CN115323275A

CN115323275A - High-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel and preparation method thereof

Info

Publication number: CN115323275A
Application number: CN202211076322.5A
Authority: CN
Inventors: 申勇峰; 尹婷玮; 贾楠; 薛文颖
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2022-09-05
Filing date: 2022-09-05
Publication date: 2022-11-11
Anticipated expiration: 2042-09-05
Also published as: CN115323275B

Abstract

A high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel and a preparation method thereof belong to the technical field of high-strength steel, and cast ingots containing rare earth elements and having uniform components are obtained by utilizing the traditional vacuum induction melting technology; and then, by combining the control of the rolling process and bainite isothermal treatment, the grain size and the phase change behavior of the TRIP steel are regulated and controlled by controlling the comprehensive factors such as the content of the added rare earth, the rolling temperature, the rolling deformation, the annealing temperature, the annealing time, the bainitization temperature and time, and the like, so that the low-carbon and low-manganese TRIP steel obtains excellent comprehensive mechanical properties and good matching of strength and ductility and toughness, and the optimal rare earth addition content range of the TRIP steel is determined. Moreover, the rare earth warm-rolled low-carbon low-manganese TRIP steel has relatively low content of alloy elements, simple process, greatly saved production cost and satisfied the requirement of light weight of automobiles.

Description

High-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel and preparation method thereof

Technical Field

The invention belongs to the technical field of high-strength steel, and particularly relates to high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel and a preparation method thereof.

Background

With the rapid growth of global economy, the prosperous development of the automobile industry is promoted. However, along with the development of automobiles, various problems such as energy consumption, environmental protection, safety and the like are generated. In recent years, in response to the development demand of the automobile industry, the concept of automobile light weight is developed, that is, on the basis of ensuring the mechanical performance and safety of automobiles, energy conservation, emission reduction, weight reduction, cost reduction and the like are realized, and the concept becomes the impetus for developing novel automobile steel in the future. The steel material is a basic material in the automobile manufacturing industry, and the high-strength steel is the most economical and considerable material for realizing the light weight of the automobile at present.

In the face of increasingly severe competition in the material industry, the steel industry is continuously developed and advanced, and the strength grade of advanced high-strength steel is continuously improved. Under the strong impact of environmental and energy problems and the concept of light weight of automobiles, many countries are beginning to take the lead, and it is becoming a great trend to further improve the performance of high-strength steel by focusing on the improvement of production technical routes. However, the automobile light weight requirement is met, and some mechanical property loss is brought. Therefore, it is necessary to develop a new method for complementing. The rare earth is called as the mother material of a new material, can improve the performance of traditional materials such as steel, aluminum and the like, and plays a role in pointing stone to form gold. The method has great significance for developing the resource advantages of the rare earth elements in the emergency situation of the automobile steel with more excellent development performance and the national rare earth strategy.

The addition of trace rare earth elements into steel can form nonmetallic inclusions with O, S elements in the steel, and the nonmetallic inclusions are used as dispersoids for pinning grain boundaries and can improve mechanical properties by refining grains. Further, the rare earth atoms have a large radius, which causes large lattice distortion, thereby exhibiting a solid-solution strengthening effect. The use of a warm rolling process, i.e. deformation in the critical zone, increases the carbon content of the retained austenite, refines the austenite grains, increases the dislocation density and produces retained austenite in more free grains and less interlaminar acicular structure to increase the stability of the retained austenite. And carrying out bainite isothermal heat treatment to generate partial bainite, and further optimizing the structure and mechanical properties of the TRIP steel with low carbon and low manganese components. By adopting strengthening means such as solid solution strengthening, fine grain strengthening and the like and treatment methods such as improving a rolling process, a heat treatment system and the like, excellent structure and mechanical properties of the automobile steel plate material can be effectively realized.

Disclosure of Invention

The invention aims to provide a high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel material and a preparation method thereof. On the premise of meeting the requirement of light weight, the contents of carbon and manganese elements are reduced, the strengthening toughening such as solid solution strengthening, fine grain strengthening and the like brought by rare earth elements is fully exerted through reasonable component design and process control, and bainite phases with certain volume fractions are obtained by adding the effects of grain refining, retained austenite stability improvement and the like brought by a warm rolling process and bainite isothermal treatment, so that the prepared low-carbon low-manganese TRIP steel has good matching of high strength and high ductility and toughness.

A high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel comprises the following chemical components in percentage by weight: 0.18 to 0.21 percent of C, 1.69 to 1.83 percent of Mn, 0.23 to 0.41 percent of Si, 1.44 to 1.65 percent of Al, 0.02 to 0.04 percent of Mo, less than or equal to 0.01 percent of Cu, less than or equal to 0.01 percent of Ni, less than or equal to 0.01 percent of Ti, less than or equal to 0.01 percent of N, 0.03 to 0.5 percent of Ce, and the balance of Fe element and inevitable impurities;

the microstructure of the high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel consists of ferrite, bainite and residual austenite, and the volume fractions of the phases are 36 +/-1%, 45 +/-1% and 20 +/-1% in sequence; the yield strength of the steel is 558 +/-50 MPa, the tensile strength is 820 +/-60 MPa, and the elongation is 46 +/-4% under the room temperature condition.

The preparation method of the high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel comprises the following steps of:

step 1: weighing raw materials according to chemical components and weight percentages of the components of the high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel, smelting, and casting to obtain a cast ingot;

step 2: heating the cast ingot to 1200 +/-20 ℃, preserving the heat for 2-4 h, carrying out homogenization treatment, starting rolling at the initial temperature of 1200 +/-20 ℃, controlling the final rolling temperature to be 850 +/-50 ℃, and air-cooling the obtained hot rolled plate to room temperature;

and step 3: carrying out warm rolling treatment on the hot rolled plate; the warm rolling process comprises the following steps: firstly, preserving heat for 30min at 750 +/-20 ℃, then rolling, and air cooling a warm-rolled steel plate to room temperature;

and 4, step 4: carrying out bainite isothermal treatment on the warm-rolled steel plate; the specific process comprises the following steps: firstly, preserving heat for 120s at 800 +/-50 ℃, then quickly quenching to 400 +/-20 ℃, preserving heat for 300s, and finally air-cooling to room temperature.

In the step 2, 7-pass rolling is carried out at the initial temperature of 1200 +/-20 ℃, and the total deformation is 92.5%.

In the step 3, rolling is carried out for 8 times to 1.5mm, and the reduction of each time is 10-20%. And (4) keeping the temperature of the steel plate at 750 +/-20 ℃ for 5min between passes so as to perform next rolling.

The key points of the invention are as follows:

1. by adding trace rare earth elements, impurity elements such as O, S and the like are adsorbed, non-metal oxygen and sulfide pinning crystal boundaries such as CeS and the like are formed, the crystal boundary migration is hindered, recrystallization is inhibited, and the effect of fine grain strengthening is achieved; promotes the precipitation of micro cementite, increases the dislocation density, and simultaneously improves the strength and the plasticity of the rare earth low-carbon low-manganese TRIP steel on the premise of not increasing the working procedures.

2. Through a hot rolling and warm rolling process, the austenite grain size of the low-carbon low-manganese TRIP steel is controlled, the dislocation density is increased, the carbon content in the retained austenite is increased, the stability of the retained austenite is improved, and the strength of the TRIP steel is promoted while the original good plasticity is maintained.

3. The rare earth warm-rolled low-carbon low-manganese TRIP steel has relatively low content of alloy elements and simple process flow; the trace rare earth elements are proved to play a remarkable strong plasticity improving effect, the excessive rare earth addition adversely affects, and meanwhile, the optimal rare earth addition range of the TRIP steel is determined.

The invention has the following effects:

the invention has the advantages that the high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel material and the preparation method thereof are provided. Obtaining an ingot containing rare earth elements and having uniform components by using a traditional vacuum induction melting technology; and then, by combining the control of the rolling process and bainite isothermal treatment, the grain size and the phase change behavior of the TRIP steel are regulated and controlled by controlling the comprehensive factors such as the content of the added rare earth, the rolling temperature, the rolling deformation, the annealing temperature, the annealing time, the bainitization temperature and time, and the like, so that the low-carbon and low-manganese TRIP steel obtains excellent comprehensive mechanical properties and good matching of strength and ductility and toughness, and the optimal rare earth addition content range of the TRIP steel is determined. Moreover, the rare earth warm-rolled low-carbon low-manganese TRIP steel has relatively low content of alloy elements and simple process, greatly saves the production cost and meets the requirement of light weight of automobiles.

Drawings

FIG. 1 is a microstructure of TRIP steel having high strength and high toughness prepared in comparative examples 1 to 2 and examples 1 to 2;

FIG. 2 is a graph showing uniaxial tensile engineering stress-strain curves of high-strength and high-toughness TRIP steels obtained in comparative examples 1 to 2 and examples 1 to 2 at room temperature.

Detailed Description

The smelting equipment adopted in the embodiment of the invention is a vacuum induction furnace.

The hot rolling equipment adopted in the embodiment of the invention is

Double-roller one-way asynchronous rolling mill.

The heat preservation equipment adopted in the embodiment of the invention is an SX-8-13 type box type resistance furnace.

The metal raw materials adopted in the embodiment of the invention are all analytical grade, and the weight purities of C powder, si powder, metal Fe, metal Mn, metal Al, metal Mo, metal Cu, metal Ni, metal Ti and rare earth Ce are all more than or equal to 99.9%.

Comparative example 1

The high-strength high-toughness warm-rolled TRIP steel comprises the following chemical components in percentage by weight: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N and the balance of Fe element and inevitable impurities, wherein the grain size of the alloy is 2.1 mu m, and the structure at room temperature is ferrite, bainite and residual austenite; the tensile strength is 865MPa, the yield strength is 466MPa, and the elongation is 38%.

The preparation method of the high-strength and high-toughness warm-rolled TRIP steel comprises the following specific steps:

step 1: c powder, si powder, metal Fe, metal Mn, metal Al, metal Mo, metal Cu, metal Ni and metal Ti are mixed according to the weight percentage: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N and the balance of Fe, wherein the total amount is 100%, the components are placed in a smelting furnace, smelted under the condition of argon gas and cast into an ingot, and the ingot is cogging into a rectangular billet with the cross section of 80mm multiplied by 80mm and the height of 100 mm;

step 2: heating the cast ingot to 1200 ℃, preserving heat for 4 hours, carrying out homogenization treatment, rolling the cast ingot to 6mm by 7 passes by taking 1200 ℃ as an initial temperature, wherein the total deformation is 92.5%, the final rolling temperature is 860 ℃, and finally placing the steel plate in air to cool to room temperature;

and step 3: and (3) further carrying out warm rolling treatment on the hot rolled plate, preserving heat for 30min at 750 ℃, and then rolling the hot rolled plate to 1.5mm in 8 passes, wherein the reduction of each pass is within 10-20%. Wherein, the temperature of the film is kept for 5min at 750 ℃ between passes. After rolling is finished, the steel plate is cooled to room temperature by air;

and 4, step 4: and carrying out bainite isothermal treatment on the warm rolled steel plate. Firstly, preserving heat for 120s at 820 ℃, then rapidly quenching to 400 ℃, preserving heat for 300s, and finally air-cooling to room temperature to obtain the warm-rolled TRIP steel with high strength and high toughness, wherein the grain size is 2.1 mu m, and the structure at room temperature is ferrite, bainite and residual austenite; the tensile strength is 865MPa, the yield strength is 466MPa, and the elongation is 38%. The microstructure morphology is shown in FIG. 1 (a), and the engineering stress-strain curve for uniaxial stretching at room temperature is shown in FIG. 2 (curve 1).

Comparative example 2

The high-strength high-toughness rare earth cold-rolled TRIP steel comprises the following chemical components in percentage by weight: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N, 0.05% of Ce, and the balance of Fe and inevitable impurities, wherein the grain size is 1.9 mu m, and the structure at room temperature is ferrite, bainite and retained austenite; the tensile strength is 736MPa, the yield strength is 527MPa, and the elongation is 48%.

The preparation method of the high-strength high-toughness rare earth cold-rolled TRIP steel comprises the following specific operations:

step 1: c powder, si powder, metal Fe, metal Mn, metal Al, metal Mo, metal Cu, metal Ni, metal Ti and rare earth Ce are mixed according to the weight percentage: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N, 0.05% of Ce and the balance of Fe, wherein the total amount is 100%, the components are placed in a smelting furnace, smelted under the condition of argon gas and cast into an ingot, and the ingot is cogging into a rectangular billet with the cross section of 80mm multiplied by 80mm and the height of 100 mm;

step 2: heating the cast ingot to 1200 ℃, preserving heat for 4 hours, carrying out homogenization treatment, rolling the cast ingot to 6mm by 7 passes by taking 1200 ℃ as an initial temperature, setting the total deformation to 92.5%, setting the final rolling temperature to 860 ℃, and finally placing the steel plate in the air to cool to the room temperature;

and 3, step 3: and (4) carrying out cold rolling treatment on the hot rolled plate. Rolling to 1.5mm at room temperature for 8 passes, wherein the reduction of each pass is within 10-20%;

and 4, step 4: and carrying out bainite isothermal treatment on the cold-rolled steel plate. Firstly, preserving heat for 120s at 820 ℃, then quickly quenching to 400 ℃, preserving heat for 300s, and finally air-cooling to room temperature to obtain the rare earth cold-rolled TRIP steel with high strength and high toughness, wherein the grain size is 1.9 mu m, and the structure at room temperature is ferrite, bainite and retained austenite; the tensile strength is 736MPa, the yield strength is 527MPa, and the elongation is 48%. The microstructure morphology is shown in FIG. 1 (b), and the engineering stress-strain curve for uniaxial stretching at room temperature is shown in FIG. 2 (curve 2).

Example 1

A high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel comprises the following chemical components in percentage by weight: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N, 0.05% of Ce, and the balance of Fe element and inevitable impurities, wherein the grain size is 1.6 mu m, and the structure at room temperature is ferrite, bainite and retained austenite; the tensile strength is 817MPa, the yield strength is 558MPa, and the elongation is 46%.

The high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel is prepared by the following specific operations:

and step 3: and (3) further carrying out warm rolling treatment on the hot rolled plate, preserving heat for 30min at 750 ℃, and then rolling the hot rolled plate to 1.5mm in 8 passes, wherein the reduction of each pass is within 10-20%. Wherein, the temperature of the film is kept for 5min at 750 ℃ between passes. After rolling is finished, the steel plate is cooled to room temperature in air;

and 4, step 4: and carrying out bainite isothermal treatment on the warm rolled steel plate. Firstly, preserving heat for 120s at 820 ℃, then rapidly quenching to 400 ℃, preserving heat for 300s, and finally air-cooling to room temperature to obtain the high-strength high-toughness rare earth warm-rolled TRIP steel, wherein the grain size is 1.6 mu m, and the structure at room temperature is ferrite, bainite and residual austenite; the tensile strength is 817MPa, the yield strength is 558MPa, and the elongation is 46%. The microstructure morphology is shown in FIG. 1 (c), and the engineering stress-strain curve for uniaxial stretching at room temperature is shown in FIG. 2 (curve 3).

From the results of comparative example 1 and example 1, it is clear that the addition of 0.05% of rare earth Ce refined the grain size from 2.1 μm to 1.6 μm, the yield strength increased from 466MPa to 558MPa, and the elongation increased from 38% to 46% as compared with the TRIP steel not containing rare earth.

From the results of comparative example 2 and example 1, it is clear that compared with the rare earth-containing cold-rolled TRIP steel, the grain size is further refined from 1.9 μm to 1.6 μm by the warm rolling process, the tensile strength is increased from 736MPa to 817MPa, the yield strength is increased from 527MPa to 558MPa, and the elongation is not obviously changed.

Example 2

A high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel comprises the following chemical components in percentage by weight: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N, 0.5% of Ce, and the balance of Fe and inevitable impurities, wherein the grain size is 3.5 mu m, and the structure at room temperature is ferrite, bainite and retained austenite; the tensile strength is 675MPa, the yield strength is 438MPa, and the elongation is 36%.

The preparation method of the high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel comprises the following specific operations:

step 1: c powder, si powder, metal Fe, metal Mn, metal Al, metal Mo, metal Cu, metal Ni, metal Ti and rare earth Ce are mixed according to the following weight percentage: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N, 0.5% of Ce and the balance of Fe, wherein the total amount is 100%, the components are placed in a smelting furnace, smelted under the condition of argon gas and cast into an ingot, and the ingot is cogging into a rectangular billet with the cross section of 80mm multiplied by 80mm and the height of 100 mm;

and 4, step 4: and carrying out bainite isothermal treatment on the warm rolled steel plate. Firstly, preserving heat for 120s at 820 ℃, then quickly quenching to 400 ℃, preserving heat for 300s, and finally air-cooling to room temperature to obtain the rare earth warm-rolled TRIP steel with high strength and high toughness, wherein the grain size is 3.5 mu m, and the structure at room temperature is ferrite, bainite and retained austenite; the tensile strength is 675MPa, the yield strength is 438MPa, and the elongation is 36%. The microstructure morphology is shown in FIG. 1 (d), and the engineering stress-strain curve for uniaxial stretching at room temperature is shown in FIG. 2 (curve 4).

Compared with the warm-rolled TRIP steel added with 0.05 percent of rare earth Ce, the addition of 0.5 percent of rare earth Ce does not refine the grain size, but coarsens the grain size to 3.5 mu m; the tensile strength is reduced from 817MPa to 675MPa, the yield strength is reduced from 558MPa to 438MPa, and the elongation is reduced from 46% to 36%. Therefore, the addition amount of the rare earth element Ce is controlled to be 0.03-0.06 percent of Ce.

Example 3

A high-strength high-toughness rare earth cold-rolled low-carbon low-manganese TRIP steel comprises the following chemical components in percentage by weight: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N, 0.5% of Ce, and the balance of Fe and inevitable impurities, wherein the grain size is 2.2 mu m, and the structure at room temperature is ferrite, bainite and retained austenite; the tensile strength is 632MPa, the yield strength is 463MPa, and the elongation is 40%.

step 1: c powder, si powder, metal Fe, metal Mn, metal Al, metal Mo, metal Cu, metal Ni, metal Ti and rare earth Ce are mixed according to the weight percentage: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N, 0.5% of Ce and the balance of Fe, wherein the total amount is 100%, the components are placed in a smelting furnace, smelted under the condition of argon gas and cast into an ingot, and the ingot is cogging into a rectangular billet with the cross section of 80mm multiplied by 80mm and the height of 100 mm;

and step 3: and carrying out cold rolling treatment on the hot rolled plate. Rolling to 1.5mm at room temperature for 8 passes, wherein the reduction of each pass is within 10-20%;

and 4, step 4: and carrying out bainite isothermal treatment on the cold-rolled steel plate. Firstly, preserving heat for 120s at 820 ℃, then quickly quenching to 400 ℃, preserving heat for 300s, and finally air-cooling to room temperature to obtain the rare earth cold-rolled TRIP steel with high strength and high toughness, wherein the grain size is 2.2 mu m, and the structure at room temperature is ferrite, bainite and retained austenite; the tensile strength is 632MPa, the yield strength is 463MPa, and the elongation is 40%.

Example 4

A high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel comprises the following chemical components in percentage by weight: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N, 0.05% of Ce and the balance of Fe element and inevitable impurities, wherein the structure at room temperature is ferrite, bainite and retained austenite; the tensile strength is 760MPa, the yield strength is 564MPa, and the elongation is 42%.

and step 3: and (3) further carrying out warm rolling treatment on the hot rolled plate, keeping the temperature at 750 ℃ for 30min, and then rolling the hot rolled plate to 1.5mm in 8 passes, wherein the reduction of each pass is within 10-20%. Wherein, the temperature of the film is kept for 5min at 750 ℃ between passes. After rolling is finished, the steel plate is cooled to room temperature in air;

and 4, step 4: and carrying out bainite isothermal treatment on the warm rolled steel plate. Firstly, preserving heat for 120s at 750 ℃, then quickly quenching to 400 ℃, preserving heat for 300s, and finally air-cooling to room temperature to obtain the rare earth warm-rolled TRIP steel with high strength and high toughness, wherein the structure at room temperature is ferrite, bainite and retained austenite; the tensile strength is 760MPa, the yield strength is 564MPa, and the elongation is 42%.

Example 5

A high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel comprises the following chemical components in percentage by weight: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N, 0.05% of Ce and the balance of Fe element and inevitable impurities, wherein the structure at room temperature is ferrite, bainite and retained austenite; the tensile strength is 797MPa, the yield strength is 555MPa, and the elongation is 43%.

The high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel is specifically operated as follows:

and 3, step 3: and (3) further carrying out warm rolling treatment on the hot rolled plate, preserving heat for 30min at 750 ℃, and then rolling the hot rolled plate to 1.5mm in 8 passes, wherein the reduction of each pass is within 10-20%. Wherein, the temperature of the film is kept for 5min at 750 ℃ between passes. After rolling is finished, the steel plate is cooled to room temperature in air;

and 4, step 4: and carrying out bainite isothermal treatment on the warm rolled steel plate. Firstly, preserving heat for 120s at 800 ℃, then rapidly quenching to 400 ℃, preserving heat for 300s, and finally air-cooling to room temperature to obtain the high-strength high-toughness rare earth warm-rolled TRIP steel, wherein the structure at room temperature is ferrite, bainite and residual austenite; the tensile strength is 797MPa, the yield strength is 555MPa, and the elongation is 43%.

Example 6

A high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel comprises the following chemical components in percentage by weight: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N, 0.05% of Ce and the balance of Fe element and inevitable impurities, wherein the structure at room temperature is ferrite, bainite and retained austenite; the tensile strength is 815MPa, the yield strength is 508MPa, and the elongation is 45%.

and 3, step 3: and (3) further carrying out warm rolling treatment on the hot rolled plate, preserving heat for 30min at 750 ℃, and then rolling the hot rolled plate to 1.5mm in 8 passes, wherein the reduction of each pass is within 10-20%. Wherein, the temperature of the film is required to be kept for 5min at 750 ℃ between passes. After rolling is finished, the steel plate is cooled to room temperature in air;

and 4, step 4: and carrying out bainite isothermal treatment on the warm rolled steel plate. Firstly, preserving heat for 120s at 850 ℃, then rapidly quenching to 400 ℃, preserving heat for 300s, and finally air-cooling to room temperature to obtain the high-strength high-toughness rare earth warm-rolled TRIP steel, wherein the structure at room temperature is ferrite, bainite and residual austenite; the tensile strength is 815MPa, the yield strength is 508MPa, and the elongation is 45%.

Claims

1. The high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel is characterized by comprising the following chemical components in percentage by weight: 0.18 to 0.21 percent of C, 1.69 to 1.83 percent of Mn, 0.23 to 0.41 percent of Si, 1.44 to 1.65 percent of Al, 0.02 to 0.04 percent of Mo, less than or equal to 0.01 percent of Cu, less than or equal to 0.01 percent of Ni, less than or equal to 0.01 percent of Ti, less than or equal to 0.01 percent of N, 0.03 to 0.5 percent of Ce, and the balance of Fe element and inevitable impurities.

2. The high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel as claimed in claim 1, wherein the microstructure comprises ferrite, bainite and retained austenite, and the volume fractions of the phases are 36 ± 1%, 45 ± 1% and 20 ± 1% in sequence; the yield strength of the alloy at room temperature is 558 +/-50 MPa, the tensile strength is 820 +/-60 MPa, and the elongation is 46 +/-4%.

3. The high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel as claimed in claim 1, wherein the chemical composition in weight percent is: 0.19% of C, 1.76% of Mn, 0.29% of Si, 1.52% of Al, 0.03% of Mo, 0.007% of Cu, 0.007% of Ni, 0.002% of Ti, 0.003% of N, 0.05% of Ce, and the balance of Fe and inevitable impurities.

4. A method for preparing the high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel as claimed in claim 1 or 2, which is characterized by comprising the following steps:

and 4, step 4: and carrying out bainite isothermal treatment on the warm rolled steel plate.

5. The method for preparing the high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel as claimed in claim 4, wherein in the step 2, 7-pass rolling is performed at the initial temperature of 1200 +/-20 ℃, and the total deformation is 92.5%.

6. The method for preparing the high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel as claimed in claim 4, wherein in the step 3, 8 passes of rolling are performed to 1.5mm, the reduction of each pass is 10-20%, and the steel plate is kept warm for 5min at 750 +/-20 ℃ between passes.

7. The method for preparing the high-strength high-toughness rare earth warm-rolled low-carbon low-manganese TRIP steel according to claim 4, wherein in the step 4, the specific process is as follows: firstly, preserving heat for 120s at 800 +/-50 ℃, then quickly quenching to 400 +/-20 ℃, preserving heat for 300s, and finally air-cooling to room temperature.