CN116695026A - A kind of ultra-high strength alloy steel and its preparation method - Google Patents

Abstract

The application provides an ultrahigh-strength alloy steel and a preparation method thereof. The ultra-high strength alloy steel comprises the following components in percentage by weight: 0.10% -0.25%, si:1.0 to 2.0 percent of Mn:0.50% -1.5%, ni:0.3% -1.0%, V:0.2 to 0.6 percent of Cr:0.3 to 1.0 percent, 0.2 to 2.0 percent of Mo, and Nb:0.1% -0.5%, al:0.03 to 0.30 percent of Ti:0.1% -0.5%, W:0.1% -0.7%, P: less than or equal to 0.008 percent, S: less than or equal to 0.008 percent, N:0.003% -0.030%, B:0.001% -0.015%, and the balance of Fe and other unavoidable impurity elements. The content of carbon and alloy elements in the steel is reduced, and the tensile strength and the hydrogen embrittlement resistance of the ultra-high strength alloy steel are improved through the cooperation of the elements.

Description

Ultra-high strength alloy steel and preparation method thereof

Technical Field

The present application relates to the technical field of metal materials, and in particular to an ultra-high strength alloy steel and a preparation method thereof.

Background Art

As construction machinery and equipment gradually develop towards large-scale and lightweight, the bearing capacity of steel is required to be continuously improved to reduce deadweight, increase effective load, improve running speed and save energy consumption. Ultra-high strength steel is a structural material with high specific strength developed according to this demand. Ultra-high strength steel refers to steel with tensile strength greater than 1400MPa and yield strength (or specified plastic extension strength) greater than 1200MPa at room temperature. It is usually also required to have certain plastic toughness, excellent fatigue resistance, good processability and low cost.

However, as the strength of steel increases, its hydrogen embrittlement sensitivity increases. Even at a low hydrogen content, hydrogen embrittlement fracture is very likely to occur. Moreover, hydrogen embrittlement fracture is without any signs, and the stress at the time of fracture is far lower than the yield strength of steel, posing a serious threat to the safety and reliability of engineering structures. At present, the most commonly used ultra-high strength steel at home and abroad is 300M steel, whose tensile strength can reach 1960MPa, but it needs to be electroplated or coated before it can be used on landing gear. To address this problem, secondary hardening ultra-high strength steels such as Aermet 100 and Ferrium M54 in high CoNi alloy systems have been developed, which have the same strength level as 300M, higher toughness and better stress corrosion resistance. However, due to the addition of expensive alloy elements in the system and the requirements of high-clean smelting process, these steels are expensive and cannot replace low-alloy ultra-high strength steels represented by 300M for large-scale application. Therefore, it is urgent to develop an ultra-high strength steel that is resistant to hydrogen embrittlement and low-cost.

Summary of the invention

The present application provides an ultra-high strength alloy steel and a preparation method thereof, so as to improve the strength, toughness and hydrogen embrittlement resistance of the alloy steel.

The first aspect of the present application provides an ultra-high strength alloy steel, which includes, by weight percentage, C: 0.10%-0.25%, Si: 1.0%-2.0%, Mn: 0.50%-1.5%, Ni: 0.3%-1.0%, V: 0.2%-0.6%, Cr: 0.3%-1.0%, Mo: 0.2%-2.0%, Nb: 0.1%-0.5%, Al: 0.03%-0.30%, Ti: 0.1%-0.5%, W: 0.1%-0.7%, P: ≤0.008%, S: ≤0.008%, N: 0.003%-0.030%, B: 0.001%-0.015%, and the balance is Fe and other inevitable impurity elements.

Furthermore, by weight percentage, the ultra-high strength alloy steel includes C: 0.12% ~ 0.24%, Si: 1.3% ~ 1.8%, Mn: 0.5% ~ 1.2%, Ni: 0.4% ~ 0.9%, V: 0.3% ~ 0.5%, Cr: 0.4% ~ 0.9%, Mo: 0.5% ~ 1.6%, Nb: 0.3% ~ 0.5%, Al: 0.05% ~ 0.25%, Ti: 0.2% ~ 0.4%, W: 0.2% ~ 0.5%, P: ≤ 0.008%, S: ≤ 0.006%, N: 0.005% ~ 0.025%, B: 0.005% ~ 0.012%, and the balance is Fe and other inevitable impurity elements.

Furthermore, the metallographic structure of the ultra-high strength alloy steel is mainly tempered lath martensite or (tempered lath martensite + bainite) + dispersed carbides or nitrides + retained austenite.

Furthermore, the unhydrogenated tensile strength of the ultra-high strength alloy steel is ≥2000MPa, and/or the elongation after fracture is ≥12%, and/or the reduction in area is greater than 40%, and/or the impact energy KV ₂ is ≥40J, and/or the grain size is above level 10; and/or the tensile strength after hydrogen embrittlement of the ultra-high strength alloy steel is ≥1980MPa, and/or the elongation after fracture after hydrogen embrittlement is ≥10%, and/or the reduction in area after hydrogen embrittlement is greater than 38%.

The second aspect of the present application provides a method for preparing an ultra-high strength alloy steel, the preparation method comprising: step S1, weighing raw materials according to the following weight percentages: C: 0.10% to 0.25%, Si: 1.0% to 2.0%, Mn: 0.50% to 1.5%, Ni: 0.3% to 1.0%, V: 0.2% to 0.6%, Cr: 0.3% to 1.0%, Mo: 0.2% to 2.0%, Nb: 0.1% to 0.5%, Al: 0. 03%～0.30%, Ti: 0.1%～0.5%, W: 0.1%～0.7%, P: ≤0.008%, S: ≤0.008%, N: 0.003%～0.030%, B: 0.001%～0.015%, the balance is Fe and other inevitable impurity elements; step S2, smelting the raw materials to obtain ingots; step S3, rolling the ingots to obtain plates; step S4, heat treating the plates to obtain ultra-high strength alloy steel.

Further, step S4 includes: heating the plate to 850°C~1050°C for quenching and heat preservation treatment for 0.5~2h, and then quenching and cooling to room temperature. Optionally, the temperature of the quenching and heat preservation treatment is 880°C~1050°C, and further optionally, the temperature of the quenching and heat preservation treatment is 920°C~1050°C; heating the plate after quenching and heat preservation treatment to 200°C~500°C for tempering and heat preservation treatment for 1~3h, and then tempering and cooling to room temperature to obtain ultra-high strength alloy steel; optionally, the temperature of the tempering and heat preservation treatment is 300°C~500°C.

Furthermore, in step S4, the temperature of the plate is raised to 850°C to 1050°C at a rate of 50 to 150°C/s.

Furthermore, the cooling rate of the quenching cooling is 30°C/s to 300°C/s.

Furthermore, the quenching cooling method is water cooling, spray cooling or air cooling.

Furthermore, the cooling method of quenching cooling is graded cooling, and the graded cooling includes: water cooling to 350±20°C, and then spray cooling or air cooling to room temperature; or spray cooling to 350±20°C, and then air cooling to room temperature.

Furthermore, the tempering cooling is air cooling.

Furthermore, step S2 comprises: heating the raw materials into molten iron, performing desulfurization pretreatment, and then performing converter smelting and vacuum refining to obtain an ingot.

Furthermore, the mass content of sulfur in the molten iron after desulfurization pretreatment is less than 0.008%.

Furthermore, electromagnetic stirring is performed on the molten iron during the converter smelting process.

Furthermore, the mass content of hydrogen in the ingot after vacuum refining is less than 1 ppm.

Further, step S3 includes: hot rolling and cold rolling the ingot, optionally, the rolling process includes: first 2 to 5 hot rollings with a total deformation of 30 to 50%; then 2 to 4 cold rollings with a total deformation of 10 to 30%; then heating to 800 to 860°C for 2 to 4 hot rollings with a total deformation of 15 to 30%; finally 2 to 5 cold rollings with a total deformation of 10 to 30%.

The present application reduces the content of carbon and alloying elements in steel, and improves the tensile strength and hydrogen embrittlement resistance of ultra-high strength alloy steel by combining various elements. In particular, the addition of Ti and V in steel can form carbides and nitrides with C and N, which can effectively hinder the movement of dislocations in steel, improve the strength and toughness of steel, and can act as an irreversible hydrogen trap to hinder the diffusion of hydrogen, which can effectively improve the hydrogen embrittlement resistance of steel. At the same time, Mo can also generate fine carbides with C, and can also increase the number of carbide hydrogen traps and carbide and substrate interface hydrogen traps, which reduces the hydrogen diffusion coefficient and hydrogen embrittlement sensitivity of steel in combination. When Cr and Ni are added together, bainite transformation in steel can be promoted, so that the strength and toughness of steel are improved.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

FIG1 shows a microscopic picture of the metallographic structure of the ultra-high strength alloy steel prepared in Example 1 of the present application.

FIG2 shows a microscopic picture of the metallographic structure of the ultra-high strength alloy steel prepared in Example 2 of the present application.

FIG3 shows a microscopic picture of the metallographic structure of the ultra-high strength alloy steel prepared in Example 3 of the present application.

FIG4 shows the EDS energy spectrum analysis result of a white dot at a certain position in the metallographic structure of the ultra-high strength alloy steel prepared in Example 1 of the present application.

FIG5 shows the EDS energy spectrum analysis result of white dots at another position in the metallographic structure of the ultra-high strength alloy steel prepared in Example 1 of the present application.

DETAILED DESCRIPTION

The following is a further detailed description of the implementation of the present application in conjunction with the accompanying drawings and examples. The detailed description of the following examples is used to exemplarily illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

As analyzed in the background of this application, a large amount of precious metal elements are added to the ultra-high strength alloy steel in the prior art, resulting in a high cost. In order to solve this problem, this application provides an ultra-high strength alloy steel and a preparation method thereof.

An embodiment of the present application provides an ultra-high strength alloy steel, which includes, by weight percentage, C: 0.10%-0.25%, Si: 1.0%-2.0%, Mn: 0.50%-1.5%, Ni: 0.3%-1.0%, V: 0.2%-0.6%, Cr: 0.3%-1.0%, Mo: 0.2%-2.0%, Nb: 0.1%-0.5%, Al: 0.03%-0.30%, Ti: 0.1%-0.5%, W: 0.1%-0.7%, P: ≤0.008%, S: ≤0.008%, N: 0.003%-0.030%, B: 0.001%-0.015%, and the balance is Fe and other inevitable impurity elements.

The present invention reduces the content of carbon and alloy elements in steel, and improves the tensile strength and hydrogen embrittlement resistance of ultra-high strength alloy steel by combining various elements.

Among them, C is a strengthening element. The higher its content, the higher the strength and hardness of the steel, but the plasticity and toughness will also decrease. The carbon content of the present application is between 0.10% and 0.25%, preferably between 0.12% and 0.24%, so as to simultaneously improve the tensile strength of the ultra-high strength alloy steel and achieve high toughness as much as possible.

Si: Silicon is an important reducing agent and deoxidizing agent in steel, which can improve the hardenability and tempering resistance of steel strip and enhance the corrosion resistance of steel. Therefore, the Si content of the present application is controlled between 1.0% and 2.0%, preferably between 1.3% and 1.8%.

Mn: Manganese is one of the main solid solution strengthening elements in ultra-high strength steel. During the smelting process of ultra-high strength steel, it can combine with sulfur to prevent the formation of ferrous sulfide and sulfide inclusions. The Mn content of this application is controlled between 0.50% and 1.5%, preferably between 0.5% and 1.2%.

Ni: Nickel is an element that stabilizes austenite and is mainly used to improve the toughness of steel. When Ni is added together with Cr, it can effectively promote bainite transformation. The Ni content of this application is controlled between 0.3% and 1.0%, preferably between 0.4% and 0.9%, to improve the strength and toughness of the alloy steel.

V: Vanadium exists in steel mainly in the form of carbides. Its main function is to refine the structure and grain of steel, but it generally reduces the hardenability of steel. Combining V with elements such as manganese, chromium, and molybdenum can improve the strength, toughness, and hydrogen embrittlement resistance of alloy steel. The V content of this application should be controlled between 0.2% and 0.6%, preferably between 0.3% and 0.5%.

Cr: The main function of chromium is to improve the hardenability of steel, so that the steel has better comprehensive mechanical properties after quenching and tempering. Therefore, the Cr content of the present application is controlled between 0.3% and 1.0%, preferably between 0.4% and 0.9%.

Mo: Molybdenum can refine the grains, which can improve the strength and toughness of steel. Mo can also increase the cooling rate range for obtaining bainite. The Mo content in this application should be controlled between 0.2% and 2.0%, preferably between 0.5% and 1.6%, which can fully improve the hydrogen embrittlement resistance of the alloy steel.

Nb: Niobium can refine the grains in steel, reduce the overheat sensitivity and temper brittleness of steel, improve the welding performance of steel, and also improve the hydrogen embrittlement resistance of steel. The Nb content of this application should be controlled between 0.1% and 0.5%, preferably between 0.3% and 0.5%, so that the hydrogen embrittlement resistance is fully improved.

Al: Aluminum is mainly used for deoxidation and grain refinement. The Al content in this application should be controlled between 0.03% and 0.30%, preferably between 0.05% and 0.25%.

Ti: Titanium can be dissolved in austenite to improve the hardenability of steel. Adding a trace amount of titanium to steel can improve the long-lasting strength of steel. Titanium is also a good deoxidizer and an effective element for fixing nitrogen and carbon. In order to give full play to the role of Ti, the Ti content of this application should be controlled between 0.1% and 0.5%, preferably between 0.2% and 0.4%.

W: Tungsten can form carbides in steel to increase the tempering stability of steel. Therefore, the W content in this application should be controlled between 0.1% and 0.7%, preferably between 0.2% and 0.5%.

N: Nitrogen combines with other elements in steel to have a precipitation strengthening effect. Therefore, the N content in this application should be controlled between 0.003% and 0.030%, preferably between 0.005% and 0.025%.

B: Boron mainly increases the hardenability of steel, which can save the use of elements such as nickel, chromium, and molybdenum. However, molybdenum can prevent or reduce temper brittleness, while boron tends to promote temper brittleness, so boron cannot completely replace molybdenum. Therefore, the B content of this application should be controlled between 0.001% and 0.015%, preferably between 0.005% and 0.012%.

P: is an impurity element that will cause segregation of steel, increase temper brittleness, reduce the plasticity and toughness of steel, and cause cold brittleness of steel. In order to minimize the impact of P, in some embodiments, the P content is controlled to be less than 0.008%.

S: is an impurity element that reduces the toughness of steel and increases the hot brittleness of steel. In order to minimize the influence of S, in some embodiments, the S content is controlled below 0.008%, preferably below 0.006%.

In particular, adding Ti and V to steel can form carbides and nitrides with C and N, which can effectively hinder the movement of dislocations in steel, improve the strength and toughness of steel, and can act as an irreversible hydrogen trap to hinder the diffusion of hydrogen, which can effectively improve the steel's resistance to hydrogen embrittlement. At the same time, Mo can also generate fine carbides with C, and can also increase the number of carbide hydrogen traps and carbide and substrate interface hydrogen traps, which reduces the hydrogen diffusion coefficient and hydrogen embrittlement sensitivity of steel. When Cr and Ni are added together, they can promote bainite transformation in steel, thereby improving the strength and toughness of steel.

In some embodiments, in order to further improve the tensile strength and hydrogen embrittlement resistance of the ultra-high strength alloy steel, the ultra-high strength alloy steel includes, by weight percentage, C: 0.12-0.24%, Si: 1.3-1.8%, Mn: 0.5-1.2%, Ni: 0.4-0.9%, V: 0.3-0.5%, Cr: 0.4-0.9%, Mo: 0.5-1.6%, Nb: 0.3%-0.5%, Al: 0.05-0.25%, Ti: 0.2-0.4%, W: 0.2%-0.5%, P: ≤0.008%, S: ≤0.006%, N: 0.005-0.025%, B: 0.005-0.012%, and the balance is Fe and other unavoidable impurity elements.

The strength of the alloy is directly related to its metallographic structure. In some embodiments, the metallographic structure of the above-mentioned ultra-high strength alloy steel is mainly tempered lath martensite or (tempered lath martensite + bainite) + diffusely distributed carbides or nitrides + residual austenite. Tempered lath martensite or (tempered lath martensite + bainite) has higher strength and better toughness than martensite (especially acicular martensite). In addition, the presence of residual austenite makes the steel have better toughness, which can effectively improve the steel's resistance to hydrogen embrittlement. The fine grains + diffusely distributed carbides or nitrides in the steel can effectively hinder the movement of dislocations and improve the strength of the steel. At the same time, they act as irreversible hydrogen traps to hinder the diffusion of hydrogen, which can effectively improve the steel's resistance to hydrogen embrittlement, thereby effectively ensuring the steel's ultra-high strength and hydrogen embrittlement resistance.

In some embodiments, the unhydrogenated tensile strength of the ultra-high strength alloy steel is ≥2000MPa, and/or the elongation after fracture is ≥12%, and/or the reduction in area is greater than 40%, and/or the impact energy KV ₂ is ≥40J, and/or the grain size is above level 10; and/or the tensile strength after hydrogen embrittlement of the ultra-high strength alloy steel is ≥1980MPa, and/or the elongation after fracture after hydrogen embrittlement is ≥10%, and/or the reduction in area after hydrogen embrittlement is greater than 38%.

The tensile strength and elongation are tested according to GB/T228.1-2021, the impact energy is tested according to GB/T229-2020, and KV ₂ is selected for testing. The grain size is tested according to GB/T 6394-2017, and the intercept method is used for rating.

Another embodiment of the present application provides a method for preparing ultra-high strength alloy steel, the preparation method comprising:

Step S1, weighing raw materials according to the following weight percentages: C: 0.10% to 0.25%, Si: 1.0% to 2.0%, Mn: 0.50% to 1.5%, Ni: 0.3% to 1.0%, V: 0.2% to 0.6%, Cr: 0.3% to 1.0%, Mo: 0.2% to 2.0%, Nb: 0.1% to 0.5%, Al: 0.03% to 0.30%, Ti: 0.1% to 0.5%, W: 0.1% to 0.7%, P: ≤0.008%, S: ≤0.008%, N: 0.003% to 0.030%, B: 0.001% to 0.015%, the balance is Fe and other unavoidable impurity elements

Step S2, smelting the raw material to obtain an ingot;

Step S3, rolling the ingot to obtain a plate;

Step S4, heat treating the plate to obtain ultra-high strength alloy steel.

The present application reduces the content of carbon and alloy elements in steel, and improves the tensile strength and hydrogen embrittlement resistance of ultra-high strength alloy steel by combining various elements. When ultra-high strength alloy steel is prepared by the above method, the tensile strength, toughness, etc. of the ultra-high strength alloy steel can be adjusted by adjusting the process parameters.

The preparation method of the present application omits the forging process, has a simple process, greatly improves production efficiency, and can also reduce energy consumption and costs, thus facilitating industrial production.

The operation of each step in the preparation method of the present application can refer to the corresponding smelting, rolling and heat treatment processes in conventional processes.

In some embodiments, the above step S2 includes: heating the raw materials into molten iron, performing desulfurization pretreatment, and then performing converter smelting and vacuum refining to obtain an ingot.

The sulfide inclusions are reduced by desulfurization pretreatment, thereby improving the product strength, wherein the desulfurization pretreatment method can refer to the existing technology, including but not limited to reducing slag desulfurization or gasification desulfurization. Preferably, the mass content of sulfur in the molten iron after the above desulfurization pretreatment is less than 0.008%.

In order to improve the uniformity of element mixing, in some embodiments, the molten iron is electromagnetically stirred during the converter smelting process.

During the vacuum refining process, further removal of impurity elements such as degassing and dephosphorization of the molten iron can be achieved. Vacuum refining can be achieved using conventional processes. By adjusting the vacuum refining conditions, the effects of degassing and de-impurity can be adjusted. The specific adjustment method can refer to the prior art and will not be described in detail in this application. In some embodiments, the mass content of hydrogen in the ingot after vacuum refining is lower than 1ppm to further improve the hydrogen embrittlement resistance of the ultra-high strength alloy steel.

In some embodiments, the above step S3 includes: hot rolling and cold rolling the ingot in sequence, and optionally, the rolling process includes: first 2 to 5 hot rollings with a total deformation of 30 to 50%; then 2 to 4 cold rollings with a total deformation of 10 to 30%; then heating to 800 to 860°C for 2 to 4 hot rollings with a total deformation of 15 to 30%; and finally 2 to 5 cold rollings with a total deformation of 10 to 30%. The back and forth hot rolling and cold rolling can destroy the casting structure of the steel ingot, refine the grains, eliminate structural defects, improve the mechanical properties of the steel, and reduce the residual stress in the steel, thereby improving the stability and fatigue resistance of the steel.

The heat treatment process can be carried out in accordance with conventional heat treatment methods, such as quenching, tempering or normalizing. In some embodiments, step S4 includes: heating the plate to 850°C to 1050°C for quenching and heat preservation treatment for 0.5 to 2 hours, and then quenching and cooling to room temperature. Optionally, the temperature of the quenching and heat preservation treatment is 880°C to 1050°C; heating the plate after quenching and heat preservation treatment to 250°C to 500°C for tempering and heat preservation treatment for 1 to 3 hours, and then tempering and cooling to room temperature to obtain ultra-high strength alloy steel. Optionally, the temperature of the tempering and heat preservation treatment is 300°C to 500°C.

The steel is quenched and heat-insulated at 850℃～1050℃ for 0.5～2h, so that the microstructure in the steel changes to lath martensite or (lath martensite + bainite) + residual austenite + nitride, carbide, which greatly improves the strength of the steel; then the steel is tempered and heat-insulated at 250℃～500℃ for 1～3h, and the lath martensite is decomposed to obtain lath martensite + dispersed carbide, which improves the toughness and hydrogen embrittlement resistance of the steel. Therefore, the above heat treatment method further improves the strength and hydrogen embrittlement resistance of the steel.

In some embodiments, in step S4, the plate is heated to 850°C to 1050°C at a rate of 50°C/s to 150°C/s. Optionally, the heating rate is 60 to 130°C/s. The heating rate can ensure the uniformity of the overall temperature of the steel billet during the heating process, while allowing the elements of the steel to diffuse and reduce the occurrence of segregation. When the temperature is too high, the surface and core temperatures of the steel will be different, resulting in thermal stress deformation or cracks; when the heating rate is too slow, the grain size of the steel will grow at a higher temperature.

After quenching and heat preservation treatment, quenching cooling is performed. The quenching cooling in the above-mentioned embodiment of the present application can adopt commonly used rapid cooling means such as oil quenching, salt bath, water quenching, etc. In some embodiments, the cooling rate of the above-mentioned quenching cooling is controlled to be 30-300°C/s to achieve the transformation of the target microstructure in the alloy steel, thereby further making the alloy steel have ultra-high strength, good toughness and resistance to hydrogen embrittlement.

In some embodiments, the quenching cooling method is water cooling, spray cooling or air cooling. The cooling speed can be adjusted by adjusting the water flow rate of water cooling, the spray pressure of spray cooling or the wind speed of air cooling. The specific operation can refer to the prior art and will not be described in detail here.

The quenching cooling can be achieved by cooling to room temperature in one step or by graded cooling. In some embodiments, the quenching cooling is graded cooling, which includes: water cooling to 350°C, then spray cooling or air cooling to room temperature; or spray cooling to 350°C, then air cooling to room temperature. The toughness of the ultra-high strength alloy steel is improved by graded cooling.

The tempering cooling operation in the above heat treatment process can also be based on the conventional tempering cooling process. In some embodiments, the above tempering cooling is air cooling to further release stress and improve the toughness of the alloy steel.

The above-mentioned preparation method of the present application can be used to obtain the ultra-high strength alloy steel mentioned in the present application.

The beneficial effects of the present application will be further illustrated below in combination with examples and comparative examples, but the scope of the present invention is not limited to these examples.

Example 1

Calculated by the mass percentage of chemical composition, the ultra-high strength alloy steel consists of: C: 0.12%, Si: 1.8%; Mn: 0.5%, Ni: 0.9%, V: 0.5%, Cr: 0.4%, Mo: 1.6%, Nb: 0.3%, Al: 0.05%, Ti: 0.4%, W: 0.5%, P: 0.008%, S: 0.008%, N: 0.005%, B: 0.012%, and the remainder is Fe and other inevitable impurity elements.

Preparation method:

The raw materials are proportioned according to the above-mentioned design components, and after being heated into molten iron, they are first pre-treated with desulfurization until the sulfur content is less than 0.008% by mass; then they are smelted in a converter, and electromagnetic stirring is used during the smelting process; finally, vacuum refining is performed, and dehydrogenation treatment is performed to reduce the hydrogen content by mass to less than 1ppm to obtain an ingot;

The ingot is hot rolled and cold rolled, first hot rolled twice, with a total deformation of 30%; then cold rolled twice, with a total deformation of 20%; then heated to 860℃ and hot rolled twice, with a total deformation of 15%; finally cold rolled twice, with a total deformation of 20%;

The plate was heated to 1050°C at 130°C/h, kept at this temperature for 1h, cooled to 350°C by water, and then spray-cooled to room temperature, wherein the cooling rate of water cooling was controlled to be 250°C/s, and the cooling rate of water spray cooling was controlled to be 150°C/s, thus completing the quenching treatment;

The quenched plate is tempered at 300°C for 1.5h and air-cooled to obtain ultra-high strength alloy steel resistant to hydrogen embrittlement.

Example 2

Calculated by the mass percentage of chemical composition, the ultra-high strength alloy steel consists of: C: 0.24%, Si: 1.3%; Mn: 1.2%, Ni: 0.4%, V: 0.3%, Cr: 0.9%, Mo: 0.5%, Nb: 0.5%, Al: 0.25%, Ti: 0.2%, W: 0.2%, P: 0.005%, S: 0.006%, N: 0.025%, B: 0.005%, and the balance is Fe and other inevitable impurity elements.

Preparation method:

The raw materials are proportioned according to the above-mentioned design components, and after being heated into molten iron, they are first pre-treated with desulfurization to reduce the sulfur content to less than 0.005% by mass, and then smelted in a converter. During the smelting process, electromagnetic stirring is used, and finally vacuum refining is performed, and dehydrogenation treatment is performed to reduce the hydrogen content to less than 0.8ppm by mass, to obtain an ingot;

The ingot is hot rolled and cold rolled, firstly, hot rolled for 5 times with a total deformation of 50%; then cold rolled for 4 times with a total deformation of 30%; then heated to 840℃ and hot rolled for 4 times with a total deformation of 30%; finally cold rolled for 5 times with a total deformation of 30%;

The plate was heated to 920°C at 60°C/h, kept at this temperature for 2h, cooled to 350°C by water spray, and then air-cooled to room temperature, wherein the cooling rate of water spray cooling was controlled to be 200°C/s, and the cooling rate of air cooling was controlled to be 50°C/s, and the quenching treatment was completed;

The quenched plate is tempered at 500°C for 2.5h and air-cooled to obtain ultra-high strength alloy steel resistant to hydrogen embrittlement.

Example 3

Calculated by the mass percentage of chemical composition, the ultra-high strength alloy steel consists of: C: 0.16%, Si: 1.5%; Mn: 0.9%, Ni: 0.6%, V: 0.4%, Cr: 0.6%, Mo: 0.8%, Nb: 0.3%, Al: 0.15%, Ti: 0.3%, W: 0.4%, P: 0.006%, S: 0.006%, N: 0.010%, B: 0.009%, and the remainder is Fe and other inevitable impurity elements.

Preparation method:

The raw materials are mixed according to the above-mentioned design components, and after being heated into molten iron, they are first pre-treated with desulfurization until the sulfur content is less than 0.005% by mass; then they are smelted in a converter, and electromagnetic stirring is used during the smelting process; finally, vacuum refining is performed, and dehydrogenation treatment is performed until the hydrogen content is less than 0.8ppm by mass to obtain an ingot;

The ingot is hot rolled and cold rolled, firstly hot rolled 3 times with a total deformation of 40%; then cold rolled 3 times with a total deformation of 20%; then heated to 800℃ and hot rolled 3 times with a total deformation of 25%; finally cold rolled 4 times with a total deformation of 25%;

The plate was heated to 970°C at 90°C/h, kept at this temperature for 1.5h, and then air-cooled to room temperature, wherein the cooling rate of the air-cooling was controlled at 60°C/s, to complete the quenching treatment;

The quenched plate is tempered at 400°C for 3 hours and air-cooled to obtain ultra-high strength alloy steel resistant to hydrogen embrittlement.

Example 4

The composition of the ultra-high strength alloy steel, by weight percentage, is as follows: C: 0.10%, Si: 2.0%, Mn: 0.50%, Ni: 0.3%, V: 0.6%, Cr: 1.0%, Mo: 0.2%, Nb: 0.1%, Al: 0.30%, Ti: 0.5%, W: 0.1%, P: ≤0.008%, S: ≤0.008%, N: 0.003%, B: 0.015%, and the balance is Fe and other unavoidable impurity elements.

The preparation method is the same as Example 2.

Example 5

The composition of the ultra-high strength alloy steel, by weight percentage, is as follows: C: 0.25%, Si: 1.0%, Mn: 1.5%, Ni: 1.0%, V: 0.2%, Cr: 0.3%, Mo: 2.0%, Nb: 0.5%, Al: 0.03%, Ti: 0.1%, W: 0.7%, P: ≤0.008%, S: ≤0.008%, N: 0.030%, B: 0.001%, and the balance is Fe and other unavoidable impurity elements.

The preparation method is the same as Example 2.

Example 6

The composition of the ultra-high strength alloy steel is the same as that of Example 2.

Preparation method:

The raw materials are proportioned according to the above-mentioned design components, and after being heated into molten iron, they are first pre-treated with desulfurization to reduce the sulfur content to less than 0.005% by mass, and then smelted in a converter. During the smelting process, electromagnetic stirring is used, and finally vacuum refining is performed, and dehydrogenation treatment is performed to reduce the hydrogen content to less than 0.8ppm by mass, to obtain an ingot;

The ingot is hot rolled and cold rolled, the ingot is hot rolled and cold rolled, firstly 5 times of hot rolling with a total deformation of 50%; then 4 times of cold rolling with a total deformation of 30%; then heated to 840℃ and hot rolled 4 times with a total deformation of 30%; finally 5 times of cold rolling with a total deformation of 30%;

The plate was heated to 920°C at 40°C/h, kept at this temperature for 2h, cooled to 350°C by water spray, and then air-cooled to room temperature, wherein the cooling rate of water spray cooling was controlled to be 200°C/s, and the cooling rate of air cooling was controlled to be 50°C/s, and the quenching treatment was completed;

The quenched plate is tempered at 500°C for 2.5h and air-cooled to obtain ultra-high strength alloy steel resistant to hydrogen embrittlement.

Example 7

The composition of the ultra-high strength alloy steel is the same as that of Example 2.

Preparation method:

The raw materials are proportioned according to the above-mentioned design components, and after being heated into molten iron, they are first pre-treated with desulfurization to reduce the sulfur content to less than 0.005% by mass, and then smelted in a converter. During the smelting process, electromagnetic stirring is used, and finally vacuum refining is performed, and dehydrogenation treatment is performed to reduce the hydrogen content to less than 0.8ppm by mass, to obtain an ingot;

The ingot is hot rolled and cold rolled, the ingot is hot rolled and cold rolled, firstly 5 times of hot rolling with a total deformation of 50%; then 4 times of cold rolling with a total deformation of 30%; then heated to 840℃ and hot rolled 4 times with a total deformation of 30%; finally 5 times of cold rolling with a total deformation of 30%;

The plate was heated to 920°C at 170°C/h, kept at this temperature for 2h, cooled to 350°C by water spray, and then air-cooled to room temperature, wherein the cooling rate of water spray cooling was controlled to be 200°C/s, and the cooling rate of air cooling was controlled to be 50°C/s, and the quenching treatment was completed;

The quenched plate is tempered at 500°C for 2.5h and air-cooled to obtain ultra-high strength alloy steel resistant to hydrogen embrittlement.

Example 8

The composition of the ultra-high strength alloy steel is the same as that of Example 2.

Preparation method:

The raw materials are proportioned according to the above-mentioned design components, and after being heated into molten iron, they are first pre-treated with desulfurization to reduce the sulfur content to less than 0.005% by mass, and then smelted in a converter. During the smelting process, electromagnetic stirring is used, and finally vacuum refining is performed, and dehydrogenation treatment is performed to reduce the hydrogen content to less than 0.8ppm by mass, to obtain an ingot;

The ingot is hot rolled and cold rolled, the ingot is hot rolled and cold rolled, firstly 5 times of hot rolling with a total deformation of 50%; then 4 times of cold rolling with a total deformation of 30%; then heated to 840℃ and hot rolled 4 times with a total deformation of 30%; finally 5 times of cold rolling with a total deformation of 30%;

The plate was heated to 850°C at 60°C/h, kept at this temperature for 2h, cooled to 350°C by water spray, and then air-cooled to room temperature, wherein the cooling rate of water spray cooling was controlled to be 300°C/s, and the cooling rate of air cooling was controlled to be 30°C/s, and the quenching treatment was completed;

The quenched plate is tempered at 200°C for 3 hours and air-cooled to obtain an ultra-high strength alloy steel resistant to hydrogen embrittlement.

Example 9

The composition of the ultra-high strength alloy steel is the same as that of Example 2.

Preparation method:

The raw materials are proportioned according to the above-mentioned design components, and after being heated into molten iron, they are first pre-treated with desulfurization to reduce the sulfur content to less than 0.005% by mass, and then smelted in a converter. During the smelting process, electromagnetic stirring is used, and finally vacuum refining is performed, and dehydrogenation treatment is performed to reduce the hydrogen content to less than 0.8ppm by mass, to obtain an ingot;

The ingot is hot rolled and cold rolled, the ingot is hot rolled and cold rolled, firstly 5 times of hot rolling with a total deformation of 50%; then 4 times of cold rolling with a total deformation of 30%; then heated to 840℃ and hot rolled 4 times with a total deformation of 30%; finally 5 times of cold rolling with a total deformation of 30%;

The plate was heated to 880°C at 60°C/h, kept at this temperature for 2h, cooled to 350°C by water spray, and then air-cooled to room temperature, wherein the cooling rate of water spray cooling was controlled to be 200°C/s, and the cooling rate of air cooling was controlled to be 50°C/s, and the quenching treatment was completed;

The quenched plate is tempered at 500°C for 2.5h and air-cooled to obtain ultra-high strength alloy steel resistant to hydrogen embrittlement.

Example 10

The composition of the ultra-high strength alloy steel is the same as that of Example 2.

Preparation method:

The raw materials are proportioned according to the above-mentioned design components, and after being heated into molten iron, they are first pre-treated with desulfurization to reduce the sulfur content to less than 0.005% by mass, and then smelted in a converter. During the smelting process, electromagnetic stirring is used, and finally vacuum refining is performed, and dehydrogenation treatment is performed to reduce the hydrogen content to less than 0.8ppm by mass, to obtain an ingot;

The ingot is hot rolled and cold rolled, the ingot is hot rolled and cold rolled, firstly 5 times of hot rolling with a total deformation of 50%; then 4 times of cold rolling with a total deformation of 30%; then heated to 840℃ and hot rolled 4 times with a total deformation of 30%; finally 5 times of cold rolling with a total deformation of 30%;

The plate was heated to 1100°C at 60°C/h, kept at this temperature for 2h, cooled to 350°C by water spray, and then air-cooled to room temperature, wherein the cooling rate of water spray cooling was controlled to be 200°C/s, and the cooling rate of air cooling was controlled to be 50°C/s, and the quenching treatment was completed;

The quenched plate is tempered at 500°C for 2.5h and air-cooled to obtain ultra-high strength alloy steel resistant to hydrogen embrittlement.

Embodiment 11

The composition of the ultra-high strength alloy steel is the same as that of Example 2.

Preparation method:

The raw materials are proportioned according to the above-mentioned design components, and after being heated into molten iron, they are first pre-treated with desulfurization to reduce the sulfur content to less than 0.005% by mass, and then smelted in a converter. During the smelting process, electromagnetic stirring is used, and finally vacuum refining is performed, and dehydrogenation treatment is performed to reduce the hydrogen content to less than 0.8ppm by mass, to obtain an ingot;

The ingot is hot rolled and cold rolled, the ingot is hot rolled and cold rolled, firstly 5 times of hot rolling with a total deformation of 50%; then 4 times of cold rolling with a total deformation of 30%; then heated to 840℃ and hot rolled 4 times with a total deformation of 30%; finally 5 times of cold rolling with a total deformation of 30%;

The plate was heated to 830°C at 60°C/h, kept at this temperature for 2h, cooled to 350°C by water spray, and then air-cooled to room temperature, wherein the cooling rate of water spray cooling was controlled to be 200°C/s, and the cooling rate of air cooling was controlled to be 50°C/s, and the quenching treatment was completed;

The quenched plate is tempered at 500°C for 2.5h and air-cooled to obtain ultra-high strength alloy steel resistant to hydrogen embrittlement.

Example 12

The composition of the ultra-high strength alloy steel is the same as that of Example 2.

Preparation method:

The raw materials are proportioned according to the above-mentioned design components, and after being heated into molten iron, they are first pre-treated with desulfurization to reduce the sulfur content to less than 0.005% by mass, and then smelted in a converter. During the smelting process, electromagnetic stirring is used, and finally vacuum refining is performed, and dehydrogenation treatment is performed to reduce the hydrogen content to less than 0.8ppm by mass, to obtain an ingot;

The ingot is hot rolled and cold rolled, the ingot is hot rolled and cold rolled, firstly 5 times of hot rolling with a total deformation of 50%; then 4 times of cold rolling with a total deformation of 30%; then heated to 840℃ and hot rolled 4 times with a total deformation of 30%; finally 5 times of cold rolling with a total deformation of 30%;

The plate was heated to 920°C at 60°C/h, kept at this temperature for 2h, cooled to 350°C by water spray, and then air-cooled to room temperature, wherein the cooling rate of water spray cooling was controlled to be 100°C/s, and the cooling rate of air cooling was controlled to be 70°C/s, and the quenching treatment was completed;

The quenched plate is tempered at 550°C for 0.5h and air-cooled to obtain an ultra-high strength alloy steel resistant to hydrogen embrittlement.

Comparative Example 1

Calculated by mass percentage of chemical composition, the composition of ultra-high strength alloy steel is: C: 0.30%, Si: 1.8%; Mn: 0.5%, Ni: 0.9%, V: 0.5%, Cr: 0.4%, Mo: 1.6%, Nb: 0.3%, Al: 0.05%, Ti: 0.4%, W: 0.5%, P: 0.008%, S: 0.008%, N: 0.005%, B: 0.012%, and the balance is Fe and other inevitable impurity elements.

The preparation method is the same as that of Example 1.

Comparative Example 2

Calculated by the mass percentage of chemical composition, the ultra-high strength alloy steel consists of: C: 0.12%, Si: 1.8%; Mn: 0.5%, Ni: 0.9%, V: 0.5%, Cr: 0.4%, Mo: 1.6%, Nb: 0.3%, Al: 0.05%, W: 0.5%, P: 0.008%, S: 0.008%, B: 0.012%, and the remainder is Fe and other inevitable impurity elements.

The preparation method is the same as that of Example 1.

Comparative Example 3

Calculated by mass percentage of chemical composition, the composition of ultra-high strength alloy steel is: C: 0.12%, Si: 1.8%; Mn: 0.5%, Ni: 0.9%, V: 0.5%, Cr: 0.2%, Mo: 0.2%, Nb: 0.3%, Al: 0.05%, Ti: 0.4%, W: 0.5%, P: 0.008%, S: 0.008%, N: 0.005%, B: 0.0005%, and the balance is Fe and other inevitable impurity elements.

The preparation method is the same as that of Example 1.

The properties of the ultra-high strength alloy steels obtained in the embodiments and comparative examples were tested in the following manner.

Tensile strength test method: according to GB/T228.1-2021.

Hydrogen embrittlement treatment: prepare a hydrogen charging solution: 1L of 3% NaCl aqueous solution + 3g of ammonium thiocyanate (NH ₄ SCN), and store it at room temperature for 18 hours for use; then use the electrochemical constant current mode with a hydrogen charging current of 5mA/cm ² to place the tensile specimen in the hydrogen charging solution for 72 hours, and then place the hydrogenated specimen in liquid nitrogen for storage.

Test methods for tensile strength, elongation after fracture and reduction of area after hydrogen embrittlement: according to GB/T228.1-2021.

Specified plastic extension strength test method: GB/T228.1-2021.

Elongation after fracture test method: according to GB/T228.1-2021.

Sectional shrinkage test method: according to GB/T228.1-2021.

Impact energy test method: according to GB/T229-2020.

Metallographic structure testing method: According to GB/T13298-2015, the metallographic structure micrographs of the ultra-high strength alloy steels of Examples 1 to 3 are recorded in Figures 1 to 3 respectively, wherein the white dots are nitrides and carbides, and the composition of nitrides and carbides can also be detected by an EDS spectrometer, wherein the EDS spectrum analysis results of the nitrides and carbides of Example 1 are shown in Figures 4 and 5, and Figures 4 and 5 are the spectrum analysis results of the white dots at different positions, respectively.

Grain size test method: According to GB/T6394-2017.

After testing, the physical and mechanical properties of the ultra-high strength alloy steels of various embodiments and comparative examples are shown in Table 1.

Claims (10)

1. An ultra-high-strength alloy steel, characterized in that, by weight percentage, the ultra-high-strength alloy steel comprises C: 0.10% to 0.25%, Si: 1.0% to 2.0%, Mn: 0.50% to 1.5% %, Ni: 0.3% to 1.0%, V: 0.2% to 0.6%, Cr: 0.3% to 1.0%, Mo: 0.2% to 2.0%, Nb: 0.1% to 0.5%, Al: 0.03% to 0.30%, Ti: 0.1% to 0.5%, W: 0.1%～0.7%, P: ≤0.008%, S: ≤0.008%, N: 0.003%～0.030%, B: 0.001%～0.015%, the balance is Fe and other unavoidable impurity elements. 2. The ultra-high-strength alloy steel according to claim 1, characterized in that, by weight percentage, the ultra-high-strength alloy steel comprises C: 0.12% to 0.24%, Si: 1.3% to 1.8%, Mn : 0.5% to 1.2%, Ni: 0.4% to 0.9%, V: 0.3% to 0.5%, Cr: 0.4% to 0.9%, Mo: 0.5% to 1.6%, Nb: 0.3% to 0.5%, Al: 0.05 %～0.25%, Ti: 0.2%～0.4%, W: 0.2%～0.5%, P: ≤0.008%, S: ≤0.006%, N: 0.005% to 0.025%, B: 0.005% to 0.012%, and the balance is Fe and other unavoidable impurity elements. 3. The ultra-high-strength alloy steel according to claim 1 or 2, characterized in that, the metallographic structure of the ultra-high-strength alloy steel is tempered lath martensite or (tempered lath martensite+ Bainite) + dispersed carbide or nitride + retained austenite, Optionally, the non-hydrogen-charged tensile strength of the ultra-high-strength alloy steel is ≥2000MPa, and/or the elongation after fracture is ≥12%, and/or the reduction of area is greater than 40%, and/or the impact energy KV ₂ ≥ 40J, and/or the grain size grade is above grade 10; and/or the tensile strength after hydrogen embrittlement of the ultra-high-strength alloy steel is ≥1980MPa, and/or the elongation after fracture after hydrogen embrittlement is ≥10%, and/or Or the reduction of area after hydrogen embrittlement is greater than 38%. 4. A preparation method of ultra-high strength alloy steel, characterized in that, the preparation method comprises: Step S1, weighing raw materials according to the following weight percentages: C: 0.10% to 0.25%, Si: 1.0% to 2.0%, Mn: 0.50% to 1.5%, Ni: 0.3% to 1.0%, V: 0.2% to 0.6% %, Cr: 0.3% to 1.0%, Mo: 0.2% to 2.0%, Nb: 0.1% to 0.5%, Al: 0.03%～0.30%, Ti: 0.1%～0.5%, W: 0.1%～0.7%, P: ≤0.008%, S: ≤0.008%, N: 0.003% ~ 0.030%, B: 0.001% ~ 0.015%, the balance is Fe and other unavoidable impurity elements Step S2, smelting the raw materials to obtain ingots; Step S3, rolling the ingot to obtain a plate; Step S4, performing heat treatment on the plate to obtain ultra-high-strength alloy steel. 5. preparation method according to claim 4, is characterized in that, described step S4 comprises: The plate is heated to 850°C-1050°C for quenching and heat preservation treatment for 0.5-2 hours, and then quenched and cooled to room temperature. Optionally, the temperature of the quenching and heat preservation treatment is 880°C-1050°C. Further optionally, the quenching The temperature of heat preservation treatment is 920℃～1050℃; Heat the plate after quenching and heat preservation treatment to 200°C to 500°C, perform tempering and heat preservation treatment for 1 to 3 hours, and then temper and cool to room temperature to obtain the ultra-high strength alloy steel; optionally, the temperature of the tempering and heat preservation treatment It is 300°C to 500°C. 6. The preparation method according to claim 5, characterized in that, in the step S4, the temperature of the plate is raised to 850°C-1050°C at a rate of 50-150°C/s. 7. The preparation method according to claim 5 or 6, characterized in that, the cooling rate of the quenching cooling is 30°C/s～300°C/s; optionally, the means of the quenching cooling are water cooling, spraying cooling or air cooling; Optionally, the quenching cooling method is graded cooling, and the graded cooling includes: water cooling to 350±20°C, and then spray cooling or air cooling to room temperature; Or spray cooling to 350±20°C, then air cooling to room temperature. 8. The preparation method according to any one of claims 4 to 7, characterized in that the tempering cooling is air cooling. 9. according to the preparation method described in any one in claim 4 to 8, it is characterized in that, described step S2 comprises: heating the raw materials into molten iron, performing desulfurization pretreatment, and then performing converter smelting and vacuum refining to obtain the ingot; Optionally, the mass content of sulfur in the molten iron after the desulfurization pretreatment is lower than 0.008%; Optionally, electromagnetic stirring is performed on molten iron during the converter smelting process; Optionally, the mass content of hydrogen in the ingot after the vacuum refining is lower than 1 ppm. 10. The preparation method according to any one of claims 4 to 9, characterized in that, the step S3 comprises: performing hot rolling and cold rolling on the ingot, optionally, the rolling process Including: 2 to 5 times of hot rolling first, with a total deformation of 30 to 50%; then 2 to 4 times of cold rolling, with a total deformation of 10 to 30%; then heating to 800 to 860°C for 2 to 4 times Hot rolling, with a total deformation of 15-30%; and finally 2-5 times of cold rolling with a total deformation of 10-30%.