CN112917093B - Manufacturing method of large-thickness-diameter ratio high-strain marine pipeline - Google Patents

Abstract

The disclosure provides a manufacturing method of a large-thickness-diameter ratio high-strain marine pipeline, and belongs to the technical field of pipeline manufacturing. The manufacturing method comprises the following steps: providing a pipeline steel plate, wherein the metallographic structure of the pipeline steel plate comprises acicular ferrite and fine-grained ferrite; providing a forming die, wherein the forming die is designed based on the design pipe diameter and the design wall thickness of the marine pipeline; forming the pipeline steel plate by using a JCO forming process through a forming die to obtain a pipeline pipe blank; and welding two longitudinal edges of the pipe blank of the pipeline together by adopting a large-dry-extension process welding gun to obtain the marine pipeline. The present disclosure may enable the manufacture of large-thickness-to-diameter ratio high-strain marine pipelines.

Description

Manufacturing method of large-thickness-diameter ratio high-strain marine pipeline

Technical Field

The disclosure belongs to the technical field of pipeline manufacturing, and particularly relates to a manufacturing method of a large-thickness-diameter ratio high-strain marine pipeline.

Background

Deep water oil gas, especially rich oil gas resource in south China sea, is a new place and a main battlefield for future energy development in China. Subsea pipelines are a major component of offshore oil and gas fields, and once leaked, they can cause serious environmental disasters. When being laid, the deepwater pipeline bears larger compression and tensile loads and even bending deformation, and in the service process, the deepwater pipeline generates larger plastic deformation due to deepwater high pressure, surge, strong underflow, seabed movement and the like, and the complex working conditions put more severe requirements on the deepwater pipeline than the overland pipeline. Onshore pipelines are not suitable for use in deep water environments.

However, the current research on large-thickness-to-diameter ratio high-strain marine pipelines is still in the blank stage in China.

Disclosure of Invention

The embodiment of the disclosure provides a manufacturing method of a large-thickness-diameter ratio high-strain marine pipeline, which can realize oil and gas transmission in a deepwater environment. The technical scheme is as follows:

the embodiment of the disclosure provides a manufacturing method of a large-thickness-diameter ratio high-strain marine pipeline, which comprises the following steps:

providing a pipeline steel plate, wherein the metallographic structure of the pipeline steel plate comprises acicular ferrite and fine-grained ferrite, and the pipeline steel plate comprises the following components in percentage by mass: 0.02 to 0.07wt%, mn: 1.50-1.80 wt%, P is less than or equal to 0.015wt%, S is less than or equal to 0.015wt%, si:0.10 to 0.30wt%, nb: 0.020-0.080 wt%, V is less than or equal to 0.03wt%, ti is less than or equal to 0.025wt%, al is less than or equal to 0.06wt%, N is less than or equal to 0.008wt%, cu is less than or equal to 0.30wt%, cr is less than or equal to 0.30wt%, mo is less than or equal to 0.30wt%, and Ni: 0.10-0.50 wt%, B is less than or equal to 0.0005wt%, pcm:0.13 to 0.18, ceq:0.34 to 0.36 percent of (Nb + V + Ti) is less than or equal to 0.15 percent by weight, O is less than or equal to 0.00025 percent by weight, and the balance is Fe and inevitable impurities;

providing a forming die, wherein the forming die is designed based on the design pipe diameter and the design wall thickness of the marine pipeline;

forming and processing the pipeline steel plate by using a JCO forming process through the forming die to obtain a pipeline pipe blank;

and welding two longitudinal edges of the pipeline pipe blank together by adopting a large-dry-extension process welding gun to obtain the marine pipeline.

Optionally, the manufacturing method further comprises:

carrying out desulphurization and slagging-off pretreatment on molten iron;

carrying out dephosphorization, decarburization, alloying and inclusion form control process treatment on the molten iron to obtain a continuous casting billet;

and hot-rolling the continuous casting slab to obtain the pipeline steel plate.

Optionally, the manufacturing method further comprises:

providing an arc striking plate and an arc quenching plate, wherein the arc striking plate and the arc quenching plate are made of the same material as the pipeline steel plate, and the arc striking plate and the arc quenching plate are made of the same thickness as the pipeline steel plate;

respectively welding the arc striking plate and the arc extinguishing plate at four corners of the pipeline steel plate;

and polishing the welding positions of the arc striking plate and the arc extinguishing plate.

Optionally, the manufacturing method further comprises:

milling X-shaped welding grooves on two longitudinal edges of the pipeline steel plate respectively, wherein the milling width of each X-shaped welding groove is 1650 +/-5 mm, each X-shaped welding groove comprises an upper groove and a lower groove, the angle of each upper groove is 38 +/-1 degrees, the angle of each lower groove is 36 +/-1 degrees, and the thicknesses of the truncated edges of the upper groove and the lower groove are 13.5 +/-0.5 mm;

and cleaning the X-shaped welding groove.

Optionally, the forming processing of the duct steel plate by using a JCO forming process includes:

feeding the pipeline steel plate into a forming die along the extension direction of the transverse edge, so that one longitudinal edge of the pipeline steel plate is bent to obtain a J-shaped pipeline steel plate;

continuously feeding the steel pipe plate, and gradually bending the part between the two longitudinal edges of the steel pipe plate in multiple steps to obtain a C-shaped steel pipe plate;

and continuously feeding the steel pipe into the steel pipe plate, so that the other longitudinal edge of the steel pipe plate is bent to obtain an O-shaped steel pipe plate, and taking the O-shaped steel pipe plate as the pipe blank.

Optionally, the manufacturing method further comprises:

performing joint closing and centering on the pipe blank of the pipeline;

and adopting a full-length continuous prewelding process of a welding line, and prewelding the two longitudinal edges of the pipe blank of the pipeline through consumable electrode active gas shielded arc welding.

Optionally, welding the two longitudinal edges of the pipe blank together by using a large dry elongation process welding gun, including:

welding the downward notches of the two longitudinal edges by adopting a welding wire with the dry elongation of 110 mm;

and welding the upper grooves of the two longitudinal edges by adopting a welding wire with the dry elongation of 130 mm.

Optionally, welding the descending notch of the two longitudinal sides includes:

performing first wire welding on the descending notches of the two longitudinal edges, wherein the current type is direct current reverse connection, the current is 1300A, and the voltage is 30V;

performing second wire welding on the descending notches of the two longitudinal edges, wherein the current type is alternating current, the current is 900A, and the voltage is 42V;

carrying out third wire welding on the descending notches of the two longitudinal edges, wherein the current type is alternating current, the current is 800A, and the voltage is 44V;

and fourth wire welding is carried out on the descending notches of the two longitudinal edges, the current type is alternating current, the current is 700A, and the voltage is 45V.

Optionally, welding the upper grooves of the two longitudinal sides includes:

performing first wire welding on the upper grooves of the two longitudinal edges, wherein the current type is direct current reverse connection, the current is 1350A, and the voltage is 30V;

performing second wire welding on the upper grooves of the two longitudinal edges, wherein the current type is alternating current, the current is 950A, and the voltage is 42V;

carrying out third wire welding on the upper grooves of the two longitudinal edges, wherein the current type is alternating current, the current is 800A, and the voltage is 44V;

and fourth wire welding is carried out on the upper grooves of the two longitudinal edges, the current type is alternating current, the current is 700A, and the voltage is 45V.

Optionally, the manufacturing method further comprises:

mechanically expanding the diameter of the marine pipeline;

grinding welding seams at two ends of the marine pipeline;

and processing welding grooves for axial welding with other adjacent marine pipelines at two ends of the marine pipeline.

The technical scheme provided by the embodiment of the disclosure has the following beneficial effects:

the metallographic structure of the pipeline steel plate is designed into acicular ferrite and fine-grained ferrite, and the component mass percentage of the pipeline steel plate is further limited, so that the pipeline steel plate has stronger strain hardening capacity, higher low-temperature fracture toughness, lower anisotropy, higher uniformity and stability of transverse and longitudinal performance. The forming die is designed according to the design pipe diameter and the design wall thickness of the marine pipeline, and the pipeline steel plate is formed and processed through the forming die by utilizing the JCO forming process, so that the straight line segment of the pipeline blank obtained after forming and processing is smaller and is close to a cylinder shape to the greatest extent. The welding gun adopting the large dry elongation process welds two longitudinal edges of the pipeline tube blank together, improves the melting speed of a welding wire of unit welding current, reduces the heat input to the pipeline tube blank, increases the heat obtained by the welding wire, can achieve the purpose of reducing the energy of the welding wire, and can better realize the welding of a thick-wall pipeline. That is to say, the manufacturing method provided by the present disclosure enables the pipe steel plate to have a strong strain hardening capability through the limitation of the material of the pipe steel plate. The size specification and the thickness-diameter ratio of the pipe blank of the pipeline are ensured by limiting the forming die and the forming process. Through the limitation on the welding process, the pipeline pipe blank with thicker wall can be welded better. In summary, the manufacturing method provided by the present disclosure can provide a large-thickness-to-diameter ratio high-strain marine pipeline to meet the oil and gas transportation requirement in a deep water environment.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

Fig. 1 is a flow chart of a method for manufacturing a large-thickness-to-diameter ratio high-strain marine pipeline according to an embodiment of the present disclosure;

FIG. 2 is a microscopic schematic view of a metallographic structure provided by an embodiment of the disclosure;

fig. 3 is a schematic structural diagram of a forming die provided in an embodiment of the disclosure;

FIG. 4 is a cross-sectional view of a pipe blank provided by an embodiment of the present disclosure;

FIG. 5 is a flow chart of another method of manufacturing a large thickness to diameter ratio high strain marine pipeline provided by embodiments of the present disclosure;

fig. 6 is a macroscopic metallographic view of a weld joint provided by an embodiment of the present disclosure.

Detailed Description

To make the objects, technical solutions and advantages of the present disclosure more apparent, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

The disclosed embodiment provides a manufacturing method of a large-thickness-diameter ratio high-strain marine pipeline, as shown in fig. 1, the manufacturing method includes:

step 101: providing a pipeline steel plate, wherein the metallographic structure of the pipeline steel plate comprises acicular ferrite a and fine-grained ferrite b (see figure 2), and the pipeline steel plate comprises the following components in percentage by mass: 0.02 to 0.07wt%, mn: 1.50-1.80 wt%, P is less than or equal to 0.015wt%, S is less than or equal to 0.015wt%, si:0.10 to 0.30wt%, nb: 0.020-0.080 wt%, V is less than or equal to 0.03wt%, ti is less than or equal to 0.025wt%, al is less than or equal to 0.06wt%, N is less than or equal to 0.008wt%, cu is less than or equal to 0.30wt%, cr is less than or equal to 0.30wt%, mo is less than or equal to 0.30wt%, and Ni: 0.10-0.50 wt%, B is less than or equal to 0.0005wt%, pcm:0.13 to 0.18, ceq:0.34 to 0.36 percent of (Nb + V + Ti) is less than or equal to 0.15 percent by weight, O is less than or equal to 0.00025 percent by weight, and the balance is Fe and inevitable impurities.

Step 102: and providing a forming die (see fig. 3), wherein the forming die is designed based on the design pipe diameter and the design wall thickness of the marine pipeline.

Illustratively, the forming die includes an upper die 100 and two lower dies 200, and a duct steel plate 300 is disposed between the upper die 100 and the lower dies 200.

Step 103: the pipe steel plate is subjected to forming processing by a JCO forming process through a forming die to obtain a pipe blank (see fig. 4).

Step 104: and welding two longitudinal edges of the pipe blank of the pipeline together by adopting a large-dry-extension process welding gun to obtain the marine pipeline.

The metallographic structure of the pipeline steel plate is designed into acicular ferrite and fine-grained ferrite, and the component mass percentage of the pipeline steel plate is further limited, so that the pipeline steel plate has stronger strain hardening capacity, higher low-temperature fracture toughness, lower anisotropy, higher uniformity and stability of transverse and longitudinal performance. The forming die is designed according to the design pipe diameter and the design wall thickness of the marine pipeline, and the pipeline steel plate is formed and processed through the forming die by utilizing the JCO forming process, so that the straight line segment of the pipeline blank obtained after forming and processing is smaller and is close to a cylinder shape to the greatest extent. The welding gun adopting the large dry elongation process welds two longitudinal edges of the pipe blank together, improves the melting speed of a welding wire of unit welding current, reduces the heat input to the pipe blank of the pipeline, increases the heat obtained by the welding wire, can achieve the purpose of reducing the energy of a welding line, and can better realize the welding of a thick-wall pipeline. That is to say, the manufacturing method provided by the present disclosure may enable the pipe steel plate to have a strong strain hardening capability through the limitation of the material of the pipe steel plate. The size specification and the thickness-diameter ratio of the pipe blank of the pipeline are ensured by limiting the forming die and the forming process. Through the limitation on the welding process, the pipeline pipe blank with thicker wall can be welded better. In conclusion, the manufacturing method provided by the disclosure can be used for manufacturing the large-thickness-diameter-ratio high-strain marine pipeline so as to meet the oil and gas conveying requirement in the deep water environment.

Fig. 5 is another method for manufacturing a marine pipeline with a large thickness to diameter ratio and a high strain ratio according to an embodiment of the present disclosure, as shown in fig. 5, the method includes:

step 501: providing a pipeline steel plate, wherein the metallographic structure of the pipeline steel plate comprises acicular ferrite and fine-grained ferrite, and the pipeline steel plate comprises the following components in percentage by mass: 0.02 to 0.07wt%, mn: 1.50-1.80 wt%, P is less than or equal to 0.015wt%, S is less than or equal to 0.015wt%, si:0.10 to 0.30wt%, nb: 0.020-0.080 wt%, V is less than or equal to 0.03wt%, ti is less than or equal to 0.025wt%, al is less than or equal to 0.06wt%, N is less than or equal to 0.008wt%, cu is less than or equal to 0.30wt%, cr is less than or equal to 0.30wt%, mo is less than or equal to 0.30wt%, and Ni: 0.10-0.50 wt%, B is less than or equal to 0.0005wt%, pcm:0.13 to 0.18, ceq:0.34 to 0.36 percent of (Nb + V + Ti) is less than or equal to 0.15 percent by weight, O is less than or equal to 0.00025 percent by weight, and the balance is Fe and inevitable impurities.

Alternatively, step 501 may be implemented by:

firstly, molten iron is subjected to desulfurization and slagging-off pretreatment.

In the implementation mode, the desulphurization and the slagging-off are two independent and closely-connected molten iron pretreatment processes, the desulphurization determines the sulfur-containing level of molten iron at the treatment end point, and the slagging-off is an important means for removing high-sulfur slag subjected to desulphurization treatment from the molten iron and determines the total amount of sulfur entering the furnace. The sulfur content in the molten iron can be adjusted through desulfurization and slagging-off pretreatment.

And then, carrying out dephosphorization, decarburization, alloying and inclusion form control process treatment on the molten iron to obtain a continuous casting billet.

In the implementation mode, through the process, high-cleanness steel smelting is realized, the pipeline steel plate has lower sulfur and phosphorus content, the size and the number of inclusions are controlled more strictly, and the uniformity and the stability of the transverse and longitudinal performance of the pipeline steel plate are ensured.

Alternatively, the slab is manufactured by a high homogenization continuous casting technique of a thick gauge, so that a slab having more excellent properties can be obtained.

And finally, hot-rolling the continuous casting billet to obtain the pipeline steel plate.

Step 502: and welding an arc striking plate and an arc extinguishing plate on the pipeline steel plate.

Alternatively, step 502 may be implemented by:

firstly, an arc striking plate and an arc extinguishing plate are provided, the arc striking plate and the arc extinguishing plate are made of the same material as the pipeline steel plate, and the arc striking plate and the arc extinguishing plate are made of the same thickness as the pipeline steel plate.

Illustratively, the length and width of the arc striking plate can be 300mm × 100mm, and the length and width of the arc extinguishing plate can be 500mm × 100mm.

And then, respectively welding the arc striking plate and the arc extinguishing plate at the four corners of the pipeline steel plate.

Therefore, the arc striking plate is arranged, so that arc striking of the welding gun before formal welding can be conveniently realized through the arc striking plate in the subsequent welding step, and the quality of the formal welding is improved. Similarly, the arc quenching plate is arranged, so that arc quenching of the welding gun after formal welding can be realized through the arc quenching plate in the subsequent welding step, and the formal welding quality is improved.

And finally, polishing the welding positions of the arc striking plate and the arc extinguishing plate.

In this way, flash can be eliminated to ensure subsequent welding quality.

Step 503: welding grooves are milled on both longitudinal edges of the pipeline steel plate respectively (see fig. 6).

Alternatively, step 503 may be implemented by:

firstly, X-shaped welding grooves are respectively milled on two longitudinal edges of a pipeline steel plate, the milling width of the X-shaped welding grooves is 1650 +/-5 mm, the X-shaped welding grooves comprise an upper groove 1 and a lower groove 2, the angle of the upper groove 1 is 38 +/-1 degrees, the angle of the lower groove 2 is 36 +/-1 degrees, and the thicknesses of the truncated edges of the upper groove 1 and the lower groove 2 are 13.5 +/-0.5 mm.

Illustratively, an X-shaped welding groove is milled on each longitudinal edge of the pipeline steel plate through an edge milling machine.

And finally, cleaning the X-shaped welding groove.

In the above implementation, the cleaned X-shaped welding groove is a clean machined surface to eliminate defects such as burrs, chips, scale, and cracks.

Step 504: pre-bending two longitudinal edges of the pipeline steel plate.

Optionally, the circular arc and the edge bending die with the transition section are adopted, and the two longitudinal edges of the pipeline steel plate are pre-bent simultaneously, so that the two longitudinal edges are always in a pure bending deformation process in the pre-bending process, and rolling can not be generated.

Illustratively, the length of the straight edge in the pre-bending process is less than or equal to 31.8mm, and the puckered value within a range of 130mm from the two longitudinal edges of the pipeline steel plate is +/-1.5 mm.

Step 505: and providing a forming die, wherein the forming die is designed based on the design pipe diameter and the design wall thickness of the marine pipeline.

Optionally, finite element analysis is performed by adopting a Mise stress theory, so that the shape of the marine pipeline is simulated on a computer, and an optimal forming die is designed according to the pipe diameter and the wall thickness of the marine pipeline.

Step 506: and (4) forming the pipeline steel plate by using a JCO forming process through a forming die to obtain a pipeline pipe blank.

Alternatively, step 506 may be implemented by:

first, the piping steel plate is fed into a forming die along the extending direction of the lateral sides so that one longitudinal side of the piping steel plate is bent by pressure to obtain a J-shaped piping steel plate.

And continuously feeding the steel pipe plate, and gradually bending the part between the two longitudinal edges of the steel pipe plate in multiple steps to obtain the C-shaped steel pipe plate.

And finally, continuously feeding the steel pipe plate to bend the other longitudinal edge of the steel pipe plate to obtain an O-shaped steel pipe plate, and taking the O-shaped steel pipe plate as a pipe blank of the pipe.

In the implementation mode, the forming curvature of the formed pipe blank of the pipeline is R240, the bending times are 25 times, the ovality is 0-15 mm, the straightness is not more than 0.10% of the total length of the steel pipe, the gap of the opening seam is not more than 100mm, the axial dislocation is not more than 5mm, and the radial dislocation is not more than 10mm.

Step 507: and prewelding the pipe blank of the pipeline.

Alternatively, step 507 may be implemented by:

firstly, the pipe blank of the pipeline is subjected to joint closing and centering.

Illustratively, a nine roll seaming machine is used to close and quickly center the pipe blank open seam to eliminate misalignment.

Then, the full-length continuous pre-welding process of the welding seam is adopted, and the two longitudinal edges of the pipe blank of the pipeline are pre-welded through consumable electrode active gas shielded arc welding.

Alternatively, the welding current may be 1000A, the welding voltage may be 26V, the welding speed may be 4.5m/min, and the linear energy may be 3.47KJ/cm.

Optionally, a laser tracking device may be used to ensure the weld quality of the pre-weld.

Step 508: the two longitudinal edges of the pipe blank are welded together using a heavy dry elongation process welding gun (see fig. 6) to obtain the marine pipeline.

Illustratively, DC-AC four-wire submerged arc welding is adopted, but the dry elongation of a welding wire is increased from 25mm-35mm in the common process to 60mm-120mm, the melting speed of the welding wire in unit welding current is improved, the heat input to a pipe blank of the pipeline is reduced, the heat obtained by the welding wire is increased, the purpose of reducing the energy of the welding wire can be achieved, and the welding of a thick-wall pipeline can be better realized.

Alternatively, step 508 may be implemented by:

first, welding was performed on the downward slopes on both longitudinal sides using a welding wire having a dry elongation of 110mm and a diameter of 4mm.

Exemplarily, firstly, performing first wire welding on the descending notches of two longitudinal sides, wherein the current type is direct current reverse connection, the current is 1300A, and the voltage is 30V; secondly, performing second wire welding on the downward notches of the two longitudinal sides, wherein the current type is alternating current, the current is 900A, and the voltage is 42V; then, carrying out third wire welding on the descending notches of the two longitudinal edges, wherein the current type is alternating current, the current is 800A, and the voltage is 44V; and finally, fourth wire welding is carried out on the descending notches of the two longitudinal sides, the current type is alternating current, the current is 700A, and the voltage is 45V.

Then, the upper grooves of both longitudinal sides were welded using a welding wire having a dry elongation of 130mm and a diameter of 4mm.

Exemplarily, firstly, performing first wire welding on upper grooves of two longitudinal sides, wherein the current type is direct current reverse connection, the current is 1350A, and the voltage is 30V; secondly, performing second wire welding on the upper grooves of the two longitudinal sides, wherein the current type is alternating current, the current is 950A, and the voltage is 42V; then, performing third wire welding on the upper grooves of the two longitudinal sides, wherein the current type is alternating current, the current is 800A, and the voltage is 44V; and then, fourth wire welding is carried out on the upper grooves on the two longitudinal sides, wherein the current type is alternating current, the current is 700A, and the voltage is 45V.

Step 509: and mechanically expanding the diameter of the marine pipeline.

Illustratively, the method adopts a stepping delivery and cylinder stroke position control mode to mechanically expand the total length of the marine pipeline, so that the internal diameter precision of the marine pipeline is ensured, the total length of the marine pipeline is straightened and rounded, the size precision of the marine pipeline is improved, and the distribution state of the stress in the marine pipeline is effectively improved.

Step 510: and (5) grinding welding seams at two ends of the marine pipeline.

In this way, provision may be made for subsequent axial welding of two adjacent marine pipes.

Illustratively, the grinding length of the welding line at the lower groove is not less than 150mm, the grinding length of the welding line at the upper groove is not less than 300mm, and the rest height of the welding line after grinding is 0mm-0.5mm.

Step 511: and welding grooves for axial welding with other adjacent marine pipelines are processed at the two ends of the marine pipeline.

In this way, two adjacent marine pipelines can be conveniently welded axially.

Illustratively, the angle of the welding groove is 30.5-34.5 °, the truncated edge is 1.6 ± 0.5mm, and the chamfer width is not more than 1.3mm.

The metallographic structure of the pipeline steel plate is designed into acicular ferrite and fine-grained ferrite, and the component mass percentage of the pipeline steel plate is further limited, so that the pipeline steel plate has stronger strain hardening capacity, higher low-temperature fracture toughness, lower anisotropy, higher uniformity and stability of transverse and longitudinal performance. The forming die is designed according to the design pipe diameter and the design wall thickness of the marine pipeline, and the pipeline steel plate is formed and processed through the forming die by utilizing the JCO forming process, so that the straight line segment of the pipeline blank obtained after forming and processing is smaller and is close to a cylinder shape to the greatest extent. The large-dry-extension process welding gun is adopted to weld the two longitudinal edges of the pipeline pipe blank together, so that the melting speed of a welding wire in unit welding current is increased, the heat input to the pipeline pipe blank is reduced, the heat obtained by the welding wire is increased, the purpose of reducing the energy of the welding wire can be achieved, and the welding of a thick-wall pipeline can be better realized. That is to say, the manufacturing method provided by the present disclosure may enable the pipe steel plate to have a strong strain hardening capability through the limitation of the material of the pipe steel plate. The size specification and the thickness-diameter ratio of the pipe blank of the pipeline are ensured by limiting the forming die and the forming process. Through the limitation on the welding process, the pipeline pipe blank with thicker wall can be welded better. In conclusion, the manufacturing method provided by the disclosure can be used for manufacturing the large-thickness-diameter-ratio high-strain marine pipeline so as to meet the oil and gas conveying requirement in the deep water environment.

Through actual manufacturing, the high-strain longitudinal submerged arc welded pipe with the steel grade of L485, the diameter of 559mm and the wall thickness of 31.8mm is manufactured through the manufacturing method provided by the disclosure. The longitudinal yield strength of the pipe body of the marine pipeline is 485-585 MPa, the longitudinal tensile strength of the pipe body is 570-700 MPa, the longitudinal yield ratio of the pipe body is not more than 0.85, and the tensile strength of a welding joint is not less than 575MPa; the average value of the impact energy of the steel pipe body in the transverse direction Xia Bi is not less than 150J at the temperature of minus 20 ℃; the Charpy impact work of the central line of the welding line, the fusion line, the position 2mm away from the fusion line and the position 5mm away from the fusion line is not less than 50J; the average value of 2 samples in a pipe body transverse drop hammer tear test at 0 ℃ is not less than 85%, the CTOD characteristic value of the crack tip opening displacement at the pipe body and the welding joint at 0 ℃ is not less than 0.15mm, and the maximum hardness value of the pipe body and the welding joint is not more than 300HV10; the ovality of the pipe body is not more than 3.5mm, the ovality of the pipe end is not more than 3mm, the straightness of the pipe body is not more than 0.15 percent of the length of the whole pipe, and the residual height of the internal and external welding lines is 0-4mm.

The following table illustrates the specific implementation of the manufacturing method provided by the present disclosure.

Table 1 shows the results of the tensile properties test of the pipe body and the weld of the marine pipeline, see table 1:

TABLE 1

Table 2 shows the results of the charpy impact toughness test of the marine pipeline body steel pipe, which is shown in table 2:

TABLE 2

Table 3 shows the DWTT toughness test results of the marine pipeline bodies, see table 3:

TABLE 3

In the above implementation, the DWTT toughness Test is referred to as Drop-Weight Tear Test (DWTT).

Table 4 is the weld joint cross section hardness value test results for marine pipeline, see table 4:

TABLE 4

In the above implementation manner, the 54 test positions may be selected according to the specification of the "weld joint hardness test method" in the national standard.

Table 5 shows the results of the CTOD toughness requirement (0 ℃) test of the marine pipeline body, see table 5:

TABLE 5

In the above implementation, the CTOD toughness requirement (0 ℃) test refers to a Crack Tip Opening Displacement test (CTOD).

Table 6 shows the results of the external dimension test of the marine pipeline, see table 6:

TABLE 6

The above description is intended to be exemplary only and not to limit the present disclosure, and any modification, equivalent replacement, or improvement made without departing from the spirit and scope of the present disclosure is to be considered as the same as the present disclosure.

Claims (7)

1. A method for manufacturing a large-thickness-diameter ratio high-strain marine pipeline is characterized by comprising the following steps:

providing a pipeline steel plate, wherein the steel grade of the steel plate is L485, the wall thickness is 31.8mm, the metallographic structure of the pipeline steel plate comprises acicular ferrite and fine-grained ferrite, and the pipeline steel plate comprises the following components in percentage by mass: 0.02 to 0.07wt%, mn: 1.50-1.80 wt%, P is less than or equal to 0.015wt%, S is less than or equal to 0.015wt%, si:0.10 to 0.30wt%, nb: 0.020-0.080 wt%, V is less than or equal to 0.03wt%, ti is less than or equal to 0.025wt%, al is less than or equal to 0.06wt%, N is less than or equal to 0.008wt%, cu is less than or equal to 0.30wt%, cr is less than or equal to 0.30wt%, mo is less than or equal to 0.30wt%, and Ni: 0.10-0.50 wt%, B is less than or equal to 0.0005wt%, pcm:0.13 to 0.18, ceq:0.34 to 0.36 percent of (Nb + V + Ti) is less than or equal to 0.15 percent by weight, O is less than or equal to 0.00025 percent by weight, and the balance is Fe and inevitable impurities;

milling X-shaped welding grooves on two longitudinal edges of the pipeline steel plate respectively, wherein the milling width of the X-shaped welding grooves is 1650 +/-5 mm, each X-shaped welding groove comprises an upper groove and a lower groove, the angle of the upper groove is 38 +/-1 degrees, the angle of the lower groove is 36 +/-1 degrees, and the thicknesses of the truncated edges of the upper groove and the lower groove are 13.5 +/-0.5 mm;

providing a forming die, wherein the forming die is designed based on the design pipe diameter and the design wall thickness of the marine pipeline;

forming the pipeline steel plate through the forming die by using a JCO forming process to obtain a pipeline pipe blank;

welding two longitudinal edges of the pipe blank of the pipeline together by adopting a large dry elongation process welding gun to obtain an ocean pipeline, wherein the large dry elongation process welding gun adopts DC-AC four-wire submerged arc welding;

when the downhill mouths of the two longitudinal sides are welded through DC-AC four-wire submerged arc welding, the dry extension of a welding wire is 110mm, first wire welding is carried out on the downhill mouths of the two longitudinal sides, the current type is direct current reverse connection, the current is 1300A, the voltage is 30V, second wire welding is carried out on the downhill mouths of the two longitudinal sides, the current type is alternating current, the current is 900A, the voltage is 42V, third wire welding is carried out on the downhill mouths of the two longitudinal sides, the current type is alternating current, the current is 800A, the voltage is 44V, fourth wire welding is carried out on the downhill mouths of the two longitudinal sides, the current type is alternating current, the current is 700A, and the voltage is 45V;

when the upper grooves of the two longitudinal sides are welded through DC-AC four-wire submerged arc welding, the dry extension of a welding wire is 130mm, first wire welding is carried out on the upper grooves of the two longitudinal sides, the current type is direct current reverse connection, the current is 1350A, the voltage is 30V, second wire welding is carried out on the upper grooves of the two longitudinal sides, the current type is alternating current, the current is 950A, the voltage is 42V, third wire welding is carried out on the upper grooves of the two longitudinal sides, the current type is alternating current, the current is 800A, the voltage is 44V, fourth wire welding is carried out on the upper grooves of the two longitudinal sides, the current type is alternating current, the current is 700A, and the voltage is 45V.

2. The manufacturing method according to claim 1, characterized by further comprising:

carrying out desulfurization and slagging-off pretreatment on molten iron;

carrying out dephosphorization, decarburization, alloying and inclusion form control process treatment on the molten iron to obtain a continuous casting billet;

and hot-rolling the continuous casting slab to obtain the pipeline steel plate.

3. The manufacturing method according to claim 1, characterized by further comprising:

providing an arc striking plate and an arc quenching plate, wherein the arc striking plate and the arc quenching plate are made of the same material as the pipeline steel plate, and the arc striking plate and the arc quenching plate are made of the same thickness as the pipeline steel plate;

respectively welding the arc striking plate and the arc quenching plate at four corners of the pipeline steel plate;

and polishing the welding positions of the arc striking plate and the arc extinguishing plate.

4. The manufacturing method according to claim 1, characterized in that the manufacturing method further comprises:

and cleaning the X-shaped welding groove.

5. The manufacturing method according to claim 1, wherein the duct steel sheet is formed by a JCO forming process including:

feeding the pipeline steel plate into a forming die along the extension direction of the transverse edge, so that one longitudinal edge of the pipeline steel plate is bent to obtain a J-shaped pipeline steel plate;

continuously feeding the steel pipe plate, and gradually bending the part between the two longitudinal edges of the steel pipe plate in multiple steps to obtain a C-shaped steel pipe plate;

and continuously feeding the steel pipe plate into the steel pipe plate to bend the other longitudinal edge of the steel pipe plate to obtain an O-shaped steel pipe plate, and taking the O-shaped steel pipe plate as the pipe blank of the pipe.

6. The manufacturing method according to claim 1, characterized by further comprising:

performing joint closing and centering on the pipe blank of the pipeline;

and pre-welding the two longitudinal edges of the pipe blank of the pipeline by adopting a full-length continuous pre-welding process of a welding line and through consumable electrode active gas shielded arc welding.

7. The manufacturing method according to claim 1, characterized by further comprising:

mechanically expanding the diameter of the marine pipeline;

grinding welding seams at two ends of the marine pipeline;

and processing welding grooves for axial welding with other adjacent marine pipelines at two ends of the marine pipeline.

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