CN103249847B - Method for manufacturing high-strength cold-rolled/hot-rolled trip steel having a tensile strength of 590 mpa grade, superior workability, and low mechanical-property deviation - Google Patents
Method for manufacturing high-strength cold-rolled/hot-rolled trip steel having a tensile strength of 590 mpa grade, superior workability, and low mechanical-property deviation Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 78
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 38
- 229910000831 Steel Inorganic materials 0.000 title claims description 121
- 239000010959 steel Substances 0.000 title claims description 121
- 229910000794 TRIP steel Inorganic materials 0.000 claims abstract description 36
- 238000005266 casting Methods 0.000 claims abstract description 12
- 238000005096 rolling process Methods 0.000 claims description 121
- 238000001816 cooling Methods 0.000 claims description 54
- 238000000137 annealing Methods 0.000 claims description 31
- 230000008569 process Effects 0.000 claims description 28
- 238000005098 hot rolling Methods 0.000 claims description 25
- 238000010438 heat treatment Methods 0.000 claims description 22
- 238000009749 continuous casting Methods 0.000 claims description 20
- 238000005097 cold rolling Methods 0.000 claims description 19
- 230000009466 transformation Effects 0.000 claims description 19
- 239000012535 impurity Substances 0.000 claims description 18
- 238000009825 accumulation Methods 0.000 claims description 16
- 238000007669 thermal treatment Methods 0.000 claims description 13
- 230000007704 transition Effects 0.000 claims description 12
- 238000004458 analytical method Methods 0.000 claims description 10
- 238000010791 quenching Methods 0.000 claims description 9
- 229910052720 vanadium Inorganic materials 0.000 claims description 8
- 238000005554 pickling Methods 0.000 claims description 6
- 229910001566 austenite Inorganic materials 0.000 description 42
- 230000000694 effects Effects 0.000 description 28
- 238000012360 testing method Methods 0.000 description 13
- 230000008859 change Effects 0.000 description 12
- 238000005516 engineering process Methods 0.000 description 10
- 238000005728 strengthening Methods 0.000 description 9
- 238000005204 segregation Methods 0.000 description 8
- 238000009628 steelmaking Methods 0.000 description 8
- 229910000859 α-Fe Inorganic materials 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 7
- 229910001567 cementite Inorganic materials 0.000 description 6
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical group C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 6
- 238000000151 deposition Methods 0.000 description 5
- 229920006395 saturated elastomer Polymers 0.000 description 5
- 230000004075 alteration Effects 0.000 description 4
- 229910001563 bainite Inorganic materials 0.000 description 4
- 230000008021 deposition Effects 0.000 description 4
- 230000006698 induction Effects 0.000 description 4
- 229910052758 niobium Inorganic materials 0.000 description 4
- 230000008520 organization Effects 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 229910000734 martensite Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
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- 230000006866 deterioration Effects 0.000 description 2
- 230000003628 erosive effect Effects 0.000 description 2
- 238000003801 milling Methods 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 238000003303 reheating Methods 0.000 description 2
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- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 238000010586 diagram Methods 0.000 description 1
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Classifications
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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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- 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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
- B21B3/02—Rolling special iron alloys, e.g. stainless steel
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- Mechanical Engineering (AREA)
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- Metallurgy (AREA)
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- Crystallography & Structural Chemistry (AREA)
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- Heat Treatment Of Steel (AREA)
Abstract
The aim of the present invention is to provide a method for manufacturing high-strength cold-rolled TRIP steel having a tensile strength of 590 MPa grade and low mechanical-property deviation, in which a thin-slab casting technique is employed to ensure superior workability and also significantly reduce widthwise and lengthwise mechanical-property deviation in a strip.
Description
Technical field
The present invention relates to a kind of manufacture tensile strength grade be 590MPa, excellent workability and mechanical property deviation little high strength cold-rolled/hot rolling TRIP(phase change induction plasticity) method of steel, more particularly, relate to a kind of utilize thin slab foundry engieering to manufacture there is excellent unit elongation and mechanical property deviation little high strength cold-rolled/method of analysis of producing hot rolled TRIP.
Background technology
Recently, along with in automotive industry to improving the fuel efficiency of motor vehicle and strengthening the demand of the safety regulations to officer and passenger, carrying out the abundant research to the high body of motor vehicle of the lightweight intensity of the anti-collision that can provide improvement.
Therefore, in order to meet light-weight characteristics and the intensity high characteristic of body of motor vehicle simultaneously, intensively developing and using the high tensile steel plate of 590MPa level or higher category.In addition, because the steel plate for motor vehicle is processed mainly through punching press, so they should have excellent press formability, in order to ensure such press formability, need the product made from steel manufacturing the phase transformation strengthening with excellent workability.In the steel grade with phase change structure, DP(two-phase) steel and TRIP(phase change induction plasticity) steel is the known high-strength steel with excellent workability.Specifically, as in known in the art, due to the high-elongation behavior caused by the phase change induction plasticity of residual austenite, so TRIP steel is widely used in the complex-shaped parts needing to have high workability.
TRIP steel is the residual austenite steel with three-phase mixed structure comprising ferrite and bainite by allowing the austenite at high temperature existed at room temperature still to retain.In this TRIP steel, suitable heating and cooling thermal treatment and add the Austenite strengthening element of such as C, Si, Mn etc., makes the austenite of 5% ~ 20% residual at room temperature.When this austenite as metastable phase stands dimensional deformation mutually, it changes martensite into.When undergoing phase transition by this way, the higher and necking down resistance of work hardening exponent can increase, and makes excellent workability compared with traditional steel.
For the method manufacturing this high strength cold-rolled TRIP steel, it is known that No. 5470529, No. 6319338, No. 6544354 and No. 6210496 United States Patent (USP) and 2003-0002581 Korean unexamined patent open, in No. 5017248 and No. 5030298 United States Patent (USP) and No. 2015391, No. 2559272, No. 2820774 and No. 1871742 Japanese Patent, disclose the method manufacturing high-strength hot-rolled TRIP steel.But these existing inventions belong to the manufacture method utilizing traditional rolling mill technology, these methods undesirably and inevitably cause occurring the problem of the deviation of significant width in mechanical property and length direction in actual production line.
Simultaneously, corresponding to Novel steelmaking process be recently subject to small section mill technique that a lot of mode of being cast by thin slab paid close attention to manufactures steel plate due to the width of band steel and the temperature contrast of length direction little and arouse attention, make it possible to produce the steel with phase change structure that deviation in mechanical property is low.But, as open disclosed at No. 02019314 European patent, No. 2009-0214377 and 2009-0151821 U.S. Patent application and WO00/055381 PCT, these inventions relate generally to after hot rolling until need to perform the operation of cooling technology in the process of batching, and do not propose to utilize micro-type rolling mill manufacture technics to have the method for the Cold-Rolled TRIP Steel of higher mechanical property.
Summary of the invention
Technical problem
Therefore, make the present invention when considering the problems referred to above occurred in prior art, and one object of the present invention be to provide a kind of manufacture tensile strength grade be 590MPa and mechanical property deviation little high strength cold-rolled/method of analysis of producing hot rolled TRIP, wherein, thin slab foundry engieering can be adopted guarantee excellent workability and reduce the deviation being with the mechanical property of steel on width and length direction significantly.
Technical scheme
To achieve these goals, the invention provides manufacture method below.
The invention provides a kind of method being manufactured Cold-Rolled TRIP Steel by following step: the steel making to comprise by weight percentage following component becomes through continuous casting the thin slab that thickness is 30mm ~ 150mm: the C of 0.05% ~ 0.20%, the Si of 0.8% ~ 2.0%, the Mn of 1.2% ~ 2.2%, the P of 0.001% ~ 0.1%, the S of 0.001% ~ 0.02%, the Al of 0.01% ~ 2.0%, the N of 0.001% ~ 0.02%, the Sb of 0.005% ~ 0.1%, total amount is 0.18% or less incidental element (Cu+Cr+Ni+Sn+Pb), and the Fe of surplus and other inevitable impurity, make described thin slab through roughing, heating, finish rolling and batch, producing hot rolled strip thus, and by the band steel after hot rolling through overpickling, cold rolling, continuous annealing and cooling heat process, wherein, performing finish rolling makes the rolling speed difference of single band steel be 15% or lower, and perform cooling heat process by this way, namely, with the rate of cooling of 1 DEG C/s ~ 20 DEG C/s, the band steel after continuous annealing is slowly cooled to 620 DEG C ~ 690 DEG C, quench with the rate of cooling of 20 DEG C/s ~ 100 DEG C/s immediately, then stand isothermal transformation thermal treatment at 310 DEG C ~ 420 DEG C.
In addition, the invention provides a kind of method being manufactured Cold-Rolled TRIP Steel by following step: the steel making to comprise by weight percentage following component becomes through continuous casting the thin slab that thickness is 30mm ~ 150mm: the C of 0.05% ~ 0.20%, the Si of 0.8% ~ 2.0%, 1.2% ~ 2.2% Mn, the P of 0.001% ~ 0.1%, S, the Al of 0.01% ~ 2.0%, N, the total amount of 0.001% ~ 0.02% of 0.001% ~ 0.02% be 0.18% or the Fe of less incidental element (Cu+Cr+Ni+Sn+Pb) and surplus and other inevitable impurity, make described thin slab through roughing, heating, finish rolling and batch, producing hot rolled strip thus, and by the band steel after hot rolling through overpickling, cold rolling, continuous annealing and cooling heat process, wherein, finish rolling is performed as in the scope of target temperature ± 20 that the rolling temperature of finish to gauge frame fallen into calculated by relational expression [910-225C-65Mn+15Si+10P] DEG C, and perform cooling heat process by this way, namely, with the rate of cooling of 1 DEG C/s ~ 20 DEG C/s, the band steel after continuous annealing is slowly cooled to 620 DEG C ~ 690 DEG C, quench with the rate of cooling of 20 DEG C/s ~ 100 DEG C/s immediately, then isothermal transformation thermal treatment is stood at 310 DEG C ~ 420 DEG C.
In addition, the invention provides a kind of method being manufactured Cold-Rolled TRIP Steel by following step: the steel making to comprise by weight percentage following component becomes through continuous casting the thin slab that thickness is 30mm ~ 150mm: the C of 0.05% ~ 0.20%, the Si of 0.8% ~ 2.0%, the Mn of 1.2% ~ 2.2%, P, the S of 0.001% ~ 0.02%, Al, the N of 0.001% ~ 0.02%, Sb, the total amount of 0.005% ~ 0.1% of 0.01% ~ 2.0% of 0.001% ~ 0.1% are 0.18% or the Fe of less incidental element (Cu+Cr+Ni+Sn+Pb) and surplus and other inevitable impurity, make described thin slab through roughing, heating, finish rolling and batch, producing hot rolled strip thus, and by the band steel after hot rolling through overpickling, cold rolling, continuous annealing and cooling heat process, wherein, continuous annealing is performed as and continuous annealing temperature is fallen into calculate in the scope of target temperature ± 15 ° C of department by relational expression [840-120C-45Mn+25Si+34P-45N-25Cu+8Cr-30Ni], and perform cooling heat process by this way, namely, with the rate of cooling of 1 DEG C/s ~ 20 DEG C/s, the band steel after continuous annealing is slowly cooled to 620 DEG C ~ 690 DEG C, quench with the rate of cooling of 20 DEG C/s ~ 100 DEG C/s immediately, then isothermal transformation thermal treatment is stood at 310 DEG C ~ 420 DEG C.
In addition, the invention provides a kind of method being manufactured Cold-Rolled TRIP Steel by following step: the steel making to comprise by weight percentage following component becomes through continuous casting the thin slab that thickness is 30mm ~ 150mm: the C of 0.05% ~ 0.20%, the Si of 0.8% ~ 2.0%, the Mn of 1.2% ~ 2.2%, P, the S of 0.001% ~ 0.02%, Al, the N of 0.001% ~ 0.02%, Sb, the total amount of 0.005% ~ 0.1% of 0.01% ~ 2.0% of 0.001% ~ 0.1% are 0.18% or the Fe of less incidental element (Cu+Cr+Ni+Sn+Pb) and surplus and other inevitable impurity, make described thin slab through roughing, heating, finish rolling and batch, producing hot rolled strip thus, and by the band steel after hot rolling through overpickling, cold rolling, continuous annealing and cooling heat process, wherein, performing finish rolling makes the rolling speed difference of single band steel be 15% or lower, finish rolling is performed as in the scope of target temperature ± 20 that the rolling temperature of finish to gauge frame fallen into calculated by relational expression [910-225C-65Mn+15Si+10P] DEG C, continuous annealing is performed as in the scope of target temperature ± 15 that continuous annealing temperature fallen into calculated by relational expression [840-120C-45Mn+25Si+34P-45N-25Cu+8Cr-30Ni] DEG C, and perform cooling heat process by this way, namely, with the rate of cooling of 1 DEG C/s ~ 20 DEG C/s, the band steel after continuous annealing is slowly cooled to 620 DEG C ~ 690 DEG C, quench with the rate of cooling of 20 DEG C/s ~ 100 DEG C/s immediately, then isothermal transformation thermal treatment is stood at 310 DEG C ~ 420 DEG C.
In the above-mentioned methods, preferably, continuous casting is performed with the casting speed of 4.5mpm or higher.In addition, preferably, roughing is performed as and makes the surface temperature of thin slab in roughing mill ingress be 950 DEG C ~ 1100 DEG C, and the accumulation draft when roughing is 65% ~ 90%.In addition, preferably, perform heating by this way, that is, the band steel after roughing is heated to 920 DEG C ~ 1150 DEG C, or keep its heat.In addition, preferably, perform by this way and batch, that is, at 480 DEG C ~ 680 DEG C, the band steel after finish rolling is batched.In addition, preferably, performing cold rolling by this way, that is, is 40% to 75% by the belt steel rolling after pickling to draft.
The invention provides a kind of method being manufactured analysis of producing hot rolled TRIP by following step: the steel making to comprise by weight percentage following component becomes through continuous casting the thin slab that thickness is 30mm ~ 150mm: the C of 0.06% ~ 0.20%, the Si of 0.8% ~ 2.0%, the Mn of 1.2% ~ 2.2%, the P of 0.001% ~ 0.1%, the S of 0.001% ~ 0.02%, the Al of 0.01% ~ 2.0%, the N of 0.001% ~ 0.02%, total amount is 0.18% or less incidental element (Cu+Ni+Sn+Pb), from the Ti of 0.001% ~ 0.1%, that selects in the Nb of 0.001% ~ the 0.1% and V of 0.001% ~ 0.1% is one or more of, and the Fe of surplus and other inevitable impurity, make described thin slab through roughing, reheat, finish rolling and batching, wherein, finish rolling is performed as and makes the rolling speed difference of single band steel be 15% or lower, and perform by this way and batch, namely, band steel after finish rolling is cooled with the rate of cooling of 25 DEG C/s or higher on the run-out table, then batches at 350 DEG C ~ 470 DEG C.
In addition, the invention provides a kind of method being manufactured analysis of producing hot rolled TRIP by following step: the steel making to comprise by weight percentage following component becomes through continuous casting the thin slab that thickness is 30mm ~ 150mm: the C of 0.06% ~ 0.20%, the Si of 0.8% ~ 2.0%, the Mn of 1.2% ~ 2.2%, the P of 0.001% ~ 0.1%, the S of 0.001% ~ 0.02%, the Al of 0.01% ~ 2.0%, the N of 0.001% ~ 0.02%, total amount is 0.18% or less incidental element (Cu+Ni+Sn+Pb), from the Ti of 0.001% ~ 0.1%, that selects in the Nb of 0.001% ~ the 0.1% and V of 0.001% ~ 0.1% is one or more of, and the Fe of surplus and other inevitable impurity, make described thin slab through roughing, reheat, finish rolling and batching, wherein, finish rolling is performed as and makes in the scope that the rolling temperature of finish to gauge frame falls into target temperature ± 20 that calculated by relational expression [910-225C-80Mn+15Si+10P] DEG C, and perform by this way and batch, namely, band steel after finish rolling is cooled with the rate of cooling of 25 DEG C/s or higher on the run-out table, then batches at 350 DEG C ~ 470 DEG C.
In addition, the invention provides a kind of method being manufactured analysis of producing hot rolled TRIP by following step: the steel making to comprise by weight percentage following component becomes through continuous casting the thin slab that thickness is 30mm ~ 150mm: the C of 0.06% ~ 0.20%, the Si of 0.8% ~ 2.0%, the Mn of 1.2% ~ 2.2%, the P of 0.001% ~ 0.1%, the S of 0.001% ~ 0.02%, the Al of 0.01% ~ 2.0%, the N of 0.001% ~ 0.02%, total amount is 0.18% or less incidental element (Cu+Ni+Sn+Pb), from the Ti of 0.001% ~ 0.1%, that selects in the Nb of 0.001% ~ the 0.1% and V of 0.001% ~ 0.1% is one or more of, and the Fe of surplus and other inevitable impurity, make described thin slab through roughing, reheat, finish rolling and batching, wherein, finish rolling is performed as and makes the rolling speed difference of single band steel be 15% or lower, finish rolling is performed as and makes in the scope that the rolling temperature of finish to gauge frame falls into target temperature ± 20 that calculated by relational expression [910-225C-80Mn+15Si+10P] DEG C, and perform by this way and batch, namely, band steel after finish rolling is cooled with the rate of cooling of 25 DEG C/s or higher on the run-out table, then batches at 350 DEG C ~ 470 DEG C.
In the above methods, preferably, continuous casting is performed with the casting speed of 4.5mpm or higher.In addition, preferably, the surface temperature that roughing is performed as the ingress making thin slab at roughing mill is 950 DEG C ~ 1100 DEG C, and accumulation draft during roughing is 65% ~ 90%.In addition, preferably, perform heating by this way, that is, the band steel after roughing is heated to 920 DEG C ~ 1150 DEG C, or keep its heat.
Beneficial effect
Manufacture tensile strength grade according to the present invention be 590MPa, excellent workability and in mechanical property deviation little high strength cold-rolled/method of analysis of producing hot rolled TRIP in, thin slab foundry engieering can be adopted guarantee excellent workability, and reduce the deviation of the band mechanical property of steel on width and length direction significantly, therefore produce have high-quality high strength cold-rolled/analysis of producing hot rolled TRIP.
In addition, thin slab foundry engieering can be eliminated and reheat technique in conventional mill, therefore conserve energy boosting productivity.
In addition, thin slab technology can be used in electric furnace by melting the waste material of such as scrap metal etc. and the steel obtained, and therefore improves the returnability of resource.
Accompanying drawing explanation
Fig. 1 illustrates the schematic diagram according to micro-type rolling mill technique of the present invention.
The description > of the label in < accompanying drawing
Embodiment
Hereinafter, detailed description of the present invention will be provided.
As mentioned above, the invention belongs to and utilize the micro-type rolling mill technique of use thin slab foundry engieering to manufacture the method for high strength cold-rolled TRIP steel, describe briefly according to micro-type rolling mill technique of the present invention with reference to Fig. 1.Stand known cold-rolling process (pickling, cold rolling, continuous annealing, cooling heat process) by the hot rolled strip of micro-type rolling mill explained hereafter and therefore obtain final Cold-Rolled TRIP Steel, eliminating the description to cold-rolling process.
Specifically, continuous caster 10 is utilized to manufacture the thin slab (a) that thickness is 30mm ~ 150mm.Compared with the slab being 200mm or thicker with the thickness utilizing the continuous caster of conventional mill to produce, this slab is thinner, is therefore referred to as thin slab.The traditional slab being 200mm or thicker due to thickness place etc. cools in the open completely, so before execution hot rolling, its needs reheat fully in reheating furnace, to have 1100 DEG C or higher surface temperature.But, because thin slab is delivered directly to roughing mill 20, and without reheating furnace, so the heat of casting technique can be utilized, therefore save energy and drastically increased productivity.
Roughing mill 20 is utilized to be the hot rolled strip having pre-determined thickness or be less than pre-determined thickness by thin slab rolling.Well heater 30 is utilized to carry out the temperature reduced in this process of compensating band steel, then utilize finishing mill 50 that the hot rolled strip (b) after heating is rolling to the final thickness of expectation, by ROT(Run Out Table, runoff table) 60 to cool, then utilize reeling machine 70 finally to batch at a predetermined temperature, thus produce the hot-rolled steel sheet of the mechanical property with expectation.
Like this, in order to compensate the difference between casting speed and rolling speed, arranging before finishing mill 50 and batching case 40, thus being batched for the first time through the hot rolled strip (b) of induction heater 30.Be 6mpm or high-speed casting technology faster owing to recently having achieved speed, so developing the endless hot rolling technique not using and batch case 40 now.
According to the high strength cold-rolled TRIP steel manufactured by micro-type rolling mill technique and cold-rolling process of the present invention by weight percentage (wt%) meter comprise: the C of 0.05% ~ 0.20%, the Si of 0.8% ~ 2.0%, the Mn of 1.2% ~ 2.2%, the P of 0.001% ~ 0.1%, the S of 0.001% ~ 0.02%, the Al of 0.01% ~ 2.0%, the N of 0.001% ~ 0.02%, the Sb of 0.005% ~ 0.1%, total amount is 0.18% or less incidental element (Cu+Cr+Ni+Sn+Pb), and the Fe of surplus and other inevitable impurity.Be described below effect and the amount of various element.
C determines the austenitic ratio do not changed in annealing region, and in isothermal transformation heat treatment process, moves to austenite diffusely thus austenite is stablized, and therefore improves ductility.If the amount of C is less than 0.05%, then the ratio regular meeting of residual austenite reduces, and makes to be difficult to guarantee mechanical property desired in the present invention.On the contrary, if the amount of C is more than 0.20%, then weldability can reduce.Therefore, preferably, the amount of C is restricted to 0.05% ~ 0.20%.
Si improves the intensity of steel plate due to solution strengthening effect, and suppresses the deposition of cementite, in the austenite therefore making C be enriched in not change, thus austenite is stablized.If the amount of Si is less than 0.8%, be then difficult to guarantee above-mentioned effect.On the contrary, if the amount of Si is more than 2.0%, then coating, erosion resistance and weldability can decline.Therefore, preferably, the amount of Si is restricted to 0.8% ~ 2.0%.
Mn is for the formation of austenite, and it has solution strengthening effect, in the rate of diffusion reducing C effectively, and suppresses the transformation in process of cooling.If the amount of Mn is less than 1.2%, is then difficult to guarantee the amount of residual austenite and is difficult to guarantee intensity desired in the present invention.On the contrary, if the amount of Mn is more than 2.2%, then the diffusion of the C during whole isothermal retention time can become insufficient, and austenitic stability is deteriorated on the contrary.Therefore, preferably, the amount of Mn is restricted to 1.2% ~ 2.2%.
P makes steel plate strengthen by solution strengthening effect, and when adding together with Si, promotes the C enrichment in austenite at isothermal transformation Heat Treatment.If the amount of P is less than 0.001%, then can not guarantee its effect, and manufacturing cost can increase.On the contrary, if the amount of P is more than 0.1%, then spot weld can be deteriorated, and fragility can increase.Therefore, preferably, the amount of P is restricted to 0.001% ~ 0.1%.
S causes the segregation of slab as the impurity element in steel, and the ductility of steel plate and weldability are reduced.The amount of S is difficult to control as being less than 0.001%.If the amount of S is more than 0.02%, then there will be the problem of the segregation of such as slab etc., and the ductility of steel plate and weldability can reduce.Therefore, preferably, the amount of S is restricted to 0.001% ~ 0.02%.
The O of acid-soluble Al in steel is combined, thus produces deoxidation, and similar to Si, and by the C in ferrite is distributed to austenite, acid-soluble Al is effective to austenitic stablizing.If the amount of acid-soluble Al is less than 0.01%, then can not guarantee above-mentioned effect.On the contrary, if the amount of acid-soluble Al exceeds 2.0%, then above-mentioned effect is saturated, and inclusion and manufacturing cost can together with increase.Therefore, preferably, the amount of acid-soluble Al is restricted to 0.01% ~ 2.0%.
N is effective to stable austenite.If the amount of N is less than 0.001%, be then difficult to guarantee above-mentioned effect.On the contrary, if the amount of N is more than 0.02%, then above-mentioned effect is saturated, and weldability and manufacturing cost can increase.Therefore, preferably, the amount of N is restricted to 0.001% ~ 0.02%.
The surface enrichment of Sb inhibited oxidation thing, therefore reduces surface imperfection, and Sb is very effective in the formation suppressing uneven surface enriched products.If the amount of Sb is less than 0.005%, be then difficult to guarantee above-mentioned effect.On the contrary, if the amount of Sb is more than 0.1%, then above-mentioned effect is saturated, and can cause the problem relevant to the deterioration of manufacturing cost and workability.Therefore, preferably, the amount of Sb is restricted to 0.005% ~ 0.1%.
Incidental element (Cu+Cr+Ni+Sn+Pb) is by being used as the waste material of charging and the impurity element brought in process for making.If their total amount is more than 0.18%, then thin slab can be caused to cast the surface crack of stream.Therefore, preferably, the total amount of these elements is restricted to 0.18% or less.
Except component above, the present invention includes Fe and other inevitable impurity of equal amount.
Describe the method that molten steel that utilization according to the present invention comprises said components manufactures high strength cold-rolled TRIP steel below in detail.
As above with reference to Fig. 1 mention, the present invention includes: micro-type rolling mill hot rolling technology, this technique comprises continuous casting, roughing, heating, finish rolling, cools and batch; Cold-rolling process, comprise pickling, cold rolling, continuous annealing and cooling heat process, characteristic technological maheup of the present invention is that the operational condition by again controlling each step manufactures the little high strength cold-rolled TRIP steel of mechanical property deviation.
Specifically, preferably, with 4.5mpm or faster cast speed perform continuous casting.Typically, compared with soft product, tensile strength is the elements (add these yuan and usually guarantee intensity) such as such as C, Mn, Si that the ladle content of 590MPa or higher category is larger, under lower casting speed, therefore more easily occur the segregation of strand.When there is segregation by this way, be difficult to guarantee intensity, and there will be transverse direction or the longitudinal bias of mechanical property.Therefore, cast speed and be set to 4.5mpm or faster.
Make continuous-casting sheet billet stand roughing by using the roughing mill being equipped with 2 ~ 4 supports and perform described roughing.Like this, preferably, perform this technique, make the surface temperature of thin slab in roughing mill ingress be 950 DEG C ~ 1100 DEG C, and accumulation draft when making roughing is 65% ~ 90%.
If the surface temperature of thin slab in roughing mill ingress is lower than 950 DEG C, then roughing load can greatly increase, and there will be edge cracks.On the contrary, if its surface temperature is higher than 1100 DEG C, then may produce San-Su type firecoat.Therefore, this surface temperature is restricted to 950 DEG C ~ 1100 DEG C.
In addition, accumulation draft during roughing is considered to important, to obtain the product with the expectation of uniform mechanical property in the present invention.Along with draft during roughing increases, the micro-distribution that manufacture TRIP steel is Mn, Si, Al etc. of required important element is become even, in addition, be with the thermograde on the width of steel and thickness direction to reduce, therefore obtain uniform mechanical property.But, if accumulation draft is less than 65%, then can not show above effect fully.On the contrary, if accumulation draft is more than 90%, then rolling deformation resistance enlarges markedly, and therefore increases manufacturing cost.Therefore, preferably, the mode being 65% ~ 90% with accumulation draft is rolled.
Preferably, perform heating by this way, that is, the band steel after roughing is heated to again 920 DEG C ~ 1150 DEG C or keep its heat.If the surface temperature of the band steel after roughing is lower than 920 DEG C, then rolling deformation resistance can enlarge markedly.On the contrary, if its surface temperature is higher than 1150 DEG C, then need high cost of energy to carry out raised temperature, and can frequently occur surperficial scale defects.Therefore, preferably, Heating temperature is restricted to 920 DEG C ~ 1150 DEG C.
Preferably, finish rolling is performed as and makes the difference of the rolling speed of single band steel be 15% or lower.High strength cold-rolled TRIP steel due to 590MPa level according to the present invention uses phase-change organization as schedule of reinforcement, so mechanical property can change based on rolling speed during finish rolling.If there is the difference of the rolling speed in the finishing mill of support more than 15%, then be difficult to obtain uniform rate of cooling on follow-up runoff table, and be difficult to obtain the coiling temperature expected, and the deviation of mechanical property therefore on the band width of steel or length direction can enlarge markedly.
In addition, in finish-rolling process, preferably the rolling temperature of finish to gauge frame is set as falling in the scope of target temperature ± 20 that calculated by relational expression [910-225C-65Mn+15Si+10P] DEG C.In traditional hot rolling technology, typically, finish rolling is made to be equal to or higher than Ar
3complete at the temperature of transition temperature, to manufacture the TRIP steel with uniform as far as possible mechanical property.But, in the present invention, with the final rolling temperature of finish to gauge frame at Ar
1transition temperature and Ar
3when mode between transition temperature performs rolling, that is, when performing rolling in the two-phase region that austenite and ferrite coexist, under same intensity, improve unit elongation, this is confirmed by test repeatedly.
When using thin slab foundry engieering to manufacture TRIP steel plate, compared with traditional hot rolling technology, because the temperature with band steel controls easier advantage, so preferably, final rolling temperature is set as at Ar
1transition temperature and Ar
3between transition temperature.In the present invention, it should be noted that, said temperature can change according to the type of component, and the rolling condition in the scope of target temperature ± 20 that calculated by relational expression [910-225C-65Mn+15Si+10P] DEG C contributes to rolling in two-phase region, and this is confirmed by test repeatedly.
The result explained by repeatedly testing confirmation is described by theory below.Such as, when having the steel of phase-change organization, in order to improve intensity and ductility simultaneously, how to make the austenite stable element of such as C, Mn etc. be enriched in the austenite do not changed and being considered to important.When performing finish rolling in two-phase region, the dispersion behavior of solute element is improved, therefore, even if when there is same component, ferrite is cleaned, and simultaneously austenite is further stabilized, even and if these effects also continue after cold rolling and annealing.
In addition, preferably, perform by this way and batch, that is, the band steel after finish rolling batches with the temperature of 480 DEG C ~ 680 DEG C.If hot-rolling coiling temperature is lower than 480 DEG C, then hot rolling intensity increases greatly, and causing undesirably can the problem of cold-rolling property.On the contrary, if this coiling temperature is higher than 680 DEG C, then the band coil of strip after hot rolling is easily out of shape.Therefore, this temperature is preferably restricted to 480 DEG C ~ 680 DEG C.
Preferably, perform cold rolling by this way, that is, by the band steel after pickling with 40% ~ 75% draft be rolled.If draft is less than 40%, then there will not be recrystallization when annealing.On the contrary, if draft is more than 75%, then rolling deformation resistance increases greatly, makes to be difficult to perform rolling.Therefore, draft is preferably restricted to 40% ~ 75%.
In addition, preferably, continuous annealing is performed by this way, that is, in the scope of target temperature ± 15 that make continuous annealing temperature fall into be calculated by relational expression [840-120C-45Mn+25Si+34P-45N-25Cu+8Cr-30Ni] DEG C.When manufacturing TRIP steel, in the region that austenite and ferrite coexist, perform annealing, this is guaranteeing that in the mechanical property expected be favourable.By repeatedly testing, by empirically being formed based on the main alloy element of such as C, Mn, Si etc. and incidental element and the coexistence changed, determine that relational expression is above to obtain better mechanical property.
If temperature is lower 15 DEG C than the value calculated by relational expression above, then austenitic ratio is too low, or there will not be recrystallization.On the contrary, if annealing thermal treatment performs at the temperature of high 15 DEG C than target temperature, then austenitic ratio is too high, and the concentration of C in austenite can be diluted, the ratio regular meeting of the residual austenite therefore in final tissue reduces, and the ratio regular meeting of martensite or bainite increases.In addition, the mass flow of steel is with can to have become problem due to high temperature.Therefore, preferably, annealing temperature is restricted to above-mentioned condition.
Finally, preferably, perform cooling heat process by this way, namely, with the rate of cooling of 1 DEG C/s ~ 20 DEG C/s, the band steel after continuous annealing is slowly cooled to 620 DEG C ~ 690 DEG C, quench with the rate of cooling of 20 DEG C/s ~ 100 DEG C/s immediately, then make it stand isothermal transformation thermal treatment at 310 DEG C ~ 420 DEG C.
Specifically, when band steel being slowly cooled to 620 DEG C ~ 690 DEG C, if to perform cooling lower than the temperature of 620 DEG C, then may precipitated carbide.On the contrary, if to perform cooling higher than the temperature of 690 DEG C, then austenite can not be stablized effectively.In addition, in process of cooling, if rate of cooling is less than 1 DEG C/s, then productivity can significantly reduce.On the contrary, if rear rate of cooling is more than 20 DEG C/s, then the diffusion of the C in the austenite in process of cooling becomes insufficient.
In addition, carrying out immediately quenching with the rate of cooling of 20 DEG C/s ~ 100 DEG C/s and making it when standing isothermal transformation thermal treatment for 310 DEG C ~ 420 DEG C, if to perform quenching lower than the speed of 20 DEG C/s, then can there is perlitic transformation or wherein deposit the bainite transformation of cementite, make to be difficult to obtain residual austenite, reduce ductility undesirably.On the contrary, if speed is more than 100 DEG C/s, then in follow-up isothermal transformation thermal treatment, the bainite transformation wherein not depositing cementite can be made to postpone, therefore obtain block thick annealed structure, cause ductility to reduce undesirably.
When isothermal transformation thermal treatment, if temperature is lower than 310 DEG C, then the C enrichment in austenite becomes insufficient.On the contrary, if temperature is higher than 420 DEG C, then can make the depositions such as cementite, cause ductility to reduce undesirably.Therefore, preferably, be above-mentioned condition by this temperature limitation.
In order to assess technique effect of the present invention, carry out test below.
Use the steel of the composition had as shown in table 1 below, each hot rolled strip is manufactured under the operational condition comprising the slab thickness in table 2, casting speed, steel slab surface temperature, rolling speed difference, final rolling temperature and annealing temperature, and the generation of the mechanical property of measuring tape steel (tensile strength, unit elongation and aberrations in property) and surperficial firecoat.Shown in result table 2 below.
In Table 1,1st ~ No. 5 steel are the hot rolled strips utilizing thin slab foundry engieering (slab thickness: 84mm) to manufacture, the 6th and No. 7 steel (slab thickness: 230mm) be the hot rolled strip manufactured under traditional milling train condition.
In table 2, steel slab surface thermometer is shown in the surface temperature of the pre-test of immediately roughing.Rolling speed difference represents by by the percent value obtained of the difference between the biggest quality flow rate in the single band steel when finish to gauge rolling and minimum mass flow rate and mass flow rate rate being divided by, wherein, rolling speed difference is low means that the change of rolling speed is little.Final rolling temperature shows whether in the scope of target temperature ± 20 that calculated by relational expression 1 DEG C, to perform rolling, and therefore compared steel 4,7 and 8 is by corresponding to Ar
3perform rolling at the temperature of the single phase region directly over transition temperature to obtain.
In the condition of 1st ~ No. 5 steel of table 2, the Heating temperature of the band steel after roughing is set to 1075 DEG C, the 6th and No. 7 steel condition in, Heating temperature is set to 1200 DEG C, and the thickness of the band steel after hot rolling is set to 3.2mm.
Pickling is carried out to the band steel after hot rolling, then with draft be 56.3% carry out cold rolling, therefore the cold rolled strip that thickness is 1.4mm is produced, under the annealing temperature of table 2 to each cold rolling after band steel carry out full annealed, 650 DEG C are slowly cooled to the rate of cooling of 7 DEG C/s, immediately with the cooling of the rate of cooling of about 70 DEG C/s, and stand isothermal transformation thermal treatment at 380 DEG C ~ 410 DEG C.
[table 1]
[table 2]
Relational expression 1=[910-225C-65Mn+15Si+10P]
Relational expression 2=[840-120C-45Mn+25Si+34P-45N-25Cu+8Cr-30Ni]
In table 2, tensile strength and unit elongation are in JIS(Japanese Industrial Standards) value measured along the direction place vertical with rolling direction of the 4/w position of No. 5 test sample book.Unit elongation is represented by the per-cent of the tension strain acted on until stretching sample ruptures, and aberrations in property represents the value obtained by deducting minimum value from the maximum value in the performance number measured along length and the width of coil of strip.In addition, TS × EI(tensile strength × unit elongation) be the parameter of the superiority of the unit elongation performance (wherein, unit elongation reduces along with the increase of intensity) that high-strength steel is shown, wherein, TS × EI is high means that tensile strength and unit elongation are all high.
If the result institute from table 2 is it is clear that according to the present invention, can produces and there is excellent unit elongation and the high strength cold-rolled TRIP steel of TS × EI and low-down mechanical property deviation.
Simultaneously, according to high-strength hot-rolled TRIP steel of the present invention by weight percentage (wt%) meter comprise: the C of 0.06% ~ 0.20%, the Si of 0.8% ~ 2.0%, 1.2% ~ 2.2% Mn, the P of 0.001% ~ 0.1%, S, the Al of 0.01% ~ 2.0%, N, the total amount of 0.001% ~ 0.02% of 0.001% ~ 0.02% be 0.18% or less incidental element (Cu+Ni+Sn+Pb), Ti from 0.001% ~ 0.1%, 0.001% ~ 0.1% Nb and 0.001% ~ 0.1% V select one or more of, and the Fe of surplus and other inevitable impurity.Be described below effect and the amount of various element.
C makes austenite stablize, and because this increasing at room temperature residual austenitic amount, therefore improves ductility.If the amount of C is less than 0.06%, then austenitic than regular meeting reduction, make to be difficult to guarantee mechanical property desired in the present invention.On the contrary, if the amount of C is more than 0.20%, then weldability can reduce.Therefore, preferably, the amount of C is restricted to 0.06% ~ 0.20%.
Si improves the intensity of steel plate due to solution strengthening effect, and suppresses the deposition of cementite, therefore promotes C enrichment in the austenite do not changed, thus austenite is stablized.If the amount of Si is less than 0.8%, be then difficult to guarantee above-mentioned effect.On the contrary, if the amount of Si is more than 2.0%, then coating, erosion resistance and weldability can decline.Therefore, preferably, the amount of Si is restricted to 0.8% ~ 2.0%.
Mn makes austenite stablize, and it has solution strengthening effect, and suppresses the transformation in process of cooling.If the amount of Mn is less than 1.2%, is then difficult to guarantee the amount of residual austenite and is difficult to guarantee intensity desired in the present invention.On the contrary, if the amount of Mn is more than 2.2%, then hot rolling can become problem.Therefore, preferably, the amount of Mn is restricted to 1.2% ~ 2.2%.
P strengthens steel plate by solution strengthening, and when adding together with Si, promotes the C enrichment in austenite.If the amount of P is less than 0.001%, then can not guarantee its effect, and manufacturing cost can increase.On the contrary, if the amount of P is more than 0.1%, then spot weld can be deteriorated, and fragility can increase.Therefore, preferably, the amount of P is restricted to 0.001% ~ 0.1%.
S causes the segregation of slab as the impurity element in steel, and the ductility of steel plate and weldability are reduced.The amount of S is difficult to control as being less than 0.001%.If the amount of S is more than 0.02%, then there will be the problem of the segregation of such as slab etc., and the ductility of steel plate and weldability can reduce.Therefore, preferably, the amount of S is restricted to 0.001% ~ 0.02%.
The O of acid-soluble Al in steel is combined, thus produces deoxidation, and similar to Si, and by the C in ferrite is distributed to austenite, acid-soluble Al is effective to austenitic stablizing.If the amount of acid-soluble Al is less than 0.01%, then can not guarantee above-mentioned effect.On the contrary, if the amount of acid-soluble Al exceeds 2.0%, then above-mentioned effect is saturated, and inclusion and manufacturing cost can together with increase.Therefore, preferably, the amount of acid-soluble Al is restricted to 0.01% ~ 2.0%.
N is effective to stable austenite.If the amount of N is less than 0.001%, be then difficult to expect above-mentioned effect.On the contrary, if the amount of N is more than 0.02%, then above-mentioned effect is saturated, and weldability can reduce and manufacturing cost can increase.Therefore, preferably, the amount of N is restricted to 0.001% ~ 0.02%.
Incidental element (Cu+Ni+Sn+Pb) is by being used as the waste material of charging and the impurity element brought in process for making.If their total amount is more than 0.18%, then thin slab can be caused to cast the surface crack of stream.Therefore, preferably, the total amount of these elements is restricted to 0.18% or less.
Therefore the steel composition formed also can be added with select from Ti, Nb and V one or more of.Although the fundamental property of these elements as high strength cold-rolled TRIP steel desired in the present invention does not produce conclusive impact, preferably, that adds in them is one or more of, accurately to control the tensile strength of product, yield strength and surface quality.
Ti, Nb and V are to improving the yield strength of steel plate and to realize fine grain size aspect be effective.If the amount of these elements is less than 0.001%, be then difficult to guarantee above-mentioned effect.On the contrary, if their amount is more than 0.1%, then manufacturing cost can increase and can form too much settling, this meeting deteriorated ferritic ductility undesirably.Therefore, the amount of Ti, Nb and V is restricted to 0.001% to 0.1%.
Except component above, the present invention includes Fe and other inevitable impurity of equal amount.
Describe the method that molten steel that utilization according to the present invention comprises said components manufactures high-strength hot-rolled TRIP steel below in detail.
As above with reference to Fig. 1 mention, micro-type rolling mill technique comprises continuous casting, roughing, heating, finish rolling, cools and batch, and characteristic technological maheup of the present invention is that the operational condition by again controlling each step manufactures the high-strength hot-rolled TRIP steel with low mechanical property deviation.
Specifically, preferably, with 4.5mpm or faster cast speed perform continuous casting.Typically, compared with soft product, tensile strength is the elements (add these yuan and usually guarantee intensity) such as ladle content more such as C, Mn, Si of 590MPa or higher category, under lower casting speed, therefore more easily occur the segregation of strand.When there is segregation by this way, be difficult to guarantee intensity, or there will be transverse direction or the longitudinal bias of mechanical property.Therefore, cast speed and be set to 4.5mpm or faster.
Make continuous-casting sheet billet stand roughing by using the roughing mill being equipped with 2 ~ 4 supports and perform described roughing.Like this, preferably, perform this technique, make the surface temperature of thin slab in roughing mill ingress be 950 DEG C ~ 1100 DEG C, and accumulation draft when making roughing is 65% ~ 90%.
If the surface temperature of thin slab in roughing mill ingress is lower than 950 DEG C, then roughing load can greatly increase, and there will be edge cracks.On the contrary, if its surface temperature is higher than 1100 DEG C, then can produce so-called San-Su type firecoat.Therefore, this surface temperature is restricted to 950 DEG C ~ 1100 DEG C.
In addition, the accumulation draft when roughing is considered to important, to obtain the product with the expectation of uniform mechanical property in the present invention.Along with the draft when roughing increases, can become even to the micro-distribution that manufacture TRIP steel is Mn, Si, Al etc. of required important element, in addition, be with the thermograde on the width of steel and thickness direction to reduce, therefore obtain uniform mechanical property.But, if accumulation draft is less than 65%, then can not show above effect fully.On the contrary, if accumulation draft is more than 90%, then rolling deformation resistance enlarges markedly, and therefore increases manufacturing cost.Therefore, preferably, be that the mode of 65% ~ 90% is to perform rolling with accumulation draft.
Preferably, perform heating by this way, that is, the band steel after roughing is heated to again 920 DEG C ~ 1150 DEG C or keep its heat.If the surface temperature of the band steel after roughing is lower than 920 DEG C, then rolling deformation resistance can enlarge markedly.On the contrary, if its surface temperature is higher than 1150 DEG C, then need high cost of energy to improve temperature, and can frequently occur surperficial scale defects.Therefore, preferably, Heating temperature is restricted to 920 DEG C ~ 1150 DEG C.
Preferably, finish rolling is performed as and makes the difference of the rolling speed of single band steel be 15% or lower.High-strength hot-rolled TRIP steel due to 590MPa level according to the present invention uses phase-change organization as schedule of reinforcement, so mechanical property can change based on rolling speed during finish rolling.If the difference of the rolling speed in finishing mill is more than 15%, then be difficult to obtain uniform rate of cooling on follow-up runoff table, and be difficult to obtain the coiling temperature expected, and the deviation of mechanical property therefore on the band width of steel or length direction can enlarge markedly.
In addition, in finish-rolling process, preferably the rolling temperature of finish to gauge frame is set as falling in the scope of the target temperature ± 20 ° C calculated by relational expression [910-225C-80Mn+15Si+10P].In traditional hot rolling technology, be typically equal to or higher than Ar
3the temperature of transition temperature is got off and is completed finish rolling, to manufacture the TRIP steel with uniform as far as possible mechanical property.But, in the present invention, be performed as in rolling and make the final rolling temperature of finish to gauge frame at Ar
1transition temperature and Ar
3when between transition temperature, when namely performing rolling in the two-phase region that austenite and ferrite coexist, under same intensity, improve unit elongation, this is by repeatedly testing and confirming.
When utilizing thin slab foundry engieering to manufacture TRIP steel plate, preferably, be with the temperature of steel to control easier advantage compared with traditional hot rolling technology by utilizing, final rolling temperature is set as at Ar
1and Ar
3between transition temperature.In the present invention, it is to be noted that, said temperature can change according to the kind of component, and the rolling condition in the scope of the target temperature ± 20 ° C calculated by relational expression [910-225C-80Mn+15Si+10P] is conducive to being rolled in two-phase region, and this is by repeatedly testing and confirming.
The result explained by repeatedly testing confirmation is described by theory below.Such as, when having the steel of phase-change organization, in order to improve intensity and ductility simultaneously, how to make the austenite stable element of such as C, Mn etc. be enriched in the austenite do not changed and being considered to important.When performing finish rolling in two-phase region, the distribution behavior of solute element is improved, and therefore, even if when there is same component, ferrite is cleaned, and austenite is further stabilized simultaneously.
In addition, perform cooling by this way, that is, with the rate of cooling of 25 DEG C/s or higher, band steel after finish rolling is cooled on the run-out table, and batch at 350 DEG C ~ 470 DEG C.If rate of cooling is on the run-out table less than 25 DEG C/s, then the austenite stable element of such as C, Mn etc. can deposit to perlite from austenite, therefore can make concentration effect deterioration.Therefore, rate of cooling is restricted to 25 DEG C or higher.
If hot-rolling coiling temperature lower than 350 DEG C, then forms martensite, and therefore intensity increases greatly, but unit elongation can reduce.On the contrary, if hot-rolling coiling temperature is higher than 470 DEG C, then the cementite deposition in steel, therefore suppresses the formation of residual austenite.Therefore, hot-rolling coiling temperature is preferably restricted to 380 DEG C ~ 490 DEG C.
Finish rolling and curling be characteristic technological maheup of the present invention, can in them both or more to combine, therefore produce the tensile strength with 590MPa level desired in the present invention and the analysis of producing hot rolled TRIP of low mechanical property deviation.
In order to assess technique effect of the present invention, perform test below.
Use the steel of the composition had as shown in table 3 below, each hot rolled strip is manufactured under the operational condition comprising the slab thickness in table 4, casting speed, steel slab surface temperature, rolling speed difference etc., and the generation of the surperficial firecoat of the mechanical property of measuring tape steel (tensile strength, unit elongation and aberrations in property) and band steel.Shown in result table 2 below.
In table 3, in the numbered steel of institute, the total amount of incidental element (Cu+Ni+Sn+Pb) is controlled as 0.18% or lower.In addition, 1st ~ No. 6 steel are the hot rolled strips utilizing thin slab foundry engieering (slab thickness: 84mm) to manufacture, the 7th and No. 8 steel (slab thickness: 230mm) be the hot rolled strip manufactured under traditional milling train condition.
In table 4, steel slab surface thermometer is shown in the surface temperature of the pre-test of immediately roughing.The percent value that accumulation draft when roughing is obtained divided by slab thickness by the difference between the slab thickness (84mm) of the ingress at roughing mill and the slab thickness (mm) in the exit at roughing mill represents.Rolling speed difference represents by by the percent value obtained of the difference between the biggest quality flow rate in band steel single during finish to gauge rolling and minimum mass flow rate and mass flow rate rate being divided by, wherein, rolling speed difference is low means that the change of rolling speed is little.Final rolling temperature shows whether in the scope of target temperature ± 20 that calculated by relational expression 3 DEG C, to perform rolling, and therefore compared steel 5,8 and 9 is by corresponding to Ar
3perform rolling at the temperature of the single phase region directly over transition temperature to obtain.
Under the condition of No. 1 ~ No. 6 steel of table 4, the Heating temperature of the band steel after roughing is set to 1060 DEG C, under the condition of No. 7 and No. 8 steel, reheats temperature and is set to 1200 DEG C.In numbered steel rate of cooling be on the run-out table set to about 70 DEG C/s, the final thickness of the band steel after hot rolling is set to 3.0mm.
[table 3]
Relational expression 3=[910-225C-80Mn-15Si+10P]
[table 4]
In table 4, tensile strength and unit elongation are the values in the 4/w position of JIS5 test sample book along the directional survey vertical with rolling direction.Unit elongation is represented by the per-cent of the tension strain acted on until sample ruptures, and aberrations in property represents the value obtained by deducting minimum value from the maximum value in the performance number measured along length and the width of coil of strip.In addition, TS × EI(tensile strength × unit elongation) be the parameter of the superiority of the unit elongation performance (wherein, unit elongation reduces along with the increase of intensity) that high-strength steel is shown, wherein, TS × EI is high means that tensile strength and unit elongation are all high.
As by from the result of table 4 institute it is clear that according to the present invention, can produce and there is excellent extensible rate and TS × EI and the low high-strength hot-rolled TRIP steel of mechanical property deviation.
Claims (11)
1. manufacture tensile strength grade be 590MPa, excellent workability and in mechanical property the method for the high strength cold-rolled TRIP steel that deviation is little, the method comprises the steps:
The steel comprising following component is by weight percentage made to become through continuous casting the thin slab that thickness is 30mm ~ 150mm: the C of 0.05% ~ 0.20%, the Si of 0.8% ~ 2.0%, the Mn of 1.2% ~ 2.2%, the P of 0.001% ~ 0.1%, the S of 0.001% ~ 0.02%, the Al of 0.01% ~ 2.0%, the N of 0.001% ~ 0.02%, the Sb of 0.005% ~ 0.1%, total amount is 0.18% or less incidental element Cu+Cr+Ni+Sn+Pb, and the Fe of surplus and other inevitable impurity, make described thin slab through roughing, heating, finish rolling and batch, producing hot rolled strip thus, and by the band steel after hot rolling through overpickling, cold rolling, continuous annealing and cooling heat process, thus produce Cold-Rolled TRIP Steel,
Wherein, perform finish rolling and make the rolling speed difference of single band steel be 15% or lower,
Performing roughing makes the accumulation draft when roughing be 65% to 90%,
Finish rolling is performed as in the scope of target temperature ± 20 that the rolling temperature of finish to gauge frame fallen into calculated by relational expression [910-225C-65Mn+15Si+10P] DEG C, and makes the final rolling temperature of finish to gauge frame at Ar
1transition temperature and Ar
3between transition temperature, and
Perform cooling heat process by this way: with the rate of cooling of 1 DEG C/s ~ 20 DEG C/s, the band steel after continuous annealing is slowly cooled to 620 DEG C ~ 690 DEG C, quench with the rate of cooling of 20 DEG C/s ~ 100 DEG C/s immediately, then stand isothermal transformation thermal treatment at 310 DEG C ~ 420 DEG C.
2. manufacture tensile strength grade be 590MPa, excellent workability and in mechanical property the method for the high strength cold-rolled TRIP steel that deviation is little, the method comprises the steps:
The steel comprising following component is by weight percentage made to become through continuous casting the thin slab that thickness is 30mm ~ 150mm: the C of 0.05% ~ 0.20%, the Si of 0.8% ~ 2.0%, the Mn of 1.2% ~ 2.2%, the P of 0.001% ~ 0.1%, the S of 0.001% ~ 0.02%, the Al of 0.01% ~ 2.0%, the N of 0.001% ~ 0.02%, the Sb of 0.005% ~ 0.1%, total amount is 0.18% or less incidental element Cu+Cr+Ni+Sn+Pb, and the Fe of surplus and other inevitable impurity, make described thin slab through roughing, heating, finish rolling and batch, producing hot rolled strip thus, and by the band steel after hot rolling through overpickling, cold rolling, continuous annealing and cooling heat process, thus produce Cold-Rolled TRIP Steel,
Wherein, perform finish rolling and make the rolling speed difference of single band steel be 15% or lower,
Performing roughing makes the accumulation draft when roughing be 65% to 90%,
Finish rolling is performed as in the scope of target temperature ± 20 that the rolling temperature of finish to gauge frame fallen into calculated by relational expression [910-225C-65Mn+15Si+10P] DEG C, and makes the final rolling temperature of finish to gauge frame at Ar
1transition temperature and Ar
3between transition temperature,
Continuous annealing is performed as in the scope of target temperature ± 15 that continuous annealing temperature fallen into calculated by relational expression [840-120C-45Mn+25Si+34P-45N-25Cu+8Cr-30Ni] DEG C, and
Perform cooling heat process by this way: with the rate of cooling of 1 DEG C/s ~ 20 DEG C/s, the band steel after continuous annealing is slowly cooled to 620 DEG C ~ 690 DEG C, quench with the rate of cooling of 20 DEG C/s ~ 100 DEG C/s immediately, then stand isothermal transformation thermal treatment at 310 DEG C ~ 420 DEG C.
3., as method according to claim 1 or claim 2, wherein, perform continuous casting with the casting speed of 4.5mpm or higher.
4. as method according to claim 1 or claim 2, wherein, performing roughing makes the surface temperature of thin slab in roughing mill ingress be 950 DEG C ~ 1100 DEG C.
5. as method according to claim 1 or claim 2, wherein, perform heating by this way: the band steel after roughing is heated to 920 DEG C ~ 1150 DEG C or keep its heat.
6., as method according to claim 1 or claim 2, wherein, perform by this way and batch: at 480 DEG C ~ 680 DEG C, the band steel after finish rolling is batched.
7. as method according to claim 1 or claim 2, wherein, perform cold rolling by this way: be 40% to 75% by the belt steel rolling after pickling to draft.
8. manufacturing tensile strength grade is 590MPa, excellent workability and a method for the little high-strength hot-rolled TRIP steel of mechanical property aspect deviation, and the method comprises the steps:
The steel comprising following component is by weight percentage made to become through continuous casting the thin slab that thickness is 30mm ~ 150mm: the C of 0.06% ~ 0.20%, the Si of 0.8% ~ 2.0%, the Mn of 1.2% ~ 2.2%, the P of 0.001% ~ 0.1%, the S of 0.001% ~ 0.02%, the Al of 0.01% ~ 2.0%, the N of 0.001% ~ 0.02%, total amount is 0.18% or less incidental element Cu+Ni+Sn+Pb, from the Ti of 0.001% ~ 0.1%, that selects in the Nb of 0.001% ~ the 0.1% and V of 0.001% ~ 0.1% is one or more of, and the Fe of surplus and other inevitable impurity, make described thin slab through roughing, reheat, finish rolling and batching, thus produce analysis of producing hot rolled TRIP,
Wherein, finish rolling is performed as and makes the rolling speed difference of single band steel be 15% or lower,
Roughing is performed as and makes the accumulation draft when roughing be 65% to 90%,
Finish rolling is performed as in the scope of target temperature ± 20 that the rolling temperature of finish to gauge frame fallen into calculated by relational expression [910-225C-65Mn+15Si+10P] DEG C, and makes the final rolling temperature of finish to gauge frame at Ar
1transition temperature and Ar
3between transition temperature, and
Perform by this way and batch: the band steel after finish rolling is cooled with the rate of cooling of 25 DEG C/s or higher on the run-out table, then batch at 350 DEG C ~ 470 DEG C.
9. method as claimed in claim 8, wherein, performs continuous casting with the casting speed of 4.5mpm or larger.
10. method as claimed in claim 8, wherein, performs roughing and makes the surface temperature of thin slab in the ingress of roughing mill be 950 DEG C ~ 1100 DEG C.
11. methods as claimed in claim 8, wherein, perform by this way and reheat: the band steel after roughing is heated to 920 DEG C ~ 1150 DEG C or keep its heat.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR10-2010-0111274 | 2010-11-10 | ||
| KR1020100111274A KR101245700B1 (en) | 2010-11-10 | 2010-11-10 | METHOD FOR MANUFACTURING TENSILE STRENGTH 590MPa CLASS COLD ROLLED TRIP STEEL WITH EXCELLENT VARIATION OF MECHANICAL PROPERTY |
| KR1020100111273A KR101245699B1 (en) | 2010-11-10 | 2010-11-10 | METHOD FOR MANUFACTURING TENSILE STRENGTH 590MPa CLASS HOT ROLLED TRIP STEEL WITH EXCELLENT VARIATION OF MECHANICAL PROPERTY |
| KR10-2010-0111273 | 2010-11-10 | ||
| PCT/KR2011/008569 WO2012064129A2 (en) | 2010-11-10 | 2011-11-10 | Method for manufacturing high-strength cold-rolled/hot-rolled trip steel having a tensile strength of 590 mpa grade, superior workability, and low mechanical-property deviation |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN103249847A CN103249847A (en) | 2013-08-14 |
| CN103249847B true CN103249847B (en) | 2015-06-10 |
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| CN201180058065.6A Expired - Fee Related CN103249847B (en) | 2010-11-10 | 2011-11-10 | Method for manufacturing high-strength cold-rolled/hot-rolled trip steel having a tensile strength of 590 mpa grade, superior workability, and low mechanical-property deviation |
Country Status (3)
| Country | Link |
|---|---|
| CN (1) | CN103249847B (en) |
| BR (1) | BR112013011409A2 (en) |
| WO (1) | WO2012064129A2 (en) |
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| CN107475627B (en) * | 2017-08-23 | 2018-12-21 | 武汉钢铁有限公司 | 600MPa grade analysis of producing hot rolled TRIP and manufacturing method based on CSP process |
| CN107557692B (en) * | 2017-08-23 | 2019-01-25 | 武汉钢铁有限公司 | 1000MPa grade analysis of producing hot rolled TRIP and manufacturing method based on CSP process |
| CN107488814B (en) * | 2017-08-23 | 2018-12-28 | 武汉钢铁有限公司 | 800MPa grade analysis of producing hot rolled TRIP and manufacturing method based on CSP process |
| CN107815593B (en) * | 2017-11-06 | 2019-01-22 | 东北大学 | A kind of economical high-aluminum low-silicon TRIP steel of automobile and preparation method thereof |
| CN110229951A (en) * | 2019-07-29 | 2019-09-13 | 湖南力方轧辊有限公司 | A kind of cold-rolling stainless steel online annealing equipment and technique |
| CN114669598B (en) * | 2022-04-07 | 2023-02-03 | 山东钢铁集团永锋临港有限公司 | Method for continuously casting 16m square billet and directly rolling bar |
| CN115094216B (en) * | 2022-06-23 | 2023-11-17 | 本钢板材股份有限公司 | Method for eliminating color difference defect of TRIP high-strength steel |
| CN115572893B (en) * | 2022-09-02 | 2023-06-16 | 武汉钢铁有限公司 | High-strength steel for automobile spoke resistant to atmospheric corrosion and manufacturing method thereof |
| CN115404332B (en) * | 2022-09-20 | 2024-01-16 | 东北大学 | Heat treatment temperature compensation device and method for ultrathin high-strength plate strip steel |
| CN115739993B (en) * | 2022-11-18 | 2023-05-23 | 浙江申吉钛业股份有限公司 | Preparation method of wide titanium alloy plate |
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- 2011-11-10 CN CN201180058065.6A patent/CN103249847B/en not_active Expired - Fee Related
- 2011-11-10 BR BR112013011409A patent/BR112013011409A2/en active Search and Examination
- 2011-11-10 WO PCT/KR2011/008569 patent/WO2012064129A2/en active Application Filing
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Also Published As
| Publication number | Publication date |
|---|---|
| CN103249847A (en) | 2013-08-14 |
| BR112013011409A2 (en) | 2016-08-02 |
| WO2012064129A2 (en) | 2012-05-18 |
| WO2012064129A3 (en) | 2012-07-12 |
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