High-strength corrosion-resistant steel plate and preparation process thereof

Abstract

The invention relates to a high-strength corrosion-resistant steel plate and a preparation process thereof, and belongs to the technical field of steel plate preparation. The method is realized through the following steps: (1) carrying out iron-based coating treatment on multi-principal-element high-entropy alloy particles, inhibiting a high-temperature interface reaction and improving the compatibility with a steel billet; (2) carrying out compression molding on the coated high-entropy alloy powder, spreading the high-entropy alloy powder on the surface of a low-carbon steel blank for heat treatment, and driving molten alloy to diffuse inwards along micropores of the steel blank by utilizing the melting point difference between the solid state of the steel blank and the molten state of the high-entropy alloy to form a gradient permeable layer; and (3) a nitriding process is combined, permeation kinetics is enhanced through the nitrogen diffusion airflow effect, and meanwhile the Cr2N / AlN nanophase is generated. Synchronous optimization of hardness and corrosion resistance is achieved, the strength and corrosion resistance of the steel plate are improved, the process energy consumption is lower than that of a traditional melting method, and the application range of the steel plate is widened.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel plate preparation, and relates to a high-strength corrosion-resistant steel plate and a preparation process thereof. Background Art

[0002] With the rapid development of industry, traditional high-strength steels face performance and cost challenges in extreme environments. Austenitic stainless steels (such as 316L) have excellent pitting corrosion resistance, but their tensile strength is generally lower than 600 MPa, making it difficult to meet higher pressure-resistant mechanical requirements; while high-strength steels strengthened by martensitic transformation (such as 17-4PH) can achieve a strength of 1200 MPa level, but due to the high carbon content, Cr23C6 carbides precipitate at grain boundaries, resulting in a more than 40% decrease in corrosion resistance. To break through this bottleneck, the academic community has proposed introducing high-entropy alloys (HEAs) as strengthening phases into the steel matrix, but the existing processes have significant defects: although the melt-solid solution method can achieve composition homogenization, the high temperature above 1600 °C will cause the dissolution of the characteristic nano-phases of HEAs, destroying their strengthening mechanism that hinders dislocation slip, and at the same time causing segregation of corrosion-resistant elements such as Cr and Mo, reducing the neutral salt spray time of the composite material to 1 / 3 of that of pure HEA; although the surface coating technology can avoid matrix melting, the coating and the steel matrix are mostly mechanically bonded, and the microcrack density at the interface exceeds 20 cracks / mm 2 , and it is prone to peeling failure under alternating stress, and the coating thickness is limited within 200 μm, unable to form a gradient strengthening effect.

[0003] In the aspect of solid-state diffusion processes, existing technologies have tried to achieve the combination of HEA and the steel matrix through hot press sintering, but face double obstacles of kinetics and thermodynamics. The diffusion coefficients of light elements such as Al and Ti in HEAs and Fe are significantly different (at 1200 °C, the diffusion coefficient of Al in γ-Fe is 1.2×10 -16 m 2 / s, while that of Cr is only 3.8×10 -17 m 2 / s), resulting in an imbalance in the element migration rate during the diffusion process, deviating from the equiatomic ratio design of HEA, and reducing the solid solution strengthening effect by more than 30%. More seriously, the uncoated HEA particles will react with the steel matrix at high temperatures to form brittle intermetallic compounds such as Fe2Al5 and FeCrσ, resulting in an interfacial fracture toughness lower than 15 MPa·m 1 / 2 . In addition, existing processes generally rely on high-energy-consuming equipment: the energy consumption per ton of products for preparing HEA-reinforced steel by the arc melting method reaches 3200 kWh, which is 70% higher than the traditional rolling process; plasma spraying requires the consumption of high-purity argon (>99.99%), increasing the production cost by 2-3 times, and the utilization rate of HEA raw materials is less than 60%, seriously restricting industrial applications.

[0004] The existing technologies are in a dilemma in the field of composite of high-entropy alloys and steel substrates: the melting method destroys the structural integrity of HEAs, solid-state diffusion is limited by the imbalance of elemental migration and interfacial brittleness, while surface coatings are difficult to achieve deep metallurgical bonding. In essence, the above methods have not solved the synergy problem among the controllability of HEA component diffusion, interfacial compatibility, and process economy. Therefore, there is an urgent need to develop a new method that can achieve gradient infiltration of HEAs at sub-melting temperatures while retaining their multi-principal element solid-solution structure, which has become a common technical problem in the research and development of high-performance structural steels. Summary of the Invention

[0005] The present invention breakthroughly proposes an iron-based coated high-entropy alloy gradient infiltration technology, which: (1) suppresses the component segregation and interfacial reaction of high-entropy alloys through an iron-based coating layer; (2) utilizes solid-liquid diffusion to achieve deep penetration; (3) synergistically strengthens the diffusion kinetics by nitriding, and successfully solves the balance problem among the retention of high-entropy alloy structure, gradient interface construction, and process economy.

[0006] The object of the present invention can be achieved through the following technical solutions:

[0007] A preparation method of a high-strength corrosion-resistant steel plate, comprising the following steps:

[0008] S1. Perform iron-based coating treatment on high-entropy alloy particles to form a high-entropy alloy material with an iron-based coating layer, so as to improve the compatibility between the high-entropy alloy and the steel billet and maintain the composition stability of the high-entropy alloy during heat treatment, and prevent element segregation;

[0009] S2. Press the iron-based coated high-entropy alloy material into a preform and then cut it into thin slices and spread them on the surface of the steel billet, and perform heat treatment in an environment significantly lower than the melting point of iron to make the high-entropy alloy material diffuse into the steel billet matrix phase.

[0010] In step S2, the heat treatment temperature is 1100 - 1400 °C.

[0011] As a preferred technical solution of the present invention, the high-entropy alloy described in step S1 contains 25 - 35 wt% Fe, 20 - 30 wt% Ni, 15 - 25 wt% Co, 10 - 20 wt% Cr, and 5 - 15 wt% Al.

[0012] The iron-based coating layer in step S1 is formed by electroless plating or mechanical ball milling coating process.

[0013] The coating layer thickness of the iron-based coating layer is 2.5 - 8 μm.

[0014] The preparation of the preform in step S2 is to mix the iron-based coated high-entropy alloy powder with 0.5 - 2 wt% polyvinyl alcohol binder and press it into a preform under a pressure of 400 - 600 MPa; the thickness of the thin slice is 1 - 2 mm.

[0015] The heat treatment is to place the spread steel billet in a vacuum furnace, heat it to 1100 - 1400°C at a rate of 2 - 10°C / min, and hold for 1 - 4 hours.

[0016] The heat treatment process is accompanied by nitriding treatment.

[0017] The nitriding pressure is 0.1 - 1 MPa, and the nitrogen concentration is 50 - 100%.

[0018] The high-entropy alloy phase has a gradient distribution from the surface to the interior of the high-strength and corrosion-resistant steel plate prepared by the method, and the high-entropy alloy phase forms a metallurgical bond with the steel matrix.

[0019] Advantages of the present invention:

[0020] (1) By constructing an iron-based coating layer on the surface of the high-entropy alloy particles, the present invention enables the high-entropy alloy to maintain stability during heat treatment, prevents element segregation; and as a diffusion bridge, improves the compatibility between the high-entropy alloy and the steel billet. The iron-based layer isolates the direct reaction between the high-entropy alloy and the steel matrix, reduces the generation amount of interfacial brittle phases (such as Fe2Al5), improves the strength of the steel, and broadens the application range of the steel plate.

[0021] (2) Based on the melting point difference between the main phase of the steel billet (melting point 1600 - 1800°C) and the high-entropy alloy (melting point about 1200°C), the high-entropy alloy diffuses into the matrix phase of the steel billet instead of just adhering to the surface; the liquid high-entropy alloy penetrates along the micropores on the surface of the steel billet under the drive of capillary force, and at the same time, the solid steel matrix restricts the excessive flow of the high-entropy alloy, forming a composition gradient, and having a synergistic effect of high strength on the surface and toughness in the core.

[0022] (3) The present invention introduces a nitriding process in heat treatment, and uses the penetration behavior of nitrogen atoms into the steel billet to generate an "airflow effect", and its concentration gradient provides an additional diffusion driving force for the high-entropy alloy melt, increasing the penetration depth. At the same time, nitrogen reacts with Cr and Al in the high-entropy alloy to generate nano-precipitation phases such as Cr2N and AlN, realizing the synchronous optimization of hardness and corrosion resistance. Specific embodiments

[0023] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following combines examples to detail the specific embodiments, structures, features and their effects according to the present invention.

[0024] The sources of raw materials involved in the following examples and comparative examples are as follows: The steel billet is purchased from Guangdong Lecong Steel World Co., Ltd., and the product number is Q890; the polyvinyl alcohol is purchased from Xinling Chemical Technology Co., Ltd., and the grade is 2488.

[0025] Example 1

[0026] A method for preparing a high-strength corrosion-resistant steel plate, comprising the following steps:

[0027] S1. Perform iron-based coating treatment on high-entropy alloy particles to form a high-entropy alloy material with an iron-based coating layer, so as to improve the compatibility between the high-entropy alloy and the steel billet and maintain the composition stability of the high-entropy alloy during heat treatment, preventing element segregation;

[0028] S2. Press the iron-based coated high-entropy alloy material into a preform and then cut it into thin slices and spread them on the surface of the steel billet. Heat-treat in an environment below the melting point of the steel billet at 1600 °C and above the melting point of the high-entropy alloy material at 1100 °C to allow the high-entropy alloy material to diffuse into the matrix of the steel billet, forming a high-entropy alloy enrichment zone on the surface layer, and improving the tensile strength and corrosion resistance of the steel plate.

[0029] In step S2, the heat treatment temperature is 1250 °C.

[0030] The high-entropy alloy described in step S1 contains 30 wt% Fe, 25 wt% Ni, 20 wt% Co, 15 wt% Cr, and 10 wt% Al.

[0031] In step S1, the iron-based coating layer is formed by electroless plating. Specifically: Immerse the high-entropy alloy material in the electroless plating solution at a temperature of 85 °C for 2 hours to form a uniform iron coating layer with a thickness of 2.5 μm; The electroless plating solution is: 80 g / L of the main salt FeSO4·7H2O, 30 g / L of the reducing agent NaH2PO2·H2O, and the pH is adjusted to 3.5 with 1 M hydrochloric acid.

[0032] The preparation of the preform in step S2 is to mix the iron-based coated high-entropy alloy powder with 1 wt% polyvinyl alcohol binder and press it into a preform under a pressure of 500 MPa; The thickness of the thin slice is 1.5 mm.

[0033] The heat treatment is to place the spread steel billet in a vacuum furnace, heat it to 1250 °C at a rate of 8 °C / min, and hold for 2.5 hours.

[0034] The heat treatment process is accompanied by nitriding treatment. The nitrogen pressure generates a diffusion driving force, increasing the penetration depth of the high-entropy alloy. At the same time, nitrogen reacts with Cr / Al to generate nano-nitrides Cr2N and AlN, further improving the corrosion resistance.

[0035] The nitriding pressure is 0.5 MPa and the nitrogen concentration is 75%.

[0036] The high-strength corrosion-resistant steel plate prepared by the method has a gradient distribution of high-entropy alloy phases from the surface to the interior, and the high-entropy alloy phase forms a metallurgical bond with the steel matrix.

[0037] Example 2

[0038] A method for preparing a high-strength corrosion-resistant steel plate, comprising the following steps:

[0039] S1. Perform iron-based coating treatment on the high-entropy alloy particles to form a high-entropy alloy material with an iron-based coating layer, so as to improve the compatibility between the high-entropy alloy and the steel billet and maintain the composition stability of the high-entropy alloy during heat treatment, preventing element segregation;

[0040] S2. Press the iron-based coated high-entropy alloy material into a preform and then cut it into thin slices and spread them on the surface of the steel billet. Heat treat in an environment below the melting point of the steel billet at 1600 °C and above the melting point of the high-entropy alloy material at 1100 °C to make the high-entropy alloy material diffuse into the steel billet matrix phase, forming a high-entropy alloy enrichment zone on the surface layer, and improving the tensile strength and corrosion resistance of the steel plate.

[0041] In step S2, the heat treatment temperature is 1110 °C.

[0042] The high-entropy alloy described in step S1 contains 35 wt% Fe, 30 wt% Ni, 20 wt% Co, 10 wt% Cr, and 5 wt% Al.

[0043] The iron-based coating layer in step S1 is coated by mechanical ball milling. Specifically: use a high-energy ball mill (ball-to-material ratio 10:1, argon protection), rotation speed 300 rpm, ball milling time 6 hours, mass ratio of iron powder to high-entropy alloy powder 1:5 to achieve iron layer coating with a thickness of 5 μm.

[0044] The preparation of the preform in step S2 is to mix the iron-based coated high-entropy alloy powder with 0.5 wt% polyvinyl alcohol binder and press it into a preform under a pressure of 400 MPa; the thickness of the thin slice is 1 mm.

[0045] The heat treatment is to place the spread steel billet in a vacuum furnace, heat it to 1100 °C at a rate of 2 °C / min, and hold for 1 hour.

[0046] The heat treatment process is accompanied by nitriding treatment. The nitrogen pressure generates a diffusion driving force, increasing the penetration depth of the high-entropy alloy. At the same time, nitrogen reacts with Cr / Al to form nano-nitrides Cr2N and AlN, further improving the corrosion resistance.

[0047] The nitriding pressure is 0.1 MPa and the nitrogen concentration is 50%.

[0048] The high-strength and corrosion-resistant steel plate prepared by the method has a gradient distribution of high-entropy alloy phases from the surface to the inside, and the high-entropy alloy phase forms a metallurgical bond with the steel matrix.

[0049] Example 3

[0050] A method for preparing a high-strength and corrosion-resistant steel plate, comprising the following steps:

[0051] S1. Perform iron-based coating treatment on high-entropy alloy particles to form a high-entropy alloy material with an iron-based coating layer, so as to improve the compatibility between the high-entropy alloy and the steel billet and maintain the compositional stability of the high-entropy alloy during heat treatment, preventing element segregation.

[0052] S2. Press the iron-based coated high-entropy alloy material into a preform and then cut it into thin slices and spread them on the surface of the steel billet. Heat-treat in an environment below the melting point of the steel billet (1600 °C) and above the melting point of the high-entropy alloy material (1100 °C) to allow the high-entropy alloy material to diffuse into the matrix of the steel billet, forming a high-entropy alloy enrichment zone on the surface layer, and improving the tensile strength and corrosion resistance of the steel plate.

[0053] In step S2, the heat treatment temperature is 1400 °C.

[0054] The high-entropy alloy described in step S1 contains 25 wt% Fe, 25 wt% Ni, 15 wt% Co, 20 wt% Cr, and 15 wt% Al.

[0055] In step S1, the iron-based coating layer is coated by mechanical ball milling. Specifically: use a high-energy ball mill (ball-to-material ratio 10:1, argon protection), rotate at 300 rpm, ball mill for 8 hours, and the mass ratio of iron powder to high-entropy alloy powder is 1:5 to achieve iron layer coating with a thickness of 8 μm.

[0056] The preform in step S2 is prepared by mixing the iron-based coated high-entropy alloy powder with 1 wt% polyvinyl alcohol binder and pressing it into a preform under a pressure of 500 MPa; the thickness of the thin slice is 2 mm.

[0057] The heat treatment is to place the spread steel billet in a vacuum furnace, heat it to 1400 °C at a rate of 10 °C / min, and hold for 3 hours.

[0058] The heat treatment process is accompanied by nitriding treatment. The nitrogen pressure generates a diffusion driving force, increasing the penetration depth of the high-entropy alloy. At the same time, nitrogen reacts with Cr / Al to form nano-nitrides Cr2N and AlN, further improving the corrosion resistance.

[0059] The nitriding pressure is 1 MPa, and the nitrogen concentration is 95%.

[0060] The high-strength and corrosion-resistant steel plate prepared by the method has a gradient distribution of high-entropy alloy phases from the surface to the interior, and the high-entropy alloy phase forms a metallurgical bond with the steel matrix.

[0061] Example 4

[0062] A method for preparing a high-strength and corrosion-resistant steel plate, comprising the following steps:

[0063] S1. Perform iron-based coating treatment on the high-entropy alloy particles to form a high-entropy alloy material with an iron-based coating layer, so as to improve the compatibility between the high-entropy alloy and the steel billet and maintain the composition stability of the high-entropy alloy during heat treatment, preventing element segregation.

[0064] S2. Press the iron-based coated high-entropy alloy material into a preform and then cut it into thin slices and spread them on the surface of the steel billet. Heat treat in an environment below the melting point of the steel billet at 1600 °C and above the melting point of the high-entropy alloy material at 1100 °C to allow the high-entropy alloy material to diffuse into the matrix of the steel billet, forming a high-entropy alloy enrichment zone on the surface layer, and improving the tensile strength and corrosion resistance of the steel plate.

[0065] In step S2, the heat treatment temperature is 1300 °C.

[0066] The high-entropy alloy described in step S1 contains 28 wt% Fe, 22 wt% Ni, 22 wt% Co, 18 wt% Cr, and 10 wt% Al.

[0067] In step S1, the iron-based coating layer is formed by electroless plating. Specifically: Immerse the high-entropy alloy material in the electroless plating solution at a temperature of 85 °C for 4 hours to form a uniform iron coating with a thickness of 3 μm; The electroless plating solution is: 80 g / L of the main salt FeSO4·7H2O, 30 g / L of the reducing agent NaH2PO2·H2O, and adjust the pH = 3.2 with 1 M hydrochloric acid.

[0068] The preparation of the preform in step S2 is to mix the iron-based coated high-entropy alloy powder with 1 wt% polyvinyl alcohol binder and press it into a preform under a pressure of 500 MPa; The thickness of the thin slice is 1.5 mm.

[0069] The heat treatment is to place the spread steel billet in a vacuum furnace, heat it to 1300 °C at a rate of 6 °C / min, and hold for 2 hours.

[0070] The heat treatment process is accompanied by nitriding treatment. The nitrogen pressure generates a diffusion driving force, increasing the penetration depth of the high-entropy alloy. At the same time, nitrogen reacts with Cr / Al to form nano-nitrides Cr2N and AlN, further improving the corrosion resistance.

[0071] The nitriding pressure is 0.7 MPa, and the nitrogen concentration is 80%.

[0072] The high-strength and corrosion-resistant steel plate prepared by the method has a gradient distribution of high-entropy alloy phases from the surface to the inside, and the high-entropy alloy phase forms a metallurgical bond with the steel matrix.

[0073] Comparative Example 1

[0074] On the basis of Example 1, in step S2, the heat treatment adopts the traditional melting method. Press the iron-based coated high-entropy alloy material into a preform and heat treat the steel billet at 1700 °C for 2.5 h, and the rest is the same as in Example 1.

[0075] Comparative Example 2

[0076] Based on Example 1, in step S2 of heat treatment, the temperature is 1000 °C, and the rest is the same as in Example 1.

[0077] Comparative Example 3

[0078] Based on Example 1, in the preparation of the preform, the high-entropy alloy powder is not coated with iron-based material, and the rest is the same as in Example 1.

[0079] Comparative Example 4

[0080] Based on Example 1, in step S2 of heat treatment, nitriding treatment is not added, and the air pressure is 0.5 MPa, and the rest is the same as in Example 1.

[0081] Performance Test:

[0082] Strength Test: The tensile properties of the steel produced in Examples 1-3 and Comparative Examples 1-5 were tested, and the yield strength and tensile properties were tested according to the provisions of the GB / T228.1-2021 standard;

[0083] Corrosion Resistance Test: The specimens were placed in a salt spray chamber to detect the corrosion resistance of the steel produced in Examples 1-3 and Comparative Examples 1-5. The temperature in the salt spray chamber was 35 °C, the relative humidity was 90%, and the salt spray settlement was 2.0 mL / h every 80 cm 2 The salt spray was a 5 wt% sodium chloride solution; the time when red rust appeared on the specimens in the salt spray experiment was observed.

[0084] Yield strength / MPa Tensile strength / MPa Corrosion resistance time / h Example 1 1684 2157 2850 Example 2 1503 2013 2700 Example 3 1520 2087 2750 Example 4 1596 2102 2800 Comparative example 1 985 1042 1550 Comparative example 2 1023 1127 1600 Comparative example 3 1254 1087 1850 Comparative example 4 1278 1574 1800

[0085] From the strength test and corrosion resistance test data of Examples 1-4 and Comparative Examples 1-2, it can be seen that in the present invention, by heat treatment in an environment below the melting point of the steel billet (1600 °C) and above the melting point of the high-entropy alloy material (1100 °C), the high-entropy alloy material diffuses into the matrix of the steel billet, and a high-entropy alloy enrichment zone is formed on the surface layer. Both the strength and corrosion resistance are significantly higher than those prepared by the traditional method of melting the high-entropy alloy material and the steel billet.

[0086] Comparing Examples 1-4 and Comparative Example 3, it can be seen that coating the high-entropy alloy material with iron-based material can maintain the stability of the high-entropy alloy during heat treatment, prevent element segregation, improve the compatibility between the high-entropy alloy and the steel billet, and the iron-based layer isolates the direct reaction between the high-entropy alloy and the steel matrix, reducing the generation amount of brittle phases at the interface (such as Fe2Al5) and improving the strength of the steel.

[0087] From the strength test and corrosion resistance test data of Examples 1-4 and Comparative Example 4, it can be seen that through nitriding treatment, the present invention utilizes the penetration behavior of nitrogen atoms into the steel billet to generate an "airflow effect", providing an additional diffusion driving force for the high-entropy alloy melt and increasing the penetration depth. At the same time, nitrogen reacts with Cr and Al in the high-entropy alloy to form nano-precipitates such as Cr2N and AlN, realizing the synchronous optimization of hardness and corrosion resistance.

[0088] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or variations equivalent to the equivalent embodiments within the scope of the technical solution of the present invention without departing from the technical solution of the present invention. However, any indirect modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-strength corrosion-resistant steel plate, characterized in that: It includes the following steps: S1. Perform iron-based coating treatment on high-entropy alloy particles to form a high-entropy alloy material with an iron-based coating layer; S2. Press the iron-based coated high-entropy alloy material into a preform and then cut it into thin slices and spread them on the surface of the steel billet, and perform heat treatment in an environment significantly lower than the melting point of iron to make the high-entropy alloy material diffuse into the matrix of the steel billet.

2. The preparation of a high-strength and corrosion-resistant steel plate according to claim 1, characterized in that: In step S2, the heat treatment temperature is 1100 - 1400 °C.

3. The preparation of a high-strength and corrosion-resistant steel plate according to claim 1, characterized in that: The high-entropy alloy described in step S1 contains 25 - 35 wt% Fe, 20 - 30 wt% Ni, 15 - 25 wt% Co, 10 - 20 wt% Cr, and 5 - 15 wt% Al.

4. The preparation of a high-strength and corrosion-resistant steel plate according to claim 1, characterized in that: The iron-based coating layer in step S1 is formed by electroless plating or mechanical ball milling coating process.

5. The preparation of a high-strength and corrosion-resistant steel plate according to claim 1, characterized in that: The preparation of the preform in step S2 is to mix the iron-based coated high-entropy alloy powder with 0.5 - 2 wt% polyvinyl alcohol binder and press it into a preform under a pressure of 400 - 600 MPa; the thickness of the thin slice is 1 - 2 mm.

6. The preparation of a high-strength and corrosion-resistant steel plate according to claim 1, characterized in that: The heat treatment is to place the spread steel billet in a vacuum furnace, heat it to 1100 - 1400 °C at a rate of 2 - 10 °C / min, and hold for 1 - 4 hours.

7. The preparation of a high-strength and corrosion-resistant steel plate according to claim 1, characterized in that: The heat treatment process is accompanied by nitriding treatment.

8. The preparation of a high-strength and corrosion-resistant steel plate according to claim 1, characterized in that: The nitriding pressure is 0.1 - 1 MPa, and the nitrogen concentration is 50 - 100%.

9. A high-strength and corrosion-resistant steel plate prepared by any of the methods of claims 1 - 8.