CN111809121B - A kind of structure-function integrated pipeline steel and its manufacturing method - Google Patents

Abstract

The invention belongs to the field of pipeline steel for oil and gas field exploitation, gathering and transportation, and particularly relates to a pipeline steel with integrated structure and function and a manufacturing method thereof. By weight percentage, the chemical composition of pipeline steel is: C 0.02～0.08%, Si≤0.3%, Mn≤1.0%, Cu 0.5～2.0%, Al≤1.0%, Ce≤0.2%, Ni 1.0～2.0%, Nb≤0.1%, V≤0.1%, Ti≤0.1%, N≤0.005%, S≤0.005%, P≤0.005%, O≤0.005%, and the balance is Fe. Through the compound addition of alloy elements such as Cu, Al, Ce, Nb, V, Ti, etc., the present invention can obtain high strength with yield strength not lower than 500MPa, tensile strength not lower than 600MPa, and impact energy at ‑20°C not lower than 180J and high resilience indicators. At the same time, the pipeline steel of the invention also has excellent resistance to SSC, HIC and unique microbial corrosion resistance, and realizes the integration of structure and function.

Description

A kind of structure-function integrated pipeline steel and its manufacturing method

technical field

The invention belongs to the field of pipeline steel for oil and gas field exploitation, gathering and transportation, and particularly relates to a pipeline steel with integrated structure and function and a manufacturing method thereof.

Background technique

Pipeline transportation is the premise and foundation of the development of oil and gas production and transportation, and is at the core of the value chain of the oil and gas industry. With the continuous consumption of oil and natural gas, the two major energy sources, oil and gas exploitation is being forced to develop towards extreme environments. Correspondingly, the selection of pipeline steel materials for oil exploration and oil and gas transportation brings a series of problems. Microbial corrosion (MIC) and hydrogen sulfide corrosion (H ₂ S), including hydrogen induced cracking (HIC) and sulfide stress corrosion cracking (SSC), are an urgent problem facing pipeline steels. How to maintain excellent corrosion resistance (H ₂ S corrosion resistance and MIC corrosion resistance) on the premise of ensuring high strength and high toughness will be of great practical significance to the development of pipeline steel. Therefore, the oil and gas field industry is eager to obtain an integrated pipeline steel with high strength, high toughness, H ₂ S corrosion resistance and MIC resistance.

SUMMARY OF THE INVENTION

In view of the above problems, the purpose of the present invention is to provide a structure-function integrated pipeline steel with high strength, high toughness, H ₂ S corrosion resistance and MIC resistance at the same time, and a manufacturing method thereof.

The technical scheme of the present invention is:

A pipeline steel with integrated structure and functions, the chemical composition of the pipeline steel is: C 0.02～0.08%, Si≤0.3%, Mn≤1.0%, Cu 0.5～2.0%, Al≤1.0%, Ce≤1.0% by weight 0.2%, Ni 1.0～2.0%, Nb≤0.1%, V≤0.1%, Ti≤0.1%, N≤0.005%, S≤0.005%, P≤0.005%, O≤0.005%, the balance is Fe;

By weight percentage, the chemical composition satisfies:

Cu+Al+Ce≥1.0% (1)

The mass ratio of Ni to Cu Ni/Cu＞0.5 (2)

Wherein, each element symbol in formulas (1) and (2) is substituted into the corresponding element content.

In the pipeline steel with integrated structure and function, the chemical composition of the pipeline steel also contains one or more of Ca, Cr, Mo and B, and the weight percentage of each of them is less than 0.5%.

The manufacturing method of the structural-function integrated pipeline steel adopts the blast furnace + out-of-furnace refining method to smelt and continuously cast slabs, or adopts the electric furnace + out-of-furnace refining method to smelt and continuously cast slabs; no matter which method is used for smelting and continuous casting. For casting, Ce element needs to be added in the later stage of smelting, and added when the oxygen content (O) and sulfur content (S) are not more than 0.005wt%, and the steel is poured immediately after stirring evenly.

In the method for manufacturing pipeline steel with integrated structure and function, the continuous casting slab is subjected to controlled rolling and controlled cooling, the rough rolling temperature is 1000-1100° C. The rolling temperature is 850~950℃, the finishing rolling temperature is 700~800℃, and the water cooling or slow stack cooling is performed after the finishing rolling.

In the method for manufacturing pipeline steel with integrated structure and function, the steel plate that is rapidly water-cooled after final rolling is treated as follows: after final rolling, water cooling is performed at a cooling rate of 10 to 30°C/s, and the water cooling temperature for termination is 500 to 600°C, and then the Heat preservation, heat preservation time = steel plate thickness × heat preservation time coefficient, the heat preservation time coefficient is 3 to 6, the unit of heat preservation time is: minutes, and the unit of steel plate thickness is: mm; after heat preservation, air-cooled to room temperature.

In the method for manufacturing pipeline steel with integrated structure and function, the steel plates that are slowly stacked and cooled after final rolling are treated as follows: after final rolling, the steel plates are stacked together and cooled to room temperature, and the stacking height is not less than 1000mm.

In the method for manufacturing pipeline steel with integrated structure and function, the room temperature yield strength of the pipeline steel is ≥500MPa, and the tensile strength is ≥600MPa; under the condition of -20°C, the impact energy of full-size V-notch is ≥180J.

According to the manufacturing method of the structural-function integrated pipeline steel, the pipeline steel has excellent anti-SSC performance, and with reference to the NACE TM0177 standard, Method A, A solution, it does not break for 720 hours under a constant load of 80% yield strength.

According to the method for manufacturing pipeline steel with integrated structure and function, pipeline steel has excellent HIC resistance. According to NACE TM 0284 standard, A solution is selected. After soaking for 96 hours, the parameters of hydrogen-induced cracking are: crack sensitivity rate CSR, crack length rate CLR and the crack thickness rate CTR is zero.

According to the method for manufacturing pipeline steel with integrated structure and function, the pipeline steel has unique MIC resistance, and the depth of pitting pit is less than 3 μm when soaked in oil and gas production water containing sulfate reducing bacteria (SRB) for 21 days.

The design idea of the present invention is:

Cu, Nb, V and Ti in steel not only have the effect of precipitation strengthening, but also have the effect of beneficial hydrogen trap, and Cu in steel also has the effect of resistance to microbial corrosion. The composite addition of Cu, Al and Ce will play a synergistic effect, which can effectively prevent H from entering into the steel, and at the same time inhibit the formation of bacterial biofilm, and play a role in microbial corrosion resistance. The composite addition of Cu, Al, Ce, Nb, V and Ti can obtain pipeline steel with excellent comprehensive performance of high strength, high toughness, SSC and HIC resistance and MIC resistance.

The content of main elements in the present invention is described as follows:

In the composition design of the structural-function integrated pipeline steel of the present invention, copper (Cu), aluminum (Al), and cerium (Ce) are the most critical alloying elements in the steel, and the composite addition of the three can achieve the purpose of the invention.

Copper (Cu): Cu is an austenite forming element in steel, and its solubility in ferrite is small, and with the decrease of temperature, the solubility decreases sharply, and Cu is almost insoluble in α-Fe at room temperature. Therefore, after the aging treatment, Cu will precipitate in the form of the second phase, thereby strengthening the steel. The addition of Cu can not only promote the formation of a protective film on the steel surface and reduce the entry of H atoms into the steel matrix, but also the nano-sized Cu-rich phase precipitated during the aging process can also act as a beneficial hydrogen trap by trapping hydrogen. Both of these effects of Cu in steel can greatly reduce the harmful effect of H on steel. Cu in steel also has microbial corrosion resistance. When the Cu content is low, the Cu-rich phase precipitated in the matrix is insufficient, and the microbial corrosion resistance is small; when the Cu content is relatively high, it will affect the impact toughness and hot workability. Negative Effects. Taking comprehensive consideration, the content of Cu in the present invention is 0.5-2.0 wt %.

Aluminum (Al): Al is an effective alloying element for deoxidation in steel, so it has a very strong bond with oxygen (O), which also makes the aluminum oxide film very stable and dense, and thus has a good barrier to hydrogen (H). ) ability to spread. The pipeline steel of the present invention adds no more than 1.0wt% of Al, considering the source of H ₂ S corrosion, that is, making full use of Al in the steel to form an oxide film to hinder the entry of H, reducing the content of H in the steel, and effectively reducing the occurrence of SSC The possibility of this, combined with the nano-sized Cu-rich phase and Ce in the steel have beneficial hydrogen trap effect, to achieve more excellent SSC resistance. Comprehensive consideration, the preferred range of Al content in the present invention is 0.1-0.6 wt %.

Cerium (Ce): Rare earth is known as "industrial vitamin" in steel. Adding an appropriate amount of rare earth to steel has multiple beneficial effects, such as purifying molten steel, optimizing grain boundaries, reducing corrosion sources, thereby improving toughness and uniform corrosion resistance of steel; rare earth steel can also refine grains and capture H atoms, thereby improving steel. The strength and toughness of steel and the reduction of hydrogen embrittlement susceptibility; moreover, the rare earth element Ce can interact with the outer surface of the bacterial cell membrane and replace the metal elements that play an important role in the bacterial life process, affecting the bacterial life process and thus having an antibacterial effect. In the present invention, adding rare earth Ce, Cu, and Al produces a synergistic effect, and can play a more excellent role. Taking comprehensive consideration, the content of rare earth Ce in the present invention is ≤0.2wt%, and the preferred range is 0.1-0.2wt%.

Nickel (Ni): Ni is an element that can effectively improve the toughness of steel, and Ni can inhibit the danger of hot embrittlement of Cu in steel, but this effect requires that the mass ratio of Ni and Cu is not less than 0.5, and the content of Ni is too high. ,increase cost. Taking comprehensive consideration, the content of Ni in the pipeline steel of the present invention is 1.0-2.0 wt %.

Preferably, the chemical compositions of Cu, Al and Ce satisfy: 1.5%wt%≤Cu+Al+Ce≤2.5%; meanwhile, the chemical compositions of Ni and Cu satisfy: 0.5≤Ni to Cu mass ratio Ni/Cu≤2.0 .

It is stipulated in the pipeline steel of the present invention that the N content should be less than or equal to 0.005wt%. Excessive N easily combines with Al in the steel to form large-sized AlN, which affects the resistance to SSC, HIC and impact toughness.

It is stipulated in the pipeline steel of the present invention that the content of O and S should be less than or equal to 0.005wt%. Rare earth Ce has the characteristics of strong chemical activity, and it is easy to form O and S inclusions. If the content of O and S is too high, it will affect the yield of Ce and form large-sized inclusions. Not only does Ce fail to play its due role, but it will deteriorate. Corrosion resistance and impact toughness.

The advantages and beneficial effects of the present invention are:

1. In the present invention, through the compound addition of alloy elements such as Cu, Al, Ce, Nb, V, Ti, etc., the yield strength is not less than 500MPa, the tensile strength is not less than 600MPa, and the impact energy at -20°C is not less than 180J. High strength and high toughness index. At the same time, the pipeline steel of the invention also has excellent resistance to SSC, HIC and unique microbial corrosion resistance, and realizes the integration of structure and function.

2. The present invention overcomes the contradictory relationship between the strength, toughness and H ₂ S corrosion resistance of steel, and considers the MIC resistance at the same time. Therefore, it is suitable for applications in harsh environments such as complex geological conditions and containing hydrogen sulfide (H ₂ S) and corrosive microorganisms. It has high strength, high toughness, resistance to hydrogen induced cracking (HIC) and sulfide stress corrosion cracking (SSC). ) and resistance to microbial corrosion (MIC).

Description of drawings

FIG. 1 is a topography of the oxide film on the steel surface of Example 3. FIG.

FIG. 2 is a topography diagram of nano-sized hydrogen traps precipitated in the tissue of Example 1. FIG.

FIG. 3 is a topography of pitting pits kept at 500° C. in Example 2. FIG.

FIG. 4 is a topography of pitting pits of Comparative Example 1 kept at 550°C.

Detailed ways

In the specific implementation process, the manufacturing method of pipeline steel of the present invention is as follows:

(1) according to the chemical composition mixed raw material of the present invention, carry out the smelting of pipeline steel through the smelting mode of blast furnace+out-of-furnace refining, oxygen content (O) and sulfur content (S) are all not more than 0.005wt% and then add Ce element, Stir evenly and perform continuous casting;

(2) Control rolling the continuous casting slab, the rough rolling start temperature is 1080°C, the rough rolling finish rolling temperature is 980°C, the finish rolling start temperature is 900°C, and the finish rolling finish temperature is 730°C.

(3) The steel plate (22.8mm) after final rolling is rapidly cooled, the cooling rate of water cooling is 23°C/s, the final cooling temperature is 500, 550 and 600°C, respectively, and then heat preservation is carried out respectively. The heat preservation time coefficient is selected as 6, and the heat preservation time For 138 minutes, air-cooled to room temperature after the heat preservation; wherein, the heat preservation time of the steel plate was kept at 3 to 6 minutes/mm, and the heat preservation coefficient was selected as 3 to 6.

The prepared steel plate was tested for mechanical properties according to the national standard. The tensile test temperature was room temperature, the size of the impact sample was 10mm×10mm×55mm, and the V-notch was used. The test temperature was -20°C.

Pitting corrosion caused by MIC is considered to be the greatest harm to materials, and pitting corrosion depth is considered to be an important indicator to quantitatively evaluate the MIC resistance of materials. In the present invention, the MIC resistance performance is evaluated by the maximum pitting pit depth on the surface of the material.

The prepared samples of Examples and Comparative Examples were immersed in oil and gas production water containing SRB for 21 days, and the maximum pitting depth caused by SRB corrosion on the surface of the samples after corrosion was detected by laser confocal microscopy.

The anti-SSC performance was evaluated according to NACE TM0177 standard, Method A, A solution, constant load loading 80% yield strength.

Evaluation of the anti-HIC performance According to the NACE TM0284 standard, A solution was selected, and the hydrogen-induced cracking parameters (crack sensitivity rate CSR, crack length rate CLR and crack thickness rate CTR) were detected after soaking for 96 hours.

In the following, the present invention will be described by comparing different examples and comparative examples, these examples are for illustrative purposes only, and the present invention is not limited to these examples.

Example 1

By weight percentage, the chemical composition of pipeline steel is: C 0.029%, Si 0.19%, Mn 0.59%, Cu 1.35%, Al 0.35%, Ce 0.15%, Ni 1.05%, Mo 0.01%, Nb 0.019%, Ti 0.017%, N0.003%, S 0.001%, P 0.002%, O 0.002%, Ca 0.005%, the balance is Fe. Among them, Cu+Al+Ce=1.85%, and Ni/Cu=0.78.

Example 2

By weight percentage, the chemical composition of pipeline steel is: C 0.027%, Si 0.19%, Mn 0.56%, Cu 1.82%, Al 0.25%, Ce 0.15%, Ni 1.03%, Cr 0.03%, Nb 0.018%, V 0.005%, Ti 0.002%, N 0.004%, S 0.001%, P 0.002%, O 0.003%, Ca 0.005%, B 0.0005%, and the balance is Fe. Among them, Cu+Al+Ce=2.22%, and Ni/Cu=0.57.

Example 3

By weight percentage, the chemical composition of pipeline steel is: C 0.033%, Si 0.20%, Mn 0.59%, Cu 1.83%, Al 0.45%, Ce 0.10%, Ni 1.94%, Mo 0.01%, Nb 0.017%, Ti 0.015%, N0.004%, S 0.001%, P 0.002%, O 0.003%, Ca 0.005%, the balance is Fe. Among them, Cu+Al+Ce=2.33%, and Ni/Cu=1.06.

Comparative Example 1

By weight percentage, the chemical composition of pipeline steel is: C 0.028%, Si 0.18%, Mn 0.59%, Cu 0.01%, Al 0.04%, Ni 0.10%, Cr 0.03%, Nb 0.02%, V 0.01%, Ti 0.01%, N 0.004%, S0.02%, P 0.03%, O 0.05%, the balance is Fe. Among them, Cu+Al+Ce=0.05%, and Ni/Cu=10.

Table 1. Corresponding properties of the holding temperature of the steel of the embodiment and the comparative example

The results of the examples show that the room temperature yield strength of the pipeline steel of the present invention is not less than 500MPa, and the tensile strength is not less than 600MPa; under the condition of -20°C, the full-size V-notch impact energy is greater than or equal to 180J. Preferably, the room temperature yield strength of the pipeline steel is greater than or equal to 600 MPa, and the tensile strength is greater than or equal to 700 MPa; under the condition of -20°C, the full-size V-notch impact energy is greater than or equal to 180 J.

The pipeline steel of the present invention has excellent anti-SSC performance, and with reference to NACE TM0177 standard Method A, solution A, it does not break for 720 hours under a constant load of 80% yield strength. This is mainly due to the formation of a dense oxide film of alumina on the surface of the material and the formation of beneficial nano-sized hydrogen traps within the tissue, see Figures 1 and 2.

The pipeline steel of the invention has excellent anti-HIC performance. Referring to the NACE TM0284 standard, solution A is selected. After immersion for 96 hours, the hydrogen-induced cracking parameters (crack sensitivity rate CSR, crack length rate CLR and crack thickness rate CTR) are all zero.

The pipeline steel of the present invention also has unique MIC resistance. After being soaked in oil and gas production water containing SRB for 21 days, the pit depth is less than 3 μm, see Figures 3 and 4 .

The above-mentioned embodiments are only intended to illustrate the technical concept and characteristics of the present invention, and the purpose thereof is to enable those who are familiar with the art to understand the content of the present invention and implement them accordingly, and cannot limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be included within the protection scope of the present invention.

Claims (9)

1. The structural-function integrated pipeline steel is characterized by comprising the following chemical components in percentage by weight: 0.02-0.08% of C, less than or equal to 0.3% of Si, less than or equal to 1.0% of Mn, 1.35-2.0% of Cu, 0.1-0.6% of Al, 0.1-0.2% of Ce0.0, 1.0-2.0% of Ni, less than or equal to 0.1% of Nb, less than or equal to 0.1% of V, less than or equal to 0.1% of Ti, less than or equal to 0.005% of N, less than or equal to 0.005% of S, less than or equal to 0.005% of P, less than or equal to 0.005% of O, and the balance of Fe;

according to weight percentage, the chemical components meet the following requirements:

Cu+Al+Ce≥1.0% （1）

mass ratio of Ni to Cu Ni/Cu > 0.5 (2)

Wherein, each element symbol in the formulas (1) and (2) is substituted into the corresponding element content;

the manufacturing method of the structure function integrated pipeline steel adopts a blast furnace and external refining mode to smelt and continuously cast a plate blank, or adopts an electric furnace and external refining mode to smelt and continuously cast a plate blank; no matter which way is adopted for smelting and continuous casting, the Ce element needs to be added at the later stage of smelting, and is added when the oxygen content O and the sulfur content S are not more than 0.005wt%, and the steel is poured and tapped immediately after being uniformly stirred;

carrying out controlled rolling and controlled cooling on the continuously cast plate blank, wherein the rough rolling starting temperature is 1000-1100 ℃, the rough rolling finishing temperature is 900-1000 ℃, the finish rolling starting temperature is 850-950 ℃, the finish rolling finishing temperature is 700-800 ℃, and the plate blank is subjected to quick water cooling or slow heap cooling after finish rolling;

the steel plate which is rapidly water-cooled after finish rolling is processed as follows: after finishing rolling, cooling with water at a cooling speed of 10-30 ℃/s, wherein the temperature of the water cooling is stopped to be 500-600 ℃, and then carrying out heat preservation, wherein the heat preservation time = the thickness of the steel plate multiplied by the heat preservation time coefficient, the heat preservation time coefficient is 3-6, and the unit of the heat preservation time is as follows: the thickness of the steel plate is given in units of: mm; after heat preservation, air cooling to room temperature;

the room temperature yield strength of the pipeline steel is more than or equal to 500MPa, and the tensile strength is more than or equal to 600 MPa; the impact energy of the full-size V-shaped notch is more than or equal to 180J at the temperature of minus 20 ℃.

2. The structurally and functionally integrated line steel as claimed in claim 1, wherein the line steel further comprises one or more of Ca, Cr, Mo and B in a weight percentage of < 0.5%.

3. A manufacturing method of the structural-functional integrated pipeline steel of claim 1, characterized in that a slab is smelted and continuously cast by adopting a blast furnace + external refining mode, or a slab is smelted and continuously cast by adopting an electric furnace + external refining mode; no matter which way is adopted for smelting and continuous casting, the Ce element needs to be added in the later smelting period, and when the oxygen content O and the sulfur content S are not more than 0.005wt%, the Ce element is added, and after the oxygen content O and the sulfur content S are uniformly stirred, the steel is immediately poured and tapped.

4. The method for manufacturing the structure-function integrated pipeline steel according to claim 3, wherein the continuous cast slab is subjected to controlled rolling and controlled cooling, the rough rolling start temperature is 1000-1100 ℃, the rough rolling finish rolling temperature is 900-1000 ℃, the finish rolling start temperature is 850-950 ℃, the finish rolling temperature is 700-800 ℃, and the rapid water cooling or slow heap cooling is performed after finish rolling.

5. The method for manufacturing the structure-function integrated pipeline steel according to claim 4, wherein the steel plate which is rapidly water-cooled after finish rolling is subjected to the following treatment: after finishing rolling, cooling with water at a cooling speed of 10-30 ℃/s, wherein the temperature of the water cooling is stopped to be 500-600 ℃, and then carrying out heat preservation, wherein the heat preservation time = the thickness of the steel plate multiplied by the heat preservation time coefficient, the heat preservation time coefficient is 3-6, and the unit of the heat preservation time is as follows: the thickness of the steel plate is given in units of: mm; and after heat preservation, air cooling to room temperature.

6. The method for manufacturing the structural-functional integrated pipeline steel according to claim 4, wherein the steel plate which is slowly cooled in heap after finish rolling is subjected to the following treatment: and stacking the steel plates after final rolling, and air-cooling to room temperature, wherein the stacking height is not less than 1000 mm.

7. The method for manufacturing a structurally and functionally integrated pipeline steel according to claim 4, wherein the pipeline steel has excellent SSC resistance, and does not break at a constant load of 80% yield strength for 720 hours according to NACE TM0177 standard, Methoda, solution A.

8. The method for manufacturing the structure-function integrated pipeline steel according to claim 4, wherein the pipeline steel has excellent HIC resistance, and the solution A is selected according to NACE TM0284 standard, and hydrogen induced cracking parameter is determined after soaking for 96 hours: the crack sensitivity rate CSR, crack length rate CLR and crack thickness rate CTR are zero.

9. The method for manufacturing the structural-functional integrated pipeline steel according to claim 4, wherein the pipeline steel has unique MIC resistance, and the depth of a pitting pit is less than 3 μm within 21 days of soaking in oil gas produced water containing Sulfate Reducing Bacteria (SRB).

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