CN112195409B - High-strength low-hardness hydrogen sulfide corrosion resistant steel and preparation method thereof - Google Patents
High-strength low-hardness hydrogen sulfide corrosion resistant steel and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
Abstract
The invention discloses high-strength low-hardness hydrogen sulfide corrosion resistant steel, which comprises the following chemical components in percentage by mass: c: 0.01 to 0.05%, Si: 0.05-0.35%, Mn: 1.10-1.40%, P: less than or equal to 0.006 percent, S: less than or equal to 0.0005 percent, Alt: 0.01 to 0.05%, Nb: 0.01-0.05%, V: 0.01-0.05%, Ti: 0.005-0.02%, Ni: 0.00-0.20%, Cr: 0.00-0.20%, Cu: 0.00-0.20%, and the balance of Fe and inevitable impurities; and carbon equivalent CEIIW：0.30～0.33％，CEPcm: 0.12 to 0.14 percent. The invention also discloses a preparation method, and the prepared steel has high strength, low hardness and excellent hydrogen sulfide corrosion resistance.
Description
Technical Field
The invention relates to the technical field of steel preparation, in particular to high-strength low-hardness hydrogen sulfide corrosion resistant steel and a preparation method thereof.
Background
Hydrogen sulfide is one of the most corrosive harmful media in petroleum and natural gas, and the stress corrosion of the hydrogen sulfide to a transmission pipeline accounts for a large proportion in the process of conveying the natural gas. When the material is used in a wet hydrogen sulfide environment, hydrogen generated by corrosion invades into steel to cause Hydrogen Bubbling (HB), Hydrogen Induced Cracking (HIC) and Sulfide Stress Corrosion Cracking (SSCC) of the material.
With respect to hydrogen sulphide, the risk of corrosion is mainly due to corrosion cracking (SSCC, HIC, etc.) caused by the penetration of hydrogen atoms in the hydrogen sulphide into the material matrix. All choices of hydrogen sulfide corrosion resistant steels focus on how to select materials that are resistant to sulfide stress corrosion cracking. In general, the materials are selected for resistance to hydrogen sulfide corrosion from the following points of view: chemical composition, hardness properties, microstructure, cold deformation, etc.
With the rapid development of the national strategy of petroleum and natural gas, the demand for high-strength hydrogen sulfide corrosion resistant steel gradually rises, the research, development and production of high-strength corrosion resistant steel with high added value are significant to the development of the whole industry, the hardness of the material brings stress concentration and becomes a hydrogen trap, and the hydrogen induced cracking of the material is caused. The strength and hardness of the material are related, and the hardness is increased to a certain extent if high strength is required.
At present, domestic hydrogen sulfide corrosion resistant steel cannot simultaneously meet the requirements of high strength, low hardness, excellent hydrogen sulfide corrosion resistance and the like. Therefore, how to develop a steel having high strength, low hardness and excellent hydrogen sulfide corrosion resistance is a technical problem to be solved.
Disclosure of Invention
The invention aims to provide high-strength low-hardness hydrogen sulfide corrosion-resistant steel and a preparation method thereof, and the prepared steel has high strength (the yield strength of the steel is 450-.
In order to achieve the above object, the present invention provides a high-strength low-hardness hydrogen sulfide corrosion resistant steel, which comprises the following chemical components by mass: c: 0.01 to 0.05%, Si: 0.05-0.35%, Mn: 1.10-1.40%, P: less than or equal to 0.006 percent, S: less than or equal to 0.0005 percent, Alt: 0.01 to 0.05%, Nb: 0.01-0.05%, V: 0.01-0.05%, Ti: 0.005-0.02%, Ni: 0.00-0.20%, Cr: 0.00-0.20%, Cu: 0.00-0.20%, and the balance of Fe and inevitable impurities; and carbon equivalent CEIIW：0.30～0.33％，CEPcm：0.12～0.14％。
Further, the carbon equivalent CEIIW，CEPcmThe calculation formula of (2) is as follows:
further, the metallographic structure of the steel is, in terms of volume fraction: 90-98% of polygonal ferrite, 2-10% of strip-shaped ferrite and substructures thereof.
Further, the grain size of the polygonal ferrite is 1 to 5 μm.
The invention also provides a preparation method of the high-strength low-hardness hydrogen sulfide corrosion resistant steel, which comprises the following steps:
obtaining a casting blank of the high-strength low-hardness hydrogen sulfide corrosion resistant steel, wherein the total compression ratio of the casting blank is more than or equal to 10;
heating, rolling and cooling the casting blank before rolling to obtain the high-strength low-hardness hydrogen sulfide corrosion resistant steel,
the rolling comprises rough rolling, intermediate billet cooling, intermediate rolling and finish rolling,
the total compression ratio of the broadening stage in rough rolling is less than or equal to 30%, and the total compression ratio of the longitudinal rolling after broadening is more than or equal to 45%;
cooling the intermediate blank at a cooling speed of 1-5 ℃/s;
the middle rolling and the finish rolling belong to the same non-recrystallization region for rolling, the deformation energy is stored, and fine grains and substructures are obtained for phase change;
the post-rolling cooling comprises: carrying out ACC laminar cooling on the finish-rolled plate at the cooling speed of 15-28 ℃/s and the final cooling temperature of 250-350 ℃; or the UFC ultra-fast cooling is carried out on the finish rolled plate, the cooling speed is 30-40 ℃/s, and the final cooling temperature is 350-450 ℃.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
the invention provides high-strength low-hardness hydrogen sulfide corrosion resistant steel and a preparation method thereof, a large number of tests are carried out, and the carbon equivalent is controlled to be CEIIW: 0.30-0.33%, CEPcm: when the content of the metal element is 0.12-0.14%, the strength, low hardness, low-temperature toughness, welding performance and hydrogen sulfide corrosion resistance (HIC and SSCC) of the steel plate are optimal. When the carbon equivalent is too high, the strength and the hardness can be greatly improved, and the hydrogen sulfide corrosion resistance is seriously deteriorated; the carbon equivalent is too low, and the strength performance can not meet the standard requirement. Through chemical components, production process and organization control, the contradiction of high strength, low hardness and hydrogen sulfide corrosion resistance is solved, the material has high strength, high toughness, low hardness and excellent hydrogen sulfide corrosion resistance, is suitable for conveying and storing components of high-sulfur oil and gas field media, and greatly prolongs the service life and improves the safety.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a metallographic microstructure of a high-strength low-hardness hydrogen sulfide corrosion-resistant steel prepared in example 1 of the present invention.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be obtained by an existing method.
The technical scheme provided by the embodiment of the invention is to provide high-strength low-hardness hydrogen sulfide corrosion resistant steel, and the general idea is as follows:
according to an exemplary embodiment of the present invention, there is provided a high-strength low-hardness hydrogen sulfide corrosion resistant steel, which comprises the following chemical components in parts by mass: c: 0.01 to 0.05%, Si: 0.05-0.35%, Mn: 1.10-1.40%, P: less than or equal to 0.006 percent, S: less than or equal to 0.0005 percent, Alt: 0.01 to 0.05%, Nb: 0.01-0.05%, V: 0.01-0.05%, Ti: 0.005-0.02%, Ni: 0.00-0.20%, Cr: 0.00-0.20%, Cu: 0.00-0.20%, and the balance of Fe and inevitable impurities; and carbon equivalent CEIIW：0.30～0.33％，CEPcm：0.12～0.14％。
In the embodiment, the carbon equivalent CEIIW，CEPcmThe calculation formula of (2) is as follows:
the application optimizes the composition elements to form the high-strength low-hardness hydrogen sulfide corrosion resistant steel with the chemical components, and is based on the following principle:
the control principle in the chemical composition design of the invention is as follows:
c: 0.01-0.05%, the strength performance of the material is improved by the C element through solid solution strengthening, and the influence of the carbon content on the strength, the hardness and the hydrogen sulfide corrosion resistance is large. A large number of tests prove that the C content is more than 0.05 percent, the strength and hardness are higher, the hydrogen sulfide corrosion resistance is poorer, the C content is less than 0.01 percent, and the strength performance is too low. Therefore, the C content of the invention is controlled within the range of 0.01-0.05%, so that the high strength, low hardness, excellent hydrogen sulfide corrosion resistance, excellent-40 ℃ low-temperature impact energy and-40 ℃ drop hammer performance can be obtained.
Si: 0.05-0.35% and Si element solid solution strengthening effect. A large number of experiments are carried out, the content of Si element is optimized, and when Si: when the content is 0.05-0.35%, C, Mn element is matched, so that stable Charpy impact property at-40 ℃, drop hammer property and good corrosion resistance can be obtained while high strength and low hardness are obtained.
Mn: 1.10-1.40%, Mn can improve austenite stability, a bainite structure with high hardness can be obtained more easily in the phase transformation process, the strength performance can be obviously improved, but too high Mn can bring about the problems of high hardness, poor center segregation of continuous casting billets and poor hydrogen sulfide corrosion resistance, and too low Mn is not enough in strength performance. Therefore, a large number of experiments show that Mn is controlled within a narrow range of 1.10-1.40%, so that high strength and low hardness of the material are ensured, and excellent hydrogen sulfide corrosion resistance, low-temperature impact energy at-40 ℃ and drop hammer performance at-40 ℃ are obtained.
P: less than or equal to 0.006 percent, S: not more than 0.0005 percent, and P, S elements are impurity elements in steel, are easy to segregate, influence the internal quality of a continuous casting billet, and are easy to segregate in a grain boundary, so that the P, S content needs to be optimized, and good low-temperature toughness, low hardness and hydrogen sulfide corrosion resistance are obtained. A large number of experiments are carried out, and the impurity elements are controlled to be P: less than or equal to 0.006 wt%, S: less than or equal to 0.0005wt percent, low hardness, low temperature toughness and good hydrogen sulfide corrosion resistance can be obtained. The invention discovers that when the P, S content is too high, hard phases appear at the places where elements are deviated, the micro-area hardness value exceeds 200HV10, and HIC hydrogen induced cracking and stress corrosion cracking are easily caused. Therefore, the invention continuously optimizes the content of P, S element through a large number of tests, and the P, S element is matched with a certain content of C, Mn, Ni, Cr and Cu element to interact, thereby obtaining low hardness, excellent hydrogen sulfide corrosion resistance, and good impact toughness and drop hammer toughness at-40 ℃.
Nb: 0.01-0.05%, V: 0.01-0.05%, Ti: 0.005-0.02%, Nb, V and Ti elements have the functions of solid solution strengthening and grain refinement, so that good strength, low-temperature toughness, low hardness and good hydrogen sulfide corrosion resistance can be obtained only by determining that the Nb content, the V content and the Ti content in the steel are controlled within the ranges of 0.01-0.05 wt%, 0.01-0.05 wt% and 0.005-0.02 wt% respectively through a large number of experiments.
Ni: 0.00-0.20%, and the Ni element is an austenite stability element, can reduce the gamma → alpha transition temperature, and can effectively improve the low-temperature toughness of the pipeline steel. Ni can improve the strength of steel by a solid solution strengthening effect and compensate for the strength reduction caused by the increase of the thickness in thick steel. Most importantly, the Ni alloy is added, so that the strength and the low-temperature toughness of the steel can be further improved. However, too much Ni will significantly increase the cost. Therefore, a large number of experiments are carried out, and the Ni content is controlled within the range of 0.00-0.20 wt%, so that the toughness and the economy are optimal.
Cu: 0.00-0.20%, and Cu element can improve the toughness and corrosion resistance of the steel plate. However, the invention has carried out a great deal of experiments and found that: when the Cu content is controlled within the range of 0.00-0.20 wt%, the steel plate has optimal structure uniformity, strength uniformity, low hardness, low-temperature toughness, cost, acid-resistant HIC and SSCC properties.
Cr: 0.00-0.20%, and the Cr element is effective for improving the tensile strength of the pipeline steel and can obviously reduce the yield ratio of the material. However, a higher Cr content is disadvantageous in terms of welding performance and acid resistance. A large number of tests are carried out, and when the Cr content is controlled within the range of 0.00-0.20%, the strength performance, the yield ratio, the low hardness and the acid resistance performance are optimal.
Carbon equivalent CEIIWControl the content of CE in the range of 0.30 to 0.33%PcmThe reason for controlling the concentration to be 0.12-0.14% is as follows: the carbon equivalent greatly contributes to the strength of the steel, can obviously improve the strength performance of the material, but is unfavorable for low-temperature toughness, hardness, welding performance and hydrogen sulfide corrosion resistance. A large number of experiments are carried out, and the carbon equivalent is controlled to be CEIIW: 0.30-0.33%, CEPcm: when the content of the metal element is 0.12-0.14%, the strength, low hardness, low-temperature toughness, welding performance and hydrogen sulfide corrosion resistance (HIC and SSCC) of the steel plate are optimal. When the carbon equivalent is too high, the strength and the hardness can be greatly improved, and the low-temperature toughness and the hydrogen sulfide corrosion resistance can be reduced; the carbon equivalent is too low, and the strength performance can not meet the standard requirement.
The mechanical properties of the high-strength low-hardness hydrogen sulfide corrosion resistant steel provided by the embodiment of the invention are as follows: the yield strength is 450-600MPa, the tensile strength is 535-760MPa, the yield ratio is 0.70-0.90, the summer specific impact energy with the toughness of-40 ℃ is more than or equal to 400J, the drop hammer shear area at-40 ℃ is more than or equal to 85 percent, the Vickers hardness HV10 is 170-190, the HIC performance crack rate of the solution A for resisting hydrogen sulfide corrosion is 0, and the SSCC test surface has no cracks. Especially, the control of the low hardness property is the key, and the low hardness directly brings the improvement of the hydrogen sulfide corrosion resistance. The invention is suitable for the conveying and storing component of the high-sulfur oil-gas field medium, greatly prolongs the service life and improves the safety, and has good application prospect.
The gist of the invention is to control the hardness value of the material, and the Vickers hardness HV10 is controlled in the range of 170-190, and the hydrogen sulfide corrosion resistance is harmless. When the hardness value is too high, stress concentration is brought to become a hydrogen trap, and the problems of hydrogen induced cracking and stress corrosion cracking are caused. Therefore, through a large number of experiments, the contents of elements such as C, Mn, P, S, Ni, Cu, Cr, Nb, V, Ti and the like are optimized, the phase change product is controlled to be a refined ferrite structure and a substructure, hard phases such as pearlite, bainite or MA island and the like are avoided, the strength can meet the requirement, the hardness value is not too high, the contradiction problems of high strength, low hardness and hydrogen sulfide corrosion resistance are solved, and meanwhile, the excellent-40 ℃ impact toughness and the drop hammer toughness are improved.
Preferably, the metallographic structure of the steel is, in volume fraction: 90-98% of polygonal ferrite, 2-10% of strip-shaped ferrite and substructures thereof. The thinned strip-shaped ferrite and the substructure thereof avoid hard phases such as pearlite, bainite, M/A islands and the like, obtain more fine polygonal ferrite structures, improve the strength, and have low hardness, which is beneficial to the performances of high strength, high toughness, low hardness, hydrogen sulfide corrosion resistance and the like of the steel plate. The volume fraction of the ferrite structure and the substructure which are very fine is 2-10%, the contradiction problems of high strength, low hardness and hydrogen sulfide corrosion resistance are solved, and the excellent-40 ℃ impact toughness and drop hammer toughness are improved.
Preferably, the grain size of the polygonal ferrite is 1 to 5 μm. The shape of the strip-shaped ferrite and the substructure thereof is irregular and fine, so the size is not easy to be measured, and the grain size of the strip-shaped ferrite and the substructure thereof is about 1 to 2 μm.
According to another exemplary embodiment of the present invention, there is also provided a method for manufacturing the high-strength low-hardness hydrogen sulfide corrosion-resistant steel, the method including:
obtaining a casting blank of the high-strength low-hardness hydrogen sulfide corrosion resistant steel, wherein the total compression ratio of the casting blank is more than or equal to 10;
heating, rolling and cooling the casting blank before rolling to obtain the high-strength low-hardness hydrogen sulfide corrosion resistant steel,
the rolling comprises rough rolling, intermediate billet cooling, intermediate rolling and finish rolling,
the total compression ratio of the broadening stage in rough rolling is less than or equal to 30%, and the total compression ratio of the longitudinal rolling after broadening is more than or equal to 45%;
cooling the intermediate blank at a cooling speed of 1-5 ℃/s;
the middle rolling and the finish rolling belong to the same non-recrystallization region for rolling, the deformation energy is stored, and fine grains and substructures are obtained for phase change;
the post-rolling cooling comprises: carrying out ACC laminar cooling on the finish-rolled plate at the cooling speed of 15-28 ℃/s and the final cooling temperature of 250-350 ℃; or the UFC ultra-fast cooling is carried out on the finish rolled plate, the cooling speed is 30-40 ℃/s, and the final cooling temperature is 350-450 ℃.
The process aims to obtain refined ferrite and a substructure, and the strength can be well improved by grain refinement without hard phases. Through a large number of tests, the specific preparation process window plays a role in obtaining a specific microstructure for subsequent phase change, so that crystal grains are refined, a hard phase is avoided, and high strength, low hardness, low-temperature toughness at-40 ℃ and excellent hydrogen sulfide corrosion resistance are finally obtained.
If the total compression ratio of the widening stage in the rough rolling is more than 30 percent, the total compression ratio of the longitudinal rolling after widening is less than or equal to 45 percent, austenite grains cannot be fully recrystallized and refined, and the refining and toughness performance of the subsequent ferrite structure is adversely affected.
If the cooling speed of the intermediate billet is less than 1 ℃/s, the refining and the toughness of austenite grains are not favorable; if the cooling rate is more than 5 ℃/s, the rolling warping and uniformity are adversely affected.
If the rolling parameters of the medium rolling and the finish rolling are not proper, the subsequent phase change refined grains and the obtained substructure are adversely affected;
the post-rolling cooling comprises: carrying out ACC laminar cooling on the finish-rolled plate at the cooling speed of 15-28 ℃/s and the final cooling temperature of 250-350 ℃; or the UFC ultra-fast cooling is carried out on the finish rolled plate, the cooling speed is 30-40 ℃/s, and the final cooling temperature is 350-450 ℃. An ideal microstructure can be obtained through a cooling process window, the ferrite microstructure and the substructure are mainly refined, and the high strength, the low hardness, the-40 ℃ low-temperature toughness and the excellent hydrogen sulfide corrosion resistance are obtained. According to the invention, through a large number of tests, the final cooling temperature interval and the cooling rate interval of ACC or UFC are determined, ferrite grains and substructures can be fully refined, hard phases such as pearlite, bainite and M/A islands are avoided, a large proportion of fine polygonal ferrite structures are obtained, the strength is improved, the hardness is not high, and the steel plate is beneficial to the performances of high strength, high toughness, low hardness, hydrogen sulfide corrosion resistance and the like of the steel plate.
In conclusion, the invention realizes that the summer specific impact energy of-40 ℃ is more than or equal to 400J, the drop hammer shear area of-40 ℃ is more than or equal to 85%, the Vickers hardness HV10 is 170-190, the cracking rate of the HIC performance of the solution A for resisting the hydrogen sulfide corrosion is 0, no crack exists in SSCC corrosion test, especially the control of low hardness performance is a key, and the low hardness directly brings the improvement of the hydrogen sulfide corrosion resistance by innovating chemical components, production process and microstructure. The invention is suitable for the conveying and storing component of the high-sulfur oil-gas field medium, greatly prolongs the service life and improves the safety, and has good application prospect.
A high-strength low-hardness hydrogen sulfide corrosion-resistant steel and a method for manufacturing the same according to the present application will be described in detail with reference to examples, comparative examples, and experimental data.
S1, examples 1-5 and comparative examples 1-3 are respectively subjected to converter smelting and continuous casting by using molten steel with chemical components shown in Table 1 to obtain casting blanks;
TABLE 1 Mass fractions of chemical components of examples and comparative examples
S2, heating the casting blank before rolling, rolling and cooling after rolling to obtain the high-strength low-hardness hydrogen sulfide corrosion resistant steel, wherein the rolling comprises rough rolling, intermediate blank cooling, intermediate rolling and finish rolling, the total compression ratio of the rough rolling in the broadening stage is less than or equal to 30%, and the total compression ratio of the broadening longitudinal rolling is more than or equal to 45%; cooling the intermediate blank at a cooling speed of 1-5 ℃/s; the middle rolling and the finish rolling belong to the same unrecrystallized area for rolling; the post-rolling cooling comprises: carrying out ACC laminar cooling on the finish-rolled plate at the cooling speed of 15-28 ℃/s and the final cooling temperature of 250-350 ℃; or the UFC ultra-fast cooling is carried out on the finish rolled plate, the cooling speed is 30-40 ℃/s, and the final cooling temperature is 350-450 ℃.
The process parameters for each group are specified in table 2.
TABLE 2 preparation of Process parameter Table
Mechanical property tests were performed on each group of samples of the finished product, and the results are shown in table 3.
TABLE 3 statistics of mechanical Properties of the examples and comparative examples
From the data in table 3, it can be seen that:
comparative example 1, carbon equivalent CEIIWLess than 0.30 percent, and the rest is the same as the embodiment 1, and has the defect of lower strength performance;
comparative example 2, carbon equivalent CEIIWMore than 0.33 percent, and the rest of the components are the same as those in the embodiment 1, so that the defects of high strength and hardness, and low-temperature toughness and hydrogen sulfide corrosion resistance are reduced;
in comparative example 3, carbon equivalent CEPcmLess than 0.12%, and the balance being the same as in example 1, the strength properties are low;
comparative example 4, carbon equivalent CEPcmMore than 0.14 percent, and the rest of the components are the same as those in the embodiment 1, so that the defects of high strength and hardness, and low-temperature toughness and hydrogen sulfide corrosion resistance are reduced;
in comparative example 5, the total casting billet reduction ratio was < 10; the total compression ratio of the broadening stage in rough rolling is more than 30 percent, the total compression ratio of the longitudinal rolling after broadening is less than 45 percent, and the rest of the steps are the same as those in the embodiment 1, so that the defects of insufficient grain refinement, and reduced strength, low-temperature toughness and hydrogen sulfide corrosion resistance are overcome;
in the comparative example 6, the cooling speed of the intermediate blank is 0.1 ℃/s and is less than the range of 1-5 ℃/s, and the rest of the method is the same as that of the example 1, so that the defects of insufficient grain refinement, reduced strength, low-temperature toughness and reduced hydrogen sulfide corrosion resistance exist;
the high-strength low-hardness hydrogen sulfide corrosion resistant steel finally prepared in the embodiments 1-5 of the invention has the advantages of high strength, low-temperature toughness, low yield ratio, low hardness, good hydrogen sulfide corrosion resistance, excellent-40 ℃ low-temperature toughness and drop hammer performance, and greatly improved service life and use safety of the material.
Description of the attached drawings 1:
FIG. 1 is a metallographic microstructure of a high-strength low-hardness hydrogen sulfide corrosion-resistant steel prepared in example 1 of the present invention; as can be seen from FIG. 1, fine polygonal ferrite is mainly used, the volume fraction thereof is 95%, and the average grain size is 3 μm; and has a small amount of long strip ferrite and substructures thereof.
In conclusion, the high-strength low-hardness hydrogen sulfide corrosion resistant steel and the preparation method thereof provided by the invention have the carbon equivalent controlled in a CEIIW: 0.30-0.33%, CEPcm: when the content of the metal element is 0.12-0.14%, the strength, low hardness, low-temperature toughness, welding performance and hydrogen sulfide corrosion resistance (HIC and SSCC) of the steel plate are optimal. Through chemical components, production process and organization control, the contradiction of high strength, low hardness and hydrogen sulfide corrosion resistance is solved, the material has high strength, high toughness, low hardness and excellent hydrogen sulfide corrosion resistance, is suitable for conveying and storing components of high-sulfur oil and gas field media, and greatly prolongs the service life and improves the safety.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (4)
1. The high-strength low-hardness hydrogen sulfide corrosion-resistant steel is characterized by comprising the following chemical components in percentage by mass: c: 0.01 to 0.05%, Si: 0.05-0.35%, Mn: 1.10-1.40%, P: less than or equal to 0.006 percent, S: less than or equal to 0.0005 percent, Alt: 0.01 to 0.05%, Nb: 0.01-0.05%, V: 0.01-0.05%, Ti: 0.005-0.02%, Ni: 0.00-0.20%, Cr: 0.00-0.20%, Cu: 0.00-0.20%, and the balance of Fe and inevitable impurities; and carbon equivalent CEIIW：0.30～0.33％，CEPcm: 0.12 to 0.14% of the carbon equivalent CEIIW，CEPcmThe calculation formula of (2) is as follows:
in the formula, C, Si, Mn, V, Ti, Ni, Cr, Cu and Mo respectively represent the percentage content of each chemical component, and the metallographic structure of the steel is calculated by volume fraction: the steel comprises 90-98% of polygonal ferrite, 2-10% of strip-shaped ferrite and substructures of the strip-shaped ferrite, wherein the Vickers hardness HV10 of the steel is 170-190, the Charpy impact energy at-40 ℃ is more than or equal to 400J, the drop-hammer shear area at-40 ℃ is more than or equal to 85%, and the steel is prepared according to the following steps:
obtaining a casting blank of the high-strength low-hardness hydrogen sulfide corrosion resistant steel, wherein the total compression ratio of the casting blank is more than or equal to 10;
heating the casting blank before rolling, rough rolling, cooling the intermediate blank, medium rolling, finish rolling and cooling after rolling to obtain the high-strength low-hardness hydrogen sulfide corrosion resistant steel,
the total compression ratio of the broadening stage in rough rolling is less than or equal to 30%, and the total compression ratio of the longitudinal rolling after broadening is more than or equal to 45%;
in the middle rolling, 1-5 passes are adopted for rolling, the rolling speed is controlled to be 2-5 m/s, the inlet temperature of the middle rolling is controlled to be 880-950 ℃, and the outlet temperature of the middle rolling is controlled to be 850-880 ℃;
in the finish rolling, 3-8 passes are adopted for rolling, the rolling speed is controlled to be 3-6 m/s, the total deformation of the finish rolling is controlled to be 50-75%, and the outlet temperature of the finish rolling is 780-840 ℃;
the cooling speed of the intermediate blank is 1-5 ℃/s,
the post-rolling cooling comprises: carrying out ACC laminar cooling on the finish-rolled plate at the cooling speed of 15-28 ℃/s and the final cooling temperature of 250-350 ℃; or the UFC ultra-fast cooling is carried out on the finish rolled plate, the cooling speed is 30-40 ℃/s, and the final cooling temperature is 350-450 ℃.
2. The high-strength low-hardness hydrogen sulfide corrosion resistant steel according to claim 1, wherein the grain size of the polygonal ferrite is 1 to 5 μm.
3. The high-strength low-hardness hydrogen sulfide corrosion resistant steel as claimed in claim 1, wherein in the rough rolling, 5-12 passes are adopted for rolling, the rolling speed is controlled to be 1-4 m/s, the total deformation of the rough rolling is controlled to be 40-60%, and the inlet temperature of the rough rolling is controlled to be 980-1080 ℃.
4. The high-strength low-hardness hydrogen sulfide corrosion resistant steel as claimed in claim 1, wherein in the heating before rolling, the size of a casting blank is controlled to be 150-400 mm, the temperature difference of the section of the casting blank is controlled to be less than or equal to 20 ℃, and the heating time is controlled to be 2-6.5 h.
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