CN114990306A - Mechanical property homogenization treatment process for variable-thickness cold-rolled steel plate - Google Patents
Mechanical property homogenization treatment process for variable-thickness cold-rolled steel plate Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 47
- 230000008569 process Effects 0.000 title claims abstract description 40
- 239000010960 cold rolled steel Substances 0.000 title claims abstract description 23
- 238000000265 homogenisation Methods 0.000 title claims abstract description 6
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 75
- 239000010959 steel Substances 0.000 claims abstract description 75
- 238000000137 annealing Methods 0.000 claims abstract description 50
- 238000001816 cooling Methods 0.000 claims abstract description 38
- 238000010438 heat treatment Methods 0.000 claims abstract description 22
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 20
- 239000000956 alloy Substances 0.000 claims abstract description 20
- 239000002994 raw material Substances 0.000 claims abstract description 20
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 12
- 238000005096 rolling process Methods 0.000 claims abstract description 11
- 229910001562 pearlite Inorganic materials 0.000 claims abstract description 10
- 238000009826 distribution Methods 0.000 claims abstract description 4
- 229910001566 austenite Inorganic materials 0.000 claims description 17
- 239000002436 steel type Substances 0.000 claims description 5
- 229910001209 Low-carbon steel Inorganic materials 0.000 claims description 3
- 238000012545 processing Methods 0.000 claims description 3
- 238000001953 recrystallisation Methods 0.000 description 21
- 239000000047 product Substances 0.000 description 15
- 230000009467 reduction Effects 0.000 description 10
- 239000013078 crystal Substances 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 9
- 238000004321 preservation Methods 0.000 description 8
- 238000010586 diagram Methods 0.000 description 4
- 238000011084 recovery Methods 0.000 description 4
- 230000007704 transition Effects 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 2
- 229910001563 bainite Inorganic materials 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 229910000760 Hardened steel Inorganic materials 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
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- 230000003068 static effect Effects 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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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
- 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
- C21D8/02—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
- 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
- C21D2211/005—Ferrite
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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
- C21D2211/009—Pearlite
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- 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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- Crystallography & Structural Chemistry (AREA)
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- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Abstract
The application discloses mechanical property homogenization treatment process of variable-thickness cold-rolled steel sheet, which comprises the following steps in sequence: s1, selecting the thickness of the raw material according to the required thickness distribution of the finished product, and ensuring that the thickness of the raw material is higher than that of the thickest area of the finished product; s2, rolling the equal-thickness steel coil raw material into variable-thickness steel according to the size requirement of the variable-thickness finished product; s3, calculating to obtain an austenitizing temperature interval corresponding to the low-alloy high-strength steel; s4, calculating to obtain a CCT curve corresponding to the low-alloy high-strength steel, determining the cooling speed in which range to cool, cooling the steel plate from the austenitizing temperature to ferrite + pearlite, and determining the cooling parameters of a cooling area according to the cooling speed range; s5 referring to the annealing process obtained in the steps S3 and S4, the variable thickness steel coil rolled in the step S2 is sent into a continuous annealing furnace for heat treatment, and the variable thickness cold rolled steel plate with high dimensional precision and uniform mechanical property is obtained. The invention ensures that the mechanical property and uniformity after annealing meet the requirements of terminal customers.
Description
Technical Field
The application relates to a metallurgical technology, in particular to a mechanical property homogenization treatment process of a variable-thickness cold-rolled steel sheet.
Background
The variable thickness cold rolled steel sheet is also called a rolled differential thickness sheet (or a rolled non-differential thickness steel sheet) at present, and the thickness thereof is continuously changed along the length direction, and the variable thickness cold rolled steel sheet is generally obtained by periodically changing the thickness of an equal thickness steel coil through a specially designed variable thickness rolling mill. In the prior art, a differential thickness plate production patent provides a periodic rolling method for producing variable-thickness plates, the method can realize variable-thickness plates with the limiting thickness ratio of 1:2 through single-pass rolling, and the production efficiency is high. The Bao steel is put out of the straight pull type rolling mill to be rolled in variable thickness, so that a single variable-thickness plate is obtained.
The rolled steel plate with variable thickness is in a rolling hard state, which cannot meet the requirements of the subsequent cold stamping process, and in order to adjust the mechanical properties of the rolled steel plate with variable thickness to meet the requirements of customers, the steel plate needs to be annealed. Annealing treatment leaves annealing stove, and present coil of strip annealing stove has two kinds: a hood-type annealing furnace and a continuous annealing furnace. (1) The heating time, the heat preservation time and the cooling time of the bell-type annealing furnace are longer, and the steel coil is placed in a coil in the bell-type annealing furnace, so that the process flexibility is low, and the bell-type annealing furnace is suitable for producing low-alloy high-strength steel or steel grade with lower strength, wherein the metallographic structure of the low-alloy high-strength steel is mainly ferrite and pearlite. Because the investment is small, the production is flexible, and the hood-type annealing furnace has strong advantages in small-scale production; (2) the continuous annealing furnace has high production efficiency, and the process parameters of the heating process, the heat preservation process and the cooling process of the strip steel can be flexibly regulated and controlled according to different varieties of requirements because the strip steel moves in the annealing furnace in a through mode, so that the development of steel grades with various strength levels can be met. But the continuous annealing furnace has large equipment investment and high productivity and is suitable for the production of products with high yield.
The rolled steel sheet was analyzed from a microscopic view, and as the reduction ratio increased, the crystal grains were gradually elongated from the first equiaxed grains, the grain boundaries increased, and the dislocation plug product at the grain boundaries, and fig. 1 shows the microstructure of HC340 (low alloy high strength steel) at different reduction ratios.
The purpose of annealing is to restore the deformed grains to their original state as much as possible. Under the action of high temperature, two changes of deformed grains occur: recovery and recrystallization. Recrystallization is to obtain new defect-free crystal grains at the grain boundary or in the crystal grains by nucleation when the temperature is higher than the recrystallization temperature, and then the new defect-free crystal grains grow up gradually, and the size of the final crystal grains is related to the heat preservation temperature and the heat preservation time. Better mechanical properties can be obtained by recrystallization annealing. The recovery occurs below the recrystallization temperature, the number of crystal lattice defects such as dislocation, vacancy and the like in the crystal boundary and the crystal grain is gradually reduced, the shape of the deformed crystal grain is not changed in the process, and the mechanical property of the steel plate has great difference from that of the original unprocessed steel plate.
The temperature at which recrystallization of the hardened steel sheet occurs is referred to as the critical recrystallization annealing temperature. Practice and theory prove that recrystallization annealing corresponding to different deformation degrees is different, the higher the reduction rate is, the lower the corresponding critical recrystallization annealing temperature is, and for HC340La low-alloy high-strength steel, the difference between the critical recrystallization annealing temperatures corresponding to 10% reduction rate and 50% reduction rate is about 150 ℃. When the continuous annealing furnace normally works, the continuous annealing furnace can only be executed according to a fixed process. If the process is not properly selected, the recrystallization degree and the recovery degree of each area of the variable-thickness cold-rolled steel sheet are different, and how to select a proper process enables the mechanical property of the variable-thickness cold-rolled steel sheet to meet the customer requirements, the uniformity is good, and the conventional process needs to be perfected.
Disclosure of Invention
The invention aims to provide a continuous annealing process treatment method, so that the mechanical property and uniformity after annealing meet the requirements of terminal customers.
In order to achieve the purpose, the invention provides the following technical scheme:
the embodiment of the application discloses mechanical property homogenization treatment process of variable-thickness cold-rolled steel sheet, which comprises the following steps in sequence:
s1, selecting the thickness of the raw material according to the required thickness distribution of the finished product, and ensuring that the thickness of the raw material is higher than that of the thickest area of the finished product;
s2, rolling the equal-thickness steel coil raw material into variable-thickness steel according to the size requirement of the variable-thickness finished product;
s3, calculating to obtain an austenitizing temperature interval corresponding to the low-alloy high-strength steel, wherein the method comprises the following steps:
when the sum of the time of the strip steel passing through the heating section and the high-temperature section is more than or equal to 5min, the austenitizing temperature is equal to the lower limit value between austenite areas and is plus 50-100 ℃;
when the sum of the time of the strip steel passing through the heating section and the high-temperature section is less than 5min, the austenitizing temperature is equal to the lower limit value between austenite areas and is plus 80-150 ℃;
s4, calculating to obtain a CCT curve corresponding to the low-alloy high-strength steel, determining the cooling speed in which range to cool, cooling the steel plate from the austenitizing temperature to ferrite + pearlite, and determining the cooling parameters of a cooling area according to the cooling speed range;
s5, referring to the annealing process obtained in the steps S3 and S4, the variable-thickness steel coil rolled in the step S2 is sent into a continuous annealing furnace to be subjected to heat treatment, and the variable-thickness cold-rolled steel plate with high dimensional accuracy and uniform mechanical property is obtained.
Preferably, in the mechanical property uniformization processing of the variable thickness cold-rolled steel sheet, in step S1, if the steel type is mild steel, the difference between the thickness of the raw material and the thickness of the finished product is selected to be 0.05-0.4 mm.
Preferably, in the mechanical property uniformization processing of the variable thickness cold-rolled steel sheet, in step S1, if the steel type is low alloy high strength steel and the thickness ratio of the steel type is close to 1:2, the difference between the thickness of the raw material and the thickness of the finished product is selected to be 0.05-0.2 mm.
The invention has the advantage that the mechanical property and uniformity after annealing meet the requirements of terminal customers.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a microstructure diagram of HC340 (low alloy high strength steel) in the prior art at different reduction ratios;
FIG. 2 is a difference diagram of a heating process of a variable thickness cold rolled steel sheet in an embodiment;
FIG. 3 is a graph showing the difference in the cooling process of a variable thickness cold rolled steel sheet in the example;
FIG. 4 shows the dimensions of the variable thickness steel plate rolled by HC340 in the embodiment;
FIG. 5 is a graph of the austenitizing temperature range and CCT for a specific embodiment;
FIG. 6 is a microstructure diagram of the variable thickness steel plate in the embodiment at 930 deg.C for 3 min;
FIG. 7 is a mechanical property diagram corresponding to the temperature of the variable thickness steel plate at 930 ℃ for 3min in the specific example.
Detailed Description
The technical solutions in the embodiments of the present invention will be described in detail below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
According to the analysis in the background art, obtaining a variable thickness cold rolled steel sheet with satisfactory mechanical properties is subject to two constraints:
(1) the variable thickness steel plate obtained by a single pass has the ratio of the thickness of the thinnest area to the thickness of the thickest area which is generally more than 1:2 due to the limitation of equipment capacity, so that the deformation rate of each area of the variable thickness cold-rolled steel plate is between 5 and 50 percent. The critical recrystallization temperatures corresponding to the regions of different thicknesses are greatly different.
(2) In the continuous annealing furnace, a steel coil passes through the annealing furnace in a strip shape, and has the following characteristics: firstly, in order to ensure the production efficiency, the time for the variable-thickness strip to pass through a heating furnace is short, so that the strip needs to be quickly heated and quickly cooled, and the total time is generally 5-8min in consideration of reasonable heat preservation and aging treatment time (according to the process requirements); secondly, due to the thickness difference of the variable-thickness steel coils, the acceleration rate and the cooling speed of different areas of the variable-thickness steel coils are different in the heating and cooling processes; thirdly, because of the large time inertia of the temperature control in the annealing furnace, the annealing process can only be implemented according to a fixed process path in principle.
Analyzing the above restriction conditions, in order to obtain a uniform finished product with up-to-standard performance from a variable thickness cold-rolled steel sheet of low alloy high strength steel whose metallographic structure is mainly ferrite and pearlite, several conditions need to be satisfied:
(1) the annealing temperature is required to be higher than the recrystallization critical annealing temperature corresponding to all thickness regions, and in order to ensure the process stability, the annealing temperature is required to be 30-50 ℃ higher than the critical recrystallization annealing temperature corresponding to the thickest region; for low alloy high strength steel, the temperature is basically about 800 ℃. If the condition can not be met, the thickest region with the minimum reduction rate can not realize recrystallization, only static recovery can occur, the corresponding structure is still in a rolling hardening state, and the thin regions with larger mechanical properties and reduction rates have larger difference;
(2) the temperature range of the condition (1) is located in the two-phase region (ferrite + austenite) of the low alloy steel with a very high probability, and the recrystallized structure is not a pure recrystallized structure but recrystallized ferrite + austenite, in which the austenite structure is generated by phase transformation. The fluctuation of the temperature of the two-phase region and the reduction rate have great influence on the phase composition ratio, and the structure in the process can cause new non-uniformity after cooling, so that the annealing process needs to be further optimized and adjusted;
(3) because the increase of the recrystallization temperature can cause new non-uniformity, the traditional recrystallization annealing process can not meet the requirements, and the phase change recrystallization process can be considered to ensure that steel plates in areas with different thicknesses are fully recrystallized and do not generate non-uniformity. This process is independent of the degree of work hardening of the steel sheet. For low-alloy high-strength steel, if the annealing temperature is increased by 100-150 ℃ on the basis of the 1 st condition, the temperature basically enters an austenite region, so that the recrystallized structure of all thickness regions can be ensured to be austenite grains through austenite recrystallization transformation, and the sizes of the recrystallized grains of the austenite region are only related to the austenitizing temperature and the austenitizing time, so that the steel plate structures corresponding to different reduction ratios are ensured to be uniform in the high-temperature austenite region;
(4) by performing the heat treatment at the austenite recrystallization temperature, it is also necessary to analyze the influence of the non-uniformity of heating during the heating and cooling processes. Since the heating rate and the cooling rate are different in the regions of different thickness of the variable thickness steel sheet in the heating process and the cooling process, there is a difference in the time for which the temperature is adjusted from one temperature to another temperature in the same heating and cooling environment. As shown in fig. 2-3, the variable thickness steel plate with the thin region of 1mm, the thick region of 2mm and the transition region of 100mm is heated from normal temperature to 950 ℃ for austenitizing treatment, the time required for the 1mm, the transition region and the 2mm region is 43,55 and 80s respectively, while the time for the heating section and the high temperature section of the strip steel in the continuous annealing furnace is generally 4-6min, and as long as the austenitizing temperature is slightly higher, the influence of temperature rise difference caused by the thickness difference can be ignored; the cooling rates at normal temperature when cooling from 950 ℃ were 1mm, for the transition zone and 2mm were 26,18 and 15 ℃/s, respectively. Generally, when the cooling rate is controlled to be 3-25 ℃/s, the structure after cooling is ensured to be ferrite + pearlite, and the structure is small. This is easily accomplished for a continuous annealing process so that the cooling rate differences of the cooling process do not affect the final product performance non-uniformity.
According to the analysis of the new process, the implementation steps of the technical scheme are as follows:
the method comprises the following steps: and selecting the thickness of the raw material according to the thickness distribution of the finished product, and ensuring that the thickness of the raw material is higher than that of the thickest area of the finished product. If the steel grade is mild steel, the difference between the thickness of the raw material and the thickness of the finished product is 0.05-0.4 mm; if the steel is low-alloy high-strength steel and the thickness ratio of the variable thickness is close to 1:2, the difference between the thickness of the raw material and the thickness of the finished product is 0.05-0.2mm, otherwise, the difference between the thickness of the raw material and the thickness of the finished product can be properly relaxed, so that the rolling load can be ensured to meet the equipment limit, and the selection of the thickness of the raw material has certain flexibility;
step two: rolling the steel coil with the same thickness in variable thickness according to the size requirement of the variable thickness to obtain the steel coil with the variable thickness, wherein the size precision and the shape of the steel coil meet the requirement;
step three: through experiments and theoretical calculation, an austenitizing temperature interval corresponding to the low-alloy high-strength steel is obtained, the austenite temperature is selected to be + 50-150 ℃ of the lower limit value of the austenitizing interval, and a specific temperature interval confirmation method needs to be determined according to the production rhythm of the continuous annealing furnace (the higher the austenitizing temperature is, the shorter the corresponding high-temperature section heat preservation time is), and the method comprises the following steps:
the sum of the time of the strip steel passing through the heating section and the high-temperature section is more than or equal to 5min, and the austenitizing temperature is equal to the lower limit value between austenite areas and is plus 50-100 ℃;
the sum of the time of the strip steel passing through the heating section and the high-temperature section is less than 5min, and the austenitizing temperature is equal to the lower limit value between austenite regions and is plus 80-150 ℃;
and selecting a proper annealing process to ensure that the heat preservation temperature of the high-temperature section is slightly greater than the critical recrystallization annealing temperature, and the heat preservation time ensures that the internal and external temperatures of the steel coil are uniform.
Step four: the CCT curve corresponding to the low-alloy high-strength steel is obtained through experiments and theoretical calculation, the cooling speed can be determined within a certain range through the interval, the steel plate can be cooled from the austenitizing temperature to ferrite and pearlite, and then the cooling parameters of a cooling zone are determined according to the cooling speed range.
Step five: and (4) according to the annealing process obtained in the third step and the fourth step, feeding the rolled variable-thickness steel coil into a continuous annealing furnace for heat treatment, thus obtaining the variable-thickness cold-rolled steel sheet which has high dimensional precision and relatively uniform mechanical property and meets the requirements of customers.
Examples are as follows:
a low alloy high strength steel 2.15mm thick, steel grade HC340mm, was rolled to the dimensions shown in FIG. 4. Wherein the thickest region is 2mm thick, and the length of the transition region is 100mm after the thinnest region is 1 mm. The difference between the thickness of the raw material and the thickness of the finished product is not too large because the difference is 1:2, and 2.15mm is selected here.
According to the chemical components and the different regional hardening rate parameters, the corresponding austenitizing temperature range and CCT curve are calculated, as shown in FIG. 5, the lower limit of the austenite temperature is approximately between 800-860 ℃, the CCT curve can show that the structure is basically ferrite + pearlite when the cooling speed is less than 10 ℃/s, the structure is ferrite + a small amount of pearlite and bainite when the cooling speed is between 10-30 ℃/s, and if the cooling speed is controlled according to 5-20 ℃/s, the grain size can be ensured to be about 8 grades, the structure difference is small, and the structure is basically ferrite + pearlite and a very small amount of bainite.
Selecting the austenitizing temperature to be 930 ℃ according to the performance parameters of the continuous annealing furnace, ensuring that the time of a high-temperature section is more than or equal to 3min, and annealing the variable-thickness steel coil according to the process to obtain the microstructure of the product shown in figure 6, (a) 9%; (b)18 percent; (c) 27; (d) 36; (e)45 percent; (f) 54%, it can be seen that the tissue uniformity in each region thereof is very good.
Through mechanical property tests, as shown in fig. 7, the yield strength is about 350MPa, the tensile strength is more than 430MPa, the fluctuation is less than 20MPa, and the elongation is more than or equal to 22%. Completely meets the standard requirements.
The present embodiments are to be considered as illustrative and not restrictive, and the scope of the patent is to be determined by the appended claims.
Claims (3)
1. A mechanical property homogenization treatment process for a variable-thickness cold-rolled steel sheet is characterized by sequentially comprising the following steps of:
s1, selecting the thickness of the raw material according to the required thickness distribution of the finished product, and ensuring that the thickness of the raw material is higher than that of the thickest area of the finished product;
s2, rolling the equal-thickness steel coil raw material into variable-thickness steel according to the size requirement of the variable-thickness finished product;
s3, calculating to obtain an austenitizing temperature interval corresponding to the low-alloy high-strength steel, wherein the method comprises the following steps:
when the sum of the time of the strip steel passing through the heating section and the high-temperature section is more than or equal to 5min, the austenitizing temperature is equal to the lower limit value between austenite areas and is plus 50-100 ℃;
when the sum of the time of the strip steel passing through the heating section and the high-temperature section is less than 5min, the austenitizing temperature is equal to the lower limit value between austenite areas and is plus 80-150 ℃;
s4, calculating to obtain a CCT curve corresponding to the low-alloy high-strength steel, determining the cooling speed in which range to cool, cooling the steel plate from the austenitizing temperature to ferrite + pearlite, and determining the cooling parameters of a cooling area according to the cooling speed range;
s5, referring to the annealing process obtained in the steps S3 and S4, the variable-thickness steel coil rolled in the step S2 is sent into a continuous annealing furnace to be subjected to heat treatment, and the variable-thickness cold-rolled steel plate with high dimensional accuracy and uniform mechanical property is obtained.
2. A process for uniformizing mechanical properties of a thick cold rolled steel sheet according to claim 1, wherein in step S1, if the steel type is mild steel, the difference between the thickness of the raw material and the thickness of the finished product is selected to be 0.05-0.4 mm.
3. A mechanical property uniformization processing of thickness-variable cold rolled steel sheet according to claim 1, wherein in step S1, if the steel type is low alloy high strength steel and the thickness-variable ratio is close to 1:2, the difference between the thickness of the raw material and the thickness of the finished product is selected to be 0.05-0.2 mm.
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JP2003073733A (en) * | 2001-08-30 | 2003-03-12 | Kawasaki Steel Corp | Method for manufacturing deformed steel plate |
US20100258216A1 (en) * | 2007-07-19 | 2010-10-14 | Corus Staal Bv | Method for annealing a strip of steel having a variable thickness in length direction |
CN106170567A (en) * | 2014-01-17 | 2016-11-30 | 艾普伦 | There is the manufacture method of the band of thickness change and corresponding band |
US20170029918A1 (en) * | 2014-01-17 | 2017-02-02 | Aperam | Method for manufacturing a strip having a variable thickness and associated strip |
CN111872149A (en) * | 2020-07-15 | 2020-11-03 | 燕山大学 | ESP-based dynamic variable rule slab performance gradient distribution forming method |
CN113695398A (en) * | 2021-09-01 | 2021-11-26 | 苏州东宝海星金属材料科技有限公司 | Manufacturing method of stainless steel rolled differential thickness plate related product |
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