High-strength heat-resistant stainless steel and preparation method thereof

Abstract

The invention belongs to the technical field of metal materials, and discloses high-strength heat-resistant stainless steel and a preparation method thereof. The chemical composition of the high-strength heat-resistant stainless steel is (FeCrNi) x (AlMo) yBz, wherein x is equal to 77-90 at%, y is equal to 9-20 at%, and z is equal to 1-3 at%; fe, Cr and Ni are equal in atomic ratio, and the atomic ratio of Al to Mo is 2: 1. The preparation method comprises the following steps that under the protective atmosphere, raw materials are subjected to induction smelting, and a smelting solution is obtained; cooling the smelting solution to obtain an alloy ingot; and performing aging treatment on the alloy ingot, and cooling to obtain the high-strength heat-resistant stainless steel. By adding a small amount of Al, Mo and B, the austenite / precipitated phase (FCC / L12) multi-principal-element stainless steel with a coherent structure is formed, good corrosion resistance is kept, and meanwhile the stainless steel has high quasi-static uniaxial tensile strength and excellent heat resistance.

Description

Technical Field

[0001] The invention relates to the technical field of metal materials, and in particular to a high-strength heat-resistant stainless steel and a preparation method thereof. Background Art

[0002] Traditional iron-based austenitic stainless steel materials have good strength, plasticity and corrosion resistance, and are widely used in many fields such as automobiles, metallurgy and nuclear power industries. However, stainless steel has low strength at room temperature, resulting in low high-temperature strength and low creep resistance. It cannot withstand high operating temperatures and high stresses in extreme environments, which limits its application range. The performance of traditional austenitic stainless steel based on mixed enthalpy design has reached its limit.

[0003] In recent years, the emergence of multi-principal alloys, namely high entropy alloys, has opened up new concepts and ideas for alloy design. This alloy designed based on configuration entropy has been proven to be one of the most promising structural materials. Its unique strong lattice distortion and hysteresis diffusion effect give the alloy a series of excellent properties, including high strength, high hardness and high plasticity, especially in extreme environments. The performance is far superior to that of traditional alloys, such as excellent high temperature performance, good low temperature plasticity and radiation resistance. However, it is still difficult for existing multi-principal alloys to simultaneously take into account high strength, corrosion resistance and heat resistance. Summary of the invention

[0004] The object of the present invention is to provide a high-strength heat-resistant stainless steel and a preparation method thereof, so as to solve the problem that the existing multi-principal alloys still have difficulty in achieving high strength, corrosion resistance and heat resistance at the same time.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a high-strength heat-resistant stainless steel, the chemical composition of the high-strength heat-resistant stainless steel is: (FeCrNi) x (AlMo) y B z ;

[0007] Wherein, x=77-90at%, y=9-20at%, z=1-3at%;

[0008] The atomic ratio of Fe, Cr and Ni is equal, and the atomic ratio of Al and Mo is 2:1.

[0009] Preferably, in the high-strength heat-resistant stainless steel, the chemical composition of the high-strength heat-resistant stainless steel includes: (FeCrNi) 77 (AlMo) 20 B3, (FeCrNi) 78 (AlMo) 20 B2, (FeCrNi) 79(AlMo) 20 B1, (FeCrNi) 82 (AlMo) 15 B3, (FeCrNi) 83 (AlMo) 15 B2, (FeCrNi) 84 (AlMo) 15 B1, (FeCrNi) 88 (AlMo)9B3, (FeCrNi) 89 (AlMo)9B2 or (FeCrNi) 90 (AlMo)9B1.

[0010] The present invention also provides a method for preparing high-strength heat-resistant stainless steel, comprising the following steps:

[0011] Under a protective atmosphere, the single substances of Fe, Cr, Ni, Al, Mo and B are induction smelted to obtain a molten liquid; the molten liquid is cooled to obtain an alloy ingot;

[0012] The alloy ingot is subjected to aging treatment and cooled to obtain high-strength heat-resistant stainless steel.

[0013] Preferably, in the method for preparing high-strength heat-resistant stainless steel, the protective atmosphere is an argon atmosphere.

[0014] Preferably, in the method for preparing high-strength heat-resistant stainless steel, the pressure of the induction melting is 0.02-0.04 MPa, and the power is 90-120 kW.

[0015] Preferably, in the method for preparing high-strength heat-resistant stainless steel, the temperature of the aging treatment is 550-700°C, and the time is 5-24 hours.

[0016] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0017] The matrix elements Fe, Cr and Ni are mainly in the designed composition of the stainless steel of the present invention, and the content x is 77-90at%, and the atomic ratio of Fe, Cr and Ni is 1:1:1; in addition, a nano-coherent precipitation phase is precipitated by doping Al and Mo (atomic ratio 2:1) elements with a content of 9-20at%, and an interstitial solid solution structure is formed by using B. Based on the mixed entropy design concept, the present invention develops a high-strength and heat-resistant multi-principal stainless steel, and forms an austenite / precipitation phase (FCC / L12) multi-principal stainless steel with a coherent structure by adding a small amount of Al, Mo and B, wherein the B element further promotes interstitial solid solution strengthening, which not only maintains good corrosion resistance, but also makes the stainless steel have both high strength (quasi-static uniaxial tensile strength) and excellent heat resistance. The present invention adjusts the ratio of basic components, changes the volume fraction of the coherent precipitation phase in the austenite parent phase, and adds trace elements Al and Mo to promote the precipitation of the nano-coherent L12 phase, and finally forms FCC / L12 coherent structure heat-resistant stainless steel, which is similar to the γ / γ coherent structure in the traditional Ni-based high-temperature alloy, has extremely low interface energy, and excellent high-temperature stability. Among them, Mo has a large atomic radius difference and modulus difference with the matrix elements, resulting in strong substitutional solid solution strengthening, and its melting point is high, which improves the thermal stability of the alloy; while B has a very small atomic radius, forms interstitial solid solution in the matrix, effectively pins dislocation movement, and improves the strength of the alloy. Precipitation strengthening, substitutional solid solution strengthening and interstitial solid solution strengthening give the heat-resistant stainless steel extremely high strength, the quasi-static uniaxial tensile strength at room temperature can reach 1600MPa, and the quasi-static uniaxial tensile strength at 700°C can reach 1000MPa. At the same time, it has excellent corrosion resistance and can be widely used in chemical, petroleum, nuclear power and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art are briefly introduced below.

[0019] Figure 1 Obtained from Example 2 (FeCrNi) 83 (AlMo) 15 Microstructure of B2 stainless steel;

[0020] Figure 2 Obtained from Example 2 (FeCrNi) 83 (AlMo) 15 Stress-strain curves of B2 stainless steel at room temperature and 700°C, where RT is room temperature. DETAILED DESCRIPTION

[0021] The present invention provides a high-strength heat-resistant stainless steel, the chemical composition of the high-strength heat-resistant stainless steel is: (FeCrNi) x(AlMo) y B z ;

[0022] Wherein, x=77-90at%, y=9-20at%, z=1-3at%;

[0023] The atomic ratio of Fe, Cr and Ni is equal, and the atomic ratio of Al and Mo is 2:1.

[0024] In the present invention, the value of x specifically includes 77 at %, 78 at %, 79 at %, 82 at %, 83 at %, 84 at %, 88 at %, 89 at % or 90 at %.

[0025] In the present invention, the value of y specifically includes 9 at %, 11 at %, 12 at %, 15 at %, 18 at % or 20 at %.

[0026] In the present invention, the value of z specifically includes 1 at %, 1.5 at %, 2 at %, 2.5 at % or 3 at %.

[0027] In the present invention, the chemical composition of the high-strength heat-resistant stainless steel preferably includes: (FeCrNi) 77 (AlMo) 20 B3, (FeCrNi) 78 (AlMo) 20 B2, (FeCrNi) 79 (AlMo) 20 B1, (FeCrNi) 82 (AlMo) 15 B3, (FeCrNi) 83 (AlMo) 15 B2, (FeCrNi) 84 (AlMo) 15 B1, (FeCrNi) 88 (AlMo)9B3, (FeCrNi) 89 (AlMo)9B2 or (FeCrNi) 90 (AlMo)9B1.

[0028] The present invention also provides a method for preparing high-strength heat-resistant stainless steel, comprising the following steps:

[0029] Under a protective atmosphere, the single substances of Fe, Cr, Ni, Al, Mo and B are induction smelted to obtain a molten liquid; the molten liquid is cooled to obtain an alloy ingot;

[0030] The alloy ingot is subjected to aging treatment and cooled to obtain high-strength heat-resistant stainless steel.

[0031] In the present invention, the Fe, Cr, Ni, Al, Mo and B single substances are preferably pre-treated before induction melting; the pre-treatment preferably includes: polishing the surfaces of the Fe, Cr, Ni, Al, Mo and B single substances, performing ultrasonic treatment in anhydrous ethanol, and drying.

[0032] In the present invention, the parameters of the pre-treatment are not limited, and schemes well known to those skilled in the art may be used.

[0033] In the present invention, the order of adding the single substances of Fe, Cr, Ni, Al, Mo and B is preferably: adding them in order from low to high melting points and from bottom to top.

[0034] In the present invention, the protective atmosphere is preferably an argon atmosphere.

[0035] In the present invention, the pressure of the induction melting is preferably 0.02-0.04 MPa, more preferably 0.022-0.028 MPa, more preferably 0.024-0.026 MPa; the power is preferably 90-120 kW, more preferably 90-110 kW, more preferably 90-100 kW.

[0036] In the present invention, the number and time of the induction melting are not limited, as long as the composition of the molten liquid is ensured to be uniform.

[0037] In the present invention, the temperature of the aging treatment is preferably 550-700°C, more preferably 570-680°C, more preferably 590-660°C; the time is preferably 5-24h, more preferably 12-22h, more preferably 15-20h.

[0038] In the present invention, the cooling method is not limited and any method known to those skilled in the art may be used.

[0039] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Example 1

[0041] This embodiment provides a high-strength heat-resistant stainless steel, whose chemical formula is (FeCrNi) 90 (AlMo)9B1, wherein the atomic ratio of Fe:Cr:Ni is 1:1:1, and the atomic ratio of Al:Mo is 2:1.

[0042] (FeCrNi)90 The preparation method of (AlMo)9B1 comprises the following steps:

[0043] The surfaces of raw materials Fe, Cr, Ni, Al, Mo, and B were polished clean, ultrasonically treated in anhydrous ethanol and dried; the raw materials were weighed according to the designed composition, and the weighed raw materials were placed in a crucible in order from low to high melting points and from bottom to top. After vacuuming, high-purity argon was filled in, and multiple induction melting was performed at a pressure of 0.024MPa and a power of 90kW to ensure uniform composition to obtain a molten liquid; the molten liquid was cooled to obtain a stainless steel ingot; and then an aging annealing treatment was performed at 590°C for 15h, and the crucible was cooled with the furnace to obtain (FeCrNi) 90 (AlMo)9B1 high strength and heat resistant stainless steel.

[0044] According to tests, the room temperature quasi-static uniaxial tensile strength of the stainless steel alloy reaches 800 MPa, the uniform strain exceeds 20%, and the quasi-static uniaxial tensile strength at 700°C is 400 MPa.

[0045] The high-strength heat-resistant stainless steel of Example 1 was immersed in a corrosion solution of 3.5wt.% NaCl for 14 days, and its corrosion current density was measured to be 0.13μA / cm 2 , with excellent corrosion resistance.

[0046] Example 2

[0047] This embodiment provides a high-strength heat-resistant stainless steel, whose chemical formula is (FeCrNi) 83 (AlMo) 15 B2, wherein the atomic ratio of Fe:Cr:Ni is 1:1:1, and the atomic ratio of Al:Mo is 2:1.

[0048] (FeCrNi) 83 (AlMo) 15 The preparation method of B2 comprises the following steps:

[0049] The surfaces of raw materials Fe, Cr, Ni, Al, Mo, and B were polished clean, ultrasonically treated in anhydrous ethanol and dried; the raw materials were weighed according to the designed composition, and the weighed raw materials were placed in a crucible in order from low to high melting points and from bottom to top. After vacuuming, high-purity argon was filled in, and multiple induction melting was performed at a pressure of 0.025 MPa and a power of 95 kW to ensure uniform composition to obtain a molten liquid; the molten liquid was cooled to obtain a stainless steel ingot; and then an aging annealing treatment was performed at 630°C for 17 hours, and the furnace was cooled to obtain (FeCrNi) 83 (AlMo) 15 B2 high strength and heat resistant stainless steel.

[0050] (FeCrNi)83 (AlMo) 15 The microstructure of B2 stainless steel is as follows Figure 1 As shown in the figure, it can be seen that a high-density nanostructured L12 phase is precipitated in the matrix phase to form a FCC / L12 coherent structure.

[0051] Figure 2 Yes (FeCrNi) 83 (AlMo) 15 The stress-strain curves of B2 stainless steel at room temperature and 700℃ high temperature show that the quasi-static uniaxial tensile strength at room temperature reaches 1600MPa with a uniform strain of 25%, and the quasi-static uniaxial tensile strength at 700℃ is 1000MPa, which has excellent comprehensive properties.

[0052] The high-strength heat-resistant stainless steel of Example 2 was immersed in a corrosion solution of 3.5wt.% NaCl for 14 days, and its corrosion current density was measured to be 0.116μA / cm 2 , with the best corrosion resistance.

[0053] Example 3

[0054] This embodiment provides a high-strength heat-resistant stainless steel, whose chemical formula is (FeCrNi) 77 (AlMo) 20 B3, wherein the atomic ratio of Fe:Cr:Ni is 1:1:1, and the atomic ratio of Al:Mo is 2:1.

[0055] (FeCrNi) 77 (AlMo) 20 The preparation method of B3 comprises the following steps:

[0056] The surfaces of the raw materials Fe, Cr, Ni, Al, Mo, and B were polished clean, ultrasonically treated in anhydrous ethanol and dried; the raw materials were weighed according to the designed composition, and the weighed raw materials were placed in a crucible in order from low to high melting points and from bottom to top. After vacuuming, high-purity argon was filled in, and multiple induction melting was performed at a pressure of 0.026MPa and a power of 100kW to ensure uniform composition to obtain a molten liquid; the molten liquid was cooled to obtain a stainless steel ingot; and then an aging annealing treatment was performed at 660°C for 20h, and the crucible was cooled with the furnace to obtain (FeCrNi) 77 (AlMo) 20 B3 high strength and heat resistant stainless steel.

[0057] According to tests, the room temperature quasi-static uniaxial tensile strength of the stainless steel alloy reaches 1200MPa, the uniform strain exceeds 20%, and the quasi-static uniaxial tensile strength at 700°C is 600MPa, which has good mechanical properties.

[0058] The high-strength heat-resistant stainless steel of Example 3 was immersed in a 3.5wt.% NaCl corrosion solution for 14 days, and its corrosion current density was measured to be 0.192μA / cm 2 , with excellent corrosion resistance.

[0059] In summary, the high-strength heat-resistant stainless steel designed and prepared in this application has excellent comprehensive properties such as high-temperature quasi-static uniaxial tensile strength and corrosion resistance, which is superior to traditional 316L stainless steel, duplex stainless steel, martensitic stainless steel and high-entropy heat-resistant stainless steel.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A high-strength heat-resistant stainless steel, characterized in that: The chemical composition of the high-strength heat-resistant stainless steel is: (FeCrNi) x (AlMo) y B z ; Wherein, x=77-90at%, y=9-20at%, z=1-3at%; The atomic ratio of Fe, Cr and Ni is equal, and the atomic ratio of Al and Mo is 2:

1.

2. The high-strength heat-resistant stainless steel according to claim 1, characterized in that: The chemical composition of the high-strength heat-resistant stainless steel includes: (FeCrNi) 77 (AlMo) 20 B3, (FeCrNi) 78 (AlMo) 20 B2, (FeCrNi) 79 (AlMo) 20 B1, (FeCrNi) 82 (AlMo) 15 B3, (FeCrNi) 83 (AlMo) 15 B2, (FeCrNi) 84 (AlMo) 15 B1, (FeCrNi) 88 (AlMo)9B3, (FeCrNi) 89 (AlMo)9B2 or (FeCrNi) 90 (AlMo)9B1.

3. The method for preparing high-strength heat-resistant stainless steel according to claim 1 or 2, characterized in that: The following steps are involved: Under a protective atmosphere, the single substances of Fe, Cr, Ni, Al, Mo and B are induction smelted to obtain a molten liquid; the molten liquid is cooled to obtain an alloy ingot; The alloy ingot is subjected to aging treatment and cooled to obtain high-strength heat-resistant stainless steel.

4. The method for preparing high-strength heat-resistant stainless steel according to claim 3, characterized in that: The protective atmosphere is argon atmosphere.

5. A method for preparing high-strength heat-resistant stainless steel according to claim 3 or 4, characterized in that: The pressure of the induction melting is 0.02-0.04 MPa, and the power is 90-120 kW.

6. A method for preparing high-strength heat-resistant stainless steel according to claim 5, characterized in that: The aging treatment is carried out at a temperature of 550 to 700° C. and for a time of 5 to 24 hours.

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