CN113088821A - Gradient grain structure high-strength and high-plasticity matching low alloy steel and preparation method thereof - Google Patents
Gradient grain structure high-strength and high-plasticity matching low alloy steel and preparation method thereof Download PDFInfo
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- CN113088821A CN113088821A CN202110361511.6A CN202110361511A CN113088821A CN 113088821 A CN113088821 A CN 113088821A CN 202110361511 A CN202110361511 A CN 202110361511A CN 113088821 A CN113088821 A CN 113088821A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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Abstract
The invention relates to a low alloy steel with a gradient grain structure and high strength and high plasticity, which comprises the following components in percentage by mass: 0.2 to 0.3, Si: 0.3 to 0.7, Mn: 1.5-1.9, P: 0.025, S: 0.025 and the balance of iron. The preparation process of the low alloy steel comprises the following steps: the method comprises the steps of preserving heat of a low-alloy steel bar-shaped test sample of raw materials at 700-800 ℃ for 1-2 hours according to mass percentage to obtain coarse-grain low-alloy steel. And secondly, carrying out torsional deformation treatment on the coarse-grained structure sample, wherein the torsional deformation rate is 60-120 degrees/min, and the deformation amount is controlled to be 180-1440 degrees. And carrying out annealing treatment on the low alloy steel sample, wherein the annealing temperature is 550-600 ℃, and the temperature is kept for 15-30 minutes and then the sample is cooled to room temperature by water. The invention utilizes the combination of room temperature torsional deformation and thermal annealing to regulate and control the performance and the tissue structure of the low alloy steel, and effectively improves the strength of the low alloy steel while maintaining the plasticity of the low alloy steel and the elongation at failure.
Description
Technical Field
The invention belongs to the technical field of alloy steel materials and preparation, and relates to a gradient grain structure high-strength and high-plasticity matching low alloy steel and a preparation method thereof.
Technical Field
The low alloy steel has the excellent characteristics of low cost, high plasticity, good welding performance, cutting performance and the like, and is applied to the engineering fields of bridges, vehicles, ships, buildings, pressure vessels, special equipment and the like. The yield strength of the low alloy steel materials widely used at present, such as Q345 and Y40Mn, is 345-600 MPa, and the elongation at failure is 20-30%. However, the lower strength limits the wide use of low alloy steels in high strength engineering applications. The traditional method for strengthening the low alloy steel, such as quenching treatment or alloying element doping, inevitably sacrifices the plasticity of the low alloy steel, and the safety and reliability of the low alloy steel cannot be ensured due to the excessively low plasticity. Therefore, a prerequisite for the widespread use of low alloy steels is to increase the strength while maintaining good plasticity.
The invention patent with publication number CN 107299302A discloses a method for improving metal gradient structure strength and plasticity matching degree, firstly, high-energy spraying surface nanocrystallization treatment is carried out on a metal plate with a clean surface, then, the plate subjected to the surface nanocrystallization treatment is rolled, the rolling reduction is controlled to be 12-30%, and finally, vacuum annealing is carried out for 30-60 min at 50-100 ℃. The steel shot blasting method can effectively solve the problems that in the prior blasting technology, after the metal plate is processed by adopting the high-carbon steel shot, the surface roughness is high, and the matching degree of the plate strength and the plasticity is low, but can not meet the requirements on the strength and the plasticity of high-strength low-alloy steel in the future.
Disclosure of Invention
The invention aims to provide the gradient grain structure high-strength and high-plasticity matching low alloy steel, which meets the requirements of the gradient grain structure high-strength and high-plasticity matching low alloy steel required by the development of vehicles, bridges, ships and the like. The invention also aims to provide a preparation method of the low alloy steel with the gradient grain structure and high matching strength and plasticity.
The technical scheme of the invention is as follows: the gradient grain structure high-strength and high-plasticity matching low alloy steel comprises the following components in percentage by mass: 0.2 to 0.3, Si: 0.3 to 0.7, Mn: 1.5-1.9, P: 0.025, S: 0.025 and the balance of iron. The low alloy steel is one in which the ferrite grain size is continuously reduced from the core to the surface of the rod-like sample in the radial direction, and has both high strength and high plasticity.
The preparation method of the low alloy steel with the gradient grain structure and high strength and plasticity matching comprises the following preparation processes:
the method comprises the following steps of: 0.2 to 0.3, Si: 0.3 to 0.7, Mn: 1.5-1.9, P: 0.025, S: and (3) preserving the heat of the 0.025 low alloy steel rod-shaped sample at the temperature of 700-800 ℃ for 1-2 hours to obtain the low alloy steel with the coarse-grained structure and uniform components.
And performing torsional deformation treatment on the coarse crystal structure sample obtained in the step by using a torsional testing machine, keeping the torsional deformation rate at 60-120 degrees/min, and controlling the deformation amount (torsional angle) at 180-1440 degrees.
And thirdly, placing the low alloy steel sample subjected to the room-temperature torsional deformation obtained in the step II into an annealing furnace for annealing treatment, wherein the annealing temperature is 550-600 ℃, and the temperature is kept for 15-30 minutes and then the sample is cooled to the room temperature by water.
The low alloy steel obtained by the invention is subjected to room temperature tensile property test in an Instron 5966 mechanical property test system, and the mechanical properties are as follows: the yield strength is 500-740 MPa, and the failure elongation is 17-22%. The mechanical property of the low alloy steel obtained by the traditional technology is that the yield strength is 345-600 MPa, and the elongation at failure is 20-30%.
The invention utilizes the combination of room temperature torsional deformation and thermal annealing to regulate and control the performance and the tissue structure of the low alloy steel to prepare the gradient grain structure high-strength and high-plasticity matched low alloy steel (without quenching treatment or doping). Compared with the low alloy steel with a single uniform structure obtained by the traditional thermal deformation technology, the low alloy steel with a gradient grain structure is prepared by combining room temperature torsional deformation and thermal annealing, the plasticity of the low alloy steel is kept, the equivalent failure elongation is kept, the strength of the low alloy steel is effectively improved by about 200MPa, and the requirements on the strength and the plasticity of the high-strength low alloy steel in the future can be met.
Drawings
FIG. 1 is an EBSD (electron back scattering) diagram of the gradient grain structure of the low alloy steel from the surface to the core;
FIG. 2 is a tensile engineering stress-strain curve of the low alloy steel of the present invention.
Detailed Description
The present invention will be described in detail with reference to the following examples and drawings. The scope of protection of the invention is not limited to the embodiments, and any modification made by those skilled in the art within the scope defined by the claims also falls within the scope of protection of the invention.
Example 1
The invention discloses a method for preparing low alloy steel with a grain structure matched with high strength and high plasticity, which comprises the following preparation processes:
the method comprises the following steps of: 0.2, Si: 0.5, Mn: 1.7, P: 0.025, S: 0.025 of the low alloy steel rod sample, and the low alloy steel with the coarse grain structure and the uniform components is obtained after 1 hour of heat preservation at the temperature of 700 ℃.
And performing torsional deformation treatment on the coarse crystal structure test sample obtained in the step by using a torsional testing machine, keeping the torsional deformation rate at 60 degrees/minute, and controlling the deformation amount (torsional angle) to reach 720 degrees.
And thirdly, placing the low alloy steel sample subjected to the room-temperature torsional deformation obtained in the step II into a muffle furnace for annealing treatment, wherein the annealing temperature is 600 ℃, and cooling the low alloy steel sample to room temperature after heat preservation for 15 minutes.
The structure of the cross section of the sample is observed by using an EBSD microscopic analysis technology, and a gradient grain structure EBSD image of the low alloy steel from the surface to the core is shown in figure 1. The average value of the ferrite grain size of the low alloy steel prepared by the method of the invention is continuously reduced from 10.2 mu m at the core part to 6.1 mu m at the surface of the gradient grain structure along the radial direction of the bar-shaped sample. Matching of high strength and high plasticity of gradient grain structure in Instron 5966 mechanical property test systemThe gold steel is subjected to room temperature tensile property test. The gauge length dimension of the tensile sample is phi 10mm multiplied by 70mm, the total length of the sample is 135mm, and the tensile strain rate is as follows: 5X 10-4s-1And measuring the length change of the gauge length of the sample by using a contact extensometer in the test process. The mechanical properties of the sample are as follows: the yield strength is 650MPa, and the elongation at failure is 18.8%.
Example 2
Another embodiment of the present invention is:
the method comprises the following steps of: 0.3, Si: 0.6, Mn: 1.6, P: 0.025, S: 0.025 of the low alloy steel rod sample, and the low alloy steel with the coarse grain structure and the uniform components is obtained after the heat preservation for 1 hour at the temperature of 750 ℃.
And secondly, performing torsional deformation treatment on the coarse crystal structure test sample obtained in the step by using a torsional testing machine, keeping the torsional deformation rate at 120 degrees/minute, and controlling the deformation amount (torsional angle) to 1440 degrees.
And thirdly, placing the low alloy steel sample subjected to the room-temperature torsional deformation obtained in the step II into a muffle furnace for annealing treatment, wherein the annealing temperature is 550 ℃, and cooling the low alloy steel sample to room temperature after heat preservation for 30 minutes.
The microstructure of the cross section of the sample is observed by an EBSD microscopic analysis technology, and the average value of the ferrite grain size of the low alloy steel prepared by the method of the invention is continuously reduced from 7.6 mu m at the center to 4.2 mu m at the surface along the radial direction of the bar-shaped sample. FIG. 2 is a graph showing the tensile engineering stress-strain curve of the low alloy steel of the present invention. And (3) testing the room-temperature tensile property of the gradient grain structure high-strength and high-plasticity matching low-alloy steel in an Instron 5966 mechanical property testing system. The gauge length dimension of the tensile sample is phi 10mm multiplied by 70mm, the total length of the sample is 135mm, and the tensile strain rate is as follows: 5X 10-4s-1And measuring the length change of the gauge length of the sample by using a contact extensometer in the test process. The mechanical properties of the sample are as follows: the yield strength is 736MPa, and the failure elongation is 17.0 percent.
Claims (4)
1. A low alloy steel with gradient grain structure and high strength and plasticity matching is characterized in that: the low alloy steel comprises the following components in percentage by mass: 0.2 to 0.3, Si: 0.3 to 0.7, Mn: 1.5-1.9, P: 0.025, S: 0.025 and the balance of iron.
2. The gradient grain structure high strength and high plasticity matched low alloy steel according to claim 1, characterized by: the low alloy steel is a low alloy steel with a gradient grain structure, wherein the grain size of ferrite is continuously reduced from the core part to the surface of a rod-shaped sample along the radial direction, and the low alloy steel has high strength and high plasticity.
3. A method for preparing the low alloy steel with the gradient grain structure and high strength and plasticity matching as claimed in claim 1, which is characterized by comprising the following steps: the preparation process comprises the following steps:
the method comprises the following steps of: 0.2 to 0.3, Si: 0.3 to 0.7, Mn: 1.5-1.9, P: 0.025, S: preserving the heat of a 0.025 low alloy steel rod-shaped sample at the temperature of 700-800 ℃ for 1-2 hours to obtain coarse-grained low alloy steel with uniform components;
carrying out torsional deformation treatment on the coarse crystal structure sample obtained in the step by using a torsional testing machine, keeping the torsional deformation rate at 60-120 degrees/min, and controlling the deformation amount (torsional angle) at 180-1440 degrees;
and thirdly, placing the low alloy steel sample subjected to the room-temperature torsional deformation obtained in the step II into an annealing furnace for annealing treatment, wherein the annealing temperature is 550-600 ℃, and the temperature is kept for 15-30 minutes and then the sample is cooled to the room temperature by water.
4. The method for preparing the gradient grain structure high-strength and high-plasticity matched low alloy steel according to claim 3, which is characterized by comprising the following steps of: the thermal annealing furnace is a muffle furnace, a resistance furnace or an electromagnetic oven.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114480808A (en) * | 2022-02-14 | 2022-05-13 | 河北工程大学 | Manganese steel in composite gradient structure and preparation method thereof |
| CN114480811A (en) * | 2022-02-14 | 2022-05-13 | 河北工程大学 | High-strength-ductility medium manganese steel with gradient structure and preparation method thereof |
| CN114749506A (en) * | 2022-03-23 | 2022-07-15 | 南京理工大学 | Gradient structure bar and preparation device and method thereof |
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Cited By (6)
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|---|---|---|---|---|
| CN114480808A (en) * | 2022-02-14 | 2022-05-13 | 河北工程大学 | Manganese steel in composite gradient structure and preparation method thereof |
| CN114480811A (en) * | 2022-02-14 | 2022-05-13 | 河北工程大学 | High-strength-ductility medium manganese steel with gradient structure and preparation method thereof |
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| CN114749506B (en) * | 2022-03-23 | 2024-02-13 | 南京理工大学 | Gradient structure bar and preparation device and method thereof |
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