WO2015135268A1

WO2015135268A1 - High-strength bolting steel and preparation method therefor

Info

Publication number: WO2015135268A1
Application number: PCT/CN2014/081896
Authority: WO
Inventors: 陈荣柱; 陈新; 赵深; 龚列谦; 林群; 陈建胜; 潘世奇; 陈植; 张晓敏; 陈显辉; 雷欢; 朱全军; 聂京凯; 肖伟民; 林琳; 李矗; 郑克; 李勇; 李武; 黄锐
Original assignee: 国家电网公司; 国网浙江省电力公司; 国网浙江省电力公司温州供电公司; 国网智能电网研究院
Priority date: 2014-03-13
Filing date: 2014-07-09
Publication date: 2015-09-17
Also published as: CA2941276A1; CA2941276C; CN103820712A

Abstract

A high-strength bolting steel and a preparation method therefor. The components of the steel are: 0.05 wt% to 0.5 wt% of rare earth elements, 0.35 wt% to 0.45 wt% of carbon, 1.2 wt% to 1.8 wt% of chromium, 0.17 wt% to 0.37 wt% of silicon, 0.4 wt% to 0.8wt % of molybdenum, 0.2 wt% to 0.4 wt% of vanadium, 0 to 0.005 wt% of niobium and the balance of ferrum. The preparation method comprises: hot forging for the bolting steel with the above components is carried out, then quenching and tempering are carried out.

Description

High-strength bolt steel and preparation method thereof

This application claims priority to Chinese Patent Application No. 201410091577.8, entitled "A High-Strength Bolt Steel and Its Preparation Method", filed on March 13, 2014, the entire contents of which is incorporated by reference. In this application.

Technical field

The invention relates to the field of metals, in particular to a high-strength bolt steel and a preparation method thereof. Background technique

In recent years, strong winds such as typhoons have frequently hit the southeastern coastal areas of China, causing massive damage to power transmission and transformation equipment, seriously affecting the safe operation of the power grid. Since the southeast coastal areas are economically developed areas in China, the power load is concentrated, and strong wind disasters often cause irreparable social damage and economic losses. The high-voltage power surge arrester in the substation is an important equipment for power system power supply. It has a low natural frequency, and some low-order natural frequencies are close to the main frequency range of strong pulsating wind such as typhoon. Under the action of strong pulsating wind, the device will undergo wind-induced vibration, which will cause stress concentration in different areas of the equipment. When this excitation causes the resonance of the device to occur, it may cause breakage and failure of the stress concentration region of the device.

The bolts of the lightning arrester equipment are generally placed in the stress concentration area to support, fix and connect. When wind-induced vibration induces stress concentration in the equipment, the bolt is usually deformed by tensile stress and bending stress. At the same time, due to the supporting action of the bolt, the deformation also causes the bending deformation of the upper porcelain column. The above series of deformations are liable to cause the entire device to fail in strong wind.

In recent years, it has been found through practice that the addition of rare earth elements to alloy steel can effectively improve the mechanical properties of alloy steels, and improve the performance indexes of materials to varying degrees. When the rare earth elements and alloy steel components are respectively made into appropriate components, Modulation, and blend optimization, may optimize material properties. Therefore, it is of great significance to carry out component optimization and performance improvement of bolt-and-gold steel for lightning arrester equipment in the field of wind arrester anti-wind. Summary of the invention

The technical problem solved by the present invention is to provide a bolt steel having high strength and plasticity and a preparation method thereof.

In view of this, the present application provides a high strength bolt steel, including: RE 0.05wt%~0.5wt%;

C 0.35wt%~0.45wt%;

Cr 1.2wt%~1.8wt%;

Si 0.17wt%~0.37wt%;

Mo 0.4wt%~0.8wt%;

V 0.2wt%~0.4wt%;

Nb 0~0.005wt%;

The balance of Fe;

The RE is one or two of La and Ce.

Preferably, the content of the RE is from 0.10% by weight to 0.48% by weight.

Preferably, the Mo content is from 0.48 wt% to 0.72 wt%.

Preferably, the Si content is from 0.20% by weight to 0.32% by weight.

Preferably, the content of the Nb is 0.002 wt% to 0.0048 wt%.

The application also provides a method for preparing high-strength bolt steel, comprising the following steps:

1) Casting steel ingots of the following composition: 0.05wt%~0.5wt% of rare earth elements,

0.35 wt% to 0.45 wt% of carbon, 1.2 wt% to 1.8 wt% of chromium, 0.17 wt% to 0.37 wt% of silicon, 0.4 wt% to 0.8 wt% of molybdenum, 0.2 wt% to 0.4 wt% of vanadium, 0~0.005wt% of lanthanum and balance iron; the rare earth element is one or two of lanthanum and cerium;

2) forging the bolt steel ingot, and annealing the forged bolt steel ingot; 3) quenching the bolt steel ingot obtained in step 2), tempering the quenched bolt steel to obtain high strength bolt steel.

Preferably, step 1) is specifically:

The raw materials of the following components are prepared: 0.05 wt% to 0.5 wt% of rare earth elements, 0.35 wt% to 0.45 wt% of carbon, 1.2 wt% to 1.8 wt% of chromium, 0.17 wt% to 0.37 wt% of silicon, 0.4 wt% ~0.8wt% molybdenum, 0.2wt%~0.4wt% vanadium, 0~0.005wt% bismuth and balance iron; the rare earth element is one or two of lanthanum and cerium;

According to the content of the above raw materials, carbon, chromium, silicon, molybdenum, vanadium, niobium and iron are smelted at 1500 ° C ~ 1600 ° C for 40 min ~ 45 min, and after 15 min ~ 25 min, the initial bolt ingot is obtained;

Re-melting the initial bolt ingot, adding one or both of niobium and tantalum, and then casting, Get the bolt ingot.

Preferably, the annealing temperature is 650 ° C ~ 700 ° C, and the annealing time is 2 ~ 3 h. Preferably, the quenching temperature is 800 ° C ~ 900 ° C, and the quenching holding time is lh ~ 2 h. Preferably, the tempering temperature is 500 ° C ~ 600 ° C, and the tempering holding time is lh ~ 2 h. The present application provides a high strength bolt steel comprising: 0.05 wt% to 0.5 wt% of rare earth elements,

0.35 wt% to 0.45 wt% of carbon, 1.2 wt% to 1.8 wt% of chromium, 0.17 wt% to 0.37 wt% of silicon, 0.4 wt% to 0.8 wt% of molybdenum, 0.2 wt% to 0.4 wt% of vanadium, 0~0.005wt% of bismuth and balance iron; bismuth or bismuth added to the bolt steel of the present application can effectively refine the grain structure of the bolt steel, reduce the hydrogen content in the steel and the diffusion and penetration of hydrogen, and reduce harmful elements in Segregation at the grain boundary to improve the strength of the steel; the added chromium element can effectively improve the oxidation and corrosion resistance of the material, improve the hardenability of the material to increase the strength; the addition of molybdenum can strengthen the grain boundary of the material and improve the material. Hardenability, tempering stability, and toughness of the material are improved. The bolt steel in the present application also adds elements such as carbon, vanadium, niobium and iron. The above metal elements interact with each other to make the bolt steel have The high strength and plasticity provide strong support, fixation and connection for the lightning protection equipment, effectively resisting the stress concentration and wind-induced deviation behavior of the arrester equipment under strong wind, and protecting the safe operation of the equipment.

The application also provides a method for preparing high strength bolt steel. In the process of preparing bolt steel, the present application first prepares a bolt steel ingot, and then forges the bolt steel ingot to fully break the crystal grain of the bolt steel ingot to prepare a fine and uniform grain; and the forged bolt The steel ingot is annealed to eliminate the stress generated during the forging process. Finally, the annealed bolt ingot is subjected to quenching treatment and tempering treatment, thereby obtaining martensite and partial austenite structure with fine grain and uniform hook, which is effective. Improve the strength and plasticity of the material. detailed description

The technical solutions in the embodiments of the present invention are described in detail below. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

The embodiment of the invention discloses a high strength bolt steel, comprising:

RE 0.05wt%~0.5wt%; c 0.35wt%~0.45wt%;

Cr 1.2wt%~1.8wt%;

Si 0.17wt%~0.37wt%;

Mo 0.4wt%~0.8wt%;

V 0.2wt%~0.4wt%;

Nb 0~0.005wt%;

The balance of Fe;

The RE is one or two of La and Ce.

Both lanthanum (La) and cerium (Ce) belong to rare earth elements. This application adds La, Ce or a mixture of La and Ce to the bolt steel. As an active element, it can effectively refine the grain structure of bolt steel and reduce hydrogen in steel. The content and the diffusion and diffusion of hydrogen reduce the segregation of hydrogen, sulfur and other harmful elements on the grain boundaries, and improve the strength, rigidity and plasticity of the steel. The content of La, Ce or La mixed with Ce in the present application is 0.05 wt% to 0.5 wt%. Within this range, the martensite and austenite structure in the steel are significantly increased, and the mechanical properties are optimized. When the content of La, Ce or La and Ce mixture is less than 0.05% by weight, the effect of the mixture may be limited due to the small content of the component, which affects the wind resistance of the material; when the content exceeds 0.5%, the material structure is Metal inclusions containing La, Ce or a mixture of La and Ce increase and increase, and the influence on material properties gradually fails to meet the wind resistance requirements of electric arresters. The content of the La, Ce or La and Ce mixture is preferably from 0.08 wt% to 0.5 wt%, more preferably from 0.10 wt% to 0.48 wt%, most preferably from 0.12 wt% to 0.40 wt%, most preferably 0.25 wt%. ~0.35wt%.

Carbon (C), as an additive element of the present application, can increase the strength, hardness and hardenability of the material. If

If the content of C is less than 0.35wt%, the bolt steel has better ductility and plasticity, but the strength, hardness and hardenability are limited. If the C content is more than 0.45wt%, the toughness and plasticity of the material are greatly reduced, and brittleness is likely to occur. It is broken, so the C content is preferably controlled to be 0.35 wt% to 0.45 wt%. The content of the C is preferably from 0.37 wt% to 0.42 wt%, more preferably from 0.35 wt% to 0.40 wt%.

The addition of chromium (Cr) element to the bolt steel can effectively improve the oxidation resistance and corrosion resistance of the material, and improve the hardenability of the material to increase the strength of the material. The content of Cr of less than 1.2% by weight is difficult to achieve the above effect, and the content of more than 1.8% by weight reduces the toughness of the material, so the content of Cr needs to be controlled to be 1.2 wt% to 1.8 wt%. The content of Cr is preferably from 1.3 wt% to 1.6 wt%, more preferably from 1.4 wt% to 1.55 wt%. Silicon (Si) element is a good deoxidizer for materials. Adding Si to bolt steel can improve the solid solution strength of bolt steel, which is beneficial to increase the tempering stability of the material. If the content of silicon is higher than 0.37 wt%, the plasticity of the material is lowered, and the content of less than 0.17 wt% lowers the effect of the deoxidizer and solid solution strengthening, and the content of the silicon is controlled to be 0.17 wt% to 0.37 wt%. The best effect. The content of the silicon is preferably from 0.20% by weight to 0.32% by weight, more preferably from 0.23% by weight to 0.30% by weight, most preferably from 0.25% by weight to 0.28% by weight.

Molybdenum (Mo) element has the effect of strengthening the grain boundary of the material, improving the hardenability of the material, enhancing the tempering stability, and improving the toughness of the material. If the content of molybdenum is less than 0.4% by weight, it is difficult to achieve the above effect; if the molybdenum content is higher than 0.8% by weight, the cost of the bolt steel is increased and the performance cannot be optimally economical, so the molybdenum content is controlled at 0.4 wt% to 0.8 wt. % can only play a good role in bolt steel. The content of the molybdenum is preferably 0.48 wt% to 0.72 wt%, more preferably 0.54 wt% to 0.68 wt%, and most preferably 0.60 wt% to 0.65 wt%.

Vanadium (V) element can effectively inhibit the diffusion of hydrogen, refine grains and improve the mechanical properties of materials. If the content of V is less than 0.2% by weight, it is difficult to exert the above effect; if it is higher than 0.4% by weight, its effect on the material structure no longer rises as the content increases, but adversely affects the mechanical properties of the material. Therefore, the vanadium content is preferably controlled to be 0.2 wt% to 0.4 wt%. The content of the vanadium is preferably from 0.25 wt% to 0.38 wt%, more preferably from 0.28 wt% to 0.35 wt%, most preferably from 0.30 wt% to 0.32 wt%.

Niobium (Nb) element can improve the toughness of the material and effectively refine the grain structure. It is a trace element inside the material. If the content is too high, the above effect will not be achieved, and the economy will be greatly reduced. Therefore, its composition should be controlled within the range of 0 to 0.005 wt%. The content of the ruthenium is preferably from 0.002% by weight to 0.0048% by weight, more preferably from 0.0035% by weight to 0.0040% by weight.

The high-strength bolt steel provided by the present application comprises: 0.05 wt% to 0.5 wt% of rare earth elements, 0.35 wt% to 0.45 wt% of carbon, 1.2 wt% to 1.8 wt% of chromium, and 0.17 wt% to 0.37 wt%. Silicon, 0.4wt%~0.8wt% molybdenum, 0.2wt%~0.4wt% vanadium, 0~0.005wt% niobium and balance iron; the rare earth element is one or two of lanthanum and cerium Kind. The active element lanthanum or cerium added to the bolt steel of the present application can effectively refine the grain structure of the bolt steel, reduce the hydrogen content in the steel and the diffusion and penetration of hydrogen, reduce the segregation of harmful elements on the grain boundary, and improve the strength of the steel. The added chromium element can effectively improve the anti-oxidation and anti-corrosion ability of the material, improve the hardenability of the material to increase the strength; the addition of molybdenum can strengthen the grain boundary of the material, improve the hardenability of the material, enhance the tempering stability, and improve The toughness of the material, the bolt steel in the application also adds elements such as carbon, vanadium, niobium and iron, and the above metal elements cooperate with each other through interaction. The bolt steel has high strength and plasticity.

The application also provides a preparation method of the above bolt steel, comprising the following steps:

2) forging the bolt steel ingot, and annealing the forged bolt steel ingot;

3) The bolt ingot obtained in the step 2) is subjected to quenching treatment, and the quenched bolt steel is tempered to obtain high-strength bolt steel.

In the process of preparing bolt steel, the present application first casts a bolt steel ingot, and then forges the prepared bolt steel ingot to fully break the internal structure of the bolt ingot, and the annealing treatment after forging is to eliminate the residual stress in the forging process. In order to obtain uniform and fine internal grains; finally, the annealed bolt steel is subjected to quenching treatment and tempering treatment to obtain martensite and partial austenite structure with small internal fine grains, thereby improving bolt steel. Strength and plasticity.

According to the present invention, in the process of preparing the bolt steel, the bolt steel ingot is first prepared. The present application adds a rare earth element lanthanum, cerium or a mixture of the two to the bolt steel. Since lanthanum and cerium are active components, during the casting process, Premature addition may cause loss of strontium and barium, so it is preferred in the present application to add the active ingredients strontium and strontium subsequently. As a preferred solution, the preparation process of the bolt steel ingot is specifically as follows:

The initial bolt ingot is remelted, and then a mixture of niobium, tantalum or both is added, and then cast to obtain a bolt ingot.

In the above process of preparing a bolt ingot, the smelting process is well known to those skilled in the art, preferably in a vacuum induction furnace.

After the preparation of the bolt ingot, the present application forges the bolt ingot to eliminate the casting process The structural defects generated in the middle, and the coarse grains of the bolt ingot are sufficiently broken by the forging process, and fine internal crystal grains can be obtained. The forging process is well known to those skilled in the art. The steel ingot is hot-rolled at 1150 °C to obtain a hot-rolled rod, and then forged in the range of 900 °C to 1030 °C, that is, hot-rolled rolling of the bolt on the flat forging machine to ensure the metal flow line along the part It is continuous and the fiber streamline is intact. The forged bolt steel is slowly cooled and then annealed, which can eliminate the residual stress during the forging process and prepare for the subsequent heat treatment. The annealing temperature is preferably 650 ° C to 700 ° C, and the annealing time of the annealing is preferably 2 to 3 h.

According to the present invention, after the bolt ingot is annealed, it is quenched, the quenching temperature is preferably 800 ° C ~ 900 ° C, the quenching holding time is preferably lh ~ 2h; finally after quenching The bolt steel ingot is subjected to tempering treatment, the temperature of the tempering treatment is preferably 500 ° C to 600 ° C, and the tempering time is preferably 1 to 2 h. After the bolt steel ingot described in the present application is subjected to quenching treatment and tempering treatment, an internal structure in which the crystal grains are all small is obtained. After the bolt steel is tempered, martensite and a part of austenite structure are obtained.

The application also provides a method for preparing high strength bolt steel. In the process of preparing bolt steel, the present application first prepares a bolt steel ingot, and then forges the bolt steel ingot to fully break the crystal grain of the bolt steel ingot to prepare a fine and uniform grain; and the forged bolt The steel ingot is annealed to eliminate the stress generated during the forging process. Finally, the annealed bolt ingot is subjected to quenching treatment and tempering treatment, thereby obtaining fine and uniform martensite and partial austenite structure, which is effectively improved. The strength and plasticity of the material.

The invention utilizes the element, element content and preparation method of the bolt steel to make the bolt material have high tensile strength and plasticity, thereby providing strong support, fixing and connection functions for the electric lightning arrester device, and effectively resisting the arrester device from occurring under strong wind. The equipment stress concentration and wind-induced offset behavior protect the safe operation of the equipment; the bolt steel material composition provided by the invention has less precious metal content, higher mechanical property and excellent cost performance. At the same time, the preparation process of the material is simple, the application is convenient, and it is convenient for large-scale promotion. The invention improves the strength and rigidity of the material, so that the natural frequency of the arrester device can be changed to some extent, the structure is prevented from resonating under the strong wind excitation, the vibration amplitude of the device structure is reduced, and the power supply of the lightning arrester device is powerful. Guarantee.

The high-strength bolt steel and the preparation method thereof provided by the present invention are described in detail below with reference to the embodiments, and the scope of protection of the present invention is not limited by the following examples. Example 1

The component weight percentage of the bolt steel of this embodiment is as follows: 0.12% Ce, 0.37% C, 1.2% Cr, 0.25% Si, 0.5% Mo, 0.3% V, 0.0048% Nb, and the rest is Fe. .

The preparation method of the bolt steel is specifically as follows: 1) compounding according to the above weight percentage; 2) melting at 1560 ° C for 40 min, holding for 25 min, sampling and casting, preparing alloy steel by using a vacuum induction furnace; 3) remelting the prepared alloy steel Adding Ce component and casting to form steel ingot; 4) hot rolling the steel ingot obtained at step 1) at 1150 ° C to obtain a hot rolled bar, forging at 900 ° C, and slowly cooling the forged steel ingot to Annealing at room temperature, annealing temperature is 650 ° C, holding time is 2 hours; 5) The material obtained in step 4) is quenched at 820 ° C, quenching time is lh, then tempered at 500 ° C, tempered After 60 min, air cooled to room temperature to obtain bolt steel. The performance of the bolt steel prepared in this example was tested. The test results are shown in Table 1.

Table 1 Performance data of bolt steel prepared in Example 1

Example 2

The component weight percentage of the bolt steel of this embodiment is as follows: 0.06% of La, 0.08% of Ce, 0.42%, 1.6% of Cr, 0.32% of Si, 0.72% of Mo, 0.28% of V, and 0.0045% of Nb, The remaining component is Fe.

The preparation method of the bolt steel is specifically as follows: 1) according to the above weight percentage; 2) using a vacuum induction furnace to smelt at 1540 ° C for 40 min, holding for 20 min, sampling and casting, preparing alloy steel; 3) remelting the prepared alloy steel, The Y component is added and cast to form a steel ingot; 4) the steel ingot obtained in the step 3) is hot-rolled at 1150 ° C to obtain a hot rolled bar, and then forged at 1030 ° C, and the forged steel ingot is slowly cooled to room temperature. Re-annealing, annealing temperature is 680 °C, holding time is 2.5 hours; 5) The material obtained in step 4) is quenched at 830 ° C, the holding time of quenching is 70 min, and then tempered at 520 ° C, back The fire time was 70 min, air cooled to room temperature, and bolt steel was obtained. The performance of the bolt steel prepared in this example was tested. The test results are shown in Table 2.

Table 2 Performance data of bolt steel prepared in this example Performance index Tensile strength (MPa) Elongation (%) Performance value 1260 12.7 Example 3

The component weight percentage of the bolt steel of this embodiment is as follows: 0.05% La, 0.35% C, 1.8% Cr, 0.17% Si, 0.40% Mo, 0.20% V, 0.005% Nb, and the remaining components are Fe. .

The preparation method of the bolt steel is specifically as follows: 1) according to the above weight percentage; 2) using a vacuum induction furnace to smelt at 1550 ° C for 45 min, holding for 25 min, sampling and casting, preparing alloy steel; 3) remelting the prepared alloy steel, Add Y component, cast to form steel ingot; 4) hot-roll the steel ingot at 1150 °C, obtain hot-rolled bar, forge at 1000 °C, slowly cool the forged steel ingot to room temperature and then anneal, annealing temperature At 700 ° C, the holding time is 3 hours; 5) The material obtained in step 4) is quenched at 800 ° C, the quenching time is, then tempered at 550 ° C, tempering time 80 min, air cooling to room temperature , get bolt steel. The performance of the bolt steel prepared in this example was tested. The test results are shown in Table 3.

Table 3 Performance data of bolt steel prepared in this example

Example 4

The component weight percentage of the bolt steel of this embodiment is as follows: 0.25% La, 0.25% Ce, 0.45% C, 1.4% Cr, 0.20% Si, 0.65% Mo, 0.4% V, 0.0012% Nb The rest of the ingredients are Fe.

The preparation method of the bolt steel is specifically as follows: 1) according to the above weight percentage; 2) using a vacuum induction furnace to smelt at 1540 ° C for 40 min, holding for 20 min, sampling and casting, preparing alloy steel; 3) remelting the prepared alloy steel, Add Y component, cast to form steel ingot; 4) hot-roll the steel ingot at 1150 °C, obtain hot-rolled bar, forge at 1030 °C, slowly cool the forged steel ingot to room temperature and then anneal, annealing temperature At 680 ° C, the holding time is 2.5 hours; 5) The material obtained in step 4) is quenched at 830 ° C, quenching time is, then tempered at 520 ° C, tempering time 70 min, air cooling to room temperature , get bolt steel. The performance of the bolt steel prepared in this example was tested. The test results are shown in Table 4.

Table 4 Performance data of bolt steel prepared in this example Performance index Tensile strength (MPa) Elongation (%) Performance value 1280 13.2 Example 5

The procedure for preparing the bolt steel in this embodiment is the same as that in the first embodiment, except that the component weight percentage of the bolt steel of the present embodiment is as follows: 0.15% La, 0.23% Ce, 0.39% C, 1.5% Cr, 0.28. % Si, 0.47% Mo, 0.38% V, 0.0014% Nb, and the remaining component is Fe. The performance of the bolt steel prepared in this example was tested. The test results are shown in Table 5.

Table 5 Performance data of bolt steel prepared in this example

Example 6

The procedure for preparing the bolt steel in this embodiment is the same as that in the first embodiment, except that the component weight percentage of the bolt steel of the present embodiment is as follows: 0.28% of Ce, 0.43% of C, 1.7% of Cr, 0.27% of Si, 0.77. % Mo, 0.33%^V, 0.0041% Nb, and the remaining component is Fe. The performance of the bolt steel prepared in this example was tested. The test results are shown in Table 6.

Table 6 Performance data of bolt steel prepared in this example

It is obvious to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the present embodiments are to be considered as illustrative and not restrictive, and the scope of the invention is defined by the appended claims All changes in the meaning and scope of equivalent elements are included in the present invention.

In addition, it should be understood that although the description is described in terms of embodiments, not every embodiment includes only one independent technical solution, and the description of the specification is merely for the sake of clarity, and those skilled in the art should regard the specification as a whole. The technical solutions in the respective embodiments may also be combined as appropriate to form other embodiments that can be understood by those skilled in the art.

-I-

Claims

Rights request

1. A high-strength bolt steel, including:

RE 0.05wt%~0.5wt%;

C 0.35wt%~0.45wt%;

Cr 1.2wt%~1.8wt%;

Si 0.17wt%~0.37wt%;

Mo 0.4wt%~0.8wt%;

V 0.2wt%~0.4wt%;

Nb 0~0.005wt%;

balance Fe;

The RE is one or both of La and Ce.

2. The high-strength bolt steel according to claim 1, characterized in that the content of RE is 0.10wt%~0.48wt%.

3. The high-strength bolt steel according to claim 1, characterized in that the content of Mo is 0.48wt%~0.72wt%.

4. The high-strength bolt steel according to claim 1, characterized in that the content of Si is 0.20wt%~0.32wt%.

5. The high-strength bolt steel according to claim 1, characterized in that the content of Nb is 0.002wt%~0.0048wt%.

6. A method for preparing high-strength bolt steel, which is characterized by including the following steps:

1) Cast bolt steel ingots with the following composition: 0.05wt%~0.5wt% rare earth elements, 0.35wt%~0.45wt% carbon, 1.2wt%~1.8wt% chromium, 0.17wt%~0.37wt% silicon, 0.4wt%~0.8wt% molybdenum, 0.2wt%~0.4wt% vanadium, 0~0.005wt% niobium and the balance iron; the rare earth element is one or both of lanthanum and cerium;

2) Forge the bolt steel ingot, and anneal the forged bolt steel ingot;

3) Quench the bolt steel ingot obtained in step 2), and temper the quenched bolt steel to obtain high-strength bolt steel.

7. The preparation method according to claim 6, characterized in that step 1) is specifically: Prepare raw materials with the following components: 0.05wt%~0.5wt% rare earth elements, 0.35wt%~0.45wt% carbon, 1.2wt%~1.8wt% chromium, 0.17wt%~0.37wt% silicon, 0.4wt% ~0.8wt% molybdenum, 0.2wt%~0.4wt% vanadium, 0~0.005wt% niobium and the balance iron; the rare earth element is one or both of lanthanum and cerium;

According to the content of the above raw materials, carbon, chromium, silicon, molybdenum, vanadium, niobium and iron are smelted at 1500°C~1600°C for 40min~45min, and the initial bolt steel ingot is obtained after holding for 15min~25min;

The initial bolt steel ingot is remelted, one or both of lanthanum and cerium are added, and then cast to obtain a bolt steel ingot.

8. The preparation method according to claim 6, characterized in that the annealing temperature is 650°C~700°C, and the annealing heat preservation time is 2~3h.

9. The preparation method according to claim 6, characterized in that the quenching temperature is 800°C~900°C, and the quenching holding time is 11! ~2h.

10. The preparation method according to claim 6, characterized in that the tempering temperature is 500°C~600°C, and the tempering holding time is 11! ~2h.