CN106133170B - High-carbon hot-rolled steel sheet and its manufacture method - Google Patents

High-carbon hot-rolled steel sheet and its manufacture method Download PDF

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CN106133170B
CN106133170B CN201580016876.8A CN201580016876A CN106133170B CN 106133170 B CN106133170 B CN 106133170B CN 201580016876 A CN201580016876 A CN 201580016876A CN 106133170 B CN106133170 B CN 106133170B
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steel plate
cementite
ferrite
hardness
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CN106133170A (en
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宫本友佳
小林崇
奥田金晴
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JFE Engineering Corp
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NKK Corp
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    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226Hot rolling
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263Modifying 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
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/001Ferrous alloys, e.g. steel alloys containing N
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/002Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/008Ferrous alloys, e.g. steel alloys containing tin
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/06Ferrous alloys, e.g. steel alloys containing aluminium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/08Ferrous alloys, e.g. steel alloys containing nickel
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/12Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32Ferrous alloys, e.g. steel alloys containing chromium with boron
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/60Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/003Cementite
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/005Ferrite
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/009Pearlite

Abstract

The present invention provides a kind of high-carbon hot-rolled steel sheet, it is using the steel added with B as blank, excellent quenching degree can also be stably obtained by being annealed in blanket of nitrogen, also, before Quenching Treatment have hardness using HRB be calculated as less than 73 and percentage of total elongation as more than 39% such excellent processability.The high-carbon hot-rolled steel sheet has following composition:Contained in terms of quality %:C:0.20~0.40%, Si:Less than 0.10%, Mn:Less than 0.50%, P:Less than 0.03%, S:Less than 0.010%, sol.Al:Less than 0.10%, N:Less than 0.0050%, B:0.0005~0.0050%, further containing more than a kind in Sb, Sn, Bi, Ge, Te, Se for adding up to 0.002~0.030%, it is more than 70% to be dissolved B amounts ratio shared in B content, and has and be made up of ferrite and cementite and the carburizing volume density in above-mentioned ferrite crystal grain is 0.08/μm2Following micro-assembly robot, hardness are calculated as less than 73 with HRB, and percentage of total elongation is more than 39%.

Description

High-carbon hot-rolled steel sheet and its manufacture method
Technical field
The present invention relates to high-carbon hot-rolled steel sheet and its manufacture method.More particularly to suppress added with the nitriding in B and top layer The high-carbon hot-rolled steel sheet and its manufacture method that effect is high, processability and quenching degree are excellent.
Background technology
Now, the automotive part such as gear class, fluid drive box part, seat harness part will be mostly in order to will belong to Mechanical structure specified in JISG 4051 is processed into after desired shape really with the hot rolled steel plate of carbon steel steel using cold working Desired hardness is protected, implements Quenching Treatment and manufactures.Therefore, turn into the hot rolled steel plate of blank need excellent cold-workability, Quenching degree, and up to the present there has been proposed various steel plates.
For example, Patent Document 1 discloses a kind of cold working intermediate carbon steel sheet, its carrying out with 100 DEG C/sec average plus When keeping being quenched to the high-frequency quenching of room temperature with 200 DEG C/sec of average cooling rate for 10 seconds at 1000 DEG C after thermal velocity heating Hardness is 500HV~900HV, in terms of quality %, contains C:0.30~0.60%, Si:0.06~0.30%, Mn:0.3~ 2.0%th, P:Less than 0.030%, S:Less than 0.0075%, Al:0.005~0.10%, N:0.001~0.01%, Cr:0.001 ~0.10%, or further contain Ni:0.01~0.5%, Cu:0.05~0.5%, Mo:0.01~0.5%, Nb:0.01~ 0.5%th, Ti:0.001~0.05%, V:0.01~0.5%, Ta:0.01~0.5%, B:0.001~0.01%, W:0.01~ 0.5%th, Sn:0.003~0.03%, Sb:0.003~0.03%, As:More than a kind of 0.003~0.03%, and its carbide Average diameter d be less than 0.6 μm, the spherical rate p of carbide is 70% less than 90%, and above-mentioned carbide is averaged The spherical rate p% of d μm of diameter and above-mentioned carbide meets d≤0.04 × p-2.6, or further it is hard before cold working Spend is 120HV less than 170HV.In addition, in patent document 1, the manufacturer as such cold working intermediate carbon steel sheet Method, disclose following method:After the steel of above-mentioned chemical composition is held in into 1050~1300 DEG C, carry out at 750~1000 DEG C The lower hot rolling for terminating rolling, after being then cooled to 500~700 DEG C with 20~50 DEG C/s cooling velocity, with the cold of 5~30 DEG C/s But speed be cooled to as defined in temperature batched, after keeping under the conditions of defined, with 600 DEG C~Ac1- 10 DEG C of temperature Annealing.
In addition, Patent Document 2 discloses a kind of steel plate for adding boron, the steel plate is contained in terms of quality %:C: 0.20%~0.45%, Si:0.05%~0.8%, Mn:0.5%~2.0%, P:0.001%~0.04%, S:0.0001% ~0.006%, Al:0.005%~0.1%, Ti:0.005%~0.2%, B:0.001%~0.01% and N:0.0001% ~0.01%, or further contain Cr:0.05%~0.35%, Ni:0.01%~1.0%, Cu:0.05%~0.5%, Mo:0.01%~1.0%, Nb:0.01%~0.5%, V:0.01%~0.5%, Ta:0.01%~0.5%, W:0.01%~ 0.5%th, Sn:0.003%~0.03%, Sb:0.003%~0.03% and As:1 kind in 0.003%~0.03% or 2 kinds More than composition, the mean concentration of the solid solution B in its region from top layer to depth untill 100 μm is more than 10ppm.In addition, Patent Document 2 discloses the phenomenon that suction nitrogen when being annealed in the atmosphere based on nitrogen, can be shown, from the viewpoint of quenching degree The B for being considered as important element combines to form BN in annealing with the N in steel, and solid solution B is reduced and can not be ensured the through hardening based on B Property improve effect.Patent Document 2 discloses in order to ensure quenching degree, it is necessary to make from top layer to depth be 100 μm untill area Solid solution B in domain is more than 10ppm, it is therefore important that the shadow of the atmosphere of the heating, annealing operation in suppression manufacturing process Ring.In addition, in patent document 2, as the manufacture method of the steel plate of such addition boron, following method is disclosed:At 1200 DEG C After being heated below to the steel of mentioned component composition, hot rolling is carried out with 800~940 DEG C of final rolling temperature, then to cool down speed After 20 DEG C/more than s of degree is cooled to less than 650 DEG C, cools down and batched at 400~650 DEG C, pickling with 20 DEG C/below s Afterwards, it is more than 95% in hydrogen and is less than -20 DEG C to 400 DEG C of dew point, more than 400 DEG C of dew point is less than -40 DEG C of gas In atmosphere, with 660 DEG C~Ac1Temperature annealed.In addition, in patent document 2, further disclose laggard in above-mentioned pickling Cold rolling is implemented in row cold rolling after above-mentioned annealing, and then with Ac1~Ac1+ 50 DEG C of temperature is annealed, and slow cooling is to Ac1- Untill 30 DEG C.
Prior art literature
Patent document
Patent document 1:No. 5048168 publications of Japanese Patent No.
Patent document 2:No. 4782243 publications of Japanese Patent No.
The content of the invention
In terms of good cold-workability is obtained, to high-carbon hot-rolled steel sheet requirement than relatively low hardness and high elongation rate.Example Such as, in the past, towards to being made by hot Forging, cutting, the steel plate that multiple processes are fabricated such as welding and be cold-pressed and being integrally formed The purposes of manufactured automobile component etc., it is desirable to which hardness is calculated as less than 73 with Rockwell hardness HRB, and percentage of total elongation (El) is more than 39% Etc. characteristic.In addition, for it is such a have compared with soft and high elongation rate and make the good high-carbon hot-rolled steel sheet of processability, it is expected excellent Different quenching degree, such as it is expected the Vickers hardness of acquisition more than HV440 after water quenching.
In the technology of patent document 1, in order to ensure 100 DEG C/sec of average heating rate high-frequency quenching when it is quench-solidifying Can, the average diameter of carbide is set to less than 0.6 μm, but C content is 0.3~0.6% etc the steel containing substantial amounts of C In, because the average grain diameter of carbide attenuates as less than 0.6 μm, so the density of carbide becomes big, easy high intensity, having can Can processability reduction.In addition, as its manufacture method, carry out the cooling control in 2 following stages, i.e. after hot rolling with 20~ After 50 DEG C/s cooling velocity is cooled to 500~700 DEG C, cooled down with 5~30 DEG C/s cooling velocity, exist and be difficult to manage The problem of cooling control.
Also the cooling control in following 2 stage is carried out in the technology of patent document 2, i.e., after hot rolling, with 20 DEG C of cooling velocity/ After more than s is cooled to less than 650 DEG C, cooled down with 20 DEG C/below s, the problem of unmanageable cooling control be present.In addition, In the technology of patent document 2, in order to improve quenching degree, the Mn of addition more than 0.5%.Although Mn improves quenching degree, but because Solution strengthening and hot rolled steel plate intensity in itself is increased, hardness is become big.
On the other hand, as the element for making quenching degree raising with micro addition, it is known to B, but also like institute in patent document 2 As record, if annealed in it will be typically used as the nitrogen of atmosphere gas as the atmosphere of main body, solid solution B be present Reduce and the problem of quenching degree improves effect as caused by B can not be obtained.In patent document 2, for it is such the problem of, by Atmosphere containing more than the 95% hydrogen or hydrogen is replaced into the atmosphere of the non-active gas such as Ar is annealed to solve, but Uprised using the cost of the heat treatment of these gases.In addition, and it is indefinite only by the technology, can be in the annealing in blanket of nitrogen Suppress to inhale nitrogen.
In order to solve the above problems, it is an object of the invention to propose high-carbon hot-rolled steel sheet and its manufacture method, the height Carbon hot rolled steel plate is annealed in blanket of nitrogen, can also stably obtained excellent using the steel added with B as blank Quenching degree, and there is before Quenching Treatment hardness to be calculated as less than 73, percentage of total elongation using HRB and such excellent add for more than 39% Work.
The present inventor etc. is to being set to less than 0.50% this Mn amount fewer than conventional steel by Mn contents and being added with the high of B The manufacturing condition of carbon hot rolled steel plate is furtherd investigate with processability, the relation of quenching degree, as a result obtains following opinion.
I) the carburizing volume density in ferrite crystal grain to the hardness of the high-carbon hot-rolled steel sheet before quenching, percentage of total elongation (it is following, Also referred to as elongation) influence greatly.In order to obtain with hardness, more than 39% percentage of total elongation that less than 73 are calculated as with HRB (El) steel plate by the carburizing volume density in ferrite crystal grain, it is necessary to be set to 0.08/μm2Below.
Ii) cooling velocity after the Finishing temperatures in the finish rolling of hot rolling and finish rolling untill 700 DEG C is to ferrite crystal grain Interior cementite Effects of Density is big.If Finishing temperatures are too high or cooling velocity is too small, in steel plate after hot rolling, nothing Method is obtained containing the steel plate with pearlite and the tissue of defined pro-eutectoid ferrite volume fraction, difficult after spheroidizing To reduce carburizing volume density.
Iii) by the way that at least one kind of in Sb, Sn, Bi, Ge, Te, Se is made an addition in steel, even if so as to real in blanket of nitrogen When applying annealing, nitriding is also prevented from, suppresses the reduction of solid solution B amounts and obtains high-hardenability.
The present invention is carried out based on such opinion, and will be used as purport below.
[1] a kind of high-carbon hot-rolled steel sheet, it has following composition:Contained in terms of quality %:C:0.20~0.40%, Si: Less than 0.10%, Mn:Less than 0.50%, P:Less than 0.03%, S:Less than 0.010%, it is dissolved aluminium (sol.Al):0.10% with Under, N:Less than 0.0050%, B:0.0005~0.0050%, further containing add up to 0.002~0.030% Sb, Sn, More than a kind in Bi, Ge, Te, Se, remainder is made up of Fe and inevitable impurity, and solid solution B amounts are shared in B content Ratio be more than 70%, there is the carburizing volume density in be made up of ferrite and cementite, above-mentioned ferrite crystal grain to be 0.08/μm2Following micro-assembly robot, hardness are calculated as less than 73 with HRB, and percentage of total elongation is more than 39%.
[2] high-carbon hot-rolled steel sheet according to above-mentioned [1], wherein, in terms of quality %, further contain and add up to More than a kind in less than 0.50% Ni, Cr, Mo.
[3] high-carbon hot-rolled steel sheet according to above-mentioned [1] or [2], wherein, it is above-mentioned to be made up of ferrite and cementite The average diameter of total cementite in tissue is 0.60 μm~1.00 μm, and the cementite average diameter in ferrite crystal grain is 0.40 More than μm.
[4] a kind of manufacture method of high-carbon hot-rolled steel sheet, it is by after with the hot roughing of steel formed as follows, with finish rolling temperature Degree:Ar3Transformation temperature~870 DEG C carry out finish rolling, 700 DEG C are cooled to 25 DEG C/s~150 DEG C/s average cooling rate, to batch Temperature:500 DEG C~700 DEG C are batched, and thus manufacture is had pearlite and more than 5% proeutectoid ferrite is calculated as with volume fraction The steel plate of body, then in Ac1The steel plate is annealed below transformation temperature, above-mentioned composition is contained in terms of quality %:C:0.20 ~0.40%, Si:Less than 0.10%, Mn:Less than 0.50%, P:Less than 0.03%, S:Less than 0.010%, sol.Al:0.10% Below, N:Less than 0.0050%, B:0.0005~0.0050%, further containing add up to 0.002~0.030% Sb, Sn, More than a kind in Bi, Ge, Te, Se, remainder is Fe and inevitable impurity.
[5] manufacture method of the high-carbon hot-rolled steel sheet according to above-mentioned [4], wherein, above-mentioned steel enters one in terms of quality % Step contains more than a kind in Ni, Cr, Mo for adding up to less than 0.50%.
The high-carbon hot-rolled steel sheet of quenching degree and excellent in workability can be manufactured according to the present invention.The high-carbon hot-rolled steel of the present invention Plate, which is suitable to blank steel plate, needs the automotive parts such as the gear class of cold-workability, fluid drive box part, seat harness part.
Embodiment
Hereinafter, the high-carbon hot-rolled steel sheet as the present invention and its manufacture method are described in detail.It should illustrate, as long as Be not particularly illustrated, then as component content unit " % " expression " quality % ".
1) form
C:0.20~0.40%
C is for element important for the intensity after being quenched.When C content is less than 0.20%, it can not pass through into Type obtains desired hardness for the heat treatment after part, specifically, cannot get more than HV440 hardness after water quenching. Therefore, it is necessary to which C content is set into more than 0.20%.On the other hand, if C content is more than 0.40%, steel plate hardening is cold to add Work is deteriorated.Therefore, C content is set to less than 0.40%.In order to obtain high quenching hardness, C content is preferably set to 0.26% More than.By the way that C content is set into more than 0.32%, more than HV440 water quenching hardness can be stably obtained, thus it is more excellent Choosing.
Si:Less than 0.10%
Si is to make the element of intensity rising by solution strengthening.Because hardening and cold working with the increase of Si contents Property be deteriorated, so Si contents are set into less than 0.10%.Si contents are preferably less than 0.05%, and more preferably less than 0.03%. Si reduces cold-workability, therefore Si contents are more few better, but if exceedingly reducing Si, then refining cost increases, therefore Si Content is preferably more than 0.005%.
Mn:Less than 0.50%
Mn be make quenching degree improve element, on the other hand, and by solution strengthening make intensity rise element.If Mn Content is more than 0.50%, then the excessive hardening of steel plate and cold-workability reduce.The banded structure as caused by Mn segregation expands in addition Exhibition, tissue become uneven, therefore have hardness, the deviation of elongation to become big trend.Therefore, by Mn contents be set to 0.50% with Under.Mn contents are preferably less than 0.45%, and more preferably less than 0.40%.It should illustrate, lower limit does not specify, in order to Suppress the precipitation of graphite, and whole C in steel plate are dissolved when Quenching Treatment heats and obtain defined quenching hardness, preferably Mn contents are set to more than 0.20%.
P:Less than 0.03%
P is the element for making intensity rising by solution strengthening.If P content more than 0.03%, the excessive hardening of steel plate and Cold-workability reduces.In addition, because reducing the intensity of crystal boundary, the degraded toughness after quenching.Therefore, P content is set to Less than 0.03%.In order to obtain the toughness after excellent quenching, P content is preferably set to less than 0.02%.Because P makes cold working Property and quenching after toughness reduce, it is advantageous to P content is more few better, but if making P reduce to more than necessity, then refining cost Increase, therefore P content is preferably more than 0.005%.
S:Less than 0.010%
S make because forming sulfide high-carbon hot-rolled steel sheet cold-workability and quenching after toughness reduce, so must not be Nondecreasing element.If S contents, more than 0.010%, the toughness after the cold-workability of high-carbon hot-rolled steel sheet and quenching is notable It is deteriorated.Therefore, S contents are set to less than 0.010%.In order to obtain the toughness after excellent cold-workability and quenching, S contents are excellent Elect less than 0.005% as.Because S reduces the toughness after cold-workability and quenching, S contents are preferably more few better, but such as Fruit reduces S to more than necessity, then refining cost increases, therefore S contents are preferably more than 0.0005%.
sol.Al:Less than 0.10%
If sol.Al contents more than 0.10%, generate AlN, austenite crystal is excessively micro- in the heating of Quenching Treatment Refinement, the generation of ferritic phase can be promoted during cooling, tissue becomes ferrite and martensite, and the hardness after quenching reduces.Therefore, Sol.Al contents are set to less than 0.10%.Sol.Al contents are preferably less than 0.06%.It should illustrate, Al has deoxidation effect Fruit, in order to be sufficiently carried out deoxidation, sol.Al contents are preferably set to more than 0.005%.
N:Less than 0.0050%
If N content is more than 0.0050%, because more than necessity forming BN so being dissolved the reduction of B amounts.Further, since shape BN, AlN more than into necessity, iron can be promoted so the excessive miniaturization of austenite crystal in the heating of Quenching Treatment, during cooling The generation of ferritic phase, the hardness after quenching reduce.Therefore, N content is set to less than 0.0050%.N content is preferably Less than 0.0045%.It should illustrate, lower limit does not have special provision, but as described above, N forms BN, AlN.If it is appropriate to be formed BN, AlN of amount, then these nitride suitably suppress the coarsening of austenite crystal in the heating of Quenching Treatment, after making quenching Toughness improve, therefore N content is preferably more than 0.0005%.
B:0.0005~0.0050%
B is the important element for improving quenching degree.The condition of the cooling velocity after finish rolling in the hot rolling based on the present invention Under, when B content is less than 0.0005%, the solid solution B amounts for postponing ferrite transformation are insufficient, therefore cannot get enough quenching degree Improve effect.Therefore, it is necessary to which B content is set into more than 0.0005%, preferably more than 0.0010%.On the other hand, B content is worked as During more than 0.0050%, the recrystallization delay of the austenite after finish rolling.As a result, the rolling set tissue development of hot rolled steel plate, The intra-face anisotropy of the mechanical property value of steel plate after annealing becomes big.Thus, wrinkle (ear) are easily produced in drawing and forming, In addition, out of roundness reduces, easily cause unfavorable condition during shaping.Therefore, it is necessary to which B content is set into less than 0.0050%.From carrying From the viewpoint of high-hardenability and reduction anisotropy, B content is preferably less than 0.0035%.Therefore, B content is set to 0.0005~0.0050%.B content is more preferably 0.0010~0.0035%.
It is more than 70% to be dissolved B amounts ratio shared in B content
In the present invention, in addition to making the optimization of above-mentioned B content, it is important that be favorably improved the solid solution B of quenching degree The control of amount.The B in solid solution condition in the B contained in steel plate is more than 70%, i.e. the solid solution B amounts in steel plate are in whole B When shared ratio is more than 70% in content (B content), it can obtain wishing the excellent quenching degree realized in the present invention.Cause This, will be dissolved B amounts ratio shared in B content and be set to more than 70%.Being dissolved B amounts ratio shared in B content is preferably More than 75%.It should illustrate, solid solution B amounts ratio shared in B content refers to { (solid solution B amounts (quality %))/(whole B contents (quality %)) } × 100 (%).
Add up to more than a kind in 0.002~0.030% Sb, Sn, Bi, Ge, Te, Se
Sb, Sn, Bi, Ge, Te, Se are with the element for suppressing the effect from the nitriding of surface of steel plate, in of the invention, are needed To contain more than a kind in Sb, Sn, Bi, Ge, Te, Se.In addition, when adding up to less than 0.002% of the content of these elements, nothing Method sees enough nitriding inhibitions.Therefore, containing a kind in Sb, Sn, Bi, Ge, Te, Se for adding up to more than 0.002% More than.The total of Sb, Sn, Bi, Ge, Te, Se content is preferably more than 0.005%.On the other hand, even if these elements contain Amount is total more than 0.030%, nitriding inhibition also saturation.In addition, these elements have the trend for being segregated in crystal boundary, therefore, If the content of these elements is total more than 0.030%, it is likely that causes embrittlement of grain boundaries.Therefore, in the present invention, containing total For more than a kind in less than 0.030% Sb, Sn, Bi, Ge, Te, Se.Sb, Sn, Bi, Ge, Te, Se content preferably add up to Less than 0.020%.
As described above, by the way that N content is set into less than 0.0050%, contains simultaneously and add up to 0.002~0.030% More than a kind in Sb, Sn, Bi, Ge, Te, Se, so as to be annealed in blanket of nitrogen in the case of also suppress from steel plate table The nitriding in face, suppress the increase of the nitrogen concentration in steel plate top layer, make from surface of steel plate to the scope along the 150 μm of depth in thickness of slab direction The difference of average nitrogen quantity of the average nitrogen quantity inside contained with containing in steel plate entirety is below 30 mass ppm.Suppress as described above Nitriding, therefore can also make to be dissolved B amounts institute in B content in the steel plate after annealing in the case of being annealed in blanket of nitrogen The ratio accounted for is more than 70%.
If from surface of steel plate into the average nitrogen quantity and steel plate entirety contained along in the range of the depth of 150 μm of thickness of slab direction The difference of the average nitrogen quantity contained becomes more more than 30 mass ppm, then is formed at BN, AlN amount of steel plate skin section and is formed at steel The difference of BN, AlN amount of plate thickness of slab immediate vicinity becomes big.In this case, produce and cannot get uniform hardness after Quenching Treatment A problem that.Therefore, it is necessary to by from surface of steel plate to the average nitrogen quantity that contains along in the range of the depth of 150 μm of thickness of slab direction with The difference of the average nitrogen quantity contained in steel plate entirety is suppressed to below 30 mass ppm.
Remainder other than the above is Fe and inevitable impurity, but in order to further improve quenching degree, Ke Yihan There is more than a kind in Ni, Cr, Mo.From the aspect of such effect is obtained, preferably comprise more than a kind in Ni, Cr, Mo and Total by its content is set to more than 0.01%.On the other hand, because these element valencys are high, 1 in Ni, Cr, Mo is used , it is necessary to which make its content adds up to less than 0.50% during kind of the above.The content of these elements preferably adds up to less than 0.20%.
2) micro-assembly robot
In the present invention, in order to improve cold-workability, it is necessary to enter to exercise the annealing (spheroidizing of cementite spheroidizing after hot rolling Annealing), form the micro-assembly robot being made up of ferrite and cementite.It should illustrate, spheroidizing is represented relative to total cementite, length and width Cementite than (major diameter/minor axis)≤3 occupies more than 90% state in terms of volume fraction.Especially for making Rockwell hardness with HRB Be calculated as less than 73 and percentage of total elongation be more than 39%, it is necessary to which the carburizing volume density in ferrite crystal grain is set into 0.08/μm2With Under.Hereinafter, carburizing volume density is also denoted as the individual number density of cementite crystal grain.
The individual number density of the cementite crystal grain of ferrite intragranular:0.08/μm2Below
The steel plate of the present invention is made up of ferrite and cementite.If the number of the cementite crystal grain in ferrite crystal grain is close Degree is high, then the hardening because dispersion-strengthened, elongation can reduce.In order that hardness is below setting and makes elongation be regulation More than value, it is necessary to which the individual number density of the cementite crystal grain in ferrite crystal grain is set into 0.08/μm2Below.Ferrite crystal grain The individual number density of interior cementite crystal grain is preferably 0.07/μm2Hereinafter, more preferably 0.06/μm2Below.It is present in Cementite diameter in ferrite crystal grain is calculated as 0.15~1.8 μm or so with major diameter because be precipitation strength to steel plate slightly The size to tell on, so by reducing the individual number density of the cementite crystal grain in ferrite crystal grain, intensity can be realized Reduce.The cementite of ferrite grain boundaries be almost helpless to it is dispersion-strengthened, so by the cementite crystal grain in ferrite crystal grain Number density is defined as 0.08/μm2Below.In addition, it should illustrate, in addition to above-mentioned ferrite and cementite, unavoidably The remainder tissues such as ground generation pearlite, as long as total volume fraction of remainder tissue is below 5% or so, then not damage The effect of the evil present invention, therefore the remainder tissue can also be contained.
The average diameter of total cementite:Cementite average diameter in 0.60 μm~1.00 μm and ferrite crystal grain:0.40μ More than m
Steel plate of the cementite average diameter less than 0.40 μm in ferrite crystal grain is because of the cementite crystalline substance in ferrite crystal grain The individual number density increase of grain, so the hardness of the steel plate after annealing rises sometimes.In order to hardness is set to desired value below, It is preferred that the cementite average diameter in ferrite crystal grain is set to more than 0.40 μm.Cementite in ferrite crystal grain it is average straight Footpath is more preferably more than 0.45 μm.
Compared with the cementite in ferrite crystal grain, the easy coarsening of cementite of ferrite grain boundaries, in order that ferrite The average diameter of cementite in crystal grain be more than 0.40 μm, it is necessary to by the average diameter of overall cementite be set to 0.60 μm with On.The average diameter of total cementite is preferably more than 0.65 μm.On the other hand, if the average diameter of total cementite is more than 1.00 μm, then during heating within the short time as image height frequency Quenching Treatment sometimes, cementite is not completely dissolved, can not become hardness Below desired value, it is therefore preferable that the average diameter of total cementite is set into less than 1.00 μm.Always cementite is average straight Footpath is more preferably less than 0.95 μm.The average diameter of above-mentioned cementite can utilize SEM observation micro-assembly robots, measure cementite crystalline substance The major diameter and minor axis of grain, so as to determine the average diameter of the cementite in the average diameter and ferrite crystal grain of total cementite.
It should illustrate, if ferritic particle diameter is excessively thick, although hardness reduces, the raising of elongation sometimes is satisfied With therefore, the ferritic average grain diameter in the tissue being made up of above-mentioned ferrite and cementite is preferably less than 12 μm, more excellent Elect less than 9 μm as.On the other hand, if ferritic average grain diameter is less than 6 μm, the hardening of steel plate meeting sometimes, therefore iron element The average grain diameter of body is preferably more than 6 μm.Above-mentioned ferritic particle diameter can utilize SEM observation micro-assembly robots and be measured.
3) mechanical property
In the present invention, carry out the automotive parts such as gear class, fluid drive box part, seat harness part by cold pressing Shaping, it is therefore desirable to excellent processability.In addition, it is necessary to increase hardness by Quenching Treatment, wear resistance is assigned to part. Therefore, it is necessary to which being reduced to below HRB73 and increase elongation the hardness of steel plate makes percentage of total elongation in addition to improving quenching degree (El) it is more than 39%.From the viewpoint of processability, the hardness of steel plate is preferably more low better, but there is also partly quenched Part, the intensity of raw sheet can influence fatigue properties.Therefore, the hardness of steel plate is preferably greater than HRB60.In addition, above-mentioned HRB can To be determined using Rockwell apparatus (B scales).In addition, percentage of total elongation can be used relative to the direction (L that rolling direction is 0 ° Direction) the JIS5 tension test sheets that cut out, using Shimadzu Seisakusho Ltd. AG10TB AG/XR cupping machine with 10mm/ minutes Tension test is carried out, the sample of fracture is measured to fetching.
4) manufacturing condition
The high-carbon hot-rolled steel sheet of the present invention manufactures as follows:Using the steel of above-mentioned composition as blank, with finish rolling after hot roughing Temperature:Ar3Desired thickness of slab is made in the hot rolling that finish rolling is implemented in transformation temperature~870 DEG C, after finish rolling, with 25 DEG C/s~150 DEG C/ S average cooling rate is cooled to 700 DEG C, with coiling temperature:500 DEG C~700 DEG C are batched, be made with pearlite and with Volume fraction is calculated as the steel plate of more than 5% pro-eutectoid ferrite, then in Ac1Implement spheroidizing below transformation temperature.Should Illustrate, the reduction ratio in finish rolling is preferably more than 85%.
Hereinafter, the restriction reason in the manufacture method of the high-carbon hot-rolled steel sheet of the present invention is illustrated.
Final rolling temperature:Ar3Transformation temperature~870 DEG C
In order to make the individual number density of the cementite crystal grain in ferrite crystal grain be 0.08/μm after annealing2Below, it is necessary to Hot rolled steel plate implementation spheroidizing to the micro-assembly robot for the pro-eutectoid ferrite that more than 5% is calculated as with pearlite and with volume fraction is moved back Fire.In the hot rolling for implementing finish rolling after hot roughing, if final rolling temperature uprises, the ratio of pro-eutectoid ferrite more than 870 DEG C Example diminishes, and cannot get the individual number density of defined cementite crystal grain after spheroidizing.In addition, the carburizing after spheroidizing Body particle diameter, ferrite particle diameter also easy coarsening.Therefore, final rolling temperature is set to less than 870 DEG C.In order to fully increase pro-eutectoid Ferritic ratio, final rolling temperature is preferably set to less than 850 DEG C.On the other hand, if final rolling temperature is less than Ar3Transformation temperature, Then after hot rolling with thick ferrite crystal grain is formed after annealing, elongation significantly reduces.Therefore, final rolling temperature is set to Ar3 It is more than transformation temperature.Final rolling temperature is preferably more than 820 DEG C.It should illustrate, using the surface temperature of steel plate as final rolling temperature.
From final rolling temperature to 700 DEG C of average cooling rate:25 DEG C/s~150 DEG C/s
In order to make the individual number density of the cementite crystal grain in ferrite crystal grain be 0.08/μm after annealing2Below, it is necessary to Hot rolled steel plate implementation spheroidizing to the micro-assembly robot for the pro-eutectoid ferrite that more than 5% is calculated as with pearlite and with volume fraction is moved back Fire.To 700 DEG C of temperature province equivalent to the temperature that ferrite and pearlite starting temperature of transformation be present after finish rolling in hot rolling Region, therefore in order that a point rate for the pro-eutectoid ferrite in steel plate after hot rolling is calculated as more than 5% with volume fraction, from finish rolling temperature The cooling velocity spent to 700 DEG C turns into key factor.Average cooling rate from final rolling temperature to 700 DEG C of temperature province is less than During 25 DEG C/s, ferrite transformation is difficult to carry out in a short time, and pearlite point rate uprises more than necessity, therefore cannot be with body Product rate is calculated as more than 5% pro-eutectoid ferrite.In addition, because generating thick pearlite, it is difficult after spheroidizing To obtain desired steel plate tissue.Therefore, the average cooling rate of the temperature province after finish rolling to 700 DEG C is set to 25 DEG C/more than s.In addition, in order to obtain 0.07/μm2Of the cementite grain of ferrite intragranular after following spheroidizing Number density, a point rate for pro-eutectoid ferrite is preferably set to more than 10% in terms of volume fraction, now, preferably by the average cooling speed Degree is set to 30 DEG C/more than s.The average cooling rate is more preferably 40 DEG C/more than s.On the other hand, if the average cooling rate More than 150 DEG C/s, then it is difficult to obtain pro-eutectoid ferrite, therefore the average cooling rate to 700 DEG C after finish rolling is set into 150 DEG C/below s.The average cooling rate is preferably 120 DEG C/below s.The average cooling rate is more preferably 100 DEG C/below s.This Outside, using the surface temperature of steel plate as the temperature.
Coiling temperature:500 DEG C~700 DEG C
After steel plate after finish rolling states cooling on the implementation, steel ring shape is coiled into 500 DEG C~700 DEG C of coiling temperature. If coiling temperature more than 700 DEG C, not only the tissue coarsening of hot rolled steel plate and desired steel can not be obtained after annealing Plate tissue, and the intensity of steel plate is too low, when coiling into steel ring shape, is deformed sometimes because of the deadweight of steel ring, therefore grasping It is not preferred on work.Therefore coiling temperature is set to less than 700 DEG C.Coiling temperature is preferably less than 650 DEG C.On the other hand, if Coiling temperature is less than 500 DEG C, then steel plate tissue becomes fine and steel plate hardening, elongation diminish and processability reduction.Therefore, Coiling temperature is set to more than 500 DEG C.Coiling temperature is preferably more than 550 DEG C.Should illustrate, using the surface temperature of steel plate as Coiling temperature.
The micro-assembly robot of steel plate after hot rolling:More than 5% pro-eutectoid ferrite is calculated as with pearlite and with volume fraction Tissue
In the present invention, after spheroidizing described later, obtain have be made up of ferrite and cementite and above-mentioned iron element The individual number density of cementite crystal grain in body crystal grain is 0.08/μm2The steel plate of following micro-assembly robot.After spheroidizing In micro-assembly robot, the influence of the micro-assembly robot of the steel plate after hot rolling is big.There is pearly-lustre by turning into the micro-assembly robot of the steel plate after hot rolling Body and be calculated as with volume fraction more than 5% pro-eutectoid ferrite tissue, desired group can be turned into after spheroidizing Knit, be accordingly changed into the high steel of processability.In addition, if being point rate without pearlite or pro-eutectoid ferrite with volume fraction Steel plate of the meter less than 5%, then in Ac1After carrying out spheroidizing below transformation temperature, it cannot get of defined cementite crystal grain Number density, armor plate strength uprise.Therefore, make to carry out hot rolling with above-mentioned condition, cool down and batch and obtain steel plate (hot rolled steel plate) Micro-assembly robot be set to there is pearlite and be calculated as with volume fraction more than 5% pro-eutectoid ferrite tissue.It is preferred that as by pearl Body of light and the tissue that more than 10% pro-eutectoid ferrite formed is calculated as with volume fraction.It should illustrate, in order to be obtained after annealing Uniform tissue, a point rate for pro-eutectoid ferrite are preferably calculated as less than 50% with volume fraction.
Annealing temperature:Ac1Below transformation temperature
Annealing (spheroidizing) is implemented to the hot rolled steel plate as above obtained.If annealing temperature is more than Ac1Transformation temperature, then Austenite separates out, and forms thick pearlitic structrure in cooling procedure after annealing, becomes uneven tissue.Therefore, will Annealing temperature is set to Ac1Below transformation temperature.It should illustrate, lower limit does not have a special provision, but from the carburizing made in ferrite crystal grain From the aspect of the individual number density of body crystal grain turns into desired value, annealing temperature is preferably more than 600 DEG C, more preferably 700 More than DEG C.It should illustrate, atmosphere gas can use any of mixed gas of nitrogen, hydrogen, nitrogen and hydrogen, preferably use these Gas, but Ar can also be used, it is not particularly limited.In addition, annealing time is preferably 0.5~40 hour.During by that will anneal Between be set to more than 0.5 hour, destination organization can be stably obtained, the hardness of steel plate can be set to below setting, will stretched Long rate is set to more than setting, therefore annealing time is preferably more than 0.5 hour.More preferably more than 8 hours.In addition, If annealing time, more than 40 hours, production rate reduces, and manufacturing cost easily becomes too much, therefore annealing time is preferably 40 Below hour.It should illustrate, the surface temperature using annealing temperature as steel plate.In addition, using annealing time as defined in maintenance The time of temperature.
It should illustrate, for the high-carbon steel of the melting present invention, converter, electric furnace can use.In addition, so melting forms High-carbon steel blanket is made by ingot casting-split rolling method or continuously casting.Blanket generally after the heating, carries out hot rolling.It should say It is bright, in the case of the blanket manufactured by continuously casting, it can apply and directly roll, change straight roll and directly rolled or for suppression Temperature reduce purpose and rolled after thermal protection.In addition, when heating blanket carries out hot rolling, in order to avoid the table as caused by scale The variation of surface state, blanket heating-up temperature is preferably set to less than 1280 DEG C.For hot rolling, in order to carry out essence with defined temperature Roll, the heating of material to be rolled can be carried out using heater meanses such as plate heaters in hot rolling.
Embodiment 1
To with steel numbering system A~J shown in table 1 chemical composition form steel carry out melting, then with table 2 shown in heat After kicker part carries out finish rolling, cooled down, batched, hot rolled steel plate is made.It should illustrate, the cooling velocity shown in table 2 is from essence To 700 DEG C of average cooling rate after rolling.Then, pickling is carried out, with the annealing conditions shown in table 2, in blanket of nitrogen (atmosphere gas Body:Nitrogen) in implement annealing (spheroidizing), manufacture thickness of slab 4.0mm, the wide 1000mm of plate hot rolled steel plate (hot-roll annealing plate). To the hot-roll annealing plate so manufactured, investigation hardness, elongation, micro-assembly robot.In addition, also to the micro-group of the hot rolled steel plate before annealing Knit and investigated.Show the result in table 2.It should illustrate, the Ar shown in table 13Transformation temperature and Ac1Transformation temperature is by automatic phase transformation instrument Obtain.
The hardness (HRB) of hot-roll annealing plate
Sample is taken from the wide central portion of the plate of the steel plate after annealing, determines at 5 points using Rockwell apparatus (B scales), obtains Average value.
The percentage of total elongation (El) of hot-roll annealing plate
The use of from the steel plate after annealing is being JIS5 tension tests that 0 ° of direction (L directions) is cut out with rolling direction Piece, tension test is carried out with 10mm/ minutes using Shimadzu Seisakusho Ltd. AG10TB AG/XR cupping machine, by the sample of fracture Elongation (percentage of total elongation) is obtained to fetching.
Micro-assembly robot
The micro-assembly robot (micro-assembly robot of hot rolled plate) of hot rolled steel plate before annealing is observed by SEM, obtains the kind of its tissue Class and pro-eutectoid ferrite divide rate.Divide rate for pro-eutectoid ferrite, by being divided into ferrite area and ferrite area Position in addition, obtain the ratio of ferrite area and obtain area occupation ratio, the volume fraction using the value as pro-eutectoid ferrite.Should Explanation is given, in the hot rolled steel plate before the annealing shown in table 2, confirms pearlite be present by above-mentioned SEM observations.
For the micro-assembly robot (micro-assembly robot of hot-roll annealing plate) of the steel plate after annealing, the sample that will be taken from the wide central portion of plate After cut-out grinding, implement nital (nital) corrosion, using sweep electron microscope, using at 1/4 of thickness of slab 5 put sentence 3000 times multiplying power shooting macrograph, observe its tissue species, and determine it is being not present on crystal boundary, Major diameter is the number of more than 0.15 μm of cementite, and the area of the number divided by the visual field of photo is obtained in ferrite crystal grain Carburizing volume density (the individual number density of cementite crystal grain).For cementite diameter, each carburizing is determined using above-mentioned macrograph The major diameter and minor axis of body crystal grain, obtain the average diameter of the cementite in whole cementite and crystal grain.For ferritic grain Footpath, grain size number is obtained using above-mentioned macrograph, calculates average crystallite particle diameter.
In addition, for the steel plate (hot-roll annealing plate) after annealing, in average N amounts and the steel plate of obtaining 150 μm of top layer as follows The difference of average N amounts, solid solution B amounts ratio shared in B content.Show the result in table 2.
The difference of the average N amounts on 150 μm of top layer and average N amounts in steel plate
The sample taken using the wide central portion of plate from the steel plate after annealing, determine the average N amounts and steel plate on 150 μm of top layer In average N amounts, obtain the average N amounts on 150 μm of top layer and the difference of the average N amounts in steel plate.It should illustrate, here 150 μm of top layer Average N amounts refer to, the N amounts contained from surface of steel plate in the range of being 150 μm of depth along thickness of slab direction.In addition, ask as follows Go out the average N amounts on 150 μm of top layer.That is, cut since the surface for the steel plate taken, by steel plate from surface cut to 150 μm Depth, this caused cutting blade is taken as sample.Determine the N amounts of N amounts in the sample as 150 μm of top layer.Top layer 150 μm average N amounts and steel plate in average N amounts melted using non-active gas-thermal conductivity method measure and obtain.So long as what is obtained The average N amounts (surface~from surface to the N amounts of the scope of 150 μm of depth) on 150 μm of top layer are with the average N amounts in steel plate (in steel N content) difference be below 30 mass ppm, then can be evaluated as that nitriding can be suppressed.
It is dissolved B amounts ratio shared in B content
Sample is taken from the wide central portion of the plate of the steel plate after annealing.The BN in steel is extracted with 10 volume %Br methanol Take, the B content separated out in the form of BN is subtracted from whole B contents in steel, obtain solid solution B amounts.Pass through { (solid solution B amount (matter Amount %))/(whole B contents (quality %)) × 100 (%) obtain in whole B contents (B content) for containing in steel of solid solution B amounts Shared ratio.As long as the ratio is more than 70 (%), then can be evaluated as that the reduction for being dissolved B amounts can be suppressed.
Steel plate hardness (quenching hardness) after quenching
Using the steel plate after annealing as raw sheet, 3 kinds of Quenching Treatments are implemented as follows, the steel plate hardness (quenching after investigation quenching Hardness), evaluate quenching degree.Show the result in table 2.
Treadmill test piece (width 15mm × length 40mm × plate is taken from the wide central portion of plate of the steel plate (raw sheet) after annealing Thick 4mm), using above-mentioned treadmill test piece, using the method (water cooling) for keeping 30s to carry out water cooling immediately at 870 DEG C, 870 The method (120 DEG C of oil coolings) that is cooled down immediately with 120 DEG C of oil is kept after 30s at DEG C to carry out Quenching Treatment.Through hardening characteristic The section to the test film after Quenching Treatment, determined using Vickers pyramid hardness testing machine under conditions of load 1kgf 5 points it is hard Spend and obtain average hardness, and be averaged hardness as quenching hardness.
In addition, the wide central portion of plate from the steel plate (raw sheet) after annealing takes disc test piece(heated using high-frequency quenching with 200 DEG C/s of firing rate, after reaching 1000 DEG C Carry out water cooling) implement Quenching Treatment.Now, Vickers pyramid hardness testing machine is utilized to the section of the test film in test film most peripheral portion 2 point hardnesses are determined under conditions of load 0.2kgf and obtain average hardness, are averaged hardness as quenching hardness.
The quenching hardness that 30s progress water coolings are kept at 870 DEG C and oil cooling is carried out at 120 DEG C is satisfied by the condition of table 3 In water cooling after hardness after hardness, 120 DEG C of oil coolings, and the quenching hardness after high-frequency quenching is met to the high-frequency quenching hardness of table 3 Situation be determined as qualified (zero), it is excellent to be evaluated as quenching degree.In addition, water cooling and at 120 DEG C after 30s is kept at 870 DEG C When any one of hardness after the hardness and high-frequency quenching water cooling of progress oil cooling is unsatisfactory for the condition shown in table 3, it is set to not conform to Lattice (×), it is poor to be evaluated as quenching degree.Should illustrate, table 3 represent can be empirically evaluated as quenching degree sufficiently with C content pair The quenching hardness answered.
According to table 2, it is known that in the hot rolled steel plate of example of the present invention, have be made up of ferrite and cementite and above-mentioned iron element Carburizing volume density in body crystal grain is 0.08/μm2Following micro-assembly robot, hardness are calculated as less than 73 with HRB, and percentage of total elongation is More than 39%, therefore cold-workability is excellent, and quenching degree is also excellent.
Table 3

Claims (4)

1. a kind of high-carbon hot-rolled steel sheet, it is had following composition, i.e., contained in terms of quality %:C:0.20~0.40%, Si: Less than 0.10%, Mn:Less than 0.50%, P:Less than 0.03%, S:Less than 0.010%, it is dissolved aluminium:Less than 0.10%, N: Less than 0.0050%, B:0.0005~0.0050%, further containing add up to 0.002~0.030% Sb, Sn, Bi, Ge, More than a kind in Te, Se, remainder is Fe and inevitable impurity, and solid solution B amounts ratio shared in B content is More than 70%, also, be made up of ferrite and cementite and carburizing volume density in the ferrite crystal grain for 0.08/ μm2The average diameter of total cementite in the tissue formed below and by the ferrite and cementite is 0.60 μm~1.00 μ M, the cementite average diameter in ferrite crystal grain is more than 0.40 μm of micro-assembly robot, and hardness is calculated as less than 73 with HRB, general extension Rate is more than 39%.
2. high-carbon hot-rolled steel sheet according to claim 1, wherein, further in terms of quality % containing add up to 0.50% with Under Ni, Cr, Mo in more than a kind.
A kind of 3. manufacture method of high-carbon hot-rolled steel sheet, after with the hot roughing of steel formed as follows, using final rolling temperature as Ar3Phase Height~870 DEG C carry out finish rolling, be cooled to 700 DEG C with 25 DEG C/s~150 DEG C/s average cooling rate, using coiling temperature as 500 DEG C~700 DEG C are batched, be thus made be calculated as with pearlite and with volume fraction more than 5% pro-eutectoid ferrite Steel plate, then, by the steel plate in Ac1Annealed below transformation temperature, wherein, the composition of the steel is to be contained in terms of quality %: C:0.20~0.40%, Si:Less than 0.10%, Mn:Less than 0.50%, P:Less than 0.03%, S:Less than 0.010%, it is dissolved aluminium: Less than 0.10%, N:Less than 0.0050%, B:0.0005~0.0050%, further contain and add up to 0.002~0.030% More than a kind in Sb, Sn, Bi, Ge, Te, Se, remainder is Fe and inevitable impurity.
4. the manufacture method of high-carbon hot-rolled steel sheet according to claim 3, wherein, the steel is further contained in terms of quality % There is more than a kind in Ni, Cr, the Mo for adding up to less than 0.50%.
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US11359267B2 (en) 2017-02-21 2022-06-14 Jfe Steel Corporation High-carbon hot-rolled steel sheet and method for manufacturing the same
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1598032A (en) * 2003-08-28 2005-03-23 杰富意钢铁株式会社 High-carbon hot-rolled steel plate,cold-rolled steel plate and making method thereof
CN1667151A (en) * 2004-03-10 2005-09-14 杰富意钢铁株式会社 High carbon hot-rolled steel sheet and method for manufacturing the same
CN105378132A (en) * 2013-07-09 2016-03-02 杰富意钢铁株式会社 High-carbon hot-rolled steel sheet and production method for same
CN105378133A (en) * 2013-07-09 2016-03-02 杰富意钢铁株式会社 High-carbon hot-rolled steel sheet and production method for same

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5317661B2 (en) 1973-08-31 1978-06-09
JP5292698B2 (en) * 2006-03-28 2013-09-18 Jfeスチール株式会社 Extremely soft high carbon hot-rolled steel sheet and method for producing the same
JP4952236B2 (en) * 2006-12-25 2012-06-13 Jfeスチール株式会社 High carbon hot rolled steel sheet and manufacturing method thereof
JP5358914B2 (en) * 2007-09-14 2013-12-04 Jfeスチール株式会社 Super soft high carbon hot rolled steel sheet
JP4782243B2 (en) 2009-03-16 2011-09-28 新日本製鐵株式会社 Boron-added steel sheet with excellent hardenability and manufacturing method
JP5458649B2 (en) * 2009-04-28 2014-04-02 Jfeスチール株式会社 High carbon hot rolled steel sheet and manufacturing method thereof
JP5056876B2 (en) * 2010-03-19 2012-10-24 Jfeスチール株式会社 Hot-rolled steel sheet with excellent cold workability and hardenability and method for producing the same
JP5594226B2 (en) * 2011-05-18 2014-09-24 Jfeスチール株式会社 High carbon steel sheet and method for producing the same
US10077491B2 (en) * 2012-01-05 2018-09-18 Jfe Steel Corporation High carbon hot rolled steel sheet and method for manufacturing the same
EP2801635B1 (en) * 2012-01-05 2017-09-20 JFE Steel Corporation High carbon hot-rolled steel sheet with excellent hardenability and minimal in-plane anisotropy, and method for producing same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1598032A (en) * 2003-08-28 2005-03-23 杰富意钢铁株式会社 High-carbon hot-rolled steel plate,cold-rolled steel plate and making method thereof
CN1667151A (en) * 2004-03-10 2005-09-14 杰富意钢铁株式会社 High carbon hot-rolled steel sheet and method for manufacturing the same
CN105378132A (en) * 2013-07-09 2016-03-02 杰富意钢铁株式会社 High-carbon hot-rolled steel sheet and production method for same
CN105378133A (en) * 2013-07-09 2016-03-02 杰富意钢铁株式会社 High-carbon hot-rolled steel sheet and production method for same

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