CN1500155A - High strength and high ductility steel plate having hyperfine crystal grain structure produced by subjecting ordinary low carbon steel to low strain working and annealing,and method for prodn. thereof - Google Patents

High strength and high ductility steel plate having hyperfine crystal grain structure produced by subjecting ordinary low carbon steel to low strain working and annealing,and method for prodn. thereof Download PDF

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CN1500155A
CN1500155A CNA028073398A CN02807339A CN1500155A CN 1500155 A CN1500155 A CN 1500155A CN A028073398 A CNA028073398 A CN A028073398A CN 02807339 A CN02807339 A CN 02807339A CN 1500155 A CN1500155 A CN 1500155A
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steel
annealing
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carbon steel
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CN1279203C (en
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ի�ٺú�
斋藤好弘
̫
辻伸泰
上路林太郎
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Japan Science and Technology Agency
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273—Final recrystallisation annealing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2201/00—Treatment for obtaining particular effects
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

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

Abstract

A high strength and high ductility low carbon steel product having a tensile strength of 800 MPa or more, a homogeneous elongation of 5 % or more, and an elongation at break of 20 % or more which is produced by a method comprising subjecting an ordinary low carbon steel or an ordinary low carbon steel added with B in an amount being 0.01 % or less and effective for accelerating martensitic transformation to working and heat treatment to prepare a product having roughened austenite crystal grains and then to cooling with water, to provide a steel product having a martensite phase in an amount of 90 % or more, and subjecting the steel product to a low strain working, specifically a cold rolling at a total rolling reduction of 20 % or more and less than 80 %, and to a low temperature annealing at 500 [deg.] C to 600 [deg.] C, to thereby form a hyperfine crystal grain ferrite structure having an average grain diameter of 1.0 [micro]m or less; and a method for producing the steel product.

Description

Obtain to have high strength, high-extension steel plate and the manufacture method thereof of ultramicro crystal kernel structure by ordinary low-carbon steel being hanged down strain processing and annealing
Technical field
The present invention relates to ordinary low-carbon steel or contain below 0.01% to promote martensitic transformation effectively the ordinary low-carbon steel of the B of amount process and thermal treatment, after AUSTENITE GRAIN COARSENING, obtain the steel of the martensitic phase more than 90% by water-cooled, with these steel in total rolling rate of compression more than 20%, less than 80% is cold rolling at most, hang down the tensile strength of strain processing and annealing acquisition more than 800MPa at 600 ℃ of annealed of less than more than 500 ℃, uniform elongation is more than 5%, and tension set is in the high strength more than 20%, the soft steel of high ductibility and this high strength, the manufacture method of the soft steel of high ductibility.
In this manual, so-called ordinary low-carbon steel is meant carbon content below 0.2%, and Mn is below 1.6%, and Si is below 0.5%, and P is below 0.05%, and simultaneously, S is at the steel below 0.05%.What is called is added the ordinary low-carbon steel of the B of trace (below 0.01%), is in order to add the steel to the effective B that measures of promotion martensitic transformation below 0.01% in aforementioned ordinary low-carbon steel by the quenching performance.
In this manual, short of special declaration, the % of described content refers to weight %.
Background technology
For the high stratification by buildings improves utilization of space, automobile, boats and ships etc. energy-conservation, and, requirement has been proposed also ferrous materials by recovery of resources.In order to satisfy the above two requirement, need ferrous materials that high strength, high ductibility are arranged, for recovery of resources, then wish to add alloying element, utilize ordinary low-carbon steel just can reach aforementioned high strength, high ductibility.
In order to satisfy aforementioned high performance, some projects have been set up to the steel requirement.In these projects, be called super metal or super iron and steel project, its target is with the crystal grain ultra micro refinement of present " the 400MPa level is formed steel ", the particle diameter of its crystal grain is reached below the 1 μ m, make intensity " 800MPa " with aforementioned twice, be ductile, and the ferrite structure steel that welds easily.
In this field, known, in order to improve intensity by the ferrite crystallization crystal grain miniaturization with steel, Hall-Petch concerns establishment, that is, by the ferritic crystallization particle diameter of refinement steel, yielding stress and tensile strength rise, and meanwhile, toughness improves.But, usually exist the problem that unit elongation reduces in tension test.
In CAMP-ISIJ Vol.11 (1998) 1031-1034, rise in the research of steel of 800MPa level in its intensity that makes of forming that steel obtains, proposed the particle diameter in ferrite-carbide structure is reached below the 1 μ m as target by the 400MPa level of easy welding.Simultaneously, as the concrete means that arrive this target, the sample of thickness 8mm is made it to be converted into austenitic processing, that is, 1100 ℃ handled for 60 seconds after, obtain martensitic structure through water-cooled, with it at 640 ℃, carry out the twin shaft hot rolling of total rolling rate of compression 90%, report claims, the ferrite structure of the steel that obtained, the axle microtexture such as have, its nominal particle size is 0.77 μ m, and tensile strength is equivalent to 760Mpa, and Vickers' hardness is 245.But, do not have in the literary composition relevant from these bulk steel, make strength trial and directly measure the report of tensile strength with test film, and then, their unit elongation is not then mentioned fully.In addition, employed here steel, in order to ensure the quenching performance, the content of Mn is up to 2.03%, and the steel that carry out formation of martensite under 640 ℃ heat condition carry out hot rolling.
And then, in exploitation for the steel of the requirement of satisfying aforementioned high strength, high tenacity high ductibility, studied the solution strengthening method of adding alloying element, the precipitation strength method, phase transformation strengthening method etc., still, owing to contain a large amount of alloying elements, so, exist and cost an arm and a leg or the problem of recycling poor performance.Therefore, carry out and reported the enhancement method that does not add alloying element, the miniaturization by crystal grain, still, these methods all are by carrying out big strain method for processing, existing the problem that needs special processing units.
The inventor etc., as the initial steel equipment structure, to adopting the ferrite-pearlite structure, by what carry out processing as big strain, piling up repeatedly in conjunction with rolling at room temperature (represented with ARB, Accumulative Roll-Bonding) making up the structure of acquisition and the variation of mechanical properties mutually with annealing studies, because after big strain processing, become the uneven structure that zone that has cementite and the zone that does not have cementite mix, so, when annealing, generate the different uneven stuff and other stuff structure of ferritic size, can not obtain required high strength, the steel of high ductibility.
In order to realize the ultra tiny ferritic grain structure of ordinary low-carbon steel, adopt idea from martensitic structure, this STX-21 project and super metal project in the exploitation that advances super iron and steel is also adopted, and not talkative this is a kind of new idea.But, in fact can not realize tensile strength in this way more than 800MPa, uniform elongation is more than 5%, and tension set is at the soft steel of the high strength more than 20%, high ductibility.Particularly, the idea that has the steel that utilize low strain processing acquisition high strength, high ductibility and high tenacity.
The problem of the application's invention is, provides a kind of and the manufacturing process of the steel of prior art need not be carried out the method that too much distortion just can be made the steel with aforementioned required characteristic, and the steel with aforementioned required characteristic are provided.
As previously described, in order to realize ultra tiny ferritic grain structure, be known as the idea of original texture with martensitic structure.But it is very difficult in manufacturing process the ordinary low-carbon steel of hardenability difference being made martensitic structure all sidedly.
The inventor etc., in order seldom to change the manufacturing process of prior art, with martensitic steel as making tensile strength more than 800MPa, uniform elongation is more than 5%, tension set is in the high strength more than 20%, the raw material of the ordinary low-carbon steel steel of high ductibility, at first, to as the martensite of raw material intensity with steel by later processing acquisition, in the middle of the research process of the relation of characteristics such as ductility, we find, after AUSTENITE GRAIN COARSENING, the martensitic phase that obtains by water-cooled is at the steel more than 90%, by low strain processing, be that total rolling rate of compression is more than 20%, cold rolling and the annealing of the highest less than 80%, can obtain to have foregoing intensity, uniform elongation, the high strength of characteristics such as tension set, the low-carbon (LC) steel of high ductibility can solve aforementioned problems.
That is,, solve aforementioned problems by with described low strain processing and annealing and combined for the steel that this is processed and annealed is specific.
The general introduction of invention
A first aspect of the present invention be a kind of with ordinary low-carbon steel or add below 0.01% to promote martensitic transformation effectively the ordinary low-carbon steel of the B of amount process with after thermal treatment, AUSTENITE GRAIN COARSENING are more than 100 μ m, the steel that obtain the martensitic phase more than 90% by water-cooled hang down the tensile strength of strain processing and annealing acquisition more than 800MPa, uniform elongation is more than 5%, and tension set is at the high strength of extending more than 20%, the low-carbon (LC) steel of high ductibility.The low-carbon (LC) steel of described high strength, high ductibility, it is characterized by, preferably hang down strain processing and annealing, be more than 20%, mostly be the cold rolling of less than 80% most and the annealing of 600 ℃ of less thaies more than 500 ℃ by total rolling rate of compression, make described steel have the ultra tiny ferrite structure of particle diameter below 1.0 μ m of average crystal grain.
A second aspect of the present invention, be that a kind of tensile strength is more than 800MPa, uniform elongation is more than 5%, tension set is in the high strength more than 20%, the manufacture method of the low-carbon (LC) steel of high ductibility, it is characterized by, with ordinary low-carbon steel or add below 0.01% to promote martensitic transformation effectively the ordinary low-carbon steel of the B of amount process and thermal treatment, after AUSTENITE GRAIN COARSENING is more than 100 μ m, obtain the steel of the martensitic phase more than 90% by water-cooled, carry out in total rolling rate of compression these steel more than 20%, the highest less than 80% cold rolling, in the annealing of 600 ℃ of less thaies more than 500 ℃, make described steel have the plain body structure of the following ultramicro crystal granulated iron of average crystal grain particle diameter 1.0 μ m.
The simple declaration of accompanying drawing
Fig. 1, be the structure photo of the opticmicroscope (OM) of the longitudinal diagram of the common low carbon steel plate (JIS-SS400, thickness 2mm) of water-cooled after 1000 ℃, 15 minutes austenitation heat treatment.
RD is a rolling direction, and ND is a thickness direction.
Fig. 2, be expression with the martensitic structure of optics observation by microscope ordinary low-carbon steel (JIS-SS400) as the microphotograph of the structure in the longitudinal section of the cold rolling material of original texture.(a) being the situation of expression 50% when cold rolling, (b) is expression 70% situation when cold rolling.
Fig. 3, be the quenched materials of expression ordinary low-carbon steel (JIS-SS400) and the nominal stress-norminal strain curve of the cold rolling material of various rolling rate of compression.A is the cold rolling material of rolling rate of compression 70%, and b is the cold rolling material of rolling rate of compression 50%, and c is the cold rolling material of rolling rate of compression 25%, and d is the quenched materials of martensitic structure, and e is the material that receives ferrite+cementite structure.
Fig. 4, be that expression is with the martensitic structure of ordinary low-carbon steel (JIS-SS400) 50% cold rolling material a as original texture, and with it (b is at 400 ℃ at all temps, c is at 500 ℃, and d is at 550 ℃, and e is at 600 ℃) curve of nominal stress-norminal strain of 30 minutes material of annealing.
Fig. 5, expression with the martensitic structure of ordinary low-carbon steel (JIS-SS400) 50% cold rolling and the annealing temperature of annealed material and the relation of mechanical properties as original texture.-●-expression tensile strength (σ B) ,-zero-expression 0.2% proof stress (σ 0.2) ,-▲-expression tension set (e) ,-△-expression uniform elongation (e 0).
Fig. 6, be as original texture, the Photomicrograph of transmission type microscope (TEM) structure in the longitudinal section of 50% cold rolling and annealed material at various temperatures with the martensitic structure of ordinary low-carbon steel (JIS-SS400).(a) being at 400 ℃, (b) is at 500 ℃, (c) is at 550 ℃, (d) is the situation of all temps annealing in the time of 30 minutes at 600 ℃.
Fig. 7, be expression with the martensitic structure of ordinary low-carbon steel (JIS-SS400) as original texture 50% cold rolling after, after utilizing ARB cold rolling 97% at 30 minutes material (zero) of all temps annealing with ferrite+pearlitic texture as original texture, in the comparison of the relation (strength-ductility balanced) of the tensile strength of 30 minutes material (△) of all temps annealing and tension set.
Fig. 8, JIS5 number tension test sheet of expression.
Implement optimised form of the present invention
Detailed description of the invention
A. concentrate explanation to be used to illustrate test method of the present invention, determinator etc.
1,1/5 the size (parallel portion length 10mm * parallel portion width 5mm) that is shaped as JIS5 test film (Fig. 8) of tension test sheet.
2, opticmicroscope ((strain) ニ コ Application (Nicon) system, ォ プ チ Off ォ ト-100S), the observation sample of TEM ((strain) Hitachi system, H-80) is made with known method.
B. with reference to description of drawings feature of the present invention.
Here, enumerate concrete example and describe, but this is just in order to be more readily understood the present invention, the present invention is not limited thereto.
Fig. 1, be with Rolled Steel For General Structure, promptly contain C 0.13% as trace ingredients, Si 0.01%, and Mn 0.37%, and P 0.02%, S 0.004%, the hot-rolled steel sheet of the thickness 2mm of the steel of sol.Al 0.04% (JIS-SS400) is handled them 15 minutes at 1000 ℃ of austenitizings as the material of accepting, with the opticmicroscope structure photo in the longitudinal section of the quenched materials of water-cooled acquisition after austenite particle diameter alligatoring to 100～200 μ m.Be a kind of contain approximately 4% just analyse ferritic thick martensitic structure.
Fig. 2 is to be the opticmicroscope structure photo in longitudinal section of the cold rolling material of 50% (a) and 70% (b) acquisition to total rolling rate of compression through the multi-pass cold rolling with quenched materials shown in Figure 1.Observe the first martensite of analysing that precipitate into original austenite grain boundary place with black contrast.Usually, the martensite of carbon steel when intactly keeping as-quenched condition constant, poor in processability, but Fig. 2 represents, soft steel martensite, the soft steel martensite that utilizes treatment process of the present invention to form at least can be cold rolled to more than 70%.
Fig. 3 is that the tension test by quenched materials shown in Figure 1, cold rolling material shown in Figure 2 obtains nominal stress-norminal strain curve.In order to carry out reference, dot to have ferrite-nominal stress of the accepting material-norminal strain curve e of cementite structure.By quenching, tensile strength rises to 1100MPa (d) from 410MPa, and then, by 25% cold rolling, rise to 1340MPa (c), by 50% cold rolling, rise to 1470MPa (b), by 70% cold rolling, rise to 1640MPa (a).But tension set is about 10% in quenched materials, be about 6% in cold rolling material.In addition, the uniform elongation of cold rolling material is below 1%.
Fig. 4 is 50% a cold rolling material shown in Figure 3 and with its nominal stress-norminal strain curve that obtains in the tension test of 30 minutes annealed material of all temps annealing.By annealing, intensity reduces, but is restored by the annealing ductility more than 500 ℃, at 500 ℃～550 ℃, and intensity decline within reason, tension set and uniform elongation obviously increase.Consequently, at 550 ℃ annealed materials (d), acquisition tensile strength is 870MPa, 0.2% proof stress 710MPa, tension set 21%, the superstrength of uniform elongation 8% and the steel of high ductibility.
Fig. 5 is the tensile strength (●-), 0.2% proof stress (zero-), tension set (▲-) of expression 50% cold rolling material and annealed material thereof and uniform elongation (△-) and the relation of annealing temperature.When annealing temperature surpassed 525 ℃, tension set and uniform elongation sharply recovered, but tensile strength from 500 ℃ to 550 ℃ between substantially constant.This is the reason that obtains the steel of superstrength, high ductibility at 550 ℃.
Fig. 6 is the photo of TEM structure in the longitudinal section of 50% cold rolling and annealed material.400 ℃ of annealed materials (a) structure is the laminate structure same with rolled stock.500 ℃ annealed material (b) such as observes at the ultra tiny crystallization crystal grain of the particle diameter 100～300nm of shape shaft in very wide scope.Do not illustrate among the figure, by the limited diffraction pattern in the visual field of (b) as can be seen, these fine equi-axed crystal are surrounded by the crystal boundary of wide-angle, do not have subgrain.550 ℃ annealed material also is same ultramicro crystal kernel structure, when at 600 ℃, observes crystal grain and spherical the separate out cementite of thickization of particle diameter to several μ m.
Can think,, make it to produce the ultramicro crystal kernel structure of 100～300nm, simultaneously, give uniform elongation necessary work hardening energy by the growth that suppresses crystal grain of separating out of this cementite that causes in time more than 500 ℃.
As mentioned above, as can be seen, make original texture,, obtain ultra tiny ferritic grain structure, obtain the soft steel of high strength, high ductibility by the low strain processing of rolling rate of compression 50% and 550 ℃ annealing with soft steel martensite.
Fig. 7 be expression as martensitic 50% cold rolling and annealed material (zero) of steel of the present invention and with the ferrite+pearlitic texture of prior art as (△) strength-ductility balanced of the big strain work material (97% cold rolling material) of original texture.As previously described, add man-hour carrying out big strain with ferrite+pearlitic texture as original texture, the structure that obtains by annealing becomes the mixed crystal kernel structure, can not obtain required high strength and high ductibility.Relative therewith, strength-ductility balanced as can be seen from Figure 7 in the martensitic cold rolling and annealed material of the present invention, expression obtains to satisfy the experimental point of the above and tension set of tensile strength 800MPa in the condition more than 20%.
Industrial utilizability
As mentioned above, for 0.13%C ordinary low-carbon steel (JIS-SS400), send out with aforementioned Bright martensitic structure carries out 50% when annealing after cold rolling as initial configuration, obtains particle diameter The ultra tiny ferritic grain structure of 100～300nm in addition, 550 ℃ of annealing 30 minutes, obtains Get tensile strength 870MPa, fracture elongation 21%, having of uniform elongation 8% is very excellent The steel of mechanical performance, its manufacture method is considered economy from foregoing equipment aspect Well, from the environment aspect, also can satisfy wanting of society aspect the circulatory system of material Ask, cause excellent effect.

Claims (5)

1, the soft steel of a kind of high strength, high ductibility, described soft steel be a kind of with ordinary low-carbon steel or add below 0.01% to promoting martensitic transformation effectively after the AUSTENITE GRAIN COARSENING of the ordinary low-carbon steel of the B of amount, the steel that obtain the martensitic phase more than 90% by water-cooled hang down the tensile strength of strain processing and annealing acquisition more than 800MPa, uniform elongation is more than 5%, and tension set is at the low-carbon (LC) steel of the high strength more than 20%, high ductibility.
2, the soft steel of high strength as claimed in claim 1, high ductibility, it is characterized by, hang down strain processing, by total rolling rate of compression be more than 20%, the cold rolling and annealing of less thaies 80% at most, make described steel have the plain body structure of the ultramicro crystal granulated iron of particle diameter below 1.0 μ m of average crystal grain.
3, the soft steel of high strength as claimed in claim 2, high ductibility is characterized by, and carries out the annealing of 600 ℃ of less thaies more than 500 ℃.
4, a kind of high strength, the manufacture method of the soft steel of high ductibility, described method is that a kind of tensile strength is more than 800MPa, uniform elongation is more than 5%, tension set is in the high strength more than 20%, the manufacture method of the low-carbon (LC) steel of high ductibility, it is characterized by, with ordinary low-carbon steel or add below 0.01% to promote martensitic transformation effectively the ordinary low-carbon steel of the B of amount process and thermal treatment, after AUSTENITE GRAIN COARSENING is more than 100 μ m, obtain the steel of the martensitic phase more than 90% by water-cooled, with these steel in total rolling rate of compression more than 20%, cold rolling and the annealing of less than 80% at most makes described steel have the plain body structure of the ultramicro crystal granulated iron of average crystal grain particle diameter below 1.0 μ m.
5, the manufacture method of high strength as claimed in claim 4, high ductibility low-carbon (LC) steel is characterized by, and is carrying out total rolling rate of compression more than 20%, at most after less thaies 80% cold rolling, carries out the annealing of 600 ℃ of less thaies more than 500 ℃.
CNB028073398A 2001-03-27 2002-03-25 High strength and high ductility steel plate having hyperfine crystal grain structure produced by subjecting ordinary low carbon steel to low strain working and annealing,and method for prodn. thereof Expired - Fee Related CN1279203C (en)

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JP90731/2001 2001-03-27
JP2001090731A JP4189133B2 (en) 2001-03-27 2001-03-27 High strength and high ductility steel sheet with ultrafine grain structure obtained by low strain processing and annealing of ordinary low carbon steel and method for producing the same

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CN1279203C CN1279203C (en) 2006-10-11

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US (2) US20040112484A1 (en)
EP (1) EP1394279B1 (en)
JP (1) JP4189133B2 (en)
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CN (1) CN1279203C (en)
DE (1) DE60205744T2 (en)
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