Manufacturing method for spiral submerged arc welded pipe with X65 steel grade and 25.4 mm wall thickness

Abstract

The present invention belongs to the technical field of submerged arc welded pipe manufacturing, and particularly relates to a manufacturing method for a spiral submerged arc welded pipe with an X65MO steel grade and a wall thickness of 25.4 mm. The aim is to solve the problems in the prior art that when the wall thickness of the steel pipe reaches the upper limit of spiral welded pipes, it is difficult to form spiral welded pipes of the X65MO steel grade and it is impossible to produce them. The method includes a forming process. In the forming process, a steel strip is made into a spiral cylinder by a former, and the steel strip passes through three forming rollers and a fourth auxiliary roller of the former in sequence; wherein: the supporting surfaces of the three forming rollers are tangent to the cylinder and the angles are adjustable, the fourth auxiliary roller is tangent to the cylinder and is located at the upper right of the three forming rollers, and the fourth auxiliary roller is tangent to the cylinder and the angle is adjustable. The present invention provides a feasible manufacturing method for a spiral submerged arc welded pipe with an X65MO steel grade and an extra-large wall thickness of 25.4 mm, improving the forming quality of the steel pipe.

Description

Technical Field

[0001] The present invention belongs to the technical field of submerged arc welded pipe manufacturing, and specifically relates to a manufacturing method for a spiral submerged arc welded pipe with a steel grade of X65MO and a wall thickness of 25.4 mm. Background Art

[0002] With the acceleration of the construction pace of economic development zones in coastal cities, the urban scale has expanded rapidly, the population has increased year by year, generating a large amount of production and domestic wastewater, which has spawned a large demand for submarine outfall pipelines. In addition to considering the working loads borne by the pipeline during normal operation, the submarine outfall pipeline also needs to consider the tensile buckling stress borne during the pipeline laying process and the residual stress after laying, as well as the impact of environmental loads on the pipeline during operation, such as the translation and vibration caused by external water pressure, wind, surges, tides, undercurrents, fishing activities, etc. on the pipeline. Therefore, there are many stringent requirements for the mechanical property strength, manufacturing process, and dimensional accuracy of steel pipes. To ensure the safety of submarine outfall pipeline laying and service operation, high-strength steel grade and large-wall-thickness steel pipes need to be selected to meet the high-strength requirements.

[0003] The conventional production process of spiral submerged arc welded pipes is relatively mature, but for the production of steel pipes with a limit wall thickness of 25.4 mm for spiral welded pipes and a steel grade of X65MO, there is no prior production example in the current existing technology. For the production of X65MO grade spiral submerged arc welded pipes, a wall thickness of 25.4 mm has reached the upper limit of the wall thickness, and the method of using existing production equipment cannot achieve uniform buckling deformation and stable forming of such high-strength and large-wall-thickness steel strips. Summary of the Invention

[0004] The present invention provides a manufacturing method for a spiral submerged arc welded pipe with a steel grade of X65MO and a wall thickness of 25.4 mm, so as to solve the problems in the prior art that the wall thickness of the steel pipe reaches the upper limit of spiral welded pipes, the forming of X65MO grade spiral welded pipes is difficult, and normal production cannot be carried out.

[0005] In order to alleviate the above technical problems, the technical solution provided by the present invention lies in:

[0006] A manufacturing method for a spiral submerged arc welded pipe with X65MO steel grade and a wall thickness of 25.4 mm, including a forming process. In the forming process, a steel strip is formed into a spiral cylinder by a former. The steel strip passes through three forming rolls and a fourth auxiliary roll of the former in sequence. Among them: the supporting surfaces of the three forming rolls are tangent to the cylinder and the angles are adjustable. The fourth auxiliary roll is tangent to the cylinder and is located at the upper right of the three forming rolls. The fourth auxiliary roll is tangent to the cylinder and the angle is adjustable. The chemical composition of the spiral submerged arc welded pipe by weight percentage is: C ≤ 0.12%, Si ≤ 0.45%, Mn ≤ 1.65%, P ≤ 0.02%, S ≤ 0.01%, Cr ≤ 0.50%, Mo ≤ 0.50%, Ni ≤ 0.5%, Cu ≤ 0.50%, Nb ≤ 0.08%, Ti ≤ 0.06%, V ≤ 0.1%, B ≤ 0.0005%, V + Nb + Ti ≤ 0.15%, and the balance is iron, CE ≤ 0.22.

[0007] Furthermore, the manufacturing method process includes uncoiling, leveling, shearing, butt welding, edge milling, steel strip feeding, forming, welding, and pipe cutting. Among them, in the forming process, the steel strip is formed into a cylinder with a diameter of 1219 mm in the former at a forming angle of 66°25″. The forming rolls include three forming rolls arranged from left to right, namely the first forming roll, the second forming roll, and the third forming roll. The parameters of the forming rolls are set as follows: the angle of the inner forming roll is 65°57″, the angle of the outer forming roll is 66°51″, the wrap angle of the first forming roll is 18°34″, the opening is 105.3 mm, the wrap angle of the third forming roll is 22°21″, the opening is 158.9 mm, and the position of the roll baffle is 111.1 mm. A deformation zone of the steel strip is formed between the first forming roll and the third forming roll. The steel strip enters the former from the first forming roll and bends and deforms in the deformation zone. At the same time, the reduction of the second forming roll is adjusted according to the yield deformation state of the steel strip and the residual stress of the steel pipe measured by the circumferential cutting method to make the steel pipe curl evenly. The cylinder passes through three lower support rolls at the outlet of the former.

[0008] Furthermore, the welding process is divided into an internal welding process and an external welding process. The internal welding process uses a double-wire submerged arc digital welding machine for automatic welding, and the external welding process uses a three-wire submerged arc digital welding machine for automatic welding, respectively forming internal and external spiral submerged arc welds; for the internal welding process, the front wire uses DC reverse connection, and the welding process parameters are: current I = 1250 - 1450 A, voltage U = 30 - 34 V; the rear wire uses AC, and the welding process parameters are: current I = 630 - 770 A, voltage U = 33 - 37 V, wire dry elongation 20 - 30 mm; wire spacing is 10 - 20 mm; welding speed is 1.0 - 1.2 m / min; weld reinforcement 0 - 3.5 mm; the internal welding process uses a mechanical follower wheel type welding automatic tracking device without deviation and delay; for the external welding process, the first wire uses DC reverse connection, and the welding process parameters are: current I = 1350 - 1550 A, voltage U = 32 - 36 V; the second wire uses AC, and the welding process parameters are: current I = 630 - 770 A, voltage U = 34 - 38 V; the third wire uses AC, and the welding process parameters are: current I = 540 - 660 A, voltage U = 35 - 39 V; wire dry elongation 20 - 30 mm, wire spacing is 10 - 20 mm; welding speed is 1.0 - 1.2 m / min; weld reinforcement 0 - 2.5 mm.

[0009] Furthermore, the edge milling process adopts a method of two rough milling passes plus one finish milling pass. The two rough milling passes process the two sides of the steel strip to produce I-shaped grooves in two progressive steps. The finish milling pass mills the upper and lower surfaces of the two sides of the 25.4 mm thick steel strip to produce upper and lower grooves respectively. The upper groove angle is 33 - 37°, the upper groove depth is 4.7 - 8.7 mm, the lower groove angle is 38 - 42°, the lower groove depth is 4.7 - 8.7 mm, the steel strip root face is 11 - 13 mm, and the final working plate width of the steel strip is processed. When the steel strip is curled and formed, the plate edges are butted, and V-shaped grooves are formed on the inner and outer surfaces of the steel pipe respectively, preparing for internal and external welding.

[0010] Furthermore, in the pipe cutting process, an optoelectronic switch sensor is set on the bridge, and the distance between the optoelectronic switch sensor and the outlet of the bridge steel pipe is equal to the set production length of the steel pipe. When the optoelectronic switch sensor detects the steel pipe, the follow-up cutter wheel of the pipe cutting trolley is started, and the steel pipe drives the pipe cutting trolley to move forward. At the same time, the plasma cutting torch on the pipe cutting trolley is started to start the pipe cutting operation. The steel pipe rotates one week, and at the same time drives the pipe cutting trolley to move forward a pitch length of the steel pipe, that is, the pipe cutting operation is completed, and the steel pipe is cut to the specified length.

[0011] Furthermore, before the forming process, there is also a plate edge pre-bending process. The plate edge pre-bending process uses a two-roll bending machine to bend the delivery edge and the free edge of the steel strip upward, pre-pressing a bend on the edge of the steel strip to avoid the phenomenon of insufficient edge deformation and edge warping of the steel strip in the former.

[0012] Furthermore, after the pipe cutting process, there are also flame chamfering, pipe end cleaning, grinding of the internal weld at the pipe end, rounding of the pipe end, X-ray inspection, ultrasonic inspection of the base metal, hydrostatic test, ultrasonic inspection of the weld, manual ultrasonic inspection, mechanical chamfering, grinding of the external weld at the pipe end, final inspection, and internal spray marking.

[0013] Furthermore, in the pipe end rounding process, a pipe end expanding machine is used to expand and round both ends of the steel pipe within a range of 150 mm from each end. The expansion amount is 0.3 - 0.6% D. The expanded section and the non-expanded section have a smooth transition. The ovality deviation ≤ 5.0 mm, the outer diameter deviation of the pipe end is -1.6 to +1.6 mm, and the difference in the average diameter between the two ends ≤ 2.0 mm. A magnetic grating ruler is set on the expanding machine to accurately control the feed amount of the expanding head, and thus control the expansion amount. In the mechanical chamfering process, a chamfering machine is used to machine a V-shaped groove at the pipe end of the steel pipe by milling. The groove angle is 17 - 19°, the root face is 1.0 - 2.0 mm, and the cutting slope ≤ 1.6 mm.

[0014] Furthermore, after the internal spray marking process, there are also mechanical shot blasting, wrapping paper at the pipe end, intermediate frequency heating, epoxy powder spraying, adhesive winding, polyethylene winding, sprinkling anti-slip particles, water spray cooling, grinding of the anti-corrosion layer at the pipe end, external spray marking, and anti-corrosion final inspection, which are used for anti-corrosion and anti-slip treatment of the submerged arc welded pipe.

[0015] Furthermore, in the mechanical shot blasting process, a shot blasting and rust removal machine is used, with steel sand and steel shot as the rust removal abrasives. The ratio of steel sand to steel shot is S460:G18 = 1:3. The surface of the steel pipe is shot blasted and rust removed, and the rust removal grade reaches the standard. In the process of sprinkling anti-slip particles, an adjustable hourglass is used to evenly sprinkle the anti-slip particles onto the surface of the just-wound polyethylene coating, and then roll-pressed to make them adhere to the surface of the polyethylene coating. The sprinkling density of the anti-slip particles is 300 g / m 2 。

[0016] The beneficial effects of the manufacturing method of the X65MO grade, 25.4 mm wall thickness spiral submerged arc welded pipe in the present invention are analyzed as follows:

[0017] A manufacturing method for X65MO grade spiral submerged arc welded pipe with a wall thickness of 25.4 mm includes a forming process. In the forming process, a steel strip is formed into a spiral cylinder by a former. The steel strip passes through three forming rolls and a fourth auxiliary roll of the former in sequence. Among them: the supporting surfaces of the three forming rolls are tangent to the cylinder and the angles are adjustable. The fourth auxiliary roll is tangent to the cylinder and is located at the upper right of the three forming rolls. The fourth auxiliary roll is tangent to the cylinder and the angle is adjustable. The chemical composition of the spiral submerged arc welded pipe by weight percentage is: C≤0.12%, Si≤0.45%, Mn≤1.65%, P≤0.02%, S≤0.01%, Cr≤0.50%, Mo≤0.50%, Ni≤0.5%, Cu≤0.50%, Nb≤0.08%, Ti≤0.06%, V≤0.1%, B≤0.0005%, V+Nb+Ti≤0.15%, and the balance is iron, and CE (pcm)≤0.22.

[0018] Compared with the production of conventional steel pipes, in this method, a fourth auxiliary roll is arranged between the lower right of the horizontal center line where the former forms the steel strip into a spiral cylinder and the upper right of the three forming rolls. The fourth auxiliary roll is tangent to the cylinder. The reasons for adding the fourth auxiliary roll are analyzed as follows: There is a vertically downward gravity acting on the steel strip at this position, which is likely to cause deformation. If the effect of gravity cannot be offset, it will lead to poor roundness of the steel pipe after forming. Therefore, the added fourth auxiliary roll exerts a force obliquely to the upper left. This force has a vertically upward component force, which can offset the effect of gravity, making the deformation of the steel strip more sufficient, the roundness more circular, and the forming quality better. Brief Description of the Drawings

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the related art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the related art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 Flow chart of the manufacturing method for X65MO grade spiral submerged arc welded pipe with a wall thickness of 25.4 mm provided by the embodiment of the present invention;

[0021] Figure 2 Schematic structural diagram of the former used in the manufacturing method for X65MO grade spiral submerged arc welded pipe with a wall thickness of 25.4 mm provided by the embodiment of the present invention;

[0022] Figure 3 Schematic structural diagram of the lower support roll at the outlet of the former used in the manufacturing method for X65MO grade spiral submerged arc welded pipe with a wall thickness of 25.4 mm provided by the embodiment of the present invention;

[0023] Figure 4 Schematic diagram of the forming process of a steel pipe in a three-roll former in the manufacturing method of an X65MO grade and 25.4 mm wall thickness spiral submerged arc welded pipe provided by the embodiment of the present invention.

[0024] Icon:

[0025] 10 - First forming roll; 11 - Second forming roll; 12 - Third forming roll; 13 - Fourth auxiliary roll; 14 - Fifth auxiliary roll; 15 - Sixth auxiliary roll; 16 - Seventh auxiliary roll; 17 - Eighth auxiliary roll; 18 - Lower support roll; 19 - Cylinder; 20 - Pipe blank; 001 - Deformation zone. Specific embodiments

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. Physical quantities in the formulas, unless otherwise specifically marked, should be understood as the basic quantities of the basic units of the International System of Units, or derived quantities derived from the basic quantities through mathematical operations such as multiplication, division, differentiation or integration.

[0028] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0029] With the accelerating pace of economic development zone construction in coastal cities, the urban scale has expanded rapidly, the population has increased year by year, generating a large amount of production and domestic wastewater, which has given rise to a large demand for submarine outfall pipelines. In addition to considering the working loads borne by the pipeline during normal operation, the tensile buckling stress borne by the pipeline during the laying process and the residual stress after laying completion also need to be considered, as well as the impact of environmental loads on the pipeline during operation, such as the translation and vibration of the pipeline caused by external water pressure, wind, surges, tides, undercurrents, fishing activities, etc. Therefore, there are many stringent requirements for the mechanical properties, manufacturing process, and dimensional accuracy of steel pipes. To ensure the safety of submarine outfall pipeline laying and service operation, high-grade steel and thick-wall steel pipes need to be selected to meet the high-strength requirements.

[0030] The conventional production process of spiral submerged arc welded pipes is relatively mature, but there is no prior production example for the production of steel pipes with a limit wall thickness of 25.4 mm and a steel grade of X65MO for spiral welded pipes. For the production of spiral submerged arc welded pipes of X65MO steel grade, a wall thickness of 25.4 mm has reached the upper limit of the wall thickness, and the method of using existing production equipment cannot achieve uniform buckling deformation and stable forming of such high-strength and thick-wall steel strips.

[0031] In view of this, please refer to Figures 1 to 4 , the present invention provides a manufacturing method for spiral submerged arc welded pipes of X65MO steel grade and 25.4 mm wall thickness, including a forming process. In the forming process, a steel strip is formed into a spiral cylinder 19 by a former. The steel strip passes through three forming rolls and a fourth auxiliary roll 13 of the former in sequence. Among them: the supporting surfaces of the three forming rolls are tangent to the cylinder 19 and the angles are adjustable. The fourth auxiliary roll 13 is tangent to the cylinder 19 and is located above the right of the three forming rolls. The fourth auxiliary roll 13 is tangent to the cylinder 19 and the angle is adjustable. The chemical composition of the spiral submerged arc welded pipe by weight percentage is: C≤0.12%, Si≤0.45%, Mn≤1.65%, P≤0.02%, S≤0.01%, Cr≤0.50%, Mo≤0.50%, Ni≤0.5%, Cu≤0.50%, Nb≤0.08%, Ti≤0.06%, V≤0.1%, B≤0.0005%, V+Nb+Ti≤0.15%, and the balance is iron, and CE≤0.22.

[0032] Compared with the production of conventional steel pipes, in this manufacturing method, a fourth auxiliary roll 13 is provided between the lower right of the horizontal center line of the spiral cylinder 19 formed by the former from the steel strip and the upper right of the three forming rolls. The fourth auxiliary roll 13 is tangent to the cylinder 19. The reasons for adding the fourth auxiliary roll 13 are analyzed as follows: There is a gravity acting vertically downward on the steel strip at this position, which easily causes deformation. If the effect of gravity cannot be offset, it will lead to poor roundness of the steel pipe after forming. Therefore, the added fourth auxiliary roll 13 applies a force obliquely to the upper left. This force has a vertically upward component, which can offset the effect of gravity, making the deformation of the steel strip more sufficient, the roundness more circular, and the forming quality better.

[0033] In an alternative solution of this embodiment, the manufacturing method process includes Module 1, and Module 1 specifically includes uncoiling, leveling, shearing, butt welding, milling the edges, steel strip delivery, forming, welding, and pipe cutting.

[0034] The specific description of the steps of Module 1 is as follows:

[0035] S1-1. Uncoiling: Use an uncoiler to open the raw material hot-rolled coil, lead out the head of the coil, and convey it to the inlet of the leveler.

[0036] S1-2. Leveling: Use a seven-roll (four upper and three lower) precision leveler to level the uncoiled steel strip. Adjust the reduction force and reduction amount according to the plate thickness and yield strength to eliminate the surface curvature of the steel strip and keep the steel strip in a straight state to ensure the subsequent steel pipe forming quality. For a steel strip with X65MO steel grade, a thickness of 25.4 mm, and a width of 1500 mm, the leveling reduction force is about 13700 KN.

[0037] S1-3. Shearing: Cut off the irregular parts at the tail of the previous coil and the head of the next coil so that they can be aligned straight.

[0038] S1-4. Butt welding: Weld the previous coil after cutting off the tail and the next coil after cutting off the head to ensure continuous forward conveyance of the steel strip and the continuity of production.

[0039] S1-5. Edge Milling: It is divided into rough milling and finish milling. Compared with the traditional edge milling method, for high-grade steel and thick-wall steel strips, an additional rough milling process is added. The two-pass rough milling and one-pass finish milling method is adopted. The two-pass rough milling process processes the two sides of the steel strip into I-shaped grooves in two progressive steps. The main purpose is to remove the oxides, grease and edge defects caused during the rolling process on both sides of the steel strip. Compared with the traditional one-pass rough milling, the two-pass rough milling can effectively disperse the milling force, ensure the milling effect, slow down the wear and damage of the cutting blades, and save the blade cost. The finish milling process mills the upper and lower sides of the two sides of the 25.4-mm-thick steel strip to form upper and lower grooves respectively. The upper groove angle is 33-37°, the upper groove depth is 4.7-8.7 mm, the lower groove angle is 38-42°, the lower groove depth is 4.7-8.7 mm, the blunt edge of the steel strip is 11-13 mm, and the final working width of the steel strip is processed. When the steel strip is coiled and formed, the edges of the plate are butted, and V-shaped grooves are formed on the inner and outer surfaces of the steel pipe respectively to prepare for internal and external welding.

[0040] S1-6. Steel Strip Delivery: The upper and lower delivery rollers of the delivery machine clamp the steel strip. When the upper and lower delivery rollers rotate, friction is generated at the contact position between the steel strip and the delivery rollers, which is the delivery force of the steel strip, dragging the steel strip to continuously move forward and feeding the steel strip into the former for forming. It is the main power source for driving the steel strip forward.

[0041] S1-8. Forming: In the forming process, the steel strip is formed into a spiral cylinder 19 by relying on the principle of three-roll plate bending forming and 5 groups of adjustable external control rollers for auxiliary forming. The former includes the first forming roller 10, the second forming roller 11 and the third forming roller 12 arranged from left to right below the cylinder 19. Each forming roller is tangent to the cylinder 19. A deformation zone 001 of the steel strip is formed between the first forming roller 10 and the third forming roller 12. The steel strip enters the former from the first forming roller 10 and is bent and deformed in the deformation zone 001. At the same time, according to the yield deformation state of the steel strip and the residual stress of the steel pipe measured by the circumferential cutting method, the reduction amount of the second forming roller 11 is adjusted to make the steel pipe evenly coiled, ensure that the pipe diameter of the steel pipe is within the process range, and the circumferential opening amount of the pipe end circumferential cutting is not more than 90 mm. The forming force of the equipment is about 17000 kN.

[0042] The steel strip is evenly curled at a certain angle (forming angle), and the edges of the plates are closely fitted to form a steel pipe blank 20. The difficulty lies in that the wall thickness of 25.4mm has reached the upper limit of the wall thickness for the production of spiral submerged arc welded pipes. The minimum yield strength of X65MO material reaches 450MPa. In order to make the steel strip deform evenly and stably form a spiral steel pipe with a diameter of 1219mm, the forming angle is set to 66°25′, the forming inner roller angle is 65°57′, the forming outer roller angle is 66°51′, the first forming roller 10 wrap angle is 18°34′, the No. 3 forming wrap angle is 22°21′, the first forming roller 10 opening is 105.3mm, the third forming roller 12 opening is 158.9mm, and the third forming roller 12 baffle position is 111.1mm. In order to ensure the quality of the forming seam and ensure the quality indicators of the steel pipe diameter, ovality, and misalignment, the former turntable and the bridge angle are adjusted according to the steel pipe design forming angle, and the angle and position of each forming roller are accurately measured and adjusted to ensure the outer dimensions and process quality of the steel pipe forming.

[0043] The former also includes 5 groups of auxiliary rollers, which are arranged around the cylinder 19 in sequence as the fourth auxiliary roller 13, the fifth auxiliary roller 14, the sixth auxiliary roller 15, the seventh auxiliary roller 16 and the eighth auxiliary roller 17. The above 5 groups of auxiliary rollers are tangent to the cylinder 19 respectively. The positions where the 5 groups of auxiliary rollers are tangent to the cylinder 19 can be adjusted in actual production, so as to better assist the steel pipe forming. Among them, the fourth auxiliary roller 13 is an auxiliary roller added compared to conventional steel pipe production. Its position is set in the area between the lower right of the horizontal center line of the cylinder 19 and the upper right of the three forming rollers. For the forming of high-grade steel and thick-walled steel pipes, the steel pipe has high strength and heavy weight, and the deformation of the steel pipe forming is not easy to control. The added fourth auxiliary roller 13 applies an oblique upper left force to the cylinder 19. This force has a vertical upward component, which can offset the effect of gravity, so that the steel strip is more fully deformed, the roundness is more round, and the forming quality is better;

[0044] A group of lower support rollers 18 are arranged below the cylinder 19 at the outlet of the former. The lower support rollers 18 include three support rollers arranged from left to right, each of which is tangent to the cylinder 19. The middle support roller is located directly below the cylinder 19, and the other two support rollers are symmetrically arranged on both sides of the middle support roller. The lower support rollers 18 are used to assist the steel pipe forming, ensure that the forming seam is tightly engaged, improve the forming accuracy and forming stability, and ensure the geometric size and tube shape quality of the steel pipe.

[0045] S1-9, Welding: One-step welding is adopted, which is divided into internal welding and external welding. Internal welding adopts double-wire submerged arc digital welding machine for automatic welding, and external welding adopts three-wire submerged arc digital welding machine for automatic welding, forming internal and external spiral submerged arc welds respectively. The welding power supply adopts digital welding power supply, and the waveform control technology of digital welding power supply is used to obtain relatively stable welding current and voltage to ensure the welding quality of the weld;

[0046] Before internal welding, the front wire is connected with reverse direct current. Set the current to 1250 - 1450 A and the voltage to 30 - 34 V; the rear wire is connected with alternating current. Set the current to 630 - 770 A and the voltage to 33 - 37 V; the dry elongation of the welding wire is 20 - 30 mm, the wire spacing is 10 - 20 mm, and the welding speed is 1.0 - 1.2 m / min; the weld reinforcement is 0 - 3.5 mm; during internal welding, a mechanical follower wheel type automatic welding tracking device without deviation and delay is adopted to ensure the accurate welding position of the weld seam and guarantee the welding quality;

[0047] For the first wire of external welding, it is connected with reverse direct current. Set the current to 1350 - 1550 A and the voltage to 32 - 36 V; the second wire is connected with alternating current. Set the current to 630 - 770 A and the voltage to 34 - 38 V, and the third wire is connected with alternating current. Set the current to 540 - 660 A and the voltage to 35 - 39 V; the dry elongation of the welding wire is 20 - 30 mm, the wire spacing is 10 - 20 mm, and the welding speed is 1.0 - 1.2 m / min; the weld reinforcement is 0 - 2.5 mm. Compared with the traditional twin-wire submerged arc welding, using three wires for external welding mainly solves problems such as difficult penetration in welding large-wall-thickness steel pipes, easy generation of welding defects, unattractive weld cap surface, and low welding efficiency. The first wire is mainly used to ensure the penetration depth, and the second and third wires are mainly used for filling and capping. Using three-wire welding slows down the crystallization speed of the molten pool to obtain a better weld microstructure, alleviates the embrittlement of the heat-affected zone microstructure, reduces the residual stress of the weld seam, and has obvious effects on ensuring the welding quality, improving the weld appearance, and increasing the welding speed.

[0048] S1 - 10. Pipe cutting: An optoelectronic switch sensor is set on the bridge, and the distance between the optoelectronic switch sensor and the outlet of the steel pipe on the bridge is equal to the set production length of the steel pipe. When the optoelectronic switch sensor detects the steel pipe, start the follower wheel of the pipe cutting trolley. The steel pipe drives the pipe cutting trolley to move forward, and at the same time, start the plasma cutting torch on the pipe cutting trolley to start the pipe cutting operation. The steel pipe rotates one week and at the same time drives the pipe cutting trolley to move forward by a pitch length of the steel pipe, that is, the pipe cutting operation is completed, and the steel pipe is cut to the specified length. The required length of the steel pipe is 12.2 ± 0.2 m, and the steel pipe is not allowed to have butt welds. This requires that the weight of the hot-rolled coil must be very accurate. It is necessary to accurately calculate the thickness deviation of the coil, the cutting amount at the head and tail, the milling amount, and the cutting amount of the butt weld. It is required that the steel mill controls the weight deviation of all coils within 1.5 tons during the rolling process of the hot-rolled coil.

[0049] In the optional solution of this embodiment, a pre-bending process of the plate edge is further included between the steel strip delivery and forming processes in Module 1, and the specific description is as follows:

[0050] S1-7. Pre-bending of the plate edge: Use a two-roll flanging machine to bend the delivery edge and the free edge of the steel strip upward, pre-press a bend on the edge of the steel strip, make the deformation of the steel strip more sufficient and smoother, avoid the phenomenon of insufficient edge deformation and edge warping of the steel strip in the former, keep the forming seam of the steel pipe flat after spiral forming, and control the "pouting" phenomenon of the forming seam.

[0051] In summary, the method of the first module solves the technical problem that the existing production equipment method cannot normally produce spiral submerged arc welded pipes with X65MO steel grade and 25.4 mm wall thickness.

[0052] In an alternative embodiment of the present embodiment, the manufacturing method of the spiral submerged arc welded pipe with X65MO steel grade and 25.4 mm wall thickness further includes a second module, and the second module specifically includes the following steps:

[0053] S2-1. Flame flat head: Use flame cutting to cut off the irregular, uneven or defective parts at the pipe end of the steel pipe, make the pipe end of the steel pipe flat and the end face regular.

[0054] S2-2. Pipe end cleaning: Use a wire wheel to rotate to remove the residual slag, molten slag, scale and other sundries adhered to the pipe end of the steel pipe, make the pipe end of the steel pipe clean, tidy and free of sundries.

[0055] S2-3. Grinding of the internal weld at the pipe end: Use an internal weld grinding machine to remove the excess height of the internal weld within at least 160 mm at both ends of the steel pipe, and the remaining weld height is 0 - 0.5 mm, and it is relatively smoothly transitioned with the adjacent pipe body surface.

[0056] S2-4. Pipe end rounding: Use a pipe end expanding machine to expand and round the 150 mm range at both ends of the steel pipe, the expansion amount is 0.3 - 0.6% D, the expanded section and the non-expanded section are smoothly transitioned, the ovality deviation ≤ 5.0 mm, the outer diameter deviation of the pipe end is -1.6 - +1.6 mm, and the difference in the average diameter at both ends ≤ 2.0 mm. A magnetic grating ruler is set on the expanding machine to accurately control the feed amount of the expanding head, and then control the expansion amount.

[0057] S2-5. X-ray flaw detection: Utilize the characteristic that X-rays can penetrate metal materials to conduct 100% industrial television inspection on the entire weld of the spiral weld of the steel pipe, and conduct DR digital radiography on the pipe end and the repaired weld to detect internal defects of the weld.

[0058] S2-6. Ultrasonic base metal flaw detection: Use a 48-channel ultrasonic automatic flaw detection device to conduct ultrasonic flaw detection on the base metal of the pipe body of the steel pipe, the flaw detection coverage area is not less than 35%, detect base metal lamination defects, and use manual ultrasonic flaw detection to recheck the suspicious defects at the flaw detection alarm positions.

[0059] S2-7. Hydrostatic test: Each steel pipe is subjected to an end-sealed hydrostatic test using a 3000-ton hydrostatic testing machine. The circumferential stress generated by the test pressure is 96% of the minimum yield strength of the steel pipe. The pressure fluctuation range is 0 - 0.5 MPa, and the pressure stabilization time is ≥15 s. During the whole process of the hydrostatic test, no leakage or deformation is allowed in the steel pipe to check the sealing performance and the strength of the pipe body, and at the same time, it plays a role in releasing the internal stress of the steel pipe.

[0060] S2-8. Ultrasonic weld inspection: A 32-channel ultrasonic automatic inspection device is used to conduct 100% ultrasonic inspection on the full weld of the spiral weld of the steel pipe. For the suspected defects at the positions where the inspection alarms, manual ultrasonic inspection is used for recheck.

[0061] S2-9. Manual ultrasonic inspection: Manually use an ultrasonic hand-held detector to check for internal weld defects, delamination and non-delamination inspection of the base metal for the welds of the 400 mm at the pipe ends of the steel pipe and the 25 mm base metal on both sides, the repaired welds, the pipe end bevel surface, and the 50 mm base metal at the pipe ends, and recheck the suspected defects at the positions where the automatic inspection alarms.

[0062] S2-10. Mechanical chamfering: The chamfering machine processes the V-shaped bevels at both ends of the steel pipe by milling. The bevel angle is 17 - 19°, the blunt edge is 1.0 - 2.0 mm, and the cut slope is ≤1.6 mm. Compared with the traditional bevel angle of 30 - 35°, a smaller bevel angle is adopted. The main purpose is to reduce the on-site welding filling amount and improve the welding efficiency.

[0063] S2-11. Grinding of the external weld at the pipe ends: Use a weld external grinding machine to remove the excess height of the external weld within at least 160 mm range at both ends of the steel pipe. The remaining weld height is 0 - 0.5 mm, and it is smoothly transitioned relative to the adjacent pipe body surface.

[0064] S2-12. Final inspection: Measure the geometric dimensions of the steel pipe such as pipe diameter, ovality, wall thickness, length, straightness, cut slope, bevel angle, blunt edge, weld excess height, and misalignment. It can be measured manually using measuring tools or automatically using a comprehensive measuring device with sensing technology. At the same time, visually inspect the external and internal surface appearance defects of the steel pipe along the full length of the steel pipe, including hard lumps, cracks, scabs, double skins, delamination, dents, scratches, etc. on the surface of the base metal and arc pits, pores, cracks, and undercutting, etc. on the welds, and visually inspect each steel pipe for the presence of welding flux, welding slag, burrs, grease, rust, etc. on the external and internal surfaces.

[0065] S2-13. Internal spraying of marks: Use a spraying method to mark the steel pipe on the internal surface of the steel pipe at least 150 mm away from the pipe ends. The marking content includes information such as the execution standard, specification, wall thickness, length, material, pipe number, furnace batch number, hydrostatic test pressure, manufacturer, and origin of the steel pipe for the identification and quality traceability of the steel pipe.

[0066] It should be noted that the order between step S2-1, flame flattening and S2-2, pipe end cleaning can be adjusted; based on "step S2-7, hydrostatic test before step S2-10, mechanical chamfering", the order between step S2-5, X-ray flaw detection, S2-6, ultrasonic base metal flaw detection, S2-7, hydrostatic test, S2-8, ultrasonic weld flaw detection, S2-9, manual ultrasonic flaw detection, S2-10, mechanical chamfering and S2-11, grinding of the external weld at the pipe end can be adjusted.

[0067] In summary, the method in the second module is to further process and inspect the spiral submerged arc welded pipe to ensure the production quality of the spiral submerged arc welded pipe.

[0068] With the rapid expansion of the urban scale and the increasing population year by year, a large amount of domestic and industrial wastewater is generated, giving rise to a large demand for submarine outfall pipelines. In addition to considering the working loads borne by the pipeline during normal operation, the tensile buckling stress borne during the pipeline laying process and the residual stress after laying, as well as the influence of environmental loads on the pipeline during operation, such as the translational and vibrational effects of external water pressure, wind, surges, tides, undercurrents, fishing activities, etc. on the pipeline, it is very important to improve the stability of the steel pipe on the seabed to ensure the safety of the laying and service operation of the submarine outfall pipeline.

[0069] In view of this, the manufacturing method of the X65MO steel grade and 25.4mm wall thickness spiral submerged arc welded pipe further includes a third module for anti-slip and anti-corrosion treatment of the steel pipe, specifically including the following steps:

[0070] S3-1, mechanical shot peening: Using a shot peening rust remover, with steel sand and steel shot as the rust removal abrasive, and the ratio of steel sand to steel shot being S460:G18 = 1:3, shot peening and rust removal are carried out on the surface of the steel pipe to make the rust removal grade reach the standard. Through mechanical shot peening and rust removal, the surface of the steel pipe reaches an appropriate cleanliness, thus ensuring that the coating adheres more firmly. Compared with the existing manual sandblasting, mechanical shot peening is more uniform, improving the rust removal quality.

[0071] S3-2, wrapping paper at the pipe end: Wrapping kraft paper on the outer surfaces at both ends of the steel pipe according to the requirements of the reserved length at the pipe end, which is convenient for subsequent processing of the reserved section at the pipe end. According to relevant technical requirements, the wrapping paper length at one end of the steel pipe is set to 350 ± 5mm here, and the wrapping paper length at the other end is 145 ± 5mm.

[0072] S3-3, intermediate frequency heating: Using an intermediate frequency coil to generate heat by passing an electric current. During the process of the steel pipe passing through the middle of the intermediate frequency coil, the heat generated by the intermediate frequency coil heats the steel pipe to about 200°C, preparing for subsequent processes such as epoxy powder spraying, adhesive winding, and polyethylene winding.

[0073] S3-4, Epoxy powder spraying: By means of high-voltage electrostatic spraying, 16 to 32 epoxy powder spray guns are used to spray epoxy powder onto the surface of the heated steel pipe, and a cyclone plus filter powder recovery device is equipped to achieve the purpose of saving raw materials and environmental protection.

[0074] S3-5, Adhesive winding: Using an extruder and a special die head, the AD adhesive material is heated to a molten state and extruded into sheets, and then wound around the pipe body in the following winding method to make it combine with the epoxy powder resin layer.

[0075] S3-6, Polyethylene winding: Using an extruder and a special die head, the PE coating material is heated to a molten state and extruded into sheets, and then wound around the pipe body in the following winding method to make it combine with the adhesive coating.

[0076] S3-7, Sprinkling anti-slip particles: Using an adjustable hourglass, the anti-slip particles are evenly sprinkled onto the surface of the just-wound polyethylene coating, and then roller-pressed to make them adhere to the surface of the polyethylene coating. The sprinkling density of the anti-slip particles is 300 g / m 2 , and the main purpose is to increase the surface friction of the steel pipe during the laying process of the steel pipe by a pipe-laying vessel to the seabed, so that the steel pipe is not easy to fall off and sink into the sea during the laying process, ensuring the laying safety.

[0077] S3-8, Water spray cooling: The steel pipe entering the water spray chamber after coating is sprayed with cooling water to quickly reduce the temperature of the steel pipe, and the surface of the coating is cooled to below 60 °C to quickly cure the anti-corrosion layer. An automatic spark leak detection device is set at the outlet of the water spray chamber to detect the leak points of the anti-corrosion coating.

[0078] S3-9, Grinding of the anti-corrosion layer at the pipe ends: Using a double-headed grinding device at the pipe ends to grind the anti-corrosion layer at both ends, and a reserved section at the pipe ends is processed. The reserved length at one end is 350 ± 5 mm, and the reserved length at the other end is 145 ± 5 mm. A chamfer of ≤ 30° is formed at the end face of the polyethylene layer, and an epoxy powder coating with a length not exceeding 20 mm is reserved at the end of the polyethylene layer.

[0079] S3-10, External spraying of marks: On the outer surface of the steel pipe at least 500 mm away from the pipe ends, the steel pipe is marked by spraying. The marking content includes information such as the execution standard, specification, wall thickness, length, material, pipe number, furnace batch number, hydrostatic test pressure, manufacturer, origin, etc. of the steel pipe, for the identification and quality traceability of the steel pipe.

[0080] S3-11, Inspection of anti-corrosion finished products: The anti-corrosion layer of the finished steel pipe that has completed anti-corrosion is inspected, including inspection items such as the thickness, appearance, and peel strength of the anti-corrosion layer. Each parameter is verified item by item to confirm that the quality of the anti-corrosion finished steel pipe meets the requirements of the technical standards. For the specific technical standards, please refer to Tables 1 to 4 below.

[0081] Table 1 Chemical composition

[0082]

[0083] Table 2 Tensile properties

[0084]

[0085] Table 3 Impact properties

[0086]

[0087] Table 4 Drop weight tear test (DWTT) properties

[0088]

[0089]

[0090] The manufacturing method of the X65MO steel grade and 25.4 mm wall thickness spiral submerged arc welded pipe provided in this embodiment can achieve the following beneficial effects:

[0091] 1. Provide a practical and effective manufacturing method for X65MO steel grade and 25.4 mm super-large wall thickness spiral submerged arc welded pipes. The physical and chemical performance test results of the X65MO steel grade and 25.4 mm super-large wall thickness spiral submerged arc welded pipes processed and manufactured by the method in this embodiment are shown in Tables 5 to 9 below, and all meet the technical standard requirements of the X65MO steel grade steel pipes in Tables 1 to 4;

[0092] Table 5 Chemical composition test results of the pipe body base material of X65MO steel grade and Φ1219×25.4 mm steel pipes

[0093]

[0094] Table 6 Chemical composition test results of the welds of X65MO steel grade and Φ1219×25.4 mm steel pipes

[0095]

[0096] Table 7 Tensile property test results of X65MO steel grade and Φ1219×25.4 mm steel pipes

[0097]

[0098] Table 8 Charpy impact property test results of X65MO steel grade and Φ1219×25.4 mm steel pipes

[0099]

[0100] Table 9 Drop weight tear test (DWTT) results of X65MO steel grade and Φ1219×25.4 mm steel pipes

[0101]

[0102] 2. Solve the problems of uniform buckling deformation, control of edge misalignment, pouting, dimensional accuracy of steel pipes, stable forming, and precise fixed-length production during the forming process of steel pipes with such high steel grades, high strength, and large wall thicknesses;

[0103] 3. Control defects such as incomplete penetration, porosity, cracks, and welding deviation inside the weld during the welding process, and significantly improve the welding quality;

[0104] 4. Carry out anti-slip and anti-corrosion treatment on the steel pipes, and improve the uniformity, adhesion strength, and anti-slip effect of the application of anti-slip particles on the anti-corrosion layer.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A manufacturing method for a spiral submerged arc welded pipe with X65MO steel grade and 25.4 mm wall thickness, characterized in that: it includes a forming process, in which a steel strip is formed into a spiral cylinder (19) by a former, and the steel strip passes through three forming rolls and a fourth auxiliary roll (13) of the former in sequence; wherein: the supporting surfaces of the three forming rolls are tangent to the cylinder (19) and the angles are adjustable, the fourth auxiliary roll (13) is tangent to the cylinder (19) and is located at the upper right of the three forming rolls, and the fourth auxiliary roll (13) is tangent to the cylinder (19) and the angle is adjustable; the chemical composition of the spiral submerged arc welded pipe by weight percentage is: C≤0.12%, Si≤0.45%, Mn≤1.65%, P≤0.02%, S≤0.01%, Cr≤0.50%, Mo≤0.50%, Ni≤0.5%, Cu≤0.50%, Nb≤0.08%, Ti≤0.06%, V≤0.1%, B≤0.0005%, V+Nb+Ti≤0.15%, the balance is iron, and CE≤0.22; the manufacturing method process includes uncoiling, leveling, shearing, butt welding, edge milling, steel strip delivery, forming, welding, and pipe cutting; wherein, in the forming process, the steel strip is formed into the cylinder (19) with a diameter of 1219 mm in the former according to a forming angle of 66°25″, the forming rolls include three forming rolls arranged from left to right, namely the first forming roll (10), the second forming roll (11) and the third forming roll (12), and the parameters of the forming rolls are set as follows: the angle of the inner forming roll is 65°57″, the angle of the outer forming roll is 66°51″, the wrap angle of the first forming roll (10) is 18°34″, the opening is 105.3 mm, the wrap angle of the third forming roll (12) is 22°21″, the opening is 158.9 mm, and the position of the roll baffle is 111.1 mm; a deformation zone (001) of the steel strip is formed between the first forming roll (10) and the third forming roll (12), the steel strip enters the former from the first forming roll (10) and is bent and deformed in the deformation zone (001), and at the same time, the reduction amount of the second forming roll (11) is adjusted according to the yield deformation state of the steel strip and the residual stress of the steel pipe measured by the circumferential cutting method to make the steel pipe curl evenly; the cylinder (19) passes through three lower supporting rolls (18) at the outlet of the former.

2. The manufacturing method for a spiral submerged arc welded pipe with X65MO steel grade and 25.4 mm wall thickness according to claim 1, characterized in that, The welding process is divided into an internal welding process and an external welding process. The internal welding process uses a double-wire submerged arc digital welding machine for automatic welding, and the external welding process uses a three-wire submerged arc welding digital welding machine for automatic welding, respectively forming internal and external spiral submerged arc welds. In the internal welding process, the front wire uses DC reverse connection, and the welding process parameters are: current I = 1250 - 1450 A, voltage U = 30 - 34 V. The rear wire uses AC, and the welding process parameters are: current I = 630 - 770 A, voltage U = 33 - 37 V, and the wire dry elongation is 20 - 30 mm. The wire spacing is 10 - 20 mm. The welding speed is 1.0 - 1.2 m / min. The weld reinforcement is 0 - 3.5 mm. The internal welding process uses a mechanical follower type welding automatic tracking device without deviation and delay. In the external welding process, the first wire uses DC reverse connection, and the welding process parameters are: current I = 1350 - 1550 A, voltage U = 32 - 36 V. The second wire uses AC, and the welding process parameters are: current I = 630 - 770 A, voltage U = 34 - 38 V. The third wire uses AC, and the welding process parameters are: current I = 540 - 660 A, voltage U = 35 - 39 V. The wire dry elongation is 20 - 30 mm, and the wire spacing is 10 - 20 mm. The welding speed is 1.0 - 1.2 m / min. The weld reinforcement is 0 - 2.5 mm.

3. The manufacturing method of the X65MO grade and 25.4 mm wall thickness spiral submerged arc welded pipe according to claim 2, characterized in that, In the edge milling process, a method of two passes of rough milling plus one pass of finish milling is adopted. In the two passes of rough milling process, the two sides of the steel strip are processed into I-shaped grooves in a two-step progressive manner. In the finish milling process, the upper and lower sides of the two sides of the 25.4 mm thick steel strip are respectively milled to form upper and lower grooves. The upper groove angle is 33 - 37°, the upper groove depth is 4.7 - 8.7 mm, the lower groove angle is 38 - 42°, the lower groove depth is 4.7 - 8.7 mm, the steel strip root face is 11 - 13 mm, and the final working width of the steel strip is processed. When the steel strip is curled and formed, the edges are butted, and V-shaped grooves are respectively formed on the inner and outer surfaces of the steel pipe, preparing for internal and external welding.

4. The manufacturing method of the X65MO grade and 25.4 mm wall thickness spiral submerged arc welded pipe according to claim 3, characterized in that, In the pipe cutting process, a photoelectric switch sensor is set on the bridge, and the distance between the photoelectric switch sensor and the outlet of the bridge steel pipe is equal to the set production length of the steel pipe. When the photoelectric switch sensor detects the steel pipe, the follower cutter wheel of the pipe cutting trolley is started, and the steel pipe drives the pipe cutting trolley to move forward. At the same time, the plasma cutting torch on the pipe cutting trolley is started to start the pipe cutting operation. The steel pipe rotates one week, and at the same time drives the pipe cutting trolley to move forward a length of one steel pipe pitch, that is, the pipe cutting operation is completed, and the steel pipe is cut to the specified length.

5. The manufacturing method of the X65MO grade and 25.4 mm wall thickness spiral submerged arc welded pipe according to claim 4, characterized in that, Before the forming process, there is also a pre-bending process for the plate edge. In the pre-bending process for the plate edge, a two-roll flanging machine is used to bend the delivery edge and the free edge of the steel strip upward, pre-pressing a bend in the edge of the steel strip to avoid insufficient edge deformation and edge warping of the steel strip in the former.

6. The manufacturing method of the X65MO grade steel, 25.4 mm wall thickness spiral submerged arc welded pipe according to claim 5, characterized in that, after the pipe cutting process, there are also flame facing, pipe end cleaning, grinding of the internal weld at the pipe end, pipe end rounding, X-ray inspection, ultrasonic inspection of the base metal, hydrostatic test, ultrasonic inspection of the weld, manual ultrasonic inspection, mechanical chamfering, grinding of the external weld at the pipe end, finished product inspection, and internal spray marking.

7. The manufacturing method of the X65MO grade steel, 25.4 mm wall thickness spiral submerged arc welded pipe according to claim 6, characterized in that, in the pipe end rounding process, a pipe end expanding machine is used to expand and round the range of 150 mm at both ends of the steel pipe. The expansion amount is 0.3 - 0.6% D. The expanded section and the non-expanded section are smoothly transitioned. The ovality deviation is ≤ 5.0 mm, the outer diameter deviation of the pipe end is -1.6 to +1.6 mm, and the difference in the average diameter of both ends is ≤ 2.0 mm. A magnetic grating ruler is set on the expanding machine to accurately control the feed of the expanding head, thereby controlling the expansion amount; in the mechanical chamfering process, a chamfering machine is used to machine a V-shaped groove at the pipe end of the steel pipe in a milling manner. The groove angle is 17 - 19°, the root face is 1.0 - 2.0 mm, and the cutting slope is ≤ 1.6 mm.

8. The manufacturing method of the X65MO grade steel, 25.4 mm wall thickness spiral submerged arc welded pipe according to claim 6, characterized in that, after the internal spray marking process, there are also mechanical shot blasting, paper winding at the pipe end, intermediate frequency heating, epoxy powder spraying, adhesive winding, polyethylene winding, sprinkling of anti-slip particles, water spray cooling, grinding of the anti-corrosion layer at the pipe end, external spray marking, and anti-corrosion finished product inspection, which are used for anti-corrosion and anti-slip treatment of the submerged arc welded pipe.

9. The manufacturing method of the X65MO grade steel, 25.4 mm wall thickness spiral submerged arc welded pipe according to claim 8, characterized in that, in the mechanical shot blasting process, a shot blasting and rust removal machine is used. Steel sand and steel shot are used as rust removal abrasives. The ratio of steel sand to steel shot is S460:G18 = 1:

3. The surface of the steel pipe is subjected to shot blasting and rust removal, and the rust removal grade reaches the standard; The process of sprinkling anti-slip particles uses an adjustable hourglass to evenly sprinkle anti-slip particles onto the surface of the just-wound polyethylene coating, and after rolling, they adhere to the surface of the polyethylene coating. The sprinkling density of the anti-slip particles is 300 g / m 2 .

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