CN115717214B - Steel for coastal atmospheric environment refining pipeline and preparation method thereof - Google Patents
Steel for coastal atmospheric environment refining pipeline and preparation method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of steel for a smelting pipeline, in particular to steel for a pipeline in a coastal atmospheric environment and a preparation method thereof. On the basis of low C, si and Mn components, harmful elements P, S are strictly controlled, and a tempered sorbite structure containing a nanoscale stable precipitated phase is obtained through a composite addition Cu, ni, ce and Al alloy element combination manufacturing process, so that the structure has the characteristics of single uniformity, fineness and compactness, and the comprehensive performance requirement of the pipeline steel plate is ensured. The mechanical property of the alloy is represented by R which is less than or equal to 395MPa at normal temperature el ≤415MPa、525MPa≤R m A is more than or equal to 555MPa and more than or equal to 35.0% and less than or equal to 38.0%. The H-resistant inner wall of the steel pipeline of the smelted pipeline obtained by the invention 2 S、Cl ‑ Corrosion of single acid medium or mixed medium, and high CI resistance of outer wall ‑ 、SO 2 The coastal industrial atmospheric medium is corroded, and the steel plate has excellent forming process performance and is suitable for application in coastal atmospheric environment.
Description
Technical Field
The invention relates to the technical field of steel for a smelting pipeline, in particular to steel for a pipeline in a coastal atmospheric environment and a preparation method thereof.
Background
Petroleum is an indispensable strategic resource as "blood in modern industry", and with the development of global economy and the aggravation of regional instability factors, the energy crisis of petroleum, natural gas and the like is increasingly highlighted. The dependence of crude oil on the outside is over 70% as the country with large petroleum energy consumption, and the dependence of crude oil on the outside is increased continuously or continuously along with the continuous enhancement of domestic oil refining capability.
The construction of the refining base in coastal areas is beneficial to offshore import of crude oil, export of chemical products and safe operation. However, the high-humidity and high-salt environment in coastal areas has potential corrosion risks for petroleum refining equipment, and particularly, process pipelines for connecting various devices, for example, the total length of a pipeline of a refining plant capable of producing tens of thousands of tons per year reaches tens of kilometers, and various oiling media are contacted in production. The inner wall of the pipeline is in a corrosive environment containing sulfides (in crude oil) and chlorine (in an auxiliary agent containing organic compounds), and the inner wall mainly generates hydrogen induced cracking and stress corrosion; the outer wall is in coastal atmosphere corrosion environment, and the outer wall is mainly corroded comprehensively. The corrosion of the inner wall and the outer wall of the refined pipeline provides great test for the safe operation of the pipeline, and the safety accidents caused by the corrosion and leakage of the pipeline are serious in price.
CN112111698A discloses "steel for exposed pipelines in a refining plant with high corrosion resistance and a production method thereof", and although the steel relates to the application of the refining pipelines, the application range is not clear, the special corrosive medium and the specific environment of the coastal atmosphere are not involved, and the corrosion environment of the application is relatively loose. CN111471935B discloses "a steel for HIC-resistant pipelines and a method for preparing the same", which relates to a steel for HIC-resistant pipelines, mainly relating to long-distance transportation conditions, and not relating to marine atmosphere environment. In addition, the components and the process of the invention can meet the HIC resistance requirement, but can not meet the complex environmental requirements of ocean atmosphere and refining high-temperature medium. CN103469094a discloses a "steel for pipeline resistant to chloride ion corrosion and its preparation method", the corrosive medium involved is chloride ion environment, used for underground pipeline engineering, the chemical composition and content are as follows: 0.008-0.02% of C, 0.05-0.15% of Si, 0.50-0.85% of Mn, less than or equal to 0.01% of P, less than or equal to 0.010% of S, 0.8-2.0% of Mo, 0.015-0.050% of Als, 0.50-1.2% of Ni, 0.02-0.08% of W, the balance of Cr, fe and unavoidable impurities, and the final state of the steel plate is controlled rolling and cooling. CN 112795842B discloses "a steel for submarine quick-link pipeline and a production method thereof", which relates to a steel for pipeline in the ocean, and has a substantial difference from the environment exposed to the ocean atmosphere and high-temperature corrosion, and a substantial difference from chemical composition and production process.
In summary, the steel for pipelines according to the presently disclosed documents has a single corrosion environment and no strict requirement on corrosion resistance, and cannot be applied to dual-medium corrosion of corrosion components in coastal industrial atmosphere and high-temperature and low-temperature oiled products.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides steel for a pipeline refined in the coastal atmosphere environment and a preparation method thereof, which are suitable for double-sided corrosion of coastal industrial atmosphere and internal industrial media and meet the requirement of the coastal petroleum refining factory on the safe and full-length periodic service of the pipeline.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
the steel for the coastal atmospheric environment refined pipeline consists of the following chemical components in percentage by weight:
0.02 to 0.06 percent of C, 0.10 to 0.30 percent of Si, 0.40 to 0.90 percent of Mn, less than or equal to 0.008 percent of P, less than or equal to 0.002 percent of S, 1.0 to 1.5 percent of Ni, 0.40 to 0.80 percent of Cu, 0.010 to 0.015 percent of Ce, 0.50 to 1.00 percent of Alt, wherein Mn+Cu=1.00 to 1.60 percent, and the balance of Fe and unavoidable impurities.
A preparation method of steel for a pipeline in coastal atmospheric environment is provided, which comprises the following technological processes: molten iron pretreatment, converter dephosphorization, converter decarburization, external refining (LF+RH), slab continuous casting, stacking slow cooling, casting blank cleaning, billet heating, finished product rolling, hot straightening, slow cooling, heat treatment, flaw detection, inspection and inspection, and the method specifically comprises the following steps:
1) Smelting process
Molten steel smelting is carried out in a converter, molten iron and scrap steel are adopted as smelting raw materials, and the content of the molten iron is controlled to be 60% -80%; dephosphorization and decarburization are separately smelted by adopting a converter, wherein dephosphorization oxygen blowing is controlled to be 8-10 min, decarburization oxygen blowing is controlled to be 9-12 min, and the mass fraction of phosphorus is finally reduced to be within 0.007%;
deep desulfurization treatment is carried out in an LF refining furnace, and the sulfur content is controlled below 0.002%;
feeding Ce wires into the steel in the later stage of refining, wherein the wire feeding speed is 250-350 m/min, the wire feeding depth is 1.5-2.5 m below the slag layer, and the thickness of the generated slag layer is 50-80 mm;
degassing is completed in an RH furnace, the net circulation time is 10-15 min, and the sedation time is 3-5 min before casting.
2) Casting process
And (3) casting by adopting a continuous casting machine after vacuum breaking, wherein the superheat degree is 20-30 ℃, the casting blank is fed into a stack for slow cooling, the stack slow cooling time is 24-48 h, and the stack is released below 300 ℃.
3) Heating process
The heating temperature of the steel billet is controlled between 1180 and 1230 ℃, and the total heating time is 5.0 to 8.5 hours.
4) Controlled cooling process
The initial rolling temperature in the rough rolling stage is 1050-1150 ℃, the accumulated rolling reduction is more than or equal to 65%, and the thickness of the intermediate billet is 2.5-4.0 times of the finished steel plate; the initial rolling temperature of the finish rolling stage is 900-940 ℃, the final rolling temperature is 850-900 ℃, and the accumulated deformation rate is more than or equal to 60%;
and (3) refining the rolled structure through two-stage rolling to obtain a pipeline steel semi-finished product with the thickness of 20-50 mm.
5) Heat treatment process
Adopting a normalizing quick cooling, quenching and tempering heat treatment process; normalizing temperature is 900-930 ℃, preserving heat for 1.0-2.0 min/mm, and rapidly cooling to 400-500 ℃; quenching temperature is 870-900 ℃, and heat preservation time is 0.5-1.0 min/mm; the tempering temperature is 620-670 ℃, and the heat preservation time is 2.0-4.0 min/mm.
Controlling the water quantity and water pressure of the quenching unit, wherein the water quantity is 100-120 m 3 And/min, water pressure of 4-7 bar, water supply/water discharge ratio of 1 (1.5-2.5), swing watering, roller speed of 0.5-1.0 m/s, cooling speed of 20-30 ℃/s, and cooling to room temperature.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention fully considers the factors of the mechanical property, the service property and the like of the steel for the smelting pipeline in the component design. In order to ensure the matrix temperature and high-temperature strength of the pipeline steel, the solid solution strengthening effect is achieved by adding the C, mn and Ni alloy elements. In addition, the corrosion resistance of the inner surface and the outer surface of the pipeline steel to different media in the service process is finished by adding Cu, ni, alt element singly or in a synergistic effect, wherein the corrosion resistance is improved by adding more than 1% of Ni; more than 0.4% of Cu forms a corrosion-resistant protective layer and cooperates with Mn to form oxide filling cracks and holes, so that the corrosion-resistant effect is achieved; more than 0.5 percent of Al is added to play a passivation role, so that the acid corrosion resistance is improved; the Ce element is used as another important element of the invention, not only changes the form of the inclusion in the smelting process and purifies molten steel, but also has a certain hydrogen capturing effect, and improves the hydrogen induced cracking performance, thereby improving the corrosion resistance.
2. The alloy element is matched with the production process. The rolling is controlled in two stages, so that the cumulative rolling reduction of rough rolling is ensured to be more than 60%, the finish rolling temperature is 850-900 ℃, the rolling structure is fully refined, and a foundation is laid for subsequent heat treatment. The heat treatment adopts the multi-process treatment of normalizing pretreatment, quenching and tempering, and can obtain a single and segregation-free fine and compact structure, wherein the normalizing pretreatment can eliminate the banded structure caused by carbon and manganese of the rolled steel plate. And then a fine single structure is obtained on the basis of normalized refined grains through quenching treatment, so that the compactness is improved. Further tempering softening is required to obtain good toughness due to the formability requirements of the pipe.
3. By the componentsThe process is implemented, and the product of the invention has excellent mechanical and corrosion resistance, such as 395 MPa-R el ≤415MPa、525MPa≤R m A is more than or equal to 555MPa and more than or equal to 35.0% and less than or equal to 38.0%; 370MPa of steel plate at 100 ℃ is less than or equal to R p0.2 R is not less than 405MPa and 240MPa of steel plate at 350 DEG C p0.2 No crack on the cold-bent surface (0 ℃) KV with D=2a and 180 DEG in the transverse direction and 285MPa or less 2 More than or equal to 310J, HBW and less than or equal to 165, A+B+C+D and less than or equal to 1.0, the grain size range is less than or equal to 1.0, and the banded segregation is 0 level. H-resistant inner wall of steel pipe 2 S、Cl - Corrosion of single acid medium or mixed medium, and high CI resistance of outer wall - 、SO 2 Corrosion resistance to atmospheric agents in coastal industries. CSR expressed as 100℃HIC is 0% and CSR expressed as 350℃HIC is 0%; the SSCC sample loaded for 4320h at the pressure of 4MPa at 100 ℃ is not broken, and the SSCC sample loaded for 2160h at the pressure of 4MPa at 350 ℃ is not broken; the corrosion rate of the steel for the refining pipeline in the marine atmospheric environment is less than or equal to 2.0mm/a.
Detailed Description
The invention discloses steel for a pipeline refined in a coastal atmosphere environment and a preparation method thereof. Those skilled in the art can, with the benefit of this disclosure, suitably modify the process parameters to achieve this. It is expressly noted that all such similar substitutions and modifications will be apparent to those skilled in the art, and are deemed to be included in the present invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those skilled in the relevant art that variations and modifications can be made in the methods and applications described herein, and in the practice and application of the techniques of this invention, without departing from the spirit or scope of the invention.
The steel for the coastal atmospheric environment refined pipeline consists of the following chemical components in percentage by weight:
0.02 to 0.06 percent of C, 0.10 to 0.30 percent of Si, 0.40 to 0.90 percent of Mn, less than or equal to 0.008 percent of P, less than or equal to 0.002 percent of S, 1.0 to 1.5 percent of Ni, 0.40 to 0.80 percent of Cu, 0.010 to 0.015 percent of Ce, 0.50 to 1.00 percent of Alt, wherein Mn+Cu=1.00 to 1.60 percent, and the balance of Fe and unavoidable impurities.
The reasons for the limited amounts of each chemical element in the C, si, mn, P, S, ni, cu, ce, alt steel sheet are described in detail below:
c: the method is an important and cheap strengthening element, a certain amount of C is added to ensure the matrix strength of the pipeline steel, but the excessive carbon content increases the segregation tendency of carbide, so that the hardness of a segregation zone is different from that of surrounding tissues, the HIC resistance of the steel is reduced, and the excessive carbon content is unfavorable for the welding performance of the pipeline and the corrosion resistance of a welding seam, so that the C content range is set to be 0.02-0.06%.
Mn: a certain amount of Mn plays a role of solid solution strengthening the pipe matrix, but segregation caused by excessive Mn easily generates high-strength and low-toughness microscopic metallographic structures such as martensite and bainite in weld joints and heat affected zones, shows extremely high hardness, increases the cracking tendency of the welded structure, and is extremely unfavorable for SSC resistance of the pipe, so that the upper limit of Mn needs to be controlled, and therefore, the Mn content range is set to 0.40% -0.90% in the invention.
Si: in addition, when the silicon content is more than 1%, a compact silicon dioxide protective film can be formed, and the corrosion resistance is improved. However, when the content of Si element is higher, the hardness of the weld joint and the heat affected zone is higher, meanwhile, the Si element is easy to segregate at the grain boundaries, thereby promoting the formation of inter-crystal cracks and increasing the corrosion risk of the pipeline, so the Si content range is set to be 0.10-0.30%.
P: the segregation is easy to occur at the austenitic grain boundary, so that the interatomic bonding force on the grain boundary of the matrix material is weakened, and the tempering brittleness of the material is large, so that the content range of P is set to be less than or equal to 0.008 percent.
S: the strip-shaped distribution of MnS and FeS nonmetallic inclusion are formed in the steel, so that the local microstructure is loose, and the sensitivity of HIC or SOHIC in a wet hydrogen sulfide environment is increased, so that the S content range is set to be less than or equal to 0.002 percent.
Ni: the Ni with a certain content can enable the self-corrosion potential of the steel exposed to the ocean atmosphere to move forward, and the stability of the matrix is improved. Meanwhile, ni can be enriched in the rust layer, so that the grains of the rust layer are refined and the compactness of the rust layer is improved. In addition, ni can promote the formation of nano-scale and superparamagnetic alpha-FeOOH in the inner rust layer to block moistureChloride ions in the wet marine atmosphere permeate, rendering the rust layer protective. However, since Ni steel has a low hydrogen evolution potential, hydrogen ions are easily reduced by discharge to promote the precipitation of free hydrogen, thereby reducing the steel in wet H 2 S resistance to corrosive environments, thus wet H 2 The Ni content of the steel in S environment should not be too high. Therefore, the Ni content range is set to be 1.0% -1.5% in the invention.
Cu: cu can accelerate the recombination speed of hydrogen atoms, thereby reducing the activity of hydrogen and improving the corrosion resistance of the material in an acidic medium. In particular saturated wet H 2 S environment, feS can be formed in steel with copper content more than 0.4% 1-x And a black protective layer of Cu, which reduces corrosion rate and hydrogen absorption rate, wherein Cu has both inner HCl and H resistance 2 S、H 2 The corrosion of the medium and the chlorine ion corrosion of the coastal environment are prevented, but too much Cu can reduce the toughness of the steel, so the Cu content range is set to be 0.40-0.80 percent.
The invention has more remarkable marine industrial atmospheric corrosion resistance effect when the Cu and Mn composite addition reaches more than 1 percent, and CuFeO is arranged in the Cu-Mn rust layer 2 And Mn of 3 O 4 The oxide in the form of the Mn+Cu alloy can well fill cracks and holes, so that the rust layer is more compact, thereby preventing chloride ions from penetrating into a matrix and improving corrosion resistance, and therefore, the Mn+Cu alloy is limited to be 1.00-1.60%.
Ce: the rare earth has stronger affinity with harmful elements such as oxygen, sulfur, phosphorus, hydrogen, nitrogen and the like in the molten steel, and after forming a stable rare earth compound, the self density of the rare earth compound is smaller than that of the molten steel, and the rare earth compound floats upwards to form slag, thereby playing a role in purifying the molten steel. In addition, by controlling the form of the inclusions, the elongated manganese sulfide inclusions are changed into spherical sulfides or oxides, so that the form of the sulfides is completely controlled, and the variability of the steel is improved. The rare earth has certain solid solubility in steel, and the segregation of sulfur, phosphorus and other low-melting-point inclusions at the grain boundary can be inhibited by the rare earth at the grain boundary, and high-melting-point compounds are formed by the rare earth and the inclusions, so that the harmful influence of the low-melting-point inclusions is reduced, the formation and the expansion tendency of intercrystalline cracks are reduced, and the high-temperature plasticity and the corrosion resistance of the steel are improved. Ce elementThe microalloying effect of the element is mainly reflected in the interaction of the rare earth and other elements at the grain boundary, so that the grain boundary structure, chemical composition and energy are changed, and meanwhile, the diffusion of other elements and the nucleation number of a new phase are influenced by the growth speed, so that the structure and the performance of the steel are changed. In addition, the rare earth has the function of hydrogen capture, so that the hydrogen-induced delayed fracture performance of the steel is improved, and the corrosion resistance of the steel is improved. Dispersion hardening, blowing rare earth oxide (CeO) into steel 2 ) The powder can improve the comprehensive mechanical property of steel and reduce the brittle transition temperature. CeO (CeO) 2 Can be used as crystallization nucleus to provide landing points, the number of nucleation is increased, crystal grains are arranged, and CeO is dispersed and distributed 2 Particles can increase the barrier effect of grain boundaries on dislocation motion. However, ce belongs to rare earth strategic resources and is not suitable for excessive addition, so the content range of Ce is set to be 0.010-0.015 percent.
Al: aluminum mainly plays a role in deoxidizing and refining grains in steel. In addition, when the aluminum content reaches a certain value, the surface of the steel is passivated, so that the steel has corrosion resistance in oxidizing acid and improves the corrosion resistance to hydrogen sulfide, but excessive aluminum can promote the graphitization tendency of the steel when used for a long time at medium and high temperature. Therefore, the Alt content range is set to be 0.50% -1.00%.
In order to obtain the comprehensive mechanical properties and corrosion resistance of the steel plate, necessary alloy elements are added, and a single and stable tissue structure is obtained through organic combination of production processes.
A manufacturing method of steel for a pipeline refined in a coastal atmosphere environment comprises the following steps:
1. the process flow is as follows: molten iron pretreatment, converter dephosphorization, converter decarburization, external refining (LF+RH), slab continuous casting, stacking slow cooling, casting blank cleaning, billet heating, finished product rolling, hot straightening, slow cooling, heat treatment, flaw detection, inspection and inspection.
2. The smelting process comprises the following steps: molten steel smelting is carried out in a converter, molten iron and high-quality scrap steel are adopted as smelting raw materials, the content of the molten iron is controlled to be 60-80%, meanwhile, the content of harmful element P is effectively reduced, dephosphorization and decarburization are separately smelted by adopting the converter, wherein dephosphorization oxygen blowing is controlled to be 8-10 min, decarburization oxygen blowing is controlled to be 9-12 min, and the mass fraction of phosphorus is finally reduced to be within 0.007%; and (3) carrying out deep desulfurization treatment in an LF refining furnace, wherein the sulfur content is controlled below 0.002%. Feeding Ce wires into the steel in the later stage of refining, wherein the wire feeding speed is 250-350 m/min, the wire feeding depth is 1.5-2.5 m below the slag layer, the treatment changes the form of nonmetallic inclusion, forms tiny sulfide and oxide nonmetallic inclusion particles of Ce, improves the axial ratio of steel billets and the like, simultaneously purifies the steel, improves the purity, improves the hydrogen resistance of the steel, and the thickness of the generated slag layer is 50-80 mm; degassing is completed in an RH furnace, the net circulation time is 10-15 min, and the sedation time is 3-5 min before casting.
3. The casting process comprises the following steps: and after vacuum breaking, casting by adopting a continuous casting machine, wherein the superheat degree is 20-30 ℃, feeding the casting blank into a stack for slow cooling, and unstacking for 24-48 hours at the temperature below 300 ℃ to prevent cracks in the casting blank caused by quenching.
4. The heating process comprises the following steps: by controlling the heating process of the steel billet, the alloy element is ensured to be fully dissolved, the growth of original austenite grains is effectively inhibited, the heating temperature of the steel billet is controlled between 1180 and 1230 ℃, and the total heating time is 5.0 to 8.5 hours.
5. And (3) controlling a cooling control process: the initial rolling temperature in the rough rolling stage is 1050-1150 ℃, the accumulated rolling reduction is more than or equal to 65%, and the thickness of the intermediate billet is 2.5-4.0 times of the finished steel plate; the initial rolling temperature of the finish rolling stage is 900-940 ℃, the final rolling temperature is 850-900 ℃, and the accumulated deformation rate is more than or equal to 60%. And (3) refining the rolled structure through two-stage rolling to obtain a pipeline steel semi-finished product with the thickness of 20-50 mm.
6. And (3) a heat treatment procedure: under the influence of tissue genetics, the rolled structure has defects of certain segregation, chain distribution of carbide and the like under the influence of smelting, and is extremely unfavorable for obtaining excellent comprehensive mechanical properties, particularly the corrosion resistance of inner and outer walls to different media, of the pipeline steel. Therefore, the structure is regulated and controlled by heat treatment, and a single uniform, segregation-free and compact stable structure is obtained to achieve the final beneficial effect of the invention, therefore, the invention adopts a normalizing quick cooling, quenching and tempering heat treatment process, and the specific process parameters and design reasons are that the normalizing pretreatment temperature is setThe temperature is 900-930 ℃, the temperature is kept for 1.0-2.0 min/mm, the steel plate is cooled to 400-500 ℃ quickly, the components of the steel billet are uneven due to the addition of segregation elements and the existence of selective crystallization, the steel billet is insufficiently dissolved and homogenized in the heating and rolling process, and a carbon and manganese enrichment area is formed in the rolled steel plate to form a banded structure. Cannot be eliminated in a single austenitizing process, inherits to the final tissue. Therefore, the austenitizing process makes the alloy elements fully solid-dissolved, the crystal structure is rearranged and refined, and after rapid cooling, the fine original structure is obtained, and the segregation band is eliminated. The quenching temperature is 870-900 ℃, the heat preservation time is 0.5-1.0 min/mm, the following technological parameters are obtained through the adjustment of the water quantity and the water pressure of a quenching unit, and the water quantity is 100-120 m 3 The water pressure is 4-7 bar, the water ratio between the water supply and the water discharge is 1 (1.5-2.5), the swing watering is carried out, the roller speed is 0.5-1.0 m/s, the cooling speed is 20-30 ℃/s, the quenching is carried out rapidly to the room temperature, the quenching is carried out on the basis of crystal grains after the steel is normalized and refined, therefore, the original quenching structure is finer, the crystal grains are not grown up after the low-temperature and short-time heat preservation, the fine and uniform single bainitic structure is obtained after the rapid cooling, and the compactness of the structure is obviously improved.
However, the bainite after quenching has the characteristics of high hardness, poor plasticity, low stability and the like, so that the formed pipe is difficult to manufacture, and the high-temperature corrosion resistance cannot be ensured. Therefore, the structure is required to be further regulated and controlled through tempering heat treatment, the tempering temperature of 620-670 ℃ is designed, the heat preservation time is 2.0-4.0 min/mm, the bainite structure is fully recovered and softened after quenching in the process, stable alloy carbide is fully dispersed and separated out, finally, the tempered sorbite structure containing a nanoscale stable separation phase is obtained, the grain size range is less than or equal to 1.0 level, and the obtained steel plate has excellent strength, elongation after fracture, low hardness and multi-medium corrosion resistance.
[ example ]
The examples are provided to illustrate the present invention in detail, and are merely a general description of the present invention and are not intended to limit the present invention.
Table 1 example chemical composition, table 2 example process parameters, table 3 example texture end effect, table 4 example nonmetallic inclusion evaluation results.
TABLE 1 example chemical composition (wt.%)
Table 2 example process parameters
TABLE 3 example organization Property Final Effect
TABLE 4 evaluation results of nonmetallic inclusion in examples
The product of the invention has excellent mechanics, such as 395MPa is less than or equal to R el ≤415MPa、525MPa≤R m A is more than or equal to 555MPa and more than or equal to 35.0% and less than or equal to 38.0%; 370MPa of steel plate at 100 ℃ is less than or equal to R p0.2 R is not less than 405MPa and 240MPa of steel plate at 350 DEG C p0.2 ≤285MPa；(0℃)KV 2 Not less than 310J, HBW and not more than 175, 180 degrees in the transverse direction, no crack on the surface after cold bending of D=2a, not more than 1.5 of A+B+C+D, not more than 1.0 of crystal grain size range, and 0 level of banded segregation.
H-resistant inner wall of steel pipe 2 S、Cl - Single acidCorrosion of sexual medium or mixed medium and high CI resistance of outer wall - 、SO 2 Corrosion resistance to atmospheric agents in coastal industries. CSR expressed as 100℃HIC is 0% and CSR expressed as 350℃HIC is 0%; the SSCC sample loaded for 4320h at the pressure of 4MPa at 100 ℃ is not broken, and the SSCC sample loaded for 2160h at the pressure of 4MPa at 350 ℃ is not broken; the corrosion rate of the steel for the refining pipeline in the marine atmospheric environment is less than or equal to 2.0mm/a.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (4)
1. The preparation method of the steel for the coastal atmosphere refining pipeline is characterized in that the steel for the coastal atmosphere refining pipeline consists of the following chemical components in percentage by weight:
0.02% -0.06% of C, 0.10% -0.30% of Si, 0.40% -0.90% of Mn, less than or equal to 0.008% of P, less than or equal to 0.002% of S, 1.0% -1.5% of Ni, 0.40% -0.80% of Cu, 0.010% -0.015% of Ce, 0.50% -1.00% of Alt, wherein Mn+Cu=1.00% -1.60% and the balance of Fe and unavoidable impurities;
the process flow is as follows: molten iron pretreatment, converter dephosphorization, converter decarburization, external refining LF+RH, slab continuous casting, stacking slow cooling, casting blank cleaning, billet heating, finished product rolling, hot straightening, slow cooling, heat treatment, flaw detection, inspection and inspection, and the method specifically comprises the following steps:
1) Smelting process
Molten steel smelting is carried out in a converter, molten iron and scrap steel are adopted as smelting raw materials, and the content of the molten iron is controlled to be 60% -80%; dephosphorization and decarburization are separately smelted by adopting a converter, wherein dephosphorization oxygen blowing is controlled to be 8-10 min, decarburization oxygen blowing is controlled to be 9-12 min, and the mass fraction of phosphorus is finally reduced to be within 0.007%;
deep desulfurization treatment is carried out in an LF refining furnace, and the sulfur content is controlled below 0.002%;
2) Casting process
Breaking vacuum, casting, wherein the superheat degree is 20-30 ℃, the casting blank is put into a stack for slow cooling, the stack slow cooling time is 24-48 h, and the stack is released below 300 ℃;
3) Heating process
The heating temperature of the steel billet is controlled between 1180 and 1230 ℃, and the total heating time is 5.0 to 8.5 hours;
4) Controlled rolling process
The initial rolling temperature in the rough rolling stage is 1050-1150 ℃, the accumulated rolling reduction is more than or equal to 65%, and the thickness of the intermediate billet is 2.5-4.0 times of the finished steel plate; the initial rolling temperature of the finish rolling stage is 900-940 ℃, the final rolling temperature is 850-900 ℃, and the accumulated deformation rate is more than or equal to 60%;
5) Heat treatment process
Adopting a normalizing quick cooling, quenching and tempering heat treatment process; the normalizing temperature is 900-930 ℃, the temperature is kept at 1.0-2.0 min/mm, and the temperature is quickly cooled to 400-500 ℃; the quenching temperature is 870-900 ℃, and the heat preservation time is 0.5-1.0 min/mm; the tempering temperature is 620-670 ℃, and the heat preservation time is 2.0-4.0 min/mm;
controlling the water quantity and water pressure of a quenching unit, wherein the water quantity is 100-120 m 3 And (3) carrying out water pressure of 4-7 bar per minute and water supply/drain ratio of 1 (1.5-2.5), swinging and watering, wherein the roller speed is 0.5-1.0 m/s, the cooling speed is 20-30 ℃/s, and cooling to room temperature.
2. The method for preparing steel for a pipeline in coastal atmosphere refining according to claim 1, wherein 1) the method further comprises feeding Ce wires into the steel in the later period of refining, the wire feeding speed is 250-350 m/min, the wire feeding depth is 1.5-2.5 m below the slag layer, and the thickness of the generated slag layer is 50-80 mm;
the degassing is completed in an RH furnace, the net circulation time is 10-15 min, and the sedation time before casting is 3-5 min.
3. The method for preparing steel for a pipeline in an coastal atmosphere according to claim 1, wherein 2) casting is performed by a continuous casting machine after vacuum breaking.
4. The method for preparing steel for coastal atmosphere refining pipelines according to claim 1, wherein 4) the pipeline steel semi-finished product with the thickness of 20-50 mm is obtained by two-stage rolling and refining of rolled state structures.
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