CN115491593B - Hot rolled thin strip steel with tensile strength more than or equal to 1800MPa and produced by adopting TSR production line and method - Google Patents
Hot rolled thin strip steel with tensile strength more than or equal to 1800MPa and produced by adopting TSR production line and method Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 81
- 239000010959 steel Substances 0.000 title claims abstract description 81
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 45
- 238000000034 method Methods 0.000 title abstract description 23
- 238000001816 cooling Methods 0.000 claims abstract description 25
- 238000005096 rolling process Methods 0.000 claims abstract description 24
- 238000005098 hot rolling Methods 0.000 claims abstract description 8
- 238000007670 refining Methods 0.000 claims abstract description 6
- 238000003723 Smelting Methods 0.000 claims abstract description 5
- 238000005266 casting Methods 0.000 claims description 18
- 238000009749 continuous casting Methods 0.000 claims description 16
- 229910000734 martensite Inorganic materials 0.000 claims description 16
- 229910052757 nitrogen Inorganic materials 0.000 claims description 10
- 230000009467 reduction Effects 0.000 claims description 10
- 229910052804 chromium Inorganic materials 0.000 claims description 5
- 239000011261 inert gas Substances 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 239000000443 aerosol Substances 0.000 claims description 3
- 229910001563 bainite Inorganic materials 0.000 claims description 2
- 239000012535 impurity Substances 0.000 claims description 2
- 238000005265 energy consumption Methods 0.000 abstract description 10
- 238000010438 heat treatment Methods 0.000 abstract description 8
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 abstract description 6
- 238000000137 annealing Methods 0.000 abstract description 4
- 238000005097 cold rolling Methods 0.000 abstract description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 abstract description 3
- 239000001569 carbon dioxide Substances 0.000 abstract description 3
- 230000003746 surface roughness Effects 0.000 abstract description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- 230000008569 process Effects 0.000 description 12
- 229910052799 carbon Inorganic materials 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 7
- 229910001566 austenite Inorganic materials 0.000 description 7
- 239000011651 chromium Substances 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- 239000010955 niobium Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 229910052796 boron Inorganic materials 0.000 description 5
- 239000011572 manganese Substances 0.000 description 5
- 229910052758 niobium Inorganic materials 0.000 description 5
- 238000010791 quenching Methods 0.000 description 5
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 4
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 4
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910052748 manganese Inorganic materials 0.000 description 4
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 4
- 230000000171 quenching effect Effects 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 229910052717 sulfur Inorganic materials 0.000 description 4
- 239000011593 sulfur Substances 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 229910052720 vanadium Inorganic materials 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 229910000797 Ultra-high-strength steel Inorganic materials 0.000 description 2
- CFJRGWXELQQLSA-UHFFFAOYSA-N azanylidyneniobium Chemical compound [Nb]#N CFJRGWXELQQLSA-UHFFFAOYSA-N 0.000 description 2
- SKKMWRVAJNPLFY-UHFFFAOYSA-N azanylidynevanadium Chemical compound [V]#N SKKMWRVAJNPLFY-UHFFFAOYSA-N 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 2
- 239000002918 waste heat Substances 0.000 description 2
- 241001391944 Commicarpus scandens Species 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- QISGROBHHFQWKS-UHFFFAOYSA-N [C].[Nb] Chemical compound [C].[Nb] QISGROBHHFQWKS-UHFFFAOYSA-N 0.000 description 1
- HJIYJLZFNBHCAN-UHFFFAOYSA-N [V].[C] Chemical compound [V].[C] HJIYJLZFNBHCAN-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- VCTOKJRTAUILIH-UHFFFAOYSA-N manganese(2+);sulfide Chemical class [S-2].[Mn+2] VCTOKJRTAUILIH-UHFFFAOYSA-N 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000007712 rapid solidification Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000010301 surface-oxidation reaction Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000003466 welding Methods 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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- 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
- B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
- B22D11/0637—Accessories therefor
- B22D11/0697—Accessories therefor for casting in a protected atmosphere
-
- 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
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/1206—Accessories for subsequent treating or working cast stock in situ for plastic shaping of strands
-
- 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
-
- 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
- B22D11/20—Controlling or regulating processes or operations for removing cast stock
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
-
- C—CHEMISTRY; METALLURGY
- 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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
The hot rolled thin strip steel with the tensile strength of more than or equal to 1800MPa grade produced by adopting a TSR production line comprises the following components in percentage by weight: c:0.28 to 0.34 percent, si:0.1-0.5%, mn:1.4 to 3.0 percent, P is less than or equal to 0.01 percent, S is less than or equal to 0.01 percent, als:0.015 to 0.050 percent, cr is not more than 1.0 percent, N is not more than 0.005 percent, nb:0.01 to 0.05 percent or V: 0.06-0.20% of one or two of the components; the production method comprises the following steps: conventional smelting and refining; pouring into a blank; hot rolling; cooling; naturally cooling to room temperature after coiling; and (5) cold forming after unreeling and blanking. The invention not only can ensure the mechanical property, but also can reduce the procedures of repeated heating, multiple dephosphorization, multipass rolling and the like of the strip steel in the production process, and can cancel the procedures of cold rolling and annealing heat treatment, thereby reducing the energy consumption by more than 70 percent and the carbon dioxide emission by more than 60 percent, and the surface roughness of the product is reduced from the traditional 1.5-3 mu m to less than 1 mu m.
Description
Technical Field
The invention relates to a steel material and a manufacturing method thereof, and particularly belongs to hot rolled thin strip steel with tensile strength of more than or equal to 1800MPa and with the tensile strength of 0.5-2.0 mm produced by adopting a double-roll thin strip casting and rolling (TSR) production line and a manufacturing method thereof.
Background
Light weight is an important way to realize the green low carbon development of the automobile industry. The advanced high-strength steel and the ultra-high-strength steel are adopted for the lightweight design and manufacture of the car body safety structural member, so that the collision safety of the whole car can be improved, the oil consumption or the energy consumption can be reduced, and the car body safety structural member is favored by automobile companies at home and abroad. The martensitic steel belongs to ultra-high strength steel and can be directly used for parts such as automobile anti-collision beams, threshold, carriages and the like; in recent years, steel companies at home and abroad start development work of ultra-high strength martensitic steel based on respective production lines.
Typical martensitic steel sheet has a tensile strength in the range of 1000 to 1800MPa and is produced by the following process route: molten steel smelting, continuous casting, cooling, casting blank heating, hot continuous rolling, cooling, coiling, uncoiling, pickling, cold rolling, coiling, uncoiling, heating, annealing, cooling and coiling. Such as the Chinese patent publication No. CN 109898018A, CN 114086071A and CN 111519109A. In the production route, the raw materials need to be repeatedly coiled and uncoiled, heated and cooled, hot rolled, cold rolled and the like, and the defects of complex process flow, long production period and high energy consumption exist, so that the production cost of the materials is greatly increased. Currently, the development of the ultra-high strength thin steel plate with low energy consumption, low cost and high quality is an important research direction of steel companies based on the national and foreign 'double carbon' policy requirement and the cost reduction requirement of automobile companies.
The near net shape steel production technology eliminates the cold rolling and annealing heat treatment procedures of the traditional sheet, directly replaces the traditional cold-rolled sheet with the hot-rolled sheet of sheet billet continuous casting and rolling or sheet strip continuous casting and rolling, has the remarkable advantages of simple process flow, consumption reduction, energy saving and low production cost, and causes wide attention in the industry. However, due to the technical characteristics of the rapid solidification process, the tissue uniformity of the produced thin strip steel is easily affected by the design of the material composition; meanwhile, as the thin slab or the thin strip is adopted for continuous casting and rolling production, the total rolling reduction of the thickness of the material is far smaller than that of the traditional process, and the fine grain strengthening effect of the structure is greatly different from that of the traditional process. Therefore, the ultra-high strength automobile sheet steel produced by adopting the near net shape technology cannot simply and directly adopt the traditional product technology, and innovation and breakthrough are required in component design and production process.
As retrieved:
the document of Chinese patent publication No. CN 106381451A discloses a hot rolled martensitic steel of 1000MPa grade produced by a CSP sheet billet continuous casting and rolling process and a production method thereof, but the martensitic steel has lower tensile strength (only 1000 MPa). The document of Chinese patent publication No. CN 112522571A discloses a method for producing a martensitic steel strip by continuous casting of a thin strip, but the method requires rapid cooling (the cooling rate is more than 120 ℃/s) of the hot rolled steel strip, so that the actual production difficulty is high and the uniformity of the product performance is difficult to ensure.
Aiming at the defects in the prior art, a novel low-cost 1800MPa grade ultra-high strength martensitic steel near-net-shape manufacturing method is researched and designed, so that the problems in the prior art are overcome.
Disclosure of Invention
The invention aims to overcome the defects of complex process, high energy consumption and large fluctuation of product performance uniformity in the prior art, and provides hot rolled thin strip steel and a method, which can reduce the energy consumption by more than 70 percent and reduce the carbon dioxide emission by more than 60 percent on the premise of ensuring the strength level, reduce the roughness of the product surface from 1.5-3 mu m to less than 1 mu m, further simplify the production flow, and ensure that a user does not need to acid wash the hot rolled thin strip steel produced by adopting a TSR production line before forming, wherein the tensile strength of the hot rolled thin strip steel is more than or equal to 1800 MPa.
Measures for achieving the above object:
the hot rolled thin strip steel with the tensile strength of more than or equal to 1800MPa grade produced by adopting a TSR production line comprises the following components in percentage by weight: c:0.28 to 0.34 percent, si:0.1 to 0.5 percent, mn:1.4 to 3.0 percent, P is less than or equal to 0.01 percent, S is less than or equal to 0.01 percent, als:0.015 to 0.050 percent, cr is not more than 1.0 percent, N is not more than 0.005 percent, nb:0.01 to 0.05 percent or V: 0.06-0.20% of one or two of the components, and the balance of Fe and unavoidable impurities; the metallographic structure is full martensite or bainite with martensite plus volume ratio not more than 10%.
Preferably: the weight percentage content of Cr is 0.46-0.95%.
Further: the weight percentage of the added B is not more than 0.001 percent.
A method for producing hot rolled thin strip steel with tensile strength more than or equal to 1800MPa by adopting a TSR production line comprises the following production steps:
1) Conventionally smelting and refining to obtain molten steel with set components;
2) Casting into thin blanks by using a twin-roll casting and rolling device, wherein: controlling the molten steel to perform protection continuous casting in conventional inert gas; continuously casting into thin blanks with the thickness of 1.0-2.5 mm at the blank pulling speed of 46-117 m/min;
3) Hot rolling to product thickness, during which: controlling the single-pass reduction ratio to be 20-60% and the final rolling temperature to be 820-1000 ℃; the thickness of the product is 0.5-2.0 mm;
4) Cooling by adopting a laminar flow mode or an aerosol mode, and cooling to a coiling temperature at a cooling speed of not less than 80 ℃/s;
5) Coiling, wherein the coiling temperature is controlled to be not more than 220 ℃;
6) Naturally cooling the mixture to the room temperature,
7) And (5) cold forming is carried out after uncoiling and blanking.
Preferably: the coiling temperature is 160-213 ℃.
The action and mechanism of each element and main process in the invention:
c: carbon is the basic element in steel and is also the most economical and effective strengthening element. The design of the carbon content is low, and the strength is reduced after hot stamping forming; however, too high a carbon content reduces the plasticity of the steel and is disadvantageous in terms of weldability. Therefore, the carbon percentage control range in the invention is 0.28-0.34% from the economical and comprehensive performance aspects.
Si: silicon plays a solid solution strengthening role in steel, and adding Si into the steel can improve the purity and deoxidization of the steel, but too high a silicon content can cause deterioration of weldability and toughness of a welding heat affected zone. Therefore, the Si content used in the present invention is in the range of 0.1 to 0.5%.
Mn: manganese has solid solution strengthening effect, and is one of important elements for improving the strength of the material; however, too high a manganese content tends to adversely affect weldability. Therefore, the upper limit of manganese is set to 3.0%, and the content of manganese added in the invention is 1.4-3.0%.
P: phosphorus is a harmful element in steel, and is easy to cause center segregation of casting blanks. Grain boundaries are easily segregated in the subsequent hot continuous rolling heating process, so that the brittleness of the steel is remarkably increased. Meanwhile, the content of the alloy is controlled below 0.01% based on cost consideration and without affecting the performance of the steel.
S sulfur is a very harmful element. Sulfur in steel is often present in the form of manganese sulfides, which inclusions deteriorate the toughness of the steel and cause anisotropy of properties, and therefore, it is necessary to control the sulfur content of the steel to be as low as possible. The sulfur content in the steel is controlled below 0.01% based on the manufacturing cost.
Als: aluminum is added for deoxidization, and when the content of Als is less than 0.015%, the effect thereof cannot be exerted; on the other hand, alumina agglomerates and inclusions are easily formed by adding a large amount of aluminum; therefore, the aluminum content is controlled to be in the range of 0.015 to 0.050%.
Cr is an important element for improving the hardenability of steel, and is dissolved in austenite to improve the stability of the austenite, thereby being beneficial to improving the hardenability of the steel; meanwhile, chromium can improve the tempering stability of steel. And after the chromium content exceeds 1.0%, the effect of improving the hardenability is rich, and the cast strip obtained by continuous casting is easy to generate surface cracks at high drawing speed, so that the strip breakage and steel leakage are caused or the surface quality of the product is affected. Therefore, the chromium content is controlled within 1.0 percent, and the weight percent of Cr is preferably 0.46 to 0.95 percent.
Nitrogen can improve the strength of the steel; however, the binding force of nitrogen, niobium and vanadium is strong, coarse niobium nitride and vanadium nitride can be formed in the high Wen Shigang, and the plasticity and toughness of the steel are seriously damaged; in addition, higher nitrogen content increases the micro-alloying element content required to stabilize the nitrogen element, thereby increasing costs. Therefore, the content of nitrogen element should be reduced as much as possible, and the nitrogen content in the present invention is controlled to be less than 0.005%.
Nb: niobium is a strong C, N carbide forming element. A small amount of niobium is added into the steel to form a certain amount of niobium carbon and niobium nitride, thereby preventing austenite grains from growing and refining the austenite grains, and greatly improving the strength and toughness of the steel after hot forming quenching; the purpose of adding a small amount of titanium into the steel is to fix the N element in the steel and avoid the combination of B and N. However, excessive niobium combines with C to form coarse carbonitrides, thereby reducing the hardness and strength of the martensite after quenching of the test steel. Therefore, the total content thereof is controlled to be in the range of 0.01 to 0.05%.
V is also a strong C, N compound forming element, can play a role in refining austenite grains, and a certain amount of vanadium carbon and vanadium nitride can be formed by adding a small amount of vanadium into the steel, so that the growth of the austenite grains is prevented, and therefore, the quenched martensite lath is smaller in size, and the strength of the steel is greatly improved. So the content is controlled to be between 0.06 and 0.20 percent.
B, boron is an element for strongly improving hardenability. The element is an optional element in the present invention. The quenching degree can be improved by times by adding only trace amount, so that other expensive metal elements are saved. The hardenability of the steel can be obviously improved by adding trace boron elements into the steel; however, the boron content is higher than 0.001%, and the cast strip obtained by continuous casting is easy to generate surface cracks at high drawing speed, thereby causing strip breakage and steel leakage or affecting the surface quality of the product. Therefore, the boron content in the present invention is controlled to 0.001% or less.
The invention controls molten steel to carry out thin strip continuous casting under the protection of conventional inert gas, and the thickness of the casting strip is 1.0-2.5 mm, because of the thinner original casting strip thickness, the subsequent hot rolling thinning pass can be effectively reduced, and the production energy consumption is reduced; however, the thickness of the cast strip is too thin, and the cast strip is easy to break under high stretching of cast rolling, so that the production continuity is affected. The molten steel is controlled to carry out continuous casting of the thin strip under the protection of conventional inert gas, so that the surface oxidation of the continuous casting thin strip can be avoided, the production strip breakage caused by pressing oxide into the continuous casting thin strip is prevented, and the surface quality of a product is improved.
The invention controls the single-pass reduction ratio to be 20-60% and the finishing temperature to be the final rolling temperature, and the larger hot rolling reduction ratio can refine the grain of the strip steel, thereby being beneficial to improving the strength of the material. However, the single pass rolling reduction is too large, which is disadvantageous for controlling the plate shape, and the rolling load increases; considering that the patent only adopts single hot rolling, the rolling reduction is controlled within 60 percent in order to ensure that the shape and thickness precision of the product plate are controllable. In order to avoid the influence on the material performance caused by mixed crystal in the hot rolling stage, the final rolling temperature cannot be lower than the cooling recrystallization temperature of high-temperature austenite; meanwhile, the oxidation thickness of the surface of the strip steel increases along with the increase of the finishing temperature, so the finishing temperature of the patent is controlled within.
The invention controls the blank drawing speed to be 46-117 m/min because the casting and rolling speed is related to the drawing speed of the continuous casting thin strip and the steel production efficiency. The high pulling speed is beneficial to improving the production efficiency, but molten steel is easy to solidify in time in the double-roll casting machine, and the breakage and the steel leakage of the casting belt are induced; lower stretching will affect production efficiency, increase production costs, simultaneously will lead to cold hardening of the cast strip, increase subsequent rolling load and energy consumption, and be detrimental to control of strip shape.
The cooling to 220 ℃ or lower at a cooling rate of 70 ℃ per second or more is controlled, and preferably the cooling coiling temperature is 160-213 ℃ because the critical cooling rate and critical finishing temperature of the thin steel plate which is developed by the invention and is converted into martensite in the cooling process are not enough to quench the thin steel plate to reach the required strength. The waste heat of the plate and the strip can be used for carrying out self-tempering treatment at the temperature of the plate, so that the internal stress generated during quenching is reduced or eliminated, and the plasticity of the strip steel is improved; meanwhile, the strip steel can utilize waste heat to reduce the deformation resistance of the strip steel, and is convenient to coil.
Compared with the prior art, the method has the advantages that through adding Nb or V or the composite addition of the Nb and the V, controlling Cr in the components or adding elements such as B in a proper amount, adopting a TSR short-flow process to produce the martensitic steel with the tensile strength of 1800MPa, not only can the mechanical property be ensured, but also the procedures of repeated heating, multiple dephosphorization, multiple pass rolling and the like of the strip steel in the production process can be reduced, and the procedures of cold rolling and annealing heat treatment can be eliminated, thereby the energy consumption can be reduced by more than 70%, the carbon dioxide emission can be reduced by more than 60%, and the surface roughness of the product is reduced from the traditional 1.5-3 mu m to less than 1 mu m.
Drawings
FIG. 1 is a view showing the metallographic structure of a steel sheet according to the present invention as fully martensitic.
Detailed Description
The present invention will be described in detail below:
table 1 is a listing of chemical components of each example and comparative example of the present invention;
table 2 is a list of the main process parameters for each example and comparative example of the present invention;
table 3 shows a list of performance test results for each of the examples and comparative examples of the present invention.
The production of each embodiment of the invention is carried out according to the following steps:
1) Conventionally smelting and refining to obtain molten steel with set components;
2) Casting into thin blanks by using a twin-roll casting and rolling device, wherein: controlling the molten steel to perform protection continuous casting in conventional inert gas; continuously casting into thin blanks with the thickness of 1.0-2.5 mm at the blank pulling speed of 46-117 m/min;
3) Hot rolling to product thickness, during which: controlling the single-pass reduction ratio to be 20-60% and the final rolling temperature to be 820-1000 ℃; the thickness of the product is 0.5-2.0 mm;
4) Cooling by adopting a laminar flow mode or an aerosol mode, and cooling to a coiling temperature at a cooling speed of not less than 70 ℃/s;
5) Coiling, wherein the coiling temperature is controlled to be not more than 220 ℃;
6) Naturally cooling the mixture to the room temperature,
7) And (5) cold forming is carried out after uncoiling and blanking.
Table 1 chemical composition (wt.%) of each example and comparative example of the present invention
Table 2 list of values of the main process parameters for each example and comparative example of the present invention
TABLE 3 Performance test results for each example and comparative example of the present invention
As can be seen from Table 3, through the TSR twin-roll strip casting process, the tensile strength of the direct cold forming of the inventive sheet steel reaches more than 1800MPa, and is far higher than the strength of the existing TSR production line products; the method has important significance for propelling the light-weight horizontal lifting of the automobile and reducing the energy consumption and carbon emission of steel production.
This embodiment is merely a best example and is not intended to limit the implementation of the technical solution of the present invention.
Claims (2)
1. The method for producing hot rolled thin strip steel with tensile strength more than or equal to 1800MPa by adopting a TSR production line is characterized by comprising the following production steps:
1) Conventionally smelting and refining to obtain molten steel with set components;
2) Casting into thin blanks by using a twin-roll casting and rolling device, wherein: controlling the molten steel to perform protection continuous casting in conventional inert gas; continuously casting into thin blanks with the thickness of 1.0-2.3 mm at the blank drawing speed of 46-85 m/min or at the blank drawing speed of 100-117 m/min;
3) Hot rolling to product thickness, during which: controlling the single-pass reduction ratio to be 20-60% and the final rolling temperature to be 820-893 ℃;
the thickness of the product is 0.5-2.0 mm;
4) Cooling by adopting a laminar flow mode or an aerosol mode, and cooling to a coiling temperature at a cooling speed of not less than 70 ℃/s;
5) Coiling, wherein the coiling temperature is controlled to be not more than 220 ℃;
6) Naturally cooling the mixture to the room temperature,
7) Cold forming after uncoiling and blanking;
the hot rolled thin strip steel produced by adopting the TSR production line has the tensile strength of more than or equal to 1800MPa, and comprises the following components in percentage by weight: c:0.31 to 0.34 percent, si:0.1 to 0.5 percent, mn:2.72 to 2.91 percent, P is less than or equal to 0.01 percent, S is less than or equal to 0.01 percent, als:0.015 to 0.050 percent, 0.83 to 1.0 percent of Cr, less than or equal to 0.005 percent of N and less than or equal to Nb:0.01 to 0.05 percent or V: 0.06-0.20% of one or two of the components, and the balance of Fe and unavoidable impurities; the metallographic structure is full martensite or bainite with martensite plus volume ratio not more than 10%.
2. The method for producing hot rolled thin strip steel with the tensile strength of more than or equal to 1800MPa by adopting a TSR production line as claimed in claim 1, which is characterized in that: the coiling temperature is 160-213 ℃.
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