CN115852242B - High-temperature high-pressure hydrogen corrosion-resistant thick steel plate and manufacturing method thereof - Google Patents
High-temperature high-pressure hydrogen corrosion-resistant thick steel plate and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses a high-temperature high-pressure hydrogen corrosion resistant thick steel plate which contains Fe and unavoidable impurities and also contains the following chemical elements in percentage by mass: c: 0.09-0.18%, si:0.20 to 0.60 percent, mn:0.35 to 0.75 percent, cr:2.35 to 3.15 percent, mo:0.50 to 1.20 percent, al(s): 0.005-0.015%, nb:0.020 to 0.050 percent, ti:0.015 to 0.030 percent, B:0.0005 to 0.0020 percent, O:0.0025 to 0.0040 percent. In addition, the invention also discloses a manufacturing method of the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate, which comprises the following steps: (1) smelting and casting: adding a deoxidizer Si, mn, ti, al in the molten steel smelting process; wherein, before molten steel casting, pre-deoxidizing is carried out according to the sequence of Si, mn and Ti, and the oxygen level of the cast molten steel is controlled to be 0.0045-0.0085 percent; then adopting Al to carry out final deoxidation, and controlling the mass percentage content of the Al in the molten steel to be 0.005-0.015%; (2) rolling; (3) quenching and tempering.
Description
Technical Field
The present invention relates to a metal material and a method for manufacturing the same, and more particularly, to a thick steel plate and a method for manufacturing the same.
Background
In recent years, as the trend of the quality of crude oil toward the emphasis, high-vulcanization and high-acidification becomes more and more evident, the market demand for high-quality crude oil becomes higher and higher.
In the prior art, the crude oil with poor quality can be treated to obtain high-quality crude oil through processing technologies such as hydrotreating, hydrocracking, hydrodesulfurization, hydrodenitrogenation and the like under high-temperature and high-pressure conditions. The technical means is also an important technical means for improving the utilization rate of crude oil and saving the energy consumption.
However, this technical solution requires that the poor crude oil is processed under extreme process conditions such as high temperature, high pressure, high hydrogen partial pressure, etc.; in this case, the steel used for producing the hydrogenation reaction vessel is required to have excellent high temperature and high pressure resistance, and in particular, excellent hydrogen corrosion resistance is required.
It is known that under the high-temperature and high-pressure reaction condition, when a large amount of hydrogen exists in a reaction container, the hydrogen with extremely small atomic radius easily enters the interior of a metal material, so that the fracture resistance and the extensibility of the material are reduced, and even hydrogen induced cracks can be formed in the interior of the metal material, so that the hydrogen corrosion damage of the material is caused, equipment is disabled, and production accidents are caused.
At present, there are two main manifestations of high temperature hydrogen corrosion: the first is that decarburization is generated on the surface of the material; the second is that decarburization and cracking occur inside the material.
When the surface of the material is corroded by hydrogen, decarburization occurs on the surface, but the depth of a decarburized layer is shallow, generally 1-2 mu m, so that the strength and hardness of the local surface of the material are reduced, meanwhile, the ductility of the material is improved, and surface decarburization generally does not cause cracks on the surface of the material. When the interior of the material is corroded by hydrogen, not only decarburization but also cracking occurs. Because hydrogen corrosion inside the material is caused by the fact that hydrogen atoms enter the metal material to chemically react with carbon elements in steel to form methane gas, when a large amount of methane gas is formed to gather near the cavities or sharp inclusions of grain boundaries, large local stress is formed inside the material, so that cracks, small cracks or bulges are generated in the material, and the strength and toughness of the material are remarkably deteriorated. Since this damage to the material is the result of a chemical reaction, with irreversible properties, this hydrogen corrosion is a permanent damage which can bring about a great accident potential for the safe operation of the equipment.
Accordingly, in order to prevent hydrogen atoms from entering the inside of steel materials and to avoid permanent hydrogen corrosion damage, some researchers have conducted a great deal of research in the prior art and employed various methods to prevent hydrogen atoms from entering the container materials.
For example: chinese patent document with publication number CN204051658U, publication date 2014, 12, 31, entitled "a hydrogenation reactor", discloses a hydrogenation reactor. The inner walls of the cylinder body and the upper and lower seal head structures of the reaction vessel in the patent are all overlaid with a stainless steel anti-corrosion layer for blocking hydrogen atoms in the vessel from entering the cylinder body and the seal head materials of the vessel, thereby reducing or avoiding the reaction of combining hydrogen and carbon elements in the entering materials to generate methane so as to improve the hydrogen corrosion resistance of the vessel.
Also for example: japanese patent publication No. JPS60200914 (A), entitled "MANUFACTURE OF STEEL SUPERIOR IN HYDROGEN CORROSION CRACKING RESISTANCE", discloses another technique for improving strength and hydrogen corrosion resistance of a steel sheet by heating the steel to within the range of Ac 3.+ -. 70 ℃ and controlling the cooling rate in the range of 600 to 400 ℃ to be not more than 1 ℃ per second during cooling to obtain a steel structure having an extremely fine pearlite structure
For another example: japanese patent publication No. JPS5923849 (a), entitled "LOW ALLOY STEEL RESISTANT TO HYDROGEN CORROSION", discloses that the hydrogen corrosion resistance of a material is improved by adding a certain amount of La element to steel so that La is combined with the remaining harmful elements in the steel.
For the analysis of the above-mentioned existing hydrogen corrosion resistant steel patents, we have found that the hydrogen corrosion resistant methods of the container materials frequently used in the prior art mainly include the following three methods:
first kind: the protective layer is added on the surface of the container material to prevent hydrogen atoms from diffusing into the container material, and the protective layer on the surface of the container material can enable enamel, stainless steel and various chemical coatings. The method can reduce the diffusion of hydrogen atoms into the material to a certain extent, and improve the hydrogen corrosion resistance of the material, but the surface of the material is required to be processed and treated for a plurality of times, so that the production cost of the material is necessarily increased, and the production period of the container is also increased.
Second kind: the method can effectively inhibit tempering embrittlement caused by residual As, sn, sb and other elements in the steel by controlling the alloy chemical components of the steel, such As adding harmful residual elements in the fixed steel of La and the like, so As to improve the stability of the steel.
Third, by controlling the heat treatment process of the low alloy steel, a specific phase transformation structure is obtained to form a specific structure type (e.g., fine, dispersed pearlite) to increase the structural stability of the steel against hydrogen corrosion. But when subjected to higher temperatures and pressures the type of structure of the material must be controlled to be bainitic to increase the yield strength of the steel.
Analysis shows that the prior art is difficult to obtain a good implementation effect, and different from the technical scheme adopted in the prior art, the inventor researches and adopts a brand new design thought, and from another angle, the high-temperature hydrogen corrosion resistance of the steel is greatly improved, so that the high-temperature high-pressure hydrogen corrosion resistance thick steel plate with excellent application prospect is obtained.
Disclosure of Invention
An object of the present invention is to provide a high-temperature high-pressure hydrogen corrosion-resistant thick steel sheet having a large amount of Ti finely dispersed in the steel 2 O 3 +Al 2 O 3 The +MnS composite inclusions can adsorb H elements entering the steel due to diffusion, reduce the concentration of the segregation of H atoms and C atoms in the steel, reduce or avoid the formation of methane gas, and further improve the high-temperature hydrogen corrosion resistance of the steel.
The high-temperature high-pressure hydrogen corrosion resistant thick steel plate has very excellent high-temperature hydrogen corrosion resistance, and has very good popularization prospect and application value; the steel can be used for effectively preparing pressure equipment, can ensure the stable and safe operation of the pressure equipment, and avoids production accidents caused by hydrogen corrosion.
In order to achieve the above object, the present invention provides a high temperature and high pressure hydrogen corrosion resistant thick steel plate, which contains Fe and unavoidable impurities, and further contains the following chemical elements in mass percent:
C：0.09～0.18％，Si：0.20～0.60％，Mn：0.35～0.75％，Cr：2.35～3.15％，Mo：0.50～1.20％，Al(s)：0.005～0.015％，Nb：0.020～0.050％，Ti：0.015～0.030％,B：0.0005～0.0020％，O：0.0025～0.0040％。
further, in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, the mass percentage of each chemical element is as follows:
c: 0.09-0.18%, si:0.20 to 0.60 percent, mn:0.35 to 0.75 percent, cr:2.35 to 3.15 percent, mo:0.50 to 1.20 percent, al(s): 0.005-0.015%, nb:0.020 to 0.050 percent, ti:0.015 to 0.030 percent, B:0.0005 to 0.0020 percent, O:0.0025 to 0.0040 percent; the balance being Fe and unavoidable impurities.
In the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, reasonable chemical component design and combined with an optimized manufacturing process are adopted, so that a large amount of Ti distributed in a tiny dispersion way can be provided in the steel 2 O 3 +Al 2 O 3 +mns composite inclusions. The tiny, spherical or nearly spherical composite inclusions can be used as hydrogen traps to absorb hydrogen atoms entering steel in the working process of high-temperature equipment for manufacturing the thick steel plate, further diffusion of the hydrogen atoms is avoided, and the hydrogen atoms and carbon elements are prevented from being combined to generate methane gas through chemical reaction, so that the high-temperature hydrogen corrosion resistance of the steel plate is greatly improved.
In fact, the nature of high temperature, high pressure, hydrogen corrosion of high temperature, hydrogen-bearing steels is due to the chemical reaction of hydrogen atoms entering the steel with carbon elements in the steel to form methane gas. Thus, the inventors contemplate that high temperature hydrogen corrosion can be controlled by controlling C and H in the steel: on the one hand, the formation of methane is prevented by the formation of a large amount of carbon elements in the carbide-fixed steel in the steel; on the other hand, there are a large number of "hydrogen traps" in the iron and steel material, such as dislocations, grain boundaries, impurity atoms, inclusions, etc., which trap hydrogen and hinder the diffusion of hydrogen, thereby avoiding or reducing the diffusion of hydrogen atoms into the interior of the material. Wherein, the inclusions are a special hydrogen trap, and when the steel contains a large number of inclusions of special components which are tiny, dispersed, spherical or nearly spherical, the inclusions can fully play the role of the hydrogen trap, fix hydrogen atoms entering the inside of the material and prevent hydrogen corrosion.
However, when the size of the inclusions is large and the edges and corners are clear, the inclusions and the matrix of the steel have very obvious micro cracks, and at this time, the inclusions are liable to become the sources of methane bubble nucleation, aggregation, growth and even cracking. Therefore, by strictly controlling the number, size, shape and type of inclusions in steel, the high-temperature hydrogen corrosion resistance of the steel can be improved.
The inventor finds that a large amount of small and dispersed spherical or nearly spherical Al can be formed in molten steel and the subsequent solidification process by controlling the types, the adding sequence, the oxygen position and the adding amount of the deoxidizer in the smelting process based on scientific and reasonable alloy component design 2 O 3 +Ti 2 O 3 +MnS composite inclusions, these Al 2 O 3 +Ti 2 O 3 The +MnS composite inclusion can be used as a hydrogen trap to absorb hydrogen atoms entering steel in the long-time high-temperature service process of the steel, so that the further diffusion of the hydrogen atoms is avoided, and the combination of the hydrogen atoms and carbon elements is prevented from generating a chemical reaction to generate methane gas, thereby greatly improving the high-temperature hydrogen corrosion resistance of the steel.
In the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, the design principle of each chemical element is as follows:
c: in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, a certain amount of C element is required to be added, and the C element can play a role in solid solution strengthening, so that the yield strength and the tensile strength of the steel plate are improved; in addition, part of C element can be combined with carbide forming elements in solid solution in steel in the heat treatment process of the steel plate and the high-temperature working process after the subsequent steel plate is manufactured into a container, and is separated out from the steel in a second phase form, so that the separation strengthening effect is achieved, the strength of the steel plate is improved, meanwhile, part of carbide separation phases with stable thermal performance can fix carbon element in the steel, and methane gas is prevented from being generated after free carbon and hydrogen element are combined. However, it should be noted that the content of the element C in the steel is not too high, and the too high content of the element C causes the welding performance of the steel plate to be reduced, which is unfavorable for the engineering application of the steel plate, so that the upper limit of the addition of the element C is controlled to be 0.18%. Based on this, in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate according to the present invention, the content of the C element is controlled to be 0.09 to 0.18% by mass in view of the performance of the steel material.
Si: in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, si element is a weak deoxidizer, and Si element and Mn element in steel can be used as pre-deoxidizers, and oxygen level in molten steel is controlled to be in an ideal range through pre-deoxidization; at this time, the steel is deoxidized by using other deoxidizers (Al and Ti), and a certain amount of target inclusions can be formed in the steel. However, if the Si content in the steel is too high, segregation of impurity elements such As As, sn, and Sb at grain boundaries is easily promoted, and temper embrittlement of the steel sheet is caused, so that the upper limit of the Si content is controlled to 0.60%. Based on this, in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate according to the present invention, the mass percentage content of Si element is controlled to be between 0.20 and 0.60% in consideration of the beneficial effects and adverse effects of Si element.
Mn: in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate of the present invention, the effect of Mn element may include two aspects; on one hand, mn element is used as a deoxidizer to pre-deoxidize molten steel, so that the oxygen level of the molten steel can be well and stably controlled in a proper range, and the subsequent deoxidizer is convenient to add so as to form proper inclusion types; on the other hand, the Mn element has a certain solid solution strengthening effect and fine grain strengthening effect, and the addition amount of the Mn element in the steel is not too low in order to ensure the strength of the steel plate, so that the mass percent of the Mn element in the steel is controlled to be not less than 0.35 percent. However, it should be noted that the content of Mn element in steel is not too high, and when the content of Mn element in steel is high, a segregation band of Mn element is easily formed at the center position of the thickness of a slab in the solidification process after casting of molten steel, and an abnormal structure is easily formed in the subsequent rolling process, so that the low-temperature impact toughness at the center position of the thickness of a steel sheet is reduced, and therefore, the upper limit of Mn element addition is controlled to 0.75%. Based on the above, in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate, the mass percentage of Mn element is controlled to be between 0.35 and 0.75 percent.
Cr: in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, a certain amount of Cr element is added, so that the oxidation resistance of the steel can be improved when the steel works at high temperature, and the high-temperature corrosion resistance of the steel can be improved. However, it should be noted that the Cr element content in the steel should not be too high, and the addition of excessive Cr element causes a decrease in the tempering embrittlement resistance of the steel, while the alloy cost of the steel increases. Based on the above, in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate, the mass percentage of Cr element is controlled to be 2.35-3.15%.
Mo: in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, the aim of controlling the addition of a proper amount of Mo element is mainly to improve the yield strength and the lasting strength of steel during high-temperature working, so that the steel can work more safely under the high-temperature long-term service condition. Accordingly, mo element is not excessively added, and when Mo content in steel is more than 1.20%, performance improvement of steel sheet is limited. Based on the above, in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate, the mass percentage of Mo element is controlled to be between 0.50 and 1.20 percent.
Al(s): in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, when the content of acid-soluble aluminum Al(s) in steel is lower than 0.0050%, mixed crystal structures are easily generated when the steel is rolled and subjected to phase change, so that the uniformity of the microstructure of the steel plate is reduced, and the impact toughness of the steel is further reduced; when the content of acid-soluble aluminum Al(s) in the steel is higher than 0.015%, magnesia-alumina spinel inclusions are easily formed in the steel, the mechanical properties of the steel plate are damaged, and the control of Al in the steel is also not facilitated 2 O 3 +Ti 2 O 3 Formation of +MnS composite inclusions. Based onIn the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, the mass percentage of the acid-soluble aluminum Al(s) in the steel is controlled to be between 0.005 and 0.015 percent.
Nb: in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, trace Nb is added into the steel to refine the microstructure of the steel so as to improve the strength and toughness of the steel; part of Nb element can be combined with C element in steel to generate NbC precipitated phase, thereby achieving the effect of refining grains, fixing free carbon in steel and avoiding high-temperature hydrogen corrosion generated after the free carbon is combined with free hydrogen. However, it should be noted that the Nb content in the steel is not too high, and when the Nb content in the steel is too high, the toughness of the weld heat affected zone of the steel sheet is lowered. Based on this, in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate according to the present invention, the mass percentage of Nb element is controlled to be 0.020 to 0.050%.
Ti: in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate of the present invention, in order to form Ti in the steel 2 O 3 The inclusion, the oxygen level in the molten steel is controlled in a proper range through the pre-deoxidation treatment of Si and Mn, and a certain amount of Ti element is added at the same time; ti is an element with stronger deoxidizing capability than Si element and Mn element, and when the activities of Ti element and O element in molten steel are different, the Ti element and the O element can react to generate different types of inclusions. In order to ensure the deoxidizing effect of the Ti element, the high-temperature high-pressure hydrogen corrosion-resistant steel sheet according to the present invention has a Ti element content of 0.015 to 0.030 mass%.
B: in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, the B element can be combined with the N element to form BN, so that the solid solution N content in the steel can be reduced, and the low-temperature toughness of the steel is improved. However, it is not preferable to add an excessive amount of B element to steel, and when B element is added too much to steel, a large amount of segregation tends to form at grain boundaries, which adversely affects the performance of steel. Based on this, in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate according to the present invention, the mass percentage of the B element is controlled to be 0.0005 to 0.0020%.
O: in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, a proper amount of O element is added into steel to form fine composite oxides, and the fine composite oxides can play a role in hydrogen absorption; when the content of O element in steel is too low, the amount of the formed composite oxide is too small, so that the hydrogen adsorption capacity of the composite oxide is obviously reduced; when the O content in the steel is too high, coarse oxides are easily formed, and the hydrogen adsorption effect of the composite oxide is not beneficial to the maximum. Based on this, in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate according to the present invention, the mass percentage of the O element is controlled to be 0.0025 to 0.0040%.
Further, in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate according to the present invention, at least one of the following chemical elements is contained:
0＜Cu≤0.30％；
0＜Ni≤0.30％。
in the technical scheme of the invention, both Cu and Ni elements can further improve the quality and performance of the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate.
Cu can improve corrosion resistance and strength of steel, but when Cu content in steel is too high, high temperature brittleness is easily generated at high temperature. Therefore, in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, the mass percentage of Cu element can be controlled to be more than 0 and less than or equal to 0.30 percent.
Correspondingly, a certain amount of Ni element is added into the steel, so that the low-temperature toughness and strength of the steel plate can be improved, but the high price of the Ni element is considered, and in order to control the production cost, the mass percentage of the Ni element in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate can be controlled to be more than 0 and less than or equal to 0.30 percent.
It should be noted that, the addition of the above elements may increase the cost of the material, and in view of the performance and cost control, at least one of the above elements may be preferably added in the technical solution of the present invention.
Further, in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate according to the present invention, among other unavoidable impurities: p is less than or equal to 0.010%, S is less than or equal to 0.010%, and N is less than or equal to 0.0050%.
In the technical scheme of the invention, the P element, the S element and the N element are all impurity elements in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate, and the content of the impurity elements in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate is reduced as much as possible under the condition of allowing technical conditions in order to obtain the steel with better performance and better quality.
P: in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, the P element is a harmful impurity element, when the steel plate works at a high temperature, the P element in the steel is easy to gather toward an austenite grain boundary, so that the concentration of the P element at the position of the austenite grain boundary is greatly increased, the binding force of the austenite grain boundary is reduced, tempering brittleness is easy to form, and finally, the steel plate is likely to crack and age. Therefore, in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate of the present invention, it is desirable that the lower the P content is, the better the steel-making cost and the operability are combined, and the mass percentage of the P element can be controlled to be P0.010% or less.
S: in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, the impurity element S is very easy to combine with Mn element in steel to generate MnS inclusion in the solidification process of the steel, and the MnS inclusion has better high-temperature plasticity, so that the MnS is easy to form long-strip-shaped and large-size inclusion extending along the rolling direction in the rolling process of the steel plate, thereby deteriorating the transverse performance, Z-direction performance and welding performance of the steel plate. Therefore, in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, the mass percentage of S element is controlled to be less than or equal to 0.010 percent by combining the conditions of steelmaking cost, operability and the like.
N: in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, when the content of N element in steel is too high, adverse effect is generated on the toughness of the steel, and particularly, after the content of solid solution N exceeds 0.005%, the low-temperature toughness of the thick steel plate is reduced. Therefore, in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, the mass percentage of N element is controlled to be less than or equal to 0.0050 percent.
Further, in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate of the invention, the thick steel plate has tiny and dispersed ballsAl in the form of 2 O 3 +Ti 2 O 3 +mns composite inclusions.
Further, in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate of the present invention, wherein Al having a particle diameter of less than 3 μm 2 O 3 +Ti 2 O 3 +MnS composite inclusions occupy all Al 2 O 3 +Ti 2 O 3 The proportion of +MnS composite inclusions is more than 60%.
Further, in the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate of the present invention, the average particle diameter of all inclusions is less than 4 μm, and the average aspect ratio of all inclusions is not more than 1.3.
Further, in the high-temperature high-pressure hydrogen corrosion-resistant steel sheet of the present invention, it has inclusions having a particle size of less than 5 μm, the volume density of the inclusions having a particle size of less than 5 μm being more than 1.0X10 3 Individual/mm 3 。
Further, in the high-temperature high-pressure hydrogen corrosion resistant thick steel plate, after the temperature is at least 550 ℃, the pressure is at least 30MPa, the hydrogen partial pressure is at least 20MPa and the temperature is maintained for at least 1000 hours, the tensile strength of the steel is higher than 550MPa, and meanwhile, the area shrinkage of the steel is not lower than 65%.
Accordingly, another object of the present invention is to provide a method for manufacturing a high-temperature high-pressure hydrogen corrosion-resistant thick steel plate, which employs an optimized manufacturing process that can form a large amount of Al in steel by controlling the kind of deoxidizer, the order of addition, the oxygen level at the time of addition, and the amount of addition in the smelting process 2 O 3 +Ti 2 O 3 +mns composite inclusions; the fine, spherical or nearly spherical composite inclusions can be used as hydrogen traps to absorb hydrogen atoms entering steel in the working process of high-temperature equipment for manufacturing the steel plate, further diffusion of the hydrogen atoms is avoided, and the hydrogen atoms and carbon elements are prevented from being combined to generate methane gas through chemical reaction, so that the high-temperature hydrogen corrosion resistance of the steel plate is greatly improved.
The high-temperature high-pressure hydrogen corrosion resistant thick steel plate obtained by the manufacturing method has very excellent high-temperature hydrogen corrosion resistance, can be used for manufacturing pressure-bearing equipment, ensures stable and safe operation of the pressure-bearing equipment, and avoids production accidents caused by hydrogen corrosion.
In order to achieve the above object, the present invention provides a method for manufacturing the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate, comprising the steps of:
(1) Smelting and casting: adding a deoxidizer Si, mn, ti, al in the molten steel smelting process; wherein, before molten steel casting, pre-deoxidizing is carried out according to the sequence of Si, mn and Ti, and the oxygen level of the cast molten steel is controlled to be 0.0045-0.0085 percent; then adopting Al to carry out final deoxidation, and controlling the mass percentage content of the Al in the molten steel to be 0.005-0.015%;
(2) Rolling;
(3) Quenching and tempering.
In the present invention, in order to sufficiently exert the adsorption effect of inclusions on hydrogen atoms, it is necessary to form a large amount of fine, uniform, dispersed spherical or nearly spherical Al in a thick steel plate 2 O 3 +Ti 2 O 3 The +MnS composite inclusions must thus be precisely controlled in terms of the law of variation of the oxygen level of the molten steel during the deoxidation of the molten steel. In order to control the oxygen level in the molten steel, proper deoxidizing elements are required to be selected and deoxidized according to a certain adding sequence; in addition, a method of adding a deoxidizing element appropriately is also selected.
In step (1) of the production method of the present invention, the present invention uses the addition sequence of Si, mn, ti, al for deoxidation in the smelting process. Firstly, si+Mn is used for pre-deoxidation, so that the free oxygen activity in molten steel can be reduced, and a proper oxygen position condition is created for the addition of a subsequent deoxidizer; secondly, si and Mn deoxidize to generate low-melting-point inclusions which are easy to gather, grow up and float up in steel slag in molten steel for removal. After weak deoxidization of Si and Mn, when oxygen level in molten steel is proper, adding proper quantity of Ti for deoxidization to further reduce free oxygen concentration in molten steel, under the set condition, a great quantity of fine, spherical or nearly spherical dispersed Ti can be formed in molten steel 2 O 3 Inclusions. Ti generated at this time 2 O 3 Inclusions are key to overall inclusion control, ti 2 O 3 Special purpose of inclusionThe interfacial energy is smaller, the adsorption capacity of the inclusions is weaker, and the inclusions are not easy to gather and grow.
Then, the oxygen level of the cast molten steel is controlled to be 0.0045 to 0.0085%, and an appropriate amount of Al element is further added to the appropriate oxygen level to further deoxidize the molten steel. Since Al element has stronger deoxidizing ability than Ti element, part of Ti 2 O 3 Ti in the inclusion is reduced, and Al atoms replace part of Ti atoms to form Ti 2 O 3 +Al 2 O 3 Composite inclusions.
It is known that Al with sharp edges and corners having a large size is easily formed in molten steel after deoxidizing Al alone if the oxygen level in the molten steel is high 2 O 3 The inclusion is also larger in interface energy of alumina inclusion, so that the adsorption capacity among the alumina inclusion is stronger, the alumina inclusion is easy to aggregate into clusters to block a casting nozzle, or large-scale inclusion is formed in steel, and high-temperature hydrogen corrosion or fault detection of the steel plate is easy to cause.
However, in the invention, the oxygen level in the casting molten steel is lower (0.0045-0.0085%) when Al element is added by Si and Mn pre-deoxidation and Ti deoxidation, and the content of the added Al element is controlled well, so that most of the Al element can replace the formed Ti 2 O 3 Part of Ti element in the inclusion is thus due to the previously generated Ti 2 O 3 The inclusions are in spherical, fine and dispersed distribution, thereby newly forming Ti 2 O 3 +Al 2 O 3 The morphology, size and distribution of the composite inclusion are basically the same as those of Ti 2 O 3 The inclusions are similar.
In addition, part of the reduced Ti element can be combined with free N in the steel to generate TiN, the TiN not only can reduce the adverse effect of solid solution nitrogen on the toughness of the steel, but also can be separated out at a high temperature above the austenitizing temperature in the subsequent slab solidification process, and plays a role in pinning austenite growth, so that the prior austenite grains of the steel are refined. When the molten steel is solidified, part of Mn element and S element can be formed as Ti in the molten steel 2 O 3 +Al 2 O 3 The composite inclusion is used as a nucleation point and attached to the inclusion to be separated out in a certain orientation relation to finally form Ti 2 O 3 +Al 2 O 3 +MnS composite inclusions, which can adsorb a large amount of hydrogen atoms.
It should be noted that the upper limit of the content of Al element in the molten steel is controlled to be lower than 0.015%, so that the formation of large-size sharp-angle alumina inclusions can be avoided, and the alumina inclusions generated by combining the rest small part of Al with oxygen in the molten steel are small in size and are not easy to aggregate; if the Al content is less than 0.005%, ti is formed in the molten steel 2 O 3 +Al 2 O 3 The density of the composite inclusions is too small to sufficiently exert the effect of the composite inclusions on adsorbing hydrogen atoms, so that it is necessary to control the content of the added Al element to be 0.005% to 0.015%.
Further, in the production method of the present invention, in the step (2), the cast slab is heated to 1060 to 1150 ℃, the finishing temperature is controlled to be more than 930 ℃, and the total cumulative reduction is controlled to be more than 65%.
In the above technical scheme of the invention, in the rolling process of the step (2), the casting blank is required to be firstly input into a heating furnace for heating, and the casting blank is preferably heated to 1060-1150 ℃. When the heating temperature of the casting blank is less than 1060 ℃, carbide and nitride of Nb in the casting blank cannot be completely dissolved, and the pinning effect of Nb on austenite grains in the rolling process can be reduced; when the temperature of the heated casting blank is higher than 1150 ℃, rapid growth of austenite grains is easily caused, and the performance of the steel is affected.
Accordingly, when rolling steel, it may be preferable to control the finishing temperature to be greater than 930 ℃ and the total cumulative reduction to be greater than 65%. This is because: under the thermal deformation condition, the steel can be completely recrystallized, so that austenite is continuously refined; if the above conditions are not satisfied, austenite grains of a larger size may exist in the steel, impairing the strength and low-temperature toughness of the steel.
Further, in the manufacturing method of the present invention, in the step (3), the quenching temperature is controlled to be 880-950 ℃, the holding time is (1.0-2.8) ×t min, and the steel sheet is cooled to room temperature after the holding is finished, wherein T represents the thickness of the steel sheet, and the unit is mm.
Further, in the manufacturing method of the present invention, in the step (3), the tempering temperature is controlled to 695 to 745 ℃, and the holding time is (2.3 to 3.6) ×t min, wherein T represents the thickness of the steel sheet in mm.
In the above technical solution of the present invention, in the quenching and tempering heat treatment process in step (3), the quenching temperature may be preferably controlled to 880-950 ℃. This is because: when the quenching temperature is lower than 880 ℃, the austenite of the steel needs to be homogenized for a long time, and the heat treatment efficiency is reduced; when the quenching temperature of the steel is higher than 950 ℃, part of austenite in the steel has a growing trend, a mixed crystal structure is easy to form, and the uniformity of the steel structure is not facilitated.
In addition, in the quenching process, the heat preservation time can be controlled to be (1.0-2.8) multiplied by T min, and the steel plate is discharged from a furnace to be cooled to room temperature after heat preservation, wherein T represents the thickness of the steel plate and is expressed in mm. This is because: when the heat preservation time of the steel at the quenching temperature is less than T min, the steel cannot be fully austenitized; when the heat preservation time of the steel exceeds 2.8T min, the austenitizing time required by the steel is exceeded, and the efficiency of the quenching process is reduced.
Accordingly, during the tempering process of step (3), the tempering temperature may be preferably controlled to 695 to 745 ℃, and the holding time is (2.3 to 3.6) ×t min, where T represents the thickness of the steel sheet in mm. When the tempering temperature of the steel is lower than 695 ℃, longer tempering time is needed, and residual quenching stress in the steel is removed, so that tempering efficiency is reduced; when the tempering temperature of the steel is higher than 740 ℃, dislocation density in the steel is greatly reduced, thereby reducing the strength of the steel. In the tempering process, when the tempering heat preservation time is lower than 2.3Tmin, the quenching stress of the steel cannot be completely removed; when the tempering heat preservation time is higher than 3.6T min, the production efficiency of the tempering process is reduced.
Compared with the prior art, the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate and the manufacturing method thereof have the following advantages and beneficial effects:
compared with the prior art, the invention adopts a brand new design thought, and achieves the effect of greatly improving the high-temperature hydrogen corrosion resistance of the material from another angle, thereby obtaining the high-temperature high-pressure hydrogen corrosion resistance thick steel plate with excellent application prospect.
The high-temperature high-pressure hydrogen corrosion resistant thick steel plate steel adopts reasonable chemical element composition design and combines and optimizes the manufacturing process, and a large amount of tiny, spherical, nearly spherical and dispersed Ti can be formed in the steel plate by properly controlling the deoxidizing agent, deoxidizing sequence and the use amount of different deoxidizing agents used in the steel smelting process 2 O 3 +Al 2 O 3 After the thick steel plate is made into pressure-bearing equipment, the special composite inclusions can absorb a large amount of H elements diffused into steel in the high-temperature service process, so that free H atoms and C atoms are prevented from being combined to generate methane gas, the formation of methane gas is reduced or avoided, and the high-temperature hydrogen corrosion resistance of the steel is improved.
The high-temperature high-pressure hydrogen corrosion resistant thick steel plate has very excellent high-temperature hydrogen corrosion resistance, and has very good popularization prospect and application value; the high-temperature high-pressure hydrogen corrosion-resistant thick steel plate is used for producing pressure-bearing equipment, so that the stable and safe operation of the pressure-bearing equipment can be ensured, and production accidents caused by hydrogen corrosion are avoided.
Detailed Description
The high-temperature high-pressure hydrogen corrosion-resistant thick steel plate and the manufacturing method thereof according to the present invention will be further explained and illustrated with reference to specific examples, which, however, do not constitute an undue limitation on the technical solution of the present invention.
Examples 1 to 7 and comparative examples 1 to 3
The high-temperature high-pressure hydrogen corrosion resistant thick steel plates of the embodiments 1 to 7 are prepared by the following steps:
(1) Smelting and casting were performed according to the chemical compositions shown in table 1: 400kg of industrial pure iron is added into a vacuum induction furnace, and a proper amount of Cr, mo, V, nb alloy is added along with the furnace according to the alloy component proportion of the steel; smelting under the vacuum degree of 15Pa at the lowest, filling argon for protection, adding proper amount of deoxidizer according to Si, mn, ti, al sequence after pure iron is completely melted, pre-deoxidizing according to the sequence of Si, mn and Ti, and controlling the oxygen level of the casting molten steel to be 0.0045-0.0085%; then adopting Al to carry out final deoxidation, and controlling the mass percentage content of the Al in the molten steel to be 0.005-0.015%; and (3) properly adjusting the addition amount of the alloy and controlling the oxygen position of free oxygen in the molten steel according to the online monitoring result of the molten steel components, and pouring into ingots.
(2) Rolling: and (3) inputting the casting blank into a heating furnace, heating to 1060-1150 ℃, controlling the final rolling temperature to be higher than 930 ℃, and rolling to obtain the steel plate with the thickness of 40mm, wherein the total accumulated rolling reduction is higher than 65%.
(3) Quenching and tempering: controlling the quenching temperature to 880-950 ℃, keeping the temperature for (1.0-2.8) multiplied by Tmin, discharging the steel plate after the heat preservation is finished, and cooling the steel plate to room temperature by water, wherein T represents the thickness of the steel plate and is expressed in mm; the tempering temperature is controlled to 695-745 ℃, and the heat preservation time is (2.3-3.6) multiplied by T min, wherein T represents the thickness of the steel plate, and the unit is mm.
In the present invention, the chemical composition design and the related process of the high temperature and high pressure hydrogen corrosion resistant steel plate of examples 1 to 7 meet the design specification requirements of the present invention.
Accordingly, the comparative steels of comparative examples 1 to 3 were also prepared by the above-mentioned process flows of "smelting, casting, rolling, quenching and tempering", but were subjected to the exchange of the deoxidizing sequences of Al and Ti, and other process conditions were within the scope of the present invention.
Table 1 shows the mass percentages of the chemical elements of the high-temperature high-pressure hydrogen corrosion-resistant steel plates of examples 1 to 7 and the comparative steels of comparative examples 1 to 3.
Table 1 (wt.%), the balance Fe and unavoidable impurities other than P, S, N
Table 2 shows the rolling and heat treatment process parameters in the above process steps for the high temperature and high pressure hydrogen corrosion resistant steel plates of examples 1 to 7 and the comparative steels of comparative examples 1 to 3.
Table 2.
It should be noted that, in the case of carrying out the above-mentioned manufacturing processes in examples 1 to 7 and comparative examples 1 to 3, after the preliminary deoxidation in the order of Si, mn and Ti in step (1), it is possible to sample the molten steels obtained in each of examples and comparative examples and to examine the oxygen levels of the molten steels after the preliminary deoxidation in each of examples and comparative examples, and the results of the relevant examination are shown in Table 3 below.
Table 3.
The high-temperature high-pressure hydrogen corrosion-resistant thick steel plates of the final product examples 1 to 7 and the comparative steels of comparative examples 1 to 3, which were finally obtained through the above-described process steps, were sampled respectively, and the inclusions of the sample steels of each example and comparative example were observed and analyzed.
In the invention, the inclusion in the steel can be extracted by adopting an electrolytic extraction method, and the precipitated phases in different scale ranges are separated through the filter membranes with different apertures; the types, contents, etc. of inclusions in the steel are analyzed by SEM (scanning electron microscope ) and EDS (Energy Dispersive Spectrometer, energy spectrometer) techniques to confirm the chemical composition of the inclusions, the particle size distribution of the inclusions is detected by a laser particle size analyzer, and the number, bulk density, type, aspect ratio, average size, etc. of precipitated phases (inclusions) in the steel are finally confirmed by image analysis software.
Through the above experiments, it can be confirmed thatThe average grain size and average aspect ratio of all inclusions in the sample steels of examples 1 to 7 and comparative examples 1 to 3 were determined, and the bulk densities of inclusions having grain sizes of less than 5 μm were analyzed and calculated while regarding Al having grain sizes of less than 3. Mu.m 2 O 3 +Ti 2 O 3 +MnS composite inclusions occupy all Al 2 O 3 +Ti 2 O 3 The proportion of +MnS composite inclusions is calculated to obtain the final observation analysis result. Accordingly, the results of the inclusion observation analysis of the obtained sample steels of examples 1 to 7 and comparative examples 1 to 3 are shown in Table 4 below.
Table 4 shows the results of the observation and analysis of inclusions in the high-temperature high-pressure hydrogen corrosion-resistant steel sheets of examples 1 to 7 and the comparative steels of comparative examples 1 to 3.
Table 4.
As shown in Table 4, it was found that the sample steels of examples 1 to 7 and comparative examples 1 to 3 each had a fine, dispersed and spherical Al 2 O 3 +Ti 2 O 3 +mns composite inclusions.
In the high-temperature high-pressure hydrogen corrosion-resistant thick steel sheets of examples 1 to 7, the volume density of inclusions having a particle size of less than 5 μm was 2.91X10 3 Individual/mm 3 -6.23×10 3 Individual/mm 3 Between them; all inclusions have an average particle size of 2.2 μm to 3.8 μm; al having an average aspect ratio of 1.07-1.28 and a particle diameter of less than 3 μm 2 O 3 +Ti 2 O 3 +MnS composite inclusions occupy all Al 2 O 3 +Ti 2 O 3 The proportion of the +MnS composite inclusion is 63-79%.
Unlike examples 1 to 7, in the comparative steels of comparative examples 1 to 3, the volume density of inclusions having a particle size of less than 5 μm was 0.52X10 3 Individual/mm 3 -0.71×10 3 Individual/mm 3 Between them; all inclusions have an average particle size of 5.5 μm to 6.3 μm; al having an average aspect ratio of 1.71-1.98 and a particle diameter of less than 3 μm 2 O 3 +Ti 2 O 3 +MnS composite inclusions occupy all Al 2 O 3 +Ti 2 O 3 The proportion of the +MnS composite inclusion is 25-41%.
After the above observation and analysis of inclusions for each of the example and comparative example steels were completed, it was possible to resample the high-temperature and high-pressure hydrogen corrosion-resistant steel plates of the finished examples 1 to 7 and the comparative example steels of comparative examples 1 to 3 and to examine the hydrogen corrosion resistance properties of the example and comparative example sample steels obtained by resampling.
Since the strength and plasticity of steel sheets gradually deteriorate with the increase of the degree of corrosion after hydrogen corrosion, the changes in tensile strength and reduction of area of steel in a tensile test can be used to evaluate the hydrogen corrosion resistance of steel materials.
In the present invention, the evaluation of the high temperature hydrogen corrosion resistance of the sample steel sheets of examples 1 to 7 and comparative examples 1 to 3 was performed as follows:
The high-temperature high-pressure hydrogen charging experiment is carried out on the steel plates of each example and comparative example, and experimental parameters are controlled as follows: the test temperature is controlled to 550 ℃, the pressure is 30MPa, the hydrogen partial pressure is 20MPa after hydrogen charging, after the test is kept for 1000 hours, the test is carried out according to GB/T228.1-2010 method for room temperature tensile test of metallic materials, and the tensile strength and the reduction of area of the steel plates of each example and the comparative example are obtained and are used for judging the hydrogen corrosion degree of the materials.
The tensile properties of the high temperature and high pressure hydrogen corrosion resistant steel plates of examples 1 to 7 and the comparative steels of comparative examples 1 to 3 after high temperature and high pressure hydrogen corrosion are shown in Table 5 below.
Table 5.
As can be seen from Table 4, the average grain size of all the inclusions in the high temperature and high pressure hydrogen corrosion resistant steel sheet of examples 1 to 7 according to the present invention is less than 4. Mu.m, and the average aspect ratio of all the inclusions is not more than 1.3 grain size; volume of inclusions smaller than 5 μmDensity is greater than 1.0X10 3 Individual/mm 3 The method comprises the steps of carrying out a first treatment on the surface of the Al less than 3 μm 2 O 3 +Ti 2 O 3 +MnS composite inclusions occupy all Al 2 O 3 +Ti 2 O 3 The proportion of the +MnS composite inclusion is more than 60 percent. The comparative steels of comparative examples 1 to 3 failed to meet the above requirements.
As can be seen from Table 5, the high temperature and high pressure hydrogen corrosion resistant thick steel plates of examples 1-7 have tensile strength of 576MPa-611MPa and area shrinkage of 68% -72% after high temperature and high pressure hydrogen charging test. The tensile strength of the comparative steels of comparative examples 1-3 after high temperature and high pressure hydrogen charging experiments is 539MPa-561MPa, and the reduction of area is 47% -56%.
The comparative steels of comparative examples 1 to 3 have lower tensile strength and far lower reduction of area than the high temperature and high pressure hydrogen corrosion resistant steel plates of examples 1 to 7, mainly because the example steels contain a large amount of Ti dispersed finely 2 O 3 +Al 2 O 3 +MnS composite oxides, which have the function of absorbing hydrogen, thereby avoiding the decrease of the tensile strength and the reduction of area of steel after hydrogen corrosion.
As can be seen from a combination of tables 4 and 5, the steels of the examples and comparative examples each contain Ti 2 O 3 +Al 2 O 3 +MnS composite inclusions, but Ti having a size of less than 3 μm in the steels of examples 1 to 7 2 O 3 +Al 2 O 3 The volume density of the +MnS composite inclusions is significantly higher than that of the steels of comparative examples 1 to 3, and is all greater than 1.0X10 3 Individual/mm 3 The method comprises the steps of carrying out a first treatment on the surface of the And the average diameter of all inclusions in the steels of examples 1 to 7 was less than 4. Mu.m, and the size of Ti was less than 3. Mu.m in the steels of examples 1 to 7 2 O 3 +Al 2 O 3 The proportion of the +MnS composite inclusion is more than 60 percent. While in the comparative example Ti 2 O 3 +Al 2 O 3 The average diameter of the +MnS composite inclusion is more than 4 mu m, ti 2 O 3 +Al 2 O 3 The volume density of the +MnS composite inclusions is less than 1.0x10 3 Individual/mm 3 Composite clip with size smaller than 3 μmThe proportion of impurities is less than 50% in total, which is caused by the different order of adding deoxidizers during the deoxidizing process.
Accordingly, since the density, average diameter and distribution ratio of inclusions in the steel products of examples 1 to 7 according to the present invention are remarkably superior, the high-temperature and high-pressure hydrogen corrosion resistant thick steel plates of examples 1 to 7 have superior high-temperature and hydrogen corrosion resistance to those of comparative examples 1 to 3, which are particularly shown that the steel products of examples 1 to 7 after being subjected to high-temperature and high-pressure hydrogen charging experiments are far better in tensile strength and reduction of area after being stretched than those of comparative examples 1 to 3.
From the above, it can be seen that the invention can form a large amount of Ti in fine dispersion distribution in the steel by controlling the types and the addition sequence of the deoxidizers during the smelting of the molten steel 2 O 3 +Al 2 O 3 +mns composite inclusions; the composite inclusions can adsorb H element entering the steel due to diffusion, reduce the concentration of the segregation of H atoms and C atoms in the steel, reduce or avoid the formation of methane gas, and further improve the high-temperature hydrogen corrosion resistance of the steel.
Therefore, the high-temperature high-pressure hydrogen corrosion resistant thick steel plate has very excellent high-temperature hydrogen corrosion resistance, and has very good popularization prospect and application value; the pressure equipment produced by adopting the steel can ensure the stable and safe operation of the pressure equipment and avoid production accidents caused by hydrogen corrosion.
It should be noted that the combination of the technical features in the present invention is not limited to the combination described in the claims or the combination described in the specific embodiments, and all the technical features described in the present invention may be freely combined or combined in any manner unless contradiction occurs between them.
It should also be noted that the above-recited embodiments are merely specific examples of the present invention. It is apparent that the present invention is not limited to the above embodiments, and similar changes or modifications will be apparent to those skilled in the art from the present disclosure, and it is intended to be within the scope of the present invention.
Claims (8)
1. The high-temperature high-pressure hydrogen corrosion-resistant thick steel plate is characterized by comprising the following chemical elements in percentage by mass:
c: 0.09-0.18%, si:0.20 to 0.60 percent, mn:0.35 to 0.75 percent, cr:2.35 to 3.15 percent, mo:0.50 to 1.20 percent, al(s): 0.005-0.015%, nb:0.020 to 0.050 percent, ti:0.015 to 0.030 percent, B:0.0005 to 0.0020 percent, O:0.0025 to 0.0040 percent; the balance of Fe and unavoidable impurities;
which has a fine, dispersed and spherical Al 2 O 3 +Ti 2 O 3 +MnS composite inclusions, wherein Al having a particle diameter of less than 3 μm 2 O 3 +Ti 2 O 3 +MnS composite inclusions occupy all Al 2 O 3 +Ti 2 O 3 The +MnS composite inclusions have a proportion of more than 60%, an average grain size of all inclusions of less than 4 μm, an average aspect ratio of all inclusions of not more than 1.3, and inclusions having a grain size of less than 5 μm, and a bulk density of inclusions having a grain size of less than 5 μm of more than 1.0X10 3 Individual/mm 3 。
2. The high temperature and high pressure hydrogen corrosion resistant steel sheet according to claim 1, further comprising at least one of the following chemical elements:
0＜Cu≤0.30％；
0＜Ni≤0.30％。
3. the high temperature and high pressure hydrogen corrosion resistant steel sheet according to claim 1, wherein, among other unavoidable impurities: p is less than or equal to 0.010%, S is less than or equal to 0.010%, and N is less than or equal to 0.0050%.
4. The high temperature and high pressure hydrogen corrosion resistant steel sheet according to claim 1, wherein the tensile strength is higher than 550MPa and the reduction of area is not lower than 65% after maintaining at least 1000 hours at a temperature of at least 550 ℃, a pressure of at least 30MPa and a hydrogen partial pressure of at least 20MPa after charging hydrogen.
5. The method for manufacturing a high-temperature high-pressure hydrogen corrosion resistant thick steel plate according to any one of claims 1 to 4, comprising the steps of:
(1) Smelting and casting: adding a deoxidizer Si, mn, ti, al in the molten steel smelting process; wherein, before molten steel casting, pre-deoxidizing is carried out according to the sequence of Si, mn and Ti, and the oxygen level of the cast molten steel is controlled to be 0.0045-0.0085 percent; then adopting Al to carry out final deoxidation, and controlling the mass percentage content of the Al in the molten steel to be 0.005-0.015%;
(2) Rolling;
(3) Quenching and tempering.
6. The method according to claim 5, wherein in the step (2), the cast slab is heated to 1060 to 1150 ℃, the finishing temperature is controlled to be more than 930 ℃, and the total cumulative reduction is controlled to be more than 65%.
7. The method according to claim 5, wherein in the step (3), the quenching temperature is controlled to be 880 to 950 ℃, the holding time is controlled to be (1.0 to 2.8) x T min, and the steel sheet is cooled to room temperature by tapping after the holding, wherein T represents the thickness of the steel sheet in mm.
8. The method according to claim 5, wherein in the step (3), the tempering temperature is controlled to 695 to 745 ℃, and the holding time is controlled to (2.3 to 3.6) x T min, wherein T represents the thickness of the steel sheet in mm.
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