CN109913759B - Preparation method of manganese steel material in double-crystal structure - Google Patents
Preparation method of manganese steel material in double-crystal structure Download PDFInfo
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- CN109913759B CN109913759B CN201910260956.8A CN201910260956A CN109913759B CN 109913759 B CN109913759 B CN 109913759B CN 201910260956 A CN201910260956 A CN 201910260956A CN 109913759 B CN109913759 B CN 109913759B
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- 229910000617 Mangalloy Inorganic materials 0.000 title claims abstract description 64
- 239000000463 material Substances 0.000 title claims abstract description 23
- 239000013078 crystal Substances 0.000 title claims abstract description 14
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 54
- 239000010959 steel Substances 0.000 claims abstract description 54
- 238000000137 annealing Methods 0.000 claims abstract description 22
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 17
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 14
- 239000002344 surface layer Substances 0.000 claims abstract description 13
- 238000000227 grinding Methods 0.000 claims abstract description 11
- 239000010410 layer Substances 0.000 claims abstract description 6
- 230000009466 transformation Effects 0.000 claims abstract description 6
- 238000010791 quenching Methods 0.000 claims abstract description 5
- 230000000171 quenching effect Effects 0.000 claims abstract description 5
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 5
- 238000010438 heat treatment Methods 0.000 claims abstract description 4
- 238000001816 cooling Methods 0.000 claims description 30
- 238000012545 processing Methods 0.000 claims description 14
- 239000011572 manganese Substances 0.000 claims description 8
- 230000001186 cumulative effect Effects 0.000 claims description 5
- 239000012535 impurity Substances 0.000 claims description 5
- 238000004321 preservation Methods 0.000 claims description 5
- 239000010935 stainless steel Substances 0.000 claims description 5
- 229910001220 stainless steel Inorganic materials 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 5
- 239000011261 inert gas Substances 0.000 claims description 3
- 238000002347 injection Methods 0.000 claims description 3
- 239000007924 injection Substances 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 8
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
- 229910052748 manganese Inorganic materials 0.000 description 5
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 4
- 238000011160 research Methods 0.000 description 3
- 238000013461 design Methods 0.000 description 2
- 230000009977 dual effect Effects 0.000 description 2
- 229910000794 TRIP steel Inorganic materials 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
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Abstract
The invention discloses a preparation method of a manganese steel material in a double-crystal structure, which comprises the following steps: (1) heating the medium manganese steel cold-rolled sheet to a certain temperature to completely austenitize the medium manganese steel cold-rolled sheet, and then quenching the medium manganese steel cold-rolled sheet to room temperature to obtain a complete martensite structure; (2) carrying out surface mechanical grinding treatment on the quenched medium manganese steel cold-rolled sheet to form a strong plastic deformation layer with a certain thickness on the surface of the steel sheet; (3) and carrying out austenite reverse phase transformation annealing on the SMAT treated medium manganese steel plate to obtain the medium manganese steel with a double-grain structure. The double-grain structure obtained by the method of the invention means that a certain thickness of the surface layer of the steel plate is submicron isometric grains, including recrystallized ferrite grains and reverse phase transformed austenite grains; the core of the steel plate is a lath-shaped structure and comprises lath-shaped tempered martensite and lamellar reverse transformation austenite. The manganese steel plate in the double-grain structure can exert the mechanical property characteristics of two grain structure structures, namely, the continuous yield is kept and the yield strength is improved.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a preparation method of a manganese steel material in a double-grain structure.
Background
The manganese content of the medium manganese steel is generally 3-10 wt.%, and the content of metastable austenite in the structure is about 30-40 vol.%. Since the proportion of austenite is much higher than that of conventional TRIP steels, the mechanical properties of medium manganese steels are more dependent on the characteristics of metastable austenite and the occurrence of its TRIP effect. The earliest report on medium manganese steel can be traced back to 1972, and in order to verify whether the Hall-Petch relationship is applicable to an ultrafine grain structure, Miller firstly designs 0.11C-5.7Mn steel, and finds that the structure of the alloy after cold rolling and annealing is all submicron equiaxed grains, wherein the alloy contains about 30 vol.% of metastable austenite, and the tensile strength and the elongation after fracture respectively reach 878MPa and 34%. In the 21 st century, medium manganese steel has gradually become a research hotspot in academic circles at home and abroad, and is considered to be one of the most promising new steel types in the advanced high-strength steel for third-generation automobiles.
The excellent mechanical properties of medium manganese steels are attributed to the dual-phase combination of tempered martensite or ferrite + metastable austenite, and the dual-phase structure is obtained by virtue of the unique alloy composition design and heat treatment process. Because the medium manganese steel has very good hardenability due to the high manganese content, the isothermal quenching process for stabilizing austenite in the traditional TRIP steel production is not suitable for the medium manganese steel any more, and therefore the content of metastable austenite in the medium manganese steel and the stability thereof are only directly related to the critical zone annealing process. During the annealing process, C, Mn element diffuses from martensite or ferrite into austenite, increasing its thermal stability so that no martensitic transformation occurs when cooling to room temperature after annealing is complete. This annealing process of the medium manganese steel to stabilize the austenite is called Austenite Reversed Transformation (ART) annealing.
The final structure of the medium manganese steel is very sensitive to the initial structure before ART annealing, the direct ART annealing (referred to as CR sample for short) of the cold rolled steel plate can obtain complete submicron equiaxed grains, although the yield limit of the CR sample is high, an obvious yield platform, namely discontinuous yield phenomenon can occur in tensile deformation, and as a result, an L ü ders strip is remained on the surface of a workpiece, which is not allowed to occur in automobile stamping parts, the lath martensite structure shape of the quenched steel plate is still maintained after the ART annealing (referred to as AQ sample for short), but the yield strength is generally low, and the intrusion resistance of automobile components can be influenced.
According to the existing research foundation, the two grain structures are prepared in the thickness direction of the medium manganese steel plate by utilizing a gradient plastic deformation method, namely the medium manganese steel with a double-grain structure is constructed, and then different mechanical property characteristics of two tissue types can be exerted: not only the yield strength and the yield ratio are improved, but also the Luders strain is avoided, and the continuous yield characteristic is kept. How to construct a double-crystal structure on the basis of the existing processing technology of the medium manganese steel and the mechanical characteristics of the medium manganese steel material have important research values.
Disclosure of Invention
The invention aims to provide a preparation method of a manganese steel material in a double-grain structure, which is characterized in that a strong plastic deformation layer is formed on the surface layer of a manganese steel plate before ART annealing through surface mechanical treatment, so that submicron-scale equiaxial grains are formed on the surface layer in the ART treatment, and the core part still keeps a lath-shaped grain structure, thereby improving the yield strength of the manganese steel and keeping the continuous yield characteristic, and obtaining the manganese steel material with high-strength plastic combination. The specific technical scheme is as follows:
a preparation method of a manganese steel material in a double-crystal structure is characterized by comprising the following steps: the chemical components by weight percentage are as follows: 0.05-0.20% of C, 0.5-2.0% of Si, 3.0-9.0% of Mn, 0.1-3.0% of Al, less than or equal to 0.005% of P, less than or equal to 0.005% of S, less than or equal to 0.006% of N, and the balance of Fe and inevitable impurities;
the preparation steps are as follows:
(1) heating a medium manganese steel cold-rolled plate with the thickness of 1-2.5 mm to 850-950 ℃ for complete austenitizing, and then quenching to room temperature at the cooling speed of 20-50 ℃/s to obtain a complete martensite structure;
(2) performing surface mechanical grinding treatment (SMAT), namely, inducing resonance of a plurality of steel shots sealed in a container by using a vibration generator, so as to continuously impact a medium manganese steel quenching steel plate fixed in the container at high speed, wherein the surface layer of the steel plate is locally subjected to severe plastic deformation by each impact of the steel ball; the SMAT treatment adopts an AISI304 stainless steel ball with the diameter of 3-7 mm, and the vibration frequency is 10-30 kHz; setting the cumulative treatment time of the SMAT on the single surface of the steel plate to be 20-60 min; in order to avoid the warping of the steel plate caused by long-time single-side mechanical grinding, after the single-side processing time is designed to be 10min, the steel plate is turned over, the other surface is continuously processed, and the SMAT processing time of the two surfaces of the steel plate is ensured to be the same; the SMAT treatment aims to form a strong plastic deformation layer with a certain thickness on the surface of the steel plate;
(3) performing ART annealing on the SMAT treated medium manganese steel plate, wherein the annealing temperature is 600-700 ℃, the heat preservation time is 3-60 min, and then cooling to room temperature at a cooling speed of 10-50 ℃/s to obtain the medium manganese steel material with a double-crystal-grain structure.
The vessel containing the steel ball and sample is evacuated or filled with an inert gas prior to SMAT processing.
And (4) cooling to room temperature at a cooling speed of 10-50 ℃/s in the step (3) by adopting air cooling, air injection cooling or water cooling.
The manganese steel in the double-grain structure is characterized in that the surface layer of the steel plate with the grain size of 30-200 mu m is submicron isometric grains, the surface layer comprises recrystallized ferrite grains and reverse phase-change austenite grains, and the grain diameter is 300-500 nm; the core of the steel plate is of a lath-shaped structure and comprises lath-shaped tempered martensite and lamellar reverse transformation austenite, the thickness of the lath or the lamellar is 100-300 nm, and the length of the lath or the lamellar is 0.3-3 mu m.
According to the invention, SMAT treatment is carried out on the quenched medium manganese steel plate, so that strong plastic deformation is accumulated in a certain thickness range of the surface layer of the steel plate, the surface layer of the steel plate is recrystallized in the subsequent ART annealing process to form submicron equiaxial grains, and the deformation layer of the SMAT treatment is limited in a certain thickness range, so that the central layer part of the steel plate is not recrystallized, and the tissue morphology of a martensite lath is still maintained. Thus, the manganese steel plate in the double-crystal structure in the thickness direction is constructed, and the mechanical property characteristics of two tissue structures can be exerted, namely the continuous yield characteristic is maintained and the yield strength is improved.
Drawings
FIG. 1 is a microstructure of a manganese steel in a dual grain structure in example 1 of the present invention.
FIG. 2 is a tensile stress-strain curve of a manganese steel having a dual grain structure according to example 1 of the present invention.
Detailed Description
In the embodiment of the invention, the thickness of the cold-rolled medium manganese steel plate is 1.0-2.5 mm.
The size of the cold-rolled medium manganese steel plate in the embodiment of the invention is 100 multiplied by 50 mm.
The vibration generating equipment used in SMAT treatment in the embodiments of the present invention may be commercially available products such as the grinder of Zhaoqing Mei Ling environmental protection machinery science and technology Co.
In the embodiment of the invention, a CMT5105 stretcher is adopted for performance test.
In the embodiment of the invention, a Zeiss Ultra 55 scanning electron microscope is adopted for tissue detection.
Example 1
1. The medium manganese steel cold-rolled sheet is heated to 850 ℃ to be completely austenitized, and then quenched to room temperature at the cooling rate of 30 ℃/s to obtain a complete martensite structure.
2. And (3) carrying out surface mechanical grinding (SMAT) treatment on the quenched medium manganese steel cold-rolled sheet. And the SMAT treatment selects an AISI304 stainless steel ball with the diameter of 5mm, and the vibration frequency is 10 kHz. The cumulative treatment time of SMAT on one side of the steel plate was set to 30 min. In order to avoid the warping of the steel plate caused by long-time single-side mechanical grinding, the single-side processing time is designed to be 10min, then the steel plate is turned over, the other surface is continuously processed, and the SMAT processing time of the two surfaces of the steel plate is ensured to be the same.
3. Performing ART annealing on the SMAT treated medium manganese steel plate, wherein the annealing temperature is 650 ℃, the heat preservation time is 60min, and then cooling to room temperature at the cooling speed of 10 ℃/s to obtain the medium manganese steel material with a double-grain structure. The superficial submicron equiaxed grains were about 92 μm thick and had an average grain diameter of about 410nm, as shown in fig. 1. The yield strength of the material is 902MPa, the tensile strength is 1079MPa, the elongation is 36.8 percent, and the product of strength and elongation is 39.7GPa percent, as shown in figure 2.
The chemical components of the medium manganese steel cold-rolled sheet in the step 1 of the embodiment are as follows by weight percent: the alloy contains 0.12% of C, 0.50% of Si, 6.1% of Mn, 0.1% of Al, 0.005% of P, 0.005% of S, 0.006% of N, and the balance of Fe and inevitable impurities.
In this example, the container containing the steel ball and the sample in step 2 is evacuated before SMAT treatment.
In this embodiment, the cooling rate of 10 ℃/s in step 3 can be air-cooled.
Example 2
1. The medium manganese steel cold-rolled sheet is heated to 900 ℃ to be completely austenitized, and then is quenched to room temperature at the cooling speed of 50 ℃/s, so that a complete martensite structure is obtained.
2. And (3) carrying out surface mechanical grinding (SMAT) treatment on the quenched medium manganese steel cold-rolled sheet. And AISI304 stainless steel balls with the diameter of 3mm are selected for SMAT treatment, and the vibration frequency is 30 kHz. The cumulative treatment time for SMAT on one side of the steel sheet was set to 60 min. In order to avoid the warping of the steel plate caused by long-time single-side mechanical grinding, the single-side processing time is designed to be 10min, then the steel plate is turned over, the other surface is continuously processed, and the SMAT processing time of the two surfaces of the steel plate is ensured to be the same.
3. Performing ART annealing on the SMAT treated medium manganese steel plate, wherein the annealing temperature is 700 ℃, the heat preservation time is 3min, and then cooling to room temperature at the cooling speed of 30 ℃/s to obtain the medium manganese steel material with a double-grain structure. The surface layer has submicron equiaxed crystal thickness of about 200 μm and average crystal diameter of about 300 nm. The yield strength of the material is 1037MPa, the tensile strength is 1153MPa, the elongation is 26.9 percent, and the product of strength and elongation is 31.0GPa percent.
The chemical components of the medium manganese steel cold-rolled sheet in the embodiment are as follows by weight percent: the alloy contains 0.05% of C, 0.5% of Si, 9.0% of Mn9, 3.0% of Al, 0.004% of P, 0.005% of S, 0.003% of N and the balance of Fe and inevitable impurities.
The container holding the steel ball and sample in step 2 of this example was filled with an inert gas prior to SMAT processing.
In the embodiment, the cooling speed of 30 ℃/s in the step 3 can be cooled to room temperature by adopting air injection.
Example 3
1. The medium manganese steel cold-rolled sheet is heated to 950 ℃ to be completely austenitized, and then is quenched to room temperature at the cooling speed of 20 ℃/s, so that a complete martensite structure is obtained.
2. And (3) carrying out surface mechanical grinding (SMAT) treatment on the quenched medium manganese steel cold-rolled sheet. And AISI304 stainless steel balls with the diameter of 7mm are selected for SMAT treatment, and the vibration frequency is 20 kHz. The cumulative treatment time for SMAT on one side of the steel sheet was set to 20 min. In order to avoid the warping of the steel plate caused by long-time single-side mechanical grinding, the single-side processing time is designed to be 10min, then the steel plate is turned over, the other surface is continuously processed, and the SMAT processing time of the two surfaces of the steel plate is ensured to be the same.
3. Performing ART annealing on the SMAT treated medium manganese steel plate, wherein the annealing temperature is 600 ℃, the heat preservation time is 30min, and then cooling to room temperature at a cooling speed of 50 ℃/s to obtain the medium manganese steel material with a double-grain structure. The surface layer has submicron equiaxed crystal thickness of about 30 μm and average crystal diameter of about 500 nm. The yield strength of the material is 820MPa, the tensile strength is 952MPa, the elongation is 26.3 percent, and the product of strength and elongation is 25.0GPa percent.
The chemical components of the medium manganese steel cold-rolled sheet in the embodiment are as follows by weight percent: the alloy contains 0.2% of C, 2.0% of Si, 3.0% of Mn3, 1.0% of Al, 0.005% of P, 0.002% of S, 0.003% of N, and the balance of Fe and inevitable impurities.
In this example, the container containing the steel ball and the sample in step 2 is evacuated before SMAT treatment.
In this embodiment, the cooling rate of 50 ℃/s in step 3 can be water cooling.
Claims (4)
1. A preparation method of a manganese steel material in a double-crystal structure is characterized by comprising the following steps: the chemical components by weight percentage are as follows: 0.05-0.20% of C, 0.5-2.0% of Si, 3.0-9.0% of Mn, 0.1-3.0% of Al, less than or equal to 0.005% of P, less than or equal to 0.005% of S, less than or equal to 0.006% of N, and the balance of Fe and inevitable impurities;
the preparation steps are as follows:
(1) heating a medium manganese steel cold-rolled plate with the thickness of 1-2.5 mm to 850-950 ℃ for complete austenitizing, and then quenching to room temperature at the cooling speed of 20-50 ℃/s to obtain a complete martensite structure;
(2) performing surface mechanical grinding (SMAT) treatment on the quenched medium manganese steel cold-rolled sheet, namely, causing resonance of a plurality of steel shots sealed in a container by using a vibration generator so as to continuously impact the medium manganese steel quenched steel sheet fixed in the container at a high speed, wherein the surface layer of the steel sheet is locally subjected to severe plastic deformation by each impact of the steel balls; the SMAT treatment adopts an AISI304 stainless steel ball with the diameter of 3-7 mm, and the vibration frequency is 10-30 kHz; setting the cumulative treatment time of the SMAT on the single surface of the steel plate to be 20-60 min; in order to avoid the warping of the steel plate caused by long-time single-side mechanical grinding, after the single-side processing time is designed to be 10min, the steel plate is turned over, the other surface is continuously processed, and the SMAT processing time of the two surfaces of the steel plate is ensured to be the same; the SMAT treatment aims to form a strong plastic deformation layer with a certain thickness on the surface of the steel plate;
(3) performing ART annealing on the SMAT treated medium manganese steel plate, wherein the annealing temperature is 600-700 ℃, the heat preservation time is 3-60 min, and then cooling to room temperature at a cooling speed of 10-50 ℃/s to obtain the medium manganese steel material with a double-crystal-grain structure.
2. The preparation method of the manganese steel material in the double-crystal grain structure as claimed in claim 1, wherein the steel material is prepared by the following steps: the vessel containing the steel ball and sample is evacuated or filled with an inert gas prior to SMAT processing.
3. The preparation method of the manganese steel material in the double-crystal grain structure as claimed in claim 1, wherein the steel material is prepared by the following steps: and (4) cooling to room temperature at a cooling speed of 10-50 ℃/s in the step (3) by adopting air cooling, air injection cooling or water cooling.
4. The preparation method of the manganese steel material in the double-crystal grain structure as claimed in claim 1, wherein the steel material is prepared by the following steps: the manganese steel in the double-grain structure is characterized in that the surface layer of the steel plate with the grain size of 30-200 mu m is submicron isometric grains, the surface layer comprises recrystallized ferrite grains and reverse phase-change austenite grains, and the grain diameter is 300-500 nm; the core of the steel plate is of a lath-shaped structure and comprises lath-shaped tempered martensite and lamellar reverse transformation austenite, the thickness of the lath or the lamellar is 100-300 nm, and the length of the lath or the lamellar is 0.3-3 mu m.
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| US8409367B2 (en) * | 2008-10-29 | 2013-04-02 | The Hong Kong Polytechnic University | Method of making a nanostructured austenitic steel sheet |
| CN105861933B (en) * | 2016-05-31 | 2017-10-17 | 东北大学 | The middle manganese TRIP steel plates and its warm-rolling preparation method of a kind of nanometer/ultra-fine |
| CN108179256A (en) * | 2018-02-06 | 2018-06-19 | 东北大学 | A kind of heat treatment method for improving Cold-Rolled TRIP Steel strength and ductility product |
| CN109457087B (en) * | 2018-12-26 | 2021-05-25 | 太原理工大学 | Process method for preparing intermetallic compound coating on metal surface |
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