CN115948694A - High-performance austenitic stainless steel plate with thickness of less than 45mm and manufacturing method thereof - Google Patents
High-performance austenitic stainless steel plate with thickness of less than 45mm and manufacturing method thereof Download PDFInfo
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Abstract
The invention provides a high-performance austenitic stainless steel plate with the thickness of 45mm below and a manufacturing method thereof, wherein the steel plate comprises the following components in percentage by weight: c:0.10% -0.15%, si: 0.7-0.9%, mn: 1.70-1.90%, P is less than or equal to 0.010%, S is less than or equal to 0.002%, cr:16.5% -17.5%, ni:6.5% -7.5%, mo:1.0% -2.0%, N:0.035% -0.055%, ce: 80-110 ppm, mg:0.05 to 0.15%, nb:0.10 to 0.15%, ti:0.5 to 0.6 percent, and the balance of Fe and inevitable impurities; the manufacturing method comprises smelting, continuous casting, heating, rolling and grain boundary engineering control; the tensile strength of the steel plate produced by the invention is more than or equal to 800MPa, the yield strength is more than or equal to 420MPa, the elongation after fracture is more than or equal to 40 percent, the impact energy at room temperature is more than or equal to 350J, the Brinell hardness is less than or equal to 230HBW, the ductile-brittle transition temperature is less than or equal to-260 ℃, and the intergranular corrosion resistance is excellent.
Description
Technical Field
The invention belongs to the field of metal materials, and particularly relates to a high-performance austenitic stainless steel plate with the thickness of less than 45mm and a manufacturing method thereof.
Background
The 300 series austenitic stainless steel generally has primary carbides with different contents, and the generation reason is that the carbides directly separated from a liquid phase are called as primary carbides due to different solubilities of alloy elements in a solid-liquid phase when the metal is solidified, and the alloy elements are segregated in the solidification process, so that the primary carbides have the following hazards, damage the continuity of the metal, cause stress concentration, reduce the machinability of the material, consume a large amount of alloy elements such as C, cr, mo and the like, and reduce the toughness and the corrosion resistance of the material; the secondary carbides with different morphological distributions exist at the same time, and the production reason is that the solidification process of a casting blank is faster, and the diffusion of carbon and alloy elements in a solid phase is slower, so that the secondary carbides are separated out from austenite, the dispersed secondary carbides can improve the strength and the wear resistance of a steel plate, simultaneously inhibit the growth of austenite grains, and reduce the ductile-brittle transition temperature of the material, but the secondary carbides, such as precipitation, aggregation and growth at the austenite grain boundary or the formation of a reticular secondary carbide, can reduce the shaping, toughness and corrosion resistance of the material. At present, no production method for high-performance austenitic stainless steel for effectively controlling the content of primary carbides and optimizing the distribution form of secondary carbides exists in China.
At present, related patents in China are few, and the related patents mainly comprise the following items:
a method for reducing chain-shaped carbide of high-performance heat-resistant stainless steel material (CN 201610498260.5) discloses a chemical component C of stainless steel: 0.08% -0.15%, si: less than or equal to 0.1 percent, mn: 0.35-0.65%, P: less than or equal to 0.015%, S: less than or equal to 0.010 percent, cr:10% -12%, mo:0.1% -0.4%, V:0.15% -0.25%, ni:0.3% -0.7%, co:2.5% -3.5%, W:2.4% -3.0%, nb:0.05 to 0.12%, N: 0.01-0.035%, B:0.01 to 0.025 percent of Al and less than or equal to 0.015 percent of Al, adding 1.5 kilograms per ton of rare earth element Zr during primary smelting, and casting to prepare an electrode bar; carrying out electroslag secondary remelting on the prepared electrode rod to prepare an electroslag steel ingot; loading the obtained electroslag ingot into a heating furnace, heating to 1150-1170 ℃, keeping the temperature for a certain time, discharging from the furnace and forging to prepare a blank; putting the prepared blank into a heating furnace, heating to 1150-1170 ℃, taking out of the furnace after keeping the temperature for a certain time, and forging into a material; the heat-resistant stainless steel material produced by the method has uniform structure, so that the high-temperature creep property and the fatigue life of the alloy material are greatly improved. In the patent, the steel plate is produced by adopting secondary electroslag remelting and forging methods, so that the production cost is high, the energy consumption is high, the pollution is serious, and the plate shape and the performance uniformity of the product are poor.
A method for producing a high-carbon martensitic stainless steel containing 0.40 to 0.80% of carbon and 11 to 16% of chromium as main components, which comprises feeding molten stainless steel from a tundish through a nozzle into a molten steel bath to cast a stainless steel sheet in a strip casting apparatus, and immediately after casting the stainless steel sheet, producing a hot-rolled annealed strip steel by an in-line roll at a reduction ratio of 5 to 40% so that primary carbides are 10 [ mu ] m or less in the microstructure of the hot-rolled annealed strip steel, is disclosed in "high-carbon martensitic stainless steel and a method for producing the same" (CN 201080058577.8). The comparison document is essentially different from the invention in that the chemical composition systems are different, the types of stainless steel are different, the thicknesses of steel plates are different, and the carbide control level of the comparison document is lower and does not reach the advanced level of 10-100 nm.
Disclosure of Invention
The present invention has been made to overcome the above problems and disadvantages and an object of the present invention is to provide a high-performance austenitic stainless steel sheet of 45mm or less and a method for manufacturing the same.
According to the invention, rare earth elements cerium and magnesium are added into chemical components, and the pulse magnetic oscillation technology PMO is combined, so that the content of primary carbides and the distribution form of secondary carbides in the continuous casting billet are effectively controlled, and the high-performance austenitic stainless steel medium plate with the thickness of below 45mm is produced. Meanwhile, by adopting a spheroidizing annealing process, a micro cold deformation process, a solid solution heat treatment process and a low-temperature long-time tempering process (grain boundary engineering), the proportion of low sigma CSL grain boundaries in the material is obviously improved under a high-carbon condition, the distribution of secondary carbides in a steel plate is optimized, the precipitation of primary carbides is further inhibited, and the intergranular corrosion resistance and the comprehensive mechanical property of the steel plate are improved.
The purpose of the invention is realized as follows:
a high-performance austenitic stainless steel plate with the thickness of less than 45mm comprises the following components in percentage by weight: c:0.10% -0.15%, si: 0.7-0.9%, mn: 1.70-1.90%, P is less than or equal to 0.010%, S is less than or equal to 0.002%, cr:16.5% -17.5%, ni:6.5% -7.5%, mo:1.0% -2.0%, N: 0.035-0.055%, ce: 80-110 ppm, mg:0.05 to 0.15%, nb:0.10 to 0.15%, ti:0.5 to 0.6 percent, and the balance of Fe and inevitable impurities.
Further, the method comprises the following steps of; nickel chromium equivalence ratio omega Nieq /ω Creq 0.6 to 0.75; wherein, ω is Nieq ＝ω Ni +40ω C +30ω N +0.5ω Mn +0.5ω Co +0.3ω Cu ；
ω Creq ＝ω Cr +1.5ω Si +ω Mo +0.5ω W +2.5ω V +1.5ω Nb +2ω Ti +2.8ω Al 。
Further, the method comprises the following steps of; the volume percentage content of the primary carbides in the steel plate is less than or equal to 1.5 percent, and the size of the secondary carbides is 10-100 nm.
Further, the method comprises the following steps of; the proportion of the low sigma CSL grain boundary in the steel plate is more than 78 percent.
Further, the method comprises the following steps of; the tensile strength of the steel plate is more than or equal to 800MPa, the yield strength is more than or equal to 420MPa, the elongation after fracture is more than or equal to 40%, the room temperature impact energy is more than or equal to 350J, the Brinell hardness is less than or equal to 230HBW, the ductile-brittle transition temperature is less than or equal to-260 ℃, and the intergranular corrosion resistance is excellent.
The design reason of the components of the invention is as follows:
c: carbon is an element that strongly forms and stabilizes austenite, and carbon easily precipitates as carbide with other alloy elements, so that an increase in carbon content results in an increase in the strength of stainless steel, but the impact toughness decreases and the ductile-brittle transition temperature increases. In addition, the existence of carbon element, supersaturated carbon will precipitate in the form of carbide, which causes the chromium depletion of adjacent area, thus the austenitic stainless steel has higher intergranular corrosion sensitivity, the invention adopts grain boundary engineering to solve in the steel plate production process, in order to ensure the steel plate strength, therefore the invention requires that the C content in the steel is controlled within the range of 0.10-0.15%.
Si: the addition of a proper amount of silicon element in the stainless steel can improve the oxidation resistance and the vulcanization resistance of the stainless steel and endow the steel with excellent corrosion resistance in strong oxidizing media such as concentrated nitric acid, concentrated sulfuric acid and the like, which is related to the formation of a silicon-rich oxide protective film on the surface of the stainless steel by the silicon. The adverse effect is that when the silicon content is less than l% and is normal in stainless steel, a higher silicon content reduces the corrosion resistance of the chromium-nickel austenitic stainless steel and significantly increases the susceptibility of the steel to solid solution intergranular corrosion. Therefore, the Si content of the invention is controlled between 0.7 and 0.9 percent.
Mn: in stainless steel, manganese remains in the steel as a deoxidizing element, and one of the important roles of manganese is embodied in nickel-saving stainless steel and high-nitrogen stainless steel, and the substitution of manganese for nickel saves nickel resources, and simultaneously increases the solubility of nitrogen and improves the strength. In austenitic stainless steels, manganese in a mass fraction of up to 2% has a negligible effect on hardness. Another important role of manganese is the formation of MnS, inhibiting the harmful effects of sulfur. Improve the high-temperature thermoplasticity of the high-chromium-nickel austenitic stainless steel. In terms of corrosion resistance, the increase of manganese deteriorates the corrosion resistance of stainless steel. It was found that as the manganese content increased. The pitting corrosion resistance of the material is reduced. An appropriate amount of manganese is beneficial, especially in combination with nitrogen, to save the rare precious metal nickel. In order to reduce the cost, however, if the amount of the additive is too large, the corrosion resistance and the ductility and toughness of the stainless steel are deteriorated. Therefore, the Mn content in the steel is controlled to be 1.70-1.90 percent by comprehensively considering the factors.
P: phosphorus is a harmful element in steel, increases cold brittleness of steel, deteriorates weldability, reduces plasticity, deteriorates cold bending properties, and P is also particularly sensitive to irradiation embrittlement. Therefore, the lower the P content in the steel, the better, the invention requires not more than 0.010%.
S: sulfur is a harmful element in general. S generally tends to form brittle sulfides with alloying elements in steel, to cause hot brittleness of steel, to reduce ductility and toughness of steel, and to accelerate radiation embrittlement. Therefore, the present invention requires that the S content in the steel should be limited to 0.002% or less.
Cr: chromium is one of the most important elements in stainless steel. In austenitic stainless steels, the interaction of chromium and nickel forms a stable austenitic structure. In a single austenitic stainless steel, the chromium content does not have a significant effect on the mechanical properties. When a ferrite phase or a sigma phase occurs in the steel, the strength of the steel is increased and the ductility and toughness are decreased as the chromium content is increased. With the increase of the Cr content, the austenite phase content is gradually reduced, and the ferrite phase content is increased; the yield strength and the tensile strength are continuously increased, the elongation is firstly reduced and then increased, the reduction of area is continuously reduced, the impact absorption power is firstly reduced and then increased, and the electrochemical corrosion resistance and the stress corrosion resistance are enhanced. Therefore, the invention requires that the Cr content in the steel is 16.5-17.5%.
Ni: in the austenitic stainless steel, the interaction of chromium and nickel forms a stable austenitic structure, and in the stable austenitic structure, nickel is added, so that the plasticity and toughness of the austenitic stainless steel can be further improved, and the austenitic stainless steel has better stainless property and corrosion resistance; however, an increase in nickel content leads to an increase in the susceptibility to intergranular corrosion of austenitic stainless steels. Therefore, the invention requires that the Ni content in the steel is controlled to be 6.5-7.5%.
Nickel chromium equivalence ratio (omega) Nieq /ω Creq )：ω Nieq ＝ω Ni +40ω C +30ω N +0.5ω Mn +0.5ω Co +0.3ω Cu ；ω Creq ＝ω Cr +1.5ω Si +ω Mo +0.5ω W +2.5ω V +1.5ω Nb +2ω Ti +2.8ω Al . In austenitic stainless steels, the interaction of chromium and nickel, i.e. the nickel-chromium equivalence ratio (ω) is the determining factor for inhibiting the precipitation of δ -ferrite, thereby forming a stable austenitic structure Nieq /ω Creq ) 0.6 to 0.75. The delta-ferrite is precipitated in the cooling process at the later stage of smelting and is caused by dendritic segregation caused by non-equilibrium phase transformation in the cooling process. The reasonable nickel-chromium equivalent ratio ensures that the delta-ferrite formed in the solidification process is distributed in a small block shape or a strip shape, and can be completely absorbed in the later rolling deformation and heat treatment processes, thereby ensuring the stability of an austenite single-phase structure, improving the low-temperature impact toughness of the product and reducing the ductile-brittle transition temperature of the product. Therefore, the invention requires that the nickel-chromium equivalence ratio in the steel is controlled to be 0.65-0.75.
Mo: molybdenum is an important alloying element widely used in stainless steels. Studies have shown that in marine atmosphere, it is difficult to completely prevent the rusting of stainless steel with chromium alone, even with chromium contents as high as approximately 24%, and molybdenum must be added. However, the beneficial effect on corrosion resistance of stainless steel is premised on the fact that the steel must contain a sufficient amount of elemental chromium. Moreover, the chromium content in the steel increases. The beneficial effect of molybdenum in the steel is also significantly increased. For austenitic stainless steel, molybdenum has a significant solid solution strengthening effect. Molybdenum also improves the corrosion resistance of the stainless steel, but too high a content of molybdenum is detrimental to the stress corrosion resistance of the austenitic stainless steel. The proper amount of molybdenum element is favorable for improving the resistance of the stainless steel to stress corrosion cracking, so the invention requires that the Mo content in the steel is controlled to be 1.0-2.0%.
N: nitrogen may partially replace nickel in austenitic stainless steels to conserve nickel. The nitrogen can also improve the corrosion resistance of the austenitic stainless steel, promote the enrichment of chromium in a passive film and improve the passivation capability of the steel; the nitrogen may form NH3 and NH4+ to raise the pH of the solution in the micro-zone. Chromium-rich nitrides are formed at the interface of the metal and the passivation film, further enhancing the stability of the passivation film. While nitrogen may also combine with molybdenum to form Ni 2 Mo 2 And N enables the passive film to be more stable, the pitting corrosion resistance and the crevice corrosion resistance of the austenitic stainless steel can be obviously improved, and the pitting corrosion resistance and the crevice corrosion resistance of the austenitic stainless steel are also improved along with the increase of the nitrogen content. However, when the nitrogen content in the steel exceeds a certain amount, the performance of the stainless steel is affected, and the cold and hot workability and cold formability of the steel are reduced, so that the invention requires that the N content in the steel is controlled to be 0.035 to 0.055%
Ce: cerium element reacts with large-size Al of 50-100 mu m in the smelting process 2 O 3 Mixing and modifying into soft CeAlO with a size of 1 μm or less 3 The fine rare earth inclusion can be used as a nucleation mass point of high-temperature ferrite to refine a dendritic structure, so that microsegregation is reduced, the size of primary carbides is reduced, the primary carbides are distributed more uniformly, and a foundation is laid for crushing large-size primary carbides and dissolving small-particle primary carbides in the subsequent rolling process, so that the content of Ce in the steel is required to be controlled to be 80-110 ppm.
Mg: in-situ smelting of magnesiumMixing with 50-100 mu m large-size Al in the smelting process 2 O 3 Mixing and combining the materials, and modifying the materials into soft and fine MgAl with the particle size of 2-6 mu m 2 O 4 The mismatching degree of fine spinel inclusions and carbides of the magnesium aluminate spinel is smaller, the magnesium aluminate spinel is easier to become the nucleation core of the carbides, so that the primary carbides are refined, and a foundation is laid for crushing large-size primary carbides and dissolving small-particle primary carbides in the subsequent rolling process, so that the Mg content in the steel is required to be controlled to be 0.05-0.15%.
Ti: the main functions of titanium in stainless steel are grain refinement and formation of titanium carbides and carbonitrides, reducing or avoiding harmful Cr 23 C 6 Type carbide precipitates, and intergranular corrosion is considered to be the precipitation of Cr from saturated austenite 23 C 6 The morphology is separated out, which causes the chromium to be poor due to austenite at the grain boundary. After Ti element is added into steel, carbon is preferentially combined with the Ti element and the Ti element to generate titanium carbide (TiC) and titanium carbonitride (Ti (C, N)), so that the condition that grain boundary is poor in chromium due to chromium carbide precipitation is avoided, intergranular corrosion is effectively prevented, and the creep strength and the endurance life of stainless steel can be improved by the precipitated TiC, therefore, the Ti content in the steel is required to be controlled to be 0.50-0.60%.
Nb: niobium is one of important alloying elements of Cr — Ni austenitic stainless steel, and its amount is inferior to molybdenum, and its effect is multifaceted, and particularly, heat-resistant stainless steel in the high temperature field is more important. Under the condition of high temperature, second phase particles Fe dispersed in the material are precipitated 2 Nb prevents the crystal grains from growing, improves the high-temperature strength and prevents the material from softening caused by high temperature. At the same time, nb element can also reduce or avoid harmful Cr 23 C 6 The carbide precipitates, the microhardness of the material is reduced, and the low-temperature toughness is effectively improved, so that the Nb content in the steel is required to be controlled to be 0.10-0.15%.
The second technical scheme of the invention is to provide a manufacturing method of a high-performance austenitic stainless steel plate with the thickness of below 45mm, which mainly comprises smelting, continuous casting, heating, rolling and grain boundary engineering control;
(1) Smelting:
the content of impurity elements is strictly controlled by using industrial pure iron in an EAF electric furnace; strictly controlling the contents of chromium and nickel components in the AOD converter, and controlling the S content to be 25-30 ppm after tapping; slagging off at the first time of converter tapping until the slag is 10-15cm, refining and feeding high-calcium wires outside an LF furnace, and strictly controlling the content of harmful elements such as P, S; vacuumizing for 15-20 min in the VOD vacuum treatment process under the protection of argon in the whole process.
(2) Continuous casting
The casting process of the SCC continuous casting billet comprises the following steps: after vacuum treatment, molten steel is poured through a 200mm section thick slab continuous casting machine under the protection of argon in the whole process, a crystallizer pulse magnetic oscillation (PMO for short) solidification homogenization technology is adopted, the superheat degree range of a tundish is 20-32 ℃, steel is drawn at a constant temperature and a constant speed, the water temperature is 17-21 ℃, the specific water amount is 0.8-1.0L/kg, the water amount of a crystallizer is 155-165 t/H, the peak current of PMO treatment is 300-350 KA, the treatment frequency is 40-45 KHz, and after a continuous casting billet is off line, a single block is immediately spread and cooled for 24-30 hours, so that the sufficient discharge of redundant H elements is ensured, and the steel billet cracking is prevented.
The PMO technology promotes nucleation through pulse current formed by double-cold pulse magnetic oscillation through an 'electro-supercooling' effect, effectively improves the isometric crystal rate of the center of a casting blank, eliminates the defect of middle shrinkage cavity, inhibits the enrichment of solidification center elements, and obviously improves the internal quality of the PMO-treated continuous casting blank. The average central equiaxial crystal proportion of the casting blank is 12-14%, the average central carbon segregation index is 1.05-1.15, and the content of primary carbide in the casting blank is less than or equal to 5.5%.
(3) Heating:
heating the steel billet by a continuous furnace at the temperature of 1220-1240 ℃; meanwhile, the heating time of the steel billet is controlled to be 7-9 min/mm.
(4) Rolling:
and (3) taking the heated steel billet out of the furnace, descaling by using a descaling box, and then performing primary descaling before the second pass and the penultimate pass. Rolling by adopting a direct rolling mode, wherein the initial rolling temperature is 1090-1120 ℃, the final rolling temperature is 750-800 ℃, the reduction rate of each pass is ensured to be 19-32%, the deformation rate of 0.6-1.2% is reserved after the final rolling to the thickness of a final finished product, and air cooling is carried out to the room temperature.
By using the low-temperature low-speed high-pressure rolling method, the lower the deformation temperature is, the larger the deformation stress is, the more beneficial the crushing of primary carbides are, and the primary carbides with small particles are easier to dissolve, so the initial rolling temperature and the final rolling temperature are properly reduced; meanwhile, the size of the primary carbide is reduced along with the increase of the hot rolling deformation, the extrusion degree of the matrix to the primary carbide is obviously improved by larger reduction, the deformation temperature is reduced along with the increase of the reduction, and the extrusion degree of the matrix to the primary carbide is correspondingly increased, so that the size of the primary carbide is effectively controlled, and therefore, the single-pass reduction is properly improved. The content of primary carbide in the rolled steel plate is controlled to be 2.0-3.5%.
(4) Grain boundary engineering control
A. The cooled steel plate enters a heat treatment furnace for spheroidizing annealing heat treatment, and the process comprises the following steps: one-stage heating temperature: 860 +/-10 ℃, net heat preservation time of 90 +/-5 min, furnace cooling to 750 +/-10 ℃, entering two stages, net heat preservation time of 135 +/-5 min, furnace cooling to room temperature, and cooling speed of 20-25 ℃/h.
After spheroidizing annealing, secondary carbides with good sphericity and uniform distribution are obtained in the structure; along with the proceeding of straightening deformation, the original crystal grains deform or even break to form more secondary carbide-shaped core particles, and the size of the secondary carbide becomes fine and uniform;
B. and (4) after cooling, the steel plate enters a cold straightening machine to finish 0.6 to 1.2 percent of cold deformation to the thickness of a finished product.
C. Then entering a solution heat treatment furnace for solution heat treatment: the process comprises the following steps: and (3) heat preservation temperature: 1080 +/-10 ℃, keeping the temperature for 2.5 +/-0.5 min/mm, and cooling to room temperature by water;
the temperature of the solution heat treatment is higher than the austenitizing temperature, and the volume fraction of primary carbides is gradually reduced along with the heat treatment;
D. finally, long-time low-temperature tempering heat treatment is carried out, and the process is as follows: and (3) heat preservation temperature: 220 +/-10 ℃, keeping the temperature for 15 +/-0.5 h and cooling in air. After tempering heat treatment, large-size strip-shaped secondary carbides precipitated at grain boundaries in the structure are refined into 10-100nm nanometer-scale secondary carbides.
By adopting the spheroidizing annealing, micro cold deformation, solid solution heat treatment and low-temperature long-time tempering process (grain boundary engineering), under the condition of high carbon, the grain boundary proportion of special structure grain boundaries (generally, low sigma CSL grain boundaries with sigma being less than or equal to 29, CSL is an abbreviation of a double site/center site) in the austenitic stainless steel is obviously improved, when the low sigma CSL grain boundary proportion is more than 78 percent, the distribution of the low sigma CSL grain boundaries is optimized, the precipitation of carbides is inhibited, the steel plate has good mechanical property, corresponding low sigma CSL grain boundary clusters are formed at the same time, and a large number of low sigma CSL grain boundaries can effectively break the network connectivity of the general large-angle grain boundaries, so that the permeation of corrosion from the surface to the inside is inhibited, and the intergranular corrosion resistance of the material is finally obviously improved. And finally, the volume percentage of the primary carbides in the finished steel plate is less than or equal to 1.5%, the secondary network carbides completely disappear and are converted into fine granular carbides, the size of the carbides is reduced from more than 100nm to 10-100nm, and the carbides are uniformly dispersed in the crystal boundary.
The invention has the following beneficial effects:
(1) In the continuous casting process, the PMO technology is adopted, the pulse current formed by secondary cooling pulse magnetic oscillation promotes nucleation through an 'electro-supercooling' effect, the equiaxial crystal rate of the center of a casting blank is effectively improved, the defect of medium shrinkage cavity is eliminated, the enrichment of solidification center elements is inhibited, and the internal quality of the PMO-treated continuous casting blank is obviously improved
(2) And controlling the content of primary carbides in the finished steel plate to be less than or equal to 1.5% by adopting grain boundary engineering, wherein the secondary network carbides completely disappear and are converted into fine granular carbides, the size of the carbides is reduced from more than 100nm to 10-100nm, and the carbides are uniformly dispersed and distributed in the grain boundaries.
(3) The tensile strength of the steel plate is more than or equal to 800MPa, the yield strength is more than or equal to 420MPa, the elongation after fracture is more than or equal to 40 percent, the impact energy at room temperature is more than or equal to 350J, the Brinell hardness is less than or equal to 230HBW, the ductile-brittle transition temperature is less than or equal to-260 ℃, and the intergranular corrosion resistance is excellent.
Drawings
FIG. 1 is a transmission electron microscope image of carbides of a stainless steel plate as an original ingot in example 1 of the present invention.
FIG. 2 is a transmission electron micrograph of carbide of a stainless steel sheet according to example 1 of the present invention, which was not subjected to grain boundary engineering treatment.
FIG. 3 is a transmission electron micrograph of carbides of a stainless steel sheet according to example 1 of the present invention, which has been subjected to grain boundary engineering treatment.
Detailed Description
The present invention is further illustrated by the following examples.
According to the embodiment of the invention, smelting, continuous casting, heating, rolling and grain boundary engineering control are carried out according to the component proportion of the technical scheme.
Rolling:
rolling by adopting a direct rolling mode, wherein the initial rolling temperature is 1090-1120 ℃, the final rolling temperature is 750-800 ℃, and the reduction rate of each pass is ensured to be 19-32%;
controlling grain boundary engineering:
A. cooling to room temperature, putting the steel plate into a heat treatment furnace, carrying out spheroidizing annealing heat treatment,
the process comprises the following steps: one-stage heating temperature: 860 +/-10 ℃, net heat preservation time is 90 +/-5 min, furnace cooling is carried out to 750 +/-10 ℃, the two stages are carried out, the net heat preservation time is 135 +/-5 min, then furnace cooling is carried out to room temperature, and the cooling speed is controlled to be 20-25 ℃/h;
B. after cooling, the steel plate enters a cold straightening machine to finish cold deformation with the straightening deformation rate of 0.6-1.2% to the thickness of a finished product;
C. then the mixture enters a solution heat treatment furnace for solution heat treatment, and the process is as follows:
and (3) heat preservation temperature: 1080 +/-10 ℃, net heat preservation time of 2.5 +/-0.5 min/mm, and water cooling to room temperature;
D. finally, long-time low-temperature tempering heat treatment is carried out, and the process comprises the following steps:
heating temperature: 220 +/-10 ℃, keeping the temperature for 15 +/-0.5 h and cooling in air.
Further, the method comprises the following steps of; the smelting process comprises the following steps: the content of impurity elements is strictly controlled by using industrial pure iron in an EAF electric furnace; strictly controlling the contents of chromium and nickel components in the AOD converter, and controlling the S content to be 25-30 ppm after tapping; slagging off the converter steel tapping, refining and feeding high-calcium wires outside an LF furnace until the slag thickness is 10-15cm; the VOD vacuum treatment process is carried out for 15-20 min under the protection of argon gas in the whole process.
Further, the method comprises the following steps of; the continuous casting process comprises the following steps: the molten steel after vacuum treatment is poured in a whole-course protection mode through argon, a crystallizer pulse magnetic oscillation PMO solidification homogenization technology is adopted, the superheat degree of a tundish is 20-32 ℃, the water temperature is 17-21 ℃, the specific water quantity is 0.8-1.0L/kg, the water quantity of a crystallizer is 155-165 t/h, the peak current of PMO treatment of the crystallizer pulse magnetic oscillation is 300-350 KA, the treatment frequency is 40-45 KHz, and the continuous casting billet is immediately cooled for 24-30 hours in a single block after being off-line.
Further, the method comprises the following steps of; after being treated by the pulse magnetic oscillation PMO of the crystallizer, the average central equiaxed crystal proportion of the casting blank is 12 to 14 percent, the average central carbon segregation index is 1.05 to 1.15, and the content of primary carbide in the casting blank is less than or equal to 5.5 percent.
Further, the method comprises the following steps of; the billet heating temperature is 1220-1240 ℃, and the billet heating time is 7-9 min/mm.
The compositions of the steels of the examples of the invention are shown in table 1. The main process parameters of steel smelting in the embodiment of the invention are shown in Table 2. The main process parameters of the steel rolling of the embodiment of the invention are shown in table 3. The main process parameters of the steel grain boundary engineering of the embodiment of the invention are shown in Table 4. The structure of the steel of the example of the invention is summarized in profile 5. The properties of the steels of the examples of the invention are shown in Table 6.
TABLE 1 composition of steels of inventive examples (wt%)
TABLE 2 Main Process parameters for Steel smelting in the inventive examples
TABLE 3 Main Process parameters for Steel Rolling according to the examples of the invention
TABLE 4 Main technological parameters of the steel grain boundary engineering of the embodiment of the invention
TABLE 5 Structure of inventive example steels
TABLE 6 Properties of steels of examples of the invention
Remarking: the intercrystalline corrosion resistance is tested by the method E in the standard GB/T4334-2020 intergranular corrosion test method for metals and alloys, and the evaluation result is qualified.
According to the method, the content of the primary carbides in the finished steel plate is controlled to be less than or equal to 1.5% by adopting the grain boundary engineering, the secondary network carbides disappear completely and are converted into fine granular carbides, the size of the carbides is reduced from more than 100nm to 10-100nm, and the carbides are uniformly dispersed and distributed in the grain boundary. The tensile strength of the produced steel plate is more than or equal to 800MPa, the yield strength is more than or equal to 420MPa, the elongation after fracture is more than or equal to 40 percent, the impact energy at room temperature is more than or equal to 350J, the Brinell hardness is less than or equal to 230HBW, the ductile-brittle transition temperature is less than or equal to-260 ℃, and the intergranular corrosion resistance is excellent.
In order to describe the present invention, the above embodiments are properly and fully described by way of examples, and the above embodiments are only used for illustrating the present invention and not for limiting the present invention, and those skilled in the relevant art can make various changes and modifications without departing from the spirit and scope of the present invention, and any modifications, equivalent substitutions, improvements, etc. made by the persons skilled in the relevant art should be included in the protection scope of the present invention, and the protection scope of the present invention should be defined by the claims.
Claims (10)
1. The high-performance austenitic stainless steel plate with the thickness of less than 45mm is characterized by comprising the following components in percentage by weight: c:0.10% -0.15%, si: 0.7-0.9%, mn: 1.70-1.90%, P is less than or equal to 0.010%, S is less than or equal to 0.002%, cr:16.5% -17.5%, ni:6.5% -7.5%, mo:1.0% -2.0%, N: 0.035-0.055%, ce: 80-110 ppm, mg:0.05 to 0.15%, nb:0.10 to 0.15%, ti:0.5 to 0.6 percent, and the balance of Fe and inevitable impurities.
2. The high-performance austenitic stainless steel sheet having a thickness of 45mm or less according to claim 1, wherein the nickel-chromium equivalence ratio ω is Nieq /ω Creq 0.6 to 0.75; wherein, ω is Nieq ＝ω Ni +40ω C +30ω N +0.5ω Mn +0.5ω Co +0.3ω Cu ；
ω Creq ＝ω Cr +1.5ω Si +ω Mo +0.5ω W +2.5ω V +1.5ω Nb +2ω Ti +2.8ω Al 。
3. The austenitic stainless steel with high performance of less than 45mm as claimed in claim 1, wherein the steel plate has primary carbides with volume percentage of less than or equal to 1.5%, and secondary carbides with size of 10-100 nm.
4. The 45mm or less high performance austenitic stainless steel sheet according to claim 1, wherein the low sigma CSL grain boundary ratio in the steel sheet is > 78%.
5. The high-performance austenitic stainless steel plate with the thickness of 45mm or less according to claim 1, characterized in that the tensile strength of the steel plate is 800MPa or more, the yield strength is 420MPa or more, the elongation after fracture is 40% or more, the impact energy at room temperature is 350J or more, the Brinell hardness is 230HBW or less, and the ductile-brittle transition temperature is 260 ℃ or less.
6. A manufacturing method of the high-performance austenitic stainless steel plate with the thickness of 45mm or less according to the claims 1-5, comprising the steps of smelting, continuous casting, heating, rolling and grain boundary engineering control, and is characterized in that:
rolling:
rolling by adopting a direct rolling mode, wherein the initial rolling temperature is 1090-1120 ℃, the final rolling temperature is 750-800 ℃, and the reduction rate of each pass is ensured to be 19-32%;
controlling grain boundary engineering:
a) And cooling the steel plate to room temperature, putting the steel plate into a heat treatment furnace, and carrying out spheroidizing annealing heat treatment, wherein the process comprises the following steps:
one-stage heating temperature: 860 +/-10 ℃, net heat preservation time is 90 +/-5 min, furnace cooling is carried out to 750 +/-10 ℃, the two stages are carried out, the net heat preservation time is 135 +/-5 min, then furnace cooling is carried out to room temperature, and the cooling speed is controlled to be 20-25 ℃/h;
b) After cooling, the steel plate enters a cold straightening machine to finish cold deformation with the straightening deformation rate of 0.6-1.2% to the thickness of a finished product;
c) Then the mixture enters a solution heat treatment furnace for solution heat treatment, and the process is as follows:
and (3) heat preservation temperature: 1080 +/-10 ℃, net heat preservation time of 2.5 +/-0.5 min/mm, and water cooling to room temperature;
d) Finally, long-time low-temperature tempering heat treatment is carried out, and the process is as follows:
heating temperature: air cooling at 220 + -10 deg.C for 15 + -0.5 h.
7. The method for manufacturing a high-performance austenitic stainless steel sheet having a thickness of 45mm or less according to claim 6, wherein: the smelting process comprises the following steps:
the content of impurity elements is strictly controlled by using industrial pure iron in an EAF electric furnace; strictly controlling the contents of chromium and nickel components in the AOD converter, and controlling the content of S in the converter to be 25-30 ppm after tapping; slagging off the converter steel tapping, refining and feeding high-calcium wires outside an LF furnace until the slag thickness is 10-15cm; vacuumizing for 15-20 min in the VOD vacuum treatment process under the protection of argon in the whole process.
8. The method for manufacturing a high-performance austenitic stainless steel sheet having a thickness of 45mm or less according to claim 6, wherein: the continuous casting process comprises the following steps:
the molten steel after vacuum treatment is poured in an argon whole-course protection manner, a crystallizer pulse magnetic oscillation PMO solidification homogenization technology is adopted, the superheat degree of a tundish is 20-32 ℃, the water temperature is 17-21 ℃, the specific water amount is 0.8-1.0L/kg, the crystallizer water amount is 155-165 t/h, the peak current of the PMO treatment of the crystallizer pulse magnetic oscillation is 300-350 KA, the treatment frequency is 40-45 KHz, and the molten steel is immediately cooled for 24-30 hours in a single block after the continuous casting billet is off line.
9. The method for manufacturing a high-performance austenitic stainless steel sheet having a thickness of 45mm or less according to claim 8, wherein:
after being treated by the pulse magnetic oscillation PMO of the crystallizer, the average central equiaxial crystal proportion of the casting blank is 12 to 14 percent, the average central carbon segregation index is 1.05 to 1.15, and the content of primary carbide in the casting blank is less than or equal to 5.5 percent.
10. The method for manufacturing a high-performance austenitic stainless steel sheet having a thickness of 45mm or less according to claim 1, wherein: the heating temperature of the steel billet is 1220 to 1240 ℃, and the heating time is 7 to 9min/mm.
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