CN106062231A - Medium-/high-carbon steel sheet and method for manufacturing same - Google Patents

Medium-/high-carbon steel sheet and method for manufacturing same Download PDF

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Publication number
CN106062231A
CN106062231A CN201580011954.5A CN201580011954A CN106062231A CN 106062231 A CN106062231 A CN 106062231A CN 201580011954 A CN201580011954 A CN 201580011954A CN 106062231 A CN106062231 A CN 106062231A
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less
carbide
content
annealing
cold
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CN106062231B (en
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竹田健悟
友清寿雅
塚野保嗣
荒牧高志
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Nippon Steel Corp
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Nippon Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • 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
    • C21D1/26—Methods of annealing
    • C21D1/32—Soft annealing, e.g. spheroidising
    • C—CHEMISTRY; METALLURGY
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
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    • 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
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    • 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
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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    • 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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
    • C21D8/0473—Final recrystallisation annealing
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    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • C—CHEMISTRY; METALLURGY
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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    • 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
    • C21D2201/05—Grain orientation
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    • 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
    • C21D2211/001—Austenite
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    • 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
    • C21D2211/002—Bainite
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    • 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
    • C21D2211/003—Cementite
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    • C21D2211/005—Ferrite
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    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite
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    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

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Abstract

The medium-/high-carbon steel sheet according to one aspect of the present invention is a steel sheet containing, in mass%, C: 0.10-1.50%, Si: 0.01-1.00%, Mn: 0.01-3.00 mass%, P: 0.0001-0.1000%, and S: 0.001-0.1000%, with the remainder having components comprising Fe and impurities, wherein the total volume fraction of martensite, bainite, pearlite, and residual austenite is 5% or less, the remainder being a composition of ferrite and carbide; the spheroidizing ratio of the carbide particles is 70 to 99%, inclusive; and the number of carbide particles that include crystal interface misorientation of 5 degrees or greater, expressed as a proportion of the carbide particles, is 20% or less with respect to the total number of carbide particles.

Description

Medium/high carbon steel sheet and manufacture method thereof
Technical field
The present invention relates to medium/high carbon steel sheet and the manufacture thereof in the shaping under high rate of straining with the drawing of excellence Method.
The application based on March 7th, 2014 in the Patent 2014-045689 of Japanese publication CLAIM OF PRIORITY, and will Its content is incorporated herein.
Background technology
Medium/high carbon steel sheet is used as the former of the drive components such as the chain of automobile, gear, clutch and saw, cutter etc. Material.Added by deep drawing by the raw material of the shape that the steel band of medium/high carbon steel or the steel formability that cuts from steel band are regulation Work, reaming are processed, are thickened the plastic workings such as processing, thinning processing and be configured to component shape.Each processing is individually implemented or By raw material is partly shaped by several cold forgings implemented therein with the high rate of straining of about 10/sec simultaneously, to work Even if requiring that the deformation under high rate of straining also has the formability of excellence, i.e. excellent drawing for raw-material steel plate Deeply.
Up to now, the technology for the drawing of the medium/high carbon steel sheet of improvement proposes more scheme (referring for example to patent Document 1～6).
Such as, in patent documentation 1, as the manufacture method of the medium/high carbon steel sheet of deep drawability excellence, disclose following Invention: to C:0.20～the hot rolled steel plate of 0.90 mass % or annealed sheet steel, at least uses surface thick in rolling final passage Rugosity Ra is the work roll of 0.20～1.50 μm, carries out finish rolling under conditions of always rolling rate is set as 20～70%, it After, implement final annealing.But, the technology disclosed in patent documentation 1 is to be improved by the roughness improving surface of steel plate to draw Deep technology rather than improved the technology improving drawing by the material brought by the control of the tissue morphology of steel, is differed Surely desired invention effect is obtained.
And then in patent documentation 2, as the high tenacity high carbon steel sheet of excellent in workability, disclose following high carbon steel sheet Invention: it has and comprises below C:0.6～1.3 mass %, Si:0.5 mass %, Mn:0.2～1.0 mass %, P:0.02 matter Below amount below %, S:0.01 mass % and remainder is essentially the composition of Fe, by hot-rolled condition, cold rolling condition and The adjustment of annealing conditions, by the greatest length of carbide be below 5.0 μm, the spherical rate of carbide be more than 90% and grain Footpath be the volume of the globular carbide of more than 1.0 μm be more than the 20% of whole globular carbide volume carbide and etc. shaft-like Ferrite is constituted.
In patent documentation 3, as the medium/high carbon steel that deep drawability is excellent, disclose and make the invention with undertissue: its C content is 0.10～0.90 mass %, and there is rate (F value) according to the ferrite grain boundaries of carbide and become the mode of more than 30% Carbide is made to be distributed in ferrite.
In patent documentation 4, as the high-carbon cold-rolled strip that deep drawing intra-face anisotropy is little, disclose following invention: Have C:0.25～0.75% steel composition, in steel, the mean diameter of carbide is more than 0.5 μm, spherical rate be 90% with On, texture meets mathematical expression " (222)/(200) >=6-8.0 × C (%) ".
In patent documentation 5, good as deep drawability and the high-carbon of wearability of high hardness or excellence can be given Steel band, discloses following invention: it is characterized in that, C content is 0.20～0.70 mass %, 50 area % of the cementite in steel More than it is graphitized.
In patent documentation 6, as the manufacture method of the cold-rolled high-carbon steel plate having excellent formability, disclose techniques below: Will containing C:0.1～0.65%, Si:0.01～0.3%, Mn:0.4～2%, sol.Al:0.01～0.1%, N:0.002～ 0.008%, the high-carbon steel of B:0.0005～0.005%, Cr:0～0.5, Mo:0～0.1 carries out hot rolling, at 300～520 DEG C Batch, at 650～(Ac1-10) DEG C, carry out coffin annealing, carry out cold rolling with the reduction ratio of 40～80%, 650～(Ac1- 10) coffin annealing is carried out at DEG C.
But, in either of which patent documentation, the steel produced when suppression is shaped under high rate of straining The crackle of the cementite within material itself and the growth/link in space that produced by the generation by crackle and drawing of causing The understanding of deep reduction and technology the most do not carry out any disclosure.
Prior art literature
Patent documentation
Patent documentation 1: Japanese Unexamined Patent Publication 2003-293042 publication
Patent documentation 2: Japanese Unexamined Patent Publication 2003-147485 publication
Patent documentation 3: Japanese Unexamined Patent Publication 2002-155339 publication
Patent documentation 4: Japanese Unexamined Patent Publication 2000-328172 publication
Patent documentation 5: Japanese Unexamined Patent Publication 6-108158 publication
Patent documentation 6: Japanese Unexamined Patent Publication 11-61272 publication
Summary of the invention
Invent problem to be solved
The present invention is in view of above-mentioned practical situation, and problem is to provide in the shaping under high rate of straining having drawing of excellence Deep medium/high carbon steel sheet and its manufacture method.
For solving the means of problem
The method solving above-mentioned problem is conducted in-depth research by the present inventors.As a result of which it is, the present inventors's understanding To: grown by the crackle (space) that produced by carbide when deformation, interconnected, thus the deformation under high rate of straining In drawing reduce.And then, the present inventors recognizes: the crackle produced by carbide was realized as a particle from the past Carbide particle present in grain boundary produce.The present inventors recognizes: by reducing the crystal in carbide particle The amount at interface, can get and display that the drawing of excellence in the deformation under high rate of straining and then in deep drawing processing, reaming Process, thicken the plastic workings such as processing, thinning processing or implement several the cold forging in these processing shows excellence simultaneously The medium/high carbon steel sheet of formability.
Additionally, the present inventors recognizes by repeating various research: steel plate as characterized above is to hot rolling bar Part and annealing conditions etc. manufacture difficulty in the case of individually making an effort, only by so-called companies such as hot rolling/annealing operations String operation reaches optimization can manufacture, thus complete the present invention.
The purport of the present invention is as described below.
(1) the medium/high carbon steel sheet that a mode of the present invention relates to be have in terms of quality % containing C:0.10～1.50%, Si:0.01～1.00%, Mn:0.01～3.00%, P:0.0001～0.1000%, S:0.0001～0.1000% and residue Part comprises the steel plate of the composition of Fe and impurity, and above-mentioned steel plate has martensite, bainite, pearlite and retained austenite The tissue that volume fraction is less than 5.0% and remainder is ferrite and carbide added up to, the spherical rate of carbide particle It is more than 70% and less than 99%, above-mentioned carbide particle comprises the above-mentioned carbonization of the grain boundary that gun parallax is more than 5 ° The number ratio of thing particle is less than 20% relative to total number of above-mentioned carbide particle.
(2) according to the medium/high carbon steel sheet described in above-mentioned (1), wherein, the mentioned component of above-mentioned steel plate can also be with quality % Meter contains Al:0.001～0.500%, N:0.0001～0.0500%, O:0.0001～0.0500%, Cr:0.001 further ～2.000%, Mo:0.001～2.000%, Ni:0.001～2.000%, Cu:0.001～1.000%, Nb:0.001～ 1.000%, V:0.001～1.000%, Ti:0.001～1.000%, B:0.0001～0.0500%, W:0.001～ 1.000%, Ta:0.001～1.000%, Sn:0.001～0.020%, Sb:0.001～0.020%, As:0.001～ 0.020%, Mg:0.0001～0.0200%, Ca:0.001～0.020%, Y:0.001～0.020%, Zr:0.001～ 0.020%, one kind or two or more in La:0.001～0.020%, Ce:0.001～0.020%.
(3) manufacture method of the medium/high carbon steel sheet that the another way of the present invention relates to, it is by described in above-mentioned (1) or (2) There is the steel billet of mentioned component when directly or carrying out heating hot rolling after cooling for the time being, more than 600 DEG C and less than 1000 DEG C Temperature field completes essence hot rolling, by more than 350 DEG C and less than the 700 DEG C hot rolled steel plates batched carry out coffin annealing, enforcement More than 10% and less than 80% cold rolling, be more than 650 DEG C and less than 780 DEG C in annealing temperature, keep in continuous annealing line Time is the cold-reduced sheet annealing after implementing under conditions of more than 30 seconds and less than 1800 seconds.
Invention effect
In accordance with the invention it is possible to provide the medium/high carbon steel of the drawing in the shaping under high rate of straining with excellence Plate and manufacture method thereof.
Accompanying drawing explanation
Fig. 1 is the figure of the shape representing the test film for measuring the drawing under high rate of straining.
Fig. 2 is the figure representing situation about cracking when deformation from the grain boundary being positioned at carbide particle.
Fig. 3 is the number ratio representing the carbide particle comprising grain boundary and the tension test under high rate of straining Time the figure of relation of drawing.
Detailed description of the invention
Hereinafter, present embodiment is described in detail.
First, the reason of the chemical composition of the steel plate limited described in present embodiment is illustrated.Wherein, about composition " % " refer to quality %.
(C:0.10～1.50%)
C is the element of the intensity being improved steel by the heat treatment of quenching.Medium/high carbon steel sheet is after forming as automobile Before the raw material of the drive components such as chain, gear, clutch and saw, cutter etc. uses, quenched by enforcement and quench back The heat treatment of fire, guarantees as the intensity required for parts or toughness.During due to C content less than 0.10%, can not get by quenching The increase of the intensity that fire brings, so using 0.10% as the lower limit of C content.On the other hand, if owing to C content exceedes 1.50%, then, after cold rolled annealed, the number ratio of the carbide at inside particles with grain boundary increases, and high answers speed change Drawing under Du reduces, so the upper limit of C content is set as 1.50%.More preferably C content is 0.15～1.30%.
(Si:0.01～1.00%)
Si is to work as deoxidizer, additionally, the carbide particle during suppression hot rolled plate is annealed and cold-reduced sheet is annealed Coarsening and the element of link.In cold-reduced sheet is annealed during carbide particle carries out Ostwald's growth, that This is positioned at neighbouring plural particle when contacting, and imports grain boundary in carbide particle.When the deformation of steel plate, Grain boundary in carbide particle becomes the starting point of crackle.In order to suppress this phenomenon, need to reduce hot rolled plate and anneal and cold rolling The speed of growth of the carbide in plate annealing.One of element of the speed of growth of its representational reduction carbide is Si.Due to When the content of Si is less than 0.01%, can not get above-mentioned effect, so being 0.01% by the lower limit set of Si content.The opposing party Face, if owing to Si content is more than 1.00%, then ferrite becomes destruction of easily splitting, and the drawing under high rate of straining reduces, So the upper limit of Si content is set as 1.00%.Si content is more preferably more than 0.05% and less than 0.80%, the most excellent Elect more than 0.08% and less than 0.50% as.
(Mn:0.01～3.00%)
Mn is coarsening and the link suppressing the carbide particle in hot rolled plate annealing and cold-reduced sheet annealing in the same manner as Si Element.During due to Mn content less than 0.01%, can not get above-mentioned effect, so by the lower limit set of Mn content being 0.01%.On the other hand, if Mn content is more than 3.00%, then when hot rolled plate annealing and cold-reduced sheet annealing, carbide becomes to be difficult to Spheroidizing, in the deformation under high rate of straining, cracks using the carbide of needle-like as starting point, and drawing reduces.Cause This, be set as 3.00% by the upper limit of Mn content.Mn content is more preferably more than 0.30% and less than 2.50%, further preferably It is more than 0.50% and less than 1.50%.
(P:0.0001～0.1000%)
P is the impurity element making ferrite grain boundaries brittle.P content is the fewest more preferred, but owing to making P contain in refining procedure Amount is less than 0.0001% by the case of steel high purity, and the time needed for refine becomes many, causes manufacturing cost It is significantly increased, so being 0.0001% by the lower limit set of P content.On the other hand, if owing to P content is more than 0.1000%, then Cracking significantly from ferrite grain boundaries during deformation under high rate of straining, drawing significantly reduces, so by P content The upper limit is set as 0.1000%.P content is more preferably more than 0.0010% and less than 0.0500%, more preferably More than 0.0020% and less than 0.0300%.
(S:0.0001～0.1000%)
S is the impurity element forming the non-metallic inclusions such as MnS, owing to non-metallic inclusion is under high rate of straining Deformation becomes the starting point that crackle produces, so S content is the fewest more preferred.But, owing to S content is decreased below 0.0001% can cause being significantly increased of refining cost, so being 0.0001% by the lower limit set of S content.On the other hand, by If in containing S more than 0.1000%, then the reduction of drawing becomes notable, so the upper limit of S content is set as 0.1000% Below.S content is more preferably more than 0.0003% and less than 0.0300%.
In present embodiment, using mentioned component as the basis of steel plate, but for improving the mechanical property of steel plate Purpose, can the most optionally contain in element described below is one kind or two or more.But, due to described below Containing not necessarily, so the lower limit of element described below is 0% of element.
(Al: be preferably 0.001～0.500%)
Al is the element that the deoxidizer as steel works.During due to Al content less than 0.001%, it is impossible to fully contained Effective, so can also be 0.001% by the lower limit set of Al content.On the other hand, if Al content is more than 0.500%, then Make ferritic embrittlement of grain boundaries, cause the reduction of drawing in the deformation under high rate of straining.Accordingly it is also possible to by Al content The upper limit be set as 0.500%.Al content is more preferably more than 0.005% and less than 0.300%, more preferably More than 0.010% and less than 0.100%.
(N: be preferably 0.0001～0.0500%)
N be promote steel bainitic transformation, simultaneously by substantial amounts of containing and cause the element of ferritic embrittlement.N contains Measure the fewest more preferred, but owing to N content to be decreased below 0.0001% increase that can cause refining cost, so can also be by The lower limit set of N content is 0.0001%.On the other hand, during due to N content more than 0.0500%, under high rate of straining Ferritic crackle is caused, so the upper limit of N content can also be set as 0.0500% during deformation.N content is more preferably More than 0.0010% and less than 0.0250%, more preferably more than 0.0020% and less than 0.0100%.
(O: be preferably 0.0001～0.0500%)
Due to O be by substantial amounts of containing and promote the element of the formation of oxide thick in steel, so O content is preferred Less.But, owing to O content to be decreased below 0.0001% increase that can cause refining cost, so can also be by 0.0001% as the lower limit of O content.On the other hand, during due to O content more than 0.0500%, steel forms thick oxidation Thing, produces the crackle using thick oxide as starting point during deformation under high rate of straining, so can also be by O content The upper limit be set as 0.0500%.O content is more preferably more than 0.0005% and less than 0.0250%, more preferably More than 0.0010% and less than 0.0100%.
(Cr: be preferably 0.001～2.000%)
Cr is coarsening and the company suppressing the carbide particle in hot rolled plate annealing and cold-reduced sheet annealing in the same manner as Si, Mn The element of knot.But, during due to Cr content less than 0.001%, can not get above-mentioned effect, so can also be by under Cr content Limit is set as 0.001%.On the other hand, if owing to Cr content is more than 2.000%, then in hot rolled plate annealing and cold-reduced sheet annealing Carbide becomes to be difficult to spheroidizing, in the deformation under high rate of straining, produces using the carbide of needle-like as starting point and splits Stricture of vagina, drawing reduces, so the upper limit of Cr content can also be set as 2.000%.Cr content be more preferably more than 0.005% and Less than 1.500%, more preferably more than 0.010% and less than 1.300%.
(Mo: be preferably 0.001～2.000%)
Mo is the coarsening suppressing the carbide particle in hot rolled plate annealing and cold-reduced sheet annealing in the same manner as Si, Mn, Cr And the element linked.During due to Mo content less than 0.001%, can not get above-mentioned effect, so can also be by under Mo content Limit is set as 0.001%.On the other hand, if owing to Mo content is more than 2.00%, then in hot rolled plate annealing and cold-reduced sheet annealing Carbide becomes to be difficult to spheroidizing, in the deformation under high rate of straining, produces using the carbide of needle-like as starting point and splits Stricture of vagina, drawing reduces, so the upper limit of Mo content can also be set as 2.00%.Mo content be more preferably more than 0.005% and Less than 1.900%, more preferably more than 0.008% and less than 0.800%.
(Ni: be preferably 0.001～2.000%)
Ni is the raising of the toughness for parts and the raising of hardenability and effective element.In order to effectively play it Effect, preferably comprises the Ni of more than 0.001%.On the other hand, if owing to Ni content is more than 2.000%, then anneal at hot rolled plate And carbide becomes to be difficult to spheroidizing during cold-reduced sheet annealing, in the deformation under high rate of straining, make with the carbide of needle-like Cracking for starting point, drawing reduces, so the upper limit of Ni content can also be set as 2.000%.Ni content is more preferably It is more than 0.005% and less than 1.500%, more preferably more than 0.005% and less than 0.700%.
(Cu: be preferably 0.001～1.000%)
Cu is the element of the intensity being increased steel by the formation of fine precipitate.In order to Developed fiber strength increases effectively The effect added, preferably comprises the Cu of more than 0.001%.On the other hand, if owing to Cu content is more than 1.00%, then moving back at hot rolled plate When fire and cold-reduced sheet annealing, carbide becomes to be difficult to spheroidizing, in the deformation under high rate of straining, with the carbide of needle-like Cracking as starting point, drawing reduces, so Cu upper content limit can also be set as 1.00%.Cu content is more preferably More than 0.003% and less than 0.500%, more preferably more than 0.005% and less than 0.200%.
(Nb: be preferably 0.001～1.000%)
Nb be formed carbonitride and suppression hot rolled plate annealing and cold-reduced sheet annealing in carbide particle coarsening and The element linked.During due to Nb content less than 0.001%, can not get above-mentioned effect, so can also be by the lower limit of Nb content It is set as 0.001%.On the other hand, if owing to Nb content is more than 1.000%, then when hot rolled plate annealing and cold-reduced sheet annealing, Carbide becomes to be difficult to spheroidizing, in the deformation under high rate of straining, produces using the carbide of needle-like as starting point and splits Stricture of vagina, drawing reduces, so the upper limit of Nb content can also be set as 1.000%.Nb content be more preferably more than 0.005% and Less than 0.600%, more preferably more than 0.008% and less than 0.200%.
(V: be preferably 0.001～1.000%)
V is also to be identically formed the carbide grain in carbonitride and suppression hot rolled plate annealing and cold-reduced sheet annealing with Nb The coarsening of son and the element of link.During due to V content less than 0.001%, can not get above-mentioned effect, so can also be by V The lower limit set of content is 0.001%.On the other hand, if owing to V content is more than 1.000%, then anneal and cold rolling at hot rolled plate During plate annealing, carbide becomes to be difficult to spheroidizing, in the deformation under high rate of straining, using the carbide of needle-like as starting point And crack, drawing reduces, so the upper limit of V content can also be set as 1.000%.V content is more preferably 0.001% Above and less than 0.750%, more preferably more than 0.001% and less than 0.250%.
(Ti: be preferably 0.001～1.000%)
Ti is also to be identically formed the carbonization in carbonitride and suppression hot rolled plate annealing and cold-reduced sheet annealing with Nb and V The coarsening of thing particle and the element of link.During due to Ti content less than 0.001%, can not get above-mentioned effect, so also may be used With by the lower limit set of Ti content for more than 0.001%.On the other hand, if owing to Ti content is more than 1.000%, then at hot rolled plate When annealing and cold-reduced sheet annealing, carbide becomes to be difficult to spheroidizing, in the deformation under high rate of straining, with the carbonization of needle-like Thing cracks as starting point, and drawing reduces, so the upper limit of Ti content can also be set as 1.000%.Ti content is more It is preferably more than 0.001% and less than 0.500%, more preferably more than 0.003% and less than 0.150%.
(B: be preferably 0.0001～0.0500%)
The element of hardenability when B is the heat treatment improving parts.Due to B content less than 0.0001% time, can not get on The effect stated, so can also be 0.0001% by the lower limit set of B content.If owing to B content is more than 0.0500%, then generating Thick Fe-B-C compound, becomes the starting point of crackle, makes drawing reduce, so also may be used during deformation under high rate of straining So that the upper limit of B content is set as 0.0500%.B content is more preferably more than 0.0005% and less than 0.0300%, further It is preferably more than 0.0010% and less than 0.0100%.
(W: be preferably 0.001～1.000%)
W is also to be identically formed the carbon in carbonitride and suppression hot rolled plate annealing and cold-reduced sheet annealing with Nb, V and Ti The coarsening of compound particle and the element of link.During due to W content less than 0.001%, can not get above-mentioned effect, so also may be used With by the lower limit set of W content for 0.001%.On the other hand, if owing to W content is more than 1.000%, then hot rolled plate annealing and During cold-reduced sheet annealing, carbide becomes to be difficult to spheroidizing, in the deformation under high rate of straining, using the carbide of needle-like as Starting point and crack, drawing reduce, so the upper limit of W content can also be set as 1.000%.W content is more preferably More than 0.001% and less than 0.450%, more preferably more than 0.001% and less than 0.160%.
(Ta: be preferably 0.001～1.000%)
Ta is also to be identically formed in carbonitride and suppression hot rolled plate annealing and cold-reduced sheet annealing with Nb, V, Ti and W The coarsening of carbide particle and the element of link.During due to Ta content less than 0.001%, can not get above-mentioned effect, institute With can also be by the lower limit set of Ta content for 0.001%.On the other hand, if Ta content is more than 1.000%, then move back at hot rolled plate When fire and cold-reduced sheet annealing, carbide becomes to be difficult to spheroidizing, in the deformation under high rate of straining, with the carbide of needle-like Cracking as starting point, drawing reduces, so the upper limit of Ta content can also be set as less than 1.000%.Ta content More preferably more than 0.001% and less than 0.750%, more preferably more than 0.001% and less than 0.150%.
(Sn: be preferably 0.001～0.020%)
Sn is the element contained in steel in the case of using steel scrap as steel raw material, and Sn content is the fewest more preferred.By When Sn content is decreased below 0.001%, the increase of refining cost can be caused, so the lower limit of Sn content can also be set It is set to 0.001%.During additionally, due to Sn content is more than 0.020%, ferrite is brittle, in the deformation under high rate of straining, Drawing reduces, so the upper limit of Sn content can also be set as 0.020%.Sn content be more preferably more than 0.001% and Less than 0.015%, more preferably more than 0.001% and less than 0.010%.
(Sb: be preferably 0.001～0.020%)
Sb is the element contained in steel in the case of using steel scrap as steel raw material in the same manner as Sn, and Sb content is the fewest The most preferred.During owing to Sb content is decreased below 0.001%, the increase of refining cost can be caused, so Sb can also be contained The lower limit set of amount is 0.001%.During additionally, due to Sb content is more than 0.020%, ferrite is brittle, at high rate of straining Under deformation in, drawing reduce, so the upper limit of Sb content can also be set as less than 0.020%.Sb content is more preferably More than 0.001% and less than 0.015%, more preferably more than 0.001% and less than 0.011%.
(As: be preferably 0.001～0.020%)
As is the element contained in the case of using steel scrap as steel raw material in the same manner as Sn and Sb, and As content is the fewest The most preferred.When As content is decreased below 0.001%, the increase of refining cost can be caused, so can also be by As content Lower limit set is 0.001%.During additionally, due to As content is more than 0.020%, ferrite is brittle, under high rate of straining In deformation, drawing reduces, so the upper limit of As content can also be set as less than 0.020%.As content is more preferably More than 0.001% and less than 0.015%, more preferably more than 0.001% and less than 0.007%.
(Mg: be preferably 0.0001～0.0200%)
Even if Mg is content is the trace element of form that also is able to control sulfide, can contain as desired.By When Mg content is less than 0.0001%, can not get this effect, so can also be 0.0001% by the lower limit set of Mg content.Separately On the one hand, during owing to excessively containing Mg, ferritic embrittlement of grain boundaries, in the deformation under high rate of straining, cause drawing Reduction, so the upper limit of Mg content can also be set as 0.0200%.Mg content be more preferably more than 0.0001% and Less than 0.0150%, more preferably more than 0.0001% and less than 0.0075%.
(Ca: be preferably 0.001～0.020%)
Even if Ca is that content is the element that trace also is able to control the form of sulfide in the same manner as Mg, can be as required And contain.During due to Ca content less than 0.001%, can not get this effect, so can also be by the lower limit set of Ca content 0.001%.On the other hand, during owing to excessively containing Ca, ferritic embrittlement of grain boundaries, the deformation under high rate of straining In, cause the reduction of drawing, so the upper limit of Ca content can also be set as 0.020%.Ca content is more preferably 0.001% Above and less than 0.015%, more preferably more than 0.001% and less than 0.010%.
(Y: be preferably 0.001～0.020%)
Even if Y is that content is the element that trace also is able to control the form of sulfide in the same manner as Mg and Ca, can basis Need and contain.During due to Y content less than 0.001%, can not get this effect, so can also be by the lower limit set of Y content 0.001%.On the other hand, during owing to excessively containing Y, ferritic embrittlement of grain boundaries, in the deformation under high rate of straining, Cause the reduction of drawing, so the upper limit of Y content can also be set as 0.020%.Y content is more preferably more than 0.001% And less than 0.015%, more preferably more than 0.001% and less than 0.009%.
(Zr: be preferably 0.001～0.020%)
Even if Zr is that content is the element that trace also is able to control the form of sulfide in the same manner as Mg, Ca, Y, Ke Yigen Contain according to needs.During due to Zr content less than 0.001%, can not get this effect, so the lower limit of Zr content can also be set It is set to 0.001%.On the other hand, during owing to excessively containing Zr, ferritic embrittlement of grain boundaries, the change under high rate of straining In shape, cause the reduction of drawing, so the upper limit of Zr content can also be set as 0.020%.Zr content is more preferably Less than 0.015%, more preferably less than 0.010%.
(La: be preferably 0.001～0.020%)
Even if La is that content is the trace effective element of morphology Control also to sulfide in the same manner as Mg, Ca, Y and Zr, Can also contain as desired.During due to La content less than 0.001%, can not get this effect, so can also be by La content Lower limit set be 0.001%.On the other hand, during owing to excessively containing La, ferritic embrittlement of grain boundaries, answer speed change high In deformation under Du, cause the reduction of drawing, so the upper limit of La content can also be set as 0.020%.La content is more excellent Elect more than 0.001% and less than 0.015% as, more preferably more than 0.001% and less than 0.010%.
(Ce: be preferably 0.001～0.020%)
Even if Ce is that content is the element that trace also is able to control the form of sulfide in the same manner as Mg, Ca, Y, Zr, La, Can also contain as desired.During due to Ce content less than 0.001%, can not get this effect, so can also be by Ce content Lower limit set be 0.001%.On the other hand, during owing to excessively containing Ce, ferritic embrittlement of grain boundaries, answer speed change high In deformation under Du, cause the reduction of drawing, so the upper limit of Ce content can also be set as 0.020%.Ce content is more excellent Elect more than 0.001% and less than 0.015% as, more preferably more than 0.001% and less than 0.010%.
It addition, in steel plate described in present embodiment, the remainder of the composition of above-mentioned narration is Fe and impurity.
Steel plate described in present embodiment in addition to there is above-mentioned one-tenth and be grouped into, due to implement the suitableeest hot rolling and Annealing, so also having ferrite and carbide is the tissue of main body, by martensite, bainite, pearlite and retained austenite The volume fraction added up to and obtain is less than 5%, and the spherical rate of carbide particle is more than 70% and less than 99%, at carbide Particle comprises total relative to carbide particle of the number ratio of carbide particle of the grain boundary that gun parallax is more than 5 ° Number is less than 20%.By this feature, can get implement under high rate of straining drawing, reaming, thicken, the plasticity such as thinning There is during the cold forging processed or they combined the steel plate of the formability of excellence.This is the new understanding that the present inventors finds.
Steel described in present embodiment substantially has the tissue of ferrite and carbide.It addition, so-called carbide, except Cementite (Fe as ferrum Yu carbon compound3C), beyond, also have the Fe atom alloying elements such as Mn, Cr in cementite The compound replaced and obtain and alloy carbide (M23C6、M6C、MC.It addition, M is Fe and other alloying element).Geneva Body, bainite, pearlite, retained austenite are preferably not included in tissue, when comprising add up to volume fraction be set as 5.0% with Under.The lower limit of the total amount of martensite, bainite, pearlite and retained austenite is not specified by.Owing to being made by described later With the structure observation of 3000 times of scanning electron microscope, arbitrary tissue all entirely without when being detected, martensite, shellfish The total amount of family name's body, pearlite and retained austenite is considered 0.0 volume %, so can also be by martensite, bainite, pearl The lower limit set of the total amount of body of light and retained austenite is 0.0%.
The regulation reason of the total amount of martensite, bainite, pearlite and retained austenite is illustrated.This enforcement Mode is that steel plate is added in cold-reduced sheet is annealed as the martensite of object of regulation, bainite, pearlite, retained austenite Hot to 2 phase regions of ferrite and austenite, the tissue generated by austenite during being cooled to room temperature.Therefore, geneva Body, bainite and pearlite are positioned in ferritic crystal boundary, and retained austenite is present in the lath interface of martensite and bainite Or on block boundary.First, when being undergone phase transition to martensite, bainite or pearlite by austenite, due to volumetric expansion, institute With residual stress in ferritic crystal boundary.Due to by residual stress partly in ferritic crystal boundary, thus at steel plate The deformation caused by mechanical load time, near crystal boundary, promote the generation in space, so remaining in ferritic crystal boundary Stress causes the reduction of drawing in the deformation under high rate of straining.Additionally, due to retained austenite is on the deformation way of steel plate In cause deformation induced trans-formation to become martensite, so the stress improved further in ferrite grain boundaries increases, encourage drawing Reduction.From above reason, in order to improve the drawing in the deformation under high rate of straining, the tissue of steel plate is made Being essentially the tissue of ferrite and carbide, martensite, bainite, pearlite and retained austenite do not comprise, at bag Containing time, it is necessary to the volume fraction of the total of martensite, bainite, pearlite and retained austenite is set as less than 5.0%.Enter And, when producing pearlitic transformation, the ratio of the carbide of needle-like also increases.The impact of acicular carbide is described below.Separately Outward, owing to carbide does not undergoes phase transition, between mother metal, stress is not concentrated, it is possible to the reduction of suppression drawing.
Then, to the spherical rate of carbide being set as that the reason of more than 70% and less than 99% describes. Owing to if the spherical rate of carbide is less than 70%, then, during stress concentrates on the carbide of needle-like, carbide ruptures and generates sky Gap, forms the plane of disruption by the link in space, so the drawing in the deformation under high rate of straining reduces.Therefore, by carbon The lower limit set of the spherical rate of compound is 70%.It addition, although spherical rate is the highest more preferred, but due in order to by spherical Rate controls to be that 100% needs are implemented to anneal the most for a long time, causes the increase of manufacturing cost, so the upper limit of spherical rate It is preferably less than 100%, is set as less than 99%.
And then, to carbide particle should comprising the carbide particle of the grain boundary that grain arrangement difference is more than 5 ° Number ratio be set as that the reason of less than 20% describes relative to total number of carbide particle.Carbide in deformation Crackle be mainly more than 5 ° from being considered grain arrangement difference present in the carbide of a particle in the prior art Grain boundary produces.In deformation under high rate of straining, produce sky by the crackle in the grain boundary of carbide Gap, these spaces link and form the plane of disruption, thus produce the reduction of drawing.Although having the crystalline substance that grain arrangement difference is more than 5 ° The ratio of the carbide of body interface is the fewest more good, but due in order to there is grain boundary that grain arrangement difference is more than 5 ° The number ratio of carbide controls in the total number relative to carbide particle less than 0.1%, needs casting, hot rolling, heat continuously Roll a series of Quality Design management in plate annealing, the annealing of cold rolling and cold-reduced sheet, the reduction of yield rate can be caused, thus excellent Select the number total number relative to carbide particle of carbide by having grain boundary that grain arrangement difference is more than 5 ° The lower limit set of ratio is 0.1%, more preferably 0.2%.Additionally, due to have the crystal that grain arrangement difference is more than 5 ° The number of the carbide at interface exceedes relative to the ratio of total number of carbide particle (following, to be sometimes abbreviated as number ratio) When 20%, the reduction of the high drawing in the deformation under rate of straining becomes notable, so the upper limit of number ratio being set as 20%, more preferably 15%, more preferably 10%.
Then, observation and assay method to the tissue of above-mentioned regulation describe.
Ferrite, carbide, martensite, bainite, the observation of pearlite use scanning electron microscope to carry out.? Before observation, carry out the sample of structure observation utilizing the wet lapping of sand paper and utilizing the average particle size with 1 μm The grinding of diamond abrasive grain, thus sightingpiston is finish-machined to minute surface.Then, use 3% nitric acid-ethanol solution to sightingpiston It is etched.Observe multiplying power in 1000～10000 times, be selected to distinguish ferrite, carbide, martensite, bainite and The multiplying power of each tissue of pearlite.In present embodiment, select 3000 times.16 thicknesss of slab 1/ are shot randomly with the multiplying power selected The visual field of 30 μ m 40 μm in 4 layers.The volume fraction of each tissue uses point count to obtain.On the macrograph of shooting, at water Put down and in vertical direction, draw the grid lines being spaced apart 2 μm, the number of the tissue of the point of intersection of grid lines is counted respectively, by The ratio of each tissue of every 1 the shooting photo of number ratio measuring of each tissue.Afterwards, can be by 16 whole institutes of macrograph The value that the measurement result of the ratio of each tissue related to is average and obtains is as the volume fraction of the tissue in each sample.
It addition, martensite presence or absence based on in-house fine carbide with bainite is distinguished.It is predominantly located at ferrum On the crystal boundary of ferritic and do not comprise carbide is organized as martensite, and comprise carbide is organized as bainite.Additionally, work as horse When family name's body is tempered martensite, owing to tempered martensite comprises carbide in inside, it is possible to be mistaken as bainite.But It is, in the steel described in present embodiment, due to obviously by martensite, bainite, pearlite and retained austenite are added up to Volume fraction be set as 5% and available good drawing, so the misidentification of martensite and bainite is to this final embodiment party The impact that the form of the steel described in formula causes is the least.It addition, ferrite is preferably set to volume fraction more than 70%.
The volume fraction of retained austenite is measured by X-ray diffraction.By by according to above-mentioned step by sightingpiston The strained layer on the surface being finish-machined to the sample of minute surface uses electric field to grind and remove, thus prepares to be used for measuring retained austenite Sample.Electric field grinds and uses 5% perchloric acid-acetum, and the voltage applying 10V is implemented.The pipe ball of X-ray selects Cu, Based on austenite (200), (220), (311) and ferritic (200), the intensity of each of (211), obtain retained austenite Volume fraction.
The observation of carbide is carried out by scanning electron microscope.The sample of structure observation utilizes sand by use After sightingpiston is finish-machined to minute surface by the grinding of the wet lapping of paper and the diamond abrasive grain that utilizes particle size to be 1 μm, use Saturated picric acid alcoholic solution is implemented etching and is prepared.The multiplying power observed is 1000～10000 times, in present embodiment, with 3000 Multiplying power again selects to comprise at 16 the visual field of more than 500 carbides on structure observation face, it is thus achieved that organization charts's picture.To obtained Organization charts's picture, by with three paddy business Co., Ltd.'s system (Win ROOF) the image analysis software as representative, measuring in detail The area of each carbide comprised in this region.Diameter of equivalent circle (" the equivalent circle of each carbide is obtained by the area of each carbide Diameter "=2 × (" area "/3.14)1/2), it is averaged value as carbide particle diameter.It addition, in order to suppress to be brought by noise The impact of evaluated error, area is 0.01 μm2Except following carbide is from the object evaluated.
Carbide particle diameter preferably in the range of more than 0.30 μm and below 1.50 μm.Owing to carbide particle diameter is less than 0.30 During μm, ferrite particle diameter becomes fine, so being 0.30 μm by the lower limit set of carbide particle diameter.If owing to carbide particle diameter surpasses Cross 1.50 μm, then in the deformation of steel plate, become easy generation space near carbide and cause the reduction of deformability, So the upper limit of carbide particle diameter is set as 1.50 μm.Additionally, the carbide that ratio is more than 3 of long axial length with short axial length is distinguished Not Wei acicular carbide, the ratio of long axial length and the short axial length carbide less than 3 is characterized as globular carbide.By globular carbide The value that obtains divided by the number of whole carbides of number as the spherical rate of carbide (cementite etc.).
The presence or absence of the grain boundary that grain arrangement difference is more than 5 ° in carbide particle uses EBSD to investigate.Evaluate The cutting plate that by steel band and cuts from steel band of sample or the position discharge lines being not given to strain of blank plate of stamping-out add Work machine cuts, using the face vertical relative to surface of steel plate as sightingpiston.Owing to the measurement accuracy of EBSD is put down by sightingpiston Smooth degree and the impact of strain given by grinding, so grinding sightingpiston by wet lapping and diamond abrasive grain and smart After being processed into minute surface, sightingpiston is implemented to eliminate the grinding of strain.Eliminate strain and grind use vibro-grinding device (Buhler system Vibromet 2), implement exporting the condition of 40% and milling time 60min.As long as use SEM-EBSD, then SEM and The device kind of Kikuchi lines detector is not particularly limited.In thickness of slab 1/4 layer, to 100 μm and plate width direction on thickness of slab direction The region of upper 100 μm measures 4 visuals field, by the image information pair of obtained grain arrangement with the mensuration stepped intervals of 0.2 μm Present in each cementite, the gun parallax of grain boundary counts with the number of the particle of the grain boundary with more than 5 °.Survey Resolving of given data uses the OIM parsing software of TSL company to carry out preferably, in order to eliminate the number of the evaluated error caused by noise According to impact, do not implement cleaning, be that 0.1 data below removes by reliability index (COINCIDENCE INDEX:CI value), Resolve.
It is set as below more than 5 μm and 60 μm, it is possible to suppression by the ferrite particle diameter of the tissue after being annealed by cold-reduced sheet The reduction of the high drawing in the deformation under rate of straining.Owing to if ferrite particle diameter is less than 5 μm, then deformability reduces, institute Being 5 μm by the lower limit set of ferrite particle diameter.If additionally, due to ferrite particle diameter is more than 60 μm, then in deformation initial stage Produce Pericarpium Pyri face on surface, promote that fracture causes the reduction of drawing using consequent concave-convex surface as starting point, so will The upper limit of ferrite particle diameter is set as below 60 μm.Measuring by sightingpiston being carried out according to above-mentioned step of ferrite particle diameter Grind and after being finish-machined to minute surface, be etched with 3% nitric acid-ethanol solution, utilize optical microscope or scanning electron aobvious Micro mirror tissues observed, is suitable for segment method to the image shot and is measured carrying out.Ferrite particle diameter be preferably more than 10 μm and Below 50 μm.
Then, the assay method of the drawing in the deformation under high rate of straining is described.
In order to measure drawing when making steel plate deform with the rate of straining of 10mm/sec and rupture, need to use institute in Fig. 1 The parallel portion shown is the special test sheet of 1.5mm.By to there is the special test sheet of parallel portion of 1.5mm with 900mm/ minute Travel speed implement tension test, the parallel of test film can be given by the rate of straining of closely 10mm/sec for the first time Portion.Additionally, the behavior of the destruction in order to correctly evaluate the steel plate as causing in the shaping of physical unit, tension test The thickness of the parallel portion of sheet and the ratio of width are also required to strictly be managed.When the deep-drawing deformation of tension test sheet, by thickness Degree direction and width the two direction produce necking down deformation.Certainly, when producing fracture when the shaping of physical unit, thickness The necking down deformation in direction is that the domination of fracture will be because of, and the impact of the necking down deformation of width is minimum.Therefore, stretching is being employed In the evaluation of test film, owing to needing the impact necking down of width deformed to remove, thus need by the width of parallel portion/ The ratio of the thickness of parallel portion is set as more than 2.The ratio of width/thickness is the biggest more preferred, and more preferably more than 4, further preferably It is more than 6.Additionally, drawing is by the change of the thickness before and after tension failure, (1) formula of use calculates.
" drawing (%) "=((" thickness of slab before test "-" post-rift thickness of slab ")/" thickness of slab before test ") × 100 ... (1)
It addition, thickness before Shi Yan by measure with micrometer the width of parallel portion central part and from central part to Vertical and parallel with the width direction of draw direction is respectively away from the thickness of 2 points of 1mm, by the measured value at 3 It is averaged and obtains.The mensuration of the thickness of post-rift sample uses the microscope of such as KEYENCE CORPORATION (VHX-1000) implement, in the same manner as before test, measure respectively and be separated into each plane of disruption of the sample of 2 by fracture In width midway portion and leave the thickness of position of 1mm to width, average as trying using the measured value at 6 Thickness after testing.The sample of the high drawing by above-mentioned test display more than 10% is evaluated as having " excellent drawing " Sample.
Then, the manufacture method of the steel plate described in present embodiment is illustrated.
The technological thought of the manufacture method of the steel plate described in present embodiment is characterised by, uses above-mentioned composition range Material, carry out a series of management of the condition of hot rolling and annealing.
The feature of the concrete manufacture method of the steel plate described in present embodiment is as described below.
Hot rolling (hot rolling) is characterised by, after having the continuous casting of slab of the composition of regulation, conventionally When carrying out hot rolling after heating after cooling directly or for the time being, 600 DEG C less than the temperature field of 1000 DEG C in terminate essence Hot rolling.By by the steel band after finish rolling on discharging roller-way (ROT) with more than 10 DEG C/sec and the rate of cooling of less than 100 DEG C/sec Coils of hot rolled is obtained at 350 DEG C less than batching within the temperature range of 700 DEG C after cooling.By coils of hot rolled is implemented Hot rolled plate coffin annealing, then implements cold rolling with the cold rolling rate of more than 10% and less than 80%, implements cold-reduced sheet annealing further, Obtain the medium/high carbon steel sheet in the deformation under high rate of straining with the drawing of excellence.
Hereinafter, the manufacture method of the steel plate described in present embodiment is specifically described.
(hot rolling)
Directly or carry out after heating after cooling for the time being after the slab (steel billet) with the composition of regulation is cast continuously During hot rolling, 600 DEG C less than the temperature field of 1000 DEG C in complete essence hot rolling, by obtained steel band more than 350 DEG C And batch within the temperature range of less than 700 DEG C.
The heating-up temperature of slab is set as more than 950 DEG C and less than 1250 DEG C, be set as heat time heating time more than 0.5 hour and Less than 3 hours.Heating-up temperature is more than 1250 DEG C or heat time heating time is little more than 3 constantly, owing to becoming from the decarburization on slab top layer Significantly, even if implementing the heat treatment of quenching, the hardness on top layer also can reduce, so parts become to can not get required wearability Deng.Therefore, the upper limit of heating-up temperature is set as less than 1250 DEG C, and the upper limit of heat time heating time is set as less than 3 hours.Additionally, add Hot temperature is less than 950 DEG C or heat time heating time is little less than 0.5 constantly, and the microscopic segregation or the gross segregation that are formed when casting do not have Eliminating, in the region of the alloying element localized rich such as steel internal residual Si and Mn, this region can cause under high rate of straining Deformation in the reduction of drawing.Therefore, it is more than 950 DEG C by the lower limit set of heating-up temperature, the lower limit of heat time heating time is set It is set to more than 0.5 hour.
Essence hot rolling preferably more than 600 DEG C and less than 1000 DEG C terminate.If essence hot-rolled temperature is less than 600 DEG C, then due to logical Crossing the increase of the deformation drag of steel, rolling load significantly improves, and then causes the increase of roller wear extent, so causing productivity ratio Reduction.Therefore essence hot-rolled temperature is set as more than 600 DEG C.If additionally, essence hot-rolled temperature is more than 1000 DEG C, then existing at steel plate On discharging roller-way in logical plate, steel plate generates the oxide skin of thickness, this oxide skin become oxygen source and make after batching ferrite or The grain boundary oxidation of pearlite, thus produce fine concavo-convex on surface.Due to using fine concavo-convex as starting point, in high strain During deformation under speed, steel plate occurs to early fracture, so fine concavo-convex meeting causes the reduction of drawing.And then, if essence hot rolling Temperature is more than 1000 DEG C, then owing to promoting that after essence hot rolling the alloying elements such as Si and Mn are to the segregation of austenite grain boundary, austenite The concentration of the alloying element in crystal grain reduces, so at the thin position of the concentration of alloying element, in hot rolled plate annealing and cold rolling Carrying out the cohesion of carbide during plate annealing, the number ratio of the carbide with grain boundary increases.Therefore, by essence hot-rolled temperature It is set as less than 1000 DEG C.
The rate of cooling of the steel band on ROT after essence hot rolling is set as more than 10 DEG C/sec and less than 100 DEG C/sec.Cooling speed When degree is less than 10 DEG C/sec, owing to rate of cooling is slow, so promoting ferritic growth, hot rolled plate forms ferrite, pearl The tissue that body of light and bainite are laminated on the thickness of slab direction of steel band.Due to such be organized in cold rolled annealed after the most residual Stay, the reduction of the drawing of steel plate can be caused, so rate of cooling to be set as more than 10 DEG C/sec.If additionally, throughout whole thicknesss of slab Being cooled down by steel band with the rate of cooling more than 100 DEG C/sec, skin section is cooled down by excess, produces bainite and martensite etc. Low temperature phase change tissue.The coiled material of 100 DEG C～room temperature it is cooled to when taking out, product in above-mentioned low temperature phase change tissue after batching Raw minute crack.Ensuing pickling and cold rolling process are difficult to removed in crack, after crack can cause cold-reduced sheet annealing The drawing of steel plate reduces.Therefore, rate of cooling is set as less than 100 DEG C/sec.It addition, the rate of cooling of above-mentioned regulation refers to Steel band after essence hot rolling by after without water filling interval water filling interval moment by water cooling be cooled on ROT To the moment of the target temperature batched, the cooling energy accepted from the cooling device that each water filling is interval, not represent from water filling Starting point average cooling rate to being batched by coiling machine.
Coiling temperature is set as more than 350 DEG C and less than 700 DEG C.If owing to coiling temperature is less than 350 DEG C, then in finish rolling The austenite phase of non-phase transformation becomes martensite, also maintains fine ferrite and cementite, cause drawing after cold-reduced sheet is annealed Reduction, so coiling temperature to be set as more than 350 DEG C.If additionally, coiling temperature is more than 700 DEG C, then due to non-phase transformation Austenite phase becomes the pearlite with thick stratiform, also remains the cementite of relatively thicker needle-like after cold-reduced sheet is annealed, So causing the reduction of drawing.Therefore coiling temperature is set as less than 700 DEG C.
The coils of hot rolled manufactured under the conditions described above directly or is implemented coffin annealing after pickling.Annealing temperature sets Being set to more than 670 DEG C and less than 770 DEG C, the retention time is set as more than 1 hour and less than 100 hours.
Coffin annealing temperature is preferably set to more than 670 DEG C and less than 770 DEG C.If annealing temperature is less than 670 DEG C, then ferrum element The coarsening of body grain and carbide particle is insufficient, causes the reduction of drawing in the deformation under high rate of straining.Therefore will Annealing temperature is set as more than 670 DEG C.If additionally, annealing temperature is more than 770 DEG C, then due to ferrite and 2 phase regions of austenite Ferritic tissue ratios in annealing excessively tails off, even if so in coffin annealing the slowest rate of cooling with 1 DEG C/hr cold But to room temperature, stratiform also cannot be avoided to be spaced the generation of thick pearlite, make the spherical rate after cold-reduced sheet annealing reduce, institute So that the drawing in deformation under high rate of straining reduces.Therefore, annealing temperature is set as less than 770 DEG C.Annealing temperature It is preferably more than 685 DEG C and less than 760 DEG C.
The retention time of coffin annealing is preferably set to more than 1 hour and less than 100 hours.If the retention time is little less than 1 Time, then the spheroidizing of the carbide in annealing due to hot rolled plate is insufficient, and after cold-reduced sheet is annealed, spherical rate is the lowest, so drawing Play the reduction of drawing.Therefore, the retention time of coffin annealing is set as more than 1 hour.Due to little more than 100 in the retention time Time such under the conditions of, being formed of the reduction that productivity ratio can be caused and the interface caused by association or the contact of carbide, so The retention time of coffin annealing is set as less than 100 hours.The lower limit of the retention time of coffin annealing is preferably 2 hours, enters One step is preferably 5 hours, and the upper limit is preferably 70 hours, more preferably 38 hours.
It addition, the atmosphere of coffin annealing is not particularly limited, can be the atmosphere of more than 95% nitrogen, the gas of more than 95% hydrogen Any one in atmosphere or air atmosphere.
Then the cold rolling reason of cold rolling rate enforcement with more than 10% and less than 80% is described.In above-mentioned heat Roll-hot rolled plate annealing operation in, will hot rolled plate anneal before and after in arbitrary time implement pickling hot rolled plate annealing Coiled material carries out cold rolling with the cold rolling rate of more than 10% and less than 80%.When cold rolling rate is less than 10%, in annealing at cold-reduced sheet, The quantity of the core of ferritic recrystallization is few, and ferrite particle diameter coarsening, to result from the deformation under high rate of straining Rupture as starting point in the Pericarpium Pyri face of surface of steel plate, so drawing reduces.Therefore, by the lower limit set of cold rolling rate it is 10%.If additionally, cold rolling rate is more than 80%, then many due to the quantity of the core of ferritic recrystallization, so annealing at cold-reduced sheet After the ferritic particle diameter that obtains excessively become fine, deformability reduces, and therefore causes in the deformation under high rate of straining The reduction of drawing.Therefore, the upper limit of cold rolling rate is set as 80%.
By to above-mentioned cold rolling rate carried out cold rolling after steel band implement cold-reduced sheet and anneal, it is possible to obtain high should Deformation under speed change degree has the medium/high carbon steel sheet of the drawing of excellence.
It addition, in cold-reduced sheet is annealed, owing to existing by cold rolling and lattice defects such as the dislocation that imports, thus in steel The diffusion frequency of each element improves.Thus, in cold-reduced sheet is annealed, carbide particle carries out Ostwald's growth, thick The carbide particle changed contacts with each other and forms a particle, becomes easily to cause and is internally formed crystal circle at carbide particle The change in face.Owing to the change of carbide particle above-mentioned in annealing for a long time becomes notable further, so cold-reduced sheet Annealing is preferably carried out in continuous annealing furnace.
Then, the condition annealed the cold-reduced sheet utilizing continuous annealing describes.Continuous annealing is preferably in annealing temperature Be more than 650 DEG C and less than 780 DEG C, the retention time be enforcement in more than 30 seconds and less than 1800 seconds.If annealing temperature is less than 650 DEG C, then the ferritic size owing to obtaining after cold-reduced sheet is annealed is fine, and deformability is low, so causing high rate of straining Under deformation in the reduction of drawing.Therefore, it it is 650 DEG C by the lower limit set of annealing temperature.If additionally, annealing temperature exceedes 780 DEG C, then the ratio of the austenite owing to generating in annealing excessively increases, so cannot suppress martensite, bayesian after the cooling period The generation of body, pearlite and retained austenite, causes the reduction of drawing.Therefore, the upper limit of annealing temperature is set as 780 DEG C. And then if the retention time was less than 30 seconds, then the ferritic size owing to obtaining after cold-reduced sheet is annealed becomes fine, so drawing Deep reduction.Therefore, it it is 30 seconds by the lower limit set of retention time.If additionally, the retention time more than 1800 seconds, then move back at cold-reduced sheet In fire during carbide particle growth, carbide particle each other comes in contact, and causes having grain boundary in particle, Drawing reduces.Therefore, the upper limit of annealing time is set as less than 1800 seconds.Although it addition, the heating speed in cold-reduced sheet annealing The temperature of degree, rate of cooling, OA band (overaging band) is not particularly limited, but remarks grind in the test described in present embodiment In studying carefully, confirm firing rate be more than 3.5 DEG C/sec and less than 35 DEG C/sec, rate of cooling be more than 1 DEG C/sec and 30 DEG C/sec Below, OA band temperature be more than 250 DEG C and less than 450 DEG C under conditions of, fully obtain the present embodiment institute as target The form of the steel plate stated.
According to the manufacture method of the steel plate described in above present embodiment, it is main body by making ferrite and carbide Tissue, by martensite, bainite, pearlite and retained austenite add up to volume fraction be set as less than 5%, by carbide The spherical rate of particle is set as more than 70% and less than 99%, will comprise the crystal that gun parallax is more than 5 ° in carbide particle The number ratio of the carbide particle at interface is set as less than 20% relative to total number of carbide particle, it is possible to obtain at height Rate of straining under implement drawing, reaming, thicken, the plastic working such as thinning or they are combined cold forging time play excellent The medium/high carbon steel sheet of formability.
Embodiment
Then, by embodiment, the effect of the present invention is illustrated.
The level of embodiment is of the implementation condition used to confirm the exploitativeness of the present invention and effect Example, the present invention is not limited to this condition example.Without departing from present subject matter and reach the object of the invention, then the present invention Various condition can be used.
By the slab (steel ingot) that casts continuously that has that the one-tenth shown in table 1 is grouped into, to heat 1.6hr at 1140 DEG C laggard Row hot rolling, is slightly hot-rolled down to the slab that thus obtained thickness is 250mm after thickness is 40mm, make the essence raw-material thick rod of hot rolling Heat up 36 DEG C, start essence hot rolling, at 880 DEG C after essence hot rolling, ROT is cooled to 520 DEG C with the rate of cooling of 45 DEG C/sec, Batching at 510 DEG C, thus manufacturing thickness of slab is the coils of hot rolled of 4.6mm.Coils of hot rolled is carried out pickling, in box annealing stove Load coiled material, after control climate is 95% hydrogen-5% nitrogen, the firing rate from room temperature to 500 DEG C is set as 100 DEG C/ Hour heat, keep 3 hours at 500 DEG C and by the temperature distribution homogenization in coiled material after, with the heating of 30 DEG C/h Speed is heated to 705 DEG C, and after keeping 24 hours at 705 DEG C further, stove is cooled to room temperature.The volume of hot rolled plate annealing will be implemented Material carries out cold rolling with the reduction ratio of 50%, is implemented at 720 DEG C keeping the cold-reduced sheet annealing of 900 seconds, and the reduction ratio with 1.2% is real Execute skin-pass, make the sample of evaluating characteristics.The drawing in deformation under the tissue of sample and high rate of straining is led to Cross above-mentioned method to be measured.
The evaluation knot of the drawing in deformation under the high rate of straining of sample manufactured shown in table 2-1 and table 2-2 Really.As shown in table 2-1 and table 2-2, the No.B-1 of example, C-1, D-1, E-1, F-1, G-1, H-1, I-1, J-1, M-1, N-1, P-1, Q-1, R-1, S-1, U-1, X-1, Y-1, Z-1, AA-1, AB-1, AC-1 are all by martensite, bainite, pearly-lustre The volume fraction that body and retained austenite add up to is less than 5%, the spherical rate of carbide particle be more than 70% and 99% with Under, carbide particle comprises the number ratio of carbide particle of the grain boundary that gun parallax is more than 5 ° relative to carbide Total number of particle is less than 20%, shows the drawing of excellence in the deformation under high rate of straining.
On the other hand, the ratio of the carbide in Comparative examples A-1 with grain boundary is few, although under high rate of straining Deformation in show excellence drawing, but C content is few, by for componentization quenching process cannot high intensity, so It is set to defective.Comparative example K-1 is few due to Mn content, promotes that the Ostwald of carbide grows in cold-reduced sheet is annealed, The ratio of the carbide with grain boundary increases, so causing the reduction of drawing.Comparative example L-1 is many due to the content of P, ferrum element Body embrittlement of grain boundaries, during deformation under high rate of straining, be full of cracks produces from ferrite grain boundaries and propagates, so causing drawing Reduce.Comparative example O-1 is many due to Mn content, and the spheroidizing of the carbide in hot rolled plate annealing and cold-reduced sheet annealing is suppressed, During deformation under high rate of straining, be full of cracks produces from the carbide of needle-like and propagates, so drawing reduction.Comparative example T-1 by Few in Si content, so promoting that the Ostwald of carbide grows in cold-reduced sheet is annealed, there is the carbonization of grain boundary The ratio of thing increases, and causes the reduction of drawing.Comparative example V-1 is many due to S content, more there is thick MnS etc. in steel Field trash, chaps and produces and development, so causing the reduction of drawing using field trash as starting point.Comparative example W-1 is due to Si content Many, the austenite generated in cold-reduced sheet is annealed becomes to be difficult to ferrite transformation in cooling, promotes bainite and pearly-lustre Body phase transformation, so the tissue ratio in addition to ferrite and carbide increases, thus causes concentrating to the stress of ferrite grain boundaries, Drawing reduces.Comparative examples A D-1 is many due to the content of C and the volume fraction of carbide, so the carbonization of grain boundary cannot be had The number ratio of thing controls below 20%, and drawing reduces.
Table 1
※ boldface letter underscore represents the example outside invention scope.
Then, in order to investigate the scope of the content allowed of other elements, will have table 3-1, table 3-2 and table 3-3 and After slab (steel ingot) that what the one-tenth shown in table 4-1, table 4-2 and table 4-3 was grouped into cast continuously heats 0.7hr at 1180 DEG C Carry out hot rolling, be slightly hot-rolled down to the slab that thus obtained thickness is 250mm after thickness is 45mm, make essence hot rolling raw-material slightly Rod heats up 48 DEG C, starts essence hot rolling, at 870 DEG C after essence hot rolling, is cooled to 510 with the rate of cooling of 45 DEG C/sec on ROT DEG C, batch at 500 DEG C, thus manufacturing thickness of slab is the coils of hot rolled of 2.6mm.Coils of hot rolled is carried out pickling, at box annealing Load coiled material in stove, after control climate is 95% hydrogen-5% nitrogen, the heating-up temperature from room temperature to 500 DEG C is set as 100 DEG C/h are heated, at 500 DEG C keep 3 hours by after the temperature distribution homogenization in coiled material, with 30 DEG C/h Firing rate is heated to 705 DEG C, and after keeping 24 hours at 705 DEG C further, stove is cooled to room temperature.After hot rolled plate annealing will be implemented Coiled material carry out cold rolling with the reduction ratio of 50%, be implemented at 700 DEG C keep 900 seconds cold-reduced sheet annealing, with the pressure of 1.0% Rate implements skin-pass, has made the sample of evaluating characteristics.
The evaluation knot of the drawing in deformation under the high rate of straining of sample manufactured shown in table 5-1～table 5-6 Really.As shown in table 5-1～table 5-6, the No.AE-1 of example, AF-1, AL-1, AM-1, AN-1, AR-1, AS-1, AV-1, AW-1, AX-1, BC-1, BD-1, BF-1, BH-1, BI-1, BJ-1, BK-1, BM-1, BN-1, BT-1 are all by martensite, shellfish The volume fraction that family name's body, pearlite and retained austenite add up to was less than 5% (including 0.0%), the spherical rate of carbide particle Be more than 70% and less than 99%, carbide particle comprises the grain boundary that gun parallax is more than 5 ° carbide particle Number ratio is less than 20% relative to total number of carbide particle, shows drawing of excellence in the deformation under high rate of straining Deeply.
On the other hand, Comparative examples A G-1, AH-1, AO-1, AT-1, AU-1, AZ-1, BA-1, BB-1, BO-1, BS-1 are respectively Owing to the content of Ce, Ca, Y, Al, Mg, As, Zr, Sn, Sb, La is many, so causing the embrittlement of ferritic crystal boundary, should high During deformation under speed change degree, drawing reduces.Comparative examples A I-1, AJ-1, AK-1, AQ-1, BE-1, BG-1, BL-1, BQ-1, BR-1 by Many in the content of Nb, W, Ti, Ni, Cr, Mo, V, Cu, Ta, the spheroidizing of the carbide in hot rolled plate annealing and cold-reduced sheet annealing is subject to Produces to be full of cracks when suppression, deformation under high rate of straining from the carbide of needle-like and propagate, so drawing reduction.Relatively Example AP-1 is many due to the content of N, and the austenite generated in cold-reduced sheet is annealed becomes to be difficult to ferrite transformation in cooling, Promote bainite and pearlitic transformation, so the tissue ratio in addition to ferrite and carbide increases, thus cause to ferrum element The stress of body crystal boundary is concentrated, and drawing reduces.The content of the O of Comparative examples A Y-1 is many, forms thick oxide in steel, high Deformation under rate of straining is chapped and produces using thick oxide as starting point and propagate, cause the reduction of drawing.Relatively Example BP-1 is many due to the content of B, generates thick Fe-B-Carbide in steel, so be full of cracks is using Fe-B-Carbide as rising Put and produce and propagate, cause the reduction of drawing.
Table 5-2
※ underscore represents the example outside invention scope.
Table 5-4
※ underscore represents the example outside invention scope.
Table 5-6
※ underscore represents the example outside invention scope.
Then, in order to investigate the impact of manufacturing condition, will have institute in table 1, table 3-1～table 3-3 and table 4-1～table 4-3 The No.B that shows, C, D, E, F, G, H, I, J, M, N, P, Q, R, S, U, X, Y, Z, AA, AB, AC, AE, AF, AL, AM, AN, AR, AS, The slab of the composition of AV, AW, AX, BC, BD, BF, BH, BI, BJ, BK, BM, BN, BT casts, for the time being with table 6-1-after cooling 1, table 6-1-2, table 6-2-1, table 6-2-2, table 7-1-1, table 7-1-2, table 7-2-1, table 7-2-2, table 8-1-1～table 8-1-3, table Shown in 8-2-1～table 8-2-3, table 9-1-1～table 9-1-3 and table 9-2-1～table 9-2-3 (hereinafter referred to as table 6,7,8,9) Heating of plate blank condition and hot-rolled condition to manufacture thickness of slab be the hot rolled strip of 3.5mm, implement hot rolled plate annealing, pickling, cold rolling, cold Roll plate annealing and make the sample for evaluating characteristics.
Table 6,7,8,9 also illustrating that, the evaluation of the drawing in the deformation under the high rate of straining of manufactured sample is tied Really.No.B-2, C-2, D-2, E-2, J-2, N-2, Q-2, X-2, Y-2, Z-2, AB-2, AC-2, AL-2, AN-2, AS-of example 2、AV-2、BC-2、BD-2、BH-2、BI-2、BJ-2、BN-2、F-3、G-3、H-3、I-3、M-3、N-3、P-3、R-3、S-3、U-3、 As AA-3, AB-3, AE-3, AF-3, AM-3, AR-3, AW-3, AX-3, BF-3, BK-3, BM-3, BT-3 are as shown in table 8, The volume fraction all martensite, bainite, pearlite and retained austenite added up to is less than 5%, the spheroidizing of carbide particle Rate is more than 70% and less than 99%, comprises the carbide particle of the grain boundary that gun parallax is more than 5 ° in carbide particle Number ratio is less than 20% relative to total number of carbide particle, shows excellence in the deformation under high rate of straining Drawing.
On the other hand, Comparative examples A A-2, BK-2, C-3, BJ-3 are as shown in table 6,7, due to essence hot-rolled temperature Height, the number ratio of the carbide with grain boundary increases, and the cooling period generation before batching is relatively thicker simultaneously Oxide skin becomes oxygen supply source, by grain boundary oxidation after batching, produces fine crack on surface, thus at high rate of straining Under deformation in chap and propagate as starting point, so causing the reduction of drawing using the crack on top layer.Comparative example R-2, BM-2, X- 3, BC-3 is low due to essence hot-rolled temperature, when oxide skin being involved in when hot rolling and roll, is formed concavo-convex at surface of steel plate, The high deformation under rate of straining is chapped and produces using concave-convex surface as starting point and develop, so drawing reduces.Comparative example U-2, AR-2, Y-3, AL-3 are high due to coiling temperature, generate needle-like and have the carbide of big thickness, cold in hot rolled plate After rolling plate annealing, the spheroidizing of acicular carbide is not the most in progress, so be full of cracks produces using the carbide of needle-like as starting point And propagate, drawing reduces.Comparative Example H-2, AM-2, Q-3, BI-3 due to coiling temperature low, the tissue of hot rolled plate is fine, cold-reduced sheet Tissue after annealing is the finest, so deformability reduces, the drawing in the high deformation under rate of straining reduces.
Comparative example G-2, AE-2, J-3, BD-3 are as shown in table 6,7, owing to cold rolling rate is high, so cold-reduced sheet moves back Tissue after fire becomes fine, and deformability reduces, and causes the reduction of drawing.Comparative example S-2, AW-2, AC-3, BH-3 are due to cold Rate of rolling is low, so the ferrite particle diameter after cold-reduced sheet annealing becomes thick, produces on top layer in the deformation under high rate of straining Raw Pericarpium Pyri face, based on the concave-convex surface formed, be full of cracks produces and development, therefore causes the reduction of drawing.Comparative example M-2, BT- 2, the temperature that Z-3, AS-3 anneal due to cold-reduced sheet is high, thus the austenite generated in annealing to compare change many, cooled Cannot suppress martensite, bainite, pearlitic transformation in journey, therefore in the deformation under high rate of straining, drawing reduces.Ratio Low compared with the temperature that example P-2, BF-2, E-3, BN-3 anneal due to cold-reduced sheet, ferrite particle diameter is fine, so deformability reduces, Drawing in the high deformation under rate of straining reduces.Comparative Example I-2, AX-2, D-3, AN-3 due to cold-reduced sheet annealing time long, Contacting with each other during carbide particle coarsening, causing, at inside particles, there is grain boundary, so causing drawing Reduce.Comparative Example F-2, AF-2, B-3, AV-3 due to cold-reduced sheet annealing time short, ferrite is fine, thus deformability reduce, Drawing in the high deformation under rate of straining reduces.
Table 6-its-1
※ underscore represents the example outside invention scope.
Table 6-1-2
※ boldface letter underscore represents the example outside invention scope.
Table 6-2-1
※ underscore represents the example outside invention scope.
Table 6-2-2
※ boldface letter underscore represents the example outside invention scope.
Table 7-1-1
※ underscore represents the example outside invention scope.
Table 7-1-2
※ boldface letter underscore represents the example outside invention scope.
Table 7-2-1
※ underscore represents the example outside invention scope.
Table 7-2-2
※ boldface letter underscore represents the example outside invention scope.
Table 8-1-1
※ underscore represents the example outside invention scope.
Table 8-1-3
※ underscore represents the example outside invention scope.
Table 8-2-1
※ underscore represents the example outside invention scope.
Table 8-2-3
※ underscore represents the example outside invention scope.
Table 9-1-1
※ underscore represents the example outside invention scope.
Table 9-1-3
※ underscore represents the example outside invention scope.
Table 9-2-1
※ underscore represents the example outside invention scope.
Table 9-2-3
※ underscore represents the example outside invention scope.
For evaluating the test film shape of the drawing of the steel plate in the deformation under high rate of straining shown in Fig. 1.Test The parallel portion of sheet is 1.5mm, is stretched with the travel speed of 900mm/ minute by this test film, makes test film rupture, by trying The drawing of steel plate is obtained in the thickness of slab change of the parallel portion central authorities before and after testing.
Used by the sample after the deformation under high rate of straining being made to stop with percentage elongation 13.4% shown in Fig. 2 The tissue of embodiment U-1 that 3% nitric acid-ethanol solution is etched and makes ferrite and carbide manifest.Visible carbide Crackle grain boundary present in the carbide particle produces.
With table 2-1 and the example of table 2-2 and comparative example, table 5-1～table 5-6, table 6, table 7, table 8 and table shown in Fig. 3 The drawing in deformation under the example of 9 and the relevant high rate of straining of comparative example has grain boundary in carbide particle The number of carbide relative to the relation of the ratio of the number of whole carbides.Know by by composition adjustment be invention model Enclosing, and the number ratio with the carbide of grain boundary is set as less than 20%, drawing significantly improves.

Claims (3)

1. a medium/high carbon steel sheet, it is characterised in that it is to have to contain in terms of quality %:
C:0.10～1.50%,
Si:0.01～1.00%,
Mn:0.01～3.00%,
P:0.0001～0.1000%,
S:0.0001～0.1000%,
And remainder comprises the steel plate of composition of Fe and impurity,
Described steel plate have by martensite, bainite, pearlite and retained austenite add up to volume fraction be less than 5.0% and Remainder is the tissue of ferrite and carbide,
The spherical rate of carbide particle is more than 70% and less than 99%,
Described carbide particle comprises the number ratio phase of the described carbide particle of the grain boundary that gun parallax is more than 5 ° Total number for described carbide particle is less than 20%.
Medium/high carbon steel sheet the most according to claim 1, it is characterised in that the described composition of described steel plate is in terms of quality % Contain further:
Al:0.001～0.500%,
N:0.0001～0.0500%,
O:0.0001～0.0500%
Cr:0.001～2.000%,
Mo:0.001～2.000%,
Ni:0.001～2.000%,
Cu:0.001～1.000%,
Nb:0.001～1.000%,
V:0.001～1.000%,
Ti:0.001～1.000%,
B:0.0001～0.0500%,
W:0.001～1.000%,
Ta:0.001～1.000%,
Sn:0.001～0.020%,
Sb:0.001～0.020%,
As:0.001～0.020%,
Mg:0.0001～0.0200%,
Ca:0.001～0.020%,
Y:0.001～0.020%,
Zr:0.001～0.020%,
La:0.001～0.020%,
Ce:0.001～0.020%,
In one kind or two or more.
3. a medium/high carbon steel sheet and manufacture method thereof, it is characterised in that described in having described in claim 1 or 2 When the steel billet of composition directly or carries out heating and carrying out hot rolling after cooling for the time being, more than 600 DEG C and the temperature of less than 1000 DEG C Territory completes essence hot rolling,
By more than 350 DEG C and less than the 700 DEG C hot rolled steel plates batched carry out coffin annealing,
Implement more than 10% and less than 80% cold rolling,
In continuous annealing line annealing temperature be more than 650 DEG C and less than 780 DEG C, the retention time be more than 30 seconds and 1800 seconds Cold-reduced sheet annealing after implementing under conditions of below.
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