CN115478212A - Carbide and intermetallic compound composite reinforced ultrahigh-strength steel and bar preparation method thereof - Google Patents
Carbide and intermetallic compound composite reinforced ultrahigh-strength steel and bar preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/007—Heat treatment of ferrous alloys containing Co
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/04—Hardening by cooling below 0 degrees Celsius
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
Abstract
The invention discloses a novel carbide and intermetallic compound composite reinforced ultrahigh-strength steel and a preparation method of a bar thereof, wherein the steel comprises the following elements in percentage by mass: c:0.20 to 0.30%, cr 1.50 to 3.50%, co: 6.00-9.00%, 0.50-2.00% of Al, 9.5% of Ni +2.2 Al, 1.50-4.00% of Mo +2/3W, 0.13-0.80% of Nb +1/3V, less than or equal to 0.005% of S, less than or equal to 0.01% of P, less than or equal to 0.10% of Si, less than or equal to 0.10% of Mn, less than or equal to 0.005% of N, less than or equal to 0.05% of Ti, and the balance of Fe and inevitable impurities. Compared with the existing steel grade, the preparation method reduces the cobalt content through alloy design and optimized element proportion, increases a proper amount of tungsten and trace elements for generating strong carbides such as niobium, vanadium and the like, and has higher mechanical property and lower production cost.
Description
Technical Field
The invention relates to the technical field of ultrahigh-strength steel materials, in particular to ultrahigh-strength steel compositely reinforced by carbide and intermetallic compounds and a preparation method of a bar thereof; because of the ultrahigh strength, the material can be applied to the fields of aerospace, petroleum, chemical industry, energy and power.
Background
The fan shaft and the low-pressure turbine shaft are key parts of the turbofan engine, the parts are required to have the characteristics of high strength, long service life, high reliability, light weight and the like, and the parts are usually made of high-strength C250 maraging steel. Unlike conventional high strength steels, C250 maraging steels are not carbon strengthened, but rather utilize intermetallic compounds (Ni) produced in a micro-carbon quenched martensitic matrix upon heat treatment 3 Ti、Fe 2 Mo, etc.) to be strengthened.
With the continuous improvement of the performance of the aviation turbofan engine, steel for manufacturing the fan shaft and the low-pressure turbine shaft is required to be safely used for a long time under the conditions of higher power, higher rotating speed and higher overload. Conventional C250 steels have failed to meet these requirements in terms of strength and fatigue life. Thus, a new GE1014 steel was developed for the manufacture of fan shafts and low pressure turbine shafts for higher power aircraft engines. Unlike C250 steel, GE1014 steel is subjected to a heat treatment process, except forProduce intermetallic compounds (NiAl, ni) 3 Al, beta-NiAl) and can also disperse and separate out a large amount of nano-scale carbides (MC, M) from a high-carbon quenched martensite matrix 2 C, etc.), thereby achieving the effect of composite reinforcement and having tensile strength and fatigue performance obviously superior to that of C250 steel.
On the other hand, although the GE1014 steel has excellent performance, the chemical components of the GE1014 steel contain a large amount of expensive cobalt elements, so that the production cost is high, and the popularization and the application of the GE1014 steel are influenced.
In view of the above, there is a need to develop a new ultra high strength steel. The steel should have the same or higher mechanical properties and preferably lower production costs than the GE1014 steel.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects in the prior art and provide a novel carbide and intermetallic compound composite reinforced ultrahigh-strength steel with higher mechanical property and lower production cost.
The technical problem to be solved can be implemented by the following technical scheme.
The ultrahigh-strength steel compositely reinforced by the carbides and the intermetallic compounds comprises the following elements in percentage by mass: c:0.20 to 0.30%, cr 1.50 to 3.50%, co:6.00 to 9.00 percent of Al, 0.50 to 2.00 percent of Ni, (9.5% + 2.2% of Al), (the content of Mo + 2/3W) is 1.50 to 4.00 percent, and (the content of Nb + 1/3V) is 0.13 to 0.80 percent, less than or equal to 0.005 percent of S, less than or equal to 0.01 percent of P, less than or equal to 0.10 percent of Si, less than or equal to 0.10 percent of Mn, less than or equal to 0.005 percent of N, less than or equal to 0.05 percent of Ti, and the balance of Fe and inevitable impurities.
Preferably, the intermetallic compound forming element Ni is 9.5% +2.2 × Al, al is 0.50-2.00%, ni is 10.50-14.00% by mass.
Preferably, the content of the carbide forming element Mo +2/3W is 1.50-4.00%, and the content of Mo is 1.00-3.00% in percentage by mass.
Preferably, the content of the carbide forming element Mo +2/3W is 1.50-4.00%, and the content of W is 0.90-1.50% by mass percent.
Preferably, the content of the carbide forming element Nb +1/3V is 0.13-0.80%, and the content of Nb is 0.01-0.60% by mass percentage.
Preferably, the content of carbide forming elements Nb +1/3V is 0.13-0.80%, and V is 0.01-0.60% by mass percent.
Preferably, among the inevitable impurities, H.ltoreq.0.0001%, O.ltoreq.0.001%, in mass%.
The tensile strength of the ultra-high strength steel is more than or equal to 2200MPa, the yield strength is more than or equal to 1900MPa, the elongation is more than or equal to 8%, the area shrinkage is more than or equal to 35%, and the grain size is more than or equal to 6 grade.
The carbide and intermetallic compound composite reinforced ultrahigh-strength steel provided by the invention mainly relates to elements such as carbon (C), chromium (Cr), nickel (Ni), aluminum (Al), molybdenum (Mo), tungsten (W), niobium (Nb), vanadium (V), cobalt (Co), titanium (Ti), silicon (Si), manganese (Mn), sulfur (S), phosphorus (P), nitrogen (N) and the like, and the influence of the elements on the invention is as follows:
carbon (C) is an effective interstitial solid solution strengthening and carbide precipitation strengthening element, and has an important influence on the strengthening effect of the ultrahigh-strength steel. The increase of the carbon content is beneficial to the formation of carbide, so that the strength and the hardness are improved, but the toughness and the welding performance of the steel can be seriously reduced by the excessively high carbon content, so that the matching of the strength and the toughness of the steel is unbalanced; therefore, the carbon content in the present invention is controlled to 0.20 to 0.30%.
Chromium (Cr) increases the hardenability of steel, and incorporation of a matrix causes displacement solid solution strengthening. Meanwhile, chromium is a stronger carbide-forming element, although the carbide-forming ability is weaker than that of molybdenum and tungsten, the diffusion temperature is lower, and the diffusion ability is stronger than that of molybdenum and tungsten, which is shown in M 2 The C nucleation is the most important function in the early stage. The improvement of the chromium content is beneficial to enhancing the corrosion resistance and the oxidation resistance of the steel, but the excessive chromium content can cause the excessively low Ms point of the martensite transformation temperature, which leads to the generation of twin crystal martensite and is not beneficial to the toughness of the steel; therefore, the chromium content of the invention is controlled between 1.50 and 3.50 percent.
Nickel (Ni) is an austenite region enlarging alloying element, and can promote the formation of reverse transformed austenite, and increase the toughness and plasticity of steel. At the same time, nickel and cobalt elements are interacted with each otherTo promote the re-dissolution of cementite as a strengthening phase M 2 The precipitation of C provides the component conditions. Nickel can also combine with aluminum to form intermetallic compounds (NiAl, ni) 3 Al, beta-NiAl) and carbide play a role in composite strengthening; however, too high nickel content leads to increased production cost, and the nickel content should be controlled within 9.5% +2.2 × al, preferably 10.50-14.00%.
Aluminium (Al) is usually added to steel as a deoxidizer, and the main function of aluminium in steel is ageing strengthening, i.e. diffusion precipitation of NiAl, ni in a martensitic matrix by heat treatment 3 Intermetallic compounds such as Al, beta-NiAl and the like strengthen the steel. Meanwhile, the aluminum can form a layer of compact oxide film Al on the surface of the steel 2 O 3 The oxidation resistance is improved; aluminum is also a ferrite forming element and promotes ferrite forming ability about 2.53 times that of chromium, so that the aluminum content cannot be too high; the aluminum content of the invention is controlled between 0.50 and 2.00 percent.
Molybdenum (Mo) and tungsten (W), both strengthening phases M 2 The main elements of C carbide have strong carbide forming tendency, and the strength and the hardness of the steel are improved; but W formed of tungsten 2 The C carbide has a temperature higher than that of Mo 2 C carbide formation temperature at which martensite dislocation recovery occurs and which produces a strengthening effect lower than that of Mo 2 C produces an effect. However, when the molybdenum and the tungsten are compounded and added into the steel in a proper proportion, the molybdenum and the tungsten interact with cobalt element, the aggregation and coarsening of carbide can be delayed and inhibited, and the corrosion resistance and the temper softening resistance of the steel are improved. Therefore, the control range of the content of the molybdenum and the tungsten in the invention is 1.50-4.00% of Mo +2/3W, and preferably 1.00-3.00% of Mo and 0.90-1.50% of W.
Niobium (Nb) and vanadium (V) are strong carbide forming elements, can form fine and dispersed carbides such as NbC, VC and the like with carbon in a matrix, and have good precipitated phase stability, which plays an important role in maintaining the stability of a sub-crystalline grain structure and improving the endurance strength of steel, and greatly improves the tempering resistance of the steel. The high-temperature mechanical property can be obviously improved by adding a small amount of niobium and vanadium into the steel; therefore, the control range of the content of niobium and vanadium of the invention is 0.13-0.80% of Nb +1/3V, preferably 0.01-0.60% of Nb and 0.01-0.60% of V.
Cobalt (Co) can effectively reduce the self-diffusion coefficient of carbon, and can inhibit the recovery of a martensite dislocation substructure in the heat treatment process, so that a large amount of dislocations are stored in the martensite lath, and conditions are provided for the dispersion and precipitation of a large amount of carbides. Meanwhile, the cobalt element can reduce the solid solubility of the molybdenum element in martensite and increase M taking molybdenum and tungsten as main elements 2 The precipitation kinetics of C carbide. Too high a cobalt content, however, reduces the impact toughness of the steel and increases the production costs; comprehensively considering, the cobalt content of the invention is controlled between 6.00 and 9.00 percent.
Titanium (Ti) is the most effective strengthening alloy element in steel, and generally, the addition of a proper amount of titanium has a remarkable aging strengthening effect, and mainly forms Ni in the aging process 3 However, the titanium element is very likely to form sharp tetragonal Ti (C, N) inclusions with carbon and nitrogen in the steel, and also form hard polygonal (Ti, mo) C inclusions with the molybdenum element to significantly reduce the toughness of the steel, so that the titanium content in the present invention is controlled to 0.05% or less.
Silicon (Si) is mainly used as a deoxidizer during smelting, can strengthen a matrix and improve the corrosion resistance and high-temperature oxidation resistance of steel, but the excessive high content of silicon can cause precipitation of harmful phases and reduce the hot workability and toughness of the steel; therefore, the silicon content of the invention is controlled below 0.10 percent.
Manganese (Mn), which is an austenite stabilizing element that can expand the austenite phase region, is a good deoxidizer and desulfurizer and generally contains a certain amount of manganese in industrial steels; in the steel, manganese can replace part of nickel to stabilize austenite, so that the production cost is reduced, the nitrogen content in the steel can be increased, the strength of the steel is ensured, and the corrosion resistance of the steel can be greatly reduced due to overhigh manganese content; therefore, the manganese content of the invention is controlled to be 0.10 percent.
Sulfur (S) exists in the steel in the form of FeS, which causes hot shortness of the steel; the melting point of FeS is 1193 ℃, and the melting point of eutectic consisting of Fe and FeS is only 985 ℃; the liquid Fe and the FeS can be dissolved infinitely, but the solubility of the FeS in solid iron is very small and is only 0.015-0.020%; therefore, when the sulfur content of the steel exceeds 0.020%, the Fe-FeS is distributed at the grain boundary in a net shape by eutectic with low melting point due to segregation in the cooling solidification process of the molten steel; the hot working temperature of the steel is 1150-1200 ℃, eutectic at the grain boundary is melted at the temperature, and the fracture of the grain boundary is caused after the steel is pressed, which is the hot brittleness of the steel; when the oxygen content in the steel is higher, the eutectic melting point formed by FeO and FeS is lower and only 940 ℃, and the hot brittleness phenomenon of the steel is further aggravated; in addition, sulfur significantly reduces the weldability of steel, causes high-temperature cracking, and generates many pores and pores in a metal weld, thereby reducing the strength of the weld; when the sulfur content exceeds 0.06%, the corrosion resistance of the steel is remarkably deteriorated; therefore, the sulfur content of the invention is controlled below 0.005%.
Phosphorus (P) steel can be completely dissolved in ferrite to improve the strength and hardness of the ferrite, but the plasticity and toughness of the steel are sharply reduced at room temperature to generate low-temperature brittleness, and the phenomenon is called cold brittleness; phosphorus is generally a harmful element in steel, mainly the precipitation of the brittle compound Fe 3 P increases the brittleness of the steel, and is particularly remarkable at low temperature; therefore, the phosphorus content of the invention is controlled below 0.01 percent.
Nitrogen (N) exists in a form of interstitial atoms in unit cells, and is more favorable for solid solution strengthening of steel due to larger atom size difference; the effect of nitrogen as an austenite stabilizing element on expanding and stabilizing an austenite structure is about 25 times that of nickel, and the solid solubility content of the nitrogen in austenite is far higher than that of ferrite; when certain aluminum and titanium elements exist in the steel, nitrogen is easy to form hard AlN, tiN or Ti (C and N) inclusion with the steel, so that the toughness of the stainless steel is seriously reduced, and therefore, the nitrogen content of the invention is controlled to be below 0.005 percent.
Compared with GE1014 steel, the new steel grade reduces the cobalt content, increases a proper amount of tungsten and trace strong carbide generating elements such as niobium, vanadium and the like, and has lower production cost due to the reduction of the cobalt content.
The invention also aims to provide a preparation method of the bar of the carbide and intermetallic compound composite reinforced ultrahigh-strength steel.
The method comprises the following steps:
s1, smelting raw materials by using a vacuum induction furnace to obtain molten steel, and die casting the molten steel to obtain an electrode rod;
s2, remelting the electrode rod obtained in the step S1 for one time or two times by adopting a VAR furnace to obtain an ultrahigh-strength steel ingot;
s3, heating the steel ingot obtained in the step S2 to 1130-1260 ℃, and cogging to obtain an intermediate forging stock;
s4, heating the intermediate forging stock obtained in the step S3 to 850-1150 ℃, and then forging or rolling a finished product to obtain an ultrahigh-strength steel bar;
and S5, carrying out heat treatment on the ultrahigh-strength steel bar obtained in the step S4.
Preferably, in step S1 of the method, the mass percentages of the elements in the molten steel are respectively: c:0.20 to 0.30%, cr 1.50 to 3.50%, co: 6.00-9.00%, 0.50-2.00% of Al, 9.5% of Ni +2.2 Al, 1.50-4.00% of Mo +2/3W, 0.13-0.80% of Nb +1/3V, less than or equal to 0.005% of S, less than or equal to 0.01% of P, less than or equal to 0.10% of Si, less than or equal to 0.10% of Mn, less than or equal to 0.005% of N, less than or equal to 0.05% of Ti, and the balance of Fe and inevitable other impurities.
Preferably, in step S1 of the method, the molding is performed in a vacuum environment.
Preferably, in step S2 of the method, the mass percentages of the elements in the high-strength steel ingot are respectively: c:0.20 to 0.30%, cr 1.50 to 3.50%, co: 6.00-9.00%, 0.50-2.00% of Al, 9.5% of Ni +2.2 Al, 1.50-4.00% of Mo +2/3W, 0.13-0.80% of Nb +1/3V, less than or equal to 0.005% of S, less than or equal to 0.01% of P, less than or equal to 0.10% of Si, less than or equal to 0.10% of Mn, less than or equal to 0.005% of N, less than or equal to 0.05% of Ti, and the balance of Fe and inevitable other impurities.
Preferably, in step S2 of the method, the mass percentages of the intermetallic compound forming elements in the high-strength steel ingot are respectively: 0.50 to 2.00 percent of Al and 10.50 to 14.00 percent of Ni by mass percentage.
Preferably, in step S2 of the method, the mass percentages of the carbide forming elements in the high-strength steel ingot are respectively: 1.00 to 3.00 percent of Mo, 0.90 to 1.50 percent of W, 0.01 to 0.60 percent of Nb and 0.01 to 0.60 percent of V by mass percent.
Preferably, in step S2 of the method, among the inevitable impurities, H is 0.0001% or less and O is 0.001% or less in mass percentage.
Preferably, the total deformation ratio from the electrode rod to the ultrahigh-strength steel finished rod is more than or equal to 4.0.
Preferably, in step S5 of the method, the heat treatment process is: firstly, carrying out solution heat treatment, heating the steel bar obtained in the step S4 to 885-915 ℃, preserving heat for 1-5 h, and then cooling with water or oil to room temperature; then cooling, placing the mixture in an environment with the temperature below-73 ℃, keeping the mixture for 1 to 8 hours, taking out the mixture, and recovering the mixture to the room temperature; heating the cooled steel bar to 480-520 ℃, preserving the heat for 4-12 h, and then air-cooling to room temperature to obtain a finished ultrahigh-strength steel bar; wherein the holding time is selected according to the diameter of the steel bar.
The invention has the following beneficial effects:
1. compared with the existing GE1014 steel, the new steel grade reduces the cobalt content, increases a proper amount of tungsten and trace elements for generating strong carbides such as niobium, vanadium and the like, and has higher mechanical property.
2. According to the ultrahigh-strength steel and the preparation method of the ultrahigh-strength steel bar, the ultrahigh-strength steel bar is obtained by means of carbide and intermetallic compound composite reinforcement, and compared with the existing GE1014 steel, the content of cobalt in the new steel is reduced, and the production cost is lower.
3. The ultra-high strength steel bar disclosed by the invention has ultra-high strength of over 2200MPa and excellent fatigue performance, can be applied to the aerospace field with higher requirements on strength, toughness and fatigue resistance, and can also be applied to the fields of petroleum, chemical industry, energy and power; in particular, in the aspect of aerospace, the ultrahigh-strength steel provided by the invention is used for replacing C250 steel and GE1014 steel and used for manufacturing fan shafts and low-pressure turbine shafts, so that the power and fuel efficiency of aircraft engines can be improved, the service life can be prolonged, the maintenance period can be shortened, and the environmental pollution can be reduced.
Detailed Description
The following provides a more detailed description of the embodiments of the present invention.
The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way.
The invention provides carbide and intermetallic compound composite reinforced ultrahigh-strength steel, which comprises the following elements in percentage by mass: c:0.20 to 0.30%, cr 1.50 to 3.50%, co: 6.00-9.00%, 0.50-2.00% of Al, 9.5% of Ni +2.2 x Al, 1.50-4.00% of Mo +2/3W, 0.13-0.80% of Nb +1/3V, less than or equal to 0.005% of S, less than or equal to 0.01% of P, less than or equal to 0.10% of Si, less than or equal to 0.10% of Mn, less than or equal to 0.005% of N, less than or equal to 0.05% of Ti, and the balance of Fe and other inevitable impurities.
The intermetallic compound forming element Ni accounts for 9.5% +2.2 xAl, and the mass percent of Al is 0.50-2.00% and the mass percent of Ni is 10.50-14.00%.
The carbide forming element Mo +2/3W is 1.50-4.00%, mo is 1.00-3.00%, W is 0.90-1.50% by mass percentage.
0.13-0.80% of carbide forming element Nb +1/3V, 0.01-0.60% of Nb and 0.01-0.60% of V, in percentage by mass.
Among the inevitable other impurities, H is less than or equal to 0.0001 percent, and O is less than or equal to 0.001 percent in percentage by mass.
The tensile strength of the ultrahigh-strength steel is more than or equal to 2200MPa, the yield strength is more than or equal to 1900MPa, the elongation is more than or equal to 8%, the area shrinkage is more than or equal to 35%, and the grain size is more than or equal to 6 grade.
Further, the preparation method of the ultrahigh-strength steel bar specifically comprises the following steps:
s1, smelting the raw materials by using a vacuum induction furnace to obtain molten steel, and die casting the molten steel to obtain an electrode rod;
the raw materials comprise industrial pure iron, metal Cr, metal Ni, metal Al, metal Co, metal Mo, metal W, metal Nb, metal V and the like, and the raw materials are smelted by a vacuum induction furnace to obtain high-purity molten steel, wherein the mass percentages of all elements of the molten steel before tapping are respectively as follows: c:0.20 to 0.30%, cr 1.50 to 3.50%, co: 6.00-9.00%, al 0.50-2.00%, ni 9.5% +2.2 x Al, mo +2/3W 1.50-4.00%, nb +1/3V 0.13-0.80%, S is less than or equal to 0.005%, P is less than or equal to 0.01%, si is less than or equal to 0.10%, mn is less than or equal to 0.10%, N is less than or equal to 0.005%, ti is less than or equal to 0.05%;
and casting the molten steel into an ingot mould in a vacuum environment of a vacuum induction furnace to obtain the electrode rod.
S2, remelting the electrode rod obtained in the step S1 in a VAR furnace for one time or two times to obtain an ultrahigh-strength steel ingot;
the mass percentages of all elements in the steel ingot are respectively as follows: c:0.20 to 0.30%, cr 1.50 to 3.50%, co: 6.00-9.00%, 0.50-2.00% of Al, 9.5% of Ni +2.2 Al, 1.50-4.00% of Mo +2/3W, 0.13-0.80% of Nb +1/3V, less than or equal to 0.005% of S, less than or equal to 0.01% of P, less than or equal to 0.10% of Si, less than or equal to 0.10% of Mn, less than or equal to 0.005% of N, less than or equal to 0.05% of Ti, and the balance of Fe and inevitable other impurities.
S3, heating the steel ingot obtained in the step S2 to 1130-1260 ℃, and cogging to obtain an intermediate forging stock;
s4, heating the intermediate forging stock obtained in the step S3 to 850-1150 ℃, and then forging or rolling a finished product to obtain an ultrahigh-strength steel bar;
the total deformation ratio from the electrode bar in the step S1 to the ultra-high strength steel finished bar in the step S4 is more than or equal to 4.0.
And S5, carrying out heat treatment on the ultrahigh-strength steel bar obtained in the step S4.
The heat treatment process comprises the following steps: firstly, carrying out solution heat treatment, heating the steel bar obtained in the step S4 to 885-915 ℃, preserving heat for 1-5 h, and then cooling with water or oil to room temperature; then cooling, placing the mixture in an environment with the temperature below-73 ℃, keeping the mixture for 1 to 8 hours, taking out the mixture, and recovering the mixture to the room temperature; heating the cooled steel bar to 480-520 ℃, preserving the heat for 4-12 h, and then air-cooling to room temperature to obtain a finished bar of the ultrahigh-strength steel; wherein the holding time is selected according to the diameter of the steel bar.
The following are more specific examples.
Example 1
S1, smelting industrial pure iron, metal Cr, metal Ni, metal Al, metal Co, metal Mo, metal W, metal Nb, metal V and the like serving as raw materials by using a vacuum induction furnace to obtain molten steel, and die casting the molten steel to obtain an electrode rod;
s2, carrying out vacuum consumable remelting smelting on the electrode rod obtained in the step S1 in a VAR furnace to obtain a steel ingot with the diameter of 508mm, wherein the chemical components of the steel ingot are shown in Table 1;
s3, heating the steel ingot obtained in the step S2 to 1180 +/-20 ℃, preserving heat for 24 hours, and performing cogging forging on a 2000-ton quick forging machine to obtain a 220mm octagonal intermediate forging stock;
s4, heating the 220mm octagonal intermediate forging stock to 1050 +/-20 ℃, preserving heat for 3 hours, forging on a 1300-ton diameter forging machine to obtain a steel bar with phi of 100mm, wherein the finish forging temperature is not lower than 850 ℃;
s5, carrying out heat treatment on the steel bar obtained in the step S4;
firstly, carrying out solution heat treatment, heating the steel bar obtained in the step S4 to 900 +/-15 ℃, and carrying out oil cooling to room temperature after heat preservation for 3 hours; then cooling, placing in an environment below-73 ℃, keeping for 4h, taking out, and naturally recovering to room temperature; and heating the cooled steel bar to 490-500 ℃, preserving the heat for 6 hours, and then air-cooling to room temperature to obtain the ultra-high strength steel bar with the diameter of phi 100 mm.
The chemical compositions of the prepared ultra-high-strength steel bar material with the diameter of 100mm are shown in a table 1;
optional 2 groups of samples are tested on the ultra-high strength steel bar with the diameter of 100mm, and the results are shown in the table 2.
Example 2
S1, smelting industrial pure iron, metal Cr, metal Ni, metal Al, metal Co, metal Mo, metal W, metal Nb, metal V and the like serving as raw materials by using a vacuum induction furnace to obtain molten steel, and die casting the molten steel to obtain an electrode rod;
s2, performing vacuum consumable remelting smelting twice on the electrode rod obtained in the step S1 in a VAR furnace to obtain a steel ingot with the diameter of 610mm, wherein the chemical components of the steel ingot are shown in Table 1;
s3, heating the steel ingot obtained in the step S2 to 1240 +/-20 ℃, preserving heat for 24 hours, and performing cogging forging on a 4000-ton quick forging machine to obtain a 280mm octagonal intermediate forging stock;
s4, heating the 280mm octagonal intermediate forging stock to 1130 +/-20 ℃, preserving heat for 3 hours, forging on a 1300-ton diameter forging machine to obtain a steel bar with phi of 150mm, wherein the finish forging temperature is not lower than 850 ℃;
s5, carrying out heat treatment on the steel bar obtained in the step S4;
firstly, carrying out solution heat treatment, heating the steel bar obtained in the step S4 to 900 +/-15 ℃, and carrying out heat preservation for 5 hours and then carrying out oil cooling to room temperature; then cooling, placing in an environment below-73 ℃, keeping for 8h, taking out, and naturally recovering to room temperature; and heating the cooled steel bar to 500-520 ℃, preserving the heat for 12 hours, and then air-cooling to room temperature to obtain the ultra-high strength steel bar with the diameter of phi 150 mm.
The chemical compositions of the prepared ultra-high-strength steel bar material with the diameter of 150mm are shown in a table 1;
optional 2 groups of samples are tested on the ultra-high strength steel bar with the diameter of 150mm, and the results are shown in the table 2.
Example 3
S1, smelting industrial pure iron, metal Cr, metal Ni, metal Al, metal Co, metal Mo, metal W, metal Nb, metal V and the like serving as raw materials by using a vacuum induction furnace to obtain molten steel, and die casting the molten steel to obtain an electrode rod;
s2, carrying out vacuum consumable remelting smelting on the electrode rod obtained in the step S1 in a VAR furnace to obtain a steel ingot with the diameter of 360mm, wherein the chemical components of the steel ingot are shown in Table 1;
s3, heating the steel ingot obtained in the step S2 to 1150 +/-20 ℃, preserving heat for 24 hours, and cogging and forging on a 2000-ton quick forging machine to obtain a 120mm square billet;
s4, heating a 120mm square billet to 1050 +/-20 ℃, preserving heat for 3 hours, rolling on a bar mill to obtain a bar with the diameter of 60mm, wherein the final rolling temperature is not lower than 850 ℃;
s5, carrying out heat treatment on the steel bar obtained in the step S4;
firstly, carrying out solid solution aging heat treatment, heating the steel bar obtained in the step S4 to 900 +/-15 ℃, preserving heat for 1h, and then cooling to room temperature by water; then cooling, placing in an environment below-73 ℃, keeping for 1h, taking out, and naturally recovering to room temperature; and then heating the stainless steel bar subjected to cooling treatment to 480-490 ℃, preserving the heat for 4 hours, and then air-cooling to room temperature to obtain the phi 60mm ultrahigh-strength steel bar.
The chemical components for preparing the ultra-high strength steel bar with the diameter of 60mm are shown in the table 1;
optional 2 groups of samples are tested on the ultra-high strength steel bar with the diameter of 60mm, and the results are shown in the table 2.
Table 1: chemical components (mass percent%) of ultra-high strength steel bar (steel ingot) and GE1014 steel of comparative example in the embodiment of the invention
| Element(s) | C | S | P | Si | Mn | Ti | Cr | Ni | Al | Co | Mo | W | Nb | V | N | H | O |
| Example 1 | 0.25 | 0.001 | 0.005 | 0.05 | 0.06 | 0.03 | 2.51 | 12.70 | 1.45 | 7.53 | 2.51 | 1.05 | 0.03 | 0.30 | 0.002 | 0.0001 | 0.0005 |
| Example 2 | 0.30 | 0.001 | 0.004 | 0.05 | 0.05 | 0.02 | 1.52 | 10.67 | 0.53 | 6.19 | 1.10 | 1.49 | 0.57 | 0.02 | 0.002 | 0.0001 | 0.0005 |
| Example 3 | 0.20 | 0.002 | 0.006 | 0.06 | 0.05 | 0.03 | 3.48 | 13.83 | 1.97 | 8.97 | 2.95 | 0.92 | 0.25 | 0.58 | 0.002 | 0.0001 | 0.0005 |
| GE1014 | 0.22 | 0.001 | 0.003 | 0.05 | 0.05 | 0.04 | 2.40 | 14.00 | 1.10 | 10.15 | 1.40 | — | — | — | 0.002 | 0.0001 | 0.0005 |
Table 2: properties of ultra-high strength steel bar according to example of the invention and comparative example GE1014 Steel
As shown in tables 1 and 2, the chemical compositions of the ultra-high strength steel bars in examples 1 to 3 are within the following element content ranges in mass percent: c:0.20 to 0.30%, cr 1.50 to 3.50%, co: 6.00-9.00%, 0.50-2.00% of Al, 9.5% + 2.2X Al, 1.50-4.00% of Mo +2/3W, 0.13-0.80% of Nb +1/3V, less than or equal to 0.005% of S, less than or equal to 0.01% of P, less than or equal to 0.10% of Si, less than or equal to 0.10% of Mn, less than or equal to 0.005% of N, less than or equal to 0.05% of Ti, and the balance of Fe and inevitable other impurities; among other inevitable impurities, H is less than or equal to 0.0001 percent, and O is less than or equal to 0.001 percent.
The ultra-high strength steel bars in the embodiments 1 to 3 have tensile strength not less than 2200MPa, yield strength not less than 1900MPa, elongation not less than 8%, area shrinkage not less than 35% and grain size not less than 6 grade. Compared with GE1014 steel, the ultrahigh-strength steel bar has the advantages that the cobalt content is reduced, a proper amount of tungsten and trace elements for generating strong carbides such as niobium and vanadium are added, the mechanical property is higher, and the production cost is lower.
The ultra-high strength steel bar disclosed by the invention has ultra-high strength of over 2200MPa and excellent fatigue performance, can be applied to the aerospace field with higher requirements on strength, toughness and fatigue resistance, and can also be applied to the fields of petroleum, chemical industry, energy and power; in particular to the aspect of aerospace, the ultra-high strength steel related to the invention is used for replacing C250 steel and GE1014 steel and is used for manufacturing fan shafts and low-pressure turbine shafts, so that the power and the fuel efficiency of aircraft engines can be improved, the service life can be prolonged, the maintenance period can be shortened, and the environmental pollution can be reduced.
Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. The ultrahigh-strength steel reinforced by the carbide and the intermetallic compound is characterized by comprising the following elements in percentage by mass:
C：0.20～0.30％；
Cr：1.50～3.50％；
Co：6.00～9.00％；
Al：0.50～2.00％；
Ni：9.5％+2.2*Al；
Mo+2/3W：1.50～4.00％；
Nb+1/3V：0.13～0.80％；
S≤0.005％；
P≤0.01％；
Si≤0.10％；
Mn≤0.10％；
N≤0.005％；
Ti≤0.05％；
the balance being Fe and unavoidable impurities.
2. The ultra-high strength steel reinforced by a combination of carbide and intermetallic compound according to claim 1, characterized in that the content of Ni in the steel is 10.50 to 14.00%.
3. The ultra-high strength steel compositely reinforced with carbides and intermetallics according to claim 1, wherein the steel grade contains 1.00 to 3.00% of Mo and 0.90 to 1.50% of W.
4. The carbide and intermetallic compound composite reinforced ultrahigh-strength steel according to claim 1, wherein the content of Nb is 0.01 to 0.60% and the content of V is 0.01 to 0.60% in the steel grade.
5. The carbide and intermetallic compound composite strengthened ultrahigh strength steel according to claim 1, wherein H is 0.0001% or less and O is 0.001% or less among the inevitable impurities.
6. The ultra-high strength steel compositely reinforced by carbide and intermetallic compounds according to claim 1, characterized in that the ultra-high strength steel has tensile strength not less than 2200MPa, yield strength not less than 1900MPa, elongation not less than 8%, area shrinkage not less than 35%, and grain size not less than 6-grade.
7. A method for producing the ultra-high strength steel bar of any one of claims 1 to 6, comprising the steps of:
s1, smelting the raw materials by using a vacuum induction furnace to obtain molten steel, wherein the mass percentages of the elements in the molten steel are as follows: c:0.20 to 0.30%, cr 1.50 to 3.50%, co: 6.00-9.00%, 0.50-2.00% of Al, 9.5% of Ni +2.2 x Al, 1.50-4.00% of Mo +2/3W, 0.13-0.80% of Nb +1/3V, less than or equal to 0.005% of S, less than or equal to 0.01% of P, less than or equal to 0.10% of Si, less than or equal to 0.10% of Mn, less than or equal to 0.005% of N, less than or equal to 0.05% of Ti, and the balance of Fe and inevitable impurities;
the molten steel is subjected to die casting to obtain an electrode bar;
s2, remelting the electrode rod obtained in the step S1 once or twice by using a VAR furnace to obtain an ultrahigh-strength steel ingot;
s3, heating the steel ingot obtained in the step S2 to 1130-1260 ℃, and cogging to obtain an intermediate forging stock;
s4, heating the intermediate forging stock obtained in the step S3 to 850-1150 ℃, and then forging or rolling a finished product to obtain an ultrahigh-strength steel bar;
and S5, carrying out heat treatment on the ultrahigh-strength steel bar obtained in the step S4.
8. The method for preparing an ultra-high strength steel bar according to claim 7, wherein the step S1, the die casting is performed in a vacuum environment.
9. The method for producing the ultra-high strength steel bar of claim 7, wherein the total deformation ratio of the electrode rod to the ultra-high strength steel bar is not less than 4.0.
10. The method for preparing an ultra-high strength steel bar according to claim 7, wherein in step S5, the heat treatment process comprises:
firstly, carrying out solution heat treatment, heating the steel bar obtained in the step S4 to 885-915 ℃, preserving heat for 1-5 h, and then cooling with water or oil to room temperature;
then, cooling, placing the mixture in an environment with the temperature of below 73 ℃ below zero, keeping the mixture for 1 to 8 hours, taking the mixture out, and recovering the mixture to the room temperature;
heating the cooled steel bar to 480-520 ℃, preserving the heat for 4-12 h, and then air-cooling to room temperature to obtain a finished ultrahigh-strength steel bar; wherein the holding time is determined according to the diameter of the steel bar.
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