CN111235465A - Corrosion-resistant high-crack-resistance submarine pipeline steel X65MO with thickness of 8-15mm and production method thereof - Google Patents

Abstract

The invention discloses corrosion-resistant high-crack-resistance submarine pipeline steel X65MO with the thickness of 8-15mm and a production method thereof, wherein the pipeline steel X65MO comprises the following chemical components in percentage by mass: 0.05 to 0.08 percent of C; 0.10 to 0.20 percent of Si; 1.00 to 1.20 percent of Mn; p is less than or equal to 0.015 percent; s is less than or equal to 0.002%; al is less than or equal to 0.040%; 0.025 to 0.035 percent of Nb; 0.015 to 0.025 percent of Ti; 0.15 to 0.25 percent of Cr; 0.0010 to 0.0020 percent of Ce; h is less than or equal to 2.0 ppm; o is less than or equal to 30 ppm; n is less than or equal to 60ppm, and the balance is Fe and inevitable impurities. The pipeline steel has the characteristics of cost economy, low-temperature toughness, crack arrest performance and corrosion resistance, and can be used as a submarine acid-resistant pipeline.

Description

Corrosion-resistant high-crack-resistance submarine pipeline steel X65MO with thickness of 8-15mm and production method thereof

Technical Field

The invention belongs to the field of metallurgical materials, particularly relates to 8-15mm thick corrosion-resistant high-crack-resistance submarine pipeline steel X65MO and a production method thereof, and particularly relates to 8-15mm thick low-cost corrosion-resistant high-crack-resistance submarine pipeline steel X65MO produced by a 2250mm hot continuous rolling unit and a production method thereof.

Background

The offshore pipeline is used as a main form of offshore oil and gas storage and transportation, connects the upstream and the downstream of offshore oil field development, is an indispensable lifeline project for offshore oil and gas field development and production, and is also the most safe, most economic and seabed oil and gas transportation mode with the least environmental damage. As the submarine pipeline is in service in a severe marine environment for a long time, the pipeline is required to bear high pressure and internal conveying pressure in deep sea and is frequently impacted by the variability of ocean current motion, so that the raw material of the pipeline steel is required to have uniform transverse and longitudinal strength, good low-temperature toughness and crack arrest performance, and particularly for the submarine pipeline steel with the acid-resistant corrosion requirement, the core technology of the manufacturing method is how to adopt the component design of relatively low-cost alloy to ensure that the submarine pipeline steel has high strength and good crack arrest performance and has excellent acid-resistant corrosion performance.

With the development and demand of the market, various domestic steel mills in recent years adopt different component designs and different production processes to develop and trial manufacture the submarine pipeline steel X65MO and obtain the industrial production result, but the research and report on the preparation method of the currently advanced 2250mm hot continuous rolling unit and the relatively low-cost alloy elements (Nb, Ti, Cr, Mo and Ce) are less.

Document CN107988562A discloses an X65-grade low-cost subsea pipeline steel and a manufacturing method thereof, the component design system is C (0.05% -0.09%) -Si (0.10% -0.30%) -Mn (1.40% -1.60%) -P (less than or equal to 0.018%) -S (less than or equal to 0.008%) -Nb (0.020% -0.040%) -Ti (0.008% -0.020%) -Cr (0.10% -0.15%) -Als (0.020% -0.060%), and the balance of Fe. The production process comprises converter smelting, casting blank, rolling and cooling control and steel coil coiling. The cost is relatively low, but the corrosion resistance is not concerned.

Document CN 106566991 a discloses "an acid-resistant submarine pipeline steel and a manufacturing method thereof", the component design system is C (0.03% -0.045%) -Si (0.15% -0.23%) -Mn (1.20% -1.35%) -Ni (0.20% -0.40%) -Cr (0.20% -0.35%), and the balance is Fe. The production process comprises casting blank-hot rolling-steel plate stacking. Belonging to the production process of medium plates.

Document CN 109234487A discloses a production method of submarine pipeline steel X65MO, which comprises the following components of C (0.03-0.08%) -Si (0.10-0.30%) -Mn (0.80-1.00%) -P (less than or equal to 0.015%) -S (less than or equal to 0.0015%) -Nb (0.020-0.020%) -Ti (0.008-0.015%) -V (0.02-0.05%) -Cr (0.10-0.30%) -Al (0.008-0.0200%), and the balance of Fe. The production process comprises the steps of converter smelting, casting blank casting, controlled rolling and controlled cooling and steel coil coiling. The product has good obdurability, good HIC resistance, but relatively high cost.

The literature of 'submarine pipeline steel X65MO toughness research' describes the toughness index of X65MO hot-rolled coils produced by horse steel, and no relevant research report is carried out on the transverse and longitudinal strength index and the HIC (hydrogen induced cracking) resistance index of products.

Disclosure of Invention

In view of one or more of the problems in the prior art, the invention provides 8-15mm thick corrosion-resistant high crack-arrest subsea pipeline steel X65MO, wherein the chemical composition of the 8-15mm thick corrosion-resistant high crack-arrest subsea pipeline steel X65MO is as follows by mass percent: 0.05 to 0.08 percent of C; 0.10 to 0.20 percent of Si; 1.00 to 1.20 percent of Mn; p is less than or equal to 0.015 percent; s is less than or equal to 0.002%; al is less than or equal to 0.040%; 0.025 to 0.035 percent of Nb; 0.015 to 0.025 percent of Ti; 0.15 to 0.25 percent of Cr; 0.0010 to 0.0020 percent of Ce; h is less than or equal to 2.0 ppm; o is less than or equal to 30 ppm; n is less than or equal to 60ppm, and the balance is Fe and inevitable impurities.

The metallographic structure of the 8-15mm thick corrosion-resistant high crack-arrest submarine pipeline steel X65MO is polygonal ferrite and acicular ferrite, and the transverse mechanical properties of the steel meet the following requirements: the yield strength is more than or equal to 500MPa, the tensile strength is more than or equal to 585MPa, the elongation is more than or equal to 39.5%, and the yield ratio is less than or equal to 0.87; the longitudinal mechanical property satisfies: the yield strength is more than or equal to 485MPa, the tensile strength is more than or equal to 562MPa, the elongation is more than or equal to 38.5 percent, and the yield ratio is less than or equal to 0.86; the HIC resistance index was 0.

The invention also provides a production method of the 8-15mm thick corrosion-resistant high-crack-resistance submarine pipeline steel X65MO, which comprises the following steps: molten iron → converter smelting → LF refining → slab casting → rolling; wherein:

the chemical components of the molten iron are mentioned above;

oxygen blowing, decarbonization and temperature rising are carried out in the smelting process of the converter, ferrosilicon, ferromanganese and ferrochrome are added for deoxidation and alloying in the later smelting period, P, S components are controlled, molten steel is prevented from being overoxidized, steel slag is prevented from entering the molten steel by adopting a residual steel operation, the tapping temperature is 1600-1650 ℃, the tapping [ P ] of the converter is less than or equal to 0.015 percent, and the [ S ] is less than or equal to 0.008 percent;

the LF refining adopts an LF + RH whole-process argon blowing process, a good reducing atmosphere is kept in the refining process, Al wires are adopted for deoxidation, ferrocolumbium, ferromolybdenum and ferrotitanium are added in the later stage of LF for alloying, and calcium treatment is carried out after the LF is finished; after RH vacuum treatment, adding cerium-iron alloy (wherein Ce accounts for 20%) for micro-alloying in three minutes before re-pressing, wherein the vacuum degree is less than or equal to 2mbar, and the deep vacuum time is more than or equal to 15 min;

in the slab continuous casting process, the superheat degree delta T of molten steel is less than or equal to 25-40 ℃, the pulling speed is controlled to be 0.90-1.10m/min, a dynamic soft reduction technology is matched, and the straightening temperature is more than or equal to 920 ℃;

the rolling process adopts a 2250mm hot continuous rolling process, the heating temperature of the plate blank is 1200-1240 ℃, the heating time is 180-240 min, the soaking temperature is 1190-1210 ℃, the soaking time is 30-60 min, and the tapping temperature is 1180 +/-20 ℃; the rough rolling mode adopts 1+5 or 3+ 3; the initial rolling temperature of the last pass of rough rolling is less than or equal to 1000 ℃, and the final rolling temperature of the rough rolling is 1040-1140 ℃; the thickness range of the intermediate blank is as follows: 40-50 mm; the finish rolling initial rolling temperature is 940-1000 ℃; the finish rolling temperature is 830-850 ℃, the coiling temperature is 500-580 ℃, and the cooling speed is controlled at 20-40 ℃/s.

Based on the technical scheme, the 8-15mm thick corrosion-resistant high-crack-resistance submarine pipeline steel X65MO forms a C-Si-Mn-Nb-Ti-Cr-Ce component design system according to the component design principle of the pipeline steel, a conventional hot rolling 2250mm controlled rolling and controlled cooling process is adopted to produce a submarine pipeline steel X65MO coiled plate with the thickness of 8-15mm, and the pipe body performance after straight seam welding pipe manufacturing meets the requirements of DNV-OS-F010 submarine pipeline system standard. The product has uniform transverse and longitudinal strength indexes, good low-temperature toughness and crack resistance, and acid corrosion resistance. The provided production process is simple and executable, a proper amount of relatively cheap rare earth cerium iron alloy is added to replace a part of Nb and Cr to carry out a low-cost design idea, the rolling and cooling control process is fully exerted, and the high-strength, high-toughness and corrosion-resistant hot-rolled coil of the material is realized through the mechanisms of fine grain strengthening and precipitation strengthening of alloy elements. Compared with the same products of other steel mills, the rare earth Ce has less added alloy, and more importantly, the rare earth Ce is added to exert the beneficial characteristics of low-temperature toughness and corrosion resistance. The industrial production of the 2250mm hot rolling production line is obtained, the popularization value is good, the product cost is economic, and the method is suitable for batch stable production of enterprises.

Detailed Description

Aiming at the defects in the prior art, the invention selects and uses a C-Si-Mn-Nb-Ti-Cr-Ce component design system, adopts the conventional hot rolling 2250mm controlled rolling and controlled cooling process to produce the submarine pipeline steel X65MO coil with the thickness of 8-15mm, and comprises the following chemical components in percentage by mass: 0.05 to 0.08 percent of C; 0.10 to 0.20 percent of Si; 1.00 to 1.20 percent of Mn; p is less than or equal to 0.015 percent; s is less than or equal to 0.002%; al is less than or equal to 0.040%; 0.025 to 0.035 percent of Nb; 0.015 to 0.025 percent of Ti; 0.15 to 0.25 percent of Cr; 0.0010 to 0.0020 percent of Ce; h is less than or equal to 2.0 ppm; o is less than or equal to 30 ppm; n is less than or equal to 60ppm, and the balance is Fe and inevitable impurities. The main alloying elements Mn and Si of the material components utilize solid solution strengthening to improve the strength of the material; nb, Ti and rare earth Ce exert fine grain strengthening to improve the toughness of the material; cr plays roles of precipitation strengthening and hardenability increasing; cr and rare earth Ce improve the acid corrosion resistance.

The invention provides a production method of corrosion-resistant high crack-resistant submarine pipeline steel X65MO, which comprises a steel-making production process and a rolling process, wherein the steel-making production process comprises the following steps: molten iron → converter smelting → LF refining → slab continuous casting. Oxygen blowing, decarbonization and temperature rise in the smelting process of the converter, ferrosilicon, ferromanganese and ferrochromium are added for deoxidation and alloying in the later smelting period, P, S components are controlled, molten steel peroxidation is prevented, steel slag is prevented from entering the molten steel by adopting a residual steel operation, the tapping temperature is 1600-1650 ℃, the tapping [ P ] of the converter is less than or equal to 0.015 percent, and the [ S ] is less than or equal to 0.008 percent; LF refining adopts an LF + RH whole-process argon blowing process, good reducing atmosphere is kept in the refining process, Al wires are adopted for deoxidation, ferrocolumbium, ferromolybdenum and ferrotitanium are added in the later period of LF for alloying, and calcium treatment is carried out after LF is finished; after RH vacuum treatment, adding cerium-iron alloy (wherein Ce accounts for 20%) for micro-alloying in three minutes before re-pressing, wherein the vacuum degree is less than or equal to 2mbar, and the deep vacuum time is more than or equal to 15 min; in the slab continuous casting process, the superheat degree delta T of molten steel is less than or equal to 25-40 ℃, the drawing speed is controlled to be 0.90-1.10m/min, and the straightening temperature is more than or equal to 920 ℃ by adopting a dynamic soft reduction technology. The rolling process comprises the following steps: heating a plate blank, descaling by high-pressure water, sizing a press, rolling by an E1R1 roughing mill, rolling by an E2R2 roughing mill, flying shears, descaling by high-pressure water, rolling by an F1-F7 finishing mill, cooling by a dense laminar flow, coiling, transporting a tray system, sampling and inspecting. Wherein the heating temperature of the plate blank is 1200-1240 ℃, the heating time is 180-240 min, the soaking temperature is 1190-1210 ℃, the soaking time is 30-60 min, and the tapping temperature is 1180 +/-20 ℃; the rough rolling mode adopts 1+5 or 3+ 3; the initial rolling temperature of the last pass of rough rolling is less than or equal to 1000 ℃, and the final rolling temperature of the rough rolling is 1040-1140 ℃; the thickness range of the intermediate blank is as follows: 40-50 mm; the finish rolling initial rolling temperature is 940-1000 ℃; the finish rolling temperature is 830-850 ℃, the coiling temperature is 500-580 ℃, and the cooling speed is controlled at 20-40 ℃/s.

The present invention will be described in detail with reference to the following examples, which are provided only for the purpose of facilitating understanding of the present invention and are not intended to limit the present invention.

Examples

In the embodiment, the method for producing the corrosion-resistant high crack-arrest submarine pipeline steel X65MO with the thickness of 8-15mm is taken as an example, and the method specifically comprises the following steps:

1) production process of steel making

1.1 component design: the design of the chemical composition was made according to the thickness of the product, as shown in table 1.

Table 1: component design (mass percentage)

1.2 converter smelting: the pretreated molten iron (S is less than or equal to 0.003 percent) enters a converter, oxygen is blown for decarburization and temperature rise, ferrosilicon, ferromanganese and ferrochrome are added for deoxidation alloying in the later period of smelting, P, S components are controlled, molten steel peroxidation is prevented, steel slag is prevented from entering the molten steel by adopting the operation of steel residue, the tapping temperature is 1600-1650 ℃, the [ P ] of the converter tapping is less than or equal to 0.015 percent, and the [ S ] is less than or equal to 0.008 percent.

1.3 refining: and an LF and RH whole-process argon blowing process is adopted, a good reducing atmosphere is kept in the refining process, Al wires are adopted for deoxidation, ferrocolumbium, ferromolybdenum and ferrotitanium are added in the later period of LF for alloying, and calcium treatment is carried out after LF is finished. After RH vacuum treatment, 50-60kg of cerium-iron alloy (Ce: 20%) is added in three minutes before re-pressing, the vacuum degree is less than or equal to 2mbar, and the deep vacuum time is more than or equal to 15 min.

1.4 continuous casting: the superheat degree delta T of the molten steel is less than or equal to 30-40 ℃, and the drawing speed is controlled at 0.90-1.10 m/min. And (3) a dynamic soft reduction technology is adopted, and the straightening temperature is more than or equal to 920 ℃, so that a casting blank is obtained.

2) Controlled rolling and cooling process

A step-type heating furnace is adopted to heat a casting blank (the heating process is shown in a table 2), a single frame R1 and a single frame R2 are adopted for rough rolling, the adopted rough rolling modes are 1+5 and 3+3, the continuous rolling process from F1 to F7 is adopted for finish rolling, and the specific controlled rolling and controlled cooling process is shown in a table 3.

Table 2: heating system of casting blank

3) Concrete production example

3.1A billet of subsea pipeline steel X65MO of the chemical composition of examples 1-2 below was produced according to the above smelting requirements, the specific composition being shown in Table 4 below.

Table 4: chemical composition of each example (mass%: percent)

3.2 obtaining the corrosion-resistant high crack-arrest submarine pipeline steel X65MO with the thickness of 8-15mm according to the component design and the hot rolling process in the 1) and the 2), wherein the performance indexes of the products are shown in tables 5-7. The test methods are referred to GB/T228.1, GB/T231.1, API RP 5L3-14, NACE TM0284 and NACE TM 0177.

Table 5: tensile Properties of the examples

Table 6: impact and DWTT properties of the respective example products

Table 7: acid corrosion resistance index of each example product

In conclusion, the corrosion-resistant high-crack-arrest submarine pipeline steel X65MO with the thickness of 8-15mm, which is obtained by the invention, has the characteristics of cost economy, low-temperature toughness, crack arrest performance and corrosion resistance, can be used for the construction of submarine acid-resistant pipeline projects, has high overall coefficient, and can meet the API 5L standard requirements on various performances of products.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (3)

1. The corrosion-resistant high-crack-resistance submarine pipeline steel X65MO with the thickness of 8-15mm is characterized in that the chemical components of the corrosion-resistant high-crack-resistance submarine pipeline steel X65MO with the thickness of 8-15mm are as follows in percentage by mass: 0.05 to 0.08 percent of C; 0.10 to 0.20 percent of Si; 1.00 to 1.20 percent of Mn; p is less than or equal to 0.015 percent; s is less than or equal to 0.002%; al is less than or equal to 0.040%; 0.025 to 0.035 percent of Nb; 0.015 to 0.025 percent of Ti; 0.15 to 0.25 percent of Cr; 0.0010 to 0.0020 percent of Ce; h is less than or equal to 2.0 ppm; o is less than or equal to 30 ppm; n is less than or equal to 60ppm, and the balance is Fe and inevitable impurities.

2. The 8-15mm thick corrosion-resistant high crack-arresting subsea pipeline steel X65MO as claimed in claim 1, wherein the metallographic structure of the 8-15mm thick corrosion-resistant high crack-arresting subsea pipeline steel X65MO is polygonal ferrite and acicular ferrite, and the transverse mechanical properties are as follows: the yield strength is more than or equal to 500MPa, the tensile strength is more than or equal to 585MPa, the elongation is more than or equal to 39.5%, and the yield ratio is less than or equal to 0.87; the longitudinal mechanical property satisfies: the yield strength is more than or equal to 485MPa, the tensile strength is more than or equal to 562MPa, the elongation is more than or equal to 38.5 percent, and the yield ratio is less than or equal to 0.86; the HIC resistance index was 0.

3. The method for producing the corrosion-resistant high crack-arrest subsea pipeline steel X65MO of 8-15mm thickness according to claim 1 or 2, comprising the following steps: molten iron → converter smelting → LF refining → slab casting → rolling; wherein:

the chemical components of the molten iron are mentioned in claim 1 or 2;

oxygen blowing, decarbonization and temperature rising are carried out in the smelting process of the converter, ferrosilicon, ferromanganese and ferrochrome are added for deoxidation and alloying in the later smelting period, P, S components are controlled, molten steel is prevented from being overoxidized, steel slag is prevented from entering the molten steel by adopting a residual steel operation, the tapping temperature is 1600-1650 ℃, the tapping [ P ] of the converter is less than or equal to 0.015 percent, and the [ S ] is less than or equal to 0.008 percent;

the LF refining adopts an LF + RH whole-process argon blowing process, a good reducing atmosphere is kept in the refining process, Al wires are adopted for deoxidation, ferrocolumbium, ferromolybdenum and ferrotitanium are added in the later stage of LF for alloying, and calcium treatment is carried out after the LF is finished; after RH vacuum treatment, adding cerium-iron alloy (wherein Ce accounts for 20%) for micro-alloying in three minutes before re-pressing, wherein the vacuum degree is less than or equal to 2mbar, and the deep vacuum time is more than or equal to 15 min;

in the slab continuous casting process, the superheat degree delta T of molten steel is less than or equal to 25-40 ℃, the pulling speed is controlled to be 0.90-1.10m/min, a dynamic soft reduction technology is matched, and the straightening temperature is more than or equal to 920 ℃;

the rolling process adopts a 2250mm hot continuous rolling process, the heating temperature of the plate blank is 1200-1240 ℃, the heating time is 180-240 min, the soaking temperature is 1190-1210 ℃, the soaking time is 30-60 min, and the tapping temperature is 1180 +/-20 ℃; the rough rolling mode adopts 1+5 or 3+ 3; the initial rolling temperature of the last pass of rough rolling is less than or equal to 1000 ℃, and the final rolling temperature of the rough rolling is 1040-1140 ℃; the thickness range of the intermediate blank is as follows: 40-50 mm; the finish rolling initial rolling temperature is 940-1000 ℃; the finish rolling temperature is 830-850 ℃, the coiling temperature is 500-580 ℃, and the cooling speed is controlled at 20-40 ℃/s.