CN115584428B - Short-flow low-cost cold-rolled DH590 steel and production method thereof - Google Patents
Short-flow low-cost cold-rolled DH590 steel and production method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 83
- 239000010959 steel Substances 0.000 title claims abstract description 83
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 26
- 238000005096 rolling process Methods 0.000 claims abstract description 27
- 238000000034 method Methods 0.000 claims abstract description 23
- 238000000137 annealing Methods 0.000 claims abstract description 18
- 238000009749 continuous casting Methods 0.000 claims abstract description 18
- 238000005097 cold rolling Methods 0.000 claims abstract description 16
- 238000005554 pickling Methods 0.000 claims abstract description 10
- 238000003723 Smelting Methods 0.000 claims abstract description 9
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 6
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 6
- 229910000859 α-Fe Inorganic materials 0.000 claims description 17
- 229910001566 austenite Inorganic materials 0.000 claims description 15
- 229910001563 bainite Inorganic materials 0.000 claims description 10
- 238000002791 soaking Methods 0.000 claims description 10
- 238000005266 casting Methods 0.000 claims description 7
- 229910001567 cementite Inorganic materials 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 7
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 claims description 7
- 229910000734 martensite Inorganic materials 0.000 claims description 7
- 229910001562 pearlite Inorganic materials 0.000 claims description 7
- 230000009467 reduction Effects 0.000 claims description 5
- 239000002253 acid Substances 0.000 claims description 4
- 238000007730 finishing process Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 238000004321 preservation Methods 0.000 claims description 3
- 238000010583 slow cooling Methods 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 229910052717 sulfur Inorganic materials 0.000 claims description 2
- 239000011777 magnesium Substances 0.000 description 9
- 239000011572 manganese Substances 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- 230000000694 effects Effects 0.000 description 4
- 230000000717 retained effect Effects 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 229910000885 Dual-phase steel Inorganic materials 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- 229910000794 TRIP steel Inorganic materials 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000010960 cold rolled steel Substances 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000002054 inoculum Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000010587 phase diagram Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/18—Controlling or regulating processes or operations for pouring
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- 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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- 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
- C21D2211/002—Bainite
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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
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- Y02P10/20—Recycling
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Abstract
The invention provides a short-process low-cost cold-rolled DH590 steel and a production method thereof, wherein the steel comprises the following components in percentage by weight: c:0.05 to 0.15 percent of Mn:1.0 to 2.0 percent, si:0.2 to 1.2 percent of Al:0.5 to 5.0 percent, P is less than or equal to 0.01 percent, S is less than or equal to 0.01 percent, N is less than or equal to 0.005 percent, ca:0.005% -0.100%, mg:0.002% -0.100%, and Al/Si:2.0 to 10.0; ca+Mg:0.05 to 0.20 percent, and the balance of Fe and unavoidable impurities. The production method comprises the steps of converter smelting, continuous casting and rolling of medium-thin slabs, pickling and cold rolling, continuous annealing and finishing; the yield strength of the steel produced by the method is more than or equal to 330MPa, the tensile strength is more than or equal to 750 MPa, the elongation after A50 fracture is more than or equal to 30%, and the hole expansion rate is more than or equal to 60%; meets the requirements of low cost and excellent extensibility and formability of automobiles.
Description
Technical Field
The invention belongs to the field of metal materials, and particularly relates to a short-process low-cost cold-rolled DH590 steel and a production method thereof.
Background
In the automotive industry, higher requirements have been put on the weight reduction, emission limitation and safety standards of the car body, and in order to better serve users, the automotive industry has increasingly demanded parts with high formability. The conventional dual-phase steel is difficult to meet the requirement of high-ductility complex cup punching, and the TRIP steel is limited to be widely used due to high alloy content and high production cost. DH steel is an English abbreviation of Dual Phase Steels with Improved Formability and is first mentioned by the VDA239-100 cold-formed steel sheet standard published by the German automobile industry Association in 2016. DH steel has good formability due to the introduction of a certain amount of retained austenite, and can overcome the defects of DP steel and TRIP steel in the application process, so that the DH steel has remarkable advantages in the future steel application market.
Patent document CN 111979490a discloses a high-ductility, high-formability cold-rolled DH590 steel and a production method thereof, which mainly comprises the following chemical components: c:0.08 to 0.14 percent of Si:0.35 to 0.75 percent of Mn:1.2% -2.2%, als:0.02% -0.50%, cr:0.03 to 0.45 percent of Mo:0.02% -0.25%, P is less than or equal to 0.01%, S is less than or equal to 0.01%, nb is less than or equal to 0.03%, and the balance is Fe and unavoidable impurities. The cold rolled DH steel with the strength grade of 590MPa is produced by the method, and has excellent ductility and formability, however, the alloy cost of the product is obviously improved by using a large amount of noble metals such as Cr, mo, nb and the like, and the production process is very complex and tedious by adopting the traditional cold rolling-continuous annealing process.
Patent document CN105274432B discloses a 600 MPa-level high yield ratio high plasticity cold rolled steel sheet and a manufacturing method thereof, which comprises the following main chemical components: c:0.06% -0.12%, si:0.02% -0.10%, mn:1.40% -2.00%, P: less than or equal to 0.015 percent, S: less than or equal to 0.010 percent of Al:0.02% -0.10%, N: less than or equal to 0.0050 percent, nb:0.015% -0.045%, ti:0.020% -0.055% and satisfies 0.035% -0.100% of Nb+Ti, and the balance of Fe and other unavoidable impurities. The invention produces cold-rolled dual-phase steel with the strength level of 600MPa and has the characteristics of high yield ratio and high plasticity, however, the invention adopts the traditional cold rolling-continuous annealing production process, the working procedure is complex, and the DP product is essentially different from DH steel.
Disclosure of Invention
The invention aims to overcome the problems and the shortcomings and provide the short-process low-cost cold rolled DH590 steel and the production method thereof, which not only can reduce the alloy cost, but also can shorten the production process in the traditional production line while meeting the basic performance index of the product.
The invention aims at realizing the following steps:
a short-flow low-cost cold-rolled DH590 steel comprises the following components in percentage by weight: c:0.05 to 0.15 percent of Mn:1.0 to 2.0 percent, si:0.2 to 1.2 percent of Al:0.5 to 5.0 percent, P is less than or equal to 0.01 percent, S is less than or equal to 0.01 percent, N is less than or equal to 0.005 percent, ca:0.005% -0.100%, mg:0.002% -0.100%, and Al/Si:2.0 to 10.0; ca+Mg:0.05 to 0.20 percent; the balance being Fe and unavoidable impurities.
The microstructure of the steel is ferrite, martensite, retained austenite and a small amount of bainite; wherein, the microstructure is as follows by volume percent: 40-80% of ferrite, 10-30% of martensite and 4-15% of residual austenite.
The yield strength of the steel is more than or equal to 330MPa, the tensile strength is more than or equal to 750 MPa, the elongation after A50 breaking is more than or equal to 30%, and the hole expansion rate is more than or equal to 60%; meets the requirements of low cost and excellent extensibility and formability of automobiles.
The reason for designing the components of the invention is as follows:
c: the carbon element guarantees the strength requirement of the steel through solid solution strengthening, and sufficient carbon element helps to stabilize austenite, so that the forming performance of the steel is improved. The content of the element C is too low to obtain the mechanical properties of the steel in the invention; too high a content can embrittle the steel and present a risk of delayed fracture. Therefore, the content of the C element is controlled to be 0.05 to 0.15 percent.
Mn: manganese is an austenite stabilizing element in steel, can enlarge an austenite phase region, reduce the critical quenching speed of the steel, and can refine grains, thereby being beneficial to solid solution strengthening to improve the strength. The content of Mn element is too low, supercooled austenite is not stable enough, and the plasticity, toughness and other processing performances of the steel plate are reduced; the too high Mn content can cause the poor welding performance of the steel plate, and the production cost is increased, which is not beneficial to industrial production. Therefore, the Mn element content is controlled to be 1.0% -2.0% in the invention.
Si: the Si element has certain solid solution strengthening effect in ferrite, so that the steel has enough strength, and meanwhile, si can inhibit the decomposition of residual austenite and the precipitation of carbide, so that the inclusions in the steel are reduced. The Si element content is too low to play a role in strengthening; the excessively high content of Si element may deteriorate the surface quality and weldability of the steel sheet. Therefore, the content of Si element is controlled to be 0.2% to 1.2% in the present invention.
Al: the aluminum element contributes to deoxidization of the molten steel. The method can also inhibit the decomposition of residual austenite and the precipitation of carbide, and accelerate the transformation of bainite to improve the coordination deformation capability. The content of Al element is too high, which not only increases the production cost, but also causes difficult continuous casting production and the like. Therefore, the content of the Al element is controlled to be 0.5-5.0%, and the content of the Al element satisfies the following conditions: 2.0 to 10.0.
P: the P element is a harmful element in steel, the plasticity and the deformability of the steel are seriously reduced, and the lower the content is, the better the steel is. In consideration of cost, the content of the P element is controlled to be less than or equal to 0.01 percent.
S: the S element is a harmful element in steel, seriously affecting the formability of the steel, and the lower the content is, the better. In view of cost, the content of S element is controlled to be less than or equal to 0.01 percent.
N: the N element is a harmful element in the steel, seriously affects the comprehensive performance of the steel, and the lower the content is, the better the content is. In view of cost, the content of N element is controlled to be less than or equal to 0.005 percent.
Ca: the addition of a small amount of Ca element is because Ca element has low price, and the Ca element can be used as a deoxidizer and an inoculant when being added into a master alloy, thereby playing a role of microalloying, further obviously refining grains and improving the comprehensive properties of steel such as plasticity, welding performance and the like; meanwhile, ca element has good desulfurization effect, can change the components, quantity and form of nonmetallic inclusion, can improve the hydrogen-induced crack resistance and lamellar tearing resistance, and can prolong the service life of parts. In order to control the production cost, the content of Ca element is controlled to be 0.005-0.100 percent.
Mg: magnesium is a good deoxidizer, desulfurizing agent and nodulizer in steel, and Mg can reduce the number of inclusions in steel, reduce the size, uniformly distribute and improve the shape. The trace magnesium can improve the carbide size and distribution of DH steel and promote the tiny and uniform carbide particles. In order to control the production cost, the content of Mg element is controlled to be 0.002% -0.100%, and the content of Ca+Mg is satisfied: 0.05 to 0.20 percent.
The second technical scheme of the invention is to provide a short-flow low-cost cold-rolled DH590 steel and a production method thereof, wherein the production method comprises converter smelting, medium-thin slab continuous casting and rolling, pickling and cold rolling, continuous annealing and finishing;
smelting in a converter: smelting by a converter to obtain molten steel which meets the following component requirements in percentage by mass: 0.05 to 0.15 percent of Mn:1.0 to 2.0 percent, si:0.2 to 1.2 percent of Al:0.5 to 5.0 percent, P is less than or equal to 0.01 percent, S is less than or equal to 0.01 percent, N is less than or equal to 0.005 percent, ca:0.005% -0.100%, mg:0.002% -0.100%, wherein Al/Si:2.0 to 10.0; ca+Mg:0.05 to 0.20 percent; the balance of Fe and unavoidable impurities, and the temperature of molten steel is between 1600 and 1700 ℃.
Continuous casting and rolling of medium thin slabs: the casting temperature is 1530-1580 ℃, the drawing speed of the casting machine is 2.5-5.5 m/min, and the thickness of the continuous casting billet is 60-115 mm. The casting blank is directly put into a furnace after being pulled out and cut, the heating temperature is controlled to be 1100-1300 ℃, the heat preservation time is 30-120 min, the initial rolling temperature is 1000-1150 ℃, the final rolling temperature is over 910 ℃, and the coiling temperature is 550-700 ℃.
Preferably, the thickness of the hot rolled steel plate after continuous casting and rolling of the medium-thin slab is 2.0-4.5 mm, and the microstructure of the hot rolled steel plate is formed by ferrite, pearlite, bainite and a small amount of cementite; the microstructure comprises, by volume, 40-80% of ferrite, 20-40% of pearlite, 5-20% of bainite, and a small amount of cementite.
Acid pickling cold rolling: the oxidized iron scales on the surface of the hot rolled steel coil are removed by acid liquor before cold rolling, and the cold rolling reduction rate is 50% -90%. Too high a reduction ratio can result in too high deformation resistance, and is difficult to roll to a target thickness; too low rolling reduction may cause a decrease in elongation of the cold-rolled steel sheet.
Continuous annealing: the belt speed is controlled at 60-240 m/min, the soaking section temperature is 780-900 ℃, the soaking time is 10-600 s, the slow cooling outlet temperature is 700-750 ℃, the rapid cooling rate is more than 25 ℃/s, the rapid cooling outlet temperature is 400-550 ℃,
and (3) finishing: the rolling force is controlled to be 1000-3000 kN and the rolling tension is 300-1500 kN in the finishing process without aging treatment and direct air cooling.
The microstructure of the cold-rolled continuous annealing product is ferrite, martensite, retained austenite and a small amount of bainite; the microstructure is as follows in volume percent: 40-80% of ferrite, 10-30% of martensite and 4-15% of residual austenite.
The soaking section temperature is 780-900 ℃, if the soaking section temperature is too high, the austenitization tends to be complete, and the ferrite proportion is insufficient, so that the ductility of the steel is reduced; if the annealing temperature is too low, the strength of the material is greatly reduced by too high a proportion of soft-phase ferrite of the final material. The soaking time is 10-600 s, if the soaking time is too long, the steel plate grains are coarse, the annealing time is too short, the steel plate is not finished with the annealing and recrystallization processes, and the elongation of the steel plate is reduced.
The short-process low-cost cold rolled DH590 steel plate with the yield strength more than or equal to 330MPa, the tensile strength more than or equal to 560 MPa, the elongation after A50 fracture more than or equal to 30 percent and the hole expansion rate more than or equal to 60 percent can be obtained through the method.
The invention has the beneficial effects that:
(1) The DH590 steel with short flow and low cost produced by the invention is prepared by optimizing the design of alloy components, taking C, mn, al, si as a main element, and not adding Cr, mo, nb, V noble metal elements, thus the alloy cost is very low.
(2) The short-flow low-cost DH590 steel produced by the invention adopts a production process of converter smelting, medium sheet billet continuous casting and rolling, pickling and cold rolling, continuous annealing and finishing, and the industrial production of the DH steel for the automobile can be realized on the traditional production line without adding new production equipment; however, the invention replaces the original continuous casting-hot feeding-hot charging-heating-hot rolling-coiling process and saves the aging process in the continuous annealing process by the continuous casting and rolling process of the medium sheet billet, obviously shortens the DH steel process flow, ensures stable production and greatly reduces the manufacturing cost of the product.
(3) The DH590 steel plate produced by the invention has the advantages of yield strength of more than or equal to 330MPa, tensile strength of more than or equal to 750 MPa, elongation after A50 fracture of more than or equal to 30%, hole expansion rate of more than or equal to 60%, and the like, and has excellent plasticity and hole expansion performance while guaranteeing the short flow and low cost of the product.
(4) The DH590 steel of low cost of short flow produced in this invention is to add the retained austenite of certain proportion on the basis of traditional cold rolling dual phase steel, under the effect of transformation induced plasticity (TRIP) effect, realize its high extension and characteristic of the high forming performance.
(5) The hot-rolled microstructure of the DH590 steel with short flow and low cost produced by the invention is composed of 40-80% of ferrite, 20-40% of pearlite, 5-20% of bainite and a small amount of cementite; the sum is 100%; the microstructure of the cold rolling continuous annealing product is 40% -80% ferrite, 10% -30% martensite and 4% -15% residual austenite.
Drawings
FIG. 1 is a golden phase diagram of a microstructure according to the present invention.
FIG. 2 is a typical engineering stress-strain curve for example 1.
Detailed Description
The invention is further illustrated by the following examples.
According to the component proportion of the technical scheme, the embodiment of the invention carries out converter smelting, continuous casting and rolling of medium-thin slabs, pickling and cold rolling, continuous annealing and finishing.
Smelting in a converter: the temperature of molten steel is 1600-1700 ℃;
continuous casting and rolling of medium thin slabs: the casting temperature is 1530-1580 ℃, the drawing speed of a casting machine is 2.5-5.5 m/min, and the thickness of a continuous casting billet is 60-115 mm; the heating temperature is 1100-1300 ℃, the heat preservation time is 30-120 min, the initial rolling temperature is 1000-1150 ℃, the final rolling temperature is over 910 ℃, and the coiling temperature is 550-700 ℃;
acid pickling cold rolling: the cold rolling reduction rate is 50% -90%;
continuous annealing: the belt speed is controlled at 60-240 m/min, the soaking section temperature is 780-900 ℃, the soaking time is 10-600 s, the slow cooling outlet temperature is 700-750 ℃, the rapid cooling rate is greater than 25 ℃/s, and the rapid cooling outlet temperature is 400-550 ℃;
and (3) finishing: the rolling force in the finishing process is controlled to be 1000-3000 kN, and the rolling tension is 300-1500 kN.
Further; the thickness of the hot rolled steel plate after continuous casting and rolling of the medium sheet billet is 2.0-4.5 mm, and the microstructure of the hot rolled steel plate is composed of ferrite, pearlite, bainite and a small amount of cementite; the microstructure comprises, by volume, 40-80% of ferrite, 20-40% of pearlite, 5-20% of bainite, and a small amount of cementite.
The composition of the steel of the example of the invention is shown in Table 1. The main technological parameters of the continuous casting and rolling of the thin slab in the steel of the embodiment of the invention are shown in table 2. The main technological parameters of pickling cold rolling and continuous annealing of the steel of the embodiment of the invention are shown in Table 3. The properties of the inventive example steels are shown in Table 4. The microstructure of the steel of the example of the invention is shown in Table 5.
TABLE 1 composition (wt%) of the inventive example steel
| Examples | C | Mn | Si | Al | Al/Si | P | S | N | Ca | Mg | Ca+Mg |
| 1 | 0.12 | 1.64 | 0.28 | 0.64 | 2.3 | 0.002 | 0.001 | 0.001 | 0.062 | 0.013 | 0.08 |
| 2 | 0.09 | 1.73 | 0.85 | 1.93 | 2.3 | 0.001 | 0.002 | 0.001 | 0.036 | 0.023 | 0.06 |
| 3 | 0.13 | 1.48 | 0.37 | 0.96 | 2.6 | 0.001 | 0.001 | 0.002 | 0.072 | 0.017 | 0.09 |
| 4 | 0.1 | 1.26 | 1.14 | 4.28 | 3.8 | 0.003 | 0.001 | 0.001 | 0.018 | 0.062 | 0.08 |
| 5 | 0.07 | 1.92 | 0.93 | 4.73 | 5.1 | 0.001 | 0.002 | 0.002 | 0.093 | 0.081 | 0.17 |
| 6 | 0.06 | 1.36 | 1.02 | 3.53 | 3.5 | 0.001 | 0.003 | 0.001 | 0.068 | 0.036 | 0.10 |
| 7 | 0.15 | 1.82 | 0.66 | 4.17 | 6.3 | 0.002 | 0.001 | 0.001 | 0.052 | 0.009 | 0.06 |
| 8 | 0.14 | 1.57 | 0.47 | 2.86 | 6.1 | 0.003 | 0.002 | 0.002 | 0.038 | 0.045 | 0.08 |
| 9 | 0.05 | 1.36 | 1.18 | 3.58 | 3.0 | 0.002 | 0.003 | 0.003 | 0.066 | 0.081 | 0.15 |
| 10 | 0.11 | 1.49 | 0.74 | 1.95 | 2.6 | 0.001 | 0.001 | 0.001 | 0.053 | 0.074 | 0.13 |
Note that: al/Si has no unit.
TABLE 2 main process parameters of continuous casting and rolling of sheet billet in the steel of the example of the invention
TABLE 3 main process parameters for pickling cold rolling and continuous annealing of the inventive example steels
TABLE 4 Properties of the inventive example Steel
As is clear from the above, the DH590 steel plate produced by the invention has the advantages of yield strength of more than or equal to 330MPa, tensile strength of more than or equal to 750 MPa, elongation after A50 breaking of more than or equal to 30%, hole expansion rate of more than or equal to 60%, and the like, and has the advantages of ensuring short flow and low cost of the product and simultaneously achieving excellent plasticity and hole expansion performance.
The present invention has been properly and fully described in the foregoing embodiments by way of example only, and not by way of limitation, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, any modification, equivalent substitution, improvement, etc. should be included in the scope of the invention, and the scope of the invention is defined by the claims.
Claims (4)
1. A short-process low-cost cold-rolled DH590 steel is characterized by comprising the following components in percentage by weight: c:0.05 to 0.15 percent of Mn:1.0 to 2.0 percent, si:0.2 to 1.2 percent of Al: 0.96-5.0%, P is less than or equal to 0.01%, S is less than or equal to 0.01%, N is less than or equal to 0.005%, ca:0.005% -0.100%, mg:0.002% -0.100%, and Al/Si:2.0 to 10.0; ca+Mg:0.05 to 0.20 percent, and the balance of Fe and unavoidable impurities; the microstructure of the steel is ferrite, martensite and residual austenite; wherein, the microstructure is as follows by volume percent: 40-80% of ferrite, 10-30% of martensite and 4-15% of residual austenite.
2. The short-process low-cost cold rolled DH590 steel of claim 1, wherein the yield strength of the steel is not less than 330MPa, the tensile strength is not less than 590MPa, the elongation after A50 break is not less than 30%, and the hole expansion rate is not less than 60%.
3. A method for producing a short-process low-cost cold-rolled DH590 steel as claimed in claim 1 or 2, comprising converter smelting, continuous casting and rolling of medium thin slabs, pickling and cold rolling, continuous annealing and finishing; the method is characterized in that:
smelting in a converter: the temperature of molten steel is 1600-1700 ℃;
continuous casting and rolling of medium thin slabs: casting temperature is 1530-1580 ℃, the drawing speed of a casting machine is 2.5-5.5 m/min, and the thickness of a continuous casting billet is 60-115 mm; the heating temperature is 1100-1300 ℃, the heat preservation time is 30-114 min, the initial rolling temperature is 1000-1150 ℃, the final rolling temperature is over 910 ℃, and the coiling temperature is 668-700 ℃;
acid pickling cold rolling: the cold rolling reduction rate is 50% -90%;
continuous annealing: the belt speed is controlled to be 60-240 m/min, the soaking section temperature is 780-900 ℃, the soaking time is 10-600 s, the slow cooling outlet temperature is 700-750 ℃, the rapid cooling rate is greater than 25 ℃/s, and the rapid cooling outlet temperature is 461-550 ℃;
and (3) finishing: the rolling force in the finishing process is controlled to be 1000-3000 kN, and the rolling tension is 300-1500 kN.
4. A method of producing a short-process low-cost cold rolled DH590 steel as claimed in claim 3, wherein:
the thickness of the hot rolled steel plate after continuous casting and rolling of the medium sheet billet is 2.0-4.5 mm, and the microstructure of the hot rolled steel plate is ferrite, pearlite, bainite and a small amount of cementite; the microstructure comprises, by volume, 40-80% of ferrite, 20-40% of pearlite, 5-20% of bainite, and a small amount of cementite.
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