CN115008135A - Production method of large-wall-thickness large-caliber longitudinal submerged arc welded pipe L555M - Google Patents

Abstract

A production method of a large-wall-thickness large-caliber JCOE longitudinal submerged arc welded pipe L555M comprises the steps of adopting a large-section 450mm casting blank and a TMCP + T production process to produce a steel plate with the wall thickness of 22-33 mm multiplied by 4330mm multiplied by 12350mm, and obtaining the large-wall-thickness large-caliber longitudinal submerged arc welded pipe L555M with excellent performance after JCOE pipe manufacturing, wherein the yield strength of the steel pipe is 570-600 MPa, the tensile strength is 680-720 MPa, the yield ratio is 0.83-0.88, the impact toughness of the pipe body at the temperature of-20 ℃ is 340-400J, the hot area is 150-180J, and the drop hammer shear area at the temperature of-20 ℃ is 90-95%. The problems of penetration of rolling force along the thickness direction, insufficient core deformation and low DWTT shearing area in the thick plate rolling process are solved, 50% -60% bainite and 20% -30% ferrite structures are obtained, and the strength and toughness of the steel plate are well matched. The difficult problem of embrittlement of the welding joint of the thick-wall L555M steel pipe is solved by a small-angle groove and low-linear-energy rapid welding method.

Description

Production method of large-wall-thickness large-caliber longitudinal submerged arc welded pipe L555M

Technical Field

The invention belongs to the technical field of steel pipe manufacturing, and relates to a production method of a large-wall-thickness large-caliber JCOE longitudinal submerged arc welded pipe L555M.

Background

Petroleum and natural gas are important strategic materials of national economy, energy growth and structural optimization adjustment drive the overall development of the petroleum and natural gas industry, and the petroleum and natural gas gradually become the most main energy resources. Due to the characteristic limitation of petroleum and natural gas, pipeline transportation has larger transportation volume, higher safety and better economy compared with railway and highway transportation, and pipeline transportation with large wall thickness, high pressure, large transportation volume and large pipe diameter is the main development trend of pipeline construction. This trend is generally achieved by increasing the strength grade of the pipeline steel. Therefore, the development of high strength grades of pipeline steel is a goal of pipeline steel researchers and producers' efforts.

Then, along with the increase of the wall thickness and the caliber of the pipeline, the production difficulty of the pipeline steel plate is higher, such as DWTT performance indexes and the like, and meanwhile, the welding of the thick-wall steel pipe is more difficult to guarantee, such as embrittlement, recurvation cracking and the like of a welding joint.

Disclosure of Invention

The invention aims to provide a production method of a large-wall-thickness large-caliber JCOE longitudinal submerged arc welded pipe L555M, which aims to solve the problem of production of the existing large-wall-thickness large-caliber steel plate, and the large-wall-thickness large-caliber longitudinal submerged arc welded pipe L555M with excellent performance is obtained, the yield strength of the steel pipe is 570-600 MPa, the tensile strength is 680-720 MPa, the yield ratio is 0.83-0.88, the-20 ℃ impact toughness of the pipe body is 340-400J, the hot area is 150-180J, and the-20 ℃ drop hammer shear area is 90-95%.

The technical scheme of the invention is as follows:

a production method of a JCOE longitudinal submerged arc welded pipe L555M with large wall thickness and large caliber is characterized in that: the steel comprises the following chemical components, by weight, 0.04% -0.05% of C, 0.15% -0.25% of Si, 1.68% -1.75% of Mn, 0.015% or less of P, 0.005% or less of S, 0.050% -0.060% of Nb, 0.10% -0.16% of Cr, 0.18% -0.25% of Ni, 0.10% -0.16% of Mo, 0.0005% -0.0010% of B, 0.020% -0.040% of ALT, and the balance of Fe and inevitable impurities; the key process steps comprise: :

(1) continuous casting: the casting blank section is 350mm multiplied by 2500mm, the casting is protected in the whole process, the superheat degree is controlled at 8-20 ℃, the pulling speed is controlled at 0.35-0.60 m/min, dynamic soft reduction is adopted, hard reduction is adopted at the solidification tail end, and the two-stage reduction amount at the solidification end point of the continuous casting blank is 7-12 mm and 3-6 mm respectively;

(2) rolling: heating at 1100-1250 ℃, heating for 300-400 min, keeping the thickness of the blank to be heated at 95-115 mm, rolling at 820-840 ℃ and rolling at 770-800 ℃ for the final time;

(3) and (3) cooling: a Mulpic multifunctional cooling mode is adopted, wherein a region A is in a DQ mode, the cooling speed is 25-30 ℃, the temperature after cooling is controlled at 500-550 ℃, a region BCD is in an ACC mode, the cooling speed is 10-15 ℃, and the temperature after cooling is controlled at 320-400 ℃;

(4) tempering: the tempering temperature is 400-420 ℃, and the furnace time is 80-100 min;

(5) pipe making: the method comprises the steps of edge milling, JCO forming, prewelding, inner welding, outer welding and expanding, wherein the height of a groove on the edge milling is 10.75-11.25 mm, the thickness of a truncated edge is 8.75-9.25 mm, 27 molding pressing passes are performed, the reduction per time is 580-590 mm, the welding speed V of four-wire submerged arc automatic welding is 120-140 cm/min, the linear energy is 45-60 kJ/cm, and the expanding rate is 0.6% -0.8%.

According to the invention, a large-section 450mm casting blank and a TMCP + T production process are adopted to produce a steel plate with the wall thickness of 22-33 mm multiplied by 4330mm multiplied by 12350mm, and after the steel plate is subjected to JCOE pipe manufacturing, the problems of center segregation, shrinkage and loosening of thick-wall pipeline steel rolled by a large single continuous casting blank are solved, and the problems of penetration of rolling force along the thickness direction, insufficient center deformation and low DWTT shearing area in the thick plate rolling process are solved. A cooling mode combining strong cooling and weak cooling is adopted, ferrite structures of 50% -60% of bainite and 20% -30% of steel plate are obtained, the strength and toughness of a steel plate are well matched, the obtained large-wall-thickness large-caliber longitudinal submerged arc welded pipe L555M with excellent performance is obtained, the yield strength of the steel pipe is 570-600 MPa, the tensile strength is 680-720 MPa, the yield ratio is 0.83-0.88, the-20-DEG C impact toughness of the pipe body is 340-400J, the hot area is 150-180J, and the-20-DEG C drop hammer shear area is 90% -95%. The difficult problem of embrittlement of the welding joint of the thick-wall L555M steel pipe is solved by a small-angle groove and low-linear-energy rapid welding method.

Drawings

FIG. 1 is a macro-photo of a weld.

Detailed Description

The present invention will be further described with reference to the following examples.

Example 1: production of phi 1422X 32.1mm L555M longitudinal submerged arc welded pipe

The steel has the chemical composition by mass percent of C =0.05%, Si =0.22%, Mn =1.70%, P =0.012%, S =0.003%, Nb =0.052%, Cr =0.13%, Ni =0.21%, Mo =0.13%, B =0.0006%, ALT =0.028%, and the balance of Fe and inevitable impurities; the key process steps are as follows:

(1) continuous casting: the section of a casting blank is 350mm multiplied by 2500mm, the casting is protected in the whole process, the superheat degree is controlled at 12 ℃, the pulling speed is controlled at 0.45m/min, dynamic soft reduction is adopted, heavy reduction is adopted at the solidification tail end, the reduction force effectively penetrates into the core, and the two sections of reduction at the solidification end point of the continuous casting blank are respectively 10mm and 5 mm;

(2) rolling: heating at 1120-1240 ℃ for 352min, and keeping the blank to be heated to 105mm in thickness, the initial rolling temperature of 830 ℃ and the final rolling temperature of 790 ℃;

(3) and (3) cooling: a Mulpic multifunctional cooling mode is adopted, wherein a region A is in a DQ mode, the cooling speed is 26 ℃, the temperature after cooling is controlled to be 510-540 ℃, a region BCD is in an ACC mode, the cooling speed is 12 ℃, and the temperature after cooling is controlled to be 330-380 ℃;

(4) tempering: tempering temperature is 405 ℃, and furnace time is 85 min;

(5) pipe making: the JCOE technology is adopted for manufacturing the pipe, and the main steps are edge milling, JCO forming, prewelding, inner welding, outer welding and expanding. The height of a groove on the milled edge is 11mm, the thickness of the truncated edge is 9.12mm, the forming and pressing pass is 27, the rolling reduction is 581-588 mm each time, the welding speed V of four-wire submerged arc automatic welding is 122-136 cm/min, the linear energy is 46-56 KJ/cm, and the diameter expansion rate is 0.62% -0.75%.

The mechanical properties of the steel pipes are shown in Table 1.

Example 2: production of phi 1422 x 22mm L555M longitudinal submerged arc welded pipe

The steel has a chemical composition content of C =0.04, Si =0.22%, Mn =1.72%, P =0.011%, S =0.003%, Nb =0.055%, Cr = 0.10-0.16%, Ni =0.20%, Mo =0.12%, B =0.0007%, ALT =0.026%, and the balance of Fe and unavoidable impurities; the key process steps are as follows:

(1) continuous casting: the section of a casting blank is 350mm multiplied by 2500mm, the casting is protected in the whole process, the superheat degree is controlled at 12 ℃, the pulling speed is controlled at 0.46m/min, dynamic soft reduction is adopted, heavy reduction is adopted at the solidification tail end, the reduction force effectively penetrates into the core, and the two sections of reduction at the solidification end point of the continuous casting blank are respectively 9mm and 4 mm;

(2) rolling: heating at 1120-1230 ℃, heating for 362min, and keeping the blank thickness at 100mm, the initial rolling temperature at 830 ℃ and the final rolling temperature at 795 ℃;

(3) and (3) cooling: a Mulpic multifunctional cooling mode is adopted, wherein a region A is in a DQ mode, the cooling speed is 26 ℃, the temperature after cooling is controlled to be 520-550 ℃, a region BCD is in an ACC mode, the cooling speed is 14 ℃, and the temperature after cooling is controlled to be 340-400 ℃;

(4) tempering: tempering temperature is 410 ℃, and furnace time is 82 min;

(5) pipe making: the JCOE technology is adopted for manufacturing the pipe, and the main steps are edge milling, JCO forming, prewelding, inner welding, outer welding and expanding. The height of the groove on the milling edge is 10.82mm, the thickness of the truncated edge is 9.15mm, 27 molding and pressing passes are performed, the reduction per time is 581-585mm, the welding speed V of four-wire submerged arc automatic welding is 125cm/min, the linear energy is 46-55KJ/cm, and the diameter expansion rate is 0.62-0.72%.

The mechanical properties of the steel pipes are shown in Table 1.

TABLE 1L 555M Steel pipe mechanical Property results

。

Claims (1)

1. A production method of a JCOE longitudinal submerged arc welded pipe L555M with large wall thickness and large caliber is characterized in that: the steel comprises the following chemical components, by weight, 0.04% -0.05% of C, 0.15% -0.25% of Si, 1.68% -1.75% of Mn, 0.015% or less of P, 0.005% or less of S, 0.050% -0.060% of Nb, 0.10% -0.16% of Cr, 0.18% -0.25% of Ni, 0.10% -0.16% of Mo, 0.0005% -0.0010% of B, 0.020% -0.040% of ALT, and the balance of Fe and inevitable impurities; the key process steps comprise:

(1) continuous casting: the casting blank section is 350mm multiplied by 2500mm, the casting is protected in the whole process, the superheat degree is controlled at 8-20 ℃, the pulling speed is controlled at 0.35-0.60 m/min, dynamic soft reduction is adopted, hard reduction is adopted at the solidification tail end, and the two-stage reduction amount at the solidification end point of the continuous casting blank is 7-12 mm and 3-6 mm respectively;

(2) rolling: heating at 1100-1250 ℃, heating for 300-400 min, keeping the thickness of the blank to be heated at 95-115 mm, rolling at 820-840 ℃ and rolling at 770-800 ℃ for the final time;

(3) and (3) cooling: a Mulpic multifunctional cooling mode is adopted, wherein a region A is in a DQ mode, the cooling speed is 25-30 ℃, the temperature after cooling is controlled at 500-550 ℃, a region BCD is in an ACC mode, the cooling speed is 10-15 ℃, and the temperature after cooling is controlled at 320-400 ℃;

(4) tempering: the tempering temperature is 400-420 ℃, and the furnace time is 80-100 min;

(5) pipe making: the method comprises the steps of edge milling, JCO forming, prewelding, inner welding, outer welding and expanding, wherein the height of a groove on the edge milling is 10.75-11.25 mm, the thickness of a truncated edge is 8.75-9.25 mm, 27 molding pressing passes are performed, the reduction per time is 580-590 mm, the welding speed V of four-wire submerged arc automatic welding is 120-140 cm/min, the linear energy is 45-60 kJ/cm, and the expanding rate is 0.6% -0.8%.

Images