High-strength corrosion-resistant steel plate and process for producing the same

Abstract

The application 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) iron-based coating treatment is carried out on multi-principal-element high-entropy alloy particles to inhibit high-temperature interface reaction and improve the compatibility with a steel blank; (2) the coated high-entropy alloy powder is pressed into shape and spread on the surface of a low-carbon steel blank for heat treatment, the difference between the melting points of the steel blank in a solid state and the high-entropy alloy in a molten state is utilized to drive the molten alloy to diffuse to the inside along the micropores of the steel blank, and a gradient permeation layer is formed; and (3) a nitriding process is combined to strengthen the permeation kinetics through the nitrogen diffusion gas flow effect and generate Cr2N / AlN nano phases at the same time. The application realizes the synchronous optimization of hardness and corrosion resistance, improves the strength and corrosion resistance of the steel plate, 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 application 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

[0002] With the rapid development of industry, traditional high-strength steel is facing challenges in performance and cost under extreme environments. Austenitic stainless steel (such as 316L) has excellent pitting corrosion resistance, but its tensile strength is generally lower than 600 MPa, which is difficult to meet higher pressure mechanical requirements; and high-strength steel (such as 17-4PH) through martensite phase transformation strengthening can achieve a strength of 1200 MPa, but the high carbon content leads to the precipitation of Cr23C6 carbide at the grain boundary, which reduces the corrosion resistance by more than 40%. In order to break through this bottleneck, the academia proposes to introduce high-entropy alloy (HEA) as a strengthening phase into the steel matrix, but the existing process has significant defects: the melting solid solution method can achieve component homogenization, but the high temperature above 1600℃ will lead to the dissolution of the characteristic nano-phase of HEA, destroy the strengthening mechanism of hindering dislocation slip, and cause the segregation of corrosion-resistant elements such as Cr and Mo, which reduces the neutral salt spray time of the composite material to 1 / 3 of that of pure HEA; the surface coating technology can avoid melting of the matrix, but the coating and the steel matrix are mostly mechanically combined, the microcrack density at the interface exceeds 20 / mm 2 , and the coating thickness is limited to within 200μm, which cannot form a gradient strengthening effect.

[0003] In the solid-state diffusion process, the existing technology attempts to realize the combination of HEA and steel matrix through hot-pressing sintering, but faces double obstacles of kinetics and thermodynamics. The diffusion coefficients of light elements such as Al and Ti in Fe are significantly different (the diffusion coefficient of Al in γ-Fe is 1.2×10 -16 m 2 / s at 1200℃, while that of Cr is only 3.8×10 -17 m 2 / s), which leads to an imbalance in the migration rate of elements during the diffusion process, deviates from the equal atomic ratio design of HEA, and reduces the solid solution strengthening effect by more than 30%. More seriously, the uncoated HEA particles will react with the steel matrix at high temperature to generate brittle intermetallic compounds such as Fe2Al5 and FeCrσ phase, which reduces the interfacial fracture toughness to less than 15MPa·m 1 / 2 . In addition, the existing process generally relies on high-energy consumption equipment: the energy consumption of arc melting method for preparing HEA reinforced steel is 3200kWh per ton of product, which is 70% higher than that of traditional rolling process; the plasma spraying needs to consume high-purity argon (>99.99%), which increases the production cost by 2-3 times, and the utilization rate of HEA raw materials is less than 60%, which seriously restricts the industrial application.

[0004] The prior art is in a dilemma in the field of high-entropy alloy and steel matrix composite: the melting method destroys the structural integrity of HEA, the solid-state diffusion is limited by the imbalance of element migration and the interface brittleness, and the surface coating is difficult to achieve deep metallurgical bonding. In essence, the above methods have not solved the coordination problem among HEA component diffusion controllability, interface compatibility and process economy. Therefore, it is urgent to develop a new method which can realize HEA gradient infiltration at sub-melting temperature while retaining its multi-principal solid solution structure, which has become a common technical problem in the field of high-performance structural steel research and development. SUMMARY

[0005] The application breaks through the iron-based coated high-entropy alloy gradient infiltration technology, which successfully solves the balance problem among high-entropy alloy structure retention, gradient interface construction and process economy by: (1) iron-based coating layer inhibiting high-entropy alloy component segregation and interface reaction; (2) using solid-liquid diffusion to realize deep infiltration; (3) nitriding cooperates to strengthen diffusion kinetics.

[0006] The object of the application can be achieved by the following technical solutions:

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

[0008] S1. Iron-based coating treatment is performed on high-entropy alloy particles to form an iron-based coated high-entropy alloy material, so as to improve the compatibility of high-entropy alloy and steel billet and maintain the stability of high-entropy alloy composition during heat treatment, preventing element segregation;

[0009] S2. The iron-based coated high-entropy alloy material is pressed into a preform and then cut into a thin sheet which is spread on the surface of the steel billet, and heat treatment is performed in an environment significantly lower than the melting point of iron, so that the high-entropy alloy material diffuses to the steel billet.

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

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

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

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

[0014] In step S2, the preform is prepared by mixing the iron-based coated high-entropy alloy powder with 0.5-2wt% polyvinyl alcohol binder, and pressing the mixture into a preform under a pressure of 400-600MPa; the thickness of the thin sheet is 1-2mm.

[0015] The heat treatment is to place the spreaded steel blank in a vacuum furnace, to increase the temperature to 1100-1400℃ at a rate of 2-10℃ / min, and to keep the temperature for 1-4 hours.

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

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

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

[0019] The beneficial effects of the present application are:

[0020] (1) The present application builds an iron-based coating layer on the surface of the high-entropy alloy particles, which maintains the metastability of the high-entropy alloy during heat treatment and prevents element segregation. As a diffusion bridge, it improves the compatibility of the high-entropy alloy and the steel blank. The iron-based layer isolates the high-entropy alloy from direct reaction with the steel matrix, reduces the amount of interfacial brittle phase (such as Fe2Al5), improves the strength of the steel, and widens the application range of the steel plate.

[0021] (2) Based on the difference in melting point between the main phase of the steel blank (melting point 1600-1800℃) and the high-entropy alloy (melting point about 1200℃), the high-entropy alloy diffuses into the steel blank phase, rather than just adhering to the surface; the liquid high-entropy alloy penetrates along the micro-pores on the surface of the steel blank under the driving force of capillary force, while the solid steel matrix restricts the excessive flow of the high-entropy alloy, forming a composition gradient, and having the synergistic effect of high strength on the surface and toughness in the core.

[0022] (3) The present application introduces nitriding process in heat treatment, which uses the penetration behavior of nitrogen atoms into the steel blank to produce "air flow effect", and the concentration gradient provides 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 form Cr2N, AlN and other nano precipitates, realizing the simultaneous optimization of hardness and corrosion resistance. DETAILED DESCRIPTION

[0023] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined purpose, the specific embodiments, structures, features and effects according to the present application are described in detail as follows in combination with examples.

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

[0025] Example 1

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

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

[0028] S2. The iron-based coated high-entropy alloy material is pressed into a preformed embryo and then cut into thin slices and spread on the surface of the steel billet. Heat treatment is performed at an environment below the melting point of the steel billet by 1600°C and above the melting point of the high-entropy alloy material by 1100°C to allow the high-entropy alloy material to diffuse into the steel billet phase, forming a high-entropy alloy enriched area on the surface, thereby improving the tensile strength and corrosion resistance of the steel plate.

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

[0030] In step S1, the high entropy alloy comprises 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 electrolessly plated, specifically by immersing the high-entropy alloy material in an electroless plating solution at a temperature of 85° C. for 2 hours to form a uniform iron coating with a thickness of 2.5 μm; the electroless plating solution comprises: 80 g / L of the main salt FeSO4·7H2O, 30 g / L of the reducing agent NaH2PO2·H2O, and 1 M hydrochloric acid to adjust the pH to 3.5.

[0032] In step S2, the preform 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 sheet is 1.5 mm.

[0033] The heat treatment comprises placing the spread steel billet in a vacuum furnace, heating the temperature to 1250° C. at a rate of 8° C. / min, and keeping the temperature for 2.5 hours.

[0034] The heat treatment process is accompanied by nitriding treatment, and the nitrogen pressure generates a diffusion driving force, which increases 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 high-entropy alloy phase distributed in a gradient 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 comprises the following steps:

[0039] S1. Iron-based coating treatment is performed on high-entropy alloy particles to form an iron-based coated high-entropy alloy material to improve the compatibility of the high-entropy alloy with the steel blank and maintain the stability of the high-entropy alloy composition during heat treatment, thereby preventing element segregation;

[0040] S2. The iron-based coated high-entropy alloy material is pressed into a preform and then cut into a thin sheet and spread on the surface of the steel blank. Heat treatment is performed at a temperature lower than the melting point of the steel blank (1600°C) and higher than the melting point of the high-entropy alloy material (1100°C) to allow the high-entropy alloy material to diffuse into the steel blank, thereby forming a high-entropy alloy-rich region on the surface layer and improving the tensile strength and corrosion resistance of the steel plate.

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

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

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

[0044] In step S2, the preform is prepared by mixing the iron-based coated high-entropy alloy powder with 0.5wt% polyvinyl alcohol binder and pressing it into a preform under a pressure of 400MPa. The thickness of the thin sheet is 1mm.

[0045] The heat treatment is performed by placing the spread steel blank in a vacuum furnace, heating it to 1100°C at a rate of 2°C / min, and maintaining the temperature for 1 hour.

[0046] The heat treatment process is accompanied by nitriding treatment. The diffusion driving force generated by nitrogen pressure increases the penetration depth of the high-entropy alloy, and the reaction between nitrogen and Cr / Al generates nanoscale nitrides Cr2N and AlN, further improving the corrosion resistance.

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

[0048] 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 phases form a metallurgical bond with the steel matrix.

[0049] Example 3

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

[0051] S1. Iron-based coating treatment is performed on high-entropy alloy particles to form an iron-based coated high-entropy alloy material, so as to improve the compatibility of the high-entropy alloy and the steel blank and maintain the stability of the high-entropy alloy composition in the heat treatment process and prevent element segregation;

[0052] S2. The iron-based coated high-entropy alloy material is pressed into a preform and then cut into a sheet and spread on the surface of the steel blank, and heat treatment is performed in an environment below the melting point 1600℃ of the steel blank and above the melting point 1100℃ of the high-entropy alloy material, so that the high-entropy alloy material diffuses to the steel blank body, and a high-entropy alloy enrichment zone is formed on the surface layer, thereby improving the tensile strength and corrosion resistance of the steel plate.

[0053] In step S2, the temperature of the heat treatment is 1400℃.

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

[0055] The iron-based coating layer in step S1 is coated by mechanical ball milling, specifically: a high-energy ball mill (ball-to-material ratio 10:1, argon protection) is used, the rotation speed is 300 rpm, the ball milling time is 8 hours, the mass ratio of iron powder to high-entropy alloy powder is 1:5, the iron layer is coated, and the thickness is 8μm.

[0056] In step S2, the iron-based coated high-entropy alloy powder is mixed with 1wt% polyvinyl alcohol binder, and the preform is pressed under a pressure of 500MPa; the thickness of the sheet is 2mm.

[0057] The heat treatment is to place the spreaded steel blank in a vacuum furnace, heat to 1400℃ at a rate of 10℃ / min, and keep for 3 hours.

[0058] The heat treatment process is accompanied by nitriding treatment, and the diffusion driving force is generated by nitrogen pressure, so that the penetration depth of the high-entropy alloy is increased, and at the same time, nitrogen reacts with Cr / Al to generate nanometer nitride Cr2N and AlN, thereby further improving the corrosion resistance.

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

[0060] 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 inside, and the high-entropy alloy phases form a metallurgical bond with the steel matrix.

[0061] Example 4

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

[0063] S1. Iron-based coating treatment is performed on high-entropy alloy particles to form an iron-based coated high-entropy alloy material, so as to improve the compatibility of the high-entropy alloy and the steel blank and maintain the stability of the high-entropy alloy composition during heat treatment, and prevent element segregation;

[0064] S2. The iron-based coated high-entropy alloy material is pressed into a preform and then cut into a sheet and spread on the surface of the steel blank, and heat treatment is performed at a temperature lower than the melting point of the steel blank (1600℃) and higher than the melting point of the high-entropy alloy material (1100℃), so that the high-entropy alloy material diffuses to the steel blank, and a high-entropy alloy enrichment zone is formed on the surface layer, thereby improving the tensile strength and corrosion resistance of the steel plate.

[0065] In step S2, the temperature of the heat treatment is 1300℃.

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

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

[0068] In step S2, the iron-based coated high-entropy alloy powder is mixed with 1wt% polyvinyl alcohol binder and pressed into a preform under a pressure of 500MPa. The thickness of the sheet is 1.5mm.

[0069] The heat treatment is performed by placing the spread steel blank in a vacuum furnace, heating to 1300℃ at a rate of 6℃ / min, and holding for 2 hours.

[0070] The heat treatment is accompanied by nitriding treatment. The diffusion driving force generated by nitrogen pressure increases the penetration depth of the high-entropy alloy, and the reaction between nitrogen and Cr / Al generates nanoscale nitrides Cr2N and AlN, further improving the corrosion resistance.

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

[0072] 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 phases are metallurgically combined with the steel matrix.

[0073] Comparative Example 1

[0074] Based on Example 1, the heat treatment in step S2 is performed by using a traditional melting method. The iron-based coated high-entropy alloy material is pressed into a preform and the steel blank is heat treated at a temperature of 1700℃ for 2.5h, and the rest is the same as in Example 1.

[0075] Comparative Example 2

[0076] On the basis of Example 1, the temperature of step S2 heat treatment is 1000℃, and the rest is consistent with Example 1.

[0077] Comparative Example 3

[0078] On the basis of Example 1, the high-entropy alloy powder in the preparation of the preform is not coated with an iron-based layer, and the rest is consistent with Example 1.

[0079] Comparative Example 4

[0080] On the basis of Example 1, no nitriding treatment is added in step S2 heat treatment, and the air pressure is 0.5MPa, and the rest is consistent with Example 1.

[0081] Performance test:

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

[0083] Corrosion resistance test: the samples are placed in a salt spray chamber to test the corrosion resistance of the steel materials prepared in Examples 1-3 and Comparative Examples 1-5, the temperature in the salt spray chamber is 35℃, the relative humidity is 90%, and the salt spray is 5wt% sodium chloride solution; the time of red rust appearing on the sample in the salt spray test is observed. 2 The salt spray is 2.0mL / h, and the salt spray is 5wt% sodium chloride solution; the time of red rust appearing on the sample in the salt spray test is 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 by heat treatment in an environment below the melting point of the steel billet 1600℃ and above the melting point of the high-entropy alloy material 1100℃, the high-entropy alloy material diffuses to the steel billet, and a high-entropy alloy enrichment zone is formed on the surface, and the strength and corrosion resistance are significantly higher than that of the traditional method of melting the high-entropy alloy material and the steel blank.

[0086] Comparing Examples 1-4 and Comparative Example 3, by coating the high-entropy alloy material with an iron-based layer, the high-entropy alloy can maintain its metastable state during heat treatment, prevent element segregation, improve the compatibility of the high-entropy alloy and the steel billet, and the iron-based layer isolates the high-entropy alloy from direct reaction with the steel matrix, the amount of brittle phase (such as Fe2Al5) generated at the interface, and the strength of the steel material is improved.

[0087] It can be seen from the strength test and corrosion resistance test data of examples 1-4 and comparative example 4 that the application uses the penetration behavior of nitrogen atoms to the inside of the steel blank to produce an "air flow effect" through nitriding treatment, to provide an additional diffusion driving force for the high-entropy alloy melt, and to increase 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, achieving simultaneous optimization of hardness and corrosion resistance.

[0088] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, without departing from the technical solution of the present application. Any indirect modification, equivalent change and modification of the above embodiments made in accordance with the technical essence of the present application, without departing from the technical solution of the present application, are still within the scope of the technical solution of the present application.

Claims

1. A method of producing a high-strength corrosion-resistant steel sheet, characterized by: Comprising the following steps: S1. Iron-based coating treatment is performed on high-entropy alloy particles to form an iron-based coated high-entropy alloy material; S2. The iron-based coated high-entropy alloy material is pressed into a preform and then cut into a thin sheet and spread on the surface of a steel billet, and heat treatment is performed at 1100-1400℃ to allow the high-entropy alloy material to diffuse into the steel billet; The high-entropy alloy comprises 25-35wt% Fe, 20-30wt% Ni, 15-25wt% Co, 10-20wt% Cr, and 5-15wt% Al; In step S2, the preform is prepared by mixing the iron-based coated high-entropy alloy powder with 0.5-2wt% polyvinyl alcohol binder and pressing it into a preform under a pressure of 400-600MPa; the thickness of the thin sheet is 1-2mm; The heat treatment process is accompanied by nitriding treatment.

2. A method of manufacturing a high-strength corrosion-resistant steel sheet according to claim 1, characterized by: In step S1, the iron-based coating layer is formed by chemical plating or mechanical ball milling coating process.

3. The method of claim 1, wherein the steel sheet is prepared by the steps of: The heat treatment is performed by placing the spread steel billet in a vacuum furnace, heating it to 1100-1400℃ at a rate of 2-10℃ / min, and maintaining the temperature for 1-4 hours. ​ 4. The method of claim 1, wherein the steel sheet is prepared by the steps of: The nitriding pressure is 0.1-1MPa, and the nitrogen concentration is 50-100%. ​ 5. A high-strength corrosion-resistant steel plate prepared by the method of any one of claims 1-4.