Patent Application
20240247350
The present disclosure relates to a metal material and a manufacturing method therefor, particularly to a seamless steel tube and a manufacturing method therefor.
In recent years, there have been frequent incidents failures induced by corrosion in oil well pipes and line pipes for transportation of gas and petroleum in major oil fields. Among these incidents, failures induced by CO2 corrosion account for a considerable proportion, resulting in substantial economic losses when they occur.
Research related to CO2 corrosion has a history of nearly a century, and some progress has been made in CO2 corrosion protection technology. Both domestic and foreign steel pipe manufacturers have successively developed a series of seamless steel pipes resistant to CO2 corrosion. At present, commercially available CO2 corrosion-resistant steel grades include corrosion-resistant alloy series, martensitic stainless steel series, and low-alloy series, such as the 1Cr series developed by Tenaris, 3Cr series such as TN80Cr3, TN95Cr3 and TN110Cr3, 13Cr series and 2205 duplex stainless steel series. V&M and JFE, as well as domestic Baosteel Group and Tianjin Iron and Steel Group, have also successfully developed the above-mentioned corrosion-resistant petroleum pipe series products.
With the change of oil and gas exploitation environment and the development of new exploitation technology, the problem of CO2 corrosion has become more prominent. In addition, given the continued downturn in the petroleum industry market, economically efficient exploitation is particularly important. Therefore, it is necessary to develop CO2 corrosion-resistant steel pipes that are more corrosion resistant than 3Cr and have superior cost-effectiveness.
From the number of papers published on CO2 corrosion in recent years, it can be seen that there are still a lot of scientific problems surrounding CO2 corrosion that have not been clarified, and the corrosion problem of oil fields has not been completely solved. With changes of oil and gas environment and the application of new exploitation technologies, the CO2 corrosion issues continue to be quite severe, presenting new demands and challenges for the development of new corrosion-resistant materials.
Both domestic and foreign scholars have conducted extensive research on the effect of Cr content on CO2 corrosion resistance. The research shows that as Cr content increases, CO2 corrosion resistance improves, but the degree of improvement varies in different content ranges. Additionally, studies have found that the influence of Mo, Cu, Ni, V, C, and other elements on CO2 corrosion may be completely opposite under different composition systems and different environmental conditions, which is the reason why the CO2 corrosion resistance among 5Cr products is quite different, and which is also the reason why both domestic and foreign steel pipe enterprises have not yet developed mature 5Cr series products.
Unlike the conventional CO2 corrosion-resistant petroleum pipe series products in the prior art, in order to avoid failures induced by CO2 corrosion in oil and gas development, the present disclosure aims to provide a seamless steel tube excellent in strength and resistance to CO2 corrosion as well as good processability. It is particularly suitable for casings, tubings and line pipes for transportation in the oil and gas environment with temperatures ranging from 60 to 90° C. and CO2 content of 0.5 MPa. Its applicability is extensive, and it holds prospects for promotion and application.
One of the objectives of the present disclosure to provide a seamless steel tube resistant to carbon dioxide corrosion, which has high strength, good processability and CO2 corrosion resistance. It is particularly suitable for casings, tubings and transmission pipelines in the oil and gas environment with temperatures ranging from 60 to 90° C. and CO2 content of 0.5 MPa. Its applicability is extensive, and it holds prospects for promotion and application.
In order to achieve the above objectives, the present disclosure provides a seamless steel tube resistant to carbon dioxide corrosion. In addition to containing Fe and inevitable impurities, the seamless steel tube further contains the following chemical elements by mass percentage:
Preferably, the seamless steel tube of the present invention consists of the following chemical elements by mass percentage:
In the seamless steel tube according to the present disclosure, the design principles of chemical elements are as follows:
For example, in the 3Cr series of steels, increasing C content benefits the CO2 resistance of the material. However, it is found by the inventors that in 5Cr series steels, the influence of C content on the CO2 resistance of materials is exactly the opposite. Therefore, the C content in the present disclosure needs to be added in synergy with elements such as Cr and Mo to find the optimal balance between material strength and resistance to CO2 corrosion. Hence, in the seamless steel tube of the present disclosure, the mass percentage of C is controlled between 0.05% and 0.18%.
In some preferred embodiments, for better results, the mass percentage of C can be controlled between 0.09% and 0.15%.
In some preferred embodiments, for better results, the mass percentage of Si can be controlled between 0.2% and 0.35%.
In some preferred embodiments, for better results, the mass percentage of Mn can be controlled between 0.3% and 0.45%.
In some preferred embodiments, for better results, the mass percentage of Cr can be controlled between 4.5% and 5.5%.
In some preferred embodiments, for better results, the mass percentage of Mo can be controlled between 0.1% and 0.25%.
In some preferred embodiments, for better results, the mass percentage of Al can be controlled between 0.025% and 0.045%.
In some preferred embodiments, for better results, the mass percentage of Ca may be controlled between 0.0015% and 0.003%.
Additionally, it should be noted that in the present disclosure, elements such as Ti, Nb, V, Ce, and La can also be further added. These elements can further improve the performance of the seamless steel tube of the present disclosure.
In the seamless steel tube of the present disclosure, the content of Ti, Nb, V, Ce, and La can be controlled to satisfy the following: 0.003%≤Ti+Nb+V+Ce+La≤0.20%. In this equation, each chemical element of the above formula is substituted with the mass percentage of the corresponding chemical element when doing the calculation. Microalloying with Ti, Nb, V, Ce, and La can to some extent improve the strength, impact toughness, and corrosion resistance of the material.
In certain preferred embodiments, for better results, the content of Ti, Nb, V, Ce, and La can be optimally controlled to satisfy the following:
However, it should be noted that the addition of the above elements will increase the cost of materials. Considering the balance between performance and cost control, it is preferable to selectively add at least one of the above elements in the technical solution of the present disclosure.
Preferably, in the seamless steel tube of the present disclosure, the content of each chemical element further satisfies at least one of the following:
In the seamless steel tube of the present disclosure, among the inevitable impurities, the following maximum mass percentages are preferred: P≤0.015%, S≤0.008%, N≤0.006%, and O≤0.0035%.
In the seamless steel tube of the present disclosure, among the inevitable impurities, the following maximum mass percentages are more preferred: P≤0.012%, S≤0.005%, N≤0.0045%, and O≤0.002%.
In the above technical solution of the present disclosure, P, S, N, and O are all inevitable impurity elements in steel. Under the conditions allowed by the technology, it is necessary to control the content of impurity elements in the steel as low as possible.
In the seamless steel tube of the present disclosure, P and S are impurity elements introduced from raw materials or the production process of steel. P can cause grain boundary embrittlement leading to a degradation of the toughness and processability of the material. S forms low-melting-point sulfides, which decrease the processability and mechanical properties of the material.
Similarly, in the seamless steel tube of the present disclosure, N and O are impurity elements introduced during smelting and casting processes. N and O are prone to form inclusions in the steel, resulting in a degradation of the material properties. Therefore, in the present disclosure, it is necessary to strictly control the content of N and O in the seamless steel tube.
Preferably, in the seamless steel tube of the present disclosure, the microstructure is tempered sorbite.
Preferably, the properties of the seamless steel tube of the present disclosure satisfy at least one of the following:
Correspondingly, another objective of the present disclosure is to provide a manufacturing method for the seamless steel tube resistant to carbon dioxide corrosion. The seamless steel tube manufactured using the manufacturing method has excellent mechanical properties and resistance to CO2 corrosion, making it particularly suitable for casings, tubings, and transmission pipelines in oil and gas environments with a CO2 content of 0.5 MPa at 60-90° C. It has excellent prospects for promotion and application.
In order to achieve the above objectives, the present disclosure provides a manufacturing method for the above seamless steel tube, and the manufacturing method includes the following steps:
In the manufacturing method of the seamless steel tube of the present disclosure, according to the chemical composition design requirements of the present disclosure, an electric furnace or converter is used for smelting+refining, casting the metal into tube billet. Then the tube billet is subjected to heating, perforating, hot rolling, and sizing to obtain a hot-rolled tube. In order to meet the requirements for tube strength and CO2 corrosion resistance in oil and gas exploitation, further quenching and tempering heat treatment is required for the hot-rolled tube obtained in step (2).
In the quenching and tempering heat treatment step of step (3) of the present disclosure, the hot-rolled tube needs to be quenched in a temperature range of 860-940° C. and held at this temperature for 15-120 min, followed by further tempering in a temperature range of 520-620° C. for 30-150 min to obtain a tempered sorbite structure. This process results in a seamless steel tube product satisfying the requirements of service conditions for strength, toughness, and CO2 corrosion resistance.
Preferably, in the manufacturing method of the present disclosure, in the heating step of step (2), the tube billet is heated at 1180-1280° C. for 120-350 min.
Preferably, in the manufacturing method of the present disclosure, in step (2), perforating, hot rolling, and sizing are performed in the range of 1160-1260° C.
In the technical solution of the present disclosure, in the heating step of step (2), the tube billet can be first heated at 1180-1280° C. for 120-350 min, and then high-temperature deformation such as high-temperature perforating, hot rolling, and sizing can be performed at 1160-1260° C. to obtain a hot-rolled tube with required gauges. In the present disclosure, the above-mentioned composition system designed in the present disclosure, when heated at 1180-1280° C. for 120-350 min, allows the tube billet to have good high-temperature plasticity. High-temperature deformation such as high-temperature perforating, hot rolling, and sizing at 1160-1260° C. is advantageous in preventing and controlling the generation of hot-rolling deformation defects.
The seamless steel tube prepared by this method exhibits almost no segregation of alloy elements and has a uniform distribution of alloy elements. Therefore, it is possible to eliminate the long-time annealing treatment step, such as spheroidizing annealing step, for the tube billet described in the prior art for alloy homogenization.
The seamless steel tube resistant to carbon dioxide corrosion and the manufacturing method therefor according to the present disclosure have the following advantages and beneficial effects:
As can be seen from the above, the present invention, through rational chemical composition design and optimized manufacturing processes, can obtain a seamless steel tube resistant to carbon dioxide corrosion. This seamless steel tube has high strength, good processability, and resistance to carbon dioxide corrosion, making it effective for use in oil and gas development to avoid perforation failure accidents.
The seamless steel tube of the present disclosure has good mechanical properties and resistance to CO2 corrosion. It has high-strength mechanical properties after quenching and tempering heat treatment and satisfies: yield strength Rp0.2≥550 MPa, tensile strength Rm≥670 MPa, elongation A50≥15%, and impact property KV8≥60 J. The prepared seamless steel tube has a weight loss corrosion rate of less than 0.08 mm/d and a pitting corrosion rate of less than 0.2 mm/d under the dynamic corrosion environment conditions of 60-90° C., 0.5 MPa CO2, 50,000 ppm Cl−, and 1 m/s, making it highly promising and valuable for widespread use and application.
Hereinafter, the seamless steel tube and the manufacturing method therefor according to the present disclosure will be further explained and described with reference to the specific embodiments and the accompanying drawings. However, this explanation and description are not intended to unduly limit the technical solution of the present disclosure.
Seamless steel tubes in Examples 1-15 and Comparative Examples 1-2 and Comparative Examples 4-5 are all produced using the following steps:
It should be noted that in the present disclosure, the chemical composition design and relevant manufacturing processes for the seamless steel tubes in Examples 1-15 meet the design specification requirements of the present disclosure. However, for the seamless steel tubes in Comparative Examples 1-5, there are parameters that do not meet the design requirements of the present disclosure in the chemical composition design and related manufacturing processes.
Table 1 lists the mass percentages of chemical elements in the seamless steel tubes in Examples 1-15 and the seamless steel tubes in Comparative Examples 1-5.
Table 2 lists specific process parameters of the seamless steel tubes in Examples 1-15 and Comparative Examples 1-5.
The seamless steel tubes in Examples 1-15 and Comparative Examples 1-5 produced after quenching and tempering heat treatment were separately sampled and subjected to various property tests to measure the mechanical properties of the seamless steel tubes in Examples 1-15 and Comparative Examples 1-5. The test results obtained are listed in Table 3.
The relevant methods for testing mechanical properties are as follows:
Charpy V-notch impact test: the test steel tubes were subjected to an impact test according to GB/T229-2020 “Metallic Materials-Charpy pendulum impact test method” to evaluate the impact properties of the steel tubes in each example and comparative example.
Table 3 lists the mechanical property test results of the seamless steel tubes in Examples 1-15 and Comparative Examples 1-5.
Accordingly, after the mechanical properties of the above-described seamless steel tubes in Examples 1-15 and Comparative Examples 1-5 were tested, the corrosion resistance, particularly resistance to CO2 corrosion, of the seamless steel tubes in each example and comparative example was further tested. This involves sampling from the seamless steel tubes in Examples 1-15 and Comparative Examples 1-5 and conducting corrosion tests. The samples from Examples 1-15 and Comparative Examples 1-5 were subjected to corrosion tests in an autoclave system under the dynamic corrosion environment conditions of 60-90° C., 0.5 MPa CO2, 50,000 ppm Cl−, and 1 m/s to obtain the weight loss corrosion rate and the pitting corrosion rate of Examples 1-15 and Comparative Examples 1-5. The test results of the relevant corrosion tests are listed in Table 4 below.
Table 4 lists the results of the CO2 corrosion resistance test of the seamless steel tubes in Examples 1-15 and the seamless steel tubes in Comparative Examples 1-5.
It can be seen from Table 3 and Table 4 that the seamless steel tubes in Examples 1-15 of the present disclosure have not only excellent mechanical properties but also good resistance to CO2 corrosion. The yield strength of the seamless steel tubes in Examples 1-15 is between 585 MPa and 936 MPa, the tensile strength is between 679 MPa and 1132 MPa, the elongation A50 is greater than or equal to 15%, and the impact property KV8 is between 61 J and 214 J. Accordingly, the seamless steel tubes in each example has a weight loss corrosion rate of less than 0.079 mm/d and a pitting corrosion rate of less than 0.152 mm/d, under the dynamic corrosion environment conditions of 60-90° C., 0.5 MPa CO2, 50,000 ppm Cl−, and 1 m/s.
In contrast to the seamless steel tubes in Examples 1-15, the seamless steel tubes in Comparative Examples 1-5 show significant fluctuations in mechanical properties, and their the weight loss corrosion rate (at least 0.136 mm/d) and the pitting corrosion rate (at least 0.266 mm/d) are higher than those of Examples 1-15, indicating poorer resistance to CO2 corrosion for the seamless steel tubes in Comparative Examples 1-5.
As shown in
In conclusion, it can be seen that the seamless steel tube resistant to carbon dioxide corrosion can be obtained by reasonable chemical composition design preferably combined with optimized manufacturing processes. The seamless steel tube has high strength, good processability, and resistance to carbon dioxide corrosion, making it suitable for applications in oil and gas development and helping prevent perforation failures. It holds significant promise and practical value.
Furthermore, the combinations of technical features described herein are not limited to the combinations specified in the claims or the specific embodiments herein. All technical features described herein may be freely combined or combined in any way unless contradicted by each other.
It should also be noted that only specific embodiments of the present disclosure have been illustrated above. It is obvious that the present disclosure is not limited to the above embodiments, and there may be various similar variations. All variations that may be derived directly or conceived by those skilled in the art from the present disclosure of the present disclosure are intended to fall within the scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202110559328.7 | May 2021 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2022/094085 | 5/20/2022 | WO |
