CN115572911B - 350MPa grade sulfuric acid dew point corrosion resistant rare earth steel and manufacturing method thereof - Google Patents

350MPa grade sulfuric acid dew point corrosion resistant rare earth steel and manufacturing method thereof Download PDF

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CN115572911B
CN115572911B CN202211387234.7A CN202211387234A CN115572911B CN 115572911 B CN115572911 B CN 115572911B CN 202211387234 A CN202211387234 A CN 202211387234A CN 115572911 B CN115572911 B CN 115572911B
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steel
rare earth
percent
sulfuric acid
dew point
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CN115572911A (en
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孙傲
刘志伟
张瑞琦
郭晓宏
吴成举
唐明宇
王鑫
苏建铭
高洪涛
孙航
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Angang Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

The invention provides a 350MPa 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:0.052% -0.073%, si:0.14 to 0.34 percent of Mn:0.38% -0.69%, P: less than or equal to 0.017 percent, S: less than or equal to 0.0050 percent, cr:0.61% -0.82%, ni:0.12 to 0.23 percent of Cu:0.11 to 0.21 percent of Sb, 0.052 to 0.082 percent of Ti, 0.014 to 0.036 percent of Sn, 0.14 to 0.28 percent of Als:0.012% -0.034%, ce:0.014% -0.024%, O: less than or equal to 4.8ppm, and the balance of Fe and unavoidable impurities; 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 and excellent comprehensive performance, particularly 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

350MPa grade sulfuric acid dew point corrosion resistant rare earth steel and manufacturing method thereof
Technical Field
The invention belongs to the field of metal materials, and particularly relates to 350 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 is commonly existed in flue gas systems taking 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 devices such as boiler preheaters and economizer apparatus, air preheater heat exchange elements, dust collectors, and flue gas and stack stacks, the sulfur content in the flue gas is relatively high to catalyze the formation of sulfides (SO 3 ) Then combines with water vapor in the flue gas to form sulfuric acid vapor, and condenses into sulfuric acid on the metal wall below the dew point temperature of sulfuric acid, thereby generating acid corrosion problem on equipment. In order to reduce the maintenance cost and prolong the safe service life of the steel structural member, it is highly required to develop acid-resistant steel with excellent sulfuric acid dew point corrosion resistance.
The invention discloses a rare earth alloy steel resistant to sulfuric acid dew point corrosion (publication number: CN 1386886A), which comprises the following components: c: less than or equal to 0.15 percent, si:0.15 to 1.20 percent of Mn:0.30 to 1.50 percent of Cu:0.20% -0.80%, W:0.10% -0.60%, mo:0.10 to 0.50 percent, 0.05 to 0.30 percent of Sn, 0.05 to 0.30 percent of Sb, less than or equal to 0.50 percent of RE and S: less than or equal to 0.035 percent, P: less than or equal to 0.035 percent, and the balance of Fe and impurities; the noble metal W is added, and the addition of W in steel tends to increase the alloy cost.
The invention discloses a rare earth sulfuric acid dew point corrosion resistant steel and a preparation method thereof (publication number: CN 111206178A), wherein the steel comprises the following components: c:0.07 to 0.11 percent of Si:0.20 to 0.50 percent of Mn:0.40% -0.65%, P: less than or equal to 0.020%, S: less than or equal to 0.035%, 0.010% -0.060% of Al, 0.85% -1.10% of Cr, cu:0.30 to 0.45 percent, 0.04 to 0.10 percent of Sb, and Ni:0.15 to 0.35 percent RE:0.001% -0.010%, and the balance of Fe and impurities. In the aspect of performance inspection, the corrosion resistance of the test steel is not given, the corrosion resistance effect is unknown, and the invention describes a laboratory smelting-rolling method, wherein a die casting process is adopted to produce the steel plate, but the die casting process cannot be used for producing the large-scale steel plate in the field actual production.
According to the technical scheme disclosed in the invention (publication number: CN 1475580A) of the rare earth addition amount optimization control method of rare earth weathering steel, 0.010-0.030% of rare earth is added into the weathering steel; although the corrosion resistance of the product is improved by adding Cu and Re, the independent addition of Cu is easy to cause the phenomenon of copper embrittlement of the steel plate, and the difficulty of the hot rolling process is increased. Meanwhile, the steelmaking and rolling process, especially the rare earth adding process, is not clear. In addition, the various mechanical property indexes of the steel are not explicitly described.
The invention discloses a rare earth element-containing coating-free weathering steel and a preparation method thereof (publication number: CN 109252092A), wherein the steel comprises the following components: c:0.03 to 0.09 percent of Si:0.10 to 0.30 percent of Mn:1.00% -1.50%, P:0.005% -0.015%, S: less than or equal to 0.005 percent, 0.35 to 0.70 percent of Cr, and Ni:0.25% -0.55%, cu:0.25% -0.55%, mo:0.03 to 0.25 percent of Re: 0.005-0.060 percent of Nb 0.015-0.040 percent of Ti 0.008-0.025 percent of Al 0.015-0.040 percent of Ca:0.003 to 0.018 percent, and the balance being Fe and impurities. The corrosion resistance of the steel is evaluated by the atmospheric corrosion resistance index I, the index is calculated according to a theoretical formula and is not verified by a corrosion test, so that the actual corrosion resistance effect is unknown; in addition, the tempering technology is adopted to improve the mechanical property of the steel, so that the technology is complex, and the production cost is increased.
The invention discloses a rare earth low alloy steel resistant to high temperature sulfuric acid dew point corrosion, which is disclosed in publication No.: the technical scheme disclosed in CN 101892438A is that the sulfuric acid dew point corrosion resistance of the product is improved by adding corrosion resistant elements such as Cr+Cu+Ni+RE, but the method has the defects that the method adopts higher Cu content and has higher production cost. The invention only emphasizes the influence on corrosion resistance, and does not give the comprehensive mechanical condition of the steel. In addition, no related steelmaking and rolling processes, especially rare earth addition processes during smelting, are provided. The adding 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 shortcomings and provide the rare earth steel for the sulfuric acid dew point corrosion resistance of 350MPa grade, which is suitable for being used in an acidic 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 invention aims at realizing the following steps:
a350 MPa grade sulfuric acid dew point corrosion resistant rare earth steel comprises the following components in percentage by weight: c:0.052% -0.073%, si:0.14 to 0.34 percent of Mn:0.38% -0.69%, P: less than or equal to 0.017 percent, S: less than or equal to 0.0050 percent, cr:0.61% -0.82%, ni:0.12 to 0.23 percent of Cu:0.11 to 0.21 percent of Sb, 0.052 to 0.082 percent of Ti, 0.014 to 0.036 percent of Sn, 0.14 to 0.28 percent of Als:0.012% -0.034%, ce:0.014% -0.024%, O: less than or equal to 4.8ppm, and the balance of Fe and unavoidable impurities.
Further, the microstructure of the rare earth steel is ferrite and pearlite, wherein the volume percentage of ferrite is 67.2-71.4%;
further, the Sn/Ce value in the rare earth steel is 10-12; 20-25 nm Ce is precipitated along grain boundary in rare earth steel 5 Sn 3 。
Furthermore, the yield strength of the rare earth steel is more than 350MPa, the tensile strength is between 512 and 531MPa, and the elongation is more than 32%.
The reason for designing the components of the invention is as follows:
c: as one of the main reinforcing elements, an increase in C content is advantageous for improvement of strength and hardness of the steel sheet, but a large amount of C adversely affects properties such as impact toughness and plasticity of the steel sheet. The content of the limiting C in the invention is 0.052-0.073%.
Si: the strong deoxidizing element in the steelmaking process can be used as a solid solution strengthening element to improve the yield strength of the steel plate, but the excessively high content not only can reduce the welding performance of the steel plate, but also can form a red iron oxide scale which is difficult to remove after the steel plate is rolled. The Si content is limited to 0.14-0.34% in the invention.
Mn: the steel mainly plays a solid solution strengthening role in steel, and can improve the tensile strength of the steel plate. However, too high Mn content causes segregation, deteriorating the weldability and formability of the steel. Therefore, the Mn content in the invention is controlled to be 0.38-0.69%.
P: although one of the alloying elements that functions as solid solution strengthening and remarkably improves corrosion resistance, segregation occurs at grain boundaries when the content is high, and the weldability, plasticity, and toughness of the steel sheet are lowered. The steel of the invention is controlled below 0.017%.
S: is a harmful impurity element, is liable to form defects such as segregation and inclusion, and deteriorates the impact toughness and hot workability of the steel sheet. Therefore, the S content in the present invention should be controlled to be 0.005% or less.
Cr: easily forming a compact oxide film Cr on the surface of the steel plate 2 O 3 The adhesive force between the rust layer and the matrix can be improved, so that the passivation capability of the steel is improved. In addition, the improvement of Cr element is favorable for refining alpha-FeOOH, so that the strength and toughness of the steel plate can be improved. However, if the content is too high, the weldability of the steel sheet is deteriorated. Therefore, the Cr content in the present invention is controlled to be 0.61% to 0.82%.
Cu: is an essential element for improving the corrosion resistance of the steel plate, and can play a solid solution strengthening role at the same time, so that the strength of the steel plate is improved, but when the content is higher, the hot shortness of the steel plate is easily caused. Meanwhile, the content range of the invention is limited to 0.11% -0.21% by considering the cost factor.
Ni: the corrosion-resistant alloy is one of elements for improving the strength and the impact toughness of the steel plate, and can not only improve the problem of copper brittleness of the steel plate, but also obviously improve the corrosion resistance of the steel plate when being reasonably matched with Cu. However, ni is a noble metal element, and the addition amount of Ni in the present invention is 0.12% to 0.23% from the viewpoint of cost control.
Ti is one of the alloying elements which play a role in strengthening. The Ti compound in the steel can effectively prevent the growth of austenite grains in the heating process, plays a role in fine grain strengthening, and TiC precipitated in the cooling process also plays a role in precipitation strengthening. And meanwhile, the welding performance of the steel plate can be improved. The range of the invention is limited to 0.014% -0.036%.
Sb is an effective element for improving corrosion resistance, plays a role in catalyzing enrichment of corrosion-resistant elements, promotes enrichment of Cu, cr and other corrosion-resistant elements on the surface of a rust layer, forms a layer of compact oxide film containing Sb, cr, cu and other corrosion-resistant elements and having obvious corrosion-resistant effect on the surface of a steel plate, and can effectively improve the acid corrosion resistance of the steel plate, but the catalytic effect is not obvious when the content of the Sb, cr, cu and other corrosion-resistant elements is low, so that the invention is limited to be 0.052-0.082%.
Sn is generally a residual impurity element in steel, and is easily segregated at grain boundaries. However, sn is an effective element for improving acid corrosion resistance and enhancing precipitation in the present invention. When being added in combination with Cr, cu and Sb elements, the corrosion resistant elements promote the enrichment of the corrosion resistant elements on the surface of the rust layer, and the generated stable-state SnO is obtained 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 The steel plate is often precipitated along grain boundaries in the cooling process, and plays a good role in precipitation strengthening. In the invention, the value of Sn/Ce is 10-12, and the content of Sn is set to be 0.14-0.28%.
Als: the main deoxidizing element is favorable for refining grains and improving the mechanical property of the steel plate, and the range of the deoxidizing element is limited to 0.012% -0.034%.
Ce: ce in the present invention has the following effects: (1) By varying Sn, al 2 O 3 The form and the type of inclusions such as MnS are obviously improved, the plasticity and the toughness of the steel are obviously improved, and the anisotropy of impact performance is especially reduced. (2) Due to the change of the morphology of the inclusions, the potential difference between the inclusions and the matrix is reduced, the trend 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 the grain boundary, and forms a Ce-Sn compound with high melting point and nanometer grade with Sn at the grain boundary to improve the strength of the steel plate. (4) The CeO particles distributed in a dispersed manner gather at the grain boundary to obviously block the movement of dislocation, so that the strength of the steel plate is improved. However, the lower Ce content in the steel does not have corrosion resistance, so that the added Ce can fully play the roleThe Ce content of the catalyst should be controlled to be 0.014% -0.024%.
O: as a harmful and strong oxidizing element in the steel, the rare earth element is easy to react with the added rare earth element to form corresponding rare earth oxide. The excessive O content can cause that a large amount of rare earth inclusions are formed in the molten steel to influence the fluidity of the molten steel, and when serious, 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 be 4.8ppm or less.
The second technical proposal of the invention is to provide a manufacturing method of the rare earth steel for the sulfuric acid dew point corrosion resistance of 350MPa level, 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, desulfurization powder is sprayed into a torpedo ladle car filled with molten iron to carry out desulfurization pretreatment, so that S is less than or equal to 0.003%, and slag removal is thorough for solid slag such as CaS, mgS and the like.
(2) Converter steelmaking:
the converter tapping temperature is 1671-1687 ℃ and the final slag alkalinity R is more than or equal to 3.5 by adopting a top-bottom composite converting process. Argon is blown in the whole tapping process, 1.51-1.67 kg/ton of molten steel modifier is added after tapping to carry out modification treatment on top slag, and the argon blowing time after adding is more than or equal to 3min.
(3) LF+RH external refining
Heating treatment is carried out in an advanced LF furnace for 25-35 min, the temperature is raised to above 1605 ℃, stirring is carried out for 5-9 min after heating, and calcium treatment is carried out, so that the content of calcium fed into molten steel is controlled to be more than or equal to 0.003%.
And then the ladle is moved out and poured into an RH furnace, at the moment, the free O content in the steel is controlled below 6ppm, the furnace temperature is controlled above 1590 ℃, 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 1.17-2.10 kg/ton of molten steel, then argon weak blowing is carried out, the inclusion in the molten steel is promoted to float upwards, the weak blowing time is 3.2-4.2 min, and the molten steel is carried out of a crane.
Continuous casting: the continuous casting process is put into a dynamic soft reduction technology, the soft reduction is controlled between 3.2 and 7.2mm, so that 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 whole process uses the protective slag to protect the molten steel so as to prevent oxygen from entering the molten steel 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 property of the water gap and ensure the smooth casting of the rare earth steel, the temperature of the tundish is controlled to be 1541-1561 ℃ and the blank pulling speed is 1.24-1.34 m/min.
Heating a casting blank: in order to ensure that each element can be fully dissolved in solid and avoid unnecessary billet oxidation loss caused by overhigh heating temperature, the temperature of a casting blank soaking section is controlled between 1224 ℃ and 1246 ℃ and the total soaking time is 185-202 min, wherein the soaking section has the heat preservation time of 34-46 min.
Rolling: the rolling process is controlled in two stages, the rough rolling finishing temperature is 1083-1103 ℃, and the thickness of the obtained intermediate blank is more than 3 times of the thickness of the finished product. The initial rolling temperature of the finish rolling is 1074-1094 ℃, and the final rolling temperature of the finish rolling is 861-883 ℃.
Laminar cooling and coiling: and (3) carrying out laminar cooling on the rolled steel plate, wherein the laminar cooling adopts rear-section concentrated cooling. The cooling rate is 11-21 ℃/s, the coiled material is cooled to 613-632 ℃, and the coiled material is cooled to room temperature in an air way.
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 reserved in the steel, but also obtaining higher rare earth yield which is more than 53 percent, and providing the rare earth steel for resisting sulfuric acid dew point corrosion, the upper yield strength of which is more than 350 MPa. The yield strength of the steel of the embodiment of the invention is more than 350MPa, the tensile strength is between 512 and 531MPa, the elongation is more than 32%, the impact power average value at minus 40 ℃ is more than 110J, the anisotropy of impact performance can be reduced, the average value of horizontal impact power and longitudinal impact power is different by not more than 4J, the steel has excellent comprehensive mechanical properties, and the corrosion rate of the steel plate is between 6.3 and 7.4mg/cm 2 H, the corrosion rate of the alloy is 17.89 to 19.96% relative to Q345B. The acid-resistant rare earth steel plate of the invention not only has simple manufacturing process, but also has excellent comprehensive performance,especially acid corrosion resistance, and can be widely applied to equipment manufacture in a flue gas treatment system taking heavy oil or coal as a main raw material.
Detailed Description
The invention is further illustrated by the following examples.
According to the technical scheme, the embodiment of the invention carries out smelting, continuous casting, casting blank heating, rolling, laminar cooling and coiling.
Heating a casting blank: the temperature of the casting blank soaking section is 1224-1246 ℃, the total furnace time is 185-202 min, and the soaking section heat preservation time is 34-46 min;
rolling: adopting a two-stage controlled rolling process, wherein the rough rolling finishing temperature is 1083-1103 ℃, and the thickness of the intermediate billet is more than 3 times of the thickness of the finished product; the initial rolling temperature of the finish rolling is 1074-1094 ℃, and the final rolling temperature of the finish rolling is 861-883 ℃;
laminar cooling and coiling: the rolled steel plate is subjected to laminar cooling, and the back section concentrated cooling is adopted for the laminar cooling; the cooling rate is 11-21 ℃/s, the coiling is carried out after cooling to 613-632 ℃, and the air cooling is carried out to the room temperature after the coiling.
Further; molten iron pre-desulfurization in the smelting process: in order to improve the smelting efficiency of the converter, desulfurizing powder is sprayed into a torpedo ladle car filled with molten iron for desulfurization pretreatment, so that S is less than or equal to 0.003%, and slag removal is thorough for solid slag such as CaS, mgS and the like;
converter steelmaking in the smelting process: adopting a top-bottom combined converting process, wherein the tapping temperature of the converter is 1671-1687 ℃, and the final slag alkalinity R is more than or equal to 3.5; argon is blown in the whole tapping process, 1.51-1.67 kg/ton of molten steel modifier is added after tapping to carry out modification treatment on top slag, and the argon blowing time after adding is more than or equal to 3min.
Further: LF+RH external refining in smelting process
Heating in LF furnace for 25-35 min to 1605 deg.C, stirring for 5-9 min, and performing calcium treatment to control the content of calcium in molten steel to 0.003% or more;
then the ladle is moved out and poured into an RH furnace, at the moment, the free O content in the steel is controlled to be lower than 6ppm and the furnace temperature is controlled to be higher than 1590 ℃, fe-Ce rare earth alloy is added into the RH furnace, then argon weak blowing is carried out, the inclusion in the molten steel is promoted to float upwards, the weak blowing time is 3-4 min, and the molten steel 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 1.17-2.10 kg/ton of steel.
Further; continuous casting: the continuous casting process is put into a dynamic soft reduction technology, the whole process uses the covering slag to protect molten steel, and the thickness of a slag layer is controlled to be more than 18 mm; the temperature of the tundish is 1541-1561 ℃, the blank pulling speed is 1.24-1.34 m/min, and the thickness of the continuous casting blank is 230-250 mm; preferably, the light reduction is controlled to 3.2-7.2 mm.
The smelting process parameters of the steel of the embodiment of the invention are shown in Table 1, the continuous casting process parameters of the steel of the embodiment of the invention are shown in Table 2, the components of the steel of the embodiment of the invention are shown in Table 3, the main heating and rolling process parameters of the steel of the embodiment of the invention are shown in Table 4, the addition amount and yield of Ce in the steel of the embodiment of the invention are shown in Table 5, the performance of the steel of the embodiment of the invention is shown in Table 6, the microstructure of the steel of the embodiment of the invention is shown in Table 7, and the total immersion corrosion test result of the steel of the embodiment of the invention is shown in Table 8.
TABLE 1 Main technological parameters for smelting Steel according to an embodiment of the invention
Figure BDA0003930477630000081
TABLE 2 main process parameters for continuous casting of steel in accordance with the embodiment of the invention
Figure BDA0003930477630000082
TABLE 3 composition (wt%) of the inventive example steel
Figure BDA0003930477630000091
Note that: s is S n /C e No unit
TABLE 4 heating and Rolling Main Process parameters of the inventive example Steel
Figure BDA0003930477630000092
TABLE 5 addition amount and yield of Ce in the inventive example steel
Figure BDA0003930477630000101
TABLE 6 mechanical Properties of the inventive example steels
Figure BDA0003930477630000102
TABLE 7 microstructure of inventive example steels
Figure BDA0003930477630000111
TABLE 8 Corrosion resistance of the inventive example steels
Figure BDA0003930477630000112
As can be seen from Table 5, the Ce yield in the examples is higher, ranging from 53.48 to 59.83%; as can be seen from Table 6, the yield strength of the steel of the embodiment of the invention is more than 350MPa, the tensile strength is between 512 and 531MPa, the elongation is more than 32%, the cold bending performance is qualified, the transverse and longitudinal performances are stable, the difference between the transverse and longitudinal strength is not more than 7MPa, and the average difference between the transverse and longitudinal impact energy is not more than 4J; the results in Table 7 show that the structure of the inventive steel is composed of ferrite and pearlite, and the structure is uniform and fine, and the grades of various inclusions are low.
The total immersion corrosion test was carried out according to the test method prescribed by JB/T7901-1999 under the conditions of 20 ℃ temperature, 20% sulfuric acid concentration and 24 hours total immersion. Table 8 shows the results of comparison of sulfuric acid corrosion resistance of the inventive example steel and the comparative steel. From Table 8, it can be seen thatThe corrosion rate of the steel plate is 6.3 to 7.4mg/cm 2 And 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.
The present invention has been properly and fully described in the foregoing embodiments by way of example only, and not by way of limitation, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, any modification, equivalent substitution, improvement, etc. should be included in the scope of the invention, and the scope of the invention is defined by the claims.

Claims (8)

1. A350 MPa grade sulfuric acid dew point corrosion resistant rare earth steel is characterized by comprising the following components in percentage by weight: c:0.052% -0.073%, si:0.14 to 0.34 percent of Mn:0.38% -0.69%, P: less than or equal to 0.017 percent, S: less than or equal to 0.0050 percent, cr:0.61% -0.82%, ni:0.12 to 0.23 percent of Cu:0.11 to 0.19 percent, 0.052 to 0.082 percent of Sb, 0.014 to 0.036 percent of Ti, 0.17 to 0.28 percent of Sn, als:0.012% -0.034%, ce:0.014% -0.024%, O: less than or equal to 4.8ppm, and the balance of Fe and unavoidable impurities;
the value of Sn/Ce in the rare earth steel is 10-12; 20-25 nm Ce is precipitated along grain boundary in rare earth steel 5 Sn 3 ；
The manufacturing method of the 350 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel comprises smelting, continuous casting, casting blank heating, rolling, laminar cooling and coiling;
heating a casting blank: the temperature of the casting blank soaking section is 1224-1246 ℃, the total furnace time is 185-202 min, and the soaking section is kept for 34-46 min;
rolling: adopting a two-stage controlled rolling process, wherein the rough rolling finishing temperature is 1083-1103 ℃, and the thickness of the intermediate billet is more than 3 times of the thickness of the finished product; the initial rolling temperature of the finish rolling is 1074-1094 ℃, and the final rolling temperature of the finish rolling is 861-883 ℃;
laminar cooling and coiling: the rolled steel plate is subjected to laminar cooling, and the back section concentrated cooling is adopted for the laminar cooling; the cooling rate is 11-21 ℃/s, the coiling is carried out after cooling to 613-632 ℃, and the air cooling is carried out to the room temperature after the coiling.
2. The 350 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel according to claim 1, wherein the microstructure is ferrite + pearlite, and wherein the ferrite is 67.2-71.4% by volume.
3. The rare earth steel for 350MPa grade sulfuric acid dew point corrosion resistance according to claim 1, wherein the yield strength of the rare earth steel is more than 350MPa, the tensile strength is 512-531 MPa, and the elongation is more than 32%.
4. The 350 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel according to claim 1, wherein:
molten iron pre-desulfurization in the smelting process: in order to improve the smelting efficiency of the converter, desulfurizing powder is sprayed into a torpedo ladle car filled with molten iron for desulfurization pretreatment, so that S is less than or equal to 0.003%, and slag removal is thorough for solid slag such as CaS, mgS and the like;
converter steelmaking in the smelting process: adopting a top-bottom combined converting process, wherein the tapping temperature of a converter is 1671-1687 ℃, and the final slag alkalinity R is more than or equal to 3.5; argon is blown in the whole tapping process, 1.51-1.67 kg/ton of molten steel modifier is added after tapping to carry out modification treatment on top slag, and the argon blowing time after adding is more than or equal to 3min.
5. The 350 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel according to claim 1, wherein: LF+RH external refining in smelting process
Heating in an LF furnace for 25-35 min, heating to above 1605 ℃, stirring for 5-9 min after heating, and performing calcium treatment to control the content of calcium fed into molten steel to be more than or equal to 0.003%;
and then the ladle is moved out and poured into an RH furnace, at the moment, the free O content in the steel is controlled to be lower than 6ppm and the furnace temperature is controlled to be higher than 1590 ℃, fe-Ce rare earth alloy is added into the RH furnace, then argon weak blowing is carried out, the inclusion in the molten steel is promoted to float upwards, the weak blowing time is 3.2-4.2 min, and the molten steel is carried out of the crane.
6. The 350 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel according to claim 1, wherein: 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 1.17-2.1 kg/ton of steel.
7. The 350 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel according to claim 1, wherein:
continuous casting: the continuous casting process is put into a dynamic soft reduction technology, the whole process uses the covering slag to protect molten steel, and the thickness of a slag layer is controlled to be more than 18 mm; the temperature of the tundish is 1541-1561 ℃, the blank pulling speed is 1.24-1.34 m/min, and the thickness of the continuous casting blank is 230-250 mm.
8. The 350 MPa-grade sulfuric acid dew point corrosion resistant rare earth steel according to claim 1, wherein: the light rolling reduction is controlled to be 3.2-7.2 mm.
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