CN100547103C - A manufacturing method of high-strength X80 steel spiral welded pipe - Google Patents

Abstract

The invention discloses a method for manufacturing a high-strength X80 steel spiral welded pipe. The base material of the welded pipe is X80 steel coil, the mass percentage of its chemical composition is: C 0.02～0.09%, Si 0.10～0.42%, Mn1.50～1.85%, P≤0.022%, S≤0.005%, Cr≤0.45 %, Ni≤0.50%, Cu≤0.30%, Mo≤0.35%, Ti≤0.025%, Nb≤0.11%, V≤0.06%, Al≤0.06%, N≤0.008%, B≤0.0005%, Pcm≤0.23 %; its processing procedures include: uncoiling, leveling, edge milling, pre-bending, forming, internal welding, external welding, pipe end expansion, parent metal layered ultrasonic inspection, weld X-ray inspection, hydraulic test, weld Ultrasonic inspection, pipe end chamfering and finished product inspection processes. The Φ1219×18.4mm, X80 steel spiral welded pipe manufactured by the technology of the present invention has successfully solved the problems of poor forming stability and weld seam performance difficult to meet technical requirements in the production and manufacture of high-strength X80 steel spiral welded pipe, and greatly improved the qualification of the product rate and production efficiency.

Description

A manufacturing method of high-strength X80 steel spiral welded pipe

technical field

The invention relates to a manufacturing technology of a spiral welded pipe, in particular to a manufacturing technology of a Φ1219×18.4mm high-strength X80 steel spiral welded pipe.

Background technique

Spiral welded steel pipe is made by spirally bending steel coils according to a certain radius of curvature and then welding them together along the gap between the steel plates. Spiral welded steel pipe has the advantages of low investment and various production varieties, so it has become the most widely used steel pipe manufacturing method in China. However, due to the limitations of its forming method and the relatively low strength of steel pipes for a long time, there are few productions of high-strength, thick-walled steel pipes. At present, the steel used in the steel pipes produced by spiral welded pipes are all X70 steel grade and below, and the maximum wall thickness is only 17.5mm. With the development of long-distance, high-pressure, and large-diameter pipeline construction, the strength and wall thickness requirements of steel pipes have increased significantly. For example, there is no published technical research on making spiral welded pipes with X80 high-strength pipeline steel. The current production method still has many problems in the production of high-strength, thick-walled spiral welded steel pipes. The main manifestations are: as the strength and wall thickness of the steel increase, the steel strip in the former, especially the belt on the delivery side The deformation of the steel edge is insufficient. At the same time, the edge trimming process commonly used at present will also cause the phenomenon of underflaring of the edge of the plate. If it is not corrected in the subsequent process, pouting and tightness in the forming seam will easily occur during the forming and occlusion during production. Defects such as outer looseness and misalignment may even cause fatal defects such as weld micro-cracks; problems such as crescent bends in the coil itself significantly affect the forming stability of the steel pipe, making the circumference and ellipticity of the steel pipe change greatly , can not effectively guarantee the stability of the steel pipe dimensions, which will have a certain impact on the on-site butt joint construction of the steel pipe; in addition, with the increase of the strength and wall thickness of the steel, the welding process becomes more difficult, and how to control the structure and performance of the weld A key issue that needs to be addressed.

Contents of the invention

The technical problem to be solved in the present invention is to provide a production process for producing X80 high-strength spiral pipeline steel welded pipe with a specification of Φ1219×18.4mm by utilizing the existing production technology of spiral welded pipe.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

In the production of spiral welded pipes, the main processes are forming and welding. Welding needs to ensure the structure and performance of the weld seam of the steel pipe, so the chemical composition of the base steel plate needs to be selected. What is used in the present invention is a controlled-rolled steel coil of low-carbon microalloy X80 steel, with a width of 1500-2000 mm and a thickness of 18.4 mm. Its chemical composition (mass percentage) is: carbon C 0.02-0.09%, silicon Si 0.10-0.42%, manganese Mn 1.50-1.85%, phosphorus P≤0.022%, sulfur S≤0.005%, chromium Cr≤0.45%, nickel Ni ≤0.50%, copper Cu≤0.30%, molybdenum Mo≤0.35%, titanium Ti≤0.025%, niobium Nb≤0.11%, vanadium V≤0.06%, aluminum Al≤0.06%, nitrogen N≤0.008%, boron B≤0.0005 %, cold cracking coefficient Pcm≤0.23%.

The processing route of spiral welded pipe is: coil uncoiling, leveling, edge milling, pre-bending, forming, internal welding, external welding, pipe end expansion, base metal layered ultrasonic inspection, weld X-ray inspection, hydraulic test , Weld seam ultrasonic inspection, pipe end chamfering, finished product inspection.

The technical key of the present invention lies in the optimization and improvement of the coil milling design, pre-bending process, welding process, pipe end diameter expansion process, and non-destructive testing technology. Compared with the existing process route for processing spiral tubes, it mainly increases Double milling process, pre-bending process, pipe end expanding process.

Among them, the double milling process is: first rough milling the I-shaped groove to ensure the removal of the plate edge defects and crescent bends caused by the steel billet and the rolling process of the steel plate, and milling the plate edge width by 5-20mm during rough milling; Milling an X-shaped groove means that the edge of the steel plate coil is cut into an X-groove with a blunt edge size of 5-8mm and a groove angle of 30°-45°; the purpose of the groove is to ensure that the thick-walled plate coil will It can penetrate through the medium, increase the welding speed, improve the weld shape, reduce the welding heat energy, reduce the influence of welding heat input on the structure and performance of the welding heat affected zone, and improve the performance of the weld heat affected zone.

The process of the pre-bending process is: use a two-roller pre-bending machine to pre-bend the delivery side and the free side of the coil. The size of the pre-bending is 1470mm in radius and 100-130mm in length.

In the forming process of large-diameter, thick-walled, and high-grade spiral welded steel pipes, it is more appropriate for the edges of the strip steel on both sides of the seam to be arc-curved or slightly open; the steel strip is in the former, Especially on the side of the delivery side, the machine arm needs to reserve space for the internal welding device, and the end forming roller is at least 50mm away from the edge of the plate. If the bending roller is not used, the deformation of the edge of the strip will be insufficient; sometimes the edge trimming process will also cause the under-flanging phenomenon of the edge of the plate, which will easily cause pouting during the forming bite, tight inside and loose outside of the forming seam, and wrong Defects such as edges seriously affect the appearance quality of the steel pipe and the subsequent welding process, and even cause fatal defects such as weld microcracks, which cannot be eliminated in the subsequent process, seriously affect the quality of the steel pipe, and cause a decline in the qualified rate of the steel pipe. Therefore, aiming at the yield strength of X80 high-strength spiral pipeline steel of Φ1219×18.4mm, a two-roller bending machine with a suitable arc was designed by means of lofting and elastic mechanics analysis. The part is pre-bent. This two-roller pre-bending device can not only adjust the deformation area of the edge of the steel strip through horizontal adjustment, but also change the force on the coil by adjusting the up and down rollers, so that the coil can achieve the expected deformation effect. During the production process, observe and measure the steel pipe quality near the weld, analyze the pre-deformation adjustment required on the delivery side and the free side, and fully pre-bend the edge of the strip, which can effectively eliminate forming defects such as pouting and misalignment, so that The quality of steel pipe forming and welding has been significantly improved.

The process of internal welding and external welding process is as follows:

Welding is the main process for manufacturing spiral pipes. Since the base material used in the steel pipe is low-carbon micro-alloyed high-strength steel, its carbon equivalent has reached more than 0.4%, and it is difficult to weld. In the welding process, in order to control the performance and welding quality of the weld, through many tests, it is determined that both the internal welding and the external welding adopt the double-wire tandem submerged arc automatic welding process, and the process parameters are: the first wire of the internal welding is DC, its current I=1000~1200A, voltage V=31~33V; the second wire is AC, its current I=430~470A, voltage V=35~37V; welding wire spacing d=10~14mm; welding speed V= 1.3～1.6m/min.

The first wire for external welding is DC, its current I=1100～1300A, voltage V=33～35V; the second wire is AC, its current I=400～450A, voltage V=35～37V; welding wire spacing d=12～ 16mm; welding speed V = 1.3 ~ 1.6m/min.

The main function of selecting the above process parameters is: the function of the first wire is mainly to ensure the penetration depth. Large welding current and low arc voltage are required; the function of the second wire is mainly to cover the surface, that is, to obtain good appearance quality, smooth transition between the weld seam and the base metal, and reduce and eliminate undercutting. It is necessary to use small welding current and high Arc voltage; the first wire cooperates with the second wire to fully exhaust and slag discharge to obtain a good weld shape and excellent quality. Using the above process, reasonably select the welding material according to the composition of the coil, and control the composition of the weld in the following range: C 0.02～0.09%, Si 0.10～0.40%, Mn 1.50～1.85%, P≤0.015%, S≤0.003 %, Cr≤0.40%, Ni≤0.30%, Cu≤0.25%, Mo≤0.35%, Ti≤0.020%, Nb≤0.090%, V≤0.04%. After welding, the metallographic structure obtained by the weld is mainly acicular ferrite + bainite, so as to ensure that the weld deposited metal has high strength and toughness, internal quality and physical and chemical properties.

The process of pipe end expansion process is as follows: cold expansion within 300mm of the steel pipe end, the maximum expansion amount is 1.5% of the diameter; the circumference deviation of the pipe end is ±1.5mm, and the ellipticity deviation is less than or equal to 2mm; There should be a smooth transition with the unexpanded section. The dimensional stability of the steel pipe end directly affects the efficiency of on-site pipeline construction. While optimizing the steel pipe forming process, the present invention increases the diameter expansion process of the steel pipe end, rounds the steel pipe end, and better controls the steel pipe end size The precision has reached the level of pipe end circumference deviation ±1.5mm and ellipticity deviation less than or equal to 2mm, which greatly improves the on-site docking efficiency of steel pipes and facilitates on-site construction operations.

In addition, the present invention also adds a plurality of detection processes using advanced non-destructive detection technology. For thick-walled, high-grade, large-diameter spiral-welded steel pipes, the probability of defects such as pores, slag inclusions, and cracks in the weld increases. The invention uses advanced non-destructive testing technology to achieve effective detection of the internal quality of the weld. By using the computer expert system for weld defect judgment, real-time scanning and analysis of weld X-ray flaw detection images, the automatic identification, marking, alarm and recording of defects are completed, and the automation of X-ray flaw detection is realized; the ultrasonic system adopts laser Automatic tracking technology, while improving its mechanical device, under the premise of ensuring the rigidity of the probe frame, the probe is in flexible contact with the steel pipe, thereby improving the accuracy and reliability of automatic ultrasonic flaw detection.

Owing to having adopted above-mentioned technical scheme, the technical progress that the present invention obtains is:

In the technology of manufacturing Φ1219×18.4mm high-strength X80 steel spiral welded pipe of the present invention, compared with the manufacture of ordinary spiral welded pipes, the process steps include double milling process, pre-bending process, and pipe end diameter expanding process, and successfully solved the problem. It solves the problems of poor forming stability and difficulty in meeting technical requirements in the production and manufacture of high-strength X80 steel spiral welded pipes, and greatly improves the pass rate and production efficiency of the product.

Welding process parameters, edge milling process and the determination of the groove size are also based on the chemical composition of the special X80 steel and the ultra-thick plate, after careful calculation and multiple tests, it has strong practicability in actual production and is The crystallization of the creative labor of all inventors. The excellent effects achieved by it have been discussed in the above technical solutions.

Detailed ways

Below in conjunction with embodiment the present invention is described in further detail:

Example 1:

The chemical composition and mechanical properties of the X80 steel coil used in this example are shown in Table 1 and Table 2. The thickness of the steel plate is 18.4mm, and the inner diameter of the steel pipe is Φ1219mm. The manufacturing process steps of steel pipe are as follows:

1. The coil is uncoiled and leveled;

2. Edge milling: first rough milling, milling off the width of the plate edge by 5-20mm; then fine milling the X-shaped groove, that is, the two butt-joint edges of the steel plate are respectively cut out with a blunt edge size of 5mm and a groove angle of 30 °～45° groove, the two sides of the steel plate are butted to form an X-shaped groove of 60°～80°;

3. Pre-bending: Pre-bend the delivery side and free side of the coiled plate on the two-roller bending machine, so that the radius size is 1470mm; the length is 100-130mm;

4. Forming: The strip steel that has undergone the above-mentioned pre-bending is rolled into a spiral cylinder with a diameter of Φ1219mm in a three-roller former;

5. Welding: Internal welding and external welding are carried out along the seam of the steel pipe cylinder. The welding process parameters are shown in Table 5, and the chemical composition of welding wire and flux is shown in Table 3 and Table 4;

6. Pipe end expansion: Cold expansion is carried out within 300mm of the steel pipe end, and the maximum expansion is 1.5% of the diameter; the circumference deviation of the pipe end is ±1.5mm, and the ellipticity deviation is ±2mm; The diameter segment should transition smoothly;

7. Flaw detection: conduct layered ultrasonic inspection and X-ray inspection on the base metal;

8. Hydrostatic test;

9. Ultrasonic inspection and ultrasonic hand detection of welds;

10. Pipe end chamfering: blunt the end edge of the steel pipe;

11. Finished product inspection.

Table 6 provides the chemical composition of the weld metal of this embodiment, and Table 7 provides the performance test results of the steel pipe and the performance requirements of the X80 steel grade pipeline steel pipe. It can be seen from the table that the steel pipe produced by the technology of the present invention is Spiral welded pipe meets the technical requirements of X80 steel grade pipeline steel pipe.

Table 1 Main chemical composition of coils (wt.%)

C Mn Si P S V+Nb+Ti Ni+Cr+Cu Cr+Mo+Mn Ceq Pcm 0.04 1.84 0.13 0.011 0.001 0.13 0.38 2.09 0.43 0.17

Table 2 Tensile test value of coil (rolling direction 30°)

Yield strength Rt_0.5(MPa) Tensile strength Rm(MPa) Yield strength ratio Rt_0.5/Rm Elongation A50mm(%) min 580 675 0.86 35 Max 635 755 0.89 42 Ave 615 715 0.86 40

Table 3 Chemical composition of welding wire (wt.%) (specific composition)

C mn Si P S Mo V+Nb+Ti B 0.05 1.45 0.14 0.008 0.002 0.39 0.085 0.005

Table 4 Chemical composition of flux (wt.%)

Mg Mn Si Ca Al 9.46 7.90 10.30 9.07 10.50

Table 5 Twin wire welding parameters

Table 6 Chemical Composition of Weld Metal (wt.%)

C Mn Si P S V+Nb+Ti Ni+Cr+Cu Cr+Mo+Mn External weld 0.05 1.84 0.14 0.012 0.001 0.13 0.41 2.10 Inner seam 0.04 1.82 0.14 0.011 0.001 0.12 0.41 2.09

Table 7 Mechanical properties of steel pipes

Example 2:

The chemical composition and mechanical properties of the X80 steel coil used in this example are shown in Table 8 and Table 9. The manufacturing process steps of the steel pipe and the chemical composition of the welding wire and the flux are the same as in Example 1, and the welding process parameters are shown in Table 10. Table 11 shows the chemical composition of the weld metal of this embodiment, and Table 12 shows the performance test results of the actual steel pipe. The performance requirements of the X80 steel grade pipeline steel pipe can be seen from the table. The welded pipe meets the technical requirements of X80 steel grade pipeline steel pipe.

Table 8 Main chemical composition of coils (wt.%)

C Mn Si P S V+Nb+Ti Ni+Cr+Cu Cr+Mo+Mn Ceq Pcm 0.04 1.82 0.24 0.013 0.001 0.082 0.60 2.12 0.42 0.18

Table 9 Tensile test values of coils (rolling direction 30°)

Yield strength Rt_0.5(MPa) Tensile strength Rm(MPa) Yield ratio Rt_0.5/Rm Elongation A50mm(%) min 560 670 0.82 38 Max 600 725 0.88 45 Ave 590 695 0.84 42

Table 10 Twin wire welding parameters

Table 11 Chemical Composition of Weld Metal (wt.%)

C Mn Si P S V+Nb+Ti Ni+Cr+Cu Cr+Mo+Mn External weld 0.04 1.69 0.28 0.014 0.001 0.063 0.47 2.02 Inner seam 0.04 1.69 0.28 0.013 0.001 0.062 0.46 2.03

Table 12 Mechanical properties of steel pipes

Example 3:

The chemical composition and mechanical properties of the X80 steel coil used in this example are shown in Table 13 and Table 14. The manufacturing process steps of the steel pipe and the chemical composition of the welding wire and the flux are the same as in Example 1, and the welding process parameters are shown in Table 15. Table 16 shows the chemical composition of the weld metal of this embodiment, and Table 17 shows the performance test results of the actual steel pipe. The performance requirements of the X80 steel grade pipeline steel pipe can be seen from the table. The welded pipe meets the technical requirements of X80 steel grade pipeline steel pipe.

Table 13 Main chemical composition of coils (wt.%)

C Mn Si P S V+Nb+Ti Ni+Cr+Cu Cr+Mo+Mn Ceq Pcm 0.03 1.54 0.26 0.011 0.001 0.10 0.73 1.87 0.38 0.14

Table 14 Tensile test values of coils (rolling direction 30°)

Yield strength Rt_0.5(MPa) Tensile strength Rm(MPa) Yield strength ratio Rt_0.5/Rm Elongation A50mm(%) Min 570 640 0.85 26 Max 580 660 0.89 49 Ave 575 650 0.88 33

Table 15 Twin wire welding parameters

Table 16 Chemical Composition of Weld Metal (wt.%)

C Mn Si P S V+Nb+Ti Ni+Cr+Cu Cr+Mo+Mn External weld 0.04 1.55 0.27 0.014 0.001 0.078 0.55 1.91 Inner seam 0.04 1.55 0.28 0.014 0.001 0.078 0.56 1.90

Table 17 Mechanical properties of steel pipes

Claims (3)

1. A method for manufacturing a high-strength X80 steel spiral welded pipe, characterized in that: the base material of the welded pipe adopts X80 high-strength controlled-rolled steel coil, and the mass percentage of its chemical composition is C 0.02-0.09%, Si 0.10-0.42%, Mn 1.50～1.85%, P≤0.022%, S≤0.005%, Cr≤0.45%, Ni≤0.50%, Cu≤0.30%, Mo≤0.35%, Ti≤0.025%, Nb≤0.11%, V≤0.06% , Al≤0.06%, N≤0.008%, B≤0.0005%, Pcm≤0.23%; its processing procedures include: uncoiling, leveling, milling, pre-bending, forming, internal welding, external welding, pipe end expansion, Base metal lamination ultrasonic inspection, weld X-ray inspection, hydraulic test, weld ultrasonic inspection, pipe end chamfering and finished product inspection process, Wherein, the process of the pre-bending process adopts a double-roller pre-bending machine to pre-bend the delivery side and the free side of the coil, and the size of the pre-bending is 1470mm in radius and 100-130mm in length; The process of the internal welding process adopts double-wire tandem submerged arc automatic welding, the first wire is DC, its current I=1000～1200A, voltage V=31～33V; the second wire is AC, its current I=430～ 470A, voltage V=35~37V; welding wire spacing d=10~14mm, welding speed V=1.3~1.6m/min; The process of the external welding process adopts double-wire tandem submerged arc automatic welding, the first wire is DC, its current I=1100～1300A, voltage V=33～35V; the second wire is AC, its current I=400～ 450A, voltage V=35~37V; welding wire spacing d=12~16mm, welding speed V=1.3~1.6m/min; High-speed flux and high-toughness submerged arc welding wire are used in both internal and external welding processes, and a laser seam automatic tracking device with a tracking accuracy of 0.25mm is used. 2. A method for manufacturing high-strength X80 steel spiral welded pipes according to claim 1, characterized in that the process of the milling process is a double milling process: first rough milling the I-shaped groove, and then fine-milling the X-shaped slope Mouth, blunt edge 5-8mm, bevel angle 30°-45°. 3. A manufacturing method of high-strength X80 steel spiral welded pipe according to claim 1, characterized in that the process of expanding the diameter of the pipe end is as follows: cold expanding within 300mm of the end of the steel pipe, the maximum amount of diameter expanding It is 1.5% of the diameter; the circumference deviation of the pipe end is ±1.5mm, and the ellipticity deviation is less than or equal to 2mm.