Ultra-high-strength high-performance sheet maraging stainless steel and preparation method thereof
Technical Field
The invention relates to an ultra-high strength high performance sheet maraging stainless steel and a preparation method thereof, belonging to the field of martensitic stainless steel.
Background
The martensite precipitation strengthened stainless steel is a new steel bell developed in the 60's of the 20 th century. The corrosion-resistant steel has the strength of the maraging strengthening steel and the corrosion resistance of the stainless steel. Due to excellent comprehensive mechanical properties, the material is often used in the fields of critical high-end equipment such as aviation, aerospace, navigation and the like.
The main reason why the martensite precipitation strengthening stainless steel can realize the ultrahigh strength is that the martensite phase transformation strengthening and the aged precipitation strengthening are superposed; the main reason for the corrosion resistance is that the addition of Cr and Mo forms a passive film on the surface, thereby providing the corrosion resistance. Table 1 shows the composition and properties of commercially available high-strength stainless steels. It can be seen that the current high-strength stainless steel has the following problems: firstly, the ductility and toughness are poorer when the strength is higher; secondly, when the mechanical property is excellent, the corrosion resistance is poor; it is difficult to unify the strength, ductility and toughness and corrosion resistance to obtain excellent comprehensive performance. Therefore, how to improve the obdurability of the stainless steel on the premise of ensuring the corrosion resistance of the stainless steel so as to meet higher requirements of engineering application on the comprehensive performance of the stainless steel is a research hotspot and difficulty in the field of stainless steel, and therefore, the research on novel ultrahigh-strength maraging stainless steel with independent intellectual property rights is urgent.
Table 1 commercial high strength stainless steel compositions and properties thereof currently on the market
The high content of Co ensures that the mechanical property of the high-strength stainless steel is excellent. When the content of Co is low or 0, the comprehensive mechanical property performance is low. The Co is added into the high-strength stainless steel to form a double-edged sword, the Co can reduce the solubility of Ti and Mo in the martensite matrix, and a precipitate phase containing Mo or Ti is formed, so that the strength is improved. Meanwhile, Co can also hinder the recovery of dislocation, reduce the size of a precipitated phase and stabilize a martensite matrix, can generate higher secondary hardening, and is a guarantee for better mechanical properties such as strength and the like. Therefore, to obtain excellent mechanical properties, a large amount of Co element is inevitably added. However, the spinodal decomposition of Cr is promoted by the addition of Co to the martensitic stainless steel, and the higher the content of Co, the greater the spinodal decomposition degree of Cr, which lowers the pitting corrosion resistance of the substrate. Therefore, an appropriate amount of Co is added. The innovation of the invention is that the alloy components, the thermal mechanical treatment process and the cold deformation process control the transformation of the high-dislocation density martensite, and improve the precipitation kinetics of the nano-phase and the nucleation and growth kinetics of the reversed transformed austenite, thereby realizing the cooperative control strengthening of the nano-phase precipitation and the martensite matrix and the toughening of the reversed transformed austenite, and realizing the improvement of the mechanical property. Meanwhile, on one hand, carbon strengthening is replaced by nano-phase strengthening, so that the carbon content is greatly reduced, and on the other hand, the pitting corrosion resistance equivalent of the alloy is improved through component optimization. The extremely low carbon content and high pitting corrosion resistance equivalent design ensures excellent corrosion resistance of the stainless steel of the present invention. Therefore, compared with the existing stainless steel, the mechanical property and the corrosion resistance of the stainless steel are improved.
The invention patent application with publication number CN 102031459 a discloses a W-containing high-strength high-toughness secondary hardening stainless steel, which comprises (by mass percent) C0.10-0.20%, Cr 11.0-13.0%, Ni 2.0-3.5%, Mo 3.5-5.5%, Co 12-15%, W0.8-3.0%, V0.1-0.6%, Nb 0.01-0.06%, Si ≤ 0.2%, Mn ≤ 0.2%, S ≤ 0.01%, P ≤ 0.01%, O ≤ 30PPm, N ≤ 30PPm, and the balance Fe; the yield strength is 1300-1600 MPa, the tensile strength is 1920-2030 MPa, and the plasticity is 10-13.5%. U.S. patent 7160399 invented ultra-high strength corrosion resistant steel; the nominal composition of the alloy named as Fernium S53 is: 14.0Co, 10.0Cr, 5.5Ni, 2.0Mo, 1.0W, 0.30V, 0.21C, and the balance Fe; the room temperature ultimate tensile strength of the Fernium S53 alloy is approximately 1980MPa and the room temperature 0.2% yield stress is approximately 1560 MPa. The invention patent application with publication number CN 110358983A discloses a precipitation hardening martensitic stainless steel and a preparation method thereof, wherein the stainless steel comprises the following specific chemical components (by mass percent), 0.14-0.20% of C, 13.0-16.0% of Cr, 0.5-2.0% of Ni, 12.0-15.0% of Co, 4.5-5.5% of Mo, 0.4-0.6% of V, less than or equal to 0.1% of Si, less than or equal to 0.5% of Mn, less than or equal to 0.01% of P, less than or equal to 0.01% of S, less than or equal to 0.10% of N, and the balance of Fe; the tensile strength is 1840-1870 MPa, the yield strength is 780-820 MPa, and the elongation is 12.5-14%. Although the three technical schemes have the performance of high-strength stainless steel, the raw material cost is high due to the high addition of Co; the content of Co is increased, so that the scroll of Cr can be decomposed, a Cr-poor area and a Cr-rich area are further generated, and the corrosion resistance of the Cr-poor area and the Cr-rich area is reduced; the carbon content is also high, the corrosion resistance is seriously deteriorated by high carbon, the existing size, form and distribution of carbide in a matrix are difficult to control, and the mechanical property is seriously deteriorated when the size is large and appears on a grain boundary; the production process of the publication No. CN 110358983A and Ferrium S53 needs two times of aging and two times of deep cooling treatment, and the process is complex.
The patent application of the invention with the publication number of CN 107653421A discloses an ultrahigh-strength maraging stainless steel with seawater corrosion resistance, wherein the specific chemical components of the stainless steel (expressed by mass percent) are that C is less than or equal to 0.03 percent, Cr is 13.0-14.0 percent, Ni is 5.5-7.0 percent, Co is 5.5-7.5 percent, Mo is 3.0-5.0 percent, Ti is 1.9-2.5 percent, Si is less than or equal to 0.1 percent, Mn is less than or equal to 0.1 percent, P is less than or equal to 0.01 percent, S is less than or equal to 0.01 percent, and the balance is Fe. The tensile strength is 1926-2032 MPa, the yield strength is 1538-1759 MPa, the elongation is 7.5-13.0%, and the pitting potential Epit is more than or equal to 0.15V. Although the strengthening mechanism of the invention is a precipitation strengthening mechanism, the type of the precipitation phase is different from that of the invention, compared with the invention, the invention has no higher mechanical property and corrosion resistance, and the strengthening mechanism and the corrosion resistance of the two inventions are completely different.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the problems of complex preparation process, low corrosion resistance and mechanical property and the like of the existing ultrahigh-strength stainless steel, the invention provides an ultrahigh-strength high-performance sheet maraging stainless steel and a preparation method thereof.
The technical scheme is as follows: the invention relates to a super-high strength high performance sheet maraging stainless steel and a preparation method thereof, wherein the stainless steel comprises the following components: the alloy material comprises, by mass, 2.0-5.0% of Co, 6.0-9.0% of Ni, 11.0-17.0% of Cr, 0.5-1.8% of Ti, 3.0-7.0% of Mo, 0.08-1.0% of Mn, 0.08-0.5% of Si, less than or equal to 0.02% of C, less than or equal to 0.003% of P, less than or equal to 0.003% of S, and the balance of Fe.
The invention principle and the component design basis of the ultra-high-strength high-performance sheet maraging stainless steel are as follows:
the invention principle is as follows: the stainless steel of the invention is not reinforced by carbon, the carbon is controlled at a very low level, and the toughness and the corrosion resistance of the stainless steel can be simultaneously improved. But the greatest problem with ultra-low carbon is low strength. According to the invention, the nano-strip structures with different dislocation densities in the martensite matrix are controlled through composition design, creative thermal mechanical treatment and different cold rolling deformation, the fine martensite strips can provide nucleation sites for precipitation phase and membranous metastable reverse transformation austenite by ice water quenching and large cold rolling deformation, meanwhile, element distribution channels are added for the reverse transformation austenite by high dislocation density, the reverse transformation austenite generated by the method is easier to generate TRIP (transformation Induced plasticity) effect when being loaded, and the plasticity and strength can be obviously improved. The precipitated phase of the invention is formed by adjusting the contents of Ni, Ti, Mo and Si to form Mo-rich R' phase and Ni3The strength of the (Ti, Mo) nano-phase is improved through cooperative strengthening, the two nano-strengthening phases are mainly represented by a cooperative precipitation relation, Ni-Ti-Mo-Si clusters which are fine in size and distributed in a dispersion mode are formed in the martensite laths or on dislocation at the early stage of aging, Mo and Si are gradually eliminated from the clusters along with the prolonging of aging time, and nano-sized Ni is formed first3The (Ti, Mo) strengthening phase, after a period of heat preservation, Mo and Si are completely removed from Ni3The surface of Ti forms a Mo-rich R' phase to wrap it, Ni3The growth of Ti is inhibited, the fine dispersion of precipitated phase is ensured, and the newly formed Mo-rich R' phase and Ni3Together, Ti provides the matrix with higher strength. These finely dispersed precipitated phases are in turn subjected to a plastic deformation processCan be used as a dislocation source, so that the dislocation is continuously added with value in the deformation process, and the plasticity is further increased. Simultaneously, Ni of DO24 structure is dispersed and distributed3The reverse transformed austenite with a film-shaped structure and dispersed distribution can be formed by the climb of edge dislocation and the diffusion of Fe atoms by taking coherent strain energy of a matrix interface as driving force of Ti, the energy required by reverse austenite nuclei is greatly reduced by high dislocation density and fine martensite laths, and a diffusion channel is provided for the growth of the reverse austenite by high dislocation density. The invention has the important innovation that the content of the expensive alloying element Co is greatly reduced, and the cost can be obviously reduced while the corrosion resistance is improved. Although the low Co content design reduces the forming capability of the Ni-Ti cluster, the precipitation of the Mo-rich R' phase and the metastable state film-like reverse austenite is realized through creative components and process optimization design, so that the strength and the ductility and toughness are remarkably improved. According to the invention, on the basis of innovations in the aspects of strengthening mechanism, corresponding components, thermal mechanical treatment design, heat treatment, cold deformation and the like, the mechanical property and the corrosion resistance are effectively improved on the basis of simple and controllable process and cost reduction.
The basis of component design is as follows: co is one of important elements to be considered in the invention, can improve Ms point and ensure that the matrix is martensite, but is a double-edged sword for martensite precipitation strengthening stainless steel. The addition of Co can reduce the solubility of Ti and Mo in the martensite matrix, form precipitates containing Mo or Ti, and further improve the strength. Co also hinders the recovery of dislocations, reduces the size of the precipitate phase and the matrix, and can produce a higher secondary hardening. However, addition of Co to martensitic stainless steel promotes spinodal decomposition of Cr, and the higher the content of Co, the greater the spinodal decomposition degree of Cr, which lowers the pitting corrosion resistance of the substrate. Meanwhile, the Co element is expensive, the content of Co is high, and the cost of the raw materials of the ultrahigh-strength stainless steel is high. Comprehensively considering that the mass percentage of Co is controlled to be 2.0-5.0%.
Ni is an important element for forming intermetallic compounds, and is formed by forming B2-Ni (Ti, Mn) and eta-Ni in the early stage3(Ti, Mo) for strengthening matrix, eta-Ni3(Ti, Mo) is also the core of the Mo-R' rich phase nucleation; in addition, Ni can strengthen the matrix and provide certain ductility and toughness for the stainless steel; ni also improves the hardenability of martensite. Meanwhile, Ni is also a main element for forming reverse austenite, but too high content of Ni promotes the formation of residual austenite in the matrix, thereby affecting the strength of the stainless steel. Comprehensively considering that the mass percentage of Ni is controlled to be 6.0-10.0%.
Mo is an important precipitation strengthening element. Mo is formed as Mo-R' rich phase and Ni3One of the main elements of (Ti, Mo). The Mo-R' rich phase is formed after long-time aging and is wrapped by Ni3Ti forms a core-shell structure with fine dispersion distribution, and the strength can be effectively improved. Mo is also an effective corrosion-resistant element, and the corrosion resistance of the material can be obviously improved by adding Mo. Meanwhile, Mo is also a forming element of ferrite, and the excessive content of Mo increases the precipitation tendency of delta ferrite, so that the content of Mo is increased, and the performance of the material is deteriorated. The mass percentage of Mo is comprehensively considered to be controlled to be 3.0-7.0%.
Cr is an important element in stainless steel. In order to ensure the corrosion resistance of the stainless steel, the mass percentage of the stainless steel is generally more than 10 percent. However, Cr is a ferrite-forming element, and the content thereof is too high, so that the content of delta ferrite in the matrix is increased, and the toughness and corrosion resistance of the material are affected. Therefore, the mass percentage of Cr is controlled to be 11.0-17.0%.
Si is one of important elements of the novel stainless steel, Si is one of main forming elements of the Mo-R 'rich phase, and the addition of Si can effectively promote the formation of the Mo-R' rich phase; si can also effectively inhibit the precipitation and growth of carbides in the martensite matrix in the tempering process, thereby preventing the occurrence of a Cr-poor area to reduce the corrosion resistance; however, too high a content of Si may seriously deteriorate the plasticity of the material. Comprehensively considering, the mass percentage of Si is controlled to be 0.08-0.50%.
Ti is a main strengthening phase forming element, which can form Ni-Ti clusters at the initial stage in preparation for the subsequent precipitation of a strengthening phase. When the content of Ti is too large, the tendency of precipitation of the precipitated phase at the boundary of the martensite lath becomes large, and when the content of the precipitated phase at the boundary of the martensite lath is too large, the precipitated phase is liable to develop into a crack source and propagate along the interface of the martensite lath, thereby initiating a quasi-cleavage crack. Comprehensively considering, the mass percentage of Ti should be controlled to be 0.3-2.0%.
Mn is mainly participated in the precipitation of nano-phase to form Ni (Mn, Ti, Mo) intermetallic compounds, thereby replacing Ti and Mo elements in a small amount and reducing the cost. Mn is a main element affecting reverse austenite. However, too high Mn content causes serious segregation of the steel slab, large thermal stress and structural stress, and deterioration of weldability. Comprehensively considering, the mass percentage of Mn should be controlled to be 0.08-1.0%.
C exists in the matrix as an impurity element in the stainless steel, and when the content of C is too high, MX or M is formed23C6Form carbides (M ═ Cr, Ti) which seriously retard the formation of reverse austenite, offset the gain of high dislocation density by cold rolling, and seriously deteriorate the toughness and corrosion resistance of steel when the size is too large, so that the C content is strictly controlled to 0.02% or less; p and S are impurity elements, and the performance of the stainless steel is seriously damaged by increasing the content of P and S, so the content is strictly controlled.
The invention relates to a super-high strength high performance sheet maraging stainless steel and a preparation method thereof, comprising the following steps:
(1) proportioning alloy elements;
(2) carrying out vacuum smelting on the electrode by using a vacuum induction smelting furnace;
(3) vacuum consumable remelting;
(4) carrying out high-temperature flame equalizing treatment;
(5) forging or hot rolling cogging;
(6) cold rolling deformation;
(7) and (6) heat treatment.
After the alloy is smelted, cooling and forming to room temperature, cutting off a riser, removing the skin, and then entering a thermal mechanical treatment process. The structure with uniform and fine size can be obtained through hot rolling cogging, cold rolling deformation and heat treatment, so that the structure has higher strength, toughness and corrosion resistance.
In the step (1), the alloy elements are proportioned, according to the mass percentage of each element in the stainless steel, metal chromium, metal nickel, metal manganese, metal molybdenum, metal cobalt, metal titanium and iron silicon are selected, and the balance is pure iron and inevitable impurities.
In the step (2), the vacuum induction smelting furnace is adopted for vacuum smelting of the electrode, high vacuum smelting is adopted in the whole process, and the vacuum degree is below 0.1 Pa; adding pure iron, metallic nickel, metallic molybdenum and metallic cobalt into the furnace, adding metallic chromium and metallic titanium into the furnace from a high-level bin, and adding industrial silicon and metallic manganese into the furnace from an alloy bin. Adding materials along with the furnace, melting down, adding high-level bin metal, completely melting, performing deoxidation alloying, and finally adding alloy bin metal. In the smelting period, the refining temperature reaches 1550-1650 ℃, the refining time is not less than 60 minutes, and the stirring time is not less than 10 minutes; sampling in front of the furnace to analyze smelting components, and then adjusting the components according to the target designed by the claim 1; and after the target components are adjusted, pouring at the temperature of 1530-1550 ℃, and carrying out ordinary heat preservation on a riser.
In the step (3), the vacuum consumable remelting is carried out at a melting speed of 100-260 Kg/h, and the vacuum degree is kept at 10 in the remelting process-2Pa and below.
In the step (4), the high-temperature homogenizing treatment is carried out, heating is carried out in air, vacuum or protective atmosphere, the heating mode is furnace heating, the heating rate is 100-180 ℃/h, heat preservation is carried out for 4-8 h at 600-900 ℃, then the temperature is raised to 1100-1300 ℃, heat preservation is carried out for 20-50 h, and furnace cooling, air cooling or oil cooling is carried out until the room temperature is reached.
In the step (5), the forging or rolling may be performed by casting or rolling into a square ingot or a round ingot; the technological conditions of forging or hot rolling cogging are as follows: heating the casting blank to 1100-1300 ℃, preserving heat for 10-24 h, and then discharging for rolling; the forging or hot rolling starting temperature is more than or equal to 1100 ℃, the finish forging or finish rolling temperature is more than or equal to 950 ℃, the total hot rolling amount of the plate is not less than 50%, and the ice-water mixture is cooled to room temperature.
In the step (6), the cold rolling deformation is carried out, the total reduction of the cold rolling of the plate is not less than 60%, and the cold rolling can be carried out to 1.5-5 mm according to the product requirements.
In the step (7), the heat treatment process includes: and (5) aging treatment.
Further, in the step (7), the aging treatment: the temperature is 450-600 ℃, the aging time is 0.5-300h, and the steel plate is air-cooled or quenched to the room temperature.
Has the advantages that: compared with the prior art, the invention has the advantages that:
(1) compared with other high-strength stainless steel, the high-strength stainless steel has the advantages that the content of noble metal is low, and the cost of raw materials is low;
(2) the stainless steel of the invention has extremely low carbon content or no carbon;
(3) the method for preparing the ultra-high strength and high performance sheet maraging stainless steel is simple, the high strength stainless steel can be obtained through different heat treatment processes, the process controllability is strong, and the industrial production is easy to realize. Finally, the stainless steel with good corrosion resistance and excellent mechanical property is obtained, the elongation of the martensitic stainless steel reaches 10.8%, and the tensile strength reaches 2713 MPa; and the pitting potential Epit can reach 0.39VSCE。
Drawings
FIG. 1 stress-strain curve of example 1 after aging;
FIG. 2 XRD profile after aging for example 1;
FIG. 3 metallographic morphology after aging of example 2;
figure 4 TEM image after aging of example 2.
Detailed Description
The ultra-high strength high performance sheet maraging stainless steel and the method for producing the same according to the present invention will be further explained and illustrated with reference to the accompanying drawings and the specific examples, which, however, should not be construed to unduly limit the technical solutions of the present invention.
Example 1
Selecting pure iron, chromium metal, nickel metal, manganese metal, molybdenum metal, cobalt metal, titanium metal and iron silicon as raw materials, wherein the stainless steel comprises the following components in percentage by mass: co 2.0, Cr 12.0, Mn 0.8, Mo 7.0, Ni 6.0, Si 0.08, Ti 1.5, and the balance Fe.
And preparing a billet by adopting vacuum melting in the whole process.
And (3) carrying out high-temperature flame equalizing treatment, heating in air in a mode of furnace heating, keeping the temperature at 700 ℃ for 4h at the heating rate of 100 ℃/h, then heating to 1100 ℃ for 20h, and cooling to room temperature in a furnace.
The technological conditions of hot rolling and cogging are as follows: heating the casting blank to 1100 ℃, preserving heat for 10 hours, and then discharging and rolling; the starting temperature of hot rolling is 1100 +/-20 ℃, the finishing temperature is more than or equal to 950 ℃, the total hot rolling amount of the plate is 60 percent, and the ice-water mixture is cooled.
The plate is cold-rolled, the total reduction of the plate is 90%, and the plate is rolled by 1.5 mm.
And (3) carrying out aging treatment on the cold-rolled sheet, wherein the aging temperature is 480 ℃, the aging time is 20h, and air cooling to room temperature.
The mechanical properties of example 2 are shown in Table 1, the average hardness is 578.3HV, the yield strength is 2330MPa, the tensile strength is 2713MPa, the elongation is 10.8%, and the pitting potential is 0.24VSCE. FIG. 1 is a stress-strain curve of example 1 after aging. FIG. 2 is an aged TEM image of example 1, from which it can be seen that the martensite laths have a high number density of dislocations.
Example 2
Selecting pure iron, chromium metal, nickel metal, manganese metal, molybdenum metal, cobalt metal, titanium metal and iron silicon as raw materials, wherein the stainless steel comprises the following components in percentage by mass: co 5.0, Cr 11.0, Mn 0.5, Mo 6.0, Ni 9.0, Si 0.5, Ti 1.8, and the balance Fe.
And preparing a billet by adopting vacuum melting in the whole process.
And (3) carrying out high-temperature flame equalizing treatment, heating in air in a mode of heating along with a furnace, keeping the temperature at 800 ℃ for 6h at a heating rate of 150 ℃/h, then heating to 1150 ℃ and keeping the temperature for 30h, and cooling to room temperature along with the furnace.
The technological conditions of hot forging and cogging are as follows: heating the casting blank to 1250 ℃, preserving heat for 10 hours, and then discharging and forging; the starting temperature of hot forging is 1200 +/-20 ℃, the final forging temperature is more than or equal to 950 ℃, the forging ratio of the forged billet is 6, and the ice-water mixture is cooled after the forging is finished.
The sample was cold rolled with a total rolling reduction of 80% and the plate was rolled to 3.0 mm.
And (3) carrying out aging treatment on the cold-rolled sheet, wherein the aging temperature is 450 ℃, the aging time is 30h, and air cooling to room temperature.
The mechanical properties of example 3 are shown in Table 1, the average hardness is 568.1HV, the yield strength is 2250MPa, the tensile strength is 2690MPa, the elongation is 10.5%, and the pitting potential is 0.19VSCE. FIG. 3 shows the metallographic morphology after aging in example 2. FIG. 4 is an aged TEM image of example 2, from which it can be seen that the martensite laths have a high number of dislocations.
The test methods for the corrosion resistance, hardness and tensile mechanical properties of the ultra-high strength and high performance sheet maraging stainless steel in the above examples are as follows.
(1) Hardness: the hardness test was carried out using an HVS-50 Vickers hardness tester with a load of 1Kg, and 5 points were hit and averaged, as shown in Table 1.
(2) Tensile mechanical properties: an electronic universal tester is adopted for carrying out a tensile test, a rectangular sample with the nominal section size of 2-3 multiplied by 4 multiplied by 20.6mm is taken, and the average values of the tensile strength, the yield strength and the elongation of 3 samples treated in the same way are listed in table 1.
(3) Corrosion resistance
The molded product is processed into a specification of 10mm x 2mm, and is exposed by 1cm after being packaged by epoxy resin2And (4) performing a test, polishing the surface to 2000# with sand paper, scrubbing with alcohol to remove oil stains, cleaning with deionized water, and drying for later use. The experimental solution was 0.1M Na2SO4+ xnacal (PH 3) experimental temperature 25 ℃. Electrochemical testing was performed using the CHI660E electrochemical workstation. A common three-electrode system is adopted for carrying out electrochemical experiments, the experiment of ultrahigh-strength stainless steel is taken as a working electrode, a Pt sheet is taken as an auxiliary electrode, and a Saturated Calomel Electrode (SCE) is taken as a reference electrode. Prior to the electrochemical experiments, the pattern was first applied with-1.2VSECThe applied potential of (2) is polarized for 5min at constant potential so as to remove the oxide film formed on the surface of the sample in the air. The system was stable for 30min and recording was started. Potentiodynamic polarization test with a scan rate of 0.5mV/S, scanningThe potential area is-0.3V (vs. open circuit potential E)OC) 1.5V (vs. reference electrode potential E)R) The test was stopped after the current change was stable. The average value was obtained after 3 measurements and is shown in Table 1.
TABLE 1 compositions and hardness, tensile properties and pitting points of the examples
Note: the contents of C, P, S and the like in each example in Table 1 correspond to the elemental composition of stainless steel.
In summary, the following steps: the invention discloses an ultra-high strength high performance sheet maraging stainless steel and a preparation method thereof, wherein the stainless steel comprises the following components: the alloy material comprises, by mass, 2.0-5.0% of Co, 6.0-9.0% of Ni, 11.0-17.0% of Cr, 0.5-1.8% of Ti, 3.0-7.0% of Mo, 0.08-1.0% of Mn, 0.08-0.5% of Si, less than or equal to 0.02% of C, less than or equal to 0.003% of P, less than or equal to 0.003% of S, and the balance of Fe. The preparation method of the ultra-high-strength high-performance sheet maraging stainless steel comprises the following steps: (1) alloy element proportioning (2) carrying out vacuum smelting on an electrode in a vacuum induction smelting furnace; (3) vacuum consumable remelting; (4) carrying out high-temperature flame equalizing treatment; (5) forging or hot rolling cogging; (6) cold rolling deformation; (7) and (6) heat treatment. According to the stainless steel, the alloy elements, the corresponding thermal mechanical treatment process and different cold rolling deformation are optimized to obtain different amounts of high dislocation densities, so that the precipitated phase and the inverted austenite are uniformly and finely distributed, and the distribution efficiency of the inverted austenite forming elements is higher. The elongation of the stainless steel reaches 10.8 percent, and the tensile strength reaches 2713 MPa; and the pitting potential Epit can reach 0.24VSCE. The ultra-high strength high performance sheet maraging stainless steel can be used in the fields of cabin materials of ocean platforms and ships, medical scalpel materials and the like.