CN1934280A - Cold rolled steel sheet and hot dipped steel sheet with superior strength and bake hardenability and method for manufacturing the steel sheets - Google Patents

Cold rolled steel sheet and hot dipped steel sheet with superior strength and bake hardenability and method for manufacturing the steel sheets Download PDF

Info

Publication number
CN1934280A
CN1934280A CNA2005800093946A CN200580009394A CN1934280A CN 1934280 A CN1934280 A CN 1934280A CN A2005800093946 A CNA2005800093946 A CN A2005800093946A CN 200580009394 A CN200580009394 A CN 200580009394A CN 1934280 A CN1934280 A CN 1934280A
Authority
CN
China
Prior art keywords
steel plate
still less
hot
steel
steel sheet
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CNA2005800093946A
Other languages
Chinese (zh)
Other versions
CN100489122C (en
Inventor
韩成豪
金兑奎
韩葙浩
高山景
阵光根
康熙宰
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Posco Holdings Inc
Original Assignee
Posco Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Posco Co Ltd filed Critical Posco Co Ltd
Publication of CN1934280A publication Critical patent/CN1934280A/en
Application granted granted Critical
Publication of CN100489122C publication Critical patent/CN100489122C/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • 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
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Abstract

Disclosed herein are a bake-hardenable high-strength cold-rolled steel sheet, a hot-dipped steel sheet thereof, and a method for manufacturing the same. The steel sheet comprises 0.0016 ~ 0.01 % of C; 0.1 % or less of Si; 0.2 ~ 1.5 % of Mn; 0.05 ~ 0.15 % of P; 0.01 % or less of S; 0.08 ~ 0.5 % of (soluble) Al; 0.0025 % or less of N; 0.003 ~ 0.1 % of Nb; 0.003 % or less of Ti; 0.01 ~ 0.4 % of Mo; 0.0005 ~ 0.005 % of B; and the balance of Fe and other unavoidable impurities, in terms of weight%. The steel sheet has fine AlN precipitates, and a grain size(ASTM No.) of 9 or more. The AlN precipitates have a grain size, which can suppress grain growth. The steel sheet has enhanced strength, bake hardenability, aging resistance, and secondary work embrittlement resistance.

Description

Have high strength and cure indurative cold-rolled steel sheet and hot dipping steel plate and preparation method thereof
Technical field
The present invention relates to be used for car body cured hardened cold-rolled steel sheet, adopt hot dipping steel plate that this cold-rolled steel sheet makes and preparation method thereof.Particularly, the present invention relates to have the cured hardened cold-rolled steel sheet that well cures ageing resistance and secondary operation brittle resistance under hardening, the room temperature, adopt hot dipping steel plate that this cold-rolled steel sheet makes and preparation method thereof.
Background technology
Outside plate (exterior plates) as car body, can cure the hardened cold-rolled steel sheet and have the tensile strength of 390Mpa usually, and because its yield strength (yield strength) and soft steel are roughly the same thereby present good ductility (ductility) when press forming (press forming).In addition, can cure (bake) hardened cold-rolled steel sheet and have a characteristic, i.e. its yield strength meeting is cured owing to the enamelled coating behind the press forming or the coating processing strengthens.
About can curing the hardened cold-rolled steel sheet, the main steel plate that adopts be by to low-carbon (LC), add phosphorus, dealuminzation (Al-killed) and cure the sclerosis value and carry out intermittently at the steel of 40～50Mpa that (batch) annealing makes.
Yet, in the time can curing the hardened cold-rolled steel sheet, although can easily guarantee plasticity and cure the two compatibility of hardening, the problem that exists productive rate to reduce by the production of intermittently annealing.
In order to improve the intermittently productive rate of annealing method, developed the method that can cure the hardened cold-rolled steel sheet has been produced in low-carbon (LC), interpolation phosphorus, the lasting annealing of dealuminzation steel.
Yet, in the time can curing the hardened cold-rolled steel sheet by lasting annealing method production, although cure hardening because comparatively faster rate of cooling thereby can easily guarantee in this method and since heating rapidly and annealing time lack the problem that has the plasticity variation.
Therefore, the cured hardened cold-rolled steel sheet that makes by continuing to anneal restrictively is applied to the automobile outer plate to the plasticity no requirement (NR).
Recently, along with the rapid progress of steel production technique, feasible amount to the solute element in the steel is optimized has feasibility.
Therefore, can be by in taking off the Al steel, adding element Ti or Nb the cured hardened cold-rolled steel sheet that comes the production plasticity to improve for example be easy to form carbonization nitrogen.Like this, because the plasticity of the cured hardened cold-rolled steel sheet by continuing annealing method production is improved, be applied to that gradually shock-resistance is had desired automobile outer plate so can cure the hardened cold-rolled steel sheet.
The still unexamined patent publication No. of Japan (Sho) 61-26757 discloses extremely low the cured hardened cold-rolled steel sheet of a kind of carbon content, and it comprises the C of 0.0005～0.015wt%; 0.05wt% or S+N still less; And Ti and Nb or its combination.
The still unexamined patent publication No. of Japan (Sho) 57-89437 discloses a kind of hardened cold-rolled steel sheet that cures, and it adopts and comprises 0.010wt% or C still less, cures the steel of sclerosis value for the interpolation Ti of about 40Mpa.
Add Ti and the amount of Nb or the amount that the rate of cooling in the annealing process is suitably controlled the solute element in the steel by suitable control, the method for above-mentioned open source literature has been given steel plate and has been cured hardening and prevent the degeneration of steel plate at other aspect of performance simultaneously.
But, according to open source literature, because in process of production must the strict amount of controlling Ti, N and S, the therefore problem that exists production cost to improve in order to ensure the curing hardening of appropriateness.
On the other hand, United States Patent (USP) 5,556,485 and 5,656,102 disclose the method that employing Ti-V base ultra low-carbon steel (ultra low carbon steel) production can be cured the hardened cold-rolled steel sheet, and described ultra low-carbon steel comprises the C of 0.0005～0.1wt%; The Mn of 0～2.5wt%; The Al of 0～0.5wt%; The N of 0～0.04wt%; The Ti of 0～0.5wt%; With 0.005～0.6% V.
In these open source literatures, for example be the carbide of VC although V can produce since its molten again (re-melting) thus temperature cross and lowly can't fully promote plasticity, therefore added about 0.02wt% or more Ti to improve plasticity.
Like this, at United States Patent (USP) 5,556, in 485 and 5,656,102, exist because the problem of the ageing resistance aspect that coarse grain (coarsegrain) causes and the problem that adds the production cost increase that a large amount of Ti cause.
Simultaneously, the still unexamined patent publication No. of Japan (Hei) 5-93502 discloses by adding Sn and has improved the indurative method of curing, and the still unexamined patent publication No. of Japan (Hei) 9-249936 discloses by adding V and Nb and reduced the method for the stress concentration (stress concentration) of grain boundary with the ductility of enhancing steel.
In addition, the still unexamined patent publication No. of Japan (Hei) 8-49038 discloses by adding Zr and has improved the method for plasticity, and the still unexamined patent publication No. of Japan (Hei) 7-278654 discloses by adding Cr and improved intensity and make the degeneration of operation hardenability value (work hardening index) (N-value) minimize the method with the reinforcement plasticity simultaneously.
Yet, these methods only are designed to improve and cure hardening or plasticity by adding alloying element, do not cure hardening, ageing resistance and secondary operation brittle resistance (secondary work em-brittlement resistance) and can not improve simultaneously.
In the method for above-mentioned open source literature, although boron adds steel as the element of known raising secondary operation brittle resistance with the amount of 5ppm, because the existence of excessive P makes ability of its raising secondary operation brittle resistance be restricted.
Further, if B is excessively added steel to improve the secondary operation brittle resistance, then excessive B can cause performance degradation, and the amount that therefore adds the B of steel is restricted.
Correspondingly, because extension-embrittlement conversion temp (ductility-brittleness transitiontemperature) (DBTT) is necessary for-20 ℃ or higher to prevent the secondary operation embrittlement, therefore need in curing hardened steel, add B other component in addition in the prior art, and investigate new working condition.
On the other hand, in order to prolong the time limit of service of vehicle part, need to strengthen solidity to corrosion.
For this reason, steel plate is usually through electroplating or hot dipping.
Although electroplating steel plate has good plating performance and good solidity to corrosion, electroplating steel plate is very expensive with respect to the hot dipping steel plate, so uses the hot dipping steel plate usually in the vehicle.
Correspondingly, in order to improve the solidity to corrosion of hot dipping steel plate, the research of hot-dip process and hot dipping steel plate is continued to carry out, and the usage degree of hot dipping steel plate has also increased.
Disclosure of an invention
Technical problem
Therefore, carry out the present invention in view of the problems referred to above, and the objective of the invention is to by adding minor N b and Al, Mo and B, suitably control ratio and the grain-size of Nb/C simultaneously, a kind of cured hardened high strength cold rolled steel plate with the hardening of curing, ageing resistance, secondary operation brittle resistance is provided, and adopts hot dipping steel plate that this cold-rolled steel sheet makes and preparation method thereof.
Technical scheme
According to an aspect of the present invention, above-mentioned and other purpose realizes by the following method: provide a kind of hardened high strength cold rolled steel plate that cures by the hot rolling of steel, cold rolling and lasting annealing, by weight percentage, described steel plate comprises: 0.0016～0.01% C; 0.1% or Si still less; 0.2～1.5% Mn; 0.05～0.15% P; 0.01% or S still less; 0.08～0.5% solvable Al; 0.0025% or N still less; 0.003～0.1% Nb; 0～0.003% Ti; 0.01～0.4% Mo; 0.0005～0.005% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7; The fine precipitation of AlN that its light plate forms when having the described steel of hot rolling, and grain-size is 9 or higher (ASTM standard No.), the fine sedimentary size of this AlN plays the inhibition that suppresses grain growing in this steel plate annealing process.
Another aspect of the present invention provides a kind of hot dipping steel plate, and described hot dipping steel plate makes by the hot rolling of steel, cold rolling, lasting annealing and hot dipping, and by weight percentage, described steel plate comprises: 0.0016～0.01% C; 0.1% or Si still less; 0.2～1.5% Mn; 0.05～0.15% P; 0.01% or S still less; 0.08～0.5% solvable Al; 0.0025% or N still less; 0.003～0.1% Nb; 0～0.003% Ti; 0.01～0.4% Mo; 0.0005～0.005% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7; The fine precipitation of AlN that its light plate forms when having the described steel of hot rolling, and grain-size is 9 or higher (ASTM standard No.), the fine sedimentary size of this AlN plays the inhibition that suppresses grain growing in this steel plate annealing process.
One side more of the present invention provides a kind of production can cure the method for hardened high strength cold rolled steel plate, said method comprising the steps of: 1200 ℃ of bloom heating or above back are passed through at Ar 3Carry out finish rolling (finish rolling) under invert point or the higher temperature and come hot rolling bloom (slab), described bloom comprises 0.0016～0.01% C, 0.1% or Si still less, 0.2～1.5% Mn, 0.05～0.15% P, 0.01% or S still less, 0.08～0.5% solvable Al, 0.0025% or N still less, 0.003～0.1% Nb, 0～0.003% Ti, 0.01～0.4% Mo, 0.0005～0.005% B and Fe and other unavoidable impurities of surplus by weight percentage, and the ratio of Nb/C is 0.3～0.7; Described hot-rolled steel sheet is reeled; Carry out cold rolling to described hot-rolled steel sheet; And to described cold-rolled steel sheet continue annealing.
The method that has an aspect that a kind of production hot dipping steel plate is provided again of the present invention said method comprising the steps of: with 1200 ℃ of bloom heating or above back at Ar 3Carrying out finish rolling under invert point or the higher temperature carries out with the hot rolling bloom, described bloom comprises 0.0016～0.01% C, 0.1% or Si still less, 0.2～1.5% Mn, 0.05～0.15% P, 0.01% or S still less, 0.08～0.5% solvable Al, 0.0025% or N still less, 0.003～0.1% Nb, 0～0.003% Ti, 0.01～0.4% Mo, 0.0005～0.005% B and Fe and other unavoidable impurities of surplus by weight percentage, and the ratio of Nb/C is 0.3～0.7; With described hot-rolled steel sheet reel (coiling); Carry out cold rolling to described hot-rolled steel sheet; Described cold-rolled steel sheet is continued annealing; Described annealed sheet steel is carried out hot dipping; And described hot dipping steel plate carried out temper rolling (temper rolling).
Brief Description Of Drawings
Above-mentioned and other purpose, feature and other advantage of the present invention can and clearly be understood in conjunction with the accompanying drawings and more by following detailed description, wherein:
Fig. 1 illustrates the chart of grain-size to the influence of curing sclerosis value and ageing index;
Fig. 2 illustrates the chart of Al content to the mechanical property influence;
Fig. 3 illustrates the chart of Mo content to the influence of curing sclerosis value and ageing index;
Fig. 4 is the microgram of the microstructure of No. 8 steel of annealing back the present invention;
Fig. 5 illustrates in the steel of No. 8 steel of the present invention, No. 6 compared steel and prior art stretch ratio (drawingratio) to the chart of the influence of DBTT;
Fig. 6 is the chart that the stress-strain curve of the aging front and back of No. 8 steel of the present invention is shown; And
Fig. 7 is that the chart of the influence of sclerosis value and ageing index is cured in the Nb/C comparison that steel of the present invention is shown.
Carry out the most preferred embodiment of invention
Now describe preferred implementation of the present invention in detail.
The requirement that can cure the cold-rolled steel sheet of sclerosis (bake-hardenable) comprises: height cures ageing index (aging index) low under sclerosis value (high bake hardening value), the room temperature and good secondary operation brittle resistance (secondary work embrittlement resistance).
Cure sclerosis or weather aging and be the phenomenon of generation when being present in calking element (interstitial elements) in the steel as solute element (solute elements) particularly the tomography (dislocations) that produces of nitrogen or carbon fixation is middle when (fix) be out of shape.When the content of solute nitrogen in the steel and carbon increased, curing the sclerosis value also increased, the weather aging because solute element is excessive simultaneously, thus cause the plasticity variation.Therefore, it is very important the quantity of solute nitrogen in the steel and carbon being carried out optimization.
Because nitrogen has higher velocity of diffusion with respect to carbon in steel, so nitrogen rather than carbon influence weather aging.
So the amount that reduces solute nitrogen is to guarantee good ageing resistance.
About reducing the method for solute nitrogen in the steel, prior art known by reducing nitrogen as much as possible content or by in steel, adding Ti and Al (forming the element of nitride) form of the nitrogen in the steel with TiN and AlN precipitated as much as possible, thereby reduce the amount of the solute nitrogen in the steel.
About solute carbon, if the content of solute carbon excessively reduces, then ageing resistance will strengthen, but (bake hardenability) degenerate (deteriorate) that cure hardening simultaneously.On the other hand, if the content of solute carbon excessively increases, then cure hardening and just strengthened, but ageing resistance has been degenerated.
Therefore, in order to guarantee good ageing resistance simultaneously and to cure hardening, must suitably control the amount of the solute carbon in the carbon.
About the method for the amount of the solute carbon of control in the steel, known by the carbon in the control steel amount or by in steel, add Ti or Nb (carbide forming element) with the carbon in the steel with TiC, Ti 4C 2S 2Precipitate carbon as much as possible with the NbC form.
According to the present invention,, need control Nb/C ratio in order to make the content of solute carbon in steel suitable.
In addition, with regard to solute carbon, even its content is identical, curing aging also can present different according to the position of the solute carbon in the steel with ageing resistance, also promptly, be in grain boundary or the crystal grain according to solute carbon and present difference, this will be described in detail following.
According to solute carbon in steel the position and relate to the mobility (mobility) of solute carbon for curing reason that hardening and ageing resistance have a Different Effects.
When solute carbon was in the crystal grain, it can relatively freely move, and therefore not only influence is cured hardening and also had influence on ageing resistance.
On the other hand, because the solute carbon potential that is in grain boundary (grain boundary) in metastable position, therefore for the minimum that influences of low temperature aging, still cures down at high temperature, solute carbon is activated and influences and cures hardening.
Like this, the solute carbon in the crystal grain influences ageing resistance and cure hardening simultaneously, but the solute carbon of grain boundary only influences and cures hardening.
Correspondingly, suitably control the position of the solute carbon in the steel, also, solute carbon is controlled at the position of grain boundary rather than in crystal grain, can guarantees ageing resistance simultaneously and cure hardening.
Like this, in order to guarantee good ageing resistance simultaneously and to cure hardening, importantly to control position and control solute carbon the proper content in steel of solute carbon in steel.
One of the present invention is characterised in that, suitably controls the content of the solute carbon in the steel and the position in steel thereof.
Also promptly, according to the present invention, the content of suitably controlling carbon and niobium is with the amount of control solute carbon, crystal grain is controlled to be have the fine-grain size and make the solute carbon in the steel as far as possible all be in the grain boundary.
As mentioned above, when crystal grain attenuated, the area of grain boundary further increased, in the steel more solute carbon potential in the grain boundary, thereby guaranteed good ageing resistance simultaneously and cured hardening.
One of result who studies as the contriver, Fig. 1 be grain-size is shown and cure hardening (BH) value and ageing index (AI) between the chart of relation.
As shown in Figure 1, when increasing, also, when crystal grain became thinner, the remarkable decline of AI value caused BH value-AI to increase gradually with respect to BH value ASTM number of crystal grain.Therefore, be appreciated that from Fig. 1 crystal grain is thin more, AI increases many more.
According to the described result of Fig. 1, the contriver attempts the crystal grain of annealed sheet steel is limited in below the preset value, makes the solute carbon that is in the grain boundary in the steel increase as far as possible.
Also promptly, understand from the result of study contriver, crystal grain need be controlled at grain-size is 9 (ASTM numbers) or bigger, makes that curing indurative degeneration minimum makes the ageing resistance maximum simultaneously.
Of the present invention another be characterised in that, makes crystal grain finer by forming fine AlN precipitation (precipitates) when the hot rolling.
Also promptly,, when hot rolling, form the AlN precipitation by in steel, adding a large amount of Al according to the present invention, the growth of inhibition crystal grain when AlN is deposited in cold-rolled steel sheet anneal, thus make crystal grain finer.
Like this, according to the present invention, the content of suitably controlling Al forms fine AlN precipitation when making hot rolling.
In addition, suitably control the sedimentary size of AlN and can guarantee to obtain fine crystal grain more.
Known Al can be used as the reductor that cures in the hardened steel and/or as the interpolation component of the AlN precipitation by thick (coarse) in order to fixing (fix) nitrogen.
The hardened steel that cures like this is prior art the unknown: wherein the content by suitable control Al makes that Al and N are in conjunction with forming fine AlN precipitation when hot rolling, thereby make crystal grain fine, make solute carbon potential in the steel in the grain boundary rather than be arranged in crystal grain, therefore guarantee good ageing resistance simultaneously and cure hardening.
Owing to need be aspect ageing resistance surpass 6 months or abovely do not present detectable variation, have a high BH value simultaneously, therefore needs can improve and cure hardening and make the minimized technology of ageing resistance simultaneously.
Aspect this, the contriver understands, and Al is used to provide the very effective element that can cure hardened steel.
Also promptly, (total amount is 0～30ppm) if any, and form the AlN precipitation this moment in steel, and only be used for fixing solute nitrogen in the steel that is added with Nb and Ti when the aluminium of solubility adds to common 0.02～0.06% scope.But, when in steel, adding 0.08% or during above soluble aluminum, can form very fine AlN precipitation, AlN suppresses the hamper of grain growing when precipitating as full annealed, make that the grain-size of steel is littler than the grain-size of the existing steel that adds Nb (containing the soluble aluminum that with good grounds existing method is added), thereby the curing hardening of reinforcement is provided and do not change the AI value.
Certainly, in adding the steel of Ti, under 1300 ℃ or above high temperature, nitrogen is precipitated as the TiN precipitation, and most of precipitation is coarse, therefore can remarkably influenced sosoloid (solid solution) or crystal grain miniaturization (grain refining).
Among Fig. 2, show the example that sclerosis (BH) value and ageing index (AI) change along with the variation of the amount of soluble aluminum that cures of hot dipping (hot-dipped) steel plate.
As can be known from Fig. 2, along with the content increase of Al, the value of BH also increases, but AI only has slight variation.
With regard to curing hardening, from Fig. 2 be appreciated that the content of soluble aluminum be preferably 0.08% or more than.
Analyze by adding Al as mentioned above and cure indurative reinforced effects, according to this result who analyzes gained, BH mainly is subjected to Ti, and the influence of the content of Nb and Al is understood that by formula 1
BH＝50-(885×Ti)-(1589×Nb)+(62×Al)---(1)
In addition, according to the present invention, suitably select hot rolling around temperature so that the crystal grain miniaturization.
If hot rolling is too high around temperature, even controlled the composition (also being the content of carbon, soluble aluminum and niobium) of steel, crystal grain is still understood chap in winding process.As a result, in full annealed (recrystallizationannealing) process grain coarsening takes place, the particle diameter that makes crystal grain have be 9 (ASTM numbers) or below, thereby make AI increase.On the contrary, if hot rolling descends to a certain degree around temperature, then the ageing resistance under the room temperature can strengthen, but the crystal grain miniaturization is excessive, and this may cause the degeneration of yield strength increase and plasticity, and causes that elongation and r value descend.
Of the present invention another is characterised in that, makes the secondary operation brittle resistance strengthen by adding suitable Mo.
Usually, vehicle part is shaped and obtains desired shape by repeating compacting (pressing).
The secondary operation degradation property is illustrated in the slight crack (crack) that forms behind first (primary) procedure in second operation work.
Be present in the granule boundary of steel and weaken connection power (coupling force) between the particle, because (P) phenomenon that makes fracture (fractures) form along granule boundary causes slight crack to produce.
In order to eliminate the secondary operation embrittlement, mainly be not add in the requirement steel.But, be to increase and the minimum solute element of rate elongation decline with respect to intensity, particularly, its advantage is cheap.
The result, strengthen in order to make steel, although P must add in the steel admittedly, nearest progress can be ignored in order to a little rising of eliminating the production cost that the secondary operation embrittlement follows simultaneously by adding other solute element beyond the P so that steel is strengthened.
But according to result of study, prediction P in a foreseeable future also will continue to be used as the element of strengthening steel.
About in the steel that adds, improving the method for secondary operation embrittlement performance, progress of research is: by adding B or making solute element be retained in the steel (for example can cure the hardened steel) in steel, increase site competitive effect (site competition effect) or the bonding force of grain boundary (bonding force) of relative P, or reduce the coiling temperature to being lower than preset value by walking around at hot rolling in the journey, make the grain boundary diffusion of P minimize, thereby prevent secondary operation fragility, but present research does not provide the perfect scheme that addresses these problems as yet.
Correspondingly, the present invention adopts Mo further to strengthen the secondary operation brittle resistance.
According to contriver's result of study, find because Mo has strengthened the bonding force of grain boundary, therefore be very beneficial for improving the secondary operation brittle resistance.
In addition, because Mo has avidity (affinity) to the solute element in the steel, therefore Mo can suppress solute element diffusion (diffusion) and off normal (dislocation) when steel stores under room temperature for a long time, thereby strengthens ageing resistance.
Fig. 3 illustrates strengthening the chart that the ageing resistance effect is analyzed the result who obtains by adding Mo, and the content as Mo increases as can be seen from Figure 3, and the BH value does not have remarkable the change, but AI descends, thereby strengthens ageing resistance.
According to analyzing the result who obtains to strengthening the ageing resistance effect by adding Mo, AI mainly is subjected to Ti, and the influence of the content of Nb and Mo is understood that by formula 2
AI＝44-(423*Ti)-(2119*Nb)-(125*Mo)---(2)
The contriver derives and obtains the optimum combination of each element, and this combination can utilize the character of Mo and prevent and cause performance degradation owing to the interpolation of excessive Mo.
In addition, according to the present invention, the content of suitably controlling B is to strengthen the secondary operation brittle resistance.
Simultaneously, according to the present invention, can use other various prior aries and strengthen the secondary operation brittle resistance, one of them examples of applications is suitably to control the coiling temperature.
Now describe the composition of steel of the present invention in detail.
Carbon (C): C is used for sosoloid is strengthened and cured the hardened element.If the content of carbon is low excessively, then the tensile strength of steel significantly descends, and can't guarantee enough hardening effects that cures because the absolute content of carbon is low in the steel, and because the elimination of the site competitive effect between solute carbon and the P makes the secondary operation brittle resistance also degenerate.
Therefore, the content of carbon preferred 0.0016% or more than, with the effect of guaranteeing that carbon adds.
On the other hand, if the too high levels of carbon, because the excessive solute carbon that would exist and can't guarantee tensile deformation (stretcher strain) to take place ageing resistance under the room temperature, thereby make the plasticity of steel and ductility descend in forming process in the steel.So the upper limit of carbon content is set at 0.01%, preferred 0.0025%.
According to the present invention, when carbon content is in 0.0016～0.0025% scope, with carbon content control to this scope ability can 95% or above level realize in practice.
Silicon (Si): Si is the element that is used to improve the intensity of steel.But along with the content of silicon increases, ductility is degenerated significantly, and because silicon makes the hot dipping ability drop, it is favourable therefore addition in the steel of silicon being minimized.
So, according to the present invention, degenerate in order to prevent the performance (performance that is coated with that comprises steel) that silicon causes, the content of silicon is restricted to 0.1% or littler, particularly 0.02% or littler.
Manganese (Mn): Mn is used to prevent that FeS from forming and the element of the thermal embrittlement that causes, and it is by being precipitated as the sulphur in the steel fully MnS and can neither reducing ductility and can make steel strengthen again so that grain-size descends simultaneously.
Add effect in order to reach sufficient manganese, preferably add 0.2% scope or above Mn.
Simultaneously, if the content of Mn surpasses 1.5%, when the intensity of steel rises rapidly since sosoloid strengthen and make the plasticity degeneration.Particularly, during production hot dipping steel plate, in annealing operation, on surface of steel plate, form a large amount of oxide compounds (for example MnO) and much be coated with defective (for example candy strip), thereby feasiblely comprised the performance degradation of the steel that is coated with sticking power (coating adherence).
Correspondingly, the content of Mn preferably in 0.2～1.5% scope, more preferably, in 0.2～1.2% scope.
Phosphorus (P): P is the alloying element of substituted (substitutional), and it can provide the highest sosoloid stiffening effect, and is used to improve the anisotropic index (anisotropy index) of (in-plane) in the plane in the intensity that improves steel.
Result of study according to the inventor, P makes that the crystal grain of hot-rolled steel sheet is thinner, form thereby be used for promoting to have (111) planar microstructure, and this microstructure is favourable for improving average r-value (plasticity-anisotropic index (plasticity-anisotropy index)) in the subsequent annealing operation.Particularly, found because the site competitive effect between carbon and the phosphorus is high more from the big more hardening of curing of amount of curing hardening P.
But the value increase of phosphorus content causes the connection power of grain boundary to weaken, thereby makes the secondary operation brittle resistance degenerate.
Correspondingly, the content of phosphorus need be limited in 0.05～0.15% scope, preferred 0.05～0.11% scope.
Sulphur (S): the content of sulphur is preferably 0.01% or littler scope.
Aluminium (Al): aluminium is the alloying element that is considered as important element among the present invention.
Al is generally used for deoxidation and the fixing solute nitrogen in the steel.But in the present invention, Al and N are combined in and form the AlN precipitation in the steel in course of hot rolling, thereby suppress grain growth and therefore promote crystal grain miniaturization in the annealing operation, and therefore improve ageing resistance and cure hardening.
For the cured hardened steel that adds Nb, mainly be to reach the crystal grain miniaturization by NbC.
But, according to the present invention because fine AlN precipitation and NbC precipitation stop grain growth together in annealing operation, so grain-size can further reduce, thereby good ageing resistance is provided and has cured hardening.
Among the present invention, the content that needs to set Al makes it that fine AlN precipitation is provided in course of hot rolling.
When the content of Al is lower than 0.08%, owing to be difficult in course of hot rolling, provide fine AlN precipitation, need be with the lower limit to 0.08% of Al content.
Preferably, the content of Al surpasses 0.1%, thereby guarantees that by the Al that adds above 0.1% the Al precipitation is finer.
Consider the surface properties and the production cost of the influence of plasticity, oxidation content (oxidized inclusion), the upper limit of Al content is preferably 0.5%, and more preferably 0.12%.
The sedimentary size of AlN should be enough to as the hamper that suppresses grain growth in the cold-rolled steel sheet annealing process, and the preferred 20 μ m () or littler of the sedimentary mean sizes of AlN.
As mentioned above when the sedimentary mean sizes of AlN be 20 μ m or more hour, obtain finer crystal grain.
Nitrogen (N): nitrogen exists with the solute state before and after annealing, and makes the plasticity of steel degenerate.In addition, because the aging of nitrogen is higher than other calking element, need to adopt Ti or Al to come nitrogen is fixed.
In the present invention, in steel, add Nb and a spot of Ti of appropriate amount, add too much nitrogen and make and produce solute nitrogen in the steel.
Therefore, the content of nitrogen is restricted to 0.0025% or littler.
Titanium (Ti): titanium joins in the steel as carbide forming element usually, and to form in steel for example be the nitride of TiN, for example be TiS or Ti 4C 2S 2Sulfide, for example be the carbide of TiC.
But according to the present invention, Ti does not add in the steel, even added Ti, consider in the starting material of steel and contain Ti that it can will be fixed to steel on a spot of nitrogen slave unit, and work in-process is fixed to steel, and the addition of Ti in steel is restricted to 0.003% or still less.
Niobium (Nb): niobium and Al, Mo are very important elements among the present invention.
Nb is potent (intensive) carbide forming element, the fixing carbon in the steel when NbC precipitates.Particularly because the precipitated phase of NbC is very fine than other precipitation, so it in the full annealed process as potent hamper with prevention (impede) grain growing, thereby make crystal grain become finer.
When the size of crystal grain diminishes as mentioned above, cure hardening and the secondary operation brittle resistance has strengthened.
But, cure hardening in order to strengthen, not only the fine effect of crystal grain there is requirement, but also predetermined amount solute carbon is had requirement.
Correspondingly,, make the crystal grain miniaturization by NbC precipitation according to the present invention, thereby and the amount of control Nb guarantee to cure hardening with the solute carbon that allows to keep predetermined amount in the steel.The content of Nb is preferably 0.003～0.1% scope, more preferably is 0.003～0.011% scope.
The sedimentary dimensional requirement of NbC is 30nm or littler.
In addition,, not only need to control the content of Nb but also also need simultaneously and control the Nb/C ratio in order to control the ageing resistance of curing under hardening and the room temperature more suitably, according to the present invention, need be with Nb/C than the scope that is controlled at 0.3～0.7.
When Nb/C than less than 0.3 the time, because the few and feasible sclerosis value of curing of the absolute value of the solute carbon in the steel descends; And work as Nb/C than greater than 0.7, even owing to the amount increase of the solute carbon in the steel makes that curing the sclerosis value rises, but ageing index also rises, thereby makes the ageing resistance under the room temperature degenerate.Correspondingly, need be with Nb/C than the scope that is restricted to 0.3～0.7.
Molybdenum (Mo): molybdenum is an another kind of very important element among the present invention.
Mo is used for strengthening the intensity of steel or is formed on the carbide of the molybdenum of steel solute state (solute state).Particularly, Mo is used for improving the bonding force of the grain boundary of steel solute state, thereby prevents the grain boundary fracture that caused by P, also, has strengthened the secondary operation brittle resistance, and the affinity of utilization and carbon suppresses the diffusion of carbon, thus the enhancing ageing resistance.
But, add the increase that too much Mo can cause production cost.
Thereby, consider Mo additive effect with respect to production cost, the content of Mo is preferably 0.01～0.4% scope, more preferably 0.01～0.1% scope.
Boron (B): boron is the calking element, is positioned at the inside of steel.B is in the solute state or combines with nitrogen and forms the BN nitride in the grain boundary.
Because therefore B needs accurately control addition according to the character generation remarkable influence of addition to steel.
Also promptly, when a spot of B adds fashionablely, B separates (segregate) in the grain boundary, has strengthened the secondary operation brittle resistance simultaneously.
But when B was higher than predetermined amount adding steel, the ductility of steel can significantly be degenerated, and intensity increasing simultaneously is so need to add the B of appropriate amount.
Therefore, according to the present invention, consider above-mentioned characteristic and the ability of producing steel by interpolation B, the amount of B is preferably 0.0005～0.005% scope, more preferably 0.0005～0.0015% scope.
Grain-size in the steel plate of the present invention is necessary for 9A (ASTM number) or higher, will satisfy aforesaid composition simultaneously.
So, when the grain-size in the steel plate is 9 (ASTM numbers) or when higher, the amount of the solute carbon of grain boundary increases, thereby make that curing hardening further strengthens, and at room temperature keeps good ageing resistance simultaneously.
On the other hand, when the grain-size in the steel plate during, can't obtain enough hardening effects of curing less than 9 (ASTM numbers).
Steel plate of the present invention contains more solute carbon in grain boundary rather than crystal grain.
Among the present invention, the preferred amounts of solute carbon is 3～6ppm in the crystal grain.
In addition, the sedimentary gravel size decision 20 μ m () or littler of the AlN that forms in the course of hot rolling.
When AlN is sedimentary when being of a size of 20 μ m, it is finer that crystal grain becomes, and makes that curing hardening further strengthens.
Steel plate of the present invention has good hardening, ageing resistance, secondary operation brittle resistance and 300Mpa or the above tensile strength of curing.
The preferred implementation of the method be used to produce steel of the present invention is now described.
After having as mentioned above the molten steel of forming (molten steel) in production, make bloom, then be heated to 1200 ℃ or above temperature by continuing casting (cast) this molten steel.The bloom of heating is at Ar 3Carry out hot rolling by finish rolling (finish rolling) under invert point or the higher temperature, preferred next-door neighbour (immediately) surpasses Ar 3900～950 ℃ of invert point, thus hot-rolled steel sheet is provided.
Bloom is heated to 1200 ℃ or the above object is, before hot rolling, give austenite (austenite) structure of the abundant homogenizing of steel plate.
Also promptly, when the temperature of bloom is lower than 1200 ℃, steel construction can have blended crystal grain rather than homogenizing austenite crystal, thereby causes the character of steel to be degenerated.
If smart hot rolled temperature is low excessively, then the edge of part and hot coiling body can become single-phase zone end to end, makes the plasticity of steel degenerate simultaneously thereby increased the anisotropy in the plane.If smart hot rolled temperature is too high, in steel, form very thick crystal grain, make that surface of steel plate forms for example defective of orange peel shape easily after processing.
So smart hot-rolled temperature must be determined according to above-mentioned all angles.
Simultaneously, too high when hot rolling around temperature, owing to increasing consequently, grain-size after the annealing can't obtain the fine effect of enough crystal grain, and owing to the phosphorus of grain boundary separates increase and occurs the secondary operation embrittlement easily.When hot rolling is low excessively around temperature, owing to the fine effect of crystal grain makes ageing resistance and secondary operation brittle resistance strengthen, but yield strength increases too much and plasticity descends simultaneously.
So hot rolling must be determined according to above-mentioned all angles around temperature.
According to the present invention, preferred 550～650 ℃ of hot-rolled temperature, more preferably 600～650 ℃.
When hot-rolled steel sheet through the erosion (acid pickling), carry out cold rolling, thereby make cold-rolled steel sheet.
At this moment, reduction ratio (reduction rate) preferred 70～80%.
Reduction ratio remain on 70% or the above object be, strengthen the plasticity (particularly r value) and the ageing resistance of steel plate by grain refining.
Simultaneously, when reduction ratio greater than 80% the time, grain refining takes place, and since reduction ratio too high make grain refining excessively and the r value descend gradually, cause hardened material (harden).
Then, cold-rolled steel sheet continues annealing by usual method.
The present invention continues annealing and can carry out under about 770～830 ℃, and is not subjected to the restriction of this condition.
Have higher recrystallization temperature owing to add the steel of Nb than the steel that adds Ti, and the present invention is to provide the steel that adds Nb, so annealing process is preferably carried out 770 ℃ or above temperature.
Also promptly, when annealing process when the temperature that is lower than 770 ℃ is carried out, yield strength has increased, simultaneously since the crystal grain of not re-crystallization exist and make rate elongation and the degeneration of r value.
On the other hand, when annealing process when the temperature that is higher than 830 ℃ is carried out, plasticity has increased.But, (characterize) because grain-size this moment less than 9 (ASTM of required crystal grain numbers) with ASTM number, AI be 30MPa or more than, ageing resistance has descended.
After continuing annealing, annealed cold-rolled steel sheet cool to room temperature then carries out hot dipping.Perhaps, continuing annealed simultaneously, cold-rolled steel sheet is cooled to the hot dipping temperature from continuing annealing temperature, then carries out hot dipping.
According to the present invention, hot dipping is not limited to certain conditions and carries out with usual method.
The temperature of hot dipping is generally about 450～500 ℃.
Then, the hot dipping steel plate carries out temper rolling (temper roilling).
At this moment, in order to ensure the ageing resistance under the room temperature with suitable cure hardening and carried out temper rolling.This temper rolling is preferably 1.2～1.5% scope than a little more than common temper rolling.
Also promptly, this temper rolling is than the reason a little more than common temper rolling: prevent the degeneration of the ageing resistance that the solute carbon in the steel causes.
But, when the stretch ratio of temper rolling is too high, though ageing resistance has strengthened, operation sclerosis (work hardening) having taken place, thereby makes the character of steel degenerate.Particularly, when adopting steel plate production hot dipping steel plate of the present invention, the over-drastic temper rolling causes being coated with (coating) sticking power degenerates, thereby makes coating stripping.
So temper rolling is determined than must and being coated with sticking power according to the ageing resistance under the room temperature.
The present invention is elaborated with reference to embodiment.
Embodiment 1
Bloom with composition as described in Table 1 is heated to 1220 ℃, adds hot finishing under 920 ℃, so that hot-rolled steel sheet to be provided.
This hot-rolled steel sheet is reeled according to the condition shown in the table 2, and carries out cold rolling and annealing.Then, the annealed cold-rolled steel sheet carries out hot dipping at 450 ℃, and the temper rolling ratio of following with about 1.5% carries out temper rolling.Then, mensuration is cured sclerosis (BH) value, ageing index (AI), grain-size (ASTM number), AlN precipitation size and ductility-fragility conversion temp (DBTT).The result is as shown in table 2.
In table 2, be that 2.0 condition is measured DBTT at stretch ratio (drawing ratio), be used to assess the secondary operation degradation property.
About No. 8 steel of the present invention, after with steel plate annealing, observe its microstructures to amplify 200 times, observed result is as shown in Figure 4.
About the steel of No. 8 steel of the present invention, No. 6 steel of control sample and prior art, studied the variation of the variation of its DBTT corresponding to draw ratio, gained the results are shown in Fig. 5.
At this moment, the ladle of the prior art is drawn together the C of 0.0019wt%; The Mn of 0.63wt%; The P of 0.056wt%; The solubility Al of 0.03wt%; The Ti of 0.005wt%; The Nb of 0.006wt%, and the N of 0.014wt%.
In addition, measure the tensile strength of No. 8 steel of the present invention before and after annealing, the gained stress-strain curve as shown in Figure 6.
In Fig. 6, instant (as-received) curve is for measuring the stress-strain curve of tensile strength immediately after making steel, and aging curve was for being transported to Thailand with steel and storing the stress-strain curve of measuring tensile strength after 6 months in 180 days.
No. 8 steel of the present invention are being transported to the torrid zone and when being stored in Thailand, and No. 8 steel of the present invention are preserved under medial temperature is 32 ℃ and about 70% humidity.
Table 1
Test piece number (Test pc No.) Form (wt%)
C Mn Si P S Sol.Al Ti Nb N Mo B Nb/C
IS 1 0.0024 0.58 0.01 0.069 0.0082 0.087 0 0.008 0.0016 0.034 0.0005 0.43
2 0.0022 0.63 0.009 0.068 0.0081 0.098 0 0.01 0.0024 0.048 0.0005 0.59
3 0.0023 0.45 0.011 0.062 0.0058 0.105 0.0025 0.0082 0.0019 0.061 0.0007 0.46
4 0.0024 0.61 0.008 0.071 0.0083 0.118 0.0015 0.0073 0.0015 0.059 0.0005 0.39
5 0.0017 0.98 0.01 0.096 0.0070 0.105 0 0.004 0.0017 0.051 0.0008 0.3
6 0.0019 1.01 0.015 0.10 0.0063 0.089 0 0.005 0.0020 0.062 0.0009 0.34
7 0.0021 1.10 0.007 0.099 0.0073 0.105 0 0.007 0.0013 0.045 0.0005 0.43
8 0.0023 0.98 0.013 0.091 0.0057 0.104 0.001 0.011 0.0013 0.098 0.0007 0.62
9 0.0020 0.43 0.01 0.030 0.008 0.30 0.003 0.008 0.0017 0.049 0.0005 0.52
10 0.0022 0.32 0.008 0.035 0.007 0.42 0.002 0.01 0.0021 0.021 0.0006 0.59
CS 1 0.0054 0.64 0.01 0.069 0.0071 0.082 0.001 0.011 0.0017 0.021 0.0007 0.26
2 0.0022 0.63 0.014 0.066 0.0085 0.040 0.025 0.009 0.0015 0.015 0.0005 0.57
3 0.0012 0.65 0.011 0.070 0.0072 0.075 0.001 0.0105 0.0019 0.059 0.0008 1.13
4 0.0021 0.93 0.008 0.096 0.0089 0.043 0 0.022 0.0017 0.021 0.0006 1.35
5 0.0022 0.59 0.009 0.062 0.0066 0.071 0.002 0.009 0.0022 0 0.0007 0.53
6 0.0019 0.99 0.007 0.099 0.0078 0.041 0.001 0.008 0.0021 0 0 0.54
7 0.0020 0.62 0.015 0.047 0.0085 0.021 0 0.010 0.0019 0 0 0.65
8 0.0023 0.98 0.016 0.120 0.0078 0.098 0.001 0.009 0.0023 0.031 0 0.50
9 0.0024 0.54 0.01 0.059 0.0087 0.29 0 0.005 0.0022 0 0.0007 0.48
10 0.0069 0.43 0.009 0.056 0.010 0.36 0.003 0.010 0.0019 0.015 0.0005 0.19
Table 2
Test piece number (Test pc No.) CT (℃) Slow down (%) AT (℃) BH value (MPa) AI (MPa) Grain-size (AsTM No.) DBTT (℃) AlN size (μ m)
IS 1 620 78 805 42.7 22.8 10.5 -50 20 or below
2 620 77 820 40.2 16.8 9.8 -40 20 or below
3 620 78 825 41.3 17.9 9.9 -50 20 or below
4 610 76 800 44.4 20.5 10.5 -60 20 or below
5 640 78 820 50.2 29.1 10.0 -40 20 or below
6 620 78 820 47.6 25.7 11.1 -50 20 or below
7 620 75 830 45.4 23.5 11.5 -40 20 or below
8 620 78 820 38.1 8.0 11.3 -40 20 or below
9 620 78 820 53.2 19.7 12.5 -70 20 or below
10 620 77 820 58.4 19.3 11.7 -60 20 or below
CS 1 620 78 810 62.0 51.2 11.2 -60 20 or below
2 640 78 820 13.1 12.5 8.1 10 20 or more than
3 620 78 810 0 0 8.2 20 20 or more than
4 630 76 800 0 0 9.1 20 20 or more than
5 620 78 810 38.3 24.1 10.9 0 20 or more than
6 630 77 820 36.4 26.6 9.2 -10 20 or more than
7 620 76 810 34.1 22.8 9.5 -10 20 or more than
8 640 78 820 40.9 20.6 9.8 0 20 or below
9 620 77 820 60.0 33.4 11.2 -60 20 or below
10 640 77 820 63.8 39.7 11.7 -70 20 or below
IS: steel of the present invention, CS: the steel of Comparative Examples, CT: coiling temperature; AT: annealing temperature
As shown in table 2, the grain-size that is appreciated that 1 to No. 10 steel of the present invention is 9.8～12.5 (ASTM numbers), and the sedimentary mean sizes of AlN is 20 μ m () or littler.
Be appreciated that from Fig. 4 No. 8 steel of the present invention have very fine crystal grain, having very simultaneously in whole microstructure, the crystal grain of homogeneous distributes.
As shown in table 2, the crystal grain of steel of the present invention is very fine, this is because steel of the present invention contains the Al of high level with respect to the steel of Comparative Examples, makes to form fine AlN precipitation in the steel of the present invention, and and the grain growing that takes place when suppressing full annealed together of NbC precipitation.
Because the fine effect of above-mentioned crystal grain is cured the sclerosis value in the scope of 38.1～58.4MPa, is used to assess the scope of the AI of ageing resistance under the room temperature at 8.0～29.1MPa.Correspondingly, be appreciated that balance is very good between BH value and the ageing resistance.
Simultaneously, as seen relatively low with respect to the higher AI value of curing for the sclerosis value, this except the fine effect of crystal grain that causes based on the AlN precipitation, the hesitation (retarding effect) of solute carbon in the steel that causes based on adding Mo also.
As seen in addition, from the secondary operation degradation property, be that DBTT under 2.0 is between-40 ℃～-70 ℃ at stretch ratio.
As seen as shown in Figure 5, with respect to No. 6 steel of Comparative Examples and the steel of prior art, No. 8 steel of the present invention make intercrystalline connection power increase have good DBTT owing to add Mo.
As shown in Figure 6, visible No. 8 steel standing storages at high temperature of the present invention 6 months or abovely have a good ageing resistance.
Therefore, be appreciated that steel of the present invention has good hardening and the secondary operation brittle resistance of curing, and under the high temperature of torrid areas standing storage 6 months or above can't be because of aging and degradation.
Simultaneously, the carbon content of No. 1 steel of Comparative Examples is 0.0054wt%, is higher than of the present invention 0.0016～0.0025% carbon content scope.Although No. 1 steel of Comparative Examples has good DBTT and very high BH value, its AI is 30MPa, and therefore, as seen its ageing resistance is degenerated significantly.Also promptly, although the grain-size in No. 1 steel of Comparative Examples is 11.2 (ASTM numbers), and it has very fine crystal grain, can satisfy the requirement of the present invention for grain-size, and high-load solute carbon makes the ageing resistance of No. 1 steel of Comparative Examples degenerate in the steel.
In addition, the solvable Al content of No. 2 steel of Comparative Examples is 0.04wt%, is lower than of the present invention 0.08～0.12% aluminium content range, and No. 2 steel of Comparative Examples also have 0.025% Ti content, are higher than Ti content of the present invention.The crystal grain of No. 2 steel of Comparative Examples is big, the BH value is low and DBTT degenerates.
Promptly, for No. 2 steel of Comparative Examples, it does not obtain precipitating the crystal grain micronized effect that brings by AlN, and the reinforced effects of BH value yet.In addition, add high-load Ti and make that most of carbon deposition that adds steel is TiC, so that almost do not give steel and cure hardening, and the minimizing of solute carbon also causes the site competitive effect between C and the P to descend in the steel, thereby make DBTT degenerate.
No. 3 steel of Comparative Examples are consistent with composition of the present invention, and difference is that carbon content is 0.0012wt%, is lower than carbon content of the present invention.
As seen, because the absolute content of carbon descends in the steel, the crystal grain of No. 3 steel of Comparative Examples is thick, BH value and AI is low, 20 ℃ DBTT degeneration.
The solvable Al content that No. 4 steel of Comparative Examples have is lower than the present invention, and Nb content is higher than the present invention.
For No. 4 steel of Comparative Examples, it does not obtain the crystal grain micronized effect that brought by Al and the reinforced effects of BH value.In addition, although the grain-size of No. 4 steel of Comparative Examples is 9.1 (ASTM numbers), satisfy grain-size requirement of the present invention, obviously add too much Nb and produced too much NbC precipitation and made and lack solute carbon in the steel, so that the BH value can't reach at all, and DBTT degenerates significantly.
Therefore compare with composition of the present invention, No. 5 steel of Comparative Examples do not contain Mo and B fully, can't expect reinforced effects aspect the secondary operation brittle resistance that is brought by Mo and B in No. 5 steel of Comparative Examples.
Also promptly, although No. 5 steel of Comparative Examples have good BH and AI value, owing to do not add Mo and B makes DBTT degenerate significantly.
The solvable Al content of No. 6 steel of Comparative Examples is lower than the present invention, and does not contain Mo fully.Although as seen No. 6 steel of Comparative Examples have good BH value and AI, do not make the connection power decline of intergranule make its DBTT degenerate owing to add Mo with respect to high-load P.
The solvable Al content of No. 7 steel of Comparative Examples is lower than the present invention, and does not contain Mo and M fully.No. 7 steel of Comparative Examples have 34.1 BH value, 22.8 AI value.Do not make DBTT degenerate owing to add Mo and B.
The P content of No. 8 steel of Comparative Examples is 0.12%, is higher than of the present invention 0.05～0.11% content, and does not comprise B.As seen,, make the reinforced effects of DBTT be restricted, particularly, do not make that DBTT is negative value (negative) owing to add B owing to added high-load P although the DBTT of No. 8 steel of Comparative Examples is enhanced by Mo.
No. 9 steel of Comparative Examples do not contain Mo, have the AI of 33.4MPa.As seen ageing resistance has been degenerated.
The Nb/C ratio that No. 10 steel of Comparative Examples have is lower than the present invention.Although have the good hardening of curing, because AI height its ageing resistance still descends owing to its BH value is high.
Embodiment 2
As table 1 with make sample according to composition and the preparation condition identical shown in 2 with No. 8 steel of the present invention, difference be Nb/C such as variation shown in Figure 7.Then, measure BH value and AI according to the variation of the ratio of Nb/C, the gained result as shown in Figure 7.
As shown in Figure 7, the ratio of Nb/C should be more than the 30MPa with the value of guaranteeing the BH value in 0.3～0.7 scope and AI is below the 30MPa.
Industrial applicability
Book is obvious as described above, according to the present invention, can provide to have good the cured hardened high strength cold rolled steel plate that cures hardening, ageing resistance and secondary operation brittle resistance, and the hot dipping steel plate that adopts this cold-rolled steel sheet to make.
Although preferred implementation of the present invention for the effect that plays explanation in this announcement, it will be appreciated by those skilled in the art that and to do various modifications, increase, replace, do not require disclosed scope and spirit of the present invention and can not depart from respective right to the present invention.

Claims (52)

1. one kind can be cured the hardened high strength cold rolled steel plate, and described cold-rolled steel sheet makes by the hot rolling of steel, cold rolling and lasting annealing, and described by weight percentage cold-rolled steel sheet comprises:
0.0016～0.01% C; 0.1% or Si still less; 0.2～1.5% Mn; 0.05～0.15% P; 0.01% or S still less; 0.08～0.5% solvable Al; 0.0025% or N still less; 0.003～0.1% Nb; 0.01～0.4% Mo; 0.0005～0.005% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
Its light plate has by described steel being carried out the fine precipitation of AlN that hot rolling forms, and the grain-size of steel plate is 9 or higher with ASTM number metering, and the fine sedimentary size of this AlN plays the inhibition that suppresses grain growing in this steel plate annealing process.
2. steel plate as claimed in claim 1 is characterized in that, the content of described Al is greater than 0.1% and be equal to or less than 0.5%.
3. steel plate as claimed in claim 1 or 2 is characterized in that, the solute carbon number amount in the described steel plate on the grain boundary is more than the solute carbon number amount in the crystal grain, and the amount of solute carbon is 3～6ppm in the crystal grain.
4. steel plate as claimed in claim 1 or 2 is characterized in that, the sedimentary mean sizes of described AlN is 20 μ m or littler.
5. steel plate as claimed in claim 3 is characterized in that, the sedimentary mean sizes of described AlN is 20 μ m or littler.
6. steel plate as claimed in claim 1 or 2 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
7. steel plate as claimed in claim 3 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
8. steel plate as claimed in claim 4 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
9. steel plate as claimed in claim 5 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
10. one kind can be cured the hardened high strength cold rolled steel plate, and described cold-rolled steel sheet makes by the hot rolling of steel, cold rolling and lasting annealing, and described by weight percentage cold-rolled steel sheet comprises:
0.0016～0.01% C; 0.1% or Si still less; 0.2～1.5% Mn; 0.05～0.15% P; 0.01% or S still less; 0.08～0.5% solvable Al; 0.0025% or N still less; 0.003～0.1% Nb; 0.003% or Ti still less; 0.01～0.4% Mo; 0.0005～0.005% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
Its light plate has by described steel being carried out the fine precipitation of AlN that hot rolling forms, and the grain-size in the steel plate is 9 or higher with ASTM number metering, and the fine sedimentary size of this AlN plays the inhibition that suppresses grain growth in this steel plate annealing process.
11. steel plate as claimed in claim 10 is characterized in that, the content of described Al is greater than 0.1% and be equal to or less than 0.5%.
12., it is characterized in that the solute carbon number amount in the described steel plate on the grain boundary is more than the solute carbon number amount in the crystal grain, and the amount of solute carbon is 3～6ppm in the crystal grain as claim 10 or 11 described steel plates.
13., it is characterized in that the sedimentary mean sizes of described AlN is 20 μ m or littler as claim 10 or 11 described steel plates.
14. steel plate as claimed in claim 12 is characterized in that, the sedimentary mean sizes of described AlN is 20 μ m or littler.
15., it is characterized in that described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation as claim 10 or 11 described steel plates.
16. steel plate as claimed in claim 12 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
17. steel plate as claimed in claim 13 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
18. steel plate as claimed in claim 14 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
19. one kind can be cured the hardened high strength cold rolled steel plate, described by weight percentage cold-rolled steel sheet comprises:
0.0016～0.0025% C; 0.02% or Si still less; 0.2～1.2% Mn; 0.05～0.11% P; 0.01% or S still less; 0.08～0.12% solvable Al; 0.0025% or N still less; 0.003～0.011% Nb; 0.01～0.1% Mo; 0.0005～0.0015% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
Its light plate have grain-size be 20 μ m or the littler fine precipitation of AlN, with count for ASTM number 9 or bigger grain-size, 30Mpa or above hardening, 30Mpa or littler ageing index, the stretch ratio of curing be-30 ℃ or following DBTT value under 2.0 the condition, the tensile strength of 340～390Mpa.
20. steel plate as claimed in claim 19 is characterized in that, the solute carbon number amount in the described steel plate on the grain boundary is more than the solute carbon number amount in the crystal grain, and the amount of solute carbon is 3～6ppm in the crystal grain.
21. one kind can be cured the hardened high strength cold rolled steel plate, described by weight percentage cold-rolled steel sheet comprises:
0.0016～0.0025% C; 0.02% or Si still less; 0.2～1.2% Mn; 0.05～0.11% P; 0.01% or S still less; 0.08～0.12% solvable Al; 0.0025% or N still less; 0.003% or Ti still less; 0.003～0.011% Nb; 0.01～0.1% Mo; 0.0005～0.0015% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
Its light plate have grain-size be 20 μ m or the littler fine precipitation of AlN, with count for ASTM number 9 or bigger grain-size, 30Mpa or above hardening, 30Mpa or littler ageing index, the stretch ratio of curing be-30 ℃ or following DBTT value under 2.0 the condition, the tensile strength of 340～390Mpa.
22. steel plate as claimed in claim 21 is characterized in that, the solute carbon number amount in the described steel plate on the grain boundary is more than the solute carbon number amount in the crystal grain, and the amount of solute carbon is 3～6ppm in the crystal grain.
23. a hot dipping steel plate, described hot dipping steel plate makes by the hot rolling of steel, cold rolling, lasting annealing, hot dipping and temper rolling, and described by weight percentage hot dipping steel plate comprises:
0.0016～0.01% C; 0.1% or Si still less; 0.2～1.5% Mn; 0.05～0.15% P; 0.01% or S still less; 0.08～0.5% solvable Al; 0.0025% or N still less; 0.003～0.1% Nb; 0.01～0.4% Mo; 0.0005～0.005% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
Its light plate has by described steel being carried out the fine precipitation of AlN that hot rolling forms, and the crystal grain in the described steel plate counts 9 or higher with ASTM number, and the fine sedimentary size of this AlN plays the inhibition that suppresses grain growing in this steel plate annealing process.
24. steel plate as claimed in claim 23 is characterized in that, the content of described Al is greater than 0.1% and be equal to or less than 0.5%.
25., it is characterized in that the solute carbon number amount in the described steel plate on the grain boundary is more than the solute carbon in the crystal grain, and the amount of solute carbon is 3～6ppm in the crystal grain as claim 23 or 24 described steel plates.
26., it is characterized in that the sedimentary mean sizes of described AlN is 20 μ m or littler as claim 23 or 24 described steel plates.
27. steel plate as claimed in claim 25 is characterized in that, the sedimentary mean sizes of described AlN is 20 μ m or littler.
28., it is characterized in that described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation as claim 23 or 24 described steel plates.
29. steel plate as claimed in claim 25 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
30. steel plate as claimed in claim 26 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
31. steel plate as claimed in claim 27 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
32. a hot dipping steel plate, described hot dipping steel plate makes by the hot rolling of steel, cold rolling, lasting annealing, hot dipping and temper rolling, and described by weight percentage hot dipping steel plate comprises:
0.0016～0.01% C; 0.1% or Si still less; 0.2～1.5% Mn; 0.05～0.15% P; 0.01% or S still less; 0.08～0.5% solvable Al; 0.0025% or N still less; 0.003～0.1% Nb; 0.003 or Ti still less; 0.01～0.4% Mo; 0.0005～0.005% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
Its light plate has by described steel being carried out the fine precipitation of AlN that hot rolling forms, and the grain-size in the steel plate counts 9 or higher with ASTM number, and the fine sedimentary size of this AlN plays the inhibition that suppresses grain growing in this steel plate annealing process.
33. steel plate as claimed in claim 32 is characterized in that, the content of described Al is greater than 0.1% and be equal to or less than 0.5%.
34., it is characterized in that the solute carbon number amount in the described steel plate on the grain boundary is more than the solute carbon in the crystal grain, and the amount of solute carbon is 3～6ppm in the crystal grain as claim 32 or 33 described steel plates.
35., it is characterized in that the sedimentary mean sizes of described AlN is 20 μ m or littler as claim 32 or 33 described steel plates.
36. steel plate as claimed in claim 34 is characterized in that, the sedimentary mean sizes of described AlN is 20 μ m or littler.
37., it is characterized in that described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation as claim 32 or 33 described steel plates.
38. steel plate as claimed in claim 34 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
39. steel plate as claimed in claim 35 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
40. steel plate as claimed in claim 36 is characterized in that, described steel plate comprises that also mean sizes is 30nm or littler NbC precipitation.
41. a hot dipping steel plate, described by weight percentage hot dipping steel plate comprises:
0.0016～0.0025% C; 0.02% or Si still less; 0.2～1.2% Mn; 0.05～0.11% P; 0.01% or S still less; 0.08～0.12% solvable Al; 0.0025% or N still less; 0.003～0.011% Nb; 0.01～0.1% Mo; 0.0005～0.0015% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
Its light plate have grain-size be 20 μ m or the littler fine precipitation of AlN, with count for ASTM number 9 or bigger grain-size, 30Mpa or above hardening BH, 30Mpa or littler ageing index AI, the stretch ratio of curing be-30 ℃ or following DBTT value under 2.0 the condition, the tensile strength of 340～390Mpa.
42. steel plate as claimed in claim 41 is characterized in that, the solute carbon number amount in the described steel plate on the grain boundary is more than the solute carbon in the crystal grain, and the amount of solute carbon is 3～6ppm in the crystal grain.
43. a hot dipping steel plate, described by weight percentage hot dipping steel plate comprises:
0.0016～0.0025% C; 0.02% or Si still less; 0.2～1.2% Mn; 0.05～0.11% P; 0.01% or S still less; 0.08～0.12% solvable Al; 0.0025% or N still less; 0.003% or Ti still less; 0.003～0.011% Nb; 0.01～0.1% Mo; 0.0005～0.0015% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
Its light plate have grain-size be 20 μ m or the littler fine precipitation of AlN, with count for ASTM number 9 or bigger grain-size, 30Mpa or above hardening BH, 30Mpa or littler ageing index AI, the stretch ratio of curing be-30 ℃ or following DBTT value under 2.0 the condition, the tensile strength of 340～390Mpa.
44. steel plate as claimed in claim 43 is characterized in that, the solute carbon number amount in the described steel plate on the grain boundary is more than the solute carbon in the crystal grain, and the amount of solute carbon is 3～6ppm in the crystal grain.
45. a production can be cured the method for hardened high strength cold rolled steel plate, said method comprising the steps of:
With bloom be heated to 1200 ℃ or above after, by at Ar 3Invert point or higher temperature are carried out finish rolling so that bloom is carried out hot rolling, and so that hot-rolled steel sheet to be provided, described bloom comprises 0.0016～0.01% C by weight percentage; 0.1% or Si still less; 0.2～1.5% Mn; 0.05～0.15% P; 0.01% or S still less; 0.08～0.5% solvable Al; 0.0025% or N still less; 0.003～0.1% Nb; 0.01～0.4% Mo; 0.0005～0.005% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
Described hot-rolled steel sheet is reeled;
Carry out cold rolling to described hot-rolled steel sheet; And
Described cold-rolled steel sheet is continued annealing.
46. a production can be cured the method for hardened high strength cold rolled steel plate, said method comprising the steps of:
With 1200 ℃ of bloom heating or above after, by at Ar 3Invert point or higher temperature are carried out finish rolling so that bloom is carried out hot rolling, and so that hot-rolled steel sheet to be provided, described bloom comprises 0.0016～0.01% C by weight percentage; 0.1% or Si still less; 0.2～1.5% Mn; 0.05～0.15% P; 0.01% or S still less; 0.08～0.5% solvable Al; 0.0025% or N still less; 0.003～0.1% Nb; 0.003% or Ti still less; 0.01～0.4% Mo; 0.0005～0.005% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
Described hot-rolled steel sheet is reeled;
Carry out cold rolling to described hot-rolled steel sheet; And
Described cold-rolled steel sheet is continued annealing.
47. a production can be cured the method for hardened high strength cold rolled steel plate, said method comprising the steps of:
After 1200 ℃ or above temperature were with the bloom homogenizing, by carrying out finish rolling 900～950 ℃ temperature so that bloom is carried out hot rolling, so that hot-rolled steel sheet to be provided, described bloom comprised 0.0016～0.0025% C by weight percentage; 0.02% or Si still less; 0.2～1.2% Mn; 0.05～0.11% P; 0.01% or S still less; 0.08～0.12% solvable Al; 0.0025% or N still less; 0.003～0.011% Nb; 0.01～0.1% Mo; 0.0005～0.0015% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
600～650 ℃ temperature described hot-rolled steel sheet is reeled;
Reduction ratio with 75～80% is carried out cold rolling to described hot-rolled steel sheet; And
770～830 ℃ temperature described cold-rolled steel sheet is continued annealing.
48. a production can be cured the method for hardened high strength cold rolled steel plate, said method comprising the steps of:
After 1200 ℃ or above temperature were with the bloom homogenizing, by carrying out finish rolling 900～950 ℃ temperature so that bloom is carried out hot rolling, so that hot-rolled steel sheet to be provided, described bloom comprised 0.0016～0.0025% C by weight percentage; 0.02% or Si still less; 0.2～1.2% Mn; 0.05～0.11% P; 0.01% or S still less; 0.08～0.12% solvable Al; 0.0025% or N still less; 0.003% or Ti still less; 0.003～0.011% Nb; 0.01～0.1% Mo; 0.0005～0.0015% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
600～650 ℃ temperature described hot-rolled steel sheet is reeled;
Reduction ratio with 75～80% is carried out cold rolling to described hot-rolled steel sheet; And
770～830 ℃ temperature described cold-rolled steel sheet is continued annealing.
49. a method of producing the hot dipping steel plate said method comprising the steps of:
With 1200 ℃ of bloom heating or above after, by at Ar 3Invert point or higher temperature are carried out finish rolling so that bloom is carried out hot rolling, and so that hot-rolled steel sheet to be provided, described bloom comprises 0.0016～0.01% C by weight percentage; 0.1% or Si still less; 0.2～1.5% Mn; 0.05～0.15% P; 0.01% or S still less; 0.08～0.5% solvable Al; 0.0025% or N still less; 0.003～0.1% Nb; 0.01～0.4% Mo; 0.0005～0.005% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
Described hot-rolled steel sheet is reeled;
Carry out cold rolling to described hot-rolled steel sheet;
Described cold-rolled steel sheet is continued annealing;
Described annealed sheet steel is carried out hot dipping; And
Described hot dipping steel plate is carried out temper rolling.
50. a method of producing the hot dipping steel plate said method comprising the steps of:
With 1200 ℃ of bloom heating or above after, by at Ar 3Invert point or higher temperature are carried out finish rolling so that bloom is carried out hot rolling, and so that hot-rolled steel sheet to be provided, described bloom comprises 0.0016～0.01% C by weight percentage; 0.1% or Si still less; 0.2～1.5% Mn; 0.05～0.15% P; 0.01% or S still less; 0.08～0.5% solvable Al; 0.0025% or N still less; 0.003～0.1% Nb; 0.003% or Ti still less; 0.01～0.4% Mo; 0.0005～0.005% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
Described hot-rolled steel sheet is reeled;
Carry out cold rolling to described hot-rolled steel sheet;
Described cold-rolled steel sheet is continued annealing;
Described annealed sheet steel is carried out hot dipping; And
Described hot dipping steel plate is carried out temper rolling.
51. a method of producing the hot dipping steel plate said method comprising the steps of:
Under 1200 ℃ or above temperature with the bloom homogenizing after, by carrying out finish rolling 900～950 ℃ temperature so that bloom is carried out hot rolling, so that hot-rolled steel sheet to be provided, described bloom comprises 0.0016～0.0025% C by weight percentage; 0.02% or Si still less; 0.2～1.2% Mn; 0.05～0.11% P; 0.01% or S still less; 0.08～0.12% solvable Al; 0.0025% or N still less; 0.003～0.011% Nb; 0.01～0.1% Mo; 0.0005～0.0015% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
600～650 ℃ temperature described hot-rolled steel sheet is reeled;
Reduction ratio with 75～80% is carried out cold rolling to described hot-rolled steel sheet; And
770～830 ℃ temperature described cold-rolled steel sheet is continued annealing;
Described annealed sheet steel is carried out hot dipping; And
Reduction ratio with 1.2～1.5% is carried out temper rolling to described hot dipping steel plate.
52. a method of producing the hot dipping steel plate said method comprising the steps of:
Under 1200 ℃ or above temperature with the bloom homogenizing after, by carrying out finish rolling 900～950 ℃ temperature so that bloom is carried out hot rolling, so that hot-rolled steel sheet to be provided, described bloom comprises 0.0016～0.0025% C by weight percentage; 0.02% or Si still less; 0.2～1.2% Mn; 0.05～0.11% P; 0.01% or S still less; 0.08～0.12% solvable Al; 0.0025% or N still less; 0.003% or Ti still less; 0.003～0.011% Nb; 0.01～0.1% Mo; 0.0005～0.0015% B; And the Fe of surplus and other unavoidable impurities; And the ratio of Nb/C is 0.3～0.7;
600～650 ℃ temperature described hot-rolled steel sheet is reeled;
Reduction ratio with 75～80% is carried out cold rolling to described hot-rolled steel sheet; And
770～830 ℃ temperature described cold-rolled steel sheet is continued annealing;
Described annealed sheet steel is carried out hot dipping; And
Reduction ratio with 1.2～1.5% is carried out temper rolling to described hot dipping steel plate.
CNB2005800093946A 2004-03-25 2005-03-22 Cold rolled steel sheet and hot dipped steel sheet with superior strength and bake hardenability and method for manufacturing the steel sheets Active CN100489122C (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
KR20040020204 2004-03-25
KR1020040020204 2004-03-25
KR1020040103610 2004-12-09

Publications (2)

Publication Number Publication Date
CN1934280A true CN1934280A (en) 2007-03-21
CN100489122C CN100489122C (en) 2009-05-20

Family

ID=37276024

Family Applications (1)

Application Number Title Priority Date Filing Date
CNB2005800093946A Active CN100489122C (en) 2004-03-25 2005-03-22 Cold rolled steel sheet and hot dipped steel sheet with superior strength and bake hardenability and method for manufacturing the steel sheets

Country Status (2)

Country Link
KR (1) KR20050095537A (en)
CN (1) CN100489122C (en)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100685037B1 (en) * 2005-09-23 2007-02-20 주식회사 포스코 Bake-hardenable cold rolled steel sheet with superior strength and aging resistance, galvannealed steel sheet using the cold rolled steel sheet and method for manufacturing the cold rolled steel sheet
KR100711475B1 (en) * 2005-12-26 2007-04-24 주식회사 포스코 Method for manufacturing high strength steel strips with superior formability and excellent coatability
KR100775339B1 (en) * 2006-11-21 2007-11-08 주식회사 포스코 Cold rolled steel sheet having excellent in-plane anisotropy and workability and the method for manufacturing the same
KR20080061855A (en) * 2006-12-28 2008-07-03 주식회사 포스코 Dual phase steel having superior deep drawing, and method for manufacturing of it
WO2009157661A2 (en) * 2008-06-23 2009-12-30 주식회사 포스코 Bake hardening steel with excellent surface properties and resistance to secondary work embrittlement, and preparation method thereof
KR101105040B1 (en) 2008-06-23 2012-01-16 주식회사 포스코 Bake Hardened Steel with Excellent Surface Properties and Secondary Working Embrittlement Resistance and Manufacturing Method Thereof
KR100989778B1 (en) * 2008-08-28 2010-10-26 현대제철 주식회사 hot-rolled steel sheet having good drawing ability and galvanizing property, and method for producing the same
KR101129944B1 (en) * 2009-02-25 2012-03-23 현대제철 주식회사 Bake-Hardenable Steel Sheet and Method for Manufacturing the Same
KR101424486B1 (en) * 2012-05-31 2014-08-04 현대제철 주식회사 Method for producing cold rolled steel sheet and cold rolled steel sheet produced using the same
CN109844158B (en) * 2016-10-17 2021-09-07 塔塔钢铁艾默伊登有限责任公司 Steel substrate for painted parts

Also Published As

Publication number Publication date
KR20050095537A (en) 2005-09-29
CN100489122C (en) 2009-05-20

Similar Documents

Publication Publication Date Title
CN100339500C (en) Ultra high strength steel composition, the process of production of an ultra high strength steel product and the product obtained
CN1204284C (en) High-strength molten-zinc-plated steel plate excellent in deposit adhesion and suitability for press forming and process for producing the same
CN1934280A (en) Cold rolled steel sheet and hot dipped steel sheet with superior strength and bake hardenability and method for manufacturing the steel sheets
CN1188534C (en) Hot dip galvanized steel plate excellent in balance of strength and ductility and coated adhesive and its manufacturing method
CN1183268C (en) High tensile hot-rolled steel sheet having excellent strain aging hardening properties and method for producing same
CN1145709C (en) High tensile cold-rolled steel sheet having excellent strain aging hardening properties
CN100335670C (en) High strength steel plate and method for production thereof
CN101065509A (en) High strength steel sheet and method for production thereof
CN1082561C (en) Ultrafine-grain steel pipe and process for manufacturing the same
CN1011987B (en) Process for production of double structure stainless cr-steel band having high strength, high ductility and low degree aeolotropy
CN1128243C (en) Cold rolled steel plate with excellent machining homogenity and its production process
CN1599802A (en) High-strength thin steel sheet drawable and excellent in shape fixation property and method of producing the same
CN1520464A (en) Nonoriented electromagnetic steel sheet
CN1263568A (en) Steel sheet for can and manufacturing method thereof
CN1788099A (en) High strength steel plate excellent in formability and method for production thereof
CN1247809C (en) Coating baking hardening type cold rolled plate with good ageing resistance and its manufacturing method
CN1010856B (en) Process for production of double structure stainless cr-steel band having high strength, high ductility and low degree aeolotropy
CN1303244C (en) High-carbon hot-rolled steel plate,cold-rolled steel plate and making method thereof
CN101037757A (en) Low yield ratio and high tension steel material excellent in toughness of weld heat-affected zone, and process for producing the same
CN1273632C (en) Super formable high strength steel sheet and method of manufacturing thereof
CN100336930C (en) Steel sheet for container and method of producing the same
CN1082560C (en) Flexible cold-rolled plate and its manufacture method
CN101052735A (en) Non-oriented electromagnetic steel sheet with excellently low iron loss
CN1720344A (en) Non-oriented magnetic steel sheet and method for production thereof
CN1084797C (en) Cold rolled steel plate of excellent moldability, panel shape characteristics and denting resistance, molten zinc plated steel plate, and manufacture thereof

Legal Events

Date Code Title Description
C06 Publication
PB01 Publication
C10 Entry into substantive examination
SE01 Entry into force of request for substantive examination
C14 Grant of patent or utility model
GR01 Patent grant
CP03 Change of name, title or address
CP03 Change of name, title or address

Address after: Seoul, South Kerean

Patentee after: POSCO Holdings Co.,Ltd.

Address before: Gyeongbuk, South Korea

Patentee before: POSCO

TR01 Transfer of patent right
TR01 Transfer of patent right

Effective date of registration: 20230515

Address after: Gyeongbuk, South Korea

Patentee after: POSCO Co.,Ltd.

Address before: Seoul, South Kerean

Patentee before: POSCO Holdings Co.,Ltd.