CN112718876A - Production process of cold-formed low-alloy high-strength steel variable-thickness plate - Google Patents
Production process of cold-formed low-alloy high-strength steel variable-thickness plate Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 57
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- 238000005096 rolling process Methods 0.000 claims abstract description 36
- 238000010008 shearing Methods 0.000 claims abstract description 24
- 230000008719 thickening Effects 0.000 claims abstract description 23
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/56—Elongation control
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D1/00—Straightening, restoring form or removing local distortions of sheet metal or specific articles made therefrom; Stretching sheet metal combined with rolling
- B21D1/02—Straightening, restoring form or removing local distortions of sheet metal or specific articles made therefrom; Stretching sheet metal combined with rolling by rollers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D43/00—Feeding, positioning or storing devices combined with, or arranged in, or specially adapted for use in connection with, apparatus for working or processing sheet metal, metal tubes or metal profiles; Associations therewith of cutting devices
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- C21D1/26—Methods of annealing
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
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- C—CHEMISTRY; METALLURGY
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- 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
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- 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
- C21D8/0242—Flattening; Dressing; Flexing
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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
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Abstract
The invention discloses a production process of a cold-formed low-alloy high-strength steel variable-thickness plate, which is characterized in that the cold-formed low-alloy high-strength steel variable-thickness plate is prepared by adopting a process of raw material selection → thickening rolling → annealing → thickening flattening → straightening shearing, the surface quality of the cold-formed low-alloy high-strength steel variable-thickness plate is good, the strength and the elongation of a transition section are consistent with those of an equal-thickness section, and hidden cracks, hidden cracks and other hidden troubles are avoided; the transition section of the cold-formed low-alloy high-strength steel variable-thickness plate provided by the invention replaces a welding seam, so that the connection strength and the performance are greatly improved, the defects of a laser tailor-welding process are overcome, the weight of parts is reduced, and the light weight of an automobile is realized.
Description
Technical Field
The invention belongs to a variable thickness plate rolling technology, and particularly relates to a production process of a cold-formed low-alloy high-strength steel variable thickness plate.
Background
The general trend of the current automobile technical development is energy conservation, environmental protection, safety, comfort, intellectualization and networking, the reduction of oil consumption and emission on the premise of ensuring performance is one of the problems which need to be solved urgently in the current automobile field, and the light weight of the automobile is an important way for solving the problem and becomes the mainstream of the modern automobile design and manufacture; considering that the mass of an automobile body accounts for 30-40% of the total weight of the automobile, and when the weight of the automobile is reduced by 100 kilograms, at least 0.6L of fuel oil can be saved per hundred kilometers, and the emission of CO2 of 5g per kilometer can be reduced; therefore, the weight reduction of the whole automobile is important for reducing the self weight of the whole automobile, improving the fuel economy of the whole automobile, saving energy and protecting environment.
In order to meet the requirements of reducing fuel consumption and pollutant emission of automobiles, low-alloy high-strength steel in the field of cold forming becomes one of the preferable materials for high-strength automobile parts, and the combination of the variable-thickness plate and the low-alloy high-strength steel reflects the idea of 'obtaining materials as required', so that the weight is reduced without losing the strength. In the prior art, when parts are manufactured by using low-alloy high-strength steels with different thicknesses, materials with different thicknesses are required to be subjected to laser tailor-welding and then are subjected to cold stamping forming to form the parts, but the strength and the forming performance of a welding seam of a tailor-welded blank are still in certain difference with those of a base metal, the requirement on the quality of the welding seam is high during forming, and a sudden change structure of the welding seam inevitably brings certain challenges to subsequent stamping processes and die manufacturing.
In view of the above, it is urgently needed to develop a method for producing a low-alloy high-strength steel plate thick plate, which can make up for the deficiency of the laser tailor-welding process, improve the performance, reduce the weight of parts, and realize the lightweight of an automobile.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a production process of a cold-formed low-alloy high-strength steel variable-thickness plate, which is characterized in that the cold-formed low-alloy high-strength steel variable-thickness plate is prepared by adopting a process of raw material selection → thickening rolling → annealing → thickening and flattening → straightening and shearing, and a transition section of the cold-formed low-alloy high-strength steel variable-thickness plate replaces a welding seam, so that the connection strength and the performance are greatly improved, the defects of a laser tailor-welding process are overcome, the weight of parts is reduced, and the light weight of an automobile is realized.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a production process of a cold-formed low-alloy high-strength steel variable-thickness plate, which comprises the following steps of:
(1) selecting raw materials, namely selecting raw material plates according to the thickness of the variable thickness plate of the standard part and the grade of steel grade;
(2) thickening and rolling, namely calculating a target profile of a finished product variable-thickness plate according to the specification of a standard part variable-thickness plate and the elongation of each equal-thickness section in a set leveling process, and then thickening and rolling according to the target profile of the finished product variable-thickness plate and the yield strength of a raw material plate to obtain a thickened rolled piece;
(3) annealing, namely annealing the thickened rolled piece to obtain a thickened annealed rolled piece;
(4) thickening and flattening, namely flattening the thickened annealed rolled piece, and controlling the elongation of each equal-thickness section to be consistent with the elongation of the corresponding equal-thickness section in the flattening process set in the step (2) to obtain a flattened and thickened coil;
(5) and straightening and shearing, namely straightening and shearing the flattened and thickened coil to obtain the cold-formed low-alloy high-strength steel thickened plate.
Preferably, in the step (1), in the raw material selection process, the thickness of the raw material plate is determined according to the thickness of the thickened plate of the standard part, that is, the thickness H of the raw material plateOriginal sourceAccording to the maximum thickness h of the standard part variable thickness platemaxAnd a minimum thickness hminDetermined, and satisfied 1.35 x hmax≤HOriginal source≤2.5*hmin；
The grade of the steel of the raw material plate is determined according to the grade of the steel of the standard part variable-thickness plate, namely the raw material plate is a low-alloy high-strength hot-rolled pickled steel coil which is at least one grade higher than the yield strength of the standard part variable-thickness plate.
Preferably, in the step (2), in the thickening rolling process, the elongation of each equal-thickness section in the set flattening process is 0.5% -3%.
Preferably, in the step (2), during the thickening rolling, the target profile of the finished variable-thickness plate comprises target lengths and target thicknesses of n equal-thickness sections and target lengths of n-1 transition sections; the transition section is used for connecting the two equal-thickness sections.
Preferably, the target lengths and target thicknesses of the n equal-thickness sections of the finished variable-thickness plate are as follows:
target length of ith equal-thickness segment: l isi＝(1-μi)*li；
Target thickness of ith equal-thickness segment: hi＝li*hi/Li；
Wherein i is 1, 2, 3, … …, n;
Lithe target length of the ith equal-thickness section of the finished variable-thickness plate is as follows, unit: mm;
lithe length of the ith equal-thickness section of the standard part variable-thickness plate is as follows: mm;
μithe elongation rate of the leveling process of the ith equal-thickness section is set to be more than or equal to 0.5 percent and less than or equal to mui≤3％；
HiThe target thickness of the ith equal-thickness section of the finished variable-thickness plate is as follows, unit: mm;
hithe thickness of the ith equal-thickness section of the standard part variable-thickness plate is as follows, unit: mm.
Preferably, the target lengths of the n-1 transition sections of the finished variable thickness plate are as follows:
target length for jth transition: kj＝kj-d；
Wherein j is 1, 2, 3, … …, n-1;
Kjthe target length of the jth transition section of the finished variable-thickness plate is as follows, unit: mm;
kjthe length of the jth transition section of the standard part variable thickness plate is as follows: mm;
d ranges from 0mm to 3 mm.
Preferably, in the step (2), the variable thickness plate mill used in the variable thickness rolling process can feed back the rolling size in real time and automatically adjust.
Preferably, in the step (3), the annealing treatment is performed in an all-hydrogen bell furnace.
Preferably, in the step (4), the equipment used in the thickening and leveling process is the same as that used in the step (2).
Preferably, in the step (5), the device used in the straightening shearing process is a variable thickness plate shearing line which is capable of automatically identifying the size profile of the variable thickness plate and feeding the variable thickness plate to length.
The production process of the cold-formed low-alloy high-strength steel variable-thickness plate provided by the invention also has the following beneficial effects:
1) according to the production process of the cold-formed low-alloy high-strength steel variable-thickness plate, the cold-formed low-alloy high-strength steel variable-thickness plate is prepared by adopting the processes of raw material selection → thickness-changing rolling → annealing → thickness-changing flattening → straightening shearing, and the transition section of the cold-formed low-alloy high-strength steel variable-thickness plate replaces a welding seam, so that the connection strength and the performance are greatly improved, the defects of a laser tailor-welding process are overcome, the weight of parts is reduced, and the light weight of an automobile is realized;
2) the production process of the cold-formed low-alloy high-strength steel variable-thickness plate can realize continuous production, and has high production efficiency and flexible thickness combination;
3) the cold-formed low-alloy high-strength steel variable-thickness plate prepared by the production process of the cold-formed low-alloy high-strength steel variable-thickness plate replaces a welding line with a transition section, is smoothly connected and has good surface quality, good metal fluidity during subsequent stamping and simple die design;
4) the transition section of the cold-formed low-alloy high-strength steel variable-thickness plate has a good energy absorption effect and better impact resistance.
Drawings
FIG. 1 is a schematic flow chart of the process for producing a cold-formed low-alloy high-strength steel variable-thickness plate according to the present invention;
FIG. 2 is a schematic view of the apparatus used in the process for producing a cold-formed low-alloy high-strength steel variable-thickness plate according to the present invention;
FIG. 3 is a schematic diagram showing the specification of a standard part variable thickness plate in embodiment 1 of the present invention;
FIG. 4 is a schematic diagram showing the specification of a standard part variable thickness plate in embodiment 2 of the present invention;
FIG. 5 is a schematic diagram showing the specification of a standard part variable thickness plate in embodiment 3 of the present invention.
Detailed Description
In order to better understand the technical solutions of the present invention, the following further describes the technical solutions of the present invention with reference to the accompanying drawings and examples.
As shown in FIG. 1, the production process of the cold-formed low-alloy high-strength steel variable-thickness plate provided by the invention comprises the following steps:
(1) selecting raw materials, namely selecting raw material plates according to the thickness of the variable thickness plate of the standard part and the grade of steel grade;
the specific process is as follows: selecting a low-alloy high-strength hot-rolled pickled steel coil with at least one level of yield strength from the raw material plate according to the yield strength of the standard part variable-thickness plate, and then selecting the maximum thickness h of the standard part variable-thickness platemaxAnd a minimum thickness hminDetermining the thickness H of the raw sheetOriginal sourceSatisfies 1.35 x hmax≤HOriginal source≤2.5*hmin；
(2) Thickening and rolling, namely calculating a target profile of a finished product variable-thickness plate according to the specification (thickness and length) of the standard part variable-thickness plate and the elongation of each equal-thickness section set in the flattening process, and then thickening and rolling according to the target profile of the finished product variable-thickness plate and the yield strength of the raw material plate to obtain a thickened rolled piece;
the specific process is as follows: the thickness of n equal-thickness sections of the variable-thickness plate of the standard part is hi(i-1, 2, 3, … …, n) and a length li(i-1, 2, 3, … …, n) and n-1 transition segments having a length kj(i ═ 1, 2, 3, … …, n-1), where the transition segment is used to join two equal thickness segments; setting the elongation rate of n equal-thickness sections in the flattening process to be mu according to the flattening process requirement of the standard variable-thickness platei(i is 1, 2, 3, … …, n), then according to the standard part variable thickness plate specification and the n equal thickness section elongation rate set in the flattening processCalculating the target contour of the finished product variable-thickness plate (comprising the target lengths and the target thicknesses of n equal-thickness sections and the target lengths of n-1 transition sections), inputting the target contour of the finished product variable-thickness plate and the yield strength of the raw material plate into a variable-thickness rolling mill (see figure 2), loading the target contour and the yield strength of the raw material plate into a control degree, and controlling and continuously adjusting the roll gap by computer calculation, so that the plate continuously changing according to the target thickness of the finished product variable-thickness plate in the rolling direction is prepared, and the rolling from the equal-thickness plate to the variable-thickness rolled piece is realized.
In the process, the target lengths of the n equal-thickness sections of the finished product variable-thickness plate are obtained by shortening the lengths of the n equal-thickness sections of the standard part variable-thickness plate according to the set elongation of the equal-thickness section corresponding to the finished product variable-thickness plate, and the target thicknesses of the n equal-thickness sections are calculated by using a volume invariant law; controlling the target length of the transition section of the finished product variable-thickness plate to be less than or equal to the length of the transition section of the standard part variable-thickness plate; the specific formula is as follows:
the target lengths and target thicknesses of the n equal-thickness sections of the finished variable-thickness plate are as follows:
target length of ith equal-thickness segment: l isi＝(1-μi)*li；
Target thickness of ith equal-thickness segment: hi＝li*hi/Li；
Wherein i is 1, 2, 3, … …, n;
Lithe target length of the ith equal-thickness section of the finished variable-thickness plate is as follows, unit: mm;
lithe length of the ith equal-thickness section of the standard part variable-thickness plate is as follows: mm;
μithe elongation rate of the leveling process of the ith equal-thickness section is set to be more than or equal to 0.5 percent and less than or equal to mui≤3％；
HiThe target thickness of the ith equal-thickness section of the finished variable-thickness plate is as follows, unit: mm;
hithe thickness of the ith equal-thickness section of the standard part variable-thickness plate is as follows, unit: mm.
The target lengths of the n-1 transitions are:
target length for jth transition: kj＝kj-d；
Wherein j is 1, 2, 3, … …, n-1;
Kjthe target length of the jth transition section of the finished variable-thickness plate is as follows, unit: mm;
kjthe length of the jth transition section of the standard part variable thickness plate is as follows: mm;
d ranges from 0mm to 3 mm.
(3) Annealing, namely annealing the thickened rolled piece to obtain a thickened annealed rolled piece;
the specific process is as follows: and (3) placing the thickened rolled piece prepared in the step (2) into an all-hydrogen bell-type furnace (such as an all-hydrogen electric heating bell-type furnace, see figure 2) to carry out annealing treatment according to a set process to obtain the thickened annealed rolled piece.
(4) Thickening and flattening, namely flattening the thickened annealed rolled piece, and controlling the elongation of each equal-thickness section to be consistent with the elongation of the equal-thickness section corresponding to the finished variable-thickness plate set in the step (2) to obtain a flattened and thickened coil;
the specific process is as follows: and (3) placing the thickened annealed rolled piece on a thickening rolling mill (see figure 2) in the step (2) for leveling to obtain a leveled thickened coil, wherein the elongation of each equal-thickness section is consistent with the shortening of the corresponding equal-thickness section set in the step (2), namely the preset leveling process elongation is met to ensure the mechanical property of each equal-thickness section of the material, and a thickness gauge and a velocimeter are used for carrying out real-time feedback adjustment on the target profile to ensure that the size of the leveled thickened plate conforms to the standard of a designed part.
(5) And (5) straightening and shearing, namely straightening and shearing the flattened and thickened coil to obtain a cold-formed low-alloy high-strength steel thickened plate.
The specific process is as follows: and (3) straightening and shearing the flat and thickened coil prepared in the step (4) on a variable thickness plate shearing line (see figure 2) capable of automatically identifying the size and the profile of the variable thickness plate and feeding the variable thickness plate in a fixed length to obtain the cold-formed low-alloy high-strength steel variable thickness plate.
Experiments prove that the cold-formed low-alloy high-strength steel variable-thickness plate prepared by the preparation process has the length tolerance of +/-2 mm and the thickness tolerance of +/-0.05 mm of each section, good surface quality, consistent strength and elongation of the transition section with those of the equal-thickness section, capability of meeting the requirements of users, no hidden danger of weld joint cracking and hidden cracking, good metal fluidity during stamping, good service and impact resistance of parts, high strength and weight reduction.
The production process of the cold-formed low-alloy high-strength steel variable-thickness plate of the invention is further described with reference to specific examples;
example 1
(1) Selecting raw materials: the standard part variable thickness plate specification is shown in fig. 3, and is 1.0-1.3 × 440 × 730mm, 440mm is the width of the standard part variable thickness plate, 730mm is the total length of the standard part variable thickness plate, wherein 1.0 equal thickness section length: 300mm, 1.3 equal thickness section: 400mm, the length of the transition section is 30mm, the steel grade of the standard part variable-thickness plate is HC340LA, and QSTE420TM acid-washed roll is selected as a raw material plate with the specification of 1.9 x 440mm according to the yield strength of the standard part variable-thickness plate which is not less than 340 MPa.
(2) Thickening and rolling: setting the elongation in the flattening process, the elongation of the equal-thickness section of 1.0: 1%, elongation of 1.3 equal thickness segment: 1.5 percent; as shown in table 1, the lengths of the equal-thickness sections of the standard part variable-thickness plate are proportionally reduced to obtain target lengths of the equal-thickness sections of the finished product variable-thickness plate, the target thicknesses of the equal-thickness sections of the finished product variable-thickness plate are calculated, and then the target lengths of the equal-thickness sections of the finished product variable-thickness plate, the target thicknesses, the target lengths of the transition sections and the yield strength of the raw material plate are input into a thickness-increasing rolling mill and loaded to a control degree, and the variable-thickness rolled piece with the thickness of 1.01-1.32 × 440mm is obtained by coiling, threading, rolling starting, inputting in a variable-procedure sequence, coiling and coiling.
TABLE 1 target Profile and raw sheet yield Strength of finished variable-thickness plates
| Equal thickness section | Transition section | Equal thickness section | |
| Target thickness mm | 1.01 | - | 1.32 |
| Target length mm | 297 | 29 | 394 |
| Yield strength MPa of raw material plate | 450 | 450 | 450 |
(3) Annealing: after the rolling is finished, annealing the thickened rolled piece through a full-hydrogen electric heating cover type furnace to obtain a thickened annealed rolled piece;
(4) thickening and flattening: carrying out variable-thickness plate flattening treatment on the variable-thickness annealed rolled piece through a variable-thickness flattening program of a variable-thickness rolling mill, wherein the elongation of a 1.01 thickness section is controlled to be 1%, and the elongation of a 1.32 thickness section is controlled to be 1.5%, so that a flattened variable-thickness coil meeting the HC340LA performance requirement is obtained;
(5) straightening and shearing: and (4) straightening and shearing the flattened and thickened coil on a variable thickness plate shearing line to obtain the cold-formed low-alloy high-strength steel variable thickness plate meeting the requirements of finished products.
Practice proves that the cold-formed low-alloy high-strength variable-thickness plate has the advantages that the precision of each section is +/-2 mm, the thickness tolerance is +/-0.05 mm, the surface quality is good, the strength and the elongation of the transition section are consistent with those of an equal-thickness section, the performance requirements of HC340LA are met, the hidden crack danger of a welding seam is avoided, the metal fluidity is good during stamping, the service and the shock resistance of parts are good, and the high strength and the weight reduction are realized.
Example 2
(1) Selecting raw materials: the standard part variable thickness plate specification is shown in fig. 4, and is 0.8-1.2 × 460 × 680mm, 460mm is the width of the standard part variable thickness plate, 680mm is the total length of the standard part variable thickness plate, wherein the length of the equal thickness section is 0.8: 240mm, 1.2 equal thickness section: 400mm, the length of the transition section is 40mm, the grade number of the steel of the standard part variable-thickness plate is B250P1, and according to the yield strength of the standard part variable-thickness plate being more than or equal to 250MPa, SAPH440 acid-washing roll is selected as the raw material plate, and the specification is 1.8 x 460 mm.
(2) Thickening and rolling: setting the elongation in the flattening process, the elongation of the equal-thickness section of 0.8: 1.25%, elongation of 1.2 equal thickness section: 2.5 percent; as shown in table 1, the lengths of the equal-thickness sections of the standard part variable-thickness plate are proportionally reduced to obtain target lengths of the equal-thickness sections of the finished product variable-thickness plate, the target thicknesses of the equal-thickness sections of the finished product variable-thickness plate are calculated, and then the target lengths of the equal-thickness sections of the finished product variable-thickness plate, the target thicknesses, the target lengths of the transition sections and the yield strength of the raw material plate are input into a thickness-increasing rolling mill and loaded to a control degree, and the variable-thickness rolled piece is wound up, threaded, rolled and started, and is sequentially input, wound up and wound down according to a variable rule to obtain the variable-thickness rolled piece of 0.81-1.23 × 460 mm.
TABLE 1 target Profile and raw sheet yield Strength of finished variable-thickness plates
| Equal thickness section | Transition section | Equal thickness section | |
| Target thickness mm | 0.81 | - | 1.23 |
| Target length mm | 237 | 39 | 390 |
| Yield strength MPa of raw material plate | 350 | 350 | 350 |
(3) Annealing: after the rolling is finished, annealing the thickened rolled piece through a full-hydrogen electric heating cover type furnace to obtain a thickened annealed rolled piece;
(4) thickening and flattening: carrying out variable-thickness plate flattening treatment on the variable-thickness annealed rolled piece through a variable-thickness flattening program of a variable-thickness rolling mill, wherein the elongation of a thickness section of 0.81 is controlled to be 1.25%, and the elongation of a thickness section of 1.23 is controlled to be 1.25%, so that a flattened variable-thickness coil meeting the performance requirement of B250P1 is obtained;
(5) straightening and shearing: and (4) straightening and shearing the flattened and thickened coil on a variable thickness plate shearing line to obtain the cold-formed low-alloy high-strength steel variable thickness plate meeting the requirements of finished products.
Practice proves that the cold-formed low-alloy high-strength variable-thickness plate has the advantages that the precision of each section is +/-2 mm, the thickness tolerance is +/-0.05 mm, the surface quality is good, the strength and the elongation of the transition section are consistent with those of an equal-thickness section, the performance requirements of B250P1 are met, the hidden crack danger of a welding seam is avoided, the metal fluidity is good during stamping, the service and the shock resistance of parts are good, and the high strength and the weight reduction are realized.
Example 3
(1) Selecting raw materials: the standard part variable thickness plate specification is shown in fig. 5, and is 0.9-1.8 × 440 × 690mm, 440mm is the width of the standard part variable thickness plate, 690mm is the total length of the standard part variable thickness plate, wherein the length of the equal thickness section is 0.9: 400mm, 1.8 equal thickness section: 200mm, the length of the transition section is 90mm, the steel grade of the standard part variable-thickness plate is HC380LA, and according to the yield strength of the standard part variable-thickness plate being more than or equal to 380MPa, S460MC acid-washed roll is selected as the raw material plate, and the specification is 2.3 x 440 mm.
(2) Thickening and rolling: setting the elongation in the flattening process, the elongation of the equal-thickness section of 0.9: 1%, elongation of 1.8 equal thickness segment: 2 percent; as shown in table 1, the lengths of the equal-thickness sections of the standard part variable-thickness plate are proportionally reduced to obtain target lengths of the equal-thickness sections of the finished product variable-thickness plate, the target thicknesses of the equal-thickness sections of the finished product variable-thickness plate are calculated, and then the target lengths of the equal-thickness sections of the finished product variable-thickness plate, the target thicknesses, the target lengths of the transition sections and the yield strength of the raw material plate are input into a thickness-increasing rolling mill and loaded to a control degree, and the variable-thickness rolled piece is wound up, threaded, rolled and started, and is sequentially input, wound up and wound down according to a variable rule to obtain the variable-thickness rolled piece of 0.91-1.84 × 460 mm.
TABLE 1 target Profile and raw sheet yield Strength of finished variable-thickness plates
| Equal thickness section | Transition section | Equal thickness section | |
| Target thickness mm | 0.91 | - | 1.84 |
| Target length mm | 396 | 88 | 196 |
| Yield strength MPa of raw material plate | 470 | 470 | 470 |
(3) Annealing: after the rolling is finished, annealing the thickened rolled piece through a full-hydrogen electric heating cover type furnace to obtain a thickened annealed rolled piece;
(4) thickening and flattening: carrying out variable-thickness plate flattening treatment on the variable-thickness annealed rolled piece through a variable-thickness flattening program of a variable-thickness rolling mill, wherein the elongation of a thickness section of 0.91 is controlled to be 1%, the elongation of a thickness section of 1.84 is controlled to be 2%, and a flattened variable-thickness coil meeting the HC380LA performance requirement is obtained;
(5) straightening and shearing: and (4) straightening and shearing the flattened and thickened coil on a variable thickness plate shearing line to obtain the cold-formed low-alloy high-strength steel variable thickness plate meeting the requirements of finished products.
Practice proves that the cold-formed low-alloy high-strength variable-thickness plate has the advantages that the precision of each section is +/-2 mm, the thickness tolerance is +/-0.05 mm, the surface quality is good, the strength and the elongation of the transition section are consistent with those of an equal-thickness section, the performance requirements of HC380LA are met, the hidden crack danger of a welding seam is avoided, the metal fluidity is good during stamping, the service and the shock resistance of parts are good, and the high strength and the weight reduction are realized.
It should be understood by those skilled in the art that the above embodiments are only for illustrating the present invention and are not to be used as a limitation of the present invention, and that changes and modifications to the above described embodiments are within the scope of the claims of the present invention as long as they are within the spirit and scope of the present invention.
Claims (10)
1. A production process of a cold-formed low-alloy high-strength steel variable-thickness plate is characterized by comprising the following steps:
(1) selecting raw materials, namely selecting raw material plates according to the thickness of the variable thickness plate of the standard part and the grade of steel grade;
(2) thickening and rolling, namely calculating a target profile of a finished product variable-thickness plate according to the specification of a standard part variable-thickness plate and the elongation of each equal-thickness section in a set leveling process, and then thickening and rolling according to the target profile of the finished product variable-thickness plate and the yield strength of a raw material plate to obtain a thickened rolled piece;
(3) annealing, namely annealing the thickened rolled piece to obtain a thickened annealed rolled piece;
(4) thickening and flattening, namely flattening the thickened annealed rolled piece, and controlling the elongation of each equal-thickness section to be consistent with the elongation of the corresponding equal-thickness section in the flattening process set in the step (2) to obtain a flattened and thickened coil;
(5) and straightening and shearing, namely straightening and shearing the flattened and thickened coil to obtain the cold-formed low-alloy high-strength steel thickened plate.
2. The process for producing a cold-formed low-alloy, high-strength steel variable-thickness plate according to claim 1, wherein in the step (1), in the raw material selection process, the thickness of the raw material plate is determined according to the thickness of the standard part variable-thickness plate, that is, the thickness H of the raw material plateOriginal sourceAccording to the maximum thickness h of the standard part variable thickness platemaxAnd a minimum thickness hminDetermined, and satisfied 1.35 x hmax≤HOriginal source≤2.5*hmin；
The grade of the steel of the raw material plate is determined according to the grade of the steel of the standard part variable-thickness plate, namely the raw material plate is a low-alloy high-strength hot-rolled pickled steel coil which is at least one grade higher than the yield strength of the standard part variable-thickness plate.
3. The process for producing a cold-formed low-alloy high-strength steel variable thickness plate according to claim 1, wherein in the step (2), the elongation of each equal-thickness section in the leveling process is set to be 0.5 to 3% in the variable thickness rolling process.
4. The process for producing a cold-formed low-alloy high-strength steel variable-thickness plate according to claim 1, wherein in the step (2), the target profile of the finished variable-thickness plate during the variable-thickness rolling process comprises target lengths and target thicknesses of n equal-thickness sections and target lengths of n-1 transition sections; the transition section is used for connecting the two equal-thickness sections.
5. The process for producing a cold-formed low-alloy high-strength steel variable-thickness plate according to claim 4, wherein the target lengths and target thicknesses of the n equal-thickness sections of the finished variable-thickness plate are as follows:
target length of ith equal-thickness segment: l isi＝(1-μi)*li；
Target thickness of ith equal-thickness segment: hi＝li*hi/Li；
Wherein i is 1, 2, 3, … …, n;
Lithe target length of the ith equal-thickness section of the finished variable-thickness plate is as follows, unit: mm;
lithe length of the ith equal-thickness section of the standard part variable-thickness plate is as follows: mm;
μithe elongation rate of the leveling process of the ith equal-thickness section is set to be more than or equal to 0.5 percent and less than or equal to mui≤3％；
HiThe target thickness of the ith equal-thickness section of the finished variable-thickness plate is as follows, unit: mm;
hithe thickness of the ith equal-thickness section of the standard part variable-thickness plate is as follows, unit: mm.
6. The process according to claim 4, wherein the target lengths of n-1 transition sections of the finished variable thickness plate are:
target length for jth transition: kj＝kj-d；
Wherein j is 1, 2, 3, … …, n-1;
Kjthe target length of the jth transition section of the finished variable-thickness plate is as follows, unit: mm;
kjthe length of the jth transition section of the standard part variable thickness plate is as follows: mm;
d ranges from 0mm to 3 mm.
7. The process for producing a cold-formed low-alloy, high-strength steel variable-thickness plate according to claim 1, wherein in the step (2), the variable-thickness plate rolling mill used in the variable-thickness rolling process can feed back the rolling size in real time and adjust automatically.
8. The process for producing a cold-formed low-alloy, high-strength steel variable-thickness plate according to claim 1, wherein the annealing treatment in the step (3) is performed in an all-hydrogen bell furnace.
9. The process for producing a cold-formed low-alloy, high-strength steel variable-thickness plate according to claim 1 or 7, wherein the equipment used in the variable-thickness flattening process in the step (4) is the same as the equipment used in the step (2).
10. The process for producing a cold-formed low-alloy high-strength steel variable-thickness plate according to claim 1, wherein in the step (5), the equipment used in the straightening and shearing process is a variable-thickness plate shearing line which is capable of automatically identifying the size profile of the variable-thickness plate and feeding the variable-thickness plate to a fixed length.
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