Rolling method of high-dimensional-precision rolled steel pipe with outer diameter of 508 mm for underwater oil and gas development

Abstract

The invention provides a rolling method of a rolled steel pipe with the outer diameter of 508 mm for underwater oil and gas development, according to the rolling method, a blank is subjected to gradient heating in an annular furnace, rolling parameters of a 508 PQF unit are strictly controlled, and the rolled steel pipe with the outer diameter of 508 mm is prepared and has good dimensional precision without sizing and machining treatment. The high-dimensional-precision seamless pipeline pipe with the outer diameter of 508 mm is used for oil and gas development and oil and gas delivery under deep sea 800 m and above underwater.

Description

Technical Field

[0001] The invention relates to the field of marine oil and gas development and seamless pipe manufacturing, in particular to a method for rolling a 508mm outer diameter high-dimensional precision rolled steel pipe for underwater oil and gas development. Background Art

[0002] Underwater oil and gas development usually requires high dimensional accuracy and high performance pipelines. The design usually takes into account issues such as misalignment after welding and requires the inner diameter dimensional accuracy of the pipe end to reach ±0.5mm or ±0.25mm or stricter. This technical requirement can be achieved through direct rolling for small-sized products, but the existing rolling process for 508mm outer diameter seamless pipes is difficult to meet the high dimensional accuracy and length requirements.

[0003] Chinese patent CN102699628A discloses a method for producing a seamless steel pipe with a diameter of 508 mm for hydrogen sulfide corrosion-resistant pipelines, which is manufactured by a 720 oblique rolling and expansion unit, using a 400 mm cross-section round billet continuously rolled into a steel pipe with a certain outer diameter as a master batch, and finally realizing a 508 mm outer diameter product through a 720REM unit. At the same time, the maximum wall thickness is 31.8 mm due to the rolling capacity of the unit, and the inner and outer diameter tolerances are large, which cannot meet the requirements of underwater oil and gas development. Chinese patent CN106180195A discloses a method for hot continuous rolling production of a 508 mm large-diameter seamless steel pipe, which only introduces the realization of 508 mm through a continuous rolling method, and does not reflect the dimensional accuracy and performance requirements of the product. The embodiment only shows the rolling of low-strength 20 steel products. At the same time, the outer diameter and process control temperature of the mother pipe are different, and the prepared seamless steel pipe is difficult to meet the key production process of high-dimensional precision steel pipes for deep sea use. Therefore, it is necessary to improve the process and improve the dimensional accuracy of the product in order to meet the demand for 508mm outer diameter high dimensional accuracy seamless pipelines for oil and gas transportation in underwater oil and gas development at deep sea depths of 800m and above. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a method for rolling a 508mm outer diameter rolled steel pipe for underwater oil and gas development. The prepared rolled steel pipe has a wall thickness greater than 28mm, a length greater than 13 meters, and high inner and outer diameter dimensional accuracy, which meets the production of high dimensional accuracy seamless pipeline pipes for deep-sea oil and gas development.

[0005] The technical solution adopted by the present invention is:

[0006] The present invention provides a rolling method for a 508 mm outer diameter high dimensional accuracy thick-wall seamless pipe for underwater oil and gas development, comprising the following steps:

[0007] (1) Ring furnace heating: The 500 mm continuous casting round billet is heated in a step-beam ring furnace with natural gas as the medium, with a temperature range of 850°C to 1300°C. The furnace time is controlled to be greater than 8 hours, and the heating is uniform to achieve the best rolling state;

[0008] (2) Punching: The roller puncher punches the heated 500 mm continuous casting round billet. The temperature of the continuous casting round billet before punching is required to be greater than 950°C, the outer diameter of the rough tube is 580-590 mm, the wall thickness is 40-60 mm, and the plug is 435-450 mm;

[0009] (3) Continuous rolling: The pierced continuous casting round billet is continuously rolled using a 508PQF continuous rolling mill and a three-roller limited mandrel PQF continuous rolling mill. The mandrel is 462.9 mm, the wall thickness is 28 to 60 mm, the wall thickness tolerance control range is -7%t to 10%t, and the length is greater than 13 meters.

[0010] (4) Sizing and cooling bed: Through the tube stripping machine and sizing machine rolling, the outer diameter of the steel pipe is controlled within the range of ±5%D and placed in the step-type cooling bed, and the turning time is controlled to be ≤2min and the bending degree of the steel pipe is ≤0.15%L;

[0011] (5) Sawing and cold straightening: The cooled steel pipe is sawn to a fixed length and cold straightened (at room temperature) to achieve a full-length curvature of ≤0.15%L to obtain a rolled steel pipe;

[0012] (6) Flaw detection and inspection: Magnetic leakage flaw detection is used to inspect the surface of the rolled steel pipe in the horizontal and vertical directions of the outer surface. The flaw detection level is F2. The outer diameter of the steel pipe, the inner diameter of the pipe end, the non-roundness of the inner diameter of the pipe end, the wall thickness, and the straightness are inspected. The accuracy of the rolled steel pipe can reach: -2.5mm≤outer diameter tolerance≤+2.5mm, -0.7mm≤inner diameter tolerance≤+0.7mm, inner diameter non-roundness of the pipe end≤3.2mm, local non-roundness≤0.5mm, -3mm≤wall thickness tolerance≤+3mm, length≥13m.

[0013] Furthermore, the gradient heating is 7-stage gradient heating, and the temperature gradient is 850°C-1080°C-1220°C-1270°C-1300°C-1280°C-1260°C.

[0014] Furthermore, the front-end reduction rate of the punching is controlled at 5-7%, and the rolling force of the punching reaches 211700-14890KN.

[0015] Furthermore, high-pressure water dephosphorization is performed before the continuous rolling, and the dephosphorization pressure is greater than 9.5 MPa.

[0016] Furthermore, high-pressure water dephosphorization is performed before sizing, and the dephosphorization pressure is greater than 7.5 MPa.

[0017] Furthermore, in the sawing, the length of the cutting head and tail is greater than 400 mm, the bevel requirement for the pipe end is ≤4 mm, and the length is greater than 12.092 meters.

[0018] Furthermore, the chemical composition of the 500 mm continuous casting round billet is: C: 0.045-0.11wt%, Si: 0.25-0.60wt%, Mn: 1.30-1.70wt%, P: ≤0.012wt%, S: ≤0.003wt%, Al: 0.020-0.060wt%, Cr: 0.05-0.15wt%, Mo: 0.11-0.20wt%, Nb: 0.015-0.03wt%, Cu: 0.01-0.06wt%, Ni: 0.05%-0.20wt%, V: 0.025-0.05wt%, Ti: 0.01-0.04wt%, B≤0.0005wt%, [H]≤2ppm, CEpcm: 0.16-0.22wt%,

[0019] CEIIW: 0.34-0.39wt%, CEpcm=C+Si / 30+Mn / 20+Cu / 20+Ni / 60+Cr / 20+Mo / 15+V / 10+5B, CEIIW=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15, the balance is Fe and unavoidable impurities.

[0020] The advantages and beneficial effects of the present invention are:

[0021] Compared with the prior art, the present invention heats the billet in a ring furnace by gradient heating and strictly controls the rolling parameters of the 508PQF unit to prepare a 508mm outer diameter rolled steel pipe with high dimensional accuracy, which can meet the demand for the preparation of 508mm outer diameter high dimensional accuracy seamless pipelines for transporting oil and gas in underwater oil and gas development at depths above 800m in the deep sea. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a rolling process flow chart of the present invention;

[0023] Figure 2 This is the inner diameter distribution diagram of the rolled steel pipe with an outer diameter of 508 mm in Example 1;

[0024] Figure 3 This is a distribution diagram of the inner diameter non-roundness of the rolled steel pipe with an outer diameter of 508 mm in Example 1;

[0025] Figure 4 This is the length distribution diagram of the 508mm outer diameter rolled steel pipe in Example 1. DETAILED DESCRIPTION

[0026] The present invention is described with reference to the accompanying drawings and embodiments to provide a 508 mm outer diameter high dimensional accuracy seamless pipeline for underwater oil and gas development.

[0027] Example 1

[0028] A 508mm outer diameter rolled steel pipe for underwater oil and gas development, with a specification of 508mmx31.8mm, the rolling method comprising the following steps:

[0029] A 500 mm high-quality continuous casting round billet is heated in a walking beam annular furnace with a center diameter of 51 meters. The chemical composition of the continuous casting round billet is as follows by mass percentage: C 0.084wt%, Si 0.24wt%, Mn 1.30wt%, P 0.012wt%, S 0.003wt%, Al0.023wt%, Cr 0.12wt%, Mo 0.11wt%, Nb 0.024wt%, Cu 0.06wt%, Ni 0.12wt%, V0.04wt%, Ti 0.010wt%, B 0.0003wt%, CEpcm: 0.18wt%, CE IIW :0.37wt%, the balance is Fe and inevitable impurities. Use natural gas as the medium for 7-stage gradient heating, the temperature range is 850℃-1080℃-1220℃-1270℃-1300℃-1280℃-1260℃, control the furnace time at 10 hours, heat evenly, achieve the best rolling state, use a two-roll oblique tapered roller piercing machine for piercing, the piercing continuous casting round billet temperature is 1000℃, the rough pipe outer diameter is 583-588mm, the wall thickness is 48mm, the head is 445mm, and the rolled structure after piercing is continuously rolled using a 508PQF continuous rolling unit three-roll limited mandrel PQF continuous rolling tube mill, the mandrel is 462.9mm, the system The computer sets the rolling target wall thickness of 32.15mm, the wall thickness tolerance control range of -6.2%t~9%t, the length of 13.43 meters, the high-pressure water dephosphorization pressure before continuous rolling is 10MPa to ensure the surface quality, and the high-pressure water dephosphorization before sizing is 8.5MPa. First, it passes through three tube stripping machines and then two sizing machines for rolling to control the outer diameter of the steel pipe within the range of ±5%D. The step-type cooling bed and the cooled rolled steel pipe are cut to length. The length of the head and tail is 900mm, the pipe end is cut obliquely to 1.6mm, and the cut length is 12.292 meters. The three rotating rollers are cold straightened to achieve a full-length curvature of 5mm. Surface inspection is carried out by leakage magnetic flaw detection. The outer surface is horizontal and vertical, and the flaw detection level is F2, which is qualified without defects. According to the furnace, the outer diameter of the tube body, the inner diameter of the tube end, the out-of-roundness of the inner diameter of the tube end, the wall thickness, and the straightness of 10 seamless tubes are sampled. The inner diameter distribution diagram of the rolled steel tube end is as follows Figure 2 As shown, the distribution diagram of the inner diameter non-roundness of the rolled steel pipe end is as follows Figure 3 As shown, the length distribution of rolled steel pipe is as follows Figure 4As shown in the figure, the precision of the produced rolled steel pipe can reach: -2.5mm≤outer diameter tolerance≤+2.5mm, -0.7mm≤inner diameter tolerance≤+0.7mm, inner diameter non-roundness of the pipe end≤3.2mm, local non-roundness≤0.5mm, -3mm≤wall thickness tolerance≤+3mm, length≥12.1m. The details are shown in Table 1.

[0030] Example 2

[0031] A 508mm outer diameter high-dimensional precision rolled steel pipe for underwater oil and gas development, with a specification of 508mmx34.9mm, a rolling method comprising the following steps: heating a 500mm high-quality continuous casting round billet (with the same composition as in Example 1) in a walking-beam annular furnace with a median diameter of 51 meters, performing 7-stage gradient heating with natural gas as the medium, the temperature range being 850°C-1080°C-1220°C-1270°C-1300°C-1280°C-1260°C, controlling the furnace time to be 10 hours, uniformly heating, achieving an optimal rolling state, using a two-roll oblique rolling tapered roller puncher for punching, controlling the top front pressing rate of the punching to be 5%, the rolling force of the punching to be 14890KN, the temperature of the punched continuous casting round billet to be 1000°C, the outer diameter of the rough pipe to be 583-58 8mm, wall thickness 53mm, top 450mm, three-roller limited mandrel PQF continuous rolling mill 508PQF continuous rolling mill, mandrel 462.9mm, system computer set rolling target wall thickness 35.25mm, wall thickness tolerance control range -6.2%t~9%t, length 13.35 meters, high-pressure water dephosphorization pressure 12MPa before continuous rolling to ensure surface quality, high-pressure water dephosphorization 9MPa before sizing, first through three tube stripping machines and then two sizing machines rolling, control the outer diameter of the steel pipe within the range of ±5%D, step-type cooling bed, the cooled steel pipe is cut to length, the length of the head and tail is 900mm, the pipe end is cut obliquely to 1.6mm, the cut length is 12.292 meters, and the three rotating rollers are cold straightened to achieve a full-length curvature of 6mm. Surface inspection is carried out using leakage magnetic flaw detection, the outer surface is horizontal and vertical, the flaw detection level is F2, and it is qualified without defects. Ten rolled steel pipes were randomly tested for outer diameter, inner diameter, out-of-roundness of inner diameter, wall thickness and straightness according to the furnace.

[0032] The precision of the rolled steel pipe produced can reach: -2.5mm≤outer diameter tolerance≤+2.5mm, -0.7mm≤inner diameter tolerance≤+0.7mm, inner diameter non-roundness of the pipe end≤3.2mm, local non-roundness≤0.5mm, -3mm≤wall thickness tolerance≤+3mm, length≥12.1m. The details are shown in Table 1.

[0033] Example 3

[0034] A 508mm outer diameter high-dimensional precision rolled steel pipe for underwater oil and gas development, with a rolling specification of 508mmx40.2mm, and a rolling method comprising the following steps: heating a 500mm high-quality continuous casting round billet (with the same composition as in Example 1) in a walking-beam annular furnace with a median diameter of 51 meters, performing 7-stage gradient heating with natural gas as the medium, with a temperature range of 850°C-1080°C-1220°C-1270°C-1300°C-1280°C-1260°C, controlling the furnace time to be 10 hours, uniformly heating, achieving an optimal rolling state, and using a two-roll oblique rolling tapered roller piercing machine for piercing, the piercing continuous casting round billet temperature is 1000°C, the rough pipe outer diameter is 583-588mm, the wall thickness is 58mm, and the head is 439mm, using three-roller limited mandrel PQF continuous tube mill 508PQF continuous rolling mill, mandrel 448.4mm, system computer set rolling target wall thickness 40mm, wall thickness tolerance control range -6.2%t~9%t, length 13.35 meters, high-pressure water dephosphorization pressure 15MPa before continuous rolling to ensure surface quality, high-pressure water dephosphorization 10MPa before sizing, first through three tube stripping machines and then two sizing machines rolling, control the outer diameter of the steel pipe within the range of ±5%D, step-type cooling bed, the cooled steel pipe is cut to length, the length of the head and tail is 900mm, the pipe end is cut obliquely to 1.6mm, the cut length is 12.292 meters, and the three rotating rollers are cold straightened to achieve a full-length curvature of 6mm. Surface inspection is carried out using leakage magnetic flaw detection, the outer surface is horizontal and vertical, the flaw detection level is F2, and it is qualified without defects. According to the furnace, 10 rolled steel pipes were randomly tested for outer diameter, inner diameter, out-of-roundness, wall thickness and straightness.

[0035] The precision of the rolled steel pipe produced can reach: -2.5mm≤outer diameter tolerance≤+2.5mm, -0.7mm≤inner diameter tolerance≤+0.7mm, inner diameter non-roundness of the pipe end≤3.2mm, local non-roundness≤0.5mm, -3mm≤wall thickness tolerance≤+3mm, length≥12.1m. The details are shown in Table 1.

[0036] Comparative Example

[0037] In the comparative example, the steel grade of the billet is No. 20 steel. The temperature of the billet out of the annular heating furnace is 1270℃. The annular heating furnace is divided into 7 temperature sections for heating, which are: 900℃, 1100℃, 1220℃, 1240℃, 1300℃, 1270℃ and 1270℃ respectively. The rough pipe size after perforation is 577mm in outer diameter and 41.55mm in thickness. The rough pipe size after continuous rolling is 530mm in outer diameter and 29.3mm in thickness. The outer diameter after sizing is 517mm and the wall thickness is 30mm. The finished product size after the sizing rack is 508mmx30mm in outer diameter. The precision of the rolled steel pipe produced can meet the standard requirements of 20 steel for onshore steel pipes.

[0038] The only difference from Example 1 is the temperature heating gradient control, the whole hole design of piercing-continuous rolling-sizing, and the key process parameters, which ultimately lead to different product quality. More than 9,000 508mmx31.8mm steel pipes have been produced using the technology in this article. The inner diameter and inner diameter out-of-roundness of most steel pipes are statistically analyzed. The distribution diagram of the actual measurement data is shown in the figure below. Figure 2 and Figure 3 .

[0039] Table 1 Precision of rolled steel pipes produced in Examples 1 to 3 and Comparative Examples

[0040]

[0041] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept, which all belong to the protection scope of the present invention.

Claims

1. A method for rolling a 508 mm outer diameter high dimensional accuracy rolled steel pipe for underwater oil and gas development, characterized in that: The following steps are involved: (1) Ring furnace heating: The 500 mm continuous casting round billet is heated in a walking beam ring furnace with natural gas as the medium for gradient heating in the temperature range of 850°C to 1300°C. The furnace time is controlled to be greater than 8 hours to ensure uniform heating; (2) Punching: The roller puncher punches the heated 500 mm continuous casting round billet. The temperature of the continuous casting round billet before punching is required to be greater than 950°C, the outer diameter of the rough tube is 580-590 mm, the wall thickness is 40-60 mm, and the plug is 435-450 mm; (3) Continuous rolling: The pierced continuous casting round billet is continuously rolled using a 508PQF continuous rolling mill and a three-roller limited mandrel PQF continuous rolling mill. The mandrel is 462.9 mm, the system sets the target wall thickness to 28 to 60 mm, the wall thickness tolerance control range is -7%t to 10%t, and the length is greater than 13 meters; (4) Sizing and cooling bed: Through the tube stripping machine and sizing machine rolling, the outer diameter of the steel pipe is controlled within the range of ±5%D, and then placed in the step-type cooling bed to control the turning time and the curvature of the steel pipe; (5) Sawing and cold straightening: The cooled steel pipe is sawn to a fixed length and cold straightened, with the full-length curvature ≤ 0.15%L to obtain a rolled steel pipe; (6) Flaw detection and inspection: Magnetic leakage flaw detection is used to inspect the surface of the rolled steel pipe in the horizontal and vertical directions of the outer surface, and the flaw detection level is F2; ​​the outer diameter of the rolled steel pipe, the inner diameter of the pipe end, the non-roundness of the inner diameter of the pipe end, the wall thickness, and the straightness are inspected. The accuracy of the rolled steel pipe can reach: -2.5mm≤outer diameter tolerance≤+2.5mm, -0.7mm≤inner diameter tolerance≤+0.7mm, inner diameter non-roundness of the pipe end≤3.2mm, local non-roundness≤0.5mm, -3mm≤wall thickness tolerance≤+3mm, and length≥13m.

2. The rolling method according to claim 1, characterized in that: The gradient heating is a 7-stage gradient heating, and the temperature gradient is 850°C-1080°C-1220°C-1270°C-1300°C-1280°C-1260°C.

3. The rolling method according to claim 1, characterized in that: The front pressing rate of the punching is controlled at 5-7%, and the rolling force of the punching reaches 211700-14890KN.

4. The rolling method according to claim 1, characterized in that: The chemical composition of the 500 mm continuous casting round billet is C: 0.045-0.11 wt%, Si: 0.25-0.60 wt%, Mn: 1.30-1.70 wt%, P: ≤0.012 wt%, S: ≤0.003 wt%, Al: 0.020-0.060 wt%, Cr: 0.05-0.15 wt%, Mo: 0.11-0.20 wt%, Nb: 0.015-0.03wt%, Cu: 0.01-0.06wt%, Ni: 0.05%-0.20wt%, V: 0.025-0.05wt%, Ti: 0.01-0.04wt%, B≤0.0005wt%, [H]≤2ppm, CEpcm: 0.16-0.22wt%, CEIIW: 0.34-0.39wt%, CEpcm=C+Si / 30+Mn / 20+Cu / 20+Ni / 60+Cr / 20+Mo / 15+V / 10+5B, CEIIW=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15, the balance is Fe and unavoidable impurities.

5. The rolling method according to claim 1, characterized in that: High-pressure water dephosphorization is performed before the continuous rolling, and the dephosphorization pressure is greater than 9.5 MPa.

6. The rolling method according to claim 1, characterized in that: High-pressure water dephosphorization is performed before sizing, and the dephosphorization pressure is greater than 7.5 MPa.

7. The rolling method according to claim 1, characterized in that: During the sawing, the length of the cutting head and tail is greater than 400 mm, the bevel requirement for the pipe end is ≤4 mm, and the length is greater than 12.092 meters.

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