CN114309127B - Inner wall surfacing small bending radius bent pipe and forming method thereof - Google Patents

Abstract

The application provides an inner wall surfacing small bending radius bent pipe and a forming method thereof; the method comprises the following steps of blanking a pipeline with proper length to be used as a main pipe of the pipeline to be bent; a build-up welding layer is arranged at a proper position inside the main pipe; carrying out cold bending on the surfacing pipe to be bent to integrally form a seamless bent pipe with an elbow section in the middle and straight pipe sections at two ends of the elbow section; putting the bent pipe into a shaping tool for shaping: the bent pipe sequentially passes through an elbow shaping die for shaping the elbow section and an elbow shaping die for shaping the whole bent pipe. The utility model provides a little bend radius return bend of inner wall build-up welding, the return bend includes elbow section and the straight tube section at elbow section both ends, the return bend is whole seamless cold-formed pipeline, elbow section inner wall sets up the build-up welding layer, the bend radius of elbow section of return bend is the return bend diameter 1 to 3 times, the return bend diameter is between 60 millimeters to 220 millimeters, the wall thickness is not less than 6 millimeters.

Description

Inner wall surfacing small bending radius bent pipe and forming method thereof

Technical Field

The application belongs to the field of bent pipes, and particularly relates to a small-bending-radius bent pipe with a built-up welding inner wall and a forming method thereof.

Background

The elbow is needed at the turning part of the elbow, and the straight pipe section, the straight pipe section and the pipeline are welded at the two ends of the elbow so as to be connected with the pipelines in two directions. In shale gas wells or deep sea areas with complex working conditions, the bends and straight pipe sections at the two ends are easy to damage due to corrosion. The main process of manufacturing the 90-degree seamless long-radius composite elbow with the straight section by the traditional process is that after the inner wall of a base metal is subjected to surfacing, the 90-degree elbow is formed by hot pressing by a hydraulic press, straight pipe sections with corresponding lengths are welded at two ports of the elbow respectively, then surfacing is carried out on the inner walls of two girth welds, and the surfacing length is about 30cm. For a 90-degree seamless long-radius composite elbow with a straight section, the process route is as follows: base metal inspection, steel pipe blanking, inner wall grinding, inner wall surfacing, sawing machine trapezoid cutting, hot press forming, pipe end groove processing, size and nondestructive detection, pipe end straight pipe welding, girth weld inner wall surfacing, ray detection, sand blasting identification and packaging. After hot press forming, the straight pipe sections are welded at the two ends of the composite elbow, the butt welding operation difficulty is high, the defect that repeated operation is easy to occur due to the fact that welding quality is not in place is overcome, the butt welding seam is required to be subjected to girth weld inner wall surfacing and ray detection, the technological process is complex, the elbow with the straight pipe sections at the two ends needs to be circulated back and forth in different working procedures when being manufactured, the production efficiency is low, the consumed time is long, and profit is greatly reduced. Because both ends of the composite elbow and the straight pipe sections are provided with the build-up layers, the build-up difficulty of the inner wall of the girth weld is high, the operation of workers is extremely labor-and time-consuming, the build-up cost of the girth weld is extremely high, and the processing cost of a single composite elbow is increased. The product performance is unstable due to the existence of butt welded seams, and as is known, the instability of the pipe fitting is increased by each welding seam, and the resistance to erosion corrosion, CO2 corrosion and fluid accelerated corrosion is reduced compared with that of the raw material. In the use process, corrosion and leakage are more likely to occur in a welding line area, particularly in a shale gas well or a deep sea area with more complicated working conditions, and once corrosion defects occur, economic loss and maintenance cost are quite considerable.

In addition, the bent pipe formed by hot press forming or medium frequency induction heating, namely the composite elbow, can influence the performance of the composite elbow because the material performance is changed due to heating in the bending process, and can further influence the service life of the composite elbow in the environment of scouring corrosion such as shale gas development. The cold press molding method has a certain limit on the diameter and the bending radius of the pipeline to be bent. For example, the cold-pushing forming method is suitable for bent pipes with bending radius larger than 5 times of pipe diameter, and is not suitable for bent pipes with small bending radius.

Patent CN201410064046.X provides a method for bending and forming an ultrathin pipe with a small radius, which comprises the following steps of tightly winding and wrapping a part to be bent of the pipe by adopting a steel wire, wherein the diameter of the steel wire is 1-3 times of the wall thickness of the pipe, and the thickness of the steel wire wrapping can be 1-4 times of the wall thickness of the pipe according to requirements. And (3) placing a core rod into the pipe wrapped with the steel wire, and performing numerical control bending forming on the pipe wrapped with the steel wire by adopting conventional numerical control bending equipment, wherein the core rod is a multi-ball core rod. The patent cn201410064046.X temporarily increases the wall thickness when the pipe is bent by a wire winding method, thereby suppressing the wall thickness reduction of the outer side of the pipe, and controlling the ovality of the bent pipe by the internally arranged multi-ball core rod. However, sliding friction is arranged between the multi-ball core rod and the inner wall of the pipe, so that the inner wall of the pipe is easy to damage. In particular, the pipe to be bent, which is provided with a weld overlay on the inner wall, cannot be bent in this way. Because the strength of the first build-up layer is relatively high, the bending requires more torque, and the torque required after winding the steel wire is greatly increased; so that the pipeline to be bent bears larger force and the inner wall quality of the curve to be bent is easily damaged. When the inner wall is provided with the surfacing layer, the friction force between the surfacing layer and the multi-ball core rod is much larger than that between the smooth inner wall and the multi-ball core rod, the multi-ball core rod can scratch the inner wall in the moving process, and the chain of the multi-ball core rod is even broken in the experimental process, so that the effect of controlling the ovality of the bent pipe can not be achieved.

Disclosure of Invention

The application provides a small bending radius bent pipe with an inner wall surfacing and a forming method thereof.

The object of the application is achieved in the following way: a method for forming a small bending radius bent pipe by inner wall surfacing comprises the following steps: (1) Blanking a pipeline with proper length to be used as a main pipe of the pipeline to be bent; (2) arranging a build-up layer at a proper position inside the main pipe; (3) Carrying out cold bending on the surfacing pipe to be bent to integrally form a seamless bent pipe with an elbow section in the middle and straight pipe sections at two ends of the elbow section; (4) putting the bent pipe into a shaping tool for shaping: the bent pipe sequentially passes through an elbow shaping die for shaping the elbow section and an elbow shaping die for shaping the whole bent pipe.

Positioning and overlaying a nickel-based alloy layer on the inner wall of the main pipe in the step (2) to serve as an overlaying layer; the build-up welding layer adopts a circumferential build-up welding method.

And (3) and (4) the bent pipe is required to be subjected to heat treatment.

The pipe bending machine comprises a frame, a pipe limiting part, a rotating part, a pipe bending die and a clamping mechanism, wherein the pipe limiting part is arranged on the frame and used for limiting the position deviation of the pipe to be bent; an inner core which can extend into the inner cavity of the pipeline to be bent so as to reduce deformation in the bending process is arranged on the frame; one end of the inner core is arranged on the frame, and the other end of the inner core always stretches into an unbent part pipeline in the pipeline to be bent.

The elbow shaping die comprises an elbow shaping upper die and an elbow shaping lower die, wherein the inner cavity of the elbow shaping upper die and the inner cavity of the elbow shaping lower die are combined into an elbow shaping inner cavity corresponding to the shape of an elbow section of the elbow; the parting surfaces of the elbow shaping upper die and the elbow shaping lower die are planes perpendicular to the bending axis of the elbow section; the elbow shaping lower die is arranged at one end of a piston of the hydraulic machine; the elbow shaping lower die is arranged on a hydraulic platform of the hydraulic machine.

The bent pipe shaping die comprises an bent pipe shaping upper die and a bent pipe shaping lower die; the longitudinal section of the upper bending die is a semicircular inner cavity, and the longitudinal section of the lower bending die is a semicircular inner cavity, so that a bending inner cavity with a circular longitudinal section is formed; the parting surfaces of the upper elbow shaping die and the lower elbow shaping die are arc-shaped surfaces taking the axis of the elbow as the axis; the bent pipe shaping lower die is respectively arranged at one end of a piston of the hydraulic machine; the bent pipe shaping lower die is arranged on a hydraulic platform of the hydraulic machine.

The utility model provides a little bend radius return bend of inner wall build-up welding, the return bend includes elbow section and the straight tube section at elbow section both ends, the return bend is whole seamless cold-formed pipeline, elbow section inner wall sets up the build-up welding layer, the bend radius of elbow section of return bend is the return bend diameter 1 to 3 times, the return bend diameter is between 60 millimeters to 220 millimeters, the wall thickness is not less than 6 millimeters.

The build-up welding layer is a nickel-based alloy layer; the weld bead of the weld overlay is annular.

The bent pipe is a cold bent pipe, the diameter of the bent pipe is smaller than 168.3 mm, and the wall thickness is between 8 and 18 mm.

The pipe orifice of the straight pipe section is provided with a stripping layer which is 10 mm to 30 mm long and is not provided with a surfacing layer, other parts of the straight pipe section are provided with surfacing layers, and the surfacing layers are in inclined transition to the stripping layer.

The beneficial effects of the application are as follows: the elbow section and the straight pipe section of the elbow are automatically integrated into a seamless elbow by cold bending, and the seamless elbow is formed at one time by a cold bending machine, so that the cost is saved, and the quality defect of a welding area caused by poor fusion of two-phase metals is avoided; and the cold bending efficiency is high, and compared with the time and working procedures of the elbow for re-welding the straight pipe section, the time cost is reduced. The ellipticity of the elbow section is corrected through the shaping tool, so that national standard requirements are met, and the roundness and the bending angle of the elbow are shaped, so that the quality of the cold-pressed elbow is guaranteed.

Drawings

FIG. 1 is a schematic view of an elbow.

FIG. 2 is a schematic diagram of a pipe bender.

Fig. 3 is another embodiment of the core.

Fig. 4 is a schematic diagram of an upper die for bend shaping.

Fig. 5 is a schematic view of the lower die for shaping the bent pipe.

Fig. 6 is a schematic diagram of the upper die for shaping the elbow.

Fig. 7 is a front view of fig. 6.

Fig. 8 is a top view of fig. 6.

Fig. 9 is a cross-sectional view taken along A-A of fig. 8.

Wherein 1 is the frame, 2 is the pipeline locating part, 3 is the rotating part, 4 is the bending die, 5 is fixture, 6 is the inner core, 60 is the inner core curved pipe section, 61 is the inner core straight pipe section, 7 is the inner core seat, 8 is the return bend, 80 is the elbow section, 81 is the straight pipe section, 82 is the weld overlay, 83 is the peel ply.

Detailed Description

The technical solution of the present application will be clearly and completely described below with reference to the accompanying drawings and specific embodiments, and it should be understood that the preferred embodiments described herein are for illustrating and explaining the present application only and are not limiting of the present application. In the present application, unless explicitly specified and defined otherwise, technical terms used in the present application should be construed in a general sense as understood by those skilled in the art to which the present application pertains. The terms "connected," "fixedly," "disposed" and the like are to be construed broadly and may be fixedly connected, detachably connected or integrally formed; can be directly connected or indirectly connected through an intermediate medium; either mechanically or electrically. Unless explicitly defined otherwise. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances. Unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact through an intervening medium. Moreover, a first feature being "above" or "over" or "upper" a second feature may be a first feature being directly above or diagonally above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under" or "beneath" or "under" the second feature may be the first feature being directly under or obliquely under the second feature, or simply indicating that the first feature is level less than the second feature. Relational terms such as first, second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.

As shown in fig. 1-9, a method for forming a small bending radius bend pipe by overlaying an inner wall is characterized in that: the method comprises the following steps: (1) Blanking a pipeline with proper length to be used as a main pipe of the pipeline to be bent; (2) disposing a build-up layer 82 at a suitable position inside the parent tube; (3) Cold bending the surfacing pipe to be bent to integrally form a seamless bent pipe 8 with an elbow section 80 in the middle and straight pipe sections 81 at two ends of the elbow section 80; (4) The bent pipe 8 is sequentially passed through an elbow shaping die for shaping the ovality or roundness of the elbow section 80 and an elbow shaping die for shaping the entire bent pipe 8.

Wherein, in the step (2), the inner wall of the main pipe can be positioned and the nickel-based alloy layer is used as a surfacing layer 82; the build-up layer 82 is formed by a hoop build-up welding method. The base materials of the weld overlay 82 and the pipe to be bent before bending are metal materials with different performances, deformation of the bending section is difficult to ensure synchronous operation in the cold bending process, a positioning weld overlay technology is adopted, and the thickness and flatness of the weld overlay and the thinning rate and ellipticity of the elbow are precisely calculated, so that the composite straight pipe meeting the technical requirements of cold bending forming is manufactured. The specific operation is as follows: and (3) overlaying N08825 on the inner wall of the steel pipe with the base material L360N to form a corrosion-resistant alloy layer. The intelligent tungsten electrode inert gas shielded welding can be utilized, and proper technological parameters such as welding speed, wire feeding speed, current and voltage values and the like are selected to obtain the alloy layer which is good in fusion, smooth in appearance, free of air holes and free of welding slag. When the root of the welding line is welded, in order to ensure that the welding line does not generate oxides after the root is welded, the argon environment needs to be controlled. The build-up welding layer has good stress corrosion cracking resistance, good pitting corrosion resistance and crevice corrosion resistance, good oxidation resistance and non-oxidation thermal acid performance, and good mechanical properties at room temperature and high temperature up to 550 ℃. Corrosion resistance in various media such as sulfuric acid, phosphoric acid, nitric acid and organic acids, alkali metals such as sodium hydroxide, potassium hydroxide and hydrochloric acid solutions is excellent.

And (3) and (4) the bent pipe is required to be subjected to heat treatment. The heat treatment method is that the bent pipe 8 is heated to 500-550 in a furnace, and the heat is preserved for about 40 minutes; and then the electric furnace is turned off, and the furnace is taken out for cooling after the temperature is reduced to 400 ℃. The temperature of the heat treatment only eliminates the internal stress generated by cold bending and does not change the performance of the material.

The whole process is as follows, and the specific implementation is as follows: before blanking, firstly checking a pipeline serving as a parent metal, blanking a pipeline with proper length according to actual requirements after the pipeline is qualified as a parent pipe of the pipeline to be bent, polishing the inner wall of the parent pipe, positioning and overlaying a nickel-based alloy layer on the inner wall of the parent pipe to form a composite pipeline to be bent, and cold-bending the pipeline to be bent on specially arranged pipe bending equipment such as a pipe bending machine. The cold-formed bent pipe 8 is subjected to heat treatment to eliminate stress generated in the cold bending process, the bent pipe section of the bent pipe is subjected to roundness shaping through a bent pipe shaping die on a hydraulic press, and then the whole bent pipe is subjected to punching shaping through the bent pipe shaping die. And (3) performing performance inspection such as groove processing, size and hardness on the shaped bent pipe 8, performing nondestructive detection, performing sand blasting identification and finally packaging.

The bend radius of the bend section 80 of the bend 8 in the above method is 1 to 3 times the diameter of the bend 8, the bend 8 has a diameter of between 60 mm and 220 mm and a wall thickness of not less than 6 mm. Of course, the larger the bending radius, the easier the cold press forming, and the method of the application can of course be used for bends 8 with bending radii greater than 3D. However, only the method of the present application can produce the cold-bending seamless bent pipe 8 with the straight pipe sections 81 at the two ends of the bent pipe section 80 with the weld overlay on the inner wall between 1D and 3D.

As shown in fig. 2, the pipe to be bent can be cold bent on a special pipe bending machine, the pipe bending machine comprises a frame 1, a pipe limiting part 2, a rotating part 3, a pipe bending die 4 and a clamping mechanism 5, wherein the pipe limiting part 2 is arranged on the frame 1 and used for limiting the position deviation of the pipe to be bent, the clamping mechanism 5 is used for clamping the pipe to be bent in the bending process, the pipe bending die 4 is fixed on the rotating part 3 and rotates coaxially with the rotating part 3, and a cold bending groove with a semicircular cross section is formed in the pipe bending die 4 along the circumference. An inner core 6 which can extend into the inner cavity of the pipeline to be bent so as to reduce deformation in the bending process is arranged on the frame 1; one end of the inner core 6 is arranged on the frame 4, and the other end of the inner core always stretches into a part of the pipe which is not bent in the pipe to be bent. The bending radius of the cold bending groove corresponds to the bending radius of the bent pipe 8 to be processed by the pipeline to be bent; the bending angle of the cold bending groove is generally 360 degrees, and can be reduced according to actual conditions, so long as the requirements can be met. The pipe stopper 2, the clamping mechanism 5 and the rotator 3 are all of the prior art, and reference is made to the structure of the CN201720387133.8 patent, and will not be described in detail. Because the existing pipe bending machine is used for bending pipes with bending radius more than 5D, the application needs to manufacture parts such as a clamping mechanism 5, a pipe bending die 4 and the like which are suitable for bending pipes with small bending radius from 1D to 3D and the like.

For bends 8 with smaller bending radii, which require a large torque during bending, the bent pipe is subjected to a large force and is subject to a large deformation, i.e. the ovality of the bent portion exceeds the standard. The provision of the inner core 6 can effectively support the pipe to be bent, thereby reducing deformation. The existing pipe bender also has a structure for arranging the inner core 6. Such as patent CN201920651017.1 and patent CN201620016060.7 and patent CN201410064046.X, where the core is mostly a few small lengths of core connected by chains, the core 6 moves relative to the tube and is spread by the chains when the tube to be bent is bent, so that it can bend inside the tube. But the sliding between the core 8 and the pipe is liable to damage the inner wall of the pipe, causing quality hazards. In particular, for the pipe to be bent having the weld overlay 82 inside, the presence of the weld overlay 82 increases the friction between the pipe to be bent and the core 6 considerably, not only damaging the weld overlay, but also breaking the chain during the experiment due to excessive friction. In the application, one end of the inner core 6 is fixed on the frame 1, and the other end of the inner core 6 always extends into a pipe which is not bent in the pipe to be bent, and the inner core 6 cannot bend together with the pipe to be bent; the friction force caused by the release of the inner core 6 and the bending part of the bent pipe to be bent is avoided, the bent pipe to be bent can be supported to a certain extent, and the overlarge change of the bending angle and the overlarge ovality are prevented. The bent pipe 8 can ensure ellipticity, bending angle and roundness of the straight pipe section to be in a standard range through a shaping tool.

Further, one end of the inner core 6 is arranged on the frame 1, and the other end of the inner core extends into a straight pipe part at the junction of an unbent part and a bending part in the pipeline to be bent. In the initial state, the part of one end of the pipeline to be bent corresponding to the straight pipe section of the bent pipe is arranged in the clamping mechanism 5, the inner core 6 is inserted into the junction of the part of the pipeline to be bent corresponding to the elbow section and the corresponding part of the straight pipe section far away from the inner core, the straight pipe part at the rear end of the pipeline to be bent gradually moves forwards and the length is reduced along with the rotation of the rotating piece 3 and the pipe bending die 4, but the position of the pipeline to be bent is unchanged relative to the frame 1, and therefore the inner core 6 does not need to move in the process of bending the pipeline to be bent.

Further, an inner core seat 7 capable of moving back and forth is arranged on the frame 1, and one end of the inner core 6 is connected with the frame 1 through the inner core seat 7. Here, the back-and-forth movement means movement toward the pipe to be bent or movement away from the pipe to be bent. The inner core holder 7 is provided to move the inner core 6 back and forth so as to adjust the position of the inner core 6 according to different pipes to be bent and avoid when the pipes to be bent are initially installed and removed.

In other embodiments, the pipe bending machine for bending the pipe with straight pipe sections at two ends of cold bending forming comprises a frame 1, a pipe limiting part 2, a rotating part 3, a pipe bending die 4 and a clamping mechanism 5, wherein the pipe limiting part 2 is arranged on the frame 1 and used for limiting the position deviation of a pipe to be bent, the clamping mechanism is used for clamping the pipe to be bent in the bending process, the pipe bending die is fixed on the rotating part 3 and rotates coaxially with the rotating part 3, and a cold bending groove with a semicircular cross section is arranged on the pipe bending die 4 along the circumference. The difference is that the frame 1 is provided with an inner core 6 which can extend into the inner cavity of the pipeline to be bent so as to reduce deformation in the bending process. As shown in fig. 3, the inner core bend section 60 of the inner core 6 corresponding to the elbow section is made of a metal material having a melting point less than 500 degrees, the inner core bend section 60 is provided with an inner core straight section 61 at both ends thereof, and the inner core bend section 60 is bent along with the pipe to be bent. The metal material-supported core bent portion having a melting point of less than 500 degrees is not taken out after being bent, and can be softened and melted in a subsequent heat treatment to flow out. The inner core bend section 60 is integral and does not need to slide relative to the pipe to be bent, without damaging the inner wall to be bent. And the two ends of the inner core bent pipe section 60 are inner core straight pipe sections 61 with larger strength, so that the inner core bent pipe section can be pressed to prevent materials from being extruded to the two ends, and the ovality of the bent pipe section in the bending process is reduced. The strength and material of the core straight tube section 61 may be referenced to the strength and material of existing non-low melting cores.

Further, the inner core bent pipe section 61 and the inner core straight pipe section 60 are hinged or connected by a chain. The connection mode can refer to patent CN201620016060.7 and other structures, wherein the hinge joint is arranged at the part of the bent pipe to be bent corresponding to the straight pipe section, so that friction damage to the overlaying layer is avoided.

In addition, a supporting groove corresponding to the outer diameter of the pipeline to be bent is formed in one side, contacting with the pipeline to be bent, of the pipeline limiting piece 2. The unbent part of the pipeline to be bent is limited and supported by the supporting groove.

The specific implementation method comprises the following steps: the pipe to be bent is placed in the clamping mechanism 5, one end of the pipe to be bent is clamped by the clamping mechanism 5, and the inner core 6 is pushed to the end of the inner core 6 to reach the junction of the corresponding elbow section 80 and the straight pipe section 81 close to the clamping mechanism 5 in the pipe to be bent. The rotating member 3 and the bending die 4 rotate together until the bending is completed. During this process, the core 6 position does not change until the bending is completed. Or the rotation piece 3 and the pipe bending die 4 rotate, the inner core seat 7 pushes the inner core 6 forwards to bend the inner core bent pipe section 61 of the inner core 6 and the pipe to be bent together, and when the heat treatment is carried out after the pipe bending forming, the inner core bent pipe section 61 of the inner core 6 is melted, so that the inner core 6 can be taken out smoothly. The pipe bending machine has high forming efficiency; for example, under the drive of an intelligent program in a cold bending machine, a straight-section long-radius composite elbow with the diameter of 88.9 mm, the wall thickness of 8 mm and the bending radius of 1.5D can be formed in 5 minutes, and the manufacturing efficiency and the product performance are improved well. The pipe bending machine can be used for bending pipes with bending radius larger than 3D. The inner wall of the bent pipe machined by the pipe bending machine can be subjected to surfacing or not.

As shown in fig. 4-9, the shaping tool for shaping the bent pipe with the straight pipe sections at two ends by cold bending comprises an elbow shaping die for shaping the ellipticity of the elbow section of the bent pipe after cold bending and an elbow shaping die for shaping the whole bent pipe after shaping by the elbow shaping die. In the prior patent CN207872792U, the diameter of the pipeline is DN50-DN65 mm and the bending radius is 5D-6D; the pipe with the bending angle of 0 to 90 degrees can be subjected to cold press molding of the bent pipe through the hydraulic mechanism, and the bent pipe section of the bent pipe subjected to cold press molding can meet the use requirement only by carrying out ellipticity shaping through the shaping die. For a pipeline with a bending radius of 1D-3D, namely the radius of the pipeline is equal to the diameter of 1 to 3 straight pipes to be bent, the bent pipe 8 formed by adopting the cold bending method is relatively flat, namely the ellipticity of the pipeline exceeds that of the pipeline with the bending radius of more than 5D after cold pressing. If the existing shaping tool, namely the elbow shaping tool, is directly used, deformation generated by shaping of the ovality of the elbow segment 80 can cause the change of the bending angle of the elbow segment 80 and the roundness of straight pipe segments at two ends to not meet the processing requirement of products because the ovality of the elbow segment exceeds the standard. In the application, after the elbow section 80 of the elbow pipe 8 is shaped, the shape of the whole elbow pipe 8 is trimmed, so that the processing requirement of the elbow pipe 8 is met. Because the pipe 8 with smaller bending diameter is larger in deformation after cold bending, the pipe is bent by adopting an intermediate frequency heating or hot pushing method in the prior art, but the temperature is higher than 900 ℃ during hot press forming, and the metal characteristics can be changed, so that the advantages of the material are reduced. The metal characteristics of the pipeline are not changed in cold bending forming, so that the material characteristics of the base material are ensured. This is very advantageous for the complex working conditions (such as shale gas wells), and the advantages of the material itself are not reduced due to the characteristic change caused by hot press molding, so that the corrosion resistance and high temperature resistance of the raw material itself are maintained. After the shaping tool is adopted, the bent pipe 8 with smaller bending diameter can be processed in a cold bending mode to obtain a qualified product, so that the performance of the bent pipe 8 is ensured.

The elbow shaping die comprises an elbow shaping upper die and an elbow shaping lower die, wherein the inner cavity of the elbow shaping upper die and the inner cavity of the elbow shaping lower die are combined into an elbow shaping inner cavity corresponding to the shape of an elbow section of the elbow; the parting surfaces of the upper bend shaping die and the lower bend shaping die are planes perpendicular to the bending axis of the bend section 80. Wherein the elbow segment 80 is bent about its bending axis, the distance of the bending axis to either end of the pipe axis of the elbow segment 80 being equal to the bending radius of the elbow segment 80. When the pipe is cooled, the ovality of the elbow section 80 changes, and the longitudinal section of the elbow section needs to be trimmed to be round by using an elbow shaping die. In general, the longitudinal section of the inner cavity of the upper elbow shaping die and the longitudinal section of the inner cavity of the lower elbow shaping die are both semicircular, and the longitudinal section of the combined elbow shaping inner cavity is circular. The longitudinal section here refers to a plane including the bending axis. The bend-shaped lumen generally does not contain portions corresponding to straight tube sections at both ends. The elbow section after shaping meets the technical requirements of GB/T12459. Fig. 4 is an upper die of the bend shaping die. The lower die of the elbow shaping die is symmetrical with the structure of fig. 4.

Or the longitudinal sections of the inner cavities of the lower die of the elbow shaping inner cavity and the upper die of the elbow shaping inner cavity are semi-elliptic, and the parting surface corresponds to the long axis of the semi-elliptic; the bend shaping cavity is elliptical and has a major axis between 0.2 mm and 2 mm longer than a minor axis. The ovality exceeds standard after cold bending of a bending channel with smaller bending radius, so the longitudinal section of the elbow shaping inner cavity can be slightly oval, wherein the axis parallel to the bending radius is a long axis, the length of the long axis is slightly larger than that of the short axis, such as about 1 millimeter, and the elbow shaping die can ensure that the ovality formed by cold bending completely disappears. The size of the bent pipe after being trimmed again by the bent pipe shaping die is easier to reach the standard, and the yield is higher.

As shown in fig. 5-9, the elbow shaping mold comprises an elbow shaping upper mold and an elbow shaping lower mold; the longitudinal section of the upper bending die is a semicircular inner cavity, and the longitudinal section of the lower bending die is a semicircular inner cavity, so that a bending inner cavity with a circular longitudinal section is formed; the parting surfaces of the upper elbow shaping die and the lower elbow shaping die comprise arc-shaped surfaces taking the axis of the elbow as an axis and inclined planes connected with two ends of the arc-shaped surfaces. (the bending angle and roundness of the elbow are further shaped by the elbow shaping die, and the roundness of the right-angle end is shaped, so that the bending angle and roundness of the whole elbow are well guaranteed; fig. 4 and 5 are perspective schematic diagrams of the lower elbow shaping die and the upper elbow shaping die respectively.

The elbow shaping lower die and the elbow shaping lower die are respectively arranged at one end of a piston of the hydraulic machine; the elbow shaping lower die and the elbow shaping lower die are arranged on a hydraulic platform of the hydraulic machine. The number of the hydraulic presses can be two, and the elbow shaping mould correspond to one hydraulic press respectively. Hydraulic presses are not shown.

The elbow shaping die and the elbow shaping die of the patent can be used no matter what bending radius or diameter or pipeline wall thickness or whether build-up welding exists on the inner wall, and the elbow shaping die can be used as long as the elbow is formed by cold bending, and two ends of the elbow are provided with straight pipe sections. Of course, a hot bent pipe may be used if there is a need for shaping.

In specific implementation, the bent pipe 8 with the straight pipe sections 81 at the two ends of the middle bent pipe section 80 which is integrally formed after cold bending is firstly placed on the lower bend shaping die on the hydraulic platform, the piston end of the hydraulic machine drives the upper bend shaping die to move downwards to be tightly pressed with the lower bend shaping die, after a period of time, the piston end drives the upper bend shaping die to move upwards, the bent pipe 8 is taken out and placed in the lower bend shaping die on the other hydraulic machine, and the piston end of the other hydraulic machine drives the upper bend shaping die to move downwards to be tightly pressed and shaped with the lower bend shaping die. After the completion, the bent pipe 8 is taken out, and the shaping is completed. The novel bent pipe can be applied to the shale oil exploitation field, and can effectively improve the performance of the bent pipe and reduce the corrosion of the bent pipe.

As shown in fig. 1, the inner wall surfacing small bending radius elbow pipe 8 comprises an elbow section 80 and straight pipe sections 81 at two ends of the elbow section 80, the elbow pipe 8 is an integral weld-free pipe, the inner wall of the elbow section 80 is provided with a surfacing layer 82, the bending radius of the elbow section 80 of the elbow pipe 8 is 1 to 3 times of the diameter of the elbow pipe, the diameter of the elbow pipe is 60 to 220 mm, and the wall thickness of the elbow pipe is not less than 6 mm. For bends with bend radii 1D to 3D, having a bend diameter of between 60 mm and 220 mm and a wall thickness of no less than 6 mm, the prior art does not have a means to produce an integral weld-free bend 8 with bend section 80 having weld overlay 82. For a pipeline with a bending radius between 1D and 3D, taking 1.5D as an example, the prior art can only produce an elbow with a build-up welding layer 82 on the inner wall, such as an elbow in patent 204986165U, and then welding straight pipe sections at two ends of the elbow; or producing a weld-free bent pipe with straight pipe sections at two ends and no build-up welding layer on the inner wall, such as the bent pipe in the patent CN 103769451B. The application relates to a bent pipe product which can be produced by adopting a novel production process.

The weld overlay 82 may be a nickel-based alloy layer; the weld overlay 82 is composed of a plurality of weld beads, and the weld beads of the weld overlay 82 are annular. The bent pipe 8 is a cold bending bent pipe, the diameter of the bent pipe 8 is smaller than 168.3 mm, and the wall thickness is between 8 and 18 mm. The performance of the hot bent pipe can change, and the performance of the material is reduced. The cold-formed bent pipe with the surfacing layer can be more suitable for more complex working conditions, such as shale gas production sites, and the cold-formed bent pipe has limitation on the diameter and the wall thickness of the bent pipe.

The stripping layer 83 which is 10 mm to 30 mm long and is not provided with the surfacing layer is arranged at the pipe orifice of the straight pipe section 81, so that liquid mixed in shale gas is effectively prevented from staying in the surfacing layer and accumulation corrosion is avoided. The other part of the straight pipe section 81 is also provided with a build-up layer 82, and the build-up layer 82 is in an inclined transition to the peeling layer 83. The bend radius of the bend 8 is preferably 1.5D, which is a common pipe fitting currently used on shale gas skid and manifold equipment in shale gas development processes. The bent pipe 8 can be processed by adopting the pipe bending method and the pipe bending machine described in the previous description and is shaped by a shaping tool. The bent pipe with the surfacing layer can avoid the damage of gravel to the inner wall under the condition that the gas well has high pressure (the flow rate is more than or equal to 30 m/s), and can effectively improve the service cycle and the site safety of the bent pipe. The elbow section and the straight pipe section are integrated seamless elbows, so that excessive welding seams near the elbows are avoided.

It should be noted that terms such as "center", "transverse", "longitudinal", "length", "width", "thickness", "height", "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. used in the description are based on the orientation or positional relationship shown in the drawings, and are used for the purposes of description of the present patent only, rather than to indicate or imply that the device or element in question must have a particular orientation, be configured and operated in a particular orientation. And therefore should not be construed as limiting the scope of the application.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description. When the combination of the technical solutions is contradictory or impossible to realize, it should be considered that the combination of the technical solutions does not exist and is not within the scope of protection claimed by the present application. Moreover, it will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the spirit of the principles of the present application.

Claims (10)

1. The inner wall surfacing small bending radius bend forming method is characterized by comprising the following steps of: the method comprises the following steps: (1) Blanking a pipeline with proper length to be used as a main pipe of the pipeline to be bent; (2) A build-up welding layer is arranged at a proper position in the main pipe, and the build-up welding layer adopts a circumferential build-up welding method; (3) Carrying out cold bending on the surfacing pipe to be bent to integrally form a seamless bent pipe with an elbow section in the middle and straight pipe sections at two ends of the elbow section; (4) putting the bent pipe into a shaping tool for shaping: the bent pipe sequentially passes through an elbow shaping die for shaping the elbow section and an elbow shaping die for shaping the whole bent pipe.

2. The method for forming the inner wall surfacing small-bending-radius bent pipe according to claim 1, wherein the method comprises the following steps of: and (3) positioning and overlaying the nickel-based alloy layer on the inner wall of the main pipe in the step (2) to serve as an overlaying layer.

3. The method for forming the inner wall surfacing small-bending-radius bent pipe according to claim 1, wherein the method comprises the following steps of: and (3) and (4) the bent pipe is required to be subjected to heat treatment.

4. The method for forming the inner wall surfacing small-bending-radius bent pipe according to claim 1, wherein the method comprises the following steps of: the pipe bending machine comprises a frame, a pipe limiting part, a rotating part, a pipe bending die and a clamping mechanism, wherein the pipe limiting part is arranged on the frame and used for limiting the position deviation of the pipe to be bent; an inner core which can extend into the inner cavity of the pipeline to be bent so as to reduce deformation in the bending process is arranged on the frame; one end of the inner core is arranged on the frame, and the other end of the inner core always stretches into an unbent part pipeline in the pipeline to be bent.

5. The method for forming the inner wall surfacing small bending radius bent pipe according to any one of claims 1-4, wherein the method comprises the following steps: the elbow shaping die comprises an elbow shaping upper die and an elbow shaping lower die, wherein the inner cavity of the elbow shaping upper die and the inner cavity of the elbow shaping lower die are combined into an elbow shaping inner cavity corresponding to the shape of an elbow section of the elbow; the parting surfaces of the elbow shaping upper die and the elbow shaping lower die are planes perpendicular to the bending axis of the elbow section; the elbow shaping lower die is arranged at one end of a piston of the hydraulic machine; the elbow shaping lower die is arranged on a hydraulic platform of the hydraulic machine.

6. The method for forming the inner wall surfacing small bending radius bent pipe according to claim 5, wherein the method comprises the following steps: the bent pipe shaping die comprises an bent pipe shaping upper die and a bent pipe shaping lower die; the longitudinal section of the upper bending die is a semicircular inner cavity, and the longitudinal section of the lower bending die is a semicircular inner cavity, so that a bending inner cavity with a circular longitudinal section is formed; the parting surfaces of the upper elbow shaping die and the lower elbow shaping die are arc surfaces taking the axis of the elbow as the axis; the bent pipe shaping lower die is respectively arranged at one end of a piston of the hydraulic machine; the bent pipe shaping lower die is arranged on a hydraulic platform of the hydraulic machine.

7. An inner wall surfacing small bending radius elbow adopting the inner wall surfacing small bending radius elbow forming method of any one of claims 1-6, wherein the elbow comprises an elbow section and straight pipe sections at two ends of the elbow section, and the inner wall surfacing small bending radius elbow forming method is characterized in that: the elbow is an integral seamless cold-bending pipeline, a weld overlay is arranged on the inner wall of the elbow section, the bending radius of the elbow section of the elbow is 1 to 3 times of the diameter of the elbow, the diameter of the elbow is 60 to 220 mm, and the wall thickness of the elbow is not less than 6 mm.

8. The inner wall surfacing small bend radius elbow according to claim 7, wherein: the build-up welding layer is a nickel-based alloy layer; the weld bead of the weld overlay is annular.

9. The inner wall surfacing small bend radius elbow according to claim 8, wherein: the bent pipe is a cold bent pipe, the diameter of the bent pipe is smaller than 168.3 mm, and the wall thickness is between 8 and 18 mm.

10. The inner wall surfacing small bend radius elbow according to claim 9, wherein: and a stripping layer which is 10 mm to 30 mm long and is not provided with a surfacing layer is arranged at the pipe orifice of the straight pipe section, the surfacing layer is arranged at the other part of the straight pipe section, and the surfacing layer is obliquely transited to the stripping layer.