CN1860247A - High strength thin steel sheet excellent in hole expansibility and ductility - Google Patents
High strength thin steel sheet excellent in hole expansibility and ductility Download PDFInfo
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- 239000010959 steel Substances 0.000 title claims abstract description 638
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- 229910052719 titanium Inorganic materials 0.000 claims abstract description 26
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 23
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 21
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 14
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 14
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- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 8
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- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 25
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Abstract
High-strength steel sheet excellent in hole-expandability and ductility, characterized by ; comprising, in mass%, C: not less than 0.01 % and not more than 0.20 %, Si: not more than 1.5 %, Al: not more than 1.5 %, Mn: not less than 0.5 % and not more than 3.5 %, P: not more than 0.2 %, S: not less than 0.0005 % and not more than 0.009 %, N: not more than 0.009 %, Mg: not less than 0.0006 % and not more than 0.01 %, O: not more than 0.005 % and Ti: not less than 0.01 % and not more than 0.20 % and/or Nb: not less than 0.01 % and not more than 0.10 %, with the balance consisting iron and unavoidable impurities, having Mn%, Mg%, S%.and 0% satisfying equations (1) to (3), and having the structure primarily comprising one or more of ferrite, bainite and martensite. [ Mg % ] ( [ O % ] / 16 0.8 ) 24[S%]([Mg%]/24[O%]/16*0.8+0.00012)*32[S%]<=0.0075/[ Mn % ].
Description
Technical field
About the 6.0mm that the present invention relates to use or following thickness of slab and have 590N/mm mainly as the automotive sheet of punch process
2Or above and then 980N/mm
2Or the reaming of above tensile strength and good high-strength steel sheet and the manufacture method thereof of ductility.
Background technology
In recent years, take the requirement that the cost due to car body lightweight, part integrally formed of the countermeasure that reduces reduces as automobile fuel and strengthen, the exploitation of the hot-rolled high-strength steel plate that press formability is good is being carried out always.In the past, as processing hot-rolled steel sheet, the known dual phase sheet steel that constitutes by ferrite and martensitic stucture.
Dual phase sheet steel is made of the complex tissue of the martensitic phase of soft ferritic phase and hard, significantly can hole take place and crack in different biphase interfaces from hardness, therefore the problem that has the reaming difference requires the purposes of high reaming to be not suitable for for ground-engaging element etc.
To this, open flat 4-88125 communique the spy, the spy opens in the flat 3-180426 communique and proposed with the manufacture method of bainite as the good hot-rolled steel sheet of the reaming of the tissue of main body, but the elongation property of this kind steel plate is relatively poor, be restricted so be suitable for part.
As the technology of taking into account reaming and ductility, open flat 6-293910 communique, spy the spy and open that 2002-180188 communique, spy are opened the 2002-180189 communique, the spy opens in the 2002-180190 communique, the steel plate of the mixed structure of ferrite+bainite has been proposed, but with the complicated etc. of the further lightweight target of automobile and parts is background, require higher reaming, the processibility and the high strength of the height that the above-mentioned technology of requirement employing can not satisfy fully.
In addition, the inventor etc. open the 2001-342543 communique the spy, the spy opens in the 2002-20838 communique, as not improving the means of reaming with the deterioration of unit elongation, find that the important point is the state of punching crackle, and find by (Ti, Nb) miniaturization of N makes the punching section generate fine uniform hole, can relax the stress concentration that reaming adds man-hour, makes the reaming raising.
And (Ti, the Nb) means of the miniaturization of N have proposed the utilization of the oxide compound of Mg system as above-mentioned.Yet, in this invention, only controlled oxide compound, and the degree of freedom of oxygen control is little, after the deoxidation available limited free oxygen total amount also less, be difficult to the dispersion state that obtains stipulating, be difficult to obtain effect of sufficient.
Summary of the invention
The present invention provides to have 590N/mm for the problem that solves above-mentioned the past proposes
2Or above and then 980N/mm
2Rank or above tensile strength, and take into account the good reaming and the high-strength steel sheet of ductility.
The present inventor is in order to relax stress concentration that reaming adds man-hour, to make the reaming raising by making perforated section generate fine uniform hole, and just (Ti, Nb) method of the miniaturization of N has repeated various tests and investigation.
It found that, in the past, sulfide is considered to cause the deterioration of reaming, but the Mg that high temperature is separated out be sulfide to (Ti, Nb) the N precipitate can play the effect of product nucleus, the Mg that low temperature is separated out be sulfide by with (Ti, Nb) competition of N is separated out and is had inhibition (Ti, Nb) the N effect of growing up, the result, Mg is the raising that sulfide helps the reaming that the TiN miniaturization brings.
And find, in order to avoid Mn is separating out of sulfide, and be that separating out of sulfide obtains above-mentioned effect by Mg, require the addition of O, Mg, Mn and S to meet some requirements, thus, with utilizing Mg separately is that oxide compound is compared, and can realize finer (Ti, Nb) the even miniaturization of N easily.And, based on this opinion, finished following invention.
(1) the good high-strength steel sheet of a kind of reaming and ductility is characterized in that: in quality %, contain
C：0.01％～0.20％、
Si:1.5% or following,
Al:1.5% or following,
Mn：0.5％～3.5％、
P:0.2% or following,
S：0.0005％～0.009％、
N:0.009% or following,
Mg：0.0006％～0.01％、
O:0.005% or following; And
Ti：0.01％～0.20％、
Among Nb:0.01%～0.10% a kind or 2 kinds, remainder is made of iron and unavoidable impurities, and Mn%, Mg%, S% and O% satisfy formula (1)～(3), and structure of steel is with a kind among ferrite, bainite and the martensite, two or more tissues as main body simultaneously.
[Mg％]≥([O％]/16×0.8)×24 (1)
[S％]≤([Mg％]/24-[O％]/16×0.8+0.00012)×32 (2)
[S％]≤0.0075/[Mn％] (3)
(2) according to above-mentioned (1) described reaming and the good high-strength steel sheet of ductility, it is characterized in that, at MgO, MgS and (Nb, Ti) in the compound precipitate of N, the precipitate of 0.05 μ m～3.0 μ m is per 1 square millimeter and contains 5.0 * 10
2Individual～1.0 * 10
7Individual.
According to above-mentioned (1) described reaming and the good high-strength steel sheet of ductility, it is characterized in that (3) in quality %, Al% and Si% also satisfy formula (4).
[Si％]+2.2×[Al％]≥0.35 (4)
According to above-mentioned (2) described reaming and the good high-strength steel sheet of ductility, it is characterized in that (4) in quality %, Al% and Si% also satisfy formula (4).
[Si％]+2.2×[Al％]≥0.35 (4)
(5) according to any one the described reaming and the good high-strength steel sheet of ductility of above-mentioned (1)～(4), it is characterized in that, in quality %, Ti%, C%, Mn% and Nb% also satisfy formula (5)～(7), structure of steel is with the tissue of bainite as main body simultaneously, and intensity surpasses 980N/mm
2
0.9≤48/12×[C％]/[Ti％]＜1.7 (5)
50227×[C％]-4479×[Mn％]＞-9860 (6)
811×[C％]+135×[Mn％]+602×[Ti％]+794×[Nb％]＞465 (7)
(6) according to any one the described reaming and the good high-strength steel sheet of ductility of above-mentioned (1)～(4), it is characterized in that, in quality %, C%, Si%, Al% and Mn% also satisfy formula (8), simultaneously structure of steel is that intensity surpasses 590N/mm with ferrite and the martensite tissue as main body
2
-100≤-300[C％]+105[Si％]-95[Mn％]+233[Al％] (8)
(7) according to above-mentioned (6) described reaming and the good high-strength steel sheet of ductility, it is characterized in that, in the crystal grain of above-mentioned structure of steel, the ratio (ds/dl) of minor axis (ds) and major diameter (dl) be 0.1 or above crystal grain exist 80% or more than.
(8) according to above-mentioned (7) described reaming and the good high-strength steel sheet of ductility, it is characterized in that, in the ferritic crystal grain of above-mentioned structure of steel, particle diameter be 2 μ m or above crystal grain exist 80% or more than.
(9) according to any one the described reaming and the good high-strength steel sheet of ductility of above-mentioned (1)～(4), it is characterized in that, in quality %, C%, Si%, Mn% and Al% also satisfy formula (8), simultaneously structure of steel is that intensity surpasses 590N/mm with ferrite and the bainite tissue as main body
2
-100≤-300[C％]+105[Si％]-95[Mn％]+233[Al％] (8)
(10) according to above-mentioned (9) described reaming and the good high-strength steel sheet of ductility, it is characterized in that, in the crystal grain of above-mentioned structure of steel, the ratio (ds/dl) of minor axis (ds) and major diameter (dl) be 0.1 or above crystal grain exist 80% or more than.
(11) according to above-mentioned (10) described reaming and the good high-strength steel sheet of ductility, it is characterized in that, in the ferritic crystal grain of above-mentioned structure of steel, particle diameter be 2 μ m or above crystal grain exist 80% or more than.
(12) manufacture method of the high-strength steel sheet that a kind of reaming and ductility are good is characterized in that: the steel that any one described one-tenth of above-mentioned (1)～(4) is grouped into, and at Ar
3Finish rolling under transformation temperature or the above finishing temperature, then cool off with 20 ℃/sec or above speed of cooling, under the temperature of 300 ℃ of less thaies, reel, make structure of steel and be with ferrite and martensite and surpass 590N/mm as the tissue and the intensity of main body
2High-strength steel sheet.
(13) manufacture method of the high-strength steel sheet that a kind of reaming and ductility are good is characterized in that: the steel that any one described one-tenth of above-mentioned (1)～(4) is grouped into, and at Ar
3Finish rolling under transformation temperature or the above finishing temperature, then be cooled to 650 ℃～750 ℃ with 20 ℃/sec or above speed of cooling, then under this temperature, carry out 15 seconds or following air cooling, cool off once again then, under the temperature of 300 ℃ of less thaies, reel, make structure of steel and be with ferrite and martensite and surpass 590N/mm as the tissue and the intensity of main body
2High-strength steel sheet.
(14) manufacture method of the high-strength steel sheet that a kind of reaming and ductility are good is characterized in that: the steel that any one described one-tenth of above-mentioned (1)～(4) is grouped into, and at Ar
3Finish rolling under transformation temperature or the above finishing temperature, then cool off with 20 ℃/sec or above speed of cooling, under 300 ℃～600 ℃ temperature, reel, make structure of steel and be with ferrite and bainite and surpass 590N/mm as the tissue and the intensity of main body
2High-strength steel sheet.
(15) manufacture method of the high-strength steel sheet that a kind of reaming and ductility are good is characterized in that: the steel that any one described one-tenth of above-mentioned (1)～(4) is grouped into, and at Ar
3Finish rolling under transformation temperature or the above finishing temperature, then be cooled to 650 ℃～750 ℃ with 20 ℃/sec or above speed of cooling, then under this temperature, carry out 15 seconds or following air cooling, cool off once again then, under 300 ℃～600 ℃ temperature, reel, make structure of steel and be with ferrite and bainite and surpass 590N/mm as the tissue and the intensity of main body
2High-strength steel sheet.
Description of drawings
Fig. 1 is the figure of the relation of expression tensile strength and unit elongation.
Fig. 2 is the figure of expression tensile strength and the relation of reaming ratio.
Fig. 3 is the figure of the relation of expression tensile strength and unit elongation.
Fig. 4 is the figure of expression tensile strength and the relation of reaming ratio.
Fig. 5 is the figure of the relation of expression unit elongation and ds/dl.
Fig. 6 is the figure of relation of the ratio of expression unit elongation and 2 μ m or above ferrite crystal grain.
Fig. 7 is the figure of the relation of expression tensile strength and unit elongation.
Fig. 8 is the figure of expression tensile strength and the relation of reaming ratio.
Fig. 9 is the figure of the relation of expression unit elongation and ds/dl.
Figure 10 is the figure of relation of the ratio of expression unit elongation and 2 μ m or above ferrite crystal grain.
Embodiment
The present invention is for the improvement of reaming, be conceived to perforated end face proterties, by under prescribed condition, adjusting the addition of O, Mg, Mn and S, making Mg is that oxide compound and sulfide are evenly separated out imperceptibly, the generation of the coarse crackle when suppressing punching, make end face proterties homogenizing, thereby improve reaming.
Below, with regard to constitutive requirements of the present invention, be elaborated.
At first, the qualification reason that is grouped into regard to the one-tenth of high-strength steel sheet of the present invention (steel plate of the present invention) is narrated.Also have, % is meant quality %.
C: be the element that the processibility to steel exerts an influence, at content more for a long time, the processibility deterioration.Particularly surpass at 0.20% o'clock, can generate the deleterious carbide of reaming (perlite, cementite), therefore be set at 0.20% or below.But, requiring the occasion of extra high reaming, be preferably set to 0.1% or below.And, from guaranteeing the viewpoint of needed intensity, 0.01% or more than be necessary.
Si: be the generation that suppresses deleterious carbide, the effective element that makes the ferrite ratio increase, unit elongation is improved, and for guaranteeing that by solution strengthening the strength of materials also is an effective elements.So, preferably add Si, but when addition increased, except chemical convertibility descended, spot weld reduced also, so the upper limit is set at 1.5%.
Al: the same with Si, be the generation that suppresses deleterious carbide, the effective element that makes the ferrite ratio increase, unit elongation is improved.For taking into account ductility and chemical convertibility, be necessary element especially.
In addition, Al is the necessary element of deoxidation in the past always, adds about 0.01～0.07% usually, the present inventor is through concentrating on studies repeatedly, found that and in low Si is, pass through heavy addition Al, also can under the situation that does not make the ductility deterioration, improve chemical convertibility.
But when addition increased, not only the raising effect of ductility reached capacity, and chemical convertibility also can reduce, and also deterioration of spot weld, so the upper limit is set at 1.5%.Handle under the strict condition in chemical conversion especially, preferred upper limit is set at 1.0%.
Mn: be to guarantee the necessary element of intensity, subsistence level adds 0.50%.And, in order to ensure hardenability, obtain stable intensity, preferably surpass 2.0% interpolation.But, during heavy addition, causing microsegregation or macrosegregation easily, these segregations make the reaming deterioration, so the upper limit is set at 3.5%.
P: be the element that improves the intensity of steel plate, and be by adding the element that solidity to corrosion is improved simultaneously with copper.But at content for a long time, can cause weldability, processibility, flexible deterioration.So, with content be set at 0.2% or below.Especially in the unchallenged occasion of solidity to corrosion, pay attention to processibility and be preferably set to 0.03% or below.
S: be one of most important interpolation element among the present invention.S combines with Mg and generates sulfide, become (Ti, the Nb) nuclear of N, and by suppressing (Ti, Nb) growing up of N help that (Ti, the Nb) miniaturization of N improves reaming tremendously.
In order to obtain this effect, 0.0005% or above interpolation be necessary, preferred 0.001% or above interpolation.But it is sulfide that superfluous interpolation can form Mn, can make the reaming deterioration on the contrary, so its upper limit is set at 0.009%.
N: (therefore Ti, Nb) N, in order to ensure processibility, lack some and are advisable to help generation.Surpassing at 0.009% o'clock, can generate thick TiN, the processibility deterioration, therefore the N amount is set at 0.009% or below.
Mg: be one of most important interpolation element among the present invention.Mg combines with oxygen and forms oxide compound, and combines formation sulfide with S.The Mg that generates is that oxide compound and Mg are sulfide, compares with the steel of the past of not adding Mg, and the size of precipitate is little, becomes homodisperse distribution.
These precipitates of fine dispersive in steel are to (Ti, Nb) the fine dispersion of N is favourable, produces effect for the raising of reaming.
But addition is when less than 0.0006%, and its effect is insufficient, 0.0006% or above interpolation be necessary.In order fully to obtain its effect, preferred 0.0015% or above interpolation.
On the other hand, surpass 0.01% interpolation, it is saturated not only to improve effect, makes the purity deterioration of steel on the contrary, make reaming and ductility deterioration, so the upper limit is set at 0.01%.
O: be one of most important interpolation element among the present invention.Combine the formation oxide compound with Mg, favourable to the raising of reaming.But superfluous interpolation can make the purity deterioration of steel, cause ductile deterioration, so the upper limit is set at 0.005%.
Ti and Nb: be one of most important interpolation element among the present invention.Ti and Nb be form carbide, to the increase effective elements of intensity, help the homogenizing of hardness and improve reaming.And can think that Ti and Nb can be that oxide compound and Mg are that sulfide is nuclear with Mg, form fine uniform nitride, this nitride when punching by forming fine hole and suppressing stress concentration, thereby can suppress the generation of coarse crackle, its result, reaming improves tremendously.
In order to make it bring into play above-mentioned effect effectively, Nb and Ti all need to add at least 0.01% or more than.
Therefore but when addition was too much, the precipitation strength meeting caused the ductility deterioration, and as the upper limit, Ti is set at 0.20%, Nb is set at 0.10%.These elements add still separately, and compound interpolation all produces effect.
In addition, in steel plate of the present invention, also can add a kind of following element, two or more.
Ca, Zr, REM: control the shape of sulfide-based inclusion, effective to the raising of reaming.In order to obtain this effect, need add at least 0.0005% or above a kind, two or more.On the other hand, when heavy addition, can make the purity of steel worsen infringement reaming and ductility on the contrary.So the upper limit is set at 0.01%.
Cu: be to improve corrosion proof element by compound interpolation with P.In order to obtain this effect, preferably add 0.04% or more than.But heavy addition can make hardenability increase, infringement ductility, so the upper limit is set at 0.4%.
Ni: the element that is the hot tearing when suppressing interpolation Cu.In order to obtain this effect, preferably add 0.02% or more than.But, hardenability is increased, infringement ductility, so the upper limit is set at 0.3%.
Mo: be the generation that suppresses cementite, the effective elements that makes the reaming raising.In order to obtain this effect, need to add 0.02% or more than.But Mo also is the element that improves hardenability, and superfluous interpolation can make ductility reduce, so the upper limit is set at 0.5%.
V: be the element that forms carbide, helps guaranteeing intensity.In order to obtain this effect, need to add 0.02% or more than.But heavy addition can make extensibility reduce, and it is also high to add cost, so the upper limit is set at 0.1%.
Cr: also the same with V, be the element that forms carbide, helps guaranteeing intensity.In order to obtain this effect, need to add 0.02% or more than.But Cr also is the element that improves hardenability, and a large amount of interpolations can make extensibility reduce, so the upper limit is set at 1.0%.
B: be to strengthen the grain boundary, improve effective element as 2 processing crackles of the problem of ultrahigh-strength steel.In order to obtain this effect, need to add 0.0003% or more than.But B also is the element that improves hardenability, and a large amount of interpolations can make ductility reduce, so the upper limit is set at 0.001%.
The present inventor concentrates on studies in order to solve above-mentioned problem, found that by the addition of O, Mg, Mn and S is adjusted under defined terms, and be that oxide compound and Mg are sulfide thereby can utilize Mg, make (Nb, Ti) the fine dispersion of N.
That is be that oxide compound is fully separated out, by making Mg; And be under the situation about separating out of sulfide suppressing Mn, control Mg is the separating out temperature of sulfide and to make Mg be that sulfide is separated out, thus the effect that can utilize as the effect of above-mentioned nuclear and suppress to grow up.For this reason, derive 3 following relational expressions.Below describe.
In the present invention, except Mg was oxide compound, also utilizing Mg was sulfide, so Mg need add with O amount or the amount more than it.But, other element such as O and Al also forms oxide compound, and the result that the present inventor concentrates on studies is, with the effective O of Mg bonded be 80% of amount of analysis, Mg adds with this amount or the amount more than it, is necessary for forming the sufficient sulfide that the raising of reaming is worked.So the addition of Mg need satisfy formula (1).
On the other hand, be the formation of sulfide for Mg, S is necessary element, but measures more for a long time at S, it is sulfide that S can become Mn.If the amount of separating out that this Mn is sulfide amount is few, then with Mg be that the combined state of sulfide exists, to the not influence of deterioration of reaming, when separating out in a large number, though details it be unclear that, then can separate out separately or be that the characteristic of sulfide exerts an influence Mg, make the reaming deterioration.Therefore, the S amount need satisfy formula (2) with respect to Mg and effective O amount.
In addition, measure under all more condition in Mn amount and S, at high temperature can separate out Mn is sulfide, and suppressing Mg is the generation of sulfide, can not obtain the abundant raising of reaming.So Mn amount and S amount need satisfy formula (3).
[Mg％]≥([O％]/16×0.8)×24 (1)
[S％]≤([Mg％]/24-[O％]/16×0.8+0.00012)×32 (2)
[S％]≤0.0075/[Mn％] (3)
For by making perforated section generate fine and uniform hole, thereby the stress concentration that makes reaming add man-hour relaxes, and to make reaming raising, the important point be (Nb, Ti) the even miniaturization of N.In that (Nb, Ti) size of N hour can not become the generation starting point of fine uniform hole, on the other hand, when oversize, can become the starting point of coarse crackle.
In addition, can think, this precipitate separate out number more after a little while, the effect that the fine-pored quantity not sufficient that produces, the coarse crackle that can not be inhibited take place when punching.
What the present inventor concentrated on studies found that, (Nb, Ti) the even and fine method of separating out of N can utilize the compound of MgO and MgS to separate out as making.Although its reason is not as yet not certainly, but find, when oxide compound adds compound utilization of sulfide, size and precipitate density as the compound precipitate of bringing into play effect, at MgO, MgS and (Nb, Ti) in the compound precipitate of N, the precipitate of 0.05 μ m～3.0 μ m is that per 1 square of mm contains 5.0 * 10
2Individual～1.0 * 10
7Individual is necessary.At this moment, even contain Al in the composite oxides
2O
3, SiO
2, can not damage this effect yet, contain MnS on a small quantity and also can not damage effect.
In addition, the dispersion state of the compound precipitate of the present invention's regulation for example can be measured quantitatively by following method.Make the extraction replica sample from any part of mother metal steel plate, use transmission electron microscope (TEM) with 5000～20000 times multiplying power, at least at 5000 μ m it
2Or above, preferably at 50000 μ m
2Or observe in the above area, measure number as the complex inclusion of object, be converted into the number of per unit area.
At this moment, oxide compound and (Nb, Ti) discriminating of N is that the crystallographic structural analysis of the electron diffraction photo that obtains by the compositional analysis that obtained by the energy dispersive type x-ray spectrometry (EDS) that is attached to TEM and by TEM carries out.Carry out the very miscellaneous occasion of such discriminating for the whole complex inclusion that will measure, simply, can follow following program.
At first, according to above-mentioned main points according to different shapes, dimension measurement number, in the middle of them as the size of object, for the different whole precipitates of shape, size according to above-mentioned main points, respectively with regard to 10 or more than differentiate, calculate oxide compound and (Nb, Ti) ratio of N.Then, the number to the inclusion of previous mensuration multiply by this ratio.
When the carbide in the steel hinders above-mentioned tem observation, make carbide assemble thickization or make its dissolving by thermal treatment, can make as the observation of the complex inclusion of object and carry out easily.
Si and Al: be at very important element aspect the organizational controls of ductility.But, Si is called as the concave-convex surface of Si oxide skin sometimes in hot-rolled process, thus, not only damage product appearance, and when imposing chemical conversion processing and coating after punching press, occurring chemical conversion sometimes, to handle the generation of film bad and tack coating is bad.
Therefore, require the purposes of chemical convertibility strictness for a part, some occasion can not be added a large amount of Si.At this moment, for take into account ductility and chemical convertibility the two, can replace Si with Al, but at Si and Al all during heavy addition, the ratio of ferritic phase increases, and can not obtain target strength.
Therefore, in order to ensure full intensity, and guarantee ductility, Si amount and Al amount need satisfy formula (4).But, especially when unit elongation becomes problem, be preferably set to 0.9 or more than.
[Si％]+2.2×[Al％]≥0.35 (4)
Secondly, just the tissue of steel plate of the present invention describes.
The present invention is the technology of the section proterties when improving punching, so structure of steel contains ferrite, bainite and martensitic any phase, can both bring into play desired effect.
But, because structure of steel influences mechanical property, so will control tissue according to desired mechanical property.
(1) with the steel plate (of the present invention steel plate B) of bainite as main body
In order to ensure the intensity that surpasses 980MPa, as mechanism for intensifying, it is necessary that using-system is strengthened, and in order to improve the especially reaming in the processibility, tissue need be set at the tissue of bainite as main body.
At this moment, when being made as ferrite mutually with the 2nd, then ductility improves, and therefore preferably contains ferrite as the 2nd phase.And steel plate B of the present invention even remaining austenite can not hinder effect of the present invention yet in tissue, is the effect that precipitate improves the end face proterties but thick cementite, perlite can reduce Mg, and is therefore not ideal.
Intensity surpasses 980N/mm
2Steel, follow high strength, ductility and reaming can deteriorations.The present inventor is in order to solve above-mentioned problem, that concentrates on studies found that, as Mg is thereby that precipitate improves punching end face proterties and improves the effect of reaming and not only guaranteed intensity but also guaranteed the means of ductility, in the structure of steel of bainite main body, the scope of the one-tenth component of regulation C, Mn, Ti, Nb is effective.
That is, the build up that precipitation strength by maximally utilising TiC and clear and definite Mn and C bring derives 3 following relational expressions to the influence of material.Below, describe.
Compare with Ti, the addition of C owing to the increase of solid solution Ti makes the unit elongation deterioration, therefore, is set at 0.9≤48/12 * C/Ti more after a little while.On the other hand, compare, when the addition of C is too high, adds in hot rolling and to pine for TiC and can separate out, not only can not obtain the effect that intensity raises with Ti, and since the 2nd mutually in the C increase of measuring follow the deterioration of reaming.
Because this also is related to Mg is the attenuating that precipitate improves the effect of end face proterties, the upper limit of 48/12 * C/Ti is set at 1.7.
That is, Ti amount and C amount need satisfy formula (5).
0.9≤48/12×C/Ti＜1.7 (5)
In the occasion of paying attention to reaming, be preferably set to 1.0≤48/12 * C/Ti＜1.3 especially.
Although owing to follow the increasing of addition of Mn, ferritic generation is suppressed, thereby the ratio of the 2nd phase increases, and the guaranteeing of intensity becomes easily, can cause the decline of unit elongation.On the other hand, C can make the 2nd sclerosis mutually, makes the reaming deterioration, but can improve unit elongation.
Therefore, surpassing 980N/mm
2Tensile strength under, in order to ensure desired unit elongation, C amount and Mn measure need satisfy formula (6).
50227×C-4479×Mn＞-9860 (6)
In order to ensure processibility, need satisfy above-mentioned 2 formula.If 780N/mm
2The steel plate of level had then not only been guaranteed intensity but also had satisfied above-mentioned 2 formula to be to be relatively easy to, but in order to ensure surpassing 980N/mm
2Intensity, add that to make the C of reaming deterioration and make the Mn of unit elongation deterioration be last resort.
In order to ensure surpassing 980N/mm
2Intensity, need not only satisfy above-mentioned 2 formula but also satisfy in the scope of formula (7) and adjust composition.
811×C+135×Mn+602×Ti+794×Nb＞465 (7)
Secondly, describe with regard to manufacture method.
In order not hinder ferritic generation, make reaming good, the finish rolling end temp need be set at Ar
3Transformation temperature or more than.But if temperature is too high, therefore the strength degradation that thickization that can cause organizing causes and the reduction of ductility are preferably set to 950 ℃ or following.
In order to suppress formation to the deleterious carbide of reaming, obtain high reaming ratio, speed of cooling need be set at 20 ℃/s or more than.
The coiling temperature can generate martensite when 300 ℃ of less thaies, thus the reaming deterioration, therefore be set be 300 ℃ or more than.
In addition, the bainite that low temperature generates, although serious not as martensite, if when existing mutually as the 2nd, deterioration is understood in reaming.Therefore preferably 350 ℃ or above the coiling.
When the coiling temperature surpasses 600 ℃, can generate deleterious perlite of reaming and cementite, therefore the coiling temperature is set at 600 ℃ or following.
Air cooling in the cooling continuously, it is effective increasing, make ductility to improve for the occupation rate that makes ferritic phase.But different according to air cooling temperature and air cooling time can generate perlite, and not only ductility reduces on the contrary, and reaming also significantly reduces.
When 650 ℃ of air cooling temperature less thaies, can generate the deleterious perlite of reaming in early days, so the air cooling temperature be set at 650 ℃ or more than.
On the other hand, when the air cooling temperature surpasses 750 ℃, not only can delay ferritic generation, be difficult to obtain the air cooling effect, and in cooling thereafter, generate perlite easily, so the air cooling temperature is set at 750 ℃ or following.
Surpass the air cooling in 15 seconds, not only ferritic increase reaches capacity, and can bring burden to thereafter speed of cooling, coiling temperature controlling, and therefore, the air cooling time set is 15 seconds or following.
(2) with ferrite and martensite steel plate (steel plate FM of the present invention) as main body
The end face control techniques is the technology of the reaming raising of relevant steel plate, therefore in order to guarantee that simultaneously ductility and reaming are higher value, need guarantee unit elongation by structure of steel.Therefore, structure of steel need be designed to ferrite and martensite tissue as main body.
At this moment, ferrite exists 50% or when above, can guarantee high ductibility especially, therefore preferably ferritic ratio is set at 50% or more than.And steel plate FM of the present invention even remaining austenite in the tissue can not hinder effect of the present invention yet, is the effect that precipitate improves the end face proterties but thick cementite and perlite can reduce Mg, so not ideal.
In the hot rolling, must form desired tissue in the short period of time after finish rolling, for the formation of desired tissue, the influence that becomes to be grouped into shows very by force.When structure of steel, improves in order to make ductility during as main body with ferrite and martensite, the important point is to guarantee the ferrite ratio.
In order to ensure to improving the effective ferrite ratio of ductility, each amount of C, Si, Mn and Al needs to satisfy following formula (8).When the value deficiency-100 of formula (8), the ferrite that can not fully be measured, the ratio of the 2nd phase increases, so the ductility deterioration.
-100≤-300[C％]+105[Si％]-95[Mn％]+233[Al％] (8)
The present inventor is ferrite and the martensite steel as main body with regard to structure of steel, is that precipitate improves punching end face proterties and under the situation of the reaming property improvement effect brought, the means of improving ductility concentrated on studies not reducing by Mg.It found that, controls ferritic shape and ferritic particle diameter, plays effective function as the means of improving ductility.Below describe.
The shape of ferrite crystal grain for steel plate FM of the present invention, is one of important indicator that makes the ductility raising.Usually, in high alloy composition system, the ferrite crystal grain that stretches on rolling direction is more.The present inventor is through concentrating on studies, and the crystal grain that found that this stretching, extension can cause the deterioration of ductility.And find that as index, reduction minor axis (ds) is effective with the probability that exists of the crystal grain of ratio (ds/dl) less than 0.1 of major diameter (dl).
For by controlling the effect that ferritic crystal grain fully obtains to improve ductility, in the ferrite crystal, (ds/dl) than be 0.1 above crystal grain existence 80% or more than be necessary.
Ferritic particle diameter is one of important indicator that makes the ductility raising in the present invention.Usually, follow high strength, crystal grain produces miniaturization.The present inventor found that through concentrating on studies for same intensity, the ferrite that crystal grain is fully grown up helps the raising of ductility.
And, in order fully to obtain the raising of ductility, in ferrite crystal grain crystal particle diameter be the crystal grain of 2 μ m or above particle diameter exist 80% or more than be necessary.
Secondly, manufacture method is described.
In order to prevent ferritic generation, make reaming good, the finish rolling end temp is set at Ar
3Transformation temperature or above be necessary.But,, can cause therefore being preferably set to 950 ℃ or following because of the strength degradation that causes of thickization of tissue and the reduction of ductility if temperature is too high.In order to suppress formation to the deleterious carbide of reaming, obtain high reaming ratio, speed of cooling be 20 ℃/s or above be necessary.
The coiling temperature can not generate martensite at 300 ℃ or when above, and strength degradation can not be guaranteed the intensity stipulated therefore to be set at 300 ℃ of less thaies.In order to ensure full intensity, and fully obtain the improvement of unit elongation thus, preferably the coiling temperature is set at 200 ℃ or following.
Air cooling in the cooling continuously, it is effective increasing, make ductility to improve for the occupation rate that makes ferritic phase.But different according to air cooling temperature and air cooling time can generate perlite, and not only ductility reduces on the contrary, and reaming also significantly reduces.
When 650 ℃ of air cooling temperature less thaies, can take place the deleterious perlite of reaming in early days, so the air cooling temperature be set at 650 ℃ or more than.
On the other hand, when the air cooling temperature surpasses 750 ℃, not only can postpone ferritic generation, be difficult to obtain the air cooling effect, and in cooling thereafter, generate perlite easily, so the air cooling temperature is set at 750 ℃ or following.
Surpass the air cooling in 15 seconds, not only ferritic increase reaches capacity, and can bring burden to thereafter speed of cooling, coiling temperature controlling, and therefore, the air cooling time set is 15 seconds or following.
(3) with ferrite and bainite steel plate (steel plate FB of the present invention) as main body
The end face control techniques is the technology of relevant reaming raising, so reaming is subjected to the ductility of mother metal and the influence of reaming (fundamental characteristics) consumingly.Particularly ground-engaging element etc. is very strong for the requirement of reaming, as fundamental characteristics, is target with the good steel plate of ductility and hole expansibility weighing apparatus, and it is necessary further making the reaming raising by the end face control techniques.
So structure of steel need be designed to ferrite and the bainite tissue as main body.At this moment, have 50% or when above, can guarantee high ductility especially at ferrite, therefore preferably the ferrite ratio is set at 50% or more than.
And steel plate FB of the present invention even remaining austenite does not hinder effect of the present invention mutually yet in the tissue, is the improve effect of precipitate to the end face proterties but thick cementite, perlite can lower Mg, and is therefore not ideal.
In the hot rolling, must form desired tissue in the short period of time after finish rolling, for the formation of desired tissue, the influence that becomes to be grouped into shows very by force.When structure of steel is main body with ferrite and bainite, improve in order to make ductility, the important point is to guarantee the ferrite ratio.
In order to ensure to improving the effective ferrite ratio of ductility, each amount of C, Si, Mn and Al needs to satisfy following formula (8).When the value deficiency-100 of formula (8), the ferrite that can not fully be measured, the ratio of the 2nd phase increases, so the ductility deterioration.
-100≤-300[C％]+105[Si％]-95[Mn％]+233[Al％] (8)
The present inventor is ferrite and the bainite steel as main body with regard to structure of steel, is that precipitate improves under the situation of the reaming property improvement effect that punching end face proterties brings not reducing by Mg, and the means of improving ductility are concentrated on studies.It found that, controls ferritic shape and ferritic particle diameter, plays effective function as the means of improving ductility.Below describe.
Ferritic shape is one of important indicator that makes the ductility raising in the present invention.Usually, in high alloy composition system, the ferrite crystal grain that stretches on rolling direction is more.The present inventor is through concentrating on studies, and the crystal grain that found that this stretching, extension can cause the deterioration of ductility.And find that as index, reduction minor axis (ds) is effective with the probability that exists of the crystal grain of ratio (ds/dl) less than 0.1 of major diameter (dl).
For by controlling the effect that ferritic crystal grain fully obtains to improve ductility, in ferrite crystal grain, (ds/dl) than be 0.1 above crystal grain existence 80% or more than be necessary.
Ferritic particle diameter is one of important indicator that makes the ductility raising in the present invention.Usually, follow high strength, crystal grain produces miniaturization.The present inventor found that through concentrating on studies for same intensity, the ferrite that crystal grain is fully grown up helps the raising of ductility.
And, in order fully to be beneficial to the raising of ductility, in ferrite crystal grain crystal particle diameter be the crystal grain of 2 μ m or above particle diameter exist 80% or more than be necessary.
Secondly, manufacture method is described.
In order to prevent ferritic generation, make reaming good that the finish rolling end temp is set at Ar
3Transformation temperature or above be necessary.But if temperature is too high, therefore the strength degradation that thickization that can cause organizing causes and the reduction of ductility are preferably set to 950 ℃ or following.
For suppress to the deleterious carbide of reaming formation, obtain high reaming ratio, speed of cooling be 20 ℃/s or above be necessary.
The coiling temperature can generate martensite when 300 ℃ of less thaies, the reaming deterioration, therefore be set at 300 ℃ or more than.
In addition, the bainite that low temperature generates, although serious like that not as martensite, when existing mutually as the 2nd, reaming meeting deterioration is therefore preferably at 350 ℃ or above coiling.
When the coiling temperature surpasses 600 ℃, can generate deleterious perlite of reaming and cementite, the temperature of therefore reeling is set at 600 ℃ or following.
Air cooling in the cooling continuously, it is effective increasing, make ductility to improve for the occupation rate that makes ferritic phase.But different according to air cooling temperature and air cooling time can generate perlite, and not only ductility reduces on the contrary, and reaming also significantly reduces.
When 650 ℃ of air cooling temperature less thaies, can take place the deleterious perlite of reaming in early days, so the air cooling temperature be set at 650 ℃ or more than.
On the other hand, when the air cooling temperature surpasses 750 ℃, not only can postpone ferritic generation, be difficult to obtain the air cooling effect, and in cooling thereafter, generate perlite easily, so the air cooling temperature is set at 750 ℃ or following.
Surpass the air cooling in 15 seconds, not only ferritic increase reaches capacity, and can bring burden to thereafter speed of cooling, coiling temperature controlling, and therefore, the air cooling time set is 15 seconds or following.
Secondly, according to embodiment the present invention is described.
[embodiment 1]
The embodiment of steel F of the present invention.
One-tenth shown in melting table 1 and the table 2 is grouped into and the steel of characteristic value, casts continuously according to usual method and makes slab.Symbol A～Z is the steel that is grouped into according to one-tenth of the present invention, in the symbol a steel in the addition of C, the b steel in the addition of Mn, the c steel in the addition of O, the e steel in the addition of S and the f steel addition of Mg outside scope of the present invention.
And the formula (1) of the formula (4) of the formula (1) of the formula (3) of the formula of a steel (5), b steel and formula (6), c steel and formula (2), d steel, the formula (2) of e steel and formula (3), f steel, the formula (7) of g steel are outside scope of the present invention.And the number of the precipitate of f steel is outside scope of the present invention.
With these steel in process furnace with 1200 ℃ or the heating of above temperature, making thickness of slab by hot rolling is the hot-rolled steel sheet of 2.6～3.2mm.About hot-rolled condition, be shown in table 3 and the table 4.
In table 3 and table 4, the air cooling of the speed of cooling of A4 and J2, B3 and F3 begins the coiling temperature of temperature, E3, G3 and Q4, respectively outside scope of the present invention.
For the hot-rolled steel sheet that obtains like this, carry out the tension test and the drifiting test of JIS5 sheet.About reaming (λ), be that the punching of 10mm adopts 60 ° of circular cone drifts to push expansion to diameter, the aperture when running through thickness of slab by crackle (d) and initial stage aperture (d0:10mm) are with λ=(d-d0)/d0 * 100 are estimated.
The TS of each test film, E1 and λ are shown in Table 2.Fig. 1 represents that relation, Fig. 2 of intensity and unit elongation represent the relation of intensity and reaming (ratio).Steel of the present invention is compared as can be known with comparative steel, and unit elongation or reaming (ratio) or the two characteristic are all better.On the other hand, the g1 steel does not obtain the intensity of target.
Like this, according to the present invention, can obtain to guarantee 980N/mm
2Prescribed strength, and hole expansibility and all good high tensile hot rolled steel sheet of ductility.
Table 1
| Steel | C | Si | Mn | P | S | N | Mg | Al | Nb | Ti | Ca | O | Appendix |
| Quality % | |||||||||||||
| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | 0.062 0.060 0.055 0.050 0.060 0.065 0.050 0.030 0.080 0.080 0.050 0.050 0.060 0.050 0.040 0.050 0.050 0.055 0.055 0.070 0.070 0.070 0.050 0.060 0.060 0.060 | 1.23 1.30 1.40 1.00 0.03 0.50 1.30 1.30 0.50 0.50 1.40 0.60 1.20 1.30 1.20 1.10 1.10 0.10 0.50 0.90 0.95 1.30 1.30 1.20 0.90 0.90 | 2.4 2.5 2.8 2.2 2.2 2.2 2.4 2.5 2.0 3.0 2.7 2.0 2.2 2.5 2.5 2.6 2.6 2.6 2.6 2.2 2.2 2.2 2.4 2.3 2.3 2.3 | 0.004 0.007 0.006 0.006 0.006 0.006 0.008 0.006 0.010 0.003 0.020 0.012 0.015 0.012 0.011 0.006 0.009 0.006 0.009 0.008 0.008 0.070 0.007 0.017 0.017 0.016 | 0.0010 0.0020 0.0025 0.0010 0.0028 0.0028 0.0025 0.0020 0.0035 0.0018 0.0025 0.0035 0.0030 0.0020 0.0025 0.0025 0.0020 0.0025 0.0020 0.0030 0.0030 0.0025 0.0025 0.0030 0.0030 0.0030 | 0.005 0.003 0.003 0.004 0.004 0.004 0.004 0.003 0.004 0.002 0.003 0.003 0.002 0.003 0.002 0.004 0.005 0.002 0.002 0.002 0.002 0.002 0.003 0.003 0.002 0.002 | 0.0023 0.0040 0.0030 0.0040 0.0030 0.0030 0.0044 0.0040 0.0017 0.0035 0.0035 0.0080 0.0050 0.0010 0.0025 0.0030 0.0030 0.0029 0.0022 0.0040 0.0035 0.0030 0.0040 0.0020 0.0032 0.0035 | 0.035 0.040 0.050 0.030 0.180 0.200 0.036 0.033 0.032 1.300 0.034 0.030 0.005 0.800 0.030 0.030 0.037 0.450 0.200 0.035 0.035 0.040 0.034 0.080 0.000 0.033 | 0.044 0.035 0.014 0.035 0.044 0.044 0.040 0.050 0.055 0.035 0.030 0.090 0.030 0.035 0.000 0.037 0.030 0.030 0.035 0.040 0.070 0.035 0.040 0.030 0.030 0.025 | 0.179 0.170 0.150 0.170 0.180 0.180 0.150 0.130 0.190 0.195 0.130 0.190 0.190 0.130 0.170 0.124 0.140 0.140 0.140 0.170 0.170 0.155 0.155 0.170 0.150 0.170 | - - - - - - - - - 0.003 - 0.002 - - 0.002 0.002 - 0.002 - 0.002 0.002 0.002 - 0.002 - - | 0.0014 0.0015 0.0012 0.0015 0.0010 0.0010 0.0011 0.0015 0.0008 0.0015 0.0015 0.0007 0.0040 0.0007 0.0012 0.0014 0.0010 0.0015 0.0015 0.0025 0.0025 0.0015 0.0015 0.0015 0.0015 0.0015 | Invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel |
| a b c d e f g | 0.210 0.050 0.060 0.050 0.055 0.070 0.070 | 1.30 1.00 1.00 0.20 1.10 0.90 0.90 | 2.2 3.6 2.2 2.5 2.5 2.2 1.4 | 0.120 0.020 0.020 0.010 0.010 0.010 0.010 | 0.0030 0.0025 0.0030 0.0028 0.0100 0.0015 0.0020 | 0.002 0.002 0.002 0.002 0.002 0.002 0.002 | 0.0031 0.0040 0.0030 0.0029 0.0040 0.0003 0.0040 | 0.005 0.030 0.035 0.030 0.020 0.025 0.030 | 0.030 0.030 0.035 0.030 0.020 0.025 0.030 | 0.080 0.170 0.170 0.150 0.150 0.170 0.170 | 0.002 - 0.002 0.002 0.002 0.002 0.002 | 0.0015 0.0015 0.0060 0.0015 0.0015 0.0015 0.0007 | Comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel |
Table 2
| Steel | Formula 1 the right | Formula 2 the right | Formula 3 the right | Formula 4 left sides | In the middle of the formula 5 | Formula 6 left sides | Formula 7 left sides | Precipitate several/mm 2 | Ar 3 ℃ | Appendix |
| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | 0.0017 0.0018 0.0014 0.0018 0.0012 0.0012 0.0013 0.0018 0.0010 0.0018 0.0018 0.0008 0.0048 0.0008 0.0014 0.0017 0.0012 0.0018 0.0018 0.0030 0.0030 0.0018 0.0018 0.0018 0.0018 0.0018 | 0.0047 0.0068 0.0059 0.0068 0.0062 0.0062 0.0079 0.0068 0.0048 0.0061 0.0061 0.0134 0.0041 0.0041 0.0053 0.0056 0.0062 0.0053 0.0044 0.0052 0.0045 0.0054 0.0068 0.0041 0.0057 0.0061 | 0.0031 0.0030 0.0027 0.0034 0.0034 0.0034 0.0031 0.0030 0.0038 0.0025 0.0028 0.0038 0.0034 0.0030 0.0030 0.0029 0.0029 0.0029 0.0029 0.0034 0.0034 0.0034 0.0031 0.0033 0.0033 0.0033 | 1.31 1.39 1.51 1.07 0.43 0.94 1.38 1.37 0.57 3.36 1.47 0.67 1.21 3.06 1.27 1.17 1.18 1.09 0.94 0.98 1.03 1.39 1.37 1.38 0.90 0.97 | 1.39 1.41 1.47 1.18 1.33 1.44 1.33 0.92 1.68 1.64 1.54 1.05 1.26 1.54 0.94 1.61 1.43 1.57 1.57 1.65 1.65 1.81 1.29 1.41 1.60 1.41 | -7815 -8184 -9779 -7342 -6840 -6589 -8238 -9691 -4940 -9419 -9582 -6447 -6840 -8686 -9188 -9134 -9134 -8883 -8883 -6338 -6338 6338 -8238 -7288 -7288 -7288 | 522 516 524 468 489 493 487 480 493 615 507 496 484 484 472 496 500 504 508 488 512 490 485 473 481 | 2.1E+03 4.3E+03 3.7E+03 3.8E+03 3.9E+03 3.9E+03 5.1E+03 4.3E+03 3.1E+03 3.7E+03 4.0E+03 9.4E+03 4.5E+03 1.7E+03 3.2E+03 3.6E+03 3.5E+03 3.4E+03 2.5E+03 4.3E+03 3.8E+03 3.5E+03 4.5E+03 2.8E+03 4.0E+03 4.3E+03 | 743 743 729 759 728 738 755 758 744 679 741 762 761 749 751 736 737 707 718 747 748 771 754 755 747 747 | Invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel |
| a b c d e f g | 0.0018 0.0018 0.0072 0.0018 0.0018 0.0018 0.0008 | 0.0056 0.0068 -0.0018 0.0053 0.0068 0.0018 0.0081 | 0.0034 0.0021 0.0034 0.0030 0.0030 0.0034 0.0054 | 1.31 1.07 1.08 0.27 1.17 0.97 0.97 | 10.50 1.18 1.41 1.33 1.47 1.65 1.65 | 694 -13613 -6840 -8686 -8435 -6338 -2755 | 539 653 476 492 488 476 372 | 3.9E+03 4.5E+03 1.5E+03 3.6E+03 8.3E+03 3.0E+02 4.7F+03 | 712 673 757 719 741 747 798 | Comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel |
* wherein, Ar
3=896-509 (C%)+26.9 (Si%)-63.5 (Mn%)+229 (P%)
Table 3
| Steel | Finishing temperature ℃ | Speed of cooling ℃/s | Air cooling begins temperature ℃ | Air cooling time s | Coiling temperature ℃ | Tensile strength N/mm 2 | Unit elongation % | % is compared in reaming | Remarks |
| A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 D1 D2 E1 E2 E3 F1 F2 F3 G1 G2 G3 H1 H2 I1 I2 J1 J2 K1 K2 L1 L2 M1 M2 N1 N2 | 920 910 920 930 920 900 910 890 910 920 890 930 930 920 920 910 910 890 920 920 930 910 900 920 910 880 870 910 890 890 910 890 890 880 890 | 70 70 40 10 70 70 70 40 70 40 70 70 70 40 70 70 40 70 70 70 40 70 40 70 40 70 10 70 70 70 40 70 50 70 30 | 680 720 - - 670 720 780 - 670 - 670 680 670 - 720 680 - 630 680 - - 690 - 680 - 670 - 670 680 670 - 670 680 680 - | 4 2 - - 5 2 3 - 3 - 4 3 3 - 3 3 - 4 3 - - 3 - 3 - 4 - 4 4 3 - 3 3 3 - | 490 580 500 480 490 300 500 500 500 480 490 550 500 480 620 500 500 500 500 480 620 480 480 520 500 500 500 450 550 500 550 480 500 500 500 | 1050 1095 1067 1057 1044 1019 1061 1073 1053 1055 993 1023 1004 1006 1076 1013 1025 1025 1015 1017 1087 1008 1020 1013 1015 1135 1147 1036 1098 1017 1054 1011 1021 1012 1024 | 14 15 14 9 14 14 10 14 12 12 16 16 16 16 15 16 16 10 14 14 14 13 13 18 18 12 7 13 13 16 17 16 16 14 14 | 64 52 69 41 64 65 63 65 62 67 74 69 68 71 40 64 64 43 67 72 39 87 91 58 61 55 39 61 52 79 73 70 69 61 64 | Invention steel invention steel invention steel comparative steel invention steel invention steel comparative steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel comparative steel invention steel invention steel comparative steel invention steel invention steel comparative steel invention steel invention steel invention steel invention steel invention steel comparative steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel |
Table 4 (continuous table 3)
| Steel | Finishing temperature ℃ | Speed of cooling ℃/s | Air cooling begins temperature ℃ | Air cooling time s | Coiling temperature ℃ | Tensile strength N/mm 2 | Unit elongation % | % is compared in reaming | Remarks |
| O1 O2 P1 P2 Q1 Q2 Q3 Q4 R1 R2 S1 S2 T1 T2 U1 U2 V1 V2 V3 W1 W2 W3 X1 X2 Y1 Y2 Z1 Z2 a1 b1 c1 d1 e1 f1 g1 | 920 910 890 900 900 890 910 920 920 920 930 910 900 910 890 890 890 900 890 920 930 910 900 930 890 910 910 910 850 900 920 900 900 910 910 | 70 70 70 70 70 150 40 40 70 40 100 70 70 40 70 40 70 70 40 70 70 40 70 70 70 70 70 70 70 70 70 70 70 70 70 | 670 690 680 700 670 660 - - 680 - 660 720 680 - 680 - 660 660 - 700 660 - 690 - 680 690 670 680 680 680 680 670 680 680 680 | 5 3 3 4 4 5 - - 3 - 5 2 3 - 4 - 3 4 - 3 3 - 3 - 4 3 3 3 3 4 3 4 3 4 3 | 500 480 480 500 500 480 480 200 500 500 500 480 480 500 480 480 520 400 550 500 580 480 500 480 480 400 500 400 480 480 500 480 480 520 500 | 999 991 1022 1032 1026 1016 1028 993 1020 1032 1028 1018 1012 1034 1036 1048 1003 993 1030 1018 1058 1020 1012 1002 997 992 1005 995 1067 1178 1001 1009 1014 1000 896 | 14 14 13 13 13 14 13 14 14 14 14 14 16 16 16 16 16 17 17 14 15 14 15 16 16 16 15 16 7 5 16 6 14 17 19 | 87 87 59 59 64 64 69 40 60 66 60 60 59 60 58 60 56 56 61 69 62 74 65 68 61 61 65 66 10 51 45 68 43 39 44 | Invention steel invention steel invention steel invention steel invention steel invention steel invention steel comparative steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel |
[embodiment 2]
The embodiment of steel FM of the present invention.
One-tenth shown in melting table 5 and the table 6 is grouped into and the steel of characteristic value, casts continuously according to usual method and makes slab.Symbol A～Z is the steel that is grouped into according to one-tenth of the present invention, in the symbol a steel in the addition of C, the b steel in the addition of Mn, the c steel in the addition of O, the e steel in the addition of S and the f steel addition of Mg outside scope of the present invention.
And the formula (1) of the formula (4) of the formula (1) of formula of b steel (3) and formula (8), c steel and formula (2), d steel, the formula (2) of e steel and formula (3), f steel is outside scope of the present invention.Also have, the number of the precipitate of f steel and g steel is outside scope of the present invention.
With these steel in process furnace with 1200 ℃ or the heating of above temperature, making thickness of slab by hot rolling is the hot-rolled steel sheet of 2.6～3.2mm.About hot-rolled condition, be shown in table 7 and the table 8.
In table 7 and table 8, the air cooling of the speed of cooling of A4 and J2, B3 and F3 begins the coiling temperature of temperature, E3, G3 and Q4 respectively outside scope of the present invention.
For the hot-rolled steel sheet that obtains like this, carry out the tension test and the drifiting test of JIS5 sheet.About reaming (λ), be that the punching of 10mm adopts 60 ° of circular cone drifts to push expansion to diameter, the aperture when running through thickness of slab by crackle (d) and initial stage aperture (d0:10mm) are with λ=(d-d0)/d0 * 100 are estimated.
The TS of each coupons, E1 and λ are shown in table 7 and the table 8.Fig. 3 represents the relation of intensity and unit elongation, and Fig. 4 represents the relation of intensity and hole expansibility (ratio).Steel of the present invention is compared as can be known with comparative steel, and unit elongation or hole expansibility (ratio) or the two characteristic are all better.
In addition, table 9 and Fig. 5 represent that the ratio (ds/dl) of minor axis (ds) and major diameter (dl) surpasses 0.1 the ratio and the relation of unit elongation.Can know that this ratio is 80% or when above, can stably obtain high unit elongation.
And table 10 and Fig. 6 are illustrated in the ferrite crystal grain, the ratio of 2 μ m or above ferrite crystal grain and the relation of unit elongation.Can know that this ratio is 80% or when above, can stably obtain high unit elongation.
Like this, according to the present invention, can obtain all good high tensile hot rolled steel sheet of hole expansibility, ductility.
Table 5
| Steel | C | Si | Mn | P | S | N | Mg | Al | Nb | Ti | Ca | O | Appendix |
| Quality % | |||||||||||||
| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | 0.060 0.055 0.060 0.060 0.060 0.065 0.060 0.060 0.070 0.170 0.060 0.065 0.060 0.060 0.070 0.130 0.060 0.080 0.050 0.060 0.035 0.040 0.060 0.060 0.065 0.060 | 0.88 0.87 0.80 0.85 0.03 0.50 1.60 0.90 1.00 1.00 1.30 0.50 1.20 1.40 1.20 0.92 1.00 0.10 0.50 0.90 0.95 1.00 1.00 1.20 0.90 0.90 | 1.2 1.2 1.2 1.1 1.2 1.2 1.5 1.4 1.3 3.3 2.0 0.7 1.4 1.5 1.4 1.6 1.6 1.6 1.6 1.4 1.4 1.5 1.2 0.8 1.2 1.9 | 0.018 0.011 0.015 0.005 0.006 0.006 0.011 0.007 0.010 0.030 0.020 0.012 0.015 0.012 0.011 0.006 0.015 0.011 0.015 0.015 0.012 0.070 0.008 0.017 0.017 0.016 | 0.0030 0.0023 0.0040 0.0020 0.0028 0.0028 0.0015 0.0037 0.0044 0.0018 0.0030 0.0085 0.0030 0.0020 0.0030 0.0035 0.0035 0.0040 0.0030 0.0030 0.0030 0.0030 0.0025 0.0030 0.0030 0.0030 | 0.003 0.003 0.003 0.004 0.004 0.004 0.003 0.003 0.004 0.002 0.003 0.002 0.002 0.003 0.002 0.004 0.005 0.001 0.002 0.002 0.002 0.002 0.003 0.003 0.002 0.002 | 0.0030 0.0040 0.0020 0.0040 0.0023 0.0023 0.0030 0.0035 0.0017 0.0035 0.0035 0.0080 0.0050 0.0010 0.0025 0.0023 0.0017 0.0029 0.0022 0.0040 0.0035 0.0030 0.0040 0.0020 0.0032 0.0035 | 0.040 0.028 0.005 0.002 0.180 0.200 0.042 0.032 0.032 1.300 0.034 0.030 0.005 0.800 0.030 0.030 0.037 0.450 0.200 0.035 0.035 0.040 0.034 0.080 0.000 0.033 | 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.020 0.010 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 | 0.025 0.020 0.020 0.025 0.025 0.025 0.020 0.020 0.030 0.025 0.025 0.035 0.190 0.020 0.020 0.000 0.010 0.025 0.025 0.020 0.025 0.020 0.020 0.020 0.025 0.025 | - - - - - - - - - - - - - - 0.002 0.002 - 0.002 - - - 0.002 - 0.002 - - | 0.0015 0.0007 0.0015 0.0015 0.0010 0.0010 0.0015 0.0015 0.0008 0.0015 0.0015 0.0007 0.0040 0.0007 0.0012 0.0014 0.0010 0.0015 0.0015 0.0025 0.0025 0.0015 0.0015 0.0015 0.0015 0.0015 | Invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel |
| a b c d e f g | 0.210 0.060 0.060 0.055 0.056 0.060 0.060 | 0.80 0.80 1.00 0.20 0.80 0.80 0.90 | 1.4 3.6 1.2 1.1 1.1 1.2 1.2 | 0.120 0.020 0.020 0.020 0.020 0.020 0.020 | 0.0030 0.0025 0.0030 0.0040 0.0100 0.0015 0.0040 | 0.002 0.002 0.002 0.002 0.002 0.002 0.002 | 0.0031 0.0040 0.0030 0.0029 0.0040 0.0003 0.0010 | 0.005 0.030 0.035 0.030 0.030 0.030 0.030 | 0.000 0.000 0.000 0.000 0.000 0.000 0.000 | 0.020 0.020 0.020 0.020 0.020 0.020 0.020 | 0.002 - - - - 0.002 0.002 | 0.0015 0.0015 0.0060 0.0015 0.0015 0.0015 0.0007 | Comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel |
Table 6
| Steel | Formula 1 the right | Formula 2 the right | Formula 3 the right | Formula 4 left sides | In the middle of the formula 8 | Precipitate several/mm 2 | Ar 3 ℃ | Appendix |
| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | 0.0018 0.0008 0.0018 0.0018 0.0012 0.0012 0.0018 0.0018 0.0010 0.0018 0.0018 0.0008 0.0048 0.0008 0.0014 0.0017 0.0012 0.0018 0.0018 0.0030 0.0030 0.0018 0.0018 0.0018 0.0018 0.0018 | 0.0054 0.0081 0.0041 0.0068 0.0053 0.0053 0.0054 0.0061 0.0048 0.0061 0.0061 0.0134 0.0041 0.0041 0.0053 0.0047 0.0045 0.0053 0.0044 0.0052 0.0045 0.0054 0.0068 0.0041 0.0057 0.0061 | 0.0061 0.0061 0.0063 0.0068 0.0061 0.0061 0.0050 0.0054 0.0058 0.0023 0.0038 0.0107 0.0054 0.0050 0.0054 0.0047 0.0047 0.0047 0.0047 0.0054 0.0054 0.0050 0.0063 0.0094 0.0063 0.0039 | 0.97 0.93 0.81 0.85 0.43 0.94 1.69 0.97 1.07 3.86 1.37 0.57 1.21 3.16 1.27 0.99 1.08 1.09 0.94 0.98 1.03 1.09 1.07 1.38 0.90 0.97 | -33 -35 -47 -33 -89 -36 17 -49 -32 43 -64 -27 -24 173 -21 -87 -56 -61 -68 -48 -36 -40 -19 51 -39 -96 | 3.8E+03 4.8E+03 3.3E+03 4.3E+03 3.2E+03 3.2E+03 3.0E+03 4.6E+03 3.5E+03 3.7E+03 4.3E+03 1.2E+04 4.5E+03 1.7E+03 3.4E+03 3.4E+03 3.0E+03 4.2E+03 3.0E+03 4.3E+03 3.8E+03 3.8E+03 4.5E+03 2.8E+03 4.0E+03 4.3E+03 | 815 816 814 819 790 800 815 802 807 633 778 835 812 810 806 754 794 759 786 804 817 823 818 851 815 773 | Invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel |
| a b c d e f g | 0.0018 0.0018 0.0072 0.0018 0.0018 0.0018 0.0008 | 0.0056 0.0068 -0.0018 0.0053 0.0068 0.0018 0.0041 | 0.0054 0.0021 0.0063 0.0068 0.0068 0.0063 0.0063 | 0.81 0.87 1.08 0.27 0.87 0.87 0.97 | -111 -269 -19 -93 -30 -41 -31 | 3.9E+03 4.5E+03 1.5E+03 4.2E+03 8.3E+03 2.0E+02 2.5E+02 | 749 663 821 808 824 815 818 | Comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel |
* wherein, Ar
3=896-509 (C%)+26.9 (Si%)-63.5 (Mn%)+229 (P%)
Table 7
| Steel | Finishing temperature ℃ | Speed of cooling ℃/s | Air cooling begins temperature ℃ | Air cooling time s | Coiling temperature ℃ | Tensile strength N/mm 2 | Unit elongation % | % is compared in reaming | Remarks |
| A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 D1 D2 E1 E2 E3 F1 F2 F3 G1 G2 G3 H1 H2 I1 I2 J1 J2 K1 K2 L1 L2 M1 M2 N1 N2 | 920 910 920 930 920 900 910 890 910 920 890 930 930 920 920 910 910 890 920 920 930 910 900 920 910 880 870 910 890 890 910 890 890 880 890 | 70 70 40 10 70 70 70 40 70 40 70 70 70 40 70 70 40 70 70 70 40 70 40 70 40 70 10 70 70 70 40 70 50 70 30 | 680 720 - - 670 720 780 - 670 - 670 680 670 - 720 680 - 630 680 - - 690 - 680 - 670 - 670 680 670 - 670 680 680 - | 4 2 - - 5 2 3 - 3 - 4 3 3 - 3 3 - 4 3 - - 3 - 3 - 4 - 4 4 3 - 3 3 3 - | 100 250 100 100 100 250 100 100 100 100 100 250 100 100 350 100 100 100 100 100 350 100 100 100 100 100 100 100 250 100 250 100 100 100 100 | 608 588 618 608 603 593 608 608 578 590 606 591 548 558 533 584 596 584 791 803 783 607 619 619 631 973 985 738 723 583 568 945 945 673 685 | 33 31 30 25 32 31 25 31 33 31 32 31 34 33 25 33 31 25 25 23 20 32 30 32 30 19 13 27 26 33 32 20 20 30 27 | 80 98 83 50 81 97 74 84 85 86 84 98 89 91 106 84 86 55 54 56 70 81 82 79 81 29 15 65 79 84 101 32 32 71 73 | Invention steel invention steel invention steel comparative steel invention steel invention steel comparative steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel comparative steel invention steel invention steel comparative steel invention steel invention steel comparative steel invention steel invention steel invention steel invention steel invention steel comparative steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel |
Table 8 (continuous table 7)
| Steel | Finishing temperature ℃ | Speed of cooling ℃/s | Air cooling begins temperature ℃ | Air cooling time s | Coiling temperature ℃ | Tensile strength N/mm 2 | Unit elongation % | % is compared in reaming | Remarks |
| O1 O2 P1 P2 Q1 Q2 Q3 Q4 R1 R2 S1 S2 T1 T2 U1 U2 V1 V2 V3 W1 W2 W3 X1 X2 Y1 Y2 Z1 Z2 | 920 910 890 900 900 890 910 920 920 920 930 910 900 910 890 890 890 900 890 920 930 910 900 930 890 910 910 910 | 70 70 70 70 70 150 40 40 70 40 100 70 70 40 70 40 70 70 40 70 70 40 70 70 70 70 70 70 | 670 690 680 700 670 660 - - 680 - 660 720 680 - 680 - 660 660 - 700 660 - 690 - 680 690 670 680 | 5 3 3 4 4 5 - - 3 - 5 2 3 - 4 - 3 4 - 3 3 - 3 - 4 3 3 3 | 100 100 100 100 100 100 100 350 100 100 100 100 100 100 100 100 100 250 100 100 250 100 100 100 100 250 100 250 | 642 642 676 676 641 641 653 611 779 791 609 609 615 627 616 628 622 602 630 610 590 602 582 587 609 589 670 645 | 32 31 30 30 31 32 29 23 26 24 33 30 32 30 32 30 32 31 30 32 31 31 33 31 32 31 30 29 | 70 76 74 72 73 72 77 95 53 59 77 84 79 81 79 79 78 96 81 80 98 87 85 84 81 98 71 90 | Invention steel invention steel invention steel invention steel invention steel invention steel invention steel comparative steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel |
| a1 b1 c1 d1 e1 f1 g1 | 850 900 920 900 900 910 910 | 70 70 70 70 70 70 70 | 680 680 680 670 680 680 680 | 3 4 3 4 3 4 3 | 100 100 100 100 100 100 100 | 683 815 604 523 493 608 516 | 20 18 31 25 34 29 33 | 40 51 40 92 45 50 50 | Comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel |
Table 9
| Steel | Finishing temperature ℃ | Speed of cooling ℃/s | Air cooling begins temperature ℃ | Air cooling time s | Coiling temperature ℃ | Tensile strength N/mm 2 | The ratio of ds/dl 〉=0.1 | Unit elongation % | % is compared in reaming | Remarks |
| A1 A5 A6 A7 A8 A9 A10 | 920 920 920 920 920 920 920 | 70 70 70 70 80 80 80 | 680 780 760 740 720 700 660 | 4 4 4 4 4 4 4 | 100 100 100 100 100 100 100 | 608 609 610 605 605 606 611 | 91％ 40％ 70％ 82％ 88％ 90％ 92％ | 33 24 25 32 33 33 33 | 80 80 80 81 81 81 80 | Invention steel comparative steel comparative steel invention steel invention steel invention steel invention steel |
Table 10
| Steel | Finishing temperature ℃ | Speed of cooling ℃/s | Air cooling begins temperature ℃ | Air cooling time s | Coiling temperature ℃ | Tensile strength N/ | 2 μ m or above ferrite crystal grain ratio | Unit elongation % | % is compared in reaming | Remarks |
| B1 B5 B6 B7 B8 B9 B10 | 920 860 880 880 920 960 960 | 70 70 70 70 70 80 80 | 670 670 670 730 730 670 730 | 5 4 4 4 5 6 6 | 100 100 100 100 100 100 100 | 603 603 601 600 603 605 605 | 88 50 68 83 90 93 94 | 32 25 26 32 33 33 33 | 81 81 81 81 81 81 81 | Invention steel comparative steel comparative steel invention steel invention steel invention steel invention steel |
[embodiment 3]
The embodiment of steel plate FB of the present invention.
One-tenth shown in melting table 11 and the table 12 is grouped into and the steel of characteristic value, casts continuously according to usual method and makes slab.Symbol A～Z is the steel that is grouped into according to one-tenth of the present invention, in the symbol a steel in the addition of C, the b steel in the addition of Mn, the c steel in the addition of O, the e steel in the addition of S and the f steel addition of Mg outside scope of the present invention.
And the formula (1) of the formula (2) of the formula (4) of the formula (1) of formula of b steel (3) and formula (8), c steel and formula (2), d steel and formula (8), e steel and formula (3), f steel is outside scope of the present invention.Also have, the number of the precipitate of f steel and g steel is outside scope of the present invention.
With these steel in process furnace with 1200 ℃ or the heating of above temperature, making thickness of slab by hot rolling is the hot-rolled steel sheet of 2.6～3.2mm.About hot-rolled condition, be shown in table 13 and the table 14.
In table 13 and table 14, the air cooling of the speed of cooling of A4 and J2, B3 and F3 begins the coiling temperature of temperature, E3, G3 and Q4 respectively outside scope of the present invention.
For the hot-rolled steel sheet that obtains like this, carry out the tension test and the drifiting test of JIS5 sheet.About reaming (λ), be that the punching of 10mm adopts 60 ° of circular cone drifts to push expansion to diameter, the aperture when running through thickness of slab by crackle (d) and initial stage aperture (d0:10mm) are with λ=(d-d0)/d0 * 100 are estimated.
The TS of each test film, E1 and λ are shown in table 13 and the table 14.Fig. 7 represents that relation, Fig. 8 of intensity and unit elongation represent the relation of intensity and hole expansibility.Steel of the present invention is compared as can be known with comparative steel, and unit elongation or hole expansibility (ratio) or the two characteristic are all better.
In addition, table 15 and Fig. 9 represent that the ratio (ds/dl) of minor axis (ds) and major diameter (dl) surpasses 0.1 the ratio and the relation of unit elongation.Can know that this ratio is 80% or when above, can stably obtain high unit elongation.In addition, table 16 and Figure 10 are illustrated in the ferrite crystal grain, have the ratio of 2 μ m or above particle diameter and the relation of unit elongation.Can know that this ratio is 80% or when above, can stably obtain high unit elongation.
Like this, according to the present invention, can obtain all good high-strength steel sheet of hole expansibility, ductility.
Table 11
| Steel | C | Si | Mn | P | S | N | Mg | Al | Nb | Ti | Ca | O | Appendix |
| Quality % | |||||||||||||
| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | 0.039 0.030 0.032 0.040 0.039 0.039 0.040 0.035 0.030 0.170 0.050 0.030 0.060 0.050 0.040 0.130 0.030 0.039 0.030 0.030 0.035 0.040 0.035 0.040 0.030 0.030 | 0.92 1.00 1.00 0.90 0.03 0.50 0.95 0.90 1.00 0.50 1.30 0.60 1.20 1.40 1.20 0.92 1.00 0.10 0.50 0.70 0.95 1.00 1.00 1.20 0.90 0.90 | 1.2 1.3 1.2 1.4 1.2 1.2 2.0 2.0 1.3 3.3 2.0 0.7 1.4 1.5 1.4 1.6 1.6 1.6 1.6 1.2 1.4 1.5 0.8 0.8 1.2 1.9 | 0.006 0.009 0.015 0.005 0.006 0.006 0.008 0.007 0.010 0.030 0.020 0.012 0.015 0.012 0.011 0.006 0.009 0.006 0.009 0.008 0.008 0.070 0.008 0.017 0.017 0.016 | 0.0028 0.0032 0.0040 0.0020 0.0028 0.0028 0.0019 0.0037 0.0044 0.0018 0.0030 0.0085 0.0030 0.0020 0.0030 0.0035 0.0035 0.0040 0.0030 0.0030 0.0030 0.0030 0.0025 0.0030 0.0030 0.0030 | 0.004 0.005 0.003 0.004 0.004 0.004 0.002 0.003 0.004 0.002 0.003 0.003 0.002 0.003 0.002 0.004 0.005 0.002 0.002 0.002 0.002 0.002 0.003 0.003 0.002 0.002 | 0.0023 0.0017 0.0020 0.0040 0.0023 0.0023 0.0044 0.0035 0.0017 0.0035 0.0035 0.0080 0.0050 0.0010 0.0025 0.0023 0.0017 0.0029 0.0022 0.0040 0.0035 0.0030 0.0040 0.0020 0.0032 0.0035 | 0.030 0.037 0.005 0.002 0.180 0.200 0.036 0.033 0.032 1.300 0.034 0.030 0.005 0.800 0.030 0.030 0.037 0.450 0.200 0.035 0.035 0.040 0.034 0.080 0.000 0.033 | 0.037 0.022 0.028 0.042 0.037 0.037 0.036 0.032 0.028 0.035 0.030 0.035 0.030 0.035 0.000 0.037 0.020 0.030 0.035 0.015 0.030 0.035 0.015 0.030 0.030 0.025 | 0.124 0.152 0.150 0.140 0.124 0.124 0.081 0.083 0.160 0.100 0.050 0.090 0.190 0.090 0.170 0.124 0.140 0.120 0.120 0.060 0.130 0.120 0.080 0.100 0.150 0.110 | - - - - - - - - - 0.003 - 0.002 - - 0.002 0.002 - 0.002 - 0.002 0.002 0.002 - 0.002 - - | 0.0014 0.0010 0.0015 0.0015 0.0010 0.0010 0.0011 0.0015 0.0008 0.0015 0.0015 0.0007 0.0040 0.0007 0.0012 0.0014 0.0010 0.0015 0.0015 0.0025 0.0025 0.0015 0.0015 0.0015 0.0015 0.0015 | Invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel |
| a b c d e f g | 0.210 0.040 0.030 0.040 0.040 0.035 0.035 | 1.30 1.00 1.00 0.20 1.10 0.90 0.90 | 1.4 3.6 1.5 1.4 1.4 1.4 1.4 | 0.120 0.020 0.020 0.010 0.010 0.010 0.010 | 0.0030 0.0025 0.0030 0.0040 0.0100 0.0015 0.0040 | 0.002 0.002 0.002 0.002 0.002 0.002 0.002 | 0.0031 0.0040 0.0030 0.0029 0.0040 0.0003 0.0010 | 0.005 0.030 0.035 0.030 0.030 0.030 0.030 | 0.015 0.015 0.035 0.030 0.020 0.025 0.030 | 0.080 0.060 0.140 0.150 0.150 0.120 0.140 | 0.002 - 0.002 0.002 0.002 0.002 0.002 | 0.0015 0.0015 0.0060 0.0015 0.0015 0.0015 0.0007 | Comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel |
Table 12
| Steel | Formula 1 the right | Formula 2 the right | Formula 3 the right | Formula 4 left sides | In the middle of the formula 8 | Precipitate several/mm 2 | Ar 3 ℃ | Appendix |
| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | 0.0017 0.0012 0.0018 0.0018 0.0012 0.0012 0.0013 0.0018 0.0010 0.0018 0.0018 0.0008 0.0048 0.0008 0.0014 0.0017 0.0012 0.0018 0.0018 0.0030 0.0030 0.0018 0.0018 0.0018 0.0018 0.0018 | 0.0047 0.0045 0.0041 0.0068 0.0053 0.0053 0.0079 0.0061 0.0048 0.0061 0.0061 0.0134 0.0041 0.0041 0.0053 0.0047 0.0045 0.0053 0.0044 0.0052 0.0045 0.0054 0.0068 0.0041 0.0057 0.0061 | 0.0061 0.0058 0.0063 0.0056 0.0061 0.0061 0.0038 0.0038 0.0058 0.0023 0.0038 0.0107 0.0054 0.0050 0.0054 0.0047 0.0047 0.0047 0.0047 0.0063 0.0054 0.0050 0.0094 0.0094 0.0063 0.0039 | 0.99 1.08 1.01 0.90 0.43 0.94 1.03 0.97 1.07 3.36 1.37 0.67 1.21 3.16 1.27 0.99 1.08 1.09 0.94 0.78 1.03 1.00 1.07 1.38 0.90 0.97 | -24 -19 -17 -45 -83 -29 -94 -98 -20 -9 -61 -6 -24 176 -12 -87 -47 -48 -62 -41 -36 -40 26 57 -29 -87 | 3.0E+03 2.8E+03 3.3E+03 4.3E+03 3.2E+03 3.2E+03 4.8E+03 4.6E+03 3.5E+03 3.7E+03 4.3E+03 1.2E+04 4.5E+03 1.7E+03 3.4E+03 3.4E+03 3.0E+03 4.2E+03 3.0E+03 4.3E+03 3.8E+03 3.8E+03 4.5E+03 2.8E+03 4.0E+03 4.3E+03 | 825 827 834 815 801 813 776 777 827 620 783 855 812 815 821 754 808 779 795 825 816 823 856 861 832 788 | Invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel |
| a b c d e f g | 0.0018 0.0018 0.0072 0.0018 0.0018 0.0018 0.0008 | 0.0056 0.0068 -0.0018 0.0053 0.0068 0.0018 0.0041 | 0.0054 0.0021 0.0050 0.0054 0.0054 0.0054 0.0054 | 1.31 1.07 1.08 0.27 1.17 0.97 0.97 | -58 -242 -38 -117 -23 -42 -42 | 3.9E+03 4.5E+03 1.5E+03 4.2E+03 8.3E+03 4.5E+02 2.5E+02 | 762 678 817 794 818 816 816 | Comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel |
* wherein, Ar
3=896-509 (C%)+26.9 (Si%)-63.5 (Mn%)+229 (P%)
Table 13
| Steel | Finishing temperature ℃ | Speed of cooling ℃/s | Air cooling begins temperature ℃ | Air cooling time s | Coiling temperature ℃ | Tensile strength N/mm 2 | Unit elongation % | % is compared in reaming | Remarks |
| A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 D1 D2 E1 E2 E3 F1 F2 F3 G1 G2 G3 H1 H2 I1 I2 J1 J2 K1 K2 L1 L2 M1 M2 N1 N2 | 920 910 920 930 920 900 910 890 910 920 890 930 930 920 920 910 910 890 920 920 930 910 900 920 910 880 870 910 890 890 910 890 890 880 890 | 70 70 40 10 70 70 70 40 70 40 70 70 70 40 70 70 40 70 70 70 40 70 40 70 40 70 10 70 70 70 40 70 50 70 30 | 680 720 - - 670 720 780 - 670 - 670 680 670 - 720 680 - 630 680 - - 690 - 680 - 670 - 670 680 670 - 670 680 680 - | 4 2 - - 5 2 3 - 3 - 4 3 3 - 3 3 - 4 3 - - 3 - 3 - 4 - 4 4 3 - 3 3 3 - | 490 580 500 480 490 300 500 500 500 480 490 550 500 480 620 500 500 500 500 480 620 480 480 520 500 500 500 450 550 500 550 480 500 500 500 | 801 846 818 808 820 795 837 849 811 813 863 893 738 740 810 771 783 783 806 808 878 772 784 834 836 990 1002 782 802 590 627 983 993 810 822 | 24 21 22 18 23 25 16 21 23 22 21 21 25 24 22 24 23 18 23 22 20 24 23 22 21 17 13 24 23 30 28 18 17 23 22 | 112 101 120 80 110 107 102 110 111 121 104 94 121 128 50 116 124 100 112 121 60 116 124 108 118 88 40 124 106 140 129 89 87 111 120 | Invention steel invention steel invention steel comparative steel invention steel invention steel comparative steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel comparative steel invention steel invention steel comparative steel invention steel invention steel comparative steel invention steel invention steel invention steel invention steel invention steel comparative steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel |
Table 14 (continuous table 13)
| Steel | Finishing temperature ℃ | Speed of cooling ℃/s | Air cooling begins temperature ℃ | Air cooling time s | Coiling temperature ℃ | Tensile strength N/mm 2 | Unit elongation % | % is compared in reaming | Remarks |
| O1 O2 P1 P2 Q1 Q2 Q3 Q4 R1 R2 S1 S2 T1 T2 U1 U2 V1 V2 V3 W1 W2 W3 X1 X2 Y1 Y2 Z1 Z2 | 920 910 890 900 900 890 910 920 920 920 930 910 900 910 890 890 890 900 890 920 930 910 900 930 890 910 910 910 | 70 70 70 70 70 150 40 40 70 40 100 70 70 40 70 40 70 70 40 70 70 40 70 70 70 70 70 70 | 670 690 680 700 670 660 - - 680 - 660 720 680 - 680 - 660 660 - 700 660 - 690 - 680 690 670 680 | 5 3 3 4 4 5 - - 3 - 5 2 3 - 4 - 3 4 - 3 3 - 3 - 4 3 3 3 | 500 480 480 500 500 480 480 200 500 500 500 480 480 500 480 480 520 400 550 500 580 480 500 480 480 400 500 400 | 830 820 873 883 817 807 819 769 738 750 787 777 608 630 809 821 818 798 845 820 860 822 812 802 821 811 801 791 | 24 23 21 21 23 24 22 23 25 24 25 23 30 28 23 22 23 23 21 23 22 22 23 22 23 22 23 23 | 103 110 106 103 107 108 119 60 118 128 111 124 138 140 111 118 110 122 117 110 99 122 112 119 111 120 112 126 | Invention steel invention steel invention steel invention steel invention steel invention steel invention steel comparative steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel invention steel |
| a1 b1 c1 d1 e1 f1 g1 | 850 900 920 900 900 910 910 | 70 70 70 70 70 70 70 | 680 680 680 670 680 680 680 | 3 4 3 4 3 4 3 | 480 480 500 480 480 520 500 | 795 859 850 782 749 788 812 | 15 12 21 15 24 22 21 | 60 105 50 115 70 78 75 | Comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel comparative steel |
Table 15
| Steel | Finishing temperature ℃ | Speed of cooling ℃/s | Air cooling begins temperature ℃ | The | Coiling temperature ℃ | Tensile strength N/mm 2 | The ratio of ds/dl 〉=0.1 | Unit elongation % | % is compared in reaming | Remarks |
| A1 A5 A6 A7 A8 A9 A10 | 920 920 920 920 920 920 920 | 70 70 70 70 80 80 80 | 680 780 760 740 720 700 660 | 4 4 4 4 4 4 4 | 490 490 480 500 500 490 490 | 801 801 796 806 806 801 801 | 91％ 30％ 60％ 82％ 88％ 90％ 92％ | 24 15 16 23 24 24 24 | 112 112 113 112 112 112 112 | Invention steel comparative steel comparative steel invention steel invention steel invention steel invention steel |
Table 16
| Steel | Finishing temperature ℃ | Speed of cooling ℃/s | Air cooling begins temperature ℃ | Air cooling time s | Coiling temperature ℃ | Tensile strength N/ | 2 μ m or above ferrite crystal grain ratio | Unit elongation % | % is compared in reaming | Remarks |
| B1 B5 B6 B7 B8 B9 B10 | 920 860 860 880 920 960 960 | 70 70 70 70 70 80 80 | 670 670 700 730 730 670 730 | 5 4 4 4 5 6 6 | 490 490 500 490 500 500 490 | 820 820 825 820 825 825 820 | 85％ 60％ 70％ 83％ 90％ 93％ 94％ | 23 15 16 23 23 23 24 | 110 110 109 110 109 109 110 | Invention steel comparative steel comparative steel invention steel invention steel invention steel invention steel |
According to the present invention, be 590N/mm for strength level
2Or above and then 980N/mm
2Or above high tensile steel plate, can provide to have unexistent unit elongation-ductility isostatic high-strength steel sheet in the past.Therefore, the present invention is for being exceedingly useful with high tensile steel plate as the industry of base material.
Claims (15)
1. reaming and the good high-strength steel sheet of ductility is characterized in that: in quality %, contain
C：0.01％～0.20％、
Si:1.5% or following,
Al:1.5% or following,
Mn：0.5％～3.5％、
P:0.2% or following,
S：0.0005％～0.009％、
N:0.009% or following,
Mg：0.0006％～0.01％、
O:0.005% or following; And
Ti：0.01％～0.20％、
Among Nb:0.01%～0.10% a kind or 2 kinds, remainder is made of iron and unavoidable impurities, and Mn%, Mg%, S% and O% satisfy formula (1)～(3), and structure of steel is with a kind among ferrite, bainite and the martensite, two or more tissues as main body simultaneously.
[Mg％]≥([O％]/16×0.8)×24 (1)
[S％]≤([Mg％]/24-[O％]/16×0.8+0.00012)×32 (2)
[S％]≤0.0075/[Mn％] (3)
2. reaming according to claim 1 and the good high-strength steel sheet of ductility is characterized in that, at MgO, MgS and (Nb, Ti) in the compound precipitate of N, the precipitate of 0.05 μ m～3.0 μ m is per 1 square millimeter and contains 5.0 * 10
2Individual～1.0 * 10
7Individual.
3. reaming according to claim 1 and the good high-strength steel sheet of ductility is characterized in that, in quality %, Al% and Si% also satisfy formula (4).
[Si％]+2.2×[Al％]≥0.35 (4)
4. reaming according to claim 2 and the good high-strength steel sheet of ductility is characterized in that, in quality %, Al% and Si% also satisfy formula (4).
[Si％]+2.2×[Al％]≥0.35 (4)
5. according to any one described reaming in the claim 1～4 and the good high-strength steel sheet of ductility, it is characterized in that, in quality %, Ti%, C%, Mn% and Nb% also satisfy formula (5)～(7), structure of steel is with the tissue of bainite as main body simultaneously, and intensity surpasses 980N/mm
2
0.9≤48/12×[C％]/[Ti％]＜1.7 (5)
50227×[C％]-4479×[Mn％]＞-9860 (6)
811×[C％]+135×[Mn％]+602×[Ti％]+794×[Nb％]＞465 (7)
6. according to any one described reaming in the claim 1～4 and the good high-strength steel sheet of ductility, it is characterized in that, in quality %, C%, Si%, Al% and Mn% also satisfy formula (8), simultaneously structure of steel is with ferrite and the martensite tissue as main body, and intensity surpasses 590N/mm
2
-100≤-300[C％]+105[Si％]-95[Mn％]+233[Al％] (8)
7. reaming according to claim 6 and the good high-strength steel sheet of ductility is characterized in that, in the crystal grain of described structure of steel, the ratio (ds/dl) of minor axis (ds) and major diameter (dl) be 0.1 or above crystal grain exist 80% or more than.
8. reaming according to claim 7 and the good high-strength steel sheet of ductility is characterized in that, in the ferritic crystal grain of described structure of steel, particle diameter be 2 μ m or above crystal grain exist 80% or more than.
9. according to any one described reaming in the claim 1～4 and the good high-strength steel sheet of ductility, it is characterized in that, in quality %, C%, Si%, Mn% and Al% also satisfy formula (8), simultaneously structure of steel is with ferrite and the bainite tissue as main body, and intensity surpasses 590N/mm
2
-100≤-300[C％]+105[Si％]-95[Mn％]+233[Al％] (8)
10. reaming according to claim 9 and the good high-strength steel sheet of ductility is characterized in that, in the crystal grain of described structure of steel, the ratio (ds/dl) of minor axis (ds) and major diameter (dl) be 0.1 or above crystal grain exist 80% or more than.
11. the high-strength steel sheet that reaming according to claim 10 and ductility are good is characterized in that, in the ferritic crystal grain of described structure of steel, particle diameter be 2 μ m or above crystal grain exist 80% or more than.
12. the manufacture method of the high-strength steel sheet that reaming and ductility are good is characterized in that: the steel that any one described one-tenth of claim 1～4 is grouped into, at Ar
3Finish rolling under transformation temperature or the above finishing temperature, then cool off with 20 ℃/second or above speed of cooling, under the temperature of 300 ℃ of less thaies, reel, make structure of steel and be with ferrite and martensite and surpass 590N/mm as the tissue and the intensity of main body
2High-strength steel sheet.
13. the manufacture method of the high-strength steel sheet that reaming and ductility are good is characterized in that: the steel that any one described one-tenth of claim 1～4 is grouped into, at Ar
3Finish rolling under transformation temperature or the above finishing temperature, then be cooled to 650 ℃～750 ℃ with 20 ℃/sec or above speed of cooling, then under this temperature, carry out 15 seconds or following air cooling, cool off once again then, under the temperature of 300 ℃ of less thaies, reel, make structure of steel and be with ferrite and martensite and surpass 590N/mm as the tissue and the intensity of main body
2High-strength steel sheet.
14. the manufacture method of the high-strength steel sheet that reaming and ductility are good is characterized in that: the steel that any one described one-tenth of claim 1～4 is grouped into, at Ar
3Finish rolling under transformation temperature or the above finishing temperature, then cool off with 20 ℃/second or above speed of cooling, under 300 ℃～600 ℃ temperature, reel, make structure of steel and be with ferrite and bainite and surpass 590N/mm as the tissue and the intensity of main body
2High-strength steel sheet.
15. the manufacture method of the high-strength steel sheet that reaming and ductility are good is characterized in that: the steel that any one described one-tenth of claim 1～4 is grouped into, at Ar
3Finish rolling under transformation temperature or the above finishing temperature, then be cooled to 650 ℃～750 ℃ with 20 ℃/second or above speed of cooling, then under this temperature, carry out 15 seconds or following air cooling, cool off once again then, under 300 ℃～600 ℃ temperature, reel, make structure of steel and be with ferrite and bainite and surpass 590N/mm as the tissue and the intensity of main body
2High-strength steel sheet.
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| JP357279/2003 | 2003-10-17 | ||
| JP2003357278A JP4317417B2 (en) | 2003-10-17 | 2003-10-17 | High strength thin steel sheet with excellent hole expandability and ductility |
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| CN100415921C CN100415921C (en) | 2008-09-03 |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103534365A (en) * | 2011-03-24 | 2014-01-22 | 安赛乐米塔尔研究与发展有限责任公司 | Hot-rolled steel sheet and associated production method |
| CN105671447A (en) * | 2014-12-05 | 2016-06-15 | Posco公司 | High strength cold rolled steel sheet having high yield ratio and excellent hole expansibility and method for manufacturing the same |
| CN105821301A (en) * | 2016-04-21 | 2016-08-03 | 河北钢铁股份有限公司邯郸分公司 | 800MPa-level hot-rolled high strength chambering steel and production method thereof |
| CN105925888A (en) * | 2016-06-21 | 2016-09-07 | 宝山钢铁股份有限公司 | 980 MPa-grade hot-rolled ferritic bainite high-reaming dual-phase steel and manufacturing method thereof |
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| JP4858295B2 (en) * | 2007-05-09 | 2012-01-18 | 住友金属工業株式会社 | Continuous casting method of high strength steel with finely dispersed precipitates and slab for high strength steel |
| CN103602890B (en) * | 2013-11-29 | 2016-08-24 | 宝山钢铁股份有限公司 | A kind of tensile strength 540MPa level high-chambering steel plate and manufacture method thereof |
| CN105925887B (en) | 2016-06-21 | 2018-01-30 | 宝山钢铁股份有限公司 | A kind of 980MPa levels hot-rolled ferrite-bainite dual-phase steel and its manufacture method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BR9804879A (en) * | 1997-04-30 | 1999-08-24 | Kawasaki Steel Co | High ductility steel product, high strength and process for its production |
| JP3872595B2 (en) * | 1998-05-08 | 2007-01-24 | 新日本製鐵株式会社 | Cold rolled steel sheet with low in-plane anisotropy and excellent formability |
| JP3545696B2 (en) * | 2000-03-30 | 2004-07-21 | 新日本製鐵株式会社 | High strength hot rolled steel sheet excellent in hole expandability and ductility and method for producing the same |
| JP3545697B2 (en) * | 2000-05-02 | 2004-07-21 | 新日本製鐵株式会社 | Low corrosion rate high strength hot rolled steel sheet excellent in hole expandability and ductility and method for producing the same |
| US7615126B2 (en) * | 2000-12-07 | 2009-11-10 | Nippon Steel Corporation | High strength hot rolled steel plate excellent in enlargeability and ductility and method for producing thereof |
-
2003
- 2003-10-17 JP JP2003357278A patent/JP4317417B2/en not_active Expired - Fee Related
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103534365A (en) * | 2011-03-24 | 2014-01-22 | 安赛乐米塔尔研究与发展有限责任公司 | Hot-rolled steel sheet and associated production method |
| CN103534365B (en) * | 2011-03-24 | 2015-04-15 | 安赛乐米塔尔研究与发展有限责任公司 | Hot-rolled steel sheet and associated production method |
| US9540719B2 (en) | 2011-03-24 | 2017-01-10 | Arcelormittal Investigacion Y Desarrollo Sl | Hot-rolled steel sheet and associated production method |
| CN105671447A (en) * | 2014-12-05 | 2016-06-15 | Posco公司 | High strength cold rolled steel sheet having high yield ratio and excellent hole expansibility and method for manufacturing the same |
| CN105671447B (en) * | 2014-12-05 | 2018-04-06 | Posco公司 | The excellent high yield of hole expandability is than type high strength cold rolled steel plate and its manufacture method |
| CN105821301A (en) * | 2016-04-21 | 2016-08-03 | 河北钢铁股份有限公司邯郸分公司 | 800MPa-level hot-rolled high strength chambering steel and production method thereof |
| CN105925888A (en) * | 2016-06-21 | 2016-09-07 | 宝山钢铁股份有限公司 | 980 MPa-grade hot-rolled ferritic bainite high-reaming dual-phase steel and manufacturing method thereof |
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| Publication number | Publication date |
|---|---|
| JP4317417B2 (en) | 2009-08-19 |
| JP2005120435A (en) | 2005-05-12 |
| CN100415921C (en) | 2008-09-03 |
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