CN116928457A - Straight welded pipe with gradually-changed wall thickness for oil gas transportation and processing method thereof - Google Patents
Straight welded pipe with gradually-changed wall thickness for oil gas transportation and processing method thereof Download PDFInfo
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- CN116928457A CN116928457A CN202210326557.9A CN202210326557A CN116928457A CN 116928457 A CN116928457 A CN 116928457A CN 202210326557 A CN202210326557 A CN 202210326557A CN 116928457 A CN116928457 A CN 116928457A
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- 238000003672 processing method Methods 0.000 title claims abstract description 11
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 218
- 239000010959 steel Substances 0.000 claims abstract description 218
- 238000003466 welding Methods 0.000 claims abstract description 129
- 238000000034 method Methods 0.000 claims abstract description 61
- 238000005096 rolling process Methods 0.000 claims abstract description 51
- 230000008569 process Effects 0.000 claims abstract description 32
- 238000009749 continuous casting Methods 0.000 claims abstract description 23
- 238000001816 cooling Methods 0.000 claims abstract description 23
- 238000004519 manufacturing process Methods 0.000 claims abstract description 17
- 238000003801 milling Methods 0.000 claims abstract description 16
- 238000007670 refining Methods 0.000 claims abstract description 14
- 238000013461 design Methods 0.000 claims abstract description 11
- 238000005452 bending Methods 0.000 claims abstract description 10
- 230000007704 transition Effects 0.000 claims abstract description 5
- 239000007789 gas Substances 0.000 claims description 45
- 238000012545 processing Methods 0.000 claims description 27
- 238000001514 detection method Methods 0.000 claims description 22
- 238000003825 pressing Methods 0.000 claims description 15
- 238000003723 Smelting Methods 0.000 claims description 14
- 230000009467 reduction Effects 0.000 claims description 13
- 238000002360 preparation method Methods 0.000 claims description 12
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 10
- 238000005266 casting Methods 0.000 claims description 9
- 238000005516 engineering process Methods 0.000 claims description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 8
- 230000035515 penetration Effects 0.000 claims description 8
- 229910001566 austenite Inorganic materials 0.000 claims description 7
- 238000001953 recrystallisation Methods 0.000 claims description 7
- 238000000465 moulding Methods 0.000 claims description 6
- 238000009659 non-destructive testing Methods 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 229910052742 iron Inorganic materials 0.000 claims description 5
- 229910052786 argon Inorganic materials 0.000 claims description 4
- 239000002994 raw material Substances 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 3
- 210000001503 joint Anatomy 0.000 abstract description 14
- 230000005540 biological transmission Effects 0.000 abstract description 5
- 238000009740 moulding (composite fabrication) Methods 0.000 abstract 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 8
- 230000008859 change Effects 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 230000002706 hydrostatic effect Effects 0.000 description 4
- 238000009847 ladle furnace Methods 0.000 description 4
- 239000003345 natural gas Substances 0.000 description 4
- 238000010276 construction Methods 0.000 description 3
- 238000007689 inspection Methods 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 239000006247 magnetic powder Substances 0.000 description 2
- 239000003209 petroleum derivative Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 241000755266 Kathetostoma giganteum Species 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000005489 elastic deformation Effects 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012806 monitoring device Methods 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L9/00—Rigid pipes
- F16L9/02—Rigid pipes of metal
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/38—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling sheets of limited length, e.g. folded sheets, superimposed sheets, pack rolling
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
- B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
- B21C37/08—Making tubes with welded or soldered seams
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/38—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling sheets of limited length, e.g. folded sheets, superimposed sheets, pack rolling
- B21B2001/386—Plates
Abstract
The invention discloses a straight welded pipe for oil and gas transmission with gradually changed wall thickness and a processing method thereof. The processing method comprises (1) structural design of a steel plate with gradually changed wall thickness; (2) preparing a steel plate with gradually-changed wall thickness; preparing a pipeline steel plate with different wall thicknesses at two ends, continuous wall thickness in the middle part and smooth transition through the processes of refining, continuous casting, controlled rolling, rolling of steel plates with gradually-changed wall thickness, controlled cooling and the like; (3) The welded pipe can meet the API standard requirement by adjusting the pipe manufacturing processes of edge milling, pre-bending, forming, welding and the like, can be used for annular welding of the oil-gas pipe network site, is connected with annular welding of parts with larger butt joint diameter and wall thickness difference, and improves the geometric dimension precision and the annular welding quality of the pipe end annular welding.
Description
Technical Field
The invention relates to the technical field of petroleum and natural gas pipes, in particular to a straight welded pipe with gradually changed wall thickness for oil and gas transportation and a processing method thereof.
Background
The pipeline is used as a high-efficiency and economic conveying mode and is a main mode for long-distance conveying of petroleum and natural gas. The existing pipeline is to connect a large number of single steel pipes in a direct girth welding mode to realize long-distance oil and gas transmission. In recent years, the occurrence of multiple trunk line pipe accident interruptions has been a general concern in the industry for the safety of the pipe itself. And (3) counting the failure cases of part of the domestic pipelines in recent years, wherein 7 cases occur at the girth weld joints in 13 cases, and analyzing the reasons: on one hand, as the toughness of the girth weld deposited metal is hard to reach the toughness of the steel pipe body by adopting the controlled rolling and cooling technology, high-toughness matching is hard to form in butt joint, so that the strength and toughness of the pipe end girth weld joint are weaker. On the other hand, the geometric dimension precision of the pipe end of the existing oil gas conveying pipe is poor, the diameter difference of the butt joint ends of the steel pipes is large, the geometric precision is insufficient, the butt joint is easy to generate the wrong edges during the girth welding, the strong assembly is easy to form internal stress, and the quality of the girth welding is influenced.
With the steady promotion of the construction of Chinese oil and gas pipeline engineering, the continuous perfection of the oil and gas pipe network and the natural gas pipe network, the construction of natural gas multi-channel construction, interconnection and intercommunication engineering, connecting line pipelines and gas storage peak shaving facilities are enhanced. However, the problems of larger diameter and wall thickness difference of the ring welding butt joint ends and insufficient geometric precision are more remarkable because the connection quantity of steel pipes, hot bent pipes, matched pipe fittings and the like in different areas is more. When in field butt joint, even if the steel pipe is welded after being forced to be rounded by using equipment such as a pipe expander and the like, the residual stress of the girth weld is large because the steel pipe is in the elastic deformation range during pipe expansion, so that the bearing capacity is reduced, or cracks are easy to induce and promote crack expansion. When the oil gas conveying pipeline is acted by external force, stress concentration is most easily formed at the circumferential weld, pipeline quality safety accidents caused by the failure of the circumferential weld joint often occur, and huge losses are brought to life, property and economic development of people.
Patent publication No. CN 110778804A discloses an oil gas conveying pipe and a manufacturing method of the oil gas conveying pipe, in which a welded layer is finished by welding the inner surface and/or the outer surface of the end of a steel pipe along the circumferential direction of the steel pipe to increase the thickness of the end of the steel pipe, thereby ensuring the butt joint precision and roundness of the end of the steel pipe. The design thought of the method is worthy of affirmation, but the method is a method for increasing the wall thickness of the end part of the steel pipe through a welding layer, the pipe making process is complex, the mechanical degree is low, the quality stability is poor, and the circumferential welding process can influence the performance of the steel pipe body.
Disclosure of Invention
The invention aims at solving the problems that in the field girth welding process, welding defects and large stress concentration are easy to occur due to large difference of diameters and wall thicknesses of two ends of butt joint and insufficient geometric precision, nondestructive detection is not facilitated, quality of a pipeline girth weld is affected and the like at complex connection parts such as steel pipes, hot bend pipes and matched pipe fittings in different areas of an oil-gas pipe network, and provides a straight welded pipe for oil-gas transportation with gradually-changed wall thickness and a processing method thereof.
The invention relates to a straight welded pipe for oil gas transmission, which adopts a steel plate with gradually changed wall thickness, and the pipe making process is adjusted to manufacture the oil gas transmission pipe with different wall thickness at two ends (the wall thickness is from thin to thick), the wall thickness in the middle part is continuous and smoothly transited, the integral performance of the pipe body is consistent, and the comprehensive mechanical property is good. The method is mainly used for the annular welding of the positions with larger butt joint diameters and wall thickness differences in the field of the oil-gas pipe network, and the two ends of the variable-wall-thickness steel pipe are respectively connected with the steel pipe, the hot bend pipe, the matched pipe fitting and the like to realize equal wall thickness or equal diameter connection, so that the geometric dimension precision of the annular welding of the pipe end is improved, the stress concentration is reduced, the welding defects are reduced, and the quality of the annular welding seam is greatly improved.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the straight welded pipe for oil and gas conveying with gradually changed wall thickness is one kind of pipe structure with gradually changed wall thickness and linearly increased wall thickness from the thin wall end to the thick wall end.
Further, the wall thickness-variable pipe body structure is an equal-outer-diameter wall thickness-variable straight welded pipe or an equal-inner-diameter wall thickness-variable straight welded pipe.
Further, the variable wall thickness pipe body structure comprises a thin wall end, a middle connecting part and a thick wall end, wherein the thin wall end is provided with a certain length, the thin wall end is communicated with the thick wall end through the middle connecting part, the middle connecting part is a pipe body with the wall thickness linearly increased, and the length of the middle connecting part is larger than that of the thin wall end and the thick wall end.
The invention also provides a processing method of the straight welded pipe for oil and gas transportation with gradually changed wall thickness, which comprises the following steps:
(1) Steel plate structure design with gradually-changed wall thickness
The steel plate with the gradually-changed wall thickness is of a steel plate structure composed of a head section, a middle section and a tail section, the wall thicknesses of the head section and the tail section are different and are equal-wall-thickness sections, the middle section is a gradually-changed wall-thickness section, the head section and the tail section respectively occupy 10% of the whole length of the steel plate, the middle section occupies 80% of the whole length of the steel plate, and the gradually-changed wall-thickness sections are linearly increased;
(2) Preparation of steel plate with gradually-changed wall thickness
Step 1) smelting molten steel;
step 2) continuously casting into a blank;
step 3) heating the continuous casting blank;
step 4) rolling control;
step 5) Rolling of Steel sheet with gradually-varied wall thickness
Finish rolling the steel plate according to the structural design requirement of the steel plate with gradually changed wall thickness;
step 6) controlling cooling;
(3) And processing the steel plate with the gradually-changed wall thickness into a finished product through a straight welded pipe processing technology with the gradually-changed wall thickness.
Further, the step 1) molten steel smelting: molten steel is smelted according to the element components of the pipeline steel plate, and the smelting raw materials are subjected to KR molten iron pretreatment, converter smelting, LF refining and RH vacuum refining in sequence to obtain molten steel meeting the element component requirements.
Further, the step 2) is continuous casting and forming: argon gas is blown for a calm time of not less than 20min before continuous casting after molten steel refining, the superheat degree of molten steel is controlled in the continuous casting process, the pouring superheat degree of a continuous casting blank is 15-33 ℃, and the reduction of casting blank is controlled, so that the thickness of the continuous casting blank/the thickness of a finished steel plate is controlled to be 6-9.
Further, the step 3) is to heat the continuous casting billet: in the heating process, the temperature is controlled to 1080-1250 ℃ to ensure that the continuous casting billet is completely austenitized and the elements are fully dissolved in solid.
Further, the step 4) controlled rolling: the rolling control process adopts two-stage rolling control, wherein the first stage is an austenite recrystallization stage, the initial rolling temperature ranges from 1080 ℃ to 1140 ℃, the final rolling temperature is higher than 1030 ℃, and the total rolling reduction is 35 to 40%, and the intermediate billet is rolled; the second stage is austenite non-recrystallization stage, the initial rolling temperature is less than 980 ℃, the final rolling temperature is 880-930 ℃, and the total reduction is more than 70%.
Further, said step 6) controls cooling: and (3) adopting an ultra-fast cooling process, wherein the cooling rate is 15-50 ℃/s, the temperature fluctuation of the whole length and width direction of the steel plate is controlled to be less than or equal to 30 ℃, the final cooling temperature of cooling is controlled to be 350-550 ℃, then the steel plate is straightened, and finally air-cooling is carried out to room temperature, so as to obtain the pipeline steel plate with different wall thicknesses at two ends, continuous and smooth transition of the wall thickness in the middle part, namely the steel plate with gradual wall thickness.
Further, the straight welded pipe processing technology with gradually changed wall thickness in the step (3) comprises the following steps:
firstly, plate detection and working procedure preparation: ultrasonic plate detection, leveling, steel plate feeding and arc welding plate striking, and during feeding: one surface of the steel plate with a variable wall thickness is the inner wall of the steel pipe; firstly, processing the thick-wall end of the steel plate;
secondly, edge milling: rough milling is firstly performed, then finish milling is performed, and a groove is processed;
third step, pre-bending: manufacturing the steel plate into an arc shape through a pre-bending machine; pressing the pre-bent outer steel plate for multiple times to form a J shape, and pressing the inner steel plate for multiple times to form a C shape;
fourth, molding: manufacturing the pre-bent steel plate into a tube shape through a forming machine; aiming at the steel plate with gradually-changed wall thickness, pressing the steel plate into an O-shaped opening;
fifth step, joint pre-welding: adopting a mixed gas shielded welding mode to perform continuous welding to finish a joint process, so as to form a continuous and reliable pre-welded joint;
sixth, submerged arc final welding: firstly, welding the inner wall of the pre-welded pipe barrel, and then welding the outer wall of the pipe barrel after internal welding; the front wire adopts direct current reverse connection to obtain enough penetration, and the rear wire adopts alternating current to fill the groove weld;
and seventhly, rounding, water pressure and nondestructive testing.
The invention has the beneficial effects that:
1. the straight welded pipe for oil gas conveying with gradually changed wall thickness has different wall thicknesses at two ends of the pipe body, and can realize equal wall thickness or equal diameter connection in the annular welding connection process of the two ends of the steel pipe with the steel pipe, the hot bend pipe or the matched pipe fitting and the like, thereby improving the geometric dimension precision of annular welding of the pipe end, reducing stress concentration, reducing welding defects and greatly improving the quality of the annular welding seam.
2. The invention designs the variable wall thickness steel plate structure with different wall thicknesses at two ends and gradually changing wall thickness at the middle part and the rolling process thereof, and realizes the uniform and stable performance of the positions of the head and the tail of the steel plate while ensuring the dimensional accuracy of the steel plate structure; the steel plate with the gradually-changed wall thickness provides powerful guarantee for real-time adjustment of the subsequent forming, welding and other pipe making processes, and ensures the high quality of welded pipes; meanwhile, the straight welded pipe with the gradually-changed wall thickness can prevent stress concentration caused by abrupt change of the pipe wall thickness, and the service safety of the welded pipe is improved.
3. The invention provides a guarantee for manufacturing the wall thickness-variable straight welded pipe with uniform performance, reliable quality and high geometric dimension precision by optimizing the processes of edge milling, pre-bending, JCO forming, pre-welding, final welding, expanding and the like of the wall thickness-variable steel plate through the wall thickness-variable straight welded pipe processing process.
Drawings
FIG. 1 is a constant diameter variable wall thickness straight welded pipe of the present invention;
FIG. 2 is a straight welded pipe with equal internal diameter and variable wall thickness according to the present invention;
fig. 3 is a schematic view showing the wall thickness variation along the length direction of the steel sheet with gradually changed wall thickness according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, but are not limited thereto. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Description of the technical terms involved: KR (Kanbara reactor) molten iron pretreatment is pretreatment for desulfurizing molten iron. LF (Ladle Furnace) refining, stirring with argon, submerged arc heating with graphite electrode under atmospheric pressure, and slag refining. RH vacuum refining is collectively referred to as RH vacuum circulation degassing refining. API (American Petroleum Institute) is an ANSI approved standardization establishment whose standardization complies with ANSI reconciliation and programming guidelines.
Example 1
The invention provides a straight welded pipe for oil gas transmission with gradually changed wall thickness, which is a pipe body structure with linearly increased wall thickness from a thin-wall end to a thick-wall end at the middle part, wherein the wall thickness of the two ends of the pipe body is different.
Further, the wall thickness variable pipe body structure is an equal-outer diameter wall thickness variable straight welded pipe (see fig. 1) or an equal-inner diameter wall thickness variable straight welded pipe (see fig. 2).
Further, the variable wall thickness pipe body structure comprises a thin wall end, a middle connecting part and a thick wall end, wherein the thin wall end is provided with a certain length, the thin wall end is communicated with the thick wall end through the middle connecting part, the middle connecting part is a pipe body with the wall thickness linearly increased, and the length of the middle connecting part is larger than that of the thin wall end and the thick wall end.
The invention also provides a processing method of the straight welded pipe for oil and gas transportation with gradually changed wall thickness, which comprises the following steps:
(1) Steel plate structure design with gradually-changed wall thickness
The steel plate with the gradually-changed wall thickness is of a steel plate structure composed of a head section, a middle section and a tail section, the wall thicknesses of the head section and the tail section are different and are equal-wall-thickness sections, the middle section is a gradually-changed wall-thickness section, the head section and the tail section respectively occupy 10% of the whole length of the steel plate, the middle section occupies 80% of the whole length of the steel plate, and the gradually-changed wall-thickness sections are linearly increased;
(2) Preparation of steel plate with gradually-changed wall thickness
Step 1) smelting molten steel;
step 2) continuously casting into a blank;
step 3) heating the continuous casting blank;
step 4) rolling control;
step 5) Rolling of Steel sheet with gradually-varied wall thickness
Finish rolling the steel plate according to the structural design requirement of the steel plate with gradually changed wall thickness;
step 6) controlling cooling;
(3) And processing the steel plate with the gradually-changed wall thickness into a finished product through a straight welded pipe processing technology with the gradually-changed wall thickness.
Further, the straight welded pipe processing technology with gradually changed wall thickness in the step (3) comprises the following steps:
firstly, plate detection and working procedure preparation: ultrasonic plate detection, leveling, steel plate feeding and arc welding plate striking, and during feeding: one surface of the steel plate with a variable wall thickness is the inner wall of the steel pipe; firstly, processing the thick-wall end of the steel plate;
secondly, edge milling: rough milling is firstly performed, then finish milling is performed, and a groove is processed;
third step, pre-bending: manufacturing the steel plate into an arc shape through a pre-bending machine; pressing the pre-bent outer steel plate for multiple times to form a J shape, and pressing the inner steel plate for multiple times to form a C shape;
fourth, molding: manufacturing the pre-bent steel plate into a tube shape through a forming machine; aiming at the steel plate with gradually-changed wall thickness, pressing the steel plate into an O-shaped opening;
fifth step, joint pre-welding: adopting a mixed gas shielded welding mode to perform continuous welding to finish a joint process, so as to form a continuous and reliable pre-welded joint;
sixth, submerged arc final welding: firstly, welding the inner wall of the pre-welded pipe barrel, and then welding the outer wall of the pipe barrel after internal welding; the front wire adopts direct current reverse connection to obtain enough penetration, and the rear wire adopts alternating current to fill the groove weld;
and seventhly, rounding, water pressure and nondestructive testing.
Example 2
On the basis of the embodiment 1, the processing method of the straight welded pipe for oil and gas transportation with gradually changed wall thickness comprises the following steps:
(1) Steel plate structure design with gradually-changed wall thickness
In the steel plate production process, the problem that the production and manufacturing process is difficult to control on line and the product quality and the product performance are difficult to control is solved by considering the sudden change of the wall thickness of the steel plate. Therefore, a steel plate structure with gradually-changed wall thickness is designed, and as shown in figure 3, the steel plate consists of a head section (A-B section), a tail section (C-D section), a conventional equal-wall-thickness section and a middle section (B-C section) gradually-changed wall-thickness section. The head section and the tail section of the steel plate with the gradually-changed wall thickness are equal-wall-thickness sections, wherein the equal-wall-thickness sections respectively account for 10% of the whole length of the steel plate, the gradually-changed wall-thickness section of the middle section accounts for 80% of the whole length of the steel plate, and the transition between the two equal-wall-thickness sections is realized by gradually changing the wall thickness from thick to thin.
(2) Preparation of steel plate with gradually-changed wall thickness
Step 1) molten steel smelting: smelting molten steel according to the element components of the pipeline steel plate, and sequentially carrying out KR molten iron pretreatment, converter smelting, LF refining and RH vacuum refining on smelting raw materials to obtain molten steel meeting the element component requirements;
and 2) continuously casting into blanks: argon gas is blown for a calm time of not less than 20min before continuous casting after molten steel refining, the superheat degree of molten steel is controlled in the continuous casting process, the pouring superheat degree of a continuous casting blank is 15-33 ℃, and the reduction of casting blank is controlled, so that the thickness of the continuous casting blank/the thickness of a finished steel plate is controlled to be 6-9.
And 3) heating the continuous casting billet in the step: in the heating process, the temperature is controlled to 1080-1250 ℃ to ensure that the continuous casting billet is completely austenitized and the elements are fully dissolved in solid.
The step 4) of controlled rolling: the rolling control process adopts two-stage rolling control, wherein the first stage is an austenite recrystallization stage, the initial rolling temperature ranges from 1080 ℃ to 1140 ℃, the final rolling temperature is higher than 1030 ℃, and the total rolling reduction is 35 to 40%, and the intermediate billet is rolled; the second stage is austenite non-recrystallization stage, the initial rolling temperature is less than 980 ℃, the final rolling temperature is 880-930 ℃, and the total reduction is more than 70%.
Preferably, the initial rolling temperature range 1120 ℃ and the final rolling temperature 1060 ℃ are adopted, the total reduction is 36%, and the intermediate billet is rolled; the second stage is austenite non-recrystallization stage, the initial rolling temperature is 970 ℃, the final rolling temperature is 920 ℃, and the total reduction is 80%.
Step 5) rolling the steel plate with gradually-changed wall thickness: based on the designed wall thickness gradual change steel plate structure, the rolling program and the pressing rate of a rolling unit are set by combining the target specification of the final steel plate, and the rolling head is a thick-wall section accounting for 10% of the whole length of the steel plate; the rolling tail part is a thin-wall section and accounts for 10% of the whole length of the steel plate; the wall thickness of the middle part gradually changes from thick to thin; the finishing mill group is provided with a heat preservation cover, so that the finishing temperature of the steel plate is ensured, and the uniformity and stability of the head and tail position performances of the steel plate are realized.
Step 6) controlling cooling: and an ultra-fast cooling process is adopted, the cooling rate is 15-50 ℃/s, the wall thickness difference at the head and tail positions of the steel plate is considered, the temperature fluctuation in the length and width directions of the whole plate is controlled to be less than or equal to 30 ℃, and the mechanical property difference of the head, tail, longitudinal and transverse of the steel plate is reduced. The final cooling temperature of cooling is controlled at 350-550 ℃, then the steel plate is straightened, and finally the steel plate is cooled to room temperature, thus obtaining the pipeline steel plate with different wall thicknesses at two ends (the wall thickness is from thin to thick), and the wall thickness of the middle part is continuous and in smooth transition, namely the steel plate with gradually changed wall thickness.
(3) Processing technology of straight welded pipe with gradually changed wall thickness
Firstly, plate detection and working procedure preparation: comprises pipeline steel plate ultrasonic plate detection, leveling, steel plate feeding and arc welding plates. The leveling requires the geometric dimension of a plate shape, the unevenness of the steel plate is required to be less than 10mm/2000mm, the plate head and the plate tail are not allowed to flex downwards, the upwarp is less than 40mm, and the probability of defects such as puckering, edge staggering and the like in the later pipe making process is reduced; the feeding requires the direction of the steel plate, and according to actual engineering requirements, whether the variable wall thickness side of the steel plate is the outer wall or the inner wall of the steel pipe is determined; meanwhile, the thick-wall end of the steel plate is a first processing and manufacturing end.
Secondly, edge milling: rough milling is firstly performed, then finish milling is performed, and a groove is processed; because the steel plate with the variable wall thickness is formed by flattening one surface of the steel plate, the wall thickness of the other surface of the steel plate is gradually changed, the groove opening angle is close to the flattened surface of the steel plate, the groove depth and the thickness processing size of the blunt edge are unchanged, the groove opening angle is kept unchanged and the groove depth is gradually changed along with the gradual change of the wall thickness; the opening angle of the groove and the depth of the groove are referred to the groove processing parameters of the conventional oil gas conveying straight welded pipe.
Third step, pre-bending: manufacturing the steel plate into an arc shape through a pre-bending machine; pressing the pre-bent outer steel plate for multiple times to form a J shape, and pressing the inner steel plate for multiple times to form a C shape; aiming at the steel plate with the gradual wall thickness, the step length is reduced, the pressing pass is improved, the residual stress is reduced, and the pass deformation is 5-10%; the steel plate is pressed by adopting smaller rolling reduction, and then the rolling reduction is gradually increased, so that the deformation of the steel plate at different wall thicknesses is ensured to be sufficient, and the optimal shape is obtained.
Fourth, molding: manufacturing the pre-bent steel plate into a tube shape through a forming machine; aiming at the steel plate with the gradual change wall thickness, in the process of pressing the steel plate into an O-shaped opening, the steel plate is pressed for a plurality of times according to different wall thicknesses, centering errors are reduced by adopting a centering block, the forming curvature of the steel pipe is checked by adopting a special inner and outer profiling, the pipe shape is monitored, the uniform deformation of the formed pipe body and the pipe end is ensured, the gap of an opening seam is basically consistent, the axial dislocation of the pipe end and the difference value of two ends are strictly controlled.
Fifth step, joint pre-welding: folding the edges of the pressed and formed opening pipe barrel by an upper die and a lower die of a stitching machine, and pre-welding to keep the shape of the steel pipe; and adjusting the pressure of the welding seam pressing mechanism according to the actual condition of the steel plate with the gradually-changed wall thickness, keeping the two sides of the welding seam straight, and tightly attaching the plate edges or keeping the gaps uniform. Adopting continuous pre-welding and mixed gas shielded automatic welding (shielding gas Ar+CO) 2 :80% +20% by mass), the wire and the welding process refer to the pre-welding parameters of a conventional oil and gas conveying straight welded pipe.
Sixth, submerged arc final welding: firstly, welding the inner wall of the pre-welded pipe barrel, and then welding the outer wall of the pipe barrel after internal welding; the front wire adopts direct current reverse connection, so that enough penetration is mainly obtained, and the rear wire adopts alternating current, so that the welding line is mainly used for filling a groove welding line, adjusting the penetration and improving the shape of the welding line. And determining specific welding parameters according to the wall thickness of the pipeline steel by adopting a 2-5 wire submerged arc welding process.
Aiming at the welding of one side with gradually changed wall thickness, when the wall thickness difference of two ends of the tube blank is less than 25%, the welding speed of the tube blank in linear movement is adjusted in real time according to the actual wall thickness, namely, the welding speed parameter is adjusted according to the wall thickness information fed back in real time through a wall thickness real-time monitoring device, so that the welding speed is always kept in a reasonable matching range, the effective filling of a welding line is ensured, and the high-quality welding of one side with variable wall thickness is realized; when the difference of the wall thicknesses at the two ends of the tube blank is more than 25%, after the filling welding of the thin-wall ends is finished, the submerged arc automatic welding mode is adopted by taking the position of unqualified penetration as a starting point, the multi-layer and multi-pass welding is carried out, the whole welding process is finished after the covering surface is reached, and specific welding parameters are determined according to the residual penetration of the welding seam. Before welding, back chipping treatment is needed, and a previous welding layer is polished and ground; the temperature difference between adjacent welding layers in welding is controlled below 150 ℃.
Seventh, rounding, water pressure and nondestructive testing: x-ray detection of a welding line, expanding of a steel pipe, hydrostatic test, ultrasonic detection of the welding line, X-ray detection of a pipe end, flat-head chamfering, finish machining of a thick-wall end of a pipe body, magnetic powder detection of the pipe end and appearance quality inspection.
For a straight welded pipe with gradually changed wall thickness, mechanical diameter expansion is adopted during diameter expansion, modular sectional control is adopted, the wall thicknesses of the pipe end and the pipe body are different, diameter expansion processes with different diameter expansion rates are adopted, step sizes are reduced, the length of each sectional diameter expansion is about 2.0-2.5 m during diameter expansion of the pipe body, and the overlapping amount of the front and rear sectional diameter expansion is ensured to be more than 0.5m; measuring ovality of the pipe ends and the pipe bodies by adopting an ovality laser automatic detection device, and ensuring geometric dimensional accuracy of the straight welded pipe bodies and the pipe ends; hydrostatic test, namely selecting relevant parameters of the hydrostatic test according to the thin wall value of the wall thickness of the pipe body and the corresponding steel grade; and referring to the actual wall thickness dimension of the engineering butt joint end, machining the thick-wall end of the steel pipe, and adjusting the diameter and roundness of the end part of the steel pipe so as to improve the geometric dimension precision of the end part of the butt joint steel pipe. Thereby obtaining the straight welded pipe for oil gas transportation, which has basically consistent pipe body performance, meets the API standard requirement, and has good comprehensive performance and gradually-changed wall thickness. Wherein the ellipticity laser automatic detection device is the prior art and is not described in detail here.
Example 3
The difference from example 2 is that this example is an application example, specifically a method for processing an X70 steel grade OD 813X 14.2-17.5mm, constant diameter variable wall thickness straight welded pipe.
1. The preparation process of the steel plate with the length of 12 meters and the wall thickness of 14.2-17.5mm and gradually changed is as follows:
smelting molten steel according to the element components of the X70 pipeline steel plate, continuously casting into a blank, and heating and rolling the continuously cast blank; finish rolling the steel plate according to the design requirement of variable wall thickness, wherein the wall thickness of the rolling head is 17.5mm, the length is 1.2m, the wall thickness of the rolling tail is 14.2mm, the length is 1.2m, and the wall thickness of the middle part is 9.6 m, and is uniformly reduced from 17.5mm to 14.2mm; and then cooling is controlled to obtain the X70 steel plate with the variable wall thickness of 14.2-17.5 mm.
2. The OD813 x 14.2-17.5mm equal outer diameter variable wall thickness straight welded pipe processing technology is as follows:
1) Plate detection and working procedure preparation: ultrasonic plate detection, leveling, steel plate feeding and arc welding. Feeding is to note that: one surface of the steel plate with a variable wall thickness is the inner wall of the steel pipe; the thick-wall 17.5mm end of the steel plate is firstly processed.
2) Edge milling of the steel plate: the outer bevel is opened at an angle of 75 degrees, the depth of the outer bevel is 5mm, the thickness of the blunt side is 4, the inner bevel is opened at an angle of 85 degrees, and the depth of the inner bevel is gradually changed along with the wall thickness.
3) And (3) forming a steel plate JCO: according to the actual wall thickness of the wall thickness-variable steel plate, the forming curvature R386.2-R389.3mm, the step length of a forming machine is 114.8mm, one radius of the steel plate is pressed into a J shape for 10 times, the other radius is performed by adopting the same method, the inner steel plate is pressed for 3 times to form a C shape, and finally the steel plate is pressed into an O shape; and the special inner and outer explorations are adopted to check the molding curvature of the steel pipe and monitor the pipe shape, so that the deformation of the steel plate at different wall thicknesses is ensured to be sufficient, and the optimal shape is obtained.
4) Seam pre-welding: and the pipe blank is subjected to continuous welding by adopting a mixed gas shielded welding mode to finish a joint process, so that a continuous and reliable pre-welding joint is formed.
5) Submerged arc final welding: the internal welding adopts three-wire submerged arc automatic welding to weld on the groove on the inner side of the steel pipe, the No. 1 welding wire is in direct current reverse connection, the current is 920A, and the voltage is 33.5V; the No. 2 welding wire adopts alternating current, the current is 750A, and the voltage is 35.5V; the welding wire No. 3 adopts alternating current, the current is 650A, and the voltage is 37V; for welding with gradual wall thickness, the welding speed is adjusted from 1.7m/min to 1.75m/min in real time. The external welding adopts three-wire submerged arc automatic welding to weld on a groove on the outer side of the steel pipe, the current 940A of the No. 1 welding wire and the voltage 34V; welding wire current No. 2, 800A, voltage 37V; wire current No. 3 620A, voltage 40V; the welding speed was 1.7m/min.
6) Rounding, water pressure and nondestructive testing: adopting modularized sectional control to mechanically expand the diameter, and expanding the diameter of the steel pipe by 0.8% of the total length; hydrostatic test, test pressure is 16.9MPa, and dwell time is more than 15s; the bevel angle of the pipe end is 22-25 degrees, and the blunt edge is 1.6 plus or minus 0.8mm; ultrasonic detection of welding seams, X-ray detection of pipe ends, magnetic powder detection of pipe ends and appearance quality inspection.
The OD 813X 14.2-17.5mm equal-diameter variable-wall-thickness straight welded pipe is shown in figure 1, wherein the end A is a thick-wall end, and the end D is a thin-wall end. The two ends of the pipe body are sampled and detected, and the results are shown in table 1:
table 1 shows the main properties of the constant diameter variable wall thickness straight welded pipe:
the results show that the different wall thickness end properties of the welded pipe of the invention are basically equivalent.
Example 4
The difference from example 3 is that this example is another application example, and specifically, the method for processing the straight welded pipe with the equal inner diameter and the variable wall thickness is a method for processing the straight welded pipe with the equal inner diameter and the variable wall thickness, wherein the X80 steel grade ID is 1370.6 multiplied by 25.7-33.8 mm.
1. The preparation process of the steel plate with the length of 12 meters and the wall thickness of 25.7-33.8mm and gradually changed is as follows:
molten steel was melted according to the elemental composition of the X80 pipeline steel sheet, and a 25.7-33.8mm variable wall thickness X80 steel sheet was obtained according to the process flow in example 3.
2. The manufacturing process of the ID1370.6 multiplied by 25.7-33.8mm equal-inner-diameter and variable-wall-thickness straight welded pipe is as follows:
1) Plate detection and working procedure preparation: ultrasonic plate detection, leveling, steel plate feeding and arc welding. Feeding is to note that: one surface of the steel plate with a variable wall thickness is the outer wall of the steel pipe; the thick-wall 30.8mm end of the steel plate is firstly processed.
2) Edge milling of the steel plate: the opening angle of the inner groove is 65 degrees, the depth of the inner groove is 11mm, and the blunt side is 8mm; the open angle of the outer bevel is 70 degrees, and the depth of the outer bevel gradually changes along with the wall thickness.
3) And (3) forming a steel plate JCO: according to the actual wall thickness of the wall thickness-variable steel plate, the forming curvature R675.2-R680.4mm, the step length of a forming machine is 114.8mm, one radius of the steel plate is pressed into a J shape for 12 times, the other radius is performed by adopting the same method, the inner steel plate is pressed for 5 times to form a C shape, and finally the steel plate is pressed into an O shape; and the special inner and outer explorations are adopted to check the molding curvature of the steel pipe and monitor the pipe shape, so that the deformation of the steel plate at different wall thicknesses is ensured to be sufficient, and the optimal shape is obtained.
4) Seam pre-welding: and adopting a mixed gas shielded welding mode to continuously weld the pipe blank to finish a joint process, wherein the pre-welding wire is BHG-2M welding wire, the diameter phi of the welding wire is 4.0 mm, and the pre-welding speed V=4.0M/min.
5) Submerged arc final welding: the internal welding adopts double-wire multi-channel submerged arc welding, the No. 1 welding wire is in direct current reverse connection, the current is 550A, and the voltage is 32V; the No. 2 welding wire adopts alternating current, current 450A and voltage 33V; the welding speed is 1.2m/min; a total of 4 layers of 8 welds. The external welding adopts double-wire multi-channel submerged arc welding, the No. 1 welding wire is in direct current reverse connection, the current is 600A, and the voltage is 33V; the No. 2 welding wire adopts alternating current, current 480A and voltage 34V; the welding speed is 1.2m/min; and (3) after 4 layers of 8 welding seams are welded, filling welding is finished at the thin-wall end, 2 layers of 2 welding is carried out by taking the position of which the penetration does not reach the standard as a starting point, and the whole welding procedure is finished after the cover surface is finished, so that the welding process is unchanged.
6) The steps of rounding, water pressure, nondestructive testing and the like are as in example 1, the outer periphery of the thick-wall end of the steel pipe is processed by referring to the actual wall thickness size of the butt joint end of the engineering, the diameter and roundness of the end of the steel pipe are adjusted, so that the geometric dimension precision of the end of the butt joint steel pipe is improved, and finally the qualified steel pipe is prepared.
The ID1370.6 multiplied by 25.7-33.8mm equal-inner-diameter variable-wall-thickness straight welded pipe is shown in figure 2, wherein the end A is a thick-wall end, and the end D is a thin-wall end. The two ends of the pipe body are sampled and detected, and the results are shown in table 2:
table 2 shows the main properties of the equal inner diameter variable wall thickness straight welded pipe:
the results show that the different wall thickness end properties of the welded pipe of the invention are basically equivalent.
Therefore, the processing method adopts the steel plate with gradually changed wall thickness, and the wall thickness at two ends is different (the wall thickness is from thin to thick) through adjusting the pipe making process, the wall thickness of the middle part is continuous and smoothly transited, the integral performance of the pipe body meets the API standard requirement, and meanwhile, the performance of the 2 end of the pipe body is basically consistent, and the comprehensive mechanical property is good. The thick-wall end of the steel pipe is machined, and the diameter and roundness of the end of the steel pipe are adjusted, so that the geometric dimension precision of the end of the butted steel pipe is improved, equal wall thickness or equal diameter connection is facilitated in field girth welding, stress concentration is reduced, welding defects are reduced, and girth weld quality is greatly improved.
The foregoing is a further detailed description of the present invention in connection with the preferred embodiments, and it is not intended to limit the embodiments of the invention to the precise forms set forth herein, but rather to enable one skilled in the art to make various simple inferences, substitutions or alternations without departing from the spirit of the invention, which is intended to be interpreted as falling within the scope of the appended claims.
Claims (10)
1. A straight welded pipe for oil gas transportation with gradually changed wall thickness is characterized in that: the straight welded pipe for oil gas conveying with gradually changed wall thickness is a pipe body structure with linearly increased wall thickness from a thin wall end to a thick wall end in the middle.
2. The straight welded pipe for oil and gas transportation with gradually changed wall thickness according to claim 1, wherein the straight welded pipe is characterized in that: the wall thickness-variable pipe body structure is an equal-outer-diameter wall thickness-variable straight welded pipe or an equal-inner-diameter wall thickness-variable straight welded pipe.
3. A straight welded pipe for oil and gas transportation with gradually changed wall thickness according to claim 1 or 2, characterized in that: the variable wall thickness pipe body structure comprises a thin wall end, a middle connecting part and a thick wall end, wherein the thin wall end is provided with a certain length, the thin wall end is communicated with the thick wall end through the middle connecting part, the middle connecting part is a pipe body with the wall thickness linearly increased, and the length of the middle connecting part is larger than that of the thin wall end and the thick wall end.
4. A processing method of a straight welded pipe for oil and gas transportation with gradually changed wall thickness is characterized by comprising the following steps: the method comprises the following steps:
(1) Steel plate structure design with gradually-changed wall thickness
The steel plate with the gradually-changed wall thickness is of a steel plate structure composed of a head section, a middle section and a tail section, the wall thicknesses of the head section and the tail section are different and are equal-wall-thickness sections, the middle section is a gradually-changed wall-thickness section, the head section and the tail section respectively occupy 10% of the whole length of the steel plate, the middle section occupies 80% of the whole length of the steel plate, and the gradually-changed wall-thickness sections are linearly increased;
(2) Preparation of steel plate with gradually-changed wall thickness
Step 1) smelting molten steel;
step 2) continuously casting into a blank;
step 3) heating the continuous casting blank;
step 4) rolling control;
step 5) Rolling of Steel sheet with gradually-varied wall thickness
Finish rolling the steel plate according to the structural design requirement of the steel plate with gradually changed wall thickness;
step 6) controlling cooling;
(3) And processing the steel plate with the gradually-changed wall thickness into a finished product through a straight welded pipe processing technology with the gradually-changed wall thickness.
5. The method for processing the straight welded pipe for oil and gas transportation with gradually changed wall thickness according to claim 4, wherein the method comprises the following steps: the step 1) molten steel smelting: molten steel is smelted according to the element components of the pipeline steel plate, and the smelting raw materials are subjected to KR molten iron pretreatment, converter smelting, LF refining and RH vacuum refining in sequence to obtain molten steel meeting the element component requirements.
6. The method for processing the straight welded pipe for oil and gas transportation with gradually changed wall thickness according to claim 4, wherein the method comprises the following steps: and 2) continuously casting into blanks: argon gas is blown for a calm time of not less than 20min before continuous casting after molten steel refining, the superheat degree of molten steel is controlled in the continuous casting process, the pouring superheat degree of a continuous casting blank is 15-33 ℃, and the reduction of casting blank is controlled, so that the thickness of the continuous casting blank/the thickness of a finished steel plate is controlled to be 6-9.
7. The method for processing the straight welded pipe for oil and gas transportation with gradually changed wall thickness according to claim 4, wherein the method comprises the following steps: and 3) heating the continuous casting billet in the step: in the heating process, the temperature is controlled to 1080-1250 ℃ to ensure that the continuous casting billet is completely austenitized and the elements are fully dissolved in solid.
8. The method for processing the straight welded pipe for oil and gas transportation with gradually changed wall thickness according to claim 4, wherein the method comprises the following steps: the step 4) of controlled rolling: the rolling control process adopts two-stage rolling control, wherein the first stage is an austenite recrystallization stage, the initial rolling temperature ranges from 1080 ℃ to 1140 ℃, the final rolling temperature is higher than 1030 ℃, and the total rolling reduction is 35 to 40%, and the intermediate billet is rolled; the second stage is austenite non-recrystallization stage, the initial rolling temperature is less than 980 ℃, the final rolling temperature is 880-930 ℃, and the total reduction is more than 70%.
9. The method for processing the straight welded pipe for oil and gas transportation with gradually changed wall thickness according to claim 4, wherein the method comprises the following steps: said step 6) controlling cooling: and (3) adopting an ultra-fast cooling process, wherein the cooling rate is 15-50 ℃/s, the temperature fluctuation of the whole length and width direction of the steel plate is controlled to be less than or equal to 30 ℃, the final cooling temperature of cooling is controlled to be 350-550 ℃, then the steel plate is straightened, and finally air-cooling is carried out to room temperature, so as to obtain the pipeline steel plate with different wall thicknesses at two ends, continuous and smooth transition of the wall thickness in the middle part, namely the steel plate with gradual wall thickness.
10. The method for processing the straight welded pipe for oil and gas transportation with gradually changed wall thickness according to claim 4, wherein the method comprises the following steps: the processing technology of the straight welded pipe with the gradually-changed wall thickness in the step (3) comprises the following steps:
firstly, plate detection and working procedure preparation: ultrasonic plate detection, leveling, steel plate feeding and arc welding plate striking, and during feeding: one surface of the steel plate with a variable wall thickness is the inner wall of the steel pipe; firstly, processing the thick-wall end of the steel plate;
secondly, edge milling: rough milling is firstly performed, then finish milling is performed, and a groove is processed;
third step, pre-bending: manufacturing the steel plate into an arc shape through a pre-bending machine; pressing the pre-bent outer steel plate for multiple times to form a J shape, and pressing the inner steel plate for multiple times to form a C shape;
fourth, molding: manufacturing the pre-bent steel plate into a tube shape through a forming machine; aiming at the steel plate with gradually-changed wall thickness, pressing the steel plate into an O-shaped opening;
fifth step, joint pre-welding: adopting a mixed gas shielded welding mode to perform continuous welding to finish a joint process, so as to form a continuous and reliable pre-welded joint;
sixth, submerged arc final welding: firstly, welding the inner wall of the pre-welded pipe barrel, and then welding the outer wall of the pipe barrel after internal welding; the front wire adopts direct current reverse connection to obtain enough penetration, and the rear wire adopts alternating current to fill the groove weld;
and seventhly, rounding, water pressure and nondestructive testing.
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