CN116445803A - Processing method for improving strength and plastic product of medium manganese steel plate - Google Patents
Processing method for improving strength and plastic product of medium manganese steel plate Download PDFInfo
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- 229910000617 Mangalloy Inorganic materials 0.000 title claims abstract description 51
- 238000003672 processing method Methods 0.000 title claims abstract description 14
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 20
- 239000010959 steel Substances 0.000 claims abstract description 20
- 238000005097 cold rolling Methods 0.000 claims abstract description 18
- 238000000137 annealing Methods 0.000 claims abstract description 14
- 238000005496 tempering Methods 0.000 claims abstract description 10
- 238000005242 forging Methods 0.000 claims abstract description 9
- 238000005098 hot rolling Methods 0.000 claims abstract description 5
- 238000010438 heat treatment Methods 0.000 claims description 25
- 238000005096 rolling process Methods 0.000 claims description 20
- 238000001816 cooling Methods 0.000 claims description 19
- 230000009467 reduction Effects 0.000 claims description 13
- 238000003723 Smelting Methods 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 6
- 239000000126 substance Substances 0.000 claims description 6
- 238000005266 casting Methods 0.000 claims description 4
- 239000002994 raw material Substances 0.000 claims description 4
- 238000012545 processing Methods 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 230000006872 improvement Effects 0.000 abstract description 2
- 238000009776 industrial production Methods 0.000 abstract description 2
- 241001417490 Sillaginidae Species 0.000 abstract 1
- 229910001566 austenite Inorganic materials 0.000 description 47
- 230000000052 comparative effect Effects 0.000 description 17
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 13
- 229910001567 cementite Inorganic materials 0.000 description 12
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 12
- 229910052748 manganese Inorganic materials 0.000 description 12
- 239000011572 manganese Substances 0.000 description 12
- 239000002245 particle Substances 0.000 description 9
- 230000009466 transformation Effects 0.000 description 9
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 8
- 229910052802 copper Inorganic materials 0.000 description 8
- 239000010949 copper Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 6
- 229910000734 martensite Inorganic materials 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 230000008569 process Effects 0.000 description 5
- 230000006911 nucleation Effects 0.000 description 4
- 238000010899 nucleation Methods 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000002068 genetic effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000004627 transmission electron microscopy Methods 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
-
- 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
-
- 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
- C21D1/32—Soft annealing, e.g. spheroidising
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- 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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- 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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
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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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
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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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- 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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
The invention discloses a processing method for improving the strength and plastic product of a medium manganese steel plate, and relates to the technical field of medium manganese steel plate processing. The invention adjusts the components of manganese steel, then smelts and pours into steel ingots, and sequentially performs forging, hot rolling, softening annealing, cold rolling, tempering and critical annealing treatment to obtain the medium manganese steel plate with high toughness. The invention improves the strength and the plastic product of the medium manganese steel plate on the whole effectively under the condition of little improvement of the production cost, and promotes the industrial production and the application of the medium manganese steel.
Description
Technical Field
The invention belongs to the technical field of medium manganese steel plate processing, and particularly relates to a processing method for improving the strength and plastic product of a medium manganese steel plate.
Background
With the environmental deterioration, the automobile conservation amount is increased, the energy conservation and emission reduction are widely focused in the world, and the automobile weight reduction becomes one of the important research and development directions of the automobile manufacturing industry. The light weight can be realized by applying advanced high-strength steel, high-strength steel hot/cold forming technology and the like.
The medium manganese steel (the mass fraction of manganese is between 3 and 12 percent) is the third-generation advanced automobile high-strength steel, and because of the excellent strength-plastic product (20 to 70GPa percent), the cold forming operation flow is possibly simplified, and the contribution is made to the light weight. After the manganese steel undergoes austenite reverse transformation through conventional annealing in cold rolling, the microstructure of the manganese steel is usually in an austenite and ferrite dual-phase structure, and in the deformation process, the residual austenite partially or completely undergoes transformation induced plasticity (TRIP) effect, and the TRIP effect can delay necking to greatly increase the elongation of the manganese steel, and the generated new-phase martensite improves the strength of the material, so that the mechanical property is optimized.
Currently, the stability of austenite is a major factor for ensuring the TRIP effect, wherein the stability is determined by coupling multiple factors such as manganese content in austenite, austenite grain size, austenite volume fraction and the like. In addition, on the one hand, to prevent the austenite from being too poor in stability, a large amount of martensite transformation occurs in the initial stage of plastic deformation, and the residual austenite content cannot ensure that the requirement of subsequent deformation leads to premature fracture. On the other hand, the austenite is prevented from being too stable, and the TRIP effect cannot be fully exerted.
In recent years, scholars at home and abroad perform isothermal tempering before austenite reverse transformation of medium manganese steel to introduce high manganese cementite particles, and the high manganese cementite particles can be used as additional austenite nucleation points. In the reverse transformation process of austenite nucleation growth, compared with austenite nucleation growth at the martensite boundary, the austenite with high manganese cementite nucleation has the excellent characteristics of high manganese content, small grain size, plastic deformation resistance and the like, but the additional isothermal tempering process phase transformation prolongs the heat treatment time, causes excessive formation and grain growth of the austenite, and conversely causes poor stability of the austenite to further deteriorate the mechanical properties of the austenite.
In addition, for the recent research conditions of the medium manganese steel plate, the strong plastic product of the medium manganese steel plate is relatively low, so how to optimize the processing technology of the medium manganese steel plate to further improve the strong plastic product of the medium manganese steel plate is a hot spot of the current research.
Disclosure of Invention
Based on the design concept of the medium manganese steel, the processing method is characterized in that the influence of a large amount of copper-rich particles and cementite double nano particles precipitated during tempering on the austenite reverse transformation of the medium manganese steel is utilized, and the processing technology is further adjusted, so that the medium manganese steel material with high toughness is prepared, and the strong plastic product of the medium manganese steel plate is obviously improved to meet the use indexes of different automobile parts.
The invention is realized by adopting the following technical scheme:
a processing method for improving the strength-plastic product of a medium manganese steel plate comprises the following steps:
step 1, smelting: smelting and casting raw materials to obtain a steel ingot; the steel ingot comprises the following main chemical components in percentage by mass:
c:0.15 to 0.18 percent, mn:10.0 to 10.32 percent of Al:1.9 to 2.1 percent, cu:1.8 to 2.2 percent of Fe and the balance of unavoidable impurities;
step 2, forging: heating the steel ingot to 1200 ℃, preserving heat for 2 hours, forging into a plate blank, and then air-cooling to room temperature;
step 3, hot rolling: heating the plate blank to 1200 ℃, preserving heat for 2 hours, then rolling, wherein the initial rolling temperature is 1200+/-50 ℃, the final rolling temperature is not lower than 900 ℃, rolling for 5-7 times to obtain a thin plate with the thickness of 4+/-0.5 mm, and then air-cooling to room temperature;
step 4, softening and annealing: heating the thin plate to 600 ℃, preserving heat for 30min, and then air-cooling to room temperature;
step 5, cold rolling: carrying out high reduction cold rolling treatment on the sheet subjected to softening annealing treatment at room temperature, and rolling for 5-7 times to obtain a cold-rolled sheet with the thickness of 1.2+/-0.2 mm;
step 6, tempering: heating the cold-rolled sheet to 450 ℃, preserving heat for 30min, and then cooling to room temperature by water;
step 7, critical annealing: and (3) rapidly heating the tempered cold-rolled sheet to 600 ℃, keeping the temperature for 30min at a heating rate of not less than 50 ℃/s, and then cooling the cold-rolled sheet to room temperature by water to obtain the high-toughness cold-rolled medium manganese steel sheet.
Preferably, the cross section of the slab in step 2 is 100mm×30mm.
Preferably, the finishing temperature in step 3 is 900-1000 ℃.
Preferably, the reduction of the high reduction cold rolling in the step 5 is 70%.
Preferably, the heating rate in step 7 is 50-70 ℃/s.
Compared with the prior art, the invention has the following beneficial effects:
on one hand, the invention combines the fixing effect of the copper-rich particles on phase boundaries and recrystallized grains to prevent the excessive formation and growth of austenite; on the other hand, the manganese-rich fine-grained austenite of the genetic cementite is fully reserved. Under the combined action of the two precipitated particles, the proper austenite grain size and austenite content are prepared, the proper stability of the austenite grain size and austenite content is ensured, the TRIP effect can be fully and harmoniously generated in the deformation process, and the excellent mechanical property is achieved. The processed medium manganese steel plate provided by the invention has the advantages that the austenite grain size and the austenite content are respectively 0.74 mu m and 49.3%, the manganese content in the manganese-rich fine-grained austenite of inherited cementite reaches 20wt.%, and the manganese content is obviously higher than the austenite manganese content (15 wt%) formed by the martensite boundary. The tensile strength of the manganese steel plate is 1250+/-15 MPa, the elongation is 45.1+/-2.9%, and the product of strength and elongation is 56.4+/-2.0 Pa%. Under the condition of little improvement of production cost, the strong plastic product of the medium manganese steel plate is effectively improved as a whole, and the industrial production and application of the medium manganese steel are promoted.
Drawings
FIG. 1 is a transmission electron microscope image of a cold-rolled sheet after tempering treatment in example 6;
FIG. 2 is a transmission electron microscope image (a) and a manganese element composition distribution diagram (b) of a manganese steel sheet in cold rolling of the example;
FIG. 3 is a scanning electron microscope image of a manganese steel sheet in cold rolling of the example and a manganese steel sheet prepared in comparative example;
FIG. 4 is an engineering stress-strain curve of a manganese steel sheet material in the cold rolling of the example and a manganese steel sheet material prepared in the comparative example;
fig. 5 is a graph showing the change in austenite content corresponding to the drawing process of the manganese steel sheet material in the cold rolling of the example and the manganese steel sheet material prepared in the comparative example.
Detailed Description
The invention will be further illustrated with reference to specific examples.
Examples
A processing method for improving the strength-plastic product of a medium manganese steel plate comprises the following specific steps:
step 1, smelting: smelting and casting raw materials to obtain a steel ingot; the steel ingot comprises the following main chemical components in percentage by mass:
c:0.15%, mn:10.32%, al:2.01%, cu:1.98% of Fe and the balance of unavoidable impurities;
step 2, forging: heating the steel ingot to 1200 ℃, preserving heat for 2 hours, forging into a slab with the cross section of 100mm multiplied by 30mm, and then air-cooling to room temperature;
step 3, hot rolling: heating the plate blank to 1200 ℃, preserving heat for 2 hours, then rolling, wherein the initial rolling temperature is 1200+/-50 ℃, the final rolling temperature is 900 ℃, and obtaining a thin plate with the thickness of 4+/-0.5 mm through 6 times of rolling, and then air cooling to room temperature;
step 4, softening and annealing: heating the thin plate to 600 ℃, preserving heat for 30min, and then air-cooling to room temperature;
step 5, cold rolling: carrying out large reduction cold rolling treatment (the reduction of the large reduction cold rolling is 70%) on the sheet subjected to the softening annealing treatment at room temperature, and carrying out 7-pass rolling to obtain a cold-rolled sheet with the thickness of 1.2+/-0.2 mm;
step 6, tempering: heating the cold-rolled sheet to 450 ℃, preserving heat for 30min, and then cooling to room temperature by water;
step 7, critical annealing: and (3) rapidly heating the tempered cold-rolled sheet to 600 ℃, keeping the temperature for 30min at a heating rate of 50 ℃/s, and then cooling the cold-rolled sheet to room temperature by water to obtain the high-toughness cold-rolled medium manganese steel sheet.
Performing transmission electron microscope observation (shown in figure 1) on the cold-rolled sheet subjected to tempering treatment in the step 6, performing morphology and density analysis on precipitated copper-rich particles and cementite, wherein two precipitated phases of relatively coarse cementite (-70 nm) and fine dispersed copper-rich particles (-10 nm) are mainly distributed in a tempered martensite matrix, and the number density of cementite (1.73X10) 13 m -2 ) Is significantly lower than the dispersed copper-rich particles (1.48 x 10 14 m -2 )，
FIG. 2 is a transmission electron microscopy morphology analysis and composition analysis of a prepared cold rolled medium manganese steel sheet, austenite (γ (θ)) nucleated with cementite having a higher manganese content (20.1 wt% vs.15.2 wt%) and finer size (-300 nmvs. -700 nm) than the austenite matrix (γ) directly nucleated with the martensite boundary.
Comparative example 1
The processing method of the medium manganese steel plate is characterized by only comprising the following main chemical components in the steel ingot in the step 1 according to the mass percentage according to the reference example:
c:0.18%, mn:10.25%, al:2.11%, the balance being Fe and unavoidable impurities.
Comparative example 2
A processing method of a medium manganese steel plate comprises the following specific steps:
step 1, smelting: smelting and casting raw materials to obtain a steel ingot; the steel ingot comprises the following main chemical components in percentage by mass:
c:0.15%, mn:10.32%, al:2.01%, cu:1.98% of Fe and the balance of unavoidable impurities;
step 2, forging: heating the steel ingot to 1200 ℃, preserving heat for 2 hours, forging into a slab with the cross section of 100mm multiplied by 30mm, and then air-cooling to room temperature;
step 3, hot rolling: heating the plate blank to 1200 ℃, preserving heat for 2 hours, then rolling, wherein the initial rolling temperature is 1200+/-50 ℃, the final rolling temperature is 900 ℃, and obtaining a thin plate with the thickness of 4+/-0.5 mm through 6 times of rolling, and then air cooling to room temperature;
step 4, softening and annealing: heating the thin plate to 600 ℃, preserving heat for 30min, and then air-cooling to room temperature;
step 5, cold rolling: carrying out large reduction cold rolling treatment (the reduction of the large reduction cold rolling is 70%) on the sheet subjected to the softening annealing treatment at room temperature, and carrying out 7-pass rolling to obtain a cold-rolled sheet with the thickness of 1.2+/-0.2 mm;
step 6, critical tempering: and heating the cold-rolled sheet to 600 ℃, preserving heat for 30min, and then cooling to room temperature by water to obtain the medium manganese steel plate.
Comparative example 3
The processing method of the medium manganese steel plate is characterized by referring to comparative example 2, wherein the difference is only that the mass percentage of main chemical components in the steel ingot in the step 1 is as follows:
c:0.18%, mn:10.25%, al:2.11%, the balance being Fe and unavoidable impurities.
Scanning electron microscope morphology observation was performed on the medium manganese steel plates prepared in examples and comparative examples 1 to 3. As shown in fig. 3, the microstructure in the sheet was found to be composed of equiaxed austenite grains + ferrite grains, and the austenite grain average size (0.74 μm) in the example was significantly smaller than that (1.12 μm) in comparative example 1, as shown in fig. 3.
The manganese steel sheets of examples and comparative examples 1 to 3 were subjected to the relevant mechanical property test, and the heat-treated steel sheets were processed into tensile test pieces according to GB/T228-2002 "tensile test method for metallic Material at room temperature", and stress strain curves are shown in FIG. 4. The medium manganese steel sheet of the example has a tensile strength of 1250MPa, and at such a high tensile strength, an elongation of 45.1% is maintained, and the comparative example 1 has a tensile strength of 1382MPa, but the plasticity is significantly reduced to 19.2%.
It can also be seen from Table 1 that the example has the most excellent strength-plastic bond and the product of strength and plastic reaches 56.4GPa% as compared with comparative example 1. XRD phase measurements were performed on the examples under deformation at each stage and comparative example 1 to analyze the austenite content and stability, the austenite content in comparative example 1 was too high to be 60%, the austenite content after tensile fracture was less than 5%, and the austenite transformation ratio was as high as 92%. While in the examples, the austenite content was-50%, the austenite content after the stretch-break was-15%, and the austenite transformation ratio was-70%, so that the austenite stability of comparative example 1 was significantly lower than that in the examples, as shown in fig. 5.
From this, compared with comparative example 1 containing no copper, the duplex precipitation of the copper-rich nanoparticles and cementite in the examples optimizes the austenite characteristics, successfully prepares austenite nucleated by cementite, refines the austenite grain size by the introduction of the copper-rich particles, prevents the excessive formation of austenite, and has both the austenite content and stability, thereby remarkably optimizing the strength-plastic product to meet the requirements of the use and future development of modern automobile steel.
TABLE 1 mechanical Property curves of inventive and comparative examples
It should be noted that the above-mentioned embodiments are only a few specific embodiments of the present invention, and it is obvious that the present invention is not limited to the above embodiments, but other modifications are possible. All modifications directly or indirectly derived from the disclosure of the present invention will be considered to be within the scope of the present invention.
Claims (5)
1. The processing method for improving the strength and plastic product of the medium manganese steel plate is characterized by comprising the following steps of:
step 1, smelting: smelting and casting raw materials to obtain a steel ingot; the steel ingot comprises the following main chemical components in percentage by mass:
c:0.15 to 0.18 percent, mn:10.0 to 10.32 percent of Al:1.9 to 2.1 percent, cu:1.8 to 2.2 percent of Fe and the balance of unavoidable impurities;
step 2, forging: heating the steel ingot to 1200 ℃, preserving heat for 2 hours, forging into a plate blank, and then air-cooling to room temperature;
step 3, hot rolling: heating the plate blank to 1200 ℃, preserving heat for 2 hours, then rolling, wherein the initial rolling temperature is 1200+/-50 ℃, the final rolling temperature is not lower than 900 ℃, rolling for 5-7 times to obtain a thin plate with the thickness of 4+/-0.5 mm, and then air-cooling to room temperature;
step 4, softening and annealing: heating the thin plate to 600 ℃, preserving heat for 30min, and then air-cooling to room temperature;
step 5, cold rolling: carrying out high reduction cold rolling treatment on the sheet subjected to softening annealing treatment at room temperature, and rolling for 5-7 times to obtain a cold-rolled sheet with the thickness of 1.2+/-0.2 mm;
step 6, tempering: heating the cold-rolled sheet to 450 ℃, preserving heat for 30min, and then cooling to room temperature by water;
step 7, critical annealing: and (3) rapidly heating the tempered cold-rolled sheet to 600 ℃, keeping the temperature for 30min at a heating rate of not less than 50 ℃ per second, and then cooling to room temperature by water.
2. The method for improving the strength and elongation of a medium manganese steel sheet according to claim 1, wherein the cross section of the slab in the step 2 is 100mm x 30mm.
3. The processing method for improving the strength and elongation of the medium manganese steel sheet according to claim 1, wherein the finishing temperature in the step 3 is 900-1000 ℃.
4. The processing method for improving the strength-plastic product of the medium manganese steel sheet according to claim 1, wherein the cold rolling reduction of the large reduction in the step 5 is 70%.
5. The processing method for improving the strength-plastic product of the medium manganese steel sheet according to claim 1, wherein the heating rate in the step 7 is 50 ℃/s to 70 ℃/s.
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