WO2024139542A1

WO2024139542A1 - High-strength corrosion-resistant anti-cracking steel, and preparation method therefor and use thereof

Info

Publication number: WO2024139542A1
Application number: PCT/CN2023/124593
Authority: WO
Inventors: 骆智超; 何佳珍; 罗兴; 樊宽远; 刘天龙; 殷福星; 郑开宏
Original assignee: 广东省科学院新材料研究所
Priority date: 2022-12-28
Filing date: 2023-10-13
Publication date: 2024-07-04
Also published as: CN115852268A; CN115852268B

Abstract

A high-strength corrosion-resistant anti-cracking steel, and a preparation method therefor and the use thereof, which relate to the technical field of metal materials. The crystal grains of the steel comprise austenite and ferrite, and the crystal grains have a slender fiber shape. The high-strength corrosion-resistant anti-cracking steel comprises the following elements in percentages by weight: C: 0.01-0.1%, Cr: 18-32%, Ni: 3-10%, Mo: 0.2-5.0%, Mn: 0.1-2.0%, Si: 0.2-1.0%, N: 0.1-0.3%, S≤0.03%, P≤0.03%, and the balance of Fe and inevitable impurities. The corrosion resistance of a material is improved by controlling the element composition of the steel, especially the ratio of C, N and Si. The slender fibrous structure grains in the material have good impact toughness, such that the mechanical properties of fatigue fracture performance, etc., of the material can be significantly improved, thereby prolonging the service life of the high-strength corrosion-resistant anti-cracking steel.

Description

High-strength corrosion-resistant and crack-resistant steel and its preparation method and application

Technical Field

The present invention relates to the technical field of metal materials, and in particular to a high-strength corrosion-resistant and crack-resistant steel and a preparation method and application thereof.

Background technique

High-strength steel is widely used in the industrial field due to its excellent mechanical properties, and high-strength bolts are one of the application examples of high-strength steel. Bolts are a commonly used fastener, widely used in daily life and industrial production fields such as construction, electronics, machinery, metallurgy, and chemical industry. Bolts can be divided into eight grades according to their performance: 3.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, and 12.9. Grades 8.8 and above (including grade 8.8) are called high-strength bolts, and the corresponding tensile strength is 800MPa. At present, high-strength bolts are often made of medium carbon steel or medium carbon alloy steel after quenching and tempering.

Due to the different application scenarios of bolts, the requirements for their performance are also different. At present, there are two main problems in the use of bolts. One is insufficient fatigue strength, and the other is high delayed fracture sensitivity. In the service process, in addition to bearing static tensile loads, bolts are also subjected to alternating loads, which will cause fatigue fracture of the bolts. Improving the yield strength of materials is the key to improving the fatigue fracture strength of materials. In addition, bolts used outdoors and at sea often corrode on the surface due to the influence of adverse factors such as dust, acid rain, and salt spray, and cause crack initiation and expansion under the action of external loads, eventually leading to bolt failure. At present, in order to solve the corrosion problem of bolts, steel materials are often tempered by adding a large amount of alloying elements such as V, Nb, and Ti. The delayed fracture sensitivity of the material is reduced by forming a precipitate phase as a hydrogen trap. However, the hydrogen embrittlement sensitivity of the tempered structure is relatively strong. This type of bolt often suffers from fatigue fracture when the strength and toughness meet the engineering requirements, causing large accidents and economic losses. Another way to prevent bolts from corroding when serving in harsh environments is to use protective coatings and protective devices on the surface of the bolts, such as electrogalvanizing, rubber Coating and adding protective sleeves, etc. However, the bolt base and the protective layer are easily separated, which is only effective in the short term. For bolts that serve for a long time, regular maintenance is required, which is complicated to operate and increases the cost. Therefore, it is urgent to propose a new steel material to solve any of the above problems.

In view of this, the present invention is proposed.

Summary of the invention

The object of the present invention is to provide a high-strength corrosion-resistant and crack-resistant steel and a preparation method and application thereof.

The present invention is achieved in that:

In a first aspect, the present invention provides a high-strength corrosion-resistant and crack-resistant steel, wherein the composition of the grains includes austenite and ferrite, and the shape of the grains is slender fiber-like.

Measured by weight percentage, the element composition of high-strength corrosion-resistant and crack-resistant steel includes C: 0.01-0.1%, Cr: 18-32%, Ni: 3-10%, Mo: 0.2-5.0%, Mn: 0.1-2.0%, Si: 0.2-1.0%, N: 0.1-0.3%, S≤0.03%, P≤0.03%, and the balance is Fe and unavoidable impurities.

In an optional embodiment, the element composition of the high strength corrosion resistant and crack resistant steel includes, by weight percentage, C: 0.01-0.1%, Cr: 21-25%, Ni: 5-8%, Mo: 1-3%, Mn: 0.2-1.3%, Si: 0.3-0.9%, N: 0.1-0.3%, S≤0.03%, P≤0.03%, and the balance is Fe and unavoidable impurities.

In an alternative embodiment, the content of austenite is 30-60%.

Preferably, the diameter of the grains is less than 20 μm, and the aspect ratio is 5-50.

In a second aspect, the present invention provides a method for preparing high-strength corrosion-resistant and crack-resistant steel as described in any of the aforementioned embodiments, comprising preparing a stainless steel raw material according to the elemental composition, and performing medium-temperature rolling on the stainless steel raw material.

In an optional embodiment, the medium-temperature rolling includes placing the stainless steel raw material in a heating device for heating and heat preservation, and then taking it out for rolling.

In an optional embodiment, the heating and insulation temperature is 500-700° C., and the insulation time is 45-60 min.

In an optional embodiment, the rolling includes reheating and heat preservation after every 2 to 4 rolling passes.

Preferably, the furnace holding temperature is 500-700° C., and the holding time is 10-20 min.

In an optional embodiment, the direction of each rolling pass is perpendicular to the direction of the previous rolling pass, and the directions of the last two rolling passes are the same.

Preferably, the rolling method is groove rolling.

In an optional embodiment, the stainless steel raw material is duplex stainless steel; the stainless steel raw material is in the shape of a square rod or a round rod.

Preferably, the deformation amount of the stainless steel raw material is 78-98%.

Preferably, the size of the square rod is 20-60 mm×20-60 mm.

Preferably, the size of the round rod is Φ(20-58) mm.

In a third aspect, the present invention provides an application of a high-strength corrosion-resistant and crack-resistant steel as in any of the aforementioned embodiments or a high-strength corrosion-resistant and crack-resistant steel prepared by a preparation method as in any of the aforementioned embodiments in the field of steel products.

Preferably, the steel product comprises high strength bolts.

Preferably, the high-strength bolts include any one of wind power connection shaft bolts and bolts for mechanical parts.

The present invention has the following beneficial effects:

The present invention provides a high-strength corrosion-resistant and crack-resistant steel and a preparation method and application thereof. By controlling the element composition in the steel, especially the content ratio of C, N, and Si, the corrosion resistance of the material is improved. The material contains two phases, austenite and ferrite, which has a lower cost than traditional austenitic stainless steel materials and is suitable for industrial production. The material contains grains of ferrite and austenite phases arranged alternately, and the shape of the grains is elongated and fibrous, resembling a bionic fiber structure. The structure has excellent impact toughness, achieving a strong-toughness balance for bolt steel. The bridging effect between the fiber structures makes the material fracture in the same way as a bamboo-wood structure, which can significantly improve the fatigue fracture performance of bolt steel, thereby increasing the service life of the bolt.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

FIG1 is a scanning electron microscope image of the high-strength corrosion-resistant and crack-resistant steel provided in Example 1 of the present invention;

FIG2 is a graph showing the tensile strength test results of high-strength corrosion-resistant and crack-resistant steels provided in the embodiments of the present invention and the comparative examples;

FIG3 is a scanning electron microscope image of the high-strength corrosion-resistant and crack-resistant steel provided in Comparative Example 5 of the present invention.

Detailed ways

In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

In a first aspect, the present invention provides a high-strength corrosion-resistant and crack-resistant steel, wherein the composition of the grains includes austenite and ferrite, and the shape of the grains is slender fiber.

In an optional embodiment, the elemental composition of the high strength corrosion resistant and crack resistant steel includes, by weight percentage, C: 0.01-0.1%, Cr: 21-25%, Ni: 5-8%, Mo: 1-3%, Mn: 0.2-1.3%, Si: 0.3-0.9%, N: 0.1-0.3%, S≤0.03%, P≤0.03%, and the remainder is Fe and unavoidable impurities.

Among them, the functions of the components of the high-strength corrosion-resistant and crack-resistant steel provided by the present invention are as follows:

Carbon (C) is an important solid solution strengthening element, which can effectively improve the strength of duplex stainless steel. However, too high a carbon content will significantly reduce the toughness, weldability and atmospheric corrosion resistance of duplex stainless steel. Taking all factors into consideration, in the present invention, the C content is limited to 0.01-0.1%.

Nitrogen (N) is an element that strongly forms and stabilizes austenite and expands the austenite phase. And the ability of N element far exceeds that of Ni element, so the precious metal Ni can be replaced by N element with lower cost. N element also has a good solid solution strengthening effect, and increases the effect of fine grain strengthening, improving the strength of duplex stainless steel without damaging its toughness. Compared with duplex stainless steel that does not contain nitrogen, adding more than 0.1% N element can significantly improve the comprehensive mechanical properties of duplex stainless steel. N element can also improve the local corrosion performance of duplex stainless steel and avoid pitting corrosion or intergranular corrosion of duplex stainless steel. In addition, N element plays a certain role in improving the creep resistance and fatigue wear resistance of duplex stainless steel. Taking all factors into consideration, in the present invention, the content of N element is limited to 0.1-0.3%.

Chromium (Cr) is the most common element in all types of stainless steel. It is an element that strongly forms and stabilizes the ferrite phase and abbreviates the austenite phase. In duplex stainless steel, in order to control the ratio of ferrite phase to austenite phase, the Cr element content is higher than the Ni element. The Cr element can increase the passivation current of the steel, make the duplex stainless steel easy to passivate, maintain the stability of the passivation film, and improve the repair ability of the passivation film after damage. However, if the chromium content is too high, in order to stabilize the austenite in the stainless steel structure, it is necessary to increase the nickel content, thereby increasing the material cost. Taking all factors into consideration, in the present invention, the Cr element content is limited to 18-32%, preferably 21-25%.

The content of nickel (Ni) in duplex stainless steel is second only to Cr, and it is an element that strongly forms austenite and expands the austenite phase. The main function of the Ni element in duplex stainless steel is to control the phase balance and ensure the relative content of iron and austenite. In addition, the Ni element can improve the plasticity, toughness and welding properties of duplex stainless steel. However, as a precious metal element, the cost of Ni is relatively high. Taking all factors into consideration, in the present invention, the content of Ni is limited to 3-10%, preferably 5-8%.

Molybdenum (Mo) is a ferrite-forming element that can promote the precipitation of ferrite, σ phase and other metal phases. Mo can significantly improve the pitting corrosion resistance of duplex stainless steel and improve the stability of the passivation film. Mo can also improve the high temperature strength and high temperature creep performance of duplex stainless steel. However, when the Mo content exceeds 5%, the duplex stainless steel will tend to become brittle. Taking all factors into consideration, in the present invention, the Mo content is limited to 0.2-5.0%, preferably 1-3%.

Manganese (Mn) element is a good deoxidizer and an austenite stabilizing element, which can expand the austenite phase region. In addition, Mn element can reduce the critical quenching speed of steel, increase the stability of austenite during cooling, and inhibit the decomposition of austenite. Mn element can also eliminate the hot brittleness of steel and improve processing performance. Taking all factors into consideration, in the present invention, the Mn element content is limited to 0.1-2.0%, preferably 0.2-1.3%.

Silicon (Si) can be used as a reducing agent and deoxidizer in the steelmaking process, which can significantly improve the elastic limit and yield strength of duplex stainless steel. Silicon combined with molybdenum, chromium, etc. can improve corrosion resistance and oxidation resistance. However, excessive silicon will reduce the welding performance of stainless steel composite materials. Taking all factors into consideration, in the present invention, the content of Si is limited to 0.2-1.0%, preferably 0.3-0.9%.

In an optional embodiment, the content of austenite is 30-60%, which is conducive to obtaining a steel material with high strength, high toughness, low cost, corrosion resistance and fracture resistance.

Preferably, in order to ensure the mechanical properties of high-strength corrosion-resistant and crack-resistant steel, the diameter of the grains is less than 20 μm and the aspect ratio is 5-50.

It should be noted that the preparation of stainless steel raw materials according to elemental composition is: raw materials containing Fe, C, Cr, Ni, Mo, Mn, Si, N, S and P are mixed in the proportion required for high-strength corrosion-resistant and crack-resistant steel, and then melted, refined, cast and hot-rolled in sequence to obtain stainless steel raw materials. The melting, refining, casting and hot-rolling processes can be conventional stainless steel preparation processes. Alternatively, the stainless steel raw materials described above in the present invention can also be commercially available materials with elemental composition that meets the requirements.

In an optional embodiment, since the high-strength corrosion-resistant and crack-resistant steel of the present invention contains both austenite and ferrite phases, duplex stainless steel can be directly used as the stainless steel raw material. Compared with austenitic stainless steel, high alloy steel and maraging steel, the duplex stainless steel provided by the present invention is It has lower cost and better corrosion resistance; compared with ordinary carbon steel materials, its strength can be greatly improved.

Preferably, the stainless steel raw material is in the shape of a square bar or a round bar, so as to be rolled at a medium temperature to obtain a bolt. In other embodiments, the stainless steel raw material may also be in the shape of a plate, a block, etc., and the shape of the stainless steel raw material is based on the final rolled shape.

Preferably, the deformation of the stainless steel raw material is 78-98%. By using a larger deformation to refine the grains and controlling the deformation of the stainless steel raw material within the above range, grains with a bionic fiber structure can be constructed, which can not only meet its strengthening and toughening requirements, but also improve its service performance.

Preferably, the size of the square rod is 20-60 mm×20-60 mm.

Preferably, the size of the round rod is Φ(20-58) mm.

In an optional embodiment, the medium-temperature rolling includes placing the stainless steel raw material in a heating device for heating and heat preservation, and rolling it immediately after taking it out.

The use of medium-temperature rolling deformation can greatly improve the yield strength and tensile strength of duplex stainless steel, while ensuring that the duplex stainless steel has high impact toughness and corrosion resistance.

In some embodiments, the present invention controls the austenite content in the stainless steel raw material, and then under the combined action of medium-temperature rolling deformation, the deformation resistance of the stainless steel raw material is low, which can ensure that the material achieves good plastic deformation. After deformation, a fibrous structure with alternating ferrite phase and austenite phase is formed, which greatly refines the grain size of the steel, thereby ensuring that the product is strengthened and toughened, and significantly improving the comprehensive mechanical properties of the product.

Preferably, in order to facilitate preparation, the heating device may be a muffle furnace.

Since the rolling temperature of the present invention is relatively low, which is lower than the recrystallization temperature of the dual-phase steel, the dual-phase steel is deformed at this temperature, and the fibers formed under the dominant recovery effect are Texture can ensure that the material has high impact toughness and achieve a balance of strength and toughness for bolt steel.

Preferably, the rolling method is groove rolling.

Preferably, the steel product comprises high strength bolts.

The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

Example 1

The present embodiment provides a high-strength, corrosion-resistant and crack-resistant steel, which is made of duplex stainless steel. The duplex stainless steel is a round rod with a diameter of 35 mm and a length of 180 mm, wherein the contents of each component are C: 0.023%, Mn: 0.96%, Si: 0.51%, P: 0.0025%, S: 0.003%, Cr: 22.04%, Ni: 4.91%, Mo: 3.06%, N: 0.17%, and the balance is Fe and unavoidable impurities.

This embodiment also provides a method for preparing the above-mentioned high-strength corrosion-resistant and crack-resistant steel, and the specific steps are as follows:

(1) Place the duplex stainless steel in a muffle furnace at 600°C and keep it warm for 45 minutes.

(2) The duplex stainless steel bar is taken out of the furnace and immediately subjected to groove rolling. The sample is rotated 90° after each rolling pass.

(3) During the rolling process, each groove is rolled for 3 passes and then returned to the furnace (600°C) for 10 min. During the last two passes, the rolling direction remains consistent to ensure the straightness of the sample.

(4) After the ninth rolling pass, the material reduction amount is 80%, and the rolled sample is placed in the air for cooling, and finally a high-strength, corrosion-resistant and crack-resistant steel with a bionic fiber structure is prepared.

The high-strength corrosion-resistant and crack-resistant steel prepared in this embodiment was placed on a GeminiSEM 300 scanning electron microscope. Observation under a microscope yielded the result shown in Figure 1. As shown in Figure 1, after the medium-temperature pass rolling of the present invention, a bionic heterogeneous fiber structure is successfully constructed, and the ferrite phase and the austenite phase are alternately arranged in the grains.

Example 2

This embodiment provides a high-strength corrosion-resistant and crack-resistant steel, the stainless steel raw material is the same as that in Embodiment 1, and the preparation method is as follows:

(4) After the twelfth rolling, the reduction of the material is 85%, and the rolled sample is placed in the air for cooling, and finally a high-strength, corrosion-resistant and crack-resistant steel with a bionic fiber structure is prepared.

Example 3

(4) After the fifteenth rolling, the material reduction amount is 90%, and the rolled sample is placed in the air for cooling, and finally a high-strength, corrosion-resistant and crack-resistant steel with a bionic fiber structure is prepared.

Example 4

This embodiment provides a high-strength corrosion-resistant and crack-resistant steel, the stainless steel raw material is the same as that in Example 1, and the preparation method is as follows:

(1) Place the duplex stainless steel in a muffle furnace at 700°C and keep it warm for 45 minutes.

(3) During the rolling process, each groove is rolled for 3 passes and then returned to the furnace (700℃) for 15 min. When rolling to the last two passes, the rolling direction remains consistent to ensure the straightness of the sample.

Example 5

Example 6

The present embodiment provides a high-strength, corrosion-resistant and crack-resistant steel, which is made of duplex stainless steel, and the duplex stainless steel is a square rod of 40mm×40mm×180mm, wherein the content of each component is C: 0.01%, Mn: 0.55%, Si: 0.45%, P: 0.003%, S: 0.003%, Cr: 25.13%, Ni: 6.25%, Mo: 3.24%, N: 0.21%, and the balance is Fe and unavoidable impurities.

(1) Place the duplex stainless steel in a 500℃ muffle furnace and keep it warm for 1h.

(2) Take the duplex stainless steel rod out of the furnace and immediately perform pass rolling. Rotate the specimen 90°.

(3) During the rolling process, each groove is rolled for 3 passes and then returned to the furnace (500°C) for 10 min. During the last two passes, the rolling direction remains consistent to ensure the straightness of the sample.

(4) After the tenth rolling, the material reduction amount is 80%, and the rolled sample is placed in the air for cooling, and finally a high-strength, corrosion-resistant and crack-resistant steel with a bionic fiber structure is prepared.

Example 7

This embodiment provides a high-strength corrosion-resistant and crack-resistant steel, the stainless steel raw material is the same as that in embodiment 6, and the preparation method is as follows:

(1) Place the duplex stainless steel in a 580℃ muffle furnace and keep it warm for 1h.

(3) During the rolling process, after three passes of rolling for each groove, the sample was returned to the furnace (580°C) and kept warm for 10 min. During the last two passes of rolling, the rolling direction remained consistent to ensure the straightness of the sample.

(4) After the twelfth rolling, the reduction of the material is 87%, and the rolled sample is placed in the air for cooling, and finally a high-strength, corrosion-resistant and crack-resistant steel with a bionic fiber structure is prepared.

Comparative Example 1

This comparative example provides a high-strength corrosion-resistant and crack-resistant steel, which is made of 304 stainless steel, which is a round bar with a diameter of 35 mm and a length of 180 mm, wherein the contents of each component are C: 0.06%, Mn: 1.09%, Si: 0.52%, P: 0.003%, S: 0.003%, Cr: 17.32%, Ni: 9.45%, Mo: 0.26%, N: 0.05%, and the balance is Fe and unavoidable impurities. The preparation method is the same as that of Example 1.

Comparative Example 2

This comparative example provides a high-strength corrosion-resistant and crack-resistant steel, which is made of 304 stainless steel, which is a round bar with a diameter of 35 mm and a length of 180 mm, wherein the contents of each component are C: 0.06%, Mn: 1.09%, Si: 0.52%, P: 0.003%, S: 0.003%, Cr: 17.32%, Ni: 9.45%, Mo: 0.26%, N: 0.05%, and the balance is Fe and unavoidable impurities. Preparation method and examples 4Same.

Comparative Example 3

This comparative example provides a high-strength corrosion-resistant and crack-resistant steel, which is made of 42CrMo medium carbon steel, which is a round bar with a diameter of 35mm and a length of 180mm, wherein the contents of each component are C: 0.44%, Mn: 0.71%, Si: 0.25%, P: 0.003%, S: 0.003%, Cr: 1.02%, Ni: 0.04%, Mo: 0.2%, and the balance is Fe and unavoidable impurities. The preparation method is the same as that of Example 1.

Comparative Example 4

This comparative example provides a high-strength corrosion-resistant and crack-resistant steel, which is made of 42CrMo medium carbon steel, which is a round bar with a diameter of 35mm and a length of 180mm, wherein the contents of each component are C: 0.44%, Mn: 0.71%, Si: 0.25%, P: 0.003%, S: 0.003%, Cr: 1.02%, Ni: 0.04%, Mo: 0.2%, and the balance is Fe and unavoidable impurities. The preparation method is the same as that of Example 4.

Comparative Example 5

This comparative example provides a high-strength corrosion-resistant and crack-resistant steel, whose stainless steel raw material is the same as that in Example 1, and the preparation method is similar, with the only difference being that: Comparative Example 5 is a commercial hot-rolled steel bar that is not processed by the medium-temperature deformation method provided by the present invention, and the structure of Comparative Example 5 is an equiaxed ferrite phase and austenite phase, and there is no fibrous structure, and its scanning structure is shown in Figure 3.

Test Example 1

The high-strength corrosion-resistant and crack-resistant steels prepared in Examples 1 to 7 and Comparative Examples 1 to 5 were subjected to room temperature tensile tests, room temperature impact tests and corrosion resistance tests, and the results shown in Table 1 were obtained, wherein the change curve of tensile strength in the tensile test is shown in Figure 2.

The instruments used in the above tests are: an electro-hydraulic servo dynamic fatigue tester produced by Shanghai Lishi Scientific Instrument Co., Ltd., an oscillographic impact toughness tester produced by Jinan Wenteng Experimental Instrument Co., Ltd., and a Gamry Interface 1000 electrochemical workstation. The electrochemical test uses a traditional three-electrode system, with an Ag/AgCl reference electrode, a platinum auxiliary electrode, and an artificial corrosive medium. Industrial sea water.

Table 1 Properties of high strength corrosion resistant and crack resistant steel

As can be seen from Table 1, the high-strength corrosion-resistant and crack-resistant steel prepared by controlling the element composition and ratio in the embodiment of the present invention has significantly improved fracture resistance and corrosion resistance, which can not only meet its toughening requirements, but also improve its service performance. Comparative Examples 1 and 2 use 304 stainless steel as the material. Even if the same medium-temperature rolling method is used, it is impossible to obtain a material with good tensile strength and good corrosion resistance. Comparative Examples 3 and 4 use 42CrMo medium carbon steel, which has very poor corrosion resistance and can hardly meet the more complex outdoor service environment.

10 in FIG2 represents an embodiment, and 20 represents a comparative example. That is, 10-1 is embodiment 1, 10-2 is embodiment 2, 10-3 is embodiment 3, 10-4 is embodiment 4, 10-5 is embodiment 5, and 10-6 is Example 6, 10-7 is Example 7, 20-1 is Comparative Example 1, 20-2 is Comparative Example 2, 20-3 is Comparative Example 3, 20-4 is Comparative Example 4, and 20-5 is Comparative Example 5. It can be found from Figure 2 that the tensile strength of the embodiment of the present invention is significantly better than that of the comparative example.

The present invention provides a high-strength corrosion-resistant and crack-resistant steel and a preparation method and application thereof, which have at least the following advantages:

By controlling the element composition in the steel, especially the content ratio of C, N, and Si, the corrosion resistance of the material is improved, and the protective process such as galvanizing is omitted, which simplifies the production process and reduces the production cost. The grains in the material are arranged alternately by ferrite phase and austenite phase, and the shape of the grains is slender fiber, which is similar to the bionic fiber structure. This organization has excellent impact toughness and achieves the balance of strength and toughness of bolt steel. The bridging effect between the fiber structures makes the material fracture in the same way as bamboo and wood structure, which can significantly improve the fatigue fracture performance of bolt steel and thus increase the service life of the bolt.

The high-strength corrosion-resistant and crack-resistant steel provided by the present invention has excellent performance, and has the characteristics of high strength, corrosion resistance, high toughness, etc. A dual-phase ultrafine fiber grain structure can be prepared by a medium-temperature rolling method. The method has a simple process and does not require unnecessary heat treatment. It can avoid environmental pollution caused by quenching and quenching media, is energy-saving and environmentally friendly, and is suitable for industrial mass production.

The high-strength corrosion-resistant and crack-resistant steel provided by the present invention has significantly improved corrosion resistance and crack resistance compared to 42CrMo medium carbon steel; can significantly improve its mechanical strength compared to traditional austenitic and duplex stainless steels; and has lower cost compared to high-temperature alloys. The high-strength corrosion-resistant and crack-resistant steel provided by the present invention has a tensile strength of more than 1300MPa, an impact toughness of more than 120J, and corrosion resistance comparable to that of austenitic stainless steel.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

A high-strength corrosion-resistant and crack-resistant steel, characterized in that the composition of the crystal grains includes austenite and ferrite, and the shape of the crystal grains is slender fiber;

Measured by weight percentage, the element composition of the high-strength corrosion-resistant and crack-resistant steel includes C: 0.01-0.1%, Cr: 18-32%, Ni: 3-10%, Mo: 0.2-5.0%, Mn: 0.1-2.0%, Si: 0.2-1.0%, N: 0.1-0.3%, S≤0.03%, P≤0.03%, and the balance is Fe and unavoidable impurities.
The high-strength corrosion-resistant and crack-resistant steel according to claim 1 is characterized in that, by weight percentage, the element composition of the high-strength corrosion-resistant and crack-resistant steel includes C: 0.01-0.1%, Cr: 21-25%, Ni: 5-8%, Mo: 1-3%, Mn: 0.2-1.3%, Si: 0.3-0.9%, N: 0.1-0.3%, S≤0.03%, P≤0.03%, and the balance is Fe and unavoidable impurities.
The high-strength corrosion-resistant and crack-resistant steel according to claim 1, characterized in that the content of austenite is 30-60%;

Preferably, the diameter of the crystal grains is less than 20 μm, and the aspect ratio is 5-50.
A method for preparing high-strength corrosion-resistant and crack-resistant steel as described in any one of claims 1 to 3, characterized in that it includes preparing stainless steel raw materials according to elemental composition and performing medium-temperature rolling on the stainless steel raw materials.
The preparation method according to claim 4 is characterized in that the medium-temperature rolling includes placing the stainless steel raw material in a heating device for heating and insulation, and then taking it out for rolling.
The preparation method according to claim 5 is characterized in that the heating and insulation temperature is 500-700° C. and the insulation time is 45-60 min.
The preparation method according to claim 5 is characterized in that the rolling includes a furnace return and heat preservation after every 2 to 4 rolling passes;

Preferably, the furnace holding temperature is 500-700° C., and the holding time is 10-20 min.
The preparation method according to claim 5 or 7 is characterized in that the square of each rolling pass The rolling direction is perpendicular to the previous rolling direction, and the last two rolling directions are the same;

Preferably, the rolling method is groove rolling.
The preparation method according to claim 5 is characterized in that the stainless steel raw material is duplex stainless steel; the shape of the stainless steel raw material is a square bar or a round bar;

Preferably, the deformation amount of the stainless steel raw material is 78-98%;

Preferably, the size of the square rod is 20-60 mm×20-60 mm;

Preferably, the size of the round rod is Φ(20-58) mm.
An application of the high-strength corrosion-resistant and crack-resistant steel as claimed in any one of claims 1 to 3, or the high-strength corrosion-resistant and crack-resistant steel prepared by the preparation method as claimed in any one of claims 4 to 9 in the field of steel products;

Preferably, the steel product comprises a high-strength bolt;

Preferably, the high-strength bolts include any one of wind power connection shaft bolts and bolts for mechanical parts.