阅读说明：本技术 具有超细亚结构的超高强高韧马氏体时效钢及其制备方法 (Ultra-high strength and high toughness maraging steel with superfine substructure and preparation method thereof ) 是由 王威 周新磊 米鹏 赵宽 孙明月 严伟 张洪林 徐斌 于 2021-08-30 设计创作，主要内容包括：本发明属于钢铁结构材料韧化技术领域,具体为一种具有超细亚结构的超高强高韧马氏体时效钢及其制备方法,所述方法适用于屈服强度大于2000MPa的马氏体时效钢,制备的棒料经过4次或4次以上循环淬火处理后,再在480-520℃下进行3-5h的时效处理,可在不降低材料的抗拉强度和屈服强度的同时,将该类马氏体时效钢的冲击韧性(AK-(v2))提升至20J以上。本发明所涉及的马氏体时效钢为超高屈服强度、同时具有良好的韧性的超高强高韧马氏体时效钢,可广泛应用于航空航天等诸多重要领域。(The invention belongs to the technical field of toughening of steel structural materials, and particularly relates to ultra-high strength and high toughness maraging steel with an ultra-fine substructure and a preparation method thereof, wherein the method is suitable for maraging steel with yield strength of more than 2000MPa, the prepared bar is subjected to cyclic quenching treatment for 4 times or more than 4 times, and then is subjected to aging treatment at 480-520 ℃ for 3-5h, so that the maraging steel can be subjected to aging treatment while the tensile strength and the yield strength of the material are not reducedImpact toughness (AK) v2 ) Lifting to above 20J. The maraging steel related by the invention is ultrahigh-strength and high-toughness maraging steel with ultrahigh yield strength and good toughness, and can be widely applied to a plurality of important fields such as aerospace and the like.)

1. The preparation method of the ultra-high strength and high toughness maraging steel with the superfine substructure is characterized in that the heat treatment process of the maraging steel is as follows: after 4 times or more than 4 times of circulating quenching treatment, carrying out aging treatment for 3-5h at 480-520 ℃.

2. The method for preparing the ultra-high strength and high toughness maraging steel with ultra-fine substructure as recited in claim 1, wherein the cyclic quenching treatment is specifically: the temperature of the sample is increased to 800-900 ℃ at the heating rate of 5-10 ℃/min, and the sample is cooled to room temperature at the cooling rate of 10-15 ℃/min after heat preservation for 10-30 min.

3. The method for preparing the ultra-high strength and toughness maraging steel with the ultra-fine substructure as recited in claim 1, wherein the maraging steel is subjected to solution treatment at 800-900 ℃ for 1-3 hours, water-cooled to room temperature after the solution treatment, then cryogenically cooled in liquid nitrogen, and then subjected to circulating quenching treatment.

4. Method for the production of a maraging steel with ultra high strength and high toughness having an ultra fine substructure according to claim 1, characterized in that the maraging steel has a yield strength of more than 2000 MPa.

5. Method for the production of a maraging steel with ultra high strength and high toughness having an ultra fine substructure according to claim 1, characterized in that the maraging steel has the following chemical composition, in mass%: 15-20 percent of Ni, 10-14 percent of Co, 4-7 percent of Mo, 0.5-1.5 percent of Ti and the balance of Fe.

6. The maraging steel with ultra-high strength and high toughness and the ultra-fine substructure, which is prepared by the method of any one of claims 1 to 5, is characterized in that the effective grain size or large-angle grain boundary in a maraging steel matrix is less than 1 um.

7. Ultra high strength and toughness maraging steel with ultra fine substructure according to claim 6, characterized in that: after the cyclic quenching treatment, the maraging steel matrix has dispersed equiaxed massive austenite phase, the volume fraction of austenite is less than 10%, and the size of austenite phase is less than 1 um.

8. Ultra high strength and toughness maraging steel with ultra fine substructure according to claim 6, characterized in that: the yield strength of the maraging steel is more than 2000MPa, and the impact toughness is more than 20J.

Technical Field

The invention belongs to the technical field of toughening of steel structural materials, and particularly relates to ultra-high-strength and high-toughness maraging steel with an ultra-fine substructure and a preparation method thereof.

Background

Maraging steel is widely used in aerospace, marine development, and military applications due to its high strength, high toughness, and good weldability. In general, aging at 450-. In the development process of pursuing 'lightweight' for key structural components, in addition to the requirement for high strength, the requirement for increasing toughness to improve the use safety of ultra-high strength steel is also stricter and stricter. However, after the tensile strength of the ultra-high strength maraging steel exceeds 1900MPa, the impact energy hardly exceeds 15J. Therefore, exploring how to improve the toughness of the ultra-high strength maraging steel under the condition of not reducing the strength is a prerequisite and key difficult problem to be solved for the ultra-high strength maraging steel to play a role in the field of 'light weight' and obtain wide engineering application.

The structure of the ultra-high strength maraging steel is martensite with high dislocation density strengthened by dispersed and precipitated nano-scale intermetallic compounds, and a small amount of residual austenite. Research has found that the martensite substructure is one of the key factors for controlling the impact toughness of maraging steel. For example, the bundle of laths in maraging steel also plays an important role in improving toughness. Therefore, the size of the ribbon bundle is also considered critical in controlling toughness. In fact, since the boundaries of the crystalline regions and the lath bundles are both high angle grain boundaries, they can be referred to as "effective grain sizes". Besides the 'substructure' in the martensite structure, the control of the retained austenite in the matrix is also an effective way to increase the toughness. A heat treatment of critical tempering is usually used to form the desired amount of austenite for higher toughness. When the tempering temperature is too high, the content of residual austenite in the steel increases and the steel is in the shape of a block with a large size, thereby affecting the yield strength of the steel. Therefore, optimizing the retained austenite in the ultrahigh-strength maraging steel is also an important way for improving the toughness of the ultrahigh-strength maraging steel.

In view of the above background, in practical engineering practice, it is important to develop ultra-high strength maraging steel having an ultra-high yield strength and good toughness to ensure the safety and reliability of a member.

Disclosure of Invention

The invention aims to provide ultra-high strength and high toughness maraging steel with an ultra-fine substructure and a preparation method thereof, and in order to achieve the aim, the technical scheme of the invention is as follows:

the preparation method of the ultra-high strength and high toughness maraging steel with the superfine substructure is characterized in that the heat treatment process of the maraging steel is as follows: after 4 times or more than 4 times of circulating quenching treatment, carrying out aging treatment for 3-5h at 480-520 ℃.

The circulating quenching treatment specifically comprises the following steps: the temperature of the sample is increased to 800-900 ℃ at the heating rate of 5-10 ℃/min, and the sample is cooled to room temperature at the cooling rate of 10-15 ℃/min after heat preservation for 10-30 min.

The maraging steel is subjected to solution treatment for 1-3h at the temperature of 800-900 ℃, cooled to room temperature after solution treatment, then subjected to cryogenic cooling in liquid nitrogen, and then subjected to circulating quenching treatment.

As a preferred technical scheme:

the heat treatment process comprises the following steps: after the cyclic quenching treatment for more than 4 times, the aging treatment is carried out for 3-5h at 480-520 ℃. The circulating quenching treatment specifically comprises the following steps: the temperature of the sample is increased to 800-900 ℃ at the heating rate of 10 ℃/min, and the sample is cooled to room temperature at the cooling rate of 10 ℃/min after heat preservation for 10-30 min.

The method is particularly suitable for maraging steel with yield strength of more than 2000MPa, and as a preferable technical scheme, the maraging steel comprises the following chemical components (in mass percent): 15-20 percent of Ni, 10-14 percent of Co, 4-7 percent of Mo, 0.5-1.5 percent of Ti and the balance of Fe.

The ultra-high strength and high toughness maraging steel with the superfine substructure prepared by the method is characterized in that the effective grain size or large angle grain boundary in the maraging steel matrix is less than 1 um.

Preferably, after the cyclic quenching treatment, the maraging steel matrix has dispersed equiaxed massive austenite phases, the size of the austenite phases is less than 1um, and the austenite content is less than 10%.

The invention has the beneficial effects that:

compared with the prior art, the method can improve the impact toughness of the ultra-high strength maraging steel with the yield strength of more than 2000MPa to more than 20J on the premise of not reducing the yield strength and the tensile strength of the material.

Drawings

FIG. 1 is a graph of tensile stress strain for a sample of example 1 of the present invention;

FIG. 2 is a graph of tensile stress strain for comparative example 1 of the present invention;

FIG. 3 phase distribution diagram of samples of example 1 of the invention, black: martensite, white: austenite;

FIG. 4 phase distribution diagram of comparative example 1 sample of the invention, black: martensite, white: austenite;

FIG. 5 is a graph of the distribution of the high angle grain boundaries of the sample of example 1 of the present invention;

FIG. 6 is a graph of the distribution of the large-angle grain boundaries of the comparative example 1 of the present invention;

FIG. 7 is a graph of tensile stress strain for the sample of example 2 of the present invention;

FIG. 8 is a graph of tensile stress strain for comparative example 2 of the present invention;

fig. 9 phase distribution diagram of samples of example 2 of the invention, black: martensite, white: austenite;

FIG. 10 phase distribution diagram of comparative example 2 sample of the invention, black: martensite, white: austenite;

FIG. 11 is a graph of the distribution of the high angle grain boundaries of the sample of example 2 of the present invention;

FIG. 12 is a graph of the distribution of the high angle grain boundaries of the comparative example 2 of the present invention;

FIG. 13 is a graph of tensile stress strain for the example 3 sample of the present invention;

FIG. 14 tensile stress strain plot of comparative example 3 sample of the invention;

FIG. 15 phase distribution diagram of samples of example 3 of the invention, black: martensite, white: austenite;

fig. 16 phase distribution diagram of comparative example 3 sample of the invention, black: martensite, white: austenite;

FIG. 17 is a graph of the distribution of the high angle grain boundaries of the sample of example 3 of the present invention;

FIG. 18 is a graph showing the distribution of the high angle grain boundaries of the comparative example 3 of the present invention.

Detailed Description

In order to make the purpose, technical solution and effect of the present application clearer and clearer, the present application is further described in detail below with reference to the accompanying drawings and examples.

Example 1

The ingredients were formulated as shown in table 1. Discharging materials in sequence according to the sequence from low melting point to high melting point, keeping the vacuum degree of 10Pa in the smelting process, and crusting and remelting for five times. The ingot after smelting is subjected to hot working and heat treatment according to the following process conditions:

(1) after the smelting is finished, the alloy is obtained through the working procedures of consumable electrode bar forging, vacuum consumable smelting and the likeCylinderA bar stock;

(2) homogenizing: the temperature is 1200 ℃, and the time is 24 h;

(2) forging: the initial forging temperature is 1150 ℃, the forging ratio is more than 5, and the forging is carried out and then air cooling is carried out to the room temperature;

(3) and (3) heat treatment: carrying out solution treatment at 850 ℃ for 1h, cooling the solution treated solution to room temperature by water, and then carrying out deep cooling at the temperature of liquid nitrogen. The temperature of the deep-frozen sample is raised to 800 ℃ at the heating rate of 5 ℃/min, the sample is cooled to room temperature at the cooling rate of 10 ℃/min after heat preservation for 20min, and 4 times of circulating quenching treatment are carried out. Then, aging treatment is carried out for 3h at 500 ℃;

(4) the material is processed into a sample after heat treatment, the room temperature tensile property and the room temperature impact property of the sample are respectively tested, and EBSD analysis is carried out on the test sample. The stretching results are shown in FIG. 1; the phase distribution is shown in FIG. 3; the large angle grain boundaries are shown in figure 5.

Comparative example 1

The difference from example 1 is that:

the first purification smelting is carried out by using a 200Kg vacuum induction smelting furnace, and then vacuum consumable remelting is carried out to obtain the second purification, wherein the content of C, O, N in the steel is controlled to be less than 20 ppm. Homogenizing the consumable ingot at 1200 ℃ for more than 8h, then forging at 1150 ℃, wherein the final forging temperature is not lower than 800 ℃, the forging ratio is more than 5, and air cooling to room temperature after forging. And (3) carrying out solution treatment on the sample at 850 ℃ for 1h by using a heat treatment furnace, cooling the sample to room temperature by water after the solution treatment, and then carrying out deep cooling at the temperature of liquid nitrogen. The samples after deep cooling are subjected to aging treatment for 2 hours at 500 ℃.

The stretching results are shown in FIG. 2; the phase distribution is shown in fig. 4; the large angle grain boundaries are shown in figure 6.

FIG. 1 is a tensile stress-strain curve of the material of example 1 of the present invention, from which it can be seen that the material has a tensile strength of 2248MPa and a yield strength of 2069 MPa; FIG. 2 is a graph of tensile stress strain for comparative example 1 of the present invention. FIG. 3 is a phase distribution diagram in example 1 of the present invention, black: martensite, white: austenite, fig. 4, is the phase distribution in comparative example 1. It can be seen that the effective grain size is refined and uniformly distributed, and austenite is distributed along a large-angle grain boundary; FIG. 5 is a distribution diagram of large-angle grain boundaries of the material of example 1 according to the present invention, and FIG. 6 is a distribution diagram of large-angle grain boundaries of the material of comparative example 1. It can be seen that the substructure in the martensite is significantly refined.

Example 2

The difference from example 1 is that:

(1) and (3) heat treatment: carrying out solution treatment at 850 ℃ for 1h, cooling the solution treated solution to room temperature by water, and then carrying out deep cooling at the temperature of liquid nitrogen. And raising the temperature of the deep-cooled sample to 810 ℃ at the heating rate of 8 ℃/min, preserving the heat for 20min, cooling the sample to room temperature at the cooling rate of 15 ℃/min, and carrying out 5 times of circulating quenching treatment. Thereafter, an aging treatment was carried out at 500 ℃ for 3 hours.

(2) The material is processed into a sample after heat treatment, the room temperature tensile property and the room temperature impact property of the sample are respectively tested, and EBSD analysis is carried out on the test sample. The stretching results are shown in FIG. 7; the phase distribution is shown in fig. 9; the distribution of high angle grain boundaries is shown in fig. 11.

Comparative example 2

The difference from example 2 is that:

(1) and (3) heat treatment: carrying out solution treatment at 850 ℃ for 1h, cooling the solution treated solution to room temperature by water, and then carrying out deep cooling at the temperature of liquid nitrogen. The samples after deep cooling are subjected to aging treatment for 3 hours at 500 ℃.

(2) The material is processed into a sample after heat treatment, the room temperature tensile property and the room temperature impact property of the sample are respectively tested, and EBSD analysis is carried out on the test sample. The stretching results are shown in fig. 8; the phases and high angle grain boundaries are shown in FIG. 10; the substructure orientation is shown in fig. 12.

Example 3

The difference from example 1 is that:

(1) and (3) heat treatment: carrying out solution treatment at 850 ℃ for 1h, cooling the solution treated solution to room temperature by water, and then carrying out deep cooling at the temperature of liquid nitrogen. The temperature of the deep-frozen sample is raised to 820 ℃ at the heating rate of 10 ℃/min, the sample is cooled to room temperature at the temperature of 15 ℃/min after being kept for 20min, and 5 times of circulating quenching treatment are carried out. Thereafter, an aging treatment was carried out at 500 ℃ for 4 hours.

(2) The material is processed into a sample after heat treatment, the room temperature tensile property and the room temperature impact property of the sample are respectively tested, and EBSD analysis is carried out on the test sample. The stretching results are shown in fig. 13; the phase distribution is shown in fig. 15; the large angle grain boundaries are shown in fig. 17.

Comparative example 3

The difference from example 3 is that:

(1) and (3) heat treatment: solution treatment is carried out for 1 hour at 850 ℃, water cooling to room temperature is carried out after the solution treatment, and then aging treatment is carried out for 4 hours at 500 ℃. The material testing is shown in figures 14, 16, 18.

TABLE 1 compositional ranges (wt%) of the components of the experimental steels

TABLE 2 comparison of the Performance of maraging steels with ultra-fine substructure with ordinary maraging steels

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.