CN115652208A - 450 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel and manufacturing method thereof - Google Patents
450 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel and manufacturing method thereof Download PDFInfo
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Abstract
The invention provides 450 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel and a manufacturing method thereof, wherein the steel comprises the following components in percentage by weight: c:0.062% -0.083%, si: 0.21-0.41%, mn:0.48% -0.79%, P: less than or equal to 0.017 percent, S: less than or equal to 0.0050%, cr:0.72% -0.97%, ni:0.17% -0.28%, cu: 0.11-0.21%, 0.072-0.102% of Sb, 0.037-0.058% of Ti, 0.29-0.43% of Sn, als:0.013% -0.036%, ce:0.026% -0.036%, O: the balance of Fe and inevitable impurities is less than or equal to 4.5 ppm; the manufacturing method comprises smelting, continuous casting, casting blank heating, rolling, laminar cooling and coiling; the acid-resistant rare earth steel plate has simple manufacturing process, excellent comprehensive performance, especially acid corrosion resistance, and can be widely applied to equipment manufacturing in a flue gas treatment system taking heavy oil or coal as a main raw material.
Description
Technical Field
The invention belongs to the field of metal materials, and particularly relates to 450 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel and a manufacturing method thereof.
Background
At present, the problem of sulfuric acid dew point corrosion commonly exists in flue gas systems which take heavy oil or coal as main fuel in a plurality of industrial fields such as electric power, metallurgy, petrochemical industry and the like. In particular, in some devices such as boiler preheaters and economizer equipment, air preheater heat exchange elements, dust collectors, flues, chimneys, etc., sulfur compounds (SO) are catalytically formed due to their relatively high sulfur content in flue gas 3 ) Then the sulfuric acid vapor is combined with the water vapor in the flue gas to form sulfuric acid vapor which is condensed into sulfuric acid on the metal wall below the dew point temperature of the sulfuric acid, and further the problem of acid corrosion to equipment is caused. In order to reduce the maintenance cost and prolong the safe service life of a steel structural member, the development of acid-resistant steel with excellent sulfuric acid dew point corrosion resistance is urgently needed.
The invention discloses a rare earth alloy steel (publication No. CN 1386886A) with sulfuric acid dew point corrosion resistance, which comprises the following components as a reinforcing element Cu-W-Sn-Re-Sb-Mo: c: less than or equal to 0.15 percent, si:0.15% -1.20%, mn:0.30% -1.50%, cu:0.20% -0.80%, W:0.10% -0.60%, mo: 0.10-0.50%, sn 0.05-0.30%, sb 0.05-0.30%, RE less than or equal to 0.50%, S: less than or equal to 0.035%, P: less than or equal to 0.035%, and the balance of Fe and impurities; the addition of noble metal W will increase the cost of alloy.
The invention discloses a rare earth sulfuric acid dew point corrosion resistant steel and a preparation method thereof (publication number: CN 111206178A), and the technical scheme comprises the following steel components: c:0.07 to 0.11%, si: 0.20-0.50%, mn:0.40% -0.65%, P: less than or equal to 0.020%, S: not more than 0.035%, al 0.010% -0.060%, cr 0.85% -1.10%, cu: 0.30-0.45%, sb 0.04-0.10%, ni:0.15% to 0.35% re:0.001 to 0.010 percent, and the balance of Fe and impurities. In the aspect of performance inspection, the corrosion resistance condition of the test steel is not given, the corrosion resistance effect is unknown, the invention explains that the method of smelting-rolling in a laboratory is a method for producing the steel plate by adopting a die casting process, but the die casting process cannot be used for producing the steel plate in a large scale in the actual production on site.
The invention discloses a rare earth addition optimization control method of rare earth weathering steel (publication No. CN 1475580A). In the technical scheme, 0.010-0.030 percent of rare earth is added into the weathering steel; although the corrosion resistance of the product is improved by adding Cu and Re, the phenomenon of copper brittleness of the steel plate is easy to occur by independently adding Cu, and the difficulty of a hot rolling process is increased. Meanwhile, the steel-making and rolling process, especially the rare earth adding process, is not clear. In addition, the mechanical property indexes of the steel are not explicitly described.
The invention relates to a coating-free weathering steel containing rare earth elements and a preparation method thereof (publication No. CN 109252092A), and the steel comprises the following components in the technical scheme: c:0.03% -0.09%, si: 0.10-0.30%, mn:1.00% -1.50%, P:0.005% -0.015%, S: not more than 0.005%, cr 0.35-0.70%, ni: 0.25-0.55%, cu:0.25% -0.55%, mo: 0.03-0.25%, re: 0.005-0.060%, nb 0.015-0.040%, ti 0.008-0.025%, al 0.015-0.040%, ca: 0.003-0.018 percent of Fe and impurities in balance. The corrosion resistance of the steel is only evaluated by an atmospheric corrosion resistance index I, the index is deduced according to a theoretical formula and is not verified by a corrosion test, so that the actual corrosion resistance effect of the steel is unknown; in addition, the invention also adopts a tempering process to improve the mechanical property of the steel, so that the process is complicated, and the production cost is increased.
The invention discloses rare earth low alloy steel resisting high-temperature sulfuric acid dew point corrosion, which comprises the following components in part by weight: the technical scheme disclosed in CN 101892438A is that corrosion resistant elements such as Cr + Cu + Ni + RE are added to improve the sulfuric acid dew point corrosion resistance of the product, but the disadvantages are that it adopts higher Cu content and higher production cost. The invention only emphasizes the influence on the corrosion resistance, and does not give the comprehensive mechanical condition of the steel. In addition, relevant steel making and rolling processes, particularly rare earth adding processes during smelting, are not provided. Because the addition method and the yield of the rare earth are difficult problems in the actual smelting process.
Disclosure of Invention
The invention aims to overcome the problems and the defects and provide the 450 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel which is suitable for being used in the acid industrial corrosion environment and the manufacturing method thereof, wherein the steel plate not only has good and stable mechanical properties, but also has higher sulfuric acid dew point corrosion resistance.
The purpose of the invention is realized as follows:
the 450 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel comprises the following components in percentage by weight: c:0.062% -0.083%, si: 0.21-0.41%, mn:0.48% -0.79%, P: less than or equal to 0.017 percent, S: less than or equal to 0.0050%, cr:0.72% -0.97%, ni:0.17% -0.28%, cu: 0.11-0.21%, 0.072-0.102% of Sb, 0.037-0.058% of Ti, 0.29-0.43% of Sn, als:0.013% -0.036%, ce:0.026% -0.036%, O: less than or equal to 4.5ppm and the balance of Fe and inevitable impurities.
Furthermore, the microstructure of the rare earth steel is ferrite, pearlite and bainite, wherein the volume percentage of the ferrite is 42.7-45.4%, the volume percentage of the pearlite is 32.4-37.1%,
further, it is characterized bySn/Ce in the rare earth steel is 11.1-12.2, and 20-25 nm Ce is precipitated from the rare earth steel along a grain boundary 5 Sn 3 。
Furthermore, the yield strength of the rare earth steel is more than 450MPa, the tensile strength is 589-626 MPa, and the elongation is more than 27%.
The invention has the following design reasons:
c: the increase in the content of C, one of the main reinforcing elements, is advantageous for improving the strength and hardness of the steel sheet, but a large amount of C adversely affects the properties of the steel sheet, such as impact toughness and plasticity. The content of C in the invention is limited to 0.062% -0.083%.
Si: the strong deoxidizing element in the steel-making process and the solid solution strengthening element can improve the yield strength of the steel plate, but the excessive content of the strong deoxidizing element not only reduces the welding performance of the steel plate, but also forms a layer of red iron oxide scale which is difficult to remove on the rolled steel plate. The content of Si is limited to 0.21-0.41 percent in the invention.
Mn: the steel mainly has a solid solution strengthening effect, and the tensile strength of the steel plate can be improved. However, too high Mn content causes segregation and deteriorates the weldability and formability of the steel. Therefore, the content of Mn in the invention is controlled to be 0.48-0.79%.
P: although one of the alloying elements has a solid solution strengthening effect and remarkably improves the corrosion resistance, segregation is likely to occur at grain boundaries at a high content to degrade the weldability, plasticity and toughness of the steel sheet. The content of the steel is controlled to be less than 0.017 percent.
S: are harmful impurity elements, easily form defects such as segregation and inclusion, and deteriorate the impact toughness and hot workability of the steel sheet. Therefore, in the present invention, the S content should be controlled to 0.0050% or less.
Cr: a compact oxide film Cr2O3 is easily formed on the surface of the steel plate, so that the adhesive force of the rust layer and a matrix can be improved, and the passivation capability of the steel is improved. In addition, the improvement of the Cr element is also beneficial to refining alpha-FeOOH, so that the strength and the toughness of the steel plate can be improved. However, if the content is too high, the weldability of the steel sheet deteriorates. Therefore, the content of Cr in the present invention is controlled to 0.72% to 0.97%.
Cu: the corrosion-resistant steel plate is an essential element for improving the corrosion resistance of the steel plate, and can play a role in solid solution strengthening to improve the strength of the steel plate. Meanwhile, in consideration of cost, the content range of the invention is limited to 0.11-0.21%.
Ni: the copper-based alloy is one of elements for improving the strength and the impact toughness of the steel plate, and when the copper-based alloy is reasonably matched with Cu for use, the problem of copper brittleness of the steel plate can be improved, and the corrosion resistance of the steel plate can be obviously improved. However, ni is a noble metal element, and the addition amount of Ni in the present invention is 0.17% to 0.28% from the viewpoint of cost control.
Ti is one of the alloy elements playing a strengthening role. The Ti compound in the steel can effectively prevent austenite grains from growing up in the heating process, and plays a role in strengthening fine grains, and TiC separated out in the cooling process also plays a role in strengthening precipitation. Meanwhile, the welding performance of the steel plate can be improved. The range of the invention is limited to 0.037% -0.058%.
Effective elements for improving corrosion resistance, plays a role in catalyzing the enrichment of corrosion-resistant elements, promotes the enrichment of corrosion-resistant elements such as Cu, cr and the like on the surface of a rust layer, so that a compact oxide film containing the corrosion-resistant elements such as Sb, cr, cu and the like and having a remarkable corrosion-resistant effect is formed on the surface of the steel plate, the acid corrosion resistance of the steel plate can be effectively improved, but the catalytic effect is not obvious when the content of the oxide film is low, so that the content of the oxide film is limited to be 0.072-0.102 percent.
Sn, which is generally a residual impurity element in steel, is easily segregated at grain boundaries. However, in the present invention, sn is an effective element for improving the acid corrosion resistance and for strengthening precipitation. When the corrosion-resistant alloy is matched with Cr, cu and Sb elements for addition, the enrichment of each corrosion-resistant element on the surface of a rust layer is promoted, and the generated stable SnO 2 The corrosion product protective film can effectively improve the acid corrosion resistance of the steel plate. When the Ce is added in a matched way, the Ce-Sn compound Ce with high melting point and 20-25 nm can be generated by the interaction of the Ce and the Ce 5 Sn 3 And the steel plate is often precipitated along the grain boundary in the cooling process of the steel plate, so that a good precipitation strengthening effect is achieved. In the present invention, the Sn/Ce value is 11.1 to 12.2, and the Sn content is set to 0.29%～0.43％。
And Als: the main deoxidizing elements are beneficial to refining crystal grains and can improve the mechanical property of the steel plate, and the range of the deoxidizing elements is limited to 0.013-0.036%.
Ce: ce in the present invention has the following effects: (1) Change of Sn and Al 2 O 3 And the forms and types of inclusions such as MnS and the like obviously improve the plasticity and toughness of the steel, and particularly can reduce the anisotropy of impact property. (2) Due to the change of the form of the inclusions, the potential difference between the inclusions and the matrix is reduced, the tendency of electrochemical corrosion in steel is reduced, and the corrosion resistance of the steel plate is effectively improved; (3) Has stronger affinity with Sn with low melting point, can obviously inhibit the segregation of Sn at grain boundary, and forms a high-melting-point nanoscale Ce-Sn compound with Sn at the grain boundary to improve the strength of the steel plate. (4) The dispersed CeO particles are gathered at the grain boundary to obviously hinder the movement of dislocation, thereby improving the strength of the steel plate. However, because the lower Ce content in the steel cannot play a role in corrosion resistance, in order to ensure that the added Ce can fully play the role, the Ce content in the steel is controlled to be 0.026% -0.036%.
O: as harmful and strong oxidizing elements in steel, the rare earth oxide is easy to react with added rare earth elements to form corresponding rare earth oxides. The high content of O can cause a large amount of rare earth inclusions to be formed in the molten steel to influence the fluidity of the molten steel, and in serious cases, the inclusions can block a water gap to cause flocculation. Therefore, the free O content in the steel of the present invention should be controlled to 4.5ppm or less.
The second technical scheme of the invention provides a manufacturing method of 450 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel, which comprises smelting, continuous casting, casting blank heating, rolling, laminar cooling and coiling;
smelting:
(1) Pre-desulphurisation of molten iron
In order to improve the smelting efficiency of the converter, the desulfurization powder is sprayed into a torpedo tank car filled with molten iron for desulfurization pretreatment, so that S is less than or equal to 0.003 percent, and solid slag such as CaS, mgS and the like needs to be thoroughly removed.
(2) Converter steelmaking:
the furnace top and bottom combined blowing process is adopted, the tapping temperature of the converter is 1674-1694 ℃, and the final slag alkalinity R is more than or equal to 3.7. Argon blowing is needed in the whole tapping process, 1.53-1.69 kg/ton molten steel modifier is needed to modify the top slag after tapping, and the argon blowing time after the addition is ensured to be more than or equal to 4min.
(3) LF + RH external refining
Heating the LF furnace for 28-38 min, heating to 1607 deg.C, stirring for 7-11 min, and treating with calcium to control the calcium content in molten steel to 0.004%.
And then the ladle is carried out and poured into an RH furnace, the free O content in the steel is controlled below 6ppm, the furnace temperature is controlled above 1593 ℃, the mass fraction of Ce in the Fe-Ce rare earth alloy added into the RH furnace is 19.4-20.6%, the adding amount of the Ce is 2.26-3.1 kg/ton of molten steel, then argon weak blowing is carried out to promote impurities in the molten steel to float, the weak blowing time is 4.2-5.2 min, and the ladle is carried out and loaded on a machine.
Continuous casting: the dynamic soft reduction technology is adopted in the continuous casting process, the soft reduction amount is controlled to be between 3.2 and 7.2mm, the center porosity and segregation are strictly controlled, the internal quality of a casting blank is ensured, and the thickness specification of the continuous casting blank is 230 to 250mm. In addition, the molten steel is protected by the protective slag in the whole process so as to prevent oxygen from entering for secondary oxidation, and the thickness of a slag layer is controlled to be more than 18 mm. In order to reduce the steel flocculation of the nozzle and ensure the smooth casting of the rare earth steel, the temperature of the tundish is controlled to be 1544-1564 ℃, and the blank drawing speed is 1.27-1.37 m/min.
Heating a casting blank: in order to ensure that all elements can be fully dissolved in solid solution during heating and avoid unnecessary billet oxidation loss caused by overhigh heating temperature, the temperature of a casting blank soaking section is controlled between 1227 and 1249 ℃, the total furnace time is 192 to 209min, and the heat preservation time of the soaking section is 37 to 49min.
Rolling: the two-stage controlled rolling process is adopted, the rough rolling outlet temperature is 1086-1106 ℃, and the thickness of the obtained intermediate billet is more than 3 times of that of the finished product. The initial rolling temperature of the finish rolling is 1077-1097 ℃, and the final rolling temperature of the finish rolling is 871-893 ℃.
Laminar cooling and coiling: and carrying out laminar cooling on the rolled steel plate, wherein the laminar cooling adopts rear-section centralized cooling. Cooling to 617-636 ℃ at the cooling rate of 16-26 ℃/s for coiling, and cooling to room temperature after coiling.
The invention has the beneficial effects that:
the invention adds Fe-Ce rare earth alloy into steel by adopting a new adding process during smelting, thereby not only ensuring that rare earth can be uniformly and stably retained in the steel, but also obtaining higher rare earth yield which is more than 53 percent, and providing the rare earth steel for resisting the dew point corrosion of sulfuric acid with the yield strength of more than 450 MPa. The yield strength of the steel of the embodiment of the invention is more than 450MPa, the tensile strength is between 589 MPa and 626MPa, the elongation is more than 27 percent, the average value of the impact energy at minus 40 ℃ is not less than 84J, the anisotropy of the impact property can be particularly reduced, the difference between the average values of the transverse impact energy and the longitudinal impact energy is not more than 3J, the steel plate has excellent comprehensive mechanical property, and the corrosion rate of the steel plate is 5.3-6.8 mg/cm 2 H, the corrosion rate of the alloy relative to Q345B is 16.45-18.27%. The acid-resistant rare earth steel plate has simple manufacturing process, excellent comprehensive performance, especially acid corrosion resistance, and can be widely applied to equipment manufacturing in a flue gas treatment system taking heavy oil or coal as a main raw material.
Detailed Description
The present invention is further illustrated by the following examples.
According to the embodiment of the invention, smelting, continuous casting, casting blank heating, rolling, laminar cooling and coiling are carried out according to the component proportion of the technical scheme.
Heating a casting blank: the temperature of a casting blank soaking section is 1227-1249 ℃, the total in-furnace time is 192-209 min, and the heat preservation time of the soaking section is 37-49 min;
rolling: a two-stage controlled rolling process is adopted, the temperature of a rough rolling outlet is 1086-1106 ℃, and the thickness of an intermediate blank is more than 3 times of that of a finished product; the initial rolling temperature of the finish rolling is 1077-1097 ℃, and the final rolling temperature of the finish rolling is 871-893 ℃. (ii) a
Laminar cooling and coiling: carrying out laminar cooling on the rolled steel plate, wherein the laminar cooling adopts rear-section centralized cooling; cooling to 617-636 ℃ at the cooling rate of 16-26 ℃/s for coiling, and cooling to room temperature after coiling.
Further, the method comprises the following steps of; the molten iron pre-desulfurization in the smelting process: in order to improve the smelting efficiency of the converter, the desulfurization powder is sprayed into a torpedo tank car filled with molten iron for desulfurization pretreatment, so that S is less than or equal to 0.003 percent, and solid slag such as CaS, mgS and the like needs to be thoroughly removed;
converter steelmaking in the smelting process: the furnace top and bottom combined blowing process is adopted, the tapping temperature of the converter is 1674-1694 ℃, and the final slag alkalinity R is more than or equal to 3.7; argon blowing is needed in the whole tapping process, 1.53-1.69 kg/ton molten steel modifier is needed to modify the top slag after tapping, and the argon blowing time after the addition is ensured to be more than or equal to 4min.
Further, the method comprises the following steps of; LF + RH external refining in the smelting process
Heating the LF furnace for 28-38 min, heating to over 1607 ℃, stirring for 7-11 min after heating, and performing calcium treatment to control the calcium content fed into the molten steel to be more than or equal to 0.004%;
then the steel ladle is moved out and poured into an RH furnace, the free O content in the steel is controlled to be below 6ppm at the time, the furnace temperature is controlled to be higher than 1593 ℃, fe-Ce rare earth alloy is added into the RH furnace, then argon is weakly blown to promote impurities in the steel ladle to float, the weak blowing time is 4.2-5.2 min, and the steel ladle is moved out of the machine; preferably, the mass fraction of Ce in the Fe-Ce rare earth alloy is 19.4-20.6%, and the addition amount is 2.26-3.1 kg per ton of steel.
Further, the method comprises the following steps of; continuous casting: the continuous casting process adopts a dynamic soft reduction technology, the molten steel is protected by the covering slag in the whole process, and the thickness of a slag layer is controlled to be more than 18 mm; the temperature of the tundish is 1544-1564 ℃, the throwing speed is 1.27-1.37 m/min, and the thickness of the continuous casting billet is 230-250 mm; preferably, the soft reduction amount is controlled to 3.2 to 7.2mm.
The smelting process parameters of the steel of the embodiment of the invention are shown in a table 1, the continuous casting process parameters of the steel of the embodiment of the invention are shown in a table 2, the components of the steel of the embodiment of the invention are shown in a table 3, the main process parameters of the heating and rolling of the steel of the embodiment of the invention are shown in a table 4, the adding amount and the yield of Ce in the steel of the embodiment of the invention are shown in a table 5, the performance of the steel of the embodiment of the invention is shown in a table 6, the microstructure of the steel of the embodiment of the invention is shown in a table 7, and the full-immersion corrosion test result of the steel of the embodiment of the invention is shown in a table 8.
TABLE 1 main process parameters for steel smelting in the examples of the present invention
TABLE 2 main process parameters for continuous casting of steel in the examples of the present invention
| Examples | Reduction/mm | Thickness of casting blank/mm | Slag thickness/mm | Tundish temperature/. Degree.C | Pulling speed m/min |
| 1 | 6.9 | 230 | 18.7 | 1544 | 1.37 |
| 2 | 7.2 | 230 | 19.0 | 1548 | 1.35 |
| 3 | 5.7 | 230 | 18.8 | 1552 | 1.33 |
| 4 | 3.9 | 230 | 19.4 | 1556 | 1.32 |
| 5 | 5.2 | 230 | 19.7 | 1561 | 1.31 |
| 6 | 6.3 | 250 | 20.6 | 1554 | 1.29 |
| 7 | 3.2 | 250 | 21.3 | 1559 | 1.28 |
| 8 | 4.8 | 250 | 21.8 | 1564 | 1.27 |
TABLE 3 composition (wt%) of steels of examples of the present invention
Note: s n /C e Without unit
TABLE 4 Main Process parameters of heating and Rolling of the steels of the examples of the present invention
TABLE 5 addition amount and yield of Ce in the steels of the examples of the present invention
TABLE 6 mechanical Properties of steels of examples of the invention
TABLE 7 microstructure of inventive example steels
TABLE 8 Corrosion resistance of steels of examples of the invention
As can be seen from Table 5, the yield of Ce in the examples is high, between 53.15 and 58.06 percent; as can be seen from Table 6, the yield strength of the steel of the embodiment of the invention is more than 450MPa, the tensile strength is between 589 and 626MPa, the elongation is more than 27 percent, the cold bending performance is qualified, the transverse and longitudinal performances are stable, the difference between the transverse and longitudinal strengths is not more than 13MPa, and the difference between the average values of the transverse and longitudinal impact work is not more than 3J; the results in Table 7 show that the steel of the invention consists of ferrite, pearlite and bainite, and has uniform and fine structure and lower grade of various inclusions.
The full-immersion corrosion test was carried out according to the test method specified in JB/T7901-1999 under the conditions of a temperature of 20 ℃, a sulfuric acid concentration of 20%, and full immersion for 24 hours. Table 8 shows the results of comparing the sulfuric acid corrosion resistance of the steels of examples of the present invention with that of the comparative steels. As can be seen from Table 8, the corrosion rates of the steel sheets of the present invention are 5.3 to 6.8mg/cm 2 H, the sulfuric acid dew point corrosion resistance of the steel of the embodiment of the invention is obviously superior to that of the comparative steel Q345B, and the durability of the steel plate in an acid corrosion environment can be effectively improved.
In order to describe the present invention, the embodiment has been described in the above for properly and fully explaining the present invention by way of example, and the above embodiment is only used for illustrating the present invention and not to limit the present invention, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and any modifications, equivalent substitutions, improvements, etc. made are all included in the protection scope of the present invention, and the protection scope of the present invention is defined by the claims.
Claims (10)
1. The 450 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel is characterized by comprising the following components in percentage by weight: c:0.062% -0.083%, si: 0.21-0.41%, mn:0.48% -0.79%, P: less than or equal to 0.017 percent, S: less than or equal to 0.0050%, cr:0.72 to 0.97%, ni:0.17% -0.28%, cu: 0.11-0.21%, 0.072-0.102% of Sb, 0.037-0.058% of Ti, 0.29-0.43% of Sn, als:0.013% -0.036%, ce: 0.026-0.036%, O: less than or equal to 4.5ppm and the balance of Fe and inevitable impurities.
2. The 450MPa grade sulfuric acid dew point corrosion resistant rare earth steel according to claim 1, wherein the microstructure is ferrite + pearlite + bainite, wherein the volume percentage of ferrite is 42.7-45.4%, and the volume percentage of pearlite is 32.4-37.1%.
3. The 450MPa grade rare earth steel for resisting the dew point corrosion of the sulfuric acid according to claim 1, wherein Sn/Ce in the rare earth steel is 11.1-12.2, and 20-25 nm Ce is precipitated along grain boundaries in the rare earth steel 5 Sn 3 。
4. The 450MPa grade sulfuric acid dew point corrosion resistant rare earth steel according to claim 1, wherein the yield strength of the rare earth steel is more than 450MPa, the tensile strength is 589-626 MPa, and the elongation is more than 27%.
5. A method for manufacturing 450MPa grade sulfuric acid dew point corrosion resistant rare earth steel according to any one of claims 1 to 4, comprising smelting, continuous casting, billet heating, rolling, laminar cooling and coiling; the method is characterized in that:
heating a casting blank: the temperature of a casting blank soaking section is 1227-1249 ℃, the total in-furnace time is 192-209 min, wherein the heat preservation time of the soaking section is 37-49 min;
rolling: a two-stage controlled rolling process is adopted, the temperature of a rough rolling outlet is 1086-1106 ℃, and the thickness of an intermediate blank is more than 3 times of that of a finished product; the initial rolling temperature of finish rolling is 1077-1097 ℃, and the final rolling temperature of finish rolling is 871-893 ℃;
laminar cooling and coiling: carrying out laminar cooling on the rolled steel plate, wherein the laminar cooling adopts rear-section centralized cooling; cooling to 617-636 deg.C at 16-26 deg.C/s, coiling, and air cooling to room temperature.
6. The method for manufacturing 450MPa grade rare earth steel for resisting sulfuric acid dew point corrosion according to claim 5, characterized in that:
the molten iron pre-desulfurization in the smelting process: in order to improve the smelting efficiency of the converter, the desulfurization powder is sprayed into a torpedo tank car filled with molten iron for desulfurization pretreatment, so that S is less than or equal to 0.003 percent, and solid slag such as CaS, mgS and the like needs to be thoroughly removed;
and in the smelting process, converter steelmaking: the furnace top and bottom combined blowing process is adopted, the tapping temperature of the converter is 1674 to 1694 ℃, and the final slag alkalinity R is more than or equal to 3.7; argon blowing is needed in the whole tapping process, 1.53-1.69 kg/ton molten steel modifier is needed to modify the top slag after tapping, and the argon blowing time after the addition is ensured to be more than or equal to 4min.
7. The method for manufacturing 450MPa grade rare earth steel for resisting sulfuric acid dew point corrosion according to claim 5, characterized in that: LF + RH external refining in the smelting process
Heating the LF furnace for 28-38 min, heating to 1607 deg.C, stirring for 7-11 min, and performing calcium treatment to control the calcium content in molten steel to be more than or equal to 0.004%;
and then the ladle is moved out and poured into an RH furnace, the free O content in the steel is controlled to be below 6ppm at the furnace temperature of 1593 ℃, fe-Ce rare earth alloy is added into the RH furnace, then argon is weakly blown to promote impurities in the molten steel to float, the weak blowing time is 4.2-5.2 min, and the steel is moved out of the machine.
8. The method for manufacturing the 350MPa grade sulfuric acid dew point corrosion resistant rare earth steel according to claim 7, characterized in that: the mass fraction of Ce in the Fe-Ce rare earth alloy is 19.4-20.6%, and the addition amount of the Ce is 2.26-3.1 kg per ton of steel.
9. The method for manufacturing 450MPa grade rare earth steel for resisting sulfuric acid dew point corrosion according to claim 5, characterized in that:
continuous casting: the continuous casting process adopts a dynamic soft reduction technology, the molten steel is protected by using the covering slag in the whole process, and the thickness of a slag layer is controlled to be more than 18 mm; the temperature of the tundish is 1544-1564 ℃, the throwing speed is 1.27-1.37 m/min, and the thickness of the continuous casting billet is 230-250 mm.
10. The method for manufacturing 450MPa grade sulfuric acid dew point corrosion resistant rare earth steel according to claim 9, characterized in that: the soft reduction amount is controlled to be 3.2-7.2 mm.
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| JPH0925536A (en) * | 1995-07-06 | 1997-01-28 | Sumitomo Metal Ind Ltd | Acid dew point corrosion resistant steel |
| JP2007239095A (en) * | 2006-02-10 | 2007-09-20 | Nippon Steel Corp | Acid corrosion resistant steel |
| CN109182911A (en) * | 2018-10-20 | 2019-01-11 | 江苏铸鸿锻造有限公司 | A kind of pressure vessel strong alloy steel forging circle of heat and preparation method thereof |
| CN113005365A (en) * | 2021-02-18 | 2021-06-22 | 包头钢铁（集团）有限责任公司 | Sulfuric acid corrosion resistant hot rolled steel plate containing rare earth cerium and preparation method thereof |
| CN115011876A (en) * | 2022-05-30 | 2022-09-06 | 鞍钢股份有限公司 | Steel for resisting high-temperature sulfuric acid dew point corrosion and manufacturing method thereof |
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| JPH0925536A (en) * | 1995-07-06 | 1997-01-28 | Sumitomo Metal Ind Ltd | Acid dew point corrosion resistant steel |
| JP2007239095A (en) * | 2006-02-10 | 2007-09-20 | Nippon Steel Corp | Acid corrosion resistant steel |
| CN109182911A (en) * | 2018-10-20 | 2019-01-11 | 江苏铸鸿锻造有限公司 | A kind of pressure vessel strong alloy steel forging circle of heat and preparation method thereof |
| CN113005365A (en) * | 2021-02-18 | 2021-06-22 | 包头钢铁（集团）有限责任公司 | Sulfuric acid corrosion resistant hot rolled steel plate containing rare earth cerium and preparation method thereof |
| CN115011876A (en) * | 2022-05-30 | 2022-09-06 | 鞍钢股份有限公司 | Steel for resisting high-temperature sulfuric acid dew point corrosion and manufacturing method thereof |
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