CN112921250A

CN112921250A - CO-resistant2Corroded steel pipe and preparation method thereof

Info

Publication number: CN112921250A
Application number: CN202110093258.0A
Authority: CN
Inventors: 武会宾; 张志慧; 顾洋; 张鹏程
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2021-01-25
Filing date: 2021-01-25
Publication date: 2021-06-08
Anticipated expiration: 2041-01-25
Also published as: CN112921250B

Abstract

The invention provides a _CO ₂ corrosion-resistant steel pipe and a preparation method thereof, and relates to the technical field of pipeline manufacturing for oil and gas gathering and transportation processes in CO ₂ flooding technology. 0.07%, Cr 6.0～8.0%, Ni 0.15～0.50%, Nb 0.01～0.06%, P≤0.005%, S≤0.005%, the rest are Fe and inevitable impurities; the preparation method is: S1, according to the established elements The mass percentage is smelted and cast to form, and the ingot is forged; S2, the billet is heated, and rough rolling is carried out; S3, the slab is trimmed and heated, and the finishing rolling is carried out; S4, the post-rolling quenching and tempering treatment is carried out; S5, Welded into tubes. The prepared steel pipe has excellent CO ₂ corrosion resistance and comprehensive mechanical properties, its corrosion rate is lower than 0.06mm/a, and the cost is low, and it has broad application prospects in the CO ₂ flooding technology oil and gas gathering and transportation process.

Description

CO-resistant2Corroded steel pipe and preparation method thereof

Technical Field

The invention relates to the technical field of steel for oil and gas, in particular to a steel with obdurability and CO resistance₂CO excellent in corrosiveness and weldability₂Oil gas gathering and transportation pipeline in oil displacement technology.

Background

With the wide application of oil and gas resources, the oil and gas reserves are reduced year by year, and the development of deep oil and gas resources becomes an important way for solving the problems. The deep oil gas resource has higher water content and CO₂In the absence of CO₂Under the condition of (2), high-temperature and high-pressure pipeline transportation can cause CO₂And (3) corrosion problem. CO 2₂-EOR (CO₂Enhanced oil recovery) technology is a high-efficiency mining and transportation technology widely applied to modern oil and gas resource industry, but as the technology is widely applied, CO in the process of carbon capture, utilization and sequestration (CCUS)₂The problem of corrosion control in pipe transportation, CO in the production and transportation system, becomes particularly important₂Corrosion problems are a key factor affecting the sustainable development of the oil and gas industry.

CO₂EOR technology is effective in increasing recovery, but with associated pipeline CO₂Corrosion problems cannot be neglected. Carbon steel has a lower cost but a poorer corrosion resistance, and the carbon steel cannot deal with the increasingly severe CO at present₂Corrosion problems; the problems of high cost and difficult large-area popularization and application exist in the corrosion prevention technologies such as continuously injecting corrosion inhibitors or adopting stainless steel and the like. In recent years, China has made great progress in the aspects of high-grade and thick pipeline steel, corrosion-resistant stainless steel and the like, but is suitable for CO resistance₂The field of the special pipe for flooding is blank, so that in order to overcome the defects of the prior art, the research of CO resistance is needed₂The corrosion steel pipe and the preparation method thereof solve or reduce one or more problems so as to meet the urgent requirements of oil gas mining and storage development in China.

Disclosure of Invention

The invention aims to provide a CO-resistant material₂The corrosion steel pipe and the preparation method thereof, wherein, microalloying CO resistance is designed and developed by adding elements such as Cr, Ni, Nb and the like₂Corrosion of steel pipe to satisfy CO resistance₂The cost of the steel pipe for corrosion is reduced as much as possible under the condition of service performance.

In order to achieve the purpose, the invention adopts the following technical scheme:

CO-resistant₂The corrosion steel pipe is characterized by comprising the following components in percentage by mass: 0.03-0.07% of C, 6.0-8.0% of Cr, 0.15-0.50% of Ni, 0.01-0.06% of Nb, less than or equal to 0.005% of P, less than or equal to 0.005% of S, and the balance of Fe and inevitable impurities.

Further, the performance indexes of the steel pipe are as follows: the yield strength is more than or equal to 520MPa, the tensile strength is more than or equal to 570MPa, and the Charpy impact energy at-20 ℃ is more than or equal to 80J.

Further, the steel pipe of the invention is CO resistant₂The corrosion performance indexes are as follows: HCO at-20 to 70 DEG C₃ ^-The concentration is 2000-4000 mg/L, SO₄ ^2-The concentration is 1000-2000 mg/L, Cl^-The concentration is 8000-12000 mg/L, CO₂Simulating CO with partial pressure of 0.1-0.5 MPa and crude oil content of more than 20%₂The CO resistance is realized in the service environment of the oil-producing and oil-collecting pipeline₂The corrosion rate of the corroded steel pipe is below 0.06 mm/a.

CO tolerance as described above₂The preparation method of the corrosion steel pipe is characterized by comprising the following steps:

s1, smelting according to the set element mass percentage, casting and molding, and forging the steel ingot;

s2, heating the steel billet, and carrying out rough rolling;

s3, finishing and heating the plate blank, and carrying out finish rolling;

s4, quenching and tempering after rolling;

and S5, welding into a pipe.

Further, the specific process of S1 includes: heating the steel ingot, and strictly controlling the forging temperature range, wherein the initial forging temperature is 1080-1150 ℃, and the final forging temperature is 910-950 ℃.

Further, the specific process of S2 includes: firstly, heating a steel billet at the temperature of not less than 1200 ℃ and preserving heat for 1.5-2 h; coarse rolling in a recrystallization area is adopted, the initial rolling temperature of the coarse rolling is 1050-1150 ℃, rolling is carried out in 5-7 passes, and the total deformation amount reaches 70-75%.

Further, the specific process of S3 includes: and (4) rolling in a non-recrystallization area, namely rolling the intermediate blank which is obtained by rolling in the rough rolling process and has the technological requirements by using a finishing mill and rolling in the finish rolling process to obtain the steel plate with the target specification.

Further, the specific rolling process of S3 includes: the initial rolling temperature of finish rolling is controlled to be 860-910 ℃, rolling is carried out in 5-7 passes, and the total rolling reduction of finish rolling is 65-70%; after finish rolling, cooling to 450-600 ℃ at a cooling speed of 15-30 ℃/s.

Further, the thermal refining process of S4 includes: quenching and tempering; comprehensively considering the performance index requirements, the quenching temperature is (900 +/-10) DEG C, and the heat preservation time is 10-30 min; the tempering process comprises the following steps: the tempering temperature is 620-650 ℃, and the heat preservation time is 35-50 min.

Further, considering the performance of the welding place comprehensively, the specific process of S5 includes: selecting manual welding to resist CO₂Corrosion welded pipe steel plate, electrode diameter: phi 3.2 mm; welding current: 90-120A.

Compared with the prior art, the invention can obtain the following technical effects: the CO resistance of the invention₂The corrosion steel pipe has excellent CO resistance₂Corrosion performance, wherein the corrosion rate is lower than 0.06 mm/a; compared with other steel pipes such as stainless steel, the composite material has lower manufacturing cost, and is good in corrosion resistance and economy and CO resistance₂And corroding the steel pipe.

Of course, it is not necessary for any one product in which the invention is practiced to achieve all of the above-described technical effects simultaneously.

Drawings

FIG. 1 CO tolerance₂The texture pattern of the parent material of the corrosion steel pipe (a-embodiment 1, b-embodiment 2);

FIG. 2 is a structural diagram of a welding part of example 1 (a weld structure; b fusion region structure; c fine crystal region structure);

FIG. 3 is a structural diagram of a welding part of example 2 (a weld structure; b fusion region structure; c fine crystal region structure);

FIG. 4 is a macroscopic corrosion topography of the example welded test plate (a example 1, b example 2);

FIG. 5 micro-erosion profile of the example welded test plate (a example 1 weld, b example 1 base material, c example 2 weld, d example 2 base material);

FIG. 6 is a process flow diagram of the present invention.

Detailed Description

In order to make the technical solution and advantages of the present invention more clear, the following detailed description of specific embodiments of the present invention is provided with reference to the drawings. It should be noted that any feature described in this specification may be replaced by other equivalent or similar alternative features, and unless expressly stated otherwise, any feature description is merely an example of a whole series of equivalent or similarly intended features. The examples are provided only for explaining and assisting understanding of the present invention, and are not intended to specifically limit the present invention.

The invention designs the components of the steel by using the low-carbon medium-chromium microalloying principle, adopts the controlled rolling and controlled cooling process to prepare and form, and adds a proper quenching and tempering process and a proper welding process to ensure that the pipe has good mechanical property and corrosion resistance.

CO-resistant₂Corrosion of steel pipes, said CO resistance₂The corrosion steel pipe comprises the following components in percentage by mass: 0.03 to 0.07 percent of C, 6.0 to 8.0 percent of Cr, 0.15 to 0.50 percent of Ni, 0.01 to 0.06 percent of Nb, less than or equal to 0.005 percent of P, less than or equal to 0.005 percent of S, and the balance of Fe and inevitable impurities.

The above CO resistance₂The preparation method of the corrosion steel pipe comprises the following steps:

step 1, according to the above-mentioned CO resistance₂Smelting the design components of the corroded steel pipe, and casting and molding; and heating the steel ingot, and forging at the initial forging temperature of 1080-1150 ℃ and the final forging temperature of 910-950 ℃.

Step 2, the rough rolling process comprises the following steps: heating the steel billet at a heating temperature of not less than 1200 ℃, and then preserving heat for 1.5-2 h; the initial rolling temperature of rough rolling is controlled to be 1050-1150 ℃, rolling is carried out in 5-7 passes, and the total deformation amount reaches 70-75%.

And 3, finishing and heating, and then performing finish rolling, wherein the finish rolling is characterized in that: and rolling the intermediate blank obtained by the rough rolling process through a finish rolling process to obtain a steel plate with the target specification. The initial rolling temperature of finish rolling is controlled to be 860-910 ℃, rolling is carried out in 5-7 passes, and the total rolling reduction of finish rolling is 65-70%. After finish rolling, the steel plate is rapidly cooled to 450-600 ℃ at a cooling speed of 15-30 ℃/s.

And 4, carrying out quenching and tempering treatment on the rolled plate blank, wherein the quenching and tempering treatment comprises quenching and tempering. Comprehensively considering the performance index requirements, the quenching temperature is (900 +/-10) DEG C, and the heat preservation time is 10-30 min; the tempering process comprises the following steps: the tempering temperature is 620-650 ℃, and the heat preservation time is 35-50 min.

Step 5, adopting manual welding to resist CO₂Corrosion welded pipe steel plate, electrode diameter: phi 3.2 mm; welding current: 90-120A.

Prepared CO-resistant₂Corroding the steel pipe, wherein the yield strength is more than or equal to 520MPa, the tensile strength is more than or equal to 570MPa, the Charpy impact energy at-20 ℃ is more than or equal to 80J, and simulating CO₂The corrosion rate of the oil displacement and production container equipment under the harsh corrosive medium condition of the service environment is less than or equal to 0.06 mm/a.

The CO resistance of the invention₂The action mechanism of the main alloy components in the Cr steel pipe in corrosion is as follows:

c: c is a carbide forming element, and carbide can improve tensile strength and yield strength, but can reduce elongation and notch impact toughness so as to influence the comprehensive mechanical properties of the steel. In terms of corrosion resistance, carbides induce the occurrence of intergranular corrosion; meanwhile, the addition of both C and Cr elements increases the carbon equivalent value, thereby affecting the weldability of the material. The increase of carbon equivalent can lead to certain increase of the hardness of the welding joint, the corresponding reduction of toughness and plasticity, and the welding performance is general. Therefore, in order to achieve a good balance between weldability and corrosion resistance, the C content in the matrix should be reduced appropriately in the development of corrosion-resistant steel grades.

Cr: related studies have shown that the corrosion rate decreases with increasing Cr content. Low carbon medium chromium steel in CO₂FeCO formation in EOR corrosion system₃And Cr (OH)₃Mixed phase multilayer film structure, the higher the Cr content in the test steel, the better the in-situ generation of corrosion product film than the ion deposition, the amorphous Cr (OH) in the codeposition layer₃The higher the content of (b), the complete and dense corrosion product film not only hinders the electrode activation reaction, but also inhibits the ion diffusion process, further reducing the corrosion rate.

Ni: the addition of the Ni element can make up the influence of the reduction of the C content on the strength, so that the steel pipe still has good mechanical property and strength of a welding part. The addition of Ni can increase the self-corrosion potential of the steel, improve the local corrosion resistance of the steel and effectively avoid the occurrence of corrosion and perforation risks of pipelines. In addition, the addition of Ni can improve the weldability of the steel, so that the steel is easy to be processed and formed in a cold and hot mode, and the preparation of the steel pipe is convenient.

Nb: nb can improve the strength and toughness of steel and refine austenite grains and recrystallization texture, but Nb adversely affects the toughness of weld heat affected zone, and therefore, the Nb content is not preferably too high in low alloy steel.

P and S: p and S are harmful elements, and P deteriorates hot workability and weldability; s can increase the cold and hot crack sensitivity and reduce the hydrogen embrittlement resistance. Inclusions containing the P, S element induce pitting which tends to cause perforation of the pipe. Therefore, it is required to reduce the content thereof in steel as much as possible.

The inevitable impurity elements mainly refer to O, H and harmful elements such As Pb, Sn, As, Sb, Bi and the like.

The invention designs and develops microalloyed corrosion-resistant steel by adding elements such as Cr, Ni, Nb and the like, and meets the requirement of CO resistance₂The cost is reduced as much as possible under the condition of corroding the service performance of the steel pipe.

The invention provides a CO-resistant material₂The preparation method of the corrosion steel pipe comprises the following preparation steps: steel making, forging, rolling, quenching and tempering and welding.

The components of the examples 1 and 2 are shown in the table 1, and the method specifically comprises the following steps:

step 1, smelting according to the components in the table 1 and casting into steel ingots; and heating the steel ingot, and forging at the initial forging temperature of 1120 ℃ and the final forging temperature of 940 ℃.

Step 2, heating the steel billet at a heating temperature of not less than 1200 ℃, preferably 1200 ℃, and then preserving heat for 1.5 hours; the initial rolling temperature of rough rolling is controlled at 1150 ℃, rolling is carried out in 7 passes, and the total deformation reaches 72%.

And 3, controlling the finish rolling initial rolling temperature to be 860-910 ℃, preferably 880 ℃, and performing rolling in 6 passes, wherein the total reduction is 64%. After finish rolling, the steel plate is rapidly cooled to 450-600 ℃ at a cooling speed of 15-30 ℃/s, and is preferably cooled to 500 ℃ at a cooling speed of 25 ℃.

And 4, quenching and tempering the rolled plate blank. Quenching temperature is 900 + -10 deg.C, preferably 900 deg.C, and keeping the temperature for 30 min; and then, carrying out a tempering process, controlling the tempering temperature at 640 ℃, and keeping the temperature for 40 min.

Step 5, selecting a gold bridge A102 welding electrode (the welding rod components are shown in the following table 2) to manually weld the low-C medium-Cr CO-resistant welding rod₂Corrosion welded pipe steel plate, electrode diameter: phi 3.2 mm; welding current: 100A.

Examples 1 and 2 were tested for corrosion resistance at 70 ℃ and CO₂The corrosion rates of the examples 1 and 2 are both below 0.06mm/a under the conditions of 0.4MPa partial pressure, 20% crude oil content and the harsher corrosion medium shown in Table 3.

CO tolerance according to the above-described method of implementation₂The results of the strength, toughness and corrosion resistance tests of the corroded steel pipes are shown in Table 4. In the bending tests in examples 1 and 2, in which the bent axis diameter was 20mm, the bending angle was 180 °, and the plane bending direction was performed, no crack was observed.

From the test results, it is clear that the comprehensive mechanical properties of examples 1 and 2 are good. CO tolerance prepared by working examples 1 and 2 of the present invention₂The microstructure and morphology of the corroded steel pipe are analyzed, and as can be seen from FIGS. 1a and 1b, the base material structures of examples 1 and 2 are bainite and a small amount of ferrite, and the structures of the two are uniform and have no obvious inclusions. As shown in FIG. 2, the weld structure of the welded portion in example 1 is austenite, the structure of ferrite + a small amount of bainite in the fusion zone, and the structure of ferrite + bainite in the fine crystal zone. As can be seen from FIG. 3, the weld structure of the welded portion in example 2 is austenite, the structure of the fusion zone is ferrite + a small amount of bainite, and the structure of the fine crystal zone is ferrite + a small amount of bainite.

FIGS. 4 and 5 are macro and micro corrosion morphology diagrams of the welding test plates of examples 1 and 2, respectively, wherein the Cr and Ni contents of the welding test plates of examples 1 and 2 are basically the same and are in the middle of the designed composition range, the Nb content of the welding test plate of example 2 is close to the upper limit, the welding seams of the welding test plates of examples 1 and 2 are not obviously corroded, the base metal is uniformly corroded, the surface of the welding test plate is corroded by a corrosion product, the corrosion product is in a crack-shaped morphology, and as a result, the welding test platesShow that both are CO resistant₂The corrosion performance is good.

In conclusion, the scheme can achieve expected effects within the range of the components and the process range designed by the invention.

Compared with the prior art, the invention has the advantages that:

the invention fully utilizes the advantages of the microalloying design concept, and the CO resistance prepared by adding elements such as Cr, Ni, Nb and the like₂The corrosion steel pipe has good comprehensive mechanical property, welding property and CO resistance₂Corrosion performance. The yield strength of the steel plate is more than or equal to 520MPa, the tensile strength is more than or equal to 570MPa, the Charpy impact energy at minus 20 ℃ is more than or equal to 80J, and CO is simulated₂The corrosion rate of the produced oil under the oil displacement and transportation service environment is less than or equal to 0.06mm/a, and the method is very suitable for CO₂And (4) preparing special production and storage equipment for the oil produced by the flooding.

The invention adopts proper heating, forging, controlled rolling and controlled cooling processes to produce the steel plate, and the steel plate has pure steel quality, less surface defects, refined structure and good processing performance and weldability; the production process of the steel pipe is simple and reasonable, the steel pipe can be welded into a pipe after being stably produced on a wide and thick plate line, and the steel pipe has high product percent of pass and positive social benefits.

CO tolerance in the present invention₂The corrosion steel pipe has the advantages of sustainability and economy while meeting the use requirements, and can effectively save the cost, thereby bringing greater economic benefits.

Table 1 examples 1 and 2 elemental composition (Wt.%)

TABLE 2 electrode composition (Wt.%)

Table 3 examples 1 and 2 concentrations of each ion in the etching medium

Table 4 mechanical properties and corrosion resistance of examples 1 and 2

Claims

1. A CO ₂ corrosion-resistant steel pipe, characterized in that the mass percentage of each component is: C 0.03-0.07%, Cr 6.0-8.0%, Ni 0.15-0.50%, Nb 0.01-0.06%, P≤0.005%, S ≤0.005%, the rest are Fe and inevitable impurities.

2. The _CO2 corrosion-resistant steel pipe according to claim 1, characterized in that the performance indicators are: yield strength≥520MPa, tensile strength≥570MPa, -20°C Charpy impact energy≥80J.

3. The CO ₂ corrosion-resistant steel pipe according to claim 1 or 2, characterized in that the CO ₂ corrosion-resistant performance index is: at a temperature of -20 to 70°C, HCO ₃ -concentration ^of 2000 to 4000 mg/L, SO ₄ ^2- Concentration of 1000～2000mg/L, Cl ^- concentration of 8000～ _12000mg /L, partial pressure of _CO2 of 0.1～0.5MPa, and crude oil content of more than 20% simulates the service environment of _CO2 flooding produced oil gathering and transportation pipeline. The corrosion rate of the steel pipe is below 0.06mm/a.

4. a preparation method of _CO2 corrosion-resistant steel pipe as claimed in claim 1, is characterized in that, comprises the following steps:

S1. Smelting and casting according to a predetermined element mass percentage, and forging the steel ingot;

S2, billet heating, rough rolling;

S3. Slab finishing and heating, finishing rolling;

S4, quenching and tempering treatment after rolling;

S5, welded into a tube.

5 . The method for preparing a CO ₂ corrosion-resistant steel pipe according to claim 4 , wherein the specific process of S1 comprises: heating the steel ingot, strictly controlling the forging temperature range, and the initial forging temperature is 1080-1150° C. 6 . The final forging temperature is 910-950℃.

6 . The preparation method of CO ₂ corrosion resistant steel pipe according to claim 4 , wherein the specific process of S2 includes: firstly heating the billet, the heating temperature is not lower than 1200° C., and the temperature is kept for 1.5-2 hours; For rough rolling in the crystallization zone, the rough rolling temperature is 1050-1150 ℃, and the rolling is divided into 5-7 passes, and the total deformation amount reaches 70-75%.

7 . The method for preparing a CO ₂ corrosion-resistant steel pipe according to claim 4 , wherein the specific process of S3 comprises: rolling in a non-recrystallization zone, and rolling through a rough rolling process to obtain an intermediate surface having process requirements. 8 . The billet is rolled by the finishing mill through the finishing rolling process to obtain the steel plate of the target specification.

8 . The preparation method of CO ₂ corrosion-resistant steel pipe according to claim 4 or 7, wherein the specific rolling process of S3 comprises: controlling the finishing rolling and opening temperature at 860-910° C., divided into 5-7 Pass rolling, the total reduction of finishing rolling is 65-70%; after finishing rolling, it is cooled to 450-600 ℃ at a cooling rate of 15-30 ℃/s.

9 . The method for preparing a CO ₂ corrosion-resistant steel pipe according to claim 4 , wherein the quenching and tempering treatment involved in S4 includes: quenching and tempering; comprehensively considering the performance index requirements, the quenching temperature is (900±10 ) ℃, the holding time is 10-30 minutes; the tempering process is: the tempering temperature is 620-650 ℃, and the holding time is 35-50 minutes.

10. The preparation method of CO ₂ corrosion-resistant steel pipe according to claim 4, characterized in that, comprehensively considering the performance of the weld, the specific process of the S5 comprises: selecting hand-welded CO ₂ corrosion-resistant welded steel pipe, electrode diameter: Φ3 .2mm; welding current: 90～120A.