CN115717214A - Steel for refining pipeline in coastal atmospheric environment and preparation method thereof - Google Patents
Steel for refining pipeline in coastal atmospheric environment and preparation method thereof Download PDFInfo
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Abstract
The invention relates to refiningThe technical field of steel for pipelines, in particular to steel for refining pipelines in coastal atmospheric environment and a preparation method thereof. On the basis of low C, si and Mn components, harmful elements P and S are strictly controlled, a tempered sorbite structure containing a nanoscale stable precipitated phase is obtained by combining a manufacturing process by adding Cu, ni, ce and Al alloy elements in a composite manner, and the structure has the characteristics of single, uniform, fine and compact structure, so that the comprehensive performance requirement of the pipeline steel plate is met. The mechanical property of the material is represented by R being more than or equal to 395MPa at normal temperature el ≤415MPa、525MPa≤R m Not more than 555MPa, 35.0% not more than A not more than 38.0%. The refining pipeline steel pipeline inner wall obtained by the invention has H resistance 2 S、Cl ‑ Single acid medium or mixed medium corrosion, high CI resistance of outer wall ‑ 、SO 2 And the coastal industry atmospheric medium is corroded, and the steel plate has excellent forming process performance and is suitable for being applied in the coastal atmospheric environment.
Description
Technical Field
The invention relates to the technical field of steel for a refining pipeline, in particular to steel for a refining pipeline in a coastal atmospheric environment and a preparation method thereof.
Background
Petroleum is an indispensable strategic resource as 'blood of modern industry', and with the development of global economy and the aggravation of regional unstable factors, the energy crisis of petroleum, natural gas and the like is increasingly prominent. As a petroleum energy resource consuming country in China, the dependence degree of crude oil on foreign matters exceeds 70 percent, and along with the continuous enhancement of the refining capacity in China, the dependence degree of crude oil on foreign matters is continuously increased.
The construction of the refinery base in coastal areas is beneficial to offshore import of crude oil, export sales of chemical products and operation safety. However, the high humidity and high salt environment in coastal areas presents a potential corrosion risk to petroleum refining equipment, especially process pipelines connecting various devices, for example, refinery pipelines with annual capacity of over ten million tons can reach the total length of dozens of kilometers, and various oil refining media are contacted in production. The inner wall of the pipeline is in a sulfide (in crude oil) containing and chlorine (in an organic compound containing assistant) containing corrosion environment, and the inner wall mainly generates hydrogen induced cracking and stress corrosion; the outer wall is in a coastal atmosphere corrosion environment, and the outer wall is mainly subjected to general corrosion. The corrosion of the inner wall and the outer wall of the refining pipeline provides great test for the safe operation of the pipeline, and the safety accidents caused by the corrosion leakage of the pipeline are all the more costly than the safety accidents caused by the corrosion leakage of the pipeline.
CN112111698A discloses 'steel for exposed pipelines of refineries and production method thereof, which has high corrosion resistance', although relating to the application of the refineries and pipelines, the application range is not clear, special corrosive medium and specific environment of coastal atmosphere are not related, and the applied corrosive environment is relatively loose. CN111471935B discloses 'HIC-resistant pipeline steel and a preparation method thereof', and relates to the HIC-resistant pipeline steel which mainly relates to long-distance transportation conditions and does not relate to marine atmospheric environment. In addition, the patent components and the process can meet the HIC resistance requirement, but cannot meet the complex environment requirements of ocean atmosphere and refining high-temperature media. CN103469094A discloses "a pipeline steel resisting chloride ion corrosion and a preparation method thereof", the corrosion medium involved is an environment containing chloride ions, and is used for underground pipeline engineering, and the chemical components and contents thereof 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, and the balance of Cr, fe and inevitable impurities, wherein the steel plate is controlled in rolling and cooling at the final state, and the steel plate component process meets the requirement of a chloride ion corrosion environment of an underground pipeline, but cannot meet the use requirement of a coastal atmospheric environment. CN 112795842B discloses 'steel for submarine fast-link pipeline and production method thereof', relating to a steel for pipeline used in ocean, which is different from the steel exposed in ocean atmosphere and high temperature corrosion environment in nature, and is different from the chemical composition and production process in nature.
In summary, the steel for pipelines according to the prior published documents has a single corrosion environment and no strict requirement on corrosion resistance, and cannot be applied to the dual medium corrosion of corrosive components in coastal industrial atmosphere and high and low temperature oil chemicals.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides the refining pipeline steel in the coastal atmospheric environment and the preparation method thereof, which are suitable for double-sided corrosion of coastal industrial atmosphere and internal industrial media and meet the requirement of offshore oil refining plants on the full-length cycle service of pipeline safety.
In order to achieve the purpose, the invention adopts the following technical scheme:
the steel for the refining pipeline in the coastal atmospheric environment comprises 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 inevitable impurities.
A preparation method of steel for a refining pipeline in a coastal atmospheric environment comprises the following process flows: molten iron pretreatment → converter dephosphorization → converter decarburization → external refining (LF + RH) → slab continuous casting → stacking slow cooling → billet cleaning → billet heating → finished product rolling → thermal straightening → slow cooling → heat treatment → flaw detection → inspection, the details are as follows:
1) Smelting process
Smelting molten steel in a converter, wherein molten iron and scrap steel are used as smelting raw materials, and the content of the molten iron is controlled to be 60-80%; the dephosphorization and the decarburization adopt a converter for separate smelting, wherein the dephosphorization oxygen blowing is controlled to be 8-10 min, the decarburization oxygen blowing is controlled to be 9-12 min, and finally the phosphorus mass fraction is reduced to be within 0.007%;
carrying out deep desulfurization treatment in an LF refining furnace, wherein the sulfur content is controlled to be below 0.002%;
feeding Ce filaments into the steel at the later stage of refining, wherein the filament feeding speed is 250-350 m/min, the filament feeding depth is 1.5-2.5 m below a slag layer, and the thickness of the generated slag layer is 50-80 mm;
degassing is finished in an RH furnace, the net cycle time is 10-15 min, and the sedation time before casting is 3-5 min.
2) Casting process
And casting by adopting a continuous casting machine after vacuum breaking, wherein the superheat degree is 20-30 ℃, the casting blank is inserted into a stack for slow cooling, the stack slow cooling time is 24-48h, and unstacking is carried out at the temperature below 300 ℃.
3) Heating process
The heating temperature of the steel billet is controlled to be 1180-1230 ℃, and the total heating time is 5.0-8.5 h.
4) Controlled cooling process
The initial rolling temperature in the rough rolling stage is 1050-1150 ℃, the cumulative reduction rate is more than or equal to 65%, and the thickness of the intermediate billet is 2.5-4.0 times of that of the finished steel plate; the initial rolling temperature in the finish rolling stage is 900-940 ℃, the finishing temperature is 850-900 ℃, and the accumulated deformation rate is more than or equal to 60%;
the rolled structure is rolled and refined in two stages to obtain a semi-finished product of the pipeline steel with the thickness of 20-50 mm.
5) Heat treatment Process
Adopting a normalizing quick cooling, quenching and tempering heat treatment process; normalizing at 900-930 deg.c, maintaining for 1.0-2.0 min/mm and fast cooling to 400-500 deg.c; 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 the quenching unit, wherein the water quantity is 100-120 m 3 Min, water pressure of 4-7 bar, water feeding and discharging ratio of 1 (1.5-2.5), swinging and watering, rolling 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 steel for the refining and chemical pipeline in the aspects of mechanical property, service performance and the like in the aspect of component design. In order to ensure the strength of the matrix of the pipeline steel at room temperature and high temperature, the solid solution strengthening effect is achieved by adding C, mn and Ni alloy elements. In addition, the corrosion resistance of the inner and outer surfaces of the pipeline steel to different mediums in the service process is completed by adding the single or synergistic action of Cu, ni and Alt elements, wherein the corrosion resistance is improved by adding more than 1 percent of Ni; more than 0.4 percent of Cu forms a corrosion-resistant protective layer and has synergistic effect with Mn to form oxides to fill cracks and holes, thereby playing a corrosion-resistant role; more than 0.5 percent of Al is added to play a role in passivation and improve the acid corrosion resistance; the Ce element is another important element in the invention, not only changes the form of inclusions in the smelting process, but also has certain hydrogen capturing function when purifying molten steel, and improves the hydrogen induced cracking performance, thereby improving the corrosion resistance.
2. The invention relates to the matching of alloy elements and a production process. The two-stage controlled rolling ensures that the accumulated reduction rate of rough rolling is more than 60 percent, the finish rolling temperature is 850-900 ℃, the rolling structure is fully refined, and the foundation is laid for the subsequent heat treatment. The heat treatment adopts multi-process treatment of normalizing pretreatment, quenching and tempering, so that a single fine compact structure without segregation can be obtained, wherein the normalizing pretreatment can eliminate a banded structure caused by carbon and manganese of a rolled steel plate. Then a fine single structure is obtained on the basis of normalizing refined grains through quenching treatment, and the compactness is improved. Due to the requirement of the forming performance of the pipe, further tempering and softening are needed to obtain good plasticity and toughness.
3. Through the implementation of the components and the process, the product has excellent mechanical and corrosion resistance, such as R is more than or equal to 395MPa el ≤415MPa、525MPa≤R m Not more than 555MPa, 35.0% not more than A not more than 38.0%; r of the steel plate is more than or equal to 370MPa at 100 DEG C p0.2 Not less than 405MPa, and not less than 240MPa and not more than R of the steel plate at 350 DEG C p0.2 No crack on the cold-bent surface (0 ℃) of less than or equal to 285MPa, 180 degrees in the transverse direction and D =2a 2 310J or more, 165 or less HBW, 1.0 or less A + B + C + D, 1.0 or less grain size range difference and 0 grade of zonal segregation. H-resistant inner wall of steel pipeline 2 S、Cl - Single acid medium or mixed medium corrosion, high CI resistance of outer wall - 、SO 2 And the corrosion resistance of the coastal industry atmosphere medium. CSR at 100 ℃ HIC is 0%, CSR at 350 ℃ HIC is 0%; the SSCC sample loaded for 4320h under the pressure of 4MPa at 100 ℃ is not broken, and the SSCC sample loaded for 2160h under 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 refining pipeline in a coastal atmospheric environment and a preparation method thereof. Those skilled in the art can modify the process parameters appropriately in view of the disclosure herein. It is expressly intended that all such similar substitutes and modifications which would be obvious to one skilled in the art are deemed to be included in the invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those of ordinary skill in the art that variations and modifications in the methods and applications described herein, as well as other suitable variations and combinations, may be made to implement and use the techniques of this invention without departing from the spirit and scope of the invention.
The steel for the refining pipeline in the coastal atmospheric environment comprises 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 inevitable impurities.
The reasons for limiting the amounts of the chemical elements C, si, mn, P, S, ni, cu, ce, and Alt in the steel sheet are as follows:
c: the high-carbon steel 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 carbide segregation tendency, causes the difference between the hardness of a segregation zone and the surrounding structure, and causes the HIC resistance of the steel to be reduced, and the excessive carbon content is not beneficial to the welding performance of the pipeline and the corrosion resistance of a welding seam, so the C content range is set to be 0.02-0.06 percent.
Mn: a certain amount of Mn plays a role in solid solution strengthening of a pipeline base body, segregation caused by excessive Mn easily generates high-strength and low-toughness micro-metallographic structures such as martensite and bainite in a welding seam and a heat affected zone, extremely high hardness is shown, the cracking tendency of the structures after welding is increased, and the SSC resistance of the pipeline is extremely unfavorable, so the upper limit of Mn needs to be controlled, and therefore the Mn content range is set to be 0.40-0.90%.
Si: in addition, when the content of silicon is more than 1%, a compact silicon dioxide protective film can be formed, and the corrosion resistance is improved. However, when the Si element content is too high, the hardness of the weld and the heat affected zone is high, and the Si element is likely to segregate at the grain boundaries, thus promoting the formation of intergranular cracks and increasing the corrosion risk of the pipe, so the Si content is set in the range of 0.10% to 0.30% in the present invention.
P: segregation is easy to occur in the austenite crystal boundary, so that the bonding force between atoms on the crystal 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 band-shaped distribution of MnS and FeS nonmetallic inclusion are formed in the steel, so that the local microstructure is loose, and the sensibility of HIC or SOHIC under the wet hydrogen sulfide environment is increased, therefore, the S content range is set to be less than or equal to 0.002 percent.
Ni: the Ni with a certain content can make the self-corrosion potential of the steel exposed in the ocean atmosphere shift forward, and the stability of the matrix is increased. 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 rust layer, and prevent chloride ions in humid marine atmosphere from permeating, so that the rust layer has protection. However, since the 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 hydrogen content in the steel in the wet state 2 S resistance in corrosive environments, therefore Wet H 2 The Ni content of the steel in the S environment is not suitable to be too high. Therefore, the Ni content range is set to be 1.0-1.5%.
Cu: cu can accelerate the recombination velocity of hydrogen atoms, further reduce the activity of hydrogen and improve the corrosion resistance of the material in an acid 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 to reduce corrosion rate and hydrogen absorption rate, wherein the Cu is internally prevented from HCl and H 2 S、H 2 When the medium is corroded, the corrosion of chloride ions in coastal environment is prevented, but the toughness of the steel is reduced by excessive Cu, so that the Cu content is set to be 0.40-0.80 percent.
The marine industrial atmosphere corrosion resistance effect is achieved when the Cu and Mn are added in a composite manner to reach more than 1 percentMore remarkably, cuFeO is arranged inside the Cu-Mn rust layer 2 And Mn 3 O 4 The oxide in the form of the oxide can well fill cracks and holes, so that the rust layer is more compact, thereby preventing chloride ions from permeating into a matrix and improving corrosion resistance, and therefore, the range of Mn + Cu in the invention is limited to 1.00-1.60%.
Ce: the rare earth has strong affinity with harmful elements such as oxygen, sulfur, phosphorus, hydrogen, nitrogen and the like in the molten steel, and after a stable rare earth compound is formed, the density of the rare earth compound is less than that of the molten steel, the rare earth compound floats upwards to form furnace slag, and the effect of purifying the molten steel is achieved. In addition, the shape of the inclusions is controlled, long manganese sulfide inclusions are changed into spherical sulfides or oxides, the shape of the sulfides is completely controlled, and the anisotropy of the steel is improved. The rare earth has certain solid melting degree in steel, segregation of sulfur, phosphorus and other low-melting-point inclusions at grain boundaries can be inhibited by segregation of the rare earth at the grain boundaries, high-melting-point compounds are formed with the inclusions, harmful effects of the low-melting-point inclusions are reduced, the tendency of formation and expansion of intergranular cracks is reduced, and the high-temperature plasticity and the corrosion resistance of steel are improved. The microalloying effect of the Ce element is mainly embodied in that the segregation of the rare earth at a grain boundary interacts with other elements to cause the change of the structure, chemical components and energy of the grain boundary, and simultaneously has certain effects on the diffusion of other elements and the quantity and growth speed of the nucleation number of a new phase, so that the structure and performance of 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 can be improved, and the corrosion resistance of the steel can be improved. Dispersion hardening by blowing rare earth oxides (CeO) into the 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 point, increase nucleation number, lower crystal grain, and disperse CeO 2 The particle can improve the barrier effect of the crystal boundary on dislocation movement. However, ce belongs to rare earth strategic resources and is not suitable to be added excessively, so that the content range of Ce is set to be 0.010-0.015 percent.
Al: the aluminum mainly plays a role in deoxidizing and refining grains in the steel. In addition, when the aluminum content reaches a certain value, the surface of the steel is passivated, the steel has corrosion resistance in oxidizing acid, and the corrosion resistance to hydrogen sulfide is improved. Therefore, the invention sets the Alt content range to be 0.50-1.00%.
In order to obtain the comprehensive mechanical property and corrosion resistance of the steel plate, necessary alloy elements are added, and a single and stable tissue structure is obtained through the organic combination of production processes.
The manufacturing method of the steel for the refining pipeline in the coastal atmospheric environment comprises the following steps:
1. the process flow is as follows: the method comprises the steps of molten iron pretreatment, converter dephosphorization, converter decarburization, external refining (LF + RH), slab continuous casting, stacking and slow cooling, casting blank cleaning, billet heating, finished product rolling, thermal straightening, slow cooling, thermal treatment, flaw detection, inspection and inspection.
2. The smelting process comprises the following steps: smelting molten steel in a converter, wherein molten iron and high-quality scrap steel are used as smelting raw materials, the content of the molten iron is controlled to be 60-80%, and simultaneously, in order to effectively reduce the content of harmful element P, dephosphorization and decarburization are separately smelted by the converter, wherein dephosphorization oxygen blowing is controlled to be 8-10 min, decarburization oxygen blowing is controlled to be 9-12 min, and finally the phosphorus mass fraction is reduced to be within 0.007%; deep desulfurization treatment is carried out in an LF refining furnace, and the sulfur content is controlled to be below 0.002%. Feeding Ce filaments into the steel at the later stage of refining, wherein the filament feeding speed is 250-350 m/min, and the filament feeding depth is 1.5-2.5 m below a slag layer, the treatment changes the form of non-metallic inclusions, forms fine particles of sulfide and oxide non-metallic inclusions of Ce, increases the steel billet equiaxial rate, purifies the steel, improves the purity and the hydrogen resistance of the steel, and the thickness of the generated slag layer is 50-80 mm; degassing is finished in an RH furnace, the net cycle time is 10-15 min, and the sedation time before casting is 3-5 min.
3. The casting process comprises the following steps: and casting by adopting a continuous casting machine after vacuum breaking, wherein the superheat degree is 20-30 ℃, the casting blank is inserted into a stack for slow cooling, the stack slow cooling time is 24-48h, and the stack is unstacked below 300 ℃, so that cracks in the casting blank caused by quenching are prevented.
4. And (3) heating process: by controlling the heating process of the steel billet, the alloy elements are ensured to be fully dissolved in the solid, the growth of original austenite grains is effectively inhibited, the heating temperature of the steel billet is controlled to be 1180-1230 ℃, and the total heating time is 5.0-8.5 h.
5. Controlling a controlled cooling process: the initial rolling temperature in the rough rolling stage is 1050-1150 ℃, the cumulative reduction rate is more than or equal to 65%, and the thickness of the intermediate billet is 2.5-4.0 times of that of the finished steel plate; the initial rolling temperature of the finish rolling stage is 900-940 ℃, the finish rolling temperature is 850-900 ℃, and the accumulated deformation rate is more than or equal to 60%. The rolled structure is rolled and refined in two stages to obtain a semi-finished product of the pipeline steel with the thickness of 20-50 mm.
6. A heat treatment process: the steel is influenced by tissue inheritance, and the rolled tissue is influenced by smelting, so that the defects of certain segregation, chain-shaped distribution of carbide and the like exist, and the steel is extremely unfavorable for obtaining excellent comprehensive mechanical properties of the pipeline steel, particularly for the corrosion resistance of inner and outer walls to different media. Therefore, the structure regulation needs to be carried out through heat treatment, a single uniform, segregation-free and compact stable structure is obtained, and the final beneficial effect of the invention is achieved. Cannot be eliminated in a single austenitizing process and is passed on to the final tissue. Therefore, austenitizing the alloy leads alloy elements to be fully dissolved, the crystal structure is rearranged and refined, and after rapid cooling, a fine original structure is obtained, and the segregation zone is eliminated. The quenching temperature is designed to be 870-900 ℃, the heat preservation time is 0.5-1.0 min/mm, and the following process parameters are obtained by adjusting the water quantity and the water pressure of a quenching unit, wherein the water quantity is 100-120 m 3 The water pressure is 4-7 bar, the water-feeding and water-discharging ratio is 1 (1.5-2.5), the water-swinging device is used for watering, the roller speed is 0.5-1.0 m/s, the cooling speed is 20-30 ℃/s, the steel is quickly cooled to room temperature, because the quenching is carried out on the basis of the crystal grains after the steel is normalized and refined, the quenching original structure is fine, the crystal grains are not grown after the low-temperature short-time heat preservation, and a fine and uniform single bainite group is obtained after the steel is quickly cooledThe compactness of the tissue is obviously improved.
However, as the bainite after quenching is characterized by high hardness, poor plasticity, low stability and the like, the molding and the pipe manufacturing are difficult, and the high-temperature corrosion resistance can not be ensured. Therefore, the structure needs 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 obtained by quenching under the process is fully recovered and softened, the stable alloy carbide is fully dispersed and precipitated, the tempered sorbite structure containing the nanoscale stable precipitated phase is finally obtained, the grain size range is less than or equal to 1.0 grade, and the obtained steel plate has excellent strength, elongation after fracture, low hardness and multi-medium corrosion resistance.
[ examples ] A method for producing a compound
The examples are intended to be illustrative of the present disclosure, and are intended to be a general description of the present disclosure, and not to be limiting.
Table 1 chemical components of examples, table 2 process parameters of examples, table 3 final effects of texture properties of examples, and table 4 evaluation results of nonmetallic inclusions of examples.
Table 1 examples chemical composition (wt%)
Table 2 example process parameters
Table 3 example texture Properties end Effect
TABLE 4 evaluation results of nonmetallic inclusions in examples
The product of the invention has excellent mechanics, such as R is more than or equal to 395MPa el ≤415MPa、525MPa≤R m Not more than 555MPa, 35.0% not more than A not more than 38.0%; r of the steel plate is more than or equal to 370MPa at 100 DEG C p0.2 R is less than or equal to 405MPa and 240MPa of steel plate at 350 DEG C p0.2 ≤285MPa；(0℃)KV 2 310J or more, 175 or less of HBW, 180 degrees in the transverse direction, no crack on the surface after cold bending with D =2a, 1.5 or less of A + B + C + D, 1.0 or less of grain size range and 0-grade of band segregation.
H-resistant inner wall of steel pipeline 2 S、Cl - Single acid medium or mixed medium corrosion, high CI resistance of outer wall - 、SO 2 And the corrosion resistance of the atmospheric medium in coastal industry. CSR expressed as HIC at 100 ℃ is 0%, CSR expressed as HIC at 350 ℃ is 0%; the SSCC sample loaded for 4320h under the pressure of 4MPa at 100 ℃ does not break, and the SSCC sample loaded for 2160h under the pressure of 4MPa at 350 ℃ does not break; 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 above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered as the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.
Claims (6)
1. The steel for the refining pipeline in the coastal atmospheric environment is characterized by comprising 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 Ni1, 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 inevitable impurities.
2. A preparation method of the steel for the refining pipeline in the coastal atmospheric environment as defined in claim 1 is characterized by comprising the following process flows: molten iron pretreatment → converter dephosphorization → converter decarburization → external refining (LF + RH) → slab continuous casting → stacking slow cooling → billet cleaning → billet heating → finished product rolling → thermal straightening → slow cooling → heat treatment → flaw detection → inspection, the details are as follows:
1) Smelting process
Molten steel smelting is carried out in a converter, molten iron and scrap steel are used as smelting raw materials, and the content of the molten iron is controlled to be 60-80%; the dephosphorization and the decarburization are separately smelted by adopting a converter, wherein the dephosphorization oxygen blowing is controlled to be 8-10 min, the decarburization oxygen blowing is controlled to be 9-12 min, and finally the phosphorus mass fraction is reduced to be within 0.007%;
carrying out deep desulfurization treatment in an LF refining furnace, wherein the sulfur content is controlled to be below 0.002%;
2) Casting process
Casting after vacuum breaking, wherein the superheat degree is 20-30 ℃, the casting blank is inserted into a stack for slow cooling, the stack slow cooling time is 24-48h, and unstacking is carried out at the temperature below 300 ℃;
3) Heating process
Controlling the heating temperature of the steel billet to be 1180-1230 ℃, and the total heating time to be 5.0-8.5 h;
4) Controlled cooling process
The initial rolling temperature in the rough rolling stage is 1050-1150 ℃, the cumulative reduction rate is more than or equal to 65%, and the thickness of the intermediate billet is 2.5-4.0 times of that of the finished steel plate; the initial rolling temperature in the finish rolling stage is 900-940 ℃, the finishing temperature is 850-900 ℃, and the accumulated deformation rate is more than or equal to 60%;
5) Heat treatment Process
Adopting normalizing fast cooling, quenching and tempering heat treatment processes; normalizing at 900-930 deg.c, maintaining for 1.0-2.0 min/mm and fast cooling to 400-500 deg.c; 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.
3. The preparation method of the steel for the refining pipeline in the coastal atmospheric environment according to claim 2, characterized in that 1) the method further comprises the step of feeding Ce wires into the steel at 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 a slag layer, and the thickness of the generated slag layer is 50-80 mm;
degassing is finished in an RH furnace, the net cycle time is 10-15 min, and the sedation time before casting is 3-5 min.
4. The method for preparing the steel for the refining pipeline in the coastal atmospheric environment according to claim 2, wherein the steel for the refining pipeline in the coastal atmospheric environment is cast by a continuous casting machine after vacuum breaking in the step 2).
5. The method for preparing the steel for the refining pipeline in the coastal atmospheric environment as claimed in claim 2, wherein in the step 4), the rolled structure is refined by two-stage rolling to obtain a pipeline steel semi-finished product with the thickness of 20-50 mm.
6. The method for preparing the steel for the refining pipeline in the coastal atmospheric environment as claimed in claim 2, wherein 5) the water amount and the water pressure of the quenching unit are controlled, and the water amount is 100-120 m 3 Min, water pressure of 4-7 bar, water feeding and discharging ratio of 1 (1.5-2.5), swinging and watering, rolling speed of 0.5-1.0 m/s, cooling speed of 20-30 ℃/s, and cooling to room temperature.
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Cited By (1)
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| CN116334493A (en) * | 2023-03-30 | 2023-06-27 | 包头钢铁（集团）有限责任公司 | 620 MPa-grade high-strength steel with welding heat affected zone at-60 ℃ and impact energy greater than 150J and preparation method thereof |
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| CN116334493A (en) * | 2023-03-30 | 2023-06-27 | 包头钢铁（集团）有限责任公司 | 620 MPa-grade high-strength steel with welding heat affected zone at-60 ℃ and impact energy greater than 150J and preparation method thereof |
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