization and growth, thereby reducing dislocation density, lowering hardness and strength, and improving plasticity and toughness. This can alleviate the reduction in plasticity and toughness caused by the upsetting process to some extent, ensuring that the material still meets specific application requirements after processing.

[0042] Furthermore, in this embodiment, the mechanical properties of the rear end of the inlet and return fluid bend are as follows: tensile strength ≥ 800 MPa, yield strength > 500 MPa, elongation after fracture A > 40%, and reduction of area Z > 53%. The inlet and return fluid bends are typically made of 304 stainless steel, which has the following mechanical properties: tensile strength ≥ 515 MPa and yield strength ≥ 205 MPa. For high-pressure pipelines, the elongation after fracture of stainless steel pipes should generally be no less than 20%; the reduction of area should also generally be kept at a high level, typically no less than 30%. Simultaneously, for the ends welded using traditional welding techniques, the weld requirements are: tensile strength ≥ 800 MPa; yield strength ≥ 455 MPa.

[0043] Therefore, it can be seen that the strength and hardness of the pipe ends are significantly improved after upsetting, while maintaining good plasticity and toughness. This is because upsetting typically causes work hardening of the metal material, increasing strength and hardness, but also reducing plasticity and toughness. This means that upset stainless steel pipes may become more brittle and prone to fracture, especially in low-temperature environments or under impact loads. Therefore, in practical applications, it is necessary to select appropriate processing techniques and post-treatment methods based on specific usage requirements to ensure that the performance of the stainless steel pipes meets engineering needs.

[0044] refer to Figure 17 as well as Figure 18 The structure shown in this embodiment includes a punch 600 and a die 800 that work together. The punch 600 is provided with a fixing seat 610, and the fixing seat 610 is provided with a slot 611 for fixing the pipe to be upheld. The die 800 is provided with a limiting groove 811 at a position corresponding to the slot 611. In use, the limiting groove 811 and the slot 611 are respectively attached to the outer surfaces of the radial sides of the pipe to clamp and fix the end of the pipe to be upheld from the top and bottom directions.

[0045] In this embodiment, the upsetting equipment also includes a mandrel for use. During upsetting, one end of the mandrel is embedded into the end of the pipe to be upset, and the other end of the mandrel is connected to the power mechanism to provide power for upsetting. Specifically, in this embodiment, the end of the mandrel is connected and fixed to the power mechanism through the power connector 700.

[0046] The mandrel is provided with an embedding section, a reducing section and an overlaying section in sequence along the axial direction. The embedding section is used to be embedded into the end of the pipe to be overlayed, and the outer diameter of the overlaying section is the same as the outer diameter of the end of the pipe after overlaying.

[0047] In some feasible embodiments, the mandrel includes a first mandrel 510 and a second mandrel 520. The first mandrel 510 is used to embed into the end of the pipe to be uptaken during the first uptake process. It includes a first embedding section 511, a first reducing section 512, and a first uptake section 513 arranged sequentially along the axial direction. The outer diameter of the first uptake section 513 is the same as the outer diameter of the pipe end after the first uptake. The diameter of the end of the first reducing section 512 near the first uptake section 513 is the same as the maximum inner diameter of the pipe end after the first uptake. Before uptake, the arc-shaped end of the first embedding section 511 is embedded into the end of the pipe to be uptaken for positioning, which facilitates the stability of the subsequent uptake process. Both the first embedding section 511 and the first reducing section 512 are circular pipe sections with gradually increasing longitudinal cross-sections, which achieves slow uptake forming. The dimensions of the formed end meet the requirements and avoid problems such as cracks and breaks during the uptake process, thus ensuring the quality of the pipe end.

[0048] Figure 10 and Figure 11 The structure shown is that of the second core rod 520, which differs from that of the first core rod 510. Figure 9 As can be seen, the second mandrel 520 is used to embed into the end of the pipe to be uptaken during secondary uptaking. It includes a second embedding section 521, a second reducing section 522, and a second uptaking section 523 arranged sequentially along the axial direction. The outer diameter of the second uptaking section 523 is the same as the outer diameter of the pipe end after secondary uptaking, and the diameter of the end of the second reducing section 522 near the second uptaking section 523 is the same as the maximum inner diameter of the pipe end after secondary uptaking. Before uptaking, the arc-shaped end of the second embedding section 521 is embedded into the end of the pipe to be uptaken to achieve fixed positioning and ensure the stability of uptaking. The second embedding section 521 and the second reducing section 522 are both integrated structures, and they are circular pipe sections with gradually increasing longitudinal cross-sections.

[0049] In some embodiments employing three-stage upsetting, the mandrel further includes a third mandrel 530. Figure 15 and Figure 16 The structure shown is that of the third core rod 530, which is different from the structures of the first core rod 510 and the second core rod 520. Figure 14 This is an illustration of the actual use of the third mandrel 530, which is used to embed into the end of the pipe to be thickened during the second thickening process. It includes a third embedding section 531, a third diameter changing section 532, and a third thickening section 533 arranged sequentially along the axial direction. The outer diameter of the third thickening section 533 is the same as the outer diameter of the pipe end after the third thickening process. The diameter of the end of the third diameter changing section 532 near the third thickening section 533 is the same as the maximum inner diameter of the pipe end after the second thickening process.

[0050] Secondly, embodiments of the present invention provide a coal mine inlet and return liquid bend, which is manufactured using the above-mentioned production method for coal mine inlet and return liquid bends. The two bend ends of the inlet and return liquid bend are integrally formed, avoiding the use of traditional welding technology to form the bend ends. This not only solves the risk of leakage in the inlet and return liquid pipes, but also reduces the professional requirements for operators.

[0051] A portion of the end of the pipe after upsetting in Examples 1-4 was taken as a sample for a tensile test of metallic materials. The calculation standard was GB / T228.1-2010. The sample shape was a bar. The test speed was 2 mm / min, and the extensometer gauge length Le was 50 mm. The test results are shown in Table 1 below. As can be seen from the results in Table 1 above, the results of the metal tensile tests on the samples in Examples 1-4 all meet the requirements for the use of coal mine inlet and outlet pipes. The tensile strength of all samples is >800 MPa, the yield strength is >500 MPa, the elongation after fracture A is >40%, and the reduction of area Z is >53%. Figures 19-20 These are data charts of tensile tests performed on the specimens in Examples 1-4. The longitudinal direction represents the tensile force borne by the specimen, and the transverse direction represents the length of the specimen stretched.

[0052] Example 2: The production method of the coal mine inlet and return fluid bend in this embodiment is basically the same as that in Example 1, except that this embodiment includes the following steps: S1: First heating, the end of the blank tube 100 is heated at 950℃ for 8 minutes.

[0053] The inner diameter, outer diameter, and wall thickness of the blank body section 130, the blank bend section 120, and the blank end section 110 are all consistent, and its outer diameter R0 is 70mm. The length of the blank end section 110 is L3, which is 210mm. The length of the blank tube 100 along the first direction is L1, and the length of the blank tube 100 along the first direction is L2. In some embodiments, L1 and L2 are consistent.

[0054] The arc angle of the blank bending section 120 is α, where α is 45°, and the specific angle can be set according to the actual situation. The length L5 of the blank body section 130 is 340mm.

[0055] S2: First-stage upsetting. The heated pipe is quickly fed into the upsetting equipment for fixation. The first mandrel 510 is then embedded into the heated end for first-stage upsetting. The thickness and shortening amount of the first-stage upsetting is 70mm, and the outer diameter R1 of the end after the first-stage upsetting is 80mm. The length L311 of the first-stage upsetting end 210 is 150mm.

[0056] S3: The end of the pipe after the first upsetting is reheated at a temperature of 1000℃ for 10 minutes to facilitate the subsequent second upsetting.

[0057] S4: Quickly feed the heated pipe into the overlaying equipment and fix it in place. After embedding the second mandrel 520 into the heated end, perform secondary overlaying. The thickness and shortening amount of the secondary overlaying is 50mm. The length dimension L321 of the second overlaying end 310 is 150mm.

[0058] S5: The ends of the pipe after the second upsetting are reheated at 1100℃ for 8 minutes.

[0059] S6: Quickly feed the heated pipe into the overlaying equipment for fixing, and after embedding the second mandrel 520 into the heated end, perform three overlaying operations. The thickness and shortening amount of the three overlaying operations is 45mm.

[0060] Example 3: The production method of the coal mine inlet and return fluid bend in this embodiment is basically the same as that in Example 1, except that this embodiment includes the following steps: S1: First heating, the end of the blank tube 100 is heated at 920℃ for 6 minutes.

[0061] The inner diameter, outer diameter, and wall thickness of the blank body section 130, the blank bend section 120, and the blank end section 110 are all consistent, and its outer diameter R0 is 68mm. The length of the blank end section 110 is L3, which is 205mm. The length of the blank tube 100 along the first direction is L1, and the length of the blank tube 100 along the first direction is L2. In some embodiments, L1 and L2 are consistent.

[0062] The arc angle of the blank bend section 120 is α, where α is 45°, and the specific angle can be set according to the actual situation. The length L5 of the blank body section 130 is 330mm.

[0063] S2: First-stage upsetting. The heated pipe is quickly fed into the upsetting equipment for fixation. The first mandrel 510 is then embedded into the heated end for first-stage upsetting. The thickness and shortening amount of the first-stage upsetting is 65mm, and the outer diameter R1 of the end after the first-stage upsetting is 78mm. The length L311 of the first-stage upsetting end 210 is 140mm.

[0064] S3: The end of the pipe after the first upsetting is reheated at a temperature of 1000℃ for 10 minutes to facilitate the subsequent second upsetting.

[0065] S4: The heated pipe is quickly fed into the overlaying equipment and fixed. After the second mandrel 520 is embedded in the heated end, a second overlay is performed. The thickness and shortening amount of the second overlay is 45mm. The length L321 of the second overlay end 310 is 140mm.

[0066] S5: The ends of the pipe after the second upsetting are reheated at a temperature of 1080℃ for 6 minutes.

[0067] S6: Quickly feed the heated pipe into the overlaying equipment for fixing, and after embedding the second mandrel 520 into the heated end, perform three overlaying operations. The thickness and shortening amount of the three overlaying operations is 40mm.

[0068] Example 4: The production method of the coal mine inlet and return fluid bend in this embodiment is basically the same as that in Example 1. The difference is that this embodiment uses a two-stage upsetting method, which includes the following steps: S1: First heating, the end of the blank tube 100 is heated at a temperature of 900℃~950℃ for 5min~8min; like Figure 1 As shown, in this embodiment, the blank tube 100 includes a straight tube body section 130, with symmetrically arranged blank bend sections 120 at both ends of the blank body section 130, and blank end sections 110 on the outer sides of both ends of the blank bend sections 120. The outer diameter and wall thickness of the blank body section 130, the blank bend sections 120, and the blank end sections 110 are all consistent. During blanking, the length of the blank end section 110 is 200mm~210mm.

[0069] S2: First-stage upsetting. The heated pipe is quickly sent to the upsetting equipment for fixation. The process time is controlled within 60 seconds to prevent excessive cooling and affect the upsetting effect. At the same time, the end of the first mandrel 510 is embedded into the heated end of the pipe to be upset and then the first-stage upsetting operation is performed. The thickening and shortening of the pipe end after the first-stage upsetting is 85mm~100mm, and the outer diameter of the pipe end after the first-stage upsetting is 75mm~80mm. S3: The end of the pipe after the first upsetting is reheated at a temperature of 950-1000℃ for 5-10 minutes.

[0070] S4: Quickly feed the heated pipe into the overlaying equipment for fixing, and then insert the second mandrel 520 into the heated end for secondary overlaying. The thickness and shortening amount of the secondary overlaying is 50mm to 65mm.

[0071] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0072] It should be noted that in the description of this application, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this application, unless otherwise stated, "a plurality of" means at least two.

[0073] The scope of the preferred embodiments of this application includes other implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order, depending on the functions involved, as will be understood by those skilled in the art to which the embodiments of this application pertain.

[0074] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A production method of a coal mine inlet and return liquid elbow, characterized in that, The blank pipe (100) is increased in length on both sides of the pipe end during blanking, the elbow section and the body section of the inlet and return liquid elbow are not changed, the pipe end on both sides is treated by multiple heating and upsetting, and the integrated end of the inlet and return liquid elbow is formed, wherein the core rod structures used in the multiple upsetting processes are different.

2. The production method of the coal mine inlet and return liquid elbow according to claim 1, characterized in that, It comprises the following steps: S1: heating, heating the end of the blanked pipe (100), the heating temperature is 900-950℃, and the heating time is 5-8min; S2: first upsetting, the heated pipe is quickly sent to the upsetting equipment for fixation, the first core rod (510) is embedded into the heated end, and the first upsetting is performed, the thickening and shortening amount of the first upsetting is 85-100mm; S3: re-heating the pipe end after the first upsetting, the heating temperature is 950-1000℃, and the heating time is 5-10min; S4: the heated pipe is quickly sent to the upsetting equipment for fixation, the second core rod (520) is embedded into the heated end, and the second upsetting is performed, the thickening and shortening amount of the second upsetting is 50-65mm.

3. The production method of the coal mine inlet and return liquid elbow according to claim 1, characterized in that, It comprises the following steps: S1: heating, heating the end of the blanked pipe (100), the heating temperature is 900-950℃, and the heating time is 5-8min; S2: first upsetting, the heated pipe is quickly sent to the upsetting equipment for fixation, the first core rod (510) is embedded into the heated end, and the first upsetting is performed, the thickening and shortening amount of the first upsetting is 60-70mm; S3: re-heating the pipe end after the first upsetting, the heating temperature is 950-1000℃, and the heating time is 5-10min; S4: the heated pipe is quickly sent to the upsetting equipment for fixation, the second core rod (520) is embedded into the heated end, and the second upsetting is performed, the thickening and shortening amount of the second upsetting is 40-50mm; S5: re-heating the pipe end after the second upsetting, the heating temperature is 1000-1100℃, and the heating time is 3-8min; S6: the heated pipe is quickly sent to the upsetting equipment for fixation, the second core rod (520) is embedded into the heated end, and the third upsetting is performed, the thickening and shortening amount of the third upsetting is 35-45mm.

4. The production method of the coal mine inlet and return liquid elbow according to claim 2 or 3, characterized in that, The pipe end after the second or third upsetting is annealed, and then the integrated end is formed, the annealing temperature is 800-850℃, and the holding time is 30-45min; And / or, the thickness of the pipe end before and after each upsetting is increased by the same amount.

5. The production method of the coal mine inlet and return liquid elbow according to claim 4, characterized in that, The mechanical properties of the end part of the return bend are: tensile strength ≥800Mpa, yield strength >500Mpa, elongation A >40%, and reduction of area Z >53%.

6. The production method of the return bend according to any one of claims 1-3, characterized in that, the upsetting device comprises a male die (600) and a female die (800) used in cooperation; the male die (600) is provided with a fixing seat (610), and the fixing seat (610) is provided with a clamping groove (611) for fixing the pipe to be upset; the female die (800) is provided with a limiting groove (811) corresponding to the position of the clamping groove (611), and the limiting groove (811) and the clamping groove (611) are respectively attached to the outer surfaces of the two sides of the pipe in use.

7. The production method of the return bend according to claim 6, characterized in that, the upsetting device further comprises a core rod, one end of the core rod is embedded into the end part of the pipe to be upset, and the other end of the core rod is connected with a power mechanism for providing the upsetting power; the core rod is sequentially provided with an embedding section, a variable-diameter section and an upsetting section along the axial direction, the embedding section is used for embedding into the end part of the pipe to be upset, and the outer diameter of the upsetting section is consistent with the outer diameter of the pipe after upsetting.

8. The production method of the return bend according to claim 7, characterized in that, the core rod comprises a first core rod (510) and a second core rod (520); the first core rod (510) is used for embedding into the end part of the pipe to be upset in the first upsetting, and comprises a first embedding section (511), a first variable-diameter section (512) and a first upsetting section (513) sequentially arranged along the axial direction, and the outer diameter of the first upsetting section (513) is the same as the outer diameter of the pipe after the first upsetting; the second core rod (520) is used for embedding into the end part of the pipe to be upset in the second upsetting, and comprises a second embedding section (521), a second variable-diameter section (522) and a second upsetting section (523) sequentially arranged along the axial direction, and the outer diameter of the second upsetting section (523) is the same as the outer diameter of the pipe after the second upsetting.

9. The production method of the return bend according to claim 8, characterized in that, the core rod further comprises a third core rod (530), the third core rod (530) is used for embedding into the end part of the pipe to be upset in the third upsetting, and comprises a third embedding section (531), a third variable-diameter section (532) and a third upsetting section (533) sequentially arranged along the axial direction, and the outer diameter of the third upsetting section (533) is the same as the outer diameter of the pipe after the third upsetting.

10. The production method of the return bend according to claim 9, characterized in that, the diameter of the end part of the first variable-diameter section (512) close to the first upsetting section (513) is the same as the maximum inner diameter of the pipe after the first upsetting; the diameter of the end part of the second variable-diameter section (522) close to the second upsetting section (523) is the same as the maximum inner diameter of the pipe after the second upsetting; The end diameter of the third variable diameter section (532) near the third thickening section (533) is the same as the maximum inner diameter of the pipe end after the second thickening.

11. A coal mine use liquid inlet and outlet elbow, characterized in that, The inlet and outlet liquid bends for coal mines are manufactured using the production method of any one of claims 1-9, wherein the two bend ends of the inlet and outlet liquid bends are integrally formed.

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