CN102959129A - Method for producing cold-rolled steel sheet, cold-rolled steel sheet, and vehicle member - Google Patents

Method for producing cold-rolled steel sheet, cold-rolled steel sheet, and vehicle member Download PDF

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CN102959129A
CN102959129A CN201180029545XA CN201180029545A CN102959129A CN 102959129 A CN102959129 A CN 102959129A CN 201180029545X A CN201180029545X A CN 201180029545XA CN 201180029545 A CN201180029545 A CN 201180029545A CN 102959129 A CN102959129 A CN 102959129A
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cold
quality
steel sheet
rolled steel
steel plate
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增冈弘之
安藤聪
山本俊佑
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JFE Steel Corp
JFE Engineering Corp
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NKK Corp
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    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23GCLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08Iron or steel
    • C23G1/085Iron or steel solutions containing HNO3
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21BROLLING OF METAL
    • B21B3/00Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B21B3/02Rolling special iron alloys, e.g. stainless steel
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226Hot rolling
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236Cold rolling
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273Final recrystallisation annealing
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C1/00Making non-ferrous alloys
    • C22C1/02Making non-ferrous alloys by melting
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/001Ferrous alloys, e.g. steel alloys containing N
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/002Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/005Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/06Ferrous alloys, e.g. steel alloys containing aluminium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/12Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/14Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/16Ferrous alloys, e.g. steel alloys containing copper
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32Ferrous alloys, e.g. steel alloys containing chromium with boron
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23GCLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00Cleaning or pickling metallic material with solutions or molten salts
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23GCLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08Iron or steel
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/26Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
    • Y10T428/263Coating layer not in excess of 5 mils thick or equivalent
    • Y10T428/264Up to 3 mils
    • Y10T428/2651 mil or less

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  • General Chemical & Material Sciences (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

Abstract

Provided is a method for producing a cold-rolled steel sheet exhibiting excellent chemical conversion processability and corrosion resistance after coating in harsh corrosive environments such as in a warm salt water immersion test or a compound cyclic corrosion test by: using a pickling solution obtained by mixing hydrochloric acid and nitric acid, the nitric acid concentration being over 100 g/L and 200 g/L or less and the ratio (R) of hydrochloric acid concentration to nitric acid concentration being 0.01 to 0.25 (HCl/HNO3), to pickle a cold-rolled steel sheet containing 0.5 to 3.0 mass % of Si and subjected to continuous annealing after being cold-rolled, in order to remove an Si-containing oxide formed on the surface layer of the steel sheet by continuous annealing; and restricting, to 85% or less, the surface coverage of an iron-based oxide formed on the surface of the steel sheet by the pickling, and preferable restricting, to 200 nm or less, the maximum thickness of the iron-based oxide. Also provided are a cold-rolled steel sheet produced by means of the aforementioned method, and a vehicle member using said cold-rolled steel sheet.

Description

The manufacture method of cold-rolled steel sheet, cold-rolled steel sheet and automobile component
Technical field
The present invention relates to manufacture method, cold-rolled steel sheet and the automobile component of cold-rolled steel sheet, particularly, it is good and by the manufacture method of solidity to corrosion after the application of salt warm water immersion test and the evaluation of compound cycle corrosion test also good cold-rolled steel sheet, by the cold-rolled steel sheet of the method manufacturing and the automobile component that uses this cold-rolled steel sheet to the present invention relates to chemical convertibility.Need to prove that the tensile strength TS that cold-rolled steel sheet of the present invention can be suitable for containing Si is the above high strength cold rolled steel plate of 590MPa.
Background technology
In recent years, from the viewpoint of the environment of preserving our planet, in the urgent need to improving the fuel efficiency of automobile.In addition, the viewpoint of crew member's safety when guaranteeing to collide is also in the urgent need to improving the security of automobile.In order to tackle above-mentioned requirements, need to realize simultaneously lightweight and the high strength of body of a motor car, for for the cold-rolled steel sheet of the material of automobile component, carry out thin-walled property by high strength just energetically.But most automobile components are made by steel plate being formed processing, therefore, these steel plates are also required good plasticity except requiring high strength.
The intensity that improves cold-rolled steel sheet has the whole bag of tricks, as the method that can realize high strength in the situation of damaging not significantly plasticity, can enumerate the solution strengthening method of the interpolation that utilizes Si.But, in the known situation in cold-rolled steel sheet, adding a large amount of Si, the particularly Si more than the 0.5 quality %, when heating steel billet, after the hot rolling or during the annealing after cold rolling, form SiO at surface of steel plate 2, Si-Mn system complex oxide etc. contains the Si oxide compound.This contains the Si oxide compound can make chemical convertibility significantly reduce, therefore, not only chemical convertibility is poor to contain the high strength cold rolled steel plate of a large amount of Si, and when behind electro dipping, being exposed to salt warm water immersion test and repeatedly carrying out in wetting-dry severe cruel corrosive environments such as compound cycle corrosion test, exist than common steel plate easier cause film peel off, the poor such problem of solidity to corrosion after the application.
As the countermeasure of improving for this problem, for example in the patent documentation 1 a kind of high strength cold rolled steel plate has been proposed, wherein, under the temperature more than 1200 ℃, steel billet is heated during hot rolling, under high pressure carry out descaling, with the nylon brush that abrasive particle is housed grinding is carried out on the surface of hot-rolled steel sheet before pickling, dipping carries out pickling 2 times in 9% hydrochloric acid trough, thereby the Si concentration of surface of steel plate is reduced.In addition, proposed a kind of high strength cold rolled steel plate in the patent documentation 2, wherein, the live width by the oxide lines that contains Si that will observe at distance surface of steel plate 1 ~ 10 μ m place is controlled at solidity to corrosion is improved.
But, for the high strength cold rolled steel plate of record in the patent documentation 1, even in the Si of cold rolling front reduction surface of steel plate concentration, owing to contain the Si oxide compound by the annealing after cold rolling in surface of steel plate formation, thereby solidity to corrosion can improve after can not expecting application.In addition, for the high strength cold rolled steel plate of record in the patent documentation 2, although solidity to corrosion can not become problem in the such corrosive environment of the salt spray testing of stipulating in JIS Z2371, but in the such severe cruel corrosive environment of salt warm water immersion test and compound cycle corrosion test, can not obtain solidity to corrosion after the sufficient application.That is, only by the Si concentration that reduces the surface of steel plate after the hot rolling or the oxide lines that minimizing contains Si, can not obtain the high strength cold rolled steel plate of excellent corrosion resistance after the application.
Therefore, as the technology that addresses the above problem, following technology is disclosed in the patent documentation 3: in annealing operation etc. by pickling remove be enriched in surface of steel plate contain the Si oxide compound, and then give the S based compound to its surface, thus, the reactivity of raising and chemical conversion treatment solution, thus chemical convertibility improved.In addition, disclose in the patent documentation 4 and in above-mentioned technology, given the technology that the P based compound replaces the S based compound.
The prior art document
Patent documentation
Patent documentation 1: TOHKEMY 2004-204350 communique
Patent documentation 2: TOHKEMY 2004-244698 communique
Patent documentation 3: TOHKEMY 2007-217743 communique
Patent documentation 4: TOHKEMY 2007-246951 communique
Summary of the invention
Invent problem to be solved
In recent years, in order to reduce industrial waste (suppressing the generation of body refuse) and to cut down operating cost, advancing the low temperature of chemical conversion treatment solution, comparing with existing chemical conversion processing condition, chemical conversion treatment solution significantly reduces the reactivity of steel plate.For the few general steel plate of the alloy addition level that in the past used, the surperficial adjustment technology before processing by the improvement chemical conversion etc., the low temperatureization of above-mentioned treatment solution can not become problem.But, for the high strength cold rolled steel plate that is added with a large amount of Si, significantly reduce because the impact that contains the Si oxide compound that is subject to being formed on the steel plate top layer in annealing operation makes with the reactive of chemical conversion treatment solution, therefore, need to improve reactive from the steel plate aspect by some means.But, for disclosed technology in patent documentation 3 and 4, even effective to existing general steel plate, also can't expect the high strength cold rolled steel plate that contains a large amount of Si is had the sufficient effect of improving of the low temperature that can tackle chemical conversion treatment solution.
The present invention finishes in view of the existing the problems referred to above of the cold-rolled steel sheet that contains a large amount of Si, though its purpose be to provide when using the chemical conversion treatment solution of low temperature chemical convertibility also after the good and application in the severe cruel corrosive environments such as the test of salt warm water immersion and compound cycle corrosion test solidity to corrosion also good cold-rolled steel sheet favourable manufacture method, by the cold-rolled steel sheet of the method manufacturing and the automobile component that uses this cold-rolled steel sheet.
For the method for dealing with problems
The inventor has carried out detailed analysis in order to address the above problem to the surface of steel plate characteristic after the annealing, and the reactive method that improves surface of steel plate and chemical conversion treatment solution is conducted in-depth research.Found that, the surface of steel plate that has carried out continuous annealing after cold rolling is carried out being formed on when strong acid washes to remove annealing containing the Si oxide skin and being very important by the surface of steel plate fraction of coverage that above-mentioned strong acid washes to reduce the ferrous oxide that is created on surface of steel plate of steel plate top layer, thereby finished the present invention.
That is, the present invention proposes a kind of manufacture method of cold-rolled steel sheet, it is characterized in that, use concentration of nitric acid to rise greater than 100g/ and below 200g/ rises, the ratio R (HCl/HNO of concentration of hydrochloric acid and concentration of nitric acid 3) steel plate of continuous annealing that to be 0.01 ~ 0.25 the acid that nitric acid and mixed in hydrochloric acid are formed to the Si that contains 0.5 ~ 3.0 quality % and after cold rolling carried out carries out pickling.
Manufacture method of the present invention is characterised in that, in the above-mentioned acid that nitric acid and mixed in hydrochloric acid are formed, concentration of nitric acid rises greater than 110g/ and below 140g/ rises, the ratio R (HCl/HNO of concentration of hydrochloric acid and concentration of nitric acid 3) be 0.03 ~ 0.25.
In addition, manufacture method of the present invention is characterised in that, at the Temperature Setting with pickle solution is to carry out 3 ~ 30 seconds above-mentioned pickling under 20 ~ 70 ℃ the condition.
In addition, manufacture method of the present invention is characterised in that, above-mentioned steel plate has following one-tenth and is grouped into: except containing Si, contain also that C:0.01 ~ 0.30 quality %, Mn:1.0 ~ 7.5 quality %, P:0.05 quality % are following, S:0.01 quality % following and below the Al:0.06 quality %, surplus by Fe and inevitably impurity consist of.
In addition, manufacture method of the present invention is characterised in that, above-mentioned cold-rolled steel sheet on the basis that mentioned component forms, also contain be selected from below the Nb:0.3 quality %, below the Ti:0.3 quality %, below the V:0.3 quality %, below the Mo:0.3 quality %, below the Cr:0.5 quality %, below the B:0.006 quality % and N:0.008 quality % with lower one or more.
In addition, manufacture method of the present invention is characterised in that, above-mentioned cold-rolled steel sheet on the basis that mentioned component forms, also contain be selected from below the Ni:2.0 quality %, below the Cu:2.0 quality %, below the Ca:0.1 quality % and REM:0.1 quality % with lower one or more.
In addition, the invention provides a kind of cold-rolled steel sheet, method manufacturing by each record in above-mentioned forms, it is characterized in that, the pickling of Si oxide skin after by continuous annealing that contain on steel plate top layer removed, and the surface coverage of the ferrous oxide of the surface of steel plate that generates by above-mentioned pickling is below 85%.
Above-mentioned cold-rolled steel sheet among the present invention is characterised in that the maximum ga(u)ge that is present in the ferrous oxide of surface of steel plate is below the 200nm.
In addition, the invention provides a kind of automobile component, it is characterized in that, use above-mentioned in each record cold-rolled steel sheet and form.
The invention effect
According to the present invention, though can provide at the Si that contains 0.5 ~ 3.0 quality % nearly and when using the chemical conversion treatment solution of low temperature chemical convertibility also good and in the severe cruel corrosive environments such as the test of salt warm water immersion and compound cycle corrosion test also good cold-rolled steel sheet of solidity to corrosion after the application.Therefore, according to the present invention, can significantly improve the tensile strength TS that contains a large amount of Si and be solidity to corrosion after the chemical convertibility of the above high strength cold rolled steel plate of 590MPa and the application, therefore can be suitable for the strength member of body of a motor car etc.
Description of drawings
Fig. 1 represents the backscattered electron image be used to the surface of steel plate of the cold-rolled steel sheet standard model No.a of the surface coverage of obtaining ferrous oxide and No.b.
Fig. 2 represents that the pixel count of backscattered electron image photo of cold-rolled steel sheet standard model No.a and No.b is with respect to the distribution plan of gray-scale value.
Fig. 3 is that the cross section of the surface of steel plate coverture after utilizing transmission electron microscope to pickling is observed and the photo that obtains.
Fig. 4 is the figure of X-ray energy spectrum (EDX) analytical results of the ferrous oxide observed in the presentation graphs 3.
Fig. 5 is the figure that utilizes GDS that the depth direction of O, Si, Mn and the Fe on the test film surface of the comparative example (No.1) of embodiment 1 and example (No.18) is distributed and measures and obtain.
Embodiment
At first basic fundamental design of the present invention is described.
The annealing operation of the use continuous annealing furnace that carries out being used for making cold-rolled steel sheet recrystallize, the tissue of giving expectation and intensity after cold rolling, processibility is usually used the gas of non-oxidizable or reductibility as atmosphere gas, and is strictly controlled dew point.Therefore, for the few common general cold-rolled steel sheet of alloy addition level, the oxidation of surface of steel plate is inhibited.But, for the steel plate of Si, Mn more than containing 0.5 quality %, even composition, the dew point of the atmosphere gas during strict control annealing, oxidation also can occur and form Si oxide compound (SiO at surface of steel plate inevitably in Si, the Mn etc. that have more oxidisability than Fe 2), Si-Mn system complex oxide etc. contains the Si oxide compound.Although mostly the formation of these oxide compounds also can along with steel plate composition and annealing atmosphere etc. change, be that both mix existence usually.And know, the above-mentioned Si of containing oxide compound not only is formed at surface of steel plate, even be formed at iron-based inside, therefore, processing the corrodibility that inhibition surface of steel plate in (zinc phosphate processing) is processed in the chemical conversion of carrying out as the matrix of electro dipping, the formation of intact chemical conversion being processed tunicle has a negative impact.
In recent years, in order to reduce the body refuse amount that produces when chemical conversion is processed and to cut down operating cost, advancing the low temperature of chemical conversion treatment solution, processing thereby chemical conversion treatment solution significantly is lower than in the past condition to the reactivity of steel plate under, carry out chemical conversion.For the few general steel plate of the alloy addition level that in the past used, by the improved surface adjustment technology etc., the change that condition is processed in above-mentioned chemical conversion can not become problem especially.But, for the steel plate that is added with a large amount of alloying constituents, particularly add a large amount of Si and realize for the high strength cold rolled steel plate of high strength, huge by the impact that above-mentioned chemical conversion processing condition change brings.Therefore, for the cold-rolled steel sheet that contains a large amount of Si, process the deterioration of condition in order to tackle chemical conversion, need to make the surface active of steel plate itself and improve reactivity with chemical conversion treatment solution.
Process the deterioration of condition in order to tackle above-mentioned chemical conversion, the inventor has carried out repeatedly research to the method for the chemical convertibility of raising steel plate.Found that carrying out strong acid with nitric acid as the surface of cold-rolled steel plate of pickle solution after to continuous annealing, to wash to remove the Si oxide skin that contains on the steel plate top layer that forms in the continuous annealing after cold rolling etc. be effective.At this, the SiO that the above-mentioned Si of containing oxide compound refers to when heating steel billet, form along the crystal boundary of surface of steel plate or steel plate inside after the hot rolling or during the annealing after cold rolling 2With the Si-Mn system complex oxide, these thickness that contain the existing layer of Si oxide compound change with steel plate composition, annealing conditions (temperature, time, atmosphere), but usually apart from the about 1 μ m of surface of steel plate.In addition, the mode that the above-mentioned Si of containing oxide skin refers to reach the level at the peak that does not occur Si and O when utilizing GDS (grow discharge optical emission spectrometry analysis) on depth direction surface of steel plate to be analyzed of removing among the present invention carries out pickling and removes containing the Si oxide skin.
Need to prove, use nitric acid to be as the reason of above-mentioned pickle solution, contain that the Si-Mn system complex oxide is soluble in acid in the Si oxide compound, but SiO 2Demonstrate insoluble, therefore, in order to be removed, to need to use and as the nitric acid of acid with strong oxidizing property the Si oxide compound that contains of surface of steel plate is removed together with iron-based.
But, according to contriver's research as can be known, by after continuous annealing, use nitric acid carry out strong acid wash remove be present in the steel plate top layer contain the Si oxide skin, although chemical convertibility is greatly improved, chemical convertibility is variation sometimes.So, its reason is further investigated, as a result new discovery, wash by the above-mentioned strong acid of nitric acid that utilizes, be oxide skin although removed Si, but by the Fe generation ferrous oxide of pickling from the surface of steel plate dissolving, this ferrous oxide covers surface of steel plate at the surface of steel plate Precipitation, makes thus the chemical convertibility variation in addition.
And find, for the oxidation that suppresses the surface of steel plate that above-mentioned nitric acid acidwashing causes, reduce the disadvantageous effect of bringing to chemical convertibility, importantly suppressing ferrous oxide is reduced to below 85% the surface of steel plate fraction of coverage of ferrous oxide in the generation of surface of steel plate, in addition, as its implementation, importantly concentration of nitric acid is controlled in the proper range and the oxidation that suppresses to be caused by nitric acid and use and be mixed with acid hydrochloric acid with oxide film execution, that nitric acid and mixed in hydrochloric acid are formed with estimated rate and carry out pickling as pickle solution.
In addition, the inventor finds, be on the basis below 85% and then to make the maximum ga(u)ge of above-mentioned ferrous oxide be that 200nm is when following in the fraction of coverage that makes the ferrous oxide that is created on surface of steel plate by pickling, chemical convertibility further improves, solidity to corrosion also further improves, and as its implementation, effectively will be controlled at as the concentration of the hydrochloric acid with oxide film execution of the part of pickle solution and carry out pickling in the proper range.
Need to prove that the atomic percent that the ferrous oxide among the present invention refers to consist of iron in the element beyond the oxygen of oxide compound is than being the oxide compound take iron as main body more than 30%.This ferrous oxide is present on the surface of steel plate with inhomogeneous thickness, be from the even thickness of several nanometers and be the different oxide compound of natural oxidation tunicle that stratiform exists.In addition, by transmission electron microscope (TEM) observe and the analytical results of the diffraction pattern (diffraction pattern) of electron diffraction as can be known, the ferrous oxide that is created on the surface of this cold-rolled steel sheet is amorphousness.
The present invention further studies and finishes above-mentioned neodoxy.
Next, the reason that the one-tenth that limits cold-rolled steel sheet of the present invention is grouped into describes.
Si:0.5 ~ 3.0 quality %
The effect (solution strengthening ability) of the intensity that improves steel in the situation of damaging not significantly processibility of Si is large, therefore be the effective element of high strength to the realization steel, but also be the element that solidity to corrosion after chemical convertibility and the application is had a negative impact.Adding in the situation of Si as the high-intensity method of realization, needing to add more than the 0.5 quality %.In addition, Si is during less than 0.5 quality %, and it is less to process the impact that the deterioration of condition brings by chemical conversion.On the other hand, when the content of Si surpassed 3.0 quality %, hot rolling and cold-rolling property significantly reduced, and brought disadvantageous effect or caused the ductility of steel plate itself to reduce to productivity.Therefore, add Si with the scope of 0.5 ~ 3.0 quality %.Be preferably the scope of 0.8 ~ 2.5 quality %.
For cold-rolled steel sheet of the present invention, will contain Si as prerequisite with above-mentioned scope, for other compositions, need only the compositing range that has for common cold-rolled steel sheet and then can allow, be not particularly limited.But, in the situation of tensile strength TS as the high strength cold rolled steel plate more than the 590MPa of in cold-rolled steel sheet of the present invention being applied to body of a motor car etc., using, preferably have following compositions and form.
C:0.01 ~ 0.30 quality %
C is to making the effective element of steel high strength, and also is that generation is had TRIP (phase change induction plasticity: Transformation Induced Plasticity) the effective element of residual austenite, bainite, martensite of effect.C is 0.01 quality % when above, can access above-mentioned effect, and on the other hand, C is 0.30 quality % when following, the reduction that can not produce weldability.Therefore, preferably add C with the scope of 0.01 ~ 0.30 quality %, more preferably add C with the scope of 0.10 ~ 0.20 quality %.
Mn:1.0 ~ 7.5 quality %
Mn be have make the steel solution strengthening and carry out high strength and improve hardening capacity, promote residual austenite, the element of effect that bainite, martensite generate.Occur during the Mn of this effect more than adding 1.0 quality %.On the other hand, Mn is 7.5 quality % when following, can access above-mentioned effect and can not cause cost to raise.Therefore, preferably add Mn with the scope of 1.0 ~ 7.5 quality %, more preferably add Mn with the scope of 2.0 ~ 5.0 quality %.
Below the P:0.05 quality %
P is that the solution strengthening ability is large but do not damage the element of drawing property, and is to realizing the effective element of high strength, therefore, preferably containing more than the 0.005 quality %.But P is the element of infringement spot weldability, can not have problems when 0.05 quality % is following.Therefore, preferably making P is below the 0.05 quality %, more preferably is below the 0.02 quality %.
Below the S:0.01 quality %
S is the impurity element of unavoidably sneaking into, and is to separate out with the form of MnS in steel and objectionable constituent that the stretch flangeability of steel plate is reduced.For stretch flangeability is reduced, preferably making S is below the 0.01 quality %.More preferably below the 0.005 quality %, more preferably below the 0.003 quality %.
Below the Al:0.06 quality %
Al is the element that adds as reductor in steel making working procedure, and is to making non-metallic inclusion that stretch flangeability reduces with the effective element of the isolated in form of slag, and therefore, preferably containing more than the 0.01 quality %.Al is 0.06 quality % when following, can access above-mentioned effect and does not cause raw materials cost to raise.Therefore, preferably making Al is below the 0.06 quality %.The scope of 0.02 ~ 0.06 quality % more preferably.
In addition, cold-rolled steel sheet of the present invention can on the basis that mentioned component forms, also contain be selected from below the Nb:0.3 quality %, below the Ti:0.3 quality %, below the V:0.3 quality %, below the Mo:0.3 quality %, below the Cr:0.5 quality %, below the B:0.006 quality % and N:0.008 quality % with lower one or more.
Thereby Nb, Ti and V form carbide or nitride, the heating phase when annealing to suppress ferritic growth and make the element of organizing miniaturization to improve plasticity, particularly stretch flangeability, in addition, Mo, Cr and B are the hardening capacity that improves steel, the element that promotes the bainite and martensite generation, therefore, can in above-mentioned scope, add.In addition, N becomes nitride with Nb, Ti or is solid-solubilized in the steel and helps the element of the high strength of steel with V-arrangement, when 0.008 quality % is following, can not form a large amount of nitride, therefore, can suppress to form the fracture that the space causes when stamping, thereby can access above-mentioned effect.
In addition, cold-rolled steel sheet of the present invention can on the basis that mentioned component forms, also contain be selected from below the Ni:2.0 quality %, below the Cu:2.0 quality %, below the Ca:0.1 quality % and REM:0.1 quality % with lower one or more.
Ni and Cu have the effect that promotes the covert generation of low-temperature phase and make the steel high strength, therefore can add in above-mentioned scope.In addition, Ca and REM are the forms of the sulfide-based inclusion of control and therefore element that the stretch flangeability of steel plate is improved can add in above-mentioned scope.
In the cold-rolled steel sheet of the present invention, the surplus except mentioned component is Fe and inevitable impurity.But, as long as in the scope of not damaging action effect of the present invention, then can add other compositions.
Next, the surface property of cold-rolled steel sheet of the present invention described.
As mentioned above, cold-rolled steel sheet of the present invention need to have and will be formed on the SiO on steel plate top layer when annealing 2Contain surface of steel plate after the Si oxide skin is removed with Si-Mn system complex oxide etc.Therefore, need to use the pickle solution that nitric acid and mixed in hydrochloric acid are formed to carry out strong acid and wash, thereby the Si oxide compound that contains that will be formed on the grain boundary portion of surface of steel plate or near surface dissolves together with iron-based and removes.
In addition, for cold-rolled steel sheet of the present invention, on the basis of removing the above-mentioned Si of containing oxide skin, the surface of steel plate fraction of coverage that also needs to wash the ferrous oxide that is created on surface of steel plate by the above-mentioned strong acid that utilizes nitric acid is reduced to below 85% in area occupation ratio.This is because when the surface coverage of ferrous oxide surpasses 85%, can hinder the solubilizing reaction of iron in the chemical conversion processing, thereby suppress the growth of the chemical conversion crystallizations such as zinc phosphate.Be preferably below 80%.
Among the present invention, the surface coverage of above-mentioned ferrous oxide is following to be obtained.
Use can detect the scanning electronic microscope (ULV-SEM) of the extremely low acceleration voltage of surface layer information, be that 2kV, operating distance are that 3.0mm, multiplying power are under the about 1000 times condition surface of steel plate after the pickling to be observed about 5 visuals field at acceleration voltage, use X-ray energy spectrometer (EDX) to carry out spectrum analysis, obtain backscattered electron image.Use image analysis software for example Image J this backscattered electron image is carried out binary conversion treatment, measure the area occupation ratio of black part, the measured value in each visual field is averaged, can access thus the surface coverage of ferrous oxide.Need to prove, as the scanning electronic microscope (ULV-SEM) of above-mentioned extremely low acceleration voltage, can enumerate for example ULTRA55 of SEISS company manufacturing, in addition, as X-ray energy spectrometer (EDX), can enumerate for example NSS312E of Thermo Fisher company manufacturing.
At this, the threshold value of above-mentioned binary conversion treatment is described.
The steel billet of Steel Mark G shown in the table 3 of embodiment described later is carried out hot rolling, cold rolling, continuous annealing and make the cold-rolled steel sheet that thickness of slab is 1.8mm under the condition shown in the No.7 of the table 4 of same embodiment described later, then under the conditions shown in Table 1 the cold-rolled steel sheet after the above-mentioned continuous annealing is carried out pickling and again pickling, after washing and the drying, implement 0.7% temper rolling, obtain different No.a and these two kinds of cold-rolled steel sheets of No.b of ferrous oxide amount of surface of steel plate.Then, as the many standard models of ferrous oxide, as the few standard model of ferrous oxide, for each steel plate, use scanning electronic microscope to obtain under these conditions backscattered electron image the cold-rolled steel sheet of No.b the cold-rolled steel sheet of above-mentioned No.a.Fig. 1 represents the backscattered electron image photo of the steel plate of No.a, No.b, and in addition, Fig. 2 represents that the pixel count of above-mentioned backscattered electron image photo of steel plate of No.a, No.b is with respect to the distribution plan of gray-scale value.Among the present invention, the above-mentioned gray-scale value (Y point) corresponding with the intersection point (X point) of distribution plan No.a, No.b shown in Figure 2 is decided to be threshold value.By the way, use above-mentioned threshold value to obtain the surface coverage of ferrous oxide of the steel plate of No.a, No.b, the result, the steel plate of No.a is that the steel plate of 85.3%, No.b is 25.8%.
[table 1]
Figure BDA00002590108400121
In addition, in order further to improve chemical convertibility and the solidity to corrosion of cold-rolled steel sheet of the present invention, preferably further making the maximum ga(u)ge of above-mentioned ferrous oxide on the fraction of coverage that makes the ferrous oxide that is created on surface of steel plate by pickling is basis below 85% is below the 200nm.This is because the maximum ga(u)ge of ferrous oxide is 200nm when following, can not hinder locally the solubilizing reaction of iron in the chemical conversion processing, thereby can not suppress locally separating out of the chemical conversion crystallization such as zinc phosphate.More preferably below the 180nm.
At this, the maximum ga(u)ge of above-mentioned ferrous oxide is following to be obtained.
At first, made 10 replicas observing with respect to the cross section of the about 8 μ m of the width of steel plate by the surface of steel plate after the pickling by focused ion beam (FIB) processing.Then, use the transmission electron microscope (TEM) of the X-ray energy spectrometer (EDX) that possesses the local message that to investigate the cross section, take pictures continuously with acceleration voltage 200kV, 100,000 times of cross section 8 μ m to each replica of multiplying power.As an example, Fig. 3 shows and utilizes TEM that the photo that obtains is observed in the tectal cross section of passing through the pickling generation that is present in surface of steel plate, and Fig. 4 shows this tectal EDX analytical results.As shown in Figure 4, above-mentioned tectum is the ferrous oxide take iron as main body, therefore, 10 replicas are measured the interval of line A with the line B of the thick of expression oxide skin of the expression steel plate iron-based shown in the cross-section photograph of Fig. 3, with wherein the maximum ga(u)ge maximum ga(u)ge as ferrous oxide.Need to prove that the condition determination of the size of above-mentioned replica, number, TEM etc. only is an illustration, certainly can suitably change.
Next, the manufacture method of cold-rolled steel sheet of the present invention described.
The manufacture method of rolled steel plate of the present invention need to be following method: after the former material of steel (steel billet) of the Si that contains 0.5 ~ 3.0 quality % is heated, carry out hot rolling, cold rolling, continuous annealing, then use the pickle solution that nitric acid and mixed in hydrochloric acid are formed to carry out pickling, thus, can remove the steel plate surface part to contain the Si oxide skin and make the surface coverage that is created on the ferrous oxide of surface of steel plate by above-mentioned pickling be below 85%, in addition, being preferably the maximum ga(u)ge that can make above-mentioned ferrous oxide is the following method of 200nm.Therefore, begin continuous annealing operation after cold rolling from steel making working procedure till, can make by ordinary method, but following condition is preferably adopted in the pickling after the continuous annealing.
Acid washing conditions after the continuous annealing
Steel plate Surface Realize after above-mentioned continuous annealing a large amount of SiO 2Contain the Si oxide compound with Si-Mn system complex oxide etc., and if do not add processing after could making chemical convertibility and application solidity to corrosion significantly reduce.Therefore, in the manufacture method of the present invention, need to use acid that nitric acid and mixed in hydrochloric acid are formed to carry out strong acid as the cold-rolled steel sheet of pickle solution after to annealing and wash and the Si oxide skin that contains on steel plate top layer is removed together with iron-based, and need to suppress Precipitation in the generation of the ferrous oxide of surface of steel plate by above-mentioned pickling.
As mentioned above, contain in the Si oxide compound, the Si-Mn system complex oxide is soluble in acid, and SiO 2Acid is demonstrated insoluble.Therefore, comprise SiO in order to remove by pickling 2At the interior Si oxide compound that contains, need to use and remove together with the iron-based of steel plate as the nitric acid of strong acid.And, wash in order to carry out the aforesaid strong acid that oxide skin is removed together with iron-based, need to make concentration of nitric acid greater than the 100g/ liter.But, because nitric acid also is the acid of strong oxidizing property, generates ferrous oxide after the Fe oxidation of stripping and separate out at surface of steel plate, can give chemical convertibility and application on the contrary after solidity to corrosion bring disadvantageous effect.Therefore, for fear of above-mentioned drawback, concentration of nitric acid need to be suppressed at below the 200g/ liter.Therefore, making concentration of nitric acid is greater than 100g/ liter and the scope below 200g/ rises.Be preferably the scope that 110 ~ 150g/ rises.
But, when only concentration of nitric acid being limited in the above-mentioned scope, being difficult to stably and will being controlled to be below 85% by the surface coverage that nitric acid acidwashing is created on the ferrous oxide of surface of steel plate.Therefore, among the present invention, in order to suppress more reliably to wash and generate ferrous oxide at surface of steel plate by the strong acid of above-mentioned use nitric acid, on the basis that concentration of nitric acid is limited in the above-mentioned scope, further use so that the ratio R (HCl/HNO of concentration of hydrochloric acid and concentration of nitric acid 3) be that to be mixed with the chloride ion with oxide film execution be that pickling is carried out in the acid of hydrochloric acid for the mode of 0.01 ~ 0.25 scope.This be because, above-mentioned ratio R is less than 0.01 o'clock, the effect of generation that suppresses above-mentioned ferrous oxide is little, on the other hand, greater than 0.25 o'clock, the meltage of steel plate reduced and can't remove and contain the Si oxide skin.
In addition, in order further to improve chemical convertibility and solidity to corrosion, preferably making the maximum ga(u)ge that is created on the ferrous oxide of surface of steel plate by pickling is below the 200nm, therefore, preferably make concentration of nitric acid in the pickle solution that nitric acid and mixed in hydrochloric acid are formed that uses in the above-mentioned pickling for rising greater than 110g/ and scope below 140g/ rises and make the ratio R (HCl/HNO of concentration of hydrochloric acid and concentration of nitric acid 3) be 0.03 ~ 0.25 scope.This is because in the time of in above-mentioned scope, the thickness that can stably make ferrous oxide is below the 200nm, can not reduce solidity to corrosion after chemical convertibility and the application.
Need to prove that the pickling of using the above-mentioned pickle solution that nitric acid and mixed in hydrochloric acid are formed is 20 ~ 70 ℃ and to make pickling time be to carry out under 3 ~ 30 seconds the condition of scope in the temperature that makes pickle solution preferably.The temperature of pickle solution is more than 20 ℃ and pickling time is more than 3 seconds the time, the steel plate top layer that forms in the time of can fully removing annealing contain the Si oxide skin, and solidity to corrosion reduces after can not making chemical convertibility and application.On the other hand, the temperature of pickle solution is below 70 ℃ and pickling time is below 30 seconds the time, can to cause the surface of steel plate roughen to make chemical conversion process tunicle inhomogeneous or the surface coverage of ferrous oxide is increased because of over-cleaning, therefore, can not make that solidity to corrosion reduces after chemical convertibility and the application.
Then, be that the cold-rolled steel sheet below 85% or the maximum ga(u)ge that further makes above-mentioned ferrous oxide are that cold-rolled steel sheet below the 200nm is made finished product through the common treatment process such as temper rolling with the fraction of coverage that makes in the above described manner the ferrous oxide of surface of steel plate carrying out pickling after the continuous annealing.
Embodiment 1
To contain C:0.125 quality %, Si:1.5 quality %, Mn:2.6 quality %, P:0.019 quality %, S:0.008 quality % and Al:0.040 quality % and surplus by Fe and inevitably the steel that consists of of impurity by the common refinery practice through converter, degassed processing etc. carry out melting, continuous casting is made the former material of steel (steel billet).This steel billet is reheated to 1150 ~ 1170 ℃ temperature, carry out the finish to gauge end temp is set as 850 ~ 880 ℃ hot rolling, under 500 ~ 550 ℃ temperature, batch the rolling material, make the hot-rolled steel sheet that thickness of slab is 3 ~ 4mm, then these hot-rolled steel sheets are carried out pickling and remove descaling, then carry out cold rollingly, make the cold-rolled steel sheet that thickness of slab is 1.8mm.Then, these cold-rolled steel sheets are heated to 750 ~ 780 ℃ soaking temperature, keep after 40 ~ 50 seconds, enforcement is cooled to 350 ~ 400 ℃ cooling with 20 ~ 30 ℃/second from above-mentioned soaking temperature and stops temperature and stop to keep in the temperature range 100 ~ 120 seconds continuous annealing in above-mentioned cooling, then, under the conditions shown in Table 2 surface of steel plate is carried out pickling, after washing and the drying, the enforcement elongation is 0.7% temper rolling, obtains the cold-rolled steel sheet of the No.1 shown in the table 2 ~ 25.
Cut test film from above-mentioned each cold-rolled steel sheet, use the scanning electronic microscope (ULV-SEM of extremely low acceleration voltage; SEISS company makes; ULTRA55), be that 2kV, operating distance are that 3.0mm, multiplying power are under 1000 times the condition surface of steel plate to be observed 5 visuals field at acceleration voltage, use X-ray energy spectrometer (EDX; Thermo Fisher company makes; NSS312E) carry out spectrum analysis, obtain backscattered electron image.Use image analysis software (Image J), the gray-scale value (Y point) corresponding with the intersection point (X point) of the distribution plan of above-mentioned standard model No.a, No.b is decided to be threshold value, this backscattered electron image is carried out binary conversion treatment, measure the area occupation ratio of black part, obtain the mean value in 5 visuals field, with its surface coverage as ferrous oxide.
In addition, cut test film from above-mentioned each cold-rolled steel sheet, after implementing under the following conditions chemical conversion processing and application processing, supply in these three kinds of corrosion tests of the test of salt warm water immersion, salt spray testing and compound cycle corrosion test, and solidity to corrosion after the evaluation application.In addition, the depth direction of O, Si, Mn and Fe that uses GDS to measure the surface of the test film that cuts from each cold-rolled steel sheet distributes.
(1) condition is processed in chemical conversion
The grease-removing agent that uses the rapids smart company of Japanese handkerchief card to make: FC-E2011, surface conditioner: PL-X and chemical conversion treating agent: パ Le ボ Application De PB-L3065, carried out under these two kinds of conditions of contrast condition of low temperature with the temperature that reduces chemical conversion treatment solution in following standard conditions, implementing to make chemical conversion to process the tunicle adhesion amount to the test film that cuts from above-mentioned each cold-rolled steel sheet is 1.7 ~ 3.0g/m 2Chemical conversion process.
<standard conditions 〉
Degreasing process: 40 ° of C for the treatment of temp, 120 seconds treatment times
Operation: pH9.5, treatment temp room temperature, 20 seconds treatment times are adjusted in spraying degreasing, surface
Chemical conversion treatment process: 35 ℃ of the temperature of chemical conversion treatment solution, 120 seconds treatment times
<low temperature condition 〉
The temperature of chemical conversion treatment solution in the above-mentioned standard conditions is reduced to 33 ℃ condition
(2) corrosion test
The electroplating coating that uses Japanese ペ イ Application ト company to make: V-50 carries out electro dipping to above-mentioned surface of having implemented the test film that chemical conversion processes so that thickness is the mode of 25 μ m, and in following three kinds of corrosion tests.
<salt warm water immersion test 〉
Utilize cutting tool to give the intersection otch defective that length is 45mm to the surface of the above-mentioned test film (n=1) of having implemented chemical conversion processing and electro dipping, then, this test film was flooded 240 hours in the NaCl solution (60 ℃) of 5 quality %, then wash and drying, carry out pasting the belt stripping test of tearing behind the adhesive tape in the otch defective part, measure the maximum that is added together about the otch defective part and peel off total width.If it is below the 5.0mm that this maximum is peeled off total width, the solidity to corrosion that then can be evaluated as in the test of salt tolerant warm water immersion is good.
<salt spray testing (SST) 〉
Utilize cutting tool to give the intersection otch defective that length is 45mm to the surface of the above-mentioned test film (n=1) of having implemented chemical conversion processing, electro dipping, then, use the NaCl aqueous solution of 5 quality %, according to the neutral brine spray testing of stipulating among the JIS Z2371:2000 this test film is carried out 1000 hours salt spray testing, then, intersection otch defective part is carried out belt stripping test, measure the maximum that is added together about the otch defective part and peel off total width.If it is below the 4.0mm that this maximum is peeled off total width, the solidity to corrosion that then can be evaluated as in the salt spray testing is good.
<compound cycle corrosion test (CCT) 〉
Utilize cutting tool to having implemented the chemical conversion processing, the intersection otch defective that length is 45mm is given on the surface of the above-mentioned test film (n=1) of electro dipping, then, this test film is carried out brine spray (the NaCl aqueous solution of 5 quality %: 35 ℃, relative humidity: 98%) * 2 hour → dry (60 ℃, relative humidity: 30%) * 2 hour → wetting (50 ℃, 95%) * 2 hour relative humidity: be cycled to repeat 90 times corrosion test as 1 circulation and with this, then, wash and drying after, intersection otch defective part is carried out belt stripping test, measure the maximum that is added together about the otch defective part and peel off total width.If it is below the 6.0mm that this maximum is peeled off total width, the solidity to corrosion that then can be evaluated as in the compound cycle corrosion test is good.
The result of above-mentioned test is recorded in the table 2 in the lump.By this result as can be known, for the steel plate of the example of under condition according to the invention, having carried out pickling after the continuous annealing, in arbitrary test in the test of salt warm water immersion, salt spray testing and compound cycle corrosion test, it is all less that maximum is peeled off total width, demonstrates solidity to corrosion after the good application.On the other hand as can be known, for the steel plate that discontented foot acid washing conditions of the present invention, the surface coverage that contains Si oxide compound or ferrous oxide of not removing surface of steel plate surpass 85% comparative example, solidity to corrosion is all relatively poor after the application.Need to prove, the depth direction of O, Si, Mn and Fe that utilizes each surface of steel plate of GDS mensuration table 2 distributes and among the result that obtains, the peak of Si and O does not appear in the steel plate that has carried out pickling under condition according to the invention, is fully removed thereby confirmed to contain the Si oxide skin.The depth direction of O, Si, Mn and Fe when as a reference, utilizing the test film of the No.18 of the No.1 of comparative example of GDS his-and-hers watches 2 and example to carry out surface analysis distributes and is shown among Fig. 5.
Figure BDA00002590108400181
Embodiment 2
The steel that will have A ~ X that one-tenth is grouped into shown in the table 3 by carry out melting through common refinery practices such as converter, degassed processing, continuous casting is made steel billet.Under the hot-rolled condition shown in the table 4, these steel billets are carried out hot rolling, make the hot-rolled steel sheet that thickness of slab is 3 ~ 4mm, carry out pickling and the oxide skin of removing surface of steel plate, then carry out cold rollingly, make the cold-rolled steel sheet that thickness of slab is 1.8mm.Then, equally under the conditions shown in Table 4 these cold-rolled steel sheets are carried out continuous annealing after, carry out under the conditions shown in Table 5 pickling, 0.7% temper rolling is implemented elongation and is in then washing and dry, obtains the cold-rolled steel sheet of No.1 ~ 30.
Figure BDA00002590108400201
Figure BDA00002590108400211
Figure BDA00002590108400221
Cut test film from above-mentioned each cold-rolled steel sheet that obtains like this, similarly to Example 1 operation, then the surface coverage of the ferrous oxide of the surface of steel plate after the mensuration pickling supplies corrosion resistant test after following tension test and application.In addition, the depth direction of O, Si, Mn and Fe that utilizes GDS to measure the surface of the test film that cuts from each cold-rolled steel sheet distributes.
(1) mechanical characteristics
The JIS5 tension test sheet (n=1) that use is stipulated from the JIS Z2201:1998 that cuts with the rectangular direction of rolling direction (C direction) carries out tension test according to the regulation of JIS Z2241:1998, measures tensile strength TS.
(2) solidity to corrosion after the application
Under the condition identical with embodiment 1, the test film that cuts from each cold-rolled steel sheet is carried out chemical conversion processing, electro dipping, make test film, similarly to Example 1 operation, supply in the test of salt warm water immersion, salt spray testing (SST) and these three kinds of corrosion tests of compound cycle corrosion test (CCT), and solidity to corrosion after the evaluation application.
The results are shown in table 4 and the table 5 of above-mentioned test.By the result as can be known, for the Si more than containing 0.5 quality % and under condition according to the invention, carried out for the high strength cold rolled steel plate of the inventive example of pickling, excellent corrosion resistance after the application not only, and also to have tensile strength TS be the above high strength of 590MPa.Need to prove that the depth direction that utilizes GDS to measure O, Si, Mn and Fe distributes and among the result that obtains, the peak of Si and O does not all appear in the steel plate that has carried out pickling under condition according to the invention, is fully removed thereby confirmed to contain the Si oxide skin.
Embodiment 3
To contain C:0.125 quality %, Si:1.5 quality %, Mn:2.6 quality %, P:0.019 quality %, S:0.008 quality % and Al:0.040 quality % and surplus by Fe and inevitably the steel that consists of of impurity carry out melting, continuous casting and make the former material of steel (steel billet).This steel billet is reheated to 1150 ~ 1170 ℃ temperature, carry out the finish to gauge end temp being set as 850 ~ 880 ℃ hot rolling, under 500 ~ 550 ℃ temperature, batch, make the hot-rolled steel sheet that thickness of slab is 3 ~ 4mm.These hot-rolled steel sheets are carried out pickling and except descaling, then carry out cold rollingly, make the cold-rolled steel sheet that thickness of slab is 1.8mm.Then, these cold-rolled steel sheets are heated to 750 ~ 780 ℃ soaking temperature, keep after 40 ~ 50 seconds, enforcement is cooled to 350 ~ 400 ℃ cooling with 20 ~ 30 ℃/second from above-mentioned soaking temperature and stops temperature and stop to keep in the temperature range 100 ~ 120 seconds continuous annealing in above-mentioned cooling, then, under the conditions shown in Table 6 surface of steel plate is carried out pickling, after washing and the drying, the enforcement elongation is 0.7% temper rolling, obtains the cold-rolled steel sheet of the No.1 shown in the table 6 ~ 12.
Cut test film from above-mentioned each cold-rolled steel sheet, use aforesaid method, measure the surface coverage and the maximum ga(u)ge that are created on the ferrous oxide of surface of steel plate by pickling.
In addition, cut test film from above-mentioned each cold-rolled steel sheet, after implementing under the following conditions chemical conversion processing and application processing, supply in these three kinds of corrosion tests of the test of salt warm water immersion, salt spray testing and compound cycle corrosion test, and solidity to corrosion after the evaluation application.
In addition, cut test film from above-mentioned each cold-rolled steel sheet, after implementing under the following conditions chemical conversion processing and application processing, supply in these three kinds of corrosion tests of the test of salt warm water immersion, salt spray testing and compound cycle corrosion test, and solidity to corrosion after the evaluation application.In addition, the depth direction of O, Si, Mn and Fe that uses GDS to measure the surface of the test film that cuts from each cold-rolled steel sheet distributes.
(1) condition is processed in chemical conversion
The grease-removing agent that uses the rapids smart company of Japanese handkerchief card to make: FC-E2011, surface conditioner: PL-X and chemical conversion treating agent: パ Le ボ Application De PB-L3065, carried out under these two kinds of conditions of contrast condition of low temperature with the temperature that reduces chemical conversion treatment solution in following standard conditions, implementing to make chemical conversion to process the tunicle adhesion amount to the test film that cuts from above-mentioned each cold-rolled steel sheet is 1.7 ~ 3.0g/m 2Chemical conversion process.
<standard conditions 〉
Degreasing process: 40 ° of C for the treatment of temp, 120 seconds treatment times
Operation: pH9.5, treatment temp room temperature, 20 seconds treatment times are adjusted in spraying degreasing, surface
Chemical conversion treatment process: 35 ℃ of the temperature of chemical conversion treatment solution, 120 seconds treatment times
<low temperature condition 〉
The temperature of chemical conversion treatment solution in the above-mentioned standard conditions is reduced to 33 ℃ condition
(2) corrosion test
The electroplating coating that uses Japanese ペ イ Application ト company to make: V-50 carries out electro dipping to above-mentioned surface of having implemented the test film that chemical conversion processes so that thickness is the mode of 25 μ m, and in the condition following three kind corrosion tests harsher than embodiment 1.
<salt warm water immersion test 〉
Utilize cutting tool to give the intersection otch defective that length is 45mm to the surface of the above-mentioned test film (n=1) of having implemented chemical conversion processing and electro dipping, then, this test film was flooded 360 hours in the NaCl solution (60 ℃) of 5 quality %, then wash and drying, carry out pasting the belt stripping test of tearing behind the adhesive tape in the otch defective part, measure the maximum that is added together about the otch defective part and peel off total width.If it is below the 5.0mm that this maximum is peeled off total width, the solidity to corrosion that then can be evaluated as in the test of salt tolerant warm water immersion is good.
<salt spray testing (SST) 〉
Utilize cutting tool to give the intersection otch defective that length is 45mm to the surface of the above-mentioned test film (n=1) of having implemented chemical conversion processing, electro dipping, then, use the NaCl aqueous solution of 5 quality %, according to the neutral brine spray testing of stipulating among the JIS Z2371:2000 this test film is carried out 1200 hours salt spray testing, then, intersection otch defective part is carried out belt stripping test, measure the maximum that is added together about the otch defective part and peel off total width.If it is below the 4.0mm that this maximum is peeled off total width, the solidity to corrosion that then can be evaluated as in the salt spray testing is good.
<compound cycle corrosion test (CCT) 〉
Utilize cutting tool to having implemented the chemical conversion processing, the intersection otch defective that length is 45mm is given on the surface of the above-mentioned test film (n=1) of electro dipping, then, this test film is carried out brine spray (the NaCl aqueous solution of 5 quality %: 35 ℃, relative humidity: 98%) * 2 hour → dry (60 ℃, relative humidity: 30%) * 2 hour → wetting (50 ℃, 95%) * 2 hour relative humidity: be cycled to repeat 120 times corrosion test as 1 circulation and with this, then, wash and drying after, intersection otch defective part is carried out belt stripping test, measure the maximum that is added together about the otch defective part and peel off total width.If it is below the 6.0mm that this maximum is peeled off total width, the solidity to corrosion that then can be evaluated as in the compound cycle corrosion test is good.
The results are shown in the table 6 of above-mentioned test.By this result as can be known, be below 85% and to make the maximum ga(u)ge of ferrous oxide be the steel plate that under the condition below the 200nm surface of steel plate after the annealing has been carried out the inventive example of pickling for the surface coverage of the ferrous oxide of the surface of steel plate after making pickling, in arbitrary test in compare the test period test of salt warm water immersion, salt spray testing and compound cycle corrosion test longer, that more carry out under the exacting terms with embodiment 1, it is all less that maximum is peeled off total width, demonstrates solidity to corrosion after the extremely good application.Need to prove that the depth direction that utilizes GDS to measure O, Si, Mn and Fe distributes and among the result that obtains, the peak of Si and O does not all appear in the steel plate that has carried out pickling under condition according to the invention, is fully removed thereby confirmed to contain the Si oxide skin.
Utilizability on the industry
Cold-rolled steel sheet constructed in accordance is excellent corrosion resistance after the application not only, and have high strength and a good processibility, therefore, the materials'use for the member of body of a motor car not only can be suitable as, and the materials'use that requires the purposes of same characteristic in the fields such as household appliances and building slab can be suitable as.

Claims (9)

1. the manufacture method of a cold-rolled steel sheet is characterized in that, use concentration of nitric acid to rise greater than 100g/ and below 200g/ rises, the ratio R (HCl/HNO of concentration of hydrochloric acid and concentration of nitric acid 3) steel plate of continuous annealing that to be 0.01 ~ 0.25 the acid that nitric acid and mixed in hydrochloric acid are formed to the Si that contains 0.5 ~ 3.0 quality % and after cold rolling carried out carries out pickling.
2. the manufacture method of cold-rolled steel sheet as claimed in claim 1 is characterized in that, in the described acid that nitric acid and mixed in hydrochloric acid are formed, concentration of nitric acid rises greater than 110g/ and below 140g/ rises, the ratio R (HCl/HNO of concentration of hydrochloric acid and concentration of nitric acid 3) be 0.03 ~ 0.25.
3. the manufacture method of cold-rolled steel sheet as claimed in claim 1 or 2 is characterized in that, at the Temperature Setting with pickle solution is to carry out 3 ~ 30 seconds described pickling under 20 ~ 70 ℃ the condition.
4. such as the manufacture method of each described cold-rolled steel sheet in the claim 1 ~ 3, it is characterized in that, described steel plate has following one-tenth and is grouped into: except containing Si, contain also that C:0.01 ~ 0.30 quality %, Mn:1.0 ~ 7.5 quality %, P:0.05 quality % are following, S:0.01 quality % following and below the Al:0.06 quality %, surplus by Fe and inevitably impurity consist of.
5. such as the manufacture method of each described cold-rolled steel sheet in the claim 1 ~ 4, it is characterized in that, described steel plate also contain on the basis that described one-tenth is grouped into be selected from below the Nb:0.3 quality %, below the Ti:0.3 quality %, below the V:0.3 quality %, below the Mo:0.3 quality %, below the Cr:0.5 quality %, below the B:0.006 quality % and N:0.008 quality % with lower one or more.
6. such as the manufacture method of each described cold-rolled steel sheet in the claim 1 ~ 5, it is characterized in that, described steel plate also contain on the basis that described one-tenth is grouped into be selected from below the Ni:2.0 quality %, below the Cu:2.0 quality %, below the Ca:0.1 quality % and REM:0.1 quality % with lower one or more.
7. cold-rolled steel sheet, form by each described method manufacturing in the claim 1 ~ 6, it is characterized in that, the pickling of Si oxide skin after by continuous annealing that contain on steel plate top layer removed, and the surface coverage of the ferrous oxide of the surface of steel plate that generates by described pickling is below 85%.
8. cold-rolled steel sheet as claimed in claim 7 is characterized in that, the maximum ga(u)ge of the ferrous oxide that is present in surface of steel plate of described cold-rolled steel sheet is below the 200nm.
9. an automobile component is characterized in that, right to use requires 7 or 8 described cold-rolled steel sheets and forms.
CN201180029545XA 2010-08-31 2011-08-25 Method for producing cold-rolled steel sheet, cold-rolled steel sheet, and vehicle member Pending CN102959129A (en)

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